US 3664863 A
Carpets are back-coated with essentially non-cellular elastomeric polyurethanes, formed and cured in situ at ambient temperature from a mixture of selected polyether-polyols, selected polyisocyanates and catalyst.
Description (OCR text may contain errors)
United States Patent Dijkhuizen et a1. 5] May 23, 1972 54] CARPETS HAVING A BACK-COATING  References Cited F IN ITU-F RNIED P YUREIHANE 0 s 0 0L UNITED STATES PATENTS  Inventors: Willem Dlikhuizen, Zuid-Laren; Pieter Johannes Adrianus Beersma Hare, both ggfrlinn ..117/161 X Netherlands 3,505,252 4 1970 Brotherton et a1 ..117/161 x  Assignee: Scholten Research N.V., Foxhol, Netherlands FOREIGN PATENTS OR APPLICATIONS 22 F] d: M 19 1969 224,254 l/1959 Australia ..161/67 1 908,188 10/1962 Great Britain ..117/161 21 App1.No.: 825,959
Primary ExaminerWilliam D. Martin Assistant ExaminerMathew R. P. Perrone,.lr. [3O] Fore'gn Application Pnomy Data Attorney-Wenderoth, Lind & Ponack May 25, 1968 Great Britain ..25,096/68 ABSTRACT  U.S.Cl. ..117/161 KP, 156/306, 156/328, Carpets are bacbcoated with essentially nomceuular 51/66, 61/150 elastomeric polyurethanes, fonned and cured in situ at am-  Int.Cl. ..B44dl/09,D04I1l/58 biem temperature from a mixture of Selected polyethep  Field ofSearch ..117/161 KP; 156/306, 328;
polyols, selected polyisocyanates and catalyst.
1 1 Claims, N0 Drawings CARPETS HAVING A BACK-COATING OF IN SITU- FORMED POLYURETHANE The present invention relates to the application of backcoatings to carpets. More particularly it relates to the application of polyurethane coatings to the back of carpets.
When reference herein is made to carpets, it will be understood that any fabric-like sheet material is contemplated, whether tufted, woven, knitted, felted, cemented or otherwise, and that the fabric may be a carpet, rug, mat, floor covering, floor tile, wall covering or the like. The carpet back-cloth may consist of natural and/or synthetic textile materials, such as jute, hessian, nylon, polypropylene and the like. The pile elements may also be built up of natural and/or synthetic textile materials, such as wool, nylon, polyacrylonitrile, polypropylene and the like.
Back-coating is widely used in the production of most types of carpets. Numerous related factors, including basic carpet construction, application techniques, the required characteristics of the finished carpet and, of course, cost determine whether to back-coat and what to use.
The main function of back-coating of carpets is adhesive.
Carpet properties which are directly effected by back-coating include the following.
l. Tuft retention or pile lock. Whereas closely woven .car-
pets of high pile density may have adequate tuft retention without a back-coating, tufted carpets have virtually no tuft retention, unless they are back-coated. With a suitable back-coating their tuft retention can be made excellent. The tuft-retention of Wilton or Axminster carpets of low pile density may also considerably be enhanced by back-coating.
2. Antifray properties. It is important to eliminate the fraying of cut edges of tufted carpets. To achieve complete antifray, an appreciable weight of coating is required, in order that all of the yarns in the carpet are contacted by the coating.
Appearance of the carpet. The back-coating will give a better handle to the carpet by introducing a certain degree of stiffness. It also affects the properties of the laid carpet; it prevents ruckling, imparts a high degree of resilience and prevents slipping of the carpet on a polished floor.
4. Dimensional stability. By locking the fibers together and by slowing their moisture loss and regain, a back-coating increases the dimensional stability of the carpet.
The back coating must have a long effectiveness. It should have a high tensile strength, it should not be dissolved by water and common solvents and not be affected by the components of the floor on which the carpet is laid. it should be capable of application by simple techniques and provide good adhesion for a secondary back-cloth.
