Soil solidification agent, and soil solidification method using the same

Abstract

To provide a soil solidification agent that is excellent in soil solidification hardness and dust scattering prevention effect.SOLUTION: A soil solidification agent contains lignin and cationic polymers. In the sum total of the lignin and cationic polymers, the lignin content is 50 wt.% or more. The lignin has a weight average molecular weight of 10,000 or more. The soil solidification agent is a colloidal aqueous solution containing the lignin and cationic polymers.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a soil solidification agent containing lignin and a soil solidification method using the same. [Background technology]

[0002] In earthworks (banking and cutting), if the finished flat ground or slope is left as is, dust will be scattered by wind etc. Also, it will be eroded by rain, and muddy water will run off, adversely affecting the surrounding area. In addition, it will become necessary to carry out additional readjustment of the eroded slope, which will increase the amount of work and have a greater impact on the surrounding area.

[0003] Normally, measures such as sprinkling water or covering the slope with sheets are taken to prevent erosion caused by dust scattering and rainwater.

[0004] However, watering must be done frequently to keep the ground surface from drying out, which is labor intensive. In addition to the installation work, sheet covering also requires management to prevent the sheet from being turned up by the wind, which is labor intensive. Furthermore, used sheets become waste.

[0005] In order to reduce the above-mentioned burden, chemicals for stabilizing the topsoil have been developed. For example, the invention in Patent Document 1 relates to a solution in which a cationic polymer, an anionic polymer (carboxymethylcellulose), and salt are dissolved in water, and is highly safe and biodegradable. In addition, the invention in Patent Document 2 relates to a decontamination method in which a suspension of clay particles and an aqueous solution of a polyion complex are sprayed on radioactive cesium-contaminated soil to peel off the topsoil from the soil, and has the advantage of being able to minimize the amount of topsoil to be removed.

[0006] Furthermore, Patent Document 3 proposes a method for producing a soil solidification composition that can be produced in a short time and has excellent workability. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2016-191048 A [Patent Document 2] Patent No. 6064220 [Patent Document 3] JP 2019-56075 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the techniques proposed in these patent documents have room for improvement in terms of soil solidification hardness, etc. In addition, since Patent Document 3 recommends the use of salt in combination, there has been a demand for improvements that would eliminate the need for salt.

[0009] Therefore, an object of the present invention is to provide a soil solidification agent that is excellent in soil solidification hardness and dust scattering prevention effects. [Means for solving the problem]

[0010] As a result of extensive efforts, the present inventors have found that the problems can be solved by the following (1) to (4): (1) A soil solidification agent in the form of a colloidal aqueous solution, comprising lignosulfonic acid having a weight-average molecular weight of 10,000 or more and 500,000 or less, or a high-molecular-weight lignin obtained by polymer-treating the lignosulfonic acid by one or more methods selected from an aldehyde condensation reaction treatment and a urethane-type crosslinking reaction treatment, and a cationic polymer, wherein the cationic polymer contains a polymer of a quaternary ammonium salt. (2) The soil solidification agent according to claim 1, wherein the colloidal aqueous solution has a total solids concentration of the high molecular weight lignin and the cationic polymer of 4 mass % or more. (3) A method for producing a soil solidification agent in the form of a colloidal aqueous solution, which is produced by subjecting lignin sulfonic acid having a weight average molecular weight of 10,000 or more and 500,000 or less, or the lignin sulfonic acid to polymer treatment by one or more methods selected from an aldehyde condensation reaction treatment and a urethane type crosslinking reaction treatment, to prepare high molecular weight lignin, and mixing the prepared high molecular weight lignin with a cationic polymer, wherein the cationic polymer contains a polymer of a quaternary ammonium salt. (4) The method for producing a soil solidification agent according to claim 3, wherein the colloidal aqueous solution has a total solids concentration of the high molecular weight lignin and the cationic polymer of 4 mass % or more. Effect of the Invention

[0011] According to the present invention, a soil solidification agent having excellent soil solidification hardness and dust scattering prevention effects can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below based on preferred embodiments thereof, but the present invention is not limited to the following embodiments.

