JPS5825353B2 - powder paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder coating that can form a cured coating film exhibiting rubber elasticity at room temperature and is suitable for powder coating methods, particularly resin spraying methods.

Traditionally, natural rubber,
There is a method of applying a liquid material made by adding a vulcanizing agent to general rubber such as synthetic rubber, dissolving or dispersing it in an appropriate medium, and then heating and vulcanizing it. It has drawbacks such as requiring a long time for the medium to volatilize, which is undesirable from a cost and pollution perspective.In order to avoid these drawbacks, in recent years powder coating methods similar to those used for resin coatings have been applied. Attempts are being made to do so.

However, even if it is possible to obtain granules with good fluidity that can be powder coated from a rubber composition made by blending natural rubber or synthetic rubber with a vulcanizing agent, it is difficult to powder-coat the granules to achieve a uniform vulcanization coating. In order to form a film, it is generally necessary to heat-treat under high pressure after painting.

For example, the inventors have discovered that neoprene or ethylene-
I actually tried powder coating using a granular material with relatively good fluidity obtained by adding vulcanizing agents, fillers, lubricants, etc. to propylene-dicyclopentadiene, etc., but after painting, I found that several dozen Although a uniform vulcanized coating film was obtained when heat-treated at about 150 to 200°C under a pressure of kg/crit, such a coating film could not be formed simply by heating.

Such high-pressure heat treatment has significant disadvantages when applying the powder coating method.

This is because if the object to be coated has a complex shape or is a small item, or if it is the inner surface of an existing structure or transportation pipe, it is generally difficult to heat treat it under high pressure. It is.

Moreover, when applying the thermal spraying method, which is currently attracting attention as a powder coating method, the advantage of this coating method is that high-pressure heat treatment must be performed after the thermal spray coating. However, the advantages of being able to form a beautiful coating film by simply applying it to the surface of the coating, which can be applied to a wider range of objects to be coated, cannot be fully utilized.

In light of these circumstances, the purpose of the present invention is to develop a material that is completely different from the conventional heat-vulcanized granular material, which can form a cured coating film exhibiting rubber elasticity using only thermal energy during or after powder coating. As a result of intensive studies for this purpose, the present inventors have developed a specific thermosetting powder coating containing a reaction product of an epoxy resin and a carboxyl group-containing rubbery polymer that is liquid at room temperature. It has been found that the above object can be successfully achieved by using granular materials and adding titanium oxide (TiO2) powder to the granular materials.
This invention has been achieved.

In other words, the present invention is characterized in that the rubbery component occupies 30 to 50% by weight of the whole, and a part or all of the carboxyl group-containing rubbery polymer, which is liquid at room temperature and constitutes the main component of the rubbery component, is reacted with an epoxy resin. Powder coating is carried out by dry mixing 0.1 to io parts by weight of titanium oxide powder per 100 parts by weight of this liquid material into a thermosetting granular material that has the property of mutually fusing together at room temperature. The present invention relates to a powder coating characterized by being endowed with possible fluidity.

The rubbery component in this invention is mainly a carboxyl group-containing rubbery polymer that is liquid at room temperature, and a typical example of this polymer is a carboxyl group-containing acrylonitrile-butadiene copolymer. Biker CTBNX (B, F, G
There is a product name manufactured by Oodrich Chemi cal.

Such polymers that are liquid at room temperature can be used alone, together with similar polymers that are solid at room temperature, or in special cases, general natural rubber such as neoprene, ethylene-problene-dicyclopencdiene, etc. A small amount of synthetic rubber may also be used.

In this invention, an epoxy resin is used together with the above-mentioned rubbery component.

This resin is usually solid at room temperature, but
Optionally, a partially liquid epoxy resin can also be used.

The use of epoxy resin is indispensable for forming a cured coating film, and the use of the above-mentioned rubber component alone does not provide sufficient mechanical strength or chemical resistance, which tends to be inferior to conventional heat-curable products. Characteristics are complemented.

Such epoxy resins include a wide variety of epoxy resins such as diglycidyl ethers of polyhydric phenols, glycidyl ethers of novolac resins, and glycidyl ethers of aliphatic polyols.

A specific example of a commercially available product is epoxy #1002 (5he
(manufactured by l1), ECN1280 (manufactured by CIBA), D
Examples include ER736 (manufactured by Dow).

