Process for production of polyamide hot melt adhesive with fillers

Abstract

The present invention relates to a process for a production of a polyamide hot melt adhesive with fillers like coloring pigments (carbon black, etc.) or functional not reactive fillers. The present invention also relates to the polyamide hot melt adhesive with fillers obtained by that process and the use thereof.

Description

[0001] Henkel AG & Co. KGaA Erol / smt

[0002] “Process for Production of Polyamide Hot Melt Adhesive with Fillers”

[0003] The present invention relates to a process for a production of a polyamide hot melt adhesive with fillers like coloring pigments (carbon black, etc.) or functional not reactive fillers. The present invention also relates to the polyamide hot melt adhesive with fillers obtained by that process and the use thereof. The obtained product is used in many industrial applications based on low pressure molding technology of application for electronic and electrical encapsulation.

[0004] Polyamide is produced through sustainable processes using dimer acids. Polyamide base resins are used in hot melt adhesive (HMA) formulations and are usually synthesized from bio-sourced diacids (such as dimer acids) with one or more different diamines.

[0005] Polyamide hot melt adhesive results from a high-temperature condensation reaction between dimer acid and polyamine. This adhesive boasts excellent heat and cold resistance, electrical and oil resistance, chemical resistance, and medium resistance. It is odorless, colorless, cures quickly, and can bond different metals and non-metals, with good compatibility with other resins.

[0006] Polyamide hot melt adhesives are versatile, suitable for bonding fabrics, leather, wood, plastics, metals, and ceramics, as well as for protecting electronic components, bookbinding, low-pressure injection molding, and tape production. These adhesives may also include auxiliary substances and additives such as fillers, plasticizers, adhesion promoters, UV absorbers, UV and heat stabilizers, optical brighteners, pigments, dyes, and desiccants.

[0007] The basic color of polyamide hot melt adhesive is amber (yellow), but it can be altered to black by adding carbon black, to white by adding titanium dioxide, or to other colors using different pigments for special applications like low-pressure injection molding. Functional fillers can also be added to enhance the cohesive strength, adhesive force, and film-forming properties of the hot melt adhesive.

[0008] In prior art, there are various processes for a production of polyamide hot melt adhesives with fillers like coloring pigments (carbon black, etc.) or functional not reactive fillers. In one of the processes, fillers are added to polyamide hot melts via dosing during extrusion of polyamide hot melts not filled base in twin screw extruder to homogenize dispersion at temperatures between 130-200°C. In the end, the obtained product is granulated. This product can also be used as a masterbatch.

[0009] In another known process, a masterbatch of polyamide hot melts and pigments (carbon black) previously obtained from co-extrusion of carbon black powder and not filled hot melt polyamide are added into a reactor where the synthesis of a not pigmented polyamide hot melt adhesive has been already completed at the level of conversion requested (max conversion). In this way, the masterbatch is added as a granulated additive into the molten mass of the polyamide hot melt adhesive at a temperature between 200-240°C. Similarly, at the end of mixing, the obtained product is granulated. Both known processes need extrusion steps because simply the direct addition of fillers like carbon black powder into the reactor at the end of the synthesis does not allow effective and efficient incorporation and dispersion of fillers with a guarantee of a homogeneous content of pigments into the batch.

[0010] In another known process, fillers in powder form are added directly to polyamide hot melt adhesives at the end of the polycondensation. However, this method still fails to provide homogeneity within the obtained product. Additionally, this method causes health and safety issues.

[0011] In known processes, carbon black is added as powder (by extrusion) directly into the polymer of natural color. This can be a final product or can be used as granulated masterbatch to be added into the polymer molten into a mixer or via extrusion. This tends to create more agglomerate.

[0012] Additionally, using a polyamide based masterbatch with the same concentration of carbon black shows both the risk of agglomerate and the risk of reactions between the polyamide in the masterbatch and the polyamide being additivated. Because acid and amino residues create localized higher molecular weight nuclei, this can lead to faster aging, an increase in viscosity, and a shorter shelf life.

[0013] There is therefore a high demand for providing a simpler process for the production of a homogeneous filled polyamide hot melt adhesives. Various attempts have been made to deal with this homogeneity associated problems.

[0014] EP0749463B1 discloses a hot-melt-type adhesive with a filler, a carbonate. The fillers are incorporated into the finished polyamide hot melt adhesives with the aid of heatable kneaders or extruders.

