Repair adhesive based on polyethylene terephthalate for anti-corrosion coatings, method for production and use thereof

Abstract

The invention relates to a method for obtaining a corrosion-resistant repair adhesive from waste PET bottles and by complete precipitation of recovered PET via a phase inversion technique. The film can be used as an adhesive and can be applied to any painted or unpainted metal surface without surface preparation, which eliminates the need for steps in the painting process and makes the process disclosed in the invention lower cost. The repair adhesive is easy to apply simply by removing the liner and applying it to the structure, does not require professional labor, has minimal durability of 2 years, and can be removed or not removed for maintenance of the paint. Under the condition of removal, the PET adhesive is easy to fall off in the conventional hydraulic spraying process.

Description

Technical Field

[0001] The present invention belongs to the field of chemical engineering, more precisely to the fields of materials and metallurgy, and describes a corrosion protection repair agent based on recycled thermoplastics such as polyethylene terephthalate (PET), for temporarily protecting damaged paint systems from corrosion, wherein the repair agent can be applied as an adhesive in liquid or solid form. Background Art

[0002] Carbon steel is one of the most widely used materials in the world due to its diverse mechanical properties and availability. Therefore, its wear is an important subject of analysis since this metal is vulnerable to corrosion under normal use conditions (such as when exposed to environments with moisture and pollutants). For example, in the oil industry, corrosion exists in all parts of the process, such as production, transportation, storage, and refining, resulting in costs in the billions of dollars. In addition to costs, due to accidents in the petrochemical industry being potentially catastrophic in terms of both loss of life and environmental impact, the importance of inhibiting corrosion in these industries becomes obvious.

[0003] Among these corrosion inhibition methods, the use of organic coatings is one of the most widely used in the industry because of its relatively low cost and good performance in preventing corrosion. These coatings act by forming a barrier between the environment and the element to be protected, preventing the aggressors from coming into contact with the metal and triggering the wear mechanism. To achieve this, the barrier formed must be impermeable to these reagents in order to effectively ensure this isolation.

[0004] However, before the regular preventive maintenance of the coating, coating deterioration is often observed, and in these cases, intervention must be carried out to restore the protection in that area. For this intervention to be effective in preventing corrosion, in addition to good technical training for the interveners, good surface preparation and the use of appropriate chemical products are also necessary. Therefore, to ensure the integrity of the structure again, it can be seen that this step can be costly as it depends on high-quality inputs, qualified labor, and time.

[0005] Regardless of the repair process employed, the maintenance team must be meticulous, because both protection systems require the surface to be free of oil, grease, oxides, salts, and other contaminants, and in the case of polymer systems, the fixing of the film is greatly affected by the substrate roughness profile.

[0006] These particularities of each system make the repair process costly because, in addition to the individual steps that affect the total execution time, a prepared and qualified execution team must be hired so that the applied repair system exhibits its best performance. However, this is not the case in practice, as the difficulty of accessing the damaged area, combined with operational errors, causes the applied repair material to deteriorate prematurely, thus compromising the integrity of the entire paint system and the metal structure.

[0007] Currently, high-performance paint systems undergo corrective maintenance through a series of several steps, which is time-consuming and costly. Additionally, although it is a recyclable material, in 2015, 240,000 tons of polyethylene terephthalate were improperly discarded, highlighting the need to find new uses for this material to avoid environmental problems. Due to the low permeability of PET to gases and water and its good chemical resistance, there is a good demand for its use as an anti-corrosion coating.

[0008] Given the situation outlined above, it is undeniable that there is a need to better utilize waste PET, and in this sense, the present invention provides various benefits for painted structures by developing a repair system based on polyethylene terephthalate obtained from post-consumer materials. The material acts as an anti-corrosion agent and is applied as a coating to the damaged area, has a low acquisition cost, and contributes to the environment by promoting the recycling of waste PET.

[0009] Prior Art

[0010] As shown below, some documents in the prior art describe anti-corrosion repair agents based on recycled polyethylene terephthalate for the corrosion protection of paint systems.

[0011] The patent document BRPI 0404257-3, entitled "PROCESSO DE ADESIVOS E ADESIVOS POLIURETANICOS ASSIM OBTIDOS" (Method for Obtaining Polyurethane Adhesives and Polyurethane Adhesives Thus Obtained), relates to polyurethane adhesives and polyester polyols obtained by a chemical recycling method of PET material, which reduces the number of steps and uses a larger amount of recycled PET in the preparation of polyols for the production of polyurethanes.

