CN121423524A - Preparation method of reinforced sand core material for casting - Google Patents

Abstract

The invention discloses a preparation method of a reinforced sand core material for casting. The method comprises the steps of firstly taking sea sand as a matrix and matching with a specific adhesive, wherein the adhesive consists of biomass modified furan resin, a composite curing agent and a reinforcing nano material. The innovation core is the synthesis of biomass modified furan resin, which is prepared by adding nanocellulose, formaldehyde and furfuryl alcohol under alkaline condition, and polymerizing with urea and residual furfuryl alcohol under acidic condition. The reinforced nano material is obtained by generating TiN nano particles in situ on the upper layer gap of the MoS _{2 2} nano sheet by a hydrothermal-calcining method. The mechanical property and the thermal stability of the sand core material prepared by the method are obviously improved through the synergistic effect of the nanocellulose and the hybrid nanomaterial, and the method is suitable for the field of high-performance casting.

Description

Preparation method of reinforced sand core material for casting

Technical Field

The application relates to the technical field of binders for casting, in particular to a reinforced sand core material for casting and a preparation method thereof, which are particularly suitable for being used as a sand binder in a sand casting process and can improve the molding quality of castings and the environmental protection of production.

Background

Casting is the basic process of metal part formation in modern manufacturing, wherein the sand core is used as a key part for forming a complex inner cavity of a casting, and the performance of the sand core directly determines the dimensional accuracy and quality of the casting. Furan resins have long been one of the most commonly used binders for sand cores because of their rapid hardening speed and good surface finish on castings. However, as the high-end equipment manufacturing industry becomes increasingly demanding with respect to casting quality, production efficiency, and environmental protection, the inherent drawbacks of conventional furan resin sand cores become more pronounced.

First, conventional furan resins are highly dependent on petrochemical products such as furfuryl alcohol, formaldehyde, and the like. This not only faces the risk of resource exhaustion, but also the synthesis and use process of the catalyst is accompanied by the emission of volatile organic compounds, which is contrary to the current concepts of green chemical industry and sustainable development. Secondly, the brittleness of the crosslinked network is larger after the traditional furan resin is cured, so that the normal-temperature strength and the thermal strength of the sand core are insufficient. Under the severe thermal shock of casting high-temperature molten metal, the sand core is easy to soften, deform and even break, so that the defects of sand washing, sand sticking, deformation and the like of castings are caused, and the yield is seriously influenced. In particular, for key components such as engine cylinder body, cylinder cover and the like with complex structure and thinner wall thickness, nearly strict requirements are put on the initial strength and high-temperature stability of the sand core. Furthermore, the mere addition of inorganic fillers or micron-sized reinforcements tends to be of limited effectiveness. The interface binding force between the materials and the resin matrix is weak, the materials are easy to agglomerate, the effective transmission of stress is difficult to realize, and micro cracks are easy to generate due to the mismatch of the thermal expansion coefficient of the materials and the resin at high temperature, and the performance is possibly deteriorated. In addition, although the conventional single curing agent (such as p-toluenesulfonic acid) can ensure the normal-temperature curing speed, the problems of excessively concentrated curing reaction, poor sand core plasticity, large pungent smell, obviously reduced curing efficiency in a high-humidity environment and the like exist, and the process stability and the operation environment are affected.

Disclosure of Invention

The invention aims to provide a preparation method of a reinforced sand core material for casting, which mainly solves the problems of insufficient strength, high gas generation amount and poor thermal stability of biomass modification of the traditional furan resin in a high-temperature environment.

The preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 1-5wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in parts by weight:

50-60 parts of biomass modified furan resin;

12-15 parts of a composite curing agent;

3-5 parts of a reinforcing nano material;

10-15 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:1-2;

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

s3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 1-15 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 1-3 minutes to obtain the reinforced sand core material for casting.

Preferably, the preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

S11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain 0.5-2wt% of fiber suspension;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.1-0.5 molNaOH to automatically titrate to maintain pH=10-11, and reacting for 6h;

and S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 2-3%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation step of the reinforced nano material is molybdenum disulfide@titanium nitride hybrid nano material comprises the following steps:

S111, dissolving sodium molybdate and thioacetamide in water according to the molar ratio of Mo to S of 1:4, and carrying out hydrothermal reaction at 160-180 ℃ to obtain MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1-M tetrabutyl titanate, adding 0.05-M urea, performing hydrothermal reaction for 2-4h at 100-160 ℃, and calcining the 2-4-h hydrothermal product at a high temperature of 800-1000 ℃ in an inert atmosphere to convert TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of TiN of 20-30%.

