Note: Descriptions are shown in the official language in which they were submitted.
~95~
This invention relates to the formulation of structural
coatings, films and the like. By the invention there is
provided an improved product (and process of producing it),
which product displays increased performance in areas related
to its structural stability. The invention flows from our
discovery that a particular substrate - coated in accordance
with the process hereafter defined and described - is not
merely provided with coating but, in addition, achieves a
dramatic and unexpected improvement in certain functional
properties.
The invention finds application in the structural
reinforcement, restoration and/or refurbishing of vitreous
containers such as bottles of all configurations, types and
sizes (for milk, soft drinks, and alcoholic or other
beverages), drinking vessels, jars, vases - in fact, glass
containers or glass surfaces of any kind and for any purpose.
The invention is also appropriate for the structural
strengthening of other materials such as porcelain and ceramic
ware. Its practical value is thus self-evident.
In one broad aspect, the invention provides a process for
forming a structural coating (as herein defined) on a vitreous,
ceramic or porcelain substrate thereby protecting and
strengthening the substrate comprising the steps of applying a
coating material containing free isocyanate groups to the
substrate and subjecting the thus-coated substrate to treatment
with a drying agent at room temperature, the drying agent being
in vapour-phase and being:
(a) ammonia, an amine or an alkanolamine; or
- 2 -
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(b) a multi-component agent comprising (i) water and (ii)
a further component selected from an amine, alkanolamine or
other hydratable compound.
~ ore specifi~ally, the invention provides a process for
forming a structural coating (as herein defined) on a glass
bottle thereby protecting and strengthening the glass bottle
comprising the steps of applying a one component coating
material containing free isocyanate groups to the surface of
the glass bottle and subjecting the thus-coated bottle to
treatment with a drying agent at room temperature, the drying
agent being:
(a) in vapour-phase and
(b) a multi-component agent comprising water and an amine.
In a further aspect, the invention provides a structural
coating (as herein defined) comprising a coating material
containing free isocyanate groups applied to a vitreous,
ceramic or porcelain substrate and dried thereon at room
temperature by a drying agent in vapour-phase, the drying agent
being:
(a) ammonia, an amine or an alkanolamine; or
(b) a multi-component agent comprising (i) water and ~ii)
a further component selected from an amine, alkanolamine or
other hydratable compound.
In a still further aspect, the invention also provides a
glass bottle the surface of which is protected and strengthened
by a structural coating (as herein defined), the coating
comprising a one component coating material containing free
isocyanate groups applied to the surface of the bottle and
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dried thereon at room temperature ~y a drying agent, the drying
agent being:
(a) in vapour-phase and
(b) a multi-component agent comprising water and an amineO
In the specification, the following is to be understood:-
1. In respect of a structural coating, retentive film orthe like which is to be, or has been, subjected to the process
of the invention - the term "drying" is to be understood as (i)
including within its ambit "curing" and as (ii) indicating that
the coating is either free from "tack", insoluble in solvent,
possessed of an advanced degree of integrity, or able to
withstand reasonable abrasion or pressure without damage. It
will also be appreciated that a dry coating may evidence any or
all of the foregoing ~uaLities.
2. The e~pression "substrate" denotes an article or
article surEace which can be structurally strengthened and/or
stabilised by the structural coating of the invention. The
substrate is vitreous, ceramic or porcelain in nature.
3. The expression "coating material" denotes a material
which, on application to the substrate and treatment with the
drying agent, will contribute to the formation of the
structural coating of the invention. The material contains
isocyanate groups, may be of the one-component type, and may
include solvent(s), additive(s) and/or surfactant(s) as
required. It may be clear, translucent or opaque.
