IL33588A - A process for making a tufted carpet having a polypropylene primary backing and tufted carpets produced thereby - Google Patents

Description

. nt nna D»IXT»DH O*SMSD o»n»oi_i A PROCESS FOR MAKING- A TUFTED CARPET HAVING A POLYPROPYLENE PRIMARY BACKING AN TUFTED CARPETS PRODUCED THEREBY This invention relates to tufted carpets. · In particular the invention relates to a method of bonding the tufts to a primary backing and Obtaining gbbd handle of the carpet using a rubber latex formulation* ■'■'>■'' : . Tufted carpets have hitherto conventionally been made by tufting pile into a woven hessian primary backing material and then applying art adhesive to bond the tufts in place and to provide dimensional stability. The jute fibres in hessian have a rough surface and many adhesives gave a satisfactory result.

Attempts have now been made to replace the hessian backing with various synthetic fibre backings and it has been found that the adhesion drops off sharply and also that the adhesive itself may crack when the carpet is handled. The problem is especially acute n the case of a woven tape polypropylene primary backing which has bad adhesion properties since it has a very smooth surface. The problem also occurs when a secondary backing or a foam backing is to be applied over the primary backing.

There is also known a carpet to the back of which is applied a latex in the form of a foam and which in turn is coated or covered with cloth* see for example French Patent No. 1533106.

According to the present invention there is provided a process for making a tufted carpet having a polypropylene primary backing which comprises inserting of a flexibile film-forming polymer in aqueous latex working form onto the back of the carpet, bringing the foam into 4ft%*m4«»eefi*e«-¼-w ½k the backing of the carpet whilst at the same time substantially collapsing the foam structure, and subsequently drying the. collapsed foam so as to complete the removal of water.

Also according to the present invention-there is provided a primary backed tufted carpet having- a polypropylene primary backing wherein the tufts are held in place by a collapsed foam latex in which the foam structure is still partially present at least adjacent the backing in the valleys between the rows of tuft backs.

It has surprisingly been found that by collapsing ,the structure of the foamed latex it is possible to obtain good tuft adhesion and good handle in a carpet having a polypropylene primary backing.

Furthermore, the resultant latex filnhas good resistance to flex cracking, such flexure occurring, for instance^' during production, handling and laying of a carpet.

A further advantage of applying a foamed latex is that it is possible to obtain good tuft-bind and abrasion properties even though the amount of latex solids applied per unit area of backing is far less than could un conveniently be applied using a conventional/foamed liquid latex.. Carpets produced by the process of the" present invention have a good handle even where a woven tape polypropylene backing is used. Such a woven tape T e a i t • The polypropylene backing is preferably woven , and may contain minor proportions o other textile materials either in the warp or the weft or in bo th. By the term "polypropylene" we mean any fibre forming polymer or copolymer containing at least $0% of propylene units in the polymer chain.

Filaments of synthetic materials including poly-propylene may be present. The backing material may have a minor proportion of its surface area cons ti tuted by natural fibres such as jute , or by tapes or filaments of other synthetic materials such as polye thylene , a polyester, a polyamide or polyacrylonitrile . The backing material need not be *a woven material and may be a sheet material such, for example , as a polypropylene non-woven fabric e. g. that sold by du Pont under the Trade name "Typar" .

The elastomer in the latex will usually contain polymerised butadiene or isoprene and may be a reactive or unreactive latex. The so-called reactive latices '* are described in more detail in British Patent No. 1 , 023 , 202. he unreactive latices are also in effect described in Patent No. 1 , 023 , 202 by omitting the reactive groups . The latices are preferably prepared from at leas t two monomers , one of which is a conjugat and the lower al , a raethacrylate , acrylonitrile , methacrylonitrile , a vinyl as alkyl substitutad butadienes, may also be employed. Where reactive groups are introduced they may be provided by a minor proportion, preferably at least about 0, 5% by weight, of a third monomer. Ahe amount of the third monomer is preferably not more than about 5% by weight of the copolymer.

