WO2009100786A1

WO2009100786A1 - Method for producing orthoester-blocked poly(meth)acrylate and use as cross-linking agent in isocyanate-based paint resins

Info

Publication number: WO2009100786A1
Application number: PCT/EP2008/065537
Authority: WO
Inventors: Bardo Schmitt; Marianne Omeis; Martina Ebert
Original assignee: Evonik Röhm Gmbh
Priority date: 2008-02-11
Filing date: 2008-11-14
Publication date: 2009-08-20
Also published as: DE102008000268A1

Abstract

The invention relates to a method for producing a poly(meth)acrylate having at least two hydroxyl groups blocked by an orthoester, wherein at least one polymerizable (meth)acrylate monomer comprising at least one OH functionality or a precursor thereof is polymerized in the presence of at least one orthoester compound at temperatures greater than 23 °C. The resulting polymer, such as orthoester-blocked copolymers of isobornyl methacrylate, methacrylic acid, 2-ethyl hexyl methacrylate, and hydroxy-ethyl methacrylate, are extremely well suited as additives to isocyanate-based paint resins for cross-linking, and produce paints or coatings having an improved property profile with regard to hardness, flexibility, and chemical resistance to polar solvents.

Description

Process for the preparation of orthoester-blocked poly (meth) acrylate and use as crosslinker in isocyanate-based coating resins

The invention relates to processes for preparing a poly (meth) acrylate having at least two hydroxyl groups blocked by an orthoester and to the use of blocked poly (meth) acrylates obtainable in coating resins, preferably as a solution polymer for preparing an isocyanate-based paint coating.

The effect of orthoester compounds as water scavengers is well known.

For the special state of the art the following documents are mentioned:

(1) WO 2005/092934 A1 = PCT / US2005 / 008887;

(2) JP60206812;

(3) JP60206802;

(4) JP01075578; and

(5) EP 231932 A1.

Document (1) describes isocyanate-based coating compositions in which orthoester groups at least partially block the hydroxyl groups of poly (meth) acrylates, whereby the orthoester groups can be removed by hydrolysis, for example by traces of water present in the coating composition, to remove the Promote crosslinking in the reaction with isocyanate compounds. According to document (1), the procedure is such that, for example, a copolymer of, for example, HEMA (hydroxyethyl methacrylate), MMA (methyl methacrylate) and IBOA (isobornyl acrylate) for about 1 hour at about 150 ⁰ C oil bath temperature with a Orthoester, for example 2 Ethoxy-1,3-dioxalane, reacting; and then the thus-obtained orthoester "blocked" copolymer is used for film-forming with an isocyanate, and films and coatings obtained in this way already have a very good hardness (measured as pendulum hardness according to DIN EN ISO 1522) as well as a very good flexibility (measured as Erichsen cupping according to DIN 53156). However, in addition to the hardness and flexibility of a paint and its resistance to chemicals, such as acids and bases, and solvents of not insignificant importance. In this case, however, it is noticeable that coatings of paints according to the document (1) have a resistance that is not sufficient for all applications, especially in the face of slightly more polar solvents such as 2-propanol or methyl ethyl ketone.

According to documents (2) and (3), it is proposed to use, as a crosslinking reagent for the production of isocyanate-based paints, resins containing polymer chains containing a plurality of silane functional groups. These functional groups serve for crosslinking and are not a repeat unit of the polymer chain. Although these "polysilanes" as crosslinkers are quite useful for some applications, they are relatively disadvantageous in terms of the hardness and flexibility of the isocyanate-based coatings available therewith. In particular, the resin formulation in (2) and (3) contains a silane-containing methacrylate. However, silane-containing groups can later hydrolyze and condense in the presence of water and then cause film formation. The resins are thus susceptible to hydrolysis and their storage stability is lower than for formulations without this component. The resulting viscosity increase is described, for example, in (2). The orthoester as a water scavenger probably has the function in this formulation to delay the reaction of crosslinking. In contrast, water interferes with isocyanate crosslinking. The orthoester as a water scavenger serves to optimize the cross-linking by reducing side reactions such as urea formation and thus blistering in the film. Also, references (4) and (5) suggest Si-containing copolymer as a crosslinker for the production of film coatings. According to (4), however, work is carried out with the addition of water.

In view of the prior art reported and discussed herein, it was an object of the invention to provide processes for preparing orthoester blocked poly (meth) acrylates which are useful as crosslinking agents for isocyanate-based paints. The resulting coating compositions and coatings thus obtained should have an improved property profile. In particular, hardness, flexibility and resistance of the coatings to chemicals and solvents should be improved in comparison to known coating systems based on poly (meth) acrylates / isocyanates.

