JP3203765B2 - Polymerization of styrene and its derivatives - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polymerizing styrene and a derivative thereof, which can obtain a soluble high molecular weight polymer free of a catalyst such as a radical initiator and an inorganic salt from a monomer of styrene or a derivative thereof.

[0002]

2. Description of the Related Art Plasma-initiated polymerization is used in various fields because a polymer can be obtained without destroying the chemical structure of a monomer. Is used for polymerization of vinyl monomers.

[0003] In this plasma-initiated polymerization method, the vapor of a liquid, a solid monomer or an aqueous solution or an emulsion thereof is added to a vapor under reduced pressure (under a pressure of about 0.01 to 100 mmHg) for 10 to 5 hours.
By applying a voltage of 00 W, an ionized gas plasma is generated, a polymerization active species is generated by the ionized gas plasma, and the polymerization active species generated in the plasma is brought into contact with a liquid surface or a solid surface, thereby forming a liquid or a solid. After the polymerization reaction starts in the solid monomer, after a predetermined time has elapsed, the contact of the partially polymerized monomer with the ionized gas plasma before reaching the final molecular weight is stopped, and the partially polymerized monomer is post-polymerized in the absence of the ionized gas plasma. It is a hurry. That is, only the polymerization initiation reaction is performed in the gas phase, and the subsequent growth and termination reactions are performed in the condensed phase (liquid phase or solid phase).

This plasma-initiated polymerization method is described, for example, in Nagata et al., J. Polym. Sci, Polym. Lett.
Ed. , 16, p309 (1978) "," D. Johnson et al., Macromolecules, 14, p118 (198).
1) ”, JP-B-59-25807, JP-B-54-11848.
As described in JP-A No. 3 (1993) -1994, after the plasma is brought into contact with the plasma for a short time, the post-polymerization occurs in a living manner. In contrast, a soluble high-molecular polymer can be obtained while maintaining the chemical structure of the starting monomer, so that the reaction analysis is easy. Further, it has characteristics such as non-catalytic polymerization free of impurities such as a radical initiator and an inorganic salt, and therefore, development of various functional polymer compounds is expected.

However, the conventional plasma-initiated polymerization method is not effective for polymerization of all monomers, for example, acrylonitrile (AN), styrene (St), vinyl acetate, N-vinyl carbazole, sodium styrene sulfonate. , N-vinylpyrrolidone, vinyl sulfonic acid, etc. are a monomer alone, a monomer solution,
It has been reported that polymerization does not start by plasma in any state of the monomer emulsion (edited by Yoshihito Nagata, Plasma Polymerization, p218, Tokyo Kagaku Dojin, Nagata, Takase, Mizumoto,
The Chemical Society of Japan No. 10, p1685-1692, 19
84), especially styrene, was said to have a polymerization inhibiting effect.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of polymerizing styrene and its derivatives, which could not be polymerized by a conventional plasma-initiated polymerization method, by a plasma-initiated polymerization method.

[0007]

The present inventors have conducted intensive studies to achieve the above object, and have found that at least one monomer selected from styrene and its derivative monomers is dissolved in an aqueous medium containing an emulsifier. After the polymerization is started by contacting with plasma, the post-polymerization is performed in the absence of plasma, whereby plasma-initiated polymerization of styrene and its derivatives, which has been considered impossible, can be performed. Finding that high-molecular-weight polymers can be produced safely, in large quantities, efficiently and economically with energy savings,
The present invention has been made.

Hereinafter, the present invention will be described in more detail. In the present invention, polymerization is initiated by contacting at least one monomer selected from styrene and its derivative monomer with plasma in an aqueous medium containing an emulsifier, The post-polymerization is performed in the absence of plasma.

Here, the above-mentioned monomers include styrene, methylstyrene, sodium styrenesulfonate and the like.

[0010] These monomers are brought into contact with the plasma in the form of an aqueous medium containing an emulsifier, that is, in the form of an emulsified solution. The emulsifier for emulsifying the monomer may be any one that uniformly emulsifies the monomer in an aqueous medium, and is not particularly limited. Examples thereof include alkali soap, organic amine soap, higher alcohols and sulfates of aromatic alcohols. Surfactants and sodium polystyrene sulfonate,
Polymer compounds such as partially saponified polyvinyl acetate and polyether are preferred. Further, a monomer containing a hydrophilic group and a hydrophobic group in one molecule such as hydroxyethyl methacrylate can also be used.

The amount of the emulsifier used is not particularly limited. However, in order to emulsify the monomer in an aqueous medium, it is usually preferable that the amount be 0.1% (% by weight, hereinafter the same) or more based on the whole charged amount.

Examples of the aqueous medium include water, a mixture of water and an alcohol such as methanol, ethanol and butanol, and a mixture of water and a ketone such as acetone and methyl ethyl ketone. It is preferable to use water alone. . If an aqueous medium, especially water, is used, the rate of polymerization will be significantly higher.

The monomer concentration in the aqueous medium is usually 0.1 to
90%, preferably 1 to 65%, more preferably 10 to
60%. Generally, in the case of an aqueous medium, a monomer concentration of 5
When the content is 0%, the polymerization rate is maximized, and the polymerization rate tends to decrease when the polymerization rate is lower or higher.

The plasma initiated polymerization in the present invention is one that initiates polymerization using a non-equilibrium ionized gas plasma and completes most of the polymerization in the absence of the plasma. The generation of the ionized gas plasma can be performed by any of the methods for generating such a plasma. The method of applying voltage can be roughly divided into two types, DC and AC.
As such, the frequency can be set in any region where an ionized gas plasma can be generated.

