MXPA97000880A - Polyureaque-based coating compositions have drying times more rapi - Google Patents

Abstract

The present invention relates to a coating composition for the preparation of a polyurea coating containing: a) an NCO prepolymer containing aromatically bound isocyanate groups and b) an aldimine corresponding to the formula X1- [N = CHCH (R1 ) (R2)] n where X represents an organic group having a valence of n and so obtained by separation of amino groups from a cyclic organic polyamine having aliphatically bound (cyclo) amino groups, R1 and R2 may be identical or different and represent organic groups which are inert to the isocyanate groups at a temperature of 100 ° C or less, or R1 and R2 together with the carbon atom will form a cycloaliphatic or heterocyclic ring, and n represents an integer having a value of at least 2, wherein the components a) and b) are present in amounts sufficient to provide an equivalents ratio of isocyanate groups to aldimine groups of about 1.0: 0.7 to 1.0: 0

Description

POLYUREA-BASED COATING COMPOSITIONS THAT HAVE MORE QUICK DRY DK TIMES A-N-TEC "^ EDEN fTES: OF THE INVENTION Cggpp of the invention * The present invention relates to coating compositions having faster drying times without substantially affecting the useful life of the coating compositions in the that the binder is based on aromatic NCO prepolymers in combination with aldimines prepared from polyamines having cyclic groups. DESCRIPTION OF PRIOR ART Moisture curable one-component coating compositions containing NCO prepolymers as binders are known. When exposed to water, generally in the form of atmospheric moisture, the prepolymers react to form urea groups. In the absence of moisture NCO prepolymers have a good stability in storage. Even after mixing with pigments that still contain residual water, the shelf life is still adequate, that is, it is generally at least 12 to 24 hours. This provides sufficient time to apply the flashback compositions before the viscosity increases to a point where it is not possible to apply the coating compositions using conventional spray equipment without adding additional solvent. One of the disadvantages of these coating compositions is that they have a relatively slow drying time, which is typically 5 to 6 hours or longer, even with NCO prepolymers prepared from aromatic polyisocyanates, ie, polyisocyanates having isocyanate groups aromatically bound. Accordingly, an object of the present invention is to provide moisture curable coating compositions that have faster drying times without simultaneously reducing the life of the coating compositions. This object can be achieved with the coating compositions of the present invention, which contain NCO prepolymers carrying aromatically bound isocyanate groups and sub-equivalent amounts of aldimines prepared from cycloaliphatic diamines. U.S. Patents 3,420,800 and 3,567,692 disclose coating compositions containing polyisocyanates and equivalent amounts of aldimines or ketimines, based on the amount of isocyanate groups. It is described that "the reaction of polyisocyanates with aldimines or ketimines in the presence of moisture is faster than the reaction of isocyanate groups with moisture." Therefore, using equivalent amounts of aldimines or ketimines, it is possible to obtain faster drying times without reduction. However, these references do not recognize that the use of coating compositions according to the present invention makes it possible to obtain faster drying times even when sub-equi The ability to obtain faster drying times when using amounts less than the equivalent amounts of aldimines is surprising because it would be expected that isocyanate groups that do not react with fast reacting aldimine groups will react slowly with water of the normal way, therefore, as the quantity d The aldimine decreases, the drying times would also be reduced because more isocyanate groups had reacted with water. However, the examples of the subject application demonstrate that this is not the case.

