A waterproof self-adhesive papermaking aid, its preparation method and application

Abstract

The present invention relates to the field of pulp and paper making aids, and particularly relates to a waterproof self-bonding paper making aid, a preparation method and an application thereof. In the present invention, organosiloxane and disulfide bonds with thermally reversible dynamic exchange properties are introduced into a polyurethane aid, and the polyurethane aid is coated on the surface of a paper-based material to prepare a multifunctional paper-based material. The paper-based material not only has strong waterproof performance based on the hydrophobic effect of organosiloxane, but also when the paper-based material is bonded and hot-pressed into a shape, without adding any adhesives, only by utilizing the interpenetrating network structure between the disulfide bonds in the molecular structure of the polyurethane aid and the paper-based fibers, self-bonding can occur between the paper-based materials.

Description

Technical Field

[0001] The invention relates to the field of pulping and papermaking additives, and in particular to a waterproof self-adhesive papermaking additive and a preparation method and application thereof. Background Art

[0002] As the most representative sustainable natural green material, paper-based materials are widely used in various fields and play an important role in daily life and production. In particular, with the development of the logistics industry in recent years, the pollution problems caused by plastic packaging products have received more and more attention. The development trends at home and abroad have shown the importance and urgency of "plastic restriction", which has brought new opportunities for the development of the paper-based packaging material industry. However,

[0003] Since the cellulose surface of natural plant fibers contains a large number of hydroxyl groups and has strong hydrophilicity, the paper-based materials that have not been modified have strong hygroscopicity. The strength index of the paper-based materials after absorbing moisture decreases significantly, which affects the subsequent use performance of the paper-based materials. Therefore, in order to improve the waterproof performance of paper-based materials, the traditional pulp and papermaking industry usually adopts a treatment method of applying sizing inside the pulp or on the surface to give paper-based materials the ability to resist liquid penetration and diffusion. However, this method not only has a cumbersome production process and a long drying time, but also with the gradual expansion of the application of paper-based materials in various fields, traditional sizing technology has long been unable to meet the requirements of certain fields for the performance of paper-based materials. For example, paper straws used in daily life, paper-based packaging cushioning materials, etc. require excellent waterproofing, and binders need to be added during the preparation process. Therefore, traditional sizing methods cannot meet the use requirements of such paper-based materials.

[0004] At present, such as pasting glue, water-based sealing glue, paper-plastic composite glue, etc. have been widely used in the sealing of instant noodle boxes, lamination of various packaging boxes, bottom sealing and edge sealing of handbags, adhesion of paper and plastic PVC, etc.; Chinese patent CN111154059 A discloses an epoxy resin modified polyetheramine enhanced water-based polyurethane emulsion and a preparation method, by introducing epoxy resin into the main chain of water-based polyurethane, the molecular chain structure is more regular than other methods, without destroying the hydroxyl groups contained in the epoxy resin, and the bonding strength, water resistance and heat resistance of water-based polyurethane are well improved. However, when using, it is necessary to wait for the moisture in the glue to dry before it will work, and it is slow to take effect, and the adhesion effect is greatly affected by moisture, that is, the adhesion is weakened or disappears in a water environment. Therefore, there is an urgent need for a waterproof self-adhesive papermaking additive. Summary of the invention

[0005] Aiming at the problems of slow effectiveness in the preparation process and great influence by water when the waterproof binder is used in paper at the present stage, the waterproof self-bonding papermaking aid provided by the present invention specifically introduces organosiloxane and disulfide bonds with thermoreversible dynamic exchange properties into the polyurethane aid, and coats the polyurethane aid on the surface of the paper-based material to prepare a multifunctional paper-based material. This paper-based material not only has strong waterproof performance based on the hydrophobic effect of organosiloxane, but also when the paper-based material is bonded and hot-pressed into shape, without adding any adhesives, only by using the thermoreversible dynamic exchange effect of the disulfide bonds in the molecular structure of the polyurethane aid and the interpenetrating network structure between the paper-based fibers, self-bonding can occur between the paper-based materials.

