NL1038104C2

NL1038104C2 - Heat-resistant, chemical resistant, room temperature curable, solvent-free resin compositions to apply as protective coating.

Info

Publication number: NL1038104C2
Application number: NL1038104A
Authority: NL
Inventors: Alexander Schoolen; Erik Alexander Bijpost; Alexander Maslow; Richard Joseph Gerardus Tersteeg
Original assignee: Holland Novochem Technical Coatings B V
Priority date: 2010-07-14
Filing date: 2010-07-14
Publication date: 2012-01-23
Also published as: WO2012011804A3; WO2012011804A2; WO2012011804A9

Description

Title: Heat-resistant, chemical resistant, room temperature curable, solvent-free resin compositions to apply as protective coating

Introduction

Iron is a crucial raw material for human beings for a 5 long time. Owing to its mechanical properties it has become an indispensable part of human society. Iron is the main compound in steel (a carbon alloy of iron), and is produced in amounts of 900 million tons annually. Steel is applied in a wide variety of tools and constructions.

10 Though the mechanical properties as such are excellent, a protection against corrosion is required. Owing to time, moisture, temperature, influence of chemicals, oxygen and possibly mechanical stress, abrasion and erosion, the surface area will be damaged irreparably. The function of the steel 15 fades away, making e.g. constructions significantly weaker. Consequently, severe damage may occur.

Studies from the United States of America have shown that corrosion causes an annual damage of approximately 300 billion US dollars, being 4% of the Gross National Product. It 20 basically means that a small improvement towards corrosion prevention can give a big economic advantage.

Currently, replacement of metal parts becomes more and more expensive owing to metal scarcity, increased demand of the world market, higher labor costs as well as to stricter 25 laws and regulations.

A widely applied method either to prevent or strongly inhibit corrosion is to use a coating. Often it contains a wide range of chemicals to obtain the right properties, e.g. binders, fillers, solvents, catalysts, biocides and pigments. 30 These coatings are complex systems, being hardly compatible 1038104 2 with other coatings and/or chemicals. Moreover, a good craftsmanship is required to obtain the desired performance. Nowadays anti-corrosion coatings comprise anti-corrosive pigments, such as zinc phosphate or calcium phosphate, alkyd 5 resin binder and a proper organic solvent.

Although a wide range of protective coating products is known, there is still a need for a product/technology meeting the following criteria: • Well commercially available raw materials 10 · Preferably bio-based • Comparable or better performance with currently available coatings • Economically affordable, preferably strongly cost reducing 15 · Easily applicable and implementable on existing systems • Preferably surface protection with one layer • Thin layers (<50 μ) effective • Robust 20 · Solvent free • Low toxic • Controlled curing time • No primer required • Strong adhesion to the surface 25 · Adjustable flexibility • Sustainable: long performance time • Repaintable • Non-flammable • Scratch resistant 30 · High heat resistance • Good resistance against chemicals • Preferably gas and/or vapor tight • Tunable system O tailor-made systems 3 • Custom-made colorable • Compatible with other chemicals

In fact these requirements are valid for the protection 5 of all kind of hard surfaces, such as glass, metals, concrete, stone, rock, wood, material (cotton, polyester etc.), plastics and ceramics.

Background 10

The requirements mentioned above cannot be sufficiently met upon applying the conventional techniques. A different approach is necessary to fulfill tomorrows' demands.

Polyimides are known for their high thermal stability, 15 acidic and solvent resistance, and excellent mechanical properties. In addition, thermoset polyimides exhibit very low creep and good tensile strength. These properties are maintained during continuous use to temperatures up to 380°C and for short excursions, as high as 500+°C. Moreover, imides 20 are not much affected by common organic solvents. It must be noted that most imides are less stable in alkaline environment. Owing to all these characteristics, polyimides are often applied in the electronics industry on printed circuit boards as well as for insulating cables. Some 25 polyimides are even used as an alternative for glass. The special features of polyimides are even recognized by the NASA (see e.g. US 4,564,663 and US 4,568,733).

The unique properties of polyimides are ascribed to the specific interaction between the electron acceptor (carbonyl 30 group) and the electron donor (nitrogen), a so-called charge transfer complex. This effect is not only valid intramolecularly, but does intermolecularly as well. For the latter, polyimide chains will stack closely together, being arranged comparable with an inorganic crystal lattice. This 35 makes polyimides impermeable for most gasses and hence, they 4 can be suitable for applications where gas and/or vapor tightness is necessary.

