DE10262200B4 - Two-component composition for preparation of polyurethane gelcoats containing a low and high molecular polyol components useful for lengthening the lamination time in using polyurethane gelcoats for coating epoxy laminates - Google Patents

Abstract

A two-component composition: (A) a polyol component containing (A1) one or more low molecular polyols of mol. wt. 60-160 g/mole, OH group concentration 20-25 mole OH groups per kg of low molecular polyol, (A2) one or more high molecular polyols, (A3) one or more light-fast aromatic amines, and (B) a polyisocyanate component containing one or more polyisocyanates. Independent claims are also included for: (1) a polyurethane gelcoat (PUG) obtainable by mixing a polyol component containing a light-fast aromatic amine with a polyisocyanate component, curing of the mixture at 120[deg]C over 1 hour, where the PUG is subjected to artificial weathering over 900 hours, in accordance with ASTM-G-53, after which the color shade change delta E was 6.5, preferably 3 at most (DIN 5033, part 4, and DIN 6174); (2) curing of the mixture under (A) and (B) above; and (3) a composite material including the gelcoat, e.g. a fan blade.

Description

The invention relates to a composite material comprising a polyurethane gelcoat and its use.

The surfaces of composite materials (for example, composites of glass fiber fabric or fleece and epoxy resin) are often less attractive and also not resistant to light and weathering. They must therefore be provided with a surface coating. Before surface treatment of epoxy resin composites, sanding and trowelling must be carried out as the direct surface coating of the composite material results in fiber orientation. An alternative to this is the use of a gelcoat.

A gelcoat is a resin system that is applied to molded parts in composite construction for the production of smooth component surfaces and at the same time gives a handsome and possibly light and weather resistant surface. For this purpose, the gelcoat resin system is added after mixing its reaction components within the processing time (pot life) as the first layer in a mold. The layer obtained after gelling is sufficiently mechanically stable so as not to be damaged when applying the synthetic resin (for example an epoxy resin) and optionally an inorganic or organic nonwoven or woven fabric (for example a glass fiber fabric or glass fiber fleece) (in-mold process). The same applies to injection methods and the application of wet laminates as well as the application of prepregs.

In order to ensure sufficient adhesion between the resin and the gelcoat, the coating with synthetic resin must take place within the lamination time of the gelcoat. Subsequently, the resin and gelcoat are completely cured.

• – Die Laminierzeit ist der Zeitraum beginnend mit dem Zeitpunkt der Klebfreiheit des in die Form applizierten Gelcoat-Films, in dem der Gelcoat-Film überlaminiert werden muss, um noch eine Haftung zwischen Gelcoat und Laminat sicherzustellen.
• – Die Topfzeit ist der Zeitraum beginnend mit der Vermischung der beiden Reaktionskomponenten bis zum Gelieren der Reaktionsmischung. Nach Beendigung der Topfzeit ist die Reaktionsmischung nicht mehr verarbeitbar.
• – Die Klebfreizeit ist der Zeitraum beginnend mit dem Auftragen der homogenen, angemischten Reaktionsmischung auf die Formoberfläche bis zum Erreichen der Klebfreiheit des applizierten Films.
• – Unter Gelzeit wird die in E-DIN VDE 0291-2 (VDE 0291-Teil 2): 1997-06 unter Punkt 9.2.1 beschriebene, bis zum Gelieren der Reaktionsmischung gemessene Zeit verstanden.

In describing the invention, the following definitions apply:

• The lamination time is the period starting from the time when the gelcoat film is tack-free in which the gelcoat film has to be over-laminated to ensure adhesion between the gelcoat and the laminate.
• - The pot life is the period starting with the mixing of the two reaction components until gelling of the reaction mixture. After completion of the pot life, the reaction mixture is no longer processable.
• - The tack-free time is the period starting with the application of the homogeneous, mixed reaction mixture to the mold surface until the adherence of the applied film is achieved.
• - Gel time is understood as the time described in E-DIN VDE 0291-2 (VDE 0291 part 2): 1997-06 under point 9.2.1 until gelling of the reaction mixture.

As gelcoat resin systems, for example, formulations based on radically curing resins such. As unsaturated polyester (UP), vinyl esters or acrylate-terminated oligomers. These resin systems are safe to use when used in conjunction with UP resins and show good adhesion to a variety of synthetic resins (composite adhesion), since hardening of the interface due to the oxygen-oxygen inhibited curing reactions on the inner gelcoat surface after the application of the synthetic resin. Many commercial UP-based gelcoats, however, do not exhibit sufficient gloss retention and are prone to chalking and hairline cracking. Further disadvantages of UP-based gelcoats are the unavoidable monomer emissions, often very high shrinkage during curing, which leads to stresses in the composite / gelcoat interface and hence poor interfacial stability, and the usually poor adhesion to composites Base of epoxy resin (EP).

• – die geringer Toleranz gegenüber. Ungenauigkeiten im Mischungsverhältnis, dies kann u. U. im gehärteten Gelcoat zu Verfärbungen und stark verminderter mechanischer Beständigkeit führen,
• – die stark exotherme Härtungsreaktion, die nur kleine Ansatzgrößen erlaubt,
• – die sehr plötzlich verlaufende Härtungsreaktion,
• – die unzureichende Witterungsstabilität,
• – die sehr schlechte Thermovergilbungsstabilität sowie
• – der hohe Preis von einigermaßen vergilbungsstabilen EP-Harzen.

For use in connection with EP composite materials, it is possible, for example, to use EP gel coats (for example from SP-Systems). EP gel coats show much better adhesion to EP composites compared to UP gel coats. EP gel coats also contain no volatile monomers and are therefore less hazardous to the working environment than the most styrene-containing UP gel coats. The disadvantages of EP gelcoats, however, are

• - the lower tolerance. Inaccuracies in the mixing ratio, this may u. U. in the cured gelcoat lead to discoloration and greatly reduced mechanical resistance,
• The highly exothermic curing reaction, which allows only small batch sizes,
• The very sudden curing reaction,
• - the insufficient weathering stability,
• - the very bad thermo-yellowing stability as well
• - The high price of reasonably yellowing-resistant EP resins.

