CN101444827B - Pyrophyllite lost foam casting coating and preparation method thereof - Google Patents

Abstract

The invention discloses a pyrophillite lost foam casting coating and a preparation method thereof. The coating comprises the following components by the mass percentage: 90% to 95.8% of pyrophillite refractory powder, 0.2% to 0.7% of sodium carboxymethyl cellulose, 1.9% to 4.4% of swell soil, 1.9% to 5.3% of soluble glass, 0.1% to 0.18% of polyethylene alkyl polyol ether, and 0.05% to 0.1% of N-octanol, and the mass percentage of the components is 100% in total, wherein, pyrophillite refractory powder is pyrophillite or mixture of pyrophillite and other refractory materials. The invention has the advantages that the pyrophillite lost foam casting coating has favorable suspension property and thixotropy, as well as excellent ventilation property and relatively high surface strength; and the preparation technology is simple, the operation is convenient, the raw material is abundant and the production cost is low. The invention is mainly used for producing refractory material on the surface of foam plastic mould of lost foam pieces.

Description

Pyrophyllite lost foam casting coating and preparation method thereof

technical field

The invention belongs to the technical field of liquid metal forming, and in particular relates to a pyrophyllite lost foam casting coating, and also relates to a preparation method of the casting coating.

Background technique

With its unique advantages, lost foam casting is known as "green casting technology" and "21st century casting technology". Since its application in my country in the 1960s, after decades of continuous development, the application field of lost foam casting has been continuously expanded, and good economic and social benefits have been obtained.

In lost foam casting, coating is one of the key technologies. Unlike ordinary sand casting, the coating of lost foam casting is applied to the surface of the foam plastic mold rather than to the mold or sand core. In view of the difference between lost foam casting and ordinary sand casting, the lost foam casting coating should not only meet the requirements for the use of ordinary casting coatings, but also play a role in the following aspects, that is, to improve the rigidity and strength of the foam plastic pattern and maintain the stability of the pattern size ; Maintain the stability of the dry sand mold during pouring; also protect the surface of the pattern from the erosion of quicksand during molding. For this reason, the lost foam casting coating is required to have high strength, high air permeability, good coating and thixotropy, and at the same time, it should be easy to clean, low in cost, and easy to operate.

The lost foam casting coating is mainly composed of refractory powder, binder, solvent, suspending agent and special additives. Refractory powder is an important component of coatings, and its properties determine the properties of coatings. When choosing refractory powder for casting coatings, many properties should be considered, such as refractoriness, thermal expansion coefficient, chemical stability at high temperature, source of raw materials, price, and degree of impact on people and the environment. Commonly used refractories include graphite powder, quartz powder, zircon powder, corundum powder, bauxite powder, magnesia powder and their mixed powder.

Graphite has high refractoriness and thermal stability, is plentiful and inexpensive, and has historically been the most commonly used refractory powder in sand cast iron coatings. However, graphite powder is black and delicate, pollutes the human body and the environment greatly, does not meet the requirements of environmental protection, and has been gradually replaced by other refractory powders. Quartz powder has a wide range of sources, low cost, and a certain degree of refractoriness, so it is widely used in coatings. The main problem of quartz powder is that its dust is easy to make people suffer from silicosis, which seriously affects the physical and mental health of operators, so its use is not recommended. Zircon powder has high fire resistance and thermal conductivity, small thermal expansion, good thermal stability, and does not chemically react with iron oxide. It is mainly used in large steel castings and important castings. Zircon powder has excellent refractory performance, but it relies heavily on imports, the price remains high, and the cost of coating is high; in addition, the associated mineral powder of zircon powder is radioactive. Corundum powder is a good refractory material, but it is short of resources and expensive, which is not conducive to popularization and use. Magnesia powder has small thermal expansion and strong resistance to alkaline slag, but its price is more expensive than quartz powder. Bauxite refractory clinker powder has small thermal expansion and high refractoriness, but its cost is higher than that of quartz powder. Therefore, it is imperative to improve the quality of castings and develop new refractory powders and casting coatings.

