A belt-type polymerization device for continuous production of super absorbent resin

Abstract

The present invention discloses a belt-type polymerization apparatus for continuously producing a superabsorbent resin. The belt-type polymerization apparatus has the following structure: (a) a polymerization reaction belt is evenly divided into a plurality of zones, wherein the number of zones M is ≥ 2; (b) the polymerization reaction belt is evenly divided into a plurality of zones, wherein the number of polymerization reaction device feed ports N is ≥ 2; and (c) the cross-sectional area ratio of the belt-type polymerization device ranges from 1 to 500, wherein the cross-sectional area ratio of the belt-type polymerization device = A / B, where A represents the cross-sectional area between the reaction belt and the ceiling of the polymerization reaction device in the width direction; and B represents the total cross-sectional area of ​​the reaction liquid on the reaction belt in the width direction before the polymerization reaction begins. The belt-type polymerization apparatus has the following beneficial effects: reducing the cross-sectional area ratio in the belt-type polymerization apparatus is beneficial for improving pressurization performance. A reduced cross-sectional area ratio reduces heat loss in the reaction device, which is beneficial for improving the strength of the superabsorbent resin.

Description

Technical Field

[0001] The present invention relates to the technical field of resin polymer belt polymerization equipment, and in particular to a belt polymerization equipment for continuously producing super absorbent resin. The polymerization equipment can more fully utilize the heat of neutralization and the reaction heat during the polymerization reaction, and is suitable for preparing high-expansion super absorbent resin materials during the implosion process. Background Art

[0002] Superabsorbent polymer (SAP), a polymer material capable of absorbing hundreds or even thousands of times its own weight in water, is widely used in sanitary products, agricultural and forestry water-retention agents, construction waterproofing materials, and food preservation ice packs. Currently, with increasing awareness of health and hygiene, the rise of sanitary products such as baby diapers, sanitary napkins, and adult diapers has significantly driven the rapid development of the superabsorbent polymer industry.

[0003] The belt polymerization process utilizes free radical polymerization, resulting in a very fast reaction speed, effectively shortening polymerization time and achieving high production efficiency. By fully utilizing the heat of acid-base neutralization and the heat of dissolution of the liquid caustic soda to reach the initiation temperature, energy consumption can be reduced. However, since the production of polyacrylate-based SAPs involves an implosion process, belt polymerization units are often large and tall to accommodate the height and volume expansion of the polymer during implosion. This results in heat loss and prevents more efficient utilization of the polymerization reaction heat.

[0004] In recent years, as the energy crisis continues to sweep the world, in order to respond to energy conservation and emission reduction and make full use of the heat generated during the polymerization reaction, it is urgent to optimize the distance between the ceiling of the reaction device and the reaction belt in the current belt reaction process. On the one hand, it can effectively reduce heat loss, and on the other hand, it can make more full use of neutralization heat and reaction heat, thereby reducing energy consumption in the reaction device.

[0005] US2005 / 0215734A1 points out that when the reactor height ratio is too low, the polymer that expands during the reaction may stick to the ceiling, resulting in an increase in the residual monomer content of the product and even preventing normal production. Products that experience particularly significant expansion during the polymerization reaction often require taller reactors.

[0006] In summary,

[0007] The present invention can realize low-cost modification of reaction equipment and produce some products with particularly significant expansion effects during the reaction process. The belt-type polymerization equipment for continuously producing superabsorbent resin can more fully utilize the neutralization heat and reaction heat during the polymerization reaction. Summary of the Invention

[0008] The technical problems to be solved by the present invention are:

[0009] A belt-type polymerization apparatus for continuously producing superabsorbent resin is provided. The belt-type polymerization apparatus divides a continuous belt-type polymerization reaction belt into several equal zones, thereby reducing the amount of solution in each reaction zone on the reaction belt, thereby reducing the amount of polymerization reactants in each reaction zone, and further reducing the expansion height of the polymer during implosion. This facilitates the production of products with particularly significant expansion effects during the reaction. Since the polymer expansion height is reduced after the zones are divided, the cross-sectional area ratio of the polymerization reaction apparatus can be reduced. While ensuring that the polymer gel does not contact the sides of the reaction bed or the ceiling during the polymerization reaction, this helps reduce heat loss during the polymerization process, more effectively utilizes the heat of neutralization and the reaction heat during the polymerization reaction, and ultimately reduces energy consumption.

