JPS63309501A - Production of water-soluble polymer - Google Patents

Abstract

PURPOSE:To obtain the title polymer low in a residual monomer content, nonpollutive to environments and useful as, e.g., a flocculant, by photopolymerizing a water-soluble monomer in a vessel so that a gel-like poly mer of a specified thickness may be obtained and polymerizing, by reirradiation with light, monomer remaining on the surface in contact with the vessel. CONSTITUTION:A water-soluble monomer such as dimethylaminoethyl (meth) acrylate (salt) is polymerized in the presence of 10-2,000ppm of a photopolymerization initiator such as benzoin ethyl ether by irradiating with light at a wavelength of 300-500nm from a high-pressure mercury vapor lamp at an irradiation intensity of 0.1-20W/m<2> in, e.g., a continuous polymerization vessel formed by providing 50 mm-high or below weirs on both sides of an endless belt in an inert gas atmosphere to obtain a gel-like polymer of water-soluble monomer of a thickness <=50mm. This polymer is withdrawn from the vessel, and the surface on the side in contact with the inside wall of the vessel is irradiated with light under conditions more severe than those in the preceding irradiation and satisfying the relationship of the formula [wherein W is the irradiation intensity (kW/m<2>) of the lamp, and T is time (min)].

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a water-soluble polymer by photopolymerization, and more particularly to a method for producing a water-soluble polymer with a small amount of residual monomer by photopolymerization. .

Water-soluble polymers are widely used in many industrial fields,
It occupies an important position in industry. Typical examples of its uses include solid-liquid separation in manufacturing processes, coagulation-sedimentation agents in industrial wastewater treatment, dewatering aids for sludge in sewage and frozen ground treatment, paper-making agents such as paper strength enhancers, and filler retention improvers; Examples include soil conditioners, thickeners, and oil recovery agents.

[Prior Art] Various methods are used to produce water-soluble polymers, but water-soluble polymerization is most commonly used.

As a method for industrially producing aqueous solution polymerization,
-126494 publication and JP-A-53-133287
The publication discloses a method of obtaining a sheet in the form of photopolymerization.

[Problems to be Solved by the Invention] However, when a water-soluble polymer is produced by the above method, unreacted monomers are left on the bottom surface of the polymer in contact with the inner wall of the polymerization vessel, particularly on the surface of the polymer in contact with the inner wall of the weir. A large amount remained, and it was not possible to obtain a product with a small amount of unreacted monomer. If there is a large amount of residual monomer in the product, for example, if it is used as a flocculant, it will be mixed into wastewater after the sludge flocculation treatment.
There is a problem of polluting the environment. Additionally, since the surface is sticky, there is a problem of it adhering to the device.

[Means for Solving the Problems] The present inventors have completed the present invention as a result of intensive research in view of the above-mentioned prior art.

The method for producing the water-soluble polymer of the present invention is as follows.

(1) A water-soluble monomer solution containing a photopolymerization initiator is polymerized under light irradiation in a container so that the layer thickness of the water-soluble monomer solution is 50 mm or less. A gel-like polymer is obtained, and (11) the surface of the gel-like polymer in contact with the inner wall of the container is irradiated with light again to polymerize the remaining monomers on the surface of the gel-like polymer.

The present invention consists of two steps. In the first step, a water-soluble monomer solution is irradiated with light to perform a polymerization reaction to obtain a gel-like polymer, and in the second step, the resulting gel-like polymer is The monomers remaining on the surface of the polymer in contact with the container are polymerized by light irradiation again, thereby reducing the amount of monomers remaining on the surface of the polymer.

First, any water-soluble monomer used in the first step may be used as long as it can produce a water-soluble polymer.

Examples of water-soluble monomers include nonionic monomers such as acrylamide, methacrylamide, dimethylacrylamide, and hydroxyethyl methacrylate; dimethylaminoethyl (meth)acrylate and its salts; diethylaminoethyl (meth)acrylate and its salts; - Dimethylamine - 2-hydroxypropyl (meth)acrylate and its salts, dimethylaminopropyl (meth)acrylamide and its salts, and the above tertiary amines are quaternized with methyl chloride, methyl bromide, methyl iodite, dimethyl sulfur, etc. cationic monomers such as dimethyldiallylammonium salts, diethyldiallylammonium salts, (meth)acrylic acid and its salts,
Examples include anionic monomers such as acrylamide methylpropanesulfonic acid and its salts.

