U.S. patent number RE29,586 [Application Number 05/723,429] was granted by the patent office on 1978-03-21 for low temperature curing process and coating compositions suitable therefor.
This patent grant is currently assigned to The Dow Chemical Company. Invention is credited to John H. Flickinger, Russell T. McFadden, Thomas R. Merlino.
United States Patent |
RE29,586 |
Merlino , et al. |
March 21, 1978 |
**Please see images for:
( Certificate of Correction ) ** |
Low temperature curing process and coating compositions suitable
therefor
Abstract
Coatings may be cured by this process below 50.degree. F. and at
temperatures as low as -10.degree. F. Suitable coating compositions
comprise a solution in an inert organic solvent of (1) a
polyaziridinyl adduct having more than one aziridinyl hydroxyalkyl
group per molecule and (2) a coreactant which may be a dicarboxylic
acid anhydride or a polyfunctional material having more than one
anhydride, .[.oxirane.]. .Iadd.glycidyl.Iaddend., thiol, sulfonic
acid or carboxylic group per molecule.
Inventors: |
Merlino; Thomas R. (North
Providence, RI), Flickinger; John H. (Houston, TX),
McFadden; Russell T. (Freeport, TX) |
Assignee: |
The Dow Chemical Company
(Midland, MI)
|
Family
ID: |
21868213 |
Appl.
No.: |
05/723,429 |
Filed: |
September 15, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
033036 |
Apr 29, 1970 |
03702349 |
Nov 7, 1972 |
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Current U.S.
Class: |
525/526; 525/375;
528/109; 528/341; 528/188; 528/172; 528/116; 525/532; 525/507;
525/132; 525/502; 525/523; 525/529; 525/533; 528/113; 528/125;
528/183; 528/211; 428/418 |
Current CPC
Class: |
C08G
59/5066 (20130101); C08G 73/0213 (20130101); Y10T
428/31529 (20150401) |
Current International
Class: |
C08G
59/50 (20060101); C08G 59/00 (20060101); C08G
73/00 (20060101); C08G 73/02 (20060101); C08L
063/00 () |
Field of
Search: |
;260/47EN,2N,83R,59EP,78.4 |
References Cited
[Referenced By]
U.S. Patent Documents
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3355437 |
November 1967 |
Tesoro et al. |
3479337 |
November 1969 |
Bulbenko et al. |
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Foreign Patent Documents
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767,118 |
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Sep 1967 |
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CA |
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1,448,507 |
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Jun 1966 |
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FR |
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Primary Examiner: Pertilla; Theodore E.
Attorney, Agent or Firm: Lindstrom; Albin R.
Claims
What is claimed is:
1. A low temperature curing process for the preparation of films
and coatings which comprises
(a) dissolving a polyaziridinyl adduct having more than one
aziridinyl hydroxyalkyl group per molecule and a coreactant for
said adduct in a volatile, inert organic solvent to provide a
coating solution thereof, wherein said coreactant is a dicarboxylic
acid anhydride or a polyfunctional material having more than one
anhydride, .[.oxirane.]. .Iadd.glycidyl.Iaddend., sulfonic acid or
carboxylic acid group per molecular and wherein the proportions of
said adduct to said coreactant on an equivalent basis ranges from
about 0.5/1 to about 2/1, respectively;
(b) applying said coating solution in a filmiform layer; and
(c) allowing said solvent to evaporate and the coating composition
to cure by exposing said layer to a temperature below about
50.degree. F. for a time sufficient for said adduct and said
coreactant to react.
2. The process of claim 1 wherein said solution contains about
equivalent proportions of said adduct to said coreactant.
3. The process of claim 1 wherein said curing temperature ranges
from about -10.degree. F. to about 50.degree. F.
4. The process of claim 1 wherein said polyaziridinyl adduct is
prepared by reacting an alkylenimine with a polyepoxide having more
than one glycidyl group per molecule in the proportions of at least
about one mole of the alkylenimine per each glycidyl group.
5. The process of claim 4 wherein said polyepoxide is a
polyglycidyl ether of a polyhydric alcohol or a polyhyric
phenol.
6. The process of claim 5 wherein said polyepoxide is a
polyglycidyl ether of a dihydric phenol.
7. The process of claim 6 wherein said dihydric phenol is bisphenol
A.
8. The process of claim 4 wherein said alkylenimine is ethylenimine
or propylenimine.
9. The process of claim 1 wherein said solution further contains an
acid catalyst.
10. A composition which is curable at temperatures below 50.degree.
F. consists of a volatile, inert organic solvent solution of
(a) a polyaziridinyl adduct having more than one aziridinyl
hydroxyalkyl group per molecule, and
(b) a coreactant which is a dicarboxylic acid anhydride or a
polyfunctional material having more than one anhydride,
.[.oxirane.]. .Iadd.glycidyl.Iaddend., or sulfonic acid group per
molecule;
wherein the proportions of said adduct to said coreactant on an
equivalent basis ranges from about 0.5/1 to about 2/1,
respectively.
