Process for applying adhesives on polymeric materials

Abstract

Methods for treating the surface of a polymeric material and methods of applying an adhesive to the treated surface of a polymeric material are provided, in particular, to polymeric materials having a low surface energy or low density.

Description

PROCESS FOR APPLYING ADHESIVES ON POLYMERIC MATERIALSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority from U.S. Provisional Patent Application No. 63 / 653,398, filed May 30, 2024 and U.S. Provisional Patent Application No. 63 / 774,840, filed March 20, 2025, the disclosures of all of which are incorporated herein by reference.FIELD

[0002] The present disclosure relates to a process for treating the surface of a polymeric material to enhance adhesiveness, in particular, to polymeric materials having a low surface energy or low density. The present disclosure also relates to a process of applying an adhesive to a treated surface.BACKGROUND

[0003] Adhesives do not evenly and strongly adhere to polymeric materials having a low surface energy or low density due to the surface being chemically inert or having low surface tension. As such, it is challenging for adhesives to properly contact the surface of the polymeric materials and form a strong bond.

[0004] For example, foams such as irradiated crosslinked polyethylene foams or ethylene vinyl acetate foams have densities in the range of 2 - 4 lbs / ft3and surface energy of about 30 dyne / cm. Adhesives, such as acrylic PSA, coated directly onto the foam and subsequently crosslinked exhibit poor anchorage of the adhesive onto the foam. Subjecting adhesive coated foams to a shear load test using a 1 kg load on a 1 square inch foam with adhesive show early failure of less than 50 minutes. The mode of failure is delamination of the adhesive from the foam. This type of failure is unacceptable in applications that require firm attachment even when exposed to temperature cycling, wind uplift, and other forces.

[0005] As a result, there remains an unmet need for (i) methods for treating low surface energy polymeric materials to improve adhesiveness and (ii) methods for applying an adhesive to a polymeric material having a low surface energy.SUMMARY

[0006] The present disclosure provides a process for treating a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface; and(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm.

[0007] The present disclosure also provides a process for applying an adhesive to a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm; and(iii) extruding an adhesive layer onto at least a portion of the treated surface.

[0008] In one form thereof, the present disclosure provides a process for applying an adhesive to a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm;(iii) extruding a curable hot-melt adhesive onto a release liner;(iv) radiating the adhesive with UV to form a partially cured adhesive layer; and(v) laminating the release liner having the partially cured adhesive layer onto the treated surface.

[0009] Further and alternative aspects and features of the disclosed invention will be apparent from the following detailed description. As will be appreciated, the methods disclosed herein are capable of being carried out and used in other and different aspects, and capable of being modified in various respects. Accordingly, it is to be understood that both the foregoing general description and the following detailed description are only exemplary and explanatory and do not restrict in any way the scope of the claimed invention.DETAILED DESCRIPTION

[0010] The present disclosure relates to (i) methods for treating the surface of a low surface energy polymeric material to enhance adhesiveness and (ii) methods of applying an adhesive to a polymeric material having a low surface energy.

[0011] The present disclosure provides a process for treating a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface; and(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm.

[0012] The present disclosure also provides a process for applying an adhesive to a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm; and(iii) extruding an adhesive layer onto at least a portion of the treated surface.

[0013] In certain aspects, the above process for applying an adhesive to a surface further comprises a step (iv) radiating a UV-curable hot-melt adhesive with UV to form a partially cured adhesive layer.

[0014] In other aspects, the present disclosure provides a process for applying an adhesive to a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm;(iii) extruding a curable hot-melt adhesive onto a release liner;(iv) radiating the adhesive with UV to form a partially cured adhesive layer; and(v) laminating the release liner having the partially cured adhesive layer onto the treated surface.

[0015] The polymeric panel of the present disclosure may comprise a thermoplastic, thermoset plastic, a cured rubber, or a foam. In certain aspects, the polymeric panel may comprise a low density foam having low surface energy.

[0016] The thermoplastic of the present disclosure may comprise polyethylene (PE), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polymethylpentene (PMP), polybutylene (PB), fluorinated ethylene propylene (FEP), ethylene vinyl acetate (EVA), polyoxymethylene (POM), polycarbonate (PC), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyvinylidene chloride (PVDC), polychlorotrifluoroethylene (PCTFE), polymethyl methacrylate (PMMA), poly etheretherketone (PEEK), polybutylene terephthalate (PBT), polyamide, thermoplastic polyurethane (TPU), cyclic olefin copolymer (COC), or a combination thereof.