The latices used to prepare the foam used in the process of the present invention maybe type. typical example, it has been proposed that when the styrene content is in excess of 60;» the term "resin latex" should be used, but the dividing line is not precise. It is possible to produce a foam having resilience with a bound styrene content of 55%» and latex having a bound styrene content of up to 80# can be used for the purposes of this invention. It is preferred to use a latex having a bound styrene content of not more than 75%· The latex used, and hence the resulting foain, is usually compounded with a filler. since otherwise the cost is higher, and the properties of the foam would not be so suitable. The precise ratio of filler to elastomer solids can be varied according to the properties desired in the foam and according to the filler being used. Broadly, the ratio of filler to elastomer may be from 1 : 1 to !? : 1 . It is however preferred to use a range of from 3·5*.1 to 1.5* 1 more preferably from 2 : 1 to 1.5: 1 . or carbon black can be used as pigments although the latter gives dark latex which is not normally desirable. Other adjuvants which may be added include surface active agents, catalysts, anti-oxidants , foam stabilizers and gel sensitizers.

The foamed latex may conveniently contain about 70% by weight of solids where the term "solids" is used to include both the elastomer and any fillers solid and^adjuvants which may be present. If an excessive amount of water is used then difficulty may be experienced in drying the foam in either the partially collapsed or completely collapsed form unless the carpet backing machine is run at very low speeds. The minimum amount of v/ater necessary is determined by that amount necessary to form a satisfactory foam structure. The solids content may thus be varied between 50% and Q0%, The amounts of latex applied may conveniently be from 3 to 32 ounces (solids) per sq.yd. (100 to 1060 gms. (solids) per sq. metre). The lower end of this range can only be applied using a foam since otherwise it takes too long to dry the latex. It is a preferred feature of the invention that the amount applied lies between 9 ounces (solids) per sq. yd. of primary backing (30* gms. (solids) per sq. metre), and 20 ounces (solids) per sq. yd. (639 gms. (solids) per sq. metre).

The foam may be prepared from the compounded foam. Conventional continuous foamers or planetary mixers are conveniently used. Conveniently the latex compound may be expanded by from % to 0 by volume during foaming.

The foam may be applied to the primary carpet backing by any convenient method. Simple pouring may be used but in large scale operations accurate metering is required and this may be achieved by using a nozzle or series of nozzles which reciprocate transversely across the tufted backing as the backing is moved, tufts down, past the nozzles. The step of "* bringing the foam into intimate contact with the backing and at the same time substantially collapsing the foam structure may take place substantially simultaneously with the foam application, or after some delay.

A preferred method of foam application which '. working is also effective to bring about the required 4wWrcwt«. ■eowbaret and foam collapse is to use a doctor roller' or just touching set so that it is just clearing^the ridges formed by the backs of the rows of stitches in the primary backing.

The doctor roller is normally stationary and forms a "nip" or "bank" of foam whose shape is defined by the backing material and the curve of the doctor roller, and feeds foam from this "bank" into the back of the carpet, as the carpet moves- past the roller.

An alternative to usin a doctor roller is to avoided. A preferred form. f blade has an operative iur edge with a radius of curvature of at least one quarter of an inch. 1 • A doctor roller or blade may also be used Working^ < if the &rifa^ e0¥A&^ and foam collapse- is brought about after some delay: .since application of foam to the backing. In this case the doctor roller is set some distance away from the backing so as to meter a thick layer of foam on. to the backing. « , ■ Alternatively an aerated latex compound ' .. may be spread on to backing by a lick roller picking up the compound from a bath and ) transferring it to the backing.

Once the foam has been brought into intimate . contact with the back of the carpet" it will fill the ridges in between the rov/s of needled stitches. It may then be desirable to exert some form of pressure on the back of the carpet whilst supporting the downward facing tufts. This pressure. may conveniently be exerted by. means of a pair of nip rollers. Where nip rollers are employed the upper roller may conveniently be free floating and exerting a downward- '' pressure equal to its own weight. The downward .· pressure by the upper roller may conveniently be from 1 to 10 lbs. per linear inch, more preferably from 3 to £ lbs. per linear inch.

Finally, the carpet having the partially collapsed foam layer thereon is dried. During the drying further destruction of the foam structure will normally occur.

The final physical state of the latex' will usually include air bubbles and it may hence be defined. as still having It should be noted that the temperature of the drying oven must not be above the softening temperature of any synthetic fibres present. Where a polypropylene backing is used a drying temperature o o of 260 F (126 C) cannot be exceeded once the water has been removed. c It .is not necessary to apply a secondary ¾J\% o¾lX¾a¾l foam co¾i¾ The primary backed carpet is already suitable for domestic use. However, if it is so desired a secondary backing may be applied by any^conventional method, the latex acting as an adhesive. A further possible modification is to apply a secondary backing before carrying out the drying step of the present invention.

Alternatively the collapsed latex coating may be used as a tie coat for a further layer of foam which is un- collapsed and forms the backing of a so-called "foam backed" carpet. In this case the further foam layer may be applied to the tie coat in conventional manner either before or after the tie coat has been dried. o ((b-F-iS^Sg- the latex into :m»po-i-R^-e-ws^e—e&ft^ae^-wi-th- the back.of the carpet and the tufts may be assisted by burnishing the back of the carpet as the final step before drying the latex.. A burnishing. roller is a highly polished roller which revolves so that its peripheral speed is faster than the speed of the backing material moving past The invention will now be illustrated with reference to the following -ixamples and also with reference to the accompanying drawings in which:- Figure 1 is a schematic side elevation of a form of apparatus including apparatus for applying and collapsing foam according to the present invention; Figure 2 is a section through a carpet produced by the apparatus of Figure 1 but showing different amounts of latex which may be applied; and Figure 3 shows an alternative form of the apparatus of Figure 1.

Referring to Figure 1 , this illustrates an apparatus for applying foam continuously to a tufted woven tape polypropylene backing and apparatus for o a sin the foam.&nd dr in the co la ed f m ex and a stenter frame 6 , and a hot air drying oven 9· In operation tufted polypropylene woven tape primary backing material 21 , is fed frofn a feed roll 22.

Speeds of up to 30 or Ή-0 ft. per minute rnay be used, with 10 ft. per minute being paricularly suitable.

The backing 21 with the pile tufts 23 inserted therein passes through the box reservoir 1 , and under the reciprocating nozzle - which moves transversely across the backing to deposit the required amount of foam thereon. The foam covered backing then passes under the doctor roller and onto the stenter frame 6 which holds the backing material taut while it passes through the oven 9. The doctor roller is set so that it is. just touching the tops of the backs of the ■ tufts pro.truding through the backing material (see Figure 2). As the backing material with its layer of foam moves towards the doctor roller 5 a "nip" or "bank" of foam 2k is built up. ¾e doctor blade then drives the desired amount of latex as -.foarrij and as partially collapsed foam into the back of the carpet. The carpet then passes to the dryer 9 which may conveniently be a 60 ft. long o steam heated recirculating, air oven operating at 120 C. The dry carpet is then wound up on the roller 25.

Drying times in the oven can be as low as 5 minutes, so making speeds of 20 to -0 ft. per minute possible on production equipment.

Referring to Figure 2, there is shown a section through a tufted carpet produced by the apparatus of Figure 1. The carpet has a woven tape polypropylene backing 22, tufts 3 and a layer of latex 26, 26a , and 26b. The layer of latex is shown having a variety f roller 5» In the alternative form of apparatus shown in Figure 3 the carpet leaving the box reservoir 1 is passed below a reciprocating nozzle 30 which moves transversely across the backing to deposit the required amount of foam thereon. The carpet and foam then travel to a pair of nip rollers 7 » 8, the top roller being free-floating and having a weight such that it exerts a downward, pressure (for example 3½ lbs. per flriner inch) across the backing material.

The ni m and to £ f i i ^ fefr the carpet backing. The nipped material then passes to a burnishing roller 10 which is set so that it slightly depresses the back of the carpet and which is driven at.a peripheral speed greater than tha speed of the carpet. With the carpet travelling at ft. per minute the peripheral speed of the burnishing roller 10 may conveniently be 30 ft. 1 ' work 7 ·'·; per minute. The burnishing roller, can serve to € *ver further; the latex(into -aep&-ifttriffl»¼frs^»feai "^-tfch' the back of ■ the carpet, and also further to destroy the foam structure. .From the burnishing roller the carpet passes to the dryer as in the Figure 1 apparatus.

It is possible, though usually unnecessary, to use the nip rolls 7 and 8 or the burnishing roller 10 or both, after the doctor roll shown in Figure 1 .

It is also possible to replace the doctor The invention will now be illustrated with reference to the following Examples; - ffxarople.1 A primary backing material comprising a ounce woven tape (split film) polypropylene fabric wherein the average width of the tapes was ·έ" , was tufted ith cut pile Evlan nylon yam (Evlan being a Registered ■ weight Trade Mark applied to a type of rayon), thef aiio of Evlan to nylon being 5: ?, at the rate of 5i rows of tufts per inch and 10 tufts per inch in each row.

To the back of the tufted backing material was applied by a doctor blade a foamed mixture comprising 100 parts (dry weight) styrene (50 )-butadiene (5ΰ#) rubber latex 200 parts (dry weight) whiting (calcium carbonate filler) the mixture having a total solids content of 70 and a B>+ cup viscosity of 60 seconds (as defined by British Standard Specification No. 1733). The desired viscosity was achieved by adding Texigel SPA2 which is a 15 aqueous solution of sodium polyacrylate.

The mixture was foamed in a planetary action mixer at 200$ expansion, and refined for 10 minutes apparatus described above with reference to Figure 1 , with a doctor blade in place of the doctor roll.

The backing material was moved forwards at the rate of 10 ft. per minute. About nine ounces of latex tuft bind properties of the resulting carpet were good. Similar results were obtained when before entering the oven, the carpet -w s passed 'through nip a pair of vertically mounted L rollers similar to those shown at 7 and 8 in Fig. 3» the pressure applied being approximately 3· 5 lbs. per linear inch width.

■Exafflfllfi, 2 The general procedure of xample 1 was repeated except that the latex used was a carboxylated styrene-butadiene-itaconic acid latex (50;¾ - ¾$> - 1^)> and that the mixture was only foamed to 100» expansion and was applied at 10 ounces per square yard. The flex roll, handle, abrasion test, and tuft bind properties of the resulting carpet were good, fixaiiiftle 3 A tufted carpet was prepared; by tufting a cu pile of rtayon/ acrylic fibre blend into a backin woven from jute warp threads and cut polypropylene film waft shots. The average width of the polypropylene tapes was ap roximately 3/32" , and the" surface area ratio of polypropylene to jute was roughly 3:1. · .

The following la-tex compound was prepared 100 parts dry weight styrene butadiene ½ » latex 1 part dry weight sodium hexametaphosphate 2^0 parts dry weight ground limestone filler 1 part dry weig t sulphonate surfactant 1 part dry weight sodium polyacryl.ate thickener Total solids content :68^ Viscosity 7000 centipoise (Brookfield Viscometer spindle Ko. *3 0' revs The compound was applied to the carpet backing by the apparatus shown in Figure 1. , the rate of applicati.on being 15 oz/sq. yd. of solids. o The carpet was then dried for 8 minutes at 3 0 F in a hot air oven.

The resulting carpet had good handle, tuft bind properties and resistance to edge warp threads fraying.

Example k- .

A compound was prepared similar to that mentioned in example 3 but with 350 parts of ground limestone filler per 1 00 part dry weight of latex with the. appropriate adjustment in water and thickener..

This compound was foamed ¾s in example 3 to give a wet foam density of 500g/litre and applied to the carpet to give 12 oz/sft. yd0 of solid material. The carpet was then dried in the conventional manner, and later coated with a resilient latex foam backing 3/ 16" thick and weighing 22 oz/sq. yd. to give a commercially acceptable product with good overall physical properties. The collapsed compound acts as a tie coat betwee the polypropylene and the foam backing, and the adliesion between these two was found to be satisfactory.

A secondary backed carpet was prepared using the compound described in example and a base carpet of spun yarn tufted into non woven polypropylene cloth sold under the Registered Trade Mark "Typar".

The neeondary cloth was conventional square weave 8 oz/nq. yd. jute. A total of 20 02/ sq. yd. of compound (dry weight) was applied to the polypropylene by expanding the wet compound by 7f/> by volume, the coating being., carried out using the technique described in the previous examples. ' The secondary jute clotli was laminated using a set of nip rollers in conventional manner. ¾e f nished laminated carpet had a peel adhesion ' of 12 lbs. /2 in. K width. Λ latex containing 76 parts by weight butadieno and 2k parts by weight acrylonitrile emulsified with rosin acid soap and having a total solids content of ?0f» was compounded to the following formul tion:- 100 parts rubber in the latex form 100 parts clay filler .5 parts- sulphur 2 parts 'zinc mcrca tobonzothiazol 1 part ainc die thylc.i t iocarbamate - parts sine oxide 1 part "Kaugawhite" (an alkylated bis phenol . antioxidant) 0. parts sodium tall oil soap • The total solids content was 50$ and the viscosity was adjusted to 7000 centipoises ' (Brookfield Viscometer, spindle 3,10 revs.- per minute) with a Ι5','ό· solution of sodium polyacryla o.

The compound was foamed and spread as in example 1 onto a carpet tufted into a woven tape polypropylene primary backing, the application . weight being 10 02/sq.yd. solids. The carpet was

Claims (1)

1. A for making a tufted carpet having a polypropylene primary which comprises Inserting carpet tufts backing and securing the tufts in place by applying a foam of flexible forming polymer aqueous late form onto the of the working the foam the backing of the carpet whilst at the same time substantially collapsing foam and subsequently drying the collapsed so as to complete the of A process as claimed in claim 1 wherein the foam is worked the backing by means a doctor roller a doctor process as in claim 2 wherein the doctor blade or doctor roller set just clearing or just backs of tufts rising from A as claimed any of the preceding wherein the backing carrying the collapsed foam is passed through pair of nip rollers before oollapsed A process in wherein the upper nip roller free A process as olalmed in any one of the preceding claims wherein the backing is burnished with burnis ing roller prior to drying the collapsed A process claimed in any one of the claims wherein the backing contains mino proportion of textile material other A process as claimed in claim wherein th said textile material a pol amide or process as claimed in any one the preceding claims wherein the latex is de ived from butadiene or isoprene and at least one other oopolymerieable vinyl process as claimed in claim 9 the vinyl compound is lower substituted a methyl or ethyl a a vinyl vinyl acetate or a A as claimed in 9 or 10 wherein the latex includes a minor proportion of a third copolymerisable monomer having reactive A process as claimed any one of preceding claims wherein the latex compound employed inoludes filler in a ratio of to elastomer o from to by A process as claimed in claim the ratio of filler elastomer is from to A process as claimed in any one of the preceding wherein the filler is a carbonate A process as claimed In any one of the preceding olalms wherein the latex compound1 contains to A process claimed any one of the preceding claims wherein the latex compound incorporated the primary backing in an amount of from ounces per square process claimed in any one of preceding claims wherein the latex compound is incorporated onto the primary hackin in an amount of from 9 20 ounces per square A process as olaimed any one of the precedin a secondary hacking is applied oyer the primary hacking after the substantial collapse the foam A process claimed any of claims 1 to 13 wherein a layer of foamed material is applied primary backing after the substantial collapse of the structure to form a foam backed the collapsed latex acting as a tie coa betwee the polypropylene primary backing and the foamed process as olaimed in claim 1 substantially as herein process as olaimed in 1 substantially as herein with reference to or Figure 3 of the accompanying A process as olaimed in claim substantiall described reference to any one of the foregoing A tufted carpet whenever produced by a cess as claimed in any one of preceding insufficientOCRQuality