Pyrophyllite is a famous non-metallic mineral in my country, and its resources are relatively abundant. Pyrophyllite is mainly composed of quartz, kaolin, and sericite, and there are also pyrophyllite mainly composed of kaolin or sericite. Pyrophyllite is a crystalline structure, a layered silicate mineral, monoclinic, and a highly disordered crystal structure. Its chemical structural formula is Al ₂ [Si ₄ O ₁₀ ](OH) ₂ , and its theoretical chemical composition is Al ₂ O ₃ 28.3%, SiO ₂ 66.7%, and H ₂ O 5.0%. Pyrophyllite has fine texture, Mohs hardness 1.5-2.0, density 2.65-2.90g/cm ³ , and refractoriness >1700°C. Pyrophyllite has many characteristics such as chemical stability, low thermal expansion, low thermal conductivity, low electrical conductivity, high insulation, high melting point, good corrosion resistance, etc., so that it is widely used in ceramics, metallurgy, building materials, chemical industry, light industry and other industrial sectors. Mainly used in refractory materials, ceramic raw materials, handicrafts and decorative materials, in the artificial diamond industry, glass fiber, fillers and candy ingredients, etc. Among them, in terms of application, the most used abroad is the production of refractory materials. Such as pyrophyllite and clay made of refractory mud, refractory coating, refractory concrete aggregate.

Pyrophyllite powder particles are mostly flaky, with small bulk density, good fluidity, medium adsorption, low hygroscopicity, general dispersibility, wettability, good suspension and partial acidity, etc., which can meet the needs of coatings for fillers. Color, hiding power, enhancement and suspension requirements. Pyrophyllite can be used in paint industry coating fillers, paper coatings, ink coatings, thermal insulation coatings, refractory coatings and architectural coatings. Hu Qinghua of Hefei University of Technology and others carried out experimental research on the application of pyrophyllite powder in interior wall coatings. The paint consists of polyvinyl alcohol, water glass, pyrophyllite powder and other fillers, water and additives. The results show that the quality index of pyrophyllite interior wall paint is obviously better than that of 106 paint, and pyrophyllite powder has replaced some fillers such as titanium dioxide, lithopone, talcum powder and light calcium carbonate. Pyrophyllite powder is an ideal paint filler, which can act as part of the color (Hu Qinghua, Physicochemical Properties and Application Research of Pyrophyllite Powder, Anhui Geology, 1996, 6(1): 52-56). It is reported that pyrophyllite powder is used as a covering or filler in paints and coatings abroad, which can make the coatings have good suspension, durability and viscosity, and avoid abrasion and shedding (Li Bowei, Wenhuachuan, review of domestic and foreign leaves The development and utilization of wax stone and talc and the quality requirements in industry, Journal of Sichuan Institute of Building Materials, 1988, 3(2): 47-68; Xu Fenglin, Xu Chuanyun. The development direction of pyrophyllite development and utilization in Zhejiang Province, China's non-metallic mineral industry guide Journal, 2007, (5): 15-17). Japan uses pyrophyllite powder as a paper-making filler, and reports point out that pyrophyllite powder is also a better paper-making coating. Studies have shown that the use of pyrophyllite mineral materials has properties such as low thermal conductivity, high strength after roasting, low density and multi-layer structure, and can be used in thermal insulation materials. After adding water and other binders to the mixed material composed of carbonaceous material, pyrophyllite mineral material and mica mineral material, a good thermal insulation coating can be formed after molding and roasting.

