JP6723632B2 - Piping friction resistance reducer and transportation medium - Google Patents

Description

The present invention relates to a pipe frictional resistance reducing agent and a transportation medium.

Piping frictional resistance occurs when a heat transport medium flows in piping such as air conditioning.
This is in a "turbulent flow" state, in which when water flows in the pipe at a certain speed, water molecules in the inner wall of the pipe and the central part are violently mixed and flow. This is because most of the pipe frictional resistance is caused by this turbulent flow motion, and it can be expected that the pipe frictional resistance can be significantly reduced by suppressing the turbulent flow (making the flow laminar).

As such a piping friction resistance reducing agent and a transportation medium, a metal coating agent and a surfactant are added to an aqueous liquid as a heat carrier medium (Patent Document 1), a quaternary ammonium salt-based surfactant, and a glycol. And at least one antifreezing agent selected from alcohol and a silicone emulsion-based defoaming agent are added to an aqueous liquid as a heat carrier medium (Patent Document 2) and a specific amine oxide-based surfactant. Friction resistance reducer composition for brine containing (Patent Document 3), (A) Water-soluble polymer compound having an average molecular weight of 100,000 or more (B) Anionic surfactant, and friction resistance reducer composition for aqueous medium (Patent Document 4) and the like are disclosed.

JP, 2011-195650, A JP, 2005-263961, A JP, 2004-323814, A JP-A-2002-20725

When the cationic surfactants disclosed in Patent Documents 1 to 3 are used, the concentration of the cationic surfactant in the transport medium decreases due to the adsorption of the cationic surfactant in the pipe, and the effect of reducing frictional resistance decreases. In addition, the transportation medium is foamed, and the cationic surfactant has a strong bactericidal action, so that there is a problem that the environmental load at the time of disposal is large.

Further, the water-soluble polymer having a predetermined molecular weight disclosed in Patent Document 4 has a problem in that the molecular weight is reduced due to friction with the inner wall of the pipe over time, and the frictional resistance reducing effect is reduced.

Therefore, it is an object of the present invention to provide a pipe frictional resistance reducer and a transportation medium which have a low environmental load at the time of disposal and can maintain an excellent frictional resistance reduction effect.

The present invention provides the following [1] to [4].
[1] Contains cellulose nanofibers,
The eddy suppression rate calculated by the following formula (1) is 85% or more,
A transport medium having a stability over time of the eddy suppression rate calculated by the following formula (2) of 94% or more.
Vortex suppression rate α (%)=100×(DVW-DVDR)/DVW... (1)
(In the formula (1), DVW and DVDR represent the vortex depth (mm) of tap water and the transport medium, respectively. The vortex depth (mm) is 90 g of tap water added to a 100 mL beaker, or transport). The depth (mm) of the vortex generated when the medium is stirred with a magnetic stirrer (stirrer: 8×30 mm, 550 rpm) is shown.
Stability of eddy suppression rate with time (%)=100×α60/α (2)
(For α60 in formula (2), 90 g of a transportation medium was added to a 100 mL beaker, and the mixture was stirred for 60 minutes at 8000 rpm using TK Robomix (manufactured by Primix Co., Ltd.), and then a magnetic stirrer (stirrer: 8×30 mm). The vortex suppression rate calculated from the above formula (1) is shown as DVDR (mm), where the depth of the vortex generated when stirring at 550 rpm) is shown.)
[2] The transport medium according to [1], wherein the number average fiber diameter of the cellulose nanofibers is 2 nm or more and 500 nm or less, the aspect ratio of the fibers is 50 or more, and the cellulose nanofiber has a cellulose type I crystal structure.
[3] The transport medium according to [1] or [2], wherein the cellulose nanofiber is anion-modified.
[4] The transport medium according to any one of [1] to [3], which contains 0.01% by mass or more and 10% by mass or less of the cellulose nanofiber.

INDUSTRIAL APPLICABILITY The pipe frictional resistance reducing agent and the transportation medium of the present invention have an effect that the environmental load at the time of disposal is small and an excellent frictional resistance reducing effect can be maintained.

Next, embodiments of the present invention will be described in detail.

The pipe frictional resistance reducing agent of the present invention contains cellulose nanofibers. The cellulose nanofiber of the present invention is a fiber obtained by defibrating a cellulose raw material to a nano size.

