Glaze composition

Abstract

To provide a glaze composition with excellent storage stability.SOLUTION: The glaze composition of the present invention comprises fine cellulose fibers and water, and at least a part of hydroxyl groups of the fine cellulose fibers is substituted with sulfate ester groups.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a glaze composition. [Background technology]

[0002] In the production of ceramics and the like, glazes are used for the purposes of improving the appearance by forming a coating, imparting color, etc., improving strength, etc. Conventionally, dextrin, sodium alginate, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, etc. have been used as dispersants for glazes (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 62-19376 [Patent Document 2] Special Publication No. 3-4495 [Patent Document 3] Japanese Patent Application Publication No. 3-193685 [Patent Document 4] Japanese Patent Application Publication No. 9-225284 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although glaze compositions containing the above-mentioned conventional dispersants have good initial dispersibility, they suffer from the problem of poor storage stability due to sedimentation (sedimentation of the glaze composition itself or its aggregates) when stored for a long period of time.

[0005] Therefore, an object of the present invention is to provide a glaze composition having excellent storage stability. [Means for solving the problem]

[0006] In order to achieve the above object, the glaze composition of the present invention comprises: Contains fine cellulose fibers and water, At least a part of the hydroxyl groups of the fine cellulose fibers is substituted with sulfate ester groups. [Effects of the Invention]

[0007] According to the present invention, by using the specified fine cellulose fibers, it is possible to provide a glaze composition having excellent storage stability. [Brief explanation of the drawings]

[0008] [Figure 1] Figure 1 is a graph showing the change over time in the transmittance (T (%)) and backscattered light intensity (BS (%)) of a glaze composition (specific gravity 1.385 g / cm3) measured using a Turbiscan tower. Figure 1(A) shows the results for a blank that does not contain fine cellulose fibers, while Figure 1(B) and Figure 1(C) show the results when the fine cellulose fibers were blended in amounts of 0.1 mass% and 0.2 mass%, respectively. [Figure 2-1] Figure 2-1 is a graph showing the change over time in backscattered light intensity (BS (%)) of a glaze composition (specific gravity 1.04 g / cm3) measured using a Turbiscan tower. Figure 2-1(A) shows the results for a blank that does not contain fine cellulose fibers, while Figure 2-1(B) and Figure 2-1(C) show the results when the fine cellulose fibers were blended in amounts of 0.01% by mass and 0.05% by mass, respectively. [Figure 2-2] Figure 2-2 is a graph showing the change over time in the backscattered light intensity (BS (%)) of a glaze composition (specific gravity 1.04 g / cm3) measured using a Turbiscan tower, and Figures 2-2(D), 2-2(E), and 2-2(F) show the results when the fine cellulose fiber content was 0.1 mass%, 0.2 mass%, and 0.3 mass%, respectively. [Figure 3-1] Figure 3-1 is a graph showing the change over time in the backscattered light intensity (BS (%)) of a glaze composition (specific gravity 1.04 g / cm3) measured using a Turbiscan tower. Figure 3-1(A) shows the results for a blank that does not contain fine cellulose fiber, while Figure 3-1(B) and Figure 3-1(C) show the results when the fine cellulose fiber content was 0.01 mass% and 0.05 mass%, respectively. [Figure 3-2] Figure 3-2 is a graph showing the change over time in the backscattered light intensity (BS (%)) of a glaze composition (specific gravity 1.04 g / cm3) measured using a Turbiscan tower, and Figures 3-2(D), 3-2(E), and 3-2(F) show the results when the amount of fine cellulose fiber blended was 0.1 mass%, 0.2 mass%, and 0.3 mass%, respectively. [Figure 4] Figure 4 is a graph showing the change over time in the backscattered light intensity (BS (%)) of a glaze composition (specific gravity 1.385 g / cm3) measured using a Turbiscan tower. Figure 4(A) shows the results for a blank that does not contain fine cellulose fiber, while Figures 4(B), 4(C), and 4(D) show the results when the fine cellulose fiber content was 0.1 mass%, 0.2 mass%, and 0.3 mass%, respectively. [Figure 5] Figure 5 is a photograph showing the results of a sedimentation test of a glaze composition (specific gravity 1.385 g / cm3), where Figure 5(A) shows the results for a blank that does not contain fine cellulose fibers, and Figure 5(B), Figure 5(C), and Figure 5(D) show the results when the fine cellulose fibers were blended in amounts of 0.1 mass%, 0.2 mass%, and 0.3 mass%, respectively. [Figure 6] Figure 6 is a photograph showing the results of a sedimentation test of a glaze composition (specific gravity 1.04 g / cm3), where Figure 6(A) shows the results for a blank that does not contain fine cellulose fibers, and Figures 6(B), 6(C), 6(D), 6(E) and 6(F) show the results when the fine cellulose fiber content was 0.01 mass%, 0.05 mass%, 0.1 mass%, 0.2 mass% and 0.3 mass%, respectively. [Figure 7] Figure 7 is a photograph showing the results of a raw glaze test of a glaze composition (specific gravity 1.385 g / cm3), where Figure 7(A) shows the results for a blank that does not contain fine cellulose fibers, and Figures 7(B), 7(C), and 7(D) show the results when the fine cellulose fibers were blended in amounts of 0.1 mass%, 0.2 mass%, and 0.3 mass%, respectively. [Figure 8] Figure 8 is a photograph showing the results of a bisque glazing test of a glaze composition (specific gravity 1.385 g / cm3), where Figure 8(A) shows the results for a blank that does not contain fine cellulose fibers, and Figure 8(B) shows the results for a sample containing 0.2 mass% fine cellulose fibers. DETAILED DESCRIPTION OF THE INVENTION

[0009] The glaze composition of the present invention contains fine cellulose fibers and water.

[0010] (fine cellulose fiber) The fine cellulose fibers have at least a portion of their hydroxyl groups substituted with sulfate ester groups. Specifically, the fine cellulose fibers have at least a portion of the hydroxyl groups (-OH groups) of the cellulose (a chain polymer in which D-glucose is bonded via β(1→4) glucoside bonds) constituting the fibers substituted with sulfate ester groups represented by formula (1).

[0011] (-OSO3 - ) r Z r+ (1) In formula (1), r is an independent natural number between 1 and 7, Z r+ When r=1, is at least one selected from the group consisting of a hydrogen ion, an alkali metal ion, a monovalent transition metal ion, an ammonium ion, an aliphatic ammonium ion, an aromatic ammonium ion, and a cationic polymer; when r=2 or more, is at least one selected from the group consisting of an alkaline earth metal ion, a polyvalent metal ion, and a compound containing two or more cationic functional groups (e.g., diamine) in the molecule.

