CN113147105A - Porous polyimide oil storage and retention structure and preparation method and application thereof - Google Patents
Porous polyimide oil storage and retention structure and preparation method and application thereof Download PDFInfo
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- 239000004642 Polyimide Substances 0.000 title claims abstract description 183
- 229920001721 polyimide Polymers 0.000 title claims abstract description 183
- 238000003860 storage Methods 0.000 title claims abstract description 96
- 230000014759 maintenance of location Effects 0.000 title claims abstract description 66
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 239000011148 porous material Substances 0.000 claims abstract description 37
- 239000002131 composite material Substances 0.000 claims abstract description 32
- 239000000463 material Substances 0.000 claims abstract description 31
- 238000005245 sintering Methods 0.000 claims description 40
- 239000002245 particle Substances 0.000 claims description 38
- 239000002243 precursor Substances 0.000 claims description 36
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- 238000009694 cold isostatic pressing Methods 0.000 claims description 10
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- 238000000034 method Methods 0.000 description 16
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- 238000001513 hot isostatic pressing Methods 0.000 description 5
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- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- 150000004984 aromatic diamines Chemical class 0.000 description 2
- HFACYLZERDEVSX-UHFFFAOYSA-N benzidine Chemical group C1=CC(N)=CC=C1C1=CC=C(N)C=C1 HFACYLZERDEVSX-UHFFFAOYSA-N 0.000 description 2
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- 102000020897 Formins Human genes 0.000 description 1
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- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 1
- GTDPSWPPOUPBNX-UHFFFAOYSA-N ac1mqpva Chemical compound CC12C(=O)OC(=O)C1(C)C1(C)C2(C)C(=O)OC1=O GTDPSWPPOUPBNX-UHFFFAOYSA-N 0.000 description 1
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- ANSXAPJVJOKRDJ-UHFFFAOYSA-N furo[3,4-f][2]benzofuran-1,3,5,7-tetrone Chemical compound C1=C2C(=O)OC(=O)C2=CC2=C1C(=O)OC2=O ANSXAPJVJOKRDJ-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B1/00—Layered products having a general shape other than plane
- B32B1/08—Tubular products
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
- B32B27/281—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42 comprising polyimides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
- B32B37/06—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the heating method
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/04—Interconnection of layers
- B32B7/10—Interconnection of layers at least one layer having inter-reactive properties
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
- F16C33/30—Parts of ball or roller bearings
- F16C33/38—Ball cages
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
- F16C33/30—Parts of ball or roller bearings
- F16C33/46—Cages for rollers or needles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/50—Properties of the layers or laminate having particular mechanical properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/50—Properties of the layers or laminate having particular mechanical properties
- B32B2307/554—Wear resistance
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2597/00—Tubular articles, e.g. hoses, pipes
Abstract
The invention provides a porous polyimide oil storage and retention structure and a preparation method and application thereof, and relates to the technical field of polyimide materials. The porous polyimide oil storage and retention structure provided by the invention comprises an oil storage layer and an oil control layer; the material of the oil storage layer is monoether type polyimide, the porosity of the monoether type polyimide is 18-26%, and the pore diameter is 1.0-3.0 mu m; the oil control layer is made of pyromellitic polyimide, the porosity of the pyromellitic polyimide is 12-18%, and the pore diameter of the pyromellitic polyimide is 0.6-1.0 mu m. The pyromellitic polyimide has low porosity and small pore diameter, can slow down the oil release rate of the composite material and improve the oil retention rate; the monoether type polyimide has high porosity and large pore diameter, and can improve the porosity and the oil storage rate of the composite material; the composite material provided by the invention has high oil storage rate and oil retention rate, good strength and wear resistance, and can meet the requirement of a high-speed high-precision bearing on the service life.
Description
Technical Field
The invention relates to the technical field of polyimide materials, in particular to a porous polyimide oil storage and retention structure and a preparation method and application thereof.
