JPS5825702B2 - powder paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder coating that has extremely excellent performance in coating fragile objects made of metals, ceramic materials, glass, etc. and imparting them with resistance to breakage. At this time, saponified ethylene-vinyl acetate copolymer is used as a powder.

Glass products, which have excellent transparency, chemical resistance, and are inexpensive, are widely used as containers, especially food bottles. It has its drawbacks.

It is a well-known fact that the appearance of glass containers that are difficult to break has been long awaited by the food industry, especially the beer, alcohol, soft drink, and various seasoning industries.

Various attempts have been made and implemented in the past to impart breakability to glass.

However, the most important condition for edible bottles is that they are inexpensive, and the best method to satisfy this condition and provide impregnability is to coat the object.

Polymeric substances with film-forming properties are generally used as coating materials suitable for such methods, and the performance required for these is that they have the ability to cover objects of irregular shape beautifully. For example, it must flow at a relatively low temperature and have an appropriate melt viscosity, it must firmly adhere to the object and have excellent strength, and it must also have weather resistance, water resistance, chemical resistance, etc. This is excellent.

A saponified product of ethylene-vinyl acetate copolymer is a coating material that satisfies these various properties.

By appropriately selecting the copolymerization ratio of ethylene and vinyl acetate, various performances can be imparted to the coating material.
The ethylene content is 80 to 80% in terms of the ability to coat irregularly shaped objects beautifully, that is, the appropriate melt viscosity.
Copolymers with a mole ratio of 90% are excellent and are already in practical use as coating materials.

However, although copolymers in this range satisfy the required performance to a certain extent, they have a few industrially extremely inconvenient problems in terms of recovery.

Firstly, if there are scratches caused by a collision etc. when the coated object, such as a bottle, is collected after being put on the market, it is extremely dangerous to reuse it as it is, and it is necessary to recoat it. be.

When recoating, it is necessary to peel off the scratched coating film, but when a high ethylene material with an ethylene content of 80 to 90 moles φ is coated, there is no easy way to peel it off from the glass surface.

Second, when old bottles are melted and recycled for reuse, it is necessary to melt the coated bottles from an operational and cost perspective, but in the case of high-ethylene products, color develops at the time of high-temperature decomposition.
The molten glass becomes colored and the quality of the recycled glass deteriorates significantly.

The present inventors comprehensively investigated the ethylene content, degree of polymerization, and degree of saponification of saponified ethylene-vinyl acetate copolymer, and found that the ethylene content ranged from 20 to 50 molar range, and the degree of polymerization was 10.
00-2000 Degree of saponification 85 molφ or more, especially 85-2000
It has been found that a saponified ethylene-vinyl acetate copolymer powder having a 99 molar width range is extremely excellent as a material for coating glass containers to impart breakage resistance.

That is, in the present invention, the ethylene content is 20 to 50 molar width, the degree of polymerization is 1000 to 2000. Powder of a saponified ethylene-vinyl acetate copolymer with a saponification degree of 85 moles or more, especially 85 to 99 moles, is applied to a fragile object made of metal, ceramic material, glass, etc. by fluid immersion, spraying, static electricity, etc. By coating with this method, a coated product with excellent performance can be obtained.

. The ethylene content of the saponified ethylene-vinyl acetate copolymer used in the present invention is preferably in the range of 20 to 50 moles.

If the ethylene content is less than 20 moles, the physical properties of the saponified copolymer will become close to those of PVA, and the water resistance will decrease, while if it exceeds 50 moles φ, the number of hydroxyl groups in the saponified copolymer will decrease. Therefore, it is not preferable in terms of adhesiveness.

Further, the degree of polymerization of the ethylene-vinyl acetate copolymer sacrificial product is preferably in the range of 1,000 to 2,000.

When the degree of polymerization exceeds 2000, the strength is excellent, but the melt viscosity is inappropriate and the fluidity characteristics are also disadvantageous.

On the other hand, if the degree of polymerization is less than 1000, although it has a suitable melt viscosity, it has disadvantages such as poor tear strength, poor toughness and flexibility, and high brittleness.

Only when the degree of polymerization is within the range of 1,000 to 2,000 can a powder coating having sufficient coating strength, a melt viscosity that allows beautiful coating, and sufficient water resistance be obtained.

Next, it has been found that by appropriately selecting the degree of saponification of the saponified ethylene-vinyl acetate copolymer, the melt viscosity can be lowered, the surface smoothness of the coating film can be improved, and the performance can be improved.

That is, among saponified ethylene-vinyl acetate copolymers, saponified products having a saponification degree of 85 molar or higher, particularly 85 to 99 molar width, preferably 93 to 97 molar width are suitable.

This made it easier to create a coating without any deterioration in performance.

In the present invention, a plasticizer can be added to the saponified ethylene-vinyl acetate copolymer in an amount of 0 to 2 weight.

In addition, polyacrylic acid resin, SB
The transparency of the coating can be improved by appropriately adding R-based polymers, epoxy resins, etc.

Next, the method for coating the object with a powder coating made of a saponified ethylene-vinyl acetate copolymer is the fluidized dipping method, which is currently generally known as a coating method for thermoplastic resin powder coatings.
Electrostatic spraying or other coating methods can be applied as appropriate.

