JP2008088290A - Poly(meth)acrylic acid partially neutralized product and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a poly(meth)acrylic acid partially neutralized product characterized by giving very little insoluble ingredients in its aqueous solution and very low viscosity of its aqueous solution and having small change with the lapse of time, and useful for a dispersant of various pigments and the like, a scale suppressor, a cleansing builder, a thickener, a binder, a medicinal substrate for fomentations and poultices, and the like. <P>SOLUTION: A poly(meth)acrylic acid partially neutralized product obtained by polymerizing a monomer mixture containing (meth)acrylic acid and (meth)acrylate salts and having 2,000,000-4,000,000 weight-average molecular weight and 1.0-1.3 molecular weight distribution represented by weight-average molecular weight/number-average molecular weight is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a poly (meth) acrylic acid partial neutralized product, a method for producing the same, and a poultice containing a powder of the poly (meth) acrylic acid partial neutralized product.

  The poly (meth) acrylic acid partially neutralized product is useful as a dispersant for various pigments, a scale inhibitor, a cleaning builder, a thickener, a binder, and a base for a medical poultice or a haptic agent. Widely used in various fields.

In general, a partially neutralized poly (meth) acrylic acid is obtained by adding an aqueous solution of a monomer mixture containing (meth) acrylic acid and (meth) acrylate, or a monomer containing (meth) acrylic acid to water. It is produced by radical polymerization of a mixed aqueous solution in which a compound that neutralizes an acid such as sodium oxide or potassium hydroxide is mixed.
For example, in JP-A-2004-10831 (Patent Document 1), a weight average molecular weight obtained by polymerizing a monomer mainly composed of (meth) acrylic acid (salt) in an aqueous medium has a weight average molecular weight of 600,000. The (meth) acrylic acid (salt) having a dispersity of 5 to 60 is described above.
According to Patent Document 1, a (meth) acrylic acid (salt) polymer having a weight average molecular weight of 600,000 or more and a dispersity of 5 to 60 can be suitably applied to various applications. In particular, it is described that it is preferable to use as a flocculant or a mud adjuster.
However, the molecular weight distribution measurement method described in Patent Document 1 requires a separately prepared standard sample, and uses a calibration curve created using the standard sample, so the information obtained is relative to the standard sample. Only the molecular weight, so there is a limit to the accuracy of the analysis, which is inconvenient for practical application.
Further, in JP-A-7-223938 (Patent Document 2), the obtained poly (meth) acrylic acid partial neutralized product is usually made into a powder by drying and pulverization, and the powder is made of water or water and glycerin. It is described that what was made into the gel form by melt | dissolving or disperse | distributing to a liquid mixture is used as bases, such as a poultice and a poultice.
However, in the poultice manufacturing company, in the process of mixing and stirring the powder of partially neutralized (meth) acrylic acid, glycerin and water, the viscosity increases excessively and the motor load of the stirrer increases, or stirring and mixing However, there is a problem that it becomes difficult to achieve stable production due to non-uniformity. In addition, since the viscosity changes with the elapsed time of stirring, there is a problem that the quality of the poultice as the final product becomes unstable.
JP 2004-10831 A Japanese Patent Laid-Open No. 7-223938

  Since the partially neutralized poly (meth) acrylic acid known so far as described in the above-mentioned patent documents has a relatively high viscosity in an aqueous solution and a large amount of insoluble matter in the aqueous solution, When the partially neutralized meth) acrylic acid is used in the form of an aqueous solution, it cannot be said that the solubility and dispersibility are sufficient, so that there is still room for improvement in terms of workability.

In order to solve the above-mentioned problems, the present inventor has developed a poly (meth) acryl having a considerably large weight average molecular weight and having a dispersity expressed by weight average molecular weight / number average molecular weight in a specific range that is extremely smaller than that of the prior art. It has been found that an acid partial neutralized product solves the above problems.
Moreover, it was not necessary to prepare a calibration curve for measuring the molecular weight, molecular weight distribution and molecular size (average RMS radius) of the polymer, and an assumption method was found in which a standard sample was unnecessary. This measurement method has high analytical accuracy and can be applied within a very wide practical range. The weight average molecular weight, dispersity, and average RMS radius in the present invention are based on numerical values measured by this method.
That is, the invention described in claim 1 of the present invention is a partially neutralized poly (meth) acrylic acid obtained by polymerizing a monomer mixture containing (meth) acrylic acid and (meth) acrylate. The poly (meth) acrylic acid partial neutralized product has a weight average molecular weight of 2 million to 4 million and a dispersity expressed by weight average molecular weight / number average molecular weight of 1.0 to 1.3. .

