JPH08193101A - Continuous production of partly neutralized copolymer of monoethylenic dicarboxylic acid and monoethylenic monocarboxylic acid - Google Patents

Abstract

PURPOSE: To continuously produce the objective copolymer with a high conversion in a short time by continuously transferring a reaction mixture obtained in a stirring reactor to a tubular reactor and adding the remainder of the starting materials thereto to further react the reaction mixture. CONSTITUTION: 100% of a monoethylenic dicarboxylic acid (A) in which 55-75mol% of the carboxyl groups have been neutralized is fed into a first reactor having a stirrer together with 80-97wt.% of a monoethylenic monocarboxylic acid (B) to react the reactants in the presence of a radical- polymerization initiator. The resulting reaction mixture containing the unreacted acid (A) is continuously transferred to one or more tubular reactors. The remainder of the acid (B) is fed in portions through two or more parts of at least one of the tubular reactors and/or through one part of each of two or more of the tubular reactors in such a manner that the acid (B) added is reacted in a residence time of 10-40 min. Thus, the objective copolymer can be produced in a short time with a low energy consumption and a high conversion.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a monoethylenically unsaturated dicarboxylic acid (hereinafter referred to as unsaturated dicarboxylic acid) and a monoethylenically unsaturated monocarboxylic acid (hereinafter referred to as unsaturated monocarboxylic acid). It is an object of the present invention to provide a method for efficiently and continuously producing a partially neutralized copolymer. The copolymer produced by the method of the present invention has a narrow molecular weight distribution and is suitable for a detergent builder.

[0002]

2. Description of the Related Art Various methods have hitherto been proposed for producing a copolymer of an unsaturated dicarboxylic acid and an unsaturated monocarboxylic acid. Many of them are primarily aimed at increasing the reaction rate of less reactive unsaturated dicarboxylic acids and reducing the amount of unreacted monomer in the final product. For example, there is a method in which both carboxylic acids are continuously polymerized at a temperature of 200 to 400 ° C. by bulk polymerization, but this method has a large amount of residual monomers and the resulting copolymer has insufficient physical properties. Further, a method of polymerizing in a state where 20 to 80% of both monomers are neutralized during the polymerization reaction has been proposed, and a copolymer having a small amount of residual monomer and favorable physical properties is obtained. This method is discontinuous, requires a lot of time and energy, and is not preferable in practice.

Further, Japanese Patent Application Laid-Open No. 59-66407 discloses a technique of continuously copolymerizing in a plurality of reactors, which has an excellent performance of co-polymerization due to low energy consumption in a short time. It is said that a merger will be obtained. The feature is that, in addition to the above-mentioned neutralization of the monomer, a part of the unsaturated monocarboxylic acid is additionally supplied to the second reactor and thereafter, and according to the embodiment, it is divided into the second reactor and thereafter. The proportion of unsaturated monocarboxylic acid supplied is 23 to 50%. However, when the amount of the additional monomer is large as described above, the molecular weight distribution of the produced copolymer is widened, the viscosity of the reaction mixture is increased, and a copolymer which is particularly preferable for a detergent builder cannot be obtained. Further, in the above-mentioned technology, regarding the reaction time, it is only described that the reaction solution is taken out from the final reactor with a residence time of 0.5 to 8 hours, preferably 1 to 5 hours, and the reaction time in each reactor is described. Etc. No details are given.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems by providing a partially neutralized copolymer of an unsaturated dicarboxylic acid and an unsaturated monocarboxylic acid in a short time with low energy consumption. It is an object of the present invention to provide a method for producing a high polymerization rate.

