Note: Descriptions are shown in the official language in which they were submitted.
- -- 1 330965
. ~..
The present invention relates to a paint or
lacquer mask, for example a mask mountable on a motor
vehicle or a part thereof during the performance of a
lacquering operation, and to methods of produaing and
using such a mask.
During lacquering operations in motor vehicle
painting, especially when the lacquer colour to be applied
is sprayed on, masks are required so that areas not to be
lacquered are not coated by paint mist. Usually, paper,
which is adsorbent and can take up the excess paint, is
used as a masking means. It is, however, disadvantageous
that the paper to be used must have a certain strength and
a certain quality in order to be suitable for this
purpose. If the paper is too thin or too light, the
; ; 15 sprayed-on paint can penetrate and reach the surface to be
protected. The costs for masking paper are therefore
relatively high. This is particularly so in the motor
vehicle industry, where great quantities of such masking
paper are consumed.
A further disadvantage of such masking paper
is that paper saturated by lacquer paint cannot be reused
for paper manufacture, due to the chemical components of
the lacquer paint. The known environmental compatibility
of the paper is not the same in the case of wastes
contaminated with lacquer. The waste paper must therefore
be deposited on special waste tips or burnt.
In German patent N 16 46 100 (Borde) issued
on January 7, 1971, there is disclosed a masking hood
which is adapted to the shape of a motor vehicle and which
includes several portions which can be tilted up. The
hood consists of a textile material provided with a
surface coating. Masking hoods of that kind are very
heavy and difficult to manipulate and can be reused only a
~J
1 330965
limited number of times, since they become stiff in time due to the
lacquer residues and no longer adaptible to the vehicle shape. Such
hoods are, moreover, very expensive.
Also known are dust protection covers of synthetic material film,
which are used in paint shops for covering parked vehicles not subjected
to the lacquer operation. The covering in this case, however, is ~;~
required in order to protect vehicles from airborne lacquer residues
so that these do not precipitate on the surfaces of such vehicles.
~ `These covers are not suitable as masks for lacquering operations,
;~10 since lacquer paint dries very rap;dly on the film and peels off on
removal of the film. The pçeled-off lacquer can fall on the neighbour-
ing, fresh1y lacquered and still wet surface, which is then spoiled.
Moreover, it is known during lacquering to place masklng films `~
of synthetic materlal over car wheels in order to protect them during
the lacquerins of the body. Here, too, there is the same problem that
the paint on the film peels off on remova1 of the fi1m and can fall
onto the~freshly lacquered surfaces. This can mean that the surface
has to be cleaned down again, preliminari-ly treated and relacquered. `~
It is known to print on synthetic materia1 fi1m, in which case the -~
film must be pre1iminarily treated by a corona process so that the
printing ink to be app1ied adheres to the film. In this process, the -
film is passed through an electric field, in which a corona discharge
takes place and leads to a surface change in the film. The causes of
this surface change have not been explained exactly. Presumably,
25 molècules are broken up in the surface region of the film and can then ~
enter into a firm connection with the printing ink. During the corona ~ `
discharge, ozone also arises, which possibly combines with the molecules ~
' ~,',.. .
1 330q65
at the surface of the film, whereby the surface tension is reduced.
Moreover, the surface could be roughened through micropores due to the
heat arising during the corona discharge so that the printing ink finds
a good adhesion base.
The printing process, however, takes place directly after the
corona treatment and the printing ink is applied in an extremely thin,
; barely measurable, layer. For that reason, the problem of a transit
time effect on the corona treatment does not arise. The corona treat- ~ -
1 ; ment need be performed only with an intensity sufficlent to allow the
ink to immediately adhere.
There is thus a need for a mask for lacquering operat~ons, which
reduces or eliminates the above-described disadvantages, is relatively
economic to manufacture, is simple and secure to handle and does not
require additional aids such as paper webs or the like. Moreover, the ;
mask should preferably be capable of being easily destroyed.
