Polysiloxane Mica Blend

Abstract

The present invention relates to a method for producing a cellulose acetate film by the use of mica and T R -D R′R′ Resin and silanol or alkoxyl (PhMeSiO 2 / 2 ) n and a polymer, wherein R, R′, and n are defined herein. The composition is useful as a coating for a substrate, and the coating exhibits good adhesion and crack resistance when subjected to elevated temperatures for several weeks.

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, heater elements for electric vehicles, exhaust systems for automobile engines, power 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] Although the high-temperature resistance of silicones ostensibly makes them promising candidates for high-temperature protective coatings and sealants, silicone rubbers are nevertheless 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. Coatings prepared from such compositions require aging at temperatures above 500°C to form ceramic-like coatings. At such extreme temperatures, the coatings are likely to crack and thermal shock fracture, and furthermore, electronic components beneath the coating's surface are susceptible to damage. Therefore, developing a composition that provides a coating resistant to cracking, delamination, and thermal shock fracture while maintaining acceptable dielectric properties for extended periods at temperatures above 300°C would be an advancement in the field of high-temperature protective coatings. Summary of the Invention

[0003] The present invention relates to a method for producing a cellulose acetate film by the use of mica and T R -D R′R′ Resin and silanol or C1-C4-alkoxy-terminated (PhMeSiO 2 / 2 ) nwherein each R and R′ is independently methyl or phenyl, n is in the range of 20 to 800, and T R -D R′R′ Resin and (PhMeSiO 2 / 2 ) n The present invention addresses a need in the art by providing a composition having a weight-to-weight ratio of total polymer to mica in the range of 10:90 to 90:10.The composition of the present invention is useful as a coating for substrates, and the coating exhibits good adhesion and crack resistance when subjected to elevated temperatures for several weeks. DETAILED DESCRIPTION OF THE INVENTION

[0004] The present invention relates to a method for producing a cellulose acetate film by the use of mica and T R -D R′R′ Resin and silanol or C1-C4-alkoxy-terminated (PhMeSiO 2 / 2 ) n wherein each R and R′ is independently methyl or phenyl, n is in the range of 20 to 800, and T R -D R′R′ Resin and (PhMeSiO 2 / 2 ) n The composition has a weight to weight ratio of the total polymer to mica in the range of 10:90 to 90:10.

[0005] "T R -D R′R′ The term "resin" refers to R-SiO 3 / 2 , R-SiO 2 / 2 (OZ), and optionally R—SiO 1 / 2 (OZ)2(T R ) repeating units and R'SiO 2 / 2 (D R′R′ ) refers to a kinetically stable three-dimensional polymer having a

[0006] R-SiO 3 / 2 The unit is represented by the following structure:

[0007] [ka] wherein each R is methyl or phenyl.

[0008] R-SiO 2 / 2 (OZ) is represented by the following structure:

[0009] [ka] where Z is H, C-C-alkyl, or C(O)CH; and RSiO 1 / 2 The (OZ)2 unit is represented by the following structure:

[0010] [ka] Resin T R Each Z in the moiety is preferably methyl or H.

[0011] R'2SiO 2 / 2 The unit is represented by the following structure:

[0012] [ka] wherein each R is independently methyl or phenyl.

[0013] "Silanol or C1-C4-alkoxy terminal (PhMeSiO 2 / 2 ) n The term "polymer" refers to polyphenylmethylsiloxane (PPhMS) containing repeating units of PhMe siloxane groups, as shown below:

[0014] [ka] wherein X is H or C1-C4-alkyl and n (or degree of polymerization or DP) is preferably from 2, or from 5, or from 20, or from 40, or from 70, or from 100, to 800, or to 500, or to 300, or to 200. R -D R′R′ Resin and (PhMeSiO 2 / 2 ) n The weight to weight ratio of the polymer preferably ranges from 20:80, or 30:70, to 80:20, or 70:30.

[0015] Micas are hydrated aluminum silicate minerals that include muscovite, biotite, chromite, phlogopite, nacreous mica, glauconite, and lepidolite, of which muscovite and phlogopite are the predominant ones. R -D R′R′ Resin and (PhMeSiO 2 / 2 ) n The w / w ratio of the total polymer ranges from 90:10, or from 80:20, or from 70:30, or from 65:35, to 10:90, or from 20:80, or from 30:70, or from 35:65.

