Note: Descriptions are shown in the official language in which they were submitted.
2~31~71
Aqueous coating compoun~ for electro dip
lacquering and its use for the preparation
of multilayered lacquer coats
This invention relates to an aqueous coating compound
for electro dip lacquering containing a binder of one
or more water-soluble or water-dispersible film forming
resins and optionally one or more conventional cross-
linking agents for film forming resins as well as dispersedpolymer particles and optionally pigments, solvents and/or
conventional additives for lacquers.
Electro dip lacquering is a known process for coat-
- ing the surface of electrically conductive objects consist-
ing, for example, of metal or plastics which are conductive
or have been rendered conductive. In this process, the
article which is to be coated is dipped in an aqueous
coating bath and, in the case of cathodic deposition,
the article is connected as cathode to a source of direct
current and the coating compound is deposited on the
surface of the workpiecé by the current. The material
adheringi to the workpiece is then physically treated
by air drying~or heating to enable it to flow and may also
be chemically cross-linked for producing a homogeneous,
smooth surface which is resistant to stone chipping.
The coating compounds used for electro dip lacquering
consist substantially of one or more electrically deposit-
able resins which can be neutralised and thereafter dispers-
ed in water and optionally other, not solely water-dispers-
ible binders (plasticizers) or cross-linking agents,
special trituration resins, pigments and fillers and
any additives and auxiliary substances required. The
properties of the films such as corrosion protection,
levelling, resistance to stone chipping and adherence
can be influenced by varying the composition of the resin
components.
20~1~71
The coating of composite steel sheets with a suspension
of a water-dispersible sol of a metal compound with an
organic synthetic resin powder is described in DE-B-
26 50 611. The coating deposited from this suspension is
cured hy heatinq, durinq which the synthetic resin powder
melts at least..temporaril~v. A water-soluble or water-
dispersible polymer is added to the suspension to improve
adherence.
Electro dip lacquer coating materials consisting
of cationic synthetic resins which are to be protonated
with acid and rendered soluble and of ionic synthetic
resin powders dispersed therein are described in EP-A-
0 052 831. These synthetic resin powders may contain
pigments and fillers. These coating compounds also melt
when stoved and undergo cross-linking to form a smooth
coating. Ionic group-containing epoxide resins, polyester
resins, acrylate resins, polyurethane resins and polya~ide
resins are described as synthetic resin powders which can
be dispersed in the coating materials.
The coating compounds described in the literature ment-
ioned above have the disadvantage that in the process
of cross-linking, the film must be heated to a temperature
above the melting temperature of the synthetic resin
powder in order that a smooth coating may be obtained.
In EP-A-0 259 181 there are described coating compounds
for electro dip lacquering based on electrically deposit-
able water-dispersible resins in which the polymer parti-
cles have a softening point at least 10 degrees Centigrade
higher than the bath temperature, a solubility parameter
differing by not more than 1.0 from the solubility parame-
ter of the water-dispersible resin, and a refractive index
differ.ng by from 0.02 to 0.3 from that of the water-
dispersible resin or a cross-linking density of from
0.01 to 5.05 mmol/g. The surfaces of these polymer micro-
particles contain ionic groups having the same polarityas the water-dispersible resin. The addition of the polymer
microparticles is said to improve the wrap-around and
: ;
2~3~ 67~
. 3
dispersion stability and impart to the coating a matt
finish as well as controlling the fluidity in the process
of electro deposition. Various disadvantages, however,
are found in the known electro dip lacquered coatings,
such as poor covering of the edges, poor adherence to
the substrate or to subsequent coats and insufficient
impact strength.
It is therefore an object of the present invention
to provide aqueous coating compounds for electro dip
lacquering which provide good adherence to the substrate
or to subsequent coats, give rise to coatings with a
smooth surface and high impact strength (for example,
good protection against stone chipping), and manifest
improved rheological properties during the stoving process
and thus ensure good covering of the edges.
It has been found that this problem may be solved
by means of an aqueous coating compound depositable at
the cathode or anode in accordance with the generic concept
defined above, characterised in that it contains,as dis~ersed
polymer particles, from 5 to 75% by weight of polymer
powders, based on the solids content of film-forming
resin and any cross-linking agent present, which polymer
powders are preferably free from ionic or ionisable groups,
have an average particle diameter of 0.1 to 100 ~m and~a
glass transition temperature of >70C (determined according
to DSC = Differential Scanning Calorimetry), and the
poly~er powders consist of
a) one or more cross linked urea-aldehyde resins, triazine-
aldehyde resins and phenol-aldehyde resins or
b) one or more uncross-linked homo- or copolymers of
acrylonitrile and/or methacrylonitrile having a weight
average molecular weight (Mw) of over 100,000 and
containing at least 70% by weight of copolymerised
acrylonitrile or
c) mixtures of a) and b)
which up to a temperature of 80C cannot be made to dissolve
or swell by the binder t water-dispersible film-forming
,
2~3~ 671
resin,cross-linking agent, trituration resin or solvent
present in the coating compound.