According to a first aspect of the present invention there is
provided~a paint or lacquer mask comprising a film of plastics material `
:: , . ~ ,, -. :
~ treated at at least one surface thereof by a corona discharge process. ~ 9~
.
~`~; According to a second aspect of the present invention there is
: . . : - ~: :. .. .
~ 20 provided a method of producing a paint or lacquer mask, comprising the `~
.~ ~ . . .
step of treating at least one surface of a film of plastics material
by a corona discharge process.
Through this treatment, it is possible for lacquer to adhere to-
the film without peeling-off when dry. It is of particular significance ~- -
that the lacquer, even when it forms a layer of appreciable thickness
-on the film, remains adhering when the film is taken off the vehicle
and possibly stressed, in particular creased. This has hitherto not
.
1 330965
been regarded as possible, since synthetic material films as is known
have a wax-like surface to which lacquer does not adhere, but peels off
even with slight stressing.
By comparison with paper, the film has a very low we;ght per unit
S area so that the waste quantity is smaller. Disposal is therefore -
s;mpler than in the case of paper, since the film can be burned and it - -
is only necessary to take care of the lacquer residues. The heating `
value of the film is relatively high, so that combustion in a heating ~ -
~; ~ system is possible. Solid residues, such as in the case of paper, do -
10 not arise to such an extent and the waste gases are not dangerous in ~ -~
..
the case of polyethylene. Merely the waste gases from the lacquer are ~-~
; to be taken care of. -
, . ,.~ . ~ .
Preferably, the surface treatment is so performed with the ;~-
intensity chosen to be so high that a surface tension or wetting
tension of at least 45 dynes per square centimetre is attained at the
film surface. With this wetting tension, it is ensured that the
,: . .
lacquer adheres in desired manner t~o the film. Known corona process ~ -~
treatment for the printing on synthetic material film merely achieve
wetting tensions of below~40 dynes per square centimetre. The ;
; 20 intensity of the prelimin~ary treatment in that case can be of such
` height, by way of the electrical power per unit area(watts per square
.
centimetre) in the corona treatment and by way of the transit speed
of the film during the treatment, that the desired surface tension or
wetting tension of at least 45 dynes per square centimetre is attained.
The intensity of the treatment can thus be set through the electrical
power per unit area (watts per square centimetre) and through the ~ -
- speed of the film, wherein a high power per unit area (watts per square
~ . ~
~' : ',,,..:
1 3 3 0 9 6 5
centimetre) takes care of a high treatment intensity at low speed.
Through choice of these parameters, the treatment can be adapted in
simple manner to the particular properties of the film material.
Expediently, the composition of the film synthetic material is
such that a surface or wetting tension of at least 45 dynes per square
centimetre is achievable after the corona treatment. The maximally ; -
achievable surface or wetting tension may be dependent on the material -
and unable to be increased as desired even in the case of the st~bngest
preliminary treatment. In order to be able to achieve adequate values,
it may be desirable to keep the proportion of alubricant as small as
possible or to dispense with the use of lubricants completely. The
intensity of the preliminary treatment and the small proportion of
lubricants both contribute towards achieving the desired result. ;~
Lubricants serve to form the film surface so that an extruded film
. - : .
hose can be opened after production. They are therefore responsible
for a wax-like repellent surface which impairs adhesion of lacquer.
Other ad~itives, for example anti-statics, have only a small influence
on the adhesion capability of the lacquer. In order further to increase
,~ . ,
the adhesion capability of the lacquer, chalk can also be added to the
20 film material, so as to provide a relatively rough surface. :~
~; The film material can consist of polyethylene, from which film
can be economically produced and which can be further processed ln simple
manner.
