CA1205264A - Process for the production of a blank for containers and blank produced by the process - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

There is described a process for the manufacture of a tubular pre-moulding from a thermoplastic material by providing a tube of thermoplastic material with a sub-stantially reduced material thickness in at least one zone. The tube is stretched in the axial direction, to obtain, when stretching the material, an orientation mainly in the axial direction of future pre-moulding.
The material is heated in at least the oriented zone or zones to a temperature above glass transition tempera-ture (Tg) and is expanded in radial direction until it makes contact with the mould walls in order to form the mouth part with adjacent neck sections of the particular pre-moulding. The material is then cooled to a tempera-ture below glass transition temperature (Tg) and the material in one end or in both ends of the tube is heated to a temperature above the glass transition temperature (Tg) and is reshaped, in order to form the closure of the particular pre-moulding. The pre-moulding as well as the apparatus to make the same are also described.

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Description

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l~hi~ appl.ication is a division of application Serial No. 35~,909 filed May 28, 1980.
The invention relates to a tubular pre-moulding of a thermoplastic~ suitable for subsequent shaping to give containers by a blow-moulding process,- and to a process and e~uipment for producing the pre~moulding.
a tube9 ~uture mouth parts and parts o~ adjacent nec~
sections are moulded to pre-mouldings, from two blank parts joined to one another, by an axial stretch process and a blow-moulding process, the parts in the transition between the two mouth parts being severed in order.to form two separate blank parts which,.after closing at ~ one of the ends and subse~uent reworking to produce the re~uisite closing surfaces at the respectiYe cther ends, each alone form a tubular pre-mouldi~g.
In a production process used for the manu~acture o~ contai~ers from a thPrmoplastic~ blanks n~rm~lly called p~e-mouldings for containers are produced from severed parts of extruded long tubes of an amorpnous thermoplasticO At one endi the severed pieces are shaped in such.a way that they ~orm the future mouth part .
vf the container, whilst they are closed at the opposite end.
The present invention eliminates certain disad-vantages connected with the production process indicated above 3 according to the known technology~

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The invention is suitable especially for the manufacture of containers from a thermoplastic of the polyester or polyamide type. Examples of such materials are polyethylene terephthalate 7 polyhexamethylene-.
adipamide, polycaprolactam, polyhexamethylene--sebacamide, polyethylene 2,6- and 1,5-naphthalate, polytetramethylene l,?-dihydroxybenzoate and copolymers of ethylene ~erephthalate, e~hylene isophthalate and similar po~ymers. The description of the invention below relates mainly to polyethylene terephthal-ate, called PET in ~he further text, but the invention ls not restricted only to the use of either this material or one of the other materials already mentioned; instead, it is also applicable to many other thermoplastics.
For a better understandin~ of the existing problem and of ~he invention, several cha~acteristic properties of the polyester polyethylene terephthalate are described below, Fro:m the literature, ~or example Properties of Polymers, by D.W. van Krevelen, Elsevier Scientific Publishing Company, 19769 lt is known that ~he properties of the material change when amorphous poly-ethylene terephthalate is oriented. Some o~ these changes are shown in the diagrams, Figures 14.3 and 14.4 on pages 317 and 319 in the book "Properties of Polymersl'~
l~e symbols used in the discussion below correspond to the symbols in the said book.
PET, like many other thermoplasti.cs 9 can be oriented by stretc~ing the material. Normally this stretching takes place at a temperature above the glass transition temperature Tg of the material. The s~rength properties of the material are improved by orienting. The literature shows that, in the case of the thermoplastic PET, an increase in the stretching ratio~, that is to say the ~uotient of the length of ~he stretched material and the length of the unstretched material, also leads to an increase in the improvement of *he ~aterial properties. When the stretchlng ratio ,~ is increased from about 2 to a little ~ore than 3~
particularly large changes in the material properties are obtained. The strength in the direction of orien-tation is here markedly improved 7 whilst at the same time the density ~ and likewise the crystallinity Xc rises and the glass transition temperat~re Tg is raised. It can be seen fr~m the diagram on p~ge 317 that, after stretch-in~ ~ith~ assuming the ~alue of ~.1, the material with-stands a force per unlt area, which corresponds to ~ = 10, coupled with a very small elongation, whilst the elonga-tion at.AL- 2.8 is substantially lar~er. In the urther text~ the term "step" is sometimes used to designate orienting which is obtained by stretching, or a reduction in thickness by about 3 times, and ~hich leads to the marked improvements o~ the material properties, indica*ed above.
I~e diagrams quoted ab~ve show changes which are obtained on mono-axial orientation of the material.
In biaxial orientation, similar effects are obtained in ~2~Z64 -- ,4 -- .

both directions of ori;entation. - Orientation is carried out as a rule by successive stretchi~gs.
~ mproved material properties, corresponding to those which are obtained by the "step" defined above, are also obtained if an amorphous material is st~etched until it flo~s and, before flowing, the material is at a tem-perature which is below the glass transiti.on temperature Tg. In a rod being dra.wn, a reduction of the diameter of aboult ~ times results in the flow zone. On drawing, the flow zone i.s c~nt]nuously displaced int~
the amorphous material~ whilst at the same time the material, which has already undergone the state of flowing, absorbs the tensile ~orces of the test rod without an additional permanent stretching.
For bottles~ defined external diameters of the mouth with the associated thread are standardised and, in-: -the technology known at present when using the moulding ; .process described as an introduction, this determines the.
greatest diameter which is permissible in the blow-moulded container body. The reasons for this are e~plained in more detail in the following text. In order to obtain an amorphous starting material ~or -the pieces ~f tube, which are to be shaped into pre-mouldings, the material must be cooled rapidly to below the glass transition temperature Tg after extruding - in the case o~ extruded tubes ~rom which the pieces of tube are severed In the case of excessive wall thickness, the mater.ia'l does no~t possess adequate heat conductivity tD