Basically, therefore, for applications in which a high light and weathering stability is required to give surface coatings based on aliphatic polyurethanes preference. When formulating PU gelcoats, however, it should be borne in mind that conventional mixtures of polyol and polyisocyanate do not gel until the reaction has proceeded very far. But then already the reaction and thus the adhesion of the PU gelcoat to the resin used for the composite material is severely limited (that is, the tack-free time is relatively long, the lamination time, however, comparatively short). The use of such a conventional product would be difficult to realize in terms of process engineering and, moreover, unreliable with regard to gelcoat / synthetic resin adhesion.

In addition, commercially available PUR gel coats (from Relius Coatings) generally have comparatively low glass transition temperatures (<40 ° C.). This greatly limits the temperature range in which such a product can be used.

To shorten the process cycle times in the manufacture of epoxy laminates, especially when an epoxy prepreg is used for laminate construction, curing temperatures above 80 ° C are often used. This is necessary even if high demands are placed on the laminate in terms of heat distortion resistance. When used in processes with hardening temperatures> 80 ° C, conventional PUR gel coats often show surface defects in the form of sink marks after demolding of the component. For this reason, the use of PUR Gelcoats at curing temperatures of> 80 ° C is limited and often requires a costly reworking to smooth the component surface.

The DE-T-690 11 540 discloses a process for producing a polyurethane film in which a polyurethane reaction mixture is prepared and this reaction mixture is sprayed onto a surface by means of a spray gun. This procedure is equipment intensive. The polyurethane reaction mixture may include amine-containing initiators contemplating aliphatic or alicyclic alkanolamines or polyamines with an amino group not directly attached to an aromatic ring.

The US-A-4,950,792 and the relatives EP-A-0 220 641 disclose various 4,4'-methylenebisanilines and their use as chain extenders or crosslinking agents for polyurethanes, as curing agents for epoxy resins and as intermediates. In a proposed method, compounds having reactive hydrogen atoms, such as OH-terminated polyesters, are first reacted with diisocyanates to form a prepolymer which is then reacted in a second step with an aromatic diamine chain extender or crosslinker (prepolymer process). A gradual curing with relatively short gel and Klebfreizeiten and at the same time comparatively long lamination times, as they are indispensable in the production of a gel coats, is not possible with this method.

If appropriate, it is also possible to proceed in such a way that, in a first step, crosslinking agent / chain extender is dissolved in the polyol and is processed with the isocyanate in a second step. In a further proposed procedure, work is carried out by the one-shot method. ( EP-A-0 220 641 , P. 12, second and third paragraphs). For this purpose, high molecular weight polyhydroxy compounds in the mixture with crosslinking agent / chain extender are reacted with diisocyanate. The examples of US-A-4,950,792 and the EP-A-0 220 641 However, deal exclusively with polyurethanes prepared by the prepolymer process.

Based on this reveals the US-A-6 013 692 the preparation of foamed polyurethane elastomers by reacting isocyanate components with compounds having at least two isocyanate-reactive hydrogen atoms and 4,4'-methylenebisanilines and a foaming agent.

The U.S. Pat. No. 5,026,815 discloses that mixtures of selected 4,4'-methylenebisanilines can be used as chain extenders for cast resin polyurethane elastomers based on p-phenylene methylene diisocyanate prepolymers.

The US-A-6 046 297 discloses mold-moldable polyurethane elastomer compositions prepared by mixing toluene diisocyanate with aliphatic diisocyanate and polyol to form a prepolymer and curing the prepolymer with aromatic diamine hardener. The polyol may be a mixture of high molecular weight polyol with low molecular weight polyol. Low prepolymer content of toluene diisocyanate reduces the tendency of the prepolymer to crack upon curing.

The DE 197 29 982 A1 relates to two-component polyurethane systems of a polyol and an isocyanate component, wherein the polyol component contains at least two amines A1 and A2 and the reactivity R1 of amine 1 to isocyanate is substantially greater than the reactivity R2 of amine 2 to isocyanate.

The US-A-5,962,617 relates to the reaction of prepolymer prepared from polyether glycol or polyester glycol and diisocyanate with aromatic amine. The prepolymer, which is formally made from polyester glycol or polyester glycol and diisocyanate, chain-extended diisocyanate, triol can be added to bring about at most 1% crosslinking (column 4, lines 29 et seq.). However, the latter documents of the prior art give no indication of a modern gelcoat.

• – eine vergleichsweise lange Laminierzeit bei für das Mischen und das Einbringen in die Form ausreichender Topfzeit und für die Filmbildung hinreichenden, aber vergleichsweise kurzen Gel- und Klebfreizeiten ergeben,
• – einfach verarbeitbar sein (d. h. keine zusätzliche Geräte für eine Heißapplikation und/oder Sprühapplikation erfordern),
• – eine gute Haftung zwischen Gelcoat und Kunstharz ergeben (insbesondere zu Epoxidharzen, bei langen Laminierzeiten),
• – ein Gelcoat ergeben, das licht- und witterungsbeständig ist und nicht zur Bildung von Haarrissen neigt,
• – eine glatte Bauteiloberfläche, frei von Einfallstellen auch bei Härtungstemperaturen zwischen 80°C und 130°C, erzeugen und
• – preiswert sein.

Accordingly, the object of the invention is to provide a composite material with polyurethane gelcoat. For this purpose, components are to be made available for a polyurethane-based gelcoat resin system which do not have the disadvantages mentioned. The components for the gelcoat resin system are intended to

• Provide a comparatively long lamination time with sufficient but for the mixing and the introduction into the mold of sufficient pot life and for the film formation, but comparatively short gel and Klebfreizeiten,
• - be easily processable (ie do not require additional equipment for hot application and / or spray application),
• - give a good adhesion between gelcoat and synthetic resin (in particular to epoxy resins, with long lamination times),
• - give a gelcoat which is resistant to light and weathering and does not tend to form hairline cracks,
• - Produce a smooth component surface, free of sink marks even at curing temperatures between 80 ° C and 130 ° C, and
• - be cheap.

