1. The electrostatic spraying UV-LED curing vacuum coating primer is characterized by comprising the following components in parts by weight:

15-35 parts of alkyd resin modified polyurethane acrylate;

0-10 parts of pure acrylate;

25-40 parts of trimethylolpropane triacrylate;

10-20 parts of a monofunctional reactive diluent monomer;

3-5 parts of a UV-LED photoinitiator;

0.03-0.2 part of a leveling agent;

0-1 part of an adhesion promoter;

0.01-0.5 part of conductive agent;

3-5 parts of an electrostatic diluent;

the hydroxyl value of the alkyd resin modified polyurethane acrylate is 50-100.

The viscosity of the UV-LED curing vacuum coating primer coating No. 4 cup is 10-30 s, and the resistivity is 5-50M omega cm.

2. The electrostatically sprayable UV-LED curable vacuum coating primer according to claim 1, wherein the UV-LED photoinitiator is at least one of 2, 2 ', 4, 4' -tetrakis (2-chlorophenyl) -5, 5 ' -bis (3, 4-dimethoxyphenyl) diimidazole, 2 ', 5-tris (2-chlorophenyl) -4- (3, 4-dimethoxyphenyl) -4 ', 5 ' -diphenyldiimidazole, 4, 4' -bis (dimethylamino) benzophenone or a combination initiator of isopropyl thioxanthone and 2, 4, 6-trimethylbenzoylethoxyphenylphosphine oxide.

3. The UV-LED curing vacuum coating primer capable of being electrostatically sprayed according to claim 1, wherein the alkyd resin modified polyurethane acrylate is used in an amount of 25 to 30 parts.

4. The electrostatically sprayable UV-LED curable vacuum coating primer according to claim 1, wherein the amount of the pure acrylate is 5 to 10 parts.

5. The electrostatically sprayable UV-LED curable vacuum coating primer according to claim 1, wherein the electrostatic diluent is one or more of diacetone alcohol, low carbon alcohols, ketones.

6. The electrostatically sprayable UV-LED curable vacuum coating primer according to claim 1, wherein the monofunctional reactive diluent monomer is at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, isobornyl methacrylate.

7. The electrostatically sprayable UV-LED curable vacuum coating primer according to claim 1, wherein the leveling agent is one or more of a polyether modified organosiloxane solution, an alkyl modified organosiloxane solution, an acrylate copolymer solution, a silicone glycol interpolymer solution.

8. The electrostatically sprayable UV-LED curable vacuum coating primer according to claim 1, wherein the adhesion promoter is one or both of a phosphate polyester polymer and a phosphate acrylate polymer.

9. The electrostatically sprayable UV-LED curable vacuum coating primer according to claim 1, wherein the conductive agent is one or both of a solution of a quaternary ammonium compound and a solution of an organic amine salt compound.

10. The method for preparing an electrostatically sprayable UV-LED curable vacuum coating primer according to any one of claims 1 to 9, comprising the steps of:

s1, adding alkyd resin modified polyurethane acrylate, pure acrylate, trimethylolpropane triacrylate and a monofunctional reactive diluent monomer into a stirring kettle according to a ratio, stirring for 2-4 hours, and dispersing uniformly;

s2, adding a UV-LED photoinitiator, a leveling agent, an adhesion promoter, a conductive agent and an electrostatic diluent, and stirring for 1-2 hours to obtain the UV-LED curing vacuum coating primer capable of being electrostatically sprayed.

Background

The photocureable coating is a coating variety which develops rapidly in the last decade, and has the characteristics of high efficiency, energy conservation, economy, environmental protection and the like. Vacuum coating technology is also a new technology developed in the last decade, and a thin metal layer can be coated on the surface of a coated part to endow a substrate with metallic luster. In the process of vacuum coating, a vacuum coating primer must be coated on the surface of a substrate, otherwise, a coated metal film is easy to fall off, and therefore, the quality of the coating greatly depends on the quality of the primer. The photocuring vacuum coating can endow the substrate with excellent metal luster, improve the product quality and have wide application prospect. At present, a small amount of technologies are available to realize electrostatic spraying of ultraviolet curing vacuum coating paint. However, most of the conventional ultraviolet curing vacuum coating materials are cured by a high-pressure mercury lamp light source, and have the defects of easy damage, high energy consumption, easy thermal deformation of workpieces, serious damage to eyes of operators and the like. Compared with a high-pressure mercury lamp light source, the UV-LED curing light source has great advantages: the service life of the UV-LED curing light source is over long, the service time of the UV-LED curing light source can reach 20000h, which is ten times (2000h) of that of the traditional mercury lamp; secondly, the lighting time is short, the UV-LED lamp can be instantly switched on and off, and the traditional mercury lamp needs to be preheated for 15 minutes; thirdly, the energy consumption is low, and the power consumption of the UV-LED lamp is only 10 percent of that of the traditional mercury lamp; fourthly, the irradiation luminosity is high, no heat radiation exists, and the production efficiency is improved; fifthly, the mercury is not contained, no ozone is generated, and the environment is protected. However, in the UV-LED curing process, the surface layer coating is often not cured completely due to the problem of oxygen inhibition, and it is difficult to achieve good curing in both the surface layer and the deep layer. Some technologies disclose UV-LED curing vacuum coating primers, but electrostatic spraying cannot be achieved, air spraying and other methods are mainly adopted for construction, the phenomenon of paint overspray is serious, the paint consumption is high, the utilization rate of the paint is low, the edge spraying quality of a product is poor, the production efficiency is low, the yield is low, the problem and the defect of air spraying can be effectively solved by electrostatic spraying, and the utilization rate and the efficiency are improved by more than one time. Therefore, a vacuum coating which is suitable for electrostatic spraying and UV-LED curing at the same time needs to be searched.

Disclosure of Invention

The invention aims to solve the technical problem of providing the UV-LED curing vacuum coating primer capable of being electrostatically sprayed, effectively and organically combining the advantages of UV-LED and electrostatic spraying, ensuring the excellent performance of a coating film, changing the construction mode of air spraying and the high-pressure mercury lamp curing mode of the traditional UV-curing vacuum coating paint, greatly improving the utilization rate of the paint, the quality of products and the production efficiency, and reducing the production cost.

The invention also aims to provide a preparation method of the UV-LED curing vacuum coating primer capable of being electrostatically sprayed.

The invention aims to be realized by the following technical scheme:

an electrostatic spraying UV-LED curing vacuum coating primer comprises the following components in parts by weight:

15-35 parts of alkyd resin modified polyurethane acrylate;

0-10 parts of pure acrylate;

25-40 parts of trimethylolpropane triacrylate;

10-20 parts of a monofunctional reactive diluent monomer;

3-5 parts of a UV-LED photoinitiator;

0.03-0.2 part of a leveling agent;

0-1 part of an adhesion promoter;

0.01-0.5 part of conductive agent;

3-5 parts of an electrostatic diluent;

the viscosity of the UV-LED curing vacuum coating primer coating No. 4 cup is 10-30 s, and the resistivity is 5-50M omega cm. The hydroxyl value of the alkyd resin modified polyurethane acrylate is 50-100.

According to the invention, alkyd resin modified polyurethane acrylate with a specific hydroxyl value and pure acrylate are selected as main resin, wherein the alkyd resin contains a large amount of hydroxyl and carboxyl, the adhesive force to substrates such as metal is good, and the alkyd resin is used for modifying the polyurethane acrylate, so that the obtained alkyd resin modified polyurethane acrylate has the advantages of high functionality, fast curing, high crosslinking density and high hardness; by controlling the hydroxyl value of the alkyd resin modified polyurethane acrylate, the adhesive force and the plating property of the resin to a base material can be further controlled; the pure acrylate has low viscosity and good flexibility, and the alkyd resin modified polyurethane acrylate and the pure acrylate with specific hydroxyl value are selected, so that the adhesive force is excellent, the curing speed is high, the functionality is high, the resistivity is low, the requirements of electrostatic spraying on the resistivity and the requirements of UV-LED bottom layer and deep layer curing are met, and the optimal curing effect is achieved.

Preferably, the UV-LED photoinitiator is at least one of 2, 2 ', 4, 4' -tetrakis (2-chlorophenyl) -5, 5 ' -bis (3, 4-dimethoxyphenyl) diimidazole (TCTM), 2 ', 5-tris (2-chlorophenyl) -4- (3, 4-dimethoxyphenyl) -4 ', 5 ' -diphenyldiimidazole (TCDM), 4, 4' -bis (dimethylamino) benzophenone (MK), or a composite initiator of Isopropyl Thioxanthone (ITX) and 2, 4, 6-trimethylbenzoylethoxyphenylphosphine oxide (TEPO). The matching effect of the UV-LED photoinitiation, the resin and the UV-LED light source is good.

Preferably, the using amount of the alkyd resin modified polyurethane acrylate is 25-30 parts.

Preferably, the amount of the pure acrylate is 5-10 parts.

Preferably, the electrostatic diluent is one or more of diacetone alcohol, low carbon alcohol and ketone.

Preferably, the monofunctional reactive diluent is at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate and isobornyl methacrylate.

Preferably, the leveling agent is one or more of a polyether modified organic siloxane solution, an alkyl modified organic siloxane solution, an acrylate copolymer solution and a silicone glycol copolymer solution.

Preferably, the adhesion promoter is one or two of phosphate ester polyester polymer and phosphate ester acrylate polymer.

Preferably, the conductive agent is one or two of a quaternary ammonium salt compound solution and an organic amine salt compound solution.

The preparation method of the UV-LED curing vacuum coating primer capable of being electrostatically sprayed comprises the following steps:

s1, adding alkyd resin modified polyurethane acrylate, pure acrylate, trimethylolpropane triacrylate and a monofunctional reactive diluent monomer into a stirring kettle according to a ratio, stirring for 2-4 hours, and dispersing uniformly;

s2, adding a UV-LED photoinitiator, a leveling agent, an adhesion promoter, a conductive agent and an electrostatic diluent, and stirring for 1-2 hours to obtain the UV-LED curing vacuum coating primer capable of being electrostatically sprayed.

Compared with the prior art, the invention has the following beneficial effects: the invention solves the problem that the photocuring vacuum coating paint can not meet the requirements of electrostatic spraying and UV-LED curing at the same time, improves the utilization rate, the production efficiency and the product quality of the paint, and reduces the energy consumption and the production cost; the invention uses a very small amount of electrostatic diluent to ensure that the conductivity of the coating formula meets the requirement of electrostatic spraying, and the VOC content of the system is low, thereby being very environment-friendly; the prepared primer has the advantages of excellent plating property, salt spray resistance, good water boiling resistance, strong adhesive force, high hardness, low price, high utilization rate of the coating, energy conservation, environmental protection and wide market prospect.

Detailed Description

The present invention is further described with reference to the following specific examples, which are not intended to limit the invention in any way, but the technical solutions obtained by using equivalent alternatives or equivalent variations are all included in the scope of the present invention as claimed in the claims. The starting reagents employed in the examples of the present invention are, unless otherwise specified, conventional commercially available starting reagents.

The parts described in the following examples are parts by mass.

The alkyd resin-modified urethane acrylate used in the following examples is an alkyd resin-modified urethane acrylate having a hydroxyl value of 50 to 100, which is manufactured by Guangdong deep exhibition industries, Inc., and the preparation process thereof is as follows:

placing 10-15 parts of isophorone diisocyanate (IPDI) and 0.02 part of catalyst into a four-neck flask provided with a mechanical stirrer, a dropping funnel and a reflux condenser, heating to 60 ℃, slowly adding 20-30 parts of pentaerythritol triacrylate, preserving heat for 3 hours after the dropping is finished, starting an-NCO value, stopping the reaction when the-NCO value is monitored to reach 5-15%, obtaining a polyurethane acrylate prepolymer with an end group containing-NCO, then adding 20-40 parts of alkyd resin with a hydroxyl value of 120-400, starting monitoring the hydroxyl value after the reaction is carried out for 3 hours, and stopping the reaction when the hydroxyl value is 50-100, thus obtaining 50-100 alkyd resin modified polyurethane acrylate.

Examples 1 to 7

S1, sequentially adding alkyd resin modified polyurethane acrylate, pure acrylate and an active diluent into a stirring kettle according to the proportion shown in Table 1, stirring for 2-4 hours, and uniformly dispersing;

s2, adding a UV-LED photoinitiator, a leveling agent, an adhesion promoter, a conductive agent and an electrostatic diluent, and stirring for 1-2 hours to obtain the UV-LED curing vacuum coating primer capable of being electrostatically sprayed.

Example 8

S1, sequentially adding alkyd resin modified polyurethane acrylate and reactive diluent into a stirring kettle according to the proportion shown in Table 1, stirring for 2-4 hours, and uniformly dispersing;

s2, adding a UV-LED photoinitiator, a leveling agent, an adhesion promoter, a conductive agent and an electrostatic diluent, and stirring for 1-2 hours to obtain the UV-LED curing vacuum coating primer capable of being electrostatically sprayed.

Comparative example 1

A photocuring vacuum coating primer is basically the same as that in example 1 in composition and proportion, except that in comparative example 1, the alkyd resin modified polyurethane acrylate in claim 1 is replaced by the same mass part of polyurethane acrylate.

Comparative example 2

The composition and the proportion of the photocuring vacuum coating primer are basically the same as those of the primer in the embodiment 1, and the difference is that in the comparative example 2, the alkyd resin modified polyurethane acrylate with the hydroxyl value of 120-150 in the same mass part is used for replacing the alkyd resin modified polyurethane acrylate with the hydroxyl value of 50-100 in the embodiment 1. The preparation process of the alkyd resin modified polyurethane acrylate with the hydroxyl value of 120-150 comprises the following steps: placing 10-15 parts of isophorone diisocyanate (IPDI) and 0.02 part of catalyst into a four-neck flask provided with a mechanical stirrer, a dropping funnel and a reflux condenser, heating to 60 ℃, slowly adding 20-30 parts of pentaerythritol triacrylate, preserving heat for 3 hours after the dropping is finished, starting an-NCO value, stopping the reaction when the-NCO value is monitored to reach 5-15%, obtaining a polyurethane acrylate prepolymer with an end group containing-NCO, then adding 30-50 parts of alkyd resin with a hydroxyl value of 120-400, starting monitoring the hydroxyl value after the reaction is carried out for 2 hours, and stopping the reaction when the hydroxyl value is 120-150, thus obtaining the alkyd resin modified polyurethane acrylate of 120-150.

Comparative example 3

The composition and the ratio of the photo-curing vacuum coating primer are basically the same as those of example 1, except that in comparative example 3, 1-hydroxycyclohexyl phenyl ketone in equal parts by mass is used for replacing an UV-LED photoinitiator MK in example 1.

Comparative example 4

An ultraviolet light curing vacuum coating primer capable of being electrostatically sprayed is produced by Guangdong deep exhibition industry Co., Ltd, and the formula and the preparation process are disclosed in patent CN105670463B example 4 of an ultraviolet light curing vacuum coating metallic paint capable of being electrostatically sprayed.

TABLE 1 examples 1-8 formulations

The primers prepared in the examples and the comparative examples were tested for comprehensive properties, and the testing methods and the testing results are shown in tables 2 and 3, respectively.

Table 2 example test results

UV-LED wavelength: ultraviolet wavelength of UV-LED curing machine.

Plating property: the appearance is flat, fat and bright, and the plating property is excellent when the plating layer does not fall off according to the check method, otherwise, the plating property is general.

Table 3 comparative example test results

UV-LED wavelength: ultraviolet wavelength of UV-LED curing machine.

Plating property: the appearance is flat, fat and bright, and the plating property is excellent when the plating layer does not fall off according to the check method, otherwise, the plating property is general.

According to the test results of the embodiment in table 2, the UV-LED curing vacuum coating primer capable of being electrostatically sprayed can be cured by UV-LEDs with the wavelengths of 365nm, 385nm and 405nm, and the coating has the advantages of excellent plating property, salt spray resistance, good water boiling resistance, high hardness, strong adhesion and the like. According to the comparison between the comparative example 1 and the example 1, after the polyurethane acrylate is modified by the alkyd resin, the active groups such as hydroxyl and carboxyl are increased, the polarity is enhanced, the resistivity of the coating is effectively reduced, and meanwhile, the adhesion is better and the curing rate is faster. According to the comparison between the comparative example 2 and the example 1, the hydroxyl value of the alkyd modified urethane acrylate resin is too large, the resistivity of the primer is reduced, and the adhesion and the plating property of the primer are not influenced, but the hydroxyl value of the alkyd modified urethane acrylate resin is increased because the using amount of the alkyd resin is increased in the resin synthesis process, and the using amount of the polyurethane prepolymer is reduced relatively, which directly results in the reduction of the functionality and the content of the curing group of the resin, so that the curing efficiency and the crosslinking density of the primer are reduced, and the performances such as hardness, water boiling resistance and the like are deteriorated. According to the comparison between the comparative example 3 and the example 1, the maximum absorption peaks of the conventional photoinitiator 1-hydroxycyclohexyl phenyl ketone are 246nm, 280nm and 333nm, and the conventional photoinitiator is not matched with a UV LED light source, so that the curing of the primer is seriously incomplete, the performance of a paint film is extremely poor, and therefore the primer needs to select the photoinitiator matched with the wavelength of the UV LED light source. According to the comparison between the comparative example 4 and the example 1, the conventional ultraviolet curing vacuum coating is not suitable for UV LED curing, on one hand, the initiation efficiency of the resin is low, and on the other hand, the initiator in the coating is not matched with the wavelength of a UV LED light source, so that the paint film is incompletely cured and has poor performance.