WO2017126566A1 - Polyurethane resin composition and process for producing same - Google Patents

Abstract

The purpose of the present invention is to provide a polyurethane resin composition having satisfactory strength, heat resistance, and water resistance and a process for producing the polyurethane resin composition. The polyurethane resin composition comprises a polyurethane resin and cellulose nanofibers that are fine fibers (average fiber diameter; about 3-500 nm) of unmodified cellulose or chemically modified cellulose, the content of the cellulose nanofibers being 0.1-10 parts by mass per 100 parts by mass of the polyurethane resin. Thus, the excellent effects are exhibited.

Description

Polyurethane resin composition and method for producing the same

The present invention relates to a polyurethane resin composition and a method for producing the same.

Polyurethane resin compositions are widely used in various fields such as adhesives, flooring materials, sealing materials, molded bodies, elastic bodies, films, optical materials, various foams such as cushions and heat insulating materials.

In all fields, plastic compositions including the polyurethane resin composition are strongly required to have higher strength (tensile stress and tensile strength), heat resistance, and water resistance. In particular, polyurethane is superior in wear resistance, oil resistance, and the like compared to other plastics, but tends to have low heat resistance and water resistance. Therefore, improvement in heat resistance and water resistance has been strongly demanded.
By the way, in recent years, attempts to use cellulose nanofibers, which are plant-derived natural raw material nanofibers, as a reinforcing material have been attracting attention in view of environmental considerations.

For example, Patent Document 1 discloses a preparation step in which a polymer emulsion containing polyurethane is mixed with an aqueous suspension of fine fibrous cellulose to produce a mixed solution, and the mixed solution is dehydrated by filtration on a porous substrate. A paper making process for forming a sheet containing moisture, a process for replacing the sheet containing moisture with an organic solvent, and a drying process for heating and drying the sheet substituted with the organic solvent. A manufacturing method is described.

JP 2012-116905 A

However, in the method of Patent Document 1, the dispersibility of fine fibrous cellulose (cellulose nanofiber) in the mixed solution is not sufficient. For this reason, since a sufficient strength enhancement effect cannot be obtained, improvement has been demanded.
Accordingly, an object of the present invention is to provide a polyurethane resin composition capable of producing a molded article having good strength, heat resistance and water resistance, and a method for producing the same.

The present invention provides the following.
(1) A polyurethane resin composition containing cellulose nanofibers and a polyurethane resin.
(2) The cellulose nanofiber includes an oxidized cellulose nanofiber in which a hydroxyl group at the C6 position in a part of glucose units constituting cellulose is a carboxyl group, and the amount of the carboxyl group of the oxidized cellulose nanofiber is oxidized. The polyurethane resin composition according to (1), which is 0.1 mmol / g to 3.0 mmol / g with respect to the absolutely dry mass of the cellulose nanofiber.
(3) The polyurethane resin composition according to (1) or (2), wherein the content of the cellulose nanofiber is 0.1 to 10 parts by mass with respect to 100 parts by mass of the polyurethane resin.
(4) The method for producing a polyurethane resin composition according to any one of (1) to (3), comprising a step of mixing the polyurethane resin aqueous dispersion and the cellulose nanofiber aqueous dispersion.
(5) a urethane prepolymer preparation step of preparing an organic solvent dispersion of a urethane prepolymer having an isocyanate terminal by reacting at least a polyol compound and a polyisocyanate compound in an organic solvent, and an organic solvent dispersion of the urethane prepolymer, (1) to (3) having a mixing step of mixing a cellulose nanofiber aqueous dispersion to obtain a mixed solution, and a polyurethane resin preparing step of preparing a polyurethane resin by mixing a curing agent with the mixed solution. The manufacturing method of the polyurethane resin composition in any one of.

According to the present invention, it is possible to provide a polyurethane resin composition capable of producing a molded article having good strength, heat resistance and water resistance, and a method for producing the same.

FIG. 1 is a graph showing the relationship between Temperature-Storage Modulus of Examples 1 to 3 and Comparative Example 1. FIG. 2 is a graph showing the relationship of Temperature-Storage Modulus in Examples 4 to 6 and Comparative Example 1.

The polyurethane resin composition of the present invention contains cellulose nanofibers and a polyurethane resin.
Hereinafter, the cellulose nanofiber, the polyurethane resin (including the urethane prepolymer), the polyurethane resin composition, and the method for producing the polyurethane resin composition will be described.

<1. Cellulose nanofiber>
The cellulose nanofibers in the polyurethane resin composition of the present invention are fine fibers of unmodified cellulose or chemically modified cellulose. Cellulose nanofibers usually have an average fiber diameter of about 3 to 500 nm, preferably 3 nm or more and 500 nm or less. Moreover, the cellulose nanofiber in the polyurethane resin composition of the present invention usually has an average aspect ratio of 50 or more. The upper limit of the aspect ratio is not particularly limited, but is usually 1000 or less.

The average fiber diameter and average fiber length of the cellulose nanofiber can be determined, for example, as follows. First, a 0.001 mass% aqueous dispersion of cellulose nanofibers is prepared. This diluted dispersion is thinly spread on a mica sample stage and heated and dried at 50 ° C. to prepare an observation sample. By measuring the cross-sectional height of the shape image of the sample observed with an atomic force microscope (AFM), the number average fiber diameter or the number average fiber length can be calculated. Further, the average aspect ratio can be calculated by the following formula: average aspect ratio = average fiber length / average fiber diameter The cellulose nanofibers in the polyurethane resin composition of the present invention can be obtained by defibrating a cellulose raw material or a cellulose raw material. It can be obtained by defibration after chemical modification, or by chemical modification after defibration of the cellulose raw material. As the cellulose nanofibers in the polyurethane resin composition of the present invention, cellulose nanofibers produced by a known method can be used. Moreover, you may use a commercial item.