The cellulose nanofibers of the present invention preferably have a number average fiber diameter of 2 nm or more and 500 nm or less, a fiber aspect ratio of 50 or more, and a cellulose I-type crystal structure.
The number average fiber diameter of the cellulose nanofibers is 2 nm or more and 500 nm or less, preferably 2 nm or more and 150 nm or less, more preferably 2 nm or more and 100 nm or less, and particularly preferably 3 nm or more and 80 nm or less. If the number average fiber diameter is less than 2 nm, the cellulose nanofibers may be dissolved and the frictional resistance reduction effect may not be exerted, and if the number average fiber diameter exceeds 500 nm, the dispersibility of the cellulose nanofibers may decrease. However, the friction reducing effect may be reduced.

From the viewpoint of dispersibility of the cellulose nanofibers, the maximum fiber diameter of the cellulose nanofibers is preferably 1000 nm or less, and particularly preferably 500 nm or less.
The number average fiber diameter and maximum fiber diameter of the cellulose nanofibers can be measured, for example, as follows. That is, an aqueous dispersion of fine cellulose having a solid content of 0.05 to 0.1% by weight is prepared, and the dispersion is cast on a hydrophilized carbon film-covered grid to obtain a transmission electron microscope. This is a (TEM) observation sample. When fibers having a large fiber diameter are included, a scanning electron microscope (SEM) image of the surface cast on glass may be observed. Then, observation with an electron microscope image is performed at a magnification of 5000 times, 10,000 times, or 50,000 times depending on the size of the constituent fibers. At that time, an axis having an arbitrary image width in vertical and horizontal directions is assumed in the obtained image, and the sample and the observation conditions (magnification, etc.) are adjusted so that 20 or more fibers intersect the axis. Then, after obtaining an observation image satisfying this condition, two vertical and horizontal axes are drawn for each image, and the fiber diameter of the fibers intersecting the axis is visually read. In this way, at least three images of non-overlapping surface portions are photographed with an electron microscope, and the value of the fiber diameter of the fibers intersecting each of the two axes is read (therefore, at least 20 fibers×2×3=120). Information on the fiber diameter of the book is obtained). The maximum fiber diameter and the number average fiber diameter are calculated from the fiber diameter data thus obtained.

The aspect ratio of the cellulose nanofibers is 50 or more, preferably 100 or more, more preferably 200 or more. If the aspect ratio is less than 50, the dispersibility of the cellulose nanofibers may decrease, and the friction reducing effect may decrease.

The aspect ratio of the cellulose nanofibers can be measured, for example, by the following method. That is, TEM obtained by casting the cellulose nanofibers on a carbon film-coated grid which has been subjected to a hydrophilization treatment and negatively staining with 2% uranyl acetate. From the image (magnification: 10000 times), the number average fiber diameter and the fiber length of the cellulose nanofibers were observed. That is, the number average fiber diameter and the fiber length were calculated according to the methods described above, and the aspect ratio was calculated according to the following formula (1) using these values.

The cellulose nanofiber is a fiber obtained by refining a naturally-occurring cellulose raw material having an I-type crystal structure. That is, in the process of biosynthesis of natural cellulose, nanofibers called microfibrils are first formed almost without exception, and these are multibunched to form a high-order solid structure.

The fact that the cellulose constituting the cellulose nanofibers has an I-type crystal structure means that, for example, in the diffraction profile obtained by wide-angle X-ray diffraction image measurement, around 2 theta=14 to 17° and 2 theta=22 to 23° It can be identified by having typical peaks at two nearby positions.

The cellulose nanofiber can be produced by a known method, and specifically, the following is performed.

For example, it can be obtained by suspending natural cellulose in water and treating it with a high-pressure homogenizer or a grinder to make it fine.

The natural cellulose is not particularly limited as long as it is cellulose derived from plants or animals, microorganisms, and kraft pulp or dissolved pulp derived from softwood or hardwood, cotton linter, lignocellulose with low cellulose purity, wood flour, plant cellulose, bacterial cellulose. And so on.