Unfortunately, polyimide materials are in general brittle, making them very sensitive for abrasion and 5 mechanical cracking. In addition, for several applications the heat resistance at high temperatures should be maintained continuously. Moreover, adhesion of solely polyimides to a hard surface, in particular metal, is not that straightforward. Reviewing these issues, polyimides posses 10 several very attractive properties, but they need to be adjusted/processed/formulated further on before they can meet the desired criteria for full protection of hard surfaces.

Many patents have been filed either to improve or to adjust the properties of polyimides. The adhesion can be 15 improved by admixing the imide with an epoxy resin and an organic solvent (WO 2005/006826). US 2007/0158869 describes the invention of adhesive films comprising polyimides and a imidazole or quinoline catalyst prepared via extrusion. A more advanced approach has been reported in WO 2008/018399, 20 comprising plasma treatment of polyimide, followed by addition of an amine solution and drying/heating.

Those skilled-in-the-arts know that the brittleness of polyimides can be overcome by addition of an epoxy resin, e.g. a bisphenol-A derivative or other reactive co-monomers. Epoxy 25 resins improve the adhesive properties as well. Alternatively, low viscous polysulfides, such as polysulfide diepoxides, can be admixed with the imide polymers. These products have lower softening and curing temperature than the polyimides. The resulting cured resins show improved toughness, good chemical 30 resistance, good thermal properties and excellent adhesion. Unfortunately, the compounds have to be dissolved in an organic solvent before a proper application is possible, due to high viscosity issues. Moreover, these compositions have shown a very limited shelf life, making it unfavorable for 35 commercial applications.

5

Bismaleimide polymer resins can be prepared in an elegant way, as for example reported in EP 2009058. Although they are often too brittle due to the high cross-link density, the physical properties meet most of the criteria. However, 5 several maleimides were found to be highly toxic, mutagenic and/or carcinogenic. As a consequence these product compositions are often not suitable.

Although bismaleimides and biscitraconimides show very strong resemblance at first sight, the presence of the methyl-10 group at the 2-position of the imide ring can give rise to completely different reaction routes (see e.g. US 5,221,717) ! Upon applying biscitraconimides in an alkaline environment, a pseudo Michael addition via the tautomeric form of biscitraconimide can occur, leading to completely different 15 coating characteristics. In a curing system, chain extension occurs via allylic H-abstraction (of both tautomers), whereas a maleimide reacts via vinylic route. Moreover, due to the tautomeric equilibrium a biscitraconimide possesses much less aromatic character compared to the bismaleimide analogue. This 20 means that the chemistry of bismaleimides is not representative for biscitracomimides and vice versa. One can clearly speak about a different class of compounds.

Citraconimide has formula 1, citraconimide tautomer has formula 2, and maleimide has formula 3 of the formula sheet.

25 Biscitraconimides do not possess carcinogenic properties, making them more attractive/favorable for a wide range of applications. However, these compounds should be modified/adjusted/formulated in a distinctive matter to achieve a useful end product.

30 Curable biscitraconimide polymers and copolymers with olefinically unsaturated materials, preferably styrene, were found to exhibit high glass temperatures, improved thermostability and solvent resistance, as reported in US 5,198,515. Moreover, in most cases no additional solvents 35 apart from the olefin have to be applied to realize efficient 6 curing. A drawback is the necessity to use olefins, such as styrene, making it unattractive for large applications owing to the volatility and toxicity.

The curing of citraconic (co)polymers can be enhanced by 5 the addition of an anionic catalyst, preferably diazobicycloalkanes and substituted imidazoles (US 5,221,717). Nevertheless the high melting points of the citraconic (co)polymers hamper easy application and implementation on currently used systems.

10 Prepolymerization of biscitraconimide, bisitaconimide and/or citraconimido-itaconimide by an anionic catalyst leads to a good viscosity and solubility properties, as taught in WO 2007/134948. The resulting products can be admixed with a reactive co-monomer to establish the desired polymer curing.

15 The prepolymers as such are stable for several days up to weeks. However, for a smooth process throughout the whole production/application chain, it is absolutely necessary to increase the shelf-life for more than months.

W02009/077420 claims to circumvent almost every mentioned 20 drawback on polyimides by applying a peroxide-free curing system comprising an epoxy compound, a polyamine and a biscitraconimide co-curing agent, preferably 1,3-bis(citraconimidomethylene)benzene . The curing time, flexibility as well as adhesion of this 2K system can be tuned 25 at wish. The coatings obtained show good chemical and scratch resistance and even auto repairing properties. In addition, upon admixing nanoparticles esthetic auto-topographic landscape formation can be created in the coatings. The curing reaction mainly occurs via a pseudo Michael addition of the 30 tautomeric isomer (itaconimide) of the biscitraconimide, initiated by the polyamine. These processes are known to be highly exothermic, making well-controlled curing impossible.

