Curing agent for epoxy resins

Abstract

Amine terminated curing agents for curing water based epoxy resins wherein the equivalent weight of active hydrogen is from 85 g to 105 g obtained by reacting polyamine with salicylic acid and subsequently reacting with epoxy resin. The invention also relates to curing compositions, curable systems, and cured compositions and coatings including such curing agents. The cured coatings find application as coatings for floor surfaces, including surfaces where food use approval is required. The cured coatings have particular application for coating the flooring of shipping containers but the use is not so limited.

Claims

1. A curing agent for epoxy resins obtained by the process of: (I) reacting polyamine with salicylic acid wherein the polyamine has two primary amine groups; and (II) reacting the product of (I) with epoxy resin wherein the epoxy equivalent weight (EEW) of the epoxy resin is from 172 g to 210 g and n is from 0.14 to 0.20; to give an amine terminated curing agent wherein the equivalent weight of active hydrogen [EW(H+)] is from 85 g to 105 g.

2. A curing agent according to claim 1 wherein the polyamine is trimethylhexane-1,6-diamine.

3. A curing agent according to claim 1 wherein the polyamine is 45% to 50% by weight isophoronediamine in trimethylhexane-1,6-diamine.

4. A curing agent according to claim 1 wherein the molar ratio of salicylic acid to polyamine is 1:9 to 1:11.

5. A curing agent according to claim 1 wherein the weight ratio of polyamine to epoxy resin is 1.9:1 to 2.1:1.

6. A water based curing composition for a water based epoxy resin composition, said curing composition including an amine terminated epoxy resin curing agent according to claim 1.

7. A water based curing composition for a water based epoxy resin composition said curing composition including: (a) an amine terminated epoxy resin curing agent according to claim 1; (b) butyl glycol ether; and (c) water.

8. A water based epoxy resin coating composition including a water based curing composition according to claim 7.

9. A water based epoxy resin coating composition formed by combining a curable epoxy resin composition (Part A) and a curing composition (Part B) wherein the Part B is a curing composition according to claim 7.

10. A kit for coating a substrate with an epoxy resin coating comprising: a first sealable container containing a curable epoxy resin composition wherein the first sealable container has sufficient free volume to accommodate the required amount of a curing agent or curing composition to cure the resin; and a second sealable container containing an amount of a curing composition according to claim 8, sufficient to cure the curable epoxy resin composition in the first sealable container.

11. A water based epoxy resin coating composition including a curing agent according to claim 1.

12. A kit for coating a substrate with an epoxy resin coating comprising: a first sealable container containing a curable epoxy resin composition wherein the first sealable container has sufficient free volume to accommodate the required amount of a curing agent or curing composition to cure the resin; and a second sealable container containing an amount of a curing agent according to claim 1 sufficient to cure the curable epoxy resin composition in the first sealable container.

Description

EXAMPLES

(1) The following examples illustrate the invention, but are not intended as a limitation thereof.

(2) Salicylic acid, diacetone alcohol, dioctyl phthalate and butyl glycol ether (2-butoxyethanol) are readily available from commercial suppliers.

(3) Bisphenol A epoxy resins, bisphenol F epoxy resins and bisphenolA/bisphenol F epoxy resins with epoxy equivalent weight (EEW) from 172 to 210 g and n of from 0.14 to 0.20 are commercially available. Examples include D.E.R. 331, available from the Dow Chemical Company, EPIKOTE and EPOTUF from Momentive Specialty Chemicals, Araldite from Huntsman Chemical Company and BEKOPDX from Cytec Industries Inc.

(4) The polyamine trimethylhexane-1,6-diamine (TMD) is commercially available from, for example, CTP Polymers and Technologies for Polymers GmbH and Huntsman Chemical Company. Commercially available TMD may comprise a mixture of isomers. For example TMD may include a mixture of 1,6-diamino-2,2,4-trimethylhexane and 1,6-diamino-2,4,4-trimethylhexane.

(5) The polyamine 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophoronediamine) is commercially available from, for example, BASF SE.

