JPH05339322A - Crosslinked sulfonated acrylamide resin - Google Patents

Abstract

PURPOSE:To obtain the title water-insoluble, highly water-absorptive impurity- free resin by copolymerizing 2-acrylamido-2-methyl-propanesulfonic acid (salt) with a small amount of a vinyl monomer and a crosslinking agent. CONSTITUTION:The title resin. is a water-insoluble one having a water absorptivity at least 500 times as high as its own weight and comprising at least 80wt.% repeating units of the formula (wherein M is H, NH4 or an alkali metal), at most 20wt.% vinyl monomer selected from among (meth)acrylic acid, p- styrenesulfonic acid, vinylfulfuric acid, (meth)allylsulfonic acid and ammonium salts and alkali metal salts thereof and at most 0.05wt.% crosslinking component. This resin has a water absorptivity several hundred to one thousand and several hundred times as high as its own weight and is practically free from impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sulfonic acid group-containing acrylamide cross-linking resin capable of absorbing a large amount of water.

[0002]

2. Description of the Related Art Materials such as non-woven fabric, paper, pulp, and sponge-like substances that absorb water in a physical structure have been used for sanitary items, diapers, disposable rags, etc. The use was not always satisfactory. In recent years, in addition to the above applications, the medical industry,
The use of materials having a chemical water-absorbing ability is progressing also in applications in the food industry or agricultural fields, and in particular, polymeric materials that are water-insoluble and hydrophilic or water-absorbing are used as separation / purification materials for various membranes and liquid chromatographic carriers. , Various applications that require water absorption and water retention, such as culture media for microorganisms and plants, contact lenses and coatings for sutured parts, or medical materials have been opened up.

Many water absorbing materials have been proposed for such applications. For example, crosslinked polyethylene oxide, polyvinylpyrrolidone, sulfonated polystyrene, etc., polyacrylamide crosslinked with a divinyl compound such as methylenebisacrylamide, saponified product of cellulose derivative or starch grafted with acrylic acid or acrylonitrile, etc. A water absorbing material using a natural or synthetic polymer substance has been proposed. However, except for the saponification product of starch-acrylonitrile graft polymer among these materials, its water absorption capacity is small and it is not satisfactory as a water absorption material, and the saponification product of starch-acrylonitrile graft polymer having a relatively high water absorption capacity. In the case of a compound, various improvements have been added to its production method, but if the process is complicated or the water content is maintained for a long period of time, the starch component will be decomposed or the gel structure will be destroyed. There is a problem with sex.

Further, a small amount of a water-soluble monomer such as an alkali metal salt of acrylic acid or methacrylic acid or acrylamide is added with a cross-linking agent such as methylenebisacryl amide or polyethylene oxide diacrylate, and a cerium salt, benzoyl peroxide, Azobisisobutyronitrile, radical polymerization catalyst such as ammonium persulfate, redox polymerization catalyst such as potassium persulfate and aniline, ammonium persulfate and monoethanolamine, suspension polymerization or emulsion polymerization, and further solution polymerization A method for obtaining a highly water-absorbent resin having a ten-fold to a few-hundred-fold amount has been proposed. However, in such a method, radical initiators, suspending agents, emulsifiers, solvents, etc. inevitably remain in the superabsorbent resin, which causes coloring, depolymerization, corrosion resistance, chemical resistance, and weather resistance. In addition to being not preferable, the water absorption capacity is insufficient depending on the use.

[0005]

On the other hand, the present inventors have found that by polymerizing various vinylic monomers by the plasma-initiated polymerization method, the linear water-soluble compound having a remarkably large molecular weight as compared with the conventional ones is used. We have obtained a direct combination, and as a monomer, 2
-A similar polymer was obtained using acrylamido-2-methylpropanesulfonic acid, and this was published in Vol. 37, No. 7 of the Textile Society of Japan (Fiber and Industry). As a result of earnest research, the present invention has been completed. An object of the present invention is to provide a sulfonic acid group-containing acrylamide cross-linking resin which is water-insoluble, has a high water absorbency of several hundred times to several thousand times, and is substantially free of impurities.