Polyurethane gel coats with a high glass transition temperature T _{G would, in} principle, be particularly well suited for this purpose. A high glass transition temperature requires a high degree of crosslinking of the polyurethane, ie the use of a highly functional polyol. However, the use of a highly functional polyol involves a very short lamination time. Therefore, it was also an object of the present invention to provide components for a polyurethane gelcoat (for a composite material) which, on the one hand, give a gel coat with high T _g , but on the other hand make it possible to extend the lamination time.

• A) eine Polyolkomponente, die
• A1) 2 bis 60 Gew.-%, bezogen auf die Gesamtmasse der Bestandteile A1, A2 und A3, ein oder mehrere niedrigmolekulare Polyole mit einem Molekulargewicht von 60 bis 160 g/mol und einer Hydroxylgruppenkonzentration von 22,3 bis 35 mol Hydroxylgruppen je kg niedrigmolekulares Polyol,
• A2) 97 bis 30 Gew.-%, bezogen auf die Gesamtmasse der
• Bestandteile A1, A2 und A3, ein oder mehrere höhermolekulare Polyole und
• A3) 0,1 bis 20 Gew.-%, bezogen auf die Gesamtmasse der Bestandteile A1, A2 und A3, ein oder mehrere lichtbeständige aromatische Amine enthält, und
• B) eine Polyisocyanatkomponente umfasst, die ein oder mehrere Polyisocyanate enthält,

und Härten der Mischung.This object is achieved by the composite material according to claims 1 to 18. The gel coat of the composite material can be prepared by mixing the components of a two-component composition which

• A) a polyol component, the
• A1) 2 to 60 wt .-%, based on the total mass of the components A1, A2 and A3, one or more low molecular weight polyols having a molecular weight of 60 to 160 g / mol and a hydroxyl group concentration of 22.3 to 35 moles of hydroxyl groups per kg low molecular weight polyol,
• A2) 97 to 30 wt .-%, based on the total mass of
• Components A1, A2 and A3, one or more higher molecular weight polyols and
• A3) 0.1 to 20 wt .-%, based on the total mass of the components A1, A2 and A3, one or more light-stable aromatic amines containing, and
• B) comprises a polyisocyanate component containing one or more polyisocyanates,

and curing the mixture.

The invention is based, inter alia, on the finding that fade-resistant aromatic amines can be added to a polyol component for the production of polyurethane gelcoats and that the mixture prepared from the polyol component used according to the invention and a polyisocyanate component has particularly good processing properties in the production of polyurethane gelcoats and above addition, a particularly light-resistant gel coat results. Cured gelcoats according to the invention have preferably a Shore D hardness of more than 65 (determined according to DIN EN ISO 868) and the elongation at break at 23 ° C is preferably greater than 10% (determined according to ASTM-D-522).

1. polyol component

The polyol component used according to the invention is characterized in that it contains at least one polyol having a comparatively low molecular weight and a comparatively high hydroxyl group concentration c _OH . The low molecular weight polyol (or the optionally two, three, four, etc. low molecular weight polyols) leads to the formation of a very close-meshed network at the beginning of the reaction of the polyol component with a polyisocyanate component (after sufficient pot life and acceptable gel time). which ensures the desired mechanical stability of the gelled gelcoat layer.

Low molecular weight polyol

In the present invention, a "low molecular weight polyol" is defined as a polyol having a molecular weight of 60 to 160 g / mol (preferably 60 to 150 g / mol, more preferably 60 to 140 g / mol, and more preferably 90 to 137 g / mol) and a hydroxyl group concentration of 22.3 to 35 moles of hydroxyl groups per kg of low molecular weight polyol.

Preferably, the hydroxyl group concentration c is _OH in the range of 25 to 34, more preferably 28 to 34 and in particular in the range of 30 to 33 moles of hydroxyl groups per kg of low molecular weight polyol.

In principle, all straight-chain or branched aliphatic glycols, triols, tetrols, pentols and mixtures thereof are suitable according to the invention as low molecular weight polyols.

Examples are the low molecular weight polyols listed below (Table 1). Table 1 Preferred low molecular weight polyols Low molecular weight polyol [G / mol] c _OH [mol / kg] ethylene glycol 62.07 32.22 1,2- and 1,3-propylene glycol 76.10 26.28 glycerol 92.10 32.58 Trimethylalmethan 106.12 28.27 Trimethylolethane ((1,1,1-tris (hydroxymethyl) -ethane) 120.15 24.97 Trimethylolpropane (1,1,1-tris (hydroxymethyl) -propane) 134.18 22.36 meso-erythritol 122.12 32.76 pentaerythritol 136.15 29.38

Preferably, the proportion of low molecular weight polyol (ie, the sum of all low molecular weight polyols in the polyol component) is in the range of 2 to 60 wt .-%, more preferably 5 to 50 wt .-%, in particular 10 to 45 wt .-% such as 20 to 40 wt %, wherein a proportion of 30 to 35 wt .-% is particularly preferred, based on the total mass of the components A1, A2 and A3 of the polyol component.

Higher molecular weight polyol

The higher molecular weight polyol present in the polyol component used according to the invention may in principle be any polyol customary for the preparation of polyurethanes, for example polyester polyol, polyether polyol, acrylate polyol and / or polyol based on dimer fatty acids. The constituents A1 and A2 comprise all polyols contained in the polyol component used according to the invention, ie. H. a polyol which is not a low molecular weight polyol as defined above is considered to be a higher molecular weight polyol for the purposes of the present specification.

