US3442731A - Method of releasably adhering sponge backed carpet to floor surfaces and adhesive used therefor - Google Patents

Description

United States Patent US. Cl. 15671 3 Claims ABSTRACT OF THE DISCLOSURE Sponge backed carpet and carpeting is releasably adhered to a variety of floor surfaces by a particular syn thetic latex adhesive based on copolymer of Z-ethylhexyl acrylate and N-tertiary-butylacrylamide.

This invention is concerned with a method for adhering sponge backed carpets and carpeting to various types of floor surfaces. It is more particularly concerned with providing a method of adhering carpeting to a floor surface whereby the carpeting will not shift in use, yet can readily be lifted and then relaid in the same or different position without the addition of further adhesive.

In modern office buildings, schools, motels, private homes and the like there is a trend to the use of fabric carpeting, particularly wall to Wall carpeting for floor coverings. Carpeting is generally more pleasing to the eye and comfortable to the foot than uncovered wood, resilient tile, terrazzo, cement, and the like. Though initially more expensive to install than other types of floor covering, carpeting is much less costly to clean and maintain. It is desirable, however, that the carpeting, once laid, not shift, creep, crawl and bunch up under the shifting of furniture and heavy loads passing across it or from the traffic of countless feet.

In homes, carpeting is normally nailed down to prevent such shi-fting. This act of nailing, however, sets up the difficult task of nail removing when and if the carpet is to be lifted for cleaning, turning to even the wear, or for any other reason. Tackless carpeting techniques are available and require the services of a skilled carpet layer as the carpet must be stretched over forms and fastened.

Most carpeting is laid with a pad of fabric, rubber, or the like, underneath it to serve as a cushion and shock absorber. Padding contributes to the comfort of walking on the carpet and to the wearlife of the carpet. A recent trend, particularly in commercial locations, is to use a combined carpeting and padding by employing a sponge backed carpeting construction. This material saves a large portion of the labor cost incurred in laying separate padding and carpeting. The sponge backing may be based on natural rubber latex, polyurethanes, or styrene-butadiene rubber latex. The adhesives of this invention are compatible with all classes of rubber sponge.

Carpeting and padding may be fastened to wood floors or through a wood edge molding, by conventional nailing techniques. Removal, however, requires removal of both the molding and the nails and holes are necessarily punched into the carpet by the nail. Where no wood floor or molding is available for nailing, the padding and carpet are laid as is with only the fraction force between floor and padding and padding and carpeting to hold the installation in place. Carpeting installed in this manner is 3,442,731 Patented May 6, 1969 "ice readily lifted for cleaning, turning, or any other purposes but tends to shift out of position and bunch up when heavy loads such as baggage or furniture are shifted across it. If the carpet has been installed by the t'ackless technique, the services of the carpet layer will again be required to place the carpet down in proper fashion.

Attempts have been made to employ adhesives to secure the sponge backed carpeting to various flooring surfaces, but to date no satisfactory adhesive has been found. An adhesive with too much strength contributes to destruction of the sponge backing or even the floor surface when the carpet is lifted; an adhesive that is too weak is not satisfactory in holding the carpeting in place under the shifting of loads, as when furniture is pushed from place to place when cleaning or rearranging the room appearance.

Quite by chance, there has now been found a particular family of adhesive copolymers that can be applied in thin coats to continuous flooring of any nature, wood, vinyl or rubber or asphalt tile, concrete, marble or metal, or to a sponge-backed carpeting, or to both the surface of said flooring and of said sponge-backed carpeting, whereby the said carpeting, once cut to the desired size and shape, can be laid in the desired spot, smoothed down, and will remain flat in the selected spot or area under trafiic of feet, wheeled trucks carrying baggage or furniture and the like, or the push shifting of heavy items of furniture and the like directly across the surface of the carpet itself. The carpet will not bunch or shift. Furthermore, after any period of time desired, either hours, days, months or years, the adhesive releases with a slight lifting force and the carpet can be lifted readily, shifted for any desired purpose, then relaid in the original, reversed, or any other desired configuration in the same room or pl-ace or in another room, without the requirement for adding any further adhesive to the carpet sponge backing. After such reinstallation-s, the carpeting has the same resistance to bunching or shifting that it had previously. If the carpet is properly cut to size no special skills or talents are required to perform a proper job of laying it.