In addition, as the cellulose nanofiber, bacterial cellulose produced by bacteria can be used. Examples of the bacterium include Acetobacter genus and the like, and more specifically, Acetobacter aceti, Acetobacter subsp., Acetobacter xylinum, and the like. To be By culturing these bacteria, cellulose is produced from the bacteria. The obtained product contains bacteria and cellulose nanofibers (bacterial cellulose) produced by the bacteria and connected to the bacteria. Therefore, the product is taken out of the medium, washed with water, or treated with an alkali. By removing the bacteria in this way, hydrous bacterial cellulose containing no bacteria can be obtained.

The cellulose nanofibers are preferably anion-modified. The anion-modified cellulose is not particularly limited, but specific examples thereof include oxidized cellulose, carboxymethyl cellulose, polyvalent carboxymethyl cellulose, long-chain carboxy cellulose, and the like. Of these, oxidized cellulose is preferable because it has excellent selectivity for hydroxyl groups on the fiber surface and mild reaction conditions.

In addition, carboxymethyl cellulose is also preferable in terms of versatility and safety.

The oxidized cellulose is prepared by using natural cellulose as a raw material, an N-oxyl compound as an oxidation catalyst in water, and a co-oxidizing agent to oxidize the natural cellulose to obtain a reactant fiber, and remove impurities. It can be obtained by a production method including a refining step of obtaining a reaction fiber impregnated with water and a dispersing step of dispersing the reaction fiber impregnated with water in a solvent.

In the oxidized cellulose, it is preferable that the hydroxyl group at the C6 position of each glucose unit in the cellulose molecule is selectively oxidized and modified to be any one of an aldehyde group, a ketone group, and a carboxyl group. From the viewpoint of dispersibility in water, the content of carboxyl groups (the amount of carboxyl groups) is preferably 1.2 to 2.5 mmol/g, more preferably 1.5 to 2.0 mmol/g.

To measure the amount of carboxyl groups in the oxidized cellulose, for example, 60 ml of 0.5 to 1 wt% slurry was prepared from a cellulose sample whose dry weight was precisely weighed, and the pH was adjusted to about 2.5 with a 0.1 M hydrochloric acid aqueous solution. After that, a 0.05 M aqueous sodium hydroxide solution is dropped to measure the electric conductivity. The measurement is continued until the pH is about 11. From the amount (V) of sodium hydroxide consumed in the neutralization step of the weak acid, the change in electrical conductivity of which is moderate, the amount of carboxyl groups can be calculated according to the following formula (2).

The amount of the carboxyl group can be adjusted by controlling the addition amount of the co-oxidant used in the oxidation step of the cellulose nanofibers and the reaction time, as described later.

The oxidized cellulose is preferably reduced with a reducing agent after the oxidative modification. As a result, a part or all of the aldehyde group and the ketone group are reduced to return to the hydroxyl group. The carboxyl group is not reduced. Then, by the reduction, the total content of the aldehyde group and the ketone group of the cellulose nanofiber measured by the semicarbazide method is preferably 0.3 mmol/g or less, particularly preferably 0 to 0.1 mmol/g. , Most preferably substantially 0 mmol/g. As a result, the decrease in the molecular weight of the cellulose nanofibers is suppressed, and the friction reducing effect can be maintained for a long period of time.

The oxidized cellulose is one that has been oxidized with a co-oxidizing agent in the presence of an N-oxyl compound such as 2,2,6,6-tetramethylpiperidine (TEMPO), and an aldehyde group generated by the oxidation reaction. It is preferable that the ketone group and the ketone group are reduced by a reducing agent because the cellulose nanofibers can be easily obtained. From the above viewpoint, it is more preferable that the reduction with the reducing agent is with sodium borohydride (NaBH ₄ ).

The total content of aldehyde groups and ketone groups is measured by the semicarbazide method, for example, as follows. That is, to the dried sample, exactly 50 ml of a 3 g/l aqueous solution of semicarbazide hydrochloride adjusted to pH=5 with a phosphate buffer solution is added, sealed tightly, and shaken for 2 days. Next, 10 ml of this solution is accurately collected in a 100 ml beaker, 25 ml of 5N sulfuric acid and 5 ml of 0.05N potassium iodate aqueous solution are added, and the mixture is stirred for 10 minutes. Then, 10 ml of a 5% potassium iodide aqueous solution was added, and immediately, using an automatic titrator, titration was performed with a 0.1 N sodium thiosulfate solution. From the titration amount and the like, according to the following formula (3), The amount of carbonyl groups (total content of aldehyde groups and ketone groups) can be determined. It should be noted that semicarbazide reacts with an aldehyde group or a ketone group to form a Schiff base (imine), but does not react with a carboxyl group. Therefore, it is considered that only the aldehyde group and the ketone group can be quantified by the above measurement.

