JPH09208544A - Production of acrylamide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a high quality acrylamide most suitable for a raw material for a polymer having a high molecular weight and good water-solubility by adding a specified additive and performing a specific treating in the hydration reaction of acrylonitrile under a copper-based catalyst. SOLUTION: This acrylamide is produced by adding meta-substituted phenols to the reaction mixture when catalytically dehydrating acrylonitrile with water under a copper-based catalyst and thereby enabling the production not to reduce the catalytic activity and to suppress the by-production of an impurity. Further, the high quality acrylamide is obtained by easily removing the added meta substituted phenols by using a strongly basic anion exchange resin in the purification process of the obtained crude acryl amide and further by bringing into contact thereof with a cation exchange resin. An acrylamide-based polymer with high molecular weight and useful for a coagulant, etc., is obtained by polymerizing the acryl amide. The ratio of acrylonitrile to water is preferably (60:40) to (5:95) by weight and meta substituted phenols are preferably used 50-5000ppm based on the amount of acrylonitrile in this reaction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing acrylamide by catalytic hydration of acrylonitrile with water in the presence of a copper catalyst. More specifically, the present invention relates to a method for producing high-quality acrylamide that enables production of a polymer having a sufficiently high molecular weight and good water solubility.

[0002]

BACKGROUND OF THE INVENTION Acrylamide has hitherto been used as an acrylamide polymer for paper-making chemicals, flocculants, petroleum recovery agents and the like, and has wide applications as a raw material comonomer for various polymers. As a method for producing acrylamide used for these purposes, the so-called sulfuric acid method was used for a long time, but in recent years, a contact method in which a reaction is carried out in the presence of a copper-based catalyst has been developed. Is being implemented industrially on behalf of.

Among the above-mentioned uses of acrylamide, the use of the coagulant, in particular, has been expanded in recent years for wastewater treatment and the like, and with this, remarkable efforts have been made to improve quality performance. Among them, the acrylamide polymer used as a flocculant is required to have a high molecular weight, which is said to directly affect its performance. The required molecular weight range is much higher than that of the acrylamide polymer required for other uses or the molecular weight required for other polymers is usually 1,000,000 or less. Furthermore, since the obtained acrylamide polymer is usually used as a flocculant by dissolving it in water, it is necessary to dissolve it quickly and without leaving any insoluble matter. Further, due to the toxicity of the acrylamide monomer, it is also required that the amount of unreacted monomer in the polymer be a very small amount, for example, 0.2% by weight or less.

[0004] These requirements are properties that are incompatible with increasing the molecular weight, which is the reason why great efforts are made to achieve them. Further, although such a high-molecular-weight acrylamide polymer is said to be only one use of acrylamide, it cannot be widely used for general purposes unless it is suitable for such use, and the method of the present invention. Relates to the production of acrylamide that can also be used in such applications.

The molecular weight referred to in the present invention is based on the test method shown in Example 1 which will be described later, and the water solubility is usually a problem in that a polymer obtained in an aqueous medium is dried. Then, the water content is stored as a dry powder of 20% by weight or less, especially about 10% by weight, and the water solubility referred to in the present invention is mainly used in this sense.

As the acrylamide, an aqueous acrylamide solution obtained by the catalytic hydration reaction of acrylonitrile may be directly subjected to the polymerization reaction, but usually, the acrylamide aqueous solution obtained after the catalytic hydration reaction of acrylonitrile is sufficiently purified before use. It For example, unreacted acrylonitrile is removed by a conventional method such as distillation, or metal ions such as copper, which are eluted from the catalyst component, and by-products such as organic acids are removed by ion exchange resin purification.
However, in order to produce an acrylamide polymer having a high molecular weight and sufficient water solubility, it is said that not only the method of producing the polymer but also the quality of the acrylamide is important. , Several methods have been proposed.

First, various methods for improving a synthetic reaction system have been reported in order to reduce the formation of by-products in the production of acrylamide by the catalytic hydration method of acrylonitrile.

For example, in Japanese Examined Patent Publication No. 50-12409, the activity of a copper-based catalyst is remarkably improved by adding a copper salt such as copper nitrate or copper acetate to the synthesis reaction system. Instead of adding a copper salt, copper is added instead. A part of the system catalyst may be converted into a copper salt, and a method of adding an inorganic acid or an organic acid has been proposed for that purpose. In this case, it is premised that the metallic copper is partially oxidized beforehand or simultaneously.

