EP2276817A1

EP2276817A1 - Synthesis of improved binders and modified tacticity

Info

Publication number: EP2276817A1
Application number: EP09728210A
Authority: EP
Inventors: Helmut Schwind; Uwe-Martin Wiesler; Cornelia Borgmann; Heike Leuninger; Thomas Schmied; Stefanie Maus; Werner Friedrich; Sven Balk
Original assignee: Evonik Roehm GmbH
Current assignee: Evonik Roehm GmbH
Priority date: 2008-04-01
Filing date: 2009-02-02
Publication date: 2011-01-26
Also published as: CA2719850A1; DE102008000914A1; RU2010144330A; US8426497B2; HK1138309A1; US20100298466A1; CN101550310A; JP2011518238A; TW201006897A; WO2009121640A1; CN101550310B; BRPI0910448A2; TWI498390B; JP5634982B2

Abstract

The invention relates to a process for preparing addition polymers for coating applications by addition polymerization of esters of acrylic acid or of methacrylic acid or of vinylaromatics or of other free-radically polymerizable vinyl compounds or of monomer mixtures that consist predominantly of such monomers, by means of a continuous addition-polymerization process. More particularly, the invention relates to a solventless method of producing addition polymers whereby it is possible to prepare binders for coating applications having superior processing properties, very good thermal stability, improved pigment wetting and higher gloss/lustre.

Description

Process for the synthesis of improved binders and modified

tacticity

Field of the invention

The invention relates to a process for the preparation of polymers for coating applications by polymerization of esters of acrylic acid or of methacrylic acid or of vinylaromatics or of other free-radically polymerizable vinyl compounds or of monomer mixtures which consist predominantly of such monomers by means of a continuous polymerization process. In particular, the invention relates to a solvent-free production process of polymers, can be represented by the binder for paint applications with better processing properties, a very good thermal stability, improved pigment wetting and a higher gloss.

State of the art

(Meth) acrylate or vinyl aromatic binders for paint applications are usually prepared in the prior art by suspension polymerization or solution polymerization. (Meth) acrylates are understood to mean both acrylic acid and its derivatives, for example their esters and also methacrylic acid and its derivatives, for example their esters and mixtures of the abovementioned components.

By contrast, the present invention describes a bulk polymerization process or, more preferably, a continuous bulk polymerization process. Such a process can be carried out without interfering solvents. Solvents can during a polymerization, for example, of (meth) acrylates cause side reactions such as chain transfer reactions, undesired termination reactions or even polymer-analogous reactions. In addition, the handling of solvents under production conditions poses a safety risk. Furthermore, the choice of the solvent can also be limited by the production process - for example, by the required reaction temperature. This, in turn, impairs the later formulation and the form of application, for example with regard to excessively long drying times due to an excessively high boiling solvent. The free choice of the solvent is additionally restricted if the microstructure of the polymer is to be modified by precise adjustment of the reaction temperature. In addition, it is known to the person skilled in the art that the polymerization of (meth) acrylates or vinylaromatics at high temperatures leads to a higher proportion of so-called head-to-head linkages. Such bonds in a polymer chain significantly reduce the thermal stability of the polymer and may, inter alia, lead to a higher residual monomer content. An alternative removal of the solvent used for production necessitates an additional, unwanted production step and additionally pollutes the environment through the use of two different solvents for production and application.

The suspension polymerization of esters of acrylic acid or of methacrylic acid or of vinylaromatics or of monomer mixtures which predominantly consist of such monomers is known in principle. This process is carried out without solvent. Compared to the bulk polymerization, however, has the great disadvantage that in this method, a large amount of water is used. This requires additional process steps such as filtration and subsequent drying. This drying is usually incomplete. Even low residual water contents, however, lead in paint applications to a significant impairment of the optical properties such as gloss or pigment dispersion. Also, a suspension polymerization can not be carried out continuously but only in batch mode. Such a process is less flexible and efficient than continuous polymerization. Another disadvantage of the suspension polymerization over other polymerization processes is the large number of excipients such as distributors, emulsifiers, anti-foaming agents or other excipients that must be used and are still contained in the final product after work-up. As an impurity, these adjuvants in a paint can, for example, result in reduced gloss levels, poorer dispersion of pigments, or specks due to poorly washed organic solvent-insoluble manifolds.

Another disadvantage is the very limited copolymerizability of polar comonomers such as (meth) acrylic acids, amino-functional or hydroxy-functional (meth) acrylates. The proportion of these monomers in the respective monomer mixture must be severely limited because of their water solubility. Another major disadvantage of the suspension polymerization is the required reaction temperature. Such a method can be carried out in a very low temperature window. Temperatures above 100 ⁰ C are basically difficult to adjust due to the water used. A theoretical implementation under pressure and temperatures above 100 ⁰ C is due to the additionally improved solubility of the monomers in such conditions in the

Water phase not recommended. At too low temperatures, however, the suspension polymerization proceeds only very slowly or incompletely and the setting of a process-compatible particle size is extremely difficult. An example of the preparation of suspension polymers as binders for coating applications can be found in DE 0 190 433.

