Spherical silver powder preparation device and preparation method for photovoltaic front conductive silver paste

Abstract

The invention relates to the technical field of conductive material production, in particular to a spherical silver powder preparation device and method for photovoltaic front conductive silver paste.The preparation device comprises a bearing seat and a roller, supports are fixedly arranged in the middles of the two ends of the top end face of the bearing seat, and the roller is arranged between the two supports; a ball milling mechanism and an auxiliary ball milling mechanism are arranged between the bearing seat and the roller, the roller is composed of a left half part and a right half part which are of a circular truncated cone structure, and a discharging mechanism and a dust-free collecting mechanism are arranged on the outer side of the right half part and the outer side of the left half part of the roller respectively; the ball milling mechanism comprises an inner driving mechanism penetrating through the axial center line of the roller, an outer driving mechanism arranged on the outer side of the left half portion of the roller and a screening type ball milling assembly located in the roller, rapid and sufficient ball milling can be achieved, the ground spherical silver powder is collected in a dust-free mode, meanwhile, the whole machine is designed in a modular mode, and therefore the whole machine is more compact in structure, and the production cost is reduced. And later operation and maintenance are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of conductive material production, and in particular to a device and a method for preparing spherical silver powder of photovoltaic front conductive silver paste. Background Art

[0002] With the increasing depletion of non-renewable energy sources such as oil and coal, the development of renewable energy has attracted more and more attention. As the most abundant and main clean energy, solar energy has attracted more and more attention. How to improve the efficiency of photovoltaic power generation has become the focus of research. Photovoltaic silver paste has become the main raw material for printed solar panels due to its excellent rheological and conductive properties. Silver powder, as the main conductive phase in solar cell silver paste, accounts for about 90% of the mass ratio in the silver paste, which plays a decisive role in the rheological and conductive properties of the silver paste. With the increasing market requirements for the photoelectric conversion efficiency of solar cells, the preparation of silver powder with excellent sintering activity and printing performance has become the focus of attention.

[0003] At present, the industrial production of two-dimensional silver powder is mainly obtained by mechanical ball milling of spherical silver powder or quasi-spherical silver powder. The preparation methods of ball milling raw materials (spherical silver powder and quasi-spherical silver powder) include physical methods (physical vapor precipitation) and chemical methods (liquid phase chemical reduction, thermal decomposition of precursors). Among them, the liquid phase reduction method has the characteristics of low investment, low cost, and easy large-scale production, and is widely used as the main silver powder production method. In the preparation process of two-dimensional silver powder, low specific surface area and high dispersibility ball milling raw materials are required as ball milling precursors. Since the characteristics of the precursor silver powder have a great influence on the grinding of two-dimensional silver powder, the reduction of the precursor silver powder should be mainly controlled in the preparation process of two-dimensional silver powder.

[0004] The prior art discloses a Chinese patent with a publication number of CN 113600825 B (IPC classification number of H01B1 / 16): a micron-sized spherical silver powder and a preparation method thereof, and discloses the following steps: S1, preparing a silver nitrate solution, adding trisodium citrate to the silver nitrate solution and mixing it to obtain a precursor solution; S2, preparing an ascorbic acid solution, adding gum arabic, polyvinyl pyrrolidone and polyethylene glycol to the ascorbic acid solution to obtain a reducing agent solution; S3, at 20-60°C and in the dark, quickly pouring the precursor solution into the reducing agent solution, and continuously stirring until the reaction is completed, so as to obtain the micron-sized spherical silver powder. The silver powder has a high sphericity and has no irregular shapes such as flakes and dendrites.

[0005] The prior art also discloses a Chinese patent with publication number CN 110369050 B (IPC classification number B02C17): a fully sealed drum ball mill, and discloses a frame, a horizontal drum is arranged on the frame, an inner lining plate is arranged on the inner wall of the drum, the inner lining plate includes a side plate and an end plate, the side plate is composed of a plurality of first ceramic single plates assembled together, the cross section of the first ceramic single plate is arc-shaped, the inner wall of the first ceramic single plate is integrally formed with an inward protrusion, the end face of the protrusion is spherical, the outer wall of the first ceramic single plate is integrally formed with a groove, the bottom surface of the groove is spherical, a bolt is bonded and fixed in the groove, the screw of the bolt extends outward to the outer sleeve of the drum and is provided with a fastening nut, an annular copper gasket is arranged between the edge of the outer wall of the first ceramic single plate and the drum, a first polyurethane adhesive is arranged between the first ceramic plate inside the copper gasket and the drum, the structure is simple, the service life is long, the working stability is high, and the noise can be effectively reduced.

[0006] However, the prior art still has certain defects. For example, in the technical solution with publication number CN 113600825 B, the "ascorbic acid-gum arabic silver nitrate" system is used to prepare the precursor silver powder. Although it is a simple liquid phase reduction, the ascorbic acid is relatively expensive, and the cost of mass production is still high.

[0007] For example, the technical solution with publication number CN 110369050 B is not convenient for quick replacement of local accessories during use, and the ball milling process only relies on changing the running trajectory of the abrasive balls to collide with the raw materials, the collision frequency and collision force are limited, and the ball milling efficiency is low. Summary of the invention

[0008] The object of the present invention is to provide a device and method for preparing spherical silver powder for photovoltaic front conductive silver paste, so as to solve the problems raised in the above background technology.

[0009] The purpose of the present invention can be achieved through the following technical solutions:

[0010] A device for preparing spherical silver powder for photovoltaic front conductive silver paste, comprising a bearing seat and a roller, wherein brackets are fixedly provided at the middle of both ends of the top surface of the bearing seat, and the roller is arranged between the two brackets, a ball milling mechanism and an auxiliary ball milling mechanism are arranged between the bearing seat and the roller, and the roller is composed of a left half and a right half arranged in a truncated cone structure, and a feeding mechanism and a dust-free collection mechanism are respectively arranged on the outer side of the right half and the outer side of the left half of the roller, and a feeding slot and a discharging slot are respectively opened at the positions of the feeding mechanism and the dust-free collection mechanism on the surface of the roller;

[0011] The ball milling mechanism comprises an inner driving mechanism penetrating the axial center line of the drum, an outer driving mechanism arranged on the outside of the left half of the drum, and a screening ball milling assembly located inside the drum.

