CN115505266A - Silicone rubber gasket and preparation method and application thereof - Google Patents
Silicone rubber gasket and preparation method and application thereof Download PDFInfo
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- C08J5/18—Manufacture of films or sheets
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
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- C08J2383/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J2383/04—Polysiloxanes
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- C08J2383/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J2383/04—Polysiloxanes
- C08J2383/07—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
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- C08J2483/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J2483/04—Polysiloxanes
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2483/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J2483/04—Polysiloxanes
- C08J2483/05—Polysiloxanes containing silicon bound to hydrogen
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- C08K7/00—Use of ingredients characterised by shape
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- C08K9/00—Use of pretreated ingredients
- C08K9/02—Ingredients treated with inorganic substances
Abstract
The invention relates to the technical field of silicone rubber gaskets, in particular to a heat-conducting silicone rubber gasket and a preparation method and application thereof. According to the invention, one-dimensional constraint orientation is carried out on short carbon fibers by using pressure, a rubber solid block is prepared by pressurizing, the length extension direction of the carbon fibers is parallel to the direction vertical to the pressure, and on the basis of the one-dimensional constraint orientation, the two-dimensional constraint orientation is carried out on the short carbon fibers by open milling and calendering, so that the orientation rate of the carbon fibers along the thickness direction of the silicone rubber gasket, namely the cosine distribution value of the angle between the length extension direction and the thickness direction of the silicone rubber gasket, namely a channel for heat conduction along the thickness direction of the silicone rubber gasket, is further improved, the one-dimensional constraint orientation has an orientation rate of 50%, and the two-dimensional constraint orientation has an orientation rate of 60-70%. And finally, cutting the long high plane of the rubber solid block to obtain the silicone rubber gasket with high orientation rate, thereby improving the heat conductivity coefficient of the silicone rubber gasket.
Description
Technical Field
The invention relates to the technical field of silicone rubber gaskets, in particular to a silicone rubber gasket, and a preparation method and application thereof.
Background
The heat-conducting silicone rubber gasket is used for electronic products, and air between a heating component and a radiator of electronic equipment is filled in gaps between the heating component and the radiator, so that heat of the electronic equipment is led out in an accelerating mode, and performance and service life of the electronic products are guaranteed. With the rapid development of high power, high density and high integration of electronic components, the increasingly prominent heat dissipation problem has become the bottleneck in the development of high-power electronic components and ultra-large-scale and ultra-high-speed integrated circuits, and especially the rapid development and popularization of 5G application technology are faced at present, so that the heat conduction performance of the silicone rubber gasket is improved, and an important development subject to be solved urgently in the current microelectronic industry is formed.
The silicon rubber has good flexibility, high-temperature performance and flame retardance, can be tightly attached between a heating component and a radiator, and is a material with low heat conductivity coefficient. The carbon fiber is a high-thermal-conductivity fiber material, the thermal conductivity coefficient in the fiber direction can exceed that of copper, and the carbon fiber has good mechanical properties and excellent heat conduction and radiation heat dissipation capabilities. By optimally designing and manufacturing the combination of the properties of the carbon fiber and the silicone rubber, it is possible to prepare a silicone rubber gasket having an ultra-high thermal conductivity. However, in the prior art, the mass content of the carbon fiber in the silicone rubber gasket is up to 40%, and the thermal conductivity coefficient of the prepared silicone rubber gasket in the thickness direction can only reach 0.5-0.7W/m.K. That is, the excellent thermal conductivity of the carbon fiber is hardly reflected in the research on the application of the thermal conductive material and the actual industrial use.
For example, japanese patent publication No. JP2005146057 discloses a method for making carbon fibers into powder with a length of 70 to 130 μm, turning the carbon fibers under the action of a magnetic field by utilizing the diamagnetism of the carbon fibers, and aligning the carbon fibers in the thickness direction of the silicone rubber pad to obtain a carbon fiber silicone rubber pad with a thermal conductivity of 14W/m · K or more. The method provides an effective sample plate for setting and manufacturing the heat conduction orientation of the carbon fiber, but the technical process of the method is complex and the manufacturing cost is high. Chinese patent publication No. CN109354874A discloses that fibrous filler, spherical filler and liquid silicone rubber are stirred into a mixture, the mixture flows through a pipe, at the outlet of the pipe, the fibers form an oriented arrangement in the mixture, the mixture is poured into a forming tank, the fibers maintain the oriented arrangement in the mixture in the forming tank, the silicone rubber mixture maintains the oriented arrangement after vulcanization, and then the silicone rubber gasket is obtained by cutting the mixture perpendicular to the oriented fibers. The method has the disadvantages that the amount of the liquid rubber is enough small to maintain the alignment of the fibers in the mixture in the forming groove, otherwise, the fibers collapse, and the silicone rubber gasket prepared by using too small amount of the silicone rubber cannot be practically used.
Disclosure of Invention
The invention aims to provide a silicone rubber gasket, a preparation method and application thereof; the silicone rubber gasket prepared by the preparation method has excellent heat-conducting property in the thickness direction, and the preparation method is simple, low in cost and suitable for industrial production.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a silicon rubber gasket, which comprises the following steps:
mixing short carbon fibers, heat-conducting filler and silicone rubber to obtain a mixture; the length of the short carbon fiber is less than or equal to 6mm;
pressurizing and vulcanizing the mixture in a mold to obtain a rubber solid block;
cutting the long high plane of the rubber solid block to obtain the silicon rubber gasket;
the orientation rate of the carbon fibers along the thickness direction of the silicon rubber gasket is 50% or more than 50%;
when the orientation ratio of the carbon fibers in the thickness direction of the silicone rubber gasket is more than 50%, the mixing comprises the following steps:
premixing the heat-conducting filler and the silicon rubber to obtain a premix;
and (3) sequentially carrying out open milling and calendering on the premix and the short carbon fiber to obtain the mixture.
