HK1092488B - New polyisocyanate mixtures, a process for their preparation and their use in coating compositions - Google Patents

Description

Polyisocyanate mixtures, process for their preparation and their use in coating compositions

Technical Field

The present invention relates to modified polyisocyanate mixtures based on polyisocyanates and polyacrylate units, to a process for their preparation and to their use as curing components in polyurethane coating compositions.

Background

For polyurethane coating compositions, in particular if they are used in the automotive, industrial or furniture industry, a particularly great value is generally the resistance of such coating compositions to various environmental influences. Often the indices are hardness, chemical and solvent resistance, scratch resistance, including so-called "reflow", light stability and weather resistance.

By "reflow" is meant the ability of the cured coating (film) to compensate for minor film damage (in the μm range) caused by scratching or impacting the film by cold flow of the coating composition to the damaged site.

In order to improve the scratch resistance, oligomeric polyisocyanates based on Hexamethylene Diisocyanate (HDI) as polyisocyanate component are frequently used. Polyurethane coating compositions prepared from such components are generally tough and elastic while having good reflow properties. Disadvantages of such coating compositions include: drying at room temperature and slightly elevated temperature was somewhat slow, and the acid resistance was only moderate. Hard, fast-drying polyurethane coating compositions having very good acid resistance are generally obtained using polyisocyanate curing agents based on isophorone diisocyanate (IPDI). However, the scratch resistance and reflow of such coating compositions are generally inadequate. In addition, polyisocyanates based on IPDI have a high viscosity and a low isocyanate content.

U.S. Pat. No. 3, 4,419,513 describes isocyanurate polyisocyanates obtained by mixed trimerization of HDI and IPDI. The patent discloses that the mixed trimer has desirable properties in terms of hardness and elasticity. The disadvantage of using such mixed trimers is that, because of the IPDI proportion which is necessary for the required hardness and rapid physical drying, the amount of isocyanate groups (relative to the molecular weight) is lower than in the case of pure HDI trimers, with the associated economic disadvantage.

EP-A0646608 relates to polyisocyanates obtained by cyclotrimerization of at least one aliphatic or cycloaliphatic diisocyanate, either after its reaction with polyfunctional alcohols or by trimerization in the presence of such alcohols. Although these polyisocyanates have a high functionality, the proportion of polyfunctional alcohols in the polyisocyanate molecules prepared reduces the weight proportion of isocyanate groups per molecule and, because of the urethane groups formed, produces a significant increase in viscosity. For polyisocyanate applications, this requires economically undesirable large amounts of polyisocyanate curing agents and increases the solvent volume to adjust the application viscosity of the coating composition.

U.S. Pat. No. 3, 4,454,317 describes polyisocyanates containing isocyanate groups which are obtainable by the trimerization of HDI. An example is given of an HDI trimer having an NCO content of 20.8% by weight and a viscosity of 14Pas at room temperature. The patent does not disclose any information about the possibility of using such high-viscosity polyisocyanates in combination with suitable polyols to prepare polyurethane coating compositions having improved chemical resistance.

The modified polyisocyanate mixtures disclosed in DE-A10013187 are notable for a high isocyanate functionality, but this is essentially achieved at the expense of the isocyanate content of the corresponding polyisocyanates. In the preparation of high-functionality or high-molecular-weight polyisocyanates by oligomerizing diisocyanates by known isocyanate reactions such as biuretization, urethanation, trimerization and allophanation, a large number of isocyanate groups are generally consumed in these isocyanate reactions which increase the molecular weight and constitute functionality. In general, the higher the molecular weight of the polyisocyanate, the greater the reduction in isocyanate content in the final product. This situation hides the disadvantages of economy.

It is therefore an object of the present invention to provide novel polyisocyanate compositions which act as curing components in polyurethane coating compositions and, in so doing, are able to satisfy the desired coating properties without the disadvantages of the prior art polyisocyanates mentioned. These new polyisocyanate compositions should be variable and should show optimum values in terms of available isocyanate content, molecular weight and functionality.

This object is achieved by using the polyacrylate-modified polyisocyanates according to the invention, which exhibit the desired properties. Such novel polyisocyanates can be prepared by reaction of known polyisocyanates with a portion of a hydroxyfunctional unsaturated compound to form urethane groups, and subsequent polymerization of the unsaturated groups and optionally copolymerization with other unsaturated compounds. These novel polyisocyanate mixtures can vary widely in their composition, their molecular weight and their functionality, and therefore in their overall properties.

