WO2019172058A1 - Method for producing polyurethane containing cellulose nanofibers - Google Patents

Abstract

[Problem] The purpose of the present invention is to provide a method for producing a polyurethane containing cellulose nanofibers, which does not require crushing of cellulose in a polyol, use of water, and a surface treatment of cellulose for the purpose of enhancing the dispersibility in resins, and which is suitable as a starting material for artificial leathers, synthetic leathers, adhesives, painting materials, coating agents and the like. [Solution] A method for producing a polyurethane containing cellulose nanofibers, which comprises the following steps (a)-(c). (a) A step for obtaining a carbonic acid ester dispersion of cellulose nanofibers by dispersing cellulose nanofibers in a carbonic acid ester. (b) A step for obtaining a cellulose nanofiber-containing polycarbonate diol dispersion by having the carbonic acid ester dispersion react with a diol compound. (c) A step for obtaining a polyurethane containing cellulose nanofibers by having the polycarbonate diol dispersion react with an isocyanate compound.

Description

Method for producing cellulose nanofiber-containing polyurethane

The present invention relates to a method for producing cellulose nanofiber-containing polyurethane and cellulose nanofiber-containing polycarbonate diol dispersion.

Polyurethane is widely used in the fields of highly durable artificial leather and synthetic leather, adhesives, paints, coating agents, films and optical materials.
In particular, when polycarbonate diol (hereinafter referred to as PCD) is used as a raw material for polyurethane, a highly durable polyurethane excellent in hydrolysis resistance and chemical resistance can be obtained compared to polyester diol and polyether diol. It has been known.

In addition, when PCD is used for leather, paints and coatings, it has excellent moisture and heat resistance, wear resistance, and weather resistance in addition to the above characteristics, so as an automobile interior material, for example, artificial leather for seat seats or synthetic leather Used as a raw material for leather and exterior paints. Further, in adhesive applications, it is used for automobiles, electronic devices, electrical devices, and the like as an adhesive having excellent durability and flexibility.

However, since carbonate bonds are less flexible than ester bonds, polyurethanes made from PCD with only carbonate bonds are less flexible than polyurethanes made from polyester polyols, especially at low temperatures, Due to poor bending and elastic recovery, there is a problem that it is brittle.

On the other hand, cellulose nanofiber (hereinafter referred to as CNF) is obtained by mechanical or chemical defibration in an aqueous medium using pulp or the like as a raw material. It is.
CNF is lightweight but has 5 times the strength of iron, has a low coefficient of thermal expansion, and does not change its elastic modulus from low temperature to high temperature. Therefore, composite materials using CNF are lightweight, high strength, and low expansion. It is expected to be resistant to rate and temperature changes.

However, the concentration of CNF dispersed in water is as low as 1 to 20% by mass, and a large amount of water needs to be removed when it is combined with a resin.
On the other hand, when pulp is defibrated in resin, the resin is generally high in viscosity and requires strong mechanical force. Also, chemically defibrated CNF such as oxidation treatment has high hydrophilicity, so it can be refined and surface-treated. CNF is a material that is difficult to handle industrially because it requires treatment.

In recent years, it has been studied to improve physical properties by blending CNF with polyurethane. For example, it is obtained by reacting a polyol composition containing CNF obtained by refining cellulose in a polyol with polyisocyanate. A polyurethane resin composition containing a polyurethane resin is disclosed (Patent Document 1).
However, in order to obtain the polyurethane resin composition described in Patent Document 1, a raw material in which cellulose is defibrated in a polyol is used. In order to ensure the physical properties required for a polyurethane resin, a polyol having a high molecular weight is used. Is required.
For example, compared to polyester polyols and polyether polyols, high-performance PCDs with a molecular weight of 1000 to 2000 are often used, and some of the polycarbonate polyols are solid at room temperature and heated to 50 ° C., the viscosity is 1000 to 15000 mPa · s. In the defibration in the polyol having such a high viscosity, it is difficult to obtain a necessary shearing force, and the defibration tends to be insufficient.
On the other hand, when a strong mechanical force is applied while heating, defibration is promoted, but deterioration such as coloring of CNF or polyol tends to occur.

JP 2013-194162 A

The present invention eliminates the need for crushing cellulose in a polyol, and does not require the use of water or surface treatment of cellulose to enhance dispersibility in a resin, thereby providing artificial leather, synthetic leather, adhesive, and paint. Another object of the present invention is to provide a method for producing CNF-containing PCD and polyurethane suitable for raw materials such as coating agents.

In order to solve the above-mentioned problems, the present inventors have intensively studied, and as a result obtained by reacting an isocyanate compound with a CNF-containing PCD dispersion obtained by reacting a carbonate ester in which CNF is dispersed with a diol compound. The CNF-containing polyurethane obtained was found to be excellent in mechanical strength and chemical resistance, and the present invention was completed.

