CN109111563B - Pigment dispersion resin for primer-topcoat cathode electrophoretic coating and preparation method thereof - Google Patents

Abstract

The invention discloses a pigment dispersion resin for a primer-topcoat cathode electrophoretic coating, which comprises a quaternization reagent and a modified epoxy resin. The pigment dispersion resin has good pigment and filler wetting dispersibility, corrosion resistance, weather resistance and flexibility, so that a paint film has good corrosion resistance and weather resistance, meanwhile, the fullness and color stability of the paint film can be remarkably improved, and the requirements of hardware such as bicycles, household appliances, decorative articles and the like on the paint film can be met.

Description

Pigment dispersion resin for primer-topcoat cathode electrophoretic coating and preparation method thereof

Technical Field

The invention relates to the technical field of electrophoretic paint, in particular to pigment dispersion resin for primer-topcoat cathode electrophoretic paint and a preparation method thereof.

Background

The electrophoretic coating is a novel coating with low pollution, energy conservation, resource conservation, protection and corrosion resistance, has the characteristics of smooth coating, good water resistance and chemical resistance and the like, is easy to realize the mechanization and automation of the coating industry, is suitable for coating workpieces with edges, corners and holes, and is widely applied to coating hardware such as automobiles, automatic vehicles, electromechanics, household appliances and the like. Most of the anticorrosive electrophoretic coatings on the market only have excellent anticorrosive performance, but often have poor weather resistance, and the electrophoretic coating needs to be coated for the second time if the electrophoretic coating has excellent anticorrosive performance and weather resistance, so that the coating process and cost are greatly increased.

Disclosure of Invention

The present invention is directed to a pigment dispersion resin for primer-topcoat cathode electrophoretic paint and a method for preparing the same, which solves one or more of the above-mentioned problems of the prior art.

The pigment dispersion resin for the primer-topcoat cathode electrophoretic coating comprises a quaternization reagent and a modified epoxy resin.

In some embodiments, the method of preparing the quaternizing agent comprises the steps of:

reacting tertiary carbonic acid glycidyl ester with secondary amine at 50-150 ℃, adding organic acid aqueous solution after epoxy groups are completely disappeared, and reacting at 70-80 ℃ to prepare the quaternization reagent.

In some embodiments, glycidyl versatate is formed by reacting versatic acid with epichlorohydrin, and has a highly branched monomer with more than ten carbon atoms, and has the following chemical structure:

wherein: r1+ R2 is 7C atoms.

In some embodiments, the secondary amine is one or more of methylethanolamine, N-ethylethanolamine, ketimine; the organic acid is one or more of formic acid, acetic acid, lactic acid, hydroxy propionic acid and isooctanoic acid.

In some embodiments, a method of preparing a modified epoxy resin comprises the steps of:

carrying out ring-opening chain extension reaction at 130-190 ℃ under the action of a catalyst by using basic epoxy resin and a chain extender, adding an isocyanate prepolymer after the theoretical epoxy equivalent is reached, carrying out grafting reaction at 130-140 ℃, and finally adding ethylene glycol butyl ether to prepare modified epoxy resin;

the basic epoxy resin is an aromatic or alicyclic compound containing 2 epoxy groups on each molecular structure, and the epoxy equivalent of the epoxy resin is between 100-600 g/mol;

the chain extender is acid, alcohol or phenol with two or more active hydrogen, and the molecular weight of the chain extender is between 50 and 4000;

the catalyst is at least one of triethanolamine, triethylamine, diethanolamine, diethylamine, triphenylphosphine bromide, dimethylbenzylamine, imidazole, dimethylimidazole and 2-ethyl-4-methylimidazole;

the isocyanate prepolymer is prepared by reacting polyisocyanate with a compound containing active hydrogen.

In some embodiments, the epoxy resin is at least one of a bisphenol a type epoxy resin, a bisphenol S type epoxy resin, a bisphenol F type epoxy resin.

In some embodiments, the chain extender is at least one of dicarboxylic acids, polyether polyols, polyester polyols, dimercaptoalcohols, bisphenols.

