Self-repairing coating and application

Abstract

The invention discloses a self-repairing coating and application thereof.According to the self-repairing coating, lignosulfonate is added into self-repairing type waterborne polyurethane, so that the strength of a polymer chain is improved, the structure is more stable, and the tensile strength of a material is improved; meanwhile, dynamic hydrogen bonds formed among the materials can support rapid self-healing of the car cover, and the self-repairing performance of the coating is effectively improved; the material can be used for surface protection of various products or articles, such as paint surface protection and glass surface protection, can significantly improve the protection effect, and has wide application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of coating composite materials, and in particular relates to a self-repairing coating and its application. Background Art

[0002] Self-healing coatings are polymer-based composite materials that are widely used in many fields such as ocean, energy, construction, transportation, aerospace, and military equipment. During use and transportation, the surface coating of equipment or components will inevitably be damaged by various external conditions, resulting in damage and cracking. If not repaired in a timely and effective manner, these defects will significantly reduce the protective effect of the coating on the substrate. At present, damaged coatings are mainly repaired or replaced manually, which is cumbersome and expensive. Self-healing coatings can restore themselves or restore their original functions under certain conditions after being damaged by external forces or environmental damage. It is an emerging intelligent protective material. The coating has the ability to repair damage by itself, which is beneficial to prolonging the service life of the coating. It has huge economic value and development space. It is one of the most important research directions in the field of coating preparation and application at home and abroad in recent years.

[0003] Take car cover as an example. It is an invisible film that is applied to the surface of the car to protect its paint surface. It can isolate the paint surface from the air and prevent it from corrosion, aging or cracking due to contact with rain, dust and some impurities. In addition, invisible car cover can also provide certain protection for a moving car against damage and scratches, while ensuring the beauty of the car body.

[0004] However, traditional self-healing coatings are generally prone to damage and have limited protective effects, which restricts their development. Therefore, it is necessary to develop a coating that can quickly self-repair after being damaged, which has a wide range of application value in improving the protective effect, maintaining the aesthetics of products or items, and extending their service life. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a self-repairing coating to solve the problems of easy damage and limited protective effect of the prior art protective coating, improve the protective effect, and be widely used to maintain the aesthetics of products or items and extend their service life.

[0006] To solve the above problems, the scheme of the present invention is as follows:

[0007] The first aspect of the present invention is to provide a self-healing coating, which is obtained by adding isocyanate and initiator to a lignin-modified self-healing waterborne polyurethane solution and stirring and mixing; the proportions of the reaction raw materials are: 30-60wt% of lignin self-healing waterborne polyurethane, 3-5wt% of isocyanate, 1-3wt% of initiator and the remainder of the first solvent; the lignin-modified self-healing waterborne polyurethane is obtained by modifying waterborne polyurethane with lignin sulfonate, and the addition amount of the lignin sulfonate is 1-5wt%.

[0008] Furthermore, the isocyanate includes but is not limited to aliphatic and alicyclic diisocyanates, preferably hexamethylene diisocyanate.

[0009] Furthermore, the initiator is an organic tin, including but not limited to dibutyltin and tributyltin.

[0010] Furthermore, the preparation method of the waterborne polyurethane comprises the following steps:

[0011] S1. Mix polytetrahydrofuran and aliphatic polyisocyanate and heat to 80-90°C for 0.5-1.5h;

[0012] S2. Add 2,2-dimethylolbutyric acid to the reaction product of step S1 and mix well, then add diacetyl oxime and the second solvent and continue the reaction for 1.5-2.5 hours;

[0013] S3. The reaction product of step S2 is cooled to 55-65°C, a tertiary amine chain extender is added, and then a diluent is added and stirred to react fully;

[0014] S4. removing the second solvent in the reaction product of step S3 to obtain waterborne polyurethane.

[0015] Preferably, the aliphatic polyisocyanate is hexamethylene diisocyanate; and / or the tertiary amine chain extender is triethylamine.