In the oxidized cellulose, the hydroxyl group at the C6 position of each glucose unit in the cellulose molecule on the fiber surface is selectively oxidatively modified to be any of an aldehyde group, a ketone group and a carboxyl group. Whether or not only the hydroxyl group at the C6 position of the glucose unit on the surface of this cellulose nanofiber is selectively oxidized can be confirmed by, for example, a ¹³ C-NMR chart. That is, the peak at 62 ppm corresponding to the C6 position of the primary hydroxyl group of the glucose unit, which can be confirmed by the ¹³ C-NMR chart of cellulose before oxidation, disappears after the oxidation reaction, and instead is a peak derived from a carboxyl group or the like (178 ppm). Peak appears from the carboxyl group). In this way, it can be confirmed that only the C6 hydroxyl group of the glucose unit is oxidized to a carboxyl group or the like.

In addition, the detection of the aldehyde group in the oxidized cellulose can also be performed by, for example, a Fehling's reagent. That is, for example, when a Fehling's reagent (a mixed solution of sodium potassium tartrate and sodium hydroxide and an aqueous solution of copper sulfate pentahydrate) was added to a dried sample and then heated at 80° C. for 1 hour, a supernatant was obtained. It is possible to judge that the aldehyde group was not detected when the blue color and the cellulose nanofiber part showed a dark blue color, and that the aldehyde group was detected when the supernatant had a yellow color and the cellulose fiber part had a red color. it can.

The cellulose nanofibers obtained by defibrating the oxidized cellulose are preferably produced by (1) oxidation reaction step, (2) reduction step, (3) refining step, (4) dispersion step (micronization treatment step), and the like, Specifically, it is preferably manufactured by the following steps.

(1) Oxidation reaction step After the natural cellulose and the N-oxyl compound are dispersed in water (dispersion medium), a cooxidant is added to start the reaction. During the reaction, 0.5M aqueous sodium hydroxide solution is added dropwise to maintain the pH at 10 to 11, and the reaction is considered to be completed when no change in pH is observed. Here, the co-oxidant is not a substance that directly oxidizes cellulose hydroxyl groups, but a substance that oxidizes an N-oxyl compound used as an oxidation catalyst.

The natural cellulose means a purified cellulose isolated from a biosynthesis system of cellulose such as a plant, an animal or a gel produced by bacteria. More specifically, softwood pulp, hardwood pulp, cotton linter, cotton lint and other cotton pulp, straw pulp, bagasse pulp and other non-wood pulp, bacterial cellulose (BC), cellulose isolated from sea squirt, seaweed Cellulose and the like isolated from can be mentioned. These may be used alone or in combination of two or more. Among these, preferred are softwood pulp, hardwood pulp, cotton linter, cotton lint and other cotton pulp, and straw pulp, bagasse pulp and other non-wood pulp. The natural cellulose is preferably subjected to a treatment for increasing the surface area such as beating, because the reaction efficiency can be increased and the productivity can be increased. In addition, when the natural cellulose that has been stored without being dried (never dry) after isolation and purification is used, since the bundle of microfibrils is likely to swell, the reaction efficiency is improved, It is preferable because the number average fiber diameter after the chemical treatment can be reduced.

The dispersion medium of natural cellulose in the reaction is water, and the concentration of natural cellulose in the reaction aqueous solution is arbitrary as long as it is a concentration capable of sufficiently diffusing the reagent (natural cellulose). Usually, it is about 5% or less with respect to the weight of the reaction aqueous solution, but the reaction concentration can be increased by using a device having a strong mechanical stirring force.

The N-oxyl compound may be, for example, a compound having a nitroxy radical which is generally used as an oxidation catalyst. The N-oxyl compound is preferably a water-soluble compound, and particularly preferably a piperidine nitroxyoxy radical, particularly 2,2,6,6-tetramethylpiperidinooxy radical (TEMPO) or 4-acetamido-TEMPO. preferable. The N-oxyl compound may be added in a catalytic amount, preferably 0.1 to 4 mmol/l, more preferably 0.2 to 2 mmol/l in the reaction aqueous solution.

