HK1258258A1

HK1258258A1 - Patterned nonwoven material

Info

Publication number: HK1258258A1
Application number: HK19100622.5A
Authority: HK
Inventors: M‧斯特兰德奎斯特; M‧斯特蘭德奎斯特
Original assignee: 易希提卫生与保健公司; 易希提衛生與保健公司
Priority date: 2015-12-08
Filing date: 2015-12-08
Publication date: 2019-11-08
Also published as: CA3007309C; RU2018123573A; WO2017097341A1; MX2018006886A; AU2015416530B2; RU2717928C2; CA3007309A1; ES2829877T3; EP3387172B1; RU2018123573A3; MX385709B; DK3387172T3; ZA201804533B; US20180363177A1; PL3387172T3; CO2018005840A2; CN108291343A; AU2015416530A1; EP3387172A1

Abstract

A patterned hydroentangled nonwoven sheet material contains at least 25 wt. % of cellulosic pulp, in which a surface area of between 1 and 20% of at least one surface has been imprinted to form a decorative or informative pattern discernible by at least one of visual or tactile differences between imprinted and non-imprinted areas. The patterned nonwoven sheet material can be produced by forming a fibrous web including thermoplastic fibres and cellulosic pulp, hydroentangling the fibrous web to form a nonwoven sheet material and drying, and then subjecting the dried nonwoven sheet material to an imprinting action provided by an energy transmitter, in particular using ultrasonic energy, on a patterned anvil at a temperature of less than 100° C. to form a patterned nonwoven sheet material.

Description

Patterned nonwovens

Technical Field

The present invention relates to a nonwoven sheet material provided with a visually non-random pattern and to a method for manufacturing such a patterned nonwoven sheet material.

Background

Absorbent nonwoven materials are used to wipe various types of spills and soils in industrial, medical, office, and household applications. They generally comprise a combination of thermoplastic polymers (synthetic fibers) and cellulose pulp for absorbing water and other hydrophilic substances as well as hydrophobic substances (oils, fats). This type of nonwoven wipe, in addition to having sufficient absorbent capacity, is also strong, flexible and soft. They can be made by a variety of methods including air-laying, wet-laying and foam-laying a mixture containing pulp on a polymer web, followed by dewatering and hydroentanglement to anchor the pulp to the polymer and finally drying. Absorbent nonwoven materials of this type and methods for their manufacture are disclosed, for example, in WO 2005/042819, WO2007/108725, WO 2008/066417 and WO 2009/031951.

For various applications, it is desirable to have visible patterns, such as graphics, logos, text, etc., on the nonwoven material so as to make them recognizable, for indicating their intended use, for promotional purposes, etc. The pattern can be applied by printing; however, printing often results in ink penetrating into the nonwoven outside the pattern, which is clearly undesirable, for example when a wipe or the like is used with a solvent during use (wiping) of the wipe.

WO 95/09261 discloses a nonwoven material having a geometrically repeating pattern formed by bonded and unbonded areas on the material. The binding region occupies 3 to 50%, in particular 5 to 35%, of the surface area of the material. There are bonded areas on the order of 8-120 per square centimeter, for example 34 bonded areas per square centimeter and each unbonded area has less than 0.3cm²The area of (a). The nonwoven material is a three layer laminate having an outer spunbond thermoplastic layer and an inner meltblown fiber layer. The laminate is patterned by calendering using heated embossing rolls. The disadvantage of these materials is that the pattern is associated with the bonding of the thermoplastic and, as a result, the pattern can only be small and at the same time must occupy a relatively large area of the nonwoven surface. This is particularly disadvantageous for absorbent nonwoven materials containing cellulose pulp or the like, wherein the bonding reduces the absorption capacity and thus thermal bonding is avoided.

It is an object of the present invention to provide a patterned nonwoven sheet material wherein the patterning does not entail the disadvantages of the prior art, such as bleeding of the printed pattern, insufficient definition of the pattern produced by hydroentanglement or a reduction in the stiffness and strength or absorption capacity of the embossing technique.

Disclosure of Invention

The present invention thus provides a preferably hydroentangled absorbent nonwoven material having a non-random, clear and visibly distinct decorative or identifying pattern on its surface. The visible pattern does not substantially reduce the absorbent capacity of the material and also ensures the retention of other product properties including softness, abrasion resistance, strength, etc. The two sides of the material may have different compositions: the lower side may have a relatively high pulp content and the upper side on which the pattern is provided may have a relatively low pulp content, or vice versa.

It is also an object of the present invention to provide a method for producing a patterned pulp-containing nonwoven, comprising subjecting the nonwoven to an embossing step, in particular a vibration embossing step, which avoids high temperatures.

