CN106700851B - Porous substrate powder coating and preparation method thereof - Google Patents

Abstract

The invention discloses a porous substrate powder coating and a preparation method thereof. The defoaming agent is a mixture of benzoin, blocked polyisocyanate B1530 and nonylphenol polyoxyethylene ether, has high crosslinking density, endows the powder coating with low surface tension, and can effectively eliminate the defects of pinholes, air holes and the like formed by escape of small molecular substances or volatile matters adsorbed on the surface of a coated workpiece in the coating in the baking process; in the coating of porous workpieces, particularly galvanized and aluminum castings have good defoaming and degassing effects. Meanwhile, the carboxyl-terminated polyester resin with high acid value and the adhesion promoter are used, so that the powder coating has good adhesion and is firmly combined with the porous substrate.

Description

Porous substrate powder coating and preparation method thereof

Technical Field

The invention belongs to the technical field of powder coatings, and particularly relates to a porous substrate powder coating and a preparation method thereof.

Background

In order to reduce the emission of volatile organic compounds, the powder coating becomes the development direction of coating industries at home and abroad, and is widely applied to the fields of household appliances, automobile manufacturing industry, buildings, chemical pipelines and the like.

With the widespread use of powder coatings, some problems have been revealed in the field of application of powder coatings, such as: the powder coating has poor leveling property, and has the problems of pinholes, shrinkage cavities, poor surface smoothness and the like; although these disadvantages of powder coatings can be significantly ameliorated by the addition of benzoin, benzoin tends to cause yellowing of the powder coating and the effect of benzoin is not ideal when the powder coating is applied specifically to a porous substrate. Therefore, there is a need for a powder coating that can be applied to porous substrates.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the porous substrate powder coating which is firmly combined with the porous substrate, has good leveling property and higher surface smoothness and the preparation method thereof.

In order to realize one of the purposes, the invention provides a porous substrate powder coating, which adopts the following technical scheme:

a porous substrate powder coating comprises the following components in parts by mass:

preferably, the polyester resin adopts carboxyl-terminated polyester resin with an acid value of 48-55 mgKOH/g.

Preferably, the melting range of the defoaming agent is 125-135 ℃, and the volatile content is less than or equal to 0.5%.

Further, the defoaming agent comprises the following components in parts by weight:

10-25 parts of benzoin;

3-7 parts of closed polyisocyanate;

3-7 parts of nonylphenol polyoxyethylene ether.

Further, the blocked polyisocyanate has the mark of Vestagon B1530.

Preferably, the filler is barium sulfate.

Preferably, the curing agent is triglycidyl isocyanurate.

Preferably, the number of the leveling agent is TEGO Glide 411; can reduce the surface tension of the system strongly and has excellent compatibility.

Preferably, the type of the adhesion promoter is Hubei laisi adhesion promoter 306; the catalyst is used for the crosslinking catalysis of polyester terminal carboxyl, and can improve the adhesive force between a coating and a substrate, thereby improving the physical and chemical properties of the powder coating, such as positive and negative impact resistance; the addition amount of the curing agent can be reduced by about 5 percent, and the curing agent has the characteristics of no yellowing, no influence on leveling and the like.

The invention also aims to provide a preparation method of the porous substrate powder coating, which comprises the following steps:

s1, weighing the components in parts by weight, premixing for 6-9 min, and stirring in a high-speed mixer;

s2, adding the powder obtained in the step S1 into an extruder for melt extrusion and tabletting, wherein the temperature of a zone I of the extruder is 90-100 ℃, and the temperature of a zone II of the extruder is 95-105 ℃;

and S3, adding the sheet materials obtained in the step S2 into a flour mill for milling, wherein the main milling speed of the flour mill is 45-50 Hz, the auxiliary milling speed is 20-35 Hz, and the screen mesh is 180-200 meshes, so that a finished product of the powder coating is obtained.

The invention has the beneficial effects that:

1) the invention provides a special powder coating for porous substrates, which is a defoaming agent prepared from a mixture of benzoin, blocked polyisocyanate and nonylphenol polyoxyethylene ether, wherein the blocked polyisocyanate introduced by the defoaming agent can participate in the reaction with residual hydroxyl in a system, so that the system gelling time can be prolonged, the melt viscosity can be reduced, and the crosslinking density can be improved; the introduced nonylphenol polyoxyethylene ether not only can be helpful for wetting a substrate, but also can be helpful for reducing the melt viscosity of a system. Therefore, the special defoaming agent adopted by the invention endows the powder coating with very low surface tension in a molten state, and can reduce the surface tension of the whole system, thereby effectively eliminating the defects of pinholes, air holes and the like formed by the escape of small molecular substances or volatile matters adsorbed on the surface of a coated workpiece in the coating in the baking process. In the coating of porous workpieces, particularly galvanized and aluminum castings have good defoaming and degassing effects.

2) The invention adopts the carboxyl-terminated polyester resin with high acid value and the adhesion promoter, so that the powder coating has better adhesion, is firmly combined with the porous substrate, and ensures the use effect.

Drawings

FIG. 1 is a diagram of the sprayed surface of the powder coating prepared by the present invention.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The polyester resin adopts carboxyl-terminated polyester resin with the acid value of 48-55 mgKOH/g; the filler is barium sulfate; the number of the leveling agent is TEGO Glide 411; the curing agent is triglycidyl isocyanurate; the adhesion promoter is a Hubeilaisi adhesion promoter 306.

Example 1

A porous substrate powder coating comprises the following components in parts by mass:

the defoaming agent comprises the following components in parts by weight:

15 parts of benzoin;

5 parts of blocked polyisocyanate;

5 parts of nonylphenol polyoxyethylene ether.

The defoaming agent prepared from the mixture of benzoin, blocked polyisocyanate and nonylphenol polyoxyethylene ether greatly improves the disadvantage that only benzoin is adopted in the prior art; the closed polyisocyanate introduced by the defoaming agent can participate in the reaction of residual hydroxyl in the system, so that the gelling time of the system can be prolonged, the viscosity of a melt is reduced, and the crosslinking density is improved; the introduced nonylphenol polyoxyethylene ether not only can be helpful for wetting a substrate, but also can be helpful for reducing the melt viscosity of a system. And the mixture ratio of the components in the embodiment enables the closed polyisocyanate to fully react with the residual hydroxyl in the system, optimizes the synergistic effect among the components, and has excellent improvement effect on the powder coating.

As shown in fig. 1, the powder coating prepared in this example is cured by spraying on a galvanized part and an aluminum casting, and has no pinholes or shrinkage cavities in the coating layer and a good surface effect; and has been applied in large scale in actual production, all with good feedback.

Example 2

A porous substrate powder coating comprises the following components in parts by mass:

the defoaming agent comprises the following components in parts by weight:

10 parts of benzoin;

3 parts of blocked polyisocyanate;

3 parts of nonylphenol polyoxyethylene ether.

The defoaming agent prepared from the mixture of benzoin, blocked polyisocyanate and nonylphenol polyoxyethylene ether greatly improves the disadvantage that only benzoin is adopted in the prior art; the closed polyisocyanate introduced by the defoaming agent can participate in the reaction of residual hydroxyl in the system, so that the gelling time of the system can be prolonged, the viscosity of a melt is reduced, and the crosslinking density is improved; the introduced nonylphenol polyoxyethylene ether not only can be helpful for wetting a substrate, but also can be helpful for reducing the melt viscosity of a system. And the mixture ratio of the components in the embodiment enables the closed polyisocyanate to fully react with the residual hydroxyl in the system, optimizes the synergistic effect among the components, and has excellent improvement effect on the powder coating.

After the powder coating prepared by the embodiment is sprayed and cured, the coating layer has no pinholes or shrinkage cavities, and has a good surface effect; and has been applied in large scale in actual production, all with good feedback.

Example 3

A porous substrate powder coating comprises the following components in parts by mass:

the defoaming agent comprises the following components in parts by weight:

25 parts of benzoin;

7 parts of blocked polyisocyanate;

7 parts of nonylphenol polyoxyethylene ether.

The defoaming agent prepared from the mixture of benzoin, blocked polyisocyanate and nonylphenol polyoxyethylene ether greatly improves the disadvantage that only benzoin is adopted in the prior art; the closed polyisocyanate introduced by the defoaming agent can participate in the reaction of residual hydroxyl in the system, so that the gelling time of the system can be prolonged, the viscosity of a melt is reduced, and the crosslinking density is improved; the introduced nonylphenol polyoxyethylene ether not only can be helpful for wetting a substrate, but also can be helpful for reducing the melt viscosity of a system. And the mixture ratio of the components in the embodiment enables the closed polyisocyanate to be just fully reacted with the residual hydroxyl in the system, optimizes the synergistic effect among the components, and has excellent improvement effect on the powder coating.

After the powder coating prepared by the embodiment is sprayed and cured, the coating layer has no pinholes or shrinkage cavities, and has a good surface effect; and has been applied in large scale in actual production, all with good feedback.

The above description is only a preferred embodiment of the present invention, and it should be noted that a person skilled in the art may make several modifications and variations without departing from the technical principle of the present invention.

Claims (8)

1. The porous substrate powder coating is characterized by comprising the following components in parts by mass:

the melting range of the defoaming agent is 125-135 ℃, and the volatile content is less than or equal to 0.5%;

the defoaming agent comprises the following components in parts by weight:

10-25 parts of benzoin;

3-7 parts of closed polyisocyanate;

3-7 parts of nonylphenol polyoxyethylene ether.

2. A porous substrate powder coating according to claim 1, wherein: the polyester resin is carboxyl-terminated polyester resin with an acid value of 48-55 mgKOH/g.

3. A porous substrate powder coating according to claim 1, wherein: the blocked polyisocyanate has the designation vestigon B1530.

4. A porous substrate powder coating according to claim 1, wherein: the filler is barium sulfate.

5. A porous substrate powder coating according to claim 1, wherein: the curing agent is triglycidyl isocyanurate.

6. A porous substrate powder coating according to claim 1, wherein: the leveling agent is TEGO Glide 411.

7. A porous substrate powder coating according to claim 1, wherein: the adhesion promoter is type Leiss 306.

8. A process for the preparation of a powder coating for a porous substrate according to any one of claims 1 to 7, characterized by the steps of:

s1, weighing the components in parts by weight, premixing for 6-9 min, and stirring in a high-speed mixer;

s2, adding the powder obtained in the step S1 into an extruder for melt extrusion and tabletting, wherein the temperature of a zone I of the extruder is 90-100 ℃, and the temperature of a zone II of the extruder is 95-105 ℃;

and S3, adding the sheet materials obtained in the step S2 into a flour mill for milling, wherein the main milling speed of the flour mill is 45-50 Hz, the auxiliary milling speed is 20-35 Hz, and the screen mesh is 180-200 meshes, so that a finished product of the powder coating is obtained.

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