JPH0749449B2 - Method for producing acrylate and acrylate-containing polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an acrylate and an acrylate-containing polymer. More specifically, the present invention relates to an acrylate that can be suitably used for producing an acrylate-containing polymer having a reduced residual monomer content, and a method for producing an acrylate-containing polymer using the acrylate.

(Prior Art) Examples of an acrylate-containing polymer of an aqueous solution obtained by polymerizing a monomer component containing an acrylate include, for example, sodium polyacrylate, acrylamide-sodium acrylate copolymer, acrylic acid-sodium acrylate. There are copolymers and the like, and these water-soluble polymer compounds are used as coagulants for water treatment, petroleum drilling mud additives, food additives, thickeners and the like.

As the water-swellable acrylate-containing polymer obtained by polymerizing the acrylate-containing monomer component, for example, acrylate cross-linked polymer, partially neutralized acrylic acid cross-linked polymer, starch-acrylate salt graft polymer. They are used as sanitary products, sanitary absorbents such as disposable diapers, water-retaining agents for agriculture and horticulture, greening, food freshness-keeping films, etc., and demand is expected to grow further in the future.

The acrylate-containing polymer is obtained by polymerizing an acrylate or a monomer component containing an acrylate, and the production method thereof is, for example, JP-A-58-10.
8,212, JP-A-58-71,907, JP-A-53-46,389,
JP-A-56-93,716, JP-A-58-49,714, JP-A-61-
No. 166,809, JP-A No. 62-22,811 and the like.

In these production methods, the acrylic acid salt used as a raw material was obtained by adding a predetermined amount of a basic substance to an aqueous solution of acrylic acid or adding acrylic acid to an aqueous solution in which a predetermined amount of a basic substance was dissolved. It is a thing.

(Problems to be Solved by the Invention) However, in the acrylate-containing polymer produced using the acrylate obtained by the method obtained by such a method, a large amount of unreacted monomer usually remains. In particular, even in a water-swellable polymer that uses a large amount of an initiator during production, the unreacted monomer is usually 700 to 3,000 pp in the polymer.
About m remains. It goes without saying that such a water-swellable acrylic acid salt-containing polymer in which a large amount of unreacted monomer remains is not preferable as a material for a wide range of water-absorbing articles including the sanitary materials. In these applications, the polymer may come into contact with human skin or be absorbed into the body, and there is a risk that it will be mixed into drinking water etc. again after being discharged into the environment due to disposal. In recent years, the demand for reduction of residual monomers has been increasing.

Generally, as a method of reducing the residual monomer of the hydrophilic polymer, the addition of ammonia or mamin (Japanese Patent Publication No.
And JP-A-50-40,689) and addition of sulfite or bisulfite (US Pat. No. 2,960,486 and JP-A-55-1).
35, 110) to reduce these compounds by adding them to the residual monomer, combined use of a low temperature decomposition type or high temperature decomposition type polymerization initiator (JP-A-50-42,280, JP-A-59-133,205).
JP-A-53-141,388) or a combination of a redox catalyst and an azo compound initiator (JP-A-50-96,689, JP-B-47-2).
No. 6,430) to polymerize and reduce the residual monomer, and to decompose and reduce by microorganisms (JP-A-60-2).
No.9,523) has been proposed.

However, although the addition of ammonia, amine, sulfite, and hydrogen sulfite has a considerable effect on the reduction of residual monomers, a small amount of these compounds has no effect, and the added compound itself has toxicity. There is a problem. In addition, the method in which a polymerization initiator is used in combination has a problem that the method using a microorganism is not industrially difficult because it does not have a sufficient effect of reducing the residual monomer.

Therefore, an object of the present invention is to provide a novel method for producing an acrylate and an acrylate-containing polymer.

Another object of the present invention is to suitably use the acrylate-containing polymer having a reduced amount of unreacted monomer as well as the production of the polymer without any loss of the essential characteristics of the acrylate-containing polymer. It is to provide a method for producing an acrylate that can be produced with high productivity.

Still another object of the present invention is to reduce the amount of water-soluble components and unreacted acrylate monomer remaining in the crosslinked polymer as well as having an excellent water absorption capacity, and as a sanitary material such as sanitary products and disposable diapers. As a water retention agent for agriculture and horticulture, greening,
Still another object is to provide a water-swellable acrylate-containing polymer suitable as a material for a wide range of other water absorbent articles.

