Modified hot runner systems for injection blow molding

Fl ELD OF THE I NVENTI ON

The present invention relates in general to new developments of thermoplastic preforms in particular of the type used for blow molding containers, and more particularly to preforms having a crystallized neck for resistance to deformation at elevated temperatures. It also relates to a method for producing said containers and, in particular, to preforms used for their production, as well as a method for producing said preforms.

BACKGROUND OF THE I NVENTI ON

The use of plastic containers as a replacement for glass or metal containers in the packaging of beverages has become increasingly popular. Several types of plastics have been used, ranging from aliphatic and aromatic polyolefins (polyethylene, polypropylene, polystyrene) over halogenated polymers (polyvinyl chloride, polyvinylidene chloride) and aliphatic polyamides (nylons) to aromatic polyesters. As far as the rigid food packaging sector is concerned, polyethylene terephthalate (PET), an aromatic polyester, is by far the most widely used resin. This choice is driven by its unique material properties, combining amongst others shatter resistance, lightweight, high mechanical strength, transparency, recyclability , ... Beverage applications, both for carbonated and non- carbonated products, constitute the single largest application area for PET containers. Most PET containers are made by stretch blow molding of preforms which have been made by processes including injection molding. In some circumstances, it is preferred that the preform resin is amorphous or only slightly semi-crystalline in nature, as this allows for stretch blow molding. Highly crystalline

preform s generally are difficult, if not im possible to stretch blow m old.

With plastic m aterials ( like PET) being derived from oil, the ongoing increases in resin, oil and energy pricing has created significant pressure on package owners to reduce the total cost of ownership of their plastic packaging m ix. This in turn drives focus on finding solutions which enable to further reduce the wall thickness of these plastic (like PET) containers ( light-weighting) whilst m aintaining the inherent overall perform ance characteristics and design flexibility. I t also challenges the plastic m aterial converting industry to increase the output of its plastic m aterial converting platform s, on processes like injection and stretch blow m olding. The com bination of reduced material utilization and increased production m anufacturing output reduces the total cost of ownership for both preform s and containers.

At the sam e tim e, in som e specific end m arket applications, increased perform ance specifications are requested on param eters including therm al stability, barrier performances and m echanical rigidity. Such a specific end m arket application requesting increased perform ance specifications for PET containers includes hot-fill containers, which m ust withstand filling with hot liquid products without significant deform ation, followed by sealing and a cooling process which creates a vacuum in the container, due to the volum e contraction of the hot filled liquid.

A particular problem associated with these hot-fill containers concerns the therm al stability of both the body, but especially the neck finish of the container throughout the hot filling process, because increase in tem perature during the process induces m olecular relaxation and shrinkage in the container m aterial. The

higher the crystallinity of the container, the m ore the container is resistant to said relaxation. When an essentially am orphous or only slightly sem i-crystalline preform is converted into a container by the stretch blow m olding process, the process conditions determ ine the am ount of crystallinity that is induced in the different container parts. Unless special precautions are taken and/or additional process steps are included, the neck finish, being clam ped and restricted from stretching, will receive alm ost no increase in crystallinity. Any increase obtained will always be negligible in com parison to the increase induced in the stretched main body.

Any container part m ade entirely of am orphous or only slightly sem i-crystalline PET m ay not have enough dim ensional stability during a standard hot-fill process to resist the relaxation process and hence m eet the specifications required when using standard threaded closures.

Unacceptable volum e shrinkage of the container and/or especially of the neck area m ay create leaks between the neck and closure, thus increasing exposure to m icro-organism s, whilst increasing gas ingress and/or egress. This can lead to non-specification com pliant quality issues and, in case of food applications, to potentially consum er hazardous situations when pathological m icro-organism s are able to grow inside the packed food m atrix.

I n these circum stances, a container com prising increased am ounts of crystalline PET, especially in the neck finish, would be preferred, as it would hold its shape during hot-fill processes.

