CN109176830B

CN109176830B - Method for manufacturing hollow ceramic membrane

Info

Publication number: CN109176830B
Application number: CN201810818462.2A
Authority: CN
Inventors: 孟文彬; 蒋玥
Original assignee: Guangdong Kangrong High Tech New Material Co ltd
Current assignee: Guangdong Kangrong High Tech New Material Co ltd
Priority date: 2018-07-24
Filing date: 2018-07-24
Publication date: 2021-06-15
Anticipated expiration: 2038-07-24
Also published as: CN109176830A

Abstract

The invention discloses a method for manufacturing a hollow ceramic membrane, which is processed by adopting a hollow ceramic membrane mould, wherein at least one totally-enclosed hollow hole is formed in the hollow ceramic membrane; the die comprises an upper outer die, a lower outer die and an inner die core, and specifically comprises the following steps: the method comprises the steps of first filling, placing a mold core, second filling, semi-dry pressing and forming, drying, removing glue and sintering, and taking out the finished hollow ceramic membrane after natural cooling and cooling. The manufacturing method solves the defects that the existing hollow ceramic cannot be manufactured into a fully-closed hollow structure, a small section is hollow, and the adjustment range of the membrane aperture is narrow, and compared with the existing method, the manufacturing method has the advantages of low equipment requirement, small equipment abrasion, simple process and high efficiency, and the manufactured hollow ceramic is integrally formed without bonding steps.

Description

Method for manufacturing hollow ceramic membrane

Technical Field

The invention relates to a ceramic filtering membrane technology, in particular to a manufacturing method of a hollow ceramic membrane.

Background

The membrane separation technology is a novel high-efficiency separation technology which realizes the separation, purification and concentration of different components of feed liquid by utilizing the selective separation function of a membrane. With the high-efficiency separation characteristic, the membrane industry is nationally oriented to be a strategic emerging industry and is supported by policies greatly. The existing ceramic membrane mainly comprises a hollow plate type or tubular membrane, and the molding process generally adopts an extrusion molding process. The hollow ceramic membranes produced by the method are of symmetrical structures with holes at two ends, glue is applied to the two ends for sealing in the later period, and the plastic connectors are generally required to be replaced if the templates are damaged due to the adoption of glue for sealing, so that the replacement cost is increased.

The patent "a forming method of ceramic vacuum filter plate (CN 101816859A)" discloses a manufacturing method of hollow filter plate, which uses foam plastic as a mold core and adopts hot-pressing process to form. The method needs vacuum pumping and pressurization heating in the forming process, is relatively complex in operation and higher in equipment requirement, and the die core is easy to deform under the heating and pressurization conditions, so that the shape of the inner cavity is changeable. The patent "vacuum ceramic filter plate and its manufacturing method (CN 101773746 a)" adopts a press forming method, but the hollow template is divided into two parts to be press formed, and then bonded together by a bonding agent after sintering, and this method has complicated process, and the bonding agent and the ceramic main body have material difference, which may cause defects after long-term use. The patent 'preparation method of hollow ceramic core for double-wall hollow blade (CN 105127373A)' discloses a preparation method of hollow ceramic core, which comprises the steps of adopting carbon powder and paraffin wax to injection-mold a core for hollow ceramic, then carrying out carbonization treatment to obtain a core with certain strength, then utilizing ceramic wax slurry to injection-mold hollow ceramic, and finally sintering together to remove paraffin wax and the carbonized core to obtain the hollow ceramic. The method has complicated process, carbonization treatment and more equipment requirements, and is difficult to manufacture hollow ceramics with smaller hole section area or hollow ceramics with slice-shaped holes, because the core with small interface has low strength and is easy to crush the core during injection molding, and meanwhile, the method can not manufacture the hollow ceramics with completely closed holes, and the core has no supporting point. The ceramic membrane molding operability is not strong by adopting wax slurry injection, stable and uniform wax slurry is difficult to form due to the fact that the powder of the ceramic membrane is generally coarse, and equipment is greatly abraded in the molding process.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a method for manufacturing a hollow ceramic membrane. The manufacturing method solves the defects that the existing hollow ceramic cannot be manufactured into a fully-closed hollow structure, a small section is hollow, and the adjustment range of the membrane aperture is narrow, and compared with the previous method, the method has the advantages of low equipment requirement, small equipment abrasion, simple process and high efficiency, and the manufactured hollow ceramic is integrally formed without bonding steps.

