EP4665573A1 - Method for encapsulating electrical cells bearing a nickel-based surface - Google Patents

Method for encapsulating electrical cells bearing a nickel-based surface

Info

Publication number
EP4665573A1
EP4665573A1 EP24703993.6A EP24703993A EP4665573A1 EP 4665573 A1 EP4665573 A1 EP 4665573A1 EP 24703993 A EP24703993 A EP 24703993A EP 4665573 A1 EP4665573 A1 EP 4665573A1
Authority
EP
European Patent Office
Prior art keywords
nickel
article
polymer material
composition
thermosetting polymer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24703993.6A
Other languages
German (de)
French (fr)
Inventor
Catherine Schoenenberger
Christian Beisele
Sophie COLLIARD
Zoubair Cherkaoui
Catherine Baron
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Huntsman Advanced Materials Switzerland GmbH
Original Assignee
Huntsman Advanced Materials Switzerland GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huntsman Advanced Materials Switzerland GmbH filed Critical Huntsman Advanced Materials Switzerland GmbH
Publication of EP4665573A1 publication Critical patent/EP4665573A1/en
Pending legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C09D175/08—Polyurethanes from polyethers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
    • C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
    • C09D133/04—Homopolymers or copolymers of esters
    • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09D133/062—Copolymers with monomers not covered by C09D133/06
    • C09D133/066—Copolymers with monomers not covered by C09D133/06 containing -OH groups
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/116—Primary casings; Jackets or wrappings characterised by the material
    • H01M50/124—Primary casings; Jackets or wrappings characterised by the material having a layered structure
    • H01M50/1245—Primary casings; Jackets or wrappings characterised by the material having a layered structure characterised by the external coating on the casing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/116—Primary casings; Jackets or wrappings characterised by the material
    • H01M50/124—Primary casings; Jackets or wrappings characterised by the material having a layered structure
    • H01M50/126—Primary casings; Jackets or wrappings characterised by the material having a layered structure comprising three or more layers
    • H01M50/129—Primary casings; Jackets or wrappings characterised by the material having a layered structure comprising three or more layers with two or more layers of only organic material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention is directed to a novel method for encapsulating an article bearing a nickel-based surface, in particular an electrical component bearing a nickel- based surface, with a thermosetting polymer as encapsulation material.
  • the method of the invention is based on application of a first coating based on a polymeric material of acrylic-based type between the article bearing a nickel-based surface and the encapsulation material.
  • the invention is also directed to kits of materials for encapsulating an article bearing a nickel-based surface and to articles resulting from the encapsulation.
  • nickel and nickel-based alloys play an important role in our economy. They offer special properties and are widely used in the assembly of a variety of products including battery components, electronic lead wires, mobile phones and others. These components can be provided with nickel layers to protect against corrosion and wear and to provide improved contact resistance.
  • potting and/or encapsulation techniques are usually used to protect the components and to optimize their performance. Potting is the process of partially or completely filling or embedding the component or assembly in an enclosure with a resin. Encapsulation is a similar process to potting, but differs in that the component is generally dipped into a mold with the resin, without necessarily filling the entire cavity.
  • Resin systems to be used for encapsulating electrical components are required to satisfy various properties, such as good adhesiveness, heat resistance and insulation property.
  • the most common types of resins used as encapsulants are polyurethane, acrylic, epoxy resin, and silicone.
  • Encapsulating the electrical components with these specialty polymeric materials can prevent thermal runaway and thermal propagation, and reduce mechanical shock and vibration under normal use conditions, as well as create a seal against moisture, solvents, and corrosive agents. These enhancements ensure better safety, increased mechanical stability, and improved long-term performance.
  • Nickel is an inherently inert material and tends to be smooth, resulting in less effective surface area, and components having surfaces predominantly containing nickel can only be joined together with adhesive bonds with great difficulty.
  • US5, 532,024 describes a way to improve the adhesion of polymeric materials to nickel surfaces by treatment of the substrate with H2O2 at temperatures above 40°C.
  • the disadvantage of this method is that it is a wet process and that it is time consuming and includes application of elevated temperature which may, in certain cases, deteriorate electrical components.
  • DE102017202851 describes a way to improve the adhesion of polymeric materials to nickel surfaces by treatment of the substrate with plasma or by heat treatment.
  • the plasma-treatment is not effective under all conditions due to negative impact on other components linked to the substrate targeted to bond at.
  • the plasma treatment may improve the adhesion values in certain cases, but it does not lead necessarily to a cohesive break pattern.
  • the applicant has surprisingly found that a cohesive break pattern can be obtained between an encapsulant material and a nickel-based surface, by combining at least two encapsulant materials which both alone would fail with adhesive break pattern.
  • the inventive method consists in applying on an article bearing a nickel-based surface, a first layer of a polymeric material (P) and a second top layer of an encapsulant material (A) wherein the polymeric material (P) adheres better to the nickel-based surface than the material (A) but would not fulfil the plenty of requirements requested to the encapsulation of electronic components and wherein the material (A) adheres so well to the polymeric material (P) that it would lead to a cohesive break in the layer of material (A).
  • the invention relates to a method to encapsulate an article bearing a nickel-based surface (S) with a thermosetting polymer material (A), the method comprising at least the steps of: i) coating at least a portion of the article surface (S) with a first curable resin composition; ii) at least partly curing the first curable resin composition to obtain a nickel-based article coated with a first layer of polymeric material (P); iii) applying at least a precursor composition of the thermosetting polymer material (A) over the first layer of polymeric material (P); iv) curing the precursor composition to obtain a top layer of thermosetting polymer material (A), wherein the first curable resin composition is selected from acrylate resins and methacrylate resins, and wherein the thermosetting polymer material (A) comprises a polymer having a Tg inferior or equal to -10°C, a tensile strength after curing in the range from 0.5 MPa to 20 MPa, the tensile strength being measured by the method ISO
  • the first curable resin composition is a two-part composition comprising at least a) a polymerizable monomer composition comprising acrylate or methacrylate esters or derivatives thereof, and b) at least an initiator.
  • the polymerizable monomer composition a) further comprises at least an acid, preferably chosen from acrylic acid, methacrylic acid, vinylacetic acid, and aery 1 oxy propionic acid, maleic acid and crotonic acid and/or at least an acid ester, preferably a phosphate ester.
  • thermosetting polymer material (A) is an epoxy resin and the precursor composition of the thermosetting polymer material (A) is a two-part composition comprising at least a) an epoxy compound and b) a curing agent.
  • the precursor composition of the thermosetting polymer material (A) according to the first or the second embodiment further comprises one or more additive selected from dyes, pigments, flameproofmg agents, softening agents, thermal aging stabilizers, and thixotropic or rheological modifier agents.
  • steps i) and iii) the first curable resin composition and the precursor composition of the thermosetting polymeric material (A) respectively are applied to said nickel-based article surface (S) in an amount to provide a dry film thickness of from 0.1 to 3 mm.
  • the first curable resin composition and the second curable resin composition are cured at ambient temperature.
  • the invention relates to a kit for encapsulating an article bearing a nickel-based surface (S), said kit comprising: i) a first curable resin composition selected from acrylate resins and methacrylate resins; ii) a precursor composition of a thermosetting polymer material (A), wherein the thermosetting polymer material comprises a polymer having a Tg inferior or equal to - 10°C, a tensile strength after curing in the range from 0.5 MPa to 20 MPa, the tensile strength being measured by the method ISO 527 and having an elongation at break after curing in the range from 5 % to 250 %, the elongation at break being measured by the method ISO 527.
  • a first curable resin composition selected from acrylate resins and methacrylate resins
  • the thermosetting polymer material comprises a polymer having a Tg inferior or equal to - 10°C, a tensile strength after
  • the invention relates to a device consisting in an encapsulated article, said device resulting from the implementation of the method according to the invention.
  • the article is selected from electrical cells bearing a nickel-based surface.
  • the invention relates to a method for manufacturing electrical and electronic insulation equipment, wherein said method comprises at least one step consisting in implementing the method for the encapsulation of an article as described above and in details hereunder.
  • the invention relates to the use of a combination of a polymeric material (P) and a thermosetting polymer material (A) for the encapsulation of one or more electrical component, in particular electrical cells, bearing a nickel -based surface, in a method as defined above and in details hereunder, for improving the resistance of the encapsulated component to heat cycles, for preventing thermal runaway and thermal propagation, and/or for reducing mechanical shock and vibration.
  • P polymeric material
  • A thermosetting polymer material
  • the term "consists essentially of followed by one or more characteristics, means that may be included in the process or the material of the invention, besides explicitly listed components or steps, components or steps that do not materially affect the properties and characteristics of the invention.
  • potting and “encapsulation” or “encapsulating” are used interchangeably, to describe the process of protecting an electronic component, especially electrical cells, by covering it with a resin according to methods well known in the art to guard against potential environmental threats.
  • thermosetting polymeric material a polymer which cures or sets into a hard shape using curing methods such as heat or radiation.
  • curing process is irreversible as it introduces a polymer network crosslinked by covalent chemical bonds.
  • curable composition is meant a composition comprising one or two- constituent composition or a prepolymer the curing of which results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble solid polymer network.
  • the curing can be initiated by heat, radiation, or chemical additives.
  • ambient temperature refers to the temperature of the surrounding work environment (e.g., the temperature of the area, building or room where the curable system is used or produced), exclusive of any temperature changes induced by a chemical reaction.
  • the ambient temperature is typically between about 10°C and about 30°C, more specifically about 25°C.
  • the term “ambient temperature” is used interchangeably with “room temperature” herein.
