JP2018130089A - Artificial culture soil - Google Patents

Abstract

An artificial culture soil having both drainage and water retention is provided. An artificial culture soil containing crosslinked cellulose fibers, wherein the cellulose fibers have a phosphate group or a substituent derived from a phosphate group, and at least partially substituted by a phosphate group or a phosphate group. It is an artificial culture soil of a lump that has a cross-linked group, and the cellulose fiber content is 90% by mass or more based on the total solid mass of the artificial culture soil. The volume change rate is 30% or less, and the moisture content is 130% or more. [Selection] Figure 2

Description

  The present invention relates to artificial culture soil. Specifically, this invention relates to the artificial culture soil containing a cellulose fiber.

  Conventionally, cellulose fibers have been widely used in clothing, absorbent articles, paper products, and the like. As the cellulose fiber, in addition to fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known.

  In recent years, artificial culture soil using cellulose fibers has also been developed. For example, Patent Document 1 discloses artificial soil particles having a fiber aggregate formed by granulating fibers. Here, the artificial soil particles contain a water absorption promoting material and a binder component that increase the initial water absorption of the fiber mass. In Patent Document 1, artificial soil particles are produced by melting a water absorption promoting material and a binder component and fixing fibers together.

JP, 2006-106629, A

  The artificial culture soil may be required to have a function equivalent to or higher than that of natural soil. For example, when artificial culture soil is used as horticultural culture soil, it is required to have conflicting characteristics such as drainage and water retention.

  In order to solve the problems of the prior art, the present inventors have proceeded with studies for the purpose of providing an artificial culture soil having both drainage and water retention.

As a result of intensive studies to solve the above problems, the present inventors can obtain an artificial culture soil having both drainage and water retention by including crosslinked cellulose fibers in the artificial culture soil. I found out.
Specifically, the present invention has the following configuration.

[1] Artificial culture soil containing crosslinked cellulose fibers.
[2] The cellulose fiber has a phosphoric acid group or a substituent derived from a phosphoric acid group, and the phosphoric acid group or the substituent derived from the phosphoric acid group is crosslinked in at least a part of the cellulose fiber. Artificial soil.
[3] The artificial culture soil according to [1] or [2], which is a lump.
[4] The artificial culture soil according to any one of [1] to [3], wherein the content of the cellulose fiber is 90% by mass or more based on the total solid mass of the artificial culture soil.
[5] The artificial culture soil according to any one of [1] to [4], wherein the volume change rate calculated by the following formula (a) is 30% or less.
Formula (a):
Volume change rate (%) = (volume of artificial culture soil after being immersed in ion exchange water for 24 hours−volume of artificial culture soil before being immersed in ion exchange water) / artificial culture soil before being immersed in ion exchange water Volume x 100
[6] The artificially cultured soil according to any one of [1] to [5], wherein a moisture content (%) calculated by the following formula (b) is 130% or more.
Formula (b):
Moisture content (%) = (Mass of artificial culture soil after being immersed in ion exchange water for 24 hours and then allowed to stand in an environment of 25 ° C. and 50% relative humidity for 24 hours, immersed in ion exchange water) Mass of artificially cultured soil before immersion) / Mass of artificially cultured soil before being immersed in ion-exchanged water × 100
[7] A method for producing artificial culture soil, comprising a step of introducing a substituent into a cellulose fiber, a step of forming a cellulose fiber having a substituent to obtain a molded product, and a step of heating the molded product.

  According to the present invention, an artificial culture soil having both freeness and water retention can be obtained.

FIG. 1 is a graph showing the relationship between the NaOH dripping amount and the pH relative to the fiber raw material. FIG. 2 is a photograph of the phosphorylated cellulose molded product obtained in the example.

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

(Artificial culture soil)
The present invention relates to an artificial culture soil containing crosslinked cellulose fibers. Since the artificial culture soil of the present invention contains crosslinked cellulose fibers, it has two contradictory characteristics such as drainage and water retention.

  Artificial cultivated soil having excellent drainage has good drainage, and is particularly preferably used as soil for horticultural plants. In order to achieve excellent drainage, it is preferable that the artificial culture soil has a property that it is difficult to expand due to water absorption. In the present invention, the artificial culture soil has an excellent water absorption property, but is characterized in that expansion due to water absorption is suppressed.

Specifically, in the artificial culture soil of the present invention, the volume change rate calculated by the following formula (a) is preferably 30% or less, more preferably 20% or less, and 15% or less. More preferably it is. Further, the volume change rate may be 0%. The freeness can be improved by setting the volume change rate calculated by the following formula (a) within the above range.
Formula (a):
Volume change rate (%) = (volume of artificial culture soil after being immersed in ion exchange water for 24 hours−volume of artificial culture soil before being immersed in ion exchange water) / artificial culture soil before being immersed in ion exchange water Volume x 100
In this specification, the volume of the artificial culture soil after being immersed in ion-exchanged water for 24 hours is that the artificial culture soil is immersed in a sufficient amount of water larger than the volume of the artificial culture soil, and in that state, This is the volume of the artificial culture soil after standing still in the room for 24 hours and then removing water drops on the surface of the artificial culture soil on the filter paper. Moreover, the volume of the artificial culture soil before being immersed in ion-exchanged water is determined by spreading the artificial culture soil before being immersed in ion-exchanged water on a filter paper and air-drying it for 24 hours in an environment of 25 ° C. and 50% relative humidity. It is the volume of the artificial culture soil after.

