Note: Descriptions are shown in the official language in which they were submitted.
10~#4S
The invention relates to the decoration of glass
articles with thermoplastic inks which ordinarily would not be
serviceable for such use, and the combining of such inks with
a coating by which they are made serviceable.
In the manufacture of glass articles, it is of - -
course often desirable or essential to apply a decoration to
the article. (As used herein, the term "decoration" is used
broadly to mean, without limitation, trademarks, labels, in-
structions for use, contents, pictures, designs, or other
written or printed material. The decoration may be translucent,
transparent, or opaque, and may be of one or more colors
including black or white.) Whatever the decoration, it must
be serviceable for the normal use of the article; that is to
say, the decoration should not smear, abrade, rub off, chip,
or be removed by whatever type of rinse or detergent wash the
article might be expected to encounter in its ordinary use
or in the handling incidental to its manufacture or filling.
Thus, the standard decorating compositions used in labeling
pop bottles, for example, are formulated to withstand abrasion
in filling lines and in use, and to resist the usual washes
and so on.
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1041~45
In order to provide such serviccability ox durability
it is the most common practice to decoxate glass bottles with
a frit-containing composition that includes a glassy component
which is bonded to the glass surface by firing at high temper-
ature. The fired,enamel-like frit fixes the coloring pigments
on the article's surface. Organic inks for ylasses are kno~m,
which also are united with the glass by firing.
Such compositions or "colors" are most frequently
applied by the screen decorating process. For screcnability
10 the composition is often made up as a viscous, water-containing ~`
slip or, alternatively, as a hot melt or thermoplastic mater-
ial which is solid at room temperature but becomes a screenable
semi-liquid paste when heated to a temperature of about 120-200F.
The decorating material, whether water slip or hot melt, is ~ -
applied to delineated regions of the glass article by being
squeegeed through a stencil in the form of a screen of silk
~ or wire which is placed in registry on the surface of the
4 article. When the screen is separated from the article, the
decorating material remains on the article in the delineated ~-
20 area and dries by loss of water (if a slip) or quickly solidi-
fies ~if a hot melt). At this stage, the decorating material -
is very poorly and impermanently adherent to the glass surface,
~nd is a waxy, chalky or powdery layer which is not service-
: .
able. It will smudge upon contact, and is too easily removable
in washing. It becomes durable and serviceable only if heated
so that it fuses and unites integrally to the glass. ~-
Thus, in order durably to bond such colors to the
glass surface, the screen decorated article has heretofore
had to be subjected to a special, high temperature firing
30 ~tep which unites the decoration with the glass surface.
Inorganic frit-containing colors must be fired at a tempera-
ture above 800F., and organic colors at temperatures of 350-
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~041845
500F. For the inor~anic colors this reheating typically
requires a cycle of roug'nly 45-60 minutes duration. For
the organics, the firing cycle is shorter, but in ~ither case
there is involved a substantial c~pital expenditure (and very
substantial space requirements) for the heating equipment
and conveyors. Moreover, there is a substan~ial operating
cost in terms of fuel, articl~ handling and maintenance. How-
ever, such firing has been necessary to bond the decoration so
as to provide permanence.
The cost of such decorating materials is relatively
high, in large part because of the expense of frit or other
bonding components and the heat treatment necessary for bond-
ing. This relatively high cost has had the affect of restrict-
ing use of such materials to relatively small surface areas
or portions of the decorated articles. (Organic colors, which
do not require quite such high temperature firing, do not pro-
vide the intensity of color of frit bonded colors, and hence
are less useful.) Speaking generally, it has not been econo-
mically practical to screen decorate a large percent of the
~-~ 20 decoratable surface area of glass containers, at least on the -
high volume product. For that reason, frit decorated containers
generally do not have large color panels, stripes or designs
covering a high percent of their surface area, although from
i~ a merchandising standpoint larger color areas would open up
new possibilities for enhancing the appeal and visibility of
,
containers.
This invention is directed to a procedure by which
3 color decoration can be applied to much larger glass surface
¦~ areas than would otherwise be economically feas1ble. MUCh
30 lower cost materials can be used, but the prolonged or high
temperature firing cycle5 that have heretofore been necessary
are avoided. At the same time, the decoration is fully
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~ 1041845
serviceable, even though it is not uni~ed with thc glass surface.
