EP3980592B1

EP3980592B1 - Magnetic fabric for molding applications

Info

Publication number: EP3980592B1
Application number: EP20749985.6A
Authority: EP
Inventors: Sudhanshu SRIVASTAVA; Warren W. Gerhardt; Emily W. Michaels; Jeffrey A. Stafford; Kurt NEUVILLE
Original assignee: Milliken and Co
Current assignee: Milliken and Co
Priority date: 2019-06-04
Filing date: 2020-06-03
Publication date: 2022-10-26
Anticipated expiration: 2040-06-03
Also published as: US20200385920A1; EP3980592A1; WO2020247493A1

Description

FIELD OF THE INVENTION

The present invention generally relates to creating magnetic scrims for easier processing for molding applications.

BACKGROUND

In some molding applications, foams such as polyurethanes are combined with other textile layers such as scrims during the molding process. The scrims can give the polyurethane additional strength and other characteristics such as fire resistance. There is a need for a scrim that is more easily inserted and positioned within the mold to reduce incorrect molding location and operator time to position the scrim.
JP S61-245372 relates to a conductive mesh fabric.

BRIEF SUMMARY

The invention relates to a magnetic scrim containing a scrim which contains a plurality of yarns and a magnetic coating covering at least a portion of the yarns of the scrim. The magnetic coating, which contains magnetic elements dispersed in a binder, where the magnetic coating is at least about 40% by weight magnetic elements, and where the magnetic coating has an areal density of at least twice the areal density of the scrim.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates one embodiment of a magnetic scrim.
Figure 2 is a photograph of one embodiment of the scrim (before being coated with the magnetic coating).

