High performance paper wet strength agent, preparation method and application

Abstract

The application discloses a high-performance paper wet strength agent as shown in structural formula (I) and application thereof in papermaking. The paper wet strength agent is prepared from a raw material including alicyclic polyamine, polybasic aliphatic amine, acrylate and epichlorohydrin, the content of hydroxyl groups in the molecular structure of the wet strength agent is high, the wet strength agent is more easily to form hydrogen bonds with hydroxyl groups of wood fibers, and the retention performance of the wet strength agent is greatly improved. Meanwhile, the presence of the hydrophobic alicyclic structure can effectively prevent the water absorption and expansion of the fibers, reduce the expansion and deformation performance of the paper sheet, and improve the wet strength of the paper. Compared with traditional wet strength agents, even at a lower dosage, the paper can still be endowed with good folding endurance, tensile strength and dry strength and other performances.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of papermaking, and relates to a wet strength agent, a preparation method and use thereof, in particular to a polyamide type paper wet strength agent. BACKGROUND

[0002] With the development of society, the use range of paper is wider and wider, and people's demand for paper for daily use shows a trend of multi-function, for example, some types of paper require high wet strength, if the paper is not specially treated, it will lose most of its strength after being wetted by water, and the addition of a wet strength agent can significantly improve the wet strength of the paper under wet conditions. Paper wet strength agents can be divided into two categories: permanent and temporary. Temporary paper wet strength agents are mainly used in paper products that are discarded after a short time, and permanent wet strength agents are usually used in corrugated board and food packaging, mainly including urea-formaldehyde resin, melamine-formaldehyde resin, polyamide polyamine epichlorohydrin resin and acrylamide polymer.

[0003] The mechanism by which the wet strength agent improves the wet strength of paper is that the hydroxyl groups in the molecular structure of the wet strength agent form hydrogen bonds with the hydroxyl groups on the fibers, so that a large amount of resin is adsorbed on the surface of the fibers. When the paper is dried, the resin remaining in the paper reacts to form a network structure on the surface of the fibers that is not destroyed by water, thereby reducing the water absorption of the fibers and preventing the fibers from swelling in water, protecting the hydrogen bonds between the fibers and improving the wet strength and dry strength of the paper.

[0004] Patent CN102898643B discloses that a carboxyl modifier is added before the alkylation reaction of a polyamide polyamine intermediate and epichlorohydrin, so as to balance the positive charge of the system, thereby realizing charge control of the PAE resin; however, in the patent, since the intermediate main chain does not have a double bond, the added unsaturated carboxyl modifier such as acrylic acid and fumaric acid is difficult to uniformly polymerize to the main chain, or the sodium chloroacetate modifier competes with the epichlorohydrin for the alkylation reaction point, so that the number of epoxide functional groups on the chain is reduced, and the wet strength effect is affected.

[0005] Patent CN100465374C discloses an epoxy polyamide resin wet strength agent and a preparation method thereof, which discloses that an unsaturated polyamide polyamine intermediate is prepared by using an unsaturated dibasic acid instead of a saturated dibasic acid; before the alkylation reaction of the unsaturated intermediate and epichlorohydrin, a vinyl cation monomer is added to perform a free radical polymerization reaction, so as to increase the polymer chain length and cation degree; the patent further improves the positive charge density of the wet strength agent, so that the positive charge is more excessive, and it is more likely to cause disorder of the wet end papermaking system.

[0006] Patent CN 10976338B discloses a method for preparing a wet-strength agent by reacting a polyamide polyamine prepolymer with epichlorohydrin and an acrylic / acrylate copolymer. However, the amines used in this method are all ethyleneamines, which have strong hydrophilicity. Paper prepared using this wet-strength agent shows a significant decrease in strength under high humidity conditions, which cannot meet the application requirements of high-performance paper industries such as disinfectant wipes.

[0007] Patent CN105386367A discloses a method for preparing a wet strength agent by modifying a cationic etherifying agent. The cationic amine compound has a low curing temperature and is easier to cure after being added to paper. However, this wet strength agent does not contain alicyclic secondary amines, and the paper prepared from it has low dry and wet strength.