In the polymerization apparatus, it is preferable that oxygen is removed from the system in which the plasma is generated, and any method can be used as the oxygen removing means as long as it can remove oxygen from the system. , For example, freezing, degassing,
A method of bubbling with an inert gas such as Ar or He or a general-purpose gas such as N ₂ can be used.

The deaeration is performed at 20 to 10 ^-5 Torr, especially at 1 to 1 Torr.
It is preferable to perform the process up to 0 ^-3 Torr. Pressure is 20To
If the pressure exceeds rr, a uniform and stable ionized gas plasma may not be obtained, and the pressure may be 10 ^-5 To.
If it is less than rr, it may not be economical and efficient, and it may be difficult to obtain ionized gas plasma. At that time, if necessary, it is frozen and degassed with a refrigerant such as liquid nitrogen. The means for degassing is not limited to the method described above.

The input energy for generating the above-mentioned ionized gas plasma in the above-mentioned monomer cannot be determined unconditionally depending on the form of the apparatus, but generally 1 to 3 × 10 ⁴ J is sufficient. After being brought into contact with the plasma, the emulsified solution is allowed to stand at a certain temperature for several hours to perform post-polymerization. The polymerization rate during the plasma initiation period is significantly smaller than the post-polymerization rate and usually does not exceed 2%. The post-polymerization time is not particularly limited because it varies depending on the type of the monomer. The post-polymerization temperature is also not limited as it varies depending on the type of the monomer, but is usually preferably 30 to 90 ° C, particularly preferably 40 to 80 ° C. If the temperature is lower than 0 ° C., post-polymerization may not be able to proceed in the above-mentioned range of the input energy.

The plasma polymerization apparatus used in the present invention is not particularly limited. For example, an apparatus as shown in FIGS. 1 and 2 can be used. In FIG.
Reference numeral 1 denotes a reaction vessel provided with an internal electrode 2 and external electrodes 3 and 3. An AC voltage having a frequency of 5 kHz is supplied from a power source 4 to the internal electrode 2.
To apply a plasma treatment to the styrene monomer solution 5. The air inside the reaction vessel 1 is frozen by liquid nitrogen 6 and deaerated by sucking it with a pump (not shown). In this figure, 7 is a ground wire, and 8 is a vacuum gauge.

FIG. 2 shows a reaction vessel 9 having external electrodes 3 and 3.
And a frequency of 13.56 MHZ from the power supply 4.
By applying an AC voltage of z to one of the external electrodes 3, the styrene monomer solution 5 is plasma-treated. The degassing of the reaction vessel 9 is performed in the same manner as in the apparatus shown in FIG.

[0020]

The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 In a 100 ml separable flask, 4.6 g of styrene, 15.4 g of water and 0.8 g of dodecylbenzenesulfonic acid (DBS) as an emulsifier were mixed and emulsified, and the same as shown in FIG. 0.1T
After freezing and degassing to orr, the ionized gas plasma was contacted at a frequency of 13.56 MHz (radio wave) and a power of 50 W, and the contact time was changed between 0 and 200 seconds. Then, in each case, post-polymerization was carried out for 7 hours while stirring in a thermostat at 60 ° C.

Thereafter, the emulsified solution was precipitated in a large amount of methanol to remove water, DBS and unreacted styrene, dried under vacuum, weighed, and the polymerization rate was determined from the yield (conversion). The results are shown in FIG.

Example 2 Styrene was polymerized in the same manner as in Example 1 except that the post-polymerization temperature was changed to 50 ° C., and the same measurement was carried out. The results are shown in FIG.

Example 3 Styrene was polymerized in the same manner as in Example 1 except that the post-polymerization temperature was changed to 40 ° C., and the same measurement was carried out. The results are shown in FIG.

Example 4 Styrene was polymerized in the same manner as in Example 1 except that the post-polymerization temperature was changed to 30 ° C., and the same measurement was carried out. The result is indicated by D in FIG.

Comparative Example 1 In a 100-ml separable flask, 4.6 g of styrene, 15.4 g of water, 0.8 g of DBS as an emulsifier, and 6 mg of potassium persulfate as a radical initiator were mixed and emulsified, and then frozen and defrosted to 0.1 Torr. After that, polymerization was carried out for 7 hours while stirring in a constant temperature bath at 40 ° C. Thereafter, the same operation as in Example 1 was performed, and the same measurement was performed. The result is indicated by E in FIG.

[0027]

According to the present invention, styrene and styrene derivative monomers which have not been polymerized by plasma-initiated polymerization can be polymerized by performing post-polymerization in a predetermined temperature range. For example, it is possible to obtain an ultrahigh molecular weight polymer which is soluble in a solvent having various characteristics of the plasma-initiated polymerization method, such as containing no impurities such as a suspending agent, a radical initiator, and an inorganic salt.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a plasma polymerization apparatus used in the present invention.

FIG. 2 is a sectional view showing another example of the plasma polymerization apparatus used in the present invention.

FIG. 3 is a graph showing the relationship between the plasma irradiation time and the polymerization rate of styrene in Examples of the present invention and Comparative Examples.

[Explanation of symbols]

 2 Internal electrode 3 External electrode 4 Styrene monomer solution

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yoshihito Nagata 124-1, Sumiyoshi, Tomobe-cho, Nishi-Ibaraki-gun, Ibaraki Prefecture (56) References JP-A-60-71615 (JP, A) . ^7, DB name) C08F 2/52

Claims (1)

(57) [Claims] 1. A method comprising: initiating polymerization by contacting at least one monomer selected from styrene and its derivative monomer with plasma in an aqueous medium containing an emulsifier, and then performing post-polymerization in the absence of plasma. Characteristic polymerization method of styrene and its derivatives.