CN118325422A - Epoxy anticorrosive coating based on photoinitiated frontal polymerization and preparation method thereof - Google Patents

Abstract

The present invention discloses an epoxy anticorrosive coating based on photoinitiated front-line polymerization and a preparation method thereof, and relates to the field of epoxy anticorrosive coatings. The coating comprises the following raw materials: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, acrylic modified cardanol resin, SEBS, zinc powder, anti-settling aid, defoamer, dispersant, adhesion promoter, photoinitiator, photosensitizer, thermal initiator. The present invention uses aliphatic epoxy resin as the main film-forming material, an adhesion promoter, zinc powder as an anticorrosive filler, and photoinitiated cationic front-line polymerization to prepare a coating with good adhesion and anticorrosive performance, while achieving rapid curing and thick coating curing under high inorganic filler content.

Description

Epoxy anticorrosive coating based on photoinitiated frontal polymerization and preparation method thereof

Technical Field

The invention relates to the technical field of epoxy anticorrosion coatings, and in particular to an epoxy anticorrosion coating based on photo-initiated frontal polymerization and a preparation method thereof.

Background technique

Metal materials play an important role in daily life, bridge construction, automobile industry and other fields due to their good mechanical properties. However, metal materials are often exposed to some corrosive media during use, which leads to the degradation of metal material performance. The economic losses caused by the corrosion of metal materials are hundreds of millions worldwide. At the same time, the corrosion of metal materials has an impact on production safety, equipment use and environmental protection that cannot be ignored.

Among the existing metal material corrosion protection technologies, applying anti-corrosion coatings is the most economical and convenient technology. Traditional anti-corrosion coatings contain a large amount of organic solvents, which are not in line with the trend of green development. Powder anti-corrosion coatings and water-based anti-corrosion coatings are gradually occupying the market share. However, powder anti-corrosion coatings require higher temperatures when curing, which consumes more energy; water-based anti-corrosion coatings have higher requirements for construction temperature and humidity, and it is difficult to completely replace traditional coatings. Photocuring coatings have the advantages of fast curing speed, low energy required, no solvents, and little environmental impact, which is in line with the current development trend of environmentally friendly coatings. Traditional photocuring coatings are difficult to achieve the curing of thick coatings and opaque coatings. The light-induced front polymerization technology generates heat after the photoinitiated monomer polymerization, and uses the heat generated by itself to further promote the curing of the material, thereby achieving the curing of thick coatings or opaque coatings.

Existing photocuring anti-corrosion coatings have the following problems: ① The thickness of the cured paint film is relatively thin; ② Most of the fillers used are light-transmitting fillers such as nano-silicon dioxide, and the added filler content is relatively low; ③ The coating shrinks severely after rapid curing, resulting in poor adhesion of the coating.

Summary of the invention

The purpose of the present invention is to provide an epoxy anticorrosive coating based on photoinitiated frontal polymerization and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

To achieve the above object, the present invention provides the following solutions:

The present invention provides an epoxy anticorrosive coating based on photoinitiated frontal polymerization, comprising the following raw material components in parts by weight:

30-63 parts of film-forming resin, 25-65 parts of zinc powder, 0.5-1.5 parts of anti-settling aid, 0.2-0.4 parts of defoaming agent, 0.2-0.5 parts of dispersant, 2.5-5.5 parts of adhesion promoter, 2-5 parts of photoinitiator, 0.1-0.4 parts of photosensitizer, and 0.5-1.5 parts of thermal initiator.

In the present invention, the film-forming resin is a mixture of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (221), hydrogenated styrene-butadiene-styrene block copolymer (SEBS) and acrylic acid-modified cardanol resin; wherein the amount of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (221) accounts for 49% to 61% of the total mass of the film-forming resin, the amount of ethylene-butadiene-styrene block copolymer (SEBS) accounts for 19% to 31% of the total mass of the film-forming resin, and the amount of acrylic acid-modified cardanol resin accounts for 9% to 31% of the total mass of the film-forming resin.

