Preform of plastic container and corresponding injection mould

Abstract

A preform (1) made of plastic material suitable for producing a bottle suitable for containing a sparkling beverage, such as sparkling wine, by stretch blow molding, said preform defining a longitudinal axis (X), said preform comprising: a neck (2) having an inner diameter value D0 greater than or equal to 17 mm, a thickness varying along said longitudinal axis (X), a minimum value of at least 4 mm; -a tubular body (3) arranged below the neck (2) and having a minimum inner diameter greater than or equal to 12 mm; and-a bottom (4) closing the tubular body (3) at a first end of the tubular body (3) opposite a second end adjacent to the neck (2), the bottom (4) having a minimum thickness greater than or equal to 3 mm; wherein the tubular body (3) comprises:-a first substantially cylindrical portion (5) close to the neck (2) having a thickness of at least 4 mm, a length along the longitudinal axis (X) of at least 30 mm, a corresponding outer diameter value D1; -a second portion (6) adjacent to said first portion (5) wherein the outer diameter gradually increases with the frustoconical profile from a value D1 to a value D2; said second portion (6) having a maximum thickness of at least 6 mm and a length along the longitudinal axis (X) of at least 20 mm; -at least one further substantially cylindrical portion (7, 8, 9) arranged between the second portion (6) and the bottom (4) and having a thickness of at least 6 mm.

Description

Technical Field

[0001] The present invention relates to a preform made of plastic material, which is suitable for industrially producing containers for filling carbonated beverages, and the containers have a "champagne" - type bottom or base. In particular, the preform is suitable for producing bottles for sparkling wine.

[0002] The present invention also relates to an injection mold for producing the preform. Background Art

[0003] The design of the preform depends on the blowing method and the subsequent use of the bottle, and all these variables must be mainly considered, such as:

[0004] - The final shape of the bottle,

[0005] - The internal volume of the bottle,

[0006] - The type of liquid to be filled, which can be highly carbonated or moderately carbonated,

[0007] - The state of the liquid, the bottle can be filled with hot or cold liquid,

[0008] - The use of the bottle, the bottle can be disposable, or reusable and thus can be refilled multiple times after recycling and disinfection.

[0009] Currently, there are no plastic bottles on the market for sparkling wine or other carbonated beverages whose necks, bodies, and bottoms are aesthetically similar to the classic glass bottles for sparkling wine, Prosecco, or champagne.

[0010] The need to develop such bottles made of plastic instead of glass stems from the fact that at least some of the raw materials for producing glass are decreasing, and the related production processes are particularly energy - consuming.

[0011] In order to produce such bottles made of plastic, many problems need to be overcome, and they must be addressed in the step of designing the corresponding preform.

[0012] For example, in order to obtain a bottle made of plastic with a "champagne" - type bottom or base, the material must be optimally distributed, especially in the area supporting the base. Therefore, the walls of the bottle have different thicknesses, and thus the wall thickness of the preform is also different. In fact, for mechanical strength under different pressure and temperature conditions, the bottom must have a clearly defined material thickness pattern.

[0013] In addition, it is quite difficult to produce a neck of a preform made of plastic material that can withstand the forces exerted by the cork from the inside and the metal hoop from the outside after blowing the bottle, filling the bottle, applying the cork, and applying the relevant metal hoop on the cork and around the neck.

[0014] Another difficulty is the choice of preform material, which does not atomize or crystallize during the cooling process in the mold cavity or during stretch blow molding.

[0015] So far, none of these problems have been overcome. Therefore, there is an urgent need to produce a preform made of plastic material that can overcome the above-mentioned drawbacks. Summary of the Invention

[0016] One object of the present invention is to produce a preform made of plastic material for producing bottles for sparkling wine or other carbonated beverages, the neck, body, and bottom of which are aesthetically similar to the classic glass bottles for sparkling wine, Prosecco, or champagne.

[0017] Another object of the present invention is to produce a preform made of plastic material, the neck of which can withstand the force applied from the inside by the cork and the force applied from the outside by the metal hoop after blowing the bottle, filling the bottle, applying the cork, and applying the metal hoop on the cork and around the neck.

