Selective double-layer molding process and equipment

Abstract

This invention relates to a molding process. In particular, this invention relates to an improved two-layer molding process that allows for the selective and localized deposition of an additional cellulose layer only at points detected as critical, with the aim of enhancing its mechanical and aesthetic features.

Description

Technical Field

[0001] This invention relates to a molding process. Specifically, it relates to an improved two-layer molding process. Background Technology

[0002] To date, bilayer thermoforming has been used to produce bilayer products (typically in the food section) with the aim of minimizing the content of raw materials and chemical products and concentrating them exclusively in the layer that comes into contact with food, thus within the limits provided by international entities regarding the issuance of biodegradable certification, and obviously within the limits provided by compliance with dietary prerequisites.

[0003] The resulting products are formed by two complete layers due to the extension of their entire surface, and these two complete layers may be made of different materials.

[0004] US20190284764 relates to the field of automatic control wet fiber paper molding technology, and more specifically, to an automatic control wet paper molding machine and a method for performing the same.

[0005] CN108517724A relates to a pulp molding equipment, and more specifically to an integrated pulp molding equipment and method.

[0006] However, when it is not necessary to provide double layers for the entire extension of the product itself, this leaves a series of problems, such as issues related to resource and material waste.

[0007] Furthermore, it is clear that the current products do not allow for a high degree of flexibility in terms of structure and aesthetics in terms of application and product personalization. Summary of the Invention

[0008] Therefore, the purpose of this invention is to solve the problems that still exist in the prior art, and this is achieved through the molding process of this invention.

[0009] The present invention also relates to an apparatus for molding.

[0010] Additional features of the device of the present invention are also provided.

[0011] By overcoming the problems of the prior art, the present invention has several and obvious advantages.

[0012] First, the special production technology according to the invention enables the production of products consisting of two independent and distinct layers (e.g., made of cellulose), which are joined together in a single molding process, and whose characteristics can be defined by the production cycle and are specific for each layer.

[0013] The manufacturing process allows for the application of reinforcing layers only when deemed appropriate, to improve mechanical or aesthetic features, thereby minimizing waste of raw materials and energy.

[0014] This is achieved by designing molds with molding and pressing units specific to each type of product, in order to create functional coupling for responding to technical design requests.

[0015] This allows for the production of high-tech products by ensuring performance that is closer to that of products made from plastic materials produced by other methods.

[0016] Furthermore, the technology according to the invention allows for technical differentiation between the two layers by imparting independent structural and aesthetic properties (e.g., mechanical resistance, surface roughness, and coloring level) to the two layers, thereby making the resulting product unique in the market, even if it is not strictly exclusive to food packaging. Attached Figure Description

[0017] These and other advantages of the invention, as well as its features and modes of use, will become apparent from the following detailed description of preferred embodiments (shown by way of example and not for limiting purposes), with reference to the accompanying drawings:

[0018] - Figures 1 to 3 Some components of the device according to the invention are shown, and some stages of the process according to the invention for preparing preforms are depicted;

[0019] - Figures 4 to 6 Some components of the device according to the invention are shown, and some stages of the process according to the invention for preparing the reinforcing layer are depicted;

[0020] - Figure 7 Some components of the device according to the invention are shown, and some stages of the process according to the invention are depicted for joining the preform and the reinforcing layer;

[0021] - Figure 8A and Figure 8B The product obtained according to the present invention is shown based on a variation of which provides a material distribution with constant density and variable thickness;

[0022] - Figure 9A and Figure 9B The product obtained according to the present invention is shown based on a variation of a material distribution with variable density and constant thickness.

[0023] - Figure 10 An example of a product obtained according to the present invention is shown, based on a variation of a material distribution with variable density and constant thickness.

[0024] - Figure 11 and Figure 12 An example of a product obtained according to the invention is shown, based on a variation of a material distribution with constant density and variable thickness. Detailed Implementation

[0025] The invention will be described in detail below with reference to the accompanying drawings.

[0026] According to the present invention, generally speaking, the use of an improved double-layer molding technique is provided to deposit additional cellulose layers in a selective and localized manner only at points deemed critical to a particular product. Depending on the product's technical requirements, the bonding of the two layers can produce different mechanical characteristics: a specific increase in density and an increase in thickness, accompanied by a relative increase in structural resistance.

