IT201900011958A1 - Metallization of plastic substrates - Google Patents

Description

Description of the invention entitled "METALLIZATION OF PLASTIC SUBSTRATES"

The present invention refers to a metallization process of plastic substrates using the physical vapor deposition (PVD) technique which includes the chemical activation of the substrate, the coating of the same with a primer and the subsequent deposition of a metal layer. The invention also refers to metallized plastic substrates obtainable according to the process. The process of the invention can be applied in various fields, such as automotive, naval, household appliances, sanitary ware and bathroom furnishings, eyeglass frames, jewelery and costume jewelery etc.

More specifically, the aforementioned metallized plastic substrates can be used for the production, among others, of decorative and structural components for the interiors and exteriors of automobiles, decorative and structural components for the nautical sector, taps and fittings, finishing components for bathroom fixtures and fittings, finishing elements for household appliances, household and kitchen utensils, eyeglass frames, costume jewelery, etc.

BACKGROUND OF THE INVENTION

The technologies currently in use for the metallization of plastic substrates of commercial interest (called palting of plastic - POP) typically make use of galvanic baths to obtain chrome coatings (characterized by known environmental problems). The substrate typically used in these processes is the acrylonitrile-butadiene-styrene copolymer (ABS) for reasons related to the chemistry of the galvanic process.

Industrially, there are examples of metallization of plastic substrates (ABS and others) with the use of vapor deposition (PVD) techniques which typically consist of a surface cleaning / activation cycle with plasma, followed by the deposition of a primer. and the application of a metallic deposit.

In the case of polypropylene (PP) this cycle is not able to guarantee good performance of the metallized piece (in most cases chromed) due to the poor adhesion between the primer and the substrate (due to the low surface energy of the polypropylene itself).

Regarding the field of plastic metallization, European patent application EP2230328 relates to a method for forming a thin metal layer using a coating method and international patent application WO2009 / 006010 relates to a method for generating a metallic pattern on a substrate.

WO2008 / 021500 relates to compositions, methods and systems for the metallization of polymeric substrates obtained by controlled radical polymerization.

In addition, patent applications WO97 / 02313, WO2018 / 154505, JP2005231128, US2009 / 0269599 and CA2026999 describe a process of photography on the plastic substrate.

Patent US6048587 and patent applications WO2006075796 and JP2006316296 concern the use of polymeric resins (primers) in order to improve primer-metal compatibility.

Below we list some documents that describe the functionalization processes of the PP.

J. Balart et al., Materials and Design 33 (2012) 1–10, concerns the improvement of adhesion properties of polypropylene substrates by UV photografting surface treatment of methyl methacrylate (MMA).

The paper M. Pantoja et al., Applied Surface Science 280 (2013) 850–857, concerns the effect of the tetraethoxy silane coating on improving the adhesion of plasma treated polypropylene.

The paper J. Balart, V et al., Journal of Applied Polymer Science 116 (2010) 3256–3264, concerns the optimization of the adhesion properties of polypropylene thanks to the modification of the surface with the photografting of acrylic acid.

J. Balart et al., Journal of Materials Science 47 (2012) 2375–2383, concerns the surface modification of polypropylene substrates with UV photografting of MMA to improve surface wettability.

However, in none of these documents has the activation of the surface of PP been used to increase the adhesion between the layers in metallized substrates, and more specifically, in multilayer metallized materials for PVD.

DEFINITIONS

Unless otherwise defined, all the terms of the art, notations and other scientific terms used herein are intended to have the meanings commonly understood by those who are experts in the technique to which this description belongs. In some cases, terms with commonly understood meanings are defined here for clarity and / or for ready reference; the inclusion of these definitions in this description should therefore not be interpreted as representing a substantial difference with respect to what is generally understood in the art.

The term "plasma treatment" here refers to a physical treatment that changes the surface energy of a solid surface thanks to the interaction of this surface with a gas in a plasma state.

The term “UV Photografting” here refers to a photochemical surface treatment in which a solid surface is functionalized with active molecules covalently bonded through UV light radiation.

The terms "approximately" and "approximately" here refer to the experimental error range, which can occur in a measurement.

The terms "comprising", "having", "including" and "containing" are to be understood as open terms (ie the meaning "comprising, but not limited to") and are to be considered as a support also for terms such as "essentially consist of ”,“ consisting essentially of ”,“ consisting of ”or“ consisting of ”.