Another disadvantage of the suspension over the bulk polymerization is the energy balance: The heating of about 50% water phase and the cooling of this water phase necessary after the polymerization are energy and time consuming. The non-continuous substance polymerization in stirred tanks or basins fundamentally leads only to incomplete reactions of the monomers and thus to high residual monomer proportions, which in turn disturb the coating properties or must be removed consuming prior to formulation.

The skilled person is a large number of different continuous

Bulk polymerization methods for the preparation of poly (meth) acrylates known. EP 0 096 901, for example, describes a continuous feed of a stirred tank with a monomer mixture consisting of styrene, α-methylstyrene and acrylic acid and the simultaneous removal of the polymer. As reaction temperatures, a range between 170 ⁰ C and 300 ⁰ C is described, without any influence of the conditions on the polymer microstructure or a distinction of the performance properties is made. Meanwhile, pipe reactors are of great importance for carrying out a continuous bulk polymerization. WO 98 04593 describes the continuous preparation of acrylate resins or copolymers of styrene, α-methylstyrene and acrylic acid. The polymerization is carried out at a temperature between 180 ⁰ C and 260 ⁰ C. The preparation of polymers of analogous composition for dispersing or emulsifier applications in a temperature range between 210 ⁰ C and 246 ⁰ C is designed in US 6,476,170. In WO 99 23119 the preparation of adhesive resins in a tubular reactor at a polymerization temperature between 100 ⁰ C and 300 ⁰ C claimed - in WO 2005 066216 the production of hot melt adhesives at temperatures below 130 ⁰ C. In none of these writings, however, the influence of different reaction temperatures on the microstructure of the polymers or the resulting performance properties, for example, mentioned in a paint formulation. The same applies to the polymerization process described in WO 98 12229. This is a variant of the tubular reactor: the circulation reactor. The aim of the claimed process was the preparation of polymethacrylates for the production of moldings. The procedure described here is limited to a relatively narrow temperature range between 135 ⁰ C and 150 ⁰ C, without this restriction being in any way due to the influence on the polymer microstructure.

A new generation of reactors for the continuous bulk polymerization of (meth) acrylates are the so-called Taylor reactors. These reactors can also be used in a wide temperature range. A detailed description of a corresponding process for the preparation of binders for coatings or adhesives or sealants can be found in WO 03 031056, without mentioning here the microstructure of polymer chains. An alternative to the continuous feed of reaction reactors is the

Reactive extrusion. In WO 2007 087465 a process for the continuous production of poly (meth) acrylates for adhesive applications is presented. The reactive extrusion has the great advantage that with short residence times, a high conversion can be achieved. However, a targeted adjustment of the microstructure of the products has not yet been described.

Reactive extrusion is in principle very similar to kneader technology. WO 2006/034875 describes a process for the continuous bulk polymerization, in particular for the homo- or copolymerization of thermoplastics and elastomers, above the glass transition temperature in a back-mixed kneading reactor. Monomers, catalysts, initiators etc. are continuously fed into the reactor and remixed with already reacted product. At the same time, reacted product is continuously removed from the mixing kneader. The method may, for. B. be applied to the continuous bulk polymerization of MMA. The unreacted monomer is separated by a residual degasser and can be recycled to the reactor. Various polymerization temperatures and their influence on the tacticity of the product have not been investigated.

WO 2007/112901 describes a process for the treatment of viscous products, in particular for carrying out homo- or copolymerization of thermoplastics and elastomers, in which a conversion of 90-98% is achieved. Monomer (s), catalyst (s) and / or initiator (s) and / or chain regulators are fed continuously to a back-mixed mixing kneader or a kneading reactor and remixed with already reacted product and the reacted product is removed from the mixing kneader. Here, the product is heated in the kneader up to a boiling temperature, parts of the reactants evaporated and an exotherm of the product absorbed by evaporative cooling. This process can be carried out without or only with very small amounts of solvents. The optimum boiling temperature is set by changing the pressure. The backmixing takes place until a predetermined viscosity of the product is reached. The viscosity is maintained by continuous addition of the educts. An investigation of the influence of the manufacturing temperature on the tacticity of the product is not described.

task

The object of the present invention was to provide improved binders on acrylate or methacrylate (hereinafter short (meth) acrylate) basis for paint formulations.

In particular, it was an object of the present invention, (meth) acrylate binder with improved over the prior art gloss values and

Wetting properties of pigments to provide. In addition, the binders should have a high thermal stability - for example

Temperatures of about 214 ⁰ C - dispose. This should be ensured by a particularly low proportion of head-to-head links in the polymer chain.

Furthermore, the binders prepared according to the invention and thus the coating formulations prepared therefrom should optionally have improved processing properties, such as, for example, reduced melt and / or solution viscosities.

