A compounded component of foundry sand additive and a preparation method thereof

Abstract

The present application relates to the technical field of foundry additives, in particular to a foundry molding sand additive compound component and a preparation method thereof, the present application crosslinks and modifies starch by using borax as a crosslinking agent and adopting a pre-gelatinization crosslinking method, so that the crosslinking bonds in the prepared starch-based binder increase, the water resistance of the starch-based binder is improved on the basis of further enhancing the bonding performance thereof; the present application uses phosphoric acid as a base material, reacts the same with metal hydroxides such as aluminum hydroxide to prepare a phosphoric acid-based binder, the phosphoric acid-based binder can play a self-hardening role on the basis of bonding when applied to bentonite, therefore, the same can be better used as an additive in the foundry industry in combination with the starch-based binder; the present application prepares a polyacrylamide solution by radical initiation polymerization of acrylamide as a monomer, and mixes the same with the compounded binder, so that the surface tension of the binder can be reduced, thereby improving the adhesion of the binder in bentonite.

Description

Technical Field

[0001] This invention relates to the field of additives for casting, specifically to a compound composition of casting sand additives and its preparation method. Background Technology

[0002] In the foundry industry, molding materials are the foundation for determining the quality of castings. The quality of molding materials depends on the type of binder. During the casting core assembly process, in order to avoid problems such as sand core falling off or floating during the dipping coating and pouring process, the molding materials need to be bonded together with the sand cores at their mating surfaces using a binder.

[0003] In foundry molding sands such as bentonite, not only binders but also self-hardening agents and other components are added as additives to improve the performance of bentonite. However, the composition of bentonite additives on the market is relatively simple, and most of them are single-component binders. If different binders can be mixed and matched, and other performance-enhancing agents are added to prepare additives for use in bentonite, the application prospects of bentonite in the foundry industry can be improved. Summary of the Invention

[0004] Technical problems to be solved

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a composite composition of foundry sand additives and its preparation method, which can effectively solve the problem of poor performance and single composition of additives in the prior art.

[0006] Technical solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A composite composition of casting sand additives, wherein the raw materials of the composite composition of casting sand additives include: starch-based binder, phosphate-based binder, polyacrylamide solution, nano-silica, coal powder and silane coupling agent;

[0009] The starch-based binder is prepared by using starch as raw material and borax as crosslinking agent, and then undergoing crosslinking modification.

[0010] The phosphate-based binder is prepared by reacting phosphoric acid with metal hydroxides such as aluminum hydroxide;

[0011] The polyacrylamide solution was prepared by free radical-initiated polymerization of acrylamide monomer.

[0012] Furthermore, the preparation steps of the starch-based binder are as follows:

[0013] S1. Weigh 100 parts by weight of 0.6% borax solution and heat it in a water bath to 46-48℃. Add 38-40 parts by weight of starch and stir at 200-300 r / min for 35-40 min. The result is recorded as the cross-linking component.

[0014] S2. The crosslinking component in S1 is filtered by vacuum filtration. After filtration three times, the resulting filter cake is placed in an oven at 56-58℃ and dried for 28-30 minutes. Then, it is ground and pulverized, passed through a 100-mesh sieve, and placed in an oven at 56-58℃ again and dried for 1-2 hours. The result is the starch-based binder.

[0015] Furthermore, the preparation steps of the phosphate-based binder are as follows:

[0016] 1) Weigh 50-58 parts by weight of aluminum hydroxide and 200 parts by weight of deionized water to prepare an aluminum hydroxide solution. Heat the solution to boiling under stirring and slowly add 28-30 parts by weight of phosphoric acid. The result is called the first component.

[0017] 2) Under stirring conditions, add 4-5 parts by weight of boric acid and 2-3 parts by weight of sodium borate to the first component. Stir at the original stirring speed for 15 minutes, then add 5-7 parts by weight of magnesium carbonate. Continue stirring for 10 minutes, then add 4-5 parts by weight of aluminum phosphate and 8-9 parts by weight of aluminum sulfate. Stir again for 30 minutes. The result is recorded as the second component.

[0018] 3) Add 7-8 parts by weight of D-sorbitol and 8-10 parts by weight of citric acid to the second component under stirring conditions, and continue stirring for 90 minutes to obtain the phosphate-based binder.

