Previously cross-linked silicone elastomer particles with an organopolymer shell as a constituent for formulating aqueous coating compositions

Previously cross-linked silicone elastomer particles with an organic-polymer shell are used as constituents for formulating aqueous coating compositions based on water-soluble or water-dilutable binders. The silicone elastomer particles contain: (a) 5 to 95% by weight, with respect to the total weight of the copolymer, of a nuclear polymer of general formula (R.sub.2 SiO.sub.2/2).sub.x (RSiO.sub.3/2).sub.y (SiO.sub.4/2).sub.z, in which x=5 to 99.5% by mole, y=0.5 to 95% by mole, z=0 to 30% by mole, and (b) 5 to 95% by weight, with respect to the total weight of the copolymer of a shell made of an organopolymer from mono- or poly-ethylenically unsaturated monomers; and R stands for the same or different monovalent alkyl or alkenyl radicals with 1 to 6 carbon atoms, aryl radicals or substituted hydrocarbon radicals.

TECHNICAL FIELD 
The invention relates to the use of precrosslinked silicone elastomer 
particles with an organic-polymer shell as a formulating constituent in 
aqueous coating compositions based on water-soluble or water-dilutable 
binders. 
BACKGROUND ART 
Aqueous coating materials comprise binders which are either soluble in or 
dilutable in water; the water-dilutable binders include resin components 
and resins which have been emulsified or rendered self-emulsifiable, and 
aqueous dispersions. Examples of water-soluble binders are modified alkyd 
resins, acrylate resins, linear and branched saturated polyester resins, 
epoxy resins, shellac and modified phenolic resins. Examples of 
water-dilutable binders are--optionally modified--dispersed or 
water-dispersible, unsaturated and saturated polyester resins, alkyd resin 
emulsions, polyurethane dispersions, one-component epoxy resin emulsions, 
emulsifiable two-component epoxy resin systems, dispersible alkyd, 
phenolic, melamine and urea resins, (meth)acrylate dispersions, 
(meth)acrylate copolymer dispersions, polystyrene and styrene copolymer 
dispersions, poly(vinyl ether) dispersions, and polyvinyl chloride and 
polyvinylidene chloride dispersions. 
In addition to water-soluble or water-dilutable binders, aqueous coating 
materials generally include pigments, fillers, water-soluble crosslinkers 
and crosslinking catalysts, and further additives such as, for example, 
levelling assistants, devolatilizing assistants and wetting agents. 
These compositions are applied in aqueous form, for example to metallic 
substrates, mineral substrates, plastics, wood, paper or glass. Following 
application, the aqueous film dries to a solid coating film. Films which 
dry at ambient temperature (room temperature) after drying in air, are 
optionally subjected to thermal conditioning/post-drying at temperatures 
up to 100.degree. C. For other types of aqueous coating material, even 
higher temperatures (120-220.degree. C.) may be necessary for film 
formation, if the latter requires the chemical reaction 
(post-crosslinking) of two or more binder components. 
The water-soluble and water-dilutable binders listed predominantly comprise 
thermoplastic or thermosetting polymers, which are generally hard but 
brittle. To improve the film properties, therefore, impact modification of 
the polymer systems is frequently necessary. Silicones are known as 
modifiers for thermoplastics and thermosets and are of particular interest 
since they not only increase the impact strength but also improve 
low-temperature flexibility, weathering stability, stability to 
fluctuating temperature stress and chemical resistance of thermoplastic or 
thermosetting organic-polymer systems. Generally disadvantageous, however, 
is the fundamental incompatibility of silicones with organic polymers. The 
incompatibility may induce flow defects in the course of use, while 
migration of the silicones gives rise to adhesion problems and problems 
associated with overcoatability. 
