Silicone high-strength low-temperature resistant resin coating with block structure and method of making

Abstract

The application discloses a kind of organic silicon high-strength low-temperature resistant resin coating containing block structure and preparation method thereof, belong to the technical field of silicone resin modification, coating includes (A) molecular chain end contains hydroxyl or at least two hydrolysable functional groups and molecular main chain side group contains other substituent group except methyl dimethylsiloxane copolymer;(B) containing block structure polysiloxane resin, wherein the block structure is obtained by reaction of (B1) rigid polysiloxane resin and (B2) flexible polysiloxane linear polymer;(C) crosslinking agent with more than two hydrolysable functional groups;(D) condensation crosslinking catalyst;(E) adhesion promoter;(F) organic solvent etc..The application realizes the synergistic unity of high strength and high toughness of coating, and widens the use temperature range of organic silicon material.

Description

Technical Field

[0001] This invention belongs to the field of silicone resin modification technology, specifically relating to a high-strength, low-temperature resistant organosilicon resin coating with a block structure and its preparation method. This coating can be used as a protective material for the surface of electronic circuit boards, suitable for long-term protection applications in complex environments and under low-temperature conditions. Background Technology

[0002] In the actual operation of electronic appliances, circuit boards are subjected to complex and variable service environments, including chemical corrosion, mechanical vibration, dust erosion, salt spray, moisture, and high and low temperature cycling. Under these varied and complex environmental conditions, circuit boards are prone to corrosion, material softening, structural deformation, and mold growth, which can lead to serious malfunctions such as short circuits, poor contact, and even system failure. Therefore, it is usually necessary to coat the surface of circuit boards with a conformal coating to form a protective coating with functions such as moisture resistance, salt spray resistance, and mold resistance. This coating, also known as conformal coating or three-proof paint, improves the environmental adaptability and reliability of the circuit boards and their components.

[0003] Currently, commonly used conformal coating systems include polyurethane, acrylic (solvent-based and UV-cured), alkyd resin, and silicone systems. Among them, silicone materials, due to their Si–O–Si molecular backbone structure, exhibit significant semi-organic and semi-inorganic characteristics. Therefore, they have outstanding advantages in high and low temperature resistance, chemical inertness, and electrical insulation properties, and have been widely used in the field of electronic protection.

[0004] However, existing silicone conformal coatings still have significant limitations in application, especially in extreme low-temperature environments where their performance deficiencies become more pronounced. Taking traditional rubber-based silicone conformal coatings as an example, their main molecular chain is typically polydimethylsiloxane, which is prone to crystallization or ordering at temperatures around -40 °C. This leads to a significant increase in material hardness and internal stress, resulting in coating cracking and even delamination from the substrate interface. On the other hand, while traditional resin-modified silicone conformal coatings improve mechanical strength to some extent, the increased proportion of rigid components in their structure still makes them prone to insufficient toughness at low temperatures, potentially leading to low-temperature brittleness. Therefore, the overall performance of existing silicone conformal coatings in extreme low-temperature environments remains significantly limited. Their low-temperature resistance is approaching or has reached its application limit, making it difficult to meet the long-term stable protection requirements under special low-temperature service conditions such as aerospace, polar equipment, and outdoor high-altitude electronic devices. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a high-strength, low-temperature resistant silicone resin coating with a block structure and its preparation method. This method combines (A) a polydimethylsiloxane copolymer with hydroxyl groups or at least two hydrolyzable functional groups at the ends of its molecular chains and substituents other than methyl groups on the side groups of its main chain, and (B) a polysiloxane resin with a block structure. The introduction of substituents other than methyl groups on the side groups of the main chain of (A) disrupts the molecular regularity of the linear polydimethylsiloxane, avoiding the problem of reduced flexibility caused by crystallization at low temperatures. Simultaneously, the use of the block structure of (B) silicone resin – linear polysiloxane – silicone resin, by introducing silicone resin segments, improves the overall mechanical strength of the material on the one hand, and effectively suppresses the crystallization behavior of the linear polysiloxane segments in the block structure at low temperatures on the other hand, achieving a synergistic unity of high strength and high toughness. This overcomes the technical bottleneck of traditional polysiloxane coatings, which struggle to balance strength and toughness at low temperatures, and broadens the operating temperature range of silicone materials.

[0006] The purpose of this invention is to develop a high-strength, low-temperature resistant silicone resin coating with a block structure, thereby broadening the operating temperature range of silicone materials, especially suitable for long-term protective applications in complex and low-temperature environments.

[0007] A high-strength, low-temperature resistant silicone resin coating with a block structure includes:

[0008] (A) A polydimethylsiloxane copolymer whose molecular chain ends contain hydroxyl groups or at least two hydrolyzable functional groups and whose molecular chain side groups contain other substituents besides methyl groups;

[0009] (B) A polysiloxane resin containing a block structure, wherein the block structure is composed of:

[0010] (B1) Rigid polysiloxane resin and

[0011] (B2) Obtained by reacting a flexible polysiloxane linear polymer;

[0012] (C) Crosslinking agents with hydrolyzable functional groups;

[0013] (D) Catalysts for condensation crosslinking;

[0014] (E) Adhesion promoter;

[0015] (F) Organic solvents, etc.