These tasks as well as other tasks not explicitly mentioned, which, however, can be easily deduced for the person skilled in the art from the introductory discussion, are solved by a method which has all the features of claim 1. Advantageous process modifications are the subject of the dependent method claims. The use of the directly resulting according to the method claims products is placed in the claims of the appropriate category under protection.

By preparing according to the invention a poly (meth) acrylate having at least two hydroxyl groups blocked by an orthoester by adding at least one polymerizable (meth) acrylate monomer comprising at least one OH functionality or a precursor thereof in the presence of at least one orthoester compound Temperatures greater than 23 ⁰ C Polymehsiert, one obtains surprisingly a polymer which, as an additive to paints based on isocyanates to obtain coatings, films or paints that have a balanced range of properties in terms of hardness, flexibility and resistance. Thus, isocyanate coatings obtained with the additive according to the invention have an approximately comparable hardness compared to the prior art (determined as Pendelhärte) and only slightly deteriorated or approximately the same flexibility (determined as Erichsen depression). However, they are clearly superior to the chemical resistance to alcohols and ketones. In this case, the procedure according to the invention differs from the prior art, for example in the form of D1 in particular by the type of blocking of the OH groups with the orthoester compound. Whereas according to D1, a "finished" copolymer is reacted with an orthoester at elevated temperature, the blocking of the OH groups in the polymer / copolymer to be used according to the invention takes place during the polymerization, ie the monomers are polymerized in the presence of the orthoester compound according to the invention. The prior art in the form of D1, however, reveals at best a subsequent reaction of the polymer in the sense of a polymer-analogous reaction.

When the term "blocking" or "blocking" is used, it is to be understood in the context of the invention that it is a reaction between the orthoester compound and at least two hydroxyl groups of a poly (meth) acrylate during the process of polymerization, i. the production of the poly (meth) acrylate comes. In this case, hydrolyzable orthoester groups can preferably be formed. The term "at least two hydroxyl groups of a poly (meth) acrylate" is not to be understood restrictively, but in particular also two hydroxyl groups which are not attached to a chain of the polymer but which are attached to two different chains of the poly ( meth) acrylate.

In a preferred embodiment of the process according to the invention, about 25% to about 100% of the hydroxyl groups of the poly (meth) acrylate which are capable of reacting with an orthoester compound are blocked. Even more preferably, at least about 40%, more preferably about 65%, and even more preferably, greater than about 75% of the hydroxyl groups present and available for reaction are blocked. The percentages are based on mole percent. If one mole of a monomer containing two hydroxyl groups is used, the indication is 75%, hydrolyzable orthoester compounds or equivalent bonds thereof have been formed with 1.5 moles of a total of 2 moles of hydroxyl groups available for bond formation.

The time of addition of the orthoester to block the OH groups of a monomeric mixture of (meth) acrylate monomers to be polymerized, at least one of which has an OH functionality or a precursor thereof, is on the one hand critical (compared to the prior art), on the other hand also relatively uncritical, compared with the reference point of the polymerization process of the monomers. Thus, addition prior to initiation of polymerization is possible, as well as addition during polymerization is possible. On the one hand, it is therefore possible to meter in the orthoester during the polymerization. But you can also submit it.

In a particularly expedient process variant, the invention provides that a) an orthoester is introduced; b) then adding to the template a) at least one polymerisable (meth) acrylate monomer which comprises at least one OH functionality or a precursor thereof; and c) the mixture obtained in b) polymehsiert at temperatures greater than 23 ⁰ C.

The reaction with the orthoester is a thermal reaction. The process of polymerization in the presence of at least one orthoester can therefore be carried out in principle over a wide temperature range. In general, you can achieve usable results even at room temperature. However, preference is given to elevated temperatures, ie temperatures of greater than room temperature, in particular greater than 23 ° C. room temperature. In a particular modification, the process of the invention is characterized in that the mixture b) is polymerized at temperatures in the range of 70 ⁰ C to 180 ⁰ C over a period of 1 h to 10 h.

Of particular interest are also processes in which the mixture b) at temperatures in the range of 110 ⁰ C to 160 ⁰ C, suitably 120 ⁰ C to 150 ⁰ C, over a period of 2 h to 6 h, preferably 3 h to 5 h, polymerized.

