Patent Grant
7928025
The present invention relates to nonwoven multilayered fibrous batts, multi-density molded articles, such as but not limited to dual-density molded acoustical parts made with the batts, and processes for making the nonwoven multilayered fibrous batts.
Plastic parts are extensively used in vehicle production. Molded polymeric fiber composites in particular are used in vehicle parts, such as liners and trims. These polymeric fiber composites often have performance specifications, such as the specifications associated with acoustical insulation. In constructs, such as interior vehicle parts, the weight of the molded part directly impacts upon the weight of the vehicle and ultimate efficiency of vehicle manufacture and operation along with the resistance of the molded part to deform or “sag”. Some fabrications of molded fibrous composite parts in the past have required multiple step molding, non-reusable components, and/or non-uniform preforms. Multilayered batt products, for instance, are known in which the constituent layers have different densities as a premolded material.
U.S. Pat. No. 7,137,477 B2 discloses sound absorbers made by predensifying separate base materials containing textile fiber material and binder with heat and pressure, and superimposing the fabrics and bonding them by action of heat and pressure without an adhesive or needle punching. One of the base materials alternatively can be predensified before the other binder containing base material is pasted onto it in the mold and densified by heat and pressure.
U.S. Pat. No. 5,079,074 discloses a dual density non-woven batt comprised of first and second batt layers that are fused together, and the first batt layer has a relatively high density and the second batt layer has a relatively low density before and after compression molding.
U.S. Pat. No. RE 39,010 discloses a lightweight acoustical system comprising an impermeable layer and an underlayment having a specific airflow resistance between about 2000 and about 5000 mks Rayls, comprising first and second fibrous layers bonded with a semi-permeable layer.
U.S. Pat. No. 4,131,664 discloses a multi-density fibrous acoustical panel comprising fibrous pad formed by incorporating suitable binding agents and a coextensive impervious membrane or film disposed intermediate of the face surface thereof.
U.S. Pat. No. 5,387,382 discloses a method for manufacturing an interior fitted part for a motor vehicle in which a staple fiber formed fabric of drawn polyethylene terephthalate matrix component and a polyester-containing binding component is subjected to precompaction and at least once during the process to an annealing process before molding.
U.S. Pat. No. 5,817,408 discloses a sound insulation structure comprising a low density layer that is high in sound-absorption coefficient and a high density layer that is a low spring constant layer. Each of the low and high density layers comprises first and second layers solely made of a first fiber and a second fiber respectively.
U.S. Pat. Nos. 6,572,723 B1 and 6,669,265 B2 disclose multilayer liners and insulators and processes for forming them in which an insulator precursor is disclosed that is formed with a polymer based blanket material formed from two composite layers having significantly different softening points or temperatures that are adhesively attached.
The present invention is directed to nonwoven multilayered thermal compression moldable fibrous batts having substantially uniform density in which a significant density difference is producible between different fibrous batt layers upon thermal compression molding thereof. These batts can be used, for example, in the fabrication of multi-density thermal compression molded articles, such as acoustical parts, and in other acoustical applications. The present invention is also directed to processes for making the nonwoven multilayered fibrous batts with substantially uniform density and multi-density thermal compression molded products made therefrom.
In one embodiment, a nonwoven multilayered thermal compression moldable fibrous batt with substantially uniform density is provided comprising needle punched first and second fibrous batt layers comprising first and second discontinuous fibers in different proportions, wherein the melt point of the first discontinuous fiber is at least 30 degrees Celsius less than melt point of the second discontinuous fiber at the same ambient conditions. The first and second fibrous batt layers are united by a needle-punched intertufted region formed between opposite surfaces of the overlaid batt layers. The nonwoven multilayered thermal compression moldable fibrous batt has substantially uniform density. In various embodiments, the proportional amount of the first discontinuous fiber is at least 5% different in the first fibrous layer when compared to the second fibrous batt layer. For example, if the first fibrous layer contains 25 wt. % first discontinuous fiber based upon the weight of the layer, then the second fibrous batt layer contains at least 30 wt. % of the first fiber based upon the weight of the layer. The fibrous batt layers are needle punched together effective to form a consolidated batt having substantially uniform density throughout. In various embodiments, the first and second fibrous batt layers of the needle punched nonwoven multilayered compression moldable fibrous batt have respective densities that are within 12% of each other. A significant density difference is producible between the first and second fibrous batt layers of the nonwoven multilayered thermal compression moldable fibrous batt having substantially uniform density upon thermal compression molding thereof.
With fibrous batts of the present invention, it is possible to custom mold a wide variety of multi-density molded articles having desired acoustical properties from a single nonwoven fibrous multilayered thermal compression moldable batt of the present invention. By controlling molding thickness, for example, the nonwoven multilayered fibrous batts constructed in accordance with various embodiments of the present invention can be custom molded in a single molding step into multi-density parts tailored to provide different balances of sound transmission loss and sound absorption properties. Further, the nonwoven multilayered batts can be custom molded in a single molding step into a wide variety of multi-density parts without need for redesigning the thermal compression moldable fibrous batt of the invention. In addition, the first and second fibrous batt layers of the nonwoven multilayered fibrous thermal compression moldable batt can be consolidated into a unitary nonwoven multilayered batt structure without need of any extraneous adhesive binders, preform fusion bonding or annealing. The first and second types of fibers also can comprise substantially the same or different fiber finish. In addition, the constituent batt layers can be formed using only two different types of fibers. These features reduce production costs and complexity.
