ARTICLE

DESCRIPTION

The invention relates to a method to manufacture an electronic device to be used in rubber articles .

In particular, the invention refers to a patch radiofrequency identi fication (RFID) device for tyre applications , to which the description will explicitly refer without loss of generality .

In the tyre industry, manufacturers have expressed the need for solutions that allow for an automated and unequivocal identi fication of tyres during their production, their use and their disposal .

For example , with speci fic reference to the production of tyres , the automated and unequivocal identi fication of the tyres can allow manufacturers to optimi ze production processes and logistics operations , support the use of automated control systems , carry out an ef ficient locali zation/tracking of the tyres and, hence , build smart tyre factories .

The solution involving the use of barcodes applied on the tyres , despite allowing manufacturers to handle the production of tyres and the production history of the single tyres , is however af fected by a series of drawbacks concerning the recording of a limited number of items of information, the reading of the codes one by one with a given line of sight and the risk of the codes being cancelled or damaged during the production and/or the normal operation/use of the tyres , thus becoming unreadable or , anyway, di f ficult to read .

An alternative to the use of barcodes involves a patch radio- frequency identi fication (RFID) device for tyres . Thi s device consists of a multi-layer planar, flexible structure , which substantially comprises two insulating layers made of PET , which are arranged in a sandwich-like manner so as to contain, between one another, an RFID chip, a first antenna connected to the chip and, at least partially, a second antenna electromagnetically coupled to the first antenna, and two outer rubber layers , each arranged so as to cover an outer surface of a respective insulating layer .

For insulating material like PET we mean "a lossless material with low relative permittivity and low electrical conductivity" .

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

As a person skil led in the art can immediately understand, i f the insulating PET layers , which enclose the antennas and the chip, are not correctly adhered to the two outer rubber layers , the RFID and the surrounding rubber of the tyre layers can be damaged . In particular, there can be a splitting up of the device , that necessarily j eopardi zes the correct operation of the device and can cause possible damages to the rubber layer where the device is housed .

Indeed, i f the insulating layers come out of the device due to the failed adhesion with the outer rubber layers , they can make cuts and cracks in the surrounding rubber of the tyre .

Basically, the same technical problem can be met in many other electronic devices to be inserted in a tyre , of which the RFID is j ust an example . Other electronic devices could be generic sensors used in tyre applications like temperature sensors , pressure sensors or even energy harvesters .

Therefore , there is the need to have a solution that ensures a correct structural stability of the electronic device to be applied in a tyre .

The inventors of this invention conceived a method capable of ful filling the aforesaid need .

The subj ect-matter of the invention is a method to manufacture an electronic device to be applied to a rubber article ; said device comprising ( i ) an electronic element , ( ii ) a covering element made of one or more layers of thermoplastic material and arranged to cover said electronic element , and ( iii ) at least a rubber layer arranged to cover at least a part of an outer surface of said covering element ; said method being characteri zed by comprising a preliminary step comprising ( a ) a deposition operation, during which an adhesive solution consisting of a basic water solution comprising a latex of an elastomer rubber and a combination of resorcinol and formaldehyde is applied on said part of one outer surface of said covering element ; and (b ) a heating operation, during which said part of the outer surface of the covering element on which the adhesive solution was applied is kept at a temperature ranging from 120 to 230 ° C for an amount of time ranging from 2 to 15 min .

Preferably, said one or more layers of thermoplastic material are in the form of textile .

Preferably, said one or more layers of thermoplastic material are made of insulating material . Preferably, said insulating material is chosen in the group comprising polyesters , polyamides , polyimides .

Preferably, said insulating material is comprised in the group consisting of PET , Nylon and polyethylene naphtalate .

Preferably, said rubber article is a tyre .

Preferably, said electronic element comprises an RFID chip, a first antenna connected to the chip and a second antenna electromagnetically coupled to the first antenna .

Said basic water solution preferably comprises a precondensed resin consisting of resorcinol and formaldehyde with isocyanate blocking groups .

Said basic water solution preferably comprises lignin and a chemical chosen between urea and thiourea .

Said elastomer rubber latex preferably comprises a latex of styrene-butadiene-vinylpyridine or a latex of a mixture of styrene-butadiene-vinylpyridine and styrenebutadiene .

A further subj ect-matter of the invention is an electronic device to be used in rubber article characteri zed by being reali zed by the method according to method of the present invention .

The invention will be best understood upon perusal of the following description of explanatory and non-limiting embodiments , with reference to the accompanying figure , which shows the radio- frequency identi fication device in an exploded view .

In the figure , number 1 indicates , as a whole , a radiofrequency identi fication (RFID) device according to the invention .

The device 1 comprises a transceiver assembly 2 , two PET layers 3 arranged in a sandwich-like manner on opposite sides of the transceiver assembly 2 and two outer rubber layers 4 , each arranged on a respective outer surface 3a of a PET layer 3 .