The polymer powders are added to the coating compounds
as products which have been milled with the binder, the
water-dispersible film-forming resin or cross-linkinq
agent, in particular with a part thereof, and/or with
a trituration resin.
It has been found in the context of the present inven-
tion that the coatings obtained by addition of the polymer
powders to the aqueous coating compounds have a smooth
surface and are free from surface defects such as pitting.
For avoiding pitting, it is conventional to add additives
or pigments which interfere with the levelling oE the film
in the stoving process and result in a markedly rough
surface. Another disadvantage is that the adherence
of subsequent coats is frequently impaired. These disad-
vantages are overcome by the present invention. In addition,
it has been shown in the context of the present invention
that the addition according to the invention of polymer
powders gives rise to excellent rheological properties,
this improvement being obtained in particular by the
addition of urea-aldehyde resin powders, triazine-aldehyde
resin powders and phenol-aldehyde resin powders. A uniformly
matt surface is thus obtained and at the same time good
covering of the edges. The properties may therefore be
graded by adjusting the quantity of aldehyde-resin powder
used. Further, exceptionally good adherence to the sub-
strate or to subsequent coats is obtained in particular
by the addition of polyacrylonitrile powders (homo- or
copolymers). The impact strength is also improved, in
particular also at low temperatures. The coating compounds
aacording to the invenbion are therefore particularly
suitable for the formation of layers protecting against
stone chipping, for example in the construction of motor
vehicles. These properties are still obtained when subse-
quent layers are applied. Optimum results in these proper-
ties can be obtained by adjusting the quantity of polyacrylo-
2~3~71
nitrile powder used.
The polymer micro particles used should not be dissolvedor caused to swell by the binder, the trituration resin
or any solvents in the binder at temperatures of up to
&0C. In other words, the micro particles should remain
unchanged under the conditions of preparation and use.
The glass transition temperature is >70C (determined
according to DSC) and is chosen so that no softening
of the cross-linked or uncross-linked polymer powders
will occur under the conditions of preparation or applica-
tion of the coating compoundssince otherwise problems
may arise when the polymer powders are milled (triturated)
to form a paste, with the result that an unstable, inhomo-
geneous product is liable to be obtained. Observing
this condition will also prevent swelling of the polymer
powders.
Since treatment of the primer coat, such as rubbing down
~annot always be avoided in the preparation of coatings,
the stoved films must have suitable properties to allow
for this; for example, they must be able to withstand
treatment with sandpaper for a sufficient length of
time. If the polymer powders soften at too low a tempera-
ture, the treatment agents rapidly become unusable.
A positive effect of the high glass transition temper-
ature is also observed in the stoved film: Polymer powders
having a glass transition temperature >70C give rise
to high impact strength.
The particle diameters of the polymer powders used
should be sufficiently small within the given range of
30 from 0.1 to 100 ~m, depending on the required thickness
of the layer, to ensure that a homogeneous and smooth
surface will be obtained on the deposited and stoved film.
Although a rough, uneven surface in many cases ensures
good adherence of the subsequent layers applied, it is
unsuitable on account of the unsatisfactory optical effectobtained, e.g. in the case of primer coats for motor
vehicles.
2031~71
The aldehyde-resin powders used in the coating compounds
according to the invention are highly cross-linked and
have no melting point. The polyacrylonitrile powders
used have a molecular weight (Mw) above 100,000. They
are not chemically cross-linked but they have no melting
point since they decompose at temperatures above 300C
before they can melt. The polymer powders used are chemic-
ally substantially inert, i.e. they do not react with
the basic film-forming resins used.
The polymer powders used may be prepared by the conven-
tional methods known to the man of the art and described
in the literature. They may already be obtained as powders
at the stage of preparation and these may then be ground
down to the required particle size but with suitable
control of the reaction conditions they may from the
start be obtained in the required particle size. The
powders obtained may be used after their separation from
the reaction medium or they may be obtained in the form
of aqueous suspensions. If suspensions are used, these
need not be stable in storage and may undergo sedimenta-
tion. For their use in the coating compounds according
to the invention, they are triturated (ground up) to
form an aqueous paste which remains stable for some time.
The usual triturating binders may be used for this purpose
and part of the binder or part of the film-forming resin
or cross-linking agent may be used.
The particle size distribution of the polymer powders
used may vary over a wide range. The composition of the
powders may be used purposefully to influence special
properties such as the rheological properties, provided
only that the maximum particle diameter does not result
in an inferior surface of the deposited, stoved lacquer
film.
