Patent Application
20230064200
The present invention relates to a method of producing a support for polyurethane-based imitation leather free of dimethylformamide (DMFa) or other solvents or water, and to a related method of producing an imitation leather free of dimethylformamide (DMFa) or other solvents.
Faux leather or imitation leather is a synthetic leather which can have an appearance similar to that of natural hide or leather, or it can be made with a certain grain even different from leather, for example with technical designs and the like.
Imitation leather consists of a polymer in the base form of simple film, to which a fabric or a nonwoven fabric (NWF) in natural fibers (e.g., cotton, linen or the like), or synthetic fibers (e.g., polyester, polyamide, and the like) or a combination thereof, or a coagulate can be applied thereto, i.e., a fabric/NWF on which a polymeric material has been impregnated or spread.
The production of imitation leather usually occurs by multilayer spreading. The process initially includes a plurality of steps of spreading various layers which will go to form the final product. Such layers are spread on a release paper support using a blade. In the final step of the process, a textile support or an NWF support or a coagulated support is applied to the plurality of layers by means of an adhesive. Finally, a printing finishing process, or an embossing, or an application of transfer papers or foils can follow if the aesthetic effect of the fabric is to be enhanced.
The coagulate is an essential element of the production process of polyurethane imitation leather, as it serves to give thickness and mechanical features to the finished product.
The coagulate is a base composed of a fabric/NWF and aromatic polyurethane in dimethylformamide (DMFa) or other solvents or in water.
Such a type of coagulate is therefore composed of fabric/NWF impregnated with coagulated polyurethane or fabric/NWF to which a layer of coagulated polyurethane is applied directly to the surface using a blade. The coagulation by impregnation occurs in a special line where the fabric/NWF, which will form the final support, is placed in a tank containing the polyurethane solution in DMFa or solvents. The fabric, which remains impregnated with the desired amount, is then immersed in a coagulation tank in which the polyurethane, deprived of the solvent, coagulates since the DMFa, being very hydrophilic, is violently captured by the water. Next, for the complete elimination of the DMFa, the coagulated fabric/NWF undergoes various washing cycles with countercurrent water. Finally, after careful squeezing, the product passes through a special dryer for complete drying and the subsequent rolling.
Despite the various washing cycles, the final coagulate maintains a high concentration of DMFa or other solvents, i.e., between 400 and 800 ppm (i.e., mg/kg). Such a percentage is no longer acceptable, as DMFa is highly toxic and dangerous, and there are numerous regulations limiting the presence thereof in fabrics.
Imitation leather production methods are known in the field, which include using polyurethane free of dimethylformamide (DMFa), as described in documents CN102 758 359 A and CN 102 758 360 B. Such documents describe a method of applying a two-component polyurethane which requires a mechanical leveling carried out by a blade. It is apparent that the contact between the blade and the polyurethane material being solidified involves an accumulation in little time of residues of solidified material below the blade until they completely obstruct the passage opening for the sliding of the material still under reaction. This results in continuous machine stops to allow the cleaning or replacement of the blade itself. Such an aspect is particularly disadvantageous and is common to all the methods of applying polyurethane with mechanical leveling.
It is the object of the present invention to solve the problems associated with the use of DMFa and other solvents for producing imitation leather, thus also reducing the emissions which are difficult to detect and allowing a high saving of caloric energy.
Therefore, it is an object of the present invention to obtain a replacement support of the coagulate for producing imitation leather, which is free of DMFa or other solvents or water.
In particular, it is the object of the present invention to provide a new method of producing a support for polyurethane-based imitation leather free of DMFa or other solvents or water, and a related new method of producing an imitation leather free of DMFa or other solvents.
Such an object is achieved by a method of producing a support for polyurethane-based imitation leather free of DMFa or other solvents or water according to claim 1, and by a related method of producing an imitation leather free of DMFa or other solvents according to claims 10, 11, 12, 13, 16. The dependent claims describe preferred embodiments of the invention.
The features and advantages of the method according to the present invention will become apparent from the following description, given by way of non-limiting example in accordance with the accompanying drawings, in which:
It is an object of the present invention to obtain a replacement support of the coagulate, that is to say a polyurethane-based support for imitation leather free of dimethylformamide (DMFa) or other solvents or water. The new support is obtained with a method in accordance with the present invention which includes using a two-component polyurethane applied homogeneously on a base. The method provides for the reaction between the two components occurring by using a high or low pressure machine (with or without mixer) and for the mixture being immediately uniformly distributed on the base by spraying.