(Means for Solving the Problems) These various purposes are as follows: (A) Acrylic acid and a basic substance are treated with water while keeping the neutralization rate of acrylic acid in the neutralization reaction system always within the range of 75 to 100 mol%. And (B) supplying a basic substance to the neutralization reaction system to adjust the neutralization rate of acrylic acid in the neutralization reaction system to 100.1 to 110 mol%.
Adjusting the neutralization rate in the neutralization reaction system in the state of 100.1 to 110 mol% for 1 to 120 minutes for aging, and (D) acrylic acid in the neutralization reaction system. Is supplied to adjust the neutralization rate of acrylic acid in the neutralization reaction system to 20 to 100.
This is achieved by a method for producing an acrylate salt by a neutralization reaction between acrylic acid and a basic substance, which is performed sequentially from the step of adjusting to mol%.

These various purposes are (A) a step of supplying acrylic acid and a basic substance to water to carry out the neutralization reaction while always keeping the neutralization rate of acrylic acid in the neutralization reaction system within the range of 75 to 100 mol%. , (B) supplying a basic substance to the neutralization reaction system so that the neutralization rate of acrylic acid in the neutralization reaction system is 100.1 to 110 mol%.
Adjusting the neutralization rate in the neutralization reaction system in the state of 100.1 to 110 mol% for 1 to 120 minutes for aging, and (D) acrylic acid in the neutralization reaction system. Is supplied to adjust the neutralization rate of acrylic acid in the neutralization reaction system to 20 to 100.
Acrylic acid obtained by polymerizing a monomer component containing at least an acrylic acid salt having a neutralization rate of 20 to 100 mol% obtained by the neutralization reaction of acrylic acid and a basic substance, which is performed by the step of adjusting to mol% It is also achieved by a method for producing a salt-containing polymer.

(Operation) Hereinafter, the present invention will be described in detail.

The basic substance that can be used to obtain the acrylate is not particularly limited as long as it is commonly used for the purpose, and examples thereof include ammonia, organic amines, alkali metal hydroxides, and alkaline earth metal Hydroxides and the like can be mentioned, and one or more of these can be used. Among these basic substances, ammonia or organic amines may cause coloring or odor of the obtained acrylate-containing polymer, but alkali metal hydroxides are easily available and The acrylate-containing polymer to be obtained is excellent in performance, and sodium hydroxide is particularly preferable.

When forming the acrylate by sequentially performing the steps (A) to (D), the steps (A) and (C) are particularly important, and even in any one of the steps (A) and (C). If it is lacking, the object of the present invention can no longer be achieved.
When simultaneously supplying acrylic acid and a basic substance to water in the step (A) for neutralization, the neutralization rate of acrylic acid is always
Although it is in the range of 75 to 100 mol%, when the neutralization rate is out of this range, the amount of unreacted monomer remaining in the obtained acrylate-containing polymer increases. It is preferably 85 to 100 mol%. Further, the step (A) is preferably carried out under a temperature condition of 20 to 50 ° C. in order to prevent generation of impurities accompanying the radical polymerization reaction.

During the aging of the step (C), the neutralization rate of acrylic acid was 100.1 to 1
The amount of unreacted monomers remaining in the obtained acrylate-containing polymer increases if the neutralization rate is outside this range. Preferably, 100.5 to 105 mol%
Is the range. The aging time is 1 to 120 minutes. If the aging time is less than 1 minute, there is no effect in obtaining an acrylate-containing polymer having a reduced amount of residual monomers, and conversely, even if the aging time exceeds 120 minutes, the effect corresponding to the aging time is improved. Is not recognized and only reduces productivity. In addition, the step (C) is preferably carried out under a temperature condition of 20 to 50 ° C. in order to obtain a sufficient aging effect and prevent the formation of impurities accompanying the radical polymerization reaction.

In the step (D), an acrylate whose neutralization ratio was once adjusted to 100.1 to 110 mol% for aging in the step (C) was used.
It is for readjustment to a neutralization rate of 20 to 100 mol%.

Therefore, the acrylate used in the present invention is (A) to
Although it is obtained through the step (D), the step (D) among these steps may be performed in the container for the neutralization reaction used in the steps (A) to (C). It may be carried out in a container used for the polymerization reaction immediately before the subsequent polymerization reaction.

The neutralization rate of the acrylate obtained in this manner through the steps (A) to (D) is 20 to 100 mol%. If the neutralization ratio of the acrylate is less than 20 mol%, not only the effect of the present invention is reduced, but the acrylate-containing polymer obtained by using this is because the water-containing gel is highly adhesive. Yes,
Inconvenient to handle in the polymerization container. On the other hand, if the neutralization ratio of the acrylate exceeds 100 mol%, the acrylate-containing polymer obtained by using it must be handled with care because of the excessive basic substance, and especially water swelling When it is used as a water-soluble polymer, it has a poor water absorption capacity.

