WO2007033722A1

WO2007033722A1 - Preform for pet bottles

Info

Publication number: WO2007033722A1
Application number: PCT/EP2006/007375
Authority: WO
Inventors: Christian Dornbach
Original assignee: Alpla-Werke Alwin Lehner Gmbh & Co. Kg
Priority date: 2005-09-20
Filing date: 2006-07-26
Publication date: 2007-03-29
Also published as: DE212006000052U1; PL64993Y1

Abstract

The invention relates to a preform (1) for producing plastic bottles, in particular PET bottles, comprising a rigid, essentially longitudinal body (2) that is closed at one end. At its opposing longitudinal end, the body (2) of the preform (1) is adjacent to a neck section (3) which is provided with an outlet opening (9). Said neck section (3) is separated from the body (3) by means of a flange-like support ring (4) projecting radially therefrom and comprises a radially protruding safety ring (5) and threaded sections (6). A section adjacent to the support ring (4) forms a section of transition (7) to the body (2) of the preform (1). At least one or more sections of the preform (1) adjacent to the body (2) (the neck section (3) and/or support ring (4) and/or a section of transition (7) to the body, which is adjacent to the support ring (4)) has or have a wall thickness which is at least partly tapered.

Description

Pref orm for PET bottles

The invention relates to a preform for plastic bottles, in particular for PET bottles which can be produced in a stretch blow molding method, according to the preamble of patent claim 1.

The usual containers made of white or colored sheet metal, glass or ceramics are increasingly being replaced by plastic containers. In particular, for the packaging of pourable media, such as cleaning utensils, personal care products, cosmetics, automotive media, etc., mainly plastic containers are used. The low weight and. the lower costs certainly play a not insignificant role in this substitution. The use of recyclable plastic materials and the overall more favorable overall energy balance in their production also contribute to promoting consumer acceptance of plastic containers, in particular plastic bottles.

The most commonly used plastic bottles are made of polyethylene terephthalate or PET and are usually produced in a so-called injection stretch blow molding process. These methods are a combination of injection molding and blow molding. In this case, a preform is first produced in an injection molding process in an injection mold. Lately, flow molding processes for the production of preforms have also been proposed. The preform has a substantially elongated, cylindrical body and is formed closed at one longitudinal end. A support ring separates the body from a neck portion with a pouring spout. This neck portion usually already has the later shape of the bottle neck. On the outside of this neck section, threaded sections or the like are usually already formed for the fixing of a closure part. The preform is after its production in a plastic injection molding removed from the mold, conditioned if necessary and placed in a blow mold of a blow molding machine, in which he finally with overpressure to the desired Form inflated and additionally stretched with a stretching mandrel. An injection blow molding process is also already known in which the blowing process takes place directly after the injection of the preform. The preform remains on the injection mandrel, and a part of the injection mold forms a portion of the blow mold.

In the manufacture of a mass-produced article, such as a plastic bottle, especially a PET bottle, the use of material is a decisive factor for competitiveness. With the very high numbers of pieces in which plastic bottles are produced, reductions in the weight of the material in the tenth of a gram range can be achieved very quickly lead to material savings in the ton range. Therefore, great efforts have been made in the past to reduce the material weight of 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 blowing and filling systems. This is an extremely unsatisfactory state both from the point of view of the operators of blowing systems and from the point of view of the bottlers of bottles produced from the preforms.

The object of the present invention is therefore to improve a preform for the production of plastic bottles, in particular PET bottles, in a stretch blow molding process in such a way that the use of material can be reduced even further. It should be possible to avoid modifications to the blowing systems and to the filling systems. The required mechanical strengths and the thermal stability of the plastic bottle made therefrom must be guaranteed. The preform should be mass-produced by injection molding or in a flow molding process.

The solution to these contradictory tasks consists in a preform for producible in a stretch blow molding bottles, especially PET bottles, which in the having indicative portion of claim 1 features listed. Further developments and / or advantageous embodiment variants of the invention are the subject of the dependent claims.