Background
The porous polyimide material has the characteristics of high oil content, good mechanical strength and the like, and can be widely applied to high-speed high-precision bearings of aerospace, high-end machine tools and high-end automobiles as a bearing retainer material. When the bearing rotates, the porous polyimide bearing retainer releases lubricating oil to the surfaces of the retainer and the rolling body; when the bearing is static, lubricating oil is sucked back into the porous polyimide retainer for storage due to the capillary action, so that the volatilization of the lubricating oil is reduced, and the cycle of oil release and storage gives the porous polyimide retainer the characteristics of long service life and no maintenance. With the progress of industrial development, higher oil content and service life requirements are provided for the porous polyimide retainer, the porosity and the oil retention rate of the porous polyimide retainer are mutually restricted, and the oil content and the oil retention rate must be improved at the same time when the service life of the retainer is prolonged. However, the existing porous polyimide material cannot simultaneously have proper porosity and oil retention rate, and cannot meet the requirement of a high-speed high-precision bearing on service life.
Disclosure of Invention
In view of the above, the present invention provides a porous polyimide oil storage and retention structure, and a preparation method and an application thereof, and the porous polyimide oil storage and retention structure provided by the present invention has a high porosity and a high oil retention rate, and can meet a requirement of a high-speed high-precision bearing on a service life.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a porous polyimide oil storage and retention structure, which comprises an oil storage layer and an oil control layer;
the material of the oil storage layer is monoether type polyimide, the porosity of the monoether type polyimide is 18-26%, and the pore diameter is 1.0-3.0 mu m;
the oil control layer is made of pyromellitic polyimide, the porosity of the pyromellitic polyimide is 12-18%, and the pore diameter of the pyromellitic polyimide is 0.6-1.0 mu m.
Preferably, the thickness ratio of the oil storage layer to the oil control layer is (2-4): 1.
preferably, the monoether type polyimide has a structure represented by formula I:
preferably, the pyromellitic polyimide has a structure represented by formula II:
the invention provides a preparation method of the porous polyimide oil storage and retention structure, which comprises the following steps:
(1) sequentially carrying out first cold isostatic pressing and cold treatment on monoether type polyimide to obtain an oil storage layer precursor; the particle size of the monoether type polyimide is 20-70 mu m;
(2) sequentially carrying out second cold isostatic pressing, sintering and heat treatment on the pyromellitic polyimide to obtain an oil control layer precursor; the particle size of the pyromellitic polyimide is 15-30 mu m;
(3) nesting and then compositely sintering the oil storage layer precursor and the oil control layer precursor to obtain a porous polyimide oil storage and retention structure;
the step (1) and the step (2) have no chronological order.
Preferably, the pressure of the first cold isostatic press is 50-90 MPa, and the time is 20-60 min.
Preferably, the temperature of the cold treatment is-120 ℃ to-40 ℃, and the time is 1-4 h.
Preferably, the pressure of the second cold isostatic press is 70-120 MPa, and the time is 20-60 min;
the sintering temperature is 350-400 ℃, the pressure is 2-10 MPa, and the time is 10-30 min;
the temperature of the heat treatment is 100-300 ℃, and the time is 1-4 h.
Preferably, the temperature of the composite sintering is 300-350 ℃, the pressure is 2-10 MPa, and the time is 10-30 min.
The invention provides an application of the porous polyimide oil storage and retention structure in the technical scheme or the porous polyimide oil storage and retention structure obtained by the preparation method in the technical scheme as a bearing retainer material.
The invention provides a porous polyimide oil storage and retention structure, which comprises an oil storage layer and an oil control layer; the material of the oil storage layer is monoether type polyimide, the porosity of the monoether type polyimide is 18-26%, and the pore diameter is 1.0-3.0 mu m; the oil control layer is made of pyromellitic polyimide, the porosity of the pyromellitic polyimide is 12-18%, and the pore diameter of the pyromellitic polyimide is 0.6-1.0 mu m. The porous polyimide oil storage and retention structure provided by the invention takes the low-porosity and small-aperture pyromellitic polyimide porous material as an oil control layer material, so that the oil release rate is slowed, and the oil retention rate is improved; the high-porosity and large-aperture pyromellitic polyimide porous material is used as an oil storage layer, so that the porosity and the oil storage rate are improved, and the porosity and the oil storage rate are connected together by sintering, so that the organic unification of the oil storage rate and the oil retention rate is realized. In addition, compared with other polyimide materials, the pyromellitic polyimide has excellent mechanical properties and good wear resistance, so that the composite material has good strength and wear resistance. The example results show that the porosity of the porous polyimide oil storage and retention structure provided by the invention is 23.6-28.4%, the oil retention rate is 98.2-99.5%, and the ring tension is 44-58 MPa, which indicates that the porous polyimide oil storage and retention structure provided by the invention has high porosity, high oil retention rate and high strength.
