JPS62223277A - Powdered epoxy resin composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. having excellent hardness, impact resistance and flexibility, consisting of a specified epoxy resin, a linear phenolic resin having phenolic hydroxyl groups at both terminals, an inorg. filler and a curing accelerator. CONSTITUTION:100pts.wt. epoxy resin (A) which is solid at 30 deg.C is blended with a linear phenolic resin (B) which is solid at 30 deg.C and has a softening point of 40-150 deg.C, an MW of 180-2,000 and at least two phenolic hydroxyl groups at both terminals, represented by the formula (wherein R is H, or CH3; n is 0 or not smaller than 1) in an amount of 0.1-1.0 equivalent of the phenolic hydroxyl group per equivalent of the epoxy group of the component A, 3-30pts. wt. inorg. filler (C) having an aspect ratio of 5-500 and an average fiber diameter of 0.05-5mum (e.g., potassium titanate whisker) and 0.1-5pts.wt. curing accelerator (D) (e.g., 2-methylimidazole).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a powdered epoxy resin composition, and particularly to an epoxy resin composition suitable as a powdered coating composition.

Powdered epoxy that contains a specific hardening agent and filler, has good impact resistance, high hardness, and flexibility, making it easy to process the coated object after forming the coating. It is related to paint.

[Conventional technology]

Powdered epoxy resin compositions, especially powdered epoxy resin paints, not only have excellent adhesiveness, corrosion resistance, insulation, and chemical resistance, but also have the following advantages. i.e. 100%
It is a mold composition that does not contain harmful solvents as an ingredient, - It is a wave type and does not require blending, and surplus materials can be recovered and reused, which contributes to resource conservation, energy conservation, and economy. It is also excellent in terms of properties, and is increasingly being used as a replacement for conventional solvent-based and liquid-based compositions, especially paints, or in completely new fields.

As the applications of such powdered epoxy resin compositions have expanded, various other properties have come to be required. One of them is bending workability. After painting, there are an increasing number of cases in which the object to be coated is subjected to bending or other processing, but conventional epoxy resin compositions are relatively hard and brittle, and bending can cause coating film defects such as cracks and peeling. This often occurs.

Methods of improving this bending property, that is, methods of imparting flexibility to the coating film, include methods of adding elastomers, methods of using rubber-modified epoxy resins, and methods of reducing crosslinking density. When such a method is used, impact resistance and surface hardness generally decrease, and as a result, coating defects such as scratches and cracks are likely to occur during the manufacturing process or in practical use (and the coating performance may deteriorate). This results in drawbacks such as significant deterioration and damage to the appearance.In general, it is difficult to achieve both mechanical strength and flexibility. The current situation is that it has not been developed yet, and its development is strongly desired.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is to meet the above-mentioned conventional demands, and more specifically, to develop a powdered epoxy resin composition that can sufficiently satisfy both mechanical strength and flexibility. It is.

[Means for solving problems]

A solution to this problem is achieved by incorporating a solid linear phenolic resin and a certain inorganic filler, particularly preferably potassium titanate whiskers, into a solid epoxy resin together with a curing accelerator. Ru. Particularly, the present invention provides (A) an epoxy resin that is solid at 30°C, (B) a linear phenolic resin that is solid at 30°C and has phenolic hydroxyl groups at both ends, and (C) an aspect ratio of 5 to 500. and its average fiber diameter is 0.05~5μ
This invention relates to a powdered epoxy resin composition characterized by comprising an inorganic filler (m) and a curing accelerator (D) as essential components.

[Structure and operation of the invention]

In the present invention, the epoxy resin used as component (A) must be solid at 30°C, and any of various epoxy resins can be used as long as this condition is satisfied. Particularly preferred examples include bisphenol A type epoxy resin and bisphenol F type epoxy resin, which are preferred because they have a certain degree of flexibility.

In this case, if it is not solid at 30°C, it may cause problems when it is made into a powder composition.

Component (B), a linear phenolic resin having phenolic hydroxyl groups at both ends that is solid at 30° C., acts as a curing agent and is also a component that exhibits flexibility in the present composition.

