Highly transparent and low gloss self-dimmed waterborne polyurethane emulsion, preparation method and application thereof

Abstract

The application discloses a kind of high-transmittance low-glossiness self-extinction waterborne polyurethane emulsion and its preparation method and application, belong to high polymer material technical field.The preparation method of the application includes the following steps: S1, preparation prepolymer: the polyester polyol of dehydration treatment and / or polyether polyol are mixed, under the protection of inert gas, and isocyanate and catalyst are added to reaction, then hydrophilic chain extender and small molecule alcohol chain extender are added, and the prepolymer is obtained after reaction is completed;S2, in the prepolymer, neutralizing agent is added to neutralize into salt;S3, acrylic ester monomer and water are emulsified;S4, after adding amine-based chain extender, the remaining isocyanate is reacted;S5, initiator is added to polymerize;S6, thickening agent, wetting agent, crosslinking agent, defoaming agent are added, and the obtained self-extinction waterborne polyurethane emulsion is obtained.The application solves the problem of poor permeability of self-extinction waterborne polyurethane, has high-transmittance low-glossiness, realizes the self-extinction of coating layer under the premise of ensuring transparency.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion. Background Technology

[0002] Common waterborne polyurethane matte resins are prepared by adding matting agents or powders to waterborne polyurethane emulsions to achieve a matte finish. However, this method has the following technical drawbacks: significant dust pollution occurs during production; after matting treatment with these powders, the coating becomes brittle, easily broken and peeling off, affecting the scratch resistance and folding resistance of the coating film; and the addition of matting agents causes precipitation, reducing the stability of the system. Therefore, the research and development of waterborne polyurethane self-matte resins without added matting agents has received widespread attention in recent years. Different applications require different gloss levels. Soft-colored matte coatings usually give people an elegant, comfortable, and tranquil feeling. For example, the surface coatings of instruments, furniture, and synthetic leather all require low-gloss coating agents and surface treatment agents. In recent years, single-component WPU matte resins have begun to attract attention in the coatings industry. WPU matte resins do not use any matting agents. They are designed with special molecular structures or latex particles, forming polyurethane particles of different sizes during the drying process, producing a rough surface and achieving a matte effect.

[0003] Currently, in the drying process of emulsified self-matting waterborne polyurethane coatings, due to the large particle size of the emulsion, there is obvious phase separation during film formation, resulting in an uneven surface that achieves a matte effect. However, excessively large emulsion particles and excessively large microspheres formed during the drying process lead to poor light absorption capacity, affecting the transparency of the coating and resulting in generally low transparency.

[0004] The prior art discloses a method for preparing a self-matting waterborne acrylic-polyurethane core-shell emulsion, comprising the following steps: Step 1: Under nitrogen protection, a polymeric diol, 2,2-dimethylolpropionic acid, a catalyst, and N-methylpyrrolidone are added to a reaction vessel, the temperature is raised to 60°C, and stirring is started to dissolve the 2,2-dimethylolpropionic acid. A mixture of diisocyanate and butanone in a mass ratio of 1:1 is added dropwise, and the addition is completed in 1 hour. The temperature is then raised to 80°C and maintained for 4 hours. The N-methylolpropionic acid content is then measured. When the CO content reaches 85-95% of the theoretical value, the temperature is lowered to 55-60℃ to obtain prepolymer one; the molar ratio of 2,2-dimethylolpropionic acid to the polymeric diol is 1-1.5:1; the molar ratio of diisocyanate to the polymeric diol is 2-3:1; the catalyst addition amount is 0.01-0.02% of the mass of the polymeric diol and 2,2-dimethylolpropionic acid blend; Step two: Add to the prepolymer one obtained in step one Neutralize with a neutralizing agent for 20-30 minutes, add water, disperse vigorously for 30 minutes, and evaporate methyl ethyl ketone to obtain prepolymer II; the molar ratio of the neutralizing agent to the 2,2-dimethylolpropionic acid is 0.9-1:1; Step 3: Add an organosilicon coupling agent to the prepolymer II obtained in Step 2 at a speed of 800-1000 rpm, mix (meth)acrylate, 2-hydroxyethyl acrylate, and (meth)acrylic acid, add 30% of the monomer mixture to the reaction flask, heat to 85°C, disperse for 30 minutes, add 20% of the catalyst dropwise, stir and polymerize for 1 hour, then simultaneously add the remaining 70% of the monomer mixture and the remaining 80% of the catalyst dropwise, completing the addition in 3.5 hours, continue the reaction at 85°C for 1 hour, heat to 90°C, continue the reaction for 1 hour, cool to 60°C, add a neutralizing agent to adjust the pH to 8.0-8.5, and cool to room temperature; after filtration, a self-matting waterborne acrylic-polyurethane core-shell emulsion is obtained. Although this matting waterborne acrylic-polyurethane emulsion also has a core-shell structure, which helps with matting, it forms a hard-core, soft-shell structure with acrylic ester as the core and PU as the shell. During film formation, the latex particles may deform, which in turn affects the self-matting effect. Furthermore, the pursuit of large emulsion particles results in excessively large microspheres formed during the drying process, leading to poor light absorption and affecting the transparency of the coating film. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects and shortcomings of existing self-matting waterborne polyurethane emulsions, which have poor overall performance in terms of self-matting and transparency. This invention provides a method for preparing a high-transparency, low-gloss self-matting waterborne polyurethane emulsion. By modifying the emulsion with acrylate, the initial particle size of the latex particles is controlled. At the same time, a core-shell structure is formed during the polyurethane emulsification process. The final coating achieves self-matting while ensuring transparency and has a low gloss.

