Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2003-02-13
2004-09-21
Boykin, Terressa (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C210S749000
Reexamination Certificate
active
06794486
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process for removing a dithio group comprised at the end of a polymer chain.
Dithio groups, bonded to an organic compound, usually confer to said compound a bad smell. The smell is at least partly due to the sulfur atoms. Polymer bearing dithio groups usually present such a bad smell. They often also present a yellow color. Such a smell and such a color may prevent their use in different fields. The smell is also an issue for the people who handle these polymers.
On another hand, dithio groups are reactive groups. Such reactivity may prevent the use of polymers comprising said groups, because it may induce some side reactions.
Recently, new radical polymerization processes involving the use of transfer agents comprising a dithio group have been developed. These processes are especially suitable for making random, block, star, branched or dendritic copolymers, and preferably di-block or tri-block copolymers. These processes are very economical, and can be used for making a number of different polymers or copolymers, that present very interesting properties. Block copolymers for example may be used for many purposes. Either the color, the smell, or the reactivity of the dithio groups may be a drawback for some uses.
Hence, there is a need for processes allowing a dithio group to be removed from polymers, or at least to be deactivated.
Patent application 01 11494, filed in France on Sep. 5, 2001, describes pyrolyzing a polymer comprising a Xanthate end-chain group, to transform said Xanthate group in a thiol group. The pyrolysis is performed in dichlorobenzene, above its boiling point. However, subjecting a polymer to such a temperature may be troublesome, and may alter it. Another process is therefore needed.
Patent application 01 11496, filed in France on Sep. 5, 2001, describes reacting a dithio group comprised in a polymer, with an organic compound comprising a hydrogen atom and a free-radical source.
It is known that hydrolyzing a polymer comprising a dithio group may remove said group. Hydrolysis of block copolymers is for example described in published U.S. patent application Ser. No. 2001-0044498-A1. However such a process is not suitable for some polymers, since it may degrade the polymer itself. For example a hydrolysis process may hydrolyze esters of acrylic acid units comprised in a polymer, as described in the above-mentioned application. Moreover, whereas hydrolysis, performed in water, may remove a dithio group, it may still be difficult or expensive to separate the dithio group by-products from the polymer. Hence, the recovered polymer may comprise said by-products and still present a bad smell and/or color.
Applicants have found an alternative process to the above-mentioned processes, in particular an alternative process to hydrolysis in water, for removing a dithio group from a polymer. In particular embodiments the process prevents undesired reactions (hydrolysis) of units comprised in the polymer such as acrylic esters units and/or avoids difficult separations steps to separate the polymer from dithio groups by-products, and leads to odorless and/or colorless polymers.
The invention also relates to a process for making a polymer or copolymer comprising a living radical polymerization step with a transfer agent comprising a dithio group, and a step of removing said group, these two steps being performed in a same solvent liquid medium. The process according to the invention is hence very simple. In particular embodiments, such a process allows together the removal of the dithio group and the separation of the polymer from the by-products. In such embodiments, the invention provides a very simple and cost-effective process addressing the color and/or the smell issues.
BRIEF SUMMARY OF THE INVENTION
Applicants have found a new process for removing dithio groups at the end of a polymer chain. The process may be a step in a process for making polymers or copolymers, comprising, before, a step of polymerizing.
The invention relates to a process for removing a dithio group comprised at the end of a polymer chain, comprising the step of reacting a polymer comprising a dithio group at at least one chain-end, with an amine compound, different from triethanol amine, in an organic solvent.
In a second aspect, the invention relates to a process for making a polymer or copolymer comprising the steps of:
a) polymerizing monomers by a living radical polymerization involving a transfer agent comprising a dithio group, to obtain a polymer or a copolymer comprising a dithio group at at least one chain-end, the polymerization being carried out in a solvent wherein the monomers and the obtained polymer or copolymer are soluble, and
b) in the step a) solvent, reacting the polymer or copolymer with an amine compound, different from triethanol amine, soluble in the solvent.
By dithio group, it is meant a group comprising a group of formula —S—(C═S)—, such as a Xanthate group, a dithioester group, a dithiocarbamate group, a dithiocarbazate group, or thioether-thione group.
By, organic solvent, it a meant a solvent comprising at least one carbon atom. Thus, the organic solvent is different from pure water. However the solvent may comprise some water, but not more than 50 weight %. It is preferably a pure organic solvent substantially comprising no water.
The polymer is preferably a block copolymer, for example a di-block or a tri-block copolymer. In a preferred embodiment, the block copolymer is obtained by a living polymerization process involving a transfer agent comprising a dithio group such as a Xanthate group, a dithioester group, a dithiocarbamate group, a dithiocarbazate group, or thioether-thione group.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
In the present specification, the molecular weight of a polymer, a copolymer, a moiety, a graft, a side-chain, a core, a branch, a block or a backbone refers to the weight-average molecular weight of said polymer, copolymer, moiety, graft, side-chain, core, branch, block or backbone. The weight-average molecular weight of the polymer or copolymer can be measured by gel permeation chromatography (GPC). In the present specification, the molecular weight of a graft, side-chain, core, branch, block or backbone refers to the molecular weight calculated from the amounts of monomers, polymers, initiators and/or transfer agents used to make the said graft, side-chain, core, branch, block or backbone. The one skilled in the art knows how to calculate these molecular weights. The ratios by weight between blocks refers to the ratios between the amounts of the compounds used to make said moieties, considering an extensive polymerization.
Typically, the molecular weight M of a block, graft, side-chain, branch, core or backbone is calculated according to the following formula:
M
=
∑
i
M
i
*
n
i
n
precursor
,
wherein M
i
is the molecular weight of a monomer i, n
i
is the number of moles of a monomer i, and n
precusor
is the number of moles of a compound the macromolecular chain of the block, graft, side-chain, branch, core or backbone will be linked to. Said compound may be a transfer agent or a transfer group, a previous block, or a graft or reactive side-chain. If it is a previous block, the number of moles may be considered as the number of moles of a compound the macromolecular chain of said previous block has been linked to, for example a transfer agent or a transfer group. It may be also obtained by a calculation from a measured value of the molecular weight of said previous block. If two blocks are simultaneously grown from a previous block, at both ends, the molecular weight calculated according to the above formula should be divided by two.
In the present specification, a unit deriving from a monomer is understood as a unit that may be directly obtained from the said monomer by polymerizing. Thus, a unit deriving from an ester of acrylic or methacrylic acid does not encompass a unit of formula —CH—CH(COOH)—, —CH—C(CH
3
)(COOH)—, —CH—CH(OH)—, —CH—C(CH
3
)(OH
Adam Herve
Liu Wan-Li
Boykin Terressa
Chimie Rhodia
LandOfFree
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