  • Tg refers to the glass transition temperature. This is the temperature below which an amorphous material behaves as a glassy solid and above which the same materials behave as if they are liquids or rubber-like solids.
  • DSC Differential Scanning calorimetry
  • DMA Dynamic Mechanical Analysis
  • TMA Thermomechanical Analysis
  • an adhesive failure is defined as follows: when the article is subjected to a load, failure, or de-bonding, the failure occurs when the encapsulant pulls away from the nickel-based surface but does not tear or split, i.e., the failure occurs at the interface between the encapsulant and the nickel-based surface of the article.
  • a cohesive failure is defined as follows: when the article is subjected to a load, failure, or de-bonding, the failure occurs in the bulk layer of the encapsulant and whereby a portion of the encapsulant remains on said encapsulant and a portion remains on the nickel-based surface of the article.
  • the present invention relates to a method to encapsulate an article bearing a nickel-based surface (S) with a thermosetting polymer material (A), the method comprising at least the steps of: i) coating at least a portion of the article surface (S) with a first curable resin composition; ii) at least partly curing the first curable resin composition to obtain a nickel-based article coated with a first layer of polymeric material (P); iii) applying at least a precursor composition of the thermosetting polymer material (A) over the first layer of polymeric material (P); iv) curing the precursor composition to obtain a top layer of thermosetting polymer material (A), wherein the first curable resin composition is selected from acrylate resins and methacrylate resins, and wherein the thermosetting polymer material comprises a polymer having a Tg inferior or equal to -10 °C, a tensile strength after curing in the range from 0.5 MPa to 20 MPa, preferably from 1 to 10 MP
  • thermosetting polymeric material (A) a thermosetting polymeric material
  • nickel surface of an article by applying a coating layer of a polymeric material (P) being an acrylate-type resin prior to the application of the thermosetting polymeric material (A).
  • thermosetting polymer material (A) the combination of the two materials (A) and (P), which both alone would fail with adhesive break pattern, allows to get a break pattern of the joint of the thermosetting polymer material (A) to the nickel- based article surface which is cohesive in the thermosetting polymer material (A).
  • the nickel-based article surface (S) is the nickel-based article surface (S)
  • nickel-based surface it is meant in the context of the present invention, a surface of an article that contains predominantly nickel.
  • the surface includes at least 50%, preferably at least 70%, more preferably at least 90%, most preferably 100% by weight of nickel.
  • the surface of the article used in the method according to the present invention may be generally any form of nickel, including pure nickel and nickel-based alloys.
  • Nickel-based alloys can include, for example, nickel-phosphorus alloys, nickeliron alloys, nickel-copper alloys, nickel-molybdenum alloys, nickel-chromium alloys, nickel-chromium-iron alloys, nickel-chromium-molybdenum alloys, nickel -titanium alloys.
  • the nickel -based surface of the article used in the method according to the present invention can also be a solid nickel surface, a plated nickel surface or a galvanized nickel surface.
  • the nickel can be plated or galvanized on any suitable metal base including, for example, copper, aluminum, aluminum alloys, iron or steel.
  • the nickel-based surface of the article is a plated nickel surface or a galvanized nickel surface.
  • plated nickel surface it is meant a metal surface that has been treated with a thin layer of nickel to protect against oxidation.
  • the plating can be achieved through electroplating, which requires an electric current, or through electroless plating, which is in autocatalytic chemical process, and includes any conventional method, such as for example, by hypophosphite nickel (II) or borate nickel.
  • galvanized nickel surface it is meant a metal surface that has been treated with a thin layer of nickel to protect against oxidation by using the hot-dip method well known in the art.
  • the nickel surface is a steel galvanized with nickel.
  • An example of this type of surface is the one commercially available under the name of Hilumin®.
  • the article used in the method according to the invention is an electrical cell, in particular an electrical cell bearing a surface made of nickel, preferably bearing a surface made of steel galvanized with nickel.
  • the article used in the method according to the invention can be selected from rotors or stators of electrical machines such as motors or generators, (power)-electronic components, batteries, switchrings of e-motors, switchgears, printed circuit boards, bushings, transformers, dry -type transformers, instrument transformers, metallic inserts embedded in the structural material of insulators.
  • electrical machines such as motors or generators, (power)-electronic components, batteries, switchrings of e-motors, switchgears, printed circuit boards, bushings, transformers, dry -type transformers, instrument transformers, metallic inserts embedded in the structural material of insulators.
  • the first curable resin composition and the polymeric material (P) are the first curable resin composition and the polymeric material (P)
  • the invention relies on the application to an article bearing a nickel-based surface (S) of a layer of a polymeric material (P) before the application of the thermosetting polymer (A) as encapsulant material.
  • the layer of the polymeric material (P) is obtained by at least partially curing a first curable resin composition after its application on the surface of the article in order to form a solid layer.
  • the first curable resin composition is advantageously liquid before curing and does not undergo cure over the time necessary for its application on the article surface.
  • the first curable resin composition advantageously comprises a two-part composition including polymerizable monomer composition comprising acrylate or methacrylate esters or derivatives thereof, and an initiator which includes a free radical generator to effect cross-linking upon mixing the two parts.
  • two-part composition is meant a composition comprising the two components as two pack systems (or kit) designed for extemporaneous mixing of the two components shortly before curing.
  • two pack systems or kit
  • crosslinks between the two components.
  • the polymerizable monomer composition comprises acrylate or methacrylate ester selected from methyl methacrylate, methyl acrylate, butyl methacrylate, t-butyl methacrylate, 2-ethylhexyacrylate, 2-ethylhexyl methacrylate, ethyl acrylate, isobomyl methacrylate, isobornyl acrylate 2-hydroxy ethyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, acrylamide, n-methyl acrylamide and mixtures thereof.
  • Further examples include acrylates or methacrylates containing monofunctionalized or polyfunctionalized monomers other than hydroxyl groups, including amido-, cyano-, chloro- and silane substituents.
  • acrylate or methacrylate esters can be advantageously chosen from a) esters of acrylic and/or methacrylic acid with mono-, di- and polyols, b) esters of acrylic acid and/or methacrylic acid with hydroxyl-functionalized polyethers, c) esters of acrylic acid and/or methacrylic acid with hydroxyl functionalized polyesters, d) esters of acrylic acid and/or methacrylic acid with hydroxyl functionalized alicyclic and aromatic compounds. These derivatives may contain further polymerizable functional groups.
  • the acrylate or methacrylate esters are selected from ethyl acrylate, methyl acrylate, methyl methacrylate and butyl methacrylate, preferably methyl methacrylate.
  • the polymerizable monomer composition further comprises at least an acid and/or at least an acid ester.
  • Suitable acids may include ethylenically unsaturated mono or polycarboxylic acids such as acrylic acid, methacrylic acid, vinylacetic acid, and acryloxypropionic acid. Acids may also include maleic acid and crotonic acid. Also included are compounds with at least one strong acid active hydrogen group, or with at least one phosphonic acid active hydrogen group, such as hydroxyethyl diphosphonic acid, phosphonic acid and derivatives thereof or oligomeric or polymeric structures with phosphonic acid functionality or similar acid strength functionality.
  • the acid is acrylic acid, methacrylic acid or a mixture thereof.
  • Suitable acid esters include phosphate acid esters, sulfonic acid esters and mixtures thereof.
  • Suitable phosphate esters are 2-hydroxy ethyl methacrylate phosphate (HEMA phosphate) and bis[2-(acryloyloxy)ethyl] hydrogen phosphate.
  • the polymerizable monomers composition comprises 2-hydroxyethyl methacrylate phosphate (HEMA phosphate) and/or methacrylic acid and/or acrylic acid.
  • HEMA phosphate 2-hydroxyethyl methacrylate phosphate
  • the polymerizable monomers composition comprises from 0.1 to 20 % by weight, preferably from 0.2 to 10% by weight, more preferably from 0.5 to 5% by weight of acid and/or an acid ester as described above.
  • the polymerizable monomers composition comprises from 0.5 to 20% by weight, preferably from 1 to 15% by weight of acid as described above, preferably methacrylic acid and/or acrylic acid.
  • the polymerizable monomers composition comprises from 0.1 to 10 % by weight, preferably from 0.1 to 5% by weight of phosphate ester as described above, preferably 2-hydroxyethyl methacrylate phosphate (HEMA phosphate) and/or bis[2-(acryloyloxy)ethyl] hydrogen phosphate.
  • phosphate ester as described above, preferably 2-hydroxyethyl methacrylate phosphate (HEMA phosphate) and/or bis[2-(acryloyloxy)ethyl] hydrogen phosphate.
  • the initiator to be used in accordance with the invention are known in the art.
  • examples of initiators to be in accordance with the invention include peroxides, hydroperoxides, peresters, peracids, and azo compounds.
  • Representative examples of peroxide and hydroperoxide compounds include, but are not limited to, benzoyl peroxide, cumene hydroperoxide, tertiary butyl hydroperoxide, dicumyl peroxide, tertiary butyl peroxide acetate, tertiary butyl perbenzoate, and combinations thereof.
  • the initiator is selected the group consisting of peroxides, hydroperoxides, and mixtures thereof.
  • the polymerizable monomer composition part and the initiator part are in a weight ratio ranging from about 20: 1 to about 1 : 1.
  • the first curable composition further comprises other additives such as epoxy resins, tougheners (coreshell, rubbers) plasticizers, coloring agents, viscosity-controlling agents, etc., that can be included in the polymerizable monomers composition part and/or the initiator part.