[0013] <Lignin> The lignin used in the present invention preferably has a methoxyl group content of 3 to 20 mass% per solid content. If the methoxyl group content is 3% or less, the amount of lignin contained is so small that no thickening effect is observed. Since lignin generally contains methoxyl groups bonded to aromatic nuclei, the methoxyl group content serves as an index of the lignin content. Usually, the methoxyl group content differs depending on the type of woody biomass, with lignin derived from coniferous trees containing 3 to 12% methoxyl groups per solid content and lignin derived from broad-leaved trees containing 8 to 20% methoxyl groups per solid content.

[0014] In the present invention, the methoxyl group content is a value measured by the quantitative determination of methoxyl groups by the Viebock and Schwappach method (see "Lignin Chemical Research Methods," pp. 336-340, published by Uni Publishing Co., Ltd. in 1994).

[0015] The lignin used in the present invention varies depending on the processing method used for woody biomass, and there are several types of lignin.

[0016] Examples of such lignin include the following lignins: lignin sulfonic acid, kraft lignin, soda lignin, soda-anthraquinone lignin, organosolv lignin, explosive lignin, sulfuric acid lignin, etc. Of these, it is preferable to use lignin sulfonic acid and kraft lignin.

[0017] The lignin used in the present invention may be one or a mixture of two or more of the above-mentioned lignins.

[0018] The lignin sulfonic acid and kraft lignin used in the present invention will be described in detail below, but the lignins are not limited to these.

[0019] (Lignosulfonic acid) Lignosulfonic acid refers to a compound in which at least a portion of lignin or its decomposition products is substituted with a sulfonic acid (salt) group. The lignosulfonic acid of the present invention usually has an S content of the sulfonic acid (salt) group of 1.0 to 6.0 mass%.

[0020] The S content of the sulfonic acid (salt) group of lignosulfonic acid refers to the amount of S contained in the sulfonic acid (salt) group relative to the solid content of lignosulfonic acid. Specifically, it is a value calculated from the following mathematical formula (1). Formula (1): S content (mass%) of sulfonic acid (salt) group = total S content (mass%) - inorganic S content (mass%) (In formula (1), the S content indicates the S content relative to the solid content of lignosulfonic acid.)

[0021] In formula (1), the total S content can be quantified by ICP atomic emission spectrometry, and the inorganic S content can be calculated as the sum of the SO3 content and the SO4 content quantified by ion chromatography.

[0022] The lignosulfonic acid of the present invention contains reducing sugars. Reducing sugars are generally left behind in the process of sulfite cooking of woody biomass. The reducing sugars are usually contained in an amount of 0.01 to 20.0 mass %.

[0023] Reducing sugars refer to sugars that exhibit reducing properties and generate aldehyde or ketone groups in a basic solution. Examples of reducing sugars include all monosaccharides, disaccharides such as maltose, lactose, arabinose, and invert sugars of sucrose, and polysaccharides. The reducing sugars contained in the alkali treatment effluent usually include cellulose, hemicellulose, and their decomposition products. Examples of decomposition products of cellulose and hemicellulose include monosaccharides such as rhamnose, galactose, arabinose, xylose, glucose, mannose, and fructose; and oligosaccharides such as xylooligosaccharides and cellooligosaccharides. The reducing sugar content can be determined by measuring the reducing sugar content using the Somogyi-Schaffer method and converting the measured value into the amount of glucose.

[0024] The lignosulfonic acid may be in an unionized state, or the hydrogen atom of the sulfonic acid group may be replaced with a counter ion. Examples of the counter ion include a sodium ion, a calcium ion, a magnesium ion, and an ammonium ion. The counter ion may be a single type of counter ion, or a combination of two or more types of counter ions.