[0010] A belt-type polymerization device for continuously producing super absorbent resin.

[0011] The structure of the belt polymerization equipment is set as follows:

[0012] (a) dividing the polymerization reaction zone into a number of equal zones, wherein the number of zones M is ≥ 2;

[0013] (b) the polymerization reaction zone is equally divided into a plurality of zones, and the number of feed ports N of the polymerization reaction device is ≥ 2;

[0014] (c) The cross-sectional area ratio of the belt polymerization device ranges from 1 to 500.

[0015] The cross-sectional area ratio of the belt polymerization device = A / B, where A represents the cross-sectional area between the reaction belt and the ceiling of the polymerization reaction device in the width direction; and B represents the total cross-sectional area of ​​the reaction liquid on the reaction belt in the width direction before the polymerization reaction begins.

[0016] In this scheme, the cross-sectional area ratio of the belt polymerization device ranges from 1 to 500: if the cross-sectional area ratio is too low, the expanded polymer during the reaction may stick to the ceiling, affecting normal production; if the cross-sectional area ratio is too high, the reaction heat cannot be fully utilized and the equipment cost is high.

[0017] Both sides of the belt polymerization equipment and the inner side of the ceiling are made of heat insulation materials, such as polyurethane foam materials, rock wool, polystyrene boards, heat reflective materials, porous materials, etc.

[0018] As a further improvement of this solution, before the polymerization reaction starts, the total cross-sectional area B of the reaction liquid on the reaction zone in the width direction is B=S1+S2+S3+...+Sn, where n is determined by the number of equally divided regions.

[0019] As a further improvement of this solution, the polymerization reaction zone is equally divided into M regions, and the number of regions M ranges from 2 to 10.

[0020] More preferably, the number is 2 to 5.

[0021] As a further improvement of this solution, the polymerization reaction zone is equally divided into several areas, and the number N of feed ports of the polymerization reaction device ranges from 2 to 10.

[0022] In this embodiment, the number of feed ports N of the polymerization reaction device is preferably 2 to 5, and the number of feed ports of the polymerization reaction device increases as the number of reaction zone divisions increases. In order to prevent the neutralization liquid from polymerizing in the feed channel, the initiator required for polymerization is added separately to each branch channel of the feed port ( Figure 3 not shown).

[0023] As a further improvement of this solution, the initiator required for the polymerization reaction is introduced into each sub-channel of the feed channel respectively.

[0024] As a further improvement of this solution, both sides of the belt polymerization equipment and the inner side of the ceiling are made of heat insulation materials.

[0025] As a further improvement of this solution, the polymerization reaction belt is divided into M equal areas using beading strips in the moving direction, and the beading strip material is any one of silicone, polyurethane, and rubber.

[0026] As a further improvement of this solution, the material of the layering strip is high-strength and high-temperature resistant silicone.

[0027] In this scheme, the reaction components in the belt-type polymerization equipment for continuous production of super absorbent resin are as follows:

[0028] The polyacrylate-based superabsorbent resin is a cross-linked polymer formed by polymerizing monomers containing at least 45 mol %, preferably at least 70 mol %, of acrylic acid salt.

[0029] As a further improvement, the starting temperature is between 50 and 100°C.

[0030] If the temperature is low, the polymerization time will be prolonged, which will reduce the production efficiency. The pressure absorption rate will also be lost at low temperature. If the temperature is too high, it will easily lead to insufficient crosslinking and increase the residual monomers. The polymerization starting temperature is preferably 50-100°C, and more preferably between 70-90°C.

[0031] As a further improvement, the polymer cross-linking agent is not particularly limited and can use substances containing bifunctional groups or even multifunctional groups, such as any one or more of N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, pentaerythritol triallyl ether, pentaerythritol triacrylate, pentaerythritol tetraacrylate, triallylamine, triallyl phosphate, and polyethyleneimine.

[0032] As a further improvement, the polymerization initiator is preferably a thermal decomposition initiator, and may be one or more selected from sodium persulfate, potassium persulfate, ammonium persulfate, sodium peracetate, sodium percarbonate, hydrogen peroxide, tert-butyl peroxide, azoamidine compounds, and azoamide compounds. The amount of the initiator in the present invention is preferably 0.001-0.50 wt%, more preferably 0.01-0.20 wt%.

