Search

EP-4223809-B1 - USE OF A (METH)ACRYLIC COMPOSITION FOR MANUFACTURING A DIELECTRIC MATERIAL AND ASSOCIATED MANUFACTURING METHOD

EP4223809B1EP 4223809 B1EP4223809 B1EP 4223809B1EP-4223809-B1

Inventors

  • HASSANZADEH, MEHRDAD
  • HELAL, Karim
  • ENSENLAZ, Leo

Dates

Publication Date
20260506
Application Date
20220208

Claims (15)

  1. Use of (meth)acrylic composition comprising: (a) 100 parts by weight of a liquid (meth)acrylic syrup comprising: (a 1 ) from 10 % by weight to 50 % by weight of one or more (meth)acrylic polymers P1, and (a 2 ) from 50 % by weight to 90 % by weight of one or more (meth)acrylic monomers M1, each monomer M1 comprising only one (meth)acrylic function per monomer and being different from methacrylic acid, (b) from 0,01 part by weight to 10 parts by weight of one (meth)acrylic monomer M2 comprising at least two (meth)acrylic functions per monomer, (c) from 0,01 part by weight to 10 parts by weight of methacrylic acid, (d) from 0,01 part by weight to 5 parts by weight of a polymerization initiator chosen from organic peroxides, and (e) from 100 parts by weight to 400 parts by weight of a mineral filler C, said mineral filler C comprising at least one filler C1 chosen from the group consisting of metal oxides, carbonates, silicates and glass, preferably chosen from metal oxides, for manufacturing a dielectric material.
  2. The use as claimed in claim 1, wherein each (meth)acrylic polymer P1 is chosen from a methyl methacrylate homopolymer and a methyl methacrylate copolymer, methyl methacrylate representing preferentially at least 50 % by weight of each (meth)acrylic polymer P1.
  3. The use as claimed in claim 2, wherein each (meth)acrylic polymer P1 is a copolymer of methyl methacrylate and of an alkyl acrylate in which the alkyl group contains from 1 to 12 carbon atoms, advantageously from 1 to 6 carbon atoms, each (meth)acrylic polymer P1 being preferably chosen from a copolymer of methyl methacrylate and of methyl acrylate and a copolymer of methyl methacrylate and of ethyl acrylate.
  4. The use as claimed in any one of claims 1 to 3, wherein each (meth)acrylic monomer M1 is chosen from acrylic acid, alkyl (meth)acrylic monomers and alkylhydroxy (meth)acrylic monomers, the alkyl or hydroxyalkyl group of these (meth)acrylic monomers being linear, branched or cyclic and containing from 1 to 22 carbon atoms, preferentially from 1 to 6 carbon atoms, the (meth)acrylic monomer M1 being preferably methyl methacrylate.
  5. The use as claimed in claim 4, wherein methyl methacrylate represents at least 50% by weight of the (meth)acrylic monomers M1.
  6. The use as claimed in any one of claims 1 to 5, wherein the (meth)acrylic monomer M2 is chosen from the group consisting of ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, 1,4-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,3-butylene glycol dimethacrylate, 1,3-butylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, ethoxylated bisphenol A dimethacrylate and ethoxylated bisphenol A diacrylate, the (meth)acrylic monomer M2 being preferably ethoxylated bisphenol A dimethacrylate or ethoxylated bisphenol A diacrylate.
  7. The use as claimed in any one of claims 1 to 6, wherein the polymerization initiator is chosen from the group consisting of tert -amyl peroxy-1-methoxycyclohexane, 1-methoxy-1- tert -butylperoxycyclohexane, 1-methoxy-1- tert- amylperoxy-3,3,5-trimethylcyclohexane, 1-methoxy-1- tert -butylperoxy-3,3,5-trimethylcyclohexane, 1-ethoxy-1- tert -amylperoxycyclohexane, 1-ethoxy-1- tert -butylperoxycyclohexane and 1-ethoxy-1- tert -butyl-3,3,5-peroxycyclohexane.
