Hydraulic composition for 3D printing and method for manufacturing three-dimensional objects

Abstract

To provide a hydraulic composition for 3D printing that is suitable for material extrusion method 3D printing, has good extrudability from a nozzle and good lamination independence (low deformation of the lower layer when laminated), and has excellent water retention.SOLUTION: A hydraulic composition for 3D printing is a hydraulic composition containing (A) water-soluble hydroxyalkylalkylcellulose, (B) polyacrylamide, (C) cement, (D) water, and (E) short fibers at least. The viscosity of a 2 mass% aqueous solution at 20°C of the component (A) water-soluble hydroxyalkylalkylcellulose is 2000 to 6000 mPa s, and the degree of anionization of the polyacrylamide of the component (B) is 6 to 40 mol%, and a 0.5 mass% aqueous solution of the polyacrylamide at 25°C (where a solvent is a 4 mass% aqueous sodium chloride solution) has a viscosity of 10 to 300 mPa s.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a hydraulic composition for 3D printing suitable for layer forming by 3D printing and a method for manufacturing a three-dimensional shaped object.

Background Art

[0002] 3D printing is a method (layer forming method) of forming a three-dimensional shape by laminating cross-sectional shapes based on three-dimensional data. The main 3D printing methods are roughly classified into four types: binder jetting method (injecting a liquid binder onto a powder bed and selectively solidifying it), directed energy deposition method (controlling the position where heat is generated and selectively melting and bonding materials), material jetting method (injecting droplets of a material and selectively depositing and solidifying them), material extrusion method (extruding a fluid material from a nozzle and solidifying it), and the like.

[0003] When using a cement-based material for 3D printing, among these, the material extrusion method is suitable. However, the properties required for the material in this case are the extrudability from the nozzle and the self-supporting property after lamination (lamination self-supporting property, low deformation property of the lower layer when laminated). Since these are conflicting properties, it has been difficult to achieve both.

[0004] In Japanese Unexamined Patent Application Publication No. 2020-105023 (Patent Document 1), in order to solve this problem, by defining the relationship between the content of a cellulose-based thickener and silica fume, it aims to achieve both extrudability and self-supporting property after lamination.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, while Patent Document 1 specifies the viscosity of a 1% by mass aqueous solution of a cellulose-based thickener for each shear rate, hydraulic compositions containing silica fume become highly thixotropic, which prevents the utilization of the properties of the cellulose-based thickener and can result in poor discharge performance and other undesirable effects.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a hydraulic composition for 3D printing that is suitable for material extrusion type 3D printing, has good extrudeability from the nozzle and self-supporting properties after lamination (laminated self-supporting properties, low deformation of the lower layer when laminated), and also has excellent water retention properties, and a method for manufacturing a three-dimensional object using the hydraulic composition for 3D printing. [Means for solving the problem]

[0008] The present inventors conducted diligent research to achieve the above objectives and, as a result, discovered that by using water-soluble hydroxyalkylalkylcellulose having a specific aqueous solution viscosity, polyacrylamide having a specific degree of anionization and in which the aqueous solution exhibits a specific viscosity when dissolved in a predetermined amount in a 4% by mass sodium chloride aqueous solution, cement, water, and short fibers, the resulting hydraulic composition for 3D printing exhibits good extrusion from a nozzle, low deformability of the lower layer when laminated, and excellent water retention, thus completing the present invention.