The modified polyisocyanate mixtures of the present invention have very good compatibility with many polyols and can be formulated into polyurethane coating compositions having a variety of properties. It has proven to be particularly advantageous when compared with the corresponding base polyisocyanates if the corresponding polyurethane coating compositions, in particular those based on HDI, have significantly improved physical drying properties and greatly increased solvent and chemical resistance, and do not have a loss in toughness and elasticity, but also have good reflow properties or high scratch resistance.

Disclosure of Invention

The invention relates to polyacrylate-modified polyisocyanates i) prepared from aromatic, araliphatic, cycloaliphatic and/or aliphatic polyisocyanates having an NCO content of 5 to 25 wt.%, an NCO functionality of 2 or more and a viscosity of 150 to 200,000mpa · s, measured at 23 ℃ with solvent-free resins; and ii) it contains at least one structural unit of the formula (I),

wherein:

r is a hydrogen or a methyl group,

R¹is a hydrocarbon radical optionally containing heteroatoms, and

R²is a hydrocarbon radical containing at least one isocyanate group and optionally urethane, allophanate, biuret, uretdione, isocyanurate and/or iminooxadiazinedione groups, and

n is a number of 1 or more.

The invention also relates to a process for preparing such polyisocyanates, which comprises:

reacting part of the isocyanate groups of the starting polyisocyanate A) with

Reaction of monoalcohols B) containing acrylate and/or methacrylate groups to form urethane groups and subsequent carbamation, or simultaneous reaction with carbamation, unsaturated groups of the reaction product obtained optionally being polymerized by free-radical initiation

The other unsaturated monomers C) are reacted.

The invention also relates to binder compositions comprising the polyacrylate-modified polyisocyanates of the invention, optionally with blocked NCO groups, and compounds with NCO-reactive groups.

The invention also relates to water-dilutable or aqueous binder compositions comprising the polyacrylate-modified polyisocyanates according to the invention, in which some of the NCO groups have been modified hydrophilically with polyether units, and also compounds having NCO-reactive groups.

Detailed Description

Hydrocarbyl radicals R²Preferably based on aromatic, cycloaliphatic, araliphatic and/or aliphatic di-and/or polyisocyanates, and preferably contains at least one structural unit which is considered optional.

The starting polyisocyanates A) include the diisocyanates and/or polyisocyanates known in polyurethane chemistry. It is immaterial whether these isocyanates are prepared by phosgene or by phosgene-free processes. Preferred starting polyisocyanates are lacquer polyisocyanates which contain urethane, uretdione, allophanate, biuret, isocyanurate and/or iminooxadiazinedione groups and are prepared from monomeric di-or triisocyanates.

Monomeric isocyanates which can be used individually or in mixtures include 1, 6-diisocyanatohexane, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate), 4, 4' -diisocyanatodicyclohexylmethane, 4-isocyanatomethyl-1, 8-octane diisocyanate, 1, 4-diisocyanatocyclohexane, 1-methyl-2, 4-diisocyanatocyclohexane and mixtures thereof, up to 35% by weight, based on the total mixture, of 1-methyl-2, 6-diisocyanatocyclohexane, and 2, 4-diisocyanatotoluene (TDI) and mixtures thereof, up to 35% by weight, based on the total mixture, of 2, 6-diisocyanatotoluene.

Preferably, lacquer polyisocyanates are used as component A). They include the lacquer polyisocyanates containing urethane groups, which are prepared, for example, by reacting 2, 4-and preferably 2, 6-diisocyanatotoluene or 1-methyl-2, 4-and optionally 1-methyl-2, 6-diisocyanatocyclohexane with substoichiometric amounts of trimethylolpropane or mixtures thereof with monomeric diols, such as the isomeric propylene glycols or butylene glycols. The preparation of these lacquer polyisocyanates containing urethane groups in virtually monomer-free form is described, for example, in DE-A1090196.

Lacquer polyisocyanates containing biuret groups include, in particular, those based on 1, 6-diisocyanatohexane, the latter being prepared as described, for example, in EP-A0003505, DE-B1101394, U.S. Pat. No. 3,010 or U.S. Pat. No. 3,977.