<1-1. Cellulose raw material>
The raw material of the cellulose nanofiber in the polyurethane resin composition of the present invention is not particularly limited, and the cellulose nanofiber can be produced from a known cellulose raw material. Examples of cellulose raw materials include plant-derived raw materials (for example, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (conifer unbleached kraft pulp (NUKP), conifer bleach kraft pulp (NBKP), hardwood) Unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.)) Examples include raw materials derived from animals (for example, ascidians), raw materials derived from algae, raw materials derived from microorganisms (for example, acetic acid bacteria (Acetobacter)), microbial products, and the like. Any of these may be sufficient as the cellulose raw material of the cellulose nanofiber in the polyurethane resin composition of this invention, and these 2 or more types of combinations may be sufficient as them. The cellulose raw material of the cellulose nanofiber in the polyurethane resin composition of the present invention is preferably a plant or microorganism-derived cellulose fiber, more preferably a plant-derived cellulose fiber.

The number average fiber diameter of the cellulose raw material is not particularly limited, and 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 can be mechanically processed by a disaggregator such as a refiner or a beater to make it about 50 μm.

<1-2. Dispersion>
When the cellulose raw material is defibrated or modified, the cellulose raw material may be dispersed to prepare a cellulose raw material dispersion. The dispersion medium for dispersing the cellulose raw material is preferably water since the cellulose raw material is hydrophilic.

<1-3. Denaturation>
In the polyurethane resin composition of the present invention, a chemically modified cellulose nanofiber in which at least a part of cellulose constituting the fiber is chemically modified may be used as the cellulose nanofiber. The cellulose nanofibers contained in the polyurethane resin composition of the present invention may be chemically modified cellulose nanofibers, or only a part of the cellulose nanofibers may be chemically modified cellulose nanofibers.

By the modification treatment, the fiber is sufficiently refined and a uniform fiber length and fiber diameter can be obtained. Therefore, since it becomes easy to exhibit the desired effect of the present invention, the cellulose nanofiber used in the polyurethane resin composition of the present invention preferably contains chemically modified cellulose nanofiber (that is, a part of the amount is chemically modified cellulose). Nanofibers), more preferably chemically modified cellulose nanofibers (ie, the total amount is chemically modified cellulose nanofibers).

The modification method for obtaining chemically modified cellulose nanofibers is not particularly limited, and examples thereof include oxidation, etherification, esterification, acetylation, silane coupling, fluorine modification, and cationization. Of these, oxidation, etherification and esterification are preferred. These modifications will be described below.

<1-3-1. Oxidation>
In the polyurethane resin composition of the present invention, when cellulose nanofibers modified by oxidation (hereinafter also referred to as oxidized cellulose nanofibers) are used, the lower limit of the amount of carboxyl groups of the oxidized cellulose nanofibers is the oxidized cellulose nanofibers. Preferably, it is 0.1 mmol / g or more, more preferably 1.0 mmol / g or more, and still more preferably 1.2 mmol / g or more with respect to the absolute dry mass. Moreover, the upper limit becomes like this. Preferably it is 3.0 mmol / g or less, More preferably, it is 2.5 mmol / g or less, More preferably, it is 2.0 mmol / g or less. Therefore, the amount of the carboxyl group of the oxidized cellulose nanofiber is preferably 0.1 mmol / g to 3.0 mmol / g, and 1.0 mmol / g to 2.5 mmol / g with respect to the absolute dry mass of the oxidized cellulose nanofiber. Is more preferable, and 1.2 mmol / g to 2.0 mmol / g is more preferable.

The oxidation of the cellulose raw material or the cellulose fiber obtained after defibrating the cellulose raw material (hereinafter also referred to as defibrated cellulose fiber) can be performed using a known method, and is not particularly limited. However, the amount of carboxyl groups is 0.1 mmol / g to 3.3 to the absolute dry weight of cellulose fibers (hereinafter also referred to as oxidized cellulose fibers) or oxidized cellulose nanofibers obtained by modifying cellulose raw materials by oxidation. It is preferable to adjust to 0 mmol / g.

Although the oxidation method is not particularly limited, an example is a method of oxidizing a cellulose raw material or defibrated cellulose fiber in water using an oxidizing agent in the presence of an N-oxyl compound and bromide, iodide or a mixture thereof. Can be mentioned.
According to this oxidation method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and at least one functional group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group is formed on the surface. Occurs. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by mass or less.

N-oxyl compound refers to a compound capable of generating a nitroxy radical. 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 capable of oxidizing the cellulose as a raw material. For example, the lower limit is preferably 0.01 mmol or more, and more preferably 0.05 mmol or more, with respect to cellulose having an absolutely dry mass of 1 g. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and still more preferably 0.05 to 0.5 mmol with respect to 1 g of cellulose having an absolutely dry mass. Further, the amount of the N-oxyl compound used is preferably an amount that gives a concentration of about 0.1 to 4 mmol / L with respect to the reaction system.