enable the central sections of the wall ~o be cooled as rapidly as required, so that the material located in the centre becomes crystalline and opaque. For this reason, viewed theoretically, the largest possible wall thickness of the extruded tubes is less than about 9 mm.
In practice, however, wall thicknesses of less than 4 mm are used as a rule. In fact, in blow-moulding of a pre-moulding having wall material of excessive thickress, problems arise due to the cooling of the material during the actual blow-moulding step and before the material reaches the wall of the mould. The blow-moulded con-tainer is no longer clear as glass and, instead, contains opaque white sections. In blow-moulding, in order to obtain con~ainers having the requisite resistance against -stresses and penetratlon of the container wall, the wall thickness of the finished container must not fall below a defined value. Moreover, a reduction of the external diameter o* the tube during the shaping of the mouih part of the pre-moulding is not-possible in accordance with known technology. The result is that the desired mouth diameter o~ the blow-moulded container is decisive ~or the diameter o~ the pre-moulding and thus for the maximum diameter of the blow-moulded container body.
If bottles of large capacity are required, these bottles are extended, according to known technology, in the axial direction after they have reached the maximum possible -diameter.- I-n additiQn to the disadvantage of a certain instability, the extension represents an unsatisfactory utilisation of the quantity of material in the container ~ ~ 52~

body since the requisite quantity of mate~ial per unit - volume of storage capacity is greater than would be necessary if both the diameter and the~length of the container body were adapted to the actual volume required.
Moreover~ the unnecessarily large surface of the con-tainer leads to a corresponding increase in the overall penetration of carbon dioxide during the s-torage of beverages containing carbonic acid.
. To utilise the material properties of the material in the best way, it is desirable that the diameter of those parts of the pre~moulding which, af-ter the blow-moulding step, represent the actual container body, is given a value which has the result that the material în the blow-moulded container body assumes the desired orientation. In containers of PET it is desirable :~ that the.material, in oonjunct:ion with blow moulding, is biaxially stretched in such a way that the product o~ the stretchings is about 9.
The above shows that, according to kn~wn tech--nology, the quantity of material in the mouth part is not determined by the calculated stresses but by the maximum diameter of the container body. As a rule, this leads to a considerable excess of material in the mouth part.
For example, in a PET bottle of 1 litre capacity, the mouth part can, according to known technology, contain up to 25-30% of the total quantity of material. Dis-regarding the lmpleasant appearance of the oversizing o~
the mouth part; this fact also results in a waste o~
material, which is of importance in the mass production ~25~2 o~ articles.
In the technology applied at present, the mouth part and ad~acent neck partsconsist of unoriented material, t~at is to say amorphous material. This means that the material in the mouth part including the adjacen~ neck parts has properties which differ from those of the c~n-tainer body. In containers of, for example, PET, *he material in the mouth part has a glass transition tem-perature Tg of 71C, whilst the glass transition tempera-ture of the material in the container body is about 81C.
It follows from this that the material in the mouth part softens at a lower temperature than the material in the container body.
It is already known, by cold-~orming of the mouth part of the blank, t~ displace material downwards from the mouth par~ in*o the sections of the blan~, which laier represent the wall sections of the container body. In this way, a certain matching of the quantity of material in the mouth part to the future stresses is achieved but, between the actual container body and the mouth part, neck sections are formed in which the material is stre~ched by a factor of less than 30 These neck sections in the moulded container thus consist of inadequately oriented material, whilst a-t the same time the wall thickness is undesirably large. This metho~ is also ~nown from Canadian Application ~o. 322,499, -filed February 28, 1979, inventor, Kjell M. Jakobsen. British Patent Specification 1,536,194 published December 20, 1978 to Carnaud Total Interplastic has disclosed a method wherein a tubular blanX, which is closed at one end and which is provided at the other end with ~L2~SZ~

beading for fixing t,he blank in a downstream blowing element, is injection-moulded and wherein the tubular blank is blow-moulded after a certain reshaping to give a container. Material in the tubular part of the blank is expanded in the radial direction at a temperature above the glass ~ransition temperature Tg in order thus to fo~m the mouth part of the containerl A container formed in the manner described possesses a mouth part and a neck section in which the material has beeM exposed to only very slight stretching and hence orienting, so that the disadvantages, already indicated, with respect to the mouth part of the known containers are also present in this container..
The invention describecl in-Bri~tish Patent Specifica-tion 1,536,194 also has the di~advantage that only a part of the material content of the injection-moulded tubular blank is utilised when reshapln~ the blank to give the ~inished container. It is obvious that the losses of materia~ ich occur in t~i~ proce~s, represent an economic disadvantage in th~ mass production of articles.

From Federa~ German O~fenlegungsschrift DOS

2,540,930, publishea April 8, 1976, a process i5 known where-in a tubular blank of PET is reshaped to give a container and wherein the container wall consists of a material which is stretched by a factor of, for~ample, more than 1.5. The bottom part of the container consists of an amorphous unoriented ma-terial, whilst the neck sections o~ the container con-sist of material which has been oriented only to a s~ight extent. As a result of heating and crystallisation, .

caused thereby, the strength l~f the material is improved in the unoriented zones which at the same time become opaque. Furthermore, a cornbination of the methods indicated above results in an undesired oversizing of the neck sections o~ the containers, whilst the latter at the same time have poorer properties than the material in the actual container body.
- The invention provides a blank which makes it possible that 9 i~ a container ~ormed from the blank, both the mouth part and the neck sections and also the container body consist of a material which is adapted to the occurring stresses and in which the material in the said parts is oriented to a satisfactory extent in,such a way that the material is stretched, at least in the axial direction, by a factor of more than 3.
This results in the advantage of a raised glass transition temperatuL~e Tg in all the said parts of the container. This means -~hat,all thesaid parts will have the same heat resistance, and this is a great advantage compared with containers which are formed according to the known technology and which, at least as far as con-tainers with mainly clear and transparent materials are concerned, have neck sections and mouth parts which are more sensitive to heat stresses than the actual container body.
Moreover, the invention enables a container of sm~lermout~ diameter to be manufactured, the length and diameter of the container body being matched to the storage capacity o~ the co,ntainer in suoh a way that the ~.~05;~6~