The present invention relates to a coating composition for the preparation of a polyurea coating containing a) an NCO prepolymer containing aromatically bound isocyanate groups and b) an aldimine corresponding to the formula X! - [N-CHCH (R?) (R2)] "where X represents an organic group having a valence of n and is obtained by separation of amino groups from a cyclic organic polyamine having (cyclo) aliphatically bound amino groupsRi and R2 can be identical or different and represent organic groups that are inert to the isocyanate groups at a temperature of 100 ° C or less, or Ri and R2 together with the carbon atom 13 form a cycloaliphatic or heterocyclic ring, and n represents an integer having a value of at least 2, wherein components a) and b) are present in amounts sufficient to provide an equivalents ratio of isocyanate groups to aldimine groups of about 1.0: 0.7 to 1.0 : 0, 1 DETAILED DESCRIPTION OF THE INVENTION According to the present invention, "polyurea" is understood as meaning a polymer containing urea groups and optionally other groups such as urethane groups. United (cyclo) aliphatically means aliphatically or cycloaliphatically attached. Component a) of the present invention is selected from NCO prepolymers containing aromatically bound isocyanate groups. These prepolymers are prepared by reacting an excess of monomeric polyisocyanates or polyisocyanate adducts, preferably multimeric diisocyanates, with organic compounds containing at least two hydroxy groups. Examples of suitable monomeric polyisocyanates include monomeric diisocyanates represented by the formula R (NCO) 2 I wherein R represents an organic group obtained by separation of isocyanate groups from an aromatic organic diisocyanate, i.e., a diisocyanate having aromatically bound isocyanate groups, and having a molecular weight of from about 112 to 1,000, preferably about;, 140 to 400. Preferred diisocyanates are those represented by the above formula wherein R represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms. Examples of suitable organic diisocyanates include 1,3- and / or 1,4-phenylene diisocyanate, 2,4 and / or 2,6-toluylene diisocyanate, 2,4- and / or 4,4'-diphenylmethane diisocyanate, 1, 5-naphthalene diisocyanate and mixtures thereof. It is also possible to use aromatic polyisopyanates containing 3 or more isocyanate groups such as 4, 4, 4-triphenylmethane diisocyanate and polymethylene polyphenylene polyisocyanates obtained by phosgenation of aniline / formaldehyde condensates According to a less preferred embodiment of the present invention, the polyisocyanate component for the preparation of the NCO prepolymers is a polyisocyanate adduct containing isocyanurate, uretdione, biuret, urethane, allophanate, carbodiimide and / or oxacliazinotrione groups and is prepared from a monomeric polyisocyanate containing aromatically bound isocyanate groups. Adducts polyisocyanates have an average functionality of 2 to 6 and an NCO content of 5 to 30% by weight In the US Patent 5,243,012, which is incorporated herein by reference, details are given regarding polyisocyanate adduct and its methods The preferred polyisocyanate adducts are polyisocyanates which they have isocyanurate groups, biuret groups and / or allophanate groups. The organic compounds containing hydroxy groups q.e. used to prepare the NCO prepolymers a) include high molecular weight compounds having molecular weights of 400 to 6,000, preferably 800 to 3,000, and optionally low molecular weight compounds with molecular weights by weight. below 400. Molecular weights are molecular weights of average # of number (Mn) and are determined by analysis of final groups (OH index).

