Polymerization catalyst and polymerization process

Details Polymerization catalyst and polymerization process Polymerization catalyst and polymerization process

1999-12-09

2002-09-10

Moore, Margaret G. (Department: 1712)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Organic compound containing

C528S023000

Reexamination Certificate

active

06448196

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to catalysts for the polymerization of siloxanes and to the use of such catalysts for the polymerization of siloxanes via ring opening of cyclic siloxanes or via condensation of silanol or alkoxy end-blocked siloxane materials or via equilibration of siloxanes. The present invention is more particularly related to phosphazene base catalysts, and especially linear phosphazene base catalysts for said polymerization.
BACKGROUND OF THE INVENTION
In EP0860461-A, there is described a process for the ring-opening polymerization of cyclosiloxanes, which comprises contacting a cyclosiloxane with 1 to 500 ppm of a phosphazene base, by weight of cyclosiloxane, in the presence of water. The phosphazene base catalyst described in that specification is preferably selected from the general formulae:
((R
1
2
)
3
P═N—)
x
(R
1
2
N)
3−x
P═NR
2
{((R
1
2
N)
3
P═N—)
x
(R
1
2
N)
3−x
P—N (H)R
2
}
+
(A)
−
and
{((R
1
2
N)
3
P═N—)
y
(R
1
2
N)
4−y
P}
+
(A)
−
in which each R
1
independently is hydrogen or an optionally substituted hydrocarbon group, or in which two R
1
groups bonded to the same N-atom may be linked to complete heterocyclic ring; R
2
is hydrogen or an optionally substituted hydrocarbon group; x is 1, 2 or 3; y is 1, 2, 3 or 4; and A is an anion.
EP0879838-A describes a process of preparing a polymer which comprises conducting ring-opening polymerization of a 4- to 10-membered cyclic monomer in the presence of a phosphazenium salt catalyst of an active hydrogen compound represented by the formula
Although these catalysts are very useful materials, the manufacturing process for many of them is often complex, using in some cases as many as 25 raw materials, solvents and intermediates in up to 12 key process steps, including low temperature manufacture, distillation, filtration, recrystallization and ion-exchange. This makes the process difficult, expensive and time consuming.
We have now surprisingly found that there is no need to make such complex phosphazene base materials for the polymerization of siloxanes. Indeed a more simple structure of phosphazene base materials, in the form of linear polyamino phosphazenium salts containing nucleophilic anions are found to be excellent catalysts for the polymerization of siloxanes, whether by ring-opening polymerization of cyclic siloxanes or by condensation of silanol or silicon-alkoxy end-blocked siloxanes. These linear phosphazene base materials can be made in a much more economic and simple process.
SUMMARY OF THE INVENTION
This invention provides a linear phosphazene base catalyst of the general formula,
wherein R denotes a hydrocarbon having up to 10 carbon atoms or wherein the two R groups on each N atom form with the N atom a heterocyclic group, X denotes an anion and n has an average value of from 1.2 to 10.
This invention also provides a process for making a linear phosphazene base catalyst comprising reacting a linear phosphonitrile halide compound with a compound selected from secondary amines and salts and metal amides thereof to form an aminated phosphazene material, followed by reacting the aminated phosphazene material in an ion exchange reaction replacing the anion of the aminated phosphazene material with a nucleophile.
This invention further provides a process of polymerization of siloxanes via equilibration and/or condensation comprising contacting the siloxanes with the linear phosphazene base catalyst of formula (1).
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, a linear phosphazene base catalyst has the general formula
wherein R denotes a hydrocarbon having 1 to 10 carbon atoms or wherein the two R groups on one N atom form with the N atom a heterocyclic group, X denotes an anion and n is from 1 to 10.
According to one aspect of the invention, a process for making a linear phosphazene base catalyst comprises reacting a linear phosphonitrile halide compound with a secondary amine or a salt of a secondary amine or a metal amide thereof to form an aminated phosphazene material, followed by an ion exchange reaction replacing the anion with a nucleophile.
According to another aspect of the invention, siloxanes are polymerized via equilibration and/or condensation in the presence of a linear phosphazene base catalyst of formula (1).
The process for making the linear phosphazene base catalysts of formula (1) uses as its main ingredient a phosphonitrile halide, preferably a phosphonitrile chloride. Using a phosphonitrile halide, which is already an ionic material, renders the manufacture of the phosphazene base catalysts simpler. Phosphonitrile halides are known and have been described in a number of patent specifications, which are hereby included by reference. Many of these patent specifications describe the use of these halides as catalysts for the polymerization of certain types of siloxanes. For example, GB 910513 discloses phosphonitrile halide catalysts for use in a process for the manufacture of stabilized high viscosity polyorganosiloxane oils and in US 3549680 phosphonitrile halide catalysts are employed in rearrangement reactions. EP 319978 describes chlorophosphonitrile catalysts for use in a process for the preparation of polydiorganosiloxanes containing a silicon-bonded hydroxyl group in each of the terminal units. Other phosphonitrile halide catalysts have been described in GB 2252969. Examples of suitable phosphonitrile halides include (Cl
3
P═N—(P═NCl
2
)
n
—PCl
3
)
+
Z
−
, wherein Z— is preferably Cl
−
or PCl
6
−
and n is 1-10, preferably 1 to 5.
Processes for making these phosphonitrile halide materials are described in many of the above mentioned specifications. One useful process includes the reaction of PCl
5
with NH
4
Cl in the presence of a suitable solvent. In an even more useful process, described in our copending application GB9827055.6, the ammonium chloride is replaced with hexamethyldisilazane. This process comprises a first step of reacting PX
5
and a disilazane under cooling in an inert non-chlorinated solvent and a second step of heating the reaction mixture to at least 50° C. for a time sufficient to produce the phosphonitrile halide. This process is particularly preferred as the phosphazene halide thus produced has a reduced level of phosphonitrile chloride having only 2 phosphorus atoms present. It has been found that phosphazene bases having only 2 phosphorus atoms, which could be made according to the present invention (formula (1) where the value of n would be 0) are less active as a catalyst for the polymerization of siloxanes.
The above processes generally produce a mixture of phosphonitrile halides; a mixture of phosphonitrile halides can be used as a starting material in the process of the invention, producing a mixture of phosphazene base catalysts. Mixtures of catalysts of formula (1) in which the average value of n is above 1 are preferred catalysts which cannot be prepared by known methods. Particularly preferred linear phosphazene base catalysts are those of formula (1) in which the average value of n is at least 1.2 up to 5 or 10, especially from 1.5 or 1.8 up to 3, as these have been found to be the most effective catalytic species for the polymerization of siloxanes.
The process for preparing the phosphazene base catalyst according to the invention is much less complex than the processes required previously for the making of phosphazene bases, for example those described e.g. by Schwesinger et al. in Liebig. Ann. 1996, 1055-1081. The catalysts according to the present invention can be made by merely reacting the phosphonitrile halide, preferably chloride, with a secondary amine of the formula R
2
NH, wherein R is selected from hydrocarbon groups having up to 10 carbon atoms, for example methyl, or the two R groups which are found on a single N atom form with the nitrogen atom a heterocyclic group, e.g. a pyrollidine group, a pyrrole group or a pyridine group for the polymerization of

Affiliated with

Also associated with

Rating

Polymerization catalyst and polymerization process does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Polymerization catalyst and polymerization process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymerization catalyst and polymerization process will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2831979