Process and apparatus for the preparation of carboxymethyl starch

Abstract

The application relates to the technical field of carboxymethyl starch preparation, in particular to a carboxymethyl starch preparation method and device, a feeding pipe is communicated with the top end of a reaction kettle, an open cap is screw-connected to the top end of the feeding pipe, an air feeding pipe is communicated with the other side of the top end of the reaction kettle, an openable outlet door is embedded into the bottom end of the reaction kettle, a heating element is fixedly connected to the inner side of the reaction kettle, a rotating shaft is rotatably connected to the inner side of the reaction kettle, a stirring rod is rotatably connected to the outer side of the rotating shaft, the cross section of the rotating shaft is in a rectangular shape, and the cross section of the stirring rod is in an elliptical shape; when early-stage stirring is carried out, the stirring rod is vertically arranged to increase the contact area with the reactants in the reaction kettle; the cross section of the stirring rod in the application is in an elliptical shape, and the surface areas of the adjacent two sides of the stirring rod are obviously different; in the early stage of the reaction, before the starch particles are obviously expanded, the stirring rod is vertically arranged to increase the stirring area and improve the stirring effect.

Description

Technical Field

[0001] This invention relates to the field of carboxymethyl starch preparation technology, specifically to a method and apparatus for preparing carboxymethyl starch. Background Technology

[0002] Carboxymethyl starch is a water-soluble anionic modified starch. Its products usually exist in the form of sodium salt. It is mainly produced by wet process, solvent process, semi-dry process, dry process, extrusion process, etc. Under alkaline conditions, starch undergoes a nucleophilic substitution reaction with monochloroacetic acid or its sodium salt. The alcohol hydroxyl group on the glucose unit of the starch molecule is replaced by the carboxymethyl group to form a new ether bond. Therefore, it is also called sodium carboxymethyl starch or carboxymethyl starch ether.

[0003] In the preparation of carboxymethyl starch, solvents are added to undergo alkalization and acidification. During alkalization and acidification, stirring is required to ensure effective dispersion. However, as the reaction proceeds and carboxymethyl groups are introduced, the starch particles expand and increase in size. The severe expansion of the starch particles leads to a rapid increase in resistance, making stirring difficult and hindering reagent diffusion. This affects the mass transfer process and thus the degree of substitution of carboxymethyl starch.

[0004] Therefore, a method and apparatus for preparing carboxymethyl starch are proposed to address the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for preparing carboxymethyl starch, in order to solve the problem mentioned in the background art that "as the reaction proceeds and carboxymethyl groups are introduced, the starch granules expand and increase in size, and the severe expansion of the starch granules makes stirring difficult, reagents are difficult to diffuse, and the mass transfer process is affected".

[0006] To achieve the above objectives, the present invention provides the following technical solution: a carboxymethyl starch preparation apparatus, comprising a reaction vessel, a feed pipe connected to the top of the reaction vessel, an open cap spirally connected to the top of the feed pipe, a gas supply pipe connected to the other side of the top of the reaction vessel, an openable outlet door embedded at the bottom of the reaction vessel, and a heating element fixedly connected to the inner side of the reaction vessel.

[0007] In use, the reactants are added through the feed pipe. To ensure the stability of the reaction, an inert gas, such as nitrogen, can be added into the reactor through the gas supply pipe. The gas supply pipe is equipped with a valve that can be switched on or off. After the reaction is completed, the reactants are discharged by opening the outlet door. The heating element is used to maintain the temperature required for the reaction.

[0008] A rotating shaft is rotatably connected to the inner side of the reactor, and a stirring rod is rotatably connected to the outer side of the rotating shaft. The cross-section of the rotating shaft is rectangular, and the cross-section of the stirring rod is elliptical. During the initial stirring, the stirring rod is set vertically to increase the contact area with the reactants inside the reactor.

[0009] The stirring rod in this invention has an elliptical cross-section, and the surface areas of adjacent sides of the stirring rod are significantly different. In the early stage of the reaction, before the starch granules have expanded significantly, the stirring rod is set vertically to increase the stirring area and improve the stirring effect.

[0010] The rotating shaft is connected to the stirring rod. The inner sides of the rotating shaft and the stirring rod are hollow. The inner side of the stirring rod is connected to the inner side of the rotating shaft. One side of the stirring rod is connected to an outlet valve. During later stirring, the outlet valve sprays inert gas. The stirring rod can be rotated to achieve a horizontal setting, changing the contact area with the reactants inside the reactor.

