Bma graphisme et decor option brokers
The invention relates to levelling agents for surface coatings having a weight-average molecular weight of from towhich are suitable for giving coating compositions, such as paints, a uniform surface. The invention further relates to the use of the levelling agents of the invention for coating formulations and to coating formulations comprising the levelling agents of the invention.
Paint surfaces are normally not entirely smooth but instead have a more or less structured surface referred to as waviness or else as orange peel. These surfaces may be finely structured, with a short wave, or coarsely structured, with a long wave. In the majority of cases, this waviness is unwanted. The structure depends on the nature and composition of the coating compositions; for example, on whether these coating compositions comprise solvents or else are solvent-free, as in the case of powder coating materials.
In the case of powder coating materials it is bma graphisme et decor option brokers necessary to add levelling agents, since without these levelling agents it is impossible to achieve a surface which is in any way smooth. It is known that poly meth acrylates and polysiloxanes may be used as levelling promoters for coatings. In the case of the polysiloxanes the compounds concerned generally comprise polydimethylsiloxanes, polymethylalkylsiloxanes, or else polyether- or polyester-modified polydimethyl- or polymethylalkylsiloxanes.
In the case of the poly meth acrylates, preference is given to the use of polymers or copolymers of alkyl acrylates having an alkyl radical chain length of C 2 -C 8such as ethyl acrylate, 2-ethylhexyl acrylate or n-butyl acrylate, for example. The products used possess in some cases molecular weights of up toThese poly meth acrylate co polymers used as levelling promoters may be used as such or as solutions in organic solvents, or else as powders applied to silica, for example.
This is normally the case particularly when they are used in powder coating materials. The amounts of such products bma graphisme et decor option brokers are used are usually from 0. This incompatibility may be increased by raising the molecular weight of these polymers.
A disadvantage then, however, is that owing to this incompatibility there may be a certain haze of the coating and the viscosity of the levelling agent becomes so high that handling for the user becomes very difficult if not impossible.
The existing polymers provide only an inadequate solution to the levelling problem in the case of coatings, and there is an urgent need for new levelling promoters which make it possible to produce absolutely smooth coating films, which is of utmost importance in the case of powder coatings in particular. Surprisingly it has been found that this objective can be achieved by adding branched polymers comprising a free-radically or ionically polymerized base molecule into which monoethylenically unsaturated macromonomeric units bma graphisme et decor option brokers been incorporated by copolymerization as levelling agents to the surface coatings.
The copolymerization of these monomers, which are very different in their molecular weight, produces highly branched polymers which despite a high overall molecular weight have a much smaller base molecule chain length, owing to the macromolecular side chains.
Furthermore, block structures with different compatibilities can be obtained by appropriately selecting the monomers for the base molecule and the monomers of the macromonomer; this cannot be done by free-radical copolymerization bma graphisme et decor option brokers low molecular weight monomers. Advantageous embodiments of the levelling agent of the invention are evident from the dependent claims.
Graft copolymers with a comb-like structure, comprising a main chain and copolymerized macromonomer side chains, are known per se.
They are used, for example, as pigment dispersants and in that case contain groups in the molecule that have affinity for the pigment. By way of example, amine-functional polymers having a macromonomer component are described in EP-A The requirements imposed on dispersants, however, are entirely different to those imposed on levelling agents. Bma graphisme et decor option brokers was therefore not obvious to use graft copolymers with a comb-like structure as levelling bma graphisme et decor option brokers. In order to prepare the levelling agents of the invention, monoethylenically unsaturated monomers are copolymerized with monoethylenically unsaturated macromonomers having molecular weights MW of from to 30, preferably from to 10, by known processes, preferably free-radically bma graphisme et decor option brokers ionically.
Preferred free-radically or ionically polymerized monomeric units of the base molecule are selected from the group consisting of alkenes and arylalkenes having from 2 to 30 carbon atoms, alkyl acrylates and alkyl methacrylates of straight-chain, branched or cyclo-aliphatic alcohols having from 1 to 22 carbon atoms, aralkyl acrylates and aralkyl methacrylates of aralkyl alcohols having from 8 to 18 carbon atoms, acrylamides and methacrylamides of straight-chain, branched or cycloaliphatic amines having from 1 to 22 carbon atoms, aminoalkyl acrylates and aminoalkyl methacrylates of straight-chain, branched or cycloaliphatic amino alcohols having from 2 to 8 carbon atoms, maleates, itaconates and fumarates of straight-chain, branched or cycloaliphatic alcohols having from 1 to 22 carbon atoms, and vinyl esters, vinyl ethers and vinyl ketones having from 3 to 20 carbon atoms.
As monomeric units of the base molecule it is also possible to use monomeric units containing polyethylene glycol, in order to allow the branched polymers of the invention to be soluble in water or emulsifiable in water. Examples of polyethylene glycol-containing monomeric units that can be used include polyethylene glycol bma graphisme et decor option brokers or polyethylene glycol monomethacrylates having from 5 to 80 carbon atoms.
It is also possible to use monomeric units containing functional groups, in order to allow later incorporation into the respective polymeric matrix or the binder. Examples of monomeric units with functional groups that can be used include acrylic acid, methacrylic acid, and hydroxyalkyl acrylates or hydroxyalkyl methacrylates of straight-chain, branched or cycloaliphatic diols having from 2 to 36 carbon atoms. In order to permit crosslinking of the hydroxy-functional levelling agents of the invention with, for example, acrylic melamine-formaldehyde resins, it is also possible to react some or all of these hydroxyl groups with isocyanates to give secondary carbamate groups, so that during the crosslinking of the system as a whole the levelling agent is left with sufficient time to orient itself at the interface, to develop its action there, and, after a certain delay, to react with the melamine-formaldehyde resin.
In order greatly to reduce the surface tension of the branched polymers of the invention, it is advantageous to copolymerize small amounts of monomeric units having perfluoroalkyl groups. As monomeric units of perfluoroalkyl groups it is possible, for example, to use perfluoroalkyl acrylates or perfluoroalkyl methacrylates having from 6 to 20 carbon atoms. The abovementioned ethylenically unsaturated monomers may be polymerized individually or in combination to give the base molecule, depending on the desired binder compatibility.
As macromonomeric units, polymers formed by free-radical or ionic addition polymerization may be used. Compounds suitable for preparing these macromonomers include preferably alkenes and arylalkenes having from 2 to 30 carbon atoms, alkyl acrylates and alkyl methacrylates of straight-chain, branched or cycloaliphatic alcohols having from 1 to 22 carbon atoms, aralkyl acrylates and aralkyl methacrylates of aralkyl alcohols having from 8 to 18 carbon bma graphisme et decor option brokers, polyethylene glycol monoacrylates or polyethylene glycol monomethacrylates having from 5 to 80 carbon atoms, hydroxyalkyl acrylates and hydroxyalkyl methacrylates of straight-chain, branched or cyclo-aliphatic diols having from 2 to 36 carbon atoms, and vinyl esters, vinyl ethers and vinyl ketones having from 3 to 20 carbon atoms.
In order drastically to reduce the surface tension of the branched polymers, it is further advantageous to copolymerize perfluoroalkyl acrylates and perfluoroalkyl methacrylates having from 6 to 20 carbon atoms into the macromonomeric units. The abovementioned ethylenically unsaturated monomers may be polymerized individually or in combination to give the macromonomeric unit, depending on the desired binder compatibility.
In order to ensure that these macromonomers carry only a single bma graphisme et decor option brokers unsaturated end group, special synthesis techniques are required. On the one hand, they can be prepared using what are known as chain transfer agents, as described in U. Cobalt complexes in concentrations of from 5 to ppm are used for this purpose.
Preference is given, for example, to pentacyanocobaltate II or diaquabis borodifluorodimethylphenylglyoximato cobaltate II. The corresponding Co III complexes are equally used. The addition polymerization is then conducted in solvents such as aromatics, ketones, acetates, alcohols or glycol ethers, for example. On the other hand, these macromonomers may be prepared by free-radical addition polymerization in the presence of a mercapto-functional carboxylic acid chain regulator, such as mercaptoacetic acid or mercaptopropionic acid, for bma graphisme et decor option brokers.
This terminal carboxyl function is reacted further with glycidyl methacrylate to give the methacryloyl-functional, polymerizable macromonomer. Hydroxy-functional chain regulators, such as mercaptoethanol or mercaptopropanol, for example, are also suitable. These polymers then carry a hydroxyl function at one end, which is reacted in accordance with known processes to give the meth acryloyl-functional polymerizable macromonomer. Further preparation options for macromonomers are cited in the review article by Koichi Ito with the title Polymeric Design bma graphisme et decor option brokers Macromonomer Technique from Prog.
In addition to the macromonomeric units obtainable by free-radical or ionic addition polymerization it is also possible to prepare the branched polymers using other macromonomers, such bma graphisme et decor option brokers monoethylenically unsaturated polydimethylsiloxanes, for example, which are obtained from monohydroxy-functional polysiloxanes by reacting them, for example, with meth acryloyl chloride or allyl chloride or by esterifying them with meth acrylic acid.