The two PET layers 3 arranged in a sandwich-like constitute a covering element arranged to completely cover the transceiver assembly 2 .

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 .

Two radio- frequency identi fication (RFID) devices of the type shown in the figure were manufactured . The two devices are di f ferent from one another only because one of them was manufactured by depositing an adhesive solution according to the invention on an outer surface 3a of each PET layer 3 .

The adhesive solution was applied on the surface 3a by means of a brush ( deposition operation) .

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

After having applied the adhesive solution ( deposition operation) , the two PET layers 3 were subj ected to a heating operation . The heating operation involved keeping the two PET layers 3 on which the adhes ive solution was applied in an oven at 220 ° C for an amount of time of 3 minutes .

Unlike what described above , according to a further embodiment of the invention, the adhesive solution comprises a pre-condensed resin consisting of resorcinol and formaldehyde with isocyanate blocking groups , lignin and a chemical chosen between urea and thiourea . This adhes ive solution of fers the advantage of not having to use formaldehyde in a free form .

After having carried out the preliminary step described above , the process goes on with a first step, in which the transceiver assembly 2 is housed between the two PET layers 3 , and, subsequently, with a second step, in which the two PET layers 3 are covered on the outside with two respective layers 4 of non-vulcani zed rubber .

Alternatively, the two PET layers 3 can be covered on the outside with two respective layers 4 of partially or totally vulcani zed rubber .

By so doing, a first RFID device was manufactured .

The second RFID device was manufactured repeating the method described above with the sole exception of not having carried out the preliminary step . In other words , in the manufacturing process of the second RFID device , the first step was carried out using the PET layers 3 without having applied the adhesive solution on them .

Unlike what described above , according to a preferred embodiment of the invention, the adhesive solution can be applied on both surfaces of the PET layers 3 .

In use , the RFID devices described above are included in a green rubber portion of a tyre . Alternatively, the RFID devices described above can be applied on a cured rubber portion of a tyre .

Once the RFID device has been inserted inside the tyre , the vulcani zation step is carried out . By so doing, the rubber layers of the RFID device , during the vulcani zation, are cross-linked with the surrounding rubber, ensuring the stability of the position of the device .

The first and the second RFID devices were subj ected to an adhesion test according to ASTM D1876 method . Said test measures the adhesion force between each one of the PET layers 3 and the respective rubber layer 4 arranged so as to cover the outer surface 3a .

Table I I shows the values obtained with the aforesaid test .

TABLE I I

The values shown in Table I I clearly prove that the method of the invention can ensure a strong adhesion between the PET layer 3 and the respective rubber layer 4 , thus avoiding a splitting up of the device and the problems caused by it .

Two other RFID devices ( the third and the fourth RFID devices ) of the type shown in the figure were manufactured .

The third and the fourth RFID devices di f fer from the first and the second RFID devices because they comprise layers 3 made of Nylon and not PET .

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

In addition, the third and the fourth RFID devices di f fer from each other in the conditions used in the heating operation (b ) .

In particular,

- for the third RFID device , the adhesive solution of table I was applied on the surface 3a of the Nylon layer by means of a brush ( deposition operation) .

After having applied the adhesive solution ( deposition operation) , the two Nylon layers 3 were subj ected to a heating operation . The heating operation involved keeping the two Nylon layers 3 on which the adhesive solution was applied in an oven at 220 ° C for an amount of time of 5 minutes .

- for the fourth RFID device , the adhesive solution of table I was applied on the surface 3a of the Nylon layer by means of a brush ( deposition operation) .

After having applied the adhesive solution ( deposition operation) , the two Nylon layers 3 were subj ected to a heating operation . The heating operation involved keeping the two Nylon layers 3 on which the adhesive solution was applied in an oven at 155 ° C for an amount of time of 10 minutes .

For the first , third and fourth RFID devices the same amount of adhesive solution was applied on the respective surfaces 3a.

The third and the fourth RFID devices were subjected to an adhesion test according to ASTM D1876 method for measuring the adhesion force between each one of the Nylon layers 3 and the respective rubber layer 4 arranged so as to cover the outer surface 3a.

Table III shows the values obtained with the aforesaid test .

TABLE III

Also the values shown in Table III clearly prove that the method of the invention can ensure a strong adhesion between the Nylon layer 3 and the respective rubber layer 4, thus avoiding a splitting up of the device and the problems caused by it.

According to the inventors, when the layers of thermoplastic material are in the form of textile, the adhesion force is greater.

Unlike what described above, instead of two layers arranged in a sandwich-like, the covering element can consist of a layer of thermoplastic material wrapped around the electronic element.

As stated above, the present invention adapts to any electronic device to be applied to a rubber article, e.g. a tyre .

Depending on the electronic device, only one rubber layer 4 can be used.