CH706926A1 - Support ring-less preform for producing plastic containers e.g. polyethylene terephthalate bottles, in stretch blow molding process, has inner shoulder extending above groove and projecting into inner wall of preform body without under-cuts - Google Patents

Abstract

The preform (1) has an elongated preform body (2) whose longitudinal end is closed. A neck portion (3) is formed at the end, and a threaded section (6) is formed at an outer wall (5) of the portion. The portion has a circulating annular groove (9) in an area between a ring-shaped flange (8) and the section. The groove is limited by an outer shoulder that extends transversely from a base of the groove to the outer wall. An inner shoulder is formed in an inner wall (11) of the portion, extends axially above the groove and projects into an inner wall of the body without under-cuts. An independent claim is also included for a plastic container.

Description

The invention relates to a supportringlose preform for the production of plastic containers in a stretch-blow molding process according to the preamble of patent claim 1.

A large number of plastic bottles and plastic containers used today are produced in a stretch blow molding process. In this method, a so-called preform of usually elongated, tube-like shape having at its one longitudinal end a bottom and at the other longitudinal end a neck portion with molded threaded portions or the like, inserted into a mold cavity of a blow mold and inflated by a medium blown with overpressure. In this case, the preform is additionally stretched in the axial direction with a retracting mandrel inserted through the neck opening. After the stretching / blowing process, the finished plastic container is removed from the blow mold.

The preform is usually made in a separate injection molding prior to the stretch blow molding process. The preforms can also be produced in a flow molding process or by extrusion blow molding. In the so-called single-stage stretch blow molding process, the preform, without intervening cooling and storage, is transformed into a plastic container immediately after its production. In most cases, however, the plastic containers are produced in a two-stage process in which the preforms are first produced, cooled and stored for later use in a separate process. The production of plastic containers takes place spatially and temporally separated in a separate stretch blow molding process. In this later stretch blow molding process, the preforms are reheated to produce plastic bottles. For example, with the aid of infrared radiation over the axial and / or radial extent of the preform, a desired temperature profile is set, which is required for the stretch blow molding process. After inserting the preform in the mold this is formed radially by means of a gas injected with overpressure and thereby stretched with a stretching rod in the axial direction. Thereafter, the finished plastic container is removed from the mold.

A large number of the known preforms has a support ring which separates the elongate preform body from the neck portion. The support ring serves to transport the preform and the plastic container produced therefrom. In the stretch blow molding apparatus, the preform is supported by the support ring on the molding tool so that only the preform body protrudes into the mold cavity. The neck portion is usually not changed during the stretch blow molding process. Between the support ring and the threaded portions formed on the neck portion, a so-called snap ring is formed, which serves as an abutment for a guarantee closure on the finished stretch-blown plastic container. Such guarantee closures are well known, for example, from beverage bottles. When unscrewing the guarantee closure, an annular portion of the guarantee closure, for which the snap ring forms an abutment, at least partially separated from the rest of the closure. As a result, even if the bottle is resealed, the consumer is informed that the bottle has already been opened once.

In the production of mass-produced articles, such as polyethylene terephthalate (PET) plastic bottles, the use of materials is a decisive factor for the competitiveness and the ecological balance. Due to the very high quantities in which plastic bottles are produced, reductions in material weight in tenths of a tenth range can be achieved very quickly lead to material savings in the tonne range. Therefore, great efforts have been made in the past to reduce the material weight of the preforms for plastic bottles, especially PET bottles. With the known from the prior art preforms believed to have reached the optimum, the plastic bottles produced from the preforms had indeed reach the required mechanical strength and temperature stability. A disadvantage of the previous efforts to reduce the weight of the material is that these often required modifications of the stretch blow molding and filling equipment. This is an extremely unsatisfactory state both from the point of view of the operators of stretch blow molding systems and from the point of view of the bottlers of plastic containers produced from the preforms.