[0011] Under the above settings, the reactor in this invention can provide effective stirring throughout the entire cycle of starch carboxymethylation, reducing or even overcoming the difficulty of stirring caused by the expansion of starch particles, facilitating the diffusion of reagents, and increasing the mass transfer process.

[0012] In this invention, the stirring rod employs two stirring methods. First, in the initial stage of the reaction, when the starch granules have not significantly expanded, the stirring resistance within the reactor is not high. By vertically setting the stirring rod, the stirring area is increased, enhancing the stirring effect. Second, in the later stage of the reaction, the stirring rod is horizontally set. After the starch granules expand, the stirring area is reduced, increasing the continuity of stirring and preventing the stirring rod from getting stuck. Simultaneously, during the later stirring process, inert gas is ejected from the outlet valve on the stirring rod. This inert gas fills the reactants, reducing their density and further facilitating continuous stirring, ensuring effective and continuous stirring. Third, when the stirring rod is horizontally set, the reduced force-bearing area increases the shear force exerted by the stirring rod on the reactants, allowing the solvent to penetrate the starch granule molecular chains during the later stages of the reaction, thus enhancing the reaction effect.

[0013] Preferably, in the preparation apparatus for carboxymethyl starch according to the present invention, the stirring rod is fixedly connected to a connecting rod through the inner side of the rotating shaft. When the stirring rod is in a vertical state, the distances from the upper and lower ends of the stirring rod to the center line of the stirring rod rotation are L1 and L2, respectively, and the length of L2 is greater than L1. The inner side of the rotating shaft is fixedly connected to a first limiting post and a second limiting post. The first limiting post and the second limiting post are respectively arranged on both sides of the connecting rod. When the rotating shaft rotates clockwise, the bottom end of the connecting rod abuts against the second limiting post to keep the stirring rod in a vertical state. When the rotating shaft rotates counterclockwise, the stirring rod rotates 90° counterclockwise and abuts against the first limiting post.

[0014] In the initial stage of the reaction, the motor rotates clockwise. Because the force-bearing area on the lower side of the stirring rod is greater than that on the upper side, the bottom end of the connecting rod abuts against the second limiting post, so the stirring rod is in a vertical state, providing stirring for reactants that do not expand significantly. In the later stage of the reaction, the motor rotates counterclockwise. Because the force-bearing area on the lower side of the stirring rod is greater than that on the upper side, the stirring rod will rotate 90° counterclockwise and abut against the first limiting post, so the stirring rod is in a horizontal state, reducing rotational resistance and ensuring the continuous rotation of the stirring rod.

[0015] Preferably, in the preparation apparatus for carboxymethyl starch according to the present invention, a motor is fixedly connected to the inner side of the bottom end of the reaction vessel, the end of the main shaft of the motor is fixedly connected to the bottom end of the rotating shaft, and a connecting plate is fixedly connected to the top end of the rotating shaft.

[0016] Preferably, in the apparatus for preparing carboxymethyl starch according to the present invention, a crankshaft is rotatably connected to the inner side of the top of the reaction vessel, the bottom end of the crankshaft is rotatably connected to the center of the top of the connecting plate, a ratchet is fixedly connected to the outer side of the bottom end of the crankshaft, a pawl is rotatably connected to the inner side of the connecting plate via a hinge, and a torsion spring is fixedly connected between the pawl and the inner side of the connecting plate. When the connecting plate rotates clockwise, the pawl will slide across the surface of the ratchet, and when the connecting plate rotates counterclockwise, the pawl will lock the ratchet, causing the crankshaft to rotate counterclockwise.

[0017] This invention incorporates a clutch mechanism between the rotating shaft and the crankshaft during clockwise and counterclockwise rotation. While ensuring effective mixing, the initial non-participation of the crankshaft reduces energy consumption.

[0018] Preferably, in the apparatus for preparing carboxymethyl starch according to the present invention, a gas cylinder is fixedly connected to the top of the reaction vessel, a piston is slidably connected to the inner side of the gas cylinder, a slide rod is fixedly connected to one end of the piston near the crankshaft, a connecting rod is rotatably connected to the side of the slide rod near the crankshaft via a hinge, and the other end of the connecting rod is rotatably connected to the outer side of the crankshaft, so that the piston reciprocates in the gas cylinder by the rotation of the crankshaft.

