MXPA06008667A - Preforms made of two or more materials and processes for obtaining them - Google Patents

Abstract

Processes for obtaining new composite preforms (26) suitable for blow-molding made of at least two different materials (4, 22), preforms obtained thereby, and articles obtained by blow-molding of these preforms. The processes employ the injection-molding of two (or more) plastic materials to form preforms that can be blow-molded into articles. In a preferred embodiment, the two materials have different colors and the resulting articles show a multi-colored effect. The two materials are notlaminated over each other. In a second preferred embodiment, the formed preform is milled out before injecting a second material.

Description

PREFORMS PREPARED WITH TWO OR MORE MATERIALS AND PROCESSES TO OBTAIN THEM FIELD OF THE INVENTION The present invention relates to an improvement in the field of injection molding-blow molding, in particular, to new preforms suitable for the blow molding of bottles (and in general any hollow article), to processes for the manufacture of these preforms and to the articles obtained by the blow molding of these preforms. The processes of the invention employ two or more materials to form the composite preforms. In a preferred embodiment, the two materials used have different colors, and the resulting bottles have a multi-colored effect.

BACKGROUND OF THE INVENTION Injection-blow molding and its injection stretch blow molding variants are commonly used to manufacture high quality hollow articles, such as industrial scale bottles. In the first step of the process, a molten plastic material is injected into a cavity of a mold formed by an inner main bar and a mold of a preform to form an intermediate in the form of a "test tube", called a "preform". The mold of the preform is then opened, and the preform is molded subsequent to blow molding or stretch blow molding. In the injection-blow molding process, the main bar supporting the molded preform is immediately transferred to a blow molded bottle having the shape of the desired hollow article. The air that passes through a valve in the main bar inflates the hot preform, which expands and takes the shape of the blow mold of the bottle. After the desired bottle has cooled enough to handle it, it is removed from the blow mold and ready to use (usually the part is allowed to cool for approximately 24 hours). More information on the injection-blow molding process of general textbooks can be obtained, for example "The Wiley Encyclopedia of Packaging Technology" (Wiley Encyclopedia of Packaging Technology), second edition (1997), published by Wiley- Interscience Publication (see page 87 in particular). In the "stretch blow molding" process (sometimes referred to as biaxially blown molding), the preform is carefully conditioned at a temperature high enough to allow the preform to inflate for biaxial molecular alignment on the side wall of a blow molded bottle. A strong air pressure and, usually, a stretch bar are used to stretch the preform in the axial (vertical) direction. Unlike bottles obtained by conventional injection-blow molding, the bottles obtained by stretch blow molding are significantly longer than the preform. PET, PP and PEN (polyethylene naphthalate) are the material chosen for the stretch blow molding process. There are different methods of blow molding by injected stretching, for example one step, two steps (also known as "reheating and blowing"). More information on blow molding processes can be obtained by injecting stretch of general textbooks, for example "The Wiley Encyclopedia of Packaging Technology" (Wiley Encyclopedia of Packaging Technology), second edition (1997), published by Wiley -lnterscience Publication (see pages 87-89 in particular). Injection-blow molding is generally used to make relatively small shaped articles, with precision neck termination, and is commonly used to manufacture bottles of relatively high value for the cosmetic or pharmaceutical industry. Injection stretch blow molding is generally used to make larger items, such as beverage containers for the soft drink industry, even though is not always like that. Unless otherwise expressly indicated, the term "injection-blow molding" is hereinafter used to designate both injection-blow molding processes and blow-stretch molding processes. Extrusion-blow molding and injection-blow molding are different processes. In extrusion-blow molding, the molten plastic is extruded (generally continuously) to form a continuous tube with the open end. The extruded plastic is cut at regular intervals, and the cuts are blow molded directly to form an article. In the extrusion-blow molding process, the molten plastic material is not preformed around a main material to form a preform. The final shape of an article produced by extrusion-blow molding is less precise and less controllable than those obtained by injection-blow molding. Further details on extrusion-blow molding can be obtained in textbooks on packaging in general, for example, in "77? E Wiley Encyclopedia of Packaging Technology" (Wiley Encyclopedia of Packaging Technology), mentioned above, in particular the pages 83-86. Extrusion-blow molding can be used to obtain laminated or co-extruded bottles with multiple layers to achieve improved physical (barrier) or aesthetic properties. Although conventional injection-blow molding provides bottles of good quality, with precise shapes, these bottles are usually manufactured from a single material and are of a single color (see, for example, US Patent No. 4,988,477). , which describes a method for producing a colored polyester container, in which the granulated PET supply is mixed with a coloring matter composition). It is not always possible to decorate bottles more by means of labels, engraving or stamping when the bottles have complex shapes; In addition, it can be expensive. Patent WO97 / 21539 has attempted to improve the appearance of bottles blow molded by injection by using two different colored materials to manufacture the bottles. In patent WO97 / 21539, an injection molding process of