That is, the present invention is a method for producing a CNF-containing polyurethane comprising the following steps (a) to (c).
(A) A step of obtaining CNF carbonate dispersion by dispersing CNF in carbonate.
(B) A step of reacting the carbonate ester dispersion with a diol compound to obtain a CNF-containing PCD dispersion.
(C) A step of obtaining a CNF-containing polyurethane by reacting the PCD dispersion with an isocyanate compound.

Moreover, this invention is a manufacturing method of the CNF containing PCD dispersion | distribution including the process of following (a) and (b).
(A) A step of obtaining CNF carbonate dispersion by dispersing CNF in carbonate.
(B) A step of reacting the carbonate ester dispersion with a diol compound to obtain a CNF-containing PCD dispersion.

The polyurethane containing CNF obtained by the production method of the present invention is useful for artificial leather, synthetic leather, adhesives, paints, coating agents, etc. as a highly functional composite material excellent in properties such as mechanical strength and heat resistance. is there. The polyurethane in the present invention includes foamed polyurethane (urethane foam).

The microscope picture of the CNF containing ethylene carbonate dispersion liquid obtained in Reference Example 1 is shown. The microscope picture of the CNF containing ethylene carbonate dispersion obtained in Reference Example 2 is shown. The microscope picture of the CNF containing PCD dispersion liquid obtained in Example 1 is shown. The microscope picture of the CNF containing PCD dispersion liquid obtained in Example 2 is shown. The microscope picture of the CNF containing polyurethane obtained in Example 4 is shown. The microscope picture of the CNF containing polyurethane obtained in Example 5 is shown. The relationship between the elongation of the polyurethane foam obtained in Example 6 and Comparative Example 2 and tensile stress is shown.

Hereinafter, the present invention will be described in detail along the manufacturing method.
The step (a) of the present invention is a step in which CNF is dispersed in a carbonate ester to obtain a CNF carbonate ester dispersion.

Examples of the method for dispersing CNF in the carbonate ester include a method of obtaining a carbonate ester in which cellulose containing CNF is dispersed by pulverizing biomass, which is a raw material of CNF, in the carbonate ester. For example, Japanese Patent Application Laid-Open No. 2017-23921. The method described in the publication can be used.
The biomass to be used may be any biological material, but it is particularly desirable to use woody, herbaceous, and cellulose plant biomass.
In addition, as a device for pulverizing biomass, ball mills, bead mills, hammer mills, rod mills, disk mills, cutter mills, jet mills, high-pressure homogenizers and ultrasonic homogenizers can be used. It is desirable to do.
Further, CNF powdered in advance can also be used. The pulverized CNF is, for example, pulverized by freeze-drying or thermal decomposition of ammonium carbonate, and has a large specific surface area. CNF can be dispersed in the ester.

Examples of the carbonic acid ester include cyclic carbonates and chain carbonates that can give PCD by reaction with a diol compound.
Examples of the cyclic carbonates include alkylene carbonates having an alkylene group having 2 to 4 carbon atoms such as ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate, propylene carbonate, and butylene carbonate are preferable. Is particularly preferred.

As the chain carbonates, dialkyl carbonate and diaryl carbonate are preferable. In the dialkyl carbonate, the alkyl group constituting the carbon group preferably has 1 to 5 carbon atoms, particularly preferably 1 to 4 carbon atoms. Specific examples include symmetric chain alkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate, and asymmetric chain alkyl carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. And dialkyl carbonates. Among these, dimethyl carbonate and diethyl carbonate are preferable.
Examples of the diaryl carbonate include diphenyl carbonate and ditolyl carbonate, and diphenyl carbonate is preferable.

For example, ethylene carbonate is used as the carbonate ester, hardwood pulp (concentration 1 wt%) is used as the woody biomass, and if it is crushed with an ultrasonic homogenizer, the thickness is about 200 nm and the length is about 50 μm. CNF is generated.

In the said process (a), since it is excellent in the reactivity in the following process (b), after refine | purifying a cellulose raw material previously, it is preferable to fibrillate the refined cellulose raw material in carbonate ester. If not purified in advance, the impurities contained in the cellulose raw material may dissolve in the carbonate ester, which may inhibit the transesterification reaction with the diol compound.
Although the purification method of a cellulose raw material is not specifically limited, The purification method shown below is illustrated. After charging the raw material cellulose and water into the pressure vessel, heating and pressurizing the pressure vessel, removing the supernatant liquid, repeating the addition of water, heating and pressurizing operations, followed by filtration and washing with water, cake-like After obtaining the cellulose, it was dried under reduced pressure to obtain a purified cellulose raw material.