In WO 2006/027 092 A1, for example, a preform for wide-mouth container is described, which has a relation to the preform in the diameter greatly expanded neck portion. In this preform is dispensed with a support ring. The support of the preform relative to the mold takes place via a circumferential annular shoulder at the transition from the preform body to the extended neck portion. For the transport of the preform and the plastic container made therefrom, specially designed grippers are required whose gripping surface is adapted to the circumferential contour of the neck portion protruding from the mold. Although this preform has a material saving due to the omission of the support ring. However, this specially designed for the production of wide-mouth containers preform requires very specially designed gripper for the transport of the preform and the plastic container made therefrom. These must intervene in a usually arbitrarily oriented threaded structure, without colliding with the thread. In addition, the preform gripped by the grippers must not be changed with regard to the orientation of its longitudinal axis, in order to avoid a tilting of the preform. With regard to the fact that the gripper attack on two opposite areas of the neck area and depending on the axial position of the contact points can easily adjust a tilting moment, it is immediately obvious that suitable gripper for the known preform must have a relatively complex structure and therefore a total of greatly increase the expenditure on equipment.

The object of the present invention is therefore to improve a preform for the production of any plastic containers, such as plastic bottles, in a stretch blow molding to the effect that the use of materials can be further reduced. The preform should also allow the production of plastic containers with standardized smaller pouring openings. It should be possible to avoid modifications to the stretch blow molding lines and to the filling lines. It should be possible to dispense with specially designed grippers for the preforms and the plastic containers produced therefrom. The required mechanical strengths and the thermal stability of the plastic containers made from the preforms must be ensured. The preform should be mass-produced with the usual production methods, in particular injection molding, extrusion or extrusion blow molding.

The solution to these problems consists in a supportringlose preform for the production of plastic containers, in particular plastic bottles, in a stretch blow molding, which has the features listed in claim 1. Further developments and / or advantageous embodiments of the invention are the subject of the dependent claims.

The invention provides a supportringloser preform for the production of plastic containers, in particular PET bottles, created in a stretch blow molding, which has a substantially elongated preform body, one longitudinal end is closed with a bottom. At its opposite longitudinal end, the preform body adjoins a neck section provided with a pouring opening, on the outer wall of which fastening means for the positive fixing of a closure part equipped with corresponding engagement means are formed. At the transition from the preform body to the neck portion, an at least partially annular circumferential flange is integrally formed, which projects radially beyond an outer wall of the preform body. In a region between the flange and the fastening means, the neck portion of the preform has a circumferential annular groove. The annular groove is bounded by the flange and in the direction of the fastening means by a return of the outer wall of the neck portion. The recess forms on an inner wall of the neck portion, an at least partially annular inner shoulder, which, viewed in the direction of the preform, extends axially above the annular groove and merges substantially free of undercuts in an inner wall of the preform.

As the well-known from the prior art preform for the production of wide-necked containers, especially wide-mouth bottles, in the stretch blow molding omitted the proposed preform on a support ring, usually for the transport of the preform, for its support in the mold, for the transport of the stretch blown Plastic bottle or for their determination or support during the application of the closure in the filling plant is used. In contrast to the known preform, the proposed preform does not require a specially designed support surface on the outer wall of the preform. Instead, an integrally formed at the transition from the preform to the neck portion, at least partially annular circumferential flange for supporting the preform on the mold of the stretch blow is used. Furthermore, the flange can serve for the positive axial fixing of a closure part. The flange can in this case serve as an abutment for the detachable guarantee strip of a screw cap or in the case of oil bottles or the like for fixing the lower part of the commonly used hinge closure. Consequently, the flange may be formed as a snap ring for closure parts. The mold does not have to be redesigned because the projection of the flange over the outer circumference of the preform body is sufficiently large. Usually, the radial projection of the flange is 0.5 mm to 20 mm. The flange may be annular in circumference. But it can also be designed segment-like. Its peripheral contour may be circular; but it can also deviate from the circular shape and be formed, for example, as a polygon.