11. The composition of claim 10 wherein said polyaziridinyl adduct
is prepared by reacting an alkylenimine with a polyepoxide having
more than one glycidyl group per molecule in the proportions of at
least about one mole of the alkylenimine per each glycidyl
group.
12. The composition of claim 11 wherein said polyepoxide is a
polyglycidyl ether of a polyhydric alcohol or a polyhydric
phenol.
13. The composition of claim 12 wherein said polyepoxide is a
polyglycidyl ether of a dihydric phenol.
14. The composition of claim 13 wherein said dihydric phenol is
bisphenol A.
15. The composition of claim 11 wherein said alkylenimine is
ethylenimine or propylenimine.
16. The composition of claim 10 wherein said solution contains
about equivalent proportions of said adduct to said coreactant.
17. The composition of claim 10 wherein said coreactant is nadic
methyl anhydride or a copolymer of styrene and maleic
anhydride.
18. The composition of claim 10 wherein said coreactant is a
polyepoxide having more than one glycidyl group per molecule.
19. The composition of claim 18 wherein said polyepoxide is a
polyglycidyl ether or a polyhydric phenol or polyhydric
alcohol.
20. The composition of claim 10 further consisting of a
pigment.
21. The composition of claim 10 further consisting of an acid
catalyst.
22. A composition which is curable at temperatures below 50.degree.
F. consists of a volatile, inert organic solvent solution of
(a) a polyaziridinyl adduct of an alkylenimine and a polyglyicdyl
ether of bisphenol A wherein said adduct has more than one
aziridinyl hydroxyalkyl ether group per molecule, and
(b) a polyepoxide having more than one glycidyl ether group per
molecule;
wherein the proportions of said adduct to said polyepoxide on an
equivalent basis ranges from about 0.5/1 to about 2/1,
respectively.
23. The composition of claim 22 wherein said alkylenimine is
ethylenimine or propylenimine.
24. The composition of claim 22 wherein said polyepoxide is a
polyglycidyl ether of a dihydric phenol.
25. The composition of claim 22 wherein said solution contains
about equivalent proportions of said adduct to said
polyepoxide.
26. The composition of claim 22 further consisting of an acid
catalyst.
27. The composition of claim 22 further consisting of a pigment.
Description
BACKGROUND OF THE INVENTION
The subject matter of this invention relates to coating
compositions which have the desirable and unexpected property of
curing at low temperatures. The compositions utilize certain
polyaziridinyl adducts in combination with a dicarboxylic acid
anhydride or a polyfunctional material having more than one group
per molecule which is reactive with the aziridinyl group.
Known coating compositions which contain coreactive materials, such
as an epoxy resin and a curing agent, normally require the
application of heat to cure same and are commonly referred to as
thermosettable. In many instances curing it an exothermic reaction,
e.g. polyepoxides, polyesters, polyurethanes, etc., which aids in
the curing reaction. While some such coating compositions may be
cured at room temperature or even as low as 50.degree. F., there is
an unfilled need for coating compositions which will cure at
temperatures below 50.degree. F.
Bulbenko et al. in U.S. 3,329,674 and U.S. 3,479,337 disclose the
preparation of certain aziridinyl compounds and their use with
carboxyl containing polymers as elastomeric binders for solid
rocket fuels.
Strother in U.S. 3,346,533 and U.S. 3,303,144 describes the use of
bis[2-(1-azirdinyl)ethyl]benzene, certain other bis aziridines and
N-(2-hydroxy akyl)aziridines (monofunctional) as useful in curing
polyepoxide resins. Cures were effected at temperatures of
75.degree. F. or higher.
SUMMARY OF THE INVENTION
Low temperature curing processes and coating materials are
particularly desirable but difficult to obtain. The subject matter
of this invention concerns compositions suitable for coating a wide
variety of substrates and which have the advantageous and
unexpected benefit of being curable at temperatures below
50.degree. F. and at temperatures as low as -10.degree. F.
Coating compositions suitable for use in the process herein
comprise an inert, volatile organic solvent solution of (1) a
polyaziridinyl adduct having more than one aziridinyl hydroxyalkyl
group per molecule and (2) a coreactant which may be a dicarboxylic
acid anhydride or a polyfunctional material having more than one
reactive .[.oxirane.]. .Iadd.glycidyl .Iaddend.group, anhydride
group, thiol group, sulfonic acid group, or carboxylic acid group
per molecule.