Step (b) of the present invention is a step of obtaining a CNF-containing PCD dispersion by reacting the carbonate ester dispersion with a diol compound. In this step, CNF may contain cellulose before pulverization.
As a method of obtaining a PCD dispersion in which CNF is dispersed by reaction with a diol compound using a carbonate ester in which CNF is dispersed, a known method for producing PCD is applied. For example, JP-A-2015-044986 And the method described in JP-A-2017-025155.

For example, PCD can be obtained through a two-stage reaction consisting of a transesterification reaction and a polycondensation reaction. Carbonate ester and diol compound are mixed at a molar ratio of 20: 1 to 1:10 and reacted at a temperature of 100 to 300 ° C. under normal pressure or reduced pressure to distill ethylene glycol and unreacted ethylene carbonate as by-products. The low molecular weight PCD of 2 to 10 units is obtained, and then the unreacted raw diol compound and ethylene carbonate are distilled off at 100 to 300 ° C. under reduced pressure, and the low molecular weight PCD is polycondensed. A PCD having a predetermined molecular weight can be obtained by adjusting the distillate amount of the raw diol compound.
In addition, when manufacturing PCD using two or more types of raw material diol compounds, the composition ratio of PCD can be calculated | required by analyzing the composition of the raw material diol compound to distill with a gas chromatograph etc., and the composition of PCD The ratio can be adjusted to an arbitrary composition ratio by adding a raw material diol compound during the reaction.

For example, PCD having a 1,6-hexanediol (hereinafter referred to as HDO) skeleton and a molecular weight of 1000 can be obtained by the following method.
A reactor equipped with a rectifying column is charged with 400 g of ethylene carbonate (hereinafter referred to as EC) containing 1% by mass of CNF, 450 g of HDO, and 0.8 g of tetrabutyl titanate as a catalyst, and the temperature is gradually raised at 50 torr. . The internal temperature is raised to 160 ° C to 170 ° C so that there is constant distillation, and the process ends when the distillation stops. In this first stage reaction, addition of EC to HDO or transesterification occurs between EC and HDO, an oligomer is formed, and the distillate is mainly ethylene glycol.
Next, the rectification column is removed, the degree of vacuum is increased to 5 torr to 0 torr, and the internal temperature is increased to 150 ° C. to 185 ° C. so that there is continuous distillation. When the distillation stops and reaches a predetermined hydroxyl value, the process is terminated. In the second-stage reaction, HDO is distilled by distillation of unreacted EC and ethylene glycol and polycondensation of low molecular weight carbonate diols, and the molecular weight increases. The distillate is mainly HDO.

In addition, a tertiary amine catalyst, an organometallic catalyst, or the like may be used for the reaction as necessary, but a step of deactivating the catalyst is unnecessary, and there is an advantage that coloring of the reaction solution is reduced. It is preferable to react without a catalyst.

The step (c) of the present invention is a step of obtaining a CNF-containing polyurethane by reacting the CNF-containing PCD dispersion with an isocyanate compound. In this step (c), a CNF-containing foamed polyurethane can be obtained depending on the reaction conditions.
Examples of the isocyanate compound include two or more isocyanate groups in the molecule, such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, water Added xylylene diisocyanate and hexamethylene diisocyanate can be used.

As the hydroxyl group of PCD that reacts with the isocyanate compound, the hydroxyl value determined in accordance with JIS K1557-1 (plastics—polyurethane raw material polyol test method—part 1: determination of hydroxyl value) may be used. The molar ratio of the hydroxyl group of PCD to the isocyanate group of the isocyanate compound ([NCO / OH]) is generally 1.0 or less. However, when a urethane prepolymer is produced, the molar ratio is more than 1.0. preferable.
For example, when producing a polyurethane sheet, PCD and an isocyanate compound are mixed from room temperature to 70 ° C., vacuum defoamed, mixed with a catalyst if necessary, and then defoamed again into a mold. Cast and heat cure at 40 ° C. to 110 ° C. for 3 to 12 hours to produce a polyurethane sheet.

In the step (c), the following chain extender, hardness adjusting agent, chain terminator, catalyst, polyol and solvent can be used.

<Chain extender>
The chain extender used in producing the polyurethane of the present invention is a low molecular weight compound having at least two active hydrogens that react with an isocyanate group in the production of a prepolymer having an isocyanate group, which will be described later. And polyamines.
Specific examples thereof include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol. Linear diols such as 1,10-decanediol and 1,12-dodecanediol; 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,2-diethyl 1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-heptanediol, 1,4-dimethylolhexane, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propane Diols having branched chains such as all and dimer diols; Diols having ether groups such as diethylene glycol and propylene glycol; 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-dihydroxyethylcyclohexane, etc. Diols having an alicyclic structure, diols having an aromatic group such as xylylene glycol, 1,4-dihydroxyethylbenzene, 4,4′-methylenebis (hydroxyethylbenzene); polyols such as glycerin, trimethylolpropane and pentaerythritol Hydroxyamines such as N-methylethanolamine and N-ethylethanolamine; ethylenediamine, 1,3-diaminopropane, hexatylenediamine, triethylenetetramine, diethylenetri Min, isophorone diamine, 4,4'-diaminodicyclohexylmethane, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropyl Polyamines such as ethylenediamine, 4,4′-diphenylmethanediamine, methylenebis (o-chloroaniline), xylylenediamine, diphenyldiamine, tolylenediamine, hydrazine, piperazine, N, N′-diaminopiperazine; and water be able to.

