Soft-feel coatings

Abstract

Soft feel coating compositions, particularly for plastic substrates, having improved chemical resistance and methods of improving the chemical resistance of soft-feel coatings are provided.

Claims

1. A soft feel coating composition comprising: a) a film forming resin matrix composition which cures to form a soft feel film having a resin matrix Tg of 80 C. to 20 C.; b) at least one solvent; and c) a stainless steel platelet shaped pigment having a density 50% to 400% greater than the density of the resin matrix composition, wherein the stainless steel platelet shaped pigment has a flattened profile that imparts chemical resistance to the coating composition.

2. The coating composition of claim 1, wherein the stainless steel platelet shaped pigment has a density 150% to 400% greater than the density of the resin matrix composition.

3. The coating composition of claim 1, wherein the stainless steel platelet shaped pigment is 5% to about 25% volume solids with respect to the total composition.

4. The coating composition of claim 3, wherein the stainless steel platelet shaped pigment is 5% to about 10% volume solids with respect to the total composition.

5. The coating composition of claim 3, wherein the stainless steel platelet shaped pigment is about 10% to about 15% volume solids with respect to the total composition.

6. The coating composition of claim 3, further comprising a flattening agent.

7. The coating composition of claim 6, wherein the flattening agent is about 2 to about 5 weight percent based on the total weight of solids in the coating composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Numerous coating compositions that are self-described to provide soft feel of soft touch coatings are described in the literature. Exemplary self-described soft-feel coatings include those taught in U.S. Pat. No. 8,313,837 and WO/2012/089827, which are incorporated herein by reference in relation to the soft-feel coating compositions, polyol resins, resin blends and isocyanates described therein. Binders and dispersions described for soft-feel coatings have been illustrated in U.S. Pat. Nos. 6,211,286 and 6,414,079 and 7,396,875, each of which is incorporated herein by reference for its teaching of soft-feel coating binders and compositions. Generally, 2K soft feel coating compositions comprise the reaction product of a polyol and an isocyanate and are thus, polyurethane coatings. 1K coatings are possible, including UV curable soft-feel coatings systems incorporating one or more UV curable resins. In solvent-borne compositions, the solvent comprises one or a blend of organic solvents, selected from the well known list of organic solvents, including ketone solvents, ester solvents, alcohols, glycol ether solvents, and glycol ether ester solvents. Exemplary, non-limiting examples of solvents that may be useful include xylene, n-butyl acetate, t-butylacetate n-butyl propionate, naptha, ethyl 3-ethoxypropionate, toluene, methyl ethyl ketone (MEK), acetone, methyl propyl ketone (MPK), methyl-n-amyl ketone (MAK), propylene glycol methylether acetate (PMA) and the like. In water-borne compositions water is typically the primary carrier and the polyols are generally water dispersible or provided as aqueous dispersions. Minor portions of suitable organic solvents may be employed.

(2) Suitable polyols may include polyester polyols, polyether polyols, polycarbonate polyols, polycarbonate polyester polyols, polyacrylic polyols, polyurethane polyols, polycaprolactone polyols, polyolefin polyols, and blends thereof. Non-hydroxyl functional resins may be employed, such as non-hydroxyl functional polyurethane resins.

(3) In one particularly useful embodiment, the resin comprises a linear polyester polyol, which may be used alone or in blends with other polyols.

(4) It is noted that the term soft-feel conventionally relates to the feel of the dried coating. The desired soft-feel of the coating is obtained by selection of resins and crosslinkers to provide a coating having the desired feel. It is believed that the soft feel derives, in part from the glass transition temperature (Tg) of the resin matrix in the cured film, and may be affected by the crosslinking density in the resin matrix. Soft feel coatings may have a resin matrix Tg (dried film) in the range of 80 C. to 20 C.

(5) For a 2K system, a polyisocyanate crosslinker may be utilized in combination with the polyol resin. Suitable polyisocyanates may be selected from isocyanate-functional materials that are well known in the art and include di-, tri- and multi-functional isocyanates as well as polyisocyanates that utilize di-, tri-, and multi-functional isocyanate material.

(6) Suitable isocyanate functional materials include but are not limited to aromatic, cycloaliphatic and aliphatic polyisocyanates such as, 1,3 and 1,4 phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, toluene-2,4- or 2,6-diisocyanate, 1,2,4-benzene triisocyanate, 1,5- and 1,4-naphthalene diisocyanate, 2,4 and 4,4 diphenylmethane diisocyanate, 3,3-dimethyl-4,4-diphenylene diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, 1,6 hexamethylene diisocyanate (HDI), isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, 2,2,4(2,4,4)-trimethyl-1,6-hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,4-diisocyanato pentane, isocyanatomethylcyclohexyl isocyanate, 1,6,11-undecane triisocynate, p- and m-tetramethylxylene diisocynate, 1,4-tetramethylene diisocyanate, 1,10-decamethylene diisocyanate, m-xylene diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, and mixtures thereof.

