Insulating paint as well as preparation method and application thereof

Abstract

The invention relates to the technical field of coatings, in particular to an insulating coating as well as a preparation method and application thereof. The insulating paint provided by the invention comprises the following components in parts by weight: 20-60 parts of epoxy resin; the epoxy resin is selected from one or more of bisphenol A epoxy resin E-39, bisphenol A epoxy resin E-44, bisphenol A epoxy resin E-51, phenolic resin F-51 and phenolic resin F-44; 20-50 parts of an anhydride curing agent; the anhydride curing agent is selected from one or more of an HY 1235 anhydride curing agent and an EK 860 anhydride curing agent; 5-25 parts of a toughening agent; 5-15 parts of a reinforcing material; 10 to 20 parts of a diluent; and 0.1-2 parts of an accelerant. The insulating paint provided by the invention is excellent in insulating property, mechanical property, environment-friendly property and construction property through matching of the specific epoxy resin and the specific anhydride curing agent, does not contain a volatile solvent, and is specially designed for spraying the surface of a dry sleeve.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, in particular to an insulating coating and a preparation method and application thereof. Background Art

[0002] With the rapid development of the power industry, dry bushings are important components in power equipment, and their insulation performance is directly related to the safe operation of the equipment. Traditional insulating coatings often contain a large amount of volatile solvents, which not only pollute the environment but also may cause damage to the equipment itself. Therefore, it is particularly important to develop an environmentally friendly insulating coating that does not contain volatile solvents and has excellent insulation performance. Summary of the invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide an insulating coating and a preparation method and application thereof. The insulating coating provided by the present invention has high insulating performance and construction performance, good mechanical properties, and does not contain volatile solvents.

[0004] The present invention provides an insulating coating, which comprises, by weight:

[0005] 20-60 parts of epoxy resin; the epoxy resin is selected from one or more of bisphenol A epoxy resin E-39, bisphenol A epoxy resin E-44, bisphenol A epoxy resin E-51, phenolic resin F-51 and phenolic resin F-44;

[0006] 20-50 parts of anhydride curing agent; the anhydride curing agent is selected from one or more of HY 1235 anhydride curing agent and EK 860 anhydride curing agent;

[0007] 5~25 parts of toughening agent;

[0008] 5~15 parts of reinforcement materials;

[0009] 10~20 parts of diluent;

[0010] Accelerator 0.1~2 parts.

[0011] The insulating coating provided in the present application is an environmentally friendly insulating coating that does not contain volatile solvents, contains epoxy resin and curing agent, takes a specific epoxy resin as a base material, and is used in combination with a specific acid anhydride curing agent to form a stable coating structure with excellent insulating properties and physical and mechanical properties; supplemented with raw materials such as toughening agents, reinforcing materials, diluents and promoters, it is possible to prepare an insulating coating with high insulating properties and mechanical properties, excellent environmental protection performance and construction performance, and the insulating coating does not contain volatile solvents, has low pollution to the environment and harm to the human body, is particularly suitable for power equipment components in the power industry that have relatively high requirements for insulating properties, and is specially designed for spraying on the surface of dry bushings.

[0012] The insulating coating of the present invention comprises 20-60 parts of epoxy resin and 20-50 parts of anhydride curing agent. The epoxy resin is used as the base material of the coating to provide excellent insulating properties and physical and mechanical properties; the anhydride curing agent can undergo a cross-linking reaction with the epoxy resin to form a stable coating film structure. Preferably, the epoxy resin is bisphenol A epoxy resin E-39; the anhydride curing agent is HY1235 anhydride curing agent and EK 860 anhydride curing agent; or, the epoxy resin is bisphenol A epoxy resin E-44; the anhydride curing agent is HY 1235 anhydride curing agent; or, the epoxy resin is phenolic resin F-44; the anhydride curing agent is EK 860 anhydride curing agent; or, the epoxy resin is bisphenol A epoxy resin E-51 and phenolic resin F-51; the anhydride curing agent is HY 1235 anhydride curing agent; or, the epoxy resin is bisphenol A epoxy resin E-39, bisphenol A epoxy resin E-44 and phenolic resin F-44; the anhydride curing agent is HY1235 anhydride curing agent and EK 860 anhydride curing agent; or, the epoxy resin is bisphenol A epoxy resin E-39; the anhydride curing agent is EK 860 anhydride curing agent.

