Cationic chain extender, its preparation method and application

Abstract

The application relates to a cationic chain extender and a preparation method and application thereof, and belongs to the technical field of high polymer materials. The cationic chain extender has a structure shown in formula I. The preparation method of the cationic chain extender comprises the following steps: after a mercaptan diol is mixed with an organic base, a halogenated alkyl quaternary ammonium salt is added to carry out a reaction, so that the cationic chain extender is obtained. The cationic chain extender provided by the application has a side chain type permanent cation structure. When the cationic chain extender is applied to water-based polyurethane emulsion, the mechanical properties of the obtained coating film can be obviously improved while the good interface function is maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular materials, and particularly relates to a cationic chain extender, a preparation method and application thereof. BACKGROUND

[0002] Waterborne polyurethane (WPU) is widely used in the fields of coatings, adhesives and functional films (such as inkjet ink-receiving layer) due to its low VOC, excellent film-forming property and mechanical / weathering performance. Currently, in order to achieve stable water dispersion, three types of hydrophilic modification paths are commonly used in industry: anionic, non-ionic and cationic. Among them, cationic WPU can significantly improve the wet adhesion and initial adhesion to substrates such as glass, cellulose and polyester by electrostatic adsorption of positive charges and negatively charged surfaces, and can quickly "fix" the anionic dye / pigment dispersion in the inkjet system, which helps to improve the clarity of the printed text and the anti-feathering ability.

[0003] The existing cationic WPU mainly uses protonated tertiary amines, that is, tertiary amines are introduced in the prepolymerization / chain extension stage, and then neutralized with organic acids to form stable cations in the emulsion stage, thereby obtaining good dispersibility and construction stability. However, during the film-forming process, as the acid volatilizes, the tertiary amine salt gradually deprotonates, and the cation density on the surface of the coating film decreases. This change is beneficial on the one hand to reduce the hydrophilicity of the coating after film formation, thereby improving the water resistance and salt mist resistance, and on the other hand, it also weakens the surface positive characteristics of the coating and the interfacial interaction with anionic substrates / dyes, which has potential performance degradation in applications that require long-term surface positive charge or long-term dye fixation.

[0004] In order to overcome the above shortcomings, industry attempts to use alkylated tertiary amines to prepare permanent quaternary ammonium salt (R4N + ) structure to maintain stable cations in the coating film. However, this route usually requires the use of dimethyl sulfate and other highly toxic alkylating agents, which poses a serious safety hazard. In addition, existing technologies often introduce cations into the polyurethane main chain skeleton, and such main chain type structure easily destroys the hydrogen bonding association and microphase separation between hard segments, resulting in a significant decrease in the mechanical properties of the coating film.

[0005] Therefore, it is urgent to propose a safe and process-friendly cationic chain extender that can maintain a permanent cationic structure while reducing the damage to the hard segment skeleton. SUMMARY

[0006] To solve the above technical problems, the present application provides a cationic chain extender, a preparation method and application thereof. The cationic chain extender is a side-chain type permanent cation, which can not only impart the obtained coating film with persistent surface positive characteristics and excellent dispersion stability when applied to waterborne polyurethane emulsion, but also avoid excessive interference with the hydrogen bonding association and microphase separation of hard segments, thereby achieving the purpose of maintaining good interfacial function while significantly improving the mechanical properties of the coating film.

[0007] To achieve the above object, the present application adopts the following technical solutions.

[0008] In a first aspect, the present application provides a cationic chain extender, which has a structure shown in Formula I:

[0009] Formula I;

[0010] wherein R1, R2, R3 are the same or different, and each is independently selected from C1-C5 alkyl;

[0011] n represents an integer of 2-6; and X is selected from halogen;

[0012] R4 is selected from any one of the following groups:

[0013] ;

[0014] The wavy line represents a connecting site;

[0015] The cationic chain extender is prepared by the following preparation method, which comprises the following steps:

[0016] After mixing the mercaptan diol with an organic base, a halogenated alkyl quaternary ammonium salt is added for reaction to obtain the cationic chain extender.

[0017] The present application designs the structure of the cationic chain extender to be a permanent cationic structure with side chains, which can make the obtained waterborne polyurethane emulsion more stable when applied to the waterborne polyurethane emulsion, can not only impart the coating film after film forming with persistent surface positive characteristics and excellent dispersion stability, but also can avoid excessive interference with the hydrogen bonding association and microphase separation of the hard segment, so as to achieve the purpose of maintaining good interface function while significantly improving the mechanical properties of the coating film.

[0018] In the structure shown in Formula I of the present application, C1-C5 in C1-C5 alkyl can be C1, C2, C3, C4 or C5; n can represent 2, 3, 4, 5 or 6.

[0019] The following are preferred technical solutions of the present application, but not as a limitation on the technical solutions provided by the present application. Through the following preferred technical solutions, the purpose and beneficial effects of the present application can be better achieved and realized.

[0020] As a preferred technical solution of the present application, R1, R2, R3 are the same or different, and each is independently selected from methyl or ethyl;

[0021] n represents 3 or 4.

[0022] In a second aspect, the present application provides a method for preparing the cationic chain extender as described in the first aspect, the method comprising the following steps:

[0023] After mixing the mercaptan diol with the organic base, the halogenated alkyl quaternary ammonium salt is added to react, to obtain the cationic chain extender.