The invention provides a preparation method of the porous polyimide oil storage and retention structure, which comprises the following steps: (1) sequentially carrying out first cold isostatic pressing and cold treatment on monoether type polyimide to obtain an oil storage layer precursor; the particle size of the monoether type polyimide is 20-70 mu m; (2) sequentially carrying out second cold isostatic pressing, sintering and heat treatment on the pyromellitic polyimide to obtain an oil control layer precursor; the particle size of the pyromellitic polyimide is 15-30 mu m; (3) and performing nested composite sintering on the oil storage layer precursor and the oil control layer precursor to obtain the porous polyimide oil storage and retention structure. In the invention, the monoether type polyimide and the pyromellitic polyimide with specific particle sizes are used as preparation raw materials, so that an oil storage layer in the composite material can be ensured to be a porous material with high porosity and large pore size, and an oil control layer is a porous material with low porosity and small pore size, thereby improving the oil storage rate and the oil retention rate of the composite material; in the sintering process of the pyromellitic polyimide, under the action of heat, air in powder gaps and low molecular gas released in particles expand and flow in the particles due to pressure difference, so that pore diameters are formed by scouring pore canals; the cold-treated monoether polyimide and the heat-treated pyromellitic polyimide can be nested together through thermal expansion and cold contraction effects in the subsequent composite sintering process, and the monoether polyimide and the pyromellitic polyimide form interference fit after the temperature is restored to room temperature; moreover, the melting point of the pyromellitic polyimide is higher than that of the monoether polyimide, the pore diameter structure of the pyromellitic polyimide is not changed in the composite sintering process, a stable microstructure can be kept, and the strength and the wear resistance of the composite material are improved; the two nested porous materials are only combined together by interference force and are easy to separate in the processing process, the two polyimide materials can be sintered together after composite sintering to form cross-linking of molecular chains, the bonding strength between the two polyimide materials is high, and the two polyimide materials are not easy to separate, so that the oil storage rate and the oil retention rate of the composite material are improved, and the requirement of a high-speed high-precision bearing on the service life can be met; moreover, the preparation method provided by the invention is simple to operate, low in production cost and suitable for industrial production.
Drawings
FIG. 1 is a schematic diagram of the oil storage and retention structure of porous polyimide prepared in example 1;
FIG. 2 is a pore size distribution diagram of the porous polyimide oil storage and retention structure prepared in example 2.
Detailed Description
The invention provides a porous polyimide oil storage and retention structure which comprises an oil storage layer and an oil control layer.
In the invention, the material of the oil storage layer is monoether type polyimide, and the porosity of the monoether type polyimide is 18-26%, preferably 19-25%, more preferably 20-24%, and most preferably 21-23%; the pore diameter of the monoether type polyimide is 1.0-3.0 μm, preferably 1.2-2.8 μm, more preferably 1.5-2.5 μm, and most preferably 2.0-2.2 μm. In the present invention, the monoether type polyimide preferably has a structure represented by formula I:
the monoether type polyimide is preferably purchased from the institute of synthetic resins of Shanghai city.