The isocyanurate group-containing paint polyisocyanates include: trimers or mixed trimers of diisocyanates as exemplified above, for example, TDI-based isocyanurate group-containing polyisocyanates as described in GB-A1060430, GB-A1506373 or GB-A1485564; and mixed trimers of TDI and 1, 6-diisocyanatohexane, as described, for example, in DE-A1644809 or DE-A3144672. Preferred isocyanurate group-containing lacquer polyisocyanates are aliphatic, aliphatic/cycloaliphatic and/or cycloaliphatic trimers or mixed trimers based on 1, 6-diisocyanatocyclohexane and/or isophorone diisocyanate, the preparation of which is described, for example, in U.S. Pat. No. 4,4324879, U.S. Pat. No. 4, 4288586, DE-A3100262, DE-A3100263, DE-A3033860 or DE-A3144672.

Other suitable lacquer polyisocyanates are those containing iminooxadiazinedione groups, which can be prepared as described, for example, in EP-A798299, EP-A896009, EP-A962454 and EP-A962455.

Particularly preferred starting polyisocyanates are those which contain urethane, uretdione, allophanate, biuret, isocyanurate and/or iminooxadiazinedione groups and which contain exclusively aliphatically and/or cycloaliphatically bound NCO groups.

The starting polyisocyanates (A) preferably have an NCO group content of 5 to 25% by weight, an average NCO functionality of 2.0 to 5.0, preferably 2.8 to 4.0, and a residual monomeric diisocyanate content of less than 1% by weight, preferably less than 0.5% by weight. The starting polyisocyanates have a viscosity of 150 to 200,000 mPa.s, measured at 23 ℃ in accordance with DIN 53019 using a rotary viscometer.

Preferred monoalcohols B) containing acrylate and/or methacrylate groups include hydroxy-functional esters of acrylic acid and/or methacrylic acid. Suitable esters include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate (the mixture of isomers formed in the addition reaction of propylene oxide to acrylic acid), hydroxypropyl methacrylate (the mixture of isomers formed in the addition reaction of propylene oxide to methacrylic acid), and butylene glycol monoacrylate.

Also suitable are the reaction products of the above-mentioned hydroxy esters of acrylic or methacrylic acid with different amounts of cyclic lactones or monoepoxides. The preferred cyclic lactone is epsilon-caprolactone and the preferred monoepoxide is ethylene oxide, propylene oxide or mixtures thereof.

Also suitable as hydroxyfunctional compounds B) are the reaction products of glycidyl acrylate or glycidyl methacrylate with monocarboxylic acids or the reaction products of acrylic acid or methacrylic acid with monoepoxides.

In addition to the (meth) acrylate-functional monoalcohols, further suitable compounds B) include allyl alcohols or alkoxylation products thereof, such as mono-, di-or polyethoxylated allyl alcohols. However, preference is given to using exclusively the aforementioned (meth) acrylate-functional alcohols as compound B).

B) In addition to the hydroxy-functional unsaturated alcohols, it is also possible to add non-functional ethylenically unsaturated monomers, such as styrene, methyl methacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, acrylonitrile, etc. These monomers do not react with the starting polyisocyanate (A), but enable the latter to copolymerize with the unsaturated groups of the alcohol B).

A) The reaction of B) can be carried out in the absence of a solvent or in the presence of a solvent. Suitable solvents are those which do not react with isocyanate groups or hydroxyl groups. Examples include aliphatic, cycloaliphatic and/or aromatic hydrocarbons, for example, alkylbenzenes, toluene and xylenes; esters, for example, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, n-hexyl acetate, 2-ethylhexyl acetate, ethyl propionate, butyl propionate, pentyl propionate, ethylene glycol monoethyl ether acetate and the corresponding methyl ether acetate; ethers, such as ethylene glycol acetate monomethyl, monoethyl, and monobutyl ether; ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl n-amyl ketone; and mixtures of these solvents.

In the urethanization reaction, A) and B) are reacted with one another in such a proportion that only some of the NCO groups of A) are consumed. Preferably, component B) is used in an amount such that no more than 40 mol% based on the moles of isocyanate groups in the starting polyisocyanate A) is converted to urethane groups, preferably no more than 30 mol%, more preferably no more than 25 mol%, most preferably no more than 20 mol%.

The carbamation may be carried out at room temperature (23 ℃), but can also be carried out at temperatures above or below this temperature. In order to accelerate the reaction, it can also be carried out at a temperature of up to 160 ℃. Higher temperatures are not preferred because uncontrolled polymerization of acrylate or methacrylate groups can occur.

Preferably, the unsaturated (meth) acrylate groups are not reacted by free-radical (co) polymerization until after the termination of the carbamation.

