A high surface tension online coating film and its preparation process

Abstract

The present invention relates to polyester films that can be used in the packaging field, and more specifically to a high-surface-tension online coating film and its preparation process. The high-surface-tension online coating film is prepared from raw materials including a polyester component, a crosslinking agent, a wetting agent, a leveling agent, and water; the polyester component is prepared from raw materials including sodium sulfonate, a diol, a dibasic acid, a chain extender, and a catalyst; the chain extender is castor oil or hydroxymethyl cellulose; and the chain extender is used to introduce a polyhydroxy raw material into the online coating film, thereby increasing the crosslinking degree of the online coating film and the proportion of more stable polyethers in the polar groups of the online coating film, thereby imparting high surface tension and excellent water resistance to the online coating film.

Description

Technical Field

[0001] The invention relates to a polyester film that can be used in the packaging field, and in particular to a high-surface-tension online coating film and a preparation process thereof. Background Art

[0002] Polyester film is a highly versatile film material with excellent optical properties, a smooth surface, good thermal stability, minimal shrinkage, and resistance to light aging. Its superior properties have led to its widespread use in packaging, electronics, and other fields. However, due to its low surface tension, polyester film has limited printing adaptability and low composite fastness with other materials.

[0003] To improve the printability of polyester film and enhance its composite strength with other materials, corona treatment or primer coating are commonly used. However, corona treatment has some drawbacks and shortcomings, such as poor treatment uniformity, localized low or high surface tension, and surface tension loss after treatment, which quickly leads to loss of effectiveness if exposed to air. Furthermore, corona-treated films often produce high levels of dust and static electricity, making them unsuitable for use as optical films.

[0004] Currently, primer treatment is typically performed using an in-line coating process. In-line coating technology involves applying the primer during the polyester film production process, completing the coating process simultaneously with the end of production. Polar substances are often added to the coating to enhance the surface tension of the in-line coated film. However, this addition of polar substances reduces the water resistance of the in-line coated film, limiting the application scenarios of primer-treated polyester film. Summary of the Invention

[0005] In order to improve the problem of poor water resistance of existing online coating films, the present application provides a high surface tension online coating film and a preparation process thereof.

[0006] In a first aspect, the present application provides a high surface tension online coating film, which adopts the following technical solution:

[0007] A high surface tension online coating film, formed by reacting an online coating liquid applied to a polyester film;

[0008] The online coating liquid is composed of the following raw materials in parts by weight:

[0009] 10-20 parts of polyester component;

[0010] 3-15 parts of a cross-linking agent;

[0011] Wetting agent 0.2-0.5 parts;

[0012] 0.2-0.5 parts of leveling agent;

[0013] 50-80 parts water;

[0014] The polyester component, in parts by weight, comprises the following raw materials:

[0015] 5-20 parts of sodium sulfonate;

[0016] 45-60 parts of diol;

[0017] 40-50 parts of dibasic acid;

[0018] Chain extender: 3-7 parts;

[0019] 0.1-0.2 parts of catalyst;

[0020] The chain extender is one of castor oil or hydroxymethyl cellulose;

[0021] The cross-linking agent is isocyanate or amino resin.

[0022] By adopting the above technical solution, a polyhydroxy raw material is introduced into the online coating film via a chain extender, which generates more ether bonds, which are more stable than ester bonds, in the polar groups of the online coating. Because ester bonds have a conjugated system and the presence of lone electron pairs on the oxygen atom, ester bonds are more susceptible to water binding and hydrolysis than ether bonds. This reduces the proportion of ester bonds in the polar groups and increases the proportion of ether bonds, resulting in high surface tension and enhanced water resistance of the online coating film. In addition, by introducing raw materials containing two or more hydroxyl groups into the online coating film, the crosslinking degree of the online coating film is increased, the density of the film layer is increased, and the number of water molecules that can penetrate the online coating film is reduced, resulting in high surface tension and good water resistance of the online coating film.

