Silicone rubber surface coating with high adhesive strength and use method

Abstract

The invention relates to a high-adhesion-strength silicone rubber surface coating and a use method thereof, and the coating is formed by uniformly coating a composition of an organosilicon benzoxazine compound containing a phenolic hydroxyl group on the surface of silicone rubber and then carrying out a thermocuring process on the surface of the silicone rubber, the composition of the organosilicon type benzoxazine compound containing the phenolic hydroxyl group is prepared from the following components in parts by mass: 100 parts of the organosilicon type benzoxazine compound containing the phenolic hydroxyl group, 0 to 10 parts of a catalyst A, 0 to 400 parts of filler, 0 to 200 parts of an auxiliary agent and 0 to 10000 parts of a solvent. The phenolic hydroxyl group-containing organosilicon benzoxazine compound composition provided by the invention can regulate and control the surface properties of a silicone rubber material, has an obvious effect, and can significantly improve the surface free energy of the silicone rubber material; the method has an obvious advantage of improving the bonding performance of a silicone rubber material interface, and after surface modification of the modifier, the bonding strength of the surface of the silicone rubber material can reach 1.25 N / mm.

Description

TECHNICAL FIELD

[0001] The present application relates to a high adhesion strength silicone rubber surface coating and a use method, belonging to the field of high polymer materials and applications. BACKGROUND

[0002] Silicone rubber refers to a high-performance elastomer with a three-dimensional network structure formed by vulcanization, with a silicon-oxygen bond as the main chain and a silicon-carbon bond as the side chain connecting various organic substituents. Silicone rubber can be divided into heat vulcanized silicone rubber (also known as high temperature vulcanized silicone rubber HTV) and room temperature vulcanized silicone rubber RTV according to the vulcanization temperature. Heat vulcanized silicone rubber is the most widely used, which can be divided into methyl silicone rubber, methyl vinyl silicone rubber, methyl vinyl phenyl silicone rubber, etc. according to the different organic groups, and is mainly used for manufacturing various silicone rubber products. Room temperature vulcanized silicone rubber is often divided into polycondensation reaction type silicone rubber and addition reaction type silicone rubber, which is mainly used as an adhesive, a potting material or a mold. Silicone rubber has excellent properties such as high and low temperature resistance, weather resistance, non-pollution, high air permeability, electrical insulation, physiological inertia, etc., and is widely used in the fields of electronics and electrical appliances, power industry, automobile industry, aerospace, etc. In addition, silicone rubber is non-toxic, biocompatible, not damaged at high temperature, and has good physical and mechanical properties, which plays an irreplaceable role in the medical industry and daily life. These applications show the diversity and importance of silicone rubber in modern industry and technology.

[0003] In recent years, with the wide application of silicone rubber in the fields of flexible electronics, biomedical and new energy, the demand for surface treatment of formed silicone rubber products to increase functional coatings or change the original surface properties is increasingly prominent, and surface modification technology is increasingly valued in the field of silicone rubber bonding and extensive research has been carried out. Due to the softness and spiral shape of the silicone rubber molecular main chain, the polarity of the silicon-oxygen bond on the main chain is reduced or offset, and the non-polar and non-reactive substituent R group is on the outside of the spiral layer, resulting in a relatively low surface energy (<30 mN / m) of silicone rubber, which makes it difficult to achieve strong interaction (such as adhesion or bonding) with other substances through chemical reaction or intermolecular forces. In order to meet the specific needs of silicone rubber surface properties in practical applications (such as enhancing adhesion, improving wettability or giving special functions), it is necessary to carry out targeted surface modification.

[0004] Surface modification is a technique that modifies the surface of a material to obtain a new surface without changing the main properties of the original material. The core problem of silicone rubber surface modification is how to efficiently introduce active groups to adjust the chemical composition of the silicone rubber material surface, control the surface roughness and topological structure of the silicone rubber, and adjust the surface energy. Surface modification technology is generally divided into physical modification method and chemical modification method.

[0005] Physical modification methods are to modify the surface of silicone rubber by plasma, ultrasound, radiation, corona discharge and other physical technologies.

[0006] (1) Mechanical polishing treatment: The surface of silicone rubber is treated by sandpaper polishing, sandblasting and other mechanical methods to increase the surface roughness, increase the contact area of the coating or adhesive with the silicone rubber surface, and improve the adhesion strength of the coating and adhesive. For example, when silicone rubber is bonded with plastic parts, the bonding strength will be significantly improved after sandblasting treatment of the surface of silicone rubber. In addition, mechanical treatment may excessively damage the material surface, and excessive roughness may affect the bonding effect.

[0007] (2) Plasma treatment: The ionized gas generated by low-pressure discharge (glow, high frequency, etc.) interacts with the material surface. Treating silicone rubber with plasma can greatly improve its bonding strength. For example, Chinese patent document CN118695937A discloses a bonding method for silicone rubber treated by plasma. The surface of silicone rubber is treated by plasma to modify it into a hydrophilic surface, and its bonding strength is increased from 0.5 kgf / cm 2 to 30 kgf / cm 2 . Plasma treatment is limited by the size of the operation equipment and cannot be used to treat the surface of large-size silicone rubber materials. Moreover, the treatment effect decreases over time and has a time limit.

[0008] (3) Corona treatment: High voltage is applied to the surface of silicone rubber to generate corona discharge. During the corona treatment process, chemical reactions such as oxidation, crosslinking, breaking and exchange occur in the main chain structure of the polymer. It is commonly used for surface treatment of materials such as silicone rubber and thin film to improve their bonding effect with other materials.

[0009] (4) Radiation treatment: Ultraviolet rays are used to irradiate the surface of silicone rubber to cause photochemical reactions on the surface of silicone rubber and introduce polar groups. In addition, gamma irradiation can also be used to treat the surface of silicone rubber, and subsequent reversible addition-fragmentation chain transfer (RAFT) and chemical grafting methods can also be used for modification of biological materials. (See the paper: Controlled Surface Modification of Silicone Rubber by Gamma-Irradiation Followed by RAFT Grafting Polymerization, European Polymer Journal, 2020, 134:109817.)