This is achieved with th~ utilization of colors which are not
bonded durably to the article, and which do not require formula-
tion with the expensive frit or bonding ingr~di~nts that
have largely been responsible for the relatively lligh costs
of the decorating colors pr~viously used. In g~neral, colors
can be used which would not, in the absence of anything more,
adequately resist the abrasion, water or alkali attack to which
the article is subjected in its ordinary use.
A thermoplastic or hot melt color is used in carry-
ing out the invention and is applied by the screen decorating
technique. It solidifies very rapidly, almost instantly, on
: .
the cooler ware. The color ~sometimes referred to hereinafter
as an "ink") is formulated so as to become semi-liquid, with
.. . .
a consistency suitable for screening, upon moderate heating.
It may be similar to known hot melt colors, except that it :
can be and desirably is compounded without the heretofore
conventional frit binding ingredients. Such components are
not necessary for bonding and, while they are not harmful,
they are not necessary. -
Hot melt colors or inks are well known per se and
usually include as the vehicle a wax or waxlike material having
a melting point between about 120 and 200~F. Examples of such
waxy vehicle constituents are carnauba wax, parafin wax,
microcrystalline wax, beeswax, palmitic acid, stearic acid, --
and solid soaps. This is preferably the bulk of the vehicle,
.
e.g., about 60-85~ by weight. The vehicle may also include
a binder for adhering the ink to the glass. For example,
about 5-25% re8in or the like is useful as a binder and hardener.
30 Ethyl cellulo~e- may also be present ~e.g., 2-15~ of the vehicle)
, ~ as a v~scosity promoter and hardening agent.
-~ The pigment or coloring ingredient incorporated
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104~t~45
with the vehicle may be particulate inorganic matcrial, e.g.,
Tio2 or Cr2O3, which is insoluble in thc vehicle, or it may
~e an organic dye, or ~ mixture of organic and inorganic color-
ants. It is desirable to omit any volatiles which would have
to be removed for solidification to occur and any solvents
which would affect the coating resin when the latter is applied.
The ink itself does not comprise tl~e invention and its consti-
tuents are not critical. From this disclosure those skilled
in the art will readily be able to formulate a variety of
~` 10 suitable thermoplastic inks.
The ink sets up rapidly when applied to the surface
i f ~tare which is at a temperature below the screening tempera-
ture, for example at ambient temperature. Second or multiple
colors having successively higher melting points can be
. sequentially overprinted on the first color, in order to pro-
j; yide a multi-color decoration. None of the layers of ink,
however, are permanently bonded to the surface of the glass,
and the process is characterized by the absence of any baking
-~ or firing operation which would unite the decoration to the
;~ 20 glass surface as a frit is united. The decoration remains on
'1~
the glass surface as a waxy deposit, and is easily removable.
`, A finely divided discrete particle fusible resin
is applied over the ink. The article is preferably heated
.~,. .
~`~ for this purpose so that upon contacting the article, the
resin particles will soften or fuse sufficiently to become at
~`~ least partially adherent to it.~ -
The article is then passed through an oven which does
~ not fire or bake the ink onto it, but which melts both the ~ -
j ~ fu~ible resin and the ink, causing the resin particles to flow
'.~, 30 together to form a smaoth, continuous film over the ink. At :
the ~ame time this heating operatlon causes some diffusion of
.~ the lnk lnto the polymerlc film. However, it is important that ;-
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~04~845
the ink docs not mi(Jrate entirely throu-Jh the coatiny film,
to the outside surface. In the final product the ink is pro-
tected by a continuous layer of polym~ric coating over it,
there being a melt-melt type bond between the sclidified resin
and ink.
It might b~ expected that the fusion of a particulate
resin over a fluid ink would cause undesirable loss of sharp-
ness or blurring of the decoration. Nonetheless, I have found
that this does not occur and a high degree of sharpness and
distinctness is maintained, and thàt in fact the melted state
of the ink during polymer fusion (and optionally, during poly-
mer laydown) facilitates or improves the bond of the polymer
~ to the ink. In this connection, it is advantageous to apply
`~ the ink throuyh a screen which is 200 mesh or finer (U. S.
- Standard) screen. Ordinarily, for applying glass frit type
decorations, 165 mesh screens are used. This results in a
¦- relatively thick lay-down of decoration and thus utilizes
`i~ a greater amount of material per unit decorated area. Use
i of screens of smaller mesh sizes has been found feasible in
20 this invention, by reason of the omission of particulate
frit component. This reduces the cost of materials used and
also contributes to maintaining sharpness of definition in
the product, in that the relatively thin layer of ink tends - -
to blur less around the edges than a thicker layer when the
polymer particles impinge on the ink and are fused over it.