The present invention is

[Chemical 2] The repeating unit represented by the formula (M represents hydrogen, ammonium or an alkali metal) is 80% by weight or more, and acrylic acid, methacrylic acid, p-styrenesulfonic acid, vinylsulfonic acid, 2-methacryloyloxyethylsulfonic acid, allyl. Sulfonic acid, methacrylic sulfonic acid, and at least one vinyl monomer selected from ammonium salts and alkali metal salts of these acids in an amount of 20% by weight or less and a crosslinking component of 0.05% by weight or less. It is a water-insoluble, sulfonic acid group-containing acrylamide-based cross-linking resin having a high water absorbency of 500 times its own weight or more.

The sulfonic acid group-containing acrylamide cross-linked resin of the present invention has excellent water absorption and has a water absorption capacity of at least 500 times, preferably 800 times, and most preferably 1000 times the weight of the resin. ..

2-Acrylamide which is applied to the present invention
2-methylpropanesulfonic acid, its ammonium salt, its alkali metal salt, its alkaline earth metal salt, or its transition metal salt (hereinafter abbreviated as AMPS) in a sulfonic acid group-containing acrylamide crosslinked resin The amount contained is 80% by weight or more, preferably 99% by weight
That is all. If the amount of AMPS is less than 40% by weight, the water absorption capacity will be insufficient.

In the present invention, 2-acrylamido-2-
A vinyl monomer may be used in combination with a monomer such as methyl propane sulfonic acid and copolymerized. These vinylic monomers are those that undergo radical polymerization and may be water-soluble, such as acrylic acid, methacrylic acid, P-styrene sulfonic acid, vinyl sulfonic acid, 2-methacryloyloxyethyl sulfonic acid, allyl sulfonic acid. , Methacryl sulfonic acid, ammonium salts of these acids, and alkali metal salts. If the vinylic monomer is water-insoluble such as acrylonitrile and methyl methacrylate, the water absorption capacity of the obtained sulfonic acid group-containing acrylamide cross-linked resin tends to decrease, and even if it is a water-soluble monomer The vinylic monomer content is at most 20% by weight, preferably 1% by weight or less, since it causes a decrease in water absorption capacity as compared with AMPS.

The crosslinking component applied to the present invention is not more than 0.05% by weight, preferably 0.0001 to 0.02% by weight,
Most preferably, it is 0.01% by weight or less, which is an essential component for crosslinking. If the cross-linking component exceeds 1% by weight, the water absorption capacity will decrease. Generally, the water absorption capacity tends to decrease as the number of cross-linking components increases, and when it is desired to obtain a high water absorption capacity, the cross-linking component is often reduced, but a general polymerization initiation method, such as emulsification using a radical polymerization initiator or ultraviolet rays. In polymerization, suspension polymerization, or solution polymerization, the molecular weight of the resin obtained is low, so if the cross-linking component is less than 0.1% by weight, solubilization or deformation in water swelling state or sticky phenomenon is observed. .. However, since the resin of the present invention has an ultrahigh molecular weight, the crosslinking component is 0.1% by weight or less, for example 0.00
Even if the content is 01% by weight or swelled with water, the shape does not collapse and no stickiness is observed.

As the crosslinking component, divinylbenzene, N
N'-methylenebisacrylamide, diallylamine,
Divinyl compounds such as diacryl methacrylamide, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 2 hydroxyethyl acrylate, 2 hydroxyethyl methacrylate, 2 hydroxypropyl acrylate, 2 hydroxypropyl methacrylate, glycidyl acrylate, glycidyl methacrylate, methylol acrylamide or methylol methacrylamide However, the present invention is not limited to these. As the crosslinking component, NN'-methylenebisacrylamide, diacrylmethacrylamide, polyethylene glycol dimethacrylate, diethylene glycol dimethacrylate, methylol acrylamide and the like are suitable.

