Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02236759 1998-05-05
F~OTECT]:VE ~ND DECO~TIvE-- PL~STI~ l_O~TING SYSTE~
~C~:B~OlJND OF THE INvENT r ON
1. FIELr~ OF THE INvENTION
The present invention is directed to the protection of
frangible objects such a- glassware and ceramics by way of
plastic coating, including the application of deco~ative
finishes 7 and to plastic~ application systems therefor.
2. ~E~CF~IFTION OF THE P~IOR ~T
The app].ication of sur-face coatings to glass products is well
known.
One type of coating comprises a so-called lubricious coating
which can be applied to the e:cterior surface of bottles and
the like, which are subj~ect to mechanical handling. The
lubricious coating diminishes the frictional contact of bottles
against each other, and agaiGst handling machinery, so as to
diminish stres~ and break:age occu~ences during processing. This
is taught in United States Fatent No. ~ b,~55 June 4 19~8.
In United States Patent INo. 4"~5,5~ Dec ~ 7, there is
taught the appplication of a protective plastic coating for
glass soft drir-k: bottles for carbonated beverages~ Such
bottles~ more particularly the larger variety of 16-ounce
capacit~ and greater~ were known to fracture upon inpact and
e:cplode in dangerous fashion, scattering glass frag~ent~.
This problem has dissapeared with the advent of plastic soft
drink bottlQ , which have superceded glass for this area of use
The abovse-mentioned protective plastic coating for glass soft
drink bottles was susceptible to damage from hot water, such
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as is encounter-ed in com~er-cial washing machine~.
There is one field of glass usage where plastic has not
supplan1:ed glass, namely in beverage glasses.
~ue to 1:he visual appeal of glass, hoth in its clarity and its
mass or "heft", and also its relatively low cost and suitability
for machine washing, as compared with the e~-:treme lightness and
higher cost of thin-walled plastic products, drinking "glasses"
of glass have retained a major share of the market. However~
even in a small populatiDn such as that of Canada, there i5 an
annual replacement requirement of some ~l~~million glasses. Much
of this figure represents breakage los~ that occurs in handling,
transportation and use.
The ha2ards associated with the breakage of glass drink-war-e
are such that its use around swimming pools constitutes a very
real sa-Fety ha2ard. In the case of a pool with a vinyl liner,
the inc:ident of broken gLass in the pool generally requires the
complete drainage of the pool, for safe remaval of the glass,
and to c~afeguard the vin~l line~ This action, in turn, may
require professional re-setting of the liner.
In addi-tion to breakages of beverage glasses which occur in
use there is also the hazard of rim chipping, which can lead
to liability claims against the prop~ietor of a har or
restaurant.
SU~ Y OF THE INvENTION
While the present disclosure and its associated research is
particu:Larly directed to the pr-otection of glassware, in the
form of drinking glasses, it will be appr-eciated that, in light
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of wide<,pr-ead other usag~es of glass and ceramics in common with
drin~;in(~ glasses, the present finding6 and teachings appear also
to appl~ ther-eto, par-ticularly in regard to aspects of safety.
The p~esent in~ention provides a method of treating a frangib:Le
object, normally subject to breakage upon impact, comprising the
steps of applying a first protective plastic coating to a majo
surface of the object in protective~ adhering relation
therewi1:h, together with an adhesion modifier to promote the
integri1iy of the object.
The adhesion modifier enhances the bonding of plastic to the
object, and in the case Df drinking glasses and the like, is
necessa~y in order for the object to withstand commercial
dishwashing, and to enable it to retain p~rticles and shards
in case of subsequent break:age.
The adhesion modifier is applied to the object, preferably prior
to the application of the first plastic coating.
The method may include the step of applying an enhancement
mater-ia:L to at least a p,3rtion of a plastic coated surface of
the obiect; most, if not all of these enhancement materials may
be comb:Lned with one or more of the applied layers.
The step of applying enhancement material may comprise
imprint:ing a perceptible patte~n on a plastic coating.
l~he perceptible patte~n may c:omprise printed text.
The method may include the step of applying a protective coat of
substantially clear plastic over the enhanced layer.
The perceptible pattern ~ay be perceptible by touch, such as
raised dots.
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The perceptible pat~ern may be vis~ally per-ceptible.