Another application in which plastic containers are subj ected to elevated tem peratures, include pasteurisable containers which, after filling and sealing, are then exposed to an elevated tem perature profile for a defined tim e period. Throughout the

pasteurization process, the sealed container m ust have dim ensional stability so as to rem ain tight and within the specified volum e tolerance.

Yet another high-tem perature application is the use of plastic returnable and refillable containers for both carbonated and non- carbonated beverages, whereby the container m ust withstand wash and reuse cycles. Such containers are filled with a carbonated or non-carbonated beverage, sold to the consum er, returned em pty, and washed in a hot, potentially caustic solution prior to refilling. These repeated cycles of therm al exposure m ake it difficult to m aintain the overall shape, appearance and threaded neck finish within the tolerances required to ensure adequate functionality and/or general consumer acceptance.

A num ber of methods have been proposed to address said problems of elevated tem perature im pact on plastic containers throughout their filling or use cycle, thereby ensuring that the required specifications for volum e shrinkage, shape retention, neck softening and others are m et.

One such m ethod consists of adding an additional manufacturing step that exposes the neck finish and/or body part of the preform or container to a heating element in order to therm ally crystallize the neck finish and/or body part of the preform or container . However, the required capital investm ents, the increased m anufacturing processing time and costs for specific m aterials and/or auxiliaries lead to an increased overall cost of ownership and increased total product cost. As previously stated, the overall cost of producing a container is very im portant and needs to be tightly controlled because of com petitive m arket and business pressures.

Alternative m ethods of strengthening the neck finish involve crystallizing select portions of the neck finish, such as the top sealing surface and flange. Again, this requires an additional heating step and increased processing time.

Another alternative is to use a high glass transition tem perature m aterial in one or m ore layers of the neck finish. Generally, this involves m ore com plex preform injection m olding procedures to achieve the necessary layered structure in the finish.

Another alternative m ethod includes specific container design and design features such as to com pensate for the developed vacuum through the hot-fill process.

A particular perform ance characteristic associated and critical to carbonated beverage containers, include barrier perform ance i.e. the control of gas ingress and/or egress. To conserve the taste of the beverage and hence increase the shelf life of the product, it is essential that the gas m ixture in the container rem ains unchanged for as long as possible after the filling process. Different m ethods are being used nowadays to enhance the barrier properties of the container walls, including passive m ethods (co-extrusion m ultilayer approaches, coating applications, nanotechnology) and active methods (oxygen scavenger incorporation) and com binations thereof. All these m ethods significantly increase the cost of ownership.

With respect to m echanical properties, com m ercial articles in general m ade out of polyesters and more specifically out of PET depend prim arily on som e degree of orientation induced during the m anufacturing processes to enhance the m echanical properties.

The degree of m olecular orientation and the physical properties of the resulting oriented article are governed o.a. by the strain rate applied during processing, by the stretch ratio, by the molecular weight of the resin and by the tem perature at which the orientation takes place. Bi-axial orientation during stretch blow m olding when transform ing a preform into a container leads to strain induced crystallization. This in turn im proves m echanical strength and barrier properties. The am ount of crystallinity reached and the crystal shape depend on the strain rate and the stretching tem perature. State of the art production m ethods are optim ized to enhance the mechanical strength by stretching the am orphous preform to m aximal strength within the lim its of the material characteristics. Typical average applied stretch ratios am ount to up to 4.5 in the circumferential direction and up to 3.2 in the axial direction. Exceeding these lim its and entering ranges of too high stretch ratios lead to the creation of m icro voids and prem ature container failure.

A particular problem when blow m olding rem ains generating enhanced m echanical strength in the neck finish and in the bottom portion of the container in light of the negligible respectively low stretch ratios in these specific areas.

Especially in the case of containers intended for filling with carbonated soft drinks this local reduction in strength leads to m ore severe container deform ation and consequently to a reduction of dissolved carbon dioxide in the soft drink and to a decreased shelf life. To alleviate the inherent weakness of these particular areas recourse is taken to preform s exhibiting significant higher wall thicknesses in neck finish and bottom area.