[0012] In a preferred embodiment, the internal driving mechanism includes a driving motor 1 fixedly mounted on the opposite side of two brackets, the output shaft ends of the two driving motors 1 are connected to a core shaft, and the opposite ends of the two core shafts are respectively provided with a cross block and a cross groove, the cross block is movably inserted into the cross groove, and the outer circumference of one end of the two core shafts located on the roller is movably sleeved with a positioning frame, and the bottom end surface of the positioning frame is movably fitted with the upper end surface of the bearing seat.

[0013] In a preferred embodiment, the external drive mechanism includes a bracket fixed on the top of the bearing seat and a gear ring fixedly mounted on the outside of the left half of the drum, a drive motor 2 is fixedly mounted on the top of the bracket, and a gear meshing with the gear ring is fixedly provided on the end of the output shaft of the drive motor 2.

[0014] In a preferred embodiment, the screening ball mill assembly includes a screen sandwiched between the right half and the left half of the drum, a plurality of groups of guide strips evenly distributed in an annular shape are arranged on the inner side of the right half of the drum, and a plurality of groups of elastic arc plates evenly distributed in an annular shape are arranged on the circumferential side surface of the core shaft inside the right half of the drum, the guide strips are arranged in a triangular prism structure, and the guide strips are arranged in a narrowing shape from the large diameter end to the small diameter end of the right half of the drum;

[0015] A plurality of elastic rods evenly distributed in an annular shape are fixedly provided at the inner edge of the small diameter end of the left half of the drum, and a rigid rod is fixedly provided at the outer peripheral edge of the core shaft inside the left half of the drum, and an arc-shaped top block of a semi-cylindrical pile structure and a striking block of a triangular prism structure are respectively provided on the side opposite to the elastic rod;

[0016] The large inner circumference of the right half of the drum and the outer circumference of the core shaft inside the right half of the drum are both provided with a plurality of T-shaped limiting grooves, and the guide lining strip and the elastic arc plate are both fixedly provided with a T-shaped limiting strip in the middle of one side facing the limiting groove at the position, and the limiting strip is slidably connected to the inside of the limiting groove at the corresponding position.

[0017] In a preferred embodiment, the auxiliary ball milling mechanism includes a bottom plate arranged at the bottom of the bearing seat and a through groove vertically penetrating the two ends of the top surface of the bearing seat, a limiting guide plate is fixedly provided at the position of the top of the bottom plate corresponding to the through groove, four springs are fixedly connected between the four corners of the opposite sides of the bottom plate and the bearing seat, and cams are fixedly sleeved at the positions of the limiting guide plates corresponding to the outer circumferences of the two core shafts.

[0018] In a preferred embodiment, the unloading mechanism includes a hopper fixedly installed at a position corresponding to the feed slot on the right half of the drum, a running slot is opened through the middle of the bottom of the hopper, a shield plate that fits the outer surface of the drum is movably passed through the inside of the running slot, and a leakage slot as large as the feed slot is opened at one end of the shield plate, two vertical plates are fixedly provided at both ends of the shield plate, an arc rod is fixedly provided on one side of the hopper, and the end of the arc rod away from the hopper movably passes through the vertical plate two at the position, a spring three is movably sleeved on the outer peripheral surface of the arc rod, and the two ends of the spring three are respectively fixedly connected to the hopper and the vertical plate two at the corresponding position.

[0019] In a preferred embodiment, the dust-free collection mechanism includes a collar movably sleeved on the outer circumference of the left half of the drum corresponding to the position of the discharge slot, the outer circumference of the collar is fixedly provided with a positioning bracket connected to the discharge slot, one side of the positioning bracket is penetrated by a channel groove, and a receiving box is movably inserted in the channel groove;

[0020] A sealing plate is movably provided at the top of the inner cavity of the channel groove, guide strips are fixedly provided at the middle of both sides of the sealing plate, guide grooves are provided at both sides of the inner cavity of the channel groove, and the guide strips are slidably connected to the corresponding guide grooves, a vertical plate 1 is fixedly provided at one end of the top surface of the sealing plate, a guide rod movably penetrating the vertical plate 1 is fixedly provided at the middle of the side of the positioning bracket frame facing the vertical plate 1, a spring 1 is movably sleeved on the outer circumference of the guide rod, and both ends of the spring 1 are respectively fixedly connected to the vertical plate 1 and the positioning bracket frame;

[0021] The collar corresponds to the end of the longitudinal depth of the cross groove, and a limiting component is also provided on the positioning bracket, the limiting component includes two groups of round rods that movably penetrate the two sides of the positioning bracket, and both ends of the two groups of round rods are respectively fixed with a limit plate and a stop bar;

[0022] A cover plate is movably fitted on the top of the material receiving box, and grooves are provided on both sides of the top surface of the material receiving box, straight rods are fixedly provided inside the two grooves, and sliders are fixedly provided on both sides of the end surface of the cover plate, which are movably sleeved on the outside of the straight rods at the corresponding positions, and two springs are movably sleeved on the outer peripheral surfaces of the two straight rods, and a stop plate is fixedly provided on the end of the top surface of the cover plate corresponding to the slider.

[0023] In a preferred embodiment, the two brackets each include a support plate fixed on the top surface of the bearing seat and a buckle plate hinged at the edge of one end of the top of the support plate, and semicircular grooves are provided in the middle of the opposite sides of the support plate and the buckle plate in a buckled state, and a clamping block is fixed in the middle of the opposite ends of the two core shafts, and a clamping groove adapted to the clamping block at the position is provided at the end of the output shaft of the two driving motors, and the clamping block and the clamping slot in the engaged state are arranged inside the circular groove formed by the two semicircular grooves at the position.