(6) Termul 200 is a nonylphenol alkoxylate emulsifier available from the Huntsman Chemical Company.

(7) Additives for epoxy resins such as curing agents, reactive diluents, pigments, defoaming agents, wetting agents, surfactants, emulsifiers, dispersants, fillers, viscosity/flow modifiers and suspension agents are known in the art and are readily available from commercial sources. Examples of commercial manufacturers of additives include Adeka Corporation, BASF SE, BYK-Chemie, Southern Clay Products, Bernd Schwegmann GmbH & Co KG, Dow Chemical Company, Huntsman Chemical Company, Dow Chemical Company, Shell Chemical Company (Momentive Specialty Chemicals) and Dow Corning Corporation.

(8) Physical characteristics such as weight and volume of solids; specific gravity; viscosity; volatile organic compound concentration; pigment concentration; extender concentration; binder concentration; and pigment volume concentration were determined using conventional techniques well known in the art.

Example 1

(9) Preparation of Amine Terminated Curing Agent

(10) Salicylic acid (5.012 kg) was dissolved in butyl glycol ether (15.036 kg). Polyamine [trimethylhexane-1,6-diamine (TMD, 57.64 kg] was added. When the reaction temperature reached >45 C., bisphenol A epoxy resin (EEW from 172 to 210 g, n=0.14-0.20, 11.862 kg) was added. The reaction temperature was allowed to drop to 75-80 C. and a further portion of epoxy resin (3.475 kg) was added. A further four portions of epoxy resin (3.475 kg each) were added. The reaction temperature was allowed to drop to 75-80 C. before the addition of each portion of epoxy resin. The total amount of bisphenol A epoxy resin added was 29.237 kg.

(11) The resulting product was a clear, colourless liquid. The equivalent weight of active hydrogen [EW(H+)] was 90-95 g.

(12) Variation of the amount of salicylic acid by +/2.5% or butyl glycol ether by +/2.5% has no appreciable effect on the properties or performance of the resulting curing agent.

(13) Variations of the amine terminated curing agent of Example 1 have been prepared using the same method as described in Example 1 with the partial replacement of 45% to 54% of the trimethylhexane-1,6-diamine by isophoronediamine.

Example 1A

(14) Preparation of Amine Terminated Curing Agent

(15) An amine terminated curing agent was prepared in accordance with the method of Example 1 using a mixture of 53.3% trimethylhexane-1,6-diamine and 46.7% isophoronediamine instead of 100% trimethylhexane-1,6-diamine.

(16) The particular form of amine terminated curing agent produced using the 53.3% trimethylhexane-1,6-diamine and 46.7% isophoronediamine polyamine mixture imparts particularly good physical properties when used as a curing agent for epoxy resins as described herein.

(17) The curing agent of Examples 1 and 1A have application as curing agents for epoxy resins. A curing agent according to the present invention can be combined, if desired, with other curing agents to modify properties of the curable resin such as curing rate and curing temperature or optimise certain properties of the cured resin such as adhesion, flexibility and chemical resistance. The curing agent can be formulated as a curing composition of a two part epoxy resin system. The curing agents of Examples 1 and 1A can be formulated as a water based curing composition.

Example 2

(18) Preparation of Water Based Curing Composition (Hardener, Part B) Termul 200 (emulsifier, 8 kg) was melted and added under stirring to the product of Example 1. Water (94.982 kg) was added, followed by butyl glycol ether (47.034 kg), Dowanol PnB (diluent, 5.612 kg), Schwego Fluor 6238 (surfactant, wetting agent, 0.281 kg), Schwego Flow 8058 (flow aid, 2.806 kg) and Dow Corning Additive 65 (defoamer, 0.112 kg).

(19) Total mass of water based curing composition: 261.71 kg; volume: 272.558 Liters; specific gravity (25 C.) 0.9604.

