EP4705081A1

EP4705081A1 - Method for manufacturing a flexible laminar product with nubuck effect

Info

Publication number: EP4705081A1
Application number: EP24761309.4A
Authority: EP
Inventors: Raymond RUCKENSTUHL; Massimo Pajusco
Original assignee: Gruppo Mastrotto SpA
Current assignee: Gruppo Mastrotto SpA
Priority date: 2023-07-25
Filing date: 2024-07-25
Publication date: 2026-03-11
Also published as: IT202300015552A1; WO2025022339A1

Abstract

A method for manufacturing a flexible laminar product with nubuck effect, comprising at least the steps of a) providing a sample (C) having a nubuck-type surface pattern intended to be reproduced, b) depositing on the surface of the sample (C) a mixture of silicone resins (R) so as to make a negative cast (M), c) gluing the cast (M) on a rigid plate-like support to create a moulding plate (T), d) heating the moulding plate (T) to a first predetermined temperature, e) depositing on the moulding plate (T) a layer of polyurethane mixture (P) having a predetermined weight, f) drying the moulding plate (T) to a second predetermined pressure, g) repeating said steps d)-f) for a predetermined number of cycles, h) cooling the moulding plate (T) to a third predetermined temperature, i) providing a base flexible laminar substrate (S), j) coupling the cooled moulding plate (T) with the base flexible laminar substrate (S) so as to form a sandwich (N), k) cross-linking the at least one layer of polyurethane mixture (P) and adhering the latter to the base flexible laminar substrate (S) and l) detaching from the moulding plate (T) a flexible laminar product (Q) having a nubuck-type effect on the exposed surface like that of the sample (C).

Description

METHOD FOR MANUFACTURING A FLEXIBLE LAMINAR PRODUCT

WITH NUBUCK EFFECT

DESCRIPTION

Field of the invention

[001] The present invention generally relates to the tanning industry and it particularly relates to a method for manufacturing a laminar product with nubuck effect.

Background art

[002] The use of leather and hides in various types of industries, such as for example the footwear, furnishing, clothing, automotive industries and the like has been long known.

[003] In the case of aesthetic objects, there is a high demand for surfaces made of leather which, besides an appropriate pigmentation, also have a determined surface pattern.

[004] Examples of surface patterns are drawings, writings, animal-skin effect and other effects adapted to confer a specific surface texture. Among the latter, the most known are the suede effect and the nubuck effect.

[005] The substantial difference between nubuck and suede leather lies in the fact that nubuck is obtained by processing the outer part of the animal hide, that is the grain side, while suede leather is obtained by processing the inner side of the animal leather, that is the flesh side.

[006] Specifically, the expression nubuck leather is used to indicate a full grain hide, generally of bovine or ovine origin, whose surface has been honed and buffed after tanning so as to obtain an exposed surface that is soft and velvet-like to touch.

[007] Specifically due to the fact that it is derived from processing the grain side only, and often from high quality hides, a nubuck effect leather is generally considered as a refined and therefore expensive item.

[008] With the aim of reducing costs, in recent years there have been developed methods for reproducing a nubuck-like effect on the surface of a hide, even on low-quality hides. [009] Generally, these methods provide for the application of a polyurethane layer on the surface of a hide by means of a release paper or the like having a pattern which mimics a nubuck-type item.

[0010] In other words, the nubuck effect is imparted on the polyurethane layer, which is firmly adhered to the exposed surface of the hide.

[0011] This allows to reproduce a nubuck-like effect on the surface of a hide without using special honing and buffing machines.

[0012] KR102402460B1 discloses a method for the serial reproduction of a “natural effect” on the surface of a hide.

[0013] The method describes the creation of a polyurethane resin cast starting from a product whose surface pattern is to be reproduced. A solution, an epoxy resin and an adhesive are then sprayed and dried in series on the cast. The entirety is then coupled with a fabric and pressed together so as to obtain a sandwich.

[0014] The sandwich is subsequently thermally treated in a special chamber and at the end of the treatment the leather with the reproduced pattern is detached from the cast, which can be used again.

[0015] KR101196315B1 discloses a method for the surface processing of hides.

[0016] The method describes the creation of a silicone cast from a product whose surface pattern is to be reproduced. Subsequently, the cast is fixed to a support so as to obtain a plate.

