KR920000031B1 - Powder coated resin composition - Google Patents

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Description

Powder Coating Resin Composition

The present invention relates to a powder coating resin composition. More specifically, the present invention relates to a powder coated polyamide resin composition capable of forming a coating film at a sufficient thickness at the edge of the article to be coated.

Polyamide powders are used as powder coatings, such as fluidized bed coatings and electrostatic coatings, which are known in the art as fluidizationdip coatings, which are good in terms of properties for friction and wear, strength and heat resistance.

Since polyamide is a thermoplastic resin, the polyamide powder before coating is basically the same as the coating film formed by coating regardless of the coating conditions, so that polyamide can be easily treated. Viscosity increase is not occurred at all, so that the fluid state is maintained until a flat surface is formed by melt fluidization of the resin in the powder coating step, and as a result, the coating film at the edge of the coated article becomes too thin and sometimes the edge is peeled off to expose the defect. have. This results in rusting or peeling of the polyamide coating film from the article while using the coated article.

The method of overcoming this drawback is to polymerize the polyamide without a polymerization regulator which forms a polyamide having a huge amino acid structure with a carboxyl group at one end of the polyamide molecule and an amino group at the other end, adding a polymerization catalyst thereto. And grinding the mixture to form a powdered preparation.

When the product is used as a powder coating, the polymerization of the molten powder is further progressed in the coating step, thereby increasing the viscosity, thereby preventing a decrease in the thickness of the coating film at the corners. Although this method can be used, it is relatively low in viscosity and difficult to form polyamides which can be used for powder coating without the use of any polymerization regulators.

Since condensation reaction of carboxylic acid with water having an amine forming an amido bond in equivalent weight forms an amide, polyamide can be easily condensed by only heating, but it is difficult to control the condensation reaction. In other words, if the condensation reaction at both ends is not suppressed to some extent by modifying the ends with a polymerization regulator such as mono- or dicarboxylic acid or mono- or diamine, the polymerization proceeds extremely, resulting in insoluble and insoluble super- High-molecular polyamides are formed.

Therefore, the polymerization degree can be controlled by keeping the heating time constant when no polymerization regulator is added. In practice, however, the time remaining in the polymerization reactor is not constant. That is, the residence time of the initial stage when taking the polymer out of the polymerization system is very different from that of the final stage. Another drawback is that ultra-high-molecular polyamides are formed by polyamides remaining on the polymerizer walls, resulting in nibs on the surface of the coating membrane.

It is an object of the present invention to provide a polyamide powder that can be condensed in a molten state in a powder coating step and does not cause no covering at the edges easily and stably.

The present invention provides a powder-coated polyamide resin composition consisting of polyamide wherein at least 70% of the end groups are carboxyl groups and polyamides where at least 70% of the end groups are amino groups.

The polyamide resin composition of the present invention is suitable for powder coating and consists of a first polyamide in which 70% or more of the end groups are carboxylic acids and a second polyamide in which 70% or more of the end groups is an amine.

The relative degree of composition in the 0.5% m-cresol solution of the composition for the first and second polyamides is from 1.10 to 1.30 and the range of total equivalents of carboxylic acid to total equivalents of amine is 40:60 to 60:40 The composition is preferred.

Using the compositions of the present invention it is possible to obtain polymer powders for powder coating.

For example, two or more of the oligomers and monomers that are reactive with each other are melted separately, and the mixture is continuously mixed with each other while spraying a mixture that is solid at normal temperature and melt viscosity of 1,000 cps or less at 300 ° C. The sprayed mixture is cooled to obtain a powder which is solid phase-polymerized to obtain a polymer powder. The composition of the present invention is used in the mixture in this way.

The present invention provides a powder for powder coating comprising a preparation of a solid polymerized composition, followed by a powder for powder coating comprising a polyamide resin composition and a polymerization catalyst.

The present invention also provides a polymer powder obtainable by the method defined above. The present invention also provides a method of powder coating an article using polymer powder.

Polyamides in the present application are polymers and oligomers that have amide bonds in the main chain and can be used for powder coating.

