Method for manufacturing electronic devices for rubber articles

Abstract

A method for manufacturing an electronic device 1 applied to a rubber article is provided. [Solution] The device comprises (i) electronic elements 5, 6, and 7, (ii) a covering element made of one or more layers 3 of a thermoplastic material arranged to cover the electronic elements 5, 6, and 7, and (iii) at least one rubber layer 4 arranged to cover at least a portion of an outer surface 3a of the covering element. The manufacturing method includes a preparation step including: (a) a deposition process in which an adhesive solution made of a basic aqueous solution containing an elastomeric rubber latex and a combination of resorcinol and formaldehyde is applied to at least a portion of one outer surface 3a of the covering element; and (b) a heat treatment in which the portion of the outer surface 3a of the covering element to which the adhesive solution has been applied is maintained at a temperature of 120 to 230°C for 2 to 15 minutes.

Description

[Technical field]

[0001] The present invention relates to a method for making electronic devices for use in rubber articles.

[0002] In particular, the present invention relates to a patch-type radio frequency identification (RFID) device for tire applications, to which reference is made herein without loss of generality. [Background technology]

[0003] Within the tire industry, manufacturers have expressed the need for a solution that allows for unambiguous, automated identification of tires throughout their lifecycle, from production through use and disposal.

[0004] For example, specifically referring to tire production, clear automatic identification of tires could enable manufacturers to optimize production processes and logistics operations, support the use of automated control systems, and efficiently locate / track tires, thus enabling them to build smart tire factories.

[0005] However, the solution of sticking barcodes on tires, although it allows manufacturers to control tire production and the production history of single tires, suffers from a series of drawbacks: only a limited amount of information can be recorded, the codes must be read one by one with a defined line of sight, and there is a risk that the codes may be cancelled or damaged during tire production or normal operation / use, making them unreadable or in any case difficult to read.

[0006] As an alternative to bar codes, there is a patch-type radio frequency identification (RFID) device for tires that consists of a multi-layered planar flexible structure that includes two insulating layers made of PET sandwiched together to contain an RFID chip, a first antenna connected to the chip, and a second antenna electromagnetically coupled at least in part to the first antenna, and two outer rubber layers that are arranged to cover the outer surface of each insulating layer. Summary of the Invention [Problem to be solved by the invention]

[0007] Here, an insulating material such as PET means a "lossless material with low dielectric constant and low electrical conductivity."

[0008] Experiments have shown that this solution has a critical point regarding the adhesion between the insulating layers and the respective rubber layers with which they are in contact.

[0009] As one skilled in the art will readily appreciate, if the PET insulating layer covering the antenna and chip is not properly bonded to the two outer rubber layers, the rubber surrounding the RFID and tire layers may be damaged, in particular the device may split, which may prevent the device from functioning properly and may damage the rubber layers in which it is housed.

[0010] In fact, if the insulating layer fails to adhere to the outer rubber layer and becomes detached from the device, it can cause cuts and cracks in the surrounding rubber of the tire.

[0011] Essentially, RFID is just one example, and many other electronic devices installed in tires could face the same technical issues, such as temperature sensors, pressure sensors or energy harvesters, typical sensors used in tire applications.

[0012] Therefore, a solution is needed to ensure the structural stability of tire-mounted electronic devices. [Means for solving the problem]

[0013] The present inventors have devised a method that can meet the aforementioned needs.

[0014] The subject of the present invention is a method for manufacturing an electronic device applied to a rubber article, the device comprising (i) an electronic element, (ii) a covering element consisting of one or more layers of a thermoplastic material arranged to cover the electronic element, and (iii) at least one rubber layer arranged to cover at least a portion of the outer surface of the covering element, the method comprising the following preparation steps: (a) a deposition treatment, in which an adhesive solution consisting of a basic aqueous solution containing a latex of an elastomeric rubber and a combination of resorcinol and formaldehyde is applied to said portion of one of the outer surfaces of the covering element; and (b) a heat treatment, in which said portion of the outer surface of the covering element to which the adhesive solution has been applied is kept at a temperature of 120 to 230°C for 2 to 15 minutes.