smallest possible quantity of material per unit volume of storage space results.
In addition~ the invention enables a container of any desired shape of the neck part to be formed from the blank, the container material in the mouth part and in the neck part also being oriented and having a crystallinity of more than l~/o; this was achieved by stretching the material to the requisite extent, for example in the case of con-tainers of PET by stretching in the axial direction by a factor of more than 3. According to known technology it was hitherto not possible to obtain such a degree of orienting, unless the mouth part and neck sections of the containers were to consist of mainly unoriented material, in which case the neck sections merge in the shortest possible distance with oriented sections of the contalner body, where the wall thickness has been reduced by a factor of at least 3. This shaping represented an attempt to reduce the size of that zone in the neck part, which has mainly amorphous material and low orientation and hence a low glass transition temperature Tg~
In accordance with one aspect of the invention, there is provided a tukular pre-moulding of a thermoplastic material, the pre-moulding having a mouth part with adjacent neck sections at one end, a closure at the other end and a tubular section between the two ends, and the closed end and the tubular section of the pre-moulding consisting mainly of arnorphous unoriented material having a ~s~

crystallinity of less than 5%. The tubular pre-moulding of the invention is characterized in that the mouth pa.rt with adjacent neck sections of the pre-moulding are oriented mainly in the axial direction of the pre-moulding by reducing the wall thickness by a factor corresponding to the reduction of thickness obtained in a sheet of the rnaterial monoaxially stretched into yielding, the crystal-.linity of the material in the mouth part and in the adjacent neck secti.ons being at most 5~/0.
According to a further aspect of-the invention, there is provided in a tubular pre-moulding o-f a thermo-plastic of polyester or polyamide type, the pre-moulding having substantially uniform initial thickness and comprising a mouth part with adjacent neck sections at one end, a closure at the other end and a tubular section between the two ends, the closecl end and the tubular section of the pre-moulding consisting mainly of amorphous unoriented material having a crystallinity of less than 5%, the improve-ment wherein the mouth part of the pre-moulding, with adjacent neck sections, consists of material which is oriented substantially by a reduction in the thickness of the material while the remainder of the pre-moulding retains its original thickness and, at least in the mouth part, the material has a lower degree of orientation in the circum-ferential dlrection of the pre-moulding as compared to the axial direction. The crystallinity of the material in the mouth part is at most 5~/0, the orientation of the mouth ~ ~r~5~

-part and adjacent neck section~ of the pre-moulding by the thicknes~ reduction providing an increased glass transition temperature Tg in the mouth part and neck sections which is substantially equal to the glass transition temperature of the tubular section when the amorphous material of the tubular section is oriented by a subsequerlt blowing of the pre-moulding to a container.
According to the invention, the tube of thermo-plastic material is cl~nped in between two rnutually separate clamping devices~ The material in the zone between the two clamping devices is stretched in the axial direction ; of the tube by shifting the clamping devices in the direction a~ay from one another. When PET is used, ~tretching by a factor of at least 3 taXes place.
According to one embodiment of the inventionO the .

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material in the tube is stretched, while-the material is at a ~emperature above the glass transition temperature Tg, whereas in another embodiment the'mater~al is stretched in the cold state9 which means that the material is at a temperature below the glass transition temperature Tg at the beginning of the stretching step. On stretching "in the cold state", the material is drawn until flow sets in.
After stretching~ at least the central sections of the drawn material are blow-mouIded at a temperature above the glass transition temperature Tg against a mould, in order to form, for example, thre~ds and, in some cases which ma~ occur, parts of'the adjacent neck sections, while two future mouth parts are in adjacent posiiions.
Subsequently, the tube is severed at the transition between the~two ~uture mouth parts. Each of the two severed blank parts thus produoed ~orm a tubular pre-moulding~ after closing at one end and, if appropriate, reworking at the other end in order to obtain the re~ui'red closure surfaces.
Tn optional embodiments o~ the invention, the material is heated before the axi~l stretching to a tem-perature above the glass transition -temperature Tg, or the stretching step is preceded by a blow-moulding step in which the heated material is subjected to a certain expansion in order to increase the diameter of -the zone.
In another embodiment o~ the invention, the mouth parts of the pre-mouldings are shaped'by simultaneous axial stretching, and blow-moulding for the purpose of a \
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radial expansion of the heated ma-terial In certain application examples, the heated ,, material zone has a temperature profile such that one or several annular zones are at a tempèrature which exceeds the temperature of the adjacent material by 3-20C, pre-ferably 10-15C. The actual drawing or stretchi~g step starts in the material zones o~ higher temperature.
In an application of the invention, wherein the material in the tube is,at the start of axial stretching of the ma~eria~ at a temperature which is less than the glass transition temperature Tg, the drawing or stretching step is initiated~ according to an optional embodiment of the invention, with the aid of press~re forces This is achievecl, for example, by means o~ a ring which sur-rounds the tube, the inner surface of therin~ being brough~
in~o contact with the outer sur~ace o~ the tube by reducing the internal diameter of the ring.
On axial stretching of the material, the external diame~er o~ the tube is reduced. As a resu7t o~ the invention, it is thus possible to produce a pre-moulding 9 , the mouth part o~ which has an external diameter ~rhich is less than the ~xternal diameter of the tube.
Equipment ~or carrying out the process comprises a number o~ stretching and blow-moulding devices, which are each provided with two clamping devices which are located at a certain spacing from one another. The clamping devices are provided for clamping a tube in, and the two sets o~ clamping devices are arranged in such a way that they can be shifted towards one another or a~ay -,. , 1~, .