Drawings

Fig. 1 illustrates a production line for manufacturing sheet material of the present disclosure.

Fig. 2 shows a patterned nonwoven according to the present disclosure.

Detailed Description

The present invention relates to a patterned hydroentangled nonwoven sheet material as defined in the appended claim 1. The present invention also relates to a method of manufacturing a patterned nonwoven sheet material as defined in the appended claim 11.

When referring to the side of the sheet material herein, this means the effective surface of the sheet, i.e., the front and back sides (also interchangeably referred to as upper and lower surfaces) of the sheet material. Where weight ratios or percentages are mentioned herein, these are on a dry matter basis (without any water or more volatile material) unless otherwise indicated. When referring to the weight or percentage of water herein, these are based on wet matter.

The patterned hydroentangled nonwoven sheet material contains cellulose fibers, preferably at least 25 wt.%, more preferably at least 40 wt.%, even more preferably at least 50 wt.%, preferably at most 80 wt.%, most preferably between 60 and 75 wt.% cellulose fibers. Cellulose fibers are further defined below and include cellulose pulp.

Further, the sheet material preferably contains thermoplastic fibers, preferably at least 10 wt.%, more preferably at least 15 wt.%, even more preferably at least 20 wt.%, most preferably at least 25 wt.%, up to e.g. 70 wt.%, preferably up to 60 wt.%, more preferably up to 50 wt.%, most preferably up to 40 wt.%. Thermoplastic fibers, also known as (synthetic or synthetic) polymer fibers, can include (continuous) filaments and (short) staple fibers or both. The sheet material (assembled web) may preferably contain between 6 and 60 wt.%, more preferably between 10 and 45 wt.%, most preferably between 15 and 35 wt.% of synthetic filaments, based on the dry solids of the assembled web. Alternatively or additionally, the sheet material may preferably contain between 3 and 50 wt.%, more preferably between 4 and 30 wt.%, most preferably between 5 and 20 wt.% of synthetic staple fibres, based on the dry solids of the assembled web. In a preferred embodiment, the sheet material contains both thermoplastic filaments and staple fibers, for example in a weight ratio of between 9:1 and 1:1, preferably between 5:1 and 1.5: 1. Thermoplastic fibers are further defined and set forth below.

In the present patterned sheet material, 1% to 20% of at least one surface has been embossed and forms a pattern discernible by visual and/or tactile means, for example by differences in reflection, brightness, smoothness, etc. between embossed and non-embossed portions, which can be perceived by sight or touch and feel. These differences are in particular differences in height.

As used herein, embossing is understood to refer to the execution of mechanical forces that result in some compression of the sheet material, as further defined and set forth below. Thus, the pattern is not discernible solely by differences in color (e.g., caused by printing, dyeing, or inking) or other differences in material composition. In a preferred embodiment, the pattern is substantially only obtained by embossing. In particular, the embossed portion of the sheet material has a thickness of between 75% and 95% of the thickness of the non-embossed portion. Thus, the stamping action results in a thickness reduction of 5-25%.

The pattern can be present on either side of the sheet material or on both sides simultaneously. In a preferred embodiment, for ease of reference, patterning (i.e., height differences) is present on only one side, which is referred to as the "front side" or "pattern side". The front side can have the same or a different material composition than the back side. The sheet material can have a largely uniform composition over its thickness. Alternatively and preferably, the sheet material may have a gradually varying composition over its thickness, while both surfaces (front and back) have substantially the same composition (in which case the inner region has a different composition) or different compositions. In a particular embodiment, the sheet material is a layered sheet having two, three or more layers of different composition, wherein, however, there is no clear transition between adjacent layers, particularly as a result of hydroentanglement. For example, the sheet can be a two-ply sheet having an opposite high pulp layer on one side and an opposite low pulp layer on the other side. The sheet can also be a three-ply sheet having adjacent high pulp, low pulp and high pulp plies. Further variants are equally possible.

In one particular embodiment, the sheet material has a high pulp (front side) surface and an opposite low pulp (back side) surface with optional additional layers therebetween, or forms a two-ply sheet without such an intermediate layer. The high pulp surface may contain at least 60 wt.% pulp fibers and the low pulp surface may contain less than 50 wt.% pulp fibers. Such percentages apply to the outermost regions, e.g., the outermost 5% of the sheet thickness. Alternatively, the high pulp surface may contain less than 30 wt.%, preferably less than 15 wt.% thermoplastic fibers and the low pulp surface may contain at least 30 wt.%, preferably greater than 50 wt.% thermoplastic fibers.