[0005]

The method for continuously producing a partially neutralized copolymer of a monoethylenically unsaturated dicarboxylic acid and a monoethylenically unsaturated monocarboxylic acid according to the present invention comprises:
The above unsaturated dicarboxylic acid was added to a first reactor having a stirring device, using monoethylenically unsaturated dicarboxylic acid and monoethylenically unsaturated monocarboxylic acid in which 55 to 75 mol% of all carboxyl groups were neutralized. And / or 80 to 97% by weight (in terms of unsaturated monocarboxylic acid) of the total charged amount of the unsaturated monocarboxylic acid and / or salt thereof is supplied to supply the radical polymerization initiator. The reaction mixture is allowed to react in the presence of the unreacted unsaturated dicarboxylic acid and / or salt thereof, and the reaction mixture is continuously transferred to at least one tubular reactor, and at least one reaction in the tubular reactor is carried out. From the plurality of locations in the reactor and / or one location in two or more reactors, the residual amount of the charged amount of the unsaturated monocarboxylic acid and / or its salt is separately and additionally supplied, and the above-mentioned satiety is additionally supplied. The residence time of monocarboxylic acids and / or salts thereof which comprises reacting a 10-40 min.

Examples of the above-mentioned "unsaturated dicarboxylic acid" include maleic acid, itaconic acid, mesaconic acid, fumaric acid, methylenemalonic acid, citraconic acid, etc., which are used as they are or in the form of a salt after neutralization. It Further, anhydrides of the above unsaturated dicarboxylic acids, such as maleic anhydride, may also be used, and those obtained by saponifying these anhydrides may also be used (above, free acids, anhydrides and salts or saponified products thereof are Collectively, hereinafter referred to as unsaturated dicarboxylic acid-based monomer.).

As the above-mentioned "unsaturated monocarboxylic acid", acrylic acid and methacrylic acid are particularly preferable, but vinyl acetic acid, allyl acetic acid, propylidene acetic acid, ethylidene propionic acid, dimethyl acrylic acid and the like can be used. These are used in the form of a salt as they are or after being neutralized (hereinafter, the free acid and its salt are collectively referred to as an unsaturated monocarboxylic acid-based monomer). The present invention
In particular, the present invention provides a production method useful for the copolymerization of maleic anhydride and acrylic acid.

The above unsaturated dicarboxylic acid and unsaturated monocarboxylic acid are neutralized or saponified in the case of an unsaturated dicarboxylic acid anhydride so that 55 to 75% of all the carboxyl groups thereof become salts, and used for the reaction. The rest is used in the free acid form. In the present invention, either an unsaturated dicarboxylic acid or a monocarboxylic acid may be neutralized or saponified, but an unsaturated dicarboxylic acid or an anhydride thereof, which is less reactive than an unsaturated monocarboxylic acid, may be neutralized or saponified. Therefore, it is preferable to increase the proportion of highly reactive reactive species, improve the polymerization rate, and increase the reaction rate. The neutralization or saponification may be performed outside the reaction system in advance, or may be performed by supplying a neutralizing agent or the like into the first reactor. Further, if necessary, a neutralizing agent or the like may be supplied together with the unsaturated monocarboxylic acid type monomer in the tubular reactor to neutralize or saponify.

The salts of unsaturated dicarboxylic acids and unsaturated monocarboxylic acids include alkali metal salts containing sodium hydroxide, potassium hydroxide, lithium hydroxide and the like as neutralizing agents, trimethylamine, triethylamine, hydroxyethylamine and the like. In addition to amine salts used as solvates, ammonium salts and the like can be used. The neutralization or saponification may be carried out either before the polymerization reaction or during the reaction step as described above, but the rate of neutralization or saponification is 55 during the whole reaction.
Must be in the range of ~ 75 mol%. If the amount is out of this range, the reactivity of the unsaturated dicarboxylic acid-based monomer will decrease, and the extent of this decrease will be the neutralization or saponification rate of 5%.
It is remarkable when it is less than 5 mol%.

The unsaturated dicarboxylic acid type monomer and the unsaturated monocarboxylic acid type monomer are the total amount of all charged amounts (for the carboxylate salt, the amount converted to the carboxylate salt, the same applies hereinafter). Is 100 parts by weight, it is preferable to use 15 to 65 parts by weight of the unsaturated dicarboxylic acid type monomer and 85 to 35 parts by weight of the unsaturated monocarboxylic acid type monomer. When the amount of the unsaturated dicarboxylic acid-based monomer is less than 15 parts by weight, it becomes difficult to impart the characteristics obtained by copolymerizing the unsaturated dicarboxylic acid to the obtained copolymer, and when it exceeds 65 parts by weight, the reactivity decreases. It is not preferable because it may occur.

