CN117143282A - Preparation method and application of low molecular weight amphoteric dry powder type polyacrylamide - Google Patents

Abstract

The invention belongs to the technical field of polymer preparation, and in particular relates to a preparation method and application of low molecular weight amphoteric dry powder polyacrylamide, wherein an anionic functional monomer with a chain transfer agent function and a cationic functional monomer with an initiator function are respectively introduced in the synthesis process of a polymer, so that the synthesized polymer has amphoteric characteristics and a branched chain structure, and the molecular weight of the polymer is controlled to be 50-70 ten thousand by matching with the chain transfer agent. The synthesized polymer gel block is granulated by a kneader, and a modifying auxiliary agent is added in the granulating process, so that the types and the amounts of anionic groups and cationic groups on a polymer molecular main chain are increased, and the anionic charges and the cationic charges are enhanced, thereby being used as a papermaking dry reinforcing agent. The polyacrylamide product has the characteristics of ultralow molecular weight, amphiprotic property, solid powder, long shelf life, convenient transportation and good use effect, and can better meet the application requirements of the papermaking field on the dry reinforcing agent.

Description

Preparation method and application of low molecular weight amphoteric dry powder polyacrylamide

Technical field

The invention belongs to the technical field of polymer preparation, and specifically relates to a preparation method and application of low molecular weight amphoteric dry powder polyacrylamide.

Background technique

Polyacrylamide (PAM) is a high molecular polymer that can be dissolved in water to form a solution. Low molecular weight polymer products can be used as dry reinforcing agents for papermaking. The appropriate molecular weight of polymers used as dry reinforcing agents for paper is generally between 100,000 and 1,000,000, and the optimal range is between 500,000 and 700,000. However, polyacrylamide products with molecular weights less than 1 million will cause colloid cutting during the production process. It is difficult to pellet and dry, so most of the mainstream polymer-based dry reinforcing agents for papermaking on the market are in the form of glue, which has a short shelf life, a large usage volume, and is inconvenient to transport.

Strength is a structural property of paper. Paper dry strengthening agents can increase the bonding force between fibers in paper, thus improving strength indicators based on bonding force, such as breaking length, ring pressure index, tightness, and surface resistance. Abrasiveness, surface roughening speed, compressive strength, etc.

Compared with starch series enhancers, polyacrylamide enhancers are used less and have good reinforcing effects, with low drainage COD load. The reinforcement of polyacrylamide is generally through the formation of a large number of hydrogen bonds between the primary amide groups in the structure and the hydroxyl groups in the pulp fiber structure, thereby greatly improving the strength of the paper. At the same time, PAM is completely water-soluble and can be well dispersed in the pulp suspension. middle. However, PAM molecules themselves are neutral and cannot be well adsorbed by paper fibers. In actual use, electrical groups need to be introduced into the molecules. They are generally divided into anionic (APAM), cationic (CPAM), and cationic (CPAM) according to their electrical properties. Amphimorph (AmPAM). Since paper is electronegative, it is necessary to add a cationic accelerator when using APAM. Generally, aluminum sulfate is used. APAM adsorbs on the fiber in the form of coordination bonds with the negative ions on the fiber under the action of AL ³⁺ to produce a reinforcing effect. It needs to be acidic. In recent years, China's papermaking environment has gradually transitioned from acidic to neutral, so the application proportion of APAM has gradually decreased. CPAM can be directly adsorbed on pulp fibers to achieve an enhanced effect by forming ionic bonds between cations and anions on the fibers. However, excessive use of CPAM may cause charge reversal problems during white water recycling in the papermaking system. The AmPAM structure contains both cationic and anionic groups, which can adjust the charge balance of anions and cations in the slurry system. The amide groups on the polymer chain combine with the hydroxyl groups on the fibers to form hydrogen bonds, and it has both anionic and cationic polymers. Its reinforcing functions and advantages promote the cross-linked network between fibers, thereby achieving a good effect of improving the strength of paper. There are reports in the literature that amphoteric polyacrylamide products can be prepared by copolymerizing a variety of anionic and cationic functional monomers. However, there are cases where the polymerization is incomplete due to the interaction between the functional monomers or the large difference in reactivity rates. , the product has a high residual content, and the use effect is not good.

Contents of the invention

The object of the present invention is to provide a preparation method and application of low molecular weight amphoteric dry powder polyacrylamide that is easy to transport, easy to store, small in usage, and good in usage.