In some embodiments, a method of preparing an isocyanate prepolymer includes the steps of:

slowly dripping a compound containing active hydrogen into a polyisocyanate compound for reaction, keeping the temperature of 70-110 ℃ after dripping is finished, and reacting for 1-5 h, wherein the molar ratio of isocyanate groups to the compound containing active hydrogen in the isocyanate prepolymer is 1: 0.45-1: 0.65;

the polyisocyanate comprises at least one of aliphatic diisocyanate, alicyclic diisocyanate and aromatic diisocyanate;

the active hydrogen-containing compound is at least one of alcohol, alcohol ether, phenol and carboxylic acid containing 1-20 carbon atoms.

In some embodiments, the polyisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate;

the compound containing active hydrogen is at least one of methanol, ethanol, isopropanol, phenol, ethylene glycol monobutyl ether, ethylene glycol ethyl ether, ethylene glycol hexyl ether, diethylene glycol monobutyl ether and diethylene glycol ethyl ether.

The preparation method of the pigment dispersion resin for the primer-topcoat cathode electrophoretic coating comprises the following steps of:

and (2) sequentially adding modified epoxy resin, a quaternization reagent and primary pure water into a reaction bottle provided with a thermometer, a stirrer and a reflux condenser pipe, stirring, heating the reaction system to 90 ℃, carrying out heat preservation reaction for 6 hours, measuring the acid value of the resin, adding secondary pure water when the acid value of the resin is less than 1, cooling to 65 ℃, carrying out heat preservation reaction for 1 hour, and finally preparing the quaternary ammonium salt type pigment dispersion resin with the solid content of 40%.

The beneficial effects are that:

the pigment dispersion resin suitable for the bottom-surface-combined cathode electrophoretic coating has good pigment and filler wetting dispersibility, corrosion resistance, weather resistance and flexibility, so that a paint film has good corrosion resistance and weather resistance, the fullness and color stability of the paint film can be obviously improved, and the requirements of hardware such as bicycles, household appliances, decorative articles and the like on the paint film can be met.

Detailed Description

The present invention will be described in further detail below with reference to embodiments.

Example 1:

the first step is as follows: preparation of quaternizing agent

In a reaction bottle provided with a thermometer, a stirrer and a reflux condenser tube, the glycidyl versatate and the methylethanolamine with the formula amount are sequentially added, the stirring is started, the temperature of a reaction system is raised to 130 ℃ to react for 1h, after epoxy groups are completely disappeared, the temperature is lowered to 70 ℃, 50% of lactic acid aqueous solution is added, the temperature is raised to 80 ℃ to react for 2h, the MEQA and MEQB values are tested, and finally the quaternization reagent with the solid content of 80% is prepared.

Specific amounts of addition are shown in table 1:

components	Dosage (g)
		Tertiary carboxylic acid glycidyl ester	480
Methylethanolamine	180
		50% lactic acid (aqueous solution)	453.6
Total amount of	1113.6

Table 1: the amount of the quaternary amination reagent raw material

The second step is that: preparation of isocyanate prepolymer

Toluene diisocyanate and methyl isobutyl ketone with the formula amount are sequentially added into a reaction bottle provided with a thermometer, a stirrer and a reflux condenser. Stirring in a nitrogen atmosphere to raise the temperature of a reaction system to 45-50 ℃, slowly dropwise adding isooctyl alcohol into the reaction system of toluene diisocyanate and methyl isobutyl ketone, wherein the temperature of the reaction system is between 50 and 55 ℃ when dropwise adding is finished within about 4-5h, after all dropwise adding are finished, raising the temperature to 75 ℃ for heat preservation reaction for 1h, measuring the content of isocyanate groups, and obtaining the isocyanate prepolymer with the solid content of 94 percent when the NCO value is 120-125 mg/g.

Specific amounts of addition are shown in table 2:

components	Dosage (g)
		Toluene diisocyanate (NCO = 480)	382.72
Methyl isobutyl ketone	44
		Isooctyl alcohol	322.77
Total amount of	749.49

Table 2: the dosage of the isocyanate prepolymer raw material

The third step: preparation of modified epoxy resin

Sequentially adding epoxy resin, bisphenol A, cardanol and methyl isobutyl ketone in formula amount into a reaction bottle provided with a thermometer, a stirrer and a reflux condenser, after the addition is finished, stirring, heating the reaction system to 100 ℃, adding a dimethylbenzylamine catalyst, after the addition is finished, heating to 180-.