The polyacrylonitrile powders used may be prepared
by conventional processes. Examples of suitable processes
are the emulsion polymerisation or suspension polymerisa-
tion of acrylonitrile or methacrylonitrile, which are
2031671
well known to the man of the art and are described in
"Chemische Technologie" by Winacker-K~chler, Volume 6,
Organische Technolgie 2, Karl Hans-Verlag Munich-Vienna
1982. The polyacrylonitrile polymer powders used according
to the invention contain at least 70% of acrylonitrile
and/or methacrylonitrile. One or more copolymerisable
monomers may be added to the acrylonitrile and/or meth-
acrylonitrile for preparing the copolymers. Examples
of such monomers include acrylic esters and methacrylic
esters of C2 to C22 alcohols, e.g. methyl methacrylate,
butyl methacrylate, octyl methacrylate, ethyl acrylate,
isobutyl acrylate, (meth)acrylic acid esters of perfluor-
inated C1 to C22 alcohols, aromatic vinyl compounds having
up to 20 carbon atoms, e.g. styrene or vinyl toluene,
the esters of maleic acid or fumaric acid with C1 to
C22 alcohols, vinyl chloride, ethylene and butadiene.
Further examples of suitable comonomers include unsat-
urated carboxylic, sulphonic and phosphonic acids and
esters thereof, such as crotonic acid, itaconic acid,
vinyl sulphonic acid, acrylamidopropyl methane sulphonic
acid, vinyl phosphonic acid and esters of these acids.
Unsaturated primary, secondary and/or tertiary amines
may also be used as comonomers, e.g. dimethylamino neopentyl
methacrylate, dimethylamino neopentyl acrylate, 2-N-morpho-
lino ethyl methacrylate, 2-N--morpholino ethyl acrylate
and amides of acrylic or methacrylic acid, e.g. acrylamide,
dimethylmethacrylamide or methyl butyl acrylamide.
Other functional monomers capable of copolymerisation
may be used in addition. They may contain hydroxyl, silane
or epoxide groups, e.g. vinyl trimethoxysilane, vinyl
tributoxysilane, methacryloxypropyl trimethoxysilane,
vinyl tristmethoxyethoxy)silane, vinyl triacetoxysilane,
hydroxyethyl methacrylate, hydroxybutylacrylate, glycidyl
acrylate, glycidyl met~acrylate and polyhydroxy ethylacryl-,
ate.
The polyacrylonitrile powders used according to the
invention should contain at least 70% by weight (based on
20316~1
the quantity of monomers used) of acrylonitrile and/or
methacrylonitrile and preferably contain above 90~.
Properties of the polyacrylonitrile powders, e.g. iheir
glass transition temperature, may be influenced by suit-
able choice of the monomers. The melt properties mayalso be influenced by these means. The particle size
distribution can be influenced by suitable choice of
the process of preparation and of the process parameters
employed therein.
The preparation in aqueous suspension is generally
carried out in the presence of suitable non-ionic, anionic
or cationic emulsifiers. Conventional protective colloids
may also be used, e.g. cellulose ethers, polyvinyl alcohols
or polyvinyl pyrrolidones. Radical polymerisation is
started with the aid of compounds conventionally used
for initiating the formation of radical chains, e.g.
azo compounds, peroxides, peresters or percarbonates.
Examples of conventional initiator systems include azo-
isobutyronitrile, benzoyl peroxide, dicyclohexyl peroxy-
dicarbonate, hydrogen peroxide, sodium persulphate andtert.-butylhydroperoxide.
The choice of monomers, comonomers and conventional
auxiliary agents is determined by the requirements to
be met by the polyacrylonitrile powder, such as the particle
diameter, the glass transition temperature, the molecular
weight and the solution properties. After the polyacrylo-
nitrile polymers have been prepared, they may be worked
up in aqueous suspension (e.g. dispersed with a resin
paste) or they may be dried to form powders and then
used for the purpose according to the invention, optionally
after a further milling process.
The cross-linked aldehyde polymer powders may be
prepared by the reaction of urea, triazine and/or phenol
with an aldehyde, preferably with formaldehyde or compounds
which split off formaldehyde. The conditions concerning the
quanti.ties of reactants used, the reaction temperature
and the reaction medium in which the reaction is carried
2031671
out may be chosen to produce cross-linked, infusible
masses. The conditions required are well known to the
man of the art.
Cross-linked triazine resins, among which the polymer
masses of melamine aldehyde, benzoguanamine aldehyde
and acetoguanamine aldehyde are preferred, cross-linked
urea resins and cross-linked phenol resins are described,
for example, in Methoden der Organischen Chemie (Houben-
Weyl), Volume 2, Makromolekulare Stoffe, in the Chapters
entitled "Polyadditions- bzw. Polycondensationsprodukte
von Carbonyl- und Thiocarbonylverbindungen" on pages
193 to 365.
Cross-linked phenol aldehyde resins are also described,
for example, in "Chemie der Phenolharze" by K.Hultzsch,
Springer-Verlag, 1950, under the heading "Resit".
