Composite organic binder as well as preparation method and application thereof

Abstract

The invention relates to the technical field of binders, and discloses a composite organic binder, a preparation method and application thereof, the preparation method comprises the following steps: weighing 55-60% of paraffin, 20-25% of beeswax, 10-15% of ethylene-vinyl acetate copolymer and 5-8% of polyvinyl alcohol; adding the weighed components into a vacuum stirrer for melting and mixing to obtain a mixed melt; pouring the mixed melt into a material containing disc, and cooling to obtain a blocky composite organic binder; the application comprises the following steps: stirring and mixing the composite organic binder and raw materials of the alumina crucible to obtain slurry; performing slip casting on the slurry to obtain a biscuit; and degreasing and sintering the biscuit to obtain the alumina crucible. The melting point of the composite organic binder is lower, and the alumina crucible prepared from the composite organic binder has the advantages of high purity and smooth surface.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alloy materials, and particularly relates to a composite organic binder, a preparation method and application thereof. BACKGROUND

[0002] Alumina crucible is a key auxiliary material in the production process of an aero-engine key part blank, can be used for melting casting alloy, and has a great influence on casting slag defect caused by impurities of the alumina crucible itself.

[0003] At present, the binder used for preparing the alumina crucible is mainly clay. Due to the innate characteristics of the clay, the content of potassium, sodium and iron is high, so that the purity of the crucible cannot be achieved, and the impurities affect the qualified rate of casting production.

[0004] Therefore, how to improve the purity of the alumina crucible is still a technical problem to be solved at present. SUMMARY

[0005] The main purpose of the present application is to provide a composite organic binder, a preparation method and application thereof, and aims to solve the technical problems in the background art.

[0006] To achieve the above-mentioned purpose, in a first aspect, the present application provides a composite organic binder, which comprises the following components in percentage by weight: 55-60% of paraffin, 20-25% of beeswax, 10-15% of ethylene-vinyl acetate copolymer and 5-8% of polyvinyl alcohol.

[0007] In a second aspect, the present application further provides a preparation method of the composite organic binder, comprising: weighing 55-60% of paraffin, 20-25% of beeswax, 10-15% of ethylene-vinyl acetate copolymer and 5-8% of polyvinyl alcohol; adding the weighed paraffin, beeswax, ethylene-vinyl acetate copolymer and polyvinyl alcohol into a vacuum stirrer to melt and mix, to obtain a mixed melt; pouring the mixed melt into a material container and cooling to obtain a block of the composite organic binder.

[0008] Preferably, the step of adding the weighed paraffin, beeswax, ethylene-vinyl acetate copolymer and polyvinyl alcohol into a vacuum stirrer to melt and mix to obtain a mixed melt comprises: adding the paraffin and beeswax into the vacuum stirrer, heating to a preset first temperature to melt, and stirring at a preset first rotating speed for a preset first time length to obtain a wax-based melt; adding the ethylene-vinyl acetate copolymer and polyvinyl alcohol into the wax-based melt, heating to a preset second temperature to melt, and stirring at a preset second rotating speed for a preset second time length to obtain the mixed melt.

[0009] Preferably, the preset first temperature is 65-75℃, the preset first rotating speed is 30-40 rpm, and the preset first time length is 1-1.5 hours.

[0010] Preferably, the preset second temperature is 90-95℃, the preset second rotating speed is 60-80 rpm, and the preset second time length is 9-10 hours.

[0011] In a third aspect, the present application further provides an application of the composite organic binder, and the composite organic binder is used for preparing an alumina crucible.

[0012] Preferably, the method for preparing the alumina crucible comprises: After the composite organic binder and raw materials of the alumina crucible are stirred and mixed, a slurry is obtained; The green body is obtained by injecting the slurry into a mold; The alumina crucible is obtained by debinding and sintering the green body.

[0013] Preferably, after the composite organic binder and raw materials of the alumina crucible are stirred and mixed, a slurry is obtained, which comprises: The active alumina, alumina, corundum, mullite, quartz and oleic acid are weighed according to the alumina crucible formula, mixed to obtain a mixture; The composite organic binder is added to the mixture, and stirred at a preset stirring temperature and a preset stirring speed for a preset third time length to obtain a slurry; wherein the mass ratio of the mixture to the composite organic binder is 4:(1-1.5).