Bromide is a compound containing bromine, and examples thereof include alkali metal bromide (for example, sodium bromide) that can be dissociated and ionized in water. Further, an iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used may be adjusted within a range that can promote the oxidation reaction. The lower limit of the total amount of bromide and iodide is, for example, preferably 0.1 mmol or more, more preferably 0.5 mmol or more, with respect to cellulose having an absolute dry mass of 1 g. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and even 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 cellulose having an absolutely dry mass.

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 more preferable. The lower limit of the amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, and further preferably 3 mmol or more with respect to 1 g of cellulose having an absolutely dry mass. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, and even more preferably 25 mmol or less and 10 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 3 to 10 mmol with respect to 1 g of cellulose having an absolutely dry mass. Further, the lower limit of 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 or less. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.

The conditions such as pH, temperature and reaction time during the oxidation reaction of cellulose are not particularly limited, and in general, the reaction proceeds efficiently even under relatively mild conditions. Therefore, the lower limit of the reaction temperature is preferably 4 ° C. or higher, more preferably 15 ° C. or higher. The upper limit is preferably 40 ° C. or lower, more preferably 30 ° C. or lower. Accordingly, the reaction temperature is preferably 4 to 40 ° C., and may be about 15 to 30 ° C., that is, room temperature. The lower limit of the pH value of the reaction solution is preferably 8 or more, more preferably 10 or more. The upper limit is preferably 12 or less, more preferably 11 or less. Therefore, the pH value of the reaction solution is preferably 8 to 12, more preferably about 10 to 11. As the reaction proceeds, carboxyl groups are generated in the cellulose, so the pH value 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 the reaction solution to maintain the pH value of the reaction solution in the above range. The reaction medium is preferably water for reasons such as ease of handling and the difficulty of side reactions.

The reaction time in the oxidation reaction can be appropriately set according to the progress of oxidation. The lower limit is usually 0.5 hours or longer. Moreover, the upper limit is 6 hours or less normally, Preferably it is 4 hours or less. Therefore, the reaction time is usually 0.5 to 6 hours, preferably about 0.5 to 4 hours.

Moreover, the oxidation reaction may be carried out in two stages. For example, the oxidized cellulose obtained by filtration after the completion of the first stage reaction is oxidized again under the same or different reaction conditions, whereby a salt (eg, sodium chloride) is produced as a by-product in the first stage reaction. Even if it inhibits, cellulose can be oxidized efficiently.

Another example of the oxidation method including carboxylation is a method of oxidizing by ozone treatment. By this oxidation reaction, at least the 2-position and 6-position hydroxyl groups of the glucopyranose ring are oxidized and the cellulose chain is decomposed. The ozone treatment is usually performed by bringing a gas containing ozone into contact with a cellulose raw material or defibrated cellulose fiber.

The lower limit of the ozone concentration in the gas containing ozone 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. Accordingly, the ozone concentration in the gas containing ozone is preferably 50 to 250 g / m ³ , and more preferably 50 to 220 g / m ³ .

The lower limit of the amount of ozone added to the cellulose raw material or defibrated cellulose fiber is preferably 0.1% by mass or more, more preferably 5% by mass when the solid content of the cellulose raw material or defibrated cellulose fiber is 100% by mass. % Or more. The upper limit is preferably 30% by mass or less. Accordingly, the amount of ozone added to the cellulose raw material or defibrated cellulose fiber is preferably 0.1 to 30% by mass when the solid content of the cellulose raw material or defibrated cellulose fiber is 100% by mass, and preferably 5 to 30%. More preferably, it is mass%.

The lower limit of the ozone treatment temperature is preferably 0 ° C or higher, more preferably 20 ° C or higher. The upper limit is preferably 50 ° C. or less. Therefore, the ozone treatment temperature is preferably 0 to 50 ° C., and more preferably 20 to 50 ° C.

Ozone treatment time is not particularly limited. The lower limit is usually 1 minute or longer, preferably 30 minutes or longer. The upper limit is usually 360 minutes or less. Accordingly, the ozone treatment time is usually about 1 to 360 minutes, preferably about 30 to 360 minutes.

If the conditions for the ozone treatment are within these ranges, excessive oxidation and decomposition of cellulose can be suppressed, and the yield of oxidized cellulose is improved.

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. For example, these oxidants are dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizer solution, and a cellulose raw material or defibrated cellulose fiber is immersed in the solution to perform a further oxidation treatment. it can.

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

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

<1-3-2. Etherification>
As etherification, carboxymethyl (ether), methyl (ether), ethyl (ether), cyanoethyl (ether), hydroxyethyl (ether), hydroxypropyl (ether), ethyl hydroxyethyl (ether) And hydroxypropylmethyl (ether). As an example, a carboxymethylation method will be described below.

When the cellulose raw material is modified by carboxymethylation, the lower limit of the degree of carboxymethyl substitution per anhydroglucose unit in the obtained carboxymethylated cellulose or carboxymethylated cellulose nanofiber is preferably 0.01 or more, 0.05 or more Is more preferable, and 0.10 or more is more preferable. 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 substitution is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and still more preferably 0.10 to 0.35.

The method of carboxymethylation is not particularly limited, and examples thereof include a method of mercerizing a cellulose raw material as a starting material and then etherifying. In the carboxymethylation reaction, a solvent is usually used. 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-butyl alcohol, isobutyl alcohol, and tertiary butyl alcohol. The mixing ratio of the lower alcohol in the mixed solvent is preferably 60 to 95% by mass. The lower limit of the amount of the solvent is usually 3 times or more in terms of mass relative to the cellulose raw material. Although the upper limit is not specifically limited, it is 20 times or less. Therefore, the amount of the solvent is preferably 3 to 20 times in terms of mass relative to the cellulose raw material.