Examples of the co-oxidizing agent include hypohalous acid or a salt thereof, halogenous acid or a salt thereof, perhalogenic acid or a salt thereof, hydrogen peroxide, perorganic acid and the like. These may be used alone or in combination of two or more. Of these, alkali metal hypohalites such as sodium hypochlorite and sodium hypobromite are preferable. When the sodium hypochlorite is used, it is preferable to proceed the reaction in the presence of an alkali metal bromide such as sodium bromide from the viewpoint of the reaction rate. The alkali metal bromide is added in an amount of about 1 to 40 times, preferably about 10 to 20 times the molar amount of the N-oxyl compound.

The pH of the reaction aqueous solution is preferably maintained in the range of about 8-11. The temperature of the aqueous solution is arbitrary at about 4 to 40°C, but the reaction can be carried out at room temperature (25°C), and the temperature control is not particularly required. In order to obtain a desired amount of carboxyl groups and the like, the degree of oxidation is controlled by the addition amount of the cooxidant and the reaction time. Usually, the reaction time is about 5-120 minutes and at most 240 minutes is completed.

(2) Reduction step It is preferable that the oxidized cellulose further undergoes a reduction reaction after the oxidation reaction. Specifically, the finely oxidized cellulose after the oxidation reaction is dispersed in purified water, the pH of the aqueous dispersion is adjusted to about 10, and the reduction reaction is performed with various reducing agents. As the reducing agent used in the present invention, a general reducing agent can be used, but LiBH ₄ , NaBH ₃ CN, NaBH _{4 and the} like are preferable. Of these, NaBH ₄ is preferable in terms of cost and availability.

The amount of reducing agent is preferably in the range of 0.1 to 4% by weight, particularly preferably in the range of 1 to 3% by weight, based on the finely divided oxidized cellulose. The reaction is carried out at room temperature or a temperature slightly higher than room temperature, usually for 10 minutes to 10 hours, preferably for 30 minutes to 2 hours.

After completion of the above reaction, the pH of the reaction mixture is adjusted to about 2 with various acids, and solid-liquid separation is performed with a centrifuge while sprinkling purified water to obtain cake-like fine oxidized cellulose. Solid-liquid separation is performed until the electric conductivity of the filtrate becomes 5 mS/m or less.

(3) Purification step Next, purification is performed for the purpose of removing unreacted co-oxidizing agents (such as hypochlorous acid) and various by-products. At this stage, the reaction fibers are usually not dispersed evenly into nanofiber units. Therefore, it is possible to obtain high-purity (99% by weight or more) reaction fibers by a normal purification method, that is, by repeating washing and filtration. Use as a dispersion of water.

As the refining method in the refining step, any apparatus can be used as long as it can achieve the above-mentioned object, such as a method using centrifugal dehydration (for example, a continuous decanter). The aqueous dispersion of the reactant fiber thus obtained has a solid content (cellulose) concentration in the range of approximately 10% by weight to 50% by weight when squeezed. Considering the subsequent dispersion step, if the solid content concentration is higher than 50% by weight, extremely high energy is required for dispersion, which is not preferable.

(4) Dispersion process (miniaturization process)
The reactant fiber (water dispersion) impregnated with water obtained in the purification step is dispersed in a dispersion medium to carry out a dispersion treatment. The viscosity increases with the treatment, and it is possible to obtain a dispersion of cellulose nanofibers which has been subjected to a fine treatment. Thereafter, the cellulose nanofibers may be dried if necessary, and as a method for drying the dispersion of the cellulose nanofibers, for example, when the dispersion medium is water, spray drying, freeze drying, vacuum drying. When a dispersion medium is a mixed solution of water and an organic solvent, a drying method using a drum dryer, a spray drying method using a spray dryer, or the like is used. In addition, the dispersion of the cellulose nanofibers may be used in a dispersion state without being dried.

As the disperser used in the dispersing step, a homomixer under high-speed rotation, a high-pressure homogenizer, an ultra-high pressure homogenizer, an ultrasonic dispersion processor, a beater, a disc refiner, a conical refiner, a double disc refiner, a grinder, etc. Use of a strong and beating device is preferable in that more efficient and high-level downsizing can be performed, and a hydrous lubricant composition can be obtained economically. Examples of the disperser include a screw mixer, paddle mixer, disper mixer, turbine mixer, disper, propeller mixer, kneader, blender, homogenizer, ultrasonic homogenizer, colloid mill, pebble mill, and bead mill grinder. You can use it. Further, two or more kinds of dispersers may be used in combination.