The technical solution adopted by the present invention to solve the technical problem is: a preparation method of low molecular weight amphoteric dry powder polyacrylamide, which includes the following steps:

1) Prepare acrylamide monomer, anionic functional monomer, and cationic functional monomer into an aqueous solution of a certain concentration in proportion, and adjust the pH of the aqueous solution between 6.5 and 7.0;

2) Spray a layer of anti-sticking agent evenly on the wall of the polymerization reactor. Adjust the temperature of the aqueous solution prepared in step 1) to 15-20°C and add it to the polymerization reactor to blow nitrogen for 30 minutes. Add the chain in sequence under the protection of nitrogen. Transfer the auxiliary agent, initiator 1 and initiator 2, control the initial temperature of the polymerization reaction at 17-22°C, and perform adiabatic polymerization for 1-2 hours;

3) After the polymerization reaches the highest temperature, keep it warm for 1 hour. Take out the obtained colloid and transfer it to the kneader for kneading and granulation. During the granulation process, add solid dispersant, modification additive one and modification additive two, and first maintain the normal temperature environment. Knead for 1 to 2 hours, then feed steam into the jacket of the kneader to keep the material at 80°C and continue kneading for 1 hour;

4) Transfer the polymer colloidal particles kneaded into flakes to a paddle-type stirred fluidized bed for drying, and then grind and sieve to obtain white polymer product powder.

Further, the weight percentage of each component in step 1) and step 2) is: acrylamide monomer 42% ~ 44%, anionic functional monomer 0.1% ~ 0.2%, cationic functional monomer 1.5% ~ 2% , chain transfer auxiliary 0.4% ~ 1%, initiator one 0.04% ~ 0.08%, initiator two 0.015% ~ 0.03%, the balance is water.

Further, in step 1), the anionic functional monomer is sodium methallylsulfonate; the cationic functional monomer is dimethylaminopropylmethacrylamide with a purity of more than 99%.

Further, the anti-sticking agent in step 2) is prepared from glycerol monostearate dissolved in liquid hot paraffin oil at 65°C, and the mass ratio of glycerol monostearate to paraffin oil is 1:4.

Further, the mid-chain transfer auxiliary agent in step 2) is sodium formate; the first initiator is azobisisobutyronitrile; the second initiator is a redox initiating system composed of potassium persulfate and sodium bisulfite. , the potassium persulfate and sodium bisulfite need to be prepared into an aqueous solution with a mass concentration of 2% before use.

Further, in step 3), the solid dispersant is 0.2% to 0.4% of the colloid weight, the first modification aid is 3% to 3.5% of the colloid weight, and the second modification aid is 0.6% to 0.9% of the colloid weight. %.

Further, the solid dispersant in step 3) is one or both of glycerol monostearate or tetraethylene glycol monostearate.

Further, in step 3), the first modification auxiliary is liquid sodium hydroxide with a mass concentration of 50%, and the second modification auxiliary is sodium hypochlorite.

An application of low molecular weight amphoteric dry powder polyacrylamide. The prepared low molecular weight amphoteric dry powder polyacrylamide is used as a dry reinforcing agent for papermaking and to evaluate various performance indicators of paper.

The low molecular weight amphoteric dry powder polyacrylamide product of the present invention is synthesized by a process of first adding a small amount of functional monomers with chain transfer and initiator functions to copolymerize and then modifying them, which is similar to the preparation method of copolymerizing a variety of anionic and cationic functional monomers. ratio, which can effectively avoid incomplete polymerization due to differences in reactivity rates. The anionic functional monomer introduced during the polymerization process also functions as a chain transfer agent. When combined with an appropriate amount of auxiliary chain transfer agent sodium formate, the molecular weight of the polymer can be better controlled between 500,000 and 700,000, which better satisfies the requirement of papermaking dry strength agent. Requirements for polymer molecular weight; the introduced cationic functional monomer also has the function of initiator, making the polymerization reaction easier, and at the same time, the synthesized polymer molecules have a branched chain structure, and the reinforcing effect is better when used as a dry strength agent. This copolymerization process gives the synthesized polymer products preliminary amphoteric characteristics; the special anti-sticking agent pre-coated on the wall of the polymerization kettle can smoothly discharge the soft colloid and facilitate subsequent kneading and granulation; the synthesized polymer The glue block enters the kneader for granulation. During the kneading process, an appropriate amount of solid dispersant is added according to the granulation effect to achieve smooth granulation. At the same time, during the granulation process, the modifying additives sodium hydroxide and sodium hypochlorite are added, and the kneading is first maintained at normal temperature. 1 to 2 hours, a cationic group (primary amine group) is added to the main chain of the polymer molecule through the Hoffman reaction, and then steam is introduced into the jacket of the kneader to keep the material at 80°C and continue kneading for 1 hour. The residual sodium hydroxide undergoes a hydrolysis reaction with the polymer under high temperature conditions, further adding an anionic group (carboxyl group) to the main chain of the molecule, and finally synthesizing a polymer containing a variety of anionic groups on the main chain of the molecule. , a low molecular weight amphoteric dry powder polymer product with cationic functional groups, which can be better used as a dry reinforcing agent for papermaking. This polymer product has an ultra-low molecular weight, but the product form is solid powder, which is different from the mainstream products currently on the market. Liquid papermaking dry strength agents have the characteristics of long shelf life, convenient transportation and good use effect, and can better meet the application needs of dry strength agents in the papermaking field.

