Latent curing agent composition and curable epoxide composition

Abstract

The present invention provides novel curing agent compositions and curable epoxide compositions. [Solution] The latent curing agent composition is characterized by containing an imidazole compound and fine fibers having a fiber width of 1 to 1000 nm, in which some of the hydroxyl groups are replaced with functional groups shown in the following structural formula (1) and a phosphonic acid ester is introduced. [Structural formula (1)] TIFF2026046529000005.tif5179

Description

Technical Field

[0001] The present invention relates to a latent curing agent composition and a curable epoxy composition.

Background Art

[0002] A latent curing agent composition for a curable epoxy composition that has good storage stability and cures by applying heat or the like has advantages such as being able to save labor for frequent mixing operations, and is widely used for sealing purposes in the electric and electronic fields and the like. However, many of the conventional latent curing agent compositions were solids. Therefore, when preparing a curable epoxy composition, it was necessary to micronize them, which had problems such as increased costs. In addition, when micronized, the bulk volume increased. Therefore, when compressed during transportation to reduce the bulk volume, a new problem of aggregation occurred. Aggregation deteriorated the dispersibility and reduced the quality of the curable epoxy composition.

[0003] On the other hand, there were also liquid latent curing agent compositions (for example, 2-ethyl-4-methylimidazole), but they had problems such as poor storage stability.

[0004] Therefore, proposals have been made to solve these problems (see, for example, Patent Document 1). However, they require phosphorous acid compounds, which is not preferable in terms of environmental load. Also, in the first place, the development of products in other forms has been desired.

Prior Art Documents

Patent Documents

[0005]

Patent Document ①

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem that the present invention aims to solve is to provide a new latent curing agent composition and a curable epoxide composition, preferably a latent curing agent composition and a curable epoxide composition with low environmental impact. [Means for solving the problem]

[0007] The inventors, through numerous tests, discovered that a composition with excellent dispersibility can be obtained through the interaction between the phosphonic acid groups of phosphonic acid-modified cellulose microfibers and imidazole compounds. This means that it is suitable for dispersion in water-soluble epoxide compositions. Of course, using cellulose fibers also has a low environmental impact. Furthermore, the imidazole compound acts as a catalyst for the curing reaction of the epoxide composition. Therefore, the following method was conceived.

[0008] (Means described in claim 1) Imidazole compounds and, This includes fine fibers with a fiber width of 1 to 1000 nm, in which some of the hydroxyl groups are replaced with functional groups shown in the following structural formula (1), and phosphonic acid esters are introduced. A latent curing agent composition characterized by the following features.

[0009] [Structural formula (1)] [ka] a, b, m, n, and p are natural numbers (where b = a × m), In structural formula (1), A1, A2, ...Ap are none, O - α is either R or OR. R is one of the following: a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group, or a derivative thereof. α is a cation consisting of organic or inorganic material.

[0010] (Means described in claim 2) The amount of functional group introduced in the above structural formula (1) is 0.06 to 3.39 mmol per gram of fine fiber. The latent curing agent composition according to claim 1.

[0011] (The means according to claim 3) Part of the hydroxy groups of the fine fibers is substituted with carbamate groups to introduce carbamate, The introduction amount of the carbamate group is 0.01 to 0.50 mmol per 1 g of the cellulose fiber, The latent curing agent composition according to claim 1.

[0012] (The means according to claim 4) An epoxy compound and the latent curing agent composition according to any one of claims 1 to 3 are included, A curable epoxy composition characterized by the above. [Advantages of the Invention]

[0013] According to the present invention, a new curing agent composition and a curable epoxy composition are obtained. [Modes for Carrying Out the Invention]

[0014] Next, modes for carrying out the invention will be described. Note that this embodiment is an example of the present invention. The scope of the present invention is not limited to the scope of this embodiment.

[0015] The curing agent composition of this embodiment has the property of curing potentially and includes an imidazole compound and fine fibers having a fiber width of 1 to 1000 nm. And in the fine fibers, part of the hydroxy groups (-OH groups) is substituted with a functional group shown in the following structural formula (1) to introduce (modify, denature) an ester of phosphonic acid (esterification).