In producing the acrylate-containing polymer of the present invention,
The monomer component essentially contains the acrylate obtained by the above procedure, but may contain other monomer (a) if necessary.

The monomer (a) can be used without particular limitation as long as it can be copolymerized with the above-mentioned acrylic acid salt, but it is a monomer having high hydrophilicity because it does not impair the water absorption property of the obtained acrylic acid salt-containing polymer. Is mainly used. Among the monomers (a) having high hydrophilicity, for example, methacrylic acid, crotonic acid, maleic acid, fumaric acid,
Itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylprobansulfonic acid, vinylbenzenesulfonic acid, (meth) acrylamide, 2
-Hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, (meth) acrylonitrile, methyl acrylate and the like can be mentioned, and one kind or a mixture of two or more kinds thereof can be used.
These other monomers (a) are used as necessary according to the purpose of use of the resulting acrylate-containing polymer, but the feature of the present invention is that the amount of the other monomer (a) used is small and it is easy to appear to some extent. Therefore, the amount of the other monomer (a) used is preferably less than 50% by weight, more preferably less than 20% by weight in the monomer component.

In obtaining the acrylic acid salt-containing polymer of the present invention having a crosslinked structure, that is, a water-swellable polymer, the following method may be adopted in order to efficiently form the crosslinked structure.

(1) A method of forming a crosslinked structure by radical polymerization reaction during aqueous solution polymerization by blending a crosslinkable monomer in the monomer component. The crosslinkable monomer can be used without limitation as long as it has two or more polymerizable double bonds in the molecule, but it shows a certain degree of water solubility and has good copolymerizability with the above-mentioned monomer component, so that a crosslinked structure can be formed efficiently. Those which give a uniform cross-linking distribution are preferable. Examples of such crosslinkable monomers include trimethylolpropane di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, (poly) ethylene glycol di (meth) acrylate. (Meth) acrylate, (poly) propylene glycol di (meth) acrylate, glycerol tri (meth) acrylate, blisterol di (meth) acrylate, N, N'-methylenebis (meth) acrylamide, triallyl cyanurate,
There are triallyl isocyanurate, triallylamine, triallyl phosphate and the like, and one or more of them can be used. These crosslinkable monomers are used in the range of 0.001 to 5 mol%, preferably 0.005 to 3 mol% based on the above-mentioned monomer components. That is,
If it is less than 0.001 mol%, the water absorption capacity will be large, but the water-soluble content will be remarkably large, whereas if it exceeds 5 mol%, the water absorption capacity of the resulting acrylate-containing polymer will be small.

(2) A method of polymerizing a monomer component in the presence of a hydrophilic polymer such as starch, cellulose or polyvinyl alcohol to form a crosslinked structure due to a graft bond during the polymerization. These hydrophilic polymers are preferably used in the range of 2 to 50% by weight, particularly 2 to 40% by weight based on the monomer component.

(3) At the time of polymerization, a crosslinking agent having two or more reactive groups in the molecule with respect to functional groups such as acid groups, hydroxyl groups, and amide groups of the monomer component is added during the polymerization. And / or a method of forming a crosslinked structure by a crosslinking reaction during drying.

Examples of the crosslinking agent used in this method include polyisocyanate compounds, polyepoxy compounds, polyamine compounds, and polyoxazoline compounds.
One or more of these can be used.
These crosslinking agents are used in the range of 0.001 to 50% by weight, preferably 0.005 to 40% by weight, based on the monomer components. If the amount used is less than 0.001% by weight, the water absorption capacity will be large, but the water-soluble content will be remarkably large, and if it exceeds 50% by weight, the water absorption capacity of the resulting acrylate-containing polymer will be small. .

(4) A method of forming a crosslinked structure by ionic crosslinking during polymerization by adding a polyvalent metal compound to the monomer component. Examples of the polyvalent metal compound used in this method include hydroxides and salts of zinc, calcium, aluminum, zirconium and the like, and one or more of them can be used.

These methods should be selected according to the intended use of the resulting acrylate-containing polymer, and in some cases, a plurality of methods may be used in combination. However, in the present invention, it is preferable to form a crosslinked structure by the method (1) from the viewpoint of water absorption of the acrylate-containing polymer obtained.

