JP7684231B2 - One-component polysiloxane anti-slip/non-slip coating - Google Patents

Description

This disclosure relates generally to polysiloxane coatings.

Anti-skid/non-slip coatings are viscous materials that provide an aggressive surface when applied by roller, spray, or brush. These materials are used on the interior and exterior decks of surface vessels to provide traction for aircraft, crew, and equipment at sea. Similar materials, although with a less aggressive profile, are used to provide traction on the exteriors of aerospace ground support equipment, on the floors of ground vehicles, and on helicopter wings.

On Navy surface vessels, traditional anti-slip coatings are viscous two-component (2K) materials containing epoxy and amine functional molecules, pigments, solvents, fillers, thickeners, and abrasive aggregates. These components are mixed together using mechanical equipment and then applied to the vessel deck via napless phenolic rollers or spray pumps. Navy anti-slip coatings fall under MIL-PRF-24667 requirements and must be present on decks where air activity occurs. Unfortunately, epoxy-amine anti-slip coatings often fail before reaching their required service life due to degradation from sunlight resulting in poor wear profile and discoloration, delamination from the deck due to poor adhesion to the underlying primer, or top breakage resulting in foreign object damage (FOD). Sailors often apply primer to areas where the anti-slip has delaminated to prevent corrosion and further delamination, despite not having the ability to apply additional anti-slip due to the inability to hand mix these viscous materials. As a result, areas of the ship's deck are often left without a wear surface during deployment, and needless to say, the deck has an unsightly, mottled appearance when covered in places with anti-skid and bare primer.

Disclosed herein is a composition comprising an organosilane polymer, a polyamide polymer, and an abrasive aggregate. The organosilane polymer is made by a process comprising reacting an amino-functional alkoxysilane with one or more polyisocyanates to form one or more adducts having unreacted isocyanate groups, and reacting the adducts with one or more multifunctional amino and/or hydroxyl compounds to form a polymer. The multifunctional amino and/or hydroxyl compounds contain alicyclic or aromatic groups. The organosilane polymer does not contain unreacted isocyanate groups.

A more complete understanding may be readily obtained by reference to the following detailed description and accompanying drawings.

Examples of alicyclic-containing organosilane polymers are given below. 1 shows the organosilane polymer when crosslinked (cured). Photographs of one-component (1K) anti-skid/non-slip coatings after application with a napless phenolic roller on 6" x 12" x 1/4" epoxy primed panels are shown.

In the following description, for purposes of explanation and not limitation, specific details are set forth to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the subject matter may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods and apparatuses are omitted so as not to obscure the present disclosure with unnecessary detail.

Polysiloxane coatings containing silicon-oxygen bonds are becoming increasingly popular within the global coatings market due to their superior outdoor durability, chemical resistance, and thermal stability, all of which are improved over coatings based on organic polymers. One-component (1K) polysiloxane anti-skid/non-slip coatings overcome the limitations of 2K epoxy-based coatings by providing a material that does not require metering and mixing of components, can be applied by roller or spray, and provides a wear surface that is durable and color-retaining upon exposure to sunlight.

The one-component polysiloxane anti-slip/non-slip coatings described herein are based on synthetic organosilane polymers that contain alicyclic and/or aromatic units in the backbone and terminate with alkoxysilane groups. These 1K anti-slip coatings also contain an amide coating polymer and an abrasive aggregate, as well as fillers, pigments, solvents, additives, and catalysts. The coatings can be applied onto a surface with a roller, spray, brush, or trowel. Once applied, the alkoxysilane groups in the polymer hydrolyze with moisture to form silanols. These silanols subsequently condense to form a hard polysiloxane/sol-gel network, providing a durable anti-slip/non-slip coating.

Organosilane polymers can be synthesized using a variety of molecules, but they must contain alicyclic or aromatic units in the backbone. These molecules include: 1) isocyanate-functional molecules such as aliphatic, cycloaliphatic, and aromatic di- or trifunctional isocyanates; 2) amine-functional alkoxysilane molecules such as 3-aminopropyltrimethoxysilane, N-butyl-3-aminopropyltrimethoxysilane, and (N-cyclohexylmethyl)methyldiethoxysilane; 3) di- and trifunctional primary and secondary amines such as isophorone diisocyanate, 1,6-hexamethylenediamine, 4,4'-methylenebis(N-sec-butylcyclohexanamine), metaxylylenediamine, and propane-1,2,3-triamine; and/or 4) hydroxyl-functional molecules such as 1,5-pentanediol, 4,4'-isopropylidenedicyclohexanol, 1,4-cyclohexanedimethanol, and dendritic polyester polyols.