These monomers can be used alone or in combination of two or more. If necessary, other monomers such as acrylonitrile, vinyl acetate, etc. may also be added to the extent that they do not impede the purpose of the present invention.

These monomers are dissolved in water by heating and stirring as necessary to prepare a monomer solution. The concentration is not particularly limited, but is 25% to 90% by weight, preferably 40% by weight.
That's all. If the monomer turbidity is low, the costs for drying and transportation are high and it takes a long time to obtain a high molecular weight polymer. On the other hand, if the monomer concentration is too high, the homogeneity of the system cannot be maintained.

Further, the pH of the monomer solution can be adjusted as appropriate to a pH suitable for the polymerization reaction.

As the photopolymerization initiator used for polymerizing the water-soluble monomer, generally known photopolymerization initiators can be used. Examples include benzoin, benzoin alkyl ether, and anthraquinone derivatives. The amount of photopolymerization initiator used is 10 to 2000 pp per water-soluble monomer solution.
If the amount of the photopolymerization initiator used is outside the above range, the polymerization may take an extremely long time, the resulting polymer may be colored, or its water solubility may be reduced.

The water-soluble polymer solution containing the above-mentioned photopolymerization initiator is kept in a reaction vessel such that the liquid layer has a thickness of 50 mm or less.

If the thickness of the liquid layer exceeds 50 m<2>, it becomes difficult to control the temperature in the polymerization process, and sufficient light irradiation cannot be performed, making it impossible to obtain a highly uniform polymer.

The container used for the polymerization reaction is not particularly limited as long as the water-soluble monomer solution can form a layer of 50 mm or less, but it may be a box-shaped container with a weir of 50 mm or less, or both ends of an endless belt. Continuous claw mold containers etc. with a weir of 5001111 or less can be preferably used. The thickness may be set to 50 mm or less using a light-transmissive film bag or the like.

The water-soluble monomer solution containing the photopolymerization initiator is irradiated with light in the reaction vessel described above to cause a polymerization reaction (hereinafter referred to as the main polymerization reaction). In order to avoid contamination with atmospheric oxygen, which is often the case, the reaction is carried out in an atmosphere of an inert gas such as nitrogen, or the opening of the container, which comes in contact with the atmosphere, is covered with a light-transmitting film or the like.

The light used in the main polymerization reaction has various wavelengths depending on the combination with the photopolymerization initiator.
Light with a wavelength in the range of 00 to 500 nm is desirable, 300 nm
Light sources that provide light of ~500 nm include high-pressure mercury lamps,
Ultra-high pressure mercury lamp.

Examples include fluorescent chemical lamps. A particularly preferred light source is a fluorescent chemical lamp manufactured by Mitsubishi Electric.

Light irradiation with an irradiation intensity of 0.1 to 20 W/m' for 5 to 200
The main polymerization reaction is completed and a gel-like polymer is obtained by carrying out the polymerization for 5 to 60 minutes at 10 to 100 W/m'.

In addition, the irradiation intensity in this specification is provided by Tokyo Kogaku Kikai ■
This was measured using UVR-4.

Next, the second step will be described.

After the main polymerization reaction is completed, light is irradiated again to the surface of the polymer, especially the surface with more residual monomer, that is, the surface in contact with the inner wall of the container.

In the case of polymerization reaction on the polymer surface due to light irradiation again,
Unlike the main polymerization reaction, the atmosphere is not particularly selected and oxygen may be mixed. The light irradiation at this time was under stronger irradiation conditions than during the main polymerization reaction, and the following formula: % formula % [where W represents the irradiation intensity of the lamp (kW/m''),
It is preferable that T be within the range indicated by J, which represents time (minutes).