[0013] The insulating coating of the present invention further comprises 5 to 25 parts of a toughening agent and 5 to 15 parts of a reinforcing material. The toughening agent can improve the toughness of the coating, and the reinforcing material can improve the hardness, wear resistance and heat resistance of the coating. The addition of the reinforcing material and the toughening agent further improves the toughness, wear resistance, heat resistance and construction performance of the coating. Preferably, the toughening agent is selected from one or more of 820 toughening agent and QS-N toughening agent; the reinforcing material is selected from one or more of silicon micropowder, alumina, ultrafine silica or nano-scale silica.

[0014] The insulating coating of the present invention further comprises 10-20 parts of a diluent and 0.1-2 parts of an accelerator. The diluent can improve the leveling performance of the coating and make the coating film smoother and flatter; the accelerator can adjust the curing speed of the coating. Preferably, the diluent is selected from one or more of 0210 diluent, XY207 diluent and XY217 diluent; the accelerator is selected from one or more of DMP-30 accelerator, S-440 accelerator, 2-methylimidazole and 2-ethyl-4-methylimidazole.

[0015] In one embodiment of the present invention, the insulating coating comprises: 35-45 parts of bisphenol A epoxy resin E-39; 12-17 parts of HY1235 anhydride curing agent and 12-17 parts of EK 860 anhydride curing agent; 8-12 parts of 820 toughening agent; 4-6 parts of nano-silicon dioxide; 10-12 parts of 0210 diluent; 0.8-1 parts of DMP-30 accelerator and 0.8-1 parts of S-440 accelerator.

[0016] In one embodiment of the present invention, the insulating coating comprises: 25 to 35 parts of bisphenol A epoxy resin E-44; 18 to 22 parts of HY 1235 anhydride curing agent; 18 to 20 parts of 820 toughening agent and 4 to 5 parts of QS-N toughening agent; 7 to 9 parts of nano-silicon dioxide; 18 to 20 parts of XY207 diluent; and 0.1 to 0.2 parts of S-440 accelerator.

[0017] In one embodiment of the present invention, the insulating coating comprises: 20 to 22 parts of phenolic resin F-44; 18 to 22 parts of EK860 anhydride curing agent; 13 to 17 parts of QS-N toughening agent; 8 to 12 parts of ultrafine silica; 13 to 17 parts of XY217 diluent; 0.4 to 0.6 parts of DMP-30 accelerator, 0.2 to 0.4 parts of 2-methylimidazole and 0.8 to 1.0 parts of 2-ethyl-4-methylimidazole.

[0018] In one embodiment of the present invention, the insulating coating comprises: 34 to 38 parts of bisphenol A epoxy resin E-51 and 18 to 22 parts of phenolic resin F-51; 45 to 50 parts of HY 1235 anhydride curing agent; 22 to 25 parts of 820 toughening agent; 10 to 14 parts of nano-scale silica; 4 to 6 parts of 0210 diluent, 4 to 6 parts of XY207 diluent and 4 to 6 parts of XY217 diluent; 0.1 to 0.3 parts of 2-methylimidazole and 0.1 to 0.3 parts of 2-ethyl-4-methylimidazole.

[0019] In one embodiment of the present invention, the insulating coating comprises: 4 to 5 parts of bisphenol A epoxy resin E-39, 35 to 40 parts of bisphenol A epoxy resin E-44 and 13 to 15 parts of phenolic resin F-44; 8 to 12 parts of HY1235 anhydride curing agent and 27 to 33 parts of EK860 anhydride curing agent; 18 to 22 parts of QS-N toughening agent; 3 to 5 parts of ultrafine silica and 8 to 10 parts of nano-scale silica; 4 to 6 parts of 0210 diluent and 5 to 7 parts of XY207 diluent; 1.5 to 2 parts of 2-methylimidazole.