Preferably, the short carbon fiber comprises acrylonitrile-based short carbon fiber or pitch-based short carbon fiber;
the diameter of the short carbon fiber is 5-12 μm.
Preferably, before mixing, the method further comprises the step of oxidizing the short carbon fibers;
the temperature of the oxidation treatment is 450-550 ℃, and the time is 2-5 h.
Preferably, the particle size of the heat-conducting filler is 1-45 μm;
the heat-conducting filler is one or more of silver, copper, silver-coated copper, nickel, aluminum, magnesium oxide, boron nitride, aluminum nitride, silicon carbide, aluminum oxide, simple carbon substance and silicon oxide.
Preferably, the mass ratio of the silicone rubber, the short carbon fibers and the heat-conducting filler is 100: (50-150): (60 to 180).
Preferably, the silicone rubber is room temperature vulcanization type liquid silicone rubber or heat vulcanization type silicone rubber;
when the orientation rate of the carbon fibers along the thickness direction of the silicone rubber gasket is 50%, the silicone rubber is room temperature vulcanization type liquid silicone rubber;
and when the orientation rate of the carbon fibers along the thickness direction of the silicone rubber gasket is more than 50%, the silicone rubber is heat-vulcanized silicone rubber.
Preferably, the room temperature vulcanization type liquid silicone rubber is addition type liquid silicone rubber or condensation type liquid silicone rubber;
the addition type liquid silicone rubber comprises alpha, omega-divinyl polydimethylsiloxane, hydrogen-containing polysiloxane, ethynyl cyclohexanol and chloroplatinic acid-divinyl tetramethyl disiloxane complex;
the condensed type liquid silicone rubber comprises alpha, omega-dihydroxy polydimethylsiloxane, tetraethoxysilane, dibutyltin dilaurate and dimethyl silicone oil.
Preferably, the mass ratio of the alpha, omega-divinyl polydimethylsiloxane to the hydrogen-containing polysiloxane to the ethynylcyclohexanol to the chloroplatinic acid-divinyl tetramethyl disiloxane complex is (80-95): (2-6): (0-2): (0.05-1);
the mass ratio of the alpha, omega-dihydroxy polydimethylsiloxane, the ethyl orthosilicate, the dibutyltin dilaurate and the dimethyl silicone oil is (90-95): (2-5): (0.2-2): (0-5).
Preferably, the viscosity of the alpha, omega-divinyl polydimethylsiloxane is 1000 to 10000mPa & s;
the hydrogen content in the hydrogenous polysiloxane is 0.2-1.6 mol%;
the viscosity of the alpha, omega-dihydroxy polydimethylsiloxane is 1000-10000 mPas.
Preferably, the heat-curable silicone rubber includes methyl vinyl silicone rubber, silicone oil, and 2, 5-dimethyl-2, 5-di-t-butylperoxyhexane;
the mass ratio of the methyl vinyl silicone rubber, the silicone oil and the 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide is (88-99): (0-12) and (0.5-2).
Preferably, the number average molecular weight of the methyl vinyl silicone rubber is 200000 to 1000000, and the vinyl content in the methyl vinyl silicone rubber is 0.1 to 0.25mol%;
the silicone oil is methyl silicone oil or hydroxyl silicone oil; the viscosity of the silicone oil is 500 to 5000 mPas.
Preferably, the pressure vulcanization is room-temperature pressure vulcanization or heating pressure vulcanization;
the heating and pressurizing vulcanization comprises heating and pressurizing constant-pressure vulcanization or heating and pressurizing constant-volume vulcanization;
the heating and pressurizing constant volume vulcanization is single-stage heating and pressurizing constant volume vulcanization or multi-stage heating and pressurizing constant volume vulcanization.
Preferably, the heating and pressurizing multi-stage constant volume vulcanization is 2-5 stages of constant volume;
the volume of the last constant volume is 0.2-1.0% less than that of the previous constant volume.
Preferably, when the multistage constant volume of heating and pressurizing is 3 sections constant volumes, and when the orientation rate of carbon fiber along silicone rubber gasket thickness direction is 50%, the specific process of the multistage constant volume of heating and pressurizing includes:
1) The first stage of constant volume: the pressure of the first stage constant volume is 3-5 MPa, the temperature is raised from room temperature to 60-100 ℃, the temperature raising time is less than or equal to 30min, and the temperature is kept for 1-2 h;
2) A second stage of constant volume: the second stage has the constant volume pressure of 5-10 MPa, the temperature of 60-100 ℃ and the time of 1-2 h;
3) And (3) third stage constant volume: the third stage has the constant volume pressure of 10-20 MPa, the temperature of 60-100 ℃ and the time of 1-4 h.
Preferably, when the heating and pressurizing multi-section constant volume is 3 sections of constant volumes, and when the orientation rate of the carbon fiber along the thickness direction of the silicone rubber gasket is 60% -70%, the specific heating and pressurizing multi-section constant volume process comprises the following steps:
1) The first stage of constant volume: the first stage constant volume pressure is 5-10 MPa, the temperature is increased from room temperature to 140 ℃ within 30-60 min, and the temperature is continuously increased to 165-175 ℃ within 30-60 min;
2) And (3) second-stage constant volume: the second stage has the constant volume pressure of 5-15 MPa, the temperature of 165-175 ℃ and the time of 1-2 h;
3) Third stage constant volume: the third stage has constant volume pressure of 10-20 MPa, temperature of 165-175 deg.c and time of 1-2 hr.
Preferably, after the heating and pressurizing are completed in multiple sections and constant volume, the method further comprises heat treatment;
the temperature of the heat treatment is 180-200 ℃, and the time is 4-8 h.
The invention also provides a silicone rubber gasket prepared by the preparation method of the technical scheme, which comprises silicone rubber, carbon fibers and a heat-conducting filler which are filled in the silicone rubber,
the orientation rate of the carbon fibers along the thickness direction of the silicon rubber gasket is 50% or 60% -70%.
