DE69409115T2 - NEW FIBER FILLING MATERIAL - Google Patents

Description

The invention relates to improvements in and relating to bonded polyester fiberfill webs, sometimes referred to as nonwoven mats, particularly to these improved webs having desirable aesthetic and performance properties, and to articles incorporating these improved webs.

In parent U.S. Patent No. 5,225,242 and in WO 93/11292, the disclosures of which are incorporated herein by reference, we created a process for making a bonded web comprising forming a mixture of polyester fiberfill in an amount of from about 70 to about 96% by weight intimately mixed with a binder fiber, preferably a bicomponent binder fiber, with binder material having a melting point lower than the softening point of the polyester fiberfill in an amount of from about 4 to about 30% by weight, forming a continuous web from the mixture, the web having a top and a bottom surface, passing the web through one or more spray zones whereby both sides of the web are sprayed with resin in a total amount of from about 10 to about 30% by weight of the sprayed web, including the resin, wherein the resin is selected so that after curing a cured resin having a glass transition temperature (Tg) of about 0º C or less is produced, heating the sprayed web in an oven to cure the resin and soften the bonding material, thereafter hot rolling the heated web to achieve intimate contact between the resin and the fibers in the sides of the web, and cooling the rolled web, wherein said hot rolling is preferably carried out using heated rolls in a calender or S-wrap configuration, and bonded webs having improved aesthetic properties and improved effectiveness as produced by such a process. The weight of the fibers in the batt (i.e. in the blend of polyester fiberfill and binder fiber) is referred to as the "area weight" of the batt, i.e. before the sealing resin is sprayed on.

However, we have found in accordance with the present invention that, surprisingly, hot rolling does not necessarily have to be carried out in order to provide a sufficient seal under which Requires that low denier fiberfill (variously referred to as subdenier or microfibers) be used to assist in sealing on at least one or both sides of the web. There is thus now provided a bonded web having a top and bottom surface, the web comprising polyester fiberfill having a denier per filament of greater than 0.2 and not more than 1 in an amount of from about 75 to about 96% and being entirely bonded with lower melting point binder material complementarily present in an amount of from about 4 to 25%, these amounts being calculated with respect to the basis weight of the web, the web having a wash fastness (WD, as defined) of at least 4 and a bending stiffness (B, as defined) of about 40 cN/cm² or less, at least one of the sides being sealed with a resin having a glass transition temperature (Tg) of about 0°C or less in an amount of from about 0.02 to about 0.35 oz/yd² (0.7 to 129 g/m²), preferably from about 0.1 to about 0.25 oz/yd² (3.4 to 8.5 g/m²) calculated with respect to the side of the web, the Seal Value (SR, as defined) of the side being at least 4, wherein the bonded web was made without the use of hot rolling. Preferably, each of the sides is so sealed.

Both metric units, for example dtex, and den are used here, where 1 dtex is the same as 0.9 den per filament (dpf).

Thus, the present invention provides fiberfill webs such as those for use in quality clothing by first preparing a homogeneous mixture of polyester fiberfill (75-96% by weight of the mixture) and a suitable binder fiber (4-25% by weight of the mixture). This mixture is converted on a carding or garnet machine to a web which can then be layered or cross-oriented to form a web mat, to the top surface (and preferably subsequently also to the bottom surface) of which a suitable latex (e.g. a colloidal dispersion of acrylic polymers and/or copolymers in water, explained in more detail below) is applied, e.g. by spraying. The sprayed web is heated, e.g. conventionally by passing through a heated oven to dry the layer(s) and polymerize the polymeric component(s) to a higher molecular weight and activate the binder fiber. This may be done in a conventional manner, for example in three passes through such an oven, two to sequentially dry and partially cure each layer after it is applied to one side, and a final pass to complete the other(s).

However, if the fiberfill is greater than 0.2 denier and less than or equal to 1 denier per filament, and if the resin applied to the sides of the web has a glass transition temperature (Tg) of about 0ºC and is applied in amounts of about 0.02 oz/yd² (0.7 g/m²) to 0.35 oz/yd² (12 g/m²), then no additional treatment, such as hot rolling, is used to prevent fiber shedding, particularly when dry fiberfill is used.