[0019] Preferably, in the apparatus for preparing carboxymethyl starch according to the present invention, the side of the gas cylinder near the crankshaft is connected to a one-way inlet valve and a one-way outlet valve. The input end of the one-way inlet valve is connected to an inlet pipe, the bottom end of the inlet pipe is connected to the inside of the reaction vessel, the output end of the one-way outlet valve is connected to an inflation pipe, the output end of the inflation pipe is connected to a rotary joint, and the output end of the rotary joint is rotatably connected to the top end of the crankshaft.

[0020] In this invention, when the rotating shaft rotates counterclockwise, the gas cylinder can continuously extract the inert gas from the reactor and then return it through the outlet valve on the stirring rod, so that the gas fills the reactants and reduces their density. When the crankshaft rotates, it drives the piston to reciprocate in the gas cylinder. When the piston moves away from the crankshaft, the one-way inlet valve opens, and the inert gas in the reactor enters the gas cylinder. When the piston moves towards the crankshaft, the one-way outlet valve opens, and the gas passes through the gas filling pipe, crankshaft, connecting plate, and rotating shaft, and is discharged through the outlet valve on the stirring rod.

[0021] A method for preparing carboxymethyl starch, comprising the following steps:

[0022] Step 1: Raw material selection. Use corn starch, potato starch or other starches as raw materials.

[0023] Step 2: Soaking and washing. Soak the raw starch in water to remove impurities and some non-starch substances, and then wash it several times to achieve the required purity.

[0024] Step 3: Drying. The washed starch is dried in a dryer to reduce moisture and facilitate subsequent chemical reactions.

[0025] Step 4: Carboxymethylation. Dry starch is placed in a reaction vessel, and an appropriate amount of sodium chloroformate and catalyst are added. The reaction is carried out under certain temperature and pressure conditions to produce sodium starch glycolate. Then, through a neutralization reaction, sodium hydroxide is used to convert it into carboxymethyl starch.

[0026] Step 5: Neutralization and washing. After the reaction is complete, add an alkaline substance to neutralize the excess sodium chloroformate, and then wash several times to remove unreacted sodium chloroformate and other byproducts.

[0027] Step 6: Dehydration and drying. The neutralized and washed carboxymethyl starch is dehydrated by centrifugation or pressure filtration, and then dried again to the predetermined moisture content.

[0028] In a preferred embodiment of the method for preparing carboxymethyl starch according to the present invention, the reaction time in step 4 is between several hours and several days.

[0029] In a preferred embodiment of the method for preparing carboxymethyl starch according to the present invention, the reaction temperature in step 4 is 40°C.

[0030] A method of using a preparation apparatus, comprising the following steps:

[0031] S1, the raw materials and reaction solvent are added by opening the cap, and inert gas is added into the reactor through the gas supply pipe. In the initial stage of the reaction, the motor rotates clockwise. Because the force-bearing area on the lower side of the stirring rod is greater than that on the upper side, the stirring rod is in a vertical state, which provides stirring for the reactants that do not expand significantly.

[0032] S2, in the later stage of the reaction, the motor rotates counterclockwise, driving the crankshaft to rotate. Because the force-bearing area on the lower side of the stirring rod is greater than that on the upper side, the stirring rod will rotate 90° counterclockwise and come into contact with the first limit post. The stirring rod is in a horizontal state, reducing the rotational resistance and ensuring the continuous rotation of the stirring rod. The outlet valve sprays out inert gas, which fills the reactants, reducing their density and further facilitating the continuous stirring.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. In the preparation apparatus for carboxymethyl starch, the reactants are added through a feed pipe. To ensure the stability of the reaction, an inert gas, such as nitrogen, can be added to the reactor through a gas supply pipe. After the reaction is completed, the reactants are discharged through an outlet door. A heating element is used to maintain the temperature during the reaction. A rotating shaft is rotatably connected to the inner side of the reactor, and a stirring rod is rotatably connected to the outer side of the rotating shaft. The rotating shaft has a rectangular cross-section, and the stirring rod has an elliptical cross-section. During the initial stirring, the stirring rod is vertically positioned to increase the contact area with the reactants inside the reactor.

