Multilayer sheet structure

Abstract

To provide a fibrous multilayer sheet structure.SOLUTION: There is provided a fibrous multilayer sheet structure comprising: at least one discontinuous fibrous layer having first and second surfaces; and at least one layer of continuous melt spun fibers on the first surface of at least one of the at least one discontinuous fibrous layer, wherein the fibers of the discontinuous fibrous layer are not melt blown fibers.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a multi-layer fibrous sheet structure. [Background technology]

[0002] U.S. Patent No. 5,308,691 to Lim et al. discloses a controlled porosity composite sheet comprising a meltblown polypropylene fibrous web laminated on at least one side to a spunbonded polypropylene fibrous sheet, the composite being prepared by calendering the assembly of component webs such that, when a two-layer composite sheet is produced, the meltblown fibrous web is in contact with a metal roll heated to 140-170°C operating against an unheated resilient roll, and when a three-layer composite sheet is produced, the spunbonded web in contact with the heated metal roll has a dtex per fiber value of less than 6. The composite sheet has a Gurley-Hill porosity of approximately 5-75 seconds, excellent mechanical and tear strength, high water vapor permeability, and low liquid permeability. These composite sheets are particularly suitable for the production of housewrap sheets and sterilization packaging sheets.

[0003] U.S. Patent No. 6,797,655 to Rudisill teaches meltblown fibers comprising at least 20% by weight of a polyester selected from the group consisting of poly(ethylene terephthalate) having an intrinsic viscosity of less than 0.55 dL / g and poly(trimethylene terephthalate) having an intrinsic viscosity of less than 0.80 dL / g. The meltblown fibers are collected as a web that can be incorporated into a composite sheet structure.

[0004] U.S. Patent No. 9,580,845 to Ashraf describes a nonwoven substrate having at least two layers of fibers, each having a top surface and a bottom surface. The nonwoven substrate may include at least one layer of spunbond fibers. The nonwoven substrate may include at least two layers of spunbond fibers. Furthermore, the nonwoven substrate may include at least one layer of carded fibers and one layer of meltblown fibers. Furthermore, the nonwoven substrate may include at least one layer of microfibers. In one embodiment, any of the fiber layers, including spunbond fibers, carded fibers, meltblown fibers, or microfibers, may include or consist of monocomponent, bicomponent, or multicomponent fibers. In one embodiment, the nonwoven substrate may include a polyolefin, such as polypropylene or polyethylene. Summary of the Invention [Means for solving the problem]

[0005] The present invention relates to a fibrous multi-layer sheet structure comprising at least one discontinuous fibrous layer having a first and second surface, and at least one layer of continuous melt-spun fibers on at least one first surface of the at least one discontinuous fibrous layer, wherein the fibers of the discontinuous fibrous layer are not melt-blown fibers. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a cross-sectional view of a first embodiment of the present invention. [Figure 2] FIG. 4 is a cross-sectional view of a second embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view of a third embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view of a fourth embodiment of the present invention. [Figure 5] FIG. 1 is a schematic diagram of one method of making the sheet structure of the present invention. [Figure 6] FIG. 10 is a cross-sectional view of a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0007] Multilayer sheet structure Figure 1 shows a cross-sectional view 10 of a first embodiment of the present invention. The fibrous multilayer sheet structure 10 includes a discontinuous fibrous layer 11 having first and second surfaces 12 and 13, respectively, and one layer 14 of continuous melt-spun fibers on the first surface 12 of the discontinuous fibrous layer 11.

[0008] 2 shows a cross-sectional view 20 of a second embodiment of the present invention. The fibrous multilayer sheet structure 20 includes a discontinuous fibrous layer 21 having first and second surfaces 22 and 23, respectively, one layer 24 of continuous meltspun fibers on the first surface 22 of the discontinuous fibrous layer 21, and a further layer 25 of continuous meltspun fibers on the second surface 23 of the discontinuous fibrous layer 21.