(20) Accordingly, the curing composition (Part B) comprises the following:

(21) (Percentages are by Weight)

(22) 1. Butyl glycol ether (15.036 kg, 5.744%);

(23) 2. Salicylic acid (5.012 kg, 1.915%);

(24) 3. Trimethylhexane-1,6-diamine (57.640 kg, 22.019%);

(25) 4. Bisphenol A epoxy resin (29.24 kg, 11.17%);

(26) 5. Termul 200 (8.0 kg, 3.056%);

(27) 6. Water (90.998 kg, 34.762%);

(28) 7. Butyl glycol ether (47.037 kg, 17.969%);

(29) 8. Dowanol PnB (5.612 kg, 2.144%);

(30) 9. Schwego Fluor 6238 (0.281 kg, 0.107%);

(31) 10. Schwego Flow 8058 (2.806 kg, 1.072%); and

(32) 11. Dow Corning Additive 65 (0.112 kg, 0.043%).

(33) Weight of solids: 38.696%; Volume of solids: 38.317%; Specific gravity (25 C.): 0.9604 g/cm.sup.3; Volatile organic compound content: 248.332 g/L.

Example 2A

(34) Preparation of Water Based Curing Composition (Hardener, Part B)

(35) A water based curing composition (Hardener, Part B) was prepared in accordance with the method of Example 2 using the product of Example 1A prepared from a mixture of 53.3% trimethylhexane-1,6-diamine and 46.7% isophoronediamine instead of 100% trimethylhexane-1,6-diamine.

(36) The Part B (hardener) of Example 2A has enhanced shelf stability in addition to good low temperature curing properties.

(37) It will be appreciated that variation in the ratios of components can alter characteristics of the curing compositions (Part B) of Examples 2 and 2A and subsequent curable compositions and cured coatings. No significant effect on the properties of Part B would be expected if the component ratios are varied within 1%.

(38) Wetting agent/surfactant Schwego Fluor can be replaced by surfactant BYK 349 without affecting the properties of Part B.

(39) The curing compositions (Hardeners) of Examples 2 and 2A have application in curing water based epoxy resins.

Example 3

(40) Preparation of Water Based Epoxy Resin (Part A)

(41) The following were added in the given order under high shear mixing:

(42) (Percentages are by Weight)

(43) 1. Bisphenol A epoxy resin [EEW 172 to 210 g, n=0.14-0.20], (200 kg, 22.415%);

(44) 2. Adeka ED523T (reactive diluent), (30 kg, 3.362%);

(45) 3. Di octyl phthalate (6 kg, 0.672%);

(46) 4. BYK 022 (defoamer) (2.5 kg, 0.280%);

(47) 5. Butyl glycol ether (solvent) (12 kg, 1.345%); and

(48) 6. Schwego Fluor 6238 (wetting agent) (2.5 kg, 0.280%).

(49) The mixture was mixed at high speed for 10 minutes.

(50) 7. Termul 200 (emulsifier) (13.5 kg, 1.513%) was heated until liquid and added.

(51) The mixture was mixed at high speed for 10 minutes.

(52) 8. Water (13 kg, 1.457%) was added over a period of 15 minutes and the emulsion was allowed to stabilize for 30 minutes.

(53) The following components were then added slowly in the following order:

(54) 9. Black oxide powder BA33 (60 kg, 6.725%));

(55) 10. Red oxide powder RA11 (30 kg, 3.362%);

(56) 11. Yellow oxide powder (30 kg, 3.362%);

(57) 12. Minbar 45B (barium sulphate), (125 kg, 14.01%);

(58) 13. Silica 300 g (silicon dioxide) (200 kg, 22.416%); and

(59) 14. Attagel 50 (rheological modifier) (13 kg, 1.457%).

(60) The mixture was dispersed at high speed for 20 minutes.

(61) The following components were premixed then added slowly to the bulk:

(62) 15. Diacetone alcohol (7 kg, 0.785%);

(63) 16. Butyl glycol ether (20 kg, 2.242%); and

(64) 17. Water (123.734 kg, 13.868%).

(65) Finally the following components were added:

(66) 18. Optiflow H600 (1 kg, 0.112%); and

(67) 19. Optiflow L100 (3 kg, 0.336%).