The invention provides a preform for the production of plastic bottles, in particular PET bottles, which has a rigid, substantially elongated body which is designed to be closed at its one longitudinal end. At its opposite longitudinal end, the body of the preform adjoins a neck section provided with a pouring opening, which is separated from the body by a radially projecting flange-like support ring and has a radially projecting guarantee ring and threaded sections. A portion adjacent to the support ring forms a transitional portion to the body of the preform. At least one or more adjoining the body section (s) of the preform (neck portion and / or support ring and / or adjacent to the support ring transition section to the body) has or have a wall thickness, which is formed at least partially tapered.

By the partial wall thickness reduction, the desired material savings can be achieved directly. Despite the area-wise reduction in wall thickness, there is no weakening of the mechanical and thermal properties of the plastic bottle produced from the preform, preferably in a stretch-blown process. Rather, it comes in the areas with reduced wall thickness in the production of plastic bottle to a batch or partial crystallization of the material. The crystallization supports the thermal resistance and also has an advantageous effect on the mechanical properties. Thus, the wall thickness reductions do not reduce, as expected, the mechanical and thermal properties. Surprisingly, the wall thickness reduction in the affected areas even has an advantageous effect in that the expected weakenings are compensated by the partial or partial crystallization of these areas. The dimensions of the preforms or the bottles inflated therefrom, which are relevant for the blowing systems and the filling systems, remain unchanged. The transport and further processing of the preform can take place analogously to the known preforms and bottles in the same stretch blow molding and filling equipment. In the process management must not be intervened.

In a first embodiment variant of the preform according to the invention, the region-wise wall thickness reduction in the neck section is formed between the support ring and the guarantee ring. The neck portion has a constant inner diameter. Between the support ring and the guarantee ring areas are provided with a reduced outer diameter, which are separated from each other in the circumferential direction of the sheath section by webs with a larger outer diameter. The webs extend axially between the guarantee ring and the support ring extend. The wall thickness reduced areas of the neck portion may also be formed as flattened areas, so that the neck portion has a non-circular outer contour in the areas between the webs. The number of wall thickness reduced areas is advantageously at least three.

The outer diameter of the neck portion in the wall thickness reduced areas is about 0.3 mm to about 0.9 mm, preferably 0.6 mm - 0.8 mm, smaller than the outer diameter of the neck portion in the region of the webs. In the case of flattened areas, this information refers to the areas with the smallest outside diameters.

The neck portion can also have a circumferential, groove-shaped neck region between the guarantee ring and the support ring, the wall thickness of which is formed reduced relative to the nominal wall thickness of the neck portion. The groove-shaped neck area closes with advantage directly to the guarantee ring. It extends approximately over half the axial length of the neck portion between the guarantee ring and the support ring. The wall thickness reduction is for example about 0.4 mm.

A further embodiment of the invention provides to make material savings on the support ring. In the preform thus formed, the supporter Portring a substantially radially extending annular surface adjacent to the transition portion to the body of the Pref orms, and a conical surface adjacent to the neck portion, on. The two surfaces bounding the support ring close to each other at an angle of about 9 ° to about 15 °, preferably about 10 ° - 12 °, a. The axial height of the support ring on the outer wall of the neck portion is about 2 mm to about 2.4 mm, preferably about 2.06 mm. Taking into account that the outer diameter of the support ring is fixed for manufacturing reasons, it is immediately apparent that the stated values lead to the desired material savings compared to the standard preforms with an angle of 16 ° and an axial height of 2.48 mm. The material savings are just chosen so that the support ring still ensures reliable transport of the preform during the production process and this securely supported even in the heated state of the blow mold.

In an alternative embodiment variant of the preform, the conical surface adjoining the neck portion is stepped. By a gradation provided approximately at half the radial extent, the conical surface is thereby subdivided into a first surface section immediately adjacent to the neck section and into a second surface section adjoining it radially. The first surface section encloses with the radial annular surface the usual from the Standardpreforms angle of about 16 °. By contrast, the stepped second surface section runs flatter and encloses an angle of approximately 6 ° with the radial annular surface. Despite the material savings resulting from the grading, the strength of the support ring remains intact.