Suitable initiators for carrying out the (co) polymerization are the known free-radical initiators based on azo or peroxy compounds which have a half-life in the temperature range specified below of a duration sufficient for the polymerization to take place, i.e.a half-life of from about 5 seconds to about 60 minutes. Suitable examples include azobisisobutyronitrile, azobis-2-methylpentanonitrile, 2 ' -azobis (2-methylpropanenitrile), 2 ' -azobis (2-methylbutyronitrile), 1 ' -azobis (cyclohexanecarbonitrile), symmetrical diacyl peroxides (e.g., acetyl, propionyl or butyryl peroxide), benzoyl peroxide (e.g., substituted with bromo, nitro, methyl or methoxy groups), lauroyl peroxide, peroxydicarbonates (e.g., diethyl, diisopropyl, dicyclohexyl and dibenzoylperoxydicarbonates), t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy-3, 5, 5-trimethylhexanoate, t-butyl perbenzoate, t-butyl peroxy diethylacetate, di-n-butyl peroxy acetate, T-butyl peroxyisobutyrate, hydroperoxides (e.g., t-butyl hydroperoxide and cumene hydroperoxide), dialkyl peroxides (e.g., dicumyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide, and di-t-amyl peroxide), 1-di-t-butylperoxy-3, 3, 5-trimethylcyclohexane, and 1, 1-di-t-butylperoxycyclohexane.

Preferably, the polymerization is carried out at 50 to 240 ℃, more preferably 60 to 220 ℃, and most preferably 70 to 200 ℃. The polymerization can be carried out under a pressure of up to 15 bar.

The amount of initiator is from 0.05% to 15% by weight, preferably from 0.1% to 10% by weight, more preferably from 0.2% to 8% by weight, based on the total amount of unsaturated compounds in B).

For the polymerization, the urethane-modified polyisocyanate mixture C) is heated to the desired polymerization temperature. A free-radical initiator is then metered into the reaction mixture, and the free-radical polymerization initiated by decomposition of the free-radical initiator is carried out at the set polymerization temperature. The polymerization temperature can also be varied as desired for specific molecular weight adjustments. After termination of the polymerization, the reaction mixture was cooled to room temperature. The resulting polyacrylate-modified polyisocyanates of the present invention are generally light colored viscous liquids or solutions if solvents are used.

Other non-functional unsaturated monomers which can be copolymerized subsequently with the unsaturated polyisocyanates C) can also be metered into the reaction mixture during the polymerization.

It is also possible to add known additives such as PU catalysts, for example N, N-dimethylbenzylamine, N-methylmorpholine, zinc octoate, tin (II) octoate or dibutyltin dilaurate, to the process of the invention.

The present invention's polyacrylic modified polyisocyanates constitute valuable starting materials for the preparation of binder compositions for the production of polyurethane-based coating, adhesive or sealing compositions.

The reactive isocyanate groups of the polyacrylate-modified polyisocyanates of the present invention can be blocked with blocking agents and then used as crosslinkers in 1K (one-pot) Polyurethane (PU) coating compositions. Suitable blocking agents include epsilon-caprolactam, butanone oxime, phenol and/or phenol derivatives, secondary amines, 3, 5-dimethylpyrazole, alkyl malonates or alkyl monoalcohols.

Suitable compounds containing NCO-reactive groups are the OH-and/or NH-functional resins known from coating technology. Examples include polyesters, polyacrylates, polyurethanes, polyureas, polycarbonates or polyethers. Also suitable are hybrid resins or mixtures of various hydroxy-functional resins.

Preferably the resins used are hydroxyl-functional and/or amino-functional and may contain carboxylic acid groups and/or sulfonic acid groups or epoxide groups. It is also possible to use non-functional resins which are dried in a physical or oxidative manner, alone or in combination with hydroxy-functional resins, as binder compounds and reaction partners for the polyisocyanate mixtures according to the invention.

The hydroxyl content of these resins is from 0.5 wt% to 15.0 wt%, preferably from 0.5 wt% to 12.0 wt%, more preferably from 1.0 wt% to 10.0 wt%, most preferably from 1.0 wt% to 8.0 wt%, based on resin solids. The acid value of the solid resin is 50mg KOH/g or less, preferably 30mg KOH/g or less, more preferably 20mg KOH/g or less, and most preferably 15mg KOH/g or less.

The aforementioned resins based on addition polymers and/or polyesters, in particular based on polyacrylates, are of particular importance for the technical specification level in the field of automotive OEMs, automotive refinishing and large motor vehicle finishing, general industrial coatings, plastic coatings, corrosion control and wood and furniture coatings. In the construction sector or for coating mineral substrates, preference is given to using polyether-based resins.

