Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
1998-04-10
2002-12-03
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S156000, C502S157000, C502S158000, C502S243000, C526S173000, C526S178000
Reexamination Certificate
active
06489262
ABSTRACT:
TABLE OF CONTENTS
1. Background Of The Invention
1.1. Technical Field
1.2. Description Of Related Art
2. Summary Of The Invention
3. Description Of The Preferred Embodiments
3.1. Examples 1 to 6
3.2. Example 4
3.3. Example 5
3.4. Example 6
3.5. Examples 7 through 20
3.6. Examples 21 through 24
3.7. Example 25
3.8. Examples 26 through 30
3.9. Examples 31 through 32
4. Claims
5. Abstract Of The Disclosure
BACKGROUND OF THE PRESENT INVENTION
1.1. Technical Field
The present invention relates to an initiation system for anionic (co)polymerization of (meth)acrylic, vinylaromatic and/or diene monomers; this new initiation system has proven to be high-performance, because it uses easy experimental conditions as regards temperature, with practically a quantitative yield, and, for example, permits simple synthesis of poly(methylmethacrylate) (PMMA) with a high content of isotactic triads (at least 75%), with a high number average molecular weight ({overscore (Mn)}), while retaining a narrow polymolecularity index Ip ({overscore (Mw)}/{overscore (Mn)}), and also controlled polymerization of acrylates, particularly primary acrylates, and the synthesis of block copolymers with blocks of isotactic PMMA and the synthesis of polydienes with high contents of the 1,4-microstructure.
1.2. Description of Related Art
In the literature, initiation systems permitting anionic polymerization of methacrylates with a high level of isotactic triads all present one limitation. This is in the area of yields, i.e., at the level of the main characteristics of polymers (Ip, {overscore (Mn)}, tacticity). Experimental conditions are generally drastic, notably requiring very low temperatures (−78° C.). Thus, in Polymer Journal, Vol. 17, No. 8, pp., 977-980 (1985), and in Polymer Journal, Vol. 18, No. 12, pp. 1037-1047, HATADA et al. report that t-C
4
H
9
MgBr prepared in diethyl ether has not caused any secondary reactions in the polymerization of methylmethacrylate in toluene at −78° C., and has formed a highly isotactic polymer with a narrow polymolecularity index. However, this process is limited to very low temperatures and does not permit synthesis of PMMA with very high molar masses.
There is, therefore, a real need in this area for more flexible operating constraints and an improvement in the processes or characteristics of the products.
SUMMARY OF THE INVENTION
The present invention relates to an initiation system composed of the reaction product of at least one cyclic siloxane and at least one organometallic compound of sufficient reactivity to open the siloxane ring.
Application of the present invention is to the preparation of homopolymers of (meth)acrylic, vinylaromatic or diene monomers, random or block copolymers of these monomers and, in particular, application to poly(methylmethacrylate) with a high content of isotactic triads.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The first objective of this invention therefore is an initiation system for anionic (co)polymerization of (meth)acrylic, vinyl-aromatic and/or diene monomers, including the reaction product
a) of at least one cyclic siloxane of Formula I:
wherein R and R′, identical or different, each represent a C
1
-C
8
, linear or branched alkyl radical, or an aryl radical, an arylalkyl or alkylaryl radical, wherein the alkyl group has from 1 to 6 atoms of carbon and p is a whole number from 3 to 6 and
b) of at least one organometallic compound with sufficient reactivity to open the siloxane ring,
the molar ratio r=no
, wherein n
0
is the number of moles of active sites deriving from the organometalic compound reacting with n moles of cyclic siloxane compound, being between 0.8p and 2p, where p represents the number of siloxane units.
In Formula (I) for cyclic siloxane, R and R′, identical or different, preferably represent a methyl radical, and p, representing the number of siloxane units, preferably is equal to 3 or 4. A particularly preferred cyclic siloxane, called Dp, with D=—(R)(R′)Si—O— and p=the number of these units, particularly preferably, is hexamethylcyclotrisiloxane (D
3
) or octamethylcyclotetrasiloxane (D
4
).