[0008] Therefore, to address the aforementioned problems, this invention provides a polyamide-epoxychloropropane wet strength agent containing an alicyclic structure. Compared to traditional wet strength agents, this agent has a high hydroxyl content, making it easier to form hydrogen bonds with the hydroxyl groups of wood pulp fibers, thus significantly improving the retention performance of the wet strength agent. Simultaneously, the presence of the hydrophobic alicyclic structure effectively prevents fiber water absorption and swelling, reduces paper stretching and deformation, and improves the wet strength of the paper. Summary of the Invention

[0009] This invention provides an alicyclic paper wet strength agent, its preparation method, and its application. This wet strength agent has the characteristics of high hydroxyl content, excellent mechanical properties, and good hydrophobicity. It is especially suitable for fields with high requirements for wet strength, such as liquid food packaging, meat and vegetable paper, and refrigerated packaging box paper.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] On the one hand, the present invention provides a wet strength agent as shown in formula (I):

[0012]

[0013] Where R1 is R2 is R3 is R4 is -S04, -N03, and -Cln is 1, 2, or 3.

[0014] On the other hand, a method for preparing the wet strength agent shown in formula (I) is also provided, comprising the following steps:

[0015] (1) Under the protection of an inert gas, an alicyclic polyamine is mixed with an acrylate and heated to react, yielding an acrylate-terminated alicyclic secondary amine.

[0016] (2) mixing the product obtained in step (1) with deionized water, adding NaOH solution as a catalyst, heating and reacting, and distilling under reduced pressure to obtain a carboxyl-terminated alicyclic polyamine;

[0017] (3) mixing the aliphatic polyamine with the product obtained in step (2), heating and reacting to obtain a polyamide prepolymer;

[0018] (4) mixing the polyamide prepolymer with epichlorohydrin, heating and reacting, adding an acid to adjust the pH of the product after the reaction is completed to obtain a wet strength agent.

[0019] In the present application, the alicyclic polyamine in step (1) is selected from one or more of 1,3-cyclohexyl dimethylamine, isophorone diamine, 4,4'-diamino dicyclohexyl methane and 1,4-cyclohexane diamine, preferably 4,4'-diamino dicyclohexyl methane.

[0020] In the present application, the acrylate in step (1) is selected from one or both of methyl acrylate and methyl methacrylate, preferably methyl acrylate.

[0021] In the present application, the molar ratio of the alicyclic polyamine to the acrylate in step (1) is 1:(1.95-2.05), preferably 1:(1.99-2.01); and / or, the reaction temperature is 40-110°C, preferably 60-80°C, and the reaction time is 3-5h, preferably 3.5-4.5h.

[0022] In the present application, the product obtained in step (1) and deionized water in step (2) are mixed uniformly at a molar ratio of 1:(1.95-2.05), preferably 1:(1.98-1:2.02); the mass concentration of the NaOH solution is 10%-30%, preferably 15%-25%; and the mass ratio of the deionized water to NaOH is 100:

[0023] (0.05-3), preferably 100:(0.1-1).

[0024] In the present application, the reaction temperature in step (2) is 70-150°C, preferably 90-120°C, and the reaction time is 2-4h, preferably 2.5-3.5h.

[0025] In the present application, the aliphatic polyamine in step (3) is selected from one or more of diethylene triamine, triethylene tetramine and tetraethylene pentamine, preferably diethylene triamine; and / or, the molar ratio of the aliphatic polyamine to the product obtained in step (2) is 1:(0.95-1.05), preferably 1:(0.99-1.01).

[0026] In the present application, the reaction temperature in step (3) is 180-300℃, preferably 200-260℃, and the reaction time is 3-10h, preferably 5-8h.

[0027] In the present application, the molar ratio of polyamide prepolymer to epichlorohydrin in step (4) is 1:(2.95-3.05), preferably 1:(2.98-1:3.02); the reaction temperature is 30-100℃, preferably 50-70℃, and the reaction time is 3-8h, preferably 4-6h; the acid used to adjust the pH is one or more of sulfuric acid, hydrochloric acid and nitric acid, and further preferably 5%-10%wt of hydrochloric acid, and the pH of the product after adjustment is 3-6.

