CN114669717B - Modified silica sol and preparation method and application thereof - Google Patents
Modified silica sol and preparation method and application thereof Download PDFInfo
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- CN114669717B CN114669717B CN202210319206.5A CN202210319206A CN114669717B CN 114669717 B CN114669717 B CN 114669717B CN 202210319206 A CN202210319206 A CN 202210319206A CN 114669717 B CN114669717 B CN 114669717B
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- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical class O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 title claims abstract description 150
- 238000002360 preparation method Methods 0.000 title abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 60
- 239000004372 Polyvinyl alcohol Substances 0.000 claims abstract description 48
- 229920002451 polyvinyl alcohol Polymers 0.000 claims abstract description 48
- 239000001866 hydroxypropyl methyl cellulose Substances 0.000 claims abstract description 37
- 229920003088 hydroxypropyl methyl cellulose Polymers 0.000 claims abstract description 37
- 235000010979 hydroxypropyl methyl cellulose Nutrition 0.000 claims abstract description 37
- UFVKGYZPFZQRLF-UHFFFAOYSA-N hydroxypropyl methyl cellulose Chemical compound OC1C(O)C(OC)OC(CO)C1OC1C(O)C(O)C(OC2C(C(O)C(OC3C(C(O)C(O)C(CO)O3)O)C(CO)O2)O)C(CO)O1 UFVKGYZPFZQRLF-UHFFFAOYSA-N 0.000 claims abstract description 37
- 239000011259 mixed solution Substances 0.000 claims abstract description 16
- 239000002994 raw material Substances 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims description 38
- 229910019142 PO4 Inorganic materials 0.000 claims description 24
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 24
- 239000010452 phosphate Substances 0.000 claims description 24
- 239000013530 defoamer Substances 0.000 claims description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 9
- 229910052710 silicon Inorganic materials 0.000 claims description 9
- 239000010703 silicon Substances 0.000 claims description 9
- 239000011230 binding agent Substances 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 7
- 229920001296 polysiloxane Polymers 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 238000005266 casting Methods 0.000 abstract description 21
- 238000005336 cracking Methods 0.000 abstract description 9
- 239000002002 slurry Substances 0.000 abstract description 9
- 239000002344 surface layer Substances 0.000 abstract description 9
- 239000000835 fiber Substances 0.000 abstract description 2
- -1 hydroxypropyl methyl Chemical group 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 19
- 238000003756 stirring Methods 0.000 description 19
- 239000006260 foam Substances 0.000 description 9
- 239000011248 coating agent Substances 0.000 description 7
- 238000000576 coating method Methods 0.000 description 7
- 238000005495 investment casting Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 5
- 239000010410 layer Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 238000004513 sizing Methods 0.000 description 4
- 239000002518 antifoaming agent Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 235000019353 potassium silicate Nutrition 0.000 description 3
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- SNAAJJQQZSMGQD-UHFFFAOYSA-N aluminum magnesium Chemical compound [Mg].[Al] SNAAJJQQZSMGQD-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241001473591 Saxifraga florulenta Species 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- CRHLEZORXKQUEI-UHFFFAOYSA-N dialuminum;cobalt(2+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Al+3].[Al+3].[Co+2].[Co+2] CRHLEZORXKQUEI-UHFFFAOYSA-N 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000005350 fused silica glass Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 239000002121 nanofiber Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 239000008747 shengyu Substances 0.000 description 1
- 125000005372 silanol group Chemical group 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000000080 wetting agent Substances 0.000 description 1
- 229910052845 zircon Inorganic materials 0.000 description 1
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Silicon Compounds (AREA)
Abstract
The invention provides a modified silica sol, a preparation method and application thereof. The raw materials of the modified silica sol comprise, by weight, 95-100 parts of the silica sol, 0.1-2 parts of polyvinyl alcohol and 0.1-2 parts of hydroxypropyl methyl cellulose. The preparation method of the modified silica sol provided by the invention comprises the following steps: mixing silica sol with polyvinyl alcohol to obtain a mixed solution A; and mixing the mixed solution A with hydroxypropyl methyl cellulose to obtain the modified silica sol. According to the modified silica sol provided by the invention, the silica sol is modified by the polyvinyl alcohol and the hydroxypropyl methyl fiber with a specific proportion, so that the modified silica sol is high in viscosity and high in adhesiveness, the wet strength of casting surface layer slurry is improved, cracking resistance is improved, and the surface quality of a casting is good.
