JPH04145185A - Structural adhesive - Google Patents

Abstract

PURPOSE:To obtain the subject one-pack type thermally curable adhesive exhibiting high peel strength even in cold district by compounding a latent curing agent to an epoxy resin component composed of a urethane-modified epoxy resin and a rubber-modified epoxy resin, etc. CONSTITUTION:The objective adhesive is produced by compounding (A) a latent curing agent selected from dicyandiamide, isophthalic acid dihydrazide, melamine derivative, etc., to (B) an epoxy resin component composed of (i) 50-80wt.% of a urethane-modified epoxy resin produced by reacting a polyether triol with a polyisocyanate compound and reacting the resultant urethane prepolymer having terminal isocyanate group with an epoxy resin having one or more hydroxyl groups, (ii) 10-40wt.% of a rubber-modified epoxy resin produced by reacting acrylonitrile-butadiene rubber or rubber particle with a bisphenol epoxy resin and (iii) the remaining part of a bisphenol F epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a structural adhesive, more specifically, a one-component thermosetting adhesive that can be applied to a welt bonding method in an automobile body assembly line, for example, In particular, it relates to a structural adhesive that exhibits excellent adhesive peel strength even in cold regions.

Problems to be Solved by Prior Art and the Invention On automobile body assembly lines, a weld bonding method that uses a combination of adhesive bonding and spot welding is used to improve the rigidity of the car body structure and provide vibration damping properties. Typically, epoxy resin-based structural adhesives are used.

However, in the driving environment of automobiles, there is no particular problem with adhesive peel strength in warm to tropical regions, but -10 to -
When running in a cold region of 30 degrees Celsius or lower, the adhesive peel strength was extremely reduced, posing two problems for practical use.

Means for Solving the Problems The inventors of the present invention have carried out extensive studies on epoxy resin-based structural adhesives that can address these problems. The inventors have discovered that a desired structural adhesive can be obtained by blending the above agents, and have completed the present invention.

That is, the present invention provides (a) a urethane-modified epoxy resin in which an epoxy resin having at least one hydroxyl group in one molecule is reacted with a urethane prepolymer containing terminal isocyanate groups, which is obtained by reacting a polyether triol with a polyisocyanate compound; 50 to 80% (by weight, the same applies hereinafter), (t) 10 to 40% of a rubber modified epoxy resin obtained by reacting acrylonitrile-butadiene rubber or rubber particles with a bisphenol type epoxy resin, and (c) the remaining amount of bisphenol F type. The present invention provides a structural adhesive characterized in that (d) a latent curing agent is blended into an epoxy resin component made of an epoxy resin.

In the present invention, the urethane-modified epoxy resin of the above component (a) is produced by reacting polyether triol with an excess amount of a polyisocyanate compound to produce a urethane prepolymer containing free isocyanate groups at the terminals (hereinafter referred to as terminal NG).
It is produced by obtaining an OH prepolymer) and reacting it with an epoxy resin having at least one hydroxyl group in one molecule (hereinafter referred to as an OH epoxy resin).

The polyether triol (i.e., polyoxyalkylene ether triol) is one of the low molecular weight active hydrogen compounds having three active hydrogen atoms (for example, triols such as glycerin, trimethylolpropane, and 1°2.6-hexanetriol). Polyoxyethylene-propylene triol is a random or block copolymer obtained by ring-opening polymerization of propylene oxide and ethylene oxide in the presence of one or more species.

Examples of the polyisocyanate compound include trimethylene diisonanate, tetramethylene diisonanate, hexamethylene diisocyanate, bentamethylene diisocyanate, 2°44- or 2244
Rimedyl hexylylene diisocyanate, dodecamethylene diisocyanate, 1,3-cyclobentanediisocyanate, 16-hexane diisocyanate (1-1
DI), 1,4-cyclohexane diisocyanate, l
.

3-cyclohexane diisocyanate, 4.4 methylene bis(cyclohexyl isocyanate), methyl 2.4
-Cyclohexane diisocyanate, methyl 2,6-cyclohexane diisocyanate, 1,4-bis(isocyanatemethyl)cyclohexane, I 3-bis(isocyanatemethyl)cyclohexane, m-phenylene diisonanate, p-phenylene diisonanate, 4
．． 4-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4.4°-diphenylmethane diisocyanate (MDI), 2.4- or 2.6-)lylene diisocyanate, 4.4°-toluidine diisonanate, aninone diisocyanate , 4°4°-diphenyl ether diisonanate, l.