a multicolored preform in an injection mold is described, wherein the different colored materials are injected sequentially through the supply channel into a conventional injection mold cavity. In accordance with WO97 / 21539, it is possible to achieve a layer distribution of the materials by careful control of various operating parameters, such as the amount of materials injected, the injection rate and the injection temperatures. However, controlling these parameters is difficult, and as illustrated in Figure 8 of WO97 / 21539, the boundaries between the layers are not precise and the process is not adapted to the manufacture of preforms that have reproducible decorative features. Likewise, this system only allows the formation of bottles with horizontal superimposed layers of different colored materials (taking the vertical axis as the axis of the bottle). The U.S. patent application no. 2002 / 0058114A1 describes a process for obtaining colored preforms of at least two colors. In this process, a base preform having a cylindrical hollow is first formed by injecting a first material from an injection point in the lower part of the base preform. The base preform is transferred to a second mold, and the gap is filled by injecting a second material from an injection point, again, into the lower part of the base preform. The process can be repeated to obtain multicolored preforms. The preforms obtained by this process are made of laminated layers, which can limit the effect of the color difference, especially when using transparent or semi-transparent materials. Moreover, the materials of different colors are distributed in layers superimposed horizontally, when the central axis of the preform is taken as a vertical axis. It would be desirable to achieve multi-colored preforms in which the color distribution is not simply reduced to horizontal layers of materials. European patent no. EP1,180,424A1 discloses a process for producing bottles having a removable, laminated outer layer for specific applications, such as those for dispensing hair colorants. It would be desirable to have a system that allows a more controlled distribution of the materials in the preforms. In particular, it would be desirable to obtain preforms in which the distribution of the first and second materials are not laminated. It is also desirable to achieve a system that allows the inclusion of shapes that are not horizontal layers of materials.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to new preforms suitable for the blow molding of bottles (and in general any hollow article), to processes for the manufacture of these preforms and to articles (for example bottles) obtained by the blow molding of these preforms , all as defined in the claims. In particular, the preferred process for making the compositions of the present invention comprises the successive steps of: i. Forming an incomplete preform by injection molding a first material in a first preform cavity; said first preform cavity is formed by the space between an inner main bar and a first preform mold, wherein said first preform cavity is adapted to leave at least one volume of the empty incomplete preform after the first material is has injected completely into said first preform cavity; said at least one void volume is intended to be occupied by the second material, ii. completing said incomplete preform by injection molding the second material to fill said at least one void volume, wherein the position of the void volume in the incomplete preform is designed so that the first material and the second material are not laminated one upon the other . Unlike prior-art preforms previously discussed, the distribution of the first and second materials in the preforms and bottles of the present invention is not limited to horizontally superimposed layers of said materials. For example, the second material can form at least one inclusion in an elaborate continuous matrix of the first material. The preforms can then be blow molded by conventional stretch blow molding or blow molding techniques. These and other attributes, aspects and advantages of the present invention will be apparent to those with experience in the industry from reading the present description.

BRIEF DESCRIPTION OF THE FIGURES Although the specification concludes with the claims that particularly state and clearly claim the invention, it is believed that the present invention will be better understood from the following description of the preferred embodiments, together with the accompanying figures, in which the reference numbers identify identical elements, and where: Figure 1 is a schematic diagram representing an illustrative two step injection process in accordance with the present invention; Figure 2 is a schematic diagram illustrating the blow molding (eg, stretch blow molding) of a preform that is obtained by the process illustrated in Figure 1 to make a bottle; Figure 3 is a schematic diagram of an illustrative process of injection-blow molding in four stages according to the present invention, wherein the injection and blow molding steps are carried out in the same machine; Figure 4 is a schematic diagram of an alternative process of injection-blow molding in four stages, which further comprises a conditioning station followed by a stretch blow molding station; Figures 5 to 13 each show two drawings: the drawing on the right side is an example of a preform made of two materials that is obtained by the processes according to the invention; the corresponding drawing on the left side is an example of a bottle which is obtained by blow molding the preform on the right side, in a suitable mold. Figure 14 is a schematic diagram of a 2 shot injection process, which can be used to manufacture a preform as illustrated in Figure 10. Figure 15 is a cross section of the first preform mold, as illustrated in FIG. Figure 14, with the first material (4) injected totally into the first mold cavity. Figure 16 is a cross section of the second preform mold, as illustrated in Figure 14, with the second material injected completely into the second mold cavity.

Figure 17 illustrates the incomplete preform obtained after the first injection step, as illustrated in Figure 14. The void volume is clearly visible. Figure 18 illustrates the completed preform after the second injection step, as illustrated in Figure 14.

DETAILED DESCRIPTION OF THE INVENTION While the specification concludes with claims that particularly state and clearly claim the invention, it is considered that the present invention will be better understood from the following description and examples, which describe and demonstrate in greater detail the preferred embodiments within the scope of the invention. present invention. The examples are provided for illustrative purposes only and are not to be construed as limiting the present invention since many variations of it are possible without deviating from its spirit and scope. All references cited are incorporated herein by reference in their entirety. The citation of any reference does not imply admitting the possibility of being considered as an industry prior to the claimed invention. All percentages are by weight of the total composition unless specifically expressed otherwise. All proportions are proportions by weight, unless specifically indicated otherwise. In the present, "to understand" means that other steps can be added, as well as other ingredients. This term includes the expressions "consists of" and "consists essentially of". As used herein, the term "bottle" refers to any hollow article that can be obtained by blow molding.

The bottles of the present invention are preferably suitable for use as a container for any type of substance, such as liquids, solids or semi-solids. The term "bottle" does not imply a particular intended use for the article. For example as used herein, the term "bottle" encompasses articles intended to contain cosmetic products (e.g. shampoos, creams, etc.), edible products (e.g. milk, soda, condiments, etc.), chemicals, etc. As used herein, the term "preform" refers to an intermediate in the form of a "test tube", which is obtained by injection molding a plastic material between a main bar and a preform (mold cavity), and is intended to be blow molded (stretch) in a bottle. Generally, the neck of the preform remains substantially unmodified during the blow molding process, while the body of the preform will expand considerably. Preforms are sometimes incorrectly referred to as "paired", although this term should be reserved to designate extruded tubular intermediates formed during an extrusion process. The cross section of the preform can be cylindrical or non-cylindrical, for example oval, square / rectangular rounded, triangular, asymmetric, etc., depending on the final desired shape of the bottle. As used herein, the term "incomplete preform" designates a preform that is only partially formed and comprises void volumes (eg holes or missing sections) that can be subsequently filled by at least one other material before the preform is formed. blow to turn it into a bottle. The empty volumes of the incomplete preform extend, at least in some parts, through the wall of the preform, i.e., from the outer surface to the internal surface of the incomplete preform. It is not required that all empty volumes extend through the entire thickness of the preform, although this is preferred. The expression "the first material and the second material are not laminated one on another" includes the situation in which the first material is not fully laminated on the second material, as well as, reciprocally, the situation in which the second material is not fully laminated on the first material. Thus, contrary to what is stated in patents no. 2002 / 0058114A1 and EP1, 180,424A1, the second material does not form a laminated layer on the first material. Undoubtedly, the first and second materials may have a certain partial overlap in some parts of the preform (for example there will be a small overlap if both materials are injected at approximately the same injection point, and there could also be certain overlaps in the boundaries between both materials). Preferably, more than 50% of the surface of the second material is not laminated on the first material, and more preferably more than 90% of the surface of the second material is not laminated on the first material. The fact that the materials are not laminated on one another gives more impressive visual effects to the finished products than the preforms of the previous industry, where the materials are laminated, especially when one of the materials is transparent or semitransparent. At this point, an embodiment of a process of the present invention will be treated in relation to Figure 1. In this embodiment, the injections of molten plastic materials to form the preform and the blow molding (stretching) of