JPS609974B2 - Resin coating method for glass containers - Google Patents

Description

Detailed Description of the Invention The present invention involves electrostatically coating three or more layers of synthetic resin powder with different physical properties on the surface of a glass container such as a glass bottle, and then forming a film by heating or baking. An improved method for processing to form three or more synthetic resin coating layers is proposed.

Glass containers such as glass bottles are widely used as containers for storing and transporting alcoholic beverages, beer, colas, juices, and other carbonated beverages. There is a risk of accidents due to flying debris, and as a measure to prevent this risk, containers coated with synthetic resin have been used.

If these resin coatings have a low hardness, they may be scratched or peeled off during handling, resulting in poor appearance and a decrease in product value during repeated use.Also, resin coatings with a high hardness will not easily be scratched, but the impact resistance of the container itself may deteriorate. Not sexual enough.

As a countermeasure against this, a proposal has been made to form a two-layer resin coating, with the inner layer being relatively elastic and the outer layer being more hard. Furthermore, in forming a resin film, electrostatic powder coating is becoming mainstream after thermal fusion coating of powder resin due to problems with solvent pollution and post-treatment when coating with solvent-based paint 0.

Formation of a resin film using this method involves electrostatically applying resin powder for the inner layer, heating it to form an inner layer film, and then electrostatically applying resin powder for the outer layer on top of this film. A method has been proposed in which a two-layer film is formed by heating the resin, but this method has the disadvantage that the heat treatment process is not only complicated but also consumes a lot of energy. Adhesive strength is also limited in terms of preventing fragments from scattering when the bottle is broken. The present invention aims to prevent the scattering of fragments when glass containers are broken, and is an improvement for forming a resin coating of three or more layers that has alkali resistance, film resistance, and durability that can withstand repeated use. This method provides a method for Therefore, the present invention relates to a resin coating method for a glass container, and the resin coating for a glass container is performed by applying electrostatic powder to the surface of the glass container when forming a synthetic resin coating on the outer surface of the glass container. After applying a synthetic resin powder sail as an inner layer, which forms a highly adhesive and elastic film with the glass surface when the resin powder is fused, an outer layer resin is applied as an intermediate layer on top of the inner layer. A synthetic resin powder that is compatible with the resin for the inner layer and has high hardness and strength due to film formation (electrostatic coating using a mixed powder of the mother and the resin powder for the inner layer as an intermediate layer) Furthermore, after electrostatically applying the resin powder for the outer layer, the coating powder layer consisting of a plurality of layers is heated or baked together with the glass container to fuse it to the surface of the container.

As described above, in the present invention, it is possible to form a plurality of layers of resin coating with only one heat treatment, and the amount of heat consumption is significantly reduced, so that the pharmaceutical effect is large.

In addition, the resins formed in the three layers are mutually compatible, and because the inner, outer, or intermediate layers form a continuous and integrated film, the adhesive strength between each resin layer is strong and peeling may occur. No,
The inner layer has strong adhesion to the glass surface, is difficult to peel off, and has elasticity, so it plays the role of absorbing the impact transmitted from the outer layer surface and preventing the glass from breaking. The flexibility of the inner layer makes it difficult for fragments to become dispersed, and therefore, the effect of suppressing scattering is large, and it is possible to obtain a glass container with excellent alkali resistance, weather resistance, scratch resistance, and durability that can withstand repeated use.

In the present invention, as the resin for the inner layer, a resin is used in which the resin film formed by heat-sealing after coating on the glass surface has appropriate elasticity and has strong adhesion to the glass surface.

Examples of these types of resins include ethylene-vinyl ester copolymers, partially saponified ethylene-pinyl ester copolymers, and carboxyl-modified products of such ethylene-vinyl ester copolymers or saponified products. ,
Ethylene-unsaturated carboxylic acid ester copolymer, carboxyl modified product and partially saponified product of ethylene-unsaturated carboxylic acid ester copolymer, ethylene-unsaturated carboxylic acid copolymer, ethylene-unsaturated carboxylic acid vinyl ester copolymer Original copolymers include ethylene-unsaturated carboxylic acid-unsaturated carboxylic acid estothermi original copolymers, etc.Vinyl esters include vinyl acetate, vinyl propion, vinyl butyrate, etc.Unsaturated carboxylic acids include acrylic acid and methacrylic acid. Examples of unsaturated carboxylic acid esters include methyl acrylate, ethyl acrylate, and methyl methacrylate.

Among these, "a particularly preferred resin for the inner layer in the method of the present invention is an ethylene-based resin having a vinyl acetate content of 5 to 30 mol%.
10 to 80% saponified product of vinyl acetate copolymer (or a saponified product of carboxyl-modified ethylene-vinyl acetate copolymer with a carboxyl base content of 0.05 to 5% by weight obtained by modifying this saponified product with carboxylic acid) In addition to the resins listed above, any resin that has strong adhesion to the glass surface and elasticity can be used without being limited to the resins listed above.

In addition, the resin for the outer layer has a melting point similar to that of the resin applied as the inner layer, has compatibility, and the formed film has physical properties such as high hardness and strength with excellent scratch resistance. Resins of the following types can be used.

In this case, the term "compatibility" means that when two or more resin powders are applied and heated and melted to form a film, they form a transparent film or exhibit physical properties that are compatible with each other.

Note that the physical properties of these two or more different resins must not be significantly different in melting point, refractive index, and expansion coefficient. As the above-mentioned outer layer resin, examples of outer layer resins that are compatible with the resins listed above as inner layer resins include, for example, vinyl acetate content of 5 to 50 mol%.
A highly saponified product of the ethylene-vinyl acetate copolymer, preferably a 70 to 100% saponified product (1), a carboxyl modified product (D) of this saponified product, or the above (1) and/or
Alternatively, a composition (m) obtained by mixing the resin of (b) with an organic polyisocyanate block may be mentioned, but in the method of the present invention, the composition (m) is particularly preferred as the resin for the outer layer.

Examples of the organic polyisocyanate blocks include aromatic, aliphatic, and alicyclic diisocyanate compounds, and compounds obtained by addition reaction of excess Z of these isocyanates with low-molecular-weight polyols.

In addition, as protective agents, blocking agents known to be used for isocyanate blocking, such as phenol-based, lactam-based, activated Z tyrene-based, alcohol-based, mercaptan-based, acid amide-based, imide-based, Amine-based substances include imidazole-based, urea-based, imine-based, oxime-based, and sulfite-based.

In addition to the resins listed above, the resins are not limited to these listed resins as long as they are compatible with resin 2 used for the inner layer.
Thermosetting resins can also be applied.

When selecting resins for the inner layer and the outer layer, if the melting points of the two are significantly different and the melting point of the resin for the outer layer is higher than that of the resin for the inner layer, the inner layer may be heated and melted after coating, and in the second tightening process. Even if a film is formed, the formation of the outer layer is not completed, resulting in an incomplete film.If you try to improve the film formation of the outer layer, the fluidity of the resin for the inner layer will increase and a falling phenomenon will occur, causing the top and bottom to overlap. This results in a film with non-uniform thickness, wrinkles or waves, resulting in a finished product with low commercial value, poor quality and strength.

Conversely, when the melting point of the resin for the inner layer is higher than that of the resin for the outer layer, even if the outer layer becomes fluidized, the inner layer remains powdery and is not formed. If the temperature rises to the film temperature, the outer layer will flow down, the inner layer powder will be mixed with it, and the film will not be uniform, or the outer phase film will have already formed with air trapped between the inner layer powder particles. This causes various troubles such as air bubbles that cannot be dissipated and remain as bubbles.

For the above reasons, when selecting resins for the inner and outer layers, it is preferable to use resins whose melting points are approximately similar.

Further, good results are obtained when the melting point of the resin for the inner layer is somewhat lower than that of the resin for the outer layer. As described above, the key point of the present invention is to coat the outer layer with a resin that is compatible with the inner layer coating resin, and by selecting such resin, three or more layers can be formed. By heating the powder layer electrostatically applied to the layer once, it becomes possible to form a transparent resin coating layer consisting of a uniform plurality of layers. Through this treatment, glass containers with a resin coating that has good adhesion to glass surfaces, excellent scratch resistance, alkali resistance, and weather resistance, are durable enough to withstand repeated use, and are less dangerous to bottle breakage. In addition, when applying electrostatically powdered resin, the resin for the outer layer is applied after the resin for the inner layer is applied. Some peeling of the inner layer resin powder that has already been applied to the powder occurs, resulting in a mixture of the two.