The thickness of the present sheet material may vary widely depending on the intended use. As an example, the sheet may have a thickness (non-embossed portion) of between 100 and 2000 μm, in particular 250-1500 μm, preferably 400-1000 μm, more preferably 500-800 μm. The thickness can be measured by methods as further described in the accompanying examples. The difference in height between the embossed (pattern) and the non-embossed portions is typically 50-250 μm, preferably 75-150 μm. The height difference can be measured by methods known in the art, for example by laser reflection measurement or by white light interferometry.

The pattern can have any form or design. They can be purely decorative or they can have information or identification functions or both and are clearly visible to the user or observer. They can include graphics (e.g., lines, circles, etc.) as well as pictures, readable characters (letters, numbers), etc. As a suitable example, a portion of the embossed layer area may form a readable character and/or logo. As an even more specific example, 2% to 15% of the stamping surface forms readable characters and/or logos and 0.5% to 3% of the stamping surface forms other patterns than readable characters or logos, in particular geometric patterns such as straight lines or curves, the percentage being based on the total surface area of the stamping surface.

For reasons of maximum absorption capacity, it is preferred that at least 10% of the total surface area of the stamping side (or sides) of the sheet material is comprised of uninterrupted at least 20cm²Preferably at least 25cm²Is formed by the non-embossed areas of (a). More preferably, at least 20%, most preferably at least 30% of the total surface area of the embossed side is constituted by such uninterrupted non-embossed areas. Such uninterrupted non-embossed regions may have any form, such as rectangular, polyhedral, circular, but also more irregular forms.

The patterned nonwoven sheet may be of any desired degree of softness, strength, and any size, and it may be colorless (white) or colored, where the color may be applied before or after the embossing step. The pattern is stable and resistant to temperature, humidity, UV/vis radiation, etc., and does not bleed.

The sheet material has excellent absorption properties for both hydrophilic and hydrophobic substances, which are not degraded by a pattern. In particular, the water absorption capacity of the final sheet material is at least 5g water per g dry sheet material, preferably at least 6g/g (with reference to distilled water at 23 ℃).

The method for manufacturing a patterned nonwoven sheet material as described above preferably comprises the steps of:

-forming a fibrous web comprising thermoplastic fibres and cellulose pulp;

-hydroentangling the fibrous web to form a nonwoven sheet material,

-drying the nonwoven sheet material to a water content of less than 10 wt.%, preferably less than 5 wt.%, down to 0.1 wt.%; and is characterized in that:

-subjecting the dried nonwoven sheet material to an embossing action provided by an energy emitter on a patterned anvil roll at a temperature of less than 100 ℃, preferably less than 60 ℃, most preferably between 30 and 50 ℃ to form a patterned nonwoven sheet material.

The energy used for imprinting is based in particular on vibration energy rather than direct impact or heat. It is therefore important that the embossing effect does not involve embossing or thermal bonding of the thermoplastic fibers to a significant extent. Embossing (with a suitably heated roller) has been found to result in a less sharp pattern and thermal bonding (which means melting of the thermoplastic) reduces the absorption capacity of the resulting sheet material.

One very useful type of vibrational (oscillatory) energy is ultrasonic energy. Ultrasound devices suitable for use in the present method are well known in the art. As an example, ultrasound equipment can be purchased, for example, from herrmannultrashall, Karlsbad, DE, or from Branson Ultrasonics, Danbury CT, USA or Dietzenbach, DE. In a preferred embodiment, the embossing action is a rotary action using a patterned anvil roll that conveys the sheet material to be embossed, as shown in fig. 1. The oscillation frequency is preferably in the higher acoustic range or more preferably in the lower ultrasonic range, for example between 15 and 100kHz, in particular between 18 and 30 kHz. The oscillation power is preferably in the range of 200-4000N, more preferably in the range of 500-2500N. The oscillation amplitude will typically be in the range of 10-100 μm.

The distance between the energy emitter (which is sometimes referred to as an ultrasonic generator in an ultrasonic apparatus) and the anvil roll is preferably short and can vary during operation. Thus, the gap between the energy emitter and the protruding portion of the anvil roll has a maximum value approximately equal to or greater than the thickness of the material to be processed and a minimum value slightly less than the thickness of the material to be processed (the imprinting stage). Thus, the gap is preferably at least 500 μm, more preferably between 600 and 2000 μm, most preferably between 800 and 1500 μm. The gap is preferably adjustable to allow for the replacement and handling of sheets of different thicknesses.

The present products and methods will now be described in more detail with reference to various embodiments and the accompanying drawings. In particular, further details of various process steps and materials to be applied in the formation of the patterned hydroentangled nonwoven sheet material are described below.