A further object was to provide an environmentally friendly process which can be carried out either solvent-free or with a maximum solvent content of 10% by weight, and which can be carried out under high conversion or with only a very small proportion of residual monomers. Another object was the requirements imposed on the high gloss properties of the binder such that the process can be carried out without the addition of auxiliaries, such as emulsifiers, stabilizers or defoamers. solution

The objects were achieved by a modified use of special continuous bulk polymerization, by means of which the (meth) acrylates can be polymerized solvent-free with high conversion and in principle can already be considered as prior art. The advantage of a bulk polymerization process over the suspension polymerization is the high purity of the products which can be prepared without the addition of auxiliaries such as emulsifiers, stabilizers, defoamers or other suspension aids. Another advantage is the freedom from water of the product. Binders prepared by suspension polymerization often show reduced gloss and sometimes also dispersancy properties in paints. This effect is due not only to the polymer microstructure, but also to the process-related residual moisture of the polymer. Another advantage of the bulk polymerization over the suspension polymerization is the use of any amounts of hydrophilic comonomers such as (meth) acrylic acids, amino- or hydroxy-functional (meth) acrylates.

The advantage over the solution polymerization is the lack or the very small proportion of volatile constituents in the polymerization process or in the primary product. The advantage of the process according to the invention over bulk polymerization in batch mode is the significantly higher conversion which can be achieved and thus the lower proportion of residual monomers in the end product. In addition, there is a higher production speed and a wider variation possibility of the process parameters.

A particular aspect of the solution according to the invention is the possibility of an individual choice of the polymerization temperature as a function of the requirements of the particular product or the respective application. The properties of the binder to be prepared in terms of gloss, thermal stability, dispersing or wetting properties of pigments and processing properties of the Binder or paint formulation surprisingly depend not only on the composition, the molecular weight, the molecular weight distribution, the functionalities and the end groups, but in particular on the microstructure of the polymer chains. By microstructure in this case is meant the tacticity and the proportion of head-to-head links in the chain of the polymer. It is known to the person skilled in the art that a poly (meth) acrylate prepared by free radicals, depending on the monomer composition, is a copolymer of syndiotactic and atactic portions (triads) with only a small proportion of isotactic triads. Polymethacrylates with particularly large syndiotactic proportions can only be prepared by means of technically complicated processes such as anionic polymerization at particularly low temperatures or metal-initiated group transfer polymerization (GTP) with stereoselective catalysts. Highly isotactic polymers, on the other hand, can almost only be realized by the latter method. A third possibility to make a stereoselective effect on a polymerization is to add a complexing agent in the form of an optically active reagent in the polymerization solution. See, for example, EP 1 611 162. However, this procedure has several disadvantages: on the one hand, it can be used efficiently only in a solution polymerization, on the other hand, the auxiliary is a further polymerization, which either has to be removed consuming or affects the optical properties of the final product ,

The preparation and accurate characterization of polymers with triad purities greater than 95% can be found, for example, in Frauenrath et al. (Macromolecules, 2001, Vol. 34, p. 14). A highly isotactic PMMA, for example, glass transition temperatures below 50 ⁰ C or 60 ⁰ C. A hochsyndiotaktisches PMMA contrast glass transition temperatures well above 130 ⁰ C. The thermal properties, but also macroscopic polymer properties change. As is known to the person skilled in the art, the change in the tacticity also influences the glass transition temperature or, in the rare case of a crystalline polymer, the melting temperature. The thermal properties continue to change the macroscopic properties of the polymer. The glass transition temperature can be regarded as an indication of chain flexibility. Of this hang too

Properties such as the melt viscosity or the solution behavior and thus in turn the solution viscosity of the materials. The skilled worker is thus readily apparent that by varying the microstructure, in particular the tacticity of a polymer chain, also aspects such as the processing properties - such as the formability in a solvent, the drying rate of a coating or the

Temperature or weather resistance of a paint - the polymer adjusts. The great influence of tacticity on crystallinity and conformation as well as the thermal properties of, for example, polypropylene can be found in Seymour et al. (Paintindia, 23 (8), pp. 19-28, 1973).

It is also known that the minimum layer thickness of a coating depends very much on the self-organization of the polymers on the surface and the chain flexibility. These important aspects of a coating are also due to the tacticity of the respective polymer. A detailed investigation with PMMA coatings can be found in Grohens et al. (Mat. Res. Soc. Symp. Vol. 629, FF1.7.1-FF1.7.7, 2001).

Surprisingly, it has been found that the compatibility with other polymers and the interaction with inorganic surfaces changes with the tacticity. One cause of this may be e.g. which would be changed with different tacticity polarity of the polymer.

Another advantage of polymers with different tacticities is thus that the microstructure - in particular the tacticity - of a polymer has an influence on the interaction at interfaces. This concerns on the one hand the liability various substrates such as metals, ceramics or concrete. In particular, compared to metal surfaces such as zinc or steel could be detected with the binders according to the invention significantly improved adhesion properties. Depending on the polymer composition, however, corresponding effects can also be expected with respect to other surfaces, such as ceramics, plastics or concrete.

