WO2023121633A1

WO2023121633A1 - Composite toe cap for protective shoe

Info

Publication number: WO2023121633A1
Application number: PCT/TR2022/051576
Authority: WO
Inventors: Cem ALTINTAŞ; Gökhan K.ÇOBAN; Alican ÇELTEKLİOĞLU
Original assignee: Coats (Türki̇ye) İpli̇k Sanayi̇i̇ Anoni̇m Şi̇rketi̇
Priority date: 2021-12-25
Filing date: 2022-12-23
Publication date: 2023-06-29

Abstract

The present invention discloses the structure and manufacture of a composite toe cap made of thermoplastic, which is used in for work safety shoes from personal protective equipment. In particular, the invention relates to a composite toe cap comprising at least one sewing layer comprising thermoplastic hybrid fibers and a preform structure comprising a bearing layer to which the sewing layer is fixed, and to a method of manufacturing the toe cap.

Description

COMPOSITE TOE CAP FOR PROTECTIVE SHOE

Technical Field

The present invention relates to the structure and manufacture of a composite toe cap made of thermoplastic for work safety shoes included in personal protective equipment.

In particular, the invention discloses composite toe caps produced by obtaining preforms from thermoplastic hybrid fibers using Tailored Fiber Placement (TFP) technology and rapid consolidation and cooling of these preforms under temperature pressure, and the related production method.

Prior Art

Recently, with the increase in industrialization, protecting people's life safety has become an important issue. Measures to be taken to minimize injuries in industry are gaining importance. One of these is the use of work safety shoes to ensure the protection of employee foot and finger health. Work safety shoes are a protective equipment used by employees to ensure foot safety in workplaces to reduce the impact of accidents by providing grounding in case of contact with electrical energy, protecting against sharp object sinking, heavy parts falling and the end of the foot against compression. In this context, the necessity of making a protective toe cap that will protect the employee from impacts and injuries caused by material falling on the foot part and damages that may occur from thermal conductivity gains importance.

Protective toe caps are a curved shaped part placed on the front of the work shoe to protect the fingers from impacts. Work safety shoes with protective toe caps in industry can be produced in two different ways according to the protection materials used in the production of protective toe caps. The first is steel or aluminum, titanium, etc. metal alloy material toe protection work shoes. However, metal alloy toecaps are heavy and not suitable for daily long term use, in addition, the high thermal conductivity of metal alloy toecaps makes them uncomfortable in very hot or cold climates. The second is toe protection work shoes with glass and carbon fiber reinforced thermoplastic and thermoset matrix composite material. The use of this type of protective toe cap is becoming increasingly widespread due to its light weight compared to steel ones. There are mostly protective toe cap guards on the market made of thermoset matrix and carbon/glass fabrics. Thermoset resins used in composite protective toe caps are brittle and have low impact damping properties. Nowadays, besides lightness, the highest possible level of impact resistance and low cost are among the features expected from protective toe caps. Considering consumer demands, it is among the demands that the protective toe caps produced can fulfill many functions together instead of providing a single function. For example, protective toe caps with multiple features, such as not only being lightweight but also having low thermal conductivity and being inexpensive or recyclable, are in demand today.

As a result of this situation, some of the developed techniques are given below.

In the utility model document number CN209359775U, carbon fiber thermoplastic special work shoe toe cap is mentioned. The design of the invention is formed by injection molding thermoplastic carbon fiber material. In this utility model, the toe is produced by injection molding, whereas in our invention, fiber placement technology is used by sewing. The components in the raw material composition of the products are also different between the utility model and our invention.

In the patent document number CN109354744A, a shoe toe manufactured with a nanocomposite is mentioned. The composite fiber composition includes glass fiber and carbon fiber. The toe cap in the document is obtained by treating the glass fiber at a temperature of 100-200°C to form a nano-composite after curing the glass fiber and laminating the carbon fiber. The composition and method disclosed in our invention are different from the content and process steps described in the present invention.

The patent document number CN201810874884 relates to a safety shoe toe made of carbon fiber thermoplastic composite material. The toe of the invention comprises 50-70% PA6 base material, 15-30% carbon fibers, 1 %-5% a flexibilizer, 5-13% antioxidant, 2-10% heat stabilizer, 1 -5% conductive parts. Our invention also uses carbon fiber and PA6 components. However, they have different ratio ranges and are processed together with different additional components.

The patent document number WO9848999A1 relates to the production of a toe made of composite plastic material and intended for use in footwear. The mentioned toe consists of organic and/or mineral fibers bonded with a thermoplastic or thermosetting resin. In our invention, resin or mineral fibers are not used, and the toe disclosed in our invention obtains its durability especially from the hybrid fiber blend. This hybrid fiber blend also provides ease of use and lightness to the product obtained in our invention.