The polyethylene film can contain a combination of different
polyethylenes and additives and have a composition of, for example,
at least 45% by weight of linear polyethylene (LLDPE), 10 to 50% by ~ ;
weight of high density polyethylene (LDPE), 0.5 to 10% by weight of ~ ; -
330~65
- 6 - ;
low density polyethylene (HDPE), 0.1 to 5% by weight of oleamides or - ;
erucamides or natural silica and up to about 5% by weight of fatty -
acid esters, dyestuffs, synthetic silica, stabilisers and processing
`~ aids, wherein the sum of these components amounts to 100% by weight.
Apart from hoods and tapes, prefabricated moulded parts, for
example for the masking of a vehicle bootlid or bonnet, can be produced
. ~ .
from the film. Such moulded parts can be tailored to the respective
use so as to be able to be mounted in simplest manner without further -
operating steps, such as cuttlng to size.
~ 10 A thus composed film can be blown out to be very thin and, in spite
`- of its small thickness, have good mechanical properties, such as high
` extenslbility and a high tear strength. -
` If the intensity of the preliminary treatment is selected so that
;~ relaxation of the surface properties of the fllm is taken into consider-
ation, the resulting mask is usable for lacquering operations taking
place some time after the preliminary treatment without reduction in
its efflcacy. In the known printing process, printing takes placè ;~
immediately after the preparation. The effect of the prellminary
. .
treatment may reduce, however, which was hitherto unknown. Since
20 lacquerlng operations usually do not take place immediately following ~ ~;
the film production, but weeks or months later, it is desirable to `
~m structure the preliminary treatment so that a sufficient adhesion base
~or the lacquer is present even after a relatively long time. In that
.
case, the intensity of the preliminary treatment ca`n be chosen to take
such account of relaxation of the surface properties of the treated
- :... -:
film that a surface or wetting tension of at least 45 dynes per square
centimetre occurs at the film surface after a time interval of about
''~ 1330q65
- 7
6 months. It has proved that the surface properties of the Film do not
significantly change after about 6 months and a quasi-stable state sets
in. The usability of the film therefore is not lost even with extended -
delays between preliminary treatment and use. This long storage life -
simplifies inventorising and enables cost savings.
The film can be made of a compound material. It then consists of ~-
.
several layers of different material chosen to correspond to the:~ :
respective task. For example, the side resting on the vehicle can
consist of a dull to sticky material so that slipping of the film on
10 the vehicle is excluded. The other side of the film can then be formed .
:~
of a material which has good adhesion properties or receives them
,: i ,
through the preliminary treatment.
The film can also be preliminarily treated on both sides. The
treated surface of such a film is not recognisable by the naked eye
; 15 and treatment of both sides ensures that a surface capable of adhesion
is invariably presented outwardly for lacquering operations.
In general, synthetic material films can be produced simply and ;~
economically, with very long strips or webs being producible without
:,, . ~
interruption. These strips can be guided through equipment which -~
operates to provide the corona process. The treatment can thereby take
place continuously.
According to a third aspect of the present invention there is
- ~.. :. ...
provided a method of palnt or lacquer coating a first surface portion `
adjoining or in the region of a second surface portion to be kept free
of the paint or lacquer used in the coating process, the method com-
prising the steps of so covering the second surface portion with a mask
according to the first aspect of the invention or produced by a method
. ~
- ~ ` 1 330965
- 8 -
according to the second aspect of the invention that said at least one `
surface of the film faces outwardly and spraying paint or lacquer onto
the first surface portion.
An embodiment of the mask and an example of the method of the
5 present invention will now be more particularly described with referencé ~g~
to the accompanying drawing, the single f;gure of which is a schematic
illustration of preliminary corona treatment equipment for performance
of a method exemplifying the invent;on.
Referring now~to the drawing, there is~shown preliminary corona ;`
10 treatment equipment ln which~a synthetic material film 1 to be treated ~`
~ `
runs over~a roller 2, which is electrically conductive and earthed.
Electrodes 3 are arranged~at a certain spac;ng above the film and are
connected by~way of a high~tension transformer 4 to an alternating
current generator 5.