[0025] The lignosulfonic acid of the present invention usually contains an inorganic salt. Examples of the inorganic salt include sodium sulfate, sodium sulfite, sodium chloride, magnesium sulfate, magnesium sulfite, magnesium chloride, calcium sulfate, calcium sulfite, calcium chloride, ammonium sulfate, ammonium sulfite, ammonium chloride, and sodium hydroxide. The content of the inorganic salt in the lignosulfonic acid is usually 1 to 25 mass%.

[0026] The lignin sulfonic acid used in the present invention may be prepared or may be a commercially available product. Examples of commercially available products include Sanex P202, Sanex P252, Sanex P321, Sanex SCP, Sunflow RH, Vanilex HW, Vanilex N, Vanilex RN, Pearlex NP, and Pearlex DP (all manufactured by Nippon Paper Industries Co., Ltd.). The preparation method is exemplified below, but is not limited to those prepared by the following preparation method.

[0027] (Method for preparing lignosulfonic acid) Lignosulfonic acid having a low degree of sulfonation can be prepared, for example, by subjecting lignocellulosic raw materials to a sulfite treatment. Among these, it is preferable to subject lignocellulosic raw materials to a sulfite cooking treatment.

[0028] The lignocellulose raw material is not particularly limited as long as it contains lignocellulose in the structure. For example, pulp raw materials such as wood and non-wood can be mentioned. Examples of wood include coniferous wood such as Yezo spruce, red pine, cedar, and cypress, and broadleaf wood such as white birch and beech. The age of the wood and the part where it is harvested are not important. Therefore, wood harvested from trees of different ages or wood harvested from different parts of a tree may be used in combination. Examples of non-wood include bamboo, kenaf, reed, and rice. The lignocellulose raw material may be one of these materials alone or two or more of them may be used in combination.

[0029] The sulfite treatment can be carried out by contacting at least one of sulfurous acid and a sulfite salt with a lignocellulosic raw material to obtain an intermediate product. The conditions for the sulfite treatment are not particularly limited as long as they allow introduction of a sulfonic acid (salt) group to the α-carbon atom of the side chain of lignin contained in the lignocellulosic raw material.

[0030] The sulfite treatment is preferably carried out by the sulfite cooking method. This allows the lignin in the lignocellulosic raw material to be sulfonated more quantitatively. The sulfite cooking method is a method in which the lignocellulosic raw material is reacted at high temperature in a solution of at least one of sulfurous acid and a sulfite salt (e.g., an aqueous solution: cooking liquid). This method has been established and is being carried out industrially as a method for producing sulfite pulp. Therefore, by carrying out the sulfite treatment by the sulfite cooking method, it is possible to improve the economic efficiency and ease of implementation.

[0031] When sulfite cooking is carried out, examples of the sulfite salt include magnesium salts, calcium salts, sodium salts and ammonium salts.

[0032] The sulfurous acid (SO2) concentration in at least one of the sulfurous acid and sulfite solutions is not particularly limited, but the ratio of mass (g) of SO2 to 100 mL of reaction solution is preferably 1 g / 100 mL or more, and more preferably 2 g / 100 mL or more when sulfite cooking is performed. The upper limit is preferably 20 g / 100 mL or less, and more preferably 15 g / 100 mL or less when sulfite cooking is performed. The SO2 concentration is preferably 1 g / 100 mL to 20 g / 100 mL, and more preferably 2 g / 100 mL to 15 g / 100 mL when sulfite cooking is performed.

[0033] The pH value of the sulfurous acid treatment is not particularly limited, but is preferably 10 or less, and more preferably 5 or less when sulfite cooking is performed. The lower limit of the pH value is preferably 0.1 or more, and more preferably 0.5 or more when sulfite cooking is performed. The pH value during the sulfurous acid treatment is preferably 0.1 to 10, and more preferably 0.5 to 5 when sulfite cooking is performed.

[0034] The temperature of the sulfite treatment is not particularly limited, but is preferably 170° C. or lower, and more preferably 150° C. or lower when sulfite cooking is performed. The lower limit is preferably 70° C. or higher, and more preferably 100° C. or higher when sulfite cooking is performed. The temperature condition of the sulfite treatment is preferably 70 to 170° C., and more preferably 100 to 150° C. when sulfite cooking is performed.