The purpose of the invention is realized by adopting the following technical scheme: a method for manufacturing a hollow ceramic membrane is characterized in that the hollow ceramic membrane is processed by a hollow ceramic membrane die, and at least one totally-enclosed hollow hole is formed in the hollow ceramic membrane; the mould comprises an upper outer mould, a lower outer mould and an inner mould core, and the upper outer mould is detachably arranged on the lower outer mould; the upper outer die and the lower outer die are enclosed to form a die cavity matched with the shape of the hollow ceramic membrane; the shape of the internal mold core is matched with the shape of a hollow hole of the hollow ceramic membrane;

the method specifically comprises the following steps:

a first filling step: weighing semi-dry ceramic powder, filling the semi-dry ceramic powder into a cavity of the lower outer mold, and flattening the ceramic powder to finish primary filling;

a step of placing a core: placing an internal mold core on the surface of the ceramic powder, wherein the internal mold core is positioned in the center of the cavity;

and a second filling step: filling the semi-dry ceramic powder into the cavity of the upper outer mold to complete the second filling, and fixing the upper outer mold on the lower outer mold;

semi-dry pressing and forming: starting a press to adjust pressure, pressing an upper outer die on a lower outer die, ejecting a hollow ceramic membrane with an inner die core inside, and transferring the hollow ceramic membrane with the inner die core inside to a burning plate by using a vacuum chuck;

and (3) drying: putting the burning bearing plate and the hollow ceramic membrane with the internal mold core into an oven for baking;

glue discharging and sintering: and putting the dried hollow ceramic membrane into a firing kiln, raising the temperature in stages, keeping the temperature, dissolving out the internal mold core in stages, forming a vacancy at the original internal mold core, naturally cooling, and taking out the finished product of the hollow ceramic membrane.

Further, the inner mold core is prepared from paraffin, a plastic reinforcing agent and a filling agent, wherein the mass ratio of the paraffin, the plastic reinforcing agent and the filling agent is (5-24): (1-3): 1.

further, the plastic reinforcing agent is one or a mixture of more than two of PP, HDPE, PET, PBT and PS; the filler is one or a mixture of more than two of graphite, wood chips and walnut sand.

Further, the internal mold core comprises the following steps:

preparation of slurry: weighing the raw materials of paraffin, plastic reinforcing agent and filler according to the formula ratio, heating to melt and stirring to prepare slurry with good fluidity;

and (3) crushing: putting the cooled solid of the slurry into a crusher to be crushed into particles with uniform thickness;

injection molding: and (4) manufacturing the internal mold core in the required shape by injection molding of an injection molding machine.

Further, in the step of crushing, the particle size of the particles is in the range of 2-4 mm; in the step of injection molding, the desired shape includes one or a combination of two or more of a cylindrical shape, a circular sheet shape, a square column shape, a square sheet shape, a fan blade shape, and a turbine shape.

Further, in the step of first and second filling, the preparation of the ceramic powder comprises the following steps:

ball milling: weighing ceramic particle aggregate, sintering aid and binder, putting into a ball mill together, and performing dry ball milling to prepare pre-milled powder;

stirring: taking out the pre-prepared powder, putting the pre-prepared powder into a stirrer, spraying water while stirring for 10 minutes, spraying a lubricant again, stirring for 30 minutes, and taking out;

and (3) staling: taking out the powder, sealing and ageing for 24 hours, sieving the aged raw material by using a screen to obtain a part of the semi-dry pressed powder, wherein the moisture content of the semi-dry pressed powder is controlled to be 5-15%.

