DE102004022683A1 - Production of polyurea spray elastomer for use in concrete repair and waterproofing, involves reacting a prepolymer derived largely from 2,4-diphenyl-methanedi-isocyanate with an amine component - Google Patents

Abstract

A method for the production of polyurea spray elastomers from polyisocyanates and amines, in which the polyisocyanate component is a prepolymer derived from 2,4-diphenylmethanedi-isocyanate (2,4-MDI) or a mixture of 2,4-MDI and 4,4-MDI containing at least 50 wt% 2,4-MDI, optionally together with other MDI-based isocyanates. A method for the production of polyurea spray elastomers (I) by reacting (a) polyisocyanates with (b) amines, in which (a) comprises (ai) reaction products of compounds containing at least two NCO-reactive hydrogens with 2,4-MDI or a mixture of 2,4-MDI and 4,4-MDI containing at least 50 wt 2,4-MDI, optionally together with (aii) mixtures of MDI and polymethylene-polyphenylene-polyisocyanates and/or (aiii) isomers of MDI which may be modified with groups other than urethane, and (b) is a mixture of (bi) polyether-amine(s) and (bii) other prim. or sec. amine(s) as chain extender(s). An independent claim is also included for polyurea spray elastomers (I) obtained by this method.

Description

object The invention relates to polyurea substitution elastomers and to a process for their production.

typical Areas of application of polyurea spray elastomers are coatings, especially for Concrete repair and water protection (roof, parking deck coatings, Bridges-, Tunnel repairs), so-called "Secondary Containment" (Coatings for catch basins of chemical, sewage or oil tanks or dangerous goods loading zones), Corrosion protection (loading areas of cargo ships, trucks, pick-ups and railway wagons) or so-called "primary containment" (sewage shafts, sewage treatment plants).

Polyurea spray elastomers are reaction products of an at least difunctional isocyanate with an at least difunctional primary or secondary amine. As amines are usually high molecular weight Polyetheramines and low molecular weight aminic chain extenders used. As isocyanates are usually those based on diphenylmethane diisocyanate (MDI) used.

When Isocyanate component, often referred to in the art as the B component, is usually a prepolymer which is based on an isomer or isomer mixture MDI based. The preparation of these isocyanate prepolymers takes place by reaction of particular hydroxyl, also also amine-terminated polyethylene or polypropylene oxides with polyisocyanates.

The Amine component, common in the art termed R component is usually a mixture of primary aliphatic polyetheramines and usually aromatic amines Chain extenders.

The main constituent of the amine component of a polyurea formulation is a mixture of polyetheramines, ie of amine-terminated di- or higher-functional polyethylene or polypropylene oxides with molecular weights of between 200 and 5000 g mol ^-1 . The aliphatic amines react faster than the aromatic components of the chain extenders and serve primarily to build up the soft phase of the polyurea spray elastomers.

Of the in polyurea formulation usually used chain extender is diethylene toluenediamine (DETDA). As compared to aliphatic Amines more unreactive component DETDA determines the curing behavior of the system. To synthesize light-stable polyureas, be also aliphatic chain extenders used. The mostly aromatic chain extenders are predominantly in incorporated the hard phase of the polyurea spray elastomers.

Polyurea spray elastomers be, as stated, mostly used as coatings. These are their liquid starting components, usually referred to as system or formulation, mixed under high pressure, on the surface to be coated sprayed and harden out there. The reaction time is usually only a few seconds.

Around to achieve optimal processing and product properties is it desirable the viscosity the liquid Output components as possible to keep low or the viscosities of isocyanate and amine component to be largely aligned. Only so can a sufficient miscibility the extremely reactive Components guaranteed become. Cause mixing errors to a reduced surface quality. Low viscosity Systems are easier to process, meaning they can operate at lower pressures and temperatures are processed. Furthermore, the reaction should not be too fast proceed to optimum distribution of the reactive starting components before its complete curing on the surface to be coated to ensure.

It There are different possibilities about the reactivity of systems for Polyurea spray elastomers decrease.

