CN112724797A - Low-temperature baking amino baking paint for automobile hub coating and preparation method thereof - Google Patents

Abstract

The invention discloses a low-temperature baking amino baking paint for automobile hub coating, which comprises the following components: the preparation method comprises the following steps: s1, grinding: mixing the polyester resin, the butylated amino resin, the high imino amino resin, the coloring pigment and the parachlorophenylacetonitrile in parts by weight, and grinding the mixture by using a grinder to obtain slurry; s2, preparing paint: the residual gas-phase silicon dioxide, dinonylphenol dinaphthalenesulfonic acid and wax slurry are added into the obtained slurry to be mixed, stirred and uniformly dispersed to obtain a mixed solution.

Description

Low-temperature baking amino baking paint for automobile hub coating and preparation method thereof

Technical Field

The invention relates to the field of hub coating, in particular to low-temperature baking amino baking paint for coating an automobile hub and a preparation method thereof.

Background

China is a world hub production and processing center, China has an extremely unique advantage in the aspect of hub production and manufacturing, China has rich aluminum ore reserves, has the advantages that electrolytic aluminum needs a large amount of electric power, the hub production and manufacturing needs a large amount of technical workers, China has the output of automobiles breaking through 2000 million, China produces a large amount of hubs, the hub export accounts for about 70% of the world hub output, the annual output is conservative calculated to be more than 2 hundred million hubs, and the hub coating consumption is increased continuously, about 50 yuan for each hub, and the hub coating consumption is about 100 hundred million.

Environmental protection, energy conservation and high efficiency are the development directions of coatings, and the coatings encouraged by the nation are high-solid low-viscosity coatings, water-based coatings, photocureable coatings and powder coatings.

At present, the automobile hub coating baking paint accounts for a large proportion, and the main stream adopts solvent type amino baking paint, which has the advantages that: high hardness, good glossiness, good plumpness and strong decoration; however, the following disadvantages also exist:

1. high-temperature baking and shaping are needed, the temperature of a workpiece needs to reach 160-;

2. the filling property is poor, a primer needs to be sprayed on the powder coating, and then the baking paint needs to be sprayed, otherwise, the sand paper marks on the powder coating cannot be covered, and the leveling cannot be ensured.

3. The re-coating resistance is poor, the wheel hub is frequently re-coated due to the limitation of yield, the existing baking varnish has poor re-coating resistance, and the problems of embrittlement, resistance, adhesion reduction and the like can occur in re-coating.

Therefore, how to solve the defects of the prior art is a subject of the present invention.

Disclosure of Invention

In order to solve the problems, the invention discloses a low-temperature baking amino baking paint for coating automobile hubs and a preparation method thereof.

In order to achieve the above purpose, the invention provides the following technical scheme: a low-temperature baking amino baking paint for automobile hub coating comprises the following components in parts by weight:

the fumed silica, namely fumed silica, is nano white powder generated by high-temperature hydrolysis of silicon halide in oxyhydrogen flame, is commonly called fumed silica, is an amorphous silica product, has a primary particle size of 7-40 nm, an aggregate particle size of about 200-500 nm, a specific surface area of 100-400 m2/g, high purity and a SiO2 content of not less than 99.8%.

Further, the molecular weight of the polyester resin is 2500, and the acid value is 5-8 KOH/g; the hydroxyl value is 84mgKOH/g, and the solid part of the polyester resin is more than or equal to 60 percent.

Further, the solid content of the butylated amino resin is more than or equal to 70%.

Further, the solid content of the high imino amino resin is more than or equal to 75 percent.

Further, the strong solvent of the oxygen acid ester is propylene glycol methyl ether acetate or p-chlorobenzene acetonitrile.

Further, the coloring pigment comprises carbon black and titanium dioxide.

A preparation method of low-temperature baking amino baking paint for automobile hub coating comprises the following steps:

s1, grinding: mixing the polyester resin, the butylated amino resin, the high imino amino resin, the coloring pigment and the parachlorophenylacetonitrile in parts by weight, and grinding the mixture by using a grinder until the fineness is 20 to 25 mu m to obtain slurry;

s2, preparing paint: and adding the rest fumed silica, dinonylphenol dinaphthalenesulfonic acid and wax slurry into the obtained slurry, mixing, stirring and uniformly dispersing to obtain a mixed solution, and adjusting the viscosity of the mixed solution to 80-100 seconds by adopting a coating-4 cup measurement to obtain the baking varnish.

