Silicone Coating Composition

Abstract

The present invention is Ph Resin and T Ph -ポリ(フェニルメチルシロキサン) The present invention relates to compositions containing the copolymers, which are useful as coatings for metal substrates, the coatings having excellent transparency, adhesion, crack resistance, and retention of dielectric properties.

Description

[Technical Field]

[0001] The present invention relates to silicone coating compositions, and more particularly to compositions that are resistant to cracking and dielectric degradation at high temperatures, and methods for preparing such compositions. The present invention relates to high-temperature protective coatings and insulating materials for protecting various equipment and devices from extremely high temperatures. For example, heating elements for electric vehicles, exhaust systems for automobile engines, power plants, and top coatings for stoves all benefit from such protective coatings. In many applications, the coating layer must withstand temperatures in excess of 300°C for several months without cracking or losing its 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 for high-temperature protective coatings and sealants. Nevertheless, silicone rubbers are not resistant to cracking above 250°C for more than two weeks. Combining silicones with inorganic fillers such as SiO2, TiO2, and Al2O3 provides compositions with long-term high-temperature resistance. However, coatings prepared from such compositions require aging at temperatures above 500°C to form ceramic-like coatings. At such extreme temperatures, the coatings can crack and undergo thermal shock failure. Furthermore, electronic elements below the coating's surface 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 at temperatures above 300°C for extended periods would be an advancement in the field of high-temperature protective coatings. Summary of the Invention

[0003] The present invention is Ph resin, T Ph-poly(phenylmethylsiloxane) copolymer and substantially free of ZO-poly(phenylmethylsiloxane)-OZ, where each Z is independently H, C1-C4-alkyl, or C(O)CH3, comprising: T Ph Resin and T Ph This invention addresses the need in the art by providing a composition comprising a resin and a copolymer of poly(phenylmethylsiloxane) in a w / w ratio ranging from 15:85 to 35:65, the resin and copolymer containing Si-OZ groups at a molar concentration ranging from 7.5 mol % to 12.0 mol %. The composition is useful as a coating for metal substrates, and the coating exhibits transparency, adhesion, and crack resistance when exposed to elevated temperatures for hundreds of hours. [Brief explanation of the drawings]

[0004] [Figure 1] 1 is a series of three 29Si NMR spectra of a composition of the present invention and two comparative compositions. DETAILED DESCRIPTION OF THE INVENTION

[0005] The present invention is Ph resin, T Ph -poly(phenylmethylsiloxane) copolymer and substantially free of ZO-poly(phenylmethylsiloxane)-OZ, where each Z is independently H, C1-C4-alkyl, or C(O)CH3, comprising: T Ph Resin and T Ph The composition has a w / w ratio of resin to copolymer of poly(phenylmethylsiloxane) in the range of 15:85 to 35:65, and the resin and copolymer contain Si-OZ groups at a molar concentration in the range of 7.5 mol % to 12.0 mol %.

[0006] T Ph The term resin refers to phenyl-SiO 3 / 2 , phenyl-SiO 2 / 2 (OZ), and optionally phenyl-SiO 1 / 2It refers to a crosslinked polymer with repeating units of (OZ)2, and is phenyl-SiO 3 / 2 The units are as follows:

[0007] [ka] where the dotted line represents the point of attachment to another silicon atom, and phenyl-SiO 2 / 2 The unit of (OZ) is:

[0008] [ka] wherein Z is H, C1-C4-alkyl, or C(O)CH3, and 1 / 2 The units of (OZ)2 are:

[0009] [ka] is expressed by

[0010] T Ph Each Z in the resin is preferably H. Ph Resins include DOWSIL™ RSN-0217 and 0220 Flake Resins (trademarks of The Dow Chemical Company or its affiliates).

[0011] T Ph Copolymer of resin and poly(phenylmethylsiloxane) (T Ph -PPhMS copolymer) is a polymer consisting of the repeating unit PPhMS:

[0012] [ka] wherein Z is as defined above and n is preferably from 20 or 40 or 70 or 100 up to 300 or 250 or 200.