[0014] Preferably, the alumina crucible formula comprises the following raw materials in the following weight percentages: active alumina 10-15%, alumina 20-25%, corundum 15-20%, mullite 7-9%, quartz 30-35% and oleic acid 1-1.5%; the preset stirring temperature is 90-95℃, the preset stirring speed is 80-120 rpm, and the preset third time length is 26-30 hours.

[0015] Compared with the alumina crucible using clay as a binder, the melting point of the binder of the present application is lower, which can be burned and volatilized in the subsequent sintering process of the crucible, and does not introduce impurity elements such as potassium and sodium, thereby improving the purity of the crucible and the production qualification rate of the crucible casting; secondly, the binder, by combining paraffin wax with beeswax, improves the flowability of the slurry and improves the filling capacity, and by adding ethylene-vinyl acetate copolymer and polyvinyl alcohol, the plasticity and strength of the green body are improved, and the problems of cracking and bulging of the green body in the sintering process are prevented, thereby ensuring the finished product quality of the alumina crucible. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 This is a schematic flowchart of a method for preparing a composite organic binder according to an embodiment of the present invention; Figure 2 This is a schematic flowchart of a method for preparing an alumina crucible according to one embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of an alumina crucible in one embodiment of the present invention. Figure 1 ; Figure 4 This is a schematic diagram of the structure of an alumina crucible in one embodiment of the present invention. Figure 2 . Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] In one embodiment, the present invention provides a composite organic binder for the preparation of an alumina crucible, the composite organic binder comprising the following components by weight percentage: 55-60% paraffin wax, 20-25% beeswax, 10-15% ethylene-vinyl acetate copolymer, and 5-8% polyvinyl alcohol.

[0019] Paraffin wax is used to enhance the plasticity of the slurry, while reducing the molding pressure of the crucible blank, improving the demolding performance of the blank, and establishing room temperature strength. Beeswax can improve the emulsification of paraffin wax, reduce the surface tension of the slurry, facilitate better bonding between refractory material particles (such as alumina in alumina crucible raw materials) and paraffin wax, reduce the viscosity of the slurry, improve the flowability of the slurry, and improve the filling ability. Ethylene-vinyl acetate copolymer (EVA) is used to improve the room temperature strength of the crucible blank and the plasticity and strength of the blank at 100~300℃, preventing cracking and bulging problems during the sintering process. Polyvinyl alcohol (PVA) is used to improve the room temperature strength of the crucible blank and the plasticity and strength of the blank at 300~500℃, preventing cracking and bulging problems during the sintering process.

[0020] It should be noted that slurry refers to a fluid with a certain viscosity, which is a mixture of alumina crucible raw materials and binder, and is used to prepare crucible blanks by means of slurry casting, extrusion molding, etc.; crucible blanks refer to the crucible prototypes after slurry molding but before debinding and sintering.

[0021] In summary, the composite organic binder of this embodiment has a lower melting point than the clay used as a binder in alumina crucibles. It can be burned off during the subsequent crucible sintering process, without introducing impurities such as potassium and sodium, thus improving the crucible purity and increasing the yield rate of crucible castings. Secondly, the binder, through the combination of paraffin and beeswax, improves the fluidity of the slurry and enhances the filling ability. The addition of ethylene-vinyl acetate copolymer and polyvinyl alcohol improves the plasticity and strength of the green blank, preventing cracking and bulging during sintering, thereby ensuring the quality of the finished alumina crucible.

[0022] refer to Figure 1 In another embodiment, the present invention also provides a method for preparing a composite organic binder, wherein the composite organic binder is the composite organic binder described in the above embodiments, and the method specifically includes the following steps: Step S10: Weigh out 55-60% paraffin wax, 20-25% beeswax, 10-15% ethylene-vinyl acetate copolymer and 5-8% polyvinyl alcohol by weight percentage.

[0023] Step S20: The weighed paraffin wax, beeswax, ethylene-vinyl acetate copolymer and polyvinyl alcohol are added to a vacuum mixer for melting and mixing to obtain a mixed melt.

[0024] Paraffin wax and beeswax have lower melting points than ethylene-vinyl acetate copolymer and polyvinyl alcohol, allowing for stepwise melting and mixing to improve the uniformity of the melt. Preferably, step S20 includes the following steps: First, the paraffin wax and the beeswax are added to a vacuum mixer, heated to a preset first temperature to melt, and stirred at a preset first speed for a preset first time to obtain a wax-based melt; wherein, the preset first temperature is 65-75°C, the preset first speed is 30-40 rpm, and the preset first time is 1-1.5 hours; Then, the ethylene-vinyl acetate copolymer and the polyvinyl alcohol are added to the wax-based melt, heated to a preset second temperature to melt, and stirred at a preset second speed for a preset second time to obtain the mixed melt; wherein, the preset second temperature is 90-95°C, the preset second speed is 60-80 rpm, and the preset second time is 9-10 hours.