This on the one hand is a variation of the amine component through the use alternative aminic chain extender of lower reactivity or by the use of so-called hybrid systems, that is by the partial replacement of otherwise hydroxy-terminated polyethers. On the other hand, the reactivity of the isocyanate component reduced by the partial replacement of 4,4'-MDI by 2,4'-MDI become.

Examples of alternative aminic chain extenders are 4,4'-methylenebis (2,6-diethyl) -aniline (MDEA), 4,4'-methylenebis- (2,6-diisopropyl) -aniline (MDIPA)), 4,4 '-Methylenbis- (3-chloro, 2,6-diethyl) aniline (MCDEA) or dimethylthio-toluenediamine (DMTDA, Ethacure ^® 300). In addition, also with reaction-chain secondary amine functionalities such as N, N'-di (sec-butyl) amino-biphenylmethan (DBMDA, Unilink 4200 ^®) or N, N'-di-sec-butyl-p-phenylenediamine (Unilink ^® 4100).

mostly receives one for one Polyurea spray elastomers with alternative chain extenders those benefits that are directly linked to slowed reactivity, for example, a higher one Surface quality or a better leveling behavior. Main disadvantage of these alternatives chain is her usually comparatively high price. Furthermore, such alternative chain extender usually a negative impact on the mechanical properties of the polyurea elastomer.

Farther are some of these chain extenders solid at room temperature (MCDEA, MDIPA) and only partially in the aliphatic Amines soluble or poorly miscible with these.

By a partial replacement of the amine by hydroxy-terminated polyethers can the reactivity the systems for Polyurea spray elastomers also be lowered. Such so-called hybrid formulations usually contain at least one catalyst, so with Standard catalysts no emission-free systems are obtained. The use of catalysts leads also to an increased Sensitivity of the elastomers to water. Overall, that is System less robust, it hardens only on comparatively dry surfaces and at moderate temperatures bubble-free or sufficiently fast. The bimodal Reaction profile of hybrid systems, which is the cause of the lower reactivity of isocyanates across from Alcohols compared to amines, can also to surfaces of inferior quality, namely lead to the formation of so-called pinholes

One increased Content of 2,4'-MDI isomers in Isocyanatprepolymer offers a number of advantages both in terms of Processing of the components as well as the final properties of the sprayed polyurea system. These benefits go causal on the opposite the 4,4'-MDI isomer significantly lower reactivity of the 2,4'-MDI isomer back.

2,4'-MDI-rich polyurea spray elastomers show in particular an improved flow and leveling behavior and thus a better surface quality. The at faster curing Polyurea systems often observed orange peel formation is pushed back. The lower reactivity of 2,4'-MDI-rich systems leads further to a better underground wetting and thus usually too an elevated one Adhesion of polyurea spray elastomers. But also the binding of the individual sprayed polyurea layers among themselves, which are sprayed in a short time sequence and from which the overall coating is ultimately built, is for 2,4'-MDI-rich formulations elevated. This is in addition to structural differences at the molecular level another reason why the mechanical property profile with increased 2,4'-MDI content generally raised. Indeed one finds for 2,4'-MDI-rich Systems for example higher elongation at break and improved elasticity.

Out The prior art discloses a number of possibilities, polyurea spray elastomers with a higher one Content of 2,4'-MDI provide.

WHERE 200228935 describes polyurea spray elastomers in their preparation As the isocyanate component an isocyanate prepolymer is used. This is made by first containing MDI 4,4'-MDI on the MDI isomer mixture of greater than 75% by weight reacted with a polyol and this NCO prepolymer on with an MDI isomer mixture having a content of 2,4'-MDI greater than 25 wt .-% mixed becomes. You get storage-stable isocyanate components of relatively low viscosity and reactivity. The resulting Polyurea spray elastomers have improved surface properties and improved mechanical properties. The disadvantage is in particular the complex preparation of Isocyanatprepolymers in a two-stage Process. Furthermore, one is through the use of MDI prepolymers with high 4,4'-MDI isomer content as a mixture component with respect to the reduction of Reactivity and viscosity of the system and the resulting improvement in surface finish. So have to usually also continue to diluents be used on the isocyanate side, which adversely affect the mechanical properties of the resulting polyurea spray elastomer can affect.