[0018] Another object of the present invention is to produce a preform made of plastic material having a neck and a longitudinal portion below the neck, the longitudinal portion being configured to obtain the best cork-opening performance of the bottle blown from the preform and being aesthetically similar to the classic glass bottles for sparkling wine, Prosecco, or champagne.

[0019] Another object of the present invention is to produce a preform having a tubular body and a bottom, which is designed to obtain an optimal blown bottle, avoid problems in neck forming, such as possible shrinkage, and the preform is thermally stable, can be filled with carbonated liquid, can be reused, and has a reliable "champagne" - type bottom, that is, it is stable on the supporting base.

[0020] Another object of the present invention is to produce an injection mold specifically designed for producing the preform.

[0021] The present invention achieves at least one of these objects, as well as other objects that will become apparent from the present specification, by a preform made of plastic material, which is suitable for producing by stretch blow molding a bottle suitable for containing a sparkling beverage (e.g., sparkling wine), the preform defining a longitudinal axis X and comprising:

[0022] - a neck having an inner diameter value D0 greater than or equal to 17 mm, the thickness varying along the longitudinal axis X and having a minimum value of at least 4 mm;

[0023] - a tubular body disposed below the neck and having a minimum inner diameter greater than or equal to 12 mm; and

[0024] - Bottom, closing the tubular body at the first end of the tubular body, the first end being opposite to the second end adjacent to the neck, the bottom having a minimum thickness greater than or equal to 3 mm;

[0025] Wherein the tubular body comprises:

[0026] - A first generally cylindrical portion adjacent to the neck, having a thickness of at least 4 mm, a length along the longitudinal axis X of at least 30 mm, and a corresponding outer diameter value of D1;

[0027] - A second portion adjacent to the first portion and preferably away from the neck, wherein the outer diameter gradually increases from the value of D1 to the value of D2 in a frustoconical profile; the second portion has a maximum thickness of at least 6 mm and a length along the longitudinal axis X of at least 20 mm;

[0028] - At least one additional generally cylindrical portion disposed between the second portion and the bottom, and having a thickness of at least 6 mm.

[0029] Another aspect of the present invention relates to an injection mold for producing the aforementioned preform, the mold comprising a plurality of molding cavities, wherein each molding cavity is defined by the cooperation of a male component or a core insert with a female component including a neck insert or a neck ring, a cavity insert, and a gate insert;

[0030] Wherein the neck insert extends along the longitudinal axis of the molding cavity so as to cover a first longitudinal portion of the molding cavity, the first longitudinal portion corresponding to the region of the preform including the aforementioned neck and the first and second portions of the tubular body;

[0031] Wherein the neck insert is provided with a first frustoconical protrusion and a second frustoconical protrusion at both ends along the longitudinal axis respectively;

[0032] Wherein a first locking element is provided for locking the male component and the neck insert together by at least adjoining the side surface of the first frustoconical protrusion;

[0033] Wherein a second locking element is provided for locking the neck insert and the cavity insert together by adjoining the side surface of the second frustoconical protrusion;

[0034] Wherein the length H1 of the first frustoconical protrusion and the length H2 of the second frustoconical protrusion measured along the longitudinal axis satisfy the following relationship:

[0035] H1 + H2 ≥ 0.2 * H

[0036] Wherein H is the length measured along the longitudinal axis, from the flat annular surface of the molding cavity corresponding to the mouth surface of the preform to the parting line between the neck insert and the cavity insert.

[0037] Each molding cavity is configured to obtain the aforementioned preform.

[0038] Further features and advantages of the present invention will become more apparent from the detailed description of exemplary but non - exclusive embodiments.

[0039] The dependent claims describe specific embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the description of the present invention, reference is made to the accompanying drawings, which are provided by way of non - limiting example, in which:

[0041] Figure 1 A side view and a cross - sectional view of a first embodiment of a preform according to the present invention are shown;

[0042] Figure 2 A side view and a cross - sectional view of a second embodiment of a preform according to the present invention are shown;

[0043] Figure 3 A cross - sectional view of a first neck variant of a preform according to the present invention is shown;

[0044] Figure 4 A cross - sectional view of a second neck variant of a preform according to the present invention is shown;

[0045] Figure 5 A cross - sectional view of a part of an injection mold for producing a preform according to the present invention is shown;

[0046] Figure 6 An example of a bottle for sparkling wine obtained from a preform according to the present invention is shown;

[0047] Figure 7 Shows Figure 6 A cross - sectional view of the bottom of a "champagne" - type bottle in

[0048] Like reference numerals and letters in the figures denote like elements or components. DETAILED DESCRIPTION OF THE INVENTION

[0049] Referring to Figures 1-4 , some examples of preforms made of plastic material are shown, which are used for producing bottles for sparkling wine or other carbonated beverages, the necks, bodies and bottoms of which are aesthetically similar to classic glass bottles for sparkling wine, Prosecco or champagne.

[0050] In all embodiments of the present invention, the preform defines a longitudinal axis X, preferably an axis of symmetry, and comprises:

[0051] - a neck (2) having an inner diameter value D0 greater than or equal to 17 mm and a thickness varying along a longitudinal axis X with a minimum value of at least 4 mm;

[0052] - a tubular body (3) disposed below the neck (2) and having a minimum inner diameter greater than or equal to 12 mm; and

[0053] - a bottom (4) closing the tubular body (3) at a first end of the tubular body (3), the first end being opposite a second end adjacent to the neck (2), the bottom (4) having a minimum thickness greater than or equal to 3 mm.

[0054] Advantageously, the minimum thickness of the bottom (4) ensures the proper formation of a bottom having a "champagne" - type shape; the minimum value of the inner diameter of the tubular body (3) allows for proper blowability of the bottle by means of a stretching rod; and the minimum inner diameter and thickness values of the neck (2) ensure the proper insertion of a cork and, after blowing the bottle, filling the bottle, applying the cork and applying a metal hoop on the cork and around the neck, sufficient resistance to the forces applied by the cork from the inside and the metal hoop from the outside.

[0055] In the present specification, a "substantially cylindrical portion" means a part of a preform that is not a perfect cylinder because a draft angle is provided only on the inner profile of the preform part or on both the inner and outer profiles of the preform part. As is well known, a draft angle is the taper applied to the vertical walls of an injection - molding assembly to assist in releasing the part from the mold.

[0056] Advantageously, to ensure an optimal distribution of the plastic material during the stretch - blow molding step of the bottle, which has a shape similar to that of a glass bottle for sparkling wine or Prosecco or champagne, the tubular body (3) comprises ( Figure 1 and Figure 2 ):

[0057] - a first substantially cylindrical portion (5) close to the neck (2) having a thickness of at least 4 mm and a length along the longitudinal axis X of at least 30 mm, with a corresponding outer diameter value D1;

[0058] - a second portion (6) adjacent to the first portion (5) and remote from the neck (2), wherein the outer diameter gradually increases from the value D1 to the value D2 in a frustoconical profile; the second portion (6) has a maximum thickness of at least 6 mm and a length along the longitudinal axis X of at least 20 mm; and

[0059] - at least one additional substantially cylindrical portion disposed between the second portion (6) and the bottom (4) and having a thickness of at least 6 mm.

[0060] In particular, by removing the cork from a bottle blown from a preform according to the invention and filled with different types of sparkling wine, it has been found in the cork-opening performance test that at least an effective cork-opening performance equivalent to that obtained with a glass bottle of similar shape can be obtained only when the preform has the following characteristics in combination:

[0061] - The inner diameter D0 of the neck 2 is greater than or equal to 17 mm, preferably in the range of 17 to 19 mm, and the thickness varies along the longitudinal axis X, with a minimum value of at least 4 mm, preferably in the range of 4 to 7 mm;

[0062] - The first substantially cylindrical portion 5 adjacent to the neck 2, having a thickness of at least 4 mm, preferably 4 to 5 mm, and a length along the longitudinal axis X of at least 30 mm, preferably in the range of 30 to 50 mm; and

[0063] - The second portion 6, which is adjacent to the first portion 5 and is farther from the neck 2 relative to the first portion 5, and has a maximum thickness of at least 6 mm and a length along the longitudinal axis X of at least 20 mm, preferably in the range of 20 to 40 mm; wherein the outer diameter gradually increases from the value D1 to the value D2 along the frustoconical profile.

[0064] Only by taking into account these dimensional limitations can the best resistance to the torsional load and axial opening force applied during the cork-opening process be obtained. The deformation of the plastic bottle is obtained outside these dimensional limitations.

