JP2008063493A - Vinylpyrrolidone-based polymer and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vinylpyrrolidone-based polymer having a reduced change of K value in an alkaline solution and a method for producing the same. <P>SOLUTION: In a method for producing the vinylpyrrolidone-based polymer by polymerizing a vinylpyrrolidone monomer in a solution using a radical polymerization initiator, a solution containing the vinylpyrrolidone monomer and a sulfite is prepared and the polymerization is performed by continuously or intermittently adding an azo-based initiator having ≤60°C 10-hour half-time temperature to the solution. By the method, a vinylpyrrolidone-based polymer expressing ≤3% rate of change in K value after 3 months preservation at 50°C is produced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vinylpyrrolidone polymer and a method for producing the same.

  Vinylpyrrolidone-based polymers generally deteriorate over time, and the K value, hue, and the like change. The K value is a constant representing the degree of polymerization proposed by the German chemist Fikencher. Hydrogen peroxide may be used as an initiator or a chain transfer agent in the production of the vinyl pyrrolidone polymer. The vinyl pyrrolidone polymer obtained by such a method has a K value over time in an alkaline solution. The change is a big problem.

On the other hand, as a method for improving the storage stability of the vinylpyrrolidone-based polymer, a method of making the oxygen concentration in the gas phase in contact with the polymer 50000 ppm or less (Japanese Patent Laid-Open No. 2001-2880), or an antioxidant Although the method of mix | blending (Unexamined-Japanese-Patent No. 2001-192457) etc. is proposed, the effect is inadequate and it has not reached the fundamental solution.
Japanese Patent Laid-Open No. 2001-2880 JP 2001-192457 A

  The present invention has been made in view of the above, and an object of the present invention is to provide a vinylpyrrolidone polymer having improved storage stability, and particularly a vinylpyrrolidone polymer having a small change in K value even in an alkaline solution and its production. It aims to provide a method.

  As a result of various studies to solve the above problems, the present inventors have used a chain transfer agent that incorporates sulfurous acid at the polymer terminal, and continuously or intermittently adding an azo-based initiator, It has been found that a vinylpyrrolidone polymer having extremely good storage stability even in an alkaline solution can be obtained, and the present invention has been completed.

  That is, the method for producing a vinylpyrrolidone polymer of the present invention is a method for producing a vinylpyrrolidone polymer in which a vinylpyrrolidone monomer is polymerized in a solution using a radical polymerization initiator, and the vinylpyrrolidone monomer and sulfite are mixed. The solution is prepared, and polymerization is carried out by continuously or intermittently adding an azo initiator having a 10-hour half-life temperature of 60 ° C. or less to this solution.

  The vinylpyrrolidone polymer of the present invention is obtained by the above production method, and the K value change rate after storage at 50 ° C. for 3 months is 3% or less.

  According to the production method of the present invention, a vinylpyrrolidone polymer having extremely good storage stability even in an alkaline solution can be obtained, and oxygen concentration can be controlled or oxidation can be prevented when the polymer is filled in a container. There is no need to add an agent.

  In addition, the risk of runaway reaction due to heat of polymerization can be suppressed by continuously or intermittently adding an azo-based initiator having a 10-hour half-life temperature of 60 ° C. or less, resulting in a significant increase in production time. In addition, production at a high concentration is possible, and a polymer solution having a wide range of concentrations can be obtained safely and efficiently.

  The vinylpyrrolidone polymer referred to in the present invention is a homopolymer of vinylpyrrolidone (N-vinyl-2-pyrrolidone, hereinafter also referred to as VP) or a copolymer of VP and another monomer, Other monomers are not particularly limited as long as they are copolymerizable with VP, and examples include acrylic acid, methacrylic acid, alkyl esters of acrylic acid (such as methyl acrylate and ethyl acrylate), and methacrylic acid. Alkyl esters (methyl methacrylate, ethyl methacrylate, etc.), aminoalkyl esters of acrylic acid (diethylaminoethyl acrylate, etc.), aminoalkyl esters of methacrylic acid, monoesters of acrylic acid and glycol, monoesters of methacrylic acid and glycol (hydroxy Ethyl methacrylate), acrylic acid Lucari metal salt, alkali metal salt of methacrylic acid, ammonium salt of acrylic acid, ammonium salt of methacrylic acid, quaternary ammonium derivative of aminoalkyl ester of acrylic acid, quaternary ammonium derivative of aminoalkyl ester of methacrylic acid, diethylamino Quaternary ammonium compounds of ethyl acrylate and methyl sulfate, vinyl methyl ether, vinyl ethyl ether, alkali metal salts of vinyl sulfonic acid, ammonium salts of vinyl sulfonic acid, styrene sulfonic acid, styrene sulfonate, allyl sulfonic acid, allyl Sulfonate, methallyl sulfonic acid, methallyl sulfonate, vinyl acetate, vinyl stearate, N-vinyl imidazole, N-vinyl acetamide, N-vinyl formamide, N-vinyl capro Kutamu, N- vinylcarbazole, acrylamide, methacrylamide, N- alkyl acrylamide, N- methylolacrylamide, N, N- methylenebisacrylamide, glycol diacrylate, glycol dimethacrylate, divinyl benzene, glycol diallyl ether.

