Patent Application
20190053630
The present disclosure generally relates to bedding products and methods of manufacture, and more particularly, to bedding products including a three-dimensional polylactide (PLA) fiber matrix layer.
One of the ongoing problems associated with all-foam mattress assemblies as well as hybrid foam mattresses (e.g., foam mattresses that include, in addition to one or more foam layers, spring coils, bladders including a fluid, and various combinations thereof) is user comfort. To address user comfort, mattresses are often fabricated with multiple layers having varying properties such as density and hardness, among others, to suit the needs of the intended user. One particular area of concern to user comfort is the level of heat buildup experienced by the user after a period of time. Additionally, some mattresses can retain a high level of moisture, further causing discomfort to the user and potentially leading to poor hygiene.
Unfortunately, the high density of foams used in current mattress assemblies, particularly those employing traditional memory foam layers that typically have fine cell structure and low airflow, generally prevents proper ventilation. As a result, the foam material can exhibit an uncomfortable level of heat to the user after a period of time.
Disclosed herein are bedding products including a three-dimensional polylactide (PLA) polymeric fiber matrix.
In one or more embodiments, a three dimensional polymeric fiber matrix layer for a mattress construction includes a plurality of randomly oriented polylactide (PLA) fibers bonded at coupling points between adjacent PLA fibers and having a free volume per unit area of the layer.
In one or more embodiments, a mattress includes at least one three dimensionally PLA fiber matrix layer comprising randomly oriented PLA fibers bonded at coupling points between adjacent fibers and having a free volume per unit area of the layer.
The disclosure may be understood more readily by reference to the following detailed description of the various features of the disclosure and the examples included therein.
The present disclosure overcomes the problems noted in the prior art by providing a mattress with one or more three-dimensional polylactide fiber matrix layers. The polylactide polymer (PLA) defining the three dimensional fiber matrix is also referred to as polylactic acid. PLA is a biodegradable thermoplastic aliphatic polyester derived from renewable sources as opposed to traditional plastics which are typically derived from non-renewable petroleum sources. Several different types of suitable polylactide polymers include racemic PLLA (poly-L-lactic Acid), regular PLLA (poly-L-lactic Acid), PDLA (poly-D-lactic Acid), PDLLA (poly-DL-lactic Acid), PLGA (poly-lactic-co-glycolic Acid), PCL (polycaprolactone), and combinations thereof.
The location of the one or more three-dimensional PLA fiber matrix layers within a mattress is not intended to be limited. In one or more embodiments, the three-dimensional PLA fiber matrix layer or layers can be disposed in proximity to the surface or bottom of the mattress. In one or more other embodiments, the three dimensional PLA fiber matrix layers are utilized as a transition layer between the base foam layer and one or more foam layers, e.g., polyurethane foam layers, latex foam layers, viscoelastic foam layers, or the like, in an all-foam mattress construction or between the innercore and one or more foam layers in a hybrid mattress construction that can further include a bladder, coil springs or the like as the base layer.
The three dimensional PLA fiber matrix layer can generally be formed via extrusion processing that results in a three dimensional random fiber orientation with varied contact points between fibers serving as bonding points to provide rigidity to the three dimensional layer.
The three dimensional PLA fiber matrix layer by itself is subject to fatigue in the shear direction such as may occur when a user rolls from side to side on the mattress including the three dimensional polymeric layer. As a result, compaction of the three dimensional polymeric fiber layer can occur as a function of use, which manifests itself over time as a change in firmness and height loss. To minimize property changes to the three dimensional PLA fiber matrix layer as a function of use, the three dimensional polymer matrix layer can be subjected to a pre-conditioning process that breaks the weaker bonds and/or structurally weaker fibers within the three dimensional polymeric fiber matrix layer.