In principle, the reaction proceeds without the use of a catalyst, only via the supply of thermal energy, be it externally or through energy released from the polymerization reaction. If desired and / or required, a catalyst can also be used.

In principle, any suitable orthoester compound can be used for the process of the invention. Of particular interest are methods according to the invention in which the orthoester is a compound of the formula (I):

R ¹ OS ✓ R ³

O 2 A ₄

RO OR ⁴

in which independently of one another are C ¹ -C ₆ -alkyl or C ₅ -C ₇ -cycloalkyl, where optionally the two radicals R ¹ and R ² can be joined together to form a five to seven membered ring containing two oxygen atoms, R ^{3 is} hydrogen, C ¹ -C ₆ -alkyl or an aromatic radical, and R ^{4 is} C 1 -C ⁶ alkyl.

C ₁ -C ₆ alkyl is understood here and throughout the disclosure to mean a linear or branched alkyl radical having one to six carbon atoms. These include, inter alia, the radicals methyl, ethyl, n-propyl, 2-propyl, n-butyl, 2-butyl, tert-butyl, n-pentyl, 2-pentyl, iso-pentyl, n-hexyl, 2-hexyl and iso-hexyl. For the purposes of the invention, the preferred radicals C ₅ -C ₇ cycloalkyl include, for example, the cyclopentyl, cyclohexyl and cycloheptyl radicals.

The aromatic radicals preferably include the phenyl and the benzyl radical. The aromatic radicals may be substituted up to four times by C ₁ -C ₆ alkyl.

Trimethylorthoformate, triethylorthoformate, trimethylorthopropionate, thethylorthopropionate and / or 2-ethoxy-1,3-dioxalane are among the orthoester compounds which are particularly preferred in the context of the invention.

Processes according to the invention of particular interest are those which are distinguished by the use of triethyl orthoformate and / or thethyl orthopropionate as the orthoester.

According to the invention, the monomer mixture to be polymethylated has at least one polymerizable (meth) acrylate monomer, which in turn has at least one hydroxyl group or OH functionality.

As well as throughout the disclosure, the term (meth) acrylate is understood to mean both acrylate and methacrylate. The OH functionality may be present on the single monomer of the mixture. Examples include monomers such as HEMA (hydroxyethyl (meth) acrylate).

By far the preferred methods for the invention, however, are those which are characterized in that

A) at least one polymerizable (meth) acrylate monomer having the formula (II)

, R *

(II) CH ₂ = C _N

COOR ⁶ wherein R ^{5 is} hydrogen or methyl and R ^{6 is} linear or branched C ¹ -C 60 alkyl, C ₅ -C ₇ cycloalkyl, which may optionally be mono- or polysubstituted by C ¹ -C ₆ alkyl, or may be an aromatic radical which may be one - or more than once, at most up to fourfold, may be substituted by C1-C6 alkyl radicals,

in mixture with

B) at least one polymerizable (meth) acrylate monomer which contains at least one hydroxyl group and / or a precursor thereof.

In this variant, therefore, at least two different polymerizable monomers are used, one of which has a blockable OH group. Equally useful are mixtures of monomers polymehsiert, wherein at least two monomers are used without blockable OH groups together with at least one monomer which has an OH group. Equally preferred are processes in which two different monomers with blockable OH groups are polymerized with at least one monomer without a blockable OH group.

The monomers without a blockable OH group are, for example, acrylic acid or methacrylic acid esters of straight-chain or branched monoalcohols having one to 60 carbon atoms. Particularly preferred are acrylic acid or methacrylic acid esters of straight-chain or branched monoalcohols having one to 20 carbon atoms. Preferred esters are alkyl acrylates and methacrylates having one to 12 carbons in the alkyl groups, even more preferred are alkyl acrylates and methacrylates having two to 8 carbons in the alkyl groups.

The particularly useful (meth) acrylate monomers include, but are not limited to, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, pentyl acrylate, Hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, lauryl methacrylate and the like.

Of particular interest are also isobornyl methacrylate and isobornyl acrylate monomers.

It is also possible to use cycloaliphatic (meth) acrylates, for example trimethylcyclohexyl acrylate, t-butylcyclohexyl acrylate, cyclohexyl methacrylate, isobornyl methacrylate, 2-ethylhexyl methacrylate and similar monomers.

Also preferred are benzyl acrylate and / or benzyl methacrylate as component A, i. Monomers of the formula II.