[0016] [Structural formula (1)] [Chemical formula] a, b, m, n, p are natural numbers (however, b = a × m), In structural formula (1), A1, A2, ··· Ap are none, O -is either R or OR. R is any one of a hydrogen atom, a saturated-straight-chain hydrocarbon group, a saturated-branched-chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-straight-chain hydrocarbon group, an unsaturated-branched-chain hydrocarbon group, an aromatic group, and derivatives thereof. α is a cation composed of an organic or inorganic substance.

[0017] Also, since the imidazole compound and the hydroxyl group of the phosphonic acid form a salt, it is preferable that at least one of a hydrogen atom and a hydroxyl group is present in the phosphonic acid group (having at least one of a hydrogen atom and a hydroxyl group bonded to at least one phosphorus atom in Structural Formula 1). When at least one of them is present, the imidazole compound and the phosphonic acid-modified CNF form a salt (bond), and the dispersibility in the composition of the phosphonic acid-modified CNF is improved.

[0018] (Imidazole compound) In this form, the imidazole compound is a compound having an imidazole group in the molecule. Specifically, for example, imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-aminomethyl-2-methylimidazole, etc. One or more can be selected and used.

[0019] (Phosphonic acid-modified microfiber) The amount of functional group shown in structural formula (1) introduced into the fine fibers is 0.06 to 3.39 mmol per gram of cellulose fiber, more preferably 0.61 to 1.75 mmol, and particularly preferably 0.95 to 1.42 mmol. If the amount introduced is less than 0.06 mmol, the cellulose fibers may not defibrillate easily, and the aqueous dispersion of cellulose fine fibers may become unstable. On the other hand, if the amount introduced exceeds 3.39 mmol, the cellulose fibers may dissolve.

[0020] The introduced amount is a value measured based on elemental analysis. A Horiba X-Max 50 001 can be used for this elemental analysis.

[0021] Phosphonic acid is a type of phosphorus oxoacid, and esters of phosphorus oxoacids are compounds in which a hydroxyl group and an oxo group (=O) are bonded to a phosphorus atom, and the hydroxyl group provides an acidic proton. Esters of phosphorus oxoacids have a high negative charge, and therefore, introducing esters of phosphorus oxoacids increases the repulsion between cellulose molecules, making it easier to defibrillate cellulose fibers. However, introducing phosphonic acid in particular reduces yellowing, which has the advantage of increasing the light transmittance of the dispersion containing the fine fibers.

[0022] In this form of fine fiber, it is more preferable that some of the hydroxyl groups are replaced with carbamate groups, thereby introducing carbamates (esters of carbamic acid). When carbamates are introduced together with phosphonic acid esters, transparency and viscosity can be further improved. Furthermore, carbamates have amino groups. Therefore, when carbamates are introduced, they interact with phosphonic acid esters. As a result, when carbamates are also introduced, the shear force of the dispersion increases, making it easier to defibrillate the cellulose fibers.

[0023] The amount of carbamate introduced is preferably 0.06 to 2.34 mmol, more preferably 0.15 to 1.28 mmol, and particularly preferably 0.39 to 1.02 mmol per gram of cellulose microfiber. If the amount introduced is less than 0.06 mmol, the light transmittance and viscosity of the dispersion may not be sufficiently increased. On the other hand, if the amount introduced exceeds 2.34 mmol, the cellulose fibers may dissolve in water. The method for calculating the amount of carbamate introduced is the Kjeldahl method.

[0024] The fiber width (average diameter of a single fiber) of the fine fibers is preferably 1 to 1000 nm, more preferably 2 to 100 nm, and particularly preferably 3 to 50 nm. If the fiber width is less than 1 nm, the cellulose may dissolve in water, potentially reducing the physical properties of the cellulose fine fibers, such as strength and viscosity. On the other hand, if the fiber width exceeds 1000 nm, it can no longer be called a cellulose fine fiber and becomes a normal cellulose fiber.

[0025] The fiber width of cellulose microfibers is measured using an electron microscope as follows: First, 100 ml of an aqueous dispersion of fine fibers with a solid content concentration of 0.01-0.1% by mass is filtered through a Teflon® membrane filter, and the solvent is replaced once with 100 ml of ethanol and three times with 20 ml of t-butanol. Next, the dispersion is freeze-dried and coated with osmium to obtain the sample. This sample is observed using an electron microscope (SEM) at a magnification of 5,000x, 10,000x, or 30,000x depending on the width of the constituent fibers. In this observation, two diagonal lines are drawn on the observed image, and then three arbitrary straight lines are drawn passing through the intersection of the diagonals. The width of a total of 100 fibers that intersect these three straight lines is then measured visually. The median diameter of these measured values ​​is defined as the fiber width.