The organometallic compound is selected, in particular, from among the compounds:
(1) of Formula (II):
(R
1
)
u
—M (II)
wherein:
R
1
represents a branched-chain alkyl radical containing 3 to 6 carbon atoms; or an aryl radical with one or more rings, possibly substituted; or an alkenyl radical at C
2
-C
6
, substituted by aryl or alkylaryl; or an alkyl radical, linear or branched, containing 1 to 6 carbon atoms, substituted by at least one phenyl group, or a C
1
-C
6
alkylaryl radical, wherein the alkyl group has from 1 to 8 carbon atoms;
M designates an alkaline metal or alkaline earth metal; the valence u is respectively 1 or 2.
(2) difunctional compounds of Formula (III):
wherein:
M′ is an alkaline metal;
R
2
represents an organic bivalent radical, whether aliphatic, cycloaliphatic, aromatic or containing at least one cycloaliphatic or aromatic group; R
2
may contain substituents;
R
3
and R
4
each independently represent an organic monovalent radical, whether aliphatic, cycloaliphatic, aromatic or containing at least one cycloaliphatic or aromatic group, R
3
and R
4
may contain substituents;
(3) monofunctional silylated compounds of Formula (IV):
wherein:
R
5
, R
6
, R
7
each independently represent an alkyl radical, linear or branched, containing 1 to 6 carbon atoms;
R
8
represents an alkylene radical, linear or branched, containing 1 to 6 carbon atoms;
M″ designates an alkaline metal or alkaline earth metal, and valence q is 1 or 2, respectively; and
(4) difunctional silylated compounds of Formula (V):
wherein:
R
9
and R
10
each independently represent a linear or branched alkyl radical containing 1 to 6 carbon atoms;
R
11
and R
12
each independently represent a linear or branched alkylene radical containing 1 to 6 carbon atoms; and
M′″ designates an alkaline metal.
The monofunctional initiators (1) of Formula (II) are selected, in particular, from between sec.-butyllithium and tert.-butyllithium.
As for difunctional compounds (2) of Formula (III), they are selected notably from between 1,1,4,4-tetraphenyl-1,4-dilithiobutane and 1,1,4,4-tetraphenyl-1,4-disodiobutane.
In Formulas (IV) and (V) above, it is preferable for R
5
, R
6
, R
7
, R
9
and R
10
to each represent a methyl, and for R
8
, R
11
and R
12
to each represent a methylene, and for M″ and M′″ to each represent lithium.
Difunctional precursors, such as lithium naphthalene, sodium naphthalene and potassium naphthalene also are used.
The inventive initiation system is generally obtained by reaction of at least one cyclic siloxane Dp with at least one organometallic compound at ambient temperature, under nitrogen, in a nonpolar solvent such as toluene. The mechanism of this reaction is that of a nucleophilic addition reaction of the organometallic compound to the electrophilic silicon atom, thus provoking the opening of the ring.
As an example, with n moles of cyclic siloxane D
3
(3 siloxane units) and n
0
moles of active sites deriving from organometalic compound R
1
M reacting with the cyclic siloxane D
3
, the reaction is as follows:
Since the medium is nonpolar, it is thought that there are associated mixed species of the form xR
1
M and 6-x R1-D-M with D:
Due to the existence of several associated mixed species, preparation of the initiation system, at ambient temperature, requires enough time to permit an equilibrium favorable to the thermodynamically most stable species to be reached. This period may, for example, be 20 hours.
The choice of the molar ration r=no
permits control of the molar ratio (R) of the silanolate species (S) obtained related to the organometallic compound acting as initiator (A) and consequently constitutes a parameter that affects this equilibrium.
The quantity of siloxane units p must be sufficient to permit formation of a complex with the active polymerization core and thus allow stabilizati
Jerome Robert
Navarro Christophe
Teyssie Philippe
Zundel Thomas
Atofina
Pennie & Edmonds LLP
Wood Elizabeth D.
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