[0015] Preferably, the layer or layers of thermoplastic material are in the form of a woven fabric.

[0016] Preferably, said layer or layers of thermoplastic material are made of an insulating material, preferably selected from the group consisting of polyesters, polyamides, polyimides.

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

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

[0019] Preferably, the electronic element comprises an RFID chip, a first antenna connected to the chip, and a second antenna 7 electromagnetically coupled to the first antenna.

[0020] The basic aqueous solution preferably contains a pre-condensed resin consisting of resorcinol having a blocked isocyanate group and formaldehyde.

[0021] The basic aqueous solution preferably includes lignin and a chemical selected from urea and thiourea.

[0022] The elastomeric rubber latex includes a styrene-butadiene-vinylpyridine latex or a mixture of styrene-butadiene-vinylpyridine and styrene-butadiene latex.

[0023] A further subject of the invention is an electronic device for use in a rubber article, which is realised by the method of the invention.

[0024] The invention will be best understood from the following description of illustrative and non-limiting embodiments, taken in conjunction with the accompanying drawing, which shows a radio frequency identification device in an exploded view. [Brief description of the drawings]

[0025] [Figure 1] In the figure, the number 1 indicates as a whole a radio frequency identification (RFID) device according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The device 1 comprises a transceiver assembly 2, two PET layers 3 sandwiched together on opposite sides of the transceiver assembly 2, and two outer rubber layers 4 disposed on the outer surfaces 3a of each of the PET layers 3.

[0027] The two sandwiched PET layers 3 constitute a cover element arranged to completely cover the transceiver assembly 2 .

[0028] The transceiver assembly 2 comprises 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 figure were manufactured, the only difference being that one was manufactured by applying an adhesive solution according to the invention to the outer surface 3a of each PET layer 3.

[0030] The adhesive solution was applied to the outer surface 3a with a brush (deposition treatment).

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

[0032] [Table 1]

[0033] After the adhesive solution was applied (deposition treatment), the two PET layers 3 were heat-treated. The heat treatment was performed by holding the two PET layers 3, on which the adhesive solution was applied, in an oven at 220° C. for 3 minutes.

[0034] Different from the above, according to a further embodiment of the present invention, the adhesive solution comprises a pre-condensed resin consisting of resorcinol with blocked isocyanate groups and formaldehyde, lignin and a chemical selected from urea and thiourea, which has the advantage that formaldehyde does not need to be used in free form.

[0035] After the above-mentioned preliminary steps, the first step is performed in which the transceiver assembly 2 is housed between two PET layers 3, and then the second step is performed in which the outside of the two PET layers 3 is covered with two unvulcanized rubber layers 4, respectively.

[0036] Alternatively, the two PET layers 3 may be covered on the outside with two partially or fully vulcanized rubber layers, respectively.

[0037] Thus, the first RFID device was manufactured.

[0038] A second RFID device was manufactured by repeating the above-mentioned method, except that the preliminary step was not performed, i.e., in the manufacturing process of the second RFID device, the first step was performed using a PET layer 3 that was not coated with an adhesive solution.

[0039] Contrary to what has been described above, according to a preferred embodiment of the invention, the adhesive solution can be applied to both sides of the PET layer 3 .

[0040] In use, the RFID device described above is contained in the uncured rubber portion of the tire.

[0041] Alternatively, the RFID device described above can be applied to the cured rubber portion of the tire.

[0042] Once the RFID device is inserted inside the tire, a vulcanization process is performed, during which the rubber layer containing the RFID device is cross-linked with the surrounding rubber, ensuring the stability of the device's position.

[0043] The first and second RFID devices were subjected to an adhesion test based on ASTM D1876, in which the adhesion strength between each PET layer 3 and each rubber layer 4 disposed so as to cover the outer surface 3a was measured.

[0044] Table II shows the values ​​obtained in the above tests.

[0045] [Table 2]

[0046] The values ​​shown in Table II clearly prove that the method of the present invention is able to ensure strong adhesion between the PET layer 3 and the respective rubber layer 4, thereby avoiding device splitting and the resulting problems.

[0047] Two further RFID devices of the type shown in the figure (a third RFID device and a fourth RFID device) were manufactured.