(7) It has been found that aliphatic polyisocyanates are particularly useful in accordance with this invention. In one embodiment, the curing agent may comprise HDI alone or in combination with another polyisocyanate.

(8) Generally, a curing agent will be used in an amount sufficient to crosslink with at least a portion of the hydroxyl groups on the polyester(s) or other hydroxyl functional resins, when present, in the resin system. The relative amounts of the polyester(s) and other resins compared to a curing agent isocyanate may be expressed by the mole ratio of the reactive isocyanate groups to reactive hydroxyl groups. The isocyanate may be present in ratio of about 0.75:1 to about 1.5:1 based on the NCO:OH ratio. In one useful embodiment, the isocyanate is present in a ratio of about 0.8:1 to about 1.2:1 based on the NCO:OH ratio. In another useful embodiment, the isocyanate is present in a ratio of about 1:1 to about 1.1:1 based on the NCO:OH ratio.

(9) The compositions taught herein may include an amount of one or more catalysts that catalyze the isocyanate hydroxyl reaction. Useful catalysts may include tertiary amines, such as triethylene diamine, N-methyl morpholine, N-ethyl morpholine, diethyl ethanolamine, 1-methyl-4-dimethylamino ethyl piperazine, 3-methoxy-N-dimethyl propyl amine, N-dimethyl-N-methyl isopropyl propylene diamine, N,N-diethyl-3-diethyl amino propylamine, N,N-dimethyl benzyl amine, dicyclohexylmethylamine, 2,4,6-tris dimethylaminomethylphenol, N,N-dimethyl cyclohexylamine, triethylamine, tri-n-butylamine, 1,8-diaza-bichloro[5,40]-undecene-7 N-methyl diethanolamine, N,N-dimethyl ethanolamine, N,N-diethyl cyclohexylamine, N,N,NN-tetramethyl-ethylene diamine, 1,4-diaza-bicyclo-[2,2,2]-octane N-methyl-N-dimethylaminoethyl-piperazine, bis-(N,N-diethylaminoethyl)-adipate, N,N-diethylbenzylamine, pentamethyldiethylene triamine, N,N,N,N-tetramethyl-1,3-butanediamine, 1,2-dimethylimidazole, 2-methylimidazole; tin compounds, such as stannous chloride, dibutyl tin di-2-ethyl hexoate, stannous octoate, dibutyl tin dilaurate, trimethyl tin hydroxide, dimethyl tin dichloride, dibutyl tin diacetate, dibutyl tin oxide, tributyl tin acetate, tetramethyl tin, dimethyl dioctyl tin, tin ethyl hexoate, tin laurate, dibutyl tin maleate, dioctyl tin diacetate; other metal organics, such as zinc octoate, phenyl mercuric propionate, lead octoate, lead naphthenate, and copper naphthenate.

(10) Particularly useful, for the present invention, is dibutyl tin dilaurate (DBTDL). Useful amounts of catalyst will be about 0.01 to 5%, based on the total weight of the resin solids.

(11) Additional additives that may be included in the composition described herein include UV inhibitors, wetting agents, flow agents, defoamers, flattening agents, plasticizers, silicone fluids, and the like.

(12) In some useful embodiments, the coating compositions described herein may include a flattening agent. Flattening agents are generally small solid particles of material that are insoluble in water and are effective to reduce gloss. Preferably, the flattening agent particles have a size of from about 0.05 to about 10 microns, but may be present in clumps or agglomerates of up to about 50 microns. The flattening agent particles may be inorganic or organic. Examples of suitable inorganic flattening agents include silicates, such as talc, and various forms of silica, such as amorphous, aerogel, diatomaceous, hydrogel and fumed silicas. Examples of suitable organic flattening agents include insoluble urea-formaldehyde resins, polyethylene, polypropylene, cellulosic fibers and polyurethane/polyurea copolymers.

(13) The amount of flattening agent in the first embodiment of the coating composition, on a solids basis, is preferably from about 1 to about 20 weight percent, more preferably from about 1 to about 10, still more preferably, about 1 to about 5 weight percent, still more preferably about 2 to about 5 weight percent based on the total weight of solids of the coating composition. In other embodiments, the flattening agent may comprise about 10 to about 20 weight percent.