[0010] The surface etching or grafting of silicone rubber surface by chemical reagents and chemical reactions is the main chemical modification method. The common chemical modification methods include chemical solution treatment method, chemical grafting treatment method and surface modifier treatment method.

[0011] (1) The chemical solution treatment method refers to the method of treating the surface of silicone rubber with specific chemical solution to introduce polar groups on the surface of silicone rubber. The commonly used chemical solution includes concentrated sulfuric acid, concentrated nitric acid and other strong oxidizing acids. The chemical treatment method uses corrosive liquid which is dangerous and harmful, has long processing time and high cost.

[0012] (2) The chemical grafting treatment method refers to the method of first treating the surface of silicone rubber to have polar groups, and then grafting hydrophilic substances to the surface of silicone rubber to improve the surface hydrophilicity. Xu Dong et al. prepared silane coupling agent Z-6020 / ethanol solution with different mass fractions, and coated it on the surface of silicone rubber to bond with glass. When w (Z-6020) =1%, the shear strength is 2.86 MPa. (See the paper: Xu Dong et al. Research on Silicone Rubber and Peeling Adhesion [J]. Electrical Porcelain Lightning Arrester, 2008(2):14-16)

[0013] (3) The surface modifier treatment method refers to the method of brushing or spraying modifier on the surface of silicone rubber to form a thin modified layer. The modified layer has good compatibility with silicone rubber and substrate, and the polar groups contained therein can interact with the substrate. This method is also called primer method. Using primer to modify the surface of silicone rubber is also an effective method to improve the adhesion strength. Chinese patent document CN104830225A discloses a primer for improving the adhesion strength between silicone rubber and polypropylene material and its preparation method, which is obtained by mixing silane coupling agent, phthalate compound, this kind of solvent, low boiling point solvent, isocyanic acid compound and organosilicon compound. The adhesion strength between polypropylene and silicone rubber is 1.50 MPa.

[0014] For the surface modification of silicone rubber catheter, the current market has formed a number of mature and series of solutions, such as directly coating hydrophilic substances on the surface of the material. The commonly used hydrophilic polymers include polyvinylpyrrolidone (PVP), polyacrylamide (PAM), polyethylene glycol (PEG), polyvinyl alcohol (PVA), etc. The silicone rubber is modified to form a hydrophilic coating or a lubricating and moisturizing layer, etc. Although these silicone rubber modification technologies and coatings have been widely promoted and applied, there are still aspects that need to be improved. For example, the polyethylene glycol modified coating is prone to oxidation and the hydrophilic coating has a short surface drying time; a large amount of photosensitive groups is used in the preparation process of the photocurable silicone rubber coating, etc. More importantly, the bonding strength of the above-mentioned medical silicone rubber coating is low, which limits the use of these silicone rubber modified coatings. (See the paper: Chen Chikun et al. Research status of medical catheter polymer super-lubricating and hydrophilic coating [J]. Polymer Bulletin, 2022, (10): 27-32)

[0015] The above-mentioned technologies can modify the surface of silicone rubber to some extent, but the bonding strength of the silicone rubber surface modification coating still needs to be further improved. SUMMARY

[0016] In view of the above-mentioned prior art, especially in view of the fact that the bonding strength of the surface modification coating of the silicone rubber material in the prior art is generally poor, the present application provides a silicone rubber surface coating with high adhesion strength and a use method, which has obvious advantages in performance regulation and interfacial bonding of silicone rubber surface. The silicone rubber surface coating with high adhesion strength provided by the present application is a composition of a phenolic hydroxyl-containing organosilicon benzoxazine compound, which forms a coating on the surface of the silicone rubber through a thermal curing process. The coating reaction conditions are simple and controllable, and the bonding strength is high; in addition, the coating itself has a large number of active groups, which provides convenient conditions for further modification of other coatings or direct functional application.

[0017] The technical solution for achieving the above-mentioned application purpose can be summarized as follows:

[0018] The silicone rubber surface coating with high adhesion strength is a composition of a phenolic hydroxyl-containing organosilicon benzoxazine compound uniformly coated on the surface of the silicone rubber, and then formed on the surface of the silicone rubber through a thermal curing process;

[0019] The composition of the phenolic hydroxyl-containing organosilicon benzoxazine compound includes the following components by mass: phenolic hydroxyl-containing organosilicon benzoxazine compound 100 parts, catalyst A 0-10 parts, filler 0-400 parts, auxiliary 0-200 parts, and solvent 0-10000 parts.

[0020] According to the present application, preferably, the phenolic hydroxyl group-containing organosilicon type benzoxazine compound has the structure shown in formula (I);

[0021] ;

[0022] Formula (I).

[0023] According to the present application, preferably, the catalyst A is benzenesulfonic acid, acetic acid, sodium hydroxide and hexanediamine, and further preferably hexanediamine, and the use amount is preferably 0-3 parts.

[0024] According to the present application, preferably, the filler is fumed white carbon black, precipitated white carbon black, carbon black, calcium carbonate, aluminum hydroxide or / and magnesium hydroxide and various special treated compounds, and more preferably silazane treated white carbon black. The use amount of the filler is 0-400 parts, and preferably 0-30 parts.

[0025] According to the present application, preferably, the auxiliary agent is thermal oxygen stabilizer, flame retardant, conductive agent, foaming agent, deep curing agent, pigment or / and plasticizer; and further preferably iron red, and the use amount is preferably 0-10 parts.

[0026] According to the present application, preferably, the solvent is toluene, tetrahydrofuran, n-hexane, petroleum ether, isopropyl alcohol, ethanol, methanol, diethyl ether, ethyl acetate and a mixture of two or more thereof, and further preferably toluene, tetrahydrofuran, n-hexane, isopropyl alcohol, diethyl ether, ethyl acetate and a mixture of two thereof; and the use amount is preferably 100-10000;

[0027] According to the present application, preferably, the solvent is a mixture of toluene and n-hexane, and the volume ratio of the two solvents is 1:0.1-10, and preferably 1:0.5-5.

[0028] According to the present application, preferably, the solvent is a mixture of tetrahydrofuran and isopropyl alcohol, and the volume ratio of the two solvents is 1:0.1-10, and preferably 1:0.5-5.

