ITMI20121868A1 - MOLD AND PROCEDURE FOR PRINTING AN EXPANDED RESIN ON AN IMPREGNABLE LAYER, AND A MOLDED PRODUCT OBTAINED WITH THIS PROCEDURE - Google Patents

Description

MOLD AND PROCEDURE FOR CO-PRINTING AN EXPANDED RESIN ON AN IMPREGNABLE LAYER, AND CO-MOLDED PRODUCT

OBTAINED WITH THIS PROCEDURE

Field of the invention

[1] The present invention relates to a mold and a process for co-molding an expanded resin onto an impregnable layer, as well as a co-molded product obtained with this process. The invention can be used to produce, for example, upholstery for armchairs and other furniture, car seats or other components of motor vehicles.

State of the art

[2] In the production of armchairs, other furniture or car components it is known to co-mold - or over-mold, if you prefer - padding of expanded foams on frames or metal inserts or of compact plastic materials. On the other hand, no satisfactory processes are currently known for co-molding foam padding with pliable and fibrous materials, such as for example a piece of felt or a fabric. In fact, in the co-molded samples made by the author of the present invention in previous experiments, the expanded foam showed considerable and undesirable defects, such as bubbles, blowholes and outgassings, as well as differences in density-density from one piece to another in the polyurethane foam, at the interface with the felt layer and the polyurethane foam mass.

[3] Being able to couple expanded foams to supports of fibrous materials by co-molding would also be very useful and desirable for example in the production of designer mobile armchairs, because it would allow for example to create soft padding with very varied and elaborate shapes, and at the same time reversibly removable from the rigid frame - for example metal or plastic material of the armchair. More generally, the possibility of coupling an expanded foam through co-molding to a piece of fibrous materials such as felt, for example, would give planners and designers much greater design freedom in the development of new products.

[4] An object of the present invention is to obviate the aforementioned drawbacks and in particular to provide an equipment and a process for co-molding foams of expanded materials, usable for example as padding, on pieces of pliable and fibrous materials such as felts, fabrics warp and weft, knitted fabrics, non-woven fabrics or layers of foam already solid at the time of co-molding.

Summary of the invention

[5] In a first aspect of the invention, this object is achieved with a mold for co-molding an expanded resin onto an impregnable layer having the characteristics according to claim 1.

In a first aspect of the invention, this object is achieved with a process for co-molding an expanded resin onto an impregnable layer having the characteristics according to claim 9.

In a third aspect, the invention relates to a co-molded product having the characteristics according to claim 14.

Further characteristics of the device are the subject of the dependent claims.

Further advantages achievable with the present invention will become more evident to those skilled in the art from the following detailed description of a particular non-limiting example of embodiment, illustrated with reference to the following schematic figures.

List of Figures

Figure 1 shows a top view, according to the section plane I-I, of a mold and an impregnable insert according to a particular embodiment of the invention;

Figure 2 shows a first side view, according to the section plane IIA-IIA, of the mold and of the impregnable insert of Figure 1;

Figure 2A shows a detail of the section of Figure 2;

Figure 2B shows a detail of a second side view, according to the section plane IIB-IIB, of the mold and the impregnable insert of Figure 1;

Figure 3 shows a perspective view of the impregnable insert before being inserted into the mold of Figure 1;

Figure 4 shows a perspective view of the insert of Figure 3 inserted in the lower half-mold of the mold of Figure 1, before co-molding;

Figure 5 shows a perspective view of the foam padding co-molded on the insert of Figure 3, inserted in the lower half-mold of the mold of Figure 1;

Figure 6 shows a first perspective view of the rear face of the padding of Figure 5, extracted from the mold of Figure 1 and before being trimmed;

Figure 6A shows a second perspective view with a detail of the rear face of the padding of Figure 5;

Figure 7 shows a first perspective view of the front face of the padding of Figure 5, extracted from the mold and before being trimmed;

Figure 7A shows a second perspective view with a detail of the front face of the padding of Figure 5;

Figure 8 shows a perspective view of the front face of the padding of Figure 5, extracted from the mold and after being trimmed.