[0015] EP1342764A3 discloses a hot melt adhesive composition for use e.g. in cars or packaging, comprising a polyolefin-polyamide graft copolymer and a mixture of tackifier resin and optionally wax, plasticizer and / or filler. Examples of fillers are silica, alumina, glass, glass beads, calcium carbonates, fibers and metal hydroxides. According to EP1342764A3, the hot melt adhesive of the invention is prepared by mixing its constituents in the molten state (except for the mineral fillers which remain solid) at temperatures between 130° C and 200° C until a homogeneous mixture is obtained. For mixing, usual devices for thermoplastics, such as extruders, cylinders, Banbury or Brabender mixers, or helical mixers are used.

[0016] CN110527440B discloses a black hot-melt adhesive tape, including its preparation process and applications. The black hot-melt adhesive tape comprises the following ingredients in parts by weight: 67-74 parts of polyamide resin, 6-9 parts of polyurethane resin, 4-6 parts of tackifying resin, 0.3-0.7 parts of heat-conducting fillers, 5-9 parts of thixotropic agent, 0.4-0.6 parts of antioxidant and 7-13 parts of carbon black. The preparation process for the black hot-melt adhesive tape comprises the following steps: S1. subjecting the polyamide resin, the polyurethane resin and the carbon black to extruded blending; S2. then, subjecting the carbon black added polyamide obtained in the S1 and polyurethane blended modified colloidal particles to extruded blending with the tackifying resin, the heat-conducting fillers, the thixotropic agent and the antioxidant; and S3, subjecting the blended colloidal particles to heated melt coating, coating the release paperwith a melt adhesive film, carrying out cooling on a water-cooling roller, and carrying out drying, thereby obtaining the black hot-melt adhesive tape.

[0017] US8883933B2 relates to a process for preparing the hot melt adhesive with pigments such as titanium dioxide as a white pigment. The hotmelt adhesive composition comprising at least one acid, in particular adipic acid, azelaic acid, sebacic acid, dimerized fatty acid or a mixture of at least two of these acids, and at least one amine, in particular ethylene diamine or hexamethylene diamine or 2,2,4-trimethyl hexamethylene diamine or s-caprolactam or 1-amino-3-aminomethyl-3,5,5-trimethyl cyclohexane (isophorone diamine) or piperazine or a mixture of at least two of these amines, in particular formed by polycondensation. Mixing, heating and melting of the hot melt adhesives is carried out in an extruder.

[0018] CN105482755B discloses a preparation of an antistatic modified hot melt adhesive comprises raw materials in parts by weight: 40 parts of polyester hot melt adhesive, 20 parts of polyamide resin, 20 parts of conductive carbon black, 5 parts of petroleum resin and 0.5 parts of antioxidant. To obtain the hot melt adhesive the polyamide resin, the petroleum resin, the antioxidant and the conductive carbon black are uniformly mixed according to the formula ratio.

[0019] However, it was found that currently, existing processes could not meet the demand for eliminating extrusion steps to add fillers to polyamide hot melt adhesives. Moreover, some of them require specific masterbatches for each polymer.

[0020] There is thus still the need for a process for a production of a polyamide hot melt adhesive with filler which has an easy dosing and mixing step of filler to the polyamide hot melt adhesive.

[0021] It was surprisingly found that this need can be addressed by dispersing at least a filler into at least a first reactive monomer of a polyamide and / or into water to form a dispersion, then dosing the dispersion to a composition containing at least a second reactive monomer of polyamide before polymerization of the reactive monomers such that the reactive monomers and the filler form a liquid homogeneous mixture. This process provides an easy dosing of the filler by avoiding extrusion steps. Moreover, it eliminates specific masterbatches. The obtained product by this process is homogenous and has an increased shelf life. Additionally, the inventive process ensures a high level of filler dispersion, resulting in enhanced surface and volume resistivity properties in the final product.

[0022] The present invention therefore provides a process for a production of polyamide hot melt adhesive composition with filler comprising a. dispersing at least a filler into at least a first reactive monomer of a polyamide and / or into water to form a dispersion, b. dosing the dispersion to a composition containing at least a second reactive monomer of polyamide before polymerization of the reactive monomers such that the reactive monomers and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler.