Suitable higher molecular weight polyols are, for. B. in the mentioned DE-T-690 11 540 described. Preferred higher molecular weight polyols are polyether polyols (polyalkoxylene compounds) which are formed by polyaddition of propylene oxide and / or ethylene oxide onto low molecular weight starters with OH groups and a functionality of 2 to 8.

Other typical higher molecular weight polyols are the polyester polyols, which are ester condensation products of dicarboxylic acids with low molecular weight polyhydric alcohols and have a functionality of 2 to 4, with preference being given to those higher molecular weight polyester polyols having a hydroxyl group concentration in the range of 6 to 15 mol / kg of higher molecular weight polyester polyol 8 to 12 moles of hydroxyl groups per kg. The higher molecular weight polyol (or optionally two, three, four etc. higher molecular weight polyols) of the polyol component ensures that a sufficiently long lamination time is available. This is important to achieve good adhesion to the resin of the composite.

• – ein Polyol auf Acrylatbasis mit einer Funktionalität von etwa 2,3 und einem Hydroxylgruppengehalt von 12,5 mol/kg,
• – ein Polyetherpolyol mit einer Funktionalität von 3 und einem Hydroxylgruppengehalt von etwa 16,5 mol/kg,
• – ein Umsetzungsprodukt aus Trimethylolpropan und Polycaprolacton mit einer Funktionalität von etwa 3 und einem Hydroxylgruppengehalt von etwa 10 mol/kg.

Particularly preferred higher molecular weight polyols are:

• An acrylate-based polyol having a functionality of about 2.3 and a hydroxyl group content of 12.5 mol / kg,
• A polyether polyol having a functionality of 3 and a hydroxyl group content of about 16.5 mol / kg,
• A reaction product of trimethylolpropane and polycaprolactone having a functionality of about 3 and a hydroxyl group content of about 10 mol / kg.

Preferably, the proportion of higher molecular weight polyol (ie the sum of all higher molecular weight polyols) in the polyol component in the range of 97 to 30 wt .-%, preferably 90 to 40 wt .-%, more preferably 80 to 45 wt .-% and in particular 70 to 50 wt .-%, based on the total mass of the components A1, A2 and A3 of the polyol component. In a preferred embodiment, the polyol component is free of aliphatic dicarboxylic acids.

Light-stable aromatic amine with low reactivity towards isocyanates

Suitable light-stable aromatic amines are, for. Tie US-A-4,950,792 . US-A-6 013 692 . U.S. Pat. No. 5,026,815 . US-A-6 046 297 and US-A-5,962,617 disclosed.

Preferred light-stable aromatic amines are characterized in that they, dissolved in toluene (20 wt .-% amine in toluene), and mixed at 23 ° C with an equimolar amount of an oligomeric HDI isocyanate (hexamethylene diisocyanate) having an NCO content of about 5.2 mol / kg and a viscosity in the range of 2750 to 4250 mPas, dissolved in toluene (80 wt .-% isocyanate in toluene), a gel time of more than 30 seconds, preferably more than 3 minutes, more preferably more than 5 Minutes and in particular more than 20 minutes.

A particularly preferred light-stable aromatic amine is characterized in that it, dissolved in toluene (25 wt .-% amine in toluene) and at 23 ° C mixed with an equimolar amount of an oligomer HDI isocyanate having an NCO content of about 5, 2 mol / kg and a viscosity in the range of 2750 to 4250 mPas, wherein the mixture, applied to inert white test plates and cured in a convection oven for 30 minutes at 80 ° C and then for 60 minutes at 120 ° C coated with a a dry film thickness of about 20 microns, wherein the coating at 300 hours artificial weathering according to ASTM G-53 (4 hours UVB 313, 4 hours condensation) a hue Delta E (according to DIN 5033 Part 4 measured and evaluated according to DIN 6174) of at most 50, preferably at most 45, in particular at most 40, such as at most 30.

Lightfast aromatic amines which are preferably used according to the invention are methylenebisanilines, in particular 4,4'-methylenebis (2,6-dialkylanilines), preferably those disclosed in US Pat US-A-4,950,792 described non-mutagenic methylenebisanilines.

Particularly suitable are the 4,4'-methylenebis (3-R ¹ -2-R ² -6-R ³ -anilines) listed in Table 2 below. Table 2 4,4'-Methylenebis (3-R ¹ -2-R ² -6-R ³ -anilines) R ¹ R ² R ³ Lonzacure M-DMA H CH ₃ CH ₃ Lonzacure M-MEA H C ₂ H ₅ CH ₃ Lonzacure M-DEA H C ₂ H ₅ C ₂ H ₅ Lonzacure M-MIPA H C ₃ H ₇ CH ₃ Lonzacure M-DIPA H C ₃ H ₇ C ₃ H ₇ Lonzacure M-CDEA Cl C ₂ H ₅ C ₂ H ₅

The light-stable aromatic amine particularly preferred according to the invention is 4,4'-methylenebis (3-chloro-2,6-diethylaniline), Lonzacure M-CDEA.

Preferably, the amount of light stable aromatic amine in the polyol component (ie, the sum of all light stable aromatic amines in the polyol component) is in the range of 0.1 to 20 wt%, preferably 0.3 to 10 wt%, more preferably 0.5 to 5 wt .-% and in particular 1 to 3 wt .-%, based on the total mass of the components A1, A2 and A3 of the polyol component.

catalysts

accelerate the polymerization reaction between polyol component and polyisocyanate component. In principle, all known for use in polyurethanes catalysts may be used, preferably those in the DE-T-690 11 540 disclosed lead, bismuth and tin catalysts, moreover, the strong base amine catalyst diazabicyclo (2,2,2) octane-1,4 and zirconium compounds.

A catalyst particularly preferred according to the invention for use in a polyol component is dibutyltin dilaurate (DBTL).