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from one another. The contact surfaces of the cla~ping devices with the tube are cooled. Appro-priate devices are provided for heating 'the material in the tube between the said sets ofclamping devices, and also the blow-moulds against which the heated.material is 'blown. , Moreover, the equipment comprises elements for closing the t~o ends of the tube before blow-moulding and also elements for applying an elevated pressure to the.closed cavity formed in this way. In certain illustrative emboaiments, a cylindrical rod is also fitted axially in the tube. Finally, an element for severing the tube into two preferably equal parts is present.
In an embodiment o~ the invention, the clamping devices are arranged in such a way that the tube can ro-tate about its own axis. In this way, heating o.~ ' the material in the zone between the two sets of clamping devices and also the severing of the tube in-to two eq~al --parts are facilitated.
In forming a blank, the tube is fixed between the ~wo clamping devices, after which the latter are shi~ted in the direction away from one another, in certai~ illus-trative embodiments after the material between the two sets vf clamping devices has first been heated to the desired temperature profile and, in certain application cases, with simultaneous radial expansion of the material in the tube or'a~ter a first radial,expansion of the material in the tube has taken place. The length of displacement relative to the length o~ the part of the

3 Zf.~l-5 tube, the material D~ which is stretched, is selected in -the case of PET in such a way that the material reaches a crystallinity o~ at least 10% on axial orientation.
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In some~cases which may occur, the cylindrical rod is introduced into the tube before the material is stretched.
In certain application examples, the rod is heated. To e~fect radial expansion, the two ends o~ the tube are-closed~ the material between the two sets of clamping . . .
--devices is heated in some cases which may occur, and the closed space in the tube is subjected to pressure, the heated material expanding in such a way tha-t it makes contact with the mould surfaces, for example for the pur-pose of moulding the mou-th thread and adjacent neck sections. When the material has cooled to a sufficient extent to reach dimensional stability, the tube is severed into ~wo parts in the severin~g element. Each o~ the two parts is closed at one end by reshaping and, if appro-priate, reworked at the other end, that is ~o say t~e mouth end, in order to produce the requisite closing sur-faces. Thus, the pre-moulding is completed.
According to the process described above, each drawing step with subsequent severing results in t~o blank parts which, after a certain reworking and reshaping, each form a blank. In this manner, no losses of material arise in the produc-tion of pre-mouldings. Of course~
the stretched material formed during the drawirlg step can be adapted in such a way that it is used ~or forming exclusiv~ely one single future mouth part with adjacent future neck sectior3s. Due to the severing of parts of ~-2re5~6~

the piece of tube 9 which can not be used for further production of the pre-moulding, however, this leads to undesired losses of material,.so that this em~odiment of the invention is only used in special cases, for example in the production of pre-mouldings which are.intended for containers having long mouth sectîons and neck sections.
Figure 1 shows, irl perspective view, a stretching and blow moulding device having ~wo sets of clamping devices~ and with the two sets of clamping devices of the stretching device being in the position for receiving a piece of tube, Figure 2 shows~ in perspective view, a stretching and blow-moulding device, with the clamping devices in the position for fixing a piece o~ tube, .Figure 3 shows a sectional view of the stretching and . blow-moulding device during the heating o~ a central part of a piece of tube, Figure 4 shows a sectlonal view o~ a stretching and blow-moulding device with the piece of tube fixed and drawn, Figure 5-shows-a sectional view of a stretchin~ and blow-moulding device with the internal volume of the piece o~ tube subjected to pressure in order ~o for.m the mouth sections and adjacent neck sections, Figure 6 shows a device for severing the piece of tube -into two separate blank par-ts, Figure 7 shows, in diagrammatic ~îew, a device for the ste~ise production o~ blank parts for pre-- mouldings.
Figure 8 shows a section~l view of a stretching and blow-m~ulding device having a device for heating an annular section in the piece o~ tube, Figure 9 s~ows a sèctional view of a stretching and blow-moulding device during the cold-arawing step of the piece of tube, Figure 10 shows a sectional view o~ a stretching and blow-moulding device after the cold-drawing step o~ the piece of tube has been carried out, Figure 11 shows a sectional view o~ a stretching and ; : blow-moulding device with the length of the ,: axially drawn zone increased, Figure 12 shows a partial section through a stretching ~: and blow-moulding devi.ce according t~ Figure 119 . in which the internal volume o~ the piece-of . tube has bee~ subjected to pressure, and in particular the forming of the neck sections adjacent to the mouth part, Fi,~ure 13 shows a completed tubular pre-moulding which - . - has been shaped from a blank part according to Figure 5, and Figure 14 shows a completed tubular pre-moulding which has been shaped from a blank part according to Figure 12.
Figures 1 and 2 show a frame on which ~wo separate sets o.~ clamping devices 20 a-b and 21 a-b are located.
In principle, the two sets of clamping devices consist ~f an upper clamping part 20a, 21a and a lower clamping part :,, .

