JPH11246604A - Production of water-soluble copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing an unsaturated dicarboxylic acid/unsaturated monocarboxylic acid copolymer with a low content of unreacted monomers without coloring. SOLUTION: A continuous polymerization apparatus comprising >=5 reactors is used and the total amount of an unsaturated dicarboxylic acid-based monomer is fed to the first reactor and an unsaturated monocarboxylic acid-based monomer is fed to each reactor from the first reactor to at least the third reactor. The unsaturated monocarboxylic acid-based monomer is not fed to at least the final reactor and the feed rates of the monomers to the respective reactors to which the unsaturated monocarboxylic acid-based monomer is fed are substantially equal to carry out the copolymerization in an aqueous medium in the presence of a water-soluble polymerization initiator in a method for producing a water-soluble copolymer comprising continuously radically copolymerizing the unsaturated dicarboxylic acid-based monomer and the unsaturated monocarboxylic acid-based monomer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention]

The present invention relates to an unsaturated dicarboxylic acid monomer or a salt thereof (hereinafter collectively referred to as an unsaturated dicarboxylic acid monomer) and an unsaturated monocarboxylic acid monomer or a salt thereof (hereinafter referred to as an unsaturated monocarboxylic acid monomer). (Collectively referred to as an acid-based monomer) in an aqueous medium. According to the present invention, the content of the unreacted unsaturated dicarboxylic acid monomer is small,
Moreover, a colorless water-soluble copolymer can be efficiently produced.

[0002]

2. Description of the Related Art Copolymers of unsaturated dicarboxylic acid monomers (hereinafter sometimes simply referred to as unsaturated dicarboxylic acids) and unsaturated monocarboxylic acid monomers (hereinafter sometimes simply referred to as unsaturated monocarboxylic acids). Is useful as a detergent builder, a scale control agent and an inorganic pigment dispersant,
There are numerous proposals for its manufacturing method. For example, using a benzoyl peroxide or the like in an organic solvent such as toluene or benzene, a method of copolymerizing an unsaturated dicarboxylic acid and an unsaturated monocarboxylic acid, or a method in which an aqueous medium has a pH of 3.
A method of copolymerizing these monomers under the conditions of 5 to 5.0 (JP-A-59-64613) is known.

According to the method described in JP-A-59-64613, the unsaturated dicarboxylic acid having poor copolymerizability is polymerized at a high reaction rate under other polymerization conditions. And a copolymer having excellent physical properties can be obtained. However, in the above-mentioned production method, since a batch-type polymerization method is employed, there is a limit to a significant improvement in productivity. In contrast, JP-A-59-66407 discloses a method in which the copolymerization is continuously performed in an aqueous medium using a plurality of reactors.
Specifically, using three reactors, the entire amount of unsaturated dicarboxylic acid is supplied to the first reactor, and at least 40% of the charged amount of unsaturated monocarboxylic acid is supplied to the first reactor. A method has been proposed in which copolymerization is carried out in an aqueous medium at a temperature of 60 to 150 ° C. while supplying the remaining unsaturated monocarboxylic acid monomer to the second and third reactors.

According to the above method, a copolymer comprising an unsaturated dicarboxylic acid unit and an unsaturated monocarboxylic acid unit can be efficiently produced, but unreacted unsaturated There was a problem that a large amount of dicarboxylic acid was contained. In the present invention, it is intended to provide a method for producing a copolymer comprising an unsaturated dicarboxylic acid unit and an unsaturated monocarboxylic acid unit efficiently and obtaining a copolymer having a low content of unreacted monomers. Assigned.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have adopted a continuous polymerization method using an apparatus comprising five or more reactors, and The unsaturated monocarboxylic acid monomer is supplied to each reactor at least up to the third reactor, and the monomer is supplied to each reactor to which the unsaturated monocarboxylic acid monomer is supplied. A reactor for reducing the residual monomer in the latter half of the polymerization by substantially equalizing the supply amount (reactor for temporarily retaining the reaction solution without supplying the monomer in order to increase the polymerization rate) ; Hereinafter, referred to as ripening apparatus), it has been found that a copolymer having few unreacted monomers and excellent physical properties can be obtained, and the present invention has been completed. That is, the present invention provides a method for producing a water-soluble copolymer in which an unsaturated dicarboxylic acid-based monomer and an unsaturated monocarboxylic acid-based monomer are continuously subjected to radical copolymerization, comprising five or more reactors. Using a continuous polymerization apparatus, supply the entire amount of the unsaturated dicarboxylic acid monomer to the first reactor, and supply the unsaturated monocarboxylic acid monomer to each reactor from the first to at least the third reactor. Supply the monomer,
At least the unsaturated monocarboxylic acid monomer is not supplied to the final reactor, and the supply amount of the monomer to each reactor to which the unsaturated monocarboxylic acid monomer is supplied is substantially reduced. Wherein the copolymerization is carried out in an aqueous medium in the presence of a water-soluble polymerization initiator. Hereinafter, the present invention will be described in more detail.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The unsaturated dicarboxylic acid monomers in the present invention include unsaturated dicarboxylic acids such as maleic acid, itaconic acid, mesaconic acid, fumaric acid, methylenemalonic acid and citraconic acid, and salts thereof. Is mentioned. Examples of the base forming an unsaturated dicarboxylic acid salt include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide or inorganic bases such as ammonia; and amines such as trimethylamine, triethylamine, and hydroxyethylamine. . Further, an acid anhydride monomer such as maleic anhydride may be used as the unsaturated dicarboxylic acid monomer. Preferred unsaturated dicarboxylic acid monomers are maleic acid monomers such as maleic acid or maleic anhydride.

