Easily-openable heat seal lid

Disclosed is an easily openable heat seal lid for sealing a vessel proper by forming a heat-sealed portion between the lid and the vessel proper, which comprises a laminate comprising at least an inner face member composed of a thermoplastic resin and a metal foil, wherein scores defining a portion to be opened are formed on the side inner than the portion to be heat-sealed so that the scores extend to the midway of the thickness direction of the metal foil, and said inner face member comprises at least one heat-sealable thermoplastic resin layer having an adhesion strength of at least 800 g/15 mm to the metal foil, a tear strength lower than 3.0 kg and a tensile modulus of at least 300 kg/cm.sup.2. In this heat seal lid, the resin layer can be broken sharply along the scores and opening can be accomplished very easily.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates to an easily-openable heat seal lid. More 
particularly, the present invention relates to a heat seal lid which 
provides a heat seal having a high heat seal strength between a vessel 
proper and the lid and can resist sterilizing conditions, for example, 
retort-sterilizing conditions, and which can easily be opened by breaking 
the lid along a score line formed thereon. 
(2) Description of the Prior Art 
A heat seal lid having a sealing capacity and an easy-open property, for 
example, a so-called peelable seal lid, is known. This peelable seal lid 
comprises a flexible substrate such as a metal foil and a heat-sealant 
layer formed on the substrate. A composition formed by incorporating a 
wax, a tackifier and an elastomer into an olefin resin such as polyolefin, 
in which the seal strength is adjusted to about 1 Kg/15 mm, is ordinarily 
used as the heat sealant. A peelable seal lid of this type is defective in 
that when the content is packed and heat sterilization is carried out, the 
seal reliability of the lid is poor. In Official Notice No. 17 of the 
Welfare Ministry of Japan (enforced on Aug. 1, 1977), it is stipulated 
that a food vessel which is heat-sealed and subjected to heat 
sterilization should have a heat seal strength of at least 2.3 Kg/15 mm. 
A heat seal lid sealed with such a high seal strength is disadvantageous in 
that peeling on the heat seal interface is manually impossible and 
therefore, opening is performed by a tool such as a knife or a can opener. 
As the lid that can easily be opened manually without using any instrument, 
there is known a so-called easy-open can lid. In this can lid, an opening 
portion is defined by scores on a lid formed of an aluminum sheet, a rivet 
is formed on the opening portion and a pull ring is secured by this rivet 
of the opening portion, and this can lid is double-seamed to a flange 
portion of a can body. 
This easy-open can lid can resist heat sterilization under pressure and has 
an excellent easy-open property. However, this can lid is defective in 
that a large quantity of expensive metallic aluminum should be used as the 
material, the processing steps are complicated and troublesome and the 
cost is considerably higher than that of the above-mentioned flexible heat 
seal lid. 
Moreover, vessels to which this easy-open lid can be applied are limited to 
those having a high heat resistance, for example, cans. For example, when 
this easy-open lid is double-seamed to a plastic cup-like vessel formed by 
drawing, it is impossible to form a seal having a high reliability, and 
when the cup-like vessel is subjected to hot packing or retort 
sterilization, since the flange of the cup is softened at high 
temperatures adopted for such treatment, formation of a reliable seal 
becomes more difficult. 
SUMMARY OF THE INVENTION 
It is therefore a primary object of the present invention to provide an 
easily-openable heat seal lid which provides a seal portion having a high 
heat seal strength and can be subjected to a sterilization treatment such 
as retort sterilization. 
Another object of the present invention is to provide an easily-openable 
heat seal lid in which at the time of opening, a laminate sheet can be 
broken smoothly and beautifully along a predetermined opening line. 
Still another object of the present invention is to provide an 
easily-openable heat seal lid which is preferably used for vessels to 
which double seaming is difficult, for example, plastic vessels, aluminum 
foil vessels and paper-plastics-aluminum foil laminated vessels. 
A further object of the present invention is to provide an easily-openable 
heat seal lid in which the amount used of an expensive metal material is 
reduced, the lid-forming operation is simplified and the manufacturing 
cost can be controlled to a relatively low level. 
In accordance with the present invention, there is provided an 
easily-openable heat seal lid for sealing a vessel proper by forming a 
heat-sealed portion between the lid and the vessel proper, which comprises 
a laminate comprising at least an inner face member composed of a 
thermoplastic resin and a metal foil, wherein scores defining a portion to 
be opened are formed on the side inner than the portion to be heat-sealed 
so that the scores extend to the midway of the thickness direction of the 
metal foil, and said inner face member comprises at least one 
heat-sealable thermoplastic resin layer having an adhesion strength of at 
least 800 g/15 mm to the metal foil, a tear strength lower than 3.0 Kg and 
a tensile modulus of at least 300 Kg/cm.sup.2. 
The present invention will now be described in detail with reference to 
embodiments illustrated in the accompanying drawings.

In the drawings, reference numeral 1 represents a heat seal lid and 
reference numeral 1' represents another heat seal lid. Reference numerals 
2 and 3 represent an inner face member composed of a thermoplastic resin 
and a metal foil, respectively, and reference numerals 6 and 6' represent 
a depress-tear top end and a grip portion, respectively. Reference 
numerals 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 and 18 represent a score, 
an opening tab, an adhesive layer, a heat-sealable adhesive layer, a resin 
protecting layer, a vessel proper, a flange or curl portion, a paper 
substrate, an aluminum foil, a polyolefin layer, an inner face member 
composed of a polyolefin and an outer face member composed of a 
polyolefin, respectively. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIGS. 1, 2 and 3, a heat seal lid 1 according to the present 
invention comprises a laminate comprising at least an inner face member 2 
composed of a thermoplastic resin and a metal foil 3. As shown in detail 
in FIG. 3, scores 7 defining a portion 5 to be opened are formed on the 
side inner than a portion 4 to be heat-sealed, so that the scores 7 extend 
to the midway of the thickness direction of the metal foil 3. An opening 
tab 8 having a depress-tear top end 6 on one end and a grip portion 6' on 
the other end is bonded to the outer face of the heat seal lid through an 
adhesive layer 9 at such a positional relation that the depress-tear top 
end 6 is substantially in agreement with the a score 7. 
In the present invention, a resin having specific properties described 
below is used for the inner face member for heat sealing, and this inner 
face member 2 is heat-fusion-bonded to the metal foil 3. This inner face 
member 2 may be either a single layer or a laminate with a layer 10 having 
a heat bondability to a metal. 
It is one of important features of the present invention that for the inner 
face member 2 for heat sealing or both the inner face member 2 and the 
layer 10, a heat-sealable thermoplastic resin film having an adhesion 
strength at least 800 g/15 mm, especially at least 1000 g/15 mm, to the 
metal foil, a tear strength lower than 3.0 Kg, especially 0.005 to 2.0 Kg, 
and a tensile modulus of at least 300 Kg/cm.sup.2, especially 1000 to 
50000 Kg/cm.sup.2, is especially selected and used. 
The present invention has been completed based on the fundamental finding 
that in order to tear a laminate of a resin film and a metal foil 
precisely and smoothly along scores formed on the metal foil, it is 
necessary that a combination of certain specific properties should be 
given to the heat-sealable resin film to be used. 