[0027] Based on this concept, it was considered to use targeted deposition of cellulose layers (reinforcing layers) only at specific points on the product during implementation through a single molding process.

[0028] The raw materials used to produce the bilayer are preferably, but not limited to, a cellulose fiber mixture of plant origin, extracted by processes commonly known in papermaking technology, followed by a mechanical, chemical, or semi-chemical paste.

[0029] For this purpose, even selective double-layer molding equipment has been designed.

[0030] First refer to Figure 1 This describes the first stage of the process according to the invention, which is performed using the equipment according to the invention.

[0031] Specifically, a tank 3 suitable for containing cellulose pulp 4 is provided. Preferably, the consistency of the cellulose pulp is between 0.3% and 0.8%, determined by appropriate dilution control. This consistency is the percentage of solid matter (fiber) in the liquid. The concentration of the mixture can be checked and possibly adjusted before it is fed into the tank using a microwave transmitter.

[0032] The first counter-mould 1 of the outer mold has a porous functional surface 2, such as a mesh surface, which has the contour of the product to be implemented. The first counter-mould 1 is then immersed in a tank 3, such that the mesh surface 2 is immersed in the cellulose pulp 4.

[0033] This means that the device according to the invention includes an actuation device for moving the core and the anti-punch.

[0034] The first mold, the anti-punch 1, has a hollow shape and includes a sleeve 5 that is connected to the external environment.

[0035] According to the present invention, suction is applied through the sleeve 5. Figure 1 (See arrow F1 in the image). For example, a vacuum of up to approximately 33 mbar can be generated using a liquid ring pump.

[0036] In this way, cellulose pulp 4 is drawn in through sleeve 5 and mesh surface 2, and the fibers therein are deposited on mesh 2 by forming a moist layer 6.

[0037] By applying a vacuum for a predetermined suction time T1, the first mold punch 1 is kept immersed in the groove 3. The suction time is set according to the desired weight of the final product, typically around 100 g / m³. 2 Up to 800g / m 2 The time T1 can vary depending on the type of fiber used and the consistency of the bath solution. Preferably, for a given weight, T1 is between 0.1 seconds and 10 seconds.

[0038] Advantageously, a vacuum flow is used to draw in dilution water and separate it for use in subsequent production cycles.

[0039] Once the suction time T1 has elapsed, the first mold anti-convex mold 1 is removed from the tank liquid. Preferably, the suction by the sleeve 5 continues during this stage, even when the first mold anti-convex mold 1 is outside the tank 3 and no longer immersed in the cellulose pulp. In this way, the first dehydration of the preform is carried out. This dehydration stage lasts for a predetermined dehydration time T2, which is set to finally obtain a dry level containing between 20% and 30% solids by weight. Time T2 can even be varied according to the cycle time. Preferably, a minimum dehydration time of 3 seconds and a maximum dehydration time of 20 seconds are considered.

[0040] The following Figure 2 This relates to subsequent stages of the process according to the invention.

[0041] Then the first mold punch 1 is brought close to the thermoforming mold 7. The thermoforming mold 7 is preferably hollow and equipped with a sleeve 8 that is connected to the external environment.

[0042] Furthermore, preferably, the thermoforming mold 7 has a mesh surface 9 shaped as a concave surface so as to receive the preform 6.

[0043] The first mold, the anti-punch 1, and the thermoforming mold 7 are then positioned along the axis at a distance D1, which is determined based on the geometry of the object and the thickness of the wet layer, for example, it includes a range of 0 to 2 mm. The distance D1 is set such that the slurry is deposited in a correct and uniform manner over the entire extension of the preform 6, and such that the wet slurry is not dragged between possible walls (or portions of walls) of the mold (which are not perfectly orthogonal to the approach direction of the mold itself) due to slippage.

[0044] At this time, the suction through the sleeve 5 of the first mold anti-punch 1 is interrupted, and compressed air is still introduced through the sleeve 5. Figure 2 (Arrow F2 in the image).

[0045] At the same time, by generating a suction flow ( Figure 2 Arrow F3 in the figure can apply a vacuum to the sleeve 8 of the thermoforming mold 7.

