Curing agent for resins and resin composition containing the same

Abstract: The present invention provides a curing agent having less odor and providing a cured resin which is excellent in appearance, mechanical properties, water resistance and chemical resistance, and a one-component type humidity-curing resin composition having excellent storage stability and providing a cured matter which is excellent in appearance and physical properties. Specifically, provided are polyaminoamides or ketimines obtainable by dehydration of 2,5- and/or 2,6-bis(aminomethyl)-bicyclo[2.2.1]heptane with carboxylic acids or ketones, a curing agent for epoxy resins using the same and a one-component type humidity-curing epoxy resin or urethane prepolymer composition containing the curing agent

Description: The present invention relates to a novel curing agent for resins, a production process for the same and uses thereof, more specifically to novel polyaminoamide obtained by dehydration-condensation of 2,5-and/or 2,6-bis(aminomethyl)-bicyclo[2,2,1]heptane (hereinafter abbreviated as NBDA) with carboxylic acids, a production process for the same and an epoxy resin composition containing them. Aliphatic polyamines such as ethylenediamine and hexamethylenediamine have so far been used widely for a curing agent for epoxy resins for the reasons that they have large curing rates arid can cause curing at room temperature and that they are liquid and therefore easy to handle. In general, however, aliphatic polyamines have the defects that they have high vapor pressures at room temperature and have an unpleasant odor and strong skin irritation. Further, since they are liable to absorb carbon dioxide in the air to cause whitening, so-called amine brushing, of the cured matter, the appearance of the cured resin is damaged in many cases. In addition thereto, physical properties of the resulting cured resin, such as flexibility, fastness to bend, impact resistance and adhesive property, and water resistance and chemical resistances such as acid resistance are not necessarily high to a sufficient extent. Further, while they have the advantage that they have a high reactivity and can cause rapid curing, the principal component and the curing agent each have to be weighed just before using, and therefore they have had a large problem on workability. Naturally, it has never been possible to use them for applications of a one-component type resin in which a pre-mixture of a principal component and the curing agent is used for the sake of an enhancement in workability or for storage. On the other hand, it is recognized that in general alicyclic polyamines such as isophoronediamine and metaxylenediamine are advantageous from the viewpoint that they have lower vapor pressures and weak stimulation to skin as compared with aliphatic polyamines. However, the preceding defects of the aliphatic polyamines cannot completely be covered. It is shown in DE-A-3,202,491 that curing of a diglycidyl ether type resin of bisphenol with non-modified NBDA which is one of alicyclic polyamines proceeds rapidly at low temperature (50°C or lower) and the cured resin has a high acid resistance. However, if NBDA is actually used for a curing agent in a non-modified form, it produces almost the same defects as those of the aliphatic polyamines described above, and it is not suited for one-component type uses as it is. While aromatic polyamines such as metaphenylenediamine and 4,4'-diaminodiphenylmethane have a small basicity and weak irritation to skin, they have low curing rates, and the majority of them is solid at room temperature. Accordingly, they have the defects that the workability is inferior and it is difficult to handle them. Usually, they do not cause curing at room temperature as it is, and therefore they are applied mainly to hot-setting uses. Accordingly, improvement by various modifications of aliphatic or alicyclic polyamines are usually tried in order to solve these defects. It is described in, for example, JP-A-54-4992 that a suitable reactivity is provided when using for a curing agent for an epoxy resin a compound obtainable by reacting 0.5 to 2.0 moles of a monoepoxy compound or an acrylic compound with 1 mole of NBDA and the resulting epoxy resin can be improved in physical properties. That is, these modified matters have