US3436245A - Flock-coated substrate and method of making the same - Google Patents

Description

April 1, 1969 R. v. GRUNDMAN 3,436,245

FLOCK COATED SUBSTRATE AND METHOD OF MAKING THE SAME Filed Nov. 8, 1965 INVENTOR.

06RM6RUNDMAN United States Patent 6 3,436,245 FLOCK-COATED SUBSTRATE AND METHOD OF MAKING THE SAME Roger V. Grundman, Roseville, Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul,

Minn., a corporation of Delaware Filed Nov. 8, 1965, Ser. No. 506,652 Int. Cl. B44d 1/52; C23d /08; B44c 1/08 US. Cl. 117-25 11 Claims ABSTRACT OF THE DISCLOSURE Flock coated substrates formed by coating the individual fibers of an open fabric substrate with a pressure-sensitive adhesive without closing the openings of the substrate, applying a fibrous flock coating to the substrate, applying a settable liquid adhesive such as a two-part polyurethane to the side of the substrate opposite the flock coating and passing the adhesive through the openings in the substrate to embed the substrate and the ends of the fibers attached thereto, and then curing the adhesive.

This invention relates to a method for flock coating of open, porous substrates and to articles produced thereby. In one embodiment the invention relates to novel flocked products having sharply outlined areas of different colors or contrasting appearance.

It has been known to produce flock-coated products by coating a substrate with an adhesive and applying a fibrous flock to the adhesive-coated substrate. The flock fibers are caused to assume an upright orientation, i.e. normal to the surface of the substrate by the use of such techniques as electrostatic application of the fibers, spray coating, or vibration of the substrate during the coating step. Except in the electrostatic process, which is not favored due to the slow production rates possible, a substantial amount of the fibers become completely embedded in the wet, flowable adhesive and thus are lost as a part of the visible flock coating. A further shortcoming of these known methods results from the fact that it has not been practical to place a stencil in contact with a wet adhesive coating. Thus, when multi-color coatings were formed, the lines between the areas of contrasting color were not sharp and distinct.

The present invention provides a method whereby a vibration type flock coating can be applied to a substrate in which practically all of the adhered flock fibers are in an upright orientation, thus making possible a significant saving in the cost of the articles. The fact that most of the fibers are adhered more nearly vertical makes possible higher production rates because of the tendency of the vertical fibers to guide additional fibers into position. The method of this invention is further characterized by the ability to apply flock or other fibrous fabric material to open, porous substrates in sharply defined patterns without any apparent intervening discontinuities due to uncoated portions between areas of contrasting appearance which form the pattern. A further advantage of the invention is that it is possible to control the flock density by varying the percentage of open area in the substrate.

It has been found that by applying a thin coating of pressure-sensitive adhesive to an open, porous substrate, such as a reticulate fabric, and employing this adhesive to retain the fibers when first applied and hold them in place during application of the permanent adhesive, the aforementioned problem of fibers lying flat and becoming completely embedded in the adhesive is substantially eliminated. Fibers which are first deposited horizontally have a tendency to come loose apparently because of a low unit pressure effect against the adhesive and eventually become readhered in an upright orientation. More particularly the invention contemplates that the flock fibers are first held in place by the pressure-sensitive adhesive and a permanent settable adhesive is then applied. A permanent settable adhesive is applied through the porous, open backside of the substrate to firmly bond the adhered ends of the fibers and thoroughly saturate the substrate to form a tough, durable, resilient backing for the article. A further advantage of the invention is that the fibers are all anchored in the adhesive to a uniform depth.

It has further been found that flock fibers may be appliedto an adhesive-coated substrate material through a flexible stencil temporarily adhered to the substrate to provide clearly defined flocked and unfiocked areas, the latter retaining their adherency toward further quantities of fiock. Flock fibers of a contrasting color can then be applied to these sharply defined areas without leaving uncoated portions between the areas of contrasting color.

In the drawing:

FIGURE 1 illustrates in schematic form a method and apparatus for producing sheet materials of this invention;

FIGURE 2 is a perspective view of an article of the present invention; and

FIGURE 3 is a broken away cross-sectional segment of the article of FIGURE 2.