In the invention, the material of the oil control layer is a pyromellitic polyimide, and the porosity of the pyromellitic polyimide is 12-18%, preferably 13-17%, more preferably 14-16%, and most preferably 15%; the aperture of the pyromellitic polyimide is 0.6-1.0 μm, preferably 0.7-0.9 μm, more preferably 0.75-0.85 μm, and most preferably 0.8 μm. In the present invention, the pyromellitic polyimide preferably has a structure represented by formula II:
in the present invention, the pyromellitic polyimide is preferably obtained by self-production, and the preparation method of the pyromellitic polyimide preferably comprises the following steps: mixing aromatic diamine 4, 4' -diaminodiphenyl methyl ether, pyromellitic dianhydride and an amide solvent in a protective atmosphere, and reacting to obtain an intermediate homogeneous solution; and mixing the intermediate homogeneous phase solution with a dehydrating agent to carry out imidization reaction to obtain the pyromellitic polyimide.
In a protective atmosphere, 4' -diaminodiphenyl methyl ether, pyromellitic dianhydride and an amide solvent are mixed and then react to obtain an intermediate homogeneous solution. The protective atmosphere in the present invention is not particularly limited, and those known to those skilled in the art may be used, such as nitrogen or argon. In the present invention, the molar ratio of 4, 4' -diaminoanisole (ODA) and pyromellitic anhydride (PMDA) is preferably 1: 1. In the present invention, the preferable amide-based solvent includes N, N-dimethylformamide or N, N-dimethylacetamide; the total mass percentage concentration of the 4, 4' -diaminodiphenyl methyl ether and pyromellitic dianhydride in the amide solvent is preferably 10-20%, and more preferably 15%. In the invention, the reaction is preferably carried out under the conditions of normal temperature, normal pressure and stirring; the stirring speed in the present invention is not particularly limited, and a stirring speed known to those skilled in the art may be used.
After the intermediate homogeneous phase solution is obtained, the intermediate homogeneous phase solution is mixed with a dehydrating agent to carry out imidization reaction, and the pyromellitic polyimide is obtained. In the present invention, the dehydrating agent is preferably toluene; the mass ratio of the intermediate homogeneous phase solution to the toluene is preferably (5-10): 1, more preferably (6-8): 1. in the present invention, the temperature of the imidization reaction is preferably 150 to 160 ℃, more preferably 155 ℃; the time of the imidization reaction is preferably 12 to 24 hours, and more preferably 16 to 20 hours. After the imidization reaction, the invention preferably further comprises the steps of placing the reaction solution of the imidization reaction in water to separate out the pyromellitic polyimide, filtering, washing the obtained solid product with ethanol, and drying to obtain the pyromellitic polyimide; the drying temperature is preferably 140-160 ℃, and more preferably 150 ℃; the drying mode is preferably vacuum drying; in the present invention, the drying time is not particularly limited, and the drying time may be set to a constant weight.
In the invention, the thickness ratio of the annular oil storage layer to the annular oil control layer is preferably 2-4: 1, more preferably 3 to 4: 1.
the invention provides a preparation method of the porous polyimide oil storage and retention structure, which comprises the following steps:
(1) sequentially carrying out first cold isostatic pressing and cold treatment on monoether type polyimide to obtain an oil storage layer precursor; the particle size of the monoether type polyimide is 20-70 mu m;
(2) sequentially carrying out second cold isostatic pressing, sintering and heat treatment on the pyromellitic polyimide to obtain an oil control layer precursor; the particle size of the pyromellitic polyimide is 15-30 mu m;
(3) nesting and then compositely sintering the oil storage layer precursor and the oil control layer precursor to obtain a porous polyimide oil storage and retention structure;
the step (1) and the step (2) have no chronological order.
In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.
According to the invention, monoether type polyimide is sequentially subjected to a first cold isostatic pressing mechanism and cold treatment to obtain an oil storage layer precursor.
In the invention, the particle size of the monoether type polyimide is 20-70 μm, preferably 20-40 μm or 40-70 μm, and more preferably 25-35 μm or 50-60 μm. In the present invention, the monoether type polyimide is preferably sieved and classified before use, and the sieving and classification in the present invention is not particularly limited, and the monoether type polyimide having a particle size of 20 to 70 μm can be obtained.
In the invention, the pressure of the first cold isostatic press is preferably 50-90 MPa, more preferably 60-80 MPa, and most preferably 70 MPa; the pressing temperature of the first cold isostatic press is preferably room temperature; the pressing time of the first cold isostatic press is preferably 20-60 min, more preferably 30-50 min, and most preferably 40 min; the first cold isostatic press pressing is preferably performed in a cold isostatic press.