Well known carpet backing compounds are styrene-butadiene copolymer latices, in which the copolymers may be carboxylated or not, natural rubber latices, emulsions of homoor copolymers of vinylacetate, acrylic acid esters and the like, and polyvinyl chloride plastisols. It has also been proposed to back-coat carpets with polyurethanes, either in the form of organic solutions of prepolymers, in the form of aqueous emulsions of blocked polymers or in the form of a foaming mixture.
In all these cases the carpet coming from the carpet producing machine must be transferred to a separate carpet backing machine. The backing machine performs essentially two operations. The first operation consists in distributing the coating material to the back of the carpet and the second consists in fixing permanently the coating thus applied by drying, gelation, vulcanization, curing or the like. For the latter operation huge dryers, usually of the hot air type, operating at temperatures up to 160 C. are needed.
An object of the present invention is to back-coat carpets with essentially non-cellular elastomeric polyurethanes, which are formed on the back of the carpet by in situ reaction of specific poly-ether-polyols and polyisocyanates. The
anchorage of the tufts obtained in this way is much better than with polyurethane foam, the tensile strength of non-cellular polyurethanes being much higher than that of polyurethane foam.
A further object of the invention is to back-coat carpets with non-cellular elastomeric polyurethanes, which cure in situ on the back of the carpet at ambient temperature in relatively short time thus obviating the need for a separate heating process.
A further object is to provide new polyurethane backing compounds for carpets which give excellent tuft anchorage, antifray properties, improved handle and dimensional stability to the carpets.
Still another object is to provide novel back-coated carpets in which the backing material consists of selected polyurethanes, and which possess improved properties.
According to the method of the present invention an essentially anhydrous, intimate mixture of a. one or more liquid or semi-liquid polyether-polyols containing wholly or partially secondary hydroxy groups, having hydroxyl numbers in the range of 365, and which are obtained by the addition of one or more alkylene oxides having from three to four carbon atoms or ethylene oxide and at least one other alkylene oxide having three to four carbon atoms to one or more polyhydroxyl compounds having at least three and preferably from three to nine hydroxyl groups, and
b. one or more liquid or semi-liquid organic polyisocyanates containing at least two isocyanate groups per mol, in which the ratio between NCO- and OH-groups is within the range from about 0,95 to about 1,5 l, and one or more catalysts for the formation of polyurethanes is applied to the back of a carpet and allowed to react in situ.
It is highly surprising that the curing of the system under these circumstances is almost complete, which contributes very much to the high strength of the new back-coatings.
The specific polyether-polyols which are used according to the invention are obtained by the addition of alkylene oxides having from two to four carbon atoms to compounds having three or more active hydrogen atoms. When ethylene oxide is used for this addition reaction polyether-polyols are formed with contain only primary hydroxyl groups. Such polyetherpolyols cannot be used in the present invention. When propylene or butylene oxides are used for the addition reaction, acid catalysts for the addition tend to produce polyetherpolyols having partly primary and secondary hydroxyl-groups in their molecules. These polyether-polyols, carrying both primary and secondary hydroxyl groups, are preferably used as the polyol component in the back-coating mixture according to the invention.
Any of the acid catalyst which have been employed to carry out alkylene oxide additions may be used to prepare the polyethers. Typical acid catalysts, which are preferably used in our invention are mineral acids or Lewis acid catalysts, such as boron trifluoride, tribromide of trichloride, and the chlorides of aluminium tin, iron and zinc. In addition, complexes of Lewis acid catalysts and other organic or inorganic compounds may also be used.
Particularly effective catalysts have proved to be boron trifluoride and its complexes. The amount of catalysts used in the condensation is not critical. An operable range is from 0,l to 1,0 percent, based on the weight of the polyether reaction mixture. The residual acid constituents in the polyether ob- 'tained may be left therein as such or they may be partially or be used as such in the process according to the invention. In a preferred embodiment of the invention such polyether-polyols are applied after a part of their secondary hydroxyl groups have been capped with hydroxyethyl groups through reaction with ethylene oxide. The simultaneous presence of secondary and primary hydroxyl groups in the polyether-polyols thus obtained improves the results to be obtained by the present invention.
