JPH10218907A - Method for utilizing waste water from polymerization of vinyl chloride monomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to inhibit the deposition of polymer scales on e.g. the inside wall of a polymerizer and to improve the surface appearance of a product obtained from the polymer by using as the medium waste water prepared by removing particles having a specified or larger particle diameter from waste water formed in producing a vinyl chloride polymer by suspension- polymerizing a vinyl chloride monomer in an aqueous medium. SOLUTION: The waste water utilized again is water once used for use where it comes into contact with a vinyl chloride polymer in the polymerization process and then freed of the vinyl chloride polymer. The waste water contains water-soluble or dispersible organic compounds, organic or inorganic salts, decomposition residues of additives, etc., such as fine polymer particles, a dispersant such as a water-soluble polymer, additives or a medium. The waste water is treated in order to inhibit the scale deposition, increased tendency toward fish eye formation, etc. Waste water prepared by removing particles with a particle diameter of 50μm or above from waste water by spontaneous sedimentation, centrifugal sedimentation, agglomeration precipitation or filtration, especially filtration is utilized again as an aqueous medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a vinyl chloride polymer. More specifically, the present invention relates to a method for producing a vinyl chloride-based polymer that can reduce the amount of wastewater from a production facility and does not impair operation stability and product quality.

[0002]

2. Description of the Related Art A vinyl chloride polymer is generally a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer (hereinafter collectively referred to as "vinyl chloride monomer"). The polymer obtained by polymerizing this is referred to as "vinyl chloride polymer") in the presence of a polymerization initiator,
It is manufactured by suspension polymerization or emulsion polymerization in an aqueous medium containing a dispersant and / or an emulsifier.

[0003] The aqueous medium used here and water used in other production processes are subjected to coagulation sedimentation treatment or activated sludge treatment to meet environmental standards after separating the obtained polymer. In general, wastewater is discharged outside the facility as wastewater.However, in recent years, reuse of wastewater has been considered for the purpose of reducing wastewater and closing facilities to improve the environment and reduce wastewater treatment costs. Have been.

[0004]

However, if the wastewater after the separation of the above-mentioned polymer is simply reused as an aqueous medium for the polymerization of vinyl chloride monomers, the polymerization apparatus and its accompanying equipment become unnecessary. The scale of the polymer adheres to the inner wall surfaces of various pipes connected to the stirring blade, the baffle, the reflux condenser, and the polymerization reactor (hereinafter collectively referred to as “polymerization reactor inner wall, etc.”) or the resulting chloride When products such as pipes, films and sheets, toys, and molded products are manufactured using vinyl-based polymers, unmelted particles called "fish eyes" remain on the surface, impairing the appearance and becoming defective. ,
And so on.

[0005]

Means for Solving the Problems In view of the above-mentioned circumstances, the present inventors have conducted intensive studies and as a result, have been able to solve the problem by removing particles having a specific particle size or more in the polymerized wastewater to be reused. The inventors have found that the present invention can be solved, and have completed the present invention. That is, the gist of the present invention is that waste water generated when a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium to produce a vinyl chloride polymer (hereinafter referred to as “polymerization waste water”). After removing particles having a particle diameter of 50 μm or more in the wastewater, a method for using the polymerization wastewater of the vinyl chloride monomer, wherein the wastewater is used as an aqueous medium for the polymerization of the vinyl chloride monomer, It exists in.

The gist of the present invention is to provide a method of using the above-mentioned polymerization wastewater in which particles having a size of 50 μm or more are removed by filtration; The present invention also provides a method of using polymerization wastewater using at least one type of separation device selected from the group consisting of a filter, an ultrafiltration membrane, and a reverse osmosis membrane. Further, the gist of the present invention is a method for utilizing the above-mentioned polymerization wastewater used after removing particles having a particle diameter of 10 μm or more in the polymerization wastewater,
Also exists.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. <Polymerization wastewater> The polymerization wastewater to be reused in the present invention is used for the purpose of coming into contact with the vinyl chloride polymer in the polymerization process of the vinyl chloride monomer, and is waste water after separating the vinyl chloride polymer. . These include the aqueous medium used for the suspension polymerization, the water injected into the polymerization system during the polymerization, the water used as a solvent for the polymerization aid added during and before and after the polymerization, and after the completion of the reaction. In the step of removing the vinyl chloride-based monomer, the step of dehydrating the vinyl chloride-based polymer, and the like, water added to the vinyl chloride-based polymer slurry is required due to the necessity of transporting the polymer and operating the equipment.