In the present invention, the temperature of the cold treatment is preferably-120 to-40 ℃, more preferably-70 to-40 ℃, and most preferably-70 ℃; the time of the cold treatment is preferably 1-4 h, more preferably 2-3 h, and most preferably 2 h; the cold treatment is preferably carried out in a cryogenic material cabinet. In the invention, the cold-treated monoether type polyimide and the heat-treated pyromellitic dianhydride type polyimide can be nested together through thermal expansion and cold contraction effects, the monoether type polyimide and the pyromellitic dianhydride type polyimide form interference fit after the temperature is restored to the room temperature, and then the interfacial-free integral material can be formed through subsequent composite sintering.
The invention carries out second cold isostatic pressing, sintering and heat treatment on the pyromellitic polyimide in sequence to obtain the precursor of the oil control layer.
In the present invention, the particle size of the pyromellitic polyimide is 15 to 30 μm, preferably 18 to 35 μm, and more preferably 20 to 30 μm. In the present invention, the pyromellitic polyimide is preferably sieved and classified before use, and the sieving and classification in the present invention is not particularly limited, and pyromellitic polyimide having a particle size of 15 to 30 μm can be obtained.
In the invention, the pressure of the second cold isostatic press is preferably 70-120 MPa, more preferably 80-110 MPa, and most preferably 90-100 MPa; the pressing time of the second cold isostatic press is preferably 20-60 min, more preferably 30-50 min, and most preferably 40 min; the second cold isostatic press pressing is preferably performed in a cold isostatic press.
In the invention, the sintering temperature is preferably 350-400 ℃, more preferably 360-390 ℃, and most preferably 370-380 ℃; the sintering pressure is preferably 2-10 MPa, more preferably 4-8 MPa, and most preferably 5-6 MPa; the sintering time is preferably 10-30 min, more preferably 15-25 min, and most preferably 20 min; the invention preferably puts the pyromellitic polyimide in a sheath, vacuumizes the sheath and then sinters the sheath in a hot isostatic pressing furnace; the material of the sheath is not particularly limited, and the sheath can deform under the conditions of 350-400 ℃ and 2-10 MPa; in the embodiments of the present inventionIn the above, the material of the sheath is preferably low carbon steel; the shape of the sheath is not specially limited, and the sheath can be selected according to actual needs. In the present invention, the degree of vacuum of the evacuation is preferably 1X 10 or less-3Pa。
In the invention, the powder particles of the pyromellitic polyimide particles are in a close packing state, and gaps are formed among the powder particles, which is similar to the rigid ball stacking principle, and in the sintering process, air in the powder gaps and low molecular gas released in the particles can expand and flow in the particles caused by pressure difference to wash a pore passage to form the pore diameter.
In the invention, the temperature of the heat treatment is preferably 100-300 ℃, more preferably 150-250 ℃, and most preferably 200 ℃; the time of the heat treatment is preferably 1-4 h, more preferably 2-3 h, and most preferably 2 h; the heat treatment is preferably carried out in an oven. In the invention, the cold-treated monoether type polyimide and the heat-treated pyromellitic dianhydride type polyimide can be nested together through thermal expansion and cold contraction effects, the monoether type polyimide and the pyromellitic dianhydride type polyimide form interference fit after the temperature is restored to the room temperature, and then the interfacial-free integral material can be formed through subsequent composite sintering.
After an oil storage layer precursor and an oil control layer precursor are obtained, the oil storage layer precursor and the oil control layer precursor are nested and then compositely sintered to obtain the porous polyimide oil storage and retention structure.
