TECHNICAL FIELD OF THE INVENTION

[0001] The present invention is directed double-knit fabrics, more particularly to double-knit fabrics for garments.

BACKGROUND

[0002] Performance fabrics manufactured for use in insulating garments often include fleece fabric, i.e. fabric having a raised or brushed fiber surface for improved insulation performance. The surface of such fabrics is often formed of fleece, which is raised, i.e., given relatively higher loft, by mechanical brushing. It has, however, been recognized that the brushing process can often result in broken fibers, which, over time, can work loose, potentially resulting in microfiber pollution. Loss of fibers, e.g., during washing, can also result in deterioration of insulation performance. Further, it is recognized that broken fibers released during washing can get into wastewater, causing pollution. It is desirable to have a low fiber loss, low weight, and high insulative fabric for use in outerwear and other garment uses.

BRIEF SUMMARY OF THE INVENTION

[0003] The invention relates to a double-knit fabric having an upper surface and a lower surface and having a warp and weft direction, where the weft direction is perpendicular to the warp direction. The double-knit fabric contains a first knit layer comprising a plurality of first yams, a second knit layer comprising a plurality of second yams, and a plurality of stuffer yams. The first knit layer forms the upper surface of the double-knit fabric and the second knit layer forms the lower surface of the double-knit fabric. The stuffer yams are located between the first knit layer and the second knit layer. The double-knit fabric contains a plurality of anchored regions and a plurality of detached regions, where the plurality of detached regions is interspersed between the anchored regions. In the anchored regions, the first fabric layer and the second fabric layer are knitted together and in the detached regions the first fabric layer and second fabric layer are unattached.

The first knit layer and the second knit layer are integrated within the anchored regions at least one method selected from the group consisting of interlacing first yams of the first knit layer among the second yams of the second knit layer, interlacing the second yams of the second knit layer among the first yams of the first knit layer, and interlacing a plurality of third yams among the first yams of the first knit layer and the second yams of the second knit layer.

The average peak distance between the first fabric layer and the second fabric layer in the detached regions is at least about 3 mm and the double-knit fabric has between about 10 and 30 detached regions per square inch. The anchored regions contain at least two knit stitches in both the warp and weft directions and the anchored regions have a width of at least about 1 mm in both the warp and weft directions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 is an illustration of a cross-section of the double-knit fabric according to one embodiment of the invention.

[0005] Figure 2a is photograph of the upper surface of the double-knit fabric according to one embodiment of the invention. Figure 2b is illustration of the photograph of Figure 2a.

[0006] Figure 3a is angled photograph of the double-knit fabric according to one embodiment of the invention. Figure 3b is illustration of the photograph of Figure 3a. DETAILED DESCRIPTION

[0007] Referring now to Figure 1 , the double-knit fabric 10 of the invention has an upper surface 10a and a lower surface b, a warp direction and a weft direction (where the weft direction is perpendicular to the warp direction), and contains a first knit layer 20, a second knit layer 30, and a plurality of stuffer yams 40. The first knit layer 20 forms the upper surface 10a of the double-knit fabric 10, the second knit layer 30 forms the lower surface 10b of the double-knit fabric 10, and the stuffer yams 40 are located between the first 20 and the second 30 knit layers.

[0008] The detached regions 420 are interspersed between the anchored regions 410. In the anchored regions 410, the first fabric layer 20 and the second fabric layer 30 are knitted together (forming a single unitary knit layer) and in the detached regions 420 the first fabric layer 20 and second fabric layer 30 are unattached (and are separate knit layers). This knitting of the first knit layer and the second knit layer is done at the same time on the same knitting machine as knitting the first knit layer and the second knit layer. This is contrasted to a quilted fabric where the two layers are formed separately and then stitched together. The stuffer yams 40 are bulky yams (shown going into the plane of the illustration) fill out the detached region 420 and give them their bump appearance. The detached regions may have any suitable shape, including, but not limited to squares, rectangles, ovals, octagons, hexagons, irregular amoeba-like shapes, jellybeans, diamonds, and elongated lines. Preferably, the detached regions are in a regular grid (which does include a horizontal/vertical grid, offset gird, brick pattern grid, and more).

