Patent Application
20230399523
The present invention relates to an aqueous paint composition comprising an acrylic polymer emulsion anionically stabilized at basic pH with a volatile base and containing self-crosslinking functionalities, an epoxy-polyamine adduct, and a high boiling glycol-ether.
The film obtained by the aqueous paint composition according to the present invention as well as the use thereof in horizontal road marking are also described.
Horizontal road marking was born in the early 1900s and plays various roles: from optical orientation tool to regulator of traffic flow; from informing drivers about oncoming dangers to driving restrictions.
Consequently, horizontal road marking plays a primary role in road safety, by reducing the number of deaths and injuries.
Road marking efficiency and durability are therefore required by both road users and road authorities. From the users' point of view, the contrast of color and luminance with the road surface are properties that should be maximized (Horberry et al., Transportation Research Part F Traffic Psychology and Behaviour 2006, 9(1):77-87). The selection of the type of materials for road marking by road administrators depends instead on many factors, including desired duration, required visibility, price and local regulations.
All systems used for this type of application consist of a pigmented coating containing partially incorporated retro-reflective elements such as glass beads.
In addition to durability and functionality of road markings, ease of application and the effect on human health and environment are primary considerations for their selection. Horizontal road marking painting systems can be divided into: bicomponent materials of epoxy, polyurethane or unsaturated acrylic nature, which cure due to the chemical reaction that occurs at the site of application, thermoplastic powders based on hydrocarbon or alkyd resins that require heat for application on the road, paints that dry upon evaporation of the dissolving solvent medium and water-based paints that harden on the application site due to the loss of neutralizing agent (e.g. ammonia).
Thermoplastic materials are essentially solvent-free and, although some of the resins required for their production are from renewable natural resources, the need for double heating (production-application) significantly increases their environmental impact.
Certain two-component systems also need heating and have toxicity issues related to the use of epoxy resin, isocyanates, or acrylic monomers as well as hazard issues due to the use of organic peroxides as reaction catalysts in situ.
In the case of solvent-based paints (solventborne), these are traditionally products that include organic binders of various nature: alkyd binders, alkyd binders in combination with chlorinated rubbers or acrylic binders, soluble in organic solvent. The solvent phase of this system results in a significant release of VOCs (volatile organic compounds) into the atmosphere.
The environmental impact of these exhalations is considerably worsened due to the photochemical decomposition that these substances undergo in the atmosphere.
During their decomposition in the atmosphere, VOCs interact with nitrogen oxides (NOx), significantly increasing ozone formation. Ground-level ozone is an important lung irritant, recognized worldwide as one of the key pollutants responsible for smog. Stability over time of solventborne paint products for road marking is on average poor, they can in fact show sedimentation and viscosity increase issues. The application of the solvent-based product generates a coating that does not exceed 400 μm. In fact, thicker films tend to form a surface skin that slows down the coating evaporation, thus requiring much longer time to dry, even in favorable conditions. The application of solventborne paints may be carried out at room temperatures from 5 to 40° C. and with a surface temperature below 50° C. Drying of such paints is strongly influenced by air, surface temperature, building of applied films, and by the mixture of solvents used.
Conversely, water-based paints have a significantly reduced impact on human health and the environment compared to other materials.
Attention to the environment has therefore pushed paint manufacturers to prefer water-based (waterborne) products.
The first waterborne paint products were marketed in the USA in the early 1980s.
These products were quite similar to solvent-based coatings. Their setting was only linked to the solvent phase (water) loss which automatically led to drying (lacquer paints). However, they suffered from a very long drying time and a parallel development of resistance to washout, severely affected by the weather conditions. In the 1990s, the so-called “quick-set” technology was introduced, which introduces ammonia into the polymer forming the binder portion of these waterborne paint products. The polymer irreversibly solidifies when the pH drops, which occurs due to ammonia evaporation.