In the present invention, when melt-mixing the above-mentioned epoxy resin and the rubbery component, a relatively high temperature is applied to melt and mix part or all of the above-mentioned carboxyl group-containing rubbery polymer, which is liquid at room temperature and forms the main component of the rubbery component. is reacted with an epoxy resin to improve the compatibility between the two and to lower the overall viscosity by increasing the molecular weight.

After that, this molten reaction product is once cooled to room temperature, and if necessary, the same or different type of epoxy resin or rubbery component is post-blended, and then a hardening agent such as barium sulfate, strontium chromate, chromium oxide, calcium carbonate, or talc is added. , optional ingredients such as fillers such as titanium oxide and pigments are blended, and when these are blended, heat is applied to the extent necessary for uniform mixing to melt and mix.

After this mixing, the mixture is cooled again and pulverized to a predetermined particle size using a freezing pulverization method using liquid nitrogen substitution to obtain thermosetting granules.

The proportion of rubbery components in the granules produced by this method is 30 to 50% by weight, preferably 30 to 36% by weight.

If it is less than 30% by weight, the final cured coating film will have low rubber elasticity, and if it exceeds 50% by weight, the amount of epoxy resin blended will decrease accordingly. Properties such as mechanical strength and chemical resistance of the cured coating film are impaired.

Among the curing agents that are known as curing agents for epoxy resins, those that are stable at room temperature and remain active at high temperatures are preferably used.

Specific examples include dicyandiamide, substituted urea, substituted thiourea, and imidazole.

The amount of the curing agent to be used differs mainly depending on the type of curing agent, but generally it is about 3 to 12 parts by weight per 100 parts by weight of the polymer consisting of the epoxy resin and the rubbery component.

Further, the blending ratio of optional components such as fillers and pigments is preferably such that the total amount thereof is usually 16 to 50% by weight of the entire composition.

The pulverized particle size when the molten mixture is cooled and then pulverized depends on the applied powder coating method, but if the molten mixture is too thick it will have a negative effect on the fluidity of the final product, so it is preferably 300μ or less. good.

After pulverization to a predetermined particle size, if some large particles are present, the above-mentioned coarse particles are removed by sieving.

The thermosetting granules obtained in this way have a property that the particles fuse together at room temperature due to the carboxyl group-containing rubbery polymer that is liquid at room temperature.
It is impossible to apply this directly to powder coating.

The inventors have developed various lubricants used in general resin powders, such as calcium carbonate, in order to eliminate the mutual fusion of the granules and impart a flow curve suitable for various powder coatings. When powder, fine titanium silicate oxide powder, etc. were dry mixed, good results were obtained in terms of imparting fluidity.

However, the final polymer powder, whose fluidity has been improved by using a lubricant other than titanium oxide powder, cannot be used to form a film when the coating is thin and cured by powder coating. Moreover, if the coating thickness was too thick, numerous pinholes would occur or the coating would become spongy, making it impossible to form the desired cured coating film.

On the other hand, it has been discovered that when titanium oxide powder is used as a lubricant, a cured coating film free of such defects can be formed.

Although the reason for this is not necessarily clear, the main reason for this is that the powder coating used in (7) in this invention has a greater compatibility, or wettability, than other lubricants, and is less likely to be absorbed inside the resin during melt-hardening. This is thought to be due to the fact that it becomes easier to be taken in.

Titanium oxide powder is commercially available and usually has a diameter of 300 to 400 mμ.
This particle size is suitable for encapsulating the titanium oxide powder inside the resin.

For example, commercially available fine powder silicic acid has several micrometers to several tens of micrometers.
The specific surface area of a powder of the order of 1 t becomes extremely large, making it difficult to melt and adhere the resin uniformly to the powder surface.On the other hand, when the particle size becomes a few microns, the amount of filling must be increased to improve fluidity. This inevitably results in an adverse effect on the coating properties.

The amount of titanium oxide powder used should be 0.1 to 10 parts by weight per 100 parts by weight of the thermosetting granules produced by the above method.

This is because if the amount is less than 0.1 part by weight, no improvement in fluidity can be obtained, and if it is more than 10 parts by weight, the cured coating film will become spongy like in the case of other lubricants.

As a method for mixing titanium oxide powder, a conventionally known dry mixing method can be used as is.

Preferably, a portion of the thermosetting granules is added during the step of obtaining the thermosetting granules, that is, the pulverization step, to prevent the granules from adhering to each other immediately after pulverization.