In addition, Khim. Tekhnol. ,
1983 (3), 3-4, by adding sulfuric acid or acrylic acid to a system using a reduced copper catalyst, both the reaction rate and the selectivity are improved, which is caused by the reaction between an acid and an oxide of copper. It is said to be due to salt.

Further, Japanese Patent Publication No. 4-57663 (PCT W
O 86/00614), a method of adding an oxidizing agent and a reagent for dissolving or reducing the oxidized catalyst in a synthesis solution in the presence of a catalyst such as Raney copper has been proposed. Combinations of copper and organic acids including acetic acid are described. This is said to reduce the formation of by-products.

Further, in JP-A-63-203654, by adding nitric acid or a nitrate and (meth) acrylic acid and / or its salt to a synthetic reaction system, it is possible to prevent deterioration of catalytic activity and deterioration of monomer quality. Is described. It has also been shown that stable production over a long period of time is possible when producing acrylamide.

Further, in JP-A-54-66618, ammonia, ureas, aromatic amines, primary amine
At least one of primary or secondary lower alkylamines, or primary or secondary lower alkanolamines
By adding a kind, it is possible to suppress the by-product of impurities that cannot be removed particularly by a usual ion exchange resin treatment, and the acrylamide polymer produced from the acrylamide thus obtained has a high molecular weight. ,
It is also shown to have sufficient water solubility. Further, it is described that these additives can be easily removed by using a strongly acidic cation exchange resin in the acrylamide purification step.

Further, according to Japanese Patent Laid-Open No. 54-73727,
Meta-substituted phenols are added to the synthetic reaction system in an amount of 0.005 to 10% by weight, preferably 0.1 to 1.0% by weight, based on the raw material acrylonitrile, and cannot be removed particularly by ordinary ion exchange resin treatment. It is possible to suppress the by-production of various impurities. Furthermore, in the purification step of acrylamide, if a strongly basic anion exchange resin is used, this additive can be easily removed. The acrylamide polymer produced is described as having a high molecular weight and sufficient water solubility.

Further, in the production of acrylamide, it is necessary to sufficiently purify acrylamide, which is usually purified with an ion exchange resin. However, some impurities may not be removed by ordinary ion exchange resin purification, and several methods have been proposed to produce higher quality acrylamide.

For example, Japanese Examined Patent Publication No. S61-40217 discloses a method of treating an acrylamide aqueous solution with a cation exchange resin and / or a weakly basic anion exchange resin in the step of purifying acrylamide so that metal ions such as copper are eluted from the catalyst component. It is described that an acrylamide polymer having a high molecular weight and sufficient water solubility cannot be obtained only by removing ionic impurities such as by-products such as organic acids. When an aqueous acrylamide solution is passed through a free base form of a strongly basic anion exchange resin, impurities are produced during the purification process, and the quality of the acrylamide polymer produced from the acrylamide thus obtained is not only poor. The polymerization reaction may not proceed depending on the polymer production conditions. However, it is described that a high-quality acrylamide aqueous solution can be easily obtained by contacting with a free base form of a strongly basic anion exchange resin and then passing through a H form of a cation exchange resin.

Further, in JP-A-56-163107, in an acrylamide purification step, an aqueous acrylamide solution is converted into an H-type cation exchange resin, a weak acid salt-type strongly basic anion exchange resin, and then an H-type weakly acidic cation exchange resin. It is described that when the acrylamide polymer is produced from the obtained acrylamide aqueous solution, the polymerization rate is increased and a high molecular weight polymer can be obtained by sequentially passing the solution.

[0017]

According to the tests conducted by the present inventors, when acrylonitrile described in JP-B-50-12409 is hydrolyzed by contact with water in the presence of a copper catalyst to produce acrylamide. The method of adding nitric acid or nitrate is an excellent method for maintaining and improving the catalytic activity, but the operation continues for a long time, probably because copper that has been oxidized over time accumulates in the reactor. The amount of impurities such as ethylene cyanohydrin and the like is increased, and the catalytic activity is decreased. Further, the quality of acrylamide is evaluated by the water solubility and molecular weight of the acrylamide polymer produced therefrom, but the quality of acrylamide obtained by this method deteriorates over time.

Further, the copper oxide accumulated in the reactor is treated with the above-mentioned Japanese Patent Publication No. 50-12409, Khim. Tekhn
ol. , 1983 (3), 3-4, and Japanese Patent Publication 4-
The method of dissolving with an acid or the like as disclosed in 57663 (PCT WO 86/00614) is effective in reducing the amount of impurities such as ethylene cyanohydrin mainly derived from copper oxide. However, the catalyst activity cannot be recovered by simply dissolving the copper oxide of the catalyst whose activity has once decreased with copper oxide or the like with an acid, and the activity may further decrease in some cases. Further, the quality of acrylamide obtained by these methods is not improved, but the quality is deteriorated depending on the acid.