[0013] The composition can be prepared by first mixing the silanol-terminated PPhMS with a crosslinking agent, preferably an acetoxylating or alkoxylating agent, in a suitable solvent and under suitable reaction conditions. Examples of suitable acetoxylating agents include alkyltriacetoxysilanes such as methyltriacetoxysilane and ethyltriacetoxysilane. Suitable alkoxylating agents include phenyltrimethoxysilane, phenyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, and ethyltriethoxysilane. A 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 polar aprotic solvents such as ethyl acetate, propyl acetate, and butyl acetate.

[0014] The acetoxy or alkoxy terminated PPhMS is then advantageously reacted with T Ph Contact with resin and T Ph Resin Ph The acetoxy- or alkoxy-terminated PPhMS is partially converted to the copolymer, and the acetoxy- or alkoxy-terminated PPhMS is completely or nearly completely consumed. The volatiles are removed from the mixture to obtain the copolymer and the free T Ph Blends with methyl methyl esters can be formed and used without further purification.

[0015] The final formed composition is substantially free of ZO-PPhMS-OZ. As used herein, "substantially free of ZO-PPhMS-OZ" means that the composition is substantially free of T Ph resin, T Ph-PPhMS copolymer, and less than 10 weight percent, preferably less than 5 weight percent, more preferably less than 1 weight percent, and most preferably less than 0.5 weight percent ZO-PPhMS-OZ, based on the weight of ZO-PPhMS-OZ.

[0016] Or, T Ph Resin and T Ph -Blends with PPHMS copolymers are Ph Resin Ph -PPhMS copolymer, and then the copolymer was subjected to sufficient T Ph The copolymer and free T Ph The composition can be prepared by forming the desired blend with

[0017] Surprisingly, T Ph Resin and T Ph It has been discovered that blending with a T-PPhMS copolymer is important to achieve a combination of transparency, crack resistance, and adhesion to substrates in thin films prepared from the composition. Ph Resin and T Ph - The w / w ratio with PPhMS copolymer ranges from 15:85 or 20:80 or 24:76 to 35:65 or 30:70 or 28:72.

[0018] Without being bound by theory, T Ph -PPhMS-copolymers are polymers of otherwise incompatible substances (T Ph It is believed that compatibilizing the ZO-PPhMS-OZ (and ZO-PPhMS-OZ) produces a clear, non-cloudy coating. Furthermore, the unreacted Si-OH groups are retained in the residual T Ph Its presence in the resin at a critical concentration provides adhesion of the coating to the substrate through hydrogen bonding of the Si-OH groups, but T Ph -PPhMS copolymer alone is insufficient.

[0019] T Ph Resin and T PhThe mole % concentration of Si-OZ groups in the blend of -PPHMS copolymers ranges from 7.5 or 9.0 or 10.5 or 11.0 mole % to 12 or 11.5 mole %. As used herein, the term mole % concentration of Si-OZ groups refers to the percentage of a sample of the composition. 29 It refers to the ratio of the area measured for the resonances associated with the Si-OZ group to the total area of ​​the resonances in the Si spectrum.

[0020] Preferably, T Ph Resin and T Ph -PPhMS copolymer 29 T as measured by Si NMR spectroscopy Ph resin, T Ph The OZ-PPhMS copolymer and the ZO-PPhMS-OZ constitute at least 90 weight percent, or at least 95 weight percent, or at least 99 weight percent, or at least 99.5 weight percent of the composition, based on the weight of the OZ-PPhMS-OZ. Alternatively, the composition contains less than 5 weight percent, or less than 1 weight percent, or less than 0.5 weight percent OZ-PPhMS-OZ.

[0021] In another aspect, the present invention provides a method for the preparation of a PPhMS having a terminal alkoxylated or acetylated PPhMS and a T Ph Resin and T Ph The total mole percent of Si-OZ groups, preferably Si-OH groups, in the resin is greater than the initial T Ph Compared with the Si-OZ group of 29 The method includes contacting for a time sufficient to achieve a 10 mole %, or 15 mole %, up to 30 mole %, or up to 25 mole % reduction in the area under the resonance between -65 ppm and -75 ppm in the Si NMR spectrum. More particularly, the method includes contacting for a time sufficient to achieve a 10 mole %, or 15 mole %, up to 30 mole %, or up to 25 mole % reduction in the area under the resonance between -65 ppm and -75 ppm in the Si NMR spectrum. Ph The method comprises contacting the resin with ZO-PPhMS-OZ in the presence of a polar aprotic solvent at a temperature ranging from 77°C or 100°C to 200°C or 150°C for a time ranging from 15 or 30 minutes to 10 hours, 5 hours or 2 hours, preferably with simultaneous distillation and removal of the solvent. This method provides a simple and efficient way to prepare a coating composition. [Example]

[0022] Measurement by nuclear magnetic resonance spectroscopy (NMR) Nuclear magnetic resonance (NMR) spectra were obtained on a Varian EX-400 5 MHz Mercury spectrometer using C6D6 or CDCl3 solvents. 29 Chemical shifts in Si-NMR spectra were referenced to internal solvent resonances and reported relative to tetramethylsilane.

[0023] Comparative Example 1-T Ph Preparation of blends of resin with hydroxyl-terminated PPhMS Hydroxyl-terminated PPhMS (65 g) with a degree of polymerization of 139 and DOWSIL™ RSN-0217 Flake Resin (T Ph A physical blend was prepared with 35 g of ethylenediamine terephthalate resin. The mole % of Si-OH groups was 29 It was determined by Si NMR spectroscopy to be 12.7 mol %, which was determined by dividing the area under the resonances in the range of −65 ppm to −75 ppm by the area of ​​all resonances appearing in the spectrum (Figure 1 a).

[0024] Example 1 - Partially Coupled T Ph Resin and T Ph Preparation of -PPhMS copolymer Hydroxyl-terminated PPhMS (65 g) with a degree of polymerization of 139, XIAMETER™ OSF-1579 Silane (5 g), and butyl acetate (50 g) were added to a 500 mL dry three-neck flask equipped with a Dean-Stark trap. The mixture was stirred under N2 at 50 °C for 30 min, and then added to DOWSIL™ RSN-0217 Flake Resin (T Ph Resin (35 g) and butyl acetate (60 g) were added to the reaction mixture. The mixture was heated to reflux for 1 hour, during which time volatiles (approximately 60 g) were gradually removed and collected in a Dean-Stark trap. The contents of the flask were cooled to room temperature and used as a coating composition without filtration or further purification. Gel permeation chromatography of the product showed that TPh This indicated incomplete conversion of the resin and an upward shift in molecular weight of the peak associated with PPhMS. 29 Si NMR spectroscopy (Fig. 1b) demonstrated the complete (or almost complete) absence of the resonance at -25 ppm associated with the acetoxylated PPhMS group (Fig. 1a), which indicates that acetoxylated PPhMS is T Ph This provides strong evidence of complete conversion to the Si-OZ copolymer. 29 Residual T was determined to be 11.3 mol % by Si NMR spectroscopy. Ph The weight percent of the resin was found to be 26.5% by gel permeation chromatography.

[0025] Comparative Example 2 - Extensively Coupled T Ph Resin and T Ph Preparation of -PPhMS T Ph The procedure of Example 1 was repeated, except that the contents of the vessel were heated to reflux for 36 hours after the addition of the resin. After removal of volatiles, the composition had a solids content of about 67% by weight. The reaction solution was cooled and used directly as a coating composition without filtration or further purification. The mole % of Si-OZ groups was: 29 It was determined to be 6.6 mol % by Si NMR spectroscopy (Fig. 1c).

[0026] Gel Permeation Chromatography (GPC) Method Gel permeation chromatography (GPC) analysis was performed using an Agilent 1260 Infinity II chromatograph equipped with a triple detector consisting of a differential refractometer, an online differential viscometer, low-angle light scattering (LALS: detection angles of 15° and 90°), and a column (2PL Gel Mixed C, Varian). Toluene (HPLC grade, Biosolve) was used as the mobile phase at a flow rate of 1 mL / min.

[0027] Time to crack measurement The cured coatings were aged at 300°C. They were checked for cracks every other day for the first 14 days, and then weekly thereafter. The cracking time was recorded when cracks were observed in the coating.

[0028] Dielectric Resistance Measurement The aged coating was kept in a room with 85% humidity for 24 hours, and then placed between electrodes to measure the current resistance with a multimeter. If the measured resistance was found to be less than 1000 ohms, the aged coating was deemed to have failed in terms of dielectric resistance.

[0029] Thermal cycling test: Each formulation was coated as a 100 μm thin film, cured at ambient temperature or 150°C, and then aged at 300°C for 10 days. Each aged sample was then subjected to 100 cycles of thermal cycling (-50°C to 150°C) using a Tenney Thermal Chamber. The aged sample was then placed in the chamber and tested from 50°C to 150°C (heating rate: 20°C / min, 10 minutes per cycle). If no cracks or delamination were observed on the thin film during the 100 cycles, the coated sample was considered to have passed the thermal cycling test.

[0030] Thermal Stability Test The compositions were tested for thermal stability. Each sample (70 parts by weight) was dissolved in butyl acetate (30 parts by weight) and coated as a 50 μm thin film on an alumina panel for cracking and adhesion testing. The thin film crack time (synonymous with dielectric failure) was recorded for each sample during aging at 300°C. The adhesion percentage was measured according to ASTM method D3359 by using a Gardco PA-2000 adhesion test kit after aging at 300°C for 240 hours. In Table 1, adhesion percentage refers to the percentage of adhesion remaining after thermal aging. The higher the percentage, the stronger the adhesion of the material to the substrate. The coating transparency, crack time, and adhesion were recorded for each coating.

[0031] [Table 1]

[0032] The data show that the compositions of the present invention are comparable to blends of resins with OZ-terminated PPhMS or more extensively coupled T Ph Resin and T Ph The results show that the composition exhibited superior transparency, crack time, and adhesion properties compared to either the blend with PPhMS copolymer. The example compositions also had measured resistances greater than 1000 ohms, confirming preservation of dielectric properties.

Claims

1. T Ｐｈ resin, T Ｐｈ -poly(phenylmethylsiloxane) copolymers, and ZO-poly(phenylmethylsiloxane)-OZ, where each Z is independently H, C, １ -C ４ -alkyl, or C(O)CH ３ a composition that is substantially free of the compound T Ｐｈ Resin and the T Ｐｈ 1. A composition comprising a resin and a copolymer of said poly(phenylmethylsiloxane) in a w / w ratio ranging from 15:85 to 35:65, and said resin and said copolymer comprising Si—OZ groups at a molar percent concentration ranging from 7.5 mol % to 12.0 mol %.

2. Said T Ｐｈ Resin and the T Ｐｈ 10. The composition of claim 1, wherein the w / w ratio of ZO-poly(phenylmethylsiloxane)-OZ to a poly(phenylmethylsiloxane) copolymer is in the range of 20:80 to 30:70, the composition comprising less than 5 weight percent ZO-poly(phenylmethylsiloxane)-OZ, the resin and the copolymer comprising Si-OZ groups at a mole % concentration in the range of 9.0 mole % to 12.0 mole %, and the poly(phenylmethylsiloxane) having a degree of polymerization in the range of 20 to 300.

3. Said T Ｐｈ Resin and the T Ｐｈ - a w / w ratio with a poly(phenylmethylsiloxane) copolymer in the range of 24:76 to 30:70, the composition comprising less than 1 weight percent ZO-poly(phenylmethylsiloxane)-OZ, the resin and the copolymer comprising Si-OZ groups in a mole % concentration in the range of 10.5 mole % to 11.5 mole %, Z being H or C(O)CH ３ 2. The composition of claim 1, wherein the poly(phenylmethylsiloxane) has a degree of polymerization in the range of 40 to 250.

4. The composition of any one of claims 1 to 3, wherein the poly(phenylmethylsiloxane) has a degree of polymerization in the range of 100 to 200.

5. Under coupling conditions, ZO-poly(phenylmethylsiloxane)-OZ and T Ｐｈ Resin and the T Ｐｈ wherein each Z is independently selected from the group consisting of H, C, C, and Z; １ -C ４ -alkyl, or C(O)CH ３ That's the method.

6. The ZO-poly(phenylmethylsiloxane)-OZ is reacted with the T in the presence of a polar protic solvent at a temperature ranging from 77° C. to 150° C. for a reaction time ranging from 15 minutes to 10 hours. Ｐｈ The method of claim 5, wherein the resin is contacted.

7. 7. The method of claim 6, wherein the solvent is ethyl acetate, propyl acetate, or butyl acetate, the reaction time is in the range of 30 minutes to 2 hours, and the method further comprises the step of distilling and removing the solvent.

8. 8. The method of claim 7, wherein the solvent is butyl acetate.

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