JP5405786B2 - Method for producing acid-type carboxymethylcellulose - Google Patents

Description

  The present invention relates to a method for producing acid-type carboxymethylcellulose, and acid-type carboxymethylcellulose produced by the method.

  Carboxymethyl cellulose can be produced by reacting cellulose contained in pulp or the like with sodium hydroxide and monochloroacetic acid. Around 1950, when this technology was developed, water was used as a solvent for this reaction. However, as the production scale increased, treatment of a large amount of wastewater became a problem. However, an organic solvent method that can be performed in a closed system using an organic solvent has been developed, and carboxymethyl cellulose can be stably produced in large quantities. At present, carboxymethylcellulose is widely used as a thickener, adhesive, etc. from the food field to civil engineering construction because it is very inexpensive and easy to handle and safe because it is water-soluble. .

  As can be seen from the fact that it is water-soluble and the production conditions described above, the commonly distributed carboxymethyl cellulose is a sodium salt (hereinafter, the sodium salt of carboxymethyl cellulose is abbreviated as “CMC-Na”).

  On the other hand, carboxymethylcellulose having a carboxy group as it is (hereinafter sometimes abbreviated as “CMC-H”) is not as common as CMC-Na because it is insoluble in neutral water. However, CMC-H itself is also used as a raw material for production such as calcium salt and ammonium salt. Therefore, a method for producing CMC-H is also being studied.

CMC-H is generally produced by a method in which a dilute sulfuric acid and an aqueous solution of CMC-Na are reacted to separate and acquire the resulting precipitate, and then excess sulfuric acid, sodium sulfate, and the like are removed by washing with water. However, due to the high cost of cleaning and wastewater treatment, it is currently produced only for special purposes. Moreover, in order to suppress the gelatinization at the time of an acid treatment like the technique of patent documents 1-2, an inorganic calcium salt etc. are added with an acid, or it treats with aldehydes before adding an acid. Improvement methods have been developed.
JP-A-4-314702 Japanese Patent Laid-Open No. 11-246601

  As described above, the production method of CMC-H has been studied so far. In any method, after exchanging sodium ions of CMC-Na with hydrogen ions using acid, excess acid or generated salt is used. It is assumed that these are removed by washing with water. Here, pure water such as deionized water or reverse osmosis filtered water can be used as washing water in laboratory-level production, but pure water is used in industrial mass synthesis due to cost problems. However, only tap water and groundwater are used.

However, tap water and well water contain various impurities even in trace amounts. For example, general tap water often contains several tens of ppm of sodium ions and chloride ions. As a result, the hydrogen ion of the carboxy group of CMC-H is ion-exchanged with sodium ion or the like to increase the hydrophilicity, and the efficiency of dehydration by filtration or the like may be reduced. Further, if water cannot be sufficiently removed at this stage, impurities contained in the cleaning water remain in the CMC. For example, when an ammonium salt of carboxymethyl cellulose (hereinafter abbreviated as “CMC-NH ₄ ”) is produced using such CMC-H as a raw material, the CMC-NH ₄ contains chloride ions as well as sodium ions. Become.

Furthermore, in general, CMC-H washed with tap water or the like can be sufficiently used, but a trace amount of impurities may cause a problem. For example, CMC-NH ₄ produced from CMC-H may be used as a binder in a battery electrode or as a viscosity modifier for an electrolyte solution in a secondary battery, but chloride ions remain in CMC-NH _4. If so, the battery function will be reduced. It is very difficult to completely remove this chloride ion when sodium ions remain in the raw material CMC-H. CMC-NH ₄ may be used as a matrix resin for paints, but if ions remain, it causes rust and peeling of the base metal. Furthermore, when alkali metal ions remain in CMC-NH ₄ , there is a problem that water resistance is impaired when used as a paint, an adhesive, a film material, or the like.

  Therefore, the problem to be solved by the present invention is to provide a method for producing acid-type carboxymethyl cellulose in which the content of impurities such as sodium ions is remarkably reduced even when inexpensive tap water or groundwater is used as washing water, and An object of the present invention is to provide a high-quality acid-type carboxymethylcellulose produced by the method and having a low impurity content.

