Low-hardness fatigue-resistant high-wear-resistance press screen rubber block and preparation method thereof

Abstract

The application discloses a kind of low hardness fatigue-resistant high wear-resistant press screen rubber block and preparation method thereof, with ordinary methyl vinyl silicone rubber, low vinyl methyl vinyl silicone rubber, white carbon black, structure control agent, coupling agent, zinc stearate, vulcanizing machine as the raw material of rubber compound, after mixing and vulcanization, spray silicone feel oil on the press screen rubber block after vulcanization, after high-temperature baking and UV treatment, obtain low hardness fatigue-resistant high wear-resistant press screen rubber block.Coupling agent is cyclic siloxane with three double bonds and long-chain alkyl, silicone feel oil contains silicone resin.Press screen rubber block has higher mechanical strength and higher resilience at lower hardness, can meet the use requirement of 100,000 times deformation amount ≤5% of film pasting.At the same time, the silicone feel oil and silicone rubber product in the high-temperature baking process, two-stage vulcanization is carried out, so that silicone feel oil and silicone rubber react and combine, improve the wear resistance and service life of silicone rubber.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature vulcanized silicone rubber product manufacturing, specifically relating to a low-hardness, fatigue-resistant, and highly wear-resistant pressure screen rubber block and its preparation method. Background Technology

[0002] With the development of modern technology, electronic products such as mobile phones, tablets, and laptops have become an indispensable part of people's lives. However, these electronic products cannot function without our display screens. As society develops, people's requirements for display screens are also getting higher and higher, gradually evolving from the previous flat screens to curved screens, foldable screens, and so on, and the requirements for screen protector technology are also getting higher and higher.

[0003] The screen bonding pad effectively attaches the LCD screen to the panel of electronic products. During the bonding process, the pad needs to deform to ensure a tighter bond and prevent air bubbles. This requires the pad to have a moderate hardness, with the deformation during bonding meeting design requirements; the Shore A hardness must be ≤35. In the manufacturing process of electronic products, the screen bonding pad is typically used approximately 100,000 times before replacement, placing high demands on its resilience and fatigue resistance. Furthermore, the bonding process involves friction between the pad and the PET film on the outer layer of the LCD screen. Therefore, the pad needs a low coefficient of friction and good abrasion resistance to ensure 100,000 repeated uses.

[0004] Currently, some products on the market need to be imported, resulting in high costs and poor economic benefits. Meanwhile, some domestically produced screen pressing blocks suffer from insufficient surface smoothness, poor wear resistance, and surface peeling after repeated use. Furthermore, some domestically produced products have a short lifespan; after 10,000 cycles, the deformation cannot be reversed, necessitating replacement.

[0005] The silicone rubber described in patent document CN106751911A, which describes low-hardness, high-strength insulating silicone rubber and its preparation method, has a high hardness and cannot meet the Shore A hardness requirement of ≤35. Furthermore, the coupling agent KH570 used in the patent cannot meet the fatigue performance requirements of this product.

[0006] In conclusion, developing a low-hardness, fatigue-resistant, and highly wear-resistant screen pressing block is of great significance. Summary of the Invention

[0007] The purpose of this invention is to provide a low-hardness, fatigue-resistant, and highly wear-resistant screen pressing adhesive block and its preparation method, which solves the problems of screen pressing adhesive blocks being not wear-resistant and having a short service life.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A low-hardness, fatigue-resistant, and wear-resistant pressure screen adhesive block, the raw material of which comprises the following components in parts by weight:

[0010] Ordinary methyl vinyl silicone rubber, 50-90 parts;

[0011] Low vinyl methyl vinyl silicone rubber, 10-50 parts;

[0012] Silica, 10-40 parts;

[0013] Structure control agent, 1-4 parts;

[0014] Coupling agent, 0.5–3 parts;

[0015] Zinc stearate, 0.1–0.5 parts;

[0016] Vulcanizing agent, 0.5 to 2 parts.

[0017] A total of 100 parts of ordinary methyl vinyl silicone rubber and low vinyl methyl vinyl silicone rubber.

[0018] Furthermore, the low-hardness, fatigue-resistant, and high-wear-resistant pressure screen adhesive block uses ordinary methyl vinyl silicone rubber with a vinyl content of 0.14-0.16% and a molecular weight of 600,000.