In the present invention, the preparation of the acrylic acid-modified cardanol resin includes the following raw materials: acrylic acid, cardanol glycidyl ether, tetrabutylammonium bromide (used to catalyze the reaction of acrylic acid and cardanol glycidyl ether), and p-methoxyphenol (used to hinder the self-polymerization reaction of acryloxy in acrylic acid when preparing the acrylic acid-modified cardanol resin).

As a further preferred embodiment of the present invention, the preparation method of the acrylic acid-modified cardanol resin comprises the following steps:

Acrylic acid, cardanol glycidyl ether, tetrabutylammonium bromide and p-methoxyphenol are mixed in a mass ratio of 15-16:99-101:0.3-0.7:0.3-0.7, and reacted at 90-110° C. until the acid value of the system is less than 5 mgKOH/g to obtain the acrylic acid-modified cardanol resin. The synthesis route is as follows:

3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is an aliphatic epoxy resin with a six-membered ring, which has excellent anti-corrosion performance and reactivity. However, in the preparation process of the anti-corrosion coating of the present invention, excessive use of it will make the coating too brittle and reduce the impact resistance, while too low a use will make it difficult for the coating to be deeply cured. The specific molecular structure of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is as follows:

As an elastomer, SEBS is added to the coating to improve the impact resistance of the coating. However, in the preparation process of the anti-corrosion coating of the present invention, if the amount is too much, the viscosity of the coating will be too high and difficult to construct. If the amount is too small, the impact resistance of the coating will not be greatly improved.

The present invention uses acrylic acid to modify the cardanol resin, so that the cardanol resin has a photocurable acryloyloxy group, and the obtained acrylic acid-modified cardanol resin has low viscosity, which is beneficial to the dispersion of fillers and the construction of coatings.

As a further preferred embodiment of the present invention, the anti-settling aid is one or both of bentonite and hydrophobic fumed silica.

After high-speed dispersion and activation in the resin, bentonite expands, making it have a certain degree of suspension, while driving other fillers in the system to resist sedimentation; due to the presence of more hydroxyl groups on the surface of fumed silica, dynamic hydrogen bond cross-linking is formed in the system. Hydrogen bonds will cross-link in the static state, the coating viscosity is relatively large, and the fillers in the system are less likely to settle. The hydrogen bond cross-linking will be destroyed during stirring or construction of the coating, and the decrease in viscosity is beneficial to the processing and coating of the coating.

As a further preferred embodiment of the present invention, the defoaming agent is a silicone defoaming agent, which is beneficial to removing bubbles generated during production or use; the dispersant is Additol VXW6208/60, which is beneficial to the dispersion of fillers in the resin matrix.

As a further preferred embodiment of the present invention, the adhesion promoter is one or both of 2-hydroxyethyl methacrylate phosphate and KH560.

Both 2-hydroxyethyl methacrylate phosphate and KH560 will chemically react with the substrate to form a chemical bond between the coating and the substrate, thereby improving the adhesion between the coating and the substrate.

As a further preferred embodiment of the present invention, the photoinitiator is a 48-52wt% solution of 4,4'-didodecylbenzeniodonium hexafluoroantimonate DGE (dodecyl glycidyl ether); and the photosensitizer is 2-isopropylthioxanthone.

4,4'-didodecylbenzeniodonium hexafluoroantimonate will be decomposed into cations after being exposed to ultraviolet light. After the cation takes a proton, it forms a highly active superacid. The superacid initiates the polymerization of the monomer and releases heat. The released heat can decompose the thermal initiator to produce active free radicals, which further decompose the cationic photoinitiator. The cycle is repeated and finally 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate and acrylic modified cardanol resin are fully polymerized and cross-linked to form a paint film.

The photosensitizer 2-isopropylthioxanthone is activated after being irradiated with light and transfers energy to the photoinitiator, thereby increasing the photoinitiating activity of the system and reducing the photoinitiating energy.