[0046] The flow of compressed air F2 and / or suction flow F3 causes the moist preform 6 to detach from the first mold punch 1 and position itself on the mesh surface 9 of the thermoforming mold 7, as... Figure 3 As shown.

[0047] Now refer to Figure 4 This shows the subsequent stages of the process to achieve the reinforcement layer 15.

[0048] According to the present invention, the molding equipment includes a second mold, a reverse punch 10.

[0049] The second mold punch 10 is preferably hollow and includes a sleeve 11 for connection with the external environment.

[0050] The second mold, the anti-punch 10, has a functional surface for forming the product to be implemented. On such a surface are porous regions 12 (e.g., for example, an imaging mesh) and non-porous regions 13.

[0051] The location, number, extension, and distribution of the porous regions 12 are determined by the type of product to be implemented and correspond to the reinforcement areas of the final product.

[0052] The second mold, the anti-convex mold 10, is positioned in the second groove 3', wherein the functional surface is immersed in the cellulose pulp 4' solution, the concentration of which can vary between 0.3% and 0.8%.

[0053] For the purpose of imparting different properties to the two layers, it is possible and sometimes preferred that the cellulose pulp 4' has different characteristics from the pulp 4 used to implement the preform 6. The distinction between the two mixtures used for the support layer and the reinforcing layer also allows for the selective incorporation of chemical additives, colors, and mineral loadings in one layer or the other.

[0054] As an example, one implementation of the reinforcing layer could be provided, where the choice of raw materials for it falls on fibers with greater length (relative to those used for the support layer 6) and generally finer blends. In fact, this allows for savings in the support layer from two perspectives: from the perspective of raw materials (considering the lower cost of shorter fibers) and from the perspective of processing (the fact that it is more refined involves less energy consumption), while simultaneously ensuring optimal mechanical properties due to the function of the reinforcing layer.

[0055] For practical reasons, trough 3' will preferably be a different and additional trough relative to trough 3. However, it is intended that, alternatively, the same trough can be used after changing the material.

[0056] According to the present invention, suction is applied through the sleeve 11. Figure 4 (See arrow F4 in the image). For example, a vacuum of up to approximately 33 mbar can be generated using a liquid ring pump.

[0057] In this way, cellulose pulp 4' is drawn in through the porous region 12 of the functional surface of the sleeve 11 and the second anti-convex mold 10, and the fibers therein are deposited on the web of the porous region 12 by forming a moist layer 15.

[0058] By applying a vacuum for a predetermined suction time T3, the second mold's reverse punch 10 is kept immersed in the groove 3'. The suction time is set according to the desired weight of the final product, typically around 100 g / m³. 2 and 800 g / m 2 The time T3 can vary depending on the type of fiber used and the consistency of the bath solution. Preferably, for a given weight, T3 is between 0.1 seconds and 10 seconds.

[0059] Advantageously, a vacuum flow is used to draw in dilution water and separate it for use in subsequent production cycles.

[0060] The result of this stage will be a layer 15 of moist cellulose fibers selectively formed in the porous region 12 of the mold 10—not necessarily single and continuous.

[0061] Once the suction time T3 has elapsed, the second mold anti-convex mold 10 is removed from the tank liquid. Preferably, the suction by the sleeve 11 continues during this stage, even when the second mold anti-convex mold 10 is outside the tank 3' and no longer immersed in the cellulose pulp. In this way, the first dehydration of the preform is carried out. This dehydration stage lasts for a predetermined dehydration time T4, which is set to achieve a final dryness level between 20% and 30%. Time T4 can even be varied depending on the cycle time. Preferably, a minimum dehydration time of 3 seconds and a maximum dehydration time of 20 seconds are considered.

[0062] Then the second mold punch 10 is brought close to the thermoforming mold 7, on which the preform 6 from the previous stage has been positioned.

[0063] The second mold, the anti-punch 10, and the thermoforming mold 7 are then positioned along the axis at a distance D2, which is determined based on the geometry of the object and the desired thickness of the wet layer, for example, it includes a range of 1 mm to 3 mm. However, the distance D2 is set such that the slurry is deposited correctly and uniformly over the entire extension of the preform 6, and such that the wet slurry is not dragged between possible walls (or portions of walls) of the mold (which are not perfectly orthogonal to the approach direction of the mold itself) due to slippage. Furthermore, the distance D2 must not damage the preform 6 (e.g., due to excessive compression).

