US 3639917 A
Heat recoverable elastomeric materials are used to form gathers in fabrics, especially disposable garments of nonwoven fabrics.
Description (OCR text may contain errors)
nlted States Patent [151 3,639,917
Althouse  Feb. 3, 1 972  HEAT RECOVERABLE ARTICLE 3,353,189 11/1967 Zimmon ..2/270 X 1,102,408 7/1914 Hubner ....2/DlG. 7  Inventor. Victor E. Althouse, Los Altos, Calif. 1,408,373 2/1922 Lustganen "2/228 Ux  Assignee: Raychem Corporation, Menlo Park, Calif. 2,027,962 1/1936 Currie 3,086,242 4/1963 Cook et a1. ..264/95  Filed: Apr. 7, 1970 Primary Examinr-Alfred R. Guest ] App! 26347 Attorney-Lyon & Lyon  US. Cl. ..2/270, 2/DIG. 7 57 BSTRACT  Int. Cl. ..A4ld 27/11 v  Field Of Search ..2/DIG. 7, 270, 125, 128, 228 Heat recoverable elastomeric materials are used to f gathers in fabrics, especially disposable garments of nonwoven  References Cited fabrics.
UNITED STATES PATENTS 8 Claims, 4 Drawing Figures 1,544,312 6/1925 G 'ay "12/228 ux PATENTEU FEB 81972 3,6390% INVENTOR V/CTOR E. ALTHOUSE A r (JP/YE Y5 HEAT RECOVERABLE ARTICLE FIELD OF THE INVENTION This invention relates to fabrics, and more especially to garments and other articles portions of which are gathered.
BACKGROUND OF THE INVENTION In recent years, increased costs of laundering, and the deliberately introduced changes in fashions, especially women s fashions, have combined to cause or accelerate the introduction of garments and other articles of fabrics which are designed to be worn or used only once or a relatively small number of times and then discarded. Such articles are generally referred to as disposable garments although it will be appreciated that some of the articles, such as sheets, are not worn. Among the many examples of such articles there may be mentioned party dresses and hospital and clean room garments.
The known reluctance of a lady to arrive at a dance or party in a dress identical to that worn by another or, indeed, identical to the dress she herself wore to any previous such occasion has led to the manufacture of garments of relatively cheap materials. Exemplary of such materials are paper, plastic, or nonwoven fabrics which can be dyed or printed in a variety of ways. Such garments can be worn on only one occasion and then be economically discarded.
Hospitals are using an increasing number of disposable articles of all types since it is often found to be cheaper or more convenient to purchase new items then clean and where necessary sterilize them before reuse. This applies to garments" of all types, whether for use by patients or staff, including fitted sheets and other shaped fabric articles.
Since an important feature of disposable garments is economic price, production costs must needs be reduced to a minimum. Thus, such materials as nonwoven fabrics and paper are used as bases for the garments, and the materials are cut and joined, such as by sewing or glueing, in the simplest manner possible. Where, however, it is necessary that a part of the garment should fit relatively tightly but resiliently over the user, such as at a wrist or waist band, it is necessary to incorporate elastic or similar material into the garment. This has been found to add considerably to the cost of such garments since the elastic has to be sewn, often by hand, into the material by a time'consuming process. Further, when such elastic is sewn into the garment, it tends to produce tear-sensitive holes, especially in plastics or nonwoven fabrics. In those cases where sewing can be tolerated, it is necessary that the elastic material be held in tension during sewing so that after sewing elastic recovery will cause the fabric to gather. That necessity naturally complicates the sewing step.
It has also been found that hospital patients become depressed if they have to wear ill-fitting, shapeless garments, so that gathers which improve the fit would be desirable if they could be economically incorporated.
SUMMARY OF THE INVENTION According to this invention, there is provided an economic process for gathering a fabric which comprises attaching a heat recoverable material which is elastomeric in its heat stable form to a portion of the fabric and heating the material to cause it to recover and gather the fabric. There is also provided by this invention a gathered fabric comprising a heat recovered elastomeric material. One object of the present invention is to provide a new and economic means and method of gathering fabrics.
A further object of the invention is to provide disposable garments having elastic portions capable of accommodating a variety of sizes.
These and other objects and advantages of the invention will be apparent from the detailed description of the invention and the accompanying drawing, in which:
FIG. 1 is a side view, partly in section, of a garment sleeve having an attached band of heat shrinkable elastomeric material.
FIG. 2 is a view of the sleeve shown in FIG. 1 after recovery of the material.
FIG. 3 is a pictorial view of a hospital gown whose cuffs have been gathered according to the invention.
FIG. 4 is a perspective view of a hospital gown whose sleeves have not been gathered by the invention.
DESCRIPTION OF THE INVENTION As used in the present specification an elastomeric material is a substance that can be stretched at room temperature to at least about twice its length and which after removal of the stretching load will immediately return to approximately its original length.