The polymerization method applied to the present invention is so-called plasma-initiated polymerization in which polymerization is initiated in the presence of ionized gas plasma and then post-polymerized in the absence of the plasma, and in an aqueous medium. It is essential to have.
As the aqueous medium, water or water and methanol, ethanol,
Examples thereof include a mixture with alcohols such as butanol and ketones such as acetone and methyl ethyl ketone, but a water-only medium is preferable. When an aqueous medium, especially an aqueous medium, is used, the polymerization rate becomes extremely high. The monomer concentration in the aqueous medium is usually 0.1 to 90% by weight, preferably 1 to 65% by weight, more preferably 10 to 60% by weight.

Generally, in the case of an aqueous medium, the monomer concentration is 5
When the amount is 0 mol%, the polymerization rate becomes maximum, and there is a tendency for the polymerization rate to decrease below or above it. The molecular weight also tends to be the same as the polymerization rate. When an organic solvent is used as a medium, not only is the polymerization rate generally slow, but it is uneconomical to remove the organic solvent in the polymerization of the water-soluble polymer as in the present invention.

The plasma-initiated polymerization in the present invention is the one in which the polymerization is initiated using a non-equilibrium ionized gas plasma, and most of the polymerization is completed in the absence of plasma. Generally, a high molecular weight, substantially linear polymer is produced, but in the case of the present invention, a polymer having a crosslinked structure is produced because a crosslinking component such as a divinyl monomer is used. The ionized gas plasma can be generated by any of the known methods for generating such plasma. For example, J. R. Hollaha
n) and AT Bell Bell "Applied Technology of Plasma Chemistry", Wiley, New York 1974 and M.
Shen version "Plasma Chemistry of Polymers" Decker. New York. 1976. That is, the monomer can be put under vacuum between the parallel plate electrodes connected to the high frequency generator, and plasma can be generated using the parallel plate either outside or inside the vacuum chamber. Alternatively, an electric field may be generated by an external induction coil to generate a plasma of ionized gas, or the oppositely charged electrodes may be directly inserted into a vacuum chamber to generate plasma.

In the present invention, the polymerization of the non-vapor phase (liquid and / or solid) monomers is initiated in the presence of ionized gas plasma and then post-polymerized in the absence of plasma. By this two-step polymerization method, it is possible to produce a large amount of an ultra-high molecular weight water-insoluble resin having a high water-absorbing ability with energy saving.

To explain the method of the present invention in more detail, the monomer aqueous medium solution is cooled and frozen with a refrigerant such as liquid nitrogen and deaerated at 10 ^-1 to 10 ^-4 Torr. Since the frozen monomer aqueous medium solution is gradually warmed, when the liquid droplets are reached, the non-solution portion (that is, the vacuum space portion) is irradiated with plasma by the above method. Usually, glow discharge is performed at 20 to 200 watts, preferably 40 to 100 watts, and water and / or monomers are converted into plasma. Irradiation time of usually 1 to 3600 seconds, preferably 10 to 60 seconds is sufficient. After the plasma irradiation, the monomer aqueous medium solution is left to stand at a constant temperature for several hours to carry out post-polymerization. The polymerization rate during the plasma initiation period is remarkably smaller than that in the post-polymerization and usually does not exceed 1 to 2%. The post-polymerization temperature and time vary depending on the kind of the monomer used and are not particularly limited, but the temperature is usually 1.0 to 60 ° C. and the time is 1 to 25 hours. Depending on the type of the monomer, if the temperature exceeds 60 ° C, thermal polymerization may occur and a low molecular weight polymer may be generated, so caution is required.

Further, the plasma-initiated polymerization has a great feature that the obtained superabsorbent resin does not contain anything other than the polymer consisting of the monomer component, unlike the other polymerization methods. That is, it is difficult to completely remove radical initiators, suspending agents, emulsifiers, solvents, etc. in other polymerization methods, but
Plasma-initiated polymerization is necessarily polymer only because these additives are not used.

[0018]

The sulfonic acid group-containing acrylamide cross-linked resin thus obtained is water-insoluble and exhibits high water absorption. That is, the resin obtained by the method of the present invention comprising, for example, 99.999% by weight of 2-acrylamido-2-methylpropanesulfonic acid and 0.001% by weight of methylenebisacrylamide has a water absorption capacity of 1400 times its own weight. Indicates. In addition, the swollen gel is not sticky, does not lose its shape, is water-insoluble that retains its form even in boiling water at 100 ° C., and does not contain any impurities. It is a resin.