As the above-mentioned "radical polymerization initiator" (hereinafter referred to as a polymerization initiator), a water-soluble initiator can be used, and examples thereof include hydrogen peroxide, sodium peroxydisulfate, ammonium peroxydisulfate, and azo- Bis- (2-aminopropane) hydrochloride and the like, and combinations thereof can be used. Redox coinitiators such as sodium sulfite, triethanolamine, ascorbic acid and salts of heavy metals may also be used in small amounts. The polymerization initiator is preferably used in an amount of 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on the total amount of the monomers.
Further, in the radical polymerization in an aqueous medium, a usual regulator such as thioglycolic acid, a chain extender such as formaldehyde, acetaldehyde and methylenebisacrylamide, divinyl glycol, etc. are added in an amount of 0.1 to 5 with respect to the total amount of the monomers. It is also possible to increase the reactivity by using about wt%.

The "first reactor having a stirring device" used in the method of the present invention is not particularly limited in its type and the like as long as it can sufficiently stir the reaction mixture, but it is equipped with an ordinary stirring blade. A tank reactor is preferred. Further, when the reaction is carried out at a relatively low temperature under normal pressure, the first reactor does not have to be a pressure vessel in particular, but when the reaction is carried out in pressurized water, it is necessary to use a pressure vessel such as an autoclave.

Specific examples of the "tubular reactor" include a tubular reactor, a tower reactor, a static mixer and the like, or a combination thereof. As a residual amount of the charged amount of the unsaturated monocarboxylic acid-based monomer and a method of additionally supplying the polymerization initiator to the tubular reactor in a divided manner, these may be directly supplied from a specific portion of the tubular reactor. However, the unsaturated monocarboxylic acid type monomer to be supplied and the polymerization initiator are premixed with the reaction mixture from the first reactor or the tubular reactor of the previous stage by an appropriate stirring device, and then the reactor of the next stage is used. Is preferable because it can be mixed rapidly and sufficiently.

Further, as the tubular reactor, a plurality of reactors having only one supply point of the unsaturated monocarboxylic acid type monomer may be connected, or a plurality of supply points may be provided in the transfer direction of the reaction mixture. One unit or two or more units may be connected together. In the present invention, the above-mentioned two types of reactors can be appropriately combined and used, and in any case, the unsaturated monocarboxylic acid-based monomer to be additionally supplied may be dividedly supplied at least twice.

The higher the number of times of the above-mentioned additional supply (which may be expressed by the concept of the number of stages), the higher the final polymerization rate becomes, and the same in the case where the proportion of unsaturated dicarboxylic acid monomer having a low reactivity is large. It is necessary to increase the number of stages to achieve the final polymerization rate. However, the polymerization rate is 99
After exceeding 0.1%, the rate of increase becomes considerably small, and practically it may be about 5 stages, and even if it is 10 stages or more, the apparatus and operation become complicated and the effect of increasing the polymerization rate becomes small.

In the method of the present invention, the unsaturated dicarboxylic acid-based monomer is supplied to the first reactor in the entire amount thereof, and the unsaturated monocarboxylic acid-based monomer is contained in the amount of "80 to 97% by weight of the total amount. Is supplied to the first reactor and copolymerized in the presence of a polymerization initiator using an aqueous medium, usually water as a medium. The reaction temperature may be in the range of 50 to 150 ° C, and is usually about 80 to 100 ° C. Further, the residence time in the first reactor is not particularly limited and is usually 120 to 300.
Minutes.

The proportion of the unsaturated monocarboxylic acid-based monomer charged into the first reactor is important. If the amount of the monomer fed into the first reactor is less than 80% by weight of the total amount charged, the molecular weight distribution of the reaction product will be small. And the viscosity becomes too high to make the operation difficult, and when it exceeds 97% by weight, the conversion rate of unsaturated dicarboxylic acid decreases.