[0009] Accordingly, the present invention provides the following hydraulic composition for 3D printing and a method for manufacturing three-dimensional objects. A hydraulic composition comprising at least (A) water-soluble hydroxyalkylalkylcellulose, (B) polyacrylamide, (C) cement, (D) water, and (E) short fibers, (A) The viscosity of a 2% by mass aqueous solution of water-soluble hydroxyalkylalkylcellulose at 20°C is 2000 to 6000 mPa·s. Furthermore, the degree of substitution (DS) of the alkoxy group of the water-soluble hydroxyalkylalkylcellulose is 1.0 to 2.0. (B) The degree of anionization of the polyacrylamide is 6 to 40 mol%, and the viscosity of a 0.5 mass% aqueous solution of the polyacrylamide at 25°C (where the solvent is a 4 mass% aqueous sodium chloride solution) is 10 to 300 mPa·s. the law of nature, (A) The amount of water-soluble hydroxyalkylalkylcellulose added is 0.1 to 0.6 parts by mass per 100 parts by mass of cement. The amount of polyacrylamide added to component (B) is 0.001 to 0.12 parts by mass per 100 parts by mass of cement. The mass ratio ((A) / (B)) of water-soluble hydroxyalkylalkylcellulose (component A) to polyacrylamide (component B) is 80 / 20 to 99.9 / 0.1. A hydraulic composition for 3D printing. 2. The mass ratio ((A) / (B)) of water-soluble hydroxyalkylalkylcellulose (component A) and polyacrylamide (component B) is 83 / 17 ~ 99.5 / 0.5 The hydraulic composition for 3D printing described in 1. 3. (A) The amount of water-soluble hydroxyalkylalkylcellulose added to Component A is per 100 parts by mass of cement 0.2 ~ 0.55 A hydraulic composition for 3D printing according to 1 or 2, which is part by mass. 4. A hydraulic composition for 3D printing according to any one of claims 1 to 3, wherein the degree of substitution (DS) of the alkoxy group of component (A) hydroxyalkylalkylcellulose is 1.3 to 2.0. 5. A hydraulic composition for 3D printing according to any one of 1 to 4, wherein the amount of polyacrylamide added to component (B) is 0.005 to 0.08 parts by mass per 100 parts by mass of cement. 6 . (E) The amount of short fibers added is 0.1 to 3 parts by volume per 100 parts by volume of the hydraulic composition. 5 A hydraulic composition for 3D printing as described in any of the above. 7 . (E) The short fibers of component (E) are at least one selected from the group consisting of polypropylene fibers, polyethylene fibers, vinylon fibers, acrylic fibers, aramid fibers, glass fibers, basalt fibers, steel fibers, and carbon fibers. 6 A hydraulic composition for 3D printing as described in any of the above. 8 . Furthermore, it contains fine aggregate 1~ 7 A hydraulic composition for 3D printing as described in any of the above. 9 . 1~ 8A method for manufacturing a three-dimensional object, which comprises pumping a hydraulic composition for 3D printing as described in any one of the above, and laminating while moving a nozzle to construct the object.

Advantages of the Invention

[0010] According to the present invention, there can be provided a hydraulic composition for 3D printing which is a cement-based material suitable for material extrusion type 3D printing, has good extrusion properties from a nozzle and self-standing properties after lamination (lamination self-standing properties, low deformation properties of the lower layer part when laminated), and also has excellent water retention properties.

Modes for Carrying Out the Invention

[0011] The hydraulic composition for 3D printing according to the present invention is a hydraulic composition containing at least (A) water-soluble hydroxyalkyl alkyl cellulose, (B) polyacrylamide, (C) cement, (D) water, and (E) short fibers, the viscosity of a 2 mass% aqueous solution of the water-soluble hydroxyalkyl alkyl cellulose as the component (A) at 20°C is 2000 to 6000 mPa·s, the degree of anionicization of the polyacrylamide as the component (B) is 6 to 40 mol%, and the viscosity of a 0.5 mass% aqueous solution of the polyacrylamide at 25°C (where the solvent is a 4 mass% aqueous sodium chloride solution) is 10 to 300 mPa·s and is characterized by the above. Note that the above "containing at least" means containing the components (A) to (E) as essential components.

[0012] The hydraulic composition for 3D printing according to the present invention is a hydraulic composition for 3D printing containing water-soluble hydroxyalkyl alkyl cellulose, polyacrylamide, cement, water, and short fibers as essential components.

[0013] ((Component (A))) In the present invention, hydroxypropyl methylcellulose (HPMC) and / or hydroxyethyl methylcellulose (HEMC) are preferably used as the water-soluble hydroxyalkylalkylcellulose.

[0014] The viscosity of a 2% by mass aqueous solution of the water-soluble hydroxyalkylalkylcellulose used in the present invention at 20°C is 2000 to 6000 mPa·s, preferably 2500 to 5500 mPa·s, more preferably 2500 to 5300 mPa·s, and even more preferably 2500 to 5000 mPa·s, from the viewpoint of achieving both extrusion from the nozzle and self-supporting properties after lamination. The viscosity of a 2% by mass aqueous solution of water-soluble hydroxyalkylalkylcellulose at 20°C can be measured using a B-type viscometer.

[0015] In the water-soluble hydroxyalkylalkylcellulose used in the present invention, the degree of substitution (DS) of the alkoxy group is preferably 1.0 to 2.0, more preferably 1.2 to 1.95, and even more preferably 1.3 to 1.92, from the viewpoint of achieving both extrusion from the nozzle and self-supporting properties after lamination. Furthermore, the number of substituted moles (MS) of hydroxyalkoxy groups in the water-soluble hydroxyalkylalkylcellulose is preferably 0.05 to 0.6, more preferably 0.1 to 0.5, and even more preferably 0.1 to 0.4, from the viewpoint of solubility during summer use.

