METHOD FOR APPLYING A MATERIAL CONTAINING A MELTABLE POLYMER, MORE PARTICULARLY A HOT-MELT ADHESIVE, ABOVE THE DECOMPOSITION TEMPERATURE THEREOF

Abstract

The invention relates to a method for applying a material containing a meltable polymer comprising the step of applying a filament of the at least partially molten material from a discharge opening of a discharge element onto a substrate. The meltable polymer has the following properties: a melting point (DSC, differential scanning calorimetry; second heating with a heating rate of 5 C./min) in a range from 40 C. to 120 C.; a glass transition temperature (DMA, dynamic mechanical analysis in accordance with DIN EN ISO 6721-1:2011) in a range from 70 C. to 30 C.; a storage modulus G (parallel plate oscillation viscometer in accordance with ISO 6721-10:2015 at a frequency of 1/s) at 20 C. above the melting point of 1.Math.10.sup.4 Paa storage modulus G (parallel plate oscillation viscometer in accordance with ISO 6721-10:2015 at a frequency of 1/s) at 10 C. below the melting point with prior heating to a temperature of 20 C. above the melting point and subsequent cooling with a cooling rate of 1 C./min of 1.Math.10.sup.7 Pa; wherein the filament has an application temperature of 100 C. above the melting point of the meltable polymer for 5 minutes during the application process and wherein the meltable polymer further has the property that the storage modulus G (parallel plate oscillation viscometer in accordance with ISO 6721-10:2015 at a frequency of 1/s) of the meltable polymer at the highest application temperature reached during the application process is smaller by a factor of 10 than the storage modulus G (parallel plate oscillation viscometer in accordance with ISO 6721-10:2015 at a frequency of 1/s) at a temperature of 20 C. above the melting point of the meltable polymer.

Claims

1. A method of applying a material comprising a fusible polymer, comprising: applying a filament of an at least partly molten material from a discharge opening of a discharge element to a substrate; wherein the fusible polymer has the following properties: a melting point within a range from 40 C. to 120 C. based on a differential scanning calorimetry 2nd heating at a heating rate of 5 C./min; a glass transition temperature within a range from 70 C. to 30 C. based on dynamic-mechanical analysis according to DIN EN ISO 6721-1:2011; a storage modulus G at 20 C. above the melting point of 1.Math.10.sup.4 Pa based on ISO 6721-10:2015 using a plate/plate oscillation viscometer at a frequency of 1/s; a storage modulus G at 10 C. below the melting point with prior heating to a temperature of 20 C. above the melting point and subsequent cooling at a cooling rate of 1 C./min of 1.Math.10.sup.7 Pa based on ISO 6721-10:2015 using a plate/plate oscillation viscometer at a frequency of 1/s; wherein the filament is applied at an application temperature of 100 C. above the melting point of the fusible polymer for 5 minutes and wherein, at a maximum application temperature attained, the fusible polymer has a storage modulus G that is smaller by a factor of 10 than the storage modulus G at a temperature of 20 C. above the melting point of the fusible polymer based on ISO 6721-10:2015 using a plate/plate oscillation viscometer at a frequency of 1/s.

2. The method as claimed in claim 1, further comprising applying the filament at a rate of 150 mm/s.

3. The method as claimed in claim 1, wherein the fusible polymer is selected such that, after storage at the maximum application temperature attained for a duration of 1 hour, the storage modulus G more than doubles, or else the storage modulus G falls to a value of less than half of a starting value based on ISO 6721-10:2015 using a plate/plate oscillation viscometer at a frequency of 1/s.

4. The method as claimed in claim 1, further comprising heating the material from a temperature of 40 C. to the maximum application temperature within 5 minutes prior to applying the material.

5. The method as claimed in claim 1, further comprising heating the material within the discharge element to the maximum application temperature, such that a viscosity of the material decreases at least by a factor of 10.

6. The method as claimed in claim 1, wherein a distance between a surface of the substrate and the discharge opening of the discharge element is 1 mm.

