JP5937066B2 - Water-absorbing and liquid-absorbing polymers - Google Patents

Description

  The present invention relates to a water-absorbing and liquid-absorbing polymer having biodegradability.

High water-absorbing polymer absorbs water several hundred times its own weight, and retains moisture absorbed at a rate of, for example, about 75% / day. For example, disposable diapers, sanitary products, agricultural and industrial products, etc. It is widely used.
Highly water-absorbing polymers are mainly made of crosslinked polyacrylic acid made from petroleum. Sanitary materials such as disposable diapers and sanitary products, medical fields such as compresses, horticulture such as soil water retention agents and sealing agents, agriculture It is used in various applications including the field of civil engineering, freshness-preserving agents, and cold-retaining agents. However, as awareness of environmental issues related to disposal and incineration after use increases and the price of crude oil rises, development of biodegradable water-absorbing polymers using recycled resources is desired, as is the case with other synthetic polymers. Yes.

Special Table 2007-515562 JP 2006-188697 JP 2008-69315 A JP-A-61-244369

Yoshimura et al, J. Appl. Polym. Sci. 99, 3251-3256 (2006).

  In a situation where water absorption of the water-absorbing polymer is expected, the target of water absorption is not pure water but contains a large amount of metal cations and proteins such as sodium ions, potassium ions, calcium ions, or magnesium ions. There are many cases. Therefore, it is actually necessary to show higher absorbability not only for pure water but also for solutions containing various metal cations and protein-containing solutions. However, the absorbability of the water-absorbing polymer proposed so far in a solution containing the metal cation or a protein-containing solution has not been sufficient. For example, crosslinked polyacrylic acid exhibits excellent water absorption capacity of up to about 1000 times in pure water, but when used in a solution containing metal cations, it aggregates instantaneously and its water absorption performance decreases sharply. End up. In addition, when a polyacrylic acid cross-linked product is used in a protein-containing solution, it instantaneously aggregates due to electrostatic interaction with hydrophilic amino acids constituting the protein or hydrophobic interaction with hydrophobic amino acids. Water absorption performance will drop rapidly.

  The present invention has been made based on such circumstances, and biodegradable water-absorbing polymers and liquid-absorbing polymers exhibiting higher absorbability than conventional solutions with respect to solutions containing various metal cations and protein-containing solutions. The purpose is to provide.

  As a result of diligent research, the present inventor made a solution or protein-containing solution containing various metal cations by forming an crosslinked structure by allowing an epoxy compound to act on a carboxymethyl cellulose salt having a substitution degree and a weight average molecular weight within a predetermined range. It has been found that the absorbability of the polymer with respect to can be greatly increased, and the present invention has been made.

  One embodiment of the present invention is obtained by crosslinking a carboxymethyl cellulose salt having a substitution degree of 0.65 to 1.4 and a weight average molecular weight of 84,600 to 125,000 with an epoxy compound, which can absorb a solution containing a metal cation and a protein-containing solution. Water-absorbing and liquid-absorbing polymers. The epoxy compound can be epichlorohydrin, ethylene glycol diglycidyl ether or a mixture thereof.

  ADVANTAGE OF THE INVENTION According to this invention, while having biodegradability, the water absorbing property and liquid absorbing polymer which show the outstanding absorptivity with respect to the solution containing various metal cations and protein containing liquid can be provided.

