JPH11236691A - Metal surface treatment method, polymerization apparatus subjected to the surface treatment, and method for producing synthetic resin using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the adhesion of scale in a polymerization apparatus in the production of a synthetic resin, and to form a stable film without a decrease in the function of preventing the adhesion of scale even when used for a long time or repeatedly. It is an object of the present invention to provide a metal surface treatment method, a polymerization apparatus which has been subjected to this treatment, and a method for producing a polymer using this apparatus. SOLUTION: An alkali metal hydroxide (b) is added to a water-insoluble liquid (a) at a weight ratio of (a) :( b) = 10.
0: The surface of the metal mainly composed of stainless steel or iron is adjusted to 50 to 2 by the mixed solution added at 0.01 to 10.0.
The heat treatment is performed in a temperature range of 00 ° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a surface of a metal mainly composed of stainless steel or iron, an apparatus for producing a synthetic resin, and a method for producing a synthetic resin using the same.

[0002]

2. Description of the Related Art When a synthetic resin is produced, a polymer adheres, stays and denatures in a polymerization apparatus to be insoluble in a monomer, a polymerization solvent and a polymer, and accumulates as a scale in the polymerization apparatus. There's a problem. By accumulating the scale generated in this polymerization device, the heat conduction efficiency of the device is reduced, and not only the polymer is not stably obtained, but also the scale is gradually peeled and mixed into the product,
This causes deterioration in appearance quality such as formation of silver streaks on the molded article using the synthetic resin and deterioration of the color tone of the product.

Conventional methods for preventing adhesion of polymer scale in the polymerization of vinyl monomers include, for example, specific polar compounds (JP-B-45-30343) and aromatic amine compounds (JP-A-51-50887). Condensates of aromatic amine compounds (JP-B-60-30681), those containing a metal salt and / or ammonium salt obtained by sulfonating a condensate of an aminonaphthalene compound and silica sol (Japanese Patent Laid-Open No. 9-87304), etc. Is known as a scale adhesion inhibitor in a reactor.

[0004] However, these conventional methods of applying a scale anti-adhesion agent involve styrene, acrylonitrile,
When polymerizing (meth) acrylic acid ester or the like, the solubility of these anti-adhesion agents to these monomers is large, and thus the durability in long-term use and repeated use is not sufficient. In addition, durability is further reduced by bulk polymerization or solution polymerization using these monomers at a high concentration. Further, the eluted scale adhesion inhibitor becomes an impurity, which may lower the quality of the product.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to prevent the adhesion of scale in a polymerization apparatus in the production of a synthetic resin, and to prevent the scale adhesion preventing function from being deteriorated even when used for a long time or repeatedly. It is an object of the present invention to provide a metal surface treatment method for forming a film, a polymerization apparatus subjected to the treatment, and a method for producing a polymer using the apparatus.

[0006]

Means for Solving the Problems The present inventors have developed a physical,
As a result of intensive studies on chemically stable coatings, the metal surface mainly composed of stainless steel or iron is treated with a solution containing a water-insoluble liquid and an alkali metal hydroxide (hereinafter referred to as a treatment mixture). After that, it has been found that the above problem can be solved by washing and removing the alkali metal hydroxide remaining on the treated surface, and the present invention has been completed.

That is, in the present invention, the weight ratio of the alkali metal hydroxide (b) to the water-insoluble liquid (a) is (a) :( b) = 100: 0.01 to 10.0. The surface of a metal containing stainless steel or iron as a main component in a temperature range of 50 to 200 ° C. (hereinafter referred to as “surface treatment”) by using the treatment mixture (d) added as described above. This is a surface treatment method.

The weight ratio of the water-insoluble liquid (a) to the alkali metal hydroxide (b) is (a) :( b) = 100: 0.0
1 to 10.0, preferably (a) :( b) = 10
0: in the range of 0.1 to 5.0. When (b) is less than 0.01, it takes a very long time to obtain a target film, and it is not efficient. When it is higher than 10.0, corrosion of the metal surface is large and is not practical.