In another embodiment, a process is provided for making a nonwoven multilayered thermal compression moldable fibrous batt comprising forming first and second precursor web layers comprising blends of first and second discontinuous fibers in different proportional amounts, wherein the first discontinuous fiber melt point is at least 30 degrees Celsius less at ambient conditions than the melt point of the second discontinuous fiber. In further embodiments, first and second precursor web layers can comprise blends of first and second discontinuous fibers in different proportional amounts, wherein the first discontinuous fiber melt point is at least 60 degrees Celsius less, or is at least about 80 degrees Celsius less, or is at least 100 degrees Celsius less, at ambient conditions than the melt point of the second discontinuous fiber. The precursor web layers are overlaid to form a nonwoven precursor web that is needle punched from opposite sides to unite the first and second precursor web layers and to form an intertufted region between opposite sides of the needled punched nonwoven precursor web, thereby forming a nonwoven multilayered thermal compression moldable fibrous batt with substantially uniform density. The needle punching can be conducted simultaneously or sequentially in separate stages from opposite sides of the nonwoven precursor web. Needle penetration depths from both sides extend partially through the thickness of the nonwoven precursor web to form the intertufted region between the opposite outer surfaces of the web that joins the batt layers via an intertufted region. The needle punching equilibrates the densities of the precursor web layers and the density of the needled thermal compression moldable batt is made substantially uniform. In various embodiments, the first and second precursor web layers can have basis weights that differ by more than about 10%, or at least about 25% and no more than about 50% prior to the needle punching, and yet can be needle punched into a batt having substantially uniform density by methods of the present invention. A needle punched multilayered batt is provided in which the precursor layers do not need to be individually needle punched or molded before they are joined into a unitary fibrous batt. The fiber proportions used in the first and second fibrous batt layers can be similar to those described herein with respect to the precursor web layers.
The resulting needle punched nonwoven multilayered fibrous batt having uniform density can be thermal compression molded into various acoustical parts in a one-step molding process. The molded parts can be fabricated using batts according to embodiments of the present invention which are formed predominantly or essentially completely with recyclable, environmentally-friendly materials. Further, the nonwoven multilayered fibrous batts can be used, for example, as blanks for making vehicle liners that absorb sound and reduce noise in the interior compartment of a vehicle. Also, the nonwoven multilayered fibrous batts can be used to form lighter molded parts than traditional plastic parts, making it possible to manufacture more efficient vehicles that consume less fuel. Another advantage of the nonwoven multilayered fibrous batts of the present invention is that they can provide improved acoustic properties in parts molded to thinner thicknesses.
By adjusting molding thickness imparted to the molded part, for example, it is possible to custom form molded parts having significantly different balances of acoustical properties from the same or similar starting multilayered fibrous batts of the present invention. In one embodiment, a dual density molded article, when made from the same starting multilayered batt material according to embodiments herein, exhibits a different balance of sound absorption and sound transmission loss properties, depending on the molded part thickness that is formed. For example, at a molded thickness of about 9 mm to about 11 mm, a dual density molded part made from the nonwoven multilayered batts of the invention can exhibit a sound transmission loss of about 1 to about 5 (dB), a primary absorption peak in the range of about 0.65 to about 0.75 between 4000 to 5000 Hz and an airflow resistance of about 200 Rayls to about 450 Rayls. By comparison, a dual density molded part made from the same multilayered fibrous batt at a molded thickness of about 3 mm to about 7 mm, can exhibit a sound transmission loss of about 10 to about 15 (dB), a primary absorption peak in the range of about 0.5 to about 0.6 between 2500 to 5000 Hz and an airflow resistance of about 2000 Rayls to about 4500 Rayls. Thus, the nonwoven multilayered batt is a highly versatile starting material allowing a molder to mold the starting batt to a thickness providing the best match with the specified or desired balance of acoustical properties for the molded part or component.
In further various embodiments, the first fibrous batt layer comprises at least 1% and not greater than 25% by weight of the layer of lower melt point first discontinuous fibers and the second fibrous batt layer comprises at least 30% by weight of the second layer of first discontinuous fibers. The first fibrous batt layer also can be formed with at least 1% and not greater than 25% by weight of the layer polyolefin fibers and at least 75% and not greater than 99% by weight polyester fibers; and the second fibrous batt layer can comprise at least 30% by weight of the second layer polyolefin fibers and up to 70% by weight of the second layer polyester fibers. In further various embodiments, the proportion of the lower melt first discontinuous fiber in the first batt layer is different from its proportion in the second batt layer by at least 10%, or at least 15%, or at least 20%, by weight. In another further embodiment, the first and second fibrous batt layers of the nonwoven thermal compression moldable multilayered fibrous batt have respective densities that are within 10%, or within 5%, or within 1% (in units of mass/volume), of one another. In another embodiment, at least a 12%, or 18%, or 24%, or 30%, density difference is producible in the first and second batt layers upon thermal compression molding of the nonwoven multilayered fibrous batt.
Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are only intended to provide a further explanation of the present invention, as claimed.
As used herein, “density” refers to fabric density in units of mass/volume, such as g/cm3. As used herein, “multi-density” or “multi-densities” refers to dual-density, tri-density, and/or quad-density (i.e., 2, 3, and/or 4 density) regions or layers.