the merit to retard curing at room temperature to improve the workability, and a coated film which is hotset therewith is evaluated to have a good impact resistance, fastness to bend and chemical resistance. However, while curing is retarded at room temperature, the resulting cured resin is insufficient in terms of glossiness, water resistance and chemical resistance and inferior in flexibility and an adhesive property. Further, while curing is retarded, it proceeds in due course, and therefore the above modifications cannot be applied to a curing agent for one-component type resins in which principal components are blended in advance with the curing agent. Some examples in which dicyandiamide, BF 3 -amine complex, adipic acid hydrazide, imidazole derivatives and urea derivatives are used for one-component type latent curing agents for epoxy resins by blending them in advance with epoxy resins are generally known, but they have the defect that heating at a high temperature for a long time is required for curing. Polyaminopolyamides derived from a variety of cyclic polyamines as curing agents for epoxy resins are disclosed in EP-A-654 465. An object of the present invention is to provide a curing agent for resins which has less odor and makes it possible to produce resins having excellent appearance, mechanical properties, water resistance and chemical resistance. The object described above have surprisingly been achieved by finding polyaminoamides obtainable by dehydrate-condensation of NBDA with carboxylic acids, wherein one equivalent of the amino groups in NBDA reacts with 0.05 to 0.80 equivalents of the carboxyl groups in the carboxylic acid and wherein no phosphor-containing dicarboxylic acids are used. The polyaminoamides have less odor, and an epoxy resin cured by using them has excellent appearance, mechanical properties, water resistance and chemical resistance. The present invention relates to: (1) a compound obtainable by dehydration of 2,5- and/or 2,6-bis(aminomethyl)-bicycio[2.2.1]heptane (norbornanediamine; hereinafter abbreviated as NBDA) with carboxylic acids wherein one equivalent of amino group in NBDA reacts with 0.05 to 0.80 equivalent of the carboxyl group in the carboxylic acids specifically, (2) the compound obtainable by dehydration is a polyaminoamide obtainable by the reaction of NBDA with carboxylic acids, more specifically, (3) polyaminoamides obtainable by the reaction of NBDA with polycarboxylic acids having 2 to 5 carboxyl groups in a molecule, (4) polyaminoamides obtainable by the reaction of NBDA with tricarboxylic acids having 3 carboxyl groups in the molecule and having a saturated or unsaturated aliphatic hydrocarbon group having 1 to 60 carbon atoms or an alicyclic hydrocarbon group having 3 to 60 carbon atoms, particularly, (5) polyaminoamides represented by Formula (1), obtainable by the reaction of NBDA with dicarboxylic acids having 2 carboxyl groups in a molecule: wherein R represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 60 carbon atoms or an alicyclic hydrocarbon group having 3 to 60 carbon atoms; n represents an integer of 0 to 2; and the position of two methylene groups bonded to a norbornane ring is either of a 2,5 position or a 2,6 position, and (6) polyaminoamides represented by Formula (2), obtainable by the reaction of NBDA with monocarboxylic acids having one carboxyl group in a molecule: wherein R' represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 60 carbon atoms or an alicyclic hydrocarbon group having 3 to 60 carbon atoms; and the position of two methylene groups bonded to a norbornane ring is either of a 2,5 position or a 2,6 position. Further, the present invention relates to: (7) a curing agent for epoxy resins, characterized by containing any of the polyaminoamides described in the above (2) to (6), (8) the epoxy resin composition containing the curing agent described in the above (7), characterized by being blended so that active hydrogen of an amino group contained in the curing agent is 0.5 to 1.5 equivalents per equivalent of the epoxy groups contained in the epoxy resin to be cured. When the polyaminoamide of the present invention is used as a curing agent for epoxy resins, the curing rate is fast, and the cured matter thereof has excellent appearance and is as well markedly excellent in mechanical