Infusible polymer masses obtained may be reduced
to the required particle size, preferably by grinding
processes using the known grinding devices for the size
reduction of particles.
The synthetic resin powders used are substantially
free from ionic groups on their surface, i.e. ionic groups
are not required for further processing to produce electro-
dip lacquer coating compounds, although the powders
may contain ionic groups or acid or basic groups for
the purpose of obtaining certain properties such as
improved stability to dispersion. Synthetic resin powders
containing acid groups may be used in the same manner
as non-ionic powders for anodically and cathodically
depositable electro dip lacquer coating compounds and
synthetic resin powders containing basic groups may also
be used for anodically and cathodically depositable electro
dip lacquer coating compounds.
The binders used for the systems capable of being
deposited at the anode or the cathode are conventional
electro dip lacquer (ETL) binders or binder mixtures.
They can be deposited at the cathode if they carry
positively charged ionic substituents or substituents
2~3~6~1
1 o
capable of being converted into such ionic groups. They can
be deposited at the anode if they carry negatively charged
substituents or substituents capable of being converted
into negatively charged groups.
The binders for anodically depositable dip lacquers
(ATL) contain basic resins which may have acid numbers
of from 35 to 300 and number average molecular weights
of from 300 to 10,000 g/mol. The acid groups may be -PO3H,
-SO3H and/or, preferably, -COOH. Basic compounds are
used as neutralizing agents, e.g. primary, secondary
or tertiary amines containing aliphatic and/or aromatic
groups, or ammonia.
Examples of basic resins include the reaction products
of maleic acid anhydride with
fatty oils or with synthetic oils such as polybutadiene
oil, polyester resins, epoxy resin esters, polyurethane
resins or poly(meth)acrylate resins. The basic resins
may be self-cross-linking or cross-linked by other compounds.
The cross-linking agents used may be triazine resins,
phenol resins and/or blocked isocyanates. sinders of
this type are widely described in the literature, e.g.
in DE-A-28 24 418.
The binaers and cross-linking agents conventionally
used for electro dip lacquering may be used for the prepara-
tion of the cathodically depositable dip lacquers (KTL)according to the invention. Examples include self-cross-
linking, film-forming basic resins as well as basic film-
forming resins which require an additional, conventional
cross-linking agent, and mixtures thereof. The resins
contain ionic groups or groups which are ionic after
neutralization.
Examples of the basic resins used in the coating
baths are described in EP-A-0 082 291, EP-A-0 234 395
and EP-A 0 209 854. These resins are conventional amino
epoxide resins containinq primary, secondary or tertiary
amino groups and having an amine number of from 45 to
120 and a hydroxyl number of from 50 to S00. The amine
2031671
1 1
number influences the solubility of the resin as well
as the quality of the surface of the stoved lacquer film.
The reactive hydroxyl groups and in some cases also the
reactive amino groups are essential for the cross-linking
reaction. Their number is at least 2, preferably not
less than 4 per molecule. If the degree of cross-linking
is too low, the films remain sensitive to external influ-
ences after they have b'een cross-linked. The epoxide
resins may also be aliphatic or cycloaliphatic hydrocarbons
which contain epoxide groups and may be prepared by epox-
idation with peracids. The amino groups are advantageously
introduced with the epoxide groups of the resin by the
addition of the NH-reactive compounds. The use of an
excess should be avoided in order to prevent contamination
with low molecular weight NH products and side reactions.
Examples of other suitable binders include the reac-
tion products of bisphenols such as bisphenol A or bisphenol
F with primary amines and formaldehyde. These may be
reacted with a conventional semi-masked isocyanate obtained as
reaction product of an aliphatic and/or aromatic di-
or polyisocyanate and a primary amine. The amines used
may be aliphatic amines and/or alkanolamines. The reaction
product should contain an average of one secondary amino
group per molecule. Any OH group present may optionally
be reacted with an epoxide compound and/or with further
isocyanate groups.
Suitable binders are described, for examp~e, in EP-A-
0 261 385. They are obtainable by copolymerisation of
glycidyl (meth)acrylates or allyl glycidyl ethers with
unsaturated monomers. Examples of suitable unsaturated
olefinic monomers include saturated linear or branched
acrylic or methacrylic acid esters, styrene and function-
alized acrylic acid and/or methacrylic acid esters. The
amino groups necessary for imparting solubility may be
introduced by reaction of the epoxide group with second-
ary amines or ami~no alcohols. Alternatively, they may
be introduced by the incorporation by polymerisation
~03~671
12
of linear or cyclic secondary or tertiary nitrogen-
containing (meth)acrylic compounds in the ester group.
The resins may be self-cross-linking or cross-linked
by external cross-linking agents. Examples of suitable
cross-linking compounds include triazine resins, blocked
isocyanates, cross-linking agents capable of trans-
esterification or trans-amidation, and cross-linking
agents containing terminal double bonds. These cross-
linking agents are well known and described in the
literature.