[0064] At this time, the suction through the sleeve 11 of the second mold anti-punch 10 is interrupted, and compressed air is still introduced through the sleeve 11. Figure 5 (Arrow F5 in the image).

[0065] At the same time, by generating a suction flow ( Figure 5 Arrow F3 in the figure can apply a vacuum to the sleeve 8 of the thermoforming mold 7.

[0066] The action of the flow of compressed air F5 and / or suction flow F3 causes the wet layer 15 to detach from the second mold anti-punch 10 and to be positioned on the preform 6 that has been positioned on the thermoforming mold 7.

[0067] There are now two overlapping wet layers 6 and 15 on the thermoforming mold 7, as follows: Figure 6 As shown.

[0068] Now for reference Figure 7 .

[0069] The device according to the invention also includes a defining mold 16, which includes a functional surface 17 (shaped to conform to the profile of the product to be implemented) and is equipped with a through hole 18. The hole 18 is preferably arranged over the entire extension of the functional surface 17.

[0070] The limiting mold 16 is positioned coaxially with and close to the thermoforming mold 7, thereby compressing the assembly of the two cover layers 6 and 15. An application of 200 N / cm² is applied. 2 and 100N / cm 2 The mechanical pressure between the limiting mold 16 and the thermoforming mold 7.

[0071] Furthermore, the limiting mold 16 and / or the die mold 7 can even be heated. For this purpose, the device according to the invention may include a heating device suitable for heating the die and the punch, such as an electric heating device.

[0072] For example, the mold can be thermally conditioned at temperatures between 150°C and 220°C.

[0073] Preferably, a vacuum is still applied to the thermoforming mold 7 ( Figure 7 (See arrow F3 in the image) to remove water and steam generated during these process stages.

[0074] Advantageously, an airflow F6 can be applied to the defining mold 16 via the sleeve 19 to facilitate the drying of the preform.

[0075] This drying stage will be extended to a predetermined drying time T5, preferably between 8 and 25 seconds, set to achieve the desired dryness level at the end. If the preform still needs to be processed in a second thermoforming station, it is preferable to remove it at a dryness level between 50% and 75%. Conversely, if it is desired to produce the final product directly, the preform can be kept dry until a final dryness level between 94% and 96%.

[0076] Based on process parameters (pressure and temperature) and the shape of the limiting mold 16, or in the case of subsequent processing in a thermoforming station with different specific limiting molds, finished products that meet the desired specifications in terms of thickness and density can be obtained.

[0077] In particular, such as Figure 8A and Figure 8B The examples shown demonstrate that products with constant density and variable thickness can be achieved. The dimensions and parameters specified in the accompanying drawings are intended as implementations, not limiting examples.

[0078] The defining mold 16 (or a specific defining mold that may be used subsequently) is designed with a shape such that the gap between the two molds is variable at the minimum approach distance to the thermoforming mold 7, for example, it includes between 0.3 mm and 1.5 mm, which is achieved by differentiating the reinforcing area (where a greater material thickness is desired than in other product areas). The applied mechanical pressure preferably includes 20 N / cm². 2 Up to 100 N / cm 2 Between, more preferably including 40 N / cm 2 Up to 60 N / cm 2 between.

[0079] The end result is that layer 6 and reinforcing layer 15 maintain a constant density. Of course, the thickness at the reinforced area of ​​layer 15 will be greater than the thickness of the product at other points.

[0080] Using this technology, different colors can be assigned to two layers in the mold during molding, for example, by obtaining a two-color product, without the need for post-production processing.

[0081] Or, for example, Figure 9A and Figure 9BAs shown, products with variable density and constant thickness can be achieved. The dimensions and parameters shown in the figures are to be considered as examples of non-limiting embodiments.

[0082] In this case, the defining mold 16 (or a specific defining mold that may be used subsequently) is designed to have a shape such that the gap between the two molds is constant at the minimum approach distance to the thermoforming mold 7, for example, it includes between 0.3 mm and 1 mm, and the thickness necessarily results in uniformity throughout the entire extension of the final product. The applied mechanical pressure preferably includes 20 N / cm². 2 and 100 N / cm 2 Between, more preferably including 40 N / cm 2 and 60 N / cm 2 between.