Polymerization to obtain the polymer of the present invention is carried out, for example, by degassing an aqueous monomer solution obtained by dissolving a monomer component, a polymerization initiator and optionally a crosslinking agent in water with an inert gas such as nitrogen gas. Cast polymerization in which polymerization is carried out by placing in a mold as described in JP-A-48-42,466, JP-A-58-49,7.
A method of polymerizing on a belt conveyor as described in No. 14. As disclosed in JP-A-57-34,101, a method of polymerizing in a kneader or the like having a stirring blade capable of subdividing a hydrous gel polymer inside, and JP-B-59-3.
This is achieved by turbidity polymerization and the like as described in No. 7,003.

The polymerization initiator is not particularly limited and may be used, for example, ammonium persulfate, potassium persulfate, hydrogen peroxide, V-50.
(Manufactured by Wako Pure Chemical Industries, Ltd., 2,2-azobis (2-aminodinopropane) hydrochloride) and the like or of these with a reducing agent such as sodium bisulfite, L-ascorbic acid and ferrous salt. Redox type initiators in combination are also used.

The acrylate-containing polymer of the present invention is usually produced via a hydrated gel, but the water content of the hydrated gel polymer is
It is usually 25 to 90% by weight, preferably 30 to 80% by weight. The amount of the polymerization initiator used is 0.0001 to 0.5% by weight, preferably 0.002 to 0.1% by weight, in the case of a water-soluble polymer, and 0.01 to 2% by weight, preferably in the case of a water-swellable polymer. It is 0.05 to 1% by weight. The hydrogel polymer obtained by the polymerization may be already crushed in some cases, but in many cases, it is preferable to make it into a form that can be dried by fragmentation. As a method of subdividing, for example, there is crushing with a meat chopper, an extruder, a kneader or the like.

The acrylate-containing polymer of the present invention can be made into a powder form by drying and pulverizing the hydrogel polymer.

Examples of the drying device used in the present invention include a conductive heat transfer type dryer, a radiant heat transfer type dryer, a hot air heat transfer type dryer, and a dielectric heating dryer, but are not particularly limited, but depending on the speed of drying. A hot air heat transfer type dryer (hereinafter referred to as a hot air dryer) is preferable. As a hot air dryer, ventilation band type, ventilation rotation type,
Examples of the drying device include a ventilation type, a parallel flow band type, a ventilation tunnel type, a ventilation groove type stirring type, a fluidized bed type, an air flow type and a spray type.

The acrylic acid salt-containing polymer thus obtained has a significantly reduced residual monomer, for example, 0.3% by weight or less in the case of a water-soluble polymer, and especially the residual monomer reduction requires water at a high level. 0.05% by weight for swellable polymers
It has been reduced to:

(Examples) Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 A distillation flask equipped with a stirrer was charged with 2744 g of ion-exchanged water. Acrylic acid (1390 g) and a 48 wt% sodium hydroxide aqueous solution (1480 g) were supplied thereto over 100 minutes while controlling so that the neutralization ratio of acrylic acid in the neutralization reaction system was always 90 to 95 mol%. At this time, the temperature of the neutralization reaction system was kept at 20 to 40 ° C by cooling. Then 48% by weight
The neutralization rate of acrylic acid in the neutralization reaction system was adjusted to 102 mol% by supplying 160 g of an aqueous sodium hydroxide solution, and the temperature of the neutralization reaction system was adjusted to 40 ° C. Aged while maintaining the condition. The pH of the neutralization reaction system during this aging period was 13.9 (25 ° C conversion). After completion of the aging, 499 g of acrylic acid was supplied to the neutralization reaction system over 10 minutes to obtain an aqueous solution of acrylic acid salt (1) having a neutralization rate of 75 mol%. The concentration of the aqueous solution of acrylate (1) is 37
% By weight.

Example 2 A distillation flask equipped with a stirrer was charged with 2520 g of ion-exchanged water. Acrylic acid (1400 g) and a 48 wt% sodium hydroxide aqueous solution (1587 g) were supplied thereto over 100 minutes while controlling so that the neutralization rate of acrylic acid in the neutralization reaction system was always 98 to 100 mol%. At this time, the temperature of the neutralization reaction system was kept at 20 to 40 ° C by cooling. Next, 53 g of 48% by weight aqueous sodium hydroxide solution was supplied to adjust the neutralization rate of acrylic acid in the neutralization reaction system to 101 mol%, and the temperature of the neutralization reaction system was adjusted to 30 ° C. for 100 minutes thereafter. This state was maintained for aging over the entire period. The pH of the neutralization reaction system during this aging period was 13.4 (25 ° C conversion). After completion of the aging, 174 g of acrylic acid was supplied to the neutralization reaction system over 5 minutes to obtain an aqueous solution of acrylic acid salt (2) having a neutralization rate of 90 mol%. The concentration of the aqueous solution of this acrylate (2) was 35% by weight.