[0006] Another object of the present invention is to provide a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion.

[0007] Another object of the present invention is to provide an application of a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion in [the present invention].

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] S1. Preparation of prepolymer: Dehydrated polyester polyol and / or polyether polyol are mixed, and diisocyanate and catalyst are added under inert gas protection. The reaction is completed at 80–90°C. Then, hydrophilic chain extender and small molecule alcohol chain extender are added, and the reaction is carried out completely at 75–80°C to obtain the prepolymer.

[0010] The R values ​​for all reactants range from 1.6 to 2.1, where R represents the ratio of isocyanate groups to hydroxyl groups.

[0011] S2. Neutralize the prepolymer by adding a neutralizing agent to form a salt;

[0012] S3. Add acrylate monomers and water to emulsify and form core-shell structured latex particles. The emulsification temperature is 20-25℃.

[0013] S4. After adding an amine chain extender, the remaining diisocyanate reacts;

[0014] S5. Add an initiator for polymerization;

[0015] S6. Add thickener, wetting agent, crosslinking agent, and defoamer to obtain a self-matting waterborne polyurethane emulsion.

[0016] Based on the total solid mass during the preparation process:

[0017] The amount of acrylate monomers used is 10-30 wt%;

[0018] The amount of hydrophilic chain extender used is 0.1–2 wt%.

[0019] The amount of small molecule alcohol chain extender used is 0.1-2 wt%.

[0020] Achieving self-matte finish in waterborne polyurethane resins requires specific particle size control during emulsion film formation. Small particle sizes cannot achieve a matte effect, while large particle sizes, while easily achieving a matte finish, result in poor transparency. This invention incorporates acrylate substances during emulsification. These substances have poor water compatibility and exist within the polyurethane structure during emulsification. High concentrations of acrylate monomers on the polyurethane latex surface penetrate into the latex particles, then self-polymerize, forming a core-shell structure different from the original polyurethane structure. After the addition of an initiator, self-polymerization occurs, creating a transition copolymer layer between the core and shell layers of the core-shell latex particles. Combining copolymer layers with different structures allows for the creation of different refractive indices, thus improving the transparency of the self-matte waterborne polyurethane emulsion and resulting in excellent transparency.

[0021] Furthermore, in the preparation method of the present invention, the content of hydrophilic groups is controlled by the addition ratio of hydrophilic chain extender, the degree of chain extension is controlled by the addition ratio of amine post-chain extender, the particle size of polyurethane latex particles is adjusted, and a suitable copolymer layer structure is matched, thereby achieving a balance between gloss and transparency.

[0022] Preferably, the particle size of the core-shell structured latex particles is 1–4 μm. For example, it can be 1.80 μm, 2.15 μm, 1.62 μm, 2.50 μm, 1.30 μm, 2.05 μm, or 1.02 μm.

[0023] In the preparation method of the high-transparency, low-gloss, self-matting waterborne polyurethane emulsion of the present invention, acrylate is used to modify the polyurethane prepolymer during the synthesis stage, forming a core-shell structure during the emulsification stage, thereby achieving self-matting while improving the light transmittance of the coating.

[0024] On the one hand, the present invention modifies the core-shell structure latex particles by acrylate, controlling the initial particle size to 1-4 μm. This avoids the formation of excessively large microspheres during the drying process due to excessively large initial particle size of the latex particles, which would result in poor light absorption and affect the transparency of the coating film. This is beneficial to improving the transparency of the coating.

[0025] On the other hand, the aqueous polyurethane emulsion obtained by the preparation method of the present invention has a soft shell-hard core structure with a large emulsion particle size. During the film formation process, there is obvious phase separation, and the coating produces a spherical particle-like micro-rough surface, thereby forming an uneven surface to achieve a matting effect. The gloss of the coating is reduced, and the latex particles are difficult to deform during film formation due to the soft shell-hard core structure, which can also improve the surface roughness and matting degree of the coating. Finally, the prepared coating achieves self-matting of the coating while ensuring transparency.