[0083] The base layer 6 and the reinforcing layer 15 are pressed to maintain a constant thickness, and then the reinforcing region 15 will have a higher density than the rest.

[0084] By altering the material density, localized mechanical stiffness was achieved without noticeable external signs, resulting in good surface uniformity of the product.

[0085] The following Figure 10 The product obtained according to the method of the invention is shown by way of example in a variation that provides a material distribution with variable density and constant thickness.

[0086] Figure 11 and Figure 12 This is an alternative example of a product obtained according to the method of the present invention, in a variation that provides a material distribution with constant density and variable thickness.

[0087] The invention has been described with reference to preferred embodiments thereof. Each of the technical solutions implemented in the preferred embodiments described herein by way of example may be advantageously combined with another in a manner different from that described to produce additional embodiments belonging to the same inventive core, however, all of which are within the protection scope of the claims reported below.

Claims

1. A selective double-layer molding process for products made of cellulose fibers, comprising the following steps: - A first cellulose moist layer (6) is formed by the first mold anti-convex die (1) to realize the preform of the product; - A second cellulose moist layer (15) is formed by a second mold anti-convex die (10), the second cellulose moist layer (15) being realized by one or more regions localized at predetermined positions, corresponding to the reinforcing regions of the product; - Make the first cellulose moist layer (6) and the second cellulose moist layer (15) overlap; - The first cellulose moist layer (6) and the second cellulose moist layer (15) are joined by a limiting mold (16) and a thermoforming mold (7) to obtain the product; - Dry the product. The limiting mold (16) has a functional surface (17) shaped such that the gap between the limiting mold (16) and the thermoforming mold (7) is variable at the minimum approach distance to the thermoforming mold (7), thereby obtaining a product whole with constant density and variable thickness, or the gap is constant, thereby obtaining a product whole with variable density and constant thickness.

2. The process according to claim 1, wherein the first cellulose moist layer (6) is formed at a dryness level of between 20% and 30%.

3. The process according to claim 1 or 2, wherein the second cellulose moist layer (15) is formed at a dryness level of between 20% and 30%.

4. The process according to claim 1 or 2, wherein the connecting step includes containing 20 N / cm 2 and 100 N / cm 2 The action of applying pressure between the limiting mold (16) and / or the thermoforming mold (7).

5. The process according to claim 1 or 2, wherein the connecting step comprises applying heating to the defining mold (16) and / or the thermoforming mold (7) at a temperature between 150°C and 220°C.

6. The process according to claim 1 or 2, wherein when the gap is variable, the gap is varied such that the thickness of the product increases at the reinforced region.

7. An apparatus for selective double-layer molding of cellulose products, comprising: - At least one tank (3, 3') suitable for containing cellulose pulp (4, 4'); - A thermoforming mold (7) comprising a mesh surface (9) shaped according to the contour of the product; - At least a first mold anti-punch (1), which includes a mesh functional surface (2) shaped according to the contour of the product; - At least a second mold anti-punch (10) includes a functional surface shaped according to the contour of the product and having a porous region (12) and a non-porous region (13), the porous region (12) corresponding to the reinforcing region of the product; - At least one defining mold (16) includes a functional surface (17) shaped to conform to the contour of the product to be implemented and equipped with a through hole (18). The functional surface (17) is shaped such that the gap between the two molds is variable at the minimum approach distance to the thermoforming mold (7), thereby obtaining a product whole with constant density and variable thickness, or the gap is constant, thereby obtaining a product whole with variable density and constant thickness.

8. The device according to claim 7, comprising an actuation device for moving the first mold anti-punch (1).

9. The apparatus according to claim 7 or 8, comprising a heating device adapted to heat the defining mold (16) and the thermoforming mold (7).

10. The apparatus according to claim 7 or 8, comprising means for applying mechanical pressure to the defining mold (16) and the thermoforming mold (7).

11. The device according to claim 7 or 8, wherein the hole (18) is arranged over the entire extension of the functional surface (17).

12. The apparatus according to claim 7 or 8, comprising means for applying a vacuum to the thermoforming mold (7), and / or for applying compressed air to the first mold punch (1) and the second mold punch (10).

Images