The invention also provides application of the carbon fiber through-thickness heat-conducting silicone rubber gasket in the technical scheme in the field of preparation of electronic products and power battery heat dissipation.
The invention provides a preparation method of a silicon rubber gasket, which comprises the following steps: mixing short carbon fibers, heat-conducting filler and silicone rubber to obtain a mixture; the length of the short carbon fiber is less than or equal to 6mm; pressurizing and vulcanizing the mixture in a mold to obtain a rubber solid block; cutting the long high plane of the rubber solid block to obtain the silicon rubber gasket; the orientation rate of the carbon fibers along the thickness direction of the silicon rubber gasket is 50% or more than 50%; when the orientation ratio of the carbon fibers in the thickness direction of the silicone rubber gasket is more than 50%, the mixing comprises the following steps: premixing the heat-conducting filler and the silicon rubber to obtain a premix; and (3) sequentially carrying out open milling and calendering on the premix and the short carbon fiber to obtain the mixture. The short carbon fibers are subjected to one-dimensional constraint orientation, namely the length extension direction of the carbon fibers is parallel to the direction perpendicular to the pressure direction only under the pressure condition in the pressure vulcanization, even on the basis of the one-dimensional constraint orientation, the two-dimensional constraint orientation is realized by open milling and calendering the premix and the short carbon fibers, the orientation rate of the carbon fibers is further improved, and finally the long high plane of the rubber solid block is cut to obtain the length extension direction of the short carbon fibers, which is consistent with the thickness direction of the silicon rubber gasket on a large probability, so that the heat conductivity coefficient of the silicon rubber gasket is improved.
Detailed Description
The invention provides a preparation method of a silicon rubber gasket, which comprises the following steps:
mixing short carbon fibers, heat-conducting filler and silicone rubber to obtain a mixture; the length of the short carbon fiber is less than or equal to 6mm;
pressurizing and vulcanizing the mixture in a mold to obtain a rubber solid block;
cutting the long high plane of the rubber solid block to obtain the silicon rubber gasket;
the orientation rate of the carbon fibers along the thickness direction of the silicon rubber gasket is 50% or more than 50%;
when the orientation ratio of the carbon fibers in the thickness direction of the silicone rubber gasket is more than 50%, the mixing comprises the following steps:
premixing the heat-conducting filler and the silicon rubber to obtain a premix;
and sequentially carrying out open milling and calendering on the premix and the short carbon fiber to obtain the mixture.
In the present invention, all the starting materials for the preparation are commercially available products known to those skilled in the art unless otherwise specified.
In the present invention, the orientation ratio refers to a cosine distribution value of an angle between a length extending direction and a thickness direction of the silicone rubber sheet, that is, a channel for conducting heat in the thickness direction of the silicone rubber sheet.
Mixing short carbon fibers, heat-conducting filler and silicone rubber to obtain a mixture; the length of the short carbon fiber is less than or equal to 6mm.
In the present invention, the diameter of the short carbon fiber is preferably 5 to 12 μm; the short carbon fibers preferably comprise acrylonitrile-based short carbon fibers or pitch-based short carbon fibers.
Before mixing, the invention preferably carries out oxidation treatment on the short carbon fiber; the temperature of the oxidation treatment is preferably 450-550 ℃, and more preferably 480-520 ℃; the time is preferably 2 to 5 hours, more preferably 3 to 4 hours.
In the present invention, the particle size of the thermally conductive filler is preferably 1 to 45 μm, more preferably 5 to 40 μm, and most preferably 6 to 10 μm.
In the invention, the heat conducting filler is preferably one or more of silver, copper, silver-coated copper, nickel, aluminum, magnesium oxide, boron nitride, aluminum nitride, silicon carbide, aluminum oxide, simple carbon and silicon oxide; the carbon simple substance is preferably one or more of artificial graphite, crystalline flake graphite and carbon black. When the heat-conducting filler is more than two of the specific choices, the proportion of the specific substances is not limited in any way, and the specific substances can be mixed according to any proportion.
In the invention, the heat-conducting filler has a synergistic heat-conducting effect, and simultaneously, carbon fibers are conveniently and uniformly dispersed in the silicone rubber, so that the stability of the heat-conducting property of the product is improved.
In the present invention, the silicone rubber is preferably a room temperature vulcanization type liquid silicone rubber or a heat vulcanization type silicone rubber; the room temperature vulcanization type liquid silicone rubber is preferably addition type liquid silicone rubber or condensation type liquid silicone rubber; the addition type liquid silicone rubber preferably comprises alpha, omega-divinyl polydimethylsiloxane, hydrogen-containing polysiloxane, ethynyl cyclohexanol and chloroplatinic acid-divinyl tetramethyl disiloxane complex; the mass ratio of the alpha, omega-divinyl dimethyl polysiloxane, hydrogen-containing polysiloxane, ethynyl cyclohexanol and chloroplatinic acid-divinyl tetramethyl disiloxane complex is preferably (80-95): (2-6): (0-2): (0.05-1), more preferably (84-92): (3-5): (0.6-1.8): (0.07 to 0.8), most preferably (87 to 90): (3.4-4.2): (1.0-1.5): (0.3-0.4). In the present invention, the viscosity of the α, ω -divinylpolydimethylsiloxane is preferably 1000 to 10000mPa · s, more preferably 3000 to 7000mPa · s. The hydrogen content in the hydrogenpolysiloxane is preferably 0.2 to 1.6mol%, more preferably 0.4 to 1.2mol%, and still more preferably 0.6 to 0.9mol%.
In the present invention, the α, ω -divinylpolydimethylsiloxane functions as a molecular structural unit of the addition-type liquid silicone rubber; the hydrogen-containing polysiloxane is a coupling agent and can be subjected to addition crosslinking with alpha, omega-divinyl polydimethylsiloxane; the ethynyl cyclohexanol can control the speed of addition crosslinking; the chloroplatinic acid-divinyl tetramethyl disiloxane complex is an addition crosslinking catalyst; the addition type liquid silicone rubber formed by the components has good flexibility and good mechanical property.