[0024] In a preferred embodiment, positioning blocks are fixedly provided at the center positions of the bottom end surfaces of the positioning support frame and the bottom end surfaces of the two positioning frames, positioning slots are provided at the positions corresponding to each positioning block on the top surface of the bearing seat, and the positioning blocks are movably inserted into the positioning slots at the corresponding positions.

[0025] The present invention also provides a method for preparing spherical silver powder of photovoltaic front conductive silver paste, which specifically comprises the following steps:

[0026] S1: silver powder reduction: prepare 300L of 100g / L silver nitrate solution in a reactor using pure water, add 2kg of polyvinyl pyrrolidone-K30, heat to 30°C, add the first portion of 30% sodium hydroxide solution, adjust the pH of the silver nitrate solution to 5.0-6.0, add 10L of 35% formaldehyde solution, stir at 100r / min, wait for the reduction reaction to proceed for 30min until the reaction is balanced, add the remaining sodium hydroxide solution step by step to promote the reaction, and age for 5min to obtain reduced silver powder for standby use;

[0027] S2: Reduced silver powder detection: After washing and solid-liquid separation, the silver powder obtained in S1 is dispersed with 0.7% stearic acid by weight of the silver powder, plated, and dried at 70°C for 24h. Physical properties and scanning electron microscopy analysis of the silver powder are performed;

[0028] S3: Silver powder ball milling: Take 4kg of the silver powder in S2 above, weigh the mass of the silver powder, dissolve 0.5% stearic acid in 500mL ethanol, heat and clarify, add it to the silver powder to be ball milled and fully disperse it, then mix it with 16kg of steel balls with a diameter of 1.5mm, collect it in a dust-free manner, and add it from the unloading mechanism on the drum into the cavity surrounded by the screen and the right half of the drum, grind it for 12h, then sieve it and set it aside;

[0029] S4: Ball milling silver powder detection: The silver powder obtained in the above S3 is cleaned with ethanol until the mass loss on ignition of the silver powder is constant, and then the physical properties of the silver powder are measured.

[0030] Beneficial effects of the present invention:

[0031] 1. The present invention uses an auxiliary ball milling mechanism to cooperate with a screening ball milling assembly driven by an internal driving mechanism and an external driving mechanism to ball mill the raw powder of the target silver powder, which can not only greatly increase the collision frequency between the raw powder and the steel balls, and realize rapid and sufficient ball milling of the raw powder, but also use a striking block to knock down the qualified target silver powder accumulated on the screen to prevent blockage;

[0032] 2. The present invention uses a dust-free collection mechanism to collect the target silver powder after ball milling in a dust-free manner, and after the collection is completed, it can be transported dust-free, without causing dust pollution to the working environment;

[0033] 3. The manufacturing device of the present invention adopts a modular design as a whole, which is convenient for assembly and disassembly, and each component can be replaced independently, thereby improving the utilization rate of effective components;

[0034] 4. The present invention uses a cheap reducing agent (such as formaldehyde) to prepare the precursor silver powder, breaking through the traditional "ascorbic acid-gum arabic silver nitrate" system and having good economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 It is a schematic diagram of the overall structure of the preparation device of the present invention from a first viewing angle;

[0037] Figure 2 is a schematic diagram of the overall structure of the preparation device of the present invention from a second viewing angle;

[0038] Figure 3 It is a schematic diagram of the overall top view of the preparation device of the present invention;

[0039] Figure 4 The present invention Figure 3 Schematic diagram of the AA section structure;

[0040] Figure 5 It is a schematic diagram of the right half of the drum structure of the preparation device of the present invention;

[0041] Figure 6 The present invention Figure 7 A schematic cross-sectional structure diagram of ;

[0042] Figure 7 The present invention Figure 6 A schematic diagram of the structure enlargement of part A;

[0043] Figure 8 It is a schematic diagram of the left half of the drum structure of the preparation device of the present invention;

[0044] Fig. 9 It is a schematic diagram of the cooperation between the positioning support frame and the material receiving box of the preparation device of the present invention;

[0045] Fig.10 It is a schematic diagram of the overall structure of the positioning support frame of the preparation device of the present invention;

[0046] Fig.11 It is a schematic diagram of the cross-sectional structure of a material receiving box of the preparation device of the present invention;

[0047] Fig.12 It is a schematic diagram of the assembly structure of the support and the mandrel of the preparation device of the present invention.

[0048] The reference numerals in the figure are as follows: 1, bearing seat; 2, bracket; 21, support plate; 22, buckle plate; 3, roller; 4, ball mill mechanism; 41, mandrel; 42, cross block; 43, cross groove; 44, guide lining strip; 45, elastic arc plate; 46, elastic rod; 47, striking block; 48, rigid rod; 49, arc top block; 410, support seat; 411, gear; 412, gear ring; 413, limiting groove; 414, limiting strip; 415, screen; 416, positioning frame; 5, dust-free collection mechanism; 51, collar; 52, positioning support frame; 521, sealing plate; 522, vertical plate 1; 523 , guide rod; 524, spring one; 53, material receiving box; 531, cover plate; 532, sink groove; 533, slider; 534, straight rod; 535, spring two; 536, stop plate; 54, channel groove; 6, unloading mechanism; 61, hopper; 62, baffle; 63, vertical plate two; 64, arc rod; 65, spring three; 66, through groove; 7, auxiliary ball milling mechanism; 71, bottom plate; 72, cam; 73, spring four; 74, through groove; 75, limiting guide plate; 8, round rod; 9, limit plate; 10, baffle; 11, positioning block; 12, positioning slot; 13, clamping block; 14, clamping slot. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] A device and method for preparing spherical silver powder for photovoltaic front conductive silver paste is a conductor or conductive object distinguished by conductive material properties and characterized by being mainly composed of metal or alloy, and the IPC classification number is H01B1.

