Waterborne polyurethane ink and preparation process thereof

Abstract

The invention discloses waterborne polyurethane ink and a preparation process thereof. The waterborne polyurethane ink comprises the following components: waterborne polyurethane; modified vegetable oil; a dispersant; a defoaming agent; an emulsifier; a leveling agent; a thickening agent; deionized water; the water-based polyurethane ink disclosed by the invention takes water as a dispersion medium, so that the emission of volatile organic compounds (VOCs) is remarkably reduced in the use process of the water-based polyurethane ink. Compared with traditional solvent-based ink, pollution to the atmospheric environment is reduced, and improvement of air quality is facilitated. Emulsion systems of traditional waterborne polyurethane printing ink are easily influenced by temperature and pH value fluctuation, carboxyl catalytic degradation and particle aggregation are caused, and then layering or viscosity abnormity is caused, while the situation is effectively improved by adding the modified vegetable oil in the waterborne polyurethane printing ink.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to a waterborne polyurethane ink and its preparation process. Background Art

[0002] As a green printing material, waterborne polyurethane ink, with water as the dispersion medium, significantly reduces the emission of volatile organic compounds (VOCs), meets international environmental protection standards, and has outstanding environmental protection advantages. However, in industrial applications, this type of ink also faces many problems.

[0003] One is the insufficient storage stability. Its emulsion system is easily affected by temperature and pH value fluctuations, resulting in carboxyl catalytic degradation and particle aggregation, and then causing delamination or abnormal viscosity. The other is the limited adhesion to non-polar substrates. Traditional waterborne polyurethanes have poor wettability to low surface energy materials such as PET and BOPP, and often rely on corona treatment or primer, which not only has high costs but also complex processes.

[0004] In view of the above problems, there is an urgent need to develop a waterborne polyurethane ink with high storage stability, strong adhesion and versatility.

[0005] Therefore, the present invention provides a waterborne polyurethane ink to solve the corresponding problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a waterborne polyurethane ink to solve the deficiencies in the prior art.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A waterborne polyurethane ink, comprising the following components in mass percentage:

[0009] Waterborne polyurethane 50%-65%;

[0010] Modified vegetable oil 14%-20%;

[0011] Dispersant 2%-3%;

[0012] Defoamer 0.8%-1.2%;

[0013] Emulsifier 2%-4%;

[0014] Leveling agent 1.5%-2%;

[0015] Thickener 1.2%-1.6%;

[0016] Deionized water to make up the balance to 100%.

[0017] As a further technical solution, the aqueous polyurethane is a carboxyl-containing polyether-type polyurethane with a molecular weight of 6000-10000 g / mol.

[0018] As a further technical solution, the preparation method of the modified vegetable oil includes the following steps:

[0019] (1) Pretreatment stage: Mix linseed oil and hydrogenated castor oil in a mass ratio of 1:5-8, dehydrate through a molecular sieve, and then heat up to 120-130 °C under nitrogen protection;

[0020] (2) Catalytic reaction: Add a solid superacid catalyst accounting for 1.5-1.8% of the mass of the mixed oil, and raise the temperature to 160-165 °C at a rate of 5 °C / min for transesterification reaction;

[0021] (3) Regulation: When the pH value of the reaction system drops to 4.5, inject glycerol accounting for 4-6% of the total raw materials as a chain transfer agent and continue the reaction for 1.5 hours;

[0022] (4) Separation and purification: Use a rotary evaporator to gradually cool down to 60 °C under a pressure of -0.09 MPa and collect the intermediate product;

[0023] (5) Secondary modification: Mix the intermediate product and hydrogen peroxide in a mass ratio of 10:1-1.2, react at 80 °C for 30 minutes, and then adsorb and remove impurities through activated carbon;

[0024] (6) Final product: Obtain the modified vegetable oil after 2 freeze-thaw cycles.

[0025] As a further technical solution, in step (1), the molecular sieve dehydration is carried out at 380 °C for 3 hours of heat preservation dehydration;

[0026] In step (2), the solid superacid catalyst is ZrO2 / SiO2 with a specific surface area of 550 m 2 / g;

[0027] Among them, the mass ratio of ZrO2 to SiO2 is 3:1.

[0028] As a further technical solution, in step (5), the hydrogen peroxide concentration is 25 wt% concentration.

[0029] As a further technical solution, in step (6), the freeze-thaw cycle is a freezing parameter: -40 °C / 24 h, and a thawing parameter: 4 °C / 1 h.

