Note: Descriptions are shown in the official language in which they were submitted.
" 1~13~3L8~
PEELABLE ADHESIVE STRUCTURE
AND METHOD FOR ITS MANUFACTURE
DESCRIPTION
Technical Field
The invention relates to a peelable adhesive
structure. Specifically, it relates to an adhesive struc-
ture having a plurality of articles, one of which ismetal, bonded together through a composite coating layer.
These plural articles can be peeled at the interfaces of
the plural types of coated layers.
Such adhesive structures, where a plurality of
articles are mutually sealed but can be peeled, have been
utilized in various technical fields, particularly in the
packaging field for containers, container covers and
sealing materials.
Background Art
There is widespread use of products utilized
as sealing materials for crowns and other container
covers. Those products are typically constructed from
sheet metal painted with a surface protective paint and
formed into shapes such as crown seals or cap seals.
The shaped products have packing adhered to their inner
surfaces. For marketing of bottled beverages having
packing used in contests, lotteries, sweepstakes and the
like, a typical marketing technique requires the purchaser ;~
of the bott~led beverage to return a prescribed number of --
packings or return a packing containing a wlnning ticXet
to a designated organization to receive some kind of
prize. In the manufacture of crowns and caps used in such
. . , ~
1~L3~L8~7
marketing techniques, the packing must easily peel from
the crown seal or cap. During manufacture of the crowns
and caps, during transport and during capping of the
container, it is essential that the packing adhere to the
5 crown or cap seals. It is also essential for the crown or
cap seals to have sufficient corrosion resistance against
the contents of the container, some of which have a strong
tendency to corrode, and be able to withstand mechanical
processes like crimping and roll on. Further, printing on
10 packing surfaces cannot directly contact the contents of
the container because such contact is unsanitary. Also,
because the packing is ordinarily applied to inner surfaces
of crown seals or caps in a fluid condition, it is advan-
tageous that the ink layer applied on inner surfaces of
15 crown seals or packs transfer so that the ink layer adheres
to the packing when it is peeled.
Adhesive constructions requiring this type of
peelability are also required for cans furnished with
20 opening mechanisms like a "pop-top" or easy-open construc-
tion. Exemplary of such constructions are those having one
or more openings used to drink the contents of the can.
The openings are provided in a can end element which in-
clude a metal element coated with a surface protective
25 paint, and pieces used for peeling are adhered thereto.
Those pieces comprise an organic resin coated metal foil
or sheet which covers the opening. This easy-open end
requires improved fastenability and-sealability between
the can end element and the peeling piece to preserve the
30 contents of the can. Also, the peeling piece must be
easily released from the can end element without damaging
it when the can is opened.
The present invention provides a peelable
35 adhesive structure useful in marketing techniques. The
3~8~
--3--
structure is corrosion resistant, sanitary and possesses
sufficient structural integrity to withstand mechanical
processes like crimping. The structure provides improved
fastenability and sealability sufficient to preserve the
5 contents of a container, yet this structure permits easy
access to the container.
Disclosure of Invention
In accordance with the present invention,an
adhesive construction is providedincluding a plurality of
articles comprising at least one metal article, adhered by
plural types of coated layers. The plural articles can be
peeled between the plural types of coated layers. The
5 present invention also provides an adhesive construction
in which the plurality of articles are adhered by means of
these coated layers so that they have a peeling strength
between about 0.05 and 5 kg/cm between a first and second
coating layer.
The present invention further provides a container
cover in which packing, particularly packing comprising
polyolefin, is peelably adhered to a crown seal, cap or
other container cover made from a metal base and plural
25 types of coating layers.
An easy-open end is provided which peelably
adheres, through the use of plural types of coating layers,
the peeling piece to the can end element that includes the
30 opening.
.~ ,
Generally, the present invention is directed to
a peelable adhesive structure comprising a plurality of
articles, which includes at least one metal article, bonded
35 together through a composite coating layer, the composite
: ,. . ; :: .:
:: .. . :: ~ :: .:. . . .
. :.:. : . . . : ~ .-. : : :
: : . ~ .
. . . : . . . :
~ ~3~
4--
coating layer comprising adjacent first and second coating
layers, the first coating layer containing vinyl resin, the
second coating layer containing epoxy resin. ~t least one
of the coating layers comprises:
(a) a peeling imparter at a concentration
of between about 50 and 200 parts by weight per
lO0 parts by weight of resin, and
(b) a saturated polyester wetting improver
at a concentration of between about 2 and 50 parts
by weight per lO0 parts by weight of resin.
The plurality of articles have a peeling strength between
5 about 0.05 and 5 kg/cm between the first and the second
coating layers.
Generally, another embodiment of the present
invention is directed to a peelable adhesive structure
20 comprising a plurality of articles, which includes at least
one metal article, bonded together through a composite
coating layer, the composite coating layer comprising
adjacent first and second coating layers, the first coating
layer containing vinyl resin, the second coating layer
25 containing epoxy resin. At least one of the coating layers
comprises:
a hydrocarbon or natural resin having a
softening point less than 180C and having
a concentration between about 50 and 200
parts by weight per lO0 parts by weight of
resin.
The vinyl resin or the epoxy resin is in the form of a
35 continuous phase. The hydrocarbon or natural resin is in
,
:~ , . . : ' , - : :-
~3~3~8~
the form of a dispersed phase. The plurality of articles
has a peeling strength between about 0.05 and 5 kg/cm
between the first and second coatLng layers.
Broadly, the present invention is alsc directed to
a method of manufacturing a peelable adhesive structure
comprising:
(a) preparing a first paint solution
containing vinyl resin and a hydrocarbon or
natural resin having a softening point less
than 180C and having a concentration between
about 50 and 200 parts by weight per lO0 parts
by weight of vinyl resin wherein the hydrocarbon
or natural resin is stably emulsified and dis-
persed in a continuous phase of the vinyl resin,
(b) applying the first paint solution onto
a metal base material to form a first coating layer,
(c) forming a second layer by applying a
second paint solution containing epoxy resin
and polyethylene oxide at a concentration of
between about 0.5 and 90 weight percent of the
epoxy resin over the first coating layer, and
(d) joining a layer of olefin resin to
the second coating layer by melt adhesion or
heat sealing.
Brief Description of Drawings
:
Features of the present invention will be
described in connection with the accompanying drawings in
35 which:
.. . ~ . . . - . : . . -
. . . . : . , . , ,
- . , ,~
.
-,
113`~1B~
Fig. l is a cross-sectional view of the peelable
adhesive structure of the present invention;
Fig. 2 is another cross-sectional view of a crown
5or cap with the present peelable structure;
Fig. 3 is a cross-sectional view of a can cover
with an easy-open mechanism of the present invention; and
Fig. 4 is a cross-sectional view of a sealed
container including the subject peelable structure.
Best Mode For Carrying Out The Invention
Referring to the drawings, Fig. l shows in cross-
section the subject peelable adhesive structure. A surface
or substrate 1 comprising a metal base material is shown
adhered or bonded to a composite coating layer comprising a
first coating layer 2 containing a vinyl resin, onto which
20iS applied a second coating layer 3 containing an epoxy
resin. A metal or plastic article 4 is adhered on top of
coating layer 3 by means of composite coating layers 2 and 3.
An important characteristic feature of the present
25adhesive structure is the discovery that when the first
coating layer 2 is constructed from vinyl resin and the
second coating layer 3 is constructed from epoxy resin, and
when a peeling imparter and a saturated polyester wetting
improver are contained in at least one of these two coating
30layers, the adhesive structure will have a peeling strength
of between about 0.05 and 5 kg/cm, preferably between abou~
0.4 and l.5 kg/cm, between the first coating layer 2 and
the second coating layer 3. Such a peeling strength
prevents peeling during ordinary handlir.g as well as under
35substantial impacts, but when required, peeling can be ~ ;~
easily accomplished without using special implements.
~ , :
~:
~3~8~
Another feature of the present invention is the
discovery that when the first coating layer 2 is constructed
from vinyl resin and the secor~d coating layer 3 is construct-
ed from epoxy resin, and at least one of these coatings
5contains hydrocarbon or natural resins which are present in
the form of a dispersed phase, the adhesive structure will
have a peeling strength of between about 0.05 and 5 kg/cm,
preferably between about 0.4 and 1.5 kg/cm, between the
first coating layer 2 and the second coating layer 3. As
0mentioned above, such peeling strengths prevent peeling
during ordinary handling and during substantial impacts,
yet peeling can be easily accomplished.