[0016] In this coating, the introduction of substituent groups other than methyl groups on the side groups of the main chain of (A) disrupts the molecular regularity of linear polydimethylsiloxane, avoiding the problem of reduced flexibility caused by crystallization at low temperatures. At the same time, the use of a block structure of (B) silicone resin-linear polysiloxane-silicone resin, by introducing silicone resin segments, improves the overall mechanical strength of the material on the one hand, and the resin body structure effectively inhibits the crystallization behavior of linear polysiloxane segments in the block structure at low temperatures, achieving a synergistic unity of high strength and high toughness, breaking through the technical bottleneck of traditional polysiloxane coatings that are difficult to balance strength and toughness at low temperatures.

[0017] Further, (A) is a polydimethylsiloxane copolymer with hydroxyl groups or at least two hydrolyzable functional groups at the ends of the molecular chain and substituents other than methyl groups on the side groups of the molecular chain, as shown in formula (I):

[0018] Formula (I)

[0019] Wherein, X is a hydroxyl group or an alkoxy group, methyl ethyl ketone oxime group, acyloxy group, alkenoxy group, etc. with 1 to 4 carbon atoms, preferably a hydroxyl or methoxy group, and m is 0, 1 or 2;

[0020] Z is an oxygen atom, or a hydrocarbon group with 1 to 4 carbon atoms, such as ethylene or propylene, or a divalent functional group as shown in formula (II):

[0021] Equation (II);

[0022] R is a hydrocarbon group, aryl group, or other substituted hydrocarbon group with 1-20 carbon atoms, substituted aryl group, etc.

[0023] R 1 It is a hydrocarbon group with 8-20 carbon atoms, such as octyl, decanyl, etc., or an aryl group such as phenyl, naphthyl, phenylethyl, etc., preferably octyl or phenyl;

[0024] R 2 Methyl or with R 1 For the same functional group, methyl or phenyl is preferred;

[0025] x and y are any values ​​from 5 to 2000, and y / (x+y) = 0.03 to 0.15; and satisfy (A) a viscosity of 100 mPa·s to 300000 mPa·s at 25°C, preferably 600 mPa·s to 100000 mPa·s. In some embodiments, the viscosity of A is 600 mPa·s to 5000 mPa·s; in other embodiments, the viscosity of A is 2000 mPa·s to 10000 mPa·s; and in still other embodiments, the viscosity of A is 10000 mPa·s to 100000 mPa·s.

[0026] The preparation method of the polysiloxane with hydroxyl groups or at least two hydrolyzable groups at the molecule end (A) is well known to those skilled in the art. It can be obtained by anionic ring-opening equilibrium reaction of methyl-containing siloxane cyclic compounds such as octamethylcyclotetrasiloxane (D4) and phenyl-containing siloxane cyclic compounds such as tetramethyltetraphenylcyclotetrasiloxane, followed by the use of water as a capping agent. See US Patent 4250290A for details. Alternatively, it can be obtained by condensation capping of the aforementioned hydroxyl-terminated polysiloxane with monomers containing multiple hydrolyzable functional groups such as methyltrimethoxysilane and tetramethoxysilane. Alternatively, it can be synthesized by anionic ring-opening equilibrium reactions of methyl-containing siloxane cyclic compounds such as octamethylcyclotetrasiloxane (D4) and phenyl-containing siloxane cyclic compounds such as tetramethyltetraphenylcyclotetrasiloxane, using vinyl-containing end-capping agents such as 1,1,3,3-tetramethyl-1,3-divinyldisiloxane for end-capping, followed by hydrosilylation of the obtained vinyl-terminated polysiloxane with hydrogen-containing polyalkoxysilanes, such as with trimethoxysilanes. The above-mentioned alkoxy-terminated modification synthesis methods are known and can be obtained through patents such as US 4962174A and US4731411A.

[0027] Further, (B) is a block-structured polysiloxane resin, wherein the block structure is obtained by reacting (B1) a rigid polysiloxane resin and (B2) a flexible linear polysiloxane polymer to form a silicone resin-linear polysiloxane-silicone block structure, the reaction process being as follows: Figure 1 As shown. Figure 1 middle, Represents R 3 n SiO (4-m-n) / 2 , ️Represents Si(CH3)2O(Si(CH3)2 O) r Si(CH3)2.

[0028] Among them, the polysiloxane resin (B1), which has a rigid structure, has the structure R 3 n R 4 m SiO (4-m-n) / 2 Among them, R 3 The group is an inert group such as alkyl, substituted alkyl, aryl, etc.; alkyl groups such as methyl, ethyl, propyl, octyl, etc., with methyl being preferred; aryl groups such as phenyl, naphthyl, methylphenyl, etc., with phenyl being preferred; substituted alkyl groups such as trifluoropropyl, perfluorooctyl, chloropropyl, etc., with trifluoropropyl being preferred; R 3 Methyl and phenyl are preferred;

[0029] R 4 For use with R in flexible polysiloxane linear polymers (B2) 5The functional groups react with each other, and the reaction can be one or more of the following: condensation reaction, hydrosilylation reaction, carbamate reaction, and reaction between amino and epoxy groups. In terms of the ease of obtaining (B1) and (B2), condensation reaction and hydrosilylation reaction are preferred, and condensation reaction is more preferred.

