Binder for casting and preparation method thereof

Abstract

The invention provides a binder for casting and a preparation method thereof, and relates to the technical field of binder preparation. The binder for casting is prepared from the following components in parts by weight: 30 to 42 parts of water glass, 0.1 to 2 parts of polyvinyl acetate rubber powder, 48 to 60 parts of argil, 5 to 12 parts of quartz sand and 0.8 to 2 parts of auxiliaries. The preparation method comprises the following steps: at the environment temperature of 20-25 DEG C, adding the polyvinyl acetate rubber powder and the assistant into the water glass, dispersing for 5-10 minutes at the speed of 200-400r / min, adding the pottery clay and the quartz sand, dispersing for 20-40 minutes at the speed of 400-800r / min, adjusting the viscosity, and discharging. The flexibility of the material is improved, and the elongation at break is obviously increased.

Description

Technical Field

[0001] The invention relates to the technical field of binder preparation, and in particular to a casting binder and a preparation method thereof. Background Art

[0002] At present, in the field of casting, binders are mainly divided into two categories: inorganic binders and organic binders. Organic binders have the disadvantages of strong pungent odor, large amounts of toxic gases generated during the casting process, serious environmental pollution, and high prices of organic resins, which greatly restrict the use of organic binders. Inorganic binders based on water glass have the advantages of not generating irritating toxic gases, no black pollution, and low prices. However, inorganic binders have the problem of having sufficient rigidity, but becoming brittle after curing in practice.

[0003] As the performance requirements of inorganic binders for casting become increasingly greater, conventional binders can no longer meet the toughness requirements. Therefore, toughening the binders has become a key research direction for inorganic binders. Currently, the toughening of binders used for sand core-shell mold assembly and sealing in the resin sand casting process mainly includes two directions: raw material modification toughening and component optimization toughening. This application aims to provide a new type of modified component for preparing toughened casting binders to overcome the problem of low toughness of existing casting binders. Summary of the invention

[0004] The purpose of the present invention is to provide a casting binder and a preparation method thereof, aiming to improve the toughness of the casting binder.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] On the one hand, the present invention provides a casting binder, which includes the following components in parts by weight: 30-42 parts of water glass, 0.1-2 parts of polyvinyl acetate rubber powder, 48-60 parts of clay, 5-12 parts of quartz sand, and 0.8-2 parts of an additive.

[0007] Furthermore, the following components are included in parts by weight: 40 parts of water glass, 1 part of polyvinyl acetate rubber powder, 50 parts of clay, 10 parts of quartz sand, and 1 part of additive.

[0008] Furthermore, adjuvants include suspending agents and emulsifiers.

[0009] Furthermore, the suspending agent includes one or more of a sodium bentonite suspending agent, a silicate suspending agent, and a cellulose suspending agent.

[0010] Furthermore, the emulsifier includes one or more of OP-10 emulsifier, OP-4 emulsifier, OP-7 emulsifier, OP-15 emulsifier, and OP-20 emulsifier.

[0011] Furthermore, the clay includes one or more of Suzhou clay, kaolin, and bentonite.

[0012] In another aspect, the present invention provides a method for preparing a casting binder, which is used to prepare any of the above casting binders, and the preparation method comprises:

[0013] When the ambient temperature is 20-25℃, add polyvinyl acetate rubber powder and additives into water glass, disperse at 200-400r / min for 5-10min, then add clay and quartz sand, disperse at 400-800r / min for 20-40min, adjust the viscosity and discharge the material.

[0014] The preparation method has the advantages of simple process and uniform dispersion of the modifier in the system.

[0015] In a specific embodiment, polyvinyl acetate rubber powder and additives are added to water glass, and the dispersion coefficient after heating can be 200, 250, 300, 350, 400 r / min.

[0016] In a specific embodiment, after adding clay and quartz sand, the dispersion coefficient can be 400, 450, 500, 550, 600, 650, 700, 750, 800 r / min.

[0017] In one embodiment, the viscosity increasing agent is added to the aggregate at 4% by weight of the aggregate.

[0018] In one embodiment, water glass is added at 3% of the mass of water glass to reduce the viscosity.