[0008] In such waste water, dispersants such as fine particles of vinyl chloride polymer, water-soluble polymer and the like, charged additives or a medium in which these are dissolved or dispersed can be dissolved or dispersed in water. Organic compounds, organic or inorganic salts, and reaction (decomposition) products of these additives in a polymerization vessel are included.

<Treatment of Polymerization Wastewater> The above-mentioned problems such as adhesion of scale and deterioration of fish eyes can be solved by removing particles having a particle diameter of 50 μm or more from the polymerization wastewater. If the polymerization wastewater in which particles having a particle diameter of 50 μm or more remain is used, the effects of the present invention cannot be obtained, and the scale adheres to the inner wall of the polymerization vessel and the fisheye deteriorates. It is preferable to remove particles having a particle diameter of 10 μm or more because the effects of the present invention become more remarkable.

[0010] The particle size of the polymer wastewater contained in the wastewater 5
Methods for removing particles of 0 μm or more include natural (gravitational) sedimentation treatment, centrifugal sedimentation treatment, coagulation sedimentation treatment, and filtration treatment. The filtration treatment is the simplest and most reliable.
It is suitable for application to the present invention. Examples of the filtration method include wire mesh, sintered metal, filter cloth, and separation membrane treatment with a microfilter, ultrafiltration membrane, reverse osmosis membrane, or the like.

In the case of performing filtration using a wire mesh, it is preferable to use a wire mesh of 400 mesh (mesh size: 37 μm) or a finer mesh. Sintered metal that allows more precise filtration,
Use of a microfilter, an ultrafiltration membrane, a reverse osmosis membrane, or the like can provide a better effect. Further, in addition to such a filtration treatment, a treatment such as centrifugal separation and gravity sedimentation may be used in combination, if necessary.

<Reuse of Polymerization Wastewater> Polymerization wastewater from which particles having a particle diameter of 50 μm or more have been removed by the above-described method,
It may be stored in an appropriate storage tank or the like and charged as appropriate as a normal aqueous medium as an aqueous medium for polymerization of the vinyl chloride monomer. Further, the water may be reused as water added into the polymerization vessel by a pump or the like after the start of polymerization or water used in other polymerization processes. In addition, it can be used not only as charging water but also as water for washing a polymerization reactor after polymerization and other facilities attached to the polymerization reactor.

<Polymerization recipe> The polymerization recipe to which the present invention is applied is a suspension polymerization of a vinyl chloride monomer carried out in an aqueous medium. There are no particular restrictions on the additives, auxiliaries, and the like used here, as long as the objects and effects of the present invention are not impaired, as long as they are commonly used in the suspension polymerization method. Further, the polymerization recipe when recycling the polymerization wastewater and the polymerization recipe when obtaining the polymerization wastewater may be the same or different. Further, water mixed with polymerization wastewater obtained by polymerization based on a plurality of different polymerization formulations may be reused.

<Monomer> The vinyl chloride monomer used in the method of the present invention includes a mixture of a vinyl chloride monomer alone and a copolymerizable monomer mainly composed of the vinyl chloride monomer. . As the other monomer copolymerizable with the vinyl chloride monomer, those commonly used in the polymerization of vinyl chloride monomers can be used without any particular limitation. Examples of the other monomers include vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, and α such as ethylene and propylene.
-Olefins, alkyl (meth) acrylates such as methyl acrylate and methyl methacrylate, and vinylidene compounds such as vinylidene chloride. These other monomers are usually 20
It is used in proportions of up to% by weight.

<Dispersant> The dispersant which can be used in the method of the present invention may be any of those conventionally used in a suspension polymerization method of a vinyl chloride monomer, and is not particularly limited. Examples of the dispersant include partially saponified polyvinyl acetate (so-called polyvinyl alcohol), cellulose derivatives such as hydroxypropylmethylcellulose, and water-soluble polymers such as gelatin. In addition, anionic surfactants such as sodium lauryl sulfate and nonionic surfactants such as sorbitan fatty acid esters and glycerin fatty acid esters may be used as the dispersing aid. These dispersants or dispersing agents can be used alone or in combination of two or more. Also,
There are no particular restrictions on the amount of these dispersants used, their types, stirring strength, polymerization temperature, types and compositions of other monomers to be copolymerized with the vinyl chloride-based monomer, and the vinyl chloride-based polymer produced. Although it varies somewhat depending on the particle size of the vinyl chloride monomer, it is generally used in the range of 0.001 to 2% by weight, preferably 0.03 to 1% by weight, based on the total amount of the vinyl chloride monomer.

