Note: Descriptions are shown in the official language in which they were submitted.
~218~
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3-129~8/~
An aqueou~ suspension for producin~ ~att_coatin~
The production of homogeneous thln coatings fro~ aqueous ~u~pension~
i8 known. StoragQ-stable squous lacquer systems based on ~ynthetic
re~in are described for exa~ple in the Ger~sn Offenlegung~schrift
~o. 2,716,118. There can be obtained therewith, on ~etal surface~,
ho~ogeneou~ i~pervious lacquer fil~s having a high glo~s and a
structurQ like that produced by po~der lacquers.
Adtitives ~uch ag are frequently used in aqueou~ lacqu2rs, for
exsmple polyethylen~ glycol, polyvlnyl pyrrolidone or glycerin, have
in general negl~gible ~tein8 effect or none at all. Other auxilia-
r~es for aqueou~ lacquers, such as ~ethyl cellulose, carboxy~ethyl
cellulose or polyacrylic acid, give rise even in 8~all a~ounts to
seriou~ faults: the fil~ has no fle~ibillty or too low a degree
thersof, easily brea~s and e~hibits levelling defectJ, pin holes and
pore~.
It has nov been found that ~lth an addition of polyv~nyl alcohol
(PVA) to squeous su~pen~ions of certain binders it i~ poa~ible to
produce a lacquer which on surfaces for~s coselngs having a ~att
sppearance. The d~sadvantages gener~lly caused by the presence of
~atting agent~, na~ely, poorer levelling and inferior ~echanlcal
properties of the fil3, do not arlse.
The invention relstes therefore to an aqueou~ suspension for
producing ~att coatlngs; the ~aterial being suspended consisting of
sn epoxide resin, a saturated polyester having terrinal carboxyl
group~, a levelling agent selected fro~ the group of polyvinylace-
tsls, polyethylene glycol, polyvinyl pyrrolidone, glycerine or
~X~
~Z1878~
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acrylic copoly~erD snd optlonally pigm~nts, and a~ ~attlng agent 8
polyvlnyl alcohol having 8 molacular welght o~ 1000 to 100,000,
preferably 5000 to 50,000.
The suspenaion preferably contalns l to 20 per cent by welght,
relative to the solid content, of PYA, ln partlcular 2 to
15 per cent by weight. The a~ount of PVA depends on the degree of
~atting requlred; thi~ beco~es contlnuously greater as the added
a~ount of PVA increase~.
An exa~ple of polyvinyl acetals i~ polyvinyl butyral
(~Movital B 30 H, regi~tered trade~ark of ~OEC~ST). An e~ample of
acryllc copolymers are "Modaflov" and "Acrylron" ~PF (reg~stered
trade~ark of MO~SA~TO snd PROTEX, respectively).
Ths aqueoufl suspension can be without plg~enta and can thu~ be used
a8 clesr lacquer. It can however contain pigment~, which can be
white or coloured, and ~ust be inert with respect to the other
lacquer constituents.
The a~ount of ~ollds in the squeoufl suepen~lon varies generally
between 15 and 60 per cent by weight.
The size of the 6uspended partlcle~ 1~ not critlcal. It can be for
sxa~ple betw~en 0.1 and 50 ~, prefersbly bet~een 1 and 20 ~.
The ~u~penslon according to the lnvention can be advantageously
prodcued by addlng PVA havlng a 301ecular weigbt of 1000 to lOO,OOO
to an aqueou~ ~uspenslon of the other co~ponents.
The su~penflion can al~o be produced by adding the other co~ponents
to a aolutlon of PVA.
A further posslbility for producing the suspen~ion according to the
invention ifl to ~elt PVA into the epoxids reflin and the sAturated
polyeflter having terminal csrboxyl groupfl and to then proce~ the
~L21~3~8~
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resultlng materlal ln a known manner into the form of a suspen~ion.
A suspension of thl~ type effects a degree of mstting lower th~n
that ef~ected by the suspension produced in the aforementioned
~anner.
The inYentlon relate~ al~o to a process for producing matt coatlngs
on surfaces, especially on those of glass or metal, preferably of
steel, but also of sluminium and tin plate~ wherein the suspension
according to the invention i8 applied to the surfaces and cured.
