US 3765974 A
Improvements in producing a bonded non-woven fabric matting where the bonding agent is located in discontinuous areas of the matting or is present in differing and varying proportions in different areas of the matting. Such a product is made by substantially uniformly impregnating the matting with a heat sensitive coagulatable binder latex, non-uniformly heating the impregnated matting to the coagulation temperature of the latex only in predetermined areas of the matting whereby coagulating the binder from the latex only in the preselected areas which have been subjected to heating to a temperature sufficient to coagulate binder from the latex, and then removing that portion of the latex from which the binder was not coagulated by the non-uniform heating.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Petersik et al.
[4 Oct. 16, 1973 SPOT-BONDED MATS AND PROCESS FOR THEIR MANUFACTURE [75 Inventors: Peter Petersik, Luetzelsachsen;
Rudolf Gaertner, Weinheim, both of Germany  Assignee: Firma Carl Freudenberg,
Weinheim, Germany  Filed: Jan. 28, 1971  Appl. No.: 110,576
Related US. Application Data  Continuation-impart of Ser. No. 848,460, Aug. 8,
 Foreign Application Priority Data Apr. 24, 1969 Germany P 19 20 836.7 Feb. 4, 1970 Germany P 20 04 988.1
 US. Cl. 156/84, 117/38, 117/42,
 Int. Cl..... B32b 31/20, 1332b 31/22, B32b 3/30  Field of Search 161/148, 170; 117/38, 42, 62, 62.2, 63; 156/155, 209, 84,
3,698,973 10/1972 Wisotzky et a1. 156/321 X 3,708,366 l/ 1973 Donnelly 156/209 3,717,528 2/1973 Peerman et aL... 156/155 X 3,704,191 11/1972 Buresh et al 156/209 X 3,424,604 l/ 1969 Fukushima et al. 117/63 3,459,627 8/1969 Vosburgh 156/209 X 2,719,806 10/1955 Nottebohm 171/170 X 2,880,113 3/1959 Drelich 161/148 X 2,940,871 6/1960 Smith-Johannsen 1 17/63 2,983,960 5/1961 Jilge 156/155 X 3,245,863 4/1966 Sonnichsen et a]. 156/84 X 3,293,095 12/1966 Pitzer 156/155 Primary Examiner--Harold Ansher Attorney-Burgess, Dinklage & Sprung [5 7] ABSTRACT Improvements in producing a bonded non-woven fabric matting where the bonding agent is located in discontinuous areas of the matting or is present in differing and varying proportions in different areas of the matting. Such a product is made by substantially uniformly impregnating the matting with a heat sensitive coagulatable binder latex, non-uniformly heating the impregnated matting to the coagulation temperature of the latex only in predetermined areas of the matting whereby coagulating the binder from the latex only in the preselected areas which have been subjected to heating to a temperature sufficient to coagulate binder from the latex, and then removing that portion of the latex from which the binder was not coagulated by the non-uniform heating.
8 Claims, 8 Drawing Figures Patented Oct. 16, 1973 2 Shanta-43km. l
Perm s// ET AL.
Patented Oct. 16, 1973 2 Sheets-Sheet It FIG.6
INVENTOR PETER PETERSIK\ ET AL SPOT-BONDED MATS AND PROCESS FOR THEIR MANUFACTURE This application is a continuation-in-part of Application Ser. No. 848,460, filed Aug. 8, 1969, now abandoned.
This invention relates to non-woven fabrics. It more particularly refers to non-woven fabrics which are particularly useful for synthetic leather or leather-like applications.
Non-woven fabrics, as this term is used in the textile arts, are mats or bats made up of staple fibers or continuous filaments where the individual fibers or portions of the individual filaments are geometrically randomly disposed with respect to each other. Such fabrics are usually made from a card lap (in the case of staple fibers) which may or may not have been passed through a cross lapper and/or a needle loom in order to further disorient the fibers with respect to each other. Non woven fabrics made up of continuous filaments are often made by laying the filaments down on a suitable fleece form directly out of the spinnerette in a random pattern. The term non-woven does not include knitted, netted, crocheted or other fabrics having fibers or filaments in a geometrically patterned array, regardless of how made.