(14) The compositions of the present invention, be they water-borne or solvent-bore, 2K or 1K, comprise a platelet shaped pigment. Platelet shaped is intended to refer to pigments having a flattened, as opposed to round or particulate type profile and includes pigments described as flake pigments, sand dollar shaped pigments and lamellar pigments. The preferred platelet shaped pigments in accordance with the invention, have an average particle size (diameter) in the range of about 10 to about 40 microns, more usefully, about 15 to about 30 microns, and in some embodiments, most usefully around 20 to 30 microns. Blends of different sized platelet shaped pigments of the same or different materials and/or size may be employed in embodiments of the present invention. Platelet shaped pigments having a density of 15 to 30 lbs/gallon may be useful. In some embodiments, it is particularly useful it the platelet shaped pigments are at least 50% (1.5 times) to 400% (5.0 times) greater than the density of the resin matrix, and in other embodiments, at least 150% (2.5 times) to 400% greater density, and in still another embodiment, at least 100% greater density, and in another embodiment at least 200% (3.0 times) greater density than the resin matrix are useful in some embodiments. Though platelet pigment loading may vary from system to system, levels in the range of 5 to about 25% volume solids, an in another embodiment, about 5 to about 10% volume solids, and in still another embodiment about 8 to about 15% volume solids and in another embodiment, about 10 to about 15% volume solids and in still another embodiment, about 12 to about 15% volume solids are particularly useful levels for chemical resistance.

(15) Though a variety of platelet shaped pigments are known, pigments selected from the group consisting of stainless steel flake pigments, fluorophlogopite pigments and calcined mica pigments are particularly preferred. Stainless steel flake pigments impart a silver or metallic hue to the coatings and are particularly useful in preparing soft feel metallic looking coatings. Fluorophlogopite flake and calcined mica pigments are particularly preferred in preparing pigmented or clear soft feel coatings.

(16) The coatings of the present invention may include, in addition to a platelet shaped pigments selected from the group consisting of stainless steel flake pigments, fluorophlogopite pigments, calcined mica pigments and blends thereof, other conventional pigments to impart color or extender pigments. Representative such pigments may include, for example, titanium dioxide, carbon black, graphite, ceramic black, lamp black, antimony sulfide, black iron oxide, aluminum pastes, yellow iron oxide, red iron oxide, iron blue, phthalo blue and green, nickel titanate, dianisidine orange, dinitroaniline orange, imidazole orange, quinacridone red, violet and magenta, toluidine red, molybdate orange, and the like. Extender pigments, such as amorphous, diatomaceous, fumed, quartz and crystalline silica, clays, aluminum silicates, magnesium aluminum silicates, talc, mica, delaminated clays, calcium carbonates and silicates, gypsum, barium sulfate, calcium zinc molybdates, zinc oxide, phosphosilicates and borosilicates of calcium, barium and strontium, barium metaborate monohydrate, and the like can also be incorporated.

(17) A useful feature of the coating compositions of the present invention is that they provide in a single coating a dry film having good adhesion to plastic substrates, improved chemical resistance and a soft feel. The coating composition herein may be applied by any conventional means to a portion or all of a plastic substrate. The compositions may be applied by spray apparatus, roller, brush, or dipping. One or more layers may be applied to the substrate wet on wet or wet on dry to a total dry film thickness of between 1 mil and 10 mils, although dry films in the range of 1 mil to 5 mils are desirable in some applications, and in others, from 1 mil to 3 mils.

(18) As described above, there are a wide variety of plastic substrates and articles of manufacture having plastic substrates to which the presently described compositions are well suited. In a particularly useful application of the coatings of the present invention, the substrate may be a portion of the interior component of a vehicle, such as a dashboard, steering wheel, knob, console or the like. Alternatively, the substrate may be a portion of a consumer or household product, such as a computer, electronic gaming or music storage and playback device.

(19) While the present invention is directed to improving chemical resistance in soft-feel coatings applied to plastic substrates, it will be noted that the coatings may be employed on other substrate materials made of metal, wood, glass, ceramic, and the like.

EXAMPLES

(20) The invention is described further by the following example, which is intended to be illustrative and by no means limiting. Except for Example formulas 12-14, all formulations are in weight percent with respect to total formulation. Examples 12-14 are based on weight.

(21) An evaluation of aluminum and stainless steel pigments in soft feel coatings was conducted on the basis of the solvent-borne formulations described below, as compared to each other and against flatted and unflattened control compositions.

