Multicomponent self-leveling thermally-conductive potting composition and uses thereof

Abstract

Novel multicomponent self-leveling thermally conductive potting compositions and the methods of making and using thereof.

Description

[0001] DI83892

[0002] MULTICOMPONENT SELF-LEVELING THERMALLY-CONDUCTIVE POTTING COMPOSITION AND USES THEREOF

[0003] BACKGROUND

[0004] [1] Conventionally, potting compounds for casting have been used to insulate and protect coils or motors incorporated in electrical or electronic equipment, and electric conductors of solid insulated switching devices. Beside thermal, mechanical, and electrical requirements, the potting compounds need to exhibit certain physical properties. In many cases, the parts that need to be potted have complicated shapes; therefore, the potting compound needs to show excellent flow and self-leveling characteristics. Thus, a need exists for improved thermally conductive epoxy compositions suitable for use in casting, potting, and encapsulation of electric and electronic parts.

[0005] SUMMARY

[0006] [2] One aspect is for a multicomponent self-leveling thermally conductive potting composition comprising: (a) a first component comprising: (i) about 0.2 wt% to about 2 wt% of a first rheology modifier; (ii) about 0.1 wt% to about 1 wt% of a first wetting and dispersing additive; (iii) about 10 wt% to about 30 wt% of a first filler; and (iv) about 20 wt% to about 40 wt% of a first epoxy resin; and (b) a second component comprising: (i) about 0.2 wt% to about 3 wt% of a second rheology modifier; (ii) about 0.1 wt% to about 1 wt% of a second wetting and dispersing additive; (iii) about 20 wt% to about 50 wt% of a second filler; and (iv) about 15 wt% to about 30 wt% of a curing agent; wherein the second rheology modifier is the same or different from the first rheology modifier, the second wetting and dispersing additive is the same or different from the first wetting and dispersing additive, and the second filler is the same or different from the first filler. In some embodiments, the first component further comprises: (v) about 2 wt% to about 10 wt% of a second epoxy resin; (vi) 0 wt% to about 5 wt% of a reactive diluent; (vii) about 0.2 wt% to about 3 wt% of an epoxy functional silane; (viii) about 0.5

[0007] 1

[0008] ME1 49046561 v.2 DI83892 wt% to about 3 wt% of a precipitated calcium carbonate; and (ix) about 10 wt% to about 50 wt% wollastonite; and in some embodiments, the first epoxy resin is a bisphenol A epoxy resin, the second epoxy resin is an epoxy and vinyl-acrylic copolymer, the reactive diluent is 1 ,4-bis(2,3-epoxypropoxy)butane, the epoxy functional silane is oxirane, 2-[[3-trimethoxysilyl]propoxy[methyl]-, and the curing agent is methyl tetrahydrophthalic anhydride. In some embodiments, the second component further comprises: (v) about 0.1 wt% to about 5 wt% of a cure accelerator; and in some embodiments, the cure accelerator is Mannich Base. In some embodiments, the first rheology modifier and / or the second rheology modifier comprises a modified urea solution. In some embodiments, the first wetting and dispersing additive and / or the second wetting and dispersing additive comprises a phosphoric acid polyester. In some embodiments, the first filler and / or the second filler comprises a calcined alumina.

[0009] [3] Another aspect is for a method of producing a cured potting composition comprising curing the aforementioned multicomponent self-leveling thermally conductive potting composition to produce the cured potting composition.

[0010] [4] A further aspect is for a cured potting composition obtained by the aforementioned method.

[0011] [5] An additional aspect is for a coil comprising the aforementioned cured potting composition.

[0012] [6] Another aspect is for an electric part comprising the aforementioned cured potting composition.

[0013] [7] Other objects and advantages will become apparent to those skilled in the art upon reference to the detailed description that hereinafter follows.

[0014] DETAILED DESCRIPTION

[0015] [8] The present composition contains a significant percentage of fillers to meet thermal conductivity requirements, yet maintains a quite low viscosity. Moreover, the composition shows excellent stability at storage at u to, e.g., about 30 °C in a pail. DI83892

[0016] [9] Comparable highly filled systems tend to phase separate under storage condition, and especially when using a liquid anhydride as curing agent, as these anhydrides has very low initial viscosity, any addition of fillers needs to be stabilized to prevent sedimentation. The conventional way to overcome this issue is to stabilize the composition by adding thixotropic agents like fumed silica; however, this usually leads to increased viscosity and has a negative impact on self-leveling properties.