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-- 19 _ 20b, 21b. In both sets o~ clamping devices, the upper part can be shifted between a~ open position and a closed positio~. In the closed position; the particular set of clamping devices fixes one end of a tube 50 in each case~ The two sets of clamping devices can be shifted from their starting positions (Figure 1) towards one another up to a smallest distance (Figure 2) which matches the length of the tube 50, and from there they can be shi~ted back again into the particular starting position.
In the starting position, the particular upper part assumes the open position and remains in the latter until the two sets of clamping devices have been shifted towards one another up to the said smallest distanoe7 In this position, the particular upper parts assume the closed position and thus cover a relatively large part of the tube 50, the latter being surrounded at the same time and being fixed by the particular set of-clampin~ devices.
While the upper parts are still in the closed position, the two sets o~ clamping devices are subsequently shiftèd back to t~e starting position. The shift of the upper parts 20a~ 21a of the ~wo sets of clamping devices is e~ected by means o~ drive mechanisms 25, 26, and a drive mechanism 24 is provided for shi~ting the two se-ts of clc~mping devices towards one another. The two upper parts slide in the grooves 22, 23 provided in the lower parts, whilst the lower parts slide in grooves 13 a-b provided in the frc~me 11.
A gripper 28 is provided for inserting the tube 50 into the clamping devices or removing i-t from the 2~
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clamping device When the two sets-o~ clamping devices are at their smallest distance ~rom one anoth-r, a heating element consisting o~ the ~wo heating jaws -29 a-b is brought into a position in which it can heat the central sections of the tube 50. The motion o~ the heating jaws i5 ef~ected by means of a drive mechanism 33 with a push-and-pull bar. A lead 31 for heating the, heating jaws, for example by means of electric power, i~
shown in the figures.
Adjoining one o~ the tWQ sets of clamping devices~
a cylindrical forming and blowing mandrel 27 is provided.
This mandrel is moved by means of a drive mechanism 39 from and to a position in which the cylindrical part of the mar~drel protrudes a little into the opening of the other ~set of clamping devices~ The mandrel protrudes into the said opening even when the two sets of clamping devices are in their starting positions.
The external diameter of the mandrel and the internal diameter of the tube 50 are ma~ched in such a way that the mandrel can be introduced into the tube.
Moreover, the mandrel is provided with a row of orifices 40 whlch lead to a cavity in the interior of the mandrel, which cavity is connected to a line 32 ~or a pressure medium.
A pressure medium is fed via the lines 30a, b7 c, e (the pressure line 30d is not shown in the figure~
to the individual drive mechanisms 24 9 25, 26, 33 and 39.
In Figure 3, the two sets of clamping devices-20 a-b? ~1 a-b are shown in the position for the smallest .
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_ 21 -distance between the sets. In addition, the figure shows the said cavity 42 in the mandrel 27, a gasket 41-between one end o~ the tube-50 and the set of clamping devices ~1 a-b and a gasket 34 between the other end of .
the tube 50 and the set of clamping devices 20 a-b.
A gaske-t 35 between the mandrel 27 and the set of clamping devices 20 a-b can also be seen. hn outlet valve 36 is located in the lower clamping device 21b. In this I way, the closed space-which can be subjected to pressure j through the ori~ices 40 is ~ormed in the mandrel 27.3 Figure 4 shows the two sets of clamping devices shifted back into their starting positions, while the ', surrounded parts o~ the tube 50 are still held ~irmly as before. The Figure shows that the mandrel 27 continues to projectinto the set ofclamping devices21a-~ A central zone 51o~the tube 50has been stretched inthe axialdirectionand hasasmaller wall thickness than theremaindero~ the tube.
In Figure 5~ the central zone 51 has been blow-moulded against the mould 57 a-b. The shaping surface of the mould corresponds to the ~orm of two mouth parts 52 a b, facing one ano-ther, ~or containers which are tobe formed fromthe blanksand arein the processof manufacture.
~igure 6 shows -the mandrel 27 in its starting position. A severing disc 58 is located in the position for severing the tube 50, that is to say at the transition be~ween the two moulded mouth parts 52 a-b.
Figure 7 shows a turntable 7 which ro-tates about a bearing 12. Next to the turntable, a number o~
positions A-U is indicated. One frame 11 with the .

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associated set of c~amping devices, drive mechanisms, tubular mandrel, heating device and the like according to ^ Figures 1-2 is looated on the'turntable-for each position.
In the positions,'-the particular working step is indicated '' diagra~atically'by the position of mandrel7'heating jaws, sets of clamping de~ices and the like~
! Figure 8 shows an embodiment of the invention, 1 which is adapted ~referably ~or so-calle~ cold-drawing o~
31 ,the tube. An annular heating element 38 is located between the two sets of clamping devices~ By means o~
this heating element, the central sections of the tube 50 are heated to an elevated temperature over an annular zone.
~igures9-10 relate to the cold-drawing of the ' tube 50. In ~i,gure 9, the formation of a centrally located drawn zone 53 has started, whilst in Figure 1 the entire centrally located dra~m zone 54 has been formed~ ~
'Figures 11 and-12 relate to a variant of the invention wherein the centrally iocated zone 51a of the' tube 50 is longer than in the previously described embodiments o~ the invention. The Iigures show only one of the two sets of clamping devices. Figure 11 sh~ws the position after drawing of the tube has been completed 9 whilst Figure 12 shows the central zone 51a (~igure 11) .after it has been bl.ow-moulded against an outer mould 59. The moulding surface of the outer mould corresponds tothe shapeof t~o mutually facing mouth parts (only one, 52a, is shown in the figure) and ,~ .

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parts of the adjacent future neck section 60a of the containers which are to be ~ormed from the blanks and are in ~he process of production. A zone 56, having the~largest diameter in the moulded ~uture neck sections, preferably has a diameter which is at least three times the original diameter of the tube.
Figures 13 and 14 show comp~eted tubular pre-mouldings, the pre-moulding according to Figure 13 h~.~ring been formed ~rom a blank part shown in Figure 5 and a pre-moulding according to F.igure 14:having been formed from a.
blank par-t sho~n in Figure 12. At one end, the pre-mouldings have a mouth part 62a, b with adjacent neck sections 63a, b~ At the other end the pre-mouldings have a closure 61a, b~ -A tubular section 64a, b can be seen between the-closure 61a, b and the neck sections 63a, b~ - .
In the production of a pre-moulding according to the invention, a iube 50 is brought into the position sho~m in Figure 1 with the aid of the gripper 28. me -two sets of slamping devices 20 and Zl are shi~ted towards one another with the aid o~ the drive mechanism 24 until the ~wo ends o~ the tube are in contac~ with the gaskets 34 and 410 The upper clamping devices are brought into their closed position with the aid o~
the drive mechanisms 25, 26, the tube 50 being ~irmly held at both its ends and at the same time being enclosed over a relatively large part. This situation is shown in-Fi~ure 2. As an alternative, the mandrel 27 was already in this phase brought beforehand into the position 3 2~52~91 which is shown in Figure 3. ~he heating jaws 29 are .brought into the heating position and remain in this position for such a perio~ as-is necessary for heating -. .
the material in-the c`entral sections of the tube to a temperature below the glass transition temperature Tg.
~le drive element 24 now shifts the two sets o~ clamping devices in the direction away from one another, the central sections of the tube being stretched, with simultaneous thinning o~ the tube wall, in such a way that the tube is given the appearance shown in Figure 4.
Preferably, stretohing amounts to at least a factor.of 3, and the reduction in thickness thus also amoun~s to a factor of 3. During the entire drawing step, the mandrel 27 is located in the interior of the tube, within the stretched zone~ and thls preven LS the stretched zone from ass~ming an undesirably small diameter.
The closed space in the interior of the tube is subjected to pressure, the material being expanded into the zone concerned until it makes contact with t~e outer mould 57. In this step, the future mouth parts and parts of the adjacent neck sections in two blank parts connected to one another are shaped to give pre-mouldings.
On contact with ~he surfaces o~ the outer mould~ the material in -the.tube is cooled so that it becomes dimen-sionally stable. With simultaneous retraction of the mandrel 27 into its star-ting position, the outer mould is opened and a severing disc Z8 divides the tube at the transition be-t~een the two future mouth parts. This prGduces two separate blank parts ~hich are closed at one ., .

