MXPA99008903A - Cellulose-binding fibres - Google Patents

Abstract

The invention relates to drylaid nonwoven materials comprising bicomponent fibres comprising a low melting polyolefin component and a high melting polyolefin component, the low melting polyolefin component constituting at least a part of the surface of the fibre and comprising a non-grafted polyolefin component and a grafted polyolefin component, wherein the grafted polyolefin component has been grafted with an unsaturated dicarboxylic acid or an anhydride thereof, e.g. with maleic acid or maleic anhydride. The bicomponent fibres have an excellent bonding affinity for natural fibres such as cellulose pulp fibres and allow the production of airlaid nonwovens with reduced generation of dust during the production process and with improved nonwoven strength properties.

Description

LINK FIBERS TO THE CELLULOSE FIELD OF THE INVENTION The present invention relates to non-woven, air-laid or dry-laid materials comprising polyolefin two-component fibers having excellent binding affinity for natural fibers such as cellulose fibers.

BACKGROUND OF THE INVENTION Hygienic absorbent products such as disposable diapers contain, in addition to a water permeable cover material, a waterproof reinforcing sheet and one or more layers for liquid distribution, an absorbent core typically comprising natural fibers such as fiber fluffy cellulose pulp, synthetic fibers based for example on polyolefin and / or polyester and a superabsorbent polymeric material (SAP). In absorbent cores of this type, the synthetic fibers, which are often bicomponent fibers for example of REF .: 31210 polypropylene / polyethylene or polyester / polyethylene, are thermobonded to each other to form a support network for the core. Ideally, synthetic fibers should be capable of not only bonding with each other, but also natural fibers and SAP, to result in a core structure that is as strong and coherent as possible, and in which natural fibers and the SAP are secured on your site within the structure. However, the existing synthetic fibers, which are used for the production of nonwovens, laid or air-laid, for example or air-laid, suffer from the disadvantage of poor bonding, for example to cellulose fibers. The problem is made worse by the fact that the natural fibers are typically relatively short, for example, fluffy pulp fibers with a length no greater than about 3 mm, as compared to synthetic fibers, which are normally (although not necessarily) considerably longer). As a result, dust problems are created in the manufacturing process, and the operation of the resulting non-woven materials is also poor, since a large proportion of the natural fibers are not bound to any of the synthetic fibers or otherwise held in place by the structure formed by the union of the synthetic fibers. It is therefore an object of the present invention to provide a synthetic two-component fiber which has an improved binding or binding affinity for natural fibers, such as fluff pulp fibers of cellulose and which is therefore particularly suitable for the production of non-woven materials, air-laid, comprising a mixture of synthetic fiber and natural fibers. European Patent EP 0465203-B1 discloses fibrous, thermally bonded wet laid networks containing bicomponent fibers comprising a first component of polyester, polyamine or polypropylene and a second component of linear low density polyethylene (LLDPE) with a density 0.88-0.945 g / cm3 and a high density grafted polyethylene (HDPE) with a density of 0.94-0.965 g / cm3 which has been grafted with maleic acid or maleic anhydride to provide groups of succinic acid or succinic anhydride throughout of the HDPE polymer.

European Patent EP 0421734-B1 describes the two-component, heat-fusible fibers, composed of two different polyolefins having melting points that differ by at least 20 ° C, the lower melting polyolefin containing from 3 to 10% by weight of a monoglyceride of a fatty acid of 12 or more carbon atoms, incorporated therein. It is reported that the fibers are easily processable without the need for an oiling agent to be applied during spinning or stretching. U.S. Patent No. 4,950,541 describes the succinic acid and succinic anhydride grafts of linear ethylene polymers obtained by grafting maleic acid or maleic anhydride onto a LDPE polymer (low density polyethylene)., LLDPE or HDPE. The grafted polymers are dyeable and can be used, for example, as the covering or protection component of a two-component fiber. U.S. Patent No. 4,684,576 discloses the prodon of grafted HDPE blends with ungrafted LDPE or LDPE, HDPE having been grafted with maleic acid or maleic anhydride to provide succinic acid or succinic anhydride groups along the HDPE polymer.