Another widely used method to capitalize on the induced crystallinity and to extend it into less oriented areas is the process called heat-setting, in which the transformation from amorphous preform to crystalline container is preformed at high temperature for rather prolonged exposure cycle times.

A particular limitation, state of the art production methods suffer from, stems from the preheating prior to stretch blow molding the container and more specifically to the heat history heat-set containers are subjected to.

In the heat-set process the preform and resulting container are exposed to significantly higher temperatures then is the case for so- called cold-drawn bottles, as e.g. used for water and carbonated soft drinks. A typical preform reheat temperature for a heat-set container amounts to 130 ⁰ C versus 90-100 ⁰ C for cold-drawn containers.

Following the preform is stretch blown in a heated container blow mold where only the inner container wall is air cooled. Typical heat-set container mold temperatures are in the range of 160 ⁰ C. In contrast a cold-drawn container is blown in a mold kept at around 20°.

This thermal treatment destroys most of the stretch induced orientation as relaxation processes have ample time to develop. As a consequence the resulting heat-set container looses a substantial amount of mechanical strength. The ultimate mechanical strength reached in the heat-set bottle is achieved predominately by additional crystallization through the prolonged thermal treatment. Overall the resulting heat-set container strength is lower than that of a typical cold-drawn container. Therefore heat-set containers necessitate higher material demand, longer process cycle times and the application of more energy compared to cold-drawn containers.

From the above it is clear that it would be desirable to provide a method of manufacturing a preform made out of crystallizable polymers for a container having a neck finish which resists deformation, particularly at elevated temperatures, characterized in that it is produced within the standard processing time frame and/or limited extensions thereof.

It is equally clear that it would be desirable to provide a method of manufacturing a preform made out of crystallizable polymers for a container having, at optimized wall thicknesses, equal or superior end performance properties including, amongst others, gas permeation resistance and mechanical strength.

According to a first embodiment of the present invention, the present invention is directed to a method for making out of crystallizable polymers an article in general, or more specifically a preform and resulting stretch blow molded container, providing equal or superior end performance characteristics. Said method includes hot runner system modifications, thereby inducing new structures both at the level of preform and/or container.

Another embodiment of the present invention provides a method and apparatus for the cost-effective manufacture of such articles in general, specifically injection molded preforms and stretch blow molded containers.

SUMMARY OF THE I NVENTI ON

The present invention describes a method for producing preforms and containers made out of crystallizable polymers, in particular of the type used for stretch blow molded containers, and more particularly preforms and containers with optimized wall thickness, yet superior overall performance characteristics, including enhanced resistance to thermal deformation both in the body and especially the neck finish, gas permeability resistance and mechanical strength.

DETAI LED DESCRI PTI ON

In the description, the following definitions have been applied for: - "Crystallizable polymer" means a polymer exhibiting both amorphous and crystalline regions when cooled to an equilibrium state below the melting point.

- "Crystallinity" means the volume fraction of the crystallizable polymer that is packed in the crystalline state. This volume fraction is calculated as P-P _a /P _c Pa where P is the density of the tested material; P ₃ is the density of pure amorphous material (e.g. PET: 1.333 g/cm ³ ); and P _c is the density of pure crystalline material (e.g. PET: 1.455 g/cm ³ ).

- "Pre-stratified structure" means the regular or irregular sequence of variations in molecular pre-alignment/orientation and/or crystallinity between different locations of the cross-section of the preform. "Stratified structure" means the regular or irregular sequence of variations in molecular pre-alignment/orientation and crystallinity between different locations of the cross-section of the container.

As stated hereinabove , while a preform with reduced crystallinity level is preferred for stretch blow m olding, a container having a higher degree of crystallinity is preferred for its overall enhanced end perform ance characteristics, including better therm al stability in case of exposure to elevated tem peratures during its filling or usage cycle, increased gas perm eation resistance and higher m echanical strength.

Unless special precautions are taken during the injection m olding process (e.g. quenching techniques) , injection m olded articles in general, specifically preforms m anufactured out of crystallizable polym ers, consist of crystalline regions, where m olecules are packed regularly and densely with strong short-range inter-chain interactions holding them together, and non-crystalline or am orphous regions, where m olecular packing is either irregular and less dense and/or to som e degree regular but even less dense than the irregular am orphous fraction.