Further, the method of adding (meth) acrylic acid and / or its salt as an acid as disclosed in JP-A-63-203654 prevents deterioration of catalyst activity and deterioration of acrylamide quality over time. Has a remarkable effect. However, the water solubility and the molecular weight of the acrylamide polymer produced from acrylamide obtained by this method are still insufficient.

Alternatively, of the ammonia, ureas, aromatic amines, primary or secondary lower alkylamines, or primary or secondary lower alkanolamines disclosed in JP-A-54-66618. In the method of adding at least one kind, not only the catalytic activity is remarkably lowered, probably because the added compound is adsorbed on the catalyst, but the quality of acrylamide is hardly improved.

Further, the method of adding meta-substituted phenols described in JP-A-54-73727 does not cause a decrease in catalytic activity, but it is obtained when the added meta-substituted phenols are not removed. The quality of the resulting acrylamide is rather poor. Next, by treating the acrylamide produced by this method with a strongly basic anion exchange resin, the added meta-substituted phenols can be removed. The acrylamide thus obtained is As compared with acrylamide obtained by the method of adding amines to the synthetic reaction system shown in JP-A-54-66618, only a slight improvement in quality is recognized, and the water solubility and molecular weight of the acrylamide polymer are Still not enough. Moreover, JP-A-54-73
The addition amount of meta-substituted phenols in 727 is as follows.
Although it is described as 0.005 to 10% by weight, preferably 0.1 to 1.0% by weight, based on acrylonitrile as a raw material, the present inventors have tested that 0.5% by weight is added. In that case, the quality improvement of acrylamide was hardly improved, and a slight quality improvement was not observed until the addition of 1.0% by weight. This method imposes too much burden on the strongly basic anion exchange resin. It cannot be put to practical use.

Further, acrylonitrile is contact-hydrated with water in the presence of a copper catalyst by a conventionally known method to produce acrylamide, and in the purification step, JP-B-61-40217 is used.
As shown in Fig. 1, when the solution is passed through a strong base anion exchange resin in the free base form and then a cation exchange resin in the H form, the water solubility of the acrylamide-based polymer produced from acrylamide obtained by this method can be determined. However, the molecular weight was completely insufficient.

Further, as shown in JP-A-56-163107, in the purification step of acrylamide, H
Water-solubility of acrylamide-based polymer produced from acrylamide obtained by this method even when it is sequentially passed through a cation exchange resin in the form of a salt, a strongly basic anion exchange resin in the form of a weak acid salt, and then a weak acid cation exchange resin in the form of H. And the molecular weight are similar to those of the acrylamide polymer produced from the acrylamide produced by the method disclosed in JP-B-61-2217, which is insufficient.

According to the present invention, in the production of acrylamide by the catalytic hydration reaction of acrylonitrile and water in the presence of a copper catalyst, it is possible to produce a polymer having a sufficiently high molecular weight and good water solubility, which is of high quality. The purpose is to produce acrylamide.

[0025]

In order to obtain sufficient water solubility and molecular weight of an acrylamide polymer obtained by polymerizing acrylamide, the present inventors have made acrylonitrile catalytically hydrated with water in the presence of a copper catalyst. As a result of diligent studies on additives to the synthetic reaction system when producing acrylamide, addition of meta-substituted phenols did not result in reduction of catalytic activity and could not be removed by ordinary ion exchange resin treatment. It is possible to suppress the by-product of impurities, and by using a strongly basic anion exchange resin in the purification step of acrylamide, the added meta-position substituted phenols can be easily removed, and then the cation exchange resin. When contacted with, the acrylamide polymer produced from the obtained acrylamide has a high molecular weight and sufficient water solubility. It found to have, in which the present invention has been completed.

That is, according to the present invention, when acrylonitrile is hydrated in the presence of a copper catalyst to produce acrylamide, a meta-substituted phenol is allowed to exist in the reaction system and then a strong basic anion exchange is carried out. This is a method for producing acrylamide, which comprises contacting with a resin to remove meta-substituted phenols existing in the reaction system, and then contacting with a cation exchange resin.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a method for producing acrylamide to which the present invention is applied will be briefly described. Examples of the copper-based catalyst used in the method of the present invention include (A) a combination of copper and copper ions in the form of copper wire, copper powder, etc. (B) those obtained by reducing a copper compound with a reducing agent (reduction Copper) (C) One obtained by decomposing a copper compound by heat (decomposed copper) and (D) obtained by developing a Raney alloy with an alkali or the like (Raney copper).