[0019] If the clay is added and dispersed evenly in the preparation method, and the rubber powder is added before the material is discharged, uneven dispersion occurs after the rubber powder is added to the sample, that is, obvious solid particles can be felt in the sample after the material is discharged, and after taking it out, it is found that it is a mass formed by the rubber powder after it meets water. In order to avoid this undesirable effect, the preparation step of the present invention is to add the rubber powder to the water glass and disperse it evenly before adding the clay.

[0020] Furthermore, before adding water glass to other components, the water glass is pre-dispersed, and the pre-dispersion parameters are 500-700 r / min and 5-10 min.

[0021] Pre-dispersing the water glass in advance can reduce the stratification phenomenon caused by the water glass standing still, and pre-dispersing can make the structure more uniform.

[0022] Furthermore, the preparation method comprises:

[0023] The ambient temperature is 20-25℃, disperse the water glass at 600r / min for 5-10min, add polyvinyl acetate rubber powder and additives into the water glass, disperse at 400r / min for 10min, add clay and quartz sand, disperse at 400r / min for 30min, adjust the viscosity and discharge the material.

[0024] Compared with the prior art, the key of the present invention is:

[0025] The present invention improves the defect of an inorganic binder mainly composed of water glass and powder materials becoming brittle after curing by reasonably adjusting the types and proportions of the components of the casting binder and coordinating the preparation method; polyvinyl acetate is selected to improve the tensile strength of the binder itself after being added, and polyvinyl acetate is toughened by physical cross-linking between molecules. The use of polyvinyl acetate rubber powder for modification can significantly improve the flexibility of the material, and the elongation at break is significantly increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference numerals refer to like components throughout the drawings.

[0027] FIG. 1 is a sample diagram of a casting binder obtained by adding polyvinyl acetate rubber powder to Example 1 of the present invention ( Figure 1a For the main view, Figure 1b is a top view);

[0028] FIG. 2 is a sample diagram of the casting binder obtained by adding polyvinyl acetate rubber powder and VAE in Example 1 of the present invention ( Figure 2a For the main view, Figure 2b is a top view). DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0030] The present invention is further described below by specific examples and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, conventional materials and conventional instruments, which can be commercially available, and the reagents and materials involved can also be synthesized by conventional synthesis methods.

[0031] The polyvinyl acetate rubber powder, multifunctional rubber powder, gelatin powder, redispersible rubber powder, VAE, lignin and butyl acrylate used below are selected from commercially available products.

[0032] Example 1

[0033] This embodiment provides a casting binder. The ambient temperature is 20°C. 400g of water glass is added to a stainless steel kettle. A high-speed disperser is used to disperse for 10 minutes at 600r / min. 20g of polyvinyl acetate rubber powder, 4g of sodium bentonite suspension agent, and 6g of OP-10 emulsifier are added to the water glass. After dispersing for 10 minutes at 400r / min, 500g of pottery clay and 100g of quartz sand are added. After dispersing for 30 minutes at 400r / min, the viscosity is adjusted and the material is discharged. The sample of the obtained casting binder is shown in the figure. Figure 1a , Figure 1b shown.

[0034] Example 2

[0035] This embodiment provides a casting binder. The ambient temperature is 25°C. 400g of water glass is added to a stainless steel kettle and dispersed at 500r / min for 8min using a high-speed disperser. 1g of polyvinyl acetate rubber powder, 3g of silicate suspending agent, and 7kg of OP-4 emulsifier are added to the water glass and dispersed at 200r / min for 5min. Then, 500g of clay and 89g of quartz sand are added and dispersed at 600r / min for 40min. After adjusting the viscosity, the material is discharged.

[0036] Example 3

[0037] This embodiment provides a casting binder. The ambient temperature is 20° C. 400 g of water glass is added to a stainless steel kettle and dispersed for 5 min using a high-speed disperser at 700 r / min. 1.5 g of polyvinyl acetate rubber powder, 5 g of cellulose suspending agent, and 5 g of OP-7 emulsifier are added to the water glass and dispersed at 300 r / min for 8 min. Then, 500 g of clay and 90 g of quartz sand are added and dispersed at 800 r / min for 20 min. After adjusting the viscosity, the material is discharged.

