Footwear assembly method using thermoplastic copolyamides as adhesive

Abstract

The invention mainly relates to the use of a copolyamide of the following formula: Aa / (X.Y)b wherein: A is at least one from among: (i) an alpha,omega-aminocarboxylic acid; (ii) a lactam; and X is at least one aliphatic diamine with 2 to 14 carbon atoms, a polyether or a polyetheramine comprising ether groups comprising 2 to 4 carbon atoms; Y is at least one aliphatic dicarboxylic acid with 6 to 22 carbon atoms; a is an integer from 1 to 3, in particular 1 or 2; and b is an integer from 1 to 3, in particular 1 or 2; said copolyamide having: o a melting temperature Tm of between 80°C and 150°C, o a melt volume-flow rate of 10 to 60 [mL / 10 min] at 160°C under 2.16 kg, as measured according to the ISO 1133 standard, and also o an enthalpy of fusion of at least 30 J / g, as measured according to the ISO 307 standard by DSC on cooling at 20K / min, for the assembly of articles by hot spraying.

Description

[0001] Shoe assembly process using thermoplastic copolyamides as adhesive

[0002] technical field

[0003] This patent application relates to the use of particular thermoplastic copolyamides by hot spraying for the assembly of articles, in particular footwear, the associated article assembly process and the articles, in particular footwear, that can be obtained by this process.

[0004] Previous technique

[0005] Shoes, especially sports shoes, are generally made by assembling different parts, including an upper, a midsole, and an outer sole.

[0006] Various methods exist for assembling these shoe components. Historically, shoes were assembled, for example, by nailing or sewing. Modern shoes, particularly those made of synthetic materials, can also be assembled using adhesives.

[0007] Hot melt adhesives are substances that are solid at room temperature and are generally free of water and solvents. They are applied in a molten state and harden upon cooling, forming an adhesive bond that ensures the assembly of two substrates to be joined. These adhesives must have a melting point compatible with the material of the shoe components and develop sufficient adhesive strength to ensure a reliable bond. Hot melt adhesives contain a thermoplastic polymer and, where applicable, a tackifying resin and / or a plasticizer.

[0008] Although it is possible to apply the adhesive using veils or films, it is advantageous to do so by hot spraying because this method is faster and more economical and is also compatible with automation of the assembly process.

[0009] Furthermore, the hot melt adhesives typically used for shoe assembly are thermoset adhesives, for example, polyurethane-based. These adhesives are incompatible with hot spray application and also present challenges during recycling. Therefore, these adhesives cannot be used in the manufacture of eco-designed products.

[0010] We are therefore looking for an adhesive for assembling items such as shoes that is suitable for hot spray application and that does not pose problems during the recycling of the items after use. Summary of the invention

[0011] The invention therefore aims to propose the use of copolyamides with a specific property profile that makes them suitable for solving the technical problem stated above. Indeed, the present invention is based on the observation that copolyamides with a melting temperature, hot viscosity, and crystallization rate as defined below allow both the deposition of a precise adhesive bead by hot spraying and also form a good quality bond, as evidenced by the energy required for separation and the observed mode of failure.

[0012] Also, according to a first aspect, the invention relates to the use of a copolyamide with the following formula:

[0013] HAS a / (XY)b (formula I) in which:

[0014] A is at least one of:

[0015] (i) an alpha-omega aminocarboxylic acid;

[0016] (ii) a lactam; and

[0017] X is at least an aliphatic diamine with 2 to 14 carbon atoms, a polyether or a polyetheramine comprising ether groups comprising 2 to 4 carbon atoms;

[0018] Y is at least an aliphatic dicarboxylic acid with 6 to 22 carbon atoms; a is an integer from 1 to 3, in particular 1 or 2; and b is an integer from 1 to 3, in particular 1 or 2; said copolyamide having: a melting temperature Tf between 80°C and 150°C, a hot melt volume index of 10 to 60 [mL / 10 min] at 160°C under 2.16 kg, as measured according to ISO 1133, and an enthalpy of crystallization of at least 5 J / g, as measured according to ISO 307 by DSC cooling at 20K / min, for the assembly of articles by hot spraying, in particular in a process known as 'hot spraying' and as defined below.

[0019] Advantageously, the copolyamide is of formula (I), where A is chosen from caprolactam, amino-11-undecanoic acid and lactam 12.

[0020] Preferably, the copolyamide has formula (I), where X is selected from linear aliphatic diamines such as ethylenediamine, putrescine, cadaverine, 1,6-hexamethylenediamine, 1,10-decamethylenediamine; branched diamines; and cyclic diamines such as piperazine. Alternatively, the copolyamide may have formula (I), where Y is a linear aliphatic dicarboxylic acid, preferably selected from adipic acid, pipelic acid, suberic acid, azelaic acid, sebacic acid, 1,11-undecanedioic acid, 1,12-dodecanedioic acid, and brassylic acid.

[0021] Preferably, the copolyamide is of formula (I) with a = 1 or 2 and b = 1 or 2, in particular with a = 2 and b = 2.

[0022] Advantageously, the copolyamide has formula (I) and comprises at least one XY unit in which X is polyethylene glycol (PEG). In particular, the copolyamide may be PA 6 / 11 / 6.12 / PEG.12 (also equivalently designated PA 6 / 6.12 / 11 / PEG.12).

[0023] Preferably, the copolyamide has a melting point (Tf) between 85 and 130°C. Advantageously, it also has a glass transition temperature (Tg) below 60°C.

[0024] Advantageously, the copolyamide allows a peel force, measured according to the t-peel test described in the examples, of at least 30N / mm.

[0025] According to a second aspect, the invention relates to a method for manufacturing articles, comprising the following steps:

[0026] (a) supply of the parts of the article to be assembled;

[0027] (b) application of a copolyamide as described above to at least one of the surfaces of at least one of the parts to be assembled, by hot spraying; and

[0028] (c) assembly of the parts to be assembled, where appropriate under application of pressure.

[0029] Preferably, the polymer component of the finished article comprises at least 70%, preferably at least 80% and in particular at least 90% by weight of thermoplastic polymer.

[0030] According to a third aspect, the invention relates to an article that can be obtained by this process, in particular a shoe, especially a sports shoe.

[0031] Description of the implementation methods

[0032] Definition of terms

[0033] The term "copolyamide" refers to a polymer formed by the copolymerization of at least two chemically distinct types of monomers, called comonomers, of which at least one, preferably two or three, and in particular all, are polyamide monomers as defined below. A comonomer other than polyamide monomers may, in particular, be a polyether monomer as defined later. A copolymer is thus formed of at least two distinct repeating units or motifs. It may also be formed of three, four, five, or more repeating units. The copolyamide in the sense of the present invention is preferably a block copolymer, in which each repeating unit forms a segment of a certain length. The term "monomer" as used in the description of polyamides should be understood to mean the monomer necessary to form a repeating unit.Indeed, the case where the repeating unit of the polyamide is formed by the association of a diacid with a diamine is special. In this case, the diamine / diacid pair (in equimolar quantities) is considered to constitute the monomer, since individually, the diacid and the diamine are not capable of polymerizing.

[0034] In the following description, any reference to a standard means the version of said standard in force on the filing date (or priority date if priority is claimed) of this application.

[0035] The term "melting temperature" refers to the temperature at which a polymer, at least partially crystalline, transitions to a viscous liquid state, as measured by differential scanning calorimetry (DSC) according to standard NF EN ISO 11 357-3 using a heating rate of 20K / min.

[0036] The term "glass transition temperature" refers to the temperature at which a polymer, at least partially amorphous, transitions from a rubbery to a glassy state, or vice versa, as measured by differential scanning calorimetry (DSC) according to standard NF EN ISO 11357-2. The minimum temperature measurable by differential scanning calorimetry depends on the equipment used and is generally around -30°C. Below this minimum temperature, or as an alternative to DSC, the glass transition temperature can be measured by dynamic mechanical analysis (DMA) according to standard ISO 6721-4 with a frequency of 1 Hz and an amplitude of 20 pm (voltage).

[0037] The term "enthalpy of crystallization" refers to the latent heat of crystallization, as measured by differential scanning calorimetry (DSC) according to the standard NF EN ISO 11 357-3.

[0038] The term "enthalpy of fusion" refers to the latent heat of fusion, as measured by differential scanning calorimetry (DSC) according to the standard NF EN ISO 11357-3.

[0039] In the context of the copolyamides of the invention, the melting temperature, the glass transition temperature (when determined by DSC), the enthalpy of crystallization, and the enthalpy of fusion are determined by applying the following DSC cycle: 1) the sample temperature is equilibrated to 20°C, 2) the sample is cooled to -30°C using a cooling ramp of 10 K / min, 3) the sample is held at -30°C for 5 minutes, 4) the sample is heated to 250°C with a heating ramp of 20 K / min, 5) the sample is held at 250°C for 5 minutes, 6) the sample is cooled to -30°C with a cooling ramp of 20 K / min, 7) the sample is held at -30°C for 5 minutes, and finally 8) the sample is heated to a temperature of 250°C with a heating ramp of 20K / min.The term "MVR" (English acronym for "melt volume rate") refers to the melt volume flow index. MVR is measured according to ISO 1133-1:2011, using an extrusion plastometer.

[0040] The nomenclature used to define polyamides is described in ISO 1874-1:1992 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", particularly on page 3 (Tables 1 and 2), and is well known to those skilled in the art. In the PAL notation, PA designates polyamide and L designates the number of carbon atoms in the amino acid or lactam. Thus, polyamide is obtained by the polycondensation of the amino acid or lactam containing L carbon atoms. In the PAMN notation, M designates the number of carbon atoms in the diamine and N designates the number of carbon atoms in the diacid.

[0041] For the purposes of this invention, "hot spray" refers to a hot melt adhesive deposition technique in which the adhesive, introduced at room temperature in a solid state, is fluidized and / or liquefied during a short heating step to a high temperature, typically at least 20°C above the melting point of the adhesive, before being directly sprayed onto the substrate to be bonded. In a hot spray process, the heated / liquefied adhesive is sprayed onto the surface of the material immediately after being fluidized / liquefied, typically up to a few seconds after being fluidized and / or liquefied. In particular, the adhesive is not stored / maintained in a fluid / liquid state in a reservoir. The hot melt adhesive, heated to such a high temperature, has significant fluidity, so it is necessarily applied to the substrate continuously, typically in the form of one or more beads.

[0042] The hot spray technique of the invention differs from a printing technique, also called droplet projection technique, in several aspects.

[0043] The first difference lies in the temperature to which the adhesive is heated. In a printing process, the hot melt adhesive is heated to a temperature just high enough to make it fluid, generally close to its melting point. In a hot spray process, the adhesive is heated to a much higher temperature, typically at least 20°C above its melting point, so that it can be easily sprayed.

[0044] Furthermore, in a printing technique, a large quantity of adhesive is preheated and kept in a fluid state in a temperature-controlled tank. Conversely, in a hot spray process, the adhesive is continuously heated and directly applied / sprayed onto the substrate to be bonded. This direct application of the fluid / liquefied adhesive is essential because it prevents the degradation and / or oxidation of the adhesive that can occur at the high temperatures used in a hot spray process. This type of degradation does not occur at the temperature ranges used in printing techniques.

[0045] Finally, in a printing technique, the hot-melt adhesive is a viscous fluid that allows for the projection / application of the adhesive onto the substrate in a specific pattern, such as dots. However, this type of pattern is impossible to achieve with a hot-spray process, as the adhesive heated to such temperatures is too fluid. Therefore, adhesive applied using a hot-spray technique results in a continuous pattern, typically in the form of beads.

[0046] In the context of the present invention and unless explicitly stated otherwise, the ratios of each of the monomers are expressed by weight, relative to the total weight of the copolyamide.

[0047] As mentioned above, the copolyamide proposed for the assembly of articles by hot spraying has the following formula:

[0048] HAS a / (XY)b (formula I) in which:

[0049] A is at least one of:

[0050] (i) an α,β-aminocarboxylic acid;

[0051] (ii) a lactam; and

[0052] X is at least an aliphatic diamine with 2 to 14 carbon atoms, a polyether or a polyetheramine comprising ether groups comprising 2 to 4 carbon atoms;

[0053] Y is at least one aliphatic dicarboxylic acid with 6 to 22 carbon atoms; a is an integer from 1 to 3, including 1 or 2; and b is an integer from 1 to 3, including 1 or 2.

[0054] Monomer A can be chosen from among α,β-aminocarboxylic acids having 8 to 16 carbon atoms, and lactams having 6 to 16 carbon atoms. Caprolactam, 11-aminoundecanoic acid, and 12-lactam are particularly preferred. It is possible to use several monomers A, including those mentioned above.

[0055] Monomer X is preferably a diamine with 2 to 10 carbon atoms, a polyether or a polyetheramine comprising ether groups comprising 2 to 4 carbon atoms.

[0056] The diamine is preferably an aliphatic diamine. In particular, it may be a linear aliphatic diamine, including ethylenediamine, putrescine, cadaverine, 1,6-hexamethylenediamine, and 1,10-decamethylenediamine. Alternatively, it may be a branched diamine. Another alternative is a cyclic diamine such as piperazine. 1,6-Hexamethylenediamine and 1,10-decamethylenediamine are particularly preferred. Of course, it is possible to use several diamines, including those mentioned above.

[0057] Polyethers containing ether groups of 2 to 4 carbon atoms are preferably polyethers containing ethylene glycol, propylene glycol, or tetramethylene glycol groups. Advantageously, polyethers are essentially composed of these groups, and are therefore polyethylene glycol (PEG), polypropylene glycol (PPG), or polytetramethylene glycol (PTMG). Polyethylene glycol (PEG) is particularly preferred among these.

[0058] When monomer X is a polyether, the resulting polymer is a copolyetheresteramide.

[0059] Polyetheramine comprising ether groups comprising 2 to 4 carbon atoms is preferably a polyether as described above but having amine groups at the end of the chain.

[0060] Polyether or polyetheramine preferably have a weight average molar mass between 300 and 10000, preferably between 500 and 5000, more preferably between 800 and 2000, respectively.

[0061] Monomer Y is preferably an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, preferably 6 to 16, and particularly 6 to 13. Linear aliphatic dicarboxylic acids are particularly preferred. Among these, adipic acid, pipelic acid, suberic acid, azelaic acid, sebacic acid, 1,11-undecanedioic acid, 1,12-dodecanedioic acid, and brassylic acid are particularly suitable. Adipic acid and 1,12-dodecanedioic acid are preferred. Several dicarboxylic acids may be used, especially those selected from the list above.

[0062] Preferably, the copolyamide has the formula (I) with a = 1 or 2 and b = 1 or 2. Particularly preferred are copolyamides with a = 2 and b = 2. In the latter case, we have a copolyamide obtained by copolymerization of two lactams, two dicarboxylic acids as well as two diamines, polyethers or polyetheramines.

[0063] Advantageously, the copolyamide comprises an XY unit in which X is a polyether, notably polyethylene glycol (PEG).

[0064] Particularly preferred is the use of copolyamide PA 6 / 11 / 6.12 / PEG.12 (also designated PA 6 / 6.12 / 11 / PEG.12).

[0065] The nature and ratio of monomers in the copolyamide can be varied to modulate the thermal property profile. For example, PA 6 / 6.12 / 11 / PEG.12 copolyamide with a ratio of 24.5 / 20.9 / 30.1 / 24.5 has a melting point of 101°C, while with a ratio of 15 / 15 / 45 / 25, it has a melting point of 120°C. Advantageously, the copolyamide has an A-membered content of 20 to 80% by weight, preferably 30 to 75% by weight, particularly 40 to 70% by weight, and especially 50 to 60% by weight. Furthermore, it is preferred that the copolyamide has a (XY)b motif content of 20 to 80% by weight, preferably 25 to 70% by weight, in particular 30 to 60% by weight, and in particular 40 to 50% by weight.

[0066] The described copolyamide also exhibits a particular property profile, namely: a melting temperature Tf between 80°C and 150°C, a hot volume melt flow index of 10 to 60 [mL / 10 min] at 160°C under 2.16 kg, as measured according to ISO 1133, and an enthalpy of crystallization of at least 5 J / g, as measured according to ISO 307 by DSC cooling at 20K / min.

[0067] According to the invention, the copolyamide has a melting temperature (Tf) between 80°C and 150°C. Such a melting temperature allows for hot spraying at a temperature low enough to be compatible with substrates of very diverse nature. Advantageously, the melting temperature (Tf) of the copolyamide is between 85°C and 130°C, preferably between 87°C and 125°C, particularly between 90°C and 120°C, even more preferably between 92°C and 115°C, particularly between 95°C and 110°C, and especially between 100°C and 105°C.

[0068] The melt volume flow rate (MVR) of copolyamide is a parameter of particular importance in hot spray printing applications. When the melt volume flow rate is too low, the copolyamide does not pass easily or at all through the spray nozzle, making application difficult or even impossible with this technique. Conversely, when the melt volume flow rate is too high, the copolyamide penetrates too deeply into the substrate, and the amount remaining on the surface may be insufficient to ensure good adhesion.

[0069] It has been observed that a copolyamide with a hot melt index by volume, as measured according to ISO 1133 at 160°C under 2.16 kg, of 10 to 60 [mL / 10 min], preferably of 12 to 50, particularly of 14 to 40 and especially of 16 to 30 [mL / 10 min] gave very satisfactory results when applied by hot spraying.

[0070] Furthermore, it was observed that a rather rapid crystallization of the copolyamide promoted the formation of a well-defined glue bead and also contributed to a good quality of assembly.

[0071] For the purposes of this discussion, rapid crystallization is considered to occur when a crystallization peak is observed during cooling at a rate of 20 K / min using differential scanning calorimetry (DSC). Crystallization is detectable by DSC through the presence of a peak at the crystallization temperature, the area of ​​which is representative of the enthalpy of crystallization of the copolyamide.

[0072] The copolyamide used according to the invention has an enthalpy of crystallization, as measured according to standard NF EN ISO 11357-3 by DSC under cooling at 20 K / min, of at least 5 J / g, preferably at least 10 J / g, in particular at least 20 J / g, and especially at least 30 J / g. As mentioned above, a sufficiently low glass transition temperature also ensures good flexibility of the parts and contributes to a sufficient hot melt index, which, as explained above, facilitates spraying. Preferably, the copolyamide has a glass transition temperature (Tg) below 60°C, advantageously, the Tg of the copolyamide is between -80°C and 60°C, preferably between -75°C and 50°C, in particular between -70°C and 40°C, and even more preferably between -65°C and 35°C.

[0073] Copolyamides used according to the invention are commercially available and can be manufactured using the usual processes described in the prior art. Reference may be made in particular to the process described in patent application EP 1533330 A1. In this process, all the reactants are introduced simultaneously into a suitable reactor, optionally adding an acid such as phosphorous acid. The entire assembly is heated under nitrogen to a typical temperature of 235°C for a typical duration of 60 minutes, after which the reactor is placed under vacuum and the reaction is continued for a typical duration of 30 minutes. Of course, the temperatures and durations can be varied to take into account the reactivity of the chosen reactants.

[0074] Copolyamides can be obtained in the presence of a dicarboxylic acid or a diamine acting as a chain regulator, depending on whether a carboxylic acid or amine group is desired at the ends of the chain. If the precursors already contain a dicarboxylic acid or a diamine, it is sufficient to use it in excess, but another dicarboxylic acid or another diamine from the groups of dicarboxylic acids and diamines defined above can also be used.

[0075] It was found that the described copolyamides possessed the properties required for the assembly of articles, particularly footwear, by hot spraying. The fact that it is a one-component hot-melt adhesive makes the process more flexible, since it is not necessary to observe the open time required for HMPUR adhesives.

[0076] Furthermore, these copolyamides are more respectful of health and the environment since they contain neither solvents nor residual isocyanates.

[0077] The copolyamides used according to the invention are also recyclable because they are thermoplastic. Thanks to the thermoplastic nature of these polyamides, articles assembled using them can be fully recycled. In particular, when articles contain a significant proportion of thermoplastic polymer or are even made entirely of thermoplastic polymer, the entire article can be ground and melted to provide a material that can be reused, thus greatly facilitating its recycling.

[0078] Finally, the use of copolyamide according to the invention advantageously makes it possible to obtain assemblies exhibiting a peel force, measured according to the t-test described in the examples, of at least 30 N / mm, in particular of at least 40 N / mm, especially of at least 50 N / mm at 23°C, and most particularly of at least 60 N / mm.

[0079] Thanks to the advantages discussed above, the use of a described copolyamide makes it possible to obtain by hot spraying articles whose assembly interface has sufficient adhesion strength and robustness to withstand prolonged use.

[0080] According to a second aspect, the invention relates to a method of manufacturing articles by assembly in which the substrates are assembled by means of a copolyamide as described above, deposited by hot spraying.

[0081] A hot spraying process according to the invention typically comprises the following successive steps:

[0082] 1) heating a copolyamide as described above to a temperature at least 20°C above the melting point of the copolyamide, and

[0083] 2) the direct deposition by spraying of the heated copolyamide onto at least one substrate.

[0084] The spray nozzle temperature is preferably chosen to be at least 20°C, preferably 40°C, advantageously at least 60°C, or even at least 80°C above the melting point of the copolyamide. The copolyamide can be deposited onto one or both of the substrates to be bonded. Advantageously, the copolyamide is deposited in the form of a bead.

[0085] For the purposes of this invention, the term "cord" refers to a continuous, elongated pattern. This pattern can be deposited in any shape. In particular, it can be rectilinear, for example in the form of one or more more or less straight lines, and / or in a sinuous form, for example in the form of waves.

[0086] For the purposes of this invention, "direct deposition" means that the heated copolyamide obtained at the end of step 1) is not kept hot for a long period of time, but is applied to the substrate a very short time after reaching the required temperature. In particular, the copolyamide is not kept hot in a thermostatically controlled tank before being applied.

[0087] It can be useful to allow a copolyamide activation time before assembly, for example, between 5 and 60 seconds. This activation time then represents the maximum permissible time between the end of the copolyamide heating (step 1) and the deposition of the heated copolyamide onto the substrate (step 2). The substrates are then assembled, preferably by applying pressure, for example, by passing them between two pneumatic rollers. The applied pressure can be between 2 and 15 bar, preferably between 4 and 12 bar. The applied force can be between 1 and 5 kN, preferably between 2 and 4 kN. Finally, the pressure application time can be chosen between 10 and 1000 seconds, preferably between 50 and 250 seconds.

[0088] Thus, a method for manufacturing articles according to the invention typically comprises the following successive steps:

[0089] 1') supplying the parts of the article to be assembled, including the substrates of the article to be assembled, 2') heating a copolyamide as described above to a temperature at least 20°C above the melting point of the copolyamide,

[0090] 3') directly spray the heated copolyamide onto at least one of the parts, and 4') assemble the parts to be joined, preferably by applying pressure. The substrates to be assembled for the manufacture of the article may be of various kinds, and in particular include or be made up of thermoplastic polymers such as polyester, polypropylene, polyacrylate, polyether, polyamide, thermoplastic polyurethane elastomer (Lycra® or elastane), PTFE, PVDF, PEBA, polybutylene, polyisoprene, aramid (Kevlar®), polybenzimidazole (PBI), polyethylene, particularly ultra-high weight polyethylene, liquid crystal polymer or microfibers.

[0091] Substrates may also include or be made of fibers of inorganic materials, such as carbon, glass, copper, aluminum, or steel.

[0092] Preferably, at least one of the substrates to be assembled comprises or is made of a polyamide. Indeed, the copolyamides described generally exhibit particularly high adhesion to this substrate.

[0093] Advantageously, the substrates to be assembled comprise at least 60%, in particular at least 70%, even more preferably at least 80%, in particular at least 90% by weight of thermoplastic polymer or are composed of thermoplastic polymer.

[0094] Indeed, using thermoplastic-based substrates to manufacture the item allows for its complete recycling after use. More specifically, the item can be ground up and then melted down to produce a material that can be reused, particularly for manufacturing new items. However, it can also be worthwhile to recycle items that contain a small portion of non-thermoplastic material.

[0095] Advantageously, the assembly process of the item, particularly the shoe, is fully automated and does not require manual labor.

[0096] The use according to the invention is particularly interesting for the manufacture of footwear, especially sports shoes. Furthermore, it may be of interest for the manufacture of clothing, bags or baskets, furniture, blinds, leisure equipment such as backpacks and tents, or even sporting equipment such as balls, kites, sails and parachutes.

[0097] In general, the copolyamide is used according to the invention by hot spray application, that is, in a molten state, directly onto the substrate(s) to be bonded. According to a third and final aspect, the invention relates to an article obtainable by the process described above.

[0098] Advantageously, these are shoes, especially sports shoes.