The supply ratio of the unsaturated monocarboxylic acid type monomer from each supply point to the tubular reactor is not particularly limited, but, for example, a method of supplying an approximately equal amount to each point may be used. Furthermore, the residence time at each supply point is "10-40 minutes"
Is. In the present invention, the residence time means a value between each supply point and does not matter whether or not an appropriate stirring device is provided. If the residence time is less than 10 minutes, the monomers supplied in the preceding stage may not react sufficiently, and if the residence time exceeds 40 minutes, the polymerization rate is hardly improved further.

Further, the polymerization initiator may be supplied to the first reactor in the total amount, or a part thereof may be supplied to the subsequent tubular reactor together with the unsaturated monocarboxylic acid type monomer. For example, 60 to 90% of the total amount may be supplied to the first reactor, and the residual amount may be supplied into the tubular reactor together with the residual amount of the unsaturated monocarboxylic acid-based monomer. It is preferable to divide and supply the remaining amount of the polymerization initiator according to the supply amount (ratio) of the monomer to the supply point, as compared with the case where the entire remaining amount is supplied in the first stage of the tubular reactor. The polymerization rate can be further improved.

[0020]

[Function] Unsaturated dicarboxylic acid has poor reactivity, while
Unsaturated monocarboxylic acids are very reactive. Therefore, in copolymerizing both, even if the total charged amount of both monomers is fed into one reactor and reacted, a considerable amount of unsaturated dicarboxylic acid remains unreacted in the reaction mixture. I will end up. Therefore, a method in which unsaturated monocarboxylic acid is dispersedly supplied and a so-called aging reaction is performed or a plurality of reactors are used, and a part of highly reactive unsaturated monocarboxylic acid is dispersedly supplied to the second reactor and thereafter. A method for increasing the polymerization rate of unsaturated dicarboxylic acid has been considered. But,
In the former case, the reaction takes a very long time, which is not practical, and in the latter case, by simply supplying the unsaturated monocarboxylic acid-based monomer in a dispersed manner, the polymerization rate of the unsaturated dicarboxylic acid is further increased, and excellent physical properties are obtained. It is not possible to obtain a copolymer having

In the present invention, the first reactor is a stirrable reactor, preferably a tank reactor equipped with stirring blades, and as a subsequent reactor, a plurality of tubular reactors and / or unsaturated monocarboxylic acids are used. By using a tubular reactor provided with a plurality of supply points for the acid-based monomer and the like, and further by specifying the ratio of the unsaturated monocarboxylic acid-based monomer to be dispersed and supplied and the residence time of each stage in the tubular reactor, By the reaction over time, a copolymer having a high polymerization rate and a narrow molecular weight distribution, which is particularly suitable for a detergent builder, is obtained. The reactor must be a combination of the above. For example, even if an attempt is made to carry out the whole reaction in a tubular reactor having a multi-stage number, there are many operational problems including insufficient stirring and mixing, and the copolymer Even if it is obtained, it has a wide molecular weight distribution and a high viscosity, which is not preferable especially for a detergent builder. Further, the monomer to be polymerized in the present invention is an unsaturated dicarboxylic acid type monomer and an unsaturated monocarboxylic acid type monomer, and a monomer copolymerizable therewith, for example, (meth) acrylamide, acrylamide dimethyl propane sulfone is preferable. The combined use of water-soluble monomers such as acid and polyalkylene glycol (meth) acrylate is also one of the embodiments of the present invention.

[0022]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. In each of the following experiments, each characteristic value was measured by the following method. Neutralization rate: Calculated from the charged amount of sodium hydroxide relative to the charged amount of acrylic acid and maleic acid. Polymerization rate: The amount of residual monomer in the reaction solution after the reaction was measured and calculated by liquid chromatography. Number average and weight average degree of polymerization: The copolymer obtained by the reaction was measured by gel permeation chromatography.

(1) Effect of Neutralization Rate on Polymerization Rate Experimental Example 1 and Comparative Experimental Examples 1 to 3 Into a CSTR reactor having an internal volume of 0.4 liter, 2.2 mol / kg of acrylic acid and 0.9 mol of maleic acid. / Kg
And sodium persulfate (hereinafter abbreviated as NPS).
0.05 mol / kg was supplied at a rate of 10 g / min, and an equivalent ratio of 0.25, 0.5, 0.66, and 0.1 to all the carboxyl groups of acrylic acid and maleic acid.
79 sodium hydroxide was added, with water as medium, 1
The reaction was carried out at 00 ° C. for 47 minutes, and each of acrylic acid and maleic acid and the total polymerization rate were measured. Table 1 shows the experimental conditions and results.