properties, water resistance and chemical resistance. NBDA which is the principal raw material for the curing agent for epoxy resins of the present invention can be prepared by publicly known methods, for example, a method in which cyanonorbornene obtainable by reacting dicyclopentadiene with acrylonitrile is reacted with hydrogen cyanide to obtain dicyanonorbornane, and then this is hydrogenated (described in JP-A-3-81255, JP-A-3-95151, JP-A-3-109361, JP-A-3-181446, JP-A-3-232850, JP-A-4-224553 and JP-A-6-184082). Any compound can be used for NBDA used in the present invention as long as the aminomethyl groups contained therein reside in 2,5 position or 2,6 position, and both may be mixed in any proportion. Polycarboxylic acids used in the present invention include monocarboxylic acids or polycarboxylic acids such as dicarboxylic acids and polymerized fatty acids all of which have a saturated or unsaturated aliphatic hydrocarbon group having 1 - 60 carbon atoms, an alicyclic hydrocarbon group having 3 - 60 carbon atoms or an aromatic hydrocarbon group having 6 - 60 carbon atoms, and a mixture thereof. Monocarboxylic acids include, for example, saturated (fatty) acids such as acetic acid, butyric acid and stearic acid, and unsaturated fatty acids such as oleic acid, linoleic acid and linolenic acid. These monocarboxylic acids may be used in the form of a mixture of two or more kinds thereof, and preferred are fatty acids comprising mainly unsaturated fatty acids obtained from natural oil & fats and containing two or more acids described above, that is, tall oil fatty acid, soybean oil fatty acid and linseed oil fatty acid. Polycarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid and dodecanedioic acid, alicyclic dicarboxylic acids such as tetrahydro-phthalic acid and hexahydrophthalic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid, polymerized fatty acids, trimellitic acid, and an adduct of anhydrous castor oil fatty acid and acrylic acid. These polycarboxylic acids may be used in the form of a mixture of two or more kinds thereof or may be used in the form of a mixture with monocarboxylic acids. More preferred polycarboxylic acid is a polymerized fatty acid. This polymerized fatty acid is obtained by polymerizing unsaturated fatty acids such as oleic acid and linoleic acid and is a mixture containing known polybasic acids such as dimer acid (dicarboxylic acid) and trimer acid (tricarboxylic acid) and unreacted monocarboxylic acids. Examples of particularly preferred polymerized fatty acids include a mixture containing 1 to 15 % by weight of monocarboxylic acid having 18 carbon atoms, 75 to 96 % by weight of dimer acid having 36 carbon atoms and 3 to 21 % by weight of trimer acid having 54 carbon atoms. Polyaminoamides of the present invention are obtained usually by charging NBDA and carboxylic acids concurrently and reacting them, wherein the reaction temperature falls in a range of 120 to 250°C, preferably 150 to 250°C. Temperatures lower than 120°C retard the reaction and may therefore not be practical. Temperatures exceeding 250°C cause the reaction to go on quickly, but since the temperature exceeds the boiling point, it may be difficult to carry out the reaction evenly over the whole reactants. With respect to the reaction time, the reaction can be continued until it is completed, and the reaction time depends on the reaction conditions and therefore is not fixed. Usually, it falls in a range of 1 to 10 hours. Polyaminoamides of the present invention can be isolated by distilling off excess NBDA and the reaction solvent if used by distillation under reduced pressure. NBDA is reacted with carboxylic acids in such an equivalent ratio that the product has active amino hydrogens. They are reacted in a range of 0.05 to 0.80 equivalent, preferably 0.1 to 0.5 equivalent of the carboxyl groups of carboxylic acids based on one equivalent of the amino group contained in NBDA. If the reaction is carried out in the range of less than 0.05 equivalent, the resulting product is liable to have strong amine odor, and it may be difficult to obtain the cured matter having excellent mechanical properties, water resistance and chemical resistance if it is used as a curing agent. If the reaction is carried out in the range exceeding 0.80 equivalent, gelation is liable to take place