4. The term "structural coating" denotes a coating (such
as an organic coating) which functions to protect, strengthen
and contain (by enveIopment or otherwise) a sabstrate to which
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it is applied. The coating is derived from the coating
material as above defined, and is effective at reduced
thicknesses not previously contemplated, i.e., thicknesses of
the order of 10-20 microns. This is not to say that the
invention is restricted to coatings and coated substrates where
the thickness is of this order fit is not so restricted as
will be evident hereafter). What is simply meant is that the
coating is effective at such reduced thicknesses. The
expression "structural coating" is, for the purposes of this
invention, to be understood as synonymous with "retentive film"
(or the like)~
5. The expression "drying agent" connotes the chemical
compound(s) which effect(s) the curing or drying of the coated
material. It may be sometimes alternatively referred to, in
this text, as a catalytic agent, or simply as a catalyst. The
drying (or catalytic) agent may be ammonia, an amine or an
alkanolamine. In another ~orm of the invention it may be a
multi-component (e.g., two-component) agent comprised of water,
as the first component, together with at least one further
component selected from an amine or alkanolamine or any other
hydratable compound which, in association with the water, will
accelerate the desired pathway. It is believed that the water
and the further component(s) interact, or interreact, to form
an agent of hydrated complex type, which agent is thereby
e~fective in drying the coated material at an accelerated rate
- and, in so doing, in structurally strengthening the substrate
upon which the material has been coated.
It was of course known to coat glass bottles prior to the
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present inventionO However, the previously known coated
bottles have invariably been characterised by coatings of
substantial thicknesses and/or have required heat to carry out
the coating process. Whilst the thus-coated bottles were
reasonably satisfactory performance wise, undue thickness of
coating, coupled with a tendency to falter if conditions of
storage, transport and usage were other than ideal, tended to
make them unattractive to users. In addition, there was
clearly scope for refinement and improvement in the coating
procedures.
It was likewise known to coat certain substrates with
coating vehicles containing curable groups and dry the vehicles
in vapour-phase. However, the known procedures were unrelated
to the areas oE the present invention. The coating of the
herein identified substrates in accordance with the herein
described process had never been contemplated - nor could the
surprising results obtained by the present invention have been
envisaged.
~ s briefly indicated above we have discovered that
particular substrates, coated in accordance with the inventi~n,
achieve a dramatic improvement in certain functional
properties. Specifically, we have discovered that glass
bottles, so coated, not only attain these improved properties
but, unexpectedly, are able to do so at coating thicknesses not
previously considered possible. ~ glass bottle of, and coated
in accordance with, the invention is thus able to achieve a
higher level o~ user acceptance. In association therewith, the
coatings, being able to be rapidly dried at room temperature,
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can be applied more efficiently and economically than is the
case with thermal application. Still further, the coatings ~n
the present invention are applied as liquid coatings which have
substantial practical advantages over powder form coatings
which also feature prominently in the prior art.
The present status of the glass bottle industry is such
that a uniform level of technology in the art is generally
available to manufacturers on a worldwide basis. Thus the same
techniques, processes, raw materials, intermediates and the
like are being utilized to produce a similar type of product.
A thin protective, structural coating as provided by this
invention, possessing a high order of abrasion resistance,
enhanced tensile strength and the ability to show excellent
adhesion to a cross section of glass or ceramic substrates,
opens up enormous possibililities for the glass container
industry. When one couples to this the fact that the
formulations herein described may be cured at room temperature
in a matter of minutes, it will be realised that the invention
provides a dramatic advance - capable of industrial
implementation on a major scale - in the glass bottle industry.
The structural coating once cured adds increased burst
strength to a glass container, lowers the possibility of
surface scoring and, in the e~ent of breakage, retains a
greater percentage of glass fragments within a close proximity
to the point of breakage. A related consequence is that
bottles may be made of thinner glass (and thus lighter in
weight) with resultant economic advantages.
In the preceding description the structural strengthening
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of the substrate has been mentionedO Whilst it is emphasised
that the specification is not to be construed as bound ~o any
particular theory of operation, it is nevertheless believed
that the increase in burst strength of a glass container,
coated in accordance with the invention, may be attributable to
the following:-
(a) the filling, by the liquid coating material, of allsurface cracks or other imperfections whereby, on curing, the
entire container is structurally strengthened; and
(b) the scavenging of water molecules, from such surface
cracks or other imperfections, by the reactive groups contained
in the coating material, thus producing a completely anhydrous
surEace which in turn inhibits the propogation of further
surface imperfections.
The invention will now be described with sequential
reference to (i) preferred sub~generic performance features and
(ii) specific detailed examples. It is to be understood that,
being merely illustrative of the invention, such ens~ling
description is not to be limitatively construed.
