POLYISOCYANURATE MATERIALS AS ELECTRICAL POTTING COMPOUNDS

Abstract

The invention relates to potting compounds which cure to polyisocyanurate plastics, to the production of said potting compounds and to the use of the potting compounds for manufacturing electrical components.

Claims

1. A casting resin having a molar ratio of isocyanate groups to isocyanate-reactive groups of at least 3:1 and a solvent content of not more than 10% by weight, wherein the casting resin comprises (i) at least one monomeric or oligomeric polyisocyanate A having an isocyanate content of at least 15% by weight; (ii) at least one inorganic filler B containing silicon oxide units having an oil number of not more than 25 g/100 g determined according to DIN EN ISO 787-5 (October 1995) and a Mohs hardness of at least 4; and (iii) at least one trimerization catalyst C.

2. The casting resin as claimed in claim 1, wherein the polyisocyanate A comprises at least 70% by weight of polyisocyanates having exclusively aliphatically and/or cycloaliphatically bonded isocyanate groups based on a total weight of polyisocyanate A.

3. The casting resin as claimed in claim 1, wherein the inorganic filler has a Mohs hardness of at least 6.

4. The casting resin as claimed in claim 1, comprising at least 30% by weight of the inorganic filler B.

5. The casting resin as claimed in claim 4, comprising at least 65% by weight of the inorganic filler B.

6. The casting resin as claimed in claim 1, wherein the trimerization catalyst C catalyzes crosslinking of isocyanate groups to afford isocyanurate groups.

7. The casting resin as claimed in claim 1, wherein, at a content of up to 65% by weight of the inorganic filler B, said casting resin has a viscosity of not more than 150 Pas after storage for one hour at 60° C.

8. The casting resin as claimed in claim 7, wherein the polyisocyanate A has a viscosity of at least 500 mPas and not more than 20 000 mPas at 25° C.

9. (canceled)

10. (canceled)

11. A process for producing an electrical component comprising a) providing the casting resin of claim 1; b) potting a not yet embedded electrical component with the casting resin provided in process step a); c) catalytically trimerizing isocyanate groups of the casting resin.

12. An electrical component produced by the process as claimed in claim 11.

13. The electrical component as claimed in claim 12, wherein the polymer matrix formed by the cured casting resin is characterized in that a temperature at which 5% by weight of mass loss occurs is at least 370° C.

14. The electrical component as claimed in claim 12, wherein the electrical component is a transformer, insulator, capacitor, semiconductor, junction sleeve for protecting cable connections, or an underground cable branch tee.

Description

EXAMPLES

Raw Materials Used

[0126] Isocyanate 1: Isocyanurate-group-containing HDI polyisocyanate produced according to example 11 of [0127] EP-A 330 966 with the exception that 2-ethylhexanol instead of 2-ethyl-1,3-hexandiol was used as the catalyst solvent. The reaction was stopped at an NCO content of the crude mixture of 42% by weight by addition of dibutyl phosphate. Subsequently, unconverted HDI was removed by thin-film distillation at a temperature of 130° C. and a pressure of 0.2 mbar.

[0128] NCO content: 23.0% by weight

[0129] NCO functionality: 3.2

[0130] Monomeric HDI: 0.1% by weight

[0131] Viscosity (23° C.): 1,200 mPas

[0132] Density (20° C.): 1.17 g/cm.sup.3

Distribution of the Oligomeric Structure Types:

[0133] Isocyanurate: 89.7 mol %

[0134] Iminooxadiazinedione 2.5 mol %

[0135] Uretdione 2.7 mol %

[0136] Allophanate: 5.1 mol %

[0137] Isocyanate 2: is an isocyanate-terminated prepolymer produced by reaction of a difunctional polypropylene glycol polyether (OH number=515 mg KOH/g) with an excess of HDI at a temperature of 80° C. After establishment of a constant NCO content the reaction was stopped by addition of dibutyl phosphate. Subsequently, unconverted HDI was removed by thin-film distillation at a temperature of 130° C. and a pressure of 0.2 mbar. [0138] NCO content: 12.5% by weight [0139] NCO functionality: 2.1 [0140] Monomeric HDI: <0.5% by weight [0141] Viscosity (23° C.): 4,250 mPas [0142] Density (20° C.): 1.10 g/cm.sup.3

[0143] Isocyanate 3: is a low-viscosity mixture of diphenylmethane 4,4′-diisocyanate (MDI) with isomers and higher-functional homologues.

[0144] NCO content: 31.5% by weight

[0145] Equivalent weight: 133 g/val

[0146] Viscosity (23° C.): 90 mPas

[0147] Density (20° C.): 1.23 g/cm.sup.3

[0148] Polyol 1: is a linear polypropylene ether polyol produced by propoxylation of 1,2-propanediol.

[0149] Hydroxyl number: 520 mg KOH/g

[0150] Viscosity (25° C.): 55 mPas

[0151] Density (25° C.): 1.00 g/cm.sup.3

[0152] Polyol 2: Glycerol (1,2,3-propanetriol) was obtained from Calbiochem with a purity of 99.0%.