[0038] Example 4

[0039] This embodiment provides a casting binder. The ambient temperature is 25° C. 350 g of water glass is added to a stainless steel kettle and dispersed at 600 r / min using a high-speed disperser for 5 min. 2 g of polyvinyl acetate rubber powder, 4 g of sodium bentonite suspending agent, and 4 g of OP-15 emulsifier are added to the water glass and dispersed at 400 r / min for 10 min. Then, 540 g of pottery clay and 100 g of quartz sand are added and dispersed at 400 r / min for 30 min. After adjusting the viscosity, the material is discharged.

[0040] Example 5

[0041] This embodiment provides a casting binder. The ambient temperature is 20° C. 350 g of water glass is added to a stainless steel kettle and dispersed at 600 r / min for 10 min using a high-speed disperser. 3 g of polyvinyl acetate rubber powder, 5 g of sodium bentonite suspending agent, and 5 g of OP-20 emulsifier are added to the water glass and dispersed at 400 r / min for 10 min. Then, 540 g of pottery clay and 97 g of quartz sand are added and dispersed at 400 r / min for 30 min. After adjusting the viscosity, the material is discharged.

[0042] Example 6

[0043] This embodiment provides a casting binder. The ambient temperature is 25° C. 300 g of water glass is added to a stainless steel kettle and dispersed at 500 r / min for 8 min using a high-speed disperser. 5 g of polyvinyl acetate rubber powder, 3 g of silicate suspending agent, and 5 kg of OP-4 emulsifier are added to the water glass and dispersed at 200 r / min for 5 min. Then, 480 g of clay and 50 g of quartz sand are added and dispersed at 600 r / min for 40 min. After adjusting the viscosity, the material is discharged.

[0044] Example 7

[0045] This embodiment provides a casting binder. The ambient temperature is 20° C. 350 g of water glass is added to a stainless steel kettle and dispersed at 700 r / min using a high-speed disperser for 5 min. 10 g of polyvinyl acetate rubber powder, 10 g of cellulose suspending agent, and 10 g of OP-7 emulsifier are added to the water glass and dispersed at 300 r / min for 8 min. Then, 600 g of pottery clay and 120 g of quartz sand are added and dispersed at 800 r / min for 20 min. After adjusting the viscosity, the material is discharged.

[0046] Comparison example

[0047] This comparative example provides a casting binder. The ambient temperature is 25°C. 400g of water glass is added to a stainless steel kettle and dispersed at 600r / min for 10min using a high-speed disperser. 4g of sodium bentonite suspending agent and 6g of OP-10 emulsifier are added to the water glass and dispersed at 400r / min for 10min. Then, 500g of clay and 100g of quartz sand are added and dispersed at 400r / min for 30min. After adjusting the viscosity, the material is discharged.

[0048] It can be observed that the samples of Example 4 and Example 5 showed different degrees of hardening after standing for 2-3 hours, so these examples were excluded.

[0049] Small samples of the casting binders obtained in Example 2, Example 3 and the control example were prepared, and the strength data were compared horizontally. The rubber powder was screened according to the characterization of the strength data.

[0050] The strength test method is: weigh the resin standard sand, resin, and curing agent according to the weight ratio of 100:1:0.5, stir and mix, pour the mixed resin sand into the mold, wait for natural curing, and demould. Use adhesive to bond the broken 8-shaped test block and place it horizontally, test the tensile strength of the resin block according to the designed time, and record and calculate the average value, which is the strength of the resin at a specific time.

[0051] The specific data of the obtained strength are shown in Table 1:

[0052] Table 1 Strength data results

[0053]

[0054]

[0055] Unit: MPa, test temperature: 26.2℃, humidity: 62%.

[0056] Comparative Example 1

[0057] The comparative example provides a casting binder. The ambient temperature is 20°C. 400g of water glass is added to a stainless steel kettle, and a high-speed disperser is used to disperse the mixture at 600r / min for 10min. 20g of multifunctional rubber powder, 4g of sodium bentonite suspending agent, and 6g of OP-10 emulsifier are added to the water glass. The mixture is dispersed at 400r / min for 10min. Then, 500g of pottery clay and 100g of quartz sand are added. The mixture is dispersed at 400r / min for 30min. After adjusting the viscosity, the mixture is discharged.