A polyol component used according to the invention may contain up to 1% by weight, more preferably 0.05 to 0.5% by weight, in particular about 0.3% by weight of catalyst, for example 0.3% by weight, based on the Total mass of the polyol component.

fillers

The polyol component of the invention preferably contains greater amounts of one or more fillers, and for the purposes of the present specification, "pigments" are included in the definition of the term "filler". Preferred fillers are talc, dolomite, filled CaCO ₃ , BaSO ₄ , quartz flour, silica, titania, molecular sieves and (preferably calcined) kaolin. The content of a polyol component in filler is preferably in the range of 10 to 80% by weight, more preferably 20 to 70% by weight, especially 35 to 55% by weight, such as 40 to 50% by weight, based on the total mass polyol. Mixtures of fillers are preferred, for example mixtures of two, three or four fillers.

In addition, ground glass fibers may be included in the polyol component, for example, milled glass fibers of less than 500 microns in length. These fibers prevent the tearing of a possible crack.

2. polyisocyanate component

Polyisocyanates preferably used in the polyisocyanate component are aliphatic isocyanates, for example those in the DE-T-690 11 540 on pages 5 and 6 disclosed biuret isocyanates. All isocyanates mentioned there are suitable.

The silicas which can be used as fillers in the polyisocyanate component are, in particular, silanized pyrogenic silicic acids. The preferred content of the polyisocyanate component on silica (a thixotropic agent) ensures that the polyol component and the polyisocyanate component result the similar viscosities of the components are well miscible and beyond the mixture of components on a vertical surface up to 1 mm wet thickness does not expire. The amount is preferably in the range of 0.1 to 5 wt .-%, more preferably 0.5 to 3 wt .-%, in particular 1 to 2 wt .-%, based on the total weight of the polyisocyanate component.

catalysts

The catalysts which can be added to the polyol component may also be present in the polyisocyanate component or instead of in the polyol component in the polyisocyanate component in the stated concentrations, with zirconium compounds being preferred as catalysts in the polyisocyanate component.

3. Additives (see textbook: "Lackadditive", Johan H. Bielemann, Weinheim, Wiley-VCH, 1998).

In addition, either the polyol component or the polyisocyanate component, or both components, may additionally contain one or more additives selected from defoaming agents, dispersants and deaerating agents.

defoamers

may be present in an amount of up to 1.0% by weight, preferably up to 0.5% by weight, based on the total mass of the component in which they are used.

vent means

may be included in an amount up to 1.0% by weight, preferably up to 0.6% by weight, based on the total weight of the component in which they are used. Many defoaming agents simultaneously act as deaerating agents.

dispersants

may be present in an amount of up to 0.5% by weight, preferably up to 0.3% by weight, based on the total weight of the component to which they are added.

The use of a light stable aromatic amine in a polyol component increases the lamination time in the reaction of the polyol component with a polyisocyanate component in the preparation of a polyurethane gelcoat.

When mixing the polyol component, the polyols are typically presented with additives in a vacuum dissolver. The fillers and pigments are then dispersed in vacuo in the polyols. For mixing the polyisocyanate component, the polyisocyanate is usually initially charged and mixed with the appropriate additives. Subsequently, the filler and the thixotropic agent are dispersed in vacuo.

The relative amounts of polyol component and polyisocyanate component are (in particular in the two-component composition used according to the invention) chosen so that hydroxyl groups and isocyanate groups react in the respectively desired molar ratio. The molar ratio of hydroxyl groups to isocyanate groups (OH: NCO) is usually in the range from 1: 3 to 3: 1, preferably 1: 2 to 2: 1, more preferably 1: 1.5 to 1.5: 1. According to a particularly preferred embodiment, the ratio OH: NCO is close to a stoichiometric molar ratio of 1: 1, d. H. in the range of 1: 1.2 to 1.2: 1, preferably 1: 1.1 to 1.1: 1, and particularly preferred is an equimolar reaction, d. H. the relative amounts of polyol component and polyisocyanate component are chosen such that the molar ratio of hydroxyl groups to isocyanate groups is about 1: 1.

Gelation of the mixture of the two components occurs either at room temperature or, if accelerated gelation is desired, at elevated temperature. For example, can be gelled at a temperature of 40, 60 or even 80 ° C. In the case of the particularly preferred mixture of the components of the two-component composition used according to the invention, however, a temperature increase to accelerate the gelation is not absolutely necessary.

When the formation of a mechanically sufficiently stable gel is completed, resin, for example epoxy resin and, if desired, glass fiber fabric or glass fiber fleece, is applied to the gel coat within the lamination time. By means of polyol components used according to the invention and two-component compositions used according to the invention, it is achieved that the lamination time available for lamination is in the range of about 20 minutes and 72 hours, typically about 48 hours. The lamination process on gelcoats is no different from the lamination processes which are used without the use of gelcoats and e.g. B. in "fiber composite structures" by M. Flemming, G. Ziegmann, S. Roth, Springer, Berlin, Heidelberg, New York, 1996, are described. The curing of the gel coats usually takes place at elevated temperature.

Another preferred embodiment relates to a composite with a polyurethane gelcoat which is obtainable by mixing a polyol component comprising a light stable aromatic amine with a polyisocyanate component and curing the mixture at 120 ° C (1 hour), wherein the polyurethane gelcoat at 900 hours of artificial weathering according to ASTM-G-53 (4 hours UVB 313, 4 hours condensation) a hue Delta E (measured according to DIN 5033 Part 4 and evaluated according to DIN 6174) of not more than 6.5, preferably less than 5, in particular smaller than 4, such as less than 3. The polyurethane gelcoat can be prepared by mixing the components of the described two-component composition and curing the mixture.

Thus, the invention relates to a composite material comprising a gelcoat and its use for the production of moldings. A particularly preferred embodiment of the molded parts are wind wings.