[0051] Example 1

[0052] Refer to the instruction manual Figure 1-8 and Fig.12A device for preparing spherical silver powder of photovoltaic front conductive silver paste according to an embodiment of the present invention comprises a supporting seat 1 and a roller 3, the roller 3 is composed of a left half and a right half arranged in a truncated cone structure, a bracket 2 is fixedly provided in the middle of both ends of the top surface of the supporting seat 1, and the roller 3 is arranged between the two brackets 2, a ball milling mechanism 4 and an auxiliary ball milling mechanism 7 are arranged between the supporting seat 1 and the roller 3, the ball milling mechanism 4 comprises an internal driving mechanism passing through the axial center line of the roller 3, an external driving mechanism arranged on the outside of the left half of the roller 3, and a screening ball milling assembly located inside the roller 3.

[0053] It should be noted that the present invention utilizes the auxiliary ball milling mechanism 7 to cooperate with the screening ball mill assembly driven by the inner driving mechanism and the outer driving mechanism to fully ball mill the raw powder of the target silver powder.

[0054] Specifically, Figure 4-8 As shown, the inner driving mechanism includes a driving motor 1 fixedly mounted on the opposite side of the two brackets 2, the output shaft ends of the two driving motors 1 are connected to the core shaft 41, and the opposite ends of the two core shafts 41 are respectively provided with a cross block 42 and a cross groove 43, the cross block 42 is movably inserted in the cross groove 43, and the outer peripheral surface of one end of the two core shafts 41 located at the roller 3 is movably sleeved with a positioning frame 416, and the bottom end surface of the positioning frame 416 is movably fitted with the upper end surface of the bearing seat 1;

[0055] The external driving mechanism includes a bracket 410 fixed on the top of the bearing seat 1 and a gear ring 412 fixedly sleeved on the outer side of the left half of the drum 3. The top of the bracket 410 is fixedly installed with a driving motor 2, and the end of the output shaft of the driving motor 2 is fixedly provided with a gear 411 meshing with the gear ring 412.

[0056] The screening ball mill assembly includes a screen 415 sandwiched between the right half and the left half of the drum 3, a plurality of groups of guide strips 44 evenly distributed in an annular shape are arranged on the inner side of the right half of the drum 3, and a plurality of groups of elastic arc plates 45 evenly distributed in an annular shape are arranged on the side surface of the mandrel 41 inside the right half of the drum 3, the guide strips 44 are arranged in a triangular prism structure, and the guide strips 44 are arranged in a narrowing shape from the large diameter end to the small diameter end of the right half of the drum 3;

[0057] A plurality of elastic rods 46 evenly distributed in a ring shape are fixedly provided on the inner edge of the small diameter end of the left half of the drum 3, and a rigid rod 48 is fixedly provided on the outer peripheral edge of the core shaft 41 on the inner side of the left half of the drum 3. An arc-shaped top block 49 of a semi-cylindrical pile structure and a triangular prism-shaped striking block 47 are respectively provided on the side opposite to the elastic rod 46.

[0058] It should be noted that the outer circumferences of the opposite ends of the left and right halves of the drum 3 are provided with connecting flanges, and the two connecting flanges are fixed by bolts, and the inner circumferences of the opposite ends of the left and right halves of the drum 3 are provided with annular grooves, and the screen 415 is clamped inside the two annular grooves and rotates synchronously with the drum 3. In addition, the rotation directions of the core shaft 41 and the drum 3 are opposite, and the elastic arc plate 45 and the elastic rod 46 are made of spring steel material.

[0059] After the raw powder and the steel balls are added into the right half of the inner cavity of the drum 3, the external controller starts the driving motor 1 and the driving motor 2 at the same time, so that the screening ball mill assembly inside the drum 3 performs ball milling on the raw powder. In this process, the mixture of the raw powder and the steel balls (hereinafter referred to as the mixture) initially approaches the screen 415 along the inner circumference of the drum 3, and then gradually moves upward under the support of the guide strip 44 as the drum 3 rotates. After rising to a certain height, the mixture will move along the guide strip 44 to the screen 415. The mixture moves in the shrinking direction and then separates from the guide strip 44. When the mixture gradually moves upward with the roller 3 under the support of the guide strip 44, the elastic arc plate 45 rotating with the core shaft 41 is always in rotation. The elastic arc plate rotating with the core shaft 41 can be used to hit the mixture falling from the guide strip 44 upward. The falling mixture will approach the screen 415 again with the help of the truncated cone-shaped roller 3. This cycle can be repeated to greatly increase the collision frequency between the raw powder and the steel ball, so as to achieve rapid and sufficient earth grinding of the raw powder.

[0060] After ball milling, the qualified target silver powder will pass through the screen 415 and flow into the left half of the drum 3. During this process, when the core shaft 41 and the drum 3 rotate in opposite directions, the arc-shaped top block 49 rotating with the core shaft 41 will push the striking block 47 to the side away from the screen 415 after contacting the striking block 47 rotating with the drum 3, so that the elastic rod 46 connected to the striking block 47 will undergo elastic deformation, and after the arc-shaped top block 49 completely passes over the striking block 47, the striking block 47 will be reset under the restoring force of the elastic rod 46 and hit the screen 415. On the one hand, the mixture collected at the screen 415 can be bounced away from the screen 415 to increase the collision frequency between the original powder and the steel balls. On the other hand, the qualified target silver powder accumulated on the screen 415 can be knocked down to prevent blockage.

[0061] Since the two core shafts 41 are connected by the matching cross block 42 and the cross slot 43, and the two core shafts 41 are driven by their corresponding driving motors, the core shafts 41 are convenient to connect and their durability is improved.