On the other hand, however, above all the dispersion of pigments or additives contained in coating compositions is influenced. The quality of wetting of pigments by the binder in a paint is of crucial importance to the color intensity and quality of the coating. The interaction of pigment and binder is determined greatly by the position of the interacting or functional groups on a polymer chain. Thus, for example, it is conceivable that in a syndiotactic triad three interacting groups can be thermodynamically brought into a spatial proximity to one another which would result in high, unfavorable chain stresses in an isotactic unit. Other steric effects or interactions are likely. Thus, with the polymerization method according to the invention, it is possible for the first time to optimally prepare a binder by means of a polymerization method which is as simple and flexible as possible, also with regard to a specific combination of substrate to be coated and pigment to be dispersed in the matrix.

Another aspect is the viscosity of the finished paint formulation. The skilled worker is aware that in the formulation of, for example, inorganic pigments in a paint, the viscosity is greatly influenced. This effect is due to the interaction between binder and pigment and is an indication of the quality of the surface wetting of the color additive. When using binders prepared according to the invention, it is surprisingly found that the initial viscosity of such a formulation can be lower and thus more favorable compared to a standard formulation with a corresponding suspension polymer. With the According to the invention, a faster and more efficient pigment dispersion is possible.

Another aspect of the paint quality is the gloss. It has already been designed that the gloss is strongly influenced by the water or solvent content in the coating matrix. Surprisingly, however, it has additionally been found that the microstructure too can bring about a great measurable effect on the gloss values of a lacquer. Depending on the polymer composition could be shown that polymers improved with lower gloss values compared to syndiotactic content considered as the standard suspension polymers which were prepared at 80 ⁰ C show.

Thus, it is possible with these methods to produce more targeted polymers with respect to these application-relevant macroscopic properties. All previously known methods for stereocontrol in the polymerization of (meth) acrylates are extremely expensive and are based on the addition of additional

Components such as special initiators or complexing agents. A simple method for influencing the polymer tacticity during the polymerization process would therefore be of great technical interest. Surprisingly, it has been found that this problem can be solved by varying the polymerization temperature and optionally adjusting the

Initiator / controller system may vary the tacticity of a polymer in a limited, but technically quite interesting frame without having to add additional components such as complexing agents to the system. It has also been found that in this regard - for reasons already explained - bulk polymerization is most suitable.

Furthermore, it is easy to conclude that this dependence of the tacticity of the polymerization temperature for monomers having larger alkyl groups than methyl groups - as in the MMA - even greater effects when comparing different microstructures can have. The same applies in particular to copolymers of monomers with sterically different demanding radicals.

A further advantage of the process according to the invention is that it can be transferred without problems to a continuous polymerization process.

A further aspect of the present invention is the preparation of (meth) acrylate-based binders which have a thermal stability up to 214 ^° C., preferably up to 230 ^° C., very particularly preferably up to 250 ^° C. By thermostability at a given temperature is meant a mass loss of less than 2% by weight in a thermogravimetry (TGA). In particular, the polymerization at higher temperatures favors the formation of so-called head-to-head linkages. These bonds in the polymer chain, in which two quaternary carbon atoms are linked together in the case of poly (meth) acrylates, exhibit thermal instability at temperatures above 150 ^° C. and can initiate the depolarization of a chain in the event of breakage. This leads to a reduced production yield and an increased residual monomer content in the polymer. In addition, such products may show reduced storage or weather stabilities due to unstable bonds.

The formation of head-to-head linkages in poly (meth) acrylates at higher polymerization temperatures is not only a phenomenon that can be observed in bulk polymerization, but also occurs

Solution polymers prepared at a suitable temperature, on. In the present invention, the problem of the head-to-head linkage and thus the reduced thermal stability has been solved in such a way that after the completed polymerization, the product is thermally post-treated. At a temperature above 120 ⁰ C, preferably above 160 ⁰ C, more preferably above 180 ⁰ C, and an internal pressure between 1 mbar and 800 mbar, preferably between 5 mbar and 400 mbar and more preferably between 10 mbar and 100 mbar , not only are volatile components such as residual monomers or optionally used solvents contained in the product removed, but also the head-to-head bindings are opened and the polymer chains concerned stabilized or depolymerized and removed the resulting low molecular weight compounds. The monomers recovered in this way can optionally even be recycled to the polymerization process. Such a procedure can be implemented in all methods described so far, such as reactive extrusion, the Taylor or tubular reactor and the kneader technology, without problems by means of a connected process step such as flash degassing or a (second) degassing extruder. Alternatively, it is possible to operate one of the last interspersed zones of the continuously operated reaction reactor at the appropriate temperature and optionally under reduced pressure. This could be, for example, the last zone of an extruder or the like.

