JP6597285B2 - Cement hardener coating agent - Google Patents

Description

  The present invention relates to a coating agent for a cement-based cured body. More specifically, the present invention relates to a coating agent for a cement-based cured body that exhibits excellent effects in improving the reinforcing property of the cement-based cured body, preventing drying shrinkage, preventing neutralization, and preventing salt damage.

  Cement-based hardened bodies such as cement paste, mortar, and concrete are widely used in civil engineering structures, building structures, concrete products, and the like. The water used for the production of the cement-based cured body is an amount of water that exceeds the theoretically required amount used for the hydration reaction or the like in order to ensure workability. This excessive water evaporation causes drying shrinkage of the cement-based hardened body to progress, and cracks are generated. On the other hand, a concrete structure is required not to crack for a long time from the viewpoint of durability, aesthetics, and the like.

  In order to prevent cracking of the cement-based cured body due to such drying, a cement-based cured body coating agent (shrinkage reducing agent, coating film curing agent, etc.) is used. In general, shrinkage reducing agents are used in a method that is mixed during the production of a cement-based cured body, and a coating curing agent is applied to the surface of the cement-based cured body by a method such as application or spraying on the surface. To use.

  Of these, all commercially available shrinkage reducing agents have been adjusted to be suitable for blending. However, it is difficult to control the quality of the mixing of the shrinkage reducing agent during the production of mortar or concrete because the entrained air is not stable. In addition, as a method of reducing shrinkage by a method other than the use of mixing, there is also known a method of applying the cement-based hardened body after it has been placed until it hardens (Patent Document 1).

  On the other hand, the coating film curing agent is for forming a film on its surface for curing concrete and the like, and for suppressing the evaporation of water from the surface by the film. Resin-based coating curing agents such as paraffin-based and aqueous emulsion-based are known (Patent Document 2).

JP 2006-143481 A Japanese Patent Laid-Open No. 11-21184

  However, the method described in Patent Document 1 has a problem that the strength and durability of the concrete are lowered, such that the surface becomes brittle after curing and poor curing occurs in a low temperature environment. Moreover, the coating film curing agent currently disclosed by patent document 2 is influenced by the temperature at the time of construction in pot life, hardening time, and it cannot be constructed when the moisture content of a construction surface is high, and its viscosity is high. Therefore, there are problems that it is difficult to handle, requires labor for construction, and a sufficient shrinkage reduction effect cannot be obtained. Further, in the cement-based cured body, there are problems of neutralization and salt damage. Neutralization is a phenomenon in which the pH of a pore solution that is essentially alkaline is lowered by the intrusion of carbon dioxide in the atmosphere into the cured body and causing a carbonation reaction. Neutralization proceeds from the surface of the hardened body, and when the steel material position such as a reinforcing bar is reached, the passive film is destroyed. As a result, the steel material is corroded, and the hardened body is cracked due to the accumulation and expansion of the corrosion products. The salt damage is a phenomenon in which corrosion of the steel material in the hardened body is promoted by the presence of chloride ions, and the volume expansion of the corrosion product causes cracking and peeling of the hardened body and a reduction in the cross section of the steel material.

  Therefore, the present invention is applied to the surface of the cement-based cured body, and exhibits excellent effects in improving the reinforcement of the cement-based cured body, preventing drying shrinkage, preventing neutralization, and preventing salt damage. It is to provide a body coating agent.

The present invention provides the following (1) to (5).
(1) A coating agent for a cement-based cured body containing cellulose nanofibers.
(2) The cellulose nanofiber includes at least one of oxidized cellulose nanofiber, carboxymethylated cellulose nanofiber, cationized cellulose nanofiber, etherified cellulose nanofiber, and esterified cellulose nanofiber. The coating agent for cement-type cured bodies according to (1).
(3) In the oxidized cellulose nanofiber, a part of the hydroxyl group at the C6 position in the glucose unit of cellulose constituting the cellulose nanofiber is oxidized to a carboxyl group, and the amount of the carboxyl group relative to the cellulose nanofiber is 0. The coating agent for hardened cementitious materials according to (2), which is 0.5 mmol / g to 3.0 mmol / g.
(4) In the carboxymethylated cellulose nanofiber, a part of the hydrogen atom of the hydroxyl group in the glucose unit of cellulose constituting the cellulose nanofiber is substituted with a carboxymethyl group, and the carboxymethyl substitution per glucose unit The coating agent for cement-type cured bodies according to (2), wherein the degree is 0.01 to 0.50.
(5) In the cationized cellulose nanofiber, a part of the hydrogen atom of the hydroxyl group in the glucose unit of cellulose constituting the cellulose nanofiber is substituted with a cationic group, and the degree of cation substitution per glucose unit is The coating agent for cement-type cured bodies according to (2), which is 0.01 to 0.40.

  The present invention is for a cement-based cured body that exhibits excellent effects in improving the reinforcing property of the cement-based cured body, preventing drying shrinkage, preventing neutralization, and preventing salt damage by applying to the surface of the cement-based cured body. A coating agent can be provided.

  The coating agent for cement-based cured bodies of the present invention (hereinafter sometimes abbreviated as “coating agent”) and a method for producing a cement-based cured body using the same will be described in detail below.

  Although the reason why the present invention exhibits excellent effects in improving the reinforcing property of cement-based cured bodies, preventing drying shrinkage, preventing neutralization, and preventing salt damage is not clear, 1) Improvement of reinforcing properties: cellulose nanofibers are fine 2) Prevention of drying shrinkage: Cellulose nanofibers have high water retention, so that rapid drying shrinkage at the initial stage of curing of the cement-based cured body is suppressed. ) Neutralization and prevention of salt damage: The cellulose fiber has a high degree of crystallinity, so it is assumed that it is caused by forming a dense structure film and exhibiting high barrier properties.