[0035] The treatment time for the sulfurizing treatment is not particularly limited, and although it depends on the conditions of the sulfurizing treatment, it is preferably 0.5 to 24 hours, and more preferably 1.0 to 12 hours.

[0036] In the sulfite treatment, it is preferable to add a compound that supplies a counter cation (salt). By adding a compound that supplies a counter cation, the pH value in the sulfite treatment can be kept constant. Examples of compounds that supply counter cations include MgO, Mg(OH)2, CaO, Ca(OH)2, CaCO3, NH3, NH4OH, NaOH, NaHCO3, and Na2CO3. The counter cation is preferably a magnesium ion.

[0037] In the sulfurous acid treatment, when a solution of at least one of sulfurous acid and sulfite is used, the solution may contain, in addition to SO2 and a counter cation (salt), a digestion and penetration agent (e.g., a cyclic ketone compound such as anthraquinone sulfonate, anthraquinone, or tetrahydroanthraquinone) as necessary.

[0038] There is no limitation on the equipment used in the sulfite treatment, and for example, generally known dissolving pulp manufacturing equipment can be used.

[0039] The intermediate product may be separated from the solution of at least one of sulfurous acid and sulfite salt according to a conventional method, for example, a method for separating the sulfurous acid pulping wastewater after sulfurous acid pulping.

[0040] The sulfite cooking treatment may produce a lignosulfonic acid with a high degree of sulfonation, in which case a lignosulfonic acid with a low degree of sulfonation can be obtained by partial desulfonation treatment. Examples of partial desulfonation methods include, but are not limited to, the method described in JP-A-58-45287.

[0041] Also, lignosulfonic acid with a low degree of sulfonation can be obtained by the method described in JP 2016-135834 A.

[0042] The lignin sulfonic acid content (wt%) was calculated by the amount of methoxyl groups present in 10 mg of sample according to the quantitative determination method of methoxyl groups described in Method in Ligin Chemistry (ed. Junzo Nakano, Uni Publishing Co., Ltd.), and converted to the lignin content (wt%).

[0043] (Kraft lignin) Kraft lignin can be used as the lignin or lignin derivative of the present invention. The above-mentioned kraft lignin is also known as thiolignin or sulfate lignin. As the kraft lignin, a prepared product or a commercially available product can be used. As a preparation method, an alkaline solution of kraft lignin, powdered kraft lignin obtained by spray-drying an alkaline solution of kraft lignin to obtain a powder, or acid-precipitated kraft lignin obtained by precipitating an alkaline solution of kraft lignin with an acid can be used.

[0044] The alkaline solution of kraft lignin can be obtained by known methods such as those described in JP-A-2000-336589, but is not limited to these methods.

[0045] Kraft lignin usually contains reducing sugars and inorganic salts, the contents of which are as exemplified above in the section on lignosulfonic acid.

[0046] As the acid-precipitated kraft lignin obtained by precipitating an alkaline solution of kraft lignin with an acid, powdered acid-precipitated kraft lignin obtained by the methods described in WO2006 / 038863, WO2006 / 031175, and WO2012 / 005677 can be used, but is not limited to these methods.

[0047] Sulfonated lignin obtained by sulfonating the above-mentioned kraft lignin may be used. For example, sulfomethylated kraft lignin sulfomethylated by the method described in "Study on the Use of Lignin (Part 3) Sulfomethylation of Thiolignin; Yasushi Oita, Junzo Nakano, Nobuhiko Migita: Mokuzai Gakkaishi, Vol. 12, No. 5, pp. 239-244 (1966)" and sulfonated lignin described in US5049661 are included.

[0048] The sulfonated lignin may be prepared or may be a commercially available product, such as POLYFON or REAX (both manufactured by Ingevity).