As used herein, “basis weight” refers to fabric weight defined in terms of mass/surface area, such as g/m2 (gsm).
As used herein, “substantially uniform density” when used to refer to a nonwoven layer or batt density (mass/volume), refers to a 12% or less difference in density.
As used herein, “significantly more dense” refers to greater than 12% more dense. As used herein, “significant density difference” refers to a density difference that is greater than 12%. For example, the term “significant density difference” when used to refer to a nonwoven density of two different batt regions or layers means that the two batt layers have a greater than 12% difference in density relative to each other. “Density difference” percentage, with respect to two molded or unmolded fibrous layers, is determined as an absolute value of the difference in the batt layer densities divided by the density of the denser batt layer, then multiplied by 100 (e.g., density difference=[(denser batt layer 1 density−less dense batt layer 2 density)/denser batt layer 1 density]×100).
As used herein, an “intertufted region” refers to a region in a batt between opposite sides of the multilayered nonwoven batt where two nonwoven fibrous batt layers are joined by needle punching of the two nonwoven fibrous batt layers from opposite sides of and partially through the thickness of the batt wherein the tufting from opposite directions overlaps at the intertufted region.
As used herein, “nonwoven multilayered fibrous batt” refers to a unitary, non-laminar homogenous fibrous structure made from plural “layers” that are fibrous and formed of different compositional homogenous fiber blends, and not discrete fiber layers laminated together.
As used herein, “melt” or “melting” refers to the transformation of the fiber in which the polymer softens and becomes sufficiently tacky to cling to other fibers within which it comes in contact, including other fibers having its same characteristics and adjacent fibers having a higher melting temperature. Melting of the fibers in the batt layers causes them to fuse to themselves and to other fibers in the batt which have not melted.
For purposes herein, acoustical properties of molded articles, inclusive of normal incidence sound absorption and normal incidence transmission loss, are determined by samples tested according to ASTM E1050-98. Airflow resistance of the molded samples, which is defined herein in units of Rayls, are determined using a C522 Gas Permeameter that measures pressure difference and flow rate in the ranges recommended by ASTM standard C522-03.
As used herein, “free of fusion prebonding” refers to a multilayered fibrous batt that has not been thermally tackified or fusion bonded prior to molding.
As used herein, “same ambient conditions” refers to same environmental conditions, such as atmospheric humidity, pressure, composition and temperature. Same ambient conditions can encompass, for example, an atmospheric air pressure value of about 1 bar and an ambient room temperature value of about 15-30 degrees Celsius.
As used herein, “different proportional amounts” refers to at least two components present in different proportions by weight. For example, a 10% proportional amount defined with respect to a fiber component A of a fiber blend or mixture containing fiber components A and B refers to a value of A/(A+B) that equals 0.1 or 10%. Proportional amounts are defined gravimetrically for purposes herein.
As used herein, “acoustical” refers to an item that is sound absorbing and that reduces sound transmission loss.
Unless indicated otherwise, “polyester(s)” as used herein refers to a polyalkylene terephthalate, such as polyethylene terephthalate (“PET”). Unless indicated otherwise, “co-polyester(s)” as used herein refers to a chemically modified polyester, a homogeneously mixed blend of polyesters, and/or an extruded blend of polyesters. As used herein, “low melt co-polyester” refers to a co-polyester that has a melt point of at least 100 degrees Celsius and not greater than 180 degrees Celsius. Unless indicated otherwise, “high melt co-polyester” as used herein refers to a co-polyester that has a melt point of greater than 180 degrees Celsius.
Unless indicated otherwise, the term “polyolefin” refers to a polymer having repeat units comprised of carbon and hydrogen atoms without ring structures. Polyalkylenes and acyclic polyalkylene copolymers are illustrative.
As used herein, “comprising” is synonymous with “including,” “containing,” “having”, or “characterized by,” and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps.
For purposes herein, “consisting essentially of”, restricts to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the invention.
As used herein, “consisting of” excludes any element, step, or ingredient not specified.
The present invention relates to thermal compression moldable needle-punched nonwoven multilayered fibrous batt materials having substantially uniform density that contain different fiber compositions in different layers thereof. The nonwoven multilayered fibrous materials can be used to make multi-density molded parts, such as acoustical components, in a single molding step. The fiber compositions used to construct the constituent fibrous layers of the batt can comprise blends of different fibers having different melt properties. Needle punching conducted from opposite sides of the construct can be used to consolidate the different fibrous layers into a unitary batt structure having substantially uniform density. By varying the proportions of the different fibers having different melt properties in different layers of the batt, the batt layers can be induced to mold to different densities relative to each other. In addition, the nonwoven multilayered fibrous materials having substantially uniform density permit custom molding of different parts having different acoustical characteristics using the same or similar starting batt material. Materials and articles of the invention have improved properties and performance, such as measured by a variety of tests including exemplary ones described herein.