[0009] 3 shows a cross-sectional view 30 of a third embodiment of the present invention. The fibrous multilayer sheet structure 30 includes a first discontinuous fibrous layer 31 having first and second surfaces 32 and 33, respectively, one layer 34 of continuous meltspun fibers on the first surface 32 of the discontinuous fibrous layer 31, and a second discontinuous fibrous layer 35 having first and second surfaces 36 and 37 on a surface of the continuous fibrous layer 34 remote from the first discontinuous fibrous layer 31.

[0010] 4 shows a cross-sectional view 40 of a fourth embodiment of the present invention. The fibrous multilayer sheet structure 40 includes a discontinuous fibrous layer 41 having first and second surfaces 42 and 43, respectively. An assembly including two layers 44 and 47 of continuous meltspun fibers is disposed on the first surface 42 of the discontinuous fibrous layer 41, and an assembly including two layers 45 and 46 of continuous meltspun fibers is disposed on the second surface 43 of the discontinuous fibrous layer 41.

[0011] Other embodiments may be envisioned, such as CCDDCC, CDCDC, CCCDCDCC or CDDCDDC, where C is a layer of continuous meltspun fibers and D is a discontinuous fiber layer.

[0012] In one embodiment of the CCDCC structure, the D layer has an area weight of 30 gsm or less. Typically, multi-layer sheet structures have an area weight of 100 gsm or less, a thickness of 100 m 3 m -2 minutes -1 and a pore size of 150 micrometers or less. More preferably, the pore size is 120 micrometers or less.

[0013] In yet another embodiment of the CCDCC structure, the D layer has an area weight of 100 gsm or less. The sheet structure has an area weight of 600 gsm or less, a 100 m 3 m -2 minutes -1 and a pore size of 150 micrometers or less. More preferably, the pore size is 120 micrometers or less.

[0014] FIGS. 1-4 illustrate an example of the present invention in which each single layer of the sheet structure, such as 31, 34, and 35, is either a discontinuous fiber layer or a continuous fiber layer; in other words, 31, 34, and 35 are D, C, and D, respectively. Other sheet structure configurations can be envisioned in which a blend of continuous and discontinuous fiber components exists within the layers of the structure. These can be considered interlocking or intermingled layers. An example of this is shown generally at 60 in FIG. 6. Layer 61 is a layer containing only discontinuous fibers, and layer 63 is a layer containing only continuous fibers. Layers 62 and 64 are blended layers containing both continuous and discontinuous fiber regions within each layer. Layer 62 contains continuous fiber regions at 62a and 62b and discontinuous fiber regions at 62c. Layer 64 contains continuous fiber regions at 64c and discontinuous fiber regions at 64a and 64b. Many combinations of continuous and discontinuous fiber regions within layers are possible. These can be oriented primarily in the machine direction or cross direction. Based on the nomenclature used in this description, the illustrative example of Figure 6 can be described as a D(CDC)C(DCD) multilayer sheet structure for layers 61-64, respectively.

[0015] In other embodiments, each discontinuous fiber layer has an areal weight range of 5 gsm to 100 gsm. In yet other embodiments, the total areal weight of each continuous meltspun filament layer ranges from 5 gsm to 500 gsm.

[0016] The C and D layers may be of the same or different chemical composition.

[0017] discontinuous fiber layer The fibers in the discontinuous fiber layer are not meltblown fibers. Meltblowing is a method of making microfibers and nanofibers by extruding a polymer melt through a small nozzle surrounded by high-velocity blowing gas. The randomly deposited fibers form a nonwoven sheet material.

[0018] Discontinuous fibers include pulp and nanofibers. In this context, nanofibers are fibers having at least one dimension less than 1 micrometer.