The two-component polyurethane 11 used is obtained from the synthesis of two components: component A and component B.
Component A is an isocyanate, preferably diphenylmethane diisocyanate (MDI) partially reacted with polyesters or polyethers.
Component B is a polyether-based or polyester-based polyol.
Preferably, the components A and B have the following properties:
The mixing ratio by weight between component B (polyol) and component A (isocyanate) is preferably between 100:30 and 100:120.
The reaction between the components A and B occurs at high or low pressure.
The two-component polyurethane 11 is deposited uniformly on the base through a spray system indicated by reference numeral 2 in the drawings. The system 2 mixes the components A and B, making them collide at high pressure, or at low pressure by using a mixer, then depositing the two-component mixture through a spray. Advantageously, the method according to the present invention provides that the mixture of components A and B is uniformly sprayed without the need for any mechanical spreading or leveling.
With particular reference to
Preferably, the dosing pump 21 has a variable ratio, with electronic control of the amount delivered and of the mixing ratio through flow controls.
The spraying unit comprises at least one high or low pressure mixing head 22 provided with at least one spray nozzle 23. The mixing head 22 and the dispenser 23 form a spray system.
Preferably, the spray system is provided with an automatic cleaning system and a mechanical purging system.
The spraying unit comprises at least one pipe 23 adapted to connect the dosing pumps 21 with the mixing head 22 of the spray system. Preferably, the pipes 23 are heated and temperature controlled with thermoregulation.
Preferably, the spraying unit is provided with a panel for adjusting the amount of product to be dispensed. The spray flow rate is variable.
Preferably, the spray system is supported above the base through a frame 24. The frame 24 is a bridge structure extending transversely above the base.
In the embodiment in
In the embodiment in
Therefore, the uniform deposition system 2 allows the two components A and B to be mixed in a liquid state, at high pressure without the need for a classic rotor or screw mixer, or at low pressure through a rotor or screw mixer.
To date, in the hypothesis of depositing the two-component mixture with the aid of a blade, it is apparent that the contact between the blade and the material under reaction (and therefore in the solidification phase) would quickly block the sliding of the two-component mixture under the blade, thus causing frequent stops for cleaning or replacing the blade itself. On the other hand, the deposition system 2 includes the spray deposition of the mixture of components A and B on the base uniformly, without the need for spreading by means of a blade. Such an aspect is particularly advantageous since it avoids the disadvantages of spreading with a blade described above, namely the need to continuously stop the process in order to clean the blade.
Such a method includes the steps of:
It should be noted that in the execution step of the method, the base 1,1' flows through the workstations.
Preferably, the method includes a final step of rolling the support 5 for imitation leather 6 to form a roll 51.
Preferably, before the rolling step, a step of removing the base 1,1' is included so that the support 5 comprises only the polyurethane layer 11 adhered to the backing 12. In the case of using release paper 1 (
The drying step of the polyurethane layer 11 is obtained by means of at least an oven 13.
In an embodiment, shown in
In an embodiment, shown in
Advantageously, in fact, the backing 12 is applied to the polyurethane layer 11 without the aid of adhesives since the adhesiveness of the reaction mixture is utilized.
Advantageously, the polyurethane layer 11 expands upon drying, giving thickness and mechanical properties to the support 5 for imitation leather 6.
Advantageously, by varying the amount of two-component mixture sprayed onto the base 1,1' or by varying the amount of expanding agent it is possible to obtain a more or less thick polyurethane layer 11. The thickness of the polyurethane layer 11 varies according to the final application.
It should be noted that the base is a release paper 1 (
The backing 12 is for example a fabric or a nonwoven fabric (NWF) composed of natural or synthetic fibers or a mixture of the two.
The present invention also relates to a method of producing an imitation layer 6,6' free of dimethylformamide (DMFa) or other solvents starting from a support 5 obtained with the above method.
It should be noted that in order to be able to use the support 5 to obtain an imitation leather 6,6' it is first necessary to remove it from the base 1,1', forming the roll 51.
In an embodiment, the method of producing an imitation leather includes only spraying the two-component mixture on a base 1,1' applying a fabric/NWF 12, and a final step of removing the base. Such an embodiment is shown in
In a further embodiment, after removing the base, the support 5 obtained with the above method and therefore completely free of DMFa or other solvents or water, is inserted in a production line of imitation leather 6,6' replacing the coagulate. The support 5 thus becomes an essential element of the production process of the imitation leather 6,6' as it serves to give thickness and mechanical features to the finished product. Such an embodiment is shown in
In such an embodiment, the method of producing an imitation leather 6 includes the steps of:
It should be noted that in the execution step of the method, the base 1,1' slides.