[0006] The technical solution of the present invention is as follows:

[0007] A waterproof self-bonding papermaking aid, comprising the following component raw materials: terminal dihydroxy polyol, terminal dihydroxy organosiloxane, terminal dihydroxy monomer containing disulfide bond, diisocyanate, terminal hydroxy hyperbranched polyester;

[0008] The molar ratio of the total hydroxyl groups (-OH) in the terminal dihydroxy polyol, terminal dihydroxy organosiloxane and terminal dihydroxy compound containing disulfide bond to the isocyanate groups (-NCO) in the diisocyanate is n(-OH):n(-NCO)=3:4, and the molar ratio of the hydroxyl groups (-OH) in the terminal hydroxy hyperbranched polyester to the isocyanate groups (-NCO) in the diisocyanate is n(-OH):n(-NCO)=1:4.

[0009] Preferably, when the terminal dihydroxy polyol and terminal dihydroxy organosiloxane are used as the soft segment and the terminal dihydroxy monomer containing disulfide bond is used as the crosslinking agent, the molar ratio of the terminal dihydroxy polyol to the terminal dihydroxy organosiloxane is 0.5:1 to 2:1, the overall molar ratio of the terminal dihydroxy polyol and terminal dihydroxy organosiloxane to the diisocyanate groups is 1:2, and the molar ratio of the terminal dihydroxy monomer containing disulfide bond to the diisocyanate groups is 1:4.

[0010] Preferably, when the terminal dihydroxy polyol and terminal dihydroxy monomer containing disulfide bond are used as the soft segment and the terminal dihydroxy organosiloxane is used as the crosslinking agent, the molar ratio of the terminal dihydroxy polyol to the terminal dihydroxy organosiloxane is 0.5:1 to 2:1, the overall molar ratio of the terminal dihydroxy polyol and terminal dihydroxy organosiloxane to the diisocyanate groups is 1:2, and the molar ratio of the terminal dihydroxy organosiloxane to the diisocyanate groups is 1:4.

[0011] Preferably, the polyol is one or both of polyethylene glycol and polytetrahydrofuran, and its molecular weight is 800-5000 g / mol; and / or, the diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-methylenebis(phenyl isocyanate); and / or, the molecular weight of the terminal dihydroxy organosiloxane is 800-5000 g / mol; and / or, the terminal dihydroxy monomer containing a disulfide bond is one or more of cystine, bis(2-hydroxyethyl) disulfide, and 2,2-diaminodiphenyl disulfide; and / or, the number of hydroxyl groups at the end of the terminal hydroxy hyperbranched polyester can be 8, 12, 24, 36, and 48, and the corresponding molecular weight is 800-5000 g / mol.

[0012] Another object of the present invention is to protect a method for preparing a waterproof self-adhesive papermaking aid, comprising the following steps:

[0013] S1. Condensation reaction occurs between the terminal dihydroxy polyol, terminal dihydroxy organosiloxane and diisocyanate under the action of the catalyst dibutyltin dilaurate to synthesize a terminal isocyanate group polyurethane prepolymer;

[0014] S2. Add the terminal hydroxy hyperbranched polyester to the reaction system S1, and through the condensation reaction of the hydroxyl groups in their molecular structures with the residual isocyanate groups in S1, prepare a hyperbranched polyurethane;

[0015] S3. Add the terminal dihydroxy monomer containing a disulfide bond to the S2 reaction system, and utilize the reaction between the two terminal hydroxyl groups and the residual isocyanate groups in the polymerization reaction to crosslink different hyperbranched polyurethanes together to synthesize a polyurethane aid with a higher crosslinking degree.

[0016] Further, the terminal dihydroxy organosiloxane in step S1 is interchanged with the terminal dihydroxy monomer containing a disulfide bond in step S3.

[0017] Further, the reaction temperature in step S1 is 40-80 °C, and the reaction time is 3-8 h.

[0018] Further, the reaction temperature in step S2 is 30-50 °C, and the reaction time is 3-6 h; and / or, the reaction temperature in step S3 is 30-50 °C, and the reaction time is 3-6 h.