[0017] A treatment agent, a first colouring agent, a second colouring agent and an adhesive are sprayed on the plate and dried in succession. The entirety is then coupled with a leather so as to form a sandwich which is pressed so as to adhere the surface pattern to the leather.

[0018] At the end of the treatment, the silicone cast is removed from the leather product and reutilised in the processing method.

[0019] A first drawback of such prior art solutions lies in the need of using a hide that does not have significant surface defects so as to ensure an appropriate adhesion of the surface layer having the reproduced pattern. [0020] Another drawback lies in the fact that such solutions can be applied only on leather and hides, not being appropriate for other types of flexible laminar products.

[0021] GB1491532A discloses a method for producing straps having a surface pattern similar to animal skins, in which there is provided a resin layer and a layer made of expandable material which can be embossed in a rigid mould having a pattern to be reproduced on the strap imparted thereon. The mould is then closed at high pressure and heated by applying a high frequency electric field so as to facilitate the expansion of the layers and the embossing thereof.

[0022] A drawback of such prior art solution lies in the high cost for providing a rigid mould and the high energy consumption stemming from the high pressure and high frequency of use.

[0023] Therefore, there arises the need for a method for the serial reproduction of a nubuck-like effect on the surface of different laminar products.

Technical problem

[0024] In the light of the prior art, the object of the present invention is to solve the technical problem of providing a method for reproducing a nubuck- like effect on the surface of a low-quality laminar product.

Summary of the invention

[0025] The object of the present invention is to solve the aforementioned problem by providing a method for producing a laminar product with a nubuck effect which is highly efficient and cost-effective.

[0026] Another object of the present invention is to provide a method for manufacturing a laminar product with a nubuck effect of the type indicated above which can be implemented on different types of laminar products.

[0027] A further object of the present invention is to provide a method for manufacturing a laminar product with anubuck effect of the type indicated above which does not require a high-quality laminar product. [0028] A further object of the present invention is to provide a method for manufacturing a laminar product with a nubuck effect of the type indicated above which can be manufactured in series continuously.

[0029] Another object of the present invention is to provide a method for manufacturing a laminar product with a nubuck effect of the type indicated above which can be implemented on standard plants known in the industry.

[0030] A further object of the present invention is to provide a method for manufacturing a laminar product with a nubuck effect of the type indicated above that is easy to implement and that does not require particular expertise da by an operator.

[0031] Another object of the present invention is to provide a method for manufacturing a laminar product with a nubuck effect of the type indicated above that requires a reduced use of consumption materials.

The objects mentioned above and others which will be more apparent hereinafter, are achieved by a method for manufacturing a flexible laminar product with a nubuck effect, comprising at least the steps of a) providing a sample having a nubuck-type surface pattern intended to be reproduced, b) depositing on the surface of the sample of a mixture of silicone resins so as to make a negative cast thereof, c) gluing the cast on a rigid plate-like support to create a moulding plate, d) heating the moulding plate to a first predetermined temperature, e) depositing on the moulding plate a layer of polyurethane mixture having a predetermined weight, f) drying the moulding plate at a second predetermined temperature, g) repeating said steps d)-f) for a predetermined number of cycles, h) cooling the moulding plate to a third predetermined temperature, i) providing a base flexible laminar substrate, j) coupling the cooled moulding plate with the base flexible laminar substrate so as to form a sandwich, k) cross-linking the at least one layer of polyurethane mixture and adhering the latter to the base laminar substrate and I) detaching from the moulding plate a flexible laminar product having on the exposed surface a nubuck-like effect like the one of the sample.

Brief description of the drawings [0032] Further characteristics and advantages of the invention will be more apparent in the light of the detailed description of a preferred but not exclusive embodiment of a method for manufacturing a laminar product with a nubuck effect like the one mentioned above, shown by way of non-limiting example with reference to the drawings below, wherein:

FIG. 1 is a block flow diagram of the steps of the method according to the present invention;

FIG. 2 is a perspective view of the step of preparing a silicone cast according to the invention;

FIG. 3 is a perspective view of a moulding plate obtained according to the method of the present invention;

FIG. 4 is a lateral view of a plant for implementing the present method;

FIG. 5 is a lateral view of a multilayer obtained during a step of the present method;

FIG. 6 is a perspective view of a flexible laminar product with a nubuck effect obtained with the present method with the relative surface enlargement.

