DE2528136A1 - BONDED NON-WOVEN FABRIC MADE OF ISOTACTIC POLYPROPYLENE FILLS AND METHOD OF MANUFACTURING THE SAME - Google Patents

Description

Dr. Ing. W: 'ir Ά * Πζ
Dr. Dietoi f. I-.iorf
Dr. Hans-Α. Browns

• HOnchtn 88, Pienzenawitf. 2t 2 ^. June 1975

TP-0004-F

EGG. DU PONT DE NEMOURS AND COMPANY 10th and Market Streets, Wilmington, Delaware 19 898, V.St.A.

Bound nonwoven fabric made from isotactic polypropylene filaments and method for making the same

This invention relates to improvements in nonwovens particularly useful as a carpet backing for needle cut pile carpets suitable.

U.S. Patent No. 3,502,538 describes one made of polypropylene thread nonwoven fabric existing carpet base. The bonded nonwoven fabric is made from nonwovens, the threads or thread sections which differ from one another in their orientation (i.e. birefringence). The less oriented Threads or thread sections are referred to as binding threads and the more strongly oriented as framework threads. Of the The degree of orientation is controlled by the extent of the stretching, which the threads experience before they are laid down on a laying surface to form a random thread fleece.

I _n US Patent No. 3,563,838 discloses a process for the preparation of a backing of nonwoven fabrics described above, the top of the

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The framework and binding threads described are made of polypropylene. These nonwovens are made up of at least two layers. In one layer, the threads are predominantly in the machine direction (i.e. in the general direction of the longitudinal dimension of the nonwoven fabric, which is also the direction of the running Tape on which these nonwovens are produced); this layer is referred to as the M-layer. In the adjacent Layer, the threads lie predominantly in the direction perpendicular to the threads of the M-layer, i.e. cross machine direction; this type of layer is called the X-layer. The layers also contain this Nonwovens have a low proportion of filaments running in the directions oblique to the machine direction and to the cross direction lie. The patent describes nonwovens with an MX sequence of layers and nonwovens with a MXM sequence of layers. When these nonwovens are in Saturated water vapor are bound, one obtains basic carpet materials with high tufted tear strength after the Tongue method that shows only a small amount of shrinkage in the dye vat.

U.S. Patent 3,821,062 describes a carpet backing in form a layered nonwoven polypropylene filament which is an improvement over that disclosed in U.S. Patent 3,563,838 disclosed carpet raw materials means. These two basic carpet materials differ from one another mainly in the binder content, in the titer and strength of the framework threads as well as in the distribution of the binding and framework threads. The bound The product shows a relatively small amount of shrinkage in the dye vat and, after the usual coating with latex, which is required in the manufacture of tufted carpets, a high tensile strength; furthermore it retains itself after applying latex a large part of its tear strength. With relatively low grammages however, these nonwovens exhibit insufficient optical opacity .

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Although the two polypropylene thread nonwovens described above Suitable as a carpet base for certain types of coniferous pile carpets, when they are used for the Manufacture of cut pile carpets highlighted certain disadvantages. This is because the needles are used when setting the nubs when the looper pulls the carpet thread off the needle. These needles that are worn or have burrs then often cut the carpet as it advances against the needle. It was also found that some of the well-known Carpet base nonwovens tend to fibrillate (or pebble) when the carpet is dyed in the vat (hereinafter referred to as defibration). When the usual second backing is then applied, these form fiber balls Places with insufficient resistance to stripping.