[0035] 2. In this apparatus for preparing carboxymethyl starch, a rotating shaft is connected to a stirring rod. The inner sides of the rotating shaft and the stirring rod are hollow, and the inner side of the stirring rod is connected to the inner side of the rotating shaft. An outlet valve is connected to one side of the stirring rod. During later stirring, the outlet valve sprays inert gas. The stirring rod can be horizontally positioned by rotation, changing the contact area with the reactants inside the reactor. The reactor in this invention can provide effective stirring throughout the entire cycle of starch carboxymethylation, reducing or even overcoming the difficulty of stirring caused by the expansion of starch particles, facilitating reagent diffusion, and increasing the mass transfer process.

[0036] 3. In this apparatus for preparing carboxymethyl starch, the stirring rod has two stirring modes. First, in the initial stage of the reaction, when the starch granules have not expanded significantly, the stirring resistance in the reactor is not very high. By setting the stirring rod vertically, the stirring area is increased, thus enhancing the stirring effect. Second, in the later stage of the reaction, the stirring rod is set horizontally. After the starch granules expand, the stirring area is reduced, increasing the continuity of stirring and preventing the stirring rod from getting stuck. Simultaneously, during the later stirring process, inert gas is sprayed from the outlet valve on the stirring rod. The inert gas fills the reactants, reducing their density and further facilitating continuous stirring, ensuring effective and continuous stirring. When the stirring rod is set horizontally, the reduced force-bearing area increases the shear force of the stirring rod on the reactants, facilitating the solvent to enter the interior of the starch granule molecular chains during the later stages of the reaction, thus increasing the reaction effect.

[0037] 4. In the preparation apparatus for carboxymethyl starch, during the initial stage of the reaction, the motor rotates clockwise. Because the force-bearing area on the lower side of the stirring rod is greater than that on the upper side, the bottom end of the connecting rod abuts against the second limiting post, so the stirring rod is in a vertical state, providing stirring for reactants that do not expand significantly. During the later stage of the reaction, the motor rotates counterclockwise. Because the force-bearing area on the lower side of the stirring rod is greater than that on the upper side, the stirring rod will rotate 90° counterclockwise and abut against the first limiting post, so the stirring rod is in a horizontal state, reducing rotational resistance and ensuring the continuous rotation of the stirring rod.

[0038] 5. In this apparatus for preparing carboxymethyl starch, the gas cylinder continuously extracts inert gas from the reactor when the rotating shaft rotates counterclockwise, and then returns it through the outlet valve on the stirring rod, so that the gas fills the reactants and reduces their density. When the crankshaft rotates, it drives the piston to reciprocate in the gas cylinder. When the piston moves away from the crankshaft, the one-way inlet valve opens, and the inert gas in the reactor enters the gas cylinder. When the piston moves towards the crankshaft, the one-way outlet valve opens, and the gas passes through the gas filling pipe, crankshaft, connecting plate, and rotating shaft, and is discharged through the outlet valve on the stirring rod. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the overall appearance and structure of the present invention;

[0040] Figure 2 This is a schematic diagram of the overall cross-sectional installation structure of the present invention;

[0041] Figure 3 This is a schematic diagram of the external structure of the rotating shaft of the present invention;

[0042] Figure 4 This is a cross-sectional view of the rotating shaft of the present invention;

[0043] Figure 5 This is a schematic diagram of the structure at the connecting rod of the present invention;

[0044] Figure 6 For the present invention Figure 2 Schematic diagram of the installation structure at point A in the diagram;

[0045] Figure 7 For the present invention Figure 3 Schematic diagram of the installation structure at point B in the diagram;

[0046] Figure 8 This is a top view of the mounting structure at the connecting plate of the present invention;

[0047] Figure 9 For the present invention Figure 8 Schematic diagram of the installation structure at point C;

[0048] Figure 10This is a schematic diagram of the external structure of the stirring rod of the present invention in a vertical state;

[0049] Figure 11 This is a schematic diagram of the external structure of the stirring rod of the present invention in a horizontal state.

