JP3128628B2 - Method for producing high polymerization degree polyacrylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polyacrylic acid having a high degree of polymerization, which is not deteriorated by heat and has excellent spinnability and adhesiveness when used as an aqueous solution.

[0002]

2. Description of the Related Art Generally, polyacrylic acid having a high degree of polymerization is
It is obtained by polymerizing acrylic acid in an aqueous solution. As another polymerization method, a so-called reverse-phase pearl polymerization method in which an aqueous solution of an acrylic acid monomer is polymerized using an organic solvent insoluble in both the monomer and the polymer as a dispersion medium is also known.

[0003]

In the method of polymerizing acrylic acid in an aqueous solution, if the obtained polyacrylic acid having a high degree of polymerization is to be dried by applying heat for the purpose of producing a powdery product, When polyacrylic acid is dissolved in water under the influence of heat, it exhibits physical properties different from the original liquid properties, and in extreme cases, is transformed into an insoluble polymer. When trying to dry by spray drying for the purpose of reducing such heat history, the degree of polymerization is so high that the polymer does not spray well and the polymer forms a spider web in the dryer and cannot be dried practically .

As another drying method, drying using a low-temperature vacuum dryer or the like is conceivable. However, the drying cost is high in terms of the amount of water to be evaporated and handling operations, which is not appropriate. When a dehydrating agent such as methanol, ethanol, or acetone is added for the purpose of reducing the drying heat history of the polymer aqueous solution, the polymer itself is solubilized and cannot be dehydrated. On the other hand, polyacrylic acid obtained by the reverse phase pearl polymerization method also becomes a water-insoluble polymer and cannot achieve its intended purpose.

In view of the above-mentioned circumstances, the present invention provides a high-temperature linearly polymerized polymer having good thermal stability, stability over time, and water solubility by precipitating and polymerizing acrylic acid using a specific mixed solvent. Thus, a method for producing polyacrylic acid has been completed.

[0006]

The process for producing polyacrylic acid having a high degree of polymerization according to the present invention comprises the steps of polymerizing acrylic acid in a mixed solvent of a saturated hydrocarbon having a boiling point of 100 ° C. or less and a ketone having a boiling point of 100 ° C. or less. By doing so, the molecular weight is 50,0
It is characterized by obtaining polyacrylic acid of 00 or more.

[0007] In the present invention, pentane, n-hexane, isohexane, 3-methylpentane, 2,3-dimethylbutane, n-heptane, 3-methylhexane, 3-ethyl Examples include chain-like saturated hydrocarbons such as pentane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, and 2,2,3-trimethylbutane. it can. The preferred boiling point of the saturated hydrocarbon used is in the range of 35-100 ° C.

[0008] Ketones having a boiling point of 100 ° C or less include:
Acetone and methyl ethyl ketone can be mentioned.

The mixing ratio of the saturated hydrocarbon having a boiling point of 100 ° C. or lower and the ketones having a boiling point of 100 ° C. or lower is preferably 100: 1 to 50 as a preferable weight ratio of the saturated hydrocarbon: ketones. Preferably, 100: 5-
30. When the mixing ratio of the ketones to the saturated hydrocarbon 100 is less than 1, the charged concentration is reduced, and the temperature control of the polymerization reaction is not sufficient. If the mixing ratio exceeds 50 and becomes excessively large, the spinnability of the obtained polymer is reduced, and it becomes impossible to obtain the desired polyacrylic acid having a high degree of polymerization.

Acrylic acid used for polymerization is 98% pure
It is preferable to use the above acrylic acid. Thus, for the purpose of improving the adhesion of the resulting polyacrylic acid, for example, other monofunctional vinyl monomers, for example, esters of methyl, ethyl, butyl, 2-ethylhexyl, hydroxyethyl, cyclohexyl, methacrylic acid, methacrylic acid, etc. Copolymerization may be carried out by adding an ester of an acid such as methyl, ethyl or butyl in an amount of 20% by weight or less.

For the purpose of adjusting the spinnability and viscosity of the obtained polyacrylic acid, for example, a polyfunctional vinyl monomer such as divinylbenzene or methylenebisacrylamide is added in an amount of 2% by weight or less to copolymerize. May be. Further, in order to adjust the properties of the aqueous solution of the polymer, a small amount of methacrylic acid or a mixture thereof may be used in addition to acrylic acid.

As the polymerization initiator, azoisobutyronitrile (AIBN), benzoyl peroxide, 2,2-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2, 4-dimethylvalironitrile) and the like, but ammonium persulfate (AP
Aqueous polymerization initiators such as S) and hydrogen peroxide are not suitable in view of the stability of the obtained polymer with time.