  The present inventor has intensively studied to solve the above problems. As a result, even when inexpensive tap water or groundwater is used as the washing water, if the washing water is kept weakly acidic by adding carbon dioxide, the cation contained in the washing water will be CMC-H. It was found that carbon dioxide itself does not remain in CMC-H, and the present invention was completed.

  The method for producing acid-type carboxymethyl cellulose according to the present invention includes a step of obtaining a precipitate by reacting an aqueous solution of a salt of carboxymethyl cellulose with an acid, and a step of washing the obtained precipitate with water. It is characterized by adding carbon dioxide to water.

  The aqueous solution of the carboxymethylcellulose salt in the above method is preferably produced by a step of reacting a biomass-derived cellulose raw material, a base and monohalogenated acetic acid in an aqueous solvent. Generally, a commercially available salt of carboxymethyl cellulose is a powder granule, and since it is shortened or finely divided, it is difficult to filter, and it can be said that dehydration efficiency is low. On the other hand, when a salt of carboxymethyl cellulose obtained from a biomass-derived cellulose raw material is used, the dehydration efficiency is dramatically increased in combination with the original effect of the present invention. Moreover, the acid-type carboxymethyl cellulose produced from the biomass-derived cellulose raw material according to the present invention is extremely excellent in water resistance because of the long fibers.

  The acid-type carboxymethyl cellulose of the present invention is produced by the above method and has an alkali metal content of 1000 ppm or less.

  As the acid-type carboxymethyl cellulose, those having a water content of 40% by mass or more and 80% by mass or less and a carbon dioxide concentration in the contained water of 0.01 g / kg or more are suitable. Normal CMC products are dried in consideration of transportation costs. However, since the dried CMC-H has a low affinity for water or the like, the reactivity in the case of using an ammonia salt or the like is low. Therefore, it is better that the CMC product contains a certain amount of moisture. However, CMC products containing moisture are susceptible to spoilage during storage. However, CMC-H produced by the method of the present invention is difficult to rot because the contained water contains carbon dioxide.

  According to the method of the present invention, it is possible to efficiently produce high-quality acid-type carboxymethylcellulose having a significantly reduced impurity content even when inexpensive tap water or groundwater is used as washing water. Furthermore, a high-quality carboxymethylcellulose salt can be produced using the acid-type carboxymethylcellulose as a raw material.

For example, high-quality CMC-NH ₄ manufactured using CMC-H according to the present invention as a raw material is a material for films such as battery electrode binders, electrolyte solution viscosity modifiers, paints, adhesives, and semipermeable membranes. It is useful as a material for hollow fiber membranes. Moreover, high quality CMC-Li, CMC-K, CMC-Na, etc. can also be manufactured from CMC-H which concerns on this invention. In addition, it is also possible to produce high-quality CMC alkaline earth metal salt or CMC polyvalent metal salt from CMC-H according to the present invention. These are insoluble in water and can be used in various applications. For example, certain CMC polyvalent metal salts are useful as catalysts.

  Thus, according to this invention, very high quality CMC-H can be manufactured, and the high quality CMC-H which concerns on this invention becomes a raw material of high quality CMC salt. Such high quality CMC salts are very useful in various applications.

  The method for producing acid-type carboxymethylcellulose according to the present invention includes a step of obtaining a precipitate by reacting an aqueous solution of a salt of carboxymethylcellulose (hereinafter sometimes simply referred to as “CMC”) with an acid, and And a step of washing the precipitate with water, and adding carbon dioxide to the washing water. Hereinafter, the method of the present invention will be described in the order of execution.

(1) CMC salt aqueous solution adjustment step The CMC salt, which is a raw material for the method of the present invention, is not particularly limited as long as it is a salt of a monovalent metal or the like that is generally water-soluble. For example, alkali metal salts such as lithium salts, sodium salts, potassium salts, and ammonium salts can be used. Among these, alkali metal salts are preferably used because they can be easily prepared, and sodium salts are particularly preferably used because they are inexpensive and easily available.

  A commercially available salt of CMC may be used, or may be prepared separately. However, some commercially available salts of CMC may be finely divided or shortened, so that it is preferably prepared separately from a biomass-derived cellulose raw material. If the particles are made finer or shorter, the efficiency of dehydration is deteriorated, the impurity content may be increased, and the original fiber characteristics of cellulose may not be utilized.