The resins which may be used herein are variously referred to by different manufacturers as "soft" or "medium soft" or even "very soft" but are characterized by having second order glass transition temperatures (Tg) of about 0°C or less. They impart both softness and drapability to the web when used, e.g., in apparel, while acting as a barrier to fiber shedding from the web. The finished webs may have a basis weight of 1.5 to 12 oz/yd² (50 to 400 g/m²) and a thickness of 0.07 to 0.20 in./oz/yd² (0.05 to 0.15 mm/g/m²). Thus, the webs of this invention are made from a blend of polyester fiberfill and binder fibers and the fibers in the side(s) are sealed with a layer of a suitably soft type of resin. The polyester fiberfill may be fully smoothed, e.g., as described herein, or may be a mixture of smoothed and unsmoothed fibers. The fiberfill may be compact, hollow, or a mixture of compact and hollow fibers, and is not limited to any type of fiber cross-section, i.e., it may have cruciform, trilobal, Y-shaped, lobed, scalloped, oval, and other non-circular cross-sections, and may also be round. The fiberfill has a denier per filament (dpf) in the range of 0.2 to 10, with a dpf of about 1.65 being very suitable, and makes up about 70 to 96 weight percent of the blend. As indicated, subdenier fibers provide a good seal in the side(s) of the bonded web and are therefore often preferred in that side(s). The individual fibers are crimped using conventional equipment and typically have 5 to 15 crimps per inch (cpi) and have a length in the range of 3/4 to 3 inches. The binder fibers make up about 4 to 30 weight percent of the web and can be core-shell (s/c), side-by-side (s/s), or monocomponent types. These can be made, for example, from (co)polyesters, polyolefins, polyolefin/polyester, polyamide/polyamide, and the like. Suitable types of binder fibers and their functions include: B. described in "Nonwovens World", March/April 1990, page 37. The initial dpf of suitable binder fibers in the blend is typically in the range of 2 to 15, with a dpf of 4 usually used. Suitable binder fibers include those disclosed in the above-mentioned U.S. patents to Scott, Pamm, Frankosky and Marcus, along with those described by Harns et al. in U.S. Patent No. 4,732,809; by Taniguchi et al. in U.S. Patent No. 4,789,592; by Tomioka et al. in U.S. Patent No. 4,500,384; by Hirose et al. in Japanese Patent Publication Kokai 57-210,015 (1982); and others known in the art which function within the oven temperatures disclosed herein. Preferred binding fibers include the commercially available "Melty 4080" (Unitika Co., Japan) and the polyolefins "ES" and "EA" (Chisso Corporation, Japan).

The cured resin layers on both sides of the web may conveniently comprise about 10 to 30% by weight of the final bonded web, with 12 to 25% being preferred for 1.65 dpf (1.83 dtex) where smaller amounts of resin tend to reduce washfastness and seal value, while larger amounts tend to increase stiffness and reduce insulation effectiveness. If only one side of the web is so sealed, only half as much resin needs to be applied. If low denier fibers (about 1 dpf or less) are used, less resin layer is needed to control the Furthermore, the amount of resin in the surface(s) does not need to depend on the basis weight of the nonwoven mat and therefore for heavier nonwovens the total resin addition can be as low as 3%, even for nonwovens made from smoothed fiber fillers. For completely dry (unsmoothed) fibers less resin is needed than when smoothed fiber filler is used.

As noted above, a resin suitable for coating has a Tg of about 0°C or less. Suitable resins are prepared from commercially available acrylic and vinyl latex compositions, including Rhoplex E-32 (Rohm and Haas Co.), TR-934 (Rohm and Haas Co.), X-4280J (Kanebo, Japan), these Hycar® latex compositions from B.F. Goodrich Co.: 26146, 26171, 26322, 26083, 26092, 2671, 26120, 2679, 26796, these latex products from National Starch and Chemical Corporation: NACRYLIC X 4445, NACRYLIC X 788-6007, NACRYLIC X 4483, NACRYLIC X 4 460, NACRYLIC X 4260, NACRYLIC X 4425, NACRYLIC X 4465, NACRYLIC 4401, NACRYLIC 78-6114, X-LINK 2873, X-LINK 2849, X-LINK 78-6119, X-LINK 2893, X-LINK 2833, X-LINK 78-6004, X-LINK 2813, RESYN 2375, DUR-O-SET E-230, DUR-O-SET E-669, and other commercially available latexes that are cured to resins with Tg values of about 0ºC or less. Some of these commercially available resins and their Tg values are listed in brochures such as one from B.F. Goodrich in 1989 entitled "HYCAR Acrylic Latexes" and one from the National Starch and Chemical Corporation entitled "Binders, Saturants, Laminants".