[0099] The invention will be explained in more detail in the examples that follow. Examples

[0100] The copolyamides described in Table 1 below were first tested for their suitability for hot spray application. Subsequently, these copolyamides were used to bond different substrates, and the quality of the bond was evaluated by measuring peel strength and studying the interface failure mode. The MVR (Mean Volume Reduction) was measured according to ISO 1133-1:2011 using a Zwick MFlow device at 160°C under a 2.16 kg load, with a preheating time of 300 s and using a die with a diameter of 2.095 mm and a length of 8.000 mm.

[0101] Table 1 - Composition of the evaluated copolyamides A. Application of an adhesive sealant by spraying

[0102] First, five horseshoe-shaped cords were formed on a 100x80mm substrate surface by spraying the different copolyamides using a hot spray device marketed by DESMA Schuhmaschinen (DESMA Sole Cell).

[0103] The depositions were carried out under the following conditions: atomization pressure (air): 1.75 bar; nozzle temperature: 80°C above the melting temperature of the copolyamide tested (between 185 and 210°C); distance between nozzle and substrate: 18 mm; and quantity of copolyamide: 2.5 g.

[0104] The quality of the deposited bead was visually inspected, particularly regarding the precision of the deposited bead. The results are summarized in Table 2 below.

[0105] Table 2 - Evaluation of hot spray deposition quality

[0106] It can be seen that the copolyamide in comparative example 4 does not allow for the deposition of a satisfactory bead, as the resulting bead pattern is wide and poorly defined. In contrast, the copolyamides in example 1 and comparative example 1 allow for the deposition of a bead of satisfactory quality with sharp contours. The copolyamides in comparative examples 2 and 3 are acceptable, although they exhibit less defined contours and a wider pattern.

[0107] B. Assembly of representative substrates of the upper and the foamed midsole Next, the different copolyamides were used to assemble a polyamide 11 textile with different representative substrates of materials used as foamed midsole, and the quality of the assembly obtained was evaluated.

[0108] To achieve this, 0.6 mm thick beads were deposited by hot spraying, as explained in section A, onto representative substrates of the foamed midsole, cut into 100 mm x 100 m pieces. After an activation time of 25 s (12 s for example C4), the substrates were joined by applying a pressure of 2.8 kN for 120 s.

[0109] The adhesion strength of the assembled samples was evaluated using a T-peel test according to ISO 11339:2022 under the following conditions:

[0110] Travel speed: 200mm / min

[0111] One to two test tubes per reference

[0112] Sensor: 1 kN

[0113] Dynamometer: Synergy 200H

[0114] 90° peeling method imposed.

[0115] The interface formed was evaluated by observing the failure mode at the end of the previously described test. Adhesive failure occurs at the interface between the adhesive and one of the two substrates, while cohesive failure occurs within the adhesive layer itself. Cohesive failure indicates that the interface behaved more strongly than the adhesive material, and these bonds are considered more satisfactory.

[0116] Based on the peel strength and failure mode obtained for each copolyamide, the quality of the resulting bond was evaluated. More specifically, a peel strength of 15 N / cm or less was considered insufficient, and a cohesive failure mode was deemed to improve the overall quality of the bond.

[0117] The results are summarized in Table 3 below.

[0118] Table 3 - Upper / Midsole Assembly

[0119] It can be seen that the copolyamide in Example 1 allows for satisfactory bonding of the studied substrates in terms of peel strength. This copolyamide also ensures a cohesive failure mode. In comparison, the copolyamides in comparison examples 1 and 2 exhibit lower peel strength, and sometimes a failure mode indicative of a weak interface.

[0120] C. Assembly of substrates representative of the outsole and the foamed midsole

[0121] Copolyamides were also tested for the assembly of representative substrate pairs of materials used as foamed midsole and outsole, as shown in Table 4 below.

[0122] The application of the copolyamide and the assembly of the substrates were carried out under the conditions indicated in section B, except for the use of a 6mm bead of glue thickness.

[0123] Polyurethane was tested as the outsole material.

[0124] The quality of the assembly obtained was evaluated according to the tests indicated in section B. The results are summarized in Table 4 below.

[0125] Table 4 - Midsole / Outsole Assemblies

[0126] It is observed that the copolyamide in Example 1 allows for satisfactory assembly quality for the evaluated substrates. D. Assembly of substrates representative of the upper and outsole

[0127] Finally, copolyamides were tested for the assembly of polyamide 11 textile with a PEBA representative of materials used as outsole, as shown in Table 5 below.