during the reaction, and therefore it may be difficult to handle it. In addition thereto, it is difficult to obtain the good cured matter if it is used as a curing agent, and therefore the cured matter is liable to have deteriorated physical properties. When polyaminoamide of the present invention is used as a curing agent for epoxy resins, it can be used as it is but is usually used in the form of a mixture with NBDA. In this case, NBDA may be added to isolated polyaminoamide. However, since usually excess NBDA is used in synthesis, it is efficient and preferred to omit the step of separating NBDA from polyaminoamide and use the reaction product as it is. Further, the curing agent according to the present invention can be used in combination with other publicly known curing agents, for example, amine adduct curing agents, Michael adduct curing agents, aliphatic polyamines, polyamines having aromatic rings and alicyclic polyamines. In this case, if the amount used of the curing agent according to the present invention is usually 20 % by weight or more based on the weight of the whole curing agent, the objects of the present invention can easily be achieved. Polyaminoamide of the present invention may be used as a curing agent for epoxy resins as it is or can be used as well in combination with curing accelerators such as phenols and tertiary amines, and auxiliaries such as pigments, fillers, extenders, reinforcing agents and inert solvents. Examples of the suitable solvent include aromatic compounds such as toluene and xylene, alcohols such as methanol, ethanol, n-propanol, isopropanol, butanol and benzyl alcohol, and ketones such as acetone and methyl ethyl ketone. They can be used alone or as a mixture thereof. When the solvent is used for the curing agent for epoxy resins containing polyaminoamide of the present invention, the proportion of the solvent is 50 % or less, preferably 30 % or less based on the whole curing agent. If the proportion of the solvent exceeds 50 %, the curing rate of the epoxy resins and the physical properties of the cured matters may be reduced at room temperature or a low temperature because of the excessive proportion of the solvent, and therefore the performances may be insufficient for curing agents. When the curing agent containing polyaminoamide according to the present invention is used for the epoxy resins, the curing agent is blended in such an amount that active hydrogens of an amino group contained in the curing agent falls usually in a range of 0.5 to 1.5 equivalent, preferably 0.8 to 1.2 equivalent per equivalent of an epoxy group contained in the epoxy resin. If the active hydrogens of the amino group are less than 0.5 equivalent, the curing may be insufficient, and the water resistance may be reduced. Meanwhile, if the active hydrogens exceed 1.5 equivalent, the epoxy resin may not be completely cured. In addition, since the active hydrogens of the amino group remains in a large quantity, the water resistance may be Lowered, and therefore such is not preferred. When polyaminoamide of the present invention is used as the curing agent for epoxy resins, curing may be carried out either at room temperature or while heating. The kinds of the epoxy resins for which the polyaminoamides of the present invention can be used as the curing agent may be any one as long as they are epoxy resins having glycidyl groups capable of reacting with active hydrogens and include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, urethane-modified epoxy resins having urethane bonds, novolak type epoxy resins, glycidyl ester type epoxy resins and glycidyl amine type epoxy resins. However, they shall not be restricted thereto. These resins may be a mixture of two or more kinds. When polyaminoamide of the present invention is used as the curing agent for epoxy resins, the resulting resins have excellent curing rates, good appearance and very good flexibility, impact resistance, water resistance, chemical resistance and adhesive property. This can be applied to uses of, for example, paints, civil construction materials, adhesives, casting resins and laminates by using together with the epoxy resins. EXAMPLES Polyaminoamides of the present invention shall be explained below in further detail with reference to referential examples, examples and comparative