The mixtures are described for use in the production of laminated structures. It has now been unexpectedly found that the two-component, polyolefin fibers, whose low-boiling component comprises an ungrafted polyolefin component and a grafted polyolefin component that has been grafted with an unsaturated dicarboxylic acid or an anhydride thereof, they have advantageous properties when used in the production of air-laid non-woven materials, including improved binding to cellulose pulp fibers and improved strength properties in the resulting non-woven materials.

BRIEF DESCRIPTION OF THE INVENTION In one aspect, the present invention relates to an air-laid non-woven material, comprising bicomponent or two-component fibers comprising a low melting point polyolefin component and a high boiling point polyolefin component, wherein the component low melting point polyolefin has a melting point at least 4 ° C lower than the melting point of the high melting point polyolefin component, the low melting point polyolefin component constitutes at least a part of the fiber surface and comprises a non-grafted polyolefin component and a grafted polyolefin component, wherein the grafted polyolefin component has been grafted with an unsaturated dicarboxylic acid or an anhydride thereof. Yet another aspect of the present invention relates to a method for the production of an air-laid non-woven material, comprising the formation of a fibrous web using non-woven air-laid equipment, the network comprising bicomponent fibers comprising a component of low melting point polyolefin and a high melting point polyolefin component, wherein the low melting point polyolefin component has a melting point at least 4 ° C lower than the melting point of the polyolefin component of high melting point, the polyolefin component having a low melting point constituting at least a part of the surface of the fiber and comprising a non-grafted polyolefin component and a grafted polyolefin component, wherein the grafted polyolefin component has been grafted with an unsaturated dicarboxylic acid or anhydride thereof, and the binding of the fibrous network results in the material not being He smoothed the air. A further aspect of the present invention relates to a two-component fiber as described above, for the production of non-woven, air-laid materials.