I n the crystalline regions, deform ation (e.g. stretching by stretch blow m olding) is m uch m ore difficult to achieve due to the strong short-range m olecular inter-chain locking m echanism mentioned. Consequently, increasing the proportion of crystalline regions, that is, the increase in crystallinity, results in reduced stretch blowing capabilities.

I n order to facilitate the stretch blow m olding process, that transform s the predom inantly am orphous preform through the intermediate step of am orphous chains orientation into a three- dimensional crystalline thus strong container, it is therefore state of the art practice to quench the polym er m elt in the injection cavity so as to prevent the crystallization in the preform . As also the neck finish is quenched, it is as void of crystallinity as the body part. Contrary to the body part however, the neck finish, being clam ped

and restricted from heat-up and stretching, cannot crystallize during the stretch blow m olding step.

The end result of the state of the art process is therefore a container with oriented crystalline body and less or non-oriented am orphous neck finish, which leads to the neck softening problem s and the currently used workarounds, as described hereinabove.

The underlying governing physical principles are as follows:

When a polym er m elt of a crystallizable polymer is cooled down rapidly, i.e. quenched, the m aterial vitrifies before the onset of crystallization can take place. The vitrification process results in a drastic restriction of the m acromolecular segm ental m obility, in other words the vitrified m acrom olecules can no longer arrange them selves efficiently so as to start building crystallites. The vitrification process also locks in any pre-alignm ent/orientation of the m acrom olecules that m ay have been present in the polym er melt at the m om ent of quenching. The vitrified m aterial is therefore am orphous in nature.

When the vitrified am orphous material is heated up in preparation for the stretch blow m olding process, the locked in pre- alignm ent/orientation is released as soon as the vitrification tem perature is reached. Since the heating cycle is very slow on a m olecular tim e scale, relaxation processes can become active and the anisotropy that m ight have been locked in during the prior vitrification of the polym er m elt m ay disappear again, leaving the m aterial to a greater extent isotropic in nature.

Next, the heated m aterial is biaxially stretched in the stretch blow m olding process. Dependent on the tem perature at which the stretch blow m olding takes place, onset and rate of induced

crystallization m ay vary. The period of tim e in which the preform is stretched to a container however is sufficiently long on a m olecular tim e scale level to warrant crystallization, as can be appreciated by those skilled in the art. I n addition, it is known to those skilled in the art that the rate of crystallization induced by the stretching process is m uch higher than any crystallization rate reached using the tem perature param eter only.

Translating the above to the state of the art practice of m anufacturing containers by the injection and stretch blow molding process, it has becom e clear why the neck finish exhibits less therm al stability than the body part of the container at the end of the stretching operation :

The body part was quenched to an am orphous state during the injection m olding process, was heated and stretch blow m olded hereby becom ing crystalline in nature as desired.

The neck finish was quenched to an am orphous state during the injection m olding process, was left cold and restricted from stretching before respectively during the stretch blow m olding process, and therefore rem ained am orphous in nature and void of any increase in crystallinity.

I n order to increase the therm al stability of the neck finish, it needs to becom e crystalline in nature. Modifications and additions to the m anufacturing process have been proposed as described earlier on. All of these suffer from being slow and hence add valuable and costly tim e to the m anufacturing process. The reason for this is to be found in the second physical phenom enon m entioned : the difference in crystallization rate between heat-induced crystallization and m echanically induced crystallization, be this by shear, flow, stretching strain or the like.

In accordance with the present invention, it has now been surprisingly found that the effect of induced pre- alignment/orientation of macromolecules in the polymer melt may be synergistic with the effect of crystallinity, in an accelerated way. By use of the both effects, articles in general, or more specifically preforms and stretch blow molded articles, specifically containers, thereof can now be obtained, having superior properties that have never been attained by conventional methods described in the prior art.