  When a commercially available CMC salt is used, the CMC salt is simply dissolved in water. The water here does not need to be pure water such as distilled water or deionized water. If insoluble components are not mixed, tap water, well water, or water purified to some extent may be used.

  The concentration of the aqueous solution may be adjusted as appropriate, and may be, for example, about 5% by mass or more and 20% by mass or less.

  When preparing an aqueous solution of CMC salt from biomass-derived cellulose raw material, a conventional method can be used. That is, the cellulose may be converted into carboxymethyl ether by reacting a biomass-derived cellulose raw material, a base and monohalogenated acetic acid in an aqueous solvent.

  The kind of cellulose raw material derived from biomass is not particularly limited. For example, hemp, kenaf, sugar cane, corn stalks and leaves; coconut husks; rice husks; wood chip dust; pruned branches; waste wood; thinned wood, etc. are crushed to remove impurities such as decolorization and lignin . Moreover, since it is also possible to use pulp products, such as paper, toilet paper, and a kitchen towel, this invention can also be applied to recycling of biomass resources. Furthermore, high-quality pulp such as rayon, celluloid, cellophane, semipermeable membrane, and cotton yarn can be used as the cellulose raw material.

  In order to prepare an aqueous solution of CMC salt from a biomass-derived cellulose raw material, monohalogenated acetic acid and a base may be allowed to act on the cellulose raw material. More specifically, the cellulose raw material is first infiltrated into an alkaline water solvent having a mass ratio of 5 to 15 times. Add monohalogenated acetic acid and base to the infiltrate. The order of addition may be changed, and the cellulose raw material may first be infiltrated into monohalogenated acetic acid and / or an aqueous solution thereof, followed by aging by adding a base. The aging time is preferably 10 minutes or longer, and may be about one day or one week.

  As monohalogenated acetic acid, monochloroacetic acid, monobromoacetic acid, monoiodinated acetic acid can be used. As the base, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used.

  Cellulose is a polymer of glucose, and each glucose unit other than the terminal part has three hydroxyl groups. This hydroxyl group is substituted by a carboxymethyl group.

  The degree of carboxymethyl etherification can be adjusted by the amounts of monohalogenated acetic acid and base used. Specifically, the number of moles of glucose constituting the cellulose can be calculated from the mass of the cellulose raw material. Although it is difficult to etherify all the hydroxyl groups, monohalogenated acetic acid having a molar number of 3 times or more of the number of moles of glucose may be used when etherification is desired, and desired when appropriate etherification is desired. The monohalogenated acetic acid at a ratio of The ratio of etherification per molecule of glucose is sometimes referred to as the degree of etherification. Usually, the degree of etherification is about 0.5 or more and 2.5 or less, but the monohalogen used depending on the degree of etherification The amount of acetic acid chloride may be determined. The base may be used in an amount of about 0.9 to 1.2 mol times that of monohalogenated acetic acid. The base may be added as an aqueous solution of about 1% or more and 5% or less.

  What is necessary is just to adjust reaction temperature and reaction time suitably. The reaction temperature is preferably about 30 ° C. or higher, but the monohalogenated acetic acid is more likely to be decomposed as the temperature is higher. Usually, the reaction time is preferably about 5 hours or more and about 30 hours or less. However, when the reaction is performed at a relatively low temperature, the reaction may be performed slowly over several months. The progress of the reaction can be determined by the turbidity or transparency of the reaction solution. That is, when the reaction does not proceed sufficiently, the cellulose is not dissolved, so the turbidity of the reaction solution is high and the transparency is low. Therefore, determine the end point of the reaction by clarifying the relationship between the turbidity etc. of the reaction solution and the progress of the reaction by preliminary experiments, etc., obtaining the reaction solution sample and measuring its turbidity etc. Can do.

  After completion of the reaction, the produced CMC salt is soluble in water, and the reaction solution becomes a homogeneous solution. The solution can be used in the next step as it is.

(2) CMC-H production | generation process Next, precipitation of CMC-H is obtained by making the aqueous solution of the salt of CMC and an acid react.

