Protective silicone coating composition containing mica
A copolymer-mica composition with specific weight ratios and molecular structures addresses the cracking and thermal shock issues of silicone coatings, ensuring stability and adhesion at high temperatures.
Patent Information
- Application Number
- JP2025519514
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-01-31
- Filing Date
- 2023-09-29
- Publication Date
- 2025-10-09
AI Technical Summary
Existing silicone-based coatings fail to withstand temperatures above 250°C for more than three weeks without cracking and are susceptible to thermal shock, leading to damage of underlying electronic elements.
A composition comprising a copolymer and mica, with a weight ratio of 10:90 to 90:10 and a molecular structure of R-(RMeSiO2/2)n, provides coatings that resist cracking and maintain dielectric properties at elevated temperatures by using a specific combination of methyl or phenyl groups and mica fillers.
The composition achieves crack resistance and thermal stability for hundreds to thousands of hours at temperatures exceeding 300°C, maintaining adhesion and dielectric properties.
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Abstract
Description
[Technical Field]
[0001] The present invention relates to silicone coating compositions, more specifically compositions that are resistant to cracking and dielectric degradation at high temperatures, and methods for preparing the compositions. High-temperature protective coatings and insulating materials are used to protect various equipment and devices from extremely high temperatures. For example, electric vehicle heater elements, exhaust systems for automobile engines, power generation plants, and stove top coatings all benefit from such protective coatings. In many applications, coating layers must withstand temperatures exceeding 300°C for several months without cracking or losing their dielectric and insulating properties, and must pass severe thermal shock tests over a wide temperature range.
[0002] The high temperature resistance of silicones ostensibly makes them promising candidates as high temperature protective coatings and sealants, but silicone rubbers are nevertheless not resistant to cracking above 250°C for more than three weeks. 2- Combinations of ethylenediamine with inorganic fillers such as ethylenediamine, TiO2, and Al2O3 provide compositions with long-term high-temperature resistance; however, coatings prepared from such compositions require aging at temperatures exceeding 500°C to form ceramic-like coatings. At such extreme temperatures, the coatings are susceptible to cracking and thermal shock failure, and further, electronic elements beneath the surface of the coating are susceptible to damage. Therefore, developing a composition that provides a coating resistant to cracking, delamination, and thermal shock failure while maintaining acceptable dielectric properties for extended periods at temperatures exceeding 300°C would be an advancement in the field of high-temperature protective coatings. Summary of the Invention
[0003] In one aspect, the present invention provides a method for producing a medicament comprising: R -(RMeSiO 2 / 2 ) nA composition comprising a copolymer and mica, wherein each R is independently methyl or phenyl; and T R -Poly(RMeSiO 2 / 2 ) n The need in the art is addressed by providing a composition in which the weight to weight ratio of copolymer to mica is in the range of 10:90 to 90:10, and n is in the range of 20 to 800. The compositions of the present invention are useful as coatings for metal, ceramic, or plastic substrates, and the coatings exhibit good adhesion and crack resistance when exposed to elevated temperatures for hundreds of hours. DETAILED DESCRIPTION OF THE INVENTION
[0004] The present invention is R -(RMeSiO 2 / 2 ) n A composition comprising a copolymer and mica, wherein R is methyl or phenyl, and T R -(RMeSiO 2 / 2 ) n The composition has a weight to weight ratio of copolymer to mica in the range of 10:90 to 90:10, and n in the range of 20 to 800.
[0005] As used herein, "T R -(RMeSiO 2 / 2 ) n The term "copolymer" refers to the R Resin units and (RmeSiO 2 / 2 ) n "T" refers to a copolymer comprising a copolymer of the formula: R Resin" is R-SiO 3 / 2 , R-SiO 2 / 2 (OZ), and optionally, R—SiO 1 / 2 It refers to a kinetically stable three-dimensional polymer having repeating units of the formula (OZ)2, where R-SiO 3 / 2 The units have the following structure:
[0006] [ka] is represented by The dotted line represents the point of attachment to another silicon atom, R-SiO 2 / 2 (OZ) units have the following structure:
[0007] [ka] is represented by Z is H, C1-C4-alkyl, or C(O)CH3, and R—SiO 1 / 2 (OZ)2 units have the following structure:
[0008] [ka]
[0009] is represented by T R Each Z in the resin is preferably H. Ph The resin is DOWSIL™ RSN-0217 Flake Resin (a registered trademark of The Dow Chemical Company or its affiliates), a commercially available T Me The resins are DOWSIL™ RSN-2403 and DOWSIL™ RSN-2405 Flake Resin.