  The artificial culture soil of the present invention is characterized in that it is excellent in water drainage and water retention while being excellent in drainage. Here, water absorption can be evaluated by the amount of water absorbed after the artificial culture soil is immersed in a sufficient amount of water for 24 hours, and water retention can be performed by immersing the artificial culture soil in a sufficient amount of water for 24 hours. It can be evaluated by the retained amount of water absorbed in step 4 with time. The artificial culture soil of the present invention has a large amount of water absorption immediately after being immersed in water and a large amount of retained water after aging.

Specifically, in the artificial culture soil of the present invention, the moisture content (%) calculated by the following formula (b) is preferably 130% or more, more preferably 140% or more, and 150%. More preferably, it is the above. In addition, the upper limit of the moisture content (%) after standing for 24 hours calculated by the following formula (b) is not particularly limited, and can be, for example, 300%. By setting the moisture content (%) after standing for 24 hours within the above range, the water retention of the artificial culture soil can be increased more effectively. In the present specification, the moisture content (%) calculated by the following formula (b) can also be referred to as a water retention rate (%).
Formula (b):
Moisture content (%) = (Mass of artificial culture soil after being immersed in ion exchange water for 24 hours and then allowed to stand in an environment of 25 ° C. and 50% relative humidity for 24 hours, immersed in ion exchange water) Mass of artificially cultured soil before immersion) / Mass of artificially cultured soil before being immersed in ion-exchanged water × 100
In the present specification, the mass of the artificial culture soil after the artificial culture soil is immersed in ion-exchanged water for 24 hours and then left in an environment of 25 ° C. and a relative humidity of 50% for 24 hours is the mass of the artificial culture soil. The artificial culture soil is immersed in a sufficient amount of water larger than the volume, and left in that state in a room at 25 ° C. for 24 hours. After that, water droplets on the surface of the artificial culture soil are removed on the filter paper, and then the relative humidity is 25 ° C. It is the mass of the artificial culture soil after being left for 24 hours in a 50% environment. Moreover, the mass of the artificial culture soil before being immersed in ion-exchanged water is determined by spreading the artificial culture soil before being immersed in ion-exchanged water on a filter paper and air-drying for 24 hours in an environment of 25 ° C. and 50% relative humidity. It is the mass of the artificial culture soil after.

In the artificial culture soil of the present invention, the water absorption rate (%) calculated by the following formula (c) is preferably 130% or more, more preferably 140% or more, and 150% or more. Is more preferable. In addition, the upper limit of the water absorption rate (%) calculated by the following formula (c) is not particularly limited, and can be, for example, 300%. By setting the water absorption rate (%) calculated by the following formula (c) within the above range, the water absorption of the artificial culture soil can be more effectively increased.
Formula (c):
Water absorption rate (%) = (mass of artificial culture soil after immersing artificial culture soil in ion exchange water for 24 hours−mass of artificial culture soil before immersion in ion exchange water) / before immersing in ion exchange water Mass of artificial culture soil x 100
In this specification, the mass of the artificial culture soil after immersing the artificial culture soil in ion-exchanged water for 24 hours is obtained by immersing the artificial culture soil in a sufficient amount of water larger than the volume of the artificial culture soil. It is the mass of the artificial culture soil after leaving still in a room at 25 ° C. for 24 hours and then removing water drops on the surface of the artificial culture soil on the filter paper. Moreover, the mass of the artificial culture soil before being immersed in ion-exchanged water is determined by spreading the artificial culture soil before being immersed in ion-exchanged water on a filter paper and air-drying it for 24 hours in an environment of 25 ° C. and 50% relative humidity. It is the mass of the artificial culture soil after.

The water content with respect to the total mass of the artificial culture soil of the present invention is preferably 50% by mass or less, more preferably 30% by mass or less, and further preferably 20% by mass or less. In the present invention, the moisture content of the artificial culture soil may be 0% by mass.
When measuring the moisture content of the artificial culture soil, the weight before and after drying for 24 hours under the condition of 105 ° C. can be measured and calculated by the following formula.
Water content (mass%) = (weight before drying−weight after drying) / weight after drying × 100

The density of the artificial culture soil of the present invention is not particularly limited, but is preferably 0.50 g / cm ³ or less, and more preferably 0.30 g / cm ³ or less. Moreover, it is preferable that the density of artificial culture soil is 0.01 g / cm ³ or more. By setting the density of the artificial culture soil within the above range, it is possible to reduce the weight of the artificial culture soil.

  The artificial culture soil of the present invention is preferably a lump. As a lump, a granular material, a powdery material, a cottony material etc. can be mentioned, for example. The average particle diameter of the lump is preferably 0.5 mm or more, more preferably 1 mm or more, and further preferably 3 mm or more. In addition, since the lump is not necessarily circular, in this specification, the average particle diameter of the lump is defined as the diameter of the circumscribed circle of the lump.