(22) TABLE-US-00001 EX. 1 EX. 2 EX. 3 EX. 4 EX. 5 EX. 6 EX. 7 Material CONTROL CONTROL 12.5% vol. 20% vol. 20% vol. 12.5% 12.5% high gloss low gloss Al. Al. Al. vol. SS vol. SS low gloss low gloss Resin A 18.60 16.11 15.31 14.04 12.70 12.47 11.45 Resin B 13.95 13.42 12.76 11.70 10.58 10.39 9.55 Solvent A 15.50 16.11 15.31 15.21 15.87 16.62 17.18 Solvent B 15.50 16.11 15.31 15.21 15.87 16.62 17.18 Catalyst A 1.72 1.48 1.42 1.30 1.17 1.15 1.06 Flow Additive 0.37 0.32 0.31 0.28 0.25 0.25 0.23 UV stabilizer 0.78 0.67 0.64 0.58 0.53 0.52 0.48 flattener 4.03 3.17 2.39 15 m aluminum sand 8.76 12.85 11.63 dollar 15 m stainless steel 13.25 12.17 flake Solvent D 15.50 16.11 15.31 15.21 15.87 16.62 17.18 HDI isocyanate A 18.07 15.65 14.88 13.64 12.34 12.11 11.13 NCO/OH 1.1 1.1 1.1 1.1 1.1 1.1 1.1

(23) Samples were mixed 5 minutes on med-high speed after the addition of the pigments. Formulas were sprayed at a 2 mil film build using a HVLP gravity feed gun 4 mm gun tip, 50 psi at wall, 29 psi at gun, fan closed turn; fluid open all the way, 2 coats, 20 sec flash between coats, 10 min RT flash 30 min@180 F. then placed in control temp and humidity room 3-5 days. Substrate: ABS plastic half smooth half grained panel.

(24) An evaluation of natural mica, calcined mica and fluorophlogopite pigments in solvent-borne and water-borne soft feel coatings was conducted on the basis of the formulations described below. Samples were prepared as described above.

(25) TABLE-US-00002 EX. 8 EX. 9 EX. 10 EX. 11 EX. 12 EX. 13 EX. 14 Material 12.5% natural 12.5% 8% FPGP 12.5% f CONTROL 12.5% 12.5% mica low calcined 30 m low FPGP WB low calcined FPGP gloss mica low gloss 5 m low gloss mica low low gloss gloss gloss gloss 5 Resin A 13.26 13.26 13.65 13.19 Resin B 11.05 11.05 11.37 10.99 Resin C 72.80 72.80 72.80 Solvent A 16.57 16.57 17.06 16.48 Solvent B 16.57 16.57 17.06 16.48 Solvent C 10.00 10.00 10.00 Catalyst A 1.23 1.23 1.26 1.22 0.12 0.12 0.12 Flow Additive 0.27 0.27 0.27 0.26 UV stabilizer 0.55 0.55 0.57 0.55 Surfactant 2.30 2.30 2.30 Defoamer 0.60 0.60 0.60 flattener 1.66 1.66 2.27 2.20 3.80 2.50 3.00 17 m mica platelet 9.38 20 m calcined mica 9.38 13.00 platelet 30 m synthetic 6.17 13.00 fluorophlogopite <15 m synthetic 9.33 fluorophlogopite Solvent D 16.57 16.57 17.06 16.48 Solvent E 3.48 3.48 3.48 HDI isocyanate A 12.88 12.88 13.26 12.81 HDI isocyanate B 10.40 10.40 10.40 NCO/OH 1.1 1.1 1.1 1.1 1.5 1.5 1.5

(26) For purposes of the Examples above:

(27) TABLE-US-00003 Material Description Resin A blend of 3 polyester polyols Resin B low Tg soft resin Desmophen 1652 available from Bayer Resin C waterborne soft polyester Proprietary resin resin Solvent A slow solvent EEP Solvent B medium solvent MAK Solvent C water Catalyst A tin catalyst DBTDL solution Flow Additive silicone flow additive Baysilone OL 17 available from Lanxess Corp. UV stabilizer Tinuvin 292 available from Air Products Surfactant Surfynol 502 available from Air Products Defoamer Byk 011 available from BYK Chemie Flattener silica flattener Acematt 3300 available from Degussa 15 m aluminum sand SSP 554 available from Silberline dollar 15 m stainless steel StaySteel 15 available from Eckart flake 17 m mica platelet Micro-Mica C4000 available from Imyres 20 m calcined mica Calcined Mica A available from EMD platelet 30 m synthetic SM10-60 available from Kuncai fluorophlogopite <15 m synthetic SM0-15 available from Kuncai fluorophlogopite Solvent D fast solvent MPK Solvent E medium solvent PMA Isocyanate A HDI isocyanate Desmodur N 3300 available from Bayer Isocyanate B HDI isocyanate Bayhydur 30 available from Bayer