[0033] When the initiator dosage is low, the unreacted monomers and residual monomers increase. When the initiator dosage is high, the water-soluble components increase.

[0034] The gel-like polymer obtained in the polymerization process is subjected to a gel crushing process and dried under specific temperature conditions to obtain a dry product. The particle size of the water-absorbent resin in the present invention is preferably adjusted to a specific range by crushing or classification. Water-absorbent resins with a particle size exceeding 850μm have an enhanced granular feel, and if used in sanitary products such as diapers, they may cause skin comfort to deteriorate. Water-absorbent resins with a particle size less than 45μm have serious dusting and may also cause blockage and affect water absorption performance. Particles of 300 to 600μm based on the JIS standard sieve are preferably 60% or more, and the average particle size is preferably between 350-500μm.

[0035] Further surface crosslinking of the dried and pulverized water-absorbent resin can increase its water absorption rate under pressure. Suitable surface crosslinking agents can include bifunctional or even multifunctional substances. Considering the safety of the materials, polyol compounds such as diethylene glycol, triethylene glycol, tetraethylene glycol, ethylene glycol, polyethylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, and 1,6-hexanediol are preferred.

[0036] In order to make the water-absorbent resin and the surface cross-linking agent mix more uniformly, the amount of volatile hydrophilic solvent added can be increased, preferably 50-90 wt %, more preferably 70-90 wt %, and even more preferably 80-85 wt %, and preferably a solvent with a boiling point below 150° C., such as water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1) This patent divides the continuous belt polymerization reaction belt into several equal zones, thereby reducing the amount of solution in a single reaction zone on the reaction belt and lowering the expansion height of the polymer during the implosion process, which is conducive to the production of products with particularly significant expansion effects during the reaction process;

[0039] 2) While ensuring that the polymer gel does not contact the sides and ceiling of the reaction bed during the polymerization reaction, the cross-sectional area ratio of the polymerization reaction device is reduced, which is beneficial to reducing heat loss during the polymerization process, more fully utilizing the neutralization heat and reaction heat during the polymerization reaction, and thus effectively reducing energy consumption;

[0040] 3) The reduction in heat loss during the polymerization process helps to improve the strength of the absorbent resin and is beneficial to the pressure absorption performance of the super absorbent resin particles. Through the mutual cooperation of this formula, equipment and process conditions, the neutralization heat and the reaction heat during the polymerization reaction are fully utilized, and the overall performance of the obtained resin is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic cross-sectional view in the width direction of a reaction zone divided into two zones in a continuous belt reactor;

[0042] The shaded portion A is the cross section between the reaction zone and the ceiling of the polymerization reactor;

[0043] Figure 2 It is a schematic cross-sectional view in the width direction of a reaction zone divided into two zones containing a reaction liquid in a continuous belt reactor;

[0044] The shaded parts S1 and S2 are the cross sections of the reaction liquid on the reaction zone divided into two areas, and B=S1+S2.

[0045] Figure 3 From left to right are schematic diagrams of the reaction liquid feed inlet with two channels, three channels, four channels and N channels.

[0046] Description of Reference Numerals

[0047] 1-reaction zone;

[0048] 2- side walls of the polymerization reaction equipment;

[0049] 3- Ceiling of polymerization equipment;

[0050] 4- Layering strips on the reaction belt to divide the area. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described below with reference to the following embodiments:

[0052] In the embodiments, wt% refers to mass percentage. The performance test methods in the embodiments and comparative examples are as follows:

[0053] (a) Salt water absorption rate

[0054] Free Swelling Capacity (FSC) refers to the free swelling water absorption rate of a unit mass of superabsorbent resin in salt water within a certain period of time.

[0055] Specifically, it refers to the water absorption rate (unit: g / g) after weighing 0.2000g of superabsorbent resin in a tea bag, immersing it in a 0.9wt% sodium chloride aqueous solution for 30 minutes to allow it to swell freely, and then hanging it for 10 minutes to remove the water. 吸水后 -m 样 -m 空白 ) / m 样 .

[0056] (b) Centrifugal water retention

[0057] Centrifuge Retention Capacity (CRC) refers to the water absorption rate of a unit mass of superabsorbent resin after free swelling in saline for a certain period of time and the removal of water by a centrifuge.

