Note: Descriptions are shown in the official language in which they were submitted.
~.o5Z962
1 The present invention relates to a method for the
manufacture of thin w~lled containers and in particular con-
cerns a modification of the method set forth in our British
Patent No. 12324/73.
In the said British Patent, we have set forth a pro-
cess of manufacturing thin walled containers wherein the con-
tainers are formed in and removed from a sheet laminate made up
of a sheet of polystyrene and a sheet of polyvinyl chloride or
a copolymer thereof adhered thereto in such a manner that after -
the formed containers have been removed from the laminate, the
remaining polystyrene sheet and polyvinyl chloride sheet can be
readily separated so that the remainder of the polystyrene can '
be re-used.
According to the present modification, the polyvinyl
chloride or copolymer sheet is replaced by a sheet of acrylonit-
rile butadiene styrene (A.B.S.~ and the polystyrene may or may
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not be replaced by polypropylene or polyethelene. This material
can be used in general purpose containers but if the containers `-
have to contain a variety of substances which must be protected ~-from gas vapour or water contamination, then the A.B.S. may have ~`
a layer of synthetic plastic material thereon which has the ` -- -
desired property or properties of gas, vapour or water imperm- ;-
eability. Such containers can be used for holding, for
example, foodstuffs ~including oils and condiments) cosmetics,
medicines, drugs and pharmaceuticals and household and indu~
trial chemicals. ~-
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lOSZ962
1 A container formed according to the present invention,
if provided with a lining on the A.B.S. and a suitable lid,
gas tight sealed to the container, can also be used for
holding carbonated beverages.
The containers are preferably formed in the laminate
by means of a thermo forming process involving pressure
deformation of locally heated regions of the laminate. The
pressure deformation may be by vacuum or pressure forming or by
moulds having male and female mould parts or by a combination
tO of these techniques.
The laminate may be formed simply by iaying the
A.B.S. sheet material layer on an extruded layer preferably ~ ;
of polystyrene, and pressing the two layers together. The
pressure is preferably applied by a pair of nip rollers
whilst the polystyrene is still slightly soft, and the rollers
; may be cooled to cause congealing of the polystyrene. The
adhesion between the sheets may be assisted by electrostatic ~ `
- attraction. By extruding the polystyrene and passing it -
bçtween rollers, there is generated on the polystyrene a - 20 negative electrostatic charge which may attract and lightly
hold the A.B.S. to the polystyrene. After removal of the
containers the remainder of the polystyrene and A.~.S.
sheets can be separated by physically overcoming the ~ `-
electrostatic attraction or by destroying it by applying
e}ectric charge by ionised air or electric field of
opposite polarity to that of the charge of the polystyrene.
If the electrostatic charge is insufficient to hold the
sheets together, the charge may be increased either by
working the polystyrene or by creating the charge by ~-
suitable electric apparatus.
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105Z96Z
1 The A.B.S. will normally be a web which is applied
to the extruded polystyrene, or in an alternative the
A.B.S. and polystyrene are extruded simultaneously and then
pressed together. -
Where the other lining material having the gas,
~; vapour, or water impermeability property or properties i8
provided, this may be a further sheet applied to the
A.B.S. at the same time as the A.B.S. i8 applied to the
polystyrene or it may have been previously applied. Instead
~f a sheet of lining material, it may be supplied in liquid
form to the A.B.S. for example by a coating process.
The aforesaid coating may be the material known
as, SARAN (Registered Trade Mark) and it may be applied
. by reverse roll coating, curtain coating, spraying, -~
` painting or the like. -~
; - The A.B.S. may be in the region of 1 to 6 thousandths -
of an inch in thickness, but the polystyrene, as it forms -
the outer case of the containers formed according to the ;
invention, will be substantially rigid and therefore be
thicker than the lining material.
The softening points of the A.B.S~ and polystyrene - `
are in the same range of temperature and thus enables -
the sheets to be thermo formed together. The shrinkage
rates of the A.B.S. and polystyrene are æuch that during
the cooling of each container after thermo forming, the
polystyrene shrinks at a higher rate than the A.B.S. and
the A.B.S. and case bind
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105Z962
1 together~ but ~here the contalner is to ~e ~illed with car-
bonated beverage and then sealed By ~eans of a lid, the ~hrink-
age rates can be the same as the pressure o~ the bcverage,
when sealed in the container will force the A.B.S. onto the
polystyrene case. The A.B.S. will in this case be provided
with an inner lining, for example of SARAN.