[0012] The fine cellulose fibers have improved hydrophilicity due to the sulfate ester groups. As a result, the dispersibility of the fine cellulose fibers when dispersed in the glaze composition is improved. Furthermore, the electronic repulsion of the introduced sulfate ester groups makes it easier to maintain the dispersed state in the glaze composition, and the storage stability of the glaze composition is also improved.

[0013] The amount of sulfate ester groups introduced into the fine cellulose fibers can be expressed as the amount of sulfur introduced based on the sulfate ester groups. The amount of sulfur introduced per 1 g (mass) of the fine cellulose fibers is, for example, higher than 0.4 mmol / g, 0.42 mmol / g to 9.9 mmol / g, 0.5 mmol / g to 9.9 mmol / g, or 0.6 mmol / g to 9.9 mmol / g.

[0014] If the amount of sulfur incorporated is higher than 0.42 mmol / g, the hydrogen bonds between the fibers are not too strong, and dispersibility in the glaze composition tends to be improved, while if it is 0.5 mmol / g or more, the electronic repulsion can be made stronger, making it easier to maintain a stable dispersion state. On the other hand, if the amount of sulfur incorporated is 9.9 mmol / g or less, a decrease in crystallinity and an increase in cost when incorporating sulfur can be suppressed.

[0015] In particular, when attention is focused on maintaining dispersibility, the amount of sulfur introduced is, for example, more than 0.42 mmol / g and not more than 3 mmol / g, 0.5 mmol / g to 3 mmol / g, 0.5 mmol / g to 2 mmol / g, or 0.5 mmol / g to 1.5 mmol / g.

[0016] The amount of sulfur introduced into the fine cellulose fibers (i.e., the amount of sulfate ester groups introduced) can be measured, for example, using a CHNS / O elemental analyzer. Alternatively, the amount of sulfur introduced can also be calculated, for example, by measuring electrical conductivity.

[0017] The average fiber length of the fine cellulose fibers can be indirectly expressed, for example, by the degree of polymerization, and is, for example, 280 or more, 300 to 1000, or 300 to 600.

[0018] When the degree of polymerization of the fine cellulose fibers is 280 or more, it is possible to prevent the fiber length from decreasing, which would otherwise weaken the entanglement of the fibers. On the other hand, when the degree of polymerization of the fine cellulose fibers is 600 or less, the dispersibility in the glaze composition tends to be high.

[0019] The method for measuring the degree of polymerization is not particularly limited, but for example, a copper-ethylenediamine method can be used. Specifically, the degree of polymerization of the fine cellulose can be measured by dissolving the fine cellulose fibers in a 0.5 M copper-ethylenediamine solution and measuring the viscosity of the solution by a viscometer.

[0020] The average fiber width of the fine cellulose fibers is not particularly limited, but is, for example, 1 nm to 1000 nm, 2 nm to 500 nm, 2 nm to 100 nm, 2 nm to 30 nm, or 2 nm to 20 nm when observed with an electron microscope.

[0021] The average fiber width of the fibrous cellulose fibers can be measured using known techniques. For example, fibrous cellulose fibers are dispersed in a dispersion medium such as pure water to prepare a dispersion liquid with a predetermined mass %. Then, this dispersion liquid is spin-coated on a silica substrate coated with PEI (polyethyleneimine), and the fibrous cellulose fibers on this silica substrate are observed. For observation, for example, a scanning probe microscope (e.g., SPM9700 manufactured by Shimadzu Corporation) can be used. Twenty fibrous cellulose fibers are randomly selected from the obtained observation image, and the fiber width of each fiber is measured and averaged to determine the average fiber width of the fibrous cellulose.

[0022] The method for preparing the fine cellulose fibers is not particularly limited, but for example, they can be prepared from pulp into which sulfate ester groups have been introduced (hereinafter referred to as "sulfate ester group-introduced pulp") by the method shown below. In the present invention, "sulfate ester group-introduced pulp" refers to a fibrous member formed by an assembly of multiple cellulose fibers, in which at least a portion of the hydroxyl groups (-OH groups) of the cellulose (a chain polymer in which D-glucose is bonded via β(1→4) glucoside) constituting the cellulose fibers contained therein have been substituted with sulfate ester groups.

[0023] The fine cellulose fibers can be prepared by directly subjecting a fiber raw material to a micronization treatment to obtain fine cellulose fibers, and then substituting at least a portion of the hydroxyl groups of the cellulose constituting the fine cellulose fibers with sulfate ester groups, or by micronizing sulfate ester group-introduced pulp as described below. The latter method has the advantage that the fine cellulose fibers can be prepared simply by carrying out the micronization treatment step.

[0024] The sulfate ester group-introduced pulp can be obtained, for example, by the following method, but is not limited to this method.

[0025] In summary, this method involves chemically treating a cellulose-containing fiber raw material (e.g., wood-based pulp (hereinafter simply referred to as "wood pulp")) to prepare sulfate ester group-introduced pulp. This chemical treatment process includes a contacting step in which the fiber raw material is brought into contact with a sulfate ester group-donating compound (described below) and urea or a urea derivative (hereinafter referred to as "urea, etc."), and a reaction step in which the fiber raw material after this contacting step is subjected to a heating reaction to substitute some of the hydroxyl groups of the cellulose with sulfate ester groups.

[0026] In this specification, the term "fibrous raw material" refers to fibrous pulp containing cellulose molecules. Pulp is a fibrous material composed of an aggregate of multiple cellulose fibers. These cellulose fibers are an aggregate of multiple fine fibers (e.g., microfibrils). These fine fibers are an aggregate of multiple cellulose molecules (hereinafter simply referred to as "cellulose"), which are chain-like polymers in which D-glucose is bonded via β(1→4) glucoside bonds. It is also preferable to wash the fiber raw material beforehand. For example, filtration and dehydration using water on a 200-mesh or 235-mesh sieve can remove excessively fine fibers and debris, which is desirable because it improves handleability during preparation. In other words, pulp is an aggregate of cellulose fibers of a size that can become residue on a 200-mesh or 235-mesh sieve.

[0027] The fiber raw material used in this method is not particularly limited as long as it contains cellulose, as described above. For example, what is generally called pulp may be used, or a material containing cellulose isolated from sea squirts, seaweed, etc., and any material composed of cellulose molecules may be used. Examples of the pulp include, but are not limited to, cotton-based pulps such as wood pulp, dissolving pulp, and cotton linter; non-wood-based pulps such as wheat straw, bagasse, paper mulberry, mitsumata, hemp, kenaf, and fruit; and recycled paper pulp prepared from recycled newspaper, magazine paper, cardboard, etc. From the viewpoint of ease of availability, wood pulp is easily used as the fiber raw material.

[0028] There are various types of wood pulp, and the use is not particularly limited, and examples thereof include papermaking pulp such as softwood kraft pulp (NBKP), hardwood kraft pulp (LBKP), thermomechanical pulp (TMP), etc. When using the above pulp as a fiber raw material, one type of pulp may be used alone, or two or more types of pulp may be used in combination.