Detailed description

[6] In this description the terms "average, average", unless otherwise specified, are to be understood as referring to an unweighted arithmetic average. Figures 1-8 relate to a mold and a process for co-molding an expanded resin onto a solid impregnable layer according to a particular embodiment of the invention. The expanded resin can be, for example, an expanded polyurethane which is sufficiently soft and yielding to be used to make cushions for armchairs, sofas or motor vehicle seats, and for example have a density comprised for example between 50-70 kg / cubic meter.

The mold 1 can be for example a mold with the walls of the molding cavity made of synthetic resin and bearing frame made of welded metal sheet; alternatively the mold 1 can be totally made of aluminum or steel.

The mold 1 can for example comprise two half-molds 3, 5 arranged to open and close reversibly so as to allow the molded piece 23 to be extracted from the molding cavity 13.

[7] The impregnable layer can be for example a piece of suitable fibrous material, such as for example a felt, a piece of weft and warp or knitted fabric. The fibers of the fibrous material can be of animal, vegetable or synthetic fibers such as for example wool, silk, cotton, jute, nylon or polyester fibers. Alternatively, the impregnable layer can be, for example, a piece of non-woven fabric or a layer of foam material or in any case with a cellular structure - such as for example polyurethane foam or a foam rubber - already solidified before being introduced into the mold itself.

Figure 2 shows an example of an impregnable layer in the form of an impregnable patch or insert 7 intended to form the back of a cushion for an armchair. The references 9, the indicate the parts intended to cover respectively the rear side of the seat and the back of the padding 23.

[8] Mold 1 internally forms:

-a molding cavity 13 arranged to receive and maintain the solid impregnable layer in a predetermined position; And

-one or more vent chambers 15.

According to an aspect of the invention, the mold 1 is arranged to ensure that, when the mold is closed and in the molding cavity 13, the expansion of one or more reagents that will form the expanded resin, such as for example an isocyanate and a polyol if the expanded resin will be a polyurethane:

at least half of its length, the outer perimeter edge of the impregnable insert 7, or more generally of the impregnable layer, faces one or more vent chambers 15 (Figures 2A, 2B);

- one or more vent chambers 15 receive the expanded resin obtained from the expansion of one or more reactants and / or any air or other aeriform expelled from the impregnable layer 7 following the expansion of the one or more reagent reagents during molding. Preferably the mold 1 is arranged to cause the one or more vent chambers 15 to be filled in an appreciable way, for example at least for half of their volume, by the expanded resin obtained by the expansion of the one or more reactants. Alternatively, the one or more vent chambers 15 can be filled, completely or partially, by any air or other aeriform expelled from the impregnable layer 7 following the expansion of the one or more reagent reagents during molding.

[9] As shown in Figures 1, 2, 2A, each vent chamber 15 can be a portion of the molding cavity 13. Preferably the outer perimeter edge of the impregnable insert 7, or more generally of the impregnable layer, faces the chamber vent 15, faces at least three-quarters of its length along the vent chamber, and even more preferably at least four-fifths of the length of the same external perimeter edge of the impregnable insert 7. In the embodiment of the attached Figures more than 9/10 of the length of the outer perimeter edge of the impregnable insert 7 overlook the vent chambers 15. In the embodiment of Figures 1-8, the impregnable insert 7 is provided, along its peripheral edge, with a plurality of extensions fixing elements 17 arranged to be clamped and pressed by the two half-molds 3, 5 when the latter close. By doing so, despite being of a relatively very pliable material such as a wool or cotton felt mat, the impregnable insert 7 is held firmly and precisely in the molding cavity, preventing it from moving and deforming in an undesirable way during the molding. expansion of reagents. Each empty space of height HB and depth WB which extends between two adjacent fixing extensions 17, or the entire and unique empty recess of height HB and depth WB that surrounds the entire perimeter of the impregnable insert 7 (Figures 1, 2A, 2B).

[10] The volume per unit of length of each vent chamber 15 can be measured, for example, in square millimeters, in square centimeters or in square meters.