According to the present invention, both the crystallinity and the pre-alignment/orientation of the macromolecules in the polymer melt govern the properties of the articles in general, specifically preforms and stretch blow molded articles, specifically containers, made out of crystallizable polymers.

The current invention combines the effect of pre- alignment/orientation of the macromolecules in the polymer melt with the well-known crystallinity effect in order to achieve the synergistic performance enhancement in the article in general, more particularly the preform and/or container.

By means of controlled local friction/shear through the introduction of modifications inside the hot runner system, the synergistic combination underlying the present invention allows introducing orientation gradients and hence stratification over the wall section of the articles made out of crystallizable polymers, including the preform and the resulting stretch blown container .

The mechanism of controlled local friction/shear and synergistic/cumulative combination of pre-alignment/orientation and crystallization of the crystallizable polymer in turn allows

creating a pre- and stratified structure across the manufactured end products, like preforms and containers, leading to end articles having high thermal resistance, gas permeation resistance and mechanical strength.

By creating said orientation gradients and pre- and stratified structures, articles like preforms can be made that will result in equal or superior end performance characteristics in the containers manufactured thereof at optimized wall thickness and/or retain the necessary dimensions in the neck finish and/or body part when the final container is being subjected to elevated temperatures during its filling or usage cycle.

By controlling the local friction/shear and resulting pre- alignment/orientation of the macromolecules of the crystallizable polymer within the injection process, the mechanisms, positions and rates of movement of the molecules thereof are regulated both in the polymer melt matrix and in the final wall matrix in the articles manufactured, like in the preform and the stretch blow molded article thereof.

More practically, in the method according to the present invention, the amount of pre-alignment/orientation of the macromolecules of the crystallizable polymer in the polymer melt and the resultant molecular orientation and orientation gradients obtained in the article in general are regulated primarily within the hot runner system. The nature - semi-crystalline or amorphous - and the distribution of this nature across selected regions of the article in general, specifically the preform after the injection molding process, is regulated primarily within the preform cavity of the injection process.

As stated above and in accordance with the present invention, the pre-alignm ent/orientation of the m acrom olecules is induced by controlling the local friction/shear within the injection process.

To generally align m acrom olecules that facilitate creation of the desired orientation gradients and pre- and stratified structures in the article in general, specifically in the preform , the polym er m elt m acrom olecules are oriented in the hot runner of the injection system by controlling the locally applied friction/shear. This can, am ongst others, be achieved by passing the m olten polym er through specially designed internal hot runner m odifications such as profiling of the bus and/or needle or placing inserts within the hot runner system . I f needed, this can be com bined with high injection pressure or repetitive com pression and decom pression cycles.

I n contrast with hot runners for state of the art injection molding processes whereby these hot runners are typically designed to avoid friction/shear when the polym er flows through the hot runner, the present invention utilizes the control of locally applied friction/shear in the said hot runner as m eans to introduce preferred pre- alignm ent/orientation of the m acrom olecules. Additional friction/shear can also be induced at the entrance to the preform cavity.

The basic principle behind this feature is the fact that the flow path or flow channel, through which the selected m aterials will flow, is being m odified from a cross-sectional point-of-view and in relation to its length. The hot runner construction is m odified in a m anner to force the polym er m elt into pre-alignment/orientation.

The variations of said m odifications of hot runner construction include configurations of the hot runner which can be obtained by

applying some of the following, non-exhaustive or non-lim itative adj ustm ents, either used alone or in com bination : i) changing the diam eter of the flow channel, ii) introducing Venturi restrictions for the m elt flow, followed by channels of defined length producing subsequent expansion of the flow, iii) appropriate sloping of said restrictions or expansions,

Practically, without being lim itative or exhaustive, this can be realized by profiling of the needle and/or the outer housing of the hot runner (bus) and/or introducing inserts (e.g. geom etrical configurations selected from one or m ore of concentric tubes, star wheels, or zones having diam eter variations) , at selected positions in the hot runner.

Additional friction/shear at the entrance to the preform cavity can be achieved by reducing the orifice hole inside the hot runner.