The terms "essentially consists of", "essentially consisting of" are to be understood as semi-closed terms, which means that no other ingredients that affect the new characteristics of the invention are included (optional excipients can therefore be included).

The terms "consists of", "consisting of" are to be understood as closed terms.

DESCRIPTION OF THE FIGURES

Figure 1. Outline of the UV photografting process of acrylates or methacrylates on the PP substrate.

Figure 2. Scheme of the seaming process of methacrylates on PP substrates.

Figure 3. a) FTIR-ATR spectra of pristine and activated PP and b) enlarged view of the region from 1900 to 650 cm <-1>.

Figure 4. Comparison of water contact angles on plasma treated PP_HEMA.

Figure 5. Microscope images of the chromate layer deposited on an epoxy primer loaded with n-SiO2 above 40% wt.

DESCRIPTION OF THE INVENTION

With regard to the metallization of plastics, in particular polyolefins, the Applicant has observed that the metallization of plastic substrates through the use of vapor phase deposition (PVD) which typically consists of a plasma-assisted cleaning / activation cycle, followed by deposition of a primer and application of a metallic deposit, is not applicable to polyolefin substrates due to poor adhesion to the substrate / primer interlayer.

The Applicant has also observed that the photografting process on the plastic substrate has not been previously described in combination with the PVD process.

The Applicant therefore posed the problem of preparing a new metallization process of plastic substrates that allows to significantly improve the substrate / primer adhesion thanks to the functionalization of the polyolefin and the selection of the most appropriate resin / primer (depending on the type of functionalization previously crimped on the surface of the polyolefin).

The inventors have experimentally found that the process of the invention allows to obtain components that exhibit excellent interlayer adhesions and therefore, compared to the PVD approach alone, greater mechanical durability of the metallized components.

In particular, in accordance with a first aspect, the present invention relates to a metallization process of plastic substrates comprising the following steps:

a) Provide a plastic substrate;

b) Subjecting this substrate to a plasma treatment in order to obtain a plasma activated substrate;

c) Subjecting this plasma-activated substrate to a UV photografting surface treatment of vinyl monomers, preferably acrylate or methacrylate monomers or other hydrophilic compounds, in order to obtain a functionalized surface;

d) Coating this functionalized surface with a photo- or heat-cross-linkable resin so as to obtain a coated substrate;

e) Depositing a metallic layer on the surface of this coated substrate so as to obtain a metallized plastic substrate.

Alternatively to the acrylate or methacrylate monomers, the hydrophilic vinyl monomers that can be used in the present invention can be selected from acrylamide (AM), N-vinylpyrrolidone (NVP), maleic anhydride (MAn), binary monomer of NVP / Man or a combination of the same.

Preferred examples of acrylates or methacrylates that can be used in the present invention are methyl methacrylate (MMA), vinyl methacrylate (VMA), glycidyl methacrylate (GMA), acrylic acid (AA), methacrylic acid (MAA), 2-hydroxyethyl methacrylate (HEMA) ) or combinations of these.

Surprisingly, the inventors have discovered that the process according to the invention allows to establish covalent and non-covalent interactions between the surface of the plastic substrate and the primer subsequently deposited above the substrate. As a consequence of this interaction, the substrate / primer adhesion is excellent. The process ends with the deposition of a metal layer (for example chromium, aluminum, etc.) above the primer for PVD, thus obtaining a metallized plastic component with excellent interlayer adhesion.

In a preferred embodiment of the invention, the plastic substrate is a polyolefin, preferably polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polybutene-1 (PB-1); more preferably polypropylene (PP).

The process of the invention also includes the step of pre-cleaning the plastic substrate with a washing solution, such as water and soap, solvents (for example acetone, isopropanol), preferably followed by a drying step.

In a preferred form, the plasma treatment step b) takes place in an atmosphere of air, preferably at a power ranging from 10 W to 300 W for a time interval ranging from 5 to 60 minutes, more preferably at a power of about 180 W and for about 15 min.

In another preferred form, the UV phtografting step c) is carried out in the liquid phase, preferably by depositing a solution of vinyl monomer, preferably an acrylate or methacrylate monomer, in an organic solvent together with a photo-initiator on the surface activated with the plasma, followed by UV activation.