Referring to the drawings and in particular
In various embodiments, the batt layers (e.g., 11 and 12) are formed from fiber blends of two or more different types of staple fibers, including relatively high melting temperature (“high melt”) staple fibers, and relatively low melting temperature (“low melt”) polymeric staple fibers. The difference in melt temperatures of the fibers makes it possible to heat the combinations of fibers present in a nonwoven fabric placed in a mold at a temperature high enough to soften the low melt fibers but not the high melt fibers. When heated in such a manner, the low melt fibers can form bonds and serve to bind together the fibers and provide the desired stiffness and shape retention characteristics. In various embodiments, the low melt staple fibers have a melting temperature that is significantly less or lower in value at ambient conditions than the melt point or melting temperature of the high melt staple fibers. The melting temperatures of the first and second fibers preferably differ sufficiently that molding conditions can be reliably controlled to selectively induce softening of only the first fibers within a fibrous batt comprised of the first and second fibers without softening the second fibers. The high melt fibers preferably comprise the major fibrous component of each batt blend, and they may be blended with one or more types of low melt polymeric fibers, such as olefin polymers and copolymers, and other suitable thermoplastic fibers.
As indicated, there is a significant difference between the melting points of the low melt thermoplastic fibers and the high melt fibers. In various embodiments, the low and high melt fibers have melt temperatures that differ by at least about 30° C., at least about 60° C., or at least about 80° C., or at least about 100° C. For example, as one illustrative non-limiting example, the low melt fiber could be polypropylene fibers having a melting temperature of about 153-158° C. and the high melt fibers could be PET fibers having a melting temperature of about 245-255° C. Other melt temperature spreads also may be used. Discontinuous and staple length polymer fibers can be provided by a conventional meltblown process, fiber/filament chopping, and so forth. The staple length and diameter of each type of fiber used in the batt layers is not particularly limited as long as the fiber is amenable to being blended and formed into homogenous fiber blends. In various embodiments, staple lengths can be used ranging from about 10 mm to about 105 mm, or more preferably about 35 mm to about 76 mm. Other staple lengths also may be used. In addition, a mixture of staple fibers having different lengths can be used for either one or both of the types of the fibers used in a fiber blend. Fiber denier can be selected from a wide range of deniers. In various embodiments, the fiber denier can be in a range of about 1 to about 20 denier per filament, or about 1.5 to about 8 denier per filament (dpf), or other deniers can be used.
The presence of small amounts of continuous filaments in the batts of this invention is not categorically excluded, although in general should be minimized to amounts not interfering with fiber treatments, for example, such as carding, crosslapping, and/or needle-punching. The low and high melt fibers can have the same or different finish. The process of the invention is not dependent on this feature. If present, a standard low fume fiber finish can be used. The fibers may be suitably colored with the use of dyes, or by the incorporation of pigments into the polymer, as is conventional.
Non-limiting examples of the chemical types of low melt fibers include polypropylenes (e.g., isotactic, amorphous, etc.), polyethylenes (e.g., low-density, high-density, etc.), polybutylene, ethylene/vinyl acetate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, polystyrene, polyvinyl chloride, polyvinylidene chloride, aliphatic polyamides (PA-11), polyurethanes, low melt co-polyesters, such as, but not limited to, PETG (i.e., PET with the terephthalic acid replaced with ethylene glycol), and blends, alloys or combinations thereof. In various embodiments, the preferred low melt fibers for use in this invention can be polypropylene fibers, which are typically blended with high melt polyester fibers. Optionally, other low melt fibers may be added to each blend. In a preferred construction the polypropylene fibers are the predominant or sole low melt fiber used in each batt layer. Suitable high melt fibers include, for example, polyesters (polyalkylene terephthalates such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT)), high melt co-polyesters, aromatic polyamides (poly m-phenylene isophthalamide (PMPI), poly p-phenylene terephthalamide (PPPT)), aliphatic polyamides (PA-4, PA-6, PA-7, PA-6,6), polycarbonate, polyacrylonitrile, polyphenylene sulfide, polyvinyl alcohol, natural fibers, such as but not limited to cotton, and blends, alloys or combinations thereof. It will be appreciated that the above illustrations of low melt and high melt types of fibers are merely exemplary, and that fibers identified above also could be used as the other type of fiber, depending on the different companion fibers and associated melting properties used in the mixture therewith. For example, it will be appreciated that compositions of the fibers could be manipulated to change (reverse) the low melt and high melt classifications of a particular combination of different types of fibers. If low melt co-polyester and PET, are used, for example, then the trimmings generated from the molding process could be recycled back into the PET fibers and reused in another multilayered fibrous batt.
In various embodiments, preferred high melt fibers are polyester fibers. In various embodiments, homopolymer fibers are used. Bicomponent (e.g., sheath-core) and other composite fiber constructions also may be used, where the diverse polymer constituents of such composite fibers may be all low melt, all high melt, or both types, depending on melting temperature(s) of other fibers co-present in the batt layer. Natural or inorganic fibers optionally may be included in the batt layers, such as but not limited to in minor amounts. In a preferred embodiment it is desirable to maximize the amount of re-usable and recyclable polymeric content of the batt layers. In a preferred embodiment, thermoplastic fibers are used for both the low melt and high melt fiber content of the batt constructed in accordance with the present teachings.