The polymerizable monomers of component B are those monomers which have one or a plurality of hydroxyl groups or OH functionality or precursors thereof. In particular, ethylenically unsaturated monomers having hydroxyl groups or OH functionality or precursors thereof include hydroxyalkyl acrylates and hydroxyalkyl methacyrylates. Particularly suitable monomers include, but are not limited to, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyisopropyl acrylate, 2, 3-dihydroxypropyl acrylate, hydroxybutyl acrylate, dihydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyisopropyl methacrylate, hydroxybutyl methacrylate, dihydroxypropyl methacrylate, dihydroxybutyl methacrylate, either alone or in admixture of two or more.

As mentioned, it is also possible to introduce the hydroxyl group or OH functionality via a precursor compound into the monomer mixture to be polymethylated. This happens, for example, via the epoxy group of a glycidyl methacrylate. A such epoxy group can be converted to an OH group by traces of water via hydrolysis during polymerization.

In addition to the monomers mentioned, it is also possible to co-polymerize further ethylenically unsaturated monomers. When these monomers are co-polymerized, their total content together is less than 50% by weight based on the total weight of the polymerizable monomers. Suitable other monomers include in a non-exhaustive list of acrylic acid and methacrylic acid, acrylamide and methacyrylamide, and derivatives such as alkoxymethyl (meth) acrylamide monomers such as methacrylamide, N-isobutoxymethylmethacrylamide and N-methylolmethacrylamide; Amino (meth) acrylates such as N, N-dimethylaminoethyl (meth) acrylate; Maleic, itaconic and fumaric anhydrides and their diesters and half esters; Vinylaromatics such as styrene, alpha-methylstyrene and vinyltoluene and Polyethylenglycolmonoacrylate and - monomethacrylate.

It is also possible to use other functional monomers such as acrylonitrile, allyl methacrylate, acetoacetoxyethyl methacrylate, methylacrylamidoglycolate methyl ether, ethyleneureaethyl methacrylate, 2-acrylamide-2-methylpropanesulfonic acid, reaction products of monoepoxyesters or monoepoxyethers with alpha-beta-unsaturated acids and reaction products of glycidyl (meth) acrylate with monofunctional acids with up to 22 carbon atoms.

In particular, the method of the invention is characterized in that no Si-containing monomers are used as the polymerizable monomers, resulting in the resulting polymer or copolymer silane groups, which could act as crosslinkers in the film production.

A special and very expedient variant of the process according to the invention uses as polymerizable monomers a mixture of isobornyl methacrylate, methacrylic acid, 2-ethylhexyl methacrylate and hydroxyethyl methacrylate. The process of the invention may be carried out in bulk or in a solvent. Preferably, the polymerization is carried out in a solvent, most suitably in an organic solvent. In particular, inert solvents are suitable here, such as aliphatic or alicyclic hydrocarbon compounds or slightly more polar solvents such as ethers or esters. Particularly useful as a solvent is, for example, n-butyl acetate.

The solution polymer according to the invention is particularly suitable as a crosslinker in coating resins based on isocyanate. For this purpose, it can either be isolated from the solution or used directly in solution directly with a suitable solids content. Preferred is the use of the solution polymer having a solids content in the range of 20 to 80% (w / w) to prepare an isocyanate-based coating.

Examples and Comparative Examples

Comparative Example 1 (V1): Resin synthesis without o-ester

66.68 g of n-butyl acetate were heated in a 4-neck round bottom flask with saber and reflux condenser to 145 ⁰ C (oil bath temperature). Nitrogen was passed through the flask at 0.25 L / min.

20.44 g of tert-butyl peroxy-2-ethylhexanoate, 82.31 g of isobornyl methacrylate, 54.87 g of 2-hydroxyethyl methacrylate, 128.95 g of 2-ethylhexyl methacrylate, 8.23 g of methacrylic acid and 4.92 g of mercaptoethanol were mixed and mixed within 4 hours added. The mixture was then stirred for 30 min at the same temperature. After cooling to 80 ^° C., 0.28 g of tert-butyl peroxy-2-ethylhexanoate were added and the mixture was stirred at 80 ^° C. for 2 hours. Finally, the mixture was diluted with 33.32 g of n-butyl acetate, stirred for another 30 min and bottled.

24.0 g of the prepared solution polymer 1 were adjusted to a solids content of 60% by dilution with 6.0 g of n-butyl acetate. Comparative Example 2 (V2): Addition of the o-ester to the polymer

To the solution polymer of Comparative Example 1, 25.0 g of triethyl orthoformate was added prior to the final adjustment of the solids content. The mixture was heated in a 4-necked round-bottomed flask with saber and reflux condenser to 145 ⁰ C (oil bath temperature) and is moved for 1 hour under inert gas atmosphere. Finally, the mixture was diluted with 33.32 g of n-butyl acetate, stirred for another 30 min and bottled.