In EP 802209 are polyurea spray elastomers high flexibility and elongation at break and with improved adhesion, which are particularly intended for direct applications in railway vehicles. They are prepared by reacting prepolymers based on MDI with amines. It is stated that polyurea spray elastomers with an increased proportion of 2,4'-MDI, in particular with a content of at least 50%, lead to products with increased flexibility. In order to ensure the adhesion of the polyurea spray elastomers, alkoxysilanes and water must be added to the system. The use of alkoxysilanes makes the systems more expensive. If you like, in EP 802 209 In addition, higher concentrations must be used to bring effective amounts of the adhesion promoter in the application area in the boundary region coating base and thereby achieve a significant improvement in adhesion, this not as a primer, but diluted in the amine component applies. An adhesion improvement is to be expected only on almost dry substrates, an application on substrates with considerable residual moisture, as they are often present in outdoor applications, is not possible. The use of even small amounts of water as an activator for the alkoxysilanes is problematic with regard to the storage stability of the amine component. The presence of water under basic conditions can lead to crosslinking of the siloxanes and thus to a change in the system properties with the storage time up to the loss of the already low adhesion improvement. The processing of the system thus becomes more complex for the user, not only in terms of the number and the components to be used. Increased amounts of water, in spite of the preferred reaction of the amines with excess isocyanate as a competing reaction, can lead to undesirable foaming of the elastomers, which, in addition, may in some cases also be due to water vapor formed under the increased application and reaction temperature.

task Thus, the invention was a simple, storage-stable polyurea Spray elastomer system with conventional To provide amine components whose isocyanate component a decreased reactivity and viscosity and which is too easy to process without the use of diluents Polyurea elastomers with improved surface properties leads.

A Another object of the invention was polyurea spray elastomers high elasticity and elongation at break at the same time high hardness provide.

task The invention further has been to simple polyurea spray elastomer systems to provide the good substrate adhesion with direct application on the substrate to be coated without the addition of adhesion promoters or the application of primers show.

• a) Polyisocyanaten mit
• b) Aminen,

dadurch gekennzeichnet, dass als Polyisocyanate a)

• ai) Umsetzungsprodukte aus Verbindungen mit mindestens zwei mit Isocyanatgruppen reaktiven Wasserstoffatomen mit 2,4'-MDI, einem Gemisch aus 2,4'-MDI und 4,4'-MDI mit einem Gehalt an 2,4'-MDI von mindestens 50 Gew.-%, gegebenenfalls gemeinsam mit
• aii) Gemischen aus MDI und Polymethylen-polyphenylen-polyisocyanaten und/oder
• aiii) Isomeren von MDI, die durch Einbau von anderen als Urethangruppen modifiziert sein können,

und als Amine b) ein Gemisch aus bi) mindestens einem Polyetheramin und bii) mindestens einem von bi) verschiedenen primären oder sekundären Amin als Kettenverlängerer eingesetzt werden.The object could surprisingly be achieved by a process for the preparation of polyurea spray elastomers by reacting

• a) polyisocyanates with
• b) amines,

characterized in that as polyisocyanates a)

• ai) reaction products of compounds having at least two isocyanate-reactive hydrogen atoms with 2,4'-MDI, a mixture of 2,4'-MDI and 4,4'-MDI having a content of 2,4'-MDI of at least 50 wt .-%, optionally together with
• aii) mixtures of MDI and polymethylene polyphenylene polyisocyanates and / or
• aiii) isomers of MDI which may be modified by incorporation of other than urethane groups,

and as amines b) a mixture of bi) at least one polyetheramine and bii) at least one of bi) different primary or secondary amine are used as chain extenders.

object The invention is therefore the said method and the after Polyurea spray elastomers prepared by this process.

Of the NCO content of the polyisocyanates a) is preferably between 10 and 22 wt .-%, in particular between 13 and 20 wt .-%.

The Reaction products ai), also referred to below as prepolymers, can alone or in combination with the mixtures of MDI and polyphenylenepolymethylene polyisocyanates aii) or with further MDI aiii) for the preparation of the polyurea elastomers be used.