Mercerization is usually performed by mixing the starting material and mercerizing agent. Examples of mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The lower limit of the amount of the mercerizing agent used is preferably 0.5 times or more, more preferably 1.0 times or more, and further preferably 1.5 times or more in terms of mole per anhydroglucose residue of the starting material. The upper limit is usually 20 times or less, preferably 10 times or less, and more preferably 5 times or less. Accordingly, the amount of the mercerizing agent used is preferably 0.5 to 20 times, more preferably 1.0 to 10 times, and further preferably 1.5 to 5 times in terms of mole per anhydroglucose residue of the starting material. preferable.

The lower limit of 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. Accordingly, the reaction temperature is usually 0 to 70 ° C., preferably 10 to 60 ° C. The lower limit of 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, the reaction time 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 lower limit of the addition amount of the carboxymethylating agent is preferably 0.05 times or more, more preferably 0.5 times or more, and still more preferably 0.8 times or more in terms of mole per glucose residue of the cellulose raw material. The upper limit is usually 10.0 times or less, preferably 5 times or less, and more preferably 3 times or less. Therefore, the addition amount of the carboxymethylating agent is preferably 0.05 to 10.0 times, more preferably 0.5 to 5 times in terms of mole per glucose residue of the cellulosic raw material, Preferably it is 0.8 to 3 times. The lower limit of the reaction temperature is usually 30 ° C. or higher, preferably 40 ° C. or higher. Moreover, the upper limit is 90 degrees C or less normally, Preferably it is 80 degrees C or less. Therefore, 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 degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose nanofibers can be determined, for example, by the following method. That is, 1) About 2.0 g of carboxymethylated cellulose (absolutely dry) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 2) 100 mL of a solution obtained by adding 100 mL of special grade concentrated nitric acid to 1000 mL of methanol is added to the Erlenmeyer flask and shaken for 3 hours to convert the carboxymethyl cellulose salt (carboxymethylated cellulose) into hydrogen-type carboxymethylated cellulose. 3) Weigh accurately 1.5 to 2.0 g of hydrogen-type carboxymethylated cellulose (absolutely dry) and place in a conical flask with a 300 mL 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 0.1N H ₂ SO ₄ using phenolphthalein as indicator. 6) Degree of carboxymethyl substitution (DS) can be 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 NaOH factor F: 0.1N H ₂ SO ₄ factor

<1-3-3. Esterification>
The method for obtaining the esterified cellulose fiber or the esterified cellulose nanofiber by esterifying the cellulose raw material or the defibrated cellulose fiber is not particularly limited. For example, the method of making a phosphorus atom containing compound (henceforth "compound A") react with a cellulose raw material or defibrated cellulose fiber is mentioned. Compound A will be described later.

Examples of the method of reacting compound A with cellulose raw material or defibrated cellulose fiber include, for example, a method of mixing a powder or aqueous solution of compound A into cellulose raw material or defibrated cellulose fiber, and a compound with a slurry of cellulose raw material or defibrated cellulose fiber Examples thereof include a method of adding an aqueous solution of A. Among these, since the uniformity of the reaction is enhanced and the esterification efficiency is increased, a method in which an aqueous solution of Compound A is mixed with a cellulose raw material, a defibrated cellulose fiber or a slurry thereof is preferable.

Examples of compound A include phosphoric acid compounds (eg, phosphoric acid, polyphosphoric acid), phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. Compound A may be in the form of a salt. Among them, a phosphoric acid compound is preferable because it is low in cost, easy to handle, and can improve the fibrillation efficiency by introducing a phosphate group into cellulose of a cellulose raw material (eg, pulp fiber). . The phosphate compound may be any compound having a phosphate group. For example, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, diphosphate Examples include potassium hydrogen, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium metaphosphate. . The phosphoric acid compound used may be a single type or a combination of two or more types. 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 Ammonium salt is preferable, sodium salt of phosphoric acid is more preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable. In addition, it is preferable to use an aqueous solution of a phosphoric acid compound in the esterification because the uniformity of the reaction is enhanced and the efficiency of introduction of phosphoric acid groups is increased. The pH value of an aqueous solution of a phosphoric acid compound is preferably 7 or less because the efficiency of introducing a phosphate group is increased. From the viewpoint of suppressing the hydrolysis of pulp fibers, the pH value is more preferably 3-7.

Examples of the esterification method include the following methods. The compound A can be added to a cellulose raw material or a suspension of defibrated cellulose fibers (for example, a solid content concentration of 0.1 to 10% by mass) with stirring to introduce phosphate groups into the cellulose. When the compound A is a phosphoric acid compound, the lower limit of the amount of the compound A added is preferably 0.2 parts by mass or more in terms of the amount of phosphorus element with respect to 100 parts by mass of the cellulose raw material or defibrated cellulose fiber, and 1 mass. Part or more is more preferable. Thereby, the yield of esterified cellulose fiber or esterified cellulose nanofiber can be further improved. The upper limit is preferably 500 parts by mass or less, and more preferably 400 parts by mass or less. Thereby, the yield corresponding to the usage-amount of the compound A can be obtained efficiently. Therefore, 0.2 to 500 parts by mass is preferable, and 1 to 400 parts by mass is more preferable.