24.0 g of the prepared solution polymer 2 were adjusted to a solids content of 60% by dilution with 6.0 g of n-butyl acetate.

Example 1 (B1): Addition of the o-ester before or during the polymerization

25.0 g of triethyl orthoformate and 62.51 g n-butyl acetate was heated in a round bottom flask with 4-HaIs- saber stirrer and reflux condenser to 145 ⁰ C (oil bath temperature). Nitrogen was passed through the flask at 0.25 L / min.

19.16 g of tert-butyl peroxy-2-ethylhexanoate, 77.16 g of isobornyl methacrylate, 51.44 g of 2-hydroxyethyl methacrylate, 120.89 g of 2-ethylhexyl methacrylate, 7.72 g of methacrylic acid and 4.61 g of mercaptoethanol were mixed and mixed within 4 hours added. The mixture was then stirred for 30 min at the same temperature. After cooling to 80 ^° C., 0.26 g of tert-butyl peroxy-2-ethylhexanoate were added and the mixture was stirred at 80 ^° C. for 2 hours. Finally, the mixture was diluted with 31, 24 g of n-butyl acetate, stirred for another 30 min and bottled.

24.0 g of the prepared solution polymer 3 were adjusted to a solids content of 60% by dilution with 6.0 g of n-butyl acetate. Filmherstellunq

4.97 g of a 60% hexamethylene diisocyanate trimer solution (HDI) were mixed with each

15.03 g of the solution polymers 1, 2 and 3 from Comparative Examples 1 and 2 or Example 1 and 0.0902 g of a 1% dibutyltin dilaurate solution (0.01% based on polymer to DBTL = catalyst) and Homogenized on a magnetic stirrer. The ratio NCO / OH was 50/50.

These mixtures were applied by means of a 100 micron Filmziehrahmens on yellow chromated aluminum sheets and for 25 min at 145 ⁰ C in

Connected and dried circulating air dryer.

The layer thickness of the obtained film was 30 ± 1.5 μm on aluminum flakes

Mechanical testing of the films

The films 1, 2 and 3 obtained according to film production corresponding to Comparative Examples 1 and 2 and Example 3, respectively, were subjected to various tests.

1. pendulum hardness

Measured according to DIN EN ISO 1522

2nd cut

With a crosshatch cutter with 6 parallel blades, two cuts were made through the films at right angles to each other. The appearance of the cut edges and the amount of chipped cuts were visually evaluated as follows:

3. Erichsentiefung Measured according to DIN 53156

4. Resistance to alkalis and acids (BART)

Measured according to the method described in DE 19850210 at 50 ⁰ C and 80 ⁰ C.

5. Chemical resistance

Reagents to be tested were brake fluid, diesel, 2-propanol and methyl ethyl ketone (MEK).

The films produced were examined for their resistance by pressing 0.70 g of pulp, soaked with 5.0 g of the respective test liquid and covered with a watch glass, on the film for 15 minutes. The watch glasses were loaded with 500 g. The films were dried at room temperature for 24 h, then the pendulum hardness was again determined at the treated sites and compared with the values of the untreated films.

6. swelling behavior

Polymer films were made as described. The substrate used was hostaphan film. After drying at 80 ^° C. for 1 day, the films were detached from the film and test specimens (mass: 3.0 × 1.5 cm) were cut to size.

These were then in 50 g of isopropanol on wire nets in clear

Wide-mouth bottles stored and weight gain determined by regular weighing after blotting with kitchen paper.

Table 1 below summarizes the results obtained:

Table 1

measured data prove the following statements:

The hardness (measured as pendulum hardness) of Films V2 and B1, each obtained using polymers made with 5% orthoester, is of comparable magnitude.

The hardness (measured as pendulum hardness) of both the film V2 and the film B1, each obtained using polymers prepared with 5% orthoester, is significantly greater than the hardness of the film V1 using a polymer was obtained, which was prepared without the addition of an orthoester.

The flexibility (measured as Erichsen depression) of the film V2 compared to the flexibility of the film B1, each obtained using polymers made with 5% orthoester, is slightly larger.

The flexibility (measured as Erichsen depression) of both the film V2 and the film B1, each obtained using polymers prepared with 5% orthoester, is greater than the flexibility of the film V1 prepared using a film Polymer was obtained, which was prepared without the addition of an orthoester.