[0049] (Method for preparing high molecular weight lignin) As the soil solidification agent of the present invention, lignins such as lignosulfonic acid, low-sulfonated lignosulfonic acid, kraft lignin, sulfomethylated kraft lignin, and sulfonated lignin as described above can be used as they are. However, in order to achieve a more excellent effect, it is also possible to use high molecular weight lignins in which the molecular weight of lignin has been increased by a polymerization treatment.

[0050] Examples of the polymerization treatment include an aldehyde condensation reaction using formaldehyde or glyoxal, an epoxy-type crosslinking reaction using a diglycidyl ether compound, and a urethane-type crosslinking reaction using an isocyanate compound. Of these, an aldehyde condensation reaction using formaldehyde and an epoxy-type crosslinking reaction using a diglycidyl ether compound are preferred.

[0051] The lower limit of the weight average molecular weight of the lignin obtained by the polymerization treatment is preferably 10,000 or more, more preferably 30,000 or more, even more preferably 50,000 or more, even more preferably 80,000 or more, even more preferably 100,000 or more, and particularly preferably 150,000 or more and 200,000 or more. The upper limit is preferably 10 million or less, more preferably 8 million or less, even more preferably 5 million or less, even more preferably 3 million or less, and particularly preferably 2 million or less, 1 million or less, and 500,000 or less. If the lower limit is less than 30,000, the soil solidification hardness when used as a soil solidification agent is not significantly exhibited, and if the upper limit is 10 million or more, the lignin has a resinous form and its solubility in water is reduced, making it difficult to mix it as a soil solidification agent.

[0052] The weight average molecular weight can be measured by a known method using gel permeation chromatography (GPC) in terms of polyethylene glycol. The measurement conditions for GPC are not particularly limited, and the following conditions can be mentioned, for example. The weight average molecular weight in the examples described later is a value measured under these conditions.

[0053] Measuring device: Tosoh Columns used: Shodex Column OH-pak SB-806HQ, SB-804HQ, SB-802.5HQ Eluent: 0.05 mM sodium nitrate / acetonitrile 8 / 2 (v / v) Standard material: Polyethylene glycol (Tosoh or GL Science) Detector: Differential refractometer (Tosoh Corporation) Calibration curve; Polyethylene glycol standard

[0054] <Cationic polymer> The cationic polymer may be of natural or synthetic origin. For example, a polymer having an amino group or a polymer of a quaternary ammonium salt, cationic cellulose, cationic starch, etc., may be used. Examples of such a polymer include dicyandiamide-formaldehyde resin, diethylenetriamine-dicyandiamide-ammonium chloride condensate, (meth)acryloyloxyalkyltrialkylammonium chloride polymer, diallyldimethylammonium chloride polymer, ethyleneimine polymer, diallylamine polymer, ammonia-epichlorohydrin-dimethylamine copolymer, polyacrylamide resin, polymethacrylate resin, polyacrylate resin, cationic cellulose, cationic starch, etc.

[0055] Moreover, two or more kinds of cationic polymers can be used in combination.

[0056] Of these, the soil solidification agent of the present invention preferably contains a cationic polymer that at least includes a polymer having an amino group or a polymer of a quaternary ammonium salt, and examples of such cationic polymers include diallyldimethylammonium chloride polymers and salts thereof, methacryloxyethyltrimethylammonium polymers and salts thereof, vinyltrimethylammonium polymers and salts thereof, and methacryloethyltrimethylammonium polymers and salts thereof.

[0057] The weight average molecular weight of the cationic polymer is preferably 10,000 or more, more preferably 50,000 or more, and particularly preferably 150,000 or more. The upper limit is preferably 1,000,000 or less, more preferably 800,000 or less, further preferably 600,000 or less, and particularly preferably 400,000 or less.

[0058] The weight average molecular weight of the cationic polymer can be measured in the same manner as the measurement method for lignin described above.

[0059] <Soil solidification agent> The soil solidification agent of the present invention contains the above-mentioned lignin and cationic polymer. It is important that the total lignin content of the lignin and the cationic polymer is 50% by weight or more.