The unsaturated monocarboxylic acid monomers include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, vinyl acetic acid, allyl acetic acid, propylidene acetic acid, ethylidene propionic acid and dimethyl acrylic acid, and salts thereof. Can be Preferred unsaturated monocarboxylic acid monomers are acrylic acid and methacrylic acid and their salts, more preferably acrylic acid and its salts.

When a polymer having a carboxyl group neutralized with a base is obtained as a water-soluble copolymer, a salt of an unsaturated dicarboxylic acid and a salt of an unsaturated monocarboxylic acid obtained by neutralization in advance are reacted. It is preferable to supply the amount of the base necessary for the desired neutralization while supplying the unsaturated dicarboxylic acid and the unsaturated monocarboxylic acid, rather than supplying the base to the vessel. The method of neutralization in the reactor produces a copolymer aqueous solution having a higher solid content.

The preferable copolymerization ratio of the unsaturated dicarboxylic acid monomer and the unsaturated monocarboxylic acid monomer is 15 to 65% by weight of the unsaturated dicarboxylic acid monomer and the unsaturated monocarboxylic acid monomer. 85 to 35% by weight. When the amount of the unsaturated dicarboxylic acid-based monomer is 15% by weight, the use of the obtained copolymer is narrowly restricted. On the other hand, when the amount exceeds 65% by weight, the unreacted unsaturated dicarboxylic acid-based monomer tends to remain.
In the present invention, other radically polymerizable monomers copolymerizable with the unsaturated dicarboxylic acid-based monomer and the unsaturated monocarboxylic acid-based monomer are based on the total amount of all the monomers. In the range of 0 to 20% by weight. Examples of such other radically polymerizable monomers include acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, acrylamide sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, vinyl phosphonic acid, allyl phosphonic acid, vinyl acetate, (meth) acryl Methyl acid,
Ethyl (meth) acrylate, hydroxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and the like. The preferred concentration of the monomer in the polymerization reaction solution comprising the aqueous medium and the above monomer is 20 to 7
0% by weight, more preferably 40 to 60% by weight. If the monomer concentration is less than 20% by weight, the productivity of the copolymer is poor, while if it exceeds 70% by weight, the viscosity of the reaction solution tends to increase.

Specific examples of the water-soluble polymerization initiator in the present invention include persulfates such as lithium persulfate, sodium persulfate, ammonium persulfate and potassium persulfate; hydrogen peroxide, azo-bis- (2-aminopropane). ) Hydrochloride and tertiary butyl hydroperoxide. Although these polymerization initiators can be used alone,
In order to increase the reaction rate of the unsaturated dicarboxylic acid, it is preferable to use two or more polymerization initiators in combination. Particularly preferably, hydrogen peroxide and persulfate are used together in a weight ratio of 1: 3 to 3: 1. According to the polymerization initiator having such a specific structure, even if the amount of the polymerization initiator used is relatively small, the amount of the unreacted unsaturated dicarboxylic acid can be reduced, and the obtained aqueous copolymer solution is colored. Is unlikely to occur. The preferred amount of the polymerization initiator to be used is 0.1 to 10 parts by weight per 100 parts by weight of the total monomers.

In addition to the above water-soluble polymerization initiators, a reducing agent which forms a redox system with them, such as sodium sulfite, triethanolamine, ascorbic acid, ferrous sulfate, nickel chloride or copper sulfate, may be used in an appropriate amount. . Further, in the above copolymerization, a chain transfer agent such as mercaptoethanol, mercaptopropionic acid or sodium diphosphite can be used.