[0026] More preferably, the particle size of the core-shell structured latex particles is 1.8 to 2.5 μm.

[0027] It should be noted that:

[0028] The dehydration treatment of polyester polyols and polyether polyols can be carried out using the following methods in specific operations:

[0029] Polyester polyol and polyether polyol were dehydrated at 120°C for 1-2 hours.

[0030] S1. The catalyst for preparing the prepolymer can be a commonly used catalyst in the art, such as one or more of organotin catalysts, organozinc catalysts, and organobismuth catalysts. The amount of catalyst used can refer to conventional amounts, based on the total solid mass in the preparation process: the amount of catalyst used ranges from 0.01 to 0.05 wt%, preferably 0.01 to 0.02 wt%.

[0031] The hydrophilic chain extender of the present invention can be a conventional hydrophilic chain extender in the art, such as one or more of carboxylic diols, sulfonate diamines and polyoxyethylene diols, preferably carboxylic diols; the carboxylic diols are further preferably dimethylolpropionic acid and / or dimethylolbutyric acid.

[0032] The amount of hydrophilic chain extender can be further preferably 1 to 3 wt%.

[0033] The alcohol chain extender of the present invention can be a conventional alcohol chain extender in the art, such as one or more alcohol chain extenders with a molecular weight of less than 500, including C2-C10 aliphatic diols or triols, preferably one or more of 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentanediol, diethylene glycol and trimethylolpropane.

[0034] The amount of alcohol chain extender used is preferably 0.5 to 1.5 wt%.

[0035] The amount of both hydrophilic chain extenders and alcohol chain extenders can affect the initial particle size of polyurethane latex particles.

[0036] The neutralizing agent of the present invention can be a conventional neutralizing agent in the art, such as one or more of triethylamine, triethanolamine, tripropylamine, ammonia, sodium hydroxide, potassium hydroxide, and dimethylethanolamine, preferably triethylamine and / or dimethylethanolamine.

[0037] The amount of neutralizing agent can be referenced from the conventional amount, based on the total solid mass in the preparation process: the amount of neutralizing agent ranges from 0.1 to 5 wt%, preferably from 0.5 to 2 wt%.

[0038] The amine-based chain extender of the present invention can be a conventional choice in the art, for example, it can be a polyamine, including polyamines with a molecular weight of less than 500, preferably one or more of ethylenediamine, 1,6-hexanediamine, 4,4-dicyclohexylmethanediamine, isophoronediamine, and diethylenetriamine, more preferably ethylenediamine and / or isophoronediamine.

[0039] The dosage of amine-based chain extenders can refer to conventional dosages, based on the total solid mass during the preparation process: the neutralizing agent dosage ranges from 0.5 to 2 wt%, preferably 0.8 to 1.6 wt%. Amine-based chain extenders can completely react the remaining isocyanate.

[0040] The initiator of the present invention can be a conventional initiator in the art, such as at least one of tert-butyl hydroperoxide, tert-amyl hydroperoxide, sodium bisulfite, sodium dithionite and isoascorbic acid, preferably tert-butyl hydroperoxide and / or isoascorbic acid; more preferably tert-butyl hydroperoxide and isoascorbic acid in a mass ratio of 2:1.

[0041] The amount of initiator can be referenced from the conventional amount, based on the total solid mass in the preparation process: the amount of neutralizer ranges from 0.01 to 2 wt%, preferably from 0.01 to 1 wt%.

[0042] In the formulation of self-matting waterborne polyurethane emulsions, thickeners, wetting agents, crosslinking agents, and defoamers are all conventional choices in the field.

[0043] The thickener is one or more of hydroxyethyl cellulose, hydroxypropyl methylcellulose, polyacrylic acid, polyacrylate, polyurethane, and high molecular weight polyethylene oxide;

[0044] The wetting agent is any one of polyether-modified organosilicon wetting agents;

[0045] The defoamer mentioned is any one of polyether-modified silicone defoamers;

[0046] The crosslinking agent is any one of carboimide crosslinking agents, aziridine, polyisocyanate, and epoxysilane;

[0047] The hand-feeling agent is any one of siloxanes with a molecular weight of (1000-30000).

[0048] In a specific embodiment, the preferred molar ratio of the neutralizing agent to the hydrophilic chain extender in S2 is 0.9 to 1.1:1. The molar ratio of the neutralizing agent to the hydrophilic chain extender directly affects the emulsification process and influences the particle size of the core-shell structured latex particles.

[0049] In a specific embodiment, based on the total solid mass during the preparation process: preferably, the total amount of polyester polyol and polyether polyol used in S1 is 40-70 wt%, and the amount of diisocyanate is 10-40 wt%.

[0050] Furthermore, the total amount of polyester polyol and polyether polyol is preferably 50-70 wt%.