The coating is desirably of the one component tor one pot)
type containing free isocyanate groups. The expression "free
isocyanate groups" includes within its ambit potentiall~ free
such groups, the meaning to be conveyed being that the
prepolymer has isocyanate groups which are releasable, or
available for reaction with water molecules or any other
compound possessing active hydrogen sites (for the purpose of
polymer propogation and/or film formation). Compounds
containing free isocyanate groups are to be understood as
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embracing all such compounds.
Accordingly, comprehended thereby are, not only
isocyanates with urethane structure and polyisocyanates, but
also those with polyisocyanurate, biuret, aLlophanate and urea
structu~e.
Particularly preferred isocyanate containing coating
materials are toluene diisocyanate (TDI) prepolymers, xylene
diisocyanate (XDI) prepolymers (hydrogenated and otherwise),
and blends thereof and based thereon. Others include
prepolymers of 4,4'-diisocyanato diphenyl methane !MDI),
trimethyl hexamethylene diisocyanate (T~DI), hexamethylene
diisocyanate tH~DI)~ isophorone diisoc~anate (IPDI) and
appropriate blends thereof.
Certain additives in usually minimal amounts (e.g., trace
quantitles to 2%) may also be preferably used in the
formulation to achieve the optimum levels of adhesion to the
substrate or to modify, as required, the rheological properties
of the coating to facilitate in its mode of application. The
adhesion promotors are typically silane based compositions, in
turn exemplified by ~-glycidoxy propyl trimethoxy silane.
Further additives may include flow promotors/surfactants, wax
emulsions and water scavengers, which are respectively
exemplified by silicone based compositions, polyethylene wax
emulsions and monofunctional isocyanates and molecular sieves.
Further additives may include organo metals and inorganic salts
in turn respectively exemplified by dibutyl tin dilauratel lead
tetrethyl, titanium acetyl acetonate, dimethyl tin dichloride
stannous and zinc octoates and bismuth nitrate and ferric
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chloride.
As indicated above the coatings and coated substrates of
the present invention are effective at reduced thicknesses -
with resultant advantages as indicated. Typically, but not
essentially, the thicknesses may be of the order of 10-20
microns ~e.g., 15 microns). However, depending upon particular
circumstances and requirements, thicker coatings (e.g., of the
order of 40 microns) may be applied. It should also be
understood that coated substrates can be recoated to any
desired thickness.
As indicated, the drying ~or catalytic) agent may be
ammonia, an amine or an alkanolamine. Alternatively it may be
a multi-component agent with the further components as set
forth above. The drying agent effects its treatment in
vapour-phase. Where the agent is a multi-component agent, the
further component may be first complexed with water molecules
as indicated above ~to form an agent of hydrated complex
type). The expression "vapour-phase" denotes that the drying
agent iS ln gaseous, vapour, or any other entrained air-borne
form (e.g., dispersion, fog or aerosol) in which it is
available for reaction. The drying operation does not require
heat being carried out at room temperature.
The expression "amine" includes within its ambit not only
those of simply primary aliphatic monofunctional structure, but
also amines characterised by (i) polyfunctionality and (ii) a
more advanced degree of hydrogen substitution. In the case of
tertiary amines these may be (a) polyfunctional, (b) aromatic,
~c) aliphatic or cycloaliphatic in nature~
-- 10 --
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The amine itself may be widely exemplified. Thus typical
examples are mono compounds such as methylamine, ethylamine,
propylamine, isopropylamine and the numerous isomers of
butylamine and polyfunctional amines such as hydrazine,
ethylene diamine, propylene diamine and diethylene triamine.
Further examples are diethylamine~ triethylamine and
dimethylethanolamine (DMEA), and ditertiary amines such as
N,N,N',N'-tetramethylethylenediamine (T~EDA) and
N,N,N',N',2-pentamethyl-1,2-propanediamine (P~T) - and, indeed,
any combination of such amines, proportioned as required,
whereby advantage may be taken of the synergistic effect of
such a combination.
Particularly preferred drying agents are
dimethylethanolamine (D~EA), N,N,N' ,N'-tetramethyl-
ethylenediamine (TMEDA) and N,N,N',N',-2-pentamethyl-
1,2-propanediamine (P~T).
The expression "vapour-phase" has been defined above.
