Method for manufacturing electronic devices for rubber articles

Abstract

A method for manufacturing an electronic device (1) applied to a rubber product. The device includes (i) electronic components (5, 6, 7), (ii) a cover element made of one or more layers of thermoplastic material (3) and configured to cover the electronic components (5, 6, 7), and (iii) at least a rubber layer (4) configured to cover at least a portion of an outer surface (3a) of the cover element. The method includes a preparatory step comprising (a) a deposition operation in which an adhesive solution consisting of an alkaline aqueous solution is applied to at least a portion of an outer surface (3a) of the cover element, the alkaline aqueous solution comprising a latex of an elastomeric rubber and a combination of resorcinol and formaldehyde; and (b) a heating operation in which a portion of the outer surface of the cover element to which the adhesive solution is applied is held at a temperature in the range of 120°C to 230°C for a time ranging from 2 to 15 minutes.

Description

[0001] This invention relates to a method for manufacturing an electronic device for rubber products.

[0002] In particular, the present invention relates to a patch radio frequency identification (RFID) device for tire applications, the description of which is expressly referred to without loss of generality.

[0003] In the tire industry, manufacturers say there is a need for solutions for automated and clear identification of tires during production, use, and disposal.

[0004] For example, specifically in tire production, automated and clear tire identification can enable manufacturers to optimize production processes and logistics operations, support the use of automated control systems, and efficiently locate / track tires, thereby establishing smart tire factories.

[0005] While allowing manufacturers to manage tire production and the production history of individual tires, solutions involving the application of barcodes to tires are subject to a number of drawbacks, including the recording of a limited number of information items, reading codes one by one within a given line of sight, and the risk that codes may be erased or damaged during tire production and / or normal operation / use, thus becoming unreadable or difficult to read in any case.

[0006] An alternative to using barcodes involves a tire patch radio frequency identification (RFID) device. This device comprises a multi-layer planar flexible structure, which essentially includes two insulating layers made of PET and two outer rubber layers. The insulating layers are arranged in a sandwich-like manner to contain an RFID chip, a first antenna connected to the chip, and a second antenna electromagnetically coupled to at least a portion of the first antenna. Each of the two outer rubber layers is configured to cover the outer surface of its respective insulating layer.

[0007] For insulating materials like PET, we are referring to “lossless materials with low relative permittivity and low conductivity”.

[0008] Experiments show that this solution has key aspects regarding the adhesion between the insulating layers and the corresponding rubber layers they contact.

[0009] As will be readily apparent to those skilled in the art, if the insulating PET layer surrounding the antenna and chip is not properly bonded to the two outer rubber layers, the rubber surrounding the RFID and tire layers will be damaged. In particular, cracking of the device may occur, which will inevitably jeopardize the proper operation of the device and may damage the rubber layers encapsulating the device.

[0010] In fact, if the insulation layers detach from the device due to poor adhesion to the outer rubber layer, they will cause cuts and cracks in the rubber surrounding the tire.

[0011] Essentially, the same technical challenges are encountered in many other electronic devices inserted into the tire, with RFID being just one example. These other electronic devices can be common sensors used in tire applications, such as temperature sensors, pressure sensors, or even energy harvesters.

[0012] Therefore, a solution is needed that ensures proper structural stability for electronic devices to be applied to tires.

[0013] The inventors of this invention have conceived of a method that can meet the above-mentioned needs.

[0014] The subject of this invention is a method for manufacturing an electronic device applied to a rubber article; said device comprising (i) an electronic component, (ii) a cover element made of one or more layers of thermoplastic material and configured to cover said electronic component, and (iii) at least a rubber layer configured to cover at least a portion of the outer surface of said cover element; the method is characterized by including a preparative step comprising (a) a deposition operation, during which an adhesive solution composed of an alkaline aqueous solution is applied to said portion of an outer surface of said cover element, said alkaline aqueous solution comprising latex of an elastomeric rubber and a combination of resorcinol and formaldehyde; and (b) a heating operation, during which said portion of the outer surface of said cover element to which the adhesive solution is applied is held at a temperature in the range of 120°C to 230°C for a time in the range of 2 to 15 minutes.

[0015] Preferably, the multiple layers of thermoplastic material are in the form of fabric.

[0016] Preferably, the multiple thermoplastic material layers are made of an insulating material. Preferably, the insulating material is selected from the group consisting of polyester, polyamide, and polyimide.

[0017] Preferably, the insulating material comprises the group consisting of PET, nylon and polyethylene naphthalate.

[0018] Preferably, the rubber product is a tire.