[0020] In one embodiment of the present invention, the insulating coating comprises: 55-60 parts of bisphenol A epoxy resin E-39; 40-50 parts of EK 860 anhydride curing agent; 8-10 parts of 820 toughening agent and 13-15 parts of QS-N toughening agent; 6-8 parts of ultrafine silica and 5-7 parts of nano-scale silica; 7-10 parts of XY207 diluent and 7-10 parts of XY217 diluent; 1-1.5 parts of 2-ethyl-4-methylimidazole.

[0021] The present invention also provides a method for preparing the insulating coating described in any of the above technical solutions, comprising the following steps: mixing the epoxy resin, anhydride curing agent, toughening agent, reinforcing material, diluent and accelerator to obtain the insulating coating.

[0022] The preparation method of the insulating coating of the present invention is simple, has low production cost, and is easy to promote and apply. Specifically, the present invention first mixes the epoxy resin, toughening agent, reinforcing material and diluent, disperses them, and obtains a premix; in certain embodiments of the present invention, the present invention first mixes the epoxy resin, toughening agent, reinforcing material and diluent in a certain proportion, and disperses them uniformly in a high-speed disperser to obtain a premix. After obtaining the premix, the present invention mixes an anhydride curing agent, an accelerator and the obtained premix to obtain the insulating coating. In certain embodiments of the present invention, the anhydride curing agent, the accelerator and the obtained premix are mixed, and continue to stir evenly, and then the obtained coating is filtered to remove impurities to ensure the purity of the coating, and then the filtered coating is packaged and stored in a cool and dry place for use.

[0023] The present invention also provides a dry bushing, which comprises a dry bushing substrate and a coating disposed on the dry bushing substrate; the coating is the insulating coating described in any of the above technical solutions. The insulating coating described in the present invention is particularly suitable for spraying on the surface of the dry bushing, effectively protecting the bushing and improving its insulation performance.

[0024] The present invention provides an insulating coating and a preparation method and application thereof. The insulating coating provided by the present invention comprises, by weight: 20 to 60 parts of epoxy resin; the epoxy resin is selected from one or more of bisphenol A epoxy resin E-39, bisphenol A epoxy resin E-44, bisphenol A epoxy resin E-51, phenolic resin F-51 and phenolic resin F-44; 20 to 50 parts of anhydride curing agent; the anhydride curing agent is selected from one or more of HY 1235 anhydride curing agent and EK 860 anhydride curing agent; 5 to 25 parts of toughening agent; 5 to 15 parts of reinforcing material; 10 to 20 parts of diluent; 0.1 to 2 parts of accelerator. The insulating coating provided by the present invention is used in combination with a specific epoxy resin and a specific anhydride curing agent, and has excellent insulating properties, mechanical properties, environmental protection properties and construction properties, does not contain volatile solvents, and is specially designed for spraying on the surface of dry bushings. DETAILED DESCRIPTION

[0025] The present invention discloses an insulating coating and a preparation method and application thereof. A person skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to a person skilled in the art and are considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application of this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0026] The present invention will be further described below in conjunction with embodiments:

[0027] Example 1

[0028] An environmentally friendly coating comprises the following components in parts by weight:

[0029] 40 parts of bisphenol A epoxy resin E-39;

[0030] 15 parts of anhydride curing agent HY1235, 15 parts of anhydride curing agent EK 860;

[0031] 10 parts toughening agent 820;

[0032] 10 parts of thinner 0210;

[0033] 5 parts of reinforcing material nano-silicon dioxide;

[0034] 1 part accelerator DMP-30 and 1 part accelerator S-440.

[0035] The components are mixed respectively according to weight proportions and stirred evenly to obtain the environmentally friendly coating sample of the present invention.

[0036] The test data are shown in Table 1:

[0037] Table 1

[0038]

[0039] Example 2

[0040] An environmentally friendly coating comprises the following components in parts by weight:

[0041] 30 parts of bisphenol A epoxy resin E-44;

[0042] 20 parts of anhydride curing agent HY 1235;

[0043] 20 parts toughening agent 820, 5 parts toughening agent QS-N;

[0044] 20 parts of diluent XY207;

[0045] 8 parts of reinforcing material nano-silicon dioxide;

[0046] 0.1 parts of accelerator S-440.

[0047] The components are mixed respectively according to weight proportions and stirred evenly to obtain the environmentally friendly coating sample of the present invention.