Although the acid used here will not be restrict | limited especially if it is water-soluble inorganic salt, For example, a sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid etc. can be used, and a sulfuric acid is suitable in this. The amount used may be appropriately adjusted, but it is necessary to use a sufficient amount of acid to convert at least all of the —CO ₂ ^— groups to —CO ₂ H. Further, if the acid concentration is too low, gelation may occur, while if the acid concentration is too high, coloring may occur. Therefore, specifically, an acid having a concentration of about 0.1 N or more and about 2 N or less may be used in an amount of about 1.5 to 5 times that of the CMC salt aqueous solution.

  Specifically, it is preferable to add an aqueous solution of a salt of CMC little by little while stirring the acid. After the addition of the acid, the reaction mixture is further stirred slowly and then allowed to stand to obtain CMC-H precipitate.

  The produced precipitate is separated from the reaction solution. In order to reduce impurities such as cations as much as possible, the liquid should be removed as much as possible at this stage. The separation means is not particularly limited, and filtration, centrifugation, decantation, and combinations of two or more thereof can be used. However, since the quality may deteriorate when CMC-H is directly exposed to air, it is preferable to take care not to expose CMC-H to air in the solid-liquid separation process.

(3) Washing process In washing the obtained precipitate with washing water, carbon dioxide is added to the washing water.

  As the washing water, it is ideal to use pure water such as distilled water, deionized water, and reverse osmosis filtered water. However, in industrial large-scale synthesis of CMC-H, it is not realistic to use high-cost pure water as cleaning water. On the other hand, tap water and groundwater are low-cost, but in the prior art, when tap water or the like is used, ions contained as impurities may convert some of the carboxy groups in CMC-H into salts, or It adheres to CMC-H as an impurity. For example, sodium ions and chloride ions impair the properties of CMC-H, and iron ions and the like color CMC-H. However, according to the present invention, extremely high quality CMC-H can be efficiently produced even when tap water or the like is used as the cleaning water. However, if cost does not matter, it is possible to obtain high-quality CMC-H more easily by using pure water as the cleaning water.

  As a cleaning method, a conventional method can be used. For example, after the obtained CMC-H is separated and obtained, a cleaning solution is quickly added so that the CMC-H does not come into direct contact with air as much as possible, and then gently stirred until bubbles are removed. Then, the operation of dehydrating after standing still may be repeated several times. The amount of washing water to be used may be adjusted as appropriate, but it can usually be about 3 to 10 times the CMC-H precipitation. Further, the standing time of the mixture of the CMC-H precipitate and the washing water is preferably 10 minutes or more, and can be stored until the next step while being left standing.

  In the conventional method, the cation contained in the washing water is exchanged with the hydrogen ion of the carboxy group in CMC-H. As a result, the hydrophobicity of CMC-H is lowered, while hydrophilicity is manifested to cause stickiness, and the efficiency of the dehydration process is lowered. In addition, the CMC having improved hydrophilicity may be mixed in the washing water, requiring treatment. However, in the method of the present invention, carbon dioxide is added to the washing water, and the pH is about 4 or less, so that the carboxy group in CMC-H is hardly converted to a salt despite the presence of a cation. . Therefore, since the hydrophobicity of CMC-H is maintained, the efficiency of the dehydration process does not decrease.

  In the method of the present invention, carbon dioxide is added to the washing water. The specific method is not particularly limited, and a conventional method may be used. For example, carbon dioxide liquefied by high pressure can be added to the washing water as a liquid through a fine tube. In addition, gaseous carbon dioxide may be sufficiently blown into the washing water in advance. It is preferable that the washing water added with carbon dioxide is immediately added to CMC-H. Further, carbon dioxide may be added to the mixture of CMC-H and washing water. Further, when the mixture is allowed to stand after adding carbon dioxide to the washing water, the container may be sealed so that carbon dioxide does not evaporate.

  Since the solubility of carbon dioxide in the washing water greatly depends on the temperature, it is preferable that the temperature of the washing water is cooled to more than 0 ° C. and about 20 ° C. or less in order to increase the solubility. Although it is difficult to judge whether or not carbon dioxide in the cleaning liquid is substantially saturated, whether or not carbon dioxide is sufficiently added to the cleaning water depends on the pH of the cleaning water being about 4 or less. It can be easily confirmed.