[0017]

[0010] Applicant found out that using certain rheology additives, in some embodiments modified urea-based rheology additives, in combination with certain wetting and dispersing additives, in some embodiments phosphoric acid polyester, in certain ratios that a formulation having excellent stability at wide temperature range (e.g., about 23 °C - about 60 °C) and excellent flow characteristics can be produced. Additionally, compositions disclosed herein show very low exotherm during cure. This is most probably due the high loading of thermally conductive fillers. Without limiting anything herein to theory, this low exotherm probably has a positive impact on potting resistance to thermal shocks.

[0018]

[0011] One aspect is for a multicomponent self-leveling thermally conductive potting composition comprising a first component comprising a first rheology modifier, a first wetting and dispersing additive, a first filler, and a first epoxy resin; and a second component comprising a second rheology modifier, a second wetting and dispersing additive, a second filler, and a curing agent.

[0019]

[0012] In some embodiments, the first rheology modifier is present in the first component in a range of about 0.2 to 2 wt.%, preferably 0.2 to 1 .5 wt.%, more preferably 0.2 to 1 wt.%, and most preferably 0.2 to 0.8 wt. %, all based on the total weight of the first component.

[0020]

[0013] In some embodiments, the first rheology modifier comprises a modified urea solution like Rheobyk 7410 ET, Rheobyk 7411 ES and Rheobyk 7420 ES available from BYK Chemie, Wesel, Germany). Other rheology modifiers may include polyamide- based thixotrope like Disparlon 6500 obtained from King Industries, Amsterdam, Netherland. Also, organic nano clay like Bentone SD2 from Elementis, Cologne, DI83892

[0021] Germany or castor oil-derivative like BYK 100 obtained from BYK Chemie, Wesel, Germany.

[0022]

[0014] In some embodiments, the first wetting and dispersing additive is present in the first component in a range of about 0.1 wt% to 1 wt%, preferably 0.1 to 0.8 wt.%, more preferably 0.1 to 0.6 wt.%, and most preferably 0.1 to 0.4 wt. %, all based on the total weight of the first component.

[0023]

[0015] In some embodiments, the first wetting and dispersing additive comprises a phosphoric acid polyester like BYK W 9010 and BYK 9011 available from BYK Chemie, Wesel, Germany). Other wetting agents like polyether-modified polydimethylsiloxane (Trade name BYK 333), solution of a salt of unsaturated polyamine amides ( BYK W- 980) can also be used.

[0024]

[0016] In some embodiments, the first filler is present in the first component in a range of about 10 wt% to about 50 wt%, preferably 10 wt. % to 40 wt.%, more preferably 10 to 30 wt.%, and most preferably 10 wt. % to 25 wt. %, all based on the total weight of the first component.

[0025]

[0017] In some embodiments, the first filler comprises a calcined alumina (e.g., Alumina Cl 5000 FG available from Almatis, Frankfurt, Germany; NO 104 RA from Nabaltec, Schwandorf, Germany; or MA88 from Saint-Gobain, Cedec, France). Other fillers that can be used in the present invention may include aluminum trihydrates (Apyral 20X available from Nabeltec).

[0026]

[0018] In some embodiments, the first epoxy resin is present in the first component in a range of about 10 wt% to about 50 wt%, preferably 10 wt. % to 40 wt.%, more preferably 10 wt.% to 35 wt. %, and most preferably 10 wt. % to 30 wt. % of the total weight of the first component. In another preferred embodiment, the first epoxy resin is present in the first component in a range of about 20 wt.% to 40 wt% of the total weight of the first component.

[0027]

[0019] In some embodiments, the first epoxy resin is a bisphenol A epoxy resin (e.g., D.E.R. ™ 331 Epoxy Resin available from Olin Corp., Clayton, MO, USA; Epon 828 from Westlake, Houston, Texas 77056, USA; or Epilox 19-04 fromm Leuna Harze, DI83892

[0028] Leuna, Germany). Alternatives may include mixture of bisphenol A and bisphenol F epoxy resins like epikote 232 from Westlake. Also, Novolac epoxy resins like DOW D.E.N 431 , D.E.N 425 & D.E.N 438 available from Westlake. Cycloaliphatic epoxy resin like 3,4-Epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate (Like celloxide 2021 P obtained from Daicel Chem Tech, Osaka, Japan) can also be used as base resin. Multifunctional epoxy resins like N, N, N', N'-tetraglycidyl-4,4'- methylenebisbenzenamine (Araldite MY 721 ) or Tri glycidyl para-aminophenol (araldite MY 0500 from Huntsman) may also be used.