By eliminating the support ring material can be saved. A currently standard 38 mm neck with a support ring for milk or juice bottles weighs approximately between 3.5 g and 5.5 g. The proposed preform is despite the same wall thickness between about 1 g and 2 g lighter than the known from the prior art preform. In addition, since the preform of the proposed preform under the flange in the span can be made smaller than a preform under a support ring, can be saved here in addition to about another gram. Thus, by the proposed preform a weight reduction of about 25% to 50%, preferably 30%, compared to the known preform can be achieved with the same wall thickness.

The cost-effectiveness of the production of preforms in the injection molding, in the extrusion process or in the flow molding process is closely linked to the distance between the individual cavities. The maximum outside diameter of a conventional preform is determined by the support ring. By eliminating the support ring reduces the maximum outer diameter, and it can be accommodated in the mold, the extrusion mold or the mold more cavities.

The circumferential annular groove in the region between the flange and the fastening means provided on the neck portion makes it possible to grasp and transport the preform with conventional transport means, for example pliers or the like. On specially trained gripper can thus be dispensed with. The annular groove is bounded by the flange and in the direction of the fastening means by a return of the outer wall of the neck portion. The recess forms on an inner wall of the neck portion an at least partially annular circumferential inner shoulder, which, seen in the direction of the preform, extends axially above the annular groove and merges substantially free of undercuts in an inner wall of the preform. Thus, the annular groove is not a groove or the like molded into the outer wall of the neck section, which abruptly and locally leads to a reduction in the wall thickness of the neck section. Rather, the constriction of the neck portion leads to a reduction of the outer diameter of the neck portion and the adjoining preform body, which leads to a not insignificant reduction in the use of materials.

The special shape of the recess with the above the annular groove arranged inner shoulder also ensures trouble-free production of the preform usually in an injection molding. The special design avoids abrupt, localized constrictions that could lead to problems in injection molding the preform by preventing enough material from entering the threaded portion of the neck portion during filling and during repressurization. As a result, sink marks, voids or not fully ejected Preform necks occur. The inventive design of the arranged with an above the annular groove inner shoulder, however, ensures during injection molding a sufficient flow of material and also favors a uniform curing, and it is a "freezing" of individual areas of the preform with greatly reduced wall thickness prevented.

The preform can be produced in a conventional manner, in particular by injection molding. By dispensing with the support ring and by the constriction in the form of the circumferential annular groove in the neck portion and the reduction of the outer diameter material is saved significantly. The inventive design of the preform for the stretch blow molding is not limited to the production of wide-necked containers, unlike the preforms of the prior art, but rather also allows the production of plastic containers, especially plastic bottles, with commercially available opening diameters of about 32 mm to about 34 mm.

By dispensing with the support ring and the support of the preform on Blasformwerkzeug on the radially projecting flange also reduces the length of the neck portion, which protrudes in the stretch blow molding from the mold, and it can be saved more material.

The annular groove has over the outer wall of the neck portion on a radial depth which is about 0.1 mm to about 1.1 mm, preferably about 0.8 mm. This ensures that the preform, even with the usual manufacturing tolerances, deformations and vibrations on the stretch blow molding machine with the conventional transport devices, such as pliers or the like, can be taken and transported.

By the annular groove on the outer wall of the neck portion having a maximum axial width of about 0.3 mm to about 3 mm, preferably about 1.5 mm, the positioning accuracy of the conventional transport devices sufficient to seize the preform safely. In these widths of the annular groove and the axial length of the neck portion can be kept low.

The neck portion of the preform has a wall thickness measured at the attachment means, which is about 0.4 mm to about 2 mm. The fastening means may be formed for example as a continuous thread, as threaded portions, as a guide grooves or projections of a bayonet closure or the like. It is understood that under threaded or threaded sections both positive, the outer wall of the neck portion superior structures, as well as negative, to be provided over the outer wall of the neck portion recessed structures. The wall thickness of the neck portion is always measured adjacent to the respective structure of the fastener. In a thread or threaded portions, the wall thickness is thus measured between the threads or threaded sections, in guide grooves or projections adjacent to the respective structure.