In DE-A 3922285 (=GB-A 2222167) (Dow Corning, laid open on Jan. 25, 1990) 
the known incompatibility of siloxanes with organic polymers is exploited 
for decorative purposes; it describes a coating composition composed of 
polydiorganosiloxane and of an aqueous dispersion of a film-forming 
polymeric material, for obtaining a hammered surface effect. Polysiloxanes 
of this kind are not suitable for the impact modification of aqueous 
coating materials, since the polysiloxane is present in emulsified form as 
a liquid in the water phase rather than as discrete particles. In the 
amount which needs to be used for impact modification, these compounds are 
exuded from the coating film. 
EP-A 586048 (Shin Etsu, published on Mar. 9, 1994) describes 
diol-functional silicone oils as additives to aqueous coating materials 
for lowering the surface tension and improving the substrate wettability; 
in this established utility, these siloxanes show better flow properties 
than polyether-modified silicone oils. Siloxanes of this kind, present in 
emulsified form, are unsuitable for impact modification. The document goes 
on to describe that in amounts employed of &gt;5% by weight there is a 
decrease in the mechanical strength of the polymer film modified with 
these compounds. 
WO-A 93/14169 (Crompton Garland Ltd., published on Jul. 22, 1993) describes 
a formulation of a crosslinkable aqueous phenolic resin emulsion and of a 
silicone resin emulsion. In the course of the crosslinking of the phenolic 
resin component there is chemical attachment of the silicone to the 
phenolic resin, as a result of which the silicone component becomes 
included in the phenolic resin matrix as a plasticizer. U.S. Pat No. 
4,803,233 (Dow Corning, granted on Feb. 7, 1989) describes aqueous 
mixtures which comprise organic polymer, silicone resin and a combination 
of three different nonionic emulsifiers. Depending on the polymer system 
and silicone component, the addition of silicone resin brings about--in 
some cases only after thermal treatment of the homogeneous 
blends--improved tensile strength, adhesion and corrosion resistance of 
the coating materials. 
An improvement in the impact strength coupled with retention of hardness is 
described neither in WO-A 93/14169 nor in U.S. Pat. No. 4,803,233. There 
is no controlled microphase separation therein, since the substances 
involved are not organic-polymer-compatible modifiers with a particulate 
structure. 
EP-A 541395 (Takemoto, published on May 5, 1993) describes aqueous coating 
compositions for thermoplastic polyester films on the basis of aqueous 
emulsions of polysiloxane-polyvinyl graft copolymers. These aqueous binder 
systems improve surface properties of the polyester films, such as 
smoothness, release properties, and water- and oil-repellency properties. 
In this case the graft copolymers are not employed as modifiers for 
organic-polymer binders in aqueous coating materials but are used as an 
aqueous coating composition with which it is possible to obtain particular 
surface properties in the context of application to thermoplastic polymer 
films. 
WO-A 90/08810 (ICI Australia Operations Proprietary Ltd., published on Aug. 
9, 1990) describes aqueous coating compositions on the basis of 
silicone-containing polymers, so-called "multi-polymer" particles. The 
"multi-polymer particles" are prepared by polymerizing the monomers in a 
mixture with silicone polymer. In this case the silicone constituent must 
be added to the monomer/monomers prior to polymer preparation and cannot 
be added as a formulation constituent to (just any) aqueous binder 
systems. The silicone component in the water-dilutable binder systems that 
are obtained in this case enhances, for example, the UV stability of the 
coating materials; an improvement in the impact strength is not described. 
Again, there is no controlled microphase separation in this case, since 
the silicone components employed are liquids or resins which do not 
comprise organic-polymer-compatible modifiers with a particulate 
structure. 
SUMMARY OF THE INVENTION 
The object on which the invention was based was to provide modifiers for 
aqueous coating compositions based on organic-polymer binders, i.e. 
aqueous coating materials, which are highly compatible with the 
organic-polymer binder and with which it is possible to improve the impact 
strength of the films obtainable therewith while at the same time 
retaining the existing, desired polymer properties, such as hardness, 
dimensional stability and mechanical strength. 