[0019] Another object of the present invention is to protect the application of the waterproof self-adhesive papermaking aid as a paper waterproof layer.

[0020] The specific process of the above application is to apply the obtained aid to the paper-based material and obtain it by hot pressing.

[0021] The synthesis route of the matrix is shown in Figure 1 、 Figure 2 ,Figure 1 The synthesis route of the papermaking aid uses terminal dihydroxy polyol and terminal dihydroxy organosiloxane as soft segments, diisocyanate as the hard segment, and terminal dihydroxy compound containing disulfide bond as the crosslinking agent, but is not limited thereto.

[0022] Figure 2 The synthesis route of the papermaking aid uses terminal dihydroxy polyol and terminal dihydroxy compound containing disulfide bond as soft segments, diisocyanate as the hard segment, and terminal dihydroxy organosiloxane as the crosslinking agent, but is not limited thereto.

[0023] In this application, the terminal dihydroxy polyol is used as the soft segment of the polyurethane. The terminal dihydroxy organosiloxane or the terminal dihydroxy monomer containing disulfide bond can be used as the soft segment of the polyurethane or as the crosslinking agent of the polyurethane. The diisocyanate is used as the hard segment of the polyurethane, and the terminal hydroxyl hyperbranched polyester is used as the core of the polyurethane.

[0024] Advantages of the present invention:

[0025] By introducing organosiloxane and disulfide bond with thermoreversible dynamic exchange performance into the polyurethane aid and coating the polyurethane aid on the surface of the paper-based material, a multifunctional paper-based material is prepared. This paper-based material not only has strong waterproof performance based on the hydrophobic effect of the organosiloxane, but also when the paper-based material is bonded and hot-pressed into shape, without adding any adhesives, only by utilizing the interpenetrating network structure between the disulfide bond in the molecular structure of the polyurethane aid and the paper-based fibers, self-bonding can occur between the paper-based materials. Description of the drawings

[0026] Figure 1 It is the synthesis route 1 of the waterproof self-bonding papermaking aid;

[0027] Figure 2 It is the synthesis route 2 of the waterproof self-bonding papermaking aid;

[0028] Figure 3 It is the comparison diagram of the contact angle between the paper-based materials prepared in Examples 1 - 6 and the original paper;

[0029] Figure 4 It is the load-bearing capacity of the paper-based material under the action of a 200 g weight;

[0030] Figure 5 It is the change situation of the bonded paper-based materials after 3 h under the load-bearing action of a 200 g weight (the self-bonding paper-based material of the scheme described in the present invention is on the left, and the paper-based material bonded with commercially available glue is on the right);

[0031] Figure 6 It is the peel strength of the paper;

[0032] Figure 7It is a surface morphology structure diagram; where a is the base paper, b is the paper coated with the polyurethane additive of Example-1, b' is the paper at the peeling part during the peeling process after the paper coated with the polyurethane additive of Example-1 is treated by the hot pressing process, c is the paper coated with the commercially available glue, and c' is the paper at the peeling part during the peeling process after the paper coated with the commercially available glue is treated by the hot pressing process;

[0033] Figure 8 It is the rheological properties of the polyurethane additives in Examples 1-3;

[0034] Figure 9 It is the rheological properties of the polyurethane additives in Examples 4-6. Detailed implementation manners

[0035] The preparation method of a waterproof / self-adhesive papermaking additive of the present invention will be further described below in conjunction with specific embodiments. The specific embodiments are to further illustrate the present invention in detail and do not limit the protection scope of the present invention. Unless otherwise specified, the reagents, equipment and methods used in the present invention are the reagents, equipment and methods commonly purchased in the market and commonly used in the technical field.

[0036] In Examples 1 to 3, terminal dihydroxy organosiloxane is used as the soft segment, and the terminal dihydroxy compound containing a disulfide bond is used as the crosslinking agent.