At the bottom of the annular groove, the neck portion has a wall thickness that differs by not more than ± 50% of the wall thickness of the neck portion of the fasteners. Preferably, the wall thickness at the bottom of the annular groove substantially corresponds to that at the fastening means. A wall thickness measured at the inner shoulder running above the annular groove corresponds essentially to 0.5 to 1.5 times the wall thickness of the neck section on the fastening means. Preferably, the wall thickness of the neck portion at the inner shoulder formed above the annular groove substantially corresponds to the wall thickness of the neck portion at the attachment means. A portion of the preform body adjoining the radially projecting flange has a wall thickness which differs by no more than ± 50% from the wall thickness of the neck portion on the fastening means. Expediently, the wall thickness of the section of the preform body adjoining the flange essentially corresponds to the wall thickness of the neck section on the fastening means. This dimensioning of the preform ensures that sufficient material is introduced into the neck section with the threaded sections during injection molding of the preform during the filling process and during pressing in for shrinkage compensation. As a result, sink marks, voids or not completely ejected Preformhälse be avoided. The wall thickness conditions promote a uniform curing process, and it is a "freezing" of individual areas of the preform with too little wall thickness prevented. An advantageous embodiment of the preform provides that the wall thicknesses of the neck portion of the attachment means, the inner shoulder and the adjoining the flange portion of the preform body substantially correspond to each other. Such a preform proves particularly for the production by injection molding as particularly advantageous, since just the particularly "structured" sections have a uniform wall thickness as possible. As a result, in the preform neck, which is not further formed in the stretch blow molding process, i. is stretched radially and / or axially, weak points avoided. This makes it possible to form the preform neck overall with a smaller wall thickness and thus to save material.

In order for the preform gripped by the transport means to be centered even better in its position, the annular groove of the outer wall of the neck portion is tapered radially inwardly. The smooth transition to the wall of the neck portion proves to be advantageous for the production process of the preform by injection molding, for example, for the uniformity of the curing of the same or for its demolding, wherein the flowing transition region forms a Entformungsschräge on the outer wall.

The preform has an inner wall which is substantially free of undercuts. As a result, the injection molding process can be carried out with a simple core, which has an immediate advantageous effect on the production costs of the preforms.

The formed in the interior of the preform neck, extending above the annular groove inner shoulder may be formed differently. For example, it may form a radial surface or be designed stepped. An advantageous embodiment of the invention provides that the inner shoulder is formed as a conical surface. In the stretch blow molding process, the conical surface allows a seal between the tuyere and the preform inside the preform. By allowing the sealing to take place inside the preform, deformations of the neck portion, in particular of the end surface bordering the pouring opening, can be avoided. Also, any damage can be prevented by the provided on the outside of the neck portion fasteners. The tuyere may have a smaller diameter because it no longer needs to receive the neck portion of the preform. The dimensioning of the blowing nozzle can be kept small in the preform formed according to the invention also in the production of plastic containers with larger diameters of the pouring opening. This has advantages with regard to the design of the tuyere, with regard to the required contact forces and also with regard to the media pressures required for the stretch blown process. By sealing in the interior of the preform, therefore, the wall thickness in the neck portion can be further reduced. This leads to a significant material savings, which has an advantageous effect on the unit cost of plastic containers. The seal in the interior of the preform allows for multiple tools a closer arrangement of the mold cavities, which also has an advantageous effect on the production of the stretched from the preforms plastic container.

The seal between the tuyere and the proposed preform takes place in the interior of the preform exclusively by an annular contact of the mouth of the tuyere with the inner shoulder formed as a conical surface. On additional sealing devices can be omitted. In order to facilitate the sealing inside the preform, the conical surface with the substantially axially extending inner wall of the neck portion encloses an angle which is about 100 ° to about 150 °.