Polyethylene, especially low density polyethylene, has been used as the 
heat-sealable resin most popularly. When a laminate formed by bonding a 
polyethylene film to a metal foil through a most commonly used adhesive, 
that is, an isocyanate type adhesive, is torn in a certain direction along 
scores, the polyethylene film protrudes the torn edge of the metal foil. 
Namely, it is very difficult to sharply tear the low density polyethylene 
film along scores, and an easy-open effect cannot be attained. It is 
believed that this is due to the fact that delamination, that is, 
interlaminar peeling, is readily caused when the laminate is torn and the 
polyethylene film or the isocyanate adhesive is excessively elongated on 
tearing. 
In the present invention, the requirement that delamination should be 
prevented between the metal foil and resin film when the laminate is torn 
along the scores and the laminate should be torn along the scores is 
satisfied by using a heat-sealable resin having an adhesion strength of at 
least 800 g/15 mm, especially at least 1000 g/15 mm, to the metal foil. 
Furthermore, the heat-sealable resin film that is used in the present 
invention should satisfy two seemingly contradictory requirements, that 
is, a tear strength lower than 3.0 Kg and a tensile modulus of at least 
300 Kg/cm.sup.2. The lower is the tear strength of the film, more easily 
torn is the film. However, whether or not the film is torn beautifully is 
influenced by the tensile modulus, and it has been found that as the 
tensile modulus of the film is higher, the film is torn more beautifully. 
For example, in case of a resin film having a high rubbery elasticity, 
even if the tear strength per se is low, the resin is elongated greatly 
while the resin is being torn, and hence, tearing becomes rather 
difficult. In contrast, in case of a resin film having a high tensile 
modulus, while the resin is being torn, the elongation of the resin film 
is controlled to a low level, and hence, tearing is advanced rather 
easily. 
In case of a resin film having an adhesion strength lower than the above 
critical value to the metal foil, when the laminate is broken along the 
score line, delamination is caused between the resin film and the metal 
foil, and hence, opening by sharp shearing along the score line becomes 
difficult. If the tensile modulus of the resin film is lower than the 
above critical value, the above trouble similarly takes place. 
Furthermore, if the tear strength of the resin film is higher than the 
above critical value, the manual opening operation becomes difficult. 
The heat-sealable resin that is preferably used for attaining the objects 
of the present invention is one that can be heat-bonded to a metal foil, 
and a thermoplastic resin containing carbonyl groups 
##STR1## 
derived from a carboxylic acid, an acid anhydride, a carboxylic acid salt, 
an ester, an amide, a urea compound or a urethane compound at a 
concentration of 1 to 1400, especially 10 to 500, milliequivalents (meq) 
per 100 g of the polymer, which has the above-mentioned physical 
properties, is advantageously used in the present invention. 
Such heat-sealable, carbonyl group-containing thermoplastic resins include 
various homopolyesters, copolyesters, homopolyamides, copolyamides, 
copolycarbonates and copolymers of olefins with carbonyl group-containing 
monomers. For example, there can be used polymers described below, so far 
as they have the above-mentioned physical properties. 
(a) Polyesters comprising recurring units represented by the following 
general formula: 
##STR2## 
wherein R.sub.1 stands for an alkylene group having 2 to 6 carbon atoms 
and R.sub.2 stands for an alkylene or arylene group having 2 to 24 carbon 
atoms. 
For example, there can be mentioned homopolyesters comprising one dibasic 
acid component selected from terephthalic acid, isophthalic acid, adipic 
acid, sebacic acid, maleic acid and fumaric acid and at glycol component 
selected from ethylene glycol, tetramethylene glycol, propylene glycol, 
diethylene glycol and triethylene glycol, and copolyesters comprising a 
plurality of monomers as one or both of the dibasic acid and glycol 
components. High-molecular-weight copolyesters comprising terephthalic 
acid units and other dibasic acid units as the dibasic acid component and 
tetramethylene glycol units as the diol component and 
high-molecular-weight copolyesters comprising benzene-dicarboxylic acid 
units as the dibasic acid component and tetramethylene glycol units and 
other diol units are especially preferred. As such high-molecular-weight 
copolyester, there can be mentioned polytetramethylene 
terephthalate/isophthalate, polytetramethylene 
terephthalate/isophthalate/adipate, polytetramethylene 
terephthalate/sebacate, polytetramethylene/ethylene terephthalate, 
polytetramethylene/polyoxyethylene terephthalate and 
polytetramethylene/polyoxyethylene terephthalate/isophthalate. 
These copolyesters may be used singly or in the form of a blend of two or 
more of them. Furthermore, these copolyesters may be used in the form of a 
blend with a polyolefin type resin such as polyethylene, polypropylene, an 
ionomer, an ethylene-vinyl acetate copolymer or modified polypropylene. 
(b) Polyamides having recurring units represented by the following general 
formula: 
##STR3## 
wherein n is a number of from 3 to 13 and n is a number of from 4 to 11. 
For example, there can be mentioned, poly-.omega.-aminocaproic acid, 
poly-.omega.-aminoheptanoic acid, poly-.omega.-aminocaprylic acid, 
poly-.omega.-aminopelargonic acid, poly-.omega.-aminodecanoic acid, 
poly-.omega.-aminoundecanoic acid, poly-.omega.-aminotridecanoic acid, 
polyhexamethylene adipamide, polyhexamethylene sebacamide, 
polyhexamethylene dodecamide, polyhexamethylene tridecamide, 
polydecamethylene adipamide, polydecamethylene sebacamide, 
polydecamethylene dodecamide, polydecamethylene tridecamide, 
polydodecamethylene adipamide, polydodecamethylene sebacamide, 
polydodecamethylene dodecamide, polydodecamethylene tridecamide, 
polytridecamethylene adipamide, polytridecamethylene sebacamide, 
polytridecamethylene dodecamide, polytridecamethylene tridecamide, 
polyhexamethylene azelamide, polydodecamethylene azelamide and 
polytridecamethylene azelamide. 
These polyamides may be used in the form of a mixture of two or more of 
them. Moreover, copolyamides comprising two or more of monomers or blends 
of these copolyamides may be used. Incidentally, the polyamide to be used 
may be modified with a small amount of a foreign component such as dimer 
acid. 
(c) Polycarbonates having recurring units represented by the following 
formula: 
##STR4## 
wherein R.sub.3 represents a hydrocarbon group having 8 to 15 carbon 
atoms, and copolycarbonates with an aliphatic or aromatic dihydroxy 
compound. 
For example, there can be mentioned poly-p-xylene glycol biscarbonate, 
poly-dihydroxydiphenylmethane carbonate, polydihydroxydiphenylethane 
carbonate, poly-dihydroxydiphenyl-2,2-propane carbonate and 
poly-dihydroxydiphenyl-1,1-ethane carbonate. 