• – Sie ist ein System aus lediglich zwei Komponenten und deshalb einfach zu verarbeiten.
• – Die Topfzeit beträgt lediglich 10 bis 15 Minuten.
• – Die Mischung aus Polyolkomponente und Polyisocyanatkomponente ist innerhalb von 20 bis 70 Minuten klebfrei, auch bei 0,5 mm Schichtdicke und Raumtemperatur. Dafür ist keine Erwärmung notwendig.
• – Die Laminierzeit liegt bei Raumtemperatur bei mehr als 72 Stunden, damit sind sehr gute Voraussetzungen für die Haftung zu EP-Laminaten gegeben.
• – Die Mischung der zwei Komponenten ist bis zu 1 mm Nassschichtdicke an einer vertikalen Fläche ablaufsicher.
• – Infolge der bevorzugt mit Kieselsäure eingestellten Viskosität der Polyisocyanatkomponente ist eine gute Mischbarkeit der zwei Komponenten gegeben.
• – Die bei der Herstellung der zwei Komponenten eingesetzten Verbindungen sind arbeitshygienisch gut handhabbar und bei der Verarbeitung emissionsfrei.
• – Die zwei Komponenten ergeben ein transparentes Gelcoat, können deshalb beliebig pigmentiert werden.
• – Die gemischten Komponenten sind auch als Spachtelmasse oder als Beschichtung, die nicht im In-Mould-Verfahren appliziert werden muss, einsetzbar.
• – Die Mischung der Komponenten ist selbstverlaufend.
• – Eine vollständige Härtung der Mischung der zwei Komponenten kann bereits bei Temperaturen von 80 bis 160°C innerhalb von 30 Minuten bis 2 Stunden erreicht werden.

The two-component composition used according to the invention offers the following advantages:

• - It is a system of only two components and therefore easy to work with.
• - The pot life is only 10 to 15 minutes.
• The mixture of polyol component and polyisocyanate component is tack-free within 20 to 70 minutes, even at 0.5 mm layer thickness and room temperature. No heating is necessary for this.
• - The lamination time is more than 72 hours at room temperature, which provides very good conditions for adhesion to EP laminates.
• - The mixture of the two components is leak-proof up to 1 mm wet layer thickness on a vertical surface.
• As a result of the viscosity of the polyisocyanate component, which is preferably adjusted with silica, good miscibility of the two components is achieved.
• The compounds used in the production of the two components are easy to handle in terms of industrial hygiene and are emission-free during processing.
• - The two components result in a transparent gelcoat, so they can be pigmented arbitrarily.
• - The mixed components can also be used as putty or as a coating that does not have to be applied in the in-mold process.
• - The mixture of components is self-leveling.
• - A complete cure of the mixture of the two components can already be achieved at temperatures of 80 to 160 ° C within 30 minutes to 2 hours.

• – Gute Bewitterungsstabilität.
• – Bei kurzer Gel- und Klebfreizeit eine lange Laminierzeit.
• – Nach der Entformung erhält man glatte Bauteiloberflächen ohne Oberflächendefekte, was mindestens teilweise auf die vergleichsweise hohe Glasübergangstemperatur T_G von höher als 60°C bis 70°C zurückgeführt werden kann.
• – Hohe Hydrolysebeständigkeit.
• – Hohe Warmformbeständigkeit, da Tg ≈ 70°C.
• – Hohe Chemikalienbeständigkeit.
• – Hohe Abriebbeständigkeit.
• – Gute Schleifbarkeit. Eine Nachbehandlung des Gelcoats ist im Prinzip nicht notwendig. Werden jedoch große Bauteile aus mehreren Einzelteilen zusammengesetzt, ist es erforderlich, die Stoßkanten durch Spachtelmassen zu verschließen. Überschüssiger Spachtel wird in der Regel abgeschliffen. Um glatte Übergänge zu erhalten, ist es notwendig, dass das Gelcoat gut schleifbar ist. Das gleiche gilt, wenn Reparaturarbeiten an einer mechanisch geschädigten Fläche erforderlich werden.

The gelcoat used has the following advantageous properties:

• - Good weathering stability.
• - For a short gel and tack free, a long lamination time.
• - After demolding one obtains smooth component surfaces without surface defects, which can be at least partially attributed to the comparatively high glass transition temperature T _G of higher than 60 ° C to 70 ° C.
• - High hydrolysis resistance.
• - High heat distortion resistance, since Tg ≈ 70 ° C.
• - High chemical resistance.
• - High abrasion resistance.
• - Good sandability. Aftertreatment of the gelcoat is not necessary in principle. However, if large components composed of several individual parts, it is necessary to close the abutting edges by putties. Excess putty is usually sanded off. In order to obtain smooth transitions, it is necessary that the gelcoat is easy to sand. The same applies if repair work on a mechanically damaged surface is required.

The invention is illustrated by the following examples.

Examples

Test methods used are described below:

Test Method 1:

Sufficient low reactivity of preferred amines

To determine the gel time, the light-stable aromatic amine dissolved in toluene (20 wt .-% amine in toluene), at 23 ° C with an equimolar amount of an oligomer HDI isocyanate having an NCO content of about 21.8% and a Viscosity of the solvent-free isocyanate of 2750 to 4250 mPas, dissolved in toluene (80 wt .-% isocyanate in toluene, eg Desmodur N3300, Bayer AG) mixed. The gel time is determined using a Sunshine Geltime meter from Sunshine Scientific Instruments.

Test Method 2:

Weathering stability of a preferred light stable aromatic amine

For this purpose, the light-stable aromatic amine was dissolved in toluene (25 wt .-% amine in toluene) at 23 ° C with an equimolar amount of an oligomeric HDI isocyanate having an NCO content of about 21.8% and a viscosity of the solvent-free isocyanate 2750 to 4250 mPas (eg Desmodur N3300, Bayer AG) to a mixture. The mixture wound on inert white test plates and cured in a convection oven for 30 minutes at 80 ° C and then for 60 minutes at 120 ° C. This gave a coating with a dry film thickness of about 20 microns. To test the weathering stability of the coating, coating-coated neutral test panels were subjected to artificial weathering according to ASTM-G-53 (4 hours UVB 313, 4 hours condensation). The color change caused by the weathering is measured after 150 and 300 hours according to DIN 5033 Part 4 and evaluated according to DIN 6174. The delta E values obtained are a measure of the color shade deviation of the weathered coating and thus the light stability of the aromatic amine.

