JPS5952657B2 - epoxy resin composition - Google Patents

Description

[Detailed description of the invention] The present invention cures rapidly by heating and has good properties.

The present invention relates to an epoxy resin composition that can provide a coating film with excellent adhesion, impact resistance, and chemical resistance. Until now, it has been known to use epoxy resin compositions as powder coatings, but the cured coatings obtained with conventional epoxy resin compositions have low adhesion, impact resistance, and bending strength, and It has the disadvantage of low resistance to strong acids, strong alkalis, and highly polar solvents.

On the other hand, solution-type phenol-epoxy resin paints, i.e., solution-type resol-type phenol resin and solid bisphenol A, are used in fields that require chemical resistance and heat resistance, such as linings or insulating varnishes for food tanks, drums, pipes, etc. It is also known to use a paint made by dissolving and mixing a type epoxy resin in a solvent, and baking this at high temperature to form a coating film while volatilizing the solvent.

However, this paint involves the volatilization of a large amount of solvent when forming a coating film, which poses a problem in terms of environmental pollution.Additionally, the above-mentioned resol type phenolic resin is usually liquid, so it cannot be prepared in the form of a powder paint. It was hot. Afterwards, attempts were made to produce solid resol-type phenolic resin using a special method and prepare powdered phenol-epoxy resin paint, but this required a long baking process of 20 minutes at 200°C. Therefore, it cannot be said that it is still fully satisfactory in practical terms. The present inventors have improved the drawbacks of these conventional epoxy resin compositions, and have developed a powder epoxy resin composition that cures rapidly by heating and provides a coating film with excellent adhesion, impact resistance, and chemical resistance. As a result of extensive research in order to obtain this product, we discovered that the objective could be achieved by blending a solid resol type phenolic resin with specific properties into a solid epoxy resin, and based on this knowledge, we The present invention has now been accomplished.

That is, the present invention uses a solid epoxy resin of 20 to 80% by weight, a softening temperature of 70 to 90°C, a gelation time of 80 seconds or more at 150°C, and a methylol index of 25 to 45.
The present invention provides an epoxy resin composition comprising 80 to 20% by weight of a solid resol type phenolic resin.

The solid resol type phenolic resin used in the present invention has a softening temperature of 70 to 90°C and a gelation time of 1 when measured according to the method specified in JIS-6910.
It is necessary that the heating time is 80 seconds or more at 50°C.

If a material with a softening temperature lower than 70°C is used, the blocking property will be poor when a coating film is formed, and if it is higher than 90°C, it will be incompatible with the epoxy resin due to low compatibility. Appropriate. On the other hand, those having a gelation time of less than 80 seconds at 150° C. not only have poor compatibility with epoxy resins but also have poor flow when formed into an epoxy resin composition, and do not form a good coating film.

Next, the methylol index referred to in the present invention refers to the characteristic absorption of benzene nuclei at 1,600 Kaiser in the infrared absorption spectrum of resol type phenolic resin measured by an infrared spectrometer, and the characteristic absorption of the benzene nucleus at 1,000 to 1,050 Kaiser. This is the ratio of strength to characteristic absorption, expressed as a percentage. If the ratio is less than 25, the composition will not only have low reactivity and take a long time to cure, but will also have poor flow and poor coating quality. It does not form a film, and if it is larger than 45, gelation tends to occur when kneaded with an epoxy resin, and the compatibility with the epoxy resin is poor, making it impossible to form a good coating film.

This solid resol type phenolic resin is produced by, for example, condensing 0.8 to 4 moles of aldehydes to 1 mole of phenols in the presence of a basic catalyst, at a softening temperature of 70 to 90°C, and
It is produced by adjusting the gelation time at 50°C to be 80 seconds or more and the methylol index to be 25 to 45, preferably 30 to 40.

Phenols used in this case include funynol, phenols substituted with an alkyl group having 1 to 6 carbon atoms, such as cresol, peropylphenol, butylphenol, tert-butylphenol, especially m-monosubstituted phenol, etc.
and bicyclic phenols such as bisphenol A, bisphenol S, and bisphenol F, and dihydric phenols such as resorcinol.

These can be used alone or in combination of two or more. Examples of aldehydes include formaldehyde, paraformaldehyde, furfural, acetaldehyde, butyraldehyde, and glyoxal, and formaldehyde in forms such as formalin and paraformaldehyde are preferred.

These aldehydes may be used alone or in combination of two or more. Examples of basic catalysts used in the condensation of phenols and aldehydes include hydroxides, carbonates, basic carbonates, oxides of alkali metals and alkaline earth metals, and inorganic salts such as weak organic acid salts. In addition to bases, examples include ammonia water, primary amines, and secondary amines.

These basic catalysts can be used alone or in combination of two or more. In the present invention, when producing these resol type phenolic resins, the condensation product is formed into a solid state at room temperature, and during or after that, the softening temperature is set at 70 to 90°C, and the gelling time at 150°C is set at 80°C. It is important to adjust the methylol index to 25-45, preferably 30-40.

Until now, several methods have been proposed for producing solid resol-type phenolic resins (for example, Japanese Patent Application Laid-open No. 47-3340, Japanese Patent Application Publication No. 50-46521, Japanese Patent Publication No. 51-62857). Publication number, Special Publication No. 5212
658, etc.), the solid resol type phenolic resins obtained by these known methods do not satisfy the conditions of softening temperature, gelling time, and methylol index described above, and therefore do not meet the objectives of the present invention. cannot be achieved. In the present invention, any method such as the above-mentioned known method, continuous concentration method using a monotube method,
A solid resol-type phenolic resin with an evaporation content of 2 to 15% at 70°C is produced by an in-water salting-out solidification method, and then heated from room temperature to 50°C for 10 to 60 seconds to produce a solid resol type phenolic resin with an evaporation content of 2 to 15%.
A solid resol type phenolic resin that satisfies the desired conditions can be obtained by maintaining the temperature at 30°C for 10 to 60 seconds, removing the gas generated during this time by appropriate means, and then rapidly cooling it to room temperature. can.

According to a preferred embodiment for producing such a solid resol-type phenolic resin, the phenolic resin is produced by any means as described above, and then the phenolic resin is produced in the hopper of a conventional single-screw or twin-screw extruder. Adjust the temperature of the cylinder so that the temperature of the cylinder is room temperature to 50℃ at the input port and 60 to 130℃ at the outlet.
A needle-like or rod-like phenol resin with a length of 2 to 20 mm can be obtained by forming the required number of holes, cooling and cutting it while continuously extruding it, or by installing a screw extrusion mechanism and cutting it in the conveying process. can get.

Furthermore, a resol type phenolic resin with an evaporation content of about 10% was added to a diameter of 100 mm. A vacuum section is provided in the middle of an extruder with an L/D of 15 to 30, and the resin is extruded from the outlet while the generated gas is removed. Although the shape of the solid resol type phenolic resin used in the present invention is not limited, needle-shaped, rod-shaped, or flake-shaped ones are preferable for mixing with the epoxy resin. The solid epoxy resin used in the present invention is a compound having two or more epoxy groups in one molecule, and a typical example is a condensate of epichlorohydrin and a bisphenol compound.

In this case, the bisphenol compounds include, for example,
2,2″-bis(4,4″-hydroxyphenyl)propane (commonly known as bisphenol A), halogenated bisphenol A, 2,2″-bis(4,4″-hydroxyphenyl)methane (commonly known as bisphenol A) Examples include xyphenylethane, phenol, or novolac type polyfunctional phenols condensed from cresol and formalin.Other examples include hydantoin, which is a mononuclear N-heterocyclic compound having an internal cyclic NH. Among them, preferred are bisphenol A diglycidyl ether type epoxy resins.These epoxy resins include
Those having a softening temperature of 65 to 140°C, particularly 85 to 130°C are preferred. As such epoxy resins, AER-661 (epoxy equivalent weight 450 to 500), AER-664 (epoxy equivalent weight 90
0-1000), AER-667 (epoxy equivalent 175
0 to 2150), Epicoat 1004 (epoxy equivalent weight: 900 to 1000), Epicoat 1007 (epoxy equivalent weight: 1750 to 2150), etc. manufactured by Shell Chemical Co., Ltd. In the present invention, it is also possible to use curing agents for commonly used epoxy resins, examples of which include novolac type phenolic resins, dicyandiamide, imidazoles, aromatic amines, and acid anhydrides. I can do it.

Relatively good results can be obtained when a novolak type phenolic resin is used in combination. To prepare the composition of the invention, 20 to 80% by weight of solid epoxy resin, preferably 40 to 60%
% by weight and 80 to 20% by weight, preferably 60 to 40% by weight, of a solid resol type phenolic resin that satisfies the conditions described above, and is heated and melted.

The heating temperature at this time is 60 to 150°C, preferably 90 to 150°C.
At a temperature lower than this, it is difficult to obtain a uniform composition, and at a temperature higher than this, the curing reaction proceeds excessively, making it impossible to obtain the desired desirable properties. According to the invention, the addition of extenders, flow control agents, reinforcing agents, fillers and pigments is possible.

These may be added after pulverization, but it is advantageous to add them during melt-mixing. Examples of these additives include glass fibers, asbestos fibers, carbon fibers, polyethylene powder, quartz powder, mineral silicates such as mica, asbestos and slate powder, kaolin, aluminum oxide, aluminum hydroxide, antimony trioxide. , silica, titanium dioxide, carbon black, oxide coloring pigments such as iron oxide or metal powders such as aluminum powder, iron powder and liquid epoxy resins. The composition obtained by mixing the composition of the present invention by a melt blending method, cooling it, and then pulverizing it has fast curing properties at high temperatures of 180°C or higher, and the resulting coating film has good adhesion. It exhibits flexibility, flexibility, high hardness, and excellent corrosion resistance, as well as water resistance, acid resistance,
Alkali resistant, highly polar solvents such as tetrahydrofuran (THF), chloroform, methyl ethyl ketone (
It also has good resistance to solvents such as MEK).

Furthermore, when using the composition for painting the inner and outer surfaces of steel pipes, the composition can be simply sprayed onto the steel pipes that have been heated to a surface temperature of 180 to 250°C, and then allowed to cool. A coating with mechanical properties is formed. Applications of the resin composition according to the present invention include, but are not limited to, the inner surfaces of drums and other cans,
It can be widely applied to applications that can be cured at high temperatures, such as protective coatings for the inner surface of pipes, electrical insulation coatings, adhesives, binders, and molding materials.

Next, the present invention will be explained in more detail with reference to Examples.

Reference example 1 1000g of phenol, 1019g of 37% formalin,
30 g of a 20% aqueous sodium hydroxide solution was charged into a reaction vessel equipped with a stirrer and a heating jacket, and reacted at 70° C. for about 30 minutes to perform a methylolation reaction.

After that, it was cooled to 40°C, 100g of 25% ammonia water was added, and the mixture was reacted again at 70°C for 2 hours, resulting in a condensation viscosity of 500Cp.
S (65°C). This condensed resin was drained and subjected to a vacuum continuous dehydrator to concentrate the evaporation content at 70° C. to 5%. After that, the inner diameter is 60mm. Charge to a twin screw extruder with L/D of 11, cylinder temperature charge zone 50
℃, and the exit zone was set to 70°C, and the residence time in each zone was set to 50 seconds, and the mixture was discharged and poured onto a cooling conveyor to obtain a solid resol type phenolic resin. Reference example
2. 940 g of phenol and 1200 g of 37% formalin were weighed into a reaction vessel equipped with a cooling jacket, and while cooling, 200 g of 25% ammonia was added in three portions, and the temperature was gradually raised to react at 70° C. for 3 hours.

