U.S. patent application number 13/375533 was filed with the patent office on 2012-03-29 for use of molecules having associative groups as hardeners for thermosetting resins.
This patent application is currently assigned to Arkema France. Invention is credited to Manuel Hidalgo, Bruno Van Hemelryck.
Application Number | 20120074353 13/375533 |
Document ID | / |
Family ID | 41600682 |
Filed Date | 2012-03-29 |
United States Patent
Application |
20120074353 |
Kind Code |
A1 |
Van Hemelryck; Bruno ; et
al. |
March 29, 2012 |
USE OF MOLECULES HAVING ASSOCIATIVE GROUPS AS HARDENERS FOR
THERMOSETTING RESINS
Abstract
The present invention pertains to the field of thermosetting or
thermoset polymers mainly used as materials, coatings, or
adhesives. The invention more specifically relates to the use of
specific molecules having associative groups including a nitrogen
heterocycle as a hardener or co-hardener of thermosetting
polymers.
Inventors: |
Van Hemelryck; Bruno;
(Chaponost, FR) ; Hidalgo; Manuel; (Brignais,
FR) |
Assignee: |
Arkema France
Colombes
FR
|
Family ID: |
41600682 |
Appl. No.: |
13/375533 |
Filed: |
June 4, 2010 |
PCT Filed: |
June 4, 2010 |
PCT NO: |
PCT/FR2010/051095 |
371 Date: |
December 14, 2011 |
Current U.S.
Class: |
252/182.17 ;
252/182.13; 252/182.26; 252/182.28; 525/420; 525/523;
548/324.5 |
Current CPC
Class: |
C08K 5/3445 20130101;
C08G 59/3263 20130101; C08G 59/5073 20130101; C08K 5/378 20130101;
C08G 65/33396 20130101 |
Class at
Publication: |
252/182.17 ;
548/324.5; 525/523; 525/420; 252/182.26; 252/182.28;
252/182.13 |
International
Class: |
C08K 5/3445 20060101
C08K005/3445; C09K 3/00 20060101 C09K003/00; C08L 77/00 20060101
C08L077/00; C07D 233/96 20060101 C07D233/96; C08L 63/00 20060101
C08L063/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2009 |
FR |
0953680 |
Claims
1. A curing agent for a thermosetting resin, comprising a molecule
carrying an associative group of formula (I): ##STR00003## in
which: R denotes a unit comprising at least one reactive functional
group, selected from alcohol, thiol or amine functional group, R'
denotes a hydrogen atom, A denotes an oxygen or sulfur atom.
2. The curing agent as claimed in claim 1, characterized in that R
is chosen from H.sub.2N--(CH.sub.2).sub.n--, HS--(CH.sub.2).sub.n--
or HO--(CH.sub.2).sub.n--, where n represents an integer between 1
and 18.
3. The curing agent as claimed in claim 1, characterized in that
said molecule carrying an associative group is chosen from:
1-(2-aminoethyl)imidazoli-done, 1-(2-hydroxyethyl)imidazolidone,
1-(2-[(2-aminoethyl)amino]ethyl)imidazolidone,
1-(2-[(2-{2-aminoethyl)amino}ethyl)amino]ethyl)imidazolidone or
N-(6-aminohexyl)-N'-(6-methyl-4-oxo-1,4-dihydropy-rimidin-2-yl)urea.
4. The curing agent as claimed in claim 1, in combination with a
cocuring agent, for improving the adhesion of said resin to a
support.
5. The curing agent as claimed in claim 1 in combination with a
cocuring compound chosen from alkyl- or arylamines and in
particular ethylenediamine, diethylenetriamine,
triethylenetetramine and tetraethylenepentamine, cyclic diamines,
in particular 1-2-diaminocyclohexane, isophoronediamine or
N,N'-diisopropylisophoronediamine, aromatic primary diamines, in
particular 4,4'-methylenedianiline,
4,4'-methylenebis(ortho-chloroaniline) or xylenediamine isomers,
such as diethyltoluenediamine, hydroxyethyldiethylenetriamine,
polyetheramines, BADGE-aliphatic amine adducts with an excess of
amine functional groups relative to the glycidyls, polyamidoamines,
polyamides, amidoamines, polymercaptans, the Mannich bases obtained
by reaction between (poly)amine, formaldehyde and (alkyl)phenols,
ketimines, dicyanodiamide, polyol epoxy resins and
polyurethane-curing polyols.
6. The curing agent as claimed in claim 1, characterized in that
the thermosetting resin is chosen from epoxy resins, polyurethane
resins, polyester resins and unsaturated polyester resins.
7. The curing agent as claimed in claim 1, in which at least two
thermosetting resins are employed.
8. The curing agent as claimed in claim 7, characterized in that
the two resins are different.
9. The curing agent as claimed in claim 1, characterized in that
the molecules carrying associative groups are used in combination
with a cocuring agent at a content of 0.1 to 50% by weight, with
respect to the total weight of the combination.
10. The curing agent as claimed in claim 1, characterized in that n
is equal to 1 or 2, and in that the thermosetting resin is present
in water or in an aqueous emulsion.
Description
[0001] The present invention relates to the field of thermosetting
polymers or thermosets used mainly as materials, coatings or
adhesives.
[0002] The invention relates more particularly to the use of
specific molecules as agents for modifying curing systems for
thermosetting polymers.
