JP2000063408A - Preparation of polymer particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and reproducibly obtain polymer particles excellent in the water absorption magnification, water absorption speed, liquid permeability and the time stability after the water absorption, by polymerizing a water soluble vinyl monomer in the aq. soln. in the presence of a hydrophobic organic solvent inert to the polymerization, an anionic surfactant, and an amphoteric surfactant. SOLUTION: An anionic surfactant to be used is a surfactant expressed by the formula. In the formula, R1 is a 6-22C alkyl or alkenyl, or a 12-24C alkylaryl; A is a 2-3C alkylene; M is an alkali metal ion, ammonium ion, or H; (m) is on the average 0-22. A water soluble vinyl monomer pref. is an olefinic unsatd. carboxylic acid and its salt. A hydrophobic organic solvent to be used is pref. in the range of 50-500 pts.wt. per 100 pts.wt. of a monomer. A totaled wt. of the anionic surfactant and the amphoteric surfactant is pref. in the range of 0.01-10 pts.wt. based on 100 pts.wt. of the monomer. A wt. ratio of the anionic surfactant/the amphoteric surfactant is pref. in the range of 0.1-10.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an excellent water absorption capacity,
The present invention relates to a method for producing amorphous polymer particles useful as a highly water-absorbent resin having a water-absorption rate and liquid permeability and being excellent in stability of gel after water absorption.

[0002]

2. Description of the Related Art In the field of hygiene products, super absorbent polymers are used for absorbent articles such as baby diapers (disposable diapers) for infants, adults or incontinence or sanitary napkins for women. Used as a water absorbent material in articles. At present, polyacrylic acid-based superabsorbent resins are the mainstream as superabsorbent resins.

Generally, a water absorbent resin having a high water absorption capacity is
Water absorption rate, liquid permeability, poor stability over time of swollen gel and gel strength, while water-absorbent resin with excellent water absorption rate, liquid permeability, stability of swollen gel over time and gel strength tends to have low water absorption capacity There is.

A method of adding an additive to a super absorbent polymer in order to attain all of these performances at a satisfactory level (for example, JP-A-7-113048 and JP-A-7-259).
No. 34, etc.) has been proposed, but it was not preferable from an economical point of view such as high manufacturing cost.

Therefore, an object of the present invention is to provide an amorphous polymer particle useful as a highly water-absorbent resin having excellent water absorption capacity, water absorption rate and liquid permeability, and excellent gel stability after water absorption. Another object of the present invention is to provide a method for easily and inexpensively producing with good reproducibility.

[0006]

Means for Solving the Problems The present invention provides a method for polymerizing a water-soluble vinyl monomer by using a hydrophobic organic solvent inert to the polymerization and an aqueous solution of the water-soluble vinyl monomer,
Provided is a method for producing amorphous polymer particles in which an anionic surfactant represented by the general formula (I) of the following [Chemical formula 4] (the same as the above-mentioned [Chemical formula 1]) and an amphoteric surfactant are present. To do.

[0007]

[Chemical 4]

The "amorphous polymer particles" in the present invention
Means non-spherical polymer particles.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method for producing the amorphous polymer particles of the present invention will be described in detail with reference to its preferred embodiments. Water-soluble vinyl monomer used in the present invention (hereinafter,
(Referred to as “monomer”) is an olefinic unsaturated carboxylic acid or salt thereof, an olefinic unsaturated carboxylic acid ester, an olefinic unsaturated sulfonic acid or salt thereof, an olefinic unsaturated phosphoric acid or salt thereof, an olefinic unsaturated phosphoric acid. Examples thereof include vinyl monomers having a polymerizable unsaturated group such as ester, olefinically unsaturated amine, olefinically unsaturated ammonium, and olefinically unsaturated amide. Among these, olefinic unsaturated carboxylic acids and salts thereof are particularly preferably used, more preferably acrylic acid, methacrylic acid, and alkali metal salts or ammonium salts thereof, and even more preferably acrylic acid or acrylic acid. Acid alkali metal salts (sodium salt, potassium salt, etc.) and acrylic acid ammonium salt are used. These monomers can be used alone or in combination.

The monomer can also be used in combination with a water-insoluble vinyl monomer copolymerizable therewith. The water-insoluble vinyl monomer has, for example, 1 to 18 carbon atoms.
Unsaturated carboxylic acid ester monomers such as acrylic acid, methacrylic acid, maleic acid and fumaric acid having an alkyl group of In this case, it is preferable that the amount of the monomer is 50% by weight or more, especially 70% by weight or more, based on the total vinyl monomer.

The concentration of the monomer in the aqueous solution of the monomer is preferably 10 to 100% by weight, more preferably 2%.
It is 0 to 100% by weight.

