TECHNICAL FIELD

The present invention relates to a method for stitching a sheet of fabric comprising high density polyethylene, a method for manufacturing an article, in particular a shoe, comprising the method for stitching, and an article obtained by this method.

BACKGROUND ART

The textile industry, in particular the shoe industry, continuously seeks fabrics for the manufacture of shoes and other accessories such as bags and wallets, which provide structural and aesthetical features which are advantageous for the products thereof.

Since 1965, DuPont has developed a group of resistant and durable lamellar products, which are made of high density polyethylene (HDPE) and are identified by the trademark Tyvek ^® . These materials are formed by the spinning of continuous filaments consisting of very fine fibres closely interconnected to one another and their subsequent bonding by heat and pressure. The result is a shiny white flashspun sheet that represents a printing surface with features of high opacity, resistance to chemical agents and strength.

In virtue of these special features, these materials may be used to manufacture protective work clothing. Due to the special structure of these materials, the traditional stitching methods are unsuitable. In particular, by using customary stitching needles and distance between one stitch and another, the material cuts the fabric and makes it impossible to manufacture articles having a good aesthetical appearance and a sufficient resistance.

GB191304259 discloses a complex device and method for stitching shoes and boots, in particular for stitching the sole of the shoe/boot to the leather part of the shoe/boot.

The device employs a curved eye needle. Devices such as that disclosed in GB191304259 are traditionally used by shoe manufacturers, but are totally unsuitable for stitching HDPE fabrics and moreover are large, complex and expensive.

DISCLOSURE OF INVENTION

An object of the present invention is therefore to provide a method for stitching which is applicable to the

HDPE based materials disclosed above allowing to obtain articles, in particular shoes having an excellent aesthetical appearance and a high resistance which is simple and cost effective.

The above said object is achieved by the present invention as it relates to a method for stitching a sheet of fabric comprising high density polyethylene (HDPE) having a grammage from 40 to 105 g/m ² , wherein a needle with a round point having a size of 65/9 and a distance between stitches from 2 to 3 stitches per centimetre with a low thread tension are used.

Another object of the present invention is to provide a method for manufacturing an article, in particular a shoe, which comprises the above said method for stitching and is suitable for the processing of the specific material .

The above said object is achieved by the present invention as it relates to a method for manufacturing an article, in particular a shoe, comprising the step of cutting at least one profile having an appropriate shape from the sheet of fabric by die-cutting, and the above said method for stitching to obtain the article.

Definitions

By the term "grammage" there is intended the weight in grams of a sheet of fabric by square meter of surface.

Detailed description

The method for stitching a sheet of fabric comprising high density polyethylene (HDPE) according to the invention uses a needle with a round point having a size of 65/9 and a distance between stitches from 2 to 3 stitches per centimetre with a low thread tension. The needle is preferably of the straight type. The size of sewing machine needles is expressed by a two-number metrical system, for example 60/8 for thin sewing needles and 120/16 for more resistant needles. The higher number refers to the metric system and defines the diameter of the needle's shaft in hundreds of mm (Nm) . The smaller number refers to the system adopted in the United States and represents an arbitrary number from 8 to 19 also used to indicate the diameter of the needle's shaft.

Preferably, the sewing machine needle system is the 134 system.

A Groz-Beckert 134 DPx5 class R size 65 needle or a Schmetz 134 Serv 5 size 65 needle may be used.

The thread used for the stitching may be for example a polyester thread having titre 40 (where 40 is the size of the thread expressed in a unit known to the skilled in the art in the shoe sector; the size of the thread varies from 10, thicker size, to 80, thinner size).

As far as the thread tension is concerned, it must be maintained low so that the thread is not too tensioned. Each sewing machine has a device, typically a screw to adjust the tension of the thread. The adjustment of the tension varies among sewing machines and there is no standard unit and value.

The high density polyethylene (HDPE) of the sheet of fabric is preferably a material that belongs to the group of products identified by the trademark Tyvek* manufactured by DuPont, in particolar Tyvek 1073.

The sheet of fabric comprising high density polyethylene (HDPE) has a grammage from 40 to 105 g/m ² . If grammages higher than 105 g/m ² are used, the fabric becomes excessively plasticated and is not sufficiently soft. If grammages lower than 40 g/m ² are used, the fabric becomes excessively fragile for use in the production of articles and accessories such as shoes or bags . The sheet of fabric comprising high density polyethylene (HDPE) preferably has a grammage from 70 g/m ² to 80 g/m ² , more preferably a grammage of 75 g/m ² .

The sheet of fabric preferably comprises a layer laminated with a vinyl adhesive of recycled and/or recyclable paper with a grammage from 25 g/m ² to 35 g/m ² .