In the binder compositions of the present invention, the equivalent ratio of free and blocked NCO groups to NCO-reactive groups in the binder is from 5: 1 to 1: 2, preferably from 2: 1 to 1: 2, more preferably from 1.5: 1 to 1: 1.5, most preferably from 1.2: 1 to 1: 1.2.

If the NCO groups of the polyacrylate-modified polyisocyanates of the invention are not blocked, the binder compositions have only a limited processing life of about 3 to 24 hours, and their processing is carried out either as such (clearcoat compositions) or preferably with the aid of known additives. These optional additives can be added to either the mixture or to the individual components prior to mixing.

Suitable additives include solvents such as ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, n-hexyl acetate, n-heptyl acetate, 2-ethylhexyl acetate, methoxypropyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, higher aromatic hydrocarbon mixtures, petroleum solvents, and mixtures thereof.

Other additives include plasticizers such as tricresyl phosphate, phthalic diesters and chlorinated paraffins, pigments and fillers such as titanium dioxide, barium sulfate, chalk and carbon black; catalysts such as N, N-dimethylbenzylamine, N-methylmorpholine, zinc octoate, tin (II) octoate and dibutyltin dilaurate; a fluidity control agent; a thickener; stabilizers such as substituted phenols; organofunctional silanes as adhesion promoters; a light stabilizer; and an ultraviolet absorber. Examples of light stabilizers are sterically hindered amines, as described, for example, in DE-A2417353 and DE-A2456864. Preferred light stabilizers are bis (1, 2, 2, 6, 6-pentamethylpiperidin-4-yl) sebacate, bis (2, 2, 6, 6-tetramethylpiperidin-4-yl) sebacate, and bis (1, 2, 2, 6, 6-pentamethylpiperidin-4-yl) n-butyl (3, 5-di-tert-butyl-4-hydroxybenzyl) malonate.

The water present in the fillers and pigments can be removed by drying beforehand or by additionally using water-absorbing agents such as molecular sieve zeolites.

The coatings obtained from the binder compositions of the invention can be dried at room temperature without any increase in temperature to give the optimum properties mentioned at the outset. However, when the binder is used as a recoat coating composition, it is often appropriate to increase the temperature to about 60 to 100 ℃, preferably 60 to 80 ℃, over 20 to 60 minutes, thereby shortening the drying time and curing time.

It is notable that the coating films obtained have a high hardness, good elasticity, good weather resistance, good chemical resistance and a high gloss. In particular, the cure time for both initial physical drying and chemical crosslinking is very short, i.e., shorter than when using non-polyacrylic modified polyisocyanates, so that the coating care article quickly becomes solvent and chemical resistant and ready for use.

The coating compositions used according to the invention are particularly suitable for finishing large motor vehicles, such as aircraft, rail vehicles, cranes and truck bodies. Further preferred fields of application are automotive refinishing and plastic coating. The coating compositions are also suitable for corrosion control applications (such as bridge and pole coatings), wood furniture coatings, general industrial coatings and automotive OEM coatings.

These coating compositions are applied by customary methods, for example spraying, pouring, dipping, brushing, spraying or roller coating. The coating compositions of the invention are suitable for the production of primers and for the production of transitional coatings, in particular for the production of pigmented topcoats, also basecoats and clearcoats, on painted substrates.

The invention is further illustrated, but is not intended to be limited, by the following examples in which all parts and percentages are by weight unless otherwise specified.

Examples

Abbreviations and ingredients used:

HEA: acrylic acid hydroxy ethyl ester

HEMA: hydroxyethyl methacrylate

HPMA: hydroxypropyl methacrylate

Desmodur HL BA：Aromatic-aliphatic polyisocyanates based on toluene diisocyanate/Hexamethylene Diisocyanate (HDI) with 60% NCO content in butyl acetate, available from Bayer MaterialScience AG, Leverkusen DE.

Desmodur IL BA：Aromatic polyisocyanates based on toluene diisocyanate, 51% in butyl acetate and 8.0% NCO content, available from Bayer MaterialScience AG, Leverkusen DE.

Desmodur 3200：Aliphatic biuret group-containing polyisocyanates based on HDI, solvent-free, NCO content 23.0%, available from Bayer MaterialScience AG, Leverkusen DE.