[0024] The method for preparing the cationic chain extender provided by the present application is simple, avoids the use of traditional high-toxicity alkylating agents such as dimethyl sulfate and iodomethane, and has the characteristics of mild synthesis conditions and high safety. In the preparation process, the mercaptan diol is deprotonated to generate a sulfur anion under the action of the organic base, and then the sulfur anion acts as a nucleophile to undergo a nucleophilic substitution reaction with the halogenated alkyl quaternary ammonium salt, thereby obtaining a cationic chain extender with a side chain type permanent cation structure, which well achieves the purpose of introducing a permanent quaternary ammonium salt group through a sulfide bond, and further enables the cationic chain extender to significantly improve the mechanical properties of the obtained coating film while maintaining good interfacial function when applied to a waterborne polyurethane emulsion.

[0025] Preferably, the mercaptan diol comprises any one of 3-mercapto-1,2-propanediol, 2-mercapto-1,3-propanediol, 3-mercapto-1,2-butanediol, or 4-mercapto-1,3-butanediol.

[0026] Preferably, the organic base comprises any one of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), or 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), or a combination of at least two thereof.

[0027] Preferably, the molar ratio of the organic base to the mercaptan diol is (1.0-2.0):1, wherein (1.0-2.0) can be, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0, and specific point values between the above point values. Due to the limitation of the length and the consideration of simplicity, the present application will not exhaustively list the specific point values included in the range.

[0028] Preferably, the mixing is performed under stirring.

[0029] It should be noted that the present application does not have special limitations on the specific speed of stirring, and the conventional speed in the art is applicable.

[0030] Preferably, the temperature of the mixing is 20-30°C, which can be, for example, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C, and specific point values between the above point values. Due to the limitation of the length and the consideration of simplicity, the present application will not exhaustively list the specific point values included in the range.

[0031] Preferably, the mixing time is 10-30 min, for example, it can be 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min, 28 min or 30 min, and specific point values between the above-mentioned point values, limited to the length and for the sake of simplicity, the present application will not be listed again the specific point values included in the range.

[0032] Preferably, the halogenated alkyl quaternary ammonium salt has the structure shown in Formula II:

[0033] Formula II;

[0034] wherein R1, R2, R3 are the same or different, each independently selected from C1-C5 alkyl;

[0035] n represents an integer of 2-6; X is selected from halogen.

[0036] In the structure shown in Formula II of the present application, C1-C5 in C1-C5 alkyl can be C1, C2, C3, C4 or C5; n can represent 2, 3, 4, 5 or 6.

[0037] As a preferred technical solution of the present application, the halogenated alkyl quaternary ammonium salt includes any one of (3-bromopropyl)-trimethylammonium bromide, (3-chloropropyl)-trimethylammonium chloride, (3-bromopropyl)-triethylammonium bromide, (3-chloropropyl)-triethylammonium chloride, (4-bromobutyl)-trimethylammonium bromide or (4-chlorobutyl)-trimethylammonium chloride.

[0038] Preferably, the molar ratio of the halogenated alkyl quaternary ammonium salt to the mercaptan diol is 1:(1.2-2.0), wherein (1.2-2.0) can be 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0, and specific point values between the above-mentioned point values, limited to the length and for the sake of simplicity, the present application will not be listed again the specific point values included in the range.

[0039] Preferably, the halogenated alkyl quaternary ammonium salt is added in the form of dropwise.

[0040] It should be noted that in the present application, the halogenated alkyl quaternary ammonium salt can be slowly added to the reaction system by dropwise addition, so that the reaction is more complete, thereby reducing the generation of by-products, and further improving the yield of the target product. There is no special limitation on the speed of dropwise addition, and the commonly used dropwise addition speed in the art is applicable.

[0041] Preferably, the reaction is carried out in the presence of solvent A.

[0042] Preferably, the solvent A comprises a polar aprotic solvent.

[0043] Preferably, the polar aprotic solvent comprises any one or a combination of at least two of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), or acetonitrile (MeCN).

[0044] Preferably, the ratio of the mass of the solvent A to the sum of the mass of the mercaptandiol, the haloalkyl quaternary ammonium salt, and the organic base is (5-10):1, wherein (5-10) can be 5, 6, 7, 8, 9, or 10, and specific point values between the aforementioned point values, the present application will not be exhaustively listed, the specific point values included in the range are not listed due to the limitation of the length and the consideration of simplicity.

[0045] Preferably, the temperature of the reaction is 50-90℃, which can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, or 90℃, and specific point values between the aforementioned point values, the present application will not be exhaustively listed, the specific point values included in the range are not listed due to the limitation of the length and the consideration of simplicity.

[0046] Preferably, the time of the reaction is 1-5 h, which can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, or 5 h, and specific point values between the aforementioned point values, the present application will not be exhaustively listed, the specific point values included in the range are not listed due to the limitation of the length and the consideration of simplicity.

[0047] Preferably, the reaction is carried out under an atmosphere of a protective gas.

[0048] Preferably, the protective gas comprises any one or a combination of at least two of nitrogen, argon, or helium.

[0049] Preferably, the method for preparing the cationic chain extender provided by the present application specifically comprises the following steps:

[0050] After the mercaptandiol, the organic base, and the solvent A are stirred at 20-30℃ for 10-30 min under an atmosphere of a protective gas, the haloalkyl quaternary ammonium salt is added, and the reaction is carried out at 50-90℃ for 1-5 h to obtain the cationic chain extender.

