JPH02147618A - Epoxy resin composition and bonding using it - Google Patents

Abstract

PURPOSE:To make it possible to coat at elevated temp. and to improve adhesiveness and resistance to shower after coating by compounding a liq. epoxy resin, a phenoxy resin, and fine powder of a blocked isocyanate and/or dicyandiamide. CONSTITUTION:100 pts.wt. epoxy resin (a) with a viscosity (at 25 deg.C) of 10-50,000cps, an epoxy equivalent of 100-500, 1.5 or more epoxy groups on average in the molecular and being liq. at ordinary temp. (e.g. bisphenol A type epoxy resin), 10-50 pts.wt. phenoxy resin (b) with an average MW of 10,000-100,000 obtd. by reacting bisphenol A with epichlorohydrin, a curing agent (c) consisting of fine powder of a blocked isocyanate and/or dicyandiamide and, if necessary, a curing accelerator, filler, etc., are compounded together to obtain the title compsn. with a viscosity of 2,000-20,000P at 50 deg.C and 500P or smaller at 100 deg.C and with which an object can be continuously coated by heating it at 80-100 deg.C. After the objects are heat-coated with this compsn., they are jointed and adhered together by heat-curing.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is made by blending a high-molecular-weight phenoxy resin with an epoxy resin that has good adhesive properties to make it highly viscous, and can be applied at high temperatures. The present invention relates to an epoxy resin composition that is capable of retaining its shape and is particularly suitable for temporarily fixing or adhering parts in processes that require shower resistance, wind pressure resistance, etc.

[Conventional technology]

Epoxy resin has excellent properties such as electrical resistance, heat resistance, rust prevention, and adhesiveness, and can be used in various forms such as liquid, paste, sheet, and powder. used in the field.

Epoxy resin adhesives, which are one of the uses of such epoxy resins, are used, for example, for bonding and sealing parts for automobiles and electrical equipment.

In the manufacturing process of parts in various fields, parts are pressed, assembled, and usually coated with a liquid epoxy resin composition that has good workability.Then, in the painting process, after being washed with a hot water shower, the parts are electrodeposited and heated. This is done by baking the paint and curing the composition to complete the bond.

[Problem to be solved by the invention]

However, the hot water shower mentioned above usually weighs 2 to 5 kg/
This is carried out at a shower pressure of about 500 ml, and since the composition has not yet been cured, there is a risk that the composition may drip or flow and fall off due to the showering2, causing problems in terms of adhesion and appearance.

It is also conceivable to use a sheet-shaped epoxy resin composition instead of a liquid one, but this has the drawbacks of poor workability and inability to be applied to parts with complex shapes.

On the other hand, it is possible to control the curing reaction rate by changing the type and amount of the curing agent, and increase the viscosity of the composition by preheating to impart shower resistance. There were disadvantages in that it was difficult to select heating conditions, etc., and the storage stability of the composition was also poor.

[Means to solve the problem]

The inventors of the present invention have conducted extensive research in view of the above circumstances, and have found that by mixing a high molecular weight phenoxy resin with a liquid epoxy resin, a high viscosity composition can be obtained, which can be easily coated into complex shapes by heating. We found that it can withstand showers without preheating.

That is, the present invention comprises (8) 100 parts by weight of an epoxy resin that is liquid at room temperature, (B) 10 to 50 parts by weight of a phenoxy resin having an average molecular weight of 10,000 to 1ooooo, and (C) a blocked isocyanate and a curing agent. An epoxy resin composition containing an appropriate amount of fine powder of dicyandiamide and/or an adhesion method using the same is provided.

The epoxy resin composition of the present invention can be applied to an adherend while heating to form an adhesive layer that does not cause the composition to drip or flow due to external pressure such as a shower, and can be applied in the next heating step. This makes it possible to obtain an adhesive cured layer with superior properties.

Component (A) in the present invention is not particularly limited as long as it is a liquid epoxy resin at room temperature, and usually has a temperature of 10 to 500 at 25°C.
It has a viscosity of 0.00 centipoise. Also, the molecular weight is 2
00 to 1000, the epoxy equivalent is about 100 to 500, and it is sufficient if it has an average of 1.5 or more epoxy groups, preferably an average of 2 or more epoxy groups in one molecule. Further, a one-sided epoxy resin or a rubber component (butadiene-acrylonitrile copolymer, etc.) can also be used in combination within the range where the viscosity after mixing becomes the above-mentioned value.

As specific examples of the above component (A), epoxy resins such as glycidyl type, bisphenol type, hexahydrobisphenol type, novolak type, and dimer acid type can be used alone or in combination of two or more types.

In addition, as component (B), its average molecular weight is 10,000.
~1oooooo, preferably 20,000 to 30,000 phenoxy resin is used. Average molecular weight is 1000
If it is less than 0, the composition will not have a thickening effect; on the other hand, if it is less than 1
If it is 00000 or more, the crosslinking density of the cured product becomes too small (too much, and the general properties deteriorate).