[0003] In contrast to thermoplastic polymers, which can be
transformed and re-transformed using heat which, with or without a
contribution of shearing mechanical energy, softens them and allows
them to flow, thermosetting polymers constitute chemically
crosslinked polymer networks, that is to say crosslinked by
irreversible crosslinking bonds of covalent type, which, once
obtained, can no longer be transformed by the action of heat. A
thermosetting resin, once the polymer network has been formed,
becomes a thermoset polymer network which will not flow under the
effect of heat, even with a contribution of shearing mechanical
energy. It is habitually said that a thermoset polymer, subjected
to the effect of a constant increase in temperature, will end up by
decomposing before being able to flow, as a result of the
robustness of the crosslinking network formed by covalent bonds.
There exists numerous systems which can result in the production of
thermoset crosslinked networks involving a great variety of
possible chemistries, such as, for example epoxy, polyurethane,
phenol/formaldehyde, melamine/formaldehyde, silicone,
urea/formaldehyde, polyester or unsaturated polyester networks. The
chapter entitled "Polymer Networks" by Karel Dusek and Miroslava
Duskova-Smrckova, in volume 3 of the series Macromolecular
Engineering [Wiley-VCH, 2007, eds. K. Matyjaszewski, Y. Gnanou and
L. Leibler], cites the main crosslinkable systems which make it
possible to obtain crosslinked polymer networks.
[0004] It is customary for a person skilled in the art to consider
that a thermoset polymer network is obtained by the mixing and
consequent reaction of at least two components, with at least one
of the two having a functionality greater than 2 with regard to the
reaction involved. It is also customary for a person skilled in the
art, in particular in the case of systems of epoxy or polyurethane
type, to call the component carrying epoxy or isocyanate functional
groups "the resin" and to call the component carrying amine or
alcohol functional groups "the curing agent". Another type of
language which may be encountered in this field is that which
assigns the name "resin" also to the polymer network being formed
or to the final polymer network. Thus, it is not uncommon to hear
talk of, for example, epoxy, polyurethane or polyester resins. As
regards epoxy systems in particular, it is therefore necessary to
take into account the context in order to determine whether the
name epoxy resin applies to the compound carrying the starting
oxirane reactive functional groups (hereinafter denoted base epoxy
resin) or whether it concerns the final network, after reaction
with a curing agent.
[0005] The curing agent, according to this name, is thus a
compound, often a polyfunctional compound, carrying reactive amine
or alcohol units. It is possible to include, as a mixture with this
curing agent, inter alia, compounds which are inert with regard to
the reaction (such as solvents) or, on the contrary, reactive
solvents or diluents which make it possible to control the reaction
and to adjust certain mechanical properties of the final product,
and also catalysts which make it possible to accelerate the
crosslinking of the reactive components.
[0006] A subject matter of the invention is thus the use of
molecules of a specific type, such as amines or alcohols carrying
associated units, as partial or complete replacement for normal
amine or alcohol curing agents, with the aim of forming materials,
coatings or adhesives having improved properties, such as, for
example a better chemical resistance, a better adhesion to
supports, a better flexibility, an optimum open time or an optimum
setting time.
[0007] The inventors have shown (examples 1 to 4) that these
specific molecules make possible, [0008] excellent catalysis of the
polymerization reaction, so that the use of a setting accelerator
is no longer necessary, [0009] improved flexibility of the final
resin, [0010] strengthening of the adhesiveness of the final epoxy
resin.
[0011] A subject matter of the invention is thus the use, as curing
agent for a thermosetting resin, of a molecule carrying an
associative group and, preferably, of a molecule carrying an
associative group of formula (I):
##STR00001##
in which: R denotes a unit comprising at least one reactive
functional group, preferably an alcohol, thiol or amine functional
group, R' denotes a hydrogen atom, A denotes an oxygen or sulfur
atom, preferably an oxygen atom.
[0012] Such a use exhibits considerable advantages in comparison
with normal curing agents since it makes it possible to partially
or completely dispense with the use of a setting accelerator and/or
of a flexibilizing agent and/or of an adhesion promoter for the
final resin.
[0013] Examples of the use of the various agents for modifying a
thermoset resin are described in detail, for example in the work by
Petrie Edward M., Epoxy Adhesives Formulations, Chemical
Engineering.
[0014] Thus, it is customary for a person skilled in the art of
epoxy resins to resort to a formulation which may require the
incorporation simultaneously of a catalyst, of a flexibilizing
agent and of an adhesion agent in the form of separate
products.
[0015] A catalyst for epoxy resins is often a tertiary amine
incorporated in the curing agent. The majority of the catalysts,
however, are not said to promote flexibility in the final
resin.
[0016] A flexibilizing agent can either be introduced with the base
epoxy resin carrying oxirane functional groups or in the curing
agent. It is a resin which is more flexible than the base epoxy
resin or a crosslinking agent having a molecular structure which is
more mobile than that of the curing agent and, in this case, it is
then a cocuring agent. However, in both cases, the modifying agent
has relatively high molecular weights which have the effect of
increasing the distance between the crosslinking nodes by the
incorporation thereof in the final polymer network, with a
significant decline in the mechanical properties of the final
resin. An alternative form of this method of modifying one of the
main components of an epoxy resin which is targeted at giving
flexibility to the finished resin is prior hybridization. It
concerns modifying the stage of producing the base epoxy resin
which makes it possible to produce modified base epoxy resins, such
as epoxy/polyamide, epoxy/vinyl or epoxy/polysulfide resins. Some
of these hybrid modifying agents improve the adhesion (case of the
epoxy resins obtained between a base epoxy resin, such as a liquid
resin of bisphenol A diglycidyl ether or "BADGE" type, and a
polyamide), but at the expense of the thermomechanical properties.