[0051] Exemplarily, with 3-mercapto-1,2-propanediol as the mercaptandiol, (3-bromopropyl)-trimethylammonium bromide as the haloalkyl quaternary ammonium salt, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the organic base, the preparation mechanism of the cationic chain extender is as follows:

[0052] .

[0053] In a third aspect, the present application provides a waterborne polyurethane emulsion, raw materials for preparing the waterborne polyurethane emulsion comprising the cationic chain extender as described in the first aspect.

[0054] The use of the specific side chain type cationic chain extender in the present application achieves the purpose of reducing the destruction of the hard segment skeleton while maintaining the permanent cationic structure, thereby significantly improving the mechanical properties of the waterborne polyurethane emulsion after film formation while maintaining good interface function, effectively solving the technical problem that the main chain type cationic structure in the prior art is easy to destroy the hydrogen bond association and microphase separation between hard segments, thereby causing the mechanical properties of the coating film to decrease significantly.

[0055] Preferably, the raw materials for preparing the waterborne polyurethane emulsion comprise the following components in parts by weight:

[0056] Diisocyanate 15-30 parts;

[0057] Polymer polyol 30-55 parts;

[0058] Cationic chain extender 5-11.5 parts;

[0059] Small molecule chain extender 1.5-3.5 parts;

[0060] Catalyst 0.1-0.5 parts;

[0061] Solvent B 20-70 parts;

[0062] Water 100-300 parts.

[0063] The present application optimizes the selection and content of the raw materials for preparing the waterborne polyurethane emulsion, which can further improve the comprehensive performance of the obtained waterborne polyurethane emulsion, so that it has better tensile strength and shorter ink drying time after film formation on the basis of maintaining emulsion stability.

[0064] In the raw materials for preparing the waterborne polyurethane emulsion provided by the present application, the weight fraction of isocyanate can be 15 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts or 30 parts, and specific point values between the above point values. Due to the limitation of the length and the consideration of simplicity, the present application does not exhaustively list the specific point values included in the range.

[0065] In the raw materials for preparing the waterborne polyurethane emulsion provided by the present application, the weight fraction of polyol can be 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, 42 parts, 45 parts, 48 parts, 50 parts, 52 parts or 55 parts, and specific point values between the above point values. Due to the limitation of the length and the consideration of simplicity, the present application does not exhaustively list the specific point values included in the range.

[0066] The weight fraction of the cationic chain extender in the preparation raw material of the aqueous polyurethane emulsion provided by the application can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts or 11.5 parts, and specific point values between the above-mentioned point values. Due to the limited space and the consideration of simplicity, the application will not list the specific point values included in the range.

[0067] The weight fraction of the small molecule chain extender in the preparation raw material of the aqueous polyurethane emulsion provided by the application can be 1.5 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts or 3.5 parts, and specific point values between the above-mentioned point values. Due to the limited space and the consideration of simplicity, the application will not list the specific point values included in the range.

[0068] The weight fraction of the catalyst in the preparation raw material of the aqueous polyurethane emulsion provided by the application can be 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts or 0.5 parts, and specific point values between the above-mentioned point values. Due to the limited space and the consideration of simplicity, the application will not list the specific point values included in the range.

[0069] The weight fraction of the solvent B in the preparation raw material of the aqueous polyurethane emulsion provided by the application can be 20 parts, 30 parts, 40 parts, 50 parts, 60 parts or 70 parts, and specific point values between the above-mentioned point values. Due to the limited space and the consideration of simplicity, the application will not list the specific point values included in the range.

[0070] The weight fraction of the water in the preparation raw material of the aqueous polyurethane emulsion provided by the application can be 100 parts, 120 parts, 150 parts, 180 parts, 200 parts, 220 parts, 250 parts, 280 parts or 300 parts, and specific point values between the above-mentioned point values. Due to the limited space and the consideration of simplicity, the application will not list the specific point values included in the range.

[0071] As a preferred technical solution of the application, the molar ratio of the cationic chain extender to the small molecule chain extender is (0.7-2.1):1, wherein (0.7-2.1) can be 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9 or 2.1, and specific point values between the above-mentioned point values. Due to the limited space and the consideration of simplicity, the application will not list the specific point values included in the range.

[0072] In the present application, by optimizing the molar ratio of the cationic chain extender and the small molecule chain extender, the comprehensive performance of the obtained waterborne polyurethane emulsion can be further improved, so that it has better tensile strength and shorter ink drying time after film formation on the basis of maintaining emulsion stability. When the molar ratio is low, the content of the cationic chain extender is low, which makes the waterborne polyurethane emulsion unstable, the average particle size increases, and the ink drying time is significantly prolonged, but the tensile strength is slightly increased because the disturbance to the hydrogen bond association and microphase separation of the hard segment is smaller.