[0012] However, the patent document uses a glycolytic polymerization method, which includes using diol to reduce the molar mass of PET, thus causing the formation of polyester; this whole step is called chemical recycling. It should be noted that compared with the said document, the present invention does not use any method for decomposing the packaging made of PET to produce by-products. Instead, the present invention includes dissolving the post-consumer PET after reducing it into sheet form (mechanical process). The said document chemically recycles PET to only use some of its by-products (polyols, polyesters), and then reacts them with isocyanates to produce polyurethane glue (the adhesive part of the tape). Therefore, the purpose of the said document is to produce the adhesive part of the adhesive tape, while the models disclosed in the present invention represent the carrier of such glue, that is, they are completely different products. In addition, the present invention uses all the chemicals present in the composition of the PET packaging.

[0013] The scientific document entitled "POLY(ETHYLENE TEREPHTHALATE) PHASE INVERSION MEMBRANES: THERMODYNAMICS AND EFFECTS OF A POOR SOLVENT ON THE MEMBRANE CHARACTERISTICS" mentions PET as a world-recognized polymer for manufacturing membranes. The said document uses a phase inversion technique to prepare PET membranes and characterize the phase separation phenomenon, as well as the performance of the membranes produced under different solution conditions.

[0014] However, the work carried out in the said document aims to produce membranes derived from virgin PET for applications in separation processes. The process used in the present invention shows differences compared with the process disclosed in the said document, resulting in different products.

[0015] The product synthesized in the said document aims to produce membranes, and for this purpose, the materials used must be porous, which is not applicable to the proposed patent because the corrosion protection barrier must be pore-free.

[0016] Therefore, in order to prevent the occurrence of porosity problems, the present invention conducts a precipitation process in ambient air for 30 minutes before using the phase inversion technique in a non-solvent solution (distilled water).

[0017] After precipitating PET on the glass surface, a phase inversion process is carried out in distilled water. According to Figure 1 , as proposed in the said document, when the PET solution is impregnated in water without precipitation in air, a porous membrane is produced, which is a quite different product from the product obtained in the present invention.

[0018] In addition, the present invention states that it is necessary to neutralize the PET membrane after the phase inversion process, thereby removing any trace of residual acid from the production process.

[0019] Another important factor (a point of difference between the present invention and the said document) is the addition of dibutyl phthalate in the range of 10% to 30% (v / v) relative to the volume of the PET solution. In addition, the unexpected addition of a plasticizer to the PET solution to produce a film with high flexibility is highlighted. The addition of a plasticizer in the present invention aims to correct problems such as high rigidity and low flexibility of the film, since this is an essential characteristic for making adhesive PET in order not to limit its application to surfaces with flat geometries only.

[0020] It should be noted that Figure 2 As shown, without the addition of plasticizers, the film becomes brittle within a few hours, which makes its application impossible.

[0021] Titled “PLASTICIZER EFFECTS ON PHYSICAL-–MECHANICAL PROPERTIES OFSOLVENT CAST SOLUPLUS The scientific literature of "FILMS" specifically deals with the evaluation of Soluplus with four different plasticizers. Characterization of the mechanical properties of films. The plasticizers chosen were polyethylene glycol 6, triethyl citrate, propylene glycol and glycerol; they were studied at three different levels (15% w / w, 20% w / w and 25% w / w). The results showed that these four plasticizers were able to reduce the glass transition temperature, tensile strength and Young's modulus of the films, while increasing the percentage elongation and toughness of the films. Among the plasticizers tested, polyethylene glycol 6 showed the greatest changes in the mechanical properties studied.

[0022] However, the document adds different plasticizers to polymers that do not belong to the terephthalate category. It is worth noting that in the document, the use of plasticizers is common in polymers that undergo thermomechanical processing, since they improve the physical and mechanical properties of the final product due to the reduction of the glass transition temperature (Tg). In this case, the study is not to produce a material by modifying the polymer by adding a plasticizer, but only to verify the effect of this addition on the physical and mechanical properties of the polymer studied. In addition, the study conducted by the document is not comparable to the study proposed by the present invention, because the focus is not on modifying the physical and mechanical properties of post-consumer PET; in fact, the goal is to completely dissolve the material to form a film and then use it as a carrier for an adhesive. In short, the present invention and the document can only be compared if they disclose the modification of the structure of post-consumer PET by adding a plasticizer and then evaluating its properties; however, the present invention produces new products from post-consumer PET.

