PRE-ORDER FOR BOTTLES OF PLASTIC MATERIAL OR WIDE-NECKED CONTAINERS Field of the Invention The invention relates to a preform for plastic bottles or wide-neck containers according to the preamble of claim 1. BACKGROUND OF THE INVENTION The previously conventional containers produced from white or colored laminated metal, glass if not ceramic are increasingly being exceeded by containers made of plastic material. In particular for the packaging of pourable media, for example cleaning utensils, body care products, cosmetics, motor vehicle means, etc., it is mainly used for plastic containers. Low weight and relatively low costs are undoubtedly key factors in this substitution. The use of recyclable plastics and, together, a more advantageous balance of energy in the production thereof, also contributes to promoting the acceptance by consumers of plastic containers, in particular plastic bottles. The plastic bottles, most frequently used, are usually produced in what is known as a method of blow molding, elongation
injection. These methods are a combination of injection molding and blow molding. In this case, a preform is first produced in an injection mold in an injection molding process. Recently, extrusion methods for producing preforms have also been proposed. The preform has a substantially elongated body, a longitudinal end of which is completely closed by a dome-shaped terminal portion. A neck portion comprising a pouring opening is joined to the other longitudinal end of the body. This portion of the neck already conventionally presents the subsequent form of the bottleneck. Usually, threaded portions or the like are also formed on the outside of this neck portion to secure a closure part. The preform is removed, after the manufacture of the same in a method of molding by injection of plastic material, the injection mold, is conditioned if necessary and introduced into a blow mold of a blowing machine, in which it is finally inflated with excess pressure to the desired shape and additionally stretched using a stretching mandrel. A method of blow molding with injection is already known in which the molding process immediately follows the injection of the preform. The preform remains in this case in the injection mandrel and part of the injection mold forms a portion of the injection mold.
blown. For the manufacture of plastic bottles or wide-neck containers having a reinforced bottom region, specific preforms are known, having a stepped or in-line bottom portion. In these preforms, the wall thickness of the preform changes in the transition to the dome-like bottom portion in a gradual manner and suddenly assumes a high value. During manufacture of preforms of this type by injection molding, the sudden change in wall thickness can lead to problems. In particular, it can be presented that, in the transition from the wall thickness of the body to the greater wall thickness of the bottom portion during the injection molding method, the local temperature increases to the maximum which deteriorates the properties of the plastic material. . Also in the blow molding method with stretching, the changes in the thickness of the preform wall, which are staggered in a succes manner, can lead to problems which manifest themselves as river uniforms in the bottle. plastic material, blow molding, completely stretched. Also, it is often desirable to form the preform, in the particularly critical region of transition from the neck portion to the body, in what is known as the preform collar, with a greater wall thickness. This also leads, in the preforms
known, to staggered changes in the wall thickness Which leads to the problems described above. US 4,044,086 describes a preform, the wall thickness from which it decreases in a substantially constant manner over its longitudinal extension, and the internal diameter i of which also decreases in a substantially constant manner from a transition to the preform collar to a transition to the terminal portion in the form of a dome. In the longitudinal extension, the wall thickness increases downwards from 1.2 mm (0.047 inches)
4. 7 mm (0.18 inches). In this way, the change in. The wall thickness along the longitudinal extension of the preform is more than 2 mm. EP 0,311,161 describes a method and an apparatus for producing multilayer thermoplastic preforms from which blow molded containers for food products and beverages can be made. The figures show a mold for manufacturing a frusto-conical preform. The mold can be used to produce preforms that subsequently have a cylindrical portion in the neck portion that fuses with the body portion by a conical portion of substantially the same wall thickness. The outer diameter of the collar of the preform decreases from the neck portion to the body portion.