7. The method as claimed in claim 1, further comprising contacting and passing the discharge element with its discharge opening over the substrate at a constant pressure.

8. The method as claimed in claim 1, further comprising applying the material to the substrate at a pressure of 0.5 bar.

9. The method as claimed in claim 1, wherein the fusible polymer comprises at least one of polyurethane, polyester, polyalkylene oxide, plasticized PVC, polyamide, polyvinyl acetate, polyethylene, polypropylene, protein, or a combination of at least two of these.

10. The method as claimed in claim 9, wherein the fusible polymer comprises a polyurethane obtained from a reaction of a polyisocyanate component and a polyol component, wherein the polyol component includes a polyesterpolyol having a no-flow point of 25 C. based on ASTM D5985.

11. The method as claimed in claim 1, wherein the fusible polymer, after heating to 20 C. above its melting point and cooling to 20 C. at a cooling rate of 4 C./min, within a temperature interval from 25 C. to 40 C. for 1 minute, has a storage modulus G of 100 kPa to 10 MPa and, after cooling to 20 C. and storage at 20 C. for 120 minutes, has a storage modulus G of 20 MPa based on ISO 6721-10:2015 using a plate/plate oscillation viscometer at a frequency of 1/s.

12. The method as claimed in claim 1, further comprising contacting the material with a second substrate after applying the material.

13. The method as claimed in claim 12, wherein the second substrate includes a hotmelt adhesive that contacts the material.

14. The method as claimed in claim 1, wherein the method is a method of producing an article from the material, the method comprising: I) applying a filament of the at least partly molten material to a carrier to obtain a layer of the material, corresponding to a first selected cross section of the article; II) applying a filament of the at least partly molten material to a previously applied layer of the material to obtain a further layer of the material, corresponding to a further selected cross section of the article and bonded to the layer applied beforehand; III) repeating II) until the article has been formed.

15. The method as claimed in claim 1, wherein the substrate is a textile, a foil, a paper, a cardboard, a foam, a mold component, part of a shoe, a circuit board for electronic circuits, an electronics housing part, or an electronic component.

Description

EXPERIMENTS

[0108] The printer used was an X400 FDM 3D printer from German RepRap GmbH, equipped with a Volcano Hotend from E3D, with a melt zone of capacity about 209 mm.sup.3.

[0109] The processing was effected using filaments of diameter about 2.8 mm, under the following method conditions unless described differently: build chamber temperature=23 C., extrusion die diameter: 0. mm.

[0110] To measure the material stability in the process, the filaments were each delivered at different nozzle temperature and different volume flow rate for about 10 minutes.

[0111] The movement speed [mm/sec] was found as the ratio of the layer thickness and layer width established in the application in correlation with the delivery volume flow rate established through a given exit nozzle. Typical values were a layer thickness of 0.1 mm and a layer width of 0.4 mm in an extrusion nozzle having a diameter of 0.4 mm.

[0112] The nozzle temperature was optionally varied within the range of 200 C.-290 C. The viscosity and storage modulus at 100 C. of the extrudate were determined with a plate/plate oscillation viscometer at a frequency of 6.28 rad/s and compared to the starting material for the filament. It was shown here that no significant decrease in molecular weights was observed in the production of the filaments from the dried powders.

[0113] It was observed that the hotmelts based on the materials of the invention, by comparison with conventional PU, EVA, PE or copolyamide hotmelts, could be extruded by the method of the invention only at comparatively high temperatures of well above 100 C. above their melting temperature.

[0114] High molecular weight hotmelts used in accordance with the invention showed comparatively poor aging characteristics over prolonged periods within the temperature range necessary for extrusion.

[0115] Only by means of very short processing times of the preferred extrusion temperatures in the method of the invention was it possible to use these hotmelts without significant loss of molecular weight and hence of bonding properties, particularly for applications with high demands on immediate strength and on long open times.

[0116] Inventive experiments are identified by * hereinafter.