However, also traditional waterborne systems have the drawback of not being able to be applied in prohibitive atmospheric conditions, such as very high humidity and temperatures below 10° C.
It is therefore apparent the need to provide new water-based products being less sensitive to temperature and able to withstand adverse environmental conditions, such as snow and heavy rain, which retain the characteristics of resistance to wear, excellent visibility and slip resistance obtainable using traditional solvent-based or thermoplastic products, but at the same time have a low environmental impact.
In relation to paint products for horizontal road marking, the inventors have observed that the obvious ecological dictates and legislation pose difficult formulation problems for paint manufacturers in order to reduce VOCs emissions when drying solvent-based products or to avoid heating of the thermoplastic products which, among other things, lead to undesirable increases in costs.
An object of the present invention is to provide new waterborne paint products which allow a film formation on the road surface which is particularly resistant to foot traffic, and having mechanical resistance performance above the standard.
A further object of the present invention is to provide new paint products which maintain or improve the performance of traditional solvent-based or thermoplastic products while having, at the same time, a low environmental impact.
The inventors have surprisingly found that the combination of substances present in the aqueous composition according to the invention accelerates the first coagulation phase and at the same time catalyzes the crosslinking process, without compromising the coalescence phase.
The main objects described above are achieved with an aqueous paint composition according to claim 1, with use thereof in horizontal road marking according to claim 14, with a coating film according to claim 15, and with a method for reducing the curing time according to claim 16.
Unless otherwise defined, all terms of the art, notations, and other scientific terms used herein are intended to have the meanings commonly understood by those skilled in the art to which this description belongs. In some cases, terms with meanings that are commonly understood are defined herein for clarity and/or ready reference; therefore, the inclusion of such definitions in the present description should not be construed as being representative of a substantial difference with respect to what is generally understood in the art.
The terms “approximately” and “about” used in the text refer to the range of the experimental error that is inherent in the execution of an experimental measurement.
The terms “comprising”, “having”, “including” and “containing” are to be intended as open-ended terms (i.e., meaning “comprising, but not limited to”), and are to be considered as a support also for terms such as “consist essentially of”, “consisting essentially of”, “consist of”, or “consisting of”.
The terms “consists essentially of”, “consisting essentially of” are to be intended as semi-closed terms, meaning that no other ingredients affecting the novel features of the invention are included (optional excipients may therefore be included).
The terms “consists of”, “consisting of” are to be intended as closed terms.
The term “acrylic polymer” is intended to indicate a pure or a styrene-modified acrylic polymer.
The term “anionically stabilized” is intended to indicate a polymer carrying a functional group in the chain which expresses an anionic charge (e.g.: R—COO−) neutralized with a countercathion (e.g.: NH4+). Once neutralized, the anionic functional group confers to the system sufficient polarity, necessary to stabilize the suspension of the polymeric colloidal particles. The release of the countercathion (volatile base) results in destabilization of the colloidal suspension and subsequent coagulation, consequently triggering the particle coalescence process.
The term “volatile base” is intended to indicate a base which should be volatile enough to be released under air-drying conditions.
The term “epoxy-polyamine adduct” is intended to indicate a polymer containing at least the following four blocks:
The term “C1-C6 alkyl”, in the present context, refers to a branched or linear hydrocarbon containing 1 to 6 carbon atoms. Examples of C1-C6 alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl.
The term “high boiling glycol-ether” is intended to indicate a compound having a boiling point comprised between 225 and 250° C.
The term “self-crosslinking functionalities” is intended to indicate the reactive functionalities of a polymer necessary for its curing/crosslinking process (polymerization/polycondensation), without the need for further reagent additions.
The term “Minimum Film Forming Temperature” (MFFT) is to be intended as the minimum film forming temperature (MFFT) of a paint or coating and is the minimum temperature at which the product, when applied to a substrate, coalesces in the form of a homogeneous and clear film.