DETAILED DESCRIPTION

Referring now to Figure 1, there is shown one embodiment of the magnetic scrim 10. The magnetic scrim 10 contains a scrim 100 having a first side 100a and a second side 100b. The scrim 100 contains a plurality of yarns. The magnetic scrim 10 also contains a magnetic coating 120 that covers at least a portion of the yarns of the scrim 100.
This magnetic scrim 10 would be placed in a mold with at least one magnet to hold the scrim in place while the mold is prepared and polyurethane (or other moldable material) is introduced and then cured in the mold.
As used herein, the term "scrim" shall mean a fabric having an open construction used as a base fabric or a reinforcing fabric, which may be manufactured as laid scrim, a woven scrim, a knit scrim, a weft-inserted warp knit scrim, a multi-axial warp knit scrim, a stitch-bonded scrim, or a cross-plied scrim. The scrim contains a plurality of yarns and the yarns may be adhesively or thermally bonded or may be unbonded to each other.
The scrim 100 may be any suitable scrim including any suitable lightweight woven, knit, or nonwoven fabric. Preferably, the scrim layer is a weft inserted warp knit scrim. A weft inserted warp knit scrim 100 contains a plurality of warp yarns 110, weft yarns 111, and stitching yarns 113. The stitching yarns 113 may have any suitable stitching pattern, including tricot stitches or pillar stitches, or other stitches. The weft yarns 111 can be laid in every course (every row of stitches from the stitching yarn), every second course (every second row of stitches from the stitching yarn), every third course (every third row of stitches from the stitching yarn) or more. How open or closed (how close together the yarns are within the scrim 100, is determined by the types and sizes of the yarns and the desired properties of the scrim 100 and magnetic scrim 10. One suitable scrim, not coated with the magnetic coating yet, is shown in Figure 2.
In one embodiment the scrim 100 comprises a plurality of yarns in a warp direction and a plurality of yarns in a weft direction defined to be approximately perpendicular to the warp direction. In another embodiment, at least a portion of the plurality of yarns in a weft direction are polyester texturized polyester yarns.
The yarns of the scrim can be any suitable yarns, include any suitable materials, structure, and thickness. The yarns making up the strip-shaped textile forming the strip-shaped substrate 200 may be any suitable yarn. "Yarn", in this application, as used herein includes a monofilament elongated body, a multifilament elongated body, ribbon, strip, fiber and tape. The term yarn includes a plurality of any one or combination of the above. The yarns may be of any suitable form such as spun staple yarn, monofilament, or multifilament, single component, bi-component, or multi-component, and have any suitable cross-section shape such as circular, multi-lobal, square or rectangular (tape), and oval. In one embodiment, the yarns are monofilament. In another embodiment, the yarns are multifilament. In another embodiment, the yarns contain mono and multifilaments. In one preferred embodiment, at least a portion of the yarns are texturized as this has been found to be beneficial in the coating process. In one embodiment, the weft yarns of the weft inserted warp yarn knit scrim are texturized.
Some suitable materials for the yarns include polyamide, aramid (including meta and para forms), rayon, PVA (polyvinyl alcohol), polyester, polyolefin, polyvinyl, nylon (including nylon 6, nylon 6,6, and nylon 4,6), polyethylene naphthalate (PEN), cotton, steel, carbon, fiberglass, steel, polyacrylic, polytrimethylene terephthalate (PTT), polycyclohexane dimethylene terephthalate (PCT), polybutylene terephthalate (PBT), PET modified with polyethylene glycol (PEG), polylactic acid (PLA), polytrimethylene terephthalate, nylons (including nylon 6 and nylon 6,6); regenerated cellulosics (such as rayon or Tencel); elastomeric materials such as spandex; high-performance fibers such as the polyaramids, and polyimides natural fibers such as cotton, linen, ramie, and hemp, proteinaceous materials such as silk, wool, and other animal hairs such as angora, alpaca, and vicuna, fiber reinforced polymers, thermosetting polymers, blends thereof, and mixtures thereof. In a preferred embodiment, the yarns comprise polyester yarns. In another embodiment, the yarns of the magnetic scrim 10 consist essentially of polyester yarns (defined to be mean at least 98% of the yarns are polyester yarns).
Referring back to Figure 1, the magnetic scrim 10 contains a magnetic coating 120. The magnetic coating 120 preferably covers at least a portion of yarns of the scrim 100. More preferably, the magnetic coating 120 covers essentially all of the surface area of the yarns in the scrim (defined as covering at least 95% of the surface area of the yarns). The magnetic coating 120 contains magnetic elements and a binder.
The magnetic elements 120 have a persistent magnetic field. As utilized herein, the term "persistent magnetic field" refers to a magnetic field that persists for an extended period of time, such as the magnetic field of a traditional permanent magnet. As is explained in detail below, the magnetic elements and magnetically responsive elements (such as some metals forming the inner walls of the mold) are magnetically attracted when in close proximity to each other. This magnetic attraction produces a force that draws and reversibly holds together the magnetic scrim 10 and the mold. The magnetic elements can be any suitable material that has a persistent magnetic field. For example, the magnetic elements can be permanent magnets made from materials such as iron, nickel, neodymium, cobalt, alloys of such metals (e.g., BaFe₃O₄, SrFe₃O₄, AlNiCo) and alloys of rare earth metals, such as NdFeB and CoSm.
The magnetic elements can have any suitable magnetic flux density. The magnetic flux density of the magnetic elements is one factor that will determine the strength of the attraction between the magnetic elements and the magnetically receptive elements. Therefore, the desired magnetic flux density of the magnetic elements will depend, at least in part, on the desired attractive force between the elements (and substrates attached to those elements). Preferably, the magnetic elements exhibit a magnetic flux density of about 50 gauss (G) or more (about 5 millitesla (mT) or more), about 100 G or more (about 10 mT or more), about 150 G or more (about 15 mT or more), or about 200 G or more (about 20 mT or more).