DETAILED DESCRIPTION OF THE INVENTION 
The invention provides for the use of precrosslinked silicone elastomer 
particles with an organic-polymer shell as a formulating constituent in 
aqueous coating compositions based on water-soluble or water-dilutable 
binders, where the silicone elastomer particles comprise 
a) from 5 to 95% by weight, based on the overall weight of the copolymer, 
of a core polymer of the general formula (R.sub.2 
SiO.sub.2/2).sub.x.(RSiO.sub.3/2).sub.y.(SiO.sub.4/2).sub.z where x=from 5 
to 99.5 mol %, y=from 0.5 to 95 mol %, z=from 0 to 30 mol %, and 
b) from 5 to 95% by weight, based on the overall weight of the copolymer, 
of a shell of an organic polymer of mono- or polyethylenically unsaturated 
monomers, 
and R denotes identical or different monovalent alkyl or alkenyl radicals 
having 1 to 6 C atoms, aryl radicals or substituted hydrocarbon radicals. 
The invention additionally provides aqueous coating compositions based on 
water-soluble or water-dilutable binders which as a formulating 
constituent comprise precrosslinked silicone elastomer particles with an 
organic-polymer shell, where the silicone elastomer particles comprise 
a) from 5 to 95% by weight, based on the overall weight of the copolymer, 
of a core polymer of the general formula (R.sub.2 
SiO.sub.2/2).sub.x.(RSiO.sub.3/2).sub.y.(SiO.sub.4/2).sub.z where x=from 5 
to 99.5 mol %, y=from 0.5 to 95 mol %, z=from 0 to 30 mol %, and 
b) from 5 to 95% by weight, based on the overall weight of the copolymer, 
of a shell of an organic polymer of mono- or polyethylenically unsaturated 
monomers, 
and R denotes identical or different monovalent alkyl or alkenyl radicals 
having 1 to 6 C atoms, aryl radicals or substituted hydrocarbon radicals. 
The precrosslinked silicone elastomer particles with an organic-polymer 
shell which are employed as a formulating constituent, and processes for 
their preparation, are described in EP-A 492376 (U.S. Pat. No. 5,223,586). 
By precrosslinked silicone elastomer particles is meant in this case that 
these particles are crosslinked by way of the proportion of (RSiO.sub.3/2) 
and (SiO.sub.4/2) units. 
The silicone elastomer particles with an organic-polymer shell preferably 
comprise 
a) from 20 to 80% by weight, based on the copolymer overall weight, of a 
core polymer (R.sub.2 
SiO.sub.2/2).sub.x.(RSiO.sub.3/2).sub.y.(SiO.sub.4/2).sub.z where x=from 
50 to 99 mol %, y=from 1 to 50 mol %; z=from 0 to 20 mol %; and 
b) from 20 to 80% by weight, based on the copolymer overall weight, of a 
shell of an organic polymer of mono- or polyethylenically unsaturated 
monomers, 
where R has the abovementioned meaning. 
The radicals R are preferably alkyl radicals, such as the methyl, ethyl, 
n-propyl, isopropyl, n-butyl, sec-butyl, amyl, hexyl radical; alkenyl 
radicals, such as the vinyl, allyl, butenyl and 1-hexenyl radical; aryl 
radicals, such as the phenyl radical; or substituted hydrocarbon radicals, 
such as halogenated hydrocarbon radicals, mercaptoalkyl radicals, 
cyanoalkyl radicals, aminoalkyl radicals, acyloxyalkyl radicals, 
hydroxyalkyl radicals. 
Particularly preferred radicals are methyl, ethyl, propyl, phenyl, vinyl, 
allyl, 1-hexenyl, 3-methacryloxypropyl and 3-mercaptopropyl, where less 
than 30 mol % of the radicals in the siloxane polymer are vinyl groups, 
3-methacryloxypropyl or 3-mercaptopropyl groups. 