[0060] If the lignin content is less than 50% by weight, sufficient hardness cannot be obtained during soil solidification, and the present invention is not suitable. The lignin content in the total of the lignin and the cationic polymer is preferably 60% by weight or more, more preferably 65% ​​by weight or more, and even more preferably 70% by weight or more. The upper limit is 99% by weight or less, preferably 97% by weight or less, and more preferably 95% by weight or less.

[0061] The soil solidification agent of the present invention may contain other components in addition to the above-mentioned lignin and cationic polymer, so long as the effects of the present invention are not adversely affected. Examples of such other components include various salts, polymer adhesives, plasticizers, dispersants, surfactants, thickeners, viscosity adjusters, preservatives, colorants, deodorizers, etc.

[0062] When other components are contained in the soil solidification agent of the present invention, the amount of the other components is preferably 10% by weight or less, more preferably 5% by weight or less, based on the total solid content of the soil solidification agent. If the amount of the other components is outside this range, there is a concern that it may be difficult to obtain the expected hardness during soil solidification.

[0063] <How to prepare soil solidification agent> The soil solidification agent of the present invention is preferably used in the form of a colloidal aqueous solution containing lignin and a cationic polymer. For example, a method for preparing such a colloidal aqueous solution may include a method in which an aqueous solution containing lignin and an aqueous solution containing a cationic polymer are prepared, and then the aqueous solution containing the cationic polymer is added and mixed while the aqueous solution containing the lignin is being stirred.

[0064] The thus obtained aqueous colloidal solution preferably has a solid content concentration of 4% by mass or more, more preferably 5% by mass or more, and the upper limit is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0065] A solid content of 4% by mass or more is suitable for the present invention because it is easy to penetrate not only the surface but also the inside of the soil when it comes into contact with the soil. On the other hand, if the solid content exceeds 20% by mass, the viscosity of the colloidal aqueous solution becomes too high, making it difficult to mix uniformly with the soil when it comes into contact with the soil, and is not suitable for the present invention.

[0066] <Soil solidification method> The soil solidification agent of the present invention is preferably infiltrated into soil after 10 minutes or more have elapsed since preparation of a colloidal aqueous solution containing lignin and a cationic polymer. The colloidal aqueous solution in which lignin and a cationic polymer have been brought into contact can form a polyion complex and solidify the soil with which it comes into contact. Among these, if the time is less than 10 minutes after contact between lignin and a cationic polymer, the formation of a polyion complex in the colloidal aqueous solution is insufficient, and even if the colloidal aqueous solution is brought into contact with soil in this state, the formation of a three-dimensional matrix between the soil and the polyion complex is insufficient, making it difficult to obtain sufficient solidification hardness of the soil, and therefore this is not suitable for the present invention.

[0067] In addition, it is more preferable to infiltrate the aqueous colloidal solution containing lignin and a cationic polymer into the soil after 15 minutes or more have elapsed, and even more preferable to infiltrate the aqueous colloidal solution containing lignin and a cationic polymer into the soil after 20 minutes or more have elapsed. As an upper limit, it is preferable to infiltrate the aqueous colloidal solution containing lignin and a cationic polymer into the soil within 24 hours after the preparation of the aqueous colloidal solution, more preferably within 20 hours, even more preferably within 10 hours, and particularly preferably within 5 hours. If more than 24 hours have elapsed after the preparation of the aqueous colloidal solution, the polyion complex will solidify too much, which is unsuitable for the present invention.

[0068] The period after the preparation of the aqueous colloidal solution containing lignin and a cationic polymer may be considered as beginning from the time when the lignin and the cationic polymer come into contact with each other.

[0069] The method for infiltrating the lignin into the soil is not particularly limited, but examples thereof include a method in which a colloidal aqueous solution containing lignin and a cationic polymer is evenly sprayed in a mist or liquid form onto the target soil (such as the ground). EXAMPLES

[0070] The present invention will be described below with reference to examples, but the scope of the present invention is not limited thereto. In the examples, % means % by weight, and parts means parts by weight, unless otherwise specified.