Examples of these include nylon 12, nylon 11, nylon 612 and other monomeric polyamides and copolymers thereof.

Polyamides where at least 70% of the end groups are carboxyl groups (hereinafter referred to as carboxyl polyamides) and polyamides where at least 70% of the end groups are amino groups (hereinafter referred to as amino polyamides) are polymerization regulators. It can be obtained easily and stably by polymerization carried out in the presence of a theoretical amount. In this method, the formation of ultra-high-molecular compounds becomes impossible because the amount of amine or carboxylic acid which is indispensable for amide formation becomes insufficient.

When diamine or dicarboxylic acid is used as the polymerization regulator, polyamides having amino or carboxyl groups are formed at both ends of the polymerization regulator. However, polyamides having an amino group or carboxyl group less than 70% of the terminal group, that is, polyamides having at least 30% of the terminal group being a carboxyl or amino group have an equivalent ratio of amino group to carboxyl group of 70:30 to 30:70, so It becomes impossible to stably polymerize. If such a polyamide can be obtained stably, the cornering shape of the article can be substantially prevented and the technique of mixing the two inert polyamides together as in the present invention will be unnecessary. However, this method does not achieve the object of the present invention because it is difficult to manufacture such a product easily and stably.

On the other hand, when a monoamine or a monocarboxylic acid is used as a polymerization regulator, the end group portion of the resulting polyamide is non-reactive, so that less than 70% of the end group is mixed with a carboxyl group with a polyamide having less than 70% of the end group as an amino group. Even so, the degree of polymerization is only slightly increased and the object of the present invention cannot be achieved.

Dicarboxylic acids which can be used in the present invention include adipic acid, dodecanedioic acid and terephthalic acid, and diamines include hexamethylenediamine and isophoronediamine. At least 90% of the carboxyl polyamide end groups are preferably carboxyl groups and at least 90% of the amino polyamide end groups are amino groups. The carboxyl polyamide and the amino polyamides themselves are polyamides that are stable when stored separately. When mixed together, the effect of the present invention is obtained because it is changed into a polymerizable polyamide. The mixing ratio of carboxyl polyamide to amino polyamide is such that the range of total carboxylic acid equivalents to total amine equivalents in the polyamide mixture ranges from 40:60 to 60:40. In this case the polymerization proceeds to be most advantageous for the coating step.

Carboxylic polyamides and amino polyamides can be mixed together in solution form in molten form. Melt mixing is carried out in such a short time that polymerization hardly occurs.

By carrying out the melt mixing without the polymerization catalyst and adding the polymerization catalyst to the powdery product after the mixing is completed, the intended coating polyamide resin composition of the present invention can be more stably obtained.

In addition, even if the finely ground carboxyl polyamide is mixed with the finely ground amino polyamide, the powder coating resin composition of the present invention can be obtained.

Additives such as pigments and stabilizers can be added to the carboxyl polyamides or amino polyamides or mixtures thereof.

In carrying out the process of the invention advantageously, the polymerization is carried out using dicarboxylic acids and diamines as polymerization regulators in an amount such that the resulting solution with 0.5% polyamide in m-cresol has a relative viscosity of 1.10 to 1.30. Thereafter, the carboxyl polyamide and the amino polyamide are formed, and then they are mixed in a molten or solution form with a dye, a stabilizer and the like as necessary to form a brittle polymerizable polyamide oligomer.

This preparation can be easily milled to form a powder. If necessary, a polymerization catalyst is added to the powder and solid phase polymerization is performed to form a powdery product having a desired molecular weight. Since the polymer polyamide is tough and not easily crushed, the polymer polyamide usually used for powder coating is indispensable to freeze grinding using liquid nitrogen, but in the present invention, grinding is extremely easy.

Since the stable carboxyl polyamide and amino polyamide are previously formed by the polymerization reaction and mixed together to form an active polymerizable polyamide, the powdered polyamide resin composition of the present invention can be easily and stably produced. This preparation can sufficiently cover the edges of the article to be powder-coated.