Suitable materials for the preform all suitable for the injection blown and stretch blow molding materials come into question. For example, these are PET, PET-G, HDPE, PP, PS, PVC, copolymers of the above plastics, bioplastics such as PEF, filled plastics and mixtures of said plastics. The plastic or the plastic mixture may contain additives, catalysts, release agents and lubricants as well as dyes. Preferably, the preform is made of PET in an injection molding process or else in a flow molding process. It is irrelevant whether all components of the plastics or plastic mixtures or only a part of these components are obtained from renewable raw materials and the remaining part of the components, for example, is obtained petrochemically.

By using a supportringless preform designed according to the invention, the total costs for the production of plastic containers with arbitrarily large opening diameters, in particular of plastic bottles, can be reduced in a stretch blow molding process. In contrast to the supportringless preforms known from the prior art, no specially designed transport means are required for transport and no modifications of the molding tools are required. The special shape of the preform leads to significant material savings, which is both economically and ecologically beneficial.

Despite the material savings, the plastic containers produced from the inventively designed preform in the stretch blow molding method have mechanical and thermal properties which are comparable to those of plastic containers produced from conventional preforms. The proposed preform is particularly suitable for the production of plastic containers in a two-stage stretch blow molding process in which the preform is first produced in a separate process, for example by injection molding, and then the preform is separated in time and / or space in a stretch blow molding process to form a plastic container. in particular a plastic bottle, is transformed. As a result, the production of the preforms, for example by injection molding, and the actual stretch blow molding process can each be carried out under optimized conditions, the different cycle times of the two different processes not influencing each other.

Further advantages and features will become apparent from the following description of an embodiment of the invention with reference to the schematic drawings not to scale true representation: <Tb> FIG. 1 <SEP> shows a semi-axially cut proposed preform; <Tb> FIG. 2 <SEP> shows an enlarged view of a neck portion of the proposed preform with indicated preform body and <Tb> FIG. 3 <SEP> shows a proposed preform inserted into a mold cavity of a mold.

Fig. 1 shows a half side axially cut preform, the overall reference numeral 1 carries. The preform 1 has an elongated preform body 2, whose one longitudinal end is designed to be closed. At its opposite end, the preform body 2 adjoins a neck portion 3, which is provided with a pouring opening 4. The neck portion 3 is provided on its outer wall 5 with threaded portions 6, which serve for the form-fitting determination of a screw cap, not shown here with an internal thread. Furthermore, it can be seen from the illustration that the preform 1 at the transition from the preform body 2 to the neck portion 3 has an annular circumferential flange 8, which protrudes radially from the jacket 7 of the preform body 2. The flange 8 serves as an abutment for the detachable guarantee strip of the screw cap for a plastic container stretched out of the preform 1 or for oil bottles or the like for fixing the lower part of a commonly used hinge closure and is often referred to as snap ring. In a region between the flange 8 and the threaded portions 6, the neck portion 2 has a circumferential annular groove 9 which is bounded by the flange 8 and by a recess 10 of the outer wall 7 of the neck portion 3. The annular groove 9 is used for the intervention of the usual means of transport, for example of grippers, for the transport of the preform. 1

The preform 1 may be formed one or more layers. In question are all suitable for injection molding and stretch blow molding materials, such as PET, PET-G, HDPE, PP, PVC or filled plastics, which may be at least partially made of renewable resources. Preferably, the preform 1 is produced in an injection molding process.