Description of the drawings

Figure 1 is a schematic flow chart of the preparation process of low molecular weight amphoteric dry powder polyacrylamide of the present invention.

Detailed ways

The following are specific embodiments of the present invention to further describe the technical solution of the present invention, but the protection scope of the present invention is not limited to these embodiments. Any changes or equivalent substitutions that do not deviate from the concept of the present invention are included in the protection scope of the present invention.

Example 1: The preparation process flow of low molecular weight amphoteric dry powder polyacrylamide is shown in Figure 1. Add acrylamide crystals to the batching container, add deionized water to fully dissolve, and add anionic functional monomers and cationic functional monomers respectively. into an aqueous solution of a certain concentration, adjust the pH of the aqueous solution to 6.8, spray a layer of anti-sticking agent evenly on the wall of the polymerization reactor, adjust the temperature of the prepared reaction solution to 18°C, and add it to the polymerization reactor to blow nitrogen for 30 minutes. Add the chain transfer auxiliary, initiator 1, and initiator 2 in sequence under protection, control the initial temperature of the polymerization reaction at 20°C, and perform adiabatic polymerization for 1 hour. After the polymerization reaches the highest temperature, keep it warm for 1 hour, and take out the resulting colloid. Transfer 2kg of colloid to a small kneader for kneading and granulation. During the granulation process, add 4g of glycerol monostearate, 60g of 50% liquid sodium hydroxide, and 13g of sodium hypochlorite. Knead for 1 hour at room temperature, and then Pour steam into the jacket of the kneader to keep the material at 80°C and continue kneading for 1 hour; transfer the polymer particles kneaded into flakes to a paddle-type stirred fluidized bed for drying, and then grind and screen to obtain a white polymer product. pink.

Among them, the weight percentage of each component is as follows: acrylamide monomer 43%, anionic functional monomer 0.1%, cationic functional monomer 1.5%, chain transfer auxiliary 0.6%, initiator one 0.05%, initiator two 0.02%, The remainder is water. The chain transfer auxiliary agent is sodium formate; the first initiator is azobisisobutyronitrile; the second initiator is a redox initiating system composed of potassium persulfate and sodium bisulfite. Both potassium persulfate and sodium bisulfite need to be formulated. An aqueous solution with a mass concentration of 2% is used again.

Example 2: Add acrylamide crystals to the batching container, add deionized water to fully dissolve them, add anionic functional monomers and cationic functional monomers respectively to prepare an aqueous solution of a certain concentration, adjust the pH of the aqueous solution to 6.5, and add it to the wall of the polymerization reactor. Spray a layer of anti-sticking agent evenly, adjust the temperature of the prepared reaction solution to 17°C, and add it to the polymerization reactor to blow nitrogen for 30 minutes. Under the protection of nitrogen, add chain transfer auxiliary, initiator one, and initiator two in sequence. The initial temperature of the polymerization reaction was controlled at 19°C, adiabatic polymerization was carried out for 1 hour, and the polymerization was raised to the highest temperature and kept for 1 hour, and the resulting colloid was taken out. Transfer 2kg of colloid to a small kneader for kneading and granulation. During the granulation process, add 8g of tetraethylene glycol monostearate, 64g of 50% liquid sodium hydroxide and 18g of sodium hypochlorite. Knead at room temperature for 2 hours. , then introduce steam into the jacket of the kneader to keep the material at 80°C and continue kneading for 1 hour; transfer the polymer particles kneaded into flakes to a paddle-type stirred fluidized bed for drying, and then grind and screen to obtain white Polymer product powder.

Among them, the weight percentage of each component is as follows: acrylamide monomer 42%, anionic functional monomer 0.2%, cationic functional monomer 1.5%, chain transfer auxiliary 0.4%, initiator one 0.06%, initiator two 0.02%, The remainder is water. The chain transfer auxiliary agent is sodium formate; the first initiator is azobisisobutyronitrile; the second initiator is a redox initiating system composed of potassium persulfate and sodium bisulfite. Both potassium persulfate and sodium bisulfite need to be formulated. An aqueous solution with a mass concentration of 2% is used again.

