JPS60248725A - Epoxy resin powder composition - Google Patents

Abstract

PURPOSE:The titled composition that contains a specific solid epoxy resin and a curing agent, thus being suitable for use as a powder coating, adhesive and a forming material, because it has low melt viscosity to improve space-filling properties and showing high adhesion and heat resistance after curing. CONSTITUTION:An epoxy resin composed of 4.4'-bis(2''.3''-epoxypropoxy)-3.3'. 5.5'-tetramethylbiphenyl, a curing agent and, when needed, a curing accelerator are mixed, crushed and classified to give the objective powder composition. As the curing agent, is preferably cited an acidic curing agent such as novlak phenolic resin, acid anhydride as well as an amine curing agent such as aromatic amine, dicyandiamide, which has most preferably a melting point over 50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has low viscosity when melted and excellent gap filling properties, as well as good adhesion and heat resistance after curing, and is useful for powder coatings, adhesives, and molding materials. The present invention relates to an epoxy resin powder composition suitable for use in various applications.

In recent years, powder compositions such as powder coatings have become pollution-free, resource-saving,
As an energy-saving paint, it is replacing conventional solvent-based paints in a wide range of applications.

However, because general powder coatings have a high viscosity when melted, they have the advantage of being able to produce a thick film finish with just a few coating operations, but they also have poor wettability with the object to be coated and penetration into fine details, i.e., gaps. It has drawbacks such as poor filling properties and thin film coating properties, and with the expansion of applications in recent years, improvements in heat resistance and adhesion are required as well as improvements in the above drawbacks.To address these issues, new materials are being developed. Development is required.

On the other hand, epoxy resins come in various forms, from liquid to solid, and are used in a wide range of fields because they can exhibit a variety of physical properties of the cured product depending on the type and the type of curing agent used in combination. ->ru.

Among these epoxy resins, epoxy resins such as solid bisphenol A type, bisphenol F type, and novolac type are known as those used in the above-mentioned powder coatings.

However, since such conventional epoxy resins generally have a relatively large molecular weight, they have a high melt viscosity (when used in powder coatings, they have poor wettability with the object to be coated, gap filling properties, It has poor thin film coating properties and is unsuitable for adhering complex structures or filling narrow gaps.Therefore, reducing the molecular weight to lower the melt viscosity of these materials is considered, but it is difficult to make powder coatings. In addition, in solid bisphenol A type and bisphenol F type epoxy resins, the chain length between the epoxy groups, which are functional groups, is long, so the crosslinking density of the cured product is low, and the heat resistance is inferior to liquid resins. The drawback is that solid novolazzi type epoxy resins have insufficient adhesion.

In addition to the above, trisglycidyl isocyanurate is known as an epoxy resin with a low molecular weight and low melt viscosity that is solid at room temperature, but this resin has the drawback of extremely low adhesive strength. Furthermore, when a liquid epoxy resin is used in a powder coating, it is necessary to semi-cure it due to the powder's staleness, which poses a problem in that the molecular weight increases and the melt viscosity increases. Further, problems similar to those described above also occur in the case of powder compositions other than powder coatings, such as adhesives and molding materials.

As a result of extensive research in view of the above circumstances, the inventors have discovered that a powder composition containing a specific solid epoxy resin and a curing agent, which will be described later, has a low melt viscosity and excellent gap-filling properties. It was discovered that it has good wettability and thin film coating properties on objects, and also exhibits high heat resistance and adhesive properties, and can be suitably used in various applications such as powder coatings, adhesives, and molding materials, and has led to the creation of this invention. Ta.

That is, the present invention provides an epoxy resin containing an epoxy resin component consisting of 4,4'-bis(2",3"-epoxypropoxy)-3,3,5,5'-tetramethylbiphenyl and a curing agent. It concerns a powder composition.

The above epoxy resin used in this invention has the structural formula (■)
; It is solid at room temperature and has a molecular weight of 98 to 10.
has a melting point of 0°C and has a melting point of, for example, 150°
It exhibits a very low viscosity of about 0.1 poise.

As a curing agent used with such an epoxy resin, various types of curing agents conventionally known as curing agents for epoxy resins can be used. Particularly suitable are compounds having a phenolic hydroxyl group such as novolac type phenolic resin, acid curing agents such as acid anhydrides, and amine curing agents such as aromatic amines, dicyandiamide, imidazoles, imidacillin, and hydrazide derivatives. and those having a melting point of 50°C or higher are optimal;
Two or more types may be used in combination.

A normal curing agent is generally used in a ratio of 05 to 1.5 equivalents of curing agent functional group per equivalent of epoxy group in the epoxy resin of the present invention, but in the case of a catalytic curing agent, 100 parts by weight of the epoxy resin is used. It is used in an amount of about 0.3 to 5 parts by weight. Here, the usual curing agents include acid anhydrides, compounds having phenolic hydroxyl groups, aromatic amines, etc., and the catalytic curing agents include imidazole, imidacillin, etc.