[0026] The axial ratio (fiber length / fiber width) of the fine fibers is preferably 3 to 1,000,000, more preferably 6 to 340,000, and particularly preferably 10 to 340,000. If the axial ratio is less than 3, it can no longer be considered fibrous. On the other hand, if the axial ratio exceeds 1,000,000, the viscosity of the dispersion (slurry) may become too high.

[0027] The degree of crystallinity of cellulose microfibers is preferably 50-100%, more preferably 60-90%, and particularly preferably 65-85%. If the degree of crystallinity is less than 50%, the strength and heat resistance may be insufficient. The degree of crystallinity can be adjusted, for example, by selecting pulp fibers, pretreatment, defibration, etc.

[0028] The degree of crystallinity is a value measured by X-ray diffraction in accordance with the "General Rules for X-ray Diffraction Analysis" of JIS-K0131 (1996). Note that microfibers have both amorphous and crystalline portions, and the degree of crystallinity represents the proportion of the crystalline portion in the entire microfiber.

[0029] The light transmittance of the dispersion of fine fibers (0.2% solids solution) is preferably 50.0% or higher, more preferably 60.0% or higher, and particularly preferably 70.0% or higher. If the light transmittance is less than 50.0%, it may be considered insufficient. The light transmittance of cellulose fine fibers can be adjusted, for example, by selecting pulp fibers, pretreatment, defibration, etc.

[0030] The light transmittance is the value obtained by measuring the light transmittance (transmittance of light at 350-880 nm) of a 0.2% (w / v) fine fiber dispersion using a Spectrophotometer U-2910 (Hitachi, Ltd.).

[0031] When the concentration of fine fibers is 1% by mass (w / w), the B-type viscosity of the dispersion is preferably 10 to 300,000 cps, more preferably 1,000 to 200,000 cps, and particularly preferably 16,000 to 100,000 cps.

[0032] Type B viscosity is a value measured in accordance with JIS-Z8803 (2011) "Method for Measuring the Viscosity of Liquids" for an aqueous dispersion of fine fibers with a solid content concentration of 1%. Type B viscosity is the resistance torque when the slurry is stirred, and a higher value means that more energy is required for stirring.

[0033] In this embodiment of the manufacturing method, a solution with a pH of less than 3, consisting of an additive (A) containing at least one of phosphonic acids and phosphonic acid metal salts, preferably further containing an additive (B) containing at least one of urea and a urea derivative, is added to cellulose fibers, and the solution is heated to introduce phosphonic acid esters, preferably phosphonic acid esters and carbamates, into the cellulose fibers. Then, the cellulose fibers into which these phosphonic acid esters, etc., have been introduced are defibrated to obtain fine fibers.

[0034] Preferably, hydroxide salts are also added to the cellulose fibers, and the cellulose fibers are washed after heating and before defibration.

[0035] As raw materials for microfibers, for example, plant-derived fibers (plant fibers), animal-derived fibers, and microbial-derived fibers can be used. These fibers can be used individually or in combination as needed. However, it is preferable to use plant fibers as cellulose fibers, and more preferable to use pulp fibers, which are a type of plant fiber. When cellulose fibers are pulp fibers, it is easy to adjust the physical properties of the microfibers.

[0036] As plant fibers, for example, wood pulp made from hardwoods, softwoods, etc., non-wood pulp made from straw, bagasse, etc., and recycled paper pulp (DIP) made from recycled waste paper, waste paper, etc. can be used. These fibers can be used individually or in combination.

[0037] As wood pulp, for example, chemical pulps such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), mechanical pulp (TMP), and recycled paper pulp (DIP) can be used. These pulps can be used individually or in combination.

[0038] Hardwood kraft pulp (LKP) may be bleached hardwood kraft pulp, unbleached hardwood kraft pulp, or semi-bleached hardwood kraft pulp. Softwood kraft pulp (NKP) may be bleached softwood kraft pulp, unbleached softwood kraft pulp, or semi-bleached softwood kraft pulp. Recycled paper pulp (DIP) may be recycled magazine pulp (MDIP), recycled newspaper pulp (NDIP), recycled corrugated paper pulp (WP), or other recycled paper pulp.