[0023] Preferably, the preparation process of the polyester component comprises the following reaction steps:

[0024] Esterification reaction:

[0025] The sodium sulfonic acid salt, diol, dibasic acid, chain extender and catalyst are mixed, and then reacted for 1-3 hours at a stirring rate of 180-250 r / min, a reaction temperature of 130-150° C. and a nitrogen atmosphere to prepare a polyester oligomer;

[0026] Polycondensation reaction:

[0027] The polyester oligomer is reacted at a vacuum pressure of 1.3-1.5 KPa and a temperature of 210-230° C. for 2-3 hours to prepare a polyester component.

[0028] Through the above technical solution, the raw materials of the polyester component are first subjected to an esterification reaction and then to a polycondensation reaction to obtain the polyester component, thereby improving the uniformity of the prior coating film and reducing the production of by-products in the polyester and polycondensation reactions, so that the online coating film has high surface tension and water resistance.

[0029] Vacuuming removes the generated water molecules, promotes the polycondensation reaction, increases the molecular weight of the polymer, and thus improves the high surface tension and water resistance of the online coating film.

[0030] In the present application, the reaction conditions of the esterification reaction and the polycondensation reaction are preferred. The esterification reaction and the polycondensation reaction are carried out step by step, so that the molecular structure of the prepared polyester component is more regular, and the online coating film has higher surface tension and water resistance.

[0031] Preferably, the dibasic acid is at least one of 2,5-furandicarboxylic acid, isophthalic acid, adipic acid and oxalic acid.

[0032] Preferably, the dibasic acid is a combination of 2,5-furandicarboxylic acid and isophthalic acid.

[0033] Through the above technical solution, dibasic acid is preferred, so that the prepared online coating film has high surface tension and excellent water resistance.

[0034] Preferably, the diol is at least one of diethylene glycol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol and 6-hexanediol.

[0035] Preferably, the diol is diethylene glycol.

[0036] Through the above technical solution, diol is preferably used, so that the prepared online coating film has excellent high surface tension.

[0037] Preferably, the catalyst is at least one of an antimony-based catalyst, a titanium-based catalyst and a tin-based catalyst.

[0038] Preferably, the catalyst is at least one of antimony trioxide, antimony glycol, tetrabutyl titanate, tetraisopropyl titanate, tetraisooctyl titanate, dibutyltin oxide and butyl stannoic acid.

[0039] Through the above technical solution, the polyester reaction is promoted and the degree of the polyester reaction is improved, so that the prepared online coating film has excellent high surface tension.

[0040] Preferably, the sodium sulfonate salt is 5-sodium sulfoisophthalate or sodium sulfosuccinic anhydride.

[0041] Through the above technical solution, sulfonate is added to the polyester component to increase the polar groups of the prepared polyester, making the polyester water-soluble and increasing the stability of the online coating liquid.

[0042] Preferably, the wetting agent is at least one of phosphate esters and polyethers; and the leveling agent is an acrylic leveling agent or a silicone leveling agent.

[0043] Preferably, the wetting agent is at least one of monolauryl phosphate, potassium monododecyl phosphate, n-dodecyl polyoxyethylene ether and nonylphenol polyoxyethylene ether; the leveling agent is at least one of GLP588, GLP303, BYK-333, BD-3055, BD-3033, BD-3053 and leveling agent LAG-601.

[0044] Preferably, the wetting agent is nonylphenol polyoxyethylene ether; and the leveling agent is a combination of GLP303 and BD-3053.

[0045] Through the above technical solution, the wetting agent and the leveling agent are used in combination, so that the online coating liquid can be better wetted and spread on the polyester film, so that the online coating liquid is in full contact with the polyester film, thereby forming better adhesion.

[0046] Acrylic leveling agents: GLP588, GLP303; silicone leveling agents: BYK-333, BD-3055, BD-3033, BD-3053 and leveling agent LAG-601.