• The chemical resistance to non-polar solutions, such as brake fluid or diesel fuel, is about the same for V1 (without orthoester), based on the untreated reference.

• The chemical resistance to non-polar solutions, such as brake fluid or diesel fuel, is only slightly worse for V2 and B1, based on the untreated reference.

• Overall, the chemical resistance to nonpolar solutions, such as brake fluid or diesel fuel, is slightly better than V1 for both V2 and B1. • Chemical resistance to more polar solvents, such as 2-methanol or MEK (methyl ethyl ketone), is worse for both V2 and B1 compared to V1 (without orthoester).

• However, the chemical resistance to more polar solvents, such as 2-methanol or MEK (methyl ethyl ketone), is significantly less deteriorated at B1 than at V2. In principle, the chemical resistance of B1 to MEK is already at the level of V1, while V2 drops significantly.

The swelling behavior (measured in 2-propanol) of a film B1 according to the invention is markedly improved both with respect to V1 and V2.

Overall, one can conclude that hardness (pendulum hardness) and flexibility (Erichsen depression) of the film B1 of the invention are absolutely comparable to V2, but that the film according to the invention in comparison to V2 has its strengths in chemical resistance to polar solvents, where he is at the level of a film without the addition of an orthoester (V1). In addition, the film according to the invention has a surprisingly improved swelling behavior compared to 2-propanol.

Claims

claims

A process for producing a poly (meth) acrylate having at least two hydroxyl groups blocked by an orthoester, comprising: adding at least one polymerizable (meth) acrylate monomer having at least one OH functionality or a precursor thereof in the presence of at least one orthoester compound Temperatures greater than 23 ⁰ C polymerized.

2. The method of claim 1, wherein a) presents an orthoester; b) then adding to the template a) at least one polymerisable (meth) acrylate monomer which comprises at least one OH functionality or a precursor thereof; and c) the mixture obtained in b) polymerized at temperatures greater than 23 ⁰ C.

3. The method according to claim 2, characterized in that polymerizing the mixture b) at temperatures in the range of 70 ⁰ C to 180 ⁰ C over a period of 1 h to 10 h.

4. The method according to claim 2 or 3, characterized in that the mixture b) at temperatures in the range of 110 ⁰ C to 160 ⁰ C, suitably 120 ⁰ C to 150 ⁰ C, over a period of 2 h to 6 h, expediently 3 hours to 5 hours, polymerizes.

5. The method according to any one of the preceding claims, characterized in that as the orthoester a compound of formula (I) presents: R ¹ O _s , R ³

(I) R ² O ' ^S OR ⁴

wherein R ¹ and R ^{2 are} independently C ¹ -C ₆ alkyl or C ₅ -C ₇ cycloalkyl, R ^{3 is} hydrogen, C ¹ -C ₆ alkyl or an aromatic radical, and R ⁴ is C ¹ -C ₆ alkyl.

6. The method according to claim 5, characterized in that the orthoester is trimethyl orthoformate, thethyl orthoformate, trimethyl orthopropionate, thethyl orthopropionate and / or 2-ethoxy-1, 3-dioxalane.

7. The method according to claim 6, characterized in that the orthoester is Thethylorthoformiat and / or Thethylorthopropionat.

8. The method according to any one of the preceding claims, characterized in that one prepares a poly (meth) acrylate copolymer, wherein

A) at least one polymerisable (meth) acrylate monomer of the formula (II)

wherein R ^{5 is} hydrogen or methyl and R ^{6 is} linear or branched d-Cβo alkyl, C ₅ -C ₇ cycloalkyl, which may optionally be mono- or polysubstituted with CrCβ alkyl, or may be an aromatic radical, optionally one or can be substituted several times, at most up to fourfold, with C1-C6 alkyl radicals,

in mixture with B) at least one polymerizable (meth) acrylate monomer which contains at least one hydroxyl group and / or a precursor thereof.

9. The method according to any one of the preceding claims 1-8, characterized in that is used as the polymerizable monomers, a mixture of isobornyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate and methacrylic acid.

10. The method according to any one of the preceding claims, characterized in that one produces a silane-free poly (meth) acrylate.

11. The method according to any one of the preceding claims, characterized in that polymehsiert in an organic solvent.

12. Solution polymer obtainable according to claim 11.

Use of the solution polymerizate of claim 12 having a solids content in the range of 20 to 80% (w / w) to produce an isocyanate-based coating.