An object of the present invention is represented by an aqueous paint composition comprising:
Preferably, the acrylic polymer has a Minimum Film Forming Temperature (MFFT) comprised between 0 and 40° C., preferably between 10 and 20° C.
Preferably, the acrylic polymer is anionically stabilized at a basic pH of between 8 and 11.
Preferably, the acrylic polymer is in the form of an anionic colloid.
Preferably, the volatile base which may be used in the present invention is selected from ammonia, morpholine, 2-methylaminoethanol, 2-dimethylaminoethanol, N-methylmorpholine and ethylenediamine. More preferably ammonia.
The self-crosslinking functionalities are obtained by introducing monomers into the chain, or external reactants, having a reactivity attributable to Michael's synthesis (diketo with amine or diketo with hydrazide), as shown in the following scheme:
Preferably, the most widely used reactive system for the functionalization of acrylic polymers is the DAAM-ADH system (Diacetone acrylamide, DAAM, and Adipic acid dihydrazide, ADH).
The diketone functionalities of the acrylic polymer (for example DAAM) react with an amine or a hydrazide that is externally added to the polymer (for example ADH).
In a preferred embodiment, the acrylic polymer containing self-crosslinking functionalities further comprises a polyamine polymer, which functions as a coagulant. The nature of said polyamine polymer is different from that of the epoxy-polyamine adduct; preferably the polyamine polymer is polymerized from a mixture of monomers comprising at least one acid monomer and at least one amino monomer. Acid monomers suitable for preparing the polyamine polymer are acrylic acid, methacrylic acid, and mixtures thereof.
Some of the amino monomers suitable for preparing the polyamine polymer include alkylaminoalkyl esters or amides of unsaturated acids, such as acrylic acid or methacrylic acid.
The polyamine polymer may be mixed with the acrylic polymer, or the two polymers may be crosslinked to each other.
Examples of polyamine polymers which can be used in the present invention and are commercially available, are described in European Patent Applications EP0409459, EP0811663 and EP0832949, the contents of which are fully incorporated herein by reference.
Without wishing to be bound by any interpretive theory, the inventors believe that the loss of ammonia, due to evaporation upon contact with air, triggers the reactivity of the coagulating polymer which, by protonating itself, reacts with the stabilizing anionic charges of the colloid surface, neutralizing them. The coagulating polymer causes the rapid loss of sensitivity to water during the first drying phase (early rain resistance).
Preferred examples of acrylic polymers which can be used in the present invention and are commercially available, are the following products:
The preferred acrylic polymers are E5, E17, E25, E30, E31, E34 and E35.
For the purposes of the present invention, epoxy-polyamine adducts having a structure that can be schematized as follows may be used:
In particular:
wherein n is comprised between 1 and 15; R1, R2, R3 and R4, which are the same or different, are independently selected from H, alkyl, amino or amide radicals.
AR consists of a prevalence of diphenyl aromatic radical, wherein R consists of ═C(—CH3)2 (Bisphenol A) or —CH2-(Bisphenol F), combined with a minority percentage of linear or branched alkyl radicals.
In the structure in question, the H of the HNR1R2 and the HNR3R4 radical, that will react with the adjacent oxirane radical to generate “the adduct”, R1R2N-adduct-NR3R4, is represented.
In particular:
The epoxy-polyamine adduct may be prepared from:
Typical examples of bis-epoxy compounds are the diglycidyl ethers of Bisphenol A and F, such as the resins: Ankarez®, Araldite®, Bekopox®, Epikote®, Epilox®, Eponac®, Eposir®, Epotec®, Epon®.
Some examples of polyethoxylated or polypropoxylated amines (e.g. Jeffamine®) that may be used are:
Preferably, the epoxy-polyamine adduct has an FT-IR spectrum with a characteristic peak at about 829 cm−1. Said peak is due to the presence of para-substituted phenyl radicals, typical of Bisphenol A or F.