[0019] The discontinuous fibers may be synthetic fibers, natural fibers, or blends thereof. Exemplary synthetic fibers include polyolefins and olefin copolymers (e.g., polypropylene, metallocene polypropylene, or polyethylene), polyesters, polysulfones, polyethersulfones, polyphenylsulfones, polyvinylidene fluoride, polylactic acid, polyvinylidene difluoride, polyimides, polyacrylonitriles, aromatic polyamides, ethylene-vinyl alcohol copolymers, cellulose acetate, or combinations thereof. The above synthetic or natural fibers may also be bicomponent or multicomponent fibers, and in some embodiments, may be in the form of sheath-core fibers or two components side by side. In this latter case, the two side by side components may be twisted together. Exemplary natural fibers include cellulose fiber precursors, such as cellulose, non-lignin-free cellulose, and cellulose derivatives, such as cotton, wood pulp, flax, hemp, and mucilage fibers, which are conventionally described, for example, from plant or animal sources (see, for example, Wikipedia link https: / / en.wikipedia.org / wiki / List_of_textile_fibres). In some embodiments, the discontinuous fibers have a length not exceeding 12 mm and a filament diameter not exceeding 11 dtex (10 denier). Cellulose acetate is also a suitable material for the fibers. In further embodiments, blends of natural and synthetic discontinuous fibers are used.

[0020] The discontinuous fibers may be monocomponent, bicomponent, or multicomponent fibers, such terms being well known in the fiber art. In one embodiment, the fibers may be bicomponent fibers having a polypropylene core and a low melting point polymer sheath or a polyester core and a low melting point copolyester or polyolefin sheath.

[0021] In some embodiments, at least one of the discontinuous fibrous layers comprises fibers of different dimensions, ie, lengths and / or diameters.

[0022] In some embodiments, the discontinuous fibrous layer has an areal weight of 5 to 100 gsm.

[0023] Melt-spun continuous fiber layer The melt-spun fiber layer comprises continuous synthetic or embedded bio-based fibers. More information on bio-based fibers can be found at the following Wikipedia link: https: / / en.wikipedia.org / wiki / Bio-based_material. One such fiber is Sorona® available from DowDuPont. In the context of the present invention, the terms fiber and filament are interchangeable.

[0024] In melt spinning, the fiber-forming material is melted for extrusion through a spinneret and then directly solidified by cooling. Melt spinning uses heat to melt the polymer to a viscosity suitable for extrusion through the spinneret. Polymers that do not decompose or degrade at the temperatures required for extrusion are used.

[0025] Preferably, the continuous melt-spun fibers are polyolefins and olefin copolymers (such as polypropylene, metallocene polypropylene or polyethylene), polysulfone, polyethersulfone, polyphenylsulfone, polyvinylidene fluoride, polyvinylidene difluoride, polyimide, polyacrylonitrile, polyester, aromatic polyamide, ethylene vinyl alcohol copolymer or cellulose acetate.

[0026] Exemplary bio-based fibers include, for example, polylactides and cellulose derivatives, which are chemically and / or biologically modified forms of cellulose used in food processing (see Encyclopedia.com at https: / / www.encyclopedia.com / education / dictionaries...pictures... / cellulose-derivatives).

[0027] The continuous fibers can be monocomponent, bicomponent, or multicomponent.

[0028] In some embodiments, the continuous meltspun fiber layer has an areal weight of 5 to 500 gsm.

[0029] In some embodiments, at least one of the continuous fiber layers comprises fibers of different sizes, i.e., diameters and / or cross-sections, and may further comprise nanoparticles.

[0030] Method for making a sheet structure Preferably, the sheet structure is made by a method in which discontinuous and continuous fiber layers are formed and consolidated in a one-step process, as shown in Figure 5, which is a schematic illustration of a process suitable for making the sheet structure described in Figure 4.

[0031] The apparatus consists of a laying belt, such as continuous belt 51. The belt moves in the direction of the arrow. On the belt are the necessary number of units required to produce the desired number of continuous and discontinuous fiber layers in the sheet structure. In FIG. 5, units 44a-47a are used to produce layers 44-47, respectively, in the sheet structure of FIG. 4. Unit 41a produces layer 41 of FIG. 4. The arrangement or number of these units can be changed to produce sheet structures with various layer configurations. Any suitable commercially available unit for spinning continuous fibers and producing discontinuous fibers can be used. After the last layer, in this case layer 47, is laid, the unconsolidated sheet structure is fed through a consolidation or calendering process, such as a pair of rolls 52a and 52b. Roll 52b may be replaced by a table. The temperature of the rolls and the pressure applied to the roll nip are adjusted to achieve the desired level of consolidation. The rolls are typically made of steel or one of steel and steel with a rubber sleeve. Such processes are widely known in the lamination art. Figures 52a and 52b can also be a combination of a perforated steel drum applying saturated steam to a fibrous sheet structure that is pressed against a rubber pre-roll. A similar type of thermal bond can also be obtained by through-gas bonding.