Example 3 A distillation flask equipped with a stirrer was charged with 2622 g of ion-exchanged water. While controlling 524 g of acrylic acid and 662 g of 50% by weight aqueous potassium hydroxide solution, the neutralization rate of acrylic acid in the neutralization reaction system is always 80 to 82 mol%.
Feed over minutes. The temperature of the neutralization reaction system at this time is
It was kept at 20-40 ° C by cooling. Next, 196 g of 50 wt% potassium hydroxide aqueous solution is supplied to make the neutralization rate of acrylic acid in the neutralization reaction system 105 mol% and the temperature of the neutralization reaction system 5
The temperature was adjusted to 0 ° C., and thereafter this state was maintained for aging for 1 minute. The pH of the neutralization reaction system during this aging period is
It was 14.0 (25 ° C conversion). After completion of the aging, 1311 g of acrylic acid was supplied to the neutralization reaction system over 40 minutes to obtain an aqueous solution of acrylic acid salt (3) having a neutralization rate of 30 mol%. The concentration of the aqueous solution of acrylate (3) is 40% by weight.
Met.

Example 4 2326 g of ion-exchanged water was charged into a distillation flask equipped with a stirrer. While controlling 1467 g of acrylic acid and 1062 g of 30% by weight aqueous ammonia solution so that the neutralization rate of acrylic acid in the neutralization reaction system is always 90 to 95 mol%.
Feed over 80 minutes. At this time, the temperature of the neutralization reaction system was kept at 20 to 40 ° C by cooling. Next, 116 g of a 30% by weight aqueous ammonia solution is supplied to make the neutralization rate of acrylic acid in the neutralization reaction system 102 mol% and the temperature of the neutralization reaction system 4
The temperature was adjusted to 0 ° C., and thereafter this state was maintained for aging for 30 minutes. The pH of the neutralization reaction system during this aging period is
It was 8.0 (25 ° C conversion). After completion of the aging, 31 g of acrylic acid was fed to the neutralization reaction system for 2 minutes to obtain an aqueous solution of acrylic acid salt (4) having a neutralization rate of 100 mol%.
The temperature of the aqueous solution of acrylate (4) was 37% by weight.
Met.

Comparative Example 1 The same distillation flask used in Example 1 was charged with 2744 g of ion-exchanged water and 1889 g of acrylic acid. There, 48
1640 g of a wt% aqueous sodium hydroxide solution was supplied over 120 minutes. The temperature of the neutralization reaction system at this time is 20 by cooling.
Keep at ~ 40 ° C. Thus, an aqueous solution of comparative acrylate (1) having a neutralization ratio of 75 mol% was obtained. The concentration of the aqueous solution of this comparative acrylic acid salt (1) was 37% by weight.

Comparative Example 2 The same distillation flask as used in Example 1 was charged with 2744 g of ion-exchanged water and 1640 g of 48% by weight sodium hydroxide aqueous solution. Thereto, 1889 g of acrylic acid was fed over 120 minutes. The temperature of the neutralization reaction system at this time is 20 by cooling.
Keep at ~ 40 ° C. Thus, an aqueous solution of comparative acrylate (2) having a neutralization ratio of 75 mol% was obtained. The concentration of the aqueous solution of this comparative acrylic acid salt (2) was 37% by weight.

Comparative Example 3 The same distillation flask as used in Example 1 was charged with 2744 g of ion-exchanged water. Acrylic acid (1889 g) and 48% by weight aqueous sodium hydroxide solution (1640 g) were supplied over 120 minutes while controlling so that the neutralization rate of acrylic acid in the neutralization reaction system was always 70 to 80 mol%. At this time, the temperature of the neutralization reaction system was kept at 20 to 40 ° C by cooling. Thus, an aqueous solution of comparative acrylate (3) having a neutralization ratio of 75 mol% was obtained. The concentration of the aqueous solution of this comparative acrylic acid salt (3) was 37% by weight.

Comparative Example 4 A distillation flask equipped with a stirrer was charged with 2,744 g of ion-exchanged water. Acrylic acid (1390 g) and 48% by weight aqueous sodium hydroxide solution (1040 g) were supplied thereto over 80 minutes while controlling the neutralization rate of acrylic acid in the neutralization reaction system to always be 60 to 70 mol%. At this time, the temperature of the neutralization reaction system was kept at 20 to 40 ° C by cooling. Next, 600 g of 48 wt% sodium hydroxide aqueous solution is supplied to adjust the neutralization rate of acrylic acid in the neutralization reaction system to 102 mol%, and the temperature of the neutralization reaction system is adjusted to 40 ° C. for 30 minutes thereafter. This state was maintained for a period of time and aged. The pH of the neutralization reaction system during this aging period was 13.9 (25 ° C conversion). After completion of the aging, 499 g of acrylic acid was supplied to the neutralization reaction system over 10 minutes to obtain an aqueous solution of comparative acrylate (4) having a neutralization ratio of 75 mol%. The concentration of the aqueous solution of the comparative acrylic acid salt (4) was 37% by weight.

