JPS6136309A - Water-absorbent resistant to salt and light - Google Patents

Abstract

PURPOSE:To produce the titled water-absorbing agent having high absorptivity of a salt-containing aqueous liquid and having high stability in water-containing state, by copolymerizing a specific sulfoalkyl (meth)acrylate monomer, a (meth) acrylic acid monomer, and a comonomer in the presence of a crosslinking agent. CONSTITUTION:The objective water-absorbing agent can be prepared by mixing (A) 20-100mol% sulfoalkyl (meth)acrylate monomer of formula I (R is H or methyl; n is 2 or 3; X is H, alkali metal or ammonium) (e.g. sulfoethyl acrylate), (B) 0-80mol% (meth)acrylic acid monomer of formula II (e.g. acrylic acid) and (C) 0-50mol% other polymerizable monomer, polymerizing the mixture in the presence of a crosslinking agent (e.g. N,N-methylenebisacrylamide), finely dividing the resultant hydrated gel of a water-insoluble water-absorbing resin, and drying and crushing the gel.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a salt-resistant and light-resistant water absorbing agent. More specifically, it relates to a water-absorbing agent that absorbs a large amount of aqueous liquid when it comes into contact with an aqueous liquid containing salts, and does not deteriorate even when exposed to light.

(Prior Art) In recent years, water-absorbing resins that absorb water tens to hundreds of times their own weight have been developed, and are used as absorbents for sanitary products, disposable diapers, etc., or as water-retaining agents for agriculture and horticulture.

Coagulant for sludge, anti-condensation agent for building materials, water stop agent for civil engineering.

Development of applications for use as a desiccant, etc. is progressing.

Examples of such water-absorbing resins include hydrolysates of starch-acrylonitrile graft polymers, ammonium starch-acrylic acid graft polymers, saponified products of vinyl acetate-Nisdale acrylate copolymers, and acrylonitrile-based copolymers. Hydrolyzates of acrylamide copolymers or crosslinked products thereof, self-crosslinking sodium polyacrylates obtained by reverse phase suspension polymerization, crosslinked partially neutralized polyacrylic acid products, etc. are known.

(Problems to be Solved by the Invention) Although these water-absorbing resins have an excellent ability to absorb large amounts of water or aqueous liquids, they do not absorb sweat or blood.

When absorbing salt-containing aqueous liquids such as urine or seawater, they have the disadvantage that their water absorption capacity is significantly reduced.

Furthermore, although these conventional water-absorbing resins are excellent in stability in a dry state, they are poor in stability in a water-absorbed state. For example, if a gel-like material that has absorbed water is exposed to sunlight, it deteriorates in just a few hours and becomes fluid, making it impossible to maintain its gel-like form. The above-mentioned drawbacks are a major obstacle when used as a water sealant.

Therefore, as a product with improved salt resistance, a crosslinked product of starch-acrylic acid-vinylphosphonic acid-N-methylpyridium chloride graft copolymer (% 15634
), sulfomethylated product of starch-sodium acrylate-acrylamide kraft copolymer crosslinked product with formalin and sodium bisulfite (JP-A-55-16016), and 2-acrylamide-2-methylpropanesulfonic acid-sodium acrylate self-crosslinked product (%Kaisei 56-16
1412) have been proposed, but these have poor light resistance and poor stability in a water-absorbed state.

Furthermore, the ability to absorb aqueous liquids containing high concentrations of salts is also insufficient. On the other hand, a method of mixing carbon black or activated carbon with water-absorbing resin in order to improve light resistance (Japanese Patent Application Laid-open No. 59-1979-
38271) has been proposed, but although this method effectively improved light resistance, it was insufficient in improving salt resistance. As described above, a water-absorbing resin that has both salt resistance and light resistance has not been known until now.

The present inventors have conducted extensive research to improve the above-mentioned problems in salt resistance and light resistance, and as a result, have completed the present invention.

(Means and effects for solving the problems) The present invention has the following features:
Sulfoalkyl (meth)acrylate system represented by the general formula % (where R is water fp, t or methyl group, n is an integer of 2 or 3, and X is hydrogen, alkali metal or ammonium group) One or more monomers selected from monomers (A) 20 to 100 moles, general formula % formula % (However, R and X represent the same elements or groups as above.)
One or more monomers selected from the (meth)acrylic acid monomers represented by (B) 0 to 80 mol%, and other polymerizable monomers (0) 0 to 50 mol% ( However, the sum of components (A), (B) and (0) is 1
00 morti. ), a monomer mixture (I) consisting of
The present invention provides a salt-resistant and light-resistant water-absorbing agent made of a water-insoluble water-absorbing resin obtained by polymerization in the presence of a crosslinking agent (I[).