This curing agent is a Ninomiya compound, so the crosslinking density of the cured product is reduced and flexibility is exhibited. The material used as component (B) is a linear phenol resin having at least 21 [1 phenolic hydroxyl groups at both ends. This phenol resin preferably has a softening point of 40 to 150.
℃, particularly preferably 60 to 120℃, and the molecular weight is 180℃.
-2000, preferably about 200-1000.

This phenol resin also needs to be linear; anything other than linear is not preferred because flexibility will be significantly impaired. Specific examples include bisphenol A, bisphenol F, or a phenol resin (1) obtained by condensing these bisphenols with shrimp herohydrin in an excess amount of the former.

・・・・・・H) (However, R is [I or CH, and n is an integer of 0 or 1 or more) The blending amount of component (B) is 1
It is preferable that the phenolic hydroxyl group is in the range of 0.1 to 1.0 equivalents, particularly 0.2 to 0.8 equivalents, and if it does not reach 0.1 equivalents, the cured product will have sufficient flexibility. If the amount is more than 1.0 equivalent, the curing speed will be slow and quick curing property will be lost, and chemical resistance and water resistance will decrease due to the excess amount of component (B). It's scary and undesirable.

In the present invention, component (B) is an essential component, but other curing agents may be used in combination. In this case, the amount of other curing agents added is usually 1 to 100 parts by weight of the epoxy resin.
It is 50 parts by weight.

In the present invention, the inorganic filler used as component (C) has an aspect ratio of 5 to 500, preferably 1.
0 to 200, and the average fiber diameter is 0.05 to 5
Preferably, those having a value of 0.05 to 2 are used. In this case, if the aspect ratio is outside the above specified range, it will be difficult to obtain sufficient impact strength or flexibility, and if the fiber diameter is outside the above range, flexibility will be similarly lost or sufficient impact strength will not be obtained. , it tends to become impossible to obtain hardness.

Potassium titanate whiskers can be exemplified as a representative example of this inorganic filler.

As this potassium titanate whisker, it is also possible to use one whose surface has been modified with a camping agent etc. to improve wettability, or one which contains water of crystallization (potassium titanate hydrate whisker). . Potassium titanate whiskers, that is, fine single crystal fibers of potassium titanate, have a fiber diameter of 0.2 to 0.5 μm, which is extremely small compared to glass fibers, etc., and have an aspect ratio of 15 to 4.
00, and its reinforcing effect is particularly large in the present invention. Furthermore, the whisker itself has high strength and high elasticity, and when added to the composition of the present invention, it exhibits good characteristics with little fiber destruction even during manufacturing processes such as kneading and pulverization. Note that the whisker preferably has a fiber length of about 5 to 70 μm from the viewpoint of manufacturing and properties.

Glass fiber as a conventional filler has a fiber diameter of about 1
3 μm, and its fiber length is about 100 μm, which is outside the scope of the present invention and is extremely thick and large compared to, for example, potassium titanate whiskers. When this is filled into an epoxy resin composition, the epoxy resin phase is separated by the large glass fibers in the coating, greatly reducing the elongation and flexibility of the coating. On the other hand, like potassium titanate whiskers, the fiber diameter is very fine, so they are uniformly dispersed in the coating, forming a continuous coating, and there is very little elongation or decrease in flexibility of the coating. Furthermore, since the aspect ratio is large as mentioned above, mechanical properties such as impact resistance and surface hardness are also greatly improved.

In the present composition, the amount of the inorganic filler added is preferably 3 to 30 parts by weight per 100 parts by weight of the epoxy resin.
If the amount is less than 3 parts by weight, the effect of addition will be small, and if it exceeds 30 parts by weight, workability in large bending operations may deteriorate.

In the present invention, a curing accelerator is used as component (D). Although component (B) acts as a curing agent,
Since component (B) alone tends to result in insufficient curing, a curing accelerator as component (D) is used in the present invention. The curing accelerator at this time is not particularly limited,
Those commonly used as curing accelerators can be used, such as aliphatic amines, aromatic amines, polyamides,
Examples include modified aliphatic amines, modified aromatic amines, imidazole compounds, imidacillin compounds, tertiary amines, dicyandiamide, hydrazide compounds, and acid anhydrides. The amount added varies depending on the type, but is generally about 0.1 to 5 parts by weight per 100 parts by weight of the epoxy resin.

