JP2020165064A - Manufacturing method of phosphorus-oxo acid-oxidized pulp - Google Patents

Abstract

To provide a manufacturing method of a phosphorus-oxo acid-oxidized pulp capable of sufficiently performing oxidization with phosphorus-oxo acid even when a recovered product using an unreacted phosphorus-oxo acid oxidizing agent recovered in a step after phosphorus-oxo acid oxidization is reused.SOLUTION: The invention relates to a manufacturing method of a phosphorus-oxo acid-oxidized pulp involving a step of oxidizing a pulp raw material using phosphorus-oxo acid in the presence of a condensation recovery product obtained by recovery and condensation of an unreacted phosphorus-oxo acid oxidizing agent recovered in a step after phosphorus-oxo acid oxidization reaction using a phosphorus-oxo acid oxidizing agent.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing phosphoroxo oxide pulp. Specifically, the present invention relates to a method for producing phosphoroxically oxidized pulp, which comprises a step of phosphorylooxidizing pulp using a recycled phosphorusoxo oxidizing agent.

In recent years, due to the substitution of petroleum resources and increasing environmental awareness, materials using reproducible natural fibers have been attracting attention. Among natural fibers, fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, particularly fibrous cellulose (pulp) derived from wood, has been widely used mainly as paper products. Further, as the fibrous cellulose, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known.

Fine fibrous cellulose can be produced by mechanically treating conventional cellulose fibers, but the cellulose fibers are strongly bonded to each other by hydrogen bonds. Therefore, a huge amount of energy is required to obtain fine fibrous cellulose by simply performing mechanical treatment. Therefore, in order to produce fine fibrous cellulose with less mechanical treatment energy, it is considered to perform pretreatment such as chemical treatment and biological treatment in addition to mechanical treatment. In particular, when a hydrophilic functional group (for example, a carboxyl group, a cation group, a phosphoric acid group, etc.) is introduced into a hydroxy group on the surface of cellulose by chemical treatment, electrical repulsion between ions occurs and the ions are hydrated. By doing so, the dispersibility in an aqueous solvent is remarkably improved. Therefore, the energy efficiency of miniaturization is higher than that in the case where no chemical treatment is performed.

For example, Patent Documents 1 and 2 disclose methods for producing phosphorylated fine fibrous cellulose and phosphorylated fine fibrous cellulose in which a phosphoric acid group forms an ester with a hydroxy group of cellulose. Further, Patent Document 3 discloses a method for producing a phosphorylated pulp which is used for a phosphorylation reaction of a polysaccharide by recovering an unreacted phosphorylating agent recovered after a phosphorylation reaction of a polysaccharide with a phosphorylating agent. There is.

International Publication No. 2013/073652 International Publication No. 2014/185505 JP-A-2017-179104

In the step of phosphorus oxo oxidation of pulp such as cellulose fiber, a reagent containing a large amount of phosphorus or urea is used. Although some of the reagents are unreacted, they are often disposed of, and there is concern that the treatment cost of wastewater generated after the phosphorus oxo oxidation step will increase. Further, as in Patent Document 3, studies on reusing unreacted phosphorus oxo oxidants have been advanced, but there are cases where the phosphor oxo oxidation of pulp does not proceed sufficiently simply by reusing the recovered product.

Therefore, in order to solve the problems of the prior art, the present inventors have reused the recovered product containing the unreacted phosphorus oxo oxidizing agent, which is recovered in the step after the phosphorus oxo oxidation reaction. , The study was carried out for the purpose of providing a method for producing a phosphorus oxo oxide pulp capable of sufficiently advancing the phosphorus oxo oxidation.

As a result of diligent studies to solve the above problems, the present inventors can reuse the recovered product containing the unreacted phosphorus oxo oxidant, which is recovered in the step after the phosphorus oxo oxidation reaction, by concentrating it. It has been found that the phosphorus oxo oxidation reaction of pulp can be sufficiently allowed to proceed even when a phosphorus oxo oxidizing agent is used.
Specifically, the present invention has the following configuration.

[1] A phosphorus oxo including a step of phosphorus oxo oxidation of a pulp raw material in the presence of a concentrated recovery product obtained by concentrating a recovery product containing an unreacted phosphorus oxo oxidant, which is recovered in a step after the phosphorus oxo oxidation reaction with a phosphorus oxo oxidizing agent. Method for producing oxidized pulp.
[2] The method for producing phosphoroxically oxidized pulp according to [1], wherein the concentrated recovered product is obtained by concentrating the recovered product by at least one method selected from circulation concentration, membrane concentration and heat-reduced pressure concentration.
[3] The method for producing a phosphorus oxo oxidized pulp according to [1] or [2], wherein the phosphorus oxo oxidizing agent contains at least one selected from a phosphorus oxo acid and a phosphorus oxo acid salt and urea.
[4] The method for producing phosphoroxo-oxidized pulp according to any one of [1] to [3], wherein the phosphorus atom concentration is 0.40% by mass or more with respect to the total mass of the concentrated recovered product.
[5] The method for producing phosphoroxo oxide pulp according to any one of [1] to [4], wherein the nitrogen atom concentration is 0.70% by mass or more with respect to the total mass of the concentrated recovered product.
[6] A method for producing fine fibrous cellulose, which comprises a step of defibrating the phosphorus oxo oxidized pulp produced by the method for producing phosphorus oxo oxidized pulp according to any one of [1] to [5].

According to the production method of the present invention, even when a recycled phosphorus oxo oxidant is used, the phosphorus oxo oxidation reaction of the pulp can be sufficiently proceeded, and a pulp into which a desired amount of phosphorus oxo acid groups are introduced can be produced. can do.

FIG. 1 is a process diagram illustrating an aspect of the method for producing phosphoroxo-oxidized pulp of the present invention. FIG. 2 is a process diagram illustrating one aspect of the method for producing phosphoroxo-oxidized pulp of the present invention. FIG. 3 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a fibrous cellulose-containing slurry having a phosphoric acid group.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments.

(Manufacturing method of phosphorus oxo oxide pulp)
The present invention relates to a method for producing phosphoroxo oxide pulp. In the method for producing phosphorus oxo oxidized pulp of the present invention, the pulp raw material is used in the presence of a concentrated recovered product obtained by concentrating the recovered product containing the unreacted phosphorus oxo oxidant, which is recovered in the step after the phosphorus oxo oxidation reaction with the phosphorus oxo oxidizing agent. Includes a step of phosphorus oxo oxidation.

Since the method for producing phosphoroxically oxidized pulp of the present invention has the above-mentioned structure, the unreacted phosphoryloxidant recovered after the phosphorylooxidation reaction of pulp can be reused. Therefore, in the present invention, it is possible to reduce the treatment cost of wastewater discharged in the manufacturing process of phosphorus oxo oxide pulp. Further, in the present invention, since the phosphorus oxo oxidation reagent used in the process of producing the phosphorus oxo oxide pulp can be reused, the content of the phosphorus oxo oxidant in the waste liquid can be reduced, and the burden on the environment can be reduced. be able to. Furthermore, since the amount of a new phosphorus oxo oxidant used for the phosphorus oxo oxidation reaction of pulp can be reduced, it is possible to suppress the production cost of the phosphorus oxo oxide pulp.