Carboxymethyl cellulose, which is one of the anion-modified cellulose nanofibers, can be produced by the following method using the cellulose raw material. That is, cellulose is used as a raw material, and a solvent contains 3 to 20 times by mass of a lower alcohol, specifically, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, or the like alone. Alternatively, a mixed medium of two or more kinds and water is used. The mixing ratio of the lower alcohol is 60 to 95% by mass. As the mercerization agent, 0.5 to 20 times mol of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide, is used per glucose residue of cellulose. A mercerization treatment is performed by mixing cellulose, a solvent, and a mercerization agent. The reaction temperature at this time is 0 to 70° C., preferably 10 to 60° C., and the reaction time is 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Then, the carboxymethylating agent is added in an amount of 0.05 to 10 times mol per glucose residue to carry out an etherification reaction. The reaction temperature at this time is 30 to 90° C., preferably 40 to 80° C., and the reaction time is 30 minutes to 10 hours, preferably 1 hour to 4 hours.

Cellulose nanofibers can be obtained by defibrating the carboxymethyl cellulose with a high-pressure homogenizer or the like. The high-pressure homogenizer is a device that pressurizes a fluid with a pump and ejects it from a very delicate gap provided in a flow path. It is possible to emulsify, disperse, defibrate, pulverize and superfine particles by the total energy such as collision between particles and shearing force due to pressure difference.

The treatment condition by the homogenizer of the present invention is not particularly limited, but the pressure condition is 30 MPa or more, preferably 100 MPa or more, more preferably 140 MPa or more. In addition, prior to the defibration/dispersion treatment with a high-pressure homogenizer, it is also possible, if necessary, to pretreat the carboxymethyl cellulose using a known mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer. is there.

In the present invention, the degree of carboxymethyl substitution per glucose unit of carboxymethyl cellulose is preferably 0.02 or more and 0.50 or less. By introducing a carboxymethyl substituent into cellulose, the cellulose electrically repels each other. Therefore, the cellulose introduced with the carboxymethyl substituent can be easily nano-disentangled. If the carboxymethyl substituent per glucose unit is less than 0.02, the nanofiber cannot be sufficiently defibrated, and thus the frictional resistance reducing effect may be significantly reduced. On the other hand, when the carboxymethyl substituent per glucose unit exceeds 0.50, carboxymethyl cellulose swells or dissolves, so that it cannot be obtained as nanofibers, and the frictional resistance reducing effect may be significantly reduced.

The transport medium of the present invention is a dispersion in which the pipe frictional resistance reducing agent and other additives are dispersed in a medium.

Other additives can be added to the transport medium of the present invention within a range that does not impair the effects of the present invention. Although not particularly limited, specifically, azobis-based copper rust inhibitors (benzotriazole, trade name Dogard, etc.), organic acid salt-based, nitrite-based and molybdate-based iron rust inhibitors, scale inhibitors, slimes Additives such as treatment agents, dispersants, preservatives and antifoaming agents may be added in predetermined amounts as necessary.

The medium of the present invention refers to an aqueous medium used for the purpose of heat transfer. Specifically, water, lower alcohol aqueous solutions such as methyl alcohol and ethyl alcohol, glycol aqueous solutions such as ethylene glycol and propylene glycol, saturated chain hydrocarbon polyhydric alcohol aqueous solutions such as D-sorbitol and other organic compound solutions, calcium chloride. Examples thereof include aqueous solutions of inorganic salts such as sodium chloride, but are not particularly limited thereto. Of these, water, lower alcohol aqueous solutions such as methyl alcohol and ethyl alcohol, and glycol aqueous solutions such as ethylene glycol and propylene glycol are preferable.

The medium of the present invention contains 0.01% by mass or more and 10% by mass or less of cellulose nanofibers, preferably 0.05% by mass or more and 5% by mass or less, and more preferably 0.1% by mass. It is 1 mass% or less. When the content of cellulose nanofibers is less than 0.01% by mass, the frictional resistance reduction effect may be significantly reduced, and when it is more than 10% by mass, the viscosity of the medium may be increased and the fluidity of the medium may be reduced. is there.

Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples. In the examples, “%” means mass basis unless otherwise specified.

[Production of cellulose nanofibers]
[Production of Cellulose Fiber A1 (for Examples)]
50 g of softwood bleached kraft pulp (NBKP) was dispersed in 4950 g of water to prepare a dispersion having a pulp concentration of 1% by mass. This dispersion was treated with Serendipiter MKCA6-3 (manufactured by Masuko Sangyo Co., Ltd.) 30 times to obtain cellulose fibers A1.

[Production of Cellulose Fiber A2 (for Examples)]
100 g of softwood pulp was put into a mixed solution of 435 g of isopropanol (IPA), 65 g of water and 9.9 g of NaOH, and stirred at 30° C. for 1 hour. 23.0 g of a 50% monochloroacetic acid IPA solution was added to this slurry system, and the temperature was raised to 70° C. and the reaction was carried out for 1.5 hours. The obtained reaction product was washed with 80% methanol, then replaced with methanol and dried to produce carboxymethylated cellulose fiber. Next, pure water was added to the cellulose fiber to dilute it to 2%, and the cellulose fiber A2 was manufactured by using a high pressure homogenizer (H11 manufactured by Sanwa Engineering Co., Ltd.) once at a pressure of 100 MPa.

[Production of Cellulose Fiber A3 (for Examples)]
To 2 g of softwood pulp, 150 ml of water, 0.25 g of sodium bromide and 0.025 g of TEMPO were added, and after sufficiently stirring and dispersing, a 13 wt% sodium hypochlorite aqueous solution (co-oxidizing agent) was added to the pulp 1. The amount of sodium hypochlorite was added to 0 g so as to be 12 mmol/g, and the reaction was started. Since the pH decreases with the progress of the reaction, 0.5N sodium hydroxide aqueous solution was added dropwise so as to maintain the pH at 10 to 11, and the reaction was continued until no change in pH was observed (reaction time: 120 minutes. ). After completion of the reaction, 0.1N hydrochloric acid was added to neutralize, and filtration and washing with water were repeated for purification to obtain cellulose fibers whose surface was oxidized. Next, pure water was added to the cellulose fiber to dilute it to 2%, and the cellulose fiber A3 was manufactured by treating it once with a high pressure homogenizer (H11 manufactured by Sanwa Engineering Co., Ltd.) at a pressure of 100 MPa.

[Production of Cellulose A′1 (for Comparative Example)]
According to the production of cellulose fiber A3, except that regenerated cellulose is used in place of the softwood pulp as the raw material, and the amount of the sodium hypochlorite aqueous solution added is 27.0 mmol/g based on 1.0 g of regenerated cellulose. Thus, cellulose A′1 was produced.
With respect to each cellulose obtained as described above, each characteristic was evaluated according to the following criteria. The results are also shown in Table 1 below.

〔Crystal structure〕
An X-ray diffractometer (RINT-Ultima3 manufactured by Rigaku Corporation) was used to measure the diffraction profile of each cellulose fiber, and the diffraction profile was measured at two positions near 2 theta=14 to 17° and 2 theta=22 to 23°. When a typical peak was observed, the crystal structure (type I crystal structure) was evaluated as “present”, and when no peak was observed, it was evaluated as “absent”.

[Number average width of shorter width]
The number average width of cellulose was observed using a transmission electron microscope (TEM) (JEM-1400 manufactured by JEOL Ltd.). That is, from each TEM image (magnification: 10000 times) negatively stained with 2% uranyl acetate after casting each cellulose fiber on the carbon film-covered grid having been subjected to the hydrophilization treatment, the narrower one was obtained according to the method described above. The number average width of was calculated.

〔aspect ratio〕
From the TEM image (magnification: 10000 times) negatively stained with 2% uranyl acetate after the cellulose was cast on the carbon film-covered grid that had been subjected to the hydrophilization treatment, the number average width and the long width of the cellulose were shorter. The number average width was observed. That is, the number average width of the shorter width and the number average width of the longer width were calculated according to the methods described above, and the aspect ratio was calculated according to the following formula (1) using these values. ..

From the results in Table 1 above, all of the celluloses A1 to A3 for Examples had a cellulose I type crystal structure in which the number average width of the shorter width was in the range of 2 to 500 nm.