[0024]

[Table 1]

According to the results shown in Table 1, the polymerization rate of acrylic acid is as high as about 94 to 95% at any neutralization rate, but maleic acid is 62.6% at a neutralization rate of 25 mol%. ,
The neutralization rate of 50 mol% is 76.7%, and the neutralization rate of 79 mol% is 77.1%, whereas the neutralization rate is 66 mol%.
It turns out that it is as high as 81.4%. Although the hydrogen ion concentration is 5.7 when the neutralization rate is 66 mol%, the copolymerizability theoretically depends on the hydrogen ion concentration, not the neutralization rate, and the monomer species or composition is significantly different. However, the optimum neutralization rate is in the range of 55 to 75 mol% within the range of monomer species and composition for obtaining a useful copolymer.

(2) Production of Copolymer Using CSTR Reactor and Tubular Reactor Having Plural Monomer Feeding Points Example 1 CSTR reactor having an internal volume of 2 liters as the first reactor,
As the second reactor, a tubular reactor having an inner diameter of 2 mm and equipped with a static mixer and having five supply points of unsaturated monocarboxylic acid-based monomers and the like was used, and according to the supply conditions of the monomers and the like shown in Table 2, 100 with water as medium
The copolymer was prepared at ° C. A supply ratio of acrylic acid or the like to each supply point of the first reactor and the second reactor, and a neutralization ratio,
The feeding rate of monomers and the like, the residence time, the polymerization rate of acrylic acid and maleic anhydride in each stage, and the weight average polymerization degree and number average polymerization degree of the obtained copolymer were measured. The results are shown in Table 2 together with the reaction conditions.

Example 2 A copolymer was produced in the same manner as in Example 1 except that the reaction conditions such as the supply conditions of monomers and the like were changed to those shown in Table 3.
The polymerization rate and degree of polymerization of each monomer were measured in the same manner as in Example 1. The results are shown in Table 3 together with the reaction conditions.

(3) Effect of additional monomer amount and number of stages Example 3 and Comparative Example 1 A copolymer was prepared in the same manner as in Example 1 except that the reaction conditions such as the feeding conditions of the monomers were changed to those shown in Table 4. Manufacture
The effect of the amount of monomer additionally supplied in the tubular reactor was examined. The polymerization rate and degree of polymerization of each monomer were measured in the same manner as in Example 1. The results are shown in Table 4 together with the reaction conditions. Comparative Example 1 has an additional monomer content of 23%.

Example 4 A copolymer was produced in the same manner as in Example 1 except that the reaction conditions such as the conditions for supplying monomers and the like were changed to those shown in Table 5.
The influence of the case where the amount of monomer additionally supplied and the number of stages of additional supply in the tubular reactor were three was examined. The polymerization rate and degree of polymerization of each monomer were measured in the same manner as in Example 1. The results are shown in Table 5 together with the reaction conditions.

Example 5 and Comparative Example 2 A copolymer was produced in the same manner as in Example 2 except that the reaction conditions such as the feeding conditions of the monomers were changed to those shown in Table 6.
The effect of the amount of monomer additionally supplied in the tubular reactor was examined. The polymerization rate and degree of polymerization of each monomer were measured in the same manner as in Example 1. The results are shown in Table 6 together with the reaction conditions. Comparative Example 2 has an additional monomer content of 23%.

Example 6 A copolymer was produced in the same manner as in Example 2 except that the reaction conditions such as the conditions for supplying monomers and the like were changed to those shown in Table 7.
The influence of the case where the amount of monomer additionally supplied and the number of stages of additional supply in the tubular reactor were three was examined. The polymerization rate and degree of polymerization of each monomer were measured in the same manner as in Example 1. The results are shown in Table 7 together with the reaction conditions.