  • additives such as epoxy resins, tougheners (coreshell, rubbers) plasticizers, coloring agents, viscosity-controlling agents, etc.
  • the first curable composition is selected from ARALDITE® 2051 and ARALDITE® 2050, commercially available from Huntsman.
  • the first curable resin composition is applied at least partially on the surface of the article with a thickness between 0.05 mm and 1 mm, preferably between 0.1 mm and 0.2 mm.
  • the layer of the first curable resin composition has regular thickness on all the surface of the article where it is applied.
  • the layer of the first curable resin composition is applied on the entire surface of the article that will be encapsulated.
  • Application of the first curable resin composition layer may be implemented by any method known to the skilled professional, like spraying, dipping, paint-brushing, spin coating, etc. . .
  • the nickel-based surface (S) of the article is cleaned and preferably dried, prior to application of the first curable resin composition.
  • the surface of the nickel-based surface (S) is cleaned with isopropanol.
  • the first curable resin composition is at least partially cured at ambient temperature, in particular at a temperature ranging from 10 to 30 °C, preferably at 23 °C to form a solid layer of polymeric material (P).
  • the first curable resin composition is at least partially cured for a period of time ranging from 15 minutes to 96 hours, preferably from 30 minutes to 72 hours, more preferably from 60 minutes to 48 hours to form a solid layer of polymeric material (P).
  • the first curable resin composition is totally cured before the application of the precursor composition for the thermosetting polymeric material (A) in step iii).
  • the layer of polymeric material (P), obtained after curing has a glass transition temperature Tg ranging from 60 °C to 170 °C, preferably from 90 °C to 150°C, more preferably from 110 °C to 140 °C.
  • the layer of polymeric material (P), obtained after curing, has an elongation at break, according to ISO 527 with a sample of thickness of 1mm, ranging from 5 and 20%, preferably from 5 to 15%.
  • the layer of polymeric material (P), obtained after curing has a tensile strength according to ISO 527 ranging from 10 to 70 MPa, preferably from 15 to 60 MPa, more preferably from 20 to 50 MPa.
  • the tensile strength is measured by the method ISO 527.
  • the polymeric material (P) according to the invention has a tensile strength higher than that of the thermosetting polymer material (A).
  • thermosetting polymeric material (A) The precursor composition of the thermosetting polymeric material (A) and the thermosetting polymeric material (A):
  • step iii) of the method according to the invention the coated, at least partially cured, article surface resulting from step ii) is encapsulated in a known manner with a precursor composition for the thermosetting polymeric material (A).
  • the precursor composition for the thermosetting polymeric material (A) comprises a polymer having a glass transition temperature Tg inferior or equal to -10 °C, preferably ranging from -50 °C to -10 °C, more preferably ranging from -50 °C to -40 °C, an elongation at break measured according to ISO 527 ranging from 5% to 250%, preferably from 5% to 100% and a tensile strength measured according to ISO 527 ranging from 0.5 to 20 MPa, preferably from 1 to 10 MPa.
  • Tg inferior or equal to -10 °C preferably ranging from -50 °C to -10 °C, more preferably ranging from -50 °C to -40 °C
  • an elongation at break measured according to ISO 527 ranging from 5% to 250%, preferably from 5% to 100%
  • a tensile strength measured according to ISO 527 ranging from 0.5 to 20 MPa, preferably from 1 to 10 MPa.
  • the precursor composition for the thermosetting polymeric material (A) comprises a polymer having a tensile modulus measured according to ISO 527 ranging from 10 MPa to 100 MPa.
  • the precursor composition for the thermosetting polymeric material (A) comprises a polymer having a thermal conductivity ranging from 0.1 to 2 W/m*K.
  • thermosetting polymeric material (A) used in the method according to the invention is selected from polyurethane, epoxy resins and mixtures thereof. According to preferred embodiment of the invention, the thermosetting polymeric material (A) is polyurethane.
  • the precursor composition for the thermosetting polymeric material (A) is a curable two-part resin system, comprising:
  • the precursor composition for the thermosetting polymeric material (A) comprises one or more fillers included as a component of the first part or the second part.
  • the precursor composition of the thermosetting polymer material (A) according to the first embodiment can further comprise, either in the first or in the second part, one or more additive selected from dyes, pigments, flameproofmg agents, softening agents, thermal aging stabilizers, and thixotropic or rheological modifier agents.
  • Non-limiting examples of suitable polyols to be used in the invention may include, but are not limited to, polyether polyols, polyester polyols, polycaprolactone polyols, polycarbonate polyols, polyurethane polyols, poly vinyl alcohols, polymers containing hydroxy functional acrylates, polymers containing hydroxy functional methacrylates, polymers containing allyl alcohols and mixtures thereof.
  • the polyol compound is selected from poly ether polyols.
  • the isocyanate components useful in the present invention are well known in the art and are organic compounds that contain two, or greater than two, isocyanate groups per molecule.
  • Isocyanate components may be aromatic, cycloaliphatic or aliphatic and may be monomeric or oligomeric compounds.
  • the isocyanate component has an NCO functionality greater than or equal to 2, preferably ranging from 2 to 3.
  • the precursor composition for the thermosetting polymeric material (A) comprises at least 30 % or more, preferably 40% or more , more preferably 50% or more by weight of fillers, preferably inorganic fillers, with regards to the total weight of the composition.
  • the precursor composition for the thermosetting polymeric material (A) comprises one or more fillers included as a component of the first part or the second part.
  • the precursor composition of the thermosetting polymer material (A) according to the second embodiment can further comprise, either in the first or in the second part, one or more additive selected from dyes, pigments, flameproofmg agents, softening agents, thermal aging stabilizers, and thixotropic or rheological modifier agents.
  • the epoxy component is prepared by methods well known in the art, in particular by reacting epichlorohydrin with a compound containing at least one phenolic compound under basic conditions, such as in an alkaline reaction medium or in the presence of a suitable base.
  • Suitable epoxy resins include, but are not limited to, butanediol diglycidyl ether, hexanediol diglycidyl ether, 1,4-cyclohexane dimethanol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, neopentyl glycol diglycidyl ether, or mixtures thereof.
  • the epoxy compound is chosen from diglycidyl ether of bisphenol A and polyglycidyl ether of phenol-formaldehyde novolak.
  • epoxy components include, but are not limited to, EPON® 826 and EPON® DPL-862 available from Shell and DEN 439 and DEN 438, available from Dow Chemical Co.
  • the epoxy component may also include an aqueous organic solvent or diluent present in an amount effective to decrease the viscosity of the system for improving the processability.
  • diluents include ketones, alcohols and glycol ethers.
  • the curing agent The curing agent
  • Suitable curing agents for use in the epoxy resin composition include, but are not limited to, amines, amides, anhydrides, phenols, and thiols.
  • the curing agent is liquid at ambient temperature and can be mixed with the epoxy compound without heating.
  • the curing agent is an amine-based curing compound chosen from aliphatic amines such as such as ethylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, and aromatic amines such as diaminodiphenylmethane (DDMs).
  • aliphatic amines such as such as ethylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, and aromatic amines such as diaminodiphenylmethane (DDMs).
  • the amount of curing agent used in the second curable composition may range of ratios of amine hydrogen equivalent weight and the epoxy equivalent is 0.9 to 1.5, preferably in the range of 0.9 to 1.1, more preferably 1.
  • the precursor composition for the thermosetting polymeric material (A) can be prepared in the conventional manner, in particular by mixing and/or blending the two- part resin system described above according to the first or the second embodiment, optionally with one or more filler, then applying it on the surface of the article already coated with the layer of polymeric material (P).
  • Application to the article can be carried out for example by dipping, trickle impregnation, vacuum pressure impregnation and/or casting.
  • the precursor composition for the thermosetting polymeric material (A) is advantageously liquid before curing and does not undergo cure over the time necessary for its application on the layer of polymeric material (P).
  • the precursor composition for the thermosetting polymeric material (A) has sufficiently low viscosity.
  • the precursor composition for the thermosetting polymeric material (A) has a viscosity before curing ranging from 0.5 to 10 poise, and preferably from 0.5 to 6 poise.
  • the precursor composition for the thermosetting polymeric material (A) is applied on the top of the layer of polymeric material (P) with a thickness between 0.05 mm and 1 mm, preferably between 0.1 mm and 0.2 mm.
  • the first layer of polymeric material (P) and the top layer of thermosetting polymeric material (A) are applied to the nickel-based article surface (S) in an amount to provide a total dry film thickness of from 0.1 to 2 mm preferably from 0.2 to 0.4 mm.
  • thermosetting polymeric material (A) is prepared by curing the precursor composition for the thermosetting polymeric material (A).
  • the precursor composition for the thermosetting polymeric material (A) is cured at a temperature ranging from 10 to 35 °C, preferably from 15°C to 30°C, advantageously at a temperature of about 23 °C.
  • the precursor composition for the thermosetting polymeric material (A) is cured for a period of time ranging from 15 minutes to 96 hours, preferably from 30 minutes to 72 hours, more preferably from 60 minutes to 48 hours to form a solid layer of thermosetting polymeric material (A).
  • fillers that may be contained in the precursor composition for the thermosetting polymeric material (A) according to the second embodiment are selected from mineral fillers or metal powders.
  • the fillers are inorganic fillers selected from the group consisting of quartz sand, quartz powder, silica, amorphous silica, fused silica, aluminium oxide, titanium oxide, zirconium oxide, Mg(OH)2, AI(OH)3, dolomite [CaMg (CCh)?], AIO(OH), silicon nitride, boron nitride, aluminium nitride, silicon carbide, boron carbide, chalk, calcium carbonate, baryte, gypsum, hydromagnesite, zeolites, talcum, mica, kaolin and wollastonite, aluminium-silicates, alumosilicates, milled glass, glass beads.
  • fillers may be silanized.
  • the fillers are AI(OH)3.
  • the precursor composition for the thermosetting polymeric material (A) comprises at least 30 % or more, preferably 40% or more , more preferably 50% or more by weight of fillers, preferably inorganic fillers, with regards to the total weight of the composition.
  • the invention relates to a kit for encapsulating an article bearing a nickel-based surface (S), said kit comprising: i) a first curable resin composition selected from acrylate resins and methacrylate resins; ii) a precursor composition of a thermosetting polymer material (A), wherein the thermosetting polymer material comprises a polymer having a Tg inferior or equal to - 10°C, a tensile strength after curing in the range from 0.5MPa to 20 MPa, preferably from 1 MPa to 10 MPa, the tensile strength being measured by the method ISO 527 and having an elongation at break after curing in the range from 5 % to 250 %, preferably from 5% to 100%, the elongation at break being measured by the method ISO 527.
  • a first curable resin composition selected from acrylate resins and methacrylate resins
  • the thermosetting polymer material comprises a polymer having a T
  • thermosetting polymer material comprises a polymer having a tensile modulus comprised between 10 MPa and 100 MPa.
  • the invention relates to a device consisting in an encapsulated article, said device resulting from the implementation of the method described above.
  • the disclosed method results in an article bearing a nickel-based surface (S) which is coated with a polymeric material (P) layer covering part or all of its surface, and an encapsulation resin layer of the thermosetting polymeric material (A) on top of the polymeric material (P) layer.
  • S nickel-based surface
  • P polymeric material
  • A thermosetting polymeric material
  • the device is an encapsulated electrical cell.
  • the invention also concerns a method for manufacturing electrical and electronic insulation equipment, wherein said method comprises at least one step consisting in implementing the method for the encapsulation of an article as described in detail above.
  • the invention relates to the use of a combination of a polymeric material (P) and a thermosetting polymer material (A) as defined in details above as encapsulant material in one or more electrical component, in particular battery cells, comprising a nickel-based surface, for improving the resistance of the encapsulated component to heat cycles, for preventing thermal runaway and thermal propagation, and/or for reducing mechanical shock and vibration.
  • a polymeric material (P) and a thermosetting polymer material (A) as defined in details above as encapsulant material in one or more electrical component, in particular battery cells, comprising a nickel-based surface
  • Hilumin® This is a steel galvanized with nickel commercially available from Tata Steel.
  • thermosetting polymer material (A) polyol component: ARATHANE® CW 30664, isocyanate component: ARATHANE® HY 30665: This is an ambient temperature-curing, 2-component polyurethane system comprising 66% of mineral fillers commercially available from Huntsman. It is based on polyetherpolyol and aromatic isocyanates.
  • the substrate specimens Prior to the application of the adhesives, the substrate specimens were cleaned with isopropanol. After drying, for C2, C4, C6 a plasma treatment was carried out to the substrates: 3 min O2 plasma at 2 mbar 360 W.
  • the data in table 1 were all determined by testing standard specimens made by lap-jointing 100 x 25 x 1 mm strips of Hilumin ®. The joint area was 12.5 x 25 mm in each case. The thickness of the adhesive layer was adjusted to 1.5 mm or 0.3 mm (adjusted with glass beads).
  • C2 and C6 show that the plasma treatment does not help at all to improve the adhesion to Hilumin®.
  • C3 is a comparative trial showing that even the methylmetacrylate-based adhesive Araldite ® 2051 does not adhere well to Hilumin®: Although it results in much higher lap shear values, it shows about 50 % adhesive failure.
  • C4 illustrates the combination of C3 with plasma: This pre-treatment improves the lap-shear strength, but the failure mode is still mainly adhesive break.
  • El and E2 are the inventive examples, demonstrating that application of a first layer in direct contact to Hilumin® and a subsequent layer of polyurethane leads to mainly cohesive break pattern in the polyurethane phase.

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Abstract

The present invention is directed to a method for encapsulating an article bearing a surface made of nickel, in particular an electrical component bearing a surface made of nickel, with a thermosetting polymer material as encapsulation material. The invention is also directed to kits of materials for encapsulating an article bearing a surface made of nickel and to articles resulting from the encapsulation. The method of the invention is based on application of a first coating based on a polymeric material of acrylic-based type between the article bearing a nickel-based surface and the encapsulation material.

Description

METHOD FOR ENCAPSULATING ELECTRICAL CELLS BEARING A NICKEL-BASED SURFACE
The present invention is directed to a novel method for encapsulating an article bearing a nickel-based surface, in particular an electrical component bearing a nickel- based surface, with a thermosetting polymer as encapsulation material. The method of the invention is based on application of a first coating based on a polymeric material of acrylic-based type between the article bearing a nickel-based surface and the encapsulation material. The invention is also directed to kits of materials for encapsulating an article bearing a nickel-based surface and to articles resulting from the encapsulation.
State of the art
From power generation to electronics to automotive manufacturing, nickel and nickel-based alloys play an important role in our economy. They offer special properties and are widely used in the assembly of a variety of products including battery components, electronic lead wires, mobile phones and others. These components can be provided with nickel layers to protect against corrosion and wear and to provide improved contact resistance.
Generally, for the above applications, potting and/or encapsulation techniques are usually used to protect the components and to optimize their performance. Potting is the process of partially or completely filling or embedding the component or assembly in an enclosure with a resin. Encapsulation is a similar process to potting, but differs in that the component is generally dipped into a mold with the resin, without necessarily filling the entire cavity.
Resin systems to be used for encapsulating electrical components are required to satisfy various properties, such as good adhesiveness, heat resistance and insulation property. The most common types of resins used as encapsulants are polyurethane, acrylic, epoxy resin, and silicone.
Encapsulating the electrical components with these specialty polymeric materials can prevent thermal runaway and thermal propagation, and reduce mechanical shock and vibration under normal use conditions, as well as create a seal against moisture, solvents, and corrosive agents. These enhancements ensure better safety, increased mechanical stability, and improved long-term performance.
However, the problem that may arise is that it is difficult to achieve good bonding of polymeric materials to nickel and nickel-based alloys constituting the surface of electrical components, especially electrical cells. Nickel is an inherently inert material and tends to be smooth, resulting in less effective surface area, and components having surfaces predominantly containing nickel can only be joined together with adhesive bonds with great difficulty.
To improve bonding properties of adhesive layers on nickel surfaces to be bonded, surface pretreatments have been proposed. US5, 532,024 describes a way to improve the adhesion of polymeric materials to nickel surfaces by treatment of the substrate with H2O2 at temperatures above 40°C. The disadvantage of this method is that it is a wet process and that it is time consuming and includes application of elevated temperature which may, in certain cases, deteriorate electrical components.
DE102017202851 describes a way to improve the adhesion of polymeric materials to nickel surfaces by treatment of the substrate with plasma or by heat treatment. However, the plasma-treatment is not effective under all conditions due to negative impact on other components linked to the substrate targeted to bond at. Also, the plasma treatment may improve the adhesion values in certain cases, but it does not lead necessarily to a cohesive break pattern.
These prior art methods are not practicable for the encapsulation of electrical accumulator cells bearing a nickel-based surface in a thermal conductive resin.
In light of these technical problems, the applicant has identified a need to improve the adhesion of an encapsulant material to nickel-based surfaces.
An object of the present invention is thus to provide materials and methods for electronic component encapsulations, in particular for electrical cells encapsulation, that allow good adhesion properties and high bonding strength to nickel-based surfaces. Improving the adhesion in this respect means mainly obtaining a cohesive break pattern in case of forced destruction of the bonding between the encapsulant and the nickel- based surface of the electronic components.
The applicant has surprisingly found that a cohesive break pattern can be obtained between an encapsulant material and a nickel-based surface, by combining at least two encapsulant materials which both alone would fail with adhesive break pattern. The inventive method consists in applying on an article bearing a nickel-based surface, a first layer of a polymeric material (P) and a second top layer of an encapsulant material (A) wherein the polymeric material (P) adheres better to the nickel-based surface than the material (A) but would not fulfil the plenty of requirements requested to the encapsulation of electronic components and wherein the material (A) adheres so well to the polymeric material (P) that it would lead to a cohesive break in the layer of material (A).
Summary of the invention
The invention relates to a method to encapsulate an article bearing a nickel-based surface (S) with a thermosetting polymer material (A), the method comprising at least the steps of: i) coating at least a portion of the article surface (S) with a first curable resin composition; ii) at least partly curing the first curable resin composition to obtain a nickel-based article coated with a first layer of polymeric material (P); iii) applying at least a precursor composition of the thermosetting polymer material (A) over the first layer of polymeric material (P); iv) curing the precursor composition to obtain a top layer of thermosetting polymer material (A), wherein the first curable resin composition is selected from acrylate resins and methacrylate resins, and wherein the thermosetting polymer material (A) comprises a polymer having a Tg inferior or equal to -10°C, a tensile strength after curing in the range from 0.5 MPa to 20 MPa, the tensile strength being measured by the method ISO 527 and having an elongation at break after curing in the range from 5 % to 250%, the elongation at break being measured by the method ISO 527.
Advantageously, the nickel-based surface (S) of the article is a solid nickel surface, a plated nickel surface or a galvanized nickel surface.