[0032] Goods The multilayer sheet structures described herein can be used to make a wide range of articles, including, but not limited to, geotextiles such as drainage, landscape structures, or sports field components, piezoelectric textiles, energy harvesting areas, advertising designs, medical packaging, filtration, gas storage containers, building materials such as house wraps, wall and under-roof covers, sound insulating or absorbing materials, filter materials such as food filters, air filters, liquid filters, vacuum cleaner filters, membrane supports, protective clothing, hygiene or medical materials such as disposable diapers, sterilization wrap, medical filters, or desiccant packs.

[0033] Test Method The tensile strength and tensile elongation were determined in accordance with DIN EN 29073-3 (1992). Basis weight (mass per unit area) was measured in accordance with BS EN ISO 9864 (2005). The thickness of each layer was determined in accordance with EN ISO 9863-1 (2016). The determination of the characteristic opening (pore) size of the sheet structures was carried out according to EN ISO 12956 (2010) based on a calibrated sand sieve. O90 is an optical method for determining opening (pore) size and correlates with ISO 12956 (2010). The test method for trapezoid tearing strength of the sheet structure was measured in accordance with ASTM D4533-91(1996). The breathability of the textile fabrics was determined according to ISO 9237:1995. [Example]

[0034] The following examples are given to illustrate the invention and should not be construed as limiting it in any manner. All parts and percentages are by weight unless otherwise indicated. Examples prepared according to the process or processes of the invention are indicated by numerical values. Controls or comparative examples are designated by letters. Data and test results for comparative examples and examples of the invention are set forth in Tables 1-4.

[0035] In the table, "SST MD" is the tensile strength in the machine direction according to test method DIN EN 29073-3 (1992) (using 50 x 200 mm specimens), and "SST XD" is the tensile strength in the cross direction (using 50 x 200 mm specimens). "Elong MD" is the elongation at break in the machine direction, and "Elong XD" is the elongation at break in the cross direction. "TTMD" is the trapezoidal tear in the machine direction, and "TTXD" is the trapezoidal tear in the cross direction. "Air Perm" is the air permeability. "O90" and "O90E" are measurements of pore size determined by optical means and physical separation (sieving), respectively. Machine direction and cross direction are terms well known in the art of laminates and fibers.

[0036] Samples were measured at 17 different locations per sheet structure and the values ​​quoted are the average of these values.

[0037] All examples were made on a conventional laying machine with a width of 600 mm.

[0038] Example 1 Example 1 was a CCDCC structure with a total areal weight of 78 gsm. The C layer combination replicated Typar® 3207 spunbond nonwoven, a continuous polypropylene filament, commercially available from DowDuPont, Wilmington, DE, with an areal weight of 68 gsm. The D layer fiber was polypropylene. The D layer weighed 10 gsm and contained short melt-spun (i.e., non-meltblown) polypropylene fibers with a nominal dtex of 1.7 (1.5 denier). The sheet structure was prepared as outlined in the description beginning with Figure 5.

[0039] Comparative example A The sheet structure was Typar® 3207, a commercially available product from DowDuPont, with a four-layer CCCC construction and a weight of 68 gsm. Each layer comprised a spunbond nonwoven fabric of continuous polypropylene filaments. The sheet structure was made as outlined in the description following Figure 5, except that element 41 was omitted.

[0040] Comparative example B The 150 gsm weight sheet structure was also a CCCC structure containing four layers, a commercially available spunbond nonwoven of continuous polypropylene filaments. This material is available from Dow DuPont as Typar® SF44. The sheet structure was made as outlined in the description beginning with Figure 5, except that element 41 was omitted.

