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Apparatus for making dimensionally stable nonwoven fibrous webs

a nonwoven fibrous, dimensionally stable technology, applied in the direction of dough shaping, manufacturing tools, food shaping, etc., can solve the problems of affecting the use of pet in high temperature applications, the melting point and the glass transition temperature, and achieve the effect of reducing the change in fiber diameter, size or physical properties

Inactive Publication Date: 2001-12-27
3M INNOVATIVE PROPERTIES CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] The present invention provides a method and apparatus for making a dimensionally stable or shrink-resistant nonwoven web of polymeric fibers. The resulting dimensionally stable, nonwoven fibrous webs can be used at higher temperatures with minimal change in fiber diameter, size, or physical properties as compared to conventional polyolefin webs. Nonwoven fibrous polyester webs dimensionally stabilized using the present method and apparatus are particularly useful as thermal and acoustical insulation.

Problems solved by technology

This reduction in melting point and glass transition temperature negatively impacts on the use of PET for high temperature applications, such as automotive engine compartment noise attenuators.

Method used

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  • Apparatus for making dimensionally stable nonwoven fibrous webs
  • Apparatus for making dimensionally stable nonwoven fibrous webs
  • Apparatus for making dimensionally stable nonwoven fibrous webs

Examples

Experimental program
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first embodiment

[0037] FIG. 1 is a perspective view of an annealing apparatus 20 designed to hold a nonwoven fibrous web 21 stationary at a plurality of tentering points during annealing or heatsetting. A plurality of retractable tentering pins 22 are mounted to a tentering pin support 24. In the embodiment illustrated in FIG. 1, the tentering pins 22 are inserted through a plurality of tentering pin holes 26 on a backing 28. The tentering apparatus 20 of FIG. 1 restrains the nonwoven web 21 along its major surface (x and y axes), but not along the z-axis. The tentering pin support 24 and the backing 28 includes a plurality of vent holes 30 to permit airflow through the surface of a nonwoven web 21 engaged with the annealing apparatus 20. The tentering apparatus 20 avoids compressing the nonwoven web 21 of microfibers during annealing to preserve the acoustical and thermal insulating properties.

[0038] Unlike conventional edge tentering used to anneal films and woven fabrics, the tentering pins 22 o...

examples 11-14

[0088] Polyethylene terephthalate (PET) nonwoven meltblown microfibrous webs with a targeted basis weight of 200 grams / meter.sup.2 were produced as described in Examples 1-5. The PET meltblown microfibrous webs were prepared from various Intrinsic Viscosity PET resins set forth in Table 3 (available from 3M Company and from Eastman Chemical Products, Inc. of Kingsport, Tenn.). The annealed webs were evaluated for the effect of I.V. on unrestrained web shrinkage in accordance with ASTM D 1204-84. The results are set forth in Table 3.

3TABLE 3 Example PET Resin % Unrestrained Shrinkage Machine No. Identification I.V. Direction 200.degree. C. / 10 minutes 11 3M 651000 0.60 57.1 12 Eastman 12440 0.74 58.3 13 Eastman 9663 0.80 58.3 14 Eastman 12822 0.95 57.1

[0089] The data of Table 3 show that I.V. did not appear to be an influencing factor on PET web dimensional stabilization within the range of 0.60 to 0.95 I.V.

example 16

[0093] A PET nonwoven acoustical insulating web was prepared as described in U.S. Pat. No. 4,118,531 (Hauser). The webs comprised 65% melt blown microfibers prepared from polyethylene terephthalate (PET) 0.6 I.V. type 651000 available from 3M Company of St. Paul, Minn. The webs also included 35% crimp bulking fibers in the form of 3.8 cm (1.5 inch) long, 6 denier (25.1 micrometers in diameter), 3.9 crimps / centimeter (10 crimps per inch) polyester staple fibers available as Type T-295 fibers from Hoechst-Celanese Co. of Somerville, N.J. The resulting web of Example 16 was tenter annealed or heatset with the tentering apparatus of Example 15.

[0094] The sample of Example 16 was tenter annealed for 10 minutes at 180.degree. C. using the tentering apparatus described in Example 1-5. The sample was removed from the oven, allowed to cool to room temperature, and removed from the tentering device. The sample of Example 16 had a web thickness of 3.4 centimeters and was evaluated in accordanc...

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Abstract

A method and apparatus for tentering nonwoven webs during annealing. The nonwoven web of thermoplastic fibers is restrained on a tentering structure at a plurality of tentering points distributed across an interior portion of the web, rather than just along its edges. The nonwoven web is annealed while restrained on the tentering structure to form a dimensionally stable nonwoven fibrous web, dimensionally stable up to at least the heatsetting temperature. The annealed nonwoven fibrous web is then removed from the tentering structure. In one embodiment, the tentering structure restrains the nonwoven fibrous web in a non-planar configuration during the annealing process. The tentering structure includes a plurality of tentering points projecting distally from a tentering support. The tentering points are positioned to be engaged with an interior portion of the web, thus restraining the web during annealing.

Description

TECHNICAL FIELD[0001] The present invention relates to a method and apparatus for making nonwoven fibrous webs that resist shrinkage when exposed to heat.BACKGROUND[0002] Typical melt spinning polymers, such as polyolefins, tend to be in a semi-crystalline state upon meltblown fiber extrusion (as measured by differential scanning calorimetry (DSC)). For polyolefins, this ordered state is due, in part, to a relatively high rate of crystallization and to the extensional polymer chains orientation in the extrudate. In meltblown extrusion, extensional orientation is accomplished with high velocity, heated air in the elongational field. Extending polymer chains from the preferred random coiled configuration and crystal formation imparts internal stresses to the polymer. Provided the polymer is above its glass transition temperature (T.sub.g) these stresses will dissipate. For meltblown polyolefins, the dissipation of stresses occurs spontaneously since the polymer's T.sub.g is well below...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): D04H1/72D04H3/03D06C3/02D04H3/08D04H3/14D04H3/16D04H5/08D06C3/00D06C3/10
CPCD04H1/72D04H3/03D04H3/08D04H3/14D04H3/16D04H5/08D06C3/02D06C3/10
Inventor THOMPSON, DELLON R.OLSON, DAVID A.PERCHA, PAMELA
Owner 3M INNOVATIVE PROPERTIES CO
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