[0047] Polyethers are preferred wetting agents, while GLP303 polyacrylic resins and BD-3053 polyether-modified organopolysiloxanes are preferred leveling agents. Polyether wetting agents have high polarity and hydrolysis resistance. Polyacrylic resin leveling agents effectively fill the polyester molecules of the online coating film after film formation, resulting in tighter connections between the molecules and increased film density.

[0048] Polyether wetting agents, polyacrylic resin leveling agents and polyether-modified organopolysiloxane leveling agents are used in combination to fill in the space between the polyester molecules of the online coating film. The wetting agent and leveling agent have good compatibility with the polyester molecules, which improves the density of the online coating film. At the same time, the leveling agent polyether-modified organopolysiloxane makes the online coating film have a certain hydrophobic property, reduces the water molecules that can enter the interior of the first coating film, reduces the hydrolysis of the hydrophilic groups in the online coating film, and makes the online coating film have high surface tension and excellent water resistance.

[0049] Preferably, the raw materials of the online coating liquid further include 8-10 parts of nano titanium dioxide dispersion, and the nano titanium dioxide dispersion, in parts by weight, includes 100 parts of water, 1-2 parts of nano titanium dioxide, 0.2-0.7 parts of sodium hexametaphosphate and 0.2-0.7 parts of hydroxymethyl cellulose;

[0050] The preparation process of the nano titanium dioxide suspension is as follows:

[0051] Nano-titanium dioxide, sodium hexametaphosphate and hydroxy cellulose are added into water, and stirred at a high speed of 2000-2500 r / min for 1-2 hours to prepare a nano-titanium dioxide dispersion.

[0052] Through the above technical solution, nano titanium dioxide is added to the online coating liquid, and the high surface tension of the nano titanium dioxide further increases the surface tension of the online coating film.

[0053] Sodium hexametaphosphate and hydroxycellulose are used in combination to improve the dispersibility of nano-titanium dioxide and the density of the online coating film. Hydroxycellulose can react with the curing agent during the film-forming process to increase the connection strength between titanium dioxide and polyester molecules, reduce the migration of nano-titanium dioxide to the online polyester film, and make the online coating film have high surface tension and reduce the attenuation of high surface tension.

[0054] Preferably, the preparation process of the online coating liquid is to mix the polyester component, crosslinking agent, wetting agent, leveling agent and water evenly to prepare a mixed liquid, and then add the nano titanium dioxide dispersion into the mixed liquid in 3-6 times, and the temperature of the mixed liquid is 40-60°C.

[0055] Through the above technical solution, the dispersibility of nano-titanium dioxide in the online coating liquid is improved, thereby increasing the surface tension of the online coating film.

[0056] In a second aspect, the present application provides a process for preparing a high surface tension online coating film.

[0057] A process for preparing a high surface tension online coating film includes the following steps:

[0058] S1 casting → S2 MDO stretching → S3 online coating → S4 heating → S5 TDO stretching → S6 winding;

[0059] In the S3 online coating step, the online coating liquid is coated on the polyester film after MDO stretching, and an online coating film is formed after a heating step, wherein the heating temperature is 110-130° C. and the heating time is 10-30 minutes;

[0060] The amount of the online coating liquid used in the online coating is 2-10g / m 2 .

[0061] By adopting the above technical solution, the online coating liquid is coated during the production process of the polyester film. The online coating step is set between MD stretching and TD stretching, and the heating before TD stretching is used to make the online coating liquid react and dry to form an online coating film, which does not affect the normal production process of the polyester film. When the production is completed, the online coating liquid forms an online coating film on the polyester film, and the production efficiency is high.

[0062] Under the conditions of a heating temperature of 110-130° C. and a heating time of 10-30 minutes, the polyester component in the online coating liquid and the curing agent, and the hydroxy cellulose and the curing agent fully react, so that the prepared online coating film has high surface tension, excellent adhesion and water resistance.

[0063] The online coating liquid of the present application is coated on a polyester film to form an online coating film. The online coating liquid is applicable to all polyester films.