Further, after the coating of the outer layer is completed, the powder recovered by removing the excess amount becomes a mixed powder of resin for the inner and outer layers. Separation of these mixed powders is generally difficult and causes problems in subsequent processing. However, in the present invention, after these mixed powders are coated as an intermediate layer on the inner coating layer, there is no problem even if the resin powder for the outer layer is further coated.

In other words, when these are heated and formed into films, the presence of the intermediate layer does not cause any essential changes in the heating process, the finished quality, or the role played by the two inner and outer layers because the resins for the inner and outer layers are compatible. However, it has the advantage that a resin coating is formed in which the inner layer, intermediate layer, and outer layer are integrated.

In addition, if you apply a thin layer of silane coupling agent to the glass surface to improve the adhesion between the resin layer to be formed as an inner layer and the glass surface before electrostatically applying the resin for the inner layer, the inner layer resin will bond to the glass surface. It is preferable to use this agent because it gives good results in improving the adhesion with the membrane.

Next, the present invention will be explained with reference to examples.

Example 1 A resin-coated bottle was produced using the following two types of resin powder.

Resin powder A-melt index 150, melt index 8 obtained by hydrolyzing an ethylene-vinyl acetate copolymer with a vinyl acetate content of 2% by weight (approximately 11 mol%)
7. Fine powder resin powder B with saponification degree of 76% - melt index of 150, vinyl acetate content of 2% by weight of ethylene -
An ethyl acetate solution of 4,4-methylene-opis (cyclohexyl isocyanate) protected with G-caprolactam was added to a fine powder with a melt index of 74 and saponification degree of 92% obtained by hydrolyzing vinyl acetate copolymer. /
Mix the OH so that the molar ratio is 0.4 to form a wet cake, then use a vacuum dryer to remove most of the ethyl acetate in the wet cake, and then use a fluidized bed dryer to remove acetic acid. Fine powder obtained by almost complete removal of ethyl, namely glass bottles for cola drinks with a capacity of 1000', which had been sprayed with a 1% aqueous solution of silane coupling agent KBM-403 (Shin-Etsu Chemical), were placed on a coating conveyor. Then, using an electrostatic powder coating method, resin powder A was first applied for 8 coats, and then recovered powder, which is a mixture of resin powders A and B, was applied for 2 coats/coat.
After applying the main coating and subsequently applying resin powder B for 8 days/application, the resin powder adhering to the gripper and the bottom of the bottle is absorbed and removed (this becomes recovered powder), and then the bottle is removed from the gripper and the bottle is removed. I put it in the furnace.

In the baking process, the resin powder B was first heated at 130 q0 for 30 minutes to melt and stain, and then heated at 210 oo for 15 minutes to cause the resin powder B to undergo a crosslinking reaction.

The performance of the resin-coated bottle thus obtained was tested according to the test method described below, and the results shown in Table 1 were obtained.

Comparative Example 1 A resin-coated bottle was prepared by applying only the resin powder A of Example 1 for 18 days, and the performance of the bottle was tested.
Shown in the table.

Comparative Example 2 A resin-coated bottle was prepared by applying only the resin powder B of Example 1 for 18 days, and its performance was tested.The results are shown in Table 1.

Comparative Example 3 A resin-coated bottle was produced in accordance with Example 1 except that a thermosetting acrylic powder coating (clear) was used as resin powder B in Example 1.

For the mound attachment, first heat at 130°C for 30 minutes to melt and label, and then heat under conditions suitable for curing the acrylic powder paint used in this test, that is, 230°C.
and heated for 15 minutes. Table 1 shows the results of testing the performance of the resin-coated bottles obtained. Comparative Example 4 A resin-coated bottle was produced in accordance with Example 1 except that an epoxy powder coating (clear) was used as resin powder B.

For the leech application, first, the material was heated at 130 pm for 3 minutes, and after melting and staining, it was heated for 3 minutes under conditions suitable for curing the epoxy powder coating used in this test, i.e., i80C0 x 3 minutes. Table 1 shows the results of testing the performance of the resin-coated bottles obtained. Table 1 Example 2 A resin-coated bottle was produced in accordance with Example 1, except that the following resin powders A and B were used in Example 1.