Monomers which are polymerized are selected from the group of (meth) acrylates, for example alkyl (meth) acrylates of straight-chain, branched or cycloaliphatic alcohols having 1 to 40 carbon atoms, for example methyl (meth) acrylate, ethyl (meth ) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate,

Pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate; Aryl (meth) acrylates such as benzyl (meth) acrylate or phenyl (meth) acrylate, each of which may be unsubstituted or substituted by 1-4-substituted aryl groups; other aromatic substituted (meth) acrylates such as naphthyl (meth) acrylate; Mono (meth) acrylates of ethers,

Polyethylene glycols, polypropylene glycols or mixtures thereof with 5-80 C atoms, such as tetrahydrofurfuryl methacrylate, methoxy (m) ethoxyethyl methacrylate, 1-butoxy-propyl methacrylate, cyclohexyloxymethyl methacrylate, benzyloxymethyl methacrylate, furfuryl methacrylate, 2-butoxyethyl methacrylate, 2-ethoxyethyl methacrylate, allyloxy-methyl methacrylate, 1 - Ethoxybutyl methacrylate, 1-ethoxyethyl methacrylate, ethoxy-methyl methacrylate, poly (ethylene glycol) methyl ether (meth) acrylate and poly (propylene glycol) methyl ether (meth) acrylate. The monomer selection may also include respective hydroxy-functionalized and / or amino-functionalized and / or mercapto-functionalized ones and / or olefinically functionalized and / or carboxyl-functionalized acrylates or methacrylates such as allyl methacrylate or hydroxyethyl methacrylate.

In addition to the (meth) acrylates set out above, the compositions to be polymerized may also contain other unsaturated monomers which are copolymerizable or homopolymehisable with the abovementioned (meth) acrylates. These include, inter alia, 1-alkenes such as 1-hexene, 1-heptane, branched alkenes such as vinylcyclohexane, 3,3-dimethyl-1-propene, 3-methyl-1-diisobutylene, 4-methyl-1-pentene, acrylonitrile , Vinyl esters such as Vinyl acetate, styrene, substituted styrenes having an alkyl substituent on the vinyl group, e.g. α-methylstyrene and α-ethylstyrene, substituted styrenes having one or more alkyl substituents on the ring such as vinyltoluene and p-methylstyrene, halogenated styrenes such as monochlorostyrenes, dichlorostyrenes, tribromostyrenes and tetrabromostyrenes; heterocyclic compounds such as 2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole , 2-methyl-1-vinylimidazole, vinyloxolane, vinylfuran, vinylthiophene, vinylthiolane, vinylthiazoles, vinyloxazoles and isoprenyl ethers; Maleic acid derivatives such as maleic anhydride, maleimide, methylmaleimide, cyclohexylmaleimide and dienes such as e.g. Divinylbenzene, and the respective hydroxy-functionalized and / or amino-functionalized and / or mercapto-functionalized and / or olefinic funtkionalisierten compounds. Furthermore, these copolymers can also be prepared in such a way that they have a hydroxyl and / or amino and / or mercapto functionality and / or an olefinic functionality in a substituent. Examples of such monomers are vinylpiperidine, 1-vinylimidazole, N-vinylpyrrolidone, 2-vinylpirrolidone, N-vinylpirrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam, N-vinylbutyrolactam, hydrogenated vinylthiazoles and hydrogenated vinyl oxazoles.

As polymerization initiators, which are usually added to the monomer phase, are the commonly used radical initiators, in particular peroxides and azo compounds. Under certain circumstances, it may be advantageous to use a mixture of different initiators. The amount used is generally in the range between 0.1 and 5 percent by weight, based on the monomer phase. Preference is given to azo compounds such as azobisisobutyronitrile, 1, 1-azobis (cyclohexancarbonithl) (WAKO V40 ^®), 2- (carbamoylazo) -isobutyronitrile (WAKO V30 ^®), or peresters such as tert

Butyl peroctoate, di (tert-butyl) peroxide (DTBP), di (tert-amyl) peroxide (DTAP), tert-butyl peroxy (2-ethylhexyl) carbonate (TBPEHC) and other high temperature decomposing peroxides as a radical initiator use. Further examples of suitable initiators are octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, monochlorobenzoyl peroxide, dichlorobenzoyl peroxide, p-ethylbenzoyl peroxide, tert-butyl perbenzoate or azobis (2,4-dimethyl) valeronitrile.

To adjust the molecular weight of the polymer formed, it is also possible to add up to 8% by weight of one or more chain regulators known per se to the monomer phase in a customary manner. Examples which may be mentioned are: mercaptans, such as n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan tert-dodecyl mercaptan or mercaptoethanol; Thioglycolic acid or thioglycolic acid esters such as thioglycolic acid isooctyl ester or thioglycolic acid lauryl ester; aliphatic chlorine compounds; Enol ether or dimeric α-methylstyrene. If branched polymers are to be prepared, the monomer phase may also contain up to about one percent by weight of polyfunctional monomers, for example ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate or divinylbenzene.

In order to optimally adjust the viscosity in the continuously operated reactor, up to 10% by weight of a solvent or a plasticizer may optionally be added to the system. For particularly high melt viscosities, such an addition may be necessary to ensure optimum mixing of the reaction solution. Preferably, a maximum of 5 wt .-% are added to the monomer mixture. Particularly preferred is the polymerization without addition of a solvent or a Plasticizer performed. There are no restrictions on the usable additives. These may be, for example, acetates, aliphatics, aromatics or else polyethers or phthalates.