Examples of the hydrophobic organic solvent inert to the polymerization used in the present invention include n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane,
Aliphatic hydrocarbons such as methylcyclohexane, benzene,
Aromatic hydrocarbons such as toluene, n-butyl alcohol,
Examples thereof include C 4-6 aliphatic alcohols such as n-amyl alcohol, aliphatic ketones such as methyl ethyl ketone, and aliphatic esters such as ethyl acetate. These hydrophobic organic solvents can be used in one kind or more.

The amount of the above-mentioned hydrophobic organic solvent to be used is usually preferably 50 to 500 with respect to 100 parts by weight of the monomer.
The amount is 0 parts by weight, more preferably 100 to 2500 parts by weight.

Further, an amphipathic solvent may be used together with the above-mentioned hydrophobic organic solvent at the time of polymerizing the monomer.
As the amphipathic solvent, methanol, ethanol,
Examples include alcohols such as propanol and 2-propanol, ketones such as acetone, and ethers such as tetrahydrofuran and dioxane. The amount of the amphipathic solvent used is preferably up to 5000 parts by weight based on 100 parts by weight of the monomer, which is the total amount with the hydrophobic organic solvent.

In the present invention, the monomers are polymerized in the presence of the anionic surfactant represented by the general formula (I) and the amphoteric surfactant. Here, the anionic surfactant and the amphoteric surfactant are used as a dispersant when polymerizing the monomer. Examples of the anionic surfactant represented by the general formula (I) include alkyl sulfuric acid ester, polyoxyethylene alkyl ether sulfuric acid ester, alkyl glyceryl ether sulfuric acid ester, polyoxyethylene alkyl ether sulfosuccinic acid ester, alkylsulfosuccinic acid amide. , Α-
Examples thereof include sulfonic acid group-containing compounds such as sulfo fatty acids and their alkali metal salts, alkaline earth metal salts, and ammonium salts. In addition, as commercial products, trade names such as "Emar E-27C" (polyoxyethylene lauryl ether sulfate sodium salt) and "Emar 20C" (polyoxyethylene lauryl ether sulfate sodium salt) (all manufactured by Kao Corporation) are available. It is illustrated.

The amphoteric surfactant is preferably a compound represented by the general formula (II) of the following [Chemical formula 5] (the same as the above [Chemical formula 2]) or the following [Chemical formula 6] (the above-mentioned [Chemical formula 6] A compound represented by the general formula (III) of the same as the chemical formula 3] or a mixture thereof is used.

[0017]

[Chemical 5]

[0018]

[Chemical 6]

Examples of the compound represented by the general formula (II) include carboxymethyldimethylcetylammonium, carboxymethyldimethylstearylammonium, sulfopropyldimethylcetylammonium, sulfopropyldimethylstearylammonium, and (2-hydroxy) sulfopropyldimethyllauryl. Examples include ammonium, phosphomethyl dimethyl cetyl ammonium, phosphomethyl dimethyl stearyl ammonium, lauryl dimethyl amine oxide and the like. These can use 1 or more types. Examples of the compound represented by the general formula (III) include carboxymethyldimethyl (laurylamidopropyl) ammonium, carboxymethyldimethyl (palmitylamidopropyl) ammonium, carboxymethyldimethyl (stearylamidopropyl) ammonium, (2- Hydroxy) sulfopropyldimethyllauryl ammonium and the like can be mentioned. These can use 1 or more types. Then, the above general formula (I
The compound represented by I) and the compound represented by the general formula (III) may be used in combination.

The total amount of the anionic surfactant and the amphoteric surfactant is 100 parts by weight of the monomer.
Preferably 0.01 to 10 parts by weight, more preferably 0.
02 to 5 parts by weight. The weight ratio of the anionic surfactant to the amphoteric surfactant (former / latter) is
Preferably 0.1 to 10, more preferably 0.5 to 10
Is. When the total amount and the weight ratio are within these ranges, polymer particles having excellent physical properties can be stably synthesized, which is preferable in terms of productivity and production cost.

Examples of the method for polymerizing the monomer using the above hydrophobic organic solvent and the aqueous solution of the monomer include the following methods (1) to (4). (1) A method in which an aqueous solution of a monomer and a hydrophobic organic solvent are mixed together and then polymerized (collective polymerization method). (2) A method in which an aqueous solution of a monomer is added dropwise to a hydrophobic organic solvent to perform sequential polymerization (sequential polymerization method). (3) A method of preliminarily dispersing a mixed solution obtained by previously mixing or dispersing an aqueous solution of a monomer with a part of a hydrophobic organic solvent while dropping it in the hydrophobic organic solvent. (4) A method in which the above (1) to (3) are used in combination.