[0019] Furthermore, in step 1) of the preparation of the phosphate-based binder, the stirring speed is 100-200 r / min, and the rate at which phosphoric acid is added in step 1) is 0.1-0.2 g / s.

[0020] Furthermore, in step 2) of the preparation of the phosphate-based binder, the stirring speed is 150-200 r / min, and the rates at which boric acid, sodium borate, magnesium carbonate, aluminum phosphate, and aluminum sulfate are added in step 2) are all 0.1-0.2 g / s.

[0021] Furthermore, in step 3) of the preparation of the phosphate-based binder, the stirring speed is 100-200 r / min, and in step 2) the addition rates of D-sorbitol and citric acid are both 0.2-0.3 g / s.

[0022] Furthermore, the method for preparing the polyacrylamide solution is as follows:

[0023] I. Weigh 7-8 parts by weight of sodium formate, 13-14 parts by weight of tetramethylethylenediamine and 1-2 parts by weight of polymethacryloyloxyethyltrimethylammonium chloride and pour them into a flask. Then add 180-200 parts by weight of sodium chloride solution with a mass concentration of 20% and heat to 60°C under stirring. The result is recorded as the mixed component.

[0024] II. At a temperature of 60℃, add 6-7 parts by weight of acrylamide, 11-13 parts by weight of methacryloyloxyethyl benzyl dimethyl ammonium chloride, 10-11 parts by weight of methacryloyloxyethyl trimethyl ammonium chloride, and 1-2 parts by weight of azobisisobutyronitrile to the mixed components. After mixing evenly, react at a constant temperature for 12 hours. Then, add 0.3-0.5 parts by weight of acetic acid and cool to room temperature. The resulting product is a polyacrylamide solution.

[0025] Furthermore, in the preparation method of the polyacrylamide solution, the stirring speed in step I is 300-500 r / min, the stirring speed in step II is 200-300 r / min, and the dropping rate of acetic acid in step II is 1 drop / s.

[0026] A method for preparing a composite additive for foundry sand, the method comprising the following steps:

[0027] Step A: Weigh 8-10 parts by weight of nano-silica and 9-10 parts by weight of coal powder and mix them. After mixing, grind them through a 200-mesh sieve and add 15-16 parts by weight of silane coupling agent KH550. Continue grinding and mixing for 5-6 minutes. The result is recorded as the component to be added.

[0028] Step B: Add 38-40 parts by weight of phosphate-based binder to 100 parts by weight of polyacrylamide solution, mix and stir, then add 8-10 parts by weight of starch-based binder, continue stirring and then add 8-11 parts by weight of the component to be added. After rapid dispersion, the resulting product is the composite component of the foundry sand additive.

[0029] Furthermore, the stirring speed in step A is 150-200 r / min, the mixing speed in step B is 200-300 r / min, the rapid dispersion speed in step B is 600-800 r / min, and the rapid dispersion stirring time is 5-6 min.

[0030] Beneficial effects

[0031] This invention provides a composite composition for a foundry sand additive and its preparation method. Compared with existing technologies, this invention has the following advantages:

[0032] 1. This invention uses borax as a crosslinking agent to modify starch through pre-gelatinization crosslinking, increasing the number of crosslinking bonds in the prepared starch-based adhesive, thereby enhancing its adhesive properties and improving its water resistance. Secondly, this invention uses phosphoric acid as a base material, reacting it with metal hydroxides such as aluminum hydroxide to prepare a phosphate-based adhesive. Applying this phosphate-based adhesive to bentonite allows it to self-harden on top of the adhesive bond. Therefore, its compatibility with starch-based adhesives makes it a better additive for use in the foundry industry.

[0033] 2. This invention uses acrylamide as a monomer to prepare a polyacrylamide solution through free radical initiation polymerization. Mixing this solution with a compounded binder can reduce the surface tension of the binder, thereby improving the adhesion of the binder to bentonite and increasing the strength of the bentonite. Adding silica and coal powder uniformly dispersed in the polyacrylamide solution as additives to bentonite can improve the seepage prevention performance of bentonite, thus enabling the prepared additives to be better applied in the foundry industry. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] The present invention will be further described below with reference to embodiments.

[0036] Example 1

[0037] This embodiment provides a composite composition of casting sand additives. The raw material composition of the composite composition of casting sand additives includes: starch-based binder, phosphate-based binder, polyacrylamide solution, nano-silica, coal powder, and silane coupling agent.