Preferably, the general chemical formula of the layered double hydroxide is [ M ^z+ _1-xM³⁺ _x(OH)₂]^a+(X^n- _a/n)·mH₂ O ], wherein z=2, M ²⁺=Ca²⁺,Mg²⁺,Zn²⁺,Ni²⁺,Mn²⁺,Co²⁺, fe ²⁺;M³⁺=Al³⁺,Cr³⁺,Mn³⁺,Fe³⁺,Ga³⁺,Co³⁺ and Ni ³⁺ are common, magnesium nitrate and aluminum nitrate are dissolved according to the molar ratio of Mg/Al of 2:1, naOH solution is dropwise added to the solution until pH=10, the coprecipitation reaction is carried out at 80 ℃ for 6 hours, and the Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O is obtained after washing and drying.

Preferably, in the step S1, 1-5 parts by weight of nanocellulose, 10-20 parts by weight of formaldehyde, 5-15 parts by weight of urea and 40-60 parts by weight of furfuryl alcohol monomer are mixed.

Preferably, in the step S1, the pH value is adjusted to 9-11, the temperature is raised to 100-110 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80-95 ℃, the pH value is adjusted to 3.5-4.5, the temperature is raised to 90-110 ℃, and the polymerization reaction is carried out for 1h. And/or;

the ultrasonic treatment time is 10-30min, and the power is 300-500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.01-0.1g/g, 0.01-0.03g/g, 0.05-0.01g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

The reinforced sand core material for casting has the advantages that:

1. The nano material builds a passivation barrier layer at the interface of resin and sand grains, effectively inhibits liquid wetting penetration, and thoroughly eliminates the sand sticking defect of castings. The biomass modified furan resin reduces the content of high-activity hydroxymethyl, realizes the gradual release of gas by matching with the pyrolysis catalytic effect of nano materials, eliminates subcutaneous pores, enables carboxyl groups of TEMPO oxidized nano cellulose and furfuryl alcohol to form stable ether bonds, breaks through the bottleneck of low thermal decomposition temperature of traditional biomass components, improves the strength of sand cores, and simultaneously enables biomass components from nano cellulose to reduce the strength of thermal decomposition residues of the resin and achieve both environmental protection and high-temperature performance.

2. The organic zirconium borate complex realizes low-temperature rapid solidification, the nano pre-dispersion system ensures the storage stability, and the nano pre-dispersion system is suitable for the existing furan resin equipment without modification.

3. TiN nano particles are introduced, and the TiN nano particles are characterized by having a high proportion of strong covalent bonds, so that excellent thermal stability and low thermal expansibility are provided. At the same time MoS ₂ sheets of material are added. The MoS ₂ sheets themselves have a layered structure and some interlaminar shear capacity. The TiN nano particles and the MoS ₂ sheet form a pinning structure in the composite material. This structure significantly increases creep resistance and dimensional stability at elevated temperatures through strong interfacial interactions and physical barriers.

4. The layered double hydroxide material is introduced, and nitrate ions are contained between the layers, and can absorb a large amount of heat when the nitrate ions are decomposed by heating, so that the gas generation rate and the heat release strength of the whole material can be reduced. More importantly, the LDH laminate structure is kept orderly stacked in the resin, and interlayer nano-space can selectively adsorb small molecular gas (such as H ₂O、CO₂) to delay the release rate of the gas, thereby reducing the total amount of generated gas and delaying the peak temperature of generated gas.

5. The friction coefficient of MoS ₂ sheet layer with very low specific crystal face is utilized to endow the material surface with excellent lubricating property, so as to obviously reduce demoulding resistance, and meanwhile, the characteristic of high coordination number of zirconium ions is utilized to form coordination bond crosslinking network, and the crosslinking point has higher bond energy and stability.