The polyaziridinyl adduct is combined with the coreactant in the
proportions on an equivalent basis of about 0.5/1.0 to 2.0/1.0
respectively. Preferably the components are combined to have an
equivalent amount of an aziridinyl group per each reactive
group.
DETAILED DESCRIPTION OF THE INVENTION
It should be understood that while the coating compositions of this
invention are curable at temperatures below about 50.degree. F. and
substantially below the freezing point of water they may also be
readily cured at temperatures of 50.degree. F. or higher.
Coatings prepared from the compositions and process of this
invention are useful, by the addition of pigments and the like, in
preparing paints but are also useful as adhesives, in preparing
laminates, as binders, for impregnating fabrics and for other
coating purposes. Films may also be prepared. Maintenance and
construction people especially in the more northern climates will
recognize the benefits and advantages for these coatings
compositions.
The coating and film forming process comprises the steps of
preparing a solution containing a polyaziridinyl adduct and a
coreactant which are more fully described hereinafter, applying the
solution in a filmiform layer and allowing the solvent to evaporate
and the coating to cure by exposing the layer to a temperature
below 50.degree. F. for a time sufficient to effect a cure by
coreaction of the components. Cure temperatures substantially below
the freezing point of water and as low as -10.degree. F. may be
used herein.
The solutions require no special methods for their preparation. A
variety of inert, volatile organic solvents are available and may
be used to prepare solutions of the coating composition components.
Depending on the ultimate purpose the solutions may be prepared as
either low or high solids content solutions. The viscosity is
readily adjusted for ease of application by the choice of solvents,
the type of each component (molecular weight, etc.) and the
proportions of each.
Typical solvents include aromatics such as benzene, toluene,
xylene, ethyl benzene and the like, lower alcohols, glycol ethers,
dioxane, tetrahydrofuran, esters, ketones and the like. Mixtures of
solvents may also be used and frequently are preferred. In general
the solvent need only be inert to the coating components dissolved
therein and be volatile at the temperature of curing. Chlorinated
hydrocarbon solvents and organic acids should be avoided since they
are not inert and will react with the aziridinyl group.
The filmiform layer may be formed by any convenient method such as
spraying, applying by brush or a roll, dipping, etc., all of which
are well known to the art and need no detailed description
herein.
Polyaziridinyl adducts having more than one aziridinyl hydroxyalkyl
group per molecule comprise one of the reactive components of the
coating compositions. Said adduct is conveniently prepared by
reacting an alkylenimine with a polyepoxide having more than one
glycidyl group per molecule whereby azirdinyl hydroxyalkyl groups
are formed.
The reaction between the alkylenimine and the glycidyl group to
produce an aziridinyl hydroxy propyl group can be shown with
ethylenimine. ##STR1## The polyaziridinyl adduct is prepared
employing such a reaction by combining at least about one mole of
alkylenimine per glycidyl group and heating at moderate
temperatures. The reaction is best run in an inert aromatic
##STR2## hydrocarbon solvent such as toluene although other inert
solvents or solvent mixtures may be used. Excesses of the
alkylenimine to ensure, completeness of reaction may be used since
the excess alkylenimine may be removed by distillation and/or use
of a vacuum and the like. The reaction may take several hours or
more depending on the temperature employed. Reaction temperatures
in the range of 50 to 80.degree. C. are satisfactory although lower
and higher temperatures may be used.
Alkylenimines useful in preparing the polyaziridinyl adducts
include ethylenimine and propylenimine which are readily available
but other alkylenimines containing an alkyl substituent of up to 8
carbon atoms may also be used.
Polyepoxides having more than one glycidyl group per molecule may
be employed to prepare the polyazirdinyl adducts of this invention.
Included within the useful polyepoxides are those wherein the
glycidyl group is attached to the resin by an oxygen atom (a
glycidyl ether), a sulfur atom (a gycidyl thioether), a carbonyl (a
glycidyl ester) and a nitrogen atom (a glycidyl amide or amine).
The above polyepoxides and their preparation are well known to the
art and are fully disclosed in Chapter 2, "Handbook of Epoxy
Resins," H. Lee and K. Neville, McGraw-Hill Book Co., New York,
1967. Many other technical articles and patents further describe
these polyepoxides.
In general the polyglycidyl ethers of polyhydric alcohols and
polyhydric phenols are preferred. Most preferred are the
polyglycidyl ethers of dihydric alcohols or dihydric phenols.
Resins based on the dihydric phenol, bisphenol A, are the most
common resins of this type.
Briefly, for purposes of illustration, polyglycidyl ethers are most
conveniently prepared by reacting an epihalohydrin, usually
epichlorohydrin, with the polyhydric alcohol or phenol by heating
in the presence of a sufficient amount of an alkali to combine with
the halogen of the halohydrin. Frequently an excess of alkali will
be utilized. Theoretically one mole of epichlorohydrin will react
with each hydroxyl group forming a glycidyl ether in the presence
of the alkali. However, the proportions of the epihalohydrin to the
hydroxyl may vary from a large excess to less than stoichiometric.