[0064] In summary, this application has the following beneficial effects:

[0065] 1. A high surface tension online coating film, the raw materials for its preparation include a polyester component, a cross-linking agent, a wetting agent, a leveling agent and water; the raw materials for the preparation of the polyester component include sodium sulfonic acid salt, a diol, a dibasic acid, a chain extender and a catalyst; the chain extender is one of castor oil or hydroxymethyl cellulose; a polyhydroxy raw material is introduced into the online coating film through the chain extender to increase the cross-linking degree of the online coating film and increase the proportion of more stable polyethers in the polar groups of the online coating film, so that the online coating film has high surface tension and excellent water resistance.

[0066] 2. In the polyester coating liquid, a wetting agent, a polyacrylic resin leveling agent and a polyether-modified organic polysiloxane leveling agent are used in combination to fill the space between the polyester molecules of the online coating film, thereby improving the density of the online coating film and making the online coating film have a certain hydrophobic property, reducing the water molecules that can enter the online coating film, and making the online coating film have high surface tension and excellent hydrolysis resistance.

[0067] 3. Nano-titanium dioxide is added to the online coating liquid. The high surface tension of nano-titanium dioxide further increases the surface tension of the online coating film. Sodium hexametaphosphate and hydroxycellulose are used in combination to improve the dispersibility of nano-titanium dioxide, the density of the online coating film, and the connection strength between titanium dioxide and polyester molecules, so that the online coating film has high surface tension and excellent water resistance. DETAILED DESCRIPTION

[0068] Preparation examples of raw materials and / or intermediates

[0069] Preparation Example 1

[0070] A polyester component, the raw material components of which are shown in Table 1, is prepared in the following steps:

[0071] Esterification reaction:

[0072] Sodium sulfonic acid salt, diol, dibasic acid, chain extender and catalyst were added to a reaction kettle connected to a condenser and mixed, and then heated to 150°C under nitrogen protection at a stirring speed of 180 r / min and reacted for 1 hour to prepare a polyester oligomer; polycondensation reaction:

[0073] The polyester oligomer was subjected to a vacuum of 1.5 KPA and heated to 210° C. for reaction for 2 h to prepare a polyester component.

[0074] Preparation Example 2-4

[0075] A polyester component differs from Preparation Example 1 in that the types and weights of the raw materials of the polyester component are different, and the reaction conditions of the esterification reaction and the polycondensation reaction are different, as shown in Table 1.

[0076] Table 1 Types and weights of raw materials for the polyester components in Preparation Examples 1-4, and the reaction conditions for esterification and polycondensation reactions

[0077]

[0078]

[0079] Preparation Example 5

[0080] A polyester component is different from Preparation Example 1 in that an equal amount of a composition of isophthalic acid and 2,5-furandicarboxylic acid in a mass ratio of 2:1 is used to replace isophthalic acid.

[0081] Preparation Example 6

[0082] A polyester component, which differs from Preparation Example 1 in that the preparation method of the polyester component is different. The preparation process is as follows: sodium sulfonate, diol, dibasic acid, chain extender and catalyst are added to a reaction kettle connected to a condenser, stirred at a stirring speed of 300 r / min, heated to 200°C under nitrogen protection, and then reacted at 200°C for 5 hours to prepare the polyester component.

[0083] Preparation Example 7

[0084] A nano-titanium dioxide dispersion, the raw material components of which are shown in Table 2, is prepared in the following steps:

[0085] Sodium hexametaphosphate and hydroxycellulose were added to water and mixed evenly. Nano-titanium dioxide was added in three portions under high-speed stirring at 2000 r / min. After the addition was completed, stirring was continued for 1 hour to prepare a nano-titanium dioxide dispersion.

[0086] Preparation Examples 8-11

[0087] A nano-titanium dioxide dispersion, which differs from Preparation 7 in that the types and weights of raw materials used in the nano-titanium dioxide dispersion are different, and the preparation conditions are different, as shown in Table 2.

[0088] Table 2 Raw material types and weight settings of nano-titanium dioxide dispersions in Preparation Examples 7-11, and preparation condition settings

[0089]

[0090]

[0091] The average particle size of the nano-titanium dioxide used in Preparation Examples 7-11 is 30±5 nm.