In various embodiments, one of the batt layers of the nonwoven multilayered fibrous batt, such as one of batt layers 11 and 12 of batt 10 illustrated in
In one preferred dual-density embodiment, one batt layer comprises at least 1% and no greater than 25% by weight of this batt layer polyolefin fibers and at least 75% and no greater than 99% by weight of this batt layer polyester fibers, and the other batt layer comprises at least 30% and no greater than 90% by weight of this batt layer polyolefin fibers and at least 10% and no greater than 70% by weight of this batt layer polyester fibers. In another preferred embodiment, one of the batt layers comprises at least 5% and no greater than 25% by weight of this batt layer polypropylene fibers and at least 75% and no greater than 95% by weight of this batt layer polyester fibers, and the other batt layer comprises at least 30% and no greater than 60% by weight of this batt layer polypropylene fibers and at least 40% and no greater than 70% by weight of this batt layer polyester fibers.
In yet another embodiment, other multi-density embodiments can be provided. For example, the batt 10 can be assembled with three or four batt layers having respective fiber mix ratios in which the low melt fiber content differs by at least 5% between each directly adjoining pair of the batt layers in the construction. A three batt layer construction could comprise, for example, batt layers containing 25%, 30%, and 35% low melt fiber, respectively, or 20%, 40%, and 30%, respectively, and so forth. For instance, a four batt layer construction could comprise batt layers containing 15%, 30%, 45% and 60% low melt fiber, respectively, or, 20%, 50%, 40%, and 30% low melt fiber, respectively, and so forth. As illustrated, while satisfying the at least 5% difference in low melt fiber content in adjoining batt layers, the amount of differences in low melt fiber content provided between each pairing of adjacent batt layers in a batt construction also can be uniform or non-uniform, and/or may or may not progressively increase/decrease, from layer to layer through the stack of batt layers of the batt. Other fiber combinations also may be used within the general requirements described herein.
Referring to
Still referring to
As illustrated in
Although illustrated as constructed from two precursor web layers 11a and 12a, it will be appreciated that precursor web 1 also optionally can be assembled having three or four precursor web layers. For example, one or both of the additional precursor web layers 13a and 14a, indicated by hatched lines in
Illustrations of several fiber mixtures precursor web build-ups in accordance with non-limiting embodiments of the present invention are described below as Precursor Web Constructs 1, 2 and 3.
Precursor Web Construct 1: 1000 gsm precursor web layer (10% 12-20 dpf polypropylene (PP)/90% 6 dpf×3 inch regenerated polyethylene terephthalate (PET) over a 800 gsm precursor web layer (50% 12-20 dpf PP/50% 6 dpf×3 inch regenerated PET).
Precursor Web Construct 2: 1000 gsm precursor web layer (10% 12-20 dpf PP/90% 6 dpf×3 inch regenerated PET) over a 800 gsm precursor web layer (35% 12-20 dpf PP/65% 6 dpf×3 inch regenerated PET).
Precursor Web Construct 3: 1000 gsm precursor web layer (25% 12-20 dpf PP/75% 6 dpf×3 inch regenerated PET) over a 800 gsm precursor web layer (50% 12-20 dpf PP/50% 6 dpf×3 inch regenerated PET). In these illustrative constructs 1-3, polypropylene represents the low melt fiber and a regenerated PET represents the high melt fiber. In addition, for constructs 1-3, for example, the polypropylene fibers and regenerated PET fibers can have the same, different, or mixed colors.
Layers 11a and 12a of nonwoven precursor web 1 are unneedled precursors of fibrous batt layers 11 and 12, respectively, of nonwoven multilayered thermal compression moldable fibrous batt 10. Fibrous batt 10 is formed by a needle-punching treatment applied to nonwoven precursor web 1. The needle punching treatment is discussed in more detail later herein. At this stage of processing, the nonwoven precursor web 1 is not a consolidated structure. In various embodiments, web layers 11a and 12a (and the optionally additional one or two web layers) are formed in substantially similar or different thicknesses at this stage of processing. The thicknesses of web layers 11a and 12a (and the optionally additional one or two web layers) are not necessarily limited other than by practical considerations. In various embodiments, the carded web layers 11a and 12a (and the optionally additional one or two web layers) each can have a thickness, for example, of about 2.5 cm to about 65 cm, or about 10 cm to about 40 cm, or other thickness values can be used. In various embodiments, the basis weights for web layers 11a and 12a are in the range of about 500 gsm to about 1500 gsm, or about 600 gsm to about 1200 gsm. It will be understood that the basis weight of the layers is essentially the same before and after needle punching.
In various embodiments, the web layers 11a and 12a (and the optionally additional one or two web layers) of the nonwoven precursor web 1 can have the same or different basis weights defined in terms of mass per unit area (e.g., g/m2 or gsm). The precursor web layer also can have the same or different densities defined as mass per unit volume (e.g., g/cm3). In various embodiments, a density difference can exist between the two (or more) unneedled web layers. In various embodiments, this density difference between the two (or more) unneedled web layers can be at least 2%, or at least 5%, or at least 10%.
As illustrated herein, multiple cards supplied by dedicated fiber mixers can be used to form multilayered nonwoven precursor web 1 comprising blends of different low melt/high melt fibers at different thickness regions thereof. The carding machines can be conventional carding machines, adapted for this process. Commercial carding machines and systems are available, for example, from Erko-Triitzschler (Dülman, Germany). It will be appreciated that other web forming devices may be adapted to incrementally build-up precursor web layers comprised of the different fiber mixtures illustrated herein. In addition, nonwoven precursor web 1 optionally may be fed to drafting means (not shown), such as conventional nonwoven web drafting means used to draft, or stretch, the batt in the warp or longitudinal direction.