The application can be carried out ln 8 known msnner u~lng an
application proce~s such as dipping, spraying, brushing, rolling,
and 80 forth. The lacquer 19 sub~equently ~toved by drying and
curing, preferably at fairly high te~peratures (for exa~ple at
100 to 200).
Surprlsingly, no ~atting effect is obtained when PVA is added to dry
powder resins.
In the following Examples, the mattlng effect 18 ~easured in ter~s
of degree of 8109~ according to DIN 67 530.
Example 1
A o1xturo of 84 g of trlglycidyllsocyanurate, 916 ~ of a saturated
polyester having terminal carboxyl groupu (acid nu~ber: 35, melting
polnt: 65C), 505 g of TiO2 as vell as lO g of a co~erclal level-
ling agent for coating powders ('~odaflow", MO~SA~TO reg. trade~ark~
i8 ~elted down in 8 Ro-kneader (BUSS, Swltzerland). The sæterisl i9
subsequently ground (particle size lOO ~) and suspended in 1815 g
o~ water. This suspenaion 18 then further gorund in a ball mill
until the ~ean particle size is about 10 ~. 76 g of polyvinyl
alcohol (PVA) havlng a mean molecular welght (M~) of 22,000 are then
added, at roo~ temperature snd with stirrlng, to the suspension and
dlssolved therein. The ~uspension thus obtalned 18 sprayed wlth a
lacquer ~pray gun onto a cleaned steel sheet. A~ter expo~ure to air
for about 15 ~lnutes, the coated sheet 18 heated for 10 mlnutes at
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200C. There lo ~ormed a 50 to 60 ~m thlc~ lacquer fll~ havlng a
degree of glosa of 40 %, 8 completely s~ooth surface and excellent
levelling.
When 152 g of PVA instead of 76 g of PVA are added to the BU3pen-
sion, there is formed a filo havlng a degree of glo8~ of 4.5 % ~nd
otherwise equally good propertie~.
A fil~ produced for comparison without an addition of PVA ha~ a
degree of gloss of 95 %; furthermore, lt has an orange-peel-llke
surfsce structure com~on in the case of powder lacquers.
Example 2
There are used, instead of triglycldyllsocyanurate as binder and the
polye~ter a~ount stated ln E~ample 1, 650 g of a solld bisphenol-A
epoxide resln havlng an epo~lde content of 0.5 to 0.6 ~ollkg and
350 g of a saturated polye3ter having ter~lnal carboxyl groups (acid
number: 60, meltlng polnt: 100-110C), with otherwise the ~ame
procedure as described in Exa~ple 1, varying s~ounts of PVA having
in 80Re case a dlfferent ~olecular weight (MW) being uset in thiR
case.
The propertles of the films produced on steel ~heets are summari~ed
in the followlng Table, together with the valueo of a compArative
tQst:
_ ~egree of
PVA-M~ PVA smount the fil~ Surface ~tructure of the film
. _
22,000 30 g 96 X ~light orange-peel effect
22,000 76 g 10 % s~ooth
15,000 76 g 20 X 8~00th
72,000 76 g 10 % s~ooth
22,000 227 g 3 % ~omewhat rough
0 g 102 % pronounced orange-peel effect
~X~8~8iL
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Example 3
A ~ixture of re~in, curing agent and levelling agent as descrlbed in
Example 1 i9 melted down wlthout the addltion of TiO2; it 18
subsequently ground and suspended in 2020 g of water. The further
procedure ls as de~cribed in Exa~ple 1, and there i~ obtained on a
glass plate a tran~parent lacquer fil~ having an opalescent appea-
rance.
Exa~ple 4
650 g of a solld epoxide resin based on bisphenol-A and having an
epoxid~ content of 0.5 to 0.6 w l/kg, 350 g o~ a saturated polyester
having ter~lnal carboxyl groups (acid number: 60, ~elting point:
100-110C), 505 g of ~2 as ~ell as 10 g of i'Moda~low~ are ~elted
together with t6 g of PVA (~W ~ 2~,000~ in a Ko-kneader. The
subsequently ground product is suApended ln 1815 g of water, snd
further ground ln a ball ~111 until the mean particle si~a i9 about
10 ~. A steel sheet is coated therewith, in the ~anner descrlbed in
Exa~ple 1, to thus obtain a fll~ having a s~ooth surface and
excellent levelling, the degree oE gloss be~ng 75 %.
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