It is also reported in the literature that pyrophyllite powder can produce various high-temperature and corrosion-resistant coatings and special coatings for metallurgical casting in the coatings industry (Yao Wenjun, Zhang Peiping, Li Shushu, Ma Liyan, Su Ke. Research status of pyrophyllite mineral resources and their application development , World Geology, 2007, 26(1): 124-129; Liu Ping. Talking about the development and utilization of pyrophyllite, IM&P Chemical Minerals and Processing, 2004, (12): 38), but only mentioned in relevant literature, There is no detailed information available, and there is no specific introduction to the coating ratio and preparation process.

Contents of the invention

The object of the present invention is to provide a pyrophyllite lost foam casting coating, which has high strength, high air permeability, good coating and thixotropy, easy cleaning and low cost.

Another object of the present invention is to provide a preparation method of the above coating.

The technical solution adopted in the present invention is that the pyrophyllite lost foam casting coating is composed of the following components by mass percentage:

Pyrophyllite refractory powder 90%～95.8%

Sodium carboxymethyl cellulose 0.2%～0.7%

Bentonite 1.9%～4.4%

Water glass 1.9%～5.3%

Polyvinyl alkyl alcohol ether 0.1%～0.18%

n-octanol 0.05%～0.1%

The total amount of the above components is 100%,

Wherein, the pyrophyllite refractory powder is pyrophyllite or a mixture of pyrophyllite and other refractory materials.

Another technical scheme adopted in the present invention is that the preparation method of the above-mentioned coating is specifically carried out in the following steps:

Step 1. According to mass percentage, take pyrophyllite refractory powder 90%～95.8%, sodium carboxymethylcellulose 0.2%～0.7%, bentonite 1.9%～4.4%, water glass 1.9%～5.3%, polyvinyl alkyl 0.1% to 0.18% of alcohol ether and 0.05% to 0.1% of n-octanol; wherein the pyrophyllite refractory powder is pyrophyllite or a mixture composed of 50% to 90% of pyrophyllite and 10% to 50% of other refractory materials by mass percentage,

Step 2. According to the mass ratio of 1:30, the sodium carboxymethylcellulose obtained in step 1 is mixed with water, stirred evenly, and left to stand for 70 to 75 hours to obtain an aqueous sodium carboxymethylcellulose solution;

According to the mass ratio of 1:5, the bentonite obtained in step 1 is mixed with water, stirred evenly, and left to stand for 70 to 75 hours to obtain a bentonite-water mixture;

Step 3, mix the pyrophyllite refractory powder obtained in step 1 and water glass, sodium carboxymethyl cellulose aqueous solution and bentonite water mixed solution obtained in step 2, and the mixed solution prepared, according to the mass ratio of 10:1, Add the mixed solution and water into a high-speed disperser, and disperse at a high speed for 3 to 5 hours to prepare a mixed paint;

Step 4. Add polyvinyl alkane and n-octanol obtained in step 1 to the mixed paint prepared in step 3 in sequence, stir for 30-40 minutes, and disperse evenly to prepare pyrophyllite lost foam casting paint.

The pyrophyllite lost foam casting coating of the present invention has good suspending properties and thixotropy, good air permeability and high surface strength, simple preparation process, convenient operation, abundant raw materials and low production cost, and is mainly used for production The refractory coating on the surface of the foam plastic model of the lost foam casting.

Detailed ways

The present invention will be described in detail below in combination with specific embodiments.

Coating of the present invention, by mass percentage, is made up of following components:

Pyrophyllite refractory powder 90%～95.8%

Sodium Carboxymethyl Cellulose 0.2%～0.7%

Bentonite 1.9%～4.4%

Water glass 1.9%～5.3%

Polyvinyl alkyl alcohol ether 0.1%～0.18%

n-octanol 0.05%～0.1%

The total amount of the above components is 100%;

The pyrophyllite refractory powder can be pyrophyllite, or it can be mixed with other refractory materials. In the pyrophyllite refractory powder made by mixing pyrophyllite and other refractory materials, the content of pyrophyllite is 50%-90% by mass percentage, the rest is other refractory materials, and the total amount of components is 100%. Other refractory materials are selected from one or a combination of two or more of quartz powder, zircon powder, corundum powder, bauxite powder or magnesia powder.