For example, and as also illustrated in
As illustrated in
As illustrated in
As generally known in the art, the needles in a needle board can be aligned with holes in a stripper plate and bedplate (not shown) through which the object to be needled passes. The reciprocating motion of the needle board forces the needles in and out of the holes in the stripper and bedplate and thus in and out of the object to be needled since the object to be needled is positioned between the stripper plate and the bedplate. The needles are set to reciprocate partially through the fabric. Barbed needles generally have long blades covered with small barbs towards one end which carry fibers from a horizontal position within a web into a more vertical position during the stroke. Barbs on the needles catch the fibers, and push some of them vertically towards the opposite side of the web (i.e., in the “z” direction), and release them as the needle is withdrawn. One directional needling allows the needle to exit the fibers cleanly before re-penetrating the web again. Through repeated strokes or punches into the web, the web becomes more densified in the punched regions forming a fibrous batt. The barb angle can be selected over a wide range. The barb angle can be, for example, within about 25°, or within about 5°, with respect to vertical, although other barb angles can be used.
Dilo needle looms, such as commercially available from Oskar Dilo Maschinenfabrik KG (Eberbach, Germany), or other commercially available needle looms, can be adapted for use in the needling process of the present invention. One exemplary Dilo needle loom that can be used is Dilo Model Di-loom DBF VE-2. Hyperpunch systems where the needles follow an elliptical path rather than straight up and down also may be used.
In various embodiments, a target density (e.g., in g/cm3) for the overall needle punched batt is selected prior to performing needle punching. As discussed, needle punching precursor webs according to embodiments of the present invention provides a consolidated batt product having substantially uniform density throughout. Based on the selected target density of the needled batt product, and known compositions and basis weights of each constituent precursor web layer of the unneedled nonwoven precursor web, the needles in the needle looms can be set to get the web or fabric to a compacted thickness by needle punching that will arrive or closely approach the target density (e.g., within 3%).
The basis weight of each precursor web layer will remain substantially constant through the needle punching operation to form fibrous batt layers, as the number of the fibers that are partly tufted from opposite directions into the adjoining batt layer is relatively small on a mass basis.
The density (“d”) of a fibrous batt or layer in units mass/volume (e.g., g/cm3) can be determined, for example, by multiplying a known basis weight (“BW”) value of the batt or batt layer times the reciprocal of the thickness (“1/T”) thereof. For example, this relationship can be represented by the formula: d=BW/T. Thus, batt or batt layer density (in units of g/cm3) will equal the basis weight (in g/cm2)×1/thickness (in cm). Also, if a target density is a preselected value for a batt, it is also possible to use the above formula to calculate the thickness of a batt layer having a known constant basis weight value that is needed to yield the selected density (i.e., T=BW/d). Thus, for example, if an overall consolidated (needled) batt density of 0.042 g/cm3 was selected as the target density of the needled consolidated batt, and the basis weight of one of the unneedled precursor web layers is 1000 g/m2 or gsm (0.1 g/cm2), and the other unneedled precursor layer is 800 g/m2 (0.08 g/cm2), it can be calculated that the precursor web layers should be needled to respective thicknesses of about 2.4 cm thick, and about 1.9 cm thick, to arrive at the target density (i.e., thickness=basis weight/target density). For purposes of this non-limiting illustration, the needled batt thus would have an overall (total) thickness of about 4.3 cm.
As discussed, needle punching parameters are selected to provide the needed level of compaction of the respective batt layers and form an intertufted region. In various embodiments, and depending on the factors discussed above, needle punching consolidation of the nonwoven precursor web into the multilayered fibrous batt can reduce the precursor web thickness by a significant total factor, such as exceeding 10:1 or more, although not limited thereto.
Factors that are controlled in the needle punching operation that effect the compaction imparted to the precursor web and intertuft region forming are needle type, maximum barb penetration depth and punch density received from each side of the precursor web. The extent of mechanical compaction imparted to either side region of the precursor web is effected by the interplay of these parameters with respect to a particular fibrous workpiece. Important needle type features in this regard include, for example, the blade shape, barb shape, barb spacing, and needle length. The needle punching is controlled such that the needles partially, but not completely, extend through the thickness of the precursor web when received from opposite sides thereof. Punch density can be determined, for example, by multiplying the needle board revolutions per minute times needle density defined as needles/meter. Needles and punch densities can be selected in combinations to arrive at level of mechanical compaction imparted into each side of the precursor web that provides batt layer densities that are substantially the same throughout the batt. In addition, the needling from opposite sides of the fabric must provide an intertufted region within the batt sufficient to join the precursor web layers together to provide a unitary consolidated batt product.
Referring to
In one illustration of
The resulting needle-punched fibrous batt is made from at least two fibrous batt layers having substantially the same density while containing different proportions of a low melt fiber. In one embodiment, the differentially needle punched batt layers each have similar densities, such as within 10%, or within 5%, or within 1% (in units of mass/volume such as g/cm3), of one another in the nonwoven multilayered fibrous batt.
The mechanical needling, such as shown in
As illustrated in
A three dimensional molded article can be subsequently formed in a molding step 30 (e.g., thermal compression molding) from the unique nonwoven multilayered fibrous batt 10 having substantially uniform density throughout. In various embodiments, the nonwoven multilayered fibrous batt generally can be heated at molders with time and temperature sufficient to make the low melt fiber component melt and flow in the adjoining batt layers without exceeding the melting temperature of the other high melt component fiber of the same layers. The batt 10 can be readily thermal compression molded into complex shapes that develop stiffness and shape-retentive characteristics. In various embodiments, the result is a dual density batt, where each of the two batt layers has a homogeneous structure. A higher percentage of low melt fibers, such as may be provided in the bottom batt layer 12 causes more binding of the fibers together when the low melt fibers melt during thermal compression molding than occurs in the top batt layer 11, for example, containing a smaller proportion of the low melt fibers. That is to say, the fibrous batt layer that contains more low melt fiber molds “more densely” than the other fibrous batt layer that contains relatively less low melt fiber and thus molds more “lofty”. In various embodiments, at least a 12%, or 18%, or 24%, or 30%, density difference is producible in the different batt layers upon thermal compression molding of the nonwoven multilayered fibrous batt. In various embodiments, the low melt fiber component can be the primary or sole binder component present in molding and consolidating the batt into a unitary molded structure. In various embodiments, the first and second precursor web layers of the batt each contain less than 5% by weight of total added binder resin added in addition to the first and second discontinuous fiber content, e.g., less than 5% by weight thermosettable binder material added in addition to the first and second discontinuous fiber content thereof. Usage amounts of thermosettable binders, e.g., those that can be problematic for recycling, can be reduced or eliminated.
Thermal compression molding basically can involve the pressing of a deformable material between two halves of a heated mold. Compression molding molds can be used on compression presses, which may be downstroking or upstroking types, and can be hydraulically operated (clamping ram or cylinder), although not limited thereto. Positive or semi-positive molds, for example, can be used to mold the nonwoven fibrous batts of the present invention. As known in the molding industry, part dimensions in the mold closing direction are directly dependent on the amount of material in the charge, as well as possible leakage or flash. Compression molding temperatures, pressures and setting times can vary depending on the batt fiber composition, desired part thickness, part shape, and so forth. Gap settings can be provided sufficient to allow the bottom layer of the nonwoven multilayered batt to densify while maintaining loft in the top layer, or vice versa.
In various embodiments, multi-density acoustical articles can be provided which include, but are not limited to, materials and parts used in systems for absorbing soundwaves and/or reducing sound transmission loss to control the acoustics in a vehicle. Referring to
Referring to
In various embodiments, dual density molded articles suitable for vehicle components can have an overall basis weight of about 1000 gsm to about 2400 gsm, or particularly about 1200 to about 2000 gsm. Molded products with other basis weights also can be provided. In various embodiments, a dual density molded article is formed from the batt comprising a molded first fibrous batt layer having a density of at least 0.3 grams/cm3 and not greater than 3 grams/cm3, and a second nonwoven fabric batt layer having a density of at least 3 grams/cm3 and not greater than 15 grams/cm3, wherein the second fibrous batt layer contains the low melt fiber in greater proportion than the first fibrous batt layer.
The needle punched multilayered fibrous batts also can be used in other molded article applications, such as, for example, non-vehicular sound barriers and/or sound absorbers, structural panels, pet beds, and so forth. These molded parts also can be formed in dual density formats in a single molding step using needle punched batts of the present invention.
In various embodiments, acoustical molded articles can be provided with needle punched multilayered fibrous batts of the present invention in which desired sound absorption and/or sound transmission loss characteristics of the molded articles can be dialed in using a similar starting batt material. For example, by merely adjusting molded part thickness, it is observed that molded parts can be provided using similar nonwoven multilayered batts of the present invention, which have a significantly different balance of sound absorption and sound transmission loss properties. In various embodiments, the dual density molded article generally has an airflow resistance of at least 200 Rayls and not greater than 5,000 Rayls. In other various embodiments, dual density molded articles having different balances of acoustical properties can be provided from the same starting multilayered batt material according to embodiments herein. For example, using a similar starting batt material made in accordance with the present invention, at a molded thickness of about 9 mm to about 11 mm, the resulting molded part can exhibit a sound transmission loss of about 1 to about 5 (dB), a primary absorption peak in the range of about 0.65 to about 0.75 between 4000 to 5000 Hz and an airflow resistance of about 200 Rayls to about 450 Rayls, while, at a molded thickness of about 3 mm to about 7 mm, the resulting molded part made from the same starting batt material can exhibit a sound transmission loss of about 10 to about 15 (dB), a primary absorption peak in the range of about 0.5 to about 0.6 between 2500 to 5000 Hz and an airflow resistance of about 2,000 Rayls to about 4,500 Rayls. As generally understood, air flow resistance directly affects the sound absorption and sound-transmitting characteristics of an acoustical material. Sound absorption acoustical properties of a molded article thus can be correlated to airflow resistance.
The present invention will be further clarified by the following examples, which are intended to be exemplary of the present invention. Unless indicated otherwise, all amounts, percentages, ratios and the like used herein are by weight.
A multilayered fibrous batt material was prepared in accordance with teachings herein which was prepared by needle punching a nonwoven precursor web having the following precursor web layer compositions:
a 1000 gsm upper precursor web layer (10% mixed colored 12-20 dpf polypropylene (PP)/90% 6 dpf×3 inch regenerated polyethylene terephthalate (PET) over a 800 gsm lower precursor web layer (50% mixed colored 12-20 dpf PP/50% 6 dpf×3 inch regenerated PET). The polypropylene fibers can be obtained, for example, from any one of a number of vendors, such as Plastex (Sumter, S.C.). The regenerated PET can be obtained, for example, from any one of a number of vendors, such as under the tradename Black PET Regenerated from Barnet USA (Arcadia, S.C.).