examples. However, the present invention shall not be restricted thereto. In the following examples, "part", "%" and "ppm" are based on weight. Referential Example 1 (preparation of NBDA) 1) Synthesis of cyanonorbornene 54.2 % of dicyclopentadiene, 45.8 % of acrylonitrile and 500 ppm of hydroquinone as a polymerization inhibitor were mixed, and this mixed solution was continuously fed into a tubular reactor (inner diameter: 8 mm) at a rate of 50 ml/hr, wherein the reaction temperature was controlled to 153°C at a residence time of the reaction solution of up to 5 hours, 170°C at a residence time of up to 7 hours and 180°C at a residence time of up to 9 hours. After this reaction reached a steady state, the reaction was further continued for 20 hours to obtain about 1 liter of crude cyanonorbornene having a purity of 95 %. This was concentrated under reduced pressure to distill off unreacted cyclopentadiene and acrylonitrile, whereby cyanonorbornene of 950 g having a purity of 99.6 % was obtained. 2) Synthesis of dicyanonorbornane A round bottom flask (glass-made; content volume 300 ml; equipped with a stirrer, a thermometer, a nitrogen-introducing tube, a heater and a cooler) was charged with 2.48 g of tetrakis(triphenylphosphite)nickel, 0.27 g of zinc chloride and 2.48 g of triphenylphosphite as catalysts and 240 g of cyanonorbornene obtained as described above, and the space part of the flask was substituted with nitrogen at room temperature. Then, the flask was maintained at 85°C while stirring to dissolve the catalysts. Next, nitrogen gas was introduced into a vessel charged with liquid hydrogen cyanide which is cooled on ice water and bubbled to generate hydrogen cyanide gas. Hydrogen cyanide of a total of 59 g was fed into the solution contained in the flask over the period of 5 hours to react. The reaction liquids obtained by three operations in total with repeating twice the same operation as that described above were blended to obtain crude dicyanonorbornane having a purity of 97 %. Further, this crude dicyanonorbornane was aerated with nitrogen gas at a rate of 500 ml/minute for 1 hour, and then insoluble matters were filtered off. A round bottom flask (glass-made; content volume 2 liters; equipped with a stirrer, a thermometer, a nitrogen-introducing tube, a heater and a cooler) was charged with 800 g of the filtrate thus obtained and 240 g of toluene, and then 160 g of a 8 % sodium hydroxide aqueous solution was added thereto followed by heating at 50°C for 1 hour while stirring. A half of the600 g of the resulting solution was transferred into a separating funnel (content volume: 2 liters), and 680 g of toluene was added to extract dicyanonorbornane. Then, the organic phase containing it was shaken with water of 400 g for washing, and this washing was repeated three times. The balance of the 600 g of the solution was treated in the separating funnel in the same manner as that described above to obtain a toluene solution of about 2400 g in all containing dicyanonorbornane of 33 %. 3) Synthesis of NBDA An autoclave (stainless steel-made, content volume: 3 liters, magnetic stirring type) was charged with 2000 g of the toluene solution containing 33 % dicyanonorbornane obtained above and 13.2 g of a Raney cobalt catalyst, and then 137 g of liquid ammonia was fed thereto. Further, hydrogen was pressed thereinto by applying an initial hydrogen pressure of 70 kg/cm 2 ·G to carry out catalytic hydrogenation at 150°C while stirring. After finishing the reaction, the catalyst was filtered off, and then NBDA was separated from toluene by distillation under reduced pressure to obtain about 600 g of NBDA having a purity of 99.8 %. Example 1 (Synthesis of polyaminoamide (1)) A reactor equipped with a stirrer, a thermometer and a condenser was charged with 154 g of NBDA and 29.2 g of adipic acid, and the temperature was elevated to 160°C under nitrogen atmosphere to carry out the reaction for 2 hours while distilling off condensation water. Then, the temperature was raised to 200°C, and the reaction was further continued for 2 hours. The termination of the reaction was judged by confirming that the distilled amount of condensation water reached the theoretical amount and that carboxylic acid (absorption by a carbonyl group of a carboxylic acid: 1700 cm -1 ) disappeared and polyaminoamide (absorption by a carbonyl group of an amide bond: 1643 cm -1 ) was produced by means of infrared absorption spectrum analysis. Excess NBDA was distilled off from this reaction solution under reduced pressure to obtain polyaminoamide involved in the present invention (hereinafter abbreviated as polyaminoamide (1)) (yield: 97 %). The results of elemental analysis, infrared absorption analysis and mass spectrometry of polyaminoamide (1) are shown below: Elemental analysis C H N Measured value 68.13 10.27 13.28 Theoretical valu 68.86 10.11 13.38 Infrared absorption spectrum: Absorption based on a carbonyl group of an amide bond: 1643 cm -1 Mass spectrometry: [M + H] + = 419 Example 2 (synthesis of polyaminoamide (2)) The reactor was charged with 154 g of NBDA and 119 g of Versadyme 216 (brand name; Henkel Hakusui Co., Ltd.) which is a dimer acid, and the temperature was elevated to 170°C under nitrogen atmosphere to carry out the reaction for 2 hours while distilling off condensation water. Then, the temperature was raised to 200°C, and the reaction was further continued for 2 hours. The termination of the reaction was confirmed in the same manner as that in Example 1, and excess NBDA was distilled off under reduced pressure to obtain polyaminoamide involved in the present invention (hereinafter abbreviated as polyaminoamide (2)) (yield: 95 %). The results of elemental analysis, infrared absorption analysis and mass spectrometry of polyaminoamide (2) are shown below: Elemental analysis C H N Measured value 77.35 11.25 6.50 Theoretical value 77.77 11.79 6.57 Barsadum 216: monomer acid 8 % dimer acid 77 % trimer acid 15 % Infrared absorption spectrum: Absorption based on a carbonyl group of an amide bond: 1644 cm -1 Mass spectrometry: [M + H] + = 836 Example 3 (synthesis of polyaminoamide (3)) The reactor was charged with 154 g of NBDA and 64 g of Aliphat 47 (brand name; Henkel Hakusui Co., Ltd.) which is a monocarboxylic acid, and the temperature was elevated to 160°C under nitrogen atmosphere to carry out the reaction for 2 hours while distilling off condensation water. Then, the temperature was raised to 200°C, and the reaction was further continued for 2 hours. The termination of the reaction was confirmed in the same manner as that in Example 1, and excess NBDA was distilled off under reduced pressure to obtain polyaminoamide involved in the present invention (hereinafter abbreviated as polyaminoamide (3)) (yield: 95 %). The results of elemental analysis, infrared absorption analysis and mass spectrometry of polyaminoamide (3) are shown below: Elemental analysis C H N Measured value 77.33 11.65 6.25 Theoretical value 77.12 12.19 6.71 C 16 saturated monocaboxylic acid 10 % C 18 saturated monocaboxylic acid 55 % C 18 unsaturated monocaboxylic acid (number of double bond: 1) 31 % C 18 unsaturated monocaboxylic acid (number of double bond: 2) 4 % Infrared absorption spectrum: Absorption based on a carbonyl group of an amide bond: 1644 cm -1 Mass spectrometry: [M + H] + = 419, 421 Example 4 The reaction solution of NBDA and adipic acid obtained in Example 1 of 25 parts by weight per 100 parts by weight of Epikote 828 (brand name; Yuka Shell Epoxy Co., Ltd., epoxy equivalent: 190 g/eq) which is a bisphenol A type epoxy resin was used as it was without distilling NBDA off to cure the resin. Example 5 The reaction solution of NBDA and Versadyme 216 obtained in Example 2 of 39 parts by weight per 100 parts by weight of Epikote 828 which is a bisphenol A type epoxy resin was used as it was without distilling NBDA off to cure the resin. Example 6 The reaction solution of NBDA and Aliphat 47 obtained in Example 3 of 27 parts by weight per 100 parts by weight of Epikote 828 which is a bisphenol A type epoxy resin was used as it was without distilling NBDA off to cure the resin. Example 7 55 Parts by weight of another new curing agent prepared by mixing the reaction solution (a mixture of excess NBDA and polyaminoamide (2)) obtained in Example 3 with benzyl alcohol so that a ratio of the reaction solution/benzyl alcohol was 7/3 was used for Epikote 828 of 100 parts by weight which is a bisphenol A type epoxy resin to cure the resin. Comparative Example 1 The same procedure as that in Example 1 was repeated, except that the charged amount of adipic acid was changed to 146 g, but the reaction solution