[0010] T R -(RMeSiO 2 / 2 ) n The copolymer contains poly(dimethylsiloxane) (PDMS) or poly(phenylmethylsiloxane) (PPhMS) units,
[0011] [ka]
[0012] Preferably, n is 20, or 40, or 70, or 100 to 800, or 500, or 300, or 200. R Base pair (RMeSiO 2 / 2 ) n The ratio of the groups is preferably in the range of 30:70 to 70:30.
[0013] T R -(RMeSiO 2 / 2 ) n The copolymer is first prepared by reacting T R Resin, silanol terminated (RMeSiO 2 / 2 ) n and a crosslinking agent, preferably an acetoxylating agent or alkoxylating agent. Examples of suitable acetoxylating agents include alkyltriacetoxysilanes such as methyltriacetoxysilane and ethyltriacetoxysilane, and suitable alkoxylating agents include phenyltrimethoxysilane, phenyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, and ethyltriethoxysilane. One commercial example of an acetoxylating agent is XIAMETER™ OSF-1579 Silane (a trademark of The Dow Chemical Company and its affiliates), which is a 50:50 w / w blend of methyltriacetoxysilane and ethyltriacetoxysilane. Suitable solvents include aprotic solvents such as ethyl acetate, propyl acetate, propyl propionate, and butyl acetate.
[0014] Then, acetoxy or alkoxy terminated (RMeSiO 2 / 2 ) n Preferably, at high temperature, T R Resin and additional solvent are contacted to form T R Resin partially or completely T R -(RMeSiO 2 / 2 ) n Copolymers were converted to acetoxy or alkoxy terminated (RMeSiO 2 / 2 ) nThe volatiles are removed from the mixture to remove the copolymer and free T. R can be used without further purification.
[0015] Commercially available T Ph An example of a PDMS copolymer is DOWSIL™ 1-2577 Conformal Coating (a registered trademark of The Dow Chemical Company or its affiliates) with a PDMS degree of polymerization (DP) of 40.
[0016] Micas are hydrated aluminum silicate minerals that include muscovite, biotite, fuchsite, phlogopite, margarite, glauconite, and lepidolite micas, of which muscovite and phlogopite micas are important. R -(RMeSiO 2 / 2 ) n The w / w ratio of copolymer to mica ranges from 10:90, or 20:80, or 30:70, or 40:60 to 90:10, or 80:20, or 70:30, or 65:35.
[0017] In another aspect of the invention, the composition comprises T R -(RMeSiO 2 / 2 ) n a) a copolymer, mica, and one or more of the following components: a) T in a concentration ranging from 1 or 5% by weight to 20 or 30% by weight based on the weight of the composition; R b) 5 to 15 weight percent of C1 to C 12 c) an aprotic solvent such as ethyl acetate, propyl acetate, butyl acetate, propyl propionate, and propylene glycol methyl ether acetate; and d) a moisture-curing catalyst such as a tin-based catalyst such as stannous octoate or stannous butanoate, or a titanium-based catalyst such as tetraisopropyl titanate, tetra-n-butyl titanate, and tetra-t-butoxytitanate.
[0018] The amount of aprotic solvent is sufficient to achieve a viscosity in the range of 20 cP, or 50 cP, or 100 cP to 20,000 cP, or 10,000 cP, or 5,000 cP, or 1,200 cP, or alternatively, the concentration of the aprotic solvent is in the range of 5, or 10, or 20 weight percent to 90, or 75, or 60 weight percent based on the weight of the composition.
[0019] In yet another aspect of the invention, the composition comprises T R -(RMeSiO 2 / 2 ) n Copolymer, mica, and C1-C 12 The compositions of the present invention comprise a silane, an aprotic solvent, and a moisture-curable catalyst. The compositions of the present invention provide coatings for metal, ceramic, or plastic substrates that are tack-free and thermally stable against cracking for hundreds or even thousands of hours. [Example]
[0020] DOWSIL™ 1-2577 Conformal Coating was used as Intermediate Example 1.