The material reduction by the modification of the support ring may be provided as a single modification of the preform, but may also be formed in combination with the area-wise wall thickness reduction in the neck portion. The combined material reduction also leads to a reduced weight of the preform. This ensures a reliable support of the preform on the transport rails or the like even with a material-reduced support ring. A further, very advantageous embodiment variant of the preform provides that the transition section adjoining the support ring to the body of the preform is formed in two parts. In this case, it has a collar portion which adjoins the support ring, and an inlet region to the body of the preform. The outer diameter of the collar portion corresponds in the circumferential direction at least in sections at most to the outer diameter of the neck portion in the region of the webs and extends axially over a length of about 1.8 mm to about 3 mm, preferably about 2 mm - 2.5 mm. The adjoining inlet region has an outer diameter which is about 0.5 mm to about 1.2 mm, preferably about 0.7 mm - 1 mm, smaller than the outer diameter of the collar portion. A collar section with a length of 2 mm and an inlet area, whose outer diameter is reduced to 24.9 mm compared with the standard diameter of 25.7 mm, lead to a total length of the transition section of about 5 mm compared to a conventional preform, for example, to a material savings of about 0.5 g , Taking into account the very high numbers in which such preforms are produced, this results in an enormous saving of material without loss of mechanical and thermal stabilities of the preform or the plastic bottles produced therefrom in stretch blow molding. This embodiment of the preforms is isolated or implemented in any combination with other embodiments of the preform.

A further embodiment variant of the preform according to the invention, which can be implemented in isolation or in any combination with the variants described above, provides that the threaded sections arranged in the neck section extend over a circumferential range of approximately 1.8 to 2.1, preferably approximately 1.85 to 2 revolutions , In the case of the commonly used preforms, the threaded sections wrap around the neck section over 2.25 turns. Surprisingly, it has been found that omitting part of the change does not lead to any appreciable deterioration in the holding forces of a screwed-on closure. The tightness of the closure is not affected.

It may also be appropriate to modify the guarantee ring in order to save material. Such a preform has a neck in the neck portion. Rantiering, of a support ring facing the annular surface, which includes an imaginary normal surface on the axis of the neck portion an angle of 0 ° to about - 2.5 ° and a conical surface is bounded, with the normal surface an angle of about 38 ° to about 45 °, preferably about 40 ° - 42 °, including. Compared with the preforms known from the prior art, in which the guarantee ring is bead-like on its side facing the threaded sections, the modification leads to a (further) saving of material.

Conveniently, the inner wall of the neck portion is provided at the transition to the mouth opening with a phase whose axial length is about 2.5 mm to about 4 mm, preferably about 3 mm. This modification leads to a slight saving in material, but is of particular interest because it allows the injection mold to be simplified with respect to the preforms with a radius at the opening mouth. In contrast to preforms with a radius at the mouth, the phase is also less prone to impacts that may occur during storage and transport to the mouth of the mouth. While it can come to a radius by blows to deformations that may affect the tightness of the bottle blown therefrom, carried out in one phase, the blows on a flat portion of the preform. As a result, the impact of the impact is mitigated and damage is avoided. The phase therefore also ensures the tightness of the closure of the bottle blown out of the preform.

For soft drink bottles or the like preferably having a volume of half to three liters, it proves to be advantageous if the preform has an inner diameter at its neck portion which is approximately 21. 76 mm to approximately 21. 96 mm, preferably 21.84 mm + 0.08 mm. The increase of the inner diameter of usually 21.74 mm to the specified values also leads to a material saving, which can be isolated or implemented in any combination with the described variants. In addition, the resulting wall thickness reduction has an overall advantageous effect on the partial or partial crystallization of the neck portion in the further processing of the preform to a plastic bottle. In principle, the described modifications of the preform in all suitable for the stretch blow molding plastics can be implemented. However, they are particularly useful in preforms made of PET.

Plastic bottles, which are produced from an embodiment of the preform according to the invention in a stretch blow molding method, have mechanical and thermal properties comparable to those of conventional preforms, despite regions of reduced wall thickness in the neck section or in the transition section. The achieved material savings, however, lead to large quantities calculated to very great economic but also ecological advantages.