[0065] In Figure 1 In the first embodiment shown, the preform includes two additional substantially cylindrical portions 8, 9 disposed between the second portion 6 and the bottom 4.

[0066] The first additional substantially cylindrical portion 8 adjacent to the second portion 6 has a first thickness of at least 6 mm and a corresponding outer diameter substantially equal to the value D2.

[0067] The second additional substantially cylindrical portion 9 disposed between the first additional substantially cylindrical portion 8 and the bottom 4 has a second thickness greater than the first thickness, preferably equal to at least 7 mm, and maintains a corresponding outer diameter substantially equal to the value D2.

[0068] The two additional portions 8, 9 have a draft angle both on the outer contour and the inner contour; while the first portion 5 has a draft angle only on the inner contour.

[0069] Such a draft angle can include, for example, a range from 0°10’ to 1°.

[0070] Preferably, the thickness variation between the first additional substantially cylindrical portion 8 and the second additional substantially cylindrical portion 9 is in the range of 0.2 to 1.0 mm.

[0071] In particular, the first thickness may be in the range of 6 to 8.3 mm, while the second thickness may be in the range of 7 to 8.5 mm.

[0072] Optionally, in this first embodiment, the inner diameter of the second part 6 gradually decreases from the value D1' to the value D3 along the frustoconical profile, preferably, the value D1' is equal to the inner diameter value D0 of the neck 2.

[0073] However, in this first embodiment, a connecting part 10 is always provided, which connects the first additional substantially cylindrical part 8 and the second additional substantially cylindrical part 9, wherein the inner diameter gradually decreases from the value D3 to the value D4 along the frustoconical profile.

[0074] If the gradual decrease in diameter from the value D1' to the value D3 is not provided in the second part 6, then in the connecting part 10, the inner diameter will gradually decrease from the value D1' to the value D4 along the frustoconical profile.

[0075] According to the first variant, the length of the second additional substantially cylindrical part 9 along the longitudinal axis X is at least 15 mm, preferably in the range of 15 to 30 mm.

[0076] According to the second variant, the length of the first additional substantially cylindrical part 8 along the longitudinal axis X is at least 20 mm, preferably in the range of 35 to 70 mm.

[0077] According to the third variant, the length of the connecting part 10 along the longitudinal axis X is at least 5 mm, preferably in the range of 5 to 10 mm.

[0078] One or more of the dimensional ranges of the different variants of the first embodiment may also be combined with each other in one or more other variants.

[0079] In Figure 2 In the second embodiment shown, the preform only includes one additional substantially cylindrical part 7, which is arranged between the second part 6 and the bottom 4.

[0080] In this second embodiment, the additional substantially cylindrical part 7 is adjacent to the second part 6 and has a thickness of at least 6 mm, preferably less than 8.5 mm, and the corresponding outer diameter is approximately equal to the value D2.

[0081] The additional part 7 has a draft angle both on the outer contour and the inner contour; while the first part 5 only has a draft angle on the inner contour.

[0082] Such a draft angle may include, for example, a range from 0°10' to 1°.

[0083] In the first variant of the second embodiment, there is provided between the neck 2 and the first part 5:

[0084] - A cylindrical extension section 11 adjacent to the neck 2, having an inner diameter equal to D0, i.e., equal to the inner diameter of the neck, and an outer diameter equal to D1, i.e., equal to the outer diameter of the first part 5; and

[0085] - An intermediate extension section 12 connecting the cylindrical extension section 11 to the first part 5, wherein the inner diameter of the intermediate extension section 12 gradually decreases from the value D0 to the value D1' in a conical profile, and wherein the outer diameter of the intermediate extension section 12 is equal to D1.

[0086] Preferably, the inner diameters of the first part 5, the second part 6, and the additional cylindrical part 7 remain substantially constant and equal to the value D1'.

[0087] In this first variant of the second embodiment, the thickness of the cylindrical extension section 11 can be in the range from 3 to 4 mm, while its length along the longitudinal axis X is less than 5 mm.

[0088] Preferably, the total length of the cylindrical extension section 11 and the intermediate extension section 12 along the longitudinal axis X is in the range from 10 to 15 mm.