was gelled, and it was impossible to use this as a curing agent. Comparative Example 2 The same procedure as that in Example 1 was repeated to obtain a curing agent, except that the charged amount of adipic acid was changed to 2.9 g. This curing agent of 21 parts by weight per 100 parts by weight of Epikote 828 which is a bisphenol A type epoxy resin was used to cure the resin. Comparative Example 3 20 parts by weight of NBDA per 100 parts by weight of Epikote 828 which is a bisphenol A type epoxy resin was used to cure the resin. Comparative Example 4 23 parts by weight of isophoronediamine, which is an alicyclic diamine, (Vestamin IPD, brand name; Huels Co., Ltd.) per 100 parts by weight of Epikote 828 which is a bisphenol A type epoxy resin was used to cure the resin. The cured matters were prepared in the following manner; each of the curing agents obtained in Examples 1 to 3 and the curing agents obtained in Comparative Examples 2 to 4 was mixed with an epoxy resin and defoamed for 3 minutes under a pressure of 20 Torr; then, the mixture was applied on a cold-rolled steel plate or a glass plate (only for a water resistance test) to a thickness of 200 µm by means of a doctor blade and left for standing at room temperature (25°C) and 80 % RH for 7 days to cure the film, whereby a test piece was prepared. This coated film was evaluated for the following items. 1) Curing rate: An epoxy resin (Epikote 828) and the curing agent were blended in the prescribed amounts under a constant temperature of 25°C. Then, a vessel was charged with 50 g of the mixture and tightly sealed after installing a thermocouple thermometer to determine time (minutes) spent for achieving a maximum temperature of the exothermic reaction. 2) Drying time: According to JIS K-5400, determined was time (hours) spent from immediately after forming the coated film till a dint was not marked or the coated film was not felt to move by nipping strongly the test piece (steel plate) in the center thereof between a thumb and a forefinger and scratches were not marked on the coated film by rubbing repeatedly the center of the coated film quickly with a fingertip. 3) Evaluation of the physical properties of the cured matters ·Pencil hardness: This is based on a pencil scratching test of JIS K-5400.6.14. That is, a lead of a pencil was applied on the coated film of the test piece (steel plate) at an angle of 45°, and the film is scratched with the pencil at a load of 1 kg, wherein the above procedure is repeated five times per one hardness in order from a pencil having a soft hardness, and a hardness at which the film is broken twice or more is recorded. ·Appearance: The surface of the coated film of the test piece is observed with naked eyes to evaluate it by four grades: o ○ well glossy, o glossy, Δ reduced in gloss, × whitening ·Water resistance and chemical resistance: A test piece is dipped in water, an aqueous solution or an organic solvent shown in Table 1 and Table 2 at room temperature for 7 days, and the appearance of the coated film is observed with naked eyes to evaluate it by four grades: o ○ well glossy, o slightly reduced in gloss, Δ a little inferior, × markedly inferior ·Adherence property Evaluation was carried out according to a cross-cut adhesion test of JIS K-5400.6.15. That is, 11 parallel lines each in length and breadth are drawn on the coated film of the test piece at a space of 1 mm by means of a cutter and a cutter guide to mark checkered cuts thereon so that 100 squares are formed in an area of 1 cm 2 . A cellophane adhesive tape is pressed strongly thereon, and the number of squares remaining after peeling the tape off is recorded. ·Flexibility: A steel-made hemi-sphere is pressed against the back face of a test piece having a coated film by means of an Erichsen tester to determine a pushed-out distance (mm) of the hemi-sphere at which cracking and peeling are observed on the coated film. ·Impact resistance: The impact resistance was tested according to JIS K-5400.6.13.3B. A test piece is put between an impact piece which has a radius of 6.35 ± 0.03 mm and is round at the tip thereof and a pedestal having a dent corresponding to the round part, wherein a weight of 500 g is fallen from the upper part, and a height (cm) at which the coated film of the test piece is broken is determined. 