[0073] When the molar ratio is high, the content of the cationic chain extender gradually increases, which makes the surface effective positive charge density increase, the emulsion particle size decrease and tend to be stable, and the ink drying time continuously shorten, but the mechanical properties first decrease and then increase due to the increased disturbance to the hard segment phase separation, and the high equivalent area improves the mechanical properties due to ionic crosslinking. When the molar ratio is too high, the surface charge density of the emulsion particles is too large, and the counter ions will be enriched around the particles, causing charge shielding and weakening the electrostatic repulsion between particles, thereby causing the aggregation between particles, so that the average particle size of the emulsion increases. At the same time, ionic crosslinking mainly comes from the electrostatic interaction between quaternary ammonium salt cations and counter ions. When the amount is appropriate, uniform ionic clusters are formed, which can be used as physical crosslinking points to enhance the mechanical properties of the coating film. When the proportion of the cationic chain extender is too high, the ionic clusters gradually gather into uneven ionic blocks, which destroys the original microphase structure and makes the crosslinking ineffective, thereby leading to the decrease of the mechanical properties of the coating film.

[0074] Preferably, the diisocyanate includes any one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), or tetramethylxylylene diisocyanate (TMXDI), or a combination of at least two of them.

[0075] Preferably, the number average molecular weight of the polymeric polyol is 2000-3000, for example, it can be 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900 or 3000, and specific point values between the above point values. Due to the consideration of brevity and simplicity, the present application will not enumerate the specific point values included in the range.

[0076] Preferably, the polymeric polyol includes any one of polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PEG), polycaprolactone diol (PCL), or polycarbonate diol (PCDL), or a combination of at least two of them.

[0077] Preferably, the small molecule chain extender includes a small molecule alcohol.

[0078] Preferably, the small molecule alcohol includes any one or a combination of at least two of ethylene glycol, propylene glycol, butylene glycol or hexylene glycol.

[0079] Preferably, the catalyst includes an organometallic catalyst.

[0080] Preferably, the organometallic catalyst includes an organobismuth catalyst and / or an organotin catalyst.

[0081] Preferably, the organobismuth catalyst includes any one or a combination of at least two of bismuth isooctoate, bismuth laurate or bismuth neodecanoate.

[0082] Preferably, the organotin catalyst includes any one or a combination of at least two of dibutyltin dilaurate (DBTDL), stannous octoate or dibutyltin diacetate.

[0083] Preferably, the solvent B includes any one or a combination of at least two of acetone, butanone or N-methyl pyrrolidone (NMP).

[0084] Preferably, the mass ratio of the cationic chain extender to the solvent B is 1:(3-7), wherein (3-7) can be 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 or 7, and specific point values between the above point values, for the sake of brevity, the present application does not exhaustively list the specific point values included in the range.

[0085] In a fourth aspect, the present application provides a preparation method of the aqueous polyurethane emulsion as described in the third aspect, the preparation method comprising the following steps:

[0086] (1) mixing diisocyanate, polymeric polyol and catalyst and then reacting to obtain a prepolymer;

[0087] (2) adding a mixture of cationic chain extender and solvent B to the prepolymer of step (1) to perform a first chain extension reaction, then adding a small molecule chain extender to perform a second chain extension reaction, and finally adding water to obtain the aqueous polyurethane emulsion.

[0088] It should be noted that in the present application, water is used as an emulsifier to make the obtained aqueous polyurethane into an emulsion state. In production and application, different state aqueous polyurethane products can be prepared according to the needs of actual application scenarios.

[0089] Preferably, the mixing of step (1) is performed under stirring.

[0090] Preferably, the temperature of the reaction of step (1) is 75-85 °C, for example it can be 75 °C, 76 °C, 77 °C, 78 °C, 79 °C, 80 °C, 81 °C, 82 °C, 83 °C, 84 °C or 85 °C, and specific point values between the aforementioned point values, the present application does not exhaustively list the specific point values included in the range for the sake of brevity and conciseness.

[0091] Preferably, the time of the reaction of step (1) is 2-3 h, for example it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3 h, and specific point values between the aforementioned point values, the present application does not exhaustively list the specific point values included in the range for the sake of brevity and conciseness.

[0092] Preferably, the temperature of the first chain extension reaction of step (2) is 75-85 °C, for example it can be 75 °C, 76 °C, 77 °C, 78 °C, 79 °C, 80 °C, 81 °C, 82 °C, 83 °C, 84 °C or 85 °C, and specific point values between the aforementioned point values, the present application does not exhaustively list the specific point values included in the range for the sake of brevity and conciseness.

[0093] Preferably, the time of the first chain extension reaction of step (2) is 0.5-1 h, for example it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h or 1 h, and specific point values between the aforementioned point values, the present application does not exhaustively list the specific point values included in the range for the sake of brevity and conciseness.

[0094] Preferably, the temperature of the second chain extension reaction of step (2) is 60-65 °C, for example it can be 60 °C, 61 °C, 62 °C, 63 °C, 64 °C or 65 °C, and specific point values between the aforementioned point values, the present application does not exhaustively list the specific point values included in the range for the sake of brevity and conciseness.

[0095] Preferably, the time of the second chain extension reaction of step (2) is 0.5-1 h, for example it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h or 1 h, and specific point values between the aforementioned point values, the present application does not exhaustively list the specific point values included in the range for the sake of brevity and conciseness.

[0096] Preferably, the water is added under stirring.

[0097] Preferably, the stirring speed is 1000-2000 rpm, for example, it can be 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm or 2000 rpm, and specific point values between the above-mentioned point values, for the sake of brevity and simplicity, the present application does not list the specific point values included in the range.

