Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a preparation method of an early-strength polycarboxylate superplasticizer, and solves the problem of high energy consumption caused by high synthesis temperature of the existing early-strength polycarboxylate superplasticizer.
In order to solve the problems, the technical scheme adopted by the invention is as follows: a preparation method of an early strength type polycarboxylate superplasticizer comprises the following steps:
s1, adding 100 and 150 parts of polyether macromonomer and 100 and 150 parts of tap water into a reaction kettle according to the proportion, stirring and dissolving the mixture into a uniform and transparent solution, and obtaining a kettle bottom solution;
s2, mixing 8-15 parts of unsaturated acid monomer, 4-10 parts of early strength functional monomer prepared in advance, 0.5-1 part of chain transfer agent and 10-30 parts of tap water into a uniform solution to obtain a dropping liquid A;
s3, mixing 0.1-0.6 part of reducing agent and 20-60 parts of tap water into a uniform solution to obtain a dropping liquid B;
s4, adding 0.5-2 parts of oxidant into the kettle bottom liquid in the step S1, after 4-6 minutes, simultaneously adding dropwise A and B into the kettle bottom liquid in the step S1 at constant speed by using a dropwise adding device at normal temperature, stirring, wherein the dropwise adding time of the dropwise A and the dropwise B is 50-70 minutes and 60-80 minutes respectively, and after dropwise adding is finished, preserving heat for 1-1.5 hours to finish reaction to obtain a polycarboxylic acid water reducing agent solution;
s5, adding a NaOH solution into the polycarboxylate superplasticizer solution obtained in the step S6 to adjust the pH value to be neutral, and obtaining a liquid, namely the early-strength polycarboxylate superplasticizer.
Further, the early strength type functional monomer in step S2 is one or more of N, N-methylene bisacrylamide, an ester synthesized from an amino acid and N-methylol acrylamide, and an ester synthesized from cinnamic acid and alcohol amine.
Further, the early strength type functional monomer described in step S2 is prepared by the following method: dissolving a certain amount of N-hydroxymethyl acrylamide and a catalyst zirconium oxychloride in N, N-dimethylformamide, slowly heating to 110-130 ℃ after the dissolution is finished, slowly adding L-glutamic acid with the same mole as that of the N-hydroxymethyl acrylamide, stirring and reacting for 4-4.5 hours, and after the reaction is finished, removing the solvent N, N-dimethylformamide by rotary evaporation to obtain an early-strength functional monomer A;
further, the early strength type functional monomer described in step S2 is prepared by the following method: placing catalysts of p-toluenesulfonic acid and triethanolamine in a dry three-neck flask, stirring, slowly adding cinnamic acid after the p-toluenesulfonic acid is dissolved, heating to the temperature of 100 ℃ and 110 ℃, stirring and reacting for 3-3.5 hours, and obtaining an early-strength functional monomer B after the reaction is finished;
further, the unsaturated acid monomer is one or more of maleic anhydride, acrylic acid, methacrylic acid, itaconic acid or fumaric acid.
Further, the amino acid is one or more of L-glutamic acid, DL-phenylalanine and sarcosine.
Further, the alcohol amine is one or more of triethanolamine, diethanolamine and triisopropanolamine;
further, the chain transfer agent is one or more of thioglycolic acid, mercaptopropionic acid, mercaptoethanol or sodium hypophosphite.
Further, the reducing agent is one or more of vitamin C, sodium sulfite, sodium bisulfite, potassium sulfite or sodium formaldehyde sulfoxylate.
Further, the oxidant is one or more of ammonium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide or potassium persulfate.
Further, the concentration of the dropping liquid A is 35-40%.
Further, the concentration of the kettle bottom is 50-55%.
Furthermore, the concentration of the dropping liquid B is 1-2%.