[0051] Furthermore, the amount of diisocyanate used is more preferably 20-35 wt%. Optimal use of diisocyanate also helps to control the particle size of core-shell structured latex particles.

[0052] The polyol of the present invention can be a polyol commonly used in the preparation of polyurethane. In specific embodiments, it may include, for example, polyester polyol and polyether polyol, with a mass ratio of polyol to polyether polyol of 35:1 to 10:1.

[0053] In a more specific embodiment, the number-average molecular weight of the polyester polyol and polyether polyol of the present invention is preferably 1000 g / mol to 2000 g / mol. The molecular weight of the polyester polyol and polyether polyol also affects the molecular weight of the final polyurethane, and thus affects the initial particle size of its core-shell structured latex particles.

[0054] More specifically, in the specific preparation method, the polyol in S1 can be one or a combination of several of the following: polycaprolactone diol, polyethylene glycol, polypropylene glycol, polytetrahydrofuran ether diol, polyethylene adipate diol, poly(1,4-butanediol adipate) diol, and poly(neopentyl adipate-1,6-hexanediol adipate).

[0055] In a specific embodiment, the polyisocyanate of the present invention is a diisocyanate such as isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), or 4,4'-dicyclohexylmethane diisocyanate (H12MDI) or a mixture thereof.

[0056] The polyisocyanate of the present invention can be one or more polyisocyanates, and when it contains two aliphatic polyisocyanates, the mass ratio of the two aliphatic polyisocyanates is 0.1 to 10:1.

[0057] In a specific embodiment, the acrylate monomers in S3 of the present invention include one or more of ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, phenyl methacrylate, and trimethacrylate.

[0058] Furthermore, the aforementioned acrylate monomers can preferably be methyl methacrylate and / or butyl methacrylate.

[0059] The amount of acrylate monomers can be further preferably 10-20 wt%.

[0060] This invention also specifically protects a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion prepared by the above-mentioned preparation method, wherein the high-transparency, low-gloss, self-matting waterborne polyurethane emulsion has a core-shell structure, with polyurethane as the core and acrylate as the shell.

[0061] The high-transparency, low-gloss, self-matting waterborne polyurethane emulsion of the present invention has the characteristics of excellent transparency, low matteness, strong velvet feel, and good leveling. It solves the problem of poor permeability caused by large particle size in the film formation process of self-matting waterborne polyurethane. It can be widely used in the preparation of paper and film tactile oils, leather finishing agents, and matte and matte coatings for printing.

[0062] Compared with the prior art, the beneficial effects of the present invention are:

[0063] The self-matting waterborne polyurethane emulsion of this invention is modified with acrylate to control the initial particle size of the latex particles, which is beneficial to improving the transparency of the coating. Simultaneously, the self-emulsifying matting waterborne polyurethane emulsion prepared by this invention has a large particle size, resulting in significant phase separation during the film drying process. This creates an uneven surface, achieving a matting effect. Furthermore, a core-shell structure is formed during polyurethane emulsification. The large latex particle size results in a spherical, micro-rough surface on the coating, reducing gloss. The soft core-hard shell structure makes it difficult for the latex particles to deform during film formation, further improving the surface roughness and matting degree of the coating. Ultimately, the prepared coating achieves self-matting while maintaining transparency. Detailed Implementation

[0064] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0065] The relevant raw material information for the embodiments and comparative examples of the present invention is as follows:

[0066] Polyester / polyether polyols:

[0067] PTMG1000 (polytetrahydrofuran ether diol, Jining Huakai Resin Co., Ltd.), with a number average molecular weight of 1000 g / mol;

[0068] PCL1000 (polycaprolactone diol, Jining Huakai Resin Co., Ltd.), with a number average molecular weight of 1000 g / mol;

[0069] Ymer N120 (polyethylene glycol monomethyl ether, Perstork), with a number average molecular weight of 1000 g / mol;

[0070] Diisocyanate:

[0071] IPDI (Isophorone diisocyanate, Wanhua Chemical Group Co., Ltd.);

[0072] HDI (hexamethylene diisocyanate, Wanhua Chemical Group Co., Ltd.);

[0073] H12MDI (4,4'-dicyclohexylmethane diisocyanate, Wanhua Chemical Group Co., Ltd.)

[0074] Neutralizing agent:

[0075] TEA (Triethylamine, BASF);

[0076] DMEA (Dimethylethanolamine, Sinopharm Chemical Reagent Co., Ltd.);

[0077] Hydrophilic chain extender:

[0078] DMPA (Dimethylolpropionic acid, Guangzhou Tengli Chemical Co., Ltd.);

[0079] DMBA (Dimethylolbutyric acid, Guangzhou Tengli Chemical Co., Ltd.);

[0080] Small molecule alcohol chain extenders:

[0081] BDO 1,4-Butanediol, Shandong Huibang New Material Technology Co., Ltd.;

[0082] TMP (trimethylolpropane), Baichuan Chemical Co., Ltd.