Some suitable organosilane polymers are disclosed in U.S. Pat. No. 10,190,020 (all publications and patents referenced throughout this application are incorporated herein by reference). The organosilane polymer has terminal alkoxysilane groups formed by reacting an amine-functional alkoxysilane with a polyisocyanate to form an adduct. There is an excess of isocyanate groups relative to the amine groups, so that the adduct has unreacted isocyanate groups. The adduct is then reacted with a difunctional amino or hydroxyl compound to consume all unreacted isocyanate groups. A typical reaction scheme is shown below. Note that the use of a diol will form urethane groups in the polymer. Alternatively, a difunctional amino or hydroxyl compound can be reacted first with an isocyanate and then with an amine-functional alkoxysilane to form the same compounds claimed herein. The claimed compounds can be made by either method. Each of the reactants may include multiple compounds of such general structure. Other reactants may be present or excluded.

The value a is 1, 2, or 3, and there is at least one alkoxy group bonded to the silicon atom. The value n is a positive integer, and the polyisocyanate has n+1 isocyanate groups. The organosilane polymer may be a mixture of the above compounds with other organosilane polymers. The mixture may include a small amount of polymer in which all the isocyanate groups have reacted with an amine-functional alkoxysilane, as shown below.

The reaction may also produce a mixture of compounds depending on the ratio of reactants. For example, if more than 50 mol% of the amine-functional alkoxysilane is used, a portion of the polyisocyanate will react completely with the amine-functional alkoxysilane, as shown above. If more than 50 mol% of the NH or OH from the difunctional amino or hydroxyl compound, respectively, is used, the reaction will produce some compounds with multiple repeat units (m) of the difunctional amino or hydroxyl compound, as shown below.

The organosilane polymer has no unreacted isocyanate groups. As used herein, "no unreacted isocyanate groups" means that enough isocyanate-reactive groups are used to react with all of the isocyanate groups, although trace amounts of unreacted isocyanate may remain.

Each R ¹ group of the amine-functional alkoxysilane can be an independently selected alkyl group, such that all R ¹ groups can be the same or of multiple types. Each R ² group of the amine-functional alkoxysilane can be an independently selected hydrogen, aryl, alkyl, cycloalkyl, ester-containing aliphatic, ester-containing fluorinated aliphatic, amide-containing aliphatic, or polysiloxane. The amine-functional alkoxysilane is a different compound than the organosilane polymer itself and may not contain urea or urethane groups. Suitable amine-functional alkoxysilanes include, but are not limited to, N-butyl-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, (N-cyclohexylmethyl)methyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, or N-[3-(trimethoxysilyl)propyl]-β-alanine butyl ester.

The ^R3 group of the polyisocyanate may be aliphatic, cycloaliphatic, or aromatic. Aliphatic isocyanates may provide better flexibility and weatherability to the coating. Suitable polyisocyanates include, but are not limited to, hexamethylene diisocyanate, homopolymers of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, homopolymers of isophorone diisocyanate, or methylene diphenyl diisocyanate, and mixtures thereof. Commercially available polymeric isocyanates may include mixtures of hexamethylene diisocyanate dimers and trimers, etc.

Each ^R4 group of the bifunctional amino compound can be independently selected hydrogen, aryl, alkyl, cycloalkyl, ester-containing aliphatic, ester-containing fluorinated aliphatic, amide-containing aliphatic, or polysiloxane. Each ^R5 group of the bifunctional amino or hydroxyl compound includes an alicyclic group, or an aromatic group, or any combination thereof. Suitable bifunctional amino or hydroxyl compounds include, but are not limited to, isophorone diamine, 1,6-hexamethylene diamine, 1,3,3-trimethyl-N-(1-methylethyl)-5-[(1-methylethyl)amino]cyclohexanemethanamine, 4,4'-methylenebis(N-sec-butylcyclohexanamine), propane-1,2,3-triamine, 1,5-pentanediol, 4,4'-isopropylidenedicyclohexanol, 1,4-cyclohexanedimethanol, or dendritic polyester polyols.

The alkoxysilane-terminated organosilane polymer may also be the specific polyureas disclosed in U.S. Pat. Nos. 9,139,753 or 9,701,868, both of which are incorporated herein by reference and the specific subject matter of which is included below. The teachings of these applications may be applied to the presently disclosed polyureas.