[0030] As a rigid resin, (B1) has a structure composed of chains containing M, D, T, and Q structures. The naming of these structures is well-known to those skilled in the art and can be found in patents such as US 12534578B2. Here, M represents Si with three organic groups attached (excluding oxygen), D represents Si with two organic groups attached (excluding oxygen), T represents Si with one organic group attached (excluding oxygen), and Q represents Si chains whose groups are all oxygen. Preferably, (B1) is an MQ resin or T resin (i.e., silsesquioxane resin) containing hydroxyl groups. MQ resin can be prepared according to US 2676182A, US 3627851A, US 3772247A, CN 100532431C, etc., or can be obtained commercially, such as XJY-8205 methylMQ resin from Jiangxi Xinjiayi New Materials Co., Ltd., and CF-90 methylMQ resin from Sichuan Chenfei Technology Co., Ltd. T resin can be prepared according to the method in US 5075153A, etc.

[0031] As a flexible linear polysiloxane polymer (B2), its structure is shown in formula (III):

[0032] Equation (III)

[0033] Where r is a value of 5-100, so that (B2) has a viscosity of 10-200 mPa·s at room temperature, preferably 20-100 mPa·s. 5 To be compatible with R in (B1) 4 Interreactive functional groups. When r is too small, the viscosity of (B2) is too low, resulting in insufficient coating toughness; when r is too large, the viscosity of (B2) is too high, making the coating prone to phase separation.

[0034] When the reaction between (B1) and (B2) is a condensation reaction, R is preferred. 4 For hydroxyl group, R 5The group is a silane group, hydroxyl group, or a group containing silaneoxy groups such as trimethoxysiloxy-Si(OCH3)3, methyldimethoxysiloxy-SiCH3(OCH3)2, etc. The reaction between (B1) and (B2) can be carried out under the action of a condensation-type catalyst that does not cause the (B2) rearrangement reaction. The catalyst can be a titanium-containing catalyst such as isopropyl titanate, butyl titanate, tert-butyl titanate; a tin-containing catalyst such as tin isooctanoate, dibutyltin dilaurate, dibutyltin diacetate, etc.; a weak acid such as formic acid, acetic acid; a weak base such as diethylamine, triethylamine, tetramethylguanidine, etc.; or a salt formed by organic carboxylic acids and organic bases such as tetramethylguanidine isooctanoate, tetramethylguanidine trifluoromethanesulfonate, etc. The amount of the catalyst is 0.01-5% of the total mass of (B1) and (B2), preferably 0.1-2%.

[0035] When the reaction between (B1) and (B2) is an addition reaction, R is preferred. 4 For vinyl, R 5 The reaction between (B1) and (B2) can be carried out in the presence of metal catalysts such as platinum, rhodium, rubidium, ruthenium, and iron, with platinum and rhodium-containing catalysts being preferred, such as Karstedt catalysts and Wilkinson's catalysts. The amount of catalyst, calculated by weight of the metal elements, is 1-100 ppm of the total amount of (B1) and (B2), preferably 5-20 ppm.

[0036] The reaction between (B1) and (B2) can be carried out under conditions containing an organic solvent that is a good solvent for both (B1) and (B2) and does not affect the reaction between them. Examples of such organic solvents include: aromatic hydrocarbon solvents, such as toluene and xylene; aliphatic hydrocarbon solvents, such as hexane, octane, and isoalkanes; ether solvents, such as diisopropyl ether and 1,4-dioxane; and mixtures of the above solvents. The amount of solvent used is 50-500 parts, preferably 100-200 parts, based on a total of 100 parts of (B1) + (B2).

[0037] The weight ratio of the reaction between (B1) and (B2) is 10-90:90-10, preferably 30-70:70-30. In the aforementioned high-strength, low-temperature resistant silicone coating, the content of (B) is 30-200 parts compared to 100 (A), preferably 50-100 parts. When the content of (B) is too low, the resulting coating strength is insufficient; when the content of (B) is too high, the viscosity of the resulting low-temperature resistant coating is too high before curing, which is not conducive to application and construction.

[0038] As a linear flexible polysiloxane (B2), it is preferred to have an alkoxy-terminated structure, such as a hydroxyl-terminated prepolymer obtained by condensation of a diekoxy monomer according to patent US6433204B1, which is then end-capped with a polyalkoxy silane such as methyltrimethoxysilane. Alternatively, octamethylcyclotetrasiloxane can be used for ring opening, followed by the use of 1,1,3,3-dimethoxysilane as a capping agent to obtain a silane-hydrosiloxane, which is then end-capped using a vinyl-containing polyalkoxy monomer such as vinyltrimethoxysilane or vinyltriethoxysilane.

[0039] Further, (C) is a crosslinking agent having two or more hydrolyzable functional groups. The hydrolyzable functional groups are alkoxy groups (such as methoxy, ethoxy, propoxy, etc.), ketoxime groups, acyloxy groups, alkenoxy groups, etc., preferably methoxy groups. When (C) contains two or more methoxy groups, it mainly includes tetramethyl orthosilicate, methyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, phenyltrimethoxysilane, phenylmethyldimethoxysilane, or 1,2-bis(trimethoxysilyl)ethane, or partial hydrolysis products thereof.

[0040] Based on weight, the amount of crosslinking agent (C) having two or more hydrolyzable functional groups is 1-10 parts, preferably 3-6 parts, compared to the sum of 100 parts of (A) and (B) excluding solvent.