[0009] The detached regions 420 and attached regions 410 may form varying amounts of the surface area of the upper surface 10a of the double-knit fabric 10 depending on the end use. Because the detached regions 420 tend to be more insulating, it is preferable to increase the amount of surface area of the detached regions 420 relative to the surface area of the upper surface 10a of the double-knit fabric 10. In one preferred embodiment, the detached region 420 form between about 60 and 99% of the surface area of the upper surface of the double-knit fabric, more preferably between about 75 and 98%, more preferably between about 85 and 96%.

[0010] In Figure 2a, there is shown a photograph of the upper surface 10a of the double-knit fabric 10 which shows the surface of the first knit layer 20. In this picture, one can see the “bumps” on the fabric which are the detached regions 420 and the lines that bound the grid of bumps being the attached regions 410. Figure 2b is an illustration of Figure 2A. In Figure 3a, there is shown a photograph of the cross-section of the double-knit fabric 10 so one can more easily see the detached regions 420 and the attached regions 410. Figure 3b is an illustration of Figure 3A.

[0011] Preferably, the double-knit fabric has between about 10 and 30 detached regions per square inch, more preferably between about 15 and 25 detached regions per square inch. It has been found that this range of regions per square inch produces an insulative fabric that has good weight, thickness, and aesthetics. In one embodiment, the detached regions 420 preferably have at least one dimension in the plane of the double-knit fabric 10 of at least about 1 mm, more preferably at least about 2 mm, more preferably at least about 3 mm. Each of the detached regions 420 contain a plurality of knit stitches.

[0012] Each of the anchored regions 410 contain at least two knit stitches in at least one of the warp and weft directions which is a departure from other doubleknitted fabrics. In a preferred embodiment, the anchored regions 410 contain at least two knit stitches in both the warp and weft directions. In another embodiment, each of the anchored regions 410 contain at least three knit stitches in at least one of the warp and weft directions, more preferably in both directions. In another embodiment, the anchored regions 410 have a width of at least about 1 mm in both the warp and weft directions, more preferably at least about 1.8 mm in both the warp and weft directions.

[0013] How tall or high the detached regions 420 are also contributes to the insulative value and look to the fabric. In one embodiment, the average peak distance between the first fabric layer and the second fabric layer in the detached regions is at least about 3 mm. The average peak distance is calculated by measuring the distance between the inner surfaces (the surfaces facing each other) of the first knit layer and the second knit layer. This distance is measured on at least 10 different detached regions and then the result is averaged. In another embodiment, the average peak distance between the first fabric layer and the second fabric layer in the detached regions is at least about 3.5 mm, more preferably at least about 4.0 mm.

[0014] In addition to the average peak distance, the entrained air factor can also be an important characteristic of the fabric. This entrained air is the air located between the upper surface 10a of the double knit fabric 10 and a wearer’s skin. This additional air also serves to insulate the wearer. The following procedure was used to calculate a measure of the entrained air.

[0015] A Keyence VHX-6000 was used to obtain a three-dimensional image of the double-knit fabric. The image should represent an area at least 2.9 cm x 3.5 cm on the double-knit fabric surface. The topography (aligned with the dominant symmetry directions of the material) of the upper surface 10a of the double-knit fabric 10 was generated using the profile line tool available with the Keyence VHX- 6000. The profile generated was an average profile, where the range is set at 5 lines and the interval is set on 300 pm. This amounts to averaging the profiles of 11 lines (5 on either side of the center line), all separated by 300 mm, or 0.03 cm. This has the effect of averaging out the fluctuations in height due to individual yam variations. The center line for this profile is oriented along the targeted direction and centered on the high points/center of the detached regions in the profile direction. For each image of a fabric specimen, there are often multiple rows and columns (at approx. Right angles to each other) of the repeated structure of detached regions. A profile is formed as described above for each distinct row and column.