Desmodur N 3300：Isocyanurate group-containing polyisocyanates based on HDI, solvent-free, NCO content 21.8%, available from Bayer MaterialScience AG, Leverkusen DE.

Desmodur N 3600：Low-viscosity, HDI-based isocyanurate group-containing polyisocyanates, solvent-free, NCO content 23.0%, available from Bayer MaterialScienceAG, Leverkusen DE.

Desmodur N 75BA：Aliphatic biuret group-containing polyisocyanates based on HDI with 75% NCO content in butyl acetate were obtained from Bayer MaterialScience AG, Leverkusen DE.

Desmodur Z 4470BA：Isocyanurate group-containing polyisocyanates based on isophorone diisocyanate, 70% in butyl acetate and an NCO content of 11.9%, available from Bayer MaterialScience AG, Leverkusen DE.

Desmodur XP 2410：Low-viscosity, iminooxadiazinedione group-containing polyisocyanates based on hexamethylene diisocyanate, solvent-free, NCO content 23.7%, available from Bayer MaterialScience AG, Leverkusen DE.

Peroxan PO 49B：Tert-butyl peroxy-2-ethylhexanoate, 49% in butyl acetate, available from Pergan GmbH, Bocholt DE.

The following properties were determined: solids content (thick film method: sealed lid, 1g sample, 1h 125 ℃, convection oven, according to DIN EN ISO 3251);viscosity (rotational viscometer VT 550 from Haake GmbH, Karlsruhe, DE, MV-DIN cup for viscosity < 10,000 mPa.s/23 ℃ C.; SV-DIN cup for viscosity > 10,000 mPa.s/23 ℃ C.); NCO content (solvent: acetone, dibutylamine excess, urea formation, titration with 1mol/l HCl, according to DIN EN ISO 11909); and Hazen colour number (Hazen colour number: Lico according to DIN 53995)400 color determinator, dr. lange GmbH, Berlin, DE).

Preparation of polyacrylate-modified polyisocyanates

To a 1-liter three-necked flask equipped with stirrer, reflux condenser and dropping funnel was added the corresponding starting polyisocyanate and, where appropriate, butyl acetate as solvent, and the starting charge was heated to 130 ℃ under nitrogen. The unsaturated monoalcohol is then metered in over a period of 10min, followed by stirring at 130 ℃ for 1hr and then setting the desired polymerization temperature (T). When this temperature is reached, a portion of the polymerization initiator, Peroxan, is addedPO 49B, after which it is stirred at the set polymerization temperature for 1 hr. The resulting mixture was then cooled to room temperature to give light-colored viscous Polyisocyanates (PICs).

The corresponding raw materials, proportions and reaction conditions are listed in table 1 below. Amounts are in grams.

The following Table 2 shows the properties of the polyisocyanates PIC 1 to 18 according to the invention.

Preparation of modified polyisocyanate PIC 19

Using the procedure of the polyisocyanates 1-18, 604.8g Desmodur was addedXP 2410 was reacted with 23.94g HEA in 35.0g butyl acetate followed by polymerization of the resulting product at 100 ℃ by addition of 0.62g t-butyl peroxy 2-ethylhexanoate in 35.64g butyl acetate. The colorless polyisocyanate mixture obtained had a solids content of 90% by weight, a viscosity of 1181 mPas, an isocyanate content of 19.8% by weight and a color number of 16 APHA.

Preparation of modified polyisocyanate PIC 20

Using the procedure of the polyisocyanates 1-18, 676.63g Desmodur was addedZ4470 was reacted with 15.63g of HPMA in 7.00g of solvent naphtha 100, and the resulting product was subsequently polymerized at 150 ℃ by addition of 0.74g of di-tert-butyl peroxide. The light-colored polyisocyanate mixture obtained had a solids content of 72.6% by weight, a viscosity of 2602 mPa.s, an isocyanate content of 10.6% by weight and a color locus of 54 APHA.

Preparation of modified polyisocyanate PIC 21

Using the procedure of the polyisocyanates 1-18, 676.62g Desmodur was addedN3200 was reacted with 22.33g of butanediol monoacrylate, and the resulting product was subsequently polymerized at 160 ℃ by adding 1.05g of di-tert-butyl peroxide. The resulting light-colored polyisocyanate mixture had a solids content of 98.8% by weight, a viscosity of 46,272mpa · s, an isocyanate content of 21.7% by weight and a color number of 50 APHA.