It is a figure which shows an example of the manufacturing flow of the water absorbing property and liquid absorbing polymer of this embodiment. 2 is a photograph of a water-absorbing and liquid-absorbing polymer of an example. It is a graph which shows the relationship between the water absorption time and the amount of water absorption when the water absorption and liquid absorption polymer of an Example from which substance amount ratio differs are used for the absorption of a pure water (a crosslinking agent is epichlorohydrin). It is a graph which shows the relationship between the water absorption time and the amount of water absorption when using for the absorption of pure water of the water absorption and liquid absorption polymer of the Example from which substance amount ratio differs (a crosslinking agent is ethylene glycol diglycidyl ether). ). It is a graph which shows the water absorption of the water absorbing property and liquid absorbing polymer of an Example. It is a graph which shows the relationship between the liquid absorption time and the amount of liquid absorption when using for the absorption of 10 mM sodium chloride aqueous solution of the water absorbing property and liquid absorbing polymer of an Example. It is a graph which shows the relationship between the liquid absorption time and the amount of liquid absorption when it used for absorption of 0.3, 0.9, and 3.8% sodium chloride aqueous solution of the water absorbing property and liquid absorbing polymer of an Example. It is a graph which shows the liquid absorption amount with respect to 10 mM sodium chloride aqueous solution 4 days after the test start of the water absorbing property and liquid absorbing polymer of the Example from which substitution degree (carboxymethylation degree) differs. It is a graph which shows the liquid absorption amount with respect to 10 mM sodium chloride aqueous solution 4 days after the start of a test of the water absorbing property and liquid absorbing polymer of the Example from which polymerization degree differs. The graph which shows the relationship between the liquid absorption time and the amount of liquid absorption when it used for absorption of various 10 mM alkali metal cation (Na ⁺ , K ⁺ , Cs ⁺ ) aqueous solution of the water absorbing property and liquid absorbing polymer of an Example. It is. The relationship between the liquid absorption time and the liquid absorption amount when subjected to absorption of various 10 mM alkaline earth metal cation (Mg ²⁺ , Ca ²⁺ ) aqueous solutions of the water-absorbing and liquid-absorbing polymers of the examples is shown. It is a graph. The relationship between the liquid absorption time and the liquid absorption amount when subjected to absorption of various 10 mM alkaline earth metal cation (Sr ²⁺ , Ba ²⁺ ) aqueous solutions of the water-absorbing and liquid-absorbing polymers of the examples is shown. It is a graph. The absorption time and absorption amount of the water-absorbing and liquid-absorbing polymers of the examples when subjected to absorption of various 10 mM divalent metal cation (Mn ²⁺ , Fe ²⁺ , Co ²⁺ ) aqueous solutions. It is a graph which shows a relationship. The water absorption time and the amount of liquid absorption when subjected to absorption of various 10 mM divalent metal cation (Ni ²⁺ , Zn ²⁺ , Cd ²⁺ ) aqueous solutions of the water-absorbing and liquid-absorbing polymers of the examples. It is a graph which shows a relationship. It is a graph which shows the relationship between water absorption time and the amount of water absorption when using for the absorption of the aqueous solution from which the acidity of the water absorption and liquid absorption polymer of an Example differs (a crosslinking agent is epichlorohydrin). It is a graph which shows the relationship between the water absorption time and the amount of water absorption when using for the absorption of the aqueous solution from which the acidity of the water absorption property and liquid absorption polymer of an Example differs (a crosslinking agent is ethylene glycol diglycidyl ether). It is a graph which shows the water absorption amount with respect to the aqueous solution from which the acidity of the water absorptivity and liquid absorptive polymer of an Example in which the acidity differs 3 days after a test start. It is a graph which shows the soil water retention effect of the water absorbing property and liquid absorbing polymer of an Example. It is a graph which shows the relationship between the liquid absorption time and the amount of liquid absorption when using for the absorption of the BSA solution of the water absorbing property and liquid absorbing polymer of an Example. It is a graph which shows the relationship between the liquid absorption time and the amount of liquid absorption when using for the absorption of the BSA solution of the water absorbing property and liquid absorbing polymer of an Example. It is a graph which shows the relationship between the liquid absorption time and the amount of liquid absorption when using for the absorption of the BSA solution of the water absorbing polymer of a comparative example. It is a graph which shows the relationship between the liquid absorption time and the amount of liquid absorption when using for the absorption of the milk of the water absorbing property and liquid absorbing polymer of an Example. It is a graph which shows the relationship between the liquid absorption time and the amount of liquid absorption when using for the absorption of the milk powder solution of the water absorbing property and liquid absorbing polymer of an Example.

Hereinafter, one embodiment of the present invention will be described in detail.
The water-absorbing and liquid-absorbing polymers of the present embodiment (hereinafter, the water-absorbing and liquid-absorbing polymers of the present embodiment and the water-absorbing and liquid-absorbing polymers of the examples are also simply referred to as polymers) Compared to a conventional water-absorbing polymer, the solution containing a metal cation or a protein-containing solution exhibits higher liquid absorbency. Here, in the present specification, the liquid absorbency means that it absorbs a solution containing a metal cation or a protein-containing liquid.
Moreover, the solution containing a metal cation refers to a solution in which one or more various metal cation components are dissolved in water or the like. Specifically, physiological saline, seawater, moisture in soil, industrial The concept includes drainage, water in which fertilizer is dissolved, and also includes body fluids such as urine and blood.
The protein-containing liquid is a liquid in which one or a plurality of various proteins are dissolved or dispersed in water or the like. Specifically, a body fluid such as urine or blood, or a secreted fluid such as milk or human milk. Can be mentioned.
The polymer of this embodiment can be obtained by allowing an epoxy compound to act on carboxymethyl cellulose salt (CMC) to cause crosslinking.

  Examples of the carboxymethyl cellulose salt include sodium salt, potassium salt, calcium salt and the like. Among these, a sodium salt (sodium carboxymethylcellulose) is preferable because it has high water solubility, and as a result, the liquid absorbability with respect to a solution containing a metal cation and a protein-containing liquid contained in the polymer of the present embodiment is further increased.