[0098] Preferably, the preparation method of the waterborne polyurethane emulsion specifically comprises the following steps:

[0099] (1) mixing diisocyanate, polymeric polyol and catalyst, and then reacting at 75-85°C for 2-3 h to obtain a prepolymer;

[0100] (2) adding a mixture of cationic chain extender and solvent B to the prepolymer of step (1), and then performing a first chain extension reaction at 75-85°C for 0.5-1 h, followed by adding a small molecule chain extender and performing a second chain extension reaction at 60-65°C for 0.5-1 h, and finally adding water under stirring at 1000-2000 rpm to obtain the waterborne polyurethane emulsion.

[0101] In a fifth aspect, the present application provides a waterborne polyurethane emulsion as described in the third aspect for use in a coating, an adhesive or a functional film.

[0102] Compared with the prior art, the present application has at least the following beneficial effects:

[0103] (1) By designing the raw materials for preparing the cationic chain extender, the present application can make it have a side chain type permanent cationic structure, and thus when applied to a waterborne polyurethane emulsion, the obtained waterborne polyurethane emulsion is more stable, which can not only impart the coating film after film formation with persistent surface positive characteristics and excellent dispersion stability, but also avoid excessive interference with hydrogen bonding and microphase separation of hard segments, thereby achieving the purpose of significantly improving the mechanical properties of the coating film while maintaining good interface function.

[0104] (2) The cationic chain extender provided by the present application can make the particle size of the obtained waterborne polyurethane emulsion be 52-128 nm, and the tensile strength of the coating film after film formation be 5.5-11.8 MPa, and the ink dry time be 10-42 s. DETAILED DESCRIPTION

[0105] In order to facilitate the understanding of the present application, the present application lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0106] The raw materials and reagents used in the following examples and application examples are all commercially available products unless otherwise specified, and part of the raw material information is as follows:

[0107] Polycarbonate diol (PCDL): number average molecular weight 2000, purchased from Shanghai Shuxu Chemical Co., Ltd. SYHP2000;

[0108] Polytetramethylene ether glycol (PTMG): number average molecular weight 2000, purchased from Mitsubishi Chemical PTMG 2000;

[0109] Polyethylene glycol (PEG): number average molecular weight 3000, purchased from Zhejiang Kaidi Chemical Co., Ltd. PEG-3000.

[0110] Example 1

[0111] The present embodiment provides a cationic chain extender and a preparation method thereof, and the preparation raw material of the cationic chain extender comprises the following components in parts by weight:

[0112] 3-mercapto-1,2-propanediol 2.81 parts;

[0113] 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) 3.96 parts;

[0114] (3-bromopropyl)-trimethylammonium bromide 3.39 parts;

[0115] N,N-dimethylformamide (DMF) 71.00 parts.

[0116] The preparation method of the cationic chain extender comprises the following steps:

[0117] After 3-mercapto-1,2-propanediol, DBU and DMF are stirred at 25°C for 20 min under the atmosphere of nitrogen, (3-bromopropyl)-trimethylammonium bromide is added, and the reaction is carried out at 70°C for 3 h to obtain the cationic chain extender.

[0118] The nuclear magnetic resonance characterization data of the cationic chain extender are as follows:

[0119] 1 H NMR (400 MHz, D2O): δ3.88-3.74(m, 1H), 3.71-3.61(m, 2H), 3.60-3.52(m, 2H), 3.18(s, 9H), 2.93-2.78(m, 4H), 1.89-1.77(quint, J=6.8 Hz, 2H).

[0120] Example 2

[0121] The embodiment provides a cationic chain extender and a preparation method thereof, and the cationic chain extender is only different from that in the embodiment 1 in that (3-bromopropyl)-trimethylammonium bromide is replaced by equimolar (3-bromopropyl)-triethylammonium bromide, and other raw material components, contents and the preparation method are the same as those in the embodiment 1.

[0122] Embodiment 3

[0123] The embodiment provides a cationic chain extender and a preparation method thereof, and the preparation raw material of the cationic chain extender comprises the following components in parts by weight:

[0124] 3-mercapto-1,2-propanediol 2.81 parts;

[0125] 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) 5.96 parts;

[0126] (4-bromobutyl)-trimethylammonium bromide 5.78 parts;

[0127] N,N-dimethylacetamide (DMAc) 80.00 parts.

[0128] The preparation method of the cationic chain extender comprises the following steps:

[0129] After 3-mercapto-1,2-propanediol, DBN and DMAc are stirred at 30 DEG C for 10 min under the atmosphere of nitrogen, (4-bromobutyl)-trimethylammonium bromide is added, and the reaction is carried out at 50 DEG C for 5 h, so that the cationic chain extender is obtained.

[0130] The nuclear magnetic characterization data of the cationic chain extender are as follows:

[0131] 1 H NMR (400 MHz, D2O): δ3.87-3.74(m, 1H), 3.72-3.61(m, 2H), 3.60-3.52(m, 2H), 3.18(s, 9H), 2.93-2.77(m, 4H), 1.92-1.80(m, 2H), 1.74-1.63(m, 2H).

[0132] Embodiment 4

[0133] The embodiment provides a cationic chain extender and a preparation method thereof, and the preparation raw material of the cationic chain extender comprises the following components in parts by weight:

[0134] 4-mercapto-1,3-butanediol 3.17 parts;

[0135] 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) 4.87 parts;

[0136] (3-bromopropyl)-trimethylammonium bromide 4.18 parts;

[0137] acetonitrile (MeCN) 98.00 parts.