(d) Furthermore, there may be used acid-modified polyolefins obtained by 
graft-polymerizing an ethylenically unsaturated carboxylic acid such as 
acrylic acid, methacrylic acid or crotonic acid or an ethylenically 
unsaturated carboxylic acid anhydride such as maleic anhydride or itaconic 
anhydride to a polyolefine such as polyethylene, polypropylene or a 
crystalline ethylene-propylene copolymer, copolymers of a vinyl ester with 
an olefin or other vinyl monomer and partial saponification products 
thereof such as an ethylene/vinyl acetate copolymer and a partially 
saponified ethylene/vinyl acetate copolymer, ionomer resins obtained by 
neutralizing copolymers of an olefin with an unsaturated carboxylic acid 
optionally with other vinyl monomer by an alkali metal, an alkaline earth 
metal or an organic base, such as Surlyns supplied by Du Pont Co., U.S.A., 
and resins obtained by oxidizing polyethylene, polypropylene or a 
crystalline ethylene/propylene copolymer with oxygen, ozone or other 
oxidant. 
Of course, these resins should satisfy the abovementioned requirements of 
the physical properties. 
It is preferred that the thickness of the inner face member film be 5 to 
100 microns, especially 10 to 70 microns. If the thickness is too large 
and exceeds the above range, shearing along the scores often becomes 
difficult, and if the thickness is too small and is below the above range, 
the heat-sealing property tends to decrease. 
Ordinarily, this inner face member film may have a single-layer structure. 
However, the film may have a multi-layer structure if desired. For 
example, there may be used a multi-layer inner face member comprising a 
layer especially excellent in the adhesion to the metal foil on the side 
contiguous to the metal foil and a layer excellent in the heat 
sealability, especially the low-temperature heat sealability and the 
adaptability to the heat-sealing operation, which is formed on the layer 
excellent in the adhesion to the metal foil. Of course, when a multi-layer 
inner face member is used, it is indispensable that the respective layer 
should satisfy the foregoing requirements of the physical properties. 
This multi-layer film can easily be obtained by co-extruding a plurality of 
resins through a multi-ply die and forming the extrudate into a film. 
If a multi-layer film such as mentioned above is used as the inner face 
member, even a heat-sealable resin having no bondability to the metal foil 
can be used as a part of the inner face member. 
As a typical instance of this multi-layer structure, there can be mentioned 
a structure comprising (a) a layer composed of a crystalline olefin resin 
formed mainly of propylene or a crystalline olefin resin having a melt 
index of 1 to 40 g/10 min and (b) an acid- or acid anhydride-modified 
olefin resin in which the main constituent monomer is the same as that of 
the resin of the layer (a). An inner face member having this multi-layer 
structure is applied so that the layer (b) is contiguous to the metal 
foil. 
The propylene resin used in this preferred embodiment has such a 
characteristic chemical structure that in the polymer chain, tertiary 
carbon atoms appear alternately, and because of this characteristic, the 
propylene resin is subject to thermal degradation. This propylene resin is 
further characterized in that crystallization is readily advanced at high 
temperatures. 
If a film of this propylene resin is fusion-bonded to a metal foil through 
the acid-modified propylene resin layer, since the acid-modified propylene 
resin contains a carboxyl group having a high affinity with the metal foil 
and the main constituent olefin units of the acid-modified propylene resin 
are the same as those of the propylene resin, a strong interlaminar 
bonding that can resist retort sterilization or tearing can be obtained. 
Furthermore, the elongation of the film is controlled by the thermal 
degradation or crystallization of the propylene resin caused at the 
fusion-bonding step. Therefore, precise and smooth tearing along the 
scores becomes possible. 
An isotactic polypropylene is especially preferred as the propylene resin. 
However, a crystalline propylene/ethylene copolymer having an ethylene 
content of up to 15 mole %, especially up to 10 mole %, can also be used 
as the propylene resin. It is ordinarily preferred that the propylene 
resin should have a melt index (ASTM D-1238) of 1 to 100 g/10 min, 
especially 5 to 100 g/10 min. If the thickness of the film of the 
propylene resin is too large, tearing of the laminate along the scores 
becomes difficult, and if the thickness is too small, the heat sealability 
is reduced. Accordingly, it is preferred that the thickness of the film of 
the propylene resin be 30 to 150.mu., especially 50 to 100.mu.. 
In accordance with another preferred embodiment of the present invention, 
an ethylene resin having a melt index (ASTM D-1238) of 1 to 40 g/10 min, 
especially 2 to 30 g/10 min, is selected and is heat-bonded to an aluminum 
foil through a layer of an acid- or acid anhydride-modified ethylene 
resin. In this embodiment, when the metal foil is broken along scores, 
also this film layer is sharply torn along the scores. Accordingly, an 
excellent easy-open property can be attained, and the appearance of the 
opened portion is very good. 
If the melt index of the ethylene resin is smaller than 1 g/10 min, the 
toughness or elongation of the inner face member becomes too high, and it 
becomes difficult to break the inner face member film precisely along the 
scores in the scored portion of the metal foil. If the melt index of the 
ethylene resin is larger than 40 g/10 min, since scores are formed on the 
metal foil, the mechanical strength of the lid per se is reduced and 
moreover, formation of a film of this ethylene resin is difficult. 
As the ethylene resin, there can be used medium-density polyethylene, 
high-density polyethylene, an ethylene-rich crystalline ethylene/propylene 
copolymer and a crystalline ethylene/butene-1 copolymer. Polyethylene 
having a density higher than 0.945 g/cc, especially high-density 
polyethylene, is suitable for attaining the objects of the present 
invention. 
When an ethylene resin and an acid-modified ethylene resin are used in 
combination according to this preferred embodiment, it is preferred that 
the total thickness of both the layers be up to 70 microns, especially 30 
to 50 microns. 
As the acid-modified olefin resin, there may be used a product obtained by 
graft-modifying an olefin resin with an ethylenically unsaturated 
carboxylic acid or its anhydride. If the inner face member is composed of 
a propylene resin, an acid-modified olefin resin comprising a propylene 
resin as the trunk polymer is used, and if the inner face member is 
composed of an ethylene resin, an acid-modified olefin resin comprising an 
ethylene resin as the trunk polymer is used. 
A preferred acid-modified olefin resin contains a carboxyl group or its 
anhydride at a concentration of 1 to 600 milliequivalents (meq)/100 g of 
the polymer, especially 10 to 300 meq/100 g of the polymer. In view of the 
easy-open property and the heat bondability, it is preferred that the 
modified olefin resin should have a melt index of at least 5 g/10 min. 
As the acid or anhydride, the following compounds may be used singly or in 
combination. 
(A) Ethylenically unsaturated carboxylic acids such as acrylic acid, 
methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, 
citraconic acid and 5-norbornene-2,3-dicarboxylic acid. 