As a result, there is a need for the production of thermoplastic matrix protective toe on with the above-mentioned light weight, high impact resistance, low thermal conductivity, low wastage during production, that is, economical and recyclable. Objectives and Brief Description of the Invention

The main purpose of the present invention is to obtain a composite shoe toe cap with high protection against foot and finger injuries as a result of occupational accidents and lighter in weight than its commercially available counterparts.

Another aim of the invention is to provide the user with high comfort and protection.

Another aim of the invention is to obtain a composite shoe toe cap with high protection without the use of metal alloys and thus without alerting X-ray machines.

Another aim of the invention is to provide a composite shoe toe cap with low thermal conductivity with the composite used, that is, a composite shoe toe cap that does not make the user feel hot and cold.

A further aim of the invention is to provide an environmentally friendly and cost-effective composite shoe toe cap which can be recycled thanks to the thermoplastic matrix used to form the invention.

Another aim of the invention is to reduce the amount of waste by producing preforms suitable for the net geometry of the product during the production of the invention..

In order to realize the above mentioned purposes, the invention is a composite toe cap for protective footwear, comprising a preform structure, wherein the preform structure comprises at least one sewing layer comprising thermoplastic hybrid fibers and a bearing layer to which the sewing layer is fixed.

In an alternative embodiment of the invention, mentioned hybrid fibers contains at least one reinforcing fiber, at least one thermoplastic and alternatively a coating chemical. Mentioned reinforcing fibers is made of carbon fiber, glass fiber or basalt fiber or mixtures thereof. These thermoplastics are made of one or more of the following raw materials: PA6, PA11 , PA12, PP, PET, PC, PBT and PA410.

In the preferred embodiment of the composite toe cap, the hybrid fibers contain 50-70% carbon fiber, 30-50% Nylon 6 and 0-3% coating chemistry by volume. The coating chemical in mentioned is preferably anionic/non-ionic a water or alcohol-based polyamide/polyurethane solution.

In another embodiment of the invention, mentioned bearing layer is made of thermoplastic polymer film or fabric. The polymer film or fabric is made of PET, PA, PP films or glass fiber woven fabric. Mentioned sewing layer comprises hybrid fibers and a sewing yarn securing mentioned hybrid fibers to the bearing layer. The mentioned sewing yarn is made of thermoplastic material.

In the preferred embodiment of the invention, the weight of the composite toe cap obtained is between 35 g-55 g.

In order to achieve the aforementioned objectives, the invention is also a composite toe cap production method for protective footwear and comprises the steps of determining the fiber passageways through which hybrid fibers can be continuously laid and sewn on the bearing layer, placing the hybrid fibers on the bearing layer using fiber placement technology by sewing and forming a preform, folding the formed preform in half from the folding line axis, consolidating the folded preform under temperature and pressure, giving the consolidated preform a toe cap shape in the mold and cooling it.

Brief Description of the Figures

In Figure 1 ; perspective view of the composite toe cap of the invention from the back is given.

In Figure 2; a perspective cross-sectional view of the composite toe cap from the back is given.

In Figure 3, a cross-sectional view of the preform forming the composite toe cap is given.

In Figure 4; a back view of the composite toe cap is given.

In Figure 5.1 , 5.2, 5.3 and 5.4; a view of example hybrid fibers layout templates of the preform forming the composite toe cap is given.

In Figure 6, a view of example sewing designs including all sewing layers of the preform forming the composite toe cap is given.

Reference Numbers

10. Composite protective toe cap

1 1. Body surface

12. Sole surface

13. Sole clearance

14. Hybrid fibers

15. Folding line

16. Bearing layer

17. Sewing layer

18. Preform structure d1 . Wall thickness of the body surface d2. Wall thickness of the sole surface d3. Wall thickness of the toe end of the toe cap

L. Sole surface width

Detailed Description of the Invention

The present invention discloses the structure and manufacture of a protective toe cap (10) formed from thermoplastic, which is used in work safety shoes from personal protective equipment.

The subject of the invention is based on the protective toe cap (10) basically composed of a preform structure (18). The mentioned preform structure (18) comprises a bearing layer (16) and sewing layers (17) positioned on this layer (16). Figure 3 shows a schematic drawing of these layers.

The sewing layer (17) in Figure 3 comprises hybrid fibers (14) co-mixed with thermoplastic matrix and sewing yarn that fixes these hybrid fibers (14) to the bearing layer (16). The sewing layer (17) is formed by fixing the hybrid fibers (14) to the bearing layer (16) with sewing yarn. Figures 5.1 - 5.3 show 3 different sewing design examples. The sewing design example shown in Figure 5.4 at the top of the folding line (15) can be given as a toe reinforcement design. It is possible to obtain preforms (18) using these and other sewing designs.