Specific amounts of addition are shown in table 3:

components	Dosage (g)
		Basic epoxy resin (EEW = 180-190)	2180
Bisphenol A	600
		Cardanol	156.2
Methyl isobutyl ketone	100
		Dimethylbenzylamine	3
Isocyanate prepolymer	700
		Ethylene glycol monobutyl ether	189.4
Total up to	3928.6

Isocyanate prepolymer: NCO value 120-

Table 3: the amount of the modified epoxy resin raw material

The fourth step: preparation of pigment dispersing resin:

and (3) sequentially adding the modified epoxy resin prepared in the third step, the quaternization reagent prepared in the first step and pure water in formula amount into a reaction bottle provided with a thermometer, a stirrer and a reflux condenser pipe, stirring, heating the reaction system to 90 ℃, carrying out heat preservation reaction for 6 hours, measuring the acid value of the resin, adding the pure water for the second time when the acid value of the resin is less than 1, cooling to 65 ℃, carrying out heat preservation reaction for 1 hour, and finally preparing the quaternary ammonium salt type pigment dispersion resin with the solid content of 40%. Specific amounts of addition are shown in table 4:

components	Dosage (g)
		Modified epoxy resin	1522.3
Quaternizing agents	499.8
		First time pure water	400
Second time pure water	2002.67
		Total up to	4424.77

Table 4: the amount of the pigment dispersion resin raw material

Preparing cathode electrophoretic paint color paste:

red paste A: as comparative examples, conventional pigment-dispersing resins were used

830g of the conventional pigment dispersion resin with the solid content of 40%, 1450g of titanium oxide, 700g of kaolin, 30g of iron oxide red, 100g of dioctyltin oxide, 100g of bismuth hydroxide and 200g of deionized water are added, and after uniform mixing, grinding is carried out for 15 hours by a ball mill, so as to obtain color slurry with the solid content of 50%.

And (3) red paste B: pigment Dispersion resin prepared in example 1 was used

830g of the pigment dispersion resin having a solid content of 40% prepared in example 1, 1450g of titanium oxide, 700g of kaolin, 30g of red iron oxide, 100g of dioctyltin oxide, 100g of bismuth hydroxide and 200g of deionized water were added, and after mixing uniformly, the mixture was ground with a ball mill for 15 hours to obtain a color paste having a solid content of 50%.

And (3) red paste C: as comparative examples, conventional pigment dispersing resins plus UV absorbers were used

830g of the conventional pigment dispersion resin with the solid content of 40%, 50g of an ultraviolet absorber, 1400g of titanium oxide, 700g of kaolin, 30g of iron oxide red, 100g of dioctyltin oxide, 100g of bismuth hydroxide and 200g of deionized water are added, and after uniform mixing, the mixture is ground by a ball mill for 15 hours to obtain color slurry with the solid content of 50%.

The above red pastes A, B and C were used to prepare cationic electrodeposition paints, respectively:

mixing 1000g of bottom-in-one cathode electrophoretic coating emulsion (HR-4000 type emulsion), 500g of red paste A and 2500g of deionized water to prepare a bottom-in-one cathode electrophoretic coating A with the solid content of 15 percent;

mixing 1000g of bottom-in-one cathode electrophoretic coating emulsion (HR-4000 type emulsion), 500g of red paste B and 2500g of deionized water to prepare a bottom-in-one cathode electrophoretic coating B with the solid content of 15 percent;

1000g of primer-topcoat cathode electrophoretic paint emulsion (HR-4000 type emulsion), 500g of red paste C and 2500g of deionized water are mixed to prepare the primer-topcoat cathode electrophoretic paint C with the solid content of 15%.

Among them, HR-4000 type emulsion was purchased from Haolison paint (Shanghai) Co., Ltd.

Test methods and criteria:

high-temperature stability of color paste

And sealing 500g of color paste in a special test bottle, placing the special test bottle into a 50 ℃ oven for high-temperature stability test, and respectively testing for 10 days to investigate whether the color paste is precipitated or not and to examine the fineness change.

●: after standing for 10 days, the color paste has no hard precipitate and no coarse particles;

very good: after standing for 10 days, the color paste has no hard precipitate, and the fineness is reverse to the thickness but still in a qualified range;

and (delta): after standing for 10 days, the color paste has no hard precipitate, and the fineness is too coarse and unqualified;

□: after standing for 10 days, the color paste has precipitate, and the fineness is too coarse and unqualified.