Among the examples of high molecular weight compounds are polyester polyols, polyether polyalcohols, polyhydroxy polycarbonates, polyhydroxy polyacetals, polyhydroxy polyacrylates, polyhydroxy polyester amides and polyhydroxypolythioethers. Polyester polyalcohols, polyether polyalcohols and polyhydroxy polycarbonates are preferred. Especially preferred are polyether polyalcohols. Suitable polyester polyols include the reaction products of polyhydric, preferably dihydric alcohols to which trihydric alcohols and polybasic, preferably dibasic, carboxylic acids can be added. Instead of these p-carboxylic acids, the corresponding carboxylic acid anhydrides or polycarboxylic acid esters of lower alcohols or mixtures thereof can be used to prepare the polyesters. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic and can be substituted, for example, by halogen atoms and / or unsaturated. Examples include succinic acid, adipic acid, acid or suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic acid anhydride, tetrahydrophthalic acid anhydride, hexydehydrophthalic acid anhydride, acid anhydride. tetrachlorophthalic acid, tetrahydrophthalic anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride, fumaric acid, dimers and trimers, such as oleic acid, which can be mixed with monomeric fatty acids, dimethyl terephthalates and bis-terephthalate. glycol. Suitable polyhydroxy alcohols include, for example, ethylene glycol, propylene glycol- (1,2) and - (1,3), buylene glycol- (1,4) and - (1,3), hexanediol - (1, 6), octanediol- (1, 8), neopentyl glycol, cyclohexane dimethanol (1,4-bis-hydroxymethylcyclohexane), 2-methyl-1,3-propanediol, 2,2,4-trimethyl-1, 3-pentanediol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycol, glycerin and trimethylolpropane. It is also possible to use lactone polyesters, for example, e-caprolactone, or hydroxycarboxylic acids, for example,? -hydroxycaproic acid. Polycarbonates containing hydroxyl groups include those obtained by reaction of diols (such as propanediol- (1, 3), butánodiol- (1, 4) and / or hexanediol- (1, 6), diethylene glycol, triethylene glycol or tetraethylene glycol) with phosgene, diaryl carbonates such as diphenylcarbonate or with cyclic carbonates such as carbonate, ethylene or propylene. Also suitable are polyester carbonates obtained by reacting the previously described polyesters or polylactones with phosgene, diaryl carbonatot or ca, cyclic rbonates. Suitable polyether polyols are obtained from the known polymer by reacting starting materials containing reactive hydrogen atoms, preferably hydroxyl groups, with alkylene oxides such as ethylene oxides, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran. , epichlorohydrin or mixtures of these alkylene oxides. It is preferred that the polyethers contain no more than about 10% by weight of ethylene oxide units. Suitable starting compounds containing reactive hydrogen atoms include the polyhydric alcohols indicated for the preparation of the polyester polyols and, in addition, water, methanol, ethanol, 1,1-hexane triol, 1,2,4-butane. triol, trimethylol ethane, pentaerythritol, mannitol, sorbitol, methyl glycoside, sucrose, phenol, isonunyl phenol, resorcin, hydroquinone, 1,1,1- or 1,1,2-tris- (hydroxyphenyl) -ethane. Polyethers which have been obtained by reaction of starting compounds containing amine compounds may also be used, but are less preferred for use in the present invention. Suitable amine starting compounds include ammonia, methyl amine, tetramethylene diamine, ethanol amine, diethanol amine, triethanolamine, ethylene diamine, diethylene triamine, triethylene tetramine, 1,6-hexane diamine, piperazine, 2,5-dimethylpiperazine. l-amiho-3-aminomethyl-3, 3, 5-trimethylcyclohexane, bis- (4-aminocyclohexyl) -methane, bis- (4-amino-3-methylcyclohexyl) -methane, 1,4-cyclohexane diamine, 1 2-propane diamine, hydrazine, amino acid hydrazides, hydrazides of semicarbazido carboxylic acids, bis-hi-drazides, bis-semicarbazides, aniline, phenylene diamine, 2,4- and 2,6-toluylene diamine, polyphenylene polymethylene or polyamines of the type obtained by condensation reaction of aniline / formaldehyde and their mixtures. Resinous materials such as phenol and cresol resins can also be used as starting materials. More details concerning low molecular weight compounds and the other high molecular weight polyhydroxy starting materials are those described in U.S. Patent 4,701,480 which is incorporated herein by reference.