  The artificial culture soil of the present invention is an aggregate of a plurality of solid materials, and is preferably a lump, for example. That is, the present invention also relates to a lump made of crosslinked cellulose fibers used as artificial culture soil. Such artificial culture soil can be used alone for plant cultivation, or may be mixed with other soils or fertilizers to constitute the soil.

(Cellulose fiber)
The artificial culture soil of the present invention contains crosslinked cellulose fibers. The content of cellulose fibers in the artificial culture soil is preferably 90% by mass or more, more preferably 95% by mass or more, and 99% by mass or more with respect to the total solid mass of the artificial culture soil. Is more preferable. In addition, the total solid content of artificial culture soil may be comprised from the cellulose fiber. That is, the artificial culture soil of the present invention does not contain additives such as binder components and absorption promoters, or a small amount even if they are contained.

In addition, the total solid content mass of artificial culture soil is the absolute dry mass of artificial culture soil. Examples of the method for completely drying the artificial culture soil include, but are not limited to, drying in an air dryer set at 105 ° C. ± 2 ° C. A device such as a weighing bottle can be used as appropriate so that the culture soil is not blown off during the measurement.
The content of cellulose fibers in the total solid content can be appropriately calculated by a method of extracting or decomposing only components or cellulose fibers contained other than cellulose fibers. The portion is composed of cellulose fibers, and the value of the total solid content is substantially close to the mass of the cellulose fibers.

  Although it does not specifically limit as a cellulose raw material for obtaining a cellulose fiber, It is preferable to use a pulp from the point that it is easy to acquire and it is cheap. Examples of the pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), oxygen bleached craft Chemical pulps such as pulp (OKP) are listed. Moreover, semi-chemical pulps such as semi-chemical pulp (SCP) and chemi-ground wood pulp (CGP), mechanical pulps such as ground wood pulp (GP), thermomechanical pulp (TMP, BCTMP) and the like can be mentioned, but are not particularly limited. Non-wood pulp includes cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, cellulose isolated from sea squirts and seaweed, chitin, chitosan, etc., but is not particularly limited. . The deinking pulp includes deinking pulp made from waste paper, but is not particularly limited. The pulp of this embodiment may be used alone or in combination of two or more. Among the above pulps, wood pulp containing cellulose and deinked pulp are preferable in terms of availability.

  In the present invention, the fiber width of the cellulose fiber having a phosphate group is not particularly limited. For example, the fiber width of the cellulose fiber having a phosphate group may be greater than 1000 nm, or 1000 nm or less. Moreover, the cellulose fiber whose fiber width is larger than 1000 nm and the cellulose fiber whose fiber width is 1000 nm or less may be mixed. In addition, when the fiber width of a cellulose fiber is 1000 nm or less, such a cellulose fiber may be called a fine fibrous cellulose.

  Here, the fiber width of the cellulose fiber can be measured by the following method by observation with an electron microscope. First, a cellulose fiber aqueous suspension having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and the suspension is cast on a carbon film-coated grid subjected to a hydrophilic treatment to obtain a sample for TEM observation. . At this time, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.

(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.

  The width of the fiber that intersects with the straight line X and the straight line Y is visually read from the observation image that satisfies the above conditions. In this way, at least three sets of images of the surface portion that do not overlap each other are observed, and the width of the fiber intersecting with the straight line X and the straight line Y is read for each image. Thus, at least 20 × 2 × 3 = 120 fiber widths are read.

  Although the average fiber length of a cellulose fiber is not specifically limited, It is preferable that it is 0.1 mm or more, and it is more preferable that it is 0.6 mm or more. Moreover, it is preferable that it is 5 mm or less, and it is more preferable that it is 2 mm or less. By setting the average fiber length of the cellulose fibers within the above range, the strength when the cellulose fibers are formed into a lump can be increased. Here, the average fiber length of the cellulose fiber can be determined by measuring the length-weighted average fiber length using, for example, a Kajaani fiber length measuring instrument (FS-200 type) manufactured by Kajaani Automation. Moreover, it can also measure using a scanning microscope (SEM), a transmission electron microscope (TEM), etc. according to the length of a fiber.

  The cellulose fiber preferably has a substituent, and more preferably has a phosphate group or a substituent derived from a phosphate group (sometimes simply referred to as a phosphate group). In the artificial culture soil of the present invention, it is preferable that a phosphate group or a phosphate-derived substituent is crosslinked in at least a part of the cellulose fiber.

The artificial culture soil of the present invention contains crosslinked cellulose fibers, and such a crosslinked structure is formed by condensation of substituents introduced into the cellulose fibers. In the case where the substituent is a phosphate group, the cellulose fibers are crosslinked by the condensation of the phosphate groups introduced into the cellulose fibers. Moreover, in this invention, the hydroxyl group which a cellulose fiber contains can be mentioned as group which can form a crosslinked structure other than a phosphate group. In this case, a plurality of ester bonds may be formed with a polyvalent carboxylic acid such as citric acid, and a methylenedioxy (—OCH ₂ O—) structure can be formed by using formaldehyde.