These chain extenders may be used alone or in combination of two or more.
Among these, 1,4-butanediol (hereinafter sometimes referred to as 1,4BD), 1,5 is preferable in that the balance of physical properties of the obtained polyurethane is preferable, and a large amount can be obtained industrially at low cost. -Pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanedimethanol, 1,4-dihydroxyethylcyclohexane, ethylenediamine, 1,3-diaminopropane, isophoronediamine, and 4,4′-diaminodicyclohexylmethane are preferred.

<Hardness adjuster>
As the hardness adjusting agent, a dihydroxy compound that is a raw material of polycarbonate diol may be used. The reason why the hardness adjusting agent is used will be described below. For example, when a polyurethane is produced using a polycarbonate diol having a large molecular weight, if the molar composition of the polyisocyanate and the chain extender is the same as that of the polycarbonate diol having a low molecular weight, the weight ratio of the polycarbonate diol in the entire polyurethane molecule increases. As a result, the elastic modulus and hardness are reduced. Therefore, by adding a dihydroxy compound or the like, which is a raw material of polycarbonate diol, as a hardness adjuster, it becomes possible to adjust the weight ratio of polycarbonate diol in the entire polyurethane equally, which is the case when polycarbonate diols having different molecular weights are used. However, it can prevent that the elasticity modulus and hardness of the obtained polyurethane fall. This method is generally widely used.

As the hardness adjusting agent, it is preferable to use a dihydroxy compound which is a raw material of polycarbonate diol. 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol 2-methyl-1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1, 16-hexadecanediol 1,18-octadecanediol, 1,20-eicosanediol, etc.

<Chain terminator>
In producing the polyurethane of the present invention, a chain terminator having one active hydrogen group can be used as necessary for the purpose of controlling the molecular weight of the resulting polyurethane.
These chain terminators include aliphatic monools such as methanol, ethanol, propanol, butanol and hexanol having one hydroxyl group, diethylamine, dibutylamine, n-butylamine, monoethanolamine and diethanolamine having one amino group. And aliphatic monoamines such as morpholine. These may be used alone or in combination of two or more.

<Catalyst>
In the polyurethane forming reaction in producing the polyurethane of the present invention, an amine catalyst such as triethylamine, N-ethylmorpholine, triethylenediamine or the like or tin such as trimethyltin laurate, dibutyltin dilaurate, dioctyltin dilaurate, dioctyltin dineodecanate, etc. Known urethane polymerization catalysts typified by organic compounds such as organic metal salts such as titanium compounds and the like can also be used. A urethane polymerization catalyst may be used individually by 1 type, and may use 2 or more types together.

<Polyols other than the polycarbonate diol of the present invention>
In the polyurethane formation reaction in producing the polyurethane of the present invention, the polycarbonate diol of the present invention may be used in combination with other polyols as necessary. Here, the polyol other than the polycarbonate diol of the present invention is not particularly limited as long as it is used in normal polyurethane production, and examples thereof include polyether polyols, polyester polyols, and polycarbonate polyols other than the present invention. Here, it is based on the combined weight of the polycarbonate diol of the present invention and other polyols. The weight ratio of the polycarbonate diol of the present invention is preferably 70% or more, more preferably 90% or more. If the weight ratio of the polycarbonate diol of the present invention is small, the balance of chemical resistance, low temperature characteristics and heat resistance, which are the characteristics of the present invention, may be lost.