[0058] Comparative Example 2

[0059] The comparative example provides a casting binder. The ambient temperature is 20°C. 400g of water glass is added to a stainless steel kettle and dispersed at 600r / min for 10min using a high-speed disperser. 20g of gelatin powder, 4g of sodium bentonite suspending agent and 6g of OP-10 emulsifier are added to the water glass and dispersed at 400r / min for 10min. Then, 500g of pottery clay and 100g of quartz sand are added and dispersed at 400r / min for 30min. After adjusting the viscosity, the material is discharged.

[0060] Comparative Example 3

[0061] The comparative example provides a casting binder. The ambient temperature is 20°C. 400g of water glass is added to a stainless steel kettle and dispersed at 600r / min for 10min using a high-speed disperser. 20g of redispersible rubber powder, 4g of sodium bentonite suspending agent and 6g of OP-10 emulsifier are added to the water glass and dispersed at 400r / min for 10min. Then, 500g of pottery clay and 100g of quartz sand are added and dispersed at 400r / min for 30min. After adjusting the viscosity, the material is discharged.

[0062] Comparative Example 4

[0063] The comparative example provides a casting binder. The ambient temperature is 20°C. 400g of water glass is added to a stainless steel kettle and dispersed at 600r / min for 10min using a high-speed disperser. 4g of sodium bentonite suspending agent and 6g of OP-10 emulsifier are added to the water glass and dispersed at 400r / min for 10min. Then, 500g of pottery clay and 100g of quartz sand are added and dispersed at 400r / min for 20min. Then, 20g of polyvinyl acetate rubber powder is added and dispersed at 400r / min for 10min. After adjusting the viscosity, the material is discharged.

[0064] Experimental example:

[0065] Small samples of the casting binders of Example 1, Control Example, and Comparative Examples 1-3 were prepared, and the strength data were compared horizontally. The rubber powder was screened according to the characterization of the strength data.

[0066] According to the above strength test method, the specific data of the strength obtained are shown in Table 2:

[0067] Table 2 Strength data results

[0068] Comparison example Polyvinyl acetate rubber powder Multifunctional rubber powder Gelatin powder Redispersible rubber powder 2h intensity 0.895 0.999 0.631 0.992 0.877 6h Intensity 1.310 1.487 1.255 1.283 1.245 24h intensity 1.578 1.651 1.628 1.424 1.487

[0069] Unit: MPa, test temperature: 25.7℃, humidity: 58%.

[0070] According to the characterization of strength data and the prices of various rubber powders, polyvinyl acetate rubber powder was selected as the additive.

[0071] By comparing Example 1 with Comparative Example 4, there are two ways to add the rubber powder: liquid phase addition and solid phase addition. In Example 1, the rubber powder is added to the water glass and dispersed evenly before adding clay, which is the liquid phase addition method. The solid phase addition method is to add the clay and disperse it evenly before adding the rubber powder before discharging. Figure 1a , Figure 1b It can be seen that the adhesive obtained in this way has a uniform and fine texture.

[0072] In comparative example 4, after adding the rubber powder to the sample, the dispersion is uneven, that is, after discharging, obvious solid particles can be felt in the sample, and after taking it out, it is found that the rubber powder is agglomerated after meeting water. In order to avoid such adverse effects, the preparation step of the present invention is to add the rubber powder to the water glass and disperse it evenly before adding the clay.

[0073] Take the finished products of Example 1 and the control example to make small samples, and obtain 3 samples respectively. Take 6 standard 8-shaped blocks of resin and break them, and record their length as the initial length, which is recorded as L. 0Use different adhesives to group and number the resin blocks, place them horizontally in a constant temperature environment for 6 hours to allow them to cure naturally. Pull the bonded resin blocks apart and record their length after breaking as L according to the number. K . Calculate the elongation at break according to the formula: e=(L K -L 0 / L 0 )×100% was used to test the elongation at break, and the data are shown in Table 3 below.

