CN1818106A - Sintered porous hollow polyurethane sponge-like metal structure and method of forming same - Google Patents

Abstract

The present invention discloses a sintered porous hollow polyurethane sponge-like metal structure and a method for forming the same. The porous hollow polyurethane sponge-like structure comprises a blasted open-cell polyurethane sponge skeleton, the skeleton having a closed-cell, semi-closed-cell or semi-open-cell structure that is hollow and has a certain geometric shape, and the outside of the hollow geometric body has an ultra-large three-dimensional specific surface area. The method comprises forming a porous substrate, coating the porous substrate with a metal, sintering the coated substrate to remove the flammable substrate, connecting the whole through metal bonds and covalent bonds in the structure to produce a hollow structure, thereby making a porous hollow polyurethane sponge-like metal structure. The porous hollow polyurethane sponge-like metal structure of the present invention can be used as an air cleaning filter carrier.

Description

Sintered porous hollow polyurethane sponge-like metal structure and method of forming same

technical field

The invention relates to a sintered porous hollow polyurethane sponge metal structure and a manufacturing method thereof.

Background technique

Usually, the air cleaning filter (also known as a catalytic converter) in the exhaust system of a vehicle engine adopts a metal honeycomb structure. With this honeycomb structure, the exhaust gas in the exhaust system can be separated from the honeycomb structure. One end of the channel is transmitted to the other end, so as to achieve the purpose of treating various harmful gases such as nitrogen monoxide and nitrogen dioxide produced after oil combustion.

US Patent No. 5,306,890 discloses such a honeycomb structure. In this structure, corrugated metal sheets are welded between two flat metal sheets to form many channel structures. The formed channel structure is wrapped and coated with a catalyst, and the formed channel structure is installed in a metal casing to form a catalytic converter. Because the corrugated structure in the catalytic converter has a large contact surface area, the catalyst coated on the surface can filter the air. However, this technology has the disadvantage that the welding process is expensive and that the metal processing of the surface area of the channel structure is limited by the state of the art.

In order to overcome the defects of the above-mentioned prior art, a method of using electric arc to treat the surface of the metal sheet to increase the surface area is proposed in US5,481,084; US5,567,395 discloses a method of providing turbulent flow generation sections in the honeycomb structure to improve A method of efficiency; US6,036,926 and WO97/15393 disclose a method of using curved reinforced metal sheets to form a honeycomb structure with a reinforced structure and improve efficiency. However, the above methods are still limited to the extent to which the contact surface area can be increased. And after a few thermal shock cycles, those extra bumps added by surface treatment to increase the surface area usually show insufficient adhesion to the metal surface and less durable adhesion.

Therefore, it is conceived to install a precision filter (or "dust collector") (US4,719,571) before the converter of the honeycomb structure or to install it parallel to the converter to mechanically control the flow of exhaust gas through it. Selected chambers to trap dust (US5,264,186). It prevents catalyst poisoning caused by this dust and reduces dust emissions. However, the process is complicated and an additional filter unit needs to be installed, which increases the cost and weight of the vehicle.

When the engine is started, it heats up the converter, and when the engine is stopped, it stalls the converter. Such repeated cycles often cause thermal shock to the structure of the converter, causing damage to the metal foil and forming holes in it, thereby reducing the efficiency of the converter or even failing it. Of course, some methods can be used to overcome it, such as improving its strength (US5,316,997) through special welding, or providing a buffer zone so that the converter will not be damaged due to thermal shock (US5,403,558, US6,467,169, US6,458,329 , US5,846,459). But this makes the buffer segment take up more space, reducing the actual usable surface area for the converter. And doing so also increases the overall volume of the converter. If the diameter of the converter is increased, the exhaust gas will pass through all channels evenly and the filtering effect will be reduced. If you increase the length of the converter, you increase the back pressure on the engine.

90% of current air pollutants come from vehicle exhaust emissions when the engine and converter have not yet reached their operating temperature. Several solutions have been envisaged for this purpose: for example, the use of zeolite or molecular sieve absorption chambers with a sparse microvoid structure (US 5,051,224, US 5,108,716) or separate preheating to make the catalytic converter more efficient. devices (US5,296,198, US5,465,573, etc.). However, this arrangement either increases back pressure, reduces fuel efficiency, or increases fuel consumption.