Detailed description of the examples and materials and methods to be used

Natural fiber

Many types of natural fibers can be used, particularly those that have water-absorbing capabilities and tend to help create a coherent sheet. Among the suitable natural fibers are predominantly cellulosic fibers, such as seed hair fibers (e.g., cotton, flax, and pulp). Wood pulp fibers are particularly suitable, and both softwood and hardwood fibers are suitable, and recycled fibers can also be used. Pulp fiber lengths can vary from about 3mm for softwood fibers to about 1.2mm for hardwood fibers and mixtures of these lengths, and even shorter for recycled fibers.

Filament yarn

A filament is a very long, theoretically infinite length of fiber that is proportional to its diameter during its manufacture. They can be manufactured by melting and extruding thermoplastic polymers through fine nozzles, followed by cooling (preferably using an air stream) and curing into a strand that can be drawn, stretched or crimped. Spunbond filaments are made in a similar manner by drawing the filaments using air to provide suitable fiber diameters of typically greater than 10 μm, typically 10-100 μm. The manufacture of spunbond filaments is described, for example, in U.S. patents 4,813,864 and 5,545,371. Chemicals for additional functions can be added to the surface of the filaments.

Spunbond and meltblown filaments as a group are referred to as spunlaid filaments, meaning that they are deposited directly in situ on a moving surface to form a downstream bonded web. Control of the "melt flow index" through selection of the polymer and temperature profile is a critical part of controlling extrusion and thus filament formation. Spunbond filaments are generally stiffer and more uniform. The filaments are laid longitudinally.

In theory, any thermoplastic polymer having sufficient consistency to allow cutting in the molten state can be used to make spunbond fibers. Examples of useful synthetic polymers are polyolefins (e.g., polyethylene and polypropylene), polyamides (e.g., nylon-6), polyesters (e.g., polyethylene terephthalate), and polylactides. Copolymers and mixtures of these polymers and natural polymers with thermoplastic properties can of course also be used.

Staple fibers

Staple fibers can be made from the same materials and by the same methods as the filaments described above. Other useful staple fibers are those made from regenerated cellulose (e.g., viscose and lyocell). They can be treated with spin finishes and crimped, but this is not necessary for the type of process that is preferred for making the present nonwoven sheet material.

The cutting of the fibre bundle is usually carried out to obtain a single cut length which can be varied by varying the distance between the knives of the cutting wheel. Different fiber lengths between 2 and 50mm are used depending on the intended use. Wet laid hydroentangled nonwovens typically use fiber lengths of 12-18mm, or as low as 9mm or less, particularly hydroentangled materials made by wet laid techniques. The strength of the material and its other properties such as surface abrasion resistance increase with increasing fiber length (same thickness and polymer for fiber). When continuous filaments are used with staple fibers and pulp, the strength of the material will be primarily from the filaments.

Shorter staple fibers enable improved materials because they have more fiber ends per gram of fiber and are more prone to movement in the Z direction (perpendicular to the plane of the web). More fibre ends will protrude from the surface of the web, thereby enhancing the textile feel. A strong bond will result in very good wear resistance. Staple fibers can be a mixture of fibers based on different polymers, having different lengths and dtex, and having different colors.

Method of producing a composite material

The pulp-containing sheet material can be formed of a material that can be applied by various techniques known in the art, including wet-laid, air-laid, dry-laid or spun-laid or it can be formed wholly or partially from a pre-formed sheet (e.g., a tissue sheet). As an example, a method for making the patterned nonwoven sheet material of the present disclosure can be as depicted in fig. 1. This method comprises the steps of: providing an endless forming fabric 1, onto which forming fabric 1 the continuous filaments 2 can be laid, for example as spunbond filaments, and through which excess air can be drawn to form a precursor of the web 3; advancing the forming fabric 1 with continuous filaments to a wet-laying stage and a so-called headbox 4, where an aqueous slurry or foam comprising a mixture 5 of natural fibers and staple fibers is wet-laid on a precursor web 3 of continuous filaments 2 and partly into the precursor web 3 of continuous filaments 2, and excess water is drained through the forming fabric 1, forming a fibrous web 6; the fibrous web 6 is advanced from the fabric 1 to a second fabric 7 to subject the fiber mixture to a hydroentanglement stage 8 where the filaments 2 and fibers are intimately mixed and bonded by the action of the water jets 10 into a nonwoven web 9. The web is then advanced to a drying stage 11 where the nonwoven web 9 is dried; and further advanced to a stage for embossing between anvil roll 20 and anvil head 21, as will be further described below, and subsequently for rolling, cutting, wrapping, etc. (stage 30).