  The proportion of vinylpyrrolidone and other monomers is not particularly limited, but if the proportion of VP is too small, it is not the object of the present invention, so that the proportion of VP is 20% by weight or more as a guide.

  Polymerization of the vinyl pyrrolidone monomer (including copolymerization of vinyl pyrrolidone and other monomers) is performed by solution polymerization. As the solvent, water or an aqueous solvent is preferably used. The aqueous solvent means a mixed solvent of one or two or more kinds of compounds that can be mixed with water, and a mixed solvent in which such a compound is mixed so that water is a main component. Examples of the compound that can be mixed with water include alcohols such as methanol, ethanol, and 1-propanol, diols such as ethylene glycol, and polyhydric alcohols such as triols such as glycerin.

  In the production method of the present invention, the monomer solution contains sulfite. Examples of sulfites that can be used in the present invention include ammonium sulfite, sodium sulfite, sodium hydrogen sulfite and the like, with ammonium sulfite being particularly preferred.

  As the concentration of the solution, the vinylpyrrolidone monomer concentration is preferably in the range of 10 to 60% by weight, more preferably 15 to 50% by weight. If the concentration is less than 10% by weight, the productivity tends to be poor and the cost tends to increase. If the concentration exceeds 60% by weight, the viscosity increases over time during the polymerization, and stirring becomes difficult and the reaction tends to be hindered. Become.

  The concentration of sulfite is preferably in the range of 0.0001 to 20% by weight, more preferably in the range of 0.001 to 10% by weight. If the concentration is less than 0.0001% by weight, it is difficult to obtain the intended stability, and if it exceeds 20% by weight, the amount of impurities in the product tends to increase.

  Polymerization is carried out by continuously or intermittently adding an azo initiator having a 10-hour half-life temperature of 60 ° C. or lower to the above solution.

  Examples of such azo initiators include 2,2′-azobis (2,4-dimethylvaleronitrile) (10 hour half-life temperature 51 ° C.), 2,2′-azobis [2- (2-imidazoline). -2-yl) propane] dihydrochloride (10-hour half-life temperature 44 ° C.), 2,2′-azobis (2-amidinopropane) dihydrochloride (10-hour half-life temperature 56 ° C.), etc. 2,2′-azobis (2,4-dimethylvaleronitrile) is preferred.

  The addition amount (total amount) of the azo initiator is preferably in the range of 0.001 to 5% by weight with respect to the vinylpyrrolidone monomer. When the amount is less than 0.001% by weight, the polymerization rate decreases, the production efficiency is deteriorated, and when it exceeds 5% by weight, the amount of impurities in the product tends to increase.

  The azo initiator may be added to the monomer solution as it is, or may be added after being dissolved in an organic solvent such as methanol, ethanol or isopropanol.

  “Adding the azo-based initiator continuously or intermittently” means adding a necessary amount of the above-mentioned azo-based initiator at a time so that a runaway reaction due to polymerization heat does not occur. It is said to be added gradually over time. Preferably, it is added so that the temperature rise in the polymerization system is 5 ° C. or less per minute. Therefore, the amount of addition per certain time may not necessarily be constant. For example, intermittent addition may be performed following continuous addition, or vice versa. The interval may be changed.

  By the above production method, a vinylpyrrolidone-based polymer having a very good storage stability with a K value change rate of 3% or less after storage at 50 ° C. for 3 months even in an alkaline solution having a pH of 7 to 10 can be obtained. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to this.

[Example 1]
500 parts of water and 500 parts of vinylpyrrolidone were mixed in a stirring vessel, and after deoxygenation by introducing nitrogen, the system was heated to 70 ° C. V-65 (2,2′-azobis (2,4-dimethylvaleronitrile), manufactured by Wako Pure Chemical Industries, Ltd., 10 hours half-life, after adding 2 parts of ammonium sulfite monohydrate to a homogeneous solution 0.45 part of a 5 wt% ethanol solution at a temperature of 51 ° C. was added intermittently 10 times every 30 minutes. At this time, the maximum temperature increase was 2 ° C. per minute. Furthermore, after adding 4.5 parts of 5 wt% V-65 ethanol solution, the mixture was heated and stirred for 1 hour to obtain a polymer solution.

[Example 2]
700 parts of water and 300 parts of vinylpyrrolidone were mixed in a stirring vessel, and after deoxygenation by introducing nitrogen, the system was heated to 70 ° C. 4.5 parts of a 5 wt% V-65 ethanol solution was continuously added over 4 hours to a uniform solution obtained by adding 1.2 parts of ammonium sulfite monohydrate. At this time, the temperature rise was at most 1.5 ° C. per minute. Furthermore, after adding 4.5 parts of 5 wt% V-65 ethanol solution, the mixture was heated and stirred for 1 hour to obtain a polymer solution.

[Comparative Example 1]
700 parts of water and 300 parts of vinylpyrrolidone were mixed in a stirring vessel, and after deoxygenation by introducing nitrogen, the system was heated to 70 ° C. 4.5 parts of a 5 wt% V-65 ethanol solution was continuously added over 4 hours to a solution which was homogenized by adding 10 parts of 30% hydrogen peroxide water. Furthermore, after adding 4.5 parts of 5 wt% V-65 ethanol solution, the mixture was heated and stirred for 1 hour to obtain a polymer solution.

[Comparative Example 2]
700 parts of water and 300 parts of vinylpyrrolidone were mixed in a stirring vessel, and after deoxygenation by introducing nitrogen, the system was heated to 70 ° C. To a uniform solution obtained by adding 2.3 parts of 0.01% aqueous copper sulfate solution, 1.8 parts of 30% aqueous hydrogen peroxide was intermittently added 10 times every 30 minutes. Further, 0.5 part of 30% hydrogen peroxide water was added, followed by heating and stirring for 1 hour to obtain a polymer solution.

[Comparative Example 3]
500 parts of water and 500 parts of vinylpyrrolidone were mixed in a stirring vessel, and after deoxygenation by introducing nitrogen, the system was heated to 70 ° C. 5 wt% V-59 (2,2′-azobis (2-methylbutyronitrile), manufactured by Wako Pure Chemical Industries, Ltd., 10 hours, to a uniform solution by adding 2 parts of ammonium sulfite monohydrate (Half-life temperature 67 ° C.) 0.45 part of ethanol solution was added every 30 minutes. In this case, the temperature inside the system suddenly increased during the polymerization and bumped, and the reaction solution was ejected from the opening of the container.

[Comparative Example 4]
500 parts of water and 500 parts of vinylpyrrolidone were mixed in a stirring vessel, and after deoxygenation by introducing nitrogen, the system was heated to 70 ° C. To this solution, 0.45 part of a 5 wt% V-65 ethanol solution was added every 30 minutes. In this case, the viscosity of the polymerization solution became very high during the polymerization, and finally it became impossible to stir. Further, when 4.5 parts of 5 wt% V-65 ethanol solution was added every 30 minutes in order to reduce the viscosity, the temperature in the system suddenly increased and bumped, as in Comparative Example 3, and the reaction solution was put into a container. It became a dangerous state of ejecting from the opening.

  The storage stability of the vinylpyrrolidone polymers obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was evaluated by an accelerated test. That is, an appropriate amount of aqueous ammonia was added to the obtained vinylpyrrolidone polymer solution to adjust the pH to alkaline, and then the solution was placed in a sealable sample bottle and stored in a 50 ° C. incubator for 3 months. Table 1 shows the K value before and after the acceleration test, the rate of change thereof, and the measured value of pH.

The K value was determined by the following measurement method. That is, the viscosity of a 1% (g / 100 ml) solution is measured. Sample concentration is converted to dry matter. If the K value is 20 or more, accurately measure 1.0 g of sample, put it in a 100 ml volumetric flask, add distilled water at room temperature, dissolve completely with shaking and add distilled water to make exactly 100 ml. To do. The sample solution is allowed to stand for 30 minutes in a thermostatic chamber (25 ± 0.2 ° C.), and then the time (flow time) for the sample solution to flow between the two mark lines is measured using an Ubbelohde viscometer. Measure several times and take the average value. In order to define the relative viscosity, the same is measured for distilled water. The two obtained flow times are corrected based on the Hagenbach-Couette correction value.

  In the above formula, C represents the concentration of the sample (%: g / 100 ml), and Z represents the relative viscosity (ηrel) of the solution having the concentration C. The relative viscosity ηrel is obtained from the following equation.

  ηrel = (solution flow time) ÷ (water flow time)

  From the results shown in the table, in Examples 1 and 2 in which a predetermined initiator was continuously or intermittently added to a solution containing vinylpyrrolidone and sulfite, the change rate of the K value was extremely small even in an alkaline solution. In contrast, in Comparative Examples 1 and 2 using hydrogen peroxide as the initiator or chain transfer agent, it can be seen that the rate of change of the K value is large.

Claims (2)

A method for producing a vinylpyrrolidone polymer in which a vinylpyrrolidone monomer is polymerized in a solution using a radical polymerization initiator,
Prepare a solution containing vinylpyrrolidone monomer and sulfite,
A method for producing a vinylpyrrolidone polymer, characterized by continuously or intermittently adding an azo initiator having a 10-hour half-life temperature of 60 ° C. or lower to this solution.   A vinylpyrrolidone polymer obtained by the production method according to claim 1 and having a K value change rate of 3% or less after storage at 50 ° C for 3 months.