Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-02-21
2003-02-04
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S089000, C526S090000, C526S131000, C526S206000, C526S217000, C526S348700
Reexamination Certificate
active
06515083
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing an isobutylene block copolymer. More particuarly, the present invention relates to a process for producing an isobutylene block copolymer by polymerizing a monomer component containing isobutylene as a major monomer and a monomer component whose major monomer is not isobutylene, which process is characterized by use of a specific mixed solvent which has an advantage in industrial handling over prior art solvents, thereby producing a block copolymer giving excellent performances.
BACKGROUND OF THE INVENTION
It is known in the art to produce an isobutylene block copolymer composed of a polymer block comprising isobutylene and a polymer block comprising an aromatic vinyl monomer by cationic polymerization of isobutylene and an aromatic vinyl monomer such as styrene. For example, U.S. Pat. No. 4,946,899 discloses a process for producing an isobutylene block copolymer in a mixed solvent composed of a combination of methyl chloride and methylcyclohexane. Also, Japanese Examined Patent Publication No. 7-59601/1995 discloses a process for producing a block copolymer from isobutylene and styrene in a mixed solvent containing methylene chloride and hexane.
In these manners, a halogenated hydrocarbon having one or two carbon atoms (e.g. methyl chloride or methylene chloride) has been widely used as a solvent for cationic polymerization because, by using it particularly in combination with an aliphatic hydrocarbon, suitable dielectric constant can be provided to stabilize a growing chain end, and to give excellent solubility of the obtained polymer.
However, such a halogenated hydrocarbon having one or two carbon atoms has disadvantageous problems; e.g. it is difficult to handle therewith, and its discharge to the environment cannot be prevented in conventional treatment methods and involves use of a large apparatus or installation, thereby raising a problem of increased costs of manufacturing. For example, methylene chloride has high solubility in water of 2.0% (20° C.), and recovery or separation of methylene chloride dissolved in water also involves use of a large apparatus, leading to increased costs. Therefore, these halogenated hydrocarbons having one or two carbon atoms are disadvantageous solvents for use in a large scale polymerization such as in industrial production.
On the other hand, there has been an attempt to use singly a halogenated hydrocarbon having three or more carbon atoms as a cationic polymerization solvent for producing an isobutylene block copolymer. For example, Faust et al. have made an attempt of the production of an isobutylene block copolymer composed of an isobutylene polymer block and a styrene polymer block by using 1-chlorobutane (n-butyl chloride) as a polymerization solvent [J. Macromol. Sci-Pure Appl. Chem., A33(3), 305(1996)]. However since involves single use of a halogenated hydrocarbon, it is difficult to adjust the dielectric constant of the polymerization solvent system, so that the concentration of a Lewis acid or the like is limited for producing a good isobutylene block copolymer and the polymerization concentration cannot be raised due to insufficient solubility of the block copolymer.
The present invention has, in view of these circumstanccs, the object to provide a process for producing an isobutylene block copolymer giving good performance, by the use of a mixed solvent which has an advantage in industrial handling over prior art, in particular, over a halogenated hydrocarbon having one or two carbon atoms.
The isobutylene block copolymer obtained according to the present invention can have a narrow molecular weight distribution and a high ratio of block copolymer, which are as much as those obtained using the halogenated hydrocarbon having one or two carbon atoms.
SUMMARY OF THE INVENTION
The present invention provides a process for producing an isobutylene block copolymer, which comprises performing cationic polymerization of a monomer component containing isobutylene as a major monomer for a polymer block composed of isobutylene as a major monomer and a monomer component whose major monomer is not isobutylene for a polymer block in which major monomer is not isobutylene in the presence of a compound represented by the following general formula (1)
wherein plural R
1
are the same or different and represent a hydrogen atom or a monovalent hydrocarbon group having one to six carbon atoms; R
2
represents a monovalent or polyvalent aromatic hydrocarbon group or a monovalent or polyvalent aliphatic hydrocarbon group; X represents a halogen atom, an alkoxyl group having one to six carbon atoms, or an acyloxyl group having one to six carbon atoms; n is equal to a valence number of R
2
and represents an integer of one to six; and plural X may be the same or different if n is two or more:
wherein said polymerization is carried out in a mixed solvent containing a monohalogenated hydrocarbon solvent and a non-halogenated hydrocarbon solvent, said monohalogenated hydrocarbon solvent comprising a primary monohalogenated hydrocarbon having three to eight carbon atoms and/or a secondary monohalogenated hydrocarbon having three to eight carbon atoms, said non-halogenated hydrocarbon solvent comprising an aliphatic hydrocarbon and/or an aromatic hydrocarbon.
DETAILED DESCRIPTION OF INVENTION
According to the present invention, a mixed solvent of a monohalogenated hydrocarbon solvent containing a primary monohalogenated hydrocarbon having three to eight carbon atoms and/or a secondary monohalogenated hydrocarbon having three to eight carbon atoms, and a non-halogenated hydrocarbon solvent containing an aliphatic hydrocarbon and/or an aromatic hydrocarbon is used as a cationic polymerization solvent for producing an isobutylene block copolymer.
The inventors of the present invention have selected primary and/or secondary monohalogenated hydrocarbons having three to eight carbon atoms as a substitution for halogenated hydrocarbons having one or two carbon atoms used in the prior art processes because of the reasons such as follows.
(1) Tertiary halogenated hydrocarbons act as a polymerization initiator, causing side reactions by production of a tertiary cation from the solvent itself as well as the objective original initiation reaction, so that they are not preferable as a cationic polymerization solvent.
(2) The less the halogen content in the halogenated hydrocarbon (i.e. ratio of halogen weight in a molecule) is, the lower its solubility in water is and further the easier it is to decompose them. Also, if the halogenated hydrocarbon has two or less carbon atoms, the solubility in water is high, and hence it is not preferable. (The solubility in water is 2.0 wt % for methylene chloride, 0.869 wt % for 1,2-dichloroethane, 0.271 wt % for 1-chloropropane, 0.08 wt % for 1-chlorobutane, and 0.02 wt % for 1-chloropentane.)
(3) If the halogenated hydrocarbon has nine or more carbon atoms, its boiling point is high, so that a lot of energy is required in removing the solvent by distillation, thereby leading to increased costs.
(4) Monohalogenated hydrocarbons have a lower specific weight because their halogen content in a molecule is smaller than that of polyhalogenated hydrocarbons. Therefore, use of a monohalogenated hydrocarbon increase the specific weight difference between an organic phase and an aqueous phase in a water-washing step, making the separation easy.
The primary monohalogenated hydrocarbon having three to eight carbon atoms and the secondary monohalogenated hydrocarbon having three to eight carbon atoms to be used in the present invention are not specifically limited. Examples of such primary and secondary monohalogenated hydrocarbons having three to eight hydrocarbons include 1-chloropropane, 1-chloro-2-methylpropane, 1-chlorobutane, 1-chloro-2-methylbutane, 1-chloro-3-methylbutane, 1-chloro-2,2-dimethylbutane, 1-chloro-3,3-dimethylbutane, 1-chloro-2,3-dimethylbutane, 1-chloropentane, 1-chloro-2-methylpentane, 1-chloro-3-methylpentane, 1-chloro-4-met
Aoyama Taizo
Hiiro Tomoki
Nakata Toshinobu
Ozawa Shinji
Connolly Bove & Lodge & Hutz LLP
Kaneka Corporation
Mullis Jeffrey
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