Detailed description of a preferred embodiment

[0033] With particular reference to the figures, there is shown a method for manufacturing a laminar product with a nubuck effect.

[0034] As shown in the block flow diagram in FIG. 1 , the method comprises an initial step a) of providing a sample C having a nubuck-type surface pattern intended to be reproduced.

[0035] Any type of object, preferably plate-like, which has a nubuck-like pattern on its exposed surface may be used as sample C.

[0036] Therefore, samples C made of leather, rubber, wood, metal, paper and the like are suitable for the method of the present invention. The nubuck effect can be obtained on the surface of the sample C through any technique known in the industry.

[0037] Obviously, given that it is intended to reproduce the nubuck effect of the sample C in question, it should not have surface defects.

[0038] Preferably, the sample C should have plan dimensions at least equal to 160cm by 300cm. [0039] In order to provide a copy of the sample C, the latter is either glued on a rigid support 2, such as for example a wooden or aluminium panel, should the sample C not be sufficiently self-supporting, or it is retained by means of vacuum or similar methods if structurally stable, with the surface having the nubuck effect facing upwards.

[0040] This allows to avoid possible deformations during the copying process.

[0041] Subsequently, there is provided a step b) of depositing a mixture of silicone resins R on the surface of the sample C so as to make a negative cast M thereof.

[0042] In an embodiment, the liquid mixture is formed by at least two silicone resins mixed together.

[0043] Preferably, as shown in FIG. 2, in order to avoid the outflow of the resin mixture R, the perimeter of the sample C is delimited with an appropriate frame 3 so as to create a containment compartment for the resin mixture R.

[0044] The mixture R is suitably distributed within the compartment levelling it using a blade or the like (not shown in the figures), and it is left to solidify.

[0045] Therefore, there is obtained a silicone cast M which represents a nubuck effect negative surface pattern of the initial sample C.

[0046] In order to confer stability to the cast M there is provided a step c) of gluing the cast M facing upwards on a rigid plate-like support 4 by interposing a fabric (not shown in the figures) to create a moulding plate T, schematically shown in FIG. 3.

[0047] In an embodiment, the rigid plate-like support 4 is an aluminium sheet measuring 0.2-0.4mm in thickness.

[0048] As will be discussed below, given that the moulding plate T will undergo several thermal treatments, an aluminium support 4 of this size provides an even distribution of heat.

[0049] Obviously, the rigid plate-like support 4 may also be made of similar conductor materials which ensure an appropriate distribution of heat.

[0050] Therefore, starting from the sample C there will be provided a plurality of moulding plates, as described above, which will be continuously treated in a plant of the type per se known in the tanning industry, for example like the one shown in FIG. 4.

[0051] Then, there is carried out a step d) of heating the moulding plate T to a first predetermined temperature and at ambient pressure.

[0052] Each moulding plate T enters into a first furnace set so that the plate T reaches such first predetermined temperature.

[0053] Suitably, the first predetermined temperature is comprised between 25°C and 140°C.

[0054] Any type of furnace can be used for this heating step d), for example air, gas, steam furnaces, with infrared lamps or similar systems known in the industry.

[0055] Subsequently, there is provided a step e) of depositing on the moulding plate T a layer of polyurethane resin P having a weight of a predetermined value.

[0056] Suitably, such predetermined weight is comprised between 5 and 161 g/m².

[0057] In order to deposit the amount of polyurethane resin P mentioned above, prior art techniques such as spray-deposition through nozzles, spreading blades or similar systems can be used.

[0058] Both water-based polyurethane resins and solvent-based polyurethane resins can be used.

[0059] Subsequently, the moulding plate T having the layer of polyurethane resin P is introduced into a second furnace.

[0060] Then, there is carried out a step f) of drying the moulding plate T at a second predetermined temperature and at ambient pressure.

[0061] Suitably, the second predetermined temperature to which the moulding plate T is brough to be dried is comprised between 25°C and 140°C. [0062] Then, there is provided a step g) of repeating the steps d)-f) for a predetermined number of cycles until the desired aesthetic effect is obtained.