[0062] Furthermore, a plurality of T-shaped limiting grooves 413 are provided on the large inner circumference of the right half of the drum 3 and the outer circumference of the core shaft 41 inside the right half of the drum 3, and a T-shaped limiting strip 414 is fixedly provided on the middle part of the side of the guide lining strip 44 and the elastic arc plate 45 facing the limiting groove 413 at the position where the limiting groove 413 is located, and the limiting strip 414 is slidably connected to the inside of the limiting groove 413 at the corresponding position.

[0063] It should be noted that the setting of the T-shaped limiting strip 414 and the T-shaped limiting groove 413 can ensure the stable insertion of the guide strip 44 and the elastic arc plate 45, and after the left half and the right half of the drum 3 are docked and installed, the screen 415 can be used to adjust the position of the guide strip 44 and the elastic arc plate 45, and the limiting groove 413 can be closed by cooperating with the side where the guide strip 44 contacts the inner surface of the drum 3 and the side where the elastic arc plate 45 contacts the outer surface of the core shaft 41, so as to prevent small-size particles from being stuck in the gap formed during the ball milling process, and at the same time, it is also convenient for the quick replacement of the guide strip 44 and the elastic arc plate 45 at a later time.

[0064] Specifically, Figure 1 and Figure 4 As shown, the auxiliary ball milling mechanism 7 includes a bottom plate 71 arranged at the bottom of the supporting seat 1 and through grooves 74 vertically penetrating the two ends of the top surface of the supporting seat 1, a limiting guide plate 75 is fixedly provided at the position of the top of the bottom plate 71 corresponding to the through groove 74, four springs 73 are fixedly connected between the four corners of the bottom plate 71 and the opposite side of the supporting seat 1, and cams 72 are fixedly sleeved at the positions of the limiting guide plates 75 at the corresponding positions on the outer circumferences of the two core shafts 41.

[0065] It should be noted that the top end of the limiting guide plate 75 is set as a semicircular structure, which can not only facilitate the top end of the limiting guide plate 75 to quickly pass through the groove 74 on the support seat 1, but also guide the support seat 1 to move upward after contacting the rotating cam 72. In the process of ball milling the raw powder, as the core shaft 41 rotates, the cam 72 will rotate synchronously with the core shaft 41, and the rotating cam 72 will intermittently contact the arc segment of the limiting guide plate 75, allowing the support seat 1 to move upward along the limiting guide plate 75 and stretch the spring four 73. When the cam 72 is separated from the limiting guide plate 75 at its position, the spring four 73 will drive the support seat to reset and generate up and down vibrations, thereby driving the ball milling part as a whole to move up and down, accelerating the collision frequency between the raw powder and the steel balls and the screening of qualified target silver powder.

[0066] Specifically, Figure 1-2 and Fig.12As shown, the two brackets 2 each include a support plate 21 fixed on the top surface of the bearing seat 1 and a buckle plate 22 hinged at the edge of one end of the top of the support plate 21, and semicircular grooves are provided in the middle of the opposite sides of the support plate 21 and the buckle plate 22 in the buckled state, and a clamping block 13 is fixed in the middle of the opposite ends of the two core shafts 41, and a clamping groove 14 adapted to the clamping block 13 at the position is provided at the end of the output shaft of the two driving motors, and the clamping block 13 and the clamping groove 14 in the engaged state are arranged inside the circular groove formed by the two semicircular grooves at the position.

[0067] It should be noted that the driving motor 1 is fixed on the outside of the support plate 21 on the bracket 2 at the location. During the assembly of the preparation device, after the left half and the right half of the roller 3 are docked, the two positioning frames 416 are erected on the top of the bearing seat 1, and the two core shafts 41 extend to the groove 14 at one end of the outside of the roller 3, which is just located inside the semicircular groove at the location, and is stuck on the outside of the block 13 at the end of the output shaft of the driving motor 1 at the location, and then the buckle plate 22 is buckled on the top of the support plate 21 and fixed with locking bolts, which greatly improves the convenience of assembly.

[0068] Example 2

[0069] Refer to the instruction manual Figure 1-5 and Figure 9-11 A device for preparing spherical silver powder of photovoltaic front conductive silver paste according to an embodiment of the present invention comprises a supporting seat 1 and a roller 3. The roller 3 is composed of a left half and a right half arranged in a truncated cone structure. A feeding mechanism 6 and a dust-free collection mechanism 5 are respectively arranged on the outer side of the right half and the outer side of the left half of the roller 3. A feeding slot and a discharging slot are respectively opened at the positions corresponding to the feeding mechanism 6 and the dust-free collection mechanism 5 on the surface of the roller 3.

[0070] Specifically, Figure 5 As shown, the unloading mechanism 6 includes a hopper 61 fixedly installed at the right half of the drum 3 at a position corresponding to the feed slot, a through slot 66 is opened through the middle of the bottom of the hopper 61, a shielding plate 62 that fits the outer surface of the drum 3 is movably penetrated inside the through slot 66, and a leakage slot as large as the feed slot is opened at one end of the shielding plate 62, and vertical plates 63 are fixedly provided at both ends of the shielding plate 62, an arc rod 64 is fixedly provided on one side of the hopper 61, and one end of the arc rod 64 away from the hopper 61 movably passes through the vertical plate 63 at the position, a spring 3 65 is movably sleeved on the outer peripheral surface of the arc rod 64, and the two ends of the spring 3 65 are respectively fixedly connected to the hopper 61 and the vertical plate 63 at the corresponding position.

[0071] It should be noted that when spring three 65 is in a natural state, the leakage groove on the baffle 62 is completely offset from the feed slot and is located on the side of the hopper 61 away from the arc rod 64. When adding the mixture, pull the vertical plate two 63 on the baffle 61 corresponding to the side of the arc rod 64 along the direction of the arc rod 64 to connect the leakage groove with the feed slot on the drum 3. After the feeding is completed, remove the force on the vertical plate two 63, and the baffle 62 is reset to its initial state under the action of the restoring force of spring three 65, and the feed slot is blocked, which is easy to operate.