Description
Technical Field
The invention belongs to the technical field of binders, and particularly relates to a modified silica sol and a preparation method and application thereof.
Background
Silica sol is a colloidal solution of silica in water and is widely used as a high-temperature binder in the investment casting industry, and is a main raw material for investment casting, and the quality, production period and manufacturing cost of shells and castings are directly affected. For a long time, the silica sol binder is continuously improved and developed, but the rapid development of the silica sol binder is restricted due to the defects of low drying speed, low shell making efficiency, poor wettability to wax molds, poor stability and the like.
For example CN112275994a discloses a silica sol for preparing a fine cast shell, said silica sol comprising a top layer component and a back layer component; the surface layer comprises zirconium powder, carbon powder, silica sol, a wetting agent and a defoaming agent; the back layer component comprises silica sol, nano fiber, mullite powder and quartz powder; the silica sol is specially used for preparing the shell of the precision casting, the porosity of the obtained shell is gradually increased from inside to outside, air holes are not easy to generate in the precision casting process, the casting with extremely high surface smoothness can be prepared, and the quality of the casting is ensured. But the shell strength including the silica sol is low.
CN111570719a discloses a silica sol modified coating for precision casting, comprising a top coating and a back coating, wherein the top coating comprises silica sol, cobalt aluminate, zirconium powder, polyvinyl alcohol and magnesium aluminum silicate; the back layer coating comprises silica sol, fused silica powder, polyvinyl alcohol and magnesium aluminum silicate. The inner surface of the mould shell comprising the silica sol modified paint is compact and has no holes, good wear resistance and simple formula. However, the wet strength of a slurry comprising a silica sol modified coating is not explored.
CN103192024a discloses a water glass and silica sol mixed binder and a preparation method thereof, the preparation method comprises: uniformly stirring water glass, silica sol solution, refractory powder and penetrating agent in a certain weight ratio at 15-30 ℃, then adding a defoaming agent for defoaming, and finally standing for more than 8 hours to obtain the water glass and silica sol mixed binder. The adhesive prepared by the method has high powder-liquid ratio of the surface coating, and the surface of the shell is smooth, so that the surface finish of the casting is improved, and the strength of the shell is uniform. But the cracking resistance of the shell is to be further improved.
Therefore, developing a silica sol with good cohesiveness, high wet strength of surface sizing agent, cracking resistance and good apparent quality of castings is a technical problem to be solved in the field.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a modified silica sol, and a preparation method and application thereof. The modified silica sol is modified by polyvinyl alcohol and hydroxypropyl methyl cellulose, so that the modified silica sol has good cohesiveness, and the surface layer slurry comprising the silica sol has high air permeability, high wet strength and cracking resistance.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a modified silica sol, wherein the raw materials of the modified silica sol comprise, by weight, 95-100 parts of silica sol, 0.1-2 parts of polyvinyl alcohol and 0.1-2 parts of hydroxypropyl methyl cellulose.
In the invention, the modified silica sol is combined with the hydroxyl groups of the polyvinyl alcohol through the silanol groups on the outer layer of the silica sol, so that the cohesiveness of the silica sol can be improved, and then the wet strength of the modified silica sol is further improved through hydroxypropyl methyl cellulose treatment; the surface layer slurry of the casting containing the modified silica sol has high wet strength and cracking resistance, so that the apparent quality of the casting is effectively improved, and the repair cost of the casting is reduced.
Preferably, the raw materials of the modified silica sol include 95-100 parts by weight of the silica sol, for example, 96 parts, 97 parts, 98 parts, 99 parts, 100 parts, etc.
Preferably, the raw material of the modified silica sol comprises 0.1 to 2 parts by weight of polyvinyl alcohol, for example, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts and the like.