Examples of the above-mentioned method for producing reduced copper include (1) a method of reducing copper oxide with hydrogen, carbon monoxide or ammonia in a gas phase (2) a salt or hydroxide of copper in an aqueous solution formalin ,
There is a method of reducing with hydrazine or sodium borohydride, and (3) a method of reducing a salt or hydroxide of copper with elemental aluminum, zinc or iron in an aqueous solution, etc. Both are considered to be elemental copper.

Examples of the above-mentioned method of producing decomposed copper include (1) a method of thermally decomposing copper hydride obtained by treating a copper compound with sodium hypozincate, etc. (2) copper formate or shu Method of thermally decomposing copper acid acid (3) Method of thermally decomposing so-called cluster copper disclosed in JP-A-49-108015, and (4) Method of directly adding copper acetylide or copper nitride to a hydration reaction system of acrylonitrile. Therefore, the main catalyst component of the obtained product is considered to be elemental copper, including that of item (4).

As an example of the method for producing the Raney copper,
(1) Copper-aluminum alloy with caustic soda, sulfuric acid, water,
Method to develop almost completely with organic amines, and (2)
There is a method of partially developing a copper-aluminum alloy with caustic soda, sulfuric acid, water, an organic amine, etc., and leaving a part of aluminum together with copper, and the main catalyst component of the obtained product is considered to be elemental copper. .

These copper-based catalysts may be supported on a commonly used carrier, or may contain a metal other than copper, such as chromium or molybdenum.

The catalytic activity itself of these copper-based catalysts differs depending on the method of preparation, but the reaction form such as a side reaction differs due to the difference of reduced copper, copper hydride, Raney copper, etc. Rather, they have the same tendency with respect to the tendency to generate impurities.

It is desirable that the catalyst avoid contact with oxygen and oxygen-containing gases before and after use. The reason is that oxygen impairs catalytic activity and increases by-products such as ethylene cyanohydrin.

The hydration reaction of acrylonitrile of the present invention is carried out in the presence of the above-mentioned copper catalyst as follows. The reaction is carried out in a suspension bed in a liquid phase or a fixed bed catalyst bed in a flow system or a batch system.

The weight ratio of acrylonitrile and water used for the hydration reaction is virtually arbitrary, but is preferably 6
It is in the range of 0:40 to 5:95, and more preferably,
The range is 50:50 to 10:90. The reaction rate of acrylonitrile is preferably 10 to 98%,
More preferably, it is in the range of 30 to 95%.

The reaction temperature in the hydration reaction between acrylonitrile and water is preferably 50 to 200 ° C, more preferably 70 to 150 ° C.

The inside of the reactor is kept at the vapor pressure at the above-mentioned temperature and composition or the pressure obtained by adding an inert gas such as nitrogen thereto, but the pressure is usually from atmospheric pressure to 10 atm.
Dissolved oxygen contained in the catalyst, acrylonitrile, water, etc. supplied to the reactor impairs the activity of the catalyst and increases by-products such as ethylene cyanohydrin, so remove them sufficiently before supplying them to the reactor. Is desirable, and for the same reason, it is desirable to keep the atmosphere in the reactor free of oxygen. The reaction liquid taken out from the reactor after the hydration reaction is mainly composed of unreacted acrylonitrile, unreacted water and acrylamide, and further contains byproducts such as ethylene cyanohydrin and copper.

The reaction solution obtained by the above reaction is concentrated by a usual evaporation or distillation operation to obtain an aqueous acrylamide solution, and unreacted acrylonitrile and water are distilled and recovered. These recovered materials can be reused as new reaction raw materials.

An acrylamide aqueous solution obtained by concentrating the above reaction solution (hereinafter, these solutions are abbreviated as acrylamide aqueous solution) is then subjected to cation exchange treatment, chelate resin treatment,
It is purified by various purification methods such as anion exchange treatment, air or oxygen gas treatment, and activated carbon treatment. Further, a so-called synthetic adsorption resin (for example, manufactured by Hokuetsu Carbon Co., Ltd., trade name: adsorption resin) used in a similar manner to the activator or the ion exchange resin can be used. The acrylamide aqueous solution may be subjected to the above-mentioned concentration treatment during or after these purification steps, or may be re-concentrated.