The phosphoric acid group in the phosphorylated cellulose fiber is a divalent functional group corresponding to the phosphoric acid obtained by removing the hydroxyl group. Specifically, it is a group represented by —PO ₃ H ₂ . The substituent derived from the phosphate group includes a substituent such as a group obtained by polycondensation of the phosphate group, a salt of the phosphate group, and a phosphate ester group, and is preferably an ionic substituent.

In the present invention, the phosphate group or the substituent derived from the phosphate group may be a substituent represented by the following formula (1).

In the formula (1), a, b, m and n each independently represent an integer (where a = b × m); α ⁿ (n is an integer from 1 to n) and α ′ are each independently Represents R or OR. R represents a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon group. , An aromatic group, or a derivative group thereof; β is a monovalent or higher cation composed of an organic substance or an inorganic substance.

  The phosphoric acid group content of the cellulose fiber is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g or more per 1 g (mass) of cellulose fibers. Is more preferably 1.00 mmol / g or more, still more preferably 1.20 mmol / g or more, particularly preferably 1.30 mmol / g or more, 1.60 mmol. / G or more is most preferable. Moreover, it is preferable that content of a phosphate group is 3.65 mmol / g or less, It is more preferable that it is 3.5 mmol / g or less, It is further more preferable that it is 3.0 mmol / g or less. In addition, in this specification, content of the phosphate group which a cellulose fiber has is equal to the strongly acidic group amount of the phosphate group which a cellulose fiber has so that it may mention later.

  The phosphate group content of the cellulose fiber can be measured by a neutralization titration method. In the measurement by the neutralization titration method, after completely converting the phosphate group to the acid form, it is refined by a mechanical treatment process (a refinement process), and the resulting fine fibrous cellulose-containing slurry is The amount introduced is determined by determining the change in pH while adding aqueous sodium hydroxide.

  Conversion of the phosphate group to the acid form involves diluting the artificial culture soil containing cellulose fibers with ion-exchanged water so that the cellulose fiber concentration becomes 2% by mass, and stirring a sufficient amount of 1N aqueous hydrochloric acid solution. This is done by adding them one by one. In the conversion of the phosphoric acid group into an acid form, the cellulose fiber-containing slurry is dehydrated to obtain a dehydrated sheet, which is then diluted again with ion-exchanged water, and the operation of adding a 1N aqueous hydrochloric acid solution is repeated, thereby producing cellulose fibers. It is preferable to completely change the phosphate group contained in the acid form. Then, after the step of converting the phosphoric acid group into an acid form, the obtained cellulose fiber-containing slurry is stirred and dispersed uniformly, and then the operation of obtaining a dehydrated sheet by filtration and dehydration is repeated, so that surplus It is preferable to wash away hydrochloric acid sufficiently.

  In the mechanical treatment process (miniaturization process), ion-exchanged water is poured into the obtained dehydration sheet to obtain a cellulose fiber-containing slurry having a cellulose fiber concentration of 0.3% by mass. Using Cleamix-2.2S manufactured by Technic Co., Ltd., treatment is performed for 30 minutes at 21500 rpm. In this way, a fine fibrous cellulose-containing slurry is obtained.

  In titration using an alkali, a change in pH value indicated by the dispersion is measured while adding a 0.1N aqueous sodium hydroxide solution to the fine fibrous cellulose-containing slurry. This neutralization titration gives two points where the increment (differential value of pH with respect to the amount of alkali dropped) is maximized in the curve plotting the measured pH against the amount of alkali (aqueous sodium hydroxide solution) added ( The point where the increment is the largest and the second largest point). Of these, the amount of alkali required up to the maximum point of increment obtained first after adding alkali (hereinafter referred to as the first end point) is equal to the amount of strongly acidic groups in the dispersion used for titration, The amount of alkali required up to the maximum point of increase obtained (hereinafter referred to as the second end point) becomes equal to the amount of weakly acidic groups in the dispersion used for titration. The alkali amount (mmol) required up to the first end point is divided by the solid content (g) in the fine fibrous cellulose-containing slurry to be titrated to obtain the first dissociated alkali amount (mmol / g). Is the phosphate group content of the cellulose fiber.

  FIG. 1 shows an example of a curve plotting measured pH against the amount of alkali (sodium hydroxide aqueous solution) added in neutralization titration. The region up to the first end point is referred to as the first region, and the region up to the second end point is referred to as the second region. There is a third region after the second region. That is, three areas appear. In FIG. 1, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is the amount of weakly acidic groups in the slurry used for titration. Is equal to