[0016] The targeted metric of analysis is related to the air space that would be formed if the fabric was laid against a surface and the high points of the profile touched the surface. The air space above the top surface of the fabric and an imaginary line that connects to the high points of the profile for each repeat unit is calculated. To do this, the profile is delineated into segments that reflect the repeat units along the direction the profile represents. The high point of the profile for each one of these segments is determined using mathematical tools (such as Excel). Within a spreadsheet, a straight line, representing a bounding layer if the high points were laying against a surface, is calculated between the high points of neighboring repeat units of the profile. At the edges of the profile, one of two things happens. If there is a maximum point at the edge of the profile, the straight line goes to that high point. If there is not a high point on the edge, the line extends from the nearest maximal point in the profile to a height which is an average height of the maximal points on the profile at the two extremes of the profile. Once this bounding line is calculated, the difference at each point in the profile between the bounding line and the top of the profile is calculated. A numeric integral is calculated of the area between the top of the profile and the bounding line. This area is then divided by the length of the image in that profile direction. This provides an entrained air height for that row or column of the image. This entrained air height is then calculated for each distinct row and column of the image and averaged together, providing the average entrained air height for that specimen. Preferably, the average entrained air height is between about 0.3 mm and 25 mm. In another embodiment, the calculated entrained air is between about 0.4 and 25 mm. In another embodiment, the calculated entrained air is between about 0.5 and 25 mm.

[0017] The first knit layer 20 contains a plurality of first yams and the second knit layer 30 contains a plurality of second yams. The yams that make up these layers can be any suitable yam. “Yam”, in this application, as used herein includes a monofilament elongated body, a multifilament elongated body, ribbon, strip, yam, tape, fiber and the like. The knit layers 20, 30 may contain one type of yam or a plurality of any one or combination of the above. The yams may be of any suitable form such as spun staple yam, monofilament, or multifilament, single component, bicomponent, or multi-component, and have any suitable cross-section shape such as circular, multi-lobal, square or rectangular (tape), and oval.

[0018] The yams of the knit layers 20, 30 may be formed of (but are not limited to) cellulosic yams (such as cotton, rayon, linen, jute, hemp, cellulose acetate, and combinations, mixtures, or blends thereof), polyester yams (e.g., poly(ethylene terephthalate) yarns, polypropylene terephthalate) (PET) yams, poly (trimethylene terephthalate) yarns), poly(butylene terephthalate) yarns, and blends thereof), polyamide yams (e.g., nylon 6 yams, nylon 6,6 yams, nylon 4,6 yams, and nylon 12 yams), polyvinyl alcohol yams, an elastic polyester-polyurethane copolymer (SPANDEX®), polypropylene yams, polyethylene yards, polyvinyl acetate yarns, polylactic acid yarns, flame-resistant meta-aramid (NOMEX®) or para-aramid, and combinations, mixtures, or blends thereof. In one preferred embodiment, the knit layers 20, 30 contain multifilament polyester yams as these have been shown to have good performance at low cost. In one embodiment, the first and second knit layers 20, 30 contain essentially all (defined as being at least about 98% by weight) multifilament polyester yams. In one embodiment, the yams that make up the knit layers 20, 30 all have approximately the same thickness or denier. In other embodiments, there is a difference in denier. In another embodiment, there may be more than one type of yam within a knit layer (varying in materials, construction, and/or denier) or the yams used may contain more than one type of fiber. In one embodiment, at least one of the first and second knit layers 20, 30 contains either nylon fibers or yams.

[0019] Referring back to Figure 1 , there are also fabric also contains a plurality of stuffer yams 40 located between the first knit layer 20 and the second knit layer 30. These stuffer yams may be any suitable yam and are preferably bulky so that they fill up the areas between the first and second knit layers and provides insulation. Preferably, the stuffer yams are a multifilament polyester yam. It has been shown that polyester yams may be easily bulked and retain their volume over time. In one preferred embodiment, the stuffer yams are faux twist textured yams. Preferably, the stuffer yams run approximately parallel to each other in the weft direction of the double-knit fabric.