[0063] Therefore, depending on the number of depositions of polyurethane resin P and thermal treatments, there may be provided a plurality of furnaces and spraying stations arranged sequentially. [0064] The number of cycles for depositing polyurethane resin P and drying depends on the depth of the nubuck pattern intended to be replicated and on the type of field where the end item will be used.

[0065] As a matter of fact, each field of application (e.g.: footwear, furnishing, clothing, automotive industries etc.) has determined requirements that need to be met by the item so as to be used.

[0066] Suitably, the predetermined number of cycles is comprised between 2 and 5.

[0067] Therefore, with a relatively low number of cycles, the present method allows to manufacture an item which can be used in various fields of application.

[0068] After depositing a specific number of layers of polyurethane resin P, there is provided a step h) of cooling the moulding plate T to a third predetermined temperature and at ambient pressure.

[0069] The plate T therefore enters into a tunnel of cold air where it is cooled to the predetermined third temperature mentioned above.

[0070] Suitably, such third predetermined temperature is comprised between 2°C and 40°C.

[0071] This cooling step h) is necessary given that after the drying of step f), the moulding plate has a temperature that is too high to be utilised in the subsequent steps of the method.

[0072] While the various moulding plates T are subjected to the steps described heretofore, in another point of the plant there is simultaneous carried out a step i) of providing a base flexible laminar substrate S.

[0073] The expression base laminar substrate S is used to indicate a flexible support on whose exposed surface it is intended to apply the nubuck effect pattern copied from the initial sample C.

[0074] The types of base laminar substrate S which can be used in the method of the present invention are selected from the group comprising natural and synthetic leathers and hides, microfibres, impregnated fabrics, resin- coated fabrics, non-woven fabrics, knitted fabrics, finished fabrics and the like. [0075] Subsequently, there is carried out a step j) of coupling between the cooled moulding plate T with the base laminar substrate S so as to form a sandwich N.

[0076] Advantageously, the steps c) to j) are all carried out at ambient pressure and solely with thermal energy supply.

[0077] The coupling between the moulding plate T with the base laminar substrate S may be carried out in two different ways.

[0078] In any case, in both ways, the step j) of coupling between the moulding plate T and the base laminar substrate S is carried out by interposing an adhesive layer A.

[0079] In a first embodiment, after the step i), there is provided a sub-step ii) of depositing a water-based or solvent-based adhesive layer A on the moulding plate T.

[0080] In the second embodiment instead, after the step i), there is provided a sub-step i2) of depositing a water-based adhesive layer A on the base flexible laminar substrate S.

[0081] Preferably, the deposition of the adhesive layer A is carried out by spraying or using a cylinder.

[0082] After applying the adhesive layer A, the coupling step j) is carried out by superimposing the base laminar substrate S with the moulding plate T so as to obtain a sandwich N, as shown in FIG. 5.

[0083] Subsequently, there is carried out a step k) of cross-linking the at least one layer of polyurethane mixture P and adhering the latter to the base laminar substrate S.

[0084] Advantageously, also this step k) may be carried out in a different manner.

[0085] In a first embodiment, the cross-linking step k) is carried out by calendering at room temperature when there is provided the sub-step ii) of depositing the adhesive layer A described above.

[0086] In other words, the sandwich N is passed between two cylinders, an upper one and a lower one, and the pressure exerted by the cylinders allows to promote the cross-linking of the at least one layer of polyurethane resin P and its adhesion to the base flexible laminar substrate S.

[0087] After calendering, the sandwich N is thermally treated, for example in a furnace, so as to complete the cross-linking.

[0088] In a second embodiment, the cross-linking step k) is carried out by pressing when there is provided the sub-step i2) of depositing the adhesive layer A.

[0089] Basically, the sandwich N is treated under a pressing machine, where the pressure and temperature exerted promote the cross-linking of the at least one layer of polyurethane resin P and its adhesion to the base flexible laminar substrate S.

[0090] Suitably, the pressing is carried out at a temperature comprised between 60°C and 160°C, at a pressure comprised between 25atm and 150atm, for a period of time comprised between 3 and 30 seconds.

[0091] In a third embodiment, the cross-linking step k) is carried out by hot calendering when there is provided the sub-step i2) of depositing the adhesive layer A.

[0092] Preferably, before carrying out this hot calendering, the sandwich N is pre-dried, for example using infrared lamps.

[0093] After the calendering, the sandwich N is thermally treated, for example in a furnace or still using infrared lamps, so as to complete the crosslinking.

[0094] Therefore, the cross-linking step k) can be carried out by calendering or pressing.

[0095] After the complete cross-linking, there is provided a final step I) of detaching from the moulding plate T a flexible laminar product Q having on the exposed surface a nubuck-like effect like the one of the initial sample C.

[0096] In other words, during the cross-linking, the at least one layer of polyurethane resin P hardens taking the shape complementary to the cast M on which it was sprayed, therefore taking the appearance representing the nubuck effect of the initial sample C. [0097] Furthermore, the at least one layer of polyurethane resin P, now representing a nubuck-like effect, adheres to the surface of the base laminar substrate S due to the pressure exerted and the adhesive layer A applied.

[0098] Therefore, after detaching the moulding plate T, there remains a flexible laminar product Q formed by the base laminar substrate S with the nubuck-like effect adhered to its exposed surface, as shown in FIG. 6.

[0099] Cleared of any resin residues, the moulding plate T can therefore be used again in the plant for manufacturing another flexible laminar product.

Quality tests

[00100] Reported below are some tests conducted on the flexible laminar product having a surface nubuck effect obtained with the method according to the present invention.

[00101] For each type of test, the minimum values required for the practical application of a nubuck product are reported.

Flexural strength test

[00102] The test is conducted according to the international standard DIN EN ISO 5402-1.

[00103] Specifically, the sample to be analysed consists of a flexible laminar product specimen having a nubuck effect which is folded on itself with the surface to be tested facing inwards. The lower end of the sample is locked using a fixed clamp of a flexometer, while the upper end is engaged by a movable clamp of the instrument, which oscillates folding the flexible laminar product for a predetermined number of cycles.

[00104] Such test was carried out both dry and by exposing the specimen to high temperature hydrolysis conditions before carrying out the cycles.

[00105] At the end of the analysis, the condition of the surface of each individual specimen was evaluated using an optical microscope so as to detect the presence of cracks and/or wrinkles.

[00106] The results obtained are reported below in Table 1.

Table 1

Flexural strength test results

[00107] As observable in Table 1 , the tested specimens did not show any signs of visible cracks and/or wrinkles, both under dry and hydrolysis conditions, even after thousands of flexion cycles.

Finishing adhesion test

[00108] The test is conducted according to the DIN EN ISO 11644 international standard.

[00109] Specifically, a 1 cm wide specimen is glued to a fixed plate using a single component cyanoacrylate adhesive.

[00110] A dynamometer is engaged to the finishing (the surface with nubuck effect) of the specimen, and a traction force is applied with a constant rate of 100mm/min and a diagram of the separation of the finishing on a distance of 30mm is recorded.

[00111] The traction is performed in some tests along the longitudinal direction of the specimen and in other tests in the transversal direction.

[00112] Three types of tests were carried out, that is dry, after leaving the specimen in demineralised water for one hour and after exposing the specimen to artificial light.

[00113] The results obtained are reported below in Table 2.

Table 2

Finishing adhesion test results

[00114] As observable in Table 2, the product obtained through the method according to the invention fully meets the requirements in all types of adhesion tests carried out.

Rubbing resistance test

[00115] The test is conducted according to the DIN EN ISO 11640 international standard.

[00116] Specifically, a specimen product with nubuck effect is fixed between two clamps and stretched by 10% along a predetermined direction. A wool felt pad is subsequently applied to a plunger with a mass of 500g which is positioned on the surface of the specimen.

[00117] The plunger arranged in contact with the surface is moved along the predetermined stretching direction of the specimen for a pre-established number of cycles.

[00118] Two types of tests were carried out, one with a dry felt pad and the other with a felt pad soaked with an alkaline solution.

[00119] At the end of the test, each sample is evaluated with respect to a 1 to 5 quality grayscale of the test.

[00120] The results obtained are reported below in Table 3.

Table 3

Rubbing resistance test results [00121] Table 3 shows that the nubuck product of the present method meets the requirements set in each type of test carried out.

[00122] In the light of the above, it is clear that a finished laminar product having a nubuck-like surface pattern obtained using the method of the present invention meets the requirements set for practical applications.