Where the drying agent is a multi-component agent, attainment
of this phase is desirably achieved by the atomisation of
predetermined quantities of water and a selected said further
component. The concentration levels, of water and the further
component, may be varied in accordance with situational
requirements. For instance, the drying may be carried out at
45~~5~ relative humidity, for example ~5%, at a temperature
within the range 20-30C (e.g., 25C). The concentration
of drying (catalytic) agent may vary in accordance with the
chosen further component. Thus for DMEA, the concentration is
preferably in the range 1203-1800 ppm, for
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example 1400 ppmO For DMI and T~EDA the xespective preferred
ranges are 700-900 ppm (more preferably 800) and 800-l000 ppm
(more preferably 900).
The coating material may be applied to the substrate by
any conventional means ~spraying, dipping, brushing) capable of
applying a film/coating on to a surface uniformly and to
specific wet film thicknesses. Once applied, the coating
material may be treated in accordance with processes previously
developed by us. One such process is described in Canadian
Patent Application No. 490,288. Another process is set
forth in Australian Patent No. 5~6,895.
Initial tests, carried out on glass containers coated in
accordance with the invèntion, indicate that the surface of
such a container has a readily controllable coefficient of
friction. ~urther tests show that the coated glass containers
are better able to withstand the vigorous treatment to which
glass containers are subjected in conventional assemblyline
container-filling and like operations. Thus a coated
container, in a moving assemblyline, is less likely to be
"popped" from its position or jammed through excess friction.
In addition adjoining surfaces of glass containers can be
rubbed together for much longer periods under increased
pressures without suffering adverseIy from dulllng, chipping,
scratching or scoring, such as presently occurs during the
transportation of these articles over long distances~
- 12 -
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In a further test, a one litre bottle, coated with a
structural coating as described herein, was found to display
greatly improved levels of fragment retention when dropped on a
hard surface frorn a height of one metre. All these tests will
be set forth and explained hereafter.
~ he coatings of the invention demonstrate remarkably good
integrity under a diverse range of exposure conditions. They
are completely inert, solvent resistant, and display no change
in characteristics after rigorous cleaning (e.g., 20 commercial
dishwasher cycles). The ability of a coated glass container to
withstand rigorous cleaning will also be demonstrated hereafter.
A further advantage is demonstrated when a ylass
container, coated in accordance with the invention, is
recycled. Because it is possible to volatilize the coating
(e.g., in a melt furnace), uncontaminated glass can once again
be available for moulding. Thus the invention involves no loss
of re-cyclable glass. Nor is it necessary to separate clear
glass from coloured glass.
We now proceed to the specific detailed examples, which
demonstrate both (i) the formation of the protective structural
coating on the substrate, and (ii) the testing of this
protected and strengthened substrate. Where abbreviations
requiring possible explanation are employed, such explanation
is provided. Where ingredient(s) are commonly known by the
trade name(s) under which they are commercially available, the
trade names are given. Otherwise, the terminology is the
standard terminology of the art.
- 13 -
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EXAMPLE 1
. _ _
A clear coating material, for coating glass bottles, was
constituted as follows:-
Component _rts by Weight
Toluene Diisocyanate Prepolymers 56.5
Aromatic Hydrocarbon Solvent 40.0
(a high flash aromatic naptha
commercially available under the trade
mark SOLVESSO 100 )
Silicone Based Flow Promoter 2.0
(product commerclally available
under the trade mark BYK 300)
Silane Based Adhesion Promoter 1.0
(product commercially available
under the trade mark SILA~IE A 187)
Wax Emulsion (polyethylene wax) 0~5
The coating material was sprayed from a conventional
siphon pot spray gun, at an application viscosity of 18 seconds
FORD Cup No. 4, onto a pristine (i~e., newly manufactured~
glass bottle rotating on a turntable within a conventional
spray booth. The coating was applied to the external surface
of the bottle to give a thickness equating to approximately lS
microns dry film.
The bottle was then placed in a drying chamber and
subjected to a gently turbulent air stream (air movement 1.5
metres per second) containing a concentration of D~EA of 1400
ppm at 25C, 65% relative humidity. After exposure to this
treatment for one minute, the chamber was evacuated and fresh
- 14 -
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air was circulated around the chamber for a post-cure period of
three minutes.
The resultant coated bottle exhibits al:L the improved
properties specified heretofore. These will be demonstrated in
ensuing Examples.