In the present invention, when acrylonitrile is contact-hydrated with water in the presence of a copper catalyst to produce acrylamide, meta-substituted phenols are added to the synthetic reaction system.
Examples of the substituent of this compound include electron withdrawing groups such as hydroxyl group, alkyl group and alkoxy group.
Specifically, resorcinol, m-cresol, 3-methoxyphenol and the like can be used.

The amount of these compounds added is 10 to 10,000 ppm, preferably 5 when expressed as the ratio of the amount of meta-substituted phenols to the weight of acrylonitrile as a raw material.
It is in the range of 0 to 5000 ppm. If it is less than this range, the water solubility and the molecular weight of the acrylamide polymer produced from the obtained acrylamide are insufficient. On the other hand, if the amount exceeds this range, the quality of acrylamide is hardly affected, but the load of the purification step becomes excessive, which is not preferable.

As the method of addition, there are a method of dissolving in raw material water or raw material acrylonitrile, a method of dissolving in a small amount of water, or a method of directly injecting into a reactor or a circulation system of a reaction solution.

In the present invention, the meta-substituted phenols added to the synthetic system can be removed by contacting the strongly basic anion exchange resin in the purification step. Examples of the strongly basic anion exchange resin used here include Levatit MP-500 (trade name, manufactured by Bayer), Levatit MP-600 (trade name, manufactured by Bayer), and Diaion PA-316 (trade name, Mitsubishi). (Chemical company) macroporous type strong basic resin, or Levatit M-5
00 (trade name, manufactured by Bayer), Diaion SA-1
Any gel type strong basic resin such as 0A (trade name, manufactured by Mitsubishi Chemical Corporation) may be used. These are usually commercially available Cl
Since it is a form, it is pre-treated with a dilute alkali to form an OH form (free base form), and then washed thoroughly with water before use.

In the present invention, the meta-substituted phenols added to the synthetic system are removed by the strongly basic anion exchange resin, and then the cation exchange resin is contacted. The cation exchange resin used here may be either strongly acidic or weakly acidic. For example, strong macroporous type acids such as Levatit SP-112 (trade name, manufactured by Bayer), Diaion PK-216 (trade name, manufactured by Mitsubishi Chemical), Amberlite IR-200C (trade name, manufactured by Organo). Resin or Revatit S-
100 (trade name, manufactured by Bayer), Diaion SK-
1B (trade name, manufactured by Mitsubishi Chemical Corporation), Amberlite IR-
Gel type strongly acidic resin such as 120B (trade name, manufactured by Organo), or macroporous type such as Levatit CNP-80 (trade name, manufactured by Bayer), Diaion WK-10 (trade name, manufactured by Mitsubishi Chemical) Any weakly acidic resin may be used. Since commercially available products are usually Na type, they are pre-treated with a dilute acid to form H type, and then washed thoroughly with water before use.

These resins can be packed in a tower and continuously contacted and purified with an aqueous acrylamide solution as a fixed bed, or can be used in a batch system. However, it is preferable to use the former for reasons such as purification efficiency and ease of operation.

Further, prior to the treatment with the strongly basic anion exchange resin and then the cation exchange resin according to the present invention, oxygen treatment may be carried out by contacting an aqueous acrylamide solution with oxygen or an oxygen-containing gas. Alternatively, the ionic impurities may be removed in advance by treatment with a weakly basic anion exchange resin.

When the acrylamide thus obtained was polymerized with acrylamide alone or with other comonomers and evaluated as an acrylamide polymer, the water solubility was remarkably improved and a sufficiently high molecular weight was obtained.

On the other hand, in the purification step of acrylamide, an acrylamide system produced from acrylamide obtained only by removing the added meta-substituted phenols with a strongly basic anion exchange resin and then not contacting with the cation exchange resin. The water solubility and molecular weight of the polymer are insufficient. Although the reason for this phenomenon is not exactly known, it is possible that the meta-substituted phenols can be removed by contact with a strongly basic anion exchange resin, but during this removal, the pH of the acrylamide aqueous solution rises and some impurities are generated. However, it is considered that some or all of this impurity is not removed, and that this impurity has an adverse effect on the production of an acrylamide polymer from acrylamide.

That is, as in the present invention, when acrylonitrile is subjected to a hydration reaction in the presence of a copper-based catalyst to produce acrylamide, a meta-substituted phenol is allowed to exist in the reaction system, and then strongly basic. High-quality acrylamide can be obtained only by contacting with an anion exchange resin to remove meta-substituted phenols existing in the reaction system and then contacting with a cation exchange resin.

Next, the method for producing a high molecular weight acrylamide polymer used as a flocculant or the like is roughly as follows.