The NCO prepolymers generally have an isocyanate content of about 0.5 to 30% by weight, preferably from about 1 to 20% by weight, and are prepared in the known manner by reaction of the aforementioned starting materials to a ratio of NCO / OH equivalents of about 1.05: 1 to 10: 1, preferably about 1.1: 1 to 3: 1. This reaction can take place in a suitable solvent which can optionally be removed by distillation after the reaction, together with the volatile starting polyisocyanates present still unreacted. According to the present invention, the NCO prepolymers also include NCO semi-prepolymers containing unreacted starting polyisocyanates in addition to the urethane group-containing prepolymers. Component b) is selected from aldimines corresponding to the formula: X? - [N = CHCH (R?) (R2)] n where X represents an organic group having a valence of n and is obtained by separating the amino groups from a cyclic organic polyamine having (cyclo) aliphatically bound amino groups , preferably a diamine and more preferably a hydrocarbon group obtained by ppr separation of the amino groups of a diamine having at least one cycloaliphatically bound amino group. Ri and R2 may be the same or different and represent organic groups that are inert to isocyanate groups at a temperature of 100 ° C or less, preferably containing 1 to , more preferably 1 to 6 carbon atoms, or R 2 together with the β-carbon atom form a cycloaliphatic or heterocyclic ring and n represents an integer having a value of at least 2, preferably 2 to 6, more preferably 2 to 4 and more preferably 2. These compounds are prepared in the known manner by reaction of primary polyamines corresponding to the formula X - (NH2) n (II) with aldehydes corresponding to the formula 0 = CHCH (Ra) (R2) (III ) Suitable polyamines include 1,3- and / or 1,4-cyclohexane diamine, l-amino-2-aminomethyl cyclopentane, 1-amino-3, 3, 5-trimethyl-5-amino-methyl-cyclohexane ( isophorone diamine or IPDA), 2,4- and / or 2,6-hexahydrotoluylene diamine, 1,3- and 1,, 4-bis (aminomethyl) -cyclohexane, xylylene diamine, a, a, a '< T '-tetramethyl-1, 3- and / or-1,4-xylylene diamine, l-amino-1-methyl- (3) -aminomethyl cyclohexane, 2,4'- and / or 4,4'-diaminodicyclohexyl methane and 3,3'-dialkyl-4, '-diamino-dicyclohexyl methanes (such as 3, 3'-dimethyl-4,4'-diamino-dicyclohexyl methane and 3,3'-diethyl-4,' -diamino- dicyclohexyl methane). Preferred diamines are l-amino-3, 3, 5-trimethyl-5-amino-ethyl-cyclohexane, 2,4- and / or 2,6-hexahydroluol diamine, 4'-diamino-dicyclohexyl methane and 3, 3 -diraetiJ.-4, 4 '-diamino-diecyclohexyl methane. Preferred in particular are 1-amino-3, 3, 5-trimethyl-5-aminomethyl-cyclohexane and 4, '-diamino-dicyclohexyl methane.

Examples of suitable aldehydes include isobutyraldehyde, 2-ethylhexanal, 2-methyl-butyraldehyde, 2-ethyl butyraldehyde, 2-methyl valeraldehyde, 2,3-imethyl valeraldehyde, 2-methyl undecanal and cyclohexane carboxyaldehyde. The aldimines can be prepared in the known manner by reacting the polyamines with the aldehydes in amounts which are "quiometric" or with an excess of aldehyde. The excess aldehyde and the water that is produced can be separated by distillation. The reactions can be carried out in organic solvents, other than ketones. The solvents can also be removed by distillation after the reaction has been completed. The binders present in the coating compositions according to the invention contain prepolymers of NCO a) and aldimines b) in sufficient quantities to provide a maximum ratio of equivalents of isocyanate groups to aldimine groups of about 1.0: 0.7, preferably about 1.0: 0.6, more preferably about 1.0: 0.55 and more preferably about 1.0: 0.5, and a minimum equivalent ratio of 1.0: 0.1, preferably 1.0: 0.15, more preferably of about 1.0: 0.2 and more preferably about 1.0: 0.25 The binders used according to the invention can be prepared by simple mixing of the individual components with each other The preparation of the binders is carried out without solvent or in the presence of the solvents conventionally used in polyurethane or polyurea coatings.

An advantage of the process according to the invention is that the amount of solvent used can be greatly reduced when compared to that required in conventional single-component moisture cured systems. Examples of suitable solvents include xylene, butyl acetate, methyl isobutyl ketone, methoxypropyl acetate, N-methyl pyrrolidone, Solvesso solvent, petroleum hydrocarbons, iso-butanol, butyl glycol, chlorobenzenes and mixtures of these solvents. In the coating compositions used for the process according to the invention, the weight ratio of the total amount of binder components a) and b) to the amount of solvent is about 40:60 to 100; Or * preferably about 60:40 to 100: 0. The coating compositions used for the processes according to the invention may also contain other auxiliary agents and additives conventionally used in polyurethane and polyurea coatings, in particular pigments, fillers, catalysts, leveling agents, anti-settling agents, UV stabilizers, and Similar.