It is envisaged that the preform (18) forming the toe cap (10) subject to the invention contains 7 different sewing layers. Accordingly, the preform (18) is consist of by using the sewing designs given as an example one or more times and folding them in half from the axis of the folding line (15) to obtain a 14-layer sewing design (see Figure 6). The sewing yarn used here is made of thermoplastic material. The bearing layer (16) can be selected from thermoplastic polymer film or fabric. Examples of such films or fabrics are PET, PA, PP films or glass fiber woven fabric.

Figure 1 shows a perspective view of the toe cap (10) from the upper back and its final form resembling the shoe toe. Accordingly, the toe cap (10) comprises a body surface (11 ) configured to cover the toe of the shoe, a sole surface (12) that facilitates the assembly of this surface (1 1 ), to the shoe sole and is configured in the form of a strip in the same plane as the sole. The width (L) of this sole surface (12) is determined to be a maximum of 10 mm according to the EN12568 standard. In the center of the sole surface (12) is the sole clearance (13), which will be filled by the sole when it is mounted on the shoe.

The toe cap (10) of the invention has different wall thicknesses in different parts in accordance with its purpose. These wall thicknesses (d1 , d2, d3) are shown in Figure 1 and Figure 2. According to the cross-sectional view given in Figure 2, in addition to wall thickness of the body surface (d1 ) and wall thickness of sole surface (d2), the wall thickness (d3) of the toe cap (10) has different dimensions. Wall thickness of the body surface (d1 ), which is important for absorbing the impact on the foot and thermal conductivity, should preferably be in the range of 2.5-5 mm; wall thickness of the sole surface (d2) should preferably be in the range of 1 .5-2.5 mm to facilitate the installation of the toe cap (10) on the shoe, and wall thickness of the toe (d3), which is important for the effective protection of the toe from impacts, should preferably be in the range of 3.5-7 mm. Accordingly, optimum protection is provided with a thickness order as d3 > d1 > d2.

Figure 4 shows a back view of the toe cap (10). This shows the body surface (1 1 ) of the toe cap (10), which is configured in a non-circular shape according to the shoe form, and the wall thickness (d1 ) of this body surface. This non-circular shape of the toe cap (10) makes it ergonomic and compatible with the shoe and toe structure.

Hybrid fibers (14) with thermoplastic matrix used in preforms (18) forming the protective toe cap (10) comprise at least one reinforcing fiber, at least one thermoplastic and alternatively a coating chemical. Hybrid fibers (14) are manufactured by selecting the reinforcing fiber from carbon fiber, glass fiber or basalt fiber types and the thermoplastic from one or a mixture of thermoplastics such as PA6, PA1 1 , PA12, PP, PET, PC, PBT and PA410. Coating chemicals are used if necessary.

The preferred embodiment of hybrid fibers (14) comprises 50-70% carbon fiber, 30-50% Nylon 6 and 0-3% coating chemistry by volume. Mentioned coating chemistry for this embodiment is preferably an anionic/non-ionic, water or alcohol based polyamide/polyurethane solution. Different combinations of hybrid fibers (14) can be produced by means of co-mixed hybrid fiber technology. Table 1 shows these ratios.

Table 1. Hybrid Fiber Blend Ratios

The hybrid fibers (14) used in the preform (18) structures are fixed on the bearing layer (16) using Tailored Fiber Placement (TFP) technology. A special sewn design program is used to lay the hybrid fibers (14) on the bearing layer (16). With these fiber orientations and ply configurations, preform structures (18) are formed. The fiber passageways through which the hybrid fibers (14) can be continuously laid and sewn on the bearing layer (16) are determined. Figures 5.1 -5.4 show these continuous passageways. Among these, the sewing layer shown in Figure 5.4 is applied only to the area corresponding to the tip of the toe.

Figures 5.1 -5.4 show sample sewing design images of hybrid fibers (14). The sewing designs in these images are at different angles and orientations and are preferably placed on top of each other in different sequences. First, a 7-layer preform (18) is obtained and then a 14-layer preform (18) structure is obtained by folding inwardly in half along the folding line (15) axis. Here, different designs are arranged to obtain a structure with different strengths. Table 3 shows the test results of specimens made of different layers. Explanations for these are given below the table.

Figure 6 shows a preferred configuration and different hybrid fiber (14) sewing designs can also be created. In the hybrid fiber (14) sewing design; the thickness of the toe (d3), thickness transitions, load bearing capacity, load transfer directions and forming parameters in the mold are taken into consideration.