Through thé applicdtlon~of a cèrtain electrical power per unit
` ; area (watts per~square cent;metre) at a certain frequency, a corona
discharge arlses between the~film l and the electrodes 3. Through
~ ~ this discharge, the surface of the film is changed so that it can later
; enter lnto `a firm connectlon~w;th spr~ayed-on lacquer paint. The
surfacë is roughened by the discharge, whereby micropores arise.
Addltionally, a chemical change~may occur so that the film can chemically ;~ ~
bond with the lacquer. The adhesion of the lacquer to the film 1 is~ ~-
appreciably improved by the treatment and peeling-off of the dried
lacquer is largely or entirely excluded.
The intensity of the preliminary treatment is determined on the
one hand by the height and frequency of the power per unit area (watts
per square centimetre) at the electrodes 3 and on the other hand by
'. ~
: . . .
` - 1 330q65 ~
the transit speed of the film 1 through the equipment. These parameters
can be changed ln simple manner for adaptation to the oompasition of '~
the film material. - ;
The intensity of the preliminary treatment is preferably set so '~
that a surface or wetting tension of at least 45 dynes per square
centimetre is attained at the surface of the film. This value is
~higher than in the case o~f known printing processes on films.
It can also be taken into consideration that the maximum achievable
. .
values are also dependent on the kind of the synthetic~material employed.
10 The material of the film can accordingly'be selected so that high ~ -
; surface tenslons are~achlevable. For thls purpose, the proportion of ;~
the usually added lubricant~can be kept as small as possible. Such
lubricants normally;ensure~thàt~the~ext~ruded fl1m hose~can be opened '' ~
after production and the~idjacent film surfaces~séparated from each ''
other. The lubricants result in a wax-like surface which is obstruct~
~ .
ive to the application of lacquer paint. The other additive substances ~'
are les~ signiflcant in thls connection. -
Polyethylene, which can be processed easily and economically, ls ~ ~ -
particularly suitable ~for the film. In trials, a preferred combination
has proved to be composed of different polyethylenes and oleamides,
., .
preferably a mixture of at least 45% by weight of'linear polyethylene
(LLDPE), 10 to 50% by welght of high pressure polyethylené (LDPE),
0.5 to 10% by weight of low pressure polyethylene (HDPE), 0.1 to 5%
by weight of oleamides-or erucamides and natural silica, and up to
25 about 5% by weight of fatty acid esters, dyestuffs, synthetic silica, ' -'
stabilisers and processing means. A film produced of this material
mixture is extenslble and tear-resistant, can be biown out to be very ~
~ ~ ,
1 33C)q65 -~ ~
- l o ~
thin and can be provided with a well adhering surface through the
preliminary corona treatment.
It has proved that the surface properties of the film change with ~
time after the prelimlnary treatment and that the surface tension falls -
5 off. The intensity of the preliminary treatment is therefore preferably ~ ;~set so high that an adequate adhes;on capability is still present when
a lacquer operation is carried out after an~extended period of time. ~-
Trials have shown that the intensity of the preliminary treatment should
preferably be set so that a surface tension of at least~45 dynes per
square centimetre is still present 6 months~ after the preliminary
treatment. After 6 months, accordlng to experience, no further
slgnificant change occurs and the surface~state of the film remains
relatl~vely~ stab1e.
The preliminary treatment of the film can be undertaken on both -
lS surfaces, in which case a~second prellminary treatment statlon can be ;;
provided. The treated~surface of the~film is not recognisable by the
naked~eyet so that in the case of a~film treated at both sides it is
ensured that a treated surface will always be presented outwardly in
a masking and lacquering operation.
Thë film thus treated can be formed into a tape or hood which can
be utllised for the masking of a motor vehicle. On the other hand, a ;~
shaped part can also be produced, by which doors, engine hoods, lids
and the like can be masked without these parts having to be cut to size
individually.
`' ~"' " '~
: : ~:.: ~ -. .
-'',"','-,
,,-,,.,,-,,.,,~, ,.
"'.''.'` ,'-,"~.'.
",,.