In any case, regardless of how the randomlay, nonwoven fabric is made, and regardless of whether such fabric is composed of staple fibers or continuous filaments, it is common in this art to bond in some way the individual fibers or filament portions together so as to increase the dimensional stability of the mat or bat product to an extent sufficient to create a fabric having physical integrity. Such bonding has been accomplished in the past by many varying techniques, includmg:
l. providing at least some thermoplastic fibers or filaments in the fabric having a lower melting or softening point than the remainder of the fibers or filaments and then heating the fabric to an extent sufficient to melt or at least tackify these fibers or filaments and cause them to bond to other fibers and- /or filaments;
2. uniformly impregnating the non-woven fabric with a liquid form bonding agent, either solution or latex, and removing the carrier liquid thereby depositing bonding agent throughout the fabric which effectively bonds the fibers or filaments together;
3. spot impregnating the non-woven fabric and proceeding as in 2); or
4. providing a plasticizer or other softening agent uniformly or spotwise through the non-woven fabric in an amount sufficient to cause the fibers or filaments of the fabric to become tacky to an extent sufficient to bond them together.
In all of these techniques the bonding generally takes place at the crossing points of the fibers or filaments, thereby retaining the textile and sometimes lofty character of the fabric.
In the manufacture of non-woven textile fabrics in the prior art the uniformly impregnated loose fiber mats were dried, in which drying process the binding agent collected in the form of lamella or webs mainly at the intersections between the fibers or filaments, as can clearly be seen in FIG. 4 of U.S. Pat. No. 2,719,802. The binding agent in this lamella form was vulcanized by the action of heat simultaneously with the drying of the fabric. The products thus manufactured, which are commercially available (under the name Vlieseline in Germany, or Pellon in the United States) are especially characterized by their springiness and elasticity. They are therefore used mainly as lining and stiffening materials in clothing.
From U.S. Pat. No. 2,545,952, it is furthermore known to imprint upon an initially loose non-woven mat fabric spots of rubbery latex or other binding agent having similar properties, such as casein, glue, natural resins, etc., making use of a roll engraved with spot depressions for the purpose. The binding agent, which is at first imprinted as spots on the surface of the mat, then sinks slowly into the interior of the mat so that a bonding action is produced also in areas underneath the imprinted surface spot of latex. This method, which is suitable only in the case of thin matting weighing up to about 60g/m is also known in Germany by the English term spot binding. Also see in this connection West German Auslegeschriften Nos. 1,098,903, 1,099,983, 1,106,285, and 1,062,204.
The spot-bonded non-woven fabrics known hitherto are softer and more water-absorbent than otherwise equivalent mats which are uniformly impregnated with binding agent. However, their tensile strength is low, as might be expected, and therefore they are usually used for the manufacture of disposable goods.
Clearly, it would be desirable to provide non-woven textile fabrics which have the water-absorbency characteristics of spot-bonded fabrics and the tensile properties of uniformly bonded fabrics. It would also be more desirable to be able to utilize non-woven fabrics having a fiber weight of higher than about 60 grams per meter, which is about the highest weight fabric the prior art has been able to work with in a spot-bonding technique, such as higher fiber weights being for example, up to about 1000 grams per meter or even more.
The objects of this invention are, therefore, to fulfill the above-recited desirable conditions.
In accord with, and fulfilling these objects, one aspect of this invention resides in a novel technique of bonding a non-woven fabric. According to this invention, a suitably formed non-woven fabric of staple fibers or of continuous filaments is substantially uniformly impregnated with a latex form bonding agent which is coagulation sensitive as a function of temperature. Such so-called heat-sensitive, coagulatable latexes are known, and it is per se known to impregnate a nonwoven fabric therewith, according to U. S. Pat. No. 2,719,802. By heat-sensitized, bonding agents are meant those in which the bonding agent abruptly flocculates (coagulates) in the form of tiny spheres or beads when a predetermined certain temperature, e.g., about 20 to C, preferably 40 to 60C, is applied. This type of heat sensitive bonding agent is commercially available and is a per se well-known product. The thus substantially uniformly impregnated non-woven fabric is then subjected to a procedure whereby binder is caused to deposit only in predetermined locations.