In the present invention, the condensed type liquid silicone rubber preferably includes α, ω -dihydroxy polydimethylsiloxane, ethyl orthosilicate, dibutyltin dilaurate, and dimethylsilicone oil; the mass ratio of the alpha, omega-dihydroxy polydimethylsiloxane, the ethyl orthosilicate, the dibutyltin dilaurate to the dimethyl silicone oil is preferably (90-95): (2-5): (0.2-2): (0 to 5), more preferably (91 to 94): (3-4): (0.5-1.2): (2-3). In the present invention, the viscosity of the α, ω -dihydroxypolydimethylsiloxane is preferably 1000 to 10000mPa · s, more preferably 3000 to 7000mPa · s.
In the present invention, the α, ω -dihydroxy polydimethylsiloxane functions as a molecular structural unit of the condensed type liquid silicone rubber; the tetraethoxysilane is a cross-linking agent and can perform condensation cross-linking reaction with alpha, omega-dihydroxy polydimethylsiloxane; the dibutyltin dilaurate is used as a catalyst for condensation crosslinking reaction; the dimethyl silicone oil is used for increasing the flexibility of the silicone rubber; the condensed type liquid silicone rubber formed by the components has good flexibility and better mechanical property.
In the present invention, the heat-curable silicone rubber preferably includes methyl vinyl silicone rubber, silicone oil, and 2, 5-dimethyl-2, 5-di-t-butylperoxyhexane; the mass ratio of the methyl vinyl silicone rubber, the silicone oil and the 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide is preferably (88-99): (0 to 12), (0.5 to 2), more preferably (90 to 93): (3-9): (0.9-1.3). In the present invention, the molecular weight of the methyl vinyl silicone rubber is preferably 200000 to 1000000, and the vinyl content in the methyl vinyl silicone rubber is preferably 0.1 to 0.25wt%, more preferably 0.15 to 0.20wt%; the silicone oil is preferably methyl silicone oil or hydroxyl silicone oil; the viscosity of the silicone oil is preferably 500 to 5000 mPas.
In the present invention, the methyl vinyl silicone rubber is a molecular structural unit of a high-temperature vulcanization type silicone rubber; the silicone oil is a plasticizer; the 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide is a coupling agent and can be crosslinked with methyl vinyl silicone rubber; the heat-curable silicone rubber composed of the above components has excellent mechanical properties and moderate flexibility.
In the present invention, the mass ratio of the silicone rubber, the short carbon fibers, and the thermally conductive filler is preferably 100: (50-150): (60 to 180), more preferably 100: (80-120): (100 to 130).
In the invention, when the orientation rate of the carbon fibers along the thickness direction of the silicone rubber sheet is 50%, the silicone rubber is preferably room temperature vulcanization type liquid silicone rubber; the mixing preferably comprises: and mixing the short carbon fiber, the heat-conducting filler and the silicone rubber to obtain the mixture. In the invention, the mixture is preferably added into a kneader according to the mixture ratio of the components in the silicone rubber and kneaded at room temperature for 30-60 min, and then the short carbon fiber and the heat-conducting filler are added and stirred for 60-120 min.
In the present invention, when the orientation ratio of the carbon fibers in the thickness direction of the silicone rubber sheet is 60% to 70%, the silicone rubber is preferably a heat-curable silicone rubber, and the mixing process includes:
premixing the heat-conducting filler and the silicon rubber to obtain a premix;
and (3) sequentially carrying out open milling and calendering on the premix and the short carbon fiber to obtain the mixture.
The heat-conducting filler and the silicon rubber are premixed to obtain the premix. In the present invention, the temperature of the premixing is preferably 30 to 90 ℃, more preferably 50 to 60 ℃; the time is preferably 30 to 120min, more preferably 50 to 100min. In the present invention, the premixing is preferably carried out in an open mill.
After the premix is obtained, the premix and the short carbon fibers are sequentially subjected to open milling and calendering to obtain the mixture. In the invention, the open milling temperature is preferably 20-80 ℃, and more preferably 30-60 ℃; the time is preferably 10 to 60min, more preferably 30 to 40min. In the present invention, the temperature of the boiling-off is preferably adjusted by cooling water. In the invention, the open mill is preferably carried out in an open mill, and the open mill preferably comprises the following processes: the initial gap of the open mill is preferably 2mm, after the premix and the short carbon fiber are added into the open mill, the open mill is opened at the open temperature for 3 to 7 minutes, and the gap of the open mill is gradually adjusted from 2mm to 1mm within 15 minutes.
In the present invention, the temperature and time of the opening and the gap between the opening rolls are controlled to further make the included angle between the longitudinal extension direction of 60wt% to 90wt% of the carbon fibers and the rotation direction of the opening rolls within the range of 0 to 30 °, thereby ensuring that the carbon fiber orientation in the longitudinal direction of the mold has a probability distribution of 60 to 70%. In the invention, the fibers can be deflected to the rotating direction by controlling the rotating direction of the open mill, so that the frictional resistance is reduced, and spontaneous deflection is formed.
In the present invention, the temperature of the rolling is preferably 20 to 40 ℃, more preferably 25 to 35 ℃; the transverse pressure of the calender is preferably from 200 to 700kN/m, more preferably from 500 to 600kN/m.
In the invention, the width of the mixture is preferably 100-1000 mm, and more preferably 300-500 mm; the thickness is preferably 0.2 to 2mm, more preferably 0.8 to 1.5mm.
After the mixture is obtained, the mixture is subjected to pressure vulcanization in a mold to obtain a rubber solid block. The pressure vulcanization comprises room-temperature pressure vulcanization or heating pressure vulcanization.
In the present invention, the temperature of the room temperature press vulcanization is preferably 10 to 35 ℃, and the pressure of the press vulcanization is preferably 3 to 25MPa.
