This invention relates to a process for producing an anti-slip treatment on a porous substrate, namely a nonwoven, textile or carpet substrate, by applying a polymer formulation, having a Tg in the range of -60°C to -40°C, to a porous material by spray, foam or print application.
In many applications it is desirable for a porous material to exhibit anti-slip properties. An anti-slip surface is one which allows the treated material to remain in place, without exhibiting tackiness or a peel strength. A non-slip surface is imparted to a porous substrate through the application of a surface treatment.
US-A-5,786,077 describes the use of colloidal silicas to produce a non-slip surface on paper.
US-A-2 187 659 describes the use of an emulsion polymer as a non-slip coating for a non-woven material. The polymer formulation is applied to a flexible web backing, dried, then the dried formulation is foamed in an added step by exposure to steam or irradiation.
JP-A 10 053742 discloses a non-slip coating for corrugated box that is a bend of a rubber latex and a synthetic polymer of Tg -10 to 20°C.
EP-A-0 549 948 describes a nonabrasive anti-slip coating having a polymer with a Tg of >-30°C and which is blended with microbeads.
JP-A 02 032171 describes an emulsion polymer with a Tg of from -22 to +10°C, plus an acrylic emulsion polymer of Tg-20 to +40°C for use as an anti-slip coating for corrugated board case.
JP-A 05 033295 describes polymers having a Tg below 0°C mixed with inorganic particles and silicone oil for corrugated sheets or liners.
WO 93/22489 discloses a vinyl floor covering having a wear layer of a flexible PVC composition which contains core-shell polymer particles. The Tg of the core polymer is in the range -50°C to 60°C, and the Tg of the shell polymer is in the range 50 to 110°C.
The problem with non-slip treatments produced by other processes is that they either fail to provide an adequate grip, or else are too tacky to the touch. A non-slip surface, in the context of the present invention, is one having an increase in the static and dynamic coefficient of friction - without being tacky. An increase in non-slip properties should have only a minimal effect of other properties of the porous material, such as fabric hand and air permeability.
Surprisingly it has been found that a nonwoven, textile or carpet material, treated by the process of the present invention, has an increased coefficient of friction, and with little or no effect on fabric hand, air permeability, or abrasiveness. The treated nonwoven, textile or carpet material also exhibits no roll blocking, which is adhesion between the plies of a roll that inhibits the ability to unwind the roll for conversion into end-use products.
Accordingly the present invention is directed to a process for providing an anti-slip coating directly deposited on a nonwoven, textile or carpet substrate comprising a) forming a polymer formulation having a Tg of from -60°C to -40°C and b) applying said polymer formulation directly onto a porous substrate by spray, foam or print application to produce at least one anti-slip non-tacky surface. The present invention is also directed to a non-slip nonwoven, textile or carpet substrate made by the process of the present invention and to a product containing said substrate.
The process of the present invention involves treating a nonwoven, structure or carpet substrate with a polymer formulation by spray, foam or print application. The formulation works by increasing the friction between the treated substrate and the counter-substrate.
The polymer formulation contains a polymer and may also contain additives, including but not limited to, tackifiers, detackifiers, pigments, surfactants, catalysts, and thickeners. Tackifiers and detackifiers may be used to adjust the Tg of the polymer formulation to that useful in the present invention. The polymer formulation has a Tg of from -60°C to -40°C, and preferably from
-50°C to -40°C. The Tg of the polymer formulation is selected to be low enough to provide anti-slip properties, while being high enough to avoid excessive tackiness.
The polymer useful in the present invention can be either aqueous-based or solvent based. An aqueous-based polymer formulation, such as an emulsion, solution, suspension or dispersion, is preferred. Most preferred is a polymer formulation based on an emulsion polymer.
Polymers useful in the present invention are those formed from ethylenically unsaturated monomers by processes known in the art. Exemplary monomers include, but are not limited to, anhydrides, vinyl esters, alpha-olefins, alkyl esters of acrylic and methacrylic acid, substituted or unsubstituted mono and dialkyl esters of unsaturated dicarboxylic acids, vinyl aromatics, unsubstituted or substituted acrylamides, cyclic monomers, monomers containing alkoxylated side chains, sulfonated monomers, and vinyl amide monomers, A combination of ethylenically unsaturated monomers may also be used.
Suitable anhydride monomers are, for example, maleic anhydride and itaconic anhydride. Suitable vinyl esters are, for example, vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl 2-ethyl-hexanoate, vinyl isooctanoate, vinyl nonanoate, vinyl decanoate, vinyl pivalate, and vinyl versatate. Suitable alkyl esters of acrylic and methacrylic acid are, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, and 2-ethyl hexyl acrylate, etc. Suitable substituted or unsubstituted mono and dialkyl esters of unsaturated dicarboxylic acids are, for example, substituted and unsubstituted mono and dibutyl, mono and diethyl maleate esters as well as the corresponding fumarates. Examples of vinyl aromatic monomers are styrene, 1-vinyl naphthalene, 2-vinyl naphthalene, 3-methyl styrene, 4-propyl styrene, t-butyl styrene, 4-cyclohexyl styrene, 4-dodecyl styrene, 2-ethyl-4-benzyl styrene, 4-(phenylbutyl) styrene, 3-isopropenyl-α, α-dimethylbenzyl isocyanate, and halogenated styrenes.