Here, in the present embodiment, the degree of substitution of the carboxymethyl cellulose salt is 0.65 to 1.4, and the weight average molecular weight is 84,600 to 125,000 (324 to 584 in terms of average polymerization degree).
Further, the degree of substitution is preferably 0.72 to 0.99, and the weight average molecular weight is preferably 84,600 to 112,000 (355 to 505 in terms of average polymerization degree), the degree of substitution is 0.72 to 0.82, and the weight average molecular weight is 84,600. It is more preferably 112,000 (355 to 505 in terms of average polymerization degree). Still more preferably, the degree of substitution is 0.72 to 0.82 and the weight average molecular weight is 84,600 to 111,000 (355 to 505 in terms of average polymerization degree), the degree of substitution is 0.72 to 0.82, and the weight average molecular weight Is more preferably 100,000 to 110,000 (450 to 495 in terms of average polymerization degree).
When the weight average molecular weight is less than 84,600, the particle size of the polymer is reduced, and the effective internal volume for holding a solution containing a metal cation or a protein-containing solution is reduced as compared with the case of being within the range. When the weight average molecular weight is larger than 125,000, the viscosity of the carboxymethylcellulose salt is rapidly increased, so that it is difficult to uniformly mix with the crosslinking agent during synthesis.
Further, when the degree of substitution is less than 0.65, the proportion of carboxylate contained in the structure of carboxymethylcellulose salt is reduced, and electrostatic repulsion of carboxylate ions is suppressed after liquid absorption, resulting in a solution containing a metal cation. The liquid absorption with respect to is reduced. If the degree of substitution is greater than 1.4, the proportion of negatively charged carboxylate ions increases after liquid absorption, and electrostatically binds to positively charged metal cations. Decreases.

On the other hand, by using a carboxymethyl cellulose salt having a substitution degree of 0.65 to 1.4 and a weight average molecular weight of 84,600 to 125,000, it is possible to enhance the liquid absorbability with respect to a solution containing a metal cation or a protein-containing solution. In particular, as a result of using a carboxymethyl cellulose salt having a substitution degree of 0.72 to 0.99 and a weight average molecular weight of 84600 to 112,000, the polymer obtained by synthesis has a better balance between particle size and carboxylate, Compared to the water-absorbing polymer, the solution containing various metal cations has extremely high liquid absorbency (1.3 to 2.2 times compared to the case where the polyacrylic acid crosslinked copolymer is absorbed). Become.
Further, the polymer of the present embodiment is provided by setting the degree of substitution of the carboxymethyl cellulose salt to 0.72 to 0.82 and the weight average molecular weight to 84600 to 112,000 (preferably 84,600 to 111,000, more preferably 100,000 to 110,000). Water absorption and liquid absorption can be further enhanced.
In the present specification, the degree of substitution refers to the ratio of carboxymethyl cellulose in which the hydroxy group of cellulose is substituted with carboxymethyl group.

  Further, as can be understood from the above description, the weight average molecular weight of the carboxymethyl cellulose salt can also be expressed by the average degree of polymerization of the carboxymethyl cellulose salt. Conversion of the weight average molecular weight to the average degree of polymerization can be performed based on the following formula (1).

DP = Mw / (162 + 80DS) (1)
In formula (1), DP represents the average degree of polymerization, Mw represents the average molecular weight, and DS represents the degree of substitution.

The epoxy compound according to the present embodiment is not particularly limited and can be appropriately set by those skilled in the art. For example, ethylene oxide, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, methyl glycidyl ether, phenyl glycidyl ether, epichlorohydride Monoepoxy compounds such as phosphorus (ECH), ethylene glycol diglycidyl ether (EGDE), polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerin nobricidyl ether, etc. Diepoxy compounds, triepoxy compounds such as glycerin triglycidyl ether and triglycidyl isocyanurate, glycerol polyglycidyl One or more selected from polyepoxy compounds such as ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, and sorbitol polyglycidyl ether can be used. Among these, epichlorohydrin, ethylene glycol diglycidyl ether, or a mixture thereof is preferable because the synthesis of the polymer of the present embodiment can proceed under mild reaction conditions.

  FIG. 1 is a diagram showing an example of a synthesis flow of a polymer of this embodiment using sodium carboxymethylcellulose as a raw material. First, sodium carboxymethyl cellulose is dissolved in an alkaline aqueous solution such as a sodium hydroxide aqueous solution. After completely dissolving at room temperature, an epoxy compound such as epichlorohydrin or ethylene glycol diglycidyl ether is dropped as a crosslinking agent. Thereafter, the reaction is performed for 6 to 24 hours while heating (for example, in a 60 ° C. hot water bath), whereby an intermolecular bridge is formed between the epoxy compound as a crosslinking agent and the cellulose hydroxyl group.