3- or 1,4-xylylene diisocyanate, ωω
'-diisocyanate 1,4-diethylbenzene and the like.

As the above 0)1 epoxy resin, for example, 2゜2-
Examples include diglycidyl ether of bis(4-hydroquinophenyl)propane [bisphenol A] and diglycidyl ether of aliphatic polyhydric alcohol.

1. When reacting the polyether triol and the polyisocyanate compound, the ratio of the two is usually set so that the isocyanate group of the latter is 1.2 to 3 equivalents to the hydroxyl group of the former, and the temperature is 60 to 120°C under a nitrogen atmosphere. , the reaction may be carried out for 1 to 6 hours. In addition, when reacting the terminal NCO prepolymer with the O■-1 epoxy resin, the ratio between the two is usually set so that the amount of hydroxyl groups in the latter is equal to or higher than that of isocyanate groups in the former (preferably 2 to 5 equivalents). Then, the reaction is continued at a temperature of 80 to 110°C until the reaction between the isone anate group and the hydroxyl group is completed.

In the present invention, the rubber-modified epoxy resin as the component (b) is a mixture of acrylonitrile-butadiene rubber or rubber particles and a bisphenol-type epoxy resin at a weight ratio of 15 to 41, preferably 13 to 3:2, and a 80 to 180° It is produced by reacting at a temperature of C.

The above-mentioned acrylonitrile-butadiene rubber or rubber particles have molecules fi in which an average of 1.5 to 25 carboxyl groups per molecule are bonded pendantly to the main chain skeleton.
A copolymer of 2000 to 6000 is used. Note that the rubber particles are obtained by drying rubber latex by a method such as a spray drying method or a flash drying method.

Examples of bisphenol-type epoxy resins include diglycidyl ether of bisphenol A1 bisphenol F1 brominated bisphenol A1 hisphenol AD, diglycidyl ether of alkylene Oquindo adduct of bisphenol A, and the like.

The epoxy resin components used in the present invention include the above (a) and (b).
It is composed by adding bisphenol F type evoquino resin as component (c) to the components, and the blending ratio of these is as follows:
(a) lff1 min 50-80%, (b) component lO-40
%, and the remainder is selected as component (c). (
If the content of component a) is less than 50%, the cold peel strength will decrease, and if it exceeds 80%, the peel strength will decrease in normal conditions. (
When component b) is less than 10%, the peel strength decreases, and when it exceeds 40%, the viscosity increases and workability deteriorates. Note that component (c), bisphenol F type, has a diluting effect, and if, for example, hisphenol A type is used instead, the viscosity increases and workability deteriorates, which is not desirable.

As the latent curing agent (d) used in the present invention, 100 to
Those activated in the temperature range of 200° C. may be used, such as nanodiamide, 44′=diaminodiphenylsulfone, imidazole or its derivatives (2-
n-heptanedecyl imidazole, etc.), isophthalic acid hydrazide, N,N'-dialkyl urea derivatives, N,
Examples include N-dialgyldiourea derivatives and melamine derivatives, and one or a mixture of two or more of these may be used. The amount of the latent curing agent is usually 5 to 2 parts per 100 parts (parts by weight, hereinafter the same) of the above epoxy resin component.
The amount may be selected within the range of 0 parts, preferably 5 to 15 parts.

If it is less than 5 parts, curing will be insufficient, and if it exceeds 20 parts, the cured product will become brittle and adhesive strength will tend to decrease.

The structural adhesive according to the present invention is constituted by blending the epoxy resin component (a=c) and the latent curing agent (d) in the above-mentioned predetermined proportions, but if necessary, ordinary additives such as Fillers (calcium carbonate, clay, silica,
talc, etc.), rust preventive materials (aluminum dihydrogen tripolyphosphate di-tetrahydrate, zinc phosphate, etc.), conductive materials [
- Killing: MeO.