<Polymerization Initiator and Other Auxiliaries> The polymerization initiator used in the method of the present invention may be any of those generally used in a method for polymerizing vinyl chloride monomers, and is not particularly limited. For example, perester compounds such as t-butyl peroxypivalate, t-butyl peroxy neodecanoate, t-hexyl peroxy pivalate, t-hexyl peroxy neodecanoate, α-cumyl peroxy neodecanoate, dilauroyl Peroxide compounds such as peroxides, percarbonate compounds such as diisopropylperoxydicarbonate and di-2-ethylhexylperoxydicarbonate, azo compounds such as azobis (2,4-dimethylvaleronitrile) and azobisisobutyronitrile. . These polymerization initiators can be used alone or in combination of two or more. The amount of the polymerization initiator varies depending on the type of the initiator, the polymerization temperature, the desired reaction time and the like, but is generally 0.01 to 100 parts by weight of the vinyl chloride monomer.
To 1 part by weight.

Further, in the method of the present invention, if necessary, various polymerizations such as a crosslinking agent, a chain transfer agent, an antioxidant, a pH adjuster, and a scale adhesion inhibitor, which are used for the polymerization of a vinyl chloride monomer. Auxiliaries can be used as appropriate, and the amount and method of adding these auxiliaries may be the same as those used in the polymerization of vinyl chloride monomers.

[0018]

EXAMPLES Next, the specific contents of the method of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. <Evaluation method> The polymerization wastewater and the produced vinyl chloride polymer were evaluated by the following methods. Measurement of particle size distribution contained in water A predetermined amount of an aqueous medium (feed water) used for polymerization is filtered through a microfilter (average pore size: 0.1 μm), and the remaining particles on the filter are washed out with deionized water, and a sample solution is sampled. And the particle size distribution of the particles in the sample solution is measured by a laser scattering type particle size distribution measuring device (LA-910, manufactured by HORIBA).
Was measured by After premixing 100 parts by weight of fisheye vinyl chloride polymer, 50 parts by weight of plasticizer (di-2-ethylhexyl phthalate (DOP)), and 3 parts by weight of lead powder stabilizer in a beaker,
The mixture is kneaded with a mill roll at 155 ° C. for 3, 4, 5, and 7 minutes, respectively. Unmelted particles (fish eyes) in a square (area 25 cm ² ) of 5 cm on a side of the obtained roll sheet
And the number of fish eyes was counted.

<Observation of adhesion state> The vinyl chloride polymer slurry produced by the polymerization was drawn out of the polymerization vessel, and the inside of the system was evacuated and replaced with nitrogen. Then, the polymerization vessel was opened and the vessel wall was lightly washed with water. After that, the state of scale adhesion to the inner wall of the polymerization vessel and the like (the vessel wall in the liquid phase portion, the vessel wall in the gas phase portion, and the baffle during the reaction) was visually confirmed.

The evaluation criteria are as follows. ○: No adhesion at all △: Partially thin adhesion ×: Adhesion over a wide range

<Examples and Comparative Examples> Standard Example 1 150 kg of deionized water was charged into a stainless steel polymerization vessel (400 liters in inner volume) equipped with a stirrer and a jacket.
After performing vacuum substitution and starting stirring, 100 kg of a vinyl chloride monomer, a saponification degree of 80% as a dispersant, and a polymerization degree of 23 were used.
A 5% aqueous solution of 90 g of water-soluble partially saponified polyvinyl acetate of No. 00 and di-2ethylhexyl peroxydicarbonate as a polymerization initiator were charged, and the temperature was raised to 58 ° C. to perform polymerization.

After terminating the reaction at the target polymerization conversion rate and recovering the vinyl chloride monomer in the polymerization vessel to atmospheric pressure, the system was evacuated to remove residual monomers. Open the polymerization vessel,
The state of adhesion of the scale at a predetermined site was observed.
The produced vinyl chloride polymer slurry was taken out and centrifugally dehydrated to obtain about 300 liters of polymerization wastewater.