[0050] In the diagram: 1. Reactor; 2. Feed pipe; 3. Opening cap; 4. Gas cylinder; 5. Inlet pipe; 6. Crankshaft; 7. Gas filling pipe; 8. Rotary joint; 9. Connecting rod; 10. Slide rod; 11. Gas filling pipe; 12. Piston; 13. Heating element; 14. Motor; 15. Rotating shaft; 16. Stirring rod; 17. Outlet valve; 18. Connecting plate; 19. Outlet gate; 20. Connecting rod; 21. First limiting post; 22. Second limiting post; 23. One-way exhaust valve; 24. One-way inlet valve; 25. Pawl; 26. Ratchet; 27. Torsion spring. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1, please refer to Figure 1-11 The present invention provides a technical solution: a carboxymethyl starch preparation device, including a reaction vessel 1, a feed pipe 2 connected to the top of the reaction vessel 1, an open cap 3 spirally connected to the top of the feed pipe 2, a gas supply pipe 11 connected to the other side of the top of the reaction vessel 1, an openable outlet door 19 embedded at the bottom of the reaction vessel 1, and a heating element 13 fixedly connected to the inner side of the reaction vessel 1.

[0053] When using this invention, the reactants are added through the feed pipe 2. In order to ensure the stability of the reaction, the invention can also add an inert gas into the reaction vessel 1 through the gas supply pipe 11. The gas supply pipe 11 is equipped with a valve, such as nitrogen. After the reaction is completed, the reactants are discharged by opening the outlet door 19. The heating element 13 is used to meet the temperature during the reaction.

[0054] A rotating shaft 15 is rotatably connected to the inner side of the reactor 1, and a stirring rod 16 is rotatably connected to the outer side of the rotating shaft 15. The cross-section of the rotating shaft 15 is rectangular, and the cross-section of the stirring rod 16 is elliptical. During the initial stirring, the stirring rod 16 is vertically positioned to increase the contact area with the reactants inside the reactor 1.

[0055] The stirring rod 16 in this invention has an elliptical cross-section, and the surface areas of adjacent sides of the stirring rod 16 are significantly different. In the early stage of the reaction, before the starch granules have expanded significantly, the stirring rod 16 is set vertically to increase the stirring area and increase the stirring effect.

[0056] The rotating shaft 15 is connected to the stirring rod 16. The inner sides of the rotating shaft 15 and the stirring rod 16 are hollow. The inner side of the stirring rod 16 is connected to the inner side of the rotating shaft 15. One side of the stirring rod 16 is connected to the outlet valve 17. During the later stirring, the outlet valve 17 sprays out inert gas. The stirring rod 16 can be set horizontally by rotating, changing the contact area with the reactants inside the reactor 1.

[0057] Under the above settings, the reaction vessel 1 in this invention can provide effective stirring throughout the entire cycle of starch carboxymethylation, reducing or even overcoming the difficulty of stirring caused by the expansion of starch particles, facilitating the diffusion of reagents, and increasing the mass transfer process.

[0058] In this invention, the stirring rod 16 has two stirring modes. In the initial stage of the reaction, when the starch granules have not expanded significantly, the stirring resistance in the reactor is not very high. By setting the stirring rod 16 vertically, the stirring area is increased, thus enhancing the stirring effect. In the later stage of the reaction, the stirring rod 16 is set horizontally. After the starch granules expand, the stirring area is reduced, increasing the continuity of stirring and preventing the stirring rod 16 from getting stuck. At the same time, during the later stirring process, the outlet valve 17 on the stirring rod 16 sprays inert gas. The inert gas fills the reactants, reducing their density and further facilitating continuous stirring, ensuring effective and continuous stirring. When the stirring rod 16 is set horizontally, the shear force of the stirring rod 16 on the reactants increases due to the reduced force-bearing area. This facilitates the solvent entering the interior of the starch granule molecular chains during the later stages of the reaction, increasing the reaction effect.

[0059] Preferably, in the preparation apparatus for carboxymethyl starch according to the present invention, a stirring rod 16 is fixedly connected to a connecting rod 20 through the inner side of a rotating shaft 15. When the stirring rod 16 is in a vertical state, the distances from the upper and lower ends of the stirring rod 16 to the center line of rotation of the stirring rod 16 are L1 and L2, respectively, and the length of L2 is greater than L1. A first limiting post 21 and a second limiting post 22 are fixedly connected to the inner side of the rotating shaft 15. The first limiting post 21 and the second limiting post 22 are respectively arranged on both sides of the connecting rod 20. When the rotating shaft 15 rotates clockwise, the bottom end of the connecting rod 20 abuts against the second limiting post 22, so that the stirring rod 16 is in a vertical state. When the rotating shaft 15 rotates counterclockwise, the stirring rod 16 rotates 90° counterclockwise and abuts against the first limiting post 21.