A preferred process for the preparation of the polymers according to the invention is the continuously operated kneader technology. A description of such a back-mixed kneading reactor for continuous bulk polymerization of the company List can be found in WO 2006/034875 or in WO 2007/112901. The polymerization is carried out above the glass transition temperature of the polymer. Monomers, catalysts, initiators etc. are continuously fed into the reactor and remixed with already reacted product. At the same time, reacted product is continuously removed from the mixing kneader. The unreacted monomer is separated by a residual degasser and can be recycled to the reactor. At the same time, the thermal aftertreatment of the polymer is carried out in this residual degasser.

This results in a broad field of application for the products produced according to the invention. The (meth) acrylate-based bulk polymers are preferably used in coatings, e.g. used on metal, plastic, ceramic or wood surfaces. An example of a coating composition is the use of the polymers according to the invention as binders in architectural paints, ships or container paints. The polymers can likewise be used in road markings, floor coatings, printing inks, heat-sealing lacquers, reactive hot melt adhesives, adhesives or sealants.

The examples given below are given for a better illustration of the present invention, but are not intended to limit the invention to the features disclosed herein. Examples

Determination of the tacticity of the polymers

The tacticity determination of the polymers produced is determined by means of 1 H

Nuclear magnetic resonance spectroscopy performed. The methyl signal of polymethacrylates in iso-, hetero- and syndiotactic triad shows in the proton spectrum resonance at 0.87, 1, 02 and 1, 21 ppm (deuterochloroform with tetramethylsilane as standard, 50 ⁰ C). Integration over these peaks provides the triad frequency.

Determination of metal adhesion of paints

The metal adhesion of a binder on a steel or a zinc surface was examined by means of cross-cut test in accordance with DIN EN ISO 2409. The evaluation of the result is carried out with values between 0 (particularly good liability) to 5 (no liability). Two values are given in the tables: the first one is the visual assessment after the cut. The second value is the assessment for an additional standard test with tape.

Determination of gloss values

The gloss values are measured according to DIN 67630. The measuring angle is indicated in each case.

Measurement of the dynamic viscosity

The measurement of the dynamic viscosity is carried out in accordance with DIN EN ISO 53018.

Measurement of glass transition temperatures

The measurement of the glass transition temperatures takes place by means of dynamic differential thermal analysis (DSC) according to DIN EN ISO 11357-1.

Thermogravimetric measurements

The thermogravimetric measurements are carried out according to DIN EN ISO 11358.

Example 1, Composition 1

Continuous bulk polymerization

A mixture consisting of 20% by weight of methyl methacrylate, 80% by weight of n-butyl methacrylate, 0.4% by weight of TBPEHC from Degussa Initiators and 0.4% by weight of ethylhexyl thioglycolate (TGEH) is continuously added to a back-mixed kneading reactor Company List, as described for example in WO 2006/034875, supplied and simultaneously reacted polymer continuously led out of the reactor. The internal temperature in the reactor is 140 ^° C. The average residence time is about 30 minutes. The polymer melt is immediately after the reactor a flash degasser from List fed, in which at a temperature of 180 ⁰ C remaining unreacted monomers are removed from the polymer and thermally unstable head-to-head linkages are broken. Between reactor and flash degasser, it is possible to take a sample for TGA measurements.

Example 2, Composition 1

As Example 1, but with 0.5% TBPEHC at an internal reactor temperature of 120 ⁰ C.

Reference Example 1, Composition 1

solution

80% (364 g) of n-butyl methacrylate and 20% (91 g) of methyl methacrylate become one

Mixed monomer stock solution. 91 g of the monomer stock solution and 140 g of n-butyl acetate are placed in a 2L jacketed reactor with paddle stirrer, reflux condenser and nitrogen inertization. 0.3 g of TGEH are dissolved in 5 g of n-butyl acetate and added to the reactor. While stirring, the mixture is heated to 60 ^° C. internal temperature. 0.55 g of Peroxan PND from Pergan GmbH dissolved in 5 g of n-butyl acetate were added. After the exothermic reaction, the remaining monomer stock solution is metered in together with 1.2 g of TGEH and 2.2 g of peroxan PND within 3 hours at an internal temperature of 60.degree. After the end of the dosing, re-initiate 1, 4 g of peroxan PND in 100 g of n-butyl acetate. The post-reaction time is three hours. It is then cooled to about 40 ⁰ C and thereby diluted with 240 g of n-butyl acetate. Reference Example 2, Composition 1

As Reference Example 1, except that a total amount of 2.73 g Peroxan PO from Pergan GmbH as an initiator and at an internal temperature of 90 ⁰ C.

Reference Example 3, Composition 1

As Reference Example 1, except that a total amount of 1, 83 g TBPB Degussa initiator as an initiator, a total amount of 0.91 g TGEH as a controller and at an internal temperature of 120 ⁰ C.