To overcome the above disadvantages, the invention provides an improvement on the nonwoven carpet backing described in U.S. Patent 3,821,062. In particular, the subject of the invention is a bonded nonwoven fabric made of isotactic polypropylene threads, which has a layer M running in the machine direction on each of its two surfaces, while a layer X running transversely to the machine direction makes up 40 to 60% of the total weight of the nonwoven fabric, each layer being substantially closed 65 to 90% by weight from scaffolding threads and 10 to 35% by weight from isotactic polypropylene as

e "sril? -t, and the threads in each layer are so arranged that the layered nonwoven fabric has directional preference values of at least 1.5 for MD / 45 °, at least 1.5 for XD / 45 °, and 3.5 to 30 for (MD + XD) / 45 °, characterized in that the framework threads of each M-layer have a middle Titer of 6 to 20 den and a firmness of at least

2 g / den and the framework threads of the X-layer have an average titer of 26 to 60 den and a strength of at least

3 g / den, which is at least 10% higher than that

TP-0004-F. g 5 2 Q 1 3 Q

Strength of the framework threads of each M-layer. In a preferred nonwoven fabric according to the invention, each M-layer accounts for about 20 to 30 % of the total weight of the nonwoven fabric.

Furthermore, the invention provides a method for producing the nonwovens described above, in which an unbonded nonwoven thread is produced by successively laying down layers of melt-spun and drawn isotactic polypropylene threads on a moving conveyor belt in such a way that the layer running in the machine direction (M-layer ), on top of which a layer running transversely to the machine direction (X layer) and finally a second layer running in the machine direction (M layer) is deposited on the X layer, the melt spinning, stretching and depositing speed being controlled in this way be that the X-layer 40 to 60 weight percent is the total weight of the nonwoven fabric, and each layer substantially 65 consists to 90 Gev.% of scaffold fibers and "1Ö to 35 wt.% of binding threads or binding portions and the threads in such a direction-dependent be deposited that the thread fleece Direction gsbevorzugungswerte of at least 1.5 45 ^0, at least 1.5 45 ° obtained for MD / XD / 45 ° and 3.5 through 30 for (MD + XD) /, whereafter the web thus produced is thermally bonded under spatial limitation, characterized in that the spinning and drawing process is controlled so that the frame threads of the M layers have an average denier of 6 to 20 denier and a strength of at least 2.2 g / den and the frame threads of the X layer have an average denier of 26 to 60 denier and a strength of at least 3.3 g / denier, which is at least 10% higher than the strength of the framework threads of each M-layer, and that the binding threads in all layers receive an elongation at break of 400 to 800 % .

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The thermally bonded nonwoven fabric according to the invention has because of its special combination of layers with special thread properties that combination of properties that are sought for a carpet base for tufted carpets. In the X-layer, the scaffolding threads have one higher titer and higher strength, the higher strength being based on a higher molecular orientation. Because The threads of the X-layer are compared to the threads of the two M-layers only because of their higher molecular orientation massively bound together. Therefore, in the bonded non-woven fabric, the threads of the X-layer have a high degree of mobility, so that when the needles of the nub placement machine penetrate the nonwoven fabric, they easily evade the needles and cannot be damaged by worn needles. Furthermore, the combination of a high thread denier is beneficial and the high strength of the framework threads of the X-layer, the resistance of the needle-pile carpets to tearing in the machine direction.

The framework threads in the two M-layers of the bonded nonwoven fabric have a lower titer and moderate strength (massive orientation). These threads show a massive Resistance to breakage and a lower cut resistance compared to needles when setting nubs. A high cut resistance of the threads in the M-layers is not necessary because the burling needles are essentially parallel move to the threads of the M layers and therefore less likely that they will cut the threads. The massively oriented framework threads of the M-layer can easily be tied to the binding threads and to each other, This results in a high resistance to shrinkage and to fraying, without reducing the tear strength thereby suffers significantly. The use of moderately oriented framework threads in the M-layers also enables the use of lower temperatures and shorter treatments

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• ψ ·

treatment times for thermal bonding. Shrinkage resistance

and fiber resistance are very valuable properties for carpets to be dyed in the tub. the The surface layers of the carpet should be resistant to shredding. The relatively low titer of the threads in each M-layer also serves to improve the optical covering power of the layered non-woven fabric.