The Mixtures of MDI and polyphenylenepolymethylene polyisocyanates aii) are commercially available and become common also referred to as raw MDI. The NCO content of these mixtures is usually between 29 and 33% by weight. If mixtures of MDI and Polyphenylenpolymethylenpolyisocyanaten aii) are used together with the prepolymers ai) is carried out their use in an amount of at most 65 wt .-%, preferably from maximum 35 wt .-%, each based on the weight of the component a).

When Isomers of MDI aiii) any mixtures of 2,2'-, 2,4- and 4,4'-MDI be used. Preferably, pure 2,4'-MDI or mixtures from 2,4'-MDI and 4,4'-MDI. The mixtures from 2,4'-MDI and 4,4'-MDI preferably a content of 2,4'-MDI from 25 to 50 wt .-%, more preferably a content of 2,4'-MDI of 50 wt .-%. For better handling of pure MDI, which is solid at room temperature, it may be due to partial Reaction of the lasocyanate groups are modified. The implementation Mostly by the incorporation of uretdione, isocyanurate or Allophanate groups. If the isomers of MDI aiii) are used, their use is in an amount of not more than 45 wt .-%, based to component a).

The Component a) preferably has an NCO content in the range between 10 and 22 wt .-%, in particular between 13 and 20 wt .-%. If the prepolymer ai) is used alone, it has an NCO content in this area. If the prepolymer in admixture with the components aii) and aiii), its NCO content can also be below this range, as he by the mixture with the components aii) and aiii) on the required value is set. If the prepolymer ai) is used in a mixture with aii) and / or aiii), is its NCO content preferably in the range between 1 and 13 wt .-%. Of the NCO content of the prepolymer ai) can thus, depending on the composition of component a), in the range between 1 and 22 wt .-% are.

For the preparation of the isocyanate prepolymers used as polyisocyanates ai) can be used as compounds having at least two isocyanate-reactive hydrogen atoms preferably hydroxyl and amine-terminated polyethylene or polypropylene oxides, polyesterols, compounds containing OH and amine groups or mixtures of these compounds with each other, the compounds with at least two isocyanate-reactive hydrogen atoms have a molecular weight between 200 and 10,000 g / mol, preferably 500 to 5000 g / mol, more preferably between 1000 and 4000 g / mol and more preferably of 2000 g mol ^-1 and a functionality of 2-4, but in particular have from 2. Particularly preferred are polyether diols having a molecular weight between 1000 and 4000 g mol ^-1 . As a rule, the isocyanate-reactive component is at least 50% by weight, preferably at least 80% by weight, of one or more of the diols described. As amines, the compounds described in more detail below as component bi) can be used. The average functionality of the resulting prepolymer a) is usually less than 2.6, preferably less than 2.2.

The main component of the amines b) is bi) at least one, preferably a mixture of at least two polyoxyalkyleneamines, so-called polyetheramines, ie of amine-terminated di- or higher functional polyalkylene, usually polyoxyethylene or polyoxypropylene oxides, with molecular weights between 200 and 5000 g mol ^{. 1} , in particular from 2000 to 5000 g mol-1 used. It is also possible to use amine-terminated PTHF. The amine groups of the polyetheramines are primarily primary amine groups. It can also, as stated, even a single polyetheramine can be used. The polyetheramines bi) are in particular diamines or triamines. Such compounds are sold, for example, by the company Huntsman under the name Jeffamine ^® or from BASF as polyetheramines.

mostly be polyamines by catalytic amination of the corresponding Polyalcohols produced.

The Polyoxyalkyleneamines bi) serve primarily to build up the soft phase in the polyurea spray elastomers.

At least a part of the amines bi) used can be substituted by polyetherols become.

Amine components, which contain both polyetheramines and polyetherols, as already stated, referred to as hybrid or mixed polyurea-polyurethane systems. Preferred is the proportion of amine hydroxyl-terminated polyether in the amine component in this invention as 50 wt .-%, more preferably it consists essentially of amine-terminated polyethers.