The monomer (A) in the present invention is a sulfoalkyl (meth)acrylate monomer represented by the above general formula, and includes sulfoethyl acrylate and its alkali metal salt or ammonium salt, sulfoethyl methacrylate and its alkali metal salt or One or more monomers are selected and used from ammonium salts, sulfopropyl acrylate and its alkali metal salts or ammonium salts, and sulfopropyl methacrylate and its alkali metal salts or ammonium salts. Monomer (A) has the effect of imparting salt resistance to the resulting water-insoluble water-absorbing resin due to the strong dissociability of the sulfonic acid group present in monomer (A).

Monomer (A) must be used in a proportion of 20 mol or more in monomer mixture (I). If the amount is as small as 20 mole drops, the resulting water-insoluble water-absorbing resin will have insufficient salt resistance, which is not preferred.

The monomer (B) in the present invention is a (meth)acrylic acid monomer represented by the above general formula, and includes, for example, acrylic acid, its alkali metal salt or ammonium salt, methacrylic acid, its alkali metal salt, or Examples include ammonium salts, and one or more monomers selected from these are used.

Monomer (B) is used in the monomer mixture (I) in a proportion of not more than 80 mol. If the amount exceeds 80 molti, it is not preferable because the salt resistance of the resulting water-insoluble water-absorbing resin will decrease.

Other polymerizable monomers (0) in the present invention include:
For example, not only water-soluble monomers such as (meth)acrylamide, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, maleic acid, itaconic acid, but also water-insoluble monomers, As long as it is copolymerizable with (A) or (B), it can be used as long as it does not significantly reduce the water absorption capacity of the resulting water-insoluble water-absorbing resin.

The amount of monomer (C) used is 50 molti or less in the monomer mixture (I), and if it is used in excess of 50 molti,
0 Monomer (A) 20 to 100 mole, Monomer (B) θ to
Among the monomer mixture (I) in the present invention consisting of 80 molti and monomer (0) θ~50 molti, the monomer (
Monomers such that the total amount of the sulfoalkyl methacrylate monomer in A) and the methacrylic acid monomer in monomer (B) is 20 mole or more in the monomer mixture (I). Select monomer (A) and monomer (B) to form a monomer mixture (
I) is preferable because it can improve the light resistance of the resulting water-insoluble water-absorbing resin. Sulfoalkyl methacrylate monomer in monomer (A) and monomer (B)
The total amount of methacrylic acid monomer in the monomer mixture (
If the amount is less than 20 mol% in I), the light resistance of the resulting water-insoluble water-absorbing resin will be insufficient depending on the type and usage ratio of the monomer mixture (I) and crosslinking agent (II) used. Sometimes.

Sulfoalkyl (meth)acrylate as the monomer (A) and (meth)acrylic acid as the monomer (B) reduce the water absorption capacity of the water-insoluble water-absorbing resin obtained when such acids are used extensively. However, it is useful for adjusting the pH of the water-absorbing resin to neutrality or other desired ranges, and for acting as a crosslinking point when polyhydric alcohol is used as the crosslinking agent (n). . Therefore, monomer (A) is an alkali metal salt of sulfoalkyl (meth)acrylate, and monomer (B) is (meth)acrylic acid 1-50
Morti and alkali metal salts of (meth)acrylic acid 50
It is preferable to use the monomer mixture CI) having a ratio of 99 moles, because it is possible to maintain a high water-absorbing capacity of the resulting water-absorbing resin and also to adjust the pH of the water-absorbing resin to neutral.

In the present invention, a water-insoluble water absorbent resin is obtained by polymerizing the monomer mixture (I) in the presence of a crosslinking agent (n). Although the monomer mixture (I) partially self-crosslinks in the polymerization in the absence of water-absorbing agents, it does not become a water-insoluble water-absorbing resin to the extent that it can generally be used as a water-absorbing agent. When polymerizing a single monomer (person) or a monomer mixture (I) with a large usage ratio of monomer (A) by appropriately selecting and using the type and amount of the crosslinking agent (n). However, the crosslinking density of the resulting water-insoluble water-absorbing resin can be easily controlled, and a water-absorbing agent with excellent salt resistance can therefore be easily obtained.