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

[Table 7]

In Examples 1 and 2, the ratio of the total amounts of acrylic acid and maleic anhydride charged was 75:25, respectively.
And 64:36, which is almost the same except that the feed rate in the tubular reactor is different accordingly, and in all of Examples 1 and 2, the proportion of acrylic acid charged into the tubular reactor is the same. It is 10% of the charged amount.

In Example 1, the degree of polymerization of acrylic acid was the first
98.10% in the reactor, finally 99.94%, maleic anhydride 91.76% in the first reactor, finally 99.94%.
73%, and in Example 2, the polymerization rate of acrylic acid was 96.89% in the first reactor, finally 99.91%, and maleic anhydride was 86.59% in the first reactor. To 9
It is 8.66%, and the polymerization rate is higher in Example 1 in which the ratio of maleic anhydride is lower. Further, the molecular weight distribution is 2.28 in Example 1 and 2. in Example 2.
Eighteen. As described above, according to each example, the polymerization rate of the unsaturated dicarboxylic acid having a low reactivity is very high in a much shorter time than in the case of the batch type aging reaction, and the copolymerization having a narrow molecular weight distribution is performed. Coalescence can be produced.

Further, according to the results of Tables 4 to 5, when the amount of the additional monomer is appropriately changed within the range of 3 to 20%, the polymerization rate of acrylic acid having high reactivity is substantially high in any reaction example. In addition, with maleic anhydride having a low reactivity, the polymerization rate tends to increase as the amount of additional monomer and the number of stages increase, but in any case, a copolymer can be efficiently obtained. I understand. In Comparative Example 1, the polymerization rates of acrylic acid and maleic anhydride are comparable to those of the Examples, but the copolymer has a large molecular weight distribution of 3.25, which is unsuitable as a detergent builder. I know there is.

Further, according to the results of Tables 6 to 7, the above Table 4
Since the ratio of maleic anhydride to acrylic acid is higher than that in the case of ~ 5, the polymerization rates of both acrylic acid and maleic anhydride are slightly lowered. However, even when the polymerization rate is lowest, the amount of additional monomer is 3%, and the number of additional reaction stages is 3,
The third-stage polymerization rates of acrylic acid and maleic anhydride are 99.95% and 96.33%, respectively, which shows that the polymerization rates are sufficiently high. In Comparative Example 2 as well, the polymerization rates of acrylic acid and maleic anhydride are comparable to those of the Examples, but like Comparative Example 1, the copolymer has a large molecular weight distribution of 3.07.

[0042]

According to the method for producing a partially neutralized copolymer of an unsaturated dicarboxylic acid and an unsaturated monocarboxylic acid of the present invention, the time required is shorter than the conventional batch-type aging reaction method, and It is possible to obtain a copolymer which can increase the polymerization rate of an unsaturated dicarboxylic acid type monomer having low reactivity and has a narrow molecular weight distribution, which is particularly suitable for a detergent builder.

Claims (1)

[Claims] 1. A first reactor having a stirrer, which uses monoethylenically unsaturated dicarboxylic acid and monoethylenically unsaturated monocarboxylic acid in which 55 to 75 mol% of the total amount of carboxyl groups is neutralized, The total amount of the unsaturated dicarboxylic acid and / or salt thereof charged and 80 to 97% by weight (in terms of unsaturated monocarboxylic acid) of the total amount of the unsaturated monocarboxylic acid and / or salt thereof are supplied, The reaction is carried out in the presence of a radical polymerization initiator, and then the reaction mixture in which the unreacted unsaturated dicarboxylic acid and / or salt thereof remains is continuously transferred to at least one tubular reactor, From a plurality of locations in one or more reactors and / or one location in two or more reactors, the residual amount of the charged amount of the unsaturated monocarboxylic acid and / or a salt thereof is separately and additionally supplied. Partially unsaturated of the monoethylenically unsaturated dicarboxylic acid and the monoethylenically unsaturated monocarboxylic acid, characterized in that the above unsaturated monocarboxylic acid and / or its salt are reacted at a residence time of 10 to 40 minutes. For continuous production of copolymers.