EXA~PLE 2
An opaque white coating material, for coating glass
bottles, was constituted as follows:-
Component Parts by Weight
Xylene Diisocyanate Prepolymers 50.0
Titanium Dioxide (pigment) 20.0
Inert Grinding Resin for pigment 5.0
(DURASOL 310; trade mark)
Ester Solvent (CORSOL EEA; trade mark) 23.8
Moisture Scavenger for pigment 1.0
(ADDITIVE TI; trade mark)
Surfactant (BYK 300; trade ~ark) 0.2
The coating ~aterial was sprayed through a conventional
siphon pot spray gun, at an application viscosity of 16 seconds
FORD Cup No. 4, onto a pristine glass bottle rotating on a
turntable within à conventional spray booth. The coating was
applied to the external surface of the bottle to give a
thickness equating to approximately 15 microns dry film.
The bottle was then placed in a drying chamber and
subjected to drying in the manner and under the conditions set
forth in Example 1. The finished product was characterised by
excellent opacity and an attractive gloss finish. In addltion
the coated bottle exhibits all the improved properties
- 15 -
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specified above.
EXA~PLE 3
Introductory:-
Eight pristine glass bottles were removed from a bottlemanufacturer's lehr with only the conventional stannic chloride
hot end coating applied. Eight identical further bottles were
removed from the lehr but, in this instance, a conventional
cold end coating of polyethylene wax had also been applied.
These bottles will be compared in Example 6 hereafter.
The eight unwaxed bottles were placed on a conveyor line
to transport them through a sidedraft spray booth and in front
of an electrostic turbo bell applicator. The applicator
applied a transparent green coating material constituted as
follows:-
_m~onent Parts by Weight
Toluene Disiocyanate Prepolymers 50.0
Aromatic Hydrocarbon Solvent 37.0
(as in Example 1)
Methyl Ethyl Ketone Solvent8.0
Organic Green Dyestuff 1.5
~SAVINYL GREEN G L S; trade mark)
Silicone Based Elow Promoter
(as in Example 1) 2.0
Silane Based Adhesion Promoter 1.0
(as in Example 1)
Wax Emulsion (as in Example 1) 0.5
The coating material was applied via the electrostatic
turbo bell to give a wet film coating equating to approximately
- 16 -
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15 microns dry film. The coated bottles (which had been spun
and which also had metal probes inserted) continued on the
conveyor line through an air curtain and into a permeation
zone. In the zone, controlled conditions of 25C, 65%
relative humidity and 1400 ppm of DMEA ~air movement 1.5 metres
per second) were maintained.
The transport time of the bottles was arranged to give one
minute permeation under these conditions. ~hereafter, the
bottles passed through an air curtain and into a post-cure air
movement for a period of three minutes. When removed from the
conveyorised line the bottles were completely dry, free of
solvent odour and demonstrated the improved properties
specified above.
_XA~PLE 4
An opaque etched amber coloured coating material was
constituted as follows:-
Component Parts by We~ht
Xylene Diisocyanate Prepolymers 25.0
Hydrogenated xylene 25.0
diisocyanate prepolymers
Aromatic Hydrocarbon Solvent 17.0
(as in Example 1)
~ethyl Ethyl Ketone Solvent 10.0
Organic Amber Dyestuff 1.5
(derived from Savinyl dye material)
Silica ~~
Silane Based Adhesion Promoter 1.0
(as in Example 1)
- 17 -
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Wax Emulsion (as in Example 1) 0.5
This coating material was applied in the manner set forth
in Example 2. Drying was carried out as per Example 1. Again,
the thus coated bottles demonstrated the advantageous
properties set forth above.
EXA~PLE 5
.
A clear coating material was constituted as follows:-
Component_ Parts by Weight
Xylene Diisocyanate Prepolymers 28.25
Hydrogenated Xylene Diisocyanate 28.25
Prepolymers
Aromatic Hydrocarbon Solvent 40.00
(as in Example 1)
Silicone Based Flow Promoter 2.00
~as in Example 1)
Silane Based Adhesion Promoter 1.00
(as in Example 1)
Wax Emulsion (as in Example 1) 0.5
The coating material was applied as per Example 1. Inthis instance drying was carried out using P~T at a
concentration of 800 ppm. The other drying conditions
~temperature etc) were as in Example lo The coated bottles
again exhibited the advantages of the invention.