[0020] In one preferred embodiment, the entire fabric is mostly polyester yams, more preferably continuous multifilament polyester yams. In another embodiment, the entire fabric (including the first knit layer, the second knit layer, the stuffer yams, and any additional yams) is essentially all (defined as at least 98% by weight) polyester yams, more preferably continuous multifilament polyester yams. [0021] Thickness of both layers 20, 30 may be any suitable thickness and may be approximately equally distributed, or one of the layers may thicker than the other. Typical thickness of the fabric is between about 0.1 and 6 mm, more preferably between about 1 and 4 mm.

[0022] The two knit layers 20 and 30 may be combined, knitted, and joined together (during knitting) in any suitable manner. A first method is interlacing first yams from the first knit layer 20 among the second yams of the second knit layer 30, meaning that a portion of the yams from the first knit layer leave the first knit layer, travel down into the second knit layer where they are interlaced with yams within the second knit layer, and then travel back up to the first knit layer.

[0023] A second method is interlacing second yams from the second knit layer 30 among the yams of the first knit layer 20, meaning that a portion of the yams from the second knit layer 30 leave the second knit layer, travel up into the first knit layer where they are interlaced with yams within the first knit layer, and then travel back down to the second knit layer to the first knit layer.

[0024] A third method is interlacing a plurality of additional yams in among the yams of the first knit layer 20 and the yams of the second knit layer 30. This means that an additional yam (which may be the same or different yam than the yams in the first or second knit layers) travels between the layers, interlacing with yams from both layers and in essence, tying them together. This additional yam may be selected from any of the yams described in reference to the yams in the first knit layer.

[0025] In a preferred embodiment, the second method is used to interlace and knit the first 20 and second 30 knit layers together. This method may be preferred because of the lower complexity during the knitting process using the circular knitting.

[0026] Preferably, the double-knit fabric has a clo value measured by test ASTM F1868 of at least about 0.2. Clo is a measure of insulative value of the fabric. In another embodiment, the double-knit fabric has a clo value measured by test ASTM F1868 of at least about 0.3, more preferably at least about 0.4. In another embodiment, 9. The double-knit fabric of claim 1 , wherein the double-knit fabric has an air permeability of at least about 150 CFM, more preferably about 175 CFM, more preferably about 200 CFM, and more preferably about 225 CFM.

[0027] When the fabric 10 is made into an article of clothing (also referred to as a garment), in one embodiment the lower surface 10b would be facing away from the wearer and upper surface 10a would be facing towards the wearer. In another embodiment, the lower surface 10b would be facing the wearer and upper surface 10a would be facing away from the wearer. The double-knit fabric 10 is a unitary material that is formed together in a knitting machine with the two layers sometimes being separate and sometimes knitted together. The layers 20 and 30 are not formed as discrete knit layers and then joined together in a later operation. The fabric 10 may be made by any suitable knitting method, including both warp knitting and weft (or circular) knitting. Circular knitting is preferred in some embodiments, as it tends to be more cost efficient. The article of clothing may be any suitable article including but not limited to a shirt, jacket, pants, tights, leggings, hat, undergarments, and socks.

[0028] In another embodiment, a garment may use the fabric in addition to other fabric. For example, a shirt might use the fabric of the invention on the torso and another fabric in the sleeves. Additionally, the fabric of the invention could also be used as an insert. Additionally, the fabric may be used for any other suitable purpose including, but not limited to, a tent, automobile covering, upholstery, mattress covers, and pet beds.

[0029] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0030] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the subject matter of this application (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open- ended terms (i.e. , meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the subject matter of the application and does not pose a limitation on the scope of the subject matter unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the subject matter described herein.

[0031] Preferred embodiments of the subject matter of this application are described herein, including the best mode known to the inventors for carrying out the claimed subject matter. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the subject matter described herein to be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the abovedescribed elements in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.