[0048] The test data are shown in Table 2:

[0049] Table 2

[0050]

[0051] Example 3

[0052] An environmentally friendly coating comprises the following components in parts by weight:

[0053] 20 parts of phenolic resin F-44;

[0054] 20 parts of anhydride curing agent EK 860;

[0055] 15 parts of toughening agent QS-N;

[0056] 15 parts of diluent XY217;

[0057] 10 parts of reinforcing material ultrafine silica;

[0058] 0.5 parts of accelerator DMP-30, 0.3 parts of 2-methylimidazole and 0.9 parts of accelerator 2-ethyl-4-methylimidazole.

[0059] The components are mixed respectively according to weight proportions and stirred evenly to obtain the environmentally friendly coating sample of the present invention.

[0060] The test data are shown in Table 3:

[0061] Table 3

[0062]

[0063] Example 4

[0064] An environmentally friendly coating comprises the following components in parts by weight:

[0065] 38 parts of bisphenol A epoxy resin E-51, 22 parts of phenolic resin F-51;

[0066] 50 parts of anhydride curing agent HY 1235;

[0067] 25 parts toughening agent 820;

[0068] 5 parts of thinner 0210, 5 parts of thinner XY207, 5 parts of thinner XY217;

[0069] 12 parts of reinforcing material nano-silicon dioxide;

[0070] 0.2 parts of accelerator 2-methylimidazole and 0.2 parts of accelerator 2-ethyl-4-methylimidazole.

[0071] The components are mixed respectively according to weight proportions and stirred evenly to obtain the environmentally friendly coating sample of the present invention.

[0072] The test data are shown in Table 4:

[0073] Table 4

[0074]

[0075] Example 5

[0076] An environmentally friendly coating comprises the following components in parts by weight:

[0077] 5 parts of bisphenol A epoxy resin E-39, 40 parts of bisphenol A epoxy resin E-44, 15 parts of phenolic resin F-44;

[0078] 10 parts of anhydride curing agent HY1235, 30 parts of anhydride curing agent EK 860;

[0079] 20 parts of toughening agent QS-N;

[0080] 5 parts of thinner 0210, 6 parts of thinner XY207;

[0081] 4 parts of reinforcing material ultrafine silica, 10 parts of reinforcing material nano-scale silica;

[0082] 2 parts of accelerator 2-methylimidazole.

[0083] The components are mixed respectively according to weight proportions and stirred evenly to obtain the environmentally friendly coating sample of the present invention.

[0084] The test data are shown in Table 5:

[0085] Table 5

[0086]

[0087] Example 6

[0088] An environmentally friendly coating comprises the following components in parts by weight:

[0089] 60 parts of bisphenol A epoxy resin E-39;

[0090] 45 parts of anhydride curing agent EK 860;

[0091] 10 parts toughener 820, 15 parts toughener QS-N;

[0092] 8 parts of diluent XY207, 8 parts of diluent XY217;

[0093] 8 parts of reinforcing material ultrafine silica, 7 parts of reinforcing material nano-scale silica;

[0094] 1.2 parts of accelerator 2-ethyl-4-methylimidazole.

[0095] The components are mixed respectively according to weight proportions and stirred evenly to obtain the environmentally friendly coating sample of the present invention.

[0096] The test data are shown in Table 6:

[0097] Table 6

[0098]

[0099] The insulating coating provided by the present invention has better performance than existing similar products. For example, it is superior to the D025 epoxy solvent-free drip resin in the prior art. The two-component B and F-class general-purpose epoxy bath-free drip resin is composed of epoxy resin, additives and an original curing system dissolved in an active diluent. Its volume resistivity is ≥10 6 MΩ·m (i.e. ≥10 14 Ω·cm), dielectric strength ≥20 MV / m (i.e. ≥20 kV / mm); volume resistivity ≥1.0×10 at 155±2℃ 2 MΩ·m (i.e. ≥10 10 Ω·cm), dielectric strength ≥16 MV / m (i.e. ≥16 kV / mm); volume resistivity ≥1.0×10 3 MΩ·m (i.e. ≥10 11 Ω·cm), dielectric strength ≥16 MV / m (i.e. ≥16 kV / mm).