the preform are brought to out in separate machines. In the first injection station (2), a first molten plastic material (4) is injected through an injection nozzle (6) into a first mold cavity (8). This mold cavity (8) is limited on the outside by a first preform mold (10) and on the inside, by a cylindrical outer main bar (12) located centrally within the mold of the preform. This first mold cavity is adapted to leave at least one volume (14) empty in the resulting preform (15) after the first material has been injected completely. This preform, which comprises at least one void volume, is referred to herein as an "incomplete" preform (15). The different solutions can be used to obtain a first mold cavity adapted to leave at least one volume (14) empty in the resulting preform after the first material has been injected completely. For example as illustrated in Figure 1, the front of the first preform mold may comprise one (or more) protruding volumes of the mold material (which may be stainless steel), which will leave by printing one or more corresponding void volumes. in the resulting incomplete preform (15). Once the first plastic material has been sufficiently cooled and solidified, the first mold of the preform can then be opened. The main bar and the incomplete preform (15) resting on it can be rotated to the second injection station (16). The second injection station (16) may comprise a second preform cavity (18) formed by the space between an inner main bar (12) and a second preform mold (20); said second preform cavity is adapted to allow the injection molding of the second molten material to fill said at least one void volume (14). After closing the second preform mold (20), the second material (22) can be injected in the molten state through a different injection nozzle (24) in the empty volume (s) (14) that will be filled with the second one. material (at least partially) for the purpose of completing the incomplete preform (15). Preferably, the respective temperatures of the first and second materials at the time of injection of the second material lead to an effective bonding of the materials. This can be easily determined by simple iterative experimentation. The injection point corresponding to the first material and the second material can be the same or different. If both materials are injected approximately at the same point (for example the lower part of the preform), there will naturally be some overlap between the two materials near the injection point of said two materials. The injection point (or injection points if the second material is injected in more than one position) of the second material may also be different from the injection point of the first material. The fact of having different injection points allows more sophisticated distribution of the materials of the preforms, for example it is possible to obtain the inclusion of the second material in the side wall of the preform, as illustrated in Figure 1. In another embodiment (not illustrated), the first and second injection steps may be carried out in the same preform mold; said preform mold comprises movable elements that close said one or more empty volumes that will be occupied with the second material during the injection of the first molten material; said demountable elements are then removed before step ii), such that said second molten material can be injected into at least one void volume previously occupied by these removable elements. The first and second materials can then be injected through a different injection nozzle. Usually different injection nozzles will be used to allow more flexibility in the design of the preform mold. It is also contemplated that the mobile elements can be exchanged and thus allow various designs and shapes to be achieved with the same injection machine. It is also contemplated that inserts that are not mobile, but interchangeable, can be used in the mold cavity of a machine, with the purpose of also increasing the versatility of an injection machine. In the schematic diagram of Figure 1, only one void volume (14) is represented, but it is clear to those experienced in the industry that several empty volumes of the incomplete preform can be filled simultaneously with the second material by using an injection nozzle with multiple heads. The injection stations, optionally equipped with injection nozzles with multiple heads, are known in the injection molding industry to form composite objects made of different plastic materials, such as toothbrush handles or mobile phone bodies. These injection stations can be easily adapted for use in the present invention for the purpose of serving as first and / or second injection stations, as described above. The second material (22) is different from the first material (4).

By "different", it is understood that the composition of the first material is not exactly the same as the composition of the second material. In particular, it is preferred that the first and second materials have a different visual appearance. For example, the first and second materials may contain different pigments, or one material may not have coloration, while the other material comprises a pigment. However, it is also preferred that the first and second materials have similar physical properties, such that the second material is properly "welded" to the first material when injected and that the preform does not tend to present cracks when it is subsequently blown. Therefore, the first and second materials are preferably of the same type of plastic. Non-limiting examples of thermoplastic material that can be commonly used as the first and second materials are: polyethylene terephthalate (PET), polypropylene (PP), polyethylene naphthalate (PEN), polyethylene glycol terephthalate (PETG), polyethylene (including low polyethylene). density, medium density polyethylene and high density polyethylene), ethylene propylene, copolymer resin, ethylene vinyl acetate copolymer resin, other polyolefin resins, polyamide resins, ionomer resins, ABS resins, polyvinyl chloride, other synthetic resins and copolymers thereof. Preferred materials are polyethylene terephthalate (PET), polypropylene (PP), polyethylene naphthalate (PEN), polyethylene glycol terephthalate (PETG), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high polyethylene. density (HDPE), and mixtures thereof. Even more preferred polymers, particularly when the preform is stretch blow molded, are polyethylene terephthalate (PET), polypropylene (PP), polyethylene glycol terephthalate (PETG) and polyethylene naphthalate (PEN). When different types of plastic material are used, they should preferably be as compatible as possible. Figure 7 of patent GB2,191, 145, provides a compatibility chart of common plastic materials in an extrusion (not injection) context. However, it is believed that this table may be useful for selecting materials in the present invention. It was found that the PETG provides excellent results in terms of resistance of the welding line (the boundaries between the materials). The preform can be completely completed after the injection of the second material, but it is also contemplated that the preform can be completed only partially after the injection of the second material, for example in modalities in which a third material or others are injected in addition. the remaining empty volumes. Again in the embodiment of Figure 1, after the second material is injected and the preform is completed, the second preform mold (20) is opened, and the main bar (12) where the complete preform (26) is seated is rotated to a removal section (28), where the completed preform of the main bar (12) is carefully removed. The main bar can be rotated back to the first preform mold to start a new cycle. At this point, the completed preform can be blow molded (stretch) to form a bottle. Of course, the completed preforms can be blow molded (stretch) in the same place of manufacture or they can be stored and subsequently transported in bulk to a specialized place for blow molding. A standard process of stretch blow molding can be employed for normal preforms. For example as illustrated in Figure 2, the completed preforms (26) can be placed on a conveyor belt for preforms (30) and reheated by a heating unit (32) in order to increase its stretch capacity and then placing them in a conventional main bar (34) in a blow molding cavity (36). The simultaneous actions of the compressed air (or other gas) passed through valves in the main bar to inflate it and the main bar (34) itself stretches the body of the preform within the preform mold. Then the blow mold is opened, and the finished bottle is ejected (38). A standard process of blow molding without stretching can also be employed. Figure 3 illustrates a four-stage process that is similar, but less automated, than the process described in Figures 1-2. In this process, the first and second injection steps can be carried out in a manner similar to that set forth in Figure 1, with similar injection stations (2, 16). While seated in the main bar, the completed preform (26) can be rotated directly to the blow molding station (40) after the second injection station. Then compressed air or other gas can be passed through one or more valves in the main bar (12) to inflate the body of the preform, in such a way that it takes the form of the blow mold (36). Alternatively, in this step, the main bar (12) can also be retracted and a main bar for stretch blow molding inserted in the preform through its neck can be adapted. The blow mold can then be opened, and the finished bottle (38) can be ejected in an ejection station (42). The main bar can then be rotated to the first ejection station (2), and a new cycle can begin. Undoubtedly, the machine can comprise up to four main bars, so that the injection steps, the blowing step and the ejection step can be carried out simultaneously with different preforms / bottles. Figure 4 is another example of a four stage process illustrating the present invention. In this process, the completed preform (26) obtained after the second injection station (16) is rotated to a conditioning station (44) comprising heaters (46), where the completed preform is reheated prior to the step of blow molding in a blow molding and ejection station (48). Finally the finished bottle (38) is ejected from the blow mold (40). The processes of Figures 3 and 4 are advantageous because the preforms are immediately transformed into finished products. However, the machines used for these processes are more complex than the machines that can be employed in a 2-step process, as illustrated in Figures 1-2, wherein the injection and blow molding stages are carried out out in different machines. While the embodiments of the invention illustrated herein describe processes and preforms made of two materials, combinations of three or more materials within the scope of the present invention are also contemplated. For example, a third injection station or more may be added to the processes described herein. The distribution of the first and second materials in the completed preforms can be controlled well by the shapes of the preform molds, and the preforms obtained with a great consistency can be reproduced. Moreover, the boundaries between the first and second materials are precise. This result can not be obtained by the process described in the prior industry document WO97 / 21539, and the preforms that can be obtained in accordance with the claimed processes are new.

Other processes than the preferred processes described above can be used to obtain these new preforms. For example, a conventional complete (fully formed) preform made of a single primary material can be formed by conventional means. One or more selected volumes of the preform can be made to form an incomplete preform, and this incomplete preform can be completed by injection molding the second material of the empty volume (s), using the same injection mold or a different one. If the Incomplete preform is returned to the first mold for further injection, the need for two injection molding stations is avoided. The second material can be injected from the same nozzle as the first material if the distribution of the first and second materials allows it (this would be the case of the preforms of Figures 7, 8, 10 and 13, for example), or from a second nozzle, which can be located in any relative position with respect to the preform. Using a second nozzle can increase the cost of the machine, but allows a greater choice of distribution of the first material in the second material, in particular for the purpose of obtaining inclusions in the side walls of the bottles, such as those illustrated in the Figures 5, 6, 9, 12 and 13. It is also possible to use a second mold to inject the second material. In accordance with the present invention, the first and second materials may be distributed in various ways and manner relative to each other, as illustrated in Figures 5 to 13. For example, the shapes that the second material may take include squares, rectangles , rectangles with rounded corners, circles or ovals, letters, words, etc. Figure 5 illustrates an example of a bottle having multiple inclusions of the second material in a continuous matrix (4) made of a first material (22). In Figure 6, the graduations are formed by the second material, which facilitates a more accurate reading of the proportion of the content remaining in the bottle if the second material (22) is transparent. Figure 7 illustrates an example of the preform and bottle, wherein the second material extends into the neck region. Figure 8 could be used to decorate and communicate a double-chamber bottle or to differentiate the front of the bottle from the back. Figure 9 illustrates a bottle with a large color panel that could be used to frame a label. Figure 10 illustrates a bottle with a colored stripe that could be used to help distinguish different variants of a brand, for example shampoo fragrances. Figure 11 illustrates a bottle having its upper portion colored. The bottles are usually filled with a margin of upper clearance to allow overfilling or expansion of the product. A problem with transparent bottles is that the customer can interpret this as a bottle that 'is not completely full'. The bottle in Figure 11 avoids this problem.

Figure 12 illustrates a curved bottle, in which the second material is distributed in areas of the bottle where it would be difficult to place a label using standard means. Figure 13 illustrates how the preform and bottle can display letters or a logo. The processes according to the invention are adapted to produce preforms and bottles made of two or more materials, wherein said materials have an accurate and reproducible distribution in the bottle. To begin with the design of the desired bottle, the preform and the blow mold required can be designed using computer simulations, for example by means of finite element analysis tools (FEA). The bottles shown in Figures 5 -13 illustrate the type of results that can be obtained by blowing the preforms that are on the right side. The first and second materials may or may not be distributed in overlapping horizontal layers. The possible distribution of the first and second materials includes, but is not limited to, cases in which: The second material (22) forms at least one, preferably two different inclusions (unconnected), in a continuous matrix made of the first material (as illustrated illustratively in Figures 5, 7, 12 and 13); the second material is not connected to the neck or the bottom of the bottle (as illustrated illustratively in Figures 5, 6, 9, 10, 11, 12 and 13); the first or second materials or both have a distribution extending from the neck (50) of the bottle to its lower part (52), as illustrated illustratively in Figure 8; the first and / or second materials form vertical or horizontal regions or layers comprising the first and second materials, respectively (as illustrated illustratively in Figures 8 and 11). In addition to their decorative functions, the preforms and composite bottles may still have additional functions: for example if the first material (4) is opaque, while the second material (22) is transparent, the user may be able to see through of the second material to see how much content remains in the bottle without opening it. The bottles according to the invention can also be useful as a protection measure against counterfeiting by dishonest merchants. Counterfeiting of high-value goods, such as cosmetics, is a growing problem, and it would be more difficult for counterfeiters to copy a bottle with two incorporated materials of different color. If it were preferred that the bottle had only one color in its entirety, another possibility is to use a first and a second material of the same color under normal conditions, but adding a UV reactive agent in one of such materials. The UV reagent agent shines when it is illuminated with an appropriate UV lamp, which could be a handheld detector, similar to those used to detect counterfeit bills. This would facilitate counterfeiting controls in places such as customs or buying centers. Figure 14 represents a schematic diagram of a two-shot injection process, illustrating a way to manufacture a preform similar to the preform of Figure 10. In this process, an incomplete preform (14) is first formed in the first station of injection (2) by injecting the first material (4) into a first specially designed mold cavity (8). The first mold cavity is designed to leave an empty volume (14), which will be filled with the second material in a later step. After injecting the first material, the incomplete preform obtained is rotated to the second injection station (16), where the second material (22) is injected to fill the empty volume (14) and complete the preform. Figures 15-18 illustrate this process in greater detail. Figure 15 is a cross section of the first mold, with the first material (4) injected completely into the first mold cavity (8). Figure 16 is a cross section of the second mold (20), with the second material (22) injected completely into the second mold cavity (18). The first material and the second material overlap slightly close to the injection point, where the materials were injected.

Figure 17 illustrates the incomplete preform obtained after the first injection step. The empty volume (14) intended to be filled with the second material is clearly visible. Figure 18 illustrates the preform completed after the second injection step, wherein the second material (22) has completed the preform. The completed preform (26) is ready for blow molding.

Claims (15)

NOVELTY OF THE INVENTION CLAIMS

1. A process for manufacturing a preform (26) suitable for blow molding in a bottle; the preform is made of at least two different materials (4, 22); the process comprises the steps of: i) forming an incomplete preform (15) by injection molding a first material (4) in a first preform cavity (8); the first preform cavity is formed by the space between an inner main bar (12) and a first preform mold (10), wherein the first preform cavity (8) is adapted to leave at least one void volume (14). ) in the incomplete preform (15) after the first material (4) has been fully injected into the first preform cavity (8); at least one void volume (14) is intended to be occupied by a second material (22), ii) at least partially complete the incomplete preform (15) by injection molding the second material (22) to at least fill partially at least one void volume (14), characterized in that the position of the void volume (14) in the incomplete preform (15) is such that the first material (4) and the second material (22) are not laminated one on top of the other.

2. The process according to claim 1, further characterized in that after the injection of the first material (4) in step i), the incomplete preform (15) is transferred to a second preform cavity (18) formed by the space between a front main bar (12) and a second preform mold (20); the second preform cavity (18) is adapted to allow the injection molding of a second material (22) to fill at least one void volume (14).

3. The process according to claim 2, further characterized in that the first preform mold (10) is opened after step i), subsequently transferring the main bar (12) and the incomplete preform (15) seated on the bar to the second preform mold (20), and the second preform mold (20) is closed before carrying out step ii).

4. The process according to claim 1, further characterized in that steps i) and ii) are carried out successively in the same preform mold; the first preform comprises at least a part a removable element that closes at least one empty volume that will be occupied with the second material during the injection of the first molten material; at least one removable element is removed before step ii), such that the second molten material can be injected into at least one void volume previously occupied by at least one removable element.

5. The process according to any of the preceding claims, further characterized in that the first material and the second material are injected from different injection points.

6. A process for manufacturing a preform (26) suitable for blow molding in a bottle; the preform is made of at least two different materials; the process comprises the steps of: i) forming a complete preform made of a first material, ii) making at least one volume of the complete preform to form an incomplete preform, iii) injecting a second material into at least one empty volume to complete the preform.

7. A suitable preform for blow molding in a bottle; the preform is made of at least two different materials (4, 22), characterized in that the first material and the second material are not laminated one on top of the other.

The preform according to claim 7, further characterized in that the first material and the second material are not distributed as horizontally superimposed layers, taking the central axis of the preform as a vertical axis.

The preform according to claim 8, further characterized in that the second material (22) forms at least one inclusion in a continuous matrix made of the first material (4)? , preferably wherein the first material forms at least two different inclusions.

The preform according to any of claims 7 to 9, further characterized in that there is no second material (22) in the neck (50) or in the lower part (52) of the preform.

The preform according to claim 7, further characterized in that the first (4) and / or the second material (22) extend from the neck (50) of the preform to its lower part (52).

12. A process for obtaining a bottle (38); the bottle is made of at least two different materials (4, 22); the process comprises the steps of: a) Obtaining a preform (26) suitable for blow molding in a bottle by the process of any of claims 1 to 5, and b) blow molding the preform to obtain the bottle (38), preferably by molding the preform by stretch blowing.

13. The process according to claim 12, further characterized in that the preform is removed from the inner main bar and optionally stored before being blow molded.

The process according to claim 12, further characterized in that the inner main bar (12) and the preform (26) seated thereon are transferred to a cavity for blow molding between steps a) and b).

15. The process or preform or bottle according to any of the preceding claims, further characterized in that the first and second materials have a different visual appearance, preferably when the first and second materials are of different colors.