Preferably, the UV photografting step takes place through an onepot reaction while the plasma activated surface is exposed to UV radiation in the presence of a solution containing both a vinyl monomer, preferably acrylate or methacrylate, and a photo-initiator.

The most used organic solvents are acetone, methanol, chloroform, carbon tetrachloride, cyclohexane, cyclohexanone, ethyl acetate, tetrahydrofuran or a mixture thereof, preferably acetone.

Preferred examples of photoinitiators that can be used in the present invention are benzophenone (BP), methylbenzoylformate (MBF), xanthone, preferably benzophenone (BP).

The volume ratio between the vinyl monomer, preferably acrylate or methacrylate monomer, and the organic solvent ranges from 1: 1 to 1:10, preferably the volume ratio is about 1: 4. The quantity of photo-initiator in the liquid phase is comprised between 1 wt% and 10 wt%, preferably 5 wt% with respect to the total weight of the vinyl monomer, preferably acrylate or methacrylate monomer.

In a preferred form, in step d) of the process of the invention, the photoo-thermo-crosslinkable resin is selected from the group formed by acrylic, polyurethane, ester and epoxy resins.

Preferred examples of resins that can be used in the present invention are monomers and prepolymers belonging to the brand Sartomer (ARKEMA), Adame (ARKEMA), Basonol (BASF), Sovermol (BASF), UNILAC UV (SIDASA), UV-LACK (Lankwitzer) , Desmodur (COVESTRO), Desmophen (COVESTRO), EPON (Hexion), Cyracure (Dow), Araldite (Huntsman).

Surprisingly, the inventors have found that the photo- or heat-crosslinkable resin (primer) has a similar functionality with the functionalized surface in order to ensure excellent compatibility (adhesion) through covalent and non-covalent interactions with the plastic substrate.

In another preferred form, the primer also includes the incorporation of an inorganic filler of nanometric dimensions (n-) (for example n-SiO2, n-TiO2, n-Ag, n-Fe2O3).

The inventors have advantageously noted that the incorporation of an inorganic filler in the primer improves the mechanical properties of the surface layer. In a preferred form, the deposition step of a metal layer e) is carried out by means of PVD above the surface of the previously deposited primer. Preferably, the metal which can be used in the present invention is selected from chromium, aluminum, zirconium, copper, nickel, titanium, carbon nitride, a combination thereof, by reactive deposition.

Preferably the deposition rate of the thin metal layer is between 0.1 and 100 nm / min, more preferably between 5 and 50 nm / min, more preferably about 13 nm / min, for a period of time from 1 to 60 min, preferably 30 min. Preferably, the thickness of the metal layer is comprised between 200 and 1000 nm, more preferably about 400 nm.

The process can also include the optional step f) of post-deposition of a further ceramic layer (SiOx) on the metal substrate thanks to a chemical vapor deposition (CVD) which allows to alter the surface properties of the metal layer (for example wettability, cleanability, hardness, etc.).

According to a second aspect, the present invention relates to metallized plastic substrates obtainable according to the process of the invention.

In accordance with a third aspect, the present invention relates to the use of metallized plastic substrates described above, for the production of decorative and structural components for the interiors and exteriors of automobiles, of decorative and structural components for the nautical sector, taps and fittings. , finishing components for sanitary ware and bathroom furniture, finishing elements for appliances, household and kitchen utensils, eyeglass frames, costume jewelery, etc.

EXPERIMENTAL SECTION

1. Materials and methods

1.1 Materials

Substrate

- Polypropylene (PP)

Functionalizing

- Methyl methacrylate (MMA)

- Vinyl methacrylate (VMA)

- Glycidyl methacrylate (GMA)

- Methacrylic acid (MAA)

- 2-hydroxy ethyl methacrylate (HEMA)

Components of the acrylic resin

- Photoinitiator: Omnirad TPO-L Ethyl (2,4,6-trimethylbenzoyl) -phenyl-phosphinate - Monomers:

tris (2- (acryloxy) ethyl) isocyanurate (TAEI)

hexane-1,6-diol diacrylate (HDDA)

pentaerythritol tetraacrylate (PETA)

Epoxy resin components

- Photoinitiator: Omnicat 4404.4-dimethyl-diphenyl iodonium hexafluorophosphate - Monomer: 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexane carboxylate (ECC)