Suitable acrylamide based monomers are, for example, acrylamide, N, N-dimethylacrylamide, N-octyl acrylamide, N-methylol acrylamide, dimethylaminoethylacrylate, etc. Suitable cyclic monomers are, for example, vinyl pyrrolidone, vinyl imidazolidone, vinyl pyridine, etc. Suitable sulfonated monomers are, for example, 2-acrylamido-2-methyl propane sulfonic acid, sodium methallyl sufonate, sodium vinyl sulfonate, sulfonated styrene, etc. Suitable vinyl amide monomers are, for example, N-vinyl formamide, N-vinyl acetamide, etc.
Preferred polymers of the invention include polymers and copolymers of styrene-butadiene, acrylonitrile, silicones, ethylene-vinyl acetate, polyurethane and acrylic monomers. Acrylic copolymers are most preferred.
Preferably the polymer is one that can undergo cross-linking during or after film formation. Most preferred is a self-cross-linking polymer.
Polymers useful in the present invention have molecular weights in the range of from 5,000 to 5,000,000, and preferably from 10,000 to 2,000,000.
It is advantageous that the polymer formulation be formulated to minimize penetration into the nonwoven, textile or carpet substrate. Thus, if the substrate is hydrophobic, a hydrophilic polymer formulation is preferred. If the substrate is hydrophilic, the polymer formulation is preferably hydrophobic.
The solids level of the formulation may vary, depending on the requirements of the application equipment. The rheology may be adjusted by dilution with water or other solvents, or the addition of a thickener.
The polymer formulation is applied to the nonwoven, textile or carpet substrate by print, foam, or spray application. Spray processes in which the polymer formulation is atomized are preferred. The polymer formulation may be sprayed using both air and airless sprays, and with both internal and external air nozzles. Nozzle spray conditions, including pressure, coating density, and spray type are selected based on the equipment employed.
The polymer formulation may be applied to the nonwoven, textile or carpet substrate as a wet foam, by means known in the art. Foaming of the formulation may occur by both mechanical and chemical means.
Print application is by means of a gravure press in which a transfer roll coats the polymer formulation onto a gravure roll having many cells, the gravure roll then transfers the polymer formulation to the nonwoven, textile or carpet material.
The polymer formulation may be used to treat one or both sides of the porous substrate depending on the application. For many applications, the anti-slip treatment is applied to one side only. The polymer formulation is typically applied at from 1 to 100 percent by weight, based on dry weight of polymer to dry substrate. Preferably the polymer formulation is applied at from 5 to 40 percent by weight, and most preferably from 5 to 25 percent by weight, based on dry weight of polymer to dry substrate.
As stated above, the polymer formulation is applied to a nonwoven, textile or carpet substrate. Uses of substrates formed by the process of the present invention include, but are not limited to mattress covers, surgical shoe covers, surgical towels, table covers, placemats, apparel interlining, food packaging liners, synthetic leather, facings, carriers and wall coverings.
Following application of the polymer formulation to the nonwoven, textile or carpet substrate, the coating is dried. Drying may occur at room temperature, or may be accelerated at elevated temperatures.
Although not needed in all applications, nonwoven, textile or carpet materials produced by the process of the present invention preferably possess breathability. Breathablility, measured by air permeability means that the treatment has coated the nonwoven, textile or carpet material, while allowing most of the pores to remain open.
A 30 gsm spunbond-melt blown nonwoven material was treated with a self-crosslinking acrylic copolymer emulsion having a Tg of -42°C, as measured by DSC. The emulsion was diluted to 30% solids and applied to the non-woven material by spraying, printing and foam coating. The material was then dried at 121°C for two minutes. The basis weight (BW) is the fabric weight in grams used per square meter of the substrate. The coefficient of friction (CoF), both static and dynamic, indicates the force in grams required to pull a 5.1 x 5.1 cm piece of the nonwoven across a cotton woven textile while under downward force of 200 grams as per ASTM D 1894 - 78. Air permeability was measured using Frazier Air Permeability IST 70.1-92. Sample 1 is the untreated nonwoven, used as a comparative. Sample 2 is for the nonwoven material treated with the polymer formulation as a liquid foam. The acrylic copolymer was formulated with 2% solids-on-solids ammonium stearate and wisking to a froth via air incorporation. The foam was metered onto the substrate. Sample 3 is the non-woven treated with the polymer formulation by means of a gravure print. Printing was done by viscosifying the polymer formulation to 400 mPas (400 cps) with 0.2% solids-on-solids hydroxyethyl cellulose. A 45 Quadrill gravure cylinder was used to apply the print pattern. Sample 4 is the non-woven treated with the polymer formulation by means of a spray. Spraying was performed using a spray nozzle, with an orifice of 0.066 cm (0.026") at 2.8 kg/cm2 (40 psi) air and 1.4 kg/cm2 (20 psi) liquid.