Further, in the step of ball milling, the ceramic particle aggregate is alumina or silicon carbide; the ceramic particle aggregate consists of two ceramic particle aggregates with different particle thicknesses, wherein the mass ratio of the coarse particles to the fine particles is (5-9): 1; the particle size of the coarse particles is 20-50 mu m, and the particle size of the fine particles is 0.5-5 mu m; the sintering aid is one or a mixture of more than two of titanium dioxide, copper oxide and chromium oxide; the binder is one or a mixture of more than two of HPMC, CMC and PVA.

Further, in the stirring step, the adding amount of the water is 5-20% of the weight of the pre-prepared powder; the lubricant accounts for 0.5-5% of the weight of the pre-prepared powder.

Further, in the drying step, the temperature of the oven is 45-55 ℃, and the baking time is 10-14 hours.

Further, in the steps of binder removal and sintering, the conditions of the step-wise temperature rise and heat preservation are as follows: heating to 180-220 ℃ for 1.5-2.5 hours, and keeping the temperature for 8-12 hours; and then heating to 600 ℃ at the speed of 1 ℃/min, finally heating to 1400 ℃ at the speed of 5 ℃/min, preserving the heat for 1.5-2.5 hours, naturally cooling to below 100 ℃, and taking out the finished product.

Compared with the prior art, the invention has the beneficial effects that:

(1) the manufacturing method has the advantages of short production flow, simple process, high efficiency, low equipment requirement and small equipment abrasion, can be used for producing the ceramic membrane with the completely closed integrally-formed hollow structure, and solves the defects that the existing hollow ceramic cannot be used for manufacturing the fully closed hollow structure, the hollow structure with the small section and the narrow membrane aperture adjusting range.

(2) In the process of manufacturing the hollow ceramic membrane, a semi-dry pressing forming technology is utilized, namely ceramic powder in a semi-dry semi-wet state is adopted, so that the shaping of the ceramic powder in the upper and lower outline molds is facilitated, and then the ceramic powder is pressed and formed, the forming process is simple, the equipment requirement is low, the size of the hollow section of the product is not limited, a small hole with the thickness of 0.5mm and the width of 1mm can be formed, the manufactured product is an integral body, the gluing process is reduced, and the product performance is better;

(3) in the process of manufacturing the hollow ceramic membrane, the formula of ceramic powder is adjusted, coarse-grain alumina or silicon carbide is used as a ceramic framework, a small amount of fine-grain high-purity alumina or silicon carbide ceramic framework and a small amount of sintering aid are added, and the acid and alkali resistance of the membrane of the ceramic membrane is enhanced because a solvent raw material is hardly added;

(4) in the process of manufacturing the hollow ceramic membrane, the raw material to be molded is prepared by adopting a high-viscosity binder, adding a lubricant and water and stirring together, so that the lubricity and the strength of a molded product are improved when the ceramic membrane is molded, and the collapse of the product and the abrasion to equipment are reduced.

(5) In the process of manufacturing the internal mold core, paraffin, plastic reinforcing agent and filling agent are used as raw materials of the internal mold core, so that the core is easy to remove at the later stage. The internal mold is easy to remove mainly through reasonable proportioning and a staged heating and heat preservation mode, paraffin is slowly melted and absorbed by pores formed by water evaporation in the ceramic at a low temperature stage below 70 ℃, vacancies are formed at the prototype core, and when the temperature reaches 150 ℃, the plastic is softened and expanded, and the pores formed by melting the paraffin give space for expansion of the plastic, so that the product is not cracked due to expansion of the plastic. The temperature continues to rise and binder in the core and product is stripped off, staged meltout and void formation reducing the likelihood of product cracking.