- Filler: nano silica (n-SiO2)

Polyurethane resin components

- Isocyanate: Desmodur L 75 Toluene diisocyanate (TDI), 75 wt% in ethyl acetate

- Polyol: Desmophen 1200 polyol polyester

1.2 Procedures

The metallization process of PP is conducted in accordance with the process of the invention, which can be summarized as follows:

- Preparation of the substrate: cleaning with a washing solution (water and soap, solvents such as acetone, isopropyl alcohol), drying and treatment with air plasma;

- Functionalization of the PP surface: UV grafting of functional methacrylates in liquid phase (solution of the active molecule in photoinitiator acetone) on the PP surface;

- Primer deposition: coating of the functionalized PP surface with a photo- or thermo-crosslinkable resin (primer) which has a similar functionality to that presented by methacrylate in order to guarantee excellent compatibility (adhesion) thanks to the covalent and non-covalent interactions covalent between primer and PP;

- Metallization: deposition of a metallic layer (preferably chromium) with PVD on the surface of the primer, previously deposited.

1.2.1 Plasma treatment

PP substrates are treated with air plasma for 15 minutes at a power of 180 W.

1.2.2 Photografting

The acrylates used as functionalizers (i.e. MMA, VMA, GMA, HEMA and VMA) were dissolved in acetone with a 1: 4 volume ratio. After the homogenization of the solution, a 5% by weight benzophenone was added (with respect to the total weight).

A certain amount of functionalizing solution containing the photoinitiator was deposited on the PP substrate. In order to create a thin layer of liquid, a quartz glass was fixed on top of the system under adequate pressure. Then the assembled unit was irradiated under UV light (high pressure mercury lamp, 1 kW) from the top side at room temperature for 15 minutes (Figure 1). After UV radiation, the samples were washed with acetone and distilled water to remove non-functionalized acrylates. Finally, the washed samples were dried at room temperature before their characterization.

1.2.3 Deposition of chromium

The Leybold LH Z400 apparatus was used to deposit a thin layer of chromium at a deposition rate of 13 nm / min (power of 35 W) for 30 minutes. The a posteriori control of the desired chromium thickness (about 400 nm) was ensured by measurements carried out with the stylus profilometer.

2. Results and discussion

2.1. Activation of the PP

As a subsequent activation process to the traditional activation of PP with plasma treatment, a photo-activated radical anchoring step is proposed. This process consists in the establishment of a covalent bond of methacrylates to the PP surface previously activated by plasma. Figure 2 shows a diagram of the anchoring process of the methacrylates on the surface of the PP. In this example, the technical feasibility of using different functional anchoring monomers, such as MMA, VMA, GMA, MAA and HEMA, was tested. The sample thus produced was called PP_X where X refers to the acronym of the methacrylate used.

FTIR-ATR analyzes (Figure 3) of functionalized PP were conducted and compared with pristine PP to verify whether the methacrylates bonded to the surface. As can be seen, the pristine PP shows only the characteristic signals of the vibration of the C-H stretching in the range 3000-2800 cm <-1>, the vibration of the symmetrical deformation of the –CH2 at 1455 cm <-1> and the vibration of the deformation symmetrical of –CH3 at 1377 cm <-1>. These signals can be observed in all activated PP surfaces.

After the functionalization process all the spectra show the signals related to the stretching vibration of the C = O group. In the case of alkyl esters (e.g. PP_MMA, PP_GMA and PP_HEMA), the carbonyl signal is centered at 1730 cm <-1>. However in the case of vinyl esters (PP_VMA) and carboxylic acid (PP_MAA), these signals are shifted to 1740 and 1700 cm <-1> respectively. Furthermore, the vibration of the C-O stretching of the ester groups can be observed at 1275 cm <-1> for saturated esters and at 1260 cm <-1> for PP_VMA. Furthermore, the intensity of the region associated with the vibration of the skeleton of the CH3 and CH2 groups (1200-1130 cm <-1>) increases in all surfaces of activated PP, with minimal differences between them due to the presence of different functional groups nearby. . Finally, some other signals related to the incorporation of specific groups were recorded, such as the symmetrical stretching vibration of the epoxy ring at 910 cm <-1> for PP_GMA, the generic stretching vibration of the O-H groups in the 3700-3550 cm region <-1> for PP_MAA and PP_HEMA, the C-O stretching in primary alcohols at 1080 cm <-1> for PP_HEMA and the vibration of the C = C bond stretching in vinyl esters at 1645 cm <-1> for PP_VMA. Hence, it can be confirmed that all methacrylates were effectively bonded to the surface of the plasma treated PP.