By selecting the type of curing agent used, various functions can be achieved in addition to the excellent gap-filling properties, high heat resistance, and adhesive properties expressed from the above-mentioned inherent properties of the epoxy resin represented by the structural formula (I). can be added. For example, dicyandiamide improves the long-term storage stability of the powder composition, acid anhydrides and phenolic resins improve heat resistance, and aromatic amines and linear phenolic resins provide a certain degree of flexibility to the cured product. , imidazoles have additional features such as fast curing properties, and it is possible to have these features together if the above-mentioned curing agents are used in combination.

In addition, in the epoxy resin powder composition of this invention,
As the epoxy resin component, other epoxy resins such as evabisphenol A type, bisphenol F type, and novolac type can be used in combination with the epoxy resin represented by the structural formula (I), if necessary. However, these other epoxy resins can be used in an amount of 50% by weight or less of the total epoxy resin component depending on the purpose of use.

Further, in the present invention, in order to accelerate curing, a curing accelerator suitable for the type of curing agent used may be blended into the powder composition as necessary. As such a curing accelerator, any conventionally known curing accelerator can be used. For example, in the case of a compound having a phenolic hydroxyl group or an acid anhydride curing agent, imidazole, dicyandiamide, imidacillin,
Examples include tertiary amines such as benzyldimethylamine, basic compounds such as imidazole in the case of aromatic amine curing agents, boron trifluoride and derivatives thereof, and the like.

Although the curing accelerator used here varies depending on the type of curing agent and the purpose of use, it is usually used at a ratio of about 0.3 to 2 parts by weight per 100 parts by weight of the epoxy resin. Furthermore, in the present invention, various additives such as fillers and colorants can be appropriately blended into the powder composition as desired.

The epoxy resin powder composition of the present invention is obtained by mixing the above-mentioned components by a known method such as a dry mixing method or a melt mixing method, followed by pulverization and classification.

The obtained composition has a low viscosity when melted, has excellent gap filling properties, and has good wettability and thin film coating properties on the object to be coated.
After curing, it exhibits excellent heat resistance and adhesion, so powder coatings,
It can be suitably used in a wide range of applications such as molding materials and adhesives.

This invention will be specifically illustrated in Examples below.

Examples 1 to 3 A blend of each component shown in the table below was pulverized by a dry mixing method, and the pulverized product was classified using a 40-mesh sieve to obtain an epoxy resin powder composition.

Comparative Examples 1 to 4 Epoxy resin powder compositions were obtained by pulverizing and classifying the compositions of the components shown in the table below in the same manner as in Examples 1 to 3.

Regarding the epoxy resin powder compositions of the above examples and comparative examples, the melt viscosity at 150°C (the melt viscosity at 150°C of the formulation excluding the curing accelerator was measured using a Brookfield viscometer), the room temperature of the cured product and shear adhesive strength at 150°C (measured according to JIS-6849),
and gap filling properties were measured. The results are shown in the table below along with the formulation composition. The gap filling property is 15wn1 in width.
Two spacers with a thickness of 0.5 mm were sandwiched and fixed between two steel plates with a length of 100 mm and a thickness of L6 +++ m, and the steel plates were heated to 150 °C. Sprinkle the powder composition into the slit-shaped gap formed between both steel plates and both spacers, pour the molten material, then hold at 180°C for 30 minutes to harden, and after cooling to room temperature, shear bonding The force was measured and expressed as a ratio (1) of the shear adhesive force measured by this method to the normal shear adhesive force at room temperature described above.

(x) The following epoxy resins A to D in the above table were used.

A... Epoxy resin of the above ♂L(I) △ B... Solid bisphenol A type epoxy resin (epoxy equivalent: 650) C... Solid novolac type epoxy resin (epoxy equivalent: 210) D... Trisglycidyl Isocyanurate As is clear from the above table, the epoxy resin powder compositions according to the present invention (Examples 1 to 3) have low melt viscosity, excellent gap filling properties, and good adhesion and heat resistance. On the other hand, powder compositions using conventionally widely used epoxy resins (Comparative Examples 1 to 3) have high melt viscosity and poor gap-filling properties, and also have insufficient adhesion and heat resistance. Powder composition using trisglycidyl isocyanurate, which is known as a low molecular weight epoxy resin with low melt viscosity (
It is clear that in Comparative Example 4), the gap-filling property was sufficient, but the adhesion was significantly inferior.

Claims (1)

[Claims] Contains an epoxy resin component consisting of (+14,4'-bis(2",3"-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl) and a curing agent. (2) The epoxy resin powder composition according to claim (1), wherein the curing agent is an acid curing agent and/or an amine curing agent.