[0023] The scientific literature titled (A) “PROPERTIES OF POST-CONSUMER POLYETHYLENE TEREPHTHALATE COATING MECHANICALLY DEPOSITED ON MILD STEELS” and (B) “PRODUCTION AND CHARACTERIZATION OF THERMALLY SPRAYED POLYETHYLENE TEREPHTHALATE COATINGS” respectively relate to post-consumer PET anti-corrosion coatings applied to carbon steel by an industrial press and thermally sprayed polymer (PET) coatings applied to 1020 steel by low velocity flame spraying technology as protection against corrosion and wear.

[0024] However, these literatures involve directly depositing micronized PET powder onto the surface of steel using thermal spraying and pressing techniques respectively. None of the studies dissolve post-consumer PET in an organic reagent to produce a solution, nor do they produce an adhesive film.

[0025] Literature (B) uses a ball milling device and a subsonic combustion spray gun type spraying device operating under high pressure conditions to process PET. Thus, by this method, PET powder is deposited onto the surface of low carbon steel. In addition, the substrate on which the film is deposited needs to be preheated to better adhere the PET powder. Briefly, this is an expensive and time-consuming process for applying the coating. Further, Literature (A) deposits micronized post-consumer PET powder onto the surface of low carbon steel. However, the production of PET powder undergoes heat treatment before the grinding process, and its deposition on the substrate occurs through a pressing process. Regarding the pressing process, it can be said that the PET powder is placed on top of the steel and then hot pressed (T = 260 °C) on the surface to adhere the film to the surface.

[0026] After clarifying the two methods, it can be seen that there is no similarity between the techniques used in the said literature and the technique proposed in the present invention.

[0027] The scientific literature titled "RECYCLING WASTE POLYESTER VIA MODIFICATION WITH A RENEWABLE FATTY ACID FOR ENHANCED PROCESSABILITY" relates to the use of renewable TOFA fatty acid as a modifier for recycled PET. For this purpose, PET was blended with different concentrations of TOFA and extruded at 240 °C. Characterization showed that the melting and recrystallization temperatures of PET shifted to lower temperatures and the glass transition temperature decreased from 91 °C to 65 °C. The addition of TOFA also produced defects in the crystalline phase, which slowed down recrystallization (an important processing parameter). The morphological changes in the plasticized PET reduced and stabilized the viscosity. These results provide a potential route for the reuse of PET waste as high-performance polymer fibers.

[0028] However, the literature aims to replace erosive additives used in the production process of packaging made of PET, mainly in the forming stage (e.g., reducing the extrusion temperature). Therefore, the literature identifies the fatty acid TOFA as a potential renewable plasticizer for post-industrial PET resin, whereby its formability can be achieved at lower temperatures. In addition, the literature attempts to change the composition of the raw material (in this case PET), which is not within the scope of the present invention.

[0029] The object of the present invention is to produce an adhesive made from used bottles, while the object of the literature is to reduce the melting temperature of PET so that, for example, temperatures above 260 °C are not required during the recycling process.

[0030] The literature titled "WHAT IS THE BEST ADHESIVE FOR BONDING PVC PLASTIC?" relates to PET, a thermoplastic material of the polyester family. PET is a lightweight, strong, and inert material that is easy to transport and recyclable. PET has extremely wide applications and can be used for food and beverage packaging, for manufacturing disposable medical devices, and industrial films and packaging.

[0031] However, the literature is a newsletter from a UK chemical company, one of whose departments is engaged in the production and sale of adhesives. The newsletter shows the properties of PET and some of its many applications. However, the newsletter only guides consumers on the importance of surface preparation when attaching PET components and which adhesives can be used among those produced by the suppliers discussed.

[0032] Therefore, no similarity was found between the newsletter and the present invention because no method for reusing PET bottles that does not significantly lose the properties of PET bottles and has anti-corrosion applications was mentioned. Summary of the Invention

[0033] The present invention aims to firstly propose a method for producing a corrosion - resistant repair adhesive based on recycled PET for temporarily protecting damaged painted systems.

[0034] In a second embodiment, the present invention relates to an adhesive film obtained by the method described above. The film exhibits good ductility and flexibility. In addition, it also has properties such as low permeability to water and gases and good chemical resistance.