Example 3: Add acrylamide crystals to the batching container, add deionized water to fully dissolve them, add anionic functional monomers and cationic functional monomers respectively to form an aqueous solution of a certain concentration, adjust the pH of the aqueous solution to 6.8, and add it to the wall of the polymerization reactor. Spray a layer of anti-sticking agent evenly, adjust the temperature of the prepared reaction solution to 15°C, and add it to the polymerization reactor to blow nitrogen for 30 minutes. Under the protection of nitrogen, add chain transfer auxiliary, initiator one, and initiator two in sequence. The initial temperature of the polymerization reaction was controlled at 17°C, adiabatic polymerization was carried out for 2 hours, and the polymerization was raised to the highest temperature and kept for 1 hour, and the resulting colloid was taken out. Transfer 2kg of colloid to a small kneader for kneading and granulation. During the granulation process, add 8g of a mixture of glycerol monostearate and tetraethylene glycol monostearate, 70g of 50% liquid sodium hydroxide, and 16g of colloid. For sodium hypochlorite, first keep it kneaded at room temperature for 1.5 hours, then introduce steam into the kneader jacket to keep the material at 80°C and continue kneading it for 1 hour; transfer the kneaded polymer particles into flakes to a paddle-type stirring fluidized bed for drying Dry, grind and sieve to obtain white polymer product powder.

Among them, the weight percentage of each component is as follows: acrylamide monomer 44%, anionic functional monomer 0.15%, cationic functional monomer 2%, chain transfer auxiliary 0.7%, initiator one 0.08%, initiator two 0.015%, The remainder is water. The chain transfer auxiliary agent is sodium formate; the first initiator is azobisisobutyronitrile; the second initiator is a redox initiating system composed of potassium persulfate and sodium bisulfite. Both potassium persulfate and sodium bisulfite need to be formulated. The aqueous solution with a mass concentration of 2% is reused.

Example 4: Add acrylamide crystals to the batching container, add deionized water to fully dissolve them, add anionic functional monomers and cationic functional monomers respectively to form an aqueous solution of a certain concentration, adjust the pH of the aqueous solution to 7.0, and add the acrylamide crystals to the wall of the polymerization reactor. Spray a layer of anti-sticking agent evenly, adjust the temperature of the prepared reaction solution to 20°C, and add it to the polymerization reactor to blow nitrogen for 30 minutes. Under the protection of nitrogen, add chain transfer auxiliary, initiator one, and initiator two in sequence. Control the initial temperature of the polymerization reaction at 22°C, perform adiabatic polymerization for 1 hour, and then maintain the temperature for 1 hour after the polymerization reaches the highest temperature, and then take out the resulting colloid. Transfer 2kg of colloid to a small kneader for kneading and granulation. During the granulation process, add 6g of glycerol monostearate, 62g of 50% liquid sodium hydroxide, and 12g of sodium hypochlorite. Knead for 1.5 hours at room temperature, and then Inject steam into the jacket of the kneader to keep the material at 80°C and continue kneading for 1 hour; transfer the polymer particles kneaded into flakes to a paddle-type stirred fluidized bed for drying, and then grind and screen to obtain a white polymer. Product powder.

Among them, the weight percentage of each component is as follows: acrylamide monomer 43%, anionic functional monomer 0.1%, cationic functional monomer 1.5%, chain transfer auxiliary 1%, initiator one 0.04%, initiator two 0.03%, The remainder is water. The chain transfer auxiliary agent is sodium formate; the first initiator is azobisisobutyronitrile; the second initiator is a redox initiating system composed of potassium persulfate and sodium bisulfite. Both potassium persulfate and sodium bisulfite need to be formulated. The aqueous solution with a mass concentration of 2% is reused.

Example 5: According to Sinopec Enterprise Standard Q/SH10201457-2015, an Ubbelohde viscometer was used to test the viscosity average molecular weight of a low molecular weight amphoteric dry powder polymer sample using the one-point method; the polymer sample was added to the pulp based on 1.5kg per ton of paper. , using the international A-grade corrugated base papermaking standards for papermaking and testing various performance indicators of the paper. The results are shown in the table below:

It can be seen from the experimental data that when the low molecular weight amphoteric dry powder polymer of the present invention is used as a dry reinforcing agent for papermaking, its tightness, ring pressure index, and fracture length are significantly improved compared with the blank sample after papermaking, and can reach It even exceeds the enhancement effect of liquid dry strength agent samples on the market. In addition, the product of the invention is in the form of dry powder, has the advantages of convenient transportation and use, and a long shelf life. It is a high-performance polymer dry strength agent product for papermaking.