[0138] The preparation method of the cationic chain extender comprises the following steps:

[0139] After 4-mercapto-1,3-butanediol, TBD and MeCN are stirred at 20℃ for 30 min under the atmosphere of nitrogen, (3-bromopropyl)-trimethylammonium bromide is added, and reaction is carried out at 90℃ for 1 h to obtain the cationic chain extender.

[0140] The nuclear magnetic characterization data of the cationic chain extender are as follows:

[0141] 1 H NMR (400 MHz, D2O): δ 3.90-3.76 (m, 1H), 3.69-3.58 (m, 2H), 3.60-3.52 (m, 2H), 3.18 (s, 9H), 2.93-2.77 (m, 4H), 1.89-1.77 (quint, J=6.8 Hz, 2H), 1.74-1.58 (m, 2H).

[0142] Application Example 1

[0143] The application example provides a water-based polyurethane emulsion and a preparation method thereof, and raw materials for preparing the water-based polyurethane emulsion comprise the following components in parts by weight:

[0144] isophorone diisocyanate (IPDI) 18 parts;

[0145] polycarbonate diol (PCDL) 35 parts;

[0146] cationic chain extender (Example 1) 6.5 parts;

[0147] 1,4-butanediol 2.89 parts;

[0148] dibutyltin dilaurate 0.2 parts;

[0149] acetone 35 parts;

[0150] deionized water 140 parts.

[0151] The preparation method of the water-based polyurethane emulsion comprises the following steps:

[0152] (1) IPDI, PCDL and dibutyltin dilaurate are mixed and reacted at 80℃ for 2.5 h to obtain a prepolymer;

[0153] (2) adding a mixture of the cationic chain extender (Example 1) and acetone into the prepolymer of step (1) to perform a first chain extension reaction at 80°C for 0.8 h, then adding 1,4-butanediol to perform a second chain extension reaction at 62°C for 0.8 h, and finally adding deionized water at 1500 rpm to obtain the aqueous polyurethane emulsion.

[0154] Application Example 2

[0155] The application example provides an aqueous polyurethane emulsion and a preparation method thereof, which are different from the application example 1 only in that the cationic chain extender (Example 1) in the application example 1 is replaced by an equal-molar amount of a cationic chain extender (Example 2), and other raw material components, contents and preparation methods are the same as those of the application example 1.

[0156] Application Example 3

[0157] The application example provides an aqueous polyurethane emulsion and a preparation method thereof, and preparation raw materials of the aqueous polyurethane emulsion include the following components in parts by weight:

[0158] hexamethylene diisocyanate (HDI) 15 parts;

[0159] polytetramethylene glycol (PTMG) 45 parts;

[0160] cationic chain extender (Example 3) 11 parts;

[0161] 1,6-hexanediol 2 parts;

[0162] bismuth neodecanoate 0.5 part;

[0163] acetone 60 parts;

[0164] deionized water 220 parts.

[0165] The preparation method of the aqueous polyurethane emulsion includes the following steps:

[0166] (1) mixing HDI, PTMG and bismuth neodecanoate and reacting at 75°C for 3 h to obtain a prepolymer;

[0167] (2) adding a mixture of the cationic chain extender (Example 3) and acetone into the prepolymer of step (1) to perform a first chain extension reaction at 75°C for 1 h, then adding 1,6-hexanediol to perform a second chain extension reaction at 65°C for 0.5 h, and finally adding deionized water at 1000 rpm to obtain the aqueous polyurethane emulsion.

[0168] Application Example 4

[0169] The application example provides a kind of water-based polyurethane emulsion and its preparation method, and the preparation raw materials of the water-based polyurethane emulsion include the following components by weight fraction:

[0170] Diphenyl methane diisocyanate (MDI) 30 parts;

[0171] Polyethylene glycol (PEG) 55 parts;

[0172] Cationic chain extender (example 4) 11 parts;

[0173] Ethylene glycol 3.2 parts;

[0174] Stannous octoate 0.3 parts;

[0175] N-methyl pyrrolidone (NMP) 45 parts;

[0176] Deionized water 300 parts.

[0177] The preparation method of the water-based polyurethane emulsion includes the following steps:

[0178] (1) MDI, PEG and stannous octoate are mixed and reacted at 85 DEG C for 2 h to obtain a prepolymer;

[0179] (2) the mixture of cationic chain extender (example 4) and NMP is added to the prepolymer of step (1), and the first chain extension reaction is carried out at 85 DEG C for 0.5 h, then ethylene glycol is added and the second chain extension reaction is carried out at 60 DEG C for 1 h, finally deionized water is added at 2000 rpm to obtain the water-based polyurethane emulsion.

[0180] Application example 5

[0181] The application example provides a kind of water-based polyurethane emulsion and its preparation method, and the difference between it and application example 1 is only that the weight fraction of cationic chain extender (example 1) in application example 1 is adjusted from 6.5 parts to 5.5 parts, and the weight fraction of 1,4-butanediol is adjusted from 2.89 parts to 3.2 parts, other raw material components, content and preparation method are same with application example 1.

[0182] Application example 6

[0183] The application example provides a kind of water-based polyurethane emulsion and its preparation method, and the difference between it and application example 1 is only that the weight fraction of cationic chain extender (example 1) in application example 1 is adjusted from 6.5 parts to 8.5 parts, and the weight fraction of 1,4-butanediol is adjusted from 2.89 parts to 2.27 parts, other raw material components, content and preparation method are same with application example 1.

[0184] Application example 7

[0185] The application example provides a kind of water-based polyurethane emulsion and its preparation method, and its difference with application example 1 is only in that the weight fraction of cationic chain extender (example 1) in application example 1 is adjusted from 6.5 parts to 10.5 parts, the weight fraction of 1,4-butanediol is adjusted from 2.89 parts to 1.64 parts, other raw material components, content and preparation method are same with application example 1.

[0186] Application example 8

[0187] The application example provides a kind of water-based polyurethane emulsion and its preparation method, and its difference with application example 1 is only in that the weight fraction of cationic chain extender (example 1) in application example 1 is adjusted from 6.5 parts to 11.3 parts, the weight fraction of 1,4-butanediol is adjusted from 2.89 parts to 1.42 parts, other raw material components, content and preparation method are same with application example 1.

[0188] Comparative application example 1

[0189] The comparative application example provides a kind of water-based polyurethane emulsion and its preparation method, and its difference with application example 1 is only in that the cationic chain extender (example 1) in application example 1 is replaced by equimolar amount of N-methyldiethanolamine (MDEA), and glacial acetic acid is added to neutralization degree 100% before emulsification and dispersion of deionized water, other raw material components, content and preparation method are same with application example 1.

[0190] The water-based polyurethane emulsion obtained in application examples 1-8 and comparative application example 1 is tested for performance, and the test method / standard is as follows:

[0191] (1) Emulsion particle size: the average particle size of water-based polyurethane emulsion is determined by Malvern laser particle size analyzer;

[0192] (2) Mechanical properties: the water-based polyurethane emulsion is added dropwise into clean glassware, the film thickness is controlled to be 3 mm, and after natural air drying, it is placed in a 60℃ oven to dry to constant weight to obtain a glue film; the glue film is cut into dumbbell shape, and the tensile rate is set to 100 mm / min according to GB / T528-2009.

[0193] (3) Ink absorption speed: water-based polyurethane emulsion is coated on PET film (purchased from Toray Industries, Inc., with the trade name Lumirror TM #75-U34) using a 100 μm coater to prepare a sample piece, which is placed in a 60℃ oven to dry for 30 min after surface drying to obtain a coated sample piece; the ink absorption quick drying time of the coated sample piece is tested according to the finger touch method in national standard GB / T 1728-1979 "Paint film, putty film drying time determination method".

[0194] The test results are shown in Table 1.

[0195] Table 1

[0196]

[0197] It can be seen from the test results that:

[0198] (1) It can be seen from application examples 1 to 8 that the cationic chain extender with a side chain type permanent cationic structure is obtained by introducing a permanent quaternary ammonium salt group through a sulfide bond in the application, which can significantly improve the mechanical properties of the obtained coating film while maintaining good interface function when applied to waterborne polyurethane emulsion, and can realize the technical effects of waterborne polyurethane emulsion with a particle size of 52-128 nm, a tensile strength of the coating film after film formation of 5.5-11.8 MPa, and an ink dry time of 10-42 s.

[0199] (2) It can be seen from the comparison of application example 1 and application example 2 that the particle size increases, the strength decreases, and the ink dry time extends in application example 2, i.e. the dispersibility and ink absorption speed of the obtained waterborne polyurethane emulsion are slightly low, and the mechanical properties are weakened, which is due to the fact that the triethyl quaternary ammonium salt in the cationic chain extender used in application example 2 has a larger volume and stronger hydrophobicity, so that the surface cation is effectively exposed, the density is reduced, and the disturbance to the hard segment hydrogen bond association and microphase separation is more significant.

[0200] (3) It can be seen from the comparison of application example 1 and application examples 5-8 that the content of the cationic chain extender in application example 5 is low, the emulsion stability is insufficient, the average particle size increases from 74 nm to 128 nm, and the ink dry time significantly extends from 18 s to 42 s, but due to the smaller disturbance to the hard segment hydrogen bond association and microphase separation, the tensile strength is slightly increased from 10.1 MPa to 11.8 MPa; in application examples 6-7, the content of the cationic chain extender increases, the effective positive charge density on the surface increases, the emulsion particle size decreases and tends to be stable, and the ink dry time continuously shortens, at the same time, due to the increasing disturbance to the hard segment phase separation, the mechanical properties first decrease and then increase, and the high equivalent area improves the mechanical properties due to ionic crosslinking; in application example 8, the content of the cationic chain extender is high, at this time, the agglomeration between particles is strengthened, so that the emulsion particle size is high, at the same time, due to the destruction of the microphase structure, the crosslinking effect is invalid, so that the tensile strength of the coating film is significantly reduced. It shows that by adjusting the molar ratio of the cationic chain extender and the small molecule chain extender, the comprehensive performance of the obtained waterborne polyurethane emulsion can be further improved, so that it has better tensile strength and shorter ink dry time on the basis of maintaining the emulsion stability.

[0201] (4) By comparing application example 1 with comparative application example 1, it can be seen that the particle size of the waterborne polyurethane emulsion obtained by comparative application example 1 increases from 74 nm to 92 nm, the tensile strength decreases from 10.1 MPa to 3.4 MPa, and the film is still not surface-dried after >72 h on PET, the reason is that the main chain cation directly inserts into the hard segment, which weakens the hydrogen bond association / microphase separation and is difficult to form surface enrichment, at the same time, since the protonated cation needs to rely on the presence of neutralizing acid, the volatilization of the neutralizing acid in the film forming process will make the cation disappear and reduce to tertiary amine group, resulting in a significant decrease in the ink absorption performance of the coating film. In contrast, the side chain type quaternary ammonium salt cationic chain extender provided by the present application can not only impart the obtained coating film with persistent surface positive characteristics and excellent dispersion stability, but also avoid excessive interference with the hydrogen bond association and microphase separation of the hard segment, thereby significantly improving the mechanical properties of the coating film while maintaining good interface function.

[0202] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A cationic chain extender, characterized by, The cationic chain extender has a structure shown in Formula I: Formula I; wherein R1, R2, R3 are the same or different, each independently selected from C1-C5 alkyl; n represents an integer of 2-6; X is selected from halogen; R4 is selected from any one of the following groups: ； the wavy line represents a connecting site; The cationic chain extender is prepared by a preparation method comprising the following steps: After mixing the mercaptan diol with the organic base, the halogenated alkyl quaternary ammonium salt is added for reaction to obtain the cationic chain extender.

2. The cationic chain extender according to claim 1, characterized in that, The R1, R2, R3 are the same or different, each independently selected from methyl or ethyl; n represents 3 or 4.

3. A process for the preparation of the cationic chain extender as claimed in claim 1 or 2, characterized in that, The preparation method comprises the following steps: After mixing the mercaptan diol with the organic base, the halogenated alkyl quaternary ammonium salt is added for reaction to obtain the cationic chain extender.

4. The method for preparing the cationic chain extender according to claim 3, characterized in that, The mercaptan diol is selected from any one of 3-mercapto-1,2-propanediol, 2-mercapto-1,3-propanediol, 3-mercapto-1,2-butanediol or 4-mercapto-1,3-butanediol; The organic base is selected from any one of 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene or 1,5,7-triazabicyclo[4.4.0]dec-5-ene or a combination of at least two; The molar ratio of the organic base to the mercaptan diol is (1.0-2.0):1; The mixing is carried out under stirring; The mixing temperature is 20-30℃, and the mixing time is 10-30 min.

5. The method for preparing the cationic chain extender according to claim 3, characterized in that, The halogenated alkyl quaternary ammonium salt has a structure shown in Formula II: Formula II; wherein R1, R2, R3 are the same or different, each independently selected from C1-C5 alkyl; n represents an integer of 2-6; X is selected from halogen; The molar ratio of the halogenated alkyl quaternary ammonium salt to the mercaptan diol is 1:(1.2-2.0); The halogenated alkyl quaternary ammonium salt is added by dropwise addition.

6. The method for preparing the cationic chain extender according to claim 3, characterized in that, The reaction is carried out in the presence of a solvent A; The solvent A is a polar aprotic solvent; The polar aprotic solvent is selected from any one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methyl pyrrolidone or acetonitrile or a combination of at least two; The ratio of the mass of the solvent A to the sum of the masses of the mercaptan diol, the halogenated alkyl quaternary ammonium salt and the organic base is (5-10):1; The reaction temperature is 50-90℃, and the reaction time is 1-5 h; The reaction is carried out in an atmosphere of a protective gas; The protective gas is selected from any one of nitrogen, argon or helium or a combination of at least two.

7. An aqueous polyurethane emulsion, characterized in that, The preparation raw materials of the aqueous polyurethane emulsion comprise the following components in the following weight fractions: diisocyanate 15-30 parts; polymer polyol 30-55 parts; the cationic chain extender of claim 1 or 2 5-11.5 parts; small molecule chain extender 1.5-3.5 parts; catalyst 0.1-0.5 parts; solvent B 20-70 parts; water 100-300 parts; The solvent B is selected from any one of acetone, butanone or N-methyl pyrrolidone or a combination of at least two.

8. The aqueous polyurethane emulsion according to claim 7, characterized in that, The molar ratio of the cationic chain extender to the small molecule chain extender is (0.7-2.1):1; The small molecule chain extender is a small molecule alcohol.

9. A process for the preparation of an aqueous polyurethane emulsion as claimed in claim 7 or 8, characterized in that, The preparation method comprises the following steps: (1) mixing diisocyanate, polymeric polyol and catalyst and then reacting to obtain a prepolymer; (2) adding a mixture of cationic chain extender and solvent B into the prepolymer of step (1) to perform a first chain extension reaction, then adding a small molecule chain extender to perform a second chain extension reaction, and finally adding water to obtain the waterborne polyurethane emulsion; The mixing of step (1) is performed under stirring; The reaction temperature of step (1) is 75-85℃, and the reaction time is 2-3 h; The first chain extension reaction temperature of step (2) is 75-85℃, and the reaction time is 0.5-1 h; The second chain extension reaction temperature of step (2) is 60-65℃, and the reaction time is 0.5-1 h; The water of step (2) is added under stirring, and the stirring speed is 1000-2000 rpm.

10. Application of the waterborne polyurethane emulsion of claim 7 or 8 in coatings, adhesives or functional films.

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