(68) Total mass of water based epoxy resin composition: 892.234 kg; volume: 545.117 Liters; weight of solids: 79.721%; volume of solids: 65.947%; specific gravity (25 C.): 1.636775 g/cm.sup.3; volatile organic compound content: 71.544 g/L; Pigment concentration 220.136 g/L; extender concentration: 596.202 g/L; binder concentration: 421.928 g/L; pigment volume concentration: 50.448 cm.sup.3/L.

(69) It will be appreciated that variation in the ratios of components can alter characteristics such as rheology or flow of the coating composition in addition to altering the degree of opacity of the cured coating and affect the rheology.

(70) Variations of component ratios within the following limits should not affect the properties of Part A:

(71) epoxy resin +/2.5%;

(72) reactive diluent +/2.5%;

(73) other liquids +/5%;

(74) powders +/10%;

(75) pigment +/5%; and

(76) water +/5%.

(77) Wetting agent/surfactant Schwego Fluor can be replaced by surfactant BYK 349 without affecting the properties of Part A.

(78) Part A (140 ml) and Part B (70 ml) when mixed to form a curable epoxy resin composition has a working time of approximately 40-50 minutes. The curing time of the coating is approximately 12 hours in ambient conditions of 5 C. to 40 C. and high humidity.

Example 4

(79) Preparation and Application of Water Based Coatable Epoxy Resin

(80) Part A (Example 3) and Part B (Example 2) were mixed in the ratio of 2:1 by volume. Mixing was achieved by mechanical mixing, or by hand mixing using a flat stirrer.

(81) Weight of solids: 70.415%; volume of solids: 56.738%; specific gravity (25 C.): 1.411 g/cm.sup.3; viscosity (25 C., Ford cup #4): 79.9 s; viscosity (25 C., Ford cup #5): 57.5 s; volatile organic compound concentration: 130.476 g/L: pigment concentration: 146.757 g/L; extender concentration: 397.468 g/L; binder concentration: 387.534 g/L; pigment volume concentration: 33.632 g/L.

(82) The curable coating resin thus formed was applied to a timber floor of a shipping container using a squeegee/spike roller or a lambswool roller.

(83) The butyl glycol ether solvent evaporates from the coating, and forms an azeotrope to remove residual water. This provided an opaque brown epoxy coating of approximately 90 micron dry film thickness. This is sufficient to cover stains and fill screw holes and other minor irregularities in the floor surface. The formulation cured overnight (approximately 12 hours) to give a hard film. Overnight curing was achieved at temperatures from 5 C. to 40 C.

Example 4A

(84) Preparation and Application of Water Based Coatable Epoxy Resin

(85) Part A (Example 3) and Part B (Example 2A) were mixed in the ratio of 2:1 by volume and applied to a timber floor of a shipping container according to the method described in Example 4.

(86) After overnight curing the coatings of Example 4 and Example 4A can withstand forklift traffic and mechanical wear and tear. After five days the coatings exhibit optimum mechanical properties. The coating of Examples 4 and 4A seal, colour and protect the timber flooring.

(87) The cured coatings are flexible, non-flaking, chemical resistant and tough. The cured coatings withstand the passage of a vehicle such as a fork lift truck during loading and unloading of the shipping container. The resulting cured coatings are believed to be suitable for food contact in accordance with the requirements of the US Food and Drug Administration in accordance with the Code of Federal Regulations Title 21, Volume 3, Part 175, section 300 (Resinous and Polymeric Coatings).

(88) The water based coatable epoxy resin of Example 4A has superior physical properties which further facilitate easy application by roller. The resin also has superior curing properties.

(89) The advantageous properties of the curable coating resin and the cured coatings are believed to be attributable, at least in part, to the amine terminated curing agents of the present invention.

(90) Approximately 2.8 liters of a curable water based epoxy resin coating composition prepared by combining one part (by volume) of Part B (Example 2) and two parts (by volume) of Part A (Example 3) will coat the timber floor of a 20 foot shipping container (approximately 14 m.sup.2) to a dry film thickness of 90 microns in a single coat.