(1) Cement-based hardened body The cement-type hardened body in the present invention is any of cement paste in which cement is mixed with water, mortar in which fine aggregate is mixed as an aggregate, and concrete in which coarse aggregate is further blended. After adding various additives as needed, the cement composition is filled (placed) in the mold, and is not adversely affected by low temperature, drying, rapid temperature changes, vibration, impact, and load. It is a cured body produced by curing while protecting (curing) for a certain period of time and finally removing it from the mold (demolding). There is no restriction | limiting in particular about the manufacturing method of a cement composition, a conveyance method, a setting method, a curing method, a management method, etc., A normal method can be employ | adopted. Below, the cement, aggregate, additive, and water, which are materials in the cement-based cured body, will be described in detail.

(1-1) Cement In the present invention, any kind of cement may be used, and two or more kinds of materials may be mixed and used. The types of cement include, for example, Portland cement (ordinary, early strength, very early strength, moderate heat, sulfate-resistant and low alkali type), various mixed cements (blast furnace cement, silica cement, fly ash cement), white Portland cement. Cement, alumina cement, super fast cement (1 clinker fast cement, 2 clinker fast cement, magnesium phosphate cement), grout cement, oil well cement, low heat cement (low heat blast furnace cement, fly ash mixed low heat heat type) Blast furnace cement, cement with high belite content), ultra-high strength cement, cement-based solidified material, eco-cement (cement manufactured using one or more of municipal waste incineration ash and sewage sludge incineration ash). Blast furnace slag, fly ash, cinder ash, clinker ash, husk ash, silica fume, silica powder, limestone powder and other fine powder, gypsum and the like may be added to the cement.

(1-2) Aggregates As aggregates, for example, sand, gravel, crushed stone; granulated slag; recycled aggregate, etc .; siliceous, clay, zircon, high alumina, silicon carbide, graphite, chromium , Refractory aggregates such as chromic and magnesia.

(1-3) Additives In the present invention, one or more conventionally known additives can be used as necessary for cement. Specifically, AE (air entrainment) agent, water reducing agent, high performance water reducing agent, AE water reducing agent, high performance AE water reducing agent, fluidizing agent, curing accelerator, rust preventive agent, adhesion mortar stabilizer, setting retarder , Shrinkage reducing agents, separation reducing agents, foaming agents (foaming agents), anti-freezing agents (cold-resistance promoters), and the like. The method of adding these additives to the cement composition is not particularly limited, and examples thereof include a method of adding to the ready-mixed concrete or the fresh concrete after the manufacture.

(1-4) Water The water that can be used for the cement composition is not particularly limited. Water other than tap water, tap water shown in JIS A 5308 Annex 9 (river water, lake water, well water, etc.), recovered water, etc. Is exemplified. The water content in the cement composition is usually 4 to 50% by weight. Generally, when the shrinkage reducing agent for cement composition is 1 to 49% by weight with respect to the water content in the cement composition, an oil-in-water emulsion and solubilization are formed.

(2) Cement-based cured body coating agent The cement-based cured body coating agent of the present invention is characterized by containing cellulose nanofibers, and the cement-based cured body containing the cellulose nanofibers of the present invention. The period during which the coating agent is applied to the surface is from the casting to the completion of curing, preferably from the end of the setting reaction of the cement-based hardened body to the age of 7 days, more preferably from the end of the setting reaction. It is a period up to 3 days of age, and an excellent effect is manifested by application during this period.
If it is earlier than the end of the setting reaction, it may cause a decrease in surface strength and poor curing. When the material is later than 7 days, the shrinkage reduction effect is reduced because the drying shrinkage progresses rapidly during the period up to here.

Here, the completion of the setting reaction of the cement-based hardened body means that for cement paste that does not substantially contain aggregate components, the end time according to JIS R 5201 “Cement physical test method”, and for mortar or concrete This means the end time specified in JIS A 1147 “Concrete setting time test method”. In addition, the age in the present invention refers to an elapsed period from the time when the raw material is mixed and poured into water to produce concrete and then placed on the mold.
The amount of the coating agent of the present invention applied to the surface of the cement-based cured body is preferably in the range of 50 to 300 g / m2, and more preferably in the range of 100 to 200 g / m2. When the amount is less than 50 g / m 2, the surface coverage may not be sufficient, which is not preferable because moisture easily evaporates and the shrinkage reduction effect is hardly exhibited. Moreover, when exceeding 300 g / m <2>, since it takes time to fully impregnate the inside of a hardening body after construction, it is unpreferable. The coating agent is dried in the range of 5 to 35 ° C.

  The coating method of the coating agent of the present invention is not particularly limited as long as it can be applied to the surface of the cement-based cured body, and may be performed by spraying, spraying, spraying, etc. in addition to coating with a roller, brush, brush, or the like. Is possible. Among these, those that can be applied uniformly on the surface of the cement-based cured body, such as application with a roller, brush or brush, or spraying with a sprayer, are preferable. The application may be performed once, or after the first application is dried, the application may be performed in a second and third time. A higher effect can be obtained by applying the layers one after another. It is preferable that the amount to be applied per time is within the above range.

  It is preferable that the solid content concentration of the cellulose nanofiber contained in the coating agent of the present invention is in the range of 0.01 to 10% by weight. When the solid content concentration of the cellulose nanofiber is less than 0.01% by weight, a sufficient effect cannot be obtained. On the other hand, if it is larger than 10% by weight, the viscosity of the coating agent becomes too high and the workability of coating is poor.

In addition to cellulose nanofibers, the coating agent of the present invention may contain one or more components contained in conventionally known coating agents for cement-based cured bodies. Examples include polyoxyalkylenes such as polyethylene glycol, polypropylene glycol, ethylene oxide methanol adducts, etc., lower alcohols added, ethylene oxide / propylene oxide block polymers, ethylene oxide / propylene oxide random polymers, glycol cycloalkyl group adducts. , Adduct with addition of methyl group at both ends of glycol, Phenyl addition product of glycol, Block polymer with addition of methylphenyl group to glycol, Addition with addition of ethylene oxide methanol at both ends of glycol and Addition of dimethylamine to glycol The shrinkage reducing agent which uses the added adduct etc. as an active ingredient can be mentioned.
In addition, in order to fix cellulose nanofibers on the cement-based cured body surface, an adhesive that exhibits water resistance of the coating, and a surfactant etc. are used in combination to sufficiently penetrate the coating agent into the cured body. Also good.