[0029]

[0020] In some embodiments, first component further comprises one or more of a second epoxy resin, a reactive diluent, an epoxy functional silane, a precipitated calcium carbonate, and wollastonite.

[0030]

[0021] In some embodiments, the second epoxy resin is present in the first component in a range of about 1 wt. % to about 10 wt. %, preferably 2 wt.% to 10 wt.%, more preferably 2 wt. % to 8 wt. %, and most preferably 2 wt. % to 6 wt. % of the total weight of the first component.

[0031]

[0022] In some embodiments, the second epoxy resin is an epoxy and vinyl-acrylic copolymer (e.g., Kaneka MX 156, Kane Ace MX 257, or Kane Ace MX 154 available from Kaneka, Osaka, Japan). In some embodiments, the second epoxy resin is the same as the first epoxy resin.

[0032]

[0023] In some embodiments, the reactive diluent is present in the first component in a range of 0 wt% to about 5 wt. %, preferably 0.1 to 5 wt.%, more preferably 0.2 to 4 wt.%, and most preferably 0.2 to 3 wt. %, all based on the total weight of the first component.

[0033]

[0024] In some embodiments, the reactive diluent is 1 ,4-bis(2,3-epoxypropoxy)butane (e.g., Araldite DY-026 available from Huntsman, The Woodlands, TX, USA; or Heloxy modifier HD from Evonik, Essen, Germany). Alternatives may include glycidyl ether of cyclohexane dimethanol (Araldite DY-C from Huntsman); hydrogenated bisphenol A epoxy resin (Eponex 1510 available from Westlake Epoxy). DI83892

[0034]

[0025] In some embodiments, the epoxy functional silane is present in the first component in a range of about 0.2 wt% to about 4 wt%, preferably 0.1 to 4 wt.%, more preferably 0.2 to 4 wt.%, and most preferably 0.2 to 3 wt. %, all based on the total weight of the first component.

[0035]

[0026] In some embodiments, the epoxy functional silane is oxirane, 2-[[3- trimethoxysilyl]propoxy[methyl]- (e.g., Silquest A-187 available from Momentive Performance Materials, Niskayuna, NY, USA. Alternative silane may include 3- glycidyloxypropyltriethoxysilane (Dynasylan GLYEO); hexadecyltrimethoxysilane-based silane (Dynsylan 9116) available from Evonik, Essen, Germany).

[0036]

[0027] In some embodiments, the precipitated calcium carbonate is present in the first component in a range of about about 0.5 wt% to about 6 wt%, preferably 0.1 to 5 wt.%, more preferably 0.5 to 5 wt.%, and most preferably 0.5 to 4 wt. %, all based on the total weight of the first component.

[0037]

[0028] Calcium carbonate is available from, e.g., Minerals Technologies, New York, NY, USA; or Calprec PR available from Calcinor, Altzo (Gipuzkoa), Spain.

[0038]

[0029] In some embodiments, wollastonite is present in the first component in a range of about 10 wt% to about 65 wt%, preferably 10 to 60 wt.%, more preferably 10 to 55 wt.%, and most preferably 10 to 50 wt. %, all based on the total weight of the first component.

[0039]

[0030] Wollastonite is available from, e.g., Imerys, Paris, France (e.g., Nyad M200, Nyglos 4W, or Nyad 400).

[0040]

[0031] In some embodiments, the second rheology modifier is present in the second component in a range of about 0.2 wt% to about 6 wt%, preferably 0.2 to 5 wt. %, more preferably 0.3 to 5 wt.%, and most preferably 0.3 to 4.5 wt. % all based on the total weight of the second component. In another embodiment, the second rheology modifer is present in the second component in a range of about 0.2 wt% to about 3 wt% of the total weight of the second component.