[0038] Starch-based binders are prepared by using starch as a raw material and borax as a crosslinking agent, and are obtained after crosslinking modification. The preparation steps of starch-based binders are as follows:

[0039] S1. Weigh 100 parts by weight of 0.6% borax solution and heat it in a water bath to 46°C. Add 38 parts by weight of starch and stir at 200 r / min for 35 min. The result is recorded as the cross-linking component.

[0040] S2. The crosslinking component in S1 is filtered by vacuum filtration. After filtration three times, the resulting filter cake is placed in an oven at 56°C and dried for 28 minutes. Then, it is ground and pulverized, passed through a 100-mesh sieve, and placed in an oven at 56°C and dried for 1 hour. The result is the starch-based binder.

[0041] Phosphate-based binders are prepared by reacting phosphoric acid with metal hydroxides such as aluminum hydroxide. The preparation steps for phosphate-based binders are as follows:

[0042] 1) Weigh 50 parts by weight of aluminum hydroxide and 200 parts by weight of deionized water and mix them to prepare an aluminum hydroxide solution. Heat the solution to boiling under stirring and slowly add 28 parts by weight of phosphoric acid. The result is called the first component.

[0043] 2) Under stirring conditions, add 4 parts by weight of boric acid and 2 parts by weight of sodium borate to the first component. Stir at the original stirring speed for 15 minutes, then add 5 parts by weight of magnesium carbonate. Continue stirring for 10 minutes, then add 4 parts by weight of aluminum phosphate and 8 parts by weight of aluminum sulfate. Stir again for 30 minutes. The result is recorded as the second component.

[0044] 3) Add 7 parts by weight of D-sorbitol and 8 parts by weight of citric acid to the second component under stirring conditions, and continue stirring for 90 minutes to obtain the phosphate-based binder.

[0045] In step 1) of the preparation of the phosphate-based binder, the stirring speed is 100 r / min, and the rate at which phosphoric acid is added in step 1) is 0.1 g / s.

[0046] In step 2) of the preparation of the phosphate-based binder, the stirring speed is 150 r / min, and the rates at which boric acid, sodium borate, magnesium carbonate, aluminum phosphate, and aluminum sulfate are added in step 2) are all 0.1 g / s.

[0047] In step 3) of the preparation of the phosphate-based binder, the stirring speed is 100 r / min, and in step 2) the D-sorbitol and citric acid are added at a rate of 0.2 g / s.

[0048] Polyacrylamide solution is prepared by free radical-initiated polymerization of acrylamide monomer. The preparation method of polyacrylamide solution is as follows:

[0049] I. Weigh 7 parts by weight of sodium formate, 13 parts by weight of tetramethylethylenediamine and 1 part by weight of polymethacryloyloxyethyltrimethylammonium chloride and pour them into a flask. Then add 180 parts by weight of sodium chloride solution with a mass concentration of 20% and heat to 60°C under stirring. The result is recorded as the mixed component.

[0050] II. At a temperature of 60℃, add 6 parts by weight of acrylamide, 11 parts by weight of methacryloyloxyethyl benzyl dimethyl ammonium chloride, 10 parts by weight of methacryloyloxyethyl trimethyl ammonium chloride and 1 part by weight of azobisisobutyronitrile to the mixed components. After mixing evenly, react at a constant temperature for 12 hours. After adding 0.3 parts by weight of acetic acid, cool down to room temperature. The resulting product is a polyacrylamide solution.

[0051] In the preparation method of polyacrylamide solution, the stirring speed in step I is 300 r / min, the stirring speed in step II is 200 r / min, and the dropping rate of acetic acid in step II is 1 drop / s.

[0052] A method for preparing a composite additive for foundry sand, the method comprising the following steps:

[0053] Step A: Weigh 8 parts by weight of nano-silica and 9 parts by weight of coal powder and mix them. After mixing, grind them through a 200-mesh sieve and add 15 parts by weight of silane coupling agent KH550. Continue grinding and mixing for 5 minutes. The result is recorded as the component to be added.

[0054] Step B: Add 38 parts by weight of phosphate-based binder to 100 parts by weight of polyacrylamide solution, mix and stir, then add 8 parts by weight of starch-based binder, continue stirring and then add 8 parts by weight of the component to be added. After rapid dispersion, the resulting product is the composite component of the foundry sand additive.