The cross-linking agent (ff) is not only effective in obtaining a water-absorbing agent with excellent salt resistance as described above, but also effective in obtaining a water-absorbing agent with excellent light resistance. and
By adjusting the amount of the crosslinking agent (I[) to be appropriate depending on the S type of the monomer mixture (I), the stability of the resulting water-absorbing resin when exposed to sunlight in a water-absorbed state can be increased. .

Examples of the crosslinking agent (II) in the present invention include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate.

Probylene glycol di(meth)acrylate.

Polyprolene glycol di(meth)acrylate.

trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol di(meth)acrylate), N, N-
Compounds with two or more ethylenically unsaturated groups in one molecule, such as methylene bisacrylamide, triallyl isocyanurate, trimethylolpropane lydialether; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, poly Polyhydric alcohols such as glycerin, propylene glycol, jetanolamine, triethanolamine, polypropylene glycol, polyvinyl alcohol, be/taerythritol, sorbitol, sorbitan, glucose, mannitol, mannitan, sho[,7' tucrose, etc.] One or more of these can be used.

The amount of the crosslinking agent (1) to be used is preferably 0.00001 to 0.00001 in molar ratio to the monomer mixture (I).
It is in the range of 0.1. If the amount exceeds 0.1, even if the resulting water-insoluble water-absorbing resin has good light resistance, the crosslinking density becomes too large, which tends to reduce the viscosity and water-absorbing ability. On the other hand, if the amount is less than o, OO001, the crosslinking density is too small and the thickening property is low, resulting in stickiness after absorbing an aqueous liquid, resulting in insufficient light resistance and initial water absorption rate.

The "1-polymerization method" for obtaining the salt-resistant and light-resistant water absorbing agent of the present invention may be any conventionally known method, including a method using a radical polymerization catalyst and a method using radiation.

Examples include methods of irradiating with electron beams, ultraviolet light, and the like.

Radical polymerization catalysts include radical generators such as hydrogen peroxide, degraded products such as benzoyl peroxide and cumene hydroperoxiside, azo compounds such as azobisiso-thyronitrile, and FAK salts such as ammonium persulfate and potassium persulfate. or a combination of these with a reducing agent such as aqueous sodium sulfite, L-ascorbic acid, or iron salt is used as a redox initiator. Examples of the polymerization solvent that can be used include water, methanol, ethanol, acetone, dimethylformamide, dimethyl sulfoxide, and mixtures thereof.

The temperature during polymerization varies depending on the type of catalyst used, but a relatively low temperature is preferable because the molecular weight of the crosslinked polymer increases. However, in order to complete the polymerization, it is necessary to
It is preferable that the temperature is within the range of 0°C or lower.As mentioned above, the crosslinking density of the water-insoluble water-absorbing resin obtained by using the crosslinking agent (II) can be freely controlled. There is no particular limit to the concentration of
Preferably, it is in the range of 60% by weight. Various forms of polymerization can be adopted, including reverse phase suspension polymerization.

Cast polymerization, a method in which a hydrogel polymer is polymerized while being fragmented by the shearing force of a double-arm kneader (%
101) is preferred.

A fragrance, a deodorizing agent, or carbon black or activated carbon may be mixed with the salt-resistant and light-resistant water absorbing agent of the present invention before or after polymerization for the purpose of further improving light resistance.

(Effects of the Invention) The salt-resistant and light-resistant water absorbing agent of the present invention obtained as described above has extremely excellent salt resistance, so it can be used not only in sweat, blood, urine, etc., but also in high concentrations such as seawater. It absorbs water-based liquids containing salts at a high absorption rate, and once absorbed, it retains water for a long time even under pressure.It also has good light resistance, so it can withstand long-term exposure to sunlight. It is an earth water agent for civil engineering because it maintains the above absorption capacity without deteriorating.

It can be effectively used as a water retention agent for agriculture and horticulture, medical hygiene materials, etc.

Hereinafter, the present invention will be explained in detail with reference to Examples, but the scope of the present invention is not limited only to these Examples.