Test Method 3:

Weathering stability of a gelcoat used according to the invention (gelcoat weathering)

A polyol component containing a light stable aromatic amine is mixed with an isocyanate component and the mixture is applied to laminate boards and cured. The resulting gelcoat is subjected to artificial weathering according to ASTM-G-53 (4 hours UVB 313, 4 hours condensation). The resulting color change is measured after 900 hours according to DIN 5033 Part 4 and evaluated according to DIN 6174. The obtained delta E values are a measure of the color stability of the gelcoat on weathering. Curing took place at 120 ° C (1 h).

Test Method 4:

Yellowing stability of a gelcoat used according to the invention in a test at elevated temperature (thermal yellowing)

As described in Test Method 3, gelcoat-coated laminate panels were prepared. The plates were 96 hours in color change is measured according to DIN 5033 Part 4 and evaluated according to DIN 6174. The Delta E values obtained are also a measure of the color stability of the gel coats.

Test Method 5:

abrasion resistance

The abrasion resistance of the gel coats was tested according to ASTM-D-4060, Taber Abraser, roll TS 10, weight 1000 g, after 500 and 1000 rounds, respectively. The abrasion was determined gravimetrically.

Abrasion values preferred according to the invention are (Table 3): Prefers Especially preferred very particularly preferred after 500 laps ≤ 30 mg ≤ 30 mg ≤ 15 mg ≤ 10 mg after 1000 laps ≤ 50 mg ≤ 50 mg ≤ 30 mg ≤ 20 mg

Test Method 6:

Determination of T _G values of gelcoats

The glass transition temperature was determined according to DIN 51007 by DSC measurements. For this purpose, a cured gelcoat specimen was heated from -10 ° C to 250 ° C at a rate of 10 K / min and the glass transition temperature determined from the heat flow through the sample according to the above-mentioned standard. The device used for this purpose is a TC11K with a measuring cell DSC 30 from Mettler.

Test Method 7:

Testing the adhesion between gelcoat and laminate

• a) ”Keine Haftung”: d. h. Ablösung der Gelcoat-Schicht vom Laminat schon vor oder während des Biegeversuchs.
• b) ”Teilweise Haftung”: d. h. Delamination in der Grenzfläche Gelcoat-Laminat (Adhäsionsbruch) beim Bruch.
• c) ”Vollständige Haftung”: d. h. keine Ablösung der Gelcoat-Schicht beim Bruch des Verbundbauteils.

A 3 cm wide and 20 cm long laminate strip of about 2 mm thickness, which is coated with a 0.7 mm thick layer of gel coats, is broken in a bending test according to DIN EN ISO 1519 on a 5 mm mandrel. The fracture edge is assessed visually. There is a distinction between:

• a) "No adhesion": ie detachment of the gelcoat layer from the laminate before or during the bending test.
• b) "Partial adhesion": ie delamination in the gelcoat laminate interface (adhesion breakage) at break.
• c) "Complete adhesion": ie no detachment of the gelcoat layer when the composite component breaks.

Example 1: Application of Test Method 1

The gel time using light stable aromatic amines was determined according to Test Method 1. The results with amines from Lonza are shown in the following Table 4: TABLE 4 Lightfast aromatic amine gel time M-DEA 357 s = 5 min 57 s M-MIPA 221 s = 4 min 41 s M-DEAC 2635 s = 43 min 55 s M-DIPA 166 s = 2 min 46 s

Example 2: Application of Test Method 2

The weathering stability of light-stable aromatic amines was determined according to Test Method 2. The results are shown in the following Table 5. Table 5 Lonzacure M-MIPA Lonzacure M-DIPA Lonzacure M-CDEA Lonzacure M-DEA Delta E 150 h 21.20 19.40 28.50 24,90 Delta E 300 h 23,10 21.10 30,20 24,90

Example 3: Preparation of polyol components

Polyol components were formulated whose constituents are given in Table 6 below. Table 6 polyol PA PB According to the invention Not according to the invention Gewichisteile parts by weight Polycaprolactone polyol (OH content about 10 mol / kg 60 90 glycerol 30 4,4'-methylene-bis (3-chloro-2, b-diethylaniline) 2 Fillers (eg talc and titanium dioxide) 50 50 molecular sieve 25 25 Light stabilizers (eg HALS and UV absorbers) 2.5 2.5 Catalyst (eg DBIL) 0.2 0.2 additives 0.5 0.5

Example 4: Polyisocyanate components

Polyisocyanate components were formulated using the ingredients listed in Table 7 below. Table 7 polyisocyanate HA [parts by weight] parts by weight Oligomer HDI biuret 100 Pyrogenic silica 2 additives 0.5

Example 5: Preparation and analysis of gel coats

Table 8 below summarizes the preparation of gelcoats and their tests. The gel coats were prepared by mixing each one polyol component, and a polyisocyanate component, heated to 20.5 to 24 ° C, in such a ratio that a stoichiometric ratio of isocyanate groups to hydroxyl groups resulted. The mixture was run for 3 minutes. The mixture was applied in a layer thickness of 500 microns on a steel mold, degreased with solvent and with a release agent, for. Zywax Watershield.

With an epoxy / Glasgelege prepreg, z. B. STRAFIL ^® GM 9.5 EN 4163/44 (Fa. Hexcel Composites) was laminated over and the composite of Gelcoatmischung substrate and was cured. Thereafter, laminate adhesion, surface finish, glass transition temperature, abrasion, thermal yellowing and weathering stability were determined.