In addition to metal catalytic converters, US Pat. No. 4,556,543 uses a catalyst-coated compression ceramic converter. US Pat. No. 6,680,101 proposes to use extrusion or extrusion molding technology to form a ceramic honeycomb structure with 400 channels/square inch.

However, the thermal shock resistance of such ceramic converters is poor, resulting in loss of performance due to cracking of the ceramic after only a limited number of heat-up/flame-off cycles. Although several approaches have been suggested that can be used to overcome this deficiency. Such as enhancing thermal shock resistance by thickening the walls of certain channels (US2004/0101654). However, these methods still cannot meet people's demand for effective catalyst carriers with light weight.

Due to the low heat capacity and thermal conductivity of ceramics, ceramic honeycomb structures take a long time to reach their operating temperature after an engine start. When the engine/converter is colder than its operating temperature, an additional filter or another preheater is required to treat the exhaust. This not only increases cost and weight, but also reduces the fuel efficiency of the vehicle.

A third typical prior art is a ceramic foam structure as disclosed in US4,451,441. It consists of using a fine ceramic foam unit (15 to 50 ppi pores/inch) as the filter and a coarse ceramic foam unit (2 to 20 ppi) as the catalyst support for the catalytic converter system. It has been proposed to provide a technical solution for catalytic applications with light weight, high surface area and much lower back pressure. Ceramic foam is formed by coating ceramic slurry on a reticulated polyurethane sponge followed by sintering it at about 750°C. In fact, the polyurethane polymer burns out during said sintering. However, since the skeleton of the ceramic foam is so small that it has little mechanical strength, it cannot transmit heat and resist shock and provide sufficient strength during service life.

No. 5,422,085 discloses a method for reducing nitrogen oxide (NOx) emissions in diesel engine exhaust. Nickel-coated polyurethane sponge (also known as nickel foam in the Chinese market) was coated with silver catalyst to treat NOx load stream. However, due to the high activity of silver with sulfides in engine exhaust environments and the insufficient corrosion and oxidation resistance of nickel in oxidizing environments, such devices have not actually been put into commercial production.

Precision machining tools are required for forming during the manufacture of ceramic honeycomb structures. The processing tool has its life cycle and maintenance period. Likewise, ceramic materials need to be well protected during transport to prevent impact damage. Therefore, the production cost is high and a new structure is required for the catalytic converter.

The present invention overcomes all the drawbacks of the prior art mentioned above. It has the advantages of large-area catalytic efficiency, effective filtration of diesel dust (particles), thermal shock resistance, short heating time, and low production cost.

Contents of the invention

The main purpose of the present invention is to provide a sintered porous hollow polyurethane sponge metal structure and its manufacturing method.

The inventors used a combustible material blasted open-cell polyurethane sponge as a porous substrate to coat the metal layer, and adopted a sintering process to form a sintered porous hollow polyurethane sponge-like metal structure. Therefore, the user can use the sintered porous hollow polyurethane sponge-like metal structure for catalyst coating or photocatalyst coating.

The present invention provides a sintered porous hollow polyurethane sponge-like metal structure, which comprises a reduced metal dodecahedron skeleton structure, which has certain hollow, rigid and closed cells of certain geometric shape, The semi-closed or semi-open structure has a super large three-dimensional specific surface area inside and outside the hollow geometry. There are metal bonds or covalent bonds in the structure to connect the whole, and the material of the porous hollow structure can withstand a sintering process with a specific temperature range; wherein at least half of the material of the porous hollow structure is formed of metal materials.

The method of the present invention comprises the steps of: using a combustible material to make a porous substrate; implementing a coating process with a metal material that can withstand the combustion temperature of the combustible material; performing a sintering process on the coated porous substrate , to remove the flammable substrate, since the metal material forms a metal bond or a covalent bond in the structure, thereby forming a monolithic structure, thereby making a sintered porous hollow polyurethane sponge-like metal structure with a porous hollow structure .