(B) Ethylenically unsaturated carboxylic anhydrides such as maleic 
anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride 
and tetrahydrophthalic anhydride. 
Maleic anhydride-modified polypropylene and maleic anhydride-modified 
polyethylene are especially suitable for attaining the objects of the 
present invention. 
The modifying treatment is accomplished by introducing the above-mentioned 
monomer into the main or side chain of the olefin resin by known means 
such as graft copolymerization or terminal treatment. For example, a 
modified olefin resin can easily be obtained by contacting a trunk polymer 
composed of an olefin resin with an acid group-containing ethylenically 
unsaturated monomer in the presence of a radical initiator or radical 
initiating means. The modified olefin resin is interposed in the thickness 
of 0.5 to 20.mu., 1 to 10.mu., between the metal foil and the olefin resin 
layer. 
Lamination of the inner face member on the metal foil is accomplished by 
applying the inner face member film onto the metal foil and subjecting the 
assembly to a heat treatment to heat-bond the inner face member to the 
metal foil. This heat bonding is carried out at a temperature higher than 
the melting or softening point of the resin but lower than the 
decomposition point thereof. The fusion bonding can easily be accomplished 
by passing the laminate maintained at the above temperature through 
between pressing rolls, and the laminate is cooled by passing it through 
between chill rolls. In the present invention, it is preferred that at 
this step, cooling of the laminate from the fusion bonding temperature to 
a temperature lower than the crystallization temperature be performed over 
a period of at least 2 seconds, especially at least 3 seconds, so that the 
degree of crystallization of the inner face member resin is increased to a 
level as high as possible. 
For production of an easily-openable heat seal lid provided with an olefin 
resin inner face member, a film of an olefin resin is heat-fusion-bonded 
to a metal foil through a modified olefin resin layer. This fusion bonding 
can be accomplished by various means. For example, there may be adopted a 
method in which a modified olefin resin is coated in the form of a film, 
powder, dispersion or solution on a metal foil, the coating is heated to 
melt the modified olefin resin, and a preformed film of an olefin resin is 
piled on the melt and is fusion-bonded to the metal foil. Coating of the 
olefin resin is performed by electrostatic coating, electrophoretic 
coating, roll coating, dip coating, bar coating, spray coating or 
fluidized dipping. Furthermore, the co-extrusion coating method can be 
adopted. Heating of the coated metal foil is accomplished by high 
frequency induction heating, infrared ray heating or hot air furnace 
heating. 
Instead of the method in which the modified olefin resin and the olefin 
resin are independently applied to the metal foil, there may be adopted a 
method in which both the resins are co-extruded through a multi-ply die 
and the extruded two-layer film is heat-fusion-bonded to the metal film. 
In the propylene resin-using embodiment of the present invention, from the 
viewpoint of the easy-open property, it is preferred that the propylene 
resin be crystallized or the crystal size be increased. The degree of 
crystallization of the propylene resin has a close relation to the density 
of the resin. In a conventional laminate for a retortable pouch, which 
includes a propylene resin as an inner face material, in view of the 
strength or heat sealability of the pouch, the fusion-bonded laminate is 
rapidly cooled to control crystallization. In contrast, according to the 
present invention, the density of the propylene resin is increased to at 
least 0.885 g/cc, especially at least 0.890 g/cc by adoption of gradual 
cooling means described hereinafter, whereby the size of spherulites is 
increased to at least 5.mu., especially at least 12.mu.. Incidentally, the 
size of spherulites can be determined according to the light scattering 
method. 
Fusion bonding of the propylene resin is carried out at a temperature 
higher than the melting point of the resin but lower than the 
decomposition temperature of the resin, especially 160.degree. to 
260.degree. C. More specifically, the fusion bonding is accomplished by 
passing the laminate maintained at the above temperature through between 
press rolls. Then, the laminate is passed through between chill rolls to 
cool the laminate. Cooling of the laminate from the fusion bonding 
temperature to a temperature lower than the crystallization temperature is 
conducted over a period of at least 2 seconds, especially at least 3 
seconds. 
In the ethylene resin-using embodiment of the present invention, from the 
viewpoint of the easy-open property, it is important that the 
above-mentioned ethylene resin layer and acid- or acid anhydride-modified 
resin layer should be applied to the metal foil so that the total 
thickness is up to 70 microns, especially 30 to 50 microns. In packages 
having a heat-sealed structure, from the viewpoint of the heat 
sealability, the thickness of the film layer is ordinarily adjusted to at 
least 70 microns. In this embodiment of the present invention, in 
contrast, the entire thickness of the inner face resin member inclusive of 
the adhesive layer is controlled to up to 70 microns, whereby it is made 
possible to break the inner face resin member precisely along scores of 
the metal foil. 
As means for controlling the thickness of the inner face resin member 
within the above-mentioned range, a method in which a preformed ethylene 
resin film is bonded to a metal foil through an acid-modified ethylene 
resin is not advantageous. From the viewpoint of the easiness in 
controlling the thickness, there is advantageously adopted a co-extrusion 
coating method in which the ethylene resin and acid-modified resin are 
co-extruded through a multi-ply die so that both the layers are contiguous 
to each other and the extrudate is coated on the metal foil. 
When an ethylene resin film having a small thickness is easily available, 
there may be adopted a method in which an acid-modified ethylene resin is 
applied in the form of a suspension, emulsion or solution on a metal foil, 
a thin film of an ethylene resin is piled on the acid-modified ethylene 
resin layer and fusion bonding is then carried out, though this method is 
interior in the operation efficiency. 
Fusion bonding of the ethylene resin is carried out in the same manner as 
in case of the propylene resin except that the fusion bonding temperature 
is adjusted to 160.degree. to 220.degree. C. 
It is most preferred that in the inner face resin member, the thickness of 
the ethylene resin layer be 10 to 35 microns and the thickness of the 
acid-modified ethylene resin be 5 to 10 microns. 
In the present invention, a foil of a light metal such as an aluminum foil 
is preferably used as the metal foil. Of course, other metal foils, such 
as an iron foil, a steel foil and a tinplate foil may be used. From the 
viewpoint of the resistance to heat sterilization, it is preferred that 
the metal foil be subjected to a preliminary treatment such as an alumite 
treatment, a boehmite treatment, a chemical treatment with phosphoric acid 
and/or chromic acid or a forming treatment. 
The metal foil should have a certain rigidity enough to enable tearing 
along scores. From this viewpoint, it is preferred that the thickness of 
the metal foil be at least 50.mu., especially at least 80.mu.. From the 
economical viewpoint and in order to prevent hurting of fingers and the 
like at the time of opening, it is preferred that the thickness of the 
metal foil be up to 200.mu., especially up to 150.mu.. 
From the viewpoints of the gas barrier property, the compression resistance 
and the resistance to falling shocks, it is important that the scores 
formed on the metal foil should remain in the midway of the thickness 
direction of the metal foil. When the easy-open property is taken into 
account together with the above characteristics, it is preferred that the 
depth of the scores be 3/10 to 7/10, especially 2/5 to 3/5, of the 
thickness of the metal foil and that the thickness of the scored portion 
of the metal foil be at least 20.mu., especially at least 30.mu.. 
The so-prepared laminate is press-formed (draw-formed) and punched, and 
treatments necessary for forming a lid, such as formation of a peripheral 
curl portion and draw-forming of a panel portion. Then, scores are formed 
on the metal foil. Then, an opening tab is attached to the top face of the 
lid by bonding or the like. Thus, an easily-openable seal lid according to 
the present invention is formed. 
The easily-openable seal lid of the present invention has a multi-layer 
structure including at least three layers. Referring to FIG. 4 
illustrating this embodiment, a resin protecting layer 11 may be formed on 
the outer face of a metal foil 3. As the resin protecting layer 11, there 
may be used a high-tenacity plastic film such as a biaxially stretched 
polyester film, a biaxially stretched polypropylene film or a biaxially 
stretched nylon film, or a coating layer of an epoxy-phenolic paint, an 
epoxy-urea paint, an epoxy-melamine paint, a vinyl paint, an acrylic paint 
or an epoxy-acrylic paint. When a plastic film is used as the resin 
protecting layer 11, it is necessary that the resin protecting layer 11 
should be completely cut at the position of scores as shown in FIG. 4. 
However, in the case where a coating is used as the resin protecting layer 
11, even if the scores 7 are covered with the coating, any particular 
disadvantage is not brought about. 
The lid of the present invention is advantageously used as a heat seal lid 
for sealing optional vessels, for example, a metal can, a wide-mouthed 
bottle, a plastic cup, a metal foil vessel, a metal foil/plastics 
composite vessel and a paper/plastics/aluminum foil composite vessel. The 
lid of the present invention is especially advantageously used for sealing 
easily buckling vessels in which double seaming is impossible and 
packaging vessels which should be subjected to hot packing and heat 
sterilization. 
Incidentally, the shape of the scores is not limited to a circular, square 
or rectangular shape for opening the entire inside of the seal portion, 
but there may be adopted a method in which scores are formed in a shape of 
a small circle or water drop only on a part of the inside of the seal 
portion. In this case, opening is effected from this small circular or 
rain drop-like scored part. 
A most preferred example of the vessel to which the lid of the present 
invention is applied is a paper vessel comprising a paper substrate, an 
aluminum foil and film layers of a polyolefin, especially an ethylene 
resin formed on both the inner and outer surfaces, for example, a 
composite can or a composite cup-like vessel. This preferred embodiment is 
illustrated in FIGS. 5, 6 and 7. 
Referring to FIGS. 5, 6 and 7, a content is hot- or cold-packed in a vessel 
proper 12, and if necessary, the inside atmosphere is replaced by steam or 
nitrogen. Then, a lid 1' is placed on the vessel proper 12 so that a 
flange 13 confronts an olefin resin film layer 2 of the lid, and the 
flange portion is heated under compression to effect heat sealing. The 
heating temperature is higher than the melting point of the film layer 2, 
and the pressure is ordinarily 1 to 10 Kg/cm.sup.2 gauge. This heat 
sealing operation can easily be accomplished by known heat sealing means 
such as a heat seal bar or high frequency induction heater. 
The vessel proper 12 of this embodiment, as shown in FIG. 7 in an enlarged 
manner, comprises a laminate including a paper substrate 14 and an 
aluminum foil 15 which are bonded together through a polyolefin layer 16 
having a polyolefin inner face member 17 on the inner surface and a 
polyolefin outer face member 18 on the outer surface, and good heat seal 
can be attained between this vessel proper and the lid of the present 
invention. 
Furthermore, the lid of the present invention can advantageously be used as 
a heat seal lid for a plastics cup obtained by vacuum forming, a 
monoaxially or biaxially stretched plastics cup obtained by air pressure 
forming or a metal foil vessel formed by draw forming. This embodiment is 
illustrated in FIG. 8. 
Referring to FIG. 8, a content is hot- or cold-packed in a plastic vessel 
proper 12 composed of, for example, polypropylene, and the inner 
atmosphere is replaced by steam or nitrogen if desired. Then, the lid 1 is 
placed on the vessel proper 12 so that a flange 13 confronts a propylene 
resin film layer 2 of the lid, and the flange portion is heated under 
pressure to effect heat sealing. The heating temperature is higher than 
the melting point of the film layer 2, and the pressure is ordinarily 1 to 
10 Kg/cm.sup.2 gauge. This heat sealing operation can easily be 
accomplished by known heat sealing means such as a heat seal bar or high 
frequency induction heater. 
The heat seal portion formed by using the lid of the present invention can 
fully resist a sterilization treatment such as hot packing, hot water 
sterilization or retort sterilization, and a high seal reliability can be 
maintained. Accordingly, a packed food can be stored stably for a long 
time, and opening can be performed very easily and assuredly. Therefore, 
great advantages can be attained according to the present invention. 
Excellent effects of the present invention will now be described in detail 
with reference to the following Examples that by no means limit the scope 
of the invention. 
EXAMPLE 1 
Maleic anhydride-grafted polypropylene having an average carboxyl group 
concentration of 180 mes/100 g of the polymer and having a melting point 
of 161.degree. C. and a melt index of 30 g/10 min was melt-extruded 
between a soft aluminum foil having the outer face coated with an 
epoxy-phenolic resin and a thickness of 100.mu. and a film composed of an 
ethylene/propylene block copolymer having a melting point of 159.degree., 
a density of 0.90 g/cm.sup.2, a melt index of 7.0 g/10 min and an ethylene 
content of 4 mole %, which film had a thickness of 50.mu., a tear strength 
of 0.3 Kg (JIS K-6772) and a tensile modulus of 13800 Kg/cm.sup.2 (ASTM 
D-638), from a T-die having a width of 650 mm through an extruder having a 
screw having a diameter of 65 mm at a resin temperature of 250.degree. C. 
in the die portion. The resulting laminate was pressed by a pair of rolls 
having diameters of 400 mm and 200 mm, respectively, which were maintained 
at normal temperature to effect temporary bonding. Then, the laminate was 
heat-pressed between a heat-treating roll having a diameter of 400 mm and 
maintained at 200.degree. C. and a silicone roll having a diameter of 200 
mm. Then, the laminate was cooled by a chill roll having a diameter of 400 
mm and a silicone roll having a diameter of 200 mm to obtain a laminate 
having a structure of epoxy-phenolic paint/100.mu.-aluminum 
foil/10.mu.-modified polypropylene layer/50.mu.-ethylene-propylene 
copolymer layer. The adhesion strength between the aluminum foil and the 
ethylene-propylene copolymer layer was 1400 g/15 mm. 
Separately, a film having a thickness of 10.mu. was prepared from the same 
modified polypropylene as described above, and the tear strength was 
measured. It was found that the tear strength was 0.01 Kg. The tensile 
modulus of the film was 14700 Kg/cm.sup.2. 
A lid having a shape as shown in FIG. 1 was prepared by subjecting the 
laminate to punching, forming, scoring and tab-attaching operations. Then, 
80 cc of water was packed in a multi-layer plastic cup of a conical shape 
having a mouth inner diameter of 65 mm, a depth of 30 mm, a flange width 
of 3 mm and a flange thickness of 0.8 mm, which was formed by the solid 
phase air pressure forming method, and the above-mentioned lid was placed 
on the cup and sealing was effected by high frequency induction heating. 
The multi-layer plastic vessel had a structure of B/B'/C/A/C/B'/B from the 
outside. A designates a saponified ethylene-vinyl acetate copolymer having 
an ethylene content of 30 mole % and a saponification degree of 99.2%, B 
represents isotactic polypropylene having a melt index of 1.4 g/10 min 
(ASTM D-1238) and a density of 0.91 g/cc (ASTM D-1505), C designates 
maleic anhydride-modified polypropylene, and B' designates a mixture 
containing A, B and C at a weight ratio of 5/93/2. 
When the so-prepared sealed vessel was heat-sealed at 120.degree. C. for 30 
minutes, no disorder or trouble was observed in the vessel. When the 
opening portion of the lid was opened by utilizing the tab, opening could 
be accomplished smoothly along a predetermined score line. The initial 
opening force was 1.2 Kg and the maximum opening force 2.1 Kg. The opening 
portion after the opening operation was free of such defects as 
delamination and feathering. 
COMATIVE EXAMPLE 1 
The same soft aluminum foil having a thickness of 100.mu. as used in 
Example 1 was laminated with the same ethylene-propylene block copolymer 
film having a thickness of 50.mu. as used in Example 1 by using an 
isocyanate type adhesive. The adhesion strength between the aluminum foil 
and the ethylene-propylene copolymer film in the resulting laminate was 
700 g/15 mm. 
A lid was prepared from this laminate in the same manner as described in 
Example 1, and the lid was placed on a water-packed multi-layer plastic 
cup and sealed in the same manner as described in Example 1. The packed 
cup was heat-sterilized at 120.degree. C. for 30 minutes. After the heat 
sterilization, the opening portion of the lid was opened. While breaking 
was advanced along the scores, delamination was caused in the bonding 
interface between the aluminum foil and the polypropylene layer. 
Therefore, continuation of smooth breaking along the scores became 
impossible and the appearance after the opening operation was extremely 
bad and withdrawal of the content was apparently hindered. 
EXAMPLE 2 
A laminate having the same structure as in Example 1 was prepared in the 
same manner as described in Example 1 except that a blend comprising 60% 
by weight of maleic anhydride-grafted polypropylene having an average 
carboxyl group concentration of 240 meq/100 g of the polymer, a melting 
point of 163.degree. C. and a melt index of 25 g/10 min, 30% by weight of 
an ethylene-propylene random copolymer having a melting point of 
158.degree. C., a density of 0.90 g/cm.sup.3, a melt index of 30 g/10 min 
and an ethylene content of 3 mole % and 10% by weight of low-density 
polyethylene having a melting point of 110.degree. C., a density of 0.928 
g/cm.sup.3 and a melt index of 10 g/10 min was used as the thermoplastic 
resin adhesive. The adhesion strength was 1450 g/15 mm. A lid was prepared 
from this laminate and the test was carried out in the same manner as 
described in Example 1. The openability was very good. 
EXAMPLES 3 THROUGH 6 
Laminate sheets having a structure as shown in Table 1 were prepared from 
materials shown in Table 1. In Examples 3 through 5, temporarily bonded 
laminates were prepared according to the two-layer co-extrusion coating 
method, and in Example 6, a temporarily bonded laminate was prepared 
according to the sandwich lamination method. The temporarily bonded 
laminates were heat-treated in the same manner as described in Example 1 
to obtain these laminate sheets. 
In Examples 3 and 4, lids having a shape shown in FIG. 5 were prepared from 
the laminates by punching, forming, scoring and tab-attaching operations. 
Then, orange juice was hot packed in a composite vessel composed of a 
paper-aluminum foil-polyethylene laminate, which had a diameter of 54 mm 
and had a tapered side wall having a height of 85 mm and an opening 
portion having an opening end formed into a curly shape and a diameter of 
70 mm, and the lid was sealed to the curly end of the opening of the cup. 
In Examples 5 and 6, full-open type lids as shown in FIG. 1 were prepared. 
Refined sake was packed in a composite vessel shown in FIG. 6, and the lid 
was sealed to the vessel. 
When these vessels were opened by pulling up opening tabs formed on the 
lids, in each vessel, opening could be accomplished smoothly along the 
predetermined score line, and the opening portion after the opening 
operation was free of delamination and feathering and was in a good state. 
COMATIVE EXAMPLE 2 
An isocyanate type anchoring agent was coated on the same soft aluminum 
foil having a thickness of 100.mu. as used in Example 3, and the same 
medium density polyethylene as used in Example 3 was coated on the coated 
surface of the aluminum foil according to the customary melt extrusion 
method to obtain a laminate having a structure of 100.mu.-aluminum 
foil/isocyanate anchoring agent layer/30.mu.-medium density polyethylene 
layer. The adhesion strength between the aluminum foil and the medium 
density polyethylene layer in this laminate was 600 g/10 mm. 
A lid was prepared from this laminate in the same manner as described in 
Example 3 and was heat-sealed to a composite cup packed with orange juice 
in the same manner as described in Example 3. When the opening portion of 
the lid along scores, delamination was caused in the bonding interface 
between the aluminum foil and the medium density polyethylene during the 
cutting operation and the appearance of the opening portion after the 
opening operation was very bad. 
COMATIVE EXAMPLE 3 
A lid was prepared in the same manner as described in Example 4 except that 
an ethylene/vinyl acetate copolymer having a vinyl acetate content of 26% 
by weight, a melt index of 5 g/10 min, a melting point of 95.degree. C., a 
thickness of 30.mu., a tear strength of 0.3 Kg and a tensile modulus of 
160 Kg/cm.sup.2 was used instead of the medium density polyethylene for 
the inner face resin layer, and the opening test of the lid was carried 
out in the same manner as described in Example 4. Since the ethylene-vinyl 
acetate copolymer of the inner face layer was elongated, opening was 
difficult. 
COMATIVE EXAMPLE 4 
A lid was prepared in the same manner as described in Example 6 except that 
low density polyethylene having a thickness of 100.mu., a tear strength of 
3.2 Kg, a tensile modulus of 1200 Kg/cm.sup.2, a melt index of 0.9 g/10 
min and a melting point of 110.degree. C. was used as the inner face resin 
layer. When this lid was subjected to the opening test, the inner face low 
density polyethylene layer could not be broken along scores and opening 
was very difficult. 
EXAMPLE 7 
The same maleic anhydride-modified polypropylene as used in Example 1, in 
which PHR of aluminum hydroxide was melt-blended, was used as the material 
of the adhesive layer, and a blend comprising 93% by weight of an 
ethylene-propylene random copolymer having a melting point of 158.degree. 