The material may typically be produced on a reticulate fabric or web 1 obtained from a supply roll 3, the fabric having previously been provided with a coating of pressure-sensitive adhesive on the top side 5. To form a multicolor flocked sheet a flexible stencil 7 made out of foam rubber or the like is brought into contact with the adhesive-coated surface 5 of the fabric, a tamping device 9 being used to uniformly attach the stencil to the fabric. A hopper 11 which may have a rotary dispensing means is provided to dispense flock fibers 12 onto the substrate. A vibrating device 13, such as a vibrating platform or rotary beater bar, is provided beneath the fabric in line with the dispensing hopper 11 to cause the flock fibers to become adhered to the pressure-sensitive adhesive in upright orientation. A suction device 15 is preferably provided to remove excess flock fibers. A foam dispenser 17 may optionally be provided to deposit through the stencil a coating of foam over the flock-coated portions of the substrate. The stencil is then caused to travel over rollers to separate the same from the fabric and excess foam may be dried therefrom by passing the same through a hot air duct 19. A second flock dispensing hopper 21 is provided to apply flock fibers 22 of a contrastingappearance to the portions of the fabric previously covered by the stencil. Another vibrating device 23 is employed to cause these flock fibers to assume an upright orientation. The foam on the first applied fibers prevents the later applied fibers of contrasting appearance from becoming adhered to the fabric in the previously coated portions and thus helps to provide a product having clearly'distinct areas of contrasting appearance. A second suction device 25 is provided to remove any unadhered excess flock 22.

The permanent adhesive 26 may advantageously be applied by first coating the same from coating means 27 to the desired thickness on an endless belt 29 of, for example, silicone rubber-coated woven fiberglas or stainless steel. A release coating, for example, of a silicone resin, may be applied to the endless belt to assist in stripping of the cured adhesive therefrom. The flock-coated fabric is then brought into pressure contact with the still liquid adhesive, the depth, solids content, viscosity, and fiber-wetting characteristics of the adhesive layer being selected so that the adhesive will penetrate the flock-coated fabric to the desired depth, preferably about one-fourth or less of the length of the fibers to embed the lower portions of the fibers as well as the fabric in the adhesive. The fabric with the settable adhesive therein is then passed over a heated drum or other curved surface 31 to force the adhesive into the coated fabric and accelerate setting thereof. The product, cured at least to a self-supporting non-fiowable condition is then stripped from the endless belt, either cut to suitable lengths or wound on a roll 33.

It will be understood that if it is desired to produce flock-coated articles which are uniformly colored across the surface thereof, the stencil 7 and the equipment associated therewith would be eliminated, and onl a single dispensing hopper 21, vibrator 23 and excess flock pickup device 25 would be used. On the other hand, if it is desired to form articles having more than two colors, a plurality of successive stencils and flock-depositing means would be used. In such cases it is generally advantageous to provide each of the successive stencils with a somewhat larger opening than the preceding stencil.

The base Web or fabric may be any porous web which is sufficiently open to permit the permanent adhesive 26 to penetrate the openings and surround the flock fibers. Examples of suitable porous webs include woven, knitted, spun, and non-woven fabrics. Natural, synthetic, and even metallic fibers have been found suitable. Webs having a Gurley densometer reading of 20 secs. per 300 ccs. can be successfully flock coated and are sufliciently open to permit the adhesive to pass through to embed the lower ends of the flock fibers. The upper limit for the size of the openings in the fabric is practically unlimited, as it is possible to flock coat one side of a net having very large openings, if desired. For multi-color webs it is generally preferred that the openings be not greater than about 3 mm.

The pressure-sensitive adhesive used for coating the web can be applied b any suitable methods, such as spray coating or roll coating with a smooth or knurled roll. The coating must be applied as a thin coating which covers the individual fibers of the base web without closing the pores or openings therein. If necessary, a stream of air may be blown through the web immediately after application of the adhesive to reopen any pores which may have been closed. Both water-based and solventbased adhesives are suitable provided that they have sufficient tack to hold the flock fibers. Rubber-resin type pressure-sensitive adhesives, e.g. based on natural rubbers, synthetic rubbers, acrylic resins, and combinations thereof, constitute the preferred class of adhesives. Where waterbased adhesives are used, precautions must be taken to eliminate the water where the permanent adhesive is a water-sensitive type such as a polyurethane.