(6) In the process of manufacturing the internal mold core, the particle size of the powder of the core can be randomly adjusted so that the pore diameter of the membrane can be freely adjusted, and the defects that the slurry is easily layered by adopting pure wax slurry injection molding, the pore diameter adjusting range is narrow, an injection port is easily blocked and the like are avoided; meanwhile, compared with extrusion molding, the equipment investment is reduced, and the abrasion of raw materials to equipment is reduced.

Drawings

FIG. 1 is a schematic structural view of a hollow ceramic membrane according to example 3;

FIG. 2 is a pictorial representation of a hollow ceramic membrane of example 3;

FIG. 3 is a schematic cross-sectional view of the hollow ceramic membrane of FIG. 2.

In the figure: 1. a hollow ceramic membrane; 2. and (4) an internal mold core.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.

In the present invention, all parts and percentages are by weight, unless otherwise specified, and the equipment and materials used are commercially available or commonly used in the art. The methods in the following examples are conventional in the art unless otherwise specified.

A method for manufacturing a hollow ceramic membrane is characterized in that the hollow ceramic membrane is processed by a hollow ceramic membrane die, and at least one totally-enclosed hollow hole is formed in the hollow ceramic membrane; the mould comprises an upper outer mould, a lower outer mould and an inner mould core, and the upper outer mould is detachably arranged on the lower outer mould; the upper outer die and the lower outer die are enclosed to form a die cavity matched with the shape of the hollow ceramic membrane; the shape of the internal mold core is matched with the shape of a hollow hole of the hollow ceramic membrane;

the method specifically comprises the following steps:

and (3) drying: putting the burning bearing plate and the hollow ceramic membrane with the internal mold core into an oven for baking; as a further embodiment, the temperature of the oven is 45-55 ℃, and the baking time is 10-14 hours;

glue discharging and sintering: putting the dried hollow ceramic membrane into a firing kiln, and carrying out staged temperature rise and heat preservation under the following conditions: heating to 180-220 ℃ for 1.5-2.5 hours, and keeping the temperature for 8-12 hours; heating to 600 ℃ at the speed of 1 ℃/min, finally heating to 1400 ℃ at the speed of 5 ℃/min, and preserving the heat for 1.5-2.5 hours to dissolve out the internal mold core in stages, so that a vacancy is formed at the original internal mold core; naturally cooling to below 100 ℃, and taking out the finished product of the hollow ceramic membrane.

The internal mold core comprises the following steps:

preparation of slurry: weighing the raw materials of paraffin, plastic reinforcing agent and filler according to the formula ratio, heating to melt and stirring to prepare slurry with good fluidity; the inner mold core is prepared from paraffin, a plastic reinforcing agent and a filling agent, wherein the mass ratio of the paraffin to the plastic reinforcing agent to the filling agent is (5-24): (1-3): 1. the plastic reinforcing agent is one or a mixture of more than two of PP, HDPE, PET, PBT and PS; the filler is one or a mixture of more than two of graphite, wood chips and walnut sand.

And (3) crushing: putting the cooled solid of the slurry into a crusher to be crushed into particles with uniform thickness; the particle size range of the particles is 2-4 mm;

injection molding: and (4) manufacturing the internal mold core in the required shape by injection molding of an injection molding machine. In a further embodiment, the desired shape includes one or a combination of two or more of regular shapes such as a cylindrical shape, a circular sheet shape, a square column shape, and a square sheet shape, and irregular shapes such as a fan blade shape and a turbine shape.

Wherein, in the steps of the first and the second filling, the preparation of the ceramic powder comprises the following steps:

ball milling: weighing ceramic particle aggregate, sintering aid and binder, putting into a ball mill together, and performing dry ball milling to prepare pre-milled powder; as a further embodiment, the ceramic particulate aggregate is alumina or silicon carbide; the ceramic particle aggregate consists of two ceramic particle aggregates with different particle thicknesses, wherein the mass ratio of the coarse particles to the fine particles is (5-9): 1; the particle size of the coarse particles is 20-50 mu m, and the particle size of the fine particles is 0.5-5 mu m; the sintering aid is one or a mixture of more than two of titanium dioxide, copper oxide and chromium oxide; the binder is one or a mixture of more than two of HPMC, CMC and PVA with high viscosity (1 ten thousand to 10 ten thousand viscosity).