[0028] In another aspect, the present application also provides the use of the wet strength agent prepared by the above method in liquid food packaging, meat and vegetable paper and cold storage packaging box paper.

[0029] The present application has the following beneficial effects:

[0030] 1. The wet strength agent is a diacid containing secondary amine prepared by Michael addition of alicyclic polyamine and acrylate, which can react with epichlorohydrin to further increase the content of hydroxyl groups in the wet strength agent, making it easier to form hydrogen bonds with wood pulp and improve retention.

[0031] 2. The six-membered ring in the wet strength agent has good hydrophobicity, and the paper prepared using the wet strength agent has a small amount of water absorption in a high humidity environment, which can impart better wet strength to the paper;

[0032] 3. Compared with the wet strength agent prepared from traditional aliphatic polyamine and aliphatic diacid, the wet strength agent provided by the present application has higher heat resistance and mechanical properties, and still has good performance when the addition amount is reduced, further providing economic benefits to customers. DETAILED DESCRIPTION

[0033] The present application will be further described below through specific examples, and the examples described in the present application are only used to illustrate the present application and do not limit the scope of the present application.

[0034] The main raw material information used in the following examples of the present application is shown in Table 1. Other raw materials and reagents not specified are obtained by commercial means.

[0035] Table 1, main raw material information

[0036]

[0037]

[0038] Wet strength agent performance test standards:

[0039] Paper preparation: pulp with 1% content was prepared according to the ratio of long fiber to short fiber 1:3, wet strength agent was added, stirred for 2 minutes, then formed into a sheet with a diameter of 200 mm on a fiber former, dried at 105℃ for 30 minutes, and placed at room temperature for 2 hours.

[0040] Dry tensile strength: GB / T 12914-1991

[0041] Wet tensile strength: GB / 465.2-1989

[0042] Retention rate: DDJ dynamic drainage instrument

[0043] Example 1

[0044] 1. Under N2 protection, 4,4'-diaminodicyclohexyl methane and methyl acrylate were reacted at a molar ratio of 1:1.99 at 80℃ for 3.5h to obtain acrylate-terminated 4,4'-diaminodicyclohexyl methane.

[0045] 2. The product obtained in step 1 was mixed uniformly with deionized water at a molar ratio of 1:1.98, 20%wt NaOH solution was added as a catalyst, heated to 90℃, reacted for 3.5h, and distilled under reduced pressure to obtain carboxyl-terminated 4,4'-diaminodicyclohexyl methane.

[0046] 3. Diethylenetriamine and the product obtained in step 2 were fed at a molar ratio of 1:1.01, heated to 200℃, and reacted for 8h to obtain a polyamide prepolymer.

[0047] 4. The polyamide prepolymer and epichlorohydrin were reacted at a molar ratio of 1:2.98 at 70℃ for 3h, 5% sulfuric acid was added to adjust the pH of the product to 6 to obtain the wet strength agent of the present application.

[0048] Example 2

[0049] 1. Under N2 protection, 4,4'-diaminodicyclohexyl methane and methyl acrylate were reacted at a molar ratio of 1:2.01 at 60℃ for 4.5h to obtain acrylate-terminated 4,4'-diaminodicyclohexyl methane.

[0050] 2. The product obtained in step 1 was mixed uniformly with deionized water at a molar ratio of 1:2.02, 20%wt NaOH solution was added as a catalyst, heated to 120℃, reacted for 2.5h, and distilled under reduced pressure to obtain carboxyl-terminated 4,4'-diaminodicyclohexyl methane.

[0051] 3. Triethylenetetramine and the product obtained in step 2 were fed at a molar ratio of 1:0.99, heated to 260℃, and reacted for 5h to obtain a polyamide prepolymer.

[0052] 4. The polyamide prepolymer is mixed with epichlorohydrin in a molar ratio of 1 :3.02, heated to 50°C, and reacted for 4 h. 7% hydrochloric acid is added to adjust the pH of the product to 5 to obtain the wet strength agent of the present application.

[0053] Example 3

[0054] 1. Isophorone diamine is mixed with methyl methacrylate in a molar ratio of 1 :2 under N2protection at 70°C for 4 h to obtain methyl methacrylate-terminated isophorone diamine.

[0055] 2. The product obtained in step 1 is mixed with deionized water in a molar ratio of 1 :2, 20% wt NaOH solution is added as a catalyst, heated to 100°C, and reacted for 3 h. Vacuum distillation is performed to obtain carboxyl-terminated isophorone diamine.

[0056] 3. Diethylenetriamine is mixed with the product obtained in step 2 in a molar ratio of 1 :1, heated to 230°C, and reacted for 6 h to obtain a polyamide prepolymer.

[0057] 4. The polyamide prepolymer is mixed with epichlorohydrin in a molar ratio of 1 :3, heated to 60°C, and reacted for 5 h. 10% sulfuric acid is added to adjust the pH of the product to 5 to obtain the wet strength agent of the present application.

[0058] Example 4

[0059] 1. 1,3-cyclohexylmethane diamine is mixed with methyl methacrylate in a molar ratio of 1 :2.01 under N2protection at 75°C for 3.7 h to obtain methyl methacrylate-terminated 1,3-cyclohexylmethane diamine.

[0060] 2. The product obtained in step 1 is mixed with deionized water in a molar ratio of 1 :2.01, 20% wt NaOH solution is added as a catalyst, heated to 105°C, and reacted for 3 h. Vacuum distillation is performed to obtain carboxyl-terminated 1,3-cyclohexylmethane diamine.

[0061] 3. Tetraethylenepentamine is mixed with the product obtained in step 2 in a molar ratio of 1 :1, heated to 240°C, and reacted for 5.5 h to obtain a polyamide prepolymer.

[0062] 4. The polyamide prepolymer is mixed with epichlorohydrin in a molar ratio of 1 :3.01, heated to 65°C, and reacted for 5 h. 8% nitric acid is added to adjust the pH of the product to 4 to obtain the wet strength agent of the present application.

[0063] Comparative Example 1

[0064] 1. Diethylenetriamine is mixed with adipic acid in a molar ratio of 1 :1.01 under N2protection at 260°C for 8 h to obtain a polyamide prepolymer.

[0065] 2. The polyamide prepolymer and epichlorohydrin were mixed according to a molar ratio of 1:1.01, and heated to 70°C, and reacted for 4h. 5% hydrochloric acid was added to adjust the pH of the product to 4, to obtain a PAE type wet strength agent.

[0066] Comparative Example 2

[0067] 1. Hexanediamine and adipic acid were reacted according to a molar ratio of 1:2.01 under N2 protection at 260°C for 8h, to obtain a carboxyl-terminated polyamide prepolymer.

[0068] 2. The prepolymer obtained in step 1 was reacted with diethylenetriamine according to a molar ratio of 1:1.01 at 260°C for 8h, to obtain a polyamide prepolymer.

[0069] The polyamide prepolymer and epichlorohydrin were mixed according to a molar ratio of 1:1.01, and heated to 70°C, and reacted for 4h. 5% hydrochloric acid was added to adjust the pH of the product to 4, to obtain a PAE type wet strength agent.

[0070] Comparative Example 3

[0071] 1. Ethylenediamine and methyl methacrylate were reacted according to a molar ratio of 1:2.01 under N2 protection at 75°C for 3.7h, to obtain methyl methacrylate-terminated ethylenediamine.

[0072] 2. The product obtained in step 1 was mixed with deionized water according to a molar ratio of 1:2.01, and 20%wt NaOH solution was added as a catalyst, and heated to 105°C, and reacted for 3h. The product was distilled under reduced pressure to obtain carboxyl-terminated ethylenediamine.

[0073] 3. Tetraethylenepentamine and the product obtained in step 2 were mixed according to a molar ratio of 1:1, and heated to 240°C, and reacted for 5.5h, to obtain a polyamide prepolymer.

[0074] 4. The polyamide prepolymer and epichlorohydrin were mixed according to a molar ratio of 1:3.01, and heated to 65°C, and reacted for 5h. 8% nitric acid was added to adjust the pH of the product to 4, to obtain the wet strength agent of the present application.

[0075] Wet strength agent performance test results

[0076]

Claims

1. A wet strength agent, the structure of which is shown in formula (I): Where R1 is R2 is R3 is R4 can be -SO4, -NO3, or -Cl, and n can be 1, 2, or 3.

2. The method for preparing the wet strength agent as described in claim 1, characterized in that, Includes the following steps: (1) Under the protection of an inert gas, an alicyclic polyamine is mixed with an acrylate and heated to react, yielding an acrylate-terminated alicyclic secondary amine; wherein the alicyclic polyamine is selected from 1,3-cyclohexyldimethylamine, isophorone diamine, 4,4'-diaminodicyclohexylmethane and 1,4-cyclohexyldiamine, and the acrylate is selected from one or two of methyl acrylate and methyl methacrylate; (2) Mix the product obtained in step (1) with deionized water, add NaOH solution as a catalyst, heat the reaction, and distill under reduced pressure to obtain carboxyl-terminated alicyclic polyamine; (3) The aliphatic polyamine is mixed with the product obtained in step (2) and fed into the mixture. The mixture is heated to react and a polyamide prepolymer is obtained. The aliphatic polyamine is diethylenetriamine. (4) Mix the polyamide prepolymer with epichlorohydrin and heat it to react; after the reaction is complete, add acid to adjust the pH of the product to obtain the wet strength agent.

3. The preparation method according to claim 2, characterized in that, The alicyclic polyamine mentioned in step (1) is '4,4'-diaminodicyclohexylmethane; and / or, the acrylate mentioned in step (1) is methyl acrylate.

4. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of alicyclic polyamine to acrylate is 1:(1.95~2.05); and / or, the reaction temperature is 40~110℃ and the reaction time is 3~5h.

5. The preparation method according to claim 4, characterized in that, In step (1), the molar ratio of alicyclic polyamine to acrylate is 1:(1.99~2.01); and / or, the reaction temperature is 60~80℃ and the reaction time is 3.5~4.5h.

6. The preparation method according to any one of claims 2-5, characterized in that, In step (2), the product obtained in step (1) is mixed with deionized water at a molar ratio of 1:(1.95 to 2.05) until homogeneous; and / or, the mass concentration of the NaOH solution is 10% to 30%; the mass ratio of the deionized water to NaOH is 100:(0.05 to 3).

7. The preparation method according to any one of claims 2-5, characterized in that, The reaction temperature in step (2) is 70–150 °C; and / or the reaction time is 2–4 h.

8. The preparation method according to claim 7, characterized in that, The reaction temperature in step (2) is 90–120°C; and / or the reaction time is 2.5–3.5 h.

9. The preparation method according to any one of claims 2-5, characterized in that, The molar ratio of the aliphatic polyamine described in step (3) to the product obtained in step (2) is 1:(0.95 to 1.05).

10. The preparation method according to any one of claims 2-5, characterized in that, In step (3), the reaction temperature is 180-300℃ and the reaction time is 3-10h.

11. The preparation method according to claim 10, characterized in that, In step (3), the reaction temperature is 200-260℃ and the reaction time is 5-8h.

12. The preparation method according to any one of claims 2-5, characterized in that, In step (4), the molar ratio of polyamide prepolymer to epichlorohydrin is 1:(2.95-3.05); the reaction temperature is 30-100℃, the reaction time is 3-8h; and / or, the acid used to adjust the pH is one or more of sulfuric acid, hydrochloric acid and nitric acid, and the pH of the product after adjustment is 3-6.

13. The preparation method according to claim 12, characterized in that, In step (4), the molar ratio of polyamide prepolymer to epichlorohydrin is 1:(2.98~1:3.02); the reaction temperature is 50~70℃ and the reaction time is 4~6h.

14. The application of the wet strength agent as described in claim 1 or the wet strength agent prepared by the preparation method as described in any one of claims 2-13 in liquid food packaging, meat and vegetable paper, and refrigerated packaging box paper.

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