Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1997-03-21
2001-03-06
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S209000, C526S278000, C526S279000, C526S292900, C526S298000, C526S313000, C526S318000, C526S320000
Reexamination Certificate
active
06197905
ABSTRACT:
The invention relates to processes for radical-initiated polymerization of unsaturated species and for the control of molecular weight and end-group functionality of the polymeric products produced from such processes. Polymers of limited molecular weights, or oligomers, are useful as precursors in the manufacture of other polymeric materials and as additives in plastics, elastomerics, and surface-coating compositions, as well as being useful in their own right in many applications.
In conventional polymerization practice, the manufacture of oligomers requires the use of an initiator which acts as a free radical source, and of a chain transfer agent. The chain transfer agent controls the molecular weight of the polymer molecule by reacting with the propagating polymer radical to terminate its growth. It then initiates a new polymer chain thus transferring the growth process from one discrete polymer molecule to another discrete polgoleule. At least a part of the chain transfer agent is incorporated into the polymer molecule and thus is consumed during the process. The incorporated residue of the chain transfer agent can lead to undesirable end-groups on the polymer.
The chain transfer agents most commonly used are alkanethiols, which possess an objectionable odour, lead to a wide distribution of molecular weight with certain monomers, do not allow the production of telechelic polymers, and offer limited scope for the preparation of polymers with a single functional end-group. Additionally, with thiols there is little scope for the chain transfer efficiency to be optimized for a particular polymerization.
The present invention provides a process for the production of lower molecular weight polymers by free radical polymerization, which process is characterized by the addition of compounds of the general Formula A to the polymerization system. The process can, by appropriate selection of the compound of Formula A, produce polymers with groups capable of further chemical reaction at one or both ends of the polymer chain.
In Formula A, R
1
can be hydrogen, but preferably represents a group capable of activating the vinylic carbon towards free radical addition. Suitable groups are phenyl and optionally substituted cast aromatic groups, alkoxycarbonyl or aryloxycarbonyl (—COOR), carboxy (—COOH), acyloxy (—O
2
CR), carbamoyl (—CONR
2
) and cyano (—CN); AND
Y is —CH
2
X(R
2
)
n
or —OR
2
;
WHERE
R
2
represents optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, or optionally substituted saturated, unsaturated, or aromatic carbocyclic or heterocyclic ring; AND
when Y is —CH
2
X(R
2
)
n
, X represents an element other than carbon selected from groups IV, V, VI, or VII of the Periodic Table or a group consisting of an element selected from groups IV, V, or VI to which is attached one or more oxygen atoms. Suitable elements X include sulphur, silicon, selenium, phosphorus, bromine, chlorine, and tin. Examples of oxygen containing groups include phosphonates, sulphoxides, sulphones, and phosphine oxides; AND
n is a number from 0 to 3, such that the valency of the group X is satisfied. When n is greater than 1, the groups represented by R
2
may be identical or different.
In Formula A, substituted rings may have a reactive substituent group directly or indirectly attached to the ring by means of a methylene group or other side-chain.
The reactive substituent groups referred to above for R
1
and/or R
2
in Formula A do not take part in the actual lowering of the molecular weight, but are installed at the ends of the polymer chains and may be capable of subsequent chemical reaction. The low molecular weight polymer containing said reactive group or groups is thereby able to undergo further chemical transformation, such as being joined with another polymer chain as described subsequently in this specification. Suitable reactive substituents include: hydroxy (—OH); amino (—NH
2
); halogen; phosphonate; trialkyoxysilyl; allyl; cyano (—CN); epoxy; and carboxylic acid (—COOH) and its derivatives, such as ester (—COOAlkyl). The substituents may alternatively be non-reactive such as alkoxy (—OAlkyl) or alkyl.
Alkyl groups referred to in this specification may contain from 1 to 32 carbon atoms. Alkenyl and alkynyl groups may contain from 2 to 32 carbon atoms. Saturated, unsaturated, or aromatic carbocyclic or heterocyclic rings may contain from 3 to 14 atoms.
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Meijs Gordon Francis
Rizzardo Ezio
Thang San Hoa
Commonwealth Scientific & Industrial Resarch Organization
Costello James A.
Deshmukh Sudhir G.
Henderson Christopher
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