Comparative Example 5 The same distillation flask used in Reference Example 1 was charged with 2744 g of ion-exchanged water. Acrylic acid (1390 g) and 48% by weight aqueous sodium hydroxide solution (1640 g) were fed over 120 minutes while controlling so that the neutralization rate of acrylic acid in the neutralization reaction system was always 102 to 105 mol%. At this time, the temperature of the neutralization reaction system was kept at 20 to 40 ° C by cooling. Next, 499 g of acrylic acid was supplied over 10 minutes, and the neutralization rate was 75%.
An aqueous solution of mol% comparative acrylate (5) was obtained. still,
The concentration of this comparative acrylate (5) in water is 37% by weight.
Met.

Example 5 A stainless steel double-armed kneading machine (kneader) with a jacket having two sigma-type blades having an inner volume of 10, an opening of 220 mm × 240 mm, a depth of 240 mm, and a blade rotation diameter of 120 mm was fitted with a lid, and this kneader was attached. 5500 g of the aqueous solution of the acrylate (1) obtained in Example 1 and an aqueous solution of a monomer component consisting of 3.4 g of trimethylolpropane triacrylate (0.05 mol% based on acrylate) (concentration of the aqueous solution: 37% by weight, Acrylic acid salt neutralization ratio (75 mol%) was fed, and nitrogen gas was blown into the reaction system to replace it with nitrogen. Then, two sigma type blades were rotated at a speed of 67 rpm and 56 rpm, respectively, and 2.8 g of ammonium persulfate and 0.7 g of sodium hydrogen sulfite as a polymerization initiator were added while heating the jacket with hot water of 35 ° C. Polymerization started 5 minutes after the addition of the polymerization initiator. 20 minutes after adding the polymerization initiator, the peak temperature in the reaction system reached 83 ° C, and the water-containing gel polymer was about
It was subdivided into fine particles with a diameter of 5 mm. Further, stirring was continued, and after 60 minutes from the start of polymerization, the lid was removed and the gel was taken out.

The fine granules of the obtained hydrous gel polymer were spread on a 50-mesh wire net and dried with hot air at a temperature of 180 ° C for 40 minutes. This dried material was pulverized using a vibration mill, and the water absorption capacity, water-soluble content and residual monomer of the acrylate-containing polymer (1) obtained by passing through a 20-mesh wire net were measured. Shown in the table.

The water absorption capacity, water-soluble content and residual monomer in the examples refer to the values measured by the following test methods.

A: Water absorption ratio 0.2g of polymer is a non-cotton tea bag bag (40mm × 150m
m), was immersed in 0.9% saline, and the weight was measured after 30 minutes. The water absorption weight when only the tea bag type bag was immersed was used as a blank, and the water absorption capacity was determined according to the following formula.

B: Water-soluble component 0.5 g of the polymer was dispersed in 1000 ml of deionized water, stirred for 12 hours and then filtered through filter paper, and the solid content of the filtrate was measured to obtain the water-soluble component according to the following formula.

C: Residual monomer 0.5 g of polymer was dispersed in 1000 ml of distilled water, stirred for 2 hours, filtered through Whatman filter paper GF / F (particle retention capacity 0.7 micron), and the filtrate was analyzed by liquid chromatography.

Examples 6 to 7 and Comparative Examples 7 to 10 The same procedure as in Example 5 was repeated except that the composition of the aqueous solution of the monomer component in Example 5 was changed as shown in Table 1, to obtain an acrylate-containing polymer. (2) to (3) and comparative acrylate-containing polymers (1 ') to (5') were obtained. The progress of the polymerization reaction and the physical properties of the obtained acrylate-containing polymer were as shown in Table 1.

