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1. WO2020109925 - FASTENER STRIP AND MANUFACTURING METHOD THEREOF

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

FASTENER STRIP AND MANUFACTURING METHOD THEREOF

TECHNICAL FIELD

The present invention generally relates to the field of bundling machinery, in particular, to fastener strips, and specifically to a scheme for the reinforcement of fastener strips

manufactured with soft materials, a diaper closure system using such a reinforced soft fastener strip, a paper diaper, or a bundling strip.

BACKGROUND

It is well known that a fastener fixing device comprises a fastener strip. Such a device is also known as an adhesive buckling member, a Velcro fastener, or a magic fastener.

“Heat Treated Profile Extruded Hook (US patent application publication No. US

20040068848 Al)”— has disclosed a method for forming a unitary polymeric projection or fastener, the method comprising a thin, strong flexible backing, and a plurality of thin spaced hook members projecting from the upper surface of the unitary backing. The method generally includes extruding a thermoplastic resin through a mold plate to form a base layer and to form spaced ridges, ribs, or hook elements protruding above a surface of the base layer. When the mold forms the spaced ridges or ribs, the cross-sectional shapes of the hook members are formed by the mold plate. The initial hook member thickness is formed by transversely cutting the ridges at spaced locations along their lengths to form discrete cut portions of the ridges.

Subsequently, the backing layer (in the direction of the ridges in the machine direction) is longitudinally stretched to separate the cut portions of the ridges; the cut portions then form spaced apart hook members. The extruded hook members or cut rib hook members are then heat treated, resulting in shrinkage of at least a portion of at least the thickness portion of the hook head by 5 to 90 %, preferably 30 to 90 %.

“Mushroom-Type Hook Strip for A Mechanical Fastener (U.S. Patent No. US 5077870 A)”— has disclosed a strip with a mushroom-type hook used for a“hook-and-loop fastener,” which has a flexible backing made of thermoplastic resin, and the mushroom-type hook is integrated with the backing; an array of upstanding stems is distributed across at least one face of the backing, each stem having a mushroom head. The mushroom-type hook strip can be produced continuously by injecting resin into cavities of a cylindrical mold while evacuating and cooling the cavities so that the cooled resin becomes molecularly oriented.

“Multiheaded Hook (U.S. Patent with application publication No. US 20060019059 Al)”— has provided a method for preferably forming a unitary polymeric hook fastener; the

fastener comprises a flexible backing and a plurality of spaced hook members projecting from the upper surface of the unitary backing, wherein each hook member comprises a plurality of hook head elements projecting in substantially the same direction. Each of the hook members comprises a stem portion with one end attached to the backing, and a head portion at the end of the stem portion opposite to the backing. The head portion can also extend from a side of the stem portion or be omitted entirely to form alternative projections which can be in other forms than the hook members. The head portion preferably projects past the stem portion on at least one of the two opposite sides. At least the hook head portions have two or more hook head elements on at least one of the two opposing sides of the stem. The hook head portions preferably have been heat treated so as to decrease the hook head thickness and thereby reducing or eliminating at least the molecular orientation of the hook head in the machine direction.

In particular, it is desirable in the art to have a relatively soft closure system and a fabric or nonwoven article that is particularly suitable for closely contacting with the human body, such as a closure system of a paper diaper.

The softness requirement is the market demand trend for disposable diapers. The current solutions for soft fastener strips generally include the following two directions:

(1) Adding a polyethylene raw material to the raw material of polypropylene. Such solution can reduce the hardness of the fastener strip as a whole; and therefore it can affect the buckling ability of the mushroom head and so on, thereby reducing the performance of the product when in use.

(2) Reducing the thickness of the base layer of the fastener strip. Such a solution can cause problems such as tearing and cracking of the fastener strips.

SUMMARY

As noted above, in particular application fields, there is a greater need for a closure system that achieves improved softness while not damaging the skin and providing reliable functionality. In particular, for paper diapers, a soft-feel closure system is needed in order to care for a baby’s delicate skin or to improve the comfort of adult paper diapers.