The polyisocyanates may be aliphatic, cycloaliphatic, or aromatic. Aliphatic polyisocyanates are more weatherable (i.e., more durable outdoors) than aromatic polyisocyanates, thereby providing greater color stability when utilized in exterior coatings. Aliphatic polyisocyanates may have a variable number of reactive isocyanate (NCO) groups per molecule, depending on their structure. Typically, the number ranges from 2.5 to 5.5. For the present coating compositions, aliphatic polyisocyanates may have more than two NCO groups per molecule. Suitable aliphatic polyisocyanates include, but are not limited to, structures based on isocyanurates (e.g., HDI and IPDI trimers), biurets, uretdiones, allophanates, oxadiazinetriones, iminooxadiazinedione, and urethane-containing prepolymers. Mixtures of these isocyanates may also be used. There are many commercially available aromatic, aliphatic, and cycloaliphatic polyisocyanates.

The N-substituted amino-functional alkoxysilane can be an N-substituted 3-aminopropyltrialkoxysilane, an N-substituted 3-aminopropylalkyldialkoxysilane, or an N-substituted dialkylalkoxysilane, where the alkyl group bonded to the silicon atom can be methyl or ethyl, and the alkoxy group bonded to the silicon atom can be methoxy, ethoxy, n-propoxy, or n-butoxy.

The N-substituents of the N-substituted amino-functional alkoxysilanes can be C ₁ to C ₁₂ alkyl, cycloalkyl, or aryl. Examples include N-methyl-3-aminopropyltrimethoxysilane, N-ethyl-3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltributoxysilane, N-ethyl-3-aminopropyltripropoxysilane, N-isopropyl-3-aminopropyltrimethoxysilane, N-tert-butyl-3-aminopropyltrimethoxysilane, N-butyl-3-aminopropyltrimethoxysilane, N-butyl-3-aminopropylmethyldimethoxysilane, N-butyl-3-aminopropyldimethyl ... Examples of suitable silanes include, but are not limited to, N-aminopropyltriethoxysilane, N-butyl-3-aminopropyltripropoxysilane, N-butyl-3-aminopropyltributoxysilane, N-isobutyl-3-aminopropyltrimethoxysilane, N-cyclohexyl-3-aminopropyltrimethoxysilane, N-hexyl-3-aminopropyltrimethoxysilane, N-nonyl-3-aminopropyltrimethoxysilane, and N-dodecyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane, many of which are commercially available.

The N-substituents of the N-substituted amino-functional alkoxysilanes may also be ester-containing aliphatic or ester-containing fluorinated aliphatic, which are formed by the Michael addition (conjugate addition) reaction between molecules bearing a reactive "ene" group, such as acrylates, and 3-aminopropyltrialkoxysilanes, 3-aminopropylalkyldialkoxysilanes, or 3-aminopropyldialkylalkoxysilanes. The conditions for the formation of adducts by Michael addition with amines are well known in the literature. Suitable acrylates include, but are not limited to, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, 4-tert-butylcyclohexyl acrylate, diethyl maleate, dimethyl maleate, dibutyl maleate, ethylene glycol methyl ether acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 2,2,2-trifluoroethyl acrylate, and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate. Examples include, but are not limited to, methyl 3-((3-(trimethoxysilyl)propyl)amino)propanoate, butyl 3-((3-(trimethoxysilyl)propyl)amino)propanoate, 2-ethylhexyl 3-((3-(trimethoxysilyl)propyl)amino)propanoate, octyl 3-((3-(trimethoxysilyl)propyl)amino)propanoate, 3,3,3-trifluoropropyl 3-((3-(trimethoxysilyl)propyl)amino)propanoate, dimethyl(3-(trimethoxysilyl)propyl)aspartate, and diethyl(3-(trimethoxysilyl)propyl)aspartate.

The N-substituents of the N-substituted amino-functional alkoxysilanes may also be amide-containing aliphatic, which are formed by the Michael addition (conjugate addition) reaction between a molecule with a reactive "ene" group, such as acrylamide, and a 3-aminopropyltrialkoxysilane, a 3-aminopropylalkyldialkoxysilane, or a 3-aminopropyldialkylalkoxysilane. Suitable acrylamides include, but are not limited to, N-ethylacrylamide, N-propylacrylamide, N-tert-butylacrylamide, N-cyclohexylacrylamide, N-ethylmaleimide, and N,N'-diethylmaleamide. Examples include, but are not limited to, N-propyl-3-((3-(trimethoxysilyl)propyl)amino)propanamide, N-butyl-3-((3-(trimethoxysilyl)propyl)amino)propanamide, N-cyclohexyl-3-((3-(trimethoxysilyl)propyl)amino)propanamide, and 1-ethyl-3-((3-(trimethoxysilyl)propyl)amino)pyrrolidine-2,5-dione.