The permanent adhesive should be a composition which is sufficiently low in viscosity to penetrate and saturate the web and adhere to the flock fibers and which, for the method and apparatus shown, will set in a relatively short time. For flock-coated articles intended for use as floor coverings it is preferred that the adhesive composition be curable to a relatively flexible state, excessive brittleness being undesirable. Examples of suitable adhesives include urethane, acrylic and rubber-based adhesives, which may be of the solvent-based type. The preferred adhesives, however, are two-part solvent-free, curable epoxy and urethane compositions, which when first mixed are in a flowable liquid form that will penetrate the fabric, wet the fibers, and then shortly cure to a tough, Well-bonded state. These adhesives are flexible and durable. Processing is simplified in that there is no solvent removal or recovery problem. It is also possible to use hot melt adhesives which in molten liquid form will penetrate the porous web, adhere to the flock, and harden on cooling. Such adhesives are not preferred, however, in applications where heat sensitivity of the product presents a pr oblem.

The preferred urethane adhesives are two-part urethane compositions based on a part A which includes a poly alkylene-ether glycol and optionall an organic polyamide, for example, 4,4'methylene bis-(2-chloroaniline) and a part B which includes an organic diisocyanate, for example, toluene diisocyanate. These compositions are curable at ambient temperatures by the incorporation into part A of a polyol-soluble organic compound of certain polyvalent metals, e.g., tin, lead, and mercury. These compositions can be cured even more rapidly at somewhat elevated temperatures, for example, 65 C. to C. Further examples of suitable polyurethane compositions are those set forth in U.S. Patent 3,201,136 issued to Harrison et al. on Aug. 17, 1965.

Instead of casting the permanent adhesive on a carrier such as endless belt 29, the same may be deposited on the surface of a sheet or web intended to become a composite part of the flock-coated construction in the form of an integral backing therefor. For example, a cured polyurethane rubber sheet, vinyl plastic sheet, or a woven cloth or the like can be bonded to the bottom of the base web 1 by means of the permanent adhesive.

The stencils used in making multi-color articles are preferably lightweight and flexible in order that they can be easily applied and removed, and will withstand vibration, if used. Yet the stencil material should be nonstretching in order that the openings therein do not become distorted. One construction which provides this desirable combination of properties is foamed elastomer backed with a fabric and/or film of dimensionally stable material. It is desirable to use a material for the stencil which has a thickness about equal to the fiber length to assist invertically orienting the fibers adjacent the edges of the openings.

While vibration-type flock coating has been described for purposes of illustration, it will be understood that electrostatic and spray flocking procedures can also be used. The fibers used in the process will typically be in the 15 to 500 denier range and will typically have a length of from 2 to 25 mm. Interesting effects can be provided by using fibers of one length for the first color applied in a two-color procedure, and to use either longer or shorter fibers for the second color. Areas of contrasting appearance can also be provided by applying fibers having the same color but different lengths or glossiness to the different areas.

The temporary protective foam may be a soap, synthetic detergent or a proteinaceous material such as gelatins and the like. The foam should be of a stable type which will withstand vibration or other processing. A particularly suitable foam is of the type used in aerosol packaged shaving creams. A relatively thin coating of foam generally sufiices. The fibers removed with the foam can be recovered and reused. If the second color fibers are shorter than those of the first applied color, the foam may be eliminated, as a small percentage of shorter fibers present among the longer fibers are not noticably visible. It has been found that if the first applied fibers are curled, for example by heat shrinking after application, the protective foam can also be eliminated, because the curled fibers prevent peneration by later applied fibers.

The invention will be further illustrated but not limited by the following example. All parts are by weight unless otherwise indicated.