[0025] That is, paraffin wax is first added to a vacuum mixer and heated to 65-75°C to melt both. Then, it is stirred and degassed under vacuum at a speed of 30-40 rpm until a uniformly mixed wax-based melt is obtained. Next, ethylene-vinyl acetate copolymer and polyvinyl alcohol are added to the wax-based melt and heated to 90-95°C to dissolve both in the wax-based melt. Then, it is stirred and degassed under vacuum at a speed of 60-80 rpm until a uniform mixed melt is obtained.

[0026] Step S30: Pour the mixed melt into a tray and cool to obtain a block of composite organic binder.

[0027] That is, the mixed melt obtained in step S20 is poured into a tray and allowed to solidify naturally. After solidification, a block of solid binder is obtained, which can then be bagged and sealed.

[0028] In another embodiment, the present invention also provides the application of a composite organic binder in the preparation of an alumina crucible.

[0029] In this embodiment, the alumina crucible includes, but is not limited to, the following: Figure 4 The single-unit crucible shown, such as Figure 3 The example shown is a conjoined crucible, etc.

[0030] refer to Figure 2 The method for preparing the alumina crucible specifically includes the following steps: Step S1: The composite organic binder and the raw materials of the alumina crucible are stirred and mixed to obtain a slurry.

[0031] In this embodiment, the alumina crucible is preferably as follows: Figure 3 The alumina crucible shown comprises two crucible bodies of different sizes and capacities. In this case, step S1 specifically includes the following steps: Step S11: Weigh out activated alumina, alumina, corundum, mullite, quartz and oleic acid according to the alumina crucible formula, and mix them to obtain a mixture.

[0032] In step S11, the alumina crucible formulation includes the following raw materials by weight percentage: 10-15% activated alumina, 20-25% alumina, 15-20% corundum, 7-9% mullite, 30-35% quartz, and 1-1.5% oleic acid.

[0033] Preferably, 15% activated alumina, 25% alumina, 20% corundum, 9% mullite, 30% quartz and 1% oleic acid are weighed by weight percentage and put into a mixing and dispersing device such as a high-speed mixer, planetary mixer or sand mill for mixing and particle size reduction to obtain a mixture.

[0034] Step S12: Add the composite organic binder to the mixture and stir for a preset third time at a preset stirring temperature and speed to obtain a slurry.

[0035] In step S12, the mass ratio of the mixture to the composite organic binder is 4:(1-1.5); the preset stirring temperature is 90-95℃; the preset stirring speed is 80-120 rpm; and the preset third duration is 26-30 hours.

[0036] Preferably, the mixture and composite organic binder are added to a vacuum mixer at a mass ratio of 4:1, and vacuum-stirred for 30 hours at a stirring temperature of 95°C and a stirring speed of 120 rpm to obtain a slurry.

[0037] Before step S2, the slurry prepared in step S1 is poured into the injection device, heated and maintained at a temperature of 90-95°C, and stirred at a speed of 30-40 rpm to ensure the fluidity of the slurry.

[0038] In step S2, the crucible mold is first preheated to 48±3℃, and then the slurry in the injection device is injected into the cavity of the crucible mold at a pressure of 100 to 130 Bar until the cavity is completely filled with slurry. After holding the pressure for 20 to 30 seconds, the green blank is finally demolded and removed.

[0039] It should be noted that for different types of alumina crucibles, appropriate crucible molds should be used for hot press molding.

[0040] Step S3: Degrease and sinter the green blank to obtain an alumina crucible.

[0041] That is, the green blank obtained in step S2 is embedded in the degreasing box with fat-absorbing powder, and then the degreasing box is placed in the oven for heating and degreasing. After degreasing is completed, the degreasing box is taken out of the oven, and the degreased green blank is taken out of the degreasing box. Then the green blank is placed in the sintering furnace for sintering and shaping.

[0042] Understandably, the alumina crucibles prepared using the above-mentioned composite organic binder have higher purity and smoother product surfaces.

[0043] The present invention will now be described through the following examples, illustrating one or more embodiments. These examples are not intended to limit the scope of the invention and / or the scope of the one or more embodiments.