The fact that the first coating layer 2 is vinyl
5resin and the second coating layer 3 is epoxy resin is
fundamental to the present invention because it increases
the adhesiveness of the coatingstoward adhered parts 1 and
4 and also adjusts the peeling strength of these two coating
interfaces to the range described above. Because either
20layer can contain the peeling imparter so that suitable
peeling can be imparted to the coating interface of both
layers and because either layer can contain the saturated
polyester wetting improver, in relation to the use of the
peeling imparter, it is possible to apply the second coating
25layer on the first coating layer. Additionally, because
either layer can contain a hydrocarbon or natural resin in
the form of a dispersed phase, that is, in an ocean-island
relationship, it is again possible to paint the second
coating layer onto the first coating layer while imparting
30suitable peelability to the coating interface between them.
These are very important discoveries.
Vinyl Resin
3~ The vinyl resin used to form the first coating
layer is preferably a copolymer of ta) vinyl chloride, and
- .
. .............................................................. :
" - - . , ~ - ~ ,,
. - - ~ '
~ , .
'
~3~37
--8--
(b) at least one other ethylenically unsaturated or vinyl
monomer such as vinyl acetate, vinyl alcohol, vinyl acetal,
acrylic acid, methacrylic acid, maleic acid, furaric acid,
itaconic acid, alkyl acrylate ester, alkly methacrylate
5 ester and vinylidene chloride. While the composition of
the vinyl chloride ta) with another vinyl monomer (b) can
be formulated in various concentrations, ordinarily the
mole ratio of a:b is between about: 95:5 and 60:40, prefer-
ably between about 90:lO and 70:30. The molecular weight
10 of the vinyl resin should ordinarily be in the molecular
weight range capable of ~orming film.
Examples of cuitable vinyl resins are vinyl
chloride-vinyl acetate copolymer, vinyl chloride-vinyl
5 acetate copolymer partially acetalated and/or partially
saponified, vinyl chloride-vinyl acetate-maleic-anhydride
copolymer and vinyl chloride-vinylidene chloride-acrylic
acid copolymer.
These vinyl resins can be used alone or in
combination with other resin modifiers. Examples of suit-
able resin modifiers are amino resins such as resol type
phenol resin, xylene-formaldehyde resin, urea resin and
melamine resin, and heat curing resins such as epoxy resin.
The vinyl resin paint used in the present inven- ~;
tion displays especially superior adhesiveness on articles
made from a metal base. Metal bases coated with this paint
have excellent processing and corrosion resistance charac- ~ -
30 teristics. For optimum properties, vinyl resin (A) and at
least one resin modifier selected from phenol resin, amino
resin and epoxy resin (B) should be formulated in concen-
trations where the mole ratio A:B is between about 60:40
and 98:2, preferably between about 70:30 and 90:lO.
~; 35
.
.
~3~187
In addition to the vinyl chloride resins described
above, other vinyl resins can be used which are well known
in the art for the vinyl resin of the present invention,
for example, those vinyl resins used in the paint industry.
~poxy Resin
~ he epoxy resin may be a high molecular weight
compound containing two or more epoxy groups in its molecu-
lQ lar structure and combinations with substances reactive withstarting groups or hardener compounds having low to high
molecular weights which are reactive to epoxy groups.
Ordinarily, epoxy resins obtained by condensation
5 of epichlorhydrin and polyhydric phenols are suitable.
Such epoxy resins have a molecular structure shown by the
following formula:
CH2-CH-CH2to-R-O-CH2-CH-CH2~n
0 OH
-o-R-o-cH2-cH\-~H2 (I)
O
25 where n`is zero or an integer, particularly an integer of
at least about 12. Polycyclic phenols, such as 2,2-bis(4-
hydroxyphenyl)propane ~hisphenol A); 2,2-bis~4-hydroxy-
phenyl) butane (bisphenol B); l,l'-bis (4-hydroxyphenyl)-
ethane, and bis (4-hydroxyphenyl)methane (bisphenol F), ~ -
30 are suitable for use as the dihydric phenol (HO-R-OH).
Bisphenol A is preferred. Precondensates (resols) of
phenols and formaldehyde like polycyclic phenols can also
be used. Preferably, the epoxy resin, used as a resin
ingredient, should have an epox~ equivalent of abou-t 140
35 to about 4,000, and preferably in the range of about 200
to about 2,500. ~ -
~,
r~
: : ': ' : , ' '
- : : .
-
~3 3~37
--10--
Hardener compounds that may be used in combination
with these epoxy resin ingredients are multifunctional
compounds reactive to epoxy groups, for example, polybasic
acids, acid anhydrides, polyamines and polyamides. O-ther
5suitable hardener compounds are ethylene diamine, diethylene
triamine, triethylene tetramine, metaphenylene diamine,
4,4'-diamino-diphenylmethane, 4,4'-diamino-diphenylsulolane,
4,4'-diamino-diphenyl ether, dimer acid polyamide, adipic
acid hydrazide, oxalic acid, anhydride phthalic acid, anhy-
lOdride maleic acid, hexahydrophthalic acid anhydride, pyro-
mellitic acid dianhydride, cyclopentadiene-methyl maleic
acid addition product, dodecyl succinic acid anhydride,
dichlormaleic acid anhydride and chlorendic acid anhydride.
The concentration of the hardener should be between
about 2 and 150 partsby weight per lO0 parts by weight of
the epoxy resin component, and preferably between about 20
and 60 parts by weight. Unless otherwise specified, con-
centration will be expressed in parts by weight.
The epoxy resin component (C) is used as the second
coating layer in the composite with at least one heat curing
resin selected from a resol type phenol-formaldehyde resin,
urea-formaldehyde resin and melamine-formaldehyde resin ~D~.
25Although the concentration ratios of the two resins can
vary over a wide range, the resins should be formulated in
concentrations such that C:D is between about 5:95 and 95:5
and preferably between about 40:60 and 90:lO by weight.
The epoxy resin ingredient (C) and the heat curing resin
30(D) can be used in the mixed state to form the second coat-
ing layer or they can be used in the precondensed state to
form that layer. Coatings comprising this combination have
particularly superior adhesive and process characteristics
to metal or plastics.
The resin composition of the second coating can
~, be further modified with vinyl resin. The above-described
. ~ .~, .
.. . . . ...
' ~: ,: '
: ~. , .: , ,, ~
:' - . ~
: :. ~ - . - . :
.~ . - : - . :
. : . . ` .
-` ~13~87
substances can be widely used as the vinyl resin. They
should be used in concentrations of between about 20 and
~00 parts per 100 parts of epoxy resin ingredient (A) and
preferably between about 100 and 300 parts.
Peeling Imparter
The peeling imparter or resin contained in at
least one of the coating layers is a hydrocarbon or natural
10 resin whose softening point, measured by the ring and ball
method, is less than about 180C and preferably less than
about 120C. Suitable peeling imparters are petroleum
resins, cumarone-indene resins, terpene resins, rosins and
rosin esters.
Known petroleum resins have petroleum saturated
hydrocarbons as their main feedstocks, like cyclopentadiene
or higher olefin hydrocarbons, which typically have from
about 9 to 11 carbon atoms. The resins are obtained by
20 heat polymerization with a catalyst. Any of these resins
can be suitably used as peeling imparters. Xnown cumarone-
indene resins are substances having a comparatively low
degree of polymerization that are polymerized under heat and
with a catalyst using feed-stocks comprising tar fractions
25 whose main ingredients are cumarone and indene. Their
softening point is ~etween 160 and 180C. These resins
can also be used in the present invention. Useful terpene
resins are synthetic or natural polymers o terpene hydro-
carbons. These resins are obtained by polymerizing terpene~
30 oil or nopinene fractions with a catalyst. It is also
possible to use so-called raw rosins, such as gum rosin
and wood rosin, as well as diesters obtained by esterifi-
cation of abietic acid in rosins, for example rosin glycer-
ine ester (ester gum), diethylene glycol abietate, 2-
35 hydrodiethylene glycol abietate, rosin monoethylene glycolester, and rosin pentaerythritol ester.
,
:
~3~37
-12-
Other hydrocarbon polymers can also be used, alone
or in combinations, with the peeling imparters, in the pre-
sent invention as long as they have a comparatively low degree
of polymerization and have softening points within the range
5described above. Low molecular weight polyethylene (poly-
ethylene wax), polypropylene, polystyrene and hydrogen
addition polystyrene can be such polymers.
As saturated polyester wetting improvers, effective
use can be made of: (I) combinations of at least one type
of dibasic acid and at least two types of diols, or (II)
combinations of at least two types of dibasic acids and a-t
least one type of diol, that have been condensed to give a
substantially linear saturated polyester. In these copoly-
5esters, different ester repeat positions may be randomly
connected or regularly connected. .