In the latter case higher molecular weight products usually result
from the interaction of the excess polyhydric compound with the
polyglycidyl ethers. In any event the resulting product is not
wholly one type of polyglycidyl ether but usually consists of a
mixture of resins of varying molecular weights which have more than
one glycidyl ether group per molecular. For this reason most
commercially available resins are mixtures of different molecular
weight polyglycidyl ethers. It is meant to include such mixtures
within the term, polyglycidyl ethers herein.
Typical polyhydric alcohols include the aliphatic diols, triols,
etc. such as 1,4-butanediol, neopentyl glycol, and the like as well
as the glycols and polyglycols such as the polyethylene oxide and
polypropylene oxide types. A variety of such polyhydric alcohols
are known in addition to those cited and would be obvious to a
skilled worker.
Polyhydric phenols include the mononuclear phenols such as
resorcinol, catechol, hydroquinone, phloroglucinol and the like.
Also included are the polynuclear phenols and most preferred are
the glycidyl polyethers prepared from bisphenol A. Other
polynuclear phenols include p,p'-dihydroxy diphenyl oxide;
p,p'-dihydroxy di-phenyl sulfone; p,p'-dihydroxybenzophenone and
the like.
Preferred polyaziridinyl adducts include those prepared from
polyglycidyl ethers of dihydric phenols wherein species according
to the following formula may be present, usually as a mixture of
different molecular weights. ##STR3## wherein R is hydrogen or an
alkyl group of 1 to 8 carbons, n is an integer between 0 and about
200 but usually between 0 and 20 and most usually between about 0
and about 10, and X may be ##STR4## --C(CH.sub.3).sub.2 --, --S--,
--SS-- or --C(CH.sub.2 CH.sub.3).sub.2 --. Most preferred are the
adducts wherein X is --C(CH.sub.3).sub.2 -- (i.e. based on
bisphenol A), and because the polyaziridinyl adducts are usually
mixtures, the average value of n for the mixture may be a
fractional number.
Coreactants which may be combined with the polyaziridinyl adduct
include a dicarboxylic acid anhydride and a polyfunctional material
having more than one anhydride, .[.oxirane.].
.Iadd.glycidyl.Iaddend., thiol, sulfonic acid or carboxylic acid
group per molecule. Each of these groups are reactive with an
aziridinyl group.
A preferred coreactant is a polyfunctional material having more
than one .[.oxirane.]. .Iadd.glycidyl .Iaddend.group per molecule.
These materials are more commonly known as polyepoxides and include
all the polyepoxides having more than one glycidyl group per
molecule previously discussed. .[., but also includes polyepoxide
resins having a different kind of an oxirane group than a glycidyl
group. For example, certain polyepoxides are prepared by the well
known method of epoxidation of unsaturated groups, and the
like..].
A variety of curing agents such as amines, acids, anhydrides, etc.
are known in the prior art for use with the above polyepoxides.
However, these curing agents cause an exothermic curing reaction
and are generally useful only at elevated temperatures or at least
at about 50.degree. F. The ability of the compositions of this
invention to not only effect good cures in the commonly used
temperature ranges but to also effect full cures without an
appreciable exotherm at temperatures well below the freezing point
of water is completely unexpected and very desirable.
Other coreactants which cure at low temperatures with said
polyaziridinyl adduct include polythiols, polysulfonic acids,
polycarboxylic acids, and anhydrides. The polythiols that may be
used according to this invention are characterized by, but not
limited thereto, the following generalized structures: ##STR5##
Polysulfonic acids may be prepared by sulfonation of polymers to
introduce more than one sulfonic acid groups or by the preparation
of polymers containing sulfonic acid groups utilizing such monomers
as styrene sulfonic acid, 2-sulfoethyl methacrylate and the
like.
Both mono- and polyanhydrides may be used as a coreactant according
to this invention. A variety of monoanhydrides such as phthalic
anhydride, succinic anhydride, itaconic anhydride, maleic
anhydride, nadic methyl anhydride and the like may be used.
Polyanhydrides include pyromellitic dianhydride, cyclopentane
tetracarboxylic dianhydride, benzophenone tetracarboxylic
dianhydride and copolymers such as styrene-maleic anhydride,
ethylene-maleic anhydride, methyl vinyl ether-maleic anhydride and
the like.
Polyfunctional carboxylic acids useful as coreactants in this
invention are copolymers of vinyl acids, such as acrylic,
methacrylic, or itaconic acid, with other vinyl monomers such as
styrene, butyl acrylate, vinyl chloride, methyl methacrylate, and
the like. These copolymers are commonly prepared in solvents of the
kind used in preparing the polyaziridinyl adducts of this invention
and are well known to those skilled in the art. Also useful are
polyfunctional acids such as phthalic acid and trimellitic
acid.