[0044] Example 1: A composite organic binder comprising the following components by weight percentage: 55% paraffin wax, 25% beeswax, 15% ethylene-vinyl acetate copolymer and 5% polyvinyl alcohol.

[0045] The preparation method of the above-mentioned composite organic binder includes the following steps: Step a: Weigh out 55% paraffin wax, 25% beeswax, 15% ethylene-vinyl acetate copolymer, and 5% polyvinyl alcohol, respectively; Step b: The paraffin wax and the beeswax are added to a vacuum mixer, heated to 70°C to melt, and stirred at 30 rpm for 1 hour. Then, the ethylene-vinyl acetate copolymer and the polyvinyl alcohol are added, heated to 95°C to melt, and then stirred at 70 rpm for 9 hours to obtain a mixed melt. Step c: Pour the mixed melt into a tray and allow it to solidify naturally to obtain a block of composite organic binder.

[0046] Example 2: A composite organic binder comprising the following components by weight percentage: 55% paraffin wax, 25% beeswax, 14% ethylene-vinyl acetate copolymer and 6% polyvinyl alcohol.

[0047] Example 3: A composite organic binder comprising the following components by weight percentage: 55% paraffin wax, 25% beeswax, 13% ethylene-vinyl acetate copolymer, and 7% polyvinyl alcohol.

[0048] Example 4: A composite organic binder comprising the following components by weight percentage: 55% paraffin wax, 25% beeswax, 12% ethylene-vinyl acetate copolymer, and 8% polyvinyl alcohol.

[0049] Example 5: A composite organic binder comprising the following components by weight percentage: 60% paraffin wax, 25% beeswax, 10% ethylene-vinyl acetate copolymer and 5% polyvinyl alcohol.

[0050] Example 6: A composite organic binder comprising the following components by weight percentage: 57% paraffin wax, 23% beeswax, 15% ethylene-vinyl acetate copolymer, and 5% polyvinyl alcohol.

[0051] Example 7: A composite organic binder comprising the following components by weight percentage: 60% paraffin wax, 20% beeswax, 15% ethylene-vinyl acetate copolymer and 5% polyvinyl alcohol.

[0052] Comparative Example 1: A composite organic binder comprising the following components by weight percentage: 55% paraffin wax, 24% beeswax, 16% ethylene-vinyl acetate copolymer, and 5% polyvinyl alcohol.

[0053] Comparative Example 2: A composite organic binder comprising the following components by weight percentage: 55% paraffin wax, 24% beeswax, 12% ethylene-vinyl acetate copolymer, and 9% polyvinyl alcohol.

[0054] Comparative Example 3: A composite organic binder comprising the following components by weight percentage: 60% paraffin wax, 25% beeswax, and 15% ethylene-vinyl acetate copolymer.

[0055] Comparative Example 4: A composite organic binder comprising the following components by weight percentage: 60% paraffin wax, 24% beeswax, and 16% ethylene-vinyl acetate copolymer.

[0056] Comparative Example 5: A composite organic binder comprising the following components by weight percentage: 60% paraffin, 25% beeswax, and 15% polyvinyl alcohol.

[0057] Comparative Example 6: A composite organic binder comprising the following components by weight percentage: 65% paraffin wax, 15% beeswax, 15% ethylene-vinyl acetate copolymer and 5% polyvinyl alcohol.

[0058] Comparative Example 7: A composite organic binder comprising the following components by weight percentage: 50% paraffin wax, 30% beeswax, 15% ethylene-vinyl acetate copolymer and 5% polyvinyl alcohol.

[0059] The composite organic binders in Examples 2-7 and Comparative Examples 1-7 are prepared using methods similar to those in Example 1. The only difference between them and Example 1 is the content of the components used, as shown in Table 1.

[0060] Table 1. Component content of composite organic binders (unit: wt%)

[0061] The following describes the preparation and testing of alumina crucibles using the composite organic binders from Examples 1-7 and Comparative Examples 1-7. The preparation method of the alumina crucibles includes the following steps: Step d: Weigh 15% activated alumina, 25% alumina, 20% corundum, 9% mullite, 30% quartz and 1% oleic acid, and mix them to obtain a mixture. Step e: Take the mixture and composite organic binder at a mass ratio of 4:1 and add them to a vacuum mixer. After mixing, a slurry is obtained. Step f: The slurry is poured and molded to obtain a blank; Step g involves degreasing and sintering the green blank to obtain an alumina crucible.