[0041] Furthermore, the catalyst for the (D) condensation crosslinking is a titanium-containing or tin-containing catalyst. The titanium-containing catalyst includes butyl titanate, tert-butyl titanate, isopropyl titanate, or titanium chelates obtained by reacting these titanates with compounds containing β-diketone structures, such as reaction chelates with ethyl acetoacetate, such as Dorf Ketal's Tyzor® 726. The tin-containing catalyst includes dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, etc. From the perspective of environmental protection and storage stability, titanium-containing catalysts are preferred.

[0042] Based on weight, the content of catalyst (D) is 0.01-10 parts, preferably 0.1-5 parts, relative to the total of 100 parts of (A) and (B) excluding solvent.

[0043] Furthermore, the adhesion promoter (E) includes silane coupling agents containing epoxy groups, such as Silquest A-187 and Silquest A-186 from Momentive; silane coupling agents containing amino groups, such as Silquest A-1100, A-1120, and A-1130 from Momentive; and coupling agents containing silicon-nitrogen heterocyclic structures, such as Silquest A-link 597 from Momentive. Coupling agents containing epoxy or amino groups are preferred.

[0044] The content of adhesion promoter (E) is 0.01-10 parts by weight, preferably 0.5-5 parts, relative to the sum of (A) and (B) excluding solvent, relative to 100 parts.

[0045] Further, the solvent (F) includes: aromatic hydrocarbon solvents, such as toluene and xylene; aliphatic hydrocarbon solvents, such as hexane, octane, and isoalkanes (e.g., trade name Isopar™ C); ether solvents, such as diisopropyl ether and 1,4-dioxane; environmentally friendly silicon-containing solvents such as hexamethyldisiloxane (e.g., trade name DOWSIL™ OS-10), octamethyltrisiloxane (e.g., trade name DOWSIL™ OS-20), decamethyltetrasiloxane (e.g., trade name DOWSIL™ OS-30), decamethylcyclopentasiloxane, methyltris(trimethylsiloxy)silane, tetra(trimethylsiloxy)silane, and mixtures of the above solvents. Toluene, isoalkanes (e.g., trade name Isopar™ C), environmentally friendly silicon-containing solvents, and octamethyltrisiloxane (e.g., trade name DOWSIL™ OS-20) are preferred.

[0046] Based on parts by weight, the content of solvent (F) is 0-500 parts, preferably 0-200 parts, relative to 100 parts of the total of (A) and (B) excluding solvent. Optionally, the total amount of F includes the solvent introduced during the reaction of (B1) and (B2) to prepare (B).

[0047] Furthermore, the block-structured high-strength low-temperature resistant silicone resin coating may also contain other components, including fillers, pigments, dyes, fluorescent indicators, heat-resistant additives, antifungal agents, and any one or more of them.

[0048] Furthermore, the block-structured high-strength, low-temperature resistant silicone resin coating can be obtained by the following method:

[0049] First, react (B1) and (B2) to obtain a multibranched block structure (B). Then, mix (A) and (B), heat the mixture, and remove the solvent introduced during the reaction of (B1) and (B2) by pressure distillation. Add (F) to adjust the solid content. Then, under anhydrous conditions, add (C), (D), and (E) to the mixture of (A), (B), and (F) in any order and stir until homogeneous. Finally, package the mixture in a sealed container, such as an iron can with a galvanized coating.

[0050] Compared with traditional silicone conformal coatings, the present invention achieves at least the following beneficial effects:

[0051] The coating prepared by this invention not only retains the inherent excellent properties of organosilicon coatings, such as good high and low temperature resistance, high adhesion, and non-corrosiveness, but also effectively overcomes the technical bottleneck of traditional polysiloxane coatings in achieving both strength and toughness at low temperatures through block modification of the molecular structure, thus realizing a synergistic improvement in both high strength and high toughness. Therefore, this organosilicon resin coating significantly broadens the operating temperature range of the material while maintaining excellent environmental adaptability, and has good application prospects. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the preparation process of block-structured polysiloxane resin B;

[0053] Figure 2 This is the DMA curve of the coating in Example 1. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0055] 1. Synthesis example

[0056] Synthesis example 1

[0057] This example prepares (A) a polydimethyl / methylphenylsiloxane copolymer with trimethoxysilyl end groups:

[0058] In a 1L four-necked flask equipped with a condenser, stirrer, and nitrogen purging device, 61.8g of phenylmethylsiloxane cyclic compound (SP302, Liaoning Xinbang, 0.454mol phenylmethylsiloxane repeating unit), 528.72g of octamethylcyclotetrasiloxane (D4, Hubei Xingfa, 7.145mol dimethylsiloxane repeating unit), and 5.64g of 1,1,3,3-tetramethyl-1,3-divinyldisiloxane (VM-18, Quzhou Jiancheng, 0.03mol) were added. The mixture was heated to 80℃, and tetramethylammonium hydroxide silanol with an alkali content of 2.2% was added. 3.84 g of salt was stirred and heated to 100-110°C for 4 hours. Then, the temperature was raised to 150°C and stirred for 30 minutes to break down the enzyme and decompose tetramethylammonium hydroxide siloxane. After changing to a distillation apparatus, the low molecular weight molecules were removed under reduced pressure at 150-160°C and a vacuum degree ≤-0.095 MPa to obtain a vinyl-terminated polydimethyl / methylphenylsiloxane copolymer with a theoretical structure as shown in (1-1). The vinyl content was tested and analyzed to be 0.27 wt%, and the viscosity at 25°C was 1200 mPa·s.