The above molecular weight refers to the number average molecular weight determined by gel permeation chromatography using Boristine as a reference material. Hereinafter, the molecular weight in the fourth invention is also a value determined in the same manner.

The above phenoxy resin is a linear polymer made by reacting bisphenol A and epichlorohydrin, and exhibits excellent properties such as flexibility and impact resistance.

In the present invention, epoxy resin (component (A)) 100
Phenoxy resin (component (B)) 10 to parts by weight
50 parts by weight, preferably 20 to 30 parts by weight.

If it is less than 10 parts by weight, no thickening effect can be obtained by adding the phenoxy resin, while if it is more than 50 parts by weight, the viscosity of the composition becomes too high, making it difficult to apply by heating.

The method of mixing the epoxy resin and the phenoxy resin can be performed by mixing the phenoxy resin in the form of powder.
It is preferable to melt and mix at 50 to 180°C from the viewpoint of thickening effect, properties of cured product, etc.

As component (c), fine powder of incyanate and/or dicyandiamide blocked with a compound that reacts with an epoxy resin, such as a phenol type or an imidazole type, is used. The dissociation temperature of the blocked isocyanate is 100 to 150[deg.] C. After dissociation, the blocked product reacts with the oxirane ring and the hydroxyl group of the side chain, and the isocyanate reacts with the hydroxyl group to be crosslinked.

The amount of the curing agent varies depending on the type and amount of the epoxy resin components (A) and (B) used, as well as the type of curing agent used, and can be set as appropriate. The amount of blocked isocyanate is usually 5 to 10 parts by weight, and the amount of dicyandiamide is usually 5 to 10 parts by weight.
12 parts by weight can be used. If it is below the above range, a sufficient crosslinked structure may not be obtained after the composition is cured, and the properties of the cured product may deteriorate.On the other hand, if it is above the above range, unreacted curing agent may remain after curing. As a result, the durability of the cured product may deteriorate.

Further, in the present invention, when the curing temperature is high and the curing time is long, a curing accelerator can be used in combination within a range that does not impair storage stability. In this case, a part of the curing reaction may proceed during preheating, and the composition may thicken.

Such curing accelerators are not particularly limited, but include, for example, alkyl-substituted guanidine-based, 3-substituted phenyl-1゜1-dimethylurea-based, imidazole-based, imidapurine-based, tertiary amine-based, monoaminopyridine-based, amineimide-based, etc. be able to.

In addition, the epoxy resin composition of the present invention may contain silica, clay, gypsum, Lucium carbonate J1, barium sulfate, quartz powder, glass fiber, within a range that does not impair the properties after painting and heat curing.
Fillers such as kaolin, mica, metal aluminum powder, alumina, hydrated alumina, aluminum hydroxide, talc, doloma, ion, zircon, zinc oxide, titanium compounds, molybdenum compounds, antimony compounds, pigments, anti-aging agents, etc. Generally used additives can also be blended as appropriate depending on the use and desired properties.

When used as an adhesive, an appropriate amount of nylon, vinyl chloride, etc. may be added to improve adhesive properties.

The composition of the present invention can be obtained by adding arbitrary components as necessary to the above liquid epoxy resin, phenoxy resin, and curing agent, and then mixing and stirring the mixture at room temperature to uniformly disperse each component. Can be done.

The epoxy resin composition of the present invention has a viscosity of 200°C at 50°C.
It is in the range of 0 to 20,000 poise and 500 poise or less at 100° C., and can be coated with a commercially available hot-melt coating device used for coating hot-melt adhesives. In this case, it is preferable to heat and melt the coating at a temperature of 80 to 100°C. If the viscosity is lower than this, the viscosity will be too high and coating will be difficult. If it is higher than this, the composition will harden inside the device and clog the nozzle, hose, etc. It may cause.

The present invention also provides an adhesion method that includes a step of applying the epoxy resin composition to an adherend under heat, preferably under the conditions described above, and a step of heating and curing the composition after bonding the adherends together. .

The curing conditions at this time are usually 150-180℃ and 30-60℃.
It takes approximately 0 minutes, and excellent adhesive properties can be obtained.

In addition, the above composition has an adhesive layer on an oil-surface steel plate of, for example, 100 to
After coating to a thickness of 300 μm and bonding the steel plates,
Even when welding at room temperature, the adhesive layer deforms due to pressure.
Can be welded. The welding conditions in this case are that the current is 60
00A~1200OA, pressurizing force 100~300kg
/cnl, and the current application time is preferably 10 to 20 cycles.

Also, after laminating, 2-5 kg / 20-60℃
Since the composition maintains a high viscosity even after showering with hot water comparable to CIJ, it is possible to maintain a good appearance without dripping or protrusion.

Moreover, since the above composition has relatively good compatibility with oil, it is excellent in bonding oil-surfaced steel plates to each other, and can also be used as a structural adhesive. Furthermore, since it has good adhesion to aluminum, glass, etc., it is also used as an adhesive between dissimilar materials such as steel plates and aluminum, glass and aluminum, etc.

〔Effect of the invention〕

Since the epoxy resin composition of the present invention has the above structure, it is possible to form an adhesive layer that can withstand external pressure such as shower pressure or wind pressure simply by applying heat. In addition, in this state, the parts can be moved and transported to the next process, improving work efficiency.

Furthermore, since the above composition uses a curing agent that reacts at high temperatures, it has good storage stability.

The composition of the present invention can be used not only in fields where adhesives have traditionally been used, but also in fields where adhesiveness and sealing properties are particularly required, such as electrical equipment, adhesion of automobile parts, sealing, etc. It can be used effectively in

〔Example〕

Examples and comparative examples of the present invention are shown below.

Parts and % herein refer to Ti amount parts and weight %.

After melt-mixing the epoxy resin and phenoxy resin in advance at 150 to 180°C for 3 hours according to the formulation shown in the table,
A curing agent, a filler, etc. were mixed at 60° C. and dispersed using a twin-screw extruder to obtain adhesives comprising the epoxy resin compositions of Examples 1 to 5 and Comparative Examples 1 to 3.

The composition properties and cured product properties of this adhesive are also shown in the table. The properties of the cured product were evaluated by using an oil-surface steel plate as the adherend and curing it at 180° C. for 30 minutes.

The evaluation method and criteria for each characteristic are as follows.

(1) Measurement was performed at temperatures of 50°C and 100°C using a viscosity increasing flow tester CEF-10OA (manufactured by Shimadzu Corporation).

(2) Apply the above adhesive for 1 m to a steel plate with shower resistance 25X 150X 1 U+
Heat coated at 100℃ to a thickness of 150 x L5
Bonded to 0X L dragon steel plate. This test piece was showered under the following conditions, and the adhesive was observed for dents and dents.

[Shower conditions]

Temperature: 40°C Pressure: 3 kg/cm Time: 1 minute Angle: 45″ from above Distance: 50 cm [Observation criteria] No change −・・−・・−・−−11−−−・−−−−
-0 dents, dents --1 x (3) Spot weldability The above adhesive was applied to an oil surface steel plate (5PCC-SD,
X 25 Xl, 6 win) D150-200. c.
j m(7) Thickness Niloo℃Nite addition 2! ! After coating and bonding, the pressure is 200 kg/c! l! Welding was carried out under the welding conditions of 15 cycles of energization time (6011z) and 7500 A current, and the weldability was evaluated.

Good ・−・・−−−m−−−・−・・−−
−−11−−−・−・−〇possible (spatter occurs, welding possible in 2 times)・・△No electricity ・−・−・−・−・−・・
-・-・−・−・−・−×(4) Storage stability Changes in viscosity and separation of resin were visually observed in an atmosphere of 40° C. for 7 days, and judged according to the following criteria.

Small viscosity change, no separation ----0 Viscosity increased by 3 times or more -・・・・・・× (5) ■ Heavy-duty hot melt melt bricator type 2000 (manufactured by Nordson) was used, and 90 to 100 It was applied to a steel plate at ℃ to see if it could be applied.

(6) Tensile shear adhesive strength According to JIS-K 6850, oil surface steel plate (SPCC-3
Measurements were carried out at 23° C. using a single overlap (D; 25×1.6 tmm).

(7) T-peel adhesive strength: Oil-surfaced steel plate (SPCC-SD; 200X25
The thickness of the adhesive was 0.15 mm, and the measurement was carried out at 23°C.

(Left below) Bisphenol A type epoxy resin average molecular weight: 380, epoxy equivalent: 185-195 Polyethylene glycol glycidyl ether average molecular weight: approximately 4
00, epoxy equivalent 185-215 Phenoxy resin average molecular weight 20000 Phenoxy resin average molecular weight 10000 Dicyandiamide fine powder imidazole blocked incyanate fine powder, dissociation temperature 120°C Imidazole, C6Z fine powder dichlorodimethylurea aluminum powder Aerosil silane cup ring agent

Claims (3)

[Claims] (1) (A) 100 parts by weight of an epoxy resin that is liquid at room temperature, (B) 10 to 50 parts by weight of a phenoxy resin having an average molecular weight of 10,000 to 100,000, and (C) a blocked isocyanate and/or as a curing agent. An epoxy resin composition containing an appropriate amount of fine powder of dicyandiamide. (2) Viscosity is 2000 to 20000 poise at 50℃, 1
The epoxy resin composition according to claim 1, which has a poise strength of 500 poise or less at 00°C and can be continuously applied to an adherend by heating to 80 to 100°C. (3) Adhesion comprising (a) heating and applying the epoxy resin composition according to claim 1 to an adherend, and (b) heating and curing the composition after bonding the adherends together. Method.