(3) Cellulose nanofiber The cement-based cured body coating agent of the present invention is characterized by containing cellulose nanofiber. Cellulose nanofibers are fine fibers obtained by subjecting a cellulose raw material to a chemical modification treatment, if necessary, followed by a fibrillation treatment. The average fiber diameter of the cellulose nanofiber is usually about 3 to 500 nm. The average fiber diameter and the average fiber length are measured by, for example, preparing a 0.001% by weight aqueous dispersion of cellulose nanofibers, spreading the diluted dispersion thinly on a mica sample stage, and drying by heating at 50 ° C. It is possible to calculate the number average fiber diameter or fiber length by preparing a sample for use and measuring the cross-sectional height of the shape image observed with an atomic force microscope (AFM).

The average aspect ratio of the cellulose nanofiber is usually 50 or more. Although an upper limit is not specifically limited, Usually, it is 1000 or less. The average aspect ratio can be calculated by the following formula. Aspect ratio = average fiber length / average fiber diameter

(3-1) Cellulose raw material The origin of the cellulose raw material that is the raw material of the cellulose nanofiber is not particularly limited. For example, plants (for example, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (conifers) Unbleached Kraft Pulp (NUKP), Conifer Bleached Kraft Pulp (NBKP), Hardwood Unbleached Kraft Pulp (LUKP), Hardwood Bleached Kraft Pulp (LBKP), Conifer Unbleached Sulfite Pulp (NUSP), Conifer Bleached Sulfite Pulp (NBSP) ) Thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (Acetobacter)), microbial products, etc. Cellulose raw materials used in the present invention , Any of these may be a combination of two or more However, it is preferably a plant or microorganism-derived cellulose raw material (for example, cellulose fiber), more preferably a plant-derived cellulose raw material (for example, cellulose fiber).

  The number average fiber diameter of the cellulose raw material is not particularly limited, but is about 30 to 60 μm in the case of softwood kraft pulp which is a general pulp, and about 10 to 30 μm in the case of hardwood kraft pulp. In the case of other pulps, those that have undergone general refining are about 50 μm. For example, when a chip or the like having a size of several centimeters is refined, it is preferably adjusted to about 50 μm by performing mechanical treatment with a disintegrator such as a refiner or beater.

(3-2) Modification The cellulose raw material has three hydroxyl groups per glucose unit, and various chemical modification treatments can be performed. In the present invention, these may or may not be modified. However, the chemical modification treatment can exhibit sufficient reinforcement when incorporated in the rubber composition. preferable. This is because the fineness of the fiber is sufficiently advanced by modification of the cellulose raw material, and a uniform fiber length and fiber diameter can be obtained. Moreover, it is because the fiber number with the fiber length and fiber diameter effective in exhibiting a reinforcement property can fully be ensured.

  The modification method for modifying the cellulose raw material is not particularly limited, and examples thereof include chemical modification such as oxidation, etherification, phosphorylation, esterification, silane coupling, fluorination, and cationization. Of these, oxidation (carboxylation), etherification, cationization and esterification are preferred. Hereinafter, these will be described in detail.

(3-2-1) Oxidation When the cellulose raw material is modified by oxidation, the amount of carboxyl groups with respect to the absolute dry weight of the obtained oxidized cellulose or cellulose nanofiber is preferably 0.5 mmol / g or more, more preferably 0.8. It is 8 mmol / g or more, more preferably 1.0 mmol / g or more. The upper limit is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, and still more preferably 2.0 mmol / g or less. Accordingly, 0.5 mmol / g to 3.0 mmol / g is preferable, 0.8 mmol / g to 2.5 mmol / g is more preferable, and 1.0 mmol / g to 2.0 mmol / g is still more preferable.

  Although the oxidation method is not particularly limited, one example is N-oxyl compound and cellulose in water using an oxidizing agent in the presence of a substance selected from the group consisting of bromide, iodide or a mixture thereof. The method of oxidizing a raw material is mentioned. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized to produce a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. Although the density | concentration of the cellulose raw material at the time of reaction is not specifically limited, 5 weight% or less is preferable.

  The N-oxyl compound refers to a compound that can generate a nitroxy radical. Examples of the nitroxyl radical include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction.

  The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize cellulose as a raw material. For example, 0.01 mmol or more is preferable and 0.02 mmol or more is more preferable with respect to 1 g of absolutely dry cellulose. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and still more preferably 0.5 mmol or less. Accordingly, the amount of N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and still more preferably 0.02 to 0.5 mmol with respect to 1 g of absolutely dry cellulose.

  The bromide is a compound containing bromine, and examples thereof include alkali metal bromide that can be dissociated and ionized in water, such as sodium bromide. Further, the iodide is a compound containing iodine, and examples thereof include alkali metal iodide. What is necessary is just to select the usage-amount of a bromide or iodide in the range which can accelerate | stimulate an oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, with respect to 1 g of absolutely dry cellulose. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and still more preferably 5 mmol or less. Therefore, the total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol with respect to 1 g of absolutely dry cellulose.

  The oxidizing agent is not particularly limited, and examples thereof include halogen, hypohalous acid, halous acid, perhalogen acid, salts thereof, halogen oxide, and peroxide. Among them, hypohalous acid or a salt thereof is preferable because it is inexpensive and has a low environmental burden, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is still more preferable. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, and still more preferably 3 mmol or more with respect to 1 g of absolutely dry cellulose. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, and even more preferably 25 mmol or less. Therefore, the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, further preferably 1 to 25 mmol, and most preferably 3 to 10 mmol with respect to 1 g of absolutely dry cellulose. When the N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more with respect to 1 mol of the N-oxyl compound. The upper limit is preferably 40 mol. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.

  Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and in general, the oxidation reaction proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4 ° C or higher, more preferably 15 ° C or higher. The upper limit is preferably 40 ° C. or lower, and more preferably 30 ° C. or lower. Accordingly, the temperature is preferably 4 to 40 ° C, and may be about 15 to 30 ° C, that is, room temperature. The pH of the reaction solution is preferably 8 or more, and more preferably 10 or more. The upper limit is preferably 12 or less, and more preferably 11 or less. Therefore, the pH of the reaction solution is preferably about 8 to 12, more preferably about 10 to 11. Usually, a carboxyl group is generated in cellulose as the oxidation reaction proceeds, and therefore the pH of the reaction solution tends to decrease. Therefore, in order to advance the oxidation reaction efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution in the above range. The reaction medium for the oxidation is preferably water for reasons such as ease of handling and the difficulty of side reactions.

  The reaction time in the oxidation can be appropriately set according to the progress of the oxidation, and is usually 0.5 hours or longer. The upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time in oxidation is usually 0.5 to 6 hours, for example, about 0.5 to 4 hours.

  Oxidation may be carried out in two or more stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt generated as a by-product in the first stage reaction. Can be oxidized well.

  Another example of the carboxylation (oxidation) method is a method of oxidizing by ozone treatment. By this oxidation reaction, at least the 2- and 6-position hydroxyl groups of the glucopyranose ring constituting cellulose are oxidized, and the cellulose chain is decomposed. The ozone treatment is usually performed by bringing a gas containing ozone and a cellulose raw material into contact with each other. The ozone concentration in the gas is preferably 50 g / m 3 or more. The upper limit is preferably 250 g / m 3 or less, and more preferably 220 g / m 3 or less. Therefore, the ozone concentration in the gas is preferably 50 to 250 g / m 3, and more preferably 50 to 220 g / m 3. The amount of ozone added is preferably 0.1 parts by weight or more and more preferably 5% by weight or more with respect to 100% by weight of the solid content of the cellulose raw material. The upper limit is usually 30% by weight or less. Therefore, the amount of ozone added is preferably 0.1 to 30% by weight and more preferably 5 to 30% by weight with respect to 100% by weight of the solid content of the cellulose raw material. The ozone treatment temperature is usually 0 ° C. or higher, preferably 20 ° C. or higher. The upper limit is usually 50 ° C. or lower. Therefore, the ozone treatment temperature is preferably 0 to 50 ° C, and more preferably 20 to 50 ° C. The ozone treatment time is usually 1 minute or longer, preferably 30 minutes or longer. The upper limit is usually 360 minutes or less. Therefore, the ozone treatment time is usually about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the condition of the ozone treatment is within the above range, it is possible to prevent the cellulose from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved.

  Further, the resulting product obtained after the ozone treatment may be further oxidized using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite; oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. Examples of the oxidation treatment method include a method in which these oxidizing agents are dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and the cellulose raw material is immersed in the oxidizing agent solution.

  The amount of the carboxyl group, carboxylate group, and aldehyde group contained in the oxidized cellulose nanofiber can be adjusted by controlling the oxidizing conditions such as the addition amount of the oxidizing agent and the reaction time.

An example of a method for measuring the amount of carboxyl groups will be described below. Prepare 60 ml of 0.5 wt% slurry (aqueous dispersion) of oxidized cellulose and add 0.1 M hydrochloric acid aqueous solution to pH 2.5, then add 0.05 N sodium hydroxide aqueous solution dropwise to adjust pH to 11. Measure the electrical conductivity until From the amount (a) of sodium hydroxide consumed in the neutralization step of the weak acid with a gradual change in electrical conductivity, it can be calculated using the following formula:
Amount of carboxyl group [mmol / g oxidized cellulose or cellulose nanofiber] = a [ml] × 0.05 / oxidized cellulose weight [g].

(3-2-2) Etherification As etherification, carboxymethyl (ether), methyl (ether), ethyl (ether), cyanoethyl (ether), hydroxyethyl (ether), hydroxypropyl (ether) ), Ethylhydroxyethyl (ether), hydroxypropylmethyl (ether) and the like. As an example, a carboxymethylation method will be described below.

  When the cellulose raw material is modified by carboxymethylation, the degree of carboxymethyl substitution per anhydroglucose unit in the obtained carboxymethylated cellulose or cellulose nanofiber is preferably 0.01 or more, more preferably 0.05 or more, and 0 More preferably, it is 10 or more. The upper limit is preferably 0.50 or less, more preferably 0.40 or less, and still more preferably 0.35 or less. Accordingly, the degree of carboxymethyl group substitution is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and still more preferably 0.10 to 0.30.

  Although the method of carboxymethylation is not specifically limited, For example, the method of mercerizing the cellulose raw material as a bottoming raw material, and etherifying after that is mentioned. A common solvent is used in the carboxymethylation reaction. Examples of the solvent include water, alcohol (for example, lower alcohol), and a mixed solvent thereof. Examples of the lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, and tertiary butanol. The mixing ratio of the lower alcohol in the mixed solvent is usually 60% by weight or more and 95% by weight or less, and preferably 60 to 95% by weight. The amount of the solvent is usually 3 times the weight of the cellulose raw material. Although an upper limit is not specifically limited, It is 20 weight times. Therefore, the amount of the solvent is preferably 3 to 20 times by weight.

  Mercerization is usually performed by mixing a bottoming raw material and a mercerizing agent. Examples of mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of the mercerizing agent used is preferably 0.5 times mol or more, more preferably 1.0 mol or more, and further preferably 1.5 times mol or more per anhydroglucose residue of the starting material. The upper limit is usually 20 moles or less, preferably 10 moles or less, more preferably 5 moles or less, and more preferably 0.5 to 20 moles, more preferably 1.0 to 10 moles. More preferably 5 to 5 moles.