Stirring: taking out the pre-prepared powder, putting the pre-prepared powder into a stirrer, spraying water while stirring for 10 minutes, spraying a lubricant again, stirring for 30 minutes, and taking out; as a further embodiment, the adding amount of the water is 5-20% of the weight of the pre-prepared powder; the lubricant accounts for 0.5-5% of the weight of the pre-prepared powder. The lubricant is one or a mixture of more than two of glycerin, vegetable oil, oleic acid and stearic acid emulsion.

The following are specific examples of the present invention, and raw materials, equipments and the like used in the following examples can be obtained by purchasing them unless otherwise specified.

Example 1: internal mold core

The manufacturing method of the internal mold core comprises the following steps:

1. preparation of slurry: 2400g of paraffin wax, 150g of PP and 150g of HDPE are weighed and added into a heatable stirrer together, the temperature is set to 180 ℃, the stirrer is started, and the paraffin wax, the PP and the HDPE are slowly melted along with the increase of the temperature. After the melting is finished, adding 300g of graphite powder, stirring for 30 minutes, pouring into a tray, and naturally cooling to room temperature;

2. and (3) crushing: taking out the cooled solid, putting the solid in a crusher, and crushing the solid into small particles with uniform particles; the particle size range of the particles is 2-4 mm;

3. injection molding: adjusting the temperature and the injection pressure of the injection molding machine, and performing injection molding to obtain a turbine-shaped mold core as shown in figure 1.

Example 2 semi-dry ceramic powder

The preparation of the semi-dry ceramic powder comprises the following steps:

1. ball milling: weighing 2400g of alumina aggregate with 200 meshes, 600g of alumina aggregate with 1 micron, fine-particle alumina aggregate serving as a reinforcing agent of coarse-particle alumina aggregate, 90g of HPMC (hydroxy propyl methyl cellulose) with 10 ten thousand of viscosity and 15g of industrial titanium dioxide, and putting the materials into a ball mill together for dry ball milling for 4 hours to prepare pre-milled powder;

2. stirring: taking out the prefabricated powder, adding the prefabricated powder into a stirrer capable of spraying water, spraying 300g of clean water while stirring for 10 minutes, spraying 15g of vegetable oil again, stirring for 30 minutes, and taking out the powder;

3. and (3) staling: sealing and ageing the powder for 24 hours; and (3) sieving the aged powder material by using a 20-mesh sieve to obtain a sieved part, namely the semi-dry pressed powder material, wherein the moisture content of the semi-dry pressed powder material is controlled to be 5-15%.

EXAMPLE 3 hollow ceramic Membrane

The preparation of the hollow ceramic membrane comprises the following steps:

1. a first filling step: 150g of the semi-dry pressing powder prepared in the embodiment 2 is weighed and filled into a cavity of a lower outer mold, and the ceramic powder is smoothed to finish the first filling;

2. a step of placing a core: placing the inner mold core prepared in the embodiment 1 on the surface of the ceramic powder, wherein the inner mold core is positioned in the center of the cavity;

3. and a second filling step: weighing 170 g of prepared semi-dry pressing powder, filling the semi-dry pressing powder into a cavity of an upper outer die to finish secondary filling, and fixing the upper outer die on a lower outer die;

4. semi-dry pressing and forming: starting a press to adjust the pressure to 60MPa, pressing an upper outer die on a lower outer die, ejecting a hollow ceramic membrane with an inner die core inside, and transferring the hollow ceramic membrane on a setter plate by using a vacuum chuck;