Advantageously, the first curable resin composition is a two-part composition comprising at least a) a polymerizable monomer composition comprising acrylate or methacrylate esters or derivatives thereof, and b) at least an initiator. Preferably, the polymerizable monomer composition a) further comprises at least an acid, preferably chosen from acrylic acid, methacrylic acid, vinylacetic acid, and aery 1 oxy propionic acid, maleic acid and crotonic acid and/or at least an acid ester, preferably a phosphate ester.
According to a first embodiment, the thermosetting polymer material (A) is a polyurethane and the precursor composition of the thermosetting polymer material (A) is a two-part composition comprising at least a) a polyol component and b) an isocyanate component.
According to a second embodiment, the thermosetting polymer material (A) is an epoxy resin and the precursor composition of the thermosetting polymer material (A) is a two-part composition comprising at least a) an epoxy compound and b) a curing agent.
Advantageously, the precursor composition of the thermosetting polymer material (A) according to the first or the second embodiment further comprises fillers, preferably at least 30% by weight of fillers.
Advantageously, the precursor composition of the thermosetting polymer material (A) according to the first or the second embodiment further comprises one or more additive selected from dyes, pigments, flameproofmg agents, softening agents, thermal aging stabilizers, and thixotropic or rheological modifier agents.
Advantageously, in steps i) and iii) the first curable resin composition and the precursor composition of the thermosetting polymeric material (A) respectively are applied to said nickel-based article surface (S) in an amount to provide a dry film thickness of from 0.1 to 3 mm.
Advantageously, in steps ii) and iv), the first curable resin composition and the second curable resin composition, respectively, are cured at ambient temperature.
According to another aspect, the invention relates to a kit for encapsulating an article bearing a nickel-based surface (S), said kit comprising: i) a first curable resin composition selected from acrylate resins and methacrylate resins; ii) a precursor composition of a thermosetting polymer material (A), wherein the thermosetting polymer material comprises a polymer having a Tg inferior or equal to - 10°C, a tensile strength after curing in the range from 0.5 MPa to 20 MPa, the tensile strength being measured by the method ISO 527 and having an elongation at break after curing in the range from 5 % to 250 %, the elongation at break being measured by the method ISO 527.
According to another aspect, the invention relates to a device consisting in an encapsulated article, said device resulting from the implementation of the method according to the invention. Preferably, the article is selected from electrical cells bearing a nickel-based surface.
According to another aspect, the invention relates to a method for manufacturing electrical and electronic insulation equipment, wherein said method comprises at least one step consisting in implementing the method for the encapsulation of an article as described above and in details hereunder.
According to another aspect, the invention relates to the use of a combination of a polymeric material (P) and a thermosetting polymer material (A) for the encapsulation of one or more electrical component, in particular electrical cells, bearing a nickel -based surface, in a method as defined above and in details hereunder, for improving the resistance of the encapsulated component to heat cycles, for preventing thermal runaway and thermal propagation, and/or for reducing mechanical shock and vibration.
Detailed description
The term "consists essentially of followed by one or more characteristics, means that may be included in the process or the material of the invention, besides explicitly listed components or steps, components or steps that do not materially affect the properties and characteristics of the invention.
The expression “comprised between X and Y” includes boundaries, unless explicitly stated otherwise. This expression means that the target range includes the X and Y values, and all values from X to Y.
For the purpose of the present invention, the terms “potting” and “encapsulation” or “encapsulating” are used interchangeably, to describe the process of protecting an electronic component, especially electrical cells, by covering it with a resin according to methods well known in the art to guard against potential environmental threats.
For the purpose of the present invention, by “thermosetting polymeric material”, is meant a polymer which cures or sets into a hard shape using curing methods such as heat or radiation. The curing process is irreversible as it introduces a polymer network crosslinked by covalent chemical bonds. By “curable composition” is meant a composition comprising one or two- constituent composition or a prepolymer the curing of which results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble solid polymer network. The curing can be initiated by heat, radiation, or chemical additives.
As used herein, the term “ambient temperature” refers to the temperature of the surrounding work environment (e.g., the temperature of the area, building or room where the curable system is used or produced), exclusive of any temperature changes induced by a chemical reaction. The ambient temperature is typically between about 10°C and about 30°C, more specifically about 25°C. The term “ambient temperature” is used interchangeably with “room temperature” herein.
For the purposes of the present invention, the term “Tg” refers to the glass transition temperature. This is the temperature below which an amorphous material behaves as a glassy solid and above which the same materials behave as if they are liquids or rubber-like solids. A variety of techniques can be used to measure Tg, including Differential Scanning calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and Thermomechanical Analysis (TMA).
For the purpose of the present invention, an adhesive failure is defined as follows: when the article is subjected to a load, failure, or de-bonding, the failure occurs when the encapsulant pulls away from the nickel-based surface but does not tear or split, i.e., the failure occurs at the interface between the encapsulant and the nickel-based surface of the article.
For the purpose of the present invention, a cohesive failure is defined as follows: when the article is subjected to a load, failure, or de-bonding, the failure occurs in the bulk layer of the encapsulant and whereby a portion of the encapsulant remains on said encapsulant and a portion remains on the nickel-based surface of the article.
Method for encapsulating an article bearing a nickel-based surface
According to a first aspect, the present invention relates to a method to encapsulate an article bearing a nickel-based surface (S) with a thermosetting polymer material (A), the method comprising at least the steps of: i) coating at least a portion of the article surface (S) with a first curable resin composition; ii) at least partly curing the first curable resin composition to obtain a nickel-based article coated with a first layer of polymeric material (P); iii) applying at least a precursor composition of the thermosetting polymer material (A) over the first layer of polymeric material (P); iv) curing the precursor composition to obtain a top layer of thermosetting polymer material (A), wherein the first curable resin composition is selected from acrylate resins and methacrylate resins, and wherein the thermosetting polymer material comprises a polymer having a Tg inferior or equal to -10 °C, a tensile strength after curing in the range from 0.5 MPa to 20 MPa, preferably from 1 to 10 MPa, the tensile strength being measured by the method ISO 527 and having an elongation at break after curing in the range from 5% to 250%, preferably from 5% to 100%, the elongation at break being measured by the method ISO 527.
The applicant has found that it is possible to improve the bonding between a thermosetting polymeric material (A) and a nickel surface of an article by applying a coating layer of a polymeric material (P) being an acrylate-type resin prior to the application of the thermosetting polymeric material (A).
It is known that acrylate-type resins can adhere better, but not perfectly to nickel- based surfaces. However, such polymeric material would not fulfil the plenty of requirements requested to the encapsulation material for electrical components and it also would fail with an adhesive break pattern.
In particular, the applicant has surprisingly found that the combination of the two materials (A) and (P), which both alone would fail with adhesive break pattern, allows to get a break pattern of the joint of the thermosetting polymer material (A) to the nickel- based article surface which is cohesive in the thermosetting polymer material (A).
The nickel-based article surface (S)
By “nickel-based surface”, it is meant in the context of the present invention, a surface of an article that contains predominantly nickel. Advantageously, the surface includes at least 50%, preferably at least 70%, more preferably at least 90%, most preferably 100% by weight of nickel.
The surface of the article used in the method according to the present invention may be generally any form of nickel, including pure nickel and nickel-based alloys. Nickel-based alloys can include, for example, nickel-phosphorus alloys, nickeliron alloys, nickel-copper alloys, nickel-molybdenum alloys, nickel-chromium alloys, nickel-chromium-iron alloys, nickel-chromium-molybdenum alloys, nickel -titanium alloys.
The nickel -based surface of the article used in the method according to the present invention can also be a solid nickel surface, a plated nickel surface or a galvanized nickel surface. The nickel can be plated or galvanized on any suitable metal base including, for example, copper, aluminum, aluminum alloys, iron or steel.
According to a preferred embodiment of the invention, the nickel-based surface of the article is a plated nickel surface or a galvanized nickel surface.
By “plated nickel surface” it is meant a metal surface that has been treated with a thin layer of nickel to protect against oxidation. The plating can be achieved through electroplating, which requires an electric current, or through electroless plating, which is in autocatalytic chemical process, and includes any conventional method, such as for example, by hypophosphite nickel (II) or borate nickel. By “galvanized nickel surface” it is meant a metal surface that has been treated with a thin layer of nickel to protect against oxidation by using the hot-dip method well known in the art.
Preferably, the nickel surface is a steel galvanized with nickel. An example of this type of surface is the one commercially available under the name of Hilumin®.
Advantageously, the article used in the method according to the invention is an electrical cell, in particular an electrical cell bearing a surface made of nickel, preferably bearing a surface made of steel galvanized with nickel.
Alternatively, the article used in the method according to the invention can be selected from rotors or stators of electrical machines such as motors or generators, (power)-electronic components, batteries, switchrings of e-motors, switchgears, printed circuit boards, bushings, transformers, dry -type transformers, instrument transformers, metallic inserts embedded in the structural material of insulators.
The first curable resin composition and the polymeric material (P)
The invention relies on the application to an article bearing a nickel-based surface (S) of a layer of a polymeric material (P) before the application of the thermosetting polymer (A) as encapsulant material. The layer of the polymeric material (P) is obtained by at least partially curing a first curable resin composition after its application on the surface of the article in order to form a solid layer.
The first curable resin composition is advantageously liquid before curing and does not undergo cure over the time necessary for its application on the article surface.
The first curable resin composition advantageously comprises a two-part composition including polymerizable monomer composition comprising acrylate or methacrylate esters or derivatives thereof, and an initiator which includes a free radical generator to effect cross-linking upon mixing the two parts.