[0019] Furthermore, the low-hardness, fatigue-resistant, and high-wear-resistant screen adhesive block uses a low-vinyl methyl vinyl silicone rubber with a vinyl content of 0.03-0.08% and a molecular weight of 600,000.

[0020] This invention introduces silicone rubber with a low vinyl content into raw rubber. Under the condition of adding approximately the same amount of silica, it achieves a lower hardness than ordinary silicone rubber without affecting the mechanical strength of the product. It can simultaneously meet the requirements of Shore A hardness ≤35, tensile strength ≥6 MPa, and elongation at break ≥400%.

[0021] Furthermore, the low-hardness, fatigue-resistant, and high-wear-resistant screen adhesive block uses at least one of precipitated silica and fumed silica.

[0022] Furthermore, the coupling agent used in the aforementioned low-hardness, fatigue-resistant, and high-wear-resistant screen adhesive block is as shown in formula (1):

[0023]

[0024] Where n is a positive integer between 8 and 16, and R is CH3 or C2H5.

[0025] The synthesis method of the coupling agent is as follows:

[0026]

[0027] In the low-hardness formulation of this invention, the use of low-vinyl content silicone rubber results in insufficient crosslinking points and poor resilience, leading to insufficient permanent deformation after 100,000 fatigue cycles. The long-chain silane coupling agent introduced in this invention, with three double bonds, provides more crosslinking points, enriches the crosslinking network, and increases the resilience of the silicone rubber. Simultaneously, the long chain of this coupling agent makes the silicone rubber molecular chains smoother, facilitating deformation. Furthermore, this long chain physically entangles with the rubber molecular chains, enabling rapid recovery after deformation and significantly improving the fatigue performance of the pressure plate adhesive block. In the examples and comparative examples, commercially available ordinary coupling agents cannot achieve this beneficial effect.

[0028] Furthermore, the low-hardness, fatigue-resistant, and high-wear-resistant pressure screen adhesive block uses at least one of α,ω-dihydroxypolydimethylsiloxane, diphenylsilanediol, and dimethyldiethoxysilane as its structuring control agent.

[0029] Furthermore, the low-hardness, fatigue-resistant, and high-wear-resistant pressure screen adhesive block uses at least one of benzoyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane peroxide as a vulcanizing agent.

[0030] Furthermore, the aforementioned low-hardness, fatigue-resistant, and high-wear-resistant screen adhesive block has its surface coated with a self-made silicone tactile oil. By weight, the silicone tactile oil consists of 100 parts of vinyl-terminated silicone oil, 5 parts of silica, 10 parts of silicone resin, 8 parts of hydrogen-containing silicone oil, 0.8 parts of catalyst, 0.1 parts of inhibitor, and 100 parts of diluent.

[0031] Furthermore, the viscosity of the vinyl-terminated silicone oil is 2000-50000 cst, and the vinyl content is 0.08-0.25 wt%; preferably, the viscosity of the vinyl-terminated silicone oil is 20000 cst, and the vinyl content is 0.15%.

[0032] Furthermore, the silicone resin is a vinyl MQ silicone resin.

[0033] Furthermore, the hydrogen content of the hydrogen-containing silicone oil is 0.1-1.2 wt%, preferably 0.5 wt%.

[0034] Furthermore, the diluent is white spirit.

[0035] While ordinary hand-feeling oils on the market can make the surface of silicone rubber products smooth and improve their stain resistance, their abrasion resistance is poor, thus losing the smooth and antistatic effect. The silicone hand-feeling oil used in this invention incorporates silicone resin, which not only improves the abrasion resistance of the oil but also increases the flexibility of the product surface, maintaining its performance even after repeated use. Furthermore, during high-temperature baking, the silicone hand-feeling oil reacts with the silicone rubber and coupling agent in the silicone rubber product, allowing for better bonding between the oil and the surface, thereby enhancing abrasion resistance.

[0036] Furthermore, the method for preparing a low-hardness, fatigue-resistant, and highly wear-resistant screen adhesive block includes the following steps:

[0037] Step 1: Add silicone rubber (ordinary methyl vinyl silicone rubber, low vinyl methyl vinyl silicone rubber), silica, coupling agent, structure control agent and zinc stearate to the kneader in batches and mix. After forming a ball, vacuum at 120°C for 2 hours and then discharge.