[0059] (1-1)

[0060] 500g of the above-mentioned vinyl-terminated polydimethyl / methylphenylsiloxane copolymer was added to a 1L four-necked flask equipped with a condenser, a stirring device, a nitrogen purging device, and a distillation device. 0.5g of Karstedt platinum catalyst with a Pt content of 5000ppm was added, followed by 6.1g of trimethoxysilane (CAS: 2487-90-3, 0.05mol). The mixture was stirred at 80°C for 6h to obtain a polydimethyl / methylphenylsiloxane copolymer with a theoretical structure as shown in (1-2) and a terminal trimethoxysilyl group. The viscosity at 25°C was 2000mPa·s.

[0061] (1-2)

[0062] Synthesis example 2

[0063] This example demonstrates the preparation of a (B2) trimethoxysilyl-terminated flexible polysiloxane linear polymer:

[0064] In a 1L four-necked flask equipped with a condenser, a stirrer, and a nitrogen purging device, 67g of 1,1,3,3-tetramethyldisiloxane (VM-29, Quzhou Jiancheng, 0.5mol) and 766g of octamethylcyclotetrasiloxane (D4, Hubei Xingfa, 10.35mol of dimethylsiloxane linkages) were added. Then, 0.83g of trifluoromethanesulfonic acid was added as a catalyst. The reaction was carried out at 50-60℃ for 5h. Then, excess calcium carbonate was added to neutralize the trifluoromethanesulfonic acid. After filtration through filter paper, the mixture was transferred to a 1L reaction glass bottle equipped with a vacuum distillation device. The low molecular weight molecules were removed under reduced pressure at 120-130°C and a vacuum degree ≤-0.095MPa to obtain a terminal hydrogen-based polydimethylsiloxane with the theoretical structure as shown in (2-1). The test analysis showed that its silicon hydrogen content was 0.12wt% and its viscosity at 25℃ was 20mPa·s.

[0065] (2-1)

[0066] In a 1L four-necked flask equipped with a condenser, a stirrer, a nitrogen purging device, and a constant-pressure titration funnel, 88.8g of vinyltrimethoxysilane (GX-171, Anhui Sibao, 0.6mol) and 0.5g of Karstedt platinum catalyst with a Pt content of 5000ppm were added. The temperature was raised to 80°C, and then 500g of the above-mentioned hydrogen-terminated polydimethylsiloxane with the structure of (2-1) was added dropwise over 1 hour. After the addition was complete, the reaction was carried out at 80-90°C for 4 hours. Then, the low molecular weight polymers were removed under reduced pressure at 100-120°C and a vacuum degree ≤-0.095MPa to obtain a trimethoxysilyl-terminated flexible polysiloxane linear polymer with a viscosity of 45mPa.s at 25°C and a theoretical structure as shown in (2-2).

[0067] (2-2)

[0068] Synthesis example 3

[0069] This example demonstrates the preparation of a polysiloxane resin (B-1) containing a block structure:

[0070] The rigid resin (B1) used in this synthesis example is a hydroxyl-containing MQ resin: In a 2L four-necked flask equipped with a Dean-Strak reflux separator, a stirring device, and a nitrogen purging device, 500g of methyl MQ resin (CF-90-2, Chenfei Technology) with a hydroxyl content of about 2% was added, followed by 800g of toluene. The resin was dissolved by stirring at room temperature and then refluxed for 2 hours to remove water. After cooling to below 80°C, 250g of the (2-2) structure of the flexible polysiloxane linear polymer with trimethoxysilyl end caps obtained in Synthesis Example 2 was added. Then, 7.5g of a 0.2% tetramethylguanidine isooctanoate solution was added, and the condensation reaction was further refluxed for 4 hours. The solid content was adjusted to 80wt% to obtain a block-structured polysiloxane resin (B-1) with a viscosity of 2000mPa·s.

[0071] Synthesis example 4

[0072] This example demonstrates the preparation of a polysiloxane resin (B-2) containing a block structure:

[0073] The rigid resin (B1) used in this synthesis example is a phenyl-containing silsesquioxane resin: 500g of the phenyl-containing silsesquioxane resin (T) prepared according to Example 1 of patent CN 100532431C was added to a 2L four-necked flask equipped with a Dean-Strak reflux separator, a stirring device, and a nitrogen purging device. Ph 0.5 T Pr 0.5 Add 800g of toluene, stir to dissolve the resin at room temperature, and reflux at reflux temperature for 2 hours to remove water. After cooling to below 80°C, add 250g of the (2-2) structure trimethoxysilyl-terminated flexible polysiloxane linear polymer obtained in Synthesis Example 2, and then add 7.5g of 0.2% tetramethylguanidine isooctanoate solution. Further reflux condensation reaction for 4 hours, adjust the solid content to 70wt%, and obtain a block structure polysiloxane resin with a viscosity of 1500mPa·s.

[0074] II. Examples and Comparative Examples

[0075] The other raw materials used in the embodiments and comparative examples of this invention are as follows:

[0076] (A) The polydimethyl / methylphenylsiloxane copolymer with trimethoxysilyl end groups prepared in Synthesis Example 1;

[0077] (A*): α,ω-trimethoxysilyl-terminated polydimethylsiloxane, end-capped 107 adhesive, grade: J-15, viscosity at 25℃: 1500 mPa.s, Jiangsu Kexing Co., Ltd.; This material contains no benzene rings and cannot withstand extremely low temperatures.