The resin of the present invention is water-insoluble, has high water absorbency, and contains no impurities, and therefore, it is useful for sanitary materials, medical industry, food industry, agricultural field and the like.

[0020]

EXAMPLES The present invention will be described in detail below with reference to examples. The water absorption capacity in the examples was measured by the following method. 0.5 g of the sample was immersed in 1 liter of water, allowed to stand at room temperature for 24 hours, suction-filtered with a glass filter to remove excess water, and the total weight of the glass filter and the water-containing sample was measured. Water absorption (g) = (total weight)-(glass filter weight) Water absorption ratio = water absorption / 0.5

Example 1 0.4 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of water and 100 ml of N, N'-methylenebisacrylamide as a crosslinking component were changed as shown in Table 1.
It was put in an ampoule of No. ³ and degassed at 10 ⁻³ Torr, and the tube was sealed. It was then frozen in liquid nitrogen and degassed three times. Next, this ampoule inserted between a pair of frozen external parallel electrodes was inserted into a high frequency generator of International Plasma Corporation Model 3001 which outputs up to 150 watts.
The glow discharge plasma was irradiated for 50 seconds with 0 watts of power. After that, the glow discharge was stopped, the tube was sealed, and the tube was left to stand in a thermostat at 25 ° C. for 10 hours. After unpacking and swelling in a large amount of water to remove unreacted monomer, washing with a large amount of ethanol and vacuum drying, the polymerization rate of the obtained resin,
The water absorption ratio was measured.

Further, 0.4 g of acrylamido-2-methylpropanesulfonic acid, 10 g of water and N, N'-methylenebisacrylamide as a cross-linking component were changed as shown in Table 1, and 0.004 g of potassium persulfate was put in a 100 ml ampoule. Vacuum degassed at 10 ^-3 torr, seal the tube, and then at 60 ° C for 24 hours
The water absorption of the resin polymerized over time is shown for comparison.

[0023]

[Table 1]

Example 2 The ratio (A / B) of 2-acrylamido-2-methylpropanesulfonic acid (A) and acrylic acid (B) was changed as shown in Table 2, and N, N'-methylenebisacrylamide was adjusted to 0. Add 001% by weight to make the total amount of monomer 4 g and water 1
The plasm initiation polymerization was carried out in the same manner as in Example 1 except that the amount was 0 g. The obtained resin was washed in the same manner as in Example 1 and the polymerization rate and the water absorption ratio were measured.

[Table 2]

Example 3 0.4 g of sodium 2-acrylamido-2-methylpropanesulfonate and 0.00004 g of diethylene oxide dimethacrylate were dissolved in 10 g of a solvent as described in Example 3, and placed in a 100 ml ampoule and frozen with liquid nitrogen. 1
^Degassed at ^0-4 torr. Next, the model 300 of the first embodiment
A glow discharge was generated at an output of 80 watts in this ampoule connected to a high frequency generator No. 1 and inserted between a pair of external parallel electrodes, and irradiation was performed for 30 seconds. After that, the glow discharge was stopped, the tube was sealed, and then discharged in a constant temperature bath at 25 ° C. for 15 hours.
Then, the container was opened and washed sufficiently with water to remove unreacted monomers, washed with a large amount of ethanol and dried to prepare a sample, and the polymerization rate and the water absorption capacity were measured.

[0026]

[Table 3]

Claims (1)

[Claims] Claims: The repeating unit represented by the formula (M represents hydrogen, ammonium or an alkali metal) is 80% by weight or more, and acrylic acid, methacrylic acid, p-styrenesulfonic acid, vinylsulfonic acid, 2-methacryloyloxyethylsulfonic acid, allyl. Sulfonic acid, methacrylic sulfonic acid, and at least one vinyl monomer selected from ammonium salts and alkali metal salts of these acids in an amount of 20% by weight or less and a crosslinking component of 0.05% by weight or less. A sulfonic acid group-containing acrylamide-based cross-linking resin, which is water-insoluble and has a high water absorbency of 500 times its own weight or more.