When reacting the compound A with the cellulose raw material or the defibrated cellulose fiber, a compound B showing basicity (hereinafter also referred to as “compound B”) may be added to the reaction system. Examples of the method of adding Compound B to the reaction system include a method of adding Compound B to a slurry of cellulose raw material or defibrated cellulose fiber, an aqueous solution of Compound A, or a slurry of cellulose raw material or defibrated cellulose fiber and Compound A. It is done.

Compound B is not particularly limited, but a nitrogen-containing compound showing basicity is more preferable. “Show basic” usually means that the aqueous solution of Compound B is pink to red in the presence of a phenolphthalein indicator and / or the pH value of the aqueous solution of Compound B is greater than 7. The nitrogen-containing compound showing basicity is not particularly limited as long as the effects of the present invention are exhibited, but a compound having an amino group is preferable. Examples of the compound having an amino group include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Of these, urea is preferable because it is easy to handle at low cost. The amount of compound B added is preferably 2 to 1000 parts by mass, and more preferably 100 to 700 parts by mass. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, preferably 30 to 480 minutes. When the conditions for the esterification reaction are in any of these ranges, it is possible to suppress cellulose from being excessively esterified and easily dissolved, and to improve the yield of phosphate esterified cellulose.

After reacting compound A with cellulose raw material or defibrated cellulose fiber, a suspension of esterified cellulose fiber or esterified cellulose nanofiber is usually obtained. The suspension of esterified cellulose fiber or esterified cellulose nanofiber is dehydrated as necessary. Heat treatment is preferably performed after dehydration. Thereby, hydrolysis of a cellulose raw material or a defibrated cellulose fiber can be suppressed. The heating temperature is preferably 100 to 170 ° C. While water is included in the heat treatment, heating is performed at 130 ° C or less (more preferably 110 ° C or less), and after removing water, heating is performed at 100 to 170 ° C. More preferably, it is processed.

In phosphate esterified cellulose, a phosphate group is introduced into the cellulose as a substituent, and the cellulose repels electrically. Therefore, phosphate esterified cellulose fibers can be easily defibrated to cellulose nanofibers (the defibration performed until the cellulose nanofibers are thus formed is also referred to as “nanodefibration”). The lower limit of the degree of phosphate group substitution per glucose unit of the phosphate esterified cellulose fiber is preferably 0.001 or more. Thereby, sufficient defibration (for example, nano defibration) can be implemented. The upper limit is preferably 0.40 or less. Thereby, swelling or melt | dissolution of phosphate esterified cellulose fiber can be suppressed, and generation | occurrence | production of the situation where a cellulose nanofiber cannot be obtained can be suppressed. Accordingly, the phosphate group substitution degree per glucose unit of the phosphate esterified cellulose fiber is preferably 0.001 to 0.40. Further, the degree of phosphate group substitution per glucose unit of cellulose nanofibers (phosphate esterified cellulose nanofibers) modified by phosphorylation is preferably 0.001 or more. The upper limit is preferably 0.40 or less. Therefore, the phosphate group substitution degree per glucose unit of the phosphate esterified cellulose nanofiber is preferably 0.001 to 0.40.

It is preferable that the phosphorylated cellulose fiber is subjected to a washing treatment such as washing with cold water after boiling. Thereby, defibration can be performed efficiently.

<1-4. Defibration>
Defibration may be performed before the cellulose raw material is subjected to a modification treatment, or chemically modified cellulose fibers (eg, oxidized cellulose fibers, carboxymethylated cellulose) after the cellulose raw material is modified. You may perform with respect to a fiber and esterified cellulose fiber (phosphate esterified cellulose fiber). Since the energy required for defibration is reduced by the modification, the defibration is preferably performed after the cellulose raw material is subjected to a modification treatment.

Defibration may be performed only once or multiple times. When performing multiple times, the time of each defibration may be anytime and may be performed at once.

The device used for defibration is not particularly limited, and examples thereof include high-speed rotation type, colloid mill type, high-pressure type, roll mill type, ultrasonic type and the like, high-pressure or ultra-high pressure homogenizer is preferable, wet type, High pressure or ultra high pressure homogenizers are more preferred. These apparatuses are preferable because a strong shearing force can be applied to a cellulose raw material or a chemically modified cellulose fiber (usually an aqueous dispersion).

In order to efficiently defibrate, the pressure applied to the cellulose raw material or the chemically modified cellulose fiber (usually an aqueous dispersion) is preferably 50 MPa or more, more preferably 100 MPa or more, and further preferably 140 MPa. That's it. The apparatus can apply the above pressure to the cellulose raw material or chemically modified cellulose fiber (usually an aqueous dispersion) and can apply a strong shearing force, so that a wet, high-pressure or ultra-high pressure homogenizer can be used. preferable.

Further, prior to defibration (preferably defibration with a high-pressure homogenizer) or, if necessary, dispersion treatment performed before defibration, pretreatment may be performed as necessary. Examples of the pretreatment include mixing, stirring, emulsification, and dispersion, and a known apparatus (eg, high-speed shear mixer) may be used.