Preferably the volume per unit of length of each vent chamber 15 is equal to or greater than the square of the thickness HB of the outer perimeter edge of the impregnable layer 7 in a substantially undeformed condition, i.e. for example not pinched or squeezed between the two half-molds 3, 5 ( Figures 2A, 2B). More preferably, the volume per unit of length of each vent chamber 15 is equal to or greater than three times the square of the thickness of the outer perimeter edge of the impregnable layer 7; more preferably it is equal to or greater than four times, and even more preferably it is equal to or greater than six-seven times the square of the thickness of the outer perimeter edge of the impregnable layer 7.

[11] Advantageously each vent chamber 15 extends, locally normal to the edge portion of the impregnable layer 7 considered each time and parallel to the ideal surface in which this edge lies, for a depth WB equal to or greater than the thickness of the outer perimeter edge of the impregnable layer 7 in an undeformed condition. More preferably the depth WB - or the depths WB- of each vent chamber are equal to or greater than three times the thickness of the outer perimeter edge of the impregnable layer 7 in an undeformed condition, and even more preferably equal to or greater than six-seven times the thickness of this external perimeter edge.

[12] Preferably the height HB of each vent chamber 15, according to the direction locally normal to the surface in which lies the portion of impregnable layer 7 adjacent to the portion of its edge considered each time, is equal to or greater than the thickness of the outer perimeter edge of the impregnable layer 7 in an undeformed condition.

Advantageously, in each vent chamber 15 there is at least one of the cavities interposed between two of the mold dividing surfaces 19 which separate the two half-molds 3, 5 from each other (Figure 2). clearly from the following in this way the expanded resin generated by the aforementioned reagents is able to fill the vent chambers better and more uniformly, further reducing the risks of bubbles, blowholes, degassing or density irregularities, in particular in the vicinity of the chambers 15.

The mold 1 can be arranged in such a way as to allow the impregnable insert 7 or other impregnable layer 7 to be placed and spread on part of the surface of the molding cavity 13, and in direct contact with part of the surface of the molding cavity 13, so that in the finished molded product a major face of the impregnable layer, or at least a large part of it, emerges from the expanded foam matrix 25 without being covered by it (Figures 2, 6, 6A)

The mold 1 is designed and particularly suitable for molding products in expanded foam preferably with open cells.

[13] An example of operation and particular use of mold 1 is now shown.

The impregnable insert 7, for example a piece of wool or cotton felt, is placed on the bottom of the molding cavity 13 (Figure 4). The fluid state reagents to be expanded, such as for example an isocyanate and a polyol, are poured into the lower half-mold, for example by pouring them directly onto the impregnable insert 7. These reagents can be poured into an open mold or through suitable injection caps suitably prepared on the mold itself.

When poured in this step, isocyanate and polyol may be a relatively viscous liquid commonly referred to as "cream" in technical jargon. Then the mold, which opened was at a suitable temperature which in the case of expanded polyurethane can be the usual 50 ° C, is closed and the "cream" of the reagents begins to crosslink, gradually expanding and solidifying and possibly developing an exothermic reaction in if known.

[14] It is assumed that the fluid cream of the isocyanate and the fluid polyol initially percolate downward into the insert 7, impregnating it; over time and as it crosslinks and solidifies, the "cream" percolates and impregnates the insert 7 less and less, until it reaches a degree of viscosity in which the outermost face of the solidified "cream", stopped before having impregnated the entire thickness of the insert 7, constitutes a barrier which retains the inner cream which is still fluid. The remaining still fluid reagents are then forced to expand in the impregnated portion of the felt -or of another impregnable layer 7- and in the empty space of the molding cavity not occupied by the insert 7. This expansion of the reagents reduces the volume available for air initially present in the molding cavity 13 and pushes the air to flow through the various vents of the mold 1, for example through the thin air spaces 21 which separate the half-molds 3, 5 in correspondence with the mold dividing surfaces 19, or through suitable holes of vent, known per se and not shown, which are made in the mold when the leaks through the cavities 21 are not sufficient (Figures 1, 2A, 2B).