Next, the obtained gel-like substance is sufficiently washed with water, dehydrated in acetone, and then air-dried to obtain the polymer of this embodiment.
The ratio between the carboxymethyl cellulose salt and the epoxy compound can be appropriately set by those skilled in the art and is not particularly limited. Here, for example, when epichlorohydrin is used, it is preferable to add 5 to 8 times the epichlorohydrin, more preferably 5 to 6 times the glucose residue equivalent substance amount of the carboxymethylcellulose salt. . By adding 5 to 8 times the amount of epichlorohydrin with respect to the glucose residue equivalent amount of carboxymethylcellulose salt, a solution or protein containing the metal cation of the polymer of the present embodiment is included, as compared with the case outside the range. The liquid absorptivity with respect to a containing liquid can be improved more.
In the case of using ethylene glycol diglycidyl ether as a crosslinking agent, 3 to 8 times, more preferably 3 to 6 times as much ethylene glycol diglycidyl ether as the amount of carboxymethylcellulose salt in terms of glucose residue is used. It is preferable to add. By adding ethylene glycol diglycidyl ether 3 to 8 times the glucose residue equivalent substance amount of the carboxymethyl cellulose salt, a solution containing the metal cation of the polymer of the present embodiment than the case outside the range, The liquid absorptivity with respect to protein containing liquid can be improved more.

The polymer of the present embodiment exhibits extremely higher liquid absorbency with respect to water and protein-containing liquids containing metal cations than conventional water-absorbing polymers such as polyacrylic acid crosslinked copolymers. Therefore, the polymer of this embodiment can be used to absorb a solution containing a metal cation. Moreover, the polymer of this embodiment can also be used for absorbing a protein-containing solution. It should be noted that those skilled in the art can naturally understand that the present invention can also be used to absorb liquids that meet the definitions of both a solution containing a metal cation and a protein-containing liquid.
Specifically, for example, an existing polyacrylic acid crosslinked copolymer can absorb only about 155 times its own weight with respect to a 10 mM sodium chloride aqueous solution. On the other hand, the polymer of the present embodiment has a liquid absorption amount of about 345 times its own weight (2.2 times compared to the polyacrylic acid crosslinked copolymer), for example, depending on the ratio between the carboxymethyl cellulose salt and the epoxy compound. Show.
In the case of a normal polyacrylic acid crosslinked copolymer, when the protein-containing liquid is absorbed, the copolymer aggregates several hours after the start of the liquid absorption, and the liquid absorption amount is greatly reduced. On the other hand, the polymer of this embodiment shows a stable liquid absorption after the liquid absorption starts and does not aggregate.
Moreover, unlike the existing polyacrylic acid crosslinked copolymer, the polymer of the present embodiment uses cellulose, which is renewable biomass, as a skeletal material and has biodegradability.
That is, according to the polymer of the present embodiment, it is possible to provide a water-absorbing and liquid-absorbing polymer that is biodegradable and has an extremely superior liquid-absorbing property compared to conventional water-absorbing polymers. Can do.
The polymer of this embodiment can be used for various applications such as daily necessities such as sanitary goods, agricultural horticulture, fine toiletries, distribution materials, civil engineering architecture, medical care, functional materials, specifically, disposable diapers, Sanitary wares, pet toilets, medical waste solidifying agents, cryogens, soil conditioners, soil water retention materials, seedling pots, seedbeds, hydroponics supports, masks for packs, cooling gels, portable toilets, DDS carriers, for hemostasis It can be used for sponges, artificial joints, gel electrolyte fuel cells, gel sensors, and the like.
More specifically illustrated, and water-retaining material in the soil which Ca ²⁺ ions and Mg ²⁺ ions are present in a large amount was absorbed an aqueous solution obtained by dissolving the Ca ²⁺ ions and Mg ²⁺ containing much fertilizer an ion coercive It is effective as a fertilizer (soil improvement material). It can also be used for offshore civil engineering, use of water between tunnel segments, and acid waste liquid solidifying agent. Furthermore, since the protein-containing liquid can also be absorbed, it can be used for a breast milk pad, a liquid waste coagulation treatment agent for medical use, and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the water-absorbing and liquid-absorbing polymers of the present invention are not limited to the forms specified by the following examples. In addition, the ratio of the carboxymethylcellulose salt and epoxy compound which concern on the following Examples 1-8 is collectively shown to Tables 1-2.