It is not necessary that the material be elastomeric when in its heat shrinkable form, i.e., prior to heat recovery, although in practice it may be. To give a gather that has give" it is only required that the material be elastomeric after recovery.
The material may be rendered heat recoverable by any of the methods known for imparting this property. In general, the material may be formed into an article having an original configuration, then deformed at an elevated temperature, and subsequently cooled while maintaining the deforming force. Such an article will retain its new configuration until it is again heated to an elevated temperature. Upon heating to the temperature of recovery, the material recovers to its previously held, heat stable configuration. Methods of achieving these results are disclosed, for example, in US. Pat. No. 2,027,962 to L. M. Currie and in US. Pat. No. 3,086,242 to P. M. Cook et al., the disclosures of which are incorporated herein by reference.
The heat recoverable material can be applied to the fabric by any conventional means, for example by using contact cements, pressure-sensitive adhesives, and heat sealing provided of course that the temperature required for heat sealing is lower than that of the recovery, or provided that recovery is prevented during the application. It is however within the scope of the invention to apply and recover in one step so long as the adhesion between the fabric and the material is sufficiently strong immediately after application to enable the material to carry the fabric with it during recovery. Where sewing can be employed, the recoverable material can be sewn to the fabric without need for the simultaneous application of tension necessary with conventional elastic elements used in garment manufacture. Of course, the particular preferred method will depend both on the material and the nature of the fabric to which it is being applied.
The shape of the heat recoverable material varies with the particular application. For example, if a sleeve of a garment is to have an elastic wristband, then a piece of recoverable material may be applied to the inside or the outside of the sleeve. The piece may be a strip or an endless band. If, for example, a garment is simply to be shaped by gathering a small portion of the fabric, a shrinkable strip may be applied to an appropriate portion of the garment. A band may be made by expanding tubing, for example, as described in the abovementioned US. Patents, and cutting off suitably sized lengths of the expanded tubing. A strip may be formed from, for example, tubing or sheet. Those skilled in the art will appreciate that a variety of effects may be achieved using recoverable material of different shapes. Further, the degree of recovery may be made to differ from one part of the material to another, so that different extents of gathering may be achieved when the material is recovered.
The material may be covered, either by the fabric itself or by other covering materials, to enhance the appearance of the garment. For example, the band to tighten a wristband may be applied to the inside of the sleeve a short distance from the end of the sleeve, and part of the end region turned in to form a hem containing the recoverable band.
The material may be caused to recover by many of the commonly used methods for recovery of such materials, such as by use ofa hot-air gun, an iron, or an oven.
In general, materials suitable for use in the invention are those containing elastomeric regions and nonelastomeric regions. It is believed that, below a transition temperature of the nonelastomeric regions, the elastomeric regions can be held in a deformed state (such as that achieved by imparting heat recoverability to the material) by the nonelastomeric regions while still allowing the gross material to display elastomeric properties. Above the transition temperature, e.g., a glass transition or crystalline melting point, the nonelastomeric regions have insufficient strength to maintain the deformation.
As elastomeric materials suitable for use in this invention, there can be mentioned by way of example those described in US Pat. No. 3,265,765 to Holden et al., the disclosure of which is incorporated by reference herein. Briefly, these materials are elastomeric block copolymers of the formula A-BA wherein each A is an independently selected nonelastomeric polymer block and B is an elastomeric polymer block. Preferably each terminal A block is formed from the same monomer or monomers. Advantageously, each end block A has an average molecular weight of 2,000 to 100,000 (preferably 5,00050,000) and has a glass transition above about 25 C. (preferably above 50 C. while the center block B has an average molecular weight of 25,000 to 1,000,000 (preferably 50,000 to 500,000) and a glass transition temperature below 10 C. (preferably below C. and more preferably below 25 C.). Advantageously the difference in glass transition temperatures of the end and center blocks is at least 40 C., and preferably above 100 C. The end blocks together advantageously constitute to 50 percent (preferably to 40 percent) by weight of the polymer.
Preferred for block B are polymers of aliphatic conjugated dienes, e.g., isoprene, methyl isoprene, butadiene homopolymers and styrene/butadiene and butadiene/acrylonitrile copolymers.
Preferred for blocks A are polymers of styrene'type monomers, e.g., styrene itself, methyl styrene and chlorostyrene.
A preferred copolymer is one in which B represents an elastomeric polyisoprene block while each A represents a polystyrene block.
Also suitable are materials disclosed in US. Pat. application No. 65,953, filed Oct. 31, 1960, by P. M. Cook (British Patent Specification No. 1,010,064), crystalline neoprene rubbers like those manufactured by E. l. du Pont de Nemours and Co., Inc., under the designation Neoprene HC, and high-ethylene content crystalline ethylene-propylene copolymer elastomers, e.g., Vistalon 3708, available from Enjay Corporation.