The structure of the present invention can be used as a dust filter and catalytic converter to treat exhaust gas from an engine by coating with a catalytic material such as platinum. Also, the sintered porous hollow polyurethane sponge metal structure can be used as a cleaning filter in exhaust and intake systems by coating with a layer of material such as photocatalyst.

Description of drawings

After reading the specific implementation manner of the present invention with reference to the accompanying drawings, readers will be able to understand the purpose, performance and advantages of the present invention at a glance. in,

Fig. 1 is the method flowchart that the present invention makes the porous hollow polyurethane spongy metal structure of sintering;

Fig. 2 is a form of the cavity inside the sintered porous polyurethane sponge-like metal structure of the present invention;

Fig. 3 shows a part of the skeleton of the porous hollow polyurethane sponge metal structure of the present invention.

Detailed ways

The present invention provides a method for fabricating sponge-like metal structures with high tensile strength, large surface area with low back pressure, low coefficient of thermal expansion, high thermal shock resistance, light weight and design Flexibility to provide pre-heated metal sponge structures to reduce complexity and efficiently improve fuel to meet needs in catalytic converter applications. At the same time, the surface area is increased to provide more efficient exhaust gas treatment while reducing the weight of the converter.

The blasted open-cell polyurethane sponge material (or similar polymeric structure) is first treated by electrochemical deposition. To ensure electrical conductivity, a copper sulfide conductive (94% by weight copper sulfide and 6% by weight epoxy adhesive) layer was precoated on the surface of the polyurethane sponge. Other conductive layers are also possible, for example, graphite, carbon black, etc. may also be used. Other methods can also be used to provide a conductive layer on the polyurethane material substrate, such as PVD, CVD, electroless plating, and the like. The resulting polyurethane sponge material is then electroplated with any desired metal or special metal composition. The latter can be achieved by adjusting the electrode and plating bath composition. After coating a specific thickness (typically from 60 to 150 microns) of metal on top of the polyurethane sponge structure and on the conductive layer, the coated porous substrate is kept in the range of 260°C-270°C to make the flame-resistant substrate Vaporize, thereby removing the substrate. The resulting metal sponge skeleton was then sintered in a reduction furnace at 350°C to 500°C in a hydrogen atmosphere for 30-45 minutes, and then the temperature was gradually increased to 650°C to 900°C in about 30 minutes. In another 60-90 minutes, the porous hollow sponge-like metal structure can be reduced by a hydrogen atmosphere in a reduction furnace at 650°C to 900°C. The sintering temperature needs to be carefully controlled so as not to melt the metal composition, but to reduce the metal compound, leaving hollow cavities of a certain geometry covered by the metal. What is shown in Fig. 2 is the situation when the geometric shape is a triangle, but actually the geometric shape of the hollow cavity can be any achievable geometric shape, which can be understood by those skilled in the art. The cavity has thermal expansion and contraction characteristics, which can reduce thermal expansion of the overall structure.

The resulting metal sponge can then be coated with the catalytic composition by previous coating techniques for catalytic converters. The resulting sponge-like metal structure is an ideal carrier body, not only can be used as a carrier for these catalysts, but the sponge-like metal structure with a fine unit structure (90 to 120ppi) can also be used as a diesel engine dust collector (or called "filter"). The cell structure is limited only by the morphology of the polyurethane sponge which has initially been blasted open. Thus, cell sizes from 5 to 150 ppi can be formed.

The voids under the metal pillars provide the metal sponge with excellent strength and thermal shock resistance. Due to the shape of the metal walls, this sponge-like metal structure has an extremely low linear thermal expansion, which provides good dimensional and thermal shock stability. The voids also allow for a reduced weight of the material while obtaining maximum surface area. The reduced weight allows less heat to be required to heat the metal sponge structure, thereby allowing faster heating of a catalytic converter made of the metal sponge structure to operating temperature.

Another benefit of the present invention is that the metal sponge can be coated on the outer surface of the skeleton using a nickel-chromium alloy. It can then be heated using a suitable current from the car's alternator or battery. It provides a pre-heated support that can be used to replace any of the prior art support materials for catalytic converters or filters/traps. This not only simplifies the current requirement to have dual chambers, but also improves fuel efficiency while reducing manufacturing costs.