In the present invention, as described above, a continuous reactor consisting of five or more reactors is used. The preferred number of reactors is five in order to satisfy both physical properties and equipment costs of the product. Or six. The reactor in the present invention,
In a continuous reaction apparatus in which a batch-like reaction is performed in multiple stages, it is a partitioned vessel for performing each batch-like reaction. When the number of reactors is four or less, the amount of unreacted monomers contained in the obtained copolymer is large, while when seven or more reactors are used, the production cost tends to increase. As each individual reactor, a tubular reactor or a tank reactor can be used, and a reactor having a stirring device is preferable. As a stirring method, in addition to stirring with a normal stirring blade, stirring by pump circulation, ultrasonic waves, or the like can be used.

[0013] The continuous reactor has a shape of each reactor and / or
Alternatively, they can be classified into several types depending on the binding mode or the like. The continuous reactor which can be preferably used in the present invention includes a multi-stage tank type device, a multi-stage annular device or a cylindrical plate which is long in either the longitudinal direction or the lateral direction, which is employed in the examples described later. Examples include a partition plate type device having a structure partitioned into reactors.

In the present invention, a monomer, a polymerization initiator and, if desired, a base are continuously supplied to a reactor by the method described below. Supply of raw material components to the reactor
It is preferable to carry out each of them in an aqueous solution state. Also,
Before starting the reaction, it is preferable that water or an aqueous solution of a separately prepared copolymer is charged into each reactor and heated to a predetermined polymerization temperature while stirring. The first reactor (hereinafter referred to as the first reactor) is supplied with the entire amount of the unsaturated dicarboxylic acid monomer charged, and each reaction from the first to at least the third reactor is performed. The unsaturated monocarboxylic acid monomer is supplied to the reactor, and the amount of the monomer supplied to each reactor to which the unsaturated monocarboxylic acid monomer is supplied is made substantially equal. Then, at least the monomer is not supplied to the final reactor so that the amount of the unreacted monomer in the copolymer as a product is as small as possible.
When the supply amount of the unsaturated monocarboxylic acid monomer to each of the reactors is not substantially equal, the amount of the unreacted unsaturated dicarboxylic acid monomer in the obtained copolymer is large, Also 2
Even if an equal amount of the unsaturated monocarboxylic acid monomer is supplied to each reactor, the amount of the unreacted unsaturated dicarboxylic acid monomer does not decrease to a satisfactory level. In the present invention, the supply amount of the monomer to each reactor to which the unsaturated monocarboxylic acid monomer is supplied is an amount obtained by dividing the total supply amount of the monomer by the number of the reactors. Within the range of 85 to 115%, the effects of the present invention are exhibited.

For example, when five reactors are used, approximately one third of the charged amount of the unsaturated monocarboxylic acid monomer is supplied to the first to third reactors, Either the fourth reactor and the fifth reactor are aged, or supply approximately 1/4 of the charged amount of the unsaturated monocarboxylic acid monomer to the first to fourth reactors. Then, there are two modes, that is, the fifth reactor is an aging device. When six reactors are used, an embodiment in which the unsaturated monocarboxylic acid monomer is supplied to the first to third reactors, and the monomer is supplied to the first to fourth reactors Supplying mode and first reactor
There are three modes of supplying the monomer to the fifth reactor.
In this case, an embodiment in which the monomer is supplied to the first to fourth reactors or an embodiment in which the monomer is supplied to the first to fifth reactors is preferable.

In addition to the above monomers, a polymerization initiator and, if necessary, a neutralizing base are supplied to the first reactor. As described above, the supply amount of the polymerization initiator is preferably 0.1 to 10 parts by weight per 100 parts by weight of the total monomers, and the supply amount of the base for neutralization is present in the first reactor. An amount that controls the degree of neutralization of the carboxyl group to 55 to 75% is preferable. When the degree of neutralization of all carboxyl groups in the reaction solution is 55% to 75%, the copolymerization reactivity of unsaturated dicarboxylic acid and unsaturated monocarboxylic acid is high, and the copolymerization proceeds smoothly. In a reactor other than the reactor, the degree of neutralization of the carboxyl group in the reaction solution is basically preferably maintained at 55% to 75%.

In the reactors after the second reactor to which the unsaturated monocarboxylic acid monomer is to be supplied, the amount of the unsaturated monocarboxylic acid to be supplied to the first reactor is substantially the same as that supplied to the first reactor. Supply carboxylic acid monomer. Further, in the reactors after the second reactor except the final reactor, it is preferable to supply a polymerization initiator and a base for neutralization as necessary. The final reactor is usually used as an aging reactor for the purpose of simply heating the reaction solution, and also as a tank for adjusting the degree of neutralization of the copolymer as the final product.