Wherein, the dropping solution A or the dropping solution B in the step S4 adopts the following dropping equipment: the stirring device comprises a frame and a stirring barrel, wherein the stirring barrel is fixed on the frame, a motor is fixed on the frame above the stirring barrel, a rotating rod is fixed on an output shaft of the motor, the lower end of the rotating rod extends to the inner bottom of the stirring barrel, and blades are fixed on the rotating rod; a cam is fixedly sleeved on the part, located above the stirring barrel, of the rotating rod, a cylinder body is fixed to the right top of the stirring barrel, a one-way air inlet valve and a one-way air outlet valve are arranged on the cylinder body, an air vent is formed in the lower end of the cylinder body, a piston is arranged inside the cylinder body, a first external thread is arranged on the outer side wall of the piston, a first internal thread matched with the first external thread is arranged on the inner side wall of the cylinder body, a first spring is arranged inside the cylinder body, one end of the first spring is fixed to the bottom of the cylinder body, and the; the upper end of the piston is fixedly connected with a piston rod, the piston rod vertically penetrates through the top of the cylinder body upwards and is in sliding sealing connection with the cylinder body, the upper end of the piston rod is fixedly provided with a shifting block of a rectangular plate arranged along the vertical direction, and in the rotating process of the cam, one end of the cam, which is farthest away from the rotating rod, can shift the shifting block; a dripping barrel is fixed on the part of the frame above the stirring barrel, a threaded column is coaxially fixed inside the dripping barrel, a sliding plate is sleeved on the periphery of the threaded column, the edge of the sliding plate is attached to and sealed with the inner side wall of the dripping barrel, and a second internal thread matched with a second external thread on the threaded column is arranged on the sliding plate; the upper part of the dripping barrel is connected with a suction pipe which is fixed on the dripping barrel, a dripping pipe which is arranged along the vertical direction is fixed on the stirring barrel, the suction pipe is communicated with the dripping pipe through a hose, and the lower end of the dripping pipe is provided with a one-way liquid outlet valve; the one-way air inlet valve is communicated with the lower part of the dropping pipe through a connecting pipe, and one end of the connecting pipe close to the dropping pipe is provided with an automatic valve; be fixed with fixed case in the frame, the hose run through fixed case the upper and lower both ends and with a lateral wall fixed connection of fixed case, the opening has been seted up at the top of fixed case, the opening internal rotation is connected with the gear, gear engagement has the rack, the one end and the hose of rack offset, the rack other end runs through fixed case's lateral wall and rotates with fixed case to be connected, the interior bottom of fixed case is fixed with the stopper of arranging along vertical direction, set up vertical spacing tooth of arranging up on the stopper, the lower extreme of rack is provided with the recess with spacing tooth matched with.
The beneficial effect that this scheme produced is:
1. the 2+2 type macromonomer EPEG is used, and the double bond activity of the monomer is higher than that of the double bond of a common carbon four or carbon five monomer, so that the addition reaction can be carried out at normal temperature without heating, the reaction time can be greatly shortened, the energy consumption can be effectively reduced, and the cost is saved.
2. According to the invention, polyether monomers with relatively large molecular weight are used, and the mother liquor of the early-strength polycarboxylate superplasticizer is synthesized by a structure of short main chain length side chains, wherein the structure is favorable for promoting cement hydration and can promote the early strength of concrete.
3. The invention uses N, N-methylene-bisacrylamide, ester synthesized by amino acid and N-hydroxymethyl acrylamide, and ester synthesized by cinnamic acid and alcohol amine as functional monomers of the early-strength water reducing agent, the monomers contain a plurality of N atoms, the N atoms contain a pair of unshared electrons and can be reacted with Ca2+And Fe3+Form complex, thus improving the solubility of the surface of cement particles and being beneficial to C3A and C4The dissolution of AF accelerates the reaction with gypsum to generate calcium sulphoaluminate. Simultaneously can reduce Ca in liquid phase2+And Al3+To further promote C3S is hydrated, so that the early strength of the concrete is improved.
4. The early strength polycarboxylate superplasticizer disclosed by the invention does not contain chloride ions, does not rust reinforcing steel bars, is safe and environment-friendly in raw materials, and is green and pollution-free.
Detailed Description
The following is further detailed by way of specific embodiments:
reference numerals in the drawings of the specification include: the device comprises a stirring barrel 10, a first fixed block 11, a motor 12, a cam 13, a rotating rod 14, a paddle 15, a cylinder 20, a one-way air inlet valve 21, a one-way air outlet valve 22, a piston 23, a first spring 24, a piston rod 25, a shifting block 26, a connecting pipe 27, an automatic valve 28, a dripping barrel 30, a sliding plate 31, a scraping plate 311, a second spring 32, a bolt 33, a suction pipe 34, a second fixed block 35, a hose 36, a dripping pipe 37, a one-way liquid outlet valve 38, a threaded column 39, a fixed box 40, a gear 41, a rack 42, a handle 43, a limiting block 44 and limiting teeth 45.