[0030] As a further technical solution, the dispersant is sodium polyacrylate.

[0031] As a further technical solution, the defoamer is an organosilicon defoamer.

[0032] As a further technical solution, the emulsifier is a compound of a non-ionic emulsifier and an anionic emulsifier in a ratio of 1:1;

[0033] The leveling agent is a silicone leveling agent;

[0034] The thickener is sodium carboxymethyl cellulose.

[0035] A preparation process of a waterborne polyurethane ink comprises the following steps:

[0036] (1) Premix the modified vegetable oil with 30% deionized water to form an oil phase; the temperature of the premixing is controlled at 55 °C;

[0037] (2) Add the emulsifier to the oil phase under stirring, and carry out high-speed shearing emulsification for 25 minutes, with the stirring speed being 500 r / min;

[0038] (3) Then add the waterborne polyurethane and continuously stir and disperse for 45 minutes, with the stirring speed being 10,000 r / min;

[0039] (4) Finally, add the dispersant, defoamer, leveling agent, thickener and the remaining deionized water in sequence, and stir at a speed of 350 r / min for 15 minutes to obtain the product.

[0040] Beneficial effects:

[0041] The waterborne polyurethane ink of the present invention uses water as a dispersion medium, and this characteristic significantly reduces the emission of volatile organic compounds (VOCs) during its use. Compared with traditional solvent-based inks, it reduces the pollution to the atmospheric environment and helps to improve air quality.

[0042] The emulsion system of traditional waterborne polyurethane inks is easily affected by fluctuations in temperature and pH value, resulting in carboxyl catalytic degradation and particle aggregation, and then causing problems such as delamination or abnormal viscosity. However, the addition of the modified vegetable oil in the present invention effectively improves this situation.

[0043] When the modified vegetable oil is added to the waterborne polyurethane ink system, the double bond structure in its molecules forms a cross-linked network with the carboxyl groups of the waterborne polyurethane; this cross-linked network enhances the stability of the emulsion system, makes the interaction between the ink particles more stable, and reduces the possibility of particle aggregation. At the same time, the modified vegetable oil can also buffer the influence of temperature and pH value changes on the emulsion system to a certain extent, reduce the risk of carboxyl catalytic degradation, and thus effectively improve the storage stability of the ink.

[0044] The hydrogenated castor oil in the modified vegetable oil has the characteristic of high melting point, which can form a continuous and dense film layer during the ink drying process, increasing the contact area and bonding force between the ink and the substrate surface. At the same time, linseed oil is rich in unsaturated fatty acids, endowing the ink with good fluidity and permeability, enabling it to better infiltrate the substrate surface. When the ink contacts the substrate, the modified vegetable oil molecules can have strong interactions with the molecules on the substrate surface, such as van der Waals forces and hydrogen bonds, thereby enhancing the adhesion between the ink and the substrate. In addition, the cross-linked network structure formed by the modified vegetable oil and the waterborne polyurethane also helps to firmly adhere the ink to the substrate surface. Description of the Drawings

[0045] Figure 1 It is a bar chart showing the change in storage viscosity of each group in the experiment. Detailed Implementation Modes

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] The following are specific embodiments

[0048] Example 1

[0049] A waterborne polyurethane ink contains the following components by mass percentage:

[0050] Waterborne polyurethane 50%;

[0051] Modified vegetable oil 14%;

[0052] Sodium polyacrylate 2%;

[0053] Organosilicon defoamer 0.8%;

[0054] Emulsifier 2%; The emulsifier is a compound of non-ionic and anionic emulsifiers in a ratio of 1:1.

[0055] Organosilicon leveling agent 1.5%;

[0056] Sodium carboxymethyl cellulose 1.2%;

[0057] Deionized water is added to make up to 100%.

[0058] The waterborne polyurethane is a carboxyl-containing polyether-type polyurethane with a molecular weight of 6000 g / mol.

[0059] The preparation method of the modified vegetable oil includes the following steps:

[0060] (1) Pretreatment stage: Mix linseed oil and hydrogenated castor oil at a mass ratio of 1:6. After dehydration by molecular sieve, heat it to 125 °C under nitrogen protection; the molecular sieve dehydration is carried out at 380 °C for 3 hours of heat preservation dehydration;

[0061] (2) Catalytic reaction: Add a solid superacid catalyst accounting for 1.6% of the mass of the mixed oil, and raise the temperature to 165 °C at a rate of 5 °C / min for transesterification reaction; the solid superacid catalyst is ZrO2 / SiO2, and the specific surface area is 550 m 2 / g;

[0062] Among them, the mass ratio of ZrO2 to SiO2 is 3:1.