In the present invention, the above-mentioned polycarbonate diol of the present invention can be modified for use in the production of polyurethane. As a modification method of polycarbonate diol, a method of introducing an ether group by adding an epoxy compound such as ethylene oxide, propylene oxide, or butylene oxide to polycarbonate diol, a polycarbonate diol, a cyclic lactone such as ε-caprolactone, adipic acid, or succinic acid is used. There is a method of introducing an ester group by reacting with dicarboxylic acid compounds such as sebacic acid and terephthalic acid and ester compounds thereof. In the ether modification, the viscosity of the polycarbonate diol is lowered by modification with ethylene oxide, propylene oxide or the like, which is preferable for reasons such as handling. In particular, the polycarbonate diol of the present invention is modified with ethylene oxide or propylene oxide, so that the crystallinity of the polycarbonate diol is lowered and the flexibility at low temperature is improved. Since the water absorption and moisture permeability of the manufactured polyurethane are increased, the performance as artificial leather / synthetic leather may be improved. However, if the addition amount of ethylene oxide or propylene oxide increases, the physical properties such as mechanical strength, heat resistance, chemical resistance and the like of the polyurethane produced using the modified polycarbonate diol decrease. -50 wt% is suitable, preferably 5-40 wt%, more preferably 5-30 wt%. In addition, the method of introducing an ester group is preferable for reasons such as handling because the viscosity of the polycarbonate diol is lowered by modification with ε-caprolactone. The amount of ε-caprolactone added to the polycarbonate diol is preferably 3 to 70% by weight, preferably 5 to 50% by weight, more preferably 10 to 40% by weight, still more preferably 15 to 30% by weight. is there. When the addition amount of ε-caprolactone exceeds 70% by weight, the hydrolysis resistance, chemical resistance, etc. of the polyurethane produced using the modified polycarbonate diol are lowered. On the other hand, if it is less than 3% by weight, the effect of reducing the viscosity is small, which is not preferable.

<Solvent>
A solvent may be used for the polyurethane formation reaction in producing the polyurethane of the present invention. Preferred solvents include amide solvents such as dimethylformamide, diethylformamide, dimethylacetamide and N-methylpyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; ketone solvents such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; tetrahydrofuran, dioxane and the like. Examples include ether solvents; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; and aromatic hydrocarbon solvents such as toluene and xylene. These solvents may be used alone or as a mixed solvent of two or more.

Among these, preferred organic solvents are methyl ethyl ketone, ethyl acetate, toluene, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and the like.
Moreover, the polyurethane of an aqueous dispersion can also be manufactured from the polyurethane composition with which the polycarbonate diol of this invention, polydiisocyanate, and the said chain extender were mix | blended.

In the step (c), when the CNF-containing foamed polyurethane is produced by reacting the CNF-containing PCD dispersion and the isocyanate compound, for example, if water is added during the reaction, the CNF-containing foamed polyurethane is obtained. In this case, the ratio (molar ratio) of the hydroxyl group (A) of PCD, the isocyanate group (B) of the isocyanate compound and water (C) is A: B = 0.95: 1.20 to 1.05: 1. 20 and A: C = 0.95: 0.20 to 1.05: 0.20.
More preferably, A: B = 0.98: 1.20 to 1.02: 1.20 and A: C = 0.98: 0.20 to 1.02: 0.20.

When producing foamed polyurethane, the reaction temperature is preferably 100 ° C. or less so that the reaction temperature does not exceed the boiling point of water as the reaction condition when adding water. Moreover, in order to disperse | distribute more after adding water, it is preferable to leave still for a while at high temperature.

In addition to adding water, examples of methods for producing foamed polyurethane include methods using chemical foaming agents, physical foaming agents, supercritical fluids, thermally expandable microcapsules, and the like.
The chemical foaming agent is one that adds dinitrosopentamethylenetetramine, azodicarbonamide, p, p′-oxybisbenzenesulfonylhydrazine, sodium hydrocarbon or the like, and generates a gas by a thermal decomposition reaction.
A physical foaming agent generates bubbles by dissolving a liquefied gas (fluorocarbon or hydrocarbon) or a supercritical fluid in a resin under high pressure and reducing the solubility by reducing the pressure or heating.

The supercritical fluid is one that is foamed by using nitrogen or carbon dioxide as a supercritical fluid at high temperature and pressure.
The thermally expandable microcapsules are obtained by wrapping hydrocarbons in thermoplastic resin capsules. The hydrocarbons are vaporized at a high temperature, and the softened capsules expand accordingly.

The CNF-containing PCD dispersion obtained in the step (b) uses a dispersion obtained by pulverizing a cellulose raw material in a carbonate ester or a dispersion obtained by dispersing powdered CNF in a carbonate ester.
When cellulose raw material is crushed in a hydrophobic medium than water, it is known that the produced CNF has a more hydrophobic surface than CNF crushed in water and is excellent in dispersibility in an organic medium. Yes.
Therefore, CNF obtained by crushing in a carbonate ester that is more hydrophobic than water is also more hydrophobic than CNF that is crushed in water, so that it has good dispersibility in the carbonate ester and is produced using this as a raw material. The CNF in the PCD also has a good dispersibility, and further, the CNF in the CNF-containing polyurethane using the CNF-containing PCD dispersion as a raw material also has a good dispersibility.
Hydrophilic CNF generally tends to cause problems such as aggregation and thickening in hydrophobic resins, and the expected characteristics may not be exhibited. However, according to the production method of the present invention, these problems are solved. Alternatively, it is possible to obtain a higher-performance polyurethane that can be reduced.
EC, which is one of carbonate esters, has almost the same dielectric constant as water and is considered to have a high affinity for hydrophilic CNF, and is a good dispersion medium for CNF.