The processing temperature is in the range of 50 to 200 ° C.,
Preferably it is in the range of 90 to 150 ° C. If the temperature is lower than 50 ° C., it takes a very long time to obtain a target film, which is not efficient. When the temperature is higher than 200 ° C., the reaction rate is high and not only a uniform film cannot be obtained, but also the corrosion of the metal surface increases, which is not practical.

Since alkali metal hydroxide may remain on the treated surface, it is preferable to remove the alkali metal hydroxide remaining after the treatment. The method is not particularly limited as long as the object can be achieved, and may be carried out by dissolving and washing with a liquid such as water that dissolves an alkali metal hydroxide, or may be removed by wiping. The water-insoluble liquid (a) is not particularly limited as long as it is water-insoluble. For example, cyclic ketones (a ′), ethylbenzene, toluene,
A water-insoluble liquid having a boiling point of 100 ° C. or higher, such as xylene, is preferred. The cyclic ketone compound (a ') includes, for example, cyclopentanone, cyclohexanone and the like, but preferably cyclohexanone is used.

The alkali metal hydroxide (b) includes lithium hydroxide, potassium hydroxide, sodium hydroxide and cesium hydroxide, and preferably sodium hydroxide is used. The above stainless steel is, for example, SUS
316, SUS316L, SUS304, SUS304
L, which is commonly used in polymerization apparatuses and the like, is not particularly limited.

Preferably, the processing mixture contains an aminoethanol compound (c) containing 100% of the cyclic ketone compound (a ').
1 to 100 parts by weight is added to the parts by weight. More preferably, the weight ratio is in the range of (a ') :( c) = 100: 2 to 70. By adding (c), the uniformity of the film is improved. If (c) is less than 1 part by weight, the effect of improving the uniformity of the film is not sufficiently exhibited, and if it exceeds 100 parts by weight, it takes a very long time to obtain a desired film, and the efficiency is poor.

The aminoethanols (c) in the present invention
The term "monoethanolamine" refers to monoethanolamine, diethanolamine, triethanolamine, etc., and preferably, monoethanolamine is used. Further, in the present invention, a treatment in which alkyl sulfoxide (e) is added at a weight ratio of cyclic ketone compound (a ′): aminoethanols (c): alkyl sulfoxide (e) = 100: 1 to 100: 1 to 100 It is preferable to use the mixed solution (f). The addition of the alkyl sulfoxide (e) increases the thickness of the film, and provides a stable polymer scale adhesion suppressing effect.

When the amount of the alkyl sulfoxide (e) exceeds 100 parts by weight, the amount of generated impurities is undesirably increased. In the present invention, subsequent to the surface treatment with the treatment mixture, it is preferable to further perform a heat treatment at 100 to 150 ° C. with a water-insoluble solvent. By this treatment, the physical stability of the film is increased, a strong film is formed, and a long-term effect of suppressing polymer scale adhesion is obtained.

The present invention is also a metal-based composite material comprising a coating layer formed on a metal surface by the surface treatment with the above-mentioned treatment mixture and a base material of stainless steel or a metal mainly composed of iron. Further, in a manufacturing apparatus for manufacturing a synthetic resin, a part or all of a part in contact with a polymerization reactor and / or a liquid containing a polymer that has exited the reactor includes the above-described coating layer and a base material. And a metal-based composite material comprising a metal containing stainless steel or iron as a main component. Further, there is provided a method for producing a synthetic resin, characterized by using the production apparatus.

The production apparatus for producing a synthetic resin in the present invention is a polymerization apparatus for bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization or the like, and may be an apparatus for continuously producing a polymer. Alternatively, a batch type polymerization apparatus may be used. The synthetic resin in the present invention includes, for example, polystyrene, acrylonitrile-styrene copolymer, PMMA, ABS resin, vinyl chloride, polyoxymethylene, polyamide, and the like.
It is a resin obtained by polymerizing various monomers.