Farther Component b) may be low molecular weight, usually aromatic and diaminic, of bi) different amines as chain extenders bii) contain. These compounds usually have a molecular weight in the range between 150 and 500 g / mol. The Amingruppen the Ketternverlängerer bii) can primary or secondarily be. The in polyurea spray elastomers mostly used chains extender is diethylene toluenediamine (DETDA). As compared to aliphatic Amines more unreactive component DETDA determines the curing behavior of the system. Accordingly, the gel time by alternative chain extender with across from Isocyanates of reduced reactivity can be controlled. To light stable Polyurea spray elastomers to receive also aliphatic chain extenders be used.

In addition, the previously listed alternative amine chain extenders such as 4,4'-methylenebis (2,6-diethyl) -aniline (MDEA), 4,4'-methylenebis- (2,6-diisopropyl) -aniline (MDIPA), 4,4'-methylenebis (3-chloro, 2,6-diethyl) aniline (MCDEA), dimethylthio-toluenediamine (DMTDA, Ethacure 300 ^®) or reaction-chain having secondary amine functionality, such as N, N'-di (sec- butyl) amino-biphenylmethan (DBMDA, Unilink 4200 ^®) or N, N'-di-sec-butyl-p-phenylenediamine (Unilink 4100 ^® be used).

Further, not necessarily required formulation ingredients are, for example - thinner, mostly reactive diluents, which, when applied, are usually added to the isocyanate component. examples for reactive the isocyanate component are alkylene carbonates. However, the Addition of reactive diluents to a deterioration of the mechanical properties and the aging resistance of the polyurea spray elastomer to lead.

The Addition of additives to the amine component is by a processable viscosity limited. Such additives are pigments, adhesion promoters, UV stabilizers, Antioxidants or other fillers. The component b) may further, in particular abrasion improvers contain. As Abriebverbesserer are preferably with silicone modified alcohols, especially glycols used.

The System is usually applied by spraying, with the components under high pressure and at elevated pressure Temperature before discharge from the spray gun in the mixing head mixed and so reacted.

The volumetric ratio, in which polyisocyanate and amine component are sprayed, is preferably 1: 1, but can also be from 30:70 up to 70:30% by volume, but preferably up to 1.1: 1.

The sprayed surface In particular, when wet, it can improve adhesion Pretreated primer. The adhesion improver can, too especially for the adhesion on damp ground, also the B- resp preferably the R-component can be added.

Examples for primers are siloxanes and functionalized siloxanes. In particular, to name are epoxy-amino or vinyl-alkoxysilanes. Further examples of commercial available Primers are titanates such as neopentyl (diallyl) oxytri (m-amino) phenyl titanate or zirconates such as neopentyl (diallyl) oxy tri (m-ethylenediamino) ethyl zirconate. Other possible Primers are 1K or 2K polyurethane systems, polyvinylamines, polyacrylates or epoxy resins. The primers can dispersed before application in water or other solvents, emulsified or solved become.

The relationship from isocyanate groups to isocyanate-reactive groups, in particular, as stated, amine groups, in the production of polyurea spray elastomers is usually between 0.90 and 1.20, especially between 1.05 and 1.15.

It was found to be replaced by the complete replacement of 4,4'-MDI by 2,4'-MDI Isocyanate prepolymer the reduced reactivity of a given polyurea formulation in an increase of the gel time by 2-3 seconds. This This is usually the case for fast standard polyurea systems have a gel time of 2 to 3 seconds, a reduction the reaction rate about a factor of 2. For fast Polyurea systems is the relative increase in surface quality with increasing 2,4'-isomer of the NCO prepolymer the strongest pronounced.

The viscosity of the prepolymers used decreases with increasing 2,4'-MDI content. 2,4'-MDI-richer systems can be processed at lower temperatures or mix better with the lower-viscosity R component at a constant temperature. It can therefore be dispensed with prepolymers with high 2,4'-MDI content on the addition of reactive thinners on the isocyanate side. With rise The 2.4'-MDI content increases at an almost constant Shore hardness, the elongation at break monotonously. Highly flexible and highly elastic coatings with high tensile and flexural modulus of elasticity are obtained over a wide temperature range.

So can the polyurea spray elastomers according to the invention Strains of 600% while largely preserving the other properties exhibit.

Surprisingly you can still find that over 2,4'-MDI rich Prepolymers with an increased NCO content unusual elastic elastomers with high elongation at break and are accessible with little abrasion. It has thus been found that the polyurea spray elastomers according to the invention an elongation at break of 350% at a hardness of Shore 60 D.