The impregnated fabric is passed through heating means which may be an unheated smooth roller or a flat plate on one side and a heated roller on the other side which heated roller has protuberances on the surface thereof. The protuberances heat those portions of the fabric which they contact or which they approach to a greater degree faster than those portions of the fabric which are disposed opposite the areas between the protuberances. Therefore, the residence time or contact time between the impregnated fabric and the heated roller protuberances and the temperature of the heated roller protuberance can be so adjusted with respect to each other and with respect to the coagulation temperature of the latex impregnant that the area of coagulation of the binder from the latex can be very carefully controlled. It is not necessary to the practice of this aspect of this invention that the protuberancecontaining roller be heated in its entirety, although this is possible and in many cases may be the most practical solution to effecting the localized heating; the roller therefore may be constructed in such a manner that only the protuberances are heated. The roller may be heated by any conventional technique, e.g., electric resistance, steam, heating liquids, direct fired heat or the like. Whether the roller acts as a heat exchanger by having heating means as an integral part of its construction or by its being heated away from the fabric and then passing the heat on to the fabric is immaterial to this aspect of this invention. What is important is only that at least the protuberances of the roller means are heated to a high enough temperature and are juxtaposed to the fabric for long enough to cause the binder to coagulate in certain preselected areas of the fabric but insufficient to cause the binder to coagulate in other, adjacent areas of the fabric.
It should be appreciated that the latex coagulation temperature, the roller protuberance temperature and the juxtaposition time are all interrelated functions and they cannot be individually defined without reference to the other. That is, for a given latex having a given coagulation temperature, a certain protuberance temperature, a particular juxtaposition time and a given spacing between fabric aNd protuberance (including zero spacing which would define simple contact or even negative spacing which would define contact accompanied by pressing of the fabric by the protuberances) are required to cause coagulation of bonding agent from the latex only in the required predetermined spots or areas where it is desired.
The routineer in the art, given the interrelations expressed above, and knowing the coagulation temperature of the latex as well as the area of latex to be coagulated by each protuberance, can easily calculate the required parameters of spacing, juxtaposition time and protuberance temperature sufficient to cause such coagulation in such predetermined areas. General operating parameter ranges are: protuberance temperature 120 to 420 C, protuberance/fabric juxtaposition time 0.1 to 3 seconds. It will be appreciated, however, that there will be readily found operating parameter combinations suitable for the purposes of this invention which are outside the scope of one or more of the ranges set forth above. The only critical parameter is that the operation be sufficient'to cause predetermined areas of binder to coagulate while preventing the remainder of the binder from coagulating.
Another aspect of this invention which will accomplish the coagulation of binder in predetermined areas of a non-woven fabric while preventing or minimizing the coagulation of binder in other areas of the fabric is to pass a substantially uniformly impregnated non woven fabric through the nip of a pair of roll means wherewith the roll means have alternating protuberances thereon, or where one roll has protuberances and the other is smooth. As the impregnated non-woven fabric passes between the rolls, the action of the alternating protuberances exerts a pressure on the fabric and on the latex impregnated therein to effectively force some or all of the latex into areas between next adjacent alternating protuberances. This action effectively localizes the latex impregnant into predetermined areas from which the binder is then coagulated by subjecting the thus treated fabric to uniform localized heating as the case may be. If heating sufficient to coagulate binder from the heat-sensitive latex is instituted immediately after treatment by the protuberance roll means, the liquid form latex will not have time to flow back to a uniform impregnation condition before the binder is coagulated therefrom. Thus the binder can be coagulated and disposed substantially only in those areas where it is desired. It is within the scope of this invention to use heated roll means or to provide separate heating means following the protuberance roll means.
By adjusting the nip pressure of the protuberance roll means it is possible to control the proportion of binder which will be forced out of those areas impressed by the protuberances into the areas between protuberances. By controlling this pressure, all or only part of the impregnated binder can be moved as desired.
Although it is considered to be less desirable, the protuberances on the pressure-exerting roll can be in mating configuration as well as alternating configuration.
In all aspects of this invention, regardless of how the latex is moved within the non-woven fabric or how spotwise coagulation is accomplished, after coagulation of the binder, the fabric is then treated to remove any remaining uncoagulated binder from the fabric. This can be accomplished by simply washing the coagulated binder containing latex-with water.
It has been found that the product produced by the above-described process is quite unique. This uniqueness manifests itself in the fact that the final spotbonded product does not have a uniform thickness and the fact that at least one of the major surfaces of the fabric product is profiled, that is, it has hills and valleys corresponding to the binder-containing areas and the areas of low or no binder concentration. One of the surprising things about the product is that the surface .valleys do not correspond to those portions of the fabric which were juxtaposed to the coagulating protuberances during binder-impregnation and coagulation but rather correspond to those portions of the fabric which were between these protuberances.