The preparation method of foundry coating of the present invention, carry out according to the following steps:

Step 1. According to mass percentage, take pyrophyllite refractory powder 90%～95.8%, sodium carboxymethylcellulose 0.2%～0.7%, bentonite 1.9%～4.4%, water glass 1.9%～5.3%, polyvinyl alkyl Alcohol ether 0.1%~0.18% and n-octanol 0.05%~0.1%; the pyrophyllite refractory powder is pyrophyllite or a mixture composed of 50%~90% pyrophyllite and 10%~50% other refractory materials by mass percentage, other The refractory material is selected from one or a combination of two or more of quartz powder, zircon powder, corundum powder, bauxite powder or magnesia powder.

Step 2. According to the mass ratio of 1:30, the sodium carboxymethylcellulose obtained in step 1 is mixed with water, stirred evenly, and left to stand for 70 to 75 hours to obtain an aqueous sodium carboxymethylcellulose solution;

According to the mass ratio of 1:5, the bentonite obtained in step 1 is mixed with water, stirred evenly, and left to stand for 70 to 75 hours to obtain a bentonite-water mixture;

Step 3, mix the pyrophyllite refractory powder obtained in step 1 and water glass, sodium carboxymethyl cellulose aqueous solution and bentonite water mixed solution obtained in step 2, and the mixed solution prepared, according to the mass ratio of 10:1, Add the mixed solution and water into a high-speed disperser, and disperse at a high speed for 3 to 5 hours to prepare a mixed paint;

Step 4. Add polyvinyl alkane and n-octanol obtained in step 1 to the mixed paint prepared in step 3 in sequence, stir for 30-40 minutes, and disperse evenly to prepare pyrophyllite lost foam casting paint.

The density of the lost foam cast iron coating prepared by the method of the invention is 1.4-1.6g/cm ³ , and the suspension rate after being placed for 72 hours is greater than 98%; the shear stress of the coating is limited to 16-19Pa. Use Tu 4 viscometer to measure the apparent viscosity value of the paint to be 40-42s. The thixotropy rate is 15% to 17%. The brushing index, drip volume and drip time of the paint are about 6.0, 0.4g and 10s, respectively. The normal temperature strength of the coating is higher than 700g/mm. The strength of the paint coating after firing at 1200°C is higher than 500g/mm. The normal temperature gas permeability of the coating is higher than 10cm ² ·(kPa·min) ^-1 , and the high temperature gas permeability is higher than 20cm ² ·(kPa·min) ^-1 .

It can be seen that the pyrophyllite coating prepared by the method of the present invention has excellent performance, good suspension and thixotropy; the coating also has good air permeability and higher surface strength, which satisfies the requirements of the coating for lost foam casting iron castings well. Require. The preparation method of the paint is simple, non-toxic, and the produced castings have high surface finish. This coating is mainly used for lost foam casting to produce cast iron, cast steel and non-ferrous alloy castings. Compared with similar foreign products, the required cost is reduced by 50% under the condition of equivalent quality. The invention overcomes the defects of expensive refractory powder and high production cost of the paint in the existing conventional casting paint preparation technology; at the same time, the casting paint containing the pyrophyllite refractory powder is smooth and has suitable viscosity. Moreover, high-quality casting coatings can be produced with cheap raw materials and a simple production process, which effectively reduces the production cost of coatings, and the quality of finished products is good.