The binder in each layer of the bonded nonwoven fabric consists of melted or partially melted polypropylene, which comes from the poorly oriented filaments which essentially melt during the binding process. The unbound Nonwoven thread, from which the nonwoven fabric is made, contains threads with essentially three degrees of molecular orientation: (1) The binding threads of the M and X layers have a low degree of orientation, (2) the framework threads of the M layers have a moderate degree of orientation, and (3) the framework threads of the X-layer have a high degree of orientation. While the massive and the strongly oriented scaffold threads are not significantly changed by the thermal bonding process, the filaments of low degree of orientation melt fully or partially during the binding process.

The directional preference of the threads in the different Layers is also important. An XD / 45 ° value (as defined below) of less than 1.5 leads to the decrease the tufted tear strength according to the tongue method, while an MD / 45 value of less than 1.5 leads to a leads to stronger shrinkage during dyeing or other heat treatment processes. It was also found that the

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TP-0004-F ψ.

'T'

The desired combination of low shrinkage and high tear strength is not achieved if the weight of the X-layer or the total weight of the M-layers is 70 % of the total weight of the nonwoven fabric. As mentioned above, the X-layer in the layered non-woven fabrics according to the invention therefore accounts for 40 to 60 % of the total weight of the non-woven fabric, while each M-layer accounts for 20 to 30 % of the total weight of the non-woven fabric.

In order to simplify the description of the method according to the invention, letters are used to indicate the order to identify in which the layers of the thread fleece are deposited, whereby the deposit begins with the bottom layer and continues to the top layer. Since the product can be viewed from both sides, it is for the labeling of the product only the relative position of the layers is important. According to this system, MXM means that first the M-layer, then the X-layer on top of the M-layer and finally another M-layer on top of the X-layer is stored. Each individual M or X layer can be deposited with the help of a large number of nozzles, the are distributed across the width of the depositing belt. Furthermore, several successive rows of nozzles can be used. If the threads from successive rows of nozzles are laid in the same general direction, this can be deposited material can be viewed as a single layer.

To further explain the invention, reference is made to the drawings.

Fig. 1 is a schematic section through a melt spinning • and Cooling device with which the polypropylene threads of high Titer and high degree of orientation for the nonwovens according to of the invention.

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Fig. 2 is a schematic representation of a device for drawing and laying a thread tape on a running Tape.

Figure 3 is a perspective view of four air jet devices for deflecting the threads in the form of layers with a directional pattern.

A general description of devices for carrying out the method according to the invention can be found in FIG US-PS 3,563,838. However, for the melt spinning and cooling of the polypropylene threads of the X-layer of the nonwoven fabric according to of the invention preferably uses an improved mechanism. In particular, the flow of the cooling air is carefully controlled in such a way that rapid cooling takes place without breaking the running threads. The device according to FIG. 1 is a modification of the device described in U.S. Patent 3,705,227. This device can optionally also for Manufacture of the threads of the M-layers are used, but is of particular value for the manufacture of the threads of the X-layer. As Fig. 1 shows, melt-spun polypropylene threads 4 come from the spinneret plate 1, in which (not shown) Openings are arranged in circles. The threads run through a radial cooling device 2 to the conveyor roller 22. An air deflector 3 in the form of an inverted cone is attached to the spinneret plate. At the top and at the bottom Flow diaphragms 5 and 6 are attached to the end of the cooling device 2. In this particular, modified embodiment used for spinning highly oriented threads from high titer is determined, the flow apertures are elliptical and are in such a position that of any point on the outer circle of the spinneret orifices a straight line (with only minor deviations) through a point on the innermost surface of the flow diaphragm 5 and a similar point of the flow diaphragm 6

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the first conveyor roller 22 of the thread drawing device can be drawn. At the same time, the major axes of the elliptical surfaces of the flow diaphragms 5 and 6 lie in a plane tangential to the surface of the roller 22. This allows for better adaptation to the natural shape of the running threads. This special design of the device according to US Pat. No. 3,705,227 enables an extremely unusual one effective cooling, which prevents threads from sticking together and the formation of highly oriented threads of high Titer is favored at high spinning speeds.