Example 1 500 ml (7) 172.8 mL of sodium salt of sulfoethyl methacrylate in a circle f'J-type sepa 2-pull flask
, y (o, so mol), acrylic acid 3.610.05 mol), sodium acrylate 14.1.9 (0,15
mol), N,N-methylene/bisacrylamide 0.
154.9 (0,001 mol) and water 2601! was added and stirred to uniformly dissolve. After purging with nitrogen, heat to 40°C in a hot water bath and add 10% ammonium persulfate aqueous solution 1
．． 0.09 and 0.5 g of 1% L-ascorbic acid aqueous solution were added, stirring was stopped, and polymerization was carried out. After polymerization starts, heat is generated,
The temperature rose to 68°C after 40 minutes.

After confirming that the temperature of the polymerization system has started to drop, turn off the water bath to
The temperature was raised to 0°0 and heated for an additional hour. The obtained water-containing resin water-containing gel was divided into small pieces, dried in a hot air dryer at 150°C for 5 hours, and crushed to obtain the water-absorbing agent (1) of the present invention.
I got it.

Example 2 220 ml of n-hexane was charged into a 500 ml four-bottle flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a nitrogen gas inlet tube, and 1.5 mL of sorbitan monostearate was added.
After adding and dissolving 8N, the atmosphere was replaced with nitrogen. Add 23.0% of the sodium salt of sulfopropyl methacrylate to the dropping funnel.
．． 9 ('0..10 mol), acrylic acid 3.6.9 (
0,05 mol), sodium acrylate 9,41,!
i' (0.10 mol), trimethylolprono(triame/-t) 0.0296 I (0.0OO 1 mol) water 5
After adding and dissolving 0 g of potassium persulfate and 0.05 F of potassium persulfate, nitrogen gas was blown into the aqueous solution to remove oxygen present in the aqueous solution. Next, the contents of the dropping funnel were added to the fourth flask and dispersed, and the polymerization reaction was continued for 3 hours by maintaining the temperature of the polymerization system at 60 to 65°C in a hot water bath while introducing a slight amount of nitrogen gas. . Thereafter, n-hexane was distilled off under reduced pressure, and the remaining water-containing gel of the water-absorbing resin was dried under reduced pressure at 80°C to obtain the water-absorbing agent (2) of the present invention. Example 3 500 ml cylindrical separable Sodium salt of sulfoethyl acrylate in flask 80.9! ! (0,40
mol), methacrylic acid -21.5 g (0.25 mol),
Sodium methacrylate 27.0 fl (0.25 mol)
, acrylamide 7, i p (0,10 mol).

Prepare glycerin 0.46 F (0,005 mol) and water 190 g, and prepare 10% ammonium persulfate aqueous solution 1
．． O, S' and 1% L-ascorbic acid aqueous solution 0.5
Polymerization was carried out in the same manner as in Example 1 using I. The obtained water-containing gel of the water-absorbing resin was divided into pieces, dried at 180°0 for 2 hours, and pulverized to obtain a water-absorbing agent (3).

Example 4 250 ml of cyclohexane was charged into the same four-bottle flask as used in Example 2, and sorbitan monostearate was added.
After adding and dissolving 2.0.9, the mixture was replaced with nitrogen. Add sulfopropyl acrylate to the dropping funnel) 9.7 F (0,
0.05 mol), 21.6 g (0.10 mol) of the sodium salt of sulfopropyl acrylate.

9.41 g (0.10 mol) of sodium acrylate.

Sodium methacrylate 5.40.9' (0.05 mol).

Diethylene glycol diacrylate 0.0428p (
0,0002 mol), 6 liters of water and 0.0 mol of potassium persulfate.
After 1 g was added and dissolved, nitrogen gas was blown into the aqueous solution to remove oxygen present in the aqueous solution. Next, the contents of the dropping funnel were added to the fourth flask and dispersed, and Example 2
After carrying out a polymerization reaction in the same manner as above, cyclohexane was distilled off, and the resulting water-containing gel of the water-absorbing resin was dried under reduced pressure at 80°C to obtain a water-absorbing agent (4) of the present invention.