[0019] Preferably, the electronic component includes an RFID chip, a first antenna connected to the chip, and a second antenna electromagnetically coupled to the first antenna.

[0020] The alkaline aqueous solution preferably contains a precondensed resin composed of resorcinol and formaldehyde with isocyanate-terminated groups.

[0021] The alkaline aqueous solution preferably contains lignin and a chemical substance selected between urea and thiourea.

[0022] The elastomer rubber latex preferably comprises a latex containing styrene-butadiene-vinylpyridine or a latex containing a mixture of styrene-butadiene-vinylpyridine and styrene-butadiene.

[0023] A further subject of the present invention is an electronic device for rubber products, characterized by being implemented by a method according to the present invention.

[0024] The invention will be best understood by referring to the accompanying drawings, which show the RFID device in exploded view, and by carefully reading the following illustrative and non-limiting description of embodiments.

[0025] In the accompanying drawings, the number 1 indicates the radio frequency identification (RFID) device according to the invention as a whole.

[0026] The device 1 includes a transceiver assembly 2, two PET layers 3 arranged in a sandwich manner on opposite sides of the transceiver assembly 2, and two outer rubber layers 4 each arranged on the corresponding outer surface 3a of the PET layers 3.

[0027] Two PET layers 3 arranged in a sandwich pattern form a cover element, which is configured to completely cover the transceiver assembly 2.

[0028] The transceiver assembly 2 includes an RFID chip 5, a first antenna 6 connected to the RFID chip 5, and a second antenna 7 electromagnetically coupled to the first antenna 6.

[0029] Two radio frequency identification (RFID) devices of the type shown in the attached figures were manufactured. These two devices differ from each other only in that one device is manufactured by depositing an adhesive solution according to the invention onto the outer surface 3a of each PET layer 3.

[0030] The adhesive solution is applied to surface 3a using a brush (deposition operation).

[0031] Table I shows the composition of the adhesive solution used, in parts by weight.

[0032] Table I

[0033] Styrene-butadiene-vinylpyridine latex 72.7 resorcinol 5.0 formaldehyde 2.3 Methylene diphenyl diisocyanate 20.0

[0034] After applying the adhesive solution (deposition operation), the two PET layers 3 are heated. The heating operation involves holding the two PET layers 3 with the applied adhesive solution in an oven at 220°C for 3 minutes.

[0035] Unlike the above, according to another embodiment of the invention, the adhesive solution comprises a precondensed resin consisting of resorcinol and formaldehyde having isocyanate-terminated groups, lignin, and a chemical substance selected between urea and thiourea. The advantage of this adhesive solution is that it eliminates the need to use free formaldehyde.

[0036] After the above preparatory steps are performed, the process continues with the first step, in which the transceiver assembly 2 is encapsulated between two PET layers 3, and then the second step is performed, in which the two PET layers 3 are covered on the outside by two corresponding uncured rubber layers 4.

[0037] Alternatively, the two PET layers 3 can be covered on the outside by two corresponding partially or fully vulcanized rubber layers 4.

[0038] In doing so, the first RFID device was created.

[0039] The second RFID device is manufactured by repeating the above method, except that the preparatory steps are omitted. In other words, the first step is performed using a PET layer 3 on which no adhesive solution is applied during the manufacturing process of the second RFID device.

[0040] Unlike the above, according to a preferred embodiment of the present invention, the adhesive solution can be applied to both surfaces of the PET layer 3.

[0041] In use, the aforementioned RFID device is included in the green rubber portion of the tire.

[0042] Optionally, the RFID device described above can be applied to the cured rubber portion of a tire.

[0043] Once the RFID device is inserted into the tire, a vulcanization process is performed. This cross-links the rubber layer of the RFID device with the surrounding rubber during vulcanization, ensuring the stability of the device's position.

[0044] The first and second RFID devices were subjected to adhesion tests according to ASTM D1876. The tests measured the adhesive force between each PET layer 3 and the corresponding rubber layer 4 configured to cover the outer surface 3a.

[0045] Table II shows the values ​​obtained using the tests described above.

[0046] Table II

[0047] First RFID device Second RFID device Adhesive strength (N / mm) 6.73 0.37

[0048] The values ​​shown in Table II clearly demonstrate that the method of the present invention can ensure a strong bond between the PET layer 3 and the corresponding rubber layer 4, thereby avoiding cracking of the device and the problems it causes.

[0049] Two more RFID devices (the third and fourth RFID devices) of the type shown in the attached diagram were manufactured.