Preparation of modified polyisocyanate PIC 22

Using the procedure of the polyisocyanates 1-18, 676.65g Desmodur was addedN75 with 16.75g HPMA 5.81g of 1: 1 methoxypropyl acetate (MPA)The reaction was carried out in xylene, and the product was subsequently polymerized by addition of 0.79g of di-tert-butyl peroxide at 145 ℃. The resulting light-colored polyisocyanate mixture had a solids content of 74.9% by weight, a viscosity of 308 mpa · s, an isocyanate content of 15.6% by weight and a color number of 16 APHA.

Preparation of modified polyisocyanate PIC 23

Using the procedure of the polyisocyanates 1-18, 676.59g Desmodur HLWith 13.40g HPMA³⁾The reaction was carried out in 9.38g of butyl acetate, and the resulting product was subsequently polymerized at 130 ℃ by adding 0.63g of t-butylperoxy-2-ethylhexanoate to a content of 50% in butyl acetate. The resulting light-colored polyisocyanate mixture had a solids content of 62.3% by weight, a viscosity of 2182mPa · s, an isocyanate content of 10.3% by weight and a color number of 39 APHA.

Preparation of modified polyisocyanate PIC 24

Using the procedure described for polyisocyanates 1-18, 676.60g Desmodur IL was madeWith 13.39g of HPMA in 11.48g of butyl acetate, and the product was subsequently polymerized at 130 ℃ by adding 0.54g of tert-butylperoxy-2-ethylhexanoate to a content of 50% in butyl acetate. The resulting light-colored polyisocyanate mixture had a solids content of 51.2% by weight, a viscosity of 2522mPa · s, an isocyanate content of 7.35% by weight and a color number of 94 APHA.

Preparation of modified polyisocyanate PIC 25

Using the procedure of the polyisocyanates 1-18, 601.9g Desmodur was addedA solution of N3600 in 35.0g of butyl acetate was reacted with 13.42g of HEMA. Thereafter 13.42g of styrene were added, followed by addition of 35.64g of ethylene0.62g of tert-butylperoxy-2-ethylhexanoate in butyl acetate the resulting mixture was polymerized at 100 ℃. The colorless polyisocyanate mixture obtained had a solids content of 89.7% by weight, a viscosity of 1531mpa · s, an isocyanate content of 18.7% by weight and a color number of 9 APHA.

Preparation of modified polyisocyanate PIC 26

Using the procedure of the polyisocyanates 1-18, 601.9g Desmodur was addedN3600 was reacted with 13.42g HEMA in 35.0g butyl acetate. Thereafter 13.42g of methyl methacrylate are added, and the mixture is subsequently polymerized at 100 ℃ by adding 0.62g of tert-butylperoxy-2-ethylhexanoate in 35.64g of butyl acetate. The colorless polyisocyanate mixture obtained had a solids content of 89.9% by weight, a viscosity of 2662 mPas, an isocyanate content of 18.9% by weight and a color number of 15 APHA.

Preparation of modified polyisocyanate PIC 27

Using the procedure of the polyisocyanates 1-18, 601.9g Desmodur was addedN3600 was reacted with 13.42g HEMA in 35.0g butyl acetate. Thereafter 13.42g of styrene were added, and the resulting mixture was subsequently polymerized by addition of 0.62g of tert-butylperoxy-2-ethylhexanoate in 35.64g of butyl acetate at 100 ℃. The colorless polyisocyanate mixture obtained had a solids content of 89.7% by weight, a viscosity of 1531mpa · s, an isocyanate content of 18.7% by weight and a color number of 9 APHA.

Preparation of modified polyisocyanate PIC 28

Using the procedure of the polyisocyanates 1-18, 601.9g Desmodur was addedXP 2410 reacted with 35.0g of butyl acetate with 13.42g of HEMA. Thereafter 13.42g of styrene are added, followed byThe resulting mixture was polymerized by adding 0.62g of tert-butyl peroxy 2-ethylhexanoate in 35.64g of butyl acetate at 100 ℃. The resulting mass-colored polyisocyanate mixture had a solids content of 89.8% by weight, a viscosity of 1010mpa · s, an isocyanate content of 18.65% by weight and a color number of 16 APHA.

Preparation of modified polyisocyanate PIC 29

Using the procedure of the polyisocyanates 1-18, 601.9g Desmodur was addedXP 2410 reacted with 13.42g HEMA in 35.0g acetobutyrate. Thereafter 13.42g of methyl methacrylate are added, and the mixture is subsequently polymerized by addition of 0.62g of tert-butyl peroxy 2-ethylhexanoate in 35.64g of butyl acetate at 100 ℃. The resulting polyisocyanate mixture had a solids content of 90.0% by weight, a viscosity of 919mpa · s, an isocyanate content of 19.2% by weight and a color number of 11 APHA.