[0029] According to the present application, preferably, the solvent is a mixture of diethyl ether and ethyl acetate, and the volume ratio of the two solvents is 1:0.1-10, and preferably 1:0.5-5.

[0030] According to the present application, preferably, the phenolic hydroxyl group-containing organosilicon type benzoxazine compound composition comprises the following components: phenolic hydroxyl group-containing organosilicon type benzoxazine compound 100 parts, catalyst A 1-3 parts, filler 1-30 parts, auxiliary agent 1-10 parts, and solvent 100-10000 parts.

[0031] According to the application, the heat curing process is to coat the composition of the phenolic hydroxyl-containing organosilicon type benzoxazine compound on the surface of the silicone rubber, and then to realize the preparation of the silicone rubber surface modification coating through programmed temperature rising.

[0032] According to the application, preferably, the programmed temperature rising is a temperature rising process from an initial temperature to a terminal temperature through a plurality of "temperature rising-constant temperature" links with a certain temperature difference as a gradient. The temperature difference is a controllable temperature gradient allowed in the silicone rubber surface modification, including any temperature difference between 5℃ and 100℃, preferably 10℃. In the "temperature rising-constant temperature" link, the temperature rising rate is any temperature rising rate between 0.1℃ / min and 20℃ / min, preferably 10℃ / min. In the "temperature rising-constant temperature" link, the constant temperature time is any time between 1 min and 180 min, preferably any time between 30 min and 150 min, more preferably 120 min. The initial temperature is any temperature between the room temperature and the terminal temperature, preferably 60℃. The terminal temperature is a temperature allowed in the silicone rubber surface modification, which can realize the best performance of the silicone rubber surface modification coating in this occasion, including a certain best curing temperature between 60℃ and 200℃ obtained through actual test.

[0033] According to the application, the use method of the silicone rubber surface coating with high adhesive strength comprises the following steps:

[0034] directly using the silicone rubber surface modification coating as the silicone rubber surface modification coating;

[0035] or bonding the silicone rubber surface modification coating with other interfaces by using an adhesive;

[0036] or coating a new coating on the surface of the silicone rubber surface modification coating.

[0037] According to the application, the phenolic hydroxyl-containing organosilicon type benzoxazine compound with the structure shown in formula (I) is also provided as the use of the silicone rubber surface modification and the preparation of the silicone rubber coating. The compound can improve the bonding performance of the silicone rubber material surface.

[0038] The beneficial effects of the application are as follows:

[0039] 1. The phenolic hydroxyl-containing organosilicon type benzoxazine compound of the application can obviously regulate the properties of the silicone rubber material surface, and can significantly improve the surface free energy of the silicone rubber material.

[0040] 2. The phenolic hydroxyl-containing organosilicon type benzoxazine compound of the application has obvious advantages in improving the bonding performance of the silicone rubber material interface, and the bonding strength of the silicone rubber material surface after the surface modification can reach 1.25 N / mm.

[0041] 3、The silicone rubber surface coating of the present application is flexible in use, and can be used as a primer or an adhesive, and can meet the modification and adhesion requirements in various occasions, and has wide application prospect and good market prospect. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The infrared spectrum of the silicone type benzoxazine compound prepared in Example 1.

[0043] Figure 2 The nuclear magnetic hydrogen spectrum of the silicone type benzoxazine compound prepared in Example 1.

[0044] Figure 3 The coating state of the silicone type benzoxazine compound mixed with different proportions of solvents in Examples 2, 8 and 9.

[0045] Figure 4 The contact angle of water with the surface of the methyl silicone rubber in Test Example 1 of the present application.

[0046] Figure 5 The contact angle of the modifier solution with the surface of the methyl silicone rubber in Test Example 2 of the present application.

[0047] Figure 6 The contact angle of water with the surface of the modified methyl silicone rubber in Test Example 3 of the present application.

[0048] Figure 7 The contact angle of water with the surface of the phenyl silicone rubber in Test Example 1 of the present application.

[0049] Figure 8 The contact angle of the modifier solution with the surface of the phenyl silicone rubber in Test Example 2 of the present application.

[0050] Figure 9 The contact angle of water with the surface of the modified phenyl silicone rubber in Test Example 3 of the present application. DETAILED DESCRIPTION

[0051] The present application provides a silicone rubber surface coating with high adhesion strength and a use method, which has obvious advantages in performance regulation and interface adhesion of silicone rubber surface. The silicone rubber surface coating with high adhesion strength provided by the present application is a composition of a silicone type benzoxazine compound containing phenolic hydroxyl groups, which forms a coating on the surface of the silicone rubber through a thermal curing process. The coating has simple and controllable reaction conditions, high bonding strength, and a large number of active groups, which provides convenient conditions for further modification of other coatings or direct functional application.

[0052] The high adhesion strength silicone rubber surface coating of the present application is a composition of a phenolic hydroxyl-containing organosilicon benzoxazine compound uniformly coated on the surface of a silicone rubber, and then formed on the surface of the silicone rubber through a thermal curing process.

[0053] The composition of the phenolic hydroxyl-containing organosilicon benzoxazine compound includes the following components by mass: 100 parts of a phenolic hydroxyl-containing organosilicon benzoxazine compound, 0-10 parts of a catalyst A, 0-400 parts of a filler, 0-200 parts of an auxiliary agent, and 0-10000 parts of a solvent.

[0054] According to the present application, the phenolic hydroxyl-containing organosilicon benzoxazine compound has the structure shown in formula (I), which can be prepared as reported in the literature (Sun, A. B. Preparation and Properties of Siloxane-Modified Benzoxazines [D]. Shandong University, 2020.).

[0055] ;

[0056] Formula (I).

[0057] According to the present application, the catalyst A is a compound capable of catalyzing the ring-opening polymerization of benzoxazine, including various types of Lewis acids and Lewis bases. In one or more preferred embodiments, the catalyst A is benzenesulfonic acid, acetic acid, sodium hydroxide, and hexanediamine, and further preferably hexanediamine, with a preferred usage of 0-3 parts.