Sodium salt of ethyl methacrylate 21.677 (0
, 10 mol), acrylic acid 3.6y (0.05 mol), sodium acrylate 9.41 g (0.10 mol).

trimethylolproban triacrylate) 0.0592
A water absorbing agent (5) of the present invention was obtained in the same manner as in Example 2, except that the amount of water was 65.9 (o, ooo moles), and the amount of potassium persulfate was 0.05.9.

Comparison row 1 Acrylic acid 1 in a 500 ml cylindrical separable flask
8.051 (0.25 mol), sodium acrylate 7
0.5 g (0.75 mol), N,N-methylenebisacrylamide 0.154.9 (0,001 mol)
and 121 g of water to prepare 10% ammonium persulfate aqueous solution 1. OI and 1% L-ascorbic acid aqueous solution 0.5
Polymerization and drying were carried out in the same manner as in Example 1 using Polymer 9.

It was pulverized to obtain a comparative water absorbing agent (1).

Comparative Example 2 The contents of the dropping funnel in Example 2 were: 4.69 (0.02 mol) of sodium salt of sulfoprovir methacrylate, 7.211 (0.10 mol) of 7-acrylic acid, 18.8.9 (0.10 mol) of sodium acrylate. (0.20 mol).

Comparative water absorbing agent (2) was obtained in the same manner as in Example 2, except that 42.59 g of water and 0.05 g of potassium peroxide were used. A comparative water absorbing agent (3) was obtained by repeating the same operation as in Example 1. The heat generated after the start of polymerization is
After 45 minutes, the temperature rose to 65°C.

Example 6 Water absorbing agents (1) to (1) obtained in Examples 1 to 5 and Comparative Examples 1 to 3
5) and comparative water absorbing agents (1) to (3), the water absorption capacity of aqueous liquids containing salts was measured by the following method.

Synthetic seawater 200 with the composition shown in Table 1 for each water absorbing agent Ili
The weight of the water-absorbing gel present on the mesh wire mesh was measured, and the number of grams was taken as the water absorption capacity. The results are shown in Table 2.

Table 2 As is clear from Table 2, the water absorbing agent of the present invention has excellent salt resistance.

In addition, in the comparative water absorbing agent (3), although some water-insoluble gel-like material was formed, most of it was water-soluble resin, so the water absorption capacity could not be measured.

Example 7 Water absorbing agents (1) to (1) obtained in Examples 1 to 5 and Comparative Examples 1 to 3
5) and comparative water absorbing agents (1) to (3), the light resistance was evaluated by the following method.

2g of each water absorbent was added to 98% of deionized water. ! In addition to i', water is absorbed to obtain a water-absorbing gel of each water absorption Jj, and this is made to a thickness of 0.02
The samples were placed in transparent polyethylene bags and exposed to sunlight.

The state of the water-absorbing gel during exposure was observed over time, and the results were evaluated using the following five-level criteria.

The evaluation results are shown in Table 3.

Light resistance Evaluation criteria Good Hard gel-like Poor E As is clear from Table 3 that it flows to the same extent as water, the water absorbing agent of the present invention has excellent light resistance.

Furthermore, since no water-absorbing gel was obtained for the comparative water-absorbing agent (3), light resistance was not evaluated.

Claims (1)

[Claims] 1. General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, R is hydrogen or a methyl group, n is an integer of 2 or 3, and X is hydrogen, an alkali metal, or an ammonium group. ) One or more monomers selected from sulfoalkyl (meth)acrylate monomers (A) 2
0 to 100 mol%, general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, R and X represent the same elements or groups as above.) 1 selected from (meth)acrylic acid monomers represented by 0 to 80 mol% of a species or two or more monomers (B), and 0 to 50 mol% of other polymerizable monomers (C) (with the exception of components (A), (B), and (C)). A salt-resistant and light-resistant water-absorbing agent made of a water-insoluble water-absorbing resin obtained by polymerizing a monomer mixture (I) consisting of (the total amount is 100 mol%) in the presence of a crosslinking agent (II).2. The total amount of the sulfoalkyl methacrylate monomer in the monomer (A) and the methacrylic acid monomer in the monomer (B) is 20 mol% or more in the monomer mixture (I). The salt-resistant and light-resistant water-absorbing agent according to claim 1, which is 3. The usage ratio of the crosslinking agent (II) to the monomer mixture (I) is 0.00001 to 0.1 in terms of molar ratio. The salt-resistant and light-resistant water absorbing agent according to claim 1 or 2.