Further, a sample of deionized water used for the preparation was separately collected, and the particle size distribution of the particles contained therein was measured by the method described above. After drying, the obtained vinyl chloride polymer was subjected to fisheye evaluation as a standard sample. The results are shown in the table. In addition, the polymerization wastewater used for preparation in the following Examples 1 to 5 and Comparative Example 1 was prepared by repeating the same procedure as in this example.

Standard Example 2 A 3% aqueous solution of 80 g of water-soluble partially saponified polyvinyl acetate having a saponification degree of 70% and a polymerization degree of 700 as a dispersant, t-butyl peroxypivalate as a polymerization initiator, and an additive as an additive Using 50 g of stearic acid, the polymerization temperature was 63
Polymerization was carried out in the same manner as in Standard Example 1 except that the temperature was changed to ° C., and about 300 liters of polymerization waste water was obtained in the same manner.

After drying, the vinyl chloride polymer was subjected to fisheye evaluation as a standard sample. The results are shown in the table. Since the pH of the polymerization waste water was 3.5, the pH was adjusted to 6.5 using an aqueous sodium hydroxide solution. The polymerization wastewater used in preparation in the following Examples 6 to 8 and Comparative Example 2 was prepared by repeating the same procedure as in this example.

Example 1 The polymerization waste water prepared in Standard Example 1 was filtered using a laminated precision metal sintered filter (average pore size: 5 μm), and the particle size distribution of particles contained in the filtered water was measured. The polymerization operation was carried out in the same manner as in Standard Example 1 except that 150 kg of the polymerization waste water after filtration was used in place of deionized water, to observe the scale adhesion state in the polymerization vessel and to evaluate the fisheye of the produced polymer. Was done. The results are shown in the table.

Example 2 The polymerization wastewater prepared in Standard Example 1 was filtered using a microfilter (average pore size: 1 μm), and the particle size distribution of the particles contained in the filtered water was measured. The polymerization operation was performed in the same manner as in Standard Example 1 except that 150 kg of the polymerization wastewater subjected to this treatment was used in place of deionized water, to observe the state of scale adhesion in the polymerization vessel and to evaluate the fisheye of the produced polymer. Was done. The results are shown in the table.

Example 3 The polymerization waste water prepared in Standard Example 1 was filtered using a 400-mesh wire net, and the particle size distribution of the particles contained in the filtered water was measured. The polymerization operation was performed in the same manner as in Standard Example 1 except that 150 kg of the polymerization wastewater subjected to this treatment was used in place of deionized water, to observe the state of scale adhesion in the polymerization vessel and to evaluate the fisheye of the produced polymer. Was done. The results are shown in the table.

Example 4 The polymerization wastewater prepared in Standard Example 1 was filtered through a laminated precision metal sintered filter (average pore size: 40 μm), and the particle size distribution of the particles contained in the filtered water was measured. The polymerization operation was performed in the same manner as in Standard Example 1 except that 150 kg of the polymerization wastewater subjected to this treatment was used in place of deionized water, to observe the state of scale adhesion in the polymerization vessel and to evaluate the fisheye of the produced polymer. Was done. The results are shown in the table.

Example 5 The polymerization waste water prepared in Standard Example 1 was filtered through a laminated precision metal sintered filter (average pore size: 20 μm), and the particle size distribution of the particles contained in the filtered water was measured. The polymerization operation was performed in the same manner as in Standard Example 1 except that 150 kg of the polymerization wastewater subjected to this treatment was used in place of deionized water, to observe the state of scale adhesion in the polymerization vessel and to evaluate the fisheye of the produced polymer. Was done. The results are shown in the table.

Comparative Example 1 150 kg of the polymerization waste water prepared in Standard Example 1 was collected without performing a treatment such as filtration, and the particle size distribution of the particles contained therein was measured. Except that this polymerization wastewater was used in place of deionized water, the same polymerization operation as in Standard Example 1 was performed, and the state of scale adhesion in the polymerization vessel and the fisheye of the produced polymer were evaluated. The results are shown in the table.

Example 6 The polymerization waste water prepared in Standard Example 2 was filtered with a laminated precision metal sintered filter (average pore size: 5 μm), and the particle size distribution of the particles contained in the filtered water was measured. The polymerization operation was performed in the same manner as in Standard Example 1 except that 150 kg of the polymerization wastewater subjected to this treatment was used in place of deionized water, to observe the state of scale adhesion in the polymerization vessel and to evaluate the fisheye of the produced polymer. Was done. The results are shown in the table.