5. and (3) drying: putting the burning bearing plate and the hollow ceramic membrane with the internal mold core into a baking oven with the set temperature of 50 ℃ for baking for 12 hours;

6. glue discharging and sintering: putting the dried product into a firing kiln, heating to 200 ℃ according to 2 hours, preserving heat for 10 hours, heating to 600 ℃ according to the speed of 1 ℃/min, finally heating to 1400 ℃ according to the speed of 5 ℃/min, preserving heat for 2 hours, dissolving out the internal mold core in stages, and forming a vacancy at the original internal mold core 2; naturally cooling to a temperature below 100 ℃, and taking out the finished product of the hollow ceramic membrane 1 as shown in figures 2-3.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.

Claims

1. The manufacturing method of the hollow ceramic membrane is characterized in that the hollow ceramic membrane is processed by adopting a hollow ceramic membrane mould, and at least one totally-enclosed hollow hole is formed in the hollow ceramic membrane; the mould comprises an upper outer mould, a lower outer mould and an inner mould core, and the upper outer mould is detachably arranged on the lower outer mould; the upper outer die and the lower outer die are enclosed to form a die cavity matched with the shape of the hollow ceramic membrane; the shape of the internal mold core is matched with the shape of a hollow hole of the hollow ceramic membrane;

the method specifically comprises the following steps:

glue discharging and sintering: putting the dried hollow ceramic membrane into a firing kiln, raising the temperature in stages, keeping the temperature, dissolving out the internal mold core in stages, forming a vacancy at the original internal mold core, naturally cooling and taking out a finished product of the hollow ceramic membrane;

the inner mold core is prepared from paraffin, a plastic reinforcing agent and a filling agent, wherein the mass ratio of the paraffin to the plastic reinforcing agent to the filling agent is (5-24): (1-3): 1.

2. the manufacturing method of claim 1, wherein the plastic reinforcing agent is one or a mixture of more than two of PP, HDPE, PET, PBT and PS; the filler is one or a mixture of more than two of graphite, wood chips and walnut sand.

3. The method of manufacturing of claim 1, wherein the internal mold core comprises the steps of:

4. The method of claim 3, wherein in the step of crushing, the particles have a size in the range of 2 to 4 mm; in the step of injection molding, the desired shape includes one or a combination of two or more of a cylindrical shape, a circular sheet shape, a square column shape, a square sheet shape, a fan blade shape, and a turbine shape.

5. The method of claim 1, wherein the step of first and second filling comprises the steps of:

6. The method of claim 5, wherein in the step of ball milling, the ceramic particle aggregate is alumina or silicon carbide; the ceramic particle aggregate consists of two ceramic particle aggregates with different particle thicknesses, wherein the mass ratio of the coarse particles to the fine particles is (5-9): 1; the particle size of the coarse particles is 20-50 mu m, and the particle size of the fine particles is 0.5-5 mu m; the sintering aid is one or a mixture of more than two of titanium dioxide, copper oxide and chromium oxide; the binder is one or a mixture of more than two of HPMC, CMC and PVA.

7. The method of claim 5, wherein in the step of stirring, the amount of water added is 5-20% of the weight of the pre-milled powder; the lubricant accounts for 0.5-5% of the weight of the pre-prepared powder.

8. The manufacturing method of claim 1, wherein in the drying step, the temperature of the oven is 45-55 ℃ and the baking time is 10-14 hours.

9. The manufacturing method according to claim 1, wherein in the steps of binder removal and sintering, the conditions of the stepwise temperature rise and heat preservation are as follows: heating to 180-220 ℃ for 1.5-2.5 hours, and keeping the temperature for 8-12 hours; and then heating to 600 ℃ at the speed of 1 ℃/min, finally heating to 1400 ℃ at the speed of 5 ℃/min, preserving the heat for 1.5-2.5 hours, naturally cooling to below 100 ℃, and taking out the finished product.