[0038] Step 2: After the rubber compound has cooled, add the vulcanizing agent to the mixed rubber on the open mill;

[0039] Step 3: Place an appropriate amount of the compounded rubber with added vulcanizing agent into the mold, vulcanize at 160℃ for 40 minutes to obtain the screen pressing rubber block;

[0040] Step 4: Spray three layers of silicone tactile oil evenly onto the screen pressing block, bake at 150℃ for 30 minutes, and then UV treat the screen pressing block coated with silicone tactile oil for 10 minutes.

[0041] The beneficial effects of this invention are as follows: the screen pressing adhesive block has high mechanical strength and high resilience while maintaining low hardness, meeting the requirement of ≤5% deformation after 100,000 applications. Simultaneously, the silicone feel oil and silicone rubber products undergo two-stage vulcanization during high-temperature baking, allowing the silicone feel oil and silicone rubber to react and bond, thus improving the wear resistance and service life of the silicone rubber. Detailed Implementation

[0042] 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.

[0043] Example 1

[0044] 70 parts of ordinary methyl vinyl silicone rubber (vinyl content 0.15%, molecular weight 600,000), 30 parts of low-vinyl methyl vinyl silicone rubber (0.05%, molecular weight 600,000), 3 parts of hydroxyl silicone oil (α,ω-dihydroxypolydimethylsiloxane, viscosity 40 MPa·s), 30 parts of fumed silica, 1 part of self-made silane coupling agent (R = -C₂H₅, n = 16), and 0.3 parts of zinc stearate were kneaded into a dough in a kneader, and then vacuumed for 2 hours (vacuum -0.08 MPa, temperature 120°C). The kneaded silicone rubber was then cooled to room temperature and left to stand for 24 hours.

[0045] Add 1 part of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane peroxide to the rubber compound on a two-roll mill, and pass through it 4 times. Take an appropriate amount of the rubber compound with the added vulcanizing agent, place it into a mold for pressing rubber blocks, vulcanize at 160°C for 40 minutes, and then remove the product.

[0046] After the product cools, evenly spray an organic silicone feel oil (the vinyl-terminated silicone oil has a viscosity of 20,000 cst and a vinyl content of 0.15%; the hydrogen-containing silicone oil has a hydrogen content of 0.5 wt%; the same applies below) onto the surface, and place it in a 180°C oven to cure for 30 minutes. Then place it in a UV box for UV treatment for 10 minutes to obtain the finished product.

[0047] Example 2

[0048] 80 parts of ordinary methyl vinyl silicone rubber (vinyl content 0.15%, molecular weight 600,000), 20 parts of low-vinyl methyl vinyl silicone rubber (0.05%, molecular weight 600,000), 3 parts of hydroxyl silicone oil (α,ω-dihydroxypolydimethylsiloxane, viscosity 40 MPa·s), 30 parts of fumed silica, 1 part of self-made silane coupling agent (R = -CH3, n = 8), and 0.3 parts of zinc stearate were kneaded into a dough in a kneader, and then vacuum-sealed for 2 hours (vacuum -0.08 MPa, temperature 120°C). The kneaded silicone rubber was then cooled to room temperature and left to stand for 24 hours.

[0049] Add 1 part of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane peroxide to the rubber compound on a two-roll mill, and pass through it 4 times. Take an appropriate amount of the rubber compound with the added vulcanizing agent, place it into a mold for pressing rubber blocks, vulcanize at 160°C for 40 minutes, and then remove the product.

[0050] After the product cools, evenly spray the surface with silicone-based hand-feel oil and cure it in a 180℃ oven for 30 minutes. Then, place it in a UV chamber for UV treatment for 10 minutes to obtain the finished product.

[0051] Example 3

[0052] 90 parts of ordinary methyl vinyl silicone rubber (vinyl content 0.14%, molecular weight 600,000), 10 parts of low-vinyl methyl vinyl silicone rubber (0.05%, molecular weight 600,000), 3 parts of hydroxyl silicone oil (α,ω-dihydroxypolydimethylsiloxane, viscosity 40 MPa·s), 30 parts of precipitated silica, 1 part of self-made silane coupling agent (R = -C₂H₅, n = 16), and 0.3 parts of zinc stearate were kneaded into a dough in a kneader, and then vacuum-sealed for 2 hours (vacuum -0.08 MPa, temperature 120°C). The kneaded silicone rubber was then cooled to room temperature and left to stand for 24 hours.