[15] The author of the present invention has in fact noticed that in the absence of the vent chambers 15 the molded product has major molding defects, in particular evident and unwanted bubbles, blowholes and degassing as well as excessive differences in density quotas from one piece to the other, both on the perimeter edges and inside the printout. It is hypothesized that the vent chambers 15 allow to eliminate or in any case considerably reduce these molding defects because it is free to collect in them, accumulating or passing before coming out through the cavities 21 interposed between two mold dividing surfaces, air or other. aeriform expelled from the impregnable layer 7 when it is impregnated by the reactants which are crosslinking and expanding.

[16] Once the crosslinking, expansion and solidification of the reagents have been completed, the mold 1 is opened and the co-molded piece 23 of expanded foam is extracted. Figure 5 shows the mold 1 open with the co-molded piece 23 still lying in the lower half-mold 5. Figures 6, 6A show the rear face of the co-molded piece 23 extracted from the mold 1, still raw and before being trimmed; it can be seen that a major face of the impregnable insert 7 can emerge from the solidified foam 25 without being - at least completely - covered by it, and the solidified foam can occupy each vent chamber 15 for all or part of its local depths WB1, WB2. The process according to the invention is particularly advantageous for producing co-molds in which at least half of the surface of a major face of the impregnable layer emerges from the solid expanded foam without being covered by said foam.

[17] If it forms the padding of both the seat and the back of an armchair, the rear face of the co-molded piece 23 can be arranged to face or in any case be turned towards the supporting frame of the armchair itself (Figures 6, 6A).

Figures 7, 7A show the front face of the co-molded piece 23 extracted from the mold 1, still raw and before being trimmed. If it forms the padding of both the seat and the back of an armchair, the front face of the co-molded piece 23 can be arranged to face the person sitting on the armchair. The perimeter edges of the co-molded piece 23 can be subsequently trimmed, for example to eliminate part or all of the length WB of the fastening extensions 17. Figure 8 shows the co-molded piece 23 'with the trimmed edges. The trimmed padding 23 can therefore be covered with a suitable lining.

[18] Thanks to the previous teachings it is possible to effectively co-mold a solid foam resin matrix on a layer of impregnable material, such as for example felt of animal, vegetable or synthetic textile fibers, weft and warp or knitted fabrics, non-woven fabric or an already solidified foam material, substantially without molding defects such as bubbles, blowholes or excessive density variations in the foam resin. In particular, the previous teachings allow co-molding with very satisfactory results, at least in the field of furniture upholstery, relatively large pieces of impregnable materials, for example with surfaces of several decimetres or square meters, even if most of the surface of the impregnable insert emerges from the expanded foam matrix without being covered by it or embedded in it, and / or even if the co-molded expanded foam matrix impregnates less than half, or in any case a part, of the thickness of the impregnable layer; which increases the manufacturing possibilities and in general the freedom of designers of furniture, automotive components or other sectors. The method and the mold according to the invention, previously described, allow to effectively co-mold impregnable layers of relatively thin fibrous materials, in which the volume of trapped air is significantly greater than that trapped in the subsequently co-molded solid expanded matrix; they also allow co-molding on impregnable layers of relatively low cost materials, such as for example felts or non-woven fabrics.

[19] The embodiments described above are susceptible to various modifications and variations without departing from the scope of protection of the present invention. For example, each vent chamber 15 can have cross sections - considered according to section planes which are locally normal both to the portion considered each time of the perimeter edge of the impregnable layer 7, and to the surface in which the portion of the impregnable layer 7 adjacent to the portion lies. edge from time to time considered - not only rectangular (Figure 2A), but also square, trapezoidal, polygonal, ovoid, circular or variously beveled or tapered. Furthermore, all the details can be replaced by technically equivalent elements. For example, the materials used, as well as the dimensions, may be any according to the technical requirements. It must be understood that an expression of the type "A includes B, C, D" or "A is formed by B, C, D" also includes and describes the particular case in which "A consists of B, C, D" . The examples and lists of possible variants of this application are intended as non-exhaustive lists.