By “two-part composition” is meant a composition comprising the two components as two pack systems (or kit) designed for extemporaneous mixing of the two components shortly before curing. When the two components are mixed/blended together and cured, they can form a cured solid coating or layer by forming chemical bonds called crosslinks between the two components.
Preferably, the polymerizable monomer composition comprises acrylate or methacrylate ester selected from methyl methacrylate, methyl acrylate, butyl methacrylate, t-butyl methacrylate, 2-ethylhexyacrylate, 2-ethylhexyl methacrylate, ethyl acrylate, isobomyl methacrylate, isobornyl acrylate 2-hydroxy ethyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, acrylamide, n-methyl acrylamide and mixtures thereof. Further examples include acrylates or methacrylates containing monofunctionalized or polyfunctionalized monomers other than hydroxyl groups, including amido-, cyano-, chloro- and silane substituents.
Derivatives of acrylate or methacrylate esters can be advantageously chosen from a) esters of acrylic and/or methacrylic acid with mono-, di- and polyols, b) esters of acrylic acid and/or methacrylic acid with hydroxyl-functionalized polyethers, c) esters of acrylic acid and/or methacrylic acid with hydroxyl functionalized polyesters, d) esters of acrylic acid and/or methacrylic acid with hydroxyl functionalized alicyclic and aromatic compounds. These derivatives may contain further polymerizable functional groups.
According to a preferred embodiment of the invention, the acrylate or methacrylate esters are selected from ethyl acrylate, methyl acrylate, methyl methacrylate and butyl methacrylate, preferably methyl methacrylate. Preferably, the polymerizable monomer composition further comprises at least an acid and/or at least an acid ester.
Suitable acids may include ethylenically unsaturated mono or polycarboxylic acids such as acrylic acid, methacrylic acid, vinylacetic acid, and acryloxypropionic acid. Acids may also include maleic acid and crotonic acid. Also included are compounds with at least one strong acid active hydrogen group, or with at least one phosphonic acid active hydrogen group, such as hydroxyethyl diphosphonic acid, phosphonic acid and derivatives thereof or oligomeric or polymeric structures with phosphonic acid functionality or similar acid strength functionality.
Preferably, the acid is acrylic acid, methacrylic acid or a mixture thereof.
Suitable acid esters include phosphate acid esters, sulfonic acid esters and mixtures thereof.
Examples of suitable phosphate esters are 2-hydroxy ethyl methacrylate phosphate (HEMA phosphate) and bis[2-(acryloyloxy)ethyl] hydrogen phosphate.
According to a preferred embodiment according to the invention, the polymerizable monomers composition comprises 2-hydroxyethyl methacrylate phosphate (HEMA phosphate) and/or methacrylic acid and/or acrylic acid.
Advantageously, the polymerizable monomers composition comprises from 0.1 to 20 % by weight, preferably from 0.2 to 10% by weight, more preferably from 0.5 to 5% by weight of acid and/or an acid ester as described above.
Preferably, the polymerizable monomers composition comprises from 0.5 to 20% by weight, preferably from 1 to 15% by weight of acid as described above, preferably methacrylic acid and/or acrylic acid.
Preferably, the polymerizable monomers composition comprises from 0.1 to 10 % by weight, preferably from 0.1 to 5% by weight of phosphate ester as described above, preferably 2-hydroxyethyl methacrylate phosphate (HEMA phosphate) and/or bis[2-(acryloyloxy)ethyl] hydrogen phosphate.
The initiator to be used in accordance with the invention are known in the art. Examples of initiators to be in accordance with the invention include peroxides, hydroperoxides, peresters, peracids, and azo compounds. Representative examples of peroxide and hydroperoxide compounds include, but are not limited to, benzoyl peroxide, cumene hydroperoxide, tertiary butyl hydroperoxide, dicumyl peroxide, tertiary butyl peroxide acetate, tertiary butyl perbenzoate, and combinations thereof. Advantageously, the initiator is selected the group consisting of peroxides, hydroperoxides, and mixtures thereof.
Advantageously the polymerizable monomer composition part and the initiator part are in a weight ratio ranging from about 20: 1 to about 1 : 1.
Advantageously, the first curable composition further comprises other additives such as epoxy resins, tougheners (coreshell, rubbers) plasticizers, coloring agents, viscosity-controlling agents, etc., that can be included in the polymerizable monomers composition part and/or the initiator part.
According to a preferred embodiment of the invention, the first curable composition is selected from ARALDITE® 2051 and ARALDITE® 2050, commercially available from Huntsman.
Advantageously, in step i) of the method according to the invention, the first curable resin composition is applied at least partially on the surface of the article with a thickness between 0.05 mm and 1 mm, preferably between 0.1 mm and 0.2 mm.
Preferably, the layer of the first curable resin composition has regular thickness on all the surface of the article where it is applied. Preferably, the layer of the first curable resin composition is applied on the entire surface of the article that will be encapsulated.
Application of the first curable resin composition layer may be implemented by any method known to the skilled professional, like spraying, dipping, paint-brushing, spin coating, etc. . .
According to a favorite embodiment, the nickel-based surface (S) of the article is cleaned and preferably dried, prior to application of the first curable resin composition. Preferably, the surface of the nickel-based surface (S) is cleaned with isopropanol.
Advantageously, in step ii) of the method according to the invention, the first curable resin composition is at least partially cured at ambient temperature, in particular at a temperature ranging from 10 to 30 °C, preferably at 23 °C to form a solid layer of polymeric material (P).
Preferably, the first curable resin composition is at least partially cured for a period of time ranging from 15 minutes to 96 hours, preferably from 30 minutes to 72 hours, more preferably from 60 minutes to 48 hours to form a solid layer of polymeric material (P). According to an embodiment, in step ii) of the method according to the invention, the first curable resin composition is totally cured before the application of the precursor composition for the thermosetting polymeric material (A) in step iii).
Advantageously, the layer of polymeric material (P), obtained after curing, has a glass transition temperature Tg ranging from 60 °C to 170 °C, preferably from 90 °C to 150°C, more preferably from 110 °C to 140 °C.
Advantageously, the layer of polymeric material (P), obtained after curing, has an elongation at break, according to ISO 527 with a sample of thickness of 1mm, ranging from 5 and 20%, preferably from 5 to 15%.
Advantageously, the layer of polymeric material (P), obtained after curing, has a tensile strength according to ISO 527 ranging from 10 to 70 MPa, preferably from 15 to 60 MPa, more preferably from 20 to 50 MPa. The tensile strength is measured by the method ISO 527. In particular, the polymeric material (P) according to the invention has a tensile strength higher than that of the thermosetting polymer material (A).
The precursor composition of the thermosetting polymeric material (A) and the thermosetting polymeric material (A):
In step iii) of the method according to the invention, the coated, at least partially cured, article surface resulting from step ii) is encapsulated in a known manner with a precursor composition for the thermosetting polymeric material (A).
According to the invention, the precursor composition for the thermosetting polymeric material (A) comprises a polymer having a glass transition temperature Tg inferior or equal to -10 °C, preferably ranging from -50 °C to -10 °C, more preferably ranging from -50 °C to -40 °C, an elongation at break measured according to ISO 527 ranging from 5% to 250%, preferably from 5% to 100% and a tensile strength measured according to ISO 527 ranging from 0.5 to 20 MPa, preferably from 1 to 10 MPa.
Preferably, the precursor composition for the thermosetting polymeric material (A) comprises a polymer having a tensile modulus measured according to ISO 527 ranging from 10 MPa to 100 MPa.
Advantageously, the precursor composition for the thermosetting polymeric material (A) comprises a polymer having a thermal conductivity ranging from 0.1 to 2 W/m*K.
Advantageously, the thermosetting polymeric material (A) used in the method according to the invention is selected from polyurethane, epoxy resins and mixtures thereof. According to preferred embodiment of the invention, the thermosetting polymeric material (A) is polyurethane.
According to a first embodiment, the precursor composition for the thermosetting polymeric material (A) is a curable two-part resin system, comprising:
(a) a first part comprising at least a polyol compound, and
(b) a second part comprising at least an isocyanate compound.
Optionally, according to this embodiment, the precursor composition for the thermosetting polymeric material (A) comprises one or more fillers included as a component of the first part or the second part.
The precursor composition of the thermosetting polymer material (A) according to the first embodiment can further comprise, either in the first or in the second part, one or more additive selected from dyes, pigments, flameproofmg agents, softening agents, thermal aging stabilizers, and thixotropic or rheological modifier agents.
The polyol compound
Non-limiting examples of suitable polyols to be used in the invention may include, but are not limited to, polyether polyols, polyester polyols, polycaprolactone polyols, polycarbonate polyols, polyurethane polyols, poly vinyl alcohols, polymers containing hydroxy functional acrylates, polymers containing hydroxy functional methacrylates, polymers containing allyl alcohols and mixtures thereof.
According to a preferred embodiment, the polyol compound is chosen from poly ether polyols and polyester polyols.
Examples of the polyester polyols include polyester polyols obtained by reacting a polyhydric alcohol and a polybasic acid. The polyhydric alcohol can be for example selected from ethylene glycol, polyethylene glycol, tetramethylene glycol, polytetramethylene glycol, 1,6-hexanediol, 3-methyl-l,5-pentanediol, 1,9-nonanediol, and 2-methyl-l,8-octanediol. The polybasic acid can be for example selected from phthalic acid, dimer acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, and the like.
The polyether polyols may be selected from polyether polyols based on ethylene oxide, polyether polyols based on propylene oxide, corresponding ethylene oxide/propylene oxide copolymers which can be either random or block copolymers, and mixtures of these polyether polyols. The ratio of ethylene oxide to propylene oxide in the ethylene oxide/propylene oxide copolymers can vary within wide limits as it is known by the skilled person.
According to a preferred embodiment, the polyol compound is selected from poly ether polyols.
The isocyanate compound
The isocyanate components useful in the present invention are well known in the art and are organic compounds that contain two, or greater than two, isocyanate groups per molecule. Isocyanate components may be aromatic, cycloaliphatic or aliphatic and may be monomeric or oligomeric compounds.
Advantageously, the isocyanate component has an NCO functionality greater than or equal to 2, preferably ranging from 2 to 3.
The “isocyanate functionality” is the number of reactive NCO groups per molecule in an isocyanate molecule or in a polymeric isocyanate. For example, most polyisocyanates, in particular MDI-type polyisocyanate compounds, contain a blend of monomeric and polymeric MDI, and the isocyanate functionality is an average functionality across the different molecular and polymeric species.
Suitable isocyanate compounds for use in the precursor composition of the thermosetting polymeric material (A) according to the invention can be selected from dodecane- 1,12-diisocyanate, 2-ethyltetramethylene-,l,4-diisocyanate, 2- methylpentamethylene-l,5-diisocyanate, tetramethylene- 1,4-diisocyanate, hexamethylene-l,6-diisocyanate (HMDI), cyclohexane-l,3-diisocyanate, cyclohexane- 1,4-diisocyanate, isophorone diisocyanate (IPDI), hexahydrotoluene-2,4-diisocyanate, hexahydrotoluene-2,5-diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, toluene-2,4-diisocyanate (2,4-TDI), toluene-2,6-diisocyanate (2,6-TDI), diphenylmethane-2,2'-diisocyanate (2,2'-MDI), diphenylmethane-4,4'-diisocyanate (4,4'-MDI), diphenylmethane-2,4'-diisocyanate (2,4'-MDI) polyphenylpolymethylene polyisocyanates (crude MDI), and mixtures thereof.
As used herein, “MDI” refers to methylene diphenyl diisocyanate, also called diphenylmethane diisocyanate, and the isomers thereof. MDI exists as one of three isomers (4,4' MDI, 2,4' MDI, and 2,2' MDI), or as a mixture of 5 two or more of these isomers. Unless specifically stated otherwise, “MDI” may also refer to, and encompass, polymeric MDI. Polymeric MDI is a compound that has a chain of three or more benzene rings connected to each other by methylene bridges, with an isocyanate group attached to each benzene ring.
Advantageously, the mass ratio between the polyol compound and the isocyanate component in the precursor composition of the thermosetting polymeric material (A) ranges from 20: 1 to 1 : 1, preferably from 20: 1 to 5: 1.
The fillers
Advantageously, fillers that may be contained in the precursor composition for the thermosetting polymeric material (A) are selected from mineral fillers or metal powders.
Preferably, the fillers are inorganic fillers selected from the group consisting of quartz sand, quartz powder, silica, amorphous silica, fused silica, aluminium oxide, titanium oxide, zirconium oxide, Mg(OH)2, AI(OH)3, dolomite [CaMg (CCh)?], AIO(OH), silicon nitride, boron nitride, aluminium nitride, silicon carbide, boron carbide, chalk, calcium carbonate, baryte, gypsum, hydromagnesite, zeolites, talcum, mica, kaolin and wollastonite, aluminium-silicates, alumosilicates, milled glass, glass beads. Optionally fillers may be silanized. Preferably, the fillers are AI(OH)3.
Advantageously, the precursor composition for the thermosetting polymeric material (A) comprises at least 30 % or more, preferably 40% or more , more preferably 50% or more by weight of fillers, preferably inorganic fillers, with regards to the total weight of the composition.
According to a second embodiment, the precursor composition for the thermosetting polymeric material (A) is a curable two-part resin system, comprising:
(a) a first part comprising at least one epoxy resin, and
(b) a second part comprising at least one curing agent.
Optionally, according to this second embodiment, the precursor composition for the thermosetting polymeric material (A) comprises one or more fillers included as a component of the first part or the second part.
The precursor composition of the thermosetting polymer material (A) according to the second embodiment can further comprise, either in the first or in the second part, one or more additive selected from dyes, pigments, flameproofmg agents, softening agents, thermal aging stabilizers, and thixotropic or rheological modifier agents.
The epoxy compound Epoxy compounds for use in the method according to the invention are compounds containing at least one vicinal epoxy group. The epoxy compound may be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic and may be substituted. The epoxy compound may also be monomeric or polymeric.
Advantageously, the epoxy component is prepared by methods well known in the art, in particular by reacting epichlorohydrin with a compound containing at least one phenolic compound under basic conditions, such as in an alkaline reaction medium or in the presence of a suitable base.
Examples of suitable epoxy resins include, but are not limited to, butanediol diglycidyl ether, hexanediol diglycidyl ether, 1,4-cyclohexane dimethanol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, neopentyl glycol diglycidyl ether, or mixtures thereof.
According to a preferred embodiment, the epoxy compound is chosen from diglycidyl ether of bisphenol A and polyglycidyl ether of phenol-formaldehyde novolak. Examples of such epoxy components include, but are not limited to, EPON® 826 and EPON® DPL-862 available from Shell and DEN 439 and DEN 438, available from Dow Chemical Co.
Optionally, the epoxy component may also include an aqueous organic solvent or diluent present in an amount effective to decrease the viscosity of the system for improving the processability. Examples of diluents include ketones, alcohols and glycol ethers.
The curing agent
Suitable curing agents for use in the epoxy resin composition include, but are not limited to, amines, amides, anhydrides, phenols, and thiols.
Advantageously, the curing agent is liquid at ambient temperature and can be mixed with the epoxy compound without heating.
Preferably, the curing agent is an amine-based curing compound chosen from aliphatic amines such as such as ethylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, and aromatic amines such as diaminodiphenylmethane (DDMs).
The amount of curing agent used must be sufficient to obtain a complete curing. The amount of curing agent used in the second curable composition may range of ratios of amine hydrogen equivalent weight and the epoxy equivalent is 0.9 to 1.5, preferably in the range of 0.9 to 1.1, more preferably 1.
The precursor composition for the thermosetting polymeric material (A) can be prepared in the conventional manner, in particular by mixing and/or blending the two- part resin system described above according to the first or the second embodiment, optionally with one or more filler, then applying it on the surface of the article already coated with the layer of polymeric material (P). Application to the article can be carried out for example by dipping, trickle impregnation, vacuum pressure impregnation and/or casting.
The precursor composition for the thermosetting polymeric material (A) is advantageously liquid before curing and does not undergo cure over the time necessary for its application on the layer of polymeric material (P).
Advantageously, the precursor composition for the thermosetting polymeric material (A) has sufficiently low viscosity. Preferably, the precursor composition for the thermosetting polymeric material (A) has a viscosity before curing ranging from 0.5 to 10 poise, and preferably from 0.5 to 6 poise.
Advantageously, in step iii) of the method according to the invention, the precursor composition for the thermosetting polymeric material (A) is applied on the top of the layer of polymeric material (P) with a thickness between 0.05 mm and 1 mm, preferably between 0.1 mm and 0.2 mm.
Advantageously, the first layer of polymeric material (P) and the top layer of thermosetting polymeric material (A) are applied to the nickel-based article surface (S) in an amount to provide a total dry film thickness of from 0.1 to 2 mm preferably from 0.2 to 0.4 mm.
The thermosetting polymeric material (A) is prepared by curing the precursor composition for the thermosetting polymeric material (A).
Advantageously, the precursor composition for the thermosetting polymeric material (A) is cured at a temperature ranging from 10 to 35 °C, preferably from 15°C to 30°C, advantageously at a temperature of about 23 °C.
Preferably, the precursor composition for the thermosetting polymeric material (A) is cured for a period of time ranging from 15 minutes to 96 hours, preferably from 30 minutes to 72 hours, more preferably from 60 minutes to 48 hours to form a solid layer of thermosetting polymeric material (A). The fillers
Advantageously, fillers that may be contained in the precursor composition for the thermosetting polymeric material (A) according to the second embodiment are selected from mineral fillers or metal powders.
Advantageously, the fillers are inorganic fillers selected from the group consisting of quartz sand, quartz powder, silica, amorphous silica, fused silica, aluminium oxide, titanium oxide, zirconium oxide, Mg(OH)2, AI(OH)3, dolomite [CaMg (CCh)?], AIO(OH), silicon nitride, boron nitride, aluminium nitride, silicon carbide, boron carbide, chalk, calcium carbonate, baryte, gypsum, hydromagnesite, zeolites, talcum, mica, kaolin and wollastonite, aluminium-silicates, alumosilicates, milled glass, glass beads. Optionally fillers may be silanized. Preferably, the fillers are AI(OH)3.
Advantageously, the precursor composition for the thermosetting polymeric material (A) comprises at least 30 % or more, preferably 40% or more , more preferably 50% or more by weight of fillers, preferably inorganic fillers, with regards to the total weight of the composition.
The kit
According to a second aspect, the invention relates to a kit for encapsulating an article bearing a nickel-based surface (S), said kit comprising: i) a first curable resin composition selected from acrylate resins and methacrylate resins; ii) a precursor composition of a thermosetting polymer material (A), wherein the thermosetting polymer material comprises a polymer having a Tg inferior or equal to - 10°C, a tensile strength after curing in the range from 0.5MPa to 20 MPa, preferably from 1 MPa to 10 MPa, the tensile strength being measured by the method ISO 527 and having an elongation at break after curing in the range from 5 % to 250 %, preferably from 5% to 100%, the elongation at break being measured by the method ISO 527.
Preferably, the thermosetting polymer material comprises a polymer having a tensile modulus comprised between 10 MPa and 100 MPa.
The features and preferences described in detail above for the first curable resin composition as well as for the precursor composition of a thermosetting polymer material (A) also apply to the kit.
The device According to a third aspect, the invention relates to a device consisting in an encapsulated article, said device resulting from the implementation of the method described above.
In particular, the disclosed method results in an article bearing a nickel-based surface (S) which is coated with a polymeric material (P) layer covering part or all of its surface, and an encapsulation resin layer of the thermosetting polymeric material (A) on top of the polymeric material (P) layer. Advantageously, there is no direct contact between the surface of the article and the thermosetting polymeric material (A).
Advantageously, the device is an encapsulated electrical cell.
Use of the method according to the invention
According to another aspect, the invention also concerns a method for manufacturing electrical and electronic insulation equipment, wherein said method comprises at least one step consisting in implementing the method for the encapsulation of an article as described in detail above.
According to another aspect, the invention relates to the use of a combination of a polymeric material (P) and a thermosetting polymer material (A) as defined in details above as encapsulant material in one or more electrical component, in particular battery cells, comprising a nickel-based surface, for improving the resistance of the encapsulated component to heat cycles, for preventing thermal runaway and thermal propagation, and/or for reducing mechanical shock and vibration.
Examples:
In the following examples, and unless otherwise indicated, the contents and percentages are given in mass.
I- Raw Materials
- Substrate (S): Hilumin®: This is a steel galvanized with nickel commercially available from Tata Steel.
- The precursor composition of the thermosetting polymer material (A): polyol component: ARATHANE® CW 30664, isocyanate component: ARATHANE® HY 30665: This is an ambient temperature-curing, 2-component polyurethane system comprising 66% of mineral fillers commercially available from Huntsman. It is based on polyetherpolyol and aromatic isocyanates. This material is characterized by low-temperature flexibility (Tg = -44 °C), high thermal conductivity (1 W/m*K), flame-retardance (UL 94 V0 1 mm) and an elongation at break of 15 % and tensile strength of 2 MPa, the elongation at break and tensile strength being measured by the method ISO 527.
- The first curable composition (P): Araldite® 2051 : This is an ambient temperature-curing, 2-component adhesive system, commercially available from Huntsman. It is a methyl methacrylate-based polymer. It has a Tg of 127 °C, a tensile strength of 40 MPa and an elongation at break of about 10 %, the elongation at break and tensile strength being measured by the method ISO 527.
II- Preparation of lap shear test specimens
Table 1
Prior to the application of the adhesives, the substrate specimens were cleaned with isopropanol. After drying, for C2, C4, C6 a plasma treatment was carried out to the substrates: 3 min O2 plasma at 2 mbar 360 W.
For C3 and C4 the mixture of Araldite® 2051 was applied in an amount related to the bonding thicknesses given in table 1 and the 2nd substrate was placed in a setup to allow adjusting the required bonding thickness of 1.5 mm. The test specimens were cured for 24 h at 23 °C.
For El and E2 a thin layer of Araldite® 2051 was applied with a brush on the substrate. After that, it was let for curing for 15 minutes at 23 °C (the product should be tack free).
RECTIFIED SHEET (RULE 91) ISA/EP Then for Cl, C2, El, C5, C6 and E2 the mixture of ARATHANE® CW 30664 ARATHANE® HY 30665 (100:7) was applied in an amount allowing the bonding thicknesses given in table 1 and the parts were let curing for 24 hours at 23 °C.
The data in table 1 were all determined by testing standard specimens made by lap-jointing 100 x 25 x 1 mm strips of Hilumin ®. The joint area was 12.5 x 25 mm in each case. The thickness of the adhesive layer was adjusted to 1.5 mm or 0.3 mm (adjusted with glass beads).
Average lap shear strengths of metal -to-metal joints were then tested according to ISO 4587.
Ill- results
Table 2
AF= adhesive failure, CF= cohesive failure
The results summarized in Table 2 with regards to Cl and C5 show that the polyurethane system does not adhere well on Hilumin®, and that it fails with an adhesive break pattern. This result is independent from the thickness of the adhesion layer.
C2 and C6 show that the plasma treatment does not help at all to improve the adhesion to Hilumin®.
C3 is a comparative trial showing that even the methylmetacrylate-based adhesive Araldite ® 2051 does not adhere well to Hilumin®: Although it results in much higher lap shear values, it shows about 50 % adhesive failure.
C4 illustrates the combination of C3 with plasma: This pre-treatment improves the lap-shear strength, but the failure mode is still mainly adhesive break.
El and E2 are the inventive examples, demonstrating that application of a first layer in direct contact to Hilumin® and a subsequent layer of polyurethane leads to mainly cohesive break pattern in the polyurethane phase.

Claims

1. A method to encapsulate an article bearing a nickel -based surface (S) with a thermosetting polymer material (A), the method comprising at least the steps of: i) coating at least a portion of the article surface (S) with a first curable resin composition; ii) at least partly curing the first curable resin composition to obtain a nickel-based article coated with a first layer of polymeric material (P); iii) applying at least a precursor composition of the thermosetting polymer material (A) over the first layer of polymeric material (P); iv) curing the precursor composition to obtain a top layer of thermosetting polymer material (A), wherein the first curable resin composition is selected from acrylate resins and methacrylate resins, and wherein the thermosetting polymer material (A) comprises a polymer having a Tg inferior or equal to -10°C, a tensile strength after curing in the range from 0.5 MPa to 20 MPa, the tensile strength being measured by the method ISO 527 and having an elongation at break after curing in the range from 5 % to 250, the elongation at break being measured by the method ISO 527.
2. The method as claimed in claim 1 wherein the nickel-based surface (S) of the article is a solid nickel surface, a plated nickel surface or a galvanized nickel surface.
3. The method as claimed in claim 1 or in claim 2, wherein the first curable resin composition is a two-part composition comprising at least a) a polymerizable monomer composition comprising acrylate or methacrylate esters or derivatives thereof, and b) at least an initiator.
4. The method as claimed in claim 3 wherein the polymerizable monomers composition further comprises at least an acid, preferably chosen from acrylic acid, methacrylic acid, vinylacetic acid, and aery 1 oxy propionic acid, maleic acid and crotonic acid and/or at least an acid ester, preferably a phosphate ester.
5. The method as claimed in anyone of the preceding claims wherein the thermosetting polymer material (A) is a polyurethane and the precursor composition of the thermosetting polymer material (A) is a two-part composition comprising at least a) a polyol component and b) an isocyanate component.
6. The method as claimed in anyone of claims 1 to 4, wherein the thermosetting polymer material (A) is an epoxy resin and the precursor composition of the thermosetting polymer material (A) is a two-part composition comprising at least a) an epoxy compound and b) a curing agent.
7. The method as claimed in any one of the preceding claims, wherein the precursor composition of the thermosetting polymer material (A) further comprises fillers, preferably at least 30% by weight of fillers.
8. The method as claimed in any one of the preceding claims, wherein the precursor composition of the thermosetting polymer material (A) further comprises one or more additive selected from dyes, pigments, flameproofmg agents, softening agents, thermal aging stabilizers, and thixotropic or rheological modifier agents.
9. The method as claimed in anyone of the preceding claims wherein in steps i) and iii) the first curable resin composition and the precursor composition of the thermosetting polymeric material (A) respectively are applied to said nickel-based article surface (S) in an amount to provide a dry film thickness of from 0.1 to 2 mm.
10. The method as claimed in anyone of the preceding claims wherein in steps ii) and iv), the first curable resin composition and the second curable resin composition, respectively, are cured at ambient temperature.
11. A kit for encapsulating an article bearing a nickel-based surface (S), said kit comprising: i) a first curable resin composition selected from acrylate resins and methacrylate resins; ii) a precursor composition of a thermosetting polymer material (A), wherein the thermosetting polymer material comprises a polymer having a Tg inferior or equal to -10°C, a tensile strength after curing in the range from 0.5 MPa to 20 MPa, the tensile strength being measured by the method ISO 527 and having an elongation at break after curing in the range from 5% to 250 %, the elongation at break being measured by the method ISO 527.
12. A device consisting in an encapsulated article, said device resulting from the implementation of the method according to any one of claims 1 to claim 10.
13. A device as claimed in claim 12, wherein the article is selected from electrical cells bearing a nickel-based surface.
14. A method for manufacturing electrical and electronic insulation equipment, wherein said method comprises at least one step consisting in implementing the method for the encapsulation of an article as claimed in any one of claims 1 to 10.
15. Use of a combination of a polymeric material (P) and a thermosetting polymer material (A) for the encapsulation of an article, bearing a nickel-based surface (S), as defined in any one of claims 1 to 10, for improving the resistance of the encapsulated component to heat cycles, for preventing thermal runaway and thermal propagation, and/or for reducing mechanical shock and vibration.
EP24703993.6A 2023-02-13 2024-02-08 Method for encapsulating electrical cells bearing a nickel-based surface Pending EP4665573A1 (en)

Applications Claiming Priority (2)

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EP23156321 2023-02-13
PCT/EP2024/053134 WO2024170393A1 (en) 2023-02-13 2024-02-08 Method for encapsulating electrical cells bearing a nickel-based surface

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US5532024A (en) 1995-05-01 1996-07-02 International Business Machines Corporation Method for improving the adhesion of polymeric adhesives to nickel surfaces
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