JPH0627126B2 - New polymerization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a novel polymerization method that can be used for emulsion polymerization of vinyl monomers, aqueous solution polymerization and the like.

[Background of the Invention]

As an organic radical polymerization initiator, some kinds of azo compounds and peroxides have been conventionally known, but the latter are generally unstable with respect to impact, heating, etc., and may cause a risk of fire, explosion, etc. It is contained. On the other hand, the former, that is, the azo compound, is relatively stable physically and chemically even though it has high activity, and the general self-induced decomposition of peroxide is not seen, and it decomposes accurately in the primary reaction, so it is easy to control. With the advantage that the azo polymerization initiator is used more and more gradually, there is a great demand for a higher performance azo polymerization initiator.

In general, most of those practically used as an azo radical polymerization initiator have a cyano group of an active group substituted on the carbon adjacent to the azo group, but this is not necessarily preferable in terms of toxicity.

One of the most useful water-soluble azo radical polymerization initiators having no cyano group is α, α′-azobis (isobutylamidine) dihydrochloride, which is a high-molecular-weight water-soluble polymer or high-molecular-weight cation. It is widely used for the polymerization of monomers that induce volatile polymers. Further, as a water-soluble azo radical polymerization initiator having a higher activity than this, α,
α'-Azobis (N, N'-dimethyleneisobutylamidine) dihydrochloride is also known.

All of these azo compounds have extremely high activity as a radical polymerization initiator and are useful, but all of them are active at a low temperature, so that they are consumed during the polymerization, and therefore the polymerization is stopped. Often, there is an end decrease. In such a case, the problem that unreacted monomers tend to remain in the polymer inevitably arises, but especially acrylamide is polymerized or copolymerized in a high-concentration aqueous solution to obtain a high-molecular weight polymer, which is used as a residual monomer amount. This problem is extremely serious when it is intended to be used for regulated applications.

Also, these azo compounds are effective in the salt form, but not in the free form.

On the other hand, α, α′-azobis (isobutyramide) is known as a non-salt type and effective azo radical polymerization initiator.

α, α'-Azobis (isobutyramide) is effective as a polymerization initiator for thermal polymerization and photopolymerization, and can reach higher temperatures than the two salt-type and highly active azoamidine-based water-soluble radical polymerization initiators. It has a suitable activation temperature and is used for the polymerization of various polymerizable olefins, vinyl esters, styrene, acrylamide, vinylpyrrolidone, etc. at the same temperature.

However, this polymerization initiator also has a drawback that it is difficult to obtain a high molecular weight polymer because it is active at high temperature (in order to obtain a high molecular weight polymer, the polymerization is initiated at a low temperature, or a catalyst addition amount is used). It is necessary to carry out the polymerization with a small amount, but the polymerization initiator is not highly active enough to achieve the purpose even if the amount used is reduced).

[Object of the Invention]

The present invention provides a novel polymerization method for vinyl monomers capable of producing a higher molecular weight polymer with less residual monomer, avoiding the so-called dead-end phenomenon that often occurs in emulsion polymerization, aqueous solution polymerization and the like. The purpose is to do.

[Structure of Invention]

The present invention relates to a salt of α, α′-azobis (isobutylamide) and α, α′-azobis (isobutylamidine) or α, α′-azobis (N, N′-dimethyleneisobutylamidine) as a polymerization initiator. It is an invention of a method for polymerizing a vinyl-based monomer, which is characterized in that a salt is used in combination.

The present inventors have noted that α, α′-azobis (isobutyramide) is a water-soluble radical polymerization initiator with high temperature and high activity, regardless of whether it is a salt type or a non-salt type. When used in combination with two types of azoamidine-based water-soluble radical polymerization initiators that are highly active at low temperature, the possibility of occurrence of dead-end phenomenon that often occurs when these are used alone is reduced, thereby The inventors have found that it is possible to produce a polymer having a higher purity and a higher molecular weight, by significantly reducing the amount of unreacted monomer remaining, and completed the present invention.

α, α′-azobis (isobutyramide) includes an anhydride and a hydrate (usually dihydrate), and α, α′-azobis (isobutyramide) used in the present invention is an anhydride. , Hydrates, and the results obtained by using either of them are not changed at all.

The optimum activation temperature of α, α'-azobis (isobutyramide) (including hydrates; the same applies hereinafter) is usually about 60 ° C to 90 ° C.
Of α, α′-azobis (isobutylamidine) and α, α′-azobis (N, N′-dimethyleneisobutylamidine) salts, which are usually at room temperature to 70 ° C., respectively.
Since it is in the range of 0 ° C and room temperature to 60 ° C, the polymerization of the present invention is
Usually, it is performed at two temperatures. That is, the polymerization reaction in the first stage is usually at room temperature to 70 ° C, and the polymerization reaction in the second stage is usually about
It is carried out at 60 ° C to 90 ° C. The polymerization time is usually about 2 to 10 hours, though it varies depending on the reaction temperatures of the first and second stages, the presence or absence of other factors affecting the reaction rate, and the type.