While not wishing to be bound by any particular theory, it is thought that the valley portions of the spotbonded product are the result of a partial collapse of the unbonded non-woven fabric structure on washing out the uncoagulated binder while the hill portions correspond to the binder-containing portions of the fabric because these portions have greater resilience and dimensional stability.
Understanding of this invention will be facilitated by reference to the drawing in which:
FIG. 1 is a schematic side elevation of a uniformly impregnated batting being juxtaposed to a protuberance containing heated roller;
FIG. 2 is an enlargement of the contacting portion of the roller and batting of FIG. 1, schematically showing collimated coagulation within the batting;
FIG. 3 is a schematic side elevation of a batting having spot-coagulated binder therein as it leaves the coagulation process;
FIG. 4 is a schematic side elevation of the spotimpregnated product after washing;
FIG. 5 is a schematic side elevation of a uniformly impregnated batting being treated with two opposing protuberance-containing rollers; and
FIG. 6 is an enlarged side elevation of the rollers of FIG. 5;
FIGS. 7 and 8 show examples of the surface of mats that have been spot-bonded according to the invention.
Referring now to the drawing, a roller 1, having protuberances 2 of given predetermined size, configuration and spacing, is rolled over a batting 3 just touching the batting, which was previously uniformly impregnated with the heat-sensitized binding agent, using a flat plate or table 1a as a base. In this depicted aspect of this invention, only the protuberances 2 of the roll 1 press against the batting 3, as it can be seen in FIG. 1. As shown in FIG. 2, the heat of the protuberance 2 is transferred to the batting by radiation and conduction such that the binding agent which is uniformly distributed in the batting, coagulates only in those areas of the batting where it has been heated by the protuberance to a coagulating temperature, e.g., in the darker area shown in FIG. 2.
The heat radiated into the batting symbolized by arrows in FIG. 2 is so intense in the juxtaposed area of the batting that after about 1 second of contact the binding agent coagulates (flocculates) in the areas directly below the protuberance 2. Heat also radiates into the batting from the adjacent areas 4 (recesses) of the roll, but the spacing of the recesses from the batting and the short contact time are so chosen that the combination is insufficient to heat that portion of the impregnant to a temperature which is sufficiently high to cause coagulation (flocculation) of the binder. The pressure exerted by the roll 1 on the batting 3 and the roll temperature are so chosen to produce the above heating and coagulation effect and the effective contact time between the roll and the mat is preferably maintained at only about 1 second at both the leading and trailing edges of the protuberances. Consequently, when the protuberance 2 touches the fabric 3 only the binding agent in the area 3a will coagulate, while the binding agent in the adjacent areas 4' and 4 will not coagulate at all or will coagulate only to a significantly lesser extent. This selective coagulation process is repeated constantly as the hot roll 1 passes over the uniformly impregnated batting. Substantially immediately or as soon as it is sufficiently heated after the juxtaposing of protuberance 2 against the batting 3, the binding agent directly under the contact surface in the batting coagulates, but it does not coagulate in the areas immediately adjacent thereto. The cross-section of coagulated binder in FIG. 2 has been shown to be rectangular. Actually it will probably be more conical, or possibly eliptical; however, since the fabric thickness is so small the actual cross-section is most difficult to determine.
If the pressure between the roll 1 and the fabric 3 is such that the protuberances 2 press into the fabric 3, the binding agent latex will be forced out from immediately below the protuberances into the interstices of the fabric disposed between protuberances (see areas marked 4' and 4" in FIG. 2). The heated roll will cause such displaced latex to coagulate in these areas 4' and 4" provided the contact time, the temperature and pressure of the roll are appropriately adjusted. Thus,
since the heat passage from the roll to the latex takes longer than the time to displace the latex, short contact times and relatively high roll pressure will cause displacement and coagulation to occur sequentially.
After the passing of the hot roll 1, some of the binding agent in the batting 3 is in the coagulated state and some remains uncoagulated. FIG. 3 is a diagrammatic representation of such a batting. It can be seen how areas 3a containing coagulated binding agent alternate with areas 41a in which the binding agent is present in the uncoagulated form. When the binding agent coagulates from a latex, it separates in the form of many small spherules, which is the reason why the structure is often referred to as a caviar or birdshot structure. It is for this reason that the structure of the coagulated binding agent is represented by dots in FIG. 3. The uncoagulated binding agent is represented by lines. After the hot roller treatment the coagulated binding agent has become fixed, but the uncoagulated binding agent can be removed from a batting simply by washing it out with water.
