DK144037B - PROCEDURE FOR MANUFACTURING SEGMENT-BONDED UNWOVEN FABRICS - Google Patents

Description

in 144037

The present invention relates to a method of producing a segmentally bonded nonwoven fabric of the kind set forth in the preamble of claim 1.

Many methods have been proposed for the preparation of bonded nonwoven fabrics, comprising in connection with a nonwoven web the use of adhesives or heat whose thermoplastic materials are contained in the web. In particular, it is known to use heat and pressure for bonding in restricted areas of the web by passing it through the gap between cage landing rollers, at least one of which is heated and carries a pattern of projections and depressions on the surface. Where the fabric is squeezed or pressed between the roller surfaces, a strong or primary bond is obtained at separate segments of the fabric, resulting in a segmentally bonded fabric. Of the 15 pairs of calendering rollers used, can either or both rollers carry patterns with projections and recesses? in the first case, the smooth roller, especially when heated directly, also tends to produce some less strong or secondary bonding over the rest of the fabric where it has not been squeezed or pressed between the rollers. This total secondary bond on one surface of the fabric tends to make the fabric stiffer.

In the latter case, when both rollers are patterned, it is known to employ patterns in the form of circumferential rings 25 or helical lines which cannot engage each other.

Calendering with such rollers does not cause any secondary bonding across the surface of the fabric, but only at the places in each surface where the fabric has been affected by a protrusion on only one side. However, this more limited secondary bonding is achieved at the expense of the fact that only a limited range of regular patterns of primary bonds can be made at the junctions of the projections as the rollers rotate.

By calendering a web between two rollers, each carrying a pattern of protrusion that was sufficiently accurately aligned one after the other, one can create any desired pattern of both primary and secondary bonding; but a preservation of such exact alignment is not practicable or at least very costly when using rollers large enough to produce broad fabrics and with projections small enough to produce fabrics with new features and an appealing appearance.

GB-PS 1,245,088 discloses a method for forming a bottom nonwoven textile material including at least some thermoplastic material by bonding in a predetermined pattern of interspaced regions by passing a textile material through the printing slot formed by a a plurality of means, at least one of which is a bonding member, which bonding member cooperates with a backpressure member and is heated to a temperature less than the softening point of the thermoplastic material and having a surface of between 50 and 1,000 forward springs per second. 6.5 cm protruding from the surface, and the projections have -5 x tips with a cross-sectional area from 6.5 x 10 mm -4 2 to 33 x 10 mm, and where between 1% and 10% of the entire area of the binding element includes the projection tips. After treatment, the bonded textile material is pulled from the pressure slot.

The manufacturing conditions in this document are subject to a number of limitations made redundant by the present invention. According to this GB-PS 1,245,088 there is a 20% limit on the bonding area, the rollers are required to have a temperature below the softening temperature and 25 very definite limits are given in terms of the size and density of the projections. The restriction on the temperature of the roller is unnecessary, and this also applies to the restriction on the size of the individual projections.

The physical and visible properties of the bound substance depend on the amount of bond, some direct and some vice versa, and the properties obtained in a substance are consequently the result of a compromise. Hitherto known fabrics have not achieved the best combination of properties for all purposes, especially as fabrics for clothing, where properties as closely as possible resemble known woven or knitted fabrics and with an attractive appearance.

144037 3

It is an object of the present invention to provide a method which enables much larger bonding areas, thereby producing a fabric that is acceptably soft and has a comfortable grip despite a bonding range of 22% - 50%.

This object is met by the fact that the method mentioned in the preamble is characterized by that of the characterizing part of claim 1, the stated object being thereby achieved due to the greater flexibility in the choice of projection patterns on each roller, the distribution 10 of the protrusions. groups of different densities and the interaction of the projections on the two rollers, the final bond area being the result of all three factors.

Fibrous webs for use in the present invention may include staple fibers or filaments or mixtures of dies. Stackable fiber webs are conveniently prepared by mapping a stacked fiber mass, and they can be prepared by a random-laying air-laying method, and filament webs can be made by a known air-laying method which utilizes an air flow to transport the filaments from a source and spread them in a random pattern on a carrier with small openings. The filaments can be given an electrostatic charge to increase their separation prior to laying on the conveyor.