The metho~i may include the step of applying a protective coat of
substanl:ially clear plastic over the perceptible pattern. The
method may include the step of applying a second protective
plastic coating over at least a portion of the major surface,
the second protective coatin~ bein~ applied prior to the first
coating, and subsequent to the application of the adhesion
modifiel-, to thereby promote the adhesive bond between the
second coating and the object.
The firc~t protective coating may be a high temperature plastic,
resistant to wear within a hot environment, such as a commercial
dishwasher.
The enh1ancement step may comprise the addition of at least one
coloured layer to the object, preferably hy the addition of
enhancement material such as colour to one of the applied
layers.
Thus, there is provided a frangible article, normally subject t~
break:age upon impact, having a first protective plastic coatinq
applied to a major surface of the object together with an
adhesion modifier, in pr~tective, adherinq relation with the
article, to promote the inteyrity of the article. The article
may incLude enhancement ~aterial applied to the article, which
may comprise a perceptible pattern imprin~ed on a plastic
coating.
The enhancement material may be selected from the group
consist:ing of print, col3ur addition, irri.descent mater-ial~
pearles,_ent material, thermally responsive colour chan~ing
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materiaL and infra-red rlesponsive luminescent material.
The art~,cle may include a layer of substantially clear plastic
over-lying the enhancement material in protective relation
th l-h
erewl .
In car-r-~Jing uut the preslent invention, in order to facilitate
the appiication of coatings to smooth glass and ceramic surfaces
and al~o to control adhesion (i.e. peel~ strength, use is made
of an adhesion modifier, to increase peel strength. Enhanced
adhe~ive characteristics for the coating are obtained with the
use of a prime coat of ol~ganofunctional silane.
In partic~lar it is found that silicones, Silane ~-llC~ and
Silane f~ b (trademark~), supplied by OSI, a Division of
Witchco Corp.,a chemical company of Connecticut, used as a
coupling agent greatly enhance the adhesion of a plastic coating
to the gliass parent material, and facilitate application of the
plastic layer.
~est result~ in adhesion enhancement of a parent glass material
were obl:ained by first applying a Silane coating to the parent
glas~ m~aterial, and permitting the coating to dry. Upon then
applying a coating of ethylene acrylic acid copolymer as the
copolymer coating it was found that the wetting and adhesion of
the copolymer coating to the parent material was significantly
enhanced. This is to distinguish from fi~-st blending one of the
Silanes with the coating material.
~ protective coating, in particular a temperatu~e-resistant
coating in the case of dl~inking glasses, was then applied over
the eth~;lene copolymer coating.
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It was found that applying a catalysed cross-lin~;eci
polyuret:hane protective outer coating yielded excellent
dishwasher protection to the ethylene copolymer, in resisting
the heat: and chemical environment of a comme~cial dishwasher.
The croc;s-link:ed polyurethane protective outer coating
possesses a degree of fle:cibility to complement the impact
~esistance of the underlying ethylene copolymer~ while
possessing a long-lastin~ clear and spark:ling appearance,
suitable with d~ink:ing g:Lasses.
The ethylene copolymer intermediate coating serves as a
cushion, in the manner oF a shock:-~bsorber.
It has been found that e~ccellent coating results and good
materia]. utili2ation are obtained using the flow coating
process., as desc~ibed in : Industrial Painting: Frinciples ~~.
P~actice by No~man ~. ~oobal 1991 page 91.
The pla~;tic i5 flow coated at about ~C~ C ciegrees, applying
low-solvent fluid plastic by no2~1e under non-impact flow
conditions, to flow a smooth laye~ over the object being
coated. In the instance of inverted glasses, these may be
rotated to facilitate application of the plastic, with eccess
plastic falling into drip pans, fo~ recycling in the process.
In addit:ion to the application of plastic coatings for
purposes of durability and safety, the p~esent p~ocess also
enables the economic int~oduction to the article, at or afte~
one or other of its coating stages, of decorative enhancement
such as colour, the prov:ision of irridescence or pearlescence,
and the application of a~iditives to provide the characteri~tic
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of therrnally-reponsive colour char-ge.
~lso contemplated is the blending of additives that glow when
illuminated under "black:" i.e. infra-red light.
The inc:Lusion of perceptible mark:ings, su~h as visible printing,
or raised Braille dots for tactile "reading" is greatly
facilitated by the provisiQn of a plastic coating tu receive
versati].e and economical application of such enhancements upon
an otherwise difficult-tD-print glass or other, ceramic surface.
5uch perceptible marking, may be protected by overlying plastic
layers.
It will be understood th~t many of the above recited
techniques and their associated advantages apply to other
frangib:le obiects such as ceramics-ware.
The virl:ual increase in article strength, and reduced
vulnerability to impact damage may permit the adoption of
less bu;Lk:y sections i.e. thinner walls and lighter structure.
Significant cost savings may be achievable due to reduction in
break:age during handling, shipping and ultimate use, and
reduced shipping charges due to weight reduction, as well as
savings in the costs of material per se for the pr-oducts.
The coating of a hollow product in an inverted position, in
a flow coating application process, removes any need to mask:-off
the interior of the hollow vessel being coated, due to the
inverted position, while facilitating recovery of excess coating
materia:L.
Spray applications, as in spray painting, have been used
success-Fully~
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The pre-ent invention thus provides a me~hod of coating an
object~ such as an open-topped glassware vessel~ including
the steps of coating a major surface of the vessel with an
ethylene acrylic acid copolymer over an organofunctional
silicone (Silane) coating, and applying a protective coating of
heat-resistant plastic tlhereover.
~pplication of the ethylene copolymer in a serie~ of set~uentia:L
coatings, with intermediate drying phases to remove the solvent
from tht~ plastic, enables the build-up of a smooth coating to a
desired thic~ness.
~ tough pr-otective plastic over-coating such as the heat
resistar-t plastic can then be applied over the ethylene
copolymer.
The use, where feas3ible, of water as the solvent has many
advantages. In one embodiment four coatings of ethylene acryl:ic
acid copolymer in water 501 ution were applied, with intermediate
drying, to build up an agregate thickness of about 4 1~2 mil
(o.(:)t~45 inches~.
Gr-eater or lesser thic~:nesses may be readily achieved.
The pre1Ferred protective outer coating is selected from the
group consisting of ther~o-setting plastics.
~lso, tilermoplastics having a minimum useful tempe~ature of
at least about 82 C. degrees and 5Ui ted to withstand
commerc.ial and household dishwashing may prove suitable,
particu:larly for ylasses.
The vessel, such as a drin~ing glassl with its applied coating
thereby provides a reinf~rced vessel having glass chip
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retention capability, and the capa~ility to withstand
commercial or- household dishwashinia.
In the case of a thermosetting plastic outer coating, the
final, t:hermosetting coal:ing is cured under predetermined
conditions of time and temper-ature.
The prot:ective outer coal:ing may be selected from a catalysed
acrylic or polyester. ~ 501 vent such as ethyl acetate may be
used, in the cae of flow-coated or sprayed-on application.
Certain ther-~oplastics having a softening point at least
close to the boiling point of water may also prove suitable for
the outer coating, in the case of drin~ing glasses.
The use of polycarbonate as a protective coating is
contemp].ated, particular-ly as an outer coating.
The coat:ings are preferably liquid, in order to utili~e a
flow-coating or spray-on process. For the copolymer cushion
layer water is the preferred solvent.
The vessel is ln a heated condition, for the application of
each of the coatings, at about ~l:) C. degrees.
Provisit~n is usually made for flash-drying off of the solvent
using infra-red panels o~ by ovens, before setting-up and curing
of the coatings occur.
It will be understood that for drin~ing glasses or commestible
dishes all the coating materials need to be "Food and Drug"
approved, and environmentally compatible.
Coating of moulded glass vessels may ta~e place on the vessel
manufac1-uring line, at comparatively low t.:emperatures.
In the case of catalysed outer coatings, these may cure at
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room temperature in some instances~
In acidition to use of the subject laminated coating for
cirin~ing glasses, its use may e tend to include glassware
such as mi~ing bowl 5, punch bowls, and the like where
improved safety is a factor~
One advantage of the pFesent invention is in the potential
use of color~ or other appearance enhancements.
In the case of normal, uncoated glassware, the economics
governing the color appl:ication process necessitate large
scale actiori, in that, wlhen adding color to glass in the
molten stage large produl-tion runs are necessary, and colour
change-overs are highly uneconomical.
~s a consequence the ran,~e of colors is generally very limited.
The sub.iect plastic coating process may include the addition
of color to the glassware, by way of or upon the coating, in one
or- other of its stages, thereby enabling small batches or even
individual color-ation of articles.