As a further preferred embodiment of the present invention, the thermal initiator is one or both of cyclohexanone peroxide dibutyl ester paste and benzopinacol. After the system is irradiated with ultraviolet light, the cationic photoinitiator is cracked to initiate polymerization and release heat, and the thermal initiator absorbs heat and cracks to generate active free radicals, and the active free radicals further crack the cationic photoinitiator. The cycle is repeated to finally form a paint film.

The paint film curing mechanism is as follows.

The present invention also provides a method for preparing the above-mentioned epoxy anticorrosive coating based on photoinitiated front-line polymerization, comprising the following steps:

The acrylic modified cardanol resin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate and SEBS are first mixed, and then the defoamer, dispersant, adhesion promoter and anti-settling aid are added for a second mixing, and then the zinc powder is added, and finally the photoinitiator, photosensitizer and thermal initiator are added to obtain the epoxy anti-corrosion coating based on photoinitiated frontline polymerization.

As a further preferred embodiment of the present invention, the temperature of the first mixing is 100°C, and the temperature of the second mixing is 25-40°C.

The more specific preparation method of the epoxy anticorrosive coating based on photoinitiated front-line polymerization of the present invention is as follows:

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, acrylic modified cardanol resin and SEBS are mixed evenly at 100°C, cooled and maintained at a temperature between 25 and 40°C, a defoamer, a dispersant, an adhesion promoter and an anti-settling aid are added in sequence while stirring, dispersed at a speed of 3000r/min for 10 to 20min, zinc powder is added and dispersed to a fineness of less than 60 microns, and finally a photoinitiator, a photosensitizer and a thermal initiator are added and dispersed evenly to obtain an epoxy anti-corrosion coating based on photoinitiated front-line polymerization.

The present invention further provides the use of the above-mentioned epoxy anticorrosion coating based on photo-initiated front-line polymerization in metal corrosion protection.

The present invention uses 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, acrylic acid-modified cardanol resin and SEBS as main film-forming substances and an adhesion promoter, uses zinc powder as an anti-corrosion filler, and adopts light-initiated cationic front polymerization technology to prepare a coating having good adhesion and anti-corrosion performance, while also having rapid curing and thick coating curing with a high inorganic filler content.

The present invention discloses the following technical effects:

(1) The present invention provides an epoxy anti-corrosion coating based on photo-initiated frontal polymerization. The photo-induced frontal polymerization technology is adopted. The coating has a fast curing speed and can be cured within 30 seconds. The curing efficiency is high and the energy consumption is low. The coating prepared by the present invention is solvent-free. All raw materials used are involved in film formation and will not cause harm to the environment and construction workers. Compared with traditional anti-corrosion coatings, the resource utilization rate is improved.

(2) The present invention uses aliphatic epoxy resin as the main film-forming substance and is combined with an adhesion promoter. Compared with acryloxy photocuring, the coating has less internal stress and higher adhesion.

(3) When the inorganic filler content of the epoxy anti-corrosion coating based on photo-initiated frontal polymerization of the present invention is above 60%, the thickness of the photocurable coating can reach above 100 microns, which solves the problem that the photocurable anti-corrosion coating is difficult to cure at a high inorganic filler content due to the absorption or reflection of light by the inorganic filler, especially the deep curing of thick coatings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a Fourier transform infrared spectrum of acrylic acid-modified cardanol resin and raw materials.

FIG2 is a front-line driving diagram during the preparation of an epoxy anticorrosive coating based on photo-initiated front-line polymerization in Example 2 of the present invention;

FIG. 3 is a physical picture of the salt spray resistance test of the epoxy anticorrosion coating based on photoinitiated frontline polymerization prepared in Examples 2 to 9 of the present invention.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

In the following examples and comparative examples of the present invention, the concentration of the 4,4'-didodecylbenzene iodonium hexafluoroantimonate DGE solution is 50 wt%.

Example 1

15.34 g of acrylic acid, 100 g of cardanol glycidyl ether, 0.577 g of tetrabutylammonium bromide and 0.577 g of p-methoxyphenol were added to a flask equipped with a thermometer and a stirring device, and reacted at 100° C. until the acid value of the system was less than 5 mgKOH/g to obtain an acrylic acid-modified cardanol resin with a viscosity of 530±50 mPa·s.