[Adjustment of transportation medium]
[Example 1]
The above-mentioned cellulose fiber A1 was diluted to 0.1% with tap water, and then stirred at 8000 rpm for 10 minutes using TK Robomix (manufactured by PRIMIX Corporation) to obtain a transportation medium.

[Examples 2 and 3]
It was prepared in the same manner as in Example 1 except that A2 and A3 were used instead of the cellulose fiber A1.

[Comparative Examples 1 to 4]
Instead of the cellulose fiber A1, A′1, xanthan gum (XG) (manufactured by Ternite Co., product name XCD polymer), polyvinylpyrrolidone (PVP) (manufactured by Dai-ichi Kogyo Seiyaku Co., product name Pitzcor K-90), carboxymethylcellulose ( CMC) (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name Serogen BSH-12) was used, and prepared in the same manner as in Example 1.

The eddy suppression rate (%) and its temporal stability (%) were evaluated by the following methods with respect to the transport media obtained in Examples 1 to 4 and Comparative Examples 1 to 4 described above. The evaluation results are shown in Table 2.
<Vortex suppression rate evaluation method>
90 g of the above-mentioned transport medium was added to a 100 mL beaker (manufactured by Shibata Scientific Co., Ltd.), and the vortex depth (mm) generated when stirred with a magnetic stirrer (stir bar: 8×30 mm, 550 rpm) was measured, and the following formula was used. The eddy suppression rate α (%) was calculated from (4).

<Evaluation method of temporal stability of eddy suppression rate>
90 g of the above-mentioned transportation medium was added to a 100 mL beaker (manufactured by Shibata Scientific Co., Ltd.), and stirred at 8000 rpm for 60 minutes using TK Robomix (manufactured by Primix Co., Ltd.). Then, the depth (mm) of the vortex generated when stirring was performed with a magnetic stirrer (stirrer: 8×30 mm, 550 rpm), and the vortex suppression rate α ₆₀ (%) was calculated from the above formula (4). Then, using the calculated α ₆₀ , the temporal stability (%) of the eddy suppression rate was calculated by the following formula (5).

As a result of the evaluation, all the transportation media of the examples showed a high frictional resistance reduction effect over time.
On the other hand, when the cellulose fiber A′1 was used, the effect of reducing the frictional resistance as in the example was not obtained. Further, when HEC, PVP, or CMC, which is a general friction resistance reducing agent, was used, the same friction resistance reduction effect as that of the example was shown, but stability with time was not obtained.

The pipe frictional resistance reducing agent and the transportation medium in the pipe of the present invention can be stably used in a liquid that is circulated, for example, in heating, cooling systems and district heating and cooling systems of various industrial plants.

Claims (4)

Contains cellulose nanofibers,
The eddy suppression rate calculated by the following formula (1) is 85% or more,
A transport medium having a stability over time of the eddy suppression rate calculated by the following formula (2) of 94% or more.
Vortex suppression rate α (%)=100×(DVW-DVDR)/DVW... (1)
(In the formula (1), DVW and DVDR represent the vortex depth (mm) of tap water and the transport medium, respectively. The vortex depth (mm) is 90 g of tap water added to a 100 mL beaker, or transport). The vortex depth (mm) generated when the medium is stirred with a magnetic stirrer (stirrer: 8×30 mm, 550 rpm) is shown.
Stability of eddy suppression rate with time (%)=100×α60/α (2)
(For α60 in the formula (2), 90 g of a transportation medium was added to a 100 mL beaker, and the mixture was stirred for 60 minutes at 8000 rpm using TK Robomix (manufactured by Primix Corporation), and then a magnetic stirrer (stirrer: 8×30 mm). The vortex suppression rate calculated from the above formula (1) is shown as DVDR (mm), where the depth of the vortex generated when stirring at 550 rpm). The transport medium according to claim 1, wherein the cellulose nanofibers have a number average fiber diameter of 2 nm or more and 500 nm or less, an aspect ratio of fibers of 50 or more, and a cellulose type I crystal structure. The transport medium according to claim 1 or 2, wherein the cellulose nanofiber is anion-modified. The transport medium according to any one of claims 1 to 3, wherein the content of the cellulose nanofibers is 0.01% by mass or more and 10% by mass or less.