[0037] Example 1:

[0038] A preparation method of a waterproof self-adhesive papermaking additive includes the following steps:

[0039] 3.33 g of polyethylene glycol (Mn = 2000 g / mol) is vacuum-dried at 120 °C for 2 h and then mixed with 2.67 g of terminal dihydroxy organosiloxane (Mn = 800 g / mol). Then it is placed in a three-necked flask and dissolved with 20 mL of N,N-dimethylformamide (DMF) under mechanical stirring at 200 r / min. Under nitrogen protection, 2.22 g of isophorone diisocyanate is added dropwise to the above solution. After mixing evenly, 0.005 g of dibutyltin dilaurate is added, and the reaction temperature of the system is adjusted to 40 °C. After reacting for 8 h, a polyurethane prepolymer with an isocyanate group at the end is obtained. 0.5 g of hyperbranched polyurethane with 8 hydroxyl groups at the end (Mn = 800 g / mol) is dissolved in 10 mL of DMF and then slowly added to the above reaction system. The reaction is carried out at 30 °C for 6 h to obtain hyperbranched polyurethane. 0.60 g of cystine is dissolved in 10 mL of DMF and then slowly added to the above reaction system. The reaction is carried out at 30 °C for 6 h to obtain a hyperbranched polyurethane solution.

[0040] Among the above components, the molar ratio of terminal dihydroxy polyol to terminal dihydroxy organosiloxane is 0.5:1.

[0041] Pour a part of the polyurethane solution into a polytetrafluoroethylene mold to prepare a polyurethane film, and use another part as an additive to coat the surface of the paper-based material to prepare a multifunctional paper-based material.

[0042] Example 2:

[0043] A preparation method of a waterproof self-adhesive papermaking additive, comprising the following steps:

[0044] Mix 2.67 g of polytetrahydrofuran (Mn = 800 g / mol) dried under vacuum at 120 °C for 2 h with 8.33 g of terminal dihydroxy organosiloxane (Mn = 5000 g / mol), then place it in a three-necked flask, and under mechanical stirring at 200 r / min, dissolve it with 20 mL of N,N-dimethylformamide (DMF). Protect with nitrogen, and gradually add 1.68 g of hexamethylene diisocyanate dropwise to the above solution using a constant pressure dropping funnel. After mixing evenly, add 0.005 g of dibutyltin dilaurate, adjust the reaction temperature of the system to 80 °C, and react for 3 h to obtain a polyurethane prepolymer with an isocyanate group at the end. Dissolve 0.83 g of hyperbranched polyurethane with 12 hydroxyl groups at the end (Mn = 2000 g / mol) in 10 mL of DMF, and slowly add it to the above reaction system, and react at 50 °C for 6 h to obtain hyperbranched polyurethane. Dissolve 0.39 g of bis(2-hydroxyethyl) disulfide in 10 mL of DMF, and slowly add it to the above reaction system, and react at 50 °C for 3 h to obtain a hyperbranched polyurethane solution.

[0045] Among the above components, the molar ratio of the terminal dihydroxy polyol to the terminal dihydroxy organosiloxane is 2:1.

[0046] Pour a part of the polyurethane solution into a polytetrafluoroethylene mold to prepare a polyurethane film, and use another part as an additive to coat the surface of the paper-based material to prepare a multifunctional paper-based material.

[0047] Example 3:

[0048] A preparation method of a waterproof self-adhesive papermaking additive, comprising the following steps:

[0049] 5.0 g of polytetrahydrofuran (Mn = 2000 g / mol) was vacuum dried at 120 °C for 2 h and then mixed with 5.0 g of terminal dihydroxy organosiloxane (Mn = 2000 g / mol). Then it was placed in a three-necked flask and dissolved with 20 mL of N,N-dimethylformamide (DMF) under mechanical stirring at 200 r / min. Under nitrogen protection, 2.50 g of 4,4'-methylenebis(phenyl isocyanate) was added dropwise to the above solution using a constant pressure dropping funnel. After mixing evenly, 0.005 g of dibutyltin dilaurate was added, and the reaction temperature of the system was adjusted to 60 °C. After reacting for 4 h, a polyurethane prepolymer with an isocyanate group at the end was obtained. 0.52 g of hyperbranched polyurethane with 48 hydroxyl groups at the end (Mn = 5000 g / mol) was dissolved in 10 mL of DMF and then slowly added to the above reaction system. The reaction was carried out at 40 °C for 4 h to obtain hyperbranched polyurethane. 0.62 g of 2,2-diaminodiphenyl disulfide was dissolved in 10 mL of DMF and then slowly added to the above reaction system. The reaction was carried out at 40 °C for 4 h to obtain a hyperbranched polyurethane solution.