In the method for producing polyacrylic acid having a high degree of polymerization of the present invention, depending on the polymerization conditions such as the mixing ratio of the saturated hydrocarbon and the ketone, the polymer precipitated during the polymerization is stably contained in the polymerization solution. In some cases, it may not be able to float and adhere to the machine wall, so that it may be necessary to add a floating stabilizer. Examples of such a floating stabilizer include polyethylene glycol, polypropylene glycol, polyoxyethylene lauryl ether, oxyethylene / oxypropylene block copolymer, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, and polyoxyethylene. Nonylphenyl ether, sorbitan monostearate and the like are preferably used.

In the present invention, the raw materials to be charged into the reaction vessel may be charged all at once, or may be divided and added sequentially according to the progress of the reaction. The temperature of the polymerization reaction is preferably in the range of 50 to 85 ° C., and the polymer produced from the slurry after the completion of the polymerization reaction is separated and dried to obtain a powdery target product.

[0015]

According to the method for producing polyacrylic acid having a high degree of polymerization of the present invention, acrylic acid as a raw material monomer is dissolved in the mixed solvent, and polyacrylic acid is precipitated as a polymer insoluble in the mixed solvent by a polymerization reaction. This is based on so-called precipitation polymerization. By using a mixture of a saturated hydrocarbon having a boiling point of 100 ° C. or lower and ketones as the mixed solvent, a high polymerization degree polyacrylic acid having an average molecular weight of at least 50,000 can be easily obtained.

Even if the slurry obtained by the polymerization is dried at a temperature of, for example, 100 ° C. for 10 hours or more, the degree of polymerization of the polymer does not decrease and the polymer does not become three-dimensional.
% Aqueous solution viscosity is also very stable. This is because a high polymer having a molecular weight of 50,000 or more obtained by polymerization in an aqueous solution is dried at a temperature of 100 ° C.
It has a clear advantage over the conventional polymerization method in which the dimensions are increased and the viscosity of a 10% aqueous solution is increased.

According to the method for producing polyacrylic acid having a high degree of polymerization of the present invention, the polymer obtained by drying the slurry produced by the polymerization with hot air has almost no residual solvent odor, and the produced slurry is treated at a temperature of 100.degree. Even a 10% aqueous solution of the polymer obtained by drying with hot air for a long time hardly feels the residual solvent odor. This includes aromatic hydrocarbons, cyclohexane, ethyl acetate / cyclohexane, toluene /
Even if the polymer obtained by using a single or mixed solvent such as alcohol has a molecular weight of 50,000 or more, the residual solvent often becomes a 10% aqueous solution by drying at a temperature of 100 ° C. for 10 hours or more. The smell can be felt-in contrast.

[0018]

EXAMPLES Hereinafter, the method for producing polyacrylic acid having a high degree of polymerization of the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 A 5-liter flask was charged with 2,550 g of n-hexane, and the temperature was raised to 60 while replacing the inside of the flask with nitrogen gas.
℃, 160 g of acrylic acid in the flask,
130 g of acetone and V-65 as a polymerization initiator
[Product name of Wako Pure Chemical Industries, Ltd. of 2,2-azobis (2,4-dimethylvaleronitrile);
5 g were added. While maintaining this solution at a temperature of 60 ° C., the reaction was waited for to start, and when the reaction started, the polymerization solution became cloudy. Therefore, the time when it was confirmed that the solution was cloudy was defined as the polymerization start time, and thereafter, acetone was added every 90 minutes. A mixed solution of acrylic acid and V-65 were successively added, and the total charged amounts of acrylic acid 1,360 g, acetone 630 g, n-hexane 2,5
50 g and 0.59 g of V-65 were charged. After the total addition of the charged raw materials by the sequential addition, the temperature was further maintained at 60 ° C. for 120 minutes to complete the polymerization. The produced polymer in the slurry obtained by the polymerization was separated, and the obtained polymer was dried at a temperature of 95 ° C. for 8 hours. The acrylic acid polymer obtained by drying was analyzed by high performance liquid chromatography (hereinafter referred to as GPC). As a result, the average molecular weight (MW) of the polymer was 70,000 to 150,000.
The 10% aqueous solution was almost odorless.

Example 2 A flask containing 5 liters was charged with 2,610 g of n-hexane.
℃, 350 g of acrylic acid in the flask,
140 g of acetone, 3 g of polypropylene glycol as a dispersant, and 0.1 g of V-65 as a polymerization initiator were added. Waiting for the reaction to start while maintaining this liquid at a temperature of 60 ° C. When the reaction starts, the polymerization liquid becomes cloudy. A mixed solution of acetone and acrylic acid and V-65 were successively added, and a total charge of 1,550 g of acrylic acid, 500 g of acetone, n-hexane 2,
610 g, 3 g of polypropylene and 0.5 of V-65
9g was charged. After the total addition of the charged raw materials by the sequential addition, the temperature was further maintained at 60 ° C. for 120 minutes to complete the polymerization. The produced polymer in the slurry obtained by the polymerization was separated, and the obtained polymer was dried at a temperature of 95 ° C. for 8 hours. GPC analysis of the acrylic acid polymer obtained by drying showed that the average molecular weight (MW) of this polymer was 20.
Between 0.000 and 400,000, the 10% aqueous solution was almost odorless.