Other additives that increase the shelf life of compositions containing polyisocyanate # s and polyaspartic acid derivatives, such as the tin compounds described in the copending application, U.S. Serial No. 08 / 171,304, the disclosure of which is incorporated herein by reference, or the zeolites described in U.S. Patent 5,444,117, the disclosure of which is incorporated herein by reference.

The properties of the coatings obtained by the process according to the present invention can be adjusted, in particular by suitable selection of the nature and proportions of the starting components a) and b). Thus, for example, the presence of linear polyhydroxy compounds of relatively high molecular weight in the pre-poly ers or i-prepolymers of component a) increases the elasticity of the coatings; while the use of branched polyhydroxy compounds to prepare the prepolymers or semi-prepolymers increases the crosslink density and the hardness of the resulting coatings. To carry out the process according to the invention, the coating compositions used in the invention are applied as one or more layers to substrates by known methods, such as spraying, brushing, dipping or flooding or by means of applicators. of rollers or of blade. The process according to the invention is suitable for the formation of coatings on various substrates, for example metal, plastics, wood, cement, concrete or glass. The process of the invention is suitable in particular for obtaining coatings on sheet steel, for example for the manufacture of automobile bodies, machine finishing panels, buckets or tanks. The substrates to be coated by the process according to the invention can be treated with suitable primers before carrying out the process according to the invention. After the substrate has been coated, examples of which have been given above, the coatings can be cured at room temperature, for example, by air drying or by so-called forced drying, or at elevated temperature. The suppression of the increase in viscosity for the coating compositions according to the invention while drying times are maintained is demonstrated in the following examples. All parts and percentages given are by weight unless otherwise indicated.

EXAMPLES The following starting materials are used in the examples: Polyisocyanate 1 An MDI prepolymer having a viscosity of 2000-3000 mPa at 25 ° C, a j ^ CO content of 8% by weight and an average equivalent weight of 525 (marketed by Bayer as Mondur 7 ^ 3) Aldimine 1 - According to the invention Bis- (4-aminocyclohexyl) -methane and ispbutyraldehyde aldimine was prepared by initial loading of 1514, 3 parts (21 equivalents) of isobutyraldehyde and then 2104.0 parts (20 equivalents) of bis- (4-amino-cyclohexyl) -methane were slowly introduced over a period of 30 minutes to avoid an exotherm. After the addition of the diamine, the reaction mixture was stirred for 1 hour. At the end of this time the agitation was stopped and the water was allowed to settle to the bottom of the reactor. The largest possible quantity of water was drained from the bottom of the reactor. The reaction mixture was then heated to 100 ° C to remove excess isobutyraldehyde. While maintaining a temperature of 100 ° C, a vacuum of approximately 20 mm Hg was applied to eliminate possible final traces of aldehyde. Then, the vacuum was increased to 1 mm Hg to remove water to a water content less than 0.05% (approximately 1 to 3 hours). Aldimine had a viscosity of 100 mPa at 25 ° C, an equivalent peel of 159, an APHA color of 70, a purity, determined by GPC of 93.5% and a water content of less than 0.05% . Aldimjna 2 - Comparison The aldlmin of 2-methyl pent <was prepared3me, tilen diamine and isobutyraldehyde, having an equivalent Reso of 112, using the procedure described for aldimine 1. Aldimjna 3 - According to the invention The aldimine of isophorone diamine and isobutyraldehyde, having an equivalent weight of 139 / using the procedure described for aldimine 1. Dibutyl tin dilaurate catalyst (Dabco T-12, from Air Products) used in the examples as a 10% solution in xylene. Examples 1-4 The ingredients set forth in Table 1 were mixed at room temperature to form coating compositions Yn • to having NCO: N equivalent ratios of 1.0: 1.0. The viscosities of the coating compositions were monitored after 24 hours and are shown in Table 1.

Table 1 Equivalent ratio NC0: N - 1.0: 1.0 Parts by weight Components * 1 2 3 4 (Co p) (Comp) (Comp) (Comp) Polyiso 1 52.5 52.5 52.5 52.5 Aldimina 1 15,9 Aldimina 2 11.2 Aldimina 3 13,9 Catalyst 0,5 Brookfield- viscosity, 3720 6900 Gelifi7600 mPa after 24 h. fallen Examples 5-9 The ingredients indicated in Table 2 were mixed to t < ambient temperature to form coating compositions having NCO: N equivalents ratios of 1.0: 0.5. The viscosities of the coating compositions were measured after 7 and 72 hours and are those indicated in Table 2.

