Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-09-25
2003-02-11
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C526S219000, C526S219100, C526S219200, C526S220000, C558S235000
Reexamination Certificate
active
06518364
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compounds useful in assisting in the emulsion polymerization of monomers in a free radical polymerization that has living-type kinetics. Heterogeneous mixtures (e.g., dispersions, etc.) and/or polymers made with the control agents and processes for polymerization are also included. In addition, some of the compounds themselves are novel.
BACKGROUND OF THE INVENTION
The use and mechanism of control agents for free radical polymerization is now generally known, see for example U.S. Pat. No. 6,153,705, WO98/01478, WO99/35177, WO99/31144, and WO98/58974, each of which is incorporated herein by reference. Nonetheless, there remains a need for new agents, which provide better properties in certain systems, such as emulsion polymerization.
For example, the previously known control agents have limited uses. Although touted as universally useful, those of skill in the art appreciate that a particular control agent is particularly useful for the control of particular monomers and monomer mixtures. The polymerization conditions under which particular control agents are particularly useful are generally not well known. Thus, a need exists for a family of related control agents that can be easily synthesized and modified so that a control agent will be readily available for polymerizing desired monomers under commercially acceptable conditions, which include high conversion at the shortest possible reaction times and lower temperatures.
Additionally, there is a strong need in the industry to make block copolymers in emulsion processes. From a process point of view, emulsions are advantageous over bulk or solution processes because emulsion processes allow for relative ease of heat removal, use of environmentally friendly water as liquid vehicle (as compared to organic solvents), ease of polymer handling and purification (e.g., stripping off residual monomers), high solid content with high molecular weight, and relatively low cost operations. From an application point of view, emulsion polymers currently are used extensively in waterborne formulations (such as coating, adhesives, and- textiles). The preparation of block copolymers in an emulsion has long been sought for without commercializable results. Although resin emulsification techniques have been used to form emulsions of thermoplastic elastomers (such as polystyrene-b-polydiene-b-polystyrene triblock copolymers), there has been no commercial significance due to high costs and limited chemical composition ranges.
Recently, living free radical polymerization (LFRP) (sometimes referred to as controlled free radical polymerization) has been shown to be a viable technique to prepare a large diversity of block copolymers. However, despite many attempts, none of these techniques have currently lead to commercial processes when applied in emulsion polymerization. Nitroxide mediated LFRP can require temperatures inappropriate for emulsion processes, with nitroxide mini-emulsion processes providing acceptable results, but with drastically limited industrial applicability. ATRP has the main drawback of introducing heavy metals in the final emulsion, which causes environmental concerns and also is detrimental to the latex stability. Several reports have shown that dithioesters in RAFT emulsion polymerization produce substantial retardation, latex that contains high level of grit, and polymer with poor control (e.g., polydispersity of 1.8 and higher) (see, for example,
Journal of Polymer Science: Part A : Polymer Chemistry
, Vol. 38, 3864-3874, 2000). Mini-emulsions have been used to alleviate these difficulties to some extent, but again this very much limits its industrial application. Moreover dithioesters impart a deep pink color to the final emulsions. Other dithiocompounds, such as dithiocarbonates (xanthates) are less prone to grit formation, but they exhibit much less control over polymer characteristics, such as polydispersity than dithioesters, dithiocarbamates and dithiocarbazates. For instance polydispersity of 3 are reported for the emulsion polymerization of butyl acrylate and styrene when dithiocarbonates are used, see. e.g.,
Macromolecular Symposia
, 2000, 150, 23 and
Journal of Polymer Science: Part A: Polymer Chemistry
, Vol. 38, 4206-4217, 2000.
This invention solves these issues by providing control agents that can be easily modified for particular monomers and monomer mixtures in emulsion systems. Certain dithiocarbazates have superior properties in providing good control over the polymer characteristics together with good latex stability and a high rate of polymerization.
SUMMARY OF THE INVENTION
This invention provides control agents that are easy to prepare and economically useful on a commercial scale in emulsion. In general, the control agents of this invention have a N—N bond covalently bonded to a thiocarbonyl moiety, with an optionally substituted double bonded alkenyl moiety. The control agents can be characterized by the general formula:
wherein R
1
is generally any group that is sufficiently labile to be expelled as its free radical form; R
4
is selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, and substituted heteroatom-containing hydrocarbyl, and combinations thereof; and R
7
and R
8
are independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, and substituted heteroatom-containing hydrocarbyl, and combinations thereof.
These control agents are used in an emulsion polymerization process by forming a heterogeneous mixture and subjecting that mixture to polymerization conditions. The heterogeneous mixture comprises the control agent, one or more monomers, water, initiator and optionally surfactant. Polymerization conditions include the pressure, temperature and other process conditions, such a polymerization method (e.g., batch, semi-batch or continuous).
Another aspect of this invention is directed toward multi-functional control agents, so that the control agents may occupy either a central portion of a polymer chain and/or two or more ends of a polymer.
Other aspects of this invention include certain of the control agents, which are novel compounds. Polymerization processes using all of the control agents of this invention and polymers that can be made with the control agents of this invention are additional aspects of this invention. In particular, the control agents of this invention provide living-type kinetics and as such allow for the preparation of desired products, including block polymers, star architectures, grafts and hyperbranched polymers.
Thus, it is an object of this invention to provide novel control agents for a living-type free radical polymerization process.
It is another object of this invention to provide novel compounds, which are useful as control agents in a free radical polymerization process.
It is a further object of this invention to provide a novel system for free radical polymerization of monomers that employs living-type kinetics.
It is still a further object of this invention to polymerize a variety of monomers under commercially acceptable conditions with a family of control agents.
It is yet a further object of this invention to make controlled architecture polymers with a polymerization process that employs a control agent.
Further aspects and objects of this invention will be evident to those of skill in the art upon review of this specification.
DETAILED DESCRIPTION OF THE INVENTION
In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below. A named R group will generally have the structure that is recognized in the art as corresponding to R groups having that name. For the purposes of illustration, representative R groups as enumerated above are defined herein. These definitions are intended to supplement and illustrate, not preclude, the definitions known to those of skill in the art.
It
Chang Han Ting
Charmot Dominique
Huefner Peter
Li Yunxiao
Asinovsky Olga
Seidleck James J.
Symyx Technologies Inc.
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