As monomers for the organic polymer component b) it is preferred to employ 
acrylic esters or methacrylic esters and also mono- and diesters of 
fumaric and maleic acid with aliphatic alcohols and diols having 1 to 10 C 
atoms, acrylamides and methacrylamides, acrylonitrile, styrene, 
p-meth-ylstyrene, o-methylstyrene, divinylbenzene, vinyl acetate, vinyl 
propionate, maleimide, vinyl chloride, mono- and divinyl ethers, ethylene, 
butadiene, isoprene and chloroprene. Particular preference is given to 
styrene and to acrylic esters and methacrylic esters of aliphatic alcohols 
having 1 to 4 C atoms, examples being methyl (meth)acrylate, butyl 
(meth)acrylate and glycidyl (meth)acrylate. Both homopolymers and 
copolymers of these monomers are suitable as the organic polymer 
component. 
The finely divided graft copolymers preferably have an average particle 
diameter of from 10 to 300 nm, with particular preference from 30 to 150 
nm. The particle sizes may vary within the abovementioned range; 
preferably, there is a monomodal particle size distribution with a 
polydispersity index of not more than .sigma..sub.2 =0.2. 
The polysiloxane graft base is prepared according to the emulsion 
polymerization process by metering in the corresponding mixture of 
monomeric silanes of the type R.sub.a Si(OR').sub.4-a, where a=0, 1 or 2, 
or, if desired, low molecular mass siloxanes of the general formula 
(R.sub.2 SiO).sub.n where n=from 3 to 8, to an agitated emulsifier/water 
mixture. The radical R has the meanings already mentioned. R' stands for 
alkyl radicals having from 1 to 6 C atoms, aryl radicals or substituted 
hydrocarbon radicals; methyl, ethyl and propyl radical being preferred. 
The silane or the silane mixture or silane/siloxane mixture is added in 
metered form. The emulsion polymerization is carried out at a temperature 
of from 30 to 90.degree. C., preferably from 60 to 85.degree. C., and 
preferably under atmospheric pressure. The pH of the polymerization 
mixture is from 1 to 4, preferably from 2 to 3. Suitable emulsifiers and 
the amounts in which they are employed are described in EP-A 492376. 
In order to obtain a monomodal particle size distribution, it is preferred 
to omit a homogenization step during the preparation of the polysiloxane 
graft base. In a further preferred embodiment, following the conclusion of 
the polymerization of the graft base, alcohol formed in the said 
polymerization, and any other volatile constituents, are removed by 
distillation. 
Examples of suitable silanes are, for silanes of the general formula 
R.sub.2 Si(OR').sub.2, dimethyl-diethoxysilane or dimethyldimethoxysilane; 
for oligomers of the formula (R.sub.2 SiO), where n=from 3 to 8, 
octamethylcyclotetrasiloxane or hexamethylcyclotrisiloxane; for silanes of 
the general formula RSi(OR').sub.3, methyltrimethoxysilane, 
phenyltriethoxysilane, 3-chloropropyltrimethoxysilane, 
3-mercaptopropyltrimethoxysilane, or methacryloxypropyltrimethoxysilane; 
and, for silanes of the general formula Si(OR').sub.4, tetramethoxysilane 
or tetraethoxysilane. 
In the last step of the preparation process the ethylenically unsaturated 
monomers already mentioned are grafted onto the polysiloxane graft base. 
Grafting takes place according to the emulsion polymerization process in 
the presence of water-soluble or monomer-soluble free-radical initiators, 
by the procedure described in EP-A 492376. With this procedure, the 
precrosslinked silicone elastomers with an organic-polymer shell are 
obtained in the form of their aqueous dispersions. It is preferred to 
establish a solids content of the aqueous dispersions of 10-60% by weight, 
with particular preference 15-50% by weight. 