The color- may be a component of one or both of the coatings,
so that the scale of a batch is no longer significant.
Consequently, the range of colors can ~e e~tended without
undue ec:onomic penalty.
~ further advantage of the subject process is that a
plastic--coated surface may be readily printed upon, using
catalysed ink:s with conventional printing processes, which
may inc].ude the use of u:Ltra-viole~ or heat curing, to
enhance dish washer and l~ear resistance~ ~n outer plastic
coat mav be applied in protective relation over the printing,
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colour or other selecte~ enhancement decoration .
~ further advantage of tlhis process is that the coatings,
whether single or laminated tan be readily applied to a
wide range of object configurations, enabling the products
to compete with equivalent plastic products.
It is contemplated that a composite vessel in accordance
with thi.s invention may be of lighter construction, having
a thinner wall constFuCtiOn~ capable of 6ustaining usage and
handling stresses. This~ for drin~ing glasses, can afford
very real savings in terms of hot water and drying requiremer7ts.
In some circumstance6 adhesion mod:ification may be desired 7
to r-educe to a selected ~egree the peel strength of a plastic
film applied to a glass object, us:ing an adhesion modifier
selected from polyethylene glycol and magnesium oside, along
the lines taught in the above-mentioned U~S.patent
No 4~:36'S,5qC3. However, adhesion enhar-cement as taught above i3
the pre~Ferred mode for- pl~otecting drinking glasses, the above
identif:ied prior art method having been found to be inadequate
in regard to its use with articles that are subject to
dishwasher use.
Testing evaluation of thle subject glasses coated in accordance
with the present inventic3n was carried out using a pendulum
impact test. With a test specimen glass i.mmoveably mounted upon
a test stand, a steel ball, positioned to impact the glass at
its more vulnerable upper portion, is released to swing through
a standard, predetermined arc, to impact the glass.
The conditions of ball weight, diameter, and7 imp~ct velocity
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were se].ected to provide a standardized test such
that in the case of unprl3tected glasses taken at random
from a standard batch of glasses, two out of ten non-coated
glasses survived the test unbro~en~
In the i.nstance of glasses of the same batch, but protectively
coated i.n accordance with the present invention, the brea~age
surviva,L rate was eight out of ten so tested, giving a factor- of
two and a half to th~ee of impr-oved break:age resistance.
The tes1- stand incorporates a heavy base carrying a rigid
mast. f~ cross bar- adjustably secured to the mast has a
pendulum cord secured th,ereto to which a steel ball of a
given weight is secured. The cross bar is adjusted in
accordance with the length of the cord selected for that
type of glass, and in accordance with the height of the
glasses being tested, such that impact of the ball will
ta~:e place against the vulnerab].e upper portion of the
glass, when supported upon the base.
For each test the ball i 13 released from d predetermined
measured height, with the cord just taut, for the ball to swing
arcuate3.y down and directly impact the ~lass being tested.
In orde~ to calibrate the test apparatus f or a given batch
of glasses, the length of the cord and the drop height are
selecteli, with corresponiing adju~tment to the height of the
cross-bar on the mast, in order to achieve a measurable high
rate of brea~;age such as ~C3~o of the virgin (untreated~ glasses.
The treated glasses are then also ~ested under precisely the
same conditions, enabling a statistical measurement of the
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improvemen~ in durability to be c~b~ained.
It i5 noteworthy that, in the destruction of the untreated
"virgin" glasses, when impacted by the ball they literally
e~plocieci into shards and fragments, being widely dispersed. In
contrast:, the coated glas6es fractured in an entirely different
mode. E~ven when glass pieces brok;e free from the protective
coating they were not si~3nificantly dispersed, but fell in close
pro~imi1:y to the point oF destruction.
It appears that the protective coa~ing functions first to
cushion the impact, to initially impede breakage of the c3lass.
Then, when failure occurs, the detachment of the glass pieces i5
impeded by the plastic bond, such that the energy of dispersion
of any 1:ree glass particLes and shards is much reduced.
In addil:ion to impact te~ting, the subject coated articles,
specifically, cirink:ing g:Lasses, were subject tu repeated
washin~ cycles in a commercial dishwasher, to establish the
commerci.al suitabili y o-F the coated glass articles.
The fle~ibility of the present process, with its sever-al
options in number and different types of coatings and
appearance enhancements provides a wide range of potential
products, beyonci the range of specific embodiments herein
illustrated.
