FIELD OF INVENTION

The present invention relates to a method for adhering polyurethane to an elastic knitted fab an end product of the method .

BACKGROUND

Compression attire is commonly used in many different types of sport. The attire is designed in a way which envelopes a user's muscle(s) to and provide support to the muscle(s) and improve circulation whilst assisting in minimizing a build-up of lactic acid in the muscle(s). Generally, a bigger muscle will require a greater compressive force while a smaller muscle will require a lesser com pressive force in order for the muscles to be supported by the compression attire in a desired manner.

Elastic fabrics currently used for compression attire typically provide uniform compressive forces for the user's muscle(s). This limits the effectiveness of the compression attire as the requisite compressive forces are not able to the applied to the respective muscles. The elastic fabrics currently used also do not affect bio-mechanical functions of muscle groups. Furthermore, com pression garments typica lly do not provide gradient compression which mimics the physiology of the user's m uscles. This is undesirable. SUMMARY

There is provided a method specifically for adhering polyurethane to an elastic knitted fabric. The method comprises filling a plura lity of recesses in a mold with a solution for forming the polyurethane; de-gassing the solution; locating a thermoplastic rubber substrate on the fabric; and heat-pressing both the thermoplastic rubber substrate and the mold at a pre-determined tem perature and at a pre-determined pressure. It is advantageous that the de-gassing minimizes air bubbles in the solution, and heat-pressing causes the polyurethane to fuse with the fabric. The method may further include spraying mold with release agent; sealing the mold in a vacuum enclosure; curing the solution for a pre-determined period of time to semi- form the polyurethane; covering the plurality of recesses with the fabric; removing the thermoplastic rubber substrate from the fabric; and removing the fabric from the mold; cooling the polyurethane at room temperature, and ageing the polyurethane in an oven.

Preferably, each of the plurality of recesses can be varied in at least one aspect such as, for example, shape of recess, depth of recess, orientation of recess relative to the mold, cross-sectional area and the like.

The method can preferably be applied either along or diagonal to a direction of fabric gradient to enhance anisotropic elastic properties of the fabric which affects compressive strength. The method can be applied to at least one panel of a completed piece of apparel. DESCRIPTION OF FIGURES

In order that the present invention may be fully understood and readily put into practical effect, there shall now be described by way of non-limitative example only preferred embodiments of the present invention, the description being with reference to the accompanying illustrative figures.

Figure 1 shows a process flow of a method of the invention.

Figure 2 shows a sample of a piece of fabric which has undergone the method of Figure 1. DESCRIPTION OF PREFERRED EMBODIMENTS

There is provided a method specifically for adhering polyurethane to an elastic knitted fabric such that characteristics of the fabric can be varied at different portions of the fabric. The method is a treatment process for fabric and is useful in most applications for sports apparel, but is not limited to use only for sports apparel. The method can also be used for other applications when characteristics (for example, stress/strain mechanical behavior) of the fabric are varied from their original form. After the fabric has undergone the method, the compressive properties of the fabric are enhanced, and during use of panels of the fabric in the form of apparel, the enhanced compressive properties of the fabric advantageously affects bio mechanics of a user's affected muscle groups when the apparel is worn by the user. This leads to improved performance and/or recovery by the user's affected muscie groups during physical activity and/or rest. This depends on the polyurethane design (in relation to, for example, cross-section, shape, spacing, shore hardness and so forth) being used on the elastic knitted fabric. In addition, the method also is able to enhance an appeal of the fabric visually and through tactile feel. Further details will be provided in the following paragraphs.

Referring to Figure 1, there is provided a method 100 specifically for adhering polyurethane to an elastic knitted fabric. The method 100 comprises spraying a release agent onto a mold (101) and filling a plurality of recesses in the mold with a solution for forming the polyurethane (102). The mold may be made from, for example, a thermoplastic rubber, copper, aluminum, and so forth. It should be appreciated that a composition of the solution can be varied depending on a type of polyurethane being used in the method 100. The composition of the solution should lead to polyurethane which can be securely adhered to the fabric over an extended duration of time. When the thermoplastic rubber mold is used, it can be configured to provide a smooth and non-stick surface even without use of a spray release agent (which is commonly required prior to filling a plurality of recesses in other typical molds made from non-thermoplastic rubber). Furthermore, each of the plurality of recesses can be varied in at least one aspect such as, for example, shape of recess, depth of recess, orientation of recess relative to the mold, cross-sectional area and so forth. A variation of each recess affects the physical characteristics of the fabric after the method 100 is carried out.

Subsequently, the method 100 includes sealing the mold in a vacuum enclosure (104) to facilitate de-gassing of the solution by removing air bubbles in the solution. Then, the solution undergoes degassing (106) such that air bubbles in the solution are minimized or removed. Minimising or removing air bubbles in the solution prevents destabilization of the appearance and physical properties (for example, hardness, density, flexibility and so forth) of polyurethane. It is likely that quality of the polyurethane will become an issue if de-gassing is not carried out. Once the quality of the polyurethane is compromised, an end product yield from using the method 100 would be lowered.

Furthermore, the method 100 includes curing the solution for a pre-determined period of time (for example, ten minutes) to semi -form the polyurethane (108). Then the plurality of recesses is covered with the fabric (110) and a thermoplastic rubber substrate is located on the fabric (112). The thermoplastic rubber substrate is used for a few reasons, namely, to shield the fabric from dirt particles and to even out a pressure applied to the fabric to enable better adhesion between the fabric and the polyurethane. Substrates made from other materials can also be used as long as the material allows the substrate to be able to shield the fabric in the aforementioned aspects.