In general the polyazirdinyl adduct and the coreactants are
combined within proportions on an equivalent basis of about 0.5/1.0
to 2.0/1.0 respectively. It is generally preferred to combine the
components so as to have one aziridinyl group present in the
solution for each glycidyl, thiol, sulfonic acid, carboxylic acid,
or anhydride group.
The following non-limiting examples further illustrate the present
invention. All parts and percentages are by weight unless otherwise
specified. The aziridinyl equivalent weight may be determined by
titration of a weighed amount of the polyaziridinyl adduct in
solution with either p-toluene sulfonic acid or tetrabutyl ammonium
iodide.
EXAMPLE 1
A polyaziridinyl adduct was prepared by mixing together in a 5
liter flask 1598 gms. of toluene, 258 gms. of ethylenimine and 1340
gms. of 75% solution in toluene of a polyglycidyl ether of
bisphenol having an epoxide equivalent weight of 670 (solution
basis). The mixture was heated at 70.degree. C. for 18 hours. The
clear solution was distilled until 1128 gms. of distillate was
removed and then 110 gms. of ethylene glycol monomethyl ether and
110 gms. of propylene glycol monomethyl ether was added and mixed
with the adduct solution.
The final solution contained 49.5% solids, had a viscosity of 350
cps., an aziridinyl equivalent weight of 1030 (solution basis) and
had a pale yellow color.
A first mixture was prepared from 20 gms. of the above adduct
solution, 0.5 gm. of a silicone leveling agent (DC-840) as a 60%
solution in toluene and 7 gms. of an 80/20 mixture of methyl ethyl
ketone and ethylene glycol monoethyl ether to give a solution
containing 37.5% solids.
A second mixture was prepared by mixing 12.4 gms. of a 75% solution
in toluene of a polyglycidyl ether of bisphenol A having an epoxide
equivalent weight of 700 (solution basis) with 15.4 gm. of the
above 80/20 solvent mixture having dissolved therein 0.19 gm. of
p-toluene sulfonic acid monohydrate to give a solution containing
33.9% solids.
The two mixtures were stored separately in capped bottles over
night at -10.+-.2.degree. F. The next morning the two mixtures were
combined with stirring and applied to cold-rolled steel panels
(chilled at -10.degree. F.) using a No. 50 Meyer rod yielding a
coating of 0.7-0.8 mil (dry). The panels were maintained at
-10.degree. F. for 9 days and periodic checks were made for extent
of cure.
After six hours the films weer dry to touch and tack free in 7
hours. Degree of cure was checked by the common pencil hardness
test and a methyl ethyl ketone (MEK) swab test. In the latter if no
cure has taken place and only evaporation of solvent the film would
be quickly marred or disturbed by merely rubbing a cotton cloth or
swab saturated with MEK across the film. No effect would be found
with a cured film. The results are summarized below.
______________________________________ Days at -10.degree. F. Film
property 1 3 7 9 ______________________________________ MEK
resistance Complete Marring No effect No effect. failure. Pencil
hardness 5B 2B B B. ______________________________________
Cure at this temperature has taken place as evidenced by the MEK
resistance and increase in pencil hardness. Films of the above
mixture were also cured at 75.degree. F. to hard, solvent resistant
films.
EXAMPLE 2
A series of comparative films were made in the manner of Example 1
to compare low temperature curability of conventional polyepoxide
curing agents to the polyaziridinyl adduct of this invention.
Two different polyaziridinyl adducts were prepared from
ethylenimine similar to Example 1 using a bisphenol-based liquid
polyepoxide having an epoxide equivalent weight (EEW) of 190
(D.E.R. 331) in one case (A-1), and in another case, (A-2) a solid
bisphenol A-based polyepoxide having an EEW of 595 (D.E.R. 671)
with the following properties as prepared, respectively.
______________________________________ A-1 A-2
______________________________________ Percent resin solids 50 50
Appearance .sup.(1) .sup.(2) Viscosity, cps 350 Aziridinyl equiv.
wt. 504 1,030 Percent epoxide Nil Nil Percent ethylenimine Nil Nil
______________________________________ .sup.(1) Clear, light
yellow. .sup.(2) Clear, yellow.
Confirmation that the desired adduct was obtained in similar cases
was obtained by infrared analysis.
A series of tests similar to Example 1 were made to evaluate the
above curing agents and a number of commonly used polyepoxide
hardeners for low temperature curability. Casting mixtures were
prepared with D.E.R. 331 and two additional tests with A-1 and A-2
combined with D.E.R. 671. The mixtures were prepared to contain
approximately equivalent amounts of aziridinyl groups and
.[.epoxide (oxirane).]. .Iadd.glycidyl .Iaddend.groups or with
commerical hardeners, the proportions were those recommended by the
manufacturer. The cast films were cured at 30.degree. F.