As a consequence, safe handling cannot be ensured, whilst reproducibility of the resulting coatings is questionable.

35 Amongst other drawbacks like shelf-life and overall stability 7 of the coating composition, a need exists to overcome these drawbacks, without loss of-, or preferably with enhanced performance.

Surprisingly, Applicant found that biscitraconimides can 5 react with either primary and/or secondary amines under alkaline conditions, forming stable compound A or partly reacted form B. The resulting products are often liquid at room temperature, making them easy to handle. Though mainly monomeric products are obtained, minor amounts of oligomeric 10 adduct originating from A and B can be formed as well. Upon applying biscitraconimides (R=R'=H), approximately 80% of products A and B are formed and 20% products A' and B'; see reaction scheme 1 of the formula sheet. Under strong alkaline conditions the reaction can be accompanied by ring-opening as 15 well, as is obvious for those skilled in the art.

The new products as such can be applied in a 2K system comprising an epoxy compound. Though the starting materials can be the same as claimed in W02009/077420, the coating characteristics, curing behavior as well as the physical 20 properties are completely different due to different reaction routes, leading to new products. Major advantages of the new invention are: highly increased safety storage and handling, well-controlled curing, novel compounds type A and B, possibly mixed with A' and B' give high chemical resistance as well as 25 excellent adhesion to several surfaces.

Description of the invention

The present invention is intended to overcome the 30 abovementioned drawbacks in the prior art by applying biscitraconimide adducts (A or B) in a well-controllable and tunable two component (co)polymer/resin system, which as such can be optimized in heat resistance, chemical resistance and toughness.

8

The products A and B are obtained via a reaction of polyamines or (poly)diamines under alkaline conditions with biscitraconimide. These new monomers are formed in a high yield. Though mainly monomeric products are obtained, minor 5 amounts of oligomeric adduct, originating from A and B can be formed as well. Upon applying biscitraconimides (R=R'=H), approximately 80% of products A and B are formed and 20% products A' and B'.

At first sight, compounds of A' and B' seem to have 10 resemblance with products claimed in WO2009/145779. It must be noted that products A and B can never be prepared following that invention. A and B are formed via, for citraconimide (or its tautomeric form, itaconimide) unique, allylic H-abstraction route.

15 In products A, A' ,B, and B' : R and R' are chosen from the groups: H, alkyl, poly(alkyl), aryl, poly(aryl), alkylene, poly(alkylene), alcohol, ester, halide, (poly)amine or (poly)sulfur.

R and R' can be equal, but not necessarily 20 X = linear alkyl ((CH2)m), branched alkyl ((CH2)m), polyethers, alkylaryl ((CH2)m(Aryl), poly(aryl), alkylene, poly (alkylene)

Aryl = benzene, naphthalene, anthracene, bis(phenyl) compounds, bis(naphtyl) compounds, bis(anthracyl) compounds 25 R" is chosen from the groups: alkylamine, arylamine, poly(alkylamine), poly(alkylalkoxyamine), amino dendrimers, polyaminoamides n = 1 - 2

30 The amines of choice are ethylene diamine (EDA) or EDA

homologues, isophorondiamine. Polyoxyalkyleneamines (Jeffamines), fatty amines, dendrimers and/or polyamino amides might be applied as well. It is generally known that mixtures of abovementioned amines are also suitable.

35 9

Products based on A or B can be admixed with epoxy resin, other co-monomers, polysulfide, fillers (e.g. silica) and/or catalysts, to obtain the required coating properties.

Moreover, the coatings can even be easily applied without the 5 use of a solvent. A very important issue observed is room temperature curing whilst obtaining high temperature resistance of the final polymer.

The invention will be explained below with a number of 10 examples. They exclusively serve to explain and not to limit the claimed protective scope of the present invention.

Examples 15 Preparation of products A and B General procedure:

An excess of a compound containing primary and/or secondary amine is warmed to 90°C whilst being stirred. The 20 biscitraconimide, e.g. Perkalink 900, is added in small amounts either in molten state or in pellets. Stirring is continued till a homogeneous solution is obtained. The reaction can also be performed at ambient temperature, but takes longer time to be completed. 1H-NMR spectroscopy has 25 confirmed that the same products will be obtained by elevated temperatures or room temperature.

Typical example : A mixture consisting of Duomeen CD and TETA, in a ratio of 30 65 % (w/w) Duomeen CD and 15 % (w/w) TETA, is warmed up to 90°C whilst stirring. Separately, 20 % (w/w) percent of Perkalink 900 is molten and carefully added to the amine mixture. An exothermic reaction will occur. After addition of all the Perkalink 900, the mixture is allowed to cool to room 10 temperature. The formation of products A and A' is confirmed by 1H-NMR spectroscopy.

