Process for producing vinyl polymers

Details Process for producing vinyl polymers Process for producing vinyl polymers

1998-02-20

2001-06-05

Teskin, Fred (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S204000, C526S220000, C526S346000

Reexamination Certificate

active

06242546

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of radical polymerization of a vinyl monomer in the presence of a specific substance, and particularly, to a process for efficiently producing a vinyl polymer which has a high molecular weight desirable for practical properties such as mechanical properties, heat resistance and the like, and which has controlled molecular weight distribution.
2. Description of the Prior Art
In conventional radical polymerization, the molecular weight of the produced polymer strongly depends on the polymerization temperature, that is, the molecular weight of the polymer obtained is restricted by the polymerization temperature. Although the polymerization temperature is typically lowered in order to achieve a high molecular weight, decrease in polymerization temperature will elongate the polymerization time and increase the amount of remaining monomer. It becomes, therefore, difficult to effect an efficient production. Similarly, although the polymerization temperature is typically elevated in order to achieve a low molecular weight, increase in polymerization temperature will so accelerate the polymerization rate that is becomes difficult to control the reaction. For these reasons, there is a wide need for a polymerization method of freely controlling the molecular weight in a radical polymerization.
As an attempt to control the molecular weight in a radical polymerization, Tatemoto et al. have reported that radical polymerization of a fluorine-containing monomer such as tetrafluoroethylene proceeds in a manner like living polymerization in the presence of an iodine compound such as CF
3
)
2
CF-I (Shozo Tatermoto,
Koubunshi-Ronbun-Shu,
49, 765 (1992)). Likewise, Otsu et al. have found that, when certain sulfur compounds were used, radical polymerization of styrene or the like occurred under light irradiation and that the extent of conversion and the molecular weight of the produced polymer increased with the time (J. Polym. sci.; part A;
polym. chem.,
32, 2911 (1994)). According to these methods, it is possible to control the molecular weight in a considerably wide range. However, these methods lack universality because they require a special polymerization initiator or a use of limited kinds of monomer.
In anionic polymerization, a precise control of the molecular weight is possible by a polymerization method called living polymerization. Recently, it has also become popular to research a polymerization system which enables living polymerization in radical polymerization. For example, it has been shown in Japanese Patent Publication No. 94-199916 A that, by using a radical polymerization initiator such as benzoly peroxide together with a stable free radical agent such as 2,2,6,6-tetramethyl-piperidinyloxy (TEMPO), a living-like polymerization of styrene can be achieved. According to this method, by selecting a polymerization condition, the molecular weight of the polymer obtained will depend not only on the polymerization temperature but also on the amounts of the initiator and the stable free radical agent used, so that one can control the molecular weight by those amounts to a certain extent.
Thus, when the above method is used, one can obtain a resin having a controlled molecular weight. However, this method has a drawback that the reaction rate in this method is so slow that it takes considerably more time compared with the usual radical polymerization to reach a high extent of conversion. In addition, coloration of the obtained polymer may sometimes occur depending on the reaction condition. Furthermore, TEMPO requires special attention in its handling and storage because it exists in radical state, and it is also very expensive. This method has thus some shortcomings that, for example, it requires more production costs compared with the conventional methods.
In view of such a situation, the present inventors have concentrated their efforts on controlling the radical reaction of vinyl monomer with the aim of increasing productivity and improving practical physical properties of radically polymerized vinyl polymers. In result, we have found by chance a method for obtaining a vinyl polymer having a high molecular weight and a restrained molecular weight distribution while retaining a high polymerization rate by including a specific substituted alkylhydroxylamine in the polymerization system, and thus completed the present invention.
SUMMARY OF THE INVENTION
The present invention provides a process for producing a vinyl polymer characterized in that, in a radical polymerization of a vinyl monomer, a substituted hydroxylamine represented by a general formula:
(in which R
1
and R
2
represent hydrogen, a (substituted) aliphatic hydrocarbon group having one or more carbon atom(s) or an aromatic hydrocarbon group) and/or a general formula:
(in which R
4
and R
4
represent a (substituted) aliphatic hydrocarbon group having one or more carbon atom(s)) is added.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is described below in more detail.
In each of R
1
and R
2
of the general formula (1) of the present invention, the aliphatic hydrocarbon group may include, for example, methyl, ethyl, isopropyl, t-butyl, butyl and the like group, and the aromatic hydrocarbon group may include, for example, phenyl, benzyl and the like group.
Similarly, —R
3
—R
4
— in the general formula (2) may include a divalent (substituted) aliphatic hydrocarbon group corresponding to those groups in the general formula (1) such as —CH
2
CH
2
—, —CH
2
CH
2
CH
2
CH
2
—, —C(CH
2
)
2
CH
2
—C(CH
2
)
2
CH
2
—, —CH
2
CH
2
CH
2
CH
2
—CH
2
CH
2
CH
2
CH
2
—, or the like.
Furthermore, the hydrocarbon groups in the above general formulas (1) and (2) may optionally be substituted, and the substituent may include, for example, an aliphatic hydrocarbon such as a methyl or ethyl group, an aromatic hydrocarbon such as a phenyl group, halogen, a halogenated hydrocarbon, a carbonyl group, a hydroxy group, an amino group, and the like.
In the present invention, the substance represented by the general formula (1) (substituted hydroxylamine) may include dimethylhydroxylamine, diethylhydroxylamine, isopropylhydroxylamine, dibenzylhydroxylamine and the like.
In the present invention, the substance represented by the general formula (2) may include N-hydroxylmaleimide, N-hydroxylsuccinimide, N-hydroxylphthalimide and the like.
In the present invention, although the radical polymerization may be initiated by any of the known methods, for example, using an initiator, heat light or radioactive rays, it is preferable to use an initiator. Although there is no special restriction on the ratio of the substance represented by the above general formulas (1) and (2) (substituted hydroxylamine) used to the radical polymerization initiator, it is preferable to use a mole ratio between the substance represented by the above general formulas (1) and (2) and the radical polymerization initiator at 0.01/1-100/1 (substance represented by the above general formulas (1) and (2)[substituted hydroxylamine]/radical polymerization initiator), more preferably at 0.1/1-10/1, and particularly preferably at 0.1/1-1.0/1. At a mole ratio of the substance represented by the above general formula (1) and (2) to the radical polymerization initiator below 0.01/1, it will be difficult to control the molecular weight and molecular weight distribution, while at a mole ratio above 100/1, the polymerization rate will decrease,
There is no special restriction on the vinyl monomer used in the present invention, and it may be exemplified by aromatic vinyl compounds, &agr;,&bgr;-unsaturated carboxylic acids, &agr;,&bgr;-unsaturated carboxylic acid esters, &agr;, &bgr;-unsaturated carboxylic amides, &agr;,&bgr;-unsaturated nitriles, vinyl carboxylates, vinyl halides, vinylidene halides, conjugated dienes and the like compounds capable of radically polymerizing.
As an aromatic vinyl compound, although styrene is typically used, other aromatic vinyl com

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