[0058] According to the present application, the filler is various additives that can improve the bonding strength of the composition to the surface of the silicone rubber. In one or more preferred embodiments, the filler is fumed silica, precipitated silica, carbon black, calcium carbonate, aluminum hydroxide, or / and magnesium hydroxide, as well as various specially treated compounds, and is more preferably silazane-treated silica. The usage of the filler is 0-400 parts, preferably 0-30 parts.

[0059] According to the present application, the auxiliary agent is various auxiliary agents that do not significantly reduce the bonding strength of the composition to the surface of the silicone rubber after being added, including various functional components and non-functional components. In one or more preferred embodiments, the auxiliary agent is a thermal oxygen stabilizer, a flame retardant, a conductive agent, a foaming agent, a deep curing agent, a pigment, or / and a plasticizer; and is further preferably iron red, with a preferred usage of 0-10 parts.

[0060] According to the present application, the solvent is an organic solvent capable of dissolving each component in the composition. In one or more preferred embodiments, the solvent is toluene, tetrahydrofuran, n-hexane, petroleum ether, isopropyl alcohol, ethanol, methanol, diethyl ether, ethyl acetate, and a mixture of two or more thereof, and further preferably toluene, tetrahydrofuran, n-hexane, isopropyl alcohol, diethyl ether, ethyl acetate, and a mixture of two thereof; and the use amount is preferably 100-10000 parts.

[0061] Preferably, the solvent can also be a mixture of toluene and n-hexane, and the volume ratio of the two solvents is 1:0.1-10, preferably 1:0.5-5. Alternatively, the solvent is a mixture of tetrahydrofuran and isopropyl alcohol, and the volume ratio of the two solvents is 1:0.1-10, preferably 1:0.5-5. Alternatively, the solvent is a mixture of diethyl ether and ethyl acetate, and the volume ratio of the two solvents is 1:0.1-10, preferably 1:0.5-5.

[0062] In one or more preferred embodiments, the composition of the phenolic hydroxyl group-containing organosilicon type benzoxazine compound comprises the following components by mass: phenolic hydroxyl group-containing organosilicon type benzoxazine compound 100 parts, catalyst A 1-3 parts, filler 1-30 parts, additive 1-10 parts, and solvent 100-10000 parts.

[0063] According to the present application, the heat curing process is to coat the composition of the phenolic hydroxyl group-containing organosilicon type benzoxazine compound on the surface of silicone rubber, and then to realize the preparation of the modified coating on the surface of silicone rubber through programmed temperature rising. In one or more preferred embodiments, the programmed temperature rising is a temperature rising process from the initial temperature to the final temperature through a plurality of "temperature rising-constant temperature" links with a certain temperature difference as the gradient. The temperature difference is a controllable temperature gradient allowed in the modification of the surface of silicone rubber, including any temperature difference between 5°C and 100°C, preferably 10°C. In the "temperature rising-constant temperature" link, the temperature rising rate is any temperature rising rate between 0.1°C / min and 20°C / min, preferably 10°C / min. In the "temperature rising-constant temperature" link, the constant temperature time is any time between 1 minute and 180 minutes, preferably any time between 30 minutes and 150 minutes, and more preferably 120 minutes. The initial temperature is any temperature between room temperature and the final temperature, preferably 60°C. The final temperature is a temperature allowed in the modification of the surface of silicone rubber, which can realize the best performance of the modified coating on the surface of silicone rubber in this case, including a certain best curing temperature obtained through actual test between 60°C and 200°C.

[0064] According to the present application, the use method of the high adhesion strength silicone rubber surface coating comprises the following steps:

[0065] directly used as a modified coating on the surface of silicone rubber;

[0066] or the silicone rubber surface modification coating is bonded to other interfaces with adhesives;

[0067] or a new coating is coated on the surface of the silicone rubber surface modification coating.

[0068] According to the present application, there is also provided the use of a phenolic hydroxyl-containing organosilicon benzoxazine compound having the structure shown in formula (I) for modifying the surface of silicone rubber and preparing a silicone rubber coating. The compound can improve the surface bonding properties of silicone rubber materials.

[0069] The present application is not described in detail, according to the prior art.

[0070] Principle of the present application:

[0071] The present application provides a silicone rubber surface coating material with high adhesion strength, which is formed on the surface of silicone rubber by a thermal curing process of a composition of a phenolic hydroxyl-containing organosilicon benzoxazine compound. The reaction route ingeniously combines the benzoxazine component and the organosilicon component together to construct a silicone rubber surface treatment system with double functions. The system takes full advantage of the low surface energy of organosilicon compounds, which can easily spread on the surface of silicone rubber materials, and the hydrogen bonding (O-H...O, O-H...N, O-H...Π) effect provided by the polar groups such as hydroxyl groups released after the ring-opening curing of benzoxazine. This design achieves double effects: on the one hand, the composition is more easily spread and infiltrated on the surface of silicone rubber through the "like dissolves like" principle; on the other hand, the special functional groups exposed on the inner and outer surfaces of the modified layer can provide high bonding strength between the coating and the silicone rubber surface, and also provide a basis for the functionalization of the coating and subsequent surface modification. This technology effectively breaks through the technical bottleneck that the wettability and bonding strength are difficult to be balanced in the traditional silicone rubber surface modification process.

[0072] .

[0073] The present application effectively inhibits the "coffee ring effect" in the surface treatment process of silicone rubber by optimizing and improving the solvent formula of the composition of the phenolic hydroxyl-containing organosilicon benzoxazine compound. When a solution containing a non-volatile solute is dried on a low surface energy substrate (such as silicone rubber), the droplet edge forms an outward capillary flow due to the fast evaporation rate, and the solute is carried to the edge and deposited, forming a ring-shaped uneven distribution. Since silicone rubber is a low surface energy material, it results in poor wettability of the solution, which exacerbates the edge pinning effect, further promotes ring deposition, and greatly affects the modification effect. (See the paper Deegan, R.D., Bakajin, O., Dupont, T.F.et al. Publisher Correction: Capillary flow as the cause of ring stains from dried liquid drops. Nature 592, E12 (2021). ). In order to overcome the coffee ring effect, the present application designs two kinds of mixed solvent solutions (preferably toluene and n-hexane, tetrahydrofuran and isopropanol, diethyl ether and ethyl acetate, etc.) strategy, through synergistic effect to regulate evaporation gradient, reduce the edge local rapid evaporation, thus solving the problem. There are similar strategies reported in the literature: the high permeability of one solvent promotes the diffusion of solute to the substrate, and the other solvent can balance the Marangoni flow and capillary flow (see the paper Sempels, W., De Dier, R., Mizuno, H.et al. Auto-production of biosurfactants reverses the coffee ring effect in a bacterial system.. Nat Commun 4, 1757 (2013). ), but the literature does not involve silicone rubber surface treatment, nor does it involve the composition formula of the present application.