~L2~5~6~
:

end by reshaping and are provided with the requisite closing surfaces at the other end by reworking. In this way, a tu~ular pre-moulding as shown in Figure 13 is obtained.
The design of the equipment for closing one end~, and likewise for the reworking, which may be necessary, of the mouth part, is not shown in the figures, but this can be in ~ccordance with any technology already known-and used. Normally, closing is effected by ~eating t~e material at one end of the tube up to a temperature above the glass transition temperature Tg. after which the end is ~orced in the axial direction against a substan-tially spherical shell which compresses the soft material and closes the end. Subsequently, the gripper 28 takes the two blank parts ~ormed out of the production equipment after the two sets of clamping devices have released the pre-mouldings. Subsequently; the course of the pro-cess described above is re;oeated.
According to a preferred embodiment o~ the inven-tio~, the production step described above is carried out with t~e aid of thP equipment shown in Figure 7. In positioD A; th~ tube is fed to the two sets o~ clamping devices, in positio~ ~ the two sets o~ clamping devices are shifted in the direction to~Jards one another, whilst simultaneously the mandrel is introduced into the tube, and in pusition C-E the central zone o~ the tube is heated, whilst in position ~ the heating process is`interrupted.
In positions G-H, the central sections o~ the tube are stretched, in position I the outer mo~lds move into -the - . , ---` 3 ~526~

moulding position, in position J the interior of the tube is subJected to pressure and'is formed to give the future mouth parts with the adjacent nec~ sections.
In position K, the outer moulds open, whilst in position ' L the mandrel is retracted into its starting position.
j .Position M is a cooling position for s-tabilising the ~o~m of the tube or, alternative-ly, is a reserve position, whilst in position N the ~ube is severed into ~wo blank parts. In position 0, the two future mouth parts are heated for reworking, if appropriate, and they obtain their final form in position P. In posi~ion ~, the devices ~or reworking the mouth parts have assumed again their starting position, and subsequently, in position S, the blank parts have been shifted in the direction tow~rds one another in order to enable the gripper to engage in position T and to enable ihe clamping ;'~ devices to open in position U, so tha~ the mouldings ~ormed can'be removed from -the prsduction equipment according to Figure 7. Advantageously9 the gri~per device here transfers the blanks to de~ices ~r closing one of their ends. Such deviGes can either be pro-vided independently o~ the equipment described in this paragraph, or they can form par~ o~ this equipment.
In the iatter case, this equipment must be pro-vided with a fur-ther number o~ positions.
During cold drawing of the central zone of the tubel the material is'heated before the drawing step with the aid of an annular heating element 38 (Figure 8) over an annular zone within the central zone. This'heating ' ' ' .

s~

element is preferably designed to heat the central zone as far as one of the sets of clamping devices. To .
con~rol the directlon o~ displacement during the flow which sets in on drawing, the material is normally cooled i~mediately nex~ to the heated annulus.in that direc-tion in which it is intended that the flow step should not.--propagate. In the embodiments in which the entire material of the tube is to be d.rawn bet~een the two sets of jaws, the r.equired cooling is obtained by the cooled ja~sO In other ëmbodiments, annular cooling devices are used which, in principle, are arranged in a manner corresponding to the arrangement of the heating device 38.
On warm-drawing of the central zone of the tube, one or several annular heating elements are used in cer-.tain application examples in order t~ produce the desired temperature pro~ile in the central zone o~ the tube before the latter is drawn~ The annular heating elements here ~requently consist ~ zones o~ ele~a-ted temperature in the heating jaws 29.
On cold-drawlng o~ the material in the central zone of the tube~ flow of the material sets in fir~t in the annular zone which has been hea-ted by the annular heating element 38. On further stretching of -~he cen-: tral zone o~ the tube, the flow zone o~ the material is displaced in the direction of the o-ther set of clamping devices, compare Figure 9, so -that, after completion of ~e stretching step, a central drawn zone has formed 9 t~e appearance o~ whlch is shown in Figure 10. On cold-drawing~ the cent.ral zone has no -tendency to~ards a - . .
. . .