According to this principle of prior hybridization of the reactants
of a two-component thermoset, other oligomeric or polymeric
flexibilizing agents can be used, in a base resin or else in the
curing agent, with, for example, alkyl diisocyanate prepolymers
reacted with the alcohol functional groups of a base epoxy resin,
or else with a silicone polymer comprising amine ends which is then
employed as coreactant of the polyamine curing agent. Other
polymeric coreactants or other additives have been developed in
order to make possible greater flexibility of the final resin, such
as liquid polybutadiene derivatives making possible the
introduction of an elastic phase into the thermoset. Finally,
polysulfides can be used either as flexibilizing agents or as
curing agents in a standard ratio 1:1 with the base epoxy resin
but, in this case, they absolutely have to be catalyzed by a
tertiary amine, such as DMP-30, for example. Furthermore, their
odor may require the addition of specific additives.
[0017] In addition to their high cost, all these polymers or
prepolymers, modified for the purpose of being able to make
possible greater flexibility of the final resin, have in common a
need to profoundly modify the processing of the thermoset with
respect to its original formulation when a need for flexibility is
required in application. Thus, it is sometimes necessary to
introduce a new type of additive into the epoxy formulation, such
as a compatibilizing agent or coupling agent which makes it
possible to limit the problems of phase separation and
heterogeneity inside the flexibilized resin, or else it is
necessary to introduce an additive which reduces the additional
viscosity caused by resorting to a thermoplastic polymer component
(case of epoxy-nylon resins, for example).
[0018] Another category of flexibility-promoting agents is that of
the reactive or nonreactive diluents. Nonreactive diluents are
formally plasticizers and not flexibilizing agents, they bring
about a deterioration in the mechanical properties of epoxy resins
and sometimes bring about a phenomenon of exudation, which is
particularly undesirable for adhesives.
[0019] The reactive diluents are non-migrating as they participate
in the formation of the polymer network. They are often long-chain
molecules comprising a monoglycidyl functionality but reactive
diluents comprising a diglycidyl functionality can contribute to
the density of the final thermoset network without, however,
improving the adhesion. They are conventionally combined with the
base epoxy component of the resin due to their compatibility.
[0020] Among the agents which promote the adhesion of thermosets,
organosilanes constitute a widely used family which are good
promoters of adhesion between the crosslinked epoxy resin and an
inorganic support carrying surface hydroxyl functional groups, for
example, an inorganic filler (such as a clay or alumina), a
composite reinforcing glass fiber or a ceramic. Organosilanes are
also used to increase the adhesion of the epoxy resin to a metal
support. They can be employed as primer coating directly on the
support or else can be incorporated in the formulating of the
thermoset. However, as the use in adhesion on metals is optimum
when the organosilane is applied as primer layer on the metal
support, this implies, in this case, a stage of pretreatment before
the deposition of the thermoset. However, organosilanes exhibit a
sensitivity to moisture which can make their use problematic and
their effectiveness uncertain. Furthermore, the use thereof on a
polymer support requires the latter to have, at its surface, free
reactive groups capable of reacting with the silanes, typically OH
groups, with the result that applications involving organosilanes
relate in particular to the preparation of composites for which it
is desired to increase the mechanical strength properties and the
durability by a coupling between the thermoset organic binder and
the inorganic or metal reinforcement.
[0021] Another type of agent which promotes the adhesion of the
epoxy polymer organic matrix to an inorganic support is that of
organometallic complexes (titanate or zirconate for example).
However, these complexes are problematic to apply due to the high
risk of overdosage, their optimum effectiveness being obtained for
the amount which provides for the formation of a single layer at
the surface of the support. The use thereof is thus instead
reserved for the surface treatment of inorganic fillers, in order
to facilitate the dispersion thereof in the organic matrix. The
role is then that of a coupling agent between inorganic filler and
resin, which does not contribute to improving the adhesion between
thermoset resin and an inorganic or metal support. Other
organometallic complexes based on chromium or on cobalt have been
studied but are of limited use due to their toxicity.
[0022] According to the invention, the use, as curing agent for a
thermosetting resin, of a molecule carrying an associative group as
defined above thus makes it possible to accelerate the setting of a
two-component thermoset resin and to contribute flexibility
without, however, seriously damaging the mechanical properties of
the final resin. The use according to the invention also makes it
possible to reinforce the adhesion of the resin on not only
inorganic or metal supports but also polymers not carrying hydroxyl
functional groups, such as PMMA, for example. The latter situation
of adhesion between thermoset resin and polymer is illustrated by
the possibility of obtaining, according to the invention, adhesion
between polymers of different natures, as in the case, for example,
of the deposition of a layer of thermoset of polyurethane type on
an epoxy thermoset underlayer.
[0023] In a preferred embodiment of the invention, the molecule
carrying an associative group comprising a nitrogenous heterocycle
is used as curing agent for at least two thermosetting resins which
are preferably different.
[0024] This embodiment is particularly advantageous since it makes
it possible to increase the adhesion between two resins while
dispensing with the use of an adhesive which exhibits the possible
disadvantage of evaporation of solvent.
[0025] This embodiment also makes it possible to dispense with the
use of a thermosetting resin partially modified by a reactant,
which resin is subsequently reacted with another resin. This is
because this second processing stage can be difficult if it
requires activation by heating, or else presents problems for the
environment if the reaction has to be carried out at ambient
temperature but while employing the chemistry of highly reactive
groups, such as isocyanates, which can be harmful to the health, on
the processing site.