On the other hand, in the manufacturing process of such products, it is found that a strip with soft-feel typically has the problem of insufficient strength; for example, in the process of manufacturing a paper diaper, the operation steps include tearing down a predetermined length of the strip segment from a strip roll. An easy-to-tear seam is typically pre-arranged on the strip; for example, a plurality of holes are pre-arranged along the width of the strip. In the operation of the production lines, strip segments need to be separated from the easy-to-tear seams in order to be attached to fabric or non-fabric products. However, in case the stripe strength is insufficient, an unintended tearing manner may occur. This situation not only causes unnecessary material loss, but also affects operation process speed. Therefore, there is an urgent need in the art to minimize unintended tearing as much as possible.

In addition, it is desirable to be able to provide a low-cost printing scheme for the fastener strips.

Additionally, it is desirable to minimize the investment in technological improvements. That is, it is possible to minimize the cost of new equipment or new process designs while improving product performance.

To achieve the above objective, the present invention provides the following technical solutions in various aspects.

The first aspect of the present invention provides a fastener strip for attachment to a mating strip, so as to provide a fastening function, the fastener strip comprising: a first film material, the first film material comprising: a substrate layer, the substrate layer comprising a first surface and a second surface opposite to the first surface; and a plurality of protruding constructions extending from the first surface of the substrate layer and integrally formed with the substrate layer (the protruding constructions are used for mechanically snapping with the corresponding constructions on the mating strip), wherein the fastener strip further comprises a second film material laminated and fixed on the second surface of the first film material, and the second film material is a separately formed film material.

The first film material and second film material can be made from the same material or from different materials. Preferably the two are made of compatible materials, so that the two are suitable for bonding with heat pressing or adhesives.

The second aspect of the invention provides a closure system of a disposable diaper, comprising the fastener strip as described in the above aspect.

The third aspect of the present invention provides a disposable diaper, comprising the fastener strip as described in the first aspect of the present invention.

The fourth aspect of the present invention provides a method of manufacturing the fastener strip as claimed, comprising the following steps: transferring a second film material to a press roller; applying a first thermoplastic material above the second film material and a cylindrical mold roller through an extruder, then the first thermoplastic material and the second film material together passing through a pressing area between the press roller and the cylindrical mold roller to form a first intermediate composite film material; and forming

protrusions complementary with a surface configuration of the cylindrical mold roller on a surface of the first thermoplastic material film layer.

The present invention has provided a novel solution for providing reinforcement for fastener strips. Because an additional reinforcement layer is adopted, the stress concentration effect on the surface of the fastener strips due to the protrusions can be counterbalanced to a certain degree.

On the other hand, as the additional reinforcement layer is prepared separately, it is possible not to consider the strength of the mushroom head provided on the fastener strip, thus allowing for a separate consideration of the desired performances of the two parts. A more flexible selection in materials and designs becomes available. For example, a biaxially-oriented polypropylene thin film can be adopted as the reinforcement film, which is softer and provides improved tear resistance. Therefore, the requirements of reinforcement and softness can both be met while ensuring that the overall thickness of the backing of the fastener strip is not increased.

In addition, other types of reinforcement films can also be adopted, such as fiber reinforced plastic thin films.

Furthermore, the separate reinforcement film adopted in the present invention provides convenience for the decoration and printing of the finished products. For example, coloring and pattern printing can be performed on the separate reinforcement film. In particular, gravure printing can be performed on the BOPP (namely, biaxially-oriented polypropylene film).

In the preparation example of the present invention, a simple apparatus arrangement is provided, so as to avoid further investment in production equipment, thereby reducing the cost for the implementation of the present invention in the production practices.

Thus, the present invention can provide a soft fastener strip with reasonable cost and improved resistance to tearing, thereby improving the operation of the product and reducing the overall production cost of the relevant products.

BRIEF DESCRIPTION OF THE DRAWINGS

Upon reading the various embodiments of the present invention with reference to the drawings, a person skilled in the art would more easily understand the objective and

characteristics of the product and production method of the present invention. The description of the drawings is as follows:

FIG. 1 schematically illustrates a fastener strip of the prior art;

FIG. 2 schematically illustrates a schematic diagram of the base film molecular chain orientation of the fastener strip of the prior art;

FIG. 3 schematically illustrates the molecular chain orientation of a biaxially-oriented polypropylene thin film;

FIG. 4 schematically illustrates the fastener strip structure having a reinforcement layer provided by one embodiment of the present invention;

FIGS. 5 A and 5B schematically illustrates the manufacturing process in the embodiment of the present invention;

FIG. 6 schematically illustrates the contrast profiles and thickness compositions of a conventional single-layer fastener strip and the double-layer fastener strip of the present invention;

FIG. 7 schematically illustrates the operation of a tensile test; and

FIGS. 8 and 9 schematically illustrate the operation of a tear test.

