METHOD FOR REMOVING ADHESIVES AND/OR INTERLAMINAR INKS ON LAMINATED PLASTIC MATERIAL

Abstract

The present invention relates to a method for removing interlaminar adhesives and/or inks on laminated plastic material, which comprises the following steps:

a) microperforating the laminated plastic material with at least one microperforation per cm.sup.2,

b) removing the ink and/or adhesive by adding a washing solution to the microperforated plastic resulting from step a),

c) separating the plastic material and the aqueous material.

Claims

1. A method for removing interlaminar adhesives and/or inks on laminated plastic material, comprising the steps of: a) microperforating the laminated plastic material with at least one microperforation per cm.sup.2, b) removing the ink and/or adhesive by adding a washing solution to the microperforated plastic resulting from step a), and c) separating the plastic material and the aqueous material.

2. The method according to claim 1, wherein the microperforation is carried out by means of microneedles, abrasive substances or laser.

3. The method according to claim 1, wherein between 1-100 microperforations per cm.sup.2 are performed in step a).

4. The method according to claim 1, prior to step a), comprising a step of conditioning and grinding the laminated plastic material to be treated.

5. The method according to claim 1, wherein the washing solution of step b) is selected from solvent solution, alkaline aqueous solution with at least one surfactant, acid solutions and/or mixtures thereof.

6. The method according to claim 1, wherein ammonia and/or acetic acid is added to the washing solution.

7. The method according to claim 1, wherein step b) of removing ink and/or adhesive is carried out in a pressure reactor, under stirring and at a maximum temperature of 150° C.

8. The method according to claim 1, wherein step b) of removing ink and/or adhesive is carried out in a pressure autoclave at a maximum temperature of 150° C.

9. The method according to claim 1, wherein step c) of separating the plastic material and aqueous material is carried out by means of a centrifuge, for 3-10 seconds at 1000-3000 rpm.

10. The method according to claim 1, comprising an additional step after step c) consisting of treating the aqueous material, for separating the ink and/or adhesives from the water.

11. The method according to claim 10, wherein the step of treating the aqueous material is carried out by means of a clarifying centrifuge.

12. The method according to claim 1, comprising an additional step after step c) consisting of separating the plastic materials.

13. The method according to claim 12, wherein the step of separating the plastic materials is carried out by means of decanting in the wet phase or by using hydrocyclones.

14. A microperforation device for laminated plastic material, comprising: a hopper for receiving the laminated plastic material from above, a pair of double rollers, rotating in opposite directions and arranged in the lower portion of the hopper, for receiving the laminated plastic material from the hopper due to the effect of gravity, and microneedles located on the rollers to perforate the laminated plastic material as it passes between the rollers.

15. The microperforation device for laminated plastic material according to claim 14, wherein the microneedles have a length that is greater than the thickness of the laminated plastic material.

Description

DESCRIPTION OF THE FIGURES

[0024] FIG. 1 shows the general diagram of a laminated plastic material.

[0025] FIG. 2 shows the general diagram of a preferred embodiment of the present invention.

[0026] FIG. 3 shows the microperforation device.

DETAILED DESCRIPTION OF THE INVENTION

[0027] As shown in FIG. 1, a laminated plastic material comprises at least two layers of plastic material (1), and an interlaminar area (2) inserted between the two layers of plastic material (1).

[0028] The laminated plastic material can come in different forms: leftover rolls from the packaging industry or finished containers with defects or from the landfill. All this material is selected, large impurities are removed and they are placed on a conveyor belt. To improve the method of the present invention, the laminated plastic material undergoes an optional grinding step; to that end, the material is ground in a specific mill (4) for plastic film until obtaining particles of size comprised between 5 and 20 cm.

[0029] Once ground, this material is subjected to microperforation and the access of the reagents to the interlaminar area (2), where the ink and adhesive to be removed are located, is thus facilitated. There are various techniques for performing microperforations, as can be the case of using microneedles, abrasives or laser. Using the microneedle technique is preferably recommended.

[0030] In the present invention, the microperforation step was carried out in a microperforation device (5), as shown in FIG. 3.

[0031] This device comprises a pair of double rollers (11) configured so that both rotate in the opposite direction and are arranged in the lower portion of a hopper (10), such that the ground laminated plastic material coming from the mill (4) falls into the hopper (10) and due to the effect of its weight is forced to pass between the rollers (11). The rollers (11) have microneedles (12) of a length greater than the total thickness of the laminate and regularly distributed between 1 and 100 per cm.sup.2. As the laminated plastic material passes between the rollers (11), the microneedles (12) cause perforations in the material that will enable the access of the reagent to the interlaminar area (2).

[0032] The already microperforated laminated plastic material is introduced into a stirring reactor (6), which comprises the washing solution, such that the chemical agents contained in the washing solution can access the interlaminar area (2) of the laminated plastic material and remove the ink and the adhesive.

[0033] Any solvent can be used as a washing solution; in the present invention, an alkaline aqueous solution with surfactant agents was preferably used. The surfactants can be cationic, ammonium or non-ionic surfactants; cationic surfactants were used in the present invention. In a preferred embodiment, ammonia and/or acetic acid was added to the washing solution, verifying that these two compounds, although not required, improve the efficiency of the process.

[0034] The conditions of the washing step depend on the adhesive that the laminar plastic material comprises, such that this step can be performed at room temperature, when the adhesive is weak, or in the case of stronger adhesives, a temperature increase in the reactor is required; however, in the case of working at temperatures higher than the boiling temperature of the reagent, using an autoclave reactor that works under pressure to avoid the evaporation of the reagent would be required. In any case, the temperature cannot exceed 150° C.

[0035] After the washing step, the plastic material together with the washing solution was introduced into a centrifuge (7) to separate the plastic material from the aqueous solution, which contains the water along with the remains of ink and adhesive. To separate both phases, as is known to a person skilled in the art, there are different techniques; however, in the present invention, the material resulting from the washing step was subjected to centrifugation such that, in addition to separating both phases, with the high shear forces produced, the separation of the sheets was favoured and with it the removal of adhesive.

[0036] In this manner, on the one hand, the delaminated plastic material without ink or adhesive is achieved, and, on the other hand, the water with the remains of the washing solution together with the ink and the adhesive is achieved.

[0037] Optionally, the method may comprise steps to complete the recycling of all materials; to that end, a step of water treatment was performed in a clarifying centrifuge (8) that separated the adhesive particles in the form of sludge and recycled the water to the main reactor. Therefore, in addition to recovering the water, the reagents are recovered, reducing operating costs. To help clean the water, flocculating and/or coagulating agents were added prior to centrifugation.

[0038] Furthermore, the delaminated plastic material was recycled. In the event that the initial laminated plastic material is formed by sheets of plastic material of different nature, for recycling to be optimal it must be subjected to separation prior to processing; this separation can be performed by means of decanting in the wet phase based on the difference in density between the different plastics, or by using hydrocyclones. In this case, being a laminated plastic material made up of PET and HPDE, a decanter (9) with water was used, such that the PET remained at the bottom while the HDPE floated, thus separating these two plastics.