[0128] The copolyamide was applied as shown in section B, except that a bead thickness of 0.8 mm was used.

[0129] The quality of the assembly obtained was evaluated according to the tests indicated in section B. The results are summarized in Table 5 below.

[0130] Table 5 - Upper / Outsole Assemblies

[0131] It can be seen that the copolyamide in Example 1 provides a satisfactory bond quality for the evaluated substrate. In comparison, the copolyamide in Comparative Example 2 exhibits insufficient peel strength, or even a failure mode indicating a weak interface. The overall results demonstrate that the use of the copolyamide according to the invention solves the technical problem posed, namely, enabling the application of a precise adhesive bead to the substrate by hot spraying and forming a high-quality bond characterized by substantial peel strength and a cohesive failure mode on the materials studied.

[0132] [List of cited documents]

[0133] EP I 533 330 Al

Claims

DEMANDS 1. Use of a copolyamide with the following formula: Aa / (XY) b (Formula I) in which: A is at least one of: (i) an alpha-omega aminocarboxylic acid; (ii) a lactam; and X is at least an aliphatic diamine with 2 to 14 carbon atoms, a polyether or a polyetheramine comprising ether groups comprising 2 to 4 carbon atoms; Y is at least an aliphatic dicarboxylic acid with 6 to 22 carbon atoms; a is an integer from 1 to 3, in particular 1 or 2; and b is an integer from 1 to 3, in particular 1 or 2; said copolyamide having: a melting temperature Tf between 80°C and 150°C, a hot melt volume index of 10 to 60 [mL / 10 min] at 160°C under 2.16 kg, as measured according to ISO 1133, and an enthalpy of crystallization of at least 5 J / g, as measured according to ISO 307 by DSC cooling at 20K / min, for the assembly of articles by hot spray.

2. Use according to claim 1, wherein the copolyamide is of formula (I), where A is selected from caprolactam, amino-11-undecanoic acid and lactam 12.

3. Use according to claim 1 or 2, wherein in the copolyamide is of formula (I), where X is selected from linear aliphatic diamines such as ethylene diamine, putrescine, cadaverine, 1,6-hexamethylene diamine, 1,10-decamethylene diamine; branched diamines; and cyclic diamines such as piperazine.

4. Use according to any one of claims 1 to 3, wherein the copolyamide is of formula (I), where Y is a linear aliphatic dicarboxylic acid, preferably selected from adipic acid, pipelic acid, suberic acid, azelaic acid, sebacic acid, 1,11-undecanedioic acid, 1,12-dodecanedioic acid and brassylic acid.

5. Use according to any one of claims 1 to 4, wherein the copolyamide is of formula (I) with a = 1 or 2 and b = 1 or 2.

6. Use according to any one of claims 1 to 5, wherein the copolyamide is of formula (I) with a = 2 and b = 2.

7. Use according to any one of claims 1 to 6, wherein the copolyamide is of formula (I) and comprises at least one XY unit in which X is polyethylene glycol (PEG).

8. Use according to any one of claims 1 to 1, wherein the copolyamide is PA 6 / 11 / 6.12 / PEG.

12.

9. Use according to any one of claims 1 to 8, wherein the copolyamide has a melting temperature (Tf) between 85 and 130°C.

10. Use according to any one of claims 1 to 9, wherein the copolyamide has a glass transition temperature (Tg) below 60°C.

11. Use according to any one of claims 1 to 10, wherein the copolyamide enables a peel force, measured according to the t-peel test described in the examples, of at least 30N / mm.

12. A method for manufacturing articles, comprising the following steps: (a) supply of the parts of the article to be assembled; (b) application of a copolyamide as defined in claims 1 to 11 onto at least one of the surfaces of at least one of the parts to be assembled, by hot spraying; and (c) assembly of the parts to be assembled, where appropriate under application of pressure.

13. A method according to claim 12, wherein the polymer component of the finished article comprises at least 70%, preferably at least 80% and in particular at least 90% by weight of thermoplastic polymer.

14. Article which can be obtained by the process according to claim 12 or 13.

15. Article according to claim 14, characterized in that it is a shoe, in particular a sports shoe.

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