The data collected in the preceding table shows that, at an NC0: N equivalent ratio of 1.0: 0.5, the life / viscosity profiles for the compositions according to the invention, which contain diamines prepared from diamines Cycloaliphatics are similar to profiles for prepolymex of NCO unmodified. In contrast, coating compositions containing aldimines prepared from aliphatic diamines did not have acceptable shelf life / viscosity profiles. The shelf life is longer for coating compositions prepared at an NCO: N equivalent ratio of 1.0: 0.5 than those prepared at an NCO: N equivalents ratio of 1.0: 1.0. . In addition, the presence of the tin catalyst resulted in a slightly longer shelf life for the coating campeosiciones according to the present invention.

Examples 10-12 The ingredients indicated in Table 3 were mixed at room temperature to form coating compositions having NCO: N equivalent ratios of 1.0: 0.25. The viscosities of the coating compositions were measured after 7 and 48 hours and are as indicated in Table 3. Coatings were also prepared from the compositions at a wet film thickness of 0.025 cm (10 mils) on glass. In Table 3, Gardner surface drying times of the coatings are given.

The data collected in the preceding table shows that at an NC0: N equivalent ratio of 1.0: 0.25, the life / viscosity profiles for the coating compositions according to the invention, containing diamines prepared from Cycloaliphatic diamines are similar to the unmodified NCO prepolymer profiles. or conversely, coating compositions containing aldimines prepared from aliphatic diamines do not have acceptable shelf life / viscosity profiles. The shelf life is longer for coating compositions prepared at an NCO: N equivalent ratio of 1.0: 0.25 which is at an NCO: N equivalents ratio of 1.0: 1.0. Furthermore, the drying time for the coating compositions according to the invention is faster than the drying times for the unmodified NCO prepolymer or the coating composition containing the aldimine prepared from the aliphatic diamine. It is very surprising that the coating compositions according to the invention have a longer shelf life and also a faster drying time than the coating compositions containing aldimines prepared from aliphatic diamines. Examples 13-16 The ingredients set forth in Table 4 were mixed at room temperature to form coating compositions at the NC0: N equivalent ratios noted in the table. The viscosities of the coating compositions were measured after 1 and 24 hours and are given in Table 4. Coatings of the compositions were prepared at a wet film thickness of 0.025 cm (10 mils) on glass. The Gardner hard drying and drying times were measured without deterioration of the coatings, which are given in Table 3. The properties of the resulting films were also measured, as shown in Table 4.

Tal? Ia 4 Parts by weight Components 13 14 15 16 (Com) (Comp) PoJ.iiso 1 52.5 52.5 52.5 52.5 Aldimina 1 15.9 8.0 4.0, Catalyst 0.5 0.1 0 , 1 0,1 Ratio of 1.0: 1.0 1,0: 0,5 1,0: 0, -25 equivalents NC0: N Brookfield vereality, mPa After 1 hour 3. 460 1. 920 2. 900 3. 300 After 24 hours 3. 720 6. 900 3. 900 4, 100 Gardner drying meter, wet film thickness applied in 0.025 cm (10 mils) glass ** Hard removed 4 h 8 '45' 45 'lh Free of deterioration > 6 h > 6 h 45 '2 h 7' Free movie properties Module, psi @ 100% E 740 793 781 789, »to | Module, psi @ 200% E 974 946 1044 Module, psi @ 300% E 1157 1023 1304 Resistance to 1936 810 1036 3795 Ultimate traction, psi Ultimate elongation,% 759 138 461 729 assistance to 256 152 267 355? Sgarro, ppi The data collected in the preceding table show that, at 'NCO: N equivalent ratios according to the present invention (Examples 15 and 16), the best combination of life / viscosity profiles and drying times is obtained when compared to moisture-cured NCO prepolymers (Example 13) or coating compositions prepared at NCO equivalent ratios: N 1.0: 1.0 (Example 14). The Gardner drying time was determined using a Gardner-Circulating Drying Time Recorder. Fixed to the touch - During the first drying stage, the film is mobile and flows partially in the marked channel. The film can be considered "fixed to the touch" when it does not return to, flow into the channel and the recording needle begins to leave a distinguishable channel. Surface drying - When the recording needle no longer leaves a distinguishable channel, but the dried top layer of the cured film begins to break, the film is considered "surface dry". Hard drying - When the recording needle does not already break the film, but moves freely on the surface, it can be considered that the cross section of the film has reached the state of "hard drying".