The application of polymeric coatings on glass
articles, including carbonated beverage bottles, is known -
~ per se. Such coatings are useful to protect the glass surface -
; from surface abrasion which otherwise would inevitably occur
30 in manufacturing, labeling, filling, packing, and/or use.
' ~ The polymeric coating prevents scratching of the underlying
gla8s, Which would reduce its strength. Thé coating also
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104184S
provides a d~gr~e of cushion a~d th~rcby softens impact blows
which might otherwlse cause breakage. Moreovcr, when applied
to a glass container for pr~ssurized beverages, the coating
resists scattering of glass fragments if the container is
broken.
In the past, polymeric coatings have be~n applied
over decorations which must first be physically united with
the glass and bonded in place. That procedure was recently
recommended in Ceramic Industry Ma~azlne, September, 1973,
pp. 34-37. In that technique the decoration is not melted
or semi-liquid during fusion of the polymer, and there is no Y
diffusion of the already hardened decoration into the coating
such that a zone or layer of mixed decoration and coating is
~l provided between the decoration and the coating.
; -~ In accordance with this inyention, the coating mater-
;~ ial which is applied over the ink is a finely divided resin
`~ which is fusible at a temperature at which the ink itself is
,~ semi-liquid. By the term "fusible" as used herein in refer-
- ~ ence to the coating, is meant that the coating particles will
heat soften so as to flow together or coalesce to form a smooth,
continuous film. Preferred for this purpose are the so-called
~ ~ ionomer resins which are ionic copolymers of alpha olefins ~
E``i and alpha, beta-ethylenically unsaturated carboxylic acids, --
~3 for example of the type described in patent No. 3,264,272.
' One such ionic copolymer material which is formed from ethylene
and methacrylic acid is available commercially from DuPont
under their trademark "Surlyn", grade AD 5001. This material
in particular has been promoted in the market by reason of
it8 clarity, elasticity and degree of adherence to glass.
tl~ 30 It begin8 to fuse ~within the above meaning) at about 204F.
' It iB not a 801vent for the ink, and does not have an adverse
chemical affect on the lnk. Other hea~-fusible resins which
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1041~45
may be used include without limitation polyethylcne, poly-
vinyl chloride ,and ethylcne vinyl ac~tate resins, in powder
form. Such resins may also be prepared as sprayable emulsions,
for gun application, with an emulsifier and a vehicle. In
this case the resin particles are dispersed in t~e liquid, but
fuse together upon heating, at a temperature at which the ink
is semi-liquid. The resin may also be prcpar~d as a screenable
liquid, for application on a screen dccorating machine.
The polymeric coatings can be applied to glass articles
by a variety of coating techniques. In the coating technique
which is presently preferred, dry fine particle resin is applied
by the electrostatic dry powder spray process. The resin parti-
cles are electrostatically charged oppositely to the glass
article (which acts as a ground) and are projected toward the
article by a relatively gentle air current. The attraction of
opposite charges draws the charged particles to the article,
to which they adhere electrostaticall~. For this purpose the
article is desirably heated to about 150-360F., which improves
the electrical conductivity of the glass. At such temperatures
20 the adhered resin particles will partially but not thoroughly -
fuse together. A final higher heating is necessary to com-
pletely fuse the particles so that they coalesce to form a
smooth, continuous coating which is adherent to the glass
surface.
Another useful method for applying the polymeric -
coating to glass articles is the fluidized bed technique.
; The resin is maintained as an aereated or fluidlzed mass while
~ the article, heated to a temperature sufficient for at least
i ! partial fusion of the resin particles, is moved through the
~ 30 bed so that it becomes coated, then is removed and heated at
" ,~
higher temperature to coalesce or ~et the paxticles and form
a gmooth continuous coating.
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~041845
~ Still another type of coating proc~ss which can ~e
- used is the electrostatic fluidi7.ed bed process. In that
process the resin particles are maintained as a fluidized bed
which is electrostatically charged. When the glass article
to be co~ted (which is grounded) is passe~ through the bed of
'' charged particles, the charge tends to adhere the particles to
~' it. Prior to coating, the glass container is heated for better
conductivity to a point at which the ink ~ecomes mel~ed, but
the heating is not sufficient to effect complete fusion of
, 10 the resin particles on the article, and a final heating at
higher temperature is used to set the plastic as a continuous
, smooth coating.