Acrylamide is used alone or together with other vinyl polymerization type comonomers. As comonomers, acrylic acid and methacrylic acid or water-soluble salts thereof: alkylaminoalkyl esters of acrylic acid and methacrylic acid or quaternary ammonium derivatives thereof: N- (dimethylaminopropyl) methacrylamide or quaternary ammonium derivatives thereof : Vinyl acetate:
Acrylonitrile etc. can be mentioned. The mixing ratio of these comonomers and acrylamide is usually 100 mol or less, especially 5 mol, per 100 mol of acrylamide.
It is 0 mol or less.

Polymerization of acrylamide with comonomers
Well-known methods such as aqueous solution polymerization and emulsion polymerization are used. Among them, the most widely used general method of aqueous solution polymerization will be described.

The total concentration of acrylamide and comonomer is usually 5-60%. As the polymerization initiator, peroxides such as potassium persulfate, ammonium persulfate, hydrogen peroxide and benzoyl peroxide: azobisisobutyronitrile, 2,
2'-azobis (4-amidinopropane) dihydrochloride,
Azo free radical initiators such as 4,4′-azobis (sodium 4-cyanovalerate): a combination of the above-mentioned peroxide and a reducing agent such as sodium bisulfite, triethanolamine, ferrous ammonium sulfate, so-called A redox catalyst is used.

Regarding the temperature of the polymerization reaction, when the total concentration of acrylamide and comonomer is 15% by weight or more and the obtained polymer has a high molecular weight of 10,000,000 or more, it is difficult to control the temperature by cooling or the like. Therefore, a form of adiabatic polymerization is usually adopted, and in this case, the temperature of the polymerization system rises due to the heat of polymerization as the polymerization proceeds. In this case, the temperature at the start of polymerization is often selected from the range of -5 to 40 ° C, and the temperature after the reaction is, for example,
Reach high temperatures of 55-100 ° C.

In order to obtain a high molecular weight of 10 million or more, especially about 15 million, the total concentration of acrylamide and comonomer, the type and concentration of the polymerization initiator to be used, the reaction temperature, etc. are devised. Similar efforts are made to reduce the amount of unreacted acrylamide to a small amount of, for example, 0.2% by weight or less. There is.

The product obtained by the above-mentioned polymerization reaction is a hydrogel, that is, a rubber-like gel containing almost the same amount of water used to make acrylamide and a comonomer as an aqueous solution, but it is usually a dry powder. In order to obtain a solid product, treatment such as water extraction or dehydration by heat drying, or crushing or crushing of a hydrogel or a dry gel is added. The acrylamide polymer may be chemically modified, for example, by heating caustic soda into a hydrous gel prior to or during these treatments so as to convert a part of the amide groups into carboxyl groups.

As a result of high molecular weight, reduction of unreacted monomers, dry powderization and, in some cases, chemical modification as described above, the resulting polymer often becomes difficult to dissolve in water and the flocculating agent It tends to lose its value as a product such as.

To solve this problem, a method of adding an insolubilizer before, during or after the polymerization reaction, a method of using a specific polymerization initiator, a method of drying the hydrogel under specific conditions, and the like are performed. .

The acrylamide to which the method of the present invention is applied is generally produced by a method comprising hydration reaction, distillation operation, various purification treatments and other incidental steps, and has a high molecular weight as described above. It is used for the production of acrylamide polymers.

[0060]

EXAMPLES The present invention will be described in more detail by way of examples. Example 1 <Production of acrylamide> Acrylonitrile was hydrated in the presence of a copper-based catalyst as follows to give
Acrylamide was obtained.

Catalyst for hydration reaction: Raney copper alloy of 80 mesh or less was developed with caustic soda by a conventional method and washed to produce Raney copper catalyst. Avoid contact with oxygen-containing gases such as air during manufacturing and subsequent handling.

Catalytic hydration reaction: 400 kg of the above catalyst was added to a reactor of SUS made of SUS and having a stirrer and a catalyst separator built therein.
g, and to this, acrylonitrile and water from which dissolved oxygen was removed in advance by using nitrogen gas were respectively 600 g / h and 900 g.
It was fed at a rate of g / h and reacted at 120 ° C. At this time, m-cresol was added to the raw material liquid so as to be 2000 ppm with respect to the weight of the raw material acrylonitrile.
The reaction solution is stirred together with the catalyst to form a suspension, and then passed through the catalyst separator and taken out of the reactor as a solution containing almost no catalyst. The reaction was continued for 3 days.