[0016] In another aspect of the invention, the composition comprises T R -D R′R′ Resin and (PhMeSiO 2 / 2 ) n Polymer, mica, and R 2 However, C1~C 12 - alkyl or aryl, R 3 is C1-C4-alkyl, such as methyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, and ethyltrimethoxysilane; 2 Si(OR 3)3 with an aprotic solvent such as propylene glycol methyl ether acetate, ethyl acetate, propyl acetate, butyl acetate, or propyl propionate, and a moisture cure catalyst, for example, 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-butoxy titanate.

[0017] The amount of aprotic solvent is sufficient to achieve a Brookfield viscosity at 25°C ranging from 20 cP, or from 50 cP, or from 100 cP to 20,000 cP, or from 10,000 cP, or from 5,000 cP, or from 1200 cP, or the concentration of the aprotic solvent ranges from 5 weight percent, or from 10 weight percent, or from 20 weight percent, to 90 weight percent, or from 75 weight percent, or from 60 weight percent, based on the weight of the composition.

[0018] In yet another aspect, the present invention is a process for preparing a cured coating on a substrate. The present invention is also an article comprising a substrate coated with the cured composition. The coating thickness generally ranges from 20 μm to 300 μm.

[0019] The compositions of the present invention provide coatings for substrates, such as metal, metal oxide, ceramic, or plastic substrates, that are non-tacky in less than 30 minutes at ambient temperature and thermally stable against cracking for hundreds or thousands of hours. [Example]

[0020] Intermediate Example 1-T R D R′R′ Resin 1, D MeMe 0.15 D PhPh 0.05 T 0.10 T Ph 0.70 Preparation of To a vessel containing a toluene mixture of MeSiCl (0.15 mol), PhSiCl (0.05 mol), MeSiCl (0.10 mol), and PhSiCl (0.70 mol) was added water (2.5 mol) slowly at room temperature. The mixture was heated at 60° C. for 4 hours to obtain T R D R′R′ A solution containing the resin was obtained. The solution was washed with water to remove the acid, then stripped under vacuum and heat to produce a solid resin, which was then converted into resin flakes by grinding.

[0021] Intermediate Example 2-T R D R′R′ Resin 2, D MeMe 0.15 T Me 0.40 T Ph 0.45 Preparation of To a vessel containing a toluene mixture of MeSiCl (0.15 mol), PhSiCl (0.45 mol), and MeSiCl (0.40 mol) was slowly added water (2.5 mol) at room temperature. The mixture was heated at 60° C. for 4 hours to obtain T R D R′R′ A solution containing the resin was obtained. The solution was washed with water to remove the acid, then stripped under vacuum and heat to produce a solid resin, which was then converted into resin flakes by grinding.

[0022] Comparative Example 1-T R D R′R′ Resin 1 and silanol-terminated (PhMeSiO 2 / 2 ) 120 Preparation of blends with Resin 1 flakes (45 pbw), silanol-terminated PPhMS (55 pbw, DP=120), butyl acetate (30 pbw), and methyltrimethoxysilane (5 pbw) were added to a flask under N, followed by tetraisopropyl titanate (1 pbw). The contents of the flask were stirred for 1 h, after which they were poured into a glass bottle and sealed under N.

[0023] Comparative Example 2-T R D R′R′Resin 2 and silanol-terminated (PhMeSiO 2 / 2 ) 120 Preparation of blends with Resin 2 flakes (90 pbw), silanol-terminated PPhMS (10 pbw, DP=120), butyl acetate (30 pbw), and methyltrimethoxysilane (5 pbw) were added to a flask under N, followed by tetraisopropyl titanate (1 pbw). The contents of the flask were stirred for 1 h, after which they were poured into a glass bottle and sealed under N.

[0024] Examples 1 and 2-T R D R′ Resin and (PhMeSiO 2 / 2 ) 120 Preparation of polymer and mica blends C-4000 Muscovite (K2Al4(Al2Si6O 20 )(OH)4 (median particle size 10.8 μm, obtained from IMERYS) was dried in vacuo at 120°C for 10 hours and then cooled to room temperature under N2. Dried mica (100 pbw) was added to a vessel containing the contents of either Comparative Example 1 (100 pbw) or Comparative Example 2 (100 pbw) and butyl acetate (30 pbw). The contents of the vessel were mixed with a mechanical stirrer under N2. The mixture was then poured into a bottle and sealed for further use.

[0025] Preparation of coatings Aluminum panels (Gardco Type A, 3" x 6") were cleaned with toluene and acetone and dried under airflow before use. A portion (2 g) of the prepared formulation was coated onto the panel using a 4-mil drawdown bar to form a film with a thickness ranging from 50 μm to 100 μm. The coated film was dried under airflow at 70°C for 30 minutes to remove the solvent. The dried film was cured at room temperature or at 200°C for 10 to 60 minutes, followed by heat aging at 300°C.

[0026] Cracking time measurement The cured coatings were aged in an oven at 300°C. Each sample was checked for cracking every other day for the first 14 days, then once a week. The time to cracking was recorded when cracking was observed in the coating.

[0027] Thermal cycling test: Each formulation was coated as a 100 μm thick film and subsequently cured at room temperature or 150°C, followed by aging at 300°C for 10 days. The samples were then subjected to 100 cycles of temperature cycling from -50°C to 150°C using a Tenney Thermal Chamber at a temperature ramp rate of 20°C / min, 10 minutes per cycle. If no cracking or delamination was observed at the end of the test, the coated sample was considered to have passed the thermal cycling test.

[0028] Table 1 shows the time-to-cracking results for samples with and without mica. TCT refers to thermal cycling test. pbw refers to parts by weight of each component in the formulation. Mica refers to C-4000 muscovite.

[0029] [Table 1]

[0030] The results show a dramatic difference in cracking time and thermal cycling test results between the blends containing mica versus the samples without mica. R D R′R′ It was discovered that excellent crack times could also be achieved for samples prepared by simply blending resin, silanol-terminated PPhMS, and mica.

[0031] The combination of PPhMS and mica alone readily peeled 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 cracking time greater than 120 hours.

Claims

1. Mica and T Ｒ -D Ｒ′Ｒ′ Resin and silanol or C １ ~C ４ -Alkoxyl-terminated (PhMeSiO ２／２ ) ｎ wherein each R and R' is independently methyl or phenyl, and n is in the range of 20 to 800; Ｒ -D Ｒ′Ｒ′ Resin and the above (PhMeSiO ２／２ ) ｎ A composition wherein the weight to weight ratio of the total polymer to said mica ranges from 10:90 to 90:

10.

2. 10. The composition of claim 1, further comprising an aprotic solvent in a concentration sufficient to achieve a Brookfield viscosity of the composition at 25°C in the range of 20 cP to 10,000 cP.

3. The mica and the T Ｒ -D Ｒ′Ｒ′ Resin and the silanol or C １ ~C ４ -Alkoxyl-terminated (PhMeSiO ２／２ ) ｎ 3. The composition of claim 2, wherein the weight to weight ratio of the total polymer ranges from 20:80 to 80:20, and the concentration of the aprotic solvent is sufficient to achieve a Brookfield viscosity at 25° in the range of 50 cP to 5,000 cP.

4. The mica and the T Ｒ -D Ｒ′Ｒ′ Resin and the silanol or C １ ~C ４ -Alkoxyl-terminated (PhMeSiO ２／２ ) ｎ The weight to weight ratio of the total polymer is in the range of 30:70 to 70:30, １ -C ４ -Alkoxyl-terminated (PhMeSiO ２／２ ) ｎ The polymer is silanol terminated (PhMeSiO ２／２ ) ｎ 3. The composition of claim 2, wherein the mica is a polymer, muscovite, biotite, chromite, phlogopite, nacre, glauconite, or lepidolite, and the concentration of the aprotic solvent is sufficient to achieve a Brookfield viscosity at 25° C. in the range of 100 cP to 1200 cP.

5. n is in the range of 5 to 300, the mica is muscovite or phlogopite, and the mica and the T Ｒ -D Ｒ′Ｒ′ Resin and the silanol-terminated (PhMeSiO ２／２ ) ｎ The composition of claim 4, wherein the weight to weight ratio of the total polymer ranges from 65:35 to 35:

65.

6. The composition of claim 4 wherein the mica is muscovite.

7. R ２ is C １ ~C １２ - alkyl or aryl, R ３ is C １ ~C ４ - alkyl, R ２ Si(OR ３ ) ３ and a moisture cure catalyst.

8. R ２ Si(OR ３ ) ３ is methyltrimethoxysilane or phenyltrimethoxysilane, the aprotic solvent is propylene glycol methyl ether acetate, ethyl acetate, propyl acetate, butyl acetate, or propyl propionate, and the moisture cure catalyst is a tin-based or titanium-based catalyst.

9. A process comprising the steps of coating a substrate with the composition of claim 7 and then curing the coating.

10. An article comprising a substrate and a coating disposed thereon having a thickness in the range of 20 μm to 300 μm, said coating comprising the cured composition of claim 7.

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