阅读说明：本技术 复合产品的生产方法 (Method for producing composite products ) 是由 S·B·加斯塔迪 于 2019-10-28 设计创作，主要内容包括：复合产品(1)的生产方法,该复合产品(1)包括芯(2),包括浸渍有固体聚氨酯材料的片材的第一层(3),以及施加到第一层(3)的基于聚合物的膜(7),其中该方法包括：-生产半成品,该半成品包括芯(2)和被固体聚氨酯材料的液体混合物前体浸渍的片材；-通过在膜(7)和第一半模(11)之间施加低压,将膜(7)粘附到第一半模(11)；-将两个半模(11,12)彼此抵靠挤压并且半成品介于两个成形表面(13)之间,以使膜(7)与液体混合物接触；-在半成品置于模具中的情况下,将液体混合物热固化以使其转变成聚氨酯固体材料,从而使膜(7)牢固地粘附至第一层(3),由此产生复合产品(1)。(A method of producing a composite product (1), the composite product (1) comprising a core (2), a first layer (3) comprising a sheet impregnated with a solid polyurethane material, and a polymer-based film (7) applied to the first layer (3), wherein the method comprises: -producing a semi-finished product comprising a core (2) and a sheet impregnated with a liquid mixture precursor of a solid polyurethane material; -adhering the film (7) to the first mould half (11) by applying a low pressure between the film (7) and the first mould half (11); -pressing the two half-moulds (11,12) against each other with the semi-finished product between the two forming surfaces (13) so as to bring the film (7) into contact with the liquid mixture; -heat curing the liquid mixture to transform it into a polyurethane solid material with the semi-finished product placed in the mould, so that the film (7) adheres firmly to the first layer (3), thereby producing the composite product (1).)

1. A method of producing a composite product (1), said composite product (1) comprising a core (2), at least one first layer (3) on a first face (4) of the core (2), said first layer (3) comprising a sheet impregnated with a solid polyurethane material, and a polymer-based film (7) applied to said first layer (3) on the side opposite to said first face (4) of the core (2),

wherein the method comprises the following steps:

-producing a semi-finished product comprising said core (2) and said sheet impregnated with said liquid mixture precursor of solid polyurethane material on a first face (4) of said core (2);

-providing a mould (10) comprising two half-moulds (11,12), each half-mould having a respective forming surface (13);

-adhering the film (7) to the forming surface (13) of a first half-mould (11) of the two half-moulds by applying a low pressure between the film (7) and the forming surface (13);

-forming the semi-finished product by pressing the two half-moulds (11,12) against each other, with the semi-finished product interposed between two forming surfaces (13), so as to bring the film (7) into contact with the liquid mixture impregnating the sheet in the first layer (3);

-heat curing the liquid mixture to transform it into the polyurethane solid material, with the semi-finished product placed in a mould, so as to firmly adhere the film (7) to the first layer (3), thereby producing a composite product (1).

2. The method according to claim 1, wherein the composite product (1) comprises a second layer (5) at a second face (6) of the core opposite to the first face (4) of the core (2), said second layer (5) comprising a further sheet impregnated with said polyurethane solid material, wherein the semi-finished product comprises said further sheet impregnated with said liquid mixture precursor of said polyurethane solid material at the second face of the core.

3. The method according to any one of the preceding claims, wherein the composite product (1) comprises a further polymer-based film applied to the second layer (5) on the side opposite to the second face (6) of the core (2),

wherein the method comprises the following steps:

-adhering the further film to the forming surface (13) of the second half-mould (12) by applying a low pressure between the further film and the forming surface of the second half-mould (12) of the two half-moulds;

-during said forming of the semifinished product, said further film is brought into contact with a liquid mixture which impregnates said further film;

-said further film adheres firmly to said second layer during said thermal curing of said liquid mixture.

4. Method according to any one of the preceding claims, wherein the core and/or the first and/or second layer has a substantially laminar extension, wherein the sheet is made of glass fibres, carbon or kevlar fibres or natural fibres, wherein the core comprises honeycomb cardboard or solid foam, and wherein the polyurethane material is based on diphenylmethane diisocyanate (MDI), and wherein the liquid mixture is a mixture of polyol and isocyanate.

5. The method of any one of the preceding claims, wherein producing the semi-finished product comprises spraying the sheet with the liquid mixture, wherein the first semi-mold comprises a respective body with the shaped surface and a cutting blade system, wherein forming the semi-finished product comprises cutting the semi-finished product at least along a contour line by the blade system, and wherein thermally curing the liquid mixture comprises maintaining the semi-finished product at a temperature above 120 ° within the mold for a given period of time.

6. The method according to any one of the preceding claims, wherein the thickness of the film (7) is greater than or equal to 10 μm and/or less than or equal to 500 μm.

7. The method according to any one of the preceding claims, wherein the membrane (7) comprises or essentially consists of one or more of the following polymers: polypropylene (PP), Polyethylene (PE), Polyamide (PA), Polystyrene (PS), polymethyl methacrylate (PMMA), Polycarbonate (PC), Acrylonitrile Butadiene Styrene (ABS).

8. Method according to any one of the preceding claims, wherein at least one face of the film in contact with the outer face of the first layer is made of polyamide and/or Polystyrene (PS) and/or Polymethylmethacrylate (PMMA) and/or Polycarbonate (PC) and/or Acrylonitrile Butadiene Styrene (ABS).

9. The method according to any one of the preceding claims, wherein the film (7) contains a uv-resistant filler and/or pigment.

10. The method according to any one of the preceding claims, wherein adhering the polymer film (7) to the forming surface (13) comprises:

-applying the film (7) on the first mold half, wherein the film (7) has a continuous peripheral portion that exceeds the forming surface along the entire periphery of the forming surface;

-applying a low pressure between said peripheral portion of the film and said first half-mould along a continuous line around the respective forming surface;

-applying, after the previous step, the low pressure between the film and the forming surface,

wherein the low pressure is greater than or equal to 0.1 bar and/or less than or equal to 0.9 bar.

Technical Field

The present invention relates to a method for producing a composite product.

Technical Field

It is known how to achieve composite products, for example composite products, typically sandwich panels, comprising a core, typically honeycomb paperboard or solid foam, and upper and lower layers of reduced thickness arranged on opposite sides of the core. Each layer is made of a glass fibre board impregnated with a polyurethane material which also partially penetrates the core, thus fixing the entire structure.

The structure thus constructed has significantly better static properties than the individual components from which it is made. The lower and upper layers function to distribute the load over a plane, while one of the roles of the core, which occupies almost the entire thickness, is to increase the flexural and torsional rigidity of the panel, depending on the distance between the layers and the median plane, which all reduce the overall weight.

Such composite panels are widely used in sports equipment, such as skis or snowboards, or in the automotive field, for example for the manufacture of load surfaces, hatboxes, box bottoms, etc.

To achieve a sandwich panel, a core and two glass fiber sheets are generally assembled together first, and then the sheets are sprayed so that they are impregnated with a liquid mixture precursor of a polyurethane material (e.g., a mixture of a polyol and an isocyanate) to make a semifinished sheet. The semi-finished product is then subjected to a hot-press forming process (for example, in the case of polyurethane, at 130 ℃; 140 ℃) in which a mould is used consisting of two mould halves which are pressed against one another and into which the semi-finished product is inserted. In this way, the semifinished product is formed by trimming of the surface and cutting of its profile, and the liquid mixture is further cross-linked to form a solid polyurethane material which fixes the final form of the sandwich panel.

Disclosure of Invention

The applicant has realised that the known production processes of composite products and the associated known composite products have some drawbacks and/or can be improved in one or more respects.

The applicant has first found that it is desirable to equip the above-mentioned composite products with at least one external surface treated to impart specific properties to the surface itself, such as one or more of the following: improved mechanical properties (e.g. scratch, abrasion, etc.), water and wash resistance, tactile properties, aesthetic properties (e.g. colour, decoration, texture, etc.), uv resistance.

Applicants have also recognized that the above-described treated surfaces can be made by coating the surface with a suitable film. However, the applicant has determined that applying the film to the above-mentioned composite product downstream of the above-mentioned moulding process, for example by lamination or gluing or thermoforming, increases the production time and/or cost of the finished composite product and/or does not guarantee the desired quality of the finished product, for example in terms of adhesion of the film or spreading uniformity ("smoothness") of the film (i.e. without wrinkles or wrinkles).

The applicant has therefore faced the problem of developing a process for the production of composite products comprising at least one surface coated with a thin polymer-based film and realizing limited times and/or costs, generally substantially comparable to those of the traditional processes, while guaranteeing the required quality in terms of spreading uniformity and/or fastness and/or persistence of the coating on the surface of the composite product.

The problem of achieving one or more of these objects is solved according to the present application by a method for producing a composite product according to the appended claims and/or having the following features.

According to one aspect, the present invention relates to a method of producing a composite product.

The composite product (when finished) comprises a core, at least one first layer on a first face of the core, the first layer comprising a sheet impregnated with a solid polyurethane material, and a polymer-based film applied to the first layer on a side opposite to the first face of the core.

Preferably, the method comprises:

-producing a semi-finished product comprising said core and said sheet impregnated with said liquid mixture precursor of solid polyurethane material on a first face of said core;

-providing a mould comprising two mould halves, each mould half having a respective forming surface;

-adhering said film to said forming surface of the first of said two half-moulds by applying a depression (depression) between said film and said forming surface;

-forming the semi-finished product by pressing the two half-moulds against each other, with the semi-finished product interposed between two forming surfaces, so as to bring the film into contact with the liquid mixture impregnating the sheet in the first layer;

-heat curing the liquid mixture to transform it into the polyurethane solid material, with the semi-finished product placed in the mould, so as to firmly adhere the film to the first layer, thereby producing a composite product.

Having a low pressure between the film and the forming surface means that a pressure lower than atmospheric pressure is created in the space defined by the film and the forming surface (in order to make them adhere to each other), or more generally that a pressure difference between the face of the film facing the forming surface and the opposite face is achieved.

The term "film" refers to a sheet of sufficient flexibility that can be shaped by moderately low pressure (e.g., greater than 0.1 bar) to adhere to the surface of a mold half. For example, depending on the polymer material selected, the sheet typically has a thickness of no greater than 1 mm.

According to the present application, the film is adhered to the first half-mould by means of low pressure and the liquid mixture is allowed to thermoset in contact with the film and the latter, so that it is possible to incorporate the film directly into the composite product during the shaping step of the semi-finished product (at least including forming and thermosetting), without further using any fixing means (such as adhesives) or process steps (such as thermoforming, rolling, etc.) as in the conventional methods described above.

The invention achieves a tight, durable and long lasting adhesion of the film to the first layer. The use of low pressure allows the film to be spread evenly, i.e. substantially without wrinkles or wrinkles, since low pressure can strain even very thin films (e.g. films with a thickness of less than 250 μm) and provide very high flexibility, which would otherwise be prone to wrinkles.

In one or more of the foregoing aspects, the invention can have one or more of the following preferred features.

Typically, said composite product (when finished) comprises a second layer on a second face of the core opposite to the first face of the core, the second layer comprising a further sheet impregnated with said polyurethane solid material, wherein said semi-finished product comprises said further sheet impregnated with said liquid mixture precursor of said polyurethane solid material at the second face of the core. In this way, the mechanical resistance of the product is enhanced.

In one embodiment, the composite product (when finished) comprises a further polymer-based film (preferably identical to the film) applied to the second layer at the side opposite to the second face of the core.

Preferably, the method comprises:

-adhering the further film to the shaping surface of the second of the two mold halves by applying a low pressure between the further film and the shaping surface of the second mold half;

-during said forming of the semi-finished product, said further film is in contact with a liquid mixture that impregnates said further sheet;

-said further film adheres firmly to said second layer during said thermal curing of said liquid mixture.

Preferably, the core and/or the first and/or second layer has a substantially laminar extension.

Preferably, the sheet is made of glass fibre, carbon or kevlar or natural fibres, more preferably glass fibres (which is very cheap).

Preferably, the core comprises (or consists of) honeycomb cardboard or solid foam (with open or closed cells), more preferably honeycomb cardboard with cells running perpendicular relative to the first face of the core (to provide rigidity and firmness).

Preferably, the polyurethane material is based on diphenylmethane diisocyanate (MDI), even more preferably 4,4 '-diphenylmethane diisocyanate (4.4' -MDI). Preferably, the liquid mixture is a mixture of a polyol and an isocyanate, more preferably MDI, even more preferably 4, 4' -MDI (due to its wide availability and affordability).

Preferably, producing said semi-finished product comprises spraying said sheet (and said further sheet) with said liquid mixture.

Preferably, said first (and/or second) half-mould comprises a respective body having said shaped surface and a cutting blade system.

Preferably, forming the semi-finished product comprises cutting the semi-finished product at least along a contour line, more preferably with the blade system.

Preferably, thermally curing the liquid mixture comprises keeping the semifinished product at a given temperature in the mould for a given period of time, more preferably at a temperature higher than 120 °, even more preferably higher than 130 °.

Preferably, the low pressure is greater than or equal to 0.1 bar and/or less than or equal to 0.9 bar.

Preferably, the thickness of the film (and of the further film) is greater than or equal to 10 μm, more preferably greater than or equal to 20 μm, even more preferably greater than or equal to 30 μm and/or less than or equal to 500 μm, more preferably less than or equal to 250 μm, even more preferably less than or equal to 200 μm or 150 μm. The thickness is sufficient to provide the surface with at least one of the above properties without significantly increasing the weight and/or thickness and/or overall cost of the composite product. In addition, the film is sufficiently flexible to be able to be shaped by moderately low pressures.

Preferably, the membrane (and the further membrane) comprises or (essentially) consists of one or more of the following polymers: polypropylene (PP), Polyethylene (PE), Polyamide (PA), Polystyrene (PS), polymethyl methacrylate (PMMA), Polycarbonate (PC), Acrylonitrile Butadiene Styrene (ABS). According to the present application, these polymers are suitable to varying degrees to impart at least one of the aforementioned properties to the surface, and/or they provide sufficient chemical/physical compatibility to bond with the polyurethane material.

Preferably, at least one surface of the film in contact with the outer surface of the first layer (and possibly the surface of the further film in contact with the outer surface of the second layer) is made of polyamide or polystyrene or polymethylmethacrylate or polycarbonate or acrylonitrile butadiene styrene, more preferably of polyamide. In fact, the applicant has verified that these polymers, in particular polyamides, have a high chemical/physical compatibility (and therefore a stable and durable adhesion) with said polyurethane materials.

Preferably, the film (and the further film) comprises a uv resistant filler and/or pigment. In this way, the finished product is protected from the harmful effects of ultraviolet light and/or has a desired aesthetic appearance.

Preferably, adhering the polymeric film (and the further film) to the (respective) forming surface comprises:

-applying the film (and the further film) on the first (and the respective second) mould half, wherein the film (and the further film) has a (continuous) peripheral portion that exceeds the forming surface along the entire periphery of the forming surface;

-applying a low pressure between the peripheral portion of the film and the first half-mould (and between the peripheral portion of the further film and the second half-mould), more preferably along a continuous line around the respective forming surface;

-applying, after the previous step, said low pressure between said film and said forming surface (and between said further film and said respective forming surface), more preferably maintaining said low pressure between said peripheral portion of said film and said first half-mould (and between said peripheral portion of said further film and said second half-mould).

The applicant has determined that the application of a low pressure of first deformation (out-of-shape) pre-tensions the film, which favours the desired spreading (e.g. the presence or absence of small or no wrinkles or folds) between the film and the forming surface after the application of a low pressure of second forming (in-shape).

Preferably, applying the film on the first mold half comprises:

-applying the film onto the frame and applying a low pressure between the film and the frame along a continuous peripheral portion of the film to connect the film to the frame (and pre-tension the film);

-subsequently applying the film onto a first mold half by bringing a frame close to said first mold half,

-subsequently applying said low pressure between said peripheral portion of said film and said first half-mould,

-subsequently, removing the low pressure between the membrane and the frame to enable removal of the frame from the first half-mould. The same is true for the other films.

In this way, the film can be moved and set on the mold half in an already pretensioned form, so that the quality of the adhesion to the forming surface is further improved.