Claims (14)

CLAIMS 1) Mold (1) for co-molding an expanded resin on a solid impregnable layer (7), comprising: -a molding cavity (13) arranged to receive and maintain in a predetermined position the impregnable layer (7) already in solid form; -one or more vent chambers (15); and the mold (1) is arranged to ensure that, when it is closed and in the molding cavity (13), the expansion and conformation of one or more reactants that will form the expanded resin takes place: - at least half of its length, the outer perimeter edge of the impregnable layer (7) faces one or more vent chambers (15); -the one or more vent chambers (15) receive the expanded resin resulting from the expansion of the one or more reactants and / or any air or other aeriform expelled from the impregnable layer following the expansion of the reagent during molding. 2) Mold (1) according to claim 1, arranged so that the volume per unit of length of the at least one vent chambers (15) is equal to or greater than the square of the thickness of the outer perimeter edge of the impregnable layer (7) in a substantially undeformed condition. 3) Mold (1) according to claim 1, wherein the volume per unit of length of the one or more vent chambers (15) is equal to or greater than three times the square of the thickness of the outer perimeter edge of the impregnable layer (7) in a substantially undeformed condition. 4) Mold (1) according to claim 1, in which each of the vent chambers (15) extends for a depth (WB) on average equal to or greater than the thickness of the outer perimeter edge of the impregnable layer (7) in a substantially undeformed condition. 5) Mold (1) according to claim 1, wherein the average height (HB) of each of the vent chambers (15) is equal to or greater than the thickness of the outer perimeter edge of the impregnable layer (7) in a substantially undeformed condition. 6) Mold (1) according to claim 1, arranged in such a way as to allow the impregnable layer (7) to be placed and spread on part of the surface of the molding cavity (13), in direct contact with this part of the surface of the molding cavity (13). 7) Mold (1) according to claim 1, comprising one or more air evacuation passages (21) designed to evacuate outside the mold (1) at least part of the air or other aeriform expelled from the impregnable layer (7) and from the molding cavity (13) during molding, and the one or more air evacuation passages (21) open at or near the one or more vent chambers. 8) Mold (1) according to claim 1, comprising at least two half-molds (3, 5) separated from each other by two or more mold dividing surfaces (19) and arranged to open reversibly so as to allow access to the inside of the cavity (13), where the one or more air evacuation passages comprise one or more empty cavities (21) interposed between two of the mold dividing surfaces (19) facing each other. 9) Process for co-molding an expanded resin on a solid impregnable layer (7), comprising the following operations: - introducing and maintaining in a predetermined position an impregnable layer (7) already in solid form in a molding cavity (13) of a mold (1), so that one or more vent chambers (15) extend along at least half the length of the outer perimeter edge of the impregnable layer (7), where the mold has the characteristics according to claim 1; - to expand and shape in the molding cavity (13) one or more reagents, transforming them into a solid expanded resin which flows into one or more vent chambers (15), or by making one or more vent chambers (15) flow into the any air or other gaseous expelled from the impregnable layer (7) following the expansion of the reagent during molding. 10) Process according to claim 9, wherein the impregnable layer (7) comprises one of the following materials: animal, vegetable or synthetic fiber felt, a weft and warp or knitted fabric, a non-woven fabric. 11) Process according to claim 9, wherein the operation of maintaining the impregnable layer (7) already in solid form in a predetermined position in the molding cavity (13) comprises the operation of placing the impregnable layer (7) and spreading it against a wall of the molding cavity so that at least a part of the impregnable layer (7) in the co-molded product (23) extracted from the mold (1) emerges from the solidified foam without being covered by it or completely embedded in it. 12) Process according to claim 9, comprising the operation of expelling through the one or more vent chambers (15) the air or other gaseous expelled from the impregnable layer (7) and from the molding cavity (13) during molding. 13) Process according to claim 9, wherein the mold (1) has the characteristics according to claim 8 and the process comprises the operation of fixing the impregnable layer (7) to the mold (1) by clamping it between the at least two half-molds (3 , 5), so as to keep it in a predetermined position inside the molding cavity (13) during molding. 14) Co-molded product obtained with the process having the characteristics according to claim 9, comprising an impregnable layer (7) and a matrix of solid expanded foam co-molded on the impregnable layer (7), in which at least half of the surface of a major face of the layer impregnable (7) emerges from the expanded solid foam matrix without being covered by said matrix or completely embedded in said matrix.