Description of the Invention The object of the present invention therefore is to provide a preform for the manufacture of plastic bottles or wide neck containers in a blow molding method with injection stretch or blow molding with injection, preforms which do not lead to problems during the manufacture of the same in a method of plastic injection molding or in a subsequent method of blow molding. In this case, it must be ensured that the required mechanical resistances and the thermal stability of the bottle continue -of plastic material, produced from the preform or the wide neck container. These objects are achieved by a preform for producing plastic bottles or wide neck containers, having the features listed in the characteristic portion of patent claim 1. The developments and / or advantageous variants of the invention form the material of the dependent claims. The invention provides a preform for manufacturing plastic bottles or wide neck containers, having a rigid, substantially elongate, frustoconical body portion that is closed at one of its longitudinal ends by a terminal portion in
dome form and at its opposite longitudinal end is attached by a preform collar to a neck portion provided with a pour opening. The preform has an outer diameter in the body portion that is reduced from the preform collar to the end portion. The body portion has a wall thickness that changes over its longitudinal extent in a substantially constant manner by up to ± 2 mm. For this purpose, it has an internal diameter that decreases in a substantially constant manner from a transition to the preform collar to a transition to the dome-shaped terminal portion. The fact that sudden changes in wall thickness is avoided leaves a margin for the problem of local exposure to heat during the injection of the preform with plastic material. This also ensures that the preform has uniform wall thicknesses on its circumference. In this way shrinkage cavities, or the like, can reliably be avoided as a consequence of the turbulences of the plastic material at the edges and corners. During the blow molding with stretching of the preform, the forces are more evenly distributed. As a result, the local overload, which can lead to weakening of the material, or overheating at the edges and corners, is avoided. As a result of the preceding changes in a way
According to the invention, the subsequent form of the generated container is already taken into account in the preform. As a result, the preform collar does not stretch excessively or too little during the blow molding method and the subsequent shoulder region of the container obtains its optimum strength. In this case, the provision can be made so that the outer diameter of the preform collar increases in size from the neck portion to the body portion at least in the partial portion that joins the body portion. This is particularly advantageous in containers of plastic material having bulky bodies. Another variant of a] a. The preform further provides that the outer diameter of the preform collar decreases in size from the neck portion to the body portion at least in the partial portion joining the body portion. This variant embodiment of the preform is used in a particularly advantageous manner in the manufacture of wide neck containers. It will be understood that the increase or reduction in external diameter can take place immediately after the transport ring. A substantially cylindrical portion that is joined by the region, the external diameter of which | varies, can also be provided first. On the other hand, . the internal diameter of the preform collar decreases, in a substantially constant manner from the neck portion
to the body portion of the preform. In order to prevent sudden transitions of the preform collar to the body portion, the outer wall and the inner wall of the preform collar include obtuse angles with the adjacent outer wall and inner wall of the body portion in each case. The angles are 130 ° less than 180 °, preferably between 158 ° and 178 ° and more preferably between 160 ° and 175 °. If the body portion of the preform has a minimum wall thickness that does not fall below 0.8 mm, sufficient stiffness and stability of the plastic container produced from the preform is ensured. On the other hand, the maximum wall thickness of the body portion does not exceed 6 mm. This ensures sufficiently rapid softening of the preform as a totality and uniform stretching of the body portion during the blow molding method. For the uniformity of the manufacturing process of the preform by injection molding, extrusion, but also by spray foaming, it has been found convenient that the body portion have an inner diameter and an outer diameter which are each reduced from the preform collar to the dome-shaped terminal portion by 0.1 mm at most 3.5 mm. A sudden change in wall thickness at the transition from the body portion to the portion is also avoided
terminal. For this purpose, the "dome-shaped" terminal portion has a wall thickness that is reduced from the wall thickness of the body portion to an injection point by 0% to 50%, preferably 20 to 50% The wall thickness at the injection point in this case is not taken into account The wall thickness at the end portion is selected in this case according to the type of background to be produced, in order to impart rigidity and optimum stability to the fully blow molded container The preform according to the invention can be produced from the conventional materials used by the stretch blow molding method, eg PET, advantageously, at least 85% of the The body portion of the preform is produced in materials selected from the group consisting of polyesters (including PET, PBT, PLA, PEN), copolyesters, polyolefins (in particular, PEj, HDPE) and polystyrenes (GPS or HIPS). to According to the invention, it is optimized inter alia for manufacturing by extrusion injection molding or spray foaming. The plastic bottles and the wide neck containers produced from the preforms incorporated according to the invention are distinguished by high mechanical strengths and high thermal stability. By
body portion 2, frustoconically incorporated > substantially elongate, rigid, a longitudinal end of which is closed by a terminal portion 3 in dome form. The other longitudinal end of the body 2 is first joined by what is known as a preform collar 8 which forms the transition from the body portion 2 to the neck portion 4 comprising a pouring opening 5. The neck portion 4 already conventionally presents the subsequent shape of the neck of the inflated bottle of plastic material or a wide neck container. Threaded portions 6 or the like are formed on the outside of the neck portion 4 to secure a closure portion. The preform 1 is produced, for example, in a method of injection molding. For example, alternative manufacturing methods are extrusion, or with appropriate raw materials, spray foaming. The preform collar 8 is separated from the neck portion 4 by a transport ring 7, which surrounds it in an annular manner. The preform collar 8 has an axial length x which is measured on its inner wall 81 and corresponds, in the illustrated example mode, to approximately one. axial length 1 of the preform collar 8 on its outer wall 82. However, the two axial extensions Ge the inner wall 81 and the outer wall 82 of the preform collar 8 do not have to
necessarily the same length. The body portion 2 of the preform 1 has jm diameter-external, which in a substantially constant manner decreases in size from the preform collar 8 to the dome-shaped terminal portion 3. The internal diameter i of the body portion 1 also in a substantially constant manner decreases in size from the preform collar 8 to the terminal portion 3. The body portion 2 has a wall thickness w that changes from. u substantially substantially constant along the longitudinal extension of the body portion 2 from the preform collar 8 to the dome-shaped terminal portion 3. In the illustrated exemplary embodiment, the wall thickness w of the body portion 2 is constantly reduced by up to + 2 mm towards the terminal portion 3. In this case, the wall thickness w of the body portion 2 of the preform 1 does not fall below a minimum wall thickness of 0.8 mm. In Figure 2 a second embodiment of the preform is denoted in its entirety by the reference number 11. Again, it has a body portion 2 that on the one hand is attached to a terminal portion 3 in the form of a dome and on the other hand is connected to a neck portion 4 by a preform collar 8. The neck portion 4 and the preform collar are separated from each other by a transport ring 7. Again, threaded portions are formed?
As can be seen from Figure 2, the thickness w of the wall of the body portion 2 increases steadily even though the external diameter decreases along its longitudinal extension. In this case, the wall thickness of the body portion 2 does not exceed a maximum wall thickness of 6 mm. In the transition from body portion 2 to dome-shaped terminal portion 3, a sudden change in wall thickness is avoided. For this purpose, the dome-shaped terminal portion has a wall thickness that is reduced from the maximum wall thickness of body portion 2 to an injection point 9 by 0% 50. The wall thickness at injection point 9 in this case is not taken into account. The wall thickness t in the terminal portion 3 in. this ca.so is selected from the type of background depending on the type of background to be produced, in order to impart rigidity and optimum stability to the recipient molded completely by blowing. An additional variant embodiment, illustrated in Figure 3, of a preform according to the invention is denoted in general by the reference number 21. ' Again, similar parts are denoted by the same reference numbers as in the preceding Figures. The body portion 2 of the preform 21 again has a wall thickness w which is reduced from the preform collar 8
the terminal 3 portion. The wall thickness of the terminal portion 3 is denoted, again, by the reference symbol t; the injection point is denoted by 9. The preform collar 8 has an external diameter d that decreases in size over the longitudinal extension of the preform collar 8 towards the body portion 2. Figure 3 shows that an inner wall 81 of the preform collar 8 fuses with the inner wall 21 of the body portion 2 of the preform 1 at an obtuse angle a. The angle of fusion IN is preferably 130 ° to less than 180 °. This measure substantially prevents sudden transitions. The preform illustrated in Figure 4 and denoted in its entirety by the reference number 31 is incorporated for example for the manufacture of a wide neck container. The neck portion 4 has an opening 5, the opening diameter of which is larger than the external diameter a of the body portion 2. Accordingly, the preform collar also has an outer diameter d which is reduced from the much larger external diameter of the neck portion 4 to the body portion 2, the external diameter a of the body portion 2 of the body portion 2. preform 1 decreases toward terminal portion 3 now only slightly. ? despite the relatively large difference in the external diameter of the preform collar 8 below the transport ring 7 and the body portion 2
joining the preform collar 8, the outer wall 82 of the preform collar 8 and the outer wall 22 of the body portion enclose at their mutual transition an obtuse angle ß from preferably 130 ° to less than 180 °. A common feature of the illustrated templates is the fact that the wall thickness w of body portion 2 is reduced or increased in size over its longitudinal extension from the transition to the collar, 8 of preform to the transition to the terminal portion 3. Dome shape of a · - substantially constant way by up to 2 mm. The internal diameter i and the external diameter a of the body portion 2 are reduced in this case from the preform collar 8 to the dome-shaped terminal portion 3 in a substantially constant manner by 0.1-3 mm- The preform incorporated in accordance with With the invention, there is no sudden change, stepwise, in the wall thickness. As a result, during the manufacture of the same by injection molding of plastic material, local exposure to heat can be avoided, and fluctuations in the wall thickness on the circumference are prevented. The modality of the preform allows the desired distribution of material in the preform that is required for the required strength and the required thermal resistance of the plastic material bottle
blow molded with stretch from it, without having to provide more material at the injection point. The invention can be applied to all plastic materials that are suitable for blow molding with injection or blow molding method with stretch and injection. Advantageously, at least 85 of the body portion of. The preform is produced from materials selected from the group consisting of polyesters (including PET, PBT, PLA, PEN), Itesterei copol, polyolefins (in particular, PP, HDPE), and polystyrenes (GPS or HIPS). The preform according to the invention is optimized for production by injection molding, by extrusion or spray foaming it serves as an intermediate product for the manufacture of plastic bottles or wide neck containers in a stretch blow molding method. of injection or blow molding with injection.