The amount of light irradiation is O, l (kW・win/
m') or more is required, and considering production efficiency, 0,
It is more preferable to set it to 2 (kWa ll1n/m'') or more.

Moreover, if the irradiation is carried out excessively, the irradiated area will be colored and a large amount of insolubilized substances will be generated. In order not to substantially change the properties of the polymer, the irradiation amount is 10 (kW・win/rn'')
The amount of irradiation required to make the amount of residual monomer on the surface equal to the amount of residual monomer in the internal polymer is 5 (
It is sufficient to use less than kW (min/m'').

The light irradiated to the polymer at this time is preferably ultraviolet light, and the wavelength of the ultraviolet lamp is sufficient in the same range as the main polymerization step, but fluorescent chemical lamps require a long wavelength to obtain the necessary irradiation amount. Time consuming and impractical.

Examples of light sources that provide light of 300 to 500 nm include high-pressure mercury lamps, ultra-high-pressure mercury lamps, and the like. An example of a commercially available product is a high-pressure mercury lamp manufactured by Ushio Electric.

The surface of the water-soluble polymer on the contact surface of the weir before being irradiated with light again was coated with 1
．． Approximately 0 to 4.0% of the 70% of the 70% remains, but the remaining 70% of the 70% can be reduced to 1.0% or less by light irradiation again. In addition, the salt viscosity of a 1% aqueous solution (1% 77g) measured with a Brookfield viscometer is 20~
1500 cps, and as long as the irradiation intensity is within the above range, the viscosity does not substantially change before and after that.

The present invention will be explained in more detail below based on Examples, but the following Examples do not limit the present invention.

[Examples] Example 1 629 g of an 80% aqueous solution of methyl chloride quaternary salt of diethylaminoethyl methacrylate and 671 g of a 50% aqueous acrylamide solution were collected and mixed.

Benzoinethyl 21ter is used as a photopolymerization initiator.
0pp, ethylenediaminetetraacetic acid disodium salt 50
Both ppm and 500 pps+ of phosphorous acid were added to the monomer solution. This monomer solution was heated to 30°C, and while stirring, ION sulfuric acid was added to adjust p)I to 4.5±0.1, and then nitrogen substitution was performed for 30 minutes. A weir was made on a stainless steel plate with a depth of 20 cs, and a polytetrafluoroethylene film was adhered to the surface so that the bottom was approximately 23 cs+X.
A 23 cm container was prepared, the above solution was poured into it, and the top was covered with a film (12+4 g) of polyvinylidene chloride coated on polyethylene terephthalate. Using a fluorescent chemical lamp made by Mitsubishi Electric ■, irradiation with ultraviolet rays was performed from above at an irradiation intensity of 2 W/m'' for 50 minutes, and then irradiated with ultraviolet rays at 50 W/rn' for 10 minutes.The gel-like polymer was taken out from the container and the film was peeled off. A sample with a length of 10cm was cut from the side dam.The sample was fixed so that the surface in contact with the dam was parallel to the high-pressure mercury lamp, and a 400W high-pressure mercury lamp manufactured by Ushio Electric was placed 5cm from the surface. (Irradiation intensity: 1kW/m
”), 0.

Irradiation was performed for 0.5, 1, 5, and 10.25 minutes.

From this sample, a prism with a weir contact surface measuring 5 feet x 25+ am and a width of 51° C.m from the weir contacting surface to the inside of the polymer was cut, dried at 60° C. for 12 hours, and crushed to obtain a sample.

Residual acrylamide was measured for this sample according to the analysis method by the Polymer Flocculant Association.

Also, add 5g of these samples to 495g of pure water,
Stir at 240-260 rpm for 4 hours, add Pharmacopoeial Salt 5.
．． After adding 84 g and stirring for another hour, the salt viscosity of a 1% aqueous solution (1% η
S) was measured.

Appearance of polymer after irradiation treatment, residual acrylamide, 1%
The results of ηS were as follows.

Table 1 Example 2 Same as Example 1 except that an aqueous solution of methyl chloride quaternary salt of dimethylaminoethyl acrylate was used instead of the aqueous solution of methyl chloride quaternary salt of dimethylaminoethyl methacrylate in Example 1. The monomer solution adjusted to A sheet-like polymer having a depth of 20 m was continuously fed into a continuous polymerization apparatus.