Turning now to
Generally, the three dimensional PLA matrix layer 10 is formed by first extruding PLA to form a plurality of fibers. Dried granules, pellets, chips, or the like of the PLA (moisture content less than 250 ppm) are fed into an extrusion apparatus, i.e., an extruder, at an elevated temperature and pressure, which is greater than the melting temperature of the PLA, i.e., about 150° C. to about 170° C. The PLA, in melt form, is then extruded through a die, which generally is a plate including numerous spaced apart apertures of a defined diameter, wherein the placement, density, and the diameter of the apertures can be the same or different throughout the plate. When different, the three dimensional PLA fiber layer can be made to have different zones of density, e.g., sectional areas can have different amounts of free volume per unit area. For example, the three dimensional PLA fiber matrix layer can include a frame-like structure, wherein the outer peripheral portion has a higher density than the inner portion; or wherein the three dimensional PLA fiber matrix layer can have a checkerboard-like pattern, wherein each square in the checkerboard has a different density than an adjacent square; or wherein the three dimensional PLA fiber matrix layer can have different density portions corresponding to different anticipated weight loads of a user thereof. The various structures of the three dimensional PLA fiber matrix layer are not intended to be limited and can be customized for any desired application. In this manner, the firmness, i.e., indention force deflection, and/or density of the three dimensional PLA fiber matrix layer can be uniform or varied depending on the die configuration and conveyor speed.
The PLA raw material is extruded into a cooling bath which results in entanglement and bonding of PLA fibers through entanglement. Concurrently, the continuously-extruded, cooled polymeric matrix is pulled onto a conveyor. The rate of conveyance and cooling bath temperature can be individually varied to further vary the thickness and density of the three dimensional polymeric fiber layer. Generally, the thickness of the three-dimensional PLA fiber matrix layer by itself can be extruded as a full width mattress material at thicknesses ranging from about 1 to about 6 inches and can be produced to topper sizes or within roll form. However, thinner or thicker thicknesses could also be used as well as wider widths if desired. The three- dimensional PLA fiber matrix layer can have a thickness ranging from 0.5 to 5.9 inches.
Suitable extruders include, but are not limited to continuous process high shear mixers such as: industrial melt-plasticating extruders, available from a variety of manufacturers including, for example, Cincinnati-Millicron, Krupp Werner & Pfleiderer Corp., Ramsey, N.J. 07446, American Leistritz Extruder Corp.; Somerville, N.J. 08876; Berstorff Corp., Charlotte, N.C.; and Davis-Standard Div. Crompton & Knowles Corp., Paweatuck, Conn. 06379. Kneaders are available from Buss America, Inc.; Bloomington, Ill.; and high shear mixers alternatively known as Gelimat™ available from Draiswerke G.m.b.H., Mamnheim-Waldhof, Germany; and Farrel Continuous Mixers, available from Farrel Corp., Ansonia, Conn. The screw components used for mixing, heating, compressing, and kneading operations are shown and described in Chapter 8 and pages 458-476 of Rauwendaal, Polymer Extrusion, Hanser Publishers, New York (1986); Meijer, et al., “The Modeling of Continuous Mixers. Part 1: The Corotating Twin-Screw Extruder”, Polymer Engineering and Science, vol. 28, No. 5, pp. 282-284 (March 1988); and Gibbons et al., “Extrusion”, Modern Plastics Encyclopedia (1986-1987). The knowledge necessary to select extruder barrel elements and assemble extruder screws is readily available from various extruder suppliers and is well known to those of ordinary skill in the art of fluxed polymer plastication.
The PLA fibers can be solid or hollow and have cross-sections that are circular or triangular or other cross sectional geometries, e.g. tri-lobular, channeled, and the like. Another type of PLA fiber has an entangled, spring-like structure. During manufacturing the PLA fiber structure is heated by extrusion to interlink the fibers to one another to provide a more resilient structure. Fibers may be randomly oriented or directionally oriented, depending on desired characteristics. Such processes are discussed in U.S. Pat. No. 8,813,286, entitled Tunable Spring Mattress and Method for Making the Same, the entirety of which is herein incorporated by reference.