[0029] The sulfate ester group-donating compound is not particularly limited as long as it is a compound capable of donating sulfate ester groups to a fiber raw material, and examples thereof include sulfamic acid, sulfamic acid salts, and sulfuryl compounds having a sulfonyl group with two oxygen atoms covalently bonded to sulfur. One of these compounds may be used alone, or two or more may be used in combination. Sulfamic acid is preferred as the sulfate ester group-donating compound because it has lower acidity than sulfuric acid and the like, a higher efficiency of introducing sulfate ester groups, is inexpensive, and is highly safe. Hereinafter, an example will be described in which sulfamic acid is used as the sulfate ester group-donating compound and urea is used as the urea and the like.

[0030] <Contact process> The contacting step is a step of contacting a fiber raw material containing cellulose with sulfamic acid and urea. This contacting step is not particularly limited as long as it is a method that can cause the contact. For example, the fiber raw material may be immersed in a reaction solution in which sulfamic acid and urea are dissolved in a solvent to impregnate the fiber raw material with the reaction solution, or the reaction solution may be applied to the fiber raw material. Alternatively, sulfamic acid and urea may be separately applied to, impregnated into, or sprayed onto the fiber raw material. Among these methods, the method of immersing the fiber raw material in the reaction solution to impregnate the fiber raw material with the reaction solution makes it easier to uniformly contact the fiber raw material with sulfamic acid and urea.

[0031] The solvent for dissolving sulfamic acid and urea is not particularly limited, and examples thereof include protic polar solvents such as water, ethanol, methanol, acetic acid, formic acid, 2-propanol, nitromethane, and aqueous ammonia; aprotic polar solvents such as acetone, ethyl acetate, tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile, dimethyl sulfoxide (DMSO), dimethyl sulfide (DMS), and dimethylacetamide (DMA); and nonpolar solvents such as diethyl ether, benzene, toluene, hexane, chloroform, and 1,4-dioxane. One of the solvents may be used alone, or two or more may be used in combination. Water is particularly preferred because it easily dissolves sulfamic acid and urea.

[0032] The fiber raw material that has been brought into contact with sulfamic acid and urea through this contacting step is sometimes referred to as "reaction liquid-impregnated fiber."

[0033] <Contact amount of reaction solution> When the reaction solution is brought into contact with the fiber raw material, it is preferable to adjust the ratio of sulfamic acid and urea in the reaction solution to the fiber raw material to a predetermined ratio. Specifically, the reaction solution is contacted so that the amounts of sulfamic acid and urea in the reaction solution are appropriate relative to the fiber raw material in the reaction solution-impregnated fiber to be subjected to the reaction step. More specifically, the contact amount of sulfamic acid relative to the fiber raw material (solid mass, which is the dry mass) in the reaction solution-impregnated fiber immediately before being subjected to the heating reaction in the reaction step is adjusted to be equal to or greater than the contact amount of urea.

[0034] For example, the reaction solution is prepared so that the mixing ratio of sulfamic acid and urea is such that the value (sulfamic acid / urea) obtained by dividing the mass parts of sulfamic acid per 100 mass parts of the solid mass of the fiber raw material in the reaction solution-impregnated fiber immediately before being subjected to the heating reaction by the mass parts of urea per 100 mass parts of the solid mass of the fiber raw material in the reaction solution-impregnated fiber immediately before being subjected to the heating reaction is 0.8 or more, 0.85 or more, or 1 or more.

[0035] Furthermore, for example, the contact amount of sulfamic acid is adjusted to be 70 parts by mass or more, 100 parts by mass or more, or 200 parts by mass or more per 100 parts by mass of the solid content mass of the fiber raw material in the reaction liquid-impregnated fiber immediately before being subjected to the heating reaction.

[0036] Furthermore, for example, the contact amount of urea, i.e., the contact amount of urea relative to the mass of solids of the fiber raw material in the reaction solution-impregnated fiber immediately before the heating reaction, is adjusted to 20 parts by mass or more, 30 parts by mass or more, or 50 parts by mass or more per 100 parts by mass of the solids of the fiber raw material while maintaining the above-mentioned relationship with sulfamic acid. Furthermore, the upper limit of the contact amount of urea is not particularly limited, but is, for example, 350 parts by mass or less, 300 parts by mass or less, or 250 parts by mass or less per 100 parts by mass of the solids of the fiber raw material.

[0037] The contact amounts of sulfamic acid and urea per 100 parts by mass of the solid content of the fiber raw material can be calculated appropriately depending on the state of the reaction solution-impregnated fiber to be subjected to the reaction step.

[0038] <State of fiber impregnated with reaction solution> The state of the reaction liquid-impregnated fiber to be subjected to the above-mentioned next reaction step may be, for example, the reaction liquid-impregnated fiber as it is, i.e., a state in which the fiber raw material is in contact with the reaction liquid without actively removing water, or a state in which the fiber raw material is in contact with the reaction liquid and water has been actively removed.

[0039] The former reaction liquid-impregnated fibers (those without active water removal) include fibers in a state where the fiber raw material is in contact with the reaction liquid (including, for example, a slurry state), and fibers prepared by removing the fiber raw material from a state where the reaction liquid is in contact with the fiber raw material and leaving it to stand.

[0040] On the other hand, the latter reaction liquid impregnated fiber (in a state where water has been actively removed) refers to a fiber obtained by intentionally removing water from a state in which the fiber raw material is in contact with the reaction liquid. Examples include fibers prepared by removing the fiber raw material from the state in which the reaction liquid and the fiber raw material are in contact and then naturally drying it by air drying or the like, fibers prepared by filtering and dehydrating the fiber raw material in a state in which the reaction liquid and the fiber raw material are in contact, fibers prepared by further air-drying the filtered and dehydrated material, fibers prepared by further drying the filtered and dehydrated material using a circulating air dryer, fibers prepared by further drying the filtered and dehydrated material using a heated dryer, fibers prepared by contacting the reaction liquid and the fiber raw material and drying it using a circulating air dryer or a heated dryer, etc.

[0041] Thus, the reaction liquid-impregnated fibers to be subjected to the reaction step may be those in a state in which the aforementioned active water removal has not been performed, or those in a state in which a certain amount of water has been removed by active water removal. Furthermore, when water is removed by drying, there is no particular problem even if the moisture content after drying is about 1%. In particular, the latter method can reduce the moisture content in the reaction liquid-impregnated fibers to be subjected to the reaction step, thereby shortening the reaction time in the heating reaction in the reaction step. This has the advantage of improving the productivity of sulfate ester group-introduced pulp. Furthermore, the method of performing a dehydration treatment has the advantage of enabling the preparation of reaction liquid-impregnated fibers more efficiently than when treating a large amount of reaction liquid.