[0055] The stirring speed in step A is 150 r / min, the stirring speed for mixing in step B is 200 r / min, the stirring speed for rapid dispersion in step B is 600 r / min, and the stirring time for rapid dispersion is 5 min.

[0056] Example 2

[0057] This embodiment provides a composite composition of casting sand additives. The raw material composition of the composite composition of casting sand additives includes: starch-based binder, phosphate-based binder, polyacrylamide solution, nano-silica, coal powder, and silane coupling agent.

[0058] Starch-based binders are prepared by using starch as a raw material and borax as a crosslinking agent, and are obtained after crosslinking modification. The preparation steps of starch-based binders are as follows:

[0059] S1. Weigh 100 parts by weight of 0.6% borax solution and heat it in a water bath to 48°C. Add 40 parts by weight of starch and stir at 300 r / min for 40 min. The result is called the cross-linking component.

[0060] S2. The crosslinking component in S1 is filtered by vacuum filtration. After filtration three times, the resulting filter cake is placed in an oven at 58°C and dried for 30 minutes. Then, it is ground and pulverized, passed through a 100-mesh sieve, and placed in an oven at 58°C again for drying for 2 hours. The result is the starch-based binder.

[0061] Phosphate-based binders are prepared by reacting phosphoric acid with metal hydroxides such as aluminum hydroxide. The preparation steps for phosphate-based binders are as follows:

[0062] 1) Weigh 58 parts by weight of aluminum hydroxide and 200 parts by weight of deionized water to prepare an aluminum hydroxide solution. Heat the solution to boiling under stirring and slowly add 30 parts by weight of phosphoric acid. The result is called the first component.

[0063] 2) Under stirring conditions, add 5 parts by weight of boric acid and 3 parts by weight of sodium borate to the first component, stir at the original stirring speed for 15 minutes, then add 7 parts by weight of magnesium carbonate, continue stirring for 10 minutes, then add 5 parts by weight of aluminum phosphate and 9 parts by weight of aluminum sulfate, stir again for 30 minutes, and the result is recorded as the second component.

[0064] 3) Add 8 parts by weight of D-sorbitol and 10 parts by weight of citric acid to the second component under stirring conditions, and continue stirring for 90 minutes to obtain the phosphate-based binder.

[0065] In step 1) of the preparation of the phosphate-based binder, the stirring speed is 200 r / min, and the rate at which phosphoric acid is added in step 1) is 0.2 g / s.

[0066] In step 2) of the preparation of the phosphate-based binder, the stirring speed is 200 r / min, and the rates at which boric acid, sodium borate, magnesium carbonate, aluminum phosphate, and aluminum sulfate are added in step 2) are all 0.2 g / s.

[0067] In step 3) of the preparation of the phosphate-based binder, the stirring speed is 200 r / min, and in step 2) the D-sorbitol and citric acid are added at a rate of 0.3 g / s.

[0068] Polyacrylamide solution is prepared by free radical-initiated polymerization of acrylamide monomer. The preparation method of polyacrylamide solution is as follows:

[0069] I. Weigh 8 parts by weight of sodium formate, 14 parts by weight of tetramethylethylenediamine and 2 parts by weight of polymethacryloyloxyethyltrimethylammonium chloride and pour them into a flask. Then add 200 parts by weight of sodium chloride solution with a mass concentration of 20% and heat to 60°C under stirring. The result is recorded as the mixed component.

[0070] II. At a temperature of 60℃, add 7 parts by weight of acrylamide, 13 parts by weight of methacryloyloxyethyl benzyl dimethyl ammonium chloride, 11 parts by weight of methacryloyloxyethyl trimethyl ammonium chloride and 2 parts by weight of azobisisobutyronitrile to the mixed components. After mixing evenly, react at a constant temperature for 12 hours. After adding 0.5 parts by weight of acetic acid, cool down to room temperature. The result is a polyacrylamide solution.

[0071] In the preparation method of polyacrylamide solution, the stirring speed in step I is 500 r / min, the stirring speed in step II is 300 r / min, and the dropping rate of acetic acid in step II is 1 drop / s.