[0092] Preparation Example 12

[0093] An online coating liquid, whose raw material components are shown in Table 2, is prepared as follows:

[0094] The polyester group, cross-linking agent, wetting agent, leveling agent and water were mixed to form a mixed solution, and then the mixed solution was heated to 40°C. Under the stirring condition of 200 r / min, the nano-titanium dioxide dispersion was added to the mixed solution in three times. After the nano-titanium dioxide dispersion was added, stirring was continued for 15 minutes.

[0095] Preparation Examples 13-15

[0096] An online coating liquid, which differs from Preparation 12 in that the types and weights of the raw materials of the online coating liquid are set differently, and the addition method of the nano-titanium dioxide dispersion is set differently, as shown in Table 3.

[0097] Table 3 Types and weight settings of raw materials for online coating solutions in Preparation Examples 12-15, and settings for adding nano-titanium dioxide dispersions

[0098]

[0099]

[0100] Preparation Example 16

[0101] An online coating liquid, which differs from Preparation Example 13 in that an equal amount of leveling agent GLP303 is used instead of the combination of leveling agent GLP303 and BD-3053.

[0102] Preparation Example 17

[0103] An online coating liquid, which differs from Preparation Example 13 in that an equal amount of leveling agent BD-3053 is used instead of the combination of leveling agent GLP303 and BD-3053.

[0104] Preparation Example 18

[0105] An online coating liquid, which differs from Preparation Example 13 in that nano-titanium dioxide dispersion is not used.

[0106] Preparation Examples 19-20

[0107] An online coating liquid, which differs from Preparation Example 13 in that the polyester component of Preparation Examples 5-6 is used in equal amounts to replace the polyester component of Preparation Example 2.

[0108] Preparation Examples 21-22

[0109] An online coating liquid is different from Preparation Example 13 in that the nano-titanium dioxide dispersion of Preparation Examples 10-11 is used in equal amounts to replace the nano-titanium dioxide dispersion of Preparation Example 8.

[0110] Example

[0111] Example 1

[0112] An online coating film is obtained by the following preparation steps:

[0113] S1 casting → S2 MDO stretching → S3 online coating → S4 heating → S5 TDO stretching → S6 winding.

[0114] Preparation of BOPET film with online coating film:

[0115] S1 casting sheet: The polyester base material is melt-extruded at 280°C to prepare a film, and the film is cooled by a cold roller at a temperature of 30°C to form a casting sheet;

[0116] S2 MDO stretching: the cast sheet was preheated at 80°C and then longitudinally stretched at a stretching temperature of 100°C and a stretching ratio of 3.5 times;

[0117] S3 online coating: the online coating liquid of Preparation Example 12 is coated on one surface of the longitudinally stretched polyester film, and the amount of the online coating liquid is 2-10 g / m 2 ;

[0118] S4 heating: the polyester film coated with the online coating liquid is heated at a temperature of 110-130°C for 10-30 minutes to form a polyester film with an online coating film;

[0119] S5 TDO stretching: The polyester film after step S4 is transversely stretched at a stretching ratio of 4.0 and a stretching temperature of 100° C., then heat-set at 180° C. and cooled at 23° C. to prepare a polyester film with an online coating liquid;

[0120] S6 Winding: The polyester film with the online coating liquid is then wound up.

[0121] In the present application, the online coating liquid is coated on the polyester film to form an online coating film. The online coating film is applicable to all polyester films, and the polyester film is not limited to the polyester film prepared in the examples of the present application.

[0122] Example 2-3

[0123] An online coating film, which differs from Example 1 in that the type and amount of the online coating liquid in step S3 are set differently, and the heating conditions in step S4 are set differently, as shown in Table 4.

[0124] Table 3 Type and dosage of online coating liquid in step S3 and heating condition setting list in step S4 during the preparation process of online coating film in Examples 1-3

[0125]

[0126] Example 4-11

[0127] An online coating film, which differs from Example 1 in that the types of online coating liquids are set differently, and the online coating liquids of Preparation Examples 15-22 are used in sequence.