Example 1
A preparation method of an early strength type polycarboxylate superplasticizer comprises the following steps:
s1, adding 120g of EPEG with the molecular weight of 4000 and 100g of tap water into the reaction kettle according to the proportion, and stirring and dissolving the mixture into uniform and transparent kettle bottom liquid;
s2, mixing 10g of acrylic acid, 4g N, N-methylene bisacrylamide, 0.5g of mercaptopropionic acid and 30g of tap water uniformly to obtain a dropping liquid A;
s3, mixing 0.15g of vitamin C and 20g of tap water uniformly to obtain a dropping liquid B;
s4, adding 0.5g of 27.5 mass percent hydrogen peroxide into the kettle bottom liquid obtained in the step S1 at normal temperature, after 5 minutes, simultaneously dropwise adding a dropping liquid A and a dropping liquid B into the kettle bottom liquid obtained in the step S1 at constant speed by using a dropwise adding device at normal temperature, stirring, wherein the dropping time of the dropping liquid A and the dropping time of the dropping liquid B are respectively 60 minutes and 70 minutes, and preserving heat for 1 hour after the dropwise adding is finished to finish the reaction to obtain a polycarboxylic acid water reducing agent solution;
s5, adding a NaOH solution into the polycarboxylate superplasticizer solution obtained in the step S4 to adjust the pH value to be neutral, and obtaining a liquid, namely the early-strength polycarboxylate superplasticizer.
Wherein, the dropping solution A or the dropping solution B in the step S4 adopts the following dropping equipment: the stirring device comprises a rack and a stirring barrel 10, as shown in fig. 1, the stirring barrel 10 is fixed on the rack, the stirring barrel 10 is cylindrical, the axis of the stirring barrel 10 is arranged along the vertical direction, a motor 12 is fixed on the part of the rack right above the stirring barrel 10, the motor 12 is electrically connected with a motor switch, the motor switch is fixed on the rack, the motor 12 rotates when the motor switch is pressed, and then the motor 12 stops rotating when the motor switch is pressed; the output shaft of motor 12 is vertical arranging downwards, is fixed with dwang 14 and agitator 10 coaxial arrangement on the output shaft of motor 12, and the lower extreme of dwang 14 extends to the interior bottom of agitator 10, and the lower extreme and the lower part of dwang 14 all are fixed with paddle 15.
The inside cauldron bottom liquid that is used for storing of agitator 10, starter motor 12, motor 12 drive dwang 14 rotates, and dwang 14 drives paddle 15 and stirs the cauldron bottom liquid.
As shown in fig. 1, a cam 13 is fixedly sleeved on a portion of the rotating rod 14 above the agitator 10, a cylinder 20 is fixed on the right top of the agitator 10, a one-way air inlet valve 21 and a one-way air outlet valve 22 are arranged at the upper end of the cylinder 20, an air vent is arranged at the lower end of the cylinder 20 and used for communicating the interior of the cylinder 20 with the outside, a piston 23 is arranged in the cylinder 20, a first external thread is arranged on the outer side wall of the piston 23, a first internal thread matched with the first external thread on the piston 23 is arranged on the inner side wall of the cylinder 20, the first external thread on the piston 23 is not self-locked with the first internal thread on the inner side wall of the cylinder 20, a first spring 24 is arranged in the cylinder 20, one end of the first spring 24 is fixed at the bottom of; when the piston 23 rotates forward under the action of an external force, the first internal thread is matched with the first external thread to enable the piston 23 to move downward, when the piston 23 rotates forward under the action of the external force, the first internal thread is matched with the first external thread to enable the piston 23 to move downward, and when the external force acting on the piston 23 disappears, the piston 23 moves upward under the action of the first spring 24, and meanwhile, the first internal thread is matched with the first external thread to enable the piston 23 to rotate reversely; piston 23's upper end fixedly connected with piston rod 25, piston rod 25 vertically upwards runs through the top of cylinder body 20 and with cylinder body 20 sliding seal connection, piston rod 25's upper end is fixed with the shifting block 26 of arranging along the horizontal direction, shifting block 26 is the rectangular plate of arranging along vertical direction, shifting block 26's quantity is provided with four and axis circumference evenly distributed about piston rod 25, the rotatory in-process of cam 13, one of them shifting block 26 can be stirred to the one end farthest away from dwang 14 on cam 13, shifting block 26 is rotatory to drive piston rod 25 and piston 23 rotatory.