The preferred reaction temperature is 90-130 ° C. If the reaction temperature is lower than 90 ° C., the polymerizability of the unsaturated dicarboxylic acid monomer is inferior, and the production of the target copolymer becomes inefficient. Is easy to color. The reaction temperature is preferably controlled as precisely as possible so as to prevent the molecular weight distribution of the obtained copolymer from becoming too wide, specifically, preferably within a range of ± 2 ° C. Further, the preferred supply rate of the monomer in each reactor is a rate at which the residence time of the monomer in the reactor is 15 to 90 minutes. The feed rate of each raw material component to the reactor is preferably controlled within a range of ± 2.5%.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention. In addition, the measuring method of the physical property regarding the copolymer obtained in each of the following examples is as follows. a. Polymerization rate: The amount of residual monomer after the reaction was measured by liquid chromatography. b. Number average molecular weight (Mn) and weight average molecular weight (M
w): Gel permeation chromatography (GP
C). The calibration curve is a standard polyacrylic acid [(Mw) 3,000, 10,000, 300,00
0] was used. c. Transmittance: The obtained reaction solution was diluted to a solid content of 10% by weight, and the transmittance at a wavelength of 400 nm (10 mm cell) was measured using a spectrophotometer.

[0020]

Example 1 A continuous polymerization apparatus (five reactors) in which a reactor, a raw material tank, a liquid feed pump, a liquid feed pipe and the like were arranged as shown in FIG. 1 was used. Here, the reactor has a stirrer
Using a SUS316 pressure-resistant reactor (capacity: 750 mL), the polymerization initiator aqueous solution was fed by a constant flow pump PU610 manufactured by GL Sciences Co., Ltd. (liquid sending amount: 0.001 to 0.000 mL /
), The other raw material aqueous solution and the reaction solution were fed by a constant flow pump CP-1-2 manufactured by Todoroki Sangyo Co., Ltd. Before the start of the polymerization, 500 mL of water was charged into each reactor, and the gas phase was replaced with nitrogen gas. During the period of continuous polymerization, the liquid volume in each reactor was controlled at 500 mL.
Acrylic acid 4.05 g / min and maleic anhydride 3.6 in an aqueous medium at a temperature of 120 ° C. in each reactor using the above apparatus.
8 g / min (molar ratio─acrylic acid: maleic anhydride = 6
(0:40). The supply of each component to each reactor was as follows. For acrylic acid, one third of the above amount was supplied from the first reactor to three reactors of the third reactor. In addition, the degree of neutralization of the reaction solution was maintained at 65 mol% through the first to fifth reactors.
As shown below, an equal weight mixture of hydrogen peroxide and disodium persulfate was used as a polymerization initiator, and sodium hydroxide was used as a neutralizing base.

(Unit: g / min) First reactor; first supply port ── acrylic acid 1.35 maleic anhydride 3.68 water 3.24 second supply port 水 素 hydrogen peroxide 0.08 disodium persulfate 0.08 water 0.95 third supply portナ ト リ ウ ム Sodium hydroxide 2.44 Water 2.64 (Total amount 14.46) (Residence time of reaction solution: 34.5 minutes) Discharge port ── Reaction solution-14.46

Second reactor; first supply port ──first reaction liquid 14.46 second supply port ──acrylic acid 1.35 water 0.34 third supply port 水 素 hydrogen peroxide 0.07 disodium persulfate 0.07 water 0.76 fourth supply Mouth ナ ト リ ウ ム Sodium hydroxide 0.49 Water 0.58 (Total amount 18.12) (Residence time of reaction solution: 27.7 minutes) Discharge port ── Reaction solution-18.12

Third reactor; first supply port ──second reaction liquid 18.12 The supply to the second, third and fourth supply ports is the same as in the second reactor. (Total amount: 21.78) (Residence time of the reaction solution: 23.3 minutes)

Fourth reactor; first supply port ──third reaction liquid 18.12 second supply port 水 素 hydrogen peroxide 0.02 disodium persulfate 0.02 water 0.24 (total amount 22.06) (retention time of reaction liquid: 23 minutes) ) Discharge port ── Reaction liquid − 22.06

Fifth reactor; first supply port 四 fourth reaction liquid 22.06 withdrawal port ── reaction liquid-22.06 (retention time of reaction liquid: 23.0 minutes) Not even supply. After the polymerization was continued for 8 hours under the above conditions, the physical properties of the liquid withdrawn from the final reactor, that is, the aqueous solution of the target copolymer were evaluated. The results are as shown in Table 1.