[0050] Among the above components, the molar ratio of the terminal dihydroxy polyol to the terminal dihydroxy organosiloxane is 1:1.

[0051] Part of the polyurethane solution was poured into a polytetrafluoroethylene mold to prepare a polyurethane film, and part was used as an additive to coat the surface of the paper-based material to prepare a multifunctional paper-based material.

[0052] Examples 4 to 6: The terminal dihydroxy compound containing a disulfide bond was used as the soft segment, and the terminal dihydroxy organosiloxane was used as the crosslinking agent.

[0053] Example 4:

[0054] A preparation method of a waterproof self-adhesive papermaking aid, comprising the following steps:

[0055] 3.33 g of polyethylene glycol (Mn = 2000 g / mol) was vacuum dried at 120 °C for 2 h and then mixed with 0.80 g of cystine. Then it was placed in a three-necked flask and dissolved in 20 mL of N,N-dimethylformamide (DMF) under mechanical stirring at 200 r / min. Under nitrogen protection, 2.22 g of isophorone diisocyanate was added dropwise to the above solution using a constant pressure dropping funnel. After mixing evenly, 0.005 g of dibutyltin dilaurate was added, and the reaction temperature of the system was adjusted to 40 °C. After reacting for 8 h, a polyurethane prepolymer with an isocyanate group at the end was obtained. 0.5 g of hyperbranched polyurethane with 8 hydroxyl groups at the end (Mn = 800 g / mol) was dissolved in 10 mL of DMF and then slowly added to the above reaction system. The reaction was carried out at 30 °C for 6 h to obtain hyperbranched polyurethane. 2.0 g of dihydroxy-terminated organosiloxane (Mn = 800 g / mol) was dissolved in 10 mL of DMF and then slowly added to the above reaction system. The reaction was carried out at 30 °C for 6 h to obtain a hyperbranched polyurethane solution.

[0056] Among the above components, the molar ratio of dihydroxy-terminated polyol to cystine is 0.5:1.

[0057] Part of the polyurethane solution was poured into a polytetrafluoroethylene mold to prepare a polyurethane film, and part was coated on the surface of the paper-based material as an additive to prepare a multifunctional paper-based material.

[0058] Example 5:

[0059] A preparation method of a waterproof self-adhesive papermaking additive, comprising the following steps:

[0060] 2.67 g of polytetrahydrofuran (Mn = 800 g / mol) was vacuum dried at 120 °C for 2 h and then mixed with 0.26 g of bis(2-hydroxyethyl) disulfide. Then it was placed in a three-necked flask and dissolved in 20 mL of N,N-dimethylformamide (DMF) under mechanical stirring at 200 r / min. Under nitrogen protection, 1.68 g of hexamethylene diisocyanate was added dropwise to the above solution using a constant pressure dropping funnel. After mixing evenly, 0.005 g of dibutyltin dilaurate was added, and the reaction temperature of the system was adjusted to 80 °C. After reacting for 3 h, a polyurethane prepolymer with an isocyanate group at the end was obtained. 0.83 g of hyperbranched polyurethane with 12 hydroxyl groups at the end (Mn = 2000 g / mol) was dissolved in 10 mL of DMF and then slowly added to the above reaction system. The reaction was carried out at 50 °C for 6 h to obtain hyperbranched polyurethane. 12.5 g of dihydroxy-terminated organosiloxane (Mn = 5000 g / mol) was dissolved in 10 mL of DMF and then slowly added to the above reaction system. The reaction was carried out at 50 °C for 3 h to obtain a hyperbranched polyurethane solution.