[0053] Add 1 part of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane peroxide to the rubber compound on a two-roll mill, and pass through it 4 times. Take an appropriate amount of the rubber compound with the added vulcanizing agent, place it into a mold for pressing rubber blocks, vulcanize at 160°C for 40 minutes, and then remove the product.

[0054] After the product cools, evenly spray the surface with silicone-based hand-feel oil and cure it in a 180℃ oven for 30 minutes. Then, place it in a UV chamber for UV treatment for 10 minutes to obtain the finished product.

[0055] Example 4

[0056] 60 parts of ordinary methyl vinyl silicone rubber (vinyl content 0.14%, molecular weight 600,000), 40 parts of low-vinyl methyl vinyl silicone rubber (0.05%, molecular weight 600,000), 2 parts of hydroxyl silicone oil (α,ω-dihydroxypolydimethylsiloxane, viscosity 40 MPa·s), 20 parts of fumed silica, 1 part of silane coupling agent (R = -C₂H₅, n = 16), and 0.3 parts of zinc stearate were kneaded into a dough in a kneader, and then vacuum-sealed for 2 hours (vacuum -0.08 MPa, temperature 120°C). The kneaded silicone rubber was then cooled to room temperature and left to stand for 24 hours.

[0057] Add 1 part dicumyl peroxide to the rubber compound on a two-roll mill and pass it through 4 times. Take an appropriate amount of the rubber compound with the added vulcanizing agent, place it into a mold for pressing rubber blocks, vulcanize at 160°C for 40 minutes, and then remove the product.

[0058] After the product cools, evenly spray the surface with silicone-based hand-feel oil and cure it in a 180℃ oven for 30 minutes. Then, place it in a UV chamber for UV treatment for 10 minutes to obtain the finished product.

[0059] Example 5

[0060] 50 parts of ordinary methyl vinyl silicone rubber (vinyl content 0.14%, molecular weight 600,000), 50 parts of low-vinyl methyl vinyl silicone rubber (0.05%, molecular weight 600,000), 4 parts of hydroxyl silicone oil (α,ω-dihydroxypolydimethylsiloxane, viscosity 40 MPa·s), 40 parts of fumed silica, 1 part of self-made silane coupling agent (R = -C₂H₅, n = 16), and 0.3 parts of zinc stearate were kneaded into a dough in a kneader, and then vacuumed for 2 hours (vacuum -0.08 MPa, temperature 120°C). The kneaded silicone rubber was then cooled to room temperature and left to stand for 24 hours.

[0061] Add 1 part of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane peroxide to the rubber compound on a two-roll mill, and pass through it 4 times. Take an appropriate amount of the rubber compound with the added vulcanizing agent, place it into a mold for pressing rubber blocks, vulcanize at 160°C for 40 minutes, and then remove the product.

[0062] After the product cools, evenly spray the surface with silicone-based hand-feel oil and cure it in a 180℃ oven for 30 minutes. Then, place it in a UV chamber for UV treatment for 10 minutes to obtain the finished product.

[0063] Comparative Example 1

[0064] The difference between Comparative Example 1 and Example 1 is that the silane coupling agent is not added.

[0065] Comparative Example 2

[0066] The difference between Comparative Example 2 and Example 1 is that the silane coupling agent is replaced with vinyltrimethoxysilane.

[0067] Comparative Example 3

[0068] The difference between Comparative Example 3 and Example 1 is that the coupling agent was replaced with n-dodecyltrimethoxysilane, the silicone hand-feel oil was not sprayed, and UV light was not applied.

[0069] Comparative Example 4

[0070] The difference between Comparative Example 4 and Example 1 is that the silicone hand-feel oil was replaced with a commercially available PU hand-feel oil.

[0071] The samples prepared in the examples and comparative examples were subjected to relevant mechanical property tests, and the testing methods are as follows:

[0072] Shore A hardness: Hardness was tested using a Shore A hardness tester according to the national standard GB / T531.1-2008.

[0073] Tensile strength: Samples were prepared and tested according to the dumbbell shape in the national standard GB / T528-2009.

[0074] Elongation at break: Samples were prepared and tested according to the dumbbell shape in the national standard GB / T528-2009.