For example, CNF-containing polyurethane can be produced by the following method.
Powdered CNF is dispersed in EC at a concentration of 1 to 5% by mass with a rotating and rotating stirrer, and cellulose containing CNF obtained by the reaction of EC and 1,6-hexanediol (HDO) is dispersed. The CNF-containing polyurethane can be prepared by reacting the prepared PCD with dicyclohexylmethane diisocyanate (HMDI).
Using dibutyltin dilaurate or the like as a catalyst for promoting urethanization, the composition is cured at an addition amount of 0.04 parts by mass with respect to 100 parts by mass of the composition comprising PCD and isocyanate. The pot life is about 20 minutes at room temperature, and the resulting polyurethane is thermoplastic. Cellulose containing CNF contains many hydroxyl groups in the molecule. However, curing is not extremely accelerated or delayed, and the curing time can be adjusted by adjusting the amount of the catalyst added. Moreover, the polyurethane which gelatinized by the presence of the cellulose containing CNF does not arise.

Hereinafter, the present invention will be described in detail with reference examples, examples and comparative examples.
<Reference Example 1> CNF-containing EC dispersion (1)
Bleached kraft pulp (NIST Standard Reference Material, 8495 Northern Softwood (Bleached Kraft Pulp)) of northern policy leaves was used as the pulp used as the raw material for CNF. The pulp sheet was cut into a square of about 1 cm and pre-pulverized into cotton or powdery cellulose using a high-speed pulverizer wonder blender (WB-1, manufactured by Osaka Chemical Co., Ltd.). Using a microscope, 50 fiber lengths from long ones were measured and averaged to be about 260 μm.
The cellulose powder was dispersed in 100 g of EC liquefied by heating to 60 ° C. so that the concentration was 0.1% by mass, and this cellulose dispersion was dispersed on a desktop wet high-pressure pulverizer (Nanovita L-ES, electric drive). And the fine pulverization was repeated to obtain a CNF-containing EC dispersion.
The pressure was gradually increased while adjusting the discharge speed, and finally pulverized 10 times at 180 MPa. The CNF in the obtained EC dispersion was a branched aggregate, but fibers of about 200 nm to 1 μm existed separately, and the dispersibility was good. A length exceeding 100 μm was generated. FIG. 1 shows a photomicrograph (400 times).

<Reference Example 2> CNF-containing EC dispersion (2)
A hardwood CNF-containing EC dispersion was obtained in the same manner as in Reference Example 1 except that hardwood (eucalyptus) bleached kraft pulp (NIST Standard Reference Material, 8496 Eucalyptus Hardwood (Bleached Kraft Pulp)) was used as the pulp.
The CNF in the obtained EC dispersion was a branched aggregate, but fibers of about 200 nm to 1 μm existed separately, and the dispersibility was good. A length exceeding 100 μm was generated. FIG. 2 shows a photomicrograph (400 times).

<Reference Example 3> CNF-containing EC dispersion (3)
A softwood pulp was used in the same manner as in Reference Example 1 to obtain a 1% by mass CNF-containing EC dispersion. However, the concentration of the initial cellulose powder is 0.2% by mass, pulverized five times at 150 MPa while gradually increasing the pressure, and then the pulverization is repeated by adding cellulose powder in increments of 0.2% by mass. Thus, the final concentration was set to 1% by mass, and pulverization was performed 10 times at 180 MPa to obtain a 1% by mass CNF-containing EC dispersion.
The CNF in the obtained dispersion was the same size as in Reference Example 1 and the dispersibility was the same.

<Example 1> Production of CNF-containing PCD dispersion (1)
A CNF-containing PCD having an HDO skeleton was prepared by reacting the 1% by mass CNF-containing EC dispersion obtained in Reference Example 3 with 1,6-hexanediol (HDO).
A 1 liter flask equipped with a stirrer and a Vigreux fractionation tube with a height of 20 cm is charged with 187 parts by mass of EC containing 1% by mass of CNF, 200 parts by mass of HDO, and 0.2 parts by mass of tetrabutyl titanate as a catalyst. The temperature was gradually raised at 50 torr. The internal temperature was raised to 160 ° C. to 170 ° C. so that there was constant distillation, and the distillation was completed when the distillation stopped.
Next, the Vigreux fractionation tube was removed, the degree of vacuum was raised to 5 torr to 0 torr, and the internal temperature was raised to 150 ° C to 185 ° C so that there was continuous distillation. When the distillation stopped, the reaction was stopped to obtain 188 parts by mass of a reaction product having a hydroxyl value of 2.15 meq / g. Since PCD has two hydroxyl groups in the molecule, the molecular weight of the obtained CNF-dispersed PCD was 930 by doubling the reciprocal of the hydroxyl value, and the CNF concentration was determined to be 1% by mass from the charged amount.
The dispersibility of CNF in the obtained PCD was equivalent to the EC dispersion used as a raw material. FIG. 3 shows a photomicrograph (400 times).
Since this CNF-dispersed PCD solidifies at room temperature, it is liquefied by heating to 100 ° C. or higher, and a clear filtrate is obtained by pressure filtration with a 0.5 μm membrane filter, and the hydroxyl value of the filtrate is determined. It was 2.15 meq / g when calculated. Therefore, the hydroxyl group of CNF did not affect the hydroxyl value of PCD.