The adhesive which exhibits the remarkable property of adhering sponge-backed carpeting to any conventional floor surface for as long a period of time as may be desired, then permits ready removal of the carpet without any destruction of the backing thereof, and reinstallation of said carpeting, is a family of emulsion copolymers of Z-ethylhexyl acrylate and N-tertiary-butylacrylamide. These are both commercially available monomeric materials.

It is surprising that only N-tertiary-butylacrylamide and Z-ethylhexyl acrylate combine to form a permanently tacky releasable adhesive. When lower and higher alkyl acrylates and methacrylates are substituted for 2-ethylhexyl acrylate or another acrylamide monomer is substituted for N-tertiary-butylacrylamide non-tacky, unstable latices result which do not have the adhesive properties of the particular combination of the invention.

The 2-ethylhexyl acrylate is readily copolymerized in an aqueous emulsion system with N-tertiary-butylacrylamide to complete conversion in ratios of 99.9/ 0.1 to 50/50 weight percent acrylate/N-tertiary-butylacrylamide. While copolymers of 50 parts and even higher N-tertiary-butylacrylamide can be made, the preferred range of the acrylamide is 10 parts and "below, and the most preferred range of N-tertiary-butylacrylamide in the adhesive copolymer is 5.0 to 7.5 parts per parts of copolymer.

A typical recipe for emulsion copolymerization of the copolymers is as follows:

Material: Parts Z-ethylhexyl acrylate 90-999 N-tertiary-butylacrylamide 0.1 Water 150 Decyl benzene sodium sulfonate 0.9 Condensation product of formaldehyde and naphthalene sulfonic acids 1.0 Sodium pyrophospha-te 0.5 Potassium persulfate 0.1

Water is charged to a glasslined polymerizer which is purged and pressured with nitrogen. Soaps and emulsifiers are added, followed by the monomers. The polymerizer is evacuated and purged with nitrogen; then the persulfate catalyst is added and the temperature is raised to 50 C. The polymerization runs to complete conversion in approximately hours at 50 C. The copolymer latex is usable directly as drawn from the polymerizer in the practice of this invention. Latex total solids runs about -55% by weight, with to being preferred.

Adhesives of this invention are evaluated in a laboratory peel test and a laboratory tack test. In the peel test a 1" x 6" strip of sponge carpet backing is brush coated with a layer of test adhesive. When the adhesive layer is dry to the touch, the strip is pressure bonded by two passages of a four pound roller to a panel of standard resilient floor tile which may be rubber, vinyl, or asphalt. The test panels are allowed to stand under no pressure for 48 hours. The test strip is then peeled back at 180 at a rate of 2" per minute and the force required to peel is registered as lbs. per inch of strip width.

The tack test is performed on a laboratory-constructed tackmeter. This is a simple triple beam balance suspended 10 inches above a scissors jack A cylindrical metal rod, eight inches long, with one end ground to a pencil-like one-sixteenth inch diameter point, is suspended from the balance pan. Test adhesive films are prepared by putting a known volume of test adhesive into exactly similar shaped open cup molds and oven drying the films at 100 C. Each test film is placed in contact at its center point with the contact rod of the tack-meter by raising the film in its mold up to the contact rod on the jack. Contact is maintained with no increase in pressure for a standard length of time seconds is sufficient). Polymers from which the films are made for the test must have percent total solids in the same general range, plus or minus 5%. After a contact time of one minute, onehalf gram weights are added to the balance at uniform time intervals (usually 5 seconds) until sufficient weight causes the contact rod to break loose from the tacky, dried polymer film. This weight has to overcome only the films tack which, after subtracting the tare weight of contact rod, is a direct measurement of tack and is easily converted to gms./sq.cn1, of force. Each film is prepared and tested in the same manner.

The following examples will serve to illustrate the invention.

EXAMPLE I The following recipe is charged to a 15 gallon glass poly'merizerr Z-ethylhexyl acrylate N-t-butylacrylamide 10 Water Decyl benzene sodium sulfonate 0.9 Cond. product of formaldehyde and naphthalene sulfonic acids 1.0 Sodium pyrophosphate 0.5 Potassium persulfate 0.1

One hundred twenty-five parts of water are charged, heated to 60 C. and evacuated until boiling. The polymerizer is pressured with nitrogen and cooled to 25 C.