From the top surface, using the same fluorescent chemical lamp as used in Example 1, the irradiation intensity was 0.2 W/m'' for 40 minutes.
Further, irradiation was carried out for 10 minutes at an irradiation intensity of 20 W/m''.Subsequently, in that state, using the same high pressure mercury lamp as used in Example 1, the light was continuously irradiated parallel to the weir contact surface at a distance of 1.
A slit of 0 cm was fixed and irradiated with light for irradiation times of 0.0.5, 1, and 2.10 minutes, and polymerization was continued for about 1 hour in each case.

The weir contact surface was 5 mm x 25 m, and the polymer was roughly cut into a prismatic shape with a width of 5 mm from the weir contact surface to the inside of the polymer.
It was dried and evaluated in the same manner as above. The results are shown in Table 2.

Table 2 Example 3 1200 g of 50% aqueous acrylamide solution and 100 g of 30% sodium acrylate were collected.

Add 200p of benzoin ethyl ether to this solution.
pm, ethylenediaminetetraacetic acid disodium salt 50p
pm, sodium sulfite 50 ppm.

Add urea to 0.5% and adjust pH with ION sulfuric acid.
was adjusted to 7.5.

This solution was purged with nitrogen for 60 minutes, then injected into a 24cm x 24cm bag made of polyethylene terephthalate film coated with vinylidene chloride in the form of a sheet with a thickness of about 20mm at its maximum center, and the bag was sealed. did.

This bag was placed almost horizontally in a constant temperature water bath at 30° C. on a stainless steel mesh so that the top surface was approximately 10 m below the liquid level. From above, using a Mitsubishi Electric fluorescent chemical lamp, ultraviolet rays were irradiated on the liquid level of the aquarium at an illuminance of 4 W/rn' for 50 minutes, and then for 10 minutes at 60 W/rrf.

The gel-like polymer was taken out of the bag, cut around the center into pieces of 5 cm x 10 cm, and a 400 W high-pressure mercury lamp made by Ushio Electric was fixed at 5 cm from the surface from above, and 0, 0. 5゜1.0,5,10.25
It was irradiated for 1 minute. Cut the surface layer to a thickness of 5 m,
Thereafter, the same treatment as in Example 1 was carried out.

However, the salt viscosity of a 1% aqueous solution was measured as follows.

Add 5g of sample to 475g of pure water and add 240 to 260
After stirring at rpm for 4 hours, adding 20 g of pharmacopoeia common salt and stirring for further 1 hour, the salt viscosity (1% ηS) was measured using a Brookfield viscometer.

Table 3 [Effects of the Invention] According to the present invention, monomers remaining on the polymer surface can be reduced in a short period of time by ultraviolet rays at a controlled dose, without changing the substantial performance of the polymer. I can do it.

For example, residual monomers are easily mixed into wastewater after sludge coagulation treatment, and are thought to have a greater impact on the environment and ecosystem than polymers, so they are highly evaluated.

In addition, it is possible to shorten the time of the polymerization process, and
Process troubles caused by monomer adhesion to equipment are eliminated, and long-term continuous production is possible.

Claims (1)

[Claims] (1) In a method for producing a water-soluble polymer by photopolymerization, (i) a water-soluble monomer solution containing a photopolymerization initiator is added to the water-soluble monomer solution in a container; Polymerize the solution under light irradiation so that the thickness of the solution layer is 50 mm or less to obtain a gel-like polymer, and (ii) irradiate the surface of the gel-like polymer in contact with the inner wall of the container with light again. A method for producing a water-soluble polymer, which comprises polymerizing residual monomers on the surface of the gel-like polymer. (2) The light irradiation is performed again using the following formula: 0.1≦W×T≦10 [In the formula, W represents the irradiation intensity of the lamp (kW/m^2), and T represents the time (minutes)] A method for producing a water-soluble polymer according to claim 1, which is carried out within the range shown in the following.