[0072] Specifically, Figure 4 and Figure 9-11 As shown, the dust-free collecting mechanism 5 includes a sleeve ring 51 movably sleeved on the outer circumference of the left half of the drum 3 corresponding to the discharge slot position, and a positioning bracket 52 connected to the discharge slot is fixedly provided on the outer circumference of the sleeve ring 51. A channel groove 54 is penetrated through one side of the positioning bracket 52, and a material receiving box 53 is movably inserted in the channel groove 54;

[0073] A sealing plate 521 is movably provided at the top of the inner cavity of the channel groove 54, and guide bars are fixedly provided at the middle of both sides of the sealing plate 521. Guide grooves are provided at both sides of the inner cavity of the channel groove 54, and the guide bars are slidably connected to the corresponding guide grooves. A vertical plate 522 is fixedly provided at one end of the top surface of the sealing plate 521, and a guide rod 523 movably penetrating the vertical plate 522 is fixedly provided at the middle of one side of the positioning bracket 52 facing the vertical plate 522. A spring 524 is movably sleeved on the outer circumference of the guide rod 523, and the two ends of the spring 524 are respectively fixedly connected to the vertical plate 522 and the positioning bracket 52;

[0074] The collar 51 corresponds to the end of the depth of the cross groove 43, and the positioning bracket 52 is also provided with a limiting component, which includes two groups of round rods 8 that movably penetrate the two sides of the positioning bracket 52, and the two ends of the two groups of round rods 8 are respectively fixed with a limit plate 9 and a stop bar 10;

[0075] A cover plate 531 is movably fitted on the top of the material receiving box 53, and grooves 532 are provided on both sides of the top surface of the material receiving box 53, and straight rods 534 are fixed inside the two grooves 532. Sliders 533 movably sleeved on the outside of the straight rods 534 are fixed on both sides of the end surface of the cover plate 531, and springs 535 are movably sleeved on the outer peripheral surfaces of the two straight rods 534. A stop plate 536 is fixed to the end of the top surface of the cover plate 531 corresponding to the slider 533.

[0076] It should be noted that, in the initial state, the sealing plate 521 completely blocks the discharge slot under the restoring force of the spring 1 524. When the target spherical silver powder is collected in real time without dust, it is only necessary to insert the corresponding end of the stop plate 536 of the receiving box 53 into the channel slot 54. During this process, the stop plate 536 will be blocked by the positioning support frame 52. As the receiving box 53 is gradually pushed in, the cover plate 531 will be pushed open by the positioning support frame 52, and the spring 1 524 will be compressed along the direction of the guide rod 523, and the sealing plate 521 will be pushed into the receiving box. 53 is pushed open, and the second spring 535 is compressed along the direction of the straight rod 534, gradually releasing the blockage of the discharge slot, allowing the qualified target spherical silver powder after screening to fall into the inside of the material receiving box 53. Since the discharge slot is in the process of movement, the material receiving is an intermittent process. After the sealing plate 521 is completely pushed open, the stopper 10 can be moved to buckle the end of the material receiving box 53 outside the channel groove 54, and the restoring force of the spring 1 524 and the second spring 535 is used to limit the stopper in the buckled state, so as to realize the position locking of the material receiving box 53;

[0077] On the contrary, when the material receiving box 53 is pulled out after the collection is completed, the sealing plate 521 will automatically reset under the restoring force of spring 1 524 to complete the sealing of the discharge slot. When the material receiving box 53 gradually separates from the channel slot 54, the cover plate 531 will automatically seal the material receiving box 53 under the restoring force of spring 2 535 to achieve dust-free transportation.

[0078] Furthermore, a positioning block 11 is fixedly provided at the center position of the bottom end surface of the positioning support frame 52 and the center position of the bottom end surfaces of the two positioning frames 416, and a positioning slot 12 is opened at the position corresponding to each positioning block 11 on the top surface of the support seat 1, and the positioning block 11 is movably inserted into the positioning slot 12 at the corresponding position.

[0079] It should be noted that during the assembly of the preparation device, after the left half and the right half of the roller 3 are connected, the positioning frame 416 and the positioning block 11 at the bottom of the positioning support frame 52 can be inserted into the positioning slot 12 at the corresponding position on the top of the support seat 1, which can enhance the support of the roller 3 while ensuring the real-time and stable progress of the material collection process.

[0080] The present invention also provides a method for preparing spherical silver powder of photovoltaic front conductive silver paste, which specifically comprises the following steps:

[0081] S1: silver powder reduction: prepare 300L of 100g / L silver nitrate solution in a reactor using pure water, add 2kg of polyvinyl pyrrolidone (PVP)-K30, heat to 30°C, add the first portion of 30% sodium hydroxide solution, adjust the pH of the silver nitrate solution to 5.0-6.0, add 10L of 35% formaldehyde solution, stir at 100r / min, wait for the reduction reaction to proceed for 30min until the reaction is balanced, add the remaining sodium hydroxide solution step by step to promote the reaction, and age for 5min to obtain reduced silver powder for standby use;

[0082] S2: Reduced silver powder detection: After washing and solid-liquid separation, the silver powder obtained in S1 is dispersed with 0.7% stearic acid by weight of the silver powder, plated, and dried at 70°C for 24h. Physical properties and scanning electron microscopy analysis of the silver powder are performed;

[0083] S3: Silver powder ball milling: Take 4kg of the silver powder in S2 above, weigh the mass of the silver powder, dissolve 0.5% stearic acid in 500mL ethanol, heat and clarify, add it to the silver powder to be ball milled and fully disperse it, then mix it with 16kg of steel balls with a diameter of 1.5mm, collect it in a dust-free manner, and add it from the unloading mechanism 6 on the drum 3 to the cavity surrounded by the screen 415 and the right half of the drum 3, grind it for 12h, and then sieve it for use;

[0084] S4: Ball milling silver powder detection: The silver powder obtained in the above S3 is cleaned with ethanol until the mass loss on ignition of the silver powder is constant, and then the physical properties of the silver powder are measured.