Detailed Description

Example 1

The preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 3wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

55 parts of biomass modified furan resin;

12 parts of a composite curing agent;

3 parts of reinforcing nano material;

10 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:1.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

And S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 1 minute to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

s11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain 0.5wt% of fiber suspension;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.1 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

and S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 2%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to a mole ratio of Mo to S of 1:4, and carrying out hydrothermal reaction for 6 hours at 160 ℃, and obtaining MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction at 120 ℃ for 2h, calcining the 2h hydrothermal product at 800 ℃ under an inert atmosphere, and converting TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of 20%.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 3 parts by weight of nanocellulose, 10 parts by weight of formaldehyde, 10 parts by weight of urea and 50 parts by weight of furfuryl alcohol monomer are mixed.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.01g/g, 0.05g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Example 2

The preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 2wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

50 parts of biomass modified furan resin;

13 parts of a composite curing agent;

4 parts of reinforcing nano material;

11 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:1.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

And S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 1 minute to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

s11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain 1wt% fiber suspension;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.3 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

And S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 2.5%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to a molar ratio of Mo to S of 1:4, and carrying out hydrothermal reaction at 170 ℃ to obtain MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction at 140 ℃ for 1.5 h, and calcining at 900 ℃ for 3h under an inert atmosphere to convert TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of TiN of 25%.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 2 parts by weight of nanocellulose, 15 parts by weight of formaldehyde, 8 parts by weight of urea and 55 parts by weight of furfuryl alcohol monomer are mixed.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.01g/g, 0.05g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Example 3

The preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 3wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

53 parts of biomass modified furan resin;

14 parts of a composite curing agent;

3 parts of reinforcing nano material;

12 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:2.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 3 minutes to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

S11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain a fiber suspension with the weight percent of 2 percent;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.3 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

And S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 3%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to a mole ratio of Mo to S of 1:4, and carrying out hydrothermal reaction at 180 ℃ to obtain MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction for 2 hours at 160 ℃, calcining the hydrothermal product at 1000 ℃ for 4 hours under an inert atmosphere, and converting TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of 30%.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 12 parts by weight of formaldehyde, 12 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are used.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.05g/g, 0.03g/g, 0.07g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Example 4

The preparation method of the reinforced sand core material for casting comprises the following steps:

S1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 5wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in parts by weight:

56 parts of biomass modified furan resin;

15 parts of a composite curing agent;

5 parts of reinforcing nano material;

14 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:2.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

s3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 10 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 3 minutes to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

S11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain a 1.5wt% fiber suspension;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.3 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

and S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 2%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to the mole ratio of Mo to S of 1:4, and carrying out hydrothermal reaction for 6 hours at 180 ℃;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction for 2 hours at 160 ℃, calcining the hydrothermal product at 1000 ℃ for 4 hours under an inert atmosphere, and converting TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of 30%.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 11 parts by weight of formaldehyde, 6 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are mixed.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.07g/g, 0.03g/g, 0.09g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Example 5

The preparation method of the reinforced sand core material for casting comprises the following steps:

S1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 4wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

58 parts of biomass modified furan resin;

15 parts of a composite curing agent;

5 parts of reinforcing nano material;

10 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:1.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 2 minutes to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

s11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain 0.8wt% fiber suspension;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.3 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

And S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 2.5%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to a mole ratio of Mo to S of 1:4, and carrying out hydrothermal reaction for 6 hours at 160 ℃, and obtaining MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction for 1.5 hours at 160 ℃, and calcining the hydrothermal product at a high temperature of 800 ℃ under an inert atmosphere to convert TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of 30%.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 11 parts by weight of formaldehyde, 6 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are mixed.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.09g/g, 0.03g/g, 0.1g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Comparative example 1

The difference between this comparative example and example 3 is that no layered double hydroxide was added, specifically:

the preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 3wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

53 parts of biomass modified furan resin;

14 parts of a composite curing agent;

3 parts of reinforcing nano material;

12 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:2.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 3 minutes to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

S11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain a fiber suspension with the weight percent of 2 percent;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.3 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

And S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 3%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforced nano material is molybdenum disulfide@titanium nitride hybrid nano material.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to a mole ratio of Mo to S of 1:4, and carrying out hydrothermal reaction at 180 ℃ to obtain MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction for 2 hours at 160 ℃, calcining the hydrothermal product at 1000 ℃ for 4 hours under an inert atmosphere, and converting TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of 30%.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 12 parts by weight of formaldehyde, 12 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are used.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.05g/g, 0.03g/g, 0.07g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Comparative example 2

The comparative example differs from example 3 in that molybdenum disulfide @ titanium nitride hybrid nanomaterial is not added, specifically:

the preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 3wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

53 parts of biomass modified furan resin;

14 parts of a composite curing agent;

3 parts of reinforcing nano material;