Especially for isocyanate prepolymers with a 2,4'-MDI Share of MDI isomer mixture greater than 50% receives Polyurea spray elastomers improved liability.

The Invention will be explained in more detail in the following examples.

used output products

• Ethacure ^® 300: 80: 20 mixture of 3,5-bis (thiomethyl) -2,4-toluene diamine and 3,5-bis (thiomethyl) -2,6-toluene diamine. Commercially available from Albemarle Europe SPRC.
• Fluid 1248: silicone glycol graft copolymer. Commercially available from Dow.
• Lonzacure ^® DETDA 80: 80: 20 mixture of 3,5-diethyl-2,4-toluenediamine and 3,5-diethyl-2,6-toluenediamine. Commercially available from Lonza Ltd. and Albemarle Europe SPRC (Ethacure ^® 100).
• Lupranat® ^® MCI: 2,4'-MDI. Commercially available from BASF AG.
• Lupranat® ^® MI: 50: 50 isomer mixture of 4,4'- and 2,4'-MDI. Commercially available from BASF AG.
• Polyetheramine D-2000: Aliphatic primary amine-terminated polypropylenediamine, M _w = 2000 g mol ^-1 . Commercially available from BASF AG or Huntsman Petrochemical Corporation (Jeffamine ^® D-2000).
• Polyetheramine T-5000: Aliphatic primary amine-terminated polypropylenetriamine, M _w = 5000 g mol ^-1 . Commercially available from BASF AG or Huntsman Petrochemical Corporation (Jeffamine ^® T-5000).
• Unilink ^® 4100: N, N'-di-sec-butyl-p-phenylenediamine. Commercially available from Dort Ketal.

Example 1 - According to the invention: 2,4'-MDI-rich polyurea elastomers

When Isocyanate component (B component) for the polyurea elastomers are prepolymers of MDI (51.6 wt .-% of the B component) and a difunctional polypropylene glycol (48.4 wt%) having an OH number made of 56 mg KOH / g. As MDI 2,4'-MDI / 4,4'-MDI isomer mixtures with a 2,4'-MDI content of the MDI isomer mixture of 0% (carbodiimide-modified 4,4'-MDI), 25%, 50%, 75% and 100% used. The resulting isocyanate prepolymers have an NCO of 15.0 ± 0.1%. and a viscosity at 25 ° C from 800 ± 100 mPas.

The standard amine R component (Resin) used consists of 62.0 wt .-% of a difunctional, amine-terminated polyoxypropylenediamine having an average molecular weight of 2000 g mol ^-1 , 10.9 wt .-% of a trifunctional, amine terminier th polyoxypropylenetriamine with an average molecular weight of 5000 g mol ^-1 and 27.1% by weight of the primary aromatic diamine diethylenetoluenediamine (DETDA).

B- and R component were on a commercially available Gusmer SR 300 spraying machine in a volume ratio of 1: 1, at a temperature of 60 to 80 ° C and a pressure of about 150 bar on Teflon plates (60 cm · 60 cm) to a polyurea elastomer with a layer thickness of 20 mm sprayed (Index 110).

The reactivity of the system (gel and tack-free times) and characteristic mechanical properties of the polyurea coatings obtained are summarized in Table 1. The pure 2,4'-MDI prepolymer has by far the lowest viscosity under application conditions, which has largely matched the viscosity of the R component (h ^{70 ° C} = 36 mPas). With increasing 2,4'-content of the isocyanate prepolymer used, the reactivity of the system decreases at almost constant Shore hardness and the surface performance and adhesion (here: on stone) increase. The elongation at break increases monotonously with the 2,4'-MDI content. The tensile and flexural modulus of elasticity is also maximal for pure 2,4'-MDI systems and is 50% flat for medium 2,4'-MDI contents. In contrast, while tensile and tear propagation tem- peratures exceed a flat maximum at medium 2,4'-MDI levels, the abrasion resistance decreases monotonically with the 2,4'-MDI content.

