Method Of Manufacturing Moisture-Cure Resin Composition

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a moisture-cure resin composition, to a moisture-cure resin composition preferably but not necessarily exclusively formed in accordance with the method, and to a paint, coating, composite, potting compound, or adhesive product comprising the moisture-cure resin composition.

BACKGROUND

It is known in the art that epoxy resins react with amines as hardeners, forming a three- dimensional network according to the following reaction scheme:

This reaction can be accelerated by the addition of accelerators. Such accelerators have a number of disadvantages. For example, trisdimethylaminomethylphenol (Ancamine K- 54 from Evonik (RTM)) or 1.2 aminoethylpiperazine, also known as AEP (Accelerator 399 from Huntsman (RTM)) are sensitive to light. Acids such as salicylic acid, paratoluene sulfonic acid, or boron trifluoride are also accelerators, but have a poor toxicological and environmental profile.

In the art, many such resin compositions are formed via isocyanate-containing intermediates, which are highly toxic. Moisture-cure resin compositions have difficulty curing when the layer thickness is too great. Typical maximum resin layer thickness is of the order of 100pm. Such resin compositions also have low chemical resistance properties, and therefore can be difficult to use in corrosive or similar environments.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to develop a moisture-cure resin composition having improved chemical and mechanical properties.

According to a first aspect of the invention, there is provided a method of producing a moisture-cure resin composition, the method comprising the steps of: preparing a hydroxy alkyl urethane modifier having the formula: where:

R ¹ is an amine residue; and

R ² and R ³ are the same or different and are selected from the group consisting of H, alkyl, and hydroxyalkyl; reacting the hydroxy alkyl urethane modifier with an epoxy silane to form a silane- modified hydroxy alkyl urethane; and reacting the silane-modified hydroxy alkyl urethane with a silyl terminated polyether to form a moisture-cure resin composition.

A moisture-cure resin composition of the type outlined here has many favourable attributes. For example, the composition has a high refractive index, close to that of glass, and can therefore be used without creating deleterious aesthetics issues. Furthermore, the composition has improved adhesion properties when compared with existing resins, particularly for adhesion to steel, glass, and ceramics. The composition is more flexible than traditional cured resins and has an improved chemical and mechanical resistances. There is good solvent resistance to xylene, MIBK, acetone, and white spirit. It is also able to be cured at thicknesses in excess of 100pm, which has been difficult to achieve for urethane-based resin compositions in the past. Optionally, during step b], the epoxy silane may be selected from the group comprising: (3-glycidoxypropyl)trimethoxysilane; (3-glycidoxypropyl)triethoxysilane; (3- glycidoxypropyl)methyldiethoxyilane; 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

Preferably, during step b], the epoxy silane may be reacted with the hydroxy alkyl urethane modifier in an equivalent weight ratio of 1 :1.

Optionally, during step c], the silyl terminated polyether may be a low-viscosity silyl terminated polyether.

During step c], the silyl terminated polyether may be selected from the group comprising: dimethoxy(methyl)silylmethylcarbamate-terminated polyether; and trimethoxy(methyl)silylmethylcarbamate-terminated polyether.

Preferably, during step c], the modified hydroxy alkyl urethane may be reacted with the silyl terminated polyether in an equivalent weight ratio of at least 1 :1.5.

Optionally, during step c], a catalyst may be used. The catalyst may comprise an amino silane, such as N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane.

Preferably, during step a], the hydroxy alkyl urethane may be prepared by reaction of a primary amine with a monocyclocarbonate.

The monocyclocarbonate may be selected from the group comprising: ethylene carbonate; 1 ,2-propylene carbonate; 1 ,2-butylene carbonate; 2,3-butylene carbonate, 1 ,2-pentylene carbonate; and 1 ,2-glycerol carbonate.

Optionally, the primary amine and monocyclocarbonate may be mixed in an equivalent weight ratio of between 1 : 1 and 1 :1.1.

The primary amine may be selected from the group comprising: 2, 2, -(2 ,2 ,4)-trimethyl- 1 ,6 hexanediamine; 1 ,6-hexanediamine; 2-methyl-1 ,5 pentanediamine; meta-xylene diamine; 1 ,3-bis(aminomethyl) cyclohexane; isophorone diamine; cyclohexane diamine; 4,4’-diaminodicyclohexyl-methane; polyoxypropylene diamines; polypropoxypropylene triamines; and phenalkamines with a ratio of between 1 :3 and 1 :4.

In a preferred embodiment, the modified hydroxy alkyl urethane modifier may be formed without any isocyanates or isocyanate-containing intermediates.

Preferably, the hydroxy alkyl urethane modifier may be provided in a ratio of between 20 parts to 40 parts by weight of the moisture-cure resin composition.

Preferably, the epoxy silane may be provided in a ratio of between 20 parts to 40 parts by weight of the moisture-cure resin composition.

Preferably, the silyl terminated polyether may be provided in a ratio of between 20 parts to 60 parts by weight of the moisture-cure resin composition.