~ost such products are safety-enhanced by the process.
Use of t:he process for permanant labelling of products, such
as iars, with lettering or Braille characters~ is contemplated.
B~IEF DESOPIPTION OF THE Dfi~WING~
~ertain embodiments of the invention are described by way
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of illustration, without limitation o~ the invention
thereto, other than as set forth in the claims hereof,
reference being made to the accompanying drawings, wherein:
Figure 1 is a view Df a drinking glass coated in accordance
with the present invention;
Figure ~ is a view of a bowl coated with the subject coating;
Figure -~ is a schematic side view of a flow coating instal-
ation for the articles presently illustrated;
Figure 4 is a t.abular summary of the pr-ocess; and,
Figure 5 is a side elevational view af a test stand for impact
te~ting of the illustrated drinking glass articles.
DET~ILED DES~IPTION OF THE INvENTION
Figure 1 shows a drin~:ing glass article l(:~, the outer
s~rface 11 of which is coated with a pr-otective coat 14, in
accordance with the present invention.
Figure ~ shows a decorative bowl 1~, the surface of which has a
protective coat 14 thereon. The coat 14 lends itself to the
application therewith both of color and of printed patterns,
etc.
~eferriny to the proces~ embodiment illustrated in Figure ~,
a moving belt 16 carries a batch of glasses lf~ past eight
work:stations. The work:~tations comprise flowcoating or spray
stations ~ 4, ~6 and ~B, having drier stations ~
and ~4 in interposed relation~ and curing station ~.
l~he dr~ying stations ~f~ 9 ~4 may comprise infra-red panels.
Figure 4 shows the sequence of steps for the illustrated
process of Figure ~.
14
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It will be understood that alternative sequences an~ different
embodiments may be produced, for the purposes of the invention.
In the testing apparatus 41~ of Figure 5 a baseplate 4~ carries a
mast 44, having a cantilever aF-m 46 adiustably secured at 48.
loop 5~ has a cord 5~ secured thereto 9 the cord 5~ car~ying a
metal ball 54.
~djacent the foot of the mast 44 a bracket 58 positions a
glass 1l:~ in secured, supported rPlation upon the baseplate 4~.
The length of the cord 5~ is selected in accordance with an
elected protocul of desired breakage of urltreated glasses, in
order to establish a basis for comparative testing of glasses
treated in accordance with the present invention.
Having determined the desired cord length in order to achieve
the des1red breakage protocol for untreated articles, the
height of the arm 46 upon the mast 44 is set so as to impact
the ball 54 against the upper, most vulnerable portion of the
glass 11:~ being tested.
TEST AFPAPATUS FOfi ~UfiA~ILITY GALIB~TION
With the testing apparatus equipped with a 94-gram steel ball,
it was found that a ~ 5~8 inch effective length of cord,
positioned such that the ball impacted the upper portion of the
test glass, as a durability test, produced a survival
probability of two out of ten for unt~-eated glasses~ i.e. an 8l~%
breakage rate.
TEST 1.
~rinking glasses treated with a Silane ~T.M.~ or~ano-functional
silicone~ were dried and then coated with a ~~mil ~ inch~
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under-coating of ethylene copolymer and a protective high
temperature outer coating of ~:~.5 mil polyurethar-e.
Three out of ten survived the durability ~impact) test,
i.e. a ~,~% brea~age r-ate.
These coated drin~:ing glasses were undamaged after 3(~ machine
dishwashings.
TEST .~
Glasses treated with the Silane ~T.~.) coating and having a
3-mil polyvinyl~utyral coating showed reduced durability on
the dishwasher test, with loss of adhesion of the protective
coating and were considered to have failed the dishwasher
test. ~reah: resistance was also inadequate~
TEST 3
~lasses with a silane coating were given four coatings of
ethylene copolymer, for a total 5 to ~ mil thic~ness, and a
high temperature coat of ~:~.5--mil polyurethane.
Eight out of ten glasses i.e. 8(:~% survived the durability test.
These glasses also survived ~ machine dic;hwashings, undamaged.
In the instances of brea~age under the impact test, high
fragment retention held virtually all the glass fragments.
While greater thic~.:nesses of ethylene copolymer can be applied,
the desired high degree of clarity and spark:le may be adversely
affected
CO~ME~GI~L USE
The method and its products have widespFead application f OF
domestic and commercial products, world-wide.
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