[0016] In water-soluble hydroxyalkylalkylcellulose, the DS of the alkoxy groups represents the degree of substitution, which is the average number of alkoxy groups per unit of anhydrous glucose. Similarly, the MS of the hydroxyalkoxy groups in water-soluble hydroxyalkylalkylcellulose represents the molar substitution, which is the average number of moles of hydroxyalkoxy groups per mole of anhydrous glucose. The DS and MS of the alkoxy groups in water-soluble hydroxyalkylalkylcellulose can be determined by converting the values ​​that can be measured using the degree of substitution analysis method for hypromellose (hydroxypropyl methylcellulose) described in the 18th edition of the Japanese Pharmacopoeia.

[0017] Furthermore, in the water-soluble hydroxyalkylalkylcellulose, preferred combinations of viscosity of a 2% by mass aqueous solution at 20°C, degree of substitution of alkoxy groups (DS), and number of substituted moles of hydroxyalkoxy groups (MS) are, when component (A) is hydroxypropylmethylcellulose, preferably the viscosity of a 2% by mass aqueous solution at 20°C is 2000 to 6000 mPa·s, the degree of substitution of methoxy groups (DS) is 1.0 to 2.0, and the number of substituted moles of hydroxypropoxy groups is... (MS): 0.05~0.6, more preferably the viscosity of a 2 mass% aqueous solution at 20°C is 2500~5500 mPa·s, and the degree of substitution of the methoxy group (DS): 1.2~1.95, and the number of substituted moles of the hydroxypropoxy group (MS): 0.1~0.5, and even more preferably the viscosity of a 2 mass% aqueous solution at 20°C is 2500~5000 mPa·s, and the degree of substitution of the methoxy group (DS): 1.3~1.92, and the number of substituted moles of the hydroxypropoxy group (MS): 0.1~0.4. Furthermore, when component (A) is hydroxyethyl methylcellulose, preferably the viscosity of a 2% by mass aqueous solution at 20°C is 2000 to 6000 mPa·s, the degree of substitution of methoxy groups (DS) is 1.0 to 2.0, and the number of substituted moles of hydroxyethoxy groups (MS) is 0.05 to 0.6. More preferably, the viscosity of a 2% by mass aqueous solution at 20°C is 2500 to 5500 mPa·s, the degree of substitution of methoxy groups (DS) is 1.2 to 1.95, and the number of substituted moles of hydroxyethoxy groups (MS) is 0.1 to 0.5. Even more preferably, the viscosity of a 2% by mass aqueous solution at 20°C is 2500 to 5000 mPa·s, the degree of substitution of methoxy groups (DS) is 1.3 to 1.92, and the number of substituted moles of hydroxyethoxy groups (MS) is 0.1 to 0.4.

[0018] The amount of water-soluble hydroxyalkylalkylcellulose added to component (A) is preferably 0.1 to 0.6 parts by mass, more preferably 0.15 to 0.57 parts by mass, and even more preferably 0.2 to 0.55 parts by mass, per 100 parts by mass of cement in component (C), from the viewpoint of imparting water retention to the hydraulic composition for 3D printing.

[0019] ((B) component) In this invention, component (B) includes polyacrylamide. The degree of anionization of polyacrylamide is 6 to 40 mol%, preferably 7 to 40 mol%, more preferably 8 to 40 mol%, and even more preferably 8 to 39 mol%, from the viewpoint of achieving both extrusion from the nozzle and self-supporting properties after lamination. The degree of anionization is defined as the percentage (mol%) of the amide groups of polyacrylamide that have been anionically modified, and can be measured by colloidal titration.

[0020] In this invention, the viscosity of a 0.5% by mass aqueous solution of polyacrylamide at 25°C (where the solvent is a 4% by mass aqueous solution of sodium chloride) is 10 to 300 mPa·s, preferably 15 to 290 mPa·s, and more preferably 20 to 280 mPa·s, from the viewpoint of achieving both extrudeability from the nozzle and self-supporting properties after lamination. 、 More preferably, the value is 25 to 270 mPa·s. The viscosity of a 0.5% by mass aqueous solution of polyacrylamide at 25°C (where the solvent is a 4% by mass aqueous solution of sodium chloride) can be measured using a B-type viscometer.

[0021] Furthermore, a suitable combination of the degree of anionization of the polyacrylamide and the viscosity of a 0.5% by mass aqueous solution at 25°C (where the solvent is a 4% by mass aqueous solution of sodium chloride) is an anionization degree of 6-40 mol% and an aqueous solution viscosity of 10-300 mPa·s, preferably an anionization degree of 7-40 mol% and an aqueous solution viscosity of 15-290 mPa·s, more preferably an anionization degree of 8-40 mol% and an aqueous solution viscosity of 20-280 mPa·s, and even more preferably an anionization degree of 8-39 mol% and an aqueous solution viscosity of 25-270 mPa·s.