The wettability properties of the activated PP surfaces were investigated using the measurements of the contact angle with water (H2O) and diiodomethane (DIM) as liquid. Furthermore, it is possible to calculate the surface energy of the treated PP surfaces from the contact angles using the OWRK method (Owens, Wendt, Rabel and Kaeble). Table 1 shows the contact angles of water (θH2O) and diiodomethane (θDIM) and the results of the surface tension (γ) and the relative dispersive (γ <d>) and polar (γ <p>) components. The initial values of the contact angle for the pristine PP using H2O and DIM were 95.5 ° and 57.1 °, respectively, which indicate a clear hydrophobic behavior and a low total surface energy with a greater dispersive component. In the case of PP_MMA and PP_VMA, the slightly lower contact angles can be attributed to a small increase in the polarity of the PP surface due to the ester group, as the terminal functional group (-CH3 for PP_MMA and CH2 = CH2) does not differ significantly from that shown by PP (-CH3). On the contrary, the hydrophilicity of PP_GMA, PP_MMA, and PP_HEMA significantly increases due to the presence of a greater number of polar hanging groups. Furthermore, the total surface tension of all activated PP surfaces was found to be greater than that reported by untreated PP.

Table 1. Contact angles of water (H2O) and diiodomethane (DIM), total surface tension (γ <tot>) and corresponding polar (γ <p>) and dispersive (γ <d>) components.

2.2 Adhesion of the primer on PP substrates

In the field of plastic metallization for PVD, primers (polymer layers between the substrate and the metal) are generally required in order to create a homogeneous, crack-free surface on which to deposit the metal. In the present invention, three different types of primers have been selected (i.e. acrylic, epoxy and urethane), deposited on both non-activated and activated PP substrates. Among these primers, the acrylic and epoxy primers are crosslinkable with UV (respectively through the radical process and through the cationic process) while the urethane-based system requires thermal crosslinking.

Accession measures

The adhesion between the layers is of great interest in multi-layer materials. In this regard, the adhesion strength of the primers to the different PP substrates was evaluated through pull-off tests. In a first step, the adhesion capacity of the acrylic resin on the untreated PP was measured, and an adhesion strength of 0.68 MPa and complete detachment of the primer from the substrate in the tested region was found. This value was slightly increased to 1.05 MPa when PP_plasma was used as a substrate. However, a complete detachment of the primer was also seen in this case. The same behavior was also observed when epoxy and urethane primers were used instead of acrylic. The slight increase in adhesion between plasma and PP when plasma treatment is applied could be related to the formation of non-covalent interactions between the primer and the substrate. The adhesion of the acrylic resin on two substrates treated with the process described in the present invention (PP_MMA and PP_VMA) was then tested, causing in both cases a mechanical fracture in the tested area (table 2).

The same results were observed for the adhesion of the epoxy resin with PP_GMA, PP_MAA and PP_HEMA, and the urethane primer with PP_MAA and PP_HEMA. The significant increase in the adhesion properties of the PP bonded primer may indicate the formation of stronger covalent bonds than the cohesive forces of PP.

Table 2. Visual analysis of substrates of a) untreated PP, b) PP_plasma, c) PP_MMA and d9 PP_VMA coated with the acrylic resin after the pull-off test.

Stability of surface activation over time

The good adhesion between the functionalized PP and the primers should be due to the good stability of the organic molecules bound to the surface compared to that found on substrates treated only with air plasma (PP_plasma). To compare the stability of PP activation using both procedures (air plasma treatment only, air plasma treatment followed by UV photografting treatment as described in the present invention), the contact angles of the PP were compared. water on PP_HEMA with those exhibited by PP treated only with air plasma, monitoring their progress for several hours. As can be seen from Figure 4, PP_plasma has a contact angle smaller than that of PP_HEMA during the first 3 hours, but the deactivation of its surface appears already significant after less than 24 hours and almost complete after 80 hours. On the contrary, the contact angle of PP_HEMA does not vary significantly during the same period of time, confirming the stability over time of the surface activated with photochemical treatments of the PP substrates.