[0074] The present application discards the previous literature reported sodium naphthalene solution treatment, plasma sputtering and other existing silicone rubber surface treatment schemes, and adopts the strategy of modifying the surface of silicone rubber with a composition of phenolic hydroxyl-containing organosilicon benzoxazine compound, which more conveniently realizes the precise regulation of the surface properties of silicone rubber and significantly improves the bonding strength between the surface of silicone rubber material and the modified coating. Due to the simple and controllable preparation conditions and high bonding strength, unexpected effects have been achieved.

[0075] The composition of the phenolic hydroxyl-containing organosilicon type benzoxazine compound designed in the application contains a benzoxazine group, which has the advantage of zero volume shrinkage during ring-opening copolymerization, so the silicone rubber surface coating material is mainly cross-linked and cured through ring-opening copolymerization of the benzoxazine group. In the previous research process of the application, the phenolic hydroxyl-containing organosilicon type benzoxazine compound was mainly used as an adhesive to bond various interfaces (see: Sun, A. B. Preparation and performance of siloxane-modified benzoxazine [D]. Shandong University, 2020). After bonding is completed, the phenolic hydroxyl-containing organosilicon type benzoxazine compound remains in the bonding site (such as a gap or a bonding surface) and cannot be contacted from the outside. In order to further study the bonding mechanism, the bonding gap is damaged to obtain a material interface with adhesive cured product remaining. Analysis of the adhesive cured product residue shows that it has good interface performance, which inspires the idea of using the phenolic hydroxyl-containing organosilicon type benzoxazine compound to modify the coating. After a large number of tests and optimization, the composition of the phenolic hydroxyl-containing organosilicon type benzoxazine compound is successfully used as a silicone rubber surface modification coating.

[0076] The use of catalyst A can accelerate the ring-opening cross-linking of the benzoxazine group, reduce the reaction temperature and shorten the reaction time. Both the general Lewis acid and the general Lewis base can promote the ring-opening process. Considering comprehensively, phenylsulfonic acid, acetic acid, sodium hydroxide and hexanediamine are preferred. Too much dosage of catalyst A will cause the cross-linking reaction to be too fast, resulting in internal defects of the adhesive system, so the addition amount of the catalyst should not be too much. Considering comprehensively, the dosage of the catalyst is preferably 0-3 parts.

[0077] The silicone rubber surface modification coating prepared in the application can be directly used as a functional coating of the silicone rubber itself; it can also be further modified with other coatings on its surface to be used in the form of a multi-layer modification coating; it can also be used as a new interface to bond the silicone rubber with other objects, solving the problem of difficult bonding of silicone rubber with traditional adhesives.

[0078] The additives include fillers and auxiliary agents. The additives can improve the performance of the coating and expand the application of the coating. For example, the additives include thermal and oxidative stabilizers, flame retardants, conductive agents, foaming agents, deep curing agents, pigments, plasticizers, and the like. Some additives can have multiple functions. For example, iron red can serve as a thermal and oxidative stabilizer, a pigment, and a reinforcing filler. The addition of special polymers can reduce the friction coefficient between the coating and a specific interface, thereby achieving super-lubricating performance. The addition of special coupling agents can improve the bonding strength between the coating and a specific interface. In summary, the use of different amounts of the additives and the combination of different additives can produce high-performance coatings that meet the needs of various occasions, and the coatings have a wide application prospect and a good market prospect.

[0079] The application is further described below by way of specific examples, but is not limited thereto.

[0080] The raw materials used in the examples are commercially available or synthesized according to the methods described in the references.

[0081] The molar ratio in the examples refers to the ratio of the amount of substance, and the part ratio refers to the mass ratio.

[0082] Example 1

[0083] The 1,3-bis(amino propyl) tetramethyl disiloxane, catechol, and formaldehyde aqueous solution were mixed in a molar ratio of 1:2:4, and the mixture was heated to 70°C and reacted for 6 hours. After purification, a phenolic hydroxyl-containing silicone-based benzoxazine compound was obtained, and the yield was 85%. The infrared spectrum is shown in FIG. 1, and the benzoxazine ring signal peaks are at 1350, 1255, and 912 cm Figure 1 -1 The hydrogen nuclear magnetic resonance spectrum is shown in FIG. 2. Figure 2 1 H NMR (400 MHz, CDCl3): δ 0.45 (s, Si-CH3, 12H), δ 0.47 (t, Si-CH2CH2CH2-, 4H), δ 1.56 (m, Si-CH2CH2CH2-, 4H), δ 2.69 (t, Si-CH2CH2CH2-, 4H), δ 3.92 (s, Ar-CH2-N, 4H), δ 4.86 (s, O-CH2-N, 4H), δ 7.05-7.20 (m, Ar-H, 6H).

[0084] Example 2

[0085] ​​The phenolic hydroxyl group-containing organosilicon type benzoxazine compound in Example 1 is coated on the surface of methyl silicone rubber by brush coating process, and a methyl silicone rubber modified coating is obtained after ladder heat curing (the curing conditions are 100℃ heating for 2h, 110℃ heating for 2h, and 120℃ heating for 2h).

[0086] Example 3

[0087] Similar to Example 2, except that the modified object is phenyl silicone rubber.

[0088] Example 4

[0089] The phenolic hydroxyl group-containing organosilicon type benzoxazine compound (100 parts) obtained in Example 1 is compounded with acetic acid (2 parts), M-5 type white carbon black treated with silazane (15 parts), and silane coupling agent KH570 (3 parts) after mixing uniformly; it is brushed on the surface of methyl silicone rubber, and a methyl silicone rubber modified coating is obtained after ladder heat curing (the curing conditions are 100℃ heating for 2h, 110℃ heating for 2h, and 120℃ heating for 2h).