The openings at the top and bottom of the cooling device are so large that the main resistance to the air flow occurs at the lower end of the cooling device and most of the cooling air is forced to the cooling device by leaving the top end. The cooling air is supplied through the inlet line 7 and, as described below, distributed so that it flows radially inward against the running threads entering the cooling chamber, whereupon the flow diaphragms 5 and 6 force the greater part of the air out of the upper end of the cooling chamber 2 and to flow briefly upwards through the center of the hollow thread bundle 4. Then the air hits the conical deflector 3 and is deflected back radially outward through the running thread bundle. The length of the conical flow diverter and the cooling air speeds depend on many factors, such as the number of threads, the throughput depending Spinning hole, spinning temperature, etc.

When melt-spinning polypropylene, which contains certain stabilizing additives, which at the spinning temperatures below A smoke evacuator will normally sublimate or decompose formation of smoke on the spinneret face used. This device also improves the cooling process.

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The threads run downwards through the cooling chamber, the walls of which consist of a cylindrical, permeable member 16. The air chamber 19 is fed through the inlet 7 with air or another cooling gas under a slight excess pressure, in order to achieve a uniform radial flow of cooling gas into the cooling chamber through the permeable organ.

Behind the flow diaphragm 6, the thread bundle 4 is elliptical Shape; the major axis of the ellipse lies in a plane tangential to the surface of the roller 22. Fig. 1 shows a section along the minor axes of the ellipses at 5 and 6. The major axes of the ellipses lie to the axis of Roller 22 parallel.

As FIG. 2 shows, the elliptical thread bundle 4 becomes a band of parallel threads as it passes the roller 22. Then the yarn runs one after the other over the rollers 23, 24, 25, 26 and 27. The speed of the increases From roller to roller. The highest increase in speed takes place between a hot roller and the next one cold roller instead. The drawing process is supported by the fact that the threads or parts of the same be heated on the grooved roller 25 and optionally on the smooth roller 23. Since the roller 23 is a smooth, cylindrical Is roller, a uniform stretching takes place between rollers 23 and 24. The roller 25, however, has grooves on, which extend in the axial direction over their surface. Those sections of the yarn that make up the hot roll surface touch between the grooves are additionally stretched, whereas those thread sections that touch the grooves bridge, not to be stretched to a significant extent. The threads coming from the roller 25 show along their length alternately strongly oriented and less oriented sections. The band of sections The drawn thread runs from the roller 27 to the guide 28.

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TP-0004-F - *

When walking past the target stick of a corona charger 29, as described in US Pat. No. 3,163,753, the threads are electrostatically charged. The band of Electrostatically charged filaments are fed into the inlet opening of the slot nozzle 30 (the type of which is shown in FIG. 6 of US Pat 3 563 838) is sucked in and exits the slot nozzle outlet for placement on the moving belt 32. 2 shows the arrangement as seen from the front end of the depositing belt 32. If multiple nozzles are used, can the sides 41 of the conveyor belt may of course be further apart. As Fig. 2 shows, the thread tape 31 is as X-layer filed. At the nozzle outlet, the thread tape is driven by an air pulse that alternates from one side and is then fed from the other side of the running thread tape, alternately deflected back and forth, so that the Threads are laid down oriented mainly transversely to the machine direction.

The general arrangement of the multiple delivery nozzles above the discharge belt can be seen from Fig. 3, which shows four slot nozzles, of which ^ ee a thread tape 31 to the porous depositing tape 32 promotes, which advances in the direction shown by arrow 40. The two front nozzles 30 extend with the width direction of their slots across the width of the depositing tape. The two rear nozzles 34 are directed so that their slot width is 40 in the machine direction. The arrangement shown in Fig. 3 is used for filing of layers in the MX order. For an MXM deposit there would be another unit behind the nozzles 34 of nozzles that would be in the same direction as nozzles 30. When a wider carpet base is made a larger number of nozzles across the width of the machine are used.