[0085] In the above steps, it should be noted that the silver nitrate, sodium hydroxide, stearic acid and ethanol involved are all analytically pure raw materials. Among them, sodium hydroxide reacts with silver nitrate to generate a white silver hydroxide precipitate. However, since the silver hydroxide precipitate is extremely unstable in water, it then decomposes into a gray silver oxide precipitate, and then formaldehyde is used to reduce the silver oxide to prepare silver powder. The relevant reaction formula is:

[0086] AgNO 3 +NaOH=AgOH↓+NaNO 3 (1)

[0087] 2AgOH=Ag 2 O↓+H 2 O (2)

[0088] Ag 2 O+HCHO=2Ag↓+HCOOH (3)

[0089] HCOOH+Ag2O=2Ag↓+CO 2 ↑+H 2 O (4)

[0090] In the above technical scheme, the circuits, electronic components and control modules involved are all existing technologies and can be fully implemented by those skilled in the art. Needless to say, the content to be protected by the present invention does not involve improvements to software and methods.

[0091] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

[0092] Finally, a few points should be explained: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, which may refer to mechanical connection or electrical connection, or internal communication between two components, or direct connection. "upper", "lower", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may change;

[0093] Secondly: In the drawings of the embodiments disclosed in the present invention, only the structures related to the embodiments disclosed in the present invention are involved, and other structures can refer to the usual design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

Claims

1. A device for preparing spherical silver powder for photovoltaic front conductive silver paste, comprising a bearing seat (1) and a roller (3), characterized in that: A bracket (2) is fixedly provided at the middle of both ends of the top surface of the bearing seat (1), and the roller (3) is arranged between the two brackets (2); a ball milling mechanism (4) and an auxiliary ball milling mechanism (7) are arranged between the bearing seat (1) and the roller (3); the roller (3) is composed of a left half and a right half arranged in a truncated cone structure; a feeding mechanism (6) and a dust-free collection mechanism (5) are respectively arranged on the outer side of the right half and the outer side of the left half of the roller (3); and a feeding slot and a discharging slot are respectively opened on the surface of the roller (3) at positions corresponding to the feeding mechanism (6) and the dust-free collection mechanism (5); The ball milling mechanism (4) comprises an internal driving mechanism that passes through the axial center line of the drum (3), an external driving mechanism that is arranged outside the left half of the drum (3), and a screening ball milling assembly that is located inside the drum (3).

2. The device for preparing spherical silver powder of photovoltaic front conductive silver paste according to claim 1, characterized in that: The inner driving mechanism comprises a driving motor 1 fixedly mounted on the opposite side of the two brackets (2), the output shaft ends of the two driving motors 1 are connected to a core shaft (41), and the opposite ends of the two core shafts (41) are respectively provided with a cross block (42) and a cross groove (43), the cross block (42) is movably inserted into the cross groove (43), and the outer peripheral surfaces of one end of the two core shafts (41) located at the roller (3) are movably sleeved with a positioning frame (416), and the bottom end surface of the positioning frame (416) is movably fitted with the upper end surface of the bearing seat (1).

3. The device for preparing spherical silver powder of photovoltaic front conductive silver paste according to claim 1, characterized in that: The external drive mechanism comprises a bracket (410) fixed on the top of the bearing seat (1) and a gear ring (412) fixedly sleeved on the outside of the left half of the roller (3); a second drive motor is fixedly mounted on the top of the bracket (410), and a gear (411) meshing with the gear ring (412) is fixedly provided at the end of the output shaft of the second drive motor.

4. The device for preparing spherical silver powder for photovoltaic front conductive silver paste according to claim 1, characterized in that: The screening ball mill assembly comprises a screen (415) sandwiched between the right half and the left half of the drum (3); a plurality of groups of flow guide strips (44) evenly distributed in an annular shape are arranged on the inner side of the right half of the drum (3); a plurality of groups of elastic arc plates (45) evenly distributed in an annular shape are arranged on the circumferential side surface of the core shaft (41) inside the right half of the drum (3); the flow guide strips (44) are arranged in a triangular prism structure, and the flow guide strips (44) are arranged in a narrowing shape from the large diameter end to the small diameter end of the right half of the drum (3); A plurality of elastic rods (46) evenly distributed in an annular shape are fixedly provided at the inner edge of the small diameter end of the left half of the roller (3), and a rigid rod (48) is fixedly provided at the outer peripheral edge of the core shaft (41) inside the left half of the roller (3), and an arc-shaped top block (49) of a semi-cylindrical pile structure and a striking block (47) of a triangular prism structure are respectively provided on the side of the rigid rod (48) opposite to the elastic rod (46); A plurality of T-shaped limiting grooves (413) are provided on the large inner circumference of the right half of the roller (3) and the outer circumference of the core shaft (41) inside the right half of the roller (3), and a T-shaped limiting strip (414) is fixedly provided on the middle part of the guide strip (44) and the elastic arc plate (45) facing the limiting groove (413) at the position where the limiting strip (413) is located, and the limiting strip (414) is slidably connected to the inside of the limiting groove (413) at the corresponding position.

5. The device for preparing spherical silver powder for photovoltaic front conductive silver paste according to claim 2, characterized in that: The auxiliary ball milling mechanism (7) comprises a bottom plate (71) arranged at the bottom of the bearing seat (1) and through grooves (74) vertically penetrating through the two ends of the top surface of the bearing seat (1); a limiting guide plate (75) is fixedly provided at the top of the bottom plate (71) at a position corresponding to the through groove (74); four springs (73) are fixedly connected between the four corners of the opposite sides of the bottom plate (71) and the bearing seat (1); and cams (72) are fixedly sleeved at the positions of the limiting guide plates (75) at the corresponding positions on the outer circumferences of the two core shafts (41).

