JPS6250304A - Novel polymerization process - Google Patents

Abstract

PURPOSE:To obtain a high-MW polymer of a low content of residual monomer, by polymerizing a vinyl monomer by using a combination of alpha,alpha'-azobis(isobutyramide) with either of specified two azoamidine compounds as a polymerization initiator. CONSTITUTION:A vinyl monomer is polymerized by using a combination of alpha,alpha'-azobis(isobutyramide) with a salt of alpha,alpha'-azobis(isobutyramidine) or a salt of alpha,alpha'-azobis(N,N'-dimethyleneisobutyramidine) as a polymerization initiator. The polymerization is usually carried out at temperatures of two levels since the optimum activation temperature of alpha,alpha'-azobis(isobutyramide) is usually about 60-90 deg.C while those of the salt of alpha,alpha'-azobis(isobutyramidine) and the salt of alpha,alpha'-azobis(N,N'-dimethyleneisobutyramidine), are usually room temperature to 70 deg.C and room temperature to 60 deg.C, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel polymerization method II) that is utilized for emulsion polymerization, aqueous solution polymerization, etc. of vinyl monomers.

[Background of the invention]

Conventionally, azo compounds and peroxides are known as organic radical polymerization initiators, but the latter are generally unstable against impact, heating, etc., and carry the risk of fire, explosion, etc. I'm reading. On the other hand, the former, i.e., azo compounds, are relatively stable physically and chemically even if they are highly active, and do not exhibit the self-induced decomposition that is common with peroxides, but decompose precisely through a first-order reaction, making them easy to control. Due to these advantages, azo polymerization initiators are gradually becoming more widely used, and there is a great demand for even higher performance azo polymerization initiators.

In general, many of the azo-based radical polymerization initiators that are put into practical use have a cyano group as an active group substituted on the carbon adjacent to the azo group, but this is not necessarily preferable in terms of toxicity and the like.

One of the most useful water-soluble azo radical polymerization initiators that do not have a cyan group is α,α′-azobis(
isobutyramidine) dihydrochloride, which is widely used in the polymerization of heptamers to induce high molecular weight water-soluble polymers and high molecular weight cationic polymers. In addition, α, α′
-Azobis(N,N'-dimethyleneisobutyramidine) dil5JjJ is also known.

All of these azo compounds have extremely high activity and are useful as radical polymerization initiators, but since they are all low-temperature active, they are consumed during polymerization, which causes the polymerization to stop. This often results in so-called dead-second reduction. In such cases, the problem inevitably arises that unreacted polymers tend to remain in the polymer, but especially when acrylamide is used in a high-strength aqueous solution, it is difficult to copolymerize it to obtain a high molecular weight polymer. This problem is extremely serious when it is intended to be used in applications where the amount of residual monomer is regulated.

Also, while these azo compounds are effective in their salt form, they are not effective in their 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, highly active azoamidine-based water-soluble radical polymerization initiators. It has an appropriate activation temperature and can be used to polymerize various polymerizable olefins, vinyl esters, styrene, acrylamide, vinylpyrrolidone, etc. at the same temperature.

However, this polymerization initiator also has the disadvantage that it is difficult to obtain a high molecular weight polymer due to its high temperature activity (in order to obtain a high molecular weight polymer, polymerization must be initiated at a low temperature or catalyst addition 15 However, the present polymerization initiator is not so highly active that the purpose can be achieved even if the amount used is reduced).

[Purpose of the invention]

The present invention is a novel vinyl yarn threading material that avoids the so-called dead-end phenomenon that often occurs in emulsion polymerization, aqueous solution polymerization, etc., and can produce higher molecular weight polymers with less residual threading. The purpose is to provide a polymerization method.

[Structure of the invention]

The present invention uses a salt of α,α′-azobis(isobutyramide) and α,α°-azobis(isobutyramidine) or α,α′-azobis(N,N′-dimethyleneisobutyramidine) as a polymerization initiator. This is an invention of a method for polymerizing a vinyl yarn spool, which is characterized in that a salt is used in combination with a salt.

The present inventors focused on the fact that α,α'-azobis(isobutyramide) is a water-soluble radical polymerization initiator with high activity at high temperatures, regardless of whether it is a 5g type or a non-salt type. By using in combination with two types of azoamidine-based water-soluble radical polymerization initiators that are highly active at low temperatures, the possibility of the dead-end phenomenon that often occurs when these are used alone is reduced, and thereby The present invention was completed based on the discovery that it is possible to significantly reduce the amount of unreacted monomer remaining and produce a polymer with higher purity and higher molecular weight.

α,α′-Azobis(isobutyramide) has anhydrous form and hydrated form (usually dihydrate), but α,α′-azobis(isobutyramide) used in the present invention is anhydrous form, Any of the hydrates may be used, and the results obtained will not change at all no matter which one is used.

The optimum activation temperature of α, α′-azobis(isobutyramide) (including hydrates, the same shall apply hereinafter) is usually about 60°C to 9°C.
0℃, and those of α,α′-azobis(isobutyramidine) salt and α,α′-azobis(N,N′-dimethyleneisobutyramidine) salt are usually room temperature to 70℃ and room temperature, respectively. -60°C, the polymerizations of the present invention are usually carried out in two stages. That is, the first stage polymerization reaction is usually carried out at room temperature to 70°C, and the second stage polymerization reaction is usually carried out at about 60°C to 90°C. Although it depends on the presence or absence and type of factors, approximately 2 to 10 hours is usually sufficient.