12 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:2.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 3 minutes to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

S11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain a fiber suspension with the weight percent of 2 percent;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.3 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

And S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 3%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nanomaterial is a layered double hydroxide.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 12 parts by weight of formaldehyde, 12 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are used.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.05g/g, 0.03g/g, 0.07g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Comparative example 3

The difference between this comparative example and example 3 is that no organozirconium borate complex is added, specifically:

the preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 3wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

53 parts of biomass modified furan resin;

14 parts of a composite curing agent;

3 parts of reinforcing nano material;

12 parts of water;

Wherein the compound curing agent is p-toluenesulfonic acid.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 3 minutes to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

S11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain a fiber suspension with the weight percent of 2 percent;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.3 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

And S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 3%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to a mole ratio of Mo to S of 1:4, and carrying out hydrothermal reaction at 180 ℃ to obtain MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction for 2 hours at 160 ℃, calcining the hydrothermal product at 1000 ℃ for 4 hours under an inert atmosphere, and converting TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of 30%.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 12 parts by weight of formaldehyde, 12 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are used.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.05g/g, 0.03g/g, 0.07g/g, respectively, of the fiber suspension.

Comparative example 4

The present comparative example differs from example 3 in that no modification of the furan resin was performed, specifically:

the preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 3wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

53 parts of furan resin;

14 parts of a composite curing agent;

3 parts of reinforcing nano material;

12 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:2.

S2, mixing the furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 3 minutes to obtain the reinforced sand core material for casting.

The preparation method of the furan resin comprises the following steps:

After ultrasonic mixing of formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to a mole ratio of Mo to S of 1:4, and carrying out hydrothermal reaction at 180 ℃ to obtain MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction for 2 hours at 160 ℃, calcining the hydrothermal product at 1000 ℃ for 4 hours under an inert atmosphere, and converting TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of 30%.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 12 parts by weight of formaldehyde, 12 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are used.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Comparative example 5

The difference between this comparative example and example 3 is that the nanocellulose used is a commercial nanocellulose

The preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 3wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

53 parts of biomass modified furan resin;

14 parts of a composite curing agent;

3 parts of reinforcing nano material;

12 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:2.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 3 minutes to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation steps of the molybdenum disulfide@titanium nitride hybrid nanomaterial comprise:

S111, dissolving sodium molybdate and thioacetamide in water according to a mole ratio of Mo to S of 1:4, and carrying out hydrothermal reaction at 180 ℃ to obtain MoS ₂ nano-sheets after centrifugal washing;

S112, dispersing MoS ₂ nano-sheets in an ethanol solution containing 0.1M tetrabutyl titanate, adding 0.05M urea, carrying out hydrothermal reaction for 2 hours at 160 ℃, calcining the hydrothermal product at 1000 ℃ for 4 hours under an inert atmosphere, and converting TiO ₂ into TiN. And (3) generating TiN nano particles in situ at the gaps of the MoS ₂ sheets, and centrifugally drying to obtain the MoS ₂ @TiN hybrid nano material with the mass fraction of 30%.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 12 parts by weight of formaldehyde, 12 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are used.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.05g/g, 0.03g/g, 0.07g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Comparative example 6

The difference between this comparative example and example 3 is that mechanically mixed MoS ₂ and TiN are used instead of in situ generated MoS ₂ @ TiN

The preparation method of the reinforced sand core material for casting comprises the following steps:

s1, preparing sea sand and an adhesive respectively, wherein the using amount of the adhesive is 3wt% of the using amount of the sea sand, and the adhesive mainly comprises the following components in percentage by weight:

53 parts of biomass modified furan resin;

14 parts of a composite curing agent;

3 parts of reinforcing nano material;

12 parts of water;

The composite curing agent is a complex of p-toluenesulfonic acid and organic zirconium borate, and the ratio of the complex of p-toluenesulfonic acid to the complex of organic zirconium borate is 10:2.

S2, mixing the biomass modified furan resin and water together and uniformly stirring, adding the reinforcing nano material, and uniformly stirring to obtain a mixture;

S3, adding the compound curing agent into the sea sand, uniformly mixing, and standing for 5 minutes to obtain a mixture;

and S4, uniformly mixing the mixture of the step S2 and the step S3, and standing for 3 minutes to obtain the reinforced sand core material for casting.