The dibasic acid ingredients in these copolyesters
may be dibasic acids described by the formula: -
HOOC-RlCOOH (II)
where Rl is a dibasic hydrocarbon group free of ethylenic
unsaturation and having from about 2 to about 15 carbon
25 atoms, and preferably from 6 to 10 carbon atoms. Suitable
acids are aromatic dibasic acids like terephthalic acid,
isophthalic acid, 2,5-dichlorterephthalic acid, napthalene-l,
5-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, and
diphenylmethane-4-4'-dicarboxylic acid, aliphatic dibasic
30acids, such as succinic acid, adipic acid, suberic acid,
azelaic acid, sebacic acid, decanedicarboxylic acid and dode-
canedicarboxylic acld, or 1,4-cyclohexanedicarboxylic acid.
The diol ingredients may be the diols described
35 by the formula:
t HO-(-R2-O-)n-H (III)
~ '
........ .
. . .
- .
", . . -
87
-13-
where R2 is an aliphatic, alicyclic or aromatic-aliphatic
dibasic hydrocarbon base, and n is an integer e~ual to or
greater than 1. Suitable diols are 1,2-ethanediol, 1,3-pro-
panediol, 1,5-pentanediol, 2,3-butanediol, 1,3-butanediol,
51,2,propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol,
neopentyl glycol, 2-ethyl-2-butyl--1, 3-propanediol, 1,6-
hexanediol, diethylene glycol, triethylene glycol, dipro-
pylene glycol, 1,4-cyclohexanedio~L, o-, m- and p-xylylene
glycol, and hexahydro-p-xylylene glycol.
Regarding the saturated polyester wetting improvers
used in the present invention, it is important that aromatic
dibasic acids comprise at least about 50 mole percent of the
dibasic acid, and preferably about at least 70 mole percent
15 to obtain desired mechanical properties and corrosion
resistance of the coating. Aliphatic dibasic acid and ali-
cyclic dibasic acids can be used as long as these concen-
tration limits are not exceeded. ~imilarly, the diol
ingreaients should comprise at least about 60 mole percent
20and preferably at least about 80 mole percent, alkylene
glycols having about 2 to 4 carbon atoms, such as 1,2-
ethanediol or 1,4-butanediol. It is possible to use
xylylene glycol, alicyclic glycols and poly(di, tri, and
the like) alkylene glycols within these concentration limits.
Polyester wetting improvers suitable for use in
the present invention may contain combinations of tere-
phthalic acid (T) and isophthalic acid (I) as the dibasic
acid ingredient, or combinations of ethylene glycol (E) and
301,4-butanediol (B) as the diol ingredient. The mole ratio
of the terephthalic acid (T) and isophthalic acid (I) can
vary over a broad range. Typical, suitable mole ratios of
tT): (I) are between about 90:10 and 10:90, and preferably
between about 70:30 and 30:70. Also, suitable mole ratios
35for ethylene glycol (E) and 1,4-butanediol (B), (E):(B),
are between about 90:10 and 10:90 and preferably between
about 60:40 and 40:60.
~., i
,
- :
- . . . ~ :
~3~87
-14--
A polyester wettin~ improver especially useful in
the present invention is a linear saturated polyester con-
taining terephthalic acid and isophthalic acid in the mole
ratios for the dibasic acid ingredient, and ethylene glycol
5 and 1,4-butanediol in the mole ratios for the diol lngredient.
Another type of polyester wetting improver especially useful
in the present invention is a linear saturated polyester
that contains, in addition to the aromatic dibasic acid
ingredient, an internal plasticizing dibasic ingredient such
10 as a fatty acid dibasic acid present at between about 1 and
100 moles per 100 moles of the aromatic acid ingredient and
preferably between about 5 and 30 moles. This dibasic ingred-
ient has about 6 to 14 carbon atoms, for example, adipic acid,
sebacic acid and dodecanedicarboxylic acid. Linear aromatic
5polyesters described in the following formula are particular-
ly suitable:
-(-T~E-)-(-T~B-)-t-I~E-)-(-I.B-)-~-s.E-)-(-s.B-)
where T is a terephthalic acid unit, I is an isophthalic
acid unit, S is a sebacic acid unit, E is an ethylene glycol
20unit and B is a 1,4-butanediol unit. These units are select-
ed so that their weights satisfy the conditions noted above.
The polyester wetting improvers of the present
invention can be made by conventional methods, except that
25they must satisfy the above requirements. These polyester
wetting improvers may have molecular weights capable of
forming film,that is, molecular weights of about 5,000 to
about 50,000 and preferably about 10,000 to about 30,000.
In the subject invention, it is particularly
important that the linear saturated polyester is used as
.~
the wetting improver. Specifically when the epoxy resin
paint is furnished directly on the coating o vinyl resin
that contains the peeling imparter, the epoxy resin paint
35will be repelled from the vinyl resin coating; and it will
. ~
:
:- : :. .: .. .
~3~8~
-15-
be difficult to form a uniform and even coating. Similarly,
this tendency is found when resins other than linear sat-
urated polyesters are contained in the epoxy resin coating,
for example, polyamide, alkyd resin and unsaturated poly-
5ester. Surprisingly, when the polyester wetting improver iscontained in the epoxy resin paint or vinyl resin paint
there will be an unexpected improvement in the wetting
properties at the interface between the two-resin paints.
Thus, it is possible to form uniform and even coatings.
Blending
In the present invention, the peeling imparters
alone or in combination with the polyester wetting improvers
are contained in one or both of the first or second coating
layers.
It is also important that the peeling imparters
be blended in amounts between about 50 and 200 parts, pre-
20ferably, between about 100 and 200 parts, per 100 parts ofvinyl chloride resin or epoxy resin. When lower concentra-
tions are used, there is no peeling effect between the two
coating layers. When high concentrations are used, defects,
such as uneven coating and orange-peel texture occurs, which
25makes manufacture of the present adhesive structure diffi-
cult. Also, when these concentration ranges are exceeded,
the processability of the metal bases on which the coatings
are applied becomes poor, the coatings become brittle, dust
increases, and cracking occurs.
It is also important that the polyester wetting
improver be blended in amounts of between about 2 and 50 `
parts per 100 parts of vinyl chloride resin and preferably
between about 10 and 30 parts. When lower concentrations
~35are used, there is no wetting improvement effect between
the two coating layers, and the defects described above will
also occur. When used in concentrations greater than those
indicated above, depending on the types of resin in the com-
bination, the mutual solubility of the resins decreases or
5 the solution becomes impossible leading to poor properties
in the coating. Even if the resins are mutually soluble,
the adhesive strength of the two resin layers will be too
great so that peeling is difficult.
In the present invention, it is preferred that the
blend amounts be set so that the peeling strength between the
two coating layers is 0.4 to l.5 kg/cm. ~ost favorable
results are achieved when the amounts are set so that the
peeling imparter is about 150 parts and the polyester wetting
5 improver is about 20 parts.
In the present invention, is is particularly de-
sirable that the vinyl resin paint contain a peeling imparter
like petroleum resins or a combination of the peeling im-
20 parter and unsaturated polyester wetting improver. Thisenhances mutual solubility between resins, wetting improve-
ment effects and peeling improvement effects.
Adhesive Structure
The adhesive structure of the present invention
can have any desired arrangement and combination as long as
it comprises multilayer coating composite having a plurality
of articles containing the described adjacent first and
30 second coating layers.
,
It is generally preferable that the article to
which the first and second coatings are applied be a metal
base material. That material may be foil or sheet surface
; 35 untreated st~el (black plate), a light metal such as
:: :
- :
-
.
. ~ . ..
~3~L87
aluminum, or surface treated steel or aluminum. Suitable
surface treated steels are steels in foil or sheet form
whose surfaces have undergone chemical treatments such as
phosphoric acid treatment, chromic acid treatment, and phos-
5 phoric acid-chromic acid treatment, electrolytic treatments
such as electrolytic chromic acid treatment and electric
tin plating treatment, or melt plating treatments such as
hot dip tin plating treatment. E~emplary sur~ace treated
aluminums are aluminums in foil or sheet form that have
10 undergone treatments like anodic oxidation treatment and
chromic acid treatment. Articles comprising these metals
can be containers such as crown seals or cap seals, can
covers or metal containers that are seamless or which are
furnished with side seams.
These metal materials should be treated with a
protective coating layer other than the first coating layer
to s~op corrosion, for example an epoxy-phenol paint or an
epoxy-amino resin paint. Of course, this protective coating
20 must form a firm adhesion, whose peeling strength is greater
than the peeling strength of the first coating layer and the
second coating layer, between the metal base material and
the first coating layer.
The second article which is adhered to the first
article by means of the first and second coating layers can
be a film, sheet or other formed products made from various
plas,ics or rubber, or various kinds of paper or composite
products, to which the metal base substance has been added.