[0060] In the initial stage of the reaction, the motor 14 rotates clockwise. Because the force-bearing area on the lower side of the stirring rod 16 is greater than that on the upper side, the bottom end of the connecting rod 20 abuts against the second limiting post 22, so the stirring rod 16 is in a vertical state, providing stirring for reactants that do not expand significantly. In the later stage of the reaction, the motor 14 rotates counterclockwise. Because the force-bearing area on the lower side of the stirring rod 16 is greater than that on the upper side, the stirring rod 16 will rotate 90° counterclockwise and abut against the first limiting post 21, so the stirring rod 16 is in a horizontal state, reducing rotational resistance and ensuring the continuous rotation of the stirring rod 16.

[0061] Preferably, in the preparation apparatus for carboxymethyl starch according to the present invention, a motor 14 is fixedly connected to the inner side of the bottom end of the reaction vessel 1, the end of the main shaft of the motor 14 is fixedly connected to the bottom end of the rotating shaft 15, and a connecting plate 18 is fixedly connected to the top end of the rotating shaft 15.

[0062] Preferably, in the apparatus for preparing carboxymethyl starch according to the present invention, a crankshaft 6 is rotatably connected to the inner side of the top of the reactor 1, the bottom end of the crankshaft 6 is rotatably connected to the center of the top of the connecting plate 18, a ratchet 26 is fixedly connected to the outer side of the bottom end of the crankshaft 6, and a pawl 25 is rotatably connected to the inner side of the connecting plate 18 via a hinge. A torsion spring 27 is fixedly connected between the pawl 25 and the inner side of the connecting plate 18. When the connecting plate 18 rotates clockwise, the pawl 25 will pass over the surface of the ratchet 26. When the connecting plate 18 rotates counterclockwise, the pawl 25 will lock the ratchet 26, causing the crankshaft 6 to rotate counterclockwise.

[0063] The present invention incorporates a clutch mechanism between the rotating shaft 15 and the crankshaft 6 during clockwise and counterclockwise rotation. This mechanism ensures effective stirring while reducing energy consumption because the crankshaft 6 is not initially involved.

[0064] Preferably, in the preparation apparatus for carboxymethyl starch of the present invention, a gas cylinder 4 is fixedly connected to the top of the reaction vessel 1, a piston 12 is slidably connected to the inner side of the gas cylinder 4, a slide rod 10 is fixedly connected to one end of the piston 12 near the crankshaft 6, a connecting rod 9 is rotatably connected to the side of the slide rod 10 near the crankshaft 6 via a hinge, and the other end of the connecting rod 9 is rotatably connected to the outer side of the crankshaft 6, so that the piston 12 reciprocates in the gas cylinder 4 by the rotation of the crankshaft 6.

[0065] Preferably, in the preparation apparatus for carboxymethyl starch according to the present invention, the side of the gas cylinder 4 near the crankshaft 6 is connected to a one-way inlet valve 24 and a one-way outlet valve 23. The input end of the one-way inlet valve 24 is connected to an inlet pipe 5, the bottom end of the inlet pipe 5 is connected to the inside of the reaction vessel 1, the output end of the one-way outlet valve 23 is connected to an inflation pipe 7, the output end of the inflation pipe 7 is connected to a rotary joint 8, and the output end of the rotary joint 8 is rotatably connected to the top end of the crankshaft 6.

[0066] In this invention, when the rotating shaft 15 rotates counterclockwise, the gas cylinder 4 can continuously extract the inert gas from the reactor 1 and then return it through the outlet valve 17 on the stirring rod 16, so that the gas fills the reactant and reduces its density. When the crankshaft 6 rotates, it drives the piston 12 to reciprocate in the gas cylinder 4. When the piston 12 moves away from the crankshaft 6, the one-way inlet valve 24 opens, and the inert gas in the reactor 1 enters the gas cylinder 4. When the piston 12 moves towards the crankshaft 6, the one-way outlet valve 23 opens, and the gas passes through the gas filling pipe 7, the crankshaft 6, the connecting plate 18, and the rotating shaft 15, and is discharged through the outlet valve 17 on the stirring rod 16.

[0067] The present invention also discloses a method of using a carboxymethyl starch preparation apparatus, the steps of which are as follows:

[0068] S1, the raw materials and reaction solvent are added by opening the opening cap 3, and inert gas is added into the reaction vessel 1 through the gas filling pipe 11. In the initial stage of the reaction, the motor 14 rotates clockwise. Because the force-bearing area on the lower side of the stirring rod 16 is greater than the force-bearing area on the upper side, the stirring rod 16 is in a vertical state, providing stirring for the reactants that do not expand significantly.