According to a second aspect of the invention, there is provided a moisture-cure resin composition comprising a modified hydroxy alkyl urethane with a silyl terminated polyether, the modified hydroxy alkyl urethane with a silyl terminated polyether being formed by reaction of a hydroxy alkyl urethane modifier having the formula: where:

R ¹ is an amine residue; and

R ² and R ³ are the same or different and are selected from the group consisting of H, alkyl, and hydroxyalkyl; with an epoxy silane and a silyl terminated polyether.

The moisture-cure resin composition may preferably further comprise a diluent silane composition. Additionally, or alternatively, the composition may further comprise a UV absorber.

The moisture-cure resin composition may further comprise a water scavenger, such as vinyltrimithoxysilane.

Optionally, there may further comprise at least one pigment or filler.

According to a third aspect of the invention, there is provided a paint, coating, composite, potting compound, or adhesive product comprising the moisture-cure resin composition in accordance with the second aspect of the invention. This may be suitable for use on any of the following substrates: wood; plastics; concrete; composites; metal; ceramic; and glass.

The invention will now be more particularly described, with reference to the indicative examples and embodiments outlined below.

DETAILED DESCRIPTION

It is possible to produce a hydroxy alkyl urethane modifier having the formula: where R1 is an amine residue, and R2 and R3 are the same or different and are selected from the group consisting of H, alkyl, and hydroxyalkyl.

The composition is formed by reacting an epoxy acrylate resin on a hydroxyalkyl urethane via a Michael addition.

One example of a hydroxy alkyl urethane modifier, hereafter referred to as HUM-1 , may be prepared as follows:

HUM-1 Preparation 142 parts of 1 ,3-bis(aminomethyl) cyclohexane (1 ,3 BAC) are introduced into a reactor equipped with a stirring and a cooling system. Then, 224 parts of polypropylene carbonates are gradually introduced over 2 hours. The reaction is exothermic and requires cooling, with the reaction mixture being maintained at a temperature of 90°C. After 8 hours at 90°C, the amine index (MEQ I gram: 0.3) is checked. The reaction temperature is maintained at 100 to 120°C until an amine index value of 0.15 is obtained. The final product has a dry extract of 96.4% (60 minutes at 100°C) and the viscosity at room temperature is high. The viscosity at 50°C is measured as 14 Pa.s. The consumption of the carbonate function is also measured by infra-red analysis (wavelength 1800cm ^-1 ) replaced by the urethane function.

To confirm the composition of the HUM-1 product, a sample was dispensed between two KBr plates to form a thin film. A transmission spectrum was recorded using a Thermo Scientific (RTM) Nicolet iS10 Fourier transform infra-red (FTIR) spectrometer.

A broad carbonyl absorption was detected at ~1727cm ^-1 which is within the region expected for a carbonyl group as part of a urethane structure. It is also similar to than expected of an acrylate. A broad absorption was measured at -1100 cm ^-1 which is indicative of the C-0 bond in an aliphatic ether.

No indication of substantial free isocyanate was detected in the region of 2285 to 2275 cm ^-1 in the recorded spectrum.

Another example of a hydroxy alkyl urethane modifier, hereafter referred to as HUM-2, may be prepared as follows:

HUM-2 Preparation

170 parts of isophorone diamine, for example Vestamin (RTM) I PDA from Evonik Operations GmbH, of Paul-Baumann-Str. 1 , 45764 Marl, Germany, are introduced into a reactor equipped with stirring and a cooling system. Then, 224 parts of propylene carbonate, for example Jeffsol (RTM) PC from Huntsman Corporation, of 10003 Woodloch Forest Drive, The Woodlands, Texas 77380, USA, are gradually introduced over approximately one hour. The reaction is exothermic achieving a reaction temperature of approximately 60°C after around 3 to 5 hours. After two further hours, the mixing is stopped. After waiting 24 hours, a highly viscous HUM product is achieved, which can be analysed after about 48 hours. Infra-red analysis at 1800cm ^-1 identifies the presence of urethane functionality.

It will be apparent that these examples of the production of hydroxy alkyl urethane modifier are indicative only, and can be any aminated hydroxy alkyl urethane modifier in accordance with the above formula.

The hydroxy alkyl urethane modifier is prepared by reaction of a primary amine with a monocyclocarbonate. The monocyclocarbonate may be selected from the group comprising: ethylene carbonate; 1 ,2-propylene carbonate; 1 ,2-butylene carbonate; 2,3- butylene carbonate, 1 ,2-pentylene carbonate; and 1 ,2-glycerol carbonate. Preferably, the primary amine and monocyclocarbonate are mixed in an equivalent weight ratio of between 1 :1 and 1 :1.1.

The primary amine is selected from the group comprising: 2,2,-(2,2,4)-trimethyl-1 ,6 hexanediamine; 1 ,6-hexanediamine; 2-methyl-1 ,5 pentanediamine; meta-xylene diamine; 1 ,3-bis(aminomethyl) cyclohexane; isophorone diamine; cyclohexane diamine; 4,4’-diaminodicyclohexyl-methane; polyoxypropylene diamines; polypropoxypropylene triamines; and phenalkamines with a ratio of between 1 :3 and 1 :4.