The drying step of the polyurethane layer 41 and of the adhesive layer 42 is obtained by means of at least an oven 13.
Preferably, the method includes a final step of rolling the imitation leather 6 to form a roll 60.
In a further embodiment, shown in
In such an embodiment, the method of producing an imitation leather 6 includes the steps of:
It should be noted that in the execution step of the method, the base 1,1' slides.
Preferably, the method includes a final step of rolling the imitation leather 6 to form a roll 60.
The drying step of the polyurethane layer 41,11 is obtained by means of at least an oven 13.
In an embodiment, shown in
In an embodiment, shown in
The method of producing an imitation leather according to the present invention can also be used to obtain a so-called double-coat, i.e., an imitation leather 6' defined on both sides. Such a method is shown in
In an embodiment, shown in
In fact, the film 17 is provided with a texture, i.e., with a grain/design, on the side opposite to that intended to come into contact with the polyurethane layer 11.
Preferably, said film 17 is a polyurethane film provided with a texture. Preferably, the polyurethane is water based.
In a further embodiment, shown in
Preferably, before applying a texture on the further polyurethane layer 11' by means of the embossing cylinder 18, the at least partial drying of this further polyurethane layer 11' is included, for example by means of a further oven 13.
It should be noted that in the execution step of the method, the base 1,1' slides.
Preferably, the method includes a final step of rolling the imitation leather 6' to form a roll 60.
The drying step of the polyurethane layer 41,11,12,11' is obtained by means of at least an oven 13.
In an embodiment, shown in
In a further embodiment, the drying step of the polyurethane layer 11,11' is performed upstream of the step of applying the backing 12, or the film 17, or the embossing. In such an example the drying is only partial.
A further method of producing a double-coat imitation leather, i.e., an imitation leather 6' defined on both sides, includes obtaining an imitation leather 6 with the method shown in
Innovatively, the method of producing a support 5 for imitation leather 6,6', and the related machine 2, in accordance with the present invention, allows to replace the polyurethane coagulate based on DMFa or other solvents with a polyurethane support free of DMFa or other solvents or water.
It should be noted that the term spray distribution or spraying is intended as the deposition of the polyurethane layer in the form of tiny or very minute droplets or particles. Such a definition includes nebulization, atomization, vaporization, spraying, pulverization. Such a definition includes distribution both with thrust with pressurized air or compressed air, and without air. Such spraying can be carried out by using guns, or nozzles, or other dispensers capable of carrying out a spray distribution.
Advantageously, with the method of producing a support for imitation leather and with the related machine in accordance with the present invention, the polyurethane material is uniformly sprayed without the need for any mechanical spreading or leveling, for example by means of a blade or other leveling devices, and this allows to work continuously without the need for interruptions to clean hardened polyurethane residues or the maintenance of such mechanical levelers.
Advantageously, moreover, the amount of polyurethane material deposited by spraying is defined by the settings of the machine 2, with the consequent possibility of easily varying the flow rate of the material and therefore the thickness of the polyurethane layer 11 of the imitation leather 6,6'.
Furthermore, the backing 12 is advantageously applied to the polyurethane layer 11 without the aid of adhesive: in fact, the method includes utilizing the reaction of the two-component mixture and therefore the adhesiveness of the mixture to attach the backing.
Advantageously, moreover, with the method in accordance with the present invention it is possible, even without the aid of solvents or filters in general, to ensure a level of emissions which are difficult to detect with a consequent high saving of caloric energy and environmental protection.
In summary, the method in accordance with the present invention allows to replace the coagulate in a simple and less polluting manner, given the absence of any type of solvent. Furthermore, such a method allows continuous production without the need for machine stops since the deposition of the polyurethane does not require any type of mechanical leveler and related maintenance. Furthermore, such a method allows the direct line-production of all the elements forming the imitation leather, with consequent reduction of production costs and saving of industrial surface, since the coagulation line is completely eliminated. Furthermore, such a method allows huge savings in energy and raw material costs compared to the current methods which include high oven temperatures or the use of adhesives, as well as a considerable saving in CO2 emissions.
It is apparent that those skilled in the art could make changes to the subject described above, without departing from the scope of protection as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102020000003401 | Feb 2020 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/051115 | 2/11/2021 | WO |