[0078] (B-1) Synthetic Example 3 prepared a polysiloxane resin containing a block structure;

[0079] (B-2) Synthesis Example 4: Polysiloxane resin containing a block structure;

[0080] (B1) Methyl MQ silicone resin, CF-90-2, Sichuan Chenfei Technology Co., Ltd., relative molecular weight 4500, hydroxyl content 2.0wt%;

[0081] (C): Methyltrimethoxysilane, D-20, Hubei Xinlantian New Materials Co., Ltd.;

[0082] (D): Ethyl acetoacetate titanium complex, Tyzor® 726, Dorf Ketal, India;

[0083] (E): 1,3,5-Tris(trimethoxysilylpropyl)isocyanurate, Silquest A-link 597, Momentive Advanced Materials Group;

[0084] (F): Isopar™ C, ExxonMobil.

[0085] Example 1

[0086] This example uses (A) prepared in Synthesis Example 1 and (B-1) prepared in Synthesis Example 3:

[0087] 300g of the trimethoxysilyl-terminated polydimethyl / methylphenylsiloxane copolymer prepared in Synthesis Example 1 and 200g (by solids content) of the block-structured polysiloxane resin prepared in Synthesis Example 3 were added to a 2L four-necked flask equipped with a stirring, nitrogen protection, and distillation apparatus. Toluene introduced during the preparation of Synthesis Example 3 was removed under conditions of 90-100°C and a vacuum degree ≤-0.095MPa. Then, 500g of Isopar™ C solvent was added to adjust the solids content to about 50%. Then, 20g of crosslinking agent (C), 5g of Silquest A-link 597, and 10g of Tyzor® 726 were added at once. After stirring evenly, the block-structured high-strength low-temperature resistant silicone coating of the present invention was obtained and sealed in a 1L galvanized iron can.

[0088] Example 2

[0089] This example uses (A) prepared in Synthesis Example 1 and (B-2) prepared in Synthesis Example 4:

[0090] All operations were the same as in Example 1, except that 200g (calculated by solid content) of the block-structured polysiloxane resin prepared in Synthesis Example 3 was replaced with the block-structured polysiloxane resin (B-2) prepared in Synthesis Example 4.

[0091] Comparative Example 1

[0092] In this example, the MQ resin with structure (B1) is used instead of (B-1) prepared in Synthesis Example 3:

[0093] All operations were the same as in Example 1, except that 200g (calculated by solid content) of the block-structured polysiloxane resin prepared in Synthesis Example 3 was replaced with MQ resin with (B1) structure, CF-90-2, which is a rigid polysiloxane resin and has a non-block structure.

[0094] Comparative Example 2

[0095] This example uses (A) prepared in Synthesis Example 1, but does not use (B) polysiloxane resin containing a block structure:

[0096] 500g of the polydimethyl / methylphenylsiloxane copolymer with trimethoxysilyl end groups prepared in Synthesis Example 1 was added, and then 500g of Isopar™ C solvent was added to adjust the solid content to about 50%. Then, 20g of crosslinking agent (C), 5g of Silquest A-link 597, and 10g of Tyzor® 726 were added at once. After stirring evenly, the mixture was sealed in a 1L galvanized iron can.

[0097] Comparative Example 3

[0098] In this example, (A*) without a phenyl structure is used instead of (A) of the present invention, and (B-1) prepared in Synthesis Example 3 is used:

[0099] All operations were the same as in Example 1, except that 300g of the trimethoxysilyl-terminated polydimethyl / methylphenylsiloxane copolymer prepared in Synthesis Example 1 was replaced with Kexin's J-15(A*).

[0100] Comparative Example 4

[0101] In this example, (A*) without a phenyl structure is used instead of (A) of the present invention, and (B-2) prepared in Synthesis Example 4 is used:

[0102] All operations were the same as in Example 2, except that 300g of the trimethoxysilyl-terminated polydimethyl / methylphenylsiloxane copolymer prepared in Synthesis Example 1 was replaced with Kexin's J-15(A*).

[0103] III. Performance Testing

[0104] The formulations of different embodiments and comparative embodiments are shown in Table 1. The resin coatings prepared in each embodiment were injected into a surface-polished polytetrafluoroethylene mold frame. After solvent evaporation, a uniform sample with a thickness of 2 mm was prepared. After curing for 7 days at 23±2℃ and 50±10RH%, its tensile strength and elongation at break were tested according to the method of GB / T 528-2009. The test results are shown in Table 2.

[0105] Different coatings were applied to the clean surface of a glass fiber reinforced epoxy resin laminate (FR-4) PCB board. After solvent evaporation, a uniform coating with a thickness of 100±20μm was prepared. After curing for 7 days at 23±2℃ and 50±10RH%, the coating was cut into squares using a 2mm blade distance grid cutter according to the method of GB / T 9286-2021. After peeling off the standard pressure-sensitive adhesive tape, the coating peeling status was observed. The adhesion level was determined according to the standard 0-5 grade classification rule. Three parallel tests were conducted on each group of samples, and the worst result was taken as the final adhesion level.

[0106] The corrosion resistance of the coating to copper in this example was determined according to GB / T 38265.5-2021. A clean standard copper mirror sample was taken, and 0.05 mL of the coating was added using a microdropper. A 25% rosin isopropanol solution was provided as a negative control. The sample was placed in a sealed environment at 25±1℃ and 50±5% RH for 24 hours. After cleaning with isopropanol and drying, the sample was observed against the light. The copper film on the copper mirror remained intact, without any translucent white spots, blackening, or perforations, indicating that the original silicone coating solution was non-corrosive to copper.