Resin Powder A - 0.4% by weight of acrylic acid was grafted onto a saponified product with a degree of saponification of 71% obtained by hydrolyzing an ethylene-vinyl acetate copolymer with a melt index of 150 and a pinyl acetate content of 2% by weight. Finely powdered resin powder B of the graft modified product (Melt Index 75) - Melt Index 150, vinyl acetate amount 2 base weight % ethylene -
Saponification degree 8 obtained by hydrolyzing pinyl acetate copolymer
A graft modified product (melt index 82) in which 0.3% by weight of acrylic acid was grafted onto 7% saponified product was
-4,4-methylenebis treated with caprolactam*
*S(cyclohexyl isocyanate) is NCO/OH
1 using a small extruder so that the molar ratio of
Table 2 shows the results of a performance test on a resin-coated bottle obtained by melting and mixing at 20 oo and then mechanically pulverizing to obtain a fine powder with an average particle size of 74 particles.

Comparative Example 5 A resin-coated bottle was prepared by applying only the resin powder A of Example 2 for 18 days, and the performance of the bottle was tested.
Shown in the table.

Comparative Example 6 A resin-coated bottle was prepared by applying only resin powder B of Example 2 18 times per bottle, and the performance of the bottle was tested.
Shown in the table.

Table 2 Examples 3 to 8 As resin powder A, the resin powder shown in Example 2 was used, and as resin powder B, the resin powder shown below was used.

Resin Powder B - Melt Index 150, 0.3% by weight of acrylic acid was grafted onto a saponified product with a degree of saponification of 87% obtained by hydrolyzing an ethylene-vinyl acetate copolymer with a vinyl acetate content of 2% by weight. An organic polyisocyanate block of the type shown in Table 3 was added to the graft modified product (melt index 82) according to the method of Example 2.
A fine powder with an average particle size of 60 to 80 French obtained by mixing the CO/OH molar ratio to 0.4 and mechanically pulverizing the resin powder according to Example 1 using the above two types of resin powders. A coated bottle was made.

However, the leveling conditions and thermal crosslinking conditions were changed to those shown in Table 3. As a result of testing the performance of the resin-coated bottle thus obtained, it was found that the appearance, alkali resistance, adhesion, scratch resistance, and shatterproof properties were all good, and that the resin-coated bottle obtained in Example 2 was approximately the same as the resin-coated bottle of Example 2. It was confirmed that the product had good performance.

Table 3 [Test Method] {1} After immersing an alkali-resistant resin-coated glass bottle in a 4% caustic soda aqueous solution of 700° for 3 hours, it was taken out and inspected for any abnormality in appearance.

■ Adhesive strength After soaking the resin-coated glass bottle in a 4% caustic soda aqueous solution of 7000 for 3 hours, take it out and wash it with water, make a cut in the resin-coated film on the 10 side with a cutter knife and test it using an Instron type tensile tester. The stress required to peel the resin film from the glass surface was measured.

{3} After crushing the scratch-resistant resin-coated glass bottle in a 4% caustic soda aqueous solution of 7000 for 3 hours, it was washed with an AGR line simulator for 6 hours.
The degree of scratches that adhered to the coated resin surface during the coating treatment was examined.

{4} After irradiating a weather-resistant resin-coated glass bottle with a sunshine-type Wesalome-Yuichi for 100 hours, it was inspected to see if there were any abnormalities in appearance.

■ Shatterproof test bottle was filled with a specified amount of carbonated water with a gas volume of 3.6, sealed, and immersed in a constant temperature water bath of 4,000 ℃ for more than 30 minutes. 75 95 of broken glass fragments when dropped horizontally from skin height
A case where % by weight or more was within a radius of lm around the point where it fell was considered to be a pass.

Claims (1)

[Scope of Claims] 1. When forming a synthetic resin coating on the outer surface of a glass container, adhesion to the glass surface occurs when the synthetic resin powder coated with electrostatic powder is fused to the surface of the glass container. After coating a synthetic resin powder (A) that forms a film with high elasticity and elasticity as an inner layer, a synthetic resin powder (A) that is compatible with the inner layer resin to be coated as an outer layer resin is applied on the inner layer as an intermediate layer. A mixed powder of the synthetic resin powder (B) which has high hardness and strength upon film formation and the resin powder for the inner layer (A) is electrostatically applied as an intermediate layer, and further the resin powder for the outer layer (B) is coated electrostatically as an intermediate layer. )
1. A method for coating a glass container with a resin, which comprises electrostatically applying the powder, and then heating or baking the coating powder layer together with the glass container to fuse it to the surface of the container. 2. The resin coating method for a glass container according to claim 1, wherein a mixed powder of an inner layer resin and an outer layer resin recovered in an electrostatic coating process is used as the mixed powder for the intermediate layer.