~ 2d~5~

! reduction of the internal diameter of -the tube 9 as long as stretching is~limited to about a factor o~-3. In ~his embodiment of the invention, it is t'hus not'necessary ' to cause the mandrel 27 to assume its position in the'tube - before the actual stretching step. Figures 11~12 show an embodiment of the invention in which the stretched central zone 51a has a greater length than in the embodi-~ ments o~ the invention so far described. When the : . .
interior of the tube is subjected to pressure~ parts of .
ad jacent neck sections are also ~ormed, in addition to the two future mouth parts, these neck sections being given a greater diameter than that of the actual mouth part.
At this stage, it is preferable to allow the future neck section to be shaped to such an extent that the greatest rise in diameter'is at-least 3-fold. This~~has the advantage that a relatively dimensionally stable neck section is formed which, durirlg t~e subsequent heating in conjunction with the shaping o~ the remaining part o~ the container, is a~fected only to a small extent. ~he appearance cf a pre-moulding, which was formed from a blank part partially shown in Figure 12, can be seen in ~igure 14. ~ ' I~ the above'description, i* was explained how the blank parts are formed by severing the drawn and shaped tube. In a preferred embodiment o~ the invention, severing of the blank parts from one another is effectea with the aid of one or several severing discs which -revolve under pressure about the circumferential surface of the tube formed at the transi-tion be~ween the two 5~

~uture mouth parts.
It was assumed in the above descrip~ion that heating of the-central material sections of the tube is e~ected-by heating jaws.- To obtain the most uniform heating o~ the material possible, the tube should pre- -ferably rotate relative to the heating element. To make this possible, the clamping devices are modified, i~ appropriate having cone-type bearings or having heating -jaws which revol~e about the t~lbe.
In the case where the central sections of the tube are drawn at an initial temperature which is below the glass transition temperature Tg, the material is heated after the drawing step-to a temperature above the glass transition temperature Tg, after whi~h the future mouth par-t and parts o~ the adjacent neck sections are shaped.
I~ addition to the abo~e description, the inven-tion is also comprised ~y the attached patent`claims.

~ ' , ' ' ` .

Claims (36)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the manufacture of a tubular pre-moulding from a thermoplastic material which com-prises providing a tube of thermoplastic material with a substantially reduced material thickness in at least one zone by stretching the tube in the axial direction, to obtain, when stretching the material, an orienta-tion mainly in the axial direction of future pre-moulding, heating the material of at least the oriented zone or zones to a temperature above glass transition temperature (Tg) and expanding it in radial direction of the tube until it makes contact with the mould walls in order to form the mouth part with ad-jacent neck sections of the particular pre-moulding, the material being cooled to a temperature below glass transition temperature (Tg) and the material in one end or in both ends of the tube being heated to a tempera-ture above the glass transition temperature (Tg) and being reshaped, in order to form the closure of the particular pre-moulding.

2. A process according to claim 1, wherein said thermoplastic material comprises a material of the polyester or polyamide type.

3. A process according to claim 1, which com-prises providing said tube with a substantially re-duced material thickness in a central zone of the tube.

4. A process according to claim 1, wherein the material comprises polyethylene terephthalate and the tube is stretched in axial direction so as to provide a reduction of the wall thickness by a factor of at least about 3.

5. A process according to claim 1, character-ized in that, during the radial expansion of the material, two mouth parts, in locations facing one another, with adjacent neck sections for two future pre-mouldings are formed and, after cooling to a tem-perature below the glass transition temperature (Tg), the tube is severed at the transition between the two future mouth parts in order to form two separate blank parts, each of the latter by itself forming a tubular pre-moulding after reworking, if appropriate, in order to produce the requisite closing surfaces on the mouth parts.

6. A process according to claim 1, character-ized in the material in the zone or zones, envisaged for axial stretching, is heated to a temperature above the glass transition temperature (Tg) before the material is stretched in the axial direction of the tube,

7. A process according to claim 5, character-ized in the material in the zone or zones, envisaged for axial stretching, is heated to a temperature above the glass transition temperature (Tg) before the material is stretched in the axial direction of the tube.

8. A process according to claim 1, character-ized in that the material in the zone or zones envisaged for axial stretching is heated to a temperature above the glass transition temperature (Tg) before the material is stretched, and stretching of the material in the axial direction of the tube and radial expansion to give the mouth of the future mouth part of the particular pre-moulding are carried out substantially simultaneously or, alternatively, the radial expansion is initiated before axial stretching.

9. A process according to claim 5, character-ized in that the material in the zone or zones envisaged for axial stretching is heated to a temperature above the glass transition temperature (Tg) before the material is stretched, and stretching of the material in the axial direction of the tube and radial expansion to give the mouth of the future mouth part of the particular pre-moulding are carried out substantially simultaneously or, alternatively, the radial expansion is initiated before axial stretching.

10. A process according to claim 1, character-ized in that the material in the zone or zones envisaged for axial stretching is, before stretching, at an initial temperature which is substantially below the glass tran-sition temperature (Tg) of the material, preferably at room temperature, and that on stretching the material is caused to flow, at least in an annular zone which is displaced in the axial direction of the tube with simultaneous substantial reduction in the thickness of the tube wall.

11. A process according to claim 5, character-ized in that the material in the zone or zones envisaged for axial stretching is, before stretching, at an initial temperature which is substantially below the glass tran-sition temperature (Tg) of the material, preferably at room temperature, and that on stretching the material is caused to flow, at least in an annular zone which is displaced in the axial direction of the tube with simul-taneous substantial reduction in the thickness of the tube wall.

12. A process according to one of claims 1, 6 or 7, characterized in that the zone or zones envisaged for axial stretching have one or several annular zones in which the temperature exceeds the temperature of the adjacent material by 3-20°C, preferably 10-15°C, or that alternatively the material of the annular zones is subjected to an external pressure, the flow during the axial stretching of the material starting in the zone or zones of elevated temperature or in the zones subjected to pressure.

13. A process according to one of claims 8, 9 or 10, characterized in that the zone or zones envisaged for axial stretching have one or several annular zones in which the temperature exceeds the temperature of the adjacent material by 3-20°C, preferably 10-15°C, or that alternatively the material of the annular zones is sub-jected to an external pressure, the flow during the axial stretching of the material starting in the zone or zones of elevated temperature or in the zones sub-jected to pressure,

14. A process according to one of claims 1, 5 or 6, characterized in that, during the radial expansion of the material in the zone having a reduced thickness of material, neck sections are formed, which are stretched in the circumferential direction of the material by a factor of more than 2.

15. A process according to one of claims 7, 8 or 9, characterized in that, during the radial expan-sion of the material in the zone having a reduced thick-ness of material, neck sections are formed, which are stretched in the circumferential direction of the material by a factor of more than 2.