When defibration is performed on a cellulose raw material or a chemically modified cellulose fiber dispersion (usually an aqueous dispersion), the lower limit of the solid content concentration of the cellulose raw material or chemically modified cellulose fiber in the dispersion Is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more. Thereby, the amount of the liquid becomes appropriate with respect to the amount of the cellulose raw material to be processed or the chemically modified cellulose fiber, which is efficient. The upper limit is usually 10% by mass or less, preferably 6% by mass or less. Thereby, fluidity | liquidity can be hold | maintained.

<2. Polyurethane resin>
The polyurethane resin is generally called a urethane resin or a urethane rubber, and is a general term for polymers having a urethane bond (—NH · CO · O—). The polyurethane resin is usually produced by a condensation reaction of a polyol compound and a polyisocyanate compound.
The ratio when the polyol compound and the polyisocyanate compound are reacted is the molar ratio of the hydroxyl group of the polyol compound to the isocyanate group of the polyisocyanate compound ([NCO / OH]) from the viewpoints of the strength of the polyurethane resin, pot life, and the like. Is preferably in the range of 1.1 to 8.0.

The method for producing the polyurethane resin is not particularly limited. For example, a polyurethane resin can be produced by reacting a polyol compound with a polyisocyanate compound in such an amount that the hydroxyl group of the polyol compound and the isocyanate group of the polyisocyanate compound have a chemical equivalent. In addition, a polyurethane prepolymer is prepared by reacting a polyol compound and a polyisocyanate compound in an amount in which the isocyanate group of the polyisocyanate compound is excessive compared with the hydroxyl group of the polyol compound, and then reacting with a curing agent to form polyurethane. Resins can also be produced.

<2-1. Polyol compound>
As the polyol compound, for example, polyoxyalkylene polyol, polyether polyol, polyester polyol, polycaprolactone polyol, polycarbonate polyol, polybutadiene polyol, hydrogenated polybutadiene polyol, polyacryl polyol, dimer diol and the like can be used. These polyols may be used alone or in combination of two or more. Among these, it is preferable to use polycarbonate polyol.

Examples of the polycarbonate polyol include polycarbonate diol, polycarbonate triol, and polycarbonate tetraol. Among these, it is preferable to use polycarbonate diol.

<2-2. Polyisocyanate compound>
As the polyisocyanate compound, one having two or more isocyanate groups in the molecule can be used. For example, toluene diisocyanate, tolylene diisocyanate, tolidine diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, carbodiimidized diphenylmethane polyisocyanate, crude diphenylmethane diisocyanate (crude MDI), xylylene diisocyanate, 1,5-naphthalene diisocyanate Tetramethylxylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, dimer acid diisocyanate, norbornene diisocyanate and the like can be used. Among these, it is preferable to use isophorone diisocyanate.

<3. Polyurethane resin composition>
The polyurethane resin composition of the present invention has the above <1. Cellulose nanofibers described in <Cellulose nanofibers> and <2. Polyurethane resin> is contained.

The content of cellulose nanofibers is preferably 0.1 to 10, more preferably 0.2 to 7, and still more preferably 0.3 to 5 with respect to 100 parts by mass of the polyurethane resin. By being in such a range, the polyurethane resin composition of the present invention can produce a molded article having both strength, heat resistance and water resistance at a high level.

The polyurethane resin composition of the present invention may contain one or more other additives as required. Other additives include, for example, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, fillers, colorants, reinforcing agents, mold release agents, flame retardants, other thermoplastic resins, surfactants, catalysts, Stabilizers, pigments, foaming agents and the like can be used. These may be added to the polyurethane resin aqueous dispersion, or may be added during kneading. The content of the additive can be freely adjusted according to the required performance of the polyurethane resin composition.

<4. Method for producing polyurethane resin composition>
The polyurethane resin composition of the present invention is applied 1) a method of mixing an aqueous dispersion of polyurethane resin and an aqueous dispersion of cellulose nanofibers to remove the solvent, and 2) applying a method for producing polyurethane using a prepolymer method. And at least a polyol compound and a polyisocyanate compound are reacted in an organic solvent to prepare an organic solvent dispersion of a urethane prepolymer having an isocyanate terminal, and the organic solvent dispersion of the urethane prepolymer and an aqueous dispersion of cellulose nanofibers. To obtain a mixed solution, and a polyurethane resin is prepared by mixing a curing agent with the mixed solution, and then the solvent is removed.
Among these, a method using a polyurethane production method using a prepolymer method is preferable from the viewpoint of strength. In addition, the production method applying the polyurethane production method using the prepolymer method is milder than the one-shot method in which a urethane compound is produced by reacting a polyol compound, polyisocyanate compound, catalyst, etc. at once. Therefore, since there are few by-products and the mixing property is good, a uniform quality polyurethane resin composition can be stably obtained, which is preferable. In addition, a urethane prepolymer is a manufacturing method of the polyurethane obtained by making a polyol compound and an excess amount of polyisocyanate compound react, It is characterized by containing an isocyanate group in the molecular terminal. The isocyanate group equivalent is not particularly limited, but is 150 to 2,000 g / eq. From the viewpoint of storage modulus and creep property. It is preferable that it is the range of these.

In the production of the polyurethane resin composition of the present invention, the method for removing the solvent is not particularly limited. For example, a method of removing the organic solvent component by heating, adding a curing agent while stirring a mixed liquid of an organic solvent dispersion of urethane prepolymer and an aqueous dispersion of cellulose nanofibers under an inert gas atmosphere. It is done.