3) Adhesion test: An epoxy resin is blended with the curing agent in the prescribed amounts, and then the blended matter is defoamed and applied on two sheets of cold-rolled steel plates (100 mm × 25 mm × 1.6 mm) in an adhesion area of 25 mm × 12.5 mm, followed by curing at 25°C for 7 days to prepare a sample for the adhesion test. The sample is measured for a tensile shear adhesive strength (kgf/cm 2 ). The test results, physical properties of the cured matters and appearance of the coated films are shown in Table 1 and Table 2. Performances of curing agents prepared in Examples 4 to 7 Example 4 5 6 7 Epikote 828 (parts) 100 100 100 100 Curing agent (parts) 25 39 27 55 Curing rate (minutes) 35 28 30 34 Drying time (hours) 5.0 4.5 5.0 3.5 Appearance o ○ o ○ o ○ o ○ Pencil hardness 2H 2H 2H 2H Adherence ( /100) 90 100 100 100 Flexibility (mm) 4.0 6.2 4.8 8.5 Impact test (cm) 30 35 30 >50 Water resistance o ○ o ○ o ○ o ○ Chemical resistance 10 % sodium hydroxide aqueous solution o ○ o ○ o ○ o ○ 10 % sulfuric acid aqueous solution ○ o ○ o ○ o ○ 5 % sodium chloride aqueous solution o ○ o ○ o ○ o ○ Methanol ○ o ○ o ○ o ○ Hexane o ○ o ○ o ○ o ○ Toluene o ○ o ○ o ○ o ○ Tensile shear adhesive strength (kgf/cm 2 ) 70 87 94 138 Performances of curing agents prepared in Comparative Examples 2 to 4 Comparative Example 2 3 4 Epikote 828 (parts) 100 100 100 Curing agent (parts) 21 20 23 Curing rate (minutes) 40 35 77 Drying time (hours) * * 7.0 Appearance Δ Δ ○ Pencil hardness HB Adherence ( /100) 80 80 0 Flexibility (mm) 0.4 0.2 0.1 Impact test (cm) 5 5 5> Water resistance × × Δ Chemical resistance 10 % sodium hydroxide aqueous solution Δ Δ ○ 10 % sulfuric acid aqueous solution × × Δ 5 % sodium chloride aqueous solution × × × Methanol Δ Δ Δ Hexane Δ Δ Δ Toluene Δ Δ Δ Tensile shear adhesive strength (kgf/cm 2 ) 35 31 15

Claims: A compound obtainable by dehydration of 2,5- and/or 2,6-bis(aminomethyl)-bicyclo[2.2.1]heptane (abbreviated as NBDA) with carboxylic acids, wherein one equivalent of the amino groups in NBDA reacts with 0.05 to 0.80 equivalents of the carboxyl groups in the carboxylic acid and wherein no phosphor-containing dicarboxylic acids are used. The compound as described in claim 1, wherein the compound obtainable by dehydration is polyaminoamide obtainable by the reaction of NBDA with carboxylic acids. Polyaminoamide as described in claim 2, obtainable by the reaction of NBDA with polycarboxylic acids having 2 to 5 carboxyl groups in the molecule. Polyaminoamide as described in claim 3, obtainable by the reaction of NBDA with tricarboxylic acids having 3 carboxyl groups in the molecule and having a saturated or unsaturated aliphatic hydrocarbon group having 1 to 60 carbon atoms or an alicyclic hydrocarbon group having 3 to 60 carbon atoms. Polyaminoamide represented by Formula (1) as described in claim 3, obtainable by the reaction of NBDA with dicarboxylic acids having 2 carboxyl groups in a molecule: wherein R represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 60 carbon atoms or an alicyclic hydrocarbon group having 3 to 60 carbon atoms; n represents an integer of 0 to 2; and the position of two methylene groups bonded to a norbornane ring is either of a 2,5 position or a 2,6 position. Polyaminoamide represented by Formula (2) as described in claim 2, obtainable by the reaction of NBDA with monocarboxylic acids having one carboxyl group in a molecule: wherein R' represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 60 carbon atoms or an alicyclic hydrocarbon group having 3 to 60 carbon atoms; and the position of two methylene groups bonded to a norbornane ring is either of a 2,5 position or a 2,6 position. A curing agent for epoxy resins, containing any of the polyaminoamides described in claims 2 to 6. The epoxy resin composition containing the curing agent described in claim 7, characterized by being blended so that active hydrogen of an amino group contained in the curing agent is 0.5 to 1.5 equivalents per equivalent of the epoxy groups contained in an epoxy resin to be cured.

Inventors: ABE TAKEYA, IWAKI TAKESHI, KARASAWA MINATO, SHIMIZU TAKUJI, ABE, TAKEYA, IWAKI, TAKESHI, KARASAWA, MINATO, SHIMIZU, TAKUJI
Applicants: MITSUI CHEMICALS INC, MITSUI CHEMICALS, INC.
Application year: 1996
Main classification: C07C233
IPC codes: C07C251, C08G59, C08L63, C07C233, C08G18