DETAILED DESCRIPTION OF THE INVENTION The term "polyolefin component" for purposes of this invention means a polyolefin-containing polymeric material of which the major part (by weight) consists of homo- or copolymers of monoolefins such as ethylene, propylene, 1-butene, 4-methyl- l-pentene, etc. Examples of such polymers are isotactic or syndiotactic polypropylene, polyethylenes of different densities, such as high density polyethylene, low density polyethylene, and linear low density polyethylene and mixtures thereof. be mixed with other non-polyolefin polymers such as polyamide or polyester, with the proviso that the polyolefins still constitute the bulk of the composition.The melts used to produce the polyolefin-containing fibers may also contain various conventional fiber additives, such as calcium stearate, antioxidants, process stabilizers, compatibilizers and pigments, including going whiteners and dyes such as Ti02 / etc. Although the present disclosure, for simplicity's sake, will refer generally to 'fibers', for example chopped fibers, it is to be understood that the present invention will also be applicable to the production of continuous polyolefin filaments, for example spunbond filaments. The term 'air-laid' non-woven refers to a non-woven material produced by a dry process, including air-laid non-woven materials, carded non-woven materials, etc. The two-component fibers may be of the shell-core type, with the core being located either eccentrically (off center) or concentrically (substantially in the center), or side-by-side type, in which each of the two The components typically have a semicircular cross section. Bicomponent fibers having irregular fiber profiles are also contemplated, for example, an oval, elliptical, delta, star, ultilobular, or other irregular cross section, as well as divisible fibers. The bicomponent fibers will typically have a high melting point and low melting point polyolefin component which comprise, respectively, polypropylene / polyethylene (the polyethylene comprises HDPE, LDPE and / or LLDPE), high density polyethylene / linear polyethylene. low density, polypropylene / polyethylene random copolymer, or random polypropylene / polypropylene copolymer. In certain cases, for example, when the two components of the fibers comprise high density polyethylene / linear low density polyethylene or polypropylene / polypropylene random copolymer, the difference in the melting points between the two polyolefin components can be very small , for example, of about 7-8 ° C and in some cases even as low as about 4-5 ° C. However, it is generally preferred that the two components have melting points that differ by at least about 20 ° C, preferably at least about 25 ° C, more preferably at least about 28 ° C, for example at least about 30 ° C . As mentioned above, a presently preferred aspect of the invention relates to an air-laid non-woven material containing polyolefin bicomponent fibers in which the low melting polyolefin component comprises an ungrafted component and a grafted component. , the grafted component has been grafted with an unsaturated dicarboxylic acid or an anhydride thereof. Examples of such acids and anhydrides are maleic acid, maleic anhydride and derivatives thereof such as citraconic acid, citraconic anhydride and pyrichinconic anhydride.; fumaric acid and derivatives thereof; unsaturated malonic acid derivatives such as 3-buten-1, 1-dicarboxylic acid, benzylidenemalonic acid and isopropylidenemalonic acid; and unsaturated succinic acid derivatives such as itaconic acid and itaconic anhydride. Maleic acid and maleic anhydride are particularly preferred as the dicarboxylic acid or the anhydride thereof. When these compounds are grafted onto a polyolefin chain, the resulting chain is provided with groups of succinic acid or succinic anhydride, respectively, grafted onto it. The grafting of the dicarboxylic acid or the anhydride thereof onto the polyolefin can be carried out in a manner that is known per se, see for example the aforementioned patents EP 0465203, US 4,950,541 and US 4,684,576. The weight ratio of the grafted polyolefin to the ungrafted polyolefin in the low melting point polyolefin component of the bicomponent fibers will be within the range of about 1:99 to 50:50, typically about 1.5: 98.5 to 30:70. , more typically about 2:98 to 20:80, for example about 3:97 to 15:85, such as about 5:95 to 10:90. Within the grafted polyolefin, the carboxylic acid content or the anhydride thereof is typically in the range of about 1-30% (by weight), typically about 2-20%, more typically about 3-15%, such as about 5- The weight ratio between the high-melting and low-melting polyolefin components will be in the range of 10:90 to 90:10, typically about 20:80 to 80:20, more typically about 30: 70 to 70:30, for example 35:65 to 65:35. As mentioned above, the air-laid non-woven materials according to the invention, comprising the bicomponent polyolefin fibers and natural fibers, can be characterized by an improved binding of the bicomponent fibers to the natural fibers, as determined by a Standardized dust test whose result reflects the quality of the bond between the two types of fibers. In this standardized test, non-woven samples air-smoothed having a basis weight of about 85 g / m2 and a thickness of about 1.1 mm are prepared using a linear velocity of 20 or 40 m / min. from a mixture of 25% by weight of the synthetic fibers that are tested and 75% by weight of a cellulose pulp fiber (for example NB 416 from Weyerhauser). The non-woven materials to be tested are generally prepared using a series of different bonding temperatures (e.g., using hot air or calendering bonding, typically a hot air furnace) in order to optimize the properties of a material non-woven given. The determination of the dust value of a non-woven material is carried out as follows. Before the measurement is carried out, the non-woven samples to be tested are conditioned for at least 12 hours to ensure that all samples have been subjected to the same temperature and humidity conditions. Since, as described below, the results are often expressed as a relative value compared to a control, the exact temperature and the relative humidity for the conditioning of the samples is not critical, as long as all the samples that are going to be compared have been subjected to the same conditions. Ambient temperature and humidity conditions can therefore be used. Before conditioning, the non-woven materials are cut into individual samples with a size of 12 x. 30 cm After conditioning, a cardboard strip with a width of 5 mm is attached to the short sides of the sample, after which the sample with the