  The mercerization reaction temperature is usually 0 ° C. or higher, preferably 10 ° C. or higher. The upper limit is usually 70 ° C. or lower, preferably 60 ° C. or lower. Therefore, the reaction temperature is usually 0 to 70 ° C, preferably 10 to 60 ° C. The reaction time is usually 15 minutes or longer, preferably 30 minutes or longer. The upper limit is usually 8 hours or less, preferably 7 hours or less. Therefore, it is usually 15 minutes to 8 hours, preferably 30 minutes to 7 hours.

  The etherification reaction is usually performed by adding a carboxymethylating agent to the reaction system after mercerization. Examples of the carboxymethylating agent include sodium monochloroacetate. The addition amount of the carboxymethylating agent is usually preferably 0.05 times mol or more, more preferably 0.5 times mol or more, and further preferably 0.8 times mol or more per glucose residue of the cellulose raw material. The upper limit is usually 10.0 times mole or less, preferably 5 moles or less, more preferably 3 times mole or less, and therefore preferably 0.05 to 10.0 times mole, more preferably 0.5 to 5, more preferably 0.8 to 3 times mol. The reaction temperature is usually 30 ° C. or higher, preferably 40 ° C. or higher, and the upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. Accordingly, the reaction temperature is usually 30 to 90 ° C, preferably 40 to 80 ° C. The reaction time is usually 30 minutes or longer, preferably 1 hour or longer. The upper limit is usually 10 hours or less, preferably 4 hours or less. Therefore, the reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours. The reaction solution may be stirred as necessary during the carboxymethylation reaction.

The measurement of the degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose nanofibers may be performed, for example, by the following method. That is, 1) About 2.0 g of carboxymethylated cellulose (absolutely dry) is precisely weighed and put into a 300 mL conical stoppered Erlenmeyer flask. 2) Add 100 mL of a solution obtained by adding 100 mL of special grade concentrated nitric acid to 1000 mL of nitric acid methanol and shake for 3 hours to convert the carboxymethylcellulose salt (carboxymethylated cellulose) to hydrogen-type carboxymethylated cellulose. 3) 1.5-2.0 g of hydrogen-type carboxymethylated cellulose (absolutely dry) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 4) Wet the hydrogen-type carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. 5) Back titrate excess NaOH with 0.1 N H2SO4 using phenolphthalein as indicator. 6) The degree of carboxymethyl substitution (DS) is calculated by the following formula:
A = [(100 × F ′ − (0.1 N H 2 SO 4) (mL) × F) × 0.1] / (absolute dry mass of hydrogenated carboxymethylated cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required for neutralizing 1 g of hydrogen-type carboxymethylated cellulose
F ′: 0.1N H 2 SO 4 factor F: 0.1 N NaOH factor

(3-2-3) Cationization When the cellulose raw material is modified by cationization, the resulting cationized cellulose nanofiber may contain a cation such as ammonium, phosphonium, sulfonium, or a group having the cation in the molecule. That's fine. The cationized cellulose nanofiber preferably includes a group having ammonium, and more preferably includes a group having quaternary ammonium.

  The cationization method is not particularly limited, and examples thereof include a method in which a cellulose raw material is reacted with a cationizing agent and a catalyst in the presence of water and / or alcohol. Examples of the cationizing agent include glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydride (eg, 3-chloro-2-hydroxypropyltrimethylammonium hydride) or a halohydrin type thereof. By using any of these, a cationized cellulose having a group containing quaternary ammonium can be obtained. Examples of the catalyst include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. As alcohol, C1-C4 alcohol is mentioned, for example. The amount of the cationizing agent is preferably 5% by weight or more, more preferably 10% by weight or more with respect to 100% by weight of the cellulose raw material. The upper limit is usually 800% by weight or less, preferably 500% by weight or less. The amount of the catalyst is preferably 0.5% by weight or more, more preferably 1% by weight or more with respect to 100% by weight of the cellulose fibers. The upper limit is usually 7% by weight or less, preferably 3% by weight or less. The amount of alcohol is preferably 50% by weight or more, more preferably 100% by weight or more, based on 100% by weight of cellulose fibers. The upper limit is usually 50000% by weight or less, preferably 500% by weight or less.

  The reaction temperature at the time of cationization is usually 10 ° C or higher, preferably 30 ° C or higher, and the upper limit is usually 90 ° C or lower, preferably 80 ° C or lower. The reaction time is usually 10 minutes or longer, preferably 30 minutes or longer. The upper limit is usually 10 hours or less, preferably 5 hours or less. The reaction solution may be stirred as necessary during the cationization reaction.

  The degree of cation substitution per glucose unit in the cationized cellulose can be adjusted by controlling the amount of cationizing agent added and the composition ratio of water and / or alcohol. The degree of cation substitution refers to the number of substituents introduced per unit structure (glucopyranose ring) constituting cellulose. In other words, the degree of cation substitution is defined as “a value obtained by dividing the number of moles of the introduced substituent by the total number of moles of hydroxyl groups of the glucopyranose ring”. Since pure cellulose has three substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of cation substitution is 3 (the minimum value is 0).

  The cation substitution degree per glucose unit of the cationized cellulose nanofiber is preferably 0.01 or more, more preferably 0.02 or more, and further preferably 0.03 or more. The upper limit is preferably 0.40 or less, more preferably 0.30 or less, and still more preferably 0.20 or less. Therefore, it is preferable that it is 0.01-0.40, 0.02-0.30 is more preferable, and 0.03-0.20 is still more preferable. By introducing a cationic substituent into cellulose, the celluloses repel each other electrically. For this reason, the cellulose which introduce | transduced the cation substituent can be nano-defibrated easily. When the degree of cation substitution per glucose unit is 0.01 or more, nano-defibration can be sufficiently performed. On the other hand, when the degree of cation substitution per glucose unit is 0.40 or less, swelling or dissolution can be suppressed, whereby the fiber form can be maintained, and a situation where nanofibers cannot be obtained is prevented. be able to.