[0041]

[0032] In some embodiments, the second rheology modifier comprises a modified urea solution (e.g., Rheobyk 7410 ET, Rheobyk 7420 ES and Rheobyk 7411 ES available DI83892 from BYK Chemie, Wesel, Germany). In some embodiments, the second rheology modifier is the same as the first rheology modifier.

[0042]

[0033] In some embodiments, the second wetting and dispersing additive is present in the second component in a range of about 0.1 wt% to about 1 wt%, preferably 0.1 to 0.8 wt.%, more preferably 0.1 to 0.6 wt.%, and most preferably 0.1 to 0.5 wt. %, all based on the total weight of the second component.

[0043]

[0034] In some embodiments, the second wetting and dispersing additive comprises a phosphoric acid polyester (e.g., BYK W 9010, BYK 9011 , available from BYK Chemie, Wesel, Germany). In some embodiments, the second wetting and dispersing additive is the same as the first wetting and dispersing additive.

[0044]

[0035] In some embodiments, the second filler is present in the second component in a range of about 20 wt% to about 70 wt%, preferably 20 to 60 wt.%, more preferably 20 to 50 wt.%, and most preferably 10 to 45 wt. % of the total weight of second component.

[0045]

[0036] In some embodiments, the second filler comprises a calcined alumina (e.g., Alumina Cl 5000 FG available from Almatis, Frankfurt, Germany; NO 104 RA from Nabaltec, Schwandorf, Germany; or MA88 from Saint-Gobain, Cedec, France). In some embodiments, the second filler is the same as the first filler.

[0046]

[0037] In some embodiments, the curing agent is present in the second component in a range of about 10 wt% to about 45 wt%, preferably 10 to 40 wt.%, more preferably 10 to 35 wt.%, and most preferably 15 to 30 wt. % % of the total weight of the second component.

[0047]

[0038] In some embodiments, the curing agent is methyl tetrahydrophthalic anhydride (e.g., available from Polynt, Scanzorosciate, Italy; Aradur 917 available form Huntsman, The Woodland TX, USA; or MTHPA-EG available from Trigon Chemie, Schluchtern, Germany).

[0048]

[0039] In some embodiments, the second component further comprises a cure accelerator. In some embodiments, the cure accelerator is present in the second component in range of about 0.1 wt% to about 5 wt%, preferably 0.1 to 4 wt.%, more DI83892 preferably 0.1 to 3 wt.%, and most preferably 0.1 to 2.5 wt. % % of the total weight of the second component.

[0049]

[0040] In some embodiments, the cure accelerator is a Mannich Base like Ancamine K54 available from Evonik, Essen, Germany, and EP 796 available from Huntsman, The Woodlands, TX, USA or Imidazole derivative like Araldite DY 070 available from Huntsman, The Woodlands, TX, USA or Curezol 2MA-OK available from Evonik, Essen, Germany or modified amine like ancamine 2442 available from Evonik, Essen, Germany.

[0050]

[0041] The potting composition may further contain any number of other useful optional additives. Useful additives include, for example, additional curatives, adhesion promoters, pigments, rubbers, plasticizers, extenders, fire-retarding agents, thixotropic agents, flow control agents, thickeners such as thermoplastic polyesters, gelling agents such as polyvinylbutyral, dyes, and antioxidants.

[0051]

[0042] Methods of producing a cured potting composition

[0052]

[0043] Another aspect is for a method of producing a cured potting composition comprising curing the aforementioned multicomponent self-leveling thermally conductive potting composition to produce the cured potting composition. The provided curable compositions are referred to as two-component (“two-part”), curable compositions because they require the mixing of two distinct parts prior to use. One is commonly referred to as a base part containing one or more curable resins, while the other is a curative part containing components reactive with the curable resin.

[0053]

[0044] The cured potting composition can be obtained by mixing and / or kneading a multicomponent composition composed of a main agent component (the first component) and a curing agent component (the second component). For example, the first component can be produced by mixing a part of the first filler and various components blended as needed with the first epoxy resin. Further, the second component can be produced by mixing the curing agent with the second filler, the curing accelerator, and various components blended as needed. Next, the cured potting composition can be obtained by mixing and / or kneading the first component and DI83892 the second component using a mixer such as a mixer and / or a kneader such as a kneader or a roll can.