  What is necessary is just to determine the frequency | count of washing | cleaning suitably. For example, the concentration of the cation contained in the cleaning water is quantitatively measured by atomic absorption analysis or ICP emission analysis, and the cleaning is repeated until the measured value of the cleaning liquid after use becomes equal to the measured value of the cleaning liquid before use. Moreover, you may confirm the effect of washing | cleaning by confirming presence of the cation contained in the washing | cleaning liquid after use qualitatively by flame reaction.

  When the washing water contains a cation, the cation remains in the CMC-H according to the amount of the washing water adhering to the washed CMC-H. Although such cations are very small, they will surely impair the product quality, so in order to obtain a higher quality CMC-H, the dehydration after thorough washing should be carried out thoroughly or in the last washing. Only pure water to which carbon dioxide is added may be used as cleaning water. Such pure water is preferably one whose electrical conductivity is close to 0.054 μS / cm of theoretical pure water.

(4) Drying process It is difficult to completely remove water from CMC-H by a general solid-liquid separation process, and CMC-H subjected to the solid-liquid separation process usually contains water. The CMC-H according to the present invention preferably contains water, but may be dried as necessary.

  In the case of drying, it can be heated at 60 ° C. or more and 120 ° C. or less for 1 hour or more and 6 hours or less. Alternatively, in order to suppress contact of CMC-H with air, it is preferable to dry under reduced pressure at about 20 ° C. or more and 100 ° C. or less for about 1 hour or more and about 6 hours or less.

  CMC-H obtained by the above method is a high-quality product in which the content of impurities such as cations is significantly reduced to a level not found in conventional products. In particular, the content of alkali metal used in the carboxymethyl etherification step, which inevitably remains in the conventional method, is significantly reduced. Specifically, the alkali metal content is 1000 ppm or less.

  The content of alkali metal remaining in CMC-H can be measured by the following method. That is, CMC-H is heated at 110 ° C. for 3 hours, and the mass of CMC-H is measured. Next, the organic component is burned by heating at 1100 ° C. for 3 hours to obtain ash. The obtained ash is added to concentrated hydrochloric acid, dissolved by heating, the solution is analyzed with an ICP spectrometer, the emission intensity of the alkali metal is measured, and the content can be determined by comparing with the intensity of the standard solution. .

  As CMC-H concerning this invention, what contains the water | moisture content of 40 to 80 mass% is preferable. Common CMC products are dried and take time to disperse in the solvent. However, if the water content is 40% by mass or more, it can be quickly used in the next step such as dispersion in a solvent, particularly in industrial mass production. On the other hand, when the water content exceeds 80% by mass, the product weight becomes excessively heavy, and the transportation cost may be a problem.

  The moisture content of CMC-H was measured accurately after the sample was precisely weighed and the moisture was completely removed by heating the sample at 110 ° C. for 3 hours in the same manner as the alkali metal content measurement. It can be calculated from

  The concentration of carbon dioxide in the water contained in the CMC-H according to the present invention is preferably 0.01 g / kg or more. Usually, when CMC contains moisture, rot during storage becomes a problem. However, since CMC-H according to the present invention is washed with washing water to which carbon dioxide is added, the contained water contains carbon dioxide in a predetermined value or more. If the concentration of carbon dioxide is 0.01 g / kg or more, the problem of decay hardly occurs. The concentration is more preferably 0.05 g / kg or more, and further preferably 0.1 g / kg or more. On the other hand, the upper limit of the concentration is not particularly limited, but is set to a saturation concentration or less.

  The carbon dioxide concentration in the water content of CMC-H can be measured as follows. First, after measuring the moisture content of the sample, the sample is heated to 40 to 100 ° C., and the generated gas is introduced into the calcium hydroxide solution. The resulting calcium carbonate is separated and dried and weighed. Thereby, since the amount of carbon dioxide generated from the water content of CMC-H can be determined, the carbon dioxide concentration in the water content can be calculated from the amount and the water content of the sample.