The final flow channels obtained in the hot runner can be very diverse in design and can be sym m etrical or non-sym m etrical as required to achieve the desired final stratified configuration of the container.

Without wishing to be bound by any theory, the physical and chem ical phenomena that form the basis for the invention will now be described:

It is com m on knowledge that quenching of isotropic polym er m elts leads to vitrification of the m acrom olecules at a tem perature, characteristic for that particular polym er, the so-called glass transition tem perature. Below the glass transition tem perature, the macrom olecular segm ental m obility is drastically restricted, as the

macromolθculθs are "frozen in". Above the glass transition temperature the macromolecular segmental mobility increases steadily with increase of temperature. As the amount of macromolecular segmental mobility increases, matrix randomization, known as relaxation, becomes more and more predominant, leading ultimately to an isotropic melt.

It is known by those skilled in the art that anisotropic, i.e. pre- aligned/oriented, polymer melts behave quite differently upon quenching/cooling. Dependent on the degree of pre- alignment/orientation, the vitrification process takes place at temperatures exceeding the characteristic glass transition temperature of the polymer and the vitrification leads to a more dense amorphous structure.

Therefore, when a polymer melt featuring different degrees of pre- alignment/orientation, such as a stratified polymer melt, is quenched, those parts exhibiting the highest degree of pre- alignment/orientation will vitrify first, i.e. at the highest temperature, whereas those parts exhibiting no pre- alignment/orientation will vitrify at the glass transition temperature. Parts featuring intermediate degrees of pre-alignment/orientation will vitrify at intermediate temperatures. The result is a highly anisotropic amorphous polymer glass, featuring regions with molecular packing ranging from fully random, i.e. irregular, to structured, i.e. pre-aligned/oriented. These orientation gradients translate into density gradients, with the structured regions featuring a higher density.

Upon reheating the cooled vitrified polymer matrix, onset of macromolecular segmental mobility will occur in the reversed order, i.e. the lower the degree of pre-alignment/orientation in the glassy

state, the earlier ( i.e. at lower tem perature) the onset of m acrom olecular segm ental mobility (which as stated before leads to random ization into an isotropic structure, i.e. relaxation) once the glass transition tem perature is crossed in the heat- up process.

From the above, it is clear that the pre-alignm ent/orientation frozen in into the glassy state during the first quenching process is retained after heating up such a polym er matrix above its glass transition tem perature. Dependent on the ultim ate tem perature reached in the heating cycle, some regions in the polymer m atrix will rem ain vitrified, namely those with increasing degrees of pre- alignm ent/orientation that vitrified at tem peratures exceeding the one reached in the heat-up cycle.

These phenom ena thus enable to m aintain the during the inj ection process in the preform induced pre- and stratified structure during the preheating prior to stretch blow m olding and then to transform the stratified am orphous structure into a stratified crystalline structure in the stretch blow m olding process.

Variations in the cooling/quenching rate in the inj ection cavity enable stream lining the nature - am orphous or sem i-crystalline - of the vitrified polym er m elt.

Whereas fast quenching locks in pre-alignm ent/orientation in the glassy vitrified state, reduced rates of cooling/quenching allow for com petition to progressively develop between the vitrification and crystallization processes.

As it is known for those skilled in the art that pre- alignm ent/orientation accelerates the rate of crystallization dram atically with respect to the heat induced crystallization,

relatively sm all differences in cooling rate can cause significant differences in the nature of the cooled polym er m atrix.

Contrary to the additional heating steps utilized in the current state of the art processing as described earlier on, the crystallization of the strongly pre-aligned/oriented polym er fraction in the pre- and stratified structure occurs on a m uch sm aller tim e scale and well within the tim e fram e typical for state of the art preform injection cycle tim es and/or lim ited extensions thereof.

Above phenom ena allow for the introduction of the regular or irregular sequence of variations in m olecular pre- alignm ent/orientation (see figure 1 OA and 1 0B) and/or crystallinity between different locations of the cross-section of the preform .