The following hardeners did not cure cast films of D.E.R. 331 at
30.degree. F. as measured by the methyl ethyl ketone rub test and
pencil hardness test:
(a) an amine hardener prepared by reacting equal amounts of D.E.R.
331 and diethylene triamine.
(b) a polyamide (D.E.R. 12) which essentially is a linear
condensation product of a long-chain dibasic acid and diethylene
triamine.
(c) bis(2-aziridinyl ethyl) benzene (ref. U.S. 3,346,533).
(d) hardener (a) plus phenethyl aziridine (ref. U.S.
3,171,826).
The following aziridinyl compounds did not cure within seven days
at 75.degree. F.
(a) 2-hydroxyethyl aziridine (ref. U.S. 3,303,144).
(b) 2-hydroxypropyl aziridine (ref. U.S. 3,303,144).
(c) 2-phenethyl aziridine.
Certain curing agents proposed as low temperature curing agents
were also included in these tests.
Epicure 862, a commercially available hardener containing thiol
groups, is characterized by the following structure: ##STR6## where
R is a bivalent aliphatic group.
Epicure 861 is a similar product to Epicure 862 but additionally
contains a tertiary amine as an accelerator. Accelerated MDA is
methylene dianiline containing salicylic acid. The results with
these hardeners and the adducts of this invention are shown in
Table I. The ability of said polyaziridinyl adducts to cure the
polyepoxides at 30.degree. F. is evident and the inferior results
with the commercial hardeners is to be noted.
TABLE I
__________________________________________________________________________
Formulation using the Formulation using polyaziridinyl adducts the
prior art of this invention. hardeners 1 2 3 4 5 6 7
__________________________________________________________________________
Components, parts by wt. in grams: D.E.R 331 7.2 3.4 20 20 20
D.E.R. 671.sup.1 26.6 12.4 Adduct A-1 20.0 20.0 Adduct A-2 20.0
20.0 Epicure 861 20 Epicure 862.sup.2 20 Accelerated MDA 11.7
p-Toluene sulfonic acid 0.17 0.13 0.27 0.19 Diluent: MEK 8.9 11.9
16.0 18.0 21.4 21.4 17.0 EE 2.2 3.0 4.0 4.4 5.3 5.3 4.1 DC 840 0.5
0.5 0.5 0.5 Percent solids in mixture 45 35 45 35 60 60 60
Tack-free time, hrs 3-5 3-5 3-5 3-5 11/2 11/2 22 Pot life at
30.degree. F. hrs 7-19 20 22 30 .sup.3 3 .sup.3 3 .sup.4 1 MEK rub:
4-5 hrs CF SM CF CF CF CF CF 20-24 hrs NE NE SM SM CF CF CF 45-50
hrs NE NE NE NE CF CF CF 140-170 hrs NE NE NE NE SM CF CF Pencil
hardness: 4-5 hrs <6B 5B <6B 5B B 5B <6B 20-24 hrs B HB 2B
B B 5B <6B 45-50 hrs HB F HB B HB 5B 2B 140-170 hrs HB F HB HB
HB 4B HB
__________________________________________________________________________
.sup.1 Grams of a 75% solids solution in xylene/methyl isobutyl
ketone. .sup.2 Containing 1% tetramethyl guanadine. .sup.3 Days.
.sup.4 Week. Note.--MEK=methyl ethyl ketone; EE=ethylene glycol
monoethyl ether; CF=complete failure; SM=slight marring; NE=no
effect.
EXAMPLE 3
Tests similar to those of the preceding examples were made in which
no p-toluene sulfonic acid catalyst was added. Adduct B-1 were
prepared from ethylenimine and D.E.R. 331 as in Example 1 and had
an aziridinyl equivalent weight of 440, solution basis, and
contained 55% solids. Adduct B-2 was prepared from ethylenimine and
D.E.R. 671 and had an aziridinyl equivalent weight of 1140,
solution basis and contained 50% solids. In making the mixtures
D.E.R. 331 and D.E.R. 671 (75% solids solution on 65/35
xylene/methyl isobutyl ketone) were combined with the adduct
employing a diluent (80/20 mixture of MEK/propylene glycol
monomethyl ether). The recipes are shown in Table II. The mixtures
were cast to give a 1 mil dry film on pre-chilled steel panels and
then cured at 30.degree. F.
