JPH07119438B2 - Acrylonitrile-A cleaning method for aromatic vinyl polymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for dissolving and removing a polymer substance adhering to a reactor wall when a copolymer containing acrylonitrile and aromatic vinyl is produced.

[Conventional technology]

Conventionally, a polymer attached to a reactor that is produced during industrial production of an acrylonitrile-based copolymer, and a finely crosslinked gel produced as a result of a hydrogen abstraction reaction by a polymer radical or an initiator radical present in a polymerization liquid for the attached polymer. Causes a problem that the heat transfer coefficient of the reactor is lowered or the product is separated from the wall of the reactor and mixed in the product, thereby impairing the appearance of the product.

Therefore, when the amount of the polymer attached to the reactor became large, it was necessary to temporarily stop the production and clean the reactor.

Conventionally, a method of cleaning a reactor with a solvent has been proposed, but in the case of cleaning with a solvent, it is generally impossible to completely remove the polymer material adhering to the wall of the reactor, and a part thereof is swollen, or A polymeric substance that did not dissolve at all remained on the vessel wall, and the cleaning effect was insufficient.

As described above, the polymer substance attached to the polymerization reactor cannot be completely dissolved and removed with a single solvent.

This is mainly because the polymer material attached to the reactor is finely crosslinked by the polymer radicals and the initiator radicals existing in the polymerization solution.

That is, the hydrogen at the α-position of the acrylonitrile group of the polymer constitutional unit is abstracted by the radical, and a reaction between the polymers occurs, so that a slightly crosslinked polymer is produced, and this slightly crosslinked polymer is hardly soluble in the solvent and remains on the vessel wall. It is supposed to do.

On the other hand, JR McCarney, Modern Plastics, p. 118, July issue, 1953, showed that an alkali metal hydroxide in a dimethylsulfoxide solvent reacts with the -CN group of the polymer side chain to cause decomposition of an acrylonitrile-based polymer. Has announced.

As a cleaning method using this alkali metal hydroxide, Japanese Patent Publication Nos. 55-8087 and 61-848, JP-A-63-39907,
The method disclosed in each publication of 63-39995 is known.

However, the solubility of the alkali metal hydroxide in the solvent used in these methods, that is, alkyl amide, alkyl diamide or alkyl sulfoxide, is insufficient, and the hydroxide does not dissolve in the solution and precipitates. However, industrial handling is not preferable because it causes problems with the transfer pump.

Further, the wettability of the reactive alkaline substance and the polymer substance is insufficient, so that the intended cleaning effect cannot be exhibited, the reaction is slow, and the cleaning time is very long.

Further, in the specification of JP-B-61-848, the cleaning effect is significantly different depending on the content of acrylonitrile in the copolymer and the amount of water in the cleaning solution, and in the case of a low acrylonitrile-containing copolymer, the water content in the cleaning solution is It is disclosed that the cleaning effect is maximized when the content is 0.03 to 3.0% by weight.

[Problems to be Solved by the Invention]

It is an object of the present invention to solve the above drawbacks of the prior art and not only to improve the solubility of hydroxide in the above-mentioned solvent but also to significantly improve the cleaning effect.

[Means for Solving the Problems]

That is, the present invention, when acrylonitrile-aromatic vinyl-based copolymer is polymerized to dissolve and remove the high molecular weight copolymer or the finely crosslinked gel-like substance attached to the reactor wall, an aprotic polar solvent 50 ~ 98.9% by weight, alkaline metal hydroxide and / or quaternary ammonium hydroxide
A method for cleaning a polymeric substance excellent in solution viscosity retention, characterized by using 0.1 to 5% by weight and at least 1 to 49.9% by weight of a compound represented by the following general formula I or II.

HOCHRCH ₂ OH ... I (HOCHRCH ₂ ) _X NH _Y ...... II However, the substituent R is H, CH ₃ or CH ₂ OH, and the index X,
Y is an integer satisfying X + Y = 3. The feature of the present invention resides in that the method of washing the polymer substance adhering to the reactor wall is significantly improved by using the compound represented by the following general formula I or II. .

HOCHRCH ₂ OH ... I (HOCHRCH ₂ ) _X NH _Y ...... II (wherein the substituent R is H, CH ₃ or CH ₂ OH, and the index X,
Y is an integer that satisfies X + Y = 3. ) The main reason for this effect is that the alkali metal hydroxide is well soluble in the compounds I and II, and is compatible with the aprotic polar solvent to form a uniform cleaning solution.
It is considered that the -CN group of the polymer adhering to the reactor wall reacts with the alkali metal hydroxyl group to decompose the polymer, resulting in a faster cleaning rate.