A thermally bondable material contained in a web used in accordance with the present invention may comprise particles of the material distributed through the web of fibers, or it may preferably be configured as spaced fibers having a lower softening or melting point than the other fibers. In the web, or in the most preferred embodiment, the web may consist wholly or partially of bicomponent fibers, one of the components being at least partially present in the surface of the fibers and having a lower softening or melting point than the other component. The fibers in a web may comprise natural, regenerated or synthetic fibers from linear organic polymeric materials such as, for example, polyesters, polyamides and copolymers of the classes of organic linear polymers. The working temperature of the calender roll (s), if both heated to a binding temperature, is in the region of the softening or melting point of the bondable material and is such that, together with the pressure between the surface of the calender rolls, it forms primary bonds in fabric segments. between the roller surfaces.

In the present invention, one or both of the calender roll pairs are formed with a pattern of groups of projections of different densities, and in such rolls the different density according to the characterizing part of claim 2 can be produced by vary the size of the projections in the various groups or in accordance with the characterizing part of claim 3 by varying the number of projections of the same size per unit. area unit of the different groups. These patterns may be formed on a calender roll by, for example, engraving methods beginning with a continuous tone positive or negative relative to the total pattern, breaking this into halftone negative or positive by an appropriate raster printing process using e.g.

25 shows a checkerboard or lined bar grid and transmits the halftone pattern to the roller by photo etching or engraving or machine engraving procedures which reproduce the total pattern as groups of projections with recesses between the projections of different densities. In order to produce a bonded fabric having the desired properties, the total amount of bonding must be adjusted so as not to produce fabrics which are either inappropriately rigid due to an excessive percentage of bonded area in the fabric surface or which are insufficiently resistant to surface wear due to a too small percentage of bonded area. At the same time, it is desirable to have a small percentage of bonded area to promote the more aesthetic grip and fall properties and a large bonded area to promote the physical properties such as wear and breakage.

A very important advantage of the present invention is that it allows for easier selection of bonded area to allow for a compromise between the aforementioned opposing effects. This is because at least three values for the bound area are involved in the final result obtained. Thus, if only two different densities for the groups of protrusions are involved in the preparation of the total pattern, then the final result will be the percentage of bound area at each density and the relative amount and distribution of each group of protrusions of the two protrusions. densities. Accordingly, it is seen that the flexibility of the steering is greatly increased compared to that which is possible with the regular protrusion patterns used so far.

At the same time, the regular patterns of fabrics with known projection patterns, such as chessboard patterns, dices, closed or open echelons, and similar projection patterns with 20 rectilinear circumferences are broken up and replaced by a more aesthetically pleasing pattern by the present invention.

In order to avoid or reduce the occurrence of rigid spots in a bonded fabric due to very dense protrusion groups on a roller for use in the present invention, it is preferred to use a very coarse grid to produce a halftone negative or positive. if this method is used and the grid can be much coarser than those normally used in halftone reproduction. It was therefore unexpected and surprising that with such coarse gratings one could still distinguish or see a good resemblance to an intricate pattern in the bound fabric. The roughness pattern used also facilitates the reproduction of a projection pattern on a roller by other engraving methods.

6 144037

Whatever method is used to reproduce the protrusion pattern on a roller, this is performed so that the pattern is reproduced on the roller with such depth for the recesses between the protrusions that they will penetrate a fibrous web during the bonding process substantially without contact between the web and the roller surface at the base of the recesses.

A roller of a calendering pair, if not of the type just described, having a different density pattern in accordance with the characterizing part of claim 5, may be a roller carrying a single regular pattern of protrusions of similar size. size, such as a chessboard pattern, a pattern of rings, screw lines or notes, or a pattern of parallelogram shaped projections in closed or open echelon, provided that the projections on the regularly patterned roller use sufficiently overlying contact with the projections of the differently patterned roller to produce a particular pattern of primary bonds that is at least similar to the 20 different pattern density groups. The pattern of the surface temperature of the second roller and / or this roller should also be such that it does not detract from the properties of the bonded fabric by providing an inappropriate amount of secondary bonding. In this way, the undesired regularity of bonded patterns produced by the known methods can be replaced by the dominant pattern of primary bonding groups of different densities, exhibiting a much more appealing appearance that can be enhanced or highlighted by coloring, such as by staining. or transfer pressure, since the primary bonds will exhibit a different affinity to the dye than that exhibited by the less strongly bonded or unbound portions of the fabric. Such coloring can be obtained simultaneously with the bond by passing a color transfer web through the calender slit with the fibrous web in accordance with the characterizing portion of claim 6, as disclosed in the disclosure to UK Patent Application No. 7 17239/75, 2172/76 and 2887/76.