Feto 3 (Me is Mn, Ba, Co, Sr, Pb
, divalent metals such as Zn, Mg, Cd, etc.) sintered metal oxide-iron oxide composite ferrite or α-Fetu
s particle powder + Ma ai +, Gu-? l :3
r'+ ImarL8 - ^ 7 - ,, voice c
11. Appropriate amounts of metal powders, oxidized metal powders such as ruthenium oxide, bismuth oxide, and iridium oxide, carbon black, graphite powder, silver-coated glass powder, etc.], plasticizers, solvents, etc. may be blended.

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

Examples 1 to 4 and Comparative Examples 1 to 5 After kneading the components in the parts shown in Table 1 below in a Nei-Goo, the mixture is passed twice through a three-roll roll and defoamed and stirred in the Nei-Goo again to prepare an adhesive.

(Margins below) Table 1 Note ■) As a polyether triol, 00 parts of polyoxypropylated glycerin (molecule ff 1450) and 118 parts of tolylene diisocyanate were mixed in a flask purged with nitrogen, heated to 80°C, and heated for 4 hours. The reaction is carried out with stirring to obtain a terminal NCO prepolymer.Next, 100 parts of diglycidyl ether of bisphenol A (epoxy equivalent: 215, hydroxyl equivalent: 900) is added to 25 parts of this prepolymer.
Epoxy equivalent weight 22
0 urethane modified epoxy resin.

■) Polytetramethylene ether glycol (molecule fi
100 parts of tolylene diisocyanate (100 parts) and 35 parts of tolylene diisocyanate are mixed in a flask purged with nitrogen, heated to 80°C, and reacted with stirring for 3 hours to obtain a terminal NCO prepolymer. Next, diglycidyl ether of bisphenol A (epoxy equivalent: 21 parts) was added to 45 parts of this prepolymer.
5. A urethane-modified epoxy resin with an epoxy equivalent of 200, which was prepared by adding 250 parts of hydroxyl equivalent (900) and reacting at 95°C for 7 hours.

■) In a flask equipped with a stirrer, a thermometer, and a condenser, 80 parts of bisphenol A type epoxy resin (manufactured by Yuka Shell Co., Ltd., Epicoat 807) with an epoxy equivalent of 215 and carboxylated acrylonitrile-butadiene rubber latex (large Luckstar 65 manufactured by Nippon Ink Chemical Industry Co., Ltd.
41G) with 20 parts of acrylonitrile-butadiene rubber particles obtained by a spray drying method, and 1208C
After 6 hours of reaction, the acid value was 0.2 and the epoxy equivalent was 450.
A rubber-modified epoxy resin is obtained.

■) The adhesives of Examples 1 to 4 and Comparative Examples 1 to 5 of "Ebiko 1-807" manufactured by Yuka Shell Co., Ltd. were subjected to the peel adhesion test shown below, and the results are shown in Table 2. .

Peel adhesion test JIS G3141 steel plate (0.8x25x150
After degreasing the surface of yx) with toluene and applying an adhesive to the surface, stack steel plates with similar degreased surfaces and pressing them together to give an adhesion area of 25 CJ.Heat harden at 180°C for 20 minutes to prepare a sample. Such samples were heated at room temperature (20°C) and at high temperature (
Using Autograph (Shimadzu Corporation, DOS-5000), the 90° peel strength of the sample was measured at a tensile rate of 20011+/min, Ckg・f/25, while holding the sample at 80°C) or cold temperature (-30°C). xff) ~ Note that a cold peel strength of 20 to 9.1725 m+++ or higher is considered acceptable.

Table 2

Claims (1)

[Claims] 1. (a) Urethane modification in which a urethane prepolymer containing a terminal isocyanate group, which is obtained by reacting a polyether triol and a polyisocyanate compound, is reacted with an epoxy resin having at least one hydroxyl group in each molecule. Consisting of 50-80% by weight of an epoxy resin, (b) 10-40% by weight of a rubber-modified epoxy resin obtained by reacting acrylonitrile-butadiene rubber or rubber particles with a bisphenol-type epoxy resin, and (c) the remaining amount of a bisphenol F-type epoxy resin. A structural adhesive characterized by blending (d) a latent curing agent into an epoxy resin component. 2. The structural adhesive according to claim 1, wherein 5 to 15 parts by weight of a latent curing agent is blended with 100 parts by weight of the epoxy resin component.