The crosslinked structure is formed by condensation of substituents (for example, phosphoric acid groups) introduced into the cellulose fiber. When a phosphate group is introduced into the cellulose fiber, the crosslinked structure is a structure in which a glucose unit of cellulose is bonded to each of two P atoms of pyrophosphate via O atoms. Therefore, when a crosslinked structure is formed, the weakly acidic group is apparently lost, and the amount of alkali required by the second end point is reduced compared to the amount of alkali required by the first end point. Here, when the phosphate groups introduced into the cellulose fiber are not condensed at all, the amount of the strongly acidic group introduced into the cellulose fiber is the same as the amount of the weakly acidic group. For this reason, the value obtained by dividing the amount of weakly acidic groups lost by forming a crosslinked structure by 2 represents the amount of crosslinked structure (number of crosslinking points). That is, the amount of cross-linking structure (number of cross-linking points) is obtained by dividing the difference between the alkali amount required until the first end point (first dissociated alkali amount) and the alkali amount required until the second end point (second dissociated alkali amount) by 2. Is equal to The amount of cross-linking structure (number of cross-linking points) is represented by the following formula (1).
Cross-linking structure amount (number of cross-linking points) = (strong acid group amount contained in cellulose fiber−weak acid group amount contained in cellulose fiber) / 2 Formula (1)

  In the present invention, the amount of crosslinked structure (number of crosslinking points) of the cellulose fiber calculated by the above formula (1) may be 0.20 mmol / g or more, preferably 0.25 mmol / g or more. More preferably, it is 30 mmol / g or more. In addition, since the upper limit of the amount of crosslinking structures (number of crosslinking points) is a value obtained by dividing the amount of strongly acidic groups contained in cellulose fibers by 2, it is, for example, 1.82 mmol / g or less.

  The cellulose fiber may have a counter ion. The counter ion may be an inorganic ion or an organic ion. As inorganic ions, monovalent metal ions typified by alkali metal ions, divalent metal ions typified by alkaline earth metal ions, ammonium ions, aluminum ions, tin ions, which are nonmetallic cations, Examples include base metal ions such as lead ions, and other transition metal ions such as silver ions, copper ions, and iron ions. Examples of the organic ions include organic ammonium ions and organic phosphonium ions. When it is desired to increase water retention, it is preferable to use a monovalent cation as a counter ion, and from the viewpoint of versatility, it is more preferable to use an ammonium ion or an alkali metal ion as a counter ion. More preferably, it is a counter ion.

(Optional component)
The artificial culture soil of the present invention may contain optional components other than cellulose fibers. Optional components include, for example, defoaming agents, lubricants, surfactants, UV absorbers, dyes, pigments, fillers, stabilizers, organic solvents miscible with water such as alcohol, preservatives, organic fine particles, and inorganic fine particles. Etc. In addition, when an arbitrary component is contained in artificial culture soil, it is preferable that it is less than 10 mass% with respect to the total solid content mass of artificial culture soil.

(Manufacturing method of artificial culture soil)
The present invention also relates to a method for producing artificial culture soil. The method for producing artificial culture soil includes a step of introducing substituents into cellulose fibers (substituent introduction step), a step of forming cellulose fibers having substituents to obtain a molded product (molding step), and heating the molded product. A process (heating process).

<Substituent introduction step>
In the substituent introduction step, the above-described substituent is preferably introduced into the cellulose fiber. The substituent is preferably a phosphate group or a phosphate-derived substituent, and the substituent introduction step is preferably a phosphate group introduction step.

  In the phosphoric acid group introducing step, at least one selected from a phosphoric acid group or a compound having a substituent derived from a phosphoric acid group and a salt thereof (hereinafter referred to as “phosphorating agent” or “compound”) A ”) can be reacted. Such a phosphorylating agent may be mixed in dry or wet cellulose fibers in the form of powder or aqueous solution. As another example, a phosphoric acid powder or an aqueous solution may be added to the cellulose fiber slurry. That is, the phosphate group introduction step includes at least a step of mixing the cellulose fiber and the phosphorylating agent.

  The phosphate group introduction step can be performed by reacting a cellulose fiber with a phosphorylating agent. This reaction is performed by at least one selected from urea and derivatives thereof (hereinafter also referred to as “compound B”). You may carry out in presence.

  As an example of a method for causing compound A to act on cellulose fibers in the presence of compound B, a method of mixing powder or aqueous solution of compound A and compound B with cellulose fibers in a dry state or a wet state can be mentioned. Another example is a method of adding powders and aqueous solutions of Compound A and Compound B to the cellulose fiber-containing slurry. Among these, since the uniformity of the reaction is high, a method of adding an aqueous solution of Compound A and Compound B to dry cellulose fibers, or a powder or an aqueous solution of Compound A and Compound B to wet cellulose fibers The method is preferred. Moreover, the compound A and the compound B may be added simultaneously, or may be added separately. Moreover, you may add the compound A and the compound B first used for reaction as aqueous solution, and remove an excess chemical | medical solution by pressing. The form of the cellulose fiber is preferably cotton or thin sheet, but is not particularly limited.

  The phosphorylating agent (compound A) is at least one selected from a compound having a phosphate group and a salt thereof. Examples of the compound having a phosphate group include, but are not limited to, phosphoric acid, lithium salt of phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, ammonium salt of phosphoric acid, and the like. Examples of the lithium salt of phosphoric acid include lithium dihydrogen phosphate, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, and lithium polyphosphate. Examples of the sodium salt of phosphoric acid include sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, and sodium polyphosphate. Examples of the potassium salt of phosphoric acid include potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate. Examples of the ammonium salt of phosphoric acid include ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium polyphosphate. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, and ammonium salt of phosphoric acid are preferably used.