Example 8 In the kneader used in Example 5, 3590 g, 17 wt% of an aqueous solution of the acrylate (4) obtained in Example 4, 1910 g of an aqueous methacrylic acid solution, and 1.4 g of N, N'-methylenebisacrylamide were used. An aqueous solution of a monomer component consisting of (aqueous solution concentration 30
(% By weight), and nitrogen gas was blown into the reaction system to replace the inside of the reaction system with nitrogen. Then rotate the two sigma-type blades at speeds of 67 and 56 rpm, respectively, and cover the jacket at 35 ° C.
Ammonium persulfate (1.0 g) and sodium bisulfite (0.25 g) were added as polymerization initiators while heating with warm water. Polymerization started 12 minutes after the addition of the polymerization initiator. 40 minutes after adding the polymerization initiator, the peak temperature in the reaction system was 76
C., the hydrogel polymer was subdivided into fine particles with a diameter of about 5 mm. After 80 minutes from the initiation of polymerization by further stirring, the lid was removed and the gel was taken out.

The obtained hydrogel polymer fine granules were subjected to the same operations as in Example 5 to obtain an acrylate-containing polymer (4).

Example 9 A distillation flask equipped with a stirrer was charged with 1944 g of ion-exchanged water. Acrylic acid (1390 g) and 48% by weight sodium hydroxide aqueous solution (1480 g) were fed thereto for 100 minutes while controlling so that the neutralization rate of acrylic acid in the neutralization reaction system was always 90 to 95 mol%. At this time, the temperature of the neutralization reaction system was kept at 20 to 40 ° C by cooling. Next, 160 g of 48% by weight aqueous sodium hydroxide solution is supplied to adjust the neutralization rate of acrylic acid in the neutralization reaction system to 102 mol%, and the temperature of the neutralization reaction system is adjusted to 40 ° C. for 30 minutes thereafter. This state was maintained for a period of time and aged. The pH of the neutralization reaction system during this aging period was 13.9 (calculated at 25 ° C). After aging,
28 g of neutralization reaction system acrylic acid was supplied over 1 minute to obtain an aqueous solution of acrylic acid salt (5) having a neutralization rate of 100 mol%. The concentration of the aqueous solution of this acrylate (5) is 37
% By weight.

The apparatus as shown in FIGS. 1 and 2, that is, two stainless steel plates with a fluororesin coating 16 on the inside.
Insert rubber packing 15 between 18 and bolt 13 and nut 19
Casting polymerizer that is fixed and sealed with (internal volume 1.6, vertical 2
30mm x width 230mm x width 30mm) Aqueous solution of acrylate (5) with a concentration of 37% by weight, which was previously substituted with nitrogen in 11 2,000
g, ammonium persulfate 0.08 g and sodium hydrogen sulfite 0.04 g were put in through the raw material inlet 12 and air was discharged through the air outlet 14. This cast polymerization apparatus was placed in a water bath equipped with a stirrer and a temperature controller, and the temperature of the water bath was maintained at 30 ° C to polymerize while removing the reaction heat. Five hours after the initiation of polymerization, the hydrogel polymer was taken out from the casting polymerization apparatus, formed into a string with a meat chopper, and spread on a 50-mesh wire mesh.
It was dried with hot air at a temperature of ° C for 60 minutes. The dried product was crushed using a vibration mill and passed through a 20-mesh wire net to obtain an acrylate-containing polymer (5).

The residual monomer amount of the obtained acrylic acid salt-containing polymer (5) was measured by a bromine addition method, and 0.2 g of the polymer was deionized water 10.
The viscosity of an aqueous solution dissolved in 0 g at 25 ° C. was measured with a Brookfield viscometer. The results are shown in Table 2.

Comparative Example 11 The same distillation flask used in Example 1 was charged with 1944 g of ion-exchanged water and 1418 g of acrylic acid. There, 48
1640 g of a weight% sodium hydroxide aqueous solution was supplied over 120 minutes. The temperature of the neutralization reaction system at this time is set by cooling.
Maintained at 20-40 ° C. Thus, an aqueous solution of comparative acrylate (6) having a neutralization ratio of 100 mol% was obtained. The concentration of this comparative acrylic acid salt (6) in water was 37% by weight.

The same operation as in Example 9 was repeated except that the comparative acrylic acid salt (6) was used in Example 9, to obtain a comparative acrylic acid-containing polymer (6 ′). This comparative acrylate-containing polymer (6 ') was tested as in Example 9 and the results are shown in Table 2.

The method for producing an acrylate according to the present invention requires a specific step, and the acrylate-containing polymer produced using the acrylate has excellent physical properties of the acrylate-containing polymer system. The amount of unreacted acrylate is significantly reduced without any damage. Therefore, the water-soluble or water-swellable acrylate-containing polymer obtained by applying the method of the present invention has no adverse effects on the human body, environment, etc., and is a flocculant for water treatment, a mud additive for petroleum drilling, a food product. It is preferably used for applications such as additives, absorbents for sanitary materials, water retention agents, and food freshness preservation films.