Second, corrosion resistance

A cold-rolled sheet (0.8 mm. about.150 mm. about.70 mm) was subjected to chemical conversion treatment (trade name, zinc phosphate treatment agent, manufactured by JAPONICA JASMIC INC.) as a to-be-coated member, which was coated with the cationic electrodeposition coating composition obtained in the examples, and the coated film was baked at 165 ℃ for 20min, with the film thickness controlled to 18 to 22 μm, and the number of blisters on the cut portion and the width of the developed portion were evaluated in accordance with the national NSS test 700h salt spray test.

●: no more than 2.0mm from the cut part, no bubble near the cut part,

very good: the side from the cutting part is not more than 2.0mm, 1-2 bubbles are formed near the cutting part,

and (delta): more than 2.0mm but less than 3.0mm from the cut part, 1-2 blisters near the cut part,

□: the size of the bubble is larger than 2.0mm but smaller than 3.0mm from the cutting part, and 2-5 bubbles are formed near the cutting part.

Third, weather resistance

Cold-rolled sheet (0.8 mm. about.150 mm. about.70 mm) was subjected to chemical conversion treatment (trade name, zinc phosphate treatment agent, manufactured by JAPONICA JASMIC INC.) and used as a part to be coated, which was coated with the cationic electrodeposition coating composition obtained in the examples, and the coated paint film was baked at 165 ℃ for 20min, the film thickness was controlled to 18 to 22 μm, and the color difference value of the paint film was evaluated according to QUV A test of national standard for 500 h.

●: color difference value less than 2

Very good: the color difference value is greater than 2 and less than 4

And (delta): the color difference value is more than 4 and less than 6

□: the color difference value is more than 6

The stability, corrosion resistance and weatherability of the primer-topcoat cathodic electrocoat A, B, C are tested in Table 5.

	Primer-topcoat cathode electrophoretic coating A	Primer-topcoat cathode electrophoretic coating B	Primer-topcoat cathode electrophoretic coating C
				Film thickness (um)	20	21	21
Stability of color paste	◎	●	△
				Corrosion resistance	●	●	●
Weather resistance	△	●	●

Table 5: experimental data

As can be seen from the above table, the primer-topcoat cathode electrophoretic coating B has better stability than the primer-topcoat cathode electrophoretic coating a, the corrosion resistance of the primer-topcoat cathode electrophoretic coating B is equivalent to that of the primer-topcoat cathode electrophoretic coating a, and the weather resistance of the primer-topcoat cathode electrophoretic coating B is better than that of the primer-topcoat cathode electrophoretic coating a; compared with the primer-topcoat cathode electrophoretic coating C, the primer-topcoat cathode electrophoretic coating B has stability obviously superior to that of the primer-topcoat cathode electrophoretic coating C, the corrosion resistance of the primer-topcoat cathode electrophoretic coating B is equivalent to that of the primer-topcoat cathode electrophoretic coating C, and the weather resistance of the primer-topcoat cathode electrophoretic coating B is equivalent to that of the primer-topcoat cathode electrophoretic coating C.

Therefore, after the pigment dispersion resin with the solid content of 40 percent prepared in the example 1 is added, the color paste stability and the weather resistance of the primer-topcoat cathode electrophoretic paint B are obviously improved compared with those of the primer-topcoat cathode electrophoretic paint A using the conventional dispersion resin; the cathode electrophoretic coating C is combined on the bottom surface, and after the ultraviolet absorber is added, the weather resistance can be improved, but the stability of the color paste is greatly reduced.

The pigment dispersing resin in the embodiment provided by the invention has good wetting and dispersing performance on inorganic pigment and filler, the contained tertiary carbonic acid group provides excellent weather resistance, acid-base resistance and water resistance of the resin, and the contained modified epoxy resin provides excellent corrosion resistance of the resin. The color paste prepared by the resin can provide good corrosion resistance and weather resistance of a paint film, and can obviously improve the fullness and color stability of the paint film.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept of the present invention, and these should be considered as within the scope of the present invention.