  The phosphorylating agent (compound A) is preferably used as an aqueous solution because the uniformity of the reaction is increased and the efficiency of introducing a phosphate group is further increased. The pH of the aqueous solution of the phosphorylating agent (compound A) is not particularly limited, but is preferably 7 or less because the efficiency of introduction of phosphoric acid groups is increased, and pH 3 or more and pH 7 or less from the viewpoint of suppressing hydrolysis of cellulose fibers. Is more preferable. The pH of the aqueous solution of Compound A may be adjusted by, for example, using a phosphoric acid group-containing compound that exhibits acidity and an alkalinity, and changing the amount ratio thereof. You may adjust pH of the aqueous solution of a phosphorylating agent (compound A) by adding an inorganic alkali or an organic alkali to what shows acidity among the compounds which have a phosphoric acid group.

  Although the addition amount of the phosphorylating agent (compound A) with respect to a cellulose fiber is not specifically limited, When the addition amount of a phosphorylating agent (compound A) is converted into a phosphorus atomic weight, the addition amount of the phosphorus atom with respect to a cellulose fiber (absolute dry mass) Is preferably 0.5 to 100% by mass, more preferably 1 to 50% by mass, and most preferably 2 to 30% by mass. If the addition amount of the phosphorus atom with respect to a cellulose fiber is in the said range, the yield of a phosphorylated cellulose fiber can be improved more. By making the addition amount of phosphorus atoms to the cellulose fiber 100% by mass or less, it is possible to balance the effect of improving the yield and the cost. On the other hand, a yield can be raised by making the addition amount of the phosphorus atom with respect to a cellulose fiber more than the said lower limit.

  Examples of the compound B used in this embodiment include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like.

  Compound B is preferably used as an aqueous solution in the same manner as Compound A. Moreover, since the uniformity of reaction increases, it is preferable to use the aqueous solution in which both compound A and compound B are dissolved. The amount of Compound B added to the cellulose fiber (absolute dry mass) is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, and 100% by mass or more and 350% by mass or less. More preferably, it is more preferably 150% by mass or more and 300% by mass or less.

  In addition to Compound A and Compound B, amides or amines may be included in the reaction system. 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 work as a good reaction catalyst.

<Molding process>
In the molding step, the cellulose fiber (pulp) that has undergone the phosphate group introduction step is molded. The cellulose fibers that have undergone the phosphate group introduction step are preferably phosphorylated chemical liquid-impregnated cellulose fibers or phosphorylated chemical liquid-impregnated pulp. In the molding step, it is preferable to mold the phosphoric acid solution-impregnated cellulose fiber (phosphorating agent solution-impregnated pulp) into a lump. For example, a phosphoric acid solution-impregnated cellulose fiber (phosphorating agent solution-impregnated pulp) can be finely chopped and then formed into a lump shape. At this time, it is preferable to mold so that the average particle size of the lump is 0.5 mm or more, more preferably to be 1 mm or more, and even more preferably to be 3 mm or more.

<Heating process>
In the heating process, the cellulose fiber (pulp) molded in the molding process is heat-treated. By providing such a heating step, a phosphate group can be efficiently introduced into the cellulose fiber, and at least a part of the phosphate group or a substituent derived from the phosphate group can be crosslinked. Thus, by forming a crosslinked structure between the cellulose fibers, a molded product (artificial culture soil) having excellent shape stability can be obtained. The artificial culture soil of the present invention can retain its shape even when wet with water, and can exhibit excellent drainage.

  As the heat treatment temperature in the heating step, it is preferable to select a temperature at which the crosslinking of the phosphate group can be promoted while suppressing the thermal decomposition and hydrolysis reaction of the cellulose fiber. In addition, the heat treatment temperature may be a temperature at which a phosphate group or a substituent derived from a phosphate group is crosslinked so that the number of crosslinking points of the cellulose fiber calculated by the above-described formula (1) is a predetermined value or more. preferable. Specifically, the heat treatment temperature is 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. Moreover, you may use a vacuum dryer, an infrared heating apparatus, and a microwave heating apparatus for a heating.

  It is preferable that the heating device used for the heat treatment is a device that can always discharge the moisture retained by the formed cellulose fiber (pulp) and the moisture generated by the addition reaction to the hydroxyl group of the fiber, such as phosphate groups, out of the system. For example, a blow type oven is preferable. If the moisture in the system is always discharged, the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphorylation, can be suppressed, and the acid hydrolysis of the sugar chain in the cellulose fiber can be suppressed. it can.

  The heat treatment time (heating time) is also affected by the heating temperature, but it is preferably 10 seconds or more and 300 minutes or less after the phosphorylating agent and the cellulose fiber are mixed and exposed to a heat source, and preferably 1 minute or more. It is more preferably 270 minutes or less, and further preferably 10 minutes or more and 120 minutes or less. In the present invention, the amount of phosphate groups introduced and the number of crosslinking points can be within the preferred ranges by setting the heat treatment temperature and the heating time to appropriate ranges.