The method for producing an acrylate according to the present invention can be carried out extremely easily industrially, and further, the method for producing an acrylate-containing polymer using the acrylate as a raw material includes the acrylic acid having the above characteristics. It is intended to provide a method for producing a salt-containing polymer with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic front view of a polymerization apparatus used in Example 9 of the present invention and Comparative Example 11, and FIG. 2 is II of FIG.
It is a sectional view taken along the line II. 11 …… Cast polymerizer, 12 …… Raw material inlet, 13 …… Bolt, 14 …… Air outlet, 15 …… Rubber packing, 16 …… Fluororesin coating, 18 …… Stainless steel plate, 19 …… Bolt .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiro Kajikawa 1 at 992 Nishikioki, Akihama, Aboshi-ku, Himeji-shi, Hyogo Pref. 1 within Nippon Catalysis Chemical Co., Ltd. Within Japan Catalysis Chemical Co., Ltd. (72) Inventor Akiaki Fujiwara, 992, Nishioki, Akihama, Aboshi-ku, Himeji-shi, Hyogo Prefecture. Within Nippon Shokubai Chemical Co., Ltd.

Claims (16)

[Claims] 1. A step of (A) supplying acrylic acid and a basic substance to water to carry out a neutralization reaction while always keeping the neutralization rate of acrylic acid in the neutralization reaction system within the range of 75 to 100 mol%. (B) supplying a basic substance to the neutralization reaction system to adjust the neutralization rate of acrylic acid in the neutralization reaction system to 100.1 to 110 mol%, (C) in the neutralization reaction system A step of aging while maintaining the neutralization rate in a state of 100.1 to 110 mol% for 1 to 120 minutes, and (D) supplying acrylic acid to the neutralization reaction system to obtain acrylic acid in the neutralization reaction system. A method for producing an acrylic acid salt by a neutralization reaction between acrylic acid and a basic substance, which comprises the steps of adjusting the sum ratio to 20 to 100 mol%. 2. The method according to claim 1, wherein the basic substance is an alkali metal hydroxide. 3. The method according to claim 1, wherein the neutralization rate of acrylic acid in the neutralization reaction system in step (A) is always in the range of 85 to 100 mol%. 4. The method according to claim 1, wherein the neutralization reaction in the step (A) is carried out at a temperature of 20 to 50 ° C. 5. The method according to claim 1, wherein the neutralization rate of acrylic acid in the neutralization reaction system in step (C) is in the range of 100.5 to 105 mol%. 6. The method according to claim 1, wherein the neutralization reaction in step (C) is carried out at a temperature of 20 to 50 ° C. 7. A step of (A) supplying acrylic acid and a basic substance to water to carry out a neutralization reaction while always keeping the neutralization rate of acrylic acid in the neutralization reaction system within the range of 75 to 100 mol%. (B) supplying a basic substance to the neutralization reaction system to adjust the neutralization rate of acrylic acid in the neutralization reaction system to 100.1 to 110 mol%, (C) in the neutralization reaction system Aging at a neutralization rate of 100.1 to 110 mol% for 1 to 120 minutes, and (D) supplying acrylic acid to the neutralization reaction system to remove acrylic acid in the neutralization reaction system. Acrylate-containing polymer comprising polymerizing a monomer component containing at least an acrylic acid salt by a sequential neutralization reaction between acrylic acid and a basic substance, the step of adjusting the neutralization rate to 20 to 100 mol% Manufacturing method. 8. The content of acrylate in the monomer component is 50 to 50.
The method according to claim 7, which is 100% by weight. 9. The method according to claim 8, wherein the acrylate-containing polymer has a crosslinked structure. 10. The method according to claim 8, wherein the monomer component contains a crosslinkable monomer. 11. The method according to claim 10, wherein the crosslinkable monomer is used in an amount of 0.001 to 5 mol% based on the monomer component. 12. The method according to claim 7, wherein the basic substance is an alkali metal hydroxide. 13. The method according to claim 7, wherein the neutralization rate of acrylic acid in the neutralization reaction system in step (A) is always in the range of 85 to 100 mol%. 14. The method according to claim 7, wherein the neutralization reaction in the step (A) is carried out at a temperature of 20 to 50 ° C. 15. The method according to claim 7, wherein the neutralization rate of acrylic acid in the neutralization reaction system in step (C) is in the range of 100.5 to 105 mol%. 16. The neutralization reaction in step (C) is 20 to 50 ° C.
8. The method of claim 7, which is performed at the temperature of.