[0090] Example 5

[0091] Similar to Example 4, except that the modified object is phenyl silicone rubber.

[0092] Example 6

[0093] The phenolic hydroxyl group-containing organosilicon type benzoxazine compound (100 parts) obtained in Example 1 is compounded with hexanediamine (2 parts), M-5 type white carbon black treated with silazane (15 parts), silane coupling agent KH550 (3 parts), and auxiliary iron red (2 parts) after mixing uniformly; it is coated on the surface of methyl silicone rubber, and a methyl silicone rubber modified coating is obtained after ladder heat curing (the curing conditions are 100℃ heating for 2h, 110℃ heating for 2h, and 120℃ heating for 2h).

[0094] Example 7

[0095] Similar to Example 6, except that the modified object is phenyl silicone rubber.

[0096] Example 8

[0097] The phenolic hydroxyl group-containing organosilicon type benzoxazine compound prepared in Example 1 is dissolved in a mixed solution of toluene and n-hexane (the volume ratio of toluene to n-hexane is 1:1) according to a mass ratio of 100:400. The above solution is brushed on the surface of methyl silicone rubber, and after the solvent is completely volatilized, heat curing is carried out under certain conditions (the curing conditions are 100℃ heating for 1h, 110℃ heating for 1h, 120℃ heating for 1h, 130℃ heating for 1h, and 140℃ heating for 1h), and a methyl silicone rubber surface modified coating is obtained.

[0098] Example 9

[0099] The operation process is similar to that of Example 8, except that the mass ratio of the phenolic hydroxyl-containing organosilicon type benzoxazine compound to the mixed solution is 100:100, the volume ratio of toluene to n-hexane is changed to 5:1, and the object of modification is phenyl silicone rubber.

[0100] Example 10

[0101] The phenolic hydroxyl-containing organosilicon type benzoxazine compound prepared in Example 1 is dissolved in a mixed solution of tetrahydrofuran and isopropanol (volume ratio of tetrahydrofuran to isopropanol is 3:2) at a mass ratio of 100:3000. The above solution is brushed on the surface of methyl silicone rubber, and after the solvent is completely volatilized, heat curing is carried out under certain conditions (curing conditions are 100°C heating for 2h, 110°C heating for 2h, 120°C heating for 2h), to obtain a methyl silicone rubber surface modification coating.

[0102] Example 11

[0103] The operation process is similar to that of Example 10, except that the object of modification is phenyl silicone rubber.

[0104] Example 12

[0105] The operation process is similar to that of Example 10, except that the mass ratio of the phenolic hydroxyl-containing organosilicon type benzoxazine compound to the mixed solution is 100:10000, and the volume ratio of tetrahydrofuran to isopropanol is changed to 3:7.

[0106] Example 13

[0107] The operation process is similar to that of Example 12, except that the object of modification is phenyl silicone rubber.

[0108] Example 14

[0109] The phenolic hydroxyl-containing organosilicon type benzoxazine compound prepared in Example 1 is dissolved in a mixed solution of diethyl ether and ethyl acetate (volume ratio of diethyl ether to ethyl acetate is 1:4) at a mass ratio of 100:6000. The above solution is brushed on the surface of methyl silicone rubber, and after the solvent is completely volatilized, heat curing is carried out under certain conditions (curing conditions are 100°C heating for 2h, 120°C heating for 2h, 140°C heating for 2h, 160°C heating for 2h, 180°C heating for 2h), to obtain a methyl silicone rubber surface modification coating.

[0110] Example 15

[0111] The operation process is similar to that of Example 14, except that the mass ratio of the phenolic hydroxyl-containing organosilicon type benzoxazine compound to the mixed solution is 100:500, the volume ratio of diethyl ether to ethyl acetate is changed to 1:2, and the object of modification is phenyl silicone rubber.

[0112] Example 16

[0113] The phenolic hydroxyl-containing organosilicon type benzoxazine compound (100 parts) obtained in Example 1 was compounded with sulfuric acid (1 part), M-5 type white carbon black treated with silazane (1 part), and silane coupling agent KH550 (3 parts), and dissolved in a mixed solution of 5000 parts (mass parts) of toluene and n-hexane (the volume ratio of toluene to n-hexane was 1:2); brushed on the surface of methyl silicone rubber, and subjected to stepwise thermal curing (the curing conditions were 100°C for 2h, 120°C for 2h, 140°C for 2h, 160°C for 2h, and 180°C for 2h), to obtain a methyl silicone rubber modified coating.

[0114] Example 17

[0115] Similar to Example 16, except that the volume ratio of toluene to n-hexane was 3:1, and the object of modification was phenyl silicone rubber.

[0116] Example 18

[0117] The phenolic hydroxyl-containing organosilicon type benzoxazine compound (100 parts) obtained in Example 1 was compounded with aniline (2 parts), M-5 type white carbon black treated with silazane (2 parts), silane coupling agent KH570 (3 parts), and silver powder (1 part), and dissolved in a mixed solution of 6000 parts of diethyl ether and ethyl acetate (the volume ratio of diethyl ether to ethyl acetate was 2:1), and mixed uniformly; brushed on the surface of methyl silicone rubber, and subjected to stepwise thermal curing (the curing conditions were 100°C for 1h, 110°C for 1h, 120°C for 1h, 130°C for 1h, and 140°C for 1h), to obtain a methyl silicone rubber modified coating.

[0118] Example 19

[0119] Similar to Example 18, except that the object of modification was phenyl silicone rubber.

[0120] Test Example 1

[0121] The water contact angle of unmodified methyl silicone rubber and phenyl silicone rubber was tested using 2 μl of deionized water as the test liquid droplet, and 3 different positions were selected for each sample to test the water contact angle, and the average value was taken as the final test result.

[0122] Test Example 2

[0123] The contact angle test was performed on unmodified methyl silicone rubber and phenyl silicone rubber using 2 μl test volume of the solution of the phenolic hydroxyl group-containing organosilicon type benzoxazine compound prepared in Example 10 as the test droplet, and the test was performed at 3 different positions for each sample, and the average value was taken as the final test result.