[0153] Filler 1: Silbond 126 EST is an epoxysilane-coated quartz filler and was obtained from Quarzwerke GmbH. According to the technical data sheet the filler absorbs 11 g of oil per 100 g of filler (DIN ISO 787-5); it has a Mohs hardness of 7.

[0154] Filler 2: Microdol 1-KN is a dolomite filler and was obtained from Omya. According to the technical data sheet the filler absorbs 15 g of oil per 100 g of filler (ISO 787/5). According to Wikipedia (retrieved 02-2019) the Mohs hardness of dolomite is 3.5-4.

[0155] Filler 3: Unispar PG W13 is a feldspar filler and was obtained from Sibelco. According to the technical data sheet the filler absorbs 22 g of oil per 100 g of filler (ISO 787/5); it has a Mohs hardness of 6.2.

[0156] Filler 4: Unispar PG W20 is a feldspar filler and was obtained from Sibelco. According to the technical data sheet the filler absorbs 19 g of oil per 100 g of filler (ISO 787/5); it has a Mohs hardness of 6.2.

[0157] Filler 5 Omycarb 2T-AV is a calcium carbonate filler and was obtained from Omya. According to the technical data sheet the filler absorbs 16 g of oil per 100 g of filler (ISO 787/5). According to Wikipedia (retrieved February 2019) the Mohs hardness of calcium carbonate (limestone) is 3.

[0158] Filler 6 Silbond 800 EST is an epoxysilane-coated quartz filler and was obtained from Quarzwerke GmbH. According to the technical data sheet the filler absorbs 26 g of oil per 100 g of filler (ISO 787/5).

[0159] Filler 7 Silbond 6000 MST is a methacryloylsilane-coated cristobalite filler and was obtained from Quarzwerke GmbH. According to the technical data sheet the filler absorbs 27 g of oil per 100 g of filler (ISO 787/5).

[0160] Filler 8 Sikron SF 800 is a quartz filler and was obtained from Quarzwerke GmbH. According to the technical data sheet the filler absorbs 28 g of oil per 100 g of filler (ISO 787/5).

[0161] Filler 9 Chinafill 200 is a kaolin filler and was obtained from Amberger Kaolinwerke Eduard Kick GmbH & Co. KG. According to the technical data sheet the filler absorbs 46 g of oil per 100 g of filler (ISO 787/5). According to Wikipedia (retrieved 02-2019) the Mohs hardness of kaolin is 2.5.

[0162] Filler 10 Silitin Z 86 is a mixture of corpuscular silica and lamellar kaolinite and was obtained from Hoffmann Mineral GmbH. According to the technical data sheet the filler absorbs 55 g of oil per 100 g of filler (ISO 787/5); the silica proportion has a Mohs hardness of 7 and the kaolinite proportion has a Mohs hardness of 2.5.

[0163] Filler 11 Silbond 006 MST is a methacryloylsilane-coated cristobalite filler and was obtained from Quarzwerke GmbH. According to the technical data sheet the filler absorbs 21 g of oil per 100 g of filler (ISO 787/5); it has a Mohs hardness of 6.5.

[0164] Prior to processing the fillers were dried at 80° C. for 12 hours with regular agitation.

[0165] Catalyst 1: Desmorapid AP 100 was obtained from Covestro AG.

[0166] Catalyst 2: Trioctylphosphine was obtained in a purity of 97% from abcr GmbH.

[0167] Catalyst 3: is a mixture of potassium acetate, 18-crown-6 and diethylene glycol in a ratio of 1.0:2.7:17.6 (obtained from Sigma-Aldrich in PA qualities and used as supplied).

[0168] Catalyst 4: Jeffcat Z-110 was obtained from Huntsman.

Determination of Electrical Properties:

[0169] The electrical properties of the materials were determined using a Keithley Model 8009 instrument which operates on the basis of ASTM D 257 (May 2007). The measurements were performed at 25° C.

Determination of Glass Transition Temperature:

[0170] Glass transition temperature was determined by DSC (differential scanning calorimetry) with a Mettler DSC 12E (Mettler Toledo GmbH, Gießen, Germany) instrument according to DIN EN 61006 (November 2004). Calibration was effected via the melt onset temperature of indium and lead. 10 mg of substance were weighed out in standard capsules. The measurement was effected by two heating runs from −50° C. to +200° C. at a heating rate of 20 K/min with subsequent cooling at a cooling rate of 20 K/min. Cooling was effected by means of liquid nitrogen. The purge gas used was nitrogen. The values reported are in each case based on evaluation of the 2nd heating curve.

Determination of Mass Loss:

[0171] Mass loss was determined by TGA (thermogravimetric analysis) according to DIN EN ISO 11358-1:2014-10. To this end about 5.5 mg of the product were heated from 25° C. to 600° C. in an open platinum crucible under a constant nitrogen stream in a TGA-8000 thermogravimetric analyzer (Perkin-Elmer). The heating rate was 20 K/minute. The temperature at which the mass loss accumulated over the measurement time had reached 5% by weight was evaluated.