The fluidized immersion method is a method in which powdered resin is fluidized by a fluid in a container (fluidized tank), and the object to be coated is heated above the softening point of the resin to be used and immersed in it, so that the resin is fused and coated on the surface. The electrostatic spray method is a method in which synthetic resin powder is electrostatically charged using a device in the form of a spray gun and coated on the surface of the object to be coated; followed by heat treatment in a suitable air circulation oven. The method involves melting the coated powder onto the surface to which it is attached.

The characteristics of the powder coating obtained by the present invention can be summarized as follows.

Although the coating film has excellent water resistance against water at temperatures below 70°C, it easily peels off from the glass surface when immersed in hot water at temperatures above 90°C or, for example, in a 3% alkali aqueous solution at 80°C.

This property shows excellent water resistance while it is on the market, but when it becomes necessary to remove the coating film due to scratches on the surface at the time of collection, the purpose can be easily achieved.

Furthermore, during the melting and regeneration of glass, the coating film of the present invention is completely incinerated at the high temperature at which the glass melts, and does not cause any coloring of the glass.

The present invention will be specifically described below with reference to Examples.

Example 1 A transparent glass plate measuring 100 x 150,777 L and 2 mm thick was degreased in advance with trichlorethylene, and then saponified ethylene-vinyl acetate copolymer (ethylene content: 30 moles, degree of polymerization: 1,600, carbon ratio: 96.6 moles) was prepared. , softening point 161°C, MI 2.94, 9/10 minutes, load 2161
) powder of 100 mesh or less was spread on the above-mentioned sheet glass and placed in an electric furnace at 200° C. for 10 minutes to heat and coat the glass.

The coating film was extremely smooth and had a thickness of about 0.2 mm.

Its water resistance and alkali resistance were extremely good as shown in Table 1.

Further, the material obtained in Example 1 was placed in a porcelain crucible, heated in an electric furnace at 700° C. for 2 hours to melt the glass, and the presence or absence of coloration of the glass was observed, but no coloration was observed.

Comparative Example 1 According to Example 1, a powder of 100 mesh or less of saponified ethylene-vinyl acetate copolymer (ethylene content 55 moles, degree of polymerization 9001, degree of saponification 83 moles φ, softening point 130°C) was used. Ta.

The thickness of the coating applied was approximately 0.2 mm.

Its water resistance and alkali resistance are shown in Table 1 below.

When the glass obtained in Comparative Example 1 was melted under the same conditions and the coloration of the molten glass was observed, light brown coloration was observed.

In Example 1, it was impossible to peel off the film by immersion in the tri-alkali aqueous solution at 70° C. or lower.

Example 2 Saponified ethylene-vinyl acetate copolymer (ethylene content 3
0 mole φ, degree of polymerization 1600. Saponification degree 96.6 mo/L
/%, softening point 162°C, MI 3.3, F/11, load 2160g) powder of 100 mesh or less was fluidized in a container (fluidized tank), degreased with trichlorethylene in advance, and heated to 170°C. A heated commercially available beer bottle was placed and the powder was fused and coated on the surface of the beer bottle.

This beer bottle was pre-dried in hot air at 80 to 90°C for 20 minutes, and then reheated in hot air at 180 to 200°C for 10 minutes.

The thickness of the coated film was approximately 0.15 mm. The results of the destructive test and fragment scattering test are shown in Tables 2 and 3 below.
As shown in the table, the collapse also shows good results.

Comparative Example 2 Saponified ethylene-vinyl acetate copolymer (ethylene content 5
5 mol φ, polymerization degree 900, saponification degree 83 mol φ, softening point 130'C, MI 1.42,! ? /10 minutes, load 3
Using a powder of 100 mesh or less (25 g), the surface of a commercially available beer bottle was fused and coated with the powder in the same manner as in Example 2.

The thickness of the coated film was approximately 0.15 mvt.

The results of the destructive test and fragment scattering test are shown in Tables 2 and 3 below.

In the above examples, MI was determined according to ASTM D-1238, and softening point was determined according to ASTM D-1525.

(1) Destructive test of unbreakable glass bottles A test bottle is fixed horizontally on a wooden stand, and the bottle is filled with water so that the internal pressure can be varied within the range of 1 to 5 kg/crL.

Next, a steel ball with a smooth surface weighing 2L7g was dropped onto a predetermined part of the bottle from a predetermined height without applying any force, and the distance the steel ball fell when 8 of the 10 balls were broken was measured. The difficulty of destruction is determined by the distance.

(2) Scattering test for breaking glass bottles A steel ball is dropped in the same way as the test method (1), and the relationship between the scattering state and internal pressure at the time of breakage is measured to determine the difficulty of scattering due to breakage.

The results of the tests conducted on beer bottles are as follows.

The pressure of a beer bottle containing beer at room temperature is 2 to 9/
cI? This amount of coating was practical as an unbreakable beer bottle.

Claims (1)

[Claims] 1 Ethylene content 20-50 moles φ, degree of polymerization 1000-
A powder coating consisting of a saponified ethylene-vinyl acetate copolymer of 2000.