In the invention, the content of the polyvinyl alcohol is more than 2 parts, so that the stability of the whole silica sol is reduced, and the service life of the modified silica sol is greatly reduced.
Preferably, the raw material of the modified silica sol comprises 0.1 to 2 parts by weight of hydroxypropyl methylcellulose, for example, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts and the like.
In the invention, the content of the hydroxypropyl methylcellulose is more than 2 parts, so that the stability of the whole silica sol is reduced, and the service life of the modified silica sol is greatly reduced.
Preferably, the silica sol has a solid content of 25 to 35%, for example, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 34%, or the like.
Preferably, the silica sol has a pH of 9.5 to 10.5, and may be, for example, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, etc.
In the invention, the pH value of the silica sol is less than 9.5, so that the modified silica sol has poor stability and extremely poor use effect; the pH value is more than 10.5, and the alkalinity is too strong, so that the polyvinyl alcohol is decomposed, the modified silica sol cannot be obtained, and the expected use effect cannot be achieved.
Preferably, the mass ratio of polyvinyl alcohol to hydroxypropyl methylcellulose in the modified silica sol is (0.5-2): 1, and may be, for example, 0.6:1, 0.75:1, 1:1, 1.5:1, 1.8:1, etc.
In the invention, the mass ratio of the polyvinyl alcohol to the hydroxypropyl methylcellulose is less than 0.5:1, which can lead to too little hydroxypropyl methylcellulose content combined in the modified silica gel, reduce the effect of the product and can not meet the market demand; and the ratio of the raw materials is more than 2:1, so that the product is unstable and the service life is short.
In the present invention, the silica sol in the mass ratio of the silica sol, the polyvinyl alcohol and the hydroxypropyl methylcellulose means the total mass of the silica sol including the solvent.
In a preferred embodiment of the present invention, the raw materials of the modified silica sol further include 0.1 to 1 part by weight of nonionic organic phosphate, for example, 0.2 part by weight, 0.3 part by weight, 0.4 part by weight, 0.5 part by weight, 0.6 part by weight, 0.7 part by weight, 0.8 part by weight, 0.9 part by weight, and the like.
In the invention, the nonionic organic phosphate is nonionic low-foam organic phosphate, so that the compatibility among polyvinyl alcohol, hydroxypropyl methyl cellulose and silica sol can be improved.
Preferably, the raw materials of the modified silica sol further comprise 0.1 to 1 part by weight of an aqueous silicone defoamer, for example, 0.2 part by weight, 0.3 part by weight, 0.4 part by weight, 0.5 part by weight, 0.6 part by weight, 0.7 part by weight, 0.8 part by weight, 0.9 part by weight and the like.
In a second aspect, the present invention provides a method for preparing the modified silica sol according to the first aspect, the method comprising:
(1) Mixing silica sol with polyvinyl alcohol to obtain a mixed solution A;
(2) And (3) mixing the mixed solution A obtained in the step (1) with hydroxypropyl methylcellulose to obtain the modified silica sol.
In the invention, the silica sol further comprises the step of stirring the silica sol before mixing the silica sol with the polyvinyl alcohol; the stirring time is 20 to 40 minutes, and may be, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, or the like.
Preferably, the stirring speed is 100 to 200rpm, for example, 110rpm, 120rpm, 140rpm, 150rpm, 160rpm, 180rpm, etc.
Preferably, the mixing time in step (1) is 1 to 2 hours, for example, 1 hour, 1.5 hours, 2 hours, etc.
Preferably, the temperature of the mixing in the step (1) is 20 to 25 ℃, and for example, 21 ℃, 22 ℃, 23 ℃, 24 ℃ and the like can be used.
Preferably, the rotational speed of the mixing in step (1) is 200 to 300rpm, and may be, for example, 220rpm, 240rpm, 260rpm, 280rpm, etc.
Preferably, the mixing in the step (1) comprises mixing 40-50% of polyvinyl alcohol with silica sol, and adding the rest of polyvinyl alcohol for mixing.
Preferably, the mixing of step (1) further comprises the step of adding a nonionic organic phosphate for mixing.
Preferably, the method for adding the nonionic organic phosphate for mixing comprises the following steps:
after mixing silica sol and polyvinyl alcohol, adding nonionic organic phosphate with the formula amount of 40-50% for first mixing, and then adding the rest nonionic organic phosphate for second mixing.
In the invention, the nonionic organic phosphate is added and mixed in batches to uniformly mix the nonionic organic phosphate with the mixed solution of the polyvinyl alcohol and the silica sol, and activate and further disperse the mixed solution of the polyvinyl alcohol and the silica sol.
Preferably, the time of the first mixing is 20 to 40min, for example, 25min, 30min, 35min, etc.
Preferably, the temperature of the first mixing is 20 to 25 ℃, for example, 21 ℃, 22 ℃, 23 ℃, 24 ℃, and the like.
Preferably, the rotational speed of the first mixing is 200 to 300rpm, and may be 220rpm, 240rpm, 260rpm, 280rpm, or the like, for example.
Preferably, the time of the second mixing is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, etc.
Preferably, the temperature of the second mixing is 35 to 45 ℃, and may be 36 ℃, 37 ℃, 38 ℃, 39 ℃,40 ℃, 41 ℃, 42 ℃, 43 ℃, 44 ℃ or the like, for example.
Preferably, the rotation speed of the second mixing is 300-400 rpm, for example, 320rpm, 340rpm, 350rpm, 360rpm, 370rpm, 380rpm, 390rpm, etc.
Preferably, the temperature of the mixing in the step (2) is 40 to 45 ℃, and may be, for example, 40 ℃, 41 ℃, 42 ℃, 43 ℃, 44 ℃, or the like.
Preferably, the mixing time in step (2) is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, etc.
Preferably, the rotational speed of the mixing in step (2) is 300 to 400rpm, and may be 320rpm, 340rpm, 350rpm, 360rpm, 370rpm, 380rpm, 390rpm, or the like, for example.
Preferably, the step (2) further comprises the step of adding an aqueous organosilicon antifoaming agent for mixing after the mixed solution A is mixed with the hydroxypropyl methylcellulose.
Preferably, the time for adding the aqueous silicone defoamer to mix is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, etc.
As a preferable technical scheme of the invention, the preparation method comprises the following steps:
(1) Mixing silica sol and polyvinyl alcohol at 20-25 ℃ for 1-2 h, and then adding optional nonionic organic phosphate for mixing to obtain a mixed solution A;
(2) Mixing the mixed solution A obtained in the step (1) with hydroxypropyl methyl cellulose for 1-3 hours at the temperature of 40-45 ℃, and then adding an optional aqueous organic silicon defoamer for continuous mixing for 1-3 hours to obtain the modified silica sol.
According to the preparation method of the modified silica sol, the polyvinyl alcohol is firstly adopted for modification, and then the hydroxypropyl methyl cellulose is adopted for modification, so that the cohesiveness of the silica sol and the wet strength of the casting surface layer slurry can be improved; the combination of the silica sol and the hydroxypropyl methylcellulose is difficult compared with polyvinyl alcohol, and if the order of the silica sol and the hydroxypropyl methylcellulose is changed, the modified silica sol has extremely poor use effect and cannot be used.
In a third aspect, the present invention provides a binder comprising a modified silica sol as described in the first aspect.
The numerical ranges recited herein include not only the recited point values, but also any point values between the recited numerical ranges that are not recited, and are limited to, and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values that the recited range includes.
Compared with the prior art, the invention has the beneficial effects that:
according to the modified silica sol provided by the invention, the silica sol is modified by the polyvinyl alcohol and the hydroxypropyl methyl cellulose with a specific proportion, so that the modified silica sol has good cohesiveness, the surface layer slurry comprising the silica sol has high wet strength and cracking resistance, and the apparent mass of the casting is good; the viscosity of the modified silica sol is more than or equal to 3.3cps, the wet strength of the surface layer slurry comprising the modified silica sol is more than or equal to 6.8MPa, and no or fewer cracks exist on the surface of the casting.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
The materials used in the examples and comparative examples of the present invention are as follows:
polyvinyl alcohol: PVA-1788 available from Shengyu New Material technology Co., ltd;
hydroxypropyl methylcellulose: HPMC-001 from Shandong Xinfuman chemical technology Co., ltd;
nonionic low foam organic phosphate: PPE 1040;
aqueous silicone defoamer: XPJ-S225.
Example 1
The embodiment provides a modified silica sol which comprises, by weight, 95 parts of silica sol (solid content is 30%), 2 parts of polyvinyl alcohol, 2 parts of hydroxypropyl methylcellulose, 0.5 part of nonionic low-foam organic phosphate and 0.5 part of aqueous organic silicon defoamer.
The embodiment provides a preparation method of the modified silica sol, which comprises the following specific steps:
(1) Placing the silica sol into a 1000mL flask, adding a stirrer, and stirring at 150rpm for 30min; slowly adding half amount of polyvinyl alcohol into the mixture under stirring condition, adjusting the stirring speed to be 250rpm, stirring for 30min, then slowly adding the other half amount of polyvinyl alcohol, heating to 20-25 ℃ when the temperature of a reaction system is lower than 20-25 ℃ in the reaction process, keeping the stirring speed to be 250rpm, continuously stirring for 1h, slowly adding half amount of nonionic low-foam organic phosphate, keeping the stirring speed to be 250rpm, continuously stirring for 30min, then raising the temperature to 40 ℃, adjusting the stirring speed to be 350rpm, slowly adding the other half amount of nonionic low-foam organic phosphate under stirring, and continuously stirring for 2h to obtain a mixed solution A;
(2) Slowly adding hydroxypropyl methyl cellulose into the mixed solution A obtained in the step (1), keeping the temperature constant at 40 ℃, keeping the stirring speed at 350rpm, and continuously stirring for 2 hours; slowly adding the aqueous organic silicon defoamer under the stirring condition, and continuously stirring for 2 hours to obtain the modified silica sol.
Example 2
The embodiment provides a modified silica sol which comprises, by weight, 95 parts of silica sol (solid content is 30%), 2 parts of polyvinyl alcohol, 1 part of hydroxypropyl methylcellulose, 1 part of nonionic low-foam organic phosphate and 1 part of aqueous organic silicon defoamer.
This example provides a method for preparing the modified silica sol, and the specific steps are the same as in example 1.
Example 3
The embodiment provides a modified silica sol which comprises, by weight, 95 parts of silica sol (solid content is 30%), 1 part of polyvinyl alcohol, 2 parts of hydroxypropyl methylcellulose, 1 part of nonionic low-foam organic phosphate and 1 part of aqueous organic silicon defoamer.
This example provides a method for preparing the modified silica sol, and the specific steps are the same as in example 1.
Example 4
The embodiment provides a modified silica sol which comprises, by weight, 95 parts of silica sol (solid content is 30%), 2 parts of polyvinyl alcohol, 1.5 parts of hydroxypropyl methylcellulose, 1 part of nonionic low-foam organic phosphate and 0.5 part of aqueous organic silicon defoamer.
This example provides a method for preparing the modified silica sol, and the specific steps are the same as in example 1.
Example 5
The embodiment provides a modified silica sol which comprises, by weight, 95 parts of silica sol (solid content is 30%), 1.5 parts of polyvinyl alcohol, 2 parts of hydroxypropyl methylcellulose, 1 part of nonionic low-foam organic phosphate and 0.5 part of aqueous organic silicon defoamer.
This example provides a method for preparing the modified silica sol, and the specific steps are the same as in example 1.
Example 6
This example provides a modified silica sol differing from example 1 only in that the polyvinyl alcohol was present in an amount of 0.5 parts, and other materials and amounts were the same as in example 1.
This example provides a method for preparing the modified silica sol, and the specific steps are the same as in example 1.