For use in the present invention, the polymers are preferably cross-linked by conventional techniques, e.g., by ir radiation or by chemical cross-linking agents, prior to impartation of heat recoverability.
Of course, the polymers can contain any of the usual additives, e.g., fillers, antioxidants, flame retardants, pigments, so long as such additives do not unduly interfere with the elastomeric properties of the material.
With reference now to the drawings, FIGS. 3 and 4 depict hospital gowns generally indicated at l. The gowns are preferably of the disposable variety and manufactured from nonwoven fabric. For reasons of economy, the sleeves 2 of the gowns are not shaped in any way and hence do not taper toward the wrists. Instead, such gowns have large diameter cuffs, as shown at 3. Those cuffs constitute a danger, as they may drag surgical instrument trays, tables, and other surfaces. Referring now to FIG. 1, there is shown a sleeve 2 ofa gown of the type illustrated in FIG. 4 to the inside of the cuff 3 of which has been attached a band 4 of heat shrinkable elastomeric material. FIG. 2 shows the same sleeve after recovery of the band 4 by heating, while FIG. 3 shows at 5 the effect on the gown 1. In similar fashion, the head band of the cap, waist, and cuffs (particularly for clean room use) of such garments can be gathered by the application of this invention.
The invention is further illustrated by the following examples ofcurrently preferred embodiments.
EXAMPLE 1 A styrene/butadiene block copolymer sample (Kraton 3125, available from the Shell Oil Co.) is formed into a slab. The slab was 3 inches X 5 inches 0.020 inches. It was then irradiated in a 1 MeV beam to a dose of 15 Mrad and expanded at 1 10 C. so that the 5-inch length became 15 inches, i.e., an expansion of 3X, and cooled while maintaining it expanded. The slab was cut in the expansion direction into strips 0.25 inches wide. Using a contact cement (Roberts' Anchor Weld 0308) one strip was bonded to each cuff ofa nonwoven fabric (du Pont Tyvek) disposable garment. The sleeve section was then heated to C., when the strip recovered to its original length and gathered the cuff. The cuff was found to be elastically deformable, i.e., it could be readily stretched to allow a hand to pass through it and thereafter form a snug fit around the wrist. The properties of Kraton 3 are described in Shell Chemical Company Technical Bulletin SCR 68-193.
Example 2 A strip of Thermofit SFR tubing, 2 inches long, 025 inches diameter and 0.020 inch wall thickness was irradiated to a dose of 20 Mrad in a 1 MeV beam. Thermofit is a trademark of Raychem Corporation. The material is a blend of a silicone rubber with a thermoplastic material, the blend being elastomeric and capable of having heat recoverability imparted to it. The tubing was heated to C. in an oven, stretched to 4 inch in length, and cooled to room temperature, while maintaining that length. It was then attached, with General Electric Silicone Contact Cement 516 to Kimlon, a cellulosic nonwoven fabric manufactured by Kimberly-Clark Corporation. Reheating to 150 C. caused the tubing to shrink, resulting in a gathered material which was elastically stretchable.
Example 3 A strip of Neoprene HC, 6 inch X 0.25 inch X 0.020 inch was irradiated as described in example 2 and similarly stretched to 12 inches at 75 C. The cooled, elongated strip was attached to Kimlon with a contact cement (Roberts Anchor-Weld 0308). Reheating to 75 C. resulted in an elastic-gathered fabric article.
Example 4 Example 3 was repeated, with the change that Vistalon 3708, an ethylene-propylene elastomer manufactured by Enjay Corporation (Standard Oil of New Jersey) was expanded at 100 C. The adhesive used was General Electric Silicone Contact Cement 576. Reheating the assembly to 100 C. produced an elastic-gathered article.
1. A shaped element gathered in at least one region at tached to a heat shrunk material selected from the group of materials which are elastomeric following heat recovery from a dimensionally heat unstable state to a dimensionally heat stable state.
2. An article according to claim 1 wherein said material is an elastomeric block copolymer having the general formula A-B-A in which each A is an independently selected nonelastic polymer block and B is an elastomeric polymer block.
3. A shaped fabric article gathered in at least one region attached to a heat shrunk material selected from the group of materials which are elastomeric following heat recovery from a dimensionally heat unstable state to a dimensionally heat stable state.
4. An article according to claim 3 wherein said material is an elastomeric block copolymer having the general formula AB-A in which each A is an independently selected nonelastomeric polymer block and B is an elastomeric polymer block.
5. A garment attached in at least one region to a heat shrinkable material, which material is selected from the group of materials which are elastomeric following heat recovery from a dimensionally heat unstable state to a dimensionally heat stable state.
8. An article according to claim 7 wherein said material is an elastomeric block copolymer having the general formula A-B-A in which each A is an independently selected nonelastomeric polymer block and B is an elastomeric polymer block.