Pattern groups of different densities can take different forms. Eg. they may represent flowers or they may be surreal or not represent real objects, while exhibiting a total pattern with different density groups.

The drawing shows patterns defined by groups of different densities, where fig. 1 shows a pattern formed by projections of circular cross-section, and FIG. 2 shows a pattern formed by linear projections, which may be circumferential rings or helical or longitudinal grooves.

FIG. 1 shows part of a floral pattern in which the flower reproductions of different tone are shown by projecting groups of different density against a background of uniform density. In this FIG. the dark areas represent flower petals, the very bright areas represent the flower cup, and the intermediate areas are the background.

FIG. 2 shows a flower and leaf pattern in which the different density groups are produced by a variation of the thickness of line patterns.

FIG. 3, a checkerboard pattern is also made by changing the thickness of the line patterns.

In one embodiment of the present invention, a 2 carded web weighing 141.6 g / m consisting of 3.3 decitex 58 mm polyamide conjugate filament filament fibers (50:50 parts by weight of sheath / core nylon 6 / nylon 66) m / min. through the gap between calendering rollers, each having a surface temperature of 215 ° C and having a linear rolling pressure of 32 kg / cm. The upper roller is patterned as shown in FIG. 3, with the thicker projections having a width of 1.1 mm and the thinner projections having a width of 0.5 mm. Each group consists of seven lines in a 12.7 mm square, and the percent roll surface area formed by these lines is 60% and 27%, respectively, for the denser and less dense areas. The lower roller is a thin-walled tube which provides enough to offset any minor surface irregularities, thus equalizing the gap pressure along the gap. This roller carries a single pattern of longitudinal notes with a width of 0.8 mm, there being sixteen such notes per unit. 25 mm of the roll circumference corresponding to 10 a projection area of 50%. The overall effect on the fibrous web passed between these rollers is that 30% of primary bonded area is produced in the dense regions and 14% in the lighter regions to produce a bonded fabric having the following properties: 15 Breakage load, kg 22 , 2 (MD)

Fracture elongation,% 27.0 (MD)

Tear strength, kg 1.7 (MD) 1.9 (CD) Bending length, cm 5.1 (MD) 20 3.7 (CD) MD = machine direction; CD = the transverse direction.

These measurements are made by the following methods: Bending Length 25 The bending length is measured according to British Standard BS3356: 1961. The bending length (cm) is the cubic root of the ratio of the bending stiffness to weight per unit weight. unit area.

Tensile Strength

The breaking strength is measured as the breaking load for 25 mm wide fabric strips when tightened at a cash rate of 100 mm / min. (on an Instron stress test device) from a measuring length of 100 mm. Stretch at break is noted simultaneously.

Claims (4)

144037 Tear Strength The load required to tear a specimen is measured on an Instron stress test device. A rectangular specimen of 100 mm x 50 mm is prepared by making a straight section in the middle of a short side and 75 mm parallel to the long sides. The two 25 mm wide ends thus formed are attached to each of their Instron jaws, spaced 50 mm apart. By separating the jaws at a right angle to the plane of the fabric at 50 mm / min. the sample is shredded and the maximum load (or average if multiple vertices were noted) is recorded. Claims. A method of making a segmentally bonded nonwoven fabric, wherein a fibrous web including at least some spaced, heat-bondable material is passed through the gap between cooperating calender rolls, both of which have patterns of protrusions, at least one of which is heated to bonding temperature, characterized in that the pattern of protrusions on one roller differs from the pattern of protrusions on the other roller, the pattern of 20 protrusions on at least one roller includes groups of protrusions of different density which together constitute the entire pattern, and that the pattern of protrusions on both rolls is chosen such that the segmental bonds formed in the web occupy an average proportion of the entire range from about $ 22 to about half. Method according to claim 1, characterized in that the different density is obtained by the size of the projections being different. Method according to claim 1, characterized in that the different density is obtained in that the number of projections 30 of uniform size is different. Method according to one or more of claims 1-3, characterized in that both rollers carry a pattern of manufacture.