(Example 1)
3.0 g of sodium carboxymethylcellulose (13.5 mmol in terms of glucose residue monomer) having a substitution degree of 0.75 and a weight average molecular weight of 106,000 (average polymerization degree of 477) was dissolved in 100 mL of a 1.5 mol / L aqueous sodium hydroxide solution. A 5-fold amount of 6.24 g (67.5 mmol) of epichlorohydrin with respect to the amount of carboxymethylcellulose sodium in terms of glucose residue was dropped, and the mixture was reacted in a 60 ° C. hot water bath for 6 hours with stirring. After the reaction, it was washed with running water until the gelled product was neutral. After dehydrating by immersing in acetone, a white solid was obtained by air drying. The solid was pulverized by a blender mill.
In Example 1, the ratio of the amount of substance in terms of glucose residue of sodium carboxymethylcellulose and the amount of substance of epichlorohydrin is 1: 5. In the following, the ratio of the amount of substance in terms of glucose residue of sodium carboxymethylcellulose and the amount of substance of epichlorohydrin or ethylene glycol diglycidyl ether is also simply referred to as the substance amount ratio.

The degree of substitution of sodium carboxymethylcellulose was measured by ¹ H NMR (determined from the signal intensity ratio of the spectrum). Moreover, the weight average molecular weight of sodium carboxymethylcellulose was measured by gel filtration chromatography. Furthermore, the average degree of polymerization of sodium carboxymethylcellulose was determined by the formula (1) from the weight average molecular weight and the degree of substitution.

DP = Mw / (162 + 80DS) (1)
In formula (1), DP represents the average degree of polymerization, Mw represents the average molecular weight, and DS represents the degree of substitution.

  FIG. 2 is a photograph showing the appearance of the polymer of Example 1. As shown in FIG. 2 (a), the polymer of Example 1 is a white powder when dried, but it absorbs water instantaneously due to the presence of water, resulting in a transparent hydrogel as shown in FIG. 2 (b). Change.

(Examples 2 to 4)
By changing the amount of epichlorohydrin charged relative to sodium carboxymethylcellulose, the change in water absorption of the resulting polymer was investigated. Example 2 The amount of epichlorohydrin added was changed to [Example 2] 7.49 g (81 mmol), [Example 3] 8.74 g (94.5 mmol), and [Example 4] 9.99 g (108 mmol), respectively. 1 to 4 were obtained under the same conditions as in Example 1. The substance amount ratio in each example is [Example 2] 1: 6, [Example 3] 1: 7, and [Example 4] 1: 8.

(Evaluation of water absorption of pure polymers of Examples 1 to 4)
FIG. 3 is a sunwet (registered trademark) manufactured by Sundia Polymer Co., Ltd., which is an existing commercial product of the polymers of Examples 1 to 4 using epichlorohydrin as a crosslinking agent and a polyacrylic crosslinked copolymer used as a comparative control. The same applies hereinafter) IM930 is a graph showing the relationship between water absorption time and water absorption. Hereinafter, the sun wet IM930 is also referred to as Comparative Example 1 or PANa. The numerical values shown in the vicinity of the water absorption time-water absorption amount curve of each example in FIG. 3 indicate the substance amount ratio in each example. The water absorption curve was determined by Japanese Industrial Standard JIS K7223 (teaback method) (the same applies to the determination of the water absorption curve and the liquid absorption curve hereinafter).
As a result, the polymers of Examples 1 to 4 all showed higher water absorption than Comparative Example 1. In particular, in the polymer of Example 1 having a substance amount ratio of 1: 5, the water absorption after 3 days from the start of the test showed the highest value of 6473 times its own weight during drying, and the water absorption was almost the same after 6 days from the start of the test. Was maintained. That is, the polymer of Example 1 synthesized at a mass ratio of 1: 5 had the highest water absorption rate.

(Example 5)
The crosslinking agent was changed from epichlorohydrin to ethylene glycol diglycidyl ether, and the water absorption of the resulting polymer was examined. Since ethylene glycol diglycidyl ether has high reactivity, it was carried out by reducing the sodium hydroxide concentration in the solvent by the following procedure.

  Example except that the concentration of sodium hydroxide aqueous solution was changed from 1.5 mol / L to 0.5 mol / L, and instead of 6.24 g (67.5 mmol) of epichlorohydrin, 11.75 g (67.5 mmol) of ethylene glycol diglycidyl ether was used. Under the same synthesis conditions as in Example 1, the polymer of Example 5 was obtained. The substance amount ratio in Example 5 is 1: 5.

(Examples 6 to 8)
Except for changing the addition amount of ethylene glycol diglycidyl ether to [Example 6] 14.1 g (81.0 mmol), [Example 7] 16.5 g (94.5 mmol), and [Example 8] 18.8 g (108 mmol), respectively. Under the same conditions as in Example 5, the polymers of Examples 6 to 8 were obtained. The substance amount ratio in each example is [Example 6] 1: 6, [Example 7] 1: 7, and [Example 8] 1: 8.