[0042] When an active drying method is used, the moisture content of the reaction solution-impregnated fibers may be reduced to about 1%, or may be removed by drying the fibers to an absolutely dry state with a moisture content significantly lower than 1%.

[0043] In this specification, the term "wet state" refers to a reaction liquid-impregnated fiber in a non-bone-dry state with a moisture content of 1% or more. For example, the term "wet state" may refer to fibers that are still impregnated with the reaction liquid, fibers that have been dehydrated to a certain extent, and fibers that have been dried to a certain extent.

[0044] In addition, in this specification, bone-dry means a state in which the moisture content is reduced to less than 1%, for example, by reducing the pressure in a desiccator containing a desiccant such as calcium chloride or diphosphorus pentoxide, or by subjecting the material to a long-term heat drying treatment.

[0045] Therefore, when the latter method (reaction method in a state where water is actively removed) is used in the contact step, the water content of the reaction solution-impregnated fiber may be brought to a non-absolutely dry state or may be brought to an absolutely dry state, but it is preferable to use the method of bringing the water content of the reaction solution-impregnated fiber to a non-absolutely dry state.

[0046] The moisture content of the reaction liquid-impregnated fiber in this specification is calculated using the following formula. Moisture content of reaction liquid-impregnated fiber (%) = 100 - (mass of solids in reaction liquid-impregnated fiber (g) / (g) of reaction liquid-impregnated fiber at the time of moisture content measurement) × 100 = {((g) of reaction liquid-impregnated fiber at the time of moisture content measurement - mass of solids in reaction liquid-impregnated fiber (g)) / (g) of reaction liquid-impregnated fiber at the time of moisture content measurement} × 100

[0047] The solids mass (g) of the reaction solution-impregnated fiber in the above formula refers to the dry mass of the reaction solution-impregnated fiber. Specifically, this refers to the dry mass adjusted to a constant weight by drying the sample at 105°C using a dryer or other device. For example, by placing the reaction solution-impregnated fiber in a dryer and drying it under specified drying conditions (e.g., 105°C for 2 hours) and measuring the mass, the mass of the reaction solution-impregnated fiber after moisture removal (i.e., the mass of the reaction solution-impregnated fiber that remains after drying under the specified drying conditions, including the fiber raw material and the reagents in the reaction solution) can be calculated. Furthermore, "constant mass" refers to a state in which moisture in the atmosphere and the raw material in the treatment facility no longer appears to move in or out. Specifically, after drying for a certain period of time (e.g., 2 hours), the change in mass between two consecutive measurements is within 1% of the mass at the start of drying (however, the second mass measurement should be at least half the drying time required for the first measurement).

[0048] The state of the fiber raw material when it is brought into contact with the reaction liquid is not particularly limited, and may be, for example, a dry state or a wet state (i.e., a moist state).

[0049] <Pre-drying process in the contact process> In the above example, the method for preparing the reaction liquid-impregnated fiber in the contacting step was described, in which the reaction liquid-impregnated fiber is prepared by actively removing water. However, when using a method for removing water while heating (pre-drying step) in this method (for example, when directly heating and drying the reaction liquid-impregnated fiber in contact with the fiber raw material, or when heating and drying the dehydrated fiber), it is desirable to adjust the heating temperature to a predetermined temperature or lower. The drying temperature in this pre-drying step is not particularly limited, but is preferably adjusted to a temperature that can remove water contained in the reaction liquid-impregnated fiber and surrounding water and does not allow the reaction to proceed. For example, the drying temperature in the pre-drying step can be adjusted so that the ambient temperature of the reaction liquid-impregnated fiber is 100°C or lower. On the other hand, from the viewpoint of workability, it is preferable to adjust the temperature to 50°C or higher. Therefore, the drying temperature in the pre-drying step in the contacting step is preferably 50°C to 100°C, or 70°C to 100°C.

[0050] <Moisture adjustment process in contact process> The contacting step may include a moisture adjustment step in which the moisture content of the fiber raw material to be contacted with the reaction solution is adjusted to fall within a predetermined range. This moisture adjustment step involves drying or humidifying the fiber raw material to achieve a predetermined moisture content. By including this moisture adjustment step, the moisture content of the fiber raw material can be made somewhat uniform when contacted with the reaction solution, etc., which may improve product stability in continuous operation. In addition, drying the fiber raw material to a certain extent to reduce the moisture content (for example, to a moisture content of 1% to 10%) has the advantage of improving storage stability.

[0051] <Reaction process> As described above, the reaction liquid-impregnated fibers prepared in the contacting step are subjected to the next reaction step. This reaction step is a step in which the cellulose fibers contained in the fiber raw material in the reaction liquid-impregnated fibers provided from the contacting step are reacted with sulfamic acid and urea to substitute at least a portion of the hydroxyl groups in the cellulose fibers with sulfate ester groups of sulfamic acid, thereby introducing sulfate ester groups into the cellulose fibers contained in the fiber raw material. That is, this reaction step is a step in which a reaction is carried out to substitute at least a portion of the hydroxyl groups in the cellulose fibers contained in the reaction liquid-impregnated fibers with sulfate ester groups.

[0052] The reaction step is not particularly limited as long as it is a method capable of substituting at least a portion of the hydroxyl groups of the cellulose fiber in the reaction solution-impregnated fiber with sulfate ester groups, and for example, a method of accelerating the reaction by heating the reaction solution-impregnated fiber can be used. Hereinafter, the reaction will be described taking as an example a case where the reaction is carried out by this heating method.

[0053] <Reaction temperature in the reaction process> The reaction temperature in the reaction step is not particularly limited, but is preferably a temperature at which sulfate ester groups can be introduced into the cellulose fibers that constitute the fiber raw material while suppressing thermal decomposition and hydrolysis of the fibers. For example, the ambient temperature of the reaction solution-impregnated fibers subjected to the reaction step is adjusted to 100°C to 200°C, 120°C to 200°C, 120°C to 180°C, or 120°C to 160°C. If the ambient temperature during heating is 200°C or less, thermal decomposition and discoloration of the fibers can be suppressed.

[0054] The heater or the like used in the reaction step is not particularly limited, and for example, a heater or the like that can heat the reaction solution-impregnated fiber after the contact step directly or indirectly while satisfying the above-mentioned requirements can be used, and known dryers, reduced pressure dryers, microwave heating devices, autoclaves, infrared heating devices, hot pressing methods using heat presses (e.g., AH-2003C manufactured by AS ONE Corporation), etc. can be used. In particular, from the viewpoint of operability, it is preferable to use a circulating air dryer because gas may be generated in the reaction step.