[0089] In a second variant of the second embodiment (not shown), the first generally cylindrical part 5 is adjacent to the neck 2, and neither the cylindrical extension section 11 nor the intermediate extension section 12 is provided. In this case, the inner diameters of the first part 5, the second part 6, and the said other generally cylindrical part 7 remain substantially constant and equal to the value D0, i.e., the inner diameter of the neck 2.

[0090] In all embodiments of the preform of the present invention, in order to further optimize the distribution of the material during the molding step of stretch blow molding and improve the opening performance of the blown bottle after filling with sparkling wine and capping, one or more of the following dimensional ranges (even all in the preferred variant) can be provided:

[0091] - The length of the first part 5 along the longitudinal axis X is in the range from 30 to 50 mm, preferably in the range from 40 to 50 mm;

[0092] - The thickness of the first part 5 is in the range from 4 to 5 mm;

[0093] - The length of the second part 6 along the longitudinal axis X is in the range from 20 to 40 mm;

[0094] - The thickness of the bottom 4 varies in the range from 3 to 6 mm;

[0095] - The minimum inner diameter of the tubular body 3 is in the range from 12 to 15 mm;

[0096] - The minimum thickness of the neck 2 is in the range from 4 to 7 mm;

[0097] - The inner diameter D0 of the neck 2 is in the range of 17 to 19 mm.

[0098] Preferably, in all embodiments, considering the particularities of the final shape of the blow-molded bottle made of plastic, the neck, body, and bottom of the blow-molded bottle are similar to the classic glass bottles for sparkling wine, Prosecco, or champagne. The material of the preform of the present invention can be selected to better avoid the risks of atomization and crystallization during the cooling step in the molding cavity and during the stretch blow molding operation. Experimentally, some materials are considered particularly suitable.

[0099] The first material selection is polyethylene furanoate (PEF), which has a barrier improvement factor, or simply BIF, equal to 8 - 10 for oxygen, 4 for carbon dioxide, and 4 for water. This selection may also not require the addition of an active or passive barrier.

[0100] The second material selection is polyethylene terephthalate (PET), preferably a modified polyethylene terephthalate obtained by the reaction of non-hydrogenated isophthalic acid with terephthalic acid and ethylene glycol. A particularly suitable material is the modified polyethylene terephthalate with a maximum level of isophthalic acid set at 7 mol%, preferably 4 - 7 mol%, replacing terephthalic acid.

[0101] Alternatively, another suitable polyester; or a bisphenol-free copolyester such as Tritan; or a biopolymer with an appropriate barrier improvement factor and a lower crystallization rate can be used.

[0102] In the case of using PET and filling the blow-molded bottle with sparkling wine, at least one additive, such as an oxygen scavenger, must be added to the PET to improve its barrier properties. The maximum pressure of sparkling wine is 3.0 bar, containing CO2 and free molecular SO2 as a preservative. Oxygen ingress must be prevented, and the shelf life is 24 months.

[0103] Preferably, the intrinsic viscosity of the selected polymeric material is in the range of 0.8 to 1.2 dL / g.

[0104] In all embodiments of the preform of the present invention, the neck 2 has a profile of the outer surface along the longitudinal axis X, which includes a concave central extension section 14 arranged between two convex end extension sections 15, 16 ( Figure 3 )(preferably consisting of it).

[0105] As Figure 4 shown, in a variant of the neck, advantageously, an external annular groove 13 is formed near the tubular body 3 in the end extension section 16 of the neck 2, and the external annular groove is adapted to insert a fixture for handling the preform.

[0106] Preferably, in all embodiments of the preform, the lower surface 17 of the neck 2 is a flat surface, in particular a completely flat surface, for improving the closure of the metal hoop on the bottleneck.

[0107] Optionally, the weight of the preform according to the invention is in the range of 80 to 100 grams, preferably in the range of 85 to 95 grams.

[0108] Preferably, the center of gravity of the preform according to the invention is located at a certain distance from the upper surface of the neck or the flat annular surface of the mouth or opening of the neck along its longitudinal axis X, and this distance is in the range of 85 to 95 mm, preferably in the range of 88 to 92 mm. This position of the center of gravity also allows for optimizing the formation of the blown bottle.

[0109] According to another aspect of the invention, a specific injection mold has been designed for industrially producing preforms according to any of the above embodiments.

[0110] As is well known, an injection mold includes a plurality of molding cavities, each of which is adapted to mold a preform.

[0111] As Figure 5 shown, each molding cavity of the mold according to the invention is defined by the cooperation of a male component 20 or a core insert and a female component, and the female component includes a neck insert 21 or a neck ring, a cavity insert 22, and a gate insert 23.

[0112] As Figure 5 shown, the shape of each molding cavity substantially corresponds to the final shape of the preform according to the invention in the cold state. The term "substantially corresponds" means that the material in the molding cavity may shrink during the cooling process.

[0113] Advantageously, the neck insert 21 extends along the longitudinal axis of the molding cavity so as to cover the longitudinal part of the molding cavity, and this longitudinal part corresponds to the area of the preform including the neck 2 and the first part 5 and the second part 6 of the tubular body 3 of the above-mentioned preform, that is, it includes the area of the preform from the mouth or opening of the neck to the second part 6 of the tubular body 3.

[0114] The neck insert 21 is respectively provided with a first frustoconical protrusion 24 and a second frustoconical protrusion 25 at both ends (considering the longitudinal axis of the cavity), which are coaxial with each other and with the longitudinal axis of the molding cavity, and taper in opposite directions.

[0115] In addition, a first locking element 26 is provided for locking the male component 20 and the neck insert 21 together by also adjoining the conical side surface of the first conical projection 24; and a second locking element 27 is provided for locking the neck insert 21 and the cavity insert 22 together by also adjoining the conical side surface of the second conical projection 25.

[0116] Advantageously, in order to effectively counteract the increased thrust on the neck insert 21 caused by the injection pressure and the elevated molding surface on the neck insert itself, the length H1 of the first conical projection 24 and the length H2 of the second conical projection 25, both measured along the longitudinal axis of the cavity, satisfy the following relationship:

[0117] H1 + H2 ≥ 0.2 * H

[0118] where H is the distance measured along the longitudinal axis from the flat annular surface of the molding cavity corresponding to the mouth surface of the preform to the parting line between the neck insert 21 and the cavity insert 22.

[0119] Another advantage can be represented by the fact that a plurality of cooling channels 28 are provided within the neck insert 21, the cooling channels 28 being arranged along a longitudinal portion of the molding cavity corresponding to a region of the preform that includes at least a first portion 5 of the neck 2 and the tubular body 3.

[0120] In Figure 5 the example, the cooling channels 28 are arranged along a longitudinal portion of the molding cavity corresponding to a region of the preform that includes the neck 2, a first portion 5 of the tubular body 3, and only a partial second portion 6 of the tubular body 3.

[0121] In a preferred variant, the cooling channels 28 are present along at least 70% of the outer contour of the longitudinal portion of the mold cavity corresponding to a region of the preform that includes the neck 2 and the first and second portions 5 and 6 of the tubular body 3. It has been found that meeting this condition can significantly improve the transparency of the blown bottle portion near the neck by keeping the bottle in an amorphous state without crystallization. In fact, in particular, at least the first portion 5 of the preform is not stretched within the mold and remains amorphous.

[0122] Preferably, at least one cooling channel 28, for example one or two cooling channels, is provided in the portion A of the mold cavity that corresponds only to the neck of the preform, and is arranged at a distance less than or equal to 5 mm, preferably at a distance of 2 to 3 mm, from the outer contour of the portion A of the mold cavity that corresponds to the neck of the preform.

Claims

1. A preform (1) made of plastic material, suitable for producing by stretch blow molding a bottle suitable for containing a sparkling beverage such as sparkling wine, said preform defining a longitudinal axis (X), said preform comprising: - a neck (2) having an inner diameter value D0 greater than or equal to 17 mm, the thickness varying along said longitudinal axis (X) and having a minimum value of at least 4 mm; - a tubular body (3) arranged below said neck (2) and having a minimum inner diameter greater than or equal to 12 mm; and - a bottom (4) closing said tubular body (3) at a first end of said tubular body (3), said first end being opposite a second end adjacent to said neck (2), said bottom (4) having a minimum thickness greater than or equal to 3 mm; wherein said tubular body (3) comprises: - a first generally cylindrical portion (5) adjacent to said neck (2), having a thickness of at least 4 mm, a length along said longitudinal axis (X) of at least 30 mm, and a corresponding outer diameter value D1; - a second portion (6) adjacent to said first portion (5) and remote from said neck (2), wherein the outer diameter gradually increases from value D1 to value D2 along a frustoconical profile; said second portion (6) having a maximum thickness of at least 6 mm and a length along the longitudinal axis (X) of at least 20 mm; - at least one additional generally cylindrical portion (7, 8, 9) arranged between said second portion (6) and said bottom (4) and having a thickness of at least 6 mm.

2. The preform according to claim 1, comprising: - a first additional generally cylindrical portion (8) adjacent to said second portion (6) and having a first thickness of at least 6 mm and a corresponding outer diameter approximately equal to value D2; - a second additional generally cylindrical portion (9) arranged between said first additional generally cylindrical portion (8) and said bottom (4) and having a second thickness greater than said first thickness, preferably equal to at least 7 mm, maintaining a corresponding outer diameter approximately equal to value D2; and - a connecting portion (10) connecting said first additional generally cylindrical portion (8) and said second additional generally cylindrical portion (9), wherein the inner diameter gradually decreases from value D3 to value D4 towards said bottom (4) along a frustoconical profile.

3. The preform according to claim 2, wherein, The thickness variation between said first additional generally cylindrical portion (8) and said second additional generally cylindrical portion (9) varies in the range of 0.2 to 1.0 mm.

4. The preform according to claim 2 or 3, wherein The length of said second additional generally cylindrical portion (9) along the longitudinal axis (X) is at least 15 mm, preferably in the range of 15 to 30 mm; preferably, wherein the length of said first additional generally cylindrical portion (8) along the longitudinal axis (X) is at least 20 mm, preferably in the range of 35 to 70 mm; and preferably, wherein the length of said connecting portion (10) along the longitudinal axis (X) is at least 5 mm, preferably in the range of 5 to 10 mm.

5. The preform according to claim 2 or 3 or 4, wherein, In the second part (6), the inner diameter gradually decreases towards the bottom (4) with a frustoconical profile from a value D1' to a value D3, preferably where the value D1' is substantially equal to the inner diameter value D0 of the neck (2).

6. The preform according to claim 1, wherein, Only one additional substantially cylindrical part (7) is provided, which is adjacent to the second part (6) and has a thickness of at least 6 mm and a corresponding outer diameter substantially equal to the value D2.

7. The preform according to claim 6, wherein, Between the neck (2) and the first part (5) there is provided: - a cylindrical extension section (11) adjacent to the neck (2), having an inner diameter equal to D0 and an outer diameter equal to D1; - an intermediate extension section (12) connecting the cylindrical extension section (11) and the first part (5), where the inner diameter gradually decreases with a frustoconical profile from a value D0 to a value D1', and the outer diameter is equal to D1; Preferably, where the inner diameters of the first part (5), the second part (6) and the additional cylindrical part (7) remain substantially constant and are equal to the value D1'.

8. The preform according to claim 7, wherein, The thickness of the cylindrical extension section (11) is in the range of 3 to 4 mm, and its length along the longitudinal axis (X) is less than 5 mm; preferably, where the total length of the cylindrical extension section (11) and the intermediate extension section (12) along the longitudinal axis (X) is in the range of 10 to 15 mm.

9. The preform according to any one of the preceding claims, wherein, The length of the first part (5) along the longitudinal axis (X) is in the range of 30 to 50 mm, preferably in the range of 40 to 50 mm; Preferably, where the thickness of the first part (5) is less than or equal to 5 mm; Preferably, where the length of the second part (6) along the longitudinal axis (X) is less than 40 mm; Preferably, where the thickness of the bottom (4) varies in the range of 3 to 6 mm; Preferably, where the thickness of the at least one additional cylindrical part (7, 8, 9) is less than 8.5 mm; Preferably, where the minimum inner diameter of the tubular body (3) is in the range of 12 to 15 mm; Preferably, where the minimum thickness of the neck (2) is in the range of 4 to 7 mm; Preferably, where the inner diameter D0 of the neck (2) is in the range of 17 to 19 mm.

10. The preform according to any one of the preceding claims, wherein the preform is made of a polymeric material selected from: - polyethylene furanoate PEF; - polyethylene terephthalate PET, preferably a modified polyethylene terephthalate obtained by the reaction of non-hydrogenated isophthalic acid with terephthalic acid and ethylene glycol; in particular, using up to 7 mol% of isophthalic acid to replace terephthalic acid; - another suitable polyester, preferably at a low crystallization rate; - a bisphenol-free copolyester, such as Tritan; or - a biopolymer having a suitable barrier improvement factor and a low crystallization rate; Preferably, where the intrinsic viscosity of the polymeric material is in the range of 0.8 to 1.2 dl / g.

11. The preform according to any one of the preceding claims, wherein, The contour of the outer surface of the neck (2) has a central concave extension section (14) between two convex end extensions (15, 16) along the longitudinal axis (X); preferably, an annular outer groove (13) is formed in the end extension (16) of the neck (2), close to the tubular body (3), and is adapted to insert a fixture for processing the preform.

12. The preform according to any one of the preceding claims, wherein, The lower surface of the neck (2) is a flat surface.

13. The preform according to any one of the preceding claims, wherein, The center of gravity of the preform is along the longitudinal axis X, and the distance (G) from the flat annular surface (18) of the mouth or opening of the neck is in the range of 85 to 95 mm; preferably, the weight of the preform is in the range of 80 to 100 grams.

14. An injection mold for producing a preform according to any one of the preceding claims, the mold comprising a plurality of molding cavities, wherein each molding cavity is defined by the cooperation of a male component (20) or a core insert and a female component, the female component including a neck insert (21) or a neck ring, a cavity insert (22) and a gate insert (23); wherein the neck insert (21) extends along the longitudinal axis of the molding cavity so as to cover a first longitudinal portion of the molding cavity corresponding to the area of the preform, the area including: the neck (2), having an inner diameter D0 greater than or equal to 17 mm, and the thickness varying along the longitudinal axis (X) and having a minimum value of at least 4 mm, and a first portion (5) of the tubular body (3), having a substantially cylindrical shape and a length of at least 30 mm along the longitudinal axis (X), and a second portion (6) of the tubular body (3), having a length of at least 20 mm along the longitudinal axis (X), and wherein the outer diameter gradually increases from a value D1 to a value D2 along a frustoconical profile; wherein the neck insert (21) is provided with a first frustoconical projection (24) and a second frustoconical projection (25) at both ends along the longitudinal axis respectively; wherein a first locking element (26) for locking the male component (20) and the neck insert (21) together is provided, the first locking element (26) being adjacent to at least the frustoconical side surface of the first frustoconical projection (24); a second locking element (27) for locking the neck insert (21) and the cavity insert (22) together is provided, the second locking element (27) being adjacent to the frustoconical side surface of the second frustoconical projection (25); wherein the length H1 of the first frustoconical projection (24) and the length H2 of the second frustoconical projection (25) measured along the longitudinal axis satisfy the following relationship: H1 + H2 ≥ 0.2 * H where H is the length measured along the longitudinal axis, from the flat annular surface of the molding cavity corresponding to the mouth surface of the preform to the separation plane between the neck insert (21) and the cavity insert (22).

15. The injection mold according to claim 14, wherein, A plurality of cooling channels (28) are provided within the neck insert (21), the cooling channels being arranged along a second longitudinal portion of the mould cavity, the second longitudinal portion corresponding to a region of the preform including at least a first portion (5) of the neck (2) and the tubular body (3); preferably, wherein the cooling channels (28) are present along at least 70% of the outer contour of a first longitudinal portion of the mould cavity, the first longitudinal portion corresponding to a region of the preform including a first portion (5) and a second portion (6) of the neck (2) and the tubular body (3).

16. The injection mold according to claim 15, wherein, At a portion (A) of the mould cavity corresponding to the neck of the preform, at a distance less than or equal to 5 mm, preferably at a distance of 2 to 3 mm, from the outer surface of the portion (A) of the mould cavity corresponding to the neck of the preform, at least one cooling channel (28) is provided.

17. The injection mold according to any one of claims 14 to 16, wherein, The shape of each mould cavity generally corresponds to the final shape of the preform according to claim 1.

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