The present invention is not limited to the above embodiments. Anyone should know that structural changes made under the inspiration of the present invention, and any technical solutions that are the same or similar to the present invention, fall within the protection scope of the present invention.

The technology, shape, and structural parts not described in detail in the present invention are all known technologies.

Claims (9)

1. The preparation method of the low molecular weight amphoteric dry powder type polyacrylamide is characterized by comprising the following steps of:

1) Preparing an acrylamide monomer, an anion functional monomer and a cation functional monomer into an aqueous solution with a certain concentration according to a proportion, and regulating the pH of the aqueous solution to be between 6.5 and 7.0;

2) Uniformly spraying a layer of anti-sticking agent on the wall of the polymerization reactor, adjusting the temperature of the aqueous solution prepared in the step 1) to 15-20 ℃, adding the aqueous solution into the polymerization reactor, blowing nitrogen for 30min, sequentially adding a chain transfer auxiliary agent, an initiator I and an initiator II under the protection of nitrogen, controlling the initial temperature of the polymerization reaction to 17-22 ℃, and carrying out adiabatic polymerization for 1-2 h;

3) Heating to the highest temperature, preserving heat for 1h, taking out the colloid, transferring the colloid into a kneader, kneading and granulating, adding a solid dispersing agent, a first modifying auxiliary agent and a second modifying auxiliary agent in the granulating process, firstly, kneading for 1-2 h under the normal temperature environment, and then introducing steam into a jacket of the kneader to keep the temperature of the material at 80 ℃ for continuous kneading for 1h;

4) And transferring the polymer colloidal particles kneaded into sheets to a slurry stirring fluidized bed for drying, and grinding and sieving to obtain white polymer product powder.

2. The method for preparing the low molecular weight amphoteric dry powder type polyacrylamide according to claim 1, wherein the weight percentages of the components in the step 1) and the step 2) are as follows: 42 to 44 percent of acrylamide monomer, 0.1 to 0.2 percent of anion functional monomer, 1.5 to 2 percent of cation functional monomer, 0.4 to 1 percent of chain transfer auxiliary agent, 0.04 to 0.08 percent of initiator I, 0.015 to 0.03 percent of initiator II and the balance of water.

3. The method for preparing the low molecular weight amphoteric dry powder type polyacrylamide according to claim 1 or 2, wherein the anionic functional monomer in the step 1) is sodium methallyl sulfonate; the cation functional monomer is dimethylaminopropyl methacrylamide with the purity of more than 99 percent.

4. The method for preparing the low molecular weight amphoteric dry powder type polyacrylamide according to claim 1 or 2, wherein the chain transfer auxiliary agent in the step 2) is sodium formate; the initiator I is azodiisobutyronitrile; the initiator II is a redox initiation system composed of potassium persulfate and sodium bisulfite, and the potassium persulfate and the sodium bisulfite are prepared into an aqueous solution with the mass concentration of 2% for reuse.

5. The method for preparing the low molecular weight amphoteric dry powder type polyacrylamide according to claim 1, wherein the anti-sticking agent in the step 2) is prepared by dissolving glycerin monostearate in liquid hot paraffin oil at 65 ℃, and the mass ratio of the glycerin monostearate to the paraffin oil is 1:4.

6. The method for preparing the low molecular weight amphoteric dry powder polyacrylamide according to claim 1, wherein the solid dispersing agent in the step 3) is 0.2-0.4% of the weight of the colloid, the first modifying auxiliary agent is 3-3.5% of the weight of the colloid, and the second modifying auxiliary agent is 0.6-0.9% of the weight of the colloid.

7. The method for preparing the low molecular weight amphoteric dry powder type polyacrylamide according to claim 1 or 6, wherein the solid dispersing agent in the step 3) is one or two of glycerol monostearate and tetraethylene glycol monostearate.

8. The method for preparing low molecular weight amphoteric dry powder type polyacrylamide according to claim 1 or 6, wherein the first modifying aid in the step 3) is liquid sodium hydroxide with a mass concentration of 50%, and the second modifying aid is sodium hypochlorite.

9. The application of the low molecular weight amphoteric dry powder type polyacrylamide is characterized in that the prepared low molecular weight amphoteric dry powder type polyacrylamide is used as a papermaking dry reinforcing agent and various performance indexes of paper are evaluated.