The degree of crosslinking of the silicone core determines its elastic 
properties and can be established specifically in a manner familiar to the 
skilled worker by an appropriate choice of the starting components, 
corresponding alkoxysilanes and/or siloxanes in order to obtain units 
(RSiO.sub.3/2) or (SiO.sub.4/2). The incorporation of silane units 
comprising olefinically unsaturated double bonds, for example vinyl 
radicals or 3-methacryloxypropyl radicals, permits a chemical bonding of 
the organic-polymer shell to the silicone core through covalent bonds in 
the subsequent graft polymerization. By choosing suitable monomers for the 
synthesis of the organic polymer shell b) it is possible to custom-tailor 
the organic-polymer shells. 
For instance, by grafting a copolymer shell comprising, for example, methyl 
methacrylate (high Tg) and n-butyl acrylate (low Tg) onto a crosslinked 
silicone core it is possible to establish specifically the softening 
temperature of the polymer shell and hence to match it precisely to the 
requirements associated with the processing of the aqueous coating 
components and the coating properties. By grafting a copolymer shell 
comprising, for example, methyl methacrylate and glycidyl methacrylate 
onto a crosslinked silicone core on the one hand it is possible by way of 
the epoxide functions introduced with glycidyl methacrylate to obtain a 
matrix attachment between modifier particles and binder resin of the 
aqueous coating composition, and on the other hand these modifier 
particles are able to act as crosslinkers in binders based on polyester 
resin. 
The most preference, accordingly, is for crosslinked silicone elastomer 
particles with a core comprising (R.sub.2 
SiO.sub.2/2).sub.x.(RSiO.sub.3/2).sub.y where x=80-99 mol % and y=1-20 mol 
%, where R can be identical or different and has the meaning R=methyl 
and/or 3-methacryloxypropyl, and with a shell of poly(methyl methacrylate) 
or copolymer shells comprising methy [sic] methacrylate and butyl acrylate 
and/or glycidyl methacrylate. 
The proportion of the core polymer, based on the overall copolymer weight, 
is with particular preference 50-80% by weight; accordingly, the 
proportion of the organic-polymer shell is with particular preference 
20-50% by weight. This corresponds to an organic-polymer degree of 
grafting of 25-100%. 
The additive nature of the precrosslinked silicone elastomer particles with 
an organic-polymer shell and the ease of incorporation as an aqueous 
dispersion permit use with all common binder systems for aqueous coating 
materials. Examples of binder systems for aqueous coating materials are, 
for water-soluble binders, modified alkyd resins, acrylate resins, linear 
and branched saturated polyester resins, epoxy resins, shellac and 
modified phenolic resins. Examples of water-dilutable binders 
are--optionally modified--dispersed or water-dispersible, unsaturated and 
saturated polyester resins, alkyd resin emulsions, polyurethane 
dispersions, one-component epoxy resin emulsions, emulsifiable 
two-component epoxy resin systems, dispersible alkyd, phenolic, melamine 
and urea resins, (meth)acrylate dispersions, (meth)acrylate copolymer 
dispersions, polystyrene and styrene copolymer dispersions, poly(vinyl 
ether) dispersions, and polyvinyl chloride and polyvinylidene chloride 
dispersions. 
For modification, the precrosslinked silicone elastomers with an 
organic-polymer shell are added preferably in the form of their aqueous 
dispersions, if desired as dispersion powders, generally in an amount of 
from 0.5 to 50% by weight, preferably from 1.0 to 3.0% by weight, in each 
case the silicone elastomer fraction based on the overall weight of 
silicone elastomer component and binder component, to the aqueous coating 
formulation. Formulations suitable for aqueous coating materials are known 
to the skilled worker from, for example, H. Kittel (ed.), Lehrbuch der 
Lacke und Beschichtungen, Volume IV, Verlag W. A. Colomb, Berlin, 
Oberschwandorf, 1976. 
The addition takes place in accordance with customary procedure for 
formulating aqueous coating materials, using stirrers or dispersing tools. 