30For example, plastics that can be used are polyolefins such
as low, medium or high density polyethylene, polypropylene,
polypentene-l, poly-4-methylpentene-l, ethylene-propylene
copolymer ethylene-vinyl acetate copolymer and ionomer,
various types of polyamides such as nylon-6, nylon-6,6,
35nylon-6,lO and nylon-12, poIyesters such as polyethylene-
., .
. :: .,
- : - .. .... .
~3g~
-18-
terephthalate and polybutyleneterephthalate, polycarbonates,
acrylonitrile copolymer such as h:igh nitrile resin and other
acrylic resins. Film made from these plastics may be un-
stretched or stretched biaxially. Suitable synthetic
5 rubbers are styrene-butadiene rubber, nitrile-butadiene
rubber, ethylene-propylene rubber,, ehtylene-propylene-
diene rubber, butyl rubber, stereo rubber and polyisobutyl-
ene rubber. It is also possible to use blends of at least
one of the plastics with at least one of the synthetic
10 rubbers. The plastic materials can also be surface treated
by corona discharge treatment or ozone treatment in order
to increase their adhesiveness on the coatings. The
articles can be used in the subject adhesive structure as
formed products such as packings.
The second article can comprise a composite
utilizing the various types of materials described above.
For example, the second article can be a laminate of metal
foil such as aluminum, provided with a film of polyolefin
20 on one surface as a heat sealing layer and with paper or
film having a higher melting point than the polyolefin
film on the other surface.
Any known protective coating layer or undercoating
25 layer can be applied between the second article and the
second coating layer. Of course, such protective coating
layers must adhere with a peeling strength between the
second article and the first coating layer greater than the
peeling strength between the first coating layer and the
30 second coating layer.
Consequently, the coating layers of the adhesive
structure are not restricted to a particular number of
coating layers, as long as the first coating layer and
35 second coating layer are adjacent. Although ordinarily
, ~,
,'`''~'' ~ ~
.
.
: ' ~ ' ~ '`' '' ` '' ' `' '
--19--
unnecessary, multilayer constructions having three, four
or more layers are within the purview of this invention.
Fig. 2 shows an adhesive structure in the form of
5 a crown or cap. A conventional protective paint layer 5 is
applied to the outside surface of crown or cap seal 1. The
seal 1 comprises a metal material such as aluminum tin-
plated steel sheet or tin-free steel (electrolytic chromic
acid treated steel sheet)~ a first coating layer 2, con-
10 taining vinyl resin, applied to the inside surface of seal1, and a second coating layer 3 containing epoxy resin
applied to first coating layer 2. Of course, a peeling
imparter and a saturated polyester wetting improver are
included in at least one of coating layers 2 and 3. A
15 printing ink layer 6, which may indicate an advertisement,
is provided on top of second coating layer 3. Then, a
packing 4 comprising polyolefin or synthetic rubber is
applied on top of second coating layer 3 and printing ink
layer 6. Packing 4 is supplied to the inside of the crown
20 or cap in a molten or semimolten state and formed in the
shape of the packing ~y compression under cooling with a
suitable stamping eIement (not shown). The packing 4 will
adhere to second coating layer 3-and printing ink layer 6.
In this crown or cap seal, first coating layer 2
is firmly joined to cap seal 1 at a peeling strength gen-
erally of at least 2 kg/cm. Second coating layer 3 and
printing ink layer 6 are firmly joined to packing 4 at a
peeling strength generally of at least 0.2 kg/cm. First
30 coated layer 2 and second coated layer 3 are adhered at a
peeling strength of between about 0.05 and 5 kg/cm, so
that packing 4 can be easily peeled from seal 1 between
first coating 2 and second coating 3.
If necessary, ink layer 6 can be printed on first
coated layer 2 in the crown or cap. Specifically, printing
. . `:
-20-
ink layer 6 can be present at the interface between first
coating layer 2 and second coating layer 3.
Another or second embodiment of the present
5 invention, not shown in Fig. 2, is directed to an adhesive
structure also in the form of a crown or cap in which a
conventional protective paint layer 5 is applied to the out-
side surface of a crown or cap seal. That seal comprises a
metal material such as aluminum, tin-plated steel sheet or
10 tin-free steel, a first coating layer 2, containing vinyl
resin and peeling imparter, applied to the inside surface
of seal 1 and a printing ink layer 6, depicting a price
marking, furnished on top of the first coating layer 2.
Then, the second coating, layer 3, containing epoxy resin,
15 is applied over the first coating layer 2 and printing ink
layer 6. Packing 4, comprising, for example, a polyolefin
or synthetic rubber, is furnished over this second coating
layer 3. Packing 4 is supplied to the inside of the crown
or cap in a molten or semimolten state and formed in the
20 shape of the packing by compression under cooling with a
suitable stamping element (not shown). Packing 4 will
adhere to the second coating layer 3. Alternatively,
packing 4 is a preformed disk, inserted inside the seal or
cap and adhered to coating layer 3 by inductive heating.
In this crown or cap seal, first coating layer
2 is firmly joined to crown or cap shell 1 generally with
a peeling strength of at least 2 kg/cm. Second coating
layer 3 is firmly joined to packing 4 at a peeling strength
30 of generally at least 0.2 kg/cm. First coating layer 2
and second coating layer 3 are adhered at a peeling strength
of between about 0.05 and 5 kg/cm. Printing ink layer 6
has a stronger adhesive strength with respect to second
coating layer 3 than to first coating layer 1. Thus, pack-
35 ing 4 together with printing ink layer 6 can be easily
. ~
~,
:
,:
. - - :- . . -
~. -
-
-
-21-
peeled from crown or cap shell 1 between first coating 2
and second coating 3.
Alternatively, printing ink layer 6 can be fur-
5 nished by printing onsecond coating layer 3 in the crown inFig. 2. Specifically, printing ink layer 6 can be located
at the interface between packing 4 and second coating layer
3.
Fig. 3 shows a can cover where the adhesive
structure includes a "pop-top" or easy-open mechanism. Can
cover 1 comprises metal materials, such as aluminum, tin-
plated steel sheet or tin-free steel, provided with opening
7 for pouring the contents of the can or beverage after
5 unsealing opening 8 for inflow or air into the can. Channel
9 is provided around can cover 1 to contain the can body
flange (not shown) and provides a two-layer wrapping.
Conventional protective paint layer 5 is furnished on the
inside surface of can cover 1. This protective paint layer
20 also protects the metal materials from direct exposure at
openings 7 and 8. Part of channel 9 contains a conventional
sealant composition layer 10.
On the outside surface of can cover 1, first
25 coating layer 2 containing vinyl resin and second coating
layer 3 containing epoxy re~sin are successively applied.
At least one of these coating layers contains the peeling
imparter and saturated polyester wetting improver described
above. Regarding the second embodiment, the first coating
30 layer 2 preferably contains the peeling imparter described
above. ~ F
Peeling piece 4, used to opsn the seal, is a
second article comprising a laminate sheet that includes a
35 polyolefin heat seal layer 12 on one side of a metal foil
~L3~7
-22-
ll, such as aluminum, and heat-resistant resin layer 13,
which can comprise polyethylene terephthalate, on the other
side of foil ll~ Peeling piece 4 includes handle 14 on one
end. Heat seal layer of peeling piece 4 faces the surface
5 on the outside layer of the can cover and is disposed to
completely cover can cover openings 7 and 8, thereby per-
mitting the can cover to be heat sealed.
Thus, by grasping handle 14 of peeling piece 4
10 and pulling it outward, the can cover may easily be opened
by causing peeling bet~een first coating layer 2 and second
coating layer 3.
Fig. 4 shows a sealed metal container with a
5 first article or container 1 formed by drawing or stamping
a metal material. Its inside surface is provided with first
coating layer 2 and second coating layer 3. Its outside
surface is provided with surface protective layer 5. The
second article is cover element 4 comprising a laminate
20 including layer 12, capable of being heat sealed on the
surface of one side of metal foil _, and a thermoplastic
resin layer 13 on the other side of foil ll~ Flange 15 is
provided on the periphery of container 1. Cover element
4 is adhered to flange 15 by a heat seal. The container
25 is opening by grasping handle 14 of cover element 4 and
pulling it upward causing peeling at the interface between
first coating 2 and second coating 3.
.
The adhesive structure of the present invention
30 can be joined by melt adhesion of polyolefin on a metal
base material that has been coated with paint. In order
to enhance the adhesive strength of the polyolefin toward
the second coating layer, it is preferred to have poly-
ethylene oxide included in the second coating layer. The
35 polyethylene oxide can have an oxygen content of between
-
.
- :.
.
: : ~:
:
.