Concentration: The obtained reaction solution was subjected to batch-type vacuum concentration to distill off the whole amount of unreacted acrylonitrile and part of unreacted water to obtain an aqueous acrylamide solution having a concentration of about 50%. The aqueous acrylamide solution contained copper.

Copper removal treatment: Strong acid cation exchange resin Levatit SP11 made into H form by pretreatment with dilute hydrochloric acid by a conventional method
150 mL of 2 (trade name, manufactured by Bayer) was packed in a glass column, and the acrylamide aqueous solution obtained by the above-mentioned additive removal treatment was passed through this at 900 mL / h. The obtained liquid has a copper content of 0.01 ppm or less and a pH of about 3.
It was 5.

Additive removal treatment: Strongly basic anion exchange resin Levacit MP500 (trade name, manufactured by Bayer) 150 m in a OH form by pretreatment with dilute caustic soda by a conventional method.
L was packed in a glass column, and the acrylamide aqueous solution obtained by the above-described concentration treatment was passed through the column at 900 mL / h. No m-cresol was detected in the obtained liquid, and pH
Was about 8.5.

Cation-exchange resin treatment: A weak acid cation-exchange resin Levatit CNP80 (trade name, manufactured by Bayer) 150 mL, which has been pretreated with dilute hydrochloric acid by a conventional method, is packed in a glass column, and the above-mentioned addition is added thereto. The acrylamide aqueous solution obtained by the agent removal treatment was passed at 900 mL / h. The pH of the obtained liquid was about 6.5. <Method for producing acrylamide polymer> The acrylamide aqueous solution obtained by the above method is polymerized by the following method,
An acrylamide polymer was obtained.

Water was added to the acrylamide solution to give a concentration of 2
The content was adjusted to 0% by weight, 500 g of this was placed in a 1 L polyethylene container, and while maintaining the temperature at 18 ° C., dissolved oxygen in the liquid was removed through nitrogen, and immediately placed in a polystyrene insulation block. Then add this to 200 × 10 ^-6 mpm
(Molar ratio to acrylamide) 4,4′-azobis (sodium 4-cyanovalerate), 200 × 1
0 ^-6 mpm of dimethylaminopropionitrile and 80
Each x10 ^-6 ammonium persulfate was dissolved in a small amount of water and quickly injected in this order. Nitrogen gas was previously passed through these reagents, and a small amount of nitrogen gas was also passed through the polyethylene container before and after the injection to prevent oxygen gas from being mixed. After the injection of the reagent and the induction period of several minutes, the temperature inside the polyethylene container was observed to rise, so the supply of nitrogen gas was stopped. After the temperature reached the peak of about 70 ° C. after about 100 minutes, the polyethylene container was taken out from the heat insulation block, immersed in water at 97 ° C. for 2 hours, and then immersed in cold water for cooling.

The hydrogel of acrylamide polymer thus obtained was divided into small pieces and ground with a meat grinder 1
It was dried with hot air of 00 ° C. for 2 hours and pulverized with a high-speed rotary blade pulverizer to obtain a dry powder acrylamide polymer. This was further sifted, and those having a mesh size of 32 to 42 were separated and used as polymer samples to be subjected to subsequent tests. The water content of the polymer samples was determined as the weight loss by drying with hot air at 125 ° C. overnight, and it was about 10% by weight for all the polymer samples. <Testing Method for Acrylamide Polymer> The water solubility and standard viscosity of the polymer sample obtained by the above method were measured by the following methods.

Water Solubility: Water solubility is 60L in 1L beaker.
Add 0 mL, add 0.66 g of polymer sample (0.6 g of pure content) while stirring with a stirrer blade of a predetermined shape, stir at 400 rpm for 2 hours, and filter the resulting solution through a 150 mesh wire mesh. Then, the water solubility was judged based on the amount of insoluble matter and the filterability. That is, ∘ for completely dissolved, ○ for near-dissolved, ○ for those that have insoluble matter, but those that can be filtered off are △, the passage of the filtrate is slow, and filtration of insoluble matter is practically impossible. Those that could not be marked as x.

Molecular weight: As for the molecular weight, a filtrate obtained by the same operation as above was used to prepare several acrylamide polymer aqueous solutions having different concentrations, to which sodium nitrate corresponding to a concentration of 1 mol / L was added to obtain a capillary type. The intrinsic viscosity was calculated using a viscometer and calculated using the following formula.

Intrinsic viscosity formula = 3.73 × 10 ⁻⁴ × [weight average molecular weight] ^0.66 It is doubtful to apply this formula to an acrylamide polymer having a molecular weight of 10 million or more. Report
on Progress in PolymerPhy
Although suggested by sics in Japan, 20, 5 (1977), it is also widely used.