The continuous filaments 2, which can be made of extruded thermoplastic pellets, can be laid directly onto the forming fabric 1, where they are allowed to form an unbonded web structure 3, wherein the filaments can move relatively freely to each other. This can be achieved by making the distance between the nozzle and the forming fabric 1 relatively large, so that the filaments are allowed to cool and thus have a reduced viscosity before they fall on the forming fabric. Alternatively, the cooling of the filaments before their laying onto the forming fabric can be effected, for example, by air. Air for cooling, drawing and stretching the filaments is drawn through the forming fabric so that the filaments follow the air into the mesh of the forming fabric to stay there. Drawing air may require a good vacuum environment. Alternatively, the filaments can be cooled by water jets.

The speed at which the filaments are laid down on the forming fabric may be higher than the speed of the forming fabric, so that irregular loops and bends can be formed as the filaments collect on the forming fabric to form a randomized precursor web. The basis weight of the formed filament precursor web 3 can advantageously be between 2 and 50g/m²In the meantime.

As described above, the mixture 5 of natural fibers and staple fibers can be wet-laid onto and partially into the precursor web 3 of spunlaid filaments to form the fibrous web 6. However, as mentioned above, such a fibrous web 6 can also be formed of materials to which various other techniques known in the art are applied.

It should also be emphasized that while the method of forming a patterned hydroentangled nonwoven sheet material as shown in fig. 1 is described primarily with reference to the use of filaments, the present disclosure of forming a patterned sheet material may also include materials formed solely from pulp and thermoplastic fibers (e.g., staple fibers) that are not filaments. Such sheet material may be formed, for example, by laying a mixture 5 of pulp and staple fibers directly onto the forming web 1, removing the water, and then hydroentangling, drying and embossing the forming web. Further alternatives are described below.

Some techniques that can be used in the laying of pulp and staple fibers and in the formation of precursor webs are described in more detail below. The method will be further elucidated with reference to fig. 1 with regard to the method stages of the hydroentanglement and embossing stages and any further processing that may occur to form a product as exemplified in fig. 2.

Wet-laid web

The mixture 5 of pulp and staple fibers (if used) can be pulped in a conventional manner, whether mixed together or pulped separately and then mixed, and conventional papermaking additives, such as wet and/or dry strength agents, retention aids, dispersants, can be added to produce a slurry of well-mixed pulp and staple fibers in water. As shown in fig. 1, the mixture 5 can be pumped through a wet-laid headbox 4 onto a moving forming fabric 1, on which forming fabric 1 the mixture 5 is laid with its freely moving filaments onto an unbonded precursor filament web 3.

Some pulp and staple fibers will enter between the filaments, but a larger part will remain on top of the web. Excess water is sucked through the web of filaments and down through the forming fabric by means of suction boxes arranged under the forming fabric.

One particularly advantageous method of depositing the short fibers (pulp and/or staple fibers) is by foam formation, which is a wet laid variant, wherein cellulose pulp and staple fibers are mixed with water and air, preferably between 0.01 and 0.1 wt.% of a non-ionic surfactant in the presence of a surfactant to form a pulp containing mixture 5. The froth may contain between 10 and 90 vol.%, preferably between 15 and 50 vol.%, most preferably between 20 and 40 vol.% air (or other inert gas). The foam is conveyed to a headbox 4 where it is laid down on top of the filament web 3 and excess water and air are drawn off.

Air-laid and dry-laid

Instead of, for example, wet-laying, the fibers can be applied by dry-laying (in which the fibers are carded and then applied directly to a support) or air-laying (in which the fibers, which may be staple fibers, are supplied into an air stream and applied to form a randomly oriented web).

Hydroentanglement

A fibrous web 6 of synthetic fibers, such as continuous filaments, and staple fibers and pulp is hydroentangled while it is supported by a fabric 7 and intimately mixed and integrated into a composite nonwoven 9. One indicative description of the hydroentangling process is given in CA patent No. 841,938.

In the hydroentangling stage 8, the different fiber types will be entangled by the action of a plurality of fine jets 10 of high pressure water impinging on the fibers. The finely moving spunlaid filaments are entangled and intertwined with themselves and with other fibers, which gives the fibers very high strength, wherein all fiber types are intimately mixed and integrated. The entangling water is drained through the forming fabric 7 and can be recycled after cleaning (not shown) if desired. The energy supply required for hydroentanglement is relatively low, i.e. the material is easy to entangle. The energy supply for the hydroentanglement can suitably be in the interval 50-500 kWh/ton.

The strength of the hydroentangled material will depend on the number of entanglement points and thus on the length of the fibres, especially when the hydroentangled material is based on staple fibres and pulp fibres only. When filaments are used, the strength will be determined primarily by the filaments and is reached quickly in the entangling. Thus, a large portion of the entanglement energy will be spent on mixing filaments and fibers to achieve good integration.