Figure 1 is a Fourier transform infrared spectra of acrylic acid modified cardanol resin and raw materials. It can be seen from the figure that due to the very strong hydrogen bonding force formed by the carboxyl group of acrylic acid, its -OH stretching vibration becomes a diffuse broad band, and a "steamed bun peak" appears in the infrared spectrum between 3425 and 2700 cm ^-1 . In the infrared spectrum of cardanol glycidyl ether, 855 cm ^-1 is the characteristic peak of epoxy. In the infrared spectrum of acrylic acid modified cardanol resin, the steamed bun peak of acrylic acid and the characteristic peak of epoxy disappear, and at the same time, the infrared characteristic peak of hydroxyl appears at 3471 cm ^-1 , indicating that the carboxyl group in acrylic acid and the epoxy in cardanol glycidyl ether undergo a ring-opening reaction.

The acrylic acid-modified cardanol resin used in Examples 2-9 and Comparative Examples 1-2 of the present invention is prepared in Example 1.

Example 2

The formulation of epoxy anticorrosion coating based on photoinitiated front-line polymerization is shown in Table 1:

Table 1

Preparation:

Mix 221, acrylic modified cardanol resin and SEBS at 100°C, cool to 25°C, add defoamer, dispersant, adhesion promoter and anti-settling agent in sequence while stirring, disperse at 3000r/min for 15 minutes, then add zinc powder and disperse to a fineness of less than 60 microns while keeping the temperature below 30±5°C. Finally, add photoinitiator, photosensitizer and thermal initiator and disperse evenly to obtain epoxy anti-corrosion coating based on photoinitiated frontline polymerization.

Example 3

The formulation of epoxy anticorrosion coating based on photoinitiated front-line polymerization is shown in Table 2:

Table 2

The preparation method is the same as Example 2.

Example 4

The epoxy anticorrosion coating formulation based on photoinitiated front-line polymerization is shown in Table 3:

table 3

The preparation method is the same as Example 2.

Example 5

The epoxy anticorrosion coating formulation based on photoinitiated front-line polymerization is shown in Table 4:

Table 4

The preparation method is the same as Example 2.

Example 6

The formulation of epoxy anticorrosive coating based on photoinitiated front-line polymerization is shown in Table 5:

table 5

The preparation method is the same as Example 2.

Example 7

The formulation of epoxy anticorrosion coating based on photoinitiated front-line polymerization is shown in Table 6:

Table 6

The preparation method is the same as Example 2.

Example 8

The epoxy anticorrosion coating formulation based on photoinitiated front-line polymerization is shown in Table 7:

Table 7

The preparation method is the same as Example 2.

Example 9

The formulation of epoxy anticorrosion coating based on photoinitiated front-line polymerization is shown in Table 8:

Table 8

The preparation method is the same as Example 2.

Comparative Example 1

The coating formula of this comparative example is shown in Table 9.

Table 9

The preparation method is the same as Example 2.

Comparative Example 2

The coating formula of this comparative example is shown in Table 10.

Table 10

The preparation method is the same as Example 2.

Effect verification example

The coatings prepared in Examples 2 to 9 and Comparative Examples 1 to 2 were stirred, and their states in the containers were observed.

The coatings prepared in Examples 2 to 9 and Comparative Examples 1 to 2 were sealed and placed in a constant temperature oven at 40° C. to avoid light, and a storage stability test (GB/T 6753.3-1986) was performed.

The coatings prepared in Examples 2 to 9 and Comparative Examples 1 to 2 were applied to a sandblasted steel plate using a 100 μm paint film applicator, and the coatings were illuminated for 30 seconds under a 395 nm LED lamp or a UV iron lamp. The coatings were tested for impact resistance (GB/T 1732-2020), adhesion (GB/T 9286-2021), pencil hardness (GB/T 6739-2022), and salt spray resistance (GB/T 1771-2007).

The results are shown in Table 11.