Further advantages and features will become apparent from the following description of an embodiment of the invention with reference to the schematic drawings. It shows in not to scale representation:

1 shows a semi-axially cut preform according to an embodiment of the invention;

Figure 2 is a half-side axially cut neck portion of the preform of Fig. 1.

3 is a sectional view of a support ring;

4 shows a half-side view of a transition region of the preform adjoining the support ring;

5 shows a sectional view of the neck section with the pouring opening;

FIG. 6 shows a guarantee ring formed on the neck section; FIG. and

Fig. 7 shows a further embodiment of the invention in half-side cut representation. A variant of a preform according to the invention is provided overall with the reference numeral 1 in FIG. The preform 1 comprises a rigid, elongate body 2 made of a thermoplastic material, which is designed to be closed at its one longitudinal end. The body 2 may be formed substantially cylindrical or conical. At the opposite end joins a neck portion 3, which has a pouring opening 9. A support ring 4 projecting substantially radially separates the neck section 3 from the body 2 of the preform 1. The support ring 4 usually serves to support the preform during transport in an injection molding plant or in a flow-compression installation, as well as for transport in a blow-molding or stretch blow molding apparatus. in which from the rigid preform by overpressure and optionally stretching a container, for example a bottle is produced. In the commercial bottles with about 0.5 to about 3 liters, the outer diameter of the support ring on the preform is often substantially unified and is for example about 33 mm + a tolerance of about 0.4 mm. The above the support ring 4 extending neck portion 3 is provided with a circumferential guarantee ring 5 and threaded portions 6. The guarantee ring 5 serves as an abutment for a guarantee strip, which is usually part of a screw cap and is connected via predetermined breaking points with a screw cap. The screw cap of the screw cap has internal thread sections and can be screwed onto the threaded sections 6 of the neck section. When unscrewing the screw cap for the first time, the guarantee ring causes the guarantee strip to be separated at the predetermined breaking points. Below the support ring 4, a transition section 7 extends to the body 2 of the preform. 1

Fig. 2 shows the neck portion 3 in an enlarged scale. The neck portion 3 has a constant inner diameter i which is, for example, about 21.76 mm to about 21.96 mm, preferably 21.84 mm + 0.08 mm. As can be seen from the illustration, the threaded portions 6 do not extend to the guarantee ring 5, as is known from the prior art preforms. In the illustrated embodiment, the threaded portions 6 are formed over a circumferential range of about 1.8 to 2.1, preferably about 1.85 to 2 full revolutions on the neck portion 3. Compared to the known from the prior art preforms, in which the Thread sections usually extend over a circumference corresponding to 2.25 revolutions, the inventive modification already means a significant material savings.

In the area between the guarantee ring 5 and the support ring 4, the neck portion is provided with reduced wall portions 31, which are separated from one another in the circumferential direction by webs 32. The reduced wall areas have a reduced outer diameter compared to the webs. For example, the outer diameter of the neck portion 3 in the reduced regions 31 is about 0.3 mm to about 0.9 mm, preferably 0.6 mm-0.8 mm, smaller than the outer diameter in the region of the webs 32.

FIG. 3 shows a modification of the support ring 4 according to the invention, which is bounded by a substantially radially extending annular surface 41 and a conical surface 42. The annular surface 41 and the conical surface 42 include an angle α, which is about 9 ° to about 15 °, preferably about 10 ° - 12 °. In this case, the support ring 4 on the outer wall of the neck portion 3 has an axial height s, which is about 2 mm to about 2.4 mm, preferably about 2.06 mm.