EXAMPLE An open woven cotton scrim which had about 12 threads per cm. was coated on one side using a rotogravure coater with about /10 gm. solids per 100 sq. cm. of pressure-sensitive adhesive comprising 94.5 parts isooctyl acrylate and 5.5 parts acrylic acid as about 10% solids in heptane. A light weight stencil in the form of an endless belt formed from a 6 mm. thick layer of polyurethane elastomeric foam laminated to an open netting was lightly pressed over the adhesive-coated surface of the scrim. 53 denier white nylon staple fibers having a length of about 4.5 mm. were coated through the openings in the stencil onto the adhesive-coated scrim while vibrating the scrim with a vibrating platen. A thin layer of detergent foam was applied over the fibers and the stencil was removed. 45 denier blue nylon staple fibers having a length of about 4 mm. were then applied while again vibrating the scrim with a vibrating platen to the portions of the scrim previously covered by the stencil. An endless silicone rubber saturated glass cloth belt was used as a casting surface for the following two-part polyurethane composition:

Part A Weight parts Polypropylene ether glycol (200 M.W.) 356 PbO 1.2 Silica (Cab-O-Sil) 16 4,4'-methylene bis-(2-chloroaniline) 21.6 Calcium Z-ethyl hexoate 1.2 Phenyl mercuric acetate 2.4 2,6-di-tert-4-methylphenol 1.6

Part B Tolylene diisocyanate 62.3 Polypropylene ether glycol (400 M.W.) 31.4 Polypropylene ether triol (400 M.W.) 6.3

The composition was continuously mixed in a ratio of 3.77 parts A for each part B, and knife-coated onto the belt to a thickness of about 1 mm. The flock-coated scrim was pulled down into the liquid reaction mixture to saturate the scrim and the lower ends of the flock fibers. The saturated scrim was passed over a drum heated to about 100 C. and reacted to a solid noncellular elastomer within a few minutes.

What is claimed is:

1. A multi-colored flock-coated substrate comprising flock fibers bonded to one side of a porous fabric, the fibers of said fabric being coated with a pressure-sensitive adhesive which does not close the openings in said fabric, said flock being present in at least two sharply defined areas of contrasting appearance, there being no apparent discontinuities in said flock due to uncoated portions between said areas, said fabric and the ends of the flock adjacent thereto being embedded to a uniform depth in a cured elastomeric adhesive which penetrates through the openings in the pressure-sensitive adhesive coated fabric.

2. The article of claim 1 wherein said adhesive is a solvent-free, catalyzed polyurethane elastomer cured at temperatures below about 100 C.

3. A method of forming flock-coated substrates comprising:

(a) providing an open, porous fabric substrate;

(b) coating the individual fibers of said substrate with a thin coating of a pressure-sensitive adhesive without closing the openings in said substrate;

(c) applying a fibrous flock coating to the adhesivecoated substrate, the flock fibers being oriented normal to the adhesive coated surface of said substrate;

((1) applying a settable liquid adhesive to the side of the substrate opposite said flock coating and passing said adhesive through the openings in the substrate to embed the substrate and the ends of said fibers attached thereto in said adhesive; and

(e) curing said adhesive.

4. The method of claim 3 wherein said fibers are oriented normal to said surface by vibrating said substrate.

5. The method of claim 3 wherein said settable adhesive is a solvent-free composition.

6. The method of claim 5 wherein said solvent-free adhesive composition isa two-part, ambient temperature curable polyurethane composition.

7. A method according to claim 3 comprising the additional steps of temporarily bonding a flexible stencil to a pressure-sensitive adhesive-coated surface of said substrate, applying flock of a first color to exposed portions of said surface through said stencil, removing said stencil from said surface, applying additional flock of contrasting appearance to said surface whereby a flock coating is formed on said surface having sharply defined areas of constrasting appearance without intervening discontinuities other than the patterns formed by said areas and then applying said settable adhesive.

8. The method of claim 7 wherein said stencil is an endless foamed elastomer belt.

9. The method of claim 7 wherein said first colored flock is coated 'with a fugitive foam prior to the application of said additional flock.

10. The method of claim 7 wherein said additional flock is of a different average fiber length than said flock of said first color.

11. The method of claim 7 wherein the back side of said coated substrate with the settable adhesive surrounds the flock fibers to a depth less than about one-fourth the thickness of said flock coating.

References Cited UNITED STATES PATENTS Re 23,741 11/1953 Summers 161-64 XR 1,394,149 10/ 1921 Cumfer et a1. 117-25 2,056,275 10/ 1936 Holdsworth 117-25 2,106,132 1/1938 Feinbloom 161-64 XR 2,602,025 7/1952 De Goeij et al. 117-5.5 XR 3,166,465 1/1965 Rahmes 161-66 ROBERT F. BURNETT, Primary Examiner. R. H. CRISS, Assistant Examiner.

US. Cl. X.R.

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