More preferably the recycled and/or recyclable paper has a grammage of about 26 g/m ² .

The sheet of fabric may have a size from 50 cm to 200 cm in length and from 50 cm to 100 cm in width. The preferred size is 100 cm in length and 70 cm in width.

The sheet of fabric is preferably coupled to at least one reinforcing sheet of cotton, polyester, Jersey, viscose or mixtures thereof, by means of a water-based vinyl adhesive. The reinforcing sheet is preferably made of polyester, so that the whole material can be disposed of with plastic waste.

The reinforcing sheet preferably has a grammage from 20 g/m ² to 30 g/m ² , more preferably a grammage of about 25 g/m ² .

The method according to the invention for manufacturing and article, in particular a shoe, comprises the step of cutting at least one profile having an appropriate shape from the sheet of fabric by die-cutting, and the method for stitching disclosed above.

Depending on the article to be manufactured, one or more profiles will have to be cut and stitched together.

The method preferably comprises a step of milling the sheet of fabric and/or a step of dyeing the sheet of fabric .

The article may be a shoe, a bag, a wallet, a keyholder, a belt, a hat etc. The article is preferably a shoe .

Examples

Example 1

In Example 1, a neutral colour ballet flat was obtained.

500 sheets of Tyvek 1073 (DuPont) having a grammage of 75 g/m ² and a size of 100 cm x 70 cm were provided.

The sheets were crumpled one by one and introduced into a milling drum (Gozzini, model 3.5 X 3.5 616 3500) together with 1 litre of a composition comprising 20% Urelux B129 (Keminter) and 80% water and 10 non-processed white skins weighing 1 kg each.

The milling drum was rotated at 6 rounds/minute for 120 minutes.

Once milling is completed, the sheets were extracted from the milling drum and were left drying for one hour in open air. The skins were extracted from the milling drum and kept for following milling cycles.

A milled sheet of fabric was cut by a dye-cutting process into several appropriately shaped pieces. The pieces were then assembled and stitched with a needle with a round point (Goz Beckert needle, model 134 DPx5 class R size 65) .

Incidentally, in an alternative example which is not shown for sake of conciseness, a Schmetz 134 Serv 5 needle having size 65 was used and the results were identical.

The resulting ballet flat was not only soft, comfortable to wear, resistant and impermeable to rain, but also had a very fine aesthetical appearance.

Example 2

The shoe obtained in Example 1 was subjected to tests for measuring resistance to tearing, to stitching, to abrasion and to repeated flexures to verify the quality thereof. The tests are standard tests in the shoe manufacturer industry. Table 1 summarises the results of the tests.

As can be seen in the third line of the table, the value of the resistance to stitching of the shoe is considerably higher than the reference value. Furthermore, when the shoe is subjected to tests for resistance to tearing, abrasion and repeated flexures, the stitches withstood optimally to the stresses.

Example 3

In Example 3, the procedure was the same as in Example

1 with the difference that the sheets were laminated with a recycled and recyclable paper (grammage 26 g/m ² ) soaked in vinyl adhesive (latex) .

Results for resistance to tearing, to stitching, to abrasion and to repeated flexures were comparable to those shown in Example 2. For the sake of conciseness these results will not be shown. Furthermore, the resulting shoe was more comfortable and softer.

Example 4

In Example 4, the procedure was the same as in Example

3 with the difference that an additional pure cotton reinforcing sheet was used. The reinforcing cotton sheet had a grammage of 25 g/m ² and was cold coupled to the milled sheet of fabric with a water-based vinyl adhesive by means of monocylindrical machinery for coupling leather (PCM Engineering) .

Results for resistance to tearing, to stitching, to abrasion and to repeated flexures were comparable to those shown in Example 2. For the sake of conciseness these resuls will not be shown. Furthermore, the resulting shoe was much more resistant.

Example 5

In Example 5, the procedure was the same as in Example 4 with the difference that, as an additional reinforcing sheet, a polyester sheet having grammage of 25 g/m ² was used.

Results for resistance to tearing, to stitching, to abrasion and to repeated flexures were comparable to those shown in Example 2. For the sake of conciseness these results will not be shown. Furthermore, the shoe was extremely solid and could be disposed of as a whole with plastic waste.

Example 6

In Example 6, the procedure was the same as in Example 1 with the difference that the sheets were dyed manually with a black paint before milling.

In particular, each sheet of fabric was dipped at a room temperature for about 5 seconds in a dying composition comprising 40% dimethyl ketone, aliphatic solvents, aniline dyes and fixing agents.

After dipping, each sheet of fabric was laid on supports covered with an absorbing material for about 2 hours . This allows the complete evaporation of the solvents contained in the paint.

Results for resistance to tearing, to stitching, to abrasion and to repeated flexures were comparable to those shown in Example 2. For the sake of conciseness these results will not be shown.

The dyeing of the shoe therefore does not modify the structural features thereof .

Example 7

In Example 7, the procedure was the same as in Example 1 with the difference that the sheets were dyed with an orange paint after milling.

In particular, each sheet of fabric was dipped for about 5 seconds in a dyeing composition comprising 40% dimethyl" ketone, aliphatic solvents, aniline dyes and fixing agents.

After dipping, each sheet of fabric was laid on supports covered with an absorbing material for about 2 hours. This allows the complete evaporation of the solvents contained in the paint.

Results for resistance to tearing, to stitching, to abrasion and to repeated flexures were comparable to those shown in Example 2. For the sake of conciseness these results will not be shown.

The dyeing of the shoe with different dyes therefore does not modify the structural features thereof.

Example 8

In Example 8, the procedure was the same as in Example 1 with the difference that the sheets were laminated with a recycled and/or recyclable paper (grammage 26 g/m ² ) soaked in vinyl adhesive (latex) and an additional reinforcing sheet of polyester was used. The reinforcing polyester sheet had a grammage of 25 g/m ² and was cold coupled to the milled sheet of fabric with a water-based vinyl adhesive by means of a monocylindrical machinery for coupling leather (PCM Engineering) .

A few sheets were manually dyed with a fuchsia paint before milling.

In particular, each sheet of fabric was dipped for about 5 seconds in a fuchsia paint comprising 40% dimethyl ketone, aliphatic solvents, aniline dyes and fixing agents.

After dipping, each sheet of fabric was laid on supports covered with an absorbing material for about 2 hours. This allows the complete evaporation of the solvents contained in the paint.

A dyed and milled sheet of fabric was cut by means of a dye-cutting process into several pieces having an appropriate shape for manufacturing a sneaker shoe. The pieces were then assembled and stitched with a needle having a round point (Goz Beckert needle, model 134 DPx5 class R size 65) using a stitching distance of 2 stitches per centimetre with a low thread tension.

The resulting shoe was subjected to a series of tests to verify the thickness, resistance to stitching, tensile strength, elongation strength, resistance to flexure, resistance to abrasion, maintenance of colour intensity upon light exposure, rubbing and aging.

Table 2 summarises the results of the tests.

* Visual observation according to grey scale 1/5 (1= Clear colour release / variation; 5= No colour release /variation) determined in the artificial light cabin using illuminating D65

** Visual observation according to the scale of the blue wool references 1/8 (1" Clear variation; 8= No variation) determined in the artificial light cabin.

As can be seen from the third line of Table 2, the shoe obtained by the method according to the invention has an excellent stitching resistance, tensile and elongation strength, flexure strength and resistance to abrasion.

From an analysis of the features of the method according to the present invention, the advantages it allows to obtain are apparent. In particular, in virtue of the fact that a straight needle with a round point having a size of 65/9 and a distance between stitches from 2 to 3 stitches per centimetre with a low thread tension are used to stitch the special material, the material maintains its resistance features. A shorter stitch would risk the tearing of the sheet of fabric, whereas the considerably broad distance between one stitch and another allows to obtain a very resistant stitching and an optimal aesthetical result.

In order to implement the method according to the invention, a simple customary sewing machine can be used, reducing- costs and room required.

The use of layer laminated with a vinyl adhesive of recycled and/or recyclable paper with a grammage from 25 g/m ² to 35 g/m ² allows to increase the softness of the fabric while maintain it light and resistant.

Furthermore, by coupling the sheet of fabric to at least one reinforcing sheet of cotton, polyester, Jersey, viscose or mixtures thereof, the material is considerably strengthened for specific applications and processing. In particular, by using a reinforcing polyester sheet, the whole product can be disposed of with plastic waste. Furthermore, by using a grammage from 20 g/m ² to 30 g/m ² for the reinforcing sheet, an optimal balance is obtained between lightness and resistance of the sheet of fabric. The method for manufacturing an article, in particular a shoe, according to the invention, allows to obtain a soft and light article which is at the same time resistant and waterproof. The article also has a pleasant aesthetical appearance.

Furthermore, the additional step of milling the sheet of fabric allows to considerably soften the sheet of fabric without modifying its resistance features. Furthermore, the resulting sheet of fabric has a pleasant aesthetic appearance. As an alternative or additionally, the additional step of dyeing the sheet of fabric allows to obtain a virtually unlimited range of colours without modifying the features of the fabric.

Finally, it is clear that modifications and variants can be made to the disclosed method without departing from the scope of protection of the appended claims.