CN114012029A - Amino resin modified silica sol and preparation method thereof - Google Patents
Amino resin modified silica sol and preparation method thereof Download PDFInfo
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- CN114012029A CN114012029A CN202111513769.XA CN202111513769A CN114012029A CN 114012029 A CN114012029 A CN 114012029A CN 202111513769 A CN202111513769 A CN 202111513769A CN 114012029 A CN114012029 A CN 114012029A
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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
- B22C1/18—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 of inorganic agents
- B22C1/186—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 of inorganic agents contaming ammonium or metal silicates, silica sols
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G12/00—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
- C08G12/02—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
- C08G12/26—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with heterocyclic compounds
- C08G12/34—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with heterocyclic compounds and acyclic or carbocyclic compounds
- C08G12/36—Ureas; Thioureas
- C08G12/38—Ureas; Thioureas and melamines
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Abstract
The invention discloses amino resin modified silica sol and a preparation method thereof, belonging to the technical field of high-precision metal investment casting. The silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 1-5% of the total mass of the silica sol, and the balance is the alkaline silica sol. According to the invention, a proper amount of amino resin is added into the traditional silica sol binder for modification, the bending strength of the finally obtained shell at normal temperature is more than 7MPa, and the roasting bending strength can be more than 11 MPa. The method has the advantages of greatly improving the wet strength and the roasting strength of the shell, reducing the residual strength, shortening the drying time, reducing the deformation of the shell, being easy to demould, having smooth surface of the casting, being simple and feasible in process, being suitable for large-scale popularization and application and having wide economic benefit.
Description
Technical Field
The invention belongs to the technical field of high-precision metal investment casting, and particularly relates to amino resin modified silica sol and a preparation method thereof.
Background
Investment precision casting refers to the process of making wax sample with wax, coating the surface of the wax sample with a plurality of layers of refractory materials such as clay and binder, heating to melt the wax and flow out, thereby obtaining a shell formed by the refractory materials, then pouring the molten metal into a shell type cavity, and after the metal is cooled, breaking the refractory materials to obtain a metal part, wherein the process for processing the metal is called investment precision casting, also called investment casting or lost wax casting. Investment precision casting production process is very complicated, mainly has the processes such as compression molding design, wax matrix preparation, shell preparation, pouring, clearance and heat treatment, and a lot of research has been carried out to investment casting in the industry at present.
The preparation of the shell is one of important links in investment casting, and how to master the process technology and the operation method of the process and know the physical and chemical reaction generated by shell manufacturing has key influence on formulating a reasonable operation process. Therefore, the analysis of the shell preparation technology is carried out, the influence of different process methods on the production of precision castings is researched, and the important significance is achieved for improving the shell preparation technology to produce high-quality precision castings, improving the production efficiency and improving the production environment. The common shell preparation processes at present comprise a water glass shell preparation process, a silica sol shell preparation process, a water glass-silica sol composite process, a 3D printing rapid shell preparation technology and the like.
The shell-making process of silica sol is a casting process which is frequently used at present, the silica sol is used as an adhesive, and the shell of the shell has high surface roughness and high dimensional accuracy, high-temperature strength and high-temperature deformation resistance, and particularly shows superiority when being applied to high-alloy castings. At present, most casting enterprises adopt the method to produce the stainless steel precision casting. However, in the process of preparing the shell, some technical problems such as cracking of the shell are often encountered. Therefore, how to effectively improve the normal temperature strength of the wax model shell and reduce the residual strength of the wax model shell is a technical problem to be solved urgently at present.
Disclosure of Invention
Aiming at the technical problems generated by the application of silica sol in the prior art, the invention provides the amino resin modified silica sol and the preparation method thereof, so as to greatly improve the strength of a shell, reduce the residual strength, shorten the drying time and improve the production efficiency.
In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:
the amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 1-5% of the mass percent, and the balance is the alkaline silica sol.
Further, the alkaline silica sol has a colloidal particle diameter of 10-20nm, a pH of 9-11 and SiO2The content is 20-30%.