Cross-linking agents based on triazines are described
e.g. in EP-A-0 245 786.
Suitable isocyanate compounds are described e.g.
in "Farbe und Lacke", 12, 1983, pages 928 et seq. These
are conventional di- or polyisocyanates based on aliphatic
and/or aromatic isocyanates or mixtures thereof which
are reacted with known blocking agents such as alcohols,
phenols, oximes, lactams, hydroxymethacrylates, alkanol-
amines, substituted secondary amines or aromatic alcohols.
Cross-linking agents of the trans-esterification or trans-
amidation type are described in DE-A-34 36 345. They
react with binders of binder systems containing hetero
atoms which carry active hydrogen atoms, such as OH,
SH or NH groups. They may also effect cross-linkingby reactionS
with carboxylic acid esters or amides.
The resins may be used as individual components (self-
cross-linking) or as mixtures. For this purpose, they
are used in a solvent-containing form and partially neutral-
ised with the required quantity of a conventional acid
such as formic acid ,! acetic acid, an alkyl phosphoric
acid or lactic acid, and they may then be dispersed in
water. Polybasic acids such as phosphoric acid or citric
acid may be used for special purposes.
It is preferred to use basic resins or mixtures
of basic resins consisting to an extent of at least 30%
by weight of amino epoxide resins. Amino epoxide resins
based on bisphenol A-amino epoxides are particularly
203~671
advantageous. These are then cross-linked with conventional
masked isocyanates or trans-esterification hardeners
or a mixture of the two.
For incorporation of the polymer powders used according
5 to the invention in the coating compounds, the polymer
powders are triturated (ground) to a paste. The polymer
powders may be ground up into a paste together with
the binder, the water-dispersible film-forming resin,
the cross-linking agent or parts thereof and/or a triturat-
10 ing resin ~paste resin), Gptionally with the additionof solvent. This process may be carried out by, for example,
dispersion in a high speed stirrer apparatus. The paste
obtained may then be ground up in a suitable apparatus
either immediately thereafter or after an intermediate
15 period of storage. Any binder, resin, cross-linking,
pigment and/or bath constituents not yet introduced may
be added at this stage and further grinding may then
optionally be carried out. The desired composition of
coating compound may then be obtained by neutralization
20 with a suitable quantity of neutralizing agent and the
addition of water.
According to another method of carrying out the process,
the usual fiim forming resins may be converted into the
aqueous phase with the formation of a solution or disper-
25 sion after neutralization. The polymer powderS are thenintroduced into this dispersion as a paste.
If the polymer powders used according to the invention
are not triturated in the binder, the binder components
or parts thereof to form a paste, then resin pastes or
30 triturating resins are used such as those conventionally
used as triturating binders for the preparation of pigment
pastes. Triturating binders of this type are described,
for example, in EP-A-0 107 088, EP-A-0 183 025 and
EP-A-0 270 877. These binders have a high wetting capacity
35 for pigments and fillers. They are required to be readily
compatible with the binder of the aqueous coating compound
and !should not alter the properties of the binder mixture.
20~71
- 14
They may cross-link with the binder by way of functional
groups.
Further, they may consist, for example, of reaction
products of modified polyepoxides, preferably based on
aliphatic or aromatic diols such as polyalkylene glycol
or bisphenol A or phenol novolaks, with primary and/or
secondary amino groups of aliphatic mono- and/or diamines.
These compounds may be further modified, e.g. to form
compounds containing oxazolidine rings, or they may be
reacted with isocyanate group-containing compounds by
way of H-reactive groups such as OH or NH.
Further examples include products based on polyepoxide
resins of aromatic or aliphatic diols option~lly
modified with functional groups such as ester groups
or masked isocyanate groups whic~. ~ay be reacted with poly-
phenols. These compounds are further reacted with primary
or secondary or tertiary amines, e.g. alkylamines, dialkyl-
amines, alkanolamines or trialkylamines or compounds
which are functionalized in the side chain.
The triturating binders are rendered soluble by the
introduction of acid or basic groups into the molecule
and neutralization of these groups with neutralizing
agents (acid or basic). The groups introduced may be,
for example, amino groups which may either be neutralized
with a conventional acid or converted into quaternary
ammonium groups by a reaction. The solubility may be
adjusted by the number of acid or basic groups introduced,
e.g. the amino functionalities.
The number of OH groups also has an influence on
the dispersibility in water.
These aqueous pastes may be prepared, for example,
by adding the quantity of acid necessary for neutraliz-
ation to a conventional pigment triturating resin dissolved
in organic solvents and then converting the resin into
a highly fluid aqueous dispersion by means of completely
salt-fr,ee water and other auxiliary substances, e.g.
wetting agents or solvents, and subsequently incorporating
2031671
~s
the pigments by means of an apparatus equlpped
wi~ high speed stirrer mechanism. Part of the film-forming
resin may also be used.