FIG. 1 is a flowchart of a method for manufacturing a sintered porous hollow polyurethane sponge-like metal structure. The sintered porous hollow polyurethane sponge-like metal structure can be widely used in liquid transfer machines for certain processing of chemical reactions. The manufacturing method comprises: using a combustible material (such as a polymer sponge) to make a porous substrate; using a metallic material that can withstand the combustion temperature of the combustible material to coat the prepared substrate; The coated porous substrate is sintered to remove the combustible substrate and form an integral porous hollow structure through the metal bond or covalent bond formed by the metal material in the structure, thereby making the sintered porous substrate of the present invention Hollow polyurethane sponge metal structure. Among them, in metals or their alloys, metallic bonds can be easily regarded as covalent bonds, and said covalent bonds are used to improve few non-metallic materials in metal bases produced by sintering or for metal bases feature improvements.

The steps of the present invention may also include the following variants: wherein, the coating process may contain two sub-process steps for coating the metal material on the combustible material, a pre-coating process and an enhanced coating process, and the pre-coating process The coating process is used to bond a layer of material on a porous substrate that allows metal plating, while the enhanced coating process is used to plate a thicker layer of metal material to construct a sintered porous hollow polyurethane sponge-like metal structure The main porous structure of the body. Among them, the pre-coating process can sputter metal or allow metal plating on the porous substrate. Among them, the pre-coating process can coat the conductive glue on the porous substrate. Wherein, the coating method of the conductive adhesive is spray coating. Among other things, the pre-coating process may place the porous substrate portion into a specified chemical solution containing materials that allow metal plating. Wherein the metallic material contains nickel or chromium to enable the use of electricity to heat the porous structure for industrial applications (such as preheating in exhaust pipes of vehicles). Wherein, the metal material includes copper, aluminum or alloys thereof. The metal used offers installation flexibility and heat resistance for the sintering process. Among them, the sintering process may include a process of generating metal deoxidation reaction in pure hydrogen gas.

The structure of the sintered porous hollow polyurethane sponge-like metal structure includes: a porous hollow structure with metal bonds or covalent bonds in the structure to connect the structure as a whole, and the material for making the porous hollow structure can withstand A sintering process with a certain temperature range (such as a temperature up to 2500 degrees Celsius); wherein at least 90% or even the entirety of the material of the porous hollow structure is formed of a metal material. The formed porous hollow polyurethane sponge metal structure is shown in FIG. 3 . The sintered porous polyurethane sponge metal structure formed by the process of the present invention has a super large three-dimensional specific surface area: 450m ² /m ³ to 28000m ² /m ³ . And the ratio of the skeleton volume of the structure body to the volume of the porous polyurethane sponge-like metal structure body is less than 3%.

Variations of the structure of the sintered porous hollow polyurethane sponge-like metal structure will be described below: wherein the porous hollow structure has small holes inside it, and the walls of the small holes are attached with residual carbon compounds produced by the sintering heating process . Among them, the porous structure can be bent, so that a specific spatial shape (such as ventilation pipes and exhaust pipes) can be formed in a specific flow liquid device that adapts to the shape of the device. Specific temperature ranges up to 2500 degrees Celsius. The porous hollow structure may be coated with catalytic material or antimicrobial material. The metal materials that can be used include copper, aluminum, tungsten or their alloys, and can also be nickel or chromium, so that the porous hollow structure can be heated by electricity for industrial application.

The present invention has a number of distinct advantages over the prior art. For example, it is a structure without welded joints, high catalytic efficiency due to the uneven porous hollow structure, effective filter diesel dust (particles) characteristics, thermal shock resistance and short heating time, etc. Also, production costs are reasonable for mass production.

In addition, due to the characteristics of the sintered porous hollow polyurethane sponge-like metal structure with the above-mentioned many benefits, the structure of the present invention can be used as a base structure to coat photocatalyst materials. The photocatalyst produces strong oxidation of hydroxyl radicals under the condition of irradiating ultraviolet rays, and now the porous and hollow polyurethane sponge-like metal structure is not oxidized, so it has broad market prospects.