E.~A~PLE 6
The burst strength properties of the two groups of bottles
referred to in Example 3 were compared by subjecting them to
the AGR Ramp Pressure test using an AGR Ramp Pressure Tester.
Before carrying out the test, the bottles were subjected to a
- 18 -
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seven minute run on an AGR Line Simulator. The results are
tabulated below.
Notes:~ 1. AGR is a recognised abbreviation, in the
art, for American Glass Research.
2. An AGR Line Simulator is a standard apparatus
which enables an observer to approximate the
effect upon bottles of the type of treatment
to which bottles are subjected during their
lifetime in normal conveyor-type filling
operations etc. The longer the simulation
time, the more severe the treatment.
3. The ramp pressure test/tester are also well
known in the art. The test is carried out
with the bottles filled with water. The
tester progressively increases pressure with
time until failure (breakage) occurs. The
pressure at failure is recorded.
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TABLE II
.
PR¢SSURE AT E`AILI~RE ( POUNDS PER SQ[lARE INCH~
Bottle1. Tin Chloride2. Tin Chloride % Improvement
Plus P.E. Wax Plus Coating Col. 2 Over
of theCol 1
Invention
1. 291.5 574.497.0
2. 335.0 490.246.3
3. 364.0 ~75.730.7
4. 226.3 575.8154.4
5. 268.3 571.5113.0
6. 332.1 481.5~5.0
7. 277.0 510.584.3
~. 206.0 452.5119.7
AVERAGE 287.5 PSI 516.5PSI 79.6
The bottles of the first column tnot coated in accordance
with the invention) give an average failure pressure of 287.5
psi. However, the second column (bottles coated in accordance
with the invention) shows an average failure pressure of 516.5
psi. This represents a very substantial improvement in
performance and thus clearly demonstrates a dramatic increase
in burst strength.
EXAMPLE 7
Fragment retention: A bottle, coated in accordance with
Example 1 and recoated to give a dry film thickness of 35-~0
microns, was filled with water and released from a height of
1.5 metres so as to land on a steel plate of 6 mm thickness.
The test called for the plate to be set at an angle of 4 to
-- 20 --
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the ground such that the resulting rebound would be directed at
a length of soft carpet. The purpose was to ensure only one
direct impact per dropO
A control bottle (not coated in accordance with the
invention) was similarly filled and tested.
The control bottle disintegrated on impact with total loss
of contents. The bottle of the invention exhibited no
discernible structural breakage.
EXAMPLE 8
Bottles coated in accordance with the invention exhibit
excellent slip characteristics (in the art called lubricity).
This is demonstrated by a standard test in which three bottles
are arranged pyramidally - two below, one above - and tilted
until the top bottle is induced to slide. The results obtained
when the test was applied to three groups of bottles (two
control groups, one group of bottles of the invention) are
tabulated below:-
TABLE III
LUBRICITY/SLIP ANGLE
_ottle TYpeSlip An~le Deqrees
Pristine ~lint Glass30 - 35
Standard Wax Treated Glass 18 - 20
Bottle Coated as per Example 2 - 11 - 13
By appropriate variation, the result with bottles coated
in accordance with the ~nvention can of course be adjusted as
required. The improved characteristics shown by the bottles of
the invention can eliminate the need for stearate or other
lubricating sprays that are currently used to facilitate the
- 21 -
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movement o~ bottles on conveyor filling lines.
EYA~PLE 9
Refurbishing : Three groups of unblemished 750 mlbottles, six in each group, were set up as follows:
Group A were subjected to no preliminary kreatment (these
are designated as standard bottles~. Group B were provided
with a 25 cm scratch, made with a glass cutter, midway between
the shoulder and heel of the bottles. Group C were similarly
scratched and were additionally coated, to a thickness
equivalent to 30 microns dry film, with the coating of Example
5.
The bottles were then subjected to the AGR ramp pressure
test as explained and described in Example 6. The results, in
kg/cm2 are tabulated below:-
STD SCRATCH SCRATCH & COA_
A B C
1. 26.0 8.5 21.8
2. 33.1 26.1 30.5
3. 13.9 14.8 22.0
4. 41.0 14.7 15.9
5. 27.0 2~.1 20.6
6. 33.5 17.2 17.3
Average 29.1 16.9 21.4
The above results demonstrate a substantial improvement ofthe bottles in Column C as compared with the bottles in Column
B. Bottles coated in accordance with the invention were thus
able to significantly approximate their original properties.