The aqueous coating compounds according to the invention
contain the usual additives, pigments and solvents used
for lacquers in addition to the polymer powders, the
binders and, if used, cross-linking agents. Conventional
pigments and fillers may be used, e.g. carbon black,
titanium dioxide, finely dispersed silicon dioxide,
aluminium silicate, metal effect pigments, organic and
inorganic colour pigments and pigments protecting against
corrosion, such as lead and chromate compounds. The
pigments and fillers may be worked up into pastes together
with the polymer powders used according to the invention
or they may be made up into pigment pastes separately,
using the same binders, binder constituents and paste
resins as those used for triturating the polymer powders
used according to the invention.
The pastes thus prepared (pastes containing the polymer
l~owders used according to the inventio~, pigment pastes and/
cr pastes containinq p~lymer p~wders an~igments) are adjusted to a
suitable viscosity for qrlnding by the addition of completely
salt-free water or solvents and are then ground in a
conventional apparatus suitable for this purpose. Further
additives may be introduced after the process of dispersion.
The pastes obtained are aqueous and have a low specific
gravity. They have a high solids content and yet have
a high resistance to sedimentation and viscosity changes
in storage.
Electro dip lacquer coating baths may then be prepared
from an aqueous dispersion of the binders and pigment
pastes. These baths are diluted to the required solids
content with water and may then be used as coating baths
for metallic or conductive substrates as known to the
man of the art. When the deposited films have levelled
out and cross-linked, dense, homogeneous electro dip
laaquer coatings are obtained. These are distinguished
- ~03~l671
16
by their good surface, good covering of the edges, good
resistance to stone chipping and low density. Due to
the low density of the coating baths, the tendency to
sedimentation is very slight and the yield is ve}y high.
Levelling out and cross-linking may take piace at
room temperature or at an elevated stoving temperature.
Further, one or more than one additional layer may be
applied to the lacquer coat obtained. Cross-linking may
be carried out after application of each individual lacquer
coat or coating is carried out wet:in-wet and all the
layers are then stoved together in a single stoving operation.
For example, a top coat lacquer or a filler and other
layers may be applied before or after stoving of the
layer which has been electrically deposited according
to the invention from an aqueous solution or dispersion.
The following build-up of lacquer is suitable for produc-
ing a metallic effect on car bodies: Cathodically deposited
electro dip primer, filler (aqueous or non-aqueous),
base lacquer (aqueous or non-aqueous) containing aluminium
particles and pigments and/or dyes, and transparent
top coat lacquer (aqueous, non-aqueous or from lacquer
powder). An aqueous or non-aqueous intermediate undercoat
for protecting against stone chipping may be applied
to the primer layer before application of the filler.
Apart from being suitable for lacquering car bodies,
the coating compounds according to the invention are
suitable for use as industrial lacquers, for example
for lacquering refrigerators, washing machines, office
furniture, agricultural machinery, building machinery,
screws, springs and accesssories and fittings for motor
vehicles.
In the following Examples, all percentages and parts
(T) are based on weight. The solids content is determined
at 150C by a method analogous to that of DIN 53 182. -
2~3167~
17
Preparation of binders:
Example 1
391 g of Diethanolamine, 189 g of 3-(N,N-dimethylamino)-
propylamine and 1147 g of an adduct of 2 mol of hexane-1,6-
diamine and 4 mol of the glycidyl ester of versatic acid
(CaduraR E 10 of Shell) are added to 5273 g of bisphenol A
epoxide resin (epoxide equivalent weight about 475) in
3000 g of ethoxypropanol as described in EP-A-12 463.
The reaction mixture is maintained at 85 to 90C for
4 hours with stirring and then at 120C for one hour.
Ethoxypropanol is then added to dilute the reaction mixture
to a solids content of 60%.
Example 2
228 Parts of bisphenol A (1 mol) are reacted with
260 parts of diethylaminopropylamine (2 mol) and 66 parts
of para-formaldehyde (91%, 2 mol) in the presence of
131 parts of toluene as azeotropic entraining agent until
42 parts of the water of reaction have been removed.
After the addition of 152 parts of diethylene glycol
dimethylether and cooling of the product to 30C, 608
parts (2 mol) of a tolylene diisocyanate half blocked
with 2-ethylhexanol are added in 45 minutes. When the
isocyanate value has been virtually reduced to zero,
1400 parts of this solution are mixed with a solution
of 190 parts of an epoxide resin based on bisphenol A
(epoxide equivalent weight about 190) and 250 parts
(1 mol) of a glycidyl ester of a saturated tertiary C9
to C11 monocarboxylic acid in 389 parts of diethylene
glycol dimethylether and the mixture is reacted at 95C
to 100C until the epoxide value is 0.