The lower limit of the cellulose nanofiber content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and still more preferably 0.8% by mass, based on the total weight of all components of the polyurethane resin. 3% by mass or more. The upper limit is preferably 10% by mass or less, more preferably 7% by mass or less, and still more preferably 5% by mass or less. When the content is 0.1% by mass or more, a sufficient effect is obtained, and when the content is 10% by mass or less, a molded article with more excellent elongation at break can be produced.

The solid concentration of the cellulose nanofiber aqueous dispersion added to the organic solvent dispersion of the urethane prepolymer is preferably in the range of 0.1 to 6% by mass, and in the range of 0.1 to 1% by mass. More preferably, the range is 0.1 to 0.6% by mass. By sufficiently diluting the aqueous dispersion of cellulose nanofibers and adding them, the dispersibility of the cellulose nanofibers is improved.
Examples of the organic solvent include methyl ethyl ketone (MEK), dimethylformamide (DMF), isopropyl alcohol (IPA), ethyl acetate, toluene and the like. Among these, it is preferable to use methyl ethyl ketone (MEK).

In the production method applying the polyurethane production method using the prepolymer method, an organic solvent dispersion of urethane prepolymer and an aqueous dispersion of cellulose nanofiber are mixed to obtain a mixed solution, and then cured to the mixed solution. A polyurethane resin is prepared by adding an agent. As the curing agent, for example, a compound having an amino group or a compound having a hydroxyl group can be used. Among these, it is preferable to use a compound having an amino group.

Examples of the compound having an amino group include ethylenediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4′-dicyclohexylmethanediamine, 3,3′-dimethyl-4, 4′-dicyclohexylmethanediamine, 1,4-cyclohexanediamine, 1,2-propanediamine, diethylenetriamine, triethylenetetramine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, polyaminochlorophenylmethane compounds (for example, “ Pandex E-50 "(manufactured by DIC), hydrazine, acid hydrazide and the like can be used. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use ethylenediamine.
In addition to the curing agent, a tertiary amine catalyst or an organometallic catalyst may be used as necessary.

The aqueous dispersion of the polyurethane resin composition obtained above can be used as the polyurethane resin composition of the present invention by defoaming treatment if necessary, and removing the aqueous solvent by drying. The resulting dried product (polyurethane resin composition of the present invention) is kneaded, press-molded to the desired shape, and then annealed (heated to relieve residual strain and fix morphological dimensions as necessary) The molded product is obtained by performing various finishing processes such as polishing and polishing.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

<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, since the pH value in the system was lowered, a 3M sodium hydroxide aqueous solution was sequentially added to adjust the pH value to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system no longer changed.
The mixture after the reaction was filtered through a glass filter to separate the pulp. The separated 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 0.55% (w / v) with water and treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa) to obtain an aqueous dispersion of oxidized cellulose nanofibers. The average fiber diameter of the oxidized cellulose nanofiber was 3 nm, and the aspect ratio was 250.

[Production of aqueous dispersion of polyurethane resin]
Polycarbonate diol (PCDL, manufactured by Asahi Kasei Chemicals) 28 g as the polyol compound, isophorone diisocyanate (IPDI, manufactured by Sigma Aldrich Japan) 9.9 g as the isocyanate compound, and dimethylolpropionic acid (DMPA, manufactured by Sigma Aldrich Japan) as the hydrophilic group introducing agent. ) 1.9 g was mixed in 40 g of methyl ethyl ketone (MEK, manufactured by Sigma-Aldrich Japan) under a nitrogen atmosphere, and 0.02 g of dibutyltin dilaurate (DBTDL, manufactured by Tokyo Chemical Industry Co., Ltd.) was further added as a catalyst at 80 ° C. By stirring for 2.5 hours, an isocyanate-terminated urethane prepolymer was obtained.

Next, 1.7 g of triethylamine (TEA, manufactured by Sigma-Aldrich Japan) as an ionizing agent, 18 g of an aqueous dispersion of the oxidized cellulose nanofiber (content of oxidized cellulose nanofiber: 0.1 part by mass with respect to 100 parts by mass of the prepolymer). 5 parts by mass) and 74.9 g of distilled water were added, and the mixture was stirred at 35 ° C. for 10 minutes under a nitrogen atmosphere to obtain a mixed solution containing a urethane prepolymer and oxidized cellulose nanofibers.

Next, 0.43 g of ethylenediamine (EDA, manufactured by Sigma-Aldrich Japan Co., Ltd.) as a curing agent is mixed with this and stirred at 80 ° C. for 2 hours in a nitrogen atmosphere, whereby an aqueous dispersion of a polyurethane resin containing cellulose nanofibers is dispersed. Got the body.

[Production and Evaluation of Polyurethane Resin Composition]
135 g of an aqueous dispersion of polyurethane resin was degassed under reduced pressure, and dried at 40 ° C. for 72 hours to obtain a plate-like dried product (polyurethane resin composition). The dried product was kneaded 10 times at 25 ° C. with an 8-inch open roll (Katsuki Iron Works), and then at 110 ° C., 5 MPa, 5 minutes with a hot plate press (Kodaira Seisakusho). And press molded. Thereafter, a sheet of polyurethane resin composition having a thickness of 1 mm (molded article) is subjected to annealing treatment at 100 ° C. under reduced pressure for 24 hours (heating to relieve residual strain and fix morphological dimensions). Got.

With respect to the sheet of this polyurethane resin composition, tensile stress and tensile strength are used as indices for reinforcement, storage elastic modulus (E ′) and loss factor (tan δ) are used as indices for heat resistance, and water resistance is indexed by the following methods. As a result, the water absorption was measured.

[Tensile stress and tensile strength]
In accordance with JIS K7161 “Plastics—Test Method for Tensile Properties”, a sheet of the above polyurethane resin composition is cut into a predetermined dumbbell-shaped test piece, and a universal tensile compression tester (UTM-10T, manufactured by A & D Co.) is used. Then, the specimen was pulled until it broke, and the tensile stress at 300% strain and the tensile strength (the first maximum tensile stress observed during the test) were measured. It shows that reinforcement property is so favorable that the value of tensile stress and tensile strength is large.

[Storage elastic modulus (E ′) and loss coefficient (tan δ)]
According to JIS K7244 “Plastics—Testing method for dynamic mechanical properties”, a sheet of the polyurethane resin composition is cut into a predetermined test piece, and a dynamic viscoelasticity measuring apparatus (model: DMAQ800, manufactured by TA Instruments) is used. The storage elastic modulus (E ′) and the loss coefficient (tan δ) were measured while changing the temperature from −100 ° C. to + 250 ° C. in a nitrogen atmosphere. In any case, the more the obtained graph is shifted to the higher temperature side, the better the heat resistance.

[Water absorption rate]
In accordance with JIS K7209 “Plastics-Determination of water absorption”, the polyurethane resin composition sheet was cut into a predetermined test piece, immersed in water for 48 hours, and then the mass of water absorbed by the test piece was measured. The water absorption was calculated as a percentage of the mass. The lower the water absorption, the better the water resistance.

<Example 2>
In the production of the aqueous dispersion of the polyurethane resin in Example 1, the oxidized cellulose nanofiber aqueous dispersion was changed to 36 g (content of oxidized cellulose nanofiber: 1.0 part by mass with respect to 100 parts by mass of the prepolymer). The same method as in Example 1 was performed.

<Example 3>
In the production of the aqueous dispersion of the polyurethane resin in Example 1, except that the oxidized cellulose nanofiber aqueous dispersion was changed to 106 g (content of oxidized cellulose nanofiber: 3.0 parts by mass with respect to 100 parts by mass of the prepolymer). The same method as in Example 1 was performed.

<Example 4>
In the production of the polyurethane resin aqueous dispersion of Example 1, before adding the oxidized cellulose nanofiber aqueous dispersion, the same amount of distilled water as the oxidized cellulose nanofiber aqueous dispersion was added, and then the oxidized cellulose nanofiber water was added. 18.1 g of the dispersion (content of oxidized cellulose nanofiber: 0.5 part by mass with respect to 100 parts by mass of the prepolymer) was added and stirred at room temperature for 10 minutes to obtain an aqueous dispersion of polyurethane resin. The same method as in Example 1 was performed.

<Example 5>
In Example 4, it was the same method as Example 4 except having changed the oxidized cellulose nanofiber aqueous dispersion to 36 g (content of oxidized cellulose nanofiber: 1.0 part by mass with respect to 100 parts by mass of the prepolymer). Carried out.

<Example 6>
In Example 4, it was the same method as Example 4 except having changed the oxidized cellulose nanofiber aqueous dispersion to 106 g (content of oxidized cellulose nanofiber: 3.0 parts by mass with respect to 100 parts by mass of the prepolymer). Carried out.

<Comparative Example 1>
In the production of the aqueous polyurethane resin dispersion of Example 1, the same procedure as in Example 1 was performed, except that the oxidized cellulose nanofiber aqueous dispersion was changed to the same amount of distilled water.

As is clear from the results of Table 1, FIG. 1 and FIG. 2, in the polyurethane resin composition sheets of Examples 1 to 6 containing oxidized cellulose nanofibers within the appropriate blending amount range, Compared with the polyurethane resin composition sheet, tensile stress, tensile strength, storage modulus, loss tangent, and swelling rate are all good, and these strengths, heat resistance, and water resistance are compatible at a high level. I understand that.

Claims (5)

Polyurethane resin composition containing cellulose nanofiber and polyurethane resin. The cellulose nanofiber includes an oxidized cellulose nanofiber in which the hydroxyl group at the C6 position in a part of glucose units constituting cellulose is a carboxyl group,
The polyurethane resin composition according to claim 1, wherein the amount of carboxyl groups of the oxidized cellulose nanofiber is 0.1 mmol / g to 3.0 mmol / g with respect to the absolute dry mass of the oxidized cellulose nanofiber. The polyurethane resin composition according to claim 1 or 2, wherein the content of the cellulose nanofiber is 0.1 to 10 parts by mass with respect to 100 parts by mass of the polyurethane resin. The method for producing a polyurethane resin composition according to any one of claims 1 to 3, further comprising a step of mixing an aqueous dispersion of polyurethane resin and an aqueous dispersion of cellulose nanofibers. A urethane prepolymer preparation step of preparing an organic solvent dispersion of a urethane prepolymer having an isocyanate terminal by reacting at least a polyol compound and a polyisocyanate compound in an organic solvent;
A mixing step of mixing the urethane prepolymer organic solvent dispersion and the cellulose nanofiber aqueous dispersion to obtain a mixed solution;
The method for producing a polyurethane resin composition according to any one of claims 1 to 3, further comprising a polyurethane resin preparation step of preparing a polyurethane resin by mixing a curing agent with the mixed solution.

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