In the invention, the heating and pressurizing vulcanization preferably comprises constant-pressure vulcanization of heating and pressurizing or constant-volume vulcanization of heating and pressurizing. The pressure of the constant pressure vulcanization by heating and pressurizing is preferably 3 to 25MPa, more preferably 5 to 20MPa, and most preferably 10 to 15MPa; the temperature is preferably 60 to 120 deg.C, more preferably 70 to 110 deg.C, most preferably 80 to 100 deg.C.
In the invention, the heating and pressurizing constant volume vulcanization preferably comprises heating and pressurizing single-stage constant volume vulcanization or heating and pressurizing multi-stage constant volume vulcanization.
In the invention, the heating and pressurizing single-stage constant volume vulcanization is preferably carried out under the heating and pressurizing conditions, and the volume is not adjusted after the solvent requirement is met at one time. In the present invention, the conditions of the single-stage constant volume vulcanization by heating and pressurizing are preferably as follows: the pressure of constant volume is 3-15 MPa, the temperature is increased from room temperature to 80-100 ℃, the time of temperature increase is less than or equal to 60min, and the time of temperature maintenance is 2-4 h.
In the invention, the heating and pressurizing multi-stage constant volume vulcanization preferably comprises 2-5 stages of constant volume, and more preferably 3 stages of constant volume. In the invention, the volume of the latter constant volume in the multi-stage constant volume vulcanization by heating and pressurizing is preferably 0.2-1.0% less than that of the former constant volume.
In the invention, when the heating and pressurizing multi-stage constant volume is 3 stages of constant volumes, and when the orientation rate of the carbon fiber along the thickness direction of the silicone rubber sheet is 50%, the specific heating and pressurizing multi-stage constant volume process preferably comprises the following steps: 1) The first stage of constant volume: the pressure of the first stage constant volume is 3-5 MPa, the temperature is raised from room temperature to 60-100 ℃, the temperature raising time is less than or equal to 30min, and the temperature is kept for 1-2 h; 2) And (3) second-stage constant volume: the second stage has the constant volume pressure of 5-10 MPa, the temperature of 60-100 ℃ and the time of 1-2 h; 3) And (3) third stage constant volume: the third stage has the constant volume pressure of 10-20 MPa, the temperature of 60-100 ℃ and the time of 1-4 h. More preferably, the method comprises the following steps: 1) A first stage of constant volume: the pressure of the first stage constant volume is 3.5-4.5 MPa, the temperature is raised to 70-90 ℃ from room temperature, the temperature raising time is 30min, and the temperature is kept for 1.2-1.6 h; 2) And (3) second-stage constant volume: the second stage has the constant volume pressure of 6-8 MPa, the temperature of 80-90 ℃ and the time of 1.4-1.7 h; 3) Third stage constant volume: the third stage has the constant volume pressure of 13-15 MPa, the temperature of 70-80 ℃ and the time of 2-3 h.
In the invention, when the heating and pressurizing multi-stage constant volume is 3 stages of constant volumes, and when the orientation rate of the carbon fibers along the thickness direction of the silicone rubber sheet is more than 50%, the specific heating and pressurizing multi-stage constant volume process preferably comprises the following steps: 1) The first stage of constant volume: the first stage constant volume pressure is 5-10 MPa, the temperature is increased from room temperature to 140 ℃ within 30-60 min, and the temperature is continuously increased to 165-175 ℃ within 30-60 min; 2) A second stage of constant volume: the second stage has the constant volume pressure of 5-15 MPa, the temperature of 165-175 ℃ and the time of 1-2 h; 3) And (3) third stage constant volume: the third stage has the constant volume pressure of 10-20 MPa, the temperature of 165-175 ℃ and the time of 1-2 h; more preferably, it comprises: 1) The first stage of constant volume: the first stage constant volume pressure is 7-8 MPa, the temperature is raised to 140 ℃ from room temperature within 40-50 min, and the temperature is continuously raised to 168-172 ℃ within 40-50 min; 2) A second stage of constant volume: the second stage constant volume pressure is 9-13 MPa, the temperature is 168-172 ℃, and the time is 1.3-1.7 h; 3) And (3) third stage constant volume: the third stage has the constant volume pressure of 13-16 MPa, the temperature of 168-172 ℃ and the time of 1.4-1.6 h.
After the pressure vulcanization is completed, the invention also preferably comprises pressure relief, and the pressure relief process is not limited in any way by the invention and can be carried out by adopting a process well known to those skilled in the art.
After the pressure relief is completed, the method also preferably comprises post-treatment, wherein the post-treatment temperature is preferably 200 ℃, and the time is preferably 6 hours.
In the present invention, the length of the solid rubber block is preferably 100 to 1000mm, the width is preferably 100 to 600mm, and the height is preferably 25 to 120mm.
After the rubber solid block is obtained, the long high plane of the rubber solid block is cut to obtain the silicon rubber gasket.
In the invention, the cutting equipment used for cutting is preferably a belt saw blade machine, a disc saw blade machine, a guillotine shear or a diamond wire cutting machine.
In the present invention, the cutting is preferably performed on a long high plane of the solid block of silicone rubber. The thickness of the heat-conducting silicon rubber gasket is preferably 0.5-5 mm.
The invention also provides a silicone rubber gasket prepared by the preparation method in the technical scheme, which comprises silicone rubber, carbon fibers and a heat-conducting filler, wherein the carbon fibers and the heat-conducting filler are filled in the silicone rubber;
the mass percentage of the short carbon fibers with the length extension direction consistent with the thickness direction of the silicone rubber gasket is preferably greater than or equal to 50%, more preferably 50-80%, and most preferably 50% or 60-70%.
In the present invention, the mass ratio of the silicone rubber, the carbon fiber and the thermally conductive filler is preferably 100: (50-150): (60 to 180), more preferably 100: (80-120): (100 to 130).