The epoxy-polyamine adducts are described in the following literature references:
Preferred examples of epoxy-polyamine adducts which can be used in the present invention and are commercially available, are the following products:
The preferred epoxy-polyamine adducts are PA30, PA31, PA32, PA35, PA40, PA42, PA44 and PA46. PA30, PA35, PA40 and PA46 are the ones which gave optimal results.
In the composition according to the invention, the epoxy-polyamine adduct as the function of adhesion promoter.
For the purposes of the present invention, the following high boiling glycol-ethers may be used (provided by way of example but not of limitation): Diethylene glycol mono butyl ether (DB), Dipropylene glycol n-butyl ether (DPnB), Propylene glycol phenyl ether (PPh), Tripropylene glycol mono methyl ether (TPM).
Preferred examples of high boiling glycol-ethers which can be used in the present invention and are commercially available, are DB and DPnB.
In the composition according to the invention, the high boiling glycol-ether functions as a coalescer.
Advantageously, the addition of the coalescer has the function to help polymer filming in colloidal form and adequately regulate the drying time of the applied coating.
Coagulation produces the precipitation of the polymer and its separation from the aqueous medium which, at this point, remains free to volatilize. The coagulated polymer reaches faster the necessary inter-colloidal distance (between particles) for the coalescence process to take place.
The direct consequence of this acceleration is a more rapid loss of sensitivity to water (resistance to washout). Complete curing and the final performance of the film remain dependent on the polymer intrinsic reactivity expressed during the crosslinking process.
The aqueous paint composition according to the invention may include one or more ingredients selected from pigments, fillers, antibacterial agents, and other specific additives.
Pigments are essential for the required final coating color. The pigment may be selected both on the basis of its characteristics for formulation use, and its behavioral/performance characteristics once inside the final coating. For the formulation/production aspect, a micronized pigment, dispersible in the aqueous medium without the need of considerable shear effort, is preferable. As for the final performance, a base material with excellent colorimetric yield and retention of the same during exposure to external agents will be preferable. Examples of pigments that can be used in the present invention are titanium dioxide, Yellow 65 Mono-azo CAS 652-34-3; Arylide Yellow 74 CAS 6358-31-2; Anthanthrone Red 168 CAS 4378-61-4; Phthalocyanine Green 7 CAS 1328-53-6; Phthalocyanine Blue 15 CAS 147-14-8.
Fillers (extenders) of various kinds are selected to optimize rheology, physical performance of the coating, and possibly to contain the costs determined by the pigmentation. The preferable extenders for rheology adjustment are micronized minerals with low oil absorption. The specific weight and particle size will affect the sedimentation of the product in tin and the resistance to abrasion. Other extenders that can positively influence the coating duration are micronized silicates that partially take part in the polymer film formation. Examples of extenders that may be used in the present invention are carbonates (CaCO3), barium sulfate, and silicates such as: kaolin, mica, talc, and silicas.
The aqueous paint composition according to the invention may include further specific additives, aimed at optimizing the paint product in the production process phase as well as its behavior during the application and drying phases. Examples of specific additives are dispersant additives, antifoam additives, anionic and non-ionic surfactants, and rheological additives.
Dispersant additives, such as polyacrylates, in the fillers and pigments dispersion phase.
Surfactants of various kinds to adjust the system surface tension, helping the dispersant in “wetting” the charges during dispersion and improving product applicability on the surface to be coated (surface wetting).
Antifoam additives that may be used in all those steps of the production process that can create foam stabilization.
Antibacterial agents are additives that are designed to prevent the development of bacterial contamination (mold, etc.). The choice of the appropriate additive is preferably made based on the nature of the binder and tested in the stability tests of the product in tin over time.
Examples of antibacterial agents that are commercially available are 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride combined with a stabilizer (sodium bicarbonate), “DOWICIL 75” from DOW Chemical, or the 1,2-benzisothiazolin-3-one in a 20% aqueous solution of dipropylene glycol, “Proxel GXL” from Lonza.