Similar products can be obtained by a reaction between Perkalink 900 and single primary and/or secondary 5 (poly)amines, such as, but not limited to, Duomeen CD, TETA, EDA, Jeffamines and mixtures thereof.

2K Coating system: A mixture of A and A' (40 % (w/w)) is admixed with 60 % 10 (w/w) of a second component mixture, consisting of 75 % (w/w)

Epikote 827, 15 % (w/w) Thioplast EPS70 and 10 % (w/w) Heloxy Modifier TP. Part of the resulting product is transferred on a steel Q-panel with a layer thickness of 30 micron. It is allowed to cure for 72 hours at room temperature.

15

Resistance tests

The treated Q-panel is treated with drops of acetic acid (8% aq), sulphuric acid (10 M), hydrochloric acid (36%) and sodium hydroxide (33%). The coating system is benchmarked with 20 the 2K system described in W02009/077420, using the same raw materials, but starting from an epoxy-citraconimide component and an amine component.

The resistance test shows that the coatings of the invention are superior in chemical resistance compared to 25 those coatings described in W02009/077420. Biggest differences in performance could be seen in aqueous acetic acid tests.

In addition, Q-panels treated with coatings according to the invention showed excellent protection in highly concentrated salt solutions, such as magnesium chloride and 30 sodium chloride, even at elevated temperatures.

Those skilied-in-the-art know that such unique coating properties can only be established by new products, originating from A and B.

11

Formula sheet 0 0 0 ( (1) (2) (3) 5 REACTION SCHEME 1 10 0 0 0 0 RR'HC^J^ ^iL.CHRR' RR'C^Jj^ ^jL^CRR'

I N-X-N I) _^ T N-X-N

|f )f Alkaline |f 0 0 0 0

R R' O O R\ R

R"^^NH IL^X.

n R" Ν γ\ /1 N R" -► Hm N-X-N Hn-1 i r 0 0

A

15 0 0 RR'HC^l^ ^IL.CHRR'

N-X-N

Mn-1 o 0 n-1 A’ 12

R R' O O

r-^n\A A^crr'

Sr r o o

B

O o

RR’HC^J^ jl^CRR' N-X-N

R-^N^Y Γ

Mn-1 O O

B’ 5 1038104

Claims

A coating composition containing 1-80% by weight of biscitraconimide adducts of formula A or B of the formula sheet, or the corresponding oligomers thereof, 0.1-40% by weight of polyamine and 5-90% by weight of a compound having at least one epoxide group, wherein in formula A and B: R and R 'are selected from the groups: H, alkyl, poly (alkyl), aryl, poly (aryl), alkylene, poly (alkylene), alcohol, ester, halide, amine or sulfur. R and R 'can be the same or different X = linear alkyl ((CH2) m), branched alkyl ((CH2) m), alkylaryl ((CH2) m (Aryl), poly (aryl), alkylene, poly (alkylene) R "is selected from the groups: alkylamine, arylamine, poly (alkylamine), poly (alkylalkoxyamine), amino dendrimers, polyaminoamides n = 1 - 2 Aryl = benzene, naphthalene, anthracene, bis (phenyl) compounds, bis (naphthyl) ) compounds, bis (anthracyl) compounds.

2. A composition according to claim 1, wherein products A and B are obtained via a reaction of polyamines or (poly) diamines with a corresponding biscitraconimide under alkaline conditions.

3. Composition according to claims 1-2, wherein the polyamine or poly (diamine) a (polydiamine => EDA Homologue), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylene pentamine (ΤΕΡΑ), pentaethylene hexamine (PEHA ), amines with a structure N- (CH 2) n -N (linear and / or branched), fatty (poly) amines, tripropylene tetramines, ethoxylated amines, 1038104 propoxylated amines, polyoxyalkylene amines (Jeffamines), dendrimers, or polyamino amides, or mixtures thereof.

A composition according to any one of claims 1 to 3, wherein the biscitraconimide is 1,3-bis (citraconimidomethylene) benzene or its tauters corresponding to it.

The composition of any one of claims 1 to 4, wherein the compound having at least one epoxide group is a reactive epoxide, glycidyl ether, or glycidyl ester.

Composition according to one or more of claims 1 to 5, further comprising fillers, in particular 15 nanoparticles or modified particles, in particular silicon dioxide.

7. Method for curing a composition according to one or more of claims 1 to 6, by heating the composition to a temperature and for a time sufficient for the curing agent, the compound comprising at least one epoxide group, and a polyamine to harden simultaneously.

The method of claim 7, wherein the curing is performed at a temperature of less than 130 ° C.

The method of claim 7 or 8, wherein the curing is performed at room temperature. 1 038 1 0 4