[0058] Specifically, it refers to the water absorption rate (unit: g / g) after weighing 0.2000g of superabsorbent resin in a tea bag, immersing it in a 0.9wt% sodium chloride aqueous solution for 30 minutes to allow it to swell freely, and then removing the water in a centrifuge (centrifugal force of 250g). Centrifugal water retention rate = (m 离心后 -m 样 -m 空白 ) / m 样 .

[0059] (c) Pressurized absorption rate

[0060] Absorption Under Pressure (AUP) refers to the water absorption rate of a unit mass of superabsorbent resin under a certain time and a certain pressure.

[0061] In fact, urine composition varies depending on the growth level of the human body, eating habits, and the environment in which it lives. If physiological saline is used as the test solution alone, it is not enough to reflect the actual absorption of urine by the water-absorbent resin material. Even due to different postures of the human body, such as static sitting, standing, and dynamic movement, the absorption rate of the water-absorbent resin under no pressure is not enough to reflect the absorption rate of the water-absorbent resin under actual human movement. Therefore, this patent starts from the water absorption rate of different solutions of the water-absorbent resin under pressure to more realistically reflect the actual application of the water-absorbent resin in the field of health. The following is the specific test method:

[0062] Pressurized absorption rate of 0.9% sodium chloride solution

[0063] Water absorption rate (unit: g / g) after 0.9000 g of the water-absorbent resin is swollen in a 0.9 wt% sodium chloride aqueous solution under a load of 4.83 kPa for 1 hour. 吸水后 -m 吸水前 ) / m 样 .

[0064] Pressurized absorption rate of artificial urine

[0065] The water absorption rate (unit: g / g) after 0.9000 g of the water-absorbent resin is swollen in artificial urine solution for 1 hour under a load of 4.83 kPa. 吸水后 -m 吸水前 ) / m 样 .

[0066] Artificial urine: sodium sulfate 0.2wt%, potassium chloride 0.2wt%, magnesium chloride hexahydrate 0.05wt%, calcium chloride dihydrate 0.025wt%, ammonium dihydrogen phosphate 0.085wt%, diammonium hydrogen phosphate 0.015wt%, deionized water 99.425wt%.

[0067] Example 1

[0068] The total width of the reaction zone in the polymerization reaction apparatus is 32 cm, and the distance between the reaction zone and the apparatus ceiling is 35 cm. The reaction zone is divided into two zones in the direction of movement using silicone strips, each 16 cm wide. 295 parts of a neutralized sodium acrylate solution mixed with 4.0 parts of 10 wt% polyethylene glycol diacrylate is divided equally into two solutions via a Y-shaped feed channel. These solutions are then mixed with 1.0 part of 5 wt% sodium persulfate in each channel and added to the reaction zone. The liquid layer thickness is 5 mm, the neutralizing solution temperature is 85°C, and the reaction zone speed is 5 m / min. After the reaction, a hydrogel is obtained. Granulation is performed using a granulator to obtain an amorphous, crushed gel. The granulated gel is placed in a forced air drying oven and dried for 1 hour at 190°C.

[0069] The dried gel was then pulverized using a grinder and sieved to obtain a sample with a particle size of 150-600 microns. A certain amount of this sample was then heat-treated with a surface crosslinker consisting of 3-propylene glycol, ethylene carbonate, and deionized water in a ratio of 0.5:0.7:5.0 to obtain a primary surface-treated sample. A secondary surface treatment was then performed using a solution of sodium lactate, aluminum sulfate, and water at a concentration of 0.6 wt% for 20 minutes at 60°C. The sample was sieved to obtain a sample with an average particle size of 400 μm, resulting in a highly absorbent resin material.

[0070] Example 2

[0071] In Example 2, the distance between the reaction zone and the apparatus ceiling was changed to 15 cm, the neutralization solution temperature was changed to 78°C, and the reaction zone was divided into four zones along the travel direction using silicone strips, each zone being 8 cm wide. A four-channel feed port was used, with 0.5 parts of 5 wt% sodium persulfate mixed in each channel. Other than this, the same procedures as in Example 1 were followed.