  As described above, the CMC-H according to the present invention is of high quality in which the content of impurities such as cations is remarkably reduced. Therefore, various CMC salts can be produced using CMC-H according to the present invention as a raw material. High-quality CMC salts are extremely useful as, for example, battery electrode binders, electrolyte solution viscosity modifiers, paints, adhesives, film materials, adhesives, and catalysts.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

  In the following experimental examples, the analysis conditions of the obtained CMC-H are as follows.

(1) Measurement of ash content After weighing about 10 g of CMC-H and precisely weighing it, the organic content is burned by heating at 1100 ° C for 3 hours, the remaining ash is quantified, and the ratio of ash to CMC-H Calculated. The ash obtained here is considered to be mainly impurities such as silicon, aluminum and iron contained in the raw material cellulose.

(2) Measurement of sodium ion content To the above ash (100 mg), concentrated hydrochloric acid (1 mL) was added and dissolved, and the solution was analyzed with an ICP emission analyzer (product name “ICPS-7000”, manufactured by Shimadzu Corporation). The luminescence intensity of sodium was measured. By comparing the obtained results with the luminescence intensity of the standard solution, the ratio of sodium ions contained in CMC-H was calculated.

(3) Water resistance performance test CMC-H (200 g), 25% aqueous ammonia (10 mL) and water (200 g) were placed in a polyethylene bag and allowed to stand overnight to obtain a viscous liquid. The amount of ammonia water used corresponds to an amount that neutralizes the carboxy group of CMC-H by about 60%. A cedar board having a thickness of 1 mm was cut into a square having a side of 10 cm. Two such cedar boards were prepared, and the viscous liquid obtained on one side was applied and pasted together, and then naturally dried for 3 days in a well-ventilated place, and further heated and dried at about 50 ° C. for 30 minutes.

  The cedar boards bonded together were immersed in tap water at 20 ° C. for one week, and then the adhesion was observed. A case where no peeling occurred was judged as ◎, a case where peeling occurred only in a part, ○, and a case where peeling completely occurred was judged as ×.

Example 1
CMC-Na (Wako Pure Chemical Industries, 100 g) was put in a polyethylene bag, and tap water (900 g) was further added. CMC-Na aqueous solution was obtained by leaving the bag moderately and leaving it still. 1N sulfuric acid (3 kg) was mixed with the aqueous solution. When the bag was moderately thawed and allowed to stand overnight, a white fine fibrous precipitate consisting of CMC-H was produced.

  The supernatant was removed by decantation to obtain a slurry. Separately, when carbon dioxide gas was passed through tap water (10 L) at a flow rate of about 25 L / min, the pH was 3.8. The tap water was quickly added to the slurry. Further, carbon dioxide gas was blown into the slurry at a flow rate of about 5 L / min, and timely stirring was performed, and then the bag was sealed and allowed to stand for 10 minutes. The supernatant was then gently removed so that the precipitate did not rise. The above operations of adding the cleaning solution, bubbling carbon dioxide and stirring, standing, and removing the cleaning solution were repeated three times. Next, the obtained CMC-H was dehydrated by filtration under reduced pressure and stored in a carbon dioxide sealed container.

  The pH of the used cleaning liquid after the first cleaning is 0.54. When the cleaning liquid is held over a gas burner for a clean teaspoon, a bright yellow flame reaction caused by sodium is observed. It was. On the other hand, the pH of the used cleaning liquid after the final cleaning was 4, and its flame reaction was weak. Moreover, after each cleaning treatment, the cleaning liquid could be removed without any particular problem.

Comparative Example 1
CMC-H was produced in the same manner as in Example 1 except that carbon dioxide gas was not blown into the cleaning liquid.

  As a result, CMC-H hardly precipitated after each washing treatment, and the supernatant separated by decantation was cloudy. When the transparency of each supernatant was measured with a fluorometer (manufactured by Optex, product name “TP-M100-5”), the transparency was 10 cm or less, and CMC with reduced hydrophobicity was obtained as a supernatant. It was observed that it was dispersed in the liquid. In addition, flame reaction was observed in the used cleaning liquid after the final cleaning.

Example 2
Deionized water was obtained by purifying the tap water with a cartridge type water purifier (manufactured by Organo). The water purifier is a mixed bed type having a cation exchange resin and an anion exchange resin, and can remove both cations and anions present in tap water. When the conductivity of the deionized water obtained was measured with a portable conductivity meter (manufactured by Yokogawa Electric Corporation), it was 0.5 μS / cm, and the deionized water was pure water containing almost no ions. I found out.