Further, the preparation method of the amino resin comprises the following steps:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at constant temperature of 35-40 ℃ for 10-20 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 10-20min to obtain a pre-reaction mixed solution;
(2) heating the pre-reaction mixed solution to 60-70 ℃, adding 0.1-0.5% polyamine cross-linking agent by mass percent under stirring, reacting for 3-5h at 70-80 ℃, then repeatedly washing by using 3% HCl, 3% pure water, 3% NaOH and pure water by mass concentration, carrying out petroleum ether extraction for 12-24h, and carrying out vacuum drying to obtain the amino resin.
Further, the acid in the step (1) is oxalic acid, sulfuric acid or phosphoric acid.
Further, the adding mode of the urea in the step (1) is as follows: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
Further, the polyamine crosslinking agent in the step (2) is obtained by mixing a polyamine compound and azoisobutyronitrile according to a mass ratio of 1: 1; the polyamine compound is one or more of diethylenetriamine, hexamethyltriethylenetetramine and pentamethyldiethylenetriamine.
A preparation method of amino resin modified silica sol comprises the following steps:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin in alkaline silica sol according to the mass ratio, and stirring and mixing uniformly.
The various materials used in the examples of the present invention are commercially available.
The melamine-formaldehyde copolymer resin with a three-dimensional network structure is prepared by a precipitation polymerization method, then a large number of amino groups are grafted under the action of azoisobutyronitrile through polyamine crosslinking reaction to form amino resin which is taken as an amino group of a hydrogen bond acceptor, and the amino resin and silica sol realize effective combination under the combined action of hydrogen bonds of silica particles with silanol groups and intermolecular van der Waals force, wherein macroscopic expression is uniform dispersion and adsorption of the silica sol particles, so that the bonding force of a substrate is greatly improved, the adhesive force of the substrate on the surface of a wax film is enhanced, and the overall strength of the substrate is finally improved. Meanwhile, the three-dimensional net-shaped structure can reduce the agglomeration of silica sol particles, promote the evaporation and diffusion of water molecules, reduce the drying time to a certain extent and improve the process efficiency.
Advantageous effects
According to the invention, a proper amount of amino resin is added into the traditional silica sol binder for modification, so that the wet strength and the roasting strength of the shell are greatly improved, the residual strength is reduced, the drying time is shortened, the shell deformation is small, the demolding is easy, the surface of the casting is smooth, the process is simple and feasible, the method is suitable for large-scale popularization and application, and the economic benefit is wide.
Drawings
FIG. 1 is a graph showing the change in flexural strength with the amount of amino resin added.
Detailed Description
The technical solution of the present invention is further described below with reference to specific embodiments, but is not limited thereto.
Example 1
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 1% by mass, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
The preparation method of the amino resin comprises the following steps:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at constant temperature of 35-40 ℃ for 10 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 10min to obtain a pre-reaction mixed solution;
(2) heating the pre-reaction mixed solution to 60-70 ℃, sequentially adding 0.1 mass percent of polyamine cross-linking agent while stirring, reacting for 3 hours at 70-80 ℃, then repeatedly washing with 3 percent of HCl, pure water, 3 percent of NaOH and pure water, carrying out petroleum ether extraction for 12 hours, and carrying out vacuum drying to obtain the amino resin.
The acid in the step (1) is oxalic acid.
The adding mode of the urea in the step (1) is as follows: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
The polyamine crosslinking agent in the step (2) is obtained by mixing a polyamine compound and azoisobutyronitrile according to a mass ratio of 1: 1; the polyamine compound is diethylenetriamine.
A preparation method of amino resin modified silica sol comprises the following steps:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin in alkaline silica sol according to the mass ratio, and stirring and mixing uniformly.
Example 2
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 2% of the mass percent, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
The preparation method of the amino resin comprises the following steps:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at the constant temperature of 35-40 ℃ for 20 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 20min to obtain a pre-reaction mixed solution;
(2) heating the pre-reaction mixed solution to 60-70 ℃, sequentially adding 0.5 mass percent of polyamine cross-linking agent while stirring, reacting for 5 hours at 70-80 ℃, then repeatedly washing with 3 percent of HCl, pure water, 3 percent of NaOH and pure water, carrying out petroleum ether extraction for 24 hours, and carrying out vacuum drying to obtain the amino resin.