~ 3~ 7
-23-
about O.l and lO percent, more suitably between about 0.5
and 5.0 percent and an average molecular weight of about
l,000 to about 50,000, more suitably about 4,000 to about
lO,000. The polyethylene oxide should be used in concen-
5 trations between about 0.5 and 90 weight percent, preferablybetween about l and 30 weight percent, of the epoxy resin.
Method of Making the Adhesive Structure
According to the preserlt invention, the coating
layers on the first article are formed by painting on that
article, which can comprise a metal base material, vinyl
resin or the resin with resin modifier, peeling imparter
and saturated polyester wetting improver in the form of
5 liquids dissolved in suitable solvents. Then, the painted
base material is dried or heated, as re~uired. Although
there are no particular restrictions on the amount of paint
applied, that is, the thickness of the first coating layer,
suitable thickness ranges for solid fractions are about 0.5
20 to about lO0 mg/m2 and particularly 3 to 50 mg/m2. Such
thickness ranges will protect the base material and provide
a suitable sealing.
The solvent used will vary depending on the
25 ingredients contained in the first coating. Suitable sol-
vents are ketones such as methyl ethyl ketone (MEK) and
methyl isobutyl ketone (MIBK), cyclic ethers such as tetra-
hydrofurane (THF) and dioxane, alcohols such as various
Cellosolves, isophorone, and diacetone alcohols, halo-
30 genated hydrocarbon solvents such as chloroform, alicyclicsolvents such as cyclohexane, and aromatic solvents such
as benzene, toluene, and xylene, used along or in combi-
nation. Although there are no particular restrictions
on the concentration of solid fraction in the paint
35 solution, lO to 70 percent, particularly 2 to 50 percent,
provided workable solutions.
- :
- ., : :
- 24 ~
Annealing conditions for the paint can be varied in different ways.
Generally, annealing should be done at temperatures of 90 to 240C. and for
10 to 30 minutes.
Regarding the second em~odiment, the vinyl resin in the first coating
layer and the epoxy resin in the second coating layer are present in the form
of continuous phases. The hydrocarbon or natural resin of the peeling impar-
ter, contained in these coating layers, is present in the form of a dispersed
phase inside the continuous phases. This feature is very important for im-
parting suitable peelability between the first coating phase and the second
coating phase while imparting the necessary wetting properties for painting
between the two phases.
Specifically, when a peeling imparter, comprising hydrocarbon or
natural resin, is present in the form of a continlous phase at the in~erface
of the tw~ coatings or in that vicinity, the adhesive strength between the
two coatings becomes low. Also, there is excessive nonuniformity in the
peeling strength. Consequently, adhesive structures of this type result in
separation at the interface between the two coatings before the two are pulled
apart and differences in peelability among individual product items.
When a peeling imparter, such as a hydrocarbon resin, is present in
the form of a continuous phase, the wetting properties between the tw~ coating
layers become very poor. As shown in Japanese Patent Application 51-145196,
filed December 4, 1976 by Kozo Yoshizaki and published June 24, 1978, it is
difficult to distribute one paint on a layer of another in a uniform manner
unless a special saturated polyester wetting improver is used.
In this regard, when hydrocarbon or natural resin is present as a
peeling imparter in the form of a dispersed ;
:
.. . ~ - , ~ .
'' -, . - .. :.. :. :'. . . ~ . :. ' :. , .
3~
phase in either of at least one of the vinyl resin coating
or the epoxy resin coating, it is possible to have a degree
of adhesion between the two coating layers such that they
will not peel under ordinary use and processing. Yet, they
5 will readily peel when pulled apart. Thus, it becomes
possible to significantly lower adhesive strength straggling
to significantly improve wetting properties betweenthe two
coating layers and even if a special wetting improver is
not used, to easily and uniformly distribute one coating
10 layer on the other coating layer.
In this second embodiment, the dispersed phase of
the hydrocarbon or natural resin has particles whose dia-
meters will be less than about lO0 microns, particularly
15 less than about 20 microns and preferably less than about 5
microns. This is important to achieving a suitable combi-
nation of peelability and wettability properties. This
importance will be readily understood by referring to the
results in Table IX in Example IX.
For the hydrocar~on or natural resin to be present
in the form of a dispersed phase in the coatings, it is
important that those resins be present in a stable, finely
dispersed state in the paint solution, and that this dis-
25 persed state be maintained until the coatings have beendried or hardened.
Specifically regarding the second embodiment, a
first coating solution contains vinyl resin and hydrocarbon
30or natural resin having a softening point of less than
about 180C in an amount between about 50 and 200 parts by
weight per lO0 parts by weight of the vinyl resin. The
hydrocarbon or natural resin is stably dispersed by emulsi-
fying in the continuous phase of the said vinyl resin. In
35 dispersed form, the palnt solution has the visual appearance
,
.: .
,.. . . . ; . ..... . ~ ~ . . ...
~::IL3~
-26-
of a stabilized white suspension. In order to obtain such
paint solutions, suitable solvents must be selected relative
to the type of resin used, and suitable dispersion means
must be selected. The selection of these solvents will
5 vary depending on the type of resin, and will be apparent
to those skilled in the art having the benefit of the
present disclosure before them.
When vinyl resin and hydrocarbon or natural resin
10 are dissolved in a solvent (a) that dissolves both of them,
for example, an aromatic solvent such as benzene, toluene
or xylene, phase separation occurs with the vinyl resin at
the bottom layer and the hydrocarbon or natural resin in
the top layer. When a solvent (b), which readily dissolves
5 the vinyl resin but does not readily dissolve the hydro-
carbon resin and which is miscible with solvent (a), for
example, a polar solvent such as ethyl acetate, tetrahydro-
furane (THF) and methylisobutylketone (MIBK), is added with
strong shearing agitation, the vinyl resin becomes a con-
20 tinuous phase, and a stable emulsion dispersed paintsolution is formed with the hydrocarbon or natural resin
present as fine particles. This solution in the dispersion
state is particularly suitable regarding the second embodi-
ment of the present invention.
When using paint solutions in this dispersed form,
the concentration of the solid resin component is important,
and should be in the range of between about 15 and 60 per-
cent, preferably between about 25 and 50 percent. The
30 weight ratio of solvent (a) to sol~ent (b) should be between
about 70:30 and 30:70, and preferably between about 40:60 -
and 60:40. Within these ranges, the hydrocarbon and natural
resin can be used in any proportions which will not separate
as a precipitant ~gel).
.
. : . : . -
- . ~
. . - ~
.. . . .. . . .
.
L13~L87
When paint solutions having the dispersed form
described are used, coatings having the dispersed state
stipulated by the present invention will be formed under
ordinary annealing conditions for paint, that is, at 90 to
5 240C and for 10 to 30 minutes.
There are no particular restrictions regarding
the thickness (paint application amount) of the first coat-
ing layer, but the range should be about 0.5 to about 100
10 mg/m2, and preferably about 3 to about 50 mg/m2, as solid
fraction, to protect the metal base and to permit satis-
factory sealing. The remaining description is identical
for both of the embodiments.
Then, the epoxy resin and hardener which can
include a peeling promoter, wetting improver and polyethyl-
ene oxide, are sprayed in the form of a paint solution
dissolved or-dispersed in a suitable solvent. That coating
is then dried to make the second coating layer on top of
20the first coating layer. Although there are no particular
restrictions on the amount of paint applied, that is, the
thickness of the second coating layer, a range of solid
fraction of about 0.5 to about 100 mg/m2, preferably 3 to
50 mg/m2, are suitable for adhesion of the second article
25to the coating layer. The solvent used can be selected
from the organic solvents mentioned above. The concentra-
tion of solid fraction in the paint solution can also be
selected from the ranges described above Eor the first
coating.
When the second article, comprising preformed -
metal foil or sheet or plastic film or sheet, is adhered
by means of the second coating layer, the second article
is attached to the second coating layer when the epoxy resin
35is not hardened or is semi-hardened. Then, the assembly is
'!
~,
~3~L87
-28-
heated as required, and adhesion is completed by hardening
the second coating layer. Here, the heat curing conditions
for the second coating layer will vary depending on the
type of epoxy resin or hardener ingredient contained in
5 the second coating layer and on the type of second article
to be adhered. Suitable conditions can ordinarily be
found within a temperature range of 10 to 250C, partic-
ularly 80 to 200C, and within a curing period of 5 to 60
minutes, particularly 15 to 30 minutes.
When adhering the second article onto the second
coating layer by hot melt adhesion or heat seal, the second
coating layer should be cured before the hot melt adhesion
or heat seal process. Here, the heat curing conditions can
5 be 80 to 200C and 15 to 30 minutes.