The invention also provides application of the carbon fiber through-thickness heat-conducting silicone rubber gasket in the technical scheme in the field of preparation of electronic products and heat dissipation of power batteries. The method of the present invention is not particularly limited, and the method may be performed by a method known to those skilled in the art. In the invention, the electronic product is preferably a smart phone, a unmanned aerial vehicle or an industrial intelligent device.
The heat conductive silicone rubber gasket, the preparation method and the application thereof provided by the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
Example 1
962g of alpha, omega-divinyl polydimethylsiloxane (with the viscosity of 5000 mPas), 30g of hydrogen-containing polysiloxane (with the hydrogen content of 0.3 mol%), 5g of ethynylcyclohexanol and 3g of chloroplatinic acid-divinyl tetramethyldisiloxane complex are added into a kneader and stirred for 30min, 750g of asphalt-based carbon fiber (with the thermal conductivity coefficient of 500W/m.K, the length of 0.1-3 mm and the diameter of 0.007-0.01 mm) and 750g of alumina (with the particle size of 2000 meshes) are added and stirred for 60min, and a mixture is obtained;
adding 2800g of the mixture into a mold, wherein the length, the width and the height of an inner cavity of the mold are respectively 20cm, 12cm and 16cm, heating and pressurizing for multi-section constant volume, controlling the thickness of a material in the mold to be 62.0mm under the conditions of room temperature and 3MPa, heating to 80 ℃ at 45min, maintaining the temperature at 80 ℃ for 60min, controlling the thickness of the material to be 61mm under the conditions of 80 ℃ and 8MPa, maintaining for 1 hour, controlling the thickness of the material to be 60mm under the conditions of 80 ℃ and 12MPa, maintaining for 2 hours, releasing the pressure, demolding, and cutting the long high plane of the silicon rubber solid block by using a diamond wire cutting machine to obtain a silicon rubber gasket with the thickness of 0.5, 1.0, 3.0, 4.0 or 5.0 mm.
Example 2
Carrying out oxidation treatment on acrylonitrile-based carbon fibers (with the thermal conductivity coefficient of 50W/m.K, the length of 0.1-0.5 mm and the diameter of 0.007-0.01 mm) in a muffle furnace, wherein the temperature of the oxidation treatment is 500 ℃ and the time is 4 hours;
980g of alpha, omega-dihydroxy polydimethylsiloxane (with the viscosity of 3000mPa & s), 15g of ethyl orthosilicate and 5g of dibutyltin dilaurate are added into a kneader and stirred for 30min, 1000g of acrylonitrile-based carbon fiber and 500g of alumina (the particle size is 2000 meshes) are added, and stirring is continued for 60min to obtain a mixture;
adding 2750g of the mixture into a mold, wherein the length, the width and the height of an inner cavity of the mold are respectively 20cm, 12cm and 16cm, heating and pressurizing for multi-section constant volume, controlling the thickness of a material in the mold to be 62.0mm under the conditions of room temperature and 3MPa, heating to 80 ℃ at 45min, maintaining the temperature at 80 ℃ for 60min, controlling the thickness of the material to be 61mm under the conditions of 80 ℃ and 8MPa, maintaining for 1 hour, controlling the thickness of the material to be 60mm under the conditions of 80 ℃ and 12MPa, maintaining for 2 hours, releasing pressure and demolding, and cutting the long high plane of the silicon rubber solid block by using a diamond wire cutting machine to obtain a silicon rubber gasket with the thickness of 0.5, 1.0, 3.0, 4.0 or 5.0 mm.
Example 3
910g of methyl vinyl silicone rubber (having a vinyl content of 0.15% by weight and a molecular weight of 600000), 15g of 2, 5-dimethyl-2, 5-di-t-butylperoxyhexane (DBPMH), 75g of hydroxy silicone oil and 750g of alumina (2000 mesh) were charged into a kneader, and kneaded at a temperature of 85 ℃ for 60 minutes to obtain a premix;
adding 750g of the premix and 250g of asphalt-based carbon fibers (with the thermal conductivity coefficient of 500W/m.K, the length of 0.1-3 mm and the diameter of 0.007-0.01 mm) into a milling machine, milling at the temperature of 60 ℃, adjusting the milling temperature through cooling water, gradually adjusting the gap of the milling machine from 2mm to 1mm within 15 minutes, stopping milling when the included angle between the length extension direction of 75wt% of the carbon fibers and the rotation direction of the milling machine is within the range of 0-30 ℃, adding the obtained mixed material into a calender, and calendering at the temperature of 20 ℃ to obtain a sheet mixed material with the width of 400mm and the thickness of 1 mm;
cutting the sheet mixture into small sheets with the length of 20cm and the width of 12cm, stacking the small sheets into 62 layers, putting the small sheets into a mold, controlling the thickness of the materials in the mold to be 61.0mm under the conditions of room temperature and 8MPa, heating to 140 ℃ after 40min, heating to 170 ℃ for 30min, and maintaining for 30min, wherein the length, the width and the height of an inner cavity of the mold are respectively 20cm, 12cm and 14cm, and heating and pressurizing for multiple sections and constant volume are carried out; controlling the thickness of the material to be 60.5mm under the conditions of 170 ℃ and 10MPa, and maintaining for 1 hour; controlling the thickness of the material to be 60mm under the conditions of 170 ℃ and 15MPa, maintaining for 2 hours, decompressing, demolding and drying in an oven at 190 ℃ for 6 hours; and cutting the long high plane of the silicon rubber solid block by using a diamond wire cutting machine to obtain the silicon rubber gasket with the thickness of 0.5, 1.0, 3.0, 4.0 or 5.0 mm.