[0035] Finally, in a third embodiment, the present invention proposes the use of the adhesive film as a corrosion - resistant repair system for painted structures, so as to be applied on - site as a coating, which forms a barrier between the environment and the element to be protected, preventing the contact of erosive agents with the metal and triggering wear mechanisms. Description of the Drawings

[0036] For a comprehensive and complete visualization of the objectives of the present invention, the attached drawings are shown as follows.

[0037] Figure 1 An example of a porous film that cannot be used for anti - corrosion purposes is shown.

[0038] Figure 2 In (a), a PET film of an unconditioned formulation immediately after its production is shown; in (b), a PET film of an unconditioned formulation that has become brittle after several hours on a workbench is shown.

[0039] Figure 3 The application of an acrylic glue to a PET film to produce an adhesive is shown.

[0040] Figure 4 In (a), a PET solution after its preparation is shown, and in (b), a PET solution applied to stainless steel is shown.

[0041] Figure 5 In (a), a PET adhesive is shown; in (b), a PET adhesive being detached from a liner is shown; in (c), a low - carbon steel substrate with a PET adhesive is shown; and in (d), a PET adhesive applied to a steel surface is shown.

[0042] Figure 6 A flow chart showing all stages of the PET adhesive production process is shown. Detailed Description of the Invention

[0043] In a first embodiment, the present invention relates to a method for obtaining a corrosion - resistant adhesive based on recycled thermoplastic materials for temporarily protecting damaged painted systems.

[0044] As Figure 6As shown in the flowchart in

[0045] I. Disinfect the recycled thermoplastic material with water, soap, and a sodium hypochlorite disinfectant solution with a concentration of 0.1% to 2.5%.

[0046] II. Cut the recycled thermoplastic material into pieces with dimensions each capable of being 0.5 cm × 0.5 cm to 3.0 cm × 3.0 cm.

[0047] III. Dissolve the pieces in a solution containing strong carboxylic acid and organic solvent in the range of acid / solvent of 5 / 95 (% v / v) to 95 / 5 (% v / v) at a ratio of 15% to 35% (m / v) to produce a film.

[0048] IV. Stir the solution obtained in (iv) at room temperature until completely dissolved.

[0049] V. Slowly add a plasticizer at a concentration within the range of 10% to 50% (v / v).

[0050] VI. Dissolve all the plasticizer until a mixture is formed.

[0051] VII. Subject the mixture to an ultrasonic bath for 5 minutes to 15 minutes.

[0052] VIII. Place the mixture in (vii) on a glass plate and let the system stand in atmospheric air for a time of 30 minutes to 90 minutes.

[0053] IX. Wait for the thermoplastic material to partially precipitate.

[0054] X. Perform a phase inversion technique by immersing the glass plate in a non-solvent bath of distilled water; and,

[0055] XI. Apply a layer of permanently sticky glue using an expander and protect it with a silicone-treated paper liner.

[0056] The repair adhesive can optionally be obtained from any recycled thermoplastic material selected from: poly(propylene), poly(ethylene), poly(vinyl chloride), poly(urethane), poly(styrene), poly(ethylene vinyl acetate), and poly(methyl methacrylate), preferably poly(ethylene terephthalate).

[0057] The dissolution of the thermoplastic material can be carried out in strong carboxylic acids and solvents in different ratios, i.e., 5 / 95 (% v / v) to 95 / 5 (% v / v). The strong carboxylic acid can be selected from trichloroacetic acid, 1,1,1,3,3,3-hexafluoro-2-propanol (HIFP), and trifluoroacetic acid (TFA) is preferably used. The organic solvent can be selected from acetone, toluene, xylene, phenol, and carbon tetrachloride, and dichloromethane (DCM) is preferably used. In addition, the ratio between the thermoplastic material (preferably PET) and the solution of the strong carboxylic acid and the solvent can be 10 / 90 (m / v%) to 40 / 60 (m / v%).