In the invention, the temperature of the composite sintering is preferably 300-350 ℃, more preferably 310-340 ℃, and most preferably 320-330 ℃; the pressure of the composite sintering is preferably 2-10 MPa, more preferably 4-8 MPa, and most preferably 5-6 MPa; the time for the composite sintering is preferably 10-30 min, more preferably 15-25 min, and most preferably 20 min; the nested oil storage layer precursor and the nested oil control layer precursor are preferably placed in a sheath, vacuumized and then compositely sintered in a hot isostatic pressing furnace, the material sheath is not specially limited, and can deform under the conditions of 300-350 ℃ and 2-10 MPa; in the embodiment of the invention, the material of the sheath is preferably low-carbon steel; book (I)The shape of the sheath is not specially limited, and the sheath can be selected according to actual needs. In the present invention, the degree of vacuum of the evacuation is preferably 1X 10 or less-3Pa. In the invention, in the composite sintering process, the oil storage layer precursor and the oil control layer precursor are nested together through a thermal expansion and cold contraction effect, and the oil storage layer precursor and the oil control layer precursor form interference fit after being recovered to room temperature. In the invention, the two nested porous materials are only combined together by interference force and are easy to separate in the processing process, the two polyimide materials can be sintered together after composite sintering to form cross-linking of molecular chains, the bonding strength between the two polyimide materials is high, and the two polyimide materials are not easy to separate and can be used for mechanical processing. The oil storage and control composite structure improves the oil storage rate and the oil retention rate of the composite material, and can meet the requirement of a high-speed high-precision bearing on the service life. In the invention, gaps are reserved among powder particles of the monoether type polyimide in a close packing state, and in the composite sintering process, the monoether type polyimide is subjected to heat action, so that air in the gaps among the powder and low molecular substances (such as diamine and dianhydride) released in the particles can expand and flow internally due to pressure difference, and pores are flushed to form the pore diameter; the melting point of the pyromellitic polyimide is higher than that of the monoether polyimide, the pore diameter structure of the pyromellitic polyimide is not changed in the composite sintering process, a stable microstructure can be kept, and the strength of the composite material is improved.
After the composite sintering, the method preferably further comprises the step of removing the sheath and then cooling to room temperature to obtain the porous polyimide oil storage and retention structure. The operation of removing the coating is not particularly limited in the present invention, and may be performed by a coating removing operation known to those skilled in the art. The cooling method of the present invention is not particularly limited, and a cooling method known to those skilled in the art may be employed; in the invention, the oil storage layer precursor and the oil control layer precursor which are nested together through the effect of thermal expansion and cold contraction form interference fit in the cooling process. The shape of the sheath is not specially limited, and the sheath can be selected according to actual needs.
The invention provides an application of the porous polyimide oil storage and retention structure in the technical scheme or the porous polyimide oil storage and retention structure obtained by the preparation method in the technical scheme as a bearing retainer material. In the invention, the porous polyimide oil storage and retention structure is preferably used as a bearing retainer material of aerospace, machine tools or automobiles.
In the invention, when the porous polyimide oil storage and retention structure is applied as a bearing retainer material, the oil storage layer is an inner layer, and the oil control layer is an outer layer.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) Dissolving aromatic diamine 4, 4' -diaminodiphenyl methyl ether (ODA) in an amide solvent under the conditions of nitrogen protection atmosphere, room temperature, normal pressure and stirring, then adding pyromellitic dianhydride (PMDA) with the same amount of substances, supplementing the solvent to enable the total mass concentration of ODA and PMDA to be 15 wt%, and stirring and reacting for 16 hours at room temperature to obtain an intermediate homogeneous solution; adding a dehydrating agent toluene into the intermediate homogeneous phase solution, uniformly mixing, heating to 155 ℃ for imidization, pouring a reaction system into water to precipitate pyromellitic polyimide after the reaction is finished, filtering, washing the obtained solid product with ethanol, and drying in vacuum at 150 ℃ to obtain pyromellitic polyimide; wherein the mass ratio of the intermediate homogeneous solution to the toluene is 5: 1.