<Washing process>
It is preferable that a washing process is further provided after the heating process. In the washing step, excess chemical solution such as a phosphorylating agent is washed away. In the washing step, it is preferable to repeat the operation of performing solid-liquid separation after pouring ion-exchanged water into a molded product (artificial culture soil) containing crosslinked cellulose fibers and stirring.

<Drying process>
It is preferable that a drying process is provided after the washing process. By providing a drying step, it is lightweight and easy to carry and an artificial culture soil can be obtained. In the drying step, it is preferable to leave the artificial culture soil in an environment of 20 ° C. or higher and 100 ° C. or lower. At this time, it is also preferable to perform air drying.

(Use)
Since the artificial culture soil of the present invention has both drainage and water retention, it is preferably used as an artificial culture soil for horticulture. Although the use of naturally-occurring soil has a problem of resource depletion, the artificially cultured soil of the present invention can be used as a substitute for such naturally-derived soil, and therefore, the role of conservation of natural resources is also expected. Is done.

In addition, when packaging soil for natural origin for sale, it is necessary to remove pathogens and pests by soot or the like after mining, but the artificial culture soil of the present invention contains pathogens and pests. Since it is not included, there is an advantage in that it is not necessary to perform a removal process.
Furthermore, since the artificial culture soil of the present invention has biodegradability, it can be easily disposed of and can function as a soil conditioner. Moreover, when a cellulose fiber is a thing which has a phosphate group, since a phosphoric acid elutes by mixing artificial culture soil in soil, the additional fertilization effect can also be anticipated.

  Hereinafter, the features of the present invention will be described more specifically with reference to Examples and Reference Examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

(Example)
<Preparation of phosphorylated cellulose molding>
As the softwood kraft pulp, Oji Paper's pulp (solid content 96 mass%, basis weight 213 g / m ² sheet form) was used as a raw material (hereinafter referred to as raw material pulp). 100 parts by mass of the above raw pulp (absolute dry mass) is impregnated with a mixed aqueous solution of ammonium dihydrogen phosphate and urea so that it becomes 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of ion-exchanged water. To obtain a chemical-impregnated pulp. After tearing the obtained chemical-impregnated pulp by hand and rounding it to a size of about 5 to 7 mm, it is dried and heat-treated in a hot air dryer at 165 ° C. for 10 minutes, and phosphoric acid groups and phosphoric acid are added to the cellulose in the pulp. A crosslinked structure was introduced to obtain a phosphorylated cellulose molded product.

  100 parts by mass of ion-exchanged water was added to 1 part by mass of the phosphorylated cellulose molded product, and after stirring with a magnetic stirrer, the phosphorylated cellulose molded product and the filtrate were separated using No2 filter paper. This operation was repeated three times, and the excess reactive chemical solution adhering to the phosphorylated cellulose molded product was removed by washing. Thereafter, the phosphorylated cellulose molded product was spread on a filter paper and air-dried for 24 hours in an environment of 25 ° C. and a relative humidity of 50%. In addition, the obtained phosphorylated cellulose molding (artificial culture soil) was as the photograph of FIG.

(Reference example)
As a reference example, commercially available horticultural kanuma soil was used. Prior to use, wood chips, sand particles and the like mixed in advance were visually removed from commercially available horticultural kanuma soil. In addition, since the powdered waste of Kanuma soil generated by rubbing adheres to the surface of the granular Kanuma soil, the surface of the garden Kanuma soil is washed with ion-exchanged water and adheres to the particle surface. After removing the powdery Kanuma soil, it was spread on a filter paper and air-dried for 24 hours in an environment of 25 ° C. and a relative humidity of 50%.

(analysis)
<Measurement of phosphate group introduction amount>
The amount of phosphate groups introduced into the phosphorylated cellulose molded product was measured by a neutralization titration method. Specifically, the phosphoric acid group contained in the cellulose fiber of the phosphorylated cellulose molding is completely converted into an acid form, and then refined by a mechanical treatment process (a refinement process). The amount of introduction was measured by determining the change in pH indicated by the slurry (dispersion) while adding a 0.1N aqueous sodium hydroxide solution to the cellulose-containing slurry.
In conversion of the phosphoric acid group into an acid form, the obtained phosphorylated cellulose molded product is diluted with ion-exchanged water so that the cellulose fiber concentration becomes 2% by mass, and a sufficient amount of 1N hydrochloric acid aqueous solution is added while stirring. It was added little by little. Next, the cellulose fiber-containing slurry is stirred for 15 minutes and then dehydrated to obtain a dehydrated sheet. Then, the slurry is diluted again with ion-exchanged water, and a 1N hydrochloric acid aqueous solution is added to repeat the phosphoric acid contained in the cellulose fiber. The group was completely changed to the acid form. Furthermore, the cellulose fiber-containing slurry was stirred and dispersed uniformly, and then the operation of obtaining a dehydrated sheet by filtration and dehydration was repeated to sufficiently wash away excess hydrochloric acid.
In the mechanical treatment process, ion-exchanged water was poured into the obtained dehydration sheet to obtain a cellulose fiber-containing slurry having a cellulose fiber concentration of 0.3% by mass. This slurry was processed for 30 minutes under the condition of 21500 rotations / minute using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.).