Example 4
Carrying out oxidation treatment on acrylonitrile-based carbon fibers (with the thermal conductivity coefficient of 50W/m.K, the length of 0.1-0.5 mm and the diameter of 0.007-0.01 mm) in a muffle furnace, wherein the temperature of the oxidation treatment is 500 ℃, and the time is 4h;
910g of methyl vinyl silicone rubber (having a vinyl content of 0.15% by weight and a molecular weight of 600000), 15g of 2, 5-dimethyl-2, 5-di-t-butylperoxyhexane (DBPMH), 75g of hydroxy silicone oil and 750g of alumina (2000 mesh) were charged into a kneader and kneaded at a temperature of 85 ℃ for 60 minutes to obtain a premix;
adding 750g of the premix and 250g of the acrylonitrile-based carbon fiber into a mill, milling at 60 ℃, adjusting the milling temperature through cooling water, gradually adjusting the gap of the mill from 2mm to 1mm within 15 minutes, stopping milling after the included angle between the length extension direction of 75wt% of the carbon fiber and the rotation direction of the mill is within the range of 0-30 ℃, adding the obtained mixed material into a calender, and calendering at 20 ℃ to form a sheet mixed material with the width of 400mm and the thickness of 1 mm;
cutting the sheet mixture into small sheets with the length of 20cm and the width of 12cm, stacking the small sheets into 62 layers, putting the small sheets into a mold, controlling the thickness of the materials in the mold to be 61.0mm under the conditions of room temperature and 8MPa, heating to 140 ℃ after 40min, heating to 170 ℃ for 30min, and maintaining for 30min, wherein the length, the width and the height of an inner cavity of the mold are respectively 20cm, 12cm and 14cm, and heating and pressurizing for multiple sections and constant volume are carried out; controlling the thickness of the material to be 60.5mm under the conditions of 170 ℃ and 10MPa, and maintaining for 1 hour; controlling the thickness of the material to be 60mm under the conditions of 170 ℃ and 15MPa, maintaining for 2 hours, releasing pressure, demolding, and drying in an oven at 190 ℃ for 6 hours; and cutting the long high plane of the silicon rubber solid block by using a diamond wire cutting machine to obtain the silicon rubber gasket with the thickness of 0.5, 1.0, 3.0, 4.0 or 5.0 mm.
Example 5
Carrying out oxidation treatment on acrylonitrile-based carbon fibers (with the thermal conductivity coefficient of 50W/m.K, the length of 0.1-0.5 mm and the diameter of 0.007-0.01 mm) in a muffle furnace, wherein the temperature of the oxidation treatment is 500 ℃, and the time is 4h;
980g of alpha, omega-dihydroxy polydimethylsiloxane (with the viscosity of 3000mPa & s), 15g of tetraethoxysilane and 5g of dibutyltin dilaurate are added into a kneader and stirred for 30min, 1000g of acrylonitrile-based carbon fiber and 500g of alumina (with the particle size of 2000 meshes) are added, and the mixture is continuously stirred for 60min to obtain a mixture;
adding 2750g of the mixture into a mold, wherein the length, the width and the height of an inner cavity of the mold are 20cm, 12cm and 16cm respectively, and heating, pressurizing and constant-pressure vulcanization is carried out, wherein the heating, pressurizing and constant-pressure vulcanization is carried out by heating from room temperature to 80 ℃ and then maintaining for 80min; maintaining for 3h at 80 ℃ and 5MPa, releasing pressure and demolding, and cutting the long high plane of the silicon rubber solid block by using a diamond wire cutting machine to obtain a silicon rubber gasket with the thickness of 0.5, 1.0, 3.0, 4.0 or 5.0 mm.
Test example
The silicone rubber pads prepared in examples 1 to 5 were subjected to a thermal conductivity test using an FM3615 thermal conductivity tester, and the test results are shown in table 1:
TABLE 1 thermal conductivity of silicone rubber gaskets prepared in examples 1 to 5
| Test number | Coefficient of thermal conductivity (W/m. K) |
| Example 1 | 7.5 |
| Example 2 | 2.1 |
| Example 3 | 9.8 |
| Example 4 | 2.8 |
| Example 5 | 1.8 |
As can be seen from table 1, the silicone rubber gaskets of the present invention all have high thermal conductivity, and as can be seen from comparing example 1 with example 3, and example 2 with example 4, the thermal conductivity can be improved by 30% in the two-dimensional constraint method and the one-dimensional constraint method, but the one-dimensional constraint method has a simpler preparation process and a lower preparation cost; compared with the embodiment 2 and the embodiment 5, the heating and pressurizing three-section constant volume vulcanization process is obviously superior to the heating and pressurizing constant pressure vulcanization process.
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 amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.
Claims (18)
1. The preparation method of the silicone rubber gasket is characterized by comprising the following steps:
mixing short carbon fibers, heat-conducting filler and silicone rubber to obtain a mixture; the length of the short carbon fiber is less than or equal to 6mm;
pressurizing and vulcanizing the mixture in a mold to obtain a rubber solid block;
cutting the long high plane of the rubber solid block to obtain the silicon rubber gasket;
the orientation rate of the carbon fibers along the thickness direction of the silicon rubber gasket is 50% or more than 50%;
when the orientation ratio of the carbon fibers in the thickness direction of the silicone rubber gasket is greater than 50%, the mixing comprises the steps of:
premixing the heat-conducting filler and the silicon rubber to obtain a premix;
and (3) sequentially carrying out open milling and calendering on the premix and the short carbon fiber to obtain the mixture.
2. The method of claim 1, wherein the short carbon fiber comprises an acrylonitrile-based short carbon fiber or a pitch-based short carbon fiber;
the diameter of the short carbon fiber is 5-12 μm.
3. The method according to claim 1 or 2, further comprising, before the mixing, subjecting the short carbon fibers to an oxidation treatment;
the temperature of the oxidation treatment is 450-550 ℃, and the time is 2-5 h.
4. The method according to claim 1, wherein the thermally conductive filler has a particle size of 1 to 45 μm;
the heat-conducting filler is one or more of silver, copper, silver-coated copper, nickel, aluminum, magnesium oxide, boron nitride, aluminum nitride, silicon carbide, aluminum oxide, simple carbon substance and silicon oxide.