In the process that the rotating rod 14 drives the cam 13 to rotate, the cam 13 rotates to stir the shifting block 26 to rotate in the positive direction, the shifting block 26 drives the piston rod 25 and the piston 23 to rotate in the positive direction, the first internal thread is matched with the first external thread to enable the piston 23 to move downwards, the piston 23 extrudes the first spring 24, negative pressure is generated inside the cylinder body 20, the one-way air inlet valve 21 is opened, the one-way air outlet valve 22 is closed, and air is sucked inside the cylinder body 20; when the cam 13 is separated from the shifting block 26, the piston 23 moves upward under the action of the first spring 24, and simultaneously the first internal thread is matched with the first external thread to enable the piston 23 to rotate reversely, so that positive pressure is generated inside the cylinder 20, the one-way air inlet valve 21 is closed, the one-way air outlet valve 22 is opened, and the cylinder 20 exhausts air. During the periodic rotation of the cam 13, the cylinder 20 intermittently sucks and discharges air to form a suction pump.
As shown in fig. 1, a dropping barrel 30 with an upward opening is fixed on a portion of the frame above the stirring barrel 10, the dropping barrel 30 is cylindrical, a threaded column 39 is coaxially fixed inside the dropping barrel 30, a sliding plate 31 is sleeved on the periphery of the threaded column 39, the edge of the sliding plate 31 is attached to and sealed with the inner side wall of the dropping barrel 30, a second internal thread matched with a second external thread on the threaded column 39 is arranged on the sliding plate 31, the second external thread and the second internal thread are not self-locked, when the sliding plate 31 moves downward under the action of external force, the second external thread is matched with the second internal thread to enable the sliding plate 31 to rotate forward, and meanwhile, the second spring 32 is compressed; when the external force acting on the slide plate 31 disappears, the second spring 32 makes the slide plate 31 move upwards, and the second external thread is matched with the second internal thread to make the slide plate 31 rotate reversely; as shown in fig. 1, scrapers 311 are fixedly arranged on the sliding plate 31, the scrapers 311 are arranged along the radial direction of the sliding plate 31, the scrapers 311 are arranged along the vertical direction, one end of the scraper 311, which is far away from the axis of the sliding plate 31, is attached to the inner side wall of the dripping bucket 30, and the number of the scrapers 311 is 4 and is circumferentially and uniformly distributed about the axis of the sliding plate 31. As shown in fig. 1 and 2, a suction pipe 34 in a shape like a letter "7" is connected to the upper portion of the dropping barrel 30, the suction pipe 34 is fixed to the dropping barrel 30 through a second fixing block 35, a dropping pipe 37 arranged in a vertical direction is fixed to the left side wall of the stirring barrel 10 through a first fixing block 11, the suction pipe 34 is communicated with the dropping pipe 37 through a hose 36, the hose 36 is made of a fluororubber material, and a one-way liquid outlet valve 38 is arranged at the lower end of the dropping pipe 37; one-way air inlet valve 21 passes through connecting pipe 27 and dropwise add the lower part intercommunication of pipe 37, the one end that is close to dropwise add pipe 37 on the connecting pipe 27 is provided with automatic valve 28, automatic valve 28 electric connection has first automatic valve switch and second automatic valve switch, first automatic valve switch and second automatic valve switch set up respectively at the interior top and the bottom of cylinder body 20, when piston 23 moves to the extreme position of top and below, first automatic valve switch and second automatic valve switch can be pressed to piston 23, when piston 23 pressed first automatic valve switch, first automatic valve 28 is opened, when piston 23 pressed the second automatic valve switch, automatic valve 28 closes.