Example 3 A flask containing 5 liters was charged with 2,550 g of n-hexane.
° C, 144 g of acrylic acid in the flask,
16 g of ethyl acrylate, 130 g of acetone and 0.15 g of V-65 as a polymerization initiator were added.
Waiting for the reaction to start while maintaining this solution at a temperature of 60 ° C. When the reaction starts, the polymerization liquid becomes cloudy. , A mixture of acetone and acrylic acid and ethyl acrylate and V-65 were successively added, and the total charge was 1,224 g of acrylic acid, 136 g of ethyl acrylate, 630 g of acetone, 2,550 g of n-hexane, and V 0.59 g of -65 was charged. After the total addition of the charged raw materials by the sequential addition, the temperature was further maintained at 60 ° C. for 120 minutes to complete the polymerization. The resulting polymer in the slurry obtained by the polymerization was separated, and the obtained polymer was dried at a temperature of 85 ° C. for 8 hours. The average molecular weight (MW) of the dried copolymer mainly composed of acrylic acid by GPC analysis is 150,000 to 300,0.
As a result, the 10% aqueous solution was almost odorless and had sufficient adhesiveness even in the presence of some water.

Example 4 A flask containing 5 liters was charged with 2,550 g of n-hexane.
Temperature, and separately placed in a 2-liter beaker, 1,360 g of acrylic acid, 2 g of divinylbenzene, and 640 of acetone.
g, and 333.7 g and 0.1 g of V-65 as a polymerization initiator were mixed into a flask, and polymerization was started at a liquid temperature of 60 ° C. The remaining monomer solution was 6
A certain amount was added and polymerized at 0 minute intervals. The viscosity was 5,000 cps / 25 ° C. when the polymerization slurry was separated and dried (temperature: 105 ° C.) to form a 10% aqueous solution. The spinnability of this solution was determined in Example 2 (viscosity of 10% aqueous solution was 4,800 cps).
/ 25 ° C). (However, Comparative Example 2 described below
Divinylbenzene was added in the same manner as in
When the viscosity of the aqueous solution is adjusted to 4,000 to 6,000 cps / 25 ° C., it is much higher in comparison with the fact that it has almost no spinnability. This indicates that the required viscosity and spinnability can be adjusted by adding a polyvalent functional group such as divinylbenzene.

Comparative Example 1 Ethyl acetate (2,226 g) was placed in a 5-liter flask.
And 954 g of cyclohexane, and the temperature was raised to 75 ° C. while replacing the inside of the flask with nitrogen gas. Then, 272 g of acrylic acid and 0.45 g of azoisobutyronitrile (referred to as AIBN) as a polymerization initiator were added to the flask. . Waiting for the reaction to start while maintaining this solution at a temperature of 75 ° C. When the reaction starts, the polymerization solution becomes cloudy. 0.23 of acid 272 g and AIBN
g of acrylic acid as a total charge.
g, ethyl acetate 2,226 g, cyclohexane 954 g
And 1.36 g of AIBN were charged. After the total addition of the charged raw materials by the sequential addition, the temperature was further increased to 75 ° C. for 120 minutes.
Minutes to complete the polymerization. The produced polymer in the slurry obtained by the polymerization was separated, and the obtained polymer was dried at a temperature of 105 ° C. for 12 hours. The average molecular weight (MW) of the acrylic acid polymer obtained by drying was 70,000 to 150,000 by GPC analysis, but 10% of the average molecular weight (MW).
The acetic acid odor remained in the aqueous solution, and the acetic acid odor did not disappear even if drying was further extended for 8 hours to remove the acetic acid odor.

Comparative Example 2 A flask containing 5 liters was charged with 3,358 g of benzene, and the temperature was raised to 80 ° C. while the inside of the flask was replaced with nitrogen gas.
After that, 187 g of acrylic acid, 17 g of methanol and 0.45 g of azoisobutyronitrile (AIBN) as a polymerization initiator were added to the flask. While maintaining this solution at a temperature of 80 ° C., the start of the reaction is waited. When the reaction starts, the polymerization solution becomes cloudy. A mixed solution of acid and methanol and AIBN were successively added, and 1,125 g of acrylic acid, 57 g of methanol, 3,358 g of benzene, and 2.36 g of AIBN were charged as total charges. After the total addition of the charged raw materials by the sequential addition, the temperature was further maintained at 80 ° C. for 120 minutes to complete the polymerization. The produced polymer in the slurry obtained by the polymerization was separated, and the obtained polymer was dried at a temperature of 105 ° C. for 12 hours. The acrylic acid polymer obtained by drying,
Average molecular weight (MW) by GPC analysis is 20,000-
At 30,000, it was not possible to obtain a target acrylic acid polymer having a high degree of polymerization of 50,000 or more.