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EXAMPLE 10
A batch of bottles coated in accordance with Example 2
(XDI) was treated as follows:-
(a) Immersion in 2% caustic soda at 85C for 15 minutes.
(b) Immersion in 6% caustic soda at 85C for 15 minutes.
No changes in gloss, colour or adhesion were detectedO
This example demonstrates tha-t bottles coated in
accordance with the invention will be able to withstand the
type of vigorous cleaning to which they would be subjected in
ordinary usage. Washing with caustic soda is orthodox practice
in breweries for the cleaning of used beer bottles.
E XAMPLE 11
A batch of bottles coated in accordance with Example 4
(amber glass) was treated as follows:-
(a) 100% brandy immersion (approximately 37% alcohol) forfour hours at 20C.
Results:
( i) No colour change compared to standard.
( ii) No loss in gloss compared to standard.
(iii) No loss in adhesion compared to standard after half
hour recovery.
( iv) No blistering, film degredation or softening.
(b) 100% industrial methylated spirits under watch glass
for four hours at 20C.
Results:-
( i) No colour change compared to standard.
( ii) No loss in gloss compared to standard.
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(iii~ Slight softening of the coating was noticed
initially; recovery was rapid.
This example demonstrates that bottles coated in
accordance with the invention should be satisfactory for the
liquor marketO
EXA~lPLE 12
Scratch resistance and glass strength are directly related
(bottles actually decrease in strength due to abrasion during
handling and transportation). A scratch in the surface of a
bottle creates a weak point and any breakage will commence at
that point. Scratch resistance is measured by rubbing two
bottles together under increasing increments of pressure. The
result is the pressure at which a scratch is noticed on either
of the bottles. The minimum standard ~or bottles is 18 kg,
i.e., at less than 18 kg a bottle is rejected.
A test - the static compression scratch test - was carried
out on (i) two control (prior art) bottles and (ii) two bottles
coated in accordance with Example 5~ In the static compression
scratch test, the two bottles are placed one on top of the
other and a static weight is placed on top of the bottles for
one minute. The surface is then examined for coating removal
and glass scratching.
With the control bottles, scratching appeared in the range
40-60 kg. ~owever t with the bottles coated in accordance with
the invention, no scratches were apparent at maximum equipment
loading of 110 kg.
EXAMPLE 13
In this example, which is related to Example 6, two
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batches, each of six bottles, were subjected to five minutes
exposure on an AGR Line Simulator and then subjected to the AGR
Ramp Pressure test. The bottles of the first batch (13) were
conventionally coated with (i) stannic chloride and (ii) the
wax product known commercially as VALSPEX*. The bottles of
the second batch (C) were coated with (i) stannic chloride and
(ii) in accordance with Example 1. The results are set forth
below:-
SURFACE TRE:AT~lENT
lB) Stannic ~C) Stannic % Improvement
Chloride Chloride (C) over (B)
plus plus
VALSPEX Coating o:E
Example 1
. . . . .. . .. _
Bottle No. P.S.I. P.S.I.
1. 246.25 348.32 41.4
2. 2~17.50 348.32 40.7
3. 230.00 297.19 29.2
4. 197.50 527.28 166.9
5. 236.25 369.09 56.2
6. 237.50 420.23 76.9
_
Total 1395.00 2310.43
Average232.50 385.1 65.6
... . _ _ _ _
NOTE:- Bottle 4 survived the upper limit o~ the test
equipment.
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The results show that the bottles coated in accordance
with the invention achieve a dramatic improvement in burst
strength.
With the coating materials and drying agents widely
variable within the hereinbefore defined parameters, it will be
appreciated that the foregoing examples could be considerably
expanded. However, the examples set forth (which are
representative o~ treatments and tests carried out in the
development of the invention) should be sufficient to clearly
illustrate the invention and the advantages thereof.
In non-limiting summary, the invention thus provides for
the protection and structural strengthening of vitreous and
other substrates. This permits the manufacturer to lower the
mass of his base material while improving its burst strength
and fragment retention characteristics. The coating material
sslay be applied and cured within processing times of short
duration (of the order of five minutes) under room temperature
conditions. It is believed that, by the invention, a
substantive advance in the art has been achieved.
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