Example 3
a) 832 Parts of the monocarbonate of Epicote 828 are
mixed with 830 parts of Capa 205 and 712 parts of diglycol
dimethylether and reacted at 70 to 140C with approximately
0.3% of BF3-etherate until the epoxide number is 0.
307 Parts of a reaction product of 174 parts of tolylene
diisocyanate (2 NCO equivalents) and 137 parts of
2~31671
2-ethylhexanol with the addition of 0.3% of benzyl trimethyl-
ammonium hydroxide (Triton B) having an isocyanate content
of about 12.8% are added to this product (solids content
70%, two carbonate equivalents) at 40 to 80C in the
presence of 0.3% of Zn-acetylacetonate as catalyst. The
reaction is carried out until the isocyanate value has
been reduced ~o a~out zero and the reaction mixture is
then adjusted to a solids content of about 70% with diglycol-
dimethylether.
b) 618 Parts of a reaction product obtained from 348
parts of tolylene diisocyanate (80% 2,4-isomer; 20% 2,6-
isomer) and 274 parts of 2-ethylhexanol with the addition
of 0.3% of benzyl trimethylammonium hydroxide as catalyst
and having a residual NCO content of 12.8% are slowly
added to 1759 parts of a bis-carbonate based on Epicote
1001R at 60 to 80C together with 0.3~ of Triton BR as
catalyst. The reaction is continued until the NCO value
has been reduced to approximately 0. The product obtained
has a solids content of 70%. 622 Parts of the reaction
product obb~ined from 137 parts of 2-ethylhexanol and
174 parts of tolylene diisocyanate with benzyl trimethyl-
ammonium hydroxide catalysis (0.3%) (NCO content about
12.8%) are added at 20 to 40C to 860 parts of bis-
hexamethylene triamine dissolved in 2315 parts of methoxy
pxopanol and the components are reacted together until
the NCO content is approximately 0. 4737 Parts of ~thé
reaction product b) and 3246 parts of reaction product
a) (in each case 70% in diglycoldimethylether) are then
added and the reaction is carried out at 60 to 90C.
The reaction is terminated at an amine number of about
32 mg KOH/g. The resulting product has a solids content
of 60%.
Example 4
768 g of Trimellitic acid anhydride and 2000 g of
a glycidyl ester of a branched tertiary C10-monocarboxylic
acid (Cadura E10R) are carefully heated to 190C with
stirring, an exothermic reaction beginning at 90C.
2l~3l67l
1 9
The reaction mixture is cooled to 140C and 2.75 g of
N,N-dimethylbenzylamine are added. The temperature is
then maintained at 145C until the acid number is below
3 mg KOH/g. A calculated quantity of Cadura R E10 is
added if necessary. The reaction product is diluted to
a solids content of 80% with 2-butoxyethanol.
Example 5
160 g of Caprolactam are slowly added with stirring
to 431 g of a solution (75~ in ethyl acetate) of a reaction
product of 3 mol of tolylene diisocyanate and 1 mol of
trimethylolpropane (Desmodur L R) at 70C. The reaction
mixture is then maintained at 70C until the NCO content
has virtually fallen to zero. 2-Butoxyethanol (204 g)
is then added and the ethyl acetate is distilled off
through a column until a solids content of 70% is obtained.
Example 6
647 g of a reaction product of 800g of refined linseed
oil and 200 g of maleic acid anhydride (mixing and heating
to 200C under inert gas until a sample gives no colour
reaction with dimethylamine) are reacted with 162 g of
colophony-maleic acid anhydride glyceric ester (Alresat
KM 201 R) for one hour at 160C and neutralized with
82 g of trimethylamine at 100C. The product obtained
is dispersed in 1946 g of water.
Preparation of binder dispersions:
Example 7
A mixture is prepared from 300 g of a resin from
Example 1 and 700 g of a resin from Example 2 (based
on the solids content). This mixture is substantially
freed from solvent by distillation. 45 g of lactic acid
(50%) are then added and the mixture is converted into
a dispersion with a solids content of about 43% by the
addition of completely salt-free water in the heat.
Example 8
550 g of a resin from Example 1, 79 g of a resin
from Example 4 and 1740 g of a resin from Example 3 are
mixed together. The mixture obtained is substantially
203167~
freed from solvent by distillation under vacuum and 63.5 g
of 20% formic acid are added with stirring. The reaction
mixture is then converted into a dispersion with a solids
content of about 38% by dilution with completely salt-free
water.