Tabelle 1: Reaktivität und Mechanik von Polyurea-Elastomeren mit unterschiedlichem 2,4'-MDI/4,4'-MDI-Isomerenverhältnis der verwendeten Prepolymerkomponente. Dynamic mechanical analysis (DMA) shows that with increased 2,4'-MDI content of the prepolymer, the elasticity of the material also increases. Both the temperature range in which the material shows elastic properties - represented here by the glass transition temperature (maximum in G "), and the quality of the elastic properties - represented here by ^{25 ° C} = G '/ G" - is for 2, 4'-MDI-rich polyurea formulations increased.

Table 1: Reactivity and mechanics of polyurea elastomers with different 2,4'-MDI / 4,4'-MDI isomer ratio of the prepolymer component used.

Example 2 - According to the invention: 2,4'-MDI-rich polyurea elastomers in the presence of abrasion improvers

The procedure was as in Example 1. However, for all polyurea elastomers listed under Example 2, a prepolymer consisting of a 50:50 2,4'-MD1: 4,4'-MDI isomer ratio (51.6 wt .-% of the prepolymer, Lupranat MI ^®, BASF AG) and a difunctional polypropylene glycol (48.4 wt .-%) with an OH number of 56 is used. Various commercially available abrasion improvers were added to this prepolymer in a concentration of 2 or 4% by weight, based on the isocyanate component (Table 2).

Tabelle 2: Mechanik von Polyurea-Elastomeren mit einem 2,4'-MD1:4,4'-MDI-Isomerenverhältnis der verwendeten Prepolymerkomponente von 50:50, dem 2 beziehungsweise 4 Gew.-% eines Abriebverbesserers zugesetzt wurden. The abrasion can be significantly improved by adding the Abriebverbesserer otherwise otherwise constant mechanism.

Table 2: Mechanics of polyurea elastomers having a 2,4'-MD1: 4,4'-MDI isomer ratio of the 50:50 prepolymer component used, to which 2% and 4% by weight, respectively, of an attrition improver were added.

Example 3 - According to the invention: 2,4'-MDI-rich polyurea elastomers based on mixtures of 2,4'-MDI and MDI prepolymers

It The procedure was as in Example 1. However, it is for the isocyanate component first a prepolymer of MI (34.3% wt.%), a 50:50 mixture of isomers from 2,4'-MDI and 4,4'-MDI, and one difunctional polypropylene glycol (65.7 wt%) having an OH number made of 56 mg KOH / g. The isocyanate prepolymer thus obtained has an NCO content of 8.6 ± 0.1 Wt .-%. By mixing with (carbodiimide-modified) 4,4'-MDI, MI or Become 2,4'-MDI Prepolymers with a total 2,4'-MDI content on the MDI isomer mixture of about 25%, 50% and 75% and obtained a total NCO content of 15.0 ± 0.1 wt .-%.

Tabelle 3: Mechanik von Polyurea-Elastomeren mit unterschiedlichem 2,4'-MDI:4,4'-MDI-Isomerenverhältnis von 25 %, 50 % beziehungsweise 75 % der verwendeten Prepolymerkomponente, hergestellt durch Mischung eines MI-Prepolymers (NCO = 8,6 %) mit 4,4'-MDI, MI beziehungsweise 2,4'-MDI. The polyurea elastomers thus obtained are similar in their mechanical properties to those of Example 1, whose isocyanate component has a corresponding 2,4'-MDI: 4,4'-MDI isomer ratio (Table 3).

Table 3: Mechanics of polyurea elastomers with different 2,4'-MDI: 4,4'-MDI isomer ratio of 25%, 50% and 75% of the prepolymer component used, prepared by mixing a MI prepolymer (NCO = 8, 6%) with 4,4'-MDI, MI and 2,4'-MDI, respectively.

Example 4 - According to the invention: 2,4'-MDI-rich polyurea elastomers with high NCO value

It The procedure was as in Example 1. For the isocyanate component 2,4'-MDI / 4,4'-MDI isomer mixtures with a 2,4'-MDI content used on MDI isomer mixture of 25% and 75%. For each the two MDI isomer ratios are each MDI prepolymers by reaction with polypropylene glycol (OH number: 56 mg KOH / g) with an NCO content of 15% (see Example 1), 17% and 19%.