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Fig. 3 also shows the arrangement of the threads in the product according to the invention. The threads of the M-layer 38 run generally in the machine direction. However, part of each thread runs in different directions because the direction is on
must be reversed at each end of the reciprocating motion in the M direction. Similarly, the threads in X-layer 39 are generally oriented in the cross-machine direction, but have portions along their length that are oriented in other directions. Finally, threads are deposited downstream of the conveying direction to a further M-layer (not shown in FIG. 3).

In the manufacture of the nonwovens according to the invention, threads of a relatively low titer are spun, drawn and deposited by the jets of air oscillating back and forth in the machine direction, while threads of a high one
Titer spun, drawn and deposited by the air jets swinging back and forth transversely to the machine direction. In addition, the threads that will later become the M-layers
should form, in sections to a lesser degree of
Molecular orientation stretched as the threads that are later
to form the X-layer. The difference in thread count
and the molecular orientation of the drawn thread sections in the M layers and the X layer is achieved by regulating the spinning speed, the drawing ratio between the smooth rollers 23 and 2k and the drawing ratio between the grooved roller 25 and the smooth roller 26. The amount of molecular orientation in the binding sections of the threads is primarily determined by the relative speeds of the rollers 23 and 24. The percentage of the binding sections in the M and X layers
is determined by the ratio of the sum of the groove widths to the total circumference of the grooved roller 25.

The filaments laid down are thermally bonded, preferably by passing through saturated steam in a binding device, as described in US Pat.

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ben is. After binding, a finish is applied in order to avoid excessive thread breaks when setting nubs. A polysiloxane as described in US Pat. No. 3,322,607 is preferably used as the finish. Too much shrinkage is prevented by spatially delimiting the fleece during the binding process. The degree of bonding influences the properties of the nonwoven. As the binding temperature increases, the tendency of the pile carpet to shrink decreases. At the same time, as the binding temperature rises, the values for the tufted tear strength according to the tongue method pass through a maximum and then decrease again. For a carpet base, a balance between the shrinkage and the tufted tear strength is necessary. The aim is to produce products that shrink by 1 to 5 % _f, preferably by 1 to 3 % . The action of excessive mechanical pressure should be avoided when using the binding device according to US Pat. No. 3,313,002, so that the fiber mobility in the X-layer is maintained. It is particularly important to avoid the application of excessive mechanical pressure if any of the outer M-layers contains more than 20 % binder, because the binder can easily melt under the action of heat and pressure and run into the X-layer, whereby the fiber mobility is reduced. However, the fiber mobility is necessary to achieve a high tufted tear strength of cut pile carpets. When constructing the nonwoven, it should be taken into account that the M-layer closest to the water vapor source has a higher heat absorption. Therefore, the defibrillation values on both sides of the nonwoven fabric can differ from one another, even if the same amount of binder has been used in each M-layer.

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Test methods

The directional preference, the tufted tear strength, the percentage shrinkage, the binder concentration, the titer of the framework threads and the thread strength are in accordance with U.S. Patent 3,821,062. The thread strength can also be determined on thread samples taken directly from the nozzles can be removed, whereby a 10 percent decrease in strength when running through the hot-binding process is taken into account represents.

Tear resistance of cut pile carpets

For this experiment, a cut pile carpet is produced using a bonded nonwoven fabric as the carpet base. Old, worn needles are used to make the carpet. The nonwoven is 2 percent by weight Polymethylhydrogensiloxane provided as a lubricant. A sample of the lubricant becomes lengthwise (in the machine direction) provided non-woven fabric so that you can