[0039] (Additive (A)) Additive (A) contains at least one of phosphonic acids and metal phosphonic acid salts. Examples of additives that can be used as additive (A) include phosphorous acid compounds such as phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, and pyrophosphorous acid. These additives can be used individually or in combination.

[0040] When adding additive (A), the cellulose fibers may be in a dry, wet, or slurry state. Additive (A) may also be in powder or aqueous solution form. However, it is preferable to add additive (A) in aqueous solution form to dry cellulose fibers due to the higher uniformity of the reaction.

[0041] The amount of additive (A) to be added is preferably 1 to 10,000 g, more preferably 100 to 5,000 g, and particularly preferably 300 to 1,500 g per 1 kg of cellulose fiber. If the amount added is less than 1 g, the effect of adding additive (A) may not be obtained. On the other hand, if the amount added exceeds 10,000 g, the effect of adding additive (A) may plateau.

[0042] (Additive (B)) Additive (B) comprises at least one of urea and / or a urea derivative. Examples of additive (B) include urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, etc. These ureas or urea derivatives can be used individually or in combination. However, the use of urea is preferred.

[0043] When additive (B) is heated, it decomposes into isocyanic acid and ammonia, as shown in the reaction equation (1) below. Isocyanic acid is highly reactive and forms a carbamate, as shown in the reaction equation (2) below. Therefore, when additive (B) is added to cellulose fibers, the introduction of carbamates is promoted.

[0044] NH2-CO-NH2→ HN=C=O+NH3…(1) Cell-OH+HN=C=O → Cell-OC-NH2…(2) Note that "Cell" refers to a cellulose molecule.

[0045] The amount of additive (B) added is preferably 0.01 to 100 mol, more preferably 0.2 to 20 mol, and particularly preferably 0.5 to 10 mol, per 1 mol of additive (A). If the amount added is less than 0.01 mol, the introduction of carbamates may not proceed. On the other hand, if the amount added exceeds 100 mol, the effect of urea addition may plateau.

[0046] (Other additives) In addition to additives (A) and (B), it is preferable to add hydroxides, particularly sodium hydroxide, to the cellulose fibers. Hydroxides function as pH adjusters and, due to their osmotic effect, facilitate the defibrillation of the cellulose fibers.

[0047] (heating) Cellulose fibers to which additives (A) and (B) have been added are heated for modification. The heating temperature is preferably 100 to 210°C, more preferably 100 to 200°C, and particularly preferably 100 to 160°C. If the heating temperature is 100°C or higher, phosphonic acid esters can be introduced. However, if the heating temperature exceeds 210°C, the degradation of cellulose will proceed rapidly, which may cause discoloration and a decrease in viscosity. Also, if the heating temperature exceeds 160°C, the B-type viscosity of the fine fibers may decrease, and the light transmittance may decrease.

[0048] The pH when heating cellulose fibers to which additives (A) or (B) have been added is preferably less than 3.0, more preferably 2.8 or less, and particularly preferably 2.5 or less. A lower pH makes it easier for phosphonic acid esters and carbamates to be introduced. However, if the pH is less than 2.1, the light transmittance and viscosity tend to decrease, and in particular, if the pH is less than 2.0, the deterioration of the cellulose fibers may progress rapidly. Therefore, the pH is preferably 2.0 or higher, more preferably 2.1 or higher.

[0049] It is preferable to heat the cellulose fibers to which additives (A) and (B) have been added until the cellulose fibers are dry. Specifically, the cellulose fibers are dried until their moisture content is preferably 10% or less, more preferably 0.1% or less, and most preferably 0.001% or less. Of course, the cellulose fibers may also be completely dry with no moisture at all.

[0050] The heating time for cellulose fibers to which additives (A) and (B) have been added is, for example, 1 to 1,440 minutes, preferably 10 to 180 minutes, and more preferably 30 to 120 minutes. If the heating time is too long, there is a risk that the introduction of phosphonic acid esters and carbamates will proceed too far. Also, if the heating time is too long, there is a risk that the cellulose fibers will turn yellow.

[0051] For heating cellulose fibers to which additives (A) and (B) have been added, for example, a hot air dryer, kiln, heated kneader, paper machine, dry pulp machine, etc., can be used.