An example of the present invention will now be des-
cribed, by way of example, with reference to the accompanying
drawings, wherein:-
Fig.l shows diagrammatically how a roll of coated
A.B,S is laid onto a polystyrene or other web to form the -~
laminate in which the containers are formed;
Figs. 2 and 3 show in sectional elevation how the
containers are formed in and removed therefrom respectively;
` Fig. 4 illustrates how the remainder of the polystyrene
and A.B.S. are separated after removal of the containers.
Fig. 5 illustrates the distal relationship amongst the
nip rollers.
Referring to the drawings, and firstly to Fig. 1, high
impact polystyrene is extruded from an extruder 12 in the form
of a web 10.
A web 14 of A.B.S., which has one side 14A coated ~` -
with gas impermeable plastics material, such as SARAN is
applied to the web 10 with its uncoated side to form a lamin~ -
ate 16. The webs 10, 14 are pressed together by nip rollers
18 to prevent the formation of air pockets between the webs
; 10, 14. The rollers 18 are water cooled and serve to cool and
congeal the soft extruded web 10 of polystyrene.
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1052962
1 As the polystyrene is extruded from extruder 12 and
as it passes round rollers 18, it acquires a negative electro-
static charge which liqhtly attracts the A.B.S. to the sheet 10,
and if such charge is insufficient, it is possible to induce the
necessary electrostatic charge on the polystyrene. We have found
however that working of the polygtyrene is sufficient to create
an electrostatic charge on the polystyrene of more than enough
capacity to hold the A.B.S. to the polystyrene. The A.B.S. i8 ~ :
wound from a reel 22 as shown.
In the laminate 16 are formed a plurality of con-
tainers by a thermo forming process involving the initial sof-
; tening of the laminate for example by heater 23. ~-
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Fig. 2 shows how one of the containers is foxmed in
the laminate 16. The laminate is heated to soften the webs and
the softened webs are located over the cavity of a vacuum form-
ing mould 24. The mould cavity is then vacated by having a ~ -~
vacuum applied thereto through the passage 26, and the laminate --
takes up the container shape as shown.
The container is now removed from the laminate, as by -
cutting by means of a circular knife indicated at 28 in fig. 3
shows the separated containers ready for filling and lidding
and it will be noticed that the container is cut from the lam- :
inate to leave a top peripheral flange 30 of which the top is - ~-
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defined by the SARAN coated face of A.B.S. 14 and the bottom by
the polystyrene outer casing 10.
A plurality of the containers are ~ormed in-and removed
from the laminate 16 and, because the webs 10, 14 are adhered
lightly together by electrostatic attraction, the web xemain-
: ders can be separated either by physically separating the webs
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1os296;~or ~y destroying the electrostatic charge by applying a reverse charge
or for electric field as indicated in Fig. 4 and the remaining
polystyrene web 10 can be reprocessed and returned to the
extruder 12.
The polystyrene and A.B.S. adhere lightly together as
explained by electrostatic attraction, but the adherence may be
assisted by a weak adhesive or if there is no electrostatic
attraction, the adherence may be achieved by the exclusion of
air from between the sheets 10, 14.
It is to be appreciated that the shape of the containers
produced in the laminate 16 is not in essence to the present
invention; the container shape is indicated by the shape of the
moulds in which the containers are formed. The resulting con-
tainers are very suitable for containing foodstuffs, medicines,
liquids and the like which must be sealed from the atmosphere
and moisture, the inner liner or coating of the A.B.S. preventing
the ingress of moisture or atmosphere. - `
In an alternative arrangement, instead of providing
a roll of A.B.S. the A.B.S. is extruded from another extruder
and the polystyrene and A.B.S. extrudates, whilst still soft,
are brought together to form the laminate. Slightly different -
shrinkage rates upon cooling of the polystyrene and A.B.S. may
; assist the adherence together of the webs. This laminate can be
used for producing containers as described without further treat-
ment, but if the containers are to contain material or items
which must be protected from the atmosphere and/or moisture
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~OSZ962
1 there will usually be a third layer to the laminate, as described
above, and at the opposite side of the A.B.S. from the poly-
styrene which will have the necessary impermeability characteristic
or characteristics. This third layer may be a coating or sheet
of SARAN, polyethylene polypropylene or polyvinyl chloride.
Furthering in any of the arrangements of the convention, ~
the polystyrene may be replaced by polyethylene. -
; The main advantage of utilizing A.B.S. is that it is ~ -
relatively cheap as compared to the previous materials we have ~
10 used for this purpose. ~ ;
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