The powder coating of this invention obtained in this way has an angle of repose (
(according to a powder tester made by the Paper Powder Engineering Research Institute) is 40
It has fluidity suitable for powder coating of more than 100%, and can be fully applied to thermal spray coating methods that particularly require fluidity.

This powder is used to apply the powder to the object to be coated by various coating methods such as the above-mentioned thermal spraying method, other scattering methods, fluidized dipping methods, and spraying methods.
When heated to 200° C., a cured coating film exhibiting rubber elasticity with sufficient adhesion or adhesion to the object to be coated is formed.

In the case of thermal spraying, a similar cured coating film can be formed by simply thermal spraying without a post-heating step by setting the heating coating conditions.

As detailed above, according to the powder coating of the present invention, a cured coating film exhibiting rubber elasticity can be formed simply by heating during or after powder coating. The application range of coating materials is wide, and the inherent advantages of thermal spraying can be taken advantage of, making it possible to provide a polymer powder with extremely high practicality.

Examples of this invention will be described below.

In the following, parts refer to parts by weight.

Example 1 Epon #1002 (epoxy resin manufactured by 5hel1) 5
Part 0 and Biker CT BN (B, F, Goo
50 parts of carboxyl group-containing rubbery polymer manufactured by drichChemica 1 (see above) and heated at 170°C in a mixer.
After the reaction melt was cooled to room temperature, 30 parts of titanium oxide as a filler and 1 part of a leveling agent were added and melt-mixed using a rubber roll at a temperature lower than the above temperature.

After that, it was cooled again and D-210 (
5 parts of epoxy curing agent (manufactured by Mukasei Kogyo Co., Ltd.) were blended and mixed at a roll temperature of 80°C.

This mixture is cooled to room temperature and pulverized by a freeze pulverization method using liquid nitrogen substitution using a hammer mill as a pulverizer.

During this pulverization, 3 parts of titanium oxide is added to the inside of the pulverizer per 100 parts of the mixture.

The resulting granules are passed through a 48-mesh sieve to remove coarse particles, and then 5 parts of titanium oxide is added to 100 parts of the mixture and mixed in a super mixer.

The powder coating of the present invention obtained in this manner has good fluidity with no particles adhering to each other at room temperature,
The angle of repose measured by a powder tester was 40-42°.

The above-mentioned composition stored at 10°C or lower is used to powder-coat the object by various methods, and after this coating,
When heat treated at 0°C, a homogeneous cured coating film was obtained.

This coating film shows good adhesion or adhesion to various coated objects, and has a tensile strength of approximately 120 kg/ffl at room temperature.
The elongation was approximately 100%.

Further, when a thin steel plate was used as the object to be coated and the coating thickness was 2 to 3 mm, the cured coating film had rubber elasticity sufficient to withstand the 180° bending test.

As can be predicted from these results, the powder coating of the present invention can be used as a soundproofing, vibrationproofing material, wear-resistant material, etc. for various coated objects.
It can also be applied as a flexible adhesive, and it can also be applied to objects with complex shapes, small articles, existing structures, the inner surfaces of transportation pipes, etc.

If it is desired to improve the storage properties of the powder coating according to Example 1, for example, 10 to 15 parts of dicyandiamide or 6 parts of dicyandiamide and 3-(P-1 rolfenil)-
By using 1,1-dimethylnirealo part, the storage temperature can be raised to about 30 parts.

Example 2 Reaction of Epon #1002 and Biker CTBN After the melt was cooled to room temperature and before adding the filler, Epon #1002 and Byker CTBN were mixed.
A powder coating material was obtained in exactly the same manner as in Example 1, except that 20 parts of 1002 was added and melted and mixed on a rubber roll.

A cured coating film obtained from this powder coating in the same manner as in Example 1 had better adhesion or adhesion to the object to be coated than in Example 1.

Other properties showed good rubber elasticity, which was almost the same as in Example 1.

Claims (1)

[Claims] 1 The rubbery component accounts for 30 to 50% by weight of the whole, and contains part or all of the carboxyl group-containing rubbery polymer that is liquid at room temperature and reacts with the epoxy resin, which is the main component of this rubbery component. 0.1 to 10 parts by weight of titanium oxide (T10
2) A powder coating that can form a cured coating film exhibiting rubber elasticity by heating during or after powder coating, which is characterized by dry mixing powder to impart fluidity that allows powder coating. .