Adj usting the cooling/quenching rate in the injection cavity appropriately (i.e. tim e and location wise) will facilitate m anufacturing in the injection molding process a preform , having substantial pre-stratified structure. Such a preform will be transform ed into a crystalline container during the sole stretch blow m olding process with no need for additional heating or processing steps to strengthen the neck finish.

Above phenom ena equally allow for the introduction of the regular or irregular sequence of variations in m olecular pre- alignm ent/orientation and crystallinity between different locations of the cross-section of the container.

By adj usting the cooling/quenching rate in the injection cavity appropriately (i.e. tim e and location wise) , it will facilitate m anufacturing in the injection m olding process of a container having substantial stratified structure in the body part. Such a

container will not need additional heating or processing steps to strengthen the neck finish.

The different levels of cooling are preferably m aintained by therm al insulation of the regions requiring lower cooling rates. This therm al insulation can be accom plished e.g. by utilizing a com bination of low and high therm al conduct m aterials as inserts.

The processes according to the present invention preferably accom plish the m aking of a preform within the preferred cycle tim es, and/or lim ited extensions thereof, for standard PET preform s of sim ilar size , design and weight by standard m ethods currently used in preform production. Said processes are enabled by tooling design and process techniques to allow for the sim ultaneous generation of orientation gradients and different degrees of crystallinity in particular locations on the preform .

The cooling of the m old in preform regions for which it is preferred that the m aterial be generally amorphous or sem i-crystalline, is accom plished by chilled fluid circulating through selected regions of the m old cavity and core.

Bearing in m ind the consideration about the m echanism of the invention described hitherto, it will be readily understood that the injection process conditions can be optim ized to the well specified range in order to m ake the articles in general, m ore particularly the preform s and resulting stretch blow molded containers of the present invention.

The present invention can be applied to various crystallizable polym ers to m anufacture articles in general, specifically preform s

and containers through processes including injection and stretch blow molding.

The preform and container may be made solely of PET or another crystallizable polymer, preferably but not exclusively an aromatic or aliphatic polyester, a blend of aromatic or aliphatic polyesters, an aromatic or aliphatic polyester copolymer or any combination thereof.

Preferred examples include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polytrimethylene naphthalate (PTN), polylactic acid (PLLA) and copolymers and blends thereof.

The preforms made out of crystallizable polymers are preferably monolayer i.e. comprised of a single layer of a base material, or they may be multilayer, including, but not limited to, those which comprise a combination of a base material and a barrier material. The material in each of these layers may be a single type of a crystallizable polymer or it may be a blend of crystallizable polymers.

In accordance with the present invention, it has also been found that the pre-alignment/orientation of the amorphous macromolecules can be further positively influenced through the utilization of a crystallizable polymer with a higher molecular weight, as once orientation has been achieved, pre-aligned macromolecules from a crystallizable polymer with a higher molecular weight exhibit a higher resistance to relaxation, herewith retaining the orientation over a longer time period.

It is clear that a method according to the present invention may have convincing advantages compared to prior art methods. In specific, for articles in general, or more particularly preforms and containers made out of crystallizable polymers by manufacturing processes including injection and stretch blow molding, through the achievement of stratification in the body and the neck finish during the injection molding step, the desired end benefits can be obtained including, amongst others, minimized dimensional variations in the neck finish under elevated temperatures due to the higher average level of crystallinity reached in the neck finish, equal or better gas permeation resistance and higher mechanical strength.

Furthermore, by the process of the present invention, the prior art steps of exposure to thermal heating elements, crystallization of select portions, utilization of high glass transition temperature materials in combination with more complex injection molding processes and/or the processes including post-mold thermal crystallization can be eliminated and the manufacturing of the said preforms and containers occurs within the usual standard manufacturing time frame and/or limited extensions thereof.

In particular for articles in general made by processes including injection and/or stretch blow molding operations, and more particularly for preforms and containers made out of crystallizable polymers, the present invention can lead to a further reduction of the article's wall thickness given the increased mechanical strength obtained from the creation of the stratification across the article wall. In turn the reduction of the wall thickness can create a substantial increase in the operational output of the injection and/or stretch blow molding process. These benefits combined allow for a further reduction of the total cost of ownership of the produced

articles in general, specifically preforms and containers made out of crystallizable polymers.