[0023] In a preferred embodiment, a process for a production of polyamide hot melt adhesive composition with filler comprising dispersing at least a filler into at least a reactive monomer of a polyamide and / or into water to form a dispersion, dosing the dispersion to a composition containing at least another reactive monomer of polyamide before polymerization of the reactive monomer(s) such that the reactive monomer(s) and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler.

[0024] In a preferred embodiment, a process for a production of polyamide hot melt adhesive composition with filler comprises dispersing at least a filler into at least a first reactive monomer of a polyamide to form a dispersion and dosing the dispersion to a composition containing at least a second reactive monomer of polyamide before polymerization of the first and second reactive monomers such that the first and the second reactive monomers and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler.

[0025] In a preferred embodiment, a process for a production of polyamide hot melt adhesive composition with filler comprises dispersing at least a filler into at least a reactive monomer of a polyamide to form a dispersion and dosing the dispersion to a composition containing at least another reactive monomer of polyamide before polymerization of the reactive monomers such that the reactive monomers and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler.

[0026] In a preferred embodiment, a process for a production of polyamide hot melt adhesive composition with filler comprises dispersing at least a filler into at least a first reactive monomer of a polyamide and water to form a dispersion and dosing the dispersion to a composition containing at least a second reactive monomer of polyamide before polymerization of the first and second reactive monomers such that the first and the second reactive monomers and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler.

[0027] In a preferred embodiment, a process for a production of polyamide hot melt adhesive composition with filler comprises dispersing at least a filler into at least a reactive monomer of a polyamide and water to form a dispersion and dosing the dispersion to a composition containing at least another reactive monomer of polyamide before polymerization of the reactive monomers such that the reactive monomers and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler. In a preferred embodiment, a process for a production of polyamide hot melt adhesive composition with filler comprises dispersing at least a filler into water to form a dispersion and dosing the dispersion to a composition containing at least a reactive monomer of polyamide before polymerization of the reactive monomer such that the reactive monomer and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler.

[0028] In a preferred embodiment, a process for a production of polyamide hot melt adhesive composition with filler comprises dispersing at least a filler into water to form a dispersion and dosing the dispersion to a composition containing at least a reactive monomer of polyamide before polymerization of the reactive monomer such that the reactive monomer and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler and removing the water generated by polycondensation.

[0029] In a preferred embodiment, the concentration of the filler is in the range of 0,00001 to 30 wt.-%, preferably 0,00001 to 10 wt.-%, more preferably 0,15 to 2.5 wt.-%, based on the total weight of the hot melt adhesive composition with filler. In a preferred embodiment the filler is 30 wt.-%, preferably 28 wt.-% based on the total weight of the hot melt adhesive composition with filler.

[0030] In a preferred embodiment, the concentration of the filler is above 0.5 wt.-% or above 1 wt.-%, based on the total weight of the hot melt adhesive composition with filler. In an embodiment it is in the range of 0,5 to 30 wt.-%, 0,5 to 10 wt.-%, 1 to 30 wt.-% or 1 to 10 wt.-% based on the total weight of the hot melt adhesive composition with filler. It is found that higher content of fillers provides a shorten process time.

[0031] In a preferred embodiment, the filler is in powder form or dispersed in water.

[0032] In a preferred embodiment, wherein the filler is a coloring pigment and / or a functional not reactive filler.

[0033] In a preferred embodiment, the filler is carbon black. The carbon black is vegetal carbon (CAS No. 7440-44-0) and / or from mineral origin like petroleum and gas feedstocks (CAS No. 1333-86-4).

[0034] In a preferred embodiment, the filler is a thermal conductive additive selected from the list of boron nitride, alumina, graphite and graphene.

[0035] In a preferred embodiment, the filler is an electrically conductive additive.

[0036] In a preferred embodiment, the reactive monomer is a dimer fatty acid monomer. Preferably it is hydrogenated dimer fatty acid.

[0037] In a preferred embodiment, the first and / or second reactive monomer is a dimer fatty acid monomer. Preferably it is hydrogenated dimer fatty acid. In a preferred embodiment, in step a, the filler is dispersed in a separate mixer equipped with a cowles stirrer.

[0038] In a preferred embodiment, in step b, the dispersion is dosed via a membrane or gear pump into a polymerization reactor. Preferably, the viscosity of the dispersion is about 30 Pa*s at room temperature.