[0058] In addition, different categories of plasticizers can alternatively be used in polymer synthesis, and the selection is as follows:

[0059] - Adipic acid derivatives (di-n-hexyl adipate (DHA), heptyl nonyl adipate (79A), di-2-ethylhexyl adipate (DOA), diisodecyl adipate (DIDA), diisononyl adipate (DINA));

[0060] - Azelaic acid derivatives (di-2-ethylhexyl azelate (DOZ));

[0061] - Benzoic acid derivatives (diethylene glycol dibenzoate, dipropylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol isobutyrate benzoate);

[0062] - Citric acid derivatives (tri-n-butyl citrate, acetyltri-n-butyl citrate);

[0063] - Epoxy derivatives (epoxidized soybean oil (ESO), epoxidized linseed oil (ELO), 2-ethylhexyl epoxythalate);

[0064] - Glycol derivatives (diethylene glycol dinonanoate, triethylene glycol di-2-methylbutyrate);

[0065] - Hydrocarbons (hydrogenated terphenyl, chlorinated paraffin (52 wt% Cl));

[0066] - Isophthalic acid derivatives (di-2-ethylhexyl isophthalate);

[0067] - Oleic acid derivatives (butyl oleate);

[0068] - Phosphoric acid derivatives (tri-2-ethylhexyl phosphate (TOP), triphenyl phosphate (TPP), tricresyl phosphate (TCP), 2-ethylhexyl diphenyl phosphate, isodecyl diphenyl phosphate);

[0069] - Phthalic acid derivatives (dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl octyl phthalate (BOP), diisobutyl phthalate (DHP), diisooctyl phthalate (DIHP), heptyl nonyl phthalate (79P), heptyl nonyl undecyl phthalate (711P), diisooctyl phthalate (DIOP), bis(2-ethylhexyl) phthalate (DOP), (n-hexyl, octyl, decyl) phthalate (610), (n-octyl, decyl) phthalate (81OP), diisodecyl phthalate (DIDP), ditridecyl phthalate (DTDP), butyl benzyl phthalate (BBP), alkyl benzyl phthalate, 261);

[0070] - Ricinoleic acid derivatives (methyl ricinoleate, n-butyl acetyl ricinoleate, castor oil);

[0071] - Sebacic acid derivatives (bis(2-ethylhexyl) sebacate (DOS));

[0072] - Stearic acid derivatives (n-butyl stearate);

[0073] - Sucrose derivatives (sucrose acetate isobutyrate (SAIB));

[0074] - Sulfonic acid derivatives ((o,p)-toluenesulfonamide, N-ethyl-(o,p)-toluenesulfonamide, alkyl sulfonates of phenol and methoxyphenol (Mesamoll ));

[0075] - Terephthalic acid derivatives (bis(2-ethylhexyl) terephthalate (DOTP);

[0076] - Trimellitic acid derivatives (tris(2-ethylhexyl) trimellitate (TOTM), heptyl nonyl trimellitate (79TM), trisisononyl trimellitate (TINTM));

[0077] - Polyesters, such as: adipic acid polyester (mol wt 6000), Paraplex G-40, adipic acid polyester (mol wt 2000), 334F, azelaic acid polyester (mol wt 2200), Platolein 9720, sebacic acid polyester (mol wt 8000), Paraplex G-25); and,

[0078] - Terpenes and derivatives (camphor, methyl hydrogenated rosin).

[0079] The glue used in the adhesive layer can be produced from elastomer-based formulations such as natural rubber, butyl rubber, nitrile rubber, styrene-butadiene rubber, acrylates or silicones. The acrylic glue is applied to the adhesive film using a Bird extender. This device ensures the uniform application and controlled thickness of the glue to the adhesive film. Figure 3 Shows how the Bird extender works when applying glue to the adhesive film. After applying the acrylic glue, a liner is applied, which acts as protection for the glue and ensures that the glue retains its properties until the moment of use.

[0080] Thus, in a second embodiment, the present invention describes the obtained repair adhesives. The adhesives are obtained as a repair system for painted structures such that they can be applied as a coating on-site, which forms a barrier between the environment and the element to be protected, preventing the erosive agent from coming into contact with the metal and triggering the wear mechanism. To this end, the formed barrier is impermeable to these reagents, which ensures effective isolation.

[0081] These adhesives are ductile and flexible, have low permeability to water and gases, and good chemical resistance, making them suitable for use as anti-corrosion coatings. As seen by scanning electron microscopy (SEM) and water absorption tests, the adhesives exhibit low film porosity. In addition, as determined by Fourier transform infrared (FTIR) bands, they have good thermal stability up to 150 °C and do not show chemical degradation in PET after being dissolved in TFA.

[0082] It is worth noting that the adhesive film is obtained relatively inexpensively and performs well in preventing corrosion, with a minimum durability of 2 years.

[0083] Finally, in a third embodiment, the present invention proposes the use of the adhesives as anti-corrosion repair agents.