Example 1

According to mass percentage, 90% of pyrophyllite, 0.7% of sodium carboxymethyl cellulose, 4.4% of bentonite, 4.62% of water glass, 0.18% of polyvinyl alkyl alcohol ether and 0.1% of n-octanol are respectively taken;

According to the mass ratio of 1:30, sodium carboxymethyl cellulose was mixed with water, stirred evenly, and left to stand for 70 hours to obtain an aqueous solution of sodium carboxymethyl cellulose;

According to the mass ratio of 1:5, bentonite and water were mixed, stirred evenly, and left to stand for 70 hours to obtain a bentonite-water mixture;

Mix pyrophyllite, water glass, sodium carboxymethyl cellulose aqueous solution and bentonite water mixture evenly, and add the mixed solution and water into the high-speed disperser according to the mass ratio of 10:1, and disperse at high speed for 4 hour, the mixed coating is obtained;

The polyvinyl alkane and n-octanol are sequentially added to the prepared mixed paint, stirred for 30 minutes, and dispersed uniformly to prepare the pyrophyllite lost foam casting paint.

Example 2

According to mass percentage, take pyrophyllite 95.8%, sodium carboxymethyl cellulose 0.2%, bentonite 1.95%, water glass 1.9%, polyvinyl alkyl alcohol ether 0.1% and n-octanol 0.05%;

According to the mass ratio of 1:30, sodium carboxymethyl cellulose was mixed with water, stirred evenly, and left to stand for 75 hours to obtain an aqueous solution of sodium carboxymethyl cellulose;

According to the mass ratio of 1:5, bentonite and water were mixed, stirred evenly, and left to stand for 75 hours to obtain a bentonite-water mixture;

Mix pyrophyllite, water glass, sodium carboxymethyl cellulose aqueous solution and bentonite water mixed solution evenly to prepare the mixed solution, according to the mass ratio of 10:1, add the mixed solution and water into the high-speed disperser, and disperse at high speed for 5 hour, the mixed coating is obtained;

Add polyvinyl alkane and n-octanol to the mixed paint in turn, stir for 40 minutes, and disperse evenly to prepare pyrophyllite lost foam casting paint.

Example 3

According to mass percentage, 92.07% of pyrophyllite, 0.5% of sodium carboxymethyl cellulose, 1.9% of bentonite, 5.3% of water glass, 0.15% of polyvinyl alkyl alcohol ether and 0.08% of n-octanol are respectively taken;

According to the mass ratio of 1:30, sodium carboxymethyl cellulose was mixed with water, stirred evenly, and left to stand for 72 hours to obtain an aqueous solution of sodium carboxymethyl cellulose;

According to the mass ratio of 1:5, bentonite and water were mixed, stirred evenly, and left to stand for 72 hours to obtain a bentonite-water mixture;

Mix pyrophyllite, water glass, sodium carboxymethyl cellulose aqueous solution and bentonite water mixture evenly to prepare a mixed solution, according to the mass ratio of 10:1, add the mixed solution and water into a high-speed disperser, and disperse at a high speed for 3 hour, the mixed coating is obtained;

The polyvinyl alkane and n-octanol are sequentially added into the mixed paint, stirred for 35 minutes, and dispersed uniformly to prepare the pyrophyllite lost foam casting paint.

Example 4

According to mass percentage, pyrophyllite and quartz powder are 90%, sodium carboxymethylcellulose 0.7%, bentonite 4.4%, water glass 4.62%, polyvinyl alkyl alcohol ether 0.18% and n-octanol 0.1%. In pyrophyllite and quartz powder, pyrophyllite is 90% by mass percentage, and quartz powder is 10%;

According to the scheme of Example 1, the pyrophyllite in Example 1 was replaced with the pyrophyllite and quartz powder in this example, that is, the pyrophyllite lost foam casting coating was prepared.

Example 5

According to mass percentage, pyrophyllite, zircon powder and corundum powder 95.8%, sodium carboxymethyl cellulose 0.2%, bentonite 1.95%, water glass 1.9%, polyvinyl alkyl alcohol ether 0.1% and n-octanol 0.05%, pyrophyllite , Zircon powder and corundum powder, pyrophyllite is 70% by mass percentage, zircon powder is 20%, and corundum powder is 10%;

According to the scheme of Example 2, the pyrophyllite in Example 2 was replaced with the pyrophyllite, zircon powder and corundum powder in this example, and the pyrophyllite lost foam casting coating was obtained.