The technical conception and the action mechanism of the invention are as follows:

1. the paint can be baked and shaped at low temperature mainly through reasonable selection of the drier and reasonable selection and collocation of the resin;

reasonable selection of the drier: the traditional sulfonic acid drier can accelerate the reaction speed and reduce the reaction temperature, but can bring about the reduction of the performance of a paint film, particularly the reduction of the salt spray resistance of the paint film, because unreacted drier remains hydrophilic, the water resistance of the paint film can be reduced, but the sulfonic acid drier has a plurality of types and great effect difference; dinonylphenol dinaphthalenesulfonic acid is selected as a drier, the influence of dinonylphenol dinaphthalenesulfonic acid on water resistance is small, and meanwhile, the optimal addition amount is found through a large number of experiments, so that the excellent performance of a paint film can be maintained while the reaction temperature is reduced;

reasonable selection and collocation of resin: the main reason that the baking temperature of the traditional high-temperature baking varnish is high is that the curing temperature of the used methylated amino resin is 140-160 ℃, and the methylated amino resin has the characteristics of good flexibility but high curing temperature; the curing temperatures of the butylated amino resin and the high imino amino resin selected by the invention are relatively low (at 120-140 ℃), but the two amino resins have the defects of poor flexibility compared with methylated amino resin, and in order to make up for the defect of insufficient flexibility, the main resin is preferably polyester resin with good flexibility to make up for the flexibility of a paint film; the polyester resin, the butylated amino resin and the high imino amino resin are reasonably mixed in proportion, so that the flexibility of a final paint film is excellent;

2. the anti-sagging property is improved by matching the solvent and the anti-sagging component;

according to the invention, the oxo-acid ester strong solvent is selected as the solvent, so that the leveling property and the glossiness of the coating can be improved, and a better solvent volatilization speed can be obtained by adding the chlorobenzonitrile in a specific proportion, so that the leveling property of the coating is ensured;

reasonable matching of the anti-sagging component: according to the formula, wax slurry and fumed silica are selected to improve the thixotropy of the coating, so that the sagging resistance is improved, the sagging resistance effect of the wax slurry is good in low shear, the thixotropy of the fumed silica is good in medium and high shear, and the optimal proportion between the wax slurry and the fumed silica is found through experiments, so that the optimal sagging resistance effect is obtained;

3. adding new components to improve filling

Reasonable selection of the filler: the traditional filler has great influence on the glossiness while increasing the filling property of a paint film, and the fumed silica is used as the filler, so that the optimal proportion of the filler is found through experiments, and the glossiness of the paint film is not influenced while the filling property of the paint film is increased; the traditional coating process is to spray a primer, fill the sand paper marks and defects well, and then spray a finish paint, so that a good paint effect can be achieved; the invention has the filling property of the primer and the glossiness of the finish paint, can avoid direct spraying of the primer, simplifies the coating process, saves energy and reduces the cost.

The hub coating has various defects and needs to be reworked, and if the performance of a paint film is reduced during recoating, such as embrittlement, adhesion reduction and the like, recoating cannot be performed, and only scrapping is performed; through the improvement, the invention ensures that the paint has excellent recoating performance, and the phenomena of embrittlement, adhesion reduction and the like (the adhesion is 0 grade after recoating for 3 times and the Baige method) can not occur after recoating for many times, thereby increasing the reworking times of recoating and reducing the scrappage of coating.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages and effects:

1. the amino baking varnish can realize low-temperature baking and shaping (the temperature of a workpiece is only 120 ℃ and lasts for about 20 minutes during processing), and can reduce energy consumption and cost;

2. high sag resistance: the hub has a complex shape and a plurality of corners and edges, and paint at the corners and the edges is easy to flow off in the coating process, so that the paint film at the parts is too thin and cannot meet the performance requirement;

3. high filling performance, no need of direct spraying of base coat, simplified coating process, saving in energy source and low cost.

Drawings

FIG. 1 is a graph showing the results of testing the curing conditions in examples 1 to 3 of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, as used herein, refer to an orientation or positional relationship indicated in the drawings that is solely for the purpose of facilitating the description and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and is therefore not to be construed as limiting the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

Example 1:

(1) mixing 60 parts of polyester resin, 10 parts of butylated amino resin, 3 parts of high imino amino resin, 3 parts of coloring pigment and 5 parts of p-chlorobenzonitrile, and grinding the mixture by using a grinder until the fineness is 20 mu m to obtain slurry; wherein the molecular weight of the polyester resin is 2500, and the acid value is 5 KOH/g; the hydroxyl value is 84mgKOH/g, the solid content of the polyester resin is more than or equal to 60 percent, the solid content of the amino resin is more than or equal to 70 percent, the solid content of the high imino amino resin is more than or equal to 75 percent, and the coloring pigment comprises carbon black and titanium pigment;

(2) adding 1 part of fumed silica, 0.1 part of dinonylphenol dinaphthalenesulfonic acid and 0.1 part of wax slurry into the slurry obtained in the first step, adding the slurry, mixing, stirring and uniformly dispersing to obtain a mixed solution, adjusting the viscosity of the mixed solution to 80 seconds (measured by a coating-4 cup), filtering and canning to obtain the baking varnish.

Example 2:

mixing 63 parts of polyester resin, 13 parts of butylated amino resin, 5 parts of high imino amino resin, 5 parts of coloring pigment and 8 parts of p-chlorobenzonitrile, and grinding the mixture by using a grinder until the fineness is 23 mu m to obtain slurry; wherein the molecular weight of the polyester resin is 2500, and the acid value is 7 KOH/g; the hydroxyl value is 84mgKOH/g, the solid content of the polyester resin is more than or equal to 60 percent, the solid content of the amino resin is more than or equal to 70 percent, the solid content of the high imino amino resin is more than or equal to 75 percent, and the coloring pigment comprises carbon black and titanium pigment;

(2) adding 2 parts of fumed silica, 0.3 part of dinonylphenol dinaphthalenesulfonic acid and 0.3 part of wax slurry into the slurry obtained in the first step, adding the slurry, mixing, stirring and uniformly dispersing to obtain a mixed solution, adjusting the viscosity of the mixed solution to 90 seconds (measured by coating 4 cups), filtering and canning to obtain the baking varnish.

Example 3:

mixing 65 parts of polyester resin, 15 parts of butylated amino resin, 8 parts of high imino amino resin, 8 parts of coloring pigment and 10 parts of p-chlorobenzonitrile, and grinding the mixture by using a grinder until the fineness is 25 mu m to obtain slurry; wherein the molecular weight of the polyester resin is 2500, and the acid value is 8 KOH/g; the hydroxyl value is 84mgKOH/g, the solid content of the polyester resin is more than or equal to 60 percent, the solid content of the amino resin is more than or equal to 70 percent, the solid content of the high imino amino resin is more than or equal to 75 percent, and the coloring pigment comprises carbon black and titanium pigment;

(2) adding 3 parts of fumed silica, 0.5 part of dinonylphenol dinaphthalenesulfonic acid and 0.5 part of wax slurry into the slurry obtained in the first step, adding the slurry, mixing, stirring and uniformly dispersing to obtain a mixed solution, adjusting the viscosity of the mixed solution to 100 seconds (measured by coating-4 cups), filtering and canning to obtain the baking varnish.

The baking lacquers obtained in examples 1 to 3 were tested for their solid content according to the national standard GB/T1725, determination of the nonvolatile content of lacquers, varnishes and plastics, and the results were as follows:

the paint film properties of the above examples 1-3 were tested as follows:

the above examples 1-3 were spray coated according to the following procedure and tested for curing conditions with the following test results:

the spraying step is as follows:

1. mixing ratio: raw lacquer and diluent were mixed as 100: (30-50) mixing;

2. spraying viscosity at 20 deg.C for 12-15 s in DIN2 cup;

3. the spraying mode is air spraying or electrostatic spraying.

The resulting curing conditions are shown in FIG. 1.

The technical means disclosed in the invention scheme are not limited to the technical means disclosed in the above embodiments, but also include the technical scheme formed by any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and such improvements and modifications are also considered to be within the scope of the present invention.

Claims (7)

1. A low-temperature baking amino baking varnish for automobile hub coating is characterized in that: the paint comprises the following components in parts by weight:

60-65 parts of polyester resin;

10-15 parts of butyl etherified amino resin;

3-8 parts of high imino amino resin;

1-3 parts of fumed silica;

5-10 parts of an oxygen-containing acid ester strong solvent;

3-8 parts of a coloring pigment;

0.1-0.5 part of dinonylphenol dinaphthalenesulfonic acid;

0.1-0.5 part of wax slurry.

2. The low-temperature baking amino baking paint for automobile hub coating according to claim 1, characterized in that: the molecular weight of the polyester resin is 2500, and the acid value is 5-8 KOH/g; the hydroxyl value is 84mgKOH/g, and the solid part of the polyester resin is more than or equal to 60 percent.

3. The low-temperature baking amino baking paint for automobile hub coating according to claim 1, characterized in that: the solid content of the butyl etherified amino resin is more than or equal to 70 percent.

4. The low-temperature baking amino baking paint for automobile hub coating according to claim 1, characterized in that: the solid content of the high imino group amino resin is more than or equal to 75 percent.

5. The low-temperature baking amino baking paint for automobile hub coating according to claim 1, characterized in that: the strong solvent of the oxygen acid esters is propylene glycol methyl ether acetate or p-chlorobenzene acetonitrile.

6. The low-temperature baking amino baking paint for automobile hub coating according to claim 1, characterized in that: the coloring pigment comprises carbon black and titanium dioxide.

7. A preparation method of low-temperature baking amino baking paint for automobile hub coating is characterized by comprising the following steps: the method comprises the following steps:

s1, grinding: mixing the polyester resin, the butylated amino resin, the high imino amino resin, the coloring pigment and the parachlorophenylacetonitrile in parts by weight, and grinding the mixture by using a grinder until the fineness is 20 to 25 mu m to obtain slurry;

s2, preparing paint: and adding the rest fumed silica, dinonylphenol dinaphthalenesulfonic acid and wax slurry into the obtained slurry, mixing, stirring and uniformly dispersing to obtain a mixed solution, and adjusting the viscosity of the mixed solution to 80-100 seconds by adopting a coating-4 cup measurement to obtain the baking varnish.

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