[0016] Furthermore, in terms of mass percentage, the reaction raw materials of the waterborne polyurethane are: 32.26% of polytetrahydrofuran, 48.38% of hexamethylene diisocyanate, 2.74% of 2,2-dihydroxymethylbutyric acid, 8.06% of dimethylglyoxime, 1.94% of triethylamine and the remainder of solvent.

[0017] Furthermore, the first solvent and / or the second solvent is acetone.

[0018] The second aspect of the present invention is to propose a self-repairing invisible film, comprising a first release layer, an adhesive layer, a self-repairing coating and a second release layer stacked in sequence from bottom to top; the self-repairing coating is obtained by coating, curing and drying the self-repairing coating material described in the first aspect on a substrate.

[0019] Furthermore, the curing temperature is 45-70°C for 0.5-1h, and the drying temperature is 90-105°C for 0.5-3h.

[0020] Furthermore, the first release layer is a PEU release film; and the second release layer is a PET release film.

[0021] Furthermore, the substrate used for the self-repairing coating includes but is not limited to common TPU, polyester fiber, PVC and other materials.

[0022] Furthermore, the adhesive layer is an acrylic pressure-sensitive adhesive layer.

[0023] Furthermore, the acrylic pressure-sensitive adhesive comprises the following components by weight percentage:

[0024] 4.4% acrylic acid, 27% 2-ethylhexyl acrylic acid, 8.9% methyl acrylate, 60% ethyl acetate; the preferred method for preparing acrylic pressure-sensitive adhesive is to use part of ethyl acetate as a solvent, and slowly heat it to 86°C with an initiator azobisisobutyl cyanide at a constant temperature, stir at a constant temperature, react for 20 minutes, condense, reflux the system and keep it warm for 6 hours. When the system temperature drops to 50°C, slowly add the second part of ethyl acetate to the system, react for 3 hours, and finally keep it warm for 1.5 hours to obtain acrylic pressure-sensitive collagen glue. Take aluminum acetylacetonate and ethyl acetate, and make the weight ratio of aluminum acetylacetonate: ethyl acetate: acrylic glue equal to 1:165:1250 to obtain acrylic pressure-sensitive adhesive.

[0025] The third aspect of the present invention is the use of the self-repairing coating described in the first aspect of the present invention or the self-repairing invisible film described in the second aspect of the present invention in protecting the surface of products or articles.

[0026] Furthermore, the surface protection includes paint protection and glass protection. Paint protection includes but is not limited to car covers, and glass protection includes but is not limited to special glass facade film protection.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention proposes a self-healing coating that adds lignin sulfonate to the self-healing waterborne polyurethane to increase the strength of the polymer chain, make the structure more stable, and improve the tensile strength of the material; at the same time, the dynamic hydrogen bonds formed between the materials can support rapid self-healing, effectively improving the self-healing performance of the coating.

[0029] The self-repairing coating material proposed in the present invention is simple to prepare, the material is easily available, and is suitable for industrial production; after the material is compounded into a self-repairing film, it can be used for surface protection of various products or articles, such as as a car cover for car paint protection and special glass protection, etc., which can significantly improve the protection effect and has broad application prospects. DETAILED DESCRIPTION

[0030] The following examples are used to illustrate the present invention, but do not limit the scope of the present invention. Without departing from the spirit and essence of the present invention, modifications or substitutions made to the methods, steps or conditions of the present invention are within the scope of the present invention.

[0031] The reagents used in the following examples are commonly used reagents in the art, and are commercially available standard products unless otherwise specified. Unless otherwise specified, the experimental methods used are methods known in the art.

[0032] Example 1 Preparation of waterborne polyurethane

[0033] 1) Mix polytetrahydrofuran and hexamethylene diisocyanate and heat to 85°C for 1 hour;

[0034] 2) Add 2,2-dihydroxymethylbutyric acid to the reaction product of step S1 and mix well, then add diacetyl oxime and acetone and continue the reaction for 1.5-2.5 hours;

[0035] 3) Cooling the reaction product of step S2 to 55-65° C., adding triethylamine, and then adding an appropriate amount of acetone to dilute and stir to react fully;

[0036] 4) removing acetone from the reaction product of step S3 by rotary evaporation for 1 h using a rotary evaporator to obtain waterborne polyurethane;

[0037] Among them, the reaction raw materials of the waterborne polyurethane are respectively: 32.26% of polytetrahydrofuran, 48.38% of hexamethylene diisocyanate, 2.74% of 2,2-dihydroxymethylbutyric acid, 8.06% of dimethylglyoxime, 1.94% of triethylamine and the rest of the solvent, calculated by mass percentage.