<Example 2> Production of CNF-containing PCD dispersion (2)
2 parts by mass of powdered CNF obtained by thermal decomposition of ammonium carbonate was added to 150 parts by mass of EC melted at 60 ° C., and mixed with a rotating and rotating stirrer to obtain EC in which CNF was dispersed. .
This 157 parts by mass of CNF-dispersed ECD and 191 parts by mass of HDO were reacted in the presence of 0.2 part by mass of tetra-n-butyl titanate in the same manner as in Example 1 to obtain 157 parts by mass of CNF-dispersed PCD. Obtained. The hydroxyl value was 4.02 meq / g, the molecular weight was 500, and the CNF concentration was 1.9% by mass.
The CNF in the obtained PCD dispersion was a branched aggregate, but the fibers were present separately and the dispersibility was good. FIG. 4 shows a micrograph (400 times).

<Example 3> Production of CNF-containing PCD dispersion (3)
<Purification of crystalline cellulose>
A pressure vessel was charged with 50 g of crystalline cellulose (FD-101) and 1 liter of pure water, and the pressure vessel was heated and maintained at 128 ° C. and a pressure of 146 kPa (1.44 atm) for 2 hours. Next, after returning to normal pressure, the supernatant was removed, 1 liter of fresh pure water was added again, the mixture was heated again, and maintained at 128 ° C. and a pressure of 146 kPa (1.44 atm) for 2 hours. The removal of the supernatant and the heating / pressurizing operation with the addition of fresh pure water were performed once more, and the operation was repeated three times. Finally, the crystalline cellulose (FD-101) was filtered off, and the crystalline cellulose (FD-101) was washed with fresh pure water and then dried at 110 ° C. under reduced pressure.

<Disintegration of purified FD-101>
1.5 parts by mass of purified FD-101 obtained above was added to 148.5 parts by mass of EC, and pulverized at 105 ° C. for 8 hours using an ultrasonic homogenizer UP400S manufactured by Heelscher Co. An EC dispersion crushed to the following thickness was obtained.
<PCD synthesis>
The reaction was performed in the same manner as in Example 2 except that the EC dispersion obtained above and 1,6-hexanediol (HDO) were used and no catalyst was used, and 0.9 mass% of crushed cellulose was contained. 160 parts by mass of PCD was obtained.

Example 4 Production of CNF-containing polyurethane (1)
The CNF-containing PCD and dicyclohexylmethane diisocyanate (HMDI) obtained in Example 1 were cured in the presence of dibutyltin dilaurate to prepare a polyurethane sheet.
The polyurethane sheet was prepared as follows, and the molar ratio of PCD hydroxyl group to HMDI isocyanate group ([NCO / OH]) was 1.0.
To 100 parts by mass of PCD melted at 70 ° C., 0.06 part of dibutyltin dilaurate was added, mixed with a rotation / revolution stirrer, and vacuum degassed. 28 parts by mass of HMDI was added to this mixture, mixed with a rotating and rotating stirrer, vacuum degassed, poured into a Teflon (registered trademark) mold so as to have a thickness of 1 mm, and left overnight at room temperature in a nitrogen atmosphere. .
Next, a polyurethane sheet in which about 0.8% by mass of CNF was dispersed was produced by gradually heating from 40 ° C. while finally heating at 70 ° C. for 3 hours.
A part of the obtained polyurethane sheet was sandwiched between a slide glass and a cover glass, and the cover glass was pressed while being heated with a heat gun, and the dispersion state of CNF was observed with a microscope as a thin-film polyurethane.
The dispersibility of CNF in the obtained polyurethane was equivalent to the PCD dispersion used as a raw material. FIG. 5 shows a photomicrograph (400 times).

<Example 5> Production of CNF-containing polyurethane (2)
Regarding the PCD obtained in Example 2, a polyurethane sheet containing about 1.2% by mass of CNF was prepared in the same manner as in Example 4.
The dispersion state of CNF was observed with a microscope in the same manner as in Example 4, and a micrograph (400 times) is shown in FIG.
The dispersibility of CNF was good, and the obtained polyurethane sheet was punched out with dumbbell No. 3, and the tensile strength was measured. The results are shown in Table 1.
As can be seen from Table 1, the polyurethane obtained in Example 5 was 2.1 times higher in tensile strength than the polyurethane containing no CNF (Comparative Example 1).