Subsequently, heat-pressing both the thermoplastic rubber substrate and the mold at a predetermined temperature (for example, 30°C to 100°C, but usually 50°C) and at a pre-determined pressure (for example, 1.5 kg/cm ² to 150 kg/cm ² , but usually 30 kg/cm ² )(114) is carried out to cause the polyurethane to adhere to the fabric. It should be appreciated that the polyurethane is adhered to the fabric in a manner whereby washing and stretching of the fabric will not result in dislodgement and peeling of the polyurethane from the fabric.

The method 100 then includes removing the thermoplastic rubber substrate from the fabric (116) and removing the fabric from the mold (118). Cooling of the polyurethane on the fabric (119) is then carried out under room temperature conditions for between one to three hours, preferably two hours. Ageing of the polyurethane (120) in an oven between six to twenty four hours(usually twenty four hours) is required to adequately ensure physical and chemical properties of polyurethane have been stabilized and that instances of dislodgement and peeling of the polyurethane from the fabric is minimized. The duration of the ageing is dependent on temperature used and the composition of the solution. The ageing temperature may range from 60°C to 80°C (typically 60°C).

It should be appreciated that the method 100 can be applied along or diagonal to a direction of fabric gradient to enhance anisotropic elastic properties of the fabric, which affects compressive strength. Furthermore, the method 100 should be applied to at least one panel of a completed piece of apparel, for example, tights, leotards, compression suits, skin suits, sports bras, ski suits and so forth.

Referring to Figure 2, there is shown a panel of fabric 300 which has undergone the method 100. The fabric 300 includes polyurethane patches 310 with different shapes, sizes, shore hardness and orientations. A design, orientation, thickness, cross sectional area, thickness, physical properties and location of the patches 310 will affect the panel of fabric 300 and will result in a controllable and adjustable compressive strength and direction on the panel of fabric 300. The design, orientation, cross sectional area, and thickness of the polyurethane patches 310 are obtained by varying at least one aspect of the recesses in the mold, such as, for example, shape of recess, depth of recess, orientation of recess relative to the mold, cross- sectional area and so forth. Typically, the patches 310 are likely to be located near the following muscle groups (although locating the patches 310 at other muscle groups is also possible): - quadriceps, hamstrings and calves (for running wear);

- trapezius, abdominal muscles, quadriceps, glutes and hamstrings, triceps (for ski wear);

- quadriceps, hamstrings, gastrocnemius and soleus (for cycling wear); and

- quadriceps, hamstrings and calves, abdominal and oblique muscles (for soccer wear). Although the aforementioned muscle groups may appear to be similar, an intensity of the activity at the respective muscle groups vary from sport to sport, and thus, compressive force required is different for the respective muscle groups and this would affect, for example, the thickness and shore hardness of the patches 310 used on the panel of fabric 300. It should be noted that the thickness of the patches 310 need not be uniform and thus, different portions of the patches 310 can have different thickness.

The method 100 can be applied on a completed body suit panel at selected sections to target certain muscle groups to enhance the bio-mechanic functions of the respective muscle groups. The method 100 can also be applied on the panel of fabric 300 at selected sections such that the panels of fabric 300 are sown together to form a completed piece of apparel. Thus the method 100 allows compression garments to be made from an elastic knitted fabric while still having the ability to have varied controlled yet dynamic gradient compression strengths at varied specific areas. Polyurethane is able to be configured to control a compressive strength of a garment using fabric adhered with polyurethane and also whether a gradient compression is able to be provided by the garment. Design elements that affect a presence of gradient compression in the garment is dependent on but not limited to, for example if stripes were used, length of stripes, cross-section variation of stripes, hardness of stripes, width thickness of stripes and so forth. The controlled compressive properties may also be similarly controlled as mentioned above. The method 100 can also be used to vary characteristics (for example, stress/strain mechanical behavior) of the panel of fabric 300 from its original form. After the panel of fabric 300 has undergone the method 100, the compressive properties of the panel of fabric 300 are enhanced with a controlled dynamic gradient. "Controlled" means that fine-tuning of the compressive force applied by the garment using the fabric is possible, while "dynamic" means a variation of the compressive force may exist at different sections on the fabric, and "gradient" means that compressive force can be made to transition in a gradual manner across the different sections so that peak compression is achieved at a pre-defined section of the garment (where desired). Ideally compression provided by the garment should have a gradient compression similar to the physiology of muscles, meaning the compression strength from one section to another gradually increases or decreases. During use of the panel of fabric 300 when in a completed piece of apparel, the controlled enhanced compressive properties of the fabric (which can be configured in a gradient manner) advantageously affects bio mechanics of a user's affected muscle groups when the apparel is worn by the user. This leads to improved performance and/or recovery by the user's affected muscle groups. In addition, the method 100 also is able to enhance an appeal of the panel of fabric 300 (in relation to visuals due to an availability of a variety of patterns and colours, and in relation to touch and feel), as a perception of the panel of fabric 300 with the patches 310 provides an assurance to the user with regard to technical controlled enhancements to the panel of fabric 300. Finally, it should be appreciated that the method 100 can be carried out using a single machine or a plurality of machines.

Whilst there have been described in the foregoing description preferred embodiments of the present invention, it will be understood by those skilled in the technology concerned that many variations or modifications in details of design or construction may be made without departing from the present invention.