[0041] The properties of these three examples are summarized in Tables 1 and 2.

[0042] [Table 1]

[0043] [Table 2]

[0044] Example 2 Example 2 was a CCDCC structure with a total areal weight of 84 gsm. The total areal weight of all four C layers was 74 gsm. These layers were similar to the previously described Typar® 3207, but with a lower areal weight. The D layer weighed 10 gsm and contained short melt-spun bicomponent fibers with a polypropylene core and a polyethylene sheath. The nominal dtex of the fibers was 1.7 (1.5 denier). The sheet structure was prepared as outlined in the description beginning with Figure 5.

[0045] Comparative example C The multilayer sheet structure was a 240 gsm CCCC construction and included four layers. Such a structure is commercially available from DowDuPont as Typar® SF70. Each layer included a spunbond nonwoven fabric of continuous polypropylene filaments. The multilayer sheet structure was made as outlined in the description beginning with FIG. 5, except that element 41 was omitted.

[0046] Comparative example D The multilayer sheet structure was a 125 gsm CCCC construction and included four layers. Such a structure is commercially available from DowDuPont as Typar® VD37. Each layer included a spunbond nonwoven sheet of continuous polypropylene filaments. The multilayers were fabricated as outlined in the description beginning with FIG. 5, except that element 41 was omitted.

[0047] Comparative Example E The multilayer sheet structure was a 90 gsm CCCC construction and included four layers. Such a structure is commercially available from DowDuPont as Typar® SF27. Each layer included a spunbond nonwoven sheet of continuous polypropylene filaments. The multilayers were fabricated as outlined in the description beginning with FIG. 5, except that element 41 was omitted.

[0048] The properties of these four examples are summarized in Tables 3 and 4.

[0049] [Table 3]

[0050] [Table 4]

[0051] The results shown in the table above illustrate the advantages of the inventive concept. Two features are particularly noticeable when the properties of the sheet structure are "normalized" by basis weight, and this type of normalized comparison is very common in the textile industry: (i) at lower basis weights, the inventive samples provide improved or equivalent mechanical strength, and (ii) at lower basis weights, the inventive samples provide reduced or equivalent pore size, a property relevant in many industrial applications.

Claims

1. A fibrous multilayer sheet structure comprising at least one discontinuous fibrous layer having a first and second surface, and at least one layer of continuous meltspun fibers on the first surface of at least one of the at least one discontinuous fibrous layer, wherein the fibers of the discontinuous fibrous layer are not meltblown fibers, and the fibrous multilayer sheet structure further comprises at least one layer of continuous meltspun fibers on the second surface of at least one of the at least one discontinuous fibrous layer, and the fibrous multilayer sheet structure is selected from CDC, CCDCC, CCCDCCC, CDCDC, CCCDCDCC, or CDDCDDC, where C is a continuous meltspun fiber layer and D is a discontinuous fibrous layer.

2. The fibrous multilayer sheet structure described in Claim 1, wherein the fibrous multilayer sheet structure is CDC or CCDCC.

3. A fibrous multilayer sheet structure as described in claim 1 or 2, wherein the fibers of the discontinuous fiber layer are short melt-spun fibers, and the short melt-spun fibers include polypropylene.

4. A fibrous multilayer sheet structure described in any one of claims 1 to 3, wherein the discontinuous fibers are synthetic fibers having a length not exceeding 12 mm and a filament diameter not exceeding 11 dtex.

5. A fibrous multilayer sheet structure described in any one of claims 1 to 4, wherein the continuous melt-spun fibers include polypropylene.

6. A fibrous multilayer sheet structure described in any one of claims 1 to 5, wherein the discontinuous fiber layer has an area weight of 5 to 100 gsm.

7. A fibrous multilayer sheet structure described in any one of claims 1 to 6, wherein at least one continuous fiber layer has an area weight of 5 to 500 gsm.

8. An article comprising a fibrous multilayer sheet structure according to any one of claims 1 to 6, said article being a geotextile structure or a landscape structure.

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