<Comparative Example 1>
For comparison, a polyurethane sheet was prepared using PCD not containing CNF, and the tensile strength was measured.
As PCD not containing CNF, the PCD obtained in Example 1 was liquefied by heating to 100 ° C. or higher, and the filtrate was filtered under pressure using a 0.5 μm membrane filter. The filtrate was transparent. It was clear. Using this filtrate, a polyurethane sheet was prepared in the same manner as in Example 4, and the tensile strength was measured. The results are shown in Table 1.

<Example 6> Production of CNF-containing foamed polyurethane CNF-containing PCD, HMDI and water were cured in the presence of dibutyltin dilaurate to produce a CNF-containing foamed polyurethane.
The CNF-containing PCD was produced in the same manner as in Example 1 except that the raw material diol was a mixture having a molar ratio of 1/1 of 1,6-hexanediol and 1,5-pentanediol. The average molecular weight was 500.
The following reaction was performed with the molar ratio of PCD hydroxyl group, HMDI isocyanate group, and water (OH / NCO / H ₂ O) being 1.0 / 1.2 / 0.2.
Add 0.72 parts by weight of water to 100 parts by weight of PCD, mix for 3 minutes with a rotating and rotating stirrer, cover the mixture with polywrap (trade name), heat at 90 ° C. for 3 minutes, and then add 63 parts by weight of HMDI. The mixture was mixed for 3 minutes with a rotating and rotating stirrer.
Furthermore, 0.13 parts by mass of dibutyltin dilaurate was added, mixed for 30 seconds with a rotation and revolution stirrer, poured into a 5 cm square resin container, and heated at 90 ° C. for 2 hours to prepare a CNF-containing foamed polyurethane sheet.

<Comparative Example 2> Production of foamed polyurethane not containing CNF For comparison, a foamed polyurethane sheet containing no CNF was prepared by the same operation as in Example 6 using PCD not containing CNF.

A sample obtained by punching the polyurethane foam obtained in Example 6 and Comparative Example 2 with a dumbbell mold and measuring the tensile stress (engineering stress) is shown in FIG.
As can be seen from FIG. 7, the CNF-containing foamed polyurethane obtained in Example 6 showed higher engineering stress at break than the foamed polyurethane containing no CNF in Comparative Example 2.

The CNF-containing PCD dispersion and CNF-containing polyurethane obtained by the production method of the present invention are excellent in mechanical strength such as tensile strength, and therefore can be used for higher-performance artificial / synthetic leather, paints / coating agents, adhesives, etc. It is.

Claims (10)

1. A method for producing a cellulose nanofiber-containing polyurethane comprising the following steps (a) to (c):
   (A) A step of dispersing cellulose nanofibers in a carbonate to obtain a carbonate dispersion of cellulose nanofibers.
   (B) A step of reacting the carbonate ester dispersion with a diol compound to obtain a cellulose nanofiber-containing polycarbonate diol dispersion.
   (C) A step of reacting the polycarbonate diol dispersion with an isocyanate compound to obtain a cellulose nanofiber-containing polyurethane.
2. The cellulose nanofiber-containing polyurethane according to claim 1, which is a cellulose nanofiber carbonate dispersion obtained by refining the cellulose raw material in the step (a) and then defibrating the cellulose raw material in a carbonate ester. Production method.
3. The method for producing a cellulose nanofiber-containing polyurethane according to claim 1 or 2, wherein the reaction is performed without a catalyst in the step (b).
4. The method for producing a cellulose nanofiber-containing polyurethane according to any one of claims 1 to 3, wherein the cellulose nanofiber-containing polyurethane is a cellulose nanofiber-containing foamed polyurethane.
5. The cellulose nanofiber-containing polyurethane according to any one of claims 1 to 4, wherein the carbonate is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and diphenyl carbonate. Manufacturing method.
6. The method for producing a polyurethane containing cellulose nanofibers according to claim 5, wherein the carbonate ester is ethylene carbonate.
7. The manufacturing method of the cellulose nanofiber containing polycarbonate diol including the process of following (a) and (b).
   (A) A step of dispersing cellulose nanofibers in a carbonate to obtain a carbonate dispersion of cellulose nanofibers.
   (B) A step of reacting the carbonate dispersion and a diol compound to obtain a cellulose nanofiber-containing polycarbonate diol.
8. The cellulose nanofiber-containing polycarbonate diol according to claim 7, which is a carbonate dispersion of cellulose nanofibers obtained by refining the cellulose raw material in the step (a) and then defibrating the cellulose raw material in a carbonate ester. Manufacturing method.
9. A method for producing a polyurethane containing the cellulose nanofiber-containing polycarbonate diol according to any one of claims 1 to 8.
10. A polyurethane comprising the cellulose nanofiber-containing polycarbonate diol according to any one of claims 1 to 9.
    
    
    

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