The preparation method of the biomass modified furan resin comprises the following steps:

Ultrasonically mixing nanocellulose, formaldehyde and furfuryl alcohol monomers, heating and preserving heat after adjusting to alkalinity, adding urea for addition reaction, adding half furfuryl alcohol to adjust to acidity, heating and polymerizing, cooling and vacuum dehydrating, adding the rest half furfuryl alcohol, and uniformly stirring to obtain the biomass modified furan resin.

Preferably, the preparation steps of the nanocellulose comprise:

S11, taking bleached wood pulp, soaking the bleached wood pulp in deionized water for swelling, crushing the bleached wood pulp by a high-shear emulsifying machine, and sieving the crushed bleached wood pulp by a 200-mesh sieve to obtain a fiber suspension with the weight percent of 2 percent;

S12, transferring the suspension into a reaction kettle, adding TEMPO and NaBr, dropwise adding NaClO solution, and simultaneously, using 0.3 molNaOH to automatically titrate to maintain pH=10, and reacting for 6 hours;

And S13, carrying out vacuum suction filtration and water washing treatment on the reaction liquid in the step S12, concentrating to obtain a dispersion liquid with the solid content of 3%, and then treating the concentrated liquid subjected to pre-cooling treatment by a high-pressure homogenizer to form a nanocrystallized dispersion form.

Preferably, the reinforcing nano material is a mixture of molybdenum disulfide @ titanium nitride hybrid nano material and layered double hydroxide.

Preferably, the preparation of the layered double hydroxide comprises the steps of dissolving magnesium nitrate and aluminum nitrate according to a Mg/Al molar ratio of 2:1, dropwise adding a NaOH solution until the pH value is 10, performing coprecipitation reaction at 80 ℃ for 6 hours, and washing and drying to obtain Mg _0.67Al_0.33(OH)₂(NO₃)_0.33·mH₂ O.

Preferably, in the step S1, 5 parts by weight of nanocellulose, 12 parts by weight of formaldehyde, 12 parts by weight of urea and 45 parts by weight of furfuryl alcohol monomer are used.

Preferably, in the step S1, the pH value is adjusted to 10, the temperature is raised to 100 ℃, the temperature is kept for 1h, the addition reaction is carried out at 80 ℃, the pH value is adjusted to 4 by acidity, the temperature is raised to 100 ℃, and the polymerization reaction is carried out for 1h. And/or;

The time of ultrasonic treatment is 10min, and the power is 500W.

Preferably, TEMPO, naBr, naClO is added in step S12 in an amount of 0.05g/g, 0.03g/g, 0.07g/g, respectively, of the fiber suspension.

Preferably, the organic zirconium borate complex is a complex formed by the reaction of tetra-n-propyl zirconate and phenylboric acid according to a molar ratio of 1:2.

Performance test:

the sand core materials prepared in examples 1 to 5 and comparative examples 1 to 6 were tested:

And (3) testing the normal-temperature compressive strength of the resin sand:

And (3) preparing the mixture, namely weighing the required amount of standard sand by using an electronic balance. The sand core material prepared by the invention is added, stirred for 60 seconds, discharged and put into a bowl-shaped sand mixer, and mixed at a low speed until sand grains uniformly wrap resin, and no agglomeration or dry sand phenomenon exists. The strength is affected by strictly controlling the mixing time, too long or too short.

Preparing a cylindrical sample preparation cylinder with the diameter of 50 x 50, coating a thin layer of release agent (such as silicone oil) on the inner wall, and pouring sand into the sample cylinder three times. After each pouring, the sample was hit 3 times with a hammer from a free fall of 50mm height on a hammer-type sample making machine. After the last hammering, the excessive sand material at the top of the sample cylinder is scraped by a scraper, so that the end face of the sample is leveled. And (3) operating a sampling machine ejector rod to slowly and stably push out the compact cylindrical sample from the sample cylinder, so as to avoid damage caused by vibration or extrusion. The pushed out wet cylindrical sample was immediately placed on a special sample curing machine that had been preheated to 180 ℃ for 60 seconds. After solidification, the sample is rapidly taken out with a crucible tongs, placed in a desiccator filled with silica gel, and cooled for at least 30 minutes to room temperature. After cooling, the diameter and height of the samples were measured, and samples with cracks, corners, bulging or oversize were removed as 50 x 50. Compressive and tensile tests were performed according to the test standards of GB/T2684 and GB/T24413-2009.