  An example of a method for measuring the degree of cation substitution per glucose unit will be described below. After drying the sample (cationized cellulose), the nitrogen content is measured with a total nitrogen analyzer TN-10 (Mitsubishi Chemical), and the degree of cationization is calculated by the following equation. The cation substitution degree here is an average value of the number of moles of substituents per mole of anhydroglucose unit.

Degree of cation substitution = (162 × N) / (1-151.6 × N)
N: Nitrogen content

(3-2-4) Esterification In the present invention, when esterified cellulose is used as the chemically modified cellulose, a method of mixing a powder or an aqueous solution of Compound A listed below with respect to the cellulose-based material, a cellulose-based material Examples include a method of adding an aqueous solution of Compound A to the slurry.

  Compound A includes phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid or esters thereof. These may take the form of salts. Among these, a compound having a phosphate group is preferable because it is low-cost, easy to handle, and can introduce a phosphate group into cellulose of pulp fiber to improve the fibrillation efficiency. Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phosphorus Examples include tripotassium acid, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, and the like. These may be used alone or in combination of two or more to introduce a phosphate group. Among these, phosphoric acid, phosphoric acid sodium salt, phosphoric acid potassium salt, phosphoric acid, from the viewpoint that phosphoric acid group introduction efficiency is high, is easy to be defibrated in the following defibrating process, and is industrially applicable. The ammonium salt is preferred. In particular, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferred. In addition, the phosphoric acid compound is desirably used as an aqueous solution because the uniformity of the reaction is increased and the efficiency of introducing a phosphate group is increased. The pH of the aqueous solution of the phosphoric acid compound is preferably 7 or less because the efficiency of introducing phosphoric acid groups is high, but is preferably 3 to 7 from the viewpoint of suppressing hydrolysis of pulp fibers.

  If an example of the manufacturing method of phosphoric ester cellulose is given, the following method can be mentioned. Compound A is added to a suspension of a cellulose-based raw material having a solid content concentration of 0.1 to 10% by weight with stirring to introduce phosphate groups into the cellulose. When the cellulose-based raw material is 100 parts by weight, the amount of Compound A added is preferably 0.2 to 500 parts by weight, more preferably 1 to 400 parts by weight, as the amount of phosphorus element. If the ratio of the compound A is more than the said lower limit, the yield of fine fibrous cellulose can be improved more. However, even if the upper limit is exceeded, the effect of improving the yield reaches its peak and only the compound A is used in vain.

  At this time, in addition to the cellulose raw material and the compound A, a powder or an aqueous solution of the compound B may be mixed. The compound B is not particularly limited, but a basic nitrogen-containing compound is preferable. The definition of “basic” is when the aqueous solution is pink to red in the presence of a phenolphthalein indicator or / and when the pH of the aqueous solution is greater than 7. Although the nitrogen-containing compound which shows the basicity used by this invention is not specifically limited as long as there exists an effect of this invention, the compound which has an amino group is preferable. For example, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like can be mentioned, but not particularly limited. Among these, urea which is easy to handle at low cost is preferable. The amount of compound B added is preferably 2 to 1000 parts by weight, and more preferably 100 to 700 parts by weight. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. The reaction time is not particularly limited, but is about 1 to 600 minutes, and more preferably 30 to 480 minutes. When the conditions for the esterification reaction are within these ranges, the cellulose can be prevented from being excessively esterified and easily dissolved, and the yield of phosphorylated esterified cellulose is improved. After dehydrating the obtained phosphate esterified cellulose suspension, it is preferable to heat-treat at 100 to 170 ° C. from the viewpoint of suppressing hydrolysis of cellulose. Furthermore, while water is contained during the heat treatment, it is preferably heated at 130 ° C. or less, preferably 110 ° C. or less, and after removing water, heat treatment is preferably performed at 100 to 170 ° C.

  It is preferable that the phosphate group substitution degree per glucose unit of phosphorylated cellulose is 0.001 to 0.40. By introducing a phosphate group substituent into cellulose, the celluloses are electrically repelled. For this reason, the cellulose which introduce | transduced the phosphate group can be nano-defibrated easily. In addition, when the phosphate group substitution degree per glucose unit is smaller than 0.001, nano-defibration cannot be sufficiently performed. On the other hand, if the degree of phosphate group substitution per glucose unit is greater than 0.40, it may swell or dissolve, and may not be obtained as a nanofiber. In order to perform defibration efficiently, it is preferable that the phosphoric esterified cellulose raw material obtained above is washed by boiling water and then washing with cold water.

(3-3) Defibration The cellulose raw material may be defibrated before or after the cellulose raw material is modified. Moreover, defibration may be performed at once or a plurality of times. In the case of multiple times, each defibration period may be any time.

  The apparatus used for defibration is not particularly limited, and examples thereof include high-speed rotating type, colloid mill type, high-pressure type, roll mill type, ultrasonic type and the like, and high-pressure or ultra-high-pressure homogenizers are preferable, and wet high pressure Or an ultra high pressure homogenizer is more preferable. It is preferable that the apparatus can apply a strong shearing force to the cellulose raw material or the modified cellulose (usually a dispersion). The pressure that can be applied by the apparatus is preferably 50 MPa or more, more preferably 100 MPa or more, and still more preferably 140 MPa or more. The apparatus is preferably a wet high-pressure or ultrahigh-pressure homogenizer capable of applying the above pressure to a cellulose raw material or modified cellulose (usually a dispersion) and applying a strong shearing force. Thereby, defibration can be performed efficiently.

  When defibration is performed on a dispersion of cellulose raw material, the solid content concentration of the cellulose raw material in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, more preferably 0.3%. % By weight or more. Thereby, the liquid quantity with respect to the quantity of a cellulose fiber raw material becomes an appropriate quantity, and is efficient. The upper limit is usually 10% by weight or less, preferably 6% by weight or less. Thereby, fluidity | liquidity can be hold | maintained.