[0107] The DMA curves of different coatings after curing were tested using a TA Q-800 DMA tester. Tensile mode was selected, the temperature range was set to 20~-85°C, and the temperature ramp was 3°C / min. The modulus change with temperature was measured. The DMA curve of the coating prepared in Example 1 is shown below. Figure 2 As shown in the figure, the turning point indicates that the material undergoes a secondary transformation and exhibits obvious crystallization.

[0108] Different coatings were applied to the surface of a clean FR-4 PCB board, which was then placed in a high and low temperature cycling aging test chamber. The aging process was carried out at a temperature range of -60°C to 105°C and a heating / cooling rate of 11°C / min. After aging for 1000 hours, the coating was observed to see if it cracked or peeled off from the PCB board.

[0109] Table 1. Formulation composition of each embodiment and comparative embodiment (unit: g)

[0110] Material Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 (A) 300 300 300 500 / / (A)* / / / / 300 300 (B-1) 200 / / / 200 / (B-2) / 200 / / / 200 (B1) / / 200 / / / (C) 20 20 20 20 20 20 (D) 10 10 10 10 10 10 (E) 5 5 5 5 5 5 (F) 500 500 500 500 500 500 total 1055 1055 1055 1055 1055 1055

[0111] Table 2 Coating performance of each embodiment and comparative embodiment

[0112] performance Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Tensile strength (MPa) 2.5 3.0 2.0 0.7 2.5 3.1 Elongation at break (%) 160 120 130 100 200 140 Adhesion (Grade) Hundreds of 0 Hundreds of 0 Hundreds of 0 Hundred Grids Level 2 Hundreds of 0 Hundreds of 0 Corrosiveness of bronze mirrors Uncorroded Uncorroded Uncorroded Uncorroded Uncorroded Uncorroded DMA modulus inflection point temperature (°C) -70 -65 -50 -60 -55 -50 Does the coating crack or peel during high and low temperature cycling? No cracks, no peeling No cracks, no peeling Slight crack, not peeled cracking and peeling Slight cracks, not peeled Slight cracks, not peeled

[0113] As demonstrated in Examples 1 and 2, using (A) a polydimethylsiloxane copolymer with hydroxyl groups or at least two hydrolyzable functional groups at the ends of the molecular chain and side groups containing substituents other than methyl groups on the main molecular chain, and (B) a polysiloxane resin containing a block structure, can reduce the modulus inflection point temperature of the coating to below -60°C (see Example 2). Figure 2 The tensile strength and elongation at break indicate that the coatings of the embodiments possess excellent strength and toughness. Furthermore, the high and low temperature cycling aging test results demonstrate that the coatings of the embodiments also exhibit excellent extreme low-temperature performance; no cracking or peeling occurred after 1000 hours of high and low temperature cycling aging. The synergistic use of (B) and (A) of the present invention not only improves the low-temperature resistance of the coating but also improves its strength and toughness, effectively overcoming the problem of traditional polysiloxane coatings struggling to balance strength and toughness at low temperatures. The copper mirror corrosion test results show that the coatings of the various embodiments of the present invention are non-corrosive to copper, indicating that the coatings prepared by the present invention have the excellent characteristic of being non-corrosive.

[0114] Comparative Example 1 uses a polydimethylsiloxane copolymer (A) with hydroxyl groups or at least two hydrolyzable functional groups at the end of the molecular chain and side groups containing substituents other than methyl groups to be compounded with a common rigid resin. Comparative Examples 3 and 4 use polysiloxane resins with hydroxyl groups or at least two hydrolyzable functional groups at the end of the molecular chain and whose main molecular chain consists entirely of dimethylsiloxane segments to be compounded with (B) polysiloxane resins containing block structures. As can be seen from Table 2, although these comparative examples can effectively improve the strength and toughness of the coating, the low-temperature resistance of the coating is insufficient, and slight cracking occurs after 1000h of high and low temperature cycling aging.

[0115] Comparative Example 2 used only (A) a polydimethylsiloxane copolymer with hydroxyl groups or at least two hydrolyzable functional groups at the end of the molecular chain and other substituents besides methyl on the side groups of the main molecular chain, without introducing (B) the block-structured polysiloxane resin of the present invention. As can be seen from Table 2, although the modulus transition temperature of the coating is reduced and the low-temperature performance is improved, the coating is not reinforced (low tensile strength and elongation at break), its strength and toughness are insufficient, and the adhesion does not reach grade 0 in the cross-cut adhesion test, resulting in cracking and peeling of the coating after 1000 hours of high and low temperature cycling aging.

[0116] This specification is intended to be illustrative rather than restrictive. Based on this invention, any substitutions and modifications made by those skilled in the art to some of the technical features without creative effort, according to the disclosed technical content, are all within the scope of protection of this invention.