The viscosity of the reactant was 1200 CPS (60°C).
The mixture was transferred to a concentrator equipped with a vacuum device, concentrated under reduced pressure at 60 mmHg until the temperature reached 80°C, immediately poured into a large amount of water, crushed in water while quenching, and centrifugally filtered to obtain a solid resin. Ta. The water content in the resin was 12%. The resin had an inner diameter of 90 mm. The mixture was put into a L/Dl7 single-screw vent extruder, the charge zone was set at 30°C, the exit zone was set at 100°C, and the generated gas was removed under reduced pressure from the middle of the extruder, so that the residence time in each zone was set at 60 seconds. It was discharged and poured onto a cooling conveyor to obtain a solid resol type phenolic resin. Reference Example 3 In the same manner as in Reference Example 2, the resin was crushed in water and then centrifugally filtered to obtain a solid resin with a water content of 12%.

This is directly put into a double starille type kneading reactor,
A solid resol type phenolic resin was obtained by successively treating the mixture at two temperatures (70° C. and 100° C.) (residence time 120 seconds in each case). Reference example 4 1000g of phenol, 920g of 37% formalin, 80g of hexamethylenetetramine, 15g of ethylenediamine
Add g and gradually raise the temperature to 70℃ while stirring.
After reacting at the same temperature for 3 hours, 400 g of 5% carboxymethyl cellulose (CMC) was added to the resulting resin, and the mixture was further stirred at the same temperature for 15 minutes to obtain a spheroidized resin.

After quenching, the supernatant liquid was removed, and the spherical resin in the lower layer was air-dried to obtain a spherical resol type phenolic resin with an average viscosity diameter of 0.5 mm. Table 1 shows the properties of the solid resol type phenolic resin obtained in the above reference examples.

Examples Using the solid resol type phenolic resins obtained in Reference Examples 1 and 2, a mixture having the composition shown in Table 2 was prepared, and after uniformly melting and mixing in the range of 100 to 110 ° C. using a kneader. , the particle size was made uniform to pass through 140 meshes, and a dry thickness of 5 was applied to a mild steel plate that was degreased using an electrostatic coating machine.
It was applied to a thickness of 0 to 100 microns, and then baked in a dryer at the temperatures shown in the table, and its physical properties were measured.

In Table 2, AER-664 and AER-667 are both epoxy resins manufactured by Asahi Kasei Industries, Ltd., and each has an epoxy equivalent of 472,955.

In addition, the numbers in each column of formulation in the table indicate parts by weight. Table 3 shows the properties of the coating film obtained.

As described above, when solid resol type phenolic resins outside the scope of the present invention in Reference Examples 3 and 4 were used, the flow during coating film formation was poor, pinholes were formed significantly, and the coating properties were also poor. It was defective.

Comparative Example Using the solid resol type phenolic resins obtained in Reference Examples 3 and 4, a mixture having the composition shown in Table 3 was prepared, and a coating film with a thickness of 50 to 100 microns was prepared in the same manner as in the example. formed.

As described above, in the composition of the present invention, since the softening temperature of the solid resol type phenolic resin used is in the range of 70 to 90°C, kneading with the solid epoxy resin is easy and uniform. A good composition can be obtained, and since the gelation time is as long as 80 seconds or more at 150° C., good flow characteristics can be imparted, and therefore a good coating film can be formed. Furthermore, the composition of the present invention has a temperature of 180°C.
It exhibits fast curing properties, curing in about 0 minutes, and is characterized by providing a coating film with a high degree of crosslinking and good corrosion resistance, adhesion, and flexibility.

Claims (1)

[Scope of Claims] 1. Solid resol type phenolic resin 80 to 80 having a solid epoxy resin of 20 to 80% by weight, a softening temperature of 70 to 90°C, a gelation time of 80 seconds or more at 150°C, and a methylol index of 25 to 45. An epoxy resin composition consisting of 20% by weight. 2. The composition according to claim 1, wherein the solid epoxy resin has a softening temperature of 65 to 140°C.