TABLE II ______________________________________ 1 2 3 4
______________________________________ Components, parts by weight,
grams: D.E.R. 331 19.8 11.2 D.E.R. 671 (75% solids in xylene/ MIBK)
41.0 28.8 Adduct B-1 (55% solids) 45.8 25.8 Adduct B-2 (50% solids)
67.6 46.8 Diluent 34.4 33.2 21.2 24.4 Percent solids of mixture 45
45 45 45 Film properties: Tack-free time, hours 2-3 2-3 2-3 2-3
Pot-life (at 30.degree. F.), hrs 48 120 48 72 MEK rub: 4-5 hours CF
CF CF CF 20-24 hours NE CF SM M 45-50 hours NE NE NE NE 140-170
hours NE NE NE NE Pencil hardness: 4-5 hours 6B <6B 6B 6B 20-24
hours B B 2B 2B 140-170 hours HB F F HB
______________________________________ Note.--M=marring.
From the above it is clear that acidic catalysts, while they
accelerate the film cures at low temperatures, are ##STR7## now
essential to the development of useful film properties within
practical time limits.
EXAMPLE 4
Similar results were also found when the polyepoxide resins in the
casting mixtures above (D.E.R. 331 or D.E.R. 671) were replaced by
an equivalent amount of each of the resis as shown in the following
description:
Polyepoxide Resin I.--N,N-bis(2,3-epoxy propyl)-O-2,3-epoxy propyl
p-aminophenol (ref. U.S. 3,235,421);
Polyepoxide Resin II.--an epoxy novolac resin having an epoxide
equivalent weight of 175-182 (D.E.N. 438).
Two polyaziridinyl adducts were made in the manner described in
Example 1 from D.E.R. 331 and ethylenimine. They are designated C-1
and C-3. In the same way adducts were made from D.E.R. 671 and
ethylenimine, and are designated C-2 and C-4. These resin solutions
had the following properties:
______________________________________ Percent Equivalent solids
wt. ______________________________________ Polyaziridinyl adduct:
C-1 55 440 C-2 45 1,285 C-3 50 505 C-4 50 1,030
______________________________________
The Epoxy Resins I and II and polyaziridinyl adducts C-1, C-2, C-3,
and C-4 were formulated into coatings on chilled steel, and allowed
to cure at 30.degree. F. The formulations and film properties are
shown in Table III.
TABLE III ______________________________________ Formulation 1 2 3
4 ______________________________________ Component, oarts by wt.,
gms.: Polyaziridinyl adduct: C-1 50.9 C-2 75.8 C-3 20.0 C-4 20.0
Polyepoxide resin I 12.0 5.9 II 6.8 3.1 p-Toluenesulfonic acid 0.16
0.13 Diluent, EE 37.1 8.3 .sup.1 8.5 .sup.1 11.5 2.1 2.9
DC-340.sup.2 0.5 0.5 Percent solids 40 40 45 35 Tack-free time,
hours 3 3 3-5 3-5 Pot life, hrs .sup.2 3.6 .sup.3 7 7-19 22 MEK rub
after: 4-5 hours CF CF CF M 20-24 hours 3M CF NE NE 45-50 hours NE
CF NE NE 140-170 hours NE NE NE NE Pencil hardness after: 4-5 hours
<6B 5B 20-24 hours HB 2B 2B B 45-50 hours F F B F 140-170 hours
2H 2H B F ______________________________________ .sup.2 Silicone
fluid. .sup.3 Days.
EXAMPLE 5
The compositions of this invention also cure well at elevated
temperatures.
A polyaziridinyl adduct similar to Example 1 was prepared initially
as a 63% solids solution and was then diluted to 50% solids by the
addition of methyl ethyl ketone (MEK). The resulting solution had
an aziridinyl equivalent weight of 525 and was designated D-1.
For preparing the casting mixtures a polyepoxide resin solution was
prepared as a 75% solution of an epoxy novolac resin in
MEK/ethylene glycol monoethyl ether (76/24). The solution had an
epoxide equivalent weight of about 240. Films were cast as before
and cured for 20 minutes at 250.degree. F. The results are shown in
Table IV.
TABLE IV
__________________________________________________________________________
1 2 3
__________________________________________________________________________
Component, parts by weight, grams: Polyaziridinyl adduct D-1 100
110 110. Polyepoxide solution 62 50 40. Ratio of aziridine/epoxide
74/100 100/100 125/100. Film properties: Thickness (mils) 1.8-2.0
1.8-2.0 1.8-2.0 Hardness (Knoop) 23.0 23.9 25.0. Adhesion Good Fair
Fair. Resistance to: 10% acetic acid 144 hrs 168 hrs., NE 168 hrs.,
NE. Glacial acetic acid 8-24 hrs 36-48 hrs 72 hrs. 10% nitric acid
168 hrs., NE 168 hrs., NE 168 hrs., NE. 50% nitric acid 8-24 hrs
8-24 hrs 8-24 hrs. MEK 144 hrs 168 hrs., NE 168 hrs., NE. Water 1
week, NE 1 week, NE 1 week, NE.