Fig. 2 shows the neck portion 3 of the preform 1 in an enlarged scale. For reasons of clarity, hatching of the cut representation has been dispensed with. The one hand by the flange 8 and the other part of the recess 10 of the outer wall 7 of the neck portion 3 limited annular groove in turn bears the reference numeral 9. As a result of the annular groove 9 is formed on an inner wall 11 of the neck portion 3, an annular circumferential inner shoulder 12 which is free of undercuts in the Inner wall 13 of the preform 2 passes. The annular groove 9 is formed such that the inner shoulder 12, viewed in the direction of the preform body 2, extends in front of or above the annular groove 9. In this case, the inner shoulder 12 extends parallel to the annular groove 9. According to the illustrated embodiment, the inner shoulder 12 is formed as an annular circumferential conical surface which forms an angle of about 100 ° to 150 ° with the inner wall 11 of the neck portion. The inner shoulder 12 formed as a conical surface can be used in the stretch blow molding process as a sealing surface opposite the mouth of the tuyere.

The neck portion 3 of the preform 1 has a measured between the threaded portions 6 wall thickness w, which is about 0.4 mm to about 2 mm. A measured at the bottom of the annular wall thickness of the neck portion 3 is provided in Fig. 2 by the reference numeral d. The wall thickness d at the bottom of the annular groove 9 differs by no more than ± 50% of the wall thickness w of the neck portion 3 between the threaded portions 6. Preferably, the wall thickness d corresponds to the bottom of the annular groove 9 is substantially the wall thickness w between the threaded portions 6 or slightly above. A wall thickness x measured at the inner shoulder 12 extending above the annular groove 9 essentially corresponds to 0.5 times to 1.5 times the wall thickness w of the neck portion 3 on the fastening means. The wall thickness x at the inner shoulder 12 formed above the annular groove 9 preferably corresponds substantially to the wall thickness w of the neck portion 2 on the fastening means 6. A portion of the preform body 2 adjoining the flange 8 has a wall thickness provided with the reference symbol b also differs by not more than ± 50% of the wall thickness w of the neck portion 3 between the threaded portions 6. The wall thickness b of the section of the preform body 2 adjoining the snap ring 7 expediently corresponds essentially to the wall thickness w of the neck section 3 between the threaded sections 6.

The circumferential annular groove 9 has over the outer wall 5 of the neck portion 3, a maximum radial depth t, which is about 0.1 mm to about 1.1 mm, preferably about 0.8 mm. A largest axial width a measured in the axial direction of the preform 1 is about 0.3 mm to about 3 mm, preferably about 1.5 mm. The circumferential annular groove 9 tapers in the direction of its bottom and forms a preferably flowing transition to the outer wall 5 of the neck portion 3.

3 shows schematically a proposed preform 1 used in a mold cavity 21 of a molding tool 20 of a stretch blow molding apparatus. In FIG. 3, only one mold half of the molding tool 20 is shown. The preform 1 used is shown in axial section in analogy to FIG. 1 on one side. The radial projection of the preform 1 formed on the flange 8 relative to the jacket 7 of the preform 2 is about 0.5 mm to about 20 mm. The larger span of the radial projection of the flange 8 results from the variability of the outer circumference of the preform 2. The smaller the outer circumference of the preform 2, the greater is at a given neck diameter of the radial projection of the flange 8 against the outer wall 7 of the preform 2. Je smaller the outer diameter of the preform 2, the lower is the material use even with larger wall thicknesses of the preform 2. The radial projection of the flange 8 is sufficient so that the preform 1 can be supported in the stretch blow molding on the mold 20 so that its neck portion 3 protrudes from the mold cavity 21. The heated preform body 2 is located inside the mold cavity 21 and is axially and radially inflated by a medium, usually air, injected with overpressure. At the same time the preform body 1 is stretched in the axial direction by a retracted stretching mandrel, not shown here. After the stretching / blowing process, the finished plastic container is removed from the mold. The circumferential groove 9 formed on the neck portion 3 allows the engagement of conventionally formed transport devices, for example grippers, for the transport of the preform 1 and the plastic container produced therefrom, which are indicated by the arrows 22 in FIG.