In the process of air suction of the cylinder 20, the cylinder 20 utilizes the siphon principle, the cylinder 20 sucks the liquid in the dripping barrel 30 through the connecting pipe 27, the dripping pipe 37, the hose 36 and the suction pipe 34, after the piston 23 moves to the lower extreme position, the piston 23 presses the second automatic valve switch, the automatic valve 28 is closed, a part of the dripping liquid drops into the stirring barrel 10 through the dripping pipe 37 under the action of gravity, a part of the dripping liquid drops back into the dripping barrel 30 under the action of gravity, after the dripping liquid enters the suction pipe 34, the dripping liquid in the dripping barrel 30 is reduced, therefore, the sliding plate 31 moves upwards under the action of the second spring 32, the second internal thread and the second external thread are matched to enable the sliding plate 31 to rotate forwards, the scraper 311 stirs the inside of the dripping barrel 30 and scrapes off the side wall of the dripping barrel 30, the dripping liquid is prevented from remaining on the inner side wall of the dripping barrel 30, after the part of the inside of the dripping pipe 37 falls back into the dripping barrel 30, the amount of the dropping liquid in the dropping barrel 30 is increased, the sliding plate 31 moves downwards under the action of the gravity of the dropping liquid, the second internal thread is matched with the second external thread to enable the sliding plate 31 to rotate forwards, the scraper 311 stirs the interior of the dropping barrel 30 and scrapes off the side wall of the dropping barrel 30, and the dropping liquid is prevented from remaining on the inner side wall of the dropping barrel 30; 20 intermittent type nature of cylinder body is breathed in, realizes the intermittent type nature dropwise add of dropping liquid to the forward and reverse rotation when realizing the up-and-down reciprocating sliding of slide 31 stirs the inside dropping liquid of dropwise add bucket 30, avoids the final quality of the influence water-reducing agent that the dropping liquid sediment that long-time dropwise add in-process caused leads to.
As shown in fig. 2, a bolt 33 is threadedly connected to the bottom of the dropping barrel 30, and the preload of the second spring 32 can be adjusted by screwing the bolt 33, so that the second spring 32 can still drive the sliding plate 31 to slide upwards after a long period of use.
Since the dropping time of the dropping liquid is constant, the amount of the dropping liquid to be dropped at each time needs to be adjusted according to the total amount of the dropping liquid to be dropped and the dropping time of the dropping liquid.
Therefore, as shown in fig. 1, a fixed box 40 is fixed on the frame, the fixed box 40 is rectangular, a through hole penetrating through the upper and lower ends of the fixed box 40 is formed in the right portion of the fixed box 40, a hose 36 penetrates through the through hole and is fixedly connected with the through hole, the right end of the hose 36 is attached to the right side wall of the fixed box 40, a rectangular opening is formed in the top portion of the fixed box 40, a gear 41 is rotatably connected to the rectangular opening, the gear 41 is engaged with a rack 42, the right end of the rack 42 is abutted to the hose 36 through a disc-shaped pressing plate (not shown in the figure), the pressing plate is parallel to the right side wall of the fixed box 40, the left end of the rack 42 penetrates through the left side wall of the fixed box 40 and is rotatably connected to the left side wall of the fixed box 40, a handle 43 is fixed to the left end of the rack 42, the handle 43 is provided to facilitate rotating the rack, set up vertical spacing tooth 45 of arranging up on the stopper 44, the shape of the cross section of spacing tooth 45 is right triangle to right triangle's hypotenuse inclines towards left side below, and the lower extreme of rack 42 is provided with the recess with spacing tooth 45 matched with, and the recess makes rack 42 can slide right under the exogenic action with spacing tooth 45 cooperation, and rack 42 can not slide left under self effort, thereby can carry on spacingly to rack 42.
By rotating the gear 41, the gear 41 drives the rack 42 to move rightwards, the extrusion plate on the rack 42 extrudes the hose 36, and the cross-sectional area of the circulation of the hose 36 is reduced, so that the flow rate of the dropping liquid flowing through the hose 36 is controlled, the dropping speed can be adjusted as required, and the principle of controlling the dropping speed is similar to that of an infusion tube used by a patient in a hospital. When the dropping rate needs to be increased, the rack 42 is rotated by the handle 43 to separate the rack 42 from the gear 41 and the limit teeth 45, and after the rack 42 is manually moved to the extreme position on the left side, the rack 42 is rotated again by the handle 43 to re-engage the rack 42 with the gear 41 and the limit teeth 45. In the same way, the adjustment of the dropping speed is realized.