[0128] Comparative Example

[0129] Comparative Example 1

[0130] An online coating film, which differs from Example 7 in that no chain extender is used in its online coating liquid, the amount of the polyester component is set to 25 kg, and the amount of the cross-linking agent component is set to 2 kg.

[0131] Comparative Example 2

[0132] An online coating film, which differs from Example 7 in that the polyester component and water in the online coating liquid are replaced by equal amounts of water-based polyurethane 951 with a solid content of 25%.

[0133] Performance testing

[0134] Test 1: Surface tension test method: The surface tension of the film is measured using a test solution with known surface tension (acrylamide and ethylene glycol diether mixture). The test standard is: JISK-6763-71. The specific method is as follows: prepare a series of mixed solutions with various surface tension values, then dip a clean cotton swab in the mixed solution and apply it to the film surface for about 600mm. 2 If the liquid film remains intact for more than two seconds, it indicates that the surface tension of the film is greater than that of the mixed liquid used. Continue testing with a solution with a higher surface tension. Conversely, if the liquid film breaks, it indicates that the surface tension of the film is less than that of the mixed liquid. Try using a liquid with a lower surface tension until the critical condition is reached. If the previous mixed liquid can spread, but the next higher mixed liquid cannot, then the surface tension of the previous mixed liquid is the surface tension of the film.

[0135] Test 2: Water Resistance Test Method: Weigh a certain amount of online coating liquid onto a dry, clean surface dish and spread it evenly. After drying to form a film, weigh it. Then, soak the film in deionized water for 48 hours. Remove it and wipe the surface with filter paper to remove moisture. Quickly weigh it and calculate the water absorption and weight gain of the film to indicate the water resistance of the film. The greater the water absorption rate of the film, the worse the water resistance.

[0136] Test 3: Adhesion Test Method: Adhesion of the online coating film was tested according to the 100-grid test method of GB / T9286-1998. Adhesion level 0 is the best and level 5 is the worst. Adhesion reflects the strength of the film's bond to the polyester substrate.

[0137] Test samples: The high surface tension films of Examples 1-11 were used as test samples, and the high surface tension films of Comparative Examples 1-2 were used as control samples.

[0138] Test results: The surface tension, water resistance and adhesion of the high surface tension films of Examples 1-11 and Comparative Examples 1-2 are shown in Table 4.

[0139] Table 4 Experimental results of surface tension, water resistance and adhesion of high surface tension films of Examples 1-11 and Comparative Examples 1-2

[0140]

[0141]

[0142] Combining Examples 1-11 and Comparative Examples 1-2 and Table 4, it can be seen that:

[0143] The surface tension, surface tension after 12 months, water resistance and adhesion of Examples 1-11 are better than those of Comparative Examples 1-2.

[0144] It is shown that by adding a chain extender, a nano-titanium dioxide dispersion, preferably a leveling agent and a wetting agent, and preferably a type of dibasic acid to the online coating liquid, the formed online coating film has high surface tension and excellent water resistance and adhesion.

[0145] Compared with Examples 5-6, the surface tension, surface tension after 12 months, water resistance and adhesion of Example 1 are better than those of Examples 5-6. This may be because the acrylic leveling agent and the silicone leveling agent of the leveling agent in Example 1 are used in combination, so that the online coating liquid is better spread on the polyester film. At the same time, the wetting agent and the leveling agent have good compatibility with the polyester molecules, which improves the density of the online coating film. At the same time, the silicone leveling agent makes the online coating film have a certain hydrophobic property, reduces the possibility of polar groups migrating into the interior of the online coating film, and makes the online coating film have excellent surface tension and anti-surface tension after 12 months; thereby, the online coating film has high surface tension and excellent hydrolysis resistance.