The polymerization method is not limited to polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization, but the film formed by the surface treatment in the present invention is a monomer and an organic solvent used as a polymerization solvent. Because of its excellent durability against styrene, monomers with high solubility in conventional scale adhesion preventing coating materials such as styrene, acrylonitrile, (meth) acrylic acid ester, (meth) acrylic acid, and vinyl acetate When the polymer is used for polymerization by a solution polymerization method or a bulk polymerization method, it particularly exhibits its characteristics. The synthetic resin manufacturing apparatus in the present invention is a raw material tank, a transfer pipe,
Examples include a pump, a reactor, and a resin purification / recovery device.

When the above-mentioned film is formed on the polymerization reactor by surface treatment, the polymer scale is not limited to a portion in contact with the polymerization solution, for example, the inner wall of the polymerization reactor, a stirring blade, a stirring shaft, a bolt, a nut and the like. It is desirable to apply a surface treatment to a portion that may adhere to form the film. In addition, the part where the liquid containing the polymer that has exited the reactor and the raw material is, for example, the liquid that contains the polymer that has exited the reactor,
Examples include a pipe for transferring to another reactor or another process, a device for removing unreacted monomer or solvent, a valve, a pump, a condenser, a monomer tank, and the like.

The procedure for applying the surface treatment of the present invention to the manufacturing apparatus is not particularly limited, but can be carried out, for example, by the following procedure. First, a mixed solution for processing is poured into a manufacturing apparatus, and this solution is uniformly mixed by stirring, circulation, or the like, and heated to a predetermined temperature by a heating medium or the like. Subsequently, the mixed solution for treatment is discharged, and the hydroxide of the alkali metal remaining on the treated surface is washed and removed. The method of cleaning is not particularly limited, and is a method in which a liquid capable of dissolving the hydroxide of the alkali metal is agitated, circulated, allowed to stand, etc., and then discharged from the apparatus, or a surface-treated apparatus. The surface may be cleaned by wiping.

In the method of the present invention, an excellent scale adhesion inhibiting effect is exhibited irrespective of the type of the polymerization initiator. However, a polymerization initiator having a crosslinking efficiency (ε) of 75 or less as defined by the following test is used. A more excellent effect is exhibited by the synergistic effect of the combination with use. In the test for measuring the crosslinking efficiency, a polymerization initiator is dissolved in cumene at a rate of 0.5 mol / liter, and the temperature is set to 110 ° C., and the heating time is set to a time that is six times the half life of the polymerization initiator at 110 ° C. Using the amount of cumene dimer generated when heated, the formula (1)
Defines the crosslinking efficiency (ε). Crosslinking efficiency ε = 100 × a / b (1) where a is the concentration of the produced cumene dimer (mol /
Liter), b is 0.5 × 10 ⁻³ (mol / liter)
It is.

[0021]

The present invention will be described below in detail with reference to examples. Evaluation method of polymer scale adhesion inhibitor film : The state of the formed film was visually observed, and the cross section of the metal on which the film was formed was observed with a scanning electron microscope (SEM) to measure the thickness of the film. .

Evaluation method of polymer scale adhesion amount : After operating for 60 days, the reactor was opened and 30 cm of the reactor wall was removed.
The polymer scale adhering to the area of × 30 cm is scraped off. Of the scraped scale, the soluble matter of methyl ethyl ketone (MEK) is dissolved, separated and removed. M left
The EK insolubles were dried and weighed.

Measurement of gel concentration in product : The weight (x) of a filter having a pore size of 2.5 μm, which was dried at 110 ° C. for 1 hour and cooled in a desiccator, was weighed in advance. About 20 g (y) of a polymer obtained as a product is dissolved in methyl ethyl ketone (MEK) at a concentration of 5% by weight, and filtered through the above filter. The filter is dried at 110 ° C. for 1 hour, cooled in a desiccator and weighed (z).
From the weight increase, the MEK-insoluble matter (gel) in the product is calculated by the formula (2).

[0024] Product color tone measurement : From the polymer obtained as a product, 5
A molded article having a size of 9 cm × 9 cm × 2.5 mm in thickness was molded, and four molded articles were stacked in the thickness direction.
The yellow index (YI) was measured by a method in accordance with No. 981. Example 1 In a 100 L reactor made of stainless steel 316, 99% by weight of cyclohexanone and NaOH1.
A mixed solution of 0% by weight was spread and heat-treated at 140 ° C. for 16 hours. The mixed solution was discharged, and the reactor was washed with water, and the state of film formation on the reactor surface was observed. The results are shown in Table 1.