  The invention according to claim 2 of the present invention is characterized in that the ratio of (meth) acrylic acid / (meth) acrylate is 45/55 to 55/45 in molar ratio. It is a partially neutralized (meth) acrylic acid.

  In addition, the invention according to claim 3 of the present invention is such that the average RMS radius measured by a multi-angle light scattering detector and a parallax refraction detector is 220 to 260 nm. It is a partially neutralized product of (meth) acrylic acid.

  The invention according to claim 4 of the present invention is characterized in that the monomer mixture is photopolymerized by irradiating an aqueous solution of the monomer mixture with light containing ultraviolet rays in the presence of a photopolymerization initiator. The method for producing a partially neutralized poly (meth) acrylic acid according to any one of claims 1 to 3.

  Moreover, invention of Claim 5 of this invention is the powder of the poly (meth) acrylic acid partial neutralized material in any one of Claims 1-3.

The invention according to claim 6 of the present invention is a powder of the partially neutralized poly (meth) acrylic acid according to claim 5 and has the following properties.
(1) Viscosity at 20 ° C. after stirring a mixed solution of 0.2% by weight of the partially neutralized poly (meth) acrylic acid, 6.7% by weight of glycerin, and 93.1% by weight of water for 15 seconds ( A) is in the range of 200 to 800 mPa · s,
(2) Viscosity at 20 ° C. after stirring a mixed solution of 0.2% by weight of the partially neutralized poly (meth) acrylic acid, 6.7% by weight of glycerin and 93.1% by weight of water for 20 minutes ( B) is in the range of 200 to 800 mPa · s, and (3) the ratio of viscosity B to viscosity A (B / A) is in the range of 0.9 to 1.1.

    The invention according to claim 7 of the present invention is a cataplasm containing the powder of the partially neutralized (meth) acrylic acid according to claim 5 or 6.

  The partially neutralized poly (meth) acrylic acid of the present invention is excellent in solubility and dispersibility in water, and can be easily handled in an aqueous solution. Dispersants such as various pigments, scale inhibitors, cleaning builders, It is useful as a base for sticky agents, binders, pharmaceutical poultices and haps, and is particularly useful as a base for medicinal poultices and haps.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to these examples, and can be appropriately modified as long as the gist of the present invention is not changed. In addition, (meth) acrylic acid means acrylic acid or methacrylic acid.

  In the present invention, (meth) acrylate means a neutralized product of (meth) acrylic acid, and is a neutralized product obtained by neutralizing (meth) acrylic acid with an alkali metal, ammonia, organic amine or the like. , Sodium (meth) acrylate, potassium (meth) acrylate, calcium (meth) acrylate, magnesium (meth) acrylate, ammonium (meth) acrylate, etc., and these may be used alone or in combination of two or more. May be. Among these, sodium (meth) acrylate is preferable. In the present invention, a (meth) acrylic acid salt in which the acid portion has been previously neutralized may be used as a raw material, and after (meth) acrylic acid is polymerized, it is partially formed by sodium hydroxide, potassium hydroxide, or the like. It may be neutralized.

  In the poly (meth) acrylic acid partial neutralized product of the present invention, other monomers can be copolymerized as long as the intended effect of the present invention is not impaired. Examples of such monomers include α-hydroxyacrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid and other unsaturated carboxylic acids and salts thereof, 2-acrylamido-2-methylpropanesulfonic acid, (meta ) Unsaturated sulfonic acids such as allyl sulfonic acid and styrene sulfonic acid, and salts thereof. If necessary, one or more of these may be used in a range of 50 mol% or less based on the total amount of (meth) acrylic acid and (meth) acrylate.

In the partially neutralized poly (meth) acrylic acid of the present invention, the ratio of (meth) acrylic acid to (meth) acrylate is usually preferably 30/70 to 70/30, more preferably in terms of mole. Is 45/55 to 55/45. When the molar ratio of (meth) acrylic acid is less than 30% or exceeds 70%, the insoluble content in the mixed liquid of the powder of partially neutralized (meth) acrylic acid, glycerin and water tends to increase. is there.
Moreover, it is preferable that the ratio of the (meth) acrylate based on all the monomers is 20 to 80% by weight.