In carrying out the present invention, by mixing carboxyl polyamide having a low polymerization degree with amino polyamide having a low polymerization degree and pulverizing the mixture and carrying out a solid phase polymerization reaction, a powder intended easily without necessarily grinding using liquid nitrogen is obtained. You can get it. The following examples illustrate the invention in more detail.

Example 1

5 kg laurolactam, 290 g dodecanedioic acid and 200 g water were placed in a 10-L autoclave. The inside of the autoclave was purged with nitrogen gas and the temperature was raised to 280 ° C. to increase the pressure in the autoclave to 25 kg / cm 2. After maintaining the temperature at 280 ° C. for 7 hours, the temperature was lowered to 250 ° C. over 1 hour while gradually reducing the vapor pressure in the autoclave to atmospheric pressure. After stirring the reaction mixture at 250 ° C. for 3 hours while blowing nitrogen into the autoclave, the polymer was placed in water that aspirates the large-scale device over 1 hour under nitrogen pressure. Can be formed.

This mass was easily crushed and the infrared absorption spectrum was consistent with nylon 12. Melting point was 117 degreeC. The relative viscosity of the polymer solution at 0.5% in m-cresol obtained at the initial stage of release through the bottom of the autoclave was 1.17. According to the benzyl alcohol solution titration, the end groups are 493 meq / kg equivalents of carboxylic acid and 12 meq / kg equivalents of amine. The 0.5% polymer solution obtained in the final step (1 hour after the start of release) in m-cresol has a relative viscosity of 1.17 as in the initial step, which means that the polymer is stably formed.

The same procedure was repeated as above, but instead of 290 g of dodecanedioic acid, 147 g of hexamethylenediamine was placed in a 10-L autoglare to form an amino polyamide in the form of a pale yellow-white mass.

The mass was brittle and easily comminuted and the infrared absorption spectrum was consistent with nylon 12. Melting point was 177 ° C. The relative viscosity of the polymer solution at 5% in m-cresol was 1.19. The end groups were 14 meq / kg equivalents of carboxylic acid and 453 meq / kg equivalents of amine. 50 parts by weight of the carboxyl polyamide thus obtained, 50 parts by weight of the amino polyamide thus obtained, 5 parts by weight of titanium oxide, and 1.0 part by weight of Irganox (10 manufactured by Ciba-Geigy Co., Ltd.) were mixed together.

The mixture was extruded at 200 ° C. with a 30 mm diameter extruder and cooled with water to form a white mass. The mass 0.5% solution in m-cresol had a relative viscosity of 1.20. The preparation was triturated with a small grinder (Sample Mill of Hosogawa Micron) at room temperature to easily obtain a powder and filtered through a 60-mesh sieve. About 90% of the powder passed through this sieve. 100 parts by weight of the powder passed through the sieve was mixed with 20 parts by weight of a 1% solution of phosphoric acid in methanol as a polymerization catalyst. The mixture was kept at 60 ° C. for 5 hours and then subjected to solid phase polymerization at 150 ° C. for 20 hours with nitrogen.

The powder 0.5% solution obtained in m-cresol had a relative viscosity of 1.61. The powder was coated on a steel sheet having a right angle and a thickness of 3 mm by flow immersion coating. The iron plate was preheated to 350 ° C. for 7 minutes, immersed for 5 seconds, left for 1 minute, and cooled with water. None of the edges of the iron plate were exposed. The 0.5% solution of the coating film in m-cresol had a relative viscosity of 1.95.

100 parts by weight of nylon 12, 5 parts by weight of titanium oxide and a stabilizer prepared by using dodecanedioic acid as a polymerization regulator were separately extruded in the same manner as in the above-described method, and the product was prepared together with liquid nitrogen. Grinding with the same mill. The resulting powder had a viscosity of 1.61. About 10% of the powder was passed through a 60-mesh sieve. When the 3 mm thick iron plate was coated by the fluid immersion coating method using the powder passed through the 60-mesh body, the edges of the iron plate were partially exposed. The relative viscosity of the coating film was 1.61.