In a preferred embodiment, the magnetic coating preferably comprises a binder and magnetic elements. The binder can be any suitable binder that will adhere to the scrim and bind together the magnetic elements. Suitable binders include urethane binders, acrylic binders, silicone binders, thermoplastic binders, thermoset binders, cements, rubber, and geopolymers. The binder preferably remains flexible after curing. Thus, in a preferred embodiment, the binder preferably is selected from the group consisting of urethane binders, acrylic binders, silicone binders, and mixtures thereof.
The magnetic elements can have any suitable particle size. Preferably, the magnetic elements have a particle size of about 100 microns or less. More preferably, the magnetic elements have a particle size of about 50 microns or less. The particle size of the material can affect the magnetic characteristics exhibited by the magnetic elements.
The magnetic elements can be present in the magnetic coating in any suitable amount. The amount of magnetic elements present in the magnetic coating may depend upon several factors, such as the desired strength of the magnetic response and the type of magnetic elements used in the magnetic coating. Generally, in order to achieve a sufficiently strong magnetic response, the magnetic elements (which may be one type of element or mixtures of multiple types of elements) generally account for an appreciable percentage of the overall magnetic coating. Preferably, the magnetic elements are present in the magnetic coating in an amount of about 20 wt.% or more, about 30 wt.% or more, about 40 wt.% or more, about 50 wt.% or more, or about 60 wt.% or more of the coating. In another preferred embodiment, the magnetic elements are present in the magnetic coating in an amount of about 90 wt.% or less. In a more preferred embodiment, the magnetic elements is present in the magnetic coating in an amount of about 20 wt.% to about 90 wt.% (e.g., about 30 wt.% to about 90 wt.%, about 40 wt.% to about 90 wt.%, about 50 wt.% to about 90 wt.%, or about 60 wt.% to about 90 wt.%), about 30 wt.% to about 80 wt.%, about 30 wt.% to about 70 wt.%, or about 40 wt.% to about 60 wt.% of the coating. In another embodiment, the magnetic elements are present in the magnetic coating in an amount of at least about 40 wt. %, more preferably at least about 60 wt. %.
The magnetic coating can be applied to the scrim in any suitable amount. The amount of coating applied to the substrate will depend upon several factors, such as the magnetic strength of the magnetic elements, the amount of magnetic elements in the coating, and the desired magnetic flux density to be exhibited by the coating 120. Due to the amount of coating 120 applied to the scrim 100 and the high content of magnetic elements in the coating, the coating has a high areal density (weight per area). In one embodiment, the magnetic coating has an areal weight of at least about twice that of the areal density of the scrim. In another embodiment, the magnetic coating has an areal weight of at least about 2.5 times that of the areal density of the untreated scrim. In one embodiment, the magnetic coating has an areal weight of at least about 40 g/m². In another embodiment, the magnetic coating has an areal weight of between about 40 and 110 g/m².
The magnetic coating 120 is applied to the scrim 100 in any suitable manner. Preferably, the coating 120 is applied from an aqueous solution (or mixture or emulsion). An aqueous based system is preferred for environmental reasons. In other embodiments, the coating is solvent based. In one embodiment, the coating 120 is coated by gravure coating, knife coating, curtain coating, printing, and transfer coating.
Through deliberate design of the scrim construction, deliberate placement of the coating via a controlled coating process, or using both of these routes, a patterned deposition of the magnetic coating is possible. This patterned specificity can give a reduced final weight of the coated scrim, reduced cost, and/or design motifs that lend greater functionality to the final article.
The pattern, if employed, could be in any suitable pattern. The pattern may be continuous or discontinuous, regular and repeating or random. "Continuous" in this application means that from one edge of the textile to the other edge there is a path that contains the pattern and that at least some of the pattern areas are connected. Examples of continuous patterns include straight lines and a grid. "Discontinuous" in this application means that the areas of the pattern are discontinuous and not touching one another. In a discontinuous pattern, there is no path from one edge of the fabric to the other that contains the pattern. Examples of discontinuous patterns include dots. Regular or repeating patterns mean that the pattern has a repeating structure to it. The pattern may also be a random pattern where there is no repeat to the pattern. In a random pattern, it is preferred that the random pattern is also discontinuous, not continuous. The pattern may take any patterned form including indicia, geometric shapes or patterns, lines (straight and curved), grids, and text.
The scrim 100 may be coated with additional layers before or after the magnetic coating 120 is applied. In one embodiment, the scrim 100 is coated with PVC (polyvinyl chloride) before being coated with the magnetic coating 120. The PVC pre-coating step may provide stability to the loose knit, giving it a structure that may be easily handled without creating any distortion in the arrangement of the warp and weft yarns. The PVC coating may also keep the warp yarns tightly bundled and the textured weft yarns fixed in a bloomed, high surface-area form.
The tightness of the warp yarns compared to the open receptiveness of the weft yarns makes this scrim substrate highly biased towards the addition of any further chemical treatment being concentrated almost exclusively in and on the weft yarns. After the magnetic coating is applied, this pronounced difference may be quantified by bisecting the fabric into separate warp and weft components. An elemental analysis of these separated yarns, detecting and quantifying the elemental signature of the magnetic elements, shows >95% by weight of the magnetic elements localized on the weft yarns.
The mold is being magnetizable so that the magnetic scrim will be attracted and attach to the mold. In one embodiment, the interior surface of the mold contains iron, nickel, cobalt, an alloys of certain rare earth metals, or mixtures thereof. Preferably, the attraction between the magnetic scrim and mold is strong enough to hold the scrim in place until other materials are introduced into the mold.
The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (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 openended 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 invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention.