Although the first coating layer and then the
second coating layer can be applied to the formed article
in the present invention, the coating layers can be applied
20 to the metal material before it is formed into the container
or its cover. When this latter technique is used, several
production advantages result because it permits better con-
trol over rusting of the metal material and because indi-
vidual articles do not require coating. Moreover, because
25 the first and second coatings of the present inven~ion
have superior processing characteristicsj ordinary process-
ing operations, such as punching, press forming, turning,
draw forming, crimping and stamping, will not damage the
coating or result in a loss of adhesion.
For applying resins such as polyolefins onto
the second coating layer by hot melt adhesion or heat
sealing, suitable temperatures are in the range of 120 to
300C, preferably 150 to 230C, depending on the type o~
35 olefin resin, and suitable melt adhesion periods are short,
on the order of milliseconds.
,
.
, . . .
: . :
' ~ -: : , , ' ' .. . ': ' '
.
. . ~ , . .
. : : ,
.
: , ~ . ' ' . ' ! ~ . ,
~3q~87
-29-
The present in~ention and its advantage~ will be
Yurther illustrated and explained by the following examples.
Example I
First, primer paints we!re prepared using vinyl
resin modified as shown in Table I with varying amounts of
phenol resin, urea resin or epoxy resin in vinyl chloride-
vinyl acetate copolymer, with the petroleum resins being
10 150 parts by weight per 100 parts by weight of the modified
vinyl resin solid fraction. Then, 10 parts by weight of
thermoplastic.saturated polyester were added and an equiva-
lent mixed solution of methylisobutyl Xetone and toluene
was added to bring the total solid fraction concentration
5 to 30 weight percent.
The first primer paints were applied on chemically
treated steel sheet 0.27 mm thick that had previously been
given surface degreasing treatment with Triclene ~termed
20 Tin Free Steel ~TFS], Toyo Kohan lToyo gohan Kaisha, Ltd.]
HAITOPPU). The painted sheet was heated at.190C ~or 10
-minutes in an electric oven to form first primer layers of
50 mg/dm2. Then, the following -three types of paint were ~ -applied in amounts of 50 mg/dm2 as second primers over the :~
25 first primer layers: (13 epoxy-polvamine paint (xylene-
methyl ethyl ketone,*EPIKOTO #1004/EPOMETO B0~1 = 80/20, ~.
equivalent mixed solvent 30 weight percent solution), (~). `.epoxy-phenol paint (EPIKOTO ~1007jPP-3005 = 80/20l.xylene~
butyl Cellosol~e, equivalent mixed solvent 30 weight percent .~
30 solutionl, and (3) epoxy-amino paint (EPIKOTO ~1004/MERAN ::
. ~11 = 80/20, xylene-butyl Cellosolvc eguivalent mixed ~ ! :
. solvent 30 weight percent solution),:and after aluminum
foil 0~05 mm thick had been pasted on top of the paint -
surfaces,.heating was carried out at 190C for 15 minutes
35 to make adhesive structures having aluminum foil-second
primer layer-first primer layer-TFS.
'~
~ * Trade Mbrk
~3q~
-30-
The peeling strengths between the aluminum foil
and the TFS sheet were measured using tension tests for
each of the various types of adhesive structures produced.
Measuring conditions for the tension tests were 180
5 peeling, pulling speed of 50 mm/min, at 20C.
The results are tabulated in Table I~
~0
'
:'
.
:
,. . . ~ :
- .. : , . :
. .
. .
--31--
. ` ~I C
K
~: r~ S
~i3 O O O O O O O O
~ . . _.,
U~ ~: V
U~ H
~1 o ~ ~ m o ~ ~ ~
~: ~ 3 u~
O 1~ o o o o o o o o D ~ lii o V
tr t) ~ ~: O ~
D rl E~ ~0
S ~ c~ a~ ~ o
X1 ~"', .
P~ ~l3 O O o O o o O o ,~
H S 6~ Om o ~;
W '~ 'S Q) .~ ~, o :
~: ~ S Q) ~0
E~ 3 ~I = = = = = = = Q #,~
~ ~3 m ~ o~¢
~v u~ ~ ~ ~ o ~
~ = = = = = = ~ ; z o ~.. .- .
~O O :.~ ~
,~ . ~ ~1 om~rcaHm
Ql ~ ~ ~ I o s . o o m ~ o~ ~ o `- -
`o o ~ ~ o ~ ~
v ~ ~ o ~-~ o
I I I o I o o o V ~ rC 0 E~
~ ~ ~ ~ ~a -rl a.) ~, h o ~ ~ ~
Sl o o o I I o I o ~ H ~ ~ ~ .
O ~1~
~ o ` 'n ~ ~ o ~ 0
-rl ~ ~ o o
~n . 1~ O O O O O - O O O ~1 ~ ~ h Q 1
~v ~ U). ~
~ P; 3 ~ -
z ~ D 1~ m
; ~;
.. . . . . ~
3~
-32-
Peeling at the interface between the first primer
layer and the second primer layer was determined in each
sample by observation with a stereomicroscope.
There was minimal variation in peeling strength
resulting from additional amounts or types of modi ied
resins in the first primer. Regarding film properties, pro-
cessability, particularly turning processability, became
worse, and cracking occurred when the concentration of
10 modified resin exceeded 50 parts based on the vinyl resin.
Example II
Phenol modified vinyl resin (30 weight percent
5 toluene, methyl isobutyl ketone solvent), modified by adding
resol to vinyl chloride-vinyl acetate copolymer (VMCH made
by Union Carbide) in solid fraction proportions of 70:30,
was combined with various hydrocarbon resins in varying
amounts. Polyester resin was added in proportions of lO
20 parts per lO0 parts of vinyl resin, and methyl ethyl ketone,
toluene and butyl Cellosolve equivalent solvents were added
to make a first primer paint whose total solid fraction con-
centration was 30 weight percent-.
The primer was applied to tin plate 0.3 mm thick
whose surface had been degreased. The painted plate was
heated at L90C for lO minutes to form a first primer layer
with a paint film of lO0 mg/dm2. Next, the epoxy-phenol
resin paints used as the second primer in Example I were
30 applied on the first primer layer. Then, a 0.05 mm aluminum
foil, as in Example I, was pasted thereon. The structure
was cured by heating at 190C for lO minutes. An adhesive
structure having aluminum foil-second primer-first primer-
tin plate was produced.
.
~ ~ ..
. .
:
37
Table II gives peeling strength measurements
between the metals of each adhesive structure using the
same conditions as in Example I.
~ 30
: 35
`
' `` ~ :
~3~3~
--3 ~--
l ~ o co o Q
O r~ ~1 IS) O O ~ N O
O) ~ p~ N ~ o O O ~1 0 ~1
P~ tO z n
o
. O O = = = = = = ~:
0 ~
a~) ~ O O
P~ I I I I I I h
,
O O~ ¦ I I I I I I I o I ~
a) ~ I I O
h ~ ~ ~ Z
S~ Z~; ol ~
. ~ ~ ~ o
e O ~O ~ N
O ~ o o o o o
O rn N O O O I I I I ~ O O ~ ~I
. Pl ' '~
~ o
O ~ *
O ~
~: " ~ ~
~ I E ~ E
~ p, U O . ~`~
'
.. ~ . . .. . . _, .. _ ; _ . .. . _
87
Peeling strength declined as the concentration of
hydrocarbon resin increased. Addition of 300 parts of
hydrocarbon resin failed to give a substantially ef~ective
adhesive structure because peeling occurred between the tin
5 plate and aluminum foil from a simple impact. However, below
20 parts of resin, the adhesive strength was too strong, and
the peelable adhesive structure, characteristic of the pre-
sent invention, was not achieved. I~hen saturated polyester
was not added and if the concentration of hydrocarbon resin
10 exceeded 300 parts, wetting of the second primer became
exceedingly poor, and the coated sheet showed a marked
deterioration.
Example III
The No. 2 blend used in Example II (150 parts of
petroleum resin per lO0 parts of phenol modified vinyl,
with lO parts of saturated polyester added, was applied on
TFS sheet as the first primer. That was heat cured at 190C
20 for lO minutes. Epoxy-phenol resin, used in Example II, was
applied as the second primer. Surface treated 0.~ mm thick
polyethylene sheet tPE), polypropylene sheet (PP) and
hardened vinyl chloride sheet (PVC), and paper (P) were
each pasted over the primers. Heat curiny was done at 130C
25 for the paper and at 90C for the other materials to make
four types of adhesive structures: PE-primer-TFS, PP-primer-
TFS, PVC-primer-TFS and paper-primer-TFS.
:
Table III shows the results of measurements of
30 the peeling strengths of each structure.