[0146] Compared with Examples 10-11, the surface tension, surface tension after 12 months, water resistance and adhesion of Example 1 are better than those of Examples 10-11. This may be because under the action of sodium hexametaphosphate and hydroxymethyl cellulose, the structure of the online coating film dispersed with nano-titanium dioxide is denser and the dispersion is more uniform, so that the online coating film has high surface tension and excellent hydrolysis resistance.

[0147] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A high surface tension online coating film, characterized in that: The coating is formed by reacting the online coating liquid applied to the polyester film; the surface tension of the high surface tension online coating film is not less than 65 dynes, The online coating liquid is composed of the following raw materials in parts by weight: 10-20 parts of polyester component; 3-15 parts of a cross-linking agent; Wetting agent 0.2-0.5 parts; 0.2-0.5 parts of leveling agent; 50-80 parts water; 8-10 parts of nano titanium dioxide dispersion; The polyester component, in parts by weight, comprises the following raw materials: 5-20 parts of sodium sulfonate; 45-60 parts of diol; 40-50 parts of dibasic acid; Chain extender: 3-7 parts; 0.1-0.2 parts of catalyst; The chain extender is castor oil or hydroxymethyl cellulose; The cross-linking agent is isocyanate; The nano-titanium dioxide dispersion comprises, by weight, 100 parts of water, 1-2 parts of nano-titanium dioxide, 0.2-0.7 parts of sodium hexametaphosphate and 0.2-0.7 parts of hydroxymethyl cellulose. The preparation process of the nano-titanium dioxide suspension is as follows: nano-titanium dioxide, sodium hexametaphosphate and hydroxymethyl cellulose are added to water, and stirred at a high speed of 2000-2500 r / min for 1-2 hours to prepare the nano-titanium dioxide dispersion.

2. The high surface tension online coating film according to claim 1, characterized in that: The preparation process of the polyester component comprises the following reaction steps: Esterification reaction: Sodium sulfonate, diol, dibasic acid, chain extender and catalyst are mixed, and then reacted for 1-3 hours at a stirring rate of 180-250 r / min, a reaction temperature of 130-150°C and a nitrogen atmosphere to prepare polyester oligomers; Polycondensation reaction: The polyester oligomer is reacted under vacuum of 1.3-1.5KPa at a temperature of 210-230°C for 2-3 hours to prepare the polyester component.

3. The high surface tension online coating film according to claim 1, characterized in that: The dibasic acid is at least one of 2,5-furandicarboxylic acid, isophthalic acid, adipic acid and oxalic acid.

4. The high surface tension online coating film according to claim 1, characterized in that: The diol is at least one of diethylene glycol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol and 6-hexanediol.

5. The high surface tension online coating film according to claim 1, characterized in that: The catalyst is at least one of an antimony-based catalyst, a titanium-based catalyst and a tin-based catalyst.

6. The high surface tension online coating film according to claim 1, characterized in that: The sodium sulfonate salt is 5-sodium sulfoisophthalate or sodium sulfobutyl succinate.

7. The high surface tension online coating film according to claim 1, characterized in that: The wetting agent is at least one of phosphate esters and polyethers; the leveling agent is an acrylic leveling agent or an organic silicon leveling agent.

8. A high surface tension online coating film according to any one of claims 1 to 7, characterized in that: The preparation process of the online coating liquid is to mix the polyester component, crosslinking agent, wetting agent, leveling agent and water evenly to prepare a mixed liquid, and then add the nano titanium dioxide dispersion into the mixed liquid in 3-6 times. The temperature of the mixed liquid is 40-60°C.

9. The process for preparing a high surface tension online coating film according to any one of claims 1 to 8, characterized in that: The method comprises the following preparation steps: S1 casting → S2 MDO stretching → S3 online coating → S4 heating → S5 TDO stretching → S6 winding; In the S3 online coating step, the online coating liquid is coated on the polyester film after MDO stretching, and an online coating film is formed after a heating step, wherein the heating temperature is 110-130° C. and the heating time is 10-30 minutes; The amount of the online coating liquid used in the online coating is 2-10 g / m2.

Images