[0038] Example 2

[0039] 1) 2 parts by mass of lignin sulfonate was dissolved in distilled water, and then 98 parts by mass of the aqueous polyurethane prepared in Example 1 was mixed, and mixed at a speed of 10000 r / min for 10 minutes to obtain a lignin self-repairing aqueous polyurethane solution.

[0040] 2) The self-healing coating is obtained by adding isocyanate and initiator to a lignin-modified self-healing water-based polyurethane solution and stirring at a speed of 100 r / min for 5 minutes; the proportions of the reaction raw materials are: 60wt% of lignin self-healing water-based polyurethane, 3wt% of hexamethylene diisocyanate, 2wt% of dibutyl tin and the remainder of acetone.

[0041] Example 3

[0042] 1) 1 part by mass of lignin sulfonate was dissolved in distilled water, and then 99 parts by mass of the aqueous polyurethane prepared in Example 1 were mixed, and mixed at a speed of 10000 r / min for 10 minutes to obtain a lignin self-repairing aqueous polyurethane solution.

[0043] 2) The self-healing coating is obtained by adding isocyanate and initiator to the lignin-modified self-healing waterborne polyurethane solution and stirring at a speed of 80r / min for 10 minutes; the proportions of the reaction raw materials are: lignin self-healing waterborne polyurethane 60wt%, hexamethylene diisocyanate 5wt%, dibutyltin 3wt% and the balance acetone.

[0044] Example 4

[0045] 1) 5 parts by mass of lignin sulfonate were dissolved in distilled water, and then 95 parts by mass of the aqueous polyurethane prepared in Example 1 were mixed, and mixed at a speed of 10000 r / min for 10 minutes to obtain a lignin self-repairing aqueous polyurethane solution.

[0046] 2) The self-healing coating is obtained by adding isocyanate and initiator to a lignin-modified self-healing water-based polyurethane solution and stirring at a speed of 90 r / min for 8 minutes; the proportions of the reaction raw materials are: 50wt% of lignin self-healing water-based polyurethane, 1wt% of hexamethylene diisocyanate, 1wt% of dibutyl tin and the remainder of acetone.

[0047] Comparative Example 1

[0048] The preparation of the self-healing coating material is the same as in Example 2, except that the lignin sulfonate modification step in step 1) is omitted, and the water-based polyurethane is directly used to carry out the reaction in step 2).

[0049] Comparative Example 2

[0050] The preparation of the self-healing coating material is the same as in Example 2, except that the further mixing and stirring step of step 2) is not included.

[0051] Experimental example

[0052] The coating materials obtained in Examples 2-4 and Comparative Examples were uniformly coated on a glass plate, cured at 50° C. for 30 minutes, and then dried at 105° C. for 1 hour to obtain self-repairing films.

[0053] 1) Mechanical properties test: The mechanical tensile properties of the coating material were tested using a texture analyzer, including tensile strength (MPa) and elongation at break (%). Each set of data was tested 3 times and the average was taken. The tensile speed was 2 mm / s, and the standard GB / T 1040.1-2018 was implemented.

[0054] 2) Self-healing efficiency test: A 0.3 cm × 5 cm scratch was made on the coating surface, and the cross-sectional area of ​​the scratch was measured using a 3D surface topography profile at 50°C and a UV intensity of 0.85 W / m 2 After 5 hours of treatment, the repaired cross-sectional area was measured and the self-repairing efficiency was calculated. Self-repairing efficiency (%) = repaired scratch cross-sectional area / original scratch cross-sectional area.

[0055] The above mechanical properties test and self-repair test results are shown in Table 1.