[0062] The test method for alumina crucibles is as follows: the viscosity of the slurry obtained in step e is measured using a standard viscometer or a measuring cup viscometer (also known as a measuring cup), and the strength of the green blank obtained in step e is measured using a universal testing machine. At the same time, the demolding condition, surface quality, and product quality of the green blank in the subsequent degreasing and sintering stages are observed and recorded. The test results are shown in Table 2.

[0063] Table 2 Test results of composite organic binders

[0064] Based on Tables 1 and 2, and comparing Examples 3, 1, and 4, it can be seen that when EVA exceeds 15%, the slurry viscosity is too high, resulting in insufficient fluidity and shrinkage compensation, making demolding impossible. Comparative Examples 2 and 5 show that when PVA exceeds 8%, demolding becomes difficult and prone to cracking, and bulging issues easily occur during degreasing and sintering. Examples 1 to 4 demonstrate that reducing EVA and increasing PVA content can improve the room temperature strength of the green body. Examples 1, 6, and 7 show that increasing paraffin wax and decreasing beeswax can improve the strength of the green body. Examples 7 and 6 show that when paraffin wax exceeds 60%, demolding becomes difficult and prone to under-filling, resulting in very low green body strength. Examples 1 and 7 show that when beeswax exceeds 30%, demolding becomes difficult and prone to under-filling, resulting in very low green body strength.

[0065] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or method. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or method that includes that element.

[0066] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A composite organic binder, characterized in that, The composite organic binder comprises the following components by weight percentage: 55-60% paraffin wax, 20-25% beeswax, 10-15% ethylene-vinyl acetate copolymer, and 5-8% polyvinyl alcohol.

2. The method for preparing the composite organic binder according to claim 1, characterized in that, include: Weigh out 55-60% paraffin wax, 20-25% beeswax, 10-15% ethylene-vinyl acetate copolymer, and 5-8% polyvinyl alcohol; The paraffin wax, beeswax, ethylene-vinyl acetate copolymer, and polyvinyl alcohol are added to a vacuum mixer for melting and mixing to obtain a mixed melt; The mixed melt is poured into a tray and cooled to obtain a block of composite organic binder.

3. The method for preparing the composite organic binder as described in claim 2, characterized in that, The process involves adding the paraffin wax, beeswax, ethylene-vinyl acetate copolymer, and polyvinyl alcohol to a vacuum mixer for melting and mixing to obtain a mixed melt, comprising: The paraffin wax and the beeswax are added to a vacuum mixer, heated to a preset first temperature to melt, and stirred at a preset first speed for a preset first time to obtain a wax-based melt. The ethylene-vinyl acetate copolymer and the polyvinyl alcohol are added to the wax-based melt, heated to a preset second temperature to melt, and stirred at a preset second speed for a preset second time to obtain the mixed melt.

4. The method for preparing the composite organic binder as described in claim 3, characterized in that, The preset first temperature is 65-75℃, the preset first rotation speed is 30-40 rpm, and the preset first duration is 1-1.5 hours.

5. The method for preparing the composite organic binder as described in claim 4, characterized in that, The preset second temperature is 90-95℃, the preset second rotation speed is 60-80 rpm, and the preset second duration is 9-10 hours.

6. The application of the composite organic binder according to claim 1, wherein the composite organic binder is used to prepare an alumina crucible.

7. The application of the composite organic binder as described in claim 6, characterized in that, The method for preparing the alumina crucible includes: The composite organic binder and the raw materials of the alumina crucible are stirred and mixed to obtain a slurry; The slurry is poured and molded to obtain a raw blank; The raw blank is degreased and sintered to obtain an alumina crucible.

8. The application of the composite organic binder as described in claim 7, characterized in that, The slurry obtained by mixing the composite organic binder and the raw materials of the alumina crucible includes: Weigh out activated alumina, alumina, corundum, mullite, quartz and oleic acid according to the alumina crucible formula, and mix them to obtain a mixture. The composite organic binder is added to the mixture, and the mixture is stirred at a preset stirring temperature and a preset stirring speed for a preset third time to obtain a slurry; wherein the mass ratio of the mixture to the composite organic binder is 4:(1~1.5).

9. The application of the composite organic binder as described in claim 8, characterized in that, The alumina crucible formulation comprises the following raw materials by weight percentage: 10-15% activated alumina, 20-25% alumina, 15-20% corundum, 7-9% mullite, 30-35% quartz, and 1-1.5% oleic acid; The preset stirring temperature is 90-95℃, the preset stirring speed is 80-120 rpm, and the preset third duration is 26-30 hours.

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