Table 1 comparative results of pressure test related to the reinforced core material for casting prepared according to the present invention

The high temperature performance of the resin sand is tested at the same time, and the test standard is used for comparing the examples and the comparative examples according to GB/T3074.1, ISO75-2:2013 and GB/T24413-2009.

Table 2 comparative results of high temperature Performance test of the enhanced core materials for casting prepared according to the present invention

As can be seen from Table 1, the molybdenum disulfide@titanium nitride hybrid nanomaterial, the layered double hydroxide and the organic zirconium borate complex of the reinforced sand core material for casting prepared by the invention have great influence on compressive and tensile strength. Meanwhile, as can be seen from table 2, the modification of furfuryl alcohol monomer without nanocellulose in comparative example 4 has a great influence on the strength at high temperature.

Testing collapsibility (sand residue percentage%) standard sand core preparation 5 samples per group of 50 x 50mm cylindrical resin sand cores prepared according to the compressive strength test method are cooled and stored in a dryer for standby, and the samples are placed in a box-type resistance furnace preheated to 700 ℃ (simulated aluminum liquid pouring temperature). Keeping the temperature for 10min according to the temperature rising rate of 10 ℃ to 300 ℃ and keeping the temperature for 30min according to the temperature rising rate of 5 ℃ to 700 ℃ when the temperature rising rate of 300 ℃ reaches to 700 ℃, and taking out after the procedure is finished and the temperature is cooled to below 70 ℃ along with the furnace. And (5) cleaning the surface of the sample by using a soft brush to remove the collapsed floating sand. The non-collapsed sand core residue was placed on a screen (pore size 0.3 mm) and purged vertically with compressed air at 0.2MPa for 60 seconds. The residual sand core mass (m ₁) was collected and weighed. Residual sand ratio is calculated, residual sand ratio (%) = (m ₁/m₀)×100%（m₀: original mass of sample)

TABLE 3 comparative results of collapsibility test of reinforced core materials for casting prepared according to the present invention

From table 3, it can be seen that nanocellulose and MoS ₂ @ TiN hybrid material are the most core components that promote collapsibility, promoting uniform decomposition through a dual mechanism of thermal conduction and lubrication.

Gas evolution test preparation of samples of total amount of gas released when resin sand is decomposed by heat (mL/g) and real-time gas evolution rate (mL/s) according to GB/T2684. If the resin sand core is tested, 1.0g of cured resin sand is placed in a quartz boat. The quartz boat is pushed into a constant temperature zone of the tube furnace which is preheated to the target temperature. Immediately start the timer and gas volume auto recorder. And continuously recording the gas generation amount within 0-120 seconds until the gas volume is not increased, and recording the total gas generation amount. Total gas evolution = final gas volume/sample mass, maximum gas evolution rate = maximum gas increment per unit time.

Table 4 comparative results of gas formation test of enhanced core materials for casting prepared according to the present invention

From table 4, it can be seen that the inhibition of the gas generation rate by nanocellulose, the addition of layered double oxide significantly reduced the total gas generation, and the synergistic modification achieved a low total amount and a gentle release balance.

It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.

Claims (10)