The acid in the step (1) is sulfuric acid.
The adding mode of the urea in the step (1) is as follows: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
The polyamine crosslinking agent in the step (2) is obtained by mixing a polyamine compound and azoisobutyronitrile according to the mass ratio of 1: 1; the polyamine compound is hexamethyltriethylenetetramine.
A preparation method of amino resin modified silica sol comprises the following steps:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin in alkaline silica sol according to the mass ratio, and stirring and mixing uniformly.
Example 3
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 3% of the mass percent, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
The preparation method of the amino resin comprises the following steps:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at the constant temperature of 35-40 ℃ for 20 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 20min to obtain a pre-reaction mixed solution;
(2) heating the pre-reaction mixed solution to 60-70 ℃, sequentially adding 0.5 mass percent of polyamine cross-linking agent while stirring, reacting for 5 hours at 70-80 ℃, then repeatedly washing with 3 percent of HCl, pure water, 3 percent of NaOH and pure water, carrying out petroleum ether extraction for 24 hours, and carrying out vacuum drying to obtain the amino resin.
The acid in the step (1) is oxalic acid.
The adding mode of the urea in the step (1) is as follows: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
The polyamine crosslinking agent in the step (2) is obtained by mixing a polyamine compound and azoisobutyronitrile according to the mass ratio of 1: 1; the polyamine compound is a mixture of diethylenetriamine, hexamethyltriethylenetetramine, pentamethyldiethylenetriamine and the like.
A preparation method of amino resin modified silica sol comprises the following steps:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin in alkaline silica sol according to the mass ratio, and stirring and mixing uniformly.
Example 4
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 4% of the mass percent, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
The preparation method of the amino resin comprises the following steps:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at the constant temperature of 35-40 ℃ for 20 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 20min to obtain a pre-reaction mixed solution;
(2) heating the pre-reaction mixed solution to 60-70 ℃, adding 0.5 mass percent of polyamine cross-linking agent under stirring, reacting for 3-5h at 70-80 ℃, repeatedly washing with 3 percent of HCl, pure water, 3 percent of NaOH and pure water, extracting for 24h by petroleum ether, and drying in vacuum to obtain the amino resin.
The acid in the step (1) is oxalic acid, sulfuric acid or phosphoric acid.
The adding mode of the urea in the step (1) is as follows: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
The polyamine crosslinking agent in the step (2) is obtained by mixing a polyamine compound and azoisobutyronitrile according to the mass ratio of 1: 1; the polyamine compound is pentamethyldiethylenetriamine.
A preparation method of amino resin modified silica sol comprises the following steps:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin into alkaline silica sol according to the mass ratio, adding water, and stirring and mixing uniformly.
Example 5
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 5% of the mass percent, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
The preparation method of the amino resin comprises the following steps:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at the constant temperature of 35-40 ℃ for 20 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 20min to obtain a pre-reaction mixed solution;
(2) heating the pre-reaction mixed solution to 60-70 ℃, sequentially adding 0.5 mass percent of polyamine cross-linking agent while stirring, reacting for 5 hours at 70-80 ℃, then repeatedly washing with 3 percent of HCl, pure water, 3 percent of NaOH and pure water, carrying out petroleum ether extraction for 24 hours, and carrying out vacuum drying to obtain the amino resin.
The acid in the step (1) is phosphoric acid.
The adding mode of the urea in the step (1) is as follows: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
The polyamine crosslinking agent in the step (2) is obtained by mixing a polyamine compound and azoisobutyronitrile according to the mass ratio of 1: 1; the polyamine compound is mass mixture of diethylenetriamine, hexamethyltriethylenetetramine and the like.
A preparation method of amino resin modified silica sol comprises the following steps:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin in alkaline silica sol according to the mass ratio, and stirring and mixing uniformly.
Comparative example 1
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 0.5% of the mass percent, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
This comparative example was conducted in the same manner as example 5 except that the addition of the amino resin was reduced.
Comparative example 2
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 8% of the mass percent, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
This comparative example was conducted in the same manner as example 5 except that the amino resin was added.
Comparative example 3
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 5% of the mass percent, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
The preparation method of the amino resin comprises the following steps:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at the constant temperature of 35-40 ℃ for 20 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 20min to obtain a pre-reaction mixed solution;
(2) heating the pre-reaction mixed solution to 60-70 ℃, adding 0.5 mass percent of polyamine compound while stirring, reacting for 5 hours at 70-80 ℃, repeatedly washing with 3 percent of HCl, pure water, 3 percent of NaOH and pure water, extracting for 24 hours by petroleum ether, and drying in vacuum to obtain the amino resin.
The acid in the step (1) is phosphoric acid.
The adding mode of the urea in the step (1) is as follows: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
And (3) the polyamine compound in the step (2) is mass mixture of diethylenetriamine, hexamethyltriethylenetetramine and the like.
A preparation method of amino resin modified silica sol comprises the following steps:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin in alkaline silica sol according to the mass ratio, and stirring and mixing uniformly.
In this comparative example, the raw materials and the preparation method were the same as those in example 5 except that azoisobutyronitrile, a crosslinking agent, was not used for the crosslinking modification.
Comparative example 4
The amino resin modified silica sol comprises alkaline silica sol and amino resin, wherein the amino resin accounts for 5% of the mass percent, and the balance is the alkaline silica sol.
The alkaline silica sol colloid has the particle size of 10-20nm, the pH value of 9-11 and SiO2The content is 20-30%.
The preparation method of the amino resin comprises the following steps:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at the constant temperature of 35-40 ℃ for 20 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 20min to obtain a pre-reaction mixed solution;
(2) and (3) keeping the temperature of the pre-reaction mixed solution at 70-80 ℃ for 5h, and then drying in vacuum to obtain the amino resin.
The acid in the step (1) is phosphoric acid.
The adding mode of the urea in the step (1) is as follows: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
A preparation method of amino resin modified silica sol comprises the following steps:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin in alkaline silica sol according to the mass ratio, and stirring and mixing uniformly.
In this comparative example, the starting materials and the preparation process were the same as in example 5 except that the polyamine compound and azoisobutyronitrile, which is a crosslinking agent, were not used for the crosslinking modification.
Performance testing
(1) Shell sample preparation
Preparing slurry: a coating was prepared by precision casting using 200 mesh mullite powder and amino-modified silica sols of different compositions as shown in examples 1-5 and comparative examples 1-4 at a powder to liquid ratio of 1.5: 1. The operation is specified according to the traditional process: and cleaning floating sand, coating slurry, spreading sand and drying, and repeatedly carrying out the four procedures for many times to obtain the shell with the required shape.
(2) Performance testing
Respectively measuring the normal temperature strength, the high temperature strength and the residual strength of the shell by referring to a test method of bending strength of JB/T13412-2018 investment casting shell, wherein the normal temperature strength is the strength after the preparation;
the high-temperature strength is that the shell is put into a furnace at 300 ℃, gradually heated to 900 ℃, kept for 2 hours, cooled to below 300 ℃, taken out of the furnace and detected;
the residual strength is that the shell is put into a furnace at 300 ℃, gradually heated to 1500 ℃, kept for 2 hours, cooled to below 300 ℃, taken out of the furnace and detected;
deformation amount: the high-temperature dead weight deformation sample is in a circular ring shape, the inner diameter of the sample is 88mm, the outer diameter of the sample is 100mm, the thickness of the sample is 20mm, the sample is roasted at 900 ℃ for 120min and cooled to room temperature, then the sample is placed into a high-temperature furnace to be heated to 1200 ℃, the temperature is kept for 60min, and the outer diameter size of the sample after high-temperature dead weight deformation is measured after the sample is cooled to room temperature. Then, the deformation of the sample is calculated according to the following disclosure:
in the formula, δ is the deformation amount of the sample at a certain temperature and time,%, a is the initial outer diameter of the sample, mm, and B is the outer diameter of the sample after deformation, mm.
The test results are shown in table 1:
table 1 results of performance testing
As can be seen from the data in Table 1, the shell prepared by the silica sol of the embodiment of the invention has high normal temperature strength, small residual strength, small high temperature deformation, easy demoulding and smooth surface. And with the increasing of the modified amino component, the strength performance shows an increasing trend. However, comparative example 2, in which the amount added was too large, resulted in a decrease in the proportion of the silica sol as the main component and a decrease in the strength, whereas comparative example 1, in which the amount added was too small, did not give an effective exertion of the modified amino component and the effect was not significant, and thus the increase in the strength was not significant. It can be seen from the graph of FIG. 1 showing the variation of bending strength with the addition amount of amino resin, that the optimum amount of amino resin is 1-5%, and the best improvement of strength property can be achieved.
In the comparative example 3 lacking the modification means, the polyamine compound has weak amino grafting and insufficient binding force with silica sol particles without the function of the crosslinking agent, and the strength is reduced macroscopically. In comparative example 4 in which the polyamine compound and the crosslinking agent were not simultaneously modified, the amino group graft amount was greatly decreased, the amino group effect was decreased, and the strength-enhancing effect was decreased. The synergistic effect of the polyamine compound and the cross-linking agent jointly promotes the amino resin and the silica sol to realize effective combination, and realizes the improvement of the matrix strength, and the amino resin and the silica sol have weak effects if the amino resin and the silica sol are not combined.
It should be noted that the above-mentioned embodiments are only some of the preferred modes for implementing the invention, and not all of them. Obviously, all other embodiments obtained by persons of ordinary skill in the art based on the above-mentioned embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.
Claims (7)
1. The amino resin modified silica sol is characterized by comprising 1-5% of alkaline silica sol and 1-5% of amino resin by mass, and the balance of alkaline silica sol.
2. The amino resin-modified silica sol according to claim 1, wherein the basic silica sol has a colloidal particle diameter of 10 to 20nm, a pH of 9 to 11, and SiO2The content is 20-30%.
3. The amino resin-modified silica sol according to claim 1, wherein the amino resin is prepared by a method comprising:
(1) adding formaldehyde into a reaction kettle, heating to 35-40 ℃, adding acid to adjust the pH value to 5-6, and adding formaldehyde according to the mass ratio: adding melamine into melamine at a ratio of 20:1, and reacting at constant temperature of 35-40 ℃ for 10-20 min; then formaldehyde is added according to the mass ratio: adding urea at a ratio of 5:1, continuously stirring for reacting for 30min, and adding formaldehyde: adding glyoxal at a ratio of 10:1, and fully reacting for 10-20min to obtain a pre-reaction mixed solution;
(2) heating the pre-reaction mixed solution to 60-70 ℃, adding 0.1-0.5% polyamine cross-linking agent by mass percent under stirring, reacting for 3-5h at 70-80 ℃, then repeatedly washing with 3% HCl, pure water, 3% NaOH and pure water, carrying out petroleum ether extraction for 12-24h, and carrying out vacuum drying to obtain the amino resin.
4. The amino resin-modified silica sol according to claim 3, wherein the acid in the step (1) is oxalic acid, sulfuric acid or phosphoric acid.
5. The amino resin-modified silica sol according to claim 3, wherein the urea is added in the step (1) by the following method: according to the mass ratio of formaldehyde: weighing urea in a ratio of 5:1, and adding the urea in three parts by mass in three times within 30 min.
6. The amino resin-modified silica sol according to claim 3, wherein the polyamine-crosslinking agent in the step (2) is a mixture of a polyamine compound and azoisobutyronitrile at a mass ratio of 1: 1; the polyamine compound is one or more of diethylenetriamine, hexamethyltriethylenetetramine and pentamethyldiethylenetriamine.
7. A method for preparing the amino resin-modified silica sol according to any one of claims 1 to 6, comprising the steps of:
(1) preparing amino resin;
(2) preparing alkaline silica sol: mixing SiO2Uniformly dispersing the particles in water to obtain alkaline silica sol;
(3) dispersing the prepared amino resin in alkaline silica sol according to the mass ratio, and stirring and mixing uniformly.
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