Reference Example 4, Composition 1

bulk

720 g of n-butyl methacrylate, 180 g of methyl methacrylate, 3.6 g of TGEH and 3.6 g of TBPEHC are mixed in a beaker and homogenized for 30 minutes with stirring. The mixture is placed in a mold consisting of two glass plates (20 x 20 cm) and a 6 mm thick plastic piping. The piping is placed between the two glass plates so that it ensures both a constant distance between the plates and the sealing of the mold. The shape is held together by brackets. The filled mold is placed in an oven at 80 ^° C. for 3 hours. The mold is then removed from the oven, allowed to cool to room temperature and the polymer plate removed from the mold.

Reference Example 5, Composition 1

As Reference Example 4, but with 2.3 g of TGEH, 4.7 g Peroxan LP from Pergan GmbH and at 120 ⁰ C oven temperature. Reference Example 6, Composition 1

suspension

In a 5L Polymehsationsgefäß with heating-cooling jacket, equipped with a stirrer and reflux condenser 3200 ml_ deionized water are introduced, the stirrer set to a speed of 300 revolutions per minute and heated to an external temperature of 40 ⁰ C. 200 g of a 13% strength aqueous solution of polyacrylic acid and 0.5 g of potassium hydrogensulfate are added and distributed by stirring. 1280 g (80%) of n-butyl methacrylate, 320 g (20%) of methyl methacrylate, 7.5 g of peroxan LP and 4 g of TGEH are mixed in a beaker and homogenized with stirring. The monomer stock solution is pumped into the reactor. The internal temperature is regulated to 85 ⁰ C. The polymerization is completed when the evolution of heat stops. The batch is cooled. The mother liquor is separated from the polymer beads through a filter suction filter, washed thoroughly with demineralized water and dried in an oven at 85 ^° C.

By way of example 2 (preparation according to the invention) and reference examples 3 (solution polymerization) and 5 (batch process in bulk), it can be shown that the polymer tacticity depends exclusively on the polymerization temperature and not on other factors of the particular polymerization process.

As already explained, the products of a batch batch polymerisation and the products of a continuous bulk polymerization process are well comparable. By means of Examples 1, 2 and 3 as well as Reference Examples 5, 6 and 7 it can be shown that the process according to the invention can be used in a very wide temperature range and thus for the preparation of polymers with very different tacticities.

Example 3, Composition 2

As in Example 1, but the mixture fed to the reactor consists of 65% n-

Butyl methacrylate, 34% methyl methacrylate, 1% methacrylic acid, 0.5% TBPEHC and 0.3% thioglycolic acid from Dr. Ing. Spiess Chemical Factory GmbH.

Reference Example 7, Composition 2

As Reference Example 4, but with 585 g of n-butyl methacrylate, 306 g of methyl methacrylate and 9 g of methacrylic acid as monomers, 2.5 g of peroxan PND and 3 g of thioglycolic acid and at 38 ⁰ C.

Reference Example 8, Composition 2

As Reference Example 6, but with 510 g of methyl methacrylate, 975 g of n-butyl methacrylate, 15 g of methacrylic acid, 7.5 g of Peroxan LP and 12 g of lauryl mercaptan from Dr. Ing. Spiess Chemical Factory GmbH. Production of the pigmented paints with binder pigment ratio 1: 0.5

A 40% solvent solution in Solvesso 100 solvent is premixed with titanium dioxide (1 to 0.5 pigmentation) as a pigment by hand. Steatite balls are placed in this mixture, the vessel is closed and moved on a roll bar for 24 hours. After completion of the dispersion process, the paint is poured off through a sieve and the dynamic viscosity of the filtrate is measured. The gloss is determined on a dried knife lift with a thickness of 200 microns. The adhesion on different substrates is examined according to the standard by means of cross-cut tests.

Compared to a product obtained by suspension polymerization binder (Reference Example 8) shows a formulation with a according to the invention and at high temperature (140 ⁰ C) produced polymer (Example 3) of the same composition significantly better gloss values and an improved metal adhesion - especially compared to the industrially very important zinc surfaces. With regard to the gloss values, the effect, as is also apparent from the comparison with a bulk polymer prepared at very low temperatures (Reference Example 7), is attributable in particular to the tacticity of the polymer. The even slightly worse gloss value of the

Suspension polymer (Referential Example 7) also over the harder (i.e., higher syndiotactic portion) bulk polymer (Reference Example 8) shows that residual water and the additives required in the suspension polymerization additionally contribute to a decrease in gloss. With regard to metal adhesion, the effect is a combination of different

Tactics (see above all comparison of zinc adhesion with reference example 7) and the excipients contained in suspension polymers (see above all the non-adherence of the formulation prepared with comparative example 8 on zinc surfaces). In addition, as expected, the formulations of binders prepared according to the invention from Example 2 contain the lowest dynamic viscosity and thus the best processing properties. In order to compare the weathering stability of the different paint formulations each other coated samples were body as follows in accordance with the respective measurement standard weathered: in successive cycles, the samples were each irradiated for eight hours at 20 ⁰ C with UV light and then at 60 ⁰ C for four Hours of dew. The coating is carried out according to the procedure described without the addition of titanium dioxide.