Claims (15)

1. Supportless preform for the production of plastic containers, in particular plastic bottles, in a stretch blow molding process with a substantially elongated preform body (2), one longitudinal end of which is closed and which at its opposite longitudinal end to a provided with a pouring opening (4) neck portion (3) adjoins the outer wall (5) fastening means (6) for the positive fixing of a corresponding engagement means equipped closure part are formed, characterized in that at the transition from the preform body (2) to the neck portion (3) an at least partially annular circumferential flange (8) integrally formed which projects radially beyond an outer wall (7) of the preform body (2), and in that the neck section (3) has, in a region between the flange (8) and the fastening means (6), a circumferential annular groove (9) extending from the flange (8). 8) and in the direction of the fastening means (6) of a a recess (10) of the outer wall (7) of the neck portion (3) is delimited, which forms on an inner wall (11) of the neck portion (3) an at least partially annular inner shoulder (12) extending in the direction of the Preformkörpers ( 2), extends axially above the annular groove (9) and merges substantially free of undercuts into an inner wall (13) of the preform body (2). 2. preform according to claim 1, characterized in that the annular groove (9) has a radial depth (t) relative to the outer wall (5) of the neck portion (3), which is about 0.1 mm to about 1.1 mm, preferably about 0.8 mm. 3. preform according to claim 1 or 2, characterized in that the annular groove (9) has a maximum axial width (a) of about 0.3 mm to about 3 mm, preferably about 1.5 mm. 4. Preform according to one of the preceding claims, characterized in that the neck portion (3) at the bottom of the annular groove (9) has a wall thickness (d) having a wall thickness (w) of the neck portion (3) on the fastening means (6) ± 50% corresponds. 5. preform according to claim 4, characterized in that the wall thickness (d) of the neck portion (3) at the bottom of the annular groove (9) substantially corresponds to the wall thickness (w) of the neck portion (3) on the fastening means (6). 6. Preform according to one of the preceding claims, characterized in that at the above the annular groove (9) extending inner shoulder (12) measured wall thickness (x) a wall thickness (w) of the neck portion (3) on the fastening means (6) ± 50% corresponds. 7. preform according to claim 6, characterized in that at the above the annular groove (9) extending inner shoulder (12) measured wall thickness (x) substantially corresponds to the wall thickness (w) of the neck portion (3) on the fastening means (6) , 8. Preform according to one of the preceding claims, characterized in that a to the flange (8) adjoining portion of the preform body (2) has a wall thickness (b), which is substantially 0.5 times to 1.5 times the wall thickness (w) corresponds to the neck portion (3) on the fastening means (6). 9. preform according to claim 8, characterized in that the wall thickness (b) of the flange (8) adjoining portion of the preform body (2) substantially corresponds to the wall thickness (w) of the neck portion (3) on the fastening means (6). 10. Preform according to one of the preceding claims, characterized in that the neck portion (3) has a to the fastening means (6) measured wall thickness (w), which is about 0.4 mm to about 2 mm. 11. Preform according to one of the preceding claims, characterized in that the annular groove (9) of the outer wall (5) of the neck portion (3) tapers radially inwardly. 12. Preform according to one of the preceding claims, characterized in that the above the annular groove (9) extending inner shoulder (12) is designed as an annular circumferential conical surface. 13. Preform according to one of the preceding claims, characterized in that it preferably in an injection molding one or more layers of a material consisting of PET, PET-G, HDPE, PP, PS, PVC, copolymers of the above plastics, bioplastics, such as PEF, filled plastics and mixtures of said plastics is made. 14. Use of a supportless preform (1) according to one of the preceding claims in a two-stage stretch blow molding process in which the preform (1) is first produced in a separate process and then temporally and / or spatially separated the preform (1) in a stretch blow molding to a plastic container, in particular a plastic bottle, is formed. 15. Plastic container, in particular plastic bottle, produced in a stretch blow molding, preferably in a two-stage Steckblasverfahren, from a supportringlose preform (1) according to one of claims 1 to 13.