The aqueous dispersion of the precrosslinked silicone elastomers with an 
organic-polymer shell can in this case be mixed in any desired order with 
the components of the aqueous coating formulation, such as binder(s), 
water, crosslinker, catalyst, pigment, thickener, filler. Mixing 
(compounding) preferably takes place in a temperature range from 
+1.degree. C. to +90.degree. C., in particular from +5.degree. C. to 
+60.degree. C. 
The aqueous coating materials modified in accordance with the invention can 
in principle be employed wherever conventional solvent-based coating 
materials or non-modified aqueous coating materials are used: They find 
application in particular for coating the metal of large steel 
constructions, (e.g. bridges, tanks, cranes and conveying equipment, 
pipelines, mining and oil extraction equipment, parts of steel works and 
chemical plants), for coating metal in the automotive sector (clearcoat, 
topcoat, interior finish, surfacer, stone-chip protection and underbody 
protection, refinishes for e.g. cars, lorries, buses, building-site and 
agricultural utility vehicles) and of rail-bound vehicles, freight 
containers, aircraft, ships (in each case exterior finishes), and also for 
the coating of metallic substrates prior to their further processing (coil 
coating), of domestic appliances (e.g. chest freezers, refrigerators, 
dishwashers, washing machines, electric ovens, etc.) and of metallic 
packaging (e.g. drums, containers, etc.). They are also used for the 
coating of furniture (wooden furniture, metal furniture, lamp housings 
etc.), of architectural components both internal and external (made from 
wood, steel, non-ferrous metal and nonferrous-metal alloys, plastics, 
concrete, mortar and plaster, e.g. window frames, exterior panelling, 
doors, gates, guttering, floors, stairs, facade components, walls, 
ceilings, heaters and radiators, tanks, lines), of cycles, signs, wheel 
rims. 
The test results in the examples demonstrate that the (impact) toughness of 
the aqueous coating materials is improved through the addition of 
precrosslinked silicone elastomer particles with an organic-polymer shell, 
with no effect on the adhesion of the coating systems and their surface 
properties and only a slight effect on the hardness of the coating 
systems. With the comparative examples it is shown that the addition of 
silicone elastomer particles without an organic-polymer shell, although 
also improving the (impact) toughness, nevertheless has a markedly adverse 
effect on the hardness of the coating materials and on their surface 
properties; consequently, what is required is not only the controlled 
microphase separation but also good compatibility of the modifier 
particles with the polymer matrix in the dried coating film. 
The reason for the good results in the examples is that owing to the 
crosslinked silicone phase the impact modifier of the invention is 
incorporated into the thermoplastic or thermosetting systems in the form 
of separate, discrete microphases with defined particle size and 
morphology. Only with complete phase separation is there an absence of the 
unwanted softening of the polymer matrix, which would result in a loss of 
or adverse effect on the properties of the polymer matrix such as 
hardness, dimensional stability and mechanical strength. In addition, the 
organic-polymer shell produces good compatibility of the particulate 
modifier with the polymer matrix of the coating binder. It is true that 
the organic-polymer shell is not absolutely necessary for the 
miscibility/colloidal compatibility of the pre-crosslinked silicone 
elastomer particles in dispersion form with water-soluble or 
water-dilutable binders; however, it is so for the polymer compatibility 
of the particles with the matrix after drying. The particle structure and 
the polymer compatibility of the particles provide a precise definition of 
the domain sizes of the modifier phase by way of the particle diameter. 
Contamination problems, adhesion problems, sedimentation problems and flow 
defects do not occur, since the precrosslinked silicone elastomer 
particles are grafted completely with an organic-polymer shell. The 
resulting coatings are overcoatable.

The examples which follow serve to illustrate the invention: 
EXAMPLE 1-2 
Comparative Examples 1-3 
In Examples 1 and 2 and in Comparative Examples 1 to 3, polyester coating 
formulations were prepared having the compositions specified in Table 1. 
In the examples in accordance with the invention, dispersion A was 
employed. In Comparative Examples 2 and 3, dispersion B was employed. The 
coating formulation of Comparative Example 1 corresponds to that of 
conventional, unmodified aqueous coating materials. 
Dispersion A 
Aqueous dispersion of silicone particles with a core comprising [R.sub.2 
SiO.sub.2/2 ].sub.x [R' SiO.sub.3/2 ].sub.y (x=95 mol-%, y=5 mol-%; 
R=methyl, R'=methyl and 3-methacryloxypropyl) and a polymethyl 
methacrylate shell (PMMA degree of grafting 50% by weight); the primary 
particle size is about 100 nm, the solids content of silicone particles 
with -an organic-polymer shell is 26.3%. 
Dispersion B 
Aqueous dispersion of silicone particles, composed of [R.sub.2 SiO.sub.2/2 
].sub.x [RSiO.sub.3/2 ].sub.y (x=95 mol-%, y=5 mol-%; R=methyl); the 
primary particle size is about 100 nm, the solids content of silicone 
particles is 19%. 
To prepare the aqueous coating formulations (Examples 1-2, Comparative 
Examples 1-3) listed in Table 1, the components specified therein were 
mixed together at ambient temperature for 20 to 30 minutes by means of a 
dissolver. 
For testing, the aqueous coating formulations were applied to metal panels 
by means of a spiral film-drawing doctor blade. Drying took place at 
ambient temperature (22.degree. C.), and the tests were carried out 3 days 
after panel application. The test results are compiled in Table 1. 
The following test methods were employed: 
Surface Nature 
The surface nature was evaluated qualitatively by visual assessment of the 
film surface. 
Overcoatability 
To assess the overcoatability, the metal panels coated with the coating 
formulations of Example 1-2 and Comparative Example 1-3 were overcoated 
again with in each case the identical coating formulation. The 
overcoatability was evaluated qualitatively by visual observation. 
Intercoat Adhesion After Overcoating 
To determine the intercoat adhesion an examination was made, after a drying 
a period of 3 days, of whether the upper coating film can be partially 
removed by peeling with a penknife. The intercoat adhesion was evaluated 
as "good" when no removal whatsoever could be found. 
Reverse Impact 
The reverse impact was determined by ball impact testing with the ERICHSEN 
ball impact tester type 304. 
Konig Pendulum Hardness 
The Konig pendulum hardness was tested in accordance with DIN 53137. 
Erichsen Indentation 
The Erichsen indentation was tested in accordance with DIN ISO 1520. 
Cross-hatch 
The cross-hatch was determined by the method of DIN 53151. 
The results show that the (impact) toughness (reverse impact) is markedly 
improved by adding the silicone elastomer particles according to the 
invention with a PMMA shell (Examples 1 and 2), with only a slight 
reduction in film hardness and with no adverse effect on adhesion and 
surface properties of the films. Although when using silicone elastomer 
particles without an organic-polymer shell (Comparative Examples 2 and 3) 
the (impact) toughness is improved to a comparable extent, film hardness, 
surface properties and adhesion after overcoating are effected in a 
markedly adverse manner. 
TABLE 1 
__________________________________________________________________________ 
Comparative 
Comparative 
Comparative 
Example 1 
Example 2 
Example 1 
Example 2 
Example 3 
__________________________________________________________________________ 
Components [parts by wt.] 