(2) Screening and grading the monoether type polyimide to obtain monoether type polyimide with the particle size of 20-40 mu m, placing the monoether type polyimide with the particle size of 20-40 mu m in a cold isostatic press, pressing for 30min by the first cold isostatic press under the conditions of 50MPa and room temperature, then placing in a low-temperature material box, and carrying out cold treatment for 2h at-70 ℃ to obtain an oil storage layer precursor; wherein, the monoether type polyimide has a structural formula shown in formula I and is purchased from the research institute of synthetic resin in Shanghai;
(3) sieving and grading the pyromellitic polyimide to obtain the pyromellitic polyimide with the particle size of 15-30 microns, placing the pyromellitic polyimide with the particle size of 15-30 microns in a cold isostatic press, pressing for 30min by a second cold isostatic press under the conditions of 90MPa and room temperature, then placing in a sheath, sintering for 10min in a hot isostatic pressing furnace under the conditions of 350 ℃ and 2MPa, then placing in an oven, and carrying out heat treatment for 2h under the condition of 200 ℃ to obtain an oil control layer precursor;
(4) and simultaneously taking out the oil storage layer precursor and the oil control layer precursor, nesting the precursors together, placing the precursors in a sheath, performing composite sintering for 20min in a hot isostatic pressing furnace at 330 ℃ and under 5MPa, removing the sheath, and cooling to room temperature to obtain the porous polyimide oil storage and retention structure, wherein the porous polyimide oil storage and retention structure is a cylindrical structure, the inner layer is an oil storage layer, and the outer layer is an oil control layer, and the schematic diagram is shown in figure 1.
Example 2
The porous polyimide oil storage and retention structure is prepared according to the method of the embodiment 1, and the difference from the embodiment 1 is that:
in the step (2), the particle size of the monoether type polyimide is 40-70 μm; the pressure of the first cold isostatic press is 90 MPa;
in the step (3), the pressure of the second cold isostatic press is 120 MPa;
the temperature of the composite sintering in the step (4) is 350 ℃, the pressure is 10MPa, and the time is 30 min.
The pore size distribution diagram of the porous polyimide oil storage and retention structure prepared in the embodiment is shown in fig. 2, and as can be seen from fig. 2, the pore size of the oil control layer of the porous polyimide oil storage and retention structure is mainly distributed in the range of 0.3-0.5 μm, the pore size of the oil storage layer is mainly distributed in the range of 1-2.25 μm, and the pore volume of the oil storage layer is far higher than that of the oil control layer. The porous polyimide oil storage and retention structure provided by the invention has the advantages of high unit mass porosity and large pore diameter of the oil storage layer, and low unit mass porosity and small pore diameter of the oil control layer.
Example 3
The porous polyimide oil storage and retention structure is prepared according to the method of the embodiment 1, and the difference from the embodiment 1 is that:
in the step (2), the particle size of the monoether type polyimide is 40-70 μm; the pressure of the first cold isostatic press is 70 MPa;
in the step (3), the pressure of the second cold isostatic press is 120 MPa; sintering under 2MPa at 380 deg.C for 10 min;
the temperature of the composite sintering in the step (4) is 340 ℃.
Comparative example 1
Screening and grading the monoether type polyimide to obtain monoether type polyimide with the particle size of 40-70 microns, placing the monoether type polyimide with the particle size of 20-40 microns in a cold isostatic press, pressing for min by the first cold isostatic press under the conditions of 70MPa and room temperature, then placing in a sheath, sintering for 20min in a hot isostatic press at 330 ℃ and 5MPa, removing the sheath, and cooling to room temperature to obtain a porous polyimide oil storage and retention structure; wherein, the monoether type polyimide has a structural formula shown in a formula I.
Comparative example 2
The preparation method comprises the steps of screening and grading the pyromellitic polyimide to obtain the pyromellitic polyimide with the particle size of 15-30 microns, placing the pyromellitic polyimide with the particle size of 15-30 microns in a cold isostatic press, pressing for 30min by a second cold isostatic press at the room temperature and the pressure of 100MPa, placing the second cold isostatic press in a sheath, sintering for 30min in a hot isostatic pressing furnace at the temperature of 380 ℃ and the pressure of 10MPa, removing the sheath, and cooling to the room temperature to obtain the porous polyimide oil storage and retention structure.
Comparative example 3
The porous polyimide oil storage and retention structure is prepared according to the method of the embodiment 1, and the difference from the embodiment 1 is that:
in the step (2), the particle size of the monoether type polyimide is 5-15 μm;
in the step (3), the particle size of the pyromellitic polyimide is 40-50 μm.