[0063] (3) Regulation: When the pH value of the reaction system drops to 4.5, inject glycerol accounting for 5% of the total raw materials as a chain transfer agent and continue the reaction for 1.5 hours;

[0064] (4) Separation and purification: Use a rotary evaporator to gradually cool down to 60 °C under a pressure of -0.09 MPa and collect the intermediate product;

[0065] (5) Secondary modification: Mix the intermediate product and hydrogen peroxide in a mass ratio of 10:1, react at 80 °C for 30 minutes, and then adsorb and remove impurities by activated carbon; the concentration of hydrogen peroxide is 25 wt%.

[0066] (6) Final product: Obtain modified vegetable oil after 2 freeze-thaw cycles; the freeze-thaw cycle is freeze parameters: -40 °C / 24 h, thaw parameters: 4 °C / 1 h.

[0067] Example 2

[0068] The difference from Example 1 is that it contains the following components by mass percentage:

[0069] Waterborne polyurethane 58%;

[0070] Modified vegetable oil 15%;

[0071] Sodium polyacrylate 2.2%;

[0072] Organosilicon defoamer 0.9%;

[0073] Emulsifier 3%; the emulsifier is a compound of non-ionic and anionic emulsifiers in a ratio of 1:1; organosilicon leveling agent 1.8%;

[0074] Sodium carboxymethyl cellulose 1.5%;

[0075] Deionized water is made up to 100% by balance.

[0076] Example 3

[0077] It is different from Example 1 in that it contains components with the following mass percentages:

[0078] Waterborne polyurethane: 60%;

[0079] Modified vegetable oil: 16%;

[0080] Sodium polyacrylate: 2.8%;

[0081] Organosilicon defoamer: 1%;

[0082] Emulsifier: 3%; the emulsifier is a compound of non-ionic and anionic emulsifiers in a ratio of 1:1; Organosilicon leveling agent: 1.6%;

[0083] Sodium carboxymethyl cellulose: 1.5%;

[0084] Deionized water: the balance to 100%.

[0085] Example 4

[0086] It is different from Example 1 in that it contains components with the following mass percentages:

[0087] Waterborne polyurethane: 65%;

[0088] Modified vegetable oil: 20%;

[0089] Sodium polyacrylate: 3%;

[0090] Organosilicon defoamer: 1.2%;

[0091] Emulsifier: 4%; the emulsifier is a compound of non-ionic and anionic emulsifiers in a ratio of 1:1; Organosilicon leveling agent: 2%;

[0092] Sodium carboxymethyl cellulose: 1.6%;

[0093] Deionized water: the balance to 100%.

[0094] The preparation process of each example is as follows:

[0095] A preparation process of waterborne polyurethane ink, comprising the following steps:

[0096] (1) Premix the modified vegetable oil with 30% of deionized water to form an oil phase; the temperature of the premixing is controlled at 55°C;

[0097] (2) Add the emulsifier to the oil phase under stirring, and carry out high-speed shear emulsification for 25 minutes, with the stirring speed being 500 r / min;

[0098] (3) Then add the waterborne polyurethane and continuously stir and disperse for 45 minutes, with the stirring speed being 10,000 r / min;

[0099] (4) Finally, a dispersant, an antifoaming agent, a leveling agent, a thickening agent and the remaining deionized water are added in sequence. After stirring at a speed of 350 r / min for 15 minutes, it is obtained.

[0100] Comparative Example 1:

[0101] Based on the technical solution of Example 1, the difference from the technical solution of Example 1 is that no modified vegetable oil is added.

[0102] Comparative Example 2:

[0103] Based on the technical solution of Example 1, the difference from the technical solution of Example 1 is that the modified vegetable oil is replaced with a conventional unmodified vegetable oil, which is a mixture of linseed oil and hydrogenated castor oil in a mass ratio of 1:6.

[0104] Test:

[0105] Stability test

[0106] The samples of the examples and comparative examples were subjected to a stability test. Referring to GB / T 6753.3-1986 "Test Method for Storage Stability of Paints", the viscosity before storage and the viscosity after storage were tested. The storage time was 30 days, and the viscosity change rate was calculated;

[0107] Table 1

[0108]

[0109]

[0110] As can be seen from Table 1, the waterborne polyurethane ink prepared by the present invention has excellent storage stability.

[0111] Adhesion test:

[0112] The adhesion of the examples and comparative examples was tested with reference to GB / T 9286-1998 "Cross-Cut Test for Paints and Varnishes Films";

[0113] Table 2

[0114] Adhesion / level Example 1 1 Example 2 1 Example 3 1 Example 4 1 Comparative Example 1 4 Comparative Example 2 4

[0115] As can be seen from Table 2, the waterborne polyurethane ink prepared by the present invention has high adhesion.

[0116] The above are only the preferred embodiments of the present invention, but the present invention is not limited to the shown implementation scope. Any changes made according to the concept of the present invention, or equivalent implementation examples modified into equivalent changes, should still be within the protection scope of the present invention when they do not exceed the spirit covered by the specification.

Claims

1. A water-based polyurethane ink, characterized in that: By weight, it contains the following components in percentage by weight: Waterborne polyurethane 50%-65%; Modified vegetable oil 14%-20%; Dispersant 2%-3%; Defoaming agent 0.8%-1.2%; Emulsifier 2%-4%; Leveling agent 1.5%-2%; Thickener 1.2%-1.6%; Deionized water was used to make the balance to 100%.

2. A water-based polyurethane ink according to claim 1, characterized in that: The waterborne polyurethane is a carboxyl-containing polyether polyurethane with a molecular weight of 6000-10000 g / mol.

3. The aqueous polyurethane ink according to claim 1, characterized in that: The modified vegetable oil preparation method comprises the following steps: (1) Pretreatment stage: linseed oil and hydrogenated castor oil are mixed in a mass ratio of 1:5-8, dehydrated through molecular sieves, and heated to 120-130°C under nitrogen protection; (2) Catalytic reaction: adding a solid superacid catalyst accounting for 1.5-1.8% of the mixed oil by weight, and heating the temperature to 160-165°C at a rate of 5°C / min to carry out transesterification reaction; (3) Regulation: When the pH value of the reaction system drops to 4.5, glycerol accounting for 4-6% of the total raw materials is injected as a chain transfer agent and the reaction is continued for 1.5 hours; (4) Separation and purification: using a rotary evaporator to gradually cool down to 60°C under a pressure of -0.09 MPa to collect the intermediate product; (5) Secondary modification: the intermediate product is mixed with hydrogen peroxide in a mass ratio of 10:1-1.2, reacted at 80°C for 30 minutes, and then impurities are removed by activated carbon adsorption; (6) Final product: Modified vegetable oil is obtained after two freeze-thaw cycles.

4. A water-based polyurethane ink according to claim 3, characterized in that: In step (1), the molecular sieve is dehydrated at 380° C. for 3 hours; The solid superacid catalyst in step (2) is ZrO2 / SiO2 with a specific surface area of ​​550 m 2 / g; Among them, the mass ratio of ZrO2 to SiO2 is 3:

1.

5. The aqueous polyurethane ink according to claim 3, characterized in that: In step (5), the concentration of hydrogen peroxide is 25 wt %.

6. The aqueous polyurethane ink according to claim 3, characterized in that: The freeze-thaw cycle in step (6) is as follows: freezing parameter: -40°C / 24h, thawing parameter: 4°C / 1h.

7. The aqueous polyurethane ink according to claim 1, characterized in that: The dispersant is sodium polyacrylate.

8. The aqueous polyurethane ink according to claim 1, characterized in that: The defoamer is an organosilicon defoamer.

9. The aqueous polyurethane ink according to claim 1, characterized in that: The emulsifier is a mixture of nonionic and anionic emulsifiers in a ratio of 1:

1. The leveling agent is a silicone leveling agent; The thickener is sodium hydroxymethylcellulose.

10. A process for preparing a water-based polyurethane ink according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) premixing the modified vegetable oil with 30% deionized water to form an oil phase; the premixing temperature is controlled at 55° C.; (2) adding an emulsifier to the oil phase under stirring, and emulsifying at high speed for 25 minutes at a stirring speed of 500 r / min; (3) adding waterborne polyurethane and continuing to stir and disperse for 45 minutes at a stirring speed of 10000 r / min; (4) Finally, add dispersant, defoamer, leveling agent, thickener and remaining deionized water in sequence, and stir at 350 r / min for 15 minutes.

Images