cardboard strips attached is weighed to a laboratory scale with an accuracy of ± 0.1 mg . The non-woven sample to be tested is then fixed with two clips that are 12 cm long, each of which is mounted on an arm. The exposed area of the non-woven, fixed material is approximately 310 cm2, which is about the size of a piece of A4 paper. One of the arms is stationary, while the other arm is rotatable and is coupled to a spring. The test is performed by rotating the arm rotatable at 45 °, so that the non-woven sample goes from a 'stretched' condition to a 'relaxed' condition, after which the rotatable arm is released, whereby the action of the spring returns the rotatable arm to its original position. The movement of the arm is stopped by the non-woven sample, which is thus subject to a small vibration and a stretching effect designed to be similar to the conditions in which a non-woven roll is held when it is unwound in the converter , resulting in vibration and stretching a loss of loose fibers on the surface of the fiber. This action is repeated 50 times. The stretch force to which the sample is subjected must of course fall within the yield strength of the non-woven material, so that the non-woven material is not substantially deformed or damaged during the test. For the same reason, and taking into consideration that the tensile strength of different non-woven materials can vary considerably, the force provided by the spring must obviously be compatible with the non-woven material to be tested, so that the material Nonwoven is on the one hand returned to its original stretched position, and subject to a slight vibration and stretching, but on the other hand not excessively stretched as to become deformed or damaged. After being subjected to the vibration / stretch action 50 times, the sample is again weighed, and the difference between the two values is calculated and expressed as mg of powder. In this standardized powder test, the result in mg will often be no more than about 15 mg, typically not more than about 10 mg, preferably not more than about 5 mg, more preferably not more than about 4 mg, still more preferably not greater of about 3 mg, and most preferably not greater than about 2 mg. For nonwovens with a particularly good affinity between synthetic fibers and natural fibers, the result can be as low as about 1 mg of powder. An alternative and often a preferred way to define the powder reduction properties of a given fiber in the standardized powder test, is in terms of reducing the amount of powder (in mg) in a standard nonwoven material prepared from of the fibers of the invention, compared to a similar nonwoven material, prepared from similar fibers without the grafted polyolefin component. In this case, the nonwoven material prepared from the fibers of the invention should show a dust reduction of at least about 40% by weight compared to the nonwoven control prepared with the control fibers, typically at least about 50% in weigh. Preferably, the reduction of the powder is at least about 60%, more preferably at least about 70%, and still more preferably at least about 80%. For fibers with particularly good binding properties to cellulose, the dust reduction can be as much as about 90% or more. Since the powder properties of a given non-woven material can vary greatly depending on factors such as the nature of the bicomponent fibers and the nature of the cellulose or other fibers, as well as for example the formation of the particular network and the In the process of bonding, it will often be preferred to compare the performance of a given fiber in terms of its percentage of dust reduction compared to a similar control fiber, instead of in terms of an absolute value in mg. It is further contemplated that the fibers of the invention will also show improved binding and fixation not only of the cellulosic fibers but also of different superabsorbent polymers (SAP) that are commonly used in hygienic absorbent products in the form of particles or fibers. Such SAPs, for example, a salt of crosslinked polyacrylic acid, are typically used in the form of superabsorbent particles in the absorbent core for example of disposable diapers, since these are capable of absorbing many times their weight in liquid and form a gel that retains the liquid after moistening. Even if the fibers of the invention are not directly bound to the SAP particles, it is contemplated that the improved bonding or bonding of the fibers of the invention to the cellulosic fibers will result in an improved structure that by itself serves to ensure that the SAP particles are maintained at the desired site in the absorbent product, thereby improving the function of the SAP. The spinning of the fibers is preferably carried out using a conventional cast yarn (also known as "" long yarn "), with the spinning and stretching being carried out in two separate steps, Alternatively, other means of manufacturing chopped fibers, in particular 'compact yarn', which is a one-step operation, can be used to carry out the invention. Methods for spinning bicomponent fibers and bicomponent filaments are well known in the art. Such methods generally involve the extrusion of the melts to produce filaments, the cooling and stretching of the filaments, the treatment of the filaments with an appropriate spin finish to result in desired surface properties, for example, using a spin finish rotating to provide hydrophilic properties when the fibers are to be used in an absorbent core and / or to provide antistatic activities, stretching of the filaments, typically, treatment with a second spinning or spinning finish, texturing of the filaments, drying the filaments and cutting the filaments to result in chopped fibers. As indicated above, the air-laid non-woven materials of the present invention typically comprise, in addition to the bicomponent polyolefin fibers, at least one additional fibrous material, in particular natural fibers or regenerated fibers, for example, selected from cellulose fibers , viscose-rayon fibers and Lyocell fibers. The cellulose fibers can be, for example, pulp fibers or cotton fibers and are in particular pulp fibers such as CTMP (chemo-thermo-mechanical pulp), sulfite pulp or kraft paper pulp ( brown paper). The fibrous network comprising the bicomponent fibers and the additional fibrous material will typically comprise 5-50% by weight of the bicomponent fibers and 50-95% by weight of the additional fibrous material, more typically 10-40% by weight of the bicomponent fibers and 60-90% by weight of the additional fibrous material, for example 15-25% by weight of the bicomponent fibers and 75-85% by weight of the additional fibrous material.

EXAMPLES EXAMPLE 1 Tests were run with different bicomponent polyolefin fibers to evaluate their binding capacity to pulp fibers or cellulose pulp. The cellulose fibers were NB 416 from Weyerhauser. The weight ratio between the bicomponent fibers and the cellulose fibers was 25:75. The bicomponent fibers tested had the following composition, fiber No. 1 being according to the present invention: 1: Core: polypropylene; cover: 10% grafted LLDPE (5% maleic acid grafted on 95% LLDPE), 90% LLDPE. 2: Fiber control; core: polypropylene; Cover: 100% LLDPE.

AL-Special-C from Danaklon A / S; polypropylene core; HDPE cover. Hercules 449 by Hercules Inc., length 5 mm, fineness 1.5 dtex; polypropylene core / polyethylene cover.

The bicomponent fibers 1, 2 and 3 all had a fineness of 1.7 dtex, a length of 6 mm and a weight ratio between the core and the cover of 35:65. The fibers were run at a very low speed of 8.33 m / min. in an air smoothing apparatus (Dan-Web, Denmark), since the main purpose of these tests was to determine the ability of the fibers to bind to cellulose. During testing, an air-laid non-woven product having a basis weight of 80 g / m2 was prepared, and the tests were initiated at the lowest possible binding temperature, after which the temperature in the oven was increased in increments of 5 or 10 ° C.

Results: The dry resistance in the transverse direction (CD), the dry resistance in the machine direction (MD) and the MD wet strength were determined on the samples produced at different temperatures as indicated below (EDANA test method) No. 20.2-89, tested at a speed of 100 m / min.). In addition, the thickness and the basis weight (g / m2) of each sample was determined, and this information (not listed below) was used to adjust the resistance values to give co or result normalized values that are comparable despite the minor differences in thickness and in the basis weight of the individual samples tested. The results are shown below.

Sample No. Temperature Resistance Strength Resistance Jnión ° C MD N / 5 cm CD N / 5 cm MD, wet N / 5 cm 1 125 25.9 25.2 25.4 1 130 20.9 20.5 18.3 1 135 23.5 22.4 20.6 1 140 23.1 22.3 20.1 145 23.9 22.5 18. O 2 125 17.46 15.43 15.13 2 130 13.63 13.32 11.62 2 135 15.17 15.06 12.66 2 140 16.25 15.72 13.49 2 145 12.77 13.08 9.78 2 150 11.28 10.77 6.77 2 155 4.15 4.26 2.23 3 130 24.01 23.37 23.59 3 140 19.34 18.08 18.57 3 150 15.59 16.66 14.42 4 130 7.98 7.78 7.98 4 140 9.23 7.93 8.73 4 150 8.83 8.93 8.83 4 160 4.21 4.31 2.26 4 170 3.24 3.14 1.27 The results of the dust test were as follows (average of 2 tests, except for fiber No. 3, which is in the range of results obtained in a greater number of test runs with this fiber): Fiber Number Powder (mg) 1 1.7 2 7.4 3 12-30 4 14.0 Compared to the control fibers PP / PE, 2, 3 and 4, the fiber 1 according to the invention gave a significantly improved result in the dust test, reflecting the generation of powder greatly reduced, a significantly improved bonding of the bicomponent fibers of the invention to the fluff pulp fibers of cellulose. Observation of the samples by microscope also revealed the binding of the bicomponent fibers of the invention to the cellulose fibers. It was also found that fiber 1 gave a bulkier nonwoven compared to fibers 2 and 3 (fiber 4 was not compared in this respect). Furthermore, as shown by the strength values given in the above table, the fibers of the invention resulted in non-woven materials with improved strength and elongation characteristics.

EXAMPLE 2 A test was made of the ability of two different fibers to bind to cellulose, in a test on a commercial line of air straightening. Air-laid non-woven materials with a basis weight of approximately 80 g / m2 and a thickness of approximately 1 mm were produced. The non-woven materials contained 25% by weight of the bicomponent fibers and 75% by weight of cellulose pulp fibers. The bicomponent fibers tested had a fineness of 1.7 dtex and a length of 6 mm. In addition to fiber No. 3 (control) described * above, a bicomponent fiber (referred to as No. 5) was tested with the same cellulose binding additive as fiber No. 1, but with a polyethylene cover component high melting point (HDPE). This fiber thus had the following composition: : Core: polypropylene; cover: 10% grafted LLDPE (5% maleic acid grafted on 95% LLDPE), 90% HDPE.

The individual non-woven samples were bonded at different temperatures at 3 ° C intervals, in order to evaluate the optimal binding temperature for the individual fibers. It was found that the non-woven materials containing bicomponent fibers of the invention (fiber 5) resulted in improved binding of the cellulose fibers, as evidenced by a reduced generation of the powder during processing, as compared to fiber control (no quantitative measurements were made in this case). In addition, the fibers of the invention resulted in non-woven materials with improved strength characteristics as evidenced by the following test results: MD Traction Resistance, dry (N / 5 cm) Fiber Temperature Union ° C Control 137 13.96 15.08 140 15.77 19.01 143 12.56 19.40 146 15.41 EXAMPLE 3 The tests were performed to illustrate the influence of the variation in the amount of the additive (LLDPE grafted with maleic acid with an active content of 5%) in the cover component. The bicomponent fibers tested had all a fineness of 1.7 dtex and a length of 6 mm. The weight ratio of core / shell for fibers 6-9 was 35:65, and 50:50 for fiber No. 10. The core was in all cases of polypropylene. The non-woven materials were produced in a commercial line of laying or air-brushing using the technology of Dan-Web, Denmark, the non-woven materials had a basis weight of approximately 80 g / m2, a thickness of approximately 1 mm, and a weight ratio of bicomponent fibers to cellulose fibers of 25:75. The samples with each of the bicomponent fibers were tested at 3 different joining temperatures, 137, 140 and 143 ° C. The coating composition of the individual fibers were as follows: 6: 5% grafted LLDPE (grafted with 5% maleic acid over 95% LLDPE), 95% LLDPE. 7: LLDPE 5% grafted (grafted with 5% maleic acid over 95% LLDPE), 95% HDPE. 8: 10% of grafted LLDPE (grafted with 5% maleic acid on 95% LLDPE), 90% HDPE. 9: 12.5% of grafted LLDPE (grafted with 5% maleic acid on 95% LLDPE), 87.5% HDPE. 10: 13% of grafted LLDPE (grafted with 5% maleic acid on 95% LLDPE), 87% HDPE.

As a control, AL-Special-C from Danaklon A / S (polypropylene core, HDPE cover, No. 3 above) was used. The wet and dry tensile strength and gation of the various non-woven materials was also tested. As the following results show, the non-woven materials containing the fibers of the invention exhibited a dry and wet tensile strength, substantially improved compared to the control non-woven materials. In addition, some of the fibers of the invention, mainly numbers 6, 7 and 8, showed gation values above those of the control fibers, while fiber 10 and to a certain degree fiber 9 showed lower gation values than for the control fibers. Suboptimal results for fibers 9 and 10 in terms of gation are believed to be related to the fact that some difficulties were experienced in spinning these fibers with a relatively large amount of the grafted component in the shell. It is believed that with further testing and optimization of the spinning process and other process parameters, it will be possible to obtain improved results for these and other fibers with a relatively large content also of the grafted polyolefin component.

A visual evaluation of the powder properties of the non-woven materials indicated that all the bicomponent fibers tested of the invention had an improved binding to the cellulose fibers compared to the control bicomponent fibers. The fibers 7 and 8 ran particularly well on the production line, and as the previous results show, excellent strength values were also obtained for the non-woven materials containing these fibers. The results of the fibers of this example in the dust test were as follows (fiber 10 was not tested): Fiber Number Powder (mg) 6 6.6 7 14.9 5.8 6.7 Control 29.9 It can be concluded from the above that, good results were obtained with all levels of additive addition, although there seemed to be a tendency to improve results with additions of approximately 5-10%.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (22)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A nonwoven, laid or air-laid material comprising bicomponent fibers and at least one additional fibrous material, the bicomponent fibers comprise a low melting point polyolefin component and a high melting point polyolefin component, characterized in the material because the low melting point polyolefin component has a melting point of at least 4 ° C lower than the melting point of the high melting point polyolefin component, the low melting point polyolefin component constitutes at least a part of the surface of the fiber and comprises a non-grafted polyolefin component and a grafted polyolefin component, wherein the grafted polyolefin component has been grafted with an unsaturated dicarboxylic acid or an anhydride thereof.

2. A non-woven, dry laid or smoothed material according to claim 1, characterized in that the grafted polyolefin component of the bicomponent fibers has been grafted with a compound selected from: maleic acid, maleic anhydride, and derivatives thereof such as citraconic acid, citraconic anhydride and pyrichocinonic anhydride; fumaric acid and derivatives thereof; unsaturated malonic acid derivatives such as 3-buten-1, 1-dicarboxylic acid, benzylidenemalonic acid and isopropylidenemalonic acid; and unsaturated succinic acid derivatives such as itaconic acid and itaconic anhydride.

3. A non-woven, dry laid or smoothed material according to claim 2, characterized in that the grafted polyolefin component of the bicomponent fibers has been grafted with maleic acid or maleic anhydride.

4. A non-woven, dry laid or smoothed material according to any of the preceding claims, characterized in that the bicomponent fibers are sheath-core type fibers in which the low melting point polyolefin component forms the shell and the sheath component. High melting point polyolefin constitutes the core.

5. A non-woven, dry laid or flattened material according to any of the preceding claims, characterized in that at least one additional fibrous material is selected from natural fibers and regenerated fibers, for example, selected from cellulose fibers, viscose fibers and fibers of Lyocell.

6. A non-woven, dry laid or smoothed material according to claim 5, characterized in that the additional fibrous material comprises fluff pulp fibers of cellulose.

7. A non-woven, dry laid or smoothed material according to any of the preceding claims, characterized in that the high melting point polyolefin component comprises polypropylene and the low melting point polyolefin component comprises at least one polyolefin selected from LLDPE , HDPE and LDPE.

8. A non-woven, dry laid or smoothed material according to any of the preceding claims, characterized in that the difference in the melting points between the low melting point component and the high melting point component of the bicomponent fibers, is at least about 20 ° C.

9. A non-woven, dry laid or smoothed material according to any of claims 1 to 6, characterized in that the high melting point polyolefin component comprises a first polypropylene, and the low melting point polyolefin component comprises a second polypropylene or a polypropylene copolymer with a melting point at least 5 ° C lower than the first polypropylene.

10. A non-woven, dry laid or flattened material according to any of the preceding claims, characterized in that the fibrous web comprises 5-50% by weight of the bicomponent fibers and 50-95% by weight of the additional fibrous material, typically 10- 40% by weight of the bicomponent fibers and 60-90% by weight of the additional fibrous material, for example 15-25% by weight of the bicomponent fibers and 75-85% by weight of the additional fibrous material.

11. A method for producing a non-woven, laid or dry-laid material, characterized in that it comprises forming a fibrous web using straightening or dry-laying equipment of non-woven material, the network comprising bicomponent fibers and at least one additional fibrous material, the bicomponent fibers comprise a low melting point polyolefin component and a high melting point polyolefin component, wherein the low melting point polyolefin component has a melting point of at least 4 ° C lower than the of the high melting point polyolefin component, the low melting point polyolefin component forms at least a part of the surface of the fiber and comprises a non-grafted polyolefin component and a grafted polyolefin component, wherein the The grafted polyolefin component has been grafted with an unsaturated dicarboxylic acid or an anhydride thereof, and the attachment of the fibrous network to result in non-woven, stretched or dry-laid material.

12. A method according to claim 11, characterized in that the additional fibrous material is selected from natural fibers and regenerated fibers, for example selected from cellulose fibers, viscose fibers and Lyocell fibers.

13. A method according to claim 12, characterized in that the additional fibrous material comprises fluff pulp fibers of cellulose.

14. A method according to any of claims 11-13, characterized in that the grafted polyolefin component of the bicomponent fibers has been grafted with a compound selected from: maleic acid, maleic anhydride, and derivatives thereof such as citraconic acid, citraconic anhydride and pyrocinchonic anhydride; fumaric acid and derivatives thereof; unsaturated malonic acid derivatives such as 3-buten-1,1-dicarboxylic acid, benzylidene alonic acid and isopropylidenemalonic acid; and unsaturated succinic acid derivatives such as itaconic acid and itaconic anhydride.

15. A method according to claim 14, characterized in that the grafted polyolefin component of the bicomponent fibers has been grafted with maleic acid or maleic anhydride.

16. A method according to any of claims 11-15, characterized in that the bicomponent fibers are core-type fibers in which the low-melting polyolefin component constitutes the shell and the high-melting polyolefin component. it constitutes the nucleus.

17. A method according to any of claims 11-16, characterized in that the high melting point polyolefin component comprises polypropylene, and the low melting point polyolefin component comprises at least one polyolefin selected from LLDPE, HDPE and LDPE.

18. A method according to any of claims 11-17, characterized in that the difference in the melting points between the low melting point component and the high melting point component of the bicomponent fibers, is at least about 20 ° C.

19. A method according to any of claims 11-16, characterized in that the high melting point polyolefin component comprises a first polypropylene, and the low melting point polyolefin component comprises a second polypropylene or a polypropylene copolymer with a melting point at least 5 ° C lower than the first polypropylene.

20. A method according to any of claims 11-19, characterized in that the fibrous network comprises 5-50% by weight of the bicomponent fibers and 50-95% by weight of the additional fibrous material, typically 10-40% by weight of the fibers. bicomponent fibers and 60-90% by weight of the additional fibrous material, for example 15-25% by weight of the bicomponent fibers and 75-85% by weight of the additional fibrous material.

21. A bicomponent fiber for the production of non-woven, stretched or dry-laid materials, the fiber is characterized in that it comprises a low melting point polyolefin component and a high melting point polyolefin component, wherein the polyolefin component of low melting point has a melting point at least 4 ° C lower than the melting point of the high melting point polyolefin component, the low melting point polyolefin component constitutes at least a part of the surface of the fiber and comprises a non-grafted polyolefin component and a grafted polyolefin component, wherein the grafted polyolefin component has been grafted with an unsaturated dicarboxylic acid or an anhydride thereof.

22. A non-woven, dry laid or flat material comprising bicomponent synthetic fibers and a natural or regenerated fibrous material, for example, cellulose pulp fibers, the bicomponent fibers comprise a low melting point polyolefin component and a low-melting component. high melting point polyolefin, characterized in that the low melting point polyolefin component has a melting point at least 4 ° C lower than the melting point of the high melting point polyolefin component, the low polyolefin component melting point constitutes at least a part of the surface of the bicomponent fibers, the bicomponent fibers have a binding affinity to natural or regenerated fibers such that the nonwoven material shows a dust value in the standardized dust test described in present, not greater than about 10 mg, preferably not greater than about 5 mg, more preferably not greater than about 4 mg, most preferably not more than 3 mg, and most preferably not more than about 2 mg.