  8. The use as claimed in any one of claims 1 to 7, wherein the mineral filler C further comprises aluminum trihydrate C2 and/or reinforcements C3, which C3 reinforcements may be chosen from glass fabrics, glass fibers and glass beads.
  9. The use as claimed in any one of claims 1 to 8, wherein the (meth)acrylic composition further comprises a coupling agent, which coupling agent is formed either by a compound chosen from aminosilanes, vinylsilanes and methacrylsilanes or by the filler C1 that is functionalized, namely by an aminosilane, vinylsilane or methacrylsilane group and, preferentially, by a methacrylsilane group.
  10. The use as claimed in any one of claims 1 to 9, wherein the (meth)acrylic composition further comprises a release agent in an amount of less than 1 part by weight, said release agent being namely chosen from natural oils.
  11. Method for manufacturing a dielectric material, said method comprising the steps of: (1) preparing a (meth)acrylic composition by mixing the following components: (a) 100 parts by weight of a liquid (meth)acrylic syrup comprising: (a 1 ) from 10 % by weight to 50 % by weight of one or more (meth)acrylic polymers P1, and (a 2 ) from 50 % by weight to 90 % by weight of one or more (meth)acrylic monomers M1, each monomer M1 comprising only one (meth)acrylic function per monomer and being different from methacrylic acid, (b) from 0,01 part by weight to 10 parts by weight of one (meth)acrylic monomer M2 comprising at least two (meth)acrylic functions per monomer, (c) from 0,01 part by weight to 10 parts by weight of methacrylic acid, (d) from 0,01 part by weight to 5 parts by weight of a polymerization initiator chosen from organic peroxides, and (e) from 100 parts by weight to 400 parts by weight of a mineral filler C, said mineral filler C comprising at least one filler C1 chosen from the group consisting of metal oxides, carbonates, silicates and glass, preferably chosen from metal oxides, and optionally (f) less than 1 part by weight of a release agent, wherein the liquid (meth)acrylic syrup (a) is prepared first and the polymerization initiator (d) is introduced in the liquid (meth)acrylic syrup (a) after the (meth)acrylic monomer M2 (b) and methacrylic acid (c) and before the mineral filler C (e) and, if present, the release agent (f), and (2) hot-molding the (meth)acrylic composition obtained at the end of step (1), the hot-molding step (2) being advantageously performed by injection, by automatic pressure gelation process (APG), by casting under vacuum or at atmospheric pressure, whereby the dielectric material is obtained.
  12. The method as claimed in claim 11, wherein the preparing step (1) is performed under vacuum, advantageously at a pressure of up to 8000 Pa, and/or at a temperature T (1) ranging from 0 °C to 30 °C, advantageously from 18 °C to 25 °C.
  13. The method as claimed in claim 11 or 12, wherein the hot-molding step (2) is performed at a temperature T (2) ranging from 85 °C to 110 °C and, preferably, under inert gas, such as dinitrogen.
  14. The method as claimed in any one of claims 11 to 13, wherein it further comprises, between steps (1) and (2), an additional step (1') of mixing the (meth)acrylic composition obtained at the end of step (1) with a coupling agent in an amount of less than 1 part by weight relative to 100 parts by weight of the liquid (meth)acrylic syrup.
  15. The method as claimed in any one of claims 11 to 14, wherein it further comprises, after step (2), a step (3) of post-curing the dielectric material obtained at the end of step (2), the post-curing step (3) being preferably performed at a temperature T (3) that is at least 10 °C higher than the temperature T (2) of the hot-molding step (2), this temperature T (3) being advantageously from 120 °C to 150 °C.