[0022] The amount of polyacrylamide added to component (B) is preferably 0.001 to 0.12 parts by mass, more preferably 0.003 to 0.1 parts by mass, and even more preferably 0.005 to 0.08 parts by mass, per 100 parts by mass of cement of component (C), from the viewpoint of achieving both extrusion from the nozzle and self-supporting properties after lamination.

[0023] Furthermore, the mass ratio ((A) / (B)) of water-soluble hydroxyalkylalkylcellulose (component A) to polyacrylamide (component B) is preferably 80 / 20 to 99.9 / 0.1, more preferably 83 / 17 to 99.5 / 0.5, and even more preferably 85 / 15 to 99 / 1, from the viewpoint of providing water retention to the hydraulic composition for 3D printing and achieving both extrusion from the nozzle and self-supporting properties after lamination.

[0024] ((C) component) Examples of cements used in the present invention include ordinary Portland cement, rapid-hardening Portland cement, moderate-heat Portland cement, blast furnace cement, silica cement, fly ash cement, alumina cement, and ultra-rapid-hardening Portland cement.

[0025] ((D) component) Examples of water used in this invention include tap water and seawater, but tap water is preferred from the viewpoint of preventing salt damage.

[0026] The amount of water added to component (D) is preferably 25 to 70 parts by mass, more preferably 28 to 67 parts by mass, and even more preferably 30 to 65 parts by mass, per 100 parts by mass of cement.

[0027] Furthermore, the amount of water used in the hydraulic composition for 3D printing is preferably 15 to 70% by mass, more preferably 16 to 65% by mass, and even more preferably 17 to 60% by mass, relative to the amount of cement, or, in the case of adding fine aggregate as described later, the total amount of cement and fine aggregate, from the viewpoint of achieving both extrusion from the nozzle and self-supporting properties after layering.

[0028] ((E) component) In this invention, organic fibers, inorganic fibers, and the like are used as short fibers. Examples of organic fibers include polypropylene fibers, polyethylene fibers, vinylon fibers, acrylic fibers, and aramid fibers. Examples of inorganic fibers include glass fibers, basalt fibers, steel fibers, and carbon fibers.

[0029] The short fibers used in the present invention are preferably at least one selected from the group consisting of polypropylene fibers, polyethylene fibers, vinylon fibers, acrylic fibers, aramid fibers, glass fibers, basalt fibers, steel fibers, and carbon fibers, and are more preferably polypropylene fibers, polyethylene fibers, or vinylon fibers. Alternatively, commercially available short fibers used in so-called fiber-reinforced concrete may be used.

[0030] The average fiber length of the short fibers of component (E) is preferably 1 to 20 mm, more preferably 3 to 18 mm, and even more preferably 5 to 15 mm, from the viewpoint of the reinforcing effect of the hydraulic composition for 3D printing and extrusion from the nozzle.

[0031] The fineness (thickness) of the short fibers of component (E) is preferably 0.1 to 1000 decitex (dtex), more preferably 1 to 100 decitex (dtex).

[0032] The short fibers of component (E) are preferably linear in shape.

[0033] The amount of short fibers added to component (E) is preferably 0.1 to 3 parts by volume, more preferably 0.13 to 2 parts by volume, and even more preferably 0.15 to 1.5 parts by volume, per 100 parts by volume of the hydraulic composition for 3D printing, from the viewpoint of reinforcing effect of the hydraulic composition for 3D printing and extrusion from the nozzle. The volume of short fibers is calculated by dividing the mass by the density.

[0034] (Other ingredients) The hydraulic composition for 3D printing of the present invention may use an antifoaming agent to control the amount of bubbles entrained by water-soluble hydroxyalkylalkylcellulose. In the present invention, oxyalkylene-based, silicone-based, alcohol-based, mineral oil-based, fatty acid-based, fatty acid ester-based, and the like are used as antifoaming agents.

[0035] Examples of oxyalkylene-based defoaming agents include polyoxyalkylenes such as (poly)oxyethylene (poly)oxypropylene adducts; (poly)oxyalkylene alkyl ethers such as diethylene glycol heptyl ether, polyoxyethylene oleyl ether, polyoxypropylene butyl ether, polyoxyethylene polyoxypropylene 2-ethylhexyl ether, and oxyethylene oxypropylene adducts to higher alcohols with 8 or more carbon atoms or secondary alcohols with 12 to 14 carbon atoms; (poly)oxyalkylene (alkyl)aryl ethers such as polyoxypropylene phenyl ether and polyoxyethylene nonylphenyl ether; and alkylenes to acetylene alcohols such as 2,4,7,9-tetramethyl-5-decine-4,7-diol, 2,5-dimethyl-3-hexine-2,5-diol, and 3-methyl-1-butyne-3-ol. Examples include acetylene ethers obtained by addition polymerization of oxides; (poly)oxyalkylene fatty acid esters such as diethylene glycol oleate, diethylene glycol lauryl ester, and ethylene glycol distearate; (poly)oxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan trioleate; (poly)oxyalkylene alkyl (aryl) ether sulfate salts such as polyoxypropylene methyl ether sodium sulfate and polyoxyethylene dodecylphenol ether sodium sulfate; (poly)oxyalkylene alkyl phosphate esters such as (poly)oxyethylene stearyl phosphate; (poly)oxyalkylene alkylamines such as polyoxyethylene laurylamine; and polyoxyalkylene amides.

[0036] Examples of silicone-based defoaming agents include dimethyl silicone oil, silicone paste, silicone emulsion, organically modified polysiloxane (polyorganosiloxane such as dimethylpolysiloxane), and fluorosilicone oil.

[0037] Examples of alcohol-based defoaming agents include octyl alcohol, 2-ethylhexyl alcohol, hexadecyl alcohol, acetylene alcohol, and glycols.

[0038] Examples of mineral oil-based defoaming agents include kerosene and liquid paraffin. Examples of fatty acid-based antifoaming agents include oleic acid, stearic acid, and alkylene oxide adducts thereof. Examples of fatty acid ester-based defoaming agents include glycerin monolicinolate, alkenyl succinic acid derivatives, sorbitol monolaurate, sorbitol trioleate, and natural waxes.

[0039] In the present invention, it is preferable to use an oxyalkylene-based defoaming agent from the viewpoint of defoaming performance.

[0040] The amount of defoaming agent added is preferably 1 to 30 parts by mass, more preferably 3 to 29 parts by mass, and even more preferably 5 to 28 parts by mass, per 100 parts by mass of water-soluble hydroxyalkylalkylcellulose, which is component (A), or preferably 1 to 38% by mass, more preferably 3 to 36% by mass, and even more preferably 1 to 35% by mass, relative to the total mass of water-soluble hydroxyalkylalkylcellulose (A) and polyacrylamide (B).

[0041] The hydraulic composition for 3D printing of the present invention may further contain fine aggregate. Suitable fine aggregates include river sand, mountain sand, sea sand, land sand, silica sand, etc., which are commonly used in the production of ready-mix concrete and as fine aggregate for plastering. The particle size is preferably 0.075 to 5 mm, more preferably 0.075 to 2 mm, and even more preferably 0.075 to 1 mm.

[0042] The amount of fine aggregate added is preferably 15 to 85 parts by mass, more preferably 20 to 80 parts by mass, and even more preferably 25 to 75 parts by mass, out of 100 parts by mass of the total amount of cement and fine aggregate.

[0043] Furthermore, a portion of the fine aggregate may be replaced with an inorganic or organic bulking agent. In this case, examples of inorganic bulking agents include fly ash, blast furnace slag, talc, calcium carbonate, silica fume, marble powder (limestone powder), perlite, and shirasu balloons. Examples of organic bulking agents include expanded polystyrene beads and crushed expanded ethylene vinyl alcohol. Generally, inorganic or organic bulking agents with a particle size of 5 mm or less are used and are suitable for this purpose.

[0044] In the present invention, other water-soluble polymeric substances other than those mentioned above can be used for the purpose of further improving both extrudeability from the nozzle and self-supporting properties after lamination. In this case, examples of water-soluble polymeric substances include synthetic polymeric substances such as polyethylene glycol and polyvinyl alcohol, and polymeric substances derived from natural products such as pectin, gelatin, casein, dieutan gum, gellan gum, xanthan gum, gellan gum, locust bean gum, and guar gum. The amount of water-soluble polymeric substance added is preferably 0.01 to 1.0 parts by mass, more preferably 0.05 to 0.8 parts by mass, and even more preferably 0.1 to 0.6 parts by mass, per 100 parts by mass of cement.

[0045] In the hydraulic composition for 3D printing of the present invention, known water-reducing agents, setting retarders, setting accelerators, expanding agents, shrinkage-reducing agents, etc., may be used as needed, to the extent that they do not interfere with the effects of the present invention.

[0046] Examples of water-reducing agents include polycarboxylic acid-based compounds such as polycarboxylic acid ethers, polycarboxylic acid ethers and crosslinked polymers, polycarboxylic acid ethers and oriented polymers, polycarboxylic acid ethers and highly modified polymers, polyether carboxylic acid polymer compounds, maleic acid copolymers, maleic acid ester copolymers, maleic acid derivative copolymers, carboxyl group-containing polyethers, polycarboxylic acid group-containing multi-component polymers with terminal sulfone groups, polycarboxylic acid graft copolymers, polycarboxylic acid compounds, and polycarboxylic acid ether polymers. Examples of melamine-based compounds include melamine sulfonic acid formalin condensates, melamine sulfonate condensates, and melamine sulfonate polyol condensates. Examples of lignin-based compounds include lignin sulfonates and their derivatives. In the present invention, it is preferable to use a polycarboxylic acid-based water-reducing agent from the viewpoint of water-reducing effect and fluidity / flow retention. The amount of water-reducing agent added is preferably 0.1 to 5 parts by mass per 100 parts by mass of cement, which is component (C).

[0047] Examples of setting retarders include oxycarboxylic acids such as gluconic acid, citric acid, and glucoheptone, or their inorganic salts such as sodium, potassium, calcium, magnesium, and ammonium; sugars such as glucose, fructose, galactose, saccharose, xylose, arabinose, ribose, oligosaccharides, and dextran; and boric acid. The amount of setting retarder added is preferably 0.005 to 10 parts by mass per 100 parts by mass of cement.

[0048] Coagulation accelerators are broadly classified into inorganic compounds and organic compounds. Inorganic compounds include chlorides such as calcium chloride and potassium chloride, nitrites such as sodium nitrite and calcium nitrite, nitrates such as sodium nitrate and calcium nitrate, sulfates such as calcium sulfate, sodium sulfate and alum, thiocyanates such as sodium thiocyanate, hydroxides such as sodium hydroxide and potassium hydroxide, carbonates such as calcium carbonate, sodium carbonate and lithium carbonate, and alumina-based compounds such as water glass, aluminum hydroxide and aluminum oxide. Organic compounds include amines such as diethanolamine and triethanolamine, calcium salts of organic acids such as calcium formate and calcium acetate, and maleic anhydride. The amount of setting accelerator to be added is preferably 0.005 to 10 parts by mass per 100 parts by mass of cement, which is component (C).

[0049] Examples of expansive agents include ettringite-based expansive agents, lime-based expansive agents, and ettringite-lime composite expansive agents. The amount of expansive agent to be added is preferably 0.5 to 30 parts by mass, more preferably 1 to 30 parts by mass, and even more preferably 3 to 25 parts by mass, per 100 parts by mass of cement, which is component (C).

[0050] Examples of shrinkage reducing agents include lower or higher alcohol alkylene oxide adducts, glycol ether derivatives, and polyether derivatives. The amount of shrinkage reducing agent added is preferably 0.1 to 0.5 parts by mass, more preferably 0.15 to 0.45 parts by mass, and even more preferably 0.2 to 0.4 parts by mass, per 100 parts by mass of cement, which is component (C).

[0051] The hydraulic composition for 3D printing of the present invention is obtained by adding all components of (A) water-soluble hydroxyalkylalkylcellulose, (B) polyacrylamide, (C) cement, (D) water, (E) short fibers, and fine aggregate as needed, together and mixing them. Alternatively, (C) cement may be mixed with (A) water-soluble hydroxyalkylalkylcellulose, (B) polyacrylamide, and (E) short fibers in advance, and this mixture may be added to a mixer. If fine aggregate is also added at this time, the mixture and fine aggregate may be mixed together, and then (D) water may be added and mixed to prepare the hydraulic composition for 3D printing of the present invention. For mixing, it is recommended to use a commercially available mortar mixer or other mixer that conforms to JIS R5201.

[0052] As described above, the hydraulic composition for 3D printing of the present invention exhibits good extrusion from the nozzle and self-supporting properties after layering (layer self-supporting properties, low deformation of the lower layer when layered), as well as excellent water retention, making it suitable for additive manufacturing, and especially for 3D printing using the material extrusion method.

[0053] The method for manufacturing a three-dimensional object according to the present invention is characterized by pumping the above-described hydraulic composition for 3D printing of the present invention and constructing the object by layering it while moving the nozzle.

[0054] The method for manufacturing a three-dimensional object according to the present invention is preferably carried out using a 3D printer apparatus that includes a tank for storing the hydraulic composition for 3D printing of the present invention, piping connected to the tank for flowing the hydraulic composition for 3D printing, a pump for pumping the hydraulic composition for 3D printing from the tank, a nozzle for discharging the hydraulic composition for 3D printing that has been pumped through the piping, a means for moving the nozzle, and a control means for controlling the pump, the means for moving, etc. Alternatively, a hopper-integrated pump may be used, in which the tank for storing the hydraulic composition for 3D printing of the present invention and the pump for pumping the hydraulic composition for 3D printing from the tank are integrated into one unit. [Examples]

[0055] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, the viscosity of the 2% by mass aqueous solution of water-soluble hydroxyalkylalkylcellulose (2% by mass aqueous solution viscosity) was measured using a B-type rotational viscometer at 20°C. The degree of anionization in polyacrylamide was measured by colloidal titration, and the 0.5% by mass aqueous solution viscosity is the viscosity of an aqueous solution obtained by dissolving polyacrylamide in a 4% by mass aqueous sodium chloride solvent in an amount equal to 0.5% by mass, and was measured using a B-type rotational viscometer at 25°C.

[0056] [Examples 1-15, Comparative Examples 1-6] <Materials used> (1) Cement (C): Ordinary Portland cement (manufactured by Taiheiyo Cement Corporation) (2) Silica sand (S): Mikawa Silica Sand No. 56 (particle size 75-425 μm, manufactured by Mikawa Silica Co., Ltd.) (3) Water: Tap water (4) Water-soluble hydroxyalkylalkylcellulose (CE): Sample details are shown in Table 1. (5) Polyacrylamide (PA): Sample details are shown in Table 2. (6) Short fibers: Polypropylene fibers, average fiber length 6 mm, density 0.91 g / cm³ 3 , fineness 13 decitex (manufactured by Valchip Co., Ltd.) (7) Antifoaming agent: SN Deformer 14HP (manufactured by Sunopco Co., Ltd.)

[0057] [Table 1] HPMC: Hydroxypropylmethylcellulose HEMC: Hydroxyethylmethylcellulose

[0058] [Table 2]

[0059] <Preparation of hydraulic composition> Using a mortar mixer conforming to JIS R 5201, and based on the materials and proportions shown in Table 3, cement and silica sand were first placed in a mixing bowl and mixed for 60 seconds at low speed (rotational motion 140 rpm, planetary motion 60 rpm). Next, water was added and mixed for 180 seconds at low speed (rotational motion 140 rpm, planetary motion 60 rpm) to obtain a hydraulic composition. The material temperature was adjusted so that the final mixing temperature was within 20 ± 3°C. CE, PA, short fibers, and defoamer were pre-mixed with the cement and then added to the mixing bowl together with the cement.

[0060] [Table 3]

[0061] <Rating> (1) Extrusion Under the following pumping conditions, a score of ○ (good) indicated that the hydraulic composition could be uniformly discharged, while a score of × (poor) indicated that it could not be discharged due to blockage in the hose or nozzle. [Pump pumping conditions (equipment used and operating conditions)] A Mono Pump 2NVL15 (manufactured by Hyoshin Equipment Co., Ltd.), an integrated hopper pump, was used. A hose with an inner diameter of 38 mm and a length of 0.5 m was attached to the discharge port of the pump, and a nozzle with an opening of 15 mm in height and 30 mm in width was attached to the end of the hose, creating a mechanism for discharging a rectangular hydraulic composition. The nozzle was fixed with its opening facing horizontally, and the hydraulic composition was discharged (extruded) at a discharge speed of 0.5 L / min. The formed rectangular hydraulic composition (formed object) was picked up by a belt conveyor synchronized with the discharge speed. The pump operating frequency was 6 Hz. (2) Self-supporting stacking Under the pump feeding conditions described above, two types of objects were fabricated: a single-layer object (as extruded) with a length of 500 mm, and a three-layer laminate (three layers of the single-layer object immediately after extrusion). 24 hours after fabrication, the width of the first layer of each of the single-layer and three-layer laminates was measured using calipers at three locations (150 mm, 250 mm, and 350 mm in the length direction). The deformation rate was calculated using the average of the three width measurements and the following formula (1). A deformation rate of 6% or less was considered to indicate excellent layered self-supporting properties. Deformation rate (%) = {(width of the first layer of the 3-layer structure) - (width of the single-layer structure)} / width of the single-layer structure × 100 (1) (3) Water retention A water retention test was conducted in accordance with JIS A 6916 Annex A (Normative) Test method for mortar for tile application (A.2.3). If the water retention rate was 75% or higher, it was considered that water separation was suppressed. The evaluation results are shown in Table 4.

[0062] [Table 4]

[0063] As a result, Examples 1 to 15, which used CE, whose 2% by mass aqueous solution viscosity at 20°C was 2000 to 6000 mPa·s, and PA, whose anionization degree was 6 to 40 mol% and whose 0.5% by mass aqueous solution (where the solvent was a 4% by mass sodium chloride aqueous solution) viscosity at 25°C was 10 to 300 mPa·s, showed good pump extrusion, and the lamination self-supporting properties (rate of change in the lower layer when laminated) and water retention rate also met the standards. In Comparative Example 1, the viscosity of a 2% by mass aqueous solution of CE at 20°C was less than 2000 mPa·s, resulting in blockage in the hose due to insufficient lubrication of the mortar, and the water retention rate also did not meet the standard. In Comparative Example 2, the viscosity exceeded 6000 mPa·s, resulting in excessive viscosity of the mortar, large deformation due to its own weight, and the lamination self-supporting ability (rate of change of the lower layer when laminated) did not meet the standard. Furthermore, in Comparative Example 3, the degree of anionization of PA was less than 6 mol%, and in Comparative Example 5, the viscosity of a 0.5 mass% aqueous solution of PA at 25°C (where the solvent is a 4 mass% sodium chloride aqueous solution) was less than 10 mPa·s. As a result, the flocculation effect was low in both cases, leading to a large rate of change in the lower layer when stacked. On the other hand, in Comparative Example 4, the degree of anionization of PA exceeded 40 mol%, and in Comparative Example 6, the viscosity of a 0.5 mass% aqueous solution of PA at 25°C (where the solvent is a 4 mass% sodium chloride aqueous solution) exceeded 300 mPa·s. As a result, the flocculation effect of PA was too strong, causing blockage in the pressure hose.

Claims

1. A hydraulic composition comprising at least (A) water-soluble hydroxyalkylalkylcellulose, (B) polyacrylamide, (C) cement, (D) water, and (E) short fibers, (A) The viscosity of a 2% by mass aqueous solution of the water-soluble hydroxyalkylalkylcellulose of component (A) at 20°C is 2000 to 6000 mPa·s, and the degree of substitution (DS) of the alkoxy group of the water-soluble hydroxyalkylalkylcellulose is 1.0 to 2.

0. (B) The degree of anionization of the polyacrylamide is 6 to 40 mol%, and the viscosity of a 0.5 mass% aqueous solution of the polyacrylamide at 25°C (where the solvent is a 4 mass% aqueous solution of sodium chloride) is 10 to 300 mPa·s. (A) The amount of water-soluble hydroxyalkylalkylcellulose added is 0.1 to 0.6 parts by mass per 100 parts by mass of cement. The amount of polyacrylamide added to component (B) is 0.001 to 0.12 parts by mass per 100 parts by mass of cement. A hydraulic composition for 3D printing, wherein the mass ratio ((A) / (B)) of water-soluble hydroxyalkylalkylcellulose (component A) to polyacrylamide (component B) is 80 / 20 to 99.9 / 0.

1.

2. The hydraulic composition for 3D printing according to claim 1, wherein the mass ratio ((A) / (B)) of water-soluble hydroxyalkylalkylcellulose of component (A) to polyacrylamide of component (B) is 83 / 17 to 99.5 / 0.

5.

3. The hydraulic composition according to claim 1 or 2, wherein the amount of water-soluble hydroxyalkylalkylcellulose of component (A) added is 0.2 to 0.55 parts by mass per 100 parts by mass of cement.

4. The hydraulic composition according to claim 1 or 2, wherein the degree of substitution (DS) of the alkoxy group of the water-soluble hydroxyalkylalkylcellulose of component (A) is 1.3 to 2.

0.

5. The hydraulic composition according to claim 1 or 2, wherein the amount of polyacrylamide added to component (B) is 0.005 to 0.08 parts by mass per 100 parts by mass of cement.

6. The hydraulic composition for 3D printing according to claim 1 or 2, wherein the amount of short fibers of component (E) added is 0.1 to 3 parts by volume per 100 parts by volume of the hydraulic composition.

7. The hydraulic composition for 3D printing according to claim 1 or 2, wherein the short fibers of component (E) are at least one selected from the group consisting of polypropylene fibers, polyethylene fibers, vinylon fibers, acrylic fibers, aramid fibers, glass fibers, basalt fibers, steel fibers, and carbon fibers.

8. The hydraulic composition for 3D printing according to claim 1 or 2, further containing fine aggregate.

9. A method for manufacturing a three-dimensional object, comprising pumping the hydraulic composition for 3D printing described in claim 1 or 2 and constructing the object by layering it while moving the nozzle.

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