[0084] The obtained anti-corrosion repair agent can be applied to any painted or unpainted metal surface in onshore and offshore areas. The present invention proposes to apply it in liquid form (as a spray) or in solid form (in the form of an adhesive tape).

[0085] For the application in liquid form, it is only necessary to deposit a solution of the dissolved thermoplastic material on the metal surface and wait for about 15 minutes to form a polymer film. Thus, the liquid application of the solution consists of directly applying a solution composed of a thermoplastic material dissolved in a strong carboxylic acid and an organic solvent.

[0086] Therefore, this solution is a base solution for producing varnish, which can be applied to different substrates by spraying (e.g., using a spray gun) or by means of a brush. In addition, by adding a thickening agent, a solution used as a gel can be obtained, which can be applied to the surface by means of a brush.

[0087] Solid application includes producing the adhesive according to the method described in the present invention and directly applying it to a metal substrate, as well as adding an adhesive layer and a silicone paper liner to protect the adhesive. It is worth noting that the function of the liner for the treated paper is to ensure its self - adhesive property in addition to protecting the adhesive from contamination.

[0088] The removal of the PET adhesive can be carried out manually or by sandblasting (e.g., by hydro - sandblasting or sandblasting with metal oxides).

[0089] To demonstrate its potential, the present invention will be described in more detail according to the implemented embodiments. It should be noted that the following description is only intended to clarify the understanding of the proposed invention and disclose the implementation manners of the present invention in more detail, rather than limiting it thereto. Therefore, variants similar to the embodiments are also within the scope of the present invention.

[0090] Example of a PET-based embodiment

[0091] In this embodiment, in order to obtain a carrier material based on polyethylene terephthalate for an anti - corrosion coating, post - consumer PET bottles are disinfected with water, soap, and a 0.1% sodium hypochlorite disinfectant solution. After disinfecting the bottles, the bottoms and tops of each bottle are removed.

[0092] The cut bottles are further cut into pieces with dimensions of approximately 1 cm×1 cm. Then, 15 g of this PET is dissolved in a solution containing trifluoroacetic acid (TFA) and dichloromethane (DCM) in a ratio of 50 / 50 (% v / v) to produce a PET film.

[0093] The solution is stirred at room temperature for 24 hours. Subsequently, dibutyl phthalate, a plasticizer, is slowly added at a concentration of 20% (v / v). After the plasticizer is completely dissolved, the mixture is subjected to an ultrasonic bath for 15 minutes to eliminate the bubbles that affect the structure of the repair carrier material.

[0094] Then the solution is deposited on a glass plate, and the system is left standing in atmospheric air for 30 minutes to allow the PET portion contained in the solution to precipitate. After the standing time, a phase - inversion technique is carried out to produce a film by complete precipitation of PET. The phase - inversion technique includes dipping the glass plate containing the PET solution into a non - solvent bath, e.g., dipping it into distilled water.

[0095] It should be noted that when impregnation is carried out immediately after the polymer is deposited on the substrate, the precipitation of the polymer in the solution occurs faster. Conducting the polymer precipitation in two stages requires more time for the evaporation of the organic solvents (trifluoroacetic acid and dichloromethane) to occur in a controlled manner during the standing time. This evaporation stage in air must be carried out in an environment with an exhaust fan because it involves the evaporation of toxic acids harmful to human health.

[0096] The function of the plasticizer is to modify the polymer matrix (in this case the PET matrix) such that its small molecules are incorporated between its chains, creating separation between them and breaking the intermolecular bonds. In this way, the film produced from this material becomes more ductile and flexible.

[0097] An acrylic-based adhesive layer with permanent adhesiveness is applied to the surface of the PET film using an expander and is protected with a silicone-treated paper liner.

[0098] The adhesive used is an acrylic-styrene copolymer composed of acrylic monomers and styrene monomers, for example, a commercially available product. The acrylic adhesive is applied to the film using a bird-type expander. This device ensures the uniform application and controlled thickness of the adhesive on the PET film. Figure 3 It shows how the bird-type expander works when applying the adhesive to the PET film. After applying the acrylic adhesive, a liner is applied, which acts as protection for the adhesive and ensures that the adhesive maintains its properties until the moment of use.