At the same time, the application field of the sintered porous hollow polyurethane sponge-like metal structure can be extended to the chemical industry (for example) to coat a catalyst layer for removal of nitrogen oxides (DeNOx) or sulfur dioxide (DeSO ₂ ).

The preferred embodiments of the present invention are described above. However, it will be apparent to those skilled in the art that various modifications may be made to the above-described embodiments without departing from the scope of the present invention as defined in the claims, and such modifications fall within within the scope stated in the claims.

Claims (17)

1. A hollow polyurethane sponge metal structure, which is a sintered porous skeleton structure with reduced metal dodecahedron, characterized in that the skeleton has a hollow, rigid and geometrically closed, semi-closed or semi-open structure inside, and the hollow rigid geometric body has an ultra-large three-dimensional specific surface area inside and outside.

2. The hollow polyurethane sponge metal structure of claim 1, wherein said trisThe specific surface area is 450m²/m³To 28000m²/m³。

3. The hollow polyurethane sponge metal structure of claim 1, wherein the ratio of the skeletal volume to the volume of the hollow polyurethane sponge metal structure is less than 3%.

4. The hollow polyurethane sponge metal structure of claim 1, wherein said hollow geometric structure has thermal expansion and contraction characteristics.

5. The hollow polyurethane sponge metal structure of claim 1, wherein at least 90% of said structure is formed of a metallic material.

6. The hollow polyurethane sponge metal structure of claim 1, wherein said structure has pores therein, and wherein the walls of said pores have residual carbon compounds resulting from the sintering process.

7. The hollow polyurethane sponge metal structure of claim 1, wherein said structure is bendable to form a specific spatial shape suitable for use in a device for flowing a liquid.

8. The hollow polyurethane sponge metal structure of claim 1, wherein said structure is coated with a catalytic or antimicrobial material.

9. The hollow polyurethane sponge metal structure of claim 5, wherein said metallic material comprises copper, nickel, tungsten or alloys thereof.

10. A method of making a hollow polyurethane sponge metal structure according to claim 1, comprising the steps of:

(a) forming a porous substrate from a combustible material;

(b) coating the surface of the porous substrate with a flame-resistant metal material capable of bearing the temperature of more than 270 ℃;

(c) maintaining the coated porous substrate at a temperature in the range of 150 ℃ to 300 ℃ to vaporize a combustible substrate to remove the combustible substrate and to join the whole by metallic or covalent bonds in the structural surface metallic material coating through the metallic material to produce the porous hollow, rigid metallic structure;

(d) after the drying procedure, carrying out electrochemical deposition and electroplating on the same metal to increase the thickness of the porous hollow spongy metal structure;

(e) and (3) gradually heating the thickened porous hollow spongy metal structure in a hydrogen reduction furnace by pure hydrogen to perform oxidation reduction: sintering in a hydrogen atmosphere at a temperature in the range of 350 ℃ to 500 ℃ for 30 to 45 minutes; the temperature is then gradually raised to 650 ℃ to 900 ℃ over about 30 minutes, and the porous hollow spongy metal structure is subsequently reduced in a reducing furnace at 650 ℃ to 900 ℃ in a hydrogen atmosphere over a further 60 to 90 minutes.

11. The method of claim 10, wherein step (b) comprises the following two substeps:

(b1) a pre-coating sub-step for adhering a layer of material that can be metal plated on the porous substrate; and

(b2) a reinforcement coating substep for electroplating a thick layer of metallic material to construct the main cellular structure of the sintered polyurethane sponge metallic structure.

12. The method of claim 11, wherein said substep (b1) comprises employing a material that sputters metal or allows for metal plating on said porous substrate.

13. The method of claim 11, wherein said substep (b1) comprises applying a conductive paste on said porous substrate.

14. The method of claim 13, wherein the step of applying the conductive paste comprises spraying.

15. The method of claim 11, wherein said substep (b1) comprises subjecting said porous substrate to a specified chemical solution containing said metal electroplatable material.

16. The method of claim 10, wherein the metallic material comprises nickel or chromium to enable heating of the structure by electricity.

17. The method of claim 10, wherein the metallic material comprises copper, aluminum, or alloys thereof.

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