Those skilled in the art will appreciate that a small amount of isocyanate groups (e.g., 1-5%) may remain unreacted in the polymer and may be used to aid adhesion to substrates or may be used to react with isocyanate-reactive materials not discussed herein. However, reacting a small percentage of the isocyanate groups on the polymer with undisclosed materials is unlikely to change the properties of the polymer and should not be considered a separate polymer. It is recommended that all isocyanate groups be reacted during the synthesis of the organosilane polymer to produce an isocyanate-free coating.

Suitable solvents for the synthesis of organosilane polymers are those that do not react with isocyanate groups. These solvents include, but are not limited to, xylene, light aromatic naphtha, mineral spirits, butyl acetate, 1-methoxy-2-propyl acetate, tert-butyl acetate, butyl propionate, pentyl propionate, ethyl 3-ethoxypropionate, 4-chlorobenzotrifluoride, tetrahydrofuran, 1,4-dioxane, dimethylacetamide, and N-methylpyrrolidone.

Catalysts may be used to accelerate the rate of hydrolysis of the alkoxysilane groups and to promote crosslinking of the resulting silanol groups to form a cured coating. Suitable catalysts include, but are not limited to, organotin compounds such as dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin bis(2-ethylhexoate), metal alkoxides such as titanium tetraisopropoxide, aluminum triethoxide, zirconium tetrabutoxide, and titanium chelates including aminoalkoxysilanes, potassium hydroxide, organic acids, inorganic acids, tertiary amines, or mixtures thereof.

Suitable pigments include, but are not limited to, titanium dioxide, carbon black, red iron oxide, yellow iron oxide, copper phthalocyanine blue, sodium aluminum sulfosilicate, chromium oxide, cobalt chromite green spinel, chrome green black hematite, nickel antimony titanium yellow rutile, and manganese-based pigments.

Polyamide polymers may be used to provide flexibility or thixotropy and may be any polymer containing amide groups contained in the polymer backbone and may be aliphatic, cycloaliphatic, or aromatic polyamides. Examples include, but are not limited to, fatty acid-based polyamides, dimerized fatty acid-based polyamides, paraphenylene terephthalamide, nylon, polyaspartate, and poly(hexamethylene adipamide).

Fillers can be any material used to fill the volume of the composition, adjust the viscosity, or improve corrosion resistance. Examples include, but are not limited to, talc, ceramic microspheres, amorphous silica, hollow glass spheres, mica, aluminum flakes, aluminum spheres, zinc particles, glass flakes, wollastonite, and calcium carbonate.

Additives can be any material included in small amounts to adjust the viscosity, impact resistance, weatherability, or other properties of the composition. These additives include, but are not limited to, pigment dispersants, rubber beads, polyethylene fibers, polypropylene fibers, hindered amine light stabilizers (HALS), ultraviolet light absorbers (UVAs), conductive polyanilines, and graphene.

Abrasive aggregate can be any particle incorporated into the composition that increases the coefficient of friction of the surface of the composition as it solidifies. It can be a rounded or angular particle of 0.10-2.5 mm in size and a Mohs hardness of 3-9. Examples include, but are not limited to, brown aluminum oxide, white aluminum oxide, walnut shells, aluminum, crushed glass, glass beads, corn cobs, melamine, acrylic, and urea.

Once the composition is applied to a surface, it can cure to form a solid coating. The alkoxysilane groups of the organosilane polymer undergo hydrolysis and condensation with each other.

Unlike two-component anti-slip coatings, one-component polysiloxane anti-slip is an all-in-one can system that does not require weighing and mixing of components. The anti-slip can be easy to mix and apply, and yet provides an aggressive, hard profile when cured. The silicon-oxygen bonds within the coating provide greater resistance to degradation from sunlight than polymers based on all-organic bonds, such as those used in epoxy-amine anti-slips, and thus the 1K anti-slip can retain its color and profile for a longer period of time. Providing enhanced outdoor durability, the 1K anti-slip can extend the service life of anti-slips on marine decks and reduce maintenance costs.

The following examples are provided to illustrate specific applications. These specific examples are not intended to limit the scope of the disclosure of this application.