In a preferred embodiment, the volume ratio between organic binder and pigments/extenders, called Pigment Volume Concentration (PVC), is comprised between 50 and 70.
This ratio has a decisive influence on the application behavior of the paint product and consequently on the performance of the coating obtained.
In a further preferred embodiment, the ratio between acrylic polymer and epoxy-amino adduct ranges from a minimum of 96/4 parts by weight (pbw) to a maximum of 86/14 parts by weight (pbw), preferably 90/10 pbw, based on the total dry residue. Preferably, the amount of high boiling glycol-ether, calculated on the total of the polymer in the formula (i.e. acrylic polymer and epoxy-amino adduct) ranges from a minimum of 10 parts by weight (pbw) to a maximum of 40 parts by weight (pbw), preferably 25 pbw, out of 100 parts by weight.
The inventors have surprisingly identified a combination of substances that accelerate the first coagulation phase and at the same time catalyze the crosslinking process, without the coalescence phase being minimally compromised.
A further object of the present invention is represented by the use of the aqueous paint composition according to the invention for horizontal road markings.
A further object of the present invention is represented by the coating film obtained by applying an aqueous paint composition according to the invention to a road surface, followed by evaporation of the aqueous medium.
An accelerated filming-crosslinking is generated in the film which rapidly brings the coating to a physical condition of complete resistance to foot traffic.
The resulting film also shows mechanical resistance performances above the standard.
A further object of the present invention is represented by a method for reducing the curing time of a road marking on a road surface comprising:
The following examples have the aim to further illustrate the invention without however limiting it.
Materials
Methods
Standard Test for Measuring the Drying Rate of the Applied Paint Film (ASTM D711-89 (1998), Standard Test Method for No-Pick-Up Time of Traffic Paint)
A calibrated weight, cylindrical in shape with two rubber rings placed on the circumference at a precise distance, is allowed to roll through a guide (slide) on a panel coated with the paint product to be tested.
The time (minutes) necessary for the film not to leave imprint on the rubber rings surrounding the cylinder is measured.
Standard Test for Abrasion Resistance of Organic Coatings (ASTM D4060-10, Standard Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser)
The paint product is applied on special panels which, after having undergone the complete drying process, are placed on a machine that perform a controlled abrasion with a CS17 abrasive wheel (3000 rpm).
The imprinting on the film after two minutes markedly shows the loss of mobility (fluidity) due to the reactive process that has already begun. After 4 minutes, the film shows a structure that is already solid enough to moderately resist the pressure of the imprinting.
It increases by about 100% at a dosage of between 94/6 and 92/8 and it stabilizes at increments of about 30% with each subsequent dosage. The dosage of 86/14 is the most reactive and comes before the system manageability limit.
The storage stability of the various dosages makes it possible to consider mixtures with ratios between 96/4 and 90/10 as single-component products stable to long term storage. 88/12 and, in particular, 86/14 ratios are to be considered as products with reduced stability and therefore commercially offered either as short term storage products or two-component systems.
In this image, tit is noted the faint marking of a vehicle tire overrun on a road marking strip applied with the product E25/PA46 90/10 (Overlapping results obtained also with: E25/PA40, E30/PA30, E30/PA40, E30/PA46, E34/PA30, E34/PA35, E35/PA30, or E35/PA35 in the same ratios) 8 minutes before on a road with the surface at 7.6° C., an ambient temperature of 11.49° C. and a humidity of 72.43%.
Surprisingly, the inventors have therefore found that the aqueous paint composition of the present invention has considerable advantages:
FT-IR Spectroscopy to Identify the Aromatic Component Resulting from the Presence of Bisphenol A or F in the Epoxy-Polyamine Adduct
The absorption band around 830 cm−1 is decisive for the identification of the presence of para-substituted phenyl radicals, typical of Bisphenol A or F (
wherein n=0.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102020000028805 | Nov 2020 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/060906 | 11/24/2021 | WO |