Tm ( C.)=melting point from DSC
Tg ( C.)=glass transition point from DSC
G (Pa)=storage modulus measured in plate/plate rheometer at 6.28 rad/s, 1% amplitude.
(Pas)=magnitude of complex viscosity measured in a plate/plate oscillation rheometer at 6.28 rad/s, 1% amplitude and a given temperature.

[0117] Table 1 describes the softening temperatures and rheology of typical products of the invention; in order to ascertain the viscosities, the material was heated to 100 C. and then cooled down in 4 C./min steps, ascertaining the storage moduli G (Pa) and viscosities (Pas) at 100 C. (G(100) and (100)), at 69 C. (G(69) and (69) and at 49 C. (G(49) and (49)):

TABLE-US-00001 TABLE 1 Product as Tg Tm G(100) (100) G(69) (69) G(49) (49) Experiment filament [ C.] [ C.] [Pa] [Pas] [Pa] [Pas] [Pa] [Pas] 1* Dispercoll U54 55 48 314000 56700 538000 91300 737000 122000 2* Dispercoll U53 57 48 336000 59100 574000 95600 766000 125000 3* Dispercoll U56 56 48 77400 17800 195000 37700 346000 61600 4* Dispercoll U58 57 48 578000 96100 798000 131000 986000 160000 5* Dispercoll U XP 2710 56 48 524000 87600 749000 122000 935000 151000 6* Dispercoll U XP 2612 56 48 308000 54600 521000 87900 745000 122000 7* Desmocoll 540/4 47 48 194000 40500 384000 71600 596000 103000 8* Desmocoll 621/2 47 48 243000 50000 471000 86500 722000 124000 9* Desmomelt VPKA 8702 47 48 21400 9170 83000 23700 216000 47200

[0118] Table 2 contains values for the change in viscosity of the materials of the invention against temperature up to the processing temperatures of the invention. Prior to the measurements conducted, the samples were dried in each case in a drying cabinet at 35 C. for 4 h (for the samples that were examined at 80 C. to 140 C.) or 72 h (for the samples that were examined at 140 C. to 200 C. and 200 C. to 290 C.), and then pressed at 80 C. with a laboratory press to give specimens.

[0119] The measurements were conducted with an ARES rheometer, from Rheometrics, PP25 mm system (to DIN 53019), at 1 Hz (w=6.28 l/s) under a nitrogen atmosphere. The heating rate for a first sample was 3 K/min (80 C. to 140 C.), for the second sample 5 K/min (140 C. to 200 C.), and for the third sample 6 K/min (200 C. to 290 C.). The measurement was divided into 3 parts with new samples each time, in order to minimize premature aging effects in the measurement of viscosity.

[0120] The data for the noninventive hotmelts were adopted from the manufacturer. The data for the noninventive hotmelts cover the typical range of hotmelt materials, for example processing viscosities of 0.5 to 20 Pas within a temperature range from 120 to 220 combined with a pot life of typically >>1 h at the recommended processing temperatures, in order to assure reliable processing.

[0121] Table 3 contains data for the thermal stability of the products of the invention in the method of the invention, with filament extrusion effected by means of a Hotend Volcano from E3D, with a melt zone of about 209 mm.sup.3, extrusion nozzle diameter 0.4 mm. The rheological data before and after extrusion were determined in a plate/plate rheometer at 100 C., 6.28 rad/s, 1% amplitude. The actual average temperature of the extrudate, according to the throughput rate and coefficient of heat transfer of the hot end or heat capacity of the product to be extruded, could be inhomogeneous from the outside inward in the extrudate, and lower than the hot end temperature defined in the programming This had a positive effect if anything on the application properties and stabilities since a higher marginal temperature can lead to a low marginal layer viscosity and a smaller pressure buildup in the extruder, and hence to higher extrusion rates. The filament thickness was about 2.8 mm in each case.

[0122] Before denotes the results of rheological measurements before the extrusion. After denotes the results of rheological measurements after the extrusion.

TABLE-US-00002 TABLE 3 Delivery volume flow Extruder rate of Exit rate G G Dwell Heat temperature filament of extradate before after time integral Experiment Material [ C.] [mm/min] [mm/sec] [Pa] [Pa] [sec] [ C. min] 18* Dispercoll U53 290 100 82 336000 82600 20 81 19* Dispercoll U56 290 100 82 77400 25100 20 81 20* Dispercoll U 58 290 100 82 578000 268000 20 81 21* Dispercoll UXP 2612 290 100 82 308000 108000 20 81 22* Desmocoll 540/4 290 100 82 194000 102000 20 81 23* Desmocoll 621/2 290 100 82 243000 137000 20 81 24 Dispercoll U 53 290 5 4 336000 1100 390 1573 25 Dispercoll U 56 290 5 4 77400 1050 390 1573 26 Dispercoll U 58 290 5 4 578000 45400 390 1573 27 Dispercoll UXP 2612 290 5 4 308000 870 390 1573 28 Desmocoll 540/4 290 5 4 194000 2500 390 1573 29 Desmocoll 621/2 290 5 4 243000 10800 390 1573 30 Dispercoll U 56 210 5 4 77400 13900 390 1053 31 Dispercoll U 53 210 5 4 336000 82000 390 1053 32 Dispercoll U 58 210 5 4 578000 176000 390 1053 33 Dispercoll UXP 2612 210 5 4 308000 54400 390 1053

[0123] It is found that, as apparent from the figures in table 3, both high extrusion temperatures and long dwell times at relatively high temperatures will lead to a significant decrease in molecular weight (decrease in viscosity/modulus) of the product, and therefore these products are not processible in conventional hotmelt extrusions without severe loss of function, and only the inventive combination of a high application temperature and short dwell time leads to sufficiently stable products and good processability.

[0124] Table 4 shows the results of the study of the aging resistance of the filaments in an air circulation oven at 290 C. and 210 C. for various dwell times. The rheological data before and after aging were compared, measured in an oscillating plate/plate rheometer at 100 C., 6.28 rad/s, 1% amplitude. For this purpose, 20 g in each case of filament were introduced into a round aluminum dish of diameter 10 cm in a preheated air circulation oven, and removed again after a defined time. In the air circulation ovens, the oven temperature is distinctly reduced by opening. Moreover, the sample takes a certain time to adopt the oven temperature. Consequently, the effective average temperature in the thermal storage in the case of short residence times is likely to be somewhat lower than the oven temperature specified.

TABLE-US-00003 TABLE 4 Oven Dwell G G Heat temperature time before after integral Experiment Material [ C.] [s] [Pa] [Pa] [ C. min] 34 Dispercoll U53 290 540 336000 23 2178 35 Dispercoll U56 290 540 77400 22 2178 36 Dispercoll U 58 290 540 578000 1000 2178 37 Dispercoll UXP 2612 290 540 308000 10 2178 38 Desmocoll540/4 290 540 194000 16400 2178 39 Desmocoll621/2 290 540 243000 6950 2178 40 Dispercoll U 54 290 540 314000 46 2178 41 Dispercoll U 2710 290 540 524000 9 2178

[0125] The oven measurement shows clearly that the products of the invention do not have adequate thermal stability at the desired method temperatures with a dwell time that is comparatively short for hotmelt applications. The high temperature is required to obtain sufficiently low processing viscosity and hence applicable products that wet suitable surfaces as adhesives. Therefore, the products of the invention cannot be processed as hotmelt by the conventional method. Only an application method that combines high temperatures with very short dwell times permits the use of the products of the invention as hotmelts with good wetting, extremely high initial strengths and sometimes excellent open times.

[0126] The diagram in FIG. 1 shows the open times and the respective viscosity of the products of the invention after cooling of the melt from 100 C. to 20 C. As shown in the diagram in FIG. 1, the viscosity values at 20 C. have been attained after 20 minutes. As shown in the diagram, for all 6 examples that are also listed in the table (Dispercoll U54, U56, U58, U XP2612, UXP 2710 and U53), the viscosity values are all within a range of good processability. As likewise indicated in the diagram by the black frame from 0 to 40 minutes on the X axis for time and from 1.0E+4 to 1.0E+07 Pa on they axis for the storage modulus, the range of good processability for the adhesives extends up to a storage modulus G of 1.0E+07 Pa. For the materials Dispercoll U53 and U56, the viscosity progression of which is shown by the two curves on the left, this means that they are processible up to about 25 minutes. For the two middle curves corresponding to Dispercoll U 58 and U XP2710, good processability up to about 35 minutes. For the two curves on the right that give the progression of viscosity for Dispercoll U XP 2612 and U XP 2710, this means that they have good processability for more than 40 minutes.

[0127] The measurements shown in table 4 and in the diagram in FIG. 1 were measured in oscillation on a Physica MCR101 instrument at 100 C. to 20 C. at a cooling rate of 4 C./min, at a frequency of 1 Hz, 1% amplitude.

[0128] It becomes clear from the cooling curves with falling temperature that the viscosity rises significantly with temperature, but also still remains within a range that permits contact bonding well below the crystallization temperature. What are shown here are thus long open times in which bonding is possible. This clearly sets the materials shown apart from standard hotmelts which, when the temperature goes below the crystallization temperature, typically harden rapidly or alternatively have to be mixed with large amounts of low molecular weight plasticizers, but these then significantly impair the mechanical properties.

[0129] Table 5 shows the result of application experiments on the products of the invention by the method of the invention to standard substrates, and the values obtained thereby by comparison with the application of comparable dispersion adhesives from the prior art.

[0130] The application method used was an X400 printer from German RepRap GmbH, equipped with a Volcano Hotend from E3D, with a melt zone of about 209 mm.sup.3 Processing was effected using filaments of diameter about 2.8 mm under the following process conditions: build chamber temperature=23 C., extrusion nozzle diameter=0.4 mm, hot end temperature 290 C., movement speed set about 250 mm/s (the movement speed always includes braking and acceleration zones at inflection points, and therefore no more precise figure is possible), at a distance from the substrate of 0.1 mm, as a result of which, on application to the substrate, the material of the invention was deformed from the extrusion nozzle and applied to the substrate in a layer thickness of 0.1 mm according to the melt pressure.

[0131] The material was applied to a PVC specimen (30% plasticizer) with dimensions of 3 cm*20 cm, coating half of the specimen (10 cm*3 cm) with the material by application in lanes. The specimen thus obtained was bonded in the coated area to a further (optionally coated) specimen under pressure, optionally after thermal activation, and, subsequently, the immediate and final strength were determined after fixed times. The results thus obtained were compared with the results of the application of typical aqueous adhesive formulations based on the products tested. 10 minutes before application of the adhesive, the PVC strip was wiped in each case with ethyl acetate for cleaning/activation of the surface. Aqueous adhesives were coated wet as a 50% dispersion onto the PVC strips with aid of a brush in layer thickness about 0.2 mm. Subsequently, the coated specimen was dried at ambient temperature and 50% humidity for 1 h. The heat activation of the dried adhesive dispersion was effected by irradiation with an IR Flash device from Funk for 10 s; the surface temperature after activation was about 86 C. Immediately after the heat activation, the PVC strips were placed on by the coated side, such that the coated surfaces had maximum overlap. The test specimen was then compressed in a press at 4 bar for 1 minute Immediately after the pressing (within 1 minute), the immediate peel strength test was then determined as a 180 peel test with a peeling speed of 100 mm/min on a Zwick tensile tester. The final strength was likewise determined at a peeling speed of 100 mm/min after 3 days.

TABLE-US-00004 Test: Peel strength PVC/PVC, 180 peel test. Sample width 30 mm Initial force 0 N Test speed speed 100 mm/min Adhesive Dispercoll U Substrate 1 PVC (30% plasticizer) Substrate 2 PVC (30% plasticizer) IR activation 10 s, surface temperature after activation about 86 C., Joining conditions 60 s, 4 bar

[0132] Table 5 summarizes the results of the adhesive test.

TABLE-US-00005 TABLE 5 Final Joining Initial strength strength Experiment Sample: Application conditions [N/mm] [N/mm] 42* U54 X400, 290 C., layer applied to one 4.8 Hotmelt thickness 0.1 mm, side, movement speed compressed about 250 mm/s directly after printing (<1 min) 43* U58 X400, 290 C., layer applied to one 8.5 Hotmelt thickness 0.1 mm, side, movement speed compressed at about 250 mm/s 4 bar, 60 s, directly after printing (<1 min) 44* U58 X400, 290 C., layer applied to both 10.4 Hotmelt thickness 0.1 mm, sides, movement speed compressed at about 250 mm/s 4 bar, 60 s, directly after printing (<1 min) 45* U58 X400, 290 C., layer applied to both 9.8 Hotmelt thickness 0.1 mm, sides, movement speed compressed by about 250 mm/s hand, 10 s, directly after printing (<1 min) 46* U58 X400, 290 C., layer applied to one 1.1 Hotmelt thickness 0.1 mm, side, movement speed compressed by about 250 mm/s hand, 10 s, directly after printing (<1 min) 47* U58 X400, 290 C., layer applied to one 2.6 Hotmelt thickness 0.1 mm, side, movement speed compressed at about 250 mm/s 4 bar, 60 s, directly after printing (<1 min) 48* U54 X400, 290 C., layer applied to both 7.3 Hotmelt thickness 0.1 mm, sides, movement speed compressed at about 250 mm/s 4 bar, 60 s, directly after printing (<1 min) 49* U54 X400, 290 C., layer applied to one 2.6 Hotmelt thickness 0.1 mm, side, movement speed compressed by about 250 mm/s hand, 10 s, directly after printing (<1 min) 50* U54 X400, 290 C., layer applied to one 6.4 Hotmelt thickness 0.1 mm, side, movement speed compressed at about 250 mm/s 4 bar, 60 s, directly after printing (<1 min) 51* U58 X400, 290 C., layer applied to both 16.3 Hotmelt thickness 0.1 mm, sides, movement speed compressed at about 250 mm/s 4 bar, 60 s, directly after printing (<1 min) 52* U54 X400, 290 C., layer applied to one 10.5 Hotmelt thickness 0.1 mm, side, movement speed 250 compressed at mm/s 4 bar, 60 s, directly after IR heat activation 53* U58 X400, 290 C., layer applied to both 15.4 Hotmelt thickness 0.1 mm, sides, movement speed 250 compressed at mm/s 4 bar, 60 s, directly after IR heat activation 54 U54 Brush, 23 C., layer applied to both 5.1 10.3 aqueous thickness 0.2 mm sides, wet, drying at 23 C. compressed at for 1 h 4 bar, 60 s, directly after IR heat activation 55 U58 Brush, 23 C., layer applied to both 5.9 11.1 aqueous thickness 0.2 mm sides, wet, drying at 23 C. compressed at for 1 h 4 bar, 60 s, directly after IR heat activation 56 U54 Brush, 23 C., layer applied to one 0.1 aqueous thickness 0.2 mm side, wet, drying at 23 C. compressed at for 1 h 4 bar, 60 s, no IR heat activation 57 U58 Brush, 23 C., layer applied to one 0.1 aqueous thickness 0.2 mm side, wet, drying at 23 C. compressed at for 1 h 4 bar, 60 s, no IR heat activation

[0133] It was found that the inventive application of a high molecular weight hotmelt leads to comparable properties to the conventional application of material-like adhesive dispersions. One advantage of the hotmelt application method of the invention in combination with the hotmelt products of the invention is that a time-consuming and costly process of drying the adhesive can be dispensed with. Moreover, application of adhesive to one side is possible. A further advantage is that, directly after application of the adhesive by the method of the invention, it was possible to undertake successful bonding with high initial strength without further heat activation.