The present invention is useful for polymerizing copolymers such as acrylonitrile-aromatic vinyl copolymers such as acrylonitrile-styrene copolymer, acrylonitrile-methyl methacrylate-styrene copolymer, acrylonitrile-styrene-N-phenylmaleimide copolymer. Is the method applied to.

A typical example of the acrylonitrile-aromatic vinyl-based copolymer applicable to the present invention will be specifically described. For example, a copolymer containing 8 to 50% by weight of an acrylonitrile unit, wherein the aromatic vinyl compound unit is Styrene, α-methylstyrene, paramethylstyrene, vinyltoluene, t
-Butyl styrene, chlorostyrene, etc.
Including 92% by weight, if necessary, as other copolymerizable monomers, acrylic acid esters such as methyl acrylate, ethyl acrylate and butyl acrylate, methyl methacrylate, ethyl methacrylate, methacrylic acid It is a copolymer comprising 0 to 45% by weight of a copolymerizable monomer unit containing a methacrylic acid ester such as butyl or a maleimide such as phenylmaleimide or orthochlorophenylmaleimide.

Further, as the polymerization method of the present copolymer, suspension polymerization, continuous solution polymerization, continuous bulk polymerization and the like can be applied.

As the aprotic polar solvent of the present invention, dimethyl sulfoxide, N, N dimethylformamide, N, N dimethylacetamide, sulfolane, hexamethylphosphoramide and the like can be used.

The amount used in the cleaning liquid is 50 to 98.9% by weight, preferably
70-85% by weight. If it is less than 50% by weight, the solvent effect of the cleaning liquid on the polymer decreases, which is not preferable. 9
If it is used in an amount of more than 8.9% by weight, the solubility of the hydroxide decreases, which is not preferable.

Use of sodium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, etc. as typical examples of the alkali metal hydroxide and quaternary ammonium hydroxide of the present invention. Can be done.

The amount of these substances used in the cleaning liquid is 0.1 to 5% by weight, preferably 0.2 to 2% by weight. Below 0.1% by weight,
The amount is insufficient to react and decompose with the CN group, and the cleaning effect is insufficient, which is not preferable. If it is used in an amount exceeding 5% by weight, a precipitate is generated in the washing solution, which is not preferable, and a reaction between the excess hydroxide and the material of the reactor is unfavorable.

The compound represented by the general formula I or II is HOCHRCH ₂ OH ... I (HOCHRCH ₂ ) _X NH _Y ...... II (wherein the substituent R is H, CH ₃ or CH ₂ OH, and the index X,
Y is an integer that satisfies X + Y = 3. ) Representative examples include ethylene glycol, 1,2 propanediol, glycerin, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, 3-amino-1,2 propanediol, etc. Can be used. These things-at least 1
The amount of seed used in the cleaning solution is 1 to 49.9% by weight, preferably 5
Is in the range of up to 20% by weight.

If it is less than 1% by weight, the solubility of the hydroxide is insufficient and the cleaning effect of the present invention cannot be expected. 49.9% by weight
If it is used in excess of the above range, the solubility of the polymer decreases, which is not preferable.

In the prior art, a copolymer having an acrylonitrile unit content of 5 to 33% by weight has a water content of 0.03% in the cleaning liquid.
~ 3.0 wt% has a significant effect, but 0.03 wt%
It is disclosed that the cleaning effect is remarkably reduced when used at less than 3.0% by weight.

The effect of the compound represented by the general formula I or II of the present invention is, as shown in Examples and Comparative Examples of the present invention, a critical value that the effect is exhibited only when used in a specific ratio like water in the prior art. However, in the range used in the present invention, there is a unique relationship between the amount used and the cleaning effect, and the polymer degrading effect is excellent.

That is, when the degradability effect of the polymer is expressed by the retention rate of the solution viscosity, the method of the prior art shown in the comparative example has a retention rate of 21 to 98% and decomposition does not proceed so much. It can be seen that the decomposition progresses faster with 9 to 20%.