[0017] The thermoset plastic of the present disclosure may comprise epoxy resins, phenolic resins, melamine formaldehyde, urea-formaldehyde, polyurethane, unsaturated polyester resins, vinyl ester resins, bismaleimide resins, silicone resins, cyanate ester resins, bakelite, diallyl phthalate resins, polyimide resins, furan resins, polybenzoxazine, polycyanurate, amino resins, or a combination thereof.

[0018] The cured rubber of the present disclosure may comprise silicone rubber, fluorosilicone rubber, butyl rubber, ethylene propylene diene monomer, polyisoprene rubber, polychloroprene rubber, nitrile rubber, chlorosulfonated polyethylene, fluoroelastomers, ethylene acrylic rubber, polyurethane rubber, styrene-butadiene rubber, silicone-modified ethylene propylene diene monomer, thermoplastic vulcanixates, acrylate rubber, perfluoroelastomers, polysulfide rubber, epichlorohydrin rubber, or a combination thereof.

[0019] The foams of the present disclosure may comprise polyethylene foam, polypropylene foam, polystyrene foam, polyvinyl chloride foam, polyurethane foam, polyisocyanurate foam, ethyl vinyl acetate foam, polyvinylidene fluoride foam, polyamide foam, polytetrafluoroethylene foam, silicone foam, polychloroprene foam, styrene-acrylonitrile foam, polycarbonate foam, phenolic foam, or a combination thereof.

[0020] In certain aspects, the foam has a density of less than 5 pounds per cubic foot, e.g., less than 5 pounds per cubic foot, less than 4.5 pounds per cubic foot, less than 4 pounds per cubic foot, less than 3.5 pounds per cubic foot, less than 3 pounds per cubic foot, less than 2.5 pounds per cubic foot, less than 2 pounds per cubic foot, less than 1.5 pounds per cubic foot, less than 1 pound per cubic foot, or less than 0.5 pounds per cubic foot. In other aspects, the foam has a density of from about 2 to about 4 pounds per cubic foot, i.e., about 2 pounds per cubicfoot, about 2.5 pounds per cubic foot, about 3 pounds per cubic foot, about 3.5 pounds per cubic foot, or about 4 pounds per cubic foot.

[0021] The polymeric panel of the present disclosure can be exposed to a plasma stream to form a treated surface, resulting in an increased surface energy. In some aspects, the surface energy of the treated surface is from about 40 to about 60 dyne / cm, i.e., about 40 dyne / cm, about 45 dyne / cm, about 50 dyne / cm, about 55 dyne / cm, or about 60 dyne / cm. In certain aspects, the surface energy of the treated surface is about 46 to about 49 dyne / cm, i.e., about 46 dyne / cm, about 46.5 dyne / cm, about 47 dyne / cm, about 47.5 dyne / cm, about 48 dyne / cm, about 48.5 dyne / cm, or about 49 dyne / cm.

[0022] The plasma stream of the present disclosure may be from a high frequency corona treater, an atmospheric plasma generator, a flame plasma generator, or a chemical plasma generator. In some aspects, the plasma stream is from a high frequency corona treater. In certain aspects, the high frequency corona treater uses high voltage energy at atmospheric air or an inert gas.

[0023] The adhesive layer of the present disclosure comprises solvent acrylic adhesive, water-based acrylic adhesive, or butyl adhesive.

[0024] In certain aspects, the adhesive layer comprises a UV-curable hot-melt adhesive. For example, the UV-curable hot-melt adhesive may comprise acrylic-based UV-curable hot- melt adhesives, polyurethane-based UV-curable hot-melt adhesives, epoxy-based UV-curable hot-melt adhesives, silicone-based UV-curable hot-melt adhesives, polyester-based UV-curable hot-melt adhesives, polyamide-based UV-curable hot-melt adhesives, polyolefin-based UV- curable hot-melt adhesives, or a combination thereof.

[0025] In some aspects, the adhesive layer comprises a pressure-sensitive adhesive composition. For example, the pressure-sensitive adhesive (PSA) composition may comprise acrylic PSA, natural rubber PSA, synthetic rubber PSA, silicone PSA, polyurethane PSA, UV- curable PSA, or a combination thereof.

[0026] In certain aspects, the adhesive layer has a thickness of from about 2 mil to about 15 mil, i.e., about 2 mil, about 3 mil, about 4 mil, about 5 mil, about 6 mil, about 7 mil, about 8 mil, about 9 mil, about 10 mil, about 11 mil, about 12 mil, about 13 mil, about 14 mil, or about 15 mil. In other aspects, the adhesive layer has a thickness from about 2 mil to about 10 mil, i.e.,about 2 mil, about 3 mil, about 4 mil, about 5 mil, about 6 mil, about 7 mil, about 8 mil, about 9 mil, or about 10 mil.

[0027] The release liner of the present disclosure comprises a paper or polymeric film.

[0028] As used herein, the term “atmospheric plasma generator” refers to a device that produces a plasma jet by passing a high-voltage through a gas at atmospheric pressure.

[0029] As used herein, the term “chemical plasma generator” refers to a device that creates plasma through chemical reactions involving reactive gases or chemical precursors.

[0030] As used herein, the term “high frequency corona treater” refers to a device that uses high-voltage, high frequency electricity, known as corona discharge, to modify the surface characteristics of a material.

[0031] As used herein, the term “plasma stream” refers to a directed flow of hot, ionized gas containing a mix of electrons, ions, and neutral particles.

[0032] As used herein, the term “pressure-sensitive adhesive (PSA)” refers to a type of nonreactive adhesive that forms a bond when pressure is applied to attach the adhesive to a surface. PSAa do not require solvent, water, or heat activation.

[0033] As used herein, the term “treated surface” refers to a surface which has been exposed to a plasma stream.

[0034] As used herein, the term “UV-curable hot-melt adhesive” refers to a thermoplastic adhesive that is applied in a molten state and solidifies upon cooling, after which, the adhesive can undergo a secondary curing process when subjected to ultraviolet (UV) light.

[0035] As used herein, the term “about”, when used in connection with recited weight percentages of the components of the present compositions, includes a deviation of ± 0.3 % from the recited weight percentage.

[0036] As used herein, the singular forms “a”, “an” and “the” include plural unless the context clearly dictates otherwise. Moreover, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, andall integers and fractions within the range. It is not intended that the scope of the disclosure be limited to the specific values recited when defining a range.EXAMPLESExample 1 : Adhesion of a UV-curable acrylic pressure sensitive adhesive to a foam panel sample

[0037] In this study, a plasma stream was generated from a high voltage and frequency corona treater, such as a LabTEC-X corona lab system. Foam panel samples were corona treated and a UV-curable acrylic pressure sensitive adhesive (acrylic Resin A 250 UV) layer was applied on the treated surface. The samples were subjected to SS Peel and Static Shear tests. The SS Peel test measures the force needed to remove a foam adhered to a stainless steel substrate. The shear load test measures the time in minutes for a 1 kg load to pull off a 1 square inch foam adhered to a substrate. Verttec TG3W is a polyethylene foam, Verttec VA2W, Verttec VA4W and Volara are polyethylene vinyl acetate foams. CF refers to cohesive failure. The results of this study are shown in Table 1.Table 1

[0038] The data indicates that with sufficient and good surface treatment and an adequate surface energy level, the adhesive will not delaminate from the foam, rather the foam will either tear or there will be cohesive failure. Foam tearing indicates excellent adhesion performance, as it demonstrates that the adhesive bond is stronger than the foam itself, while cohesive failure indicates a strong bond to the substrate, but insufficient internal strength of the adhesive.Example 2: Replica of Example 1.

[0039] In this study, the corona treatment procedure and tests of Example 1 were repeated. The results of the study are shown in Table 2.Table 2Comparative Example 1

[0040] A UV-curable acrylic pressure sensitive adhesive (acrylic Resin A 250 UV) layer was applied on a foam panel surface. The samples were subjected to SS Peel and Static Shear tests. The SS Peel test measures the force needed to remove a foam adhered to a stainless steel substrate. The shear load test measures the time in minutes for a 1 kg load to pull off a 1 square inch foam adhered to a substrate. Volara is a polyethylene vinyl acetate foam.

[0041] The results of the study are shown in Table 3.Table 3

[0042] The data indicates that regardless of the coat weight, without sufficient and good surface treatment and an adequate surface energy level, the adhesive will delaminate from the foam, resulting in a short failure time and indicating inferior adhesion performance.ASPECTS

[0043] Aspect 1 is a process for treating a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface; and(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm.

[0044] Aspect 2 is the process according to Aspect 1 , wherein the polymeric panel is a thermoplastic, thermoset plastic, a cured rubber or a foam.

[0045] Aspect 3 is the process according to Aspect 2, wherein the foam comprises a polyurethane foam, phenolic foam, polyisocyanurate foam, polypropylene foam, polyethylene foam, or polyethylene vinyl acetate foam.

[0046] Aspect 4 is the process according to Aspect 2 or 3, wherein the foam has a density of less than 5 pounds per cubic foot or from about 2 to about 4 pounds per cubic foot.

[0047] Aspect 5 is the process according to any one of Aspects 1 to 4, wherein the surface energy of the treated surface is about 46 to about 49 dyne / cm.

[0048] Aspect 6 is the process according to any one of Aspects 1 to 5, wherein the plasma stream is from a high frequency corona treater, atmospheric plasma generator, flame plasma generator, or chemical plasma generator.

[0049] Aspect 7 is the process according to any one of Aspects 1 to 6, wherein the high frequency corona treater uses high voltage energy at atmospheric air or an inert gas.

[0050] Aspect 8 is a process for applying an adhesive to a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm; and(iii) extruding an adhesive layer onto at least a portion of the treated surface.

[0051] Aspect 9 is the process according to Aspect 8, wherein the polymeric panel is a thermoplastic, thermoset plastic, a cured rubber or a foam.

[0052] Aspect 10 is the process according to Aspect 9, wherein the foam comprises a polyurethane foam, phenolic foam, polyisocyanurate foam, polypropylene foam, polyethylene foam, or polyethylene vinyl acetate foam.

[0053] Aspect 11 is the process according to any one of Aspects 8 to 10, wherein the foam has a density of less than 5 pounds per cubic foot or from about 2 to about 4 pounds per cubic foot.

[0054] Aspect 12 is the process according to any one of Aspects 8 to 11, wherein the surface energy of the treated surface is about 46 to about 49 dyne / cm.

[0055] Aspect 13 is the process according to any one of Aspects 8 to 12, wherein the plasma stream is from a high frequency corona treater, atmospheric plasma generator, flame plasma generator, or chemical plasma generator.

[0056] Aspect 14 is the process according to any one of Aspects 8 to 13, wherein the high frequency corona treater uses high voltage energy at atmospheric air or an inert gas.

[0057] Aspect 15 is the process according to any one of Aspects 8 to 14, wherein the adhesive layer comprises solvent acrylic adhesive, water-based acrylic adhesive, or butyl adhesive.

[0058] Aspect 16 is the process according to any one of Aspects 8 to 15, wherein the adhesive layer comprises a UV-curable hot-melt adhesive.

[0059] Aspect 17 is the process according to any one of Aspects 8 to 16, further comprising a step (iv) radiating a UV-curable hot-melt adhesive with UV to form a partially cured adhesive layer.

[0060] Aspect 18 is the process according to any one of Aspects 8 to 17, wherein the adhesive layer has a thickness of from about 2 mil to about 15 mil.

[0061] Aspect 19 is the process according to any one of Aspects 8 to 18, wherein the adhesive layer comprises a pressure-sensitive adhesive composition.

[0062] Aspect 20 is a process for applying an adhesive to a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm;(iii) extruding a curable hot-melt adhesive onto a release liner;(iv)radiating the adhesive with UV to form a partially cured adhesive layer; and(v) laminating the release liner having the partially cured adhesive layer onto the treated surface.

[0063] Aspect 21 is the process according to Aspect 20, wherein the release liner comprises paper or a polymeric film.

[0064] Aspect 22 is the process according to Aspect 20 or 21, wherein the adhesive layer has a thickness of from about 2 to about 10 mil.

[0065] Aspect 23 is the process according to any one of Aspects 20 to 22, wherein the polymeric panel is a thermoplastic, thermoset plastic, a cured rubber or a foam.

[0066] Aspect 24 is the process according to any one of Aspects 20 to 23, wherein the foam comprises a polyurethane foam, phenolic foam, polyisocyanurate foam, polypropylene foam, polyethylene foam, or polyethylene vinyl acetate foam.

[0067] Aspect 25 is the process according to any one of Aspects 20 to 24, wherein the foam has a density of less than 5 pounds per cubic foot or from about 2 to about 4 pounds per cubic foot.

[0068] Aspect 26 is the process according to any one of Aspects 20 to 25, wherein the surface energy of the treated surface is about 46 to about 49 dyne / cm.

[0069] Aspect 27 is the process according to any one of Aspects 20 to 26, wherein the plasma stream is from a high frequency corona treater, atmospheric plasma generator, flame plasma generator, or chemical plasma generator.

[0070] Aspect 28 is the process according to any one of Aspects 20 to 27, wherein the high frequency corona treater uses high voltage energy at atmospheric air or an inert gas.

[0071] Aspect 29 is the process according to any one of Aspects 20 to 28, wherein the adhesive layer comprises solvent acrylic adhesive, water-based acrylic adhesive, or butyl adhesive.

[0072] Aspect 30 is the process according to any one of Aspects 20 to 29, wherein the adhesive layer comprises a pressure-sensitive adhesive composition.

Claims

CLAIMSWhat is claimed is:

1. A process for treating a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm.

2. The process of claim 1, where the polymeric panel is a thermoplastic, thermoset plastic, a cured rubber, or a foam.

3. The process of claim 2, wherein the foam comprises a polyurethane foam, phenolic foam, polyisocyanurate foam, polypropylene foam, polyethylene foam, or polyethylene vinyl acetate foam.

4. The process of claim 2 or 3, wherein the foam has a density of less than 5 pounds per cubic foot or from about 2 to about 4 pounds per cubic foot.

5. The process of claim 1, wherein the surface energy of the treated surface is about 46 to about 49 dyne / cm.

6. The process of claim 1 , wherein the plasma stream is from a high frequency corona treater, atmospheric plasma generator, flame plasma generator, or chemical plasma generator.

7. The process of claim 6, wherein the high frequency corona treater uses high voltage energy at atmospheric air or an inert gas.

8. A process for applying an adhesive to a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm; and(iii) extruding an adhesive layer onto at least a portion of the treated surface.

9. The process of claim 8, where the polymeric panel is a thermoplastic, thermoset plastic, a cured rubber, or a foam.

10. The process of claim 9, wherein the foam comprises a polyurethane foam, phenolic foam, polyisocyanurate foam, polypropylene foam, polyethylene foam, or polyethylene vinyl acetate foam.

11. The process of claim 9 or 10, wherein the foam has a density of less than 5 pounds per cubic foot or from about 2 to about 4 pounds per cubic foot.

12. The process of claim 8, wherein the surface energy of the treated surface is about 46 to about 49 dyne / cm.

13. The process of claim 8, wherein the plasma stream is from a high frequency corona treater, atmospheric plasma generator, flame plasma generator, or chemical plasma generator.

14. The process of claim 13, wherein the high frequency corona treater uses high voltage energy at atmospheric air or an inert gas.

15. The process of claim 8, wherein the adhesive layer comprises solvent acrylic adhesive, water-based acrylic adhesive, or butyl adhesive.

16. The process of claim 8, wherein the adhesive layer comprises a UV-curable hot- melt adhesive.

17. The process of claim 16, further comprising a step (iv) radiating the UV-curable hot- melt adhesive with UV to form a partially cured adhesive layer.

18. The process of claim 8, where the adhesive layer has a thickness of from about 2 mil to about 15 mil.

19. The process of claim 8, wherein adhesive layer comprises a pressure-sensitive adhesive composition.

20. A process for applying an adhesive to a surface, the process comprising:(i) providing at least one polymeric panel having at least one surface;(ii) exposing the at least one surface to a plasma stream to form a treated surface having a surface energy of from about 40 to about 60 dyne / cm;(iii) extruding a curable hot-melt adhesive onto a release liner;(iv) radiating the adhesive with UV to form a partially cured adhesive layer; and(v) laminating the release liner having the partially cured adhesive layer onto the treated surface.

21. The process of claim 20, wherein the release liner comprises paper or polymeric film.

22. The process of claim 20, wherein the adhesive layer has a thickness of from about 2 to about 10 mil.

23. The process of claim 20, where the polymeric panel is a thermoplastic, thermoset plastic, a cured rubber, or a foam.

24. The process of claim 23, wherein the foam comprises a polyurethane foam, phenolic foam, polyisocyanurate foam, polypropylene foam, polyethylene foam, or polyethylene vinyl acetate foam.

25. The process of claim 23 or 24, wherein the foam has a density of less than 5 pounds per cubic foot or from about 2 to about 4 pounds per cubic foot.

26. The process of claim 20, wherein the surface energy of the treated surface is about 46 to about 49 dyne / cm.

27. The process of claim 20, wherein the plasma stream is from a high frequency corona treater, atmospheric plasma generator, flame plasma generator, or chemical plasma generator.

28. The process of claim 27, wherein the high frequency corona treater uses high voltage energy at atmospheric air or an inert gas.

29. The process of claim 20, wherein the adhesive layer comprises solvent acrylic adhesive, water-based acrylic adhesive, or butyl adhesive.

30. The process of claim 20, wherein adhesive layer comprises a pressure-sensitive adhesive composition.

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