[0100] For example, the F858 epoxy solvent-free drip resin is superior to the prior art. It is composed of special epoxy resin, heat-resistant curing agent, accelerator and active diluent. Its volume resistivity is ≥10 6 MΩ·m (i.e. ≥10 14 Ω·cm), dielectric strength ≥25 MV / m (i.e. ≥25 kV / mm); volume resistivity ≥10 at 155℃ 3 MΩ·m (i.e. ≥10 11 Ω·cm), dielectric strength ≥20 MV / m (i.e. ≥20 kV / mm).

[0101] For example, D027 epoxy solvent-free impregnation resin is superior to the prior art. It is made of epoxy resin, unsaturated acid (anhydride), active diluent and additives through moderate polymerization reaction. Its volume resistivity is ≥10 6 MΩ·m (i.e. ≥10 14 Ω·cm), dielectric strength ≥25 MV / m, dielectric loss factor ≤0.010; volume resistivity ≥10 at 155℃ 3 MΩ·m (i.e. ≥10 11 Ω·cm), dielectric strength ≥22 MV / m, dielectric loss factor ≤0.030; volume resistivity ≥10 after immersion in water at 23±2℃ for 7 days 4 MΩ·m (i.e. ≥10 12 Ω·cm).

[0102] Comparative Example 1

[0103] A coating comprising the following components in parts by weight:

[0104] 100 parts of bisphenol A epoxy resin E-51;

[0105] 20 parts of amine curing agent TETA (highly toxic);

[0106] 25 parts toughening agent 820;

[0107] 5 parts of thinner 0210, 5 parts of thinner XY207, 5 parts of thinner XY217;

[0108] 12 parts of reinforcing material nano-silicon dioxide.

[0109] The components were mixed respectively according to weight proportions and stirred evenly to obtain a coating sample.

[0110] The test data are shown in Table 7:

[0111] Table 7

[0112]

[0113] Comparative Example 2

[0114] A coating comprising the following components in parts by weight:

[0115] 30 parts of bisphenol A epoxy resin E-44;

[0116] 30 parts of anhydride curing agent HY 1235;

[0117] 20 parts toughening agent 820, 5 parts toughening agent QS-N;

[0118] 20 parts of diluent XY207;

[0119] 8 parts of reinforcing material nano-silicon dioxide;

[0120] 0.1 parts of accelerator S-440.

[0121] The components were mixed respectively according to weight proportions and stirred evenly to obtain a coating sample.

[0122] The test data are shown in Table 8:

[0123] Table 8

[0124]

[0125] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An insulating coating, characterized in that: In parts by weight, it includes: 20-60 parts of epoxy resin; the epoxy resin is selected from one or more of bisphenol A epoxy resin E-39, bisphenol A epoxy resin E-44, bisphenol A epoxy resin E-51, phenolic resin F-51 and phenolic resin F-44; 20-50 parts of anhydride curing agent; the anhydride curing agent is selected from one or more of HY 1235 anhydride curing agent and EK 860 anhydride curing agent; 5~25 parts of toughening agent; 5~15 parts of reinforcement materials; 10~20 parts of diluent; Accelerator 0.1~2 parts.

2. The insulating coating according to claim 1, characterized in that: The epoxy resin is bisphenol A epoxy resin E-39; the anhydride curing agent is HY1235 anhydride curing agent and EK 860 anhydride curing agent; Alternatively, the epoxy resin is bisphenol A epoxy resin E-44; the anhydride curing agent is HY 1235 anhydride curing agent; Alternatively, the epoxy resin is phenolic resin F-44; the anhydride curing agent is EK 860 anhydride curing agent; Alternatively, the epoxy resin is bisphenol A epoxy resin E-51 and phenolic resin F-51; the anhydride curing agent is HY1235 anhydride curing agent; Alternatively, the epoxy resin is bisphenol A epoxy resin E-39, bisphenol A epoxy resin E-44 and phenolic resin F-44; the anhydride curing agent is HY1235 anhydride curing agent and EK 860 anhydride curing agent; Alternatively, the epoxy resin is bisphenol A epoxy resin E-39; and the anhydride curing agent is EK 860 anhydride curing agent.