The manufacture of the webs generally begins with the conventional opening and blending of the polyester fiberfill and the binding fiber, followed by carding or garnetting to produce a web. This web may be layered with other webs from a series of carding or garnetting machines, or it may be cross-oriented and combined with other webs to form an unbonded web mat. This web mat is then sprayed with the latex composition on one or both sides of the web mat and passed into the oven to cure the resin and bond the binding fibers. The oven treatment is carried out for 2 to 5 minutes at 150 - 190 ºC and can conveniently be done in three passes through the web as noted above. The webs have the basis weight and thickness ranges indicated above.

The nonwovens of the present invention have desirable levels of thermal resistance or insulation, usually reported as CLO values (see U.S. Patent No. 4,514,455 to Hwang). The nonwovens of the present invention desirably have a CLO value of at least about 0.36 CLO/oz/yd² (0.01 CLO/g/m²), and preferably 0.48 CLO/oz/yd² (0.014 CLO/g/m²) or more.

It is understood that the components and processes described here should be selected to produce the nonwovens of the invention. Care must be taken in selecting combinations to produce these. For example, the slickener on the fiber and the latex applied to the nonwoven should be selected to adhere sufficiently so that the finished nonwoven can, for example, have sufficient wash resistance.

TEST PROCEDURE

The CLO values are achieved in the manner described by Hwang above.

The wash fastness ("WD") of the nonwovens of the invention is evaluated using the procedures of ASTM D-4770-88. In the examples, the size of the nonwoven pieces was 24 inches x 24 inches. The wash fastness values are recorded from measurements taken in accordance with Section 8.6.1. The nonwovens of the invention have a value of 3 or more (scale in Section 8.5).

Fiber shedding or penetration through the face fabric is measured as the Seal Value ("SR") using the method described by LeVan in U.S. Patent No. 4,869,771 (after 3 wash cycles), with a Seal Value (SR) of 5 being very good and a Seal Value (SR) of 1 being poor. The nonwovens of the invention have a Seal Value (SR) of 3 or more (after 3 wash cycles). In Table 2 (Example 3), the Seal Values are additionally recorded after one wash cycle (1W) and after 3 wash cycles (3W) and compared to the initial values before each wash (NEW).

The softness or drapability of the inventive Nonwovens are measured according to German Industrial Standard 53362 Cantilever (DIN 53362 Cantilever), which determines the bending stiffness ("B") of the nonwoven mat in the machine and cross machine directions and reports it as an overall value; the combined results are for drapability and softness. Nonwoven mat samples are cut to 25 cm long and 2.5 cm wide and cut in both the machine direction (MD) and cross machine direction (XD). Each test sample is weighed and its weight is recorded as "W". Then the bending length ("LU") is determined by sliding the sample horizontally on a platform until the front part of the bent sample reaches an angle of 41 degrees and 30 seconds. Then the following calculation is made:

B = F₁ (LU + 2)³

where B = bending stiffness in cN/cm²

LU = bending length in cm

F₁ = 9.8 (W + L)

W = weight of the sample in g

L = length of the sample in cm.

The nonwovens of the invention have a flexural stiffness (where "B" is the sum of the values determined for samples of the nonwoven in the machine and cross directions) of 80 cN/cm2 or less, with a lower flexural stiffness being preferred.

The invention is further illustrated in the following Example in which all parts and percentages, unless otherwise indicated, are by weight calculated with respect to the "BW" (basis weight, i.e., based only on the amount of polyester fiberfill and binder fiber, i.e., excluding the added resin sprayed onto the sides to improve the seal).

EXAMPLE

Various nonwoven mat samples were made and tested, with the results shown in the table. The binder fiber was "Melty 4080" (4 dpf) in each case, but different fibers were used in the fiber filler.

Samples A, B, C and D were prepared from a commercially available blend of polyester fibres consisting of 37.5% smoothed fibres at 1.65 dpf (finished with a silicone slickener), 37.5% dry fibres at 1.65 dpf (without silicone slickener) and 25% binder fiber. The blend was processed on conventional carding and crosslapping equipment similar to the equipment described in Example 1 of U.S. Patent No. 5,225,242. The resulting batts were passed through a triple pass oven maintained at about 165°C. The batts (except for A) were sprayed with equal amounts of a soft resin (glass transition temperature (Tg) equal to -10°C)) on each side so that the total resin addition was as indicated in the table based on "BW", the basis weight of fiber in the batt at this stage, which was about 4.5 oz/yd² (150 g/m²). One side of the batt was sprayed with resin prior to entering the first pass and the other side was sprayed prior to entering the second pass. It is important that the entire fleece mat was exposed to a temperature high enough for a sufficient time to ensure complete curing of the resin and fixation of the binding fibre (generally 1 minute is sufficient once the fleece has reached 165 ºC). The fleece mats were then calendered in a separate operation which served to seal the surfaces and reduce fluffiness.