Therefore, if the batting shown in FIG. 3 is immersed in running water, only the uncoagulated binding agent is washed away from areas 4a, but the coagulated binding agent will not be washed away from areas 3a.
The spot-bonded fabric resulting from the washing process is represented diagrammatically by FIG. 4. The areas 3a containing coagulated binding agent alternate with areas 4a, which are substantially free of binding agent. Such a fabric is very soft, elastic and airpermeable. Its water absorbency is remarkably high. It is distinguished from the spot-bonded fabrics that have previously been known, by its substantially better mechanical properties, particularly its tensile strength. It is outstandingly suitable for further working into artificial leathers, household products, clothing, luggage, lining materials, surface fabrics, show materials, automobile roof liners, upholstery, floor coverings, etc.
It should be noted from considering FIG. 4 that one of the major surfaces of the spot-bonded fabric, that is, the surface which was juxtaposed to the roller having protuberances thereon, does not have a flat profile as do uniformly bonded or unbonded fabrics. Rather, it has hills l0 and valleys 11 which correspond to the bonded and unbonded portions thereof, respectively.
According to one particular embodiment of the invention shown in FIG. 5, a similar product can be produced except that the washing step can be dispensed with, or at least reduced. In this embodiment the batting 3, which is first uniformly impregnated with binding agent, is run between a pair of rolls 5, 6 (see FIG. 5), both rolls being provided with protuberances 8 and 9, and 7, respectively. The rolls are rotated synchronously so that in the gap between them a protuberance 7 of the lower roll 6 will mesh with and be disposed in an area between the protuberances 8 and 9 of the upper roll 5, as shown in FIG. 6. As the impregnated batting 3 passes through the gap between such studded rolls, the pressure distribution is, of course, irregular, and the binding agent tends to be displaced from the high-pressure areas toward the low-pressure areas, that is, from the area of smallest gap to the area of largest gap. Thus the binder tends to be concentrated in the areas between the protuberances 8 and 7 or 7 and 9, respectively, while the portion of the fabric directly adjacent each protuberance tends to have little or no binder latex left therein. If the roll protuberances are heated as set forth above, substantially all of the impregnated binder will be coagulated but since the binder latex has also been displaced, the profile of concentration of coagulated binder in the product will also generally correspond to that shown in FIG. 4. In this embodiment of this invention the final product also has a profiled surface. However, in this case the hills, while corresponding to the portions of high binder concentration, also correspond to those areas of the impregnated batting which were between the roller protuberances rather than juxtaposed to the roller protuberances as in the embodiment depicted in FIGS. 1 and 2.
In this embodiment, the roll temperature should be kept as low as possible, for it can be seen that the displacement of the binding agent must take place before the coagulation begins. If the studded rolls had high temperatures, the coagulation might occur before or during the displacement of the binder latex. It is essential to avoid this because, as already stated above once the binding agent has coagulated, it is fixed in place, and then cannot be removed either by pressure or by washing.
In the embodiment represented in FIGS. 1 and 2, the roll 1 can be at a higher temperature than in the embodiment of FIGS. 5 and 6 because the pressure in this first embodiment may be substantially less, or even non-existent, and hence the heat transfer is not as intense as in the embodiment of FIGS. 5 and 6. The contact pressure and the speed of the revolving roll (the contact time) depends upon the pattern of the roll protuberances and the dimensions of the roll, and on the sensitization temperature of the binding agent in the mat. The optimum values in each case can, however, be determined quite simply by experiment or. calculation. The minimum temperature of the roll, when considered in combination with the roll speed, must, of course, be high enough to produce coagulation of the binding agent in the areas 3a directly beneath the protuberance 2 (see FIG. 2). On the other hand, the temperature should not be so high as to induce coagulation, at the same running speed, in the adjacent areas 4a.