A nonwoven precursor web was formed with multiple cards and crosslapping as described above. The precursor web was reduced in thickness to about 2 inches using a V-shape compression belt that fed a multi-staged Fehrer AG (of Germany) needle loom system (Fehrer machine models NL28 and NL26). A down-stroking, relatively lower density needle-punch was applied to the batt or web layer, i.e., the batt side containing the lower proportion of polypropylene fiber, and then, the opposite side of the batt received an up-stroking, higher density needle-punch. In this regard, the needle looms were arranged such that the upper, higher PP content precursor web layer received a needle-punching density of about 3000 strokes/meter (1500 pins/meter, 850 rpm, 70 mm max. stroke distance) using Foster CBA type needles, and the other lower precursor web layer received a needle-punching density of about 5000 strokes/meter (3000 pins/meter, 950 rpm, 60 mm max. Stroke distance) using Foster CBA type needles.
The resulting needle punched batt material was used in forming multiple molded articles (“variants”), in which molded part thickness was a variable that was investigated. The mold used comprised a 2008 model passenger vehicle trunk side mold. The molding conditions were convection heating to a core temperature of 200° C. then molded in chilled mold set at 40° C. for 60 seconds. Gap settings were set sufficient to allow the bottom layer to densify while maintaining some loft in the top layer in a one-step molding step. Acoustical properties of the variants were then determined and compared.
Test Procedures:
Sound absorption and sound transmission of the molded samples 1 and 2 were tested per ASTM E 1050-98 in a lab at room temperature, approximately 23° C., at 1 atmospheric pressure, and 50% relative humidity. The sample was mounted with the sound source coming toward the denser side of the sample, (i.e., denser side of the samples faced the noise source). The test was carried from about 500 Hz to about 5500 Hz. The sound transmission loss results are shown in
Airflow resistance of the molded samples was determined using a C522 Gas Permeameter that measures pressure difference and flow rate in the ranges recommended by ASTM standard C522-03. Resistance characteristics are computed from measured values. A number of characteristics of the test material, including specific air flow resistance (rayl), and airflow resistivity (rayl/m) were determined. The airflow resistance test results are shown in Table 1.
Test Results Discussion:
As shown in
With regard to the sound absorption data, again using the same variant, the absorption properties were modified from a 0.5-0.6 absorption of sound over a broad spectrum (from 2500 to 5000 Hz.) to a primary absorption peak of 0.7 between 4000-5000 Hz. The airflow resistance measurements also showed that one mold variant could be custom molded, such as by changing molded part thickness, to provide a dual density product having a significantly different balance of sound absorption and sound transmission loss characteristics.
From the foregoing, it will be observed that modifications and variations can be affected without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no specific limitation with respect to the specific embodiments illustrated herein is intended or should be inferred. This invention can, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2059132 | McDermott | Oct 1935 | A |
| 4131664 | Flowers et al. | Dec 1978 | A |
| 4522876 | Hiers | Jun 1985 | A |
| 4568581 | Peoples, Jr. | Feb 1986 | A |
| 4935295 | Serafini | Jun 1990 | A |
| 4966799 | Lucca et al. | Oct 1990 | A |
| 5079074 | Steagall et al. | Jan 1992 | A |
| 5132166 | Adams et al. | Jul 1992 | A |
| 5387382 | Fottinger et al. | Feb 1995 | A |
| 5436046 | Sakamoto | Jul 1995 | A |
| 5741380 | Hoyle et al. | Apr 1998 | A |
| 5817408 | Orimo et al. | Oct 1998 | A |
| 5824246 | Reetz | Oct 1998 | A |
| 5841081 | Thompson et al. | Nov 1998 | A |
| 5853510 | Lawson | Dec 1998 | A |
| 6048809 | Brow et al. | Apr 2000 | A |
| 6296076 | Hiers et al. | Oct 2001 | B1 |
| 6572723 | Tilton et al. | Jun 2003 | B1 |
| 6669265 | Tilton et al. | Dec 2003 | B2 |
| 6726980 | Staelgraeve et al. | Apr 2004 | B2 |
| 6827894 | Tilton et al. | Dec 2004 | B1 |
| 6955845 | Poole et al. | Oct 2005 | B1 |
| RE39010 | Gish et al. | Mar 2006 | E |
| 7011181 | Albin, Jr. | Mar 2006 | B2 |
| 7055649 | Tompson et al. | Jun 2006 | B2 |
| 7137477 | Keller et al. | Nov 2006 | B2 |
| 7157137 | Wenstrup | Jan 2007 | B2 |
| 7166547 | Tilton et al. | Jan 2007 | B2 |
| 7182172 | Albin, Jr. | Feb 2007 | B2 |
| 20020137421 | Desroches et al. | Sep 2002 | A1 |
| 20030124940 | Michael | Jul 2003 | A1 |
| 20040231914 | Thompson et al. | Nov 2004 | A1 |
| Number | Date | Country |
|---|---|---|
| 0717161 | Mar 2002 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20100081354 A1 | Apr 2010 | US |