3. The insulating coating according to claim 1, characterized in that: The toughening agent is selected from one or more of 820 toughening agent and QS-N toughening agent.

4. The insulating coating according to claim 1, characterized in that: The reinforcing material is selected from one or more of silicon micropowder, alumina, ultrafine silicon dioxide or nano-scale silicon dioxide.

5. The insulating coating according to claim 1, characterized in that: The diluent is selected from one or more of 0210 diluent, XY207 diluent and XY217 diluent.

6. The insulating coating according to claim 1, characterized in that: The accelerator is selected from one or more of DMP-30 accelerator, S-440 accelerator, 2-methylimidazole, and 2-ethyl-4-methylimidazole.

7. The insulating coating according to any one of claims 1 to 6, characterized in that: include: 35~45 parts of bisphenol A epoxy resin E-39; 12~17 parts of HY1235 anhydride curing agent and 12~17 parts of EK 860 anhydride curing agent; 8~12 parts of 820 toughening agent; 4~6 parts of nano-silicon dioxide; 10~12 parts of 0210 thinner; 0.8~1 part of DMP-30 accelerator and 0.8~1 part of S-440 accelerator; or, 25~35 parts of bisphenol A epoxy resin E-44; 18~22 parts of HY 1235 anhydride curing agent; 18~20 parts of 820 toughening agent and 4~5 parts of QS-N toughening agent; 7~9 parts of nano-silicon dioxide; 18~20 parts of XY207 diluent; 0.1~0.2 parts of S-440 accelerator; or, 20~22 parts of phenolic resin F-44; 18-22 parts of EK 860 anhydride curing agent; 13~17 parts of QS-N toughening agent; 8-12 parts of ultrafine silicon dioxide; 13~17 parts of XY217 diluent; 0.4~0.6 parts of DMP-30 accelerator, 0.2~0.4 parts of 2-methylimidazole and 0.8~1.0 parts of 2-ethyl-4-methylimidazole; or, 34-38 parts of bisphenol A epoxy resin E-51 and 18-22 parts of phenolic resin F-51; 45~50 parts of HY 1235 anhydride curing agent; 22~25 parts of 820 toughening agent; 10-14 parts of nano-silicon dioxide; 4~6 parts of 0210 thinner, 4~6 parts of XY207 thinner and 4~6 parts of XY217 thinner; 0.1-0.3 parts of 2-methylimidazole and 0.1-0.3 parts of 2-ethyl-4-methylimidazole; or, 4~5 parts of bisphenol A epoxy resin E-39, 35~40 parts of bisphenol A epoxy resin E-44 and 13~15 parts of phenolic resin F-44; 8~12 parts of HY1235 anhydride curing agent and 27~33 parts of EK 860 anhydride curing agent; 18~22 parts of QS-N toughening agent; 3-5 parts of ultrafine silica and 8-10 parts of nano-sized silica; 4~6 parts of 0210 thinner and 5~7 parts of XY207 thinner; 1.5~2 parts of 2-methylimidazole; or, 55~60 parts of bisphenol A epoxy resin E-39; 40~50 parts of EK 860 anhydride curing agent; 8~10 parts of 820 toughening agent and 13~15 parts of QS-N toughening agent; 6-8 parts of ultrafine silica and 5-7 parts of nano-sized silica; 7~10 parts of XY207 diluent and 7~10 parts of XY217 diluent; 1 to 1.5 parts of 2-ethyl-4-methylimidazole.

8. The method for preparing the insulating coating according to any one of claims 1 to 7, characterized in that: The following steps are involved: The epoxy resin, anhydride curing agent, toughening agent, reinforcing material, diluent and accelerator are mixed to obtain the insulating coating.

9. The method for preparing the insulating coating according to claim 8, characterized in that: The following steps are involved: S1) mixing and dispersing the epoxy resin, toughening agent, reinforcing material and diluent to obtain a premix; S2) mixing an anhydride curing agent, an accelerator and the premix obtained in step S1) to obtain the insulating coating.

10. A dry type casing, characterized in that: It includes a dry type casing substrate and a coating arranged on the dry type casing substrate; The coating is the insulating coating described in any one of claims 1 to 7.

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