[0055] <Reaction time in the reaction process> The heating time (i.e., reaction time) when the heating method is used as the reaction step is not particularly limited, but is, for example, 1 minute or more, 5 minutes or more, 10 minutes or more, or 15 minutes or more when the reaction temperature is adjusted to be within the above range, and from the viewpoints of operability and cost, is 5 to 300 minutes, or 5 to 120 minutes.

[0056] By carrying out the above steps, a pulp having sulfate ester groups introduced therein can be prepared.

[0057] <Cleaning process after reaction process> After the reaction step, a washing step may be included in which the sulfate ester group-introduced pulp is washed. The sulfate ester group-introduced pulp has an acidic surface due to the influence of sulfamic acid (a sulfate ester group-donating compound). Furthermore, unreacted reaction liquid is still present. Therefore, by providing a washing step in which the reaction is completely terminated and excess reaction liquid is removed to neutralize the pulp, handling can be improved.

[0058] This washing step is not particularly limited, and may be performed, for example, so long as the sulfate ester group-introduced pulp is substantially neutral. For example, a method of washing the sulfate ester group-introduced pulp with pure water or the like until it becomes neutral can be used. Alternatively, neutralization washing using an alkaline solution or the like may be performed. When performing such neutralization washing, examples of the alkaline compound contained in the alkaline solution include inorganic alkaline compounds and organic alkaline compounds. Examples of inorganic alkaline compounds include hydroxides, carbonates, and phosphates of alkali metals. Examples of organic alkaline compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammonium, aromatic ammonium, heterocyclic compounds, and hydroxides of heterocyclic compounds.

[0059] The method for separating the sulfate ester group-introduced pulp in the washing step is not particularly limited, and may be any method as long as the sulfate ester group-introduced pulp and the wash water can be separated by filtration. For example, the sulfate ester group-introduced pulp after the reaction can be washed using a stainless steel sieve with a mesh size of 243 μm (70 mesh) to 20 μm (635 mesh), 132 μm (120 mesh) to 45 μm (300 mesh), or 75 μm (200 mesh) to 45 μm (300 mesh).

[0060] <Physical properties of sulfate ester group-introduced pulp> The physical properties of the sulfate ester group-introduced pulp thus prepared are not particularly limited, but are, for example, as follows:

[0061] <Amount of sulfate ester groups introduced> The amount of sulfate ester groups introduced per 1 g (solid mass) of sulfate ester group-introduced pulp is preferably adjusted to, for example, 0.6 mmol / g or more, 0.8 mmol / g or more, 1 mmol / g or more, or 1.2 mmol / g or more.

[0062] The upper limit is not particularly limited, but from the viewpoint of suppressing fiber collapse and cost increases resulting from decreased crystallinity, the amount of sulfate ester groups introduced per 1 g (solid mass) of sulfate ester group-introduced pulp is, for example, 9.9 mmol / g or less, or 5 mmol / g or less.

[0063] From the viewpoint of viscosity, the sulfate ester group-introduced pulp is preferably prepared as follows. By setting the amount of sulfate ester groups introduced per 1 g (solid content mass) of sulfate ester group-introduced pulp within the following ranges, a decrease in viscosity in the dispersion can be suppressed. For example, the upper limit of the amount of sulfate ester groups introduced per 1 g (solid content mass) of sulfate ester group-introduced pulp is 3.5 mmol / g or less, 2 mmol / g or less. The lower limit is, for example, 0.6 mmol / g or more, 1 mmol / g or more, or 1.5 mmol / g or more. For example, the amount of sulfate ester groups introduced per 1 g (solid content mass) of sulfate ester group-introduced pulp can be adjusted to 0.6 mmol / g to 3.5 mmol / g, 1 mmol / g to 2.5 mmol / g, or 1.5 mmol / g to 2 mmol / g.

[0064] The dispersion medium constituting the dispersion liquid of sulfate ester group-introduced pulp is not particularly limited, but is preferably one that can exhibit the viscosity and other properties described above. Examples of dispersion media include protic polar solvents such as water, ethanol, methanol, acetic acid, formic acid, 2-propanol, nitromethane, and aqueous ammonia; aprotic polar solvents such as acetone, ethyl acetate, tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile, dimethyl sulfoxide (DMSO), dimethyl sulfide (DMS), and dimethylacetamide (DMA); and nonpolar solvents such as dimethyl ether, benzene, toluene, hexane, chloroform, and 1,4-dioxane. These solvents may be used alone or in combination. From the standpoint of ease of handling, protic polar solvents such as water, ethanol, methanol, acetic acid, formic acid, and aqueous ammonia may be used.

[0065] <Method for measuring the amount of sulfate ester groups introduced> The amount of sulfate ester groups introduced into sulfate ester group-introduced pulp can be evaluated by the amount of sulfur introduced due to sulfate ester groups, or by directly measuring the sulfate ester groups. For example, the amount of sulfate ester groups introduced into pulp can be measured using a CHNS / O elemental analyzer. The amount of sulfate ester groups introduced into pulp can also be calculated by measuring electrical conductivity.

[0066] <Crystallinity> The sulfate ester group-introduced pulp may have, for example, a cellulose type I crystal structure as its crystalline structure, and its crystallinity may be 75% or less. From the viewpoint of maintaining the fiber shape, the crystallinity of the sulfate ester group-introduced pulp is preferably 30% or more. From the viewpoint of viscosity, the crystallinity of the sulfate ester group-introduced pulp is, for example, 70% or less, 65% or less, or 60% or less. Furthermore, from the viewpoint of handleability in the method for preparing the sulfate ester group-introduced pulp, the crystallinity of the sulfate ester group-introduced pulp is, for example, 30% or more, or 40% or more.

[0067] <Method for measuring crystallinity> The crystallinity of the sulfate ester group-introduced pulp can be measured, for example, using an X-ray diffraction device.

[0068] Sulfate ester group-introduced pulp has excellent viscosity due to, for example, a predetermined degree of crystallinity. Specifically, the viscosity of a pulp having a typical I-type crystal structure is on the order of several tens to several hundreds of mPa·s when measured using a B-type viscometer at 20°C and rotated at 6 rpm for 3 minutes, whereas sulfate ester group-introduced pulp can exhibit excellent viscosity (for example, several thousand mPa·s or more) that was previously unimaginable for conventional pulp.

[0069] <Average fiber length> The average fiber length of the sulfate ester group-introduced pulp is not particularly limited, and is, for example, 0.2 mm to 2 mm, 0.2 mm to 1.8 mm, 0.2 mm to 1.5 mm, or 0.2 mm to 1 mm.

[0070] <Short fiber rate (%)> The sulfate ester group-introduced pulp may also contain pulp having a short fiber length as described below. Examples of this short fiber length pulp (hereinafter referred to as "short fiber") include pulp having a fiber length of 0.04 mm or more and 0.2 mm or less in the fiber length distribution. The content (%) of short fibers in the sulfate ester group-introduced pulp (i.e., short fiber rate (%)) is, for example, 10% or more, 15% or more.