[0054]

[0045] The steps used to prepare and cure the provided curable compositions can be carried out by any number of entities within a manufacturing supply chain. In some embodiments, a manufacturer may prepare and package a two-part curable composition for a customer, who then uses the two-part curable composition in an automotive or aerospace manufacturing, maintenance, or repair process. In some embodiments, the end user may participate at least in part in formulating and mixing the base part and / or curative part of the curable composition.

[0055]

[0046] A further aspect is for a cured potting composition obtained by the aforementioned method. The cured potting composition is suitable for insulation of, e.g., electronic devices. Specific examples of suitable articles using the cured potted composition include coils, capacitors, or resistors in which a part is sealed or protected with the cured product; and electric or electronic equipment including the coils, capacitors, or resistors. In addition, the cured potting composition may be suitably used in solid insulated switching devices containing an electric insulating part.

[0056] EXAMPLES

[0057]

[0047] The present disclosure is further described without however wanting to limit the disclosure thereto. All parts and percentages are by weight unless otherwise indicated.

[0058]

[0048] Table 1 (Materials Used) DI83892

[0059]

[0049] Preparation of Part A (Base Resin) and Part B (Hardener):

[0060]

[0050] Part A of the curable adhesive precursor composition was prepared by combining the ingredients as listed in Table 2 using a high-speed mixer (DAC 600.2 VAC-P Speed mixer, from Hauschild Engineering).

[0061]

[0051] In a first step the liquid components for Part A were mixed for 1 min at speed 3000 rpm. Then all other ingredients were added and mixed for 2 min at 3000 rpm. The complete mixture was then mixed under reduced pressure of about 50 mbar for 1 min at speed of 3000 rpm.

[0062]

[0052] The same procedure was used to produce different compositions of Part B according to below Table 3.

[0063]

[0053] Table 2 (Composition of Part A)

[0064]

[0054] Table 3 (Composition of different Part B) DI83892

[0065]

[0055] The obtained Part A and Part B were smooth uniform pastes.

[0066]

[0056] The mix ratio of Parts B and A when used for evaluation was 1 :1 by volume.

[0067]

[0057] Evaluation:

[0068]

[0058] Storage stability test of Part B:

[0069]

[0059] Stability of each component was determined in form of checking homogeneity, viscosity increase, phase separation or sedimentation. To determine storage stability about 200 g of each component was filled into glass container, closed, and sealed by parafilm. To prevent humidity ingress, the containers containing the hardener parts were flushed with nitrogen before sealing. The filled containers were then stored at 23 °C as well as at 40 °C. The aspect & homogeneity was determined visually every week. Table 4 below summarize the obtained results and observations.

[0070]

[0060] Table 4 (Stability evaluation of hardener parts) DI83892

[0071]

[0061] Table 4 shows that example formula F1 delivered very dry composition that cannot be processed by conventional dispensing unit. Therefore, no further tests have been performed on this formulation.

[0072]

[0062] Composition of F2, F3, and F3 contains in addition to the wetting agent different amount of rheology modifier ranging from 0% to 0.5% of total formulation. However, all these formulations were phase separated when stored for one week at 23 °C. Due to this this reason, no stability tests were done at 40 °C for these formulations.

[0073]

[0063] Only a composition of the present disclosure showed excellent stability even after 6 weeks at 23 °C and at 40 °C. Therefore, this composition was subjected to further tests related to the intentional use of the products as thermally conductive potting, casting compounds for electrical and electronic components. The overall performance results and used test methods on the novel composition are summarized in Table 5.

[0074]

[0064] Table 5 (Performance & Test Method) DI83892

[0075]

[0065] Test Methods & Equipment:

[0076]

[0066] The density was measured as described in ISO 1183 on Pyknometer from Anto Paar at 20 °C.

[0077]

[0067] Viscosity was measure according to DIN 54458 on CS-50 Rheometer from Bohlin instruments. Viscosity tests were performed at 23 °C and at 60 °C.

[0078]

[0068] The thermal conductivity was measured according to ASTM D5470-12 on cured 2 mm thick round specimens. Test specimens were prepared by mixing part A and B with mix ratio of 1 : 1 by volume.

[0079]

[0069] The mixed product was casted in rounded Teflon mold having dimension of 30 mm diameter and 2 mm thickness. The specimen was then cured for 2h at 80 °C and post cured for 1 h at 100 °C. The cured specimens were tested as described in above mentioned norm on the TIM Tester instrument from FFW Stuttgart.