[0124] Test Example 3

[0125] The contact angle test was performed on the methyl silicone rubber modified coating and the phenyl silicone rubber modified coating prepared in Example 8 and Example 9 using 2 μl test volume of deionized water as the test droplet, and the test was performed at 3 different positions for each sample, and the average value was taken as the final test result.

[0126] Test Example 4

[0127] The surface free energy of the methyl silicone rubber and the phenyl silicone rubber and the phenolic hydroxyl group-containing organosilicon type benzoxazine compound coating was quantitatively analyzed using the Owens-Wendt-Rabel-Kaelble (OWRK) model. Two standard test liquids with different polarities were selected: deionized water (polar liquid, 2 μL) and diiodomethane (non-polar liquid, 1 μL), and the test was performed at 5 different positions for each sample, and the average value was taken as the final test result.

[0128] Test Example 5

[0129] According to the “Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)” (National Standard: GB / T 7124-2008), the phenolic hydroxyl group-containing organosilicon type benzoxazine compound obtained in Example 1 was directly brushed on the methyl silicone rubber of the national standard size, and was heat-cured under certain conditions (the curing conditions were 100°C heating for 2 h, 110°C heating for 2 h, and 120°C heating for 2 h). After curing, it was placed for 1 day. Then the tensile shear strength was measured by a tensile testing machine.

[0130] Test Example 6

[0131] The operation process was similar to that of Test Example 5, except that the object to be bonded was a phenyl silicone rubber.

[0132] Test Example 7

[0133] According to the “Determination of Tensile Shear Strength of Vulcanized Rubber and Metal Bonding” (National Standard: GB / T 13936-2014), the methyl silicone rubber with a modified coating obtained in Example 8 was bonded to a standard size iron sheet using 502 and pressure was applied, and after being placed at room temperature for 1 day, the 180° peeling strength was measured by a tensile testing machine.

[0134] Test Example 8

[0135] The operation process is similar to that of Test Example 8, except that the object to be bonded is phenyl silicone rubber with a modified coating.

[0136] Test Example 9

[0137] According to the Determination of Tensile Shear Strength of Vulcanized Rubber and Metal Bonding (National Standard: GB / T 13936-2014), the 502 adhesive is uniformly coated on the surface of the treated iron sheet, quickly combined with the unmodified methyl silicone rubber sample and applied pressure, and then placed at room temperature for 1 day to cure. The 180° peel strength is measured by a tensile testing machine.

[0138] Test Example 10

[0139] The operation process is similar to that of Test Example 9, except that the object to be bonded is unmodified phenyl silicone rubber.

[0140] The contact angle data tested in Test Examples 1-3 are listed in Table 1. As can be seen from the data in Table 1, the water contact angles of the unmodified methyl silicone rubber and phenyl silicone rubber are both greater than 110°, and the surface energy is low, making it difficult to be infiltrated by polar modifiers or adhesives. The contact angle of the solution of the phenolic hydroxyl-containing organosilicon-based benzoxazine compound prepared in Example 10 with the surfaces of the two silicone rubbers becomes about 30°, showing good infiltration and spreading properties, providing the necessary premise for the modification of the silicone rubber surface. After the surfaces of the two silicone rubbers are modified using the phenolic hydroxyl-containing organosilicon-based benzoxazine compound in the present application, the water contact angles of the two silicone rubber surfaces become about 100°, showing a certain degree of hydrophobicity. The change in data from 110° to 100° proves the successful modification of the phenolic hydroxyl-containing organosilicon-based benzoxazine compound on the surface of the silicone rubber, and on the other hand, the data indicates that the surface of the modified silicone rubber is still good for contact and infiltration with organic reagents, which provides the possibility for subsequent functionalization of the modified silicone rubber. In the current large number of literature on surface modification of silicone rubber, the surface of the modified silicone rubber changes from hydrophobic to hydrophilic, while in the present application, the surface of the silicone rubber is hydrophobic before and after modification, only the hydrophobicity is slightly reduced. This difference is the most important difference between the present application and similar literature in the same field, and is also an innovation point of the present application.

[0141] Table 1 Contact angles corresponding to different interface types

[0142]

[0143] Figure 3The three pictures from left to right are the effect pictures of Example 2 (modification after directly smearing the phenolic hydroxyl-containing organosilicon type benzoxazine compound on the surface of silicone rubber), Example 8 (modification after brushing the solution of phenolic hydroxyl-containing organosilicon type benzoxazine compound on the surface of methyl silicone rubber), and Example 9 (modification after brushing the solution of phenolic hydroxyl-containing organosilicon type benzoxazine compound on the surface of phenyl silicone rubber). It can be seen from the three pictures that when the phenolic hydroxyl-containing organosilicon type benzoxazine compound is directly smeared on the surface of silicone rubber for modification, a clear "coffee ring effect" is produced, and a uniform coating cannot be formed. However, when the solution formula designed in the present application is used, the modification effect on the surface of silicone rubber is excellent, and a uniform coating can be formed. This shows that the present application effectively suppresses the "coffee ring effect" in the surface treatment process of silicone rubber by optimizing and improving the solvent formula of the phenolic hydroxyl-containing organosilicon type benzoxazine compound composition. The above process shows that the technology in the present application has significant innovation and achieves good results.

[0144] The surface free energy data of different types of surfaces obtained in Test Example 4 are shown in Table 2. The surface free energy of unmodified methyl silicone rubber and phenyl silicone rubber is low and the surface has no active groups. Based on the characteristics of the silicone rubber itself, it is difficult for traditional modifiers to wet and spread on the surface of silicone rubber, and it is difficult to form a modified coating with strong bonding force. For the same reason, the adhesion performance of silicone rubber is also poor. After the phenolic hydroxyl-containing organosilicon type benzoxazine compound and its composition prepared in the present application are brushed and modified using the solution formula, the surface free energy of the silicone rubber is greatly improved. This shows that the successful modification of the surface of silicone rubber has achieved innovative results.