DETAILED DESCRIPTION

The preferred embodiments provided by the invention are described below with reference to the accompanying drawings. Similar or identical parts are described in the accompanying drawings using similar reference signs. The different features disclosed herein may be used alone or in combination with one another; there is no stipulation that the invention is limited to a particular combination described herein. As such, the description provided is not intended to limit the scope of the claims.

The description may employ the phrases like“in one embodiment,”“in the

embodiment,”“in some embodiments,” or“in other embodiments,”; each may respectively refer to one or a plurality of the same or different embodiments disclosed herein.

Please refer to FIG. 1; a fastener strip 10 of the prior art is shown. The fastener strip 10 has a substantially continuous thermoplastic resin backing 12, an array of mushroom heads 14 (mushroom-shaped projections or hooks) formed integrally with the backing, and each mushroom head 14 having a stem 16.

Such a fastener strip structure 10 can interact with the other corresponding components by, for example, being releasably affixed to a fabric penetrable by the mushroom-shaped hooks 14 or by being configured such that the hook face of the fastener strip of two similar structures are joined together as a mechanical fixation device. The mating fastener strip can also be made into other styles.

Embodiment 1

The first embodiment of the present invention provides improvements to the above existing product. Please refer to FIG. 4; a fastener strip 20 of the present invention is

schematically illustrated. The buckle strip has the following features: having a substantially continuous thermoplastic material backing 17, and an array of mushroom heads 14 integral with the backing, each mushroom head 14 having a stem 16 (a plurality of protruding constructions). The thermoplastic material backing 17 and the mushroom head 14 integral with the backing together form the first film material. Furthermore, a reinforcement film 18 (second film material) is laminated on the back side of the thermoplastic resin backing 17.

In addition, please refer to FIG. 4; the thermoplastic resin backing 17 having a thinner thickness is shown. The backing 17 has a thickness of T2, and the reinforcement film 18 has a thickness of T3. The total of thickness T2 plus thickness T3 is preferably not greater than the thickness T of the thermoplastic resin backing 12 of the fastener strip 10.

An apparatus suitable for extruding and forming an orientable thermoplastic resin film can be used to produce the fastener strip of Embodiment 1.

Available thermoplastic resins that can be extruded and adopted include polyesters such as polyethylene terephthalate, polyamides such as nylon, polystyrene-acrylonitrile,

polyacrylonitrile-butamoldne-styrene, and polyolefins such as polypropylene.

The present invention seeks to avoid or reduce the unintended tearing and breaking of the fastener strip through changing product structure.

Please see the fastener strip shown in FIG. 1. Because the backing surface is provided with an array of mushroom-shaped protrusions or hooks 14 and each protruding structure is integrally formed with the thermoplastic resin backing 12, such protruding structures provides a stress concentration point when the backing body is acted upon by a force. The effect of undesirable stress concentration may be one of the reasons why the thermoplastic resin backing 12 is prone to tearing.

Furthermore, please refer to FIG. 2. During the molding process, the base film of the fastener strip is stretched in the machine direction, i.e., the length direction, to some degrees; therefore, the polymer molecular chain has a certain orientation, thereby causing the polymer molecular chain orientation to be weak in the width direction of the fastener strip. This is another reason why the fastener strips are prone to unintended tearing.

Certainly, the problem of easy tearing can be solved by simply considering, for example, the thickness of the material or of the backing; however, such a means may compromise other properties of the product.

Based on the above considerations, the backing of the fastener strip in the first embodiment comprises two film materials; that is, a reinforcement film 18 (second film material) is laminated on the back side of the thermoplastic resin backing 17. Therefore, the fastener strip of the present invention has a double-layer backing, which may also be referred to as a double-layer fastener strip hereinafter.

The advantage of the first embodiment is that the reinforcement film 18 (second film material), formed separately, is relatively independent from the array of mushroom-shaped protrusions or hooks 14. As such, the impact of stress concentration is reduced, thereby providing a reinforcement effect. Furthermore, when the reinforcement film 18 (second film material) is prepared, the simultaneous formation of the array of mushroom heads 14 as in the prior art does not need to be considered; thus, it is easy to further select, design, or process the material of the reinforcement film 18, which can provide a more flexible solution for the purpose of the reinforcement of the film material.

On the back side of the thermoplastic resin backing 17, the reinforcement film 18 (second film material) can be laminated by applying a suitable adhesive, and then bonding the two.

In addition, in the case when the thermoplastic resin backing 17 and the reinforcement film 18 (second film material) are both made of thermoplastic resin materials and both have good compatibility, then the two can be bonded through thermal lamination.

Embodiment 2

The fastener strip 20 provided in the second embodiment has the same construction as in Embodiment 1, thus the same reference numerals are employed. A difference of the second embodiment lies in providing a preferred combination of materials as well as providing improvements to the reinforcement film 18 (second film material).

In the conventional technique, fastener strips 10 and an array of mushroom heads 14 manufactured with polypropylene materials alone can provide sufficient strength to implement a proper fastener interlocking closure system. However, the thermoplastic material backing 17 is usually not soft enough. Attempts have been made to improve the components of the material itself. For example, polypropylene is co-blended with polyethylene in the hope of achieving suitable softness; however, such a solution would reduce the rigidity of the product as a whole, thereby degrading the fastener function of the fastener strip 10. Similarly, softness can be improved by simply reducing the thickness of the base layer of the fastener strip; yet, the incidences of tearing and breaking the fastener strip will be increased.

The above Embodiment 1 has provided the most basic structural design of the present invention. In the second embodiment, additional technical means are further provided.

In the second embodiment, the first film material (the thermoplastic material backing 17 and an array of mushroom heads 14 with stems 16) and the second film material (reinforcement film 18) are both formed with polypropylene material. The flat surfaces of the two are placed face to face and laminated; and the two are bonded through the process of heat pressing or sticking.

The thickness of the reinforcement film 18 is preferably in a range between 25 and 35 um.

The advantage of the second embodiment is that the fastener is formed by bonding two parts having the same material, which shows good compatibility, thereby providing a manufacturing process that is easy to implement.

Embodiment 3

On the basis of the second embodiment, further preferred schemes are provided. In the third embodiment, a special reinforcement film 18 designed separately is adopted; the special reinforcement film 18 is a biaxially-oriented polypropylene (BOPP) thin film. Please refer to FIG. 3 which schematically shows that the polypropylene thin film is stretched in the length direction and width direction, so as to impart an orientation to the polymer molecular chain. A biaxially-oriented polypropylene thin film is softer than the conventional base film of fastener strips and has higher mechanical strength.

The third embodiment has provided further advantages as follows: the body of the first film material can be made thinner; the second film material has good softness and mechanical properties; the total thickness of the first film material and the second film material has not substantially exceeded the thickness of the backing 12 of the fastener strip 10 of the prior art; yet, the softness and tear resistance are significantly improved while maintaining the locking function of the array of the mushroom heads 14.

The thickness of the reinforcement film 18 is preferably in a range between 25 and 35 um.

Embodiment 4

The fourth embodiment has illustrated a preferred preparation method for the fastener strip of the present invention. This embodiment will be explained by taking the preparation of the fastener strip 20 of the second embodiment and third embodiment as an example.

Please refer to FIG. 5 A. The second film material (reinforcement film 18) is prepared in advance; the reinforcement film 18 is a biaxially-oriented polypropylene thin film. The reinforcement film 18 is passed to a press roller 62 through a transfer roller 60; and as the press roller 62 rotates, the reinforcement film 18 arrives at the lower part of the mold opening of an extruder 32.

The polypropylene material feed stream 30 is fed into the extruder 32; the heated molten polypropylene material is fed into the gap between the rotating cylindrical mold roller 36 and the reinforcement film 18 through the mold opening 34. A plurality of cavities 38 are provided on the cylindrical surface of the mold 36; vacuum is provided through an external vacuum system (not shown); and the hot melt polypropylene material rapidly flows into the cavities 38. The mold is water cooled (the cooling device is not shown). The laminate of the cured polypropylene material and the reinforcement film 18 is peeled off from the cylindrical mold 36 through a peeling roller 44, which then serves as a material web 42 with an array of upstanding stems 48. The material web can be wound into rolls or directly supplied to the next process as shown in FIG. 5B.

As shown in FIG. 5B, the material web 42 is conveyed between two calendering rollers 52 and 53; and the calendering roller 52 in contact with the stems 48 has a predetermined temperature that heats the tip of the upstanding stems 48 to a temperature beyond the flow point of the polypropylene material, so as to form the mushroom head 14 as shown in FIG. 4. Please refer to FIG. 4; the stem 48 is deformed to form a mushroom head 14 with a stem 16.

In contrast with conventional single-layer buckling members, the present invention has provided a double-layer buckling member. Please refer to FIG. 6; the conventional products and products of the embodiments of the present invention are shown in contrast. The upper part of FIG. 6 shows a conventional fastener strip formed with a single film material comprising a base film and mushroom head constructions protruding from the base film and the thickness of the base film is Tl. The lower part of FIG. 6 shows the fastener strip of the embodiment of the present invention that has a construction of a double-layer buckling member. That is, the fastener strip is formed with two layers of film materials, with the thickness of the first film material body being T2 and the thickness of the second film material being T3. Preferably, the total of the thicknesses T2 plus thickness T3 is approximately similar with Tl.

The thickness of the double-layer buckling member provided by the present invention can be similar to the thickness of the conventional single-layer buckling member. The thickness of the backing of the buckling member can be adjusted by adjusting the gap between the roller 62 and the cylindrical mold roller 36.

Additionally, the equipment of the present invention can also be used generally with the production equipment that produces conventional single-layer buckling members. The transfer roller 60 for the reinforcement film 18 is not a newly added component; in conventional equipment, the transfer roller 60 is used to deliver a small segment of guiding film when the equipment starts to operate; after the operation of the equipment becomes normal, the transfer of the guiding film is stopped. In the present invention, there is no need to transfer the guiding film because the reinforcement film 18 is transferred throughout the operation, and the reinforcement film 18 may also function as the guiding film.

The subsequent processing steps may also include the step of arranging an easy-to-tear construction, which may be arranged in a variety of ways known in the prior art; for example, virtual cut points are arranged in the width direction of the strip product; a plurality of through-holes are approximately linearly arranged in the width direction of the fastener strip; and notches are arranged on the edge of the strip, or a combination thereof.

Sample and Test Analysis


1. Material Composition of the First Set of Samples:

Comparative Example 1 : a single-layer magic fastener, magic fastener of 100 g/m2 made of polypropylene, with 3M market supply model No. CHK-02846.

Embodiment 1 : a magic fastener with a reinforcement layer, magic fastener of 100 g/m2 made of polypropylene, with 3M market supply model No. CHK-02846; and a biaxially-oriented thin film tape of 100 g/m2.

2. Material Composition of the Second Set of Samples:

Comparative Example 2: a single-layer magic fastener, magic fastener of 191 g/m2 made of polypropylene, with 3M market supply model No. CHK-01084.

Embodiment 2: a magic fastener with a reinforcement layer: magic fastener of 100 g/m2 made of polypropylene, with 3M market supply model No. CHK-02846; a biaxially-oriented thin film tape of 31 g/m2.

3. The sample preparation method of Embodiment 1 and Embodiment 2: applying the biaxially-oriented thin film to the surface of the base film of the magic fastener; rolling with a 5 kg roller once.

4. Test Method

4a. Tensile Test

Please refer to FIG. 7; the tensile test is schematically shown. The tear test includes the following adjustments and steps:

(1) Test environment: temperature 23 +/ 2 °C; Humidity: 50 +/- 5%

(2) Cut sample: 25 mm (width direction) x 50 mm (length direction)

(3) Test instrument: Instron tensile test instrument, configured as follows:

Grip distance: 100 mm

Test speed: 300 mm/min

(4) The test sample was tightly clamped by the upper and lower grips; and the start button was pressed.

(5) Record: breaking point, unit N/25 mm

4b. Tear Test:

Please refer to FIGS. 8 and 9; the tear test is schematically shown. The tear test includes the following adjustments and steps:

(1) Test environment: temperature 23 +/ 2 °C; Humidity: 50 +/- 5%

(2) Cut magic fastener sample: 50 mm (width direction) x 30 mm (length direction)

(3) Test instrument: Instron tensile test instrument, configured as follows

Grip distance: 10 mm Test speed: 300 mm/min

(4) The test sample is tightly clamped by the upper and lower grips; and the start button was pressed.

(5) Record: peak, unit: gram-force

5. Test Results

Test of First Set of Samples


Test Results of the Second Set:


Conclusion: the grammage and thickness of the magic fastener with a reinforcement layer of the sample in the embodiment of the present invention are both smaller than those of a single-layer magic fastener; but the tensile strength and tear strength are greater.

Note that although machine production is adopted in the embodiments, which is to fix two layers of films through thermal bonding, whereas the experimental sample is bonded using glue, the mechanical strengths of the obtained films with these two methods are similar when compared in practice.

The present invention further includes at least the following concepts:

Concept 1 : A fastener strip for attachment to a mating strip, so as to provide a fastening function,

the fastener strip comprising:

a first film material, wherein the first film material comprises: a substrate layer, the substrate layer comprising a first surface and a second surface, the second surface being opposite to the first surface; and a plurality of protruding constructions extending from the first surface of the substrate layer and integrally formed with the substrate layer, and

a second film material laminated and fixed on the second surface of the first film material, the second film material being a separately formed film material.

Concept 2: The fastener strip of Concept 1, wherein both the first film material and the second film material are made of a thermoplastic polymeric material.

Concept 3: The fastener strip of Concept 1 or 2, wherein the thermoplastic polymeric material is polypropylene, or a mixture of polypropylene and polyethylene.

Concept 4: The fastener strip of any one of Concepts 1 to 3, wherein the first film material and the second film material are formed from the same material.

Concept 5: The fastener strip of Concept 4, wherein both the first film material and the second film material are made of polypropylene.

Concept 6: The fastener strip of any one of Concepts 1 to 5, wherein the second film material is a BOPP film, namely, a biaxially-oriented polypropylene film.

Concept 7: The fastener strip of Concept 1 or 2, wherein the second film material is a fiber-reinforced plastic film.

Concept 8: The fastener strip of Concept 1 or 2, wherein the first film material and the second film material are bonded with heat pressing and/or an adhesive.

Concept 9: The fastener strip of any one of Concepts 1 to 8, wherein the second film material has one of a bump pattern, a printed pattern, and a color design, or a combination thereof formed thereon in advance.

Concept 10: The fastener strip of any one of Concepts 1 to 8, wherein the fastener strip has an easy-to-tear construction.

Concept 11 : The fastener strip of any one of Concepts 1 to 8, wherein the easy-to-tear construction is selected from the following: at least one virtual cut point, a plurality of through-holes generally distributed in a straight line in a width direction of the fastener strip, a notch arranged on an edge of the strip, or a combination thereof.

Concept 12: A closure system of a disposable diaper, comprising the fastener strip of any one of the preceding concepts.

Concept 13: A disposable diaper, comprising the fastener strip of any one of the preceding Concepts 1 to 11.

Concept 14: A method of manufacturing a fastener strip, comprising the following steps: transferring a second film material to a press roller,

applying a first thermoplastic material above the second film material and a cylindrical mold roller through an extruder, then the first thermoplastic material and the second film material together passing through a pressing area between the press roller and the cylindrical mold roller to form a first intermediate composite film material comprising the first film material formed from the first thermoplastic material; and forming protrusions complementary with a surface configuration of the cylindrical mold roller on a first surface of the first film material.

Concept 15: The method of manufacturing the fastener strip of Concept 14, further comprising a further configuring processing on the protrusions to form a mushroom head construction.

Concept 16: The method of manufacturing the fastener strip of Concept 14 or 15, further comprising arranging an easy-to-tear construction.

Although the present invention has been described in detail with reference to the accompanying drawings, it is to be understood that the disclosed processing methods and devices shall not constitute a limitation to the present invention. Various modifications to the aforementioned embodiments can be easily made by a person skilled in the art without departing from the scope of the present invention.