Tabelle 4: Mechanik von Polyurea-Elastomeren mit unterschiedlichem NCO-Gehalt von 15 %, 17 % beziehungsweise 19 % bei einem 2,4'-MDI:4,4'-MDI-Isomerenverhältnis von 25 beziehungsweise 75 % der verwendeten Prepolymerkomponente. For the 2,4'-MDI-richer MDI prepolymer (2,4'-MDI / 4,4'-MDI: 75%) polyurea elastomers of increased hardness with comparatively high elongation and good abrasion behavior are obtained.

Table 4: Mechanics of polyurea elastomers with different NCO contents of 15%, 17% and 19% respectively at a 2,4'-MDI: 4,4'-MDI isomer ratio of 25 and 75% of the prepolymer component used.

Claims (17)

A process for the preparation of polyurea spray elastomers by reacting a) polyisocyanates with b) amines, characterized in that as polyisocyanates a) ai) reaction products of compounds having at least two isocyanate-reactive hydrogen atoms with 2,4'-MDI, a mixture of , 4'-MDI and 4,4'-MDI with a content of 2,4'-MDI of at least 50 wt .-% optionally together with aii) mixtures of MDI and polymethylene polyphenylene polyisocyanates and / or aiii) isomers of MDI, which may be modified by incorporation of other than urethane groups, and as amines b) a mixture of bi) at least one polyetheramine and bii) at least one of bi) different primary or secondary amine used as a chain extender. Method according to claim 1, characterized in that the NCO content of the polyisocyanates a) is between 10 and 22% by weight. lies. Method according to claim 1, characterized in that the NCO content of the polyisocyanates a) is between 13 and 20% by weight. lies. Method according to claim 1, characterized in that that the middle functionality of the polyisocyanate a) is less than 2.6. Method according to claim 1, characterized in that that the middle functionality of the polyisocyanate a) is less than 2.2. Method according to claim 1, characterized in that the NCO content of the reaction products ai) is 1 to 22% by weight. Method according to claim 1, characterized in that the NCO content of the reaction products ai) is 5 to 20% by weight. Method according to claim 1, characterized in that that the NCO content of the mixtures of MDI and polymethylene polyphenylene polyisocyanates aii) is 29 to 33 wt .-%. Method according to claim 1, characterized in that the proportion of mixtures of MDI with polyphenylenepolymethylene polyisocyanates aii) 0 to 65% by weight, based on that used for the preparation of the polyisocyanate a) Isocyanate. Method according to claim 1, characterized in that the proportion of mixtures of MDI with polyphenylenepolymethylene polyisocyanates aii) 0 to 35% by weight, based on that used for the preparation of the polyisocyanate a) Isocyanate. Method according to claim 1, characterized in that that the proportion of MDI aiii) 0 to 45 wt .-%, based on the Preparation of the polyisocyanate a) isocyanate used. Process according to Claim 1, characterized in that the polyetheramines bi) are amine-terminated polyoxyethylene or polyoxypropylene oxides having molecular weights of between 200 and 5000 g mol ^-1 . Method according to claim 1, characterized in that that the primary or secondary Amines as chain extenders bii) a molecular weight in the range between 150 and 500 g / mol to have. Method according to claim 1, characterized in that that the primary or secondary Amines as chain extenders bii) are from the group containing diethylenetoluenediamine, 4,4'-methylenebis- (2,6-diethyl) -aniline (MDEA), 4,4'-methylenebis- (2,6-diisopropyl) -aniline (MDIPA), 4,4'-methylenebis (3-chloro, 2,6-diethyl) -aniline (MCDEA), dimethylthio-toluenediamine (DMTDA), secondary amine functions such as N, N'-di (sec-butyl) amino biphenylmethane (DBMDA) or N, N'-di-sec-butyl-p-phenylenediamine. Method according to claim 1, characterized in that that component b) 0 to 50 wt .-%, based on the component b) containing at least one polyol. Method according to claim 1, characterized in that that component b) 0 to 20 wt .-%, based on the component b) containing at least one polyol. Polyurea spray elastomers, preparable according to one of the claims 1 to 12.