Therefore, it can be concluded that the incorporation of functional monomers grafted to the surface of PP substrates through the UV photographting process is a simple strategy to ensure excellent stability over time of the surface functionalization of the substrate, improving the adhesion capacity of many different primers.

2.3 deposition of chromium

Chromium was deposited by PVD on PP substrates coated with different primers (for example acrylic, epoxy and urethane resins) and the final appearance of these materials is regular and equally bright on all surfaces. Profilometer measurements confirmed that in all cases the thickness of the chromium layer is about 400 nm.

In order to determine the presence of cracks on the chromium layer, the samples obtained were observed under an optical microscope. None of the samples show cracks or imperfections, regardless of the primer used.

In order to study the adhesion capacity of Cr on primers, pull-off tests were conducted on chromed materials. Initially, the adhesion of Cr on the primers (for example acrylic, epoxy and urethane) deposited and cross-linked on PP_plasma was determined, observing the complete detachment of the primer from the substrate. The same test was repeated on all crosslinked primers on the appropriately functionalized PP substrates. In these cases the mechanical fracture of the PP was observed, as it was observed in the adhesion tests conducted without a Cr layer. It can be concluded that the adhesion of Cr is excellent on all the primers studied.

The presence of covalently bonded links between the PP and the primer therefore significantly improves the adhesion properties of the multilayer material, which in these cases has an even greater adhesion force than the cohesive forces of PP.

Improvement of mechanical properties

In order to improve the mechanical properties of the outermost layer, an inorganic filler (for example n-SiO2) was incorporated into the primer. The epoxy primer was selected and n-SiO2 was dispersed into the resin before crosslinking with a concentration of up to 40 wt%. The primer thus obtained was called Epoxy_X%, in which X refers to the concentration of n-SiO2 expressed in wt%. Microindentation tests were conducted on epoxy resins loaded with n-SiO2 to study the surface hardness of the materials based on the Vickers indentation hardness (HIT), the indentation modulus (EIT) and the maximum indentation depth (hmax). The incorporation of the inorganic filler shows a clear improvement in the strength of the primer, increasing HIT and EIT up to about 160 N / mm <2> and 2.4 GPa respectively, when compared with the unfilled epoxy resin and the one containing a content of 40 wt % of n-SiO2. The results are shown in Table 3.

Table 3. Microindentation results obtained on epoxy primers loaded with n-SiO2.

The influence of the incorporation of n-SiO2 on the presence of cracks or defects on the chromated PP was studied under an optical microscope. As can be seen from Figure 5, only the epoxy resin loaded with 40 wt% of n-SiO2 has appreciable defects on the Cr layer. Therefore, despite the increase in the mechanical properties of the resin, the incorporation of n-SiO2 fillers above 30 wt% is not recommended.

3. Conclusions

The activation of PP surfaces through functionalization with different methacrylates by means of UV radiation is confirmed by FTIR and by tests on contact angles. The effect of the photografting process on the adhesion between PP and the primers was found with pull-off tests. In cases of plasma activated PP, the adhesion between the substrate and the primer is relatively low regardless of the primer used and a complete detachment of the primer from the PP is observed. However, a marked improvement in adhesion strength was observed when PP was activated by photografting, evidence that could be caused by the formation of covalent bonds between PP-primers and the long-term stability of this process compared to that of plasma treatment. . Finally, the PP substrates were chromed by PVD, obtaining a bright and homogeneous Cr surface in which, in no case, are cracks present. The adhesion strength of the PP-Primer-Cr multilayer material was determined with pull-off tests, finding a trend similar to that observed for non-chromed substrates. Furthermore, the improvement of mechanical properties with the addition of a dispersion of inorganic fillers (e.g., n-SiO2) in the primer has been demonstrated thanks to microindentation tests.

In conclusion, the results clearly demonstrate that the process for the metallization of PP of the present invention, based on the chemical activation of the substrate with a process of photografting and a further deposition of a primer, is more efficient than the already existing methods thanks to the improvement of the PP-primer adhesion. Furthermore, this process allows to improve the long-term stability of the surface activation and allows to select the primer in an arbitrary manner according to the type of functional monomer used during the photografting process in order to maximize its adhesion to the substrate.