[0052] (Pre-processing) Prior to introducing phosphonic acid esters or carbamates into cellulose fibers, or after introducing phosphonic acid esters or carbamates, the cellulose fibers may be subjected to pretreatment such as beating, if necessary. By pretreating the pulp fibers prior to defibration, the number of defibration steps can be significantly reduced, thereby reducing the energy required for defibration.

[0053] Cellulose fibers can be pretreated by physical or chemical methods, preferably by both physical and chemical methods. The physical and chemical pretreatments can be performed simultaneously or separately.

[0054] As a physical pretreatment method, beating is preferred. When cellulose fibers are beating, they are trimmed. Therefore, entanglement between cellulose fibers is prevented (agglomeration is prevented). From this viewpoint, beating is preferably carried out until the freeness of the cellulose fibers is 700 ml or less, more preferably until it is 500 ml or less, and particularly preferably until it is 300 ml or less.

[0055] The freeness of the cellulose fibers was measured in accordance with JIS P8121-2 (2012). Beating can be performed using, for example, a refiner or beater.

[0056] Examples of chemical pretreatment methods include hydrolysis of polysaccharides with acid (acid treatment), hydrolysis of polysaccharides with enzymes (enzyme treatment), swelling of polysaccharides with alkali (alkali treatment), oxidation of polysaccharides with oxidizing agents (oxidation treatment), and reduction of polysaccharides with reducing agents (reduction treatment). However, as a chemical pretreatment method, enzymatic treatment is preferred, and it is even more preferable to apply one or more treatments selected from acid treatment, alkali treatment, and oxidation treatment. Alkali treatment will be described in detail below.

[0057] One method of alkaline treatment involves immersing cellulose fibers, to which phosphonic acid esters or the like have been introduced, in an alkaline solution.

[0058] The alkali compound contained in the alkaline solution may be an inorganic alkali compound or an organic alkali compound. Examples of inorganic alkali compounds include hydroxides of alkali metals or alkaline earth metals, carbonates of alkali metals or alkaline earth metals, and phosphorus oxoates of alkali metals or alkaline earth metals. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide. Examples of alkali metal carbonates include lithium carbonate, lithium bicarbonate, potassium carbonate, potassium bicarbonate, sodium carbonate, and sodium bicarbonate. Examples of alkaline earth metal carbonates include calcium carbonate. Examples of alkali metal phosphorus oxoates include lithium phosphate, potassium phosphate, trisodium phosphate, and disodium hydrogen phosphate. Examples of alkaline earth metal phosphates include calcium phosphate and calcium hydrogen phosphate.

[0059] Examples of organic alkali compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammonium compounds, aromatic ammonium compounds, heterocyclic compounds and their hydroxides, carbonates, phosphates, etc. Specifically, examples include ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, N,N-dimethyl-4-aminopyridine, ammonium carbonate, ammonium bicarbonate, and diammonium hydrogen phosphate.

[0060] The solvent in the alkaline solution may be either water or an organic solvent, but it is preferably a polar solvent (water, an alcohol, or other polar organic solvent), and more preferably an aqueous solvent containing at least water.

[0061] The pH of the alkaline solution at 25°C is preferably 9 or higher, more preferably 10 or higher, and particularly preferably 11 to 14. A pH of 9 or higher results in a higher yield of cellulose microfibers. However, if the pH exceeds 14, the handling of the alkaline solution deteriorates.

[0062] (Washing) It is preferable to wash cellulose fibers into which phosphonic acid esters or the like have been introduced before defibrillation. By washing the cellulose fibers, by-products and unreacted substances can be washed away. Furthermore, if this washing is performed prior to the alkaline treatment in the pretreatment, the amount of alkaline solution used in the alkaline treatment can be reduced.

[0063] Cellulose fibers can be cleaned using, for example, water or organic solvents.

[0064] (Fibreation) Cellulose fibers to which phosphonic acid esters or the like have been introduced are washed and then defibrated (micronized). Through this defibration process, the pulp fibers become microfibrillated, forming cellulose nanofibers (cellulose nanofibers (CNF)).

[0065] When defibrating cellulose fibers, it is preferable to have the cellulose fibers in slurry form. The solid content concentration of this slurry is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and particularly preferably 1.0 to 5.0% by mass. If the solid content concentration is within the above range, defibration can be performed efficiently.

[0066] The defibration of cellulose fibers can be carried out by selecting one or more means from among homogenizers such as high-pressure homogenizers and high-pressure homogenization devices, millstone-type friction machines such as grinders and crushers, refiners such as conical refiners and disc refiners, and various bacteria. However, it is preferable to carry out the defibration of cellulose fibers using a device or method that uses a water flow, especially a high-pressure water flow, to make them finer. With this device or method, the resulting cellulose fine fibers have very high dimensional uniformity and dispersion uniformity. In contrast, if a grinder that grinds between rotating grinding wheels is used, for example, it is difficult to uniformly make the cellulose fibers finer, and in some cases, some undissolved fiber clumps may remain.

[0067] Examples of grinders used for defibrating cellulose fibers include the Mascoloider from Masuko Sangyo Co., Ltd. Examples of devices that use high-pressure water jets for micronization include the Starburst (registered trademark) from Sugino Machine Co., Ltd. and the Nanovater (registered trademark) from Yoshida Machinery Industry Co., Ltd. Furthermore, examples of high-speed rotary homogenizers used for defibrating cellulose fibers include the Creamix-11S from M-Technique.

[0068] When cellulose fibers were defibrated using two methods—grinding between rotating grinding wheels and micronization with high-pressure water jets—and the resulting fibers were observed under a microscope, it was found that the fibers obtained by micronization with high-pressure water jets had a more uniform fiber width.

[0069] Defibrillation by high-pressure water flow is preferably carried out by pressurizing a dispersion of cellulose fibers with a pressure booster to, for example, 30 MPa or more, preferably 100 MPa or more, more preferably 150 MPa or more, and particularly preferably 220 MPa or more (high-pressure conditions), ejecting it from a nozzle with a pore diameter of 50 μm or more, and then reducing the pressure so that the pressure difference is, for example, 30 MPa or more, preferably 80 MPa or more, and more preferably 90 MPa or more (reduced pressure conditions). The pulp fibers are defibrillated by the cleavage phenomenon caused by this pressure difference. If the pressure in the high-pressure conditions is low, or if the pressure difference from the high-pressure conditions to the reduced pressure conditions is small, the defibrillation efficiency decreases, and it becomes necessary to repeat the defibrillation (ejection from the nozzle) to achieve the desired fiber width.

[0070] For defibration using a high-pressure water jet, a high-pressure homogenizer is preferred. A high-pressure homogenizer is a homogenizer capable of ejecting a cellulose fiber slurry at a pressure of, for example, 10 MPa or more, preferably 100 MPa or more. When cellulose fibers are treated with a high-pressure homogenizer, collisions between cellulose fibers, pressure differences, microcavitation, etc., act to effectively defibration the cellulose fibers. Therefore, the number of defibration treatments can be reduced, and the efficiency of cellulose fine fiber production can be increased.

[0071] For high-pressure homogenizers, it is preferable to use one that causes cellulose fiber slurry to collide with opposing streams in a straight line. Specifically, for example, an opposing-impact high-pressure homogenizer (microfluidizer®, wet jet mill) is used. In this apparatus, two upstream channels are formed so that the pressurized cellulose fiber slurry collides with opposing streams at the confluence. The cellulose fiber slurry collides at the confluence, and the collided cellulose fiber slurry flows out from the downstream channel. The downstream channel is provided perpendicular to the upstream channel, forming a T-shaped channel. When such an opposing-impact high-pressure homogenizer is used, the energy supplied from the high-pressure homogenizer is converted into collision energy to the maximum extent possible, so that cellulose fibers can be defibrillated more efficiently.

[0072] The defibration of cellulose fibers is preferably carried out in such a way that the average fiber width, average fiber length, degree of crystallinity, etc., of the resulting cellulose fine fibers meet the desired values ​​or evaluation.

[0073] (Imidazole composition) By mixing an imidazole compound with a phosphonic acid ester, an imidazole composition, which is a liquid curable composition at room temperature, can be produced. Imidazole compounds include those that are solid at room temperature, such as 2-methylimidazole or 2-phenylimidazole, and those that are liquid at room temperature, such as 2-ethyl-4-methylimidazole. Any of these imidazole compounds can be mixed with a phosphoous acid ester to produce a (latent) curing agent composition that is liquid at room temperature.

[0074] In this regard, it is possible to obtain a curing agent composition even when using microfibers to which esters of other phosphoric acids have been introduced, rather than microfibers to which esters of phosphorous acid have been introduced. The resulting curing agent composition will be in the form of a solid or a liquid.

[0075] This form of curing agent composition can be used in one-component curable epoxide compositions and two-component curable epoxide compositions. However, since it is stable at room temperature when mixed with an epoxide compound and can be stored for a long period of time without increasing the viscosity of the curable epoxide composition, its effects can be more fully exhibited when used in one-component curable epoxide compositions.

[0076] The curing agent composition in this embodiment may optionally contain other epoxy curing agents, inert organic or inorganic pigments, dyes, colorants, anti-fading agents, anti-halation agents, fluorescent whitening agents, surfactants, plasticizers, flame retardants, antioxidants, fillers, antistatic agents, defoaming agents, flow regulators, accelerators, retarders, thickeners, light stabilizers, antifungal agents, antibacterial agents, preservatives, magnetic materials, etc.

[0077] The curable epoxide composition in this embodiment can be mixed with an epoxide compound to form a curable one-component epoxide composition, and the resulting curable epoxide composition can be used as an adhesive, paint, coating, sealant, or impregnation agent.

[0078] (Epoxy composition) The one-component curable epoxide composition of this embodiment can be obtained by mixing an epoxide compound having an average of more than one epoxy group in its molecule with the curing agent composition described above. As mentioned above, the curing agent composition of this embodiment has excellent dispersibility, so this mixing is extremely easy.

[0079] More specifically, for example, if the imidazole compound is a solid, it can be made liquid by mixing it with fine fibers into which an ester of phosphonic acid has been introduced, and then mixed with an epoxide compound to obtain a one-component curable epoxide composition. Alternatively, if the imidazole compound is a liquid, it is possible to obtain a one-component curable epoxide composition by simultaneously mixing the epoxide compound, the imidazole compound, and fine fibers into which an ester of phosphorous acid has been introduced, or by mixing any two of the three compounds and then mixing in the remaining compound to obtain a one-component curable epoxide composition.

[0080] The preferred epoxide compounds for use in this embodiment of one-component epoxide composition are compounds that have an average of more than one epoxy group in their molecule.Specifically, these include glycidyl ethers obtained by reacting polyhydric phenols such as bisphenol A, bisphenol F, bisphenol S, hexahydrobisphenol A, tetramethylbisphenol A, tetramethylbisphenol F, catechol, resorcinol, cresol novolac, tetrabromobisphenol A, trihydroxybiphenyl, benzophenone, bisresorcinol, bisphenolhexafluoroacetone, hydroquinone, triphenylmethane, tetraphenylethane, and bixylenol with epichlorohydrin; polyglycidyl ethers obtained by reacting aliphatic polyhydric alcohols such as glycerin, neopentyl glycol, ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, polyethylene glycol, and polypropylene glycol with epichlorohydrin; glycidyl ether esters obtained by reacting hydroxycarboxylic acids such as p-oxybenzoic acid and β-oxynaphthoic acid with epichlorohydrin; phthalic acid, methylphthalic acid, isophthalic acid, terephthalic acid, and tetrahydrophthalic acid Examples of suitable materials include: acids, polyglycidyl esters obtained from polycarboxylic acids such as hexahydrophthalic acid, endomethylenetetrahydrophthalic acid, endomethylenehexahydrophthalic acid, trimellitic acid, and polymerized fatty acids; glycidylaminoglycidyl ethers obtained from aminophenols and aminoalkylphenols; glycidylaminoglycidyl esters obtained from aminobenzoic acid; glycidylamines obtained from aniline, toluidine, tribromaniline, xylylenediamine, diaminocyclohexane, bisaminomethylcyclohexane, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, etc.; epoxidized polyolefins; glycidyl hydantoin; glycidylalkyl hydantoin, triglycidyl cyanurate; or monoepoxides such as butyl glycidyl ether, phenyl glycidyl ether, alkylphenyl glycidyl ether, glycidyl benzoate ester, and styrene oxide. One or more of these can be used in combination.

[0081] The fine fibers incorporating phosphonic acid esters are components for curing one-component curable epoxide compositions. However, the mass ratio or molar ratio of these fibers to the epoxide compound in the one-component epoxide composition is not particularly limited, as long as the one-component epoxide composition can be cured to any desired degree of gelation. In other words, curable epoxide compositions are used for various applications such as adhesives, coatings, sealants, and impregnations. Since the desired curing state, curing time, and usage conditions differ depending on the application, the mass ratio or molar ratio of these fibers to the epoxide compound in the one-component epoxide composition can be appropriately selected.

[0082] The epoxide composition may optionally contain epoxy curing agents, inert organic or inorganic pigments, dyes, colorants, anti-fading agents, anti-halation agents, fluorescent whitening agents, surfactants, plasticizers, flame retardants, antioxidants, fillers, antistatic agents, defoaming agents, flow regulators, accelerators, retarders, thickeners, light stabilizers, antifungal agents, antibacterial agents, preservatives, magnetic materials, etc.

[0083] Examples of epoxy curing agents that may be used as needed in curable epoxide compositions include acid anhydrides, amines, phenols, dihydrazines, Lewis acids, Brønsted salts, polymer captons, isoicyanates, blocked isocyanates, and dicyandiamides.

[0084] The curable epoxide composition of this embodiment is a thermosetting epoxide composition that does not harden at room temperature (e.g., 0°C to 40°C), but hardens rapidly upon heating (e.g., 60°C to 200°C), and can be used as an adhesive, paint, coating, sealant, or impregnating agent. [Examples]

[0085] Next, embodiments of the present invention will be described. An experiment was conducted to produce cellulose microfibers by adding phosphonic acid and urea to cellulose fibers, heating and washing them, and then defibrating them. Bleached softwood kraft pulp was used as the cellulose fiber. Defibration was performed using a high-pressure homogenizer to achieve an average fiber diameter of approximately 3-4 nm. The obtained cellulose microfibers were added to distilled water to a solid content of 0.1 wt%, and the cellulose microfibers were dispersed in the water.

[0086] Next, 20 mL of the 0.1 wt% cellulose fine fiber, 5 mL of polyglycerol-based epoxy resin, and 0.5 g of 2-ethyl-4-methylimidazole were added to a vial, and the mixture was stirred at 2000 rpm for 30 seconds and then at 2200 rpm for 30 seconds using a mixing machine (ARE310, manufactured by Thinky Co., Ltd.) to obtain an epoxide composition.

[0087] Various epoxide compositions were cast onto PP trays and allowed to stand at 120°C for 1 hour, after which their curing properties were evaluated using a Yasuda gel timer. Specifically, each composition was dropped onto an OHP sheet, bar-coated (100 μm thick), and then allowed to stand at 120°C for 30 minutes. The resulting films were evaluated using the pencil hardness test according to JIS K5600-5-4.

[0088] Furthermore, various compositions were poured into resin molds and heated in an oven at 120°C and 90°C to obtain cured products. The obtained cured products were cut into 10mm x 50mm pieces and tested using a material testing machine (Shimadzu AG-5kNIS) in accordance with JIS K7161, with a chuck distance of 30mm and a tensile speed of 30mm / min.

[0089] [Table 1] [Industrial applicability]

[0090] The present invention can be used as a curing agent composition and a curable epoxide composition.

Claims

1. Imidazole compounds and, This includes fine fibers with a fiber width of 1 to 1000 nm, in which some of the hydroxyl groups are replaced with functional groups shown in the following structural formula (1) and phosphonic acid esters are introduced. A latent curing agent composition characterized by the following features. [Structural formula (1)] 【Chemistry 1】 a, b, m, n, and p are natural numbers (where b = a × m), In structural formula (1), A1, A2, ... Ap are none, O － α is either R or OR. R is one of the following: a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an aromatic group, or a derivative thereof. α is a cation consisting of organic or inorganic material.

2. The amount of functional group introduced in the above structural formula (1) is 0.06 to 3.39 mmol per gram of fine fiber. The latent curing agent composition according to claim 1.

3. Some of the hydroxyl groups in the aforementioned fine fibers are replaced with carbamate groups, thereby introducing carbamates. The amount of carbamate group introduced is 0.01 to 0.50 mmol per gram of cellulose fiber. The latent curing agent composition according to claim 1.

4. The composition comprises an epoxide compound and the latent curing agent composition according to any one of claims 1 to 3. A curable epoxide composition characterized by the following features.

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