Another method of preparing such macromonomers is described in the U. The products then are likewise acryloyl- or methacryloyl-functional dimethylpolysiloxanes. The monoethylenically unsaturated macromonomeric units used to prepare the levelling agents of the invention preferably have at one end a structure selected from the structures.
The levelling agents of the invention are prepared in a way the skilled worker knows, by means for example of free-radical addition polymerization in organic solvents bma graphisme et decor option brokers in bulk using peroxides or azo compounds as free-radical initiators. Examples of suitable solvents include esters such as ethyl acetate, n-butyl acetate or 1-methoxypropyl acetate and also aromatic solvents, such as toluene or xylene, and ketones, such as methyl isobutyl ketone or methyl ethyl ketone.
The choice of solvent is guided by the later intended use of the copolymer of the invention. Suitable initiators include peroxides such as tert-butyl peroxobenzoate or dibenzoyl peroxide, for example.
It is, however, also possible to use azo compounds such as azoisobutyronitrile AIBNfor example. Preferably, peroxides are used. Also possible is the preparation of these compounds by ionic addition polymerization, for example by addition polymerization initiated with organometallic compounds, or by Group Transfer Polymerization GTP.
The molecular weights of the branched polymers of the invention are situated in the range from to , preferably from 10, to 75, with particular preference from 15, to 50, The branched polymers may also be subsequently modified by means of polymer-analogous reaction.
For example, a reactive double bond and acid function may be incorporated by reacting a branched polymer containing hydroxy-functional monomeric units in its base molecule with maleic anhydride. Further particular anhydrides for introducing the acid function are, for example, succinic anhydride and phthalic anhydride; in this context, hydroxy-functional monomeric units within a branched polymer may also be esterified with bma graphisme et decor option brokers different anhydrides.
For better solubility in water, the acid function may be converted to its salt form using alkanolamines, for example. The levelling agents of the invention are used in the coating formulations in relatively small amounts of from 0.
In solvent-borne coating materials it is preferred to use levelling agents which are dissolved in solvents similar to those in which the coating materials themselves are dissolved. In radiation-curing systems, the levelling agents are preferably dissolved in corresponding monomers. Moreover, these levelling agents may be incorporated into wax melts in accordance with the German patent application DE-A 22 and so converted into free-flowing solid forms, if the levelling agents of the invention are viscous, tacky resins.
In aqueous powder slurries, a modification of the powder coating, the levelling agents may be added in the bma graphisme et decor option brokers of an aqueous emulsion. In accordance with the prior art, these emulsions are prepared with the aid of emulsifiers. The invention additionally relates to coating formulations which contain the levelling agent of the invention in a concentration of from 0. The invention is illustrated by the following examples.
In the case of molecularly non-uniform substances, the bma graphisme et decor option brokers molecular weights abbreviated below to MW represent average values of the weight average. Unless stated otherwise, parts and percentages are always by weight. Under reflux, a mixture of After the end of the addition, reaction is carried out for two hours more.
The result is a polymer having a terminal carboxyl function. Then 12 g of glycidyl methacrylate and a suitable catalyst, e. The polymer thus prepared contains a terminal methacryloyl function capable of further polymerization. The molecular weight is The macromonomers described in the table below were prepared analogously using glycidyl methacrylate.
The methacryloyl-functional polydimethylsiloxane is prepared by transesterifying a monohydroxy-functional polydimethylsiloxane with methyl acrylate in accordance with known techniques. Macromonomer 18 polydimethylsiloxane MW about Macromonomer 19 polydimethylsiloxane MW about 20, Macromonomer 20 polydimethylsiloxane MW about 30, A glass flask provided with stirrer, thermometer, distillation attachment, dropping funnel and nitrogen inlet pipe is charged with 3.
Throughout the reaction, nitrogen is passed bma graphisme et decor option brokers the mixture. The average molecular weight is determined as being approximately 15, by gel permeation chromatography using polystyrene as a comparison standard. Although levelling agents having free hydroxyl groups are advantageous in respect of their ability to be incorporated into the binders by covalent bonding, it is known that under certain circumstances, where an additional coating is applied, they may lead to a deterioration in the intercoat adhesion.
For this reason it may be sensible to block some or all of these hydroxyl groups by known techniques, such as by etherification or acetylation, for example. After this time, free hydroxyl groups can no longer be detected in the IR spectrum. A polymer with a slight yellow coloration is obtained. An exothermic reaction ensues. After 90 minutes, isocyanate groups can no longer be detected in the IR spectrum. After this time, anhydride bands can no longer be detected in the IR spectrum.
A solution with a slight yellow coloration is obtained. The performance of the polymers of the invention was tested by an application in a powder coating material and in a conventional solvent-borne coating material. This was taken into account for the initial weight of Uralac P