[00123] It should also be observed that the method of the present invention requires a relatively low number of processing steps compared to techniques known in the industry.

[00124] Therefore, in the light of the above, it is clear that the present method for the surface processing of flexible laminar materials achieves the pre- established objects and in particular it allows the production of finished products with nubuck effect suitable for practical applications starting from a base laminar substrate selected from the group comprising natural and synthetic leathers and hides, microfibres, impregnated fabrics, resin-coated fabrics, non-woven fabrics, knitted fabrics, finished fabrics and the like.

[00125] The method according to the invention is susceptible to numerous modifications and variants all falling within the scope of protection outlined in the attached claims.

[00126] Although the method been described with particular reference to the attached figures, the reference numerals used in the description and in the claims are meant for improving the intelligibility of the invention and do not limit the claimed scope of protection in any manner whatsoever.

[00127] Throughout the description, reference to “an embodiment” or “the embodiment” or “some embodiments” indicate that a particular characteristic, structure or element described is comprised in at least one embodiment of the object of the present invention.

Industrial applicability

[00128] The present invention can be applied at industrial level because it can be manufactured on industrial scale by industries belonging to the leather tanning and finishing industry.

Claims

1 . A method for manufacturing a flexible laminar product with a nubuck effect, comprising at least the following steps: a) providing a sample (C) having a nubuck-type surface pattern to be reproduced; b) depositing on the surface of said sample (C) a mixture of silicone resins (R) so as to make a negative cast (M); c) gluing said cast (M) facing upwards onto a rigid plate-like support by interposing a fabric to create a moulding plate (T); d) heating said moulding plate (T) to a first predetermined temperature and at ambient pressure; e) depositing on said moulding plate (T) a layer of polyurethane mixture (P) having a weight of a predetermined value; f) drying said moulding plate (T) to a second predetermined temperature and at ambient pressure; g) optional repetition of said steps d) - f) for a predetermined number of cycles; h) cooling said moulding plate (T) to a third predetermined temperature and at ambient pressure; i) providing a base flexible laminar substrate (S); j) coupling said cooled moulding plate (T) with said base laminar substrate (S) so as to form a sandwich (N); k) cross-linking the at least one layer of polyurethane mixture (P) and adhesion of the latter to said base laminar substrate (S) so as to obtain a flexible laminar product (Q) having a nubuck-like effect on the exposed surface like that of the sample (C). l) detaching said fully cross-linked flexible laminar product (Q) from said moulding plate (T); characterised in that said steps from c) to j) are all carried out at ambient pressure and solely with thermal energy supply, said step j) of coupling between said moulding plate (T) and said base laminar substrate (S) being carried out by interposing an adhesive layer (A), said cross-linking step k) being carried out by calendering or pressing.

2. Method as claimed in claim 1 , wherein after said step i) of providing said base laminar substrate (S) there is provided a sub-step ii) of depositing a water-based or solvent-based adhesive layer (A) on said moulding plate (T).

3. Method as claimed in claim 2, wherein said cross-linking step k) is carried out by calendering at room temperature when said deposition sub-step ii) is provided.

4. Method as claimed in claim 1 , wherein after said step i) of providing said base laminar substrate (S) there is provided a sub-step i2) of depositing a water-based adhesive layer(A) on said base laminar substrate (S).

5. Method as claimed in claim 4, wherein said cross-linking step k) is carried out by pressing when said deposition sub-step i2) is provided.

6. Method as claimed in claim 5, wherein said pressing is carried out at a temperature comprised between 60°C and 160°C, at a pressure comprised between 25atm and 150atm, for a period of time comprised between 3 and 30 seconds.

7. Method as claimed in claim 1 , wherein said first and second predetermined temperature are comprised between 25°C and 140°C.

8. Method as claimed in claim 1 , wherein said predetermined weight is comprised between 5 and 161g/m².

9. Method as claimed in claim 1 , wherein said predetermined number of cycles is comprised between 2 and 5.

10. Method as claimed in claim 1 , wherein said third predetermined temperature is comprised between 2°C and 40°C.

11. Method as claimed in claim 1 , wherein said base flexible laminar substrate (S) is selected from the group comprising natural and synthetic leathers and hides, microfibres, impregnated fabrics, resin-coated fabrics, nonwoven fabrics, knitted fabrics, finished fabrics and the like.