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20.3 cm wide strips received. These strips are trimmed in a 5/32 gauge cut pile napping machine (in which the spacing between the needles is 0.396 cm) arranged so that a strip over a width of 15.3 cm with the help of old needles (randomly selected from a supply of needles that have been used for about 1000 hours) is trimmed with pile. All needles are »Eisbar 1269/350" needles with a 0.318 cm thick spigot end. The non-woven material is made in the machine direction using a twisted polyamide staple fiber yarn (two-strand yarn made from single capillaries with a worsted number of 2.25) in a density of ό, 5 tufts each 2.54 cm occupied with pile, so that a cut pile carpet with a pile height of 1.27 cm and on each side of the part covered with pile a 2.5 cm wide unoccupied one Nonwoven strips remain free. The fleece covered with pile with the 2.54 cm wide selvedge on each side are cut into 8 inch strips (in the machine direction). The tufted tear strength of the cut pile carpets is then determined by the tongue method in the same way as is done with studded pile carpets, namely by tearing in the machine direction.

Fiber resistance

This test is a modification of ASTM test standard D 1375, Part C, Brush and Sponge Process. Square specimens are cut out of the bonded nonwoven, which are shown in in the M-direction and in the X-direction are each 25.4 cm long. The samples are placed around flat sample holders made of galvanized steel that are rectangular in shape (10.8 cm 29.2 cm). The side to be examined is directed outwards. The holders are covered with # 100 sandpaper to prevent the To prevent specimens from attempting, and the specimens are attached to the holders with magnets. The total weight of Steel strip and magnet is 550 -5g. Then the Samples face down on the upright

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attached to the bristles of the pilling test device, and the Fibrous brush is placed under the samples for 10 seconds run. The next level of the ASTM testing process, namely the circular rubbing of the samples with a sponge in order to roll up the free fiber ends into fiber balls, is omitted. The appearance of the nonwoven is assessed visually by comparing it with standard samples. Samples Get brush disintegration values from 1 to 5 », with 1 being extremely fibrous and 5 being practically free of fibrils. The nonwovens according to the invention have, compared to the previously known products of the same degree of shrinkage, a relatively high resistance to shredding.

Percentage optical opacity

This is a photometric test to determine opacity of nonwovens. Separate measurements are made of those of a white background, that of a black background, that of the nonwoven in contact with the white background and that of the black background in contact with the same amount of light reflected from the nonwoven fabric to be examined. the Measurements are made on at least five different parts of each test nonwoven. One uses one in trade available device, which consists of a search device connected by a cable to a measuring device (including light source, optical system and photocells), a power source and control elements. The percentage of optical opacity is calculated from the measured reflectivity according to the following equation:

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R - R Percentage optical opacity = [1 - - J χ 100

^R WB " ^E BB

where R _WD = reflectivity of the white background (for which the meter is calibrated to display 100),

R _13x . = Reflectivity of the black background

Ϊ5Ϊ5

(for which the measuring device is calibrated so that it displays 0),

^R FWB ~ ^Re ^ l ^exibility S ^{en of the} nonwoven fabric against the white background,

^R FBB ^{= reflectivity of the} nonwoven fabric against the black background.

The nonwovens according to the invention have a given weight per unit area compared to the previously known nonwovens a high optical opacity. For comparison purposes, the nonwovens made of threads of the same color depth and of the same shade.

Examples 1 to 5

An experimental device similar to that according to FIGS. 1 and 2 is used for the production of five nonwovens according to the invention used. The details of the spinning, drawing and the discarding procedure are given in Table I for each example. As a result of being passed over the grooved roller 25, which is heated to 135 to 140 ° C., the threads are very stretched Frame sections and less stretched binding sections.

In all examples, the amount of nonwoven deflection is adjusted so that the M and X layers in the middle areas used for sampling comply with the prescribed show percentage by weight of fibers. The pro-

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Behavior areas are in the middle of the width of the nonwovens and contain representative portions of each of the deposited M and X layers. Located on the margins Parts of the nonwovens are not used for sampling. The structure of the five nonwovens is summarized in Table II. The properties of the bonded nonwovens result on their own and when used as basic carpet materials from Table III.