Claims (7)

1. The pigment dispersion resin for the primer-topcoat cathode electrophoretic coating is characterized by comprising a quaternizing agent and a modified epoxy resin;

wherein: the preparation method of the modified epoxy resin comprises the following steps: carrying out ring-opening chain extension reaction at 130-190 ℃ under the action of a catalyst by using basic epoxy resin and a chain extender, adding an isocyanate prepolymer after the theoretical epoxy equivalent is reached, carrying out grafting reaction at 130-140 ℃, and finally adding ethylene glycol butyl ether to prepare modified epoxy resin;

the preparation method of the quaternizing agent comprises the following steps:

reacting tertiary carbonic acid glycidyl ester with secondary amine at 50-150 ℃, adding organic acid aqueous solution after epoxy groups completely disappear, and reacting at 70-80 ℃ to prepare a quaternization reagent;

the glycidyl versatate is generated by reacting versatic acid with epoxy chloropropane, contains more than ten highly branched monomers with carbon atoms, and has the following chemical structure:

wherein: r1+ R2 is 7C atoms;

the preparation method of the pigment dispersion resin comprises the following steps: adding modified epoxy resin, a quaternization reagent and pure water into a reaction bottle provided with a thermometer, a stirrer and a reflux condenser, after the addition is finished, starting the stirrer to heat the reaction bottle to 90 ℃, preserving heat, reacting for 6 hours, measuring the acid value of the resin, adding the pure water again when the acid value of the resin is less than 1, cooling to 65 ℃, preserving heat, reacting for 1 hour, and finally preparing the pigment dispersion resin.

2. The pigment dispersion resin for a primer-topcoat cathode electrophoretic paint according to claim 1, wherein the secondary amine is one or more of methylethanolamine, N-ethylethanolamine, ketimine; the organic acid is one or more of formic acid, acetic acid, lactic acid, hydroxy propionic acid and isooctanoic acid.

3. The pigment-dispersion resin for primer-topcoat cathode electrodeposition paint according to claim 1,

the basic epoxy resin is an aromatic or alicyclic compound containing 2 epoxy groups on each molecular structure, and the epoxy equivalent of the epoxy resin is between 100 and 600 g/mol;

the chain extender is acid, alcohol or phenol with two or more active hydrogen, and the molecular weight of the chain extender is between 50 and 4000;

the catalyst is at least one of triethanolamine, triethylamine, diethanolamine, diethylamine, triphenylphosphine bromide, dimethylbenzylamine, imidazole, dimethylimidazole and 2-ethyl-4-methylimidazole;

the isocyanate prepolymer is prepared by reacting polyisocyanate with a compound containing active hydrogen.

4. The pigment dispersion resin for primer-topcoat cathode electrophoretic paint according to claim 3, wherein the epoxy resin is at least one of bisphenol A epoxy resin, bisphenol S epoxy resin, and bisphenol F epoxy resin.

5. The pigment dispersion resin for a primer-topcoat cathode electrophoretic paint according to claim 3, wherein the chain extender is at least one of dicarboxylic acid, polyether polyol, polyester polyol, dimercaptoalcohol, and bisphenol compounds.

6. The pigment-dispersion resin for primer-topcoat cathode electrophoretic paint according to claim 3, wherein the isocyanate prepolymer is prepared by a method comprising the following steps:

slowly dripping a compound containing active hydrogen into a polyisocyanate compound for reaction, keeping the temperature of 70-110 ℃ after dripping is finished, and reacting for 1-5 h, wherein the molar ratio of isocyanate groups to the compound containing active hydrogen in the isocyanate prepolymer is 1: 0.45-1: 0.65;

the polyisocyanate comprises at least one of aliphatic diisocyanate, alicyclic diisocyanate and aromatic diisocyanate;

the compound containing active hydrogen is at least one of alcohol, alcohol ether, phenol and carboxylic acid containing 1-20 carbon atoms.

7. The pigment-dispersion resin for primer-topcoat cathode electrophoretic paint according to claim 6, wherein the polyisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and trimethylhexamethylene diisocyanate;

the compound containing active hydrogen is at least one of methanol, ethanol, isopropanol, phenol, ethylene glycol monobutyl ether, ethylene glycol ethyl ether, ethylene glycol hexyl ether, diethylene glycol monobutyl ether and diethylene glycol ethyl ether.