In this manner, the modified hydroxy alkyl urethane modifier is formed without any isocyanates or isocyanate-containing intermediates.

Once the hydroxy alkyl urethane modifier has been produced, an epoxy silane can be introduced. This acts as a coupling agent. One example of an epoxy silane may be Glymo or (3-glycidoxypropyl)trimethoxysilane. However, other epoxy silanes could be considered, such as 3-glycidoxypropyl)triethoxysilane; (3- glycidoxypropyhmethyldiethoxyilane; 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and

2-(3,4-epoxycyclohexyl)ethyltnethoxysilane. In a preferred embodiment, the hydroxy alkyl urethane modifier is mixed with the epoxy silane in a 1 :1 by weight ratio. For example, in one indicative embodiment, propylene carbonate is mixed with isophorone diamine in a ratio of 114 parts to 86 parts respectively to form the hydroxy alkyl urethane modifier HUM-2. This is then reacted with 200 parts Glymo. The Glymo reacts with the residual hydroxy group of the hydroxy alkyl urethane modifier, thereby creating a silane-modified hydroxy alkyl urethane.

The epoxy silane increases the reactivity of the hydroxy alkyl urethane modifier with silyl terminated polyethers (STPE). Examples of STPE known in the art include SILRES (RTM) 6290, Geniosil (RTM) XB-502, Geniosil (RTM) E-10, and Geniosil (RTM) E-30, all from Wacker Chemie AG, Hanss-Seidel-Platz 4, 81737, Munich, Germany. A low- viscosity STPE is preferred, however, such as SILRES (RTM) 6290.

In the example provided above, 600 parts of SILRES (RTM) 6290 were mixed with the silane-modified hydroxy alkyl urethane, thus generating a moisture-cure resin composition.

In an alternative example of a manufacturing method, it may be possible to prepare a HUM product based on propylene carbonate and isophorone diamine. At the end of the exothermy, after around 2 to 4 hours of mixing, depending on volume, an epoxy silane is added, such as Geniosil (RTM) XL 80. This is added in a 1 :1 ratio with the HUM product, at approximately 20°C. This is treated as being 20 parts HUM to 20 parts epoxy silane.

After 24 hours, at approximately 20°C, 60 parts of silyl terminated polyether, such as SILRES (RTM) 6920 is added.

Additional moisture-cure resin compositions have been tested, with different component ratios. Effective formulations which have been identified include combining HUM product based on propylene carbonate and isophorone diamine in 40 parts with Geniosil (RTM) GF80 in 20 parts, with 40 parts of SILRES (RTM) 6920. A further effective formulation has been found to be feasible with HUM product based on propylene carbonate and isophorone diamine in 40 parts with Geniosil (RTM) GF80 in 40 parts, with 20 parts of SILRES (RTM) 6920.

It has therefore been demonstrated that viable moisture-cure resin compositions can be formed where the hydroxy alkyl urethane modifier is provided in a ratio of between 20 parts to 40 parts by weight of the final composition, where the epoxy silane is provided in a ratio of between 20 parts and 40 parts of the final composition, and where the silyl terminated polyether is provided in a ratio of between 20 parts and 60 parts.

It is expected that viable formulations may be formed where the hydroxy alkyl urethane modifier is provided in a ratio of between 10 parts to 70 parts by weight of the final composition, where the epoxy silane is provided in a ratio of between 10 parts and 70 parts of the final composition, and where the silyl terminated polyether is provided in a ratio of between 10 parts and 80 parts.

The moisture-cure resin composition has many uses. For example, a clear coating can be made. This can be created by mixing the moisture-cure resin composition as described above, with a catalyst, such as Geniosil (RTM) GF9. This may be in a ratio of 95 parts to 5 parts, typically after 24 hours. The coating will be applicable in this form; however, a reactive diluent can also be added, such as SILRES (RTM) 1316 5, here added in 15 parts to adjust the viscosity of the resin composition, typically after a further 24 hours. The final product is then clear, like water, and has a low viscosity.

Additional components, such as a UV absorber (1 part) or a water scavenger (1 part), such as vinyltrimithoxysilane, can also be included to improve the properties of the coating.

Pigmentation could also be added. For example, a pigmented coating has been prepared by mixing 85 parts of the clear coating outlined above with 15 parts of a pigment concentrate RAL 7040 Holcolzac CC. This is merely one exemplary test for the incorporation of pigmentation, and it will be apparent that a wide range of pigments could be introduced to produce different types of coatings.

Other applications of the composition might include paints, varnishes, floor coatings, electricals, composites, adhesives, potting, and industrial coating.

It is therefore possible to provide a moisture-cure resin composition which has improved mechanical and chemical properties compared with those in the art, and the method of formation thereof avoids any isocyanate-containing intermediates. The silanation of a HUM product produces many benefits in terms of curability and hardness.

The words ‘comprises/comprising’ and the words ‘having/including’ when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps, or components, but do not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined herein.