Various other additives that have been conventionally used may be added to the present composition depending on the use or purpose. For example, hardening agents, fillers, pigments, and other various additives, etc.
It may be added within a range that does not deteriorate the properties.

Although the means for preparing the composition of the present invention is not particularly limited, it is desirable to melt-mix the epoxy resin and the inorganic filler, particularly preferably potassium titanate whiskers, in advance to improve wettability.

The composition of the present invention can be used in any of the various fields in which powdered epoxy resin compositions have conventionally been used, and is particularly suitable as a coating composition.

〔Example〕

EXAMPLES The present invention will be explained in more detail by showing Examples and Comparative Examples below.

Examples 1 to 8 and Comparative Examples 1 to 4 After tri-blending each predetermined component with a dry mixer (Henschel mixer) at the predetermined blending amounts shown in Table 1,
After melt-kneading using a press machine (Conneader PR46 manufactured by Busu Co., Ltd.), the mixture was pulverized and classified to obtain a powder composition with a 120-mesh pass.

In Examples 6 to 8 in Table 1, a linear phenol resin having a molecular weight of 400 was used as the component (B).

The methods for measuring various physical properties in Table 1 are as follows.

0 tensile elongation at break Silicon-treated steel plate is preheated to 200℃ and painted using the fluidized dipping method. After that, heat cure at 200℃ for 10 minutes to 0.25~0
．． A coating film with a thickness of 3+w+a was obtained. This coating film is Tensilon V
23℃, 5mm at TM-3 (Toyo Baldwin)
A tensile test was performed at /min.

After degreasing and grid blasting a steel plate with 0 bending workability and a pencil hardness of 6ma + thickness, it was preheated to 220°C and electrostatically sprayed to a film thickness of 25mm.
It was coated to a thickness of 0 μm. Thereafter, it was heated at 200° C. for 10 minutes to prepare a sample.

Bending workability is JIS-Z-2248rtll+ at 23℃
The bending deformability was examined at an inner bending radius of 12 m++ in accordance with the ``Bending Method''.

○: The crank cannot be inserted.

×: The crank is inserted.

Pencil hardness is according to JIS-5400 with a load of 1 kg.
This was done until there were no scratches.

A steel plate with a 0 impact strength of 91 II and 11 thickness was prepared in the same manner as the bending workability sample, tested in accordance with ASTM G-14, and determined by the presence or absence of a conductive portion using an IKV pinhole tester.

Further, details of each component used in Table 1 are as follows.

0 Cresol novolak: Epoxy equivalent 220, type epoxy resin softening point 90''C- (component A) O linear phenol resin: Hydroxyl group equivalent 250, compound (1) of RζCH3 0 Potassium titanate, ta fiber diameter Approx. 03 μm, scar aspect ratio approx. 300 Talesol novolak: Softening point 80°C resin (other) 0 Glass fiber: Fiber diameter approx. 13 μm, aspect ratio 8 (or more)

Claims (3)

[Claims] (1) (A) An epoxy resin that is solid at 30°C, (B) A linear phenolic resin that is solid at 30°C and has phenolic hydroxyl groups at both ends, (C) An epoxy resin whose aspect ratio is 5 to 500 and whose aspect ratio is 5 to 500. A powdered epoxy resin composition comprising, as essential components, an inorganic filler having an average fiber diameter of 0.05 to 5 μm, and (D) a curing accelerator. (2) Component (C) is 3 to 30 parts by weight per 100 parts by weight of (A) epoxy resin, component (B) is per equivalent of epoxy group in the epoxy resin,
The composition according to claim 1, wherein the proportion of phenolic hydroxyl groups is 0.1 to 1.0 equivalent. (3) The composition according to claim 1 or 2, wherein the inorganic filler of component (C) is potassium titanate whiskers.