[0075] Static friction coefficient: tested according to national standard GB / T10006-1988.

[0076] Fatigue performance: Compression test was conducted according to national standard GB / T1687-1993.

[0077] The test results of the examples and comparative examples are shown in Table 1:

[0078] Table 1 Performance test results of the examples and comparative examples

[0079]

[0080]

[0081] Note: Coupling agent A is vinyltrimethoxysilane, and coupling agent B is n-dodecyltrimethoxysilane.

[0082] As can be seen from Table 1 above, the screen pressing blocks obtained in Examples 1-5 have a Shore A hardness ≤35, tensile strength ≥6 MPa, elongation at break ≥400%, good surface smoothness, and static friction coefficient ≤0.3 μm. s It has excellent wear resistance, with a permanent deformation rate of ≤5% after 100,000 cycles.

[0083] Comparative Example 1, without the addition of a self-made silane coupling agent, exhibited poor permanent deformation after 100,000 cycles, failing to meet usage requirements. Comparative Example 2, due to the high reactivity of vinyltrimethoxysilane, resulted in a significant increase in hardness, excessively short elongation, and high crosslinking density. Fatigue led to high heat generation after 100,000 cycles, but permanent deformation actually decreased. Comparative Example 3, with the addition of inactive long-chain alkane, only served a physical plasticizing effect; tensile strength and fatigue test results did not meet requirements. Comparative Example 4 used commercially available PU hand-feel oil, which, while exhibiting good wear resistance, had poor smoothness and antistatic properties, poor adhesion to silicone rubber, and a significant decrease in surface smoothness after repeated use, failing to meet usage requirements.

[0084] Although the invention has been described herein with reference to illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter combination within the scope of this disclosure. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A low-hardness, fatigue-resistant, and highly wear-resistant screen adhesive block, characterized in that, Its compound rubber raw materials include the following components in parts by weight: Ordinary methyl vinyl silicone rubber, 50-90 parts; Low vinyl methyl vinyl silicone rubber, 10-50 parts; Silica, 10-40 parts; Structure control agent, 1-4 parts; Coupling agent, 0.5-3 parts; Zinc stearate, 0.1~0.5 parts; Vulcanizing agent, 0.5~2 parts; The ordinary methyl vinyl silicone rubber has a vinyl content of 0.14-0.16% and a molecular weight of 600,000; The low-vinyl methyl vinyl silicone rubber has a vinyl content of 0.03-0.08% and a molecular weight of 600,000. The coupling agent is shown in formula (1): ； Equation (1) Where n is a positive integer from 8 to 16, and R is CH3 or C2H5; After the screen pressing adhesive block is vulcanized and molded, a self-made organic silicone tactile oil is sprayed on the surface, and then baked and treated with UV light. The homemade silicone hand-feel oil is composed of vinyl-terminated silicone oil, silica, silicone resin, hydrogen-containing silicone oil, catalyst, inhibitor, and diluent.

2. The low-hardness, fatigue-resistant, and high-wear-resistant screen adhesive block according to claim 1, characterized in that, The silica is either precipitated silica or fumed silica.

3. The low-hardness, fatigue-resistant, and high-wear-resistant screen adhesive block according to claim 1, characterized in that, The structuring control agent is at least one of α,ω-dihydroxypolydimethylsiloxane, diphenylsilanediol, and dimethyldiethoxysilane.

4. The low-hardness, fatigue-resistant, and high-wear-resistant screen adhesive block according to claim 1, characterized in that, The vulcanizing agent is at least one selected from benzoyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane peroxide.

5. The method for preparing the low-hardness, fatigue-resistant, and high-wear-resistant pressure screen adhesive block according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Add ordinary methyl vinyl silicone rubber, low vinyl methyl vinyl silicone rubber, structure control agent, silica, coupling agent and zinc stearate to a kneader in batches and mix them. After forming a ball, vacuum the mixture and discharge it. Step 2: After the rubber compound has cooled, add the vulcanizing agent to the mixed rubber on the open mill; Step 3: Place an appropriate amount of the compounded rubber with added vulcanizing agent into the mold, vulcanize, and obtain the screen pressing rubber block; Step 4: Evenly spray the screen pressing adhesive block with silicone tactile oil, bake it, and then perform UV treatment on the screen pressing adhesive block sprayed with silicone tactile oil.

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