Comparative Example 3 2,550 cyclohexane was added to a 5-liter flask.
g, and the temperature was raised to 65 ° C. while the inside of the flask was replaced with nitrogen gas.
60 g, acetone 130 g and V- as a polymerization initiator
0.15 g of 65 was added. Waiting for the reaction to start while maintaining this solution at a temperature of 60 ° C. When the reaction starts, the polymerization solution becomes cloudy. A mixed solution of acetone and V-65 were sequentially added, and 1,360 g of acrylic acid, 630 g of acetone, 2,550 g of cyclohexane, and 0.59 g of V-65 were charged as total charges. After the total addition of the charged raw materials by the sequential addition, the temperature was further maintained at 65 ° C. for 120 minutes to complete the polymerization. The produced polymer in the slurry obtained by the polymerization was separated, and the obtained polymer was dried at a temperature of 95 ° C. for 8 hours. The average molecular weight of the dried acrylic acid polymer by GPC analysis (M
W) was 150,000 to 200,000, but the 10% aqueous solution was turbid, and the odor of cyclohexane remained. Further, the state of the 10% aqueous solution was examined by changing the drying temperature to 105 ° C., but no change was observed.

Comparative Example 4 Cyclohexane 3,000 was placed in a 5-liter flask.
g, and the temperature was raised to 75 ° C. while replacing the inside of the flask with nitrogen gas. Then, 45 g of acrylic acid, 30 g of water, and Newcol 40 (trade name of Nippon Emulsifier Co., Ltd .; the same applies hereinafter) in the flask. Of ammonium persulfate (APS) 0.15 as a polymerization initiator
g was added and the temperature of the solution was maintained at 75 ° C. for 20 minutes. Then, a mixture of acrylic acid and water, Newcol 4
0 and APS were added successively and sequentially to give a total charge of 900 g of acrylic acid, 600 g of water, 2,55 g of cyclohexane.
0 g, APS 0.59 g and Newcol 40 1
8 g was charged. After the total amount of the charged raw materials was added by the continuous sequential addition, the polymerization was completed by further maintaining the temperature at 75 ° C. for 120 minutes, the polymer was separated from the obtained slurry, and the polymer was dried at a temperature of 95 ° C. for 4 hours. The obtained acrylic acid polymer was soluble in water before drying, but was in a swollen state after drying and was not completely dissolved in water.

[0027]

The process for producing polyacrylic acid having a high degree of polymerization according to the present invention comprises subjecting acrylic acid to precipitation polymerization in a mixed solvent of a saturated hydrocarbon having a boiling point of 100 ° C. or lower and a ketone having a boiling point of 100 ° C. or lower. By using such a specific mixed solvent, a high polymerization degree polyacrylic acid having an average molecular weight of 50,000 or more can be easily and inexpensively obtained.

However, the polyacrylic acid having a high degree of polymerization obtained by this method is extremely stable without lowering the degree of polymerization or becoming three-dimensional upon drying, and has a residual solvent odor. Almost no spinnability,
Because of its excellent adhesive properties, it has wide utility as a thickener and adhesive.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 20/06

Claims (5)

(57) [Claims] 1. Acrylic acid is polymerized in a mixed solvent of a saturated hydrocarbon having a boiling point of 100 ° C. or less and a ketone having a boiling point of 100 ° C. or less to obtain polyacrylic acid having an average molecular weight of 50,000 or more. A method for producing polyacrylic acid having a high degree of polymerization. 2. The saturated hydrocarbon has a boiling point of 35 to 10.
2. The method for producing polyacrylic acid with a high degree of polymerization according to claim 1, wherein the hydrocarbon is a chain saturated hydrocarbon in the range of 0 ° C. 3. The mixing ratio between the saturated hydrocarbon and the ketone is 100: 1 to 50 by weight of saturated hydrocarbon: ketone.
The method for producing a high polymerization degree polyacrylic acid according to claim 1, wherein 4. The method according to claim 1, wherein the acrylic acid contains 20% by weight or less of another monofunctional vinyl monomer. 5. The method according to claim 1, wherein said acrylic acid contains 2% by weight or less of another polyfunctional vinyl monomer.