  Prior to defibration (preferably defibration with a high-pressure homogenizer) or dispersion treatment performed before defibration as necessary, pretreatment may be performed as necessary. The pretreatment may be performed using a mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer.

  Hereinafter, although an example is given and the present invention is explained still in detail, the present invention is not limited to these.

<Example 1>
[Production of oxidized cellulose nanofibers]
Bleached unbeaten kraft pulp derived from conifers (whiteness 85%), 5.00 g (absolutely dry), 39 mg of TEMPO (Sigma Aldrich) and 0.05 mmol of sodium bromide (absolutely dry) The solution was added to 500 ml of an aqueous solution in which 1.0 mmol) was dissolved in 1 g of cellulose, and stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that sodium hypochlorite was 5.5 mmol / g, and the oxidation reaction was started at room temperature. During the reaction, the pH in the system was lowered, but a 3M sodium hydroxide aqueous solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system no longer changed. The reaction mixture was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. This was adjusted to 1.0% (w / v) with water and treated with an ultra-high pressure homogenizer (20 ° C., 150 Mpa) three times to obtain an oxidized cellulose nanofiber dispersion. The average fiber diameter was 3 nm and the aspect ratio was 250.

[Manufacture of coating agent for cement-based cured bodies]
A 0.5 wt% aqueous dispersion of the above oxidized cellulose nanofiber was used as a concrete coating agent.
[Manufacture of cement composition (green concrete)]
In the water cement ratio (W / C), fine aggregate ratio (s / a), and unit amount concrete mixing conditions shown in Table 1, three equal amounts of ordinary Portland cement (density = 3.16 g / m 3, Specific surface area = 3330 cm2 / g), fine aggregate (abbreviation: S, Kakegawa mountain sand, density = 2.58 g / m3) and coarse aggregate (abbreviation: G, Ome hard sandstone crushed stone, density = 2.67 g / m3) ) Was used to knead the concrete in a room with an ambient temperature of 20 ° C. In all categories, 1% by weight of AE water reducing agent standard type Floric S manufactured by Floric Co., Ltd. was added to the cement weight. AE150 (main component polyoxyethylene type) manufactured by Floric Co., Ltd. is set so that the target slump is 19 ± 1 cm and the target air amount is set to 4.5 ± 1.5%. Surfactant). After the concrete was produced, the shrinkage reducing agent was mixed with 2% by weight of the shrinkage reducing agent with respect to the cement weight and stirred with the mixer to obtain a cement composition (green concrete).

[Production and evaluation of hardened concrete]
In order to evaluate the degree of reinforcement, prevention of drying shrinkage, prevention of neutralization, and salt damage when the above coating agent is applied, the concrete concrete is used to evaluate the degree of salt damage by the following methods. Produced and measured for compressive strength, length change rate, neutralization depth, and apparent diffusion coefficient of chloride ions.

[Compressive strength]
Measured according to JIS A1108 “Testing method for compressive strength of concrete”. That is, immediately after placing the concrete, a cylindrical specimen having a diameter of 100 mm and a height of 200 mm is prepared, and after 24 hours, the mold is removed, and the above coating agent is applied to the side surface so that the coating amount becomes 100 g / m2. And dried at room temperature. This was further stored for 4 weeks in a state where the ambient temperature was maintained at 20 ± 2 ° C. and the humidity at 60 ± 5%. Was used to apply a load at a speed at which the increase in compressive stress was 0.6 ± 0.4 N / mm 2 per second, and the compressive strength was measured from the maximum load indicated by the testing machine until the specimen was broken. As compared with the reference product to which the coating agent was not applied, the measurement result was indicated as “◯”, the case where it was equivalent as “Δ”, and the case where it was low as “X”.

[Length change rate]
Measured according to JIS A 1129 “Testing method for length change of mortar and concrete”. That is, immediately after placing the concrete, a 100 × 100 × 400 mm rectangular parallelepiped specimen is prepared, and after 24 hours, it is demolded, and the side is marked, and the coating agent is applied at a coating amount of 100 g / m 2. It was applied to the entire surface and dried at room temperature. This specimen was immersed in water at 20 ± 2 ° C. and cured until the age of the material reached 7 days. Next, the sample was dried with the ambient temperature kept at 20 ± 2 ° C. and the humidity kept at 60 ± 5%, and the lengths of the engraved lines were measured immediately after drying and 13 weeks after the start of drying. The amount of change in the length of the engraved line immediately after drying and the length of the engraved line 13 weeks after the start of drying was calculated as a ratio to the length of the engraved line immediately after drying, and was defined as the rate of change in length. The measurement results were compared with a reference product to which the coating agent was not applied, where ◯ was small, Δ was equivalent, and x was large.

[Neutralization depth]
Measured according to JIS A 1153 “Testing method for accelerated neutralization of concrete”. That is, a test piece having a square cross section and a side length of 100 mm and a length of 400 mm was prepared, and the coating agent was applied to the entire surface so that the coating amount was 100 g / m 2. Dried. This specimen is cured in a humid state at a temperature of 20 ± 2 ° C until the age of 4 weeks, and then left to stand in a constant temperature and humidity chamber at a relative humidity of 60 ± 5% and a temperature of 20 ± 2 ° C until the age of 8 weeks. did. During the ages of 7 to 8 weeks, the surface to be tested, the bottom surface, and both end surfaces of the specimen were sealed so as not to have pinholes and sufficient to block carbon dioxide. After 8 weeks of age, the mixture was allowed to stand for 13 weeks under conditions for promoting neutralization at a temperature of 20 ± 2 ° C., a relative humidity (60 ± 5)%, and a carbon dioxide concentration (5 ± 0.2)%. After that, the specimen was split at a position approximately 60 mm from the end at a right angle to the length direction of the specimen, and the phenolphthalein solution was sprayed onto the measurement surface to the extent that the liquid did not drip with a sprayer. After the part was stabilized, the distance from the concrete surface to the part colored in magenta was measured. The measurement results were compared with a reference product to which the coating agent was not applied, where ◯ was short, Δ was equivalent, and x was long.