[0071] (Production Example 1: Lignin Mixture 1) Sanex P321 (a powder containing lignin sulfonic acid, manufactured by Nippon Paper Industries Co., Ltd., molecular weight 11,700, lignin sulfonate content 60% by weight) was diluted to a solids concentration of 5% by mass (lignin sulfonic acid concentration 3% by mass) to prepare an aqueous solution called lignin mixture 1.

[0072] (Production Example 2: Lignin Mixture 2) A stainless steel reaction vessel equipped with a thermometer, a stirrer, and a reflux device and lined with glass was charged with 85 parts of lignin sulfonic acid Pearlex NP (manufactured by Nippon Paper Industries Co., Ltd., lignin sulfonate content 89% by weight), 271 parts of ion-exchanged water, 9 parts of 37% formaldehyde (manufactured by Wako Pure Chemical Industries), and 25 parts of 72% sulfuric acid (manufactured by Wako Pure Chemical Industries), and heated to 100 ° C. under stirring. After heating, the mixture was reacted for 2 hours while maintaining the temperature at 100 ° C. After cooling and neutralizing to pH 7 with calcium hydroxide, the gypsum generated by neutralization was removed by filtration. A high molecular weight lignin sulfonic acid solution with a solid content concentration of 5 mass% (lignin sulfonic acid concentration 4.3 wt%, lignin mixture 2) was obtained by adding water. The weight average molecular weight of the high molecular weight lignin sulfonic acid contained in the obtained lignin mixture 2 was 348,700.

[0073] (Production Example 3: Cationic Polymer 1) An aqueous solution of polydiallyldimethylammonium chloride (manufactured by Merck, weight average molecular weight 200,000 to 350,000) with a solid content concentration of 20% by mass was diluted with distilled water to a solid content concentration of 5% by weight to prepare cationic polymer 1.

[0074] Example 1 The cationic polymer 1 (2 ml) obtained in Production Example 3 was gradually added to the lignin mixture 1 (8 ml) obtained in Production Example 1 while stirring and mixing, to obtain a colloidal aqueous solution 1 with a solid content concentration of 5 mass % (lignosulfonic acid:cationic polymer=70.6:29.4. However, the total solid content of lignosulfonic acid and cationic polymer is 100 weight %). 11 minutes after the start of the addition of the cationic polymer, colloid solution 1 (4 parts) was dripped evenly onto black soil (18 parts) evenly spread in an aluminum cup (area 20 cm3, thickness 2 cm). The dripping state was visually observed. After dropping, the sample was dried in an explosion-proof dryer (40°C) for 12 hours and then evaluated as follows.

[0075] <Appearance> The solidification properties of the black soil in the aluminum cup obtained in Example 1 were visually evaluated according to the following criteria. ○: It can be seen that the black soil particles are clumping together, and solidification is progressing. △: Some of the black soil was confirmed to have aggregated, but the rest was not solidified. ×: There is no change in the state of the black soil before and after the addition, and it has not solidified.

[0076] <Hardness> The black soil in the aluminum cup obtained in Example 1 was touched with the index finger, and the hardness was calculated from the feel according to the following criteria. 〇: The shape is maintained even when the black soil is lightly pressed. △: Although it has solidified, when the black soil is lightly pressed, its shape changes. ×: When the black soil is lightly pressed, the finger is buried and the soil does not solidify.

[0077] <Wind resistance test> After measuring the total weight WA of the black soil in the aluminum cup obtained in Example 1, air was blown for 5 minutes with a dryer at an angle of 45 degrees and a distance of 25 cm at a wind speed of 10 m / s (room temperature). After that, the total weight WB of the black soil in the aluminum cup was measured, and the weight loss rate (WA-WB) / WA×100 was calculated and evaluated according to the following criteria. 〇: Weight reduction rate is 10% or less ×: Weight loss rate exceeds 10%

[0078] <Thickness> The solidified black soil was removed from the aluminum cup without crumbling, and the thickness of the black soil was measured using a digital caliper (As One Corporation, Model BDC200). The measurement was performed three times, and the solidified thickness was calculated from the average value.