The filtrate obtained by the above-mentioned water solubility test is a polymer aqueous solution having a concentration of 0.1% when the water solubility is good. To this, sodium chloride corresponding to a concentration of 1 mol / L was added to prepare a BL solution. The viscosity was measured using a BL viscometer using a BL adapter at a rotor rotation number of 60 rpm at 25 ° C. (standard viscosity). Since the standard viscosity obtained by such a method is commonly used as a value having a correlation with the molecular weight, it was also used in this example. When evaluated by such a method, the water solubility of the obtained polymer was good and the molecular weight was sufficient.

Examples 2 to 6 In the catalytic hydration reaction of Example 1, m-cresol was contained in the raw material liquid at 2000 relative to the weight of the raw material acrylonitrile.
Example 1 except that the addition amount to be in ppm, the ion exchange resin used in the additive removal treatment, and the ion exchange resin used in the cation exchange resin treatment are shown in Table 1. The same operation was performed. No additive was detected in the obtained acrylamide in any case. When the finally obtained acrylamide polymer was evaluated, the water solubility was good and the molecular weight was sufficient as in Example 1.

Comparative Example 1 In the catalytic hydration reaction of Example 1, m-cresol was added to the raw material liquid at 2000 p with respect to the weight of the raw material acrylonitrile.
The same operation as in Example 1 was carried out except that nothing was added to the addition so that the pm was reached. The water solubility of the finally obtained acrylamide polymer was not entirely satisfactory.

Comparative Example 2 In the catalytic hydration reaction of Example 1, m-cresol was added to the starting solution at 2000 p with respect to the weight of the starting acrylonitrile.
The same operation as in Example 1 was carried out except that the amount of phenol added was adjusted to 1700 ppm shown in Table 1 so that the concentration was adjusted to pm. No additives were detected in the obtained acrylamide. The water solubility of the finally obtained acrylamide polymer was not sufficiently satisfactory.

Comparative Examples 3 to 6 In the catalytic hydration reaction of Example 1, m-cresol was added to the raw material liquid at 2000 p with respect to the weight of the raw material acrylonitrile.
The same operation as in Example 1 was carried out except that the cation-exchange resin treatment was not carried out. No additives were detected in the obtained acrylamide. The water solubility of the finally obtained acrylamide polymer was not satisfactory.

Comparative Example 7 In the catalytic hydration reaction of Example 1, the same operation as in Example 1 was performed except that the weakly basic anion exchange resin MP62 was used in the additive removal treatment. The additive was detected in the obtained acrylamide aqueous solution, and the water solubility of the finally obtained acrylamide polymer was not completely satisfactory.

Comparative Example 8 In the catalytic hydration reaction of Example 1, the same operation as in Example 1 was performed except that the treatment after the decoppering treatment was not performed. Additives were present in the obtained acrylamide aqueous solution, and the water solubility of the finally obtained acrylamide polymer was not completely satisfactory.

[0079]

[Table 1]

[0080]

From the results shown in Table 1, acrylonitrile was
Hydration reaction in the presence of a copper-based catalyst, when producing acrylamide, by adding a smaller amount of meta-substituted phenols to the reaction system than before, after hydration reaction, contact with a strongly basic anion exchange resin, By removing the meta-substituted phenols existing in the reaction system and contacting them with a cation exchange resin, the quality of the obtained acrylamide can be remarkably improved. That is, it is clear that the water solubility of the acrylamide polymer obtained by polymerizing this is remarkably improved and the molecular weight thereof is sufficiently large.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 41/04 B01J 41/04 Z C07B 63/00 7419-4H C07B 63/00 F C07C 231/06 9547-4H C07C 231/06 231/24 9547-4H 231/24 // C07B 61/00 300 C07B 61/00 300 (72) Inventor Kazuya Katayama 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd. In the company

Claims (2)

[Claims] 1. When hydrating acrylonitrile in the presence of a copper catalyst to produce acrylamide, a meta-substituted phenol is allowed to exist in the reaction system and then contacted with a strongly basic anion exchange resin. A method for producing acrylamide, characterized in that meta-substituted phenols existing in the reaction system are removed and then contacted with a cation exchange resin. 2. The weight ratio of acrylonitrile and water in the reaction system is in the range of 60:40 to 5:95, and the amount of the meta-substituted phenols present is 5 relative to the weight of acrylonitrile.
The method for producing acrylamide according to claim 1, wherein the acrylamide content is in the range of 0 to 5000 ppm.