Examples of vinyl yarn threads that can be polymerized or copolymerized by the method of the present invention include various olefins, styrene,
Examples include, but are not limited to, methyl acrylate, methyl methacrylate, acrylonitrile, acrylamide, vinyl pyridine, vinyl pyridine, and vinyl pyrrolidone.

There is no particular restriction on the selection of the polymerization method, such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc. However, since the polymerization initiators used in the present invention are all water-soluble, emulsion polymerization or aqueous solution polymerization is usually selected. Emulsion polymerization is used for polymerizable vinyl monomers that are insoluble or poorly soluble in water, such as acrylonitrile, methyl methacrylate, and vinyl acetate.
In the case of water-soluble monomers such as vinylpyrrolidone, aqueous solution polymerization is preferably selected. There are no particular restrictions on the emulsifier used in emulsion polymerization, and various surfactants such as nonionic or anionic surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, etc. If so, a cationic one such as an alkyl ammonium salt is selected as appropriate depending on the type of hepatomer used and the physical properties of the desired polymer. Emulsion polymerization is carried out by subjecting a desired monomer to a polymerization or copolymerization reaction using the polymerization initiator according to the present invention, a predetermined amount of water, and an emulsifier while stirring. In this case, the produced polymer is usually obtained as an emulsion and isolated as a finely powdered polymer by salting out or freezing. Unlike other polymerization methods such as solution polymerization, in the case of emulsion polymerization, it is possible to obtain a polymer with a small degree of dispersion from styrene, acrylic monomers, etc. by selecting one condition. Aqueous solution polymerization is
This is carried out by dissolving a desired monomer in water and polymerizing or copolymerizing it using the polymerization initiator according to the present invention while stirring or standing still. In this case, the produced polymer is usually obtained as a highly viscous solution, and a highly pure polymer can be isolated by distilling off the solvent or adding a precipitant. The amount of the polymerization initiator used is usually about 0.01 to 1% by weight in total in the case of emulsion polymerization based on the total amount of monomers, and about 0.01 to 1% by weight in total in the case of aqueous solution polymerization. It is about 5% by weight, and α,α°-azobis(isobutyramide) and α
, a salt of α′-azobis(isobutyramidine) or α,
There is no particular restriction on the proportion of α′-azobis(N,N′-dimethyleneisobutyramidine) salt used.
It is optional and is appropriately selected depending on other polymerization conditions, the polymer used, the properties of the desired polymer, etc. The amount of emulsifier used in emulsion polymerization is usually about 0.5 to 20% by weight based on the total amount of the monomers.

According to the novel polymerization method of the present invention, by using two types of aqueous radical polymerization initiators, a non-salt type and a salt type, which do not have cyano groups and have different optimum activation temperatures, the appearance of the so-called dead-end phenomenon can be prevented. At the same time, unreacted monomers, which tend to remain in the polymer in such cases, can be significantly reduced. Further, the resulting polymer has a high molecular weight and little branching due to the characteristics of the polymerization initiator of the present invention.

Examples are shown below, but the present invention is not limited in any way by these examples.

〔Example〕

Examples 1 to 5, Comparative Examples 1 to 3 Thermometer 200 g of styrene, 4 g of sodium lauryl sulfate,
400 g of distilled water was added and mixed uniformly by stirring at 250 rp+n. A predetermined amount of a polymerization initiator was added thereto, polymerization was carried out at 50°C for 3 hours under a nitrogen stream, and further aging reaction was carried out at 70°C for 3 hours to obtain a homogeneous emulsion. Table 1 shows the results.
Shown below.

For comparison, Table 1 also shows the results obtained when a polymerization initiator was used alone.

Table 1 However, AIBA: α,α′-azobis(isobutyramide) V-5 (α,α′-azobisisobutyramidine)
Dihydrochloride VA-044: Shows a, a'-7zobis(N,N'-dimethyleneisobutyramidine) dihydrochloride, respectively.

Examples 6 to 8 Comparative Examples 4 to 6 200 g of acrylamide and 300 g of distilled water were placed in a 1-cross 4-neck separable flask equipped with a thermometer, nitrogen inlet tube, and stirrer.
g and stirred to dissolve. A predetermined amount of a polymerization initiator was added to this, and polymerization was carried out in a nitrogen stream at 40°C.

Polymerization started after 2 to 5 minutes, and an increase in internal temperature was observed as the polymerization proceeded, but the polymerization continued at that temperature for 10 hours to obtain a rubbery polymer.

The solution viscosity and residual monomer amount of a 1% aqueous solution were determined using the powdered polymer after drying the bipedal rubber-like polymer, and the results are shown in Table 2 along with the results when a polymerization initiator was used alone for comparison. show.

1B type rotational viscometer rotor No. 3 8 rpm 25°
[Effects of the Invention] As described above, the present invention provides a new and effective polymerization method for vinyl monomers, and according to the polymerization method of the present invention, emulsion polymerization and aqueous solution polymerization It is possible to avoid the so-called dead-end phenomenon that often occurs in polymers, etc., and to significantly reduce unreacted particles that tend to remain in the target polymer in such cases. This has a remarkable effect in that a polymer with a higher molecular weight and a lower molecular weight can be obtained.

Claims (1)

[Claims] (1) Salt of α,α′-azobis(isobutyramide) and α,α′-azobis(isobutyramidine) or salt of α,α′-azobis(N,N′-dimethyleneisobutyramidine) as a polymerization initiator A method for polymerizing vinyl monomers, characterized by using the above methods in combination.