[0061] Among the above components, the molar ratio of the terminal dihydroxy polyol to the terminal dihydroxy organosiloxane is 2:1.

[0062] Pour a part of the polyurethane solution into a polytetrafluoroethylene mold to prepare a polyurethane film, and coat a part of it on the surface of the paper-based material as an additive to prepare a multifunctional paper-based material.

[0063] Example 6:

[0064] A preparation method of a waterproof self-adhesive papermaking additive, comprising the following steps:

[0065] Dissolve 5.0 g of polytetrahydrofuran (Mn = 2000 g / mol) in vacuum at 120 °C for 2 h, mix it with 0.62 g of 2,2-diaminodiphenyl disulfide, then place it in a three-necked flask, and under mechanical stirring at 200 r / min, dissolve it with 20 mL of N,N-dimethylformamide (DMF). Protect it with nitrogen, and gradually add 2.50 g of 4,4'-methylenebis(phenyl isocyanate) to the above solution dropwise using a constant pressure dropping funnel. After mixing evenly, add 0.005 g of dibutyltin dilaurate, adjust the reaction temperature of the system to 60 °C, and react for 4 h to obtain a polyurethane prepolymer with an isocyanate group at the end. Dissolve 0.52 g of hyperbranched polyurethane with 48 hydroxyl groups at the end (Mn = 5000 g / mol) in 10 mL of DMF, and slowly add it to the above reaction system, and react at 40 °C for 4 h to obtain hyperbranched polyurethane. Dissolve 5.0 g of terminal dihydroxy organosiloxane (Mn = 2000 g / mol) in 10 mL of DMF, and slowly add it to the above reaction system, and react at 40 °C for 4 h to obtain a hyperbranched polyurethane solution.

[0066] Among the above components, the molar ratio of the terminal dihydroxy polyol to the terminal dihydroxy organosiloxane is 1:1.

[0067] Pour a part of the polyurethane solution into a polytetrafluoroethylene mold to prepare a polyurethane film, and coat a part of it on the surface of the paper-based material as an additive to prepare a multifunctional paper-based material.

[0068] Implementation effect example

[0069] I. Conduct a contact angle test on the original paper and the multifunctional paper-based material prepared by the above example scheme. The experimental results are shown in Figure 3 , from Figure 3 It can be seen that the polyurethane papermaking additive prepared by the scheme of the present invention can significantly improve the waterproof performance of the paper-based material.

[0070] II. Measure the self-adhesive performance of the paper-based material by the peel strength.

[0071] First, use a rotary evaporator to concentrate the concentration of the polyurethane additive to 50%. Then, use a coating rod to evenly coat the polyurethane additive on the surface of the paper and air-dry it at room temperature to obtain a multifunctional paper-based material. Lay this paper flat above the base paper of the same size, and then put the two papers into a hot press at the same time. Control the temperature of the hot press at 100 °C, the pressure at 1000 kg, and the time at 10 min. Use a 200 g weight to measure the load-bearing capacity of the bonded paper-based material, and use a universal tensile machine to measure the peel strength of the paper. The experimental results are as Figure 4 , Figure 5 and Figure 6 shown:

[0072] Through Figure 4 it can be observed that the load-bearing capacity of the bonded paper-based material can reach 200 g (the weight of the weight). In addition, the same test was carried out on the paper-based material with a commercially available glue. Through Figure 5 it was found (the left side is the self-bonding paper-based material of the present invention, and the right side is the paper-based material bonded with the commercially available glue) that under the load of a 200 g weight, after 3 h, the self-bonding paper-based material prepared by the present invention still maintains good bonding performance, while the paper-based material bonded with the commercially available glue shows obvious tearing phenomenon.