16. A process according to one of claims i, 5 or 6, characterized in that this is used for a thermo-plastic of polyester or polyamide type, for example polyethylene terephthalate, polyhexamethylene-adipamide, polycaprolactam, polyhexamethylene-sebacamide, poly-ethylene 2,6- and 1,5- naphthalate, polytetramethylene 1,2-dihydroxybenzoate and copolymers of ethylene terephthalate, ethylene isophthalate or other similar polymeric plastics.

17. A process according to one of claims 7, 8 or 9, characterized in that this is used for a thermo-plastic of polyester or polyamide type, for example polyethylene terephthalate, polyhexamethylene-adipamide, polycaprolactam, polyhexamethylene-sebacamide, poly-ethylene 2,6- and 1,5- naphthalate, polytetramethylene 1,2-dihydroxybenzoate and copolymers of ethylene tere-phthalate, ethylene isophthalate or other similar poly-meric plastics.

18. A process for the manufacture of a tubular pre-moulding from a thermoplastic material comprising the steps of axially stretching a tube of the thermo-plastic material to a substantially reduced material thickness in at least a central zone of a tube while substantially maintaining the diameter of the tube in the axially stretched section in said central zone, the reduction being by a factor sufficient to cause yielding and orienting of the material substantially in the axial direction of the future pre-moulding, the axial stretching of the tube being effected at a temperature not greater than the glass transition temperature of the thermoplastic material, heating the material in one of the oriented zones to a tem-perature above the glass transition temperature and expanding said material in the radial direction of the tube until it makes contact with mould walls to form a mouth part with adjacent neck sections of the pre-moulding, cooling the material to a temperature below the glass transition temperature, heating the material in at least one end of the tube to a temperature above the glass transition temperature, and reshaping said end to form the closure of the pre-moulding.

19. A process according to claim 18, wherein, during the radial expansion of the material, two mouth parts, in locations facing one another, with adjacent neck sections for two future pre-mouldings are formed and, after cooling to a temperature below the glass transition temperature, the tube is severed at the transition between the two future mouth parts in order to form two separate blank parts, each of the latter by itself forming a tubular pre-moulding.

20. A process according to claims 18 or 19, wherein the material in the zone envisaged for axial stretching, is heated to a temperature above the glass transition temperature before the material is stretched in the axial direction of the tube.

21. A process according to claims 18 or 19, wherein the material in the zone for axial stretching is, before stretching, at an initial temperature which is substantially below the glass transition tempera-ture of the material, and that on stretching the material is caused to flow, at least in an annulr zone which is displaced in the axial direction of the tube with simultaneous substantial reduction in the thick-ness of the tube wall.

22. A process according to claim 18, wherein the zone envisaged for axial stretching has at least one annular zone subjected to an external pressure, the flow during the axial stretching of the material starting in the zone subjected to pressure.

23. A process according to claim 18, wherein during the radial expansion of the material in the zone having a reduced thickness of material, neck sections are formed which are stretched in the circum-ferential direction of the material by a factor of more than 2.

24. A process according to claim 18, charac-terized in that the thermoplastic material is selec-ted from the group consisting of a polyester or poly-amide.

25. A process according to claim 18, wherein the zone envisaged for axial stretching has at least one annular zone in which the temperature exceeds the temperature of the adjacent material by from 3° to 20°C., the flow during the axial stretching of the material starting in the zone of elevated temperature.

26. A process according to claim 18, wherein the thermoplastic material is polyethylene tereph-thalate and orientation of the material in the stretched portion of the tube by axial stretching is adjusted to effect an increase in glass transition temperature in said stretched portion such that in the formation of a container by blow-moulding the pre-moulding, said container will have equalized glass transition temper-ature therethroughout.

27. A process according to claim 26, wherein the polyethylene terephthalate material is stretched to yielding by a reduction of thickness of at least about 3.

28. A method of producing a tubular pre-moulding of a thermoplastic material, the pre-moulding comprising a mouth part with adjacent neck section at one end, a closure at the other end and a tubular section between the two ends, said method comprising providing a tubular blank consisting mainly of orientable material, orienting the mouth part, and adjacent neck section of the blank to form said pre-moulding by reducing the thickness of the material while retaining the original thickness of the remainder of the blank, the reduction of the thickness and the orientation of the mouth part and adjacent neck section providing an increased glass transition temperature Tg in said mouth part and neck section which is substantially equal to the glass transition temperature of said tubular section when the orientable material of the tubular section is oriented by a subsequent reshaping of the pre-moulding to a container.

29. A method as claimed in claim 28, wherein the orientable material of the blank is substantially amorphous with a crystallinity of less than 5%.

30. A method as claimed in claim 28, wherein the material of the blank is at a temperature below the glass transition temperatures in said mouth part and adjacent neck region at the commencement of re-ducing the thickness thereof.

31. A method as claimed in claim 28, comprising radially expanding the axially oriented material of the mouth part and adjacent neck section after heating said material to a temperature above the glass transi-tion temperature.

32. A method as claimed in claim 28, wherein said thermoplastic material is selected from the group consisting of polyethylene terephthalate, polyhexa-methylene adipamide, polycaprolactam, polyhexamethy-lene sebacamide, polyethylene 2,6- and 1,5-naphthalate, polytetramethylene 1,2-dihydroxybenzoate and copolymers of ethylene terephthalate and ethylene isophthalate.

33. A method as claimed in claim 28, wherein said thermoplastic material is polyethylene tereph-thalate and is reduced in thickness by at least about 3 while concurrently being stretched axially.

34. A method as claimed in claim 28, wherein the orientation of the mouth part and adjacent neck section obtained by reduction of thickness provides a crystallinity of between 10 and 20%.

35. A method according to claim 28, wherein said thermoplastic material is of polyester or polyamide type.

36. A method according to claim 28 or 35, wherein the reducing of the thickness of the material while retaining the original thickness of the remainder of the blank is such that at least said mouth part has a lower degree of orientation in the circumferential direction as compared to the axial direction.