(Evaluation of water absorption of the polymers of Examples 5 to 8 with respect to pure water)
FIG. 4 is a graph showing the relationship between the water absorption time and the water absorption amount of the polymers of Examples 5 to 8. The numerical values shown in the vicinity of the water absorption time-water absorption curve of each example in FIG. 4 indicate the substance amount ratio in each example.
As a result, the polymers of Examples 5 to 8 all showed higher water absorption than the comparative examples. In particular, in the polymer of Example 5 having a substance amount ratio of 1: 5, the water absorption after 6 days from the start of the test showed the highest value of 2306 times its own weight during drying. Therefore, it was revealed that even when ethylene glycol diglycidyl ether was used as a cross-linking agent, a polymer synthesized with a mass ratio of 1: 5 showed a particularly high water absorption. Further, when the polymer of Example 6 having a substance amount ratio of 1: 6 was used, the water absorption amount was 2170 times, almost equivalent to that of Example 5. However, further improvement in water absorption can be expected by setting the ratio of ethylene glycol diglycidyl ether in the substance amount ratio to be lower. Therefore, when using ethylene glycol diglycidyl ether as a crosslinking agent, add 3 to 8 times, more preferably 3 to 6 times, ethylene glycol diglycidyl ether to the amount of carboxymethyl cellulose salt equivalent to glucose residues. It is preferable to do.

  Epichlorohydrin was allowed to act on sodium carboxymethylcellulose having different degrees of substitution and average molecular weight to obtain a polymer. Polymers were synthesized under the same conditions as in Example 1 except that the degree of substitution or average molecular weight of sodium carboxymethylcellulose was different (Examples 9 to 12, Comparative Examples 2 to 3). Table 3 shows the degree of substitution and the weight average molecular weight of sodium carboxymethylcellulose according to Examples 9-12 and Comparative Examples 2-3. For sodium carboxymethylcellulose synthesized from bleached pulp, sodium carboxymethylcellulose with different weight average molecular weight and degree of substitution was synthesized by adjusting temperature and reaction time based on the method described in Thermochimica Acta 494 (2009) 115-122. did.

In addition to the polymer of Example 1, the water absorption of the polymers of Examples 9 to 12 and Comparative Examples 2 to 3 was also examined. The results are shown in FIG. As can be seen from FIG. 5, the water absorption after 6 days from the start of the test of the polymer of the example showed a higher water absorption than the comparative example.
When the weight average molecular weight of sodium carboxymethylcellulose is 83,000 or more, an increase in water absorption can be confirmed as compared with the case where the weight average molecular weight is less than 83,000. In particular, the use of sodium carboxymethyl cellulose having a weight average molecular weight of 83,000 or more and a substitution degree in the range of 0.72 to 0.82 significantly increases the water absorption.

(Evaluation of liquid absorption for sodium chloride aqueous solution)
FIG. 6 is a graph showing the amount of liquid absorbed in a 10 mM sodium chloride aqueous solution for the polymers of Example 4 and Example 6. The polymer obtained by epichlorohydrin crosslinking (Example 4) and the polymer obtained by ethylene glycol diglycidyl ether crosslinking (Example 6) show higher liquid absorption than Comparative Example 1 (PANa). Showed superiority.
FIG. 7 shows the liquid absorbency of the polymers of Example 4 and Example 8 with respect to aqueous sodium chloride solutions (0.3%, 0.9%, and 3.8%) having different concentrations. From FIG. 7, at any concentration, the polymers of Examples 4 and 8 showed higher liquid absorption than Comparative Example 1 (PANa).

Furthermore, the polymers of Examples and Comparative Examples were produced using sodium carboxymethylcellulose having different substitution degrees and weight average molecular weights, and the liquid absorbability of these 10 mM sodium chloride aqueous solutions was confirmed.
Specifically, the polymers of Examples and Comparative Examples were obtained by allowing epichlorohydrin or ethylene glycol diglycidyl ether to act on sodium carboxymethylcellulose having the substitution degree and weight average molecular weight shown in Table 4. . When epichlorohydrin was used, a polymer was synthesized under the same conditions as in Example 4 except that the degree of substitution or weight average molecular weight of carboxymethyl cellulose sodium was different. Similarly, when ethylene glycol diglycidyl ether was used, a polymer was synthesized under the same conditions as in Example 6 except that the degree of substitution or weight average molecular weight of sodium carboxymethylcellulose was different. Regarding sodium carboxymethylcellulose synthesized from bleached pulp, sodium carboxymethylcellulose having a different weight average molecular weight and substitution degree was synthesized by adjusting the reaction time based on the method described in Thermochimica Acta 494 (2009) 115-122.
Table 4, FIG. 8, and FIG. 9 show the amount of liquid absorption after 4 days from the start of liquid absorption of each polymer. In FIG. 9, the horizontal axis represents the average degree of polymerization of the carboxymethyl cellulose salt corresponding to the weight average molecular weight (the degree of polymerization is also referred to as the CMC degree of polymerization).