[0026] As an example of the present invention and as regards more
particularly thermosetting resins comprising epoxy functional
groups, the endemic defects of these epoxy resins, which are the
excessive stiffness and their lack of adhesion, are for the first
time improved by the same modifying agent, in the form of a
molecule carrying an associative group. To date, modifying the
flexibility of the finished epoxy resin was obtained either by
modifying the base pre-resin or resin carrying epoxy functional
groups or by addition of reactive solvent, such as a fatty
monoepoxide. For its part, the adhesion of the finished epoxy resin
was improved by the addition of adhesion-promoting agents of
silylated type, for example, with the result that the two
properties, stiffness and adhesion, involve significant
modifications to the polymer network and complicated the processing
thereof in terms of formulating.
[0027] The term "curing agent" is understood to mean, within the
meaning of the present invention, a compound capable of bringing
about chemical crosslinking of a polymer network via irreversible
crosslinking bonds of covalent type which, once they have been
obtained, can no longer be transformed by the action of heat.
[0028] The associated units according to the invention are units
comprising nitrogenous heterocycles which are capable of creating,
between units of at least two different molecules, complementary
physical bonds of hydrogen bond type.
[0029] The term "associative groups" is understood to mean groups
capable of associating with one another via hydrogen, ionic and/or
hydrophobic bonds. They are, according to a preferred form of the
invention, groups capable of associating via hydrogen bonds,
comprising a nitrogenous heterocycle, preferably a dinitrogenous
heterocycle, generally having 5 or 6 ring members, and preferably
comprising a carbonyl group. Examples of associative groups which
can be used according to this preferred form of the invention are
imidazolidinyl, bis-ureyl, ureido-pyrimidyl groups. The
imidazolidinyl group is preferred.
[0030] In a preferred embodiment, these molecules carrying
associative groups are used in combination with normal curing
agents of amine or alcohol type, which makes it possible to adjust
the properties of the thermoset resins obtained, such as the
adhesion to supports and the flexibility.
[0031] Thus, in a preferred embodiment of the invention, the use of
a molecule carrying an associative group comprising a nitrogenous
heterocycle takes place in combination with a cocuring agent, that
is to say a normal curing agent, in order to increase the adhesion
of said resin to a support.
[0032] As is presented in example 4, the use of such a molecule
carrying an associative group in combination with a cocuring agent
makes it possible to increase the adhesion to the support of a
thermosetting resin in comparison with a resin which does not
comprise this type of molecule carrying an associative group.
Preferably, in the molecule carrying an associative group of
formula (I) R is chosen from H.sub.2N--(CH.sub.2).sub.n--,
HS--(CH.sub.2).sub.n-- or HO--(CH.sub.2).sub.n--, where n
represents an integer between 1 and 18.
[0033] In particular, the molecules carrying associative groups
comprising, in addition to a nitrogenous heterocycle, at least one
amine or alcohol functional group are particularly preferred.
Furthermore, when these molecules exhibit a water-soluble nature,
which is the case in particular when, in the above formulae, n is
equal to 1 or 2, in the H.sub.2N--(CH.sub.2).sub.n--,
HS--(CH.sub.2).sub.n-- or HO--(CH.sub.2).sub.n-- units, this makes
it possible to use them as curing agent for thermosetting resins in
water or in an aqueous emulsion. This embodiment is of great
industrial and commercial interest for the preparation, in
particular, of aqueous-based coatings and adhesives.
[0034] Another subject matter of the invention is thus the use of a
molecule of formula (I), characterized in that n is equal to 1 or
2, and in that the thermosetting resin is present in water or in an
aqueous emulsion.
[0035] Thus, said molecule carrying an associative group is
preferably chosen from: 1-(2-aminoethyl)imidazolidone, also known
as 1-(2-aminoethyl)imidazolidin-2-one (UDETA),
1-(2-hydroxyethyl)imidazolidone (HEIO),
1-(2-[(2-aminoethyl)amino]ethyl)imidazolidone (UTETA),
1-(2-[(2-{2-aminoethylamino}ethylamino]ethyl)imidazolidone (UTEPA)
or
N-(6-aminohexyl)-N'-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)urea
(UPy).
[0036] The compounds UDETA, UTETA and UTEPA can be obtained by
reaction of urea with a polyamine. For example, UDETA, UTETA and
UTEPA can be respectively prepared by reacting urea with
diethylenetriamine (DETA), triethylenetetramine (TETA) and
tetraethylenepentamine (TEPA). The compound HEIO can be obtained by
reaction of urea with the corresponding diaminoalcohol, namely
2-[(2-aminoethyl)amino]ethanol.
[0037] As indicated above, although the molecules carrying
associative groups can be used alone as curing agents for
thermosetting resin, these molecules are preferably used as a
mixture with other curing agents.
[0038] Thus, in the case where these molecules carrying associative
groups are used in combination with normal curing agents, they are
used at a content of 0.1 to 50% by weight, with respect to the
total weight of the combination.
[0039] Mention may be made, among the compounds which may be used
as normal curing agents or as cocuring agents according to the
invention, of: [0040] alkyl- or arylamines and in particular linear
ethylene polyamines, such as ethylenediamine, diethylenetriamine
(DETA), triethylenetetramine (TETA) and tetraethylenepentamine
(TEPA), cyclic diamines, in particular 1-2-diaminocyclohexane,
isophoronediamine or N,N'-diisopropylisophoronediamine, aromatic
primary diamines, such as 4,4'-methylenedianiline,
4,4'-methylenebis(ortho-chloroaniline) (or MBOCA), xylenediamine
isomers, such as diethyltoluenediamine (or DETDA), [0041] adducts
of ethylene oxide or propylene oxide with a polyamine, such as
DETA, for example, hydroxyethyldiethylpnetriamine, the
polyetheramines sold by Huntsman, under the trade name
Jeffamine.RTM. D-20.00, T-403, [0042] BADGE-aliphatic amine adducts
with an excess of amine functional groups relative to the
glycidyls, polyamidoamines, for example Versamid.RTM. 140 from
Cognis Corp. or Epikure.RTM. 3090 from Hexion, [0043] polyamides,
such as Epi-cure.RTM. 3090 and Epikure.RTM. 3100-ET-60 from Hexion,
[0044] the amidoamines obtained by condensation between a fatty
acid and a polyamine, such as Ancamide.RTM.-260A.RTM. and
Ancamide.RTM. 501 from Air Products, [0045] "flexibilized"
polyamides such as Epi-cure.RTM. 3164 from Hexion, [0046]
polymercaptans such as Capcure.RTM. 3830-81, from Cognis Corp.,
[0047] the Mannich bases obtained by reaction between (poly)amine,
formaldehyde and (alkyl)phenols, such as Epi-cure.RTM. 190, 195,
197 from Hexion, [0048] ketimines for example Epikure.RTM. 3502
from Hexion, [0049] the dicyanodiamide (DICY) Amicure.RTM. CG-1200
from Air Products, [0050] base polyol epoxy resins making crosslink
polyisocyanates, for example, Epikote.RTM. 1007 and 1009 from
Hexion, and [0051] polyurethane-curing polyols and polyol
esters.
[0052] In one embodiment of the invention, the molecule carrying an
associative group according to the invention can be used in
combination with a setting-accelerating agent and/or a
flexibilizing agent and/or an adhesion promoting agent or even in
combination with another molecule carrying an associative group. It
is thus possible to envisage, for example, the use of UDETA and
HEIO as curing agent or cocuring agent for a polyurethane/polyurea
resin.
[0053] The epoxy or polyurethane setting accelerator can be a
tertiary amine, such as the Jeffcat.RTM. catalyst for polyurethanes
from Huntsman, a phenol, such as Epikure.RTM. 3253 from Huntsman,
Lewis acids for catalyzing the reaction with the epoxy oxiranes or
2-ethyl-4-methylimidazole (EMI).
[0054] The flexibilizing agent can be a difunctional resin which is
more flexible than the base resin and can then be employed alone or
in co-crosslinking with the normal curing agent or else the
flexibilizing agent can be found among long-chain molecules
comprising a monoglycidyl functionality or sometimes a diglycidyl
functionality (in the case of epoxy resins).
[0055] The adhesion-promoting agent can be chosen from an
organosilane, an organometallic complex of titanate or zirconate
type and more generally from the abovementioned compounds.
[0056] Other additives can be used in combination with the
molecules according to the invention. They are, for example,
solvents or diluents, which are or are not reactive, catalysts for
the crosslinking reaction and monofunctional compounds other than
the molecules carrying associative groups according to the
invention. Mention may be made, among the non-reactive solvents of
Epodil.RTM. 748 from Air Products, mention may be made, among
non-reactive additives of dibutyl phthalate, coal pitch, or pine
oil, mention may be made, among reactive diluents for epoxy resins,
of glycidyl alkyl ethers, styrene oxide or butanediol diglycidyl
ether, mention may be made from among crosslinking catalysts, of
dicyanodiamide (DICY) (e.g. Amicure CG-1200 from Air Products),
tertiary amines, such as Epikure.RTM. 3253 from Huntsman, or all
the tertiary amines of the Jeffcat.RTM. range from Huntsman,
mention may be made among the fillers particularly valued in the
context of the invention, of talc, calcined silica, alumina,
silicates, clays, calcium carbonate, aluminum trioxide as flame
retardant, metal powders or carbon nanotubes as thermally or
electrically conducting agent.
[0057] The term "thermosetting resin" is understood to mean, within
the meaning of the present invention, a polymer which can be
crosslinked chemically by a curing agent to give a thermoset resin
which, once obtained, can no longer be transformed by the action of
heat. In other words, the thermosetting resin, once the polymer
network has been formed, becomes a thermoset polymer network which
will not flow under the effect of heat, even with a contribution of
shearing mechanical energy.
[0058] Preference is given, among thermosetting resins to those
comprising epoxy, isocyanate or acid units, such as those which
result in the production of thermoset networks of epoxy,
polyurethane or polyester type by reaction with the molecule
carrying associative groups carrying, in addition to a nitrogenous
heterocycle, an amine or alcohol functional group.
[0059] As regards the epoxy resins to be crosslinked using the
curing agent according to the invention, mention may be made, by
way of example, of epoxidized resins exhibiting a functionality,
defined as the number of epoxide functional groups per molecule, at
least equal to 2, such as bisphenol A diglycidyl ether, butadiene
diepoxide, 3,4-epoxycyclohexylmethyl
3,4-epoxycyclohexanecarboxylate, vinylcyclohexene dioxide,
4,4'-di(1,2-epoxyethyl)diphenyl ether,
4,4'-di(1,2-epoxyethyl)biphenyl,
2,2-bis(3,4-epoxycyclohexyl)propane, resorcinol diglycidyl ether,
phloroglucinol diglycidyl ether, bis(2,3-epoxycyclopentyl)ether,
2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,5-epoxy)cyclohexane-m-dioxane,
bis(3,4-epoxy-6-methylcyclohexyl) adipate,
N,N'-m-phenylenebis(4,5-epoxy-1,2-cyclohexane-dicarboxamide), a
diepoxy compound comprising a hydantoin ring and the like. Such
resins can be generally represented by the formula (II):
##STR00002##
in which R3 is a group of formula --CH.sub.2--O--R4-O--CH.sub.2--
in which R4 is a divalent group chosen from alkylene groups having
from 2 to 12 carbon atoms and also comprising at least one
substituted or unsubstituted aliphatic or aromatic ring. Use may
also be made of polyepoxidized resins comprising three or more
epoxide groups per molecule, such as, for example, p-aminophenol
triglycidyl ether, polyaryl glycidyl ethers,
1,3,5-tri(1,2-epoxy)benzene, 2,2',4,4'-tetraglycidoxybenzophenone,
tetraglycidoxytetraphenyle-thane, the polyglycidyl ether of the
phenol/formaldehyde resin of novolac type, glycerol triglycidyl
ether, trimethyloipropane triglycidyl ether and
tetraglycidyl-4,4'-diaminodiphenylmethane.
[0060] As regards the isocyanate resins to be crosslinked according
to the invention, mention may be made of hexamethylene diisocyanate
(HMDI), trimethylhexamethylene diisocyanates (TMDIs), such as
2,2,4-trimethylhexamethylene diisocyanate and
2,4,4-trimethylhexamethylene diisocyanate, undecane triisocyanates
(UNTIs), 2-methylpentane diisocyanate, isophorone diisocyanate,
norbornane diisocyanate (NBDI),
1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated XDI),
bis(4-isocyanatocyclohexyl)methane (H12MDI), 2,4- or 2,6-toluene
diisocyanate (TDI), diphenylmethane diisocyanates (MDIs),
1,5-naphthalene diisocyanate (NDI), p-phenylene diisocyanate
(PPDI), adducts comprising at least two isocyanate functional
groups and formed by condensation between compounds comprising at
least two isocyanate functional groups among those mentioned and
compounds carrying other functional groups which react with the
isocyanate functional groups, such as, for example, hydroxyl, thiol
or amine functional groups.
[0061] Mention may be made, among polyisocyanates, of modified
polyisocyanates, such as those comprising carbodiimide groups,
urethane groups, isocyanurate groups, urea groups or biurea
groups.
[0062] As regards the polyols which make it possible to crosslink
the polyisocyanates in order to obtain polyurethanes and in which
the molecule carrying an associative functional group according to
the invention, such as HEIO, can be directly incorporated, mention
may be made in particular of glycerol, ethylene glycol,
trimethylolpropane, pentaerythritol, polyether polyols, for example
those obtained by condensation of an alkylene oxide or a mixture of
alkylene oxides with glycerol, ethylene glycol, trimethylolpropane
or pentaerythritol, or polyester polyols, for example those
obtained from polycarboxylic acids, in particular oxalic acid,
malonic acid, succinic acid, adipic acid, maleic acid, fumaric
acid, isophthalic acid or terephthalic acid, with glycerol,
ethylene glycol, trimethylolpropane or pentaerythritol.
[0063] The polyether polyols obtained by addition of alkylene
oxides, in particular ethylene oxide and/or propylene oxide, to
aromatic amines, in particular the mixture of 2,4- and
2,6-toluenediamine, are also suitable.
[0064] Mention may be made, as other types of polyols, of in
particular polythioethers comprising hydroxyl ends, polyamides,
polyesteramides, polycarbonates, polyacetals, polyolefins and
polysiloxanes.
[0065] As regards the polyester and unsaturated polyester resins
obtained by reaction of a polyacid with a polyol, mention may be
made, for the acid component, of succinic acid, pentanedioic acid,
adipic acid, maleic acid, fumaric acid, itaconic acid and
anhydrides of these acids, heptanedioic acid, octanedioic acid,
azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid,
brassylic acid, tetradecanedioic acid, hexadecanedioic acid,
octadecanedioic acid, octadecenedioic acid, eicosanedioic acid,
docosanedioic acid and fatty acid dimers comprising 36 carbons.
[0066] The abovementioned fatty acid dimers are dimerized fatty
acids obtained by oligomerization or polymerization of unsaturated
monobasic fatty acids comprising a long hydrocarbon chain (such as
linoleic acid and oleic acid), as described in particular in the
document EP 0 471 566.
[0067] When the diacid is cycloaliphatic, it can comprise the
following carbon-based backbones: norbornylmethane,
cyclohexylmethane, dicyclohexylmethane, dicyclohexylpropane,
di(methylcyclohexyl) or di(methylcyclohexyl) propane.
[0068] When the diacid is aromatic, it is chosen from phthalic
acid, terephthalic acid, isophthalic acid, tetrahydrophthalic acid,
trimellitic acid and naphthalenic diacids and anhydrides of these
acids.
[0069] As regards the polyols, a compound having a molecule
comprising at least two hydroxyl groups which make it possible to
crosslink the polyacids in order to obtain polyesters, mention may
be made of ethylene glycol, propylene glycol, butylene glycol,
1,6-hexamethylene glycol, diethylene glycol, dipropylene glycol,
neopentyl glycol, triethylene glycol, glycerol, trimethylolethane,
trimethylolpropane, pentaerythritol, 1,3-trimethylene glycol,
1,4-tetramethylene glycol, 1,8-octamethylene glycol,
1,10-decamethylene glycol, 1,4-cyclohexanedimethanol, polyether
diols, such as PEG, PPG or PTMG, dicarboxylic acid units, such as
terephthalic acid, and glycol (ethanediol) or butanediol units.
[0070] It is also possible to obtain polyesteramides when a ternary
mixture of HEIO, UDETA and polyol is employed with one of the
diacids mentioned.
[0071] A better understanding of the invention will be obtained in
the light of the following nonlimiting examples.
EXAMPLES
Protocol for the Preparation of the Finished Epoxy Resins for Use
in Examples 1 to 4
[0072] The epoxy resin formulations according to the invention were
obtained in the following way: [0073] 100 g or 25 g of a base epoxy
resin are weighed out in a disposable plastic beaker, then [0074]
the necessary amount of curing agent, calculated according to the
stoichiometric principle known to a person skilled in the art, that
is to say one equivalent of NH per epoxide equivalent, is added.
The weight in grams of curing agent to be added is thus equal to
(HEW/EGC).times.weight of base resin involved, in grams, with HEW
(Hydrogen Equivalent Weight, expressed in g/eq) defined by the
molar mass of the curing agent in grams divided by the number of
active hydrogens, in this case, the number of NH, each NH being
capable of reacting with one epoxide group, and EGC (Epoxy Group
Content, expressed in millimol of epoxide functional groups per
kilogram of base epoxy resin), EGC and HEW being indicated by the
suppliers of base resin and curing agent respectively, [0075] the
molecule carrying the associative functional group according to the
invention is added, simultaneously with the curing agent or via the
curing agent after rapid homogenization using a stick, at a content
of a few % by weight of the final resin, and [0076] mixing is
carried out with a mechanical stirrer for 1 minute.
Example 1
Acceleration of the Setting of an Epoxy Resin According to the
Invention
[0076] [0077] preparation of the formulations according to the
common protocol described above, [0078] monitoring the temperature
as a function of the progression of the exothermic crosslinking
using an immersed thermocouple. The desired effect of the addition
of a catalyst is to shorten the setting time of a resin/curing
agent mixture regarded as too slow. The open time, defined by the
time during which it is possible to use and to apply the
formulation before the latter becomes too viscous, indeed even
solid, generally corresponds, for the liquid system studied, to a
doubling of the viscosity. This time is similar to the time
necessary for the development of the exothermicity maximum; it is
for this reason that the time for reaching the maximum temperature
during the crosslinking was compared, for an epoxy resin/curing
agent formulation and for the same formulation with the addition of
the molecule carrying an associative functional group according to
the invention. [0079] Formulation A: [0080] Base epoxy resin
Epikote.RTM. 828 EL from Hexion (resin based on bisphenol A): 100 g
[0081] Curing agent Cetepox.RTM. 1312 NFH from Aditya Birla
Chemicals (mixture of isophoronediamine, CAS No. 2855-13-2 and of
benzyl alcohol, this mixture being claimed to be more reactive with
regard to epoxy resins than pure isophoronediamine): 62.2 g [0082]
Formulation B: Formulation A with in addition 6.5 g of
1-(2-aminoethyl)imidazolidin-2-one CAS No. 6281-42-1, i.e. 4% by
weight of the final resin [0083] Formulation C: Formulation A with
in addition 11.3 g of 1-(2-aminoethyl)imidazolidin-2-one, i.e. 7%
by weight of the final resin [0084] Formulation D: [0085] Base
epoxy resin Epikote.RTM. 828 EL: 100 g [0086] Curing agent
Epikure.RTM. 943 from Hexion (pure isophoronediamine): 23.2 g
[0087] Formulation E: Formulation D with in addition 4.9 g of
1-(2-aminoethyl)imidazolidin-2-one, i.e. 4% by weight of the final
resin [0088] Formulation F: Formulation D with in addition 8.6 g of
1-(2-aminoethyl)imidazolidin-2-one, i.e. 6.5% by weight of the
final resin [0089] Formulation G: [0090] Base epoxy resin
Epikote.RTM. 240 from Hexion (mixture of epoxy resin based on
bisphenol A and of epoxy resin based on bisphenol F, in the
presence of a reactive diluent consisting of linear
C.sub.10-C.sub.14 molecules of monoglycidyl functionality): 100 g
[0091] Curing agent Cetepox.RTM. 1312 NFH: 62.2 g [0092]
Formulation H: Formulation G with in addition 6.5 g of
1-(2-aminoethyl)imidazolidin-2-one, i.e. 4% by weight of the final
resin.
[0093] The results of the maximum exothermicity times (in minutes)
are collated in the following table 1:
TABLE-US-00001 TABLE 1 Formulation A B C D E F G H Maximum
106.degree. C. 106.degree. C. 133.degree. C. 133.degree. C.
169.degree. C. 172.degree. C. 66.degree. C. 104.degree. C.
temperature recorded in .degree. C. Time at the 62' 40' 30' 167'
117' 58' 96' 34' maximum temperature in minutes
[0094] It is seen that the addition of a few percent of
1-(2-aminoethyl)imidazolidin-2-one to the liquid formulations A, D
or G makes possible a reduction in the time for reaching the
maximum exothermicity which ranges from approximately 35% for
formulation A (in comparison with C) up to 65% for D (in comparison
with F) and G (in comparison with H), which makes it possible to
rely on a shortening of the open time for each formulation in the
same proportions. It is noted that the effect of accelerating the
crosslinking by the use of 1-(2-aminoethyl)imidazolidin-2-one with
a' commercial curing agent is greatest for formulations D and G,
which are the least reactive of the epoxy systems tested.
Example 2
Acceleration of the Setting of an Epoxy Resin According to the
Invention: Comparison with a Tertiary Amine Catalyst
[0095] The comparison related to the use of the catalyst
tetramethylpropylenediamine (TMPDA) CAS No. 110-95-2 which has a
molecular weight very close to that of
1-(2-aminoethyl)imidazolidin-2-one (130 g/mol versus 129 g/mol
respectively) and which, due to its two tertiary amine functional
groups is regarded as a good catalyst for epoxy resins. The TMPDA
used is sold by Arkema France under its normal name of
tetramethylpropylenediamine.
