Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1997-09-12
2001-08-07
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S312000, C528S322000, C528S331000, C528S332000, C528S335000, C528S336000, C528S339000, C528S392000
Reexamination Certificate
active
06271339
ABSTRACT:
The present invention relates to new prepolymers having maleimide functions, to a process for preparing them, and to their uses as constituents of polymerizable and/or crosslinkable compositions.
A large number of thermocurable compositions comprising monofunctional or polyfunctional maleimide monomers are known, said maleimides being sought for as a rule because they provide the thermocured compositions with a good thermal resistance.
It is desirable to provide compounds bearing maleimide functions, and, especially, aliphatic maleimides, in order to formulate radiation curable compositions, involving both compounds comprising electron depleted double bonds and compounds comprising electron enriched double bonds, said compounds bearing maleimide functions acting as compounds comprising electron depleted double bonds.
However, the synthesis of maleimides remains very difficult, which renders these compounds very expensive, and, consequently, which renders also very expensive the compositions of which they make part. This is particularly true in the case of the aliphatic maleimides, for which the yields of synthesis which are obtained are very poor.
In general, maleimides are prepared by opening the maleic anhydride by an amine, forming an amic acid, on which a ring forming reaction results in a maleimide. In general this ring forming is carried out in the presence of acetic anhydride possibly with a catalyst such as a tertiary amine and/or a metal salt. When the ring forming reaction is complete, the maleimide is precipitated by adding water to the medium and the maleimide is recovered by filtration. The excess of water causes the reaction by-products to precipitate, together with the maleimide, which requires one or several supplemental recrystallisation steps in order to obtain a pure compound. Furthermore, this process leads to the formation of large amounts of effluents (acetic acid). These processes are therefore expensive and difficult to carry out on an industrial scale.
Maleimides can also be prepared by reaction of maleic anhydride with an isocyanate. This process, which requires purification steps, is also expensive and difficult to carry out on an industrial scale.
It may be also pointed out that maleimides which are in general available on the market (generally aromatic ones) are hardly soluble, which prevents their using in a number of applications.
Besides, the maleimides introduced as monomers may induce migration problems if they are not completely polymerized in the polymerized compositions.
In order to mitigate the very important disadvantages of maleimide monomers, namely their high cost (due to the complexity of the preparation process and to the low yield) and to their insoluble character, various attempts have been described in the literature.
For instance, polymers (polyesters, polyamides, polyimides) terminated by maleimide groups have been described. In order to prepare these polymers, functionalized maleimide monomers are used, which are very often aromatic maleimides, because they are the ones which may be synthetized with acceptable yields and, consequently, with a comparatively lesser cost. The resulting polymers have the disadvantages of being in practice restricted to those ended by aromatic maleimides, and of requiring a process of preparation comprising several steps, because it is necessary to synthetize beforehand the maleimide which will have to be isolated ; consequently, this process is expensive and it is very difficult to carry it into effect on an industrial scale.
We have now found that prepolymers, which comprise a sufficient amount of maleimide functions and which can therefore be directly used in the abovementioned applications, can be obtained by a process which involves no purification step, in which all the reagents introduced make part of the structure of the final prepolymers and in which only operations which are very easy to carry out on an industrial scale are involved (among others, requiring neither operations of crystallisation, filtration, and so on, nor discarding effluents), namely breaking away from all the difficulties of the prior art and offering moreover the advantage of not being restricted to maleimides N-substituted by aromatic groups introduced in these prepolymers. Furthermore the process results in maleimides of a polymeric nature which have the advantage of presenting a low capability of migration in the polymerized composition.
The subject of the present invention is thus prepolymers having maleimide functions (f):
wherein each of R
1
and R
2
represents independently H, a C
1-
C
12
alkyl group or a halogen,
said prepolymers consisting in the reaction products:
of at least one maleic anhydride represented by formula I:
wherein R
1
and R
2
are such as defined above;
of at least one compound (II) having at least one —NH
2
function and at least another function F selected from the group consisting of —OH, —NH
2
, —NH—, —COOH,
R
3
representing a C
1
-C
5
alkyl group;
of at least one compound (III) capable of forming the chain of the prepolymers by polycondensation and/or polyaddition,
said compound(s) (II) having first reacted with said maleic anhydride(s) (I) in order to open the maleic anhydride rings with formation of maleamic acid functions (f′):
said maleamic acid functions having then been at least partially closed again under the action of heat into maleimides N-substituted by groups functionalized by a function F,
the chain of said prepolymers having been formed by polycondensation and/or polyaddition:
of the N-substituted maleimide formed bearing the function F;
of compound(s) (III);
of uncyclized products bearing or not a function F formed simultaneously with said N-substituted maleimides;
of maleic anhydride(s) (I) which could have remained in excess after their opening by compound(s) (II);
the functionalities of compound(s) (III) being selected in order to allow the constitution of the chain with the grafting of said N-substituted maleimides on the chain directly by their function F when the latter is at least one selected among —OH, —NH
2
, —NH— and —COOH, or after transesterification of the functions F when the latter are —COOR
3
or —OCOR
3
in order to allow the condensation or the addition of said N-substituted maleimide on the chain,
the functionalities and proportions of compounds (II) and (III) having been selected in order to exclude any gelation of the reaction medium.
In the prepolymer according to the invention, in general the compound(s) (II) has (have) reacted with anhydride(s) (I) under stoechiometric or substantially stoechiometric conditions or in excess of anhydride(s) (I) with respect to compound(s) (II).
Preferably, the anhydride of formula (I) is maleic anhydride.
The compounds (II) are especially selected among the compounds represented by the formulae H
2
N-A-OH, H
2
N-A-COOH, H
2
N-A-COOR
3
,
and H
2
N-A-NH
2
, wherein A represents a straight, branched or cyclic alkylene group, or an arylene group, it being possible for said groups to be interrupted by oxygen or sulfur atoms, or by —NR
4
— groups, wherein R
4
represents hydrogen or alkyl.
As examples of these compounds (II),
aminoalcohols, such as ethanolamine, propanolamine, isopropanolamine, 2-(2-aminoethoxy)ethanol, N-(2-aminoethyl)ethanolamine;
aminoacids, such as valine, p-amino-benzoic acid, alanine, 2-aminohexanoic acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 2-aminoisobutyric acid;
the methyl or ethyl esters of the abovementioned aminoacids;
the esters of carboxylic acids having 2 to 5 carbon atoms, such as acetic acid, with the abovementioned aminoalcohols;
diamines, such as ethylenediamine, 2-methyl-1,5-pentamethylenediamine, hexamethylenediamine, 2,2,4- and/or 2,4,4-trimethylhexamethylenediamine, dodecamethylenediamine, 5-methylnonamethylenediamine, decamethylenediamine, isophoronediamine, bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, bis(3-methyl-4-amino-5-ethylcyclohexyl)methane, 1,2-bis(4-aminocyclohexyl)ethane, 2,2′-bis(4-aminocyclohexyl)propane, 2,
Strub Henri
Thepot Phillippe
Cozen and O'Connor
Fein Michael B.
Hampton-Hightower P.
Sartomer Company, Inc.
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