  From Table 4, FIG. 8, and FIG. 9, it can be understood that when sodium carboxymethylcellulose has a substitution degree of 0.65 to 1.4 and a weight average molecular weight of 84,600 to 125,000, the liquid absorbency with respect to a 10 mM sodium chloride aqueous solution is greatly improved.

(Evaluation of liquid absorption for solutions containing other metal cations)
Moreover, the liquid absorptivity with respect to another metal cation aqueous solution was also confirmed. Specifically, using the polymer of Example 4 and the polymer of Example 6, various alkali metal ions ( ₁₁ Na ⁺ , ₁₉ K ⁺ ,
₅₅ Cs ⁺ ) aqueous solution, various alkaline earth metal ions ( ₁₂ Mg ²⁺ , ₂₀ Ca ²⁺ , ₂₈ Sr ²⁺ , ₅₆ Ba ²⁺ ) aqueous solution, and various divalent metal ions ( ₂₇ Co ²⁺ , ₂₅ Mn ^{2 +} , ₂₆ Fe ²⁺ , ₂₈ Ni ²⁺ , ₃₀ Zn ²⁺ , ₄₈ Cd ²⁺ ) solution was confirmed.
Various aqueous solutions were prepared by dissolving chlorides of each metal ion in pure water so that the metal ion concentration was 10 mM.

  The results are shown in FIGS. As can be understood from FIGS. 10 to 14, the polymers of Example 4 and Example 6 have high liquid absorption even for aqueous solutions of various alkali metal ions, various alkaline earth metal ions, and various divalent metal ions. Showed sex.

(Evaluation of water absorption for aqueous solutions with different acidities)
FIG. 15 shows the 0.1 mol / L citrate-sodium citrate buffer solution (pH 3.0), 0.1 mol / L acetic acid-sodium acetate buffer solution (pH 5.0), and 0.1 mol / L of the polymer of Example 4. It is a graph which shows the relationship between water absorption time and water absorption when using for water absorption of a glycine-sodium hydroxide buffer solution (pH 9.0). All salt concentrations were the same (0.1 mol / L) in order to evaluate the water absorption of the solution acidity.

  The water absorption capacity of the polymer is caused by the dissociation of the carboxylic acid sodium salt in the structure represented by the following chemical formula (2), and free sodium cations generate osmotic pressure to generate the water absorption capacity. The binding carboxylate anion functions to expand the volume of the material by electronic repulsion and retain water.

  In general organic molecules, the dissociation constant of carboxylic acid is about pKa = 4.0 to 4.6, and in the case of a water-absorbing polymer such as a polyacrylic acid copolymer, the amount of water absorption with respect to an acidic aqueous solution decreases rapidly. On the other hand, the polymer of Example 4 showed higher water absorption than the comparative example at any pH. That is, it became clear that it was possible to use it under an acidic aqueous solution that was difficult with conventional water-absorbing polymers.

  FIG. 16 shows a 0.1 mol / L citric acid-sodium citrate buffer solution (pH 3.0), 0.1 mol / L acetic acid-sodium acetate buffer solution of the polymer of Example 8 obtained by cross-linking with ethylene glycol diglycidyl ether. It is a graph which shows the relationship between water absorption time and the amount of water absorption when using for water absorption of (pH 5.0) and 0.1 mol / L glycine-sodium hydroxide buffer solution (pH 9.0). Similar to the polymer of Example 4 obtained by epichlorohydrin crosslinking, it showed a high water absorption with respect to the acidic aqueous solution, and it was revealed that it can be used under the acidic aqueous solution.

  FIG. 17 collectively shows the amount of water absorbed in the acidic aqueous solution after 3 days of water absorption for the polymers of Example 4 and Example 8. The polymer of Example 4 obtained by epichlorohydrin cross-linking exhibited a much higher water absorption than the comparative example for any acidic aqueous solution. In addition, the polymer of Example 8 obtained by cross-linking with ethylene glycol diglycidyl ether also showed higher water absorption than the comparative example with respect to the acidic solution.

(Evaluation of soil water retention effect)
In order to clarify the soil water retention effect of the polymer of the example, the polymer of the example was added to and mixed with the culture soil, and the water retention effect was tested. 1.2 g (0.1 wt) of the polymer of Example 4 in a mixture of 1080 g (90 wt%) of culture soil, 60 g of permiculite (made by Kitamatsu Ltd., 5 wt%), and 60 g of peat moss (made by Kitamatsu Ltd., 5 wt%) %) Was added and mixed well, and 600 mL of pure water was added to absorb water. The soil was collected at regular intervals, and the amount of water was measured using a halogen-type moisture meter.

  Similarly, the water content of the soil was measured by the same method except that the amount of polymer added was changed to 3.0 g (0.25 wt%) and 6.0 g (0.5 wt%).