As shown in fig. 1, the method can include hydroentangling a fibrous web 6 containing a precursor filament web 3 on which filament web 3 a mixture of staple fibers and pulp fibers has been wet laid or the like. Before the pulp-containing mixture 5 (with or without staple fibres) is laid down by the headbox 4, the precursor filament web 3 may be subjected to a pre-bonding stage, or may even be supplied as a pre-bonded web that can be treated as a normal web by a rolling and unrolling operation, even if it does not yet have its final strength for use as a wiping material (not shown). The pulp fibres in 5 can be mixed and entangled rather easily and also adhere in such a filament web and/or longer staple fibres. However, polymeric staple fibers that may be present in 5 may be more difficult to entangle and force down into the pre-bonded web, and it is often necessary to use longer staple fibers (e.g., 12-18mm) to obtain sufficient entanglement bonding points to securely capture the polymeric fibers in the web.

Prior to the laying-up of the pulp-containing mixture 5, the precursor filament web 3 may preferably be substantially unbonded, i.e. extensive bonding (e.g. thermal bonding) of the precursor filament web 3 should not occur before the pulp-containing mixture 5 (with or without staple fibers) is deposited by the headbox 4. During entanglement, the filaments should preferably move relatively to a large extent freely with respect to each other to the staple fibres and pulp fibres to mix and rotate into the filament web.

At this point in the process the thermal bonds between the filaments in the web will act as a blockage preventing staple and pulp fibres from entering the web in the vicinity of these bonds, as they will keep the filaments immovable in the vicinity of the thermal bonds. The "screening effect" of the web will be enhanced and will result in a more bi-faceted material. By "non-thermally bonded" is meant that the filaments are not exposed to excessive heat and pressure, such as between heated rollers that compress some of the filaments to such an extent that they will soften and/or melt together to deform at the point of contact. Some bonding points may be caused by residual tackiness at the moment of laying, in particular for meltblown fibers, but these bonding points will not deform at the contact points and therefore have no significant negative effect on the properties of the material.

Thus, the method as described herein and as shown in fig. 1 may result in a high flexibility of the unbonded filament web to facilitate the entrainment of the polymeric staple fibers and thus allow the use of shorter fibers. The fibres can be in the range of 2 to 8mm, preferably 3 to 7mm, but longer staple fibres can also be used.

The entangling stage 8 can comprise several transverse bars with rows of nozzles from which very fine water jets 10 under very high pressure are directed at the fibrous web to provide entanglement of the fibers. The water jet pressure can then be adjusted to a specific pressure profile with different pressures in different rows of nozzles.

Alternatively, the fibrous web can be transferred to a second entangling fabric prior to hydroentanglement. In this case, the web can also be hydroentangled and dried, etc. before being conveyed, by means of a first hydroentangling station having one or more bars with rows of nozzles. The hydroentangled wet web 9 is then dried, which can be done using conventional web drying equipment, preferably of the type used for tissue paper drying, such as through-air drying or yankee drying.

The structure of the material can be altered by further processing (e.g., micro-creping), etc. It is also possible to add different additives to the material, for example wet strength agents, adhesive chemicals, latexes, release agents, etc. to the nonwoven material. A composite patterned nonwoven fabric according to the present invention can be made to have a thickness of 20-120g/m²Preferably 50 to 80g/m²Total basis weight of (c).

Imprint method

A method and apparatus for embossing a nonwoven is shown in fig. 1. The wet-laid or foam-laid hydroentangled green sheet material 9 is dried in a dryer 11 and then transported on an anvil roll 20 along a guide roll 22 to produce an impression sheet material 23. The ultrasonic anvil roll 20 is actuated by a drive gear 24, which rotates clockwise in this view. Energy is applied by anvil 21 provided with an ultrasonic generator 25 and an oscillation booster 26.

The anvil roll 20 is of suitable dimensions to allow the continuous sheet to move at a significant speed of, for example, 2-10m/s, preferably 3-6m/s (180-360 m/min). The anvil roll may have a diameter of e.g. 50-200cm and a width (height of the cylinder) between 1 and 3 m. The rotation speed is controllable and for an anvil roll with a diameter of 1m the rotation speed (in radians per second) will be the same as the speed of the passing sheet, i.e. the tangential speed of the rotating roll corresponds to e.g. 25-60 revolutions per minute (rpm). It is important to ensure that the rotation speed is finely adjusted to the conveyance speed of the sheet material so that the sheet material does not move relative to the anvil roll 20 while being in contact with the anvil roll 20, thereby avoiding damage to the sheet material.

The environmental conditions can be suitably applied during sonication. The temperature of the sheet at the location of the embossing is preferably less than 100 c, more preferably less than 60 c, most preferably between 30 and 50 c. Further operating conditions of the ultrasound device can be as described above.