In the above polymerization, the surfactants (the anionic surfactant and the amphoteric surfactant) are also included.
Examples of the method of allowing the presence of the above include the methods shown in the following (A) to (D). (A) A method of previously dispersing a surfactant in a hydrophobic organic solvent. (B) A method of previously dissolving or dispersing a surfactant in an aqueous solution of a monomer. (C) A method of gradually adding a surfactant while carrying out the above-mentioned polymerization. (D) A method in which the above (i) to (c) are used in combination.

When carrying out the above-mentioned polymerization, a known polymerization initiator is usually used. Examples of the polymerization initiator include dialkyl peroxides, alkyl peresters, hydroperoxides, persulfates, perchlorates,
Halogenates, azo compounds, hydrogen peroxide / ferrous salts, persulfates / sulfites, cumene hydroperoxide / first
Examples thereof include redox initiators such as iron salts and hydrogen peroxide / L-ascorbic acid. One or more of these polymerization initiators can be used. Among these polymerization initiators, persulfate and 2,2′-azobis (2-amidinopropane) dihydrochloride are preferably used.

The addition amount of the above-mentioned polymerization initiator is preferably 0.01 to 10 parts by weight, more preferably 0.02 to 5 parts by weight with respect to 100 parts by weight of the monomer in order to smoothly carry out the polymerization.
Parts by weight.

The method of adding the polymerization initiator is not particularly limited, but a method of previously adding the polymerization initiator to the aqueous monomer solution is preferable.

The polymerization temperature of the monomer in the above polymerization is
Preferably 20 to 200 ° C., more preferably 40 to 10
It is 0 ° C.

In carrying out the production method of the present invention, a known cross-linking agent can be added before, during, after, or after the polymerization. Examples of the cross-linking agent include polyallyl compounds, polyvinyl compounds, polyglycidyl ethers, haloepoxy compounds, polyaldehydes,
Examples thereof include polyols, polyamines, hydroxyvinyl compounds, and inorganic salts or organic metal salts that generate polyvalent ions such as calcium, magnesium, zinc and aluminum. After the above polymerization is completed, desired amorphous polymer particles can be obtained by performing azeotropic dehydration, drying and the like.

[0028]

EXAMPLES "%" in Examples and Comparative Examples means "% by weight". Prior to Examples and Comparative Examples, test methods will be described.

[Calculation Method of Average Particle Size] 100 g of polymer
Was classified using a JIS sieve, and the average particle size was determined from the weight fraction of each fraction.

[Equilibrium Swelling Water Absorption Measurement Method] Polymer 1 g
Was dispersed in a large excess of physiological saline solution (0.9% saline solution, manufactured by Otsuka Pharmaceutical Co., Ltd.), and the polymer was swollen until its water absorption reached an equilibrium state. The weight (W) of the obtained swollen polymer is measured, and the value obtained by dividing this value by the weight W ₀ of the polymer before water absorption, that is, the value of W / W ₀ is the equilibrium swollen water absorption ( g /
g).

[Measurement Method of Water Absorption Amount Representing Water Absorption Rate] Using a device (Demand Wettability Tester) shown in FIG. 1 which is generally known as a device for carrying out the DW method, as shown in FIG. 0.3 g of polymer P was sprayed on the polymer spraying table 2 (70 mmφ, No. 2 filter paper was placed on the glass filter No. 1) in which the liquid level of W was set to the same water level, and the polymer was sprayed The water absorption is set to 0, and the water absorption after 60 seconds (this water absorption is measured by a burette scale indicating the amount of decrease in the water level of the physiological saline W),
This value was taken as the water absorption amount (ml) representing the water absorption speed.

[Measurement Method of Flow Rate of Saline Solution] Device 10 shown in FIG. 2 (inner diameter 25.6 mm, length about 500 mm)
(Burette consisting of a glass cylinder tube of (cylindrical part)) was filled with 0.5 g of the polymer, and the polymer was equilibrated and swollen by using excess physiological saline, and the liquid level was adjusted to 200 ml from the lower part, and a cock was placed, Make sure that the swollen polymer P has settled sufficiently as shown in the figure, open the cock, and let the physiological saline W show two marked lines L (150 m from the bottom) as shown in the figure.
The time required to pass between the point (1 point) and M (the point 100 ml from the bottom) (50 ml liquid volume) was measured, and the liquid volume between the marked lines (m
l) is divided by the measurement time (min) and the flow rate (ml / m)
in).

[Evaluation Method of Time Stability of Gel After Swelling] 1 g of the polymer was swollen with 45 g of a physiological saline solution containing 0.03% L-ascorbic acid, which was sealed in a screw tube and kept at 40 ° C. for 3 days. Left for hours. By observing the state of the gel at that time, the temporal stability of the gel after swelling was evaluated. The evaluation of the temporal stability of the gel after swelling was carried out in three stages according to the criteria shown in Table 1 for the fluidity, spinnability and shape retention of the gel. In this evaluation, ○
In the case of the above evaluation, it is shown to be suitable as a water-absorbing substance used for sanitary napkins, disposable diapers, adult sheets, tampons, sanitary cotton and the like.