(91) A 2.8 liter kit for coating the floor of a 20 foot shipping container includes a sealable container of a volume of at least 3 liters containing 1.867 liters of Part A (Example 3) and a sealable container containing 0.933 liters of Part B (Example 2).

(92) Part B is added to the container of Part A and the mixture is mixed mechanically or by hand to give a water based curable epoxy resin coating composition. This coating composition is then applied to the floor of a 20 foot shipping container using an applicator such as a squeegee or lambswool roller. This volume is sufficient to cover the floor of the container (approximately 14 m.sup.2) to a 90 micron dry film thickness without wastage.

(93) Similarly, two 2.8 liter kits can be used for coating the floor of a 40 foot shipping container.

ADVANTAGES

(94) An advantage of the preferred embodiment of the present invention is that the amine terminated curing agent is suitable for formulating in a water based curing composition which can be used to cure water based epoxy resin coating systems.

(95) The amine terminated curing agent is believed to impart good physical properties when formulated as a curing composition for water based epoxy resins. Epoxy resin coating compositions as described herein including the curing agent have superior properties which facilitate easy application by roller. The applied coatings have good curing characteristics under a variety of environmental conditions. The resulting cured coatings have good physical properties.

(96) The epoxy resin coating system according to the preferred embodiment is suitable for coating in conditions of high relative humidity and, unlike solvent based polyurethane resins, is not sensitive to blushing. The coating system is applicable over a wide range of temperatures and is completely curable down to ambient temperatures of 5 C.

(97) An advantage of the preferred embodiment of the water based epoxy resin coating is that a floor substrate of a shipping container can be refurbished quickly and economically under a wide variety of environmental ambient conditions. The shipping container is out of circulation for a short period of time.

(98) The coating resin is simple to mix and apply. No specialised training is required.

(99) The level of personal protective equipment required is lower than would be required for a solvent based coating system.

(100) The preferred embodiment of the coating resin can be applied to a timber floor using a roller or squeegee. A coating of sufficient thickness can be achieved with a single coat applied with a roller, so multiple coats are not required to achieve the required degree of coverage. Although the coating can be applied by spraying, there is no need for spray application. Accordingly it is not necessary to tape up the walls of the container to protect them from overspray.

(101) The applied coating is quick to cure. There is a sufficient degree of curing overnight to allow passage of forklift traffic over the floor of the shipping container without causing damage to the coated floor surface. This further minimises the time that the container is out of circulation and unavailable for use.

(102) There is a low VOCC (volatile organic compound content) associated with the coating process using the preferred embodiment of the water based coatable epoxy resin of the present invention. It is a low emission process. There is no perceptible residual or lingering odour after overnight curing.

(103) The applied coating adheres to various grades and types of timber, so it is suitable for use on mixed timber flooring commonly found in container floors. The coating also adheres to aluminium alloy commonly used for flooring of refrigerated shipping containers.

(104) The cured coating provides a sealing and protective surface to the substrate. In a preferred embodiment the coating can be coloured.

(105) The cured coating is flexible, non-flaking, chemical resistant and tough. It is suitable for use in containers for food transportation such as shipping containers and food delivery trucks. The curable coating resin is also suitable for other applications, and can be used to coat surfaces such as flooring of food preparation areas, abattoirs and the like.

(106) The advantageous handling and application properties of the curable coating resin, the curing properties and the physical properties of the cured coating are believed to be attributable, at least in part, to the amine terminated curing agents of the present invention.

(107) A two part water based epoxy resin may be provided in a kit form with sufficient quantities of Part A and Part B to coat the floor of a 20 foot shipping container to the correct coating thickness. No measuring of the components is required, and there is no waste resin or resin components to store or dispose of. The mixing process is simple and requires no measuring. The application process is straightforward and requires no specialised skills or training.

VARIATIONS

(108) It will of course be realised that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein set forth.

(109) Throughout the description and claims of this specification the word comprise and variations of that word such as comprises and comprising, are not intended to exclude other additives, components, integers or steps.