Example 2 1 consisting of stainless steel 316
In a 00 L reactor, 90% by weight of cyclohexanone,
A mixed solution of 9% by weight of ethanolamine and 1% by weight of NaOH was poured thereinto, and heated at 140 ° C. for 16 hours. The mixed solution was discharged, and the reactor was washed with water, and the state of film formation on the reactor surface was observed. The results are shown in Table 1.

Example 3 A mixed solution having the same composition as in Example 2,
After using a similar reactor and heating at the same temperature, the mixed solution was discharged, and then ethylbenzene was poured in and reheated at 130 ° C. for 8 hours, and then the reactor was washed with water.
The state of film formation on the reactor surface was observed. The results are shown in Table 1.

Example 4: 10 made of steel (SS41)
A mixed solution of 49.5% by weight of cyclohexanone, 10% by weight of ethanolamine, 40% by weight of dimethyl sulfoxide, and 0.5% by weight of NaOH was charged into a 0 L reactor, and heated at 150 ° C. for 8 hours. The mixed solution was discharged, and the reactor was washed with water, and the state of film formation on the reactor surface was observed. The results are shown in Table 1.

Comparative Example 1 A reactor was treated in the same manner as in Example 2 except that heating was not performed, and the state of film formation on the reactor surface was observed. The results are shown in Table 1. Example 5: Using a reactor surface-treated in the same manner as in Example 1, a polymerization temperature of 135 ° C., 21 wt.% Of acrylonitrile as a monomer, 49 wt.% Of a styrene monomer, 30 wt.% Of a polymerization solvent, and t-Butylpero as a polymerization initiator.
xyisopropylmonocarbonate
An acrylonitrile-styrene copolymer was produced by continuous solution polymerization using 0.03 parts by weight, and the polymer on the reactor wall after 60 days of operation was obtained during a period in which a product having a gel concentration of 30 ppm or less in the product was obtained. Table 2 shows the amount of scale attached, the state of the film, and the color tone of the product.

Example 6 An acrylonitrile-styrene copolymer was produced by continuous solution polymerization in the same manner as in Example 5 except that a reactor surface-treated in the same manner as in Example 2 was used. Table 2 shows the amount of polymer scale adhering to the reactor wall, the state of the film, and the color of the product after the device was operated for 60 days while the product having a concentration of 30 ppm or less was obtained.

Example 7: An acrylonitrile-styrene copolymer was produced by continuous solution polymerization in the same manner as in Example 5 except that a reactor surface-treated in the same manner as in Example 3 was used. Table 2 shows the amount of polymer scale adhering to the reactor wall, the state of the film, and the color of the product after the device was operated for 60 days while the product having a concentration of 30 ppm or less was obtained.

Example 8: An acrylonitrile-styrene copolymer was produced by continuous solution polymerization in the same manner as in Example 5 except that the reactor surface-treated in the manner of Example 4 was used, and the gel in the product was obtained. Table 2 shows the amount of polymer scale adhering to the reactor wall, the state of the film, and the color of the product after the device was operated for 60 days while the product having a concentration of 30 ppm or less was obtained.

Example 9: 2,2'-A as a polymerization initiator
zobis (2-methylbutyronitri
le) An acrylonitrile-styrene copolymer was produced by continuous solution polymerization in the same manner as in Example 7 except that 0.05 parts by weight was used and polymerization was carried out at 116 ° C., and the gel concentration of the product was 30 ppm or less. The period during which the product is available, 60
Table 2 shows the amount of polymer scale adhered to the reactor wall, the state of the film, and the color tone of the product after operating for one day.

Comparative Example 2 An acrylonitrile-styrene copolymer was produced by continuous solution polymerization in the same manner as in Example 6, except that no surface treatment was applied to the reactor.
Table 2 shows the amount of polymer scale adhered to the reactor wall, the state of the film, and the color of the product after 60 days of operation while the product having a gel concentration of 30 ppm or less in the product was obtained.

Comparative Example 3 An acrylonitrile-styrene copolymer was produced by continuous solution polymerization in the same manner as in Example 7 except that no surface treatment was applied to the reactor.
Table 2 shows the amount of polymer scale adhered to the reactor wall, the state of the film, and the color of the product after 60 days of operation while the product having a gel concentration of 30 ppm or less in the product was obtained.

[0035]

[Table 1] * C, D, E, and Na in the composition represent cyclohexanone, dimethyl sulfoxide, monoethanolamine, and sodium hydroxide, respectively.

[0036]

[Table 2] *: The term indicates a term during which a product having a gel concentration of 30 ppm or less in the product is obtained. * 1: During the production period, the gel concentration in the product was less than 30 ppm. * 2: The amount of polymer scale attached.

[0037]

According to the metal surface treatment method of the present invention, it is possible to obtain a metal-based composite material having a uniform physically and chemically stable film on the surface of the metal, and apply this material to the surface of the polymerization apparatus. The application can prevent the adhesion of the polymer scale. Since the state of the film does not change even after the polymerization, the effect is exhibited even when used for a long time or repeatedly. Further, in the manufacturing apparatus having the film of the present invention, it is possible to obtain a synthetic resin having a small amount of gel and a good color tone.

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Claims (11)

[Claims] An alkali metal hydroxide (b) is added to a water-insoluble liquid (a), and the weight ratio thereof is (a) :( b) = 10.
0: The surface of the metal mainly composed of stainless steel or iron is adjusted to 50 to 2 by the mixed solution added at 0.01 to 10.0.
A method for treating a metal surface, comprising performing a heat treatment in a temperature range of 00 ° C. 2. The method for treating a metal surface according to claim 1, wherein the water-insoluble liquid (a) is a cyclic ketone compound. 3. A mixed liquid (d) comprising a cyclic ketone compound (a ′) and an aminoethanol (c), wherein the weight ratio thereof is (a ′) :( c) = 100: 1 to 100. And a mixture of alkali metal hydroxide (b) such that the weight ratio (d) :( b) is 100: 0.01 to 10.0. A method for treating a metal surface, comprising heating the surface of the metal to be heated in a temperature range of 50 to 200C. 4. A mixed solution comprising a cyclic ketone compound (a ′), an aminoethanol (c) and an alkyl sulfoxide (e), wherein the weight ratio is (a ′) :( c) :( e) =
The mixed solution (f) having a ratio of 100: 1 to 100: 1 to 100 is mixed with the alkali metal hydroxide (b) by adding (f) :( b) to 10
0: The surface of the metal mainly composed of stainless steel or iron is adjusted to 50 to 2 by the mixed solution added at 0.01 to 10.0.
A method for treating a metal surface, comprising performing a heat treatment in a temperature range of 00 ° C. 5. The cyclic ketone compound is cyclohexanone,
The metal surface treatment method according to any one of claims 2 to 4, wherein the aminoethanols are ethanolamine, and the alkyl sulfoxide is dimethyl sulfoxide. 6. A metal which is subjected to a heat treatment at 100 to 150 ° C. while being brought into contact with a non-water-soluble solvent, following the method for treating a metal surface according to claim 1. Surface treatment method. 7. A coating layer formed on a metal surface by the metal surface treatment method according to any one of claims 1 to 6,
A metal-based composite material comprising a base material of stainless steel or a metal containing iron as a main component. 8. A production apparatus for producing a synthetic resin, wherein a part or all of a part which comes into contact with a polymerization reactor and / or a liquid containing a raw material or a polymer exiting the reactor is contacted. An apparatus for producing a synthetic resin, comprising the metal-based composite material as described above. 9. A method for producing a synthetic resin, comprising using the production apparatus according to claim 8. 10. The method according to claim 9, wherein the synthetic resin is a resin synthesized from a monomer containing unsaturated nitrile and aromatic vinyl. 11. The manufacturing method according to claim 10, wherein
A method for producing a synthetic resin, comprising using, as a polymerization initiator, at least one or more polymerization initiators selected from polymerization initiators having a crosslinking efficiency of 75 or less.