1. A method for preparing a reinforcing sand core material for casting, characterized by comprising the following steps: S1. Prepare sea sand and adhesive separately. The amount of adhesive is 1-5 wt% of the amount of sea sand. The adhesive mainly consists of the following components in the following weight ratio: 50-60 parts of biomass-modified furan resin; 12-15 parts of composite curing agent; 3-5 parts of reinforcing nanomaterials; 10-15 parts water; The composite curing agent is a complex of p-toluenesulfonic acid and organozirconium borate, and the ratio of p-toluenesulfonic acid to organozirconium borate is 10:1~2. S2. Mix the above biomass-modified furan resin and water together and stir evenly, then add the above reinforcing nanomaterials and stir evenly again to obtain a mixture; S3. Add the above-mentioned composite curing agent to the above-mentioned sea sand, mix evenly, and let stand for 1-15 minutes to obtain a mixture; S4. Mix the mixture from steps S2 and S3 together evenly, and let it stand for 1-3 minutes to obtain the reinforcing sand core material for casting. 2. The method for preparing the reinforcing sand core material for casting according to claim 1, characterized in that the method for preparing the biomass-modified furan resin includes the following steps: Nanocellulose, formaldehyde and furfuryl alcohol monomers were ultrasonically mixed, adjusted to alkalinity and heated and kept warm. Urea was then added to carry out an addition reaction. Subsequently, half of the furfuryl alcohol was added to adjust to acidity and heated to polymerize. After cooling and vacuum dehydration, the remaining half of the furfuryl alcohol was added and stirred evenly to obtain biomass modified furan resin. 3. The method for preparing the reinforcing sand core material for casting according to claim 1, characterized in that the preparation step of the nanocellulose includes: S11. Take bleached wood pulp, soak it in deionized water to swell, pulverize it with a high-shear emulsifier, and pass it through a 200-mesh sieve to obtain a 0.5-2wt% fiber suspension; S12. Transfer the suspension to the reactor, add TEMPO and NaBr, then add NaClO solution dropwise while maintaining pH at 10-11 by automatic titration with 0.1-0.5 mol NaOH. React for 6 hours. S13. The reaction solution in S12 is vacuum filtered and washed with water to concentrate it into a dispersion with a solid content of 2-3%. The concentrated solution after pre-cooling is then processed by a high-pressure homogenizer to form a nano-dispersion. 4. The method for preparing the reinforcing sand core material for casting according to claim 2, wherein the reinforcing nanomaterial is a mixture of molybdenum disulfide@titanium nitride hybrid nanomaterial and layered double hydroxide. 5. The method for preparing the reinforcing sand core material for casting according to claim 2, characterized in that the preparation steps of the reinforcing nanomaterial being a molybdenum disulfide@titanium nitride hybrid nanomaterial include: S111. Sodium molybdate and thioacetamide were dissolved in water at a Mo:S molar ratio of 1:4 and hydrothermally reacted at 160-180℃ for 6 h; MoS2 nanosheets were obtained after centrifugation and washing. S112. MoS₂ nanosheets were dispersed in an ethanol solution containing 0.1 M tetrabutyl titanate, and 0.05 M urea was added. After hydrothermal reaction at 100-160℃ for 2-4 h, the hydrothermal product was calcined at 800-1000℃ for 2-4 h under an inert atmosphere to convert TiO₂ into TiN. TiN nanoparticles were generated in situ in the interlayer gaps of MoS₂ , and after centrifugation and drying, MoS₂ @TiN hybrid nanomaterials with a TiN mass fraction of 20-30% were obtained. 6. The method for preparing the reinforcing sand core material for casting according to claim 2, characterized in that the layered double hydroxide generally has the chemical formula [M z+ 1-x</sub> M 3+ x (OH) 2 ] a+ (X n- a/n )·mH 2 O; usually z=2, M 2+ = Ca 2+ , Mg 2+ , Zn 2+ , Ni 2+ , Mn2+  , Co2+ and Fe 2+ ; M  3+  = Al 3+ , Cr 3+  , Mn3+, Fe 3+ , Ga 3+ , Co 3+ and Ni 3+ ; magnesium nitrate and aluminum nitrate are dissolved at a Mg/Al molar ratio of 2:1, NaOH solution is added dropwise until pH=10, co-precipitation reaction is carried out at 80℃ for 6h, and the mixture is washed and dried to obtain Mg 0.67 Al 0.33 (OH) 2 (NO 3 ) 0.33 ·mH 2 O. 7. The method for preparing reinforcing sand core material for casting according to claim 2, characterized in that, in step S1, there are 1-5 parts by weight of nanocellulose, 10-20 parts by weight of formaldehyde, 5-15 parts by weight of urea and 40-60 parts by weight of furfuryl alcohol monomer. 8. The method for preparing reinforcing sand core material for casting according to claim 2, characterized in that, in step S1, the pH value is adjusted to 9-11, the temperature is raised to 100-110℃, held for 1 hour, and an addition reaction is carried out at 80-95℃; the pH value is adjusted to 3.5-4.5, the temperature is raised to 90-110℃, and a polymerization reaction is carried out for 1 hour. and/or; The ultrasonic treatment time is 10-30 minutes, and the power is 300-500W. 9. The method for preparing the reinforcing sand core material for casting according to claim 3, characterized in that the amounts of TEMPO, NaBr, and NaClO added in step S12 are 0.01-0.1 g/g, 0.01-0.03 g/g, and 0.05-0.01 g/g of the fiber suspension, respectively. 10. The method for preparing the reinforcing sand core material for casting according to claim 1, wherein the organoborate zirconium complex is a complex formed by the reaction of tetrapropyl zirconate and phenylboronic acid in a molar ratio of 1:2.