Preparation of piqment pastes:
Example 9
180 g of Dibutyl tin oxide and 295 g of basic lead
silicate are added with vigorous stirring to 110 g of
2-butoxyethanol, 10 g of 2,4,7,9-tetramethyl-5-decine-
4,7-diol, 11 g of acetic acid, 310 g of a binder according
to EP-A-0 183 025, Example 3 (55% in 2-butoxyethanol)
and 340 g of completely salt-free water. The paste obtained
is adjusted to a suitable viscosity with about 100 g
of ethoxypropanol and ground to the required particle
size in a pearl mill. -
Example 10
9.5 g of Formic acid (50%), 518 g of a commercial
cross-linked urea formaldehyde powder having a glass
transition temperature of 85C and particle sizes ranging
from less than 1 to 22 ~m are added to 233 g of a paste
resin according to EP-A-0 138 025, Example 3, 55% in
2-butoxyethanol, using a high speed stirrer, and 1150 g
of completely salt-free water are added and the mixture
obtained is ground in a pearl mill. After grinding, 730 g
of a paste according to Example 9 and 1150 g of completely
salt-free water are added with further vigorous stirring.
A stable pigment paste is obtained, whose solids content
may be adjusted if necessary.
Example 11
The procedure is the same as in Example 10 but with
only 345 g of urea formaldehyde powder and the addition
of 173 g of a commercial polyacrylonitrile powder contain-
ing about 7~ of methyl acrylate and having a glass trans-
ition temperature (according to DSC) above 90C, a molecu-
lar weight above 100,000 and a particle size of from <1
to 95 ~m. The paste obtained is ground down to the
2~31~71
21
required fineness of grain and adjusted to a suitable
viscosity for storage by the addition of water.
Example 12
The procedure is the same as in Example 10 but with
only 172 g of a urea formaldehyde powder and the addition
of 72 g of a high molecular weight commercial polyacrylo-
nitrile powder containing about 0.7% of methyl acrylate
as comonomer and having a molecular weight of 400,000,
a glass transition temperature (according to DSC) of
75C and a particle size range of from 3 to 12 ~m, and
174 g of titanium dioxide. A stable pigment paste is
obtained.
Example 13
175 g of a paste resin according to EP-A-0 183 025,
Example 3 (55~ in butyl glycol) are mixed with 5 g of
acetic acid (100%), 800 g of completely salt-free water,
300 g of a paste of Example 9, 400 g of a polyacrylo-
nitrile powder analogous to that of Example 12 and 30 g
of carbon black, using an apparatus with high speed
stirrer, e.g. a dissolver. After adjustment of the viscos-
ity with about 60 g of water, the mixture is ground to
the required particle size in a pearl mill and the viscosity
may subsequently be adjusted for storage if necessary.
Preparation and use of an anodicallY depositable lacquer:
Exam~le 14
500 g of a resin from Example 6 are mixed with 48 g
of a urea formaldehyde powder analogous to that of Example
10 and with 72 g of a polyacrylonitrile powder analogous
to that of Example 11 and the mixture is ground in a
pearl mill. The mixture is then diluted with 1100 g of
the binder from Example 6 and made up into an anodically
depositable lacquer by the addition of 1480 g of completely
salt-free water. This lacquer is deposited under the
usual conditions. A homogeneous, smooth and elastic film
is obtained.
2~31671
22
Preparation and use of cathodically deposi_able lacquers:
.
Example 15
1100 g of a dispersion from Example 7 are diluted
with 1540 g of completely salt-free water and 360 g of
a paste from Example 10 are addecl with vigorous stirring.
Steel sheets are coated at the cathode in known manner
and stoved at 180~C for 30 minutes.
The surface of the film (20 ~m) is smooth, homogeneous
and uniformly matt. The edges of the substrate are uniform-
10 ly covered.
Example 16
1100 g of a dispersion from Example 7 are diluted
with 1540 g of completely salt free water and 360 g of
a paste from Example 11 are added with stirring. Steel
15 sheets are coated at the cathode and stoved as in Example
15. A film having a thickness of about 20 ,um is obtained.
The film is smooth with a tough elasticity and uniformly
semi-matt.
Example 17
1250 g of a dispersion from Example 8 are diluted
with 1200 g of completely salt-free water. 360 g of a
paste from Example 12 are then added. The solids content
is adjusted to about 19% by the addition of water.
This cathodic dip lacquering (KTL) bath is used to coat
25 steel sheets and the coatings are cross-linked as in
Example 15. The dry film thickness is about 30 ~m. The
surface is homogeneous, smooth, tough-elastic and semi-matt.
The adherence to the substrate is satisfactory.
Example 18
550 g of the binder from Example 1, 31 g of the
binder from Example 4 and 169 g of the binder from Example
5 are mixed with 3.7 g of formic acid (50%) per 100 g
of solids content in a dissolver. 400 g of a paste from
Example 13 are added and the mixture is then slowly diluted
35 with 1900 g of completely salt-free water. After the
mixture has been stirred for at least 24 hours, it is
used for coating steel sheets and the coatings are stoved
~ ~3~671
at 165C for 30 minutes. The surface is homogeneous,
smooth and tough-elastic.
:, :
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