[0069] S2, in the later stage of the reaction, the motor 14 rotates counterclockwise, driving the crankshaft 6 to rotate. Because the force-bearing area on the lower side of the stirring rod 16 is greater than that on the upper side, the stirring rod 16 will rotate 90° counterclockwise and come into contact with the first limiting post 21. The stirring rod 16 is in a horizontal state, reducing the rotational resistance and ensuring the continuous rotation of the stirring rod 16. The outlet valve 17 sprays out inert gas, which fills the reactants, reducing their density and further facilitating the continuous stirring.

[0070] This invention also discloses a method for preparing carboxymethyl starch, the steps of which are:

[0071] Step 1: Raw material selection. Use corn starch, potato starch or other starches as raw materials.

[0072] Step 2: Soaking and washing. Soak the raw starch in water to remove impurities and some non-starch substances, and then wash it several times to achieve the required purity.

[0073] Step 3: Drying. The washed starch is dried in a dryer to reduce moisture and facilitate subsequent chemical reactions.

[0074] Step 4: Carboxymethylation. Dry starch is placed in reactor 1, and an appropriate amount of sodium chloroformate (NaOCCl) and catalyst are added. The reaction is carried out under certain temperature and pressure conditions to produce sodium starch alkoxide. Then, through a neutralization reaction, sodium hydroxide is used to convert it into carboxymethyl starch.

[0075] Step 5: Neutralization and washing. After the reaction is complete, add an alkaline substance to neutralize the excess sodium chloroformate, and then wash several times to remove unreacted sodium chloroformate and other byproducts.

[0076] Step 6: Dehydration and drying. The neutralized and washed carboxymethyl starch is dehydrated by centrifugation or pressure filtration, and then dried again to the predetermined moisture content.

[0077] In a preferred embodiment of the method for preparing carboxymethyl starch according to the present invention, the reaction time in step 4 is between several hours and several days.

[0078] In a preferred embodiment of the method for preparing carboxymethyl starch according to the present invention, the reaction temperature in step 4 is 40°C.

[0079] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for preparing carboxymethyl starch, comprising a reactor (1), characterized in that: The top end of the reaction kettle (1) is communicated with a feeding pipe (2), the top end of the feeding pipe (2) is screw-connected with an open cap (3), the other side of the top end of the reaction kettle (1) is communicated with a gas feeding pipe (11), the bottom end of the reaction kettle (1) is embedded with an openable outlet door (19), the inner side of the reaction kettle (1) is fixedly connected with a heating element (13); the inner side of the reaction kettle (1) is rotatably connected with a rotating shaft (15), the outer side of the rotating shaft (15) is rotatably connected with a stirring rod (16), the section of the rotating shaft (15) is arranged in a rectangular shape, the section of the stirring rod (16) is arranged in an oval shape; the rotating shaft (15) is communicated with the stirring rod (16), the inner sides of the rotating shaft (15) and the stirring rod (16) are hollow, the inner side of the stirring rod (16) is communicated with the inner side of the rotating shaft (15), one side of the stirring rod (16) is communicated with an outlet valve (17); the stirring rod (16) is fixedly connected with a connecting rod (20) through the inner side of the rotating shaft (15), in the vertical state of the stirring rod (16), the distances from the upper end and the lower end of the stirring rod (16) to the rotating center line of the stirring rod (16) are L1 and L2 respectively, and the length of L2 is greater than the length of L1, the inner side of the rotating shaft (15) is fixedly connected with a first limiting column (21) and a second limiting column (22), the first limiting column (21) and the second limiting column (22) are arranged on the two sides of the connecting rod (20) respectively, when the rotating shaft (15) rotates clockwise, the bottom end of the connecting rod (20) abuts against the second limiting column (22) to make the stirring rod (16) in the vertical state, when the rotating shaft (15) rotates counterclockwise, the stirring rod (16) rotates counterclockwise by 90° and abuts against the first limiting column (21); the bottom end of the inner side of the reaction kettle (1) is fixedly connected with a motor (14), the main shaft end of the motor (14) is fixedly connected with the bottom end of the rotating shaft (15), the top end of the rotating shaft (15) is fixedly connected with a connecting disc (18), and the top end of the rotating shaft (15) is communicated with the center of the connecting disc (18); the top end of the inner side of the reaction kettle (1) is rotatably connected with a crankshaft (6), the bottom end of the crankshaft (6) is rotatably connected with the top center of the connecting disc (18) and is communicated, the bottom end of the outer side of the crankshaft (6) is fixedly connected with a ratchet wheel (26), the inner side of the connecting disc (18) is rotatably connected with a ratchet pawl (25) through a hinge, the ratchet pawl (25) and the inner side of the connecting disc (18) are fixedly connected with a torsional spring (27), when the connecting disc (18) rotates clockwise, the ratchet pawl (25) will slide across the surface of the ratchet wheel (26), when the connecting disc (18) rotates counterclockwise, the ratchet pawl (25) will be clamped in the ratchet wheel (26) to drive the crankshaft (6) to rotate counterclockwise.The top end of the reaction kettle (1) is fixedly connected with a gas cylinder (4), the inner side of the gas cylinder (4) is slidably connected with a piston (12), one end of the piston (12) close to the crankshaft (6) is fixedly connected with a slide rod (10), one side of the slide rod (10) close to the crankshaft (6) is rotatably connected with a connecting rod (9) through a hinge, the other end of the connecting rod (9) is rotatably connected with the outer side of the crankshaft (6), the reciprocating motion of the piston (12) in the gas cylinder (4) is realized through the rotation of the crankshaft (6); one side of the gas cylinder (4) close to the crankshaft (6) is communicated with a one-way air inlet valve (24) and a one-way air outlet valve (23), the input end of the one-way air inlet valve (24) is communicated with an air inlet pipe (5), the bottom end of the air inlet pipe (5) is communicated with the inner side of the reaction kettle (1), the output end of the one-way air outlet valve (23) is communicated with a gas charging pipe (7), the output end of the gas charging pipe (7) is communicated with a rotary joint (8), and the output end of the rotary joint (8) is rotatably connected with the top end of the crankshaft (6).