[0074] Table 3 Test results

[0075]

[0076] It can be seen from Table 3 that, compared with the control example, the elongation at break of the modified sample is significantly increased, because polyvinyl acetate is toughened by physical cross-linking between molecules.

[0077] Based on Example 1, other auxiliary materials were added to the polyvinyl acetate for testing. The test was performed in the same manner as above. The strength data and elongation at break are shown in Table 4:

[0078] Table 4 Test results

[0079]

[0080] In the experiment, because the temperature and humidity conditions were different during different experiments, and all were compared with the samples of the blank control group, the data value of the blank control group was counted as 1, and the data of other groups were all ratios. The aggregates were all sodium-based water glass + clay + suspending agent + emulsifier, and other auxiliary materials were added on this basis to verify the toughening effect.

[0081] FIG2 is a sample of the casting binder obtained after adding polyvinyl acetate rubber powder and VAE in Example 1 of the present invention. As shown in the figure, the emulsion has poor compatibility with water glass and cannot be uniformly mixed into the same system, because the main components of VAE are vinyl acetate and ethylene, and water glass does not react with VAE, but the addition of water glass destroys the protective film on the surface of vinyl acetate, causing it to agglomerate, so it is not compatible with water glass. Therefore, it cannot be added to the system as an auxiliary material.

[0082] The gas phase SiO used in the experiment 2 It is hydrophilic. When a certain amount is added during the dispersion process, it will quickly absorb the water in the water glass, causing the sample to dry out. There are a large number of silanol groups on the surface of fumed silica, which interact to form hydrogen bonds when in contact with water molecules. Macroscopically speaking, fumed silica absorbs the water in the water glass before it is evenly dispersed, resulting in the inability to evenly mix the solid and liquid phases, thus causing drying out.

[0083] According to the data in Table 4, it can be seen that the toughening effect of adding other auxiliary materials on the basis of adding polyvinyl acetate is not ideal, and the toughening effect of multiple components is not as good as that of a single component. The more organic auxiliary materials there are, the lower the strength is. It is considered that there will be reactions between organic components. Therefore, the modified component of the present invention is only polyvinyl acetate rubber powder.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A casting binder, characterized in that: The invention comprises the following components in parts by weight: 30-42 parts of water glass, 0.1-2 parts of polyvinyl acetate rubber powder, 48-60 parts of pottery clay, 5-12 parts of quartz sand and 0.8-2 parts of auxiliary agent.

2. The casting binder according to claim 1, characterized in that: The composition includes the following components by weight: 40 parts of water glass, 1 part of polyvinyl acetate rubber powder, 50 parts of clay, 10 parts of quartz sand and 1 part of auxiliary agent.

3. The casting binder according to claim 1, characterized in that: Adjuvants include suspending agents and emulsifiers.

4. The casting binder according to claim 3, characterized in that: The suspending agent includes one or more of a sodium bentonite suspending agent, a silicate suspending agent, and a cellulose suspending agent.

5. The casting binder according to claim 3, characterized in that: The emulsifier includes one or more of OP-10 emulsifier, OP-4 emulsifier, OP-7 emulsifier, OP-15 emulsifier and OP-20 emulsifier.

6. The casting binder according to claim 1, characterized in that: The clay includes one or more of Suzhou clay, kaolin and bentonite.

7. A method for preparing a casting binder, characterized in that: Used to prepare the casting binder according to any one of claims 1 to 6, the preparation method comprising: When the ambient temperature is 20-25℃, add polyvinyl acetate rubber powder and additives into water glass, disperse at 200-400r / min for 5-10min, then add clay and quartz sand, disperse at 400-800r / min for 20-40min, adjust the viscosity and discharge the material.

8. The method for preparing a casting binder according to claim 7, characterized in that: Before adding water glass to other components, the water glass is pre-dispersed, and the pre-dispersion parameters are 500-700r / min and dispersion for 5-10min.

9. The method for preparing a casting binder according to claim 8, characterized in that: The preparation method comprises: The ambient temperature is 20-25℃, disperse the water glass at 600r / min for 5-10min, add polyvinyl acetate rubber powder and additives into the water glass, disperse at 400r / min for 10min, add clay and quartz sand, disperse at 400r / min for 30min, adjust the viscosity and discharge the material.

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