The PLA fibers and their characteristics are selected to provide desired tuning characteristics. One measurement of “feel” for a cushion is the indentation- force-deflection, or IFD. Indentation force-deflection is a metric used in the flexible foam manufacturing industry to assess the “firmness” of a sample of foam such as memory foam. To conduct an IFD test, a circular flat indenter with a surface area of 323 square centimeters (50 sq. inches—8″ in diameter) is pressed against a foam sample usually 100 mm thick and with an area of 500 mm by 500; mm (ASTM standard D3574). The foam sample is first placed on a flat table perforated with holes to allow the passage of air. It then has its cells opened by being compressed twice to 75% “strain”, and then allowed to recover for six minutes. The force is measured 60 seconds after achieving 25% indentation with the indenter. Lower scores correspond with less firmness; higher scores with greater firmness. The IFD of the three dimensional PLA fiber matrix layer tested in this manner and configured for use in a mattress has an IFD ranging from 5 to 25 pounds-force. The density of the three dimensional PLA fiber matrix layer ranges from 1.5 to 6 lb/ft3. Subsequent to preconditioning, if applicable, the three dimensional PLA fiber matrix layer can have a density of 1.6 to 7 lb/ft3 and an IFD of 4 to 24.9 pounds-force.
As noted above, in some embodiments the three dimensional PLA fiber matrix layer can be pre-conditioned.
In one or more embodiments, the platen 64 can sized to be substantially similar to the sleeping area of the mattress and/or the three dimensional PLA fiber matrix layer 52. In such embodiments, the system 50 may be used to pre- condition a substantial portion of the mattress. Moreover, in such embodiments, the system 50 may be used to pre-condition the head, body and foot portions of the mattress surface simultaneously. In still other embodiments, the system 50 may be configured as desired depending on the nature of the pre-conditioning. For example, the platen 62 may be sized and shaped to selectively pre-condition either a middle portion or edge portion or both of the mattress and/or the three dimensional PLA fiber matrix layer 52. In another example, the system 50 may be configured with a plurality of platens 63 for pre-conditioning different portions of the mattress by applying similar or different loads. In certain embodiments, the platen 62 may be moveable along the length or width of the mattress and equipped with a cylindrical roller such that the platen 62 may roll along the surface of the mattress to progressively compress the mattress and/or the three dimensional PLA fiber matrix layer 52. Generally, in other embodiments and practices, it could be that the device shown in
Generally, the thickness of the lower base layer 302 is within a range of 4 inches to 10 inches, with a range of about 6 inches to 8 inches thickness in other embodiments, and a range of about 6 to 6.5 inches in still other embodiments. The lower base layer can be formed of open or closed cell foams, including without limitation, viscoelastic foams, non-viscoelastic foams, latex foam, polyurethane foams, and the like.
The lower base layer 302 can have a density of 1 pound per cubic foot (lb/ft3) to 6 lb/ft3. In other embodiments, the density is 1 lb/ft3 to 5 lb/ft3 and in still other embodiments, from 1.5 lb/ft3 to 4 lb/ft3. By way of example, the density can be about 1.5 lb/ft3. The indention force deflection (IFD), is within a range of 20 to 40 pounds-force, wherein the hardness is measured in accordance with ASTM D-3574.
Alternatively, the lower base layer 302 can be a coil spring innercore disposed within a cavity defined by a bucket assembly, wherein the bucket assembly includes a planar base layer and side rails disposed about a perimeter of the planar base layer.
The at least one upper foam layer 306 defines a cover panel overlying the three dimensional PLA matrix fiber layer 304. The cover panel can be formed from one or more viscoelastic foam and/or non-viscoelastic foam layers depending on the intended application. The foam itself can be of any open or closed cell foam material including without limitation, latex foams, natural latex foams, polyurethane foams, combinations thereof, and the like. The cover panel has planar top and bottom surfaces. The thickness of the cover panel is generally within a range of about 0.5 to 2 inches in some embodiments, and less than 1″ in other embodiments so as to provide the benefits of motion separation and increased airflow from the underlying foam layer 104. The density of the at least one upper foam layer 306 is within a range of 1 to 5 lb/ft3 in some embodiments, and 2 to 4 lb/ft3 in other embodiments. The hardness is within a range of about 10 to 20 pounds-force in some embodiments, and less than 15 pounds-force in other embodiments. In one embodiment, the cover panel is at a thickness of 0.5″, a density of 3.4 lb/ft3, and a hardness of 14 pounds-force.
In one or more embodiments, each of the various multiple stacked mattress layers 302, 304, and 306 can be formed of the three dimensional PLA fiber matrix.
The various multiple stacked mattress layers 302, 304, and 306 may be adjoined to one another using an adhesive or may be thermally bonded to one another or may be mechanically fastened to one another as may be desired for different applications.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