Claims (19)

CLAIMS 1. A substrate metallization process comprising the following steps: a) Provide a plastic substrate; b) Subjecting this substrate to an air plasma treatment in order to obtain a plasma activated substrate; c) Subjecting this plasma-activated substrate to a UV photografting surface treatment with vinyl monomers, preferably acrylate or methacrylate monomers or other hydrophilic compounds, in order to obtain a functionalized surface; d) Coating this functionalized surface with a photo- or heat-cross-linkable resin so as to obtain a coated substrate; e) Depositing a metallic layer on the surface of this coated substrate so as to obtain a metallized plastic substrate. The process according to claim 1, wherein the plastic substrate is a polyolefin, preferably polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polybutene-1 (PB-1), more preferably polypropylene (PP). The process according to claims 1 and 2, further comprising the step of pre-washing the plastic substrate with a washing solution, preferably followed by a drying step. The process according to any one of claims 1 to 3, wherein step b) is carried out with air plasma, preferably at a power of between 10 W and 300 W for a period of time from 5 to 60 min, more preferably at a power of about 180 W for about 15 min. The process according to any one of claims 1 to 4, in which the UV photografting step c) takes place in the liquid phase, preferably by depositing a solution of a vinyl monomer, preferably an acrylate or methacrylate monomer, in an organic solvent together to a photoinitiator on the surface of the plasma-activated substrate. The process according to claim 5, wherein the hydrophilic vinyl monomer is selected from acrylamide (AM), N-vinylpyrrolidone (NVP), maleic anhydride (MAn), binary monomers NVP / MAn, methyl methacrylate (MMA) vinyl methacrylate (VMA ), glycidyl methacrylate (GMA), acrylic acid (AA), methacrylic acid (MAA), 2-hydroxyethyl methacrylate (HEMA) and combinations thereof. The process according to claim 5 or 6, wherein the organic solvent is selected from the group comprising acetone, methanol, chloroform, carbon tetrachloride, cyclohexane, cyclohexanone, ethyl acetate, tetrahydrofuran, and a mixture thereof, preferably acetone . The process according to any one of claims 5 to 7, wherein the volume ratio between the vinyl monomer, preferably acrylate or methacrylate monomer, and the organic solvent is from 1: 1 to 1:10, more preferably the volume ratio is approximately 1: 4. The process according to any one of claims 5 to 8, wherein the photoinitiator is selected from the group comprising benzophenone (BP), methylbenzoyl formate (MBF) and xanthone, preferably benzophenone. The process according to any one of claims 5 to 9, wherein the amount of photoinitiator in the liquid phase is comprised between 1 wt% and 10 wt%, preferably 5 wt% with respect to the total weight of the vinyl monomer, preferably acrylate monomer or methacrylate. The process according to any one of claims 1 to 10, wherein the photo- or thermo-crosslinkable resin of step d) is selected from the group comprising acrylic, polyurethane, ester and epoxy resin. 12. The process according to any one of claims from 1 to 11, in which the coating step d) further comprises the incorporation of an inorganic filler, preferably n-SiO2, n-TiO2, n-Ag or n-Fe2O3. 13. The process according to any one of claims from 1 to 12, in which step e) takes place for PVD. The process according to any one of claims 1 to 13, wherein the metal layer is of chromium, aluminum, zirconium, copper, nickel, titanium, carbon nitride or combinations thereof. The process according to any one of claims 1 to 14, wherein the deposition rate of the metal layer is between 0.1 and 100 nm / min, preferably between 5 and 50 nm / min, more preferably about 13 nm / min, for a period of time from 1 to 60 min, preferably 30 min. The process according to any one of claims 1 to 15, wherein the thickness of the metal layer is between 200 and 1000 nm, preferably about 400 nm. The process according to any one of claims 1 to 16, further comprising a post-treatment step f) obtained by depositing a ceramic layer on the aforementioned metallized substrate. 18. A metallized plastic substrate obtainable according to the process of any one of claims 1 to 17. 19. Use of the metallized plastic substrate according to claim 18, for the production of decorative and structural components for interior and exterior of automobiles, decorative and structural components for the nautical sector, taps and fittings, finishing components for sanitary ware and bathroom furniture, elements finishing for appliances, household and kitchen utensils, eyeglass frames or costume jewelery.