[0145] Table 2 Surface free energy corresponding to different interface types

[0146]

[0147] The peel strength and / or adhesive strength of Examples 7-10 were tested according to "Determination of Tensile Shear Strength of Adhesives (Rigid Materials to Rigid Materials)" (National Standard: GB / T 7124-2008) and "Determination of Tensile Shear Strength of Vulcanized Rubber and Metal Bonding" (National Standard: GB / T 13936-2014), and the results are shown in Table 3.

[0148] Table 3 Test results of peel strength and adhesive strength

[0149]

[0150] *Note: Comparative Example 1 is the adhesion data of silicone rubber in the patent (Publication No.: CN 117924754A).

[0151] **Note: Comparative Example 2 is the bonding data of silicone rubber in the patent (Publication No: CN 105037758A).

[0152] The silicone rubber surface modifier of the present application has a significant bonding effect on the modified silicone rubber surface (1.22 N / mm in Test Example 7 and 1.25 N / mm in Test Example 8), which is much greater than the bonding strength when the commercially available 502 adhesive is directly bonded to the silicone rubber (both <0.02 N / mm in Test Example 9 and Test Example 10). The experimental data show that the silicone rubber surface modifier of the present application greatly improves the bondable performance of the silicone rubber after modifying the surface of the silicone rubber, which is much higher than the bonding strength of various adhesives reported in the literature. The formulation of the modified coating is the key to the good bonding performance of the silicone rubber surface modifier of the present application to the silicone rubber material. The interfacial bonding strength of the modified silicone rubber is significantly improved, the failure mode is changed from interfacial failure to material cohesive failure, a stable and reliable bonding effect is achieved, the effectiveness of the surface modification is verified, which is also a significant difference between the present application and the similar literature.

[0153] In summary, the silicone rubber surface modifier of the present application slightly reduces the hydrophobicity of the silicone rubber after modifying the silicone rubber, but the change is not large; the generated new silicone rubber coating has the characteristics of easy bonding, and the bondable performance is significantly improved compared with the traditional silicone rubber surface; in particular, the bonding strength of the generated silicone rubber coating to the silicone rubber surface is high, and a significant technical breakthrough has been achieved.

Claims

1. A high adhesion strength silicone rubber surface coating characterized by, The coating is a composition of a phenolic hydroxyl-containing organosilicon type benzoxazine compound uniformly coated on the surface of silicone rubber, and then formed on the surface of silicone rubber through a heat curing process; The composition of the phenolic hydroxyl-containing organosilicon type benzoxazine compound comprises the following components by mass: 100 parts of the phenolic hydroxyl-containing organosilicon type benzoxazine compound, 0-10 parts of catalyst A, 0-400 parts of filler, 0-200 parts of auxiliary agent, and 0-10000 parts of solvent.

2. The high adhesion strength silicone rubber surface coating according to claim 1, characterized in that, The phenolic hydroxyl-containing organosilicon type benzoxazine compound has a structure shown in formula (I); ； Formula (I).

3. The high adhesion strength silicone rubber surface coating according to claim 1, characterized in that, The catalyst A is benzene sulfonic acid, acetic acid, sodium hydroxide, and hexanediamine.

4. The high adhesion strength silicone rubber surface coating according to claim 1, characterized in that, The filler is fumed white carbon black, precipitated white carbon black, carbon black, calcium carbonate, aluminum hydroxide, or / and magnesium hydroxide, and various special treated compounds.

5. The high adhesion strength silicone rubber surface coating of claim 1, wherein, The auxiliary agent is a thermal oxygen stabilizer, a flame retardant, a conductive agent, a foaming agent, a deep curing agent, a pigment, or / and a plasticizer; preferably iron red.

6. The high adhesion strength silicone rubber surface coating of claim 1, wherein, The solvent is toluene, tetrahydrofuran, n-hexane, petroleum ether, isopropyl alcohol, ethanol, methanol, diethyl ether, ethyl acetate, and a mixture of two or more thereof; further preferably toluene, tetrahydrofuran, n-hexane, isopropyl alcohol, diethyl ether, ethyl acetate, and a mixture of two thereof; the use amount is preferably 100-10000 parts; Preferably, the solvent is a mixture of toluene and n-hexane, the volume ratio of the two solvents is 1:0.1-10, preferably 1:0.5-5; or the solvent is a mixture of tetrahydrofuran and isopropyl alcohol, the volume ratio of the two solvents is 1:0.1-10, preferably 1:0.5-5; or the solvent is a mixture of diethyl ether and ethyl acetate, the volume ratio of the two solvents is 1:0.1-10, preferably 1:0.5-5.

7. The high adhesion strength silicone rubber surface coating of claim 1, wherein, The composition of the phenolic hydroxyl-containing organosilicon type benzoxazine compound comprises the following components by mass: 100 parts of the phenolic hydroxyl-containing organosilicon type benzoxazine compound, 1-3 parts of catalyst A, 1-30 parts of filler, 1-10 parts of auxiliary agent, and 100-10000 parts of solvent.

8. The high adhesion strength silicone rubber surface coating of claim 1, wherein, The heat curing process is a process of coating the composition of the phenolic hydroxyl-containing organosilicon type benzoxazine compound on the surface of silicone rubber, and then realizing the preparation of the modified coating on the surface of silicone rubber through programmed temperature rising. Preferably, the programmed temperature rising is a temperature rising process from an initial temperature to a final temperature through a plurality of "temperature rising-constant temperature" links with a certain temperature difference as a gradient; the temperature difference is any temperature difference between 5℃ and 100℃, preferably 10℃; in the "temperature rising-constant temperature" link, the temperature rising rate is any temperature rising rate between 0.1℃ / min and 20℃ / min, preferably 10℃ / min; in the "temperature rising-constant temperature" link, the constant temperature time is any time between 1 min and 180 min, preferably any time between 30 min and 150 min, more preferably 120 min.

9. A method for using the high adhesion strength silicone rubber surface coating according to any one of claims 1-8, comprising the following steps: directly used as a modified coating on the surface of silicone rubber; or the silicone rubber surface modification coating is bonded to other interfaces with an adhesive; or a new coating is applied on the surface of the silicone rubber surface modification coating.

10. Use of the phenolic hydroxyl group-containing organosilicon benzoxazine compound of the structure represented by formula (I) according to claim 2 as a silicone rubber surface modifier, for preparing a silicone rubber coating.

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