In all examples, the threads are spun from the melt of a polypropylene with a melt index of 3 »2-0.4, determined according to ASTM test standard D 1238-65T, which contains 0.068 to 0.078 % carbon black as pigment. The spun threads are gray and have the same color depth and hue. Nonwovens with an MXM structure are produced by depositing the melt-spun polypropylene threads from three spinnerets arranged in series above the depositing belt. Each spinneret feeds a separate suction nozzle. The output of the individual spinnerets is placed one after the other on a moving conveyor belt. First an M-layer is deposited at the front end of the depositing tape, then an X-layer and finally another M-layer is deposited. The belt speed is adjusted so that nonwovens are produced with the weights per unit area given in Table III.

As Table II shows, the nonwovens in the X-layer have the threads of higher denier and in the M-layers the threads of a lower titer. The threads in the X-layer have a higher orientation than the threads in the M-layers. The high degree of orientation is reflected in the high strength of the threads.

The properties of the nonwovens according to Table II The carpet bases and carpets produced are shown in Table III. The nonwovens described in Table II

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are bound by passing through the water vapor binding device according to US Pat. No. 3,313,002. The deposited threads and the depositing tape run out of the depositing area directly through this binding device. The steam temperature in the Binding device is set so that a nonwoven fabric

. . ,,. , preferably by less than 3%,

arises, which shrinks by less than 5%, /. The tendency to ' Shrinkage is reduced by using higher temperatures. However, the temperature is kept so low that the tear strength of the knobbed pile carpets made from the nonwovens is still at least 0.24 - ^. In

g / m

temperatures in the range of 148 to 152 ° C are used in these examples. (If you work with higher belt speeds, higher temperatures are necessary for a sufficient bond.) From Table III it can be seen that the carpet base materials obtained in this way have a fiberization value of at least 3.0 and preferably of at least 4 at basis weights of 98 to 125 g / m 2 , 0 on at least one surface and an opacity of at least 77 % .

The basic carpet materials explained in Table III are used, as indicated in the test methods, for the production of knobbed pile carpets and cut pile carpets. These nonwovens according to the invention have a high tufted tear strength in dimple pile carpets. Furthermore, these basic materials are suitable for the production of cut pile carpets and are less sensitive to the nature of the knobbed setting needles. Table III shows that the cut pile carpets made with old needles have a tufted tear strength of more than 20.4 kg. This feature, combined with the high shred resistance and high opacity make the backing for a _t very valuable product.

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Table I Process conditions of the examples

Example 1 2 5 4 5

Surface speed of roller 26

M layers, m / min X layers, m / min

Draw ratio of the drawn sections * M layers
X-layer

Elongation at break of the undrawn sections **

M layers, %
X layers,%

Remarks

* The draw ratio is determined from the ratio of the surface speed of the roller 26 to the surface speed the roller 22 is calculated.

** The mean elongation at break is determined on sections of high titre, those from threads deposited on the conveyor belt have been cut out before binding.

200 threads per spinneret are deposited in each M-layer, 150 threads per spinneret in each X-layer, with the exception of the Example 2, in which only 100 threads are deposited in the X-layer per spinneret.

660 660 505 505 660 537 645 537 495 537 1.8 1.8 1.8 1.8 1.8 3.5 4.0 3.6 3.3 3.5 466 481 478 524 548 595 551 577 637 595

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Table II

fa ") nonwoven structure in the examples * · '

Example 1 2 3 4 5

Framework titer, the M-layer X-layer M-layer

Framework thread strength, g / denCb)

M-layer X-layer M-layer

Binder in the layers,% by weight ^(c 'M-layer X-layer M-layer

Directional preference values * · 'MD / 45 ⁰
XD / 45 °
(MD + XD) / 45 °

Remarks

^v 'In each example, the weight of each M layer is 25% and the weight of the X-layer 50% of the total nonwoven weight.

'The thread samples are the threads coming from the nozzles or taken from the bonded nonwovens. From the strength values of the thread samples coming from the nozzles 10% deducted to take into account the effect of the binding.