〔Example〕

Examples 1-8, Comparative Examples 1-8 High-molecular-weight AS copolymer having a composition of 30% by weight of acrylonitrile (A) and 70% by weight of styrene (S) and 10% methyl ethyl ketone (MEK) solution at 25 ° C. and viscosity of 28.1 cp. For the combination, a chemical cleaning solution was used, and the decomposition rate was examined from the decrease in the molecular weight due to the main chain cleavage.

In a 200 ml ampoule bottle, put 100 g of the cleaning liquid shown in Table 1, warm to 80 ° C, replace with nitrogen, add 5 g of AS copolymer having a viscosity of 7 and hold at 80 ° C for 2 hours while shaking. Reprecipitate the decomposition product in a large amount of methanol from 100 ° C
After vacuum drying for 24 hours, the viscosity of 10% MEK solution at 25 ° C was measured. Table 1 shows the composition of various cleaning solutions, the solution viscosity after cleaning the copolymer, and the solution viscosity before cleaning and the retention rate of the viscosity.

Examples 9 to 13 and Comparative Examples 9 to 13 In this example, decomposition rates of acrylonitrile-based high molecular weight copolymers having various compositions were investigated from the viewpoint of reduction in molecular weight.

In a 200 ml ampoule bottle, put 95 gr of dimethyl sulfoxide, 4.5 gr of water (or monoethanolamine D5) and 0.5 gr of sodium hydroxide, heat to 120 ° C., and then replace with nitrogen,
5gr of acrylonitrile-based copolymer powder having various compositions shown in Table 2 was charged and shaken at 120 ° C for 4 hours, and then reprecipitated in a large amount of methanol,
After vacuum drying at 0 ° C for 24 hours, the viscosity of 10% MEK solution at 25 ° C was measured. Table 2 shows the composition of various copolymers and the compounds (I), (II) or water in the cleaning liquid, the solution viscosity retention ratio calculated from the solution viscosity of the copolymer before cleaning and the solution viscosity after cleaning. Indicated.

Examples 14 to 16 and Comparative Examples 14 to 16 In this example, a 10% MEK solution at 25 ° C. having a composition of 30% by weight of acrylonitrile and 70% by weight of styrene, a high molecular weight AS copolymer having a viscosity of 28.1 cp was chemically washed. At this time, the influence of coexistence of acrylonitrile monomer in the system on the decomposition rate of the copolymer was examined.

In a 200 ml ampoule bottle, add 95 g of dimethyl sulfoxide, 4.5 g of water or monoethanolamine (MEA), 0.5 g of sodium hydroxide and acrylonitrile in the amount shown in Table 3 to 100 parts by weight of these and heat to 80 ° C. Then, after substituting with nitrogen, add 5 g of an AS copolymer having a particle size of 7 and shake.
After holding at 80 ° C for 2 hours, the decomposed product was reprecipitated in a large amount of methanol, vacuum dried at 100 ° C for 24 hours, and then the viscosity of 10% MEK solution at 25 ° C was measured. Table 3 shows whether the compounds (I), (II) or water in the washing solution, the number of parts by weight of the acrylonitrile monomer added, the solution viscosity after washing and the solution viscosity 28.1p of the copolymer before washing and after decomposition The solution viscosity retention rate calculated from the solution viscosity is shown.

Example 17 40 g of an AS copolymer gelled product (acrylonitrile, styrene copolymer was continuously produced by bulk polymerization for 6 months on the side wall in the separable flask of 1), and then the reactor was opened and collected from the wall surface. (Acrylonitrile content 31.8% by weight of unreacted monomer removed by methyl ethyl ketone insoluble gel) was made into a plate and fixed by wrapping it in a 10-mesh wire netting, and 760 g of dimethyl sulfoxide, 36 g of monoethanolamine, and hydroxylation. Add a chemical cleaning solution composition consisting of 4 g of sodium, under a nitrogen stream at 80 ° C, rotating speed of stirrer 60 rp
washed with m. The wire net was taken out every hour, and the attached cleaning liquid was replaced with methanol, and then vacuum dried for 15 minutes, and the weight of the undissolved gel content inside the wire net was measured. In this embodiment, 4
By the time the weight of undissolved gel decreased over time,
After that, the weight became almost 0, indicating that the washing dissolution was completed within 4 hours.

Comparative Example 17 36 g of water was used in place of the monoethanolamine in the chemical cleaning liquid composition in Example 17, and the same gelation product and the same experimental procedure were used for cleaning and dissolution. In this comparative example, the weight of the undissolved gel decreased with time until after heating for 15 hours, but after that, the weight became almost 0, indicating that at least 14 hours were required for washing and dissolution.

Example 18 83 g of an AS copolymer swollen gel product (acrylonitrile, styrene copolymer was continuously produced by bulk polymerization for 6 months on the side wall in the separable flask of 1), and then the reactor was opened and collected from the wall surface. Methyl ethyl ketone sparingly soluble gelling product with acrylonitrile content of 31.8% by weight containing polymer content of 48% by weight and acrylonitrile monomer of 11.2% by weight)
The plate is wrapped in a wire mesh of 10 mesh and fixed, and 760 g of dimethyl sulfoxide and 36 mg of monoethanolamine
and a chemical cleaning liquid composition consisting of 4 g of sodium hydroxide were added, and the composition was washed under a nitrogen stream at 80 ° C. at a rotation speed of a stirrer of 60 rpm. The wire net was taken out every hour, and the attached cleaning liquid was replaced with methanol, and then vacuum dried for 15 minutes, and the weight of the undissolved gel content inside the wire net was measured. In this example, the weight of the undissolved gel portion decreased with time until 6 hours, but after that, the weight became almost 0, and the washing dissolution was completed within 6 hours even in the system containing the acrylonitrile monomer. I showed that.

Comparative Example 18 36 g of water was used in place of the monoethanolamine in the chemical cleaning liquid composition in Example 18, and other similar gel products,
Washing and dissolution were carried out by the same experimental procedure. In this comparative example, the weight of the undissolved gel component decreased with time until 28 hours, but after that, the weight became almost 0, and in the system containing the acrylonitrile monomer, at least 28% was required for washing dissolution.
It showed that it needed time.

Example 19 In this example, an acrylonitrile-styrene copolymer is continuously produced on an industrial scale for 6 months, and the gelled product is washed and dissolved with the following chemical cleaning liquid composition for polymerization of 11 m ³ in volume.

On the wall surface and agitator surface in the main polymerization tank, various gelled substances or high molecular weights are mainly formed of gelled substance having acrylonitrile content of 31.8% by weight, which is hardly soluble in methyl ethyl ketone, and polymer content 48% and acrylonitrile monomer 11.2% by weight. It has been found from calculation and actual measurement that the copolymer has about 500 kg of adhesion.

Now, in a separate tank, a chemical cleaning liquid composition consisting of 11 t of dimethyl sulfoxide, 520 g of monoethanolamine and 27 kg of sodium hydroxide was prepared and then introduced into the nitrogen-substituted main polymerization tank. At a liquid temperature of 80 ° C, 10
When the system was mixed at a rotational speed of rpm and kept for 24 hours, the polymer concentration in the solution approached the calculated limit value of 2% by weight. However, considering the dead space in the polymerization tank, the stirrer was used. Was rotated in reverse and held for another 24 hours. After the completion of washing, the washing liquid was collected through a collecting system, the inside of the polymerization tank was replaced with a clean solvent, and the inside was opened. As a result, no traces of gelled matter were observed, including the inner wall surface of the polymerization tank and the stirrer surface.

Comparative Example 19 Examples 1 to 8 were carried out by using a cleaning liquid having a composition of 95% by weight of dimethyl sulfoxide and 5% by weight of monoethanolamine.
The same operation was performed and the solution viscosity was measured. The viscosity measurement result was 28.1 (cp), and the viscosity retention rate was 100%.

〔The invention's effect〕

The present invention is to find a polymer cleaning solution comprising an aprotic polar solvent and an alkali metal hydroxide or a quaternary ammonium hydroxide and a specific compound. The cleaning effect is significantly improved, and the cleaning time can be greatly shortened.

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Claims (1)

[Claims] 1. An aprotic polar solvent for dissolving and removing a high molecular weight copolymer or a finely cross-linked gel-like substance adhering to a reactor wall when polymerizing an acrylonitrile-aromatic vinyl copolymer. To 98.9% by weight, alkaline metal hydroxide and / or quaternary ammonium hydroxide 0.1 to 5% by weight, and at least one compound represented by the following general formula I or II 1 to 49.9% by weight. A method for cleaning a polymer substance having excellent solution viscosity retention, characterized by using. HOCHRCH ₂ OH I (HOCHRCH ₂ ) _X NH _Y II (provided that the substituent R is H, CH ₃ or CH ₂ OH, and the indices X and Y are integers satisfying X + Y = 3.)