Description

TECHNICAL FIELD The present invention relates to the use of a particular (meth)acrylic composition for manufacturing a dielectric material and to an associated method for manufacturing a dielectric material, the dielectric material having particularly good dielectric and mechanical properties, particularly long-term behavior under specific mission profile. It is specified that, in the remainder of this patent application, the expression "dielectric material" is taken to mean a material in which electric current does not flow freely. The atoms of the material have tightly bound electrons which cannot readily move. Such a dielectric material can be used in the electrical industry, whether low, medium or high voltage, or in the electronics industry. PRIOR ART In the electrical and electronic industry, electrically insulating materials, more commonly known as dielectric materials, are typically obtained from curable resins which, after polymerization, form a stable, infusible, three-dimensional network. Among the curable resins, the so-called "epoxy resins" are widely used, as they allow obtaining cured materials with good mechanical and dielectric properties. Epoxy resins are obtained from compositions which comprise at least one precursor of this epoxy resin and a cross-linking agent, such as acid anhydrides. However, some acid anhydrides being classified by the European Chemicals Agency as substances of very high concern (SVHC), they could be subjected to an authorization procedure with before being used. There is therefore a clear need to find an alternative to curable resin compositions that use acid anhydrides as cross-linking agents. Such an alternative is namely taught in document EP 3 587 461 B2, referenced [1] hereinafter in the present description, which discloses the use of a particular (meth)acrylic composition for manufacturing of a dielectric material. This particular (meth)acrylic composition comprises: (a) 100 parts by weight of a liquid (meth)acrylic syrup comprising: (a1) from 10 % by weight to 50 % by weight of one or more (meth)acrylic polymers P1, and(a2) from 50 % by weight to 90 % by weight of one or more (meth)acrylic monomers M1, each monomer M1 comprising only one (meth)acrylic function per monomer,(b) from 100 parts by weight to 200 parts by weight of a mineral filler C, said mineral filler C comprising at least one filler C1 chosen from the group consisting of metal oxides, carbonates, silicates and glass, preferably chosen from metal oxides,(c) from 0,01 part by weight to 5 parts by weight of one (meth)acrylic monomer M2 comprising at least two (meth)acrylic functions per monomer,(d) from 0,01 part by weight to 10 parts by weight of a (meth)acrylic monomer M3, the monomer M3 being: . either a (meth)acrylic monomer M31 comprising only one (meth)acrylic function per monomer, the monomer M31 being different from the monomer(s) M1,. or a (meth)acrylic monomer M32 comprising at least two (meth)acrylic functions per monomer, the monomer M32 being different from the monomer M2,e) from 0,01 part by weight to 5 parts by weight of a polymerization initiator chosen from organic peroxides, and(f) optionally, a coupling agent. However, the dielectric material manufactured by using the (meth)acrylic composition of document [1] presents some drawbacks, namely in terms of thermal resistance, the minimum thermal class A according to standard IEC 60085 being not always reached. In addition, some difficulties are encountered when manufacturing the dielectric material from this (meth)acrylic composition, one of which being a limited pot life at room temperature (about 20 °C to 25 °C), i.e. a limited working time after mixing of the different components forming the (meth)acrylic composition for its subsequent transformation, namely by molding. The aim of the present invention is therefore to propose a new (meth)acrylic composition which can be used for manufacturing a dielectric material, which is provided with high mechanical and dielectric properties over time and at temperatures at which the dielectric material is used, particularly at permanent operating temperatures up to 105 °C during 40 years. SUMMARY OF THE INVENTION The aim mentioned above is achieved, firstly, by using a particular (meth)acrylic composition for manufacturing a dielectric material. According to the present invention, this particular (meth)acrylic composition comprises: (a) 100 parts by weight of a liquid (meth)acrylic syrup comprising: (a1) from 10 % by weight to 50 % by weight of one or more (meth)acrylic polymers P1, and(a2) from 50 % by weight to 90 % by weight of one or more (meth)acrylic monomers M1, each monomer M1 comprising only one (meth)acrylic function per monomer and being different from methacrylic acid,(b) from 0,01 part by weight to 10 parts by weight of one (meth)acrylic monomer M2 comprising at least two (meth)acrylic functions per monomer,(c) from 0,01 part by weight to 10 parts by weight of methacrylic acid,