Example 7
This example provides a modified silica sol differing from example 1 only in that the hydroxypropyl methylcellulose was present in an amount of 0.5 parts, and the other materials and amounts were the same as in example 1.
This example provides a method for preparing the modified silica sol, and the specific steps are the same as in example 1.
Comparative example 1
This comparative example provides a modified silica sol differing from example 1 only in that the polyvinyl alcohol was 4 parts, and other raw materials and amounts were the same as in example 1.
This comparative example provides a method for preparing the modified silica sol, and the specific procedure is the same as in example 1.
Comparative example 2
This comparative example provides a modified silica sol differing from example 1 only in that the hydroxypropyl methylcellulose was 4 parts, and other materials and amounts were the same as in example 1.
This comparative example provides a method for preparing the modified silica sol, and the specific procedure is the same as in example 1.
Comparative example 3
This comparative example provides a modified silica sol differing from example 1 only in that the modified silica sol has no polyvinyl alcohol therein, and other raw materials and amounts thereof are the same as those of example 1.
This comparative example provides a method for preparing the modified silica sol, and the specific procedure is the same as in example 1.
Comparative example 4
This comparative example provides a modified silica sol differing from example 1 only in that there is no hydroxypropyl methylcellulose in the modified silica sol, and other materials and amounts are the same as in example 1.
This comparative example provides a method for preparing the modified silica sol, and the specific procedure is the same as in example 1.
Comparative example 5
This comparative example provides a silica sol supplied by Guangdong and silicon articles Inc., which was not modified with polyvinyl alcohol and hydroxypropyl methylcellulose.
Performance testing
(1) pH value: measured by a pH meter;
(2) Viscosity: measured by a viscometer;
(3) Wet strength: adopting a JB/T13038-2017 method to test;
(4) Apparent mass: mixing 1 part of the modified silica sol provided in examples 1 to 7 and comparative examples 1 to 4 with 1 part of the silica sol provided in comparative example 5 and 4.4 parts of powder liquid of refractory materials (zircon powder, manufacturer: 40 kg/bag of Yixing city ancient king technology Co., ltd.) to prepare surface layer slurry, and observing surface crack condition after casting; judgment standard: the surface has no obvious cracks, the crack content is less than 3%, and the surface is marked as 'excellent'; crack content is greater than 3%, noted as "bad".
The specific test results are shown in table 1:
TABLE 1
As can be seen from the table, the modified silica sol provided by the invention has high viscosity and excellent adhesiveness by modifying the silica sol with polyvinyl alcohol and hydroxypropyl methylcellulose in a specific ratio; and the wet strength and air permeability of the casting surface sizing agent can be improved, and the cracking resistance is improved, so that the apparent quality of the casting is good.
From examples 1 to 5, the modified silica sol is alkaline, and accords with the use habit of the investment casting industry; the viscosity of the modified silica sol is 3.3-4.2 cps, the wet strength of the surface sizing agent comprising the modified silica sol is 6.8-7.9 MPa, and the surface of the casting has no or fewer cracks; as is clear from comparison of examples 1 and examples 6 to 7, when the polyvinyl alcohol and the hydroxypropyl methylcellulose in the modified silica sol are not in a specific ratio, the wet strength is lowered and the surface quality of the casting is deteriorated; as is clear from comparison of example 1 with comparative examples 1 to 4, when the combination or the proportion is not preferable in the present invention, the wet strength of the surface layer slurry is lowered or the surface quality of the casting is deteriorated, and the cracks are more; as can be seen from comparison of example 1 and comparative example 5, the modified silica sol provided by the invention has better performance in all aspects than the common unmodified silica sol.
In summary, the modified silica sol provided by the invention is modified by the polyvinyl alcohol and the hydroxypropyl methyl fiber, so that the cohesiveness of the silica sol can be improved, the wet strength of casting surface sizing agent is improved, the defects of cracking resistance, good air permeability, shell cracking, swelling and the like are avoided, the apparent quality of castings is improved, and the production cost is reduced.
While the foregoing is directed to embodiments of the present invention, other and further details of the invention may be had by the present invention, it should be understood that the foregoing description is merely illustrative of the present invention and that no limitations are intended to the scope of the invention, except insofar as modifications, equivalents, improvements or modifications are within the spirit and principles of the invention.
Claims (25)
1. The modified silica sol is characterized in that the raw materials of the modified silica sol comprise, by weight, 95-100 parts of silica sol, 0.1-2 parts of polyvinyl alcohol and 0.1-2 parts of hydroxypropyl methyl cellulose;
the mass ratio of polyvinyl alcohol to hydroxypropyl methylcellulose in the modified silica sol is (0.5-2): 1.
2. The modified silica sol according to claim 1, wherein the silica sol has a solids content of 25 to 35%.
3. The modified silica sol of claim 1, wherein the silica sol has a pH of 9.5 to 10.5.
4. The modified silica sol according to claim 1, wherein the raw material of the modified silica sol further comprises 0.1 to 1 part by weight of a nonionic organic phosphate.
5. The modified silica sol according to claim 1, wherein the raw material of the modified silica sol further comprises 0.1 to 1 part by weight of an aqueous silicone defoamer.
6. A method of preparing a modified silica sol according to any one of claims 1 to 5, comprising:
(1) Mixing silica sol with polyvinyl alcohol to obtain a mixed solution A;
(2) And (3) mixing the mixed solution A obtained in the step (1) with hydroxypropyl methylcellulose to obtain the modified silica sol.
7. The method according to claim 6, wherein the mixing time in the step (1) is 1 to 2 hours.
8. The method according to claim 6, wherein the temperature of the mixing in the step (1) is 20 to 25 ℃.
9. The method according to claim 6, wherein the rotational speed of the mixing in the step (1) is 200 to 300rpm.
10. The method according to claim 6, wherein the mixing in the step (1) comprises mixing 40-50% of the polyvinyl alcohol with the silica sol, and adding the rest of the polyvinyl alcohol for mixing.
11. The method of claim 6, wherein the step (1) further comprises the step of adding a nonionic organic phosphate for mixing.
12. The method of claim 11, wherein the adding the nonionic organic phosphate for mixing comprises:
after mixing silica sol and polyvinyl alcohol, adding nonionic organic phosphate with the formula amount of 40-50% for first mixing, and then adding the rest nonionic organic phosphate for second mixing.
13. The method of claim 12, wherein the first mixing is for a period of 20 to 40 minutes.
14. The method of claim 12, wherein the first mixing is at a temperature of 20-25 ℃.
15. The method of claim 12, wherein the first mixing is at a speed of 200 to 300rpm.
16. The method of claim 12, wherein the second mixing is for a period of 1 to 3 hours.
17. The method of claim 12, wherein the second mixing is at a temperature of 35-45 ℃.
18. The method of claim 12, wherein the second mixing is at a speed of 300 to 400rpm.
19. The method according to claim 6, wherein the temperature of the mixing in the step (2) is 40 to 45 ℃.
20. The method according to claim 6, wherein the mixing time in the step (2) is 1 to 3 hours.
21. The method according to claim 6, wherein the rotational speed of the mixing in the step (2) is 300 to 400rpm.
22. The method according to claim 6, wherein the mixing of the mixed solution A and the hydroxypropyl methylcellulose in the step (2) further comprises the step of adding an aqueous silicone defoamer for mixing.
23. The method of claim 6, wherein the aqueous silicone defoamer is added and mixed for a period of 1 to 3 hours.
24. The method of manufacturing according to claim 6, characterized in that the method of manufacturing comprises:
(1) Mixing silica sol and polyvinyl alcohol at 20-25 ℃ for 1-2 h, and then adding optional nonionic organic phosphate for mixing to obtain a mixed solution A;
(2) Mixing the mixed solution A obtained in the step (1) with hydroxypropyl methyl cellulose for 1-3 hours at the temperature of 40-45 ℃, and then adding an optional aqueous organic silicon defoamer for continuous mixing for 1-3 hours to obtain the modified silica sol.
25. A binder comprising the modified silica sol of any one of claims 1 to 5.
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