5. The method according to claim 1, wherein the mass ratio of the silicone rubber, the short carbon fiber, and the thermally conductive filler is 100: (50-150): (60-180).
6. The production method according to claim 1, wherein the silicone rubber is a room-temperature vulcanization type liquid silicone rubber or a heat vulcanization type silicone rubber;
when the orientation rate of the carbon fibers along the thickness direction of the silicone rubber gasket is 50%, the silicone rubber is room temperature vulcanization type liquid silicone rubber;
when the orientation rate of the carbon fibers along the thickness direction of the silicone rubber gasket is greater than 50%, the silicone rubber is heat-vulcanized silicone rubber.
7. The production method according to claim 6, wherein the room-temperature-vulcanizing type liquid silicone rubber is an addition type liquid silicone rubber or a condensation type liquid silicone rubber;
the addition type liquid silicone rubber comprises alpha, omega-divinyl polydimethylsiloxane, hydrogen-containing polysiloxane, ethynyl cyclohexanol and chloroplatinic acid-divinyl tetramethyl disiloxane complex;
the condensed type liquid silicone rubber comprises alpha, omega-dihydroxy polydimethylsiloxane, ethyl orthosilicate, dibutyltin dilaurate and simethicone.
8. The preparation method according to claim 7, wherein the α, ω -divinylpolydimethylsiloxane, the hydrogenpolysiloxane, the ethynylcyclohexanol, and the chloroplatinic acid-divinyltetramethyldisiloxane complex are present in a mass ratio (80 to 95): (2-6): (0-2): (0.05-1);
the mass ratio of the alpha, omega-dihydroxy polydimethylsiloxane, the ethyl orthosilicate, the dibutyltin dilaurate to the dimethyl silicone oil is (90-95): (2-5): (0.2-2): (0-5).
9. The method according to claim 7 or 8, wherein the α, ω -divinylpolydimethylsiloxane has a viscosity of 1000 to 10000 mPa-s;
the hydrogen content in the hydrogenpolysiloxane is 0.2-1.6 mol%;
the viscosity of the alpha, omega-dihydroxy polydimethylsiloxane is 1000-10000 mPas.
10. The production method according to claim 6, wherein the heat-vulcanizable silicone rubber comprises methyl vinyl silicone rubber, silicone oil and 2, 5-dimethyl-2, 5-di-t-butylperoxyhexane;
the mass ratio of the methyl vinyl silicone rubber, the silicone oil and the 2, 5-dimethyl-2, 5-di-tert-butyl hexane peroxide is (88-99): (0-12) and (0.5-2).
11. The method of claim 10, wherein the number average molecular weight of the methyl vinyl silicone rubber is 200000 to 1000000, and the vinyl content of the methyl vinyl silicone rubber is 0.1 to 0.25mol%;
the silicone oil is methyl silicone oil or hydroxyl silicone oil; the viscosity of the silicone oil is 500 to 5000 mPas.
12. The method of claim 1, wherein the press vulcanization is room temperature press vulcanization or elevated temperature press vulcanization;
the heating and pressurizing vulcanization comprises heating and pressurizing constant-pressure vulcanization or heating and pressurizing constant-volume vulcanization;
the heating and pressurizing constant volume vulcanization is single-stage heating and pressurizing constant volume vulcanization or multi-stage heating and pressurizing constant volume vulcanization.
13. The preparation method according to claim 12, wherein the heating and pressurizing multi-stage constant volume vulcanization is carried out to 2 to 5 stages of constant volumes;
the volume of the latter constant volume is 0.2-1.0% less than that of the former constant volume.
14. The preparation method according to claim 11, wherein when the multi-stage constant volume by heating and pressurizing is 3 stages of constant volume, and when the orientation rate of the carbon fibers along the thickness direction of the silicone rubber sheet is 50%, the specific process of multi-stage constant volume by heating and pressurizing comprises the following steps:
1) The first stage of constant volume: the pressure of the first stage constant volume is 3-5 MPa, the temperature is raised from room temperature to 60-100 ℃, the temperature raising time is less than or equal to 30min, and the temperature is kept for 1-2 h;
2) A second stage of constant volume: the second stage has the constant volume pressure of 5-10 MPa, the temperature of 60-100 ℃ and the time of 1-2 h;
3) And (3) third stage constant volume: the third stage has the constant volume pressure of 10-20 MPa, the temperature of 60-100 ℃ and the time of 1-4 h.
15. The preparation method according to claim 11, wherein when the multi-stage constant volume by heating and pressurizing is 3 stages of constant volume, and when the orientation rate of the carbon fibers in the thickness direction of the silicone rubber sheet is 60% to 70%, the specific process of the multi-stage constant volume by heating and pressurizing comprises the following steps:
1) The first stage of constant volume: the first stage constant volume pressure is 5-10 MPa, the temperature is increased from room temperature to 140 ℃ within 30-60 min, and the temperature is continuously increased to 165-175 ℃ within 30-60 min;
2) And (3) second-stage constant volume: the second stage has the constant volume pressure of 5-15 MPa, the temperature of 165-175 ℃ and the time of 1-2 h;
3) Third stage constant volume: the third stage has the constant volume pressure of 10-20 MPa, the temperature of 165-175 ℃ and the time of 1-2 h.
16. The preparation method of claim 15, further comprising a heat treatment after the completion of the warming and pressurizing of the multi-stage constant volume;
the temperature of the heat treatment is 180-200 ℃, and the time is 4-8 h.
17. The silicone rubber gasket prepared by the preparation method of any one of claims 1 to 16, comprising a silicone rubber and carbon fibers and a heat conductive filler filled in the silicone rubber,
the orientation rate of the carbon fibers in the thickness direction of the silicone rubber gasket is 50% or >50%.
18. Use of the carbon fiber through-thickness thermally conductive silicone rubber gasket of claim 17 in the manufacture of electronic products and power cell heat dissipation applications.
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