No deterioration - When the recording needle does not already deteriorate the surface of the film throughout the film, it can be considered "free from deterioration". Although the invention has been described in detail in the foregoing for illustrative purposes, it is to be understood that this detail only has the aforementioned purpose and that variations thereof may be made by those skilled in the art without departing from the spirit and scope of the invention except in what may be limited by the claims.

Claims (12)

1. CLAIMS 1. A coating composition for the preparation of a ppliurea coating containing a) an NCO prepolymer containing aromatically bound ispcianate groups and b) an aldimine corresponding to the formula Xa- [N = CHCH (R!) (R2 )] "Where X represents an organic group that has a valence of n and is obtained by separation of amino groups from a cyclic organic polyamine having amino groups (cyclo) aliphatically bound, Ri and R2 may be identical or different and represent organic groups that are inert to the isocyanate groups at a temperature of 100 ° C or less, or Ri and R2 together with the β-carbon atom form a cycloaliphatic ring or heterocyclic, and n represents an integer having a value of at least 2, wherein components a) and b) are present in amounts sufficient to provide an equivalents ratio of isocyanate groups to aldimine groups of about 1.0: 0, 7 to 1.0: 0.1.
2. 2. The composition according to claim 1 wherein Ri and R2 are hydrocarbon radicals containing 1 to 6 carbon atoms.
3. 3 The compositions according to claim 1 wherein Ri and R2 are methyl groups.
4. 4. The composition according to claim 1 wherein X is the group obtained by separating the amino groups of isophorone diamine or bis- (4-aminociclohexyl) -methane.
5. 5. The compositions according to claim 2 wherein X is the group obtained by separating the amino groups of isophorone diamine or bis- (4-aminociclohexyl) -methane.
6. 6. The composition according to claim 3 wherein X is the group obtained by separating the amino groups of isophorone diamine or bis- (4-aminociclohexyl) -methane.
7. 7. A coating composition for the preparation of a polyurea coating containing a) an NCO prepolymer containing aromatically bound isocyanate groups and b) an aldimine corresponding to the formula Xi-tN-CHCHIR) (R2)] "where X represents an organic group that has a valence of n and is obtained by separation of amino groups from a cyclic organic polyamine having amino groups (cyclo) aliphatically bound, Ri and R2 may be identical or different and represent orgaganic groups which are inert to the isocyanate groups at a temperature of 100 ° C or less, or Ri and R2 together with the atom of β carbon form a ring cycloaliphatic or hetejrocyclic, and n represents an integer having a value of at least 2, wherein components a) and b) are present in amounts sufficient to provide an equivalents ratio of isocyanate groups to aldimine groups of about 1.0: 0 , 6 to 1.0: 0.2.
8. 8. The composition according to claim 7 wherein Ri and R2 are hydrocarbon radicals of 1 to 6 carbon atoms.
9. 9. The compositions of claim 7 wherein Ri and R2 are methyl groups.
10. 10. The composition according to claim 7 wherein X is the group obtained by separating the amino groups of isophorone diamine or bis- (4-aminociclohexyl) -methane.
11. 11. The composition according to claim 8 wherein X is the group obtained by separating the amino groups of ispforone diamine or bis- (4-aminocyclohexyl) -methane.
12. 12. The composition according to claim 9 wherein X is the group obtained by separating the a1 groups of isophorone diamine or bis- (4-aminociclohexyl) -methane.