__________________________________________________________________________
EXAMPLE 6
Casting solutions were prepared from polyaziridinyl adducts as
described below and nadic methyl anhydride (NMA) and films prepared
therefrom were cured at 30.degree. F.
A polyaziridinyl adduct solution similar to Example 1 was prepared
from D.E.R. 331 and ethylenimine, and had the following properties:
55% resin solids, viscosity 230 centipoise, equivalent weight, 440.
It was designated E-1.
A second polyaziridinyl adduct solution similar to B-2 of Example 2
was prepared from D.E.R. 661 and ethylenimine, and had the
following properties: 50% resin solids and equivalent weight 1140.
It was designated E-2.
The polyaziridinyl adduct solutions E-1 and E-2 were chilled to
30.degree. F. and mixed with nadic-methyl anhydride, also at
30.degree. F. The solutions were cast as 1. mil dry films on steel
chilled to 30.degree. F. and allowed to cure. The formuations and
film properties are shown in Table V.
TABLE V ______________________________________ 1 2
______________________________________ Components, parts by wt.
grams: NMA 16.1 6.9 E-1 79.8 E-2 86.2 Propylene glycol monomethyl
ether 4.1 6.9 Pot life, hours 1/4 1/4 Tack-free, time, min 30 30
Pencil hardness: 11/2 hrs 5B <6B 12 hrs HB 2B 168 hrs 2H HB MEK
rub: 11/3 hrs .sup.(1) .sup.(1) 168 hrs .sup.(1) .sup.(1)
______________________________________ .sup.1 No effect.
Similar results to the above are obtained when the nadic methyl
anhydride is replaced with an equivalent amount (anhydride basis)
of a copolymer of styrenemaleic anhydride.
EXAMPLE 7
Polyaziridinyl adducts made from bisphenol A diglycidyl ether
resins were prepared as previously described in Example 1, one
having an aziridinyl equivalent weight of 440 (on a solution basis,
55% solids) and the other 1285, at 45% solids. The first resin
solution is designated F-1 and the second, F-2.
A carboxylated acrylic solution polymer was prepared by heating the
following mixture at 80.degree. C. for 18 hours, with stirring, in
a glass 2-liter reactor:
______________________________________ Gms.
______________________________________ Propylene glycol monomethyl
ether 500 Butyl acrylate 250 Methyl methacrylate 200 Methacrylic
acid 50 Azobis (isobutyronitrile) 5
______________________________________
The polymer solution was clear and colorless, and had a carboxyl
content (CO.sub.2 H) of 2.61% and a resin solids content of 49%.
The solution was designated as C. The three solutions were used in
formulating coatings systems as follows:
______________________________________ 1 2
______________________________________ Polyaziridinyl adduct: F-1,
gms 11.5 F-2, gms 26.9 Carboxyl acrylic polymer solution, gms 47.4
35.8 Ethylene glycol monoethyl ether, gms 41.1 37.3 Percent resin
solids of mixture 30.0 30.0
______________________________________
The above blends were made by diluting the polyaziridinyl adduct
solution with half of the glycol ether, and the carboxylated
polymer solution with the other half, chilling the two solutions to
30.degree. F. and mixing the two just prior to use.
Films of the solution mixture were cast with a No. 38 Meyer rod on
standard Q panels which had been prechilled to 30.degree. F. The
films were allowed to cure at 30.degree. F. and tested as shown
below after various periods of time.
______________________________________ 1 2
______________________________________ Gel time of mixture, hours
41/2 7 Tack-free time, hours 11/2 11/2 MEK rub after: 4 hours CF CF
24 hours CF CF 48 hours NE SM 168 hours SM SM Pencil hardness
after: 24 hours HB 2B 48 hours H-- 2B 168 hours 3H 2H
______________________________________ Note.--CF=complete failure;
SM=slight marring; NE=no effect.
From the above it can be seen that these compositions are capable
of curing in thin films at low temperatures to give protective
coatings which are resistant to physical abrasion and attack by
solvents.
The compositions of this invention fully cure to a hard solvent
resistant film by merely standing at temperatures ranging from well
below the freezing point of water and higher. As indicated,
elevated temperatures may also be employed to cure same. The cure
may be accelerated by including a catalytic amount of an acid
catalyst in said compositions but the catalyst is not essential.
Typical catalysts include p-toluene sulfonic acid, phosphoric acid,
various phosphoric acid esters, such as di-2-ethylhexyl acid
phosphate, and the like. Proportions of about 1% and lower up to
about 5% are sufficient to accelerate the cure.
It will be understood that the present invention is not limited to
the specific details described above but may embody various
modifications insofar as they are defined in the following
claims.
* * * * *