Determination of Pot Life:

[0172] To determine pot life the two components were mixed and analyzed in a rheometer at 60° C. for one hour. The reported viscosity value was the value determined after precisely one hour. An AntonPaar MCR301 rheometer was employed. The plate/plate system PP25 with peltier heating C-PTD200 was employed.

[0173] Measurement profile: frequency f=1 Hz; amplitude gamma=5% [0174] T=60° C., 60 min.

Determination of Shore Hardness:

[0175] Shore hardnesses were measured according to DIN 53505 (August 2000) using a Zwick 3100 Shore hardness tester (from Zwick) at 23° C. and 50% atmospheric humidity.

Comparative Tests:

[0176]

TABLE-US-00001 EHL EHL EHL EHL EHL EHL EHL EHL EHL EHL 11- 11- 11- 11- 11- 11- 11- 11- 11- 11- 79/24 73/25-1 73/35 73-36 73-25 73-42 73-44 73-30 73-45 73-41 ON V 1 V 2 V 3 V 4 V 5 V 6 V 7 V 8 V 9 V 10 Isocyanate 1 —   35 g   35 g   35 g   35 g   35 g   35 g   35 g   35 g   35 g Isocyanate 3 25.8 g — — — — — — — — — Polyol 1 4.58 g — — — — — — — — — Polyol 2 4.58 g — — — — — — — — — 11 Filler 1   65 g — — — — — — — — — 15 Filler 2 —   65 g   65 g   65 g — — — — — — 16 Filler 5 — — — —   65 g — — — — — 26 Filler 6 — — — — —   65 g — — — — 27 Filler 7 — — — — — —   65 g — — — 28 Filler 8 — — — — — — —   65 g — — 46 Filler 9 — — — — — — — —   65 g — 55  Filler 10 — — — — — — — — —   65 g Catalyst 1 — 1.49 g — — 1.49 g — — 1.49 g — — Catalyst 2 — — 0.18 g — — — — — — — Catalyst 3 — — 1.05 g — — — — — — — Catalyst 4 — — — 0.09 g — 0.09 g 0.09 g — 0.09 g 0.09 g Viscosity ** 312 173 139 213 ** 209 ** ** ** after 1 h Pas Pas Pas Pas Pas at 60° C. ** In these experiments the fillers were not able to be processed into a liquid mixture with the other input materials. The viscosity therefore could not be determined.

Inventive Experiments:

[0177]

TABLE-US-00002 EHL EHL EHL EHL EHL EHL EHL EHL EHL EHL EHL 11- 11- 11- 11- 11- 11- 11- 11- 11- 11- 11- 73/7- 73/13 73/15- 73/17- 73/27- 73-28- 73- 73- 73- 73- 73- 3 1 1 1 2 3 37 38 39 40 43 ON E 1 E 2 E 3 E 4 E 5 E 6 E 7 E 8 E 9 E 10 E 10 Isocyanate 1   35 g   35 g   35 g   28 g   35 g   35 g   35 g   35 g   35 g   35 g   35 g Isocyanate 2 — — —   7 g — — — — — — — 11 Filler 1   65 g   65 g   65 g   65 g   65 g   65 g — — — — — 22 Filler 3 — — — — — —   65 g   65 g — — — 19 Filler 4 — — — — — — — —   65 g   65 g — 21  Filler 11 — — — — — — — — — —   65 g Catalyst 1 1.49 g — 1.49 g 1.49 g — — 1.49 g — 1.49 g — — Catalyst 2 — 0.18 g 0.18 g — — — — — — — — Catalyst 3 — 1.05 g — — — — — — — — — Catalyst 4 — — — — 0.09 g 0.18 g — 0.09 g — 0.09 g 0.09 g Viscosity 72 79 86 92 46 48 94 43 40 25 102 after 1 h Pas Pas Pas Pas Pas Pas Pas Pas Pas Pas Pas at 60° C.

[0178] All test specimens were cured within 30 minutes in an oven at 180° C.

Properties of the Cured Test Specimens:

[0179]

TABLE-US-00003 EHL EHL EHL EHL EHL EHL EHL EHL 11- 11- 11- 11- 11- 11- 11- 11- 73/24 73/7-3 73/13-1 73/15-1 71/17-1 73/25-1 73/27-2 73/28-3 V E1 E2 E3 E4 E5 E6 E7 Glass — 102 85 100 76 79 77 108 transition Shore — 84 82 84 72 74 83 83 hardness D Relative — 3.48 3.13 3.88 3.56 4.88 3.43 3.29 permittivity Loss factor — 1.87 × 1.62 × 2.21 × 2.76 × 9.77 × 1.07 × 9.72 × at 100 Hz 10.sup.−2 10.sup.−2 10.sup.−2 10.sup.−2 10.sup.−2 10.sup.−2 10.sup.−3 Temperature — 464 436 470 394 427 445 479 at 5% by weight mass loss [° C.]