  In Example 1, CMC-H was produced in the same manner except that the pure water was used as the washing water. As a result, the cleaning liquid could be removed without any problem after each cleaning process.

Examples 3-5
As a cellulose raw material, a high-quality kitchen towel, a normal-quality kitchen towel, or toilet paper containing recycled pulp was used from commonly available daily items. Assuming that these cellulose raw materials consist only of cellulose, a reaction for carboxymethyl etherification of two of the three hydroxyl groups of each glucose unit constituting each cellulose raw material was performed. Specifically, each cellulose raw material (162 g) was put in a separate polyethylene bag, a sufficient amount of water (162 g) was added to immerse all the cellulose raw materials, and left for 1 hour. Next, monochloroacetic acid (63 g) was added to thoroughly dissolve the cellulose raw material, and allowed to stand overnight. Next, sodium hydroxide in the same mole as the added monochloroacetic acid was added. When the exotherm began, the reaction mixture was cooled with cold water. After the exotherm had subsided, the polyethylene bag was soaked in a 40 ° C. water bath for 1 hour to allow the reaction to proceed. Further, the hot water heater was turned off and aged overnight while immersed in the hot water bath to obtain an aqueous solution of CMC-Na.

  CMC-H was produced in the same manner as in Example 1 except that the obtained CMC-Na aqueous solution was used. As a result, regardless of which cellulose raw material was used, the cleaning liquid could be removed very efficiently after each cleaning treatment. This is because CMC-Na obtained from a biomass-derived cellulose raw material is relatively bulky and has good water drainage because treatments such as miniaturization and fiber shortening are not performed unlike commercially available CMC-Na. it is conceivable that.

Comparative Example 2
In the same manner as in Examples 3 to 5, a CMC-Na aqueous solution was obtained from a high-quality kitchen towel. CMC-H was produced in the same manner as in Example 1 except that the obtained CMC-Na aqueous solution was used and carbon dioxide gas was not blown into the cleaning liquid.

  As a result, CMC-H hardly precipitated after each cleaning treatment, and it took a very long time to remove the used cleaning liquid. In addition, flame reaction was observed in the used cleaning liquid after the final cleaning.

  The results of analyzing the CMC-H produced above are shown in Table 1.

As described above, in Comparative Examples 1 and 2, it was difficult for CMC-H to precipitate after each cleaning treatment, and it took a very long time to remove the used cleaning liquid. In addition, sodium ions contained in the used cleaning solution did not disappear after three washes. This is thought to be due to the fact that sodium ions are chemically bonded to CMC-H as -CO ₂ Na rather than adhering to CMC-H, thereby increasing the hydrophilicity of CMC-H. It is done. Moreover, the sodium ion content of CMC-H obtained in Comparative Examples 1 and 2 exceeds 10,000 ppm.

On the other hand, the sodium ion content contained in CMC-H produced by the method of the present invention is 1,000 ppm or less, which is very high quality. Moreover, it is considered that the —CO ₂ H group is maintained, but the hydrophobicity is sufficiently maintained in the CMC-H produced by the method of the present invention, and the efficiency of the solid-liquid separation treatment is extremely high. . Therefore, it was demonstrated that extremely high quality CMC-H can be efficiently produced by the method of the present invention.

Claims (3)

A method for producing acid-type carboxymethylcellulose, comprising:
A process comprising: obtaining a precipitate by reacting an aqueous solution of a salt of carboxymethyl cellulose with an acid; and washing the resulting precipitate with washing water; and adding carbon dioxide to the washing water. Method.   The manufacturing method of Claim 1 including the process of obtaining the aqueous solution of the salt of carboxymethylcellulose by making the cellulose raw material derived from biomass, a base, and monohalogenated acetic acid react in an aqueous solvent. Produced by the method according to claim 1 or 2 state, and are the 1000ppm or less A alkali metal content, moisture content 40% by mass or more and 80 mass% or less, and carbon dioxide concentration in water containing 0. acid type carboxymethyl cellulose, characterized in der Rukoto or 01G / kg.