Table 11

Among them, the impact resistance of comparative example 1 was poor, and the next experiment could not be carried out; the paint film of comparative example 2 was not completely cured, and the next experiment could not be carried out.

As shown in Table 11 and Figure 3, the epoxy anticorrosive coating based on photoinitiated front-line polymerization prepared by the present invention has good impact resistance, adhesion and salt spray resistance. Comparative Example 1 has a high content of 221, which increases the rigid structure and cross-linking degree of the coating after curing, and ultimately leads to a brittle paint film and poor impact resistance. Comparative Example 2 has a low content of 221, and it is difficult to achieve front-line polymerization after photoinitiation, resulting in incomplete curing of the bottom of the coating.

The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims (10)

1. An epoxy anticorrosive coating based on photoinitiated frontline polymerization, characterized in that it comprises the following raw material components in parts by mass: 30-63 parts of film-forming resin, 25-65 parts of zinc powder, 0.5-1.5 parts of anti-settling aid, 0.2-0.4 parts of defoaming agent, 0.2-0.5 parts of dispersant, 2.5-5.5 parts of adhesion promoter, 2-5 parts of photoinitiator, 0.1-0.4 parts of photosensitizer, 0.5-1.5 parts of thermal initiator; The film-forming resin is a mixture of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, hydrogenated styrene-butadiene-styrene block copolymer and acrylic acid-modified cardanol resin; wherein the amount of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate accounts for 49% to 61% of the total mass of the film-forming resin, the ethylene-butadiene-styrene block copolymer accounts for 19% to 31% of the total mass of the film-forming resin, and the acrylic acid-modified cardanol resin accounts for 9% to 31% of the total mass of the film-forming resin. 2. The epoxy anticorrosive coating based on photoinitiated front-line polymerization according to claim 1, characterized in that the preparation method of the acrylic acid-modified cardanol resin comprises the following steps: Acrylic acid, cardanol glycidyl ether, tetrabutylammonium bromide and p-methoxyphenol are mixed in a mass ratio of 15-16:99-101:0.3-0.7:0.3-0.7, and reacted at 90-110° C. until the acid value of the system is lower than 5 mgKOH/g to obtain the acrylic acid-modified cardanol resin. 3. The epoxy anticorrosive coating based on photoinitiated frontline polymerization according to claim 1, characterized in that the anti-settling aid is one or both of bentonite or hydrophobic fumed silica. 4. The epoxy anticorrosive coating based on photoinitiated frontline polymerization according to claim 1, characterized in that the defoamer is a silicone defoamer; and the dispersant is Additol VXW6208/60. 5. The epoxy anticorrosive coating based on photoinitiated front-line polymerization according to claim 1, characterized in that the adhesion promoter is one or both of 2-hydroxyethyl methacrylate phosphate and KH560. 6. The epoxy anticorrosive coating based on photoinitiated front-line polymerization according to claim 1, characterized in that the photoinitiator is a 4,4'-didodecylbenzeniodonium hexafluoroantimonate DGE solution with a concentration of 48-52wt%; and the photosensitizer is 2-isopropylthioxanthone. 7. The epoxy anticorrosive coating based on photoinitiated frontal polymerization according to claim 1, characterized in that the thermal initiator is one or both of cyclohexanone dibutyl peroxide paste and benzopinacol. 8. The method for preparing the epoxy anticorrosive coating based on photoinitiated front-line polymerization according to any one of claims 1 to 7, characterized in that it comprises the following steps: The acrylic modified cardanol resin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate and SEBS are first mixed, and then the defoamer, dispersant, adhesion promoter and anti-settling aid are added for a second mixing, and then the zinc powder is added, and finally the photoinitiator, photosensitizer and thermal initiator are added to obtain the epoxy anti-corrosion coating based on photoinitiated frontline polymerization. 9 . The preparation method according to claim 8 , characterized in that the temperature of the first mixing is 100° C., and the temperature of the second mixing is 25-40° C. 10. Use of the epoxy anticorrosion coating based on photoinitiated frontal polymerization as claimed in any one of claims 1 to 7 in metal corrosion protection.