Examples of pulp raw materials include wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, and is, for example, broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and unbleached kraft pulp (UKP). ) And chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP), etc. Examples include mechanical pulp. The non-wood pulp is not particularly limited, and examples thereof include cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. The deinking pulp is not particularly limited, and examples thereof include deinking pulp made from used paper. As the pulp, one of the above types may be used alone, or two or more types may be mixed and used.

<Linoxo oxidation process to obtain recovered product>
The step of producing the phosphorus oxo oxide pulp of the present invention includes a step of phosphorylating the pulp raw material. In this phosphorus oxo oxidation step, a concentrated recovery product obtained by concentrating the recovery product containing an unreacted phosphorus oxo oxidation agent, which is a recovery product recovered in another step after the phosphorus oxo oxidation reaction, is used. That is, in the process for producing the phosphorus oxo oxide pulp of the present invention, first, a phosphorus oxo oxidation step for obtaining a recovered product is performed.

The phosphorus oxo oxidant used in the phosphorus oxo oxidation reaction step for obtaining a recovered product contains a compound containing a phosphorus atom and capable of forming an ester bond with cellulose in pulp (hereinafter, also referred to as compound A). Compound A preferably has at least one selected from a phosphoric acid and a phosphoric acid salt. More specifically, the compound A includes, but is not limited to, phosphoric acid or a salt thereof, phosphorous acid or a salt thereof, dehydration condensed phosphoric acid or a salt thereof, and anhydrous phosphoric acid (diphosphorus pentoxide). As the phosphoric acid, those having various puritys can be used, and for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid can be used. Examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). The dehydration-condensed phosphoric acid is one in which two or more molecules of phosphoric acid are condensed by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphorous acids, dehydration-condensed phosphates include phosphoric acid, phosphorous acid or dehydration-condensed phosphoric acid lithium salts, sodium salts, potassium salts, ammonium salts, etc. It can be a sum. Of these, from the viewpoints that the introduction efficiency of phosphoric acid groups is high, the defibration efficiency is more likely to be improved in the defibration process described later, the cost is low, and it is easy to apply industrially, sodium phosphate and sodium phosphate A salt, a potassium salt of phosphoric acid, or an ammonium salt of phosphoric acid is preferable, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate is more preferable.

In the phosphorus oxo oxidation step for obtaining the recovered product, the reaction between the pulp raw material containing cellulose and Compound A is carried out in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “Compound B”). Is preferable. That is, the phosphorus oxo oxidizing agent is preferably an agent containing at least one selected from a phosphorus oxo acid and a phosphorus oxo acid salt and urea.

Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like. From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. Further, from the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

As an example of the method of allowing the compound A to act on the pulp raw material in the coexistence with the compound B, there is a method of mixing the compound A and the compound B with the pulp raw material in a dry state, a wet state or a slurry state. Of these, since the reaction uniformity is high, it is preferable to use a pulp raw material in a dry state or a wet state, and it is particularly preferable to use a pulp raw material in a dry state. The form of the pulp raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Examples of the compound A and the compound B include a method of adding the compound A and the compound B to the pulp raw material in the form of a powder or a solution dissolved in a solvent, or in a state of being heated to a melting point or higher and melted. Of these, since the reaction uniformity is high, it is preferable to add the solution in the form of a solution dissolved in a solvent, particularly in the state of an aqueous solution. Further, compound A and compound B may be added to the pulp raw material at the same time, may be added separately, or may be added as a mixture. The method of adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the pulp raw material may be immersed in the solution to absorb the liquid and then taken out, or the pulp raw material may be added. The solution may be dropped into the water. Further, the required amounts of compound A and compound B may be added to the pulp raw material, or after the excess amounts of compound A and compound B are added to the pulp raw material, respectively, the surplus compound A and compound B are added by pressing or filtering. It may be removed.

When the phosphorus oxo oxidizing agent is an agent containing compound A and compound B, the pH of the solution containing the phosphorus oxo oxidizing agent (the solution containing the phosphorus oxo oxidizing agent) is preferably 7 or less, more preferably 6 or less. The pH of the solution containing the phosphorus oxo oxidizing agent may be adjusted, for example, by using a compound having a phosphorus oxo acid group in combination with a compound showing acidity and a compound showing alkalinity, and changing the amount ratio thereof. The pH of the solution containing the phosphorus oxo oxidizing agent may be adjusted by adding an inorganic alkali or an organic alkali to a compound having a phosphorus oxo acid group and showing acidity.

The amount of compound A added to the pulp raw material is such that the amount of phosphorus atom added to the pulp raw material (absolute dry mass) is 0.5% by mass or more and 100% by mass or less when the amount of compound A added is converted to the phosphorus atomic weight. It is preferable, it is more preferably 1% by mass or more and 50% by mass or less, and further preferably 2% by mass or more and 30% by mass or less. Further, the addition amount of the compound B to the pulp raw material (absolute dry mass) is such that the addition amount of the nitrogen atom to the pulp raw material (absolute dry mass) is 5% by mass or more and 200 when the addition amount of the compound B is converted into the nitrogen atomic weight. It is preferably 20% by mass or more, more preferably 150% by mass or less, and further preferably 45% by mass or more and 100% by mass or less.

In the reaction between the pulp raw material containing cellulose and compound A, for example, amides or amines may be contained in the reaction system in addition to compound B. Examples of amides include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like. Among these, triethylamine is known to act as a good reaction catalyst.

In the phosphorus oxo oxidation step, it is preferable to add or mix compound A or the like to the pulp raw material and then heat-treat the pulp raw material. As the heat treatment temperature, it is preferable to select a temperature at which a phosphorus oxo acid group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 250 ° C. or lower, and further preferably 130 ° C. or higher and 200 ° C. or lower. In addition, equipment having various heat media can be used for the heat treatment, for example, a stirring drying device, a rotary drying device, a disk drying device, a roll type heating device, a plate type heating device, a fluidized layer drying device, and an air stream. A drying device, a vacuum drying device, an infrared heating device, a far infrared heating device, a microwave heating device, and a high frequency drying device can be used.

In the heat treatment according to the present embodiment, for example, compound A is added to a thin sheet-shaped pulp raw material by a method such as impregnation and then heated, or the pulp raw material and compound A are heated while kneading or stirring with a kneader or the like. Can be adopted. As a result, it becomes possible to suppress uneven concentration of the compound A in the pulp raw material and more uniformly introduce the phosphoroxo acid group onto the surface of the cellulose fiber contained in the pulp raw material. This is because when water molecules move to the surface of the pulp raw material due to drying, the dissolved compound A is attracted to the water molecules by surface tension and also moves to the surface of the pulp raw material (that is, uneven concentration of compound A is caused. It is considered that this is due to the fact that it can be suppressed.

Further, the heating device used for the heat treatment always keeps the water content retained by the slurry and the water content generated by the dehydration condensation (phosphate esterification) reaction between the compound A and the hydroxyl group contained in the cellulose or the like in the pulp raw material. It is preferable that the device can be discharged to the outside of the device system. Examples of such a heating device include a ventilation type oven and the like. By constantly discharging the water in the apparatus system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphate esterification, and also to suppress the acid hydrolysis of the sugar chain in the fiber. it can.

The heat treatment time is preferably 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and 10 seconds or more and 800 seconds or less after substantially removing water from the pulp raw material. Is more preferable.

After the above-mentioned phosphorus oxo oxidation reaction, the recovered product containing the unreacted phosphorus oxo oxidant is recovered. After the phosphorus oxo oxidation reaction, a reaction product is obtained, and the reaction product contains a phosphorus oxo oxide pulp and an unreacted phosphorus oxo oxidant. A recovered product is obtained by separating the solution containing the unreacted phosphorus oxo oxidant from the reaction product. For example, the reaction product can be filtered and the filtrate can be recovered to separate the solution containing the unreacted phosphorus oxo oxidant. The solution containing the unreacted phosphorus oxo oxidant can also be separated by centrifugal dehydration or squeezing of the reaction product.

<Concentration process>
In the production method of the present invention, after separating the solution containing the unreacted phosphorus oxo oxidant, a step of concentrating the recovered product is provided. Examples of the concentration step include a circulation concentration step, a membrane concentration step, a heat concentration step, a vacuum concentration step, a heat pressure reduction concentration step, and the like. Above all, the concentration step is preferably at least one step selected from a circulation concentration step, a membrane concentration step, and a heating / reducing pressure concentration step. That is, the concentrated recovery product obtained through the concentration step is at least one selected from circulation concentration, membrane concentration, and heat-decompression concentration of the recovery product recovered after separating the solution containing the unreacted phosphorus oxo oxidizing agent. It is preferable that it is obtained by concentrating by the method of. The concentration step may be a step in which two or more steps are combined.

In the circulation concentration step, the step of recovering the solution containing the unreacted phosphorus oxo oxidant is repeated by adding the recovered product obtained after separating the solution containing the unreacted phosphorus oxo oxidant to the pulp raw material which has been subjected to the phosphorus oxo oxidation treatment again. This is the process to be performed. That is, the unreacted phosphorus oxo oxidant remaining in the pulp raw material is washed away with the recovered product to increase the concentration of the unreacted phosphorus oxo oxidant in the recovered product recovered again. The number of circulations is preferably 3 or more, and more preferably 10 or more. The number of circulations is the number of times a solution containing a phosphorus oxo oxidizing agent is added to the pulp raw material. By setting the number of circulations within the above range, the concentration of the phosphorus oxo oxidant in the recovered product after concentration can be sufficiently increased.

In the membrane concentration step, a reverse osmosis (RO) membrane, a nanofiltration (NF) membrane, or the like can be used. Of these, reverse osmosis (RO) membranes are preferably used. The membrane treatment method adopted in the membrane concentration step is not particularly limited, and for example, a simple filtration method (total filtration method) in which treated water is supplied in a direction perpendicular to the membrane surface and a membrane surface. On the other hand, a cross-flow filtration method or the like in which treated water is supplied in parallel directions can be adopted.

In the heating and vacuum concentration step, the recovered product obtained after separating the solution containing the unreacted phosphorus oxo oxidant is heated and pressurized to volatilize the solvent for concentration. In the heating / reducing pressure concentrating step, for example, an evaporator, a vacuum concentrator, or the like can be used. The treatment temperature in the heating / reducing pressure concentration step is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, and even more preferably 40 ° C. or higher. The treatment temperature in the heating / reducing pressure concentration step is preferably 90 ° C. or lower. Further, the processing pressure in the heating / reducing pressure concentration step is preferably 1000 hPa or less, more preferably 500 hPa or less, and further preferably 200 hPa or less.

A concentrated and recovered product can be obtained by undergoing the concentration step as described above. The concentrated recovered product naturally contains an unreacted phosphorus oxo oxidant. That is, the concentrated recovered product contains at least one selected from phosphoric acid and phosphoroxoate. Here, the phosphorus atom concentration in the concentrated and recovered product is preferably 0.40% by mass or more, more preferably 0.50% by mass or more, and 1.00 by mass, based on the total mass of the concentrated and recovered product. It is more preferably mass% or more, more preferably 1.50 mass% or more, further preferably 2.00 mass% or more, and particularly preferably 2.50 mass% or more. The phosphorus atom concentration in the concentrated and recovered product is preferably 8% by mass or less with respect to the total mass of the concentrated and recovered product. By setting the phosphorus atom concentration in the concentrated recovered product within the above range, the phosphorus oxo oxidation reaction of pulp can be sufficiently proceeded even when a recycled phosphorus oxo oxidant is used, and a desired amount of phosphorus oxo acid groups can be allowed to proceed. It becomes easier to produce pulp in which is introduced.

A color reaction can be used to measure the phosphorus atom concentration. Specifically, the phosphorus atom concentration in the concentrated recovered product can be measured using a digital pack test for all phosphorus (manufactured by Kyoritsu RIKEN Co., Ltd.). Specifically, add 1 mL of a sample, 1 drop of R-1 reagent, and 0.5 mL of R-2 reagent to a pressure-resistant bottle and shake. After that, heating is continued for 30 minutes after steam begins to be emitted in the high-pressure decomposer. After 30 minutes, remove from the decomposer, cool to 20 ° C., add 4 drops of R-3 reagent, and shake. Put the whole amount of the prepared solution in a tube containing a color reagent, shake it several times, and then measure it by a digital pack test.

In addition, the concentrated recovered product contains urea. The nitrogen atom concentration in the concentrated recovered product is preferably 0.70% by mass or more, more preferably 1.00% by mass or more, and 3.00% by mass or more, based on the total mass of the concentrated recovered product. It is even more preferably 5.00% by mass or more, further preferably 10.00% by mass or more, and particularly preferably 12.00% by mass or more. Further, the nitrogen atom concentration in the concentrated recovered product is preferably 25% by mass or less with respect to the total mass of the concentrated recovered product. By setting the nitrogen atom concentration in the concentrated recovered product within the above range, the phosphoroxyoxidation reaction of pulp can be sufficiently proceeded even when a recycled phosphoroxooxidant is used, and a desired amount of phosphoroxoic acid groups can be promoted. It becomes easier to produce pulp in which

A color reaction can be used to measure the nitrogen atom concentration. Specifically, the nitrogen atom concentration in the concentrated recovered product can be measured using a digital pack test for total nitrogen (manufactured by Kyoritsu RIKEN Co., Ltd.). Specifically, add 1 mL of a sample, 1 drop of R-1 reagent, and 0.5 mL of R-2 reagent to a pressure-resistant bottle and shake. After that, heating is continued for 30 minutes after steam begins to be emitted in the high-pressure decomposer. After 30 minutes, remove from the decomposer, cool to 20 ° C., add 2 drops of R-3 reagent, and shake. Put the whole amount of the prepared solution in a tube containing a color reagent, shake for 1 minute, and then measure by digital pack test.

<Linoxo oxidation process>
The method for producing phosphoroxo-oxidized pulp of the present invention includes a step of phosphor-oxidizing a pulp raw material in the presence of a concentrated recovered product obtained through the above-mentioned steps. The reaction conditions in the step of phosphorylating the pulp raw material in the presence of the concentrated recovered product are preferably the same as the reaction conditions in the above-mentioned <phosphoroxo oxidation step for obtaining the recovered product>.

FIG. 1 is a process diagram illustrating an aspect of the method for producing phosphoroxo-oxidized pulp of the present invention. As shown in FIG. 1, in the method for producing phosphorus oxo oxidized pulp of the present invention, the recovered product recovered after the phosphorus oxo oxidation reaction of the pulp raw material with the phosphorus oxo oxidizing agent is concentrated, and the obtained concentrated recovered product is used as the pulp raw material. Includes the step of phosphooxidizing the pulp. As described above, the present invention relates to a method for producing phosphoroxo-oxidized pulp in the presence of a concentrated recovered product.

The recovered product is separated and recovered from the reaction product of the phosphorus oxo oxidation reaction. That is, the method for producing phosphorus oxo oxide pulp of the present invention includes a phosphorus oxo oxidation reaction step of the pulp raw material for obtaining a recovered product. The reaction product after undergoing the phosphorus oxo oxidation reaction step of the pulp raw material for obtaining the recovered product contains the phosphorus oxo oxide pulp and the unreacted phosphorus oxo oxidant, and is a solution containing the unreacted phosphorus oxo oxidant from the reaction product. The recovered product can be obtained by separating. That is, it is preferable to further include a step of separating the recovered product containing the unreacted phosphorus oxo oxidizing agent from the reaction product after the phosphorus oxo oxidation reaction of the pulp raw material for obtaining the recovered product. In the separation step, the recovered product is separated from the reaction product, and at the same time, the phosphorus oxo oxidized pulp obtained in the phosphorus oxo oxidation reaction step of the pulp raw material for obtaining the recovered product is also obtained.

The separation step is a step of separating the recovered product from the reaction product after the phosphorus oxo oxidation reaction of the pulp raw material for obtaining the recovered product described above. When the reaction product is in the form of a solid substance, a solvent such as ion-exchanged water is added to the reaction product in the separation step. Since the unreacted phosphorus oxo oxidizing agent and the like contained in the reaction product are dissolved in the added solvent, the recovered product can be obtained by uniformly stirring and filtering to obtain a liquid phase. When the reaction product is in the form of a slurry, solid-liquid separation can also be performed in the separation step. The recovered product can be obtained by filtering and obtaining a liquid phase in the solid-liquid separation step.

The recovered product recovered after the phosphorus oxo oxidation reaction contains an unreacted phosphorus oxo oxidant. That is, the recovered product contains a phosphorus oxo oxidizing agent that was not consumed in the phosphorus oxo oxidation reaction of the pulp raw material for obtaining the recovered product. Such a recovered product is again used for the phosphor oxo oxidation reaction of the pulp raw material. That is, the recovered product can be rephrased as a reusable phosphorus oxo oxidant-containing solution.

The recovered product will contain at least a part of the phosphorus oxo oxidizing agent used in the phosphorus oxo oxidation reaction step of the pulp raw material for obtaining the recovered product. As described above, since the phosphorus oxo oxidizing agent preferably contains at least one selected from phosphorus oxo acid and phosphorus oxo acid salt and urea, the recovered product is also selected from phosphorus oxo acid and phosphorus oxo acid salt. It is preferable that at least one of these and urea is contained.

FIG. 1 illustrates an embodiment in which the recovered product is concentrated and then returned to the upstream phosphorus oxo oxidation reaction step and used as a phosphorus oxo oxidant (phosphoroxo oxidant-containing solution). As shown in FIG. 1, the phosphorus oxo oxidation reaction of the pulp raw material is a continuous reaction, and the concentrated recovery product may be used as the phosphorus oxo oxidizing agent-containing solution from any stage of the continuous reaction. Although a phosphorus oxo oxidant may be newly added to the concentrated recovery product, it is preferable to use only the concentrated recovery product as the phosphorus oxo oxidant-containing solution.

The concentrated recovered product may be returned to the upstream phosphorus oxo oxidation reaction step again, or may be used as a phosphorus oxo oxidant-containing solution in another phosphorus oxo oxidation reaction step. FIG. 2 is a process diagram illustrating a case where the concentrated recovered product is used in another phosphorus oxo oxidation reaction step. In FIG. 2, first, the first phosphorus oxo oxidation reaction of the first pulp raw material is carried out by the phosphorus oxo oxidizing agent. As the reaction product of the first phosphorus oxo oxidation reaction, an unreacted phosphorus oxo oxidizing agent and the first phosphorus oxo oxide pulp are obtained, and in the first separation step, the recovered product is recovered and the recovered product is concentrated. Next, the obtained concentrated and recovered product is used as a phosphorus oxo oxidizing agent-containing solution of the second pulp raw material, and a second phosphorus oxo oxidation reaction is carried out. After the second phosphorus oxo oxidation reaction, an unreacted phosphorus oxo oxidant and a second phosphorus oxo oxide pulp are obtained as reaction products, and in the second separation step, the recovered product is recovered again and concentrated. In the second separation step, a second phosphorus oxo oxide pulp is obtained at the same time as the recovery of the concentrated recovered product. The present invention relates to such a method for producing a second phosphorus oxo oxide pulp.

When the present invention is a method for producing phosphoroxo-oxidized pulp including the steps shown in FIG. 2, the first pulp raw material and the second pulp raw material may be of the same type or different types. .. Further, the reaction conditions of the first phosphorus oxo oxidation reaction step and the second phosphorus oxo oxidation reaction step may be the same conditions or different conditions.

Although not shown in FIG. 2, the concentrated recovered product recovered in the second separation step may be further used as a phosphorus oxo oxidizing agent-containing solution of the third pulp raw material. In this case, an unreacted phosphorus oxo oxidant and a third phosphorus oxo oxide pulp are obtained as reaction products of the third phosphorus oxo oxidation reaction, and in the third separation step, they are separated into a concentrated recovered product and a third phosphorus oxo oxide pulp. To. As described above, the concentrated recovered product recovered by the phosphorus oxo oxidation reaction of the pulp raw material may be reused a plurality of times.

In the step of phosphorus oxo oxidation of the pulp raw material in the presence of the concentrated recovered product, when the amount of the concentrated recovered product added is converted into the phosphorus atomic weight contained in the recovered product, the amount of phosphorus atom added to the pulp raw material (absolute dry mass) is calculated. It is preferably 0.5% by mass or more and 100% by mass or less, more preferably 1.0% by mass or more and 50% by mass or less, and further preferably 2% by mass or more and 30% by mass or less. The amount of nitrogen atoms added to the pulp raw material (absolute dry mass) is preferably 5% by mass or more and 200% by mass or less, more preferably 20% by mass or more and 150% by mass or less, and 45% by mass or more and 100%. It is more preferably mass% or less. When the amount of phosphorus atom and nitrogen atom added to the pulp raw material is within the above range, the pulp raw material can be efficiently phosphorylated.

The step of phosphoroxooxidizing the pulp raw material in the presence of the concentrated recovered material may be performed at least once, but may be repeated a plurality of times. In this case, it is preferable because more phosphorus oxo acid groups are introduced. Further, in the present invention, in order to further increase the concentration of the phosphorus oxo oxidant in the concentrated recovered product, a phosphorus oxo oxidant may be added separately from the recovered product, and another additive may be added separately from the phosphorus oxo oxidant. May be good.

<Washing process>
A washing step may be provided after the phosphorus oxo oxidation step, if necessary. The washing step is performed, for example, by washing the phosphorus oxo oxide pulp with water or an organic solvent. Further, the cleaning step may be performed after each step described later, and the number of cleanings performed in each cleaning step is not particularly limited.

<Alkaline treatment process>
If necessary, an alkali treatment step may be provided after the phosphorus oxo oxidation step. The alkaline treatment method is not particularly limited, and examples thereof include a method of immersing phosphorusoxo oxide pulp in an alkaline solution.

The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In the present embodiment, for example, sodium hydroxide or potassium hydroxide is preferably used as the alkaline compound because of its high versatility. Further, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.

The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5 ° C. or higher and 80 ° C. or lower, and more preferably 10 ° C. or higher and 60 ° C. or lower. The immersion time of the phosphorus oxo oxide pulp in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the phosphorus oxo oxide pulp. Is more preferable.

In order to reduce the amount of the alkaline solution used in the alkaline treatment step, it is preferable to provide a cleaning step after the phosphorus oxo oxidation step and before the alkaline treatment step.

<Acid treatment process>
An acid treatment step may be provided after the phosphorus oxo oxidation step, if necessary. For example, the phosphorus oxo oxidation step, the acid treatment, and the alkali treatment may be performed in this order.

The method of acid treatment is not particularly limited, and examples thereof include a method of immersing phosphorusoxo oxide pulp in an acidic solution containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably 10% by mass or less, and more preferably 5% by mass or less, for example. The pH of the acidic solution used is not particularly limited, but is preferably 0 or more and 4 or less, and more preferably 1 or more and 3 or less. As the acid contained in the acidic solution, for example, an inorganic acid, a sulfonic acid, a carboxylic acid or the like can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chloric acid, chloric acid, perchloric acid, phosphoric acid, boric acid and the like. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid and the like. Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid and the like. Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more and 120 minutes or less, and more preferably 10 minutes or more and 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1,000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the phosphorus oxo oxide pulp. Is more preferable.

<Other processes>
In the process for producing phosphoroxo-oxidized pulp, a filtration step may be further provided in addition to the above-mentioned steps. In the filtration step, foreign substances, suspended solids (SS) and the like in the dispersion can be removed by using a filter medium such as a filter. As the filter, for example, a ceramic filter can be used. Further, it is also preferable to use microfiltration (MF membrane) and ultrafiltration (UF membrane) in the filtration step.

(Linoxo oxide pulp)
The present invention may relate to the phosphorus oxo oxide pulp produced by the method for producing the phosphorus oxo oxide pulp described above. The phosphorus oxo oxide pulp has a phosphorus oxo acid group. In addition, in this specification, a phosphorus oxo acid group also includes a substituent derived from a phosphorus oxo acid group.

The phosphoroxo acid group is, for example, a substituent represented by the following formula (1). The phosphorus oxo acid group is, for example, a divalent functional group obtained by removing a hydroxy group from phosphoric acid. Specifically, it is a group represented by −PO ₃ H ₂ . The phosphorus oxo acid group also includes a substituent derived from the phosphorus oxo acid group, and the substituent derived from the phosphorus oxo acid group includes a substituent such as a salt of the phosphorus oxo acid group and a phosphorus oxo acid ester group. The substituent derived from the phosphoric acid group may be contained in the phosphoric oxide pulp as a group in which the phosphoric acid group is condensed (for example, a pyrophosphate group). Further, the phosphorous acid group may be, for example, a phosphorous acid group (phosphonic acid group), and the substituent derived from the phosphorous acid group may be a salt of the phosphorous acid group or the like.

In the formula (1), a, b and n are natural numbers, and m is an arbitrary number (where a = b × m). ^{α 1, α 2, ···,} a number of alpha ⁿ and alpha 'is O ^- a and the remainder is either R, the OR. It is also possible that all of each α ⁿ and α'are O ⁻ . R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, and an unsaturated-branched chain hydrocarbon, respectively. A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. Further, in the formula (1), n is preferably 1.

Examples of the saturated-linear hydrocarbon group include, but are not limited to, a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like. Examples of the saturated-branched chain hydrocarbon group include an i-propyl group and a t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentyl group, a cyclohexyl group and the like. Examples of the unsaturated-linear hydrocarbon group include a vinyl group, an allyl group and the like, but are not particularly limited. Examples of the unsaturated-branched chain hydrocarbon group include an i-propenyl group and a 3-butenyl group, but are not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentenyl group, a cyclohexenyl group and the like. Examples of the aromatic group include a phenyl group and a naphthyl group, but are not particularly limited.

Further, as the inducing group in R, a functional group in which at least one of functional groups such as a carboxy group, a hydroxy group, or an amino group is added or substituted with respect to the main chain or side chain of the above-mentioned various hydrocarbon groups. The group is mentioned, but is not particularly limited. The number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less.

β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include aliphatic ammonium or aromatic ammonium, and examples of monovalent or higher valent cations composed of inorganic substances include ions of alkali metals such as sodium, potassium, and lithium. Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions, and the like, but the present invention is not particularly limited. These may be applied alone or in combination of two or more. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion which is hard to yellow when the pulp raw material containing β is heated and is easily industrially used, but is not particularly limited. Note that β ^{b +} may be an organic onium ion.

The amount of the phosphorus oxo acid group introduced into the phosphorus oxo oxide pulp is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g per 1 g (mass) of the phosphorus oxo oxide pulp, for example. It is more preferably g or more, and particularly preferably 1.00 mmol / g or more. The amount of the phosphorus oxo acid group introduced into the phosphorus oxo oxide pulp is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of the phosphorus oxo oxide pulp, for example. It is more preferably 50 mmol / g or less, and particularly preferably 3.00 mmol / g or less. In the production method of the present invention, it is particularly preferable to concentrate the recovered product so that the amount of the phosphorus oxo acid group introduced into the phosphorus oxo oxide pulp can be 1.00 mmol / g or more. By setting the amount of the phosphorus oxo acid group introduced within the above range, when the phosphorus oxo oxide pulp is miniaturized, the miniaturization can be facilitated and the stability of the fine fibrous cellulose can be enhanced. Become. Here, the denominator in the unit mmol / g indicates the mass of the phosphorus oxo oxide pulp when the counter ion of the phosphorus oxo acid group is a hydrogen ion (H ⁺ ).

The amount of the phosphorus oxo acid group introduced into the phosphorus oxo oxide pulp can be measured by, for example, a neutralization titration method. In the measurement by the neutralization titration method, the introduction amount is measured by determining the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing the phosphorus oxo oxide pulp.

FIG. 3 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a slurry containing a phosphorus oxo oxide pulp having a phosphorus oxo acid group. The amount of the phosphorus oxo acid group introduced into the phosphorus oxo oxide pulp is measured, for example, as follows.
First, the slurry containing the phosphorus oxo oxide pulp is treated with a strongly acidic ion exchange resin. If necessary, the same defibration treatment as the defibration treatment step described later may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin.
Next, the change in pH is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in the upper part of FIG. 3 is obtained. The titration curve shown in the upper part of FIG. 3 plots the measured pH with respect to the amount of alkali added, and the titration curve shown in the lower part of FIG. 3 plots the pH with respect to the amount of alkali added. The increment (differential value) (1 / mmol) is plotted. In this neutralization titration, two points are confirmed in which the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point. The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociated acid of the phosphorus oxo oxide pulp contained in the slurry used for titration, and the amount of alkali required from the first end point to the second end point. The amount is equal to the amount of the second dissociated acid of the phosphorus oxo oxide pulp contained in the slurry used for the titration, and the amount of alkali required from the start to the second end point of the titration is the phosphorus oxo oxide pulp contained in the slurry used for the titration. Is equal to the total amount of dissociated acid. Then, the value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated is the amount of phosphorus oxo acid group introduced (mmol / g). The amount of phosphorus oxo acid group introduced (or the amount of phosphorus oxo acid group) simply means the amount of the first dissociated acid.
In FIG. 3, the region from the start of titration to the first end point is referred to as a first region, and the region from the first end point to the second end point is referred to as a second region. For example, when the phosphoric acid group is a phosphoric acid group and the phosphoric acid group causes condensation, the amount of weakly acidic groups in the phosphoric acid group (also referred to as the second dissociated acid amount in the present specification) is apparently It decreases, and the amount of alkali required for the second region is smaller than the amount of alkali required for the first region. On the other hand, the amount of strongly acidic groups in the phosphorus oxo acid group (also referred to as the first dissociated acid amount in the present specification) is the same as the amount of phosphorus atoms regardless of the presence or absence of condensation. Further, when the phosphorous acid group is a phosphorous acid group, the weakly acidic group does not exist in the phosphorous acid group, so that the amount of alkali required for the second region is reduced or the amount of alkali required for the second region is reduced. May be zero. In this case, the titration curve has one point where the pH increment is maximized.

Since the denominator of the above-mentioned phosphorus oxo acid group introduction amount (mmol / g) indicates the mass of the acid type pulp, the phosphorus oxo acid group amount of the acid type pulp (hereinafter, the phosphorus oxo acid group amount (acid type)). Is called). On the other hand, when the counterion of the phosphorus oxo acid group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of the pulp when the cation C is a counterion. , The amount of phosphorus oxo acid groups (hereinafter, the amount of phosphorus oxo acid groups (C type)) contained in the pulp in which the cation C is a counter ion can be determined.
That is, it is calculated by the following formula.
Phosphoric acid group amount (C type) = Phosphoric acid group amount (acid type) / {1+ (W-1) x A / 1000}
A [mmol / g]: Total amount of anion derived from phosphoric acid group in pulp (total amount of dissociated acid of phosphoric acid group)
W: Formula amount per valence of cation C (for example, Na is 23, Al is 9)

In the measurement of the amount of phosphorus oxo acid groups by the titration method, if the amount of one drop of the sodium hydroxide aqueous solution is too large or the titration interval is too short, the amount of phosphorus oxo acid groups will be lower than the original value. It may not be obtained. As an appropriate dropping amount and titration interval, for example, it is desirable to titrate 10 to 50 μL of a 0.1 N sodium hydroxide aqueous solution every 5 to 30 seconds. Further, in order to eliminate the influence of carbon dioxide dissolved in the linoxo-oxidized pulp-containing slurry, for example, it is desirable to measure while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration to the end of titration.

(Manufacturing method of fine fibrous cellulose)
The present invention also relates to a method for producing fine fibrous cellulose, which comprises a step of defibrating the phosphorus oxo oxidized pulp produced by the above-mentioned method for producing phosphorus oxo oxidized pulp. In the present specification, fibrous cellulose having a fiber width of 1000 nm or less may be referred to as fine fibrous cellulose or CNF. The fiber width of the fine fibrous cellulose may be 1000 nm or less, preferably 100 nm or less, and more preferably 8 nm or less.

The fiber width of the fine fibrous cellulose can be measured, for example, by observation with an electron microscope. The average fiber width of the fine fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fine fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Is particularly preferable. By setting the average fiber width of the fine fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the fine fibrous cellulose in water as a cellulose molecule, and to more easily exhibit the effects of the fine fibrous cellulose to improve strength, rigidity and dimensional stability. be able to. The fine fibrous cellulose is, for example, monofibrous cellulose.

The average fiber width of the fine fibrous cellulose is measured as follows, for example, using an electron microscope. First, an aqueous suspension of fine fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a hydrophilized carbon film-coated grid for TEM observation. Use as a sample. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Next, observation is performed using an electron microscope image at a magnification of 1000 times, 5000 times, 10000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification should be adjusted so as to satisfy the following conditions.
(1) A straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y that intersects the straight line perpendicularly is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber intersecting the straight line X and the straight line Y is visually read with respect to the observation image satisfying the above conditions. In this way, at least three sets of observation images of surface portions that do not overlap each other are obtained. Next, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. As a result, at least 20 fibers × 2 × 3 = 120 fibers are read. Then, the average value of the read fiber widths is taken as the average fiber width of the fine fibrous cellulose.

The fiber length of the fine fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and 0.1 μm or more and 600 μm or less. More preferred. By setting the fiber length within the above range, destruction of the crystal region of the fine fibrous cellulose can be suppressed. It is also possible to set the slurry viscosity of the fibrous cellulose in an appropriate range. The fiber length of the fine fibrous cellulose can be obtained by, for example, image analysis by TEM, SEM, or AFM.

The fine fibrous cellulose preferably has an I-type crystal structure. Here, the fact that the fine fibrous cellulose has an I-type crystal structure can be identified in the diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418 Å) monochromatic with graphite. Specifically, it can be identified by having typical peaks at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. The ratio of the type I crystal structure to the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. As a result, even better performance can be expected in terms of heat resistance and low coefficient of linear thermal expansion. The crystallinity is determined by a conventional method from the X-ray diffraction profile measured and the pattern (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

The axial ratio (fiber length / fiber width) of the fine fibrous cellulose is not particularly limited, but is preferably 20 or more and 10000 or less, and more preferably 50 or more and 1000 or less. By setting the axial ratio to the above lower limit value or more, it is easy to form a sheet containing fine fibrous cellulose. In addition, sufficient viscosity can be easily obtained when the solvent dispersion is produced. By setting the axial ratio to the above upper limit value or less, for example, when treating fine fibrous cellulose as an aqueous dispersion, it is preferable in that handling such as dilution becomes easy.

<Fiber processing>
The step of producing the fine fibrous cellulose includes a step of defibrating the phosphorylated pulp produced by the above-mentioned method for producing phosphorylated pulp. Fine fibrous cellulose can be obtained by defibrating the phosphorusoxo oxide pulp in the defibration treatment step. In the defibration treatment step, for example, a defibration treatment apparatus can be used. The defibrating apparatus is not particularly limited, but for example, a high-speed defibrator, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure collision type crusher, a ball mill, a bead mill, a disc type refiner, a conical refiner, and a twin shaft. A kneader, a vibration mill, a homomixer under high speed rotation, an ultrasonic disperser, or a beater can be used. Among the above-mentioned defibration processing devices, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, and an ultra-high-pressure homogenizer, which are less affected by crushed media and less likely to cause contamination.

In the defibration treatment step, for example, it is preferable to dilute the phosphorus oxo oxide pulp with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and an organic solvent such as a polar organic solvent can be used. The polar organic solvent is not particularly limited, but for example, alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents and the like are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone, methyl ethyl ketone (MEK) and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

The solid content concentration of the phosphorus oxo oxide pulp during the defibration treatment can be appropriately set. Further, the slurry obtained by dispersing the phosphorus oxo oxide pulp in a dispersion medium may contain a solid content other than the phosphorus oxo oxide pulp such as urea having a hydrogen bond property.

Through such a defibration treatment step, a dispersion liquid containing fibrous cellulose having a fiber width of 1000 nm or less can be obtained. An arbitrary component may be added to the dispersion liquid after the defibration treatment. Examples of the optional component include a hydrophilic polymer, a hydrophilic low molecule, and an organic ion. In addition, the fine fibrous cellulose-containing dispersion has optional components such as a surfactant, a coupling agent, an inorganic layered compound, an inorganic compound, a leveling agent, an antiseptic, an antifoaming agent, an organic particle, a lubricant, and an antistatic agent. , UV protection agents, dyes, pigments, stabilizers, magnetic powders, orientation promoters, plasticizers, dispersants, and cross-linking agents, which may contain one or more.

(Use)
The above-mentioned phosphoroxo-oxidized pulp is phosphor-oxidized using a recycled phosphorus-oxo oxidant, but the amount of phosphorus oxo acid group introduced is the phosphor-oxo acid obtained by phosphor-oxidation using a non-recycled phosphor-oxo oxidant. It is at the same level as the amount of group introduced, and the amount of phosphorus oxo acid group introduced is sufficient. Therefore, it is easy to make fine fibrous cellulose, and the degree of fineness is also good. The transparency of the fine fibrous cellulose-containing slurry or fine fibrous cellulose-containing sheet containing such fine fibrous cellulose is sufficiently high. From the viewpoint of utilizing such characteristics, fine fibrous cellulose is suitable for applications of light-transmitting substrates such as various display devices and various solar cells. It is also suitable for applications such as substrates for electronic devices, materials for home appliances, window materials for various vehicles and buildings, interior materials, exterior materials, and packaging materials. Further, it is suitable for applications where the sheet itself is used as a reinforcing material in addition to threads, filters, woven fabrics, cushioning materials, sponges, and abrasives. In addition, the fibrous cellulose of the present invention can also be used as a thickener for various purposes (for example, additives to foods, cosmetics, cement, paints, inks, etc.).

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

[Example 1]
<Linoxo oxidation reaction process>
As softwood kraft pulp, pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheet, dissociated and measured according to JIS P 8121 has a Canadian standard drainage degree (CSF) of 700 ml). Used as a raw material. To 100 parts by mass of the coniferous kraft pulp (absolute dry mass), a mixed aqueous solution of ammonium dihydrogen phosphate and urea (solution containing a phosphorus oxo oxidizing agent) is added, and 45 parts by mass of ammonium dihydrogen phosphate (the number of parts by mass of phosphorus atom is 12). By mass), urea was squeezed to 120 parts by mass, and ion-exchanged water was 150 parts by mass to obtain a chemical-impregnated pulp. The pulp was heated with a hot air dryer to introduce a phosphorus oxo acid group into the cellulose in the pulp to obtain a phosphorus oxo oxidized pulp A.

<Concentration process (circulation concentration)>
Ion-exchanged water is poured into the solid containing the unreacted phosphorus oxo oxidant and the phosphorus oxo oxide pulp obtained in the above <phosphorox oxidation reaction step> so that the concentration of the phosphorus oxo oxide pulp is 10% by mass or less, and the mixture is stirred and uniform. The filtrate was collected by suction filtration to obtain a solution A containing an unreacted phosphorus oxo oxidizing agent. Using the obtained solution A, the phosphorylated phosphorylated pulp containing the unreacted phosphoroxyoxidant is diluted so that the concentration of the phosphorylated pulp is 10% by mass or less, and the filtrate is collected by suction filtration. As a result, a solution B having a higher phosphorus and nitrogen concentration than the solution A was obtained. This operation was repeated 15 times to obtain a concentrated solution C. The phosphorus atom concentration and the nitrogen atom concentration of the solution C were measured by the method described later.

<Measurement of phosphorus atom concentration>
The color reaction was used to measure the phosphorus atom concentration. Solution C containing a phosphorus oxo oxidizing agent was measured using a digital pack test for all phosphorus (manufactured by Kyoritsu RIKEN Co., Ltd.). Specifically, 1 mL of a sample, 1 drop of R-1 reagent, and 0.5 mL of R-2 reagent were added to a pressure-resistant bottle and shaken. After that, heating was continued for 30 minutes after steam began to be emitted in the high-pressure decomposer. After 30 minutes, it was taken out from the decomposer, cooled to 20 ° C., 4 drops of R-3 reagent was added, and the mixture was shaken. The whole amount of the prepared solution was put into a tube containing a color reagent, shaken several times, and then measured by a digital pack test.

<Measurement of nitrogen atom concentration>
The color reaction was used to measure the nitrogen atom concentration. A solution containing a phosphorus oxo oxidizing agent was measured using a digital pack test for total nitrogen (manufactured by Kyoritsu RIKEN Co., Ltd.). Specifically, 1 mL of a sample, 1 drop of R-1 reagent, and 0.5 mL of R-2 reagent were added to a pressure-resistant bottle and shaken. After that, heating was continued for 30 minutes after steam began to be emitted in the high-pressure decomposer. After 30 minutes, it was taken out from the decomposer, cooled to 20 ° C., 2 drops of R-3 reagent was added, and the mixture was shaken. The whole amount of the prepared solution was put into a tube containing a color reagent, shaken for 1 minute, and then measured by a digital pack test.

<Linoxo acid esterification reaction>
Separately, as softwood kraft pulp, pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheets, separated and measured according to JIS P 8121) has a Canadian standard drainage degree (CSF) of 700 ml. ) Was used as a pulp raw material, 3.14 g of solution C was added per 1 g of the pulp raw material, and the pulp was heated at 160 ° C. for 11 minutes in a blower dryer to obtain phosphoroxo-oxidized pulp B.

<Washing / alkali (neutralization) treatment process>
Next, the obtained phosphorus oxo oxide pulp B was washed. In the washing treatment, the pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of phosphorus oxo-oxidized pulp B is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. Was done by. When the electric conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

Next, the washed phosphorus oxo oxide pulp B was neutralized as follows. First, the washed phosphorus oxo oxide pulp B is diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide solution is added little by little with stirring to obtain a phosphorus oxo oxide pulp slurry having a pH of 12 or more and 13 or less. It was. Next, the phosphorus oxo oxide pulp slurry was dehydrated to obtain a neutralized phosphorus oxo oxide pulp B.

Further, the phosphorus oxo oxide pulp B after the neutralization treatment was subjected to the above washing treatment. The infrared absorption spectrum of the phosphorus oxo oxide pulp B thus obtained was measured using FT-IR. As a result, absorption of the phosphate group based on P = O was observed around 1230 cm ^-1 , and it was confirmed that the phosphate group was added to the pulp. Further, when the obtained phosphorus oxo oxide pulp B was tested and analyzed by an X-ray diffractometer, two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less, were located. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals.