FIG. 18 is a graph showing the measured soil water retention effect of the polymer of Example 4. In FIG. 18, each water amount after the passage of time when the water retention amount at the start of the test is taken as 100 is plotted.
In the absence of the polymer, only 71.3% water was retained after 11 days, whereas by adding only 0.1% of the polymer of the example, 78.4% water was retained, 7.1% The water retention effect was confirmed. In addition, with the increase in the amount of polymer added in Example 4, the soil water retention effect became remarkable, and after 11 days, 82.7% water was retained when 0.25% was added, and 85.6% water was retained when 0.5% was added.

(Examination of liquid absorbency to protein-containing liquid)
Example 1 and Example 5 high for aqueous solutions of bovine serum albumin (BSA: Wako Pure Chemical Industries) set to 1 mg / mL, 2 mg / mL, 5 mg / mL, 10 mg / mL and 25 mg / mL The amount of molecules absorbed was determined by JISK7223. As a comparative example, an acrylic acid-based water-absorbing polymer (Sun Wet IM930 manufactured by Sundia Polymer Co., Ltd., Comparative Example 1) was used.

The results are shown in FIGS. FIG. 19 shows the liquid absorption amount of the polymer of Example 1 with respect to the BSA aqueous solution. FIG. 20 shows the liquid absorption amount of the polymer of Example 5 with respect to the BSA aqueous solution. FIG. 21 shows the liquid absorption amount of the acrylic acid-based aqueous polymer.
As can be understood from FIGS. 19 to 21, the polymers of Example 1 and Example 5 exhibited high absorption characteristics with respect to the protein-containing solution (BSA aqueous solution).

Milk (Snow Brand Megmilk Milk, Protein 33.0mg / mL), Milk Powder (Wakodo Co., Ltd., Formula Milk Powder “Yes Yes”, Protein 15.2mg / mL) solution was also absorbed using the polymers of Example 1 and Example 5. Sex was evaluated. Evaluation was performed based on JIS K7223.
The results are shown in FIGS. 22 and 23. For the milk and powdered milk solutions that are high protein aqueous solutions, the polymers of Example 1 and Example 5 showed higher liquid absorbency than the comparative example.
The acrylic acid-based water-absorbing polymer of the comparative example absorbs liquid after the start of liquid absorption, but after a few hours, it aggregates with proteins and the like, and the liquid absorption amount rapidly decreases. On the other hand, the polymers of Example 1 and Example 5 show stable liquid absorption after the liquid absorption starts and do not aggregate. Therefore, it was clarified that the polymers of Examples have high liquid absorbency with respect to solutions containing proteins such as milk.

Claims (8)

Crosslinking a carboxymethyl cellulose salt having a degree of substitution of 0.65 to 1.4 and a weight average molecular weight of 84,600 to 125,000 with an epoxy compound ,
The epoxy compound is epichlorohydrin;
A water-absorbing and liquid-absorbing polymer capable of absorbing a solution containing a metal cation and a protein-containing solution, wherein the substance amount of epichlorohydrin is 5 to 8 times that of the carboxymethyl cellulose salt in terms of glucose residue Manufacturing method.   The method for producing a water-absorbing and liquid-absorbing polymer according to claim 1, wherein the substance amount of epichlorohydrin is 5 to 6 times the glucose residue equivalent substance amount of carboxymethylcellulose salt. Crosslinking a carboxymethyl cellulose salt having a degree of substitution of 0.65 to 1.4 and a weight average molecular weight of 84,600 to 125,000 with an epoxy compound ,
The epoxy compound is ethylene glycol diglycidyl ether;
The amount of ethylene glycol diglycidyl ether is 3 to 8 times the amount of carboxymethyl cellulose salt equivalent to glucose residue, and can absorb solutions containing metal cations and protein-containing solutions. Method for producing molecules . The method for producing a water-absorbing and liquid-absorbing polymer according to claim 3, wherein the amount of ethylene glycol diglycidyl ether is 3 to 6 times the amount of carboxymethylcellulose salt converted to glucose residues. The degree of substitution of the carboxymethyl cellulose salt is 0.72 to 0.99, and the weight average molecular weight is 84,600 to 112,000, The water absorption and liquid absorption according to any one of claims 1 to 4 For producing a conductive polymer . The degree of substitution of the carboxymethylcellulose salt is 0.72 to 0.82, and the weight average molecular weight is 84,600 to 112,000, The water absorption and liquid absorption according to any one of claims 1 to 4 For producing a conductive polymer . The method for producing a water-absorbing and liquid-absorbing polymer according to claim 6 , wherein the carboxymethylcellulose salt has a weight average molecular weight of 84,600 to 111,000 . The method for producing a water-absorbing or liquid-absorbing polymer according to any one of claims 1 to 7, wherein the carboxymethylcellulose salt is sodium carboxymethylcellulose .

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