Whereas in the spot-bonding technique that has been practiced hitherto, the binding agent is deposited only locally on the surface of the batting in the areas where the bonding spots were desired, the new method differs from the prior art in that the batting is first impregnated quite uniformly as in non-spot-bonding, prior-art fabric production methods. This makes it possible to manufacture denser mats. It is readily understood that when binding agent is printed only on the batting surface, and will then be caused to penetrate through the batting thickness, only thin mats can be used, since the imprinted dot of binding agent only slightly penetrates into the batting interstices underneath it. Deep penetration all the way to the back of the mat, if possible is most desired in producing spot-bonded fabrics be cause otherwise the fabric structure, which is not too strong to begin with, may delaminate. It is for this reason that only thin batts having a weight up to 60 g/m have been imprinted by the prior-art spot-bonding methods, whereas the process of this invention is capable of spot-bonding batts having fiber weights of up to about l000 g/m or more.
Uniform binder latex impregnations, such as practiced in the method of the invention, may be accomplished according to any of the known procedures (see, e.g., NONWOVEN FABRICS, published by Non- Woven Associates, P.O. Box 328, Cambridge 39, 1959, pp 25-28). These impregnations are substantially independent of the thickness of the batting. It is easily possible to uniformly impregnate batts having a fiber weight of 1000 glm In these batts, then, the binder can be made to coagulate according to the invention at certain points through the entire structure, while other areas in the final product will then be rendered substantially free of binding agent.
The spot-bonding method according to the invention, therefore, is not limited, as is the prior-art spot-bonding method, to thin batting.
The starting batt according to the invention can be produced with a card or cross lapper or in any other conventional manner. It may be in needled or unneedled form. The filaments may be staple or continuous and may be of substantially any conventional fiber material. There are no limitations with respect to the composition of the fibers or the use of a multiplicity of different fibers and/or filaments in the same mat. It can be said, therefore, that any desired batting can be spotbonded according to the process of the invention.
The binding agents to be used according to the invention must, of course, all be coagulatable and in addition, heat coagulation sensitive, i.e., the binding agent present initially in the latex impregnant must be capable of coagulating as a function of temperature in the form of bird-shot when a certain temperature is reached usually between 20 and C.
The invention is of particular value, however, in the production of imitation leathers comprising a composite of a continuous coating of suitable polymeric material joined to one major surface of a non-woven fabric. There is now often a desire to produce an imitation leather the surface of which appears to have folds or creases in it, which thus resembles worn leather which has been crumpled. The effect is generally called wet leather. Attempts have been made to achieve this effect by applying a suitable coating of a polymer onto a non-woven fabric, thereby producing a product having a smooth surface; and then crumpling the composite product so as to give the desired creases in the surface. This product has proven to be somewhat less than satisfactory because after a short time the creases generally disappear and the product regains its smooth surface.
The spot-bonded or line-bonded non-woven fabrics made according to this invention, however, are exceptionally well-suited to use in producing such creased surfaced wet leather. This is achieved by producing a spot-bonded non-woven fabric according to the practice set forth hereinabove so that the first and second areas, that is, the bindencontaining and binder-free areas, respectively, are arranged in an irregular pattern with at least some of the second areas (i.e., the areas having less or no coagulated bonding agent) being in the form of elongated irregular streaks. Generally the bonded and the bond-free areas are arranged in a pattern resembling that obtained in the surface of leather or crumpling the leather. A coating of a suitable polymeric material such as polyvinyl chloride, is applied to a major surface of this non-woven fabric and adhered thereto in the usual way whereby producing a resultant imitation leather which has a permanent pattern of elongated irregular streaks in it. This product has the desired creased effect permanently in its surface.
Although any non-woven fabric can be used in the practice of this invention, the preferred non-woven fabric is a needled fabric. The fabric preferably is one that contains shrinkable fibers and which has been shrunk by conventional techniques in order to consolidate it, generally after needling. The area of fabric shrinkage should be at least 20 percent, and preferably 50 percent or more. The shrunken fabric is then impregnated with coagulatable binder in the manner described above and the desired distribution of binding agent achieved. The desired polymeric coating can then be applied on the spot-bonded nonwoven fabric by any convenient process. For example, a counter coat process can be used. In this process a polyurethane or other suitable coating material is spread on a carrier and the non-woven fabric is then pressed onto the coating material and the composite so produced subsequently stripped from the carrier. This type of coating is usually glossy.
It may be desirable to additionally crumple the laminated product in a conventional mechanical manner so as to accentuate the veined effect that is obtained by practing this invention. The veined effect is permanent.
The following is an Example of the invention.
A fleece consisting of 70 percent of viscose rayon fibers and 30 percent of polyester shrinkable fibers with a total fiber weight of 200 g per square meter is prepared, needled and then shrunk by heating in the conventional manner. The shrinkage in area is 45 50 percent. Accordingly, the weight of the fabric after shrinking is 440 500 g/sq.m. This shrunk fleece is then uniformly impregnated with a conventional commercial heat-sensitive colored polyacrylate latex (Perbunan N 4 M produced by Farbenfabriken Bayer) to a wet pickup of latex of about 150 percent. Impregnation is by conventional techniques. The impregnated fleece is then passed through the nip of two heated contoured rolls having protuberances in the form of irregular longitudinal lines which resemble veins. The rolls are heated externally to about 250C.
The impregnated latex is thereby first displaced away from the protuberances into the areas between next adjacent protuberances (see FIGS. 5 and 6) in accordance with the pattern thereof and the binder is then coagulated in such location by the heating effect of the rolls. The temperature of the rolls and the speed of travel of the fabric through their nip are selected appropriately to achieve the desired effect. The fabric is thereafter passed through a cold water bath and uncoagulated binder and/or auxiliary agents are washed out. After subsequently drying the product, a sheet-like structure having the roll pattern on both sides is obtained.
This product may be split longitudinally if desired, for example, on a conventional leather splitting machine, in order to produce a partially bonded nonwoven fabric having one profiled surface and one smooth surface. The upper and lower splits can both satisfactorily be used for the next stage in the process, just as the unsplit product can so be used.
The next stage in the process is to apply a coating of 50 grams per square meter of a conventional polyurethane onto the profiled surface by the counter coat process. After curing, the product is subjected to an additional mechanical creasing and crumpling operation and thus attains an irreversible creased effect. This product is excellently adapted to use in the manufacture of, for example, purses, handbags, shoes, clothing, upholstery and the like.
What is claimed is:
1. Process of producing a spot-bonded non-woven fabric which comprises:
A. forming a batting of geometrically randomly disposed filaments or fibers which can be needled and which contain shrinkable fibers;
B. substantially uniformly impregnating such batting with a liquid form latex containing a temperature sensitive coagulatable binder;
C. contacting said impregnated batting with a heated depth contoured surface means;
D. heating at least portions of said impregnated batting to an extent sufficient to coagulate at least a portion of said binder from said latex into spherules in the interstices of said fabric, wherein the combination of said steps C and D causes said coagulated binder to concentrate in predetermined areas in said batting, said binder-containing areas of said fabric having a greater thickness than the other areas of said fabric, which are vein-like in appearance;
E. washing out substantially all uncoagulated binder from said batting; and
F. drying said batting.
2. Process as claimed in claim 1, including passing said substantially uniformly impregnated batting through the nip of a pair of heated toothed rollers, each of which has protuberances which alternate with respect to each other, wherein said protuberances force said impregnated latex into the area of said batting between said protuberances, and coagulating said latex in said areas.
3. Process as claimed in claim 1 wherein said steps C & D are carried out simultaneously with a contact time of about 1 second at a temperature of about to 420C.
4. Process as claimed in claim 1 including the additional step of applying a polymeric film form coating comprising vinyl chloride or polyurethane to at least one surface of said spot bonded non-woven fabric which was contacted by said heated depth contoured surface means.
5. Process as claimed in claim 1 including needling the batting produced in step A.
6. Process as claimed in claim 1 including profiling both major surfaces of said batting.
7. Process as claimed in claim 6 including longitudinally splitting said profiled, spot-bonded batting between the major surfaces thereof.
8. Process as claimed in claim 7 including applying a polymer coating to the profiled surfaces of said split batting.
i ig? UNITED STATES PA'iENT 015mm CERTIFICATE Oi? CORRECTION Patent No. 3,765,974 Dated October l6,'l974' Inventorun Peter Petersk, and Rudolf Gaertner -It is certified that error appears in the above-identified patent V and that said Letgers Patent are hereby corrected 55 shown below:
Col. 2; line 31 "fiore" should be "most" Col. 35 1ine 34 "and" Should be "an Col. 6, line 10 "4la".should be "4a" vSigned and sealed this 27th day of August 1974.
(SEALl Attest: MCCOY M. GIBSON,-JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents