CN108296423B - Casting binder, preparation method thereof and method for preparing 3D printing precoated sand by using binder and modified straw powder - Google Patents
Casting binder, preparation method thereof and method for preparing 3D printing precoated sand by using binder and modified straw powder Download PDFInfo
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- CN108296423B CN108296423B CN201711024028.9A CN201711024028A CN108296423B CN 108296423 B CN108296423 B CN 108296423B CN 201711024028 A CN201711024028 A CN 201711024028A CN 108296423 B CN108296423 B CN 108296423B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/167—Mixtures of inorganic and organic binding agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
- B22C5/04—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose by grinding, blending, mixing, kneading, or stirring
- B22C5/0409—Blending, mixing, kneading or stirring; Methods therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y70/00—Materials specially adapted for additive manufacturing
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Abstract
The invention discloses a casting binder which is prepared from fatty alcohol sodium sulfate, alkylphenol ethoxylates, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent, water, hydroxyl-containing acrylate monomer, acrylate monomer with higher glass transition temperature, acrylate monomer with lower glass transition temperature and oxidant according to the mass ratio of 2-3:3-5:2:1-2:0.3-0.5:100:2-3:50-60:10-12: 0.3-0.5. Also discloses a method for preparing 3D printing precoated sand by using the modified straw powder, which comprises the following steps: pretreatment of straw powder; modifying raw sand; preparing the casting binder; and 3D printing preparation of precoated sand. The invention carries out modification treatment on the raw sand, and the raw sand is connected through chemical bonds, thereby enhancing the strength of the material. The phenolic resin is replaced, formaldehyde is not contained, and the environment is protected.
Description
Technical Field
The invention belongs to the technical field of preparation of casting materials, and particularly relates to a casting binder, a preparation method of the casting binder, and a method for preparing 3D printing coated sand by using the binder and modified straw powder.
Background
The binder is one of the essential raw materials for the casting production, and its role in the casting production is self-evident. The main function of the casting binder is to form a continuous binding film with a certain strength on the granular or powdery molding material to form a casting mold. The binding mechanism of the binder is divided into a physical film-forming binder and a chemical film-forming binder. The research and popularization of the clean and nontoxic binder are beneficial to energy conservation and emission reduction in the casting industry, and can effectively reduce pollution and protect the environment. The development of application research of the novel adhesive for casting is of great significance.
The performance of the binder has an important influence on the quality of the precoated sand, people are dedicated to research on how to improve the performance of the phenolic resin, and foreign countries have developed special resins with different performances, such as high-strength low-gas-forming resin, easy-collapsibility resin and the like, and reports that the modified polyester resin is adopted to replace the phenolic resin are also provided, but the modified phenolic resin is not comprehensively popularized and is still generally adopted.
Most of the existing 3D printing precoated sand uses phenolic resin as a coating agent, and few of the prior 3D printing precoated sand modifies the original sand and slightly crosslinks the resin through chemical bonds to enhance the strength of the material. The modifier is needed to modify the raw sand to achieve the purpose of enhancing the strength of the material. The straws are rich in a large number of hydroxyl functional groups, so that the straws can be used as a modifier, the raw sand and the straws can be subjected to graft polymerization reaction by a certain chemical means, and the raw sand and the straws are connected by chemical bonds to realize the modification treatment of the raw sand. Because the straw is agricultural waste, the cost is reduced by using the straw, and the problem of environmental pollution caused by straw burning is solved.
Disclosure of Invention
The invention aims to provide a casting binder and a preparation method thereof.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the casting binder is prepared from 2-3:3-5:2:1-2:0.3-0.5:100:2-3:50-60:10-12:0.3-0.5 by mass ratio of sodium fatty alcohol sulfate, alkylphenol polyoxyethylene, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent, water, hydroxyl-containing acrylate monomer, acrylate monomer with higher glass transition temperature, acrylate monomer with lower glass transition temperature and oxidant.
Preferably, the hydroxyl-containing acrylate monomer is one or more of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and acrylic acid;
the acrylate monomer with higher glass transition temperature is one or more of isobornyl methacrylate, methacrylic acid and methyl methacrylate;
the acrylate monomer with lower glass transition temperature is one or more of hexyl methacrylate, butyl acrylate and n-octyl acrylate.
The preparation method of the casting binder comprises the following steps:
a: weighing and mixing fatty alcohol sodium sulfate, alkylphenol ethoxylates, electrolyte, a sodium dihydrogen phosphate buffer system, a reducing agent and water according to a mass ratio at the temperature of 74-86 ℃ to obtain a mixed solution A;
b: weighing and mixing hydroxyl-containing acrylate monomers, acrylate monomers with higher glass transition temperature and acrylate monomers with lower glass transition temperature according to a mass ratio to obtain a mixed solution B;
c: pouring the mixed solution B into the mixed solution A, and stirring for 11-18 min to obtain a pre-emulsion;
d: and mixing the pre-emulsion and water according to the mass ratio of 1:1, dropwise adding an oxidant, and carrying out heat preservation reaction to obtain the casting binder.
Furthermore, in the step D, dropwise adding an oxidant into the mixed solution within 1h at the temperature of 72-78 ℃, and then carrying out heat preservation reaction for 6 h.
The application of the casting binder in the preparation method of the 3D printing precoated sand.
The raw materials of the casting binder disclosed by the invention do not contain phenolic resin, so that the prepared casting binder does not contain formaldehyde, and is safer and more environment-friendly. Meanwhile, the casting binder disclosed by the invention is good in bonding effect, is more suitable for being used in preparation of precoated sand, and can improve the strength of a precoated sand casting. In addition, the preparation method adopted by the invention is simple to operate, and the preparation process is environment-friendly and pollution-free.
A method for preparing 3D printing precoated sand by using modified straw powder comprises the following steps:
(1) pretreatment of straw powder: at room temperature, putting 6-8 parts of IPDI and 0.3-0.5 part of initiator into a reaction vessel, then dropwise adding 12 parts of octadecanol, reacting at constant temperature for 1.8-2.4h, and taking out reaction liquid; soaking the straw powder in distilled water, a sodium hydroxide solution and an ethanol solution in sequence, and drying the straw powder to constant weight; mixing the straw powder and the reaction liquid according to the mass ratio of 100-120:8, performing melt modification after mixing, and cooling to obtain modified straw powder;
(2) raw sand modification treatment: washing raw sand with water, soaking the raw sand for 24 hours in an acid solution with the concentration of 1-5mol/L, and taking out the raw sand to dry; weighing the dried raw sand, the modified straw powder and the coupling agent according to the mass ratio of 100-120:25-30:3-5, mixing and stirring, and cooling to room temperature to obtain modified raw sand;
(3) preparation of a casting binder: preparing a casting binder according to the preparation method of the casting binder;
(4) preparation of 3D printing precoated sand: mixing and stirring the modified raw sand, the casting binder, the reinforcing agent, the toughening agent and the lubricant according to the mass ratio of 150-180:30-50:10-15:8-10:2-3, and cooling the mixture to obtain the 3D printing coated sand.
Furthermore, the 3D printing coated sand obtained in the step (4) is crushed, and the particle size of the crushed 3D printing coated sand is 180-200 meshes.
Furthermore, the drying temperature in the step (2) is 100-; the temperature during mixing and stirring is 180-220 ℃, and the mixing and stirring is carried out for 0.9-1.2 h.
Furthermore, the modified raw sand obtained after cooling in the step (2) is crushed, and the particle size of the crushed modified raw sand is 180-200 meshes.
Furthermore, the mixing and stirring time in the step (4) is 26min-35 min.
Compared with the prior art, the invention has the advantages that:
according to the invention, the straw powder is modified, the raw sand is grafted and polymerized with the cellulose in the modified straw powder through the coupling agent, then the raw sand reacts with the prepared casting binder, and the raw sand is connected by chemical bonds instead of intermolecular forces, so that the material strength is enhanced. The normal-temperature tensile strength of a casting film prepared by the 3D printing precoated sand prepared by the method is 4.1-5.0MPa, the normal-temperature bending strength is 2.9-3.4MPa, and the strength of the casting film is far higher than that of a casting film prepared by 3D printing precoated sand sold in the market.
Meanwhile, the casting binder prepared by the method replaces phenolic resin, does not contain formaldehyde, and is safer and more environment-friendly. But also changes the straws which are usually burnt by people into valuable, reduces the pollution to the environment and has lower cost.
Detailed Description
The following will clearly and completely describe the technical solutions in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the embodiment, an extruder is used for carrying out melting modification treatment on the straw powder, wherein the screw from the feeding hole to the discharging hole is divided into three regions, namely a conveying section, a melting section and a smelting section. The temperature of the conveying section is not too high, and the conveying and the shearing action of the materials in the conveying section are influenced by the too high temperature; if the temperature is too low, the screw is stressed too much or is easy to be locked. The temperature of the conveying section is generally slightly close to the temperature of the melting section. The temperature of the melting section is too low, and the cladding property of the rear section is poor; if the temperature is too high, the warm refining and shearing action becomes small, and even high-temperature degradation occurs. And in the smelting section, materials are thinned and dispersed in the section to form an ideal size and structure. According to the raw materials used in the present invention, the temperature of the conveying section of the extruder used in the present embodiment is 80-100 ℃, the temperature of the melting section is 100-.
In the embodiment, when the extruder is used for melt modification, the rotation speed of the main machine of the extruder is controlled to be 12-15 rpm, and the feeding speed is controlled to be 100-150 rpm.
Example 1
In this embodiment, the method for preparing 3D printing coated sand by using modified straw powder includes the following steps:
(1) pretreatment of straw powder: at room temperature, 6 parts of IPDI and 0.4 part of organotin initiator are placed in a reaction vessel, then 12 parts of octadecanol are added drop by drop, and after a constant temperature reaction for 1.8h, reaction liquid is taken out; soaking the straw powder in distilled water, a sodium hydroxide solution and an ethanol solution in sequence, and drying the straw powder to constant weight; mixing the straw powder and the reaction liquid according to the mass ratio of 100:8, carrying out melt modification after mixing, and cooling to obtain modified straw powder;
wherein, the rotating speed of a main machine of an extruder used for melt modification is controlled at 13 revolutions per minute, and the feeding speed is controlled at 120 revolutions per minute; the temperature of the conveying section of the extruder is 80 ℃, the temperature of the melting section is 100 ℃, and the temperature of the melting section is 120 ℃;
(2) raw sand modification treatment: washing raw sand with water, soaking the raw sand in an acid solution with the concentration of 3mol/L for 24 hours, taking out the raw sand, drying the raw sand at 150 ℃, and taking out the raw sand after drying; weighing the raw sand, the modified straw powder, the silane coupling agent and the titanate coupling agent mixture according to the mass ratio of 100:25:5, mixing and stirring at 200 ℃, cooling to room temperature, crushing, and taking the modified raw sand with the particle size of 180 meshes;
(3) preparation of a casting binder:
weighing a mixture of fatty alcohol sodium sulfate, alkylphenol polyoxyethylene, electrolyte, a sodium dihydrogen phosphate buffer system, a reducing agent, water, 2-hydroxyethyl acrylate, isobornyl methacrylate, hexyl methacrylate and n-octyl acrylate and an oxidizing agent according to the mass ratio of 2:3:2:1:0.5:100:2:50:12: 0.4.
A: mixing fatty alcohol sodium sulfate, alkylphenol polyoxyethylene, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent and water at 74 ℃ to obtain mixed solution A;
b: mixing 2-hydroxyethyl acrylate, isobornyl methacrylate, hexyl methacrylate and n-octyl acrylate to obtain a mixed solution B;
c: pouring the mixed solution B into the mixed solution A, and stirring for 11min to obtain a pre-emulsion;
d: mixing the pre-emulsion and water in a mass ratio of 1:1 in a reaction kettle, dropwise adding an oxidant into the reaction kettle within 1h at the temperature of 72 ℃, and carrying out heat preservation reaction for 6h to obtain the casting binder.
(4) Preparation of 3D printing precoated sand: mixing and stirring the modified raw sand, the casting binder, the glass fiber, the methyl methacrylate resin and the paraffin wax for 29min according to the mass ratio of 150:30:15:8:3, cooling the mixture, crushing, and taking 3D printing precoated sand with the particle size of 180 meshes.
Example 2
In this embodiment, the method for preparing 3D printing coated sand by using modified straw powder includes the following steps:
(1) pretreatment of straw powder: at room temperature, placing 7 parts of IPDI and 0.5 part of organotin initiator in a reaction vessel, then dropwise adding 12 parts of octadecanol, reacting at constant temperature for 2.0h, and taking out reaction liquid; soaking the straw powder in distilled water, a sodium hydroxide solution and an ethanol solution in sequence, and drying the straw powder to constant weight; mixing the straw powder and the reaction liquid according to the mass ratio of 110:8, carrying out melt modification after mixing, and cooling to obtain modified straw powder;
wherein, the rotating speed of a main machine of an extruder used for melt modification is controlled at 14 revolutions per minute, and the feeding speed is controlled at 100 revolutions per minute; the temperature of the conveying section of the extruder is 100 ℃, the temperature of the melting section is 110 ℃, and the temperature of the melting section is 110 ℃;
(2) raw sand modification treatment: washing raw sand with water, soaking the raw sand for 24 hours in an acid solution with the concentration of 4mol/L, taking out the raw sand, drying the raw sand at 100 ℃, and taking out the raw sand after drying; weighing the raw sand, the modified straw powder and the titanate coupling agent according to the mass ratio of 120:27:4, mixing and stirring at 180 ℃, cooling to room temperature, crushing, and taking the modified raw sand with the particle size of 190 meshes to obtain modified raw sand;
(3) preparation of a casting binder:
weighing fatty alcohol sodium sulfate, alkylphenol polyoxyethylene, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent, water, 2-hydroxypropyl acrylate, a mixture of methacrylic acid and methyl methacrylate, n-octyl acrylate and oxidizing agent according to the mass ratio of 2.5:4:2:1:0.3:100:2:55:11: 0.3.
A: mixing fatty alcohol sodium sulfate, alkylphenol polyoxyethylene, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent and water at 76 ℃ to obtain mixed solution A;
b: mixing acrylic acid-2-hydroxypropyl ester, methacrylic acid, methyl methacrylate and n-octyl acrylate to obtain a mixed solution B;
c: pouring the mixed solution B into the mixed solution A, and stirring for 15min to obtain a pre-emulsion;
d: mixing the pre-emulsion and water in a mass ratio of 1:1 in a reaction kettle, dropwise adding an oxidant into the reaction kettle within 1h at the temperature of 75 ℃, and carrying out heat preservation reaction for 6h to obtain the casting binder.
(4) Preparation of 3D printing precoated sand: mixing and stirring the modified raw sand, the casting binder, the mixture of carbon black and silicon dioxide, ethyl methacrylate resin and fatty amide according to the mass ratio of 160:35:10:9:2 for 26min, cooling the mixture, crushing, and taking 3D printing precoated sand with the particle size of 190 meshes.
Example 3
In this embodiment, the method for preparing 3D printing coated sand by using modified straw powder includes the following steps:
(1) pretreatment of straw powder: at room temperature, putting 8 parts of IPDI and 0.3 part of organic bismuth initiator into a reaction container, then dropwise adding 12 parts of octadecanol, reacting at constant temperature for 2.0h, and taking out reaction liquid; soaking the straw powder in distilled water, a sodium hydroxide solution and an ethanol solution in sequence, and drying the straw powder to constant weight; mixing the straw powder and the reaction liquid according to the mass ratio of 120:8, carrying out fusion modification after mixing, and cooling to obtain modified straw powder;
wherein, the rotating speed of a main machine of an extruder used for melt modification is controlled at 15 revolutions per minute, and the feeding speed is controlled at 130 revolutions per minute; the temperature of the conveying section of the extruder is 90 ℃, the temperature of the melting section is 100 ℃, and the temperature of the melting section is 110 ℃;
(2) raw sand modification treatment: cleaning raw sand with water, soaking the raw sand for 24 hours in an acid solution with the concentration of 5mol/L, taking out the raw sand, drying the raw sand at 180 ℃, and taking out the raw sand after drying; weighing the raw sand, the modified straw powder and the titanate coupling agent according to the mass ratio of 110:29:5, mixing and stirring at 210 ℃, cooling to room temperature, crushing, and taking the particle size of 200 meshes to obtain modified raw sand;
(3) preparation of a casting binder:
weighing fatty alcohol sodium sulfate, alkylphenol polyoxyethylene, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent, water, a mixture of acrylic acid-2-hydroxypropyl acrylate and acrylic acid, a mixture of methacrylic acid and methyl methacrylate, butyl acrylate and oxidizing agent according to the mass ratio of 2:5:2:1.5:0.4:100:3:60:10: 0.5.
A: mixing fatty alcohol sodium sulfate, alkylphenol polyoxyethylene, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent and water at 80 ℃ to obtain mixed solution A;
b: mixing acrylic acid-2-hydroxypropyl ester, acrylic acid, methacrylic acid, methyl methacrylate and butyl acrylate to obtain a mixed solution B;
c: pouring the mixed solution B into the mixed solution A, and stirring for 18min to obtain a pre-emulsion;
d: mixing the pre-emulsion and water in a mass ratio of 1:1 in a reaction kettle, dropwise adding an oxidant into the reaction kettle within 1h at the temperature of 78 ℃, and carrying out heat preservation reaction for 6h to obtain the casting binder.
(4) Preparation of 3D printing precoated sand: mixing and stirring the modified raw sand, the casting binder, manganese dioxide, vinyl acetate resin and metal soap type calcium stearate according to the mass ratio of 170:50:12:10:3 for 30min, cooling the mixture, crushing, and taking 3D printing precoated sand with the particle size of 200 meshes after crushing.
Example 4
In this embodiment, the method for preparing 3D printing coated sand by using modified straw powder includes the following steps:
(1) pretreatment of straw powder: at room temperature, 6.5 parts of IPDI, 0.4 part of organotin initiator and organobismuth initiator mixture are placed in a reaction vessel, 12 parts of octadecanol is added dropwise, and after 2.4 hours of constant temperature reaction, reaction liquid is taken out; soaking the straw powder in distilled water, a sodium hydroxide solution and an ethanol solution in sequence, and drying the straw powder to constant weight; mixing the straw powder and the reaction liquid according to the mass ratio of 115:8, carrying out melt modification after mixing, and cooling to obtain modified straw powder;
wherein, the rotating speed of a main machine of an extruder used for melt modification is controlled at 12 revolutions per minute, and the feeding speed is controlled at 150 revolutions per minute; the temperature of the conveying section of the extruder is 90 ℃, the temperature of the melting section is 120 ℃, and the temperature of the melting section is 120 ℃;
(2) raw sand modification treatment: cleaning raw sand with water, soaking the raw sand for 24 hours in an acid solution with the concentration of 1mol/L, taking out the raw sand, drying the raw sand at 200 ℃, and taking out the raw sand after drying; weighing the raw sand, the modified straw powder and the silane coupling agent according to the mass ratio of 106:30:3, mixing and stirring at 220 ℃, cooling to room temperature, crushing, and taking the particle size of 200 meshes to obtain modified raw sand;
(3) preparation of a casting binder:
weighing fatty alcohol sodium sulfate, alkylphenol polyoxyethylene, electrolyte, a sodium dihydrogen phosphate buffer system, a reducing agent, water, a mixture of 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate, isobornyl methacrylate, hexyl methacrylate and an oxidizing agent according to the mass ratio of 3:3:2: 0.4:100:3:50:12: 0.4.
A: mixing fatty alcohol sodium sulfate, alkylphenol polyoxyethylene, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent and water at 86 ℃ to obtain mixed solution A;
b: mixing acrylic acid-2-hydroxyethyl ester, acrylic acid-2-hydroxypropyl ester, acrylic acid, isobornyl methacrylate and glass methyl hexyl acrylate to obtain a mixed solution B;
c: pouring the mixed solution B into the mixed solution A, and stirring for 16min to obtain a pre-emulsion;
d: mixing the pre-emulsion and water in a mass ratio of 1:1 in a reaction kettle, dropwise adding an oxidant into the reaction kettle within 1h at the temperature of 76 ℃, and carrying out heat preservation reaction for 6h to obtain the casting binder.
(4) Preparation of 3D printing precoated sand: mixing and stirring the modified raw sand, the casting binder, carbon black, a mixture of vinyl acetate resin and methyl methacrylate resin, and a mixture of higher fatty acid and fatty amide according to a mass ratio of 180:40:14:9:2 for 35min, cooling the mixture, crushing, and crushing to obtain the 3D printing precoated sand with the particle size of 200 meshes.
Comparative example 1
The preparation method of the commercially available 3D printing precoated sand comprises the following process steps:
(1) pretreating the gem sand: washing the jewellery sand with water, soaking the jewellery sand in a hexadecyl trimethyl ammonium bromide aqueous solution with the mass percentage concentration of 1%, standing at room temperature for 10 hours, filtering, washing with water to be neutral, and drying to obtain pretreated jewellery sand;
(2)3D printing precoated sand preparation: adding 89% of pretreated jewel sand, 5% of thermoplastic polyimide, 4% of phenolic resin, 1.0% of bisphenol A dianhydride and 1.0% of glycerin monostearate into a stirrer according to mass percentage, starting the stirrer to rotate at 120 revolutions per minute, grinding for 30min, adding 1 mL/9 g of acetone according to the liquid-solid ratio of the added acetone to the jewel sand, starting a grinder to rotate at 120 revolutions per minute, grinding for 30min, and drying to obtain the 3D printing precoated sand.
The 3D printing coated sand prepared in examples 1 to 4 and the commercially available 3D printing coated sand in comparative example 1 were subjected to performance tests, respectively, to obtain the following test results:
1. normal temperature tensile strength performance test
The casting films prepared from the 3D printing precoated sand prepared in the examples 1 to 4 and the casting films prepared from the commercially available 3D printing precoated sand in the comparative example 1 were subjected to a room-temperature tensile strength performance test, and the test results are shown in the following table:
| example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 | |
| Tensile strength/MPa at normal temperature | 4.1 | 4.2 | 5.0 | 4.9 | 3.8 |
As can be seen from the table above, the cast film piece prepared from the 3D printing precoated sand prepared by the method has higher tensile strength at normal temperature than the cast film piece prepared from the commercially available 3D printing precoated sand.
2. Normal temperature bending strength test
The 3D-printed precoated sand prepared in examples 1 to 4 was used to prepare a casting, and the 3D-printed precoated sand prepared in the commercial market in comparative example 1 was used to prepare a casting, and the bending strength test was performed, and the test results are shown in the following table:
| example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 | |
| Normal temperature bending strength/MPa | 3.0 | 2.9 | 3.4 | 3.1 | 2.4 |
As can be seen from the table above, the cast film prepared from the 3D printing precoated sand prepared by the invention has higher bending strength at normal temperature than the cast film prepared from the commercially available 3D printing precoated sand.
3. Formaldehyde content test
The 3D printing coated sand prepared in examples 1 to 4 and the commercially available 3D printing coated sand in comparative example 1 were subjected to a formaldehyde content test, and the test results are shown in the following table:
| example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 | Environment(s) | |
| Formaldehyde content/mg/m3 | 0.18 | 0.18 | 0.18 | 0.18 | 12.7 | 0.18 |
As can be seen from the above table, compared with the commercially available 3D printing coated sand, the 3D printing coated sand prepared by the present invention does not contain formaldehyde.
4. Cost comparison
The cost of the 3D printing precoated sand prepared by the embodiments 1-4 is 1.0 yuan/kg, 1.3 yuan/kg, 1.4 yuan/kg and 1.3 yuan/kg respectively, while the cost of the 3D printing precoated sand sold in the market is 2.0-8.0 yuan/kg, so that the product of the invention is low in price and can be used for large-scale mass production.
According to the invention, the straw powder is modified, the raw sand is grafted and polymerized with the cellulose in the modified straw powder through the coupling agent, and then reacts with the prepared casting binder to replace intermolecular force connection and connect through chemical bonds, so that the material strength is enhanced. The normal-temperature tensile strength of a casting film prepared by the 3D printing precoated sand prepared by the method is 4.1-5.0MPa, the normal-temperature bending strength is 2.9-3.4MPa, and the strength of the casting film is far higher than that of a casting film prepared by 3D printing precoated sand sold in the market.
Meanwhile, the casting binder prepared by the method replaces phenolic resin, does not contain formaldehyde, and is safer and more environment-friendly. But also changes the straws which are usually burnt by people into valuable, reduces the pollution to the environment and has lower cost.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. The casting binder is characterized by being prepared from fatty alcohol sodium sulfate, alkylphenol ethoxylate, electrolyte, sodium dihydrogen phosphate buffer system, reducing agent, water, hydroxyl-containing acrylate monomer, acrylate monomer with higher glass transition temperature, acrylate monomer with lower glass transition temperature and oxidant according to the mass ratio of 2-3:3-5:2:1-2:0.3-0.5: 2-3:50-60:10-12: 0.3-0.5.
2. The foundry binder of claim 1, wherein the hydroxyl-containing acrylate monomer is one or more of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and acrylic acid;
the acrylate monomer with higher glass transition temperature is one or more of isobornyl methacrylate, methacrylic acid and methyl methacrylate;
the acrylate monomer with lower glass transition temperature is one or more of hexyl methacrylate, butyl acrylate and n-octyl acrylate.
3. A method of preparing a foundry binder as defined in claim 1 or 2, including the steps of:
a: weighing and mixing fatty alcohol sodium sulfate, alkylphenol ethoxylates, electrolyte, a sodium dihydrogen phosphate buffer system, a reducing agent and water according to a mass ratio at the temperature of 74-86 ℃ to obtain a mixed solution A;
b: weighing and mixing hydroxyl-containing acrylate monomers, acrylate monomers with higher glass transition temperature and acrylate monomers with lower glass transition temperature according to a mass ratio to obtain a mixed solution B;
c: pouring the mixed solution B into the mixed solution A, and stirring for 11-18 min to obtain a pre-emulsion;
d: and mixing the pre-emulsion and water according to the mass ratio of 1:1, dropwise adding an oxidant, and carrying out heat preservation reaction to obtain the casting binder.
4. The preparation method of the foundry binder according to claim 3, characterized in that in the step D, the oxidant is dropwise added into the mixed solution within 1h at the temperature of 72-78 ℃, and then the mixture is subjected to heat preservation reaction for 6 h.
5. Use of the foundry binder of claim 1 or 2 in a method of preparing 3D-printed precoated sand.
6. A method for preparing 3D printing precoated sand by using modified straw powder is characterized by comprising the following steps:
(1) pretreatment of straw powder: at room temperature, putting 6-8 parts of IPDI and 0.3-0.5 part of initiator into a reaction vessel, then dropwise adding 12 parts of octadecanol, reacting at constant temperature for 1.8-2.4h, and taking out reaction liquid; soaking the straw powder in distilled water, a sodium hydroxide solution and an ethanol solution in sequence, and drying the straw powder to constant weight; mixing the straw powder and the reaction liquid according to the mass ratio of 100-120:8, performing melt modification after mixing, and cooling to obtain modified straw powder;
(2) raw sand modification treatment: cleaning raw sand with water, soaking the raw sand for 24 hours in an acid solution with the concentration of 1-5mol/L, taking out the raw sand, drying, and taking out the raw sand; weighing the raw sand, the modified straw powder and the coupling agent according to the mass ratio of 100-;
(3) preparation of a casting binder: preparing a foundry binder in accordance with the method of preparing a foundry binder of claim 3;
(4) preparation of 3D printing precoated sand: mixing and stirring the modified raw sand, the casting binder, the reinforcing agent, the toughening agent and the lubricant according to the mass ratio of 150-180:30-50:10-15:8-10:2-3, and cooling the mixture to obtain the 3D printing coated sand.
7. The method for preparing 3D printing coated sand by using modified straw powder as claimed in claim 6, further comprising a crushing step of crushing the 3D printing coated sand obtained in the step (4), wherein the particle size of the crushed 3D printing coated sand is 180-200 meshes.
8. The method for preparing 3D printing coated sand by using the modified straw powder as claimed in claim 6 or 7, wherein the mixing and stirring time in the step (4) is 26-35 min.
9. The method for preparing 3D printing coated sand by using modified straw powder as claimed in claim 6 or 7, wherein the drying temperature in the step (2) is 100-200 ℃; the temperature during mixing and stirring is 180-220 ℃, and the mixing and stirring is carried out for 0.9-1.2 h.
10. The method for preparing 3D printing coated sand by using modified straw powder as claimed in claim 9, wherein the modified raw sand obtained after cooling in step (2) is crushed, and the particle size of the crushed modified raw sand is 180-200 meshes.
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