[0073] Through Figure 6 it is shown that after the polyurethane additives prepared in Examples 1-6 are coated on the paper material and the paper is self-bonded, the bonded paper-based materials have a relatively high peel strength, which indicates that the polyurethane papermaking additive prepared by the experimental scheme described in the present invention can endow the paper-based material with relatively high self-bonding performance.

[0074] III. In order to further prove the change situation of the bonded paper-based material during the peeling process, taking the polyurethane additive prepared in Example -1 as an example, the applicant of the present invention used a scanning electron microscope to observe the morphological structure changes on the surface of the paper-based before and after tearing.

[0075] Figure 7 a is the surface morphological structure of the uncoated base paper, and obvious fiber filaments can be seen. Figure 7 b and Figure 7 b’ are respectively the morphological structures of the paper coated with the polyurethane additive in Example -1 and the surface of the paper after peeling. Through Figure 7 b and Figure 7It can be seen that the fiber structure on the surface of the paper coated with the polyurethane additive is covered. After being treated by the hot pressing process and through the peel strength test, the bonded paper-based material is torn, and obvious cellulose filamentous structures appear on the paper surface again. Moreover, compared with the original paper, there are obvious fiber burrs on the fiber surface. This indicates that during the peeling process, it is the structure of cellulose itself that is damaged, rather than the additive itself having poor adhesion. In contrast, for the paper coated with the commercially available glue, after the same peel strength test, although obvious fibers can also be seen at the peeling interface, there is still glue on the fiber surface ( Figure 7 c and 7c’), which shows that the polyurethane additive prepared by the experimental scheme described in the present invention has a strong self-bonding function for the paper-based material.

[0076] IV. In order to analyze the self-bonding mechanism of the additive to the paper, we used a high-efficiency rotational rheometer to measure the dynamic rheological properties of the polyurethane additive film

[0077] Through Figure 8 and Figure 9 it can be observed that for the polyurethane additives prepared in Examples 1-6, at 60 °C and low frequency, the storage modulus G’ (solid) and the loss modulus G’’ (hollow) intersect. This indicates that polyurethane can reach the viscous flow state at temperatures above 60 °C, and the molecular chains themselves have strong dynamic exchange capabilities. When the polyurethane additive is coated on the paper-based surface, at the hot pressing temperature of the hot press, molecular chain entanglements are formed between the polyurethane molecular chains and the paper-based fibers, and dynamic exchange occurs through the disulfide bonds in the polyurethane molecular chains, resulting in the formation of an interpenetrating network between the polyurethane and cellulose, and thus generating a self-bonding effect.

Claims

1. A waterproof self - adhesive papermaking aid, characterized in that, It includes the following component raw materials: terminal dihydroxy polyol, terminal dihydroxy organosiloxane, terminal dihydroxy monomer containing disulfide bond, diisocyanate, and terminal hydroxy hyperbranched polyester; The molar ratio of the total hydroxyl groups (-OH) in the terminal dihydroxy polyol, terminal dihydroxy organosiloxane, and terminal dihydroxy compound containing disulfide bond to the isocyanate groups (-NCO) in the diisocyanate is n(-OH):n(-NCO)=3:4, and the molar ratio of the hydroxyl groups (-OH) in the terminal hydroxy hyperbranched polyester to the isocyanate groups (-NCO) in the diisocyanate is n(-OH):n(-NCO)=1:4; The preparation method of the waterproof self-adhesive papermaking aid includes: reacting the terminal dihydroxy polyol, terminal dihydroxy organosiloxane, and diisocyanate to generate a terminal isocyanate group polyurethane prepolymer, then adding the terminal hydroxy hyperbranched polyester to prepare hyperbranched polyurethane, and finally adding the terminal dihydroxy monomer containing disulfide bond to synthesize the waterproof self-adhesive papermaking aid; Or, the preparation method of the waterproof self-adhesive papermaking aid includes: reacting the terminal dihydroxy polyol, terminal dihydroxy monomer containing disulfide bond, and diisocyanate to generate a terminal isocyanate group polyurethane prepolymer containing disulfide bond, then adding the terminal hydroxy hyperbranched polyester to prepare hyperbranched polyurethane, and finally adding the terminal dihydroxy organosiloxane containing disulfide bond to synthesize the waterproof self-adhesive papermaking aid.

2. The waterproof self-adhesive papermaking aid according to claim 1, wherein When the terminal dihydroxy polyol and terminal dihydroxy organosiloxane are used as the soft segments and the terminal dihydroxy monomer containing disulfide bond is used as the cross-linking agent, the molar ratio of the terminal dihydroxy polyol to the terminal dihydroxy organosiloxane is 0.5:1 to 2:1, the overall molar ratio of the terminal dihydroxy polyol and terminal dihydroxy organosiloxane to the diisocyanate groups is 1:2, and the molar ratio of the terminal dihydroxy monomer containing disulfide bond to the diisocyanate groups is 1:

4.

3. The waterproof self-adhesive papermaking aid according to claim 1, characterized in that, When the terminal dihydroxy polyol and terminal dihydroxy monomer containing disulfide bond are used as the soft segments and the terminal dihydroxy organosiloxane is used as the cross-linking agent, the molar ratio of the terminal dihydroxy polyol to the terminal dihydroxy organosiloxane is 0.5:1 to 2:1, the overall molar ratio of the terminal dihydroxy polyol and terminal dihydroxy organosiloxane to the diisocyanate groups is 1:2, and the molar ratio of the terminal dihydroxy organosiloxane to the diisocyanate groups is 1:

4.

4. The waterproof self-adhesive papermaking aid according to claim 1, wherein, The polyol is one or both of polyethylene glycol and polytetrahydrofuran, and its molecular weight is 800-5000 g / mol; and / or, the diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-methylenebis(phenyl isocyanate); and / or, the molecular weight of the terminal dihydroxy organosiloxane is 800-5000 g / mol; and / or, the terminal dihydroxy monomer containing disulfide bond is one or more of cystine, bis(2-hydroxyethyl) disulfide, and 2,2-diaminodiphenyl disulfide; and / or, the number of hydroxyl groups at the end of the terminal hydroxy hyperbranched polyester is selected from one or more of 8, 12, 24, 36, and 48, and the corresponding molecular weight is 800-5000 g / mol.

5. A preparation method of the waterproof self-adhesive papermaking aid according to claim 1, characterized in that, It includes the following steps: S1. Condensation reaction occurs between terminal dihydroxy polyol, terminal dihydroxy organosiloxane and diisocyanate under the action of the catalyst dibutyltin dilaurate to synthesize a terminal isocyanate group polyurethane prepolymer; S2. Add terminal hydroxyl hyperbranched polyester to the reaction system S1, and prepare hyperbranched polyurethane by the condensation reaction between the hydroxyl groups in their molecular structures and the residual isocyanate groups in S1; S3. Add a terminal dihydroxy monomer containing a disulfide bond to the reaction system of S2, and crosslink different hyperbranched polyurethanes together by the reaction between the hydroxyl groups at both ends of this compound and the residual isocyanate groups in the polymerization reaction to synthesize a polyurethane auxiliary with a relatively high crosslinking degree.

6. The preparation method according to claim 5, characterized in that, Exchange the terminal dihydroxy organosiloxane in step S1 with the terminal dihydroxy monomer containing a disulfide bond in step S3.

7. The preparation method according to claim 5, wherein In step S1, the reaction temperature is 40 - 80 °C and the reaction time is 3 - 8 h.

8. The preparation method according to claim 5, characterized in that, In step S2, the reaction temperature is 30 - 50 °C and the reaction time is 3 - 6 h; and / or, in step S3, the reaction temperature is 30 - 50 °C and the reaction time is 3 - 6 h.

9. Application of the waterproof self - adhesive papermaking auxiliary as claimed in claim 1 or the waterproof self - adhesive papermaking auxiliary prepared by the preparation method as claimed in claim 5 as a paper waterproof layer.

10. The application according to claim 9, characterized in that Apply the obtained auxiliary to the paper - based material and perform hot pressing to obtain.

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