[0079] Example 2 A colloidal aqueous solution 2 (lignin sulfonic acid: cationic polymer = 77.5: 22.5) with a solid content concentration of 5 mass% was obtained in the same manner as in Example 1, except that lignin mixture 1 was changed to lignin mixture 2. Counting from the start of addition of the cationic polymer, 15 minutes later, colloidal solution 1 (4 parts) was evenly dripped onto black soil (18 parts) evenly spread in an aluminum cup (area 20 cm3, thickness 2 cm). The dripping state was visually observed. After dropping, the sample was dried in an explosion-proof dryer (40°C) for 12 hours and then evaluated as follows.

[0080] Example 3 The cationic polymer 1 (0.5 ml) obtained in Production Example 3 was gradually added to the lignin mixture 2 (9.5 ml) obtained in Production Example 2 while stirring and mixing, to obtain a colloidal aqueous solution 3 (lignin sulfonic acid:cationic polymer = 94.2:5.8) with a solid content concentration of 5 mass %. Thereafter, evaluation was performed using black soil in the same manner as in Example 2.

[0081] Comparative Example 1 An evaluation was carried out using black soil in the same manner as in Example 1, except that the lignin mixture 1 (4 ml) obtained in Production Example 1 was directly used instead of the aqueous colloidal solution.

[0082] Comparative Example 2 An evaluation was carried out using black soil in the same manner as in Example 1, except that the lignin mixture 2 (4 ml) obtained in Production Example 2 was directly used instead of the aqueous colloidal solution.

[0083] Comparative Example 3 Evaluation was carried out using black soil in the same manner as in Example 1, except that the cationic polymer 1 (4 ml) obtained in Production Example 3 was directly used instead of the aqueous colloidal solution.

[0084] Comparative Example 4 The cationic polymer (6 ml) obtained in Production Example 3 was gradually added to the lignin mixture 1 (4 ml) obtained in Production Example 1 while stirring and mixing, to obtain a colloidal solution 4 (lignin sulfonic acid:cationic polymer = 28.6:71.4) with a solid content concentration of 5 mass%. Thereafter, evaluation was performed using black soil in the same manner as in Example 1.

[0085] Comparative Example 5 The cationic polymer (6 ml) obtained in Production Example 3 was gradually added to the lignin mixture 2 (4 ml) obtained in Production Example 2 while stirring and mixing, to obtain a colloidal solution 5 (lignin sulfonic acid:cationic polymer = 36.4:63.6) with a solid content concentration of 5 mass%. Thereafter, evaluation was performed using black soil in the same manner as in Example 1.

[0086] [Table 1]

Claims

1. A soil solidification agent in the form of a colloidal aqueous solution, comprising lignin sulfonic acid having a weight average molecular weight of 10,000 or more and 500,000 or less, or a high molecular weight lignin obtained by polymer-treating the lignin sulfonic acid by one or more methods selected from an aldehyde condensation reaction treatment and a urethane-type crosslinking reaction treatment, and a cationic polymer, wherein the cationic polymer comprises a polymer of a quaternary ammonium salt.

2. 2. The soil solidification agent according to claim 1, wherein the colloidal aqueous solution has a total solids concentration of the high molecular weight lignin and the cationic polymer of 4 mass % or more.

3. A method for producing a soil solidification agent in the form of a colloidal aqueous solution, which is produced by using lignosulfonic acid having a weight-average molecular weight of 10,000 or more and 500,000 or less, or by subjecting the lignosulfonic acid to polymer treatment by one or more methods selected from an aldehyde condensation reaction treatment and a urethane-type crosslinking reaction treatment to prepare high molecular weight lignin, and mixing the high molecular weight lignin with a cationic polymer, wherein the cationic polymer contains a polymer of a quaternary ammonium salt.

4. 4. The method for producing a soil solidification agent according to claim 3, wherein the colloidal aqueous solution has a total solids concentration of the high molecular weight lignin and the cationic polymer of 4 mass % or more.

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