-
. ~
.,.~ :
~: : .,
~3~3~8~7
-36-
TABLE III
Peeling
No. Construction Strength
1 PE-primer-TFS 0.66
2 PP-primer-TFS 0.5
3 PVC-primer-TFS 0.30
4 Paper-primer-TFS 0.95
In all cases, peeling occurred between the primers
15 in their two layers, notwithstanding differences in the
types of construction materials.
Example IV
First and second primer solutions in the blends
shown in Table IV were applied to a tin plate 0.3 mm thick
that had been given degreasing treatment. Adhesive
structures having aluminum foil-first primer layer-second :
primer layer-tin plate were made by the same process as
25 in Example I. The same peeling tests as in Example I were
performed on each sample. The results are tabulated in ;-
Table IV.
: ~ -
: ` ` : :
: ~
--37--
.C
a)
U~ U ~ U~~9
~
~ o o o
,1
a~
~ ~ . .
~,~ ~ ~1
~ h
.,
Ul o o o o o ~o o ~ ~
O o o ,1 0 ~ O ~1 ~,
U ~ ~3
5~
~ p:; ,1
r~
~)
P~ ~
H *
~r
* *
~ O ~ P; ~ ~ P;~ ~2
U~ o o o C~ o o
O o o CO o o
O
S~
Q)
.~ U U t).
P~ ~ ~ ~ *
~ C) O C~ *
'E4
.~ :
.
~:
:
~ ~ .
~3~7
-3~
All blends peeled at suitable strengths regard-
less of whether the petroleum resin and polyester resin
were included in the first primer layer and/or the second
pr~mer layer.
Example V
No. 1 to No. 9 of the ~irst primers used in
Example II were applied to TFS sheet and heat cured. Then,
10 polyethylene oxide dissolved in hot xylene (concentration
1.0, softening point 135C, total oxygen concentration 4.3
percent) was added to the epoxy-phenol resin used in Exam-
ple II up to an amount equal to 10 weight percent of the
entire resin. It was dispersed to make a product where the
15 solid fraction concentration of the entire paint was 30
weight percent. This was applied on the first primer as the
second primer and heat cured at 190C for 15 minutes. Then,
commercial alkyd ink was printed on the second primer layer
of the metal coated sheets, having the two primer layers, by
20 a conventional offset printing method. It was dried to make
printed coated metal sheet of the construction called ink-
primer-TFS.
: . ~
Then, the coated sheet was stamped out using
25 conventional technology, to make crown shells having
printed surfaces on their inner sides.
Then, the low density polyethylene, used in
.
Example III, was passed through a conventional extruder (~
30 20 mm, L/D 10). The molten polyethylene flowed at about 1 ~ -
g per crown ovèr the insides of the crowns. They were
punched with`a~metal plate to apply polyethylene liners to
the crown shells. After cooling, the liners were peeled
from the crown shells. Stamping, turning and other
35 process charact~eri~stics required-fo~ stamping out crowns
and corrosion resistance to outdoor exposure were eval-
uated. The results are compiled in Table V. ~`
. ~
:
: . , ,, , ~ : :.: - :
. .:. - :
.: - ~. - . .- : .... ..
~L~3~7
-39-
TABLE V
.
Sample Corrision
No. Peelability Processability Resistance
X* O O
2 /~ O O
3 O O O
4 O O O
O X X
6 O O O
7 O O O
8 O O O
9 O O O
-~
*Liner unpeelable
When the concentration of petroleum resin was
less than 20 parts by weight, the adhesive strength
20 between the first primer layer and the second primer layer
was strong. As a result, the polyethylene liner could not
be peeled. However, when the concentration exceeded 200
parts by weight, small pieces of film ~dust) were formed
- during crown manufacture. Because liner adhesive strength
25 was low, the polyethylene liners fell off during transport
of the crown~making them impractical. All the other
blends had suitable peeling strengths. Their processabil-
ity and corrosion resistance were good, and the blends had
sufficient capacity for crown sealing. A]so, the second
30 primer layers and the printed articles were transferred to
the polyethylene liner after peeling.
~ .
.. , ~ :
:,
-
. : ; ;
. : , ' - : ' :. .
~3~ 3L87
-40-
Example VI
First primer paints were prepared with vlnyl
5 resin modified as shown in Table VI with phenol resin,
urea resin or epoxy resin in vinyl chloride-vinyl acetate
copolymer, with the petroleum resins being 150 parts by
weight per 100 parts by weight of the modified vinyl resin
solid fraction. Then, a xylene/methylisobutyl ketone
10 mixed solvent in a ratio of 40:30 was added. The mixture
was agitated and heated (60C, 2000 rpm, 15 minutes) to
bring the total solid fraction concentration to 30 weight
percent.
The first primer paints were applied in the
manner described in Example I, however, the thickness of
the aluminum foil was 0.01 mm.
Peeling strengths were measured in the manner
20 and under the conditions described in Example I. Peeling
at the interface between the first and second primer
layers was observed with a stereomicroscope. The results
are tabulated in Table VI. -
.
,
~;
~3C~ 37
--41--
~
V
K e
~; s
~: V V
U~ ~ ~
.
V C ~ O
~ co ~ D o u~ cn o D rl
,y Ul ~ ~ ~ O
S~ ~ o o o o o o o o ~
rC a~ ~; K r~ O
~e D ~ne
rl U~ O
~ S~ o t~ ~ ~ co ~ ~ In ~~ S~ ~
O P~ D u~ Ln ul c3 rl rl
~ ~ ....................... ~ ~ er.
~ ~ ~ O O O O O O O O
~ a~
O ~ eP:~ K ~1
~V ~ ~, ~ O O
~: a) ~ ~ o ~ ~
L~l 10 U) U') ~ O O O ~ ~1 ~ O
o o o o o 3 o4 o rd ~ ~ o
) ~ ~ u~ ~:
P~ Q~ -1~ D r~
~ a)~ m
m
E~ I O Q, ~ ~ ~ ~ ~ O O
~' ~ u~ ~
u~ ~ ~ H Z ` D I
~ ~rl ~ om~ru~m
o ~ p;o~
~ u~ ~ ~o o
I ~ I I o I o o
~i 1~ N .--1 ~1 0 ~ 0 0 =~
(a ~rl I V ~
O . ~ o ~ o
Q V ~ ~
e I I , , O i O O O ~ rl a) Q! 5-, o ~ F~
O ~)1 ~ ~1 ~~I S~ h 5: :5 K Q
~5 ~ O C) ~ ~ ,9 q~ ~
a) sl o o o I Io I o ~1 V ~ ~ ~ t~ ~l : :
~: e p~ e
rl O ~1 r
U~ ~ ~ O ~ X
~ ~ ~ O ~ ~
v -O ~ J Q~ O: O
:C 5 ~ Q`
h ~ o o o o o o o o ¦
~n ~) 5-~ V .
o l ~1 N ~ ~ U)
~ ~
:
L87
-42-
The results were the same as those described in
Example I.
Example V:CI
Phenol modified vinyl resin (30 weight percent
toluene, methyl isobutyl ketone solvent) modified by aading
resol to vinyl chloride-vinyl acetate copolymer (VMCC made
by Union Carbide) in solid fraction proportions of 70:30
10 was combined with various hydrocarbon resins in varying ~ :
amounts. Solvents, such as toluelle THF, were added. This
mixture was agitated in the manner described in Example YI
to obtain a first primer paint with a total solid fraction
concentration of 30 weight percent. -
The primer was applied in the manner descri~ed in
Example II, however, the thickness of the aluminum foil was ~
O.Ol mm. Peeling strength between the metals of each adhesive ~.
structure were measured in the same manner and under the same
20 conditions as in Example I. The results are tabulated in
Table VII.
.
. ;?
- ._
,
35 * Trade Mark ~ :
~A
.. . ............. .. .. . .. - ,~
. . . .. . , , . , ~ . , ,, , . .... ... ~ ;.. .. ~ , .
- 4 3-
~:
~ ~,~
~ ~ e ~ ~ co O ~
~ ~ O ~ ~I CO ~
O h ~ 1~ 1 o o o ~1 o ~1
a) ~ ,Y ~1
Z; 0~
~:
a) ,l o
E~
,ol
O M
o ~1 O
S-l Ul I I I I I I I o 1 5_
~tr;
O 0
,1 O
~: h o V
~ u~ ~ I I I I I I o I I a) ~
1 :~ O O U~ ~1 ~ o
~ 1
H O ~) :~
H t.) 0
~ S~ ~ ~ ~ ~
~3 ~ ~ rl O ~ ~
~ ~ ~; ~ O I I ~ ~ æ
~ I ~
u~
.,,
o
,~ o o o o o
O ~n ~ o o o I I I I .