Example 2

The polymerization was carried out using dodecanedioic acid or hexamethylenediamine as a polymerization regulator and 0.2% phosphoric acid in the usual manner. Nylon 12 pellets (0.5% solution in m-cresol) with 98 meq / kg equivalent of carboxylic acid and 20 meq / kg equivalent of amine and a relative viscosity of 1.61 were prepared with 21 meq / kg equivalent of carboxylic acid and 115 meq / kg equivalent of amine and relative viscosity. The same amount was mixed in a nylon 12 pellet (0.5% solution in m-cresol) having a value of 1.59. Liquid nitrogen was used to mill the mixture together to form a powder that passed through a 200-mesh. An iron plate 1 mm thick was electroplated with this powder, heated to 240 ° C. for 6 minutes and cooled with water. The 0.5% solution of the coating membrane in m-cresol had a relative viscosity of 1.75.

500 g of aminoundecanoic acid, 4 g of adipic acid and 1 g of phosphoric acid were placed in a container. The mixture was heated to 210 ° C. with nitrogen for 1 hour and then heated to 250 ° C. for 3 hours to form carboxyl polyamide. The infrared absorption spectrum of the preparation was consistent with nylon 11. The melting point was 185 ° C. and the 0.5% solution of the preparation in m-cresol had a relative viscosity of 1.50. This preparation had 115 meq / kg equivalent of carboxylic acid and 18 meq / kg equivalent of amine.

In the same manner as described above, an amino polyamide was prepared from 500 g of 11-aminoundecanoic acid, 3.5 g of hexamethylenediamine, and 1 g of phosphoric acid. The infrared absorption spectrum of the preparation was consistent with nylon 11. The melting point of this preparation was 185 ° C. and the product 0.5% solution in m-cresol had a relative viscosity of 1.48. This preparation was 21 meq / kg equivalent of carboxylic acid and 135 meq / kg equivalent of amine.

The carboxyl polyamide was mixed with the same amount of amino polyamide and the mixture was kneaded and then extruded with a 20 mm diameter extruder to form pellets. The relative viscosity of the pellet 0.5% solution in m-cresol solution was 1.59.

The pellets were ground with a small mill using liquid nitrogen. The pulverized product that could not pass through the 60-mesh sieve was repeatedly ground to obtain about 300 g of the powder passing through the 60-mesh sieve. An iron sheet having a thickness of 3 mm was coated with the powder thus formed by the fluidized dip coating method. The iron plate was preheated to 350 ° C. for 7 minutes, then immersed for 5 minutes, left for 1 minute and cooled with water. There was no exposed part of the iron plate edge. The 0.5% solution of the coating film in m-cresol had a relative viscosity of 1.99.

Comparative Example 1

5 kg of laurolactam and 200 g of water were placed in a 10-L autoclave. The inside of the autoclave was purged with nitrogen. When the temperature was set to 280 ° C, the pressure in the autoclave reached 25 kg / cm 2. The temperature was maintained at 280 ° C. for 7 hours and then the temperature was lowered to 250 ° C. over 1 hour while gradually reducing the vapor pressure in the autoclave to atmospheric pressure. The polymer was then slowly released through the bottom over 1 hour under nitrogen pressure.

The 0.5% polymer solution obtained in the initial stage, released through the bottom in m-cresol, had a relative viscosity of 1.58. The end groups of the preparation were 61 meq / kg equivalents of carboxylic acid and 64 meq / kg equivalents of amine. The 0.5% polymer solution (1 hour after start of release) obtained in the first step in m-cresol had a relative viscosity of 1.75. This fact implies that during the release process, the polymerization proceeds and it is difficult to form a polymer having the intended viscosity.

Claims (5)

At least 70% of the end groups are carboxylic acids and at least 70% of the end groups are amines, the second polyamide being suitable for powder coating. The composition of claim 1, wherein the relative viscosity in the 0.5% methacresol solution is 1.10 to 1.30. A composition according to claim 1 or 2, wherein the range of total equivalents of carboxylic acid to total equivalents of amine for the first and second polyamides is from 40:60 to 60:40. A powder coating powder comprising a product obtained by subjecting the composition as defined in claim 2 to a solid phase polymerization reaction. A powder coating powder comprising the polyamide resin composition as defined in claim 1 and a polymerization catalyst.