Comparative example 4
The porous polyimide oil storage and retention structure is prepared according to the method of the embodiment 1, and the difference from the embodiment 1 is that:
in the step (2), the particle size of the monoether type polyimide is 80-90 μm;
in the step (3), the particle size of the pyromellitic polyimide is 1-5 μm.
The performance test results of the porosity, the oil retention rate and the ring tension of the oil storage structure, the oil control structure and the composite material in the porous polyimide oil storage and retention structures prepared in the embodiments 1 to 3 and the comparative examples 1 to 4 are shown in table 1, and the test is performed according to MIL-P-29609, wherein the test condition of the oil retention rate is centrifugal oil throwing; centrifuge rotation speed 3000 rpm:
TABLE 1 Performance test results of porous polyimide oil-storing and-retaining structures prepared in examples 1 to 3 and comparative examples 1 to 4
As can be seen from Table 1, the porosity of the porous polyimide oil storage and retention structure provided by the invention is 23.6-28.4%, the oil retention rate is 98.2-99.5%, the ring tension is 44-58 MPa, the particle size of the monoether type polyimide in the comparative example 3 is too small, many pores are blocked in the sintering process, and therefore the porosity is very low; in comparative example 4, the small particle size of the pyromellitic dianhydride type results in too small pore size of the oil control structure, and the oil cannot be thrown out, so the retention rate is 100%. The porous polyimide oil storage and retention structure provided by the invention has high porosity, high oil retention rate and high strength.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A porous polyimide oil storage and retention structure is characterized by comprising an oil storage layer and an oil control layer;
the material of the oil storage layer is monoether type polyimide, the porosity of the monoether type polyimide is 18-26%, and the pore diameter is 1.0-3.0 mu m;
the oil control layer is made of pyromellitic polyimide, the porosity of the pyromellitic polyimide is 12-18%, and the pore diameter of the pyromellitic polyimide is 0.6-1.0 mu m.
2. The composite porous material according to claim 1, wherein the thickness ratio of the oil reservoir layer to the oil control layer is (2-4): 1.
3. the porous polyimide oil storage and retention structure of claim 1 or 2, wherein the monoether type polyimide has a structure represented by formula I:
4. the porous polyimide oil storage and retention structure of claim 1 or 2, wherein the pyromellitic polyimide has a structure represented by formula II:
5. the preparation method of the porous polyimide oil storage and retention structure as claimed in any one of claims 1 to 4, characterized by comprising the following steps:
(1) sequentially carrying out first cold isostatic pressing and cold treatment on monoether type polyimide to obtain an oil storage layer precursor; the particle size of the monoether type polyimide is 20-70 mu m;
(2) sequentially carrying out second cold isostatic pressing, sintering and heat treatment on the pyromellitic polyimide to obtain an oil control layer precursor; the particle size of the pyromellitic polyimide is 15-30 mu m;
(3) nesting and then compositely sintering the oil storage layer precursor and the oil control layer precursor to obtain a porous polyimide oil storage and retention structure;
the step (1) and the step (2) have no chronological order.
6. The preparation method according to claim 5, wherein the pressure of the first cold isostatic press is 50-90 MPa, and the time is 20-60 min.
7. The preparation method according to claim 5, wherein the cold treatment is carried out at-120 ℃ to 40 ℃ for 1 to 4 hours.
8. The preparation method of claim 5, wherein the pressure of the second cold isostatic press is 70-120 MPa, and the time is 20-60 min;
the sintering temperature is 350-400 ℃, the pressure is 2-10 MPa, and the time is 10-30 min;
the temperature of the heat treatment is 100-300 ℃, and the time is 1-4 h.
9. The preparation method according to claim 5, wherein the temperature of the composite sintering is 300-350 ℃, the pressure is 2-10 MPa, and the time is 10-30 min.
10. Use of the porous polyimide oil-storing and retaining structure according to any one of claims 1 to 4 or the porous polyimide oil-storing and retaining structure obtained by the preparation method according to any one of claims 5 to 8 as a bearing retainer material.
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