Result:

The gelcoat formulation used according to the invention shows in comparison even after 72 hours lamination time and subsequent 1 hour curing of the composite in a vacuum bag at 120 ° C significantly better adhesion properties than the non-inventive PUR formulations. The surface of the gelcoat layer has no interference from sink marks and is thus different from non-inventive PUR gel coats. In addition, the gelcoat formulation exhibits significantly improved yellowing, weathering and abrasion resistance over both the commercial PUR and EP gelcoat formulations. The glass transition temperature of the PUR Gelcoats used is with 70 ° C in the proximity of what one can expect from epoxy Gelcoats. This results in a significantly increased hot-forming resistance of the gel coats used in comparison to commercially available PUR gel coats.

Claims (20)

A composite comprising a polyurethane gelcoat preparable by mixing the components of a bicomponent composition A) a polyol component, the A1) 2 to 60 wt .-%, based on the total mass of the components A1, A2 and A3, one or more low molecular weight polyols having a molecular weight of 60 to 160 g / mol and a hydroxyl group concentration of 22.3 to 35 moles of hydroxyl groups per kg low molecular weight polyol, A2) 97 to 30 wt .-%, based on the total mass of the components A1, A2 and A3, one or more higher molecular weight polyols and A3) 0.1 to 20 wt .-%, based on the total mass of the components A1, A2 and A3, one or more light-stable aromatic amines containing, and B) comprises a polyisocyanate component containing one or more polyisocyanates, and curing the mixture. A composite material according to claim 1, characterized in that the light-stable aromatic amine dissolved in toluene (20 wt .-% amine in toluene) at 23 ° C mixed with an equimolar amount of an oligomeric HDI isocyanate having an NCO content of about 5 , 2 mol / kg and a viscosity in the range of 2750 to 4250 mPas, dissolved in toluene (80 wt .-% isocyanate in toluene), a gel time of more than 30 seconds, preferably more than 3 minutes, more preferably more than 5 minutes, in particular more than 20 minutes (determined according to E-DIN VDE 0291-2, 1997-06, point 9.2.1) A composite material according to claim 1, characterized in that the light-stable aromatic amine dissolved in toluene (25 wt .-% amine in toluene), mixed at 23 ° C with an equimolar amount of an oligomeric HDI isocyanate having an NCO content of about 5 , 2 mol / kg and a viscosity in the range of 2750 to 4250 mPas, a mixture results, wherein the mixture, applied to inert white test plates and cured in a convection oven for 30 minutes at 80 ° C and then cured for 60 minutes at 120 ° C. Coating with a dry film thickness of about 20 microns, and the coating at 300 hours artificial weathering according to ASTM G-53 (4 hours UVB 313, 4 hours condensation) a hue Delta E (measured according to DIN 5033 Part 4 and according to DIN 6174 evaluated) of at most 50, preferably at most 45, more preferably at most 40, such as at most 30. A composite material according to claim 2 or claim 3, characterized in that the light-stable aromatic amine is a methylenebisaniline, in particular a 4,4'-methylenebis (2,6-dialkylaniline). Composite according to Claim 3, characterized in that the photostable aromatic amine is 4,4'-methylenebis (3-chloro-2,6-diethylaniline). Composite material according to one of the preceding claims, characterized in that the proportion of photostable aromatic amine in the polyol component, based on the total mass of the constituents A1, A2 and A3 of the polyol component, in the range of 0.3 to 10 wt .-%, more preferably 0.5 to 5 wt .-% and in particular 1 to 3 wt .-% is. Composite material according to one of the preceding claims, characterized in that the proportion of low molecular weight polyol in the polyol component, based on the total mass of the constituents A1, A2 and A3 of the polyol component, in the range of 5 to 50 wt .-%. A composite material according to claim 7, characterized in that the proportion of low molecular weight polyol in the polyol component, based on the total mass of the constituents A1, A2 and A3 of the polyol component, in the range of 10 to 45 wt .-%, more preferably 20 to 40 wt .-% and in particular 30 to 35 wt .-% is. Composite material according to one of the preceding claims, characterized in that the hydroxyl group concentration of the low molecular weight polyol is in the range of 25 to 34, more preferably in the range of 28 to 34 and in particular in the range of 30 to 33 moles of hydroxyl groups per kg of low molecular weight polyol. A composite material according to claim 9, characterized in that the low molecular weight polyol is selected from straight-chain or branched-chain glycols, triols, tetrols and pentols, preferably ethylene glycol, 1,2- and 1,3-propylene glycol, glycerol, trimethylolmethane, trimethylolethane, trimethylolpropane, meso- Erythritol and pentaerythritol, especially glycerol. Composite material according to one of the preceding claims, characterized in that the polyol component is free of aliphatic dicarboxylic acids. Composite material according to one of the preceding claims, characterized in that the higher molecular weight polyol is selected from polyester polyols and polyether polyols, acrylate polyols and polyols based on dimer fatty acids. Composite material according to one of the preceding claims, characterized in that the proportion of higher molecular weight polyol in the polyol component, based on the total mass of the constituents A1, A2 and A3 of the polyol component, in the range 90 to 40 wt .-%, more preferably 80 to 45 wt. % and in particular 70 to 50 wt .-% is. Composite material according to one of the preceding claims, characterized in that the polyol component additionally contains one or more catalysts. Composite material according to one of the preceding claims, characterized in that the polyisocyanate component additionally contains silica, in particular silanized fumed silica. Composite material according to one of the preceding claims, characterized in that the polyol component additionally contains one or more fillers selected from talc, silica, titanium dioxide, molecular sieves, dolomite, quartz powder, precipitated CaCO ₃ , BaSO ₄ and kaolin. Composite material according to one of the preceding claims, characterized in that the polyol component additionally contains one or more additives selected from defoaming agents, dispersants, deaerating agents and catalysts. Composite material according to one of the preceding claims, characterized in that the polyisocyanate component additionally contains one or more additives selected from defoaming agents, dispersants, deaerators, and catalysts. Use of the composite material according to one of the preceding claims for the production of molded parts. Use according to claim 19, characterized in that the molded part is a wind vane.