[0034]

[Table 1]

[Examples 1 to 8 and Comparative Examples 1 to 4] 100
400 ml of cyclohexane as a hydrophobic organic solvent was charged into a 0 ml four-necked flask, nitrogen gas was blown into the flask to expel dissolved oxygen, and the temperature was raised to 75 ° C. In a separate flask, 102.0 g of acrylic acid is added to ion-exchanged water 2
The mixture was diluted with 5.5 g and neutralized with 136 g of 30% sodium hydroxide aqueous solution while cooling from the outside. Next, 0.408 g of potassium persulfate as a polymerization initiator dissolved in 13 g of ion-exchanged water was added to and dissolved in the aqueous solution of this monomer, and then nitrogen gas was blown to remove oxygen remaining in the aqueous solution. / An aqueous solution of the initiator was obtained.
The surfactants listed below were added to these two flasks as a dispersant by the method shown in Table 2. A: Polyoxyethylene lauryl ether sulfate sodium salt (average ethylene oxide addition mole number = 2)
25% aqueous solution of B: 30% aqueous solution of carboxymethyldimethyllauryl ammonium C: 30% aqueous solution of carboxymethyldimethylstearyl ammonium D: 30% aqueous solution of carboxymethyldimethyl (laurylamidopropyl) ammonium E: Sulfoxymethyldimethyllauryl ammonium 30% aqueous solution F: ethyl cellulose G: sorbitan monostearate (manufactured by Kao, trade name "Reodol SP-S10")

Monomers / initiators were added to the 4-neck flask above (optionally surfactants were also added therein).
The aqueous solution of was added dropwise over 60 minutes to polymerize. After completion of the polymerization, azeotropic dehydration was performed using a dehydration tube to adjust the water content of the polymer particles to 40 parts by weight with respect to 100 parts by weight of the polymer particles. After that, 0.1 g of polyglycerol polyglycidyl ether (Nagase Kasei Kogyo KK, trade name Denacol EX-512) dissolved in 2.5 g of water was added as a cross-linking agent, and reacted at 75 to 80 ° C. for 2 hours. Let Then, azeotropic dehydration was further performed to adjust the water content of the polymer particles to 30 parts by weight with respect to 100 parts by weight of the polymer particles. After cooling, cyclohexane was removed by decantation,
By drying at 100 ° C. under a condition of 6.67 kPa, partially cross-linked acrylic acid (sodium) polymer particles having an amorphous shape and granular gel were obtained. However, in Comparative Examples 1 and 2, true spherical polymer particles were obtained. The average particle size of the obtained polymer particles, the equilibrium swelling water absorption amount, the water absorption amount indicating the water absorption speed, the liquid saline passing speed, and the gel temporal stability after swelling were measured. The results are shown in [Table 2].

[0037]

[Table 2]

[0038]

According to the present invention, it has a high water absorption capacity,
Amorphous polymer particles, which are excellent in breathability, liquid permeability, and stability of gel after water absorption and are useful as superabsorbent resin, can be manufactured by simple operation with excellent productivity and mass production. can do.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a water absorption amount measuring device used in Examples and Comparative Examples, which represents a water absorption rate.

FIG. 2 is a schematic view showing an apparatus for measuring the flow rate of physiological saline used in Examples and Comparative Examples.

[Explanation of symbols]

1 Measuring device for water absorption that shows water absorption rate of polymer 2 Polymer spreading table 3 bullets 10 Measuring device for physiological saline flow rate W physiological saline P polymer M, L mark

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Claims (3)

[Claims] 1. When polymerizing a water-soluble vinyl monomer using a hydrophobic organic solvent inert to the polymerization and an aqueous solution of the water-soluble vinyl monomer, the compound represented by the following general formula (I) A method for producing amorphous polymer particles in which an anionic surfactant and an amphoteric surfactant are present. [Chemical 1] 2. The amphoteric surfactant is a compound represented by the general formula (II) of the following [Chemical formula 2], a compound represented by the general formula (III) of the following [Chemical formula 3], or a mixture thereof. A method for producing an amorphous polymer particle according to claim 1. [Chemical 2] [Chemical 3] 3. The water-soluble vinyl monomer 100 having a total amount of the anionic surfactant and the amphoteric surfactant.
0.01 to 10 parts by weight relative to parts by weight, and the weight ratio of the anionic surfactant and the amphoteric surfactant (the former /
The method for producing amorphous polymer particles according to claim 1 or 2, wherein the latter is 0.1 to 10.