C., a density of 0.90 g/cm.sup.3, a melt index of 25 g/10 min and an 
ethylene content of 7 mole % and low density polyethylene having a melting 
point of 110.degree. C., a density of 0.920 g/cm.sup.3 and a melt index of 
10 g/10 min was used as the material of the inner face resin layer. These 
two resins were temporarily laminated on an uncoated surface of a soft 
aluminum foil having a thickness of 100.mu. and an outer surface coated 
with an epoxy-phenolic paint according to the two-layer co-extrusion 
coating method. The temporarily bonded laminate was heat-treated in the 
same manner as described in Example 1 to obtain a laminate having a 
structure of epoxy-phenolic paint/100.mu.-aluminum foil/10.mu.-modified 
polypropylene layer/40.mu.-polyethylene-propylene blend layer. The 
adhesion strength between the aluminum foil and the modified polypropylene 
layer in this laminate was 1800 g/15 mm. 
Separately, a film having a thickness of 10.mu. was prepared from the 
above-mentioned modified polypropylene used for the laminate, and the tear 
strength of the film was measured. It was found that the tear strength was 
0.01 Kg. The tensile modulus was 14800 Kg/cm.sup.2. Furthermore, a film 
having a thickness of 40.mu. was prepared from the above-mentioned 
ethylene-propylene random copolymer/low density polyethylene blend. The 
tear strength was 0.1 Kg and the tensile modulus was 11600 Kg/cm.sup.2. 
The above-mentioned laminate was subjected to punching, forming, scoring 
and tab-attaching operations and a lid similar to that obtained in Example 
1 was prepared. 
A laminate comprising a soft aluminum foil having an outer face coated with 
an epoxy-phenolic resin and a thickness of 120.mu. and an 
ethylene-propylene block copolymer having a thickness of 70.mu. as the 
inner face material was formed on a frustoconical cup provided with a top 
end-curled flange portion having a width of 3 mm, which had a mouth 
diameter of 65 mm and a depth of 30 mm. The resulting cup was packed with 
potato salad, and the above-mentioned lid was placed on the cup and 
heatsealed thereto by a high frequency induction heating sealer. 
When the so-prepared sealed vessel was subjected to retort sterilization at 
120.degree. C. for 30 minutes, no disorder or trouble was observed. When 
the vessel was opened in the opening portion of the lid by utilizing the 
tab, opening could be accomplished smoothly along the predetermined score 
line. The initial opening force was 1.0 Kg and the maximum opening force 
was 1.9 Kg. Delamination or feathering was not caused at all. 
EXAMPLES 8 THROUGH 10 
A thermoplastic resin heat-bondable to a metal, as shown in Table 2, was 
heat-bonded as the inner face resin layer to a soft aluminum foil having 
an outer surface coated with an epoxy-phenolic paint and a thickness of 
100.mu., according to a method shown in Table 2, and the assembly was 
cooled by chill rolls to obtain a laminate. 
A lid having a shape shown in FIG. 1 was prepared by subjecting the 
laminate to punching, forming, scoring and tab-attaching operations. 
Then, 80 cc of water was packed in a formed cup similar to that obtained in 
Example 7, which comprised a soft aluminum foil having an outer face 
coated with an epoxy-phenolic paint and a thickness of 120.mu., and the 
lid was placed on the cup and sealed by a high frequency sealer. 
In Examples 8 and 9, the obtained sealed cups were subjected to retort 
sterilization at 145.degree. C. for 10 minutes, and in Example 10, the 
sealed cup was subjected to retort sterilization at 120.degree. C. for 30 
minutes. In each cup, no disorder or trouble was observed. When the sealed 
cups were opened in the opening portions of the lids by utilizing the 
tabs, in each case, opening could be performed smoothly along the 
predetermined score line. The initial opening forces and maximum opening 
forces were as shown in Table 2. In each case, the opening portion after 
the opening operation was free of delamination or feathering and had a 
good appearance. 
COMATIVE EXAMPLE 5 
Procedures of Example 9 were repeated in the same manner except that an 
aluminum foil having an outer face coated with an epoxy-phenolic paint, on 
an uncoated inner face of which a nylon 12/nylon 6 was heat-bonded, was 
used as the aluminum foil. The adhesion strength of the laminate was as 
low as 600 g/15 mm. This adhesion strength was further reduced by retort 
sterilization, and when the vessel was opened by utilizing the tab, 
delamination was caused. 
EXAMPLES 11 THROUGH 13 
A thermoplastic resin inner face member shown in Table 3 was heat-bonded to 
a soft aluminum foil having an outer face coated with an epoxy-phenolic 
resin and a thickness of 100.mu. through a thermoplastic resin adhesive 
shown in Table 3 according to a method shown in Table 3. The laminate was 
cooled by chill rolls, and a lid was prepared from this laminate in the 
same manner as described in Example 1. 
Then, 80 cc of water was packed in a formed cup similar to that obtained in 
Example 7, which was composed of a laminate comprising a soft aluminum 
foil having an outer face coated with an epoxy-phenolic paint and a 
thermoplastic resin inner face member shown in Table 3, and the lid was 
placed on the cup and sealed thereto by a high frequency induction heating 
sealer. 
In Example 11, the sealed vessel was subjected to retort sterilization at 
145.degree. C. for 10 minutes, and in Examples 12 and 13, the sealed 
vessels were subjected to retort sterilization at 120.degree. C. for 30 
minutes. In each case, no disorder or trouble was observed. When these 
vessels were opened in the opening portions by utilizing the tabs, in each 
case, opening could be accomplished smoothly along the score line. The 
initial opening forces and maximum opening forces were as shown in Table 
3. In each case, the opening portion after the opening operation was free 
of delamination or feathering and had a good appearance. 
The foregoing Examples are summarized in Tables 1 through 3. 
TABLE 1 
__________________________________________________________________________ 
Adhesive Layer 
Thickness 
FAe-Ad 
TAd 
EAd 
Example No. 
Material (.mu.) 
(g/15mm) 
(Kg) 
(Kg/cm.sup.2) 
__________________________________________________________________________ 
3 maleic anhydride-modified linear 
8 1400 0.02 
1,800 
low density polyethylene 
(MI = 2.7, density = 0.920) 
4 maleic anhydride-modified 
5 1200 0.01 
1,150 
ethylene-vinyl acetate copolymer 
(vinyl acetate content = 5 wt %, 
MI = 4, m.p. = 105.degree. C.) 
5 maleic anhydride-modified 
5 1050 0.01 
9,800 
high density polyethylene 
(MI = 24, density = 0.953, 
m.p. = 132.degree. C.) 
6 maleic anhydride-modified 
5 1350 0.01 
9,900 
high density polyethylene 
(MI = 24, density = 0.953, 
m.p. = 132.degree. C.), 1 wt % of 
aluminum hydroxide 
__________________________________________________________________________ 
Initial 
Maximum 
Inner Face Resin Layer 
Opening 
Opening 
Thick- 
FAd-Fm 
TFm 
EFm Force 
Force 
Example No. 
Material ness (.mu.) 
(g/15mm) 
(Kg) 
(Kg/cm.sup.2) 
(Kg) (Kg) 
__________________________________________________________________________ 
3 medium density 
30 3500 0.3 
7,400 
1.1 2.0 
polyethylene 
(MI = 15, density = 
0.949, m.p. = 128.degree. C.) 
4 medium density 
35 3800 0.3 
7,400 
1.1 2.0 
polyethylene 
(MI = 15, density = 
0.949, m.p. = 128.degree. C.) 
5 high density poly- 
40 5200 0.4 
9,500 
1.2 2.1 
ethylene (MI = 6, 
density = 0.952, 
m.p. = 130.degree. C.) 
6 high density poly- 
40 4900 0.4 
9,300 
1.2 2.1 
ethylene (MI = 2, 
density = 0.954, 
m.p. = 132.degree.C.) 
__________________________________________________________________________ 
Note 
FAeAd (g/15mm): adhesion strength between metal foil and adhesive layer 
FAdFm (g/15mm): adhesion strength between adhesive layer and inner face 
resin layer 
TAd (Kg): tear strength (JIS K6772) of adhesive layer 
TFm (Kg): tear strength (JIS K6772) of adhesive layer 
EAd (Kg/cm.sup.2): tensile modulus (ASTM D638) of adhesive layer 
EFm (Kg/cm.sup.2): tensile modulus (ASTM D638) of adhesive layer 
TABLE 2 
__________________________________________________________________________ 
Material for Heat-Bondable Thermoplastic 
Treatment of Resin Inner Face Layer 
Inner Face of Thickness 
F T E 
Example No. 
Aluminum Foil 
Material (.mu.) 
(g/15mm) 
(Kg) 
(Kg/cm.sup.2) 
__________________________________________________________________________ 
8 epoxy-phenolic 
20 wt % of polyethylene 
50 1150 0.3 
4100 
paint terephthalate, 40 wt % of 
polyethylene terephthalate/ 
isophthalate, 40 wt % of 
polybutylene terephthalate/ 
isophthalate 
9 epoxy-phenolic 
nylon 12/nylon 6 copolymer 
40 950 0.4 
12000 
paint 
10 not treated 
maleic anhydride-modified 
40 1250 0.5 
14500 
polypropylene (average carbonyl 
group concentration = 120 
meq/100 g polymer, m.p. = 162.degree. C. 
MI = 7.0 g/10 min, density = 
0.90 g/cc) 
__________________________________________________________________________ 
Inner Face Resin Layer of Formed Cup 
Initial 
Maximum 
Thickness 
Opening 
Opening 
Lamination 
Example No. 
Material (.mu.) Force (Kg) 
Force (Kg) 
Method 
__________________________________________________________________________ 
8 20 wt % of polyethylene 
50 1.1 2.0 heat-lamina- 
terephthalate, 40 wt % of tion 
polyethylene terephthalate/ 
isophthalate, 40 wt % of 
polybutylene terephthalate/ 
isophthalate 
9 nylon 12 30 1.1 2.1 heat lamina- 
tion 
10 ethylene-propylene block 
70 1.2 2.2 heat lamina- 
copolymer tion 
(MI = 9.0 g/10 min, 
m.p. = 157.degree. C., density = 
0.90 g/cc) 
__________________________________________________________________________ 
Note 
F (g/15mm): adhesion strength between metal foil and heatbondable 
thermoplastic resin inner face layer 
T (Kg): tear strength (JIS K6772) of heatbondable thermoplastic inner fac 
layer 
E (Kg/cm.sup.2): tensile modulus (ASTM D638) of heatbondable thermoplasti 
inner face layer 
TABLE 3 
__________________________________________________________________________ 
Material for 
Treatment of Adhesive Layer 
Inner Face of Thickness 
FAe-Ad 
TAd 
EAd 
Example No. 
Aluminum Foil 
Material (.mu.) 
(g/15mm) 
(Kg) 
(Kg/cm.sup.2) 
__________________________________________________________________________ 
11 epoxy-phenolic 
20 wt % of polyethylene 
20 1100 0.1 
3900 
paint terephthalate, 30 wt % of 
polyethylene terephthalate/ 
isophthalate, 35 wt % of 
polybutylene terephthalate/ 
isophthalate, 15 wt % of 
Surlyn .RTM. 
12 epoxy-phenolic 
polyethylene terephthalate/ 
10 900 0.1 
3800 
paint isophthalate (m.p. = 165.degree. C.) 
13 epoxy-phenolic 
50 wt % of polyethylene tere- 
10 1000 0.1 
3700 
paint phthalate/isophthalate, 
50 wt % of polybutylene tere- 
phthalate 
__________________________________________________________________________ 
Inner Face Resin Layer 
Thick- 
ness 
FAd-Fm 
TFm 
EFm Lamination 
Example No. 
Material (.mu.) 
(g/15mm) 
(Kg) 
(Kg/cm.sup.2) 
Method 
__________________________________________________________________________ 
11 40 wt % of polyethylene tere- 
40 1500 0.2 
4700 heat lamination 
phthalate/isophthalate, of two-layer 
60 wt % of polybutylene tere- co-extruded film 
phthalate/isophthalate 
12 ethylene glycol/cyclohexyl 
30 1700 0.2 
3600 lamination of two- 
dimethyl alcohol terephthalate layer co-extruded 
copolymer film and post heat 
treatment 
13 ethylene glycol/1,4-butane 
30 1600 0.2 
2800 lamination of two- 
diol/neopentyl glycol/ layer co-extruded 
terephthalate/sebacate film and post heat 
copolymer treatment 
__________________________________________________________________________ 
Initial 
Maximum 
Opening 
Opening 
Inner Face Resin Layer of Formed Cup 
Force 
Force 
Example No. 
Material Thickness (.mu.) 
(Kg) (Kg) 
__________________________________________________________________________ 
11 polyethylene terephthalate/ 
50 1.1 2.0 
isophthalate (m.p = 165.degree. C.) 
12 ethylene glycol/cyclohexyl 
40 0.8 1.9 
dibutyl alcohol tere- 
phthalate copolymer 
13 polyethylene terephthalate 
20 1.0 2.0 
__________________________________________________________________________ 
Note 
FAeAd (g/15mm): adhesive strength between metal foil and adhesive layer 
FAdFm (g/15mm): adhesive strength between adhesive layer and inner face 
resin layer 
TAd (Kg): tear strength (JIS K6772) of adhesive layer 
TFm (Kg): tear strength (JIS K6772) of inner face resin layer 
EAd (Kg/cm.sup.2): tensile modulus (ASTM D638) of adhesive layer 
EFm (Kg/cm.sup.2): tensile modulus (ASTM D638) of adhesive layer