6. The device for preparing spherical silver powder of photovoltaic front conductive silver paste according to claim 1, characterized in that: The unloading mechanism (6) comprises a hopper (61) fixedly mounted on the right half of the drum (3) at a position corresponding to the feed slot opening, a running slot (66) penetrating the middle of the bottom of the hopper (61), a shielding plate (62) movably penetrating the inner part of the running slot (66) and fitting the outer surface of the drum (3), and a leakage slot as large as the feed slot opening is opened at one end of the shielding plate (62), and two vertical plates (63) are fixedly mounted at both ends of the shielding plate (62), an arc rod (64) is fixedly mounted on one side of the hopper (61), and one end of the arc rod (64) away from the hopper (61) movably penetrates the vertical plate (63) at the position, and a spring (65) is movably sleeved on the outer peripheral surface of the arc rod (64), and the two ends of the spring (65) are respectively fixedly connected to the hopper (61) and the vertical plate (63) at the corresponding position.

7. The device for preparing spherical silver powder for photovoltaic front conductive silver paste according to claim 2, characterized in that: The dust-free collection mechanism (5) comprises a sleeve (51) movably sleeved on the outer peripheral surface of the left half of the drum (3) corresponding to the discharge slot position, a positioning support frame (52) connected to the discharge slot is fixedly provided on the outer peripheral surface of the sleeve (51), a channel groove (54) is penetrated through one side of the positioning support frame (52), and a material receiving box (53) is movably inserted into the interior of the channel groove (54); A sealing plate (521) is movably provided at the top end of the inner cavity of the channel groove (54), and guide bars are fixedly provided at the middle parts of both sides of the sealing plate (521). Guide grooves are provided at both sides of the inner cavity of the channel groove (54), and the guide bars are slidably connected to the corresponding guide grooves. A vertical plate (522) is fixedly provided at one end of the top surface of the sealing plate (521), and a guide rod (523) movably penetrating the vertical plate (522) is fixedly provided at the middle part of the side of the positioning support frame (52) facing the vertical plate (522). A spring (524) is movably sleeved on the outer peripheral surface of the guide rod (523), and the two ends of the spring (524) are respectively fixedly connected to the vertical plate (522) and the positioning support frame (52); The collar (51) corresponds to the end of the longitudinal depth of the cross groove (43), and a limiting component is also provided on the positioning bracket (52), the limiting component comprising two groups of round rods (8) movably penetrating the two sides of the positioning bracket (52), and the two ends of the two groups of round rods (8) are respectively fixed with a limiting plate (9) and a blocking bar (10); A cover plate (531) is movably fitted on the top of the material receiving box (53), and both sides of the top surface of the material receiving box (53) are provided with recessed grooves (532), and straight rods (534) are fixedly provided inside the two recessed grooves (532). Both sides of the end surface of the cover plate (531) are fixedly provided with sliders (533) movably sleeved on the outside of the straight rods (534) at the position, and the outer peripheral surfaces of the two straight rods (534) are movably sleeved with springs (535). A stopper plate (536) is fixedly provided on the top surface of the cover plate (531) corresponding to one end of the slider (533).

8. The device for preparing spherical silver powder of photovoltaic front conductive silver paste according to claim 2, characterized in that: The two brackets (2) each comprise a support plate (21) fixedly arranged on the top end surface of the bearing seat (1) and a buckle plate (22) hingedly connected to the edge position of one end of the top of the support plate (21), and semicircular grooves are provided in the middle of the opposite sides of the support plate (21) and the buckle plate (22) in a buckled state, and a clamping block (13) is fixedly arranged in the middle of the opposite ends of the two core shafts (41), and a clamping groove (14) adapted to the clamping block (13) at the position is provided at the end of the output shaft of the two driving motors, and the clamping block (13) and the clamping groove (14) in the buckled state are both arranged inside the circular groove formed by the two semicircular grooves at the position.

9. The device for preparing spherical silver powder for photovoltaic front conductive silver paste according to claim 7, characterized in that: A positioning plug (11) is fixedly provided at the center position of the bottom end surface of the positioning support frame (52) and the center position of the bottom end surfaces of the two positioning frames (416); a positioning slot (12) is provided at the top end surface of the bearing seat (1) at a position corresponding to each positioning plug (11), and the positioning plug (11) is movably plugged into the inside of the positioning slot (12) at the corresponding position.

10. A method for preparing spherical silver powder for photovoltaic front conductive silver paste, relating to the device for preparing spherical silver powder for photovoltaic front conductive silver paste according to any one of claims 1 to 9, characterized in that: The specific steps include the following: S1: silver powder reduction: prepare 300L of 100g / L silver nitrate solution in a reactor using pure water, add 2kg of polyvinyl pyrrolidone-K30, heat to 30°C, add the first portion of 30% sodium hydroxide solution, adjust the pH of the silver nitrate solution to 5.0-6.0, add 10L of 35% formaldehyde solution, stir at 100r / min, wait for the reduction reaction to proceed for 30min until the reaction is balanced, add the remaining sodium hydroxide solution step by step to promote the reaction, and age for 5min to obtain reduced silver powder for standby use; S2: Reduced silver powder detection: After washing and solid-liquid separation, the silver powder obtained in S1 is dispersed with 0.7% stearic acid by weight of the silver powder, plated, and dried at 70°C for 24h. Physical properties and scanning electron microscopy analysis of the silver powder are performed; S3: Silver powder ball milling: Take 4 kg of the silver powder in S2 above, weigh the mass of the silver powder, dissolve 0.5% stearic acid in 500 mL of ethanol, heat and clarify, add it to the silver powder to be ball milled and fully disperse it, then mix it with 16 kg of steel balls with a diameter of 1.5 mm, collect it in a dust-free manner, and add it from the unloading mechanism (6) on the drum (3) to the cavity surrounded by the screen (415) and the right half of the drum (3), grind it for 12 hours, and then sieve it for use; S4: Ball milling silver powder detection: The silver powder obtained in the above S3 is cleaned with ethanol until the mass loss on ignition of the silver powder is constant, and then the physical properties of the silver powder are measured.

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