[0056] Table 1: Self-healing performance test results

[0057] Group Tensile strength MPa Elongation at break % Self-repair efficiency % Example 1 45.5 630 98.5 Example 2 44.8 617 98.1 Example 3 41.1 605 98.0 Comparative Example 1 21.3 355 53.6 Comparative Example 2 23.7 331 43.5

[0058] As can be seen from Table 1, the self-repairing coating prepared by the present invention has relatively excellent self-repairing performance, and has excellent mechanical properties such as tensile strength and elongation at break, which meets the wide application requirements of self-repairing coatings. Comparative Examples 1 and 2 have relatively serious performance degradation due to the fact that they have not been modified or further reacted with lignin sulfonate. This shows that the addition of lignin sulfonate in the preparation of self-repairing waterborne polyurethane increases the strength of the polymer chain in the car cover, makes the structure more stable, and improves the tensile strength of the car cover; at the same time, the dynamic hydrogen bonds formed between the materials can support the rapid self-healing of the car cover, effectively improving the self-repairing performance of the car cover.

[0059] The present invention is not limited to what is described in the specification and implementation modes, and therefore, additional advantages and improvements can be easily realized by those familiar with the art. Therefore, without departing from the spirit and scope of the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details, representative schemes and described embodiments.

Claims

1. A self-repairing coating, characterized in that: The self-healing waterborne polyurethane modified by lignin is prepared by adding isocyanate and initiator to a lignin-modified self-healing waterborne polyurethane solution and stirring and mixing; the proportions of the reaction raw materials are: 30-60wt% of lignin self-healing waterborne polyurethane, 3-5wt% of isocyanate, 1-3wt% of initiator and the remainder of the first solvent; the self-healing waterborne polyurethane modified by lignin is prepared by modifying waterborne polyurethane with lignin sulfonate, and the addition amount of the lignin sulfonate is 1-5wt%.

2. The self-repairing coating according to claim 1, characterized in that: The preparation method of the waterborne polyurethane comprises the following steps: S1. Mix polytetrahydrofuran and aliphatic polyisocyanate and heat to 80-90°C for 0.5-1.5h; S2. Add 2,2-dimethylolbutyric acid to the reaction product of step S1 and mix well, then add diacetyl oxime and the second solvent and continue the reaction for 1.5-2.5 hours; S3. The reaction product of step S2 is cooled to 55-65°C, a tertiary amine chain extender is added, and then a diluent is added and stirred to react fully; S4. removing the second solvent in the reaction product of step S3 to obtain waterborne polyurethane.

3. The self-repairing coating according to claim 2, characterized in that: The aliphatic polyisocyanate is hexamethylene diisocyanate; and / or the tertiary amine chain extender is triethylamine.

4. The self-repairing coating according to claim 3, characterized in that: In terms of mass percentage, the reaction raw materials of the waterborne polyurethane are: 32.26% of polytetrahydrofuran, 48.38% of hexamethylene diisocyanate, 2.74% of 2,2-dihydroxymethylbutyric acid, 8.06% of dimethylglyoxime, 1.94% of triethylamine and the remainder of solvent.

5. The self-repairing coating according to claim 2, characterized in that: The first solvent and / or the second solvent is acetone.

6. Self-repairing invisible film, characterized in that: It comprises a first release layer, an adhesive layer, a self-repairing coating and a second release layer stacked in sequence from bottom to top; the self-repairing coating is obtained by coating, curing and drying the self-repairing coating material according to any one of claims 1 to 5 on a substrate.

7. The self-repairing invisible film according to claim 6, characterized in that: The first release layer is a PEU release film; the second release layer is a PET release film.

8. The self-repairing invisible film according to claim 6, characterized in that: The adhesive layer is an acrylic pressure-sensitive adhesive layer.

9. Use of the self-repairing coating according to any one of claims 1 to 5 or the self-repairing invisible film according to claim 6 in protecting the surface of products or articles.

10. The use according to claim 9, characterized in that: The surface protection includes paint surface protection and glass surface protection.