[0026]

Example 2 Using a continuous polymerization apparatus consisting of six reactors, four reactors from a first reactor to a fourth reactor were used.
Substantially the same operation as in Example 1 was performed except that one-fourth of the charged amount of acrylic acid was supplied. Table 1 shows the results of evaluating the physical properties of the liquid extracted from the final reactor.

[0027]

Comparative Example 1 Using a continuous polymerization apparatus comprising three reactors, 40% by weight of the charged amount of acrylic acid was supplied to the first reactor, and 60% of the charged amount of acrylic acid was supplied to the second reactor.
% By weight. The feed rate of each raw material was selected as follows so that the total residence time would be approximately the same as in Example 1. Other conditions were basically the same as those in Example 1. (Unit: g / min) First reactor; First supply port ── Acrylic acid 1.16 Maleic anhydride 2.64 Water 3.09 Second supply port 水 素 Hydrogen peroxide 0.03 Disodium persulfate 0.03 Water 0.34 Third supply port ── Water Sodium oxide 1.82 Water 1.98 (Total amount 11.09) (Residence time of reaction solution: 45.1 minutes) Discharge port ──Reaction solution-11.09

Second reactor; first supply port ──first reaction liquid 11.09 second supply port ──acrylic acid 1.74 water 0.45 third supply port 水 素 hydrogen peroxide 0.03 disodium persulfate 0.03 water 0.34 fourth supply Mouth ナ ト リ ウ ム Sodium hydroxide 0.63 Water 0.69 (Total amount 15.01) (Residence time of reaction solution: 33.3 minutes) Discharge port ── Reaction solution-15.01

[0029] Third reactor; first supply port 液 second reaction liquid 15.01 second supply port ── hydrogen peroxide 0.001 disodium persulfate 0.001 water 0.14 (total amount 15.17) (retention time of reaction liquid: 33.0 minutes) ) Withdrawal port ──Reaction liquid-15.17 The physical properties of the withdrawn liquid from the final reactor after the polymerization was continued for 8 hours under the above conditions are as shown in Table 1.

[0030]

Comparative Example 2 Using a continuous polymerization apparatus consisting of five reactors, supplying 50% by weight of the charged amount of acrylic acid to the first reactor, and supplying the second reactor and the third reactor with:
25% by weight of the charged amount of acrylic acid was supplied. Other conditions were substantially the same as those in Example 1. Table 1 shows the physical properties of the liquid discharged from the final reactor.

[0031]

According to the present invention, a copolymer comprising an unsaturated dicarboxylic acid and an unsaturated monocarboxylic acid can be efficiently produced, and the unsaturated dicarboxylic acid and the unsaturated monocarboxylic acid can be produced under relatively mild reaction conditions. The acid can be polymerized at a high polymerization rate. As a result, the copolymer obtained by the present invention has a low content of unreacted monomers and a low coloring.

[0032]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a polymerization apparatus in which five reactors are connected by a flow pipe. ───Reactor ───Material tank ───Liquid pipe ───Liquid pump ───Reaction liquid ───Stirring blade ───Stirring motor ───Product outlet From the left, the first reactor, the second reactor, and the fifth reactor. In FIG. 1, the first reactor contains the entire amount of an unsaturated dicarboxylic acid monomer (for example, maleic anhydride), an unsaturated monocarboxylic acid (for example, acrylic acid), a polymerization initiator, and a part of sodium hydroxide. The second and third reactors are supplied with an unsaturated monocarboxylic acid, a polymerization initiator and sodium hydroxide, and the fourth reactor is supplied with a polymerization initiator.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tsugio Kimura 1 Nagoya City, Nagoya City, Aichi Prefecture

Claims (2)

[Claims] 1. A method for producing a water-soluble copolymer in which an unsaturated dicarboxylic acid monomer and an unsaturated monocarboxylic acid monomer are continuously subjected to radical copolymerization, comprising a continuous reactor comprising five or more reactors. Using a polymerization apparatus, supply the entire amount of the unsaturated dicarboxylic acid monomer to the first reactor, and feed the unsaturated monocarboxylic acid monomer to each reactor from the first to at least the third reactor. Monomer without supplying the unsaturated monocarboxylic acid monomer to at least the final reactor, and supplying the monomer to each reactor to which the unsaturated monocarboxylic acid monomer is supplied. And the supply amount of
A production method, wherein the copolymerization is carried out in an aqueous medium in the presence of a water-soluble polymerization initiator. 2. The water-soluble polymerization initiator comprises hydrogen peroxide and persulfate, and their weight ratio is 1: 3 to 3: 1.
The method for producing a water-soluble copolymer according to claim 1, which is a mixture of the following.