2. A process for the preparation of carboxymethyl starch, characterized in that, The steps are as follows using the preparation device of claim 1: Step 1: raw material selection, using corn starch, potato starch or other sources of starch as the original raw material; Step 2: soaking and washing, soaking the raw starch in water to remove impurities and part of the non-starch substances, and then washing multiple times to meet the purity requirements; Step 3: drying, the washed starch is dried by a dryer to reduce moisture for subsequent chemical reactions; Step 4: carboxymethylation, the dried starch is placed in a reaction kettle (1), an appropriate amount of sodium chloroformate and a catalyst are added, and the reaction is carried out under certain temperature and pressure conditions, the reaction generates sodium starch glycolate, which is then converted into carboxymethyl starch by neutralization reaction with sodium hydroxide; Step 5: neutralization and washing, after the reaction is completed, an alkaline substance is added to neutralize the excess sodium chloroformate, and then multiple washings are performed to remove unreacted sodium chloroformate and other by-products; Step 6: dehydration and drying, the neutralized and washed carboxymethyl starch is dehydrated by centrifugation or pressure filtration, and then dried again to a predetermined moisture content.

3. The method for preparing carboxymethyl starch according to claim 2, characterized in that, In step 4, the reaction time is between several hours and several days.

4. The method of preparing carboxymethyl starch according to claim 3, characterized in that, In step 4, the reaction temperature is 40°C.

5. A method of using the preparation device of claim 1, wherein, The steps are as follows; S1, by opening the opening cap (3), the raw material and the reaction solvent are added, and inert gas is added to the reaction kettle (1) through the gas inlet pipe (11), in the initial stage of the reaction, the motor (14) rotates clockwise, because the force area of the lower side of the stirring rod (16) is greater than that of the upper side, the stirring rod (16) is in a vertical state, providing stirring for the reaction material with little expansion; S2, in the later stage of the reaction, the motor (14) rotates counterclockwise, driving the crankshaft (6) to rotate, because the force area of the lower side of the stirring rod (16) is greater than that of the upper side, the stirring rod (16) will rotate counterclockwise by 90° and be in contact with the first limiting column (21), the stirring rod (16) is in a horizontal state, reducing the rotation resistance and ensuring the continuous rotation of the stirring rod (16), the outlet valve (17) sprays inert gas, which fills the reaction material, further facilitating the continuous stirring.

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