The hydroxyl number of the polyether-polyols should be within the range of 100 to 365 and preferably in the range of 200 to 300. The polyether-polyol should be of a liquid or semiliquid nature at ambient temperatures or slightly above that.
Typical polyhydroxyl compounds suitable as starting materials for the preparation of the polyethers are triols, such as glycerol, trimethylol propane and hexanetriol, tetrols, such as erythritol and pentaerythritol, pentols, such as arabitol and xylitol, hexols, such as sorbitol and mannitol, glycosides, such as methyl glucoside, ethylene glycol glucoside and glycerol glucoside and monoand polysaccharides, such as arabinose, glucose, sucrose, lactose, dextrin and starch. In general polyhydroxyl compounds with cylic nulei are preferred, since they yield polyurethane resins with outstanding properties.
Mixtures of these polyhydroxyl compounds may also be used. These polyhydroxyl compounds are preferably reacted in a substantially dry state with the alkylene oxide, although small amounts of water may be present.
The alkylene oxides which may be reacted with the polyhydroxyl compounds to form the polyether useful in this invention are those which have from two to four carbon atoms, such as ethylene oxide, propylene oxide, l,2-butylene oxide, 1,3-butylene oxide, 2,3-butylene oxide and isobutylene oxide. These alkylene oxides may be used singly (with the exception of ethylene oxide) or in admixture. Propylene oxide is the preferred alkylene oxide in our invention. Since ethylene oxide produces polyethers containing only primary hydroxylgroups, this alkylene oxide is only used together with other alkylene oxides. It is employed in relatively low quantities in order to introduce the desired amount of primary hydroxyl groups in polyether-polyols which otherwise do not contain primary hydroxyl groups.
Representative examples of organic polyisocyanates containing at least two isocyanate groups per mol are all those which are liquid or semi-liquid under the conditions of use. For this reason it may be necessary to apply heat to certain polyisocyanates, in order to raise their temperature above their melting points, or to add a minor amount of a solvent. The liquid or semi-liquid, melted polyisocyanate may then be mixed with the polyether.
I Suitable organic polyisocyanates include 2,4 tolylene diisocyonate, 2,6 tolylene diisocyanate, commercially available mixtures containing 65 or 80 percent of 2,4 tolylene diisocyanate and 35 or percent of 2,6 tolylene diisocyanate, 1,3 benzene diisocyanate, 1,4 benzene diisocyanate, technical or pure 4,4 diphenylmethane diisocyanate, polymethylene polyphenylisocyanate, 3,3'dimethyl diphenylmethane diisocyanate and l, l-diphenylcyclclohexyl 4,4-diisocyanate. Instead of the simple polyisocyanates, it is possible to use liquid or semi-liquid prepolymers, especially those which contain predetermined proportions of the selected polyethers. Furthermore polyfunctional isocyanates which are produced from polyisocyanates and water with biuret formation are also to be considered, e.g. a liquid triisocyanate obtained from 3 mols of hexamethylene diisocyanate and 1 mol of water. Polycarbodiimides with terminal free isocyanate groups are also suitable. Due to their low vapor pressure and resulting low toxicity the liquid or semi-liquid polyvalent polyisocyanates having an average functionality higher than 2 are preferred.
Mixtures of polyisocyanates may likewise be employed. In case the acidity of the polyisocyanate is too high, it may be necessary to neutralize the acid residues by addition of basic compounds, such as tertiary amines.
In accordance with this invention the polyether containing hydroxyl groups and the polyisocyanate are used in relative amounts corresponding to a NCO/OH ratio within the range of 0,95164 to 1,5. 0,95 NCO/OH ratios outside these limits, the physical properties of the polyurethane resins are generally somewhat less good. Preferably the NCO/OH ratio is from about 1,01 to 1,20.
The catalysts which are needed to make the reaction mixture curable at ambient temperatures comprise organometal compounds or metal salts of carboxylic acids derived from polyvalent metals such as tin, cobalt, lead, cadmium, titane, and zinc. Typical of such catalysts are dibutyltin dilaurate, dibutyltin di-2-ethylhexoate, dibutyltin diversatate, stannous octoate and the like. These catalysts may be present in amounts ranging from 0,05 to 2,0 percent based on the weight of the reaction mixture. They are advantageously used in combination with amine type catalysts, such as triethylene diamine, tetramethylbutane diamine and the like.
The intimate mixture of the reactants is made by pumping said reactants or premixed compounds thereof to the mixing chamber of a commercial polyurethane machine from where it is dispensed in the form of fine particles or as a thin layer, for instance, by means of a spraying nozzle. It is evenly deposited on the back of the carpet to be coated, where it is left to cure. Within a couple of minutes the coating will have lost its tack and the carpet may be stored by winding the same on rollers. If desired, the back-coated carpet, while still being in a tacky state, may be contacted with a second layer of hessian or burlap. The sandwich is then passed through a pair of nip rollers and allowed to cure. In this way a secondary cloth-back with a very neat appearance is obtained.
It should be noted that in order to get the best performance of the polyurethane resin, the reaction mixture which forms the polyurethane elastomer should not substantially foam. Since water reacts with isocyanates with formation of carbon dioxide, its content should be as low as possible. Therefore the reactants should be virtually anhydrous and it is desirable to include a water scavenger in the reaction mixture, such as molecular sieves, hydrolysable esters or the like, like orthoformic acid esters or titanic acid esters.
Other substances, which may be added to the reaction mixture are pigments, fillers, plasticizers, anti oxidants, surfactants, stabilizers and the like. The surfactants, for instance, may be added in order to increase the penetration of the polyurethane in the backing cloth and around the piles so as to firmly bond the pile to the backing cloth. In some instances small amounts of diluting agents, which decrease the viscosity of the reaction mixture, may also be added to increase the penetration. These agents will not perform as blowing agents, because of the thin layers which are applied to the back of the carpet, a usual coating consisting of about 200 250 g polyurethane mix per m The back-coated carpets made according to the invention exhibit a very good tuft anchorage, and have a pleasant handle and a desirable flexibility. The abrasion resistance and the dimensional stability is very high as shown by wear trials. The carpets perfectly withstand a heat ageing test and have a distinct chemical inertness.
The following examples illustrate various embodiments of this invention. The parts referred to are by weight.
EXAMPLE I A mixture is prepared according to the following formula: 75 parts of an acid catalyzed dextrose and propylene oxide based polyol, hydroxyl-number 280, containing secondary and primary hydroxyl groups 2,2 parts of sodium aluminium silicate 0,4 part of dibutyltin diversatate 0,35 part of tetramethylbutane diamine This premixed compound is pumped into the mixing head of a two-component polyurethane spraying device.
The other component consists of 64,2 parts of 4,4'-diphenylmethane diisocyanate. The reaction mixture is deposited on the back of a tufted carpet consisting of jute back-cloth and nylon piles, in an amount of 250 g/m". The reaction mixture reacts and cures at ambient temperature in a couple of minutes, to yield a back coated carpet. The anchorage of the tufts in the carpet and the wear resistance of the carpet are very good.
EXAMPLE 2 A premix is made of the following ingredients 100 parts of an acid catalyzed starch and propylene oxide based polyol, hydroxyl-number 220, containing secondary and primary hydroxyl groups 5 parts of methylene chloride 3 parts of sodium aluminium silicate 0,4 part of dibutyltin dialurate 0,4 part of tetramethylbutane diamine. This compound is fed as one component to a two component spraying gun, the other component consisting of 56 parts of 4,4'-diphenylmethane diisocyanate. The mixture is sprayed on a polypropylene fabric tufted with polypropene yarns. lt cures in situ in a very short time at ambient temperature. The adhesion of the polyurethane to the mat is excellent. The tuft anchorage is very good.
EXAMPLE 3 A mixture of the following composition is prepared: 100 parts of a base catalyzed addition product of glycerol and propylene oxide, hydroxyl numer 260.
5 parts of methylene chloride 0,4 part of dibutyltin diversatate 0,35 part of tetramethylbutane diamine.
This mixture is pumped into the mixing head of a two-component polyurethane spraying device. The other component consists of 67,1 parts of 4,4-diphenylmethane diisocyanate. The reaction mixture is sprayed on the back of a tufted carpet consisting of jute cloth and nylon loop piles in an amount of 320 g/m Another jute cloth is contacted with the tacky reaction mixture and the secondary backed carpet is passed through a pair of nip rollers and allowed to cure at ambient temperature.
The average tuft bind as measured by a dynamometer is 6,2 kg per loop. The adhesion of the secondary back cloth is rather good. When the polyetherpolyol is replaced by an ethylene oxide capped hydroxypropylether of glycerol with hydroxyl number 260 the average tuft bind is 6,8 kg per loop, whereas the addition of the secondary back cloth also has improved.
We claim l. Back-coated carpet comprising tufted carpet with a backing material consisting essentially of 200-320 g/m of a substantially non-cellular elastomeric polyurethane as the in situ product of reaction of a substantially anhydrous mixture of a liquid or semi-liquid polyether polyol containing secondary hydroxyl groups and having a hydroxyl number of to 365 selected from the group consisting of addition products of a polyhydroxyl compound having from three to nine hydroxyl groups and an alkylene oxide having from three to four carbon atoms, addition products of a polyhydroxyl compound having from three to nine hydroxyl groups, an alkylene oxide having from three to four carbon atoms and ethylene oxide, and mixtures of such addition products, and an aromatic polyisocyanate selected from the group consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-benzene diisocyanate, 1,4-benzene diisocyanate, 4,4-diphenylmethane diisocyanate, polymethylene polyphenylisocyanate, 3,3- dimethyl diphenylmethane diisocyanate, 1,1-diphenylcyclohexyl-4,4-diisocyanate and mixtures thereof, the ratio between NCO groups and OH groups being within the range 2. The carpet according to claim 1 in which the polyetherpolyol also contains primary hydroxyl groups and has been obtained by an acid catalysed addition of one or more alkylene oxides having from three to four carbon atoms to one or more polyhydroxyl compounds having from three to nine hydroxyl groups.
3. The carpet according to claim 1 in which the polyetherpolyol also contains primary hydroxyl groups and has been obtained by capping a polyether-polyol which contains strictly secondary hydroxyl groups with ethylene oxide.
4. The carpet according to claim 1 in which the alkylene oxide is propylene oxide.
5. The carpet according to claim 1 in which the polyhydroxyl compound contains a cyclic nucleus.
6. The carpet according to claim 5 in which the polyhydroxyl compound is a glycoside, a monosaccharide or a polysaccharide.
7. The carpet according to claim 1 in which the polyisocyanate is 4,4'-diphenylmethane diisocyanate.
8. The carpet according to claim 1 in which the ratio between NCO-groups and OH-groups is from about 1.01 to about 1.20: l.
9. The carpet according to claim 1 in which the intimate mixture of one or more polyether-polyols, polyisocyanates and catalysts is allowed to cure at ambient temperature.
10. The carpet according to claim 1 in which the intimate mixture of one or more polyether-polyols, polyisocyanates and catalysts also contains a water scavenger.
11. Back-coated carpets according to claim 1, tufted with average tuft bond of at least 6.2 kg per loop.