[0039] In a preferred embodiment, in case the filler is dispersed into water to form a dispersion, a further step is removing the water generated by polycondensation which is performed after step b.

[0040] In a preferred embodiment, filler is particularly carbon black and the first reactive monomer is dimer fatty acid. It is possible to dose carbon black starting with a very low percentage in the entire batch with more homogeneity. The concentration of the carbon black in the liquid dimer fatty acid dispersion media is in the range of 0,00001 to 30 wt.-%, preferably 0,00001 to 10 wt.-%, more preferably 0,15 to 2.5 wt.-%, based on the total weight of the hot melt adhesive composition with filler.

[0041] In a preferred embodiment, the composition comprises dimer fatty acid, dispersion of the filler into the dimer fatty acid, linear diacid, ethylenediamine, piperazine, polyetheramine (Jeffamine). Preferably linear diacid is sebacic acid.

[0042] In a preferred embodiment, the composition comprises dimer fatty acid as a reactive monomer, dispersion of filler into the dimer fatty acid as another reactive monomer, linear diacid, ethylenediamine, piperazine, polyetheramine (Jeffamine). Preferably linear diacid is sebacic acid.

[0043] In a preferred embodiment, the stoichiometric amount of dimer fatty acid is the sum of moles from dimer fatty acid and dispersion of the filler into the dimer fatty acid.

[0044] In a preferred embodiment, the concentration of the filler is in the range of 2-40 wt.-%, preferably 8 wt.-%, and the concentration of the first reactive monomer is in the range of 60-98%, %, preferably 92 wt.-%, based on the total weight of the dispersion. Preferably, carbon black is in the powder form.

[0045] In a preferred embodiment, the concentration of the filler is in the range of 2-40 wt.-%, preferably 8 wt.-%, and the concentration of the reactive monomer is in the range of 60-98%, %, preferably 92 wt.-%, based on the total weight of the dispersion. Preferably, carbon black is in the powder form.

[0046] The use of the obtained product by the mentioned process for electronic and electrical encapsulation is also under the scope of the invention.

[0047] The obtained product by the mentioned process is also under the scope of the invention. The obtained product has filler agglomerates with diameters below 50 pm as measured according to the image analysis mentioned below. In a preferred embodiment, the dimer fatty acid dispersion is a viscous liquid (black) that is dosed as the standard dimer in the needed amount.

[0048] In a preferred embodiment, if a final concentration of carbon black is 2 wt.-% (UV stabilization) based on the total weight of the hot melt adhesive composition with filler, the weight of the carbon black dimer fatty acid dispersion is 10 times more than that in case of just coloring where carbon black is max 0,2 wt-%. The difference to stoichiometric is balanced by standard dimer fatty acid.

[0049] The method according to the invention provides flexibility for dosing both low and high concentration (e.g. 0,2 or 2 wt-% respectively) of carbon black with exactly the same method and with quite higher precision and with the same concentration in the entire batch without fluctuation. This is normally not possible or is complicated with other known methods. For instance, extrusion at low concentration requires the use of solid masterbatches and dosing equipment with a certain precision whereas at higher concentration pure carbon black can be used with appropriate dosing equipment. Moreover, dosing during the extrusion exposes the batch to the risk of fluctuations throughout the production and potentially leading to moments of overdosing (altering properties) or underdosing / stoppages, which can result in altered final properties.

[0050] The total stoichiometry balances equivalent of acid and amine and the reaction is a polycondensation with formation of amide bonds and elimination of water.

[0051] Fillers like carbon black (or any other type of pigment) does not obviously interfere with polymerization. The process is the same as a standard polycondensation and is monitored through end group analysis and viscosity measurements.

[0052] At the end, the filled (pigmented) polyamide hot melt adhesive has same characteristics of the same grade produced with standard known method. However, the invention shortens the process time and provides homogeneous distribution and concentration of pigment in the batch. This will result in a more homogeneous rheology behavior and surprisingly in a slower ageing in normal storage conditions.

[0053] Fillers (pigments) dispersion in one reactive monomer allows the use of this preparation as a raw material with same chemical reactivity of the monomer but simultaneously with the function of dosing and dispersing a precise amount of the functional filler in liquid form (no dust) into the polymerization reactor. Reaction can take same time of pigment free synthesis. It will not require any extrusion processing. It will not require manufacturing of multiple masterbatches. It will not trigger gel formation due to acid and amino residual group of polyamides masterbatch. Therefore, the present invention reduces the aging speed and the increase in viscosity or rheology changes in the obtained product. This makes it possible to use the obtained product in the correct application conditions without risk of failures. Normally masterbatches extrusion dosing depends upon the precision of the dosing equipment (to be dimensioned depending on the concentration to add) and might be uneven all along the extrusion time. Batch at the beginning and at the end might risk concentration fluctuations.

[0054] A preferred embodiment provides a black polyamide hot melt adhesive by using as one of the monomers, a dispersion of carbon black powder into dimer fatty acid. This raw material is a part of the dimer fatty acid content in the polymer formula. It has been surprisingly found that this process reacts and results into a better dispersion of the needed amount of carbon black for making the resulting black polyamide hot melt adhesive UV resistant or just colored in black. It is realized that dispersion of carbon black in the obtained product is very effective, better than using solid state masterbatches based on polyamide. Moreover, the reactivity of all monomers is not negatively affected.

[0055] In a preferred embodiment, carbon black can also be a slurry in water, but preferred is in dimer fatty acid. The obtained product is a black product and shows a better viscosity stability under accelerated ageing, improving the shelf life of the product.

[0056] A preferred embodiment provides is a medium-low viscosity dispersion of carbon black into one of the reactive monomers (preferably dimer fatty acid) and the use of this dispersion as fraction of the monomer composition. It is a "liquid color" where the liquid component is one of the monomers. At the end, the monomer polymerizes, and the carbon black remains unreacted but well dispersed.

[0057] Another aspect of the invention is dispersing the filler (carbon black) into water to form a dispersion and added the dispersion at the beginning of polymerization with all other monomers. Then water evaporates during the production of the polyamide hot melt adhesive and removed as the water by product of polycondensation while the carbon black remains well dispersed and unreacted. In any case the dispersion would be the one it is preferred.

[0058] In a preferred embodiment, the carbon black dispersed in water is vegetal carbon (CAS No. 7440- 44-0). Carbon Black from mineral origin (petroleum and gas feedstocks.) (CAS No. 1333-86-4) is also used in the present invention.

[0059] Adding the filler (pigment) in one of the reactive monomers or in water at the beginning of the polymerization do not interfere with the “building” of the polymer. Using water as dispersant is different only in the media used for dispersing. Water in this case is not a monomer but basically will be removed like the water generated by the polycondensation, again without interfering with the building of the polymer.

[0060] Adding monomers in water is quite common with some amine (piper amine or hexamethylenediamine). Water is distilled off at the beginning of the polymerization and later on totally removed by pulling vacuum. Having filler (like carbon black) dispersed since the beginning of polymerization reduces sensibly the risk of agglomerate and poor dispersion that it is observed when mixing in the reactor is carried later by addition of powder or master batches in granules. A better dispersion is also positive for improving UV protection.

[0061] A preferred embodiment provides a colored / pigmented polyamide hot melt adhesive or additivated with not reactive fillers (i.e. thermal conductive additives like boron nitride, alumina, graphite, graphene etc.) to obtain either thermal conductive and or both electrically insulating or conductive polyamide hot melt adhesives.

[0062] In a preferred embodiment, black and UV stable polyamide is obtained. Moreover, thermal conductive encapsulating polyamide hot melt adhesive is obtained by dispersion of thermal conductive fillers.

[0063] The invention provides a homogenous dispersion of the fillerwithin the polyamide hot melt adhesive because it is done before the polymerization when all the monomers form a liquid homogeneous mixture. At the end, the monomer polymerizes, and the filler remains unreacted but well dispersed.

[0064] The invention provides dosing of various concentration of the fillers in an easy way to produce filled polyamide hot melt. The fillers can be pigments and / or functional fillers. The obtained filled polyamide hot melt may have properties like just colored, UV stable, TC, electrical conductive etc. based on the fillers.

[0065] In a preferred embodiment, at least a filler is dispersed into at least a reactive monomer of polyamide and forms a dispersion. Then the dispersion is dosed to a composition containing at least another monomer of polyamide before polymerization. By this way the reactive monomers and the filler form a liquid homogeneous mixture. Preferably the reactive monomers are dimer fatty acids.

[0066] In a preferred embodiment, at least a filler is dispersed into at least a reactive monomer of polyamide and water to form a dispersion. Then the dispersion is dosed to a composition containing at least another monomer of polyamide before polymerization. By this way the reactive monomers and the filler form a liquid homogeneous mixture. Preferably the reactive monomers are dimer fatty acids.

[0067] In a preferred embodiment, at least a filler is dispersed into water to form a dispersion. Then the dispersion is dosed to a composition containing at least a monomer of polyamide before polymerization. By this way the reactive monomer and the filler form a liquid homogeneous mixture. The water is removed by polycondensation. Preferably the reactive monomer is dimer fatty acid.

[0068] The invention eliminates the need of specific masterbatches for each polyamide hot melts. It is achieved by dispersing the fillers (pigment) into the monomer that is common to all polymer backbone and dosing fillers in the necessary amount for differentiating the obtained product just by acting on its concentration in the formula. The invention improves the obtained product’s shelf life. Slow sedimentation and slower viscosity increase in the obtained product is achieved.

[0069] In a preferred embodiment dimer fatty acid is Pripol 1019 or Pripol 1006.

[0070] A preferred embodiment is used for encapsulating electronics and contacts connecting these cells. They were intended to remain outdoors, so they required UV stability, achieved through the use of carbon black and other UV-resistant additives.

[0071] Table 1 presents two different polyamide hot melt adhesive compositions. Composition 1 exhibits a higher amount of dispersion, while Composition 2 shows a lower amount of dispersion. In both cases, carbon black is used as the filler and carbon black content is 8% + / -0,5 % in the carbon black fatty acid dispersions.

[0072] Table 1 : Components of the composition 1 and 2

[0073] Based on composition 1 and 2, polyamide hot melt adhesive with filler is produced using both a standard method, in which carbon black fillers are incorporated into the finished polyamide hot melt adhesives using a twin-screw extruder, and an inventive method. In standard technology, it is very difficult to achieve very low concentrations of additives by the use of standard equipments through twin -screw extruders and it is common to first manufacture a masterbatch of higher concentration and then dilute the masterbatch in the polymerization vessel. On the other hand, concentrations higher than 1 .0-2.0% are no longer possible through the use of a masterbatch and they require the direct addition of fillers at the extruder.

[0074] For composition 1 , Example 1 was prepared using the standard method, while Example 2 was obtained using the inventive method. Similarly, for composition 2, Example 3 was prepared by the standard method through the preventive usage of a masterbatch, and Example 4 by the inventive method.

[0075] Some basic characteristics of Examples 1 to 4 are shown in Table 2.

[0076] Table 2: Characteristics of examples 1-4

[0077] According to Table 1 , in composition 1 , the carbon black fatty acid dispersion is 25 + / - 2,5% whereas in composition 2 the carbon black fatty acid dispersion is 2.7 + / - 2.7%. In both Examples 2 and 4, the inventive process enables easy dosing of the dispersion, regardless of its amount within the composition.

[0078] As seen from Table 1 , there is no significant difference in the final product obtained by the standard and inventive processes. Further tests are applied to Examples 1 to 2.

[0079] Image analysis:

[0080] Test Method: A sample of hot melt adhesive was pressed at 200 °C between microscope glass slides to form a film approximately 6 mm in diameter and ~30 pm thick. The sample was then analyzed using optical light transmission microscopy at 20X magnification.

[0081] Image analysis of Example 1 and 2 are given in Figure 1 and 2, respectively.

[0082] The dispersion quality of carbon black in Example 2, obtained by the inventive process is illustrated in Figure 1. As shown, carbon black agglomerates with diameters below 50 pm are achieved, indicating a high level of dispersion. Image analysis reveals an average agglomerate diameter of 10 ± 16 pm. Lenght 5758.97 pm in the middle of Figure 1 refers to the lateral length of the picture imaged. In contrast, Figure 2 illustrates the dispersion quality of Example 1 , obtained by the standard method, in which carbon black fillers are incorporated into the finished polyamide hot melt adhesives using a twin-screw extruder. In this case, agglomerate diameters exceed 50 pm and can reach over 200 pm. Image analysis indicates an average agglomerate diameter of 136 ± 57 pm.

[0083] These results clearly demonstrate the superior effect of the inventive method in enhancing carbon black dispersion.

[0084] Volume resistivity and surface resistivity performance:

[0085] Test Method: A sample of hot melt adhesive was pressed at 200 °C between microscope glass slides to form a film approximately 8 mm in diameter and ~1 mm thick. The sample was then analyzed using Keithley Model 8009 - circular electrode for volume and surface resistivity under a voltage of 500V.

[0086] The volume resistivity (VR) and surface resistivity (SR) performance of Examples 1 and 2 is presented in Figure 3. As previously described, in the standard process, carbon black fillers are incorporated into the finished polyamide hot melt adhesives using a twin-screw extruder. In contrast, in Example 2, the fillers are incorporated via the inventive process.

[0087] Surface resistivity (SR) measurements were taken on both sides of the plaque, designated as sides A and B. For Example 1 , SR values differ between the two sides — 4.0 x 1 o13Q / sq on side A and 6.0 x 1013Q / sq on side B — indicating inhomogeneity. In contrast, Example 2 shows consistent SR values on both sides, with a significantly higher resistivity of 1 .9 x 1 o14Q / sq. Volume resistivity (VR) is also improved in Example 2, measured at approximately 2.2 x 1012Q cm, compared to only 4.0 x 1 O11Q'cm in Example 1 . In conclusion, the inventive process provides a product with significantly enhanced surface and volume resistivity properties compared to the standard method.

[0088] Figure 1 : Image analysis of Example 1

[0089] Figure 2: Image analysis of Example 2

[0090] Figure 3: The volume resistivity (VR) and surface resistivity (SR) performance of Examples 1 and 2

Claims

Claims:1 . Process for production of polyamide hot melt adhesive composition with filler comprising a. dispersing at least a filler into at least a first reactive monomer of a polyamide and / or into water to form a dispersion, b. dosing the dispersion to a composition containing at least a second reactive monomer of polyamide before polymerization of the reactive monomers such that the reactive monomers and the filler form a liquid mixture to obtain a polyamide hot melt adhesive composition with filler.

2. Process for production of polyamide hot melt adhesive composition with filler according claim 1 , wherein the concentration of the filler is in the range of 0,00001 to 30 wt.-%, preferably 0,15 to 2.5 wt.-%, based on the total weight of the hot melt adhesive composition with filler.

3. Process for production of polyamide hot melt adhesive composition with filler according to claim 1 or 2, wherein the filler is in powder form or dispersed in water.

4. Process for production of polyamide hot melt adhesive composition with filler according to any one of preceding claims, wherein the filler is a coloring pigment and / or a functional not reactive filler.

5. Process for production of polyamide hot melt adhesive composition with filler according to claim 4, wherein the filler is carbon black.

6. Process for production of polyamide hot melt adhesive composition with filler according to claim 5, wherein the carbon black is vegetal carbon and / or from mineral origin like petroleum and gas feedstocks.

7. Process for production of polyamide hot melt adhesive composition with filler according to claim 4, wherein the filler is a thermal conductive additive selected from the list of boron nitride, alumina, graphite and graphene.

8. Polyamide hot melt adhesive composition with filler according to any one of preceding claims, wherein the concentration of the filler is in the range of 2-40 wt.-%, and the concentration of the first reactive monomer is in the range of 60-98%, based on the total weight of the dispersion.

9. Process for production of polyamide hot melt adhesive composition with filler according to any one of preceding claims, wherein the first and / or second reactive monomer is dimer fatty acid monomers.

10. Process for production of polyamide hot melt adhesive composition with filler according to claim 9, wherein the dimer fatty acid is hydrogenated dimer fatty acid.

11. Process for production of polyamide hot melt adhesive composition with filler according to any one of preceding claims, wherein in step a, the filler is dispersed in a separate mixer equipped with a cowles stirrer.

12. Process for production of polyamide hot melt adhesive composition with filler according to any one of preceding claims, wherein in step b, the dispersion is dosed via a membrane or gear pump into a polymerization reactor.

13. Process for production of polyamide hot melt adhesive composition with filler according to claim 9, wherein the composition comprises dimer fatty acid, dispersion of the filler into the dimer fatty acid, linear diacid, ethylenediamine, piperazine, polyetheramine.

14. Polyamide hot melt adhesive composition with filler obtained by the process according to any one of the preceding claims wherein the poylamide hot melt composition with filler comprises filler agglomerates with diameters below 50 pm, as determined according to the method described in the description.

15. Use of polyamide hot melt adhesive composition with filler according to claim 14 for electronic and electrical encapsulation.

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