Example 1
Synthesis of organosilane polymer - Aliphatic isocyanate based on hexamethylene diisocyanate uretdione (Desmodur N-3400, Covestro) is dissolved in 4-chlorobenzotrifluoride (Sigma-Aldrich) (~1.2/1 by weight isocyanate/solvent) in a 1 L 4-neck round bottom flask equipped with a nitrogen inlet, mechanical stirrer, and thermometer. Vinyltrimethoxysilane (Gelest) is then added as a moisture scavenger. Using an addition funnel, N-butyl-3-aminopropyltrimethoxysilane (Gelest) (3/5 equivalents of NH to equivalents of NCO) is added dropwise to the solution while maintaining the temperature at 50-60°C. Once the addition is complete, the aliphatic cyclic diamine 1,3,3-trimethyl-1-aminomethyl-5-aminocyclohexane (Clearlink 1080, Dorf Ketal) (equivalents of NH to equivalents of NCO ratio 2/5) is added dropwise again maintaining the temperature at 50-60° C. After the addition, the reaction is stirred for an additional 30 min to 1 hr until all isocyanate groups are consumed according to FTIR analysis. The structure of one polymer made from the reaction is shown in FIG. 1.

Example 2
One-component anti-skid/non-slip formulation - A one-component anti-skid/non-slip coating is prepared by mixing the organosilane polymer from Example 1 with titanium dioxide (R-960, Chemours), inorganic black pigment (Black 30C940, Shepherd Pigments), inorganic blue pigment (Blue 30C527, Shepherd Pigments), and ceramic microspheres (W-610, 3M), followed by the addition of an amide-containing polymer (Crayvallac PA4BA20, Palmer Holland), fibrillated high density polyethylene fibers (Mini Fibers, Inc.), 12-30 mesh glass beads (Blast-O-Lite), and dibutyltin dilaurate (Sigma-Aldrich). The range of percentages in the formulations are shown in Table 1. After mixing, the coating is applied onto epoxy primed steel panels using a 9 inch napless phenolic roller (Grainer) and then cured for 14 days at 72°F and 40-60% relative humidity. Figure 2 shows the structure of one crosslinked (cured) organosilane polymer made from the reaction. Figure 3 shows an example of a roller applied anti-skid/non-slip coating after overnight curing. The polysiloxane coating is hard to the touch after 1 day.

The amount of organosilane polymer used depends on the application. For example, a non-slip formulation for stairs will use a high percentage of polymer and a low percentage of aggregate and filler. A high friction non-skid surface for a driveway will use a lower percentage of polymer and a higher percentage of aggregate and filler.

Obviously, many modifications and variations are possible in light of the above teachings. It should therefore be understood that the claimed subject matter may be practiced otherwise than as specifically described. For example, references to claim elements in the singular using the articles "a," "an," "the," or "said" are not to be construed as limiting the element to the singular.

Claims (10)

An organosilane polymer comprising:
reacting an amino-functional alkoxysilane with one or more polyisocyanates to form one or more adducts having unreacted isocyanate groups;
reacting the adduct with one or more multifunctional amino and/or hydroxyl compounds such that the polymer does not contain unreacted isocyanate groups, the multifunctional amino and/or hydroxyl compounds containing alicyclic or aromatic groups and selected from the group consisting of isophorone diamine, m-xylylene diamine, 4,4'-methylene bis(N-sec-butylcyclohexanamine), 4,4'-isopropylidenedicyclohexanol, 1,4-cyclohexanedimethanol, and dendritic polyester polyols containing alicyclic or aromatic groups;
A polyamide polymer;
A composition comprising an abrasive aggregate. The composition of claim 1, wherein the amino-functional alkoxysilane is N-butyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, or (N-cyclohexylmethyl)methyldiethoxysilane. The composition of claim 1, wherein the polyisocyanate is hexamethylene diisocyanate, a homopolymer of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, a homopolymer of isophorone diisocyanate, or methylene diphenyl diisocyanate. The composition of claim 1, wherein the polyamide polymer contains aliphatic groups, aromatic groups, or both. The composition of claim 1, wherein the abrasive aggregate is a rounded or angular particle. The abrasive aggregate is a particle having an average diameter of 0.10 to 2.5 mm, and the abrasive aggregate has an average Mohs hardness of 3 to 9.
The composition of claim 1. The composition of claim 1 further comprising a solvent, a pigment, a filler, an additive, or a catalyst. Applying the composition of claim 1 onto a surface;
curing said composition by reaction of said alkoxysilane groups with atmospheric moisture and subsequent condensation of the silanol groups. A one-component polysiloxane anti-skid/non-slip coating made by the method of claim 8 . 10. The one-component polysiloxane anti-skid/non-slip coating of claim 9 , wherein the composition is applied by roller, spray, or trowel.

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