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14.2 13.3 11.5 14.5 14.0 32.5 47.1 35.3 33.6 33.6 12.8 12.0 14.5 14.4 10.3 2.7 2.4 2.6 2.4 2.8 3.7 3.7 3.5 3.6 3.6 2.2 2.4 2.7 2.9 2.8 12th 12th 12th 12th 32 12th 12th 12th 23 12th 12th 12th 12th 12th 32 2.0 2.8 2.6 2.4 2.6 2.9 2.9 2.6 1.5 2.8 5.7 5.2 3.9 5.4

^v 'Calculated as percent by weight of non-drawn thread

Sections according to the equation % undrawn = total arc length of the grooves _{χ 1 (χ)}

Total circumference of the grooved roller

^ '' Determined using the random method.

Table III

Properties of the basic carpet materials
and carpets of the examples example Running in, % 1 2 3 4th 5 Carpet base Basis weight, g / m 125 125 98 102 119 Opacity, % 79 80 80 81 77 Fiberization values
of the M layers first, with steam
treated layer 4.7 4.6 5.0 5.0 4.4 other layer 4.5 4.1 3.5 4.0 3.3 Knobbed carpet Tufted tear
strength, kg 47 41 24 25th 46 g / n? 0.38 0.32 0.35 0.34 0.39 1.7 1.8 1.5 1.7 2.2

Cut pile carpet, made with worn needles, tufted tear resistance, kg 24 21 29 24

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Claims (3)

EI du Pont de Nemours
and Company ■ te. June 24, 1975 TP-OOOVF Claims (Iy Bound nonwoven fabric made of isotactic polypropylene threads, which has a layer M running in the machine direction on each of its two surfaces, while a layer X running transversely to the machine direction makes up 40 to 60% of the total weight of the nonwoven fabric, each layer being essentially 65 to 90% by weight .% of scaffold fibers and 10 to 35 wt.% of isotactic polypropylene as a binder is, and the threads arranged in each layer so that the laminated nonwoven fabric Richtungsbevorzugungswerte of at least 1.5 for MD / 45 °, for at least 1.5 XD / 45 ° and 3.5 to 30 for (MD + XD) / 45 °, characterized in that the framework threads of each M-layer have an average titer of 6 to 20 den and a strength of at least 2 g / den and the structural threads of the X-layer have an average titer of 26 to 60 den and a strength of at least 3 g / den, which is at least 10% higher than the strength of the structural threads of each M-layer . 2. Bound nonwoven fabric according to claim 1, characterized in that each M-layer makes up about 20 to 30 % of the total weight of the nonwoven fabric. 3. Process for the production of nonwovens according to claim 1, in which an unbound thread fleece by successive laying down of layers of melt-spun and stretched isotactic polypropylene filaments are produced on a moving conveyor belt in such a way that - 22 - 5098S3 / 0738 first the layer running in the machine direction (M-layer), on top of this a layer running transversely to the machine direction (X-layer) and finally on the X-layer a second layer running in the machine direction (M-layer) is deposited, whereby the conditions the melt spinning, the drawing and the laying speed are controlled so that the X-layer forms 40 to 60 percent by weight of the total weight of the nonwoven fabric and each layer consists essentially of 65 to 90 percent by weight of scaffolding threads and 10 to 35 percent by weight of binding threads, and the Threads are laid in such a direction-dependent manner that the thread fleece receives preferred directional values of at least 1.5 for MD / 45 °, at least 1.5 for XD / 45 ° and 3.5 to 30 for (MD + XD) / 45 °, whereupon it does so produced fleece is thermally bound with spatial delimitation, characterized in that the spinning and VerstreekungsVorgang is controlled so that the framework threads of the M-layers one average thread denier of 6 to 20 den and a strength of at least 2.2 g / den and the framework threads of the X-layer have an average denier of 26 to 60 den and a strength of at least 3.3 g / den, which by at least 10 % higher than the strength of the framework threads of each M-layer, and that the binding threads in all layers have an elongation at break of 400 to 800 % . - 23 - 509883/0738 Blank page