[0083] Acrylate monomers:

[0084] MMA (methyl methacrylate, Jiaxing United Chemical Co., Ltd.) acrylate

[0085] KH550 (Amino-terminated silane coupling agent, Shanghai Kaiyin Chemical Co., Ltd.)

[0086] Amine-based chain extenders:

[0087] IPDA (Isophorone Diamine, Wanhua Chemical Group Co., Ltd.);

[0088] EDA (ethylenediamine, Sinopharm Chemical Reagent Co., Ltd.);

[0089] DETA (Diethylenetriamine, Sinopharm Chemical Reagent Co., Ltd.)

[0090] Initiator:

[0091] tert-butyl hydroperoxide (TBHP):

[0092] Isoascorbic acid: Aladdin Chemical Reagent;

[0093] Silok50 (a hand feel agent, from Silok Corporation);

[0094] Silok 8022 (wetting agent, Silok Corporation);

[0095] TEGO810 (defoamer, EVONIK additive);

[0096] 9302 (crosslinking agent, Beijing Baiyuan Chemical Co., Ltd.);

[0097] ASE60 (thickener, Dow Chemical).

[0098] Example 1

[0099] A method for preparing a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion includes the following steps:

[0100] S1. Preparation of prepolymer: Add 150g PTMG1000 and 10g Ymer N120 to a three-necked flask, dehydrate at 120℃, cool to 50℃, and then add 13.4g HDI and 70.2g H under a nitrogen atmosphere. 12 MDI and 1 drop of bismuth acid catalyst were reacted at 90°C for 1.5 h. The temperature was then lowered to 70°C and 2 g of BDO and 2.5 g of DMPA were added. The reaction was carried out at 75-80°C for 2 h. The NCO% was tested and found to be close to the theoretical value of 4.58%, thus obtaining the prepolymer.

[0101] S2. Cool to 45℃, dissolve in 150g acetone solvent, mix for 15 mins, react for 5 mins, then add 1.603g triethylamine, and react at 40℃ for 5 mins.

[0102] S3. Add 24.8g MMA, and emulsify with 520g ice water under shear dispersion conditions (1500r / mins) at an emulsification temperature of 25℃.

[0103] S4. Then add a mixed solution of 6.15g EDA and 61.5g water dropwise, and stir at 25°C for 10 minutes;

[0104] S5. Add 0.048g TBHP and isoascorbic acid (mass ratio 2:1) dropwise over 15min, then remove acetone and residual MMA monomer by vacuum distillation;

[0105] S6. A mixture of 1.0% thickener, 0.5% hand feel agent, 1% wetting agent, and 0.3% defoamer was stirred at 1000 r / mins for 10 mins to obtain an acrylic-modified waterborne polyurethane resin with a solid content of approximately 30 wt% and an average particle size of 1800 nm.

[0106] In S1, the R value of all reactants is 1.73;

[0107] The amount of acrylate monomers used is 10 wt%.

[0108] The amount of hydrophilic chain extender used is 1.0 wt%.

[0109] The amount of small molecule alcohol chain extender used is 0.8 wt%.

[0110] The molar ratio of neutralizing agent to hydrophilic chain extender is 0.85:1.

[0111] The total amount of polyether polyol used is 64.4 wt%, and the amount of diisocyanate used is 33.6 wt%.

[0112] Example 2

[0113] A method for preparing a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion includes the following steps:

[0114] S1. Preparation of prepolymer: 150g PTMG1000 and 6g Ymer N120 were added to a three-necked flask and dehydrated at 120℃. After cooling to 50℃, 13.4g HDI, 61.5g IPDI and 1 drop of bismuth acid catalyst were added under a nitrogen atmosphere and reacted at 90℃ for 1.5h. After cooling to 70℃, 2g TMP and 2.5g DMPA were added and reacted at 75-80℃ for 2h. The NCO% was tested and found to be close to the theoretical value of 4.96%, thus obtaining the prepolymer.

[0115] S2. Cool to 45℃, dissolve in 150g acetone solvent, mix for 15 mins, react for 5 mins, then add 1.886g triethylamine, and react at 40℃ for 5 mins.

[0116] S3. Add 23.58g MMA, and emulsify with 520g ice water under shear dispersion conditions (1500r / mins) at an emulsification temperature of 25℃.

[0117] S4. Then add a mixed solution of 7.11g EDA and 71.1g water dropwise, and stir at 25°C for 10 minutes.

[0118] S5. Add 0.028g TBHP and isoascorbic acid (mass ratio 2:1) dropwise over 15min, then remove acetone and residual MMA monomer by vacuum distillation;

[0119] S6. A mixture of 1.0% thickener, 0.5% hand feel agent, 1% wetting agent, and 0.3% defoamer was stirred at 1000 r / mins for 10 mins to obtain an acrylic-modified waterborne polyurethane resin with a solid content of approximately 30 wt% and an average particle size of 2150 nm.

[0120] In S1, the R value of all reactants is 1.81;

[0121] The amount of acrylate monomers used is 10 wt%.

[0122] The amount of hydrophilic chain extender used is 1.0 wt%.

[0123] The amount of small molecule alcohol chain extender used is 0.8 wt%.

[0124] The molar ratio of neutralizing agent to hydrophilic chain extender is 1:1.

[0125] The total amount of polyether polyol used is 66.1 wt%, and the amount of diisocyanate used is 31.8 wt%.

[0126] Example 3

[0127] A method for preparing a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion includes the following steps:

[0128] S1. Preparation of prepolymer: 150g PCL1000 and 6g Ymer N120 were added to a three-necked flask and dehydrated at 120℃. After cooling to 50℃, 13.4g HDI, 61.5g IPDI and 1 drop of bismuth acid catalyst were added under a nitrogen atmosphere and reacted at 90℃ for 1.5h. After cooling to 70℃, 2g BDO and 2.5g DMPA were added and reacted at 75-80℃ for 2h. The NCO% was tested and found to be close to the theoretical value of 5.30%, thus obtaining the prepolymer.

[0129] S2. Cool to 45℃, dissolve in 150g acetone solvent, mix for 15 mins, react for 5 mins, then add 1.886g triethylamine, and react at 40℃ for 5 mins.

[0130] S3. Add 24g MMA, and emulsify with 520g ice water under shear dispersion conditions (1500r / mins) at an emulsification temperature of 25℃.

[0131] S4. Add a mixed solution of 7.05g EDA and 70.5g water dropwise, and stir at 25℃ for 10mins;

[0132] S5. Add 0.028g TBHP and isoascorbic acid (mass ratio 2:1) dropwise over 15min, then remove acetone and residual MMA monomer by vacuum distillation;

[0133] S6. A mixture of 1.0% thickener, 0.5% hand feel agent, 1% wetting agent, and 0.3% defoamer was stirred at 1000 r / mins for 10 mins to obtain an acrylic-modified waterborne polyurethane resin with a solid content of approximately 30 wt% and an average particle size of 1800 nm.

[0134] In S1, the R value of all reactants is 1.72;

[0135] The amount of acrylate monomers used is 10 wt%.

[0136] The amount of hydrophilic chain extender used is 1.0 wt%.

[0137] The amount of small molecule alcohol chain extender used is 0.8 wt%.

[0138] The molar ratio of neutralizing agent to hydrophilic chain extender is 1:1.

[0139] The total amount of polyether polyol and polyester polyol used was 66.2 wt%, and the amount of diisocyanate used was 31.8 wt%.

[0140] The mass ratio of polyether polyol to polyester polyol is 25:1.

[0141] Example 4

[0142] The preparation method of a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion is basically the same as that in Example 3, except that the mass ratio of polyester polyol to polyether polyol is 35:1.

[0143] Example 5

[0144] A method for preparing a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion is basically the same as that in Example 3, except that the mass ratio of polyester polyol to polyether polyol is 10:1.

[0145] Example 6

[0146] The preparation method of a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion is basically the same as that in Example 3, except that the amount of acrylate monomers used is 30wt%.

[0147] Example 7

[0148] The preparation method of a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion is basically the same as that in Example 3, except that the amount of hydrophilic chain extender used is 2wt%.

[0149] Comparative Example 1

[0150] A method for preparing an aqueous polyurethane emulsion includes the following steps:

[0151] Add 150g PTMG1000 and 5g Ymer N120 to a three-necked flask, dehydrate at 120℃, cool to 50℃, and then add 10.6g HDI and 78.5g H under a nitrogen atmosphere. 12The reaction was carried out with MDI and 1 drop of bismuth acid catalyst at 90℃ for 1.5 h. The temperature was then lowered to 70℃ and 2 g TMP and 2.5 g DMPA were added. The reaction was carried out at 75-80℃ for 2 h. The NCO% was tested to be close to the theoretical value of 6.11%.

[0152] The prepolymer was cooled to 45°C, dissolved in 220g of acetone, and mixed for 15 minutes. Then, 1.509g of triethylamine was added, and the mixture was reacted at 40°C for 5 minutes.

[0153] Emulsify with 500g of water under shear dispersion conditions (1500r / mins).

[0154] Then, a mixed solution of 6.55 g of EDA and 65.5 g of water was added dropwise, and the mixture was stirred at 25 °C for 10 mins. Acetone was then removed by vacuum distillation.

[0155] A self-matte waterborne polyurethane with a solid content of approximately 31 wt% and an average particle size of 3260 nm was obtained by mixing a thickener of 1.0%, a hand feel agent of 0.5%, a wetting agent of 1%, and a defoamer of 0.3% with 1000 r / mins for 10 mins.

[0156] The R value for all reactants is 1.93.

[0157] The amount of hydrophilic chain extender used is 1 wt%.

[0158] The amount of small molecule alcohol chain extender used is 0.8 wt%.

[0159] The molar ratio of neutralizing agent to hydrophilic chain extender is 0.85:1.

[0160] Comparative Example 2

[0161] A method for preparing an aqueous polyurethane emulsion includes the following steps:

[0162] 150g PCL1000, 5g Ymer N120, 2g BDO, and 2.5g DMPA were added to a three-necked flask for dehydration at 120℃. After cooling to 50℃, 13.6g HDI, 60.2g IPDI, and 1 drop of bismuth acid catalyst were added under a nitrogen atmosphere to carry out the reaction. The small molecule alcohol chain extender was added before the diisocyanate. The reaction was carried out at 90℃ for 3 hours, and the NCO% was close to the theoretical value of 5.58%.

[0163] The prepolymer was cooled to 45°C, dissolved in 150g of acetone, and mixed for 15 minutes. Then, 1.509g of triethylamine was added, and the mixture was reacted at 40°C for 5 minutes.

[0164] Emulsify with 520g of water under shear dispersion conditions (1500r / mins).

[0165] Then, a mixed solution of 7.25 g of EDA and 72.5 g of water was added dropwise, and the mixture was stirred at 25°C for 10 minutes.

[0166] Then, acetone was removed by vacuum distillation, and a thickener of 1.0%, a hand feel agent of 0.5%, a wetting agent of 1%, and a defoamer of 0.3% were compounded. The mixture was stirred at 1000 r / mins for 10 mins to obtain a self-matting waterborne polyurethane with a solid content of about 28 wt% and an average particle size of 3570 nm.

[0167] The R value for all reactants is 1.79.

[0168] The amount of hydrophilic chain extender used is 1.1 wt%.

[0169] The amount of small molecule alcohol chain extender used is 0.86 wt%.

[0170] The molar ratio of neutralizing agent to hydrophilic chain extender is 1:1.

[0171] Comparative Example 3

[0172] A method for preparing an aqueous polyurethane emulsion includes the following steps:

[0173] 150g PCL1000, 10g Ymer N120, 2g TMP, and 2.0g DMPA were added to a three-necked flask for dehydration at 120℃. After cooling to 50℃, 13.6g HDI, 60.2g IPDI, and 1 drop of bismuth acid catalyst were added under a nitrogen atmosphere to carry out the reaction. The reaction was carried out at 90℃ for 3 hours, and the NCO% was tested to be close to the theoretical value of 5.90%.

[0174] The prepolymer was cooled to 45°C, dissolved in 150g of acetone, and mixed for 15 minutes. Then, 1.509g of triethylamine was added, and the mixture was reacted at 40°C for 5 minutes.

[0175] Emulsify with 520g of water under shear dispersion conditions (1500r / mins).

[0176] Then, a mixed solution of 7.11 g of EDA and 71.1 g of water was added dropwise, and the mixture was stirred at 25°C for 10 minutes.

[0177] Then, acetone was removed by vacuum distillation, and a thickener of 1.0%, a hand feel agent of 0.5%, a wetting agent of 1%, and a defoamer of 0.3% were compounded. The mixture was stirred at 1000 r / mins for 10 mins to obtain a self-matting waterborne polyurethane with a solid content of about 28 wt% and an average particle size of 3570 nm.

[0178] The R value for all reactants is 1.78.

[0179] The amount of hydrophilic chain extender used was 0.84 wt%.

[0180] The amount of small molecule alcohol chain extender used is 0.84 wt%.

[0181] The molar ratio of neutralizing agent to hydrophilic chain extender is 0.85:1.

[0182] Result detection

[0183] The waterborne polyurethane emulsions of the above embodiments and comparative examples were subjected to the following performance tests, and the specific test methods are as follows:

[0184] Solid content test method: Take an appropriate amount of M0 emulsion in a container made of tin foil, weigh M1, dry at 125℃ to constant weight, record the weight of M2 after baking, and calculate the solid content as (M1-M2) / M0.

[0185] Particle size testing method: Malvern laser particle size analyzer was used.

[0186] Blackness test method: Use a 20µm film scraper to scrape the film, dry it at 100℃ for about 1 minute, and observe the blackness and transparency effect (1-5 points, 5 points is the best).

[0187] Gloss test method: Apply film with a 20µm film scraper, dry at 100℃ for about 1 minute, and test the gloss with a gloss meter.

[0188] Method for room temperature bending resistance test: Scrape the film with a 20um film scraper, dry it at 100℃ for about 1 minute, cut it into 4*7cm strips, 3 in each direction of warp and weft, and test it with a room temperature bending instrument.

[0189] Alcohol resistance test method: Apply a film using a 20µm scraper, dry at 100℃ for about 1 minute, let stand for 1 day, take 95% industrial ethanol, and test 20 times with a wet and dry rubbing fastness tester. Observe whether there are any defects such as peeling or brightening on the coating surface (1-5 points, 5 points is the best).

[0190] Scratch resistance test method: Scrape the film with a 20um scraper, dry at 100℃ for about 1 minute, then scratch with a fingernail and observe whether there are any scratches on the surface (1-5 points, 5 points is the best).

[0191] The specific test results are shown in Table 1 below:

[0192]

[0193] In Table 1, the lower the gloss of the film, the better the matting effect; the greater the blackness, the better the transparency.

[0194] Table 1 shows that, through the comparison of Examples 1-3 and Comparative Examples 1-2, it is evident that in the preparation process of the waterborne polyurethane emulsion, the present invention modifies the waterborne polyurethane using acrylates, such as methyl methacrylate, and adjusts the emulsion particle size to achieve self-matting while improving transparency. Furthermore, the prepared high-transparency, low-gloss, self-matting waterborne polyurethane emulsion exhibits a room-temperature flexural resistance of 10 cycles or more, a wet rub resistance test, an alcohol resistance test grade of 3 or higher, and a scratch resistance grade of 3 or higher, demonstrating excellent mechanical properties. Comparative Examples 1-3 were not prepared according to the preparation conditions and steps of the present invention; therefore, they not only had lower blackness and poorer transparency, but also lower wet rub resistance and alcohol resistance test grades.

[0195] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high-transparency, low-gloss, self-matting waterborne polyurethane emulsion, characterized in that, Includes the following steps: S1. Preparation of prepolymer: Dehydrated polyester polyol and / or polyether polyol are mixed, and diisocyanate and catalyst are added under inert gas protection. The reaction is completed at 80~90℃. Then, hydrophilic chain extender and small molecule alcohol chain extender are added, and the reaction is completed at 75~80℃ to obtain the prepolymer. The R values ​​for all reactants range from 1.6 to 2.1, where R represents the ratio of isocyanate groups to hydroxyl groups. S2. Neutralize the prepolymer by adding a neutralizing agent to form a salt; S3. Add acrylate monomers and water to emulsify and form core-shell structured latex particles. The emulsification temperature is 20~25℃. S4. After adding an amine chain extender, the remaining diisocyanate reacts. S5. Add an initiator for polymerization; S6. Add thickener, wetting agent, crosslinking agent, and defoamer to obtain a self-matting waterborne polyurethane emulsion. Based on the total solid mass during the preparation process: The amount of acrylate monomers used is 10–30 wt%; The amount of hydrophilic chain extender used is 0.1–2 wt%; The dosage of small molecule alcohol chain extender is 0.1–2 wt%; The particle size of the core-shell structured latex particles is 1~4μm; In step S3, the core-shell structured latex particles have an acrylic core and a polyurethane shell. The acrylate monomers in S3 include one or more of the following: ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, phenyl methacrylate, and trimethacrylate.

2. The preparation method of the high-transparency, low-gloss, self-matting waterborne polyurethane emulsion as described in claim 1, characterized in that, The molar ratio of the neutralizing agent and the hydrophilic chain extender in S2 is 0.9 to 1.1:

1.

3. The preparation method of the high-transparency, low-gloss, self-matting waterborne polyurethane emulsion as described in claim 1, characterized in that, Based on the total solid mass during the preparation process, the total amount of polyester polyol and / or polyether polyol in S1 is 40~70wt%, and the amount of diisocyanate is 10~40wt%.

4. The preparation method of the high-transparency, low-gloss, self-matting waterborne polyurethane emulsion as described in claim 1, characterized in that, The mass ratio of polyol to polyether polyol is 35:1 to 10:

1.

5. The method for preparing the high-transparency, low-gloss, self-matting waterborne polyurethane emulsion as described in claim 1, characterized in that, The number average molecular weights of the polyester polyols and polyether polyols in S1 are 1000 g / mol to 2000 g / mol.

6. The method for preparing the high-transparency, low-gloss, self-matting waterborne polyurethane emulsion as described in claim 1, characterized in that, The diisocyanate is isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), or 4,4'-dicyclohexylmethane diisocyanate (HDI). 12 One or more mixtures of MDI.

7. A high-transparency, low-gloss, self-matting waterborne polyurethane emulsion prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The high-transparency, low-gloss, self-matting waterborne polyurethane emulsion is an acrylic-modified polyurethane core-shell structure.

8. The use of the high-transparency, low-gloss, self-matting waterborne polyurethane emulsion of claim 7 in the preparation of paper and film tactile oils, leather finishing agents, and matte and matte coatings for printing.

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