[0080]

[0070] Volume resistivity was determined according to IEC 60093 using a Hochohm - Messgerate HM 308 test cell (from Friedland / Fetronic, Germany). DI838Q2

[0081]

[0071] 1 mm thick test plates were obtained by filling a mixed and degassed resin formulation consisting of Part A and Part B (Mix ratio 1 :1 ) into specimen mold and curing the resin for 2 h at 80 °C followed by 1 h at 100 °C.

[0082]

[0072] Dielectric constant and loss factor were determined according to IEC 60250 at 50 Hz and 500 V / mm using a “E.T.N Seeflec DXS 506” test equipment from Mesatec (Switzerland). 1 mm thick test plates were obtained by filling a mixed and degassed resin formulation consisting of Part A and Part B into the specimen mold. The composition was cured for 2 h at 80 °C followed by 1 h at 100 °C.

[0083]

[0073] An equipment type TA Instruments Trios from company Waters TA Instruments was used to determine coefficient of thermal expansion. Specimens of 2 mm X 5 mm X 15 mm were prepared by molding mixed and degassed product into Teflon mold and cured for 2h at 80 °C followed by 1 h at 100 °C.

[0084]

[0074] Dielectric strength was measured on 2 mm thick cured samples on b2 electronic equipment, type BA80 from Austria. The test was conducted according to ASTM O- O A.

Claims

DI83892CLAIMSWhat is claimed is:1 . A multicomponent self-leveling thermally conductive potting composition comprising:(a) a first component comprising:(i) about 0.2 wt% to about 2 wt% of a first rheology modifier;(ii) about 0.1 wt% to about 1 wt% of a first wetting and dispersing additive;(iii) about 10 wt% to about 30 wt% of a first filler; and(iv) about 20 wt% to about 40 wt% of a first epoxy resin; and(b) a second component comprising:(i) about 0.2 wt% to about 3 wt% of a second rheology modifier;(ii) about 0.1 wt% to about 1 wt% of a second wetting and dispersing additive;(iii) about 20 wt% to about 50 wt% of a second filler; and(iv) about 15 wt% to about 30 wt% of a curing agent; wherein the second rheology modifier is the same or different from the first rheology modifier, the second wetting and dispersing additive is the same or different from the first wetting and dispersing additive, and the second filler is the same or different from the first filler.

2. The multicomponent self-leveling thermally conductive potting composition of claim 1 , wherein the first component further comprises:(v) about 2 wt% to about 10 wt% of a second epoxy resin;(vi) 0 wt% to about 5 wt% of a reactive diluent;(vii) about 0.2 wt% to about 3 wt% of an epoxy functional silane;(viii) about 0.5 wt% to about 3 wt% of a precipitated calcium carbonate; and(ix) about 10 wt% to about 50 wt% wollastonite.15ME1 49046561 v.2DI838923. The multicomponent self-leveling thermally conductive potting composition of claim 2, wherein the first epoxy resin is a bisphenol A epoxy resin, the second epoxy resin is an epoxy and vinyl-acrylic copolymer, the reactive diluent is 1 ,4-bis(2,3- epoxypropoxy)butane, the epoxy functional silane is oxirane, 2-[[3- trimethoxysilyl]propoxy[methyl]-, and the curing agent is methyl tetrahydrophthalic anhydride.

4. The multicomponent self-leveling thermally conductive potting composition of any one of claims 1-3, wherein the second component further comprises:(v) about 0.1 wt% to about 5 wt% of a cure accelerator.

5. The multicomponent self-leveling thermally conductive potting composition of claim 4, wherein the cure accelerator is Mannich Base.

6. The multicomponent self-leveling thermally conductive potting composition of any one of claims 1-5, wherein the first rheology modifier and / or the second rheology modifier comprises a modified urea solution.

7. The multicomponent self-leveling thermally conductive potting composition of any one of claims 1-6, wherein the first wetting and dispersing additive and / or the second wetting and dispersing additive comprises a phosphoric acid polyester.

8. The multicomponent self-leveling thermally conductive potting composition of any one of claims 1-7, wherein the first filler and / or the second filler comprises a calcined alumina.

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