[0048] The third and fourth RFID devices differ from the first and second RFID devices in that layer 3 is constructed from nylon rather than PET.

[0049] In particular, the two layers 3 of the third and fourth RFID devices are in the form of a textile.

[0050] Furthermore, the third and fourth RFID devices are subjected to different conditions for the heat treatment (b).

[0051] especially, - In the third RFID device, the adhesive solution of Table I was applied by brush to the surface 3a of the nylon layer (deposition treatment). After the adhesive solution was applied (deposition treatment), the two nylon layers 3 were heat-treated. The heat treatment was performed by holding the two nylon layers 3, onto which the adhesive solution was applied, in an oven at 220° C. for 5 minutes.

[0052] - In the fourth RFID device, the adhesive solution of Table I was applied by brush to the surface 3a of the nylon layer (deposition treatment). After the adhesive solution was applied (deposition treatment), the two nylon layers 3 were heat-treated. The heat treatment was performed by holding the two nylon layers 3, on which the adhesive solution was applied, in an oven at 155° C. for 10 minutes.

[0053] For the first, third and fourth RFID devices, the same amount of adhesive solution was applied to each surface 3a.

[0054] The third and fourth RFID devices were adhesion tested according to ASTM D1876 to measure the adhesion between each of the nylon layers 3 and each of the rubber layers 4 disposed over the outer surface 3a.

[0055] Table III shows the values ​​obtained in the above tests.

[0056] [Table 3]

[0057] The values ​​shown in Table III also clearly demonstrate that the method of the present invention ensures strong adhesion between the nylon layer 3 and the respective rubber layer 4, thereby avoiding device fragmentation and the resulting problems.

[0058] According to the inventors, adhesion is greater if the layer of thermoplastic material is in the form of a woven fabric.

[0059] Differently from the above, the covering element can consist of a layer of thermoplastic material wrapped around the electronic component, instead of two layers arranged in a sandwich.

[0060] As mentioned above, the present invention applies to any electronic device that is applied to a rubber article, such as a tire.

[0061] Depending on the electronic device, only one rubber layer 4 may be used.

Claims

1. A method for the manufacture of an electronic device (1) applied to a rubber article, comprising the steps of: The device is (i) electronic elements (5, 6, 7); (ii) a covering element consisting of one or more layers (3) of thermoplastic material arranged so as to completely cover said electronic components (5, 6, 7); (iii) at least one rubber layer (4) arranged to cover at least a part of the outer surface (3a) of the covering element opposite the electronic components (5, 6, 7); Equipped with The method comprises: (a) a deposition process in which an adhesive solution is applied to the portion of the outer surface (3a) of the covering element, the adhesive solution being an aqueous basic solution containing a latex of an elastomeric rubber and a combination of resorcinol and formaldehyde; (b) a heat treatment in which the portion of the outer surface (3a) of the covering element on which the adhesive solution has been applied is kept at a temperature of 120-230° C. for 2-15 minutes; The manufacturing method includes a preparation step.

2. The method according to claim 1, wherein the layer or layers (3) of thermoplastic material are in the form of a woven fabric.

3. 3. The method according to claim 1 or 2, wherein the layer or layers (3) of thermoplastic material are made of insulating material.

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

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

6. The method of any one of claims 1 to 5, wherein the basic aqueous solution comprises a pre-condensed resin consisting of resorcinol having blocked isocyanate groups and formaldehyde.

7. 7. The method of claim 6, wherein the basic aqueous solution comprises lignin and a chemical selected from urea and thiourea.

8. The method of any one of claims 1 to 7, wherein the elastomeric rubber latex comprises a styrene-butadiene-vinylpyridine latex or a mixture of styrene-butadiene-vinylpyridine and styrene-butadiene latex.

9. The method of any one of claims 1 to 8, wherein the rubber article is a tire.

10. The method according to any one of claims 1 to 9, wherein the electronic element comprises an RFID chip (5), a first antenna (6) connected to the chip (5), and a second antenna (7) electromagnetically coupled to the first antenna (6) or to the RFID chip with an electrically coupled antenna.

11. An electronic device for use in a rubber article, realised by the method according to any one of claims 1 to 10.

Images