The comparison of the loss of gloss and the adhesion values to metal adhesions shows that the different binders have comparable weathering stabilities.

By DSC measurements, the dependence of the glass transition temperatures T ₉ on the respective Takitzität can be shown. In particular, the comparison of the polymers of Example 3 and Reference Example 8 gives - with identical polymer composition - a difference in glass transition temperatures of more than 5 ⁰ C. This difference is due solely to the tacticity - and thus to the polymerization temperature.

Thermogravimetry measurements (TGA measurements) of the material produced according to the invention from Example 3 - in each case before and after the degassing step - result in a significant improvement in the thermostability of the polymer. The thermally treated samples show up to a temperature of 214 ⁰ C to a suspension polymers (Reference Example 8) and in batch process prepared substance polymers (Reference Example 7) comparable thermal stability.

Thus, according to the invention, it is possible to prepare binders which, despite a significantly higher reaction temperature, have a comparable thermal stability or weathering stability to polymers represented by established production processes. These properties can be attributed to a comparatively low proportion of head-to-head linkages in the polymer.

Claims

claims

1. Paint formulations containing a (meth) acrylate-based binder with better pigment dispersing properties, a better gloss and a high thermal stability,

characterized in that

the polymer is prepared via a continuous bulk polymerization process having a reaction temperature which is between 20 ^° C. and 250 ^° C.

and that the syndiotactic portion of the binder deviates by at least 5% from that of a polymer of the same monomer composition prepared by suspension polymerization at 80 ^° C.

2. paint formulations according to claim 1

characterized in that

a.) The binder of a monomer mixture consisting exclusively of

Monomers and initiators and optionally chain transfer agents and a maximum of 10 wt .-% solvent is prepared, and b.) The binder has a thermal stability up to 214 ⁰ C.

3. A process for the preparation of (meth) acrylate-based binders for coating compositions according to claim 2

characterized in that

a.) By setting a suitable reaction temperature, the tacticity of

Polymer is influenced and b.) By a thermal aftertreatment in the process, the polymers

Thermostability to at least 214 ⁰ C.

4. A process for the preparation of (meth) acrylate-based binders for coating compositions according to claim 3

characterized in that

the reaction temperature is above 100 ⁰ C, and that the glass transition temperature is lower by 2 ⁰ C than a polymer of the same

Composition prepared by suspension polymerization at 80 ^° C.

5. A process for the preparation of (meth) acrylate-based binders for coating compositions according to claim 3

characterized in that

the polymerization is carried out in a Taylor reactor.

6. A process for the preparation of (meth) acrylate-based binders for coating compositions according to claim 3

characterized in that

the polymerization is carried out in an extruder.

7. A process for the preparation of (meth) acrylate-based binders for coating compositions according to claim 3

characterized in that

the polymerization is carried out in a kneader.

8. A process for the preparation of (meth) acrylate-based binders for coating compositions according to claim 3

characterized in that

the polymerization is carried out in a tubular reactor.

9. A process for the preparation of (meth) acrylate-based binders for coating compositions according to claim 3

characterized in that

the polymerization is carried out in a stirred tank with continuous monomer feed and continuous polymer removal.

10. A process for the preparation of (meth) acrylate-based binders for coating compositions according to claim 3

characterized in that

by a thermal treatment at a reaction temperature of more than 160 ⁰ C in a reactor downstream device, the thermal stability of the binder is improved to 214 ⁰ C.

11. A process for preparing (meth) acrylate-based binders according to claim 3

characterized in that

by thermal post-treatment in a zone of the reactor having a reaction temperature of more than 160 ⁰ C, the thermal stability of the binder is improved to 214 ⁰ C.

12. bulk polymerization process according to claim 3

characterized in that

the monomer mixture may contain up to 10% by weight of a solvent or plasticizer.

13. A (meth) acrylate-based binder for coating compositions, which can be prepared according to the polymerization process in claim 3.

14. A (meth) acrylate-based binder for coating agent, which is preparable according to the polymerization process in claim 3 and additionally contains styrene and / or other free-radically polymerizable vinyl compounds.

15. Use of the binder according to claim 13 in paint formulations for

Coating of metal, plastic, ceramic or wood surfaces.

16. Use of the binder according to claim 15 in ship or container colors.

17. Use of the binder according to claim 15 in architectural colors.

18. Use of the binder according to claim 13 in road markings or floor coatings.

19. Use of the binder according to claim 13 in printing inks.

20. (meth) acrylate-based binders for reactive hot melt adhesives or heat sealing varnishes, which can be prepared according to the polymerization process in claim 3.

21. A binder based on (meth) acrylate for adhesives or sealants, which can be prepared according to the polymerization process in claim 3.