Examples of vinyl monomers that can be polymerized or copolymerized by the method of the present invention include various olefins, styrene,
Examples thereof include methyl acrylate, methyl methacrylate, acrylonitrile, acrylamide, vinyl acetate, vinyl pyridine and vinyl pyrrolidone, but it goes without saying that they are not limited to these.

Bulk, solution, emulsion, suspension polymerization is not particularly limited in the selection of the polymerization method, but since the polymerization initiator used in the present invention is water-soluble, emulsion polymerization or aqueous solution polymerization is usually selected, styrene , Acrylonitrile, methyl methacrylate, vinyl acetate, etc., emulsion polymerization in the case of water-insoluble or sparingly soluble polymerizable vinyl monomers, acrylamide,
In the case of water-soluble monomers such as vinylpyrrolidone, aqueous solution polymerization is preferably selected. The emulsifier used for emulsion polymerization is not particularly limited, and various surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, etc., nonionic or anionic type, and necessary In that case, a cationic type such as an alkylammonium salt is appropriately selected according to the kind of the monomer used and the physical properties of the intended polymer. Emulsion polymerization is carried out by polymerizing or copolymerizing a desired monomer with stirring using the polymerization initiator according to the present invention and a predetermined amount of water and an emulsifier. In this case, the produced polymer is usually obtained as an emulsion and is isolated as a finely divided polymer by salting out or freezing. Unlike other polymerization methods such as solution polymerization, in the case of emulsion polymerization, a polymer having a low degree of dispersion can be obtained from styrene, an acrylic monomer or the like by selecting the conditions. Aqueous solution polymerization
It is carried out by dissolving a desired monomer in water and polymerizing or copolymerizing with the polymerization initiator according to the present invention with stirring or standing. In this case, the produced polymer is usually obtained as a high-viscosity solution, and the polymer with high purity can be isolated by distilling off the solvent or adding a precipitating agent. The addition amount of the above-mentioned polymerization initiator used in the polymerization method of the present invention is usually about 0.01 to 1% by weight in the case of emulsion polymerization and about 0.001 in the case of aqueous solution polymerization with respect to the total amount of the monomers. ~ 0.5 wt%, α,
α′-azobis (isobutylamide) and α, α′-azobis (isobutylamidine) salt or α, α′-azobis (N, N′-dimethyleneisobutylamidine) salt,
There is no particular restriction on the usage ratio with and it is arbitrary,
It is appropriately selected depending on other polymerization conditions, monomers used, properties of the intended polymer, and the like. The amount of the emulsifier used for emulsion polymerization is usually about the total amount of the same monomers.
It is about 0.5 to 20% by weight.

According to the novel polymerization method of the present invention, a so-called dead-end phenomenon appears by using two kinds of non-salt type and salt type aqueous azo radical polymerization initiators having no cyano group and having different optimum activation temperatures. It can prevent the possibility, while at the same time significantly reducing the unreacted monomers that are likely to remain in the polymer. The resulting polymer has a high molecular weight and less branching due to the characteristics of the polymerization initiator of the present invention.

Examples will be shown below, but the present invention is not restricted by these examples.

〔Example〕

Examples 1 to 5 and Comparative Examples 1 to 3 Thermometer A 14-necked flask equipped with a nitrogen introduction tube and a stirrer was charged with 200 g of styrene, 4 g of sodium lauryl sulfate and 400 g of distilled water, and uniformly stirred and mixed at 250 rpm. A predetermined amount of a polymerization initiator was added thereto, polymerization was carried out under a nitrogen stream at 50 ° C. for 3 hours, and further aging reaction was carried out at 70 ° C. for 3 hours to obtain a uniform emulsion. The results are shown in Table 1.

Table 1 also shows the results when the polymerization initiator was used alone for comparison.

Are shown respectively.

Examples 6 to 8 Comparative Examples 4 to 6 200 g of acrylamide and 300 g of distilled water were added to a 14-neck separable flask equipped with a thermometer, a nitrogen introducing tube, and a stirrer, and dissolved by stirring. A predetermined amount of a polymerization initiator was added thereto, and the mixture was polymerized at 40 ° C under a nitrogen stream. Polymerization was started after 2 to 5 minutes, and an increase in internal temperature was observed as the polymerization proceeded, but the polymerization was continued at that temperature for 10 hours to obtain a rubbery polymer.

Using the powdered polymer after drying the rubber-like polymer 1
% Aqueous solution viscosity and the amount of residual monomer were determined, and for comparison, the results are shown in Table 2 together with the results when the polymerization initiator was used alone.

[Effects of the Invention] As described above, the present invention provides a novel and effective polymerization method for vinyl monomers. According to the polymerization method of the present invention, it is possible to perform emulsion polymerization, aqueous solution polymerization, and the like. The so-called dead-end phenomenon that often occurs can be avoided and unreacted monomer that tends to remain in the target polymer in such a case can be significantly reduced, and high purity, less branching, and higher molecular weight can be achieved. The polymer has a remarkable effect in that it is obtained.

Claims (1)

[Claims] 1. A salt of α, α′-azobis (isobutylamide) and α, α′-azobis (isobutylamidine) or α, α′-azobis (N, N′-dimethyleneisobutylamidine) as a polymerization initiator. A method for polymerizing a vinyl-based monomer, which is characterized in that it is used in combination with the salt.