Claims

A magnetic scrim (10) comprising:
a scrim (100) comprising a plurality of yarns (110, 111, 113);

a magnetic coating (120) covering at least a portion of the yarns (110, 111, 113) of the scrim (100), wherein the magnetic coating (120) comprises magnetic elements and a binder, wherein the magnetic coating (120) is at least about 40% by weight magnetic elements, and wherein the magnetic coating (120) has an areal density of at least twice the areal density of the scrim (100).
The magnetic scrim (10) of claim 1, wherein the scrim (100) is a laid scrim or wherein the scrim (100) is a woven scrim.
The magnetic scrim (10) of claim 1, wherein the scrim (100) is a knit scrim, optionally
wherein the scrim (100) is a weft inserted warp knit scrim.
The magnetic scrim (10) of any one of the preceding claims, wherein the yarns (110, 111, 113) of the scrim (100) comprise polyester yarns, optionally
wherein at least a portion of the polyester yarns are texturized polyester yarns.
The magnetic scrim (10) of claim 1, wherein the scrim (100) comprises a plurality of yarns (110) in a warp direction and a plurality of yarns (111) in a weft direction defined to be approximately perpendicular to the warp direction.
The magnetic scrim (10) of claim 5, wherein at least a portion of the plurality of yarns (111) in a weft direction are polyester texturized polyester yarns and/or
further comprises a plurality of stitching yarns (113) in the warp direction.
The magnetic scrim (10) of any one of the preceding claims, wherein the magnetic elements comprise a material selected from the group consisting of iron, nickel, neodymium, and cobalt.
The magnetic scrim (10) of any one of the preceding claims, wherein the magnetic coating (120) has an areal density of at least 2.5 times the areal density of the scrim (100).
The magnetic scrim (10) of any one of the preceding claims, wherein the magnetic coating (120) is at least about 70% by weight magnetic elements.
The magnetic scrim (10) of any one of the preceding claims, wherein the magnetic scrim (10) further comprises a layer of PVC between the yarns (110, 111, 113) and the magnetic coating (120).
The magnetic scrim (10) of any one of the preceding claims, wherein the magnetic coating (120) is in a pattern.
The magnetic scrim (10) of any one of the preceding claims, wherein the magnetic elements have an average particle size range of between about 50 nm to 50 microns.
A method of manufacturing the magnetic scrim (10) of any one of the preceding claims, wherein the magnetic coating (120) is applied onto the scrim (100) from an aqueous mixture.
The method of claim 13, wherein the magnetic coating (120) is applied by coating.
The method of claim 14, wherein the magnetic coating (120) is applied by padding.