[0099] The liquid application of the PET solution involves directly applying a solution composed of PET dissolved in trifluoroacetic acid and dichloromethane. A solution containing 20% (m / m) PET dissolved in 50% (v / v) dichloromethane (DCM) and 50% (v / v) trifluoroacetic acid (TFA) can be used. It is important to note that this solution does not contain a tackifying resin, a plasticizer, or an adhesive in its composition. This solution is the base solution for producing a varnish, which can be applied to different substrates by spraying with a spray gun on a metal surface or by means of a brush to form a polymer film after 5 minutes. It can also be used as a gel applied to the surface by means of a brush.

[0100] Figure 4 A shows a PET solution with a composition of 20% (m / m) PET, 50% (v / v) TFA, and 50% (v / v) DCM. Figure 4 B shows the PET solution applied to the stainless steel surface using a brush.

[0101] The solid application includes producing a PET adhesive according to the steps of the method for producing a PET film described in the present invention and directly applying it to a metal substrate, and adding an acrylic adhesive layer, followed by applying a silicone paper liner to protect the adhesive.

[0102] The gasket is a material commonly used for adhesives in the market. Figure 5 Shown before application ( Figure 5 A) and after removal of the gasket ( Figure 5 B) of the PET-based adhesive. Figure 5 C shows the steel substrate before applying the film to the surface of the steel substrate, and Figure 5 D shows the steel substrate after applying the adhesive to the surface of the steel substrate.

[0103] Those skilled in the art will understand the knowledge shown and will be able to reproduce the present invention with the stated embodiments and other variations covered by the scope of the appended claims.

Claims

1. A method for producing a repair adhesive, characterized in that The following steps are included: I. Disinfect the recycled thermoplastic material with water, soap, and a sodium hypochlorite disinfectant solution having a concentration of 0.1% to 2.5%. II. Cut the recycled thermoplastic material into pieces each having a size capable of being 0.5 cm × 0.5 cm to 3.0 cm × 3.0 cm. III. Dissolve the pieces in a solution containing a strong carboxylic acid and an organic solvent in a range of acid / solvent of 5 / 95 (% v / v) to 95 / 5 (% v / v) at a ratio of 15% to 35% (m / v) to produce a film, wherein the ratio between the thermoplastic material and the solution of the strong carboxylic acid and the solvent can be 10 / 90 (m / v%) to 40 / 60 (m / v%). IV. Stir the solution obtained in (iv) at room temperature until the material is dissolved. V. Slowly add a plasticizer at a concentration within the range of 10% to 50% (v / v). VI. Dissolve all the plasticizer until a mixture is formed. VII. Subject the mixture to an ultrasonic bath for a time of 5 minutes to 15 minutes. VIII. Deposit the mixture from (vii) on a glass plate, and let the system stand in atmospheric air for a time of 30 minutes to 90 minutes. IX. Wait for the thermoplastic material to partially precipitate. X. Perform a phase inversion technique by dipping the glass plate in a non-solvent bath of distilled water; and, XI. Apply a layer of glue having permanent adhesiveness using an expander, and protect the layer with a silicone-treated paper liner.

2. The production method according to claim 1, characterized in that In step (I), the thermoplastic material is selected from poly(propylene), poly(ethylene), poly(vinyl chloride), poly(urethane), poly(styrene), poly(ethylene vinyl acetate), and poly(methyl methacrylate), preferably poly(ethylene terephthalate).

3. The production method according to claim 1, characterized in that Step (III) can be carried out at different ratios of the strong carboxylic acid, the organic solvent, and the thermoplastic material.

4. The production method according to claim 3, characterized in that The strong carboxylic acid used can be selected from trifluoroacetic acid, trichloroacetic acid, and 1,1,1,3,3,3-hexafluoro-2-propanol (HIFP).

5. The production method according to claim 3, characterized in that The organic solvent used can be selected from acetone, dichloromethane, toluene, xylene, phenol, and carbon tetrachloride.

6. The production method according to claim 4 or 5, characterized in that Preferably, trifluoroacetic acid (TFA) and dichloromethane (DCM) are used.