[0021] Intermediate Example 2 - T with DP=50 Me Preparation of -PPhMS copolymer Silanol-terminated PPhMS (65 g, n = 50), XIAMETER™ OSF-1579 Silane (OSF-1579, 5 g), and butyl acetate (50 g) were added to a 500 mL, three-necked, dry flask equipped with a Dean-Stark trap under nitrogen. The temperature was increased to 50°C, and the mixture was stirred for 30 minutes. DOWSIL™ RSN-2403 Flake Resin (2403 resin, 35 g) and butyl acetate (60 g) were added to the reaction mixture, which was then heated to reflux for 1 hour, during which a mixture of acetic acid and HO (approximately 1.5 g) was collected at the bottom of the Dean-Stark trap. A portion of the solvent (approximately 60 g) was then slowly removed to yield a solids content of approximately 68 wt%. The reaction solution was cooled and used directly in a coating composition without filtration or further purification.
[0022] Intermediate Example 3 - T with DP=60 Me Preparation of -PDMS copolymer Silanol-terminated PDMS (65 g, n = 60), XIAMETER™ OSF-1579 Silane (OSF-1579, 5 g), and butyl acetate (50 g) were added to a 500 mL, three-necked, dry flask equipped with a Dean-Stark trap under nitrogen. The temperature was increased to 50 °C, and the mixture was stirred for 30 minutes. DOWSIL™ RSN-2403 Flake Resin (2403 resin, 35 g) and butyl acetate (60 g) were added to the reaction mixture, which was then heated to reflux for 1 hour, during which a mixture of acetic acid and HO (approximately 1.5 g) was collected at the bottom of the Dean-Stark trap. A portion of the solvent (approximately 60 g) was then slowly removed to yield a solids content of approximately 68 wt %. The reaction solution was cooled and used directly in a coating composition without filtration or further purification.
[0023] Comparative Example 1 was prepared by combining Intermediate 1 with tetraisopropyl titanate (1 pbw).
[0024] Examples 1 to 5-T Ph -Preparation of a mixture of PDMS and mica C-4000 Muscovite Mica (K2Al4(Al2Si6O 20)(OH)4, median particle size 10.8 μm, obtained from IMERYS), or MRX muscovite mica (median particle size 11.4 μm), or HRX phlogopite mica (K2(Mg,Fe)6(Al2Si6O 20 )(OH,F)₄, median particle size 10.6 μm, obtained from Arctic Minerals) was dried under vacuum at 120 °C for 10 h and cooled to room temperature under N₂. A sufficient amount of T was added to achieve a viscosity in the range of 500–2000 cPs. Ph Dry mica was added to a vessel containing a mixture of PDMS (DP=40, see Table 1), tetraisopropyl titanate (1 pbw), and butyl acetate, and the contents were mixed with a mechanical stirrer. The mixture was then stored under N.
[0025] Comparative Example 2 was prepared by mixing Intermediate 2 with tetraisopropyl titanate (1 pbw).
[0026] Example 6-T Me Preparation of a mixture of -PPhMS and mica Dry mica (100pbw), (100pbw), tetraisopropyl titanate (1pbw), T Me The mixture was added to a vessel containing PPhMS copolymer (100 pbw, Intermediate 2) and butyl acetate (60 pbw). The contents of the vessel were mixed with a mechanical stirrer under N. The mixture was then poured into a bottle and sealed for further use.
[0027] Comparative Example 3 was prepared by mixing Intermediate 3 with tetraisopropyl titanate (1 pbw).
[0028] Example 7-T Me -Preparation of a mixture of PDMS and mica Dry mica (100pbw), (100pbw), tetraisopropyl titanate (1pbw), T Me -PDMS copolymer (100 pbw, Intermediate 3), and butyl acetate (630 pbw) were added to a vessel containing the contents of the vessel mixed with a mechanical stirrer under N2. The mixture was then poured into a bottle and sealed for further use.
[0029] Long-term high temperature resistance test Each sample was coated onto an aluminum panel at a coating thickness of 100 μm, then heat cured and aged in an oven at 300° C. The film cracking time was recorded (in days) as the first visible cracking event in the coating.
[0030] Table 1 shows the thermal stability of the coatings as measured by time to crack. A crack time of at least 10 days was considered a pass. The weight percent loading of mica was calculated as 100 wt.% minus T Ph -PDMS, or 100% by weight minus T Me -PDMS, or 100% by weight minus T Me -Report as PPhMS.
[0031] [Table 1]
[0032] The data show a dramatic difference in resistance to cracking for the mica-containing coatings. The coatings also exhibited acceptable uniformity and adhesion throughout the test period. Ph or T Me The resin and mica combination alone was found to fail the crack test within 2 days, while the PDMS or PPhMS and mica combination alone readily delaminated from the substrate at 300° C. Furthermore, of the fillers tested - silica, calcium carbonate, aluminum silicate, calcium silicate, alumina, ferric oxide, and mica - mica was found to be the only class of filler that exhibited a crack time greater than 120 hours.
[0033] Example 8 - Preparation of Room Temperature Non-Tacky Coating Methyltrimethoxysilane (10 parts by weight) and titanium tetra-t-butoxide (0.5 parts by weight) were added to the composition of Example 1. A sample of this composition was applied to an aluminum panel at a coating thickness of 100 μm. The coating became tack-free in 10 minutes at room temperature with 50% humidity. The coating was then subjected to a heat aging test at 300°C and found to be crack-free for over 100 days.
Claims
1. T Ｒ -(RMeSiO ２／２ ) ｎ A composition comprising a copolymer and mica, wherein each R is independently methyl or phenyl; Ｒ -(RMeSiO ２／２ ) ｎ A composition wherein the weight to weight ratio of copolymer to said mica is in the range of 10:90 to 90:10 and n is in the range of 20 to 800.
2. 10. The composition of claim 1, further comprising an aprotic solvent in a concentration sufficient to achieve a composition viscosity in the range of 20 cP to 10,000 cP.
3. T in the copolymer Ｒ Unit pair (RMeSiO ２／２ ) ｎ 3. The composition of claim 2, wherein the weight to weight ratio of units ranges from 30:70 to 70:30, the mica is muscovite or phlogopite, and the concentration of the aprotic solvent is sufficient to achieve a viscosity in the range of 50 cP to 5,000 cP.
4. Said T Ｒ -(RMeSiO ２／２ ) ｎ 4. The composition of claim 3, wherein the weight to weight ratio of copolymer to mica ranges from 20:80 to 80:20 and the concentration of the aprotic solvent is sufficient to achieve a viscosity in the range of 100 cP to 1200 cP.
5. Said T Ｒ -(RMeSiO ２／２ ) ｎ The composition of claim 4, wherein the weight to weight ratio of copolymer to mica ranges from 30:70 to 70:
30.
6. Said T Ｒ -(RMeSiO ２／２ ) ｎ The composition of claim 5, wherein the weight to weight ratio of copolymer to mica ranges from 40:60 to 60:
40.
7. The mica is muscovite, Ｒ -(RMeSiO ２／２ ) ｎ But, T Ｐｈ -(dimethylSiO ２／２ ) ｎ , or T Ｍｅ -(dimethylSiO ２／２ ) ｎ , or T Ｍｅ -(phenylmethylSiO ２／２ ) ｎ The composition according to any one of claims 1 to 6, wherein
8. A composition comprising, based on the weight of said composition, T Ｒ -(RMeSiO ２／２ ) ｎ copolymer, mica, and C １ ~C １２ Alkyl-tri-C １ ~C ４ - an alkoxysilane, an aprotic solvent, and a moisture-curable catalyst, wherein each R is independently methyl or phenyl; Ｒ a composition wherein the weight to weight ratio of PDMS copolymer to said mica is in the range of 20:80 to 80:20, and the concentration of said aprotic solvent is sufficient to achieve a viscosity in the range of 50 cP to 5,000 cP.
9. Said T Ｒ -(RMeSiO ２／２ ) ｎ But, T Ｐｈ -(dimethylSiO ２／２ ) ｎ , or T Ｍｅ -(dimethylSiO ２／２ ) ｎ , or T Ｍｅ -(phenylmethylSiO ２／２ ) ｎ 9. The composition of claim 8, wherein the mica is muscovite mica.