Claims

1. A high-strength, low-temperature resistant organosilicon resin coating with a block structure, characterized in that, Includes the following components: A. A polydimethylsiloxane copolymer whose molecular chain ends with hydroxyl groups or at least two hydrolyzable functional groups and whose molecular chain side groups contain substituents other than methyl groups; B is a polysiloxane resin containing a block structure, wherein the block structure is composed of: B1 has rigid polysiloxane resin and B2 is obtained by reacting flexible polysiloxane linear polymers; C is a cross-linking agent with hydrolyzable functional groups; Catalysts for D-condensation crosslinking; E adhesion promoter; F organic solvent; The structure of A is as follows: ， Wherein, X is a hydroxyl group, an alkoxy group with 1 to 4 carbon atoms, a methyl ethyl ketone oxime group, an acyloxy group, or an alkenyloxy group; m is 0, 1, or 2; Z is an oxygen atom, or a hydrocarbon group with 1 to 4 carbon atoms, or a divalent functional group as shown below: ； R is a hydrocarbon group, aryl group, substituted hydrocarbon group or substituted aryl group with 1-20 carbon atoms; R 1 It is a hydrocarbon group or aryl group with 8-20 carbon atoms; R 2 It is methyl, or with R 1 Same functional groups; x and y are any values ​​from 5 to 2000, y / (x+y)=0.03~0.15; and the viscosity of A at 25℃ is 100mPa.s~300000mPa.s; The structure of B1 is R 3 n R 4 m SiO (4-m-n) / 2 , where R 3 It is an alkyl, substituted alkyl, or aryl group; R 4 To be consistent with R in B2 5 The functional groups that react with each other, calculated by weight, have a content of 30-200 parts of B compared to 100 parts of A; the weight ratio of B1 to B2 is 10-90:90-10. The structure of B2 is as follows: ， Where r is a value of 5-100, so that B2 has a viscosity of 10-200 mPa·s at room temperature.

2. The high-strength, low-temperature resistant organosilicon resin coating with a block structure according to claim 1, characterized in that, The mutual reactions are one or more of the following: condensation reaction, hydrosilylation reaction, carbamate reaction, and reaction between amino and epoxy groups.

3. The high-strength, low-temperature resistant organosilicon resin coating with a block structure according to claim 2, characterized in that, The reaction between B1 and B2 is a condensation reaction, R 4 For hydroxyl group, R 5 The catalyst is a silane group, hydroxyl group, or a group containing a silane group; B1 and B2 are carried out in the presence of a condensation catalyst that does not cause the B2 rearrangement reaction, and the amount of the catalyst is 0.01-5% of the total mass of B1 and B2; the condensation catalyst that does not cause the B2 rearrangement reaction is selected from one of isopropyl titanate, butyl titanate, tert-butyl titanate, tin isooctanoate, dibutyltin dilaurate, dibutyltin diacetate, formic acid, acetic acid, diethylamine, triethylamine, tetramethylguanidine, isooctanoate of tetramethylguanidine, and trifluoromethanesulfonate of tetramethylguanidine.

4. The high-strength, low-temperature resistant organosilicon resin coating with a block structure according to claim 2, characterized in that, The reaction between B1 and B2 is an addition reaction, R 4 For vinyl, R 5 It is a silane group; the reaction between B1 and B2 is carried out in the presence of a metal catalyst containing one of the following elements: platinum, rhodium, rubidium, ruthenium, or iron; the amount of catalyst is 1-100 ppm of the total amount of B1 and B2, calculated by weight of the metal element.

5. The high-strength, low-temperature resistant organosilicon resin coating with a block structure according to claim 3 or 4, characterized in that, The reaction between B1 and B2 is carried out under conditions containing an organic solvent, which is selected from one or more of toluene, xylene, hexane, octane, isoalkanes, diisopropyl ether, and 1,4-dioxane. The amount of organic solvent used is 50-500 parts based on 100 parts of the total mass of B1 and B2.

6. The high-strength, low-temperature resistant organosilicon resin coating with a block structure according to claim 5, characterized in that, The C is tetramethyl orthosilicate, methyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, phenyltrimethoxysilane, phenylmethyldimethoxysilane, or 1,2-bis(trimethoxysilyl)ethane; calculated by weight, the content of C is 1-10 parts compared to 100 parts of the total mass of A and B excluding solvent.

7. The high-strength, low-temperature resistant organosilicon resin coating with a block structure according to claim 6, characterized in that, D is one of tetrabutyl titanate, tert-butyl titanate, isopropyl titanate, and the reaction chelates of these titanates with ethyl acetoacetate, or one of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate. The E includes silane coupling agents containing epoxy groups, silane coupling agents containing amino groups, and coupling agents containing silicon-nitrogen heterocyclic structures; The F mentioned is one or more of toluene, xylene, hexane, octane, isoalkanes, diisopropyl ether, 1,4-dioxane, hexamethyldisiloxane, octamethyltrisiloxane, decamethylcyclopentasiloxane, methyltris(trimethylsiloxy)silane, and tetra(trimethylsiloxy)silane; Relative to 100 parts of the total mass of A and B excluding solvent, the content of D is 0.01-10 parts, the content of E is 0.01-10 parts, and the content of F is 0-500 parts.

8. The method for preparing the block-structured organosilicon high-strength low-temperature resistant resin coating according to any one of claims 1 to 7, characterized in that, Includes the following steps: First, react B1 and B2 to obtain a multi-branched block structure B. Then, mix A and B, and remove the solvent introduced during the reaction of B1 and B2 by pressure distillation. Add F to adjust the solid content. Then, under anhydrous conditions, add C, D, and E in any order to the mixture of A, B, and F and stir evenly to obtain a high-strength, low-temperature resistant organosilicon resin coating containing a block structure.

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