[0072] Comparative Example 1

[0073] The reaction zone in the polymerization apparatus has a width of 32 cm and a distance of 60 cm between the reaction zone and the apparatus ceiling. 295 parts of a neutralized solution of sodium acrylate, mixed with 4.0 parts of 10 wt% polyethylene glycol diacrylate and 2.8 parts of 5 wt% sodium persulfate, are added to the reaction zone to a thickness of 5 mm. The neutralization solution temperature is 85°C and the reaction zone speed is 5 m / min. After the reaction is completed, a hydrogel is obtained. Granulation is performed in a granulator to produce an amorphous, crushed gel. The granulated gel is then dried in a forced air drying oven at 190°C for 1 hour.

[0074] The dried gel was then pulverized using a grinder and sieved to obtain a sample with a particle size of 150-600 microns. A certain amount of this sample was then heat-treated with a surface crosslinker consisting of 3-propylene glycol, ethylene carbonate, and deionized water in a ratio of 0.5:0.7:5.0 to obtain a primary surface-treated sample. A secondary surface treatment was then performed using a solution of sodium lactate, aluminum sulfate, and water at a concentration of 0.6 wt% for 20 minutes at 60°C. The sample was sieved to obtain a sample with an average particle size of 400 μm, resulting in a highly absorbent resin material.

[0075] Table 1: Performance test table of high absorbent resin of the present invention

[0076]

[0077] The experimental data from the Examples and Comparative Examples in Table 1 demonstrate that reducing the cross-sectional area ratio improves pressurization performance. This is presumably because a lower cross-sectional area ratio reduces heat loss within the reactor, which in turn improves the strength of the water-absorbent resin. The increased number of reaction zones reduces the height of polymer expansion. Under the same production load, reactors with lower cross-sectional area ratios can still meet production requirements.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent transformations made using the present invention are within the scope of patent protection of the present invention.

Claims

1. A belt-type polymerization device for continuously producing super absorbent resin, characterized in that: The structure of the belt polymerization equipment is set as follows: (a) dividing the polymerization reaction zone into a number of equal zones, wherein the number of zones M is ≥ 2; (b) the polymerization reaction zone is equally divided into a number of zones, and the number of feed ports N of the belt polymerization equipment is ≥ 2; (c) The cross-sectional area ratio of the belt polymerization device ranges from 30 to 70, where the cross-sectional area ratio of the belt polymerization device = A / B, where A represents the cross-sectional area between the reaction belt and the ceiling of the belt polymerization device in the width direction; and B represents the total cross-sectional area of ​​the reaction liquid on the reaction belt in the width direction before the polymerization reaction begins. The polymerization reaction belt is divided into M equal areas by using layering strips in the moving direction, and the layering strips are made of any one of silicone, polyurethane, and rubber.

2. The belt-type polymerization equipment for continuous production of super absorbent resin according to claim 1, characterized in that: Before the start of the polymerization reaction, the total cross-sectional area B of the reaction liquid on the reaction zone in the width direction is B=S1+S2+S3+...+Sn, where n is determined by the number of equally divided regions.

3. The belt-type polymerization equipment for continuous production of super absorbent resin according to claim 1, characterized in that: The polymerization reaction zone is equally divided into M regions, and the number of regions M ranges from 2 to 10.

4. The belt-type polymerization equipment for continuous production of super absorbent resin according to claim 1, characterized in that: The polymerization reaction zone is equally divided into M regions, and the number of regions M ranges from 2 to 5.

5. The belt-type polymerization equipment for continuous production of super absorbent resin according to claim 1, characterized in that: The number N of feed ports of the belt polymerization equipment ranges from 2 to 10.

6. The belt-type polymerization equipment for continuous production of super absorbent resin according to claim 1, characterized in that: The number of feed ports N of the belt polymerization equipment is 2 to 5.

7. The belt-type polymerization equipment for continuous production of super absorbent resin according to claim 1, characterized in that: The initiator required for the polymerization reaction is introduced into each branch channel of the feed channel respectively.

8. The belt-type polymerization equipment for continuous production of super absorbent resin according to claim 1, characterized in that: Both sides of the belt-type polymerization equipment and the inner side of the ceiling are made of heat-insulating materials.

9. The belt-type polymerization equipment for continuous production of super absorbent resin according to claim 1, characterized in that: The material of the layering strip is high-strength and high-temperature resistant silicone.

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