FIG. 4 schematically shows the transition region provided with the reference numeral 7 to the body 2 of the preform, which extends below the support ring 4. The transition region 7 is formed in two parts and comprises an adjacent to the support ring collar portion 71 and an inlet region 72. The collar portion has an outer diameter at least partially corresponds in the circumferential direction at least the outer diameter of the neck portion in the region of the webs and axially over a length b of about 1.8 mm to about 3 mm, preferably about 2 mm - 2.5 mm. The adjoining inlet portion 72 to the body 2 has an outer diameter, which is about 0.5 mm to about 1.2 mm, preferably about 0.7 mm - 1 mm, smaller than the outer diameter of Bundab- section 71. While in the known preforms of the transition section over its entire axial length has the same larger standard outside diameter, for example, 25.7 mm, is in the inventive variant this standard outer diameter is provided only in the collar portion 71. Also there, the outer diameter need not be constant over the entire circumference, but may be provided in analogy to the formation of the neck region (Fig. 2) with reduced diameter areas, which are separated from each other by webs with the standard outer diameter. In the adjoining the collar portion 71 inlet region 72, the outer diameter tapers to, for example, 24.7 mm. This tapered outer diameter is maintained until the adjoining body portion 3 is again provided with a larger outer diameter by design.

5 shows the neck section 8 provided with the pouring opening 9. In particular, a circumferential phase 8 is provided in the region of the pouring opening 9 which extends axially over a length p of approximately 2.5 mm to approximately 4 mm, preferably approximately 3 mm.

FIG. 6 shows the guarantee ring 5 provided on the neck portion 3 of the preform. This ring is bounded by an annular surface 51 and a conical surface 52. The annular surface 51 encloses with a normal surface N on an axis of the neck portion 3 a negatively counted angle γ of 0 ° to about - 2.5 °. The conical surface encloses with the normal surface an angle β of about 38 ° to about 45 °, preferably about 40 ° - 42 °.

FIG. 7 shows a further embodiment variant of the preform according to the invention. Like reference numerals designate like elements. The enlarged neck portion 3 again has a constant inner diameter i. In the area between the guarantee ring 5 and the support ring 4, the neck portion 3 is formed with a circumferential, groove-shaped, tapered region 33, which has a wall thickness reduced in relation to the wall thickness of the neck portion 3. The wall thickness reduction of the groove-shaped area is for example about 0.4 mm. The groove-shaped region 33 directly adjoins the guarantee ring 5 and extends approximately over half the axial length of the neck region between the guarantee ring 5 and the support ring 4. The embodiment of the preform according to FIG. 7 has a further modification in the region of the support ring 4. This is in turn bounded by a radial annular surface 41 and a conical surface 42. The conical surface 42 is stepped. A step 423, which is provided approximately at half the radial extent of the conical surface, divides the conical surface 42 into a first surface section 421 directly adjoining the neck section 3 and into a second surface section 422 adjoining it radially. The first surface section 421 closes the radial annular surface 41 an angle α of about 16 °. This corresponds to the angle of the boundary surfaces in support rings of conventional preforms. The second surface section 422 graduated in relation to the first surface section 421 encloses an angle δ of approximately 6 ° with the radial annular surface 41. Despite the resulting tapering of the wall thickness of the support ring 4 in its outer circumferential region, the stability of the support ring 4 is maintained in order to ensure reliable transport of the preform.

All described with reference to the exemplary embodiment of the inventive preform modifications contribute more or less to a reduction in material. The modifications may be provided either alone or in any combination with each other on the preform. In principle, the described modifications of the preform can be implemented in all plastics suitable for the stretch blow molding process. However, they are particularly useful in preforms made of PET. Plastic bottles, which are produced from a variant of the preform according to the invention in a stretch blow molding process, have mechanical and thermal properties that are comparable to those of conventional preforms, although in some regions in the neck section or in the transition section of reduced wall thicknesses. The achieved material savings, however, lead to large quantities calculated to very great economic but also ecological advantages.

Claims

claims

1. preform for the production of plastic bottles, in particular PET bottles, with a rigid, substantially elongate body (2), at its one

Longitudinal end is formed closed and adjacent at its opposite longitudinal end to a with a pouring opening (9) neck portion (3) which is separated from a radially projecting, flange-like support ring (4) from the body (2) and a guarantee ring (5) and threaded portions (6), characterized in that one or more adjoining the body (2) portion (s) of the preform (1) (neck portion 3 and / or support ring 4 and / or adjacent to the support ring 4 transition section 7 to the body. 2 ) has or have a wall thickness, which is formed at least partially reduced.

2. preform according to claim 1, characterized in that the neck portion (3) has a constant inner diameter (i) and between the support ring (4) and the guarantee ring (5) areas (31) are provided with a reduced outer diameter, in Umf Angsrichtung the Halsab- section (3) in each case by webs (32) are separated from each other with a larger outer diameter, which extend axially between the guarantee ring (5) and the support ring (4).

3. preform according to claim 2, characterized in that the outer diameter of the neck portion (3) in the reduced areas (31) is about 0.3 mm to about 0.9 mm, preferably 0.6 mm - 0.8 mm, smaller than the outer diameter in the Footbridges (32).

4. preform according to claim 1, characterized in that the neck portion (3) has a constant inner diameter (i) and formed between the support ring (4) and the guarantee ring (5) has a circumferential, groove-shaped region (33) with a reduced wall thickness is.

5. preform according to claim 4, characterized in that the groove-shaped portion (33) is provided following the guarantee ring (5).

6. preform according to claim 4 or 5, characterized in that the groove-shaped portion (33) extends approximately over half the axial length of the neck portion (3) between the support ring (4) and the guarantee ring (5).

7. Preform according to one of the preceding claims, characterized marked, that the support ring (4) has a substantially radially extending annular surface (41) adjacent to the transition portion (7), and a conical surface (42) which is connected to the neck portion (3) adjacent to each other, which enclose an angle (α) of about 9 ° to about 15 °, preferably 10 ° -12 °, and an axial height (s) of the support ring (4) on the outer wall of the neck. Section (2) is about 2 mm to about 2.4 mm, preferably about 2.06 mm.

8. Preform according to any one of claims 1-6, characterized in that the support ring (4) has a substantially radially extending annular surface (41) which adjoins the transition portion (J), and a conical surface (42) which is connected to the neck portion (3) is adjacent and stepped formed, has.

9. preform according to claim 8, characterized in that the conical surface (42) by a step (423) in two surface portions (421, 422) is divided, which connect radially to each other, and the gradation (423) approximately in half the radial extent of Conical surface (42) is provided.

10. preform according to claim 8 or 9, characterized in that an immediately adjacent to the neck portion (3) adjacent first surface portion (421) of the conical surface (42) with the annular surface (41) encloses an angle of about 16 °, and a radially subsequent , stepped second surface portion (422) with the

Ring surface (41) encloses an angle (δ) of about 6 °.

11. Preform according to one of the preceding claims, characterized in that the transition section (7) is formed in two parts and a to the support ring (4) adjacent collar portion (71) whose outer diameter in the circumferential direction at least partially at most the outer diameter of the neck portion ( 3) in the region of the webs (32) and extends axially over a length (b) of about 1.8 mm to about 3 mm, preferably about 2 mm - 2.5 mm, and an adjoining inlet region (72) whose outer diameter about 0.5 mm to about 1.2 mm, preferably about 0.7 mm - 1 mm, is smaller than the outer diameter of the collar portion (71).

12. Preform according to one of the preceding claims, characterized in that the neck portion (3) over a circumferential range of about 1.8 to 2.1, preferably about 1.85 to 2 revolutions with the threaded portions (6) is equipped.

13. Preform according to one of the preceding claims, characterized in that the guarantee ring (5) of the support ring (4) facing annular surface (51) having an imaginary normal surface (N) on the axis of the neck portion (3) an angle ( γ) from 0 ° to about - 2.5 °, and one

Conical surface (52) is bounded with the normal surface (N) an angle (ß) of about 26 ° to about 45 °, preferably about 30 °, includes.

14. Preform according to one of the preceding claims, characterized in that the inner wall of the neck portion (3) at the transition to the mouth opening (9) is provided with a phase (8) whose axial length (p) is about 2.5 mm to about 4 mm, preferably about 3 mm.

15. Preform according to one of the preceding claims, characterized in that it consists of PET.

16. Plastic bottle produced from a preform according to one of the preceding claims in a stretch blow molding.