Further method

The structure of the material can be altered by further processing (e.g., micro-creping, etc.) before or after embossing. It is also possible to add different additives to the material, for example wet strength agents, adhesive chemicals, latexes, release agents, etc. to the nonwoven material. After the embossing step, the material can be wound into a parent roll. The material can then be converted to the appropriate format and packaged in known manner. A composite patterned nonwoven fabric according to the present invention can be made to have a thickness of 20-120g/m²Preferably 40 to 80g/m²Total basis weight of (c).

Fig. 2 illustrates an example of one patterned sheet 27 of the present disclosure. The depicted square 28 (half of which has an internal imprint 29 and the other half is empty) has a cell size of about 70 x 70 mm. It has a relative non-embossed surface area of about 85% of the total area and up to 40cm²Without interruption of the non-embossed area.

Examples of the invention

Test method-basis weight

Basis weight (grammage) can be set forth by following the following criteria for determining basis weightThe test method of principle(s) determines: WSP 130.1.R4(12) (standard test method for mass per unit area). A test piece of 100X 100mm was punched out of the sample sheet. The test piece is randomly selected from the entire sample and should be free of folds, wrinkles and any other deviating deformations. The test pieces were conditioned at 23 ℃ and 50% RH (relative humidity) for at least 4 hours. A stack of 10 test pieces was weighed on a calibrated balance. Basis weight (gram weight) is the weight weighed divided by the total area (0.1 m)²) And recorded as the average with standard deviation.

Test method-thickness

The thickness of the sheet material described herein can be determined by a test method following the principles of the standard test method for nonwoven thickness according to EDANA, wsp120.6.r4 (12). A device according to this standard is available from IM TEKNIKAB, Sweden, with a micrometer (model ID U-1025) available from Mitutoyo Corp, Japan. The sheets of the material to be measured are cut into 200X 200mm test pieces and conditioned (23 ℃, 50% RH ≧ 4 hours). During the measurement, the sheet material is placed under the presser foot and then lowered. The thickness value of the sheet is then read after the pressure value has stabilized. The measurement is done by a precision micrometer, in which the distance between a fixed reference plate produced by the sample and the parallel presser foot is measured.

The measuring area of the presser foot is 5 x 5 cm. The pressure applied during the measurement was 0.5 kPa. Five measurements were performed on different areas of the sliced test piece to determine the thickness as an average of the five measurements.

Test method-Water absorption

The amount of water that can be retained per g wipe in g is determined as follows:

five 100X 100mm square test specimens were cured at 80 ℃ for 30 minutes and conditioned at 23 ℃ at 50% RH for at least 4 hours. Each adjusted sample was weighed with an accuracy of 0.01g and placed in a sample holder that held the sample at three sample corners so that the sample hung in a straight vertical position with the free corner pointing down. The suspended sample was lowered into deionized water (23 °) in a flat-bottom bowl and allowed to soak in deionized water during 60 seconds. The sample was then removed from the water and allowed to hang in its straight vertical orientation in the holder with the freely hanging corner pointing down to drip water for 120 seconds, and then weighed. The Water Absorption (WA) is calculated from the formula WA ═ m/Md, where Md is the weight before soaking (drying) and Mw is the weight after soaking and dripping, and is expressed in g/g. The average water absorption values of five samples were recorded.

Test method-wiping Capacity

The amount of fluid that can be wiped off by the wipe (in percent of a given amount) is determined as follows:

round test pieces of 190mm diameter, cured at 80 ℃ for 30 minutes and conditioned at 23 ℃, 50% RH for at least 4 hours were weighed and then a number of test pieces having a weight as close as possible to 3.6g together were placed in layers aligned on top of each other to form a wipe sample. The wiped sample was placed flat in the center of a circular plastic wiped surface of a circular sample holder of plastic foam (Bulpren R60 from Recticcel), both the surface and the sample holder having a diameter of 113 mm. Excess sample material is folded around the side edges of the sample holder and attached thereto. Water (10 g per 3.6g sample) was spread into a bundle having a length of 200mm on a steel plate of 500X 1200 mm. The sample holder was attached to a robot programmed to perform six linear wipes on the steel surface for each sample and one applied water jet, with the circular plastic wipe surface of the holder carrying the wiped sample subjected to a pressure of 200g on the steel surface. The robot and control unit can be obtained from Thermo CRS. For each wipe, the robot wiped the steel surface with a wipe sample in a linear direction along and aligned with the water jet at a speed of 80cm/s, with each linear wiping action being 400mm in length and starting 100mm in front of the wipe contacting one end of the water jet before the first wipe and terminating 100mm from the other end of the water jet present before the first wipe. The wiped samples were weighed after each wipe. The water uptake for each wiping action and sample was calculated as a percentage of the amount applied on the plate (10 g per 3.6g of sample). The above procedure was repeated for each of the six samples and the average water amount per wiping action was calculated. In case the test material has two different sides, three samples are placed with the respective sides facing the sample holder and three samples are placed with the opposite sides facing the sample holder (as is the case in the example below).

Example 1

A nonwoven absorbent sheet material was produced as shown in fig. 1 (items 1-11) by the following method: a web of polypropylene filaments was laid on a running transfer fabric and then a pulp dispersion containing 88:12 weight proportions of wood pulp and polyester staple fibers and 0.01-0.1 wt.% of a nonionic surfactant (ethoxylated fatty alcohol) was applied to the polymer web by a foam forming process in a headbox, introducing a total of about 30 vol.% air (based on total foam volume). The weight proportion of polypropylene filaments was 25 wt.%, based on the dry solids of the final product. These amounts are selected so as to achieve a final product basis weight of 80g/m². The combined fibrous web is then subjected to hydroentanglement using a plurality of water jets at an increased pressure of 40-100bar, which increased pressure of 40-100bar provides a total energy supply of about 180kWh/t at the hydroentanglement step, as measured and calculated as described in CA 841938, pages 11-12, and subsequently dried.

The hydroentangled and dried sheet was then embossed in an ultrasonic device as depicted in fig. 1 (items 21-26). The anvil roll has a raised portion of about 15% of the surface area forming lines and text patterns. The embossed sheet had a pattern as depicted in fig. 2.

Reference example

The same nonwoven as in example 1 was made, but it was not embossed.

Results

The nonwovens of example 1 and the reference example were analyzed and tested according to the test methods above. The results are presented in the table below.

Table: test results for reference product (non-embossed) and embossed product

The test results show that the embossed nonwoven (example 1) has at least the same properties as the non-embossed nonwoven (reference example).

Claims

1. A patterned hydroentangled nonwoven sheet material containing at least 25 wt.% of cellulose pulp, wherein between 1% and 20% of the surface area of at least one surface has been embossed to form a pattern discernible by visual and/or tactile differences between embossed and non-embossed areas.

2. The sheet material of claim 1, wherein the visual and/or tactile differences comprise height differences between embossed and non-embossed portions.

3. Sheet material according to claim 1 or 2, containing 40-80 wt.%, preferably 50-75 wt.% pulp fibers and 15-60 wt.%, preferably 25-50 wt.% thermoplastic fibers.

4. The sheet material of claim 3, wherein the thermoplastic fibers comprise thermoplastic filaments and/or staple fibers.

5. The sheet material of claim 4 containing between 10 to 45 wt.% thermoplastic filaments.

6. The sheet material of any one of claims 1-5, wherein the sheet material has a high pulp surface and an opposite low pulp surface.

7. The sheet material of claim 6, wherein the high pulp surface contains at least 60 wt.% pulp fibers and the low pulp surface contains less than 50 wt.% pulp fibers and at least 30 wt.% thermoplastic fibers.

8. The sheet material of any one of the preceding claims, wherein a portion of the embossed layer area forms a readable character and/or logo.

9. The sheet material of any one of the preceding claims, wherein at least 10% of the total surface area of the stamping surface consists of at least 20cm²Preferably at least 25cm²Is formed by the uninterrupted non-embossed area.

10. The sheet material of any one of the preceding claims, having a water absorption capacity of at least 5 g/g.

11. A method of making a patterned nonwoven sheet material comprising the steps of:

-forming a fibrous web comprising thermoplastic fibres and cellulose pulp;

-hydroentangling the fibrous web to form a nonwoven sheet material;

-drying the nonwoven sheet material to a water content of less than 10 wt.%;

the method is characterized in that:

-subjecting the dried nonwoven sheet material to an embossing action provided by an energy emitter on a patterned anvil roll at a temperature of less than 100 ℃, preferably less than 60 ℃ to form a patterned nonwoven sheet material.

12. The method according to claim 11, wherein the energy comprises vibrational energy, in particular ultrasonic energy.

13. The method according to claim 11 or 12, wherein the distance between the energy emitter and the anvil roll has an adjustable gap of between 600 and 2000 μ ι η.

14. The method according to any one of claims 11-13, wherein the embossing action is a rotational action using a patterned anvil roll.

15. The method of any of claims 11-14, which does not include embossing or thermal bonding of thermoplastic fibers.

16. The method according to any one of claims 11-15, wherein the fibrous web is formed by laying a thermoplastic polymer web and applying a suspension containing pulp onto the polymer web.

17. The method of any one of claims 11-16, wherein the patterned nonwoven sheet material is a sheet material of any one of claims 1-10.