Example 6

According to mass percentage, respectively take pyrophyllite, corundum powder, bauxite powder and magnesia powder 92.07%, sodium carboxymethyl cellulose 0.5%, bentonite 1.9%, water glass 5.3%, polyvinyl alkyl alcohol ether 0.15% and n-octane Alcohol 0.08%, in pyrophyllite, corundum powder, bauxite powder and magnesia powder, by mass percentage, pyrophyllite is 50%, corundum powder 10%, magnesia powder 10%, bauxite powder is 30%;

According to the scheme of Example 3, the pyrophyllite in Example 3 was replaced with the pyrophyllite, corundum powder, bauxite powder and magnesia powder in this example to obtain the pyrophyllite lost foam casting coating.

Claims (7)

1. a Pyrophillite lost foam casting coating is characterized in that, by mass percentage, is made up of following component:

Pyrophillite refractory powder 90%～95.8%

Sodium carboxymethylcellulose 0.2%～0.7%

Bentonite 1.9%～4.4%

Waterglass 1.9%～5.3%

Polyethylene alkyl alcohol ether 0.1%～0.18%

N-octyl alcohol 0.05%～0.1%

The said components total amount is 100%,

Wherein, the pyrophillite refractory powder is the mixture of pyrophillite or pyrophillite and other refractory materials.

2. cast paint according to claim 1 is characterized in that, in the mixture of pyrophillite and other refractory materials, according to mass percent, pyrophillite is 50%～90%, and surplus is other refractory materials, each component total amount 100%.

3. cast paint according to claim 1 is characterized in that, the particle size diameter of described pyrophillite is 0.063～0.088mm.

4. cast paint according to claim 1 is characterized in that, described other refractory materials are selected from one or more the combination in silica flour, zirconium English powder, schmigel, aluminium vanadine powder or the magnesia powder.

5. the preparation method of the described cast paint of claim 1 is characterized in that, specifically carries out according to the following steps:

Step 1, is by mass percentage got pyrophillite refractory powder 90%～95.8%, sodium carboxymethylcellulose 0.2%～0.7%, bentonite 1.9%～4.4%, waterglass 1.9%～5.3%, polyethylene alkyl alcohol ether 0.1%～0.18% and n-octyl alcohol 0.05%～0.1% respectively; Wherein the pyrophillite refractory powder is pyrophillite or the mixture be made up of 50%～90% pyrophillite and 10%～50% other refractory materials by mass percentage,

Step 2, according to 1: 30 mass ratio, the sodium carboxymethylcellulose that step 1 is obtained mixes with water, stirs, and leaves standstill 70～75 hours, makes sodium carboxymethyl cellulose solution;

According to 1: 5 mass ratio, the bentonite that step 1 is obtained mixed with water, stirs, and left standstill 70～75 hours, made the bentonite water mixed liquid;

Sodium carboxymethyl cellulose solution and bentonite water mixed liquid that step 3, the pyrophillite refractory powder that step 1 is obtained and waterglass, step 2 make mix, the mixed solution that makes, mass ratio according to 10: 1, this mixed solution and water are added in the high speed dispersor, high speed dispersion 3～5 hours makes compo;

Step 4, the polyethylene alkane that step 1 is obtained and n-octyl alcohol add in the compo that step 3 makes successively, stir 30～40 minutes, are uniformly dispersed, and make Pyrophillite lost foam casting coating.

6. method according to claim 5 is characterized in that, in the mixture of pyrophillite and other refractory materials, according to mass percent, pyrophillite is 50%～90%, and surplus is other refractory materials, each component total amount 100%.

7. method according to claim 5 is characterized in that, described other refractory materials are selected from one or more the combination in silica flour, zirconium English powder, schmigel, aluminium vanadine powder or the magnesia powder.