In the titration using an alkali, a change in pH value indicated by the dispersion was measured while adding a 0.1N sodium hydroxide aqueous solution to the fine fibrous cellulose-containing slurry. This neutralization titration gives two points where the increment (differential value of pH with respect to the amount of alkali dropped) is maximized in the curve plotting the measured pH against the amount of alkali added (the point at which the increment is maximum). And the second largest point). Of these, the amount of alkali required up to the maximum incremental point (hereinafter referred to as the first end point) obtained for the first time after adding alkali is equal to the amount of strongly acidic group in the dispersion used for titration. The amount of alkali required up to the maximum point of increment obtained (hereinafter referred to as the second end point) is equal to the amount of weakly acidic groups in the dispersion used for titration.
The alkali amount (mmol) required up to the first end point is divided by the solid content (g) in the titration target dispersion to obtain the first dissociated alkali amount (mmol / g). The amount introduced.

<Measurement of the number of crosslinking points>
The crosslinked structure is considered to be formed by dehydration condensation between phosphate groups introduced into the cellulose fiber. That is, the crosslinked structure is a structure in which a glucose unit of cellulose is bonded to each of two P atoms of pyrophosphate via O atoms. Therefore, when the crosslinked phosphate group is formed, the weakly acidic group is apparently lost, and the amount of alkali required by the second end point is reduced as compared with the amount of alkali required by the first end point. That is, the number of crosslinking points is equal to a value obtained by dividing the difference between the alkali amount required until the first end point (first dissociated alkali amount) and the alkali amount required until the second end point (second dissociated alkali amount) by 2.

(Evaluation)
The water retention characteristics of the phosphorylated cellulose molded product (artificial culture soil) of the example were evaluated.

<Measurement of water absorption and drainage>
One 100 mL capacity glass graduated cylinder with a known mass was prepared, and each of the phosphorylated cellulose moldings that had been washed and dried and the Kanuma soil that had been dried after washing were put to 55 mL, and the weight was measured. Ion exchange water was poured into the graduated cylinder to such an extent that the phosphorylated cellulose molded product or Kanuma soil was sufficiently immersed, and left in a room at 25 ° C. for 24 hours. After each sample was sufficiently absorbed by water, water was separated using No. 2 filter paper, spread on the filter paper to remove water droplets on the surface, and then returned to the measuring cylinder to measure volume and weight (Table 2). .

<Measurement of water retention rate (change in moisture content over time)>
Take 50 mL each of the washed phosphorylated cellulose molded product and the washed and dried Kanuma soil, add ion-exchanged water to the extent that the phosphorylated cellulose molded product or Kanuma soil is sufficiently immersed, and leave it at 25 ° C. for 24 hours. did. After each sample was sufficiently absorbed by water, water was separated using No. 2 filter paper and spread on the filter paper to remove water droplets on the surface. Thereafter, each sample was put into a 200 mL plastic cup, and after measuring the weight, it was allowed to stand in a laboratory at 25 ° C. and a relative humidity of 50%, and the weight was measured every few days to confirm the change in water content. (Table 3).

  As shown in Tables 2 and 3, the phosphorylated cellulose moldings of the examples were excellent in water absorption and water retention. Moreover, in the phosphorylated cellulose molded product of the Example, it can be said that it is excellent in drainage because the increase in volume after water absorption is suppressed despite the large amount of water absorption.

Claims (7)

  Artificial culture soil containing crosslinked cellulose fibers. The cellulose fiber has a phosphate group or a substituent derived from a phosphate group,
The artificial culture soil according to claim 1, wherein the phosphate group or a phosphate-derived substituent is crosslinked in at least a part of the cellulose fiber.   The artificial culture soil according to claim 1 or 2, which is a lump.   Content of the said cellulose fiber is 90 mass% or more with respect to the total solid content mass of the said artificial culture soil, The artificial culture soil of any one of Claims 1-3. The artificial culture soil according to any one of claims 1 to 4, wherein a volume change rate calculated by the following formula (a) is 30% or less.
Formula (a):
Volume change rate (%) = (volume of artificial culture soil after being immersed in ion exchange water for 24 hours−volume of artificial culture soil before being immersed in ion exchange water) / artificial culture soil before being immersed in ion exchange water Volume x 100 The artificial culture soil according to any one of claims 1 to 5, wherein a moisture content (%) calculated by the following formula (b) is 130% or more.
Formula (b):
Moisture content (%) = (Mass of artificial culture soil after being immersed in ion exchange water for 24 hours and then allowed to stand in an environment of 25 ° C. and 50% relative humidity for 24 hours, immersed in ion exchange water) Mass of artificially cultured soil before immersion) / Mass of artificially cultured soil before being immersed in ion-exchanged water × 100 Introducing a substituent into the cellulose fiber;
Forming a cellulose fiber having the substituent to obtain a molded product;
And a step of heating the molded article.