Having the increased mechanical strength of the finally blown container also allows for the absorption of the vacuum upon cooling of the liquid which enables the making of containers having a simpler design and geometry compared to conventional containers having vacuum panels and/or other specially designed features in the bottle geometry allowing the vacuum absorption.

The above advantages make the articles of the present invention very suitable for high speciality applications including hot-fill applications and diverse carbonated and/or non- carbonated beverage applications.

EXAMPLES

1. Injection System (Figure 1) a. A commercially available grade of a crystallizable polymer, being PET, is taken within a classical IV range of 0.78 -

0.82, like reference M&G Cobiter 80. b. The polymer material referenced under 1a. is converted on a classical injection machine, like type Huskey, operated at typical machine settings :

O Extruder Barrel 270 - 290 ⁰ C

O Nozzle 270 - 290 ⁰ C

O Manifold 275 - 295 ⁰ C

O Gates 280 - 300 ⁰ C

O Mold Cooling Water 10 - 15 ⁰ C

O Cycle Time 10 - 60 seconds

c. Position 1b is repeated with a commercially available grade of a crystallizable polymer, being PET, with an increased IV range of 0.82 - 0.86, like reference M&G Cleartuf Max. d. Position 1b is repeated with a commercially available grade of a crystallizable co-polymer, being PET based, within a classical IV range of 0.78 - 0.82, like reference M&G Cleartuf 8006.

2. Hot runner system a. Positions 1a through 1d are executed with normal classical hot runner configuration for injected preform production. b. Positions 1a through 1d are repeated with the incorporation of specific hot runner modifications as referenced under figures 2 through 9.

3. Injection Preform a. Positions described under 1 and 2 are executed with the use of an industry available preform suitable for an injection stretch blow molded bottle of a selected volume size. b. Position 3a is repeated but with the use of an industry available preform suitable for an injection stretch blow molded bottle, the preform having a reduced axial stretch ratio for the selected volume size. c. Position 3a is repeated with adapted preform mold temperatures in-between 8 and 60 ⁰ C for either neck and/or body area. d. Position 3b is repeated with adapted preform mold temperatures in-between 8 and 60 ⁰ C for either neck and/or body area.

4. Preform Reheating process a. The preforms obtained from positions 3a through 3d are reheated on an conventional blow molding machine, like

Sidθl, operated under preform reheat temperature range of 90 to 95 ⁰ C. b. The performs obtained from positions 3a through 3d are reheated on an conventional blow molding machine, like Sidel, operated under preform reheat temperature range of

100 to 110 ⁰ C. c. The performs obtained from positions 3a through 3d are reheated on an conventional blow molding machine, like Sidel, operated under preform reheat temperature range of 120 to 130 ⁰ C.

5. Blow molding process a. The performs obtained from positions 4a through 4c are blown in a conventional blow mold suitable for an injection stretch blow molded bottle of the selected size operated at mold temperature of 23 ⁰ C. b. The performs obtained from positions 4a through 4c are blown in a conventional blow mold suitable for an injection stretch blow molded bottle of the selected size operated at mold temperature of 80 ⁰ C. c. The performs obtained from positions 4a through 4c are blown in a conventional heat set blow mold suitable for an injection stretch blow molded bottle of the selected size operated at mold temperature of 160 ⁰ C.

The above example demonstrate the benefits as set out in the description with respect to end functional properties including improvements on mechanical strength, barrier performance, dimensional stability and optimized wall thickness about 0.2 mm of the resulting stretch blown container as the general injection and blow molding processing output. The resulting containers are ideally used for hot fill applications (with shrinkage percentage being less

than about 4%) and for diverse carbonated and/or non-carbonated beverage applications.

In the specification and the figures only typical embodiments have been disclosed. Specific terms have been used in a generic and descriptive sense and done not for the purpose of limitation. As apparent to those skilled in the art, it should be understood that this invention is not to be unduly limited to the illustrative example as set out hereinabove.