The partially neutralized poly (meth) acrylic acid of the present invention is obtained by radical polymerization of (meth) acrylic acid, (meth) acrylate and other monomer mixtures. It is also possible to polymerize a mixture of (meth) acrylic acid and other monomers and alkali metal hydroxide, ammonia, etc., which are compounds that neutralize the acid.
Examples of the polymerization method include known polymerization methods such as aqueous solution polymerization method, slurry polymerization method, turbid polymerization, and emulsion polymerization. From the viewpoint of solvent removal, solvent safety, and surfactant incorporation, aqueous solution polymerization method may be used. Is preferred.
In the aqueous solution polymerization method, an aqueous solution of the monomer is adjusted to a predetermined concentration, and dissolved oxygen in the reaction system is sufficiently replaced with an inert gas, and then a radical polymerization initiator is added, and if necessary, heating or ultraviolet rays are added. It is a method of performing a polymerization reaction by irradiating light.
In the present invention, the polymerization reaction is possible even at a low temperature, the reaction progress rate is good, and the low polymerization product and the gel-like product can be reduced. Is preferred to photopolymerize the monomer mixture.
Hereinafter, the photopolymerization method will be described.

  There is no restriction | limiting in particular as a photoinitiator, A well-known photoinitiator is suitably selected according to the objective and used. For example, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] tetrahydrate, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′- Azo photopolymerization initiators such as azobis (N, N′-dimethyleneisobutylamidine), 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane], 1-benzoyl- Examples include ketones such as 1-hydroxycyclohexane and benzophenone, benzoin and alkyl ethers thereof, benzyl ketals, and anthraquinone derivatives, among which azo photopolymerization initiators are preferable.

  It is preferable that the usage-amount of a photoinitiator is 10-10000 ppm with respect to all the monomers, More preferably, it is 10-5000 ppm. When the photopolymerization initiator is less than 10 ppm, polymerization does not occur sufficiently, and when it exceeds 10,000 ppm, the degree of polymerization of the resulting polymer is lowered.

The chain transfer agent is used for adjusting the molecular weight of the resulting partially neutralized poly (meth) acrylic acid and the viscosity of the aqueous solution, and for reducing the insoluble content.
Chain transfer agents include mercaptoethanol, mercaptopropionic acid, thioglycols, sulfur-containing compounds such as thioacetic acid, alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, and phosphorous compounds such as phosphorous acid and sodium phosphite. And hypophosphite compounds such as sodium hypophosphite, and these may be used alone or in combination of two or more. Among these chain transfer agents, sulfur-containing compounds are preferable, and 2-mercaptoethanol, 3-mercaptopropionic acid, and thioglycolic acid are more preferable.

  The amount of the chain transfer agent used is preferably 1 to 500 ppm, more preferably 1 to 300 ppm, based on all monomers. If the chain transfer agent is less than 1 ppm, a sufficient effect cannot be obtained, and if it exceeds 500 ppm, the degree of polymerization is lowered, which is not preferable. Since the chain transfer agent affects the aqueous solution insoluble content of the resulting poly (meth) acrylic acid partial neutralized product, it is desirable to adjust the amount of use as appropriate.

As light to be irradiated upon photopolymerization, ultraviolet rays and / or visible rays are used, and among these, ultraviolet rays are preferably used. The ultraviolet illuminance is determined in consideration of the type of monomer, the type and concentration of the photopolymerization initiator, the viscosity of the target polymer, and the polymerization time, but is generally 0.01 to 1000 mW / cm ² . it is preferred, more preferably from 0.05~100mW / cm ^2, more preferably from 0.1 to 10 MW / cm ^2. The ultraviolet illuminance may be constant during the polymerization or may be changed during the polymerization. The light source is not particularly limited as long as it can emit ultraviolet rays and / or visible rays capable of photopolymerizing monomers, and examples thereof include light emitting diodes, fluorescent lamps for trapping and photochemistry, fluorescent blue lamps, metal halide lamps. A high-pressure mercury lamp, a black light fluorescent lamp, a black light mercury lamp, a black light bulb-type fluorescent lamp, or the like can be used. Among these, it is preferable to use a light emitting diode, a black light fluorescent lamp, or the like. One light source or two or more light sources may be used.

  In the presence of a photopolymerization initiator, when an aqueous solution of a monomer mixture containing (meth) acrylic acid and (meth) acrylate is irradiated with light containing ultraviolet light to cause photopolymerization, a light source and a single amount It is preferable to irradiate light between the aqueous solutions of the body mixture with a light-transmitting material having an ultraviolet transmittance of 80% or more in the wavelength range of 330 to 370 nm interposed. That is, the light from the light source passes through the light transmissive material and reaches the aqueous solution of the monomer mixture. Thereby, it can photopolymerize effectively using the ultraviolet-ray of the wavelength range of 330-370 nm, and can greatly improve the conversion rate from a monomer to a polymer. In addition, since the illuminance of light increases, it is possible to produce a polymer with a small degree of dispersion (a narrow molecular weight distribution) with little variation in the degree of polymerization. Therefore, the obtained poly (meth) acrylic acid partially neutralized product is excellent in solubility and dispersibility when made into an aqueous solution, and the viscosity change with time is greatly reduced, and the insoluble matter is greatly reduced.

In addition, the atmosphere in which the photopolymerization reaction is performed may be an inert gas such as nitrogen or carbon dioxide in the air, but normally, under an inert gas atmosphere such as nitrogen or carbon dioxide in order to prevent polymerization inhibition due to the presence of oxygen, A nitrogen atmosphere is particularly preferable. The photopolymerization reaction is usually performed in an airtight chamber filled or supplied with this inert gas.
As described above, examples of the light transmissive material include borosilicate glass and quartz glass. Boric acid (B ₂ O ₃ ) is 5 to 20% (particularly 10% to 16%), and SiO ₂ is 65 to 90. % (Particularly 70 to 85%) of borosilicate glass is preferred. In addition, the transmittance | permeability is the value measured using the spectral irradiance meter (For example, USR-40V by Ushio Electric Co., Ltd.).

  This light-transmitting material is provided on the upper surface of the airtight chamber, and transmits light from a light source installed outside the airtight chamber so that the monomer mixture inside can be irradiated. The shape of the light transmissive material is not particularly limited as long as it is usually a flat plate, and the thickness is not particularly limited, but may be about 0.7 mm to 21 mm from the viewpoint of light transmittance and strength.

  At the start of the polymerization reaction, the reaction solution is preferably maintained at 0 to 80 ° C, more preferably 0 to 30 ° C, and further preferably 5 to 15 ° C. Cooling may be required to maintain the temperature, and this cooling method is not particularly limited. Usually, the outer periphery of the reaction vessel is cooled with a refrigerant (for example, cold water, cold methanol, etc.) or the like. The photopolymerization reaction of the aqueous solution of the monomer mixture may be either batch type or continuous type. When the photopolymerization reaction is carried out batchwise, the light irradiation time (polymerization time) is preferably 1 to 240 minutes, more preferably 5 to 120 minutes, and further preferably 15 to 60 minutes.

Although the production method of the present invention can be carried out either batchwise or continuously, it is preferable to employ a continuous polymerization method because of excellent productivity.
The operation of the apparatus of the continuous polymerization method is specifically as follows. An aqueous solution of the monomer mixture is continuously supplied from one of the movable belts so as to maintain a target depth. In this case, in order to prevent polymerization inhibition of the monomer mixture by oxygen, it is preferable to continuously supply an inert gas such as nitrogen into the hermetic chamber. The belt continuously moves together with the aqueous solution of the monomer mixture, and the aqueous solution of the monomer mixture is supplied under a fixed light source. The aqueous solution of the monomer mixture is polymerized by light irradiated from the light source.

  As an apparatus for producing a partially neutralized poly (meth) acrylic acid by a continuous polymerization method, for example, an apparatus shown in FIG. 1 of JP-A No. 2002-3509 is exemplified.

  The partially neutralized poly (meth) acrylic acid obtained by the polymerization method can be cut, pulverized and dried according to a conventional method to obtain a powder product. The pulverization conditions are not particularly limited, but an impact-type or rotary-type pulverizer may be used, and drying may be performed with a hot air dryer or the like at 70 to 140 ° C.

The pulverization of the powder is preferably 83 mesh pass product, particularly preferably 83 mesh pass and 100 mesh on product. In the case of these powder particles, since the powder particles are uniform (the particle size distribution is sharp), the solubility and dispersibility of the powder in water are uniform.
On the other hand, the 100-mesh pass product may cause so-called “mamako” and lower the aqueous solution viscosity. Moreover, since powder fluidity | liquidity worsens, there exists a possibility of obstruct | occluding in transport piping.

  In addition, the mesh of the said powder follows the prescription | regulation of JIS-Z8801-1 "Sieving sieve metal mesh sieve". Further, the mesh path means passing through the sieve of the mesh (mesh opening), and mesh-on means not passing through the sieve of the mesh (mesh opening). Therefore, 83 mesh pass means passing through a sieve having a sieve opening of 0.180 mm, and 100 mesh on means not passing through a sieve having a sieve opening of 0.150 mm.

The weight average molecular weight of the partially neutralized poly (meth) acrylic acid of the present invention is 2 million to 4 million, preferably 2.2 to 3.2 million.
Moreover, the dispersity (Mw / Mn) represented by weight average molecular weight (Mw) / number average molecular weight (Mn) is 1.0 to 1.3, preferably 1.15 to 1.25. . When the dispersity approaches 1.0, it is extremely difficult to produce industrially. When the dispersity exceeds 1.3, the (meth) acrylic acid partial neutralized powder, glycerin and water are mixed in a mixed solution. Insoluble matter tends to increase.

Moreover, it is preferable that the average RMS radius of the poly (meth) acrylic acid partial neutralized product of the present invention measured by a multi-angle light scattering detector and a parallax refraction detector is 220 to 260 nm.
When the average RMS radius is less than 220 nm, the shape retention property of the poultice becomes poor, and there is a risk of the back penetration of the poultice into the nonwoven fabric and the protrusion. When it exceeds 260 nm, There is a possibility that the insoluble content in the mixed liquid of Japanese powder, glycerin and water increases.

Moreover, the viscosity of the 0.2 weight% aqueous solution in 20 degreeC of the powder of the partial neutralization product of poly (meth) acrylic acid of this invention is about 200-600 mPa * s, and it is preferable that it is 300-550 mPa * s. When the viscosity of the 0.2% by weight aqueous solution is less than 200 mPa · s or more than 600 mPa · s, workability when using a partially neutralized poly (meth) acrylic acid powder in an aqueous solution is significantly reduced. .
The viscosity of the 0.2% by weight aqueous solution was determined by dissolving the powder of partially neutralized poly (meth) acrylic acid in water and allowing it to stand for 24 hours from the start of dissolution so that the viscosity becomes constant. ) A value measured with a BM viscometer manufactured by Tokyo Keiki Co., Ltd. under the conditions of 20 ° C. and 30 rpm.
Moreover, the viscosity at 20 ° C. of a mixed solution comprising 0.2% by weight of the partially neutralized poly (meth) acrylic acid of the present invention, 6.7% by weight of glycerol, and 93.1% by weight of water has a viscosity of 200 to 800 mPa · s. It is preferable that it is 300-700 mPa * s. The viscosity is a value measured under the conditions of 20 ° C. and 30 rpm with a BM viscometer manufactured by Tokyo Keiki Co., Ltd. as described above.

Furthermore, the poly (meth) acrylic acid partially neutralized powder of the present invention is different from the conventional poly (meth) acrylic acid partially neutralized powder, and does not cause significant fluctuations in viscosity when used as an aqueous solution. There is a feature. Specifically, it has the following physical properties. The viscosity is a value measured under the same conditions as above.
(1) Viscosity at 20 ° C. after stirring a mixed solution of 0.2% by weight of the partially neutralized poly (meth) acrylic acid, 6.7% by weight of glycerin, and 93.1% by weight of water for 15 seconds ( A) is in the range of 200 to 800 mPa · s (preferably 300 to 700 mPa · s),
(2) Viscosity at 20 ° C. after stirring a mixed solution of 0.2% by weight of the partially neutralized poly (meth) acrylic acid, 6.7% by weight of glycerin and 93.1% by weight of water for 20 minutes ( B) is in the range of 200 to 800 mPa · s (preferably 300 to 700 mPa · s), and (3) the ratio of viscosity B to viscosity A (B / A) is 0.9 to 1.1 (preferably 0). .92 to 1.08).

  As described above, the powder of the partially neutralized poly (meth) acrylic acid of the present invention has a very small difference between the viscosity immediately after the aqueous solution and the viscosity after stirring for a certain period of time, which facilitates industrial handling. Workability is improved dramatically.

  A poultice or hap by mixing and preparing the powder of partially neutralized poly (meth) acrylic acid of the present invention and various additives such as surfactant, glycerin, water, pigment, filler, medicinal component, etc. An agent base can be produced.

  Hereinafter, the present invention will be described in detail by way of examples. In addition, description of only% and a part means weight% and a weight part.

Example 1
(Acrylic acid / sodium acrylate = 50/50 mol%)
An aqueous solution of a monomer mixture containing 98% acrylic acid 138 g (1.88 mol), 36% sodium acrylate aqueous solution 491 g (1.88 mol), and pure water 411 g is placed in a polypropylene tray as a reaction tank. While maintaining the temperature of 10 ° C., dissolved oxygen was expelled with nitrogen. Thereafter, 0.28 g (950 ppm with respect to the monomer) of 2,2′-azobis (2-methylpropionamidine) dihydrochloride and 0.0037 g of 2-mercaptoethanol were diluted with pure water under a nitrogen stream. Was added as a 1% aqueous solution to prepare an aqueous solution of the monomer mixture.
Next, a black light manufactured by Toshiba Corp. that emits 300 to 450 nm having a peak wavelength of 352 nm through a borosilicate glass having a thickness of 5 mm (trade name: Pyrex (registered trademark) manufactured by Corning) as a light transmissive material. Using a fluorescent lamp, the UV illuminance meter UIT-150 (UVD-S365) manufactured by USHIO ELECTRIC CO., LTD. Was installed so that the ultraviolet illuminance would be 0.4 mW / cm ^2. Started.
After the start of exposure, after the polymerization temperature reaches a peak (about 60 ° C.), it is switched to a black light mercury lamp manufactured by Toshiba Corporation that emits 300 to 450 nm, and the ultraviolet illuminance is set to 6.0 mW / cm ^2. Minute irradiation was performed to obtain a hydrous gel-like substance. The hydrogel material was pulverized with a minced meat machine, dried, and pulverized with an impact pulverizer to obtain a powder.
Table 1 shows measurement results of molecular weight / dispersion degree and average RMS radius of partially neutralized polyacrylic acid, Table 2 shows measurement results of viscosity of partially neutralized polyacrylic acid powder, and Table 3 shows evaluation results of cataplasm Show.

<Measurement of molecular weight and average RMS radius>
Samples were separated by size exclusion chromatography under the following conditions, and detection, molecular weight distribution and molecular size (average RMS radius) were determined using a multi-angle light scattering detector and a differential refractive index detector.
Analysis conditions Detector Multi-angle light scattering detector Wyatt technology DAWN HELEOS
Differential Refractive Index Detector Wyatt technology Optilab rEX
Column Shodex SB-806M HQ
Eluent Na ₂ HPO ₄ 4.0 g / L solution (pH = 10.2 NaOH adjustment)
Flow rate 1.0 mL / min

<Measurement of 0.2% aqueous solution viscosity>
In a 500 ml conical beaker, 399.2 g of pure water was added, 0.8 g of partially neutralized polyacrylic acid was added, and the mixture was stirred with a magnetic stirrer for 2 hours to prepare a 0.2 wt% aqueous solution. The viscosity of the prepared solution was measured with a B-type viscometer under the conditions of 20 ° C. and 30 rpm.
<Measurement of 0.2% glycerin aqueous dispersion viscosity>
10 g of glycerin was put into a 500 ml beaker, and then 0.3 g of partially neutralized polyacrylic acid was added and stirred for 30 seconds. Thereafter, 140 g of pure water was added and stirred for 15 seconds to prepare a dispersion of 0.2% by weight of partially neutralized polyacrylic acid, 6.7% by weight of glycerin, and 93.1% by weight of pure water. The viscosity of the prepared solution was measured with a B-type viscometer under the conditions of 20 ° C. and 30 rpm.
Thereafter, stirring was continued at 150 rpm with a jar tester, and after 10 minutes and 20 minutes, the viscosity was measured with a B-type viscometer at 20 ° C. and 30 rpm.
<Calculation method of change with time of viscosity of 0.2% glycerin aqueous dispersion>
Change with time = (viscosity after 20 minutes / viscosity after 15 seconds)

<Evaluation of poultice>
Blended at the following ratio, the resulting preparation was spread on a nonwoven fabric to prepare a poultice.
Evaluation of viscosity increase and liquid uniformity during preparation of the poultice, spreadability of the poultice to the nonwoven fabric, penetration of the poultice to the non-woven fabric, and protrusion of the poultice to the non-woven fabric were performed.
Polyacrylic acid partially neutralized product 6.5 parts Carboxyvinyl polymer 1.5 parts Carboxymethylcellulose sodium 1.0 part Gelatin 3.0 parts Glycerin 20.0 parts Propylene glycol 5.0 parts Dry aluminum hydroxide gel 0.08 parts Sorbitan fatty acid ester 0.3 part Polyoxyethylene hydrogenated castor oil 0.5 part Light liquid paraffin 3.0 part Lactic acid 1.0 part Water 58.12 part

Example 2
(Acrylic acid / sodium acrylate = 50/50 mol%)
Except that the amount of 2,2′-azobis (2-methylpropionamidine) dihydrochloride was changed to 0.22 g, the same operation as in Example 1 was performed to obtain a partially neutralized polyacrylic acid powder. Obtained.
Table 1 shows measurement results of molecular weight / dispersion degree and average RMS radius of partially neutralized polyacrylic acid, Table 2 shows measurement results of viscosity of partially neutralized polyacrylic acid powder, and Table 3 shows evaluation results of cataplasm Show.

Example 3
(Acrylic acid / sodium acrylate = 55/45 mol%)
The same procedure as in Example 2 was performed except that 154 g (2.10 mol) of 98% acrylic acid, 448 g (1.72 mol) of 36% aqueous sodium acrylate solution, and 438 g of pure water were used. A Japanese powder was obtained.
Table 1 shows measurement results of molecular weight / dispersion degree and average RMS radius of partially neutralized polyacrylic acid, Table 2 shows measurement results of viscosity of partially neutralized polyacrylic acid powder, and Table 3 shows evaluation results of cataplasm Show.

Example 4
(Acrylic acid / sodium acrylate = 45/55 mol%)
Except for changing to 138 g (1.82 mol) of 98% acrylic acid, 491 g (1.88 mol) of 36% aqueous sodium acrylate solution and 411 g of pure water, the same operation as in Example 2 was carried out, A Japanese powder was obtained.
Table 1 shows measurement results of molecular weight / dispersion degree and average RMS radius of partially neutralized polyacrylic acid, Table 2 shows measurement results of viscosity of partially neutralized polyacrylic acid powder, and Table 3 shows evaluation results of cataplasm Show.

Comparative Example 1
As a reaction vessel, 203 g (2.76) of 98% acrylic acid was placed in a stainless steel dewar.
Mol), 694 g (2.66 mol) of 36% sodium acrylate and 600 g of pure water were mixed, and then the dissolved oxygen was purged with nitrogen while maintaining the temperature of the aqueous solution of the monomer mixture at 10 ° C. Thereafter, 0.0% of t-butyl hydroperoxide was added under a nitrogen stream.
135 g, 0.135 g of sodium formate, 0.0675 g of sodium persulfate, and 0.027 g of sodium erythorbate were added and left for 12 hours. Thereafter, the hydrogel material was pulverized, dried and pulverized to obtain a partially neutralized polyacrylic acid powder.
Table 1 shows measurement results of molecular weight / dispersion degree and average RMS radius of partially neutralized polyacrylic acid, Table 2 shows measurement results of viscosity of partially neutralized polyacrylic acid powder, and Table 3 shows evaluation results of cataplasm Show.

Comparative Example 2
A powder of partially neutralized polyacrylic acid was obtained in the same manner as in Comparative Example 1 except that sodium formate was changed to 0.0675 g and sodium erythorbate was changed to 0.009 g.
Table 1 shows measurement results of molecular weight / dispersion degree and average RMS radius of partially neutralized polyacrylic acid, Table 2 shows measurement results of viscosity of partially neutralized polyacrylic acid powder, and Table 3 shows evaluation results of cataplasm Show.

In Examples 1 to 4, by adding a sulfur-containing organic substance, the insoluble content of the 0.2% aqueous solution viscosity is 0 to 0.2 ml, and the change with time of the 0.2% glycerin aqueous dispersion viscosity is 0.75 or more. A good polymer was obtained. A polymer having a weight average molecular weight (Mw) of 236 to 29,290,000 and a high molecular weight, a degree of dispersion (Mw / Mn) of 1.18 to 1.21, and a sharp molecular weight distribution was obtained. The average RMS radius is also large, suggesting that it exists in a linear polymer, and it is presumed that the low molecular weight is one of the causes of the reduction of cataplasm performance.
As a result, the evaluation results with the cataplasm showed good results for all the evaluation items.

On the other hand, Comparative Example 1 is a partially neutralized sodium polyacrylate obtained by a polymerization method that is not photopolymerization, and the insoluble content of the 0.2% aqueous solution viscosity is as large as 2 ml, and the 0.2% glycerin aqueous dispersion viscosity. Was as large as 0.64, and the measured value of the 0.2% glycerin aqueous dispersion viscosity at 15 seconds was as high as 1300 mPa · s or more.
A polymer having a weight average molecular weight (Mw) of 1.43 million and a relatively low molecular weight as compared with Examples 1 to 4, a dispersity (Mw / Mn) of 1.32 and a broad molecular weight distribution was obtained. .
Suggests that the mean RMS radius is small and exists in a thread-like polymer,
This is considered to be one of the causes of insufficient crosslinking reaction during the preparation of a poultice. If the cross-linking reaction of the poultice is insufficient, it is presumed that the strike-through or the protrusion occurs. As proved, the evaluation results with the cataplasm showed poor results for all the evaluation items.
Further, Comparative Example 2 produced by the same method as Comparative Example 1 also showed the same tendency as Comparative Example 1.

In the comparison of the partially neutralized sodium polyacrylate when the 0.2 wt% aqueous solution viscosity is substantially the same, the insoluble content of the 0.2 wt% aqueous solution is 0 to 0.2 ml. Contributes to the improvement of stability and quality at the time of production at a cataplasm manufacturing company. Moreover, it measured with the B-type viscosity meter (20 degreeC, 30 rpm) of the dispersion liquid which consists of 6.7 weight% of the said polyacrylic acid partial neutralized material of said 0.2 weight% and a pure water 93.1 weight%. The fact that the viscosity is low even with slight stirring for 15 seconds means that it is easy to handle industrially and that there is little decrease in viscosity over time due to stirring. Japanese products can be provided.
Furthermore, the polymer obtained in the Examples has a weight average molecular weight (Mw) of 236 to 29,290,000 and a high molecular weight, but a dispersity (Mw / Mn) of 1.18 to 1.21 and a sharp molecular weight distribution. All the evaluation items for the poultices show good results, and it can be expected that the production stability and quality stability of the poultice preparations at the poultice preparation company are improved.

  The partially neutralized poly (meth) acrylic acid of the present invention has very little aqueous solution insoluble matter, low viscosity in aqueous solution, and little change with time, so solubility and dispersibility when used in an aqueous solution state Because it is excellent in terms of workability, it is useful as a base for dispersants such as various pigments, scale inhibitors, cleaning builders, thickeners, binders, pharmaceutical poultices and haptic agents. And is particularly useful as a base for pharmaceutical poultices and haptics.

Claims (7)

  A partially neutralized poly (meth) acrylic acid obtained by polymerizing a monomer mixture containing (meth) acrylic acid and (meth) acrylate, having a weight average molecular weight of 2 million to 4 million, And the poly (meth) acrylic acid partial neutralized product whose dispersity represented by a weight average molecular weight / number average molecular weight is 1.0-1.3.   2. The partially neutralized poly (meth) acrylic acid according to claim 1, wherein the ratio of (meth) acrylic acid / (meth) acrylate is 45/55 to 55/45 in molar ratio.   The poly (meth) acrylic acid partial neutralized product according to claim 1 or 2, wherein an average RMS radius measured by a multi-angle light scattering detector and a parallax refraction detector is 220 to 260 nm.   4. The monomer mixture is photopolymerized by irradiating an aqueous solution of the monomer mixture with light containing ultraviolet rays in the presence of a photopolymerization initiator. 5. Of producing a partially neutralized poly (meth) acrylic acid.   The powder of the partially neutralized poly (meth) acrylic acid according to any one of claims 1 to 3. A powder of the partially neutralized poly (meth) acrylic acid according to claim 5 and having the following properties:
(1) Viscosity at 20 ° C. after stirring a mixed solution of 0.2% by weight of the partially neutralized poly (meth) acrylic acid, 6.7% by weight of glycerin, and 93.1% by weight of water for 15 seconds ( A) is in the range of 200 to 800 mPa · s,
(2) Viscosity at 20 ° C. after stirring a mixed solution of 0.2% by weight of the partially neutralized poly (meth) acrylic acid, 6.7% by weight of glycerin and 93.1% by weight of water for 20 minutes ( B) is in the range of 200 to 800 mPa · s, and (3) the ratio of viscosity B to viscosity A (B / A) is in the range of 0.9 to 1.1.   A cataplasm containing the powder of the partially neutralized (meth) acrylic acid according to claim 5 or 6.