7. The production method according to claim 1, characterized in that In step (V), different classes of plasticizers can be used, and the plasticizers are selected from: - Adipic acid derivatives (di-n-hexyl adipate (DHA), heptyl nonyl adipate (79A), di-2-ethylhexyl adipate (DOA), diisodecyl adipate (DIDA), diisononyl adipate (DINA)); - Azelaic acid derivatives (di-2-ethylhexyl azelate (DOZ)); - Benzoic acid derivatives (diethylene glycol dibenzoate, dipropylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol isobutyrate benzoate); - Citric acid derivatives (tri-n-butyl citrate, acetyl tri-n-butyl citrate); - Epoxy derivatives (epoxidized soybean oil (ESO), epoxidized linseed oil (ELO), epoxytall oil-2-ethylhexyl ester); - Diol derivatives (diethylene glycol dinonanoate, triethylene glycol di-2-methylbutyrate); - Hydrocarbons (hydrogenated terphenyl, chlorinated paraffin (52 wt% Cl)); - Isophthalic acid derivatives (di-2-ethylhexyl isophthalate); - Oleic acid derivatives (butyl oleate); - Phosphate derivatives (tri-2-ethylhexyl phosphate (TOP), triphenyl phosphate (TPP), tricresyl phosphate (TCP), 2-ethylhexyl diphenyl phosphate, isodecyl diphenyl phosphate); -Phthalic acid derivatives (dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl octyl phthalate (BOP), diishexyl phthalate (DHP), diisooctyl phthalate (DIOP), di-2-ethylhexyl phthalate (DOP), (n-hexyl, octyl, decyl) phthalate (610), (n-octyl, decyl) phthalate (810P), diisodecyl phthalate (DIDP), ditridecyl phthalate (DTDP), butyl benzyl phthalate (BBP), alkyl benzyl phthalate, 261); - Ricinoleic acid derivatives (methyl ricinoleate, n-butyl acetyl ricinoleate, castor oil); - Sebacic acid derivatives (di-2-ethylhexyl sebacate (DOS)); - Stearic acid derivatives (n-butyl stearate); - Sucrose derivatives (sucrose acetate isobutyrate (SAIB)); -sulfonic acid derivatives ((o,p)-toluenesulfonamides, N-ethyl-(o,p)-toluenesulfonamides, alkyl sulfonates of phenol and methoxyphenol ) - Terephthalic acid derivatives (bis(2-ethylhexyl) terephthalate (DOTP)); - Trimellitic acid derivatives (tri(2-ethylhexyl) trimellitate (TOTM), heptyl nonyl trimellitate (79TM), triisononyl trimellitate (TINTM)); - Polyester, such as: adipic acid polyester (mol wt 6000), G-40, adipic acid polyester (mol wt 2000), 334F, azelaic acid polyester (mol wt 2200), 9720, sebacic acid polyester (mol wt 8000), G-25); and, - Terpenes and derivatives (camphor, methyl hydrogenated rosin).

8. The production method according to claim 7, characterized in that Di-n-butyl phthalate is preferably used.

9. The production method according to claim 8, characterized in that The glue is applied by means of a bird-shaped spreader.

10. A repair adhesive obtained by the method according to any one of claims 1 to 9, characterized in that Is ductile and flexible, has low permeability to water and gases, and exhibits chemical resistance and thermal stability up to 150 °C.

11. The repair adhesive according to claim 10, characterized in that Is waterproof and provides effective insulation.

12. The repair adhesive according to claim 11 or 11, characterized in that Has a minimum durability of 2 years.

13. Use of the repair adhesive according to any one of claims 10 to 12, characterized in that Is used as an anti-corrosion repair agent applied to any painted or unpainted metal surface in onshore and offshore areas.

14. The use according to claim 13, wherein The application is carried out in liquid form as a spray or in solid form as an adhesive tape.

15. The use according to claim 14, characterized in that For the application in liquid form, a solution of a dissolved thermoplastic material, preferably a solution of PET, is deposited on the metal surface by spraying or with the aid of a brush to form a polymer film after 5 minutes.

16. The use according to claim 15, characterized in that The solution comprises a solution directly applied consisting of a thermoplastic material dissolved in a strong carboxylic acid and an organic solvent.

17. Use according to claim 16, characterized in that The solution preferably has a composition of 20% (w / w) PET, 50% (v / v) TFA and 50% (v / v) DCM.

18. The use according to any one of claims 15 to 17, characterized in that Also includes using the solution as a gel that can be applied to the surface with the aid of a brush.

19. The use according to claim 14, characterized in that The application in solid form includes producing the adhesive according to the method according to any one of claims 1 to 9, directly applying the adhesive to a metal substrate, and adding an adhesive layer and a silicone paper liner to protect the adhesive.

20. The use according to claim 13, wherein The adhesive can be removed manually or by sandblasting.

21. The use according to claim 20, characterized in that The sandblasting can be, for example, hydroblasting or sandblasting with metal oxides.

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