,` A further description of the invention and its advan-
tages is given in connection with the accompanying drawings,
in which: -
' Figure 1 is an axial section of a narrow neck glass
bottle decorated and polymer coated in accordance with the
'~ invention, with the relative thicknesses of the ink and the -
polymer layers greatly exaggerated for purposes of illustration.
Figure 2 is an enlarged section showing the zone
of interdiffusion of ink and polymer; and '
' ~ Figure 3 is a flow diagram illustrating in abbreviat- :' -ed form the steps of carrying out a method in accordance with
. ~ . .
,~ the invention. ' -
The following examples set forth several alternative ~
~ techniques for carrying out the invention, but they should - -
s, not be taken as representing the only specific processes for '--
~ doing so. '~'-
-, , Example I This example constitutes the presently preferred
30 method of carrying,out the invention for screen decoration of - '
a conventlonal soda-lime glass pop bottle and the~ applying
: a Su~lyncoating. The bottl~s may optionally have first been
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1041~45
given a standar~ p~rol~tic metal oxide (TiO2 or SnO2) coating
and olcfinic lubricity coating, for exampl~ as described in
Patent No. 3,323,889, but this docs not affect the decorating
or coating steps. - -
The decorating color is a non-reactive ~lot melt ~r
thermoplastic ink. It contains a vehicle whicll is a wax or
waxlike material having a melting point of about 120-200F.,
preferably abollt 165F. No volatiles (requiring evaporation
for the ink to solidif~) are present. ~n organic or inorganic
pigment is mixed with the vehicle. No frit is needed and none
is ~cluded. The ink would not be serviceable if not protected
by the polymeric overcoat, being deficient in adherence and
wash resistance. Such inks can be obtained from Drakenfeld
Colors, Hercules Incorporated, Washington, Pa., under their
designation Hot Organics, and from other sources. They are
usually supplled in the form of a solid block which is melted
on a heated screen for application, to establish a soft,
melted-butterlike consistency for application through the screen.
The decorating color is screened onto the container -
, . : ",-,
on a conventional screen decorating machine, fox example, as
manufactured by Carl Strutz & Co., Mars, Pa., Applied Color
Equipment Co., Sapulpa Okla.; and Star Equipment Co., Washington,
.~ Pa. Depending on the particular sllk screening screen printing ~-
~,~'A machine used, the ink may be applied at high rates, e.g., 200
bottles per minute. A further description of hot melt screen
decorating is given in Patent No. 2,731,912. A 200 mesh to 300
me~h screen is desirable, for minimum ink usage and thickness.
The decoration may include a label, trademark, printed informa- -
tion, a design, etc. The squeegeed compositlon will solidify
~ery rapidly after withdrawal of the screen stencil, on a
bottle which i~ es8entially at ambient tempe~ature, e.g., 72F.
The æolidified material is a waxy, æomewhat chalky layer which
. .
cb/ ~ 11 -
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1041t~45
is not united to or bondcd on the glass and can ~asily be
washed or scratch~d off. Nonetheless, no fusion, bonding
or firing step is used; in fact, th~ in~ would not form any
better bond with the glass if it were fired at high temperature.
If the ink decorated but uncoated articles are exposed to a
standard simulated line tester (such as the Amèrican Glass
Research ~buse Line Simulator), the ink is so abraded as to
be completely unacceptable; similarly, if exposed to a rinse
test to simulate the exposure as given by industrial rinsers
(such as the Emhart Rinser), the ink fails. The decoration
? iS not serviceable unless and until coated.
A number of different colors o~ ink can be super-
imposed in quick succession on the article to produce intrica~e
multi-color designs or decorations, using a multiple color
decorating machine.
In accordance with the practice of this inventLon,
the resin is applied directly over the decoration, without
bonding reaction or curing of the ink. Preferably, Surlyn ~ -
resin powder is applied by the electrostatic dry powder spray
process. The bottles are carried on a continuous line by
- chucks whlch grip them at the finish (i.e., the cap or closure
end portion~. The bottles are first carried through an oven
- :
and preheated to a temperature of about 300-360F. (surface
temperature as measured by optical pyrometer). Such heating
improves the electrical conductivity of the bottles so that
. they can better act as grounds in the resin coating step,
which improves the effectiveness of electrostatic coating step. -
The resin is sprayed by a conventional dry powder spray appar-
atus, for example a DeVilbiss Model No. 348, operated at 60
kv DC output. The 8prayed, charged particles adhexe to the
f grounded bottles and partially fuse upon contact.