Soaps and pyrophosphate are added, followed by the monomers. The polymerizer is purged with nitrogen and the potassium persulfate, dissolved in the balance of the water, is pressured into the charge. The polymerizer is heated to 50 C. and run to complete conversion in 30 hours. The final latex, marked A, has a total solids of 39.4%, When tested as an adhesive, latex A registers 20 oz. per inch width in the peel test and 580 gm./sq.cm. in the laboratory tack tests. Tack tests are run in duplicate and the results are averaged. Similar polymerizations are run with the following charging ratios and test results.

Z-ethylhcxyl acrylate/N-tert. Peel test, Tack test, butylacrylamide 0z./in. width gm./sq. cm.

When the peel test and tack test results are plotted versus percent N-tert.-butylacrylamide charged, the range of maximum adhesion is found to occur when 5 to 7.5 parts are used.

When N-methylolacrylamide is substituted for N-tertiary-butylacrylamide, the latex produced is unstable. When ethyl acrylate and lauryl methacrcylate are substituted for 2-e'thylhexyl acrylate, the latices are non-tacky and do not form an adhesive.

EXAMPLE II The 2-ethylhexyl aerylate/N-tertiary-butylacrylamide latex of Run A, Example I, was applied with a short fiber (mohair) paint type roller to the natural rubber sponge backing of 20 square yards (10 yds. 2 yds.) of a commercial grade carpet. Half the length of carpet was laid over concrete floor; half the length over asphalt tile floor. The floor was not cleaned before the test.

The cemented carpet was laid out in the chosen position in a heavily traveled hallway by merely unrolling it in place and pressing down the ends by hand. The carpet was subjected to heavy morning, midday and evening foot traffic and constant light foot traffic during the work day. Ofiice and laboratory hand trucks carrying ice, gas cylinders, laboratory supplies and mail crossed it daily.

In one month, the carpet, which was rimmed by open floor on all sides, had not shifted or bunched under any of the trafiic load applied. After 30 days the carpet was easily rolled up. The removal did not cause any tearing in the sponge backing of the carpet.

The floor was then cleaned by the building maintenance floor cleaning machine using detergent and hot water. The rolled up carpet was allowed to stand for 3 days; then was unrolled in place again and observed for 3 more days under the same trafiic as before, The tacky adhesive held the strip firmly in place and was still tacky to the touch when the test strip was again rolled up and stored.

I claim:

1. The method of releasably adhering sponge-backed carpet to a floor surface comprising spreading on the said floor surface and/or the said sponge backing surface of said carpet an adhesive layer of a synthetic latex comprising a 35% to 55% total solids copolymer of 99.5- 90-0 parts by weight 2-ethylhexyl acrcylate and 0.5-10.0 parts by weight N-terti-ary-butylacrylamide.

2. The method of releasably adhering sponge-backed carpet to a floor surface comprising spreading on the said floor surface and on said sponge-backing surface of said carpet an adhesive latex which comprises 0.5-10 parts by weight N-tertiary-butylacrylamide and 99.5-90 parts by weight 2-ethylhexyl acrylate.

5 6 3. A permanently tacky, releasable adhesive compris- 3,014,829 1 2/1961 Curtin 156-71 X ing a copolymer of 0.5-10.0 parts by weight N-tertiary- 3,135,647 6/1964 Wheeley 156-71 X butylacryl-gmide and 99.5-90.0 parts by weight Z-echyl- 3,157,562 11/1964 Kine et a1. 161-170 hexyl acryl-ate. 3,248,260 4/ 1966 Cangerak et a1 117-161 References Cited 5 3,332,827 7/1967 Griffith et a1. 156-71 X UNITED STATES PATENTS HAROLD ANSHER, Primary Examiner. 2,541,465 2/1951 Dickey 260-861 X U S C1 XR 2,761,856 9/1956 Suen et a1. 260-861 X 2,808,388 10/ 1957 Hellm'ann 260-8 156-332, 247; 260-861, 29.6

UNITED STATES PATENT OFFICE 56g PGERTIFICATE 0F CORRECTION Patent No 3,1m2,731 Dated y 969 Inventofli) J6EE F. ANDERSON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I /T 101m 1, line 59 "carpeting" shofild be --carpet-- line 66, .1

"fraction" should be --friction--.

column 6, line t "Cangersk et 81" should be --Langerak et al-- SIGNED AND SEALED APR 7 4970 Atlas: 4

i E. SW, JR- I. l fis ifiioner of Pawn