Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1998-04-10
2001-11-20
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S152000, C502S158000, C502S171000
Reexamination Certificate
active
06319875
ABSTRACT:
TABLE OF CONTENTS
PAGE
1.
Background Of The Invention
2
1.1.
Technical Field
2
1.2.
Description Of Related Art
3
2.
Summary Of The Invention
4
3.
Description Of The Preferred Embodiments
5
3.1.
Example 1
11
3.2.
Example 2 (comparative)
16
3.3.
Example 3
18
3.4.
Example 4 (comparative)
18
3.5.
Example 5
21
3.6.
Example 6 (comparative)
21
3.7.
Examples 7 and 8
22
3.8.
Examples 9 and 10
22
3.9.
Example 11
22
3.10.
Example 12
23
3.11.
Example 13
23
4.
Claims
25
5.
Abstract Of The Disclosure
30
6.
Drawing(s)
1. BACKGROUND OF THE PRESENT INVENTION
1.1. Technical Field
The present invention relates to an initiation system for the anionic polymerization of (meth)acrylic monomers, this system being particularly useful for initiation of anionic polymerization of methyl methacrylate in order to get syndiotactic poly(methyl methacrylate) (PMMA), for initiation of anionic polymerization of monomer acrylates where the carbon in &agr; of the oxygen of the ester is tertiary, secondary or particularly primary (hereafter we will use the designation of tertiary, secondary or primary acrylate), for initiation of random or block copolymerization of (meth)acrylic monomers, as well as for the formation of star copolymers comprising arms formed of (meth)acrylic blocks linked to the core or node formed from a multifunctional compound (for example a deactivating agent or a monomer leading to a polymer, whether or not crosslinked).
1.2. Description of Related Art
In European Patent Application EP-A-0524054, the anionic polymerization of alkyl (meth)acrylates using an initiation system comprising a monofunctional or difunctional initiator and a ligand formed by an alkoxy alcoholate of an alkaline metal is described.
With this process, polymerization is well controlled, especially at low temperatures.
The anionic synthesis of syndiotactic PMMA or polyacrylates with controlled mass and polymolecularity required the use of sterically “encumbered” initiators to avoid secondary reactions during initiation. Since the use of pure butyllithium (n-, sec.-, tert.-) as initiator does not permit an initiation efficiency of more than 20% to be achieved, the system proposed to date generally included (1) the initiator 1,1-diphenylhexyllithium - reaction product of n-butyllithium with 1,1-diphenylethylene - and (2) an alkoxy alcoholate ligand as described in EP-A-0524054. The use of 1,1-diphenylethylene makes this process more expensive.
PMMA intrinsically, that is, when it contains nothing other than repetitive units, has a remarkable resistance to aging. Conventional initiation with 1,1-diphenylhexyllithium—the bearer of two aromatic rings—entails the presence of aromatic groups fixed at the beginning of the polymer chain. It is well known that the presence of aromatic groups diminishes the resistance to aging of polymers that contain them, which thus entails a disadvantage for the PMMA.
Th. Zundel, J. Ming Yu, L. Lestel, D. Teyssié and S. Boileau, Macromol. Symp. 88, 177-189 (1994) described trimethylsilylmethyllithium as an initiator for anionic polymerization for cyclosiloxanes and vinyl monomers. Although this article indicates that this organolithiated compound also initiates anionic polymerization of methyl methacrylate, only a few preliminary results were reported. With methyl methacrylate, there are extensive secondary reactions when the polymerization takes place at 0° C. according to the process described, which entails a broad distribution of molecular weights, regardless of the solvent used. In all cases, the number average molecular weights (Wn) measured are significantly higher than the theoretical values. This probably is due to the fact that the initiation rate is low compared to the propagation rate. A substantial fraction of the initiator remains unused upon completion of polymerization. The microstructures of samples of PMMA obtained by this process were analyzed by NMR
1
H. They are similar to those observed traditionally for PMMAs prepared with initiators of the organolithium type. A high level of isotactic triads is observed in toluene with lithium counter-ions. In contrast to this, the syndiotactic triads predominate when the polymerization takes place in THF at −78° C. or when AlEt
3
is added to the organolithium initiator in toluene. Now, PMMA with a high level of syndiotactic triads is interesting, because the polymer then has a higher glass transition temperature and thus greater heat resistance. In the prior process, PMMA could not be prepared except with maximum contents of syndiotactic triads of 67%, by working in the presence of an additive such as AlEt3 over a very long period (16 hours), in a polar medium at very low temperatures. This process is thus far from being usable in industry.
2. SUMMARY OF THE INVENTION
The initiation system comprises (1) at least one silylated initiator and (2) at least one alkaline metal alcoholate as ligand. The silylated initiator may be monofunctional and selected in particular from among the compounds of Formula (I) or difunctional and selected in particular from among the compounds of Formula (II):
wherein R
1
, R
2
, R
3
each independently represent a C
1
-C
8
alkyl radical, linear or branched; R
4
is a linear or branched C
1
-C
8
alkylene radical; M is an alkaline metal or alkaline earth metal (valence q of 1 or 2); R
5
and R
6
each independently represent an alkyl radical, linear or branched, at C
1
-C
8
; R
7
, R
8
each independently represent a C
1
-C
8
alkylene radical, linear or branched; M′ is an alkaline metal. Application is to the preparation of (meth)acrylic (co)polymers.
3. DESCRIPTION OF THE PREFERRED EMBODIMENTS
The filing Company discovered that, by combining a silylated initiator, particularly trimethylsilylmethyllithium, a “poor initiator”, with a ligand consisting of an alkaline metal alcoholate, particularly of the type described in EP-A-0524054 above, an initiation system for the anionic (co)polymerization of (meth)acrylic monomers is obtained, which presents numerous advantages and permits resolution of the problems posed in the prior state of the art.
The first objective of this invention therefore is an initiation system for anionic (co)polymerization of (meth)acrylic monomers comprising:
(1) at least one silylated initiator; and
(2) at least one alkaline metal alcoholate as ligand.
The silylated initiator may be monofunctional; it is then chosen, in particular, from among the compounds of Formula (I):
R
1
, R
2
, R
3
each independently represent an alkyl radical, linear or branched, containing 1 to 8 carbon atoms;
R
4
represents an alkylene radical, linear or branched, containing 1 to 8 carbon atoms;
M designates an alkaline metal or alkaline earth metal (valence q is 1 or 2).
The silylated initiator is also difunctional, and is then chosen, in particular, from among the compounds of Formula (II):
wherein:
R
5
and R
6
each independently represent a linear or branched alkyl radical containing 1 to 8 carbon atoms;
R
7
and R
8
each independently represent a linear or branched alkylene radical containing 1 to 8 carbon atoms; and
M′ designates an alkaline metal.
In Formula (I) or (II) above, R
1
, R
2
, R
3
, R
5
and R
6
each preferably represent an alkyl radical with, preferably, 1 to 4 carbon atoms and very particularly, a methyl radical; R
4
, R
7
and R
8
each preferably represent an alkylene radical with 1 or 2 carbon atoms and particularly the methylene radical, and M and M′ each preferably represent lithium. A particularly appropriate initiator is trimethylsilylmethyllithium.
As for alkaline metal alcoholates (2), they may be chosen from among those of Formula (III):
ROM″ (III)
wherein:
M″ represents an alkaline metal; and
R represents a radical of Formula (IV):
R
9
(OR
10
)
p
(IV)
wherein:
R
9
represents an alkyl radical, linear or branched, with 1 to 8 carbon atoms, an aryl radical, an arylalkyl radical, or alkylaryl, wherein the alkyl radical has 1 to 8 carbon atoms;
R
10
represents an alkylene radical, linear or branched, with 1 to 4 carb
Jerome Robert
Maurer Andreas R.
Muller Axel H. E.
Navarro Christophe
Zundel Thomas
Elf Atochem S.A.
Pennie & Edmonds LLP
Wood Elizabeth D.
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