1. Halwedrol O .times. 47-2/40 W.sup.a) 
50.0 50.0 50.0 50.0 50.0 
(40% in H.sub.2 O) 
2. Kronos TiO.sub.2 -2130.sup.b) 
25.0 25.0 25.0 25.0 25.0 
3. Dispersion A 12.5 23.0 -- -- -- 
4. Dispersion B -- -- -- 12.5 23.0 
5. Reolate 255.sup.c) 
0.5 0.5 0.5 0.5 0.5 
Proportion of silicone elastomer 
16 30 -- -- -- 
particles with PMMA shell based on 
binder (solids/solids) in % 
Proportion of silicone elastomer 
-- -- -- 12 22 
particles based on binder 
(solids/solids) in % 
Silicone component based on binder 
11 20 -- 12 22 
(solid/solid) 
Dry film thickness in .mu.m 
26 26 28 32 31 
Mechanical values 
Reverse impact (in .times. lbs) 
40 60 12 46 60 
Konig pendulum hardness 
56 54 67 46 42 
Erichsen indentation (mm, steel panel) 
&gt;6 &gt;6 &gt;6 &gt;6 &gt;6 
Cross-hatch Gt 0 Gt 0 Gt 0 Gt 0 Gt 0 
Surface smooth 
smooth 
smooth 
rough rough 
Overcoatability yes yes yes yes yes 
Intercoat adhesion after overcoating 
good good good moderate 
moderate 
__________________________________________________________________________ 
.sup.a) Fattyacid-modified polyester resin from HuttenesAlbertus 
Lackrohstoffe 
.sup.b) TiO.sub.2 pigment from KronosTitan 
.sup.c) Polyacrylatebased thickener from KronosTitan 
EXAMPLES 3 and 4 
Comparative Example 4 
The procedure was similar to that for Examples 1-2 and Comparative Examples 
1-3 with the difference that aqueous coating materials based on a 
two-component epoxy resin coating material were tested. In the Examples 3 
and 4 in accordance with the invention, dispersion A was again employed 
for modification. The coating formulation of Comparative Example 4 was not 
modified. 
To prepare the aqueous coating formulations listed in Table 2 (Examples 
3-4, Comparative Example 4) the components specified therein were mixed 
together at ambient temperature for 20 to 30 minutes by means of a 
dissolver. The aqueous coating formulations were applied to aluminium 
panels and to metal panels by means of a spiral film-drawing doctor blade. 
Drying took place at ambient temperature (22.degree. C.). The tests were 
carried out 3 days after panel application, in a manner similar to the 
abovementioned test specifications. The test results are compiled in Table 
2. 
The results show, that the (impact) toughness (reverse impact) is markedly 
improved by adding the silicone elastomer particles according to the 
invention with a PMMA shell (Examples 3 and 4), with only a slight 
reduction in film hardness. 
TABLE 2 
______________________________________ 
Compar- 
ative 
Example Example Example 
3 4 4 
______________________________________ 
Components [parts by wt.] 
1. Epires ER 8 (100%).sup.a) 
43.5 43.5 43.5 
2. Borchigol VL 73 S.sup.b) 
0.2 0.2 0.2 
3. Kronos TiO.sub.2 - 2160.sup.c) 
45.0 45.0 45.0 
4. Dispersion A 15.25 30.50 -- 
5. Blanc Fix Micro.sup.d) 
10.0 10.0 10.0 
6. Demineralized water 
about 20 about 20 about 20 
7. Epilink DP 700 (55% in 
66.7 66.7 66.7 
H2O [sic]).sup.e) 
Proportion of silicone 
5.0 10.0 -- 
elastomer particles with 
PMMA shell based on 
binder (solids/solids) 
in % 
Dry film thickness in .mu.m 
24 26 33 
(metal panel) 
Dry film thickness in .mu.m 
23 24 33 
(aluminium panel) 
Mechanical values 
Reverse impact (in .times. lbs) 
66 &gt;80 4 
(metal panel) 
Reverse impact (in .times. lbs) 
40 46 4 
(aluminum panel) 
Konig pendulum hardness 
89 89 118 
(metal panel) 
Konig pendulum hardness 
88 83 108 
(aluminium panel) 
______________________________________ 
.sup.a) Twocomponent epoxy resin coating material based on bisphenol A/F 
from Air Products 
.sup.b) Leveling agent based on fatty acid esters, from Borchers 
.sup.c) TiO.sub.2 pigment from KronosTitan 
.sup.d) Barium sulphatebased filler from Sachtleben 
.sup.e) Polyamine adduct hardener from Air Products