After removal from the spray apparatus, the adherent
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104~845
p~rticulate resin particles are then set b~ hcating to form a
smooth continuous ~ilm. This is done by passing the bottles
through a continuous oven at a temperature of about 3~0 to
600F., for a period of 3 minutes to 45 seconds. This melts
the ink to a semi-liquid state, however the melted ink does
not "ball up" or run, but remains in place on the glass as
a semi-liquid as the resin particles fuse over it. In the
case of Surlyn, the resin also cures or cross-links as it
j ~ forms the final hardened coating. The bottles are air cooled
to 250, then quenched by a water rinse to about 200F. (this
prevents hazing of the plastic coating).
In the final product, the decorating color is not
united to the glass as a frit-containing ink would be. It
adheres to the glass like a wax, and is further protected on
the glass by the polymeric film over it, which is bonded to
the glass in regions beyond those covered by the decorating
color. The polymer coating adds a depth and brilliance to the
decoration which an uncoated bottle does not display. The
coating is much thinner than the glass wall, and is suitably
. 20 about 5 mils thick, but this is not critical.
If the polymeric coating is carefully removed by
stripping or peeling it from the bottle, it can be seen that -~
an area of ink remains on the bottle as a thin film, while
some of the ink is pulled off with the polymer. It has
. diffused into the polymer, not all the way through the latter, -
but partially into it. A slanting or wedgelike slice through
the film makes apparent the interdiffusion of the ink and
J polymer. This is believed to improve the bond of the polymer
through the ink. The ink is not brittle and retains its thermo-
30 plastic chaxacter, but the coating protects it so that the
. ink i8 not removed or affected by the ordinary use of the
bottle,
,~ ~
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1041845
~, E~ple II In this example th~ polymeric coating is applied
~, ,
', to a screen dccorated bottle by the electrostatic fluidized
bed process.
The scr~en decoration is applied as in Example I.
After the decorating step, the bot~]~s are preheated to about
150-360E~. (surface t~mperature as measured by optical pyro-
: .,
meter).
The bottles are then carried through an electro-
statically charged fluidized bed of the coating resin particles.
The charging apparatus is operated at 30,000 to 90,000 volts
DC. After removal from the bed, the ad~erent particulate resin
particles are,then set by heating to form a smooth continuous
film. The in~ is melted and the adherent particulate material
is fused over it by passing the bottles through an oven at a
peak temperature of 390F., over a three minute period. The ',
coating is complete after cooling.
If the plastic coating is carefully cut and peeled "',
away from the bottle, again it is found that the decorating
color is interdiffused with the polymeric coating. Application
of too thick a decoration can cause difusion through the coat-
ing, which is often detrimental to appearance.
Example III It should be understood that the invention is
not limited to single color decorations. Where two or more '
colors are to be applied, they are applied sequentially as
hot melts, and set up rapidly. In the subsequent resin fusion -
step, all of the colors remelt, but they do not mix undesirably --
or blur during the fusion.
~ t
~ ~ Example IV ~he coating provides maximum protection for the
~, ,~ - ..
~, ' article if it covers substantially the entire surface of the
', , 30 , artiCls excepting the fin~sh portion. However, where protection
~or the article is not a prime consideration, use of the ink , '
plu~ coating on even limited areas can provide a full service-
, ~ , .
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~0~1845
ability of the ink, and a degree of protcction for the ylass
surface, with minimal cost i.ncrease, For example, the coating
may be applied only to a limited area, so as just to cover the
decoration and a small adjaccnt glass surface area. For this
purpose, it is advantageous to use a polymeric coating composi- ..
tion which itself is screenable, so that it can be screened or
over the coating, preferably on the same decorating machine
as that used to apply the ink. This has the advantage of elim-
inating need for separate coating-applying spray or fluidized
bed, or the like. The coating is heated until fused over the
ink. :
While the foregoing examples illustrate various details ~:
of embodiments of the invention in order that others may prac-
: ' tice the same, it will be understood that the invention is -
not limited to utilization of these specific techniques set
~' forth therein, but may be carried out in accordance with other
`~ techniques within the scope of the following claims. -
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