From the sealing values in the table, it can be seen that under these conditions, even with 8% resin (sample B), the sealing of the web with 1.65 dpf fibers had not improved due to the effect of calendering after 1 wash cycle, and even with 15% resin (sample C), the sealing had improved after 1 wash cycle but was still unsatisfactory after 3 cycles. At 25% resin, the sealing value of the surface of sample D under these conditions was satisfactory (after three wash cycles).

The nonwoven mats were also tested for fiber failure by enclosing them in a fabric with a yarn count of 104 x 84 and a Frazier air permeability value of 13.2 ft³/min at a pressure drop of 0.5 inches of water column.

Samples E and F were the same as samples A and D, respectively, except that they were tested in a fabric with a yarn count of 102 x 84 and a Frazier value of 48. Since nonwoven mats with 0.7 dpf were also tested in a more permeable fabric than samples A - D were tested, the results for samples E and F (1.65 dpf) are included in the table to bridge the values between samples AD and GQ. Sample E without resin failed when new due to the openness of the fabric, but after three wash cycles had felted sufficiently that its failure properties improved. The initial seal value of sample F was 5 and this had a satisfactory seal value, ie after 3 wash cycles.

Samples G, H, I and J were made from a blend of approximately 85 pounds of dry polyester fiber (0.7 dpf, 0.78 dtex, 1.5 inch cut length, 12 cpi, without special smoothing finish) and 15 pounds of binder fiber. These samples were sprayed with resin, calendered and tested as samples E and F.

Samples K and L were made from a blend of approximately 55 pounds of similar slickened 0.7 dpf fiber, finished with a silicone slickener, 27 pounds of dry (unslickened) 0.7 dpf fiber, and 18 pounds of binder fiber. These samples were not calendered, as indicated by the two asterisks in the table, but gave good sealing values.

Samples M, O, P and Q were made in a similar manner from the same type of blend as K and L, but were made to higher basis weights as can be seen and also had good seal values even though less resin (less than 10%) was added and even though they were not calendered due to the use of low dpf fiber. N was calendered (unlike the others). Comparison of these results shows that calendering was not necessary to improve the seal value (when the subdenier fibers were used with the soft resin).

Samples G to L were all tested for fiber failure using the fabric with a Frazier value of 48.

Accordingly, in the table, samples K - M and O - Q are all inventive samples, whereas the other comparisons show some without sprayed resin, some with normal denier fiberfill whose seal values after washing are inadequate, and some that have been calendered. TABEL

* indicates the total amount of resin sprayed onto (both surfaces of) the fleece, calculated in oz/yd² and g/m² (half amounts indicate amounts on each side).

** indicates that no calendering was carried out after oven curing.

Claims (6)

1. A bonded nonwoven fabric having a top and bottom surface, the nonwoven fabric comprising polyester fiberfill having a denier per filament of greater than 0.2 and not more than 1 in an amount of from about 75 to 96% and being entirely bonded with lower melting point binder material complementarily present in an amount of from about 4 to 25%, such amounts being calculated with respect to the basis weight of the nonwoven fabric, the nonwoven fabric having a wash fastness (WD, as defined) of at least 4 and a bending stiffness (B, as defined) of about 40 cN/cm² or less, at least one of the sides being sealed with a resin having a glass transition temperature (Tg) of about 0ºC or less in an amount of from about 0.7 g/m² (0.02 oz/yd²) to about 12 g/m² (0.35 oz/yd²) calculated with respect to the side of the web, wherein the seal value (SR) of the side is at least 4, and wherein the bonded web is produced without the use of hot rolling. 2. The nonwoven fabric of claim 1 wherein the amount of resin is about 3.4 to about 8.5 g/m² (about 0.1 to about 0.25 oz/yd²). 3. A nonwoven fabric according to claim 1 or 2, wherein each of the top and bottom surfaces is sealed with the resin in said amount and has a sealing value of at least 4. 4. A process for making a bonded web according to claim 1, claim 2 or claim 3, said process comprising making a homogeneous mixture of 75-96% by weight of the polyester fiberfiller and 4-25% by weight of the binding material in fiber form, converting the mixture on a carding or garnet machine into a web which is layered or cross-laid to form a web mat, applying the resin to the top of the web and heating the web to cure the resin and bond the binding fibers, and in which no hot rolling is carried out on the web. 5. The method according to claim 4, wherein the resin is sprayed onto the fleece. 6. A method according to claim 4 or claim 5, wherein the fleece is heated in three passes through a heated oven.