Preforms (18) are produced on sewing machines specially developed for technical textiles. In this production, hybrid fibers (14) are sewn and placed on the bearing layer (16) with the use of sewing yarn and different types of sewing at a specified direction and frequency. These placements can be in a way to cover the entire bearing layer (16) or in a way to cover the area of the thick areas to be reinforced (e.g. toe cap, Figure 5.4).

The production of the protective toe cap (10) is based on the rapid consolidation of these preforms (18) under certain temperature and pressure after being folded in half on the folding line (15) axis, simultaneously forming the toe cap in the mold and cooling it. The temperature value used for forming the preform structures (18) is preferably between 260 - 280°C and the pressure value used is preferably between 150 - 200 psi. With the applied temperature, the bearing layer (16) and the sewing yarns melt, allowing the hybrid fibers (14) to stay together and integrate the structure. With the applied pressure, the preforms (18) are shaped in the mold. The mold is then cooled to around 60°C and the final product, the toe cap (10), is obtained. The weight of the toe cap (10) produced in our invention is between 35-55 gr.

By examining the thermoplastic protective toe caps and the test standards and methods used for the validation of these toe caps, the conformity of the inventive toe caps (10) with the minimum values specified in the table below applied in ASTM and EN standard tests was measured. Table 2. Minimum test values according to ASTM F2412-18a and EN12568 standards

The manufactured toe caps (10) were subjected to compression and impact tests in accordance with ASTM F2412-18a standard and the results are as shown in the table below.

Table 3. Test results according to ASTM F2412-18a standard

Five different samples were formed by using different sewing layers in different sequences. When the test results given in Table 3 are compared with the reference values (ASTM F2412-18a) given in Table 2, it is seen that the hybrid fiber (14) samples successfully passed the impact tests in terms of the energy value they absorbed. Looking at the compression test results, it is seen that all of the samples prepared with different fiber arrangements successfully passed the test by at least doubling the 12.7 mm limit specified in the standard. In the impact test, which was performed to test more severe conditions and sudden heavy object drops, R2 and R4 designs could not withstand the impact and failed the test. No fracture was observed in the R1 design, but it failed the test with a result below the limit value. R3 and R5 samples passed the compression test with a value above the limit as in the impact test and were determined as safe samples.

Claims

1 . A composite toe cap (10) for protective shoes characterized in that it comprises a preform (18) structure comprising

- at least one sewing layer (17) comprising thermoplastic hybrid fibers (14), and

- a bearing layer (16) to which the sewing layer (17) is fixed.

2. The composite toe cap (10) according to Claim 1 characterized in that the hybrid fibers (14) comprise at least one reinforcing fiber, at least one thermoplastic and alternatively a coating chemical.

3. The composite toe cap (10) according to Claim 2 characterized in that the hybrid fibers (14) are made of carbon fiber, glass fiber or basalt fiber or mixtures thereof.

4. A composite toe cap (10) according to Claim 2 characterized in that mentioned thermoplastics are made of one or more of the raw materials PA6, PA1 1 , PA12, PP, PET, PC, PBT and PA410.

5. The composite toe cap (10) according to Claim 2 characterized in that the hybrid fibers (14) comprise 50-70% carbon fiber, 30-50% of Nylon 6 and 0-3% of coating chemistry by volume.

6. A composite toe cap (10) according to Claim 2 characterized in that mentioned coating chemical is an anionic/non-ionic, water or alcohol based polyamide/polyurethane solution.

7. A composite toe cap (10) according to Claim 1 characterized in that the bearing layer (16) is made of thermoplastic polymer film or fabric.

8. Composite toe cap (10) according to Claim 7 characterized in that the polymer film or fabric in the bearing layer (16) is made of PET, PA, PP films or glass fiber woven fabric.

9. The composite toe cap (10) according to Claim 1 characterized in that the sewing layer (17) comprises a sewing yarn fixing the hybrid fibers (14) to the bearing layer (16).

10. Composite toe cap (10) according to Claim 9 characterized in that mentioned sewing yarn is made of thermoplastic material.

11. Composite toe cap (10) according to any of the previous claims characterized in that its weight is between 35-55 gr.

9 Production method of a composite toe cap (10) for protective shoes characterized by the following steps of

- determining fiber passageways through which hybrid fibers (14) can be sewed by laying them continuously on a bearing layer (16), - the hybrid fibers (14) are inserted into the bearing layer (16) using fiber placement technology and forming preform (18), folding the formed preform (18) in half along the axis of a folding line (15),

- consolidation of the folded preform (18) under temperature and pressure,

- shaping the consolidated preform (18) into a toe cap in the mold, and cooling. The production method of a composite toe cap (10) according to Claim 12 characterized in that the temperature value applied to the folding preform (18) is between 260 - 280°C. The production method of a composite toe cap (10) according to Claim 12 characterized in that the pressure value applied to the folding preform (18) is between 150 - 200 psi.