[0072] A method for preparing a composite additive for foundry sand, the method comprising the following steps:

[0073] Step A: Weigh 10 parts by weight of nano-silica and 10 parts by weight of coal powder and mix them. After mixing, grind them through a 200-mesh sieve and add 16 parts by weight of silane coupling agent KH550. Continue grinding and mixing for 6 minutes. The result is recorded as the component to be added.

[0074] Step B: Add 40 parts by weight of phosphate-based binder to 100 parts by weight of polyacrylamide solution, mix and stir, then add 10 parts by weight of starch-based binder, continue stirring and then add 11 parts by weight of the component to be added. After rapid dispersion, the resulting product is the composite component of the foundry sand additive.

[0075] The stirring speed in step A is 200 r / min, the stirring speed for mixing in step B is 300 r / min, the stirring speed for rapid dispersion in step B is 800 r / min, and the stirring time for rapid dispersion is 6 min.

[0076] Example 3

[0077] This embodiment provides a composite composition of casting sand additives. The raw material composition of the composite composition of casting sand additives includes: starch-based binder, phosphate-based binder, polyacrylamide solution, nano-silica, coal powder, and silane coupling agent.

[0078] Starch-based binders are prepared by using starch as a raw material and borax as a crosslinking agent, and are obtained after crosslinking modification. The preparation steps of starch-based binders are as follows:

[0079] S1. Weigh 100 parts by weight of 0.6% borax solution and heat it in a water bath to 47°C. Add 39 parts by weight of starch and stir at 300 r / min for 38 min. The result is recorded as the cross-linking component.

[0080] S2. The crosslinking component in S1 is filtered by vacuum filtration. After filtration three times, the resulting filter cake is placed in an oven at 57°C and dried for 29 minutes. Then, it is ground and pulverized, passed through a 100-mesh sieve, and placed in an oven at 57°C and dried for 2 hours. The result is the starch-based binder.

[0081] Phosphate-based binders are prepared by reacting phosphoric acid with metal hydroxides such as aluminum hydroxide. The preparation steps for phosphate-based binders are as follows:

[0082] 1) Weigh 54 parts by weight of aluminum hydroxide and 200 parts by weight of deionized water to prepare an aluminum hydroxide solution. Heat the solution to boiling under stirring and slowly add 29 parts by weight of phosphoric acid. The result is called the first component.

[0083] 2) Under stirring conditions, add 5 parts by weight of boric acid and 2 parts by weight of sodium borate to the first component. Stir at the original stirring speed for 15 minutes, then add 6 parts by weight of magnesium carbonate. Continue stirring for 10 minutes, then add 5 parts by weight of aluminum phosphate and 9 parts by weight of aluminum sulfate. Stir again for 30 minutes. The result is recorded as the second component.

[0084] 3) Add 7 parts by weight of D-sorbitol and 9 parts by weight of citric acid to the second component under stirring conditions, and continue stirring for 90 minutes to obtain the phosphate-based binder.

[0085] In step 1) of the preparation of the phosphate-based binder, the stirring speed is 150 r / min, and the rate at which phosphoric acid is added in step 1) is 0.2 g / s.

[0086] In step 2) of the preparation of the phosphate-based binder, the stirring speed is 180 r / min, and the rates at which boric acid, sodium borate, magnesium carbonate, aluminum phosphate, and aluminum sulfate are added in step 2) are all 0.2 g / s.

[0087] In step 3) of the preparation of the phosphate-based binder, the stirring speed is 150 r / min, and in step 2) the D-sorbitol and citric acid are added at a rate of 0.2 g / s.

[0088] Polyacrylamide solution is prepared by free radical-initiated polymerization of acrylamide monomer. The preparation method of polyacrylamide solution is as follows:

[0089] I. Weigh 7 parts by weight of sodium formate, 14 parts by weight of tetramethylethylenediamine and 2 parts by weight of polymethacryloyloxyethyltrimethylammonium chloride and pour them into a flask. Then add 190 parts by weight of sodium chloride solution with a mass concentration of 20% and heat to 60°C under stirring. The result is recorded as the mixed component.

[0090] II. At a temperature of 60℃, add 7 parts by weight of acrylamide, 13 parts by weight of methacryloyloxyethyl benzyl dimethyl ammonium chloride, 11 parts by weight of methacryloyloxyethyl trimethyl ammonium chloride and 2 parts by weight of azobisisobutyronitrile to the mixed components. After mixing evenly, react at a constant temperature for 12 hours. After adding 0.4 parts by weight of acetic acid, cool down to room temperature. The result is a polyacrylamide solution.

[0091] In the preparation method of polyacrylamide solution, the stirring speed in step I is 400 r / min, the stirring speed in step II is 300 r / min, and the dropping rate of acetic acid in step II is 1 drop / s.

[0092] A method for preparing a composite additive for foundry sand, the method comprising the following steps:

[0093] Step A: Weigh 9 parts by weight of nano-silica and 10 parts by weight of coal powder and mix them. After mixing, grind them through a 200-mesh sieve and add 15 parts by weight of silane coupling agent KH550. Continue grinding and mixing for 6 minutes. The result is recorded as the component to be added.

[0094] Step B: Add 39 parts by weight of phosphate-based binder to 100 parts by weight of polyacrylamide solution, mix and stir, then add 9 parts by weight of starch-based binder, continue stirring and then add 10 parts by weight of the component to be added. After rapid dispersion, the resulting product is the composite component of the foundry sand additive.

[0095] The stirring speed in step A is 180 r / min, the stirring speed for mixing in step B is 200 r / min, the stirring speed for rapid dispersion in step B is 700 r / min, and the stirring time for rapid dispersion is 6 min.

[0096] Comparative Example 1

[0097] The casting sand additive compound and its preparation method in this comparative example are roughly the same as those in Example 1. The main difference is that the starch-based binder in Example 1 is replaced with starch.

[0098] Comparative Example 2

[0099] The casting sand additive compound and its preparation method in this comparative example are roughly the same as those in Example 1. The main difference is that the phosphate-based binder in Example 1 is replaced with SOSIDER series molding sand binder in this comparative example 2.

[0100] Comparative Example 3

[0101] The casting sand additive compound component and its preparation method in this comparative example are roughly the same as those in Example 1. The main difference is that the polyacrylamide solution in Example 1 is replaced with a 10% (w / w) aqueous solution of polyoxyethylene alkylphenol ether.

[0102] Performance testing

[0103] The composite components of the foundry sand additives prepared in Examples 1-3 and Comparative Examples 1-3 were labeled as Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. The performance of Examples 1-3 and Comparative Examples 1-3 was then tested. The specific testing methods and items are as follows:

[0104] 1. The casting sand additive compound components prepared in Examples 1-3 and Comparative Examples 1-3 were added to bentonite at an addition rate of 10%. After mixing, the initial strength of bentonite with different additives added at different temperatures was tested, and the data obtained are recorded in the table below.

[0105] 2. The casting sand additive compound components prepared in Examples 1-3 and Comparative Examples 1-3 were added to bentonite at an addition amount of 10%. After mixing, the permeability coefficient of bentonite with different additives was tested, and the data obtained are recorded in the table below.

[0106]

[0107] The data in the table above shows that the bentonite with the casting sand additive compound prepared in Examples 1-3 has higher strength and better impermeability. This indicates that the casting sand additive compound prepared in Examples 1-3 can improve the performance of bentonite. Therefore, the casting sand additive compound and its preparation method provided by this invention have better market application value.

[0108] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0109] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite composition of additives for foundry sand, characterized in that, The raw material composition of the casting sand additive compound includes: 8-10 parts by weight of starch-based binder, 38-40 parts by weight of phosphate-based binder, 100 parts by weight of polyacrylamide solution, and 8-11 parts by weight of the component to be added, wherein the component to be added includes: 8-10 parts by weight of nano-silica, 9-10 parts by weight of coal powder, and 15-16 parts by weight of KH550 silane coupling agent. The starch-based binder is prepared by using starch as raw material and borax as crosslinking agent, and then undergoing crosslinking modification. The phosphate-based binder is prepared by reacting phosphate with aluminum hydroxide; the preparation steps of the phosphate-based binder are as follows: 1) Weigh 50-58 parts by weight of aluminum hydroxide and 200 parts by weight of deionized water to prepare an aluminum hydroxide solution. Heat the solution to boiling under stirring and slowly add 28-30 parts by weight of phosphoric acid. The result is called the first component. 2) Under stirring conditions, add 4-5 parts by weight of boric acid and 2-3 parts by weight of sodium borate to the first component. Stir at the original stirring speed for 15 minutes, then add 5-7 parts by weight of magnesium carbonate. Continue stirring for 10 minutes, then add 4-5 parts by weight of aluminum phosphate and 8-9 parts by weight of aluminum sulfate. Stir again for 30 minutes. The result is recorded as the second component. 3) Add 7-8 parts by weight of D-sorbitol and 8-10 parts by weight of citric acid to the second component under stirring conditions, and continue stirring for 90 minutes to obtain the phosphate-based binder; The polyacrylamide solution was prepared by free radical-initiated polymerization of acrylamide monomer.

2. The composite composition of a foundry sand additive according to claim 1, characterized in that, The preparation steps of the starch-based binder are as follows: S1. Weigh 100 parts by weight of 0.6% borax solution and heat it in a water bath to 46-48℃. Add 38-40 parts by weight of starch and stir at 200-300 r / min for 35-40 min. The result is recorded as the cross-linking component. S2. The crosslinking component in S1 is filtered by vacuum filtration. After filtration three times, the resulting filter cake is placed in an oven at 56-58℃ and dried for 28-30 minutes. Then, it is ground and pulverized, passed through a 100-mesh sieve, and placed in an oven at 56-58℃ again and dried for 1-2 hours. The result is the starch-based binder.

3. The composite composition of a foundry sand additive according to claim 1, characterized in that, In step 1) of the preparation of the phosphate-based binder, the stirring speed is 100-200 r / min, and the rate at which phosphoric acid is added in step 1) is 0.1-0.2 g / s.

4. The composite composition of a foundry sand additive according to claim 1, characterized in that, In step 2) of the preparation of the phosphate-based binder, the stirring speed is 150-200 r / min, and the rates at which boric acid, sodium borate, magnesium carbonate, aluminum phosphate, and aluminum sulfate are added in step 2) are all 0.1-0.2 g / s.

5. The composite composition of a foundry sand additive according to claim 1, characterized in that, In step 3) of the preparation of the phosphate-based binder, the stirring speed is 100-200 r / min, and the addition rates of D-sorbitol and citric acid in step 3) are both 0.2-0.3 g / s.

6. The composite composition of a foundry sand additive according to claim 1, characterized in that, The method for preparing the polyacrylamide solution is as follows: I. Weigh 7-8 parts by weight of sodium formate, 13-14 parts by weight of tetramethylethylenediamine and 1-2 parts by weight of polymethacryloyloxyethyltrimethylammonium chloride and pour them into a flask. Then add 180-200 parts by weight of sodium chloride solution with a mass concentration of 20% and heat to 60°C under stirring. The result is recorded as the mixed component. II. At a temperature of 60℃, add 6-7 parts by weight of acrylamide, 11-13 parts by weight of methacryloyloxyethyl benzyl dimethyl ammonium chloride, 10-11 parts by weight of methacryloyloxyethyl trimethyl ammonium chloride, and 1-2 parts by weight of azobisisobutyronitrile to the mixed components. After mixing and stirring evenly, react at a constant temperature for 12 hours. Then, add 0.3-0.5 parts by weight of acetic acid dropwise and cool to room temperature. The resulting product is a polyacrylamide solution.

7. The composite composition of a foundry sand additive according to claim 6, characterized in that, In the preparation method of the polyacrylamide solution, the stirring speed in step I is 300-500 r / min, the stirring speed in step II is 200-300 r / min, and the dropping rate of acetic acid in step II is 1 drop / s.

8. A method for preparing a composite additive for foundry sand according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: Step A: Weigh 8-10 parts by weight of nano-silica and 9-10 parts by weight of coal powder, mix and stir, grind through a 200-mesh sieve and add 15-16 parts by weight of silane coupling agent KH550, continue grinding and mixing for 5-6 minutes, and record the result as the component to be added. Step B: Add 38-40 parts by weight of phosphate-based binder to 100 parts by weight of polyacrylamide solution, mix and stir, then add 8-10 parts by weight of starch-based binder, continue stirring and then add 8-11 parts by weight of the component to be added. After rapid dispersion, the resulting product is the composite component of the foundry sand additive.

9. The method for preparing a composite additive for foundry sand according to claim 8, characterized in that, The mixing speed in step A is 150-200 r / min, the mixing speed in step B is 200-300 r / min, the rapid dispersion speed in step B is 600-800 r / min, and the rapid dispersion time is 5-6 min.

Images