[0050] The third and fourth RFID devices differ from the first and second RFID devices because they include a layer 3 made of nylon instead of PET.

[0051] In particular, the two layers 3 of the third and fourth RFID devices are in the form of fabric.

[0052] In addition, the third and fourth RFID devices differ from each other in the conditions used in the heating operation (b).

[0053] in particular,

[0054] - For the third RFID device, the adhesive solution in Table I is applied to the surface 3a of the nylon layer by means of a brush (deposition operation).

[0055] After applying the adhesive solution (deposition operation), the two nylon layers 3 are heated. The heating operation involves holding the two nylon layers 3 with the applied adhesive solution in an oven at 220°C for 5 minutes.

[0056] - For the fourth RFID device, the adhesive solution in Table I is applied to the surface 3a of the nylon layer by means of a brush (deposition operation).

[0057] After applying the adhesive solution (deposition operation), the two nylon layers 3 are heated. The heating operation involves holding the two nylon layers 3 with the applied adhesive solution in an oven at 155°C for 10 minutes.

[0058] For the first, third, and fourth RFID devices, the same amount of adhesive solution is applied to the corresponding surface 3a.

[0059] The third and fourth RFID devices were subjected to adhesion tests according to the ASTM D1876 method to measure the adhesive force between each nylon layer 3 and the corresponding rubber layer 4 configured to cover the outer surface 3a.

[0060] Table III shows the values ​​obtained using the tests described above.

[0061] Table III

[0062] Third RFID device Fourth RFID device Adhesive strength (N / mm) 6.9 7.9

[0063] Furthermore, the values ​​shown in Table III clearly demonstrate that the method of the present invention can ensure a strong bond between the nylon layer 3 and the corresponding rubber layer 4, thereby avoiding cracking of the device and the problems it causes.

[0064] According to the inventors, the adhesive force is greater when the thermoplastic material layer is in the form of a fabric.

[0065] Unlike the above, instead of the two layers configured in a sandwich-like manner, the covering element can consist of a layer of thermoplastic material wrapped around the electronic component.

[0066] As described above, the present invention is applicable to any electronic device used in rubber products such as tires.

[0067] Depending on the electronic device, only one rubber layer 4 may be used.

Claims

1. A method for manufacturing an electronic device (1) to be applied to a rubber article; said device comprising (i) electronic components (5, 6, 7), (ii) a covering element made of one or more layers (3) of thermoplastic material and configured to cover said electronic components (5, 6, 7), and (iii) at least a rubber layer (4) configured to cover at least a portion of an outer surface (3a) of said covering element; said method being characterized by comprising a preliminary step comprising (a) a deposition operation, during which an adhesive solution consisting of an aqueous alkaline solution comprising a latex of elastomeric rubber and a combination of resorcinol and formaldehyde is applied on said portion of one outer surface (3a) of said covering element; and (b) a heating operation, during which said portion of the outer surface (3a) of the covering element to which the adhesive solution has been applied is kept at a temperature ranging from 120°C to 230°C for an amount of time ranging from 2 minutes to 15 minutes.

2. The method of claim 1, wherein, Said one or more layers (3) of thermoplastic material are in the form of a fabric.

3. The method according to claim 1 or 2, characterized in that, Said one or more layers (3) of thermoplastic material are made of an insulating material.

4. The method of claim 3, wherein, Said insulating material is selected from the group comprising polyester, polyamide, polyimide.

5. The method of claim 4, wherein, Said insulating material is included in the group consisting of PET, nylon and polyethylene naphthalate.

6. The method according to claim 1 or 2, characterized in that, Said aqueous alkaline solution comprises a pre-condensed resin consisting of resorcinol and formaldehyde having isocyanate end groups.

7. The method of claim 6, wherein, Said aqueous alkaline solution comprises lignin and a chemical selected between urea and thiourea.

8. The method of claim 1 or 2, wherein, Said latex of elastomeric rubber comprises a latex of styrene-butadiene-vinylpyridine or a mixture of latexes of styrene-butadiene-vinylpyridine and styrene-butadiene.

9. The method of claim 1 or 2, wherein, Said rubber article is a tyre.

10. The method of claim 1 or 2, wherein, Said electronic components comprise an RFID chip (5), a first antenna (6) connected to said chip (5), and a second antenna (7) electromagnetically coupled to said first antenna (6) or an RFID chip having an electrically coupled antenna.

11. An electronic device for a rubber article, characterized by, It is achieved by the method according to any one of the preceding claims. It is achieved by the method according to any one of the preceding claims.

Images