Formulation G=Formulation G of example 1 Formulation I=Formulation
G of example 1 with in addition 4% by weight of TMPDA Formulation
J=Formulation G of example 1 with in addition 4% by weight of
1-(2-aminoethyl)imidazolidin-2-one Formulation K=Formulation D of
example 1 Formulation L=Formulation D of example 1 with in addition
4% by weight of TMPDA Formulation M=Formulation D of example 1 with
in addition 4% by weight of 1-(2-aminoethyl)imidazolidin-2-one,
that is to say like formulation E of example 1.
[0096] The results of the times in minutes for reaching the
exothermicity maximum are given in the following table 2:
TABLE-US-00002 TABLE 2 Formulation G I J K L M Time at the maximum
96' 60' 34' 167' 140' 117' temperature in minutes
[0097] The use of 1-(2-aminoethyl)imidazolidin-2-one makes it
possible to achieve a greater decrease in the setting time of the
formulations G and K tested than with the bi-catalyst TMPDA of
similar molecular weight.
Example 3
Flexibilization of an Epoxy Resin According to the Invention
[0098] The flexibility of a crosslinked resin can be measured in
several ways. Its Shore hardness was measured according to the
standard NF T 51109.
[0099] The Shore hardness measurements were obtained with a needle
durometer having the trademark symbol Andilog.RTM.. The device is
calibrated in order to obtain a hardness of 100 for a hardened
steel comprising 0.9% of carbon and of 35 for mild steels. In order
to confirm the flexibility of the final resin by use of the
molecule carrying an associative functional group according to the
invention was retained over time, each resin was maintained at
50.degree. C. for several days and its Shore hardness was regularly
measured (standard NF T 51109). According to this test, maintaining
at 50.degree. C. for 10 days corresponds approximately to aging for
6 months at ambient temperature.
Formulation A=Formulation A of example 1 Formulation B=Formulation
B of example 1 Formulation C=Formulation C of example 1
[0100] Results expressed as Shore hardness as a function of time at
50.degree. C., in days. Time zero corresponds to the hardness
measurement after reaction between the base resin and the curing
agent comprising 1-(2-aminoethyl)imidazolidin-2-one (formulations B
and C) or not comprising 1-(2-aminoethyl)imidazolidin-2-one
(formulation A), that is to say after complete development of the
exotherm caused by the crosslinking and return of the resin to
ambient temperature. The measurements given in table 3 are the
means of 5 hardness measurements.
TABLE-US-00003 TABLE 3 Formulation A B C Hardness at time 0 23.5 14
21 Hardness at 3 days at 22.9 15.9 22.1 50.degree. C. Hardness at 4
days at 24.2 17 20.1 50.degree. C. Hardness at 10 days at 26.8 18.1
23.3 50.degree. C.
[0101] The overall decline in the hardness of formulation B in
comparison with the reference A in example 3 shows the
flexibilizing effect on the final resin of the use of 4% of the
molecule carrying the associative functional group according to the
invention. This effect persists during the aging test, which
consists in maintaining the resin under hot conditions for 10
days.
Example 4
Reinforcement of the Adhesion of an Epoxy Resin
[0102] The improvement in the adhesion of a finished epoxy resin to
various supports by virtue of the use of a molecule carrying an
associative functional group according to the invention was
measured according to a "tearing-off" test, standard ISO 2409.
[0103] The principle consists in producing a criss-cross pattern on
a resin, the crosslinking of which has taken place on different
supports, by making parallel and perpendicular incisions in the
resin. The criss-cross pattern is composed of 25 squares with
dimension of 1 mm by 1 mm and with a thickness of 100 .mu.m. The
incisions have to penetrate as far as the support of the paint
film. A strip of adhesive tape is placed on the criss-cross pattern
produced, which strip is quickly torn off after 5 minutes. The
adhesion is then characterized by the number of small squares torn
off by the tape. The fewer squares torn off, the better the
adhesion is judged to be. [0104] Formulation N: [0105] Base resin
Epikote.RTM. 828 EL: 25 g [0106] Curing agent Ancamine.RTM. 2609
(Eurochem Kimya): 10 g. [0107] Ancamine.RTM. 2609 is a mixture of
diprimary alkyl- and arylamines, that is to say having two
--NH.sub.2 functional groups which react with epoxides, catalyzed
by a phenol (p-(t-butyl)phenol) [0108] Formulation O=Formulation N
incorporating in addition 1-(2-aminoethyl)imidazolidin-2-one (1.45
g, i.e. 4% by weight of the final resin) [0109] Formulation
P=Formulation N incorporating in addition 2.6 g of
1-(2-aminoethyl)imidazolidin-2-one (7% by weight of the final
resin).
[0110] The results of the tearing-off test on various supports, as
number of squares remaining adhered after tearing off the tape, are
collated in the following table 4.
TABLE-US-00004 TABLE 4 Formulation N O P Number of squares
remaining on a 1 15 18 ceramic support with a highly impervious
surface Number of squares remaining on a 1 5 15 polythethyl
methacrylate (PMMA) support Number of squares remaining on 1 5 10
carbon steel XC18
[0111] Formulations O and P exhibit a much lower tearing-Off than
the reference N; the incorporation in the initial formulation of a
few percent by weight of 1-(2-aminoethyl)imidazolidin-2-one very
markedly improves the adhesion of the finished epoxy resin to
ceramic, steel and polymer exhibiting carbonyl groups, such as
PMMA.
* * * * *