<Machine processing process>
Ion-exchanged water was added to the obtained phosphorus oxo oxide pulp B to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) 6 times at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. By X-ray diffraction, it was confirmed that this fine fibrous cellulose maintained the cellulose type I crystal. The fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm.

<Measurement of introduction amount of phosphorus oxo acid group>
The amount of phosphorus oxo acid groups in the fine fibrous cellulose (equal to the amount of phosphorus oxo acid groups in the phosphorus oxo oxide pulp B) is the content obtained by adding ion-exchanged water to the fine fibrous cellulose dispersion containing the target fine fibrous cellulose. Was 0.2% by mass, and the measurement was carried out by performing treatment with an ion exchange resin and then titrating with an alkali.
For the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) having a volume of 1/10 was added to the fine fibrous cellulose-containing slurry, and the mixture was shaken for 1 hour. After that, it was poured on a mesh having a mesh size of 90 μm to separate the resin and the slurry.
Further, in the titration using alkali, the change in the pH value indicated by the slurry is changed while adding 10 μL of a 0.1 N sodium hydroxide aqueous solution to the fine fibrous cellulose-containing slurry treated with the ion exchange resin every 5 seconds. It was done by measuring. The titration was carried out while blowing nitrogen gas into the slurry from 15 minutes before the start of the titration. In this neutralization titration, two points are observed in which the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point (FIG. 3). The amount of alkali required from the start of the titration to the first end point is equal to the amount of the first dissociated acid in the slurry used for the titration. Further, the amount of alkali required from the start of titration to the second end point becomes equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first end point divided by the solid content (g) in the slurry to be titrated is the amount of phosphorus oxo acid groups (first dissociated acid amount) (mmol / g). ). Further, the value obtained by dividing the amount of alkali (mmol) required from the start of titration to the second end point by the solid content (g) in the slurry to be titrated was defined as the total amount of dissociated acid (mmol / g).

[Example 2]
<Concentration process (membrane concentration)>
The solution A obtained in the <concentration step (circulation concentration)> of [Example 1] is subjected to a reverse osmosis membrane (manufactured by DOWN FILMTEC ^TM ) installed in a cross-flow flat membrane tester (SEPA CFII manufactured by GE Water Technologies). By treating with SW30HR-380), a concentrated solution D was obtained. <Linoxo acid esterification reaction>, <washing / alkali (neutralization) treatment step>, and <mechanical treatment step> were carried out in the same manner as in Example 1 except that this solution D was used.

[Example 3]
<Concentration step (concentration by heating under reduced pressure)>
The solution A obtained in the <concentration step (circulation concentration)> of [Example 1] was placed in a 500 mL eggplant flask, and concentrated under reduced pressure using a rotary evaporator (manufactured by Tokyo Rika Kikai Co., Ltd.). At that time, the bottom of the flask was immersed in a water bath at 40 ° C. to promote concentration and obtain a solution E. Solution E was diluted to a phosphorus concentration of 3.8% by mass to obtain Solution E'. <Linoxo acid esterification reaction>, <washing / alkali (neutralization) treatment step>, and <mechanical treatment step> were carried out in the same manner as in Example 1 except that this solution E'was used.

[Example 4]
<Linoxo oxidation reaction process>
As softwood kraft pulp, pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheet, dissociated and measured according to JIS P 8121 has a Canadian standard drainage degree (CSF) of 700 ml). Used as a raw material. To 100 parts by mass of the coniferous kraft pulp (absolute dry mass), a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea (a solution containing a phosphorus oxo oxidizing agent) is added, and 33 parts by mass of phosphorous acid (the number of parts by mass of phosphorus atom is 12). By mass), 120 parts by mass of urea, and 150 parts by mass of ion-exchanged water were squeezed to obtain a chemical-impregnated pulp. The pulp was heated with a hot air dryer to introduce a phosphorus oxo acid group into the cellulose in the pulp to obtain a phosphorus oxo oxidized pulp C.

Ion-exchanged water is poured into the solid containing the unreacted phosphorus oxo oxidant and the phosphorus oxo oxide pulp obtained in the above <phosphorox oxidation reaction step> so that the concentration of the phosphorus oxo oxide pulp is 10% by mass or less, and the mixture is stirred uniformly. The filtrate was dispersed and diluted, and the filtrate was recovered by suction filtration to obtain a solution F containing an unreacted phosphorus oxo oxidizing agent. Using the obtained solution F, the unreacted phosphorus oxo oxidant and the phosphorus oxo oxide pulp were diluted so that the concentration of the phosphorus oxo oxide pulp was 10% by mass or less, and the filtrate was collected by suction filtration to obtain more phosphorus than the solution F. A solution G having a high nitrogen concentration was obtained. By repeating this operation 15 times, a concentrated solution H was obtained. The phosphorus atom concentration and the nitrogen atom concentration of the solution H were measured by the method described above.

<Linoxo acid esterification reaction>
Separately, as softwood kraft pulp, pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheets, separated and measured according to JIS P 8121) has a Canadian standard drainage degree (CSF) of 700 ml. ) Was used as a pulp raw material, 3.00 g of solution H was added per 1 g of the pulp raw material, and the pulp was heated at 160 ° C. for 11 minutes in a blower dryer to obtain phosphoroxo-oxidized pulp D. The <washing / alkali (neutralization) treatment step> and the <mechanical treatment step> were carried out in the same manner as in Example 1 except that the phosphorus oxo oxide pulp D was used.

[Comparative Example 1]
The <phosphoroacid esterification reaction>, <washing / alkali (neutralization) treatment step>, and <mechanical treatment step> were carried out in the same manner as in Example 1 except that the solution A was used without concentration.

As is clear from Table 1, in the examples, phosphorus oxo oxidized pulp and fine fibrous cellulose into which a predetermined amount or more of phosphorus oxo acid groups were introduced were obtained. On the other hand, in the comparative example, the introduction of the phosphorus oxo acid group was not detected in the phosphorus oxo oxidized pulp and the fine fibrous cellulose.

Claims (6)

In the presence of a concentrated recovered product obtained by concentrating a recovered product containing an unreacted phosphorus oxo oxidant, which is recovered in a step after the phosphorus oxo oxidation reaction with a phosphorus oxo oxidizing agent, a step of phosphorylating the pulp raw material is included. Production method. The method for producing phosphoroxo-oxidized pulp according to claim 1, wherein the concentrated recovered product is obtained by concentrating the recovered product by at least one method selected from circulation concentration, membrane concentration and heat-reduced pressure concentration. The method for producing a phosphorus oxo oxidized pulp according to claim 1 or 2, wherein the phosphorus oxo oxidizing agent contains at least one selected from a phosphorus oxo acid and a phosphorus oxo acid salt, and urea. The method for producing phosphoroxo-oxidized pulp according to any one of claims 1 to 3, wherein the phosphorus atom concentration is 0.40% by mass or more with respect to the total mass of the concentrated recovered product. The method for producing phosphoroxo-oxidized pulp according to any one of claims 1 to 4, wherein the nitrogen atom concentration is 0.70% by mass or more with respect to the total mass of the concentrated recovered product. A method for producing fine fibrous cellulose, which comprises a step of defibrating the phosphorus oxo oxidized pulp produced by the method for producing phosphorus oxo oxidized pulp according to any one of claims 1 to 5.