Example 7 The polymerization waste water prepared in Standard Example 2 was filtered through a hollow fiber type reverse osmosis membrane, and the particle size distribution of the particles contained in the filtered water was measured. The polymerization operation was performed in the same manner as in Standard Example 1 except that 150 kg of the polymerization wastewater subjected to this treatment was used in place of deionized water, to observe the state of scale adhesion in the polymerization vessel and to evaluate the fisheye of the produced polymer. Was done. The results are shown in the table.

Example 8 The polymerization wastewater prepared in Standard Example 2 was filtered through a laminated precision metal sintered filter (average pore size: 20 μm), and the particle size distribution of the particles contained in the filtered water was measured. The polymerization operation was performed in the same manner as in Standard Example 1 except that 150 kg of the polymerization wastewater subjected to this treatment was used in place of deionized water, to observe the state of scale adhesion in the polymerization vessel and to evaluate the fisheye of the produced polymer. Was done. The results are shown in the table.

Example 9 The polymerization waste water prepared in Standard Example 2 was subjected to solid-liquid separation using a 3000 G centrifugal dehydrator, and the particle size distribution of the particles contained in the supernatant was measured. Polymerization wastewater 1 after this treatment
The polymerization operation was performed in the same manner as in Standard Example 1 except that 50 kg was used in place of deionized water, and the scale adhesion state in the polymerization vessel was observed and the fisheye of the produced polymer was evaluated. The results are shown in the table.

Comparative Example 2 150 kg of the polymerization waste water prepared in Standard Example 2 was collected without performing a treatment such as filtration, and the particle size distribution of the particles contained therein was measured. Except that this polymerization wastewater was used in place of deionized water, the same polymerization operation as in Standard Example 1 was performed, and the state of scale adhesion in the polymerization vessel and the fisheye of the produced polymer were evaluated. The results are shown in the table.

<Evaluation of Results> The results shown in the above Examples and Comparative Examples reveal the following points. (1) Comparison between Examples 1 to 5 and Comparative Example 1, and Example 6
9 to Comparative Example 2, the polymerization wastewater was used to obtain a particle diameter of 50.
By reusing after removing particles of μm or more,
In particular, it can be seen that fish eyes when kneaded for a long time (5 minutes, 6 minutes) are improved. In addition, the adhesion of scale is reduced. (2) When Examples 1 and 2 and Examples 6 and 7 are compared with other Examples and Comparative Examples, fisheye and scale adhesion are further improved by using polymerization wastewater containing no particles having a particle diameter of 10 μm or more. It can be seen that it is improved.

[0038]

By using the method of the present invention, the polymerization wastewater can be reused without causing scale adhesion to the inner wall of the polymerization vessel or a problem with the product quality. However, environmental effects such as reduction of wastewater are extremely large.

[0039]

[Table 1] No: target = standard example, actual = example, ratio = comparative example Aqueous medium: F = deionized water, R1 (2) = polymerization wastewater of standard example 1 (2) Particles in aqueous medium:% ≧ 50 (10 ) μm = 50 (10) Particle content of at least 10 μm (% by weight) Fish eyes: 3-4-5-6 minutes = number of fish eyes per kneading time

Claims (5)

[Claims] 1. A suspension of a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer (hereinafter collectively referred to as “vinyl chloride monomer”) in an aqueous medium. After removing particles having a particle diameter of 50 μm or more from waste water (hereinafter, referred to as “polymerization waste water”) generated during the production of a vinyl chloride polymer by turbid polymerization, the waste water is treated with a vinyl chloride monomer. A method for utilizing polymerization wastewater, which is used as an aqueous medium for polymerization. 2. The method according to claim 1, wherein particles having a particle diameter of 50 μm or more are removed by filtration. 3. The method according to claim 2, wherein the filtration is performed using a wire mesh. 4. The method according to claim 1, wherein the filtration is at least one selected from the group consisting of a sintered metal filter, an ultrafiltration membrane, and a reverse osmosis membrane.
The method for utilizing polymerization wastewater according to claim 2, wherein the method is performed using a kind of separation device. 5. The method according to claim 1, wherein particles having a particle size of 10 μm or more in the polymerization waste water are removed before use.