" ~ O Q p; ~ ~
a) ~ o o a) o
,1 o u~
Z ~
~ ~ :
,~ ~ .. ......
:> o ,~
,~ o = = - - = = = = ~ ~ Q~
,~ ~ o
O ~ IH rl tn
~:
~ ~ o a
a) ~ ~ o a
~ O ~ ~ ~ ~r u7 ~D ~ CO ~ ~ ~rl O
Z `
i~ ~: O ~ ~ E~
U~
:: : ,: : - ,,
.
, ~ : : ` , .
::
- :- :. , , ~. , :: : -
~3~7
-44-
Peeling strength declined as the concentration of
hydrocarbon resin increased. Addition of 300 parts of hydro-
carbon failed to give a substantially effective adhesive
structure, because peeling occurred between the tin plate
5 and aluminum foil from a simple impact. However, below 20
parts of resin, the adhesive strength was too strong, and
the peelable adhesive structure, characteristic of the
present invention, was not achieved.
Example VIII
The No. 2 blend used in Example I ~150 parts of
petroleum resin per lO0 parts of phenol modified vinyl) was
applied on TFS sheet as the first primer. After heat curing
(190C, lO minutes), the epoxyphenol resin used in Example
II was applied as the second primer. Surface treated 0.22
mm thick polyethylene sheet (PE), polypropylene sheet (PP)
and hardened vinyl chloride sheet (PVC), and paper (P) were
each pasted over the primers. Heat curing was done at 130C
20 for the paper and at 90C for the other materials to make
four types of adhesive structures: PE-primer-TFS, PP-
primer-TFS, PVC-primer-TFS and paper-primer-TFS.
Table VIII shows the results of measurements of
25 the peeling strengths of each structure.
TABLE VIII
Peeling
No. Construction Strength
l PE-primer-TFS 0.73
2 PP-primer-TFS 0.54
3 PVC-primer-TFS 0.37
4 Paper-primer-TFS l.Ol
-
.; . - - ~ - : ~, . ..
-, .~
,, . ~ . : '
- ~ , : . . : . : - .,
8'7
-45-
In all cases, peeling occurred between the primers
in their two layers, notwithstanding differences in the
types of construction materials.
Example IX
Petroleum resin was added to the modifiea vinyl
resin used in Example VI at 150 parts by weight per 100 parts
by weight of vinyl resin. Solvent mixtures of SORUBESSO
10 ~100, xylene and ethyl acetate wer~e used with the mixture
ratios varied as shown in Table IX. The total solid frac-
tion concentration was set at 30 weight percent to make the
first primer paints. The vinyl resin, petroleum resin and
mixed solvent were agitated and heated to 60C, using a high
15 speed homogenizer at 3000 rpm for 10 minutes. The resulting -
primers were inspected using a suitable measurement appara-
tus. After measuring the dispersed particle sizes of the
petroleum resin in the primers, they were applied onto tin
plate by the same operations as in Example II. The primers
20 were then cured. Second primers were applied in the same
manner described in Example II, and aluminum foil was
attached to make the construction aluminum foil-second
primer-first-primer-tin plate.
:
Peeling strength betwe~n metals was measured under
the same conditions as in Example I for these constructions.
The results are tabulated in Table IX. Also, the degree of
variation in peeling strenghts was shown using a ~ariation
coefficient. --
- ` _
-
* Trade Mark
': -
-. ~ ~ ' 1
. .
-. . ; : - ~ , . ,
~:~L3~L87
-46-
O ~ ~
o o o o o
~1 O~,l O
~) t) .
~t~
~1 ~ O o ~ Lr o ~1
-1 ~, o o ~i -i o ~1
a) ~).Y 3
O
a) ~ o
~ aJ a
10 ~
~1 ~ ~ ~t ~ I O
O ~
c~ o ~ X
O ~ ~ O U~ ~ O V~ ~
~ ~ O O O
., ~aJ h v
O ~ O (~ O t~ Q, ~ t~
XIJ E~ O S~ O 1:
H~I l;] ~1 ~ Qt ~ Qt C) -IJ
0~ Il~
a~
~ ~,
E~
~ o o o o o o a
~ ~ ~ o ,1
~ a~ ~ 5~
o
,, a~
.,, ~ o o o o o o
u~ ~ ~ ~r ~ ~ ~ a~
25 ~Q X ~ .
~,)
o
~ ,~
a) # ~J
~1 o a
O U~ o o o o o o
u~u~ co ~;r ~`I ~ f~ ''
~1 :.
~t ~ .:
o a)
u~ o '-
h
. (~ .
zo ~ st P-
:
~:;
.
~3~8~
-47-
When the concentration of the solvents was varied,
the dispersed particle diameters of the petroleum resin in
the solutions varied. As a result, there were marked vari-
ations in wetting of the second primer, and variations in
5 the peeling strengths between the metals.
When the concentration c>f ethyl acetate in the
solvent mixture was small, the dispersion solution separated
into layers within a short time after agitation. When the
10 concentration was large, precipitation occurred from the
petroleum resin system, and painting was impossible.
Example X
After forming a base coat layer (epoxyamino paint),
printing, and an overcoat layer (epoxyester paint) on one
side of a TFS surface, which surface comprises the outer
surfaces of crowns, the other surface was painted with
first primers No. 1 to No. 9 used in Example VII. ~hey were
20 heat cured. Then, a commercial alkyd ink was printed and
dried on the first primer layer using a conventional offset
printing method. Polyethylene oxide dissolved in hot xylene
(concentration 1.0, softening point 135C, total oxygen
concentration 4.3 percent) was added to the epoxy-urea resin
25 used in Example VII until it amounted to 20 weight percent of
the total resin. It was dispersed, and the product, whose
solid fraction concentration in the total paint was 30 weight
percent, was painted as a second primer over these partially
printed first primer layers. Heat curing was done at 190C
30 for 15 minutes. Thus, the metal sheet was coated on both
sides and printed.
.~ .
Next, crown shells were formed Erom the coated
sheet with a crown forming press. The size of the shells
35 was that of a Type 5 Crown size (inner diameter 26.6 mm)
in JIS S-9017.
`
, . ' ' , .
; '
, - ; , .. :
, : ~ . , - :
~ 3~87
-~8-
Then, the low density polyethylene used in Example
VIII was passed through a conventional extruder (~ 20 mm,
L/D lO). The extruded molten polyethylene flowed onto the
insides of the crowns at about l g per crown, and was formed
5 into polyethylene liners in the crown shells by punching
with a metal plate.
Then, the liners were peeled from the crown shells.
They were evaluated with respect to their processability
10 during punching and turning required for crown shells and
with respect to their corrosion resistance under outdoor
exposure. The liners were also evaluated for dust generation
using a tumbling test (500 crown shells were placed into a
stainless cylindrical vessel (30 cm inner diameter, 50 cm
15 high), given 2100 revolutions at 70 rpm). Weight differences
were measured before and after the test to find the amount of
dust generated by coating separation. The results are shown
in Table X.
, ,' ' '
. ~ . . .
.~,, .
:
.
:: . . .,. . ~ -
.
- :.
- ~3C~
--49--
e
o
rl
r~ ~ O
~ ~ ~ ~ ~ ,~
o
a
o ~:
X s~ ~,1 O O O O X O O O O
s~ U~
~3 o
C~ ~
E~ ~
rl
U~ O O O O ~ O O O O
a~
U
~o
t4 a)
,4
.,, a)
~ Q,
,~
~ X ~ O O X O O O O ~ .
o a)
:
p~
~ ~ .
O ~ ~ ~ ~r ~ ~D ~ CO
~æ
U~
.... . .
, .... . .
: .
.
::
'-
, , . : :- ' . - ~.
~3`~ 7
-50-
When the concentration of petroleum resin was
less than 20 parts by weight, the adhesive strength between
the first primer layer and the second primer layer was
strong. As a resul-t, the polyethylene liner was impossible
5 to peel. On the other hand, when the concentration of the
resin exceeded 200 parts by weight, there was a large for-
mation of small pieces of film (dust), and because liner
adhesive strength was low, the polyethylene liners fell off
during crown transport rendering them impractical. All the
10 other blends had suitable peeling strengths. Their process-
ability and corrosion resistance were good, and they were
found to have sufficient capacity as crowns for sealing.
Also, the second primerlayers and the printed parts trans-
ferred to the polyethylene liner after peeling.
It is not intended to limit the present invention
to the specific embodiments described above. Other changes
may be made in the peelable adhesive structure specifically
described without departing from the scope and teachings of
20 the present invention. The invention is intended to encom-
pass all other embodiments, alternatives and modifications
consistent with it.
.
:, : . .
- ~: - ~ ~:: . .