Example 2
A preparation method of an early strength type polycarboxylate superplasticizer comprises the following steps:
s1, dissolving 30g N-hydroxymethyl acrylamide and 1g of catalyst zirconium oxychloride in N, N-dimethylformamide, slowly heating to 120 ℃ after the dissolution is finished, slowly adding L-glutamic acid with the same mole as that of the N-hydroxymethyl acrylamide, stirring for reaction for 4 hours, and after the reaction is finished, removing the solvent N, N-dimethylformamide through oil pump rotary evaporation to obtain the early strength functional monomer.
S2, adding 100g of EPEG with the molecular weight of 4000 and 100g of tap water into the reaction kettle according to the proportion, and stirring and dissolving the mixture into uniform and transparent kettle bottom liquid;
s3, mixing 12g of acrylic acid, 6g of the early strength type functional monomer obtained in the step S1, 0.6g of thioglycolic acid and 30g of tap water to form uniform dropping liquid A;
s3, mixing 0.6g of sodium formaldehyde sulfoxylate and 50g of tap water into uniform dripping liquid B;
s5, adding 2g of ammonium persulfate into the kettle bottom liquid obtained in the step S1 at normal temperature, after 5 minutes, simultaneously adding a dropping liquid A and a dropping liquid B into the bottom liquid obtained in the step I at constant speed by using a dropping device at normal temperature, stirring, wherein the dropping time of the dropping liquid A and the dropping time of the dropping liquid B are respectively 60 minutes and 70 minutes, and preserving heat for 1 hour after the dropping is finished to finish the reaction to obtain a polycarboxylic acid water reducing agent solution;
s6, adding a NaOH solution into the polycarboxylate superplasticizer solution obtained in the step S5 to adjust the pH value to be neutral, and obtaining a liquid, namely the early-strength polycarboxylate superplasticizer.
Example 3
A preparation method of an early strength type polycarboxylate superplasticizer comprises the following steps:
s1, placing 1g of catalyst p-toluenesulfonic acid and 60g of triethanolamine in a dry three-neck flask, stirring, slowly adding 20g of cinnamic acid after the p-toluenesulfonic acid is dissolved, heating to 110 ℃, stirring for reaction for 3 hours, and obtaining triethanolamine cinnamate (unsaturated amine monomer) after the reaction is finished;
s2, adding 100g of EPEG with the molecular weight of 4000 and 100g of tap water into the reaction kettle according to the proportion, and stirring and dissolving the mixture into uniform and transparent kettle bottom liquid;
s3, mixing 10g of acrylic acid, 5g of triethanolamine cinnamate (unsaturated amine monomer) obtained in the step S1, 0.8g of mercaptoethanol and 12g of tap water to form uniform dropping liquid A;
s4, mixing 0.6g of sodium formaldehyde sulfoxylate and 50g of tap water into uniform dripping liquid B;
s5, adding 3g of ammonium persulfate into the kettle bottom liquid obtained in the step S2 at normal temperature, after 5 minutes, simultaneously adding dropwise-added liquid A and dropwise-added liquid B into the kettle bottom liquid obtained in the step S1 at constant speed by using a dropwise adding device at normal temperature, stirring, wherein the dropwise adding time of the dropwise-added liquid A and the dropwise-added liquid B is 60 minutes and 70 minutes respectively, and preserving heat for 1 hour after the dropwise adding is finished to finish the reaction to obtain a polycarboxylic acid water reducing agent solution;
s6, adding a NaOH solution into the polycarboxylate superplasticizer solution obtained in the step S5 to adjust the pH value to be neutral, and obtaining a liquid, namely the early-strength polycarboxylate superplasticizer.
The concrete test of the inventive example was compared with a commercially available early strength polycarboxylate superplasticizer (comparative example). The mechanical properties of the concrete are carried out according to the method specified in GB/T50080-2002 Standard for testing the mechanical properties of common concrete, and the test results of the C50 concrete are shown in the following table:
TABLE 1 comparison of the Properties of several early Strength type polycarboxylic acid Water reducers
As can be seen from Table 1, compared with the commercial early strength polycarboxylate superplasticizer, the early strength polycarboxylate superplasticizer prepared by the embodiment of the invention has the advantages of high water reducing rate and good concrete workability, and can obviously improve the early strength of concrete.
The foregoing is merely an example of the present invention and common general knowledge of known specific structures and features of the embodiments is not described herein in any greater detail. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.