[0071] From the viewpoint of handleability, the sulfate ester group-introduced pulp has a short fiber content (%) (i.e., short fiber ratio (%)) of, for example, 10% to 70%, 10% to 60%, 10% to 50%, 10% to 45%, or 15% to 45% in terms of fiber length distribution.

[0072] <Average fiber width> The average fiber width of the sulfate ester group-introduced pulp is not particularly limited, and is, for example, 5 μm to 100 μm, 10 μm to 50 μm, 20 μm to 40 μm, or 20 μm to 30 μm.

[0073] <Method for measuring average fiber length, average fiber width, and fiber distribution> The average fiber length and average fiber width of the sulfate ester group-introduced pulp can be measured, for example, using a fiber tester or fiber length distribution measuring instrument manufactured by Lorentzen & Wettley in accordance with ISO 16065-2: 2007. The fiber length distribution and fiber width distribution of the sulfate ester group-introduced pulp can be measured, for example, using a fiber length distribution measuring instrument in accordance with ISO 16065-2: 2007.

[0074] <Viscosity> When the crystallinity of sulfate ester group-introduced pulp is equal to or less than the aforementioned value, the dispersion has a predetermined viscosity. For example, when the crystallinity of sulfate ester group-introduced pulp is 70% or less, the viscosity of the dispersion obtained by dispersing sulfate ester group-introduced pulp in water is 1,000 mPa·s or more, 5,000 mPa·s or more, or 10,000 mPa·s or more. In particular, when the crystallinity of sulfate ester group-introduced pulp is 60% or less, the viscosity of the dispersion tends to increase. Furthermore, this tendency becomes even stronger when the average fiber length is 1 mm or less.

[0075] <Viscosity measurement method> The viscosity (mPa·s) of sulfate ester group-introduced pulp can be measured, for example, using a B-type viscometer at a measurement temperature of 20°C, with measurements performed at rotation speeds of 6 rpm and 60 rpm. The thixotropy index (TI) can also be calculated from each viscosity value. TI value = (viscosity at 6 rpm) / (viscosity at 60 rpm)

[0076] The TI value can be adjusted as appropriate, and when a high TI value is required, the lower limit of the TI value is, for example, 3 or more, 4 or more, or 5 or more. The upper limit of the TI value is, for example, 10 or less, 8 or less, 6 or less, or 5 or less. On the other hand, when a low TI value is preferred, the lower limit is, for example, 1 or more, and the upper limit is, for example, 3 or less, or 2.5 or less.

[0077] <Method for preparing fine cellulose fibers> The fine cellulose fibers can be obtained by subjecting the sulfate ester group-introduced pulp prepared as described above to a fine pulping treatment step.

[0078] <Fine-grain processing process> The refining step in this method is a step of refining the sulfate ester group-introduced pulp to fine fibers of a predetermined size (e.g., nano-level). The processing equipment used in this refining step is not particularly limited as long as it has the above-mentioned functions. For example, the processing equipment may be a low-pressure homogenizer, a high-pressure homogenizer, a grinder (a stone-type grinder), a ball mill, a cutter mill, a jet mill, a single-screw extruder, a twin-screw extruder, an ultrasonic agitator, a household mixer, or the like, but is not limited to these. Among these, it is desirable to use a high-pressure homogenizer because it can apply force evenly to the material and is excellent at homogenizing.

[0079] When a high-pressure homogenizer is used in the pulp refining step, the sulfate ester group-introduced pulp is supplied in a dispersed state in an aqueous dispersion medium such as water. Hereinafter, the dispersion in which the sulfate ester group-introduced pulp is dispersed may be referred to as a slurry. The solids concentration of the sulfate ester group-introduced pulp in this slurry is not particularly limited and is, for example, 0.1% by mass to 20% by mass.

[0080] For example, if a slurry containing sulfate ester group-introduced pulp with a solid content adjusted to 0.5% by mass is fed to a processing device such as a high-pressure homogenizer, a dispersion of fine cellulose fibers with the same solid content dispersed in an aqueous dispersion medium can be obtained. That is, in this case, a dispersion with a solid content of 0.5% by mass can be obtained.

[0081] The water retention of the sulfate ester group-introduced pulp to be subjected to the refining treatment step is not particularly limited, but is preferably adjusted so as to facilitate refining using the above-mentioned equipment. For example, from the viewpoint of refining treatment efficiency and energy consumption reduction, it is desirable to use sulfate ester group-introduced pulp prepared to have a high water retention. From this viewpoint, it is preferable to use sulfate ester group-introduced pulp prepared to have a water retention of 150% or more, 200% or more, 250% or more, 300% or more, or 500% or more. From the viewpoint of the recovery rate of fine cellulose fibers, the water retention rate is, for example, 10,000% or less. Thus, from the viewpoints of refining treatment efficiency and recovery rate, the water retention rate of the sulfate ester group-introduced pulp to be subjected to the refining treatment step is 150% to 10,000%, 200% to 10,000%, 220% to 10,000%, 250% to 5,000%, or 250% to 2,000%.

[0082] The amount of the fine cellulose fibers in the total amount of the glaze composition (fine cellulose fiber ratio) is not particularly limited, but is, for example, 0.3% by mass or less, 0.2% by mass or less. The lower limit of the fine cellulose fiber ratio is not particularly limited, but is, for example, 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more. As mentioned above, conventional glazes tend to settle when stored for a long period of time, requiring stirring each time they are used. In contrast, the glaze composition of the present invention containing the fine cellulose fibers is less susceptible to settling during long-term storage and has excellent storage stability, thereby reducing the workload of stirring each time they are used. Furthermore, the glaze composition of the present invention containing the fine cellulose fibers also exhibits the effect of suppressing dripping and unevenness, as demonstrated in the examples described below.

[0083] (water) The water is preferably ion-exchanged water or pure water. The amount of water in the total amount of the glaze composition may be, for example, the remainder of the other components.

[0084] The components of the glaze composition other than the fine cellulose fibers and the water are not particularly limited, and examples thereof include frit made of glass or the like, feldspar, limestone, kaolin, silica stone, frog's eye clay, kibushi clay, nickel oxide, calcium carbonate, cobalt oxide, copper oxide, zinc oxide, and the like.

[0085] The glaze composition can be prepared, for example, by mixing the fine cellulose fibers, the water, and other additive components by a conventionally known method.

[0086] The glaze composition can be used for various purposes, such as ceramic glaze, porcelain glaze, and furnace glaze. [Example]

[0087] A colored glaze was prepared by adding 2% by mass of nickel oxide to each component of the basic glaze composition (Table 1) and mixing them uniformly. When the particle size distribution of the colored glaze was measured, it was found that 90% or more of the particles had a particle size of 30 μm or less.

[0088] [Table 1]

[0089] Using the color glaze, a 1% by mass aqueous dispersion of fine cellulose fiber, and water, glaze compositions were prepared with the blending amounts of fine cellulose fiber (fine cellulose fiber ratio) of 0% by mass (blank, pH 7.84), 0.1% by mass (pH 7.78), 0.2% by mass (pH 7.91), and 0.3% by mass (pH 7.61), and the specific gravity of each glaze composition was 1.385 g / cm 3 The viscosity was adjusted to (Baume 40). The 1% by mass aqueous dispersion of the fine cellulose fibers was prepared as follows.

[0090] (Preparation of sulfate ester group-introduced pulp) Softwood kraft pulp (NBKP) (hereinafter simply referred to as "pulp") with an average fiber length of 2.54 mm, manufactured by Marusumi Paper Co., Ltd., was washed with a large amount of ion-exchanged water and then drained through a 75 μm (200 mesh) sieve. The solids concentration of a portion of the pulp obtained in this manner was measured, and found to be 21.6% by mass. The ion-exchanged water used was homemade and had an electrical conductivity of >0.2 μS / cm; hereafter, this will be referred to as pure water. The wet pulp was then spread on an aluminum tray and placed in a dryer at 105°C for approximately 1 hour, where it was dried until the moisture content reached approximately 1%.

[0091] <Contact process> 1000 g of the reaction solution was added to 20 g of pulp (solid content mass), and the pulp was impregnated with the reaction solution. The reaction solution was an aqueous solution in which sulfamic acid and urea were mixed at a concentration ratio (g / L) of sulfamic acid:urea = 2:1 (180 g / L:90 g / L). The sulfamic acid used was a 99.8% purity product manufactured by Fuso Chemical Co., Ltd., and the urea used was a 99.0% purity product (special grade) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0092] The pulp impregnated with the reaction solution was dehydrated by suction filtration and spread on an aluminum tray. The aluminum tray was then placed in a dryer in an 80°C atmosphere and dried to prepare reaction solution-impregnated pulp. The moisture content of this reaction solution-impregnated pulp was 5% or less. Filter paper (manufactured by Advantech, model number: No. 2) was used for the suction filtration.

[0093] <Reaction process> The reaction solution-impregnated pulp was subjected to a heating reaction using a dryer. The temperature of the thermostatic chamber of the dryer was 140°C, and the heating time was 30 minutes. After heating, the reaction solution-impregnated pulp was washed until it became neutral, thereby preparing sulfate ester group-introduced pulp with an introduction amount of 1.39 mmol / g. The washing was performed by adding a large amount of pure water to the reaction solution-impregnated pulp to form a slurry, and then neutralizing it by adding sodium bicarbonate (manufactured by Nacalai Tesque, Inc., purity 99.5%) until no more bubbles were generated.

[0094] (Preparation of aqueous dispersion of fine cellulose fibers) The sulfate ester group-introduced pulp was subjected to defibration treatment five times using a high-pressure homogenizer (Yoshida Kikai Kogyo Co., Ltd., "Nanovaita", pressure: 60 MPa) to prepare a 1% by mass aqueous dispersion of fine cellulose fibers.

[0095] [Dispersion stability evaluation 1] The dispersion stability of 20 mL of glaze compositions containing 0 mass% (blank), 0.1 mass%, and 0.2 mass% of the fine cellulose fiber was evaluated by scanning the transmittance (T (%)) and backscattered light intensity (BS (%)) every 15 minutes for 5 hours using a Turbiscan Tower (Turbiscan Tower manufactured by Formulaction). The results are shown in Figure 1. Figures 1(A), 1(B), and 1(C) show the results for the samples containing 0 mass% (blank), 0.1 mass%, and 0.2 mass% of the fine cellulose fiber, respectively.

[0096] As can be seen from Figure 1(A), when the proportion of fine cellulose fibers was 0% by mass (blank), the transmittance curve and backscattered light intensity curve changed at a constant rate, with the transmittance curve descending 14 mm in 5 hours and the backscattered light intensity curve descending 7 mm in 5 hours. On the other hand, as can be seen from Figure 1(B), when the proportion of fine cellulose fibers was 0.1% by mass, the transmittance curve remained unchanged and the backscattered light intensity curve only descended 4 mm in 5 hours. Furthermore, as can be seen from Figure 1(C), when the proportion of fine cellulose fibers was 0.2% by mass, there was no change in the transmittance curve and the backscattered light intensity curve. These results confirmed that glaze compositions containing fine cellulose fibers have excellent dispersibility, and that adding 0.2% by mass of fine cellulose fibers results in a glaze composition with extremely excellent dispersibility.

[0097] [Dispersion stability evaluation 2] Specific gravity: 1.04g / cm 3The dispersion stability of 20 mL of the glaze composition was evaluated by scanning the backscattered light intensity (BS (%)) every 15 minutes for 5 hours using the Turbiscan tower. 3 Glaze compositions containing 0.01% by mass (pH 7.65) and 0.05% by mass (pH 7.71) of the fine cellulose fiber were also prepared. Furthermore, due to the change in the specific gravity of the glaze composition, the amount of base glaze in each glaze composition was 1 / 10 of that in the dispersion stability evaluation 1 described above. The results are shown in Figures 2-1 and 2-2. Figures 2-1(A), 2-1(B), 2-1(C), 2-2(D), 2-2(E), and 2-2(F) show the results for samples containing 0% by mass (blank), 0.01%, 0.05%, 0.1%, 0.2%, and 0.3% by mass of the fine cellulose fiber, respectively.

[0098] As can be seen from Figures 2-1 and 2-2, the higher the proportion of the fine cellulose fibers, the slower the sedimentation (the occurrence of precipitates), and this tendency was particularly pronounced when the proportion of the fine cellulose fibers exceeded 0.05% by mass. These results confirmed that even when the amount of base glaze such as feldspar, limestone, kaolin, or silica was small, the glaze composition containing the fine cellulose fibers had excellent dispersibility, and that adding 0.05% by mass of the fine cellulose fibers resulted in a glaze composition with even better dispersibility.

[0099] [Dispersion stability evaluation 3] Specific gravity: 1.04g / cm 3 The dispersion stability of 20 mL of the glaze composition was further evaluated by scanning the backscattered light intensity (BS (%)) every 24 hours for 7 days using the Turbiscan tower. The results are shown in Figures 3-1 and 3-2. Figures 3-1(A), 3-1(B), 3-1(C), 3-2(D), 3-2(E), and 3-2(F) show the results for the cases where the fine cellulose fiber content was 0% by mass (blank), 0.01% by mass, 0.05% by mass, 0.1% by mass, 0.2% by mass, and 0.3% by mass, respectively.

[0100] As can be seen from Figures 3-1 and 3-2, the higher the proportion of the fine cellulose fibers, the slower the sedimentation (the occurrence of precipitates), and this tendency was particularly pronounced when the proportion of the fine cellulose fibers exceeded 0.05% by mass. These results confirmed that even when the blending amount of base glaze such as feldspar, limestone, kaolin, or silica was small, the glaze composition containing the fine cellulose fibers had excellent dispersibility, and that blending 0.05% by mass of the fine cellulose fibers provided a glaze composition with excellent dispersibility for a long period of time.

[0101] [Sedimentation test] The glaze compositions (specific gravity 1.385 g / cm) containing 0 mass% (blank), 0.1 mass%, 0.2 mass%, and 0.3 mass% of the fine cellulose fiber were used. 3 The settling velocity of the fine cellulose fiber (Baume 40) was confirmed by scanning the backscattered light intensity (BS (%)) every 24 hours for 7 days using the Turbiscan tower. The results are shown in Figure 4. Figures 4(A), 4(B), 4(C), and 4(D) show the results when the fine cellulose fiber ratio was 0% by mass (blank), 0.1% by mass, 0.2% by mass, and 0.3% by mass, respectively.

[0102] As can be seen from Figure 4(A), when the proportion of the fine cellulose fibers was 0% by mass (blank), there was no change in the backscattered light intensity curve after one day (24 hours), indicating that sedimentation occurred all at once. On the other hand, as can be seen from Figures 4(B) to 4(D), it was confirmed that in the glaze compositions containing the fine cellulose fibers, the sedimentation rate decreased as the amount of the fine cellulose fibers added increased.

[0103] Sedimentation test using a measuring cylinder (specific gravity 1.385 g / cm 3 (Baume 40))] 500 mL of glaze compositions containing 0% by mass (blank), 0.1% by mass, 0.2% by mass, and 0.3% by mass of the fine cellulose fiber were placed in a measuring cylinder and allowed to stand for 7 days, after which the occurrence of sedimentation was evaluated. The results are shown in Figure 5. Figure 5(A), Figure 5(B), Figure 5(C), and Figure 5(D) show the results for the samples containing 0% by mass (blank), 0.1% by mass, 0.2% by mass, and 0.3% by mass of the fine cellulose fiber, respectively.

[0104] As can be seen from Figure 5(A), when the proportion of fine cellulose fibers was 0% by mass (blank), sedimentation occurred. On the other hand, as can be seen from Figure 5(B), when the proportion of fine cellulose fibers was 0.1% by mass, sedimentation occurred, but not as much as in the blank. Furthermore, as can be seen from Figures 5(C) and 5(D), when the proportion of fine cellulose fibers was 0.2% by mass and 0.3% by mass, no sedimentation occurred. From these results, it was confirmed that glaze compositions containing fine cellulose fibers suppress sedimentation during long-term storage and have excellent storage stability, and that this effect is remarkable when 0.2% by mass or more of fine cellulose fibers are blended.

[0105] Sedimentation test using a measuring cylinder (specific gravity 1.04 g / cm 3 )] Specific gravity: 1.04g / cm 3 A sedimentation test using a measuring cylinder was also carried out on the glaze composition prepared as above. The results are shown in Figure 6. Figures 6(A), 6(B), 6(C), 6(D), 6(E), and 6(F) show the results when the fine cellulose fiber ratio was 0 mass% (blank), 0.01 mass%, 0.05 mass%, 0.1 mass%, 0.2 mass%, and 0.3 mass%, respectively.

[0106] As can be seen from Figure 6(A), when the proportion of the fine cellulose fibers was 0% by mass (blank), sedimentation occurred. On the other hand, as can be seen from Figure 6(B), when the proportion of the fine cellulose fibers was 0.01% by mass, sedimentation occurred, but not to the same extent as in the blank. Furthermore, as can be seen from Figures 6(C) to 6(F), when the proportion of the fine cellulose fibers was 0.05% by mass to 0.3% by mass, no sedimentation occurred. These results confirmed that when the amount of base glaze containing feldspar, limestone, kaolin, silica, etc. was small, significant storage stability was achieved even when the amount of fine cellulose fibers was 0.05% by mass.

[0107] [Raw test] 300 μL of each glaze composition containing 0% by mass (blank), 0.1% by mass, 0.2% by mass, and 0.3% by mass of the fine cellulose fiber was measured with a micropipette and dropped onto a horizontal clay plate. The clay plate was then turned vertically, and the drip distances after 1 minute were compared. The results are shown in Figure 7. Figures 7(A), 7(B), 7(C), and 7(D) show the results for the samples containing 0% by mass (blank), 0.1% by mass, 0.2% by mass, and 0.3% by mass of the fine cellulose fiber, respectively.

[0108] 7(A) to 7(D), the dripping distance was 83 mm when the ratio of the fine cellulose fibers was 0% by mass (blank), 32 mm when it was 0.1% by mass, 28 mm when it was 0.2% by mass, and 13 mm when it was 0.3% by mass, and the dripping distance became shorter as the ratio of the fine cellulose fibers increased. These results confirmed that the addition of the fine cellulose fibers can suppress dripping in the glaze composition.

[0109] [Bisque firing glaze application test] One liter of each of the glaze compositions containing 0% by mass (blank) and 0.2% by mass of fine cellulose fiber was poured into a hand-held measuring cup and stirred. Immediately after stirring, and 30 minutes, 1 hour, 3 hours, and 5 hours after stirring, the biscuit blocks were gently immersed to 10 cm below the liquid surface for 3 seconds and then slowly pulled out. They were fired in an oxidizing atmosphere at 1250°C and compared. The results are shown in Figure 8. Figure 8(A) shows the results for the blank sample containing 0% by mass of fine cellulose fiber; (A-1) shows the results immediately after stirring; (A-2), (A-3), (A-4), and (A-5) show the results 30 minutes, 1 hour, 3 hours, and 5 hours after stirring, respectively. Figure 8(B) shows the results when the proportion of fine cellulose fibers is 0.2% by mass, where (B-1) is the result immediately after stirring, and (B-2), (B-3), (B-4) and (B-5) are the results 30 minutes, 1 hour, 3 hours and 5 hours after stirring, respectively.

[0110] As can be seen from Figures 8(A) and 8(B), it was confirmed that the addition of the fine cellulose fibers suppressed the occurrence of unevenness.

Claims

1. Contains fine cellulose fibers and water, A glaze composition, wherein at least a portion of the hydroxyl groups of the fine cellulose fibers are substituted with sulfate ester groups.

2. The glaze composition according to claim 1, wherein the blending amount of the fine cellulose fibers is 0.2 mass % or less.

3. The glaze composition according to claim 1 or 2, wherein the blending amount of the fine cellulose fibers is 0.05% by mass or more.

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