[Apparent diffusion coefficient of chloride ion]
In accordance with the Standard Specification for Concrete Standards (Japan Society of Civil Engineers), the apparent diffusion coefficient of chloride ions in concrete by immersion (JSCE-G-572-2013) It was measured. That is, a cylindrical specimen having a diameter of 100 mm and a height of 200 mm was prepared, and the coating agent was applied on the entire surface so that the coating amount was 100 g / m 2 and dried at room temperature. This specimen was cured for 4 weeks, and during the curing, the upper and lower sides of the specimen were cut 25 mm and formed to a height of 150 mm. After curing, leave only one circular surface of the specimen, cover the other surface with epoxy resin paint, leave it in a room with a temperature of 20 ± 2 ℃ and relative humidity (60 ± 5)% for 4 days, and then temperature 20 Stored in water at ± 2 ° C for 24 hours. After immersing this specimen in a sodium chloride solution at a temperature of 20 ± 2 ° C. and a concentration of 10% for 91 days, the chloride ions adhering to the open face of the specimen were removed, and 5 different depths from the open face In this place, a test piece was cut out using a concrete cutter, total chloride ions were measured, and the distribution was subjected to regression analysis to calculate the apparent diffusion coefficient. The measurement result was compared with a reference product to which the coating agent was not applied, and the case where it was small was evaluated as “◯”, the case where it was equivalent as “Δ”, and the case where it was large as “X”.

<Example 2>
In Example 1, the hardened concrete body was manufactured by the same method as Example 1 except having changed the application quantity of the coating agent into 150 g / m < ² >.

<Example 3>
In Example 1, the hardened concrete body was manufactured by the same method as Example 1 except having changed the oxidized cellulose nanofiber to the carboxymethylated cellulose nanofiber manufactured by the following method.

[Production of carboxymethylated cellulose nanofibers]
In a stirrer capable of mixing pulp, 200 g of dry pulp (NBKP (conifer bleached kraft pulp), manufactured by Nippon Paper Industries Co., Ltd.) and 111 g of dry weight of sodium hydroxide (2. 25 mol) and water was added so that the pulp solid content was 20% (w / v). Thereafter, after stirring at 30 ° C. for 30 minutes, 216 g of sodium monochloroacetate (in terms of active ingredient, 1.5 times mol per glucose residue of pulp) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and stirred for 1 hour. Thereafter, the reaction product was taken out, neutralized, and washed to obtain a carboxymethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit. This was made into 1% solid content with water, and fibrillated by treatment with a high-pressure homogenizer 5 times at 20 ° C. and 150 MPa to obtain carboxymethylated cellulose nanofibers. The average fiber diameter was 15 nm and the aspect ratio was 50.

<Example 4>
In Example 1, a hardened concrete was produced by the same method as in Example 1 except that the oxidized cellulose nanofiber was changed to a cationized cellulose nanofiber produced by the following method.

[Production of cationized cellulose nanofibers]
Add pulp (NBKP, manufactured by Nippon Paper Industries Co., Ltd.) in dry weight of 200g and sodium hydroxide in dry weight of 24g to pulper that can stir the pulp, and add water so that the pulp solid concentration is 15%. It was. Then, after stirring for 30 minutes at 30 ° C., the temperature was raised to 70 ° C., and 200 g (in terms of active ingredient) of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added as a cationizing agent. After reacting for 1 hour, the reaction product was taken out, neutralized and washed to obtain a cation-modified pulp having a cation substitution degree of 0.05 per glucose unit. This was made into 1% of solid concentration, and it processed twice by the high pressure homogenizer at 20 degreeC and the pressure of 140 Mpa. The average fiber diameter was 25 nm and the aspect ratio was 50.

<Comparative Example 1>
In Example 1, a hardened concrete was produced in the same manner as in Example 1 except that the coating agent was not applied.

  As is clear from the results in Table 1, in Examples 1 to 4 in which a coating agent containing cellulose nanofibers was applied, the compression strength was higher than that in Comparative Example 1 in which no coating agent was applied. Since both the carbonation depth and the apparent diffusion coefficient of chloride ions are both small, it can be seen that the effects of improving the reinforcing property, preventing drying shrinkage, preventing neutralization, and preventing salt damage are exhibited.

Claims (4)

A coating agent for a cement-based cured body containing cellulose nanofiber, wherein the cellulose nanofiber is oxidized cellulose nanofiber, carboxymethylated cellulose nanofiber, cationized cellulose nanofiber, etherified cellulose nanofiber, esterified cellulose A coating agent for a hardened cementitious material, comprising at least one of nanofibers.
In the oxidized cellulose nanofiber, a part of the hydroxyl group at the C6 position in the glucose unit of cellulose constituting the cellulose nanofiber is oxidized to a carboxyl group, and the amount of the carboxyl group relative to the cellulose nanofiber is 0.5 mmol / The coating agent for cement-type hardening bodies of Claim 1 which is g-3.0 mmol / g.
In the carboxymethylated cellulose nanofiber, a part of the hydroxyl group hydrogen atom in the glucose unit of cellulose constituting the cellulose nanofiber is substituted with a carboxymethyl group, and the degree of carboxymethyl substitution per glucose unit is 0. The coating agent for cement-type hardened | cured material of Claim 1 which is 0.01-0.50.
  In the cationized cellulose nanofiber, a part of the hydrogen atom of the hydroxyl group in the glucose unit of cellulose constituting the cellulose nanofiber is substituted with a cationic group, and the cation substitution degree per glucose unit is 0.01. The coating agent for cement-type cured bodies according to claim 1, which is ˜0.40.