Application examples

These examples describe the preparation of coating compositions based on polyisocyanates PIC which can be used, the use of these coating compositions and the testing of the resulting coating films, in comparison with the corresponding starting polyisocyanates which have not been modified with polyacrylates.

The general properties of the coatings were evaluated by preparing clear varnishes. For this purpose, the polyisocyanates are mixed individually with the polyols in an NCO/OH equivalent ratio of 1: 1. The polyol used is DesmophenA870, which is a polyacrylate polyol obtained from Bayer MaterialScience AG, Leverkusen DE, having a solids content of 70% in butyl acetate, a viscosity of 3500 mPa.s at 23 ℃, an acid number of 7.5mg KOH/g (based on the supplied form) and an OH content of 2.95% by weight (based on the supplied form). The following amounts of additives were applied, based on the resin solids (sum of the solids fractions of polyol and polyisocyanate).

A mixture of solvent naphtha 100, methoxypropyl acetate, xylene and n-butyl acetate (1: 1) was added, giving a base content of 56 wt% and an additive content of 2 wt%. The leveling time (DIN 53211, 4mm nozzle) of the resulting varnish was 25 seconds. The varnish is a sprayable formulation having a VOC (volatile organic Compound) content of 3.51 bs/gal.

The activation life was tested by measuring the increase in viscosity of the varnish over 7 hr.

The resulting varnish was coated on glass plates at 23 ℃ and 50% relative humidity, dried for 30min at room temperature and 60 ℃ while determining the drying rate (DIN 53150) and stored at room temperature for 7 days. The thickness of the dried film is 55 to 60 μm. Then test Knig hardness (DIN 53157), gurley gloss at 20 °, Haze (DIN 67530), and water and solvent resistance, the latter two being tested with water, super gasoline, methoxypropyl acetate and xylene (after curing at 60 ℃ for 30min, immediately and after 1, 4 and 7 days).

Table 3 below illustrates the test results for the test varnish of the present invention and the comparative varnish.

The varnishes based on the polyacrylate modified polyisocyanate of the present invention and the comparative varnish based on polyisocyanate B) both had long processing lives without a significant viscosity increase therebetween and both produced high gloss varnish films with very low Haze (Haze) values. The tests also show that the coatings according to the invention based on PIC 1, 2, 4 and 5, in contrast to the comparative varnish based on unmodified polyisocyanate B1, exhibit faster drying properties, higher hardness and slightly better solvent resistance. The varnishes according to the invention based on PIC 8, PIC 9, PIC 11 and PIC 12 also gave the same results when compared with the comparative varnish based on the unmodified polyisocyanate B2. These test results illustrate the clear advantages of the varnishes of the invention, especially in terms of important properties such as drying speed, hardness and early water and solvent resistance, which play an important role especially in automotive refinishing.

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (2)

1. A process for preparing polyacrylate-modified polyisocyanates i) from aromatic, araliphatic, cycloaliphatic and/or aliphatic polyisocyanates having an NCO content of 5 to 25% by weight and an NCO functionality of > 2 and a viscosity of 150 to 200,000 mPas, measured on solvent-free resins at 23 ℃ in accordance with DIN 53019 using a rotary viscometer; and ii) contains at least one structural unit of the formula (I),

wherein:

r is a hydrogen or a methyl group,

R¹is a hydrocarbon radical optionally containing heteroatoms, and

R²containing at least one isocyanate group and optionally a urethane, allophanate, biuret, uretdione, isocyanurate or imino groupA hydrocarbon group of a diazinedione group, and

n is a number of 1 or more,

the method comprises the following steps:

reacting part of the isocyanate groups of the starting polyisocyanate A) with

Monohydric alcohols B) containing acrylate and/or methacrylate groups react to form urethane groups, and

after, or simultaneously with, the carbamation, the unsaturated groups of the reaction product obtained are reacted, optionally with further unsaturated monomers C), by free-radical-initiated polymerization.

2. The process of claim 1 wherein the starting polyisocyanate A) comprises a polyisocyanate containing urethane, uretdione, allophanate, biuret, isocyanurate or imino groupsDiazinedione groups and NCO groups, which are exclusively combined with aliphatic and/or cycloaliphatic groups.