Results

(28) Panels were measured for gloss at 60 using a gloss meter. For low gloss applications, a gloss measure of less than 5 is particularly desirable. The panels were ranked for feel by grip, slip, and softness. Chemical resistance was testing using GMW14445 test for sunscreen and bug repellant resistance. For purposes of these evaluations, useful grip ratings were SM-M, slip ratings of SM-M, softness ratings of 7 to 10, and SB test results of 2.0 or lower on both smooth and grained portions of the panel.

(29) TABLE-US-00004 Feel Rankings: grip/slip Feel Rankings 1-10 VHvery high 1hardcoat Hhigh 2hardcoat with some flexibility MHmoderate high 3slight indication of soft feel Mmoderate 4some softness SMslight to moderate 5semisoft Sslight 6semisoft-soft VSvery slight 7soft coat GM standard VVSvery very slight 8softer than GM standard Tr.trace 9very soft Nnone 10very soft and compressible

(30) TABLE-US-00005 GMW14445 Sun and Bug Test Ratings (SB test) 4.0+ solution dissolved through substrate 3.6-4.0 moderate to severe wrinkling and blistering of film 3.2-3.5 slight to moderate wrinkling and blistering of film 3.1 first sign of wrinkling 3.0 first sign of blistering 2.5-2.9 moderate-severe swelling/staining 2.1-2.4 slight-moderate swelling, moderate staining 2.0-passing; no swelling, some staining 1.5-1.9 no swelling, slight staining 1.0-1.4 very slight staining 0.1-0.9 trace evidence of staining 0 no evidence of staining

Examples 1-7

(31) TABLE-US-00006 EX. 1 EX. 2 EX. 3 EX. 4 EX. 5 EX. 6 EX. 7 Gloss 60 80.9 2.0 56.7 39.1 2.5 8.9 2.3 Feel grip VH SM-M H MH-H VS MH SM-M Feel slip Tr. M VS VS-S MH S M Softness 1-10 10 8 7 5.5 4 9 8 GMW14445 test 4.0/4.0 4.0/4.0 2.5/3.0 2.0/2.0 3.8/4.0 2.0/2.0 2.0/2.0 for sun/bug (SB) chemical resistance (smooth/grained) SB failure mode Wrinkling Wrinkling Blistering Pass Wrinkling Pass Pass Cross section NA NA horizontal horizontal random horizontal horizontal analysis for barrier alignment

Examples 8-14

(32) TABLE-US-00007 EX. 8 EX. 9 EX. 10 EX. 11 EX. 12 EX. 13 EX. 14 Gloss 60 1.6 2.0 2.0 2.0 2.1 3.1 1.8 feel grip SM SM SM-M SM-M M SM-M SM-M feel slip M M M M M M M softness 1-10 7 7 7.5 7.5 8 7 7 GMW14445 test 3.5/4.0 1.5/1.5 1.5/1.5 1.5/1.5 4.0/4.0 2.0/3.0 2.0/2.0 for sun/bug (SB) chemical resistance (smooth/grained) SB failure mode Swelling/ pass pass pass wrinkling travel in pass wrinkling grain cross section horizontal horizontal horizontal horizontal NA horizontal horizontal analysis for barrier alignment

Analysis

(33) Although aluminum pigments work as a chemical barrier as shown in example 4, the feel was negatively impacted. Cross section analysis indicates that the pigment dispersed throughout the entire film. In example 5, cross section analysis indicated the aluminum particles become unaligned in the presence of flattener. This system failed chemical resistance tests much like the control examples 1 and 2. The added flattener and aluminum greatly reduce the feel of the film. The high density of stainless steel, it is believed, enabled the particles to align horizontally in a condensed layer in the film near the substrate and away from the surface. Less of the stainless steel pigment was needed to pass chemical resistance testing and cross section analysis indicated no harmful interaction with the stainless steel pigment and the flattener pigment, and feel is retained at the surface of the film.

(34) Fluorophlogopite demonstrates success at levels as low at 8% volume solids in soft feel coatings. Examples 10 and 11 illustrate some role of particle size. The volume solids were higher in the smaller synthetic fluorophlogopite (example 11), but chemical resistance was better in the larger particles size in example 10.

(35) The waterborne examples demonstrate the versatility of the invention taught herein to improve chemical resistance.

(36) While the invention has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims.