Multifunctional self-adhesive modifier for automatically bonding plastic and silicone rubber

Abstract

The invention provides an enhanced silicone rubber composition containing a multifunctional self-adhesion modifier with a specific formula, wherein the modifier is added in a manner of premixing an independent additive. The modifier is suitable for commercially available common liquid silicone rubber, especially food contact grade and non-post-curing grade liquid silicone rubber, and the obtained enhanced liquid silicone rubber especially has significantly improved adhesive strength to a plastic substrate. The process of modifying the liquid silicone rubber by using the reinforcing agent is high in efficiency, no special requirement or harsh condition exists, and the cost benefit is high.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application No. 18 / 336,055 filed on June 16, 2023, the disclosure of which is incorporated herein by reference. Technical Field

[0002] The present invention relates to the modification and reinforcement of organic polymer rubbers. Specifically, the present invention relates to a multifunctional self-adhesive modifier for automatic bonding of food contact grade, non-post-curing grade and high-transparency grade liquid silicone rubber to plastic substrates. Background Art

[0003] Liquid silicone rubber is a rubber produced by a two-component system (i.e., component A and component B base resin), which is formed by reinforcing the long chain of polysiloxane with specific silica added as a catalyst and a crosslinking agent. Liquid silicone rubber is characterized by high raw material consistency, and the mixing and generation of the product is also carried out in the liquid phase.

[0004] Liquid silicone rubber has advantages over other rubber or similar materials due to its high biocompatibility, high durability, high chemical resistance, thermal stability and high electrical insulation. Therefore, liquid silicone rubber is widely used in different applications and uses in different industries. Liquid silicone rubber is available in different formulations on the market, which is not only easy to obtain, but also has specific grades, including food grade, non-post-curing, and resistance to mechanical and chemical wear.

[0005] It is a common practice to enhance the different properties of liquid silicone rubber by using additives. Specifically, in order to improve the bonding strength of ordinary liquid silicone rubber with other materials, the most common and conventional method is to apply a bonding primer manually. However, applying a bonding primer manually is labor-intensive and time-consuming.

[0006] To solve the above problems, self-adhesive liquid silicone rubber (SA-LSR) obtained by chemically grafting reactive groups into component A or B base resins has been developed. However, currently commercially available SA-LSR only provides adhesive properties to substrates of limited types of materials, and different SA-LSRs need to be used for various plastics. In addition, the application of SA-LSR is limited due to the limited availability of various regulatory levels (e.g., food contact, non-post-curing) and functions, as well as high cost. Summary of the invention

[0007] Therefore, an object of the present invention is to provide a reinforced liquid silicone rubber having enhanced adhesive properties, multifunctional functions and compliance, and an efficient and low-cost manufacturing process that is compatible with existing liquid silicone rubber manufacturing processes.

[0008] One aspect of the present invention provides a self-adhesive rubber composition having adjustable bonding strength to a plastic substrate, comprising: Commercially available ordinary liquid silicone rubber substrate; and The self-adhesive modifying additive is selected from: a crosslinking agent selected from organosilanes, organoacrylates or their derivatives; Selected from platinum-based complexes, organic peroxides or its derivatives; or mixtures or combinations thereof; The mass ratio of the silicone rubber substrate to the self-adhesive modification additive is 100:0.5 to 100:10.

[0009] In one embodiment, the plastic substrate is selected from polycarbonate, polybutylene terephthalate, polyetheretherketone or polyphenylsulfone.

[0010] In one embodiment, the liquid silicone rubber base includes two components, one of which is an alkenyl-containing organopolysiloxane and the other is a linear or branched organohydrogenpolysiloxane.

[0011] In one embodiment, the commercially available liquid silicone rubber substrate is selected from food-grade liquid silicone rubber; non-post-curing liquid silicone rubber or highly transparent liquid silicone rubber.

[0012] In one embodiment, the liquid silicone rubber matrix is ​​selected from food-grade liquid silicone rubber; non-post-curing liquid silicone rubber or high-transparency liquid silicone rubber.

[0013] In one embodiment, the organosilane is selected from tetraalkyl orthosilicates; (epoxy-organo)trialkoxysilanes or any derivatives; copolymers or mixtures thereof.

[0014] In one embodiment, the tetraalkyl orthosilicate has the formula Si(OR l )4, where R l Selected from the following monovalent hydrocarbons: A straight or branched alkyl group having equal to or less than 8 carbon atoms; An alkoxy group having 4 or less carbon atoms; or Toluene.

[0015] In one embodiment, the (epoxy-organo)trialkoxysilane has one of the following formulae: wherein R2 is a divalent hydrocarbon group containing 2 to 4 carbon atoms; R3 and R5 are alkyl groups containing 1 to 3 carbon atoms; and R4 is a divalent alkoxy group consisting of 2 to 4 carbon atoms.

[0016] In one embodiment, the organic acrylate is selected from ethyl acrylate, butyl acrylate, propyl acrylate, N,N-dimethylacrylamide, methacrylic acid, N-isopropylacrylamide, 2-hydroxyethyl methacrylate, 3-[tris(trimethylsiloxy)silyl]propyl methacrylate, acrylate functional carbosilane molecules, methacrylate functional carbosilane molecules, dipentaerythritol pentaacrylate, ethoxylated pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate; pentaerythritol triacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, or a mixture thereof.

[0017] In one embodiment, the organic peroxide is selected from dibenzoyl peroxide, tert-butyl perbenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, bis(2,4-dichlorobenzoyl)peroxide, di-tert-butyl peroxide, and mixtures thereof.

[0018] In one embodiment, the platinum-based complex is selected from platinum black, platinum chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and an olefin, or bisacetoacetate platinum.

[0019] In other embodiments, the amount of tetraalkyl orthosilicate is about 0.8 to 1.2 weight percent relative to the weight of the liquid silicone rubber.

[0020] In one embodiment, the amount of (epoxy-organic)trialkoxysilane is about 0.8 to 4.8 weight percent relative to the weight of the liquid silicone rubber.

[0021] In one embodiment, the amount of the organic acrylate is about 0.8 to 3.6 weight percent relative to the weight of the liquid silicone rubber.

[0022] In one embodiment, the amount of the organic peroxide is about 0.4 to 1.8 weight percent relative to the weight of the liquid silicone rubber.

[0023] In other embodiments, the amount of the platinum-based complex is about 0.5 to 1000 parts per million relative to the weight of the liquid silicone rubber.

[0024] In a second aspect of the present invention, there is also provided a method for improving the bonding strength of liquid silicone rubber using the above-mentioned modifier, comprising: Providing liquid silicone formed from commercially available liquid silicone Rubber resin; and By introducing an adjustable amount of the modifier of claim 1 into the liquid silicone rubber Pigment or additive metering units for liquid silicone rubber processors at temperatures between 20°C and 30°C and pressures between 0.3 MPa and 0.6 MPa; Among them, the bonding strength of the enhanced liquid silicone rubber can be adjusted by adjusting the amount of the above-mentioned modifier; wherein the amount of the modifier is less than 10 weight percent of the liquid silicone rubber base; and The curing time is less than 10% longer than that of unmodified liquid silicone rubber.

[0025] In one embodiment of the second aspect, the shear strength of the reinforced liquid silicone rubber is at least 0.6 MPa, wherein at least 6 weight percent of the modifier of the liquid silicone rubber base is added. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to better understand the various embodiments described herein and to more clearly show how these various embodiments may be implemented, at least one embodiment will be shown and described with reference to the drawings.

[0027] Figure 1 The general process of manufacturing self-adhesive liquid silicone rubber using the multi-purpose self-adhesive modifier of the present invention is described. By selecting a commercially available two-component system ordinary liquid silicone rubber, the component A and B base resins are mixed with the multi-purpose self-adhesive modifier of the present invention, and the pigment metering unit (i.e., the C unit shown) is added before mixing. The subsequent manufacturing process follows the traditional liquid silicone rubber manufacturing process. The produced self-adhesive liquid silicone rubber can be used to automatically adhere to a plastic surface or substrate.

[0028] Figure 2 The multifunctional self-adhesive modifier can couple with the cross-linked liquid silicone rubber skeleton and adhere to the plastic substrate at the same time.

[0029] Figure 3 An example of a chemical structure of a versatile self-adhesive modifier is shown. The vinyl group of the modifier is used to attach to the liquid silicone rubber backbone, and the epoxide and acrylate functional groups are used to bond to different types of plastic substrates. DETAILED DESCRIPTION

[0030] In the following description, the structure and modification method of the self-adhesive liquid silicone rubber are described as preferred examples. It is obvious to those skilled in the art that modifications, including additions and / or substitutions, can be made without departing from the scope and spirit of the invention. Specific details may be omitted in order not to obscure the invention; however, this disclosure is written to enable those skilled in the art to practice the teachings herein without undue experimentation.

[0031] Various processes will be described below to provide examples of at least one embodiment of the claimed subject matter. The embodiments described below do not limit any claimed subject matter, and any claimed subject matter may encompass processes or systems different from those described below. The claimed subject matter is not limited to processes or systems having all the features of any process or system described below or features common to multiple or all processes or systems described below. The process or system described below may not be an embodiment of any claimed subject matter. Any subject matter disclosed in the process or system described below but not claimed in this document may be the subject of another protective instrument, such as a continuing patent application, and the applicant, inventor, or owner has no intention of abandoning, giving up, or dedicating any such subject matter to the public through disclosure in this document.

[0032] In addition, it should be understood that for simplicity and clarity of explanation, reference numerals may be repeated in the accompanying drawings to indicate corresponding or similar elements where deemed appropriate. In addition, in order to provide a thorough understanding of the embodiments described herein, many specific details are set forth. However, those of ordinary skill in the art will appreciate that the embodiments described herein may be practiced without these specific details. In other cases, well-known methods, processes, and components are not described in detail to avoid confusing the embodiments described herein. In addition, this description should not be considered to limit the scope of the embodiments described herein.

[0033] It should be noted that terms of degree such as "substantially" and "approximately" as used herein refer to a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree can be construed as including a certain deviation of the modified term if such deviation would not negate the meaning of the term it modifies.

[0034] Furthermore, the recitation of numerical ranges by endpoints herein include all numbers and fractions subsumed therein. It should also be understood that all numbers and fractions thereof are assumed to be modified by the term “about”, meaning that a certain amount of variation to the referenced number may be made if the end result is not significantly changed.

[0035] According to a first aspect of the present invention, there is provided a self-adhesive rubber composition having adjustable adhesive strength to a plastic substrate, comprising a commercially available liquid silicone rubber base and a selected self-adhesive modifier additive selected from a crosslinking agent selected from an organic silane, an organic acrylate or a derivative thereof; or a mixture or combination thereof. More specifically, the mass ratio of the silicone rubber base to the self-adhesive modifier is in the range of 100:0.5 to 100:10.

[0036] In some embodiments, the plastic substrate is selected from polycarbonate, polybutylene terephthalate, polyetheretherketone, or polyphenylsulfone.

[0037] The liquid silicone rubber matrix in the composition is a two-component liquid silicone rubber, one part of which can be an alkenyl-containing organopolysiloxane, and the other part can be a linear or branched organohydrogenpolysiloxane. The grade of the selected liquid silicone rubber can be food contact grade, non-post-curing grade or high transparency grade.

[0038] The organosilane crosslinking agent may be selected from tetraalkyl orthosilicates, (epoxy-organo)trialkoxysilanes or any derivatives, copolymers or mixtures thereof.

[0039] The tetraalkyl orthosilicate crosslinking agent may have Si(OR l )4, where R l The tetraalkyl orthosilicate may be present in an amount of about 0.8 to 1.2 weight percent relative to the weight of the liquid silicone rubber base.

[0040] The (epoxy-organic)trialkoxysilane crosslinker may have one of the following formulae: Where R 2 is a divalent hydrocarbon group containing 2 to 4 carbon atoms; R 3 and R 5 is an alkyl group containing 1 to 3 carbon atoms; R4 is a divalent alkoxy group consisting of 2 to 4 carbon atoms. In addition, the amount of the (epoxy-organic) trialkoxysilane may be about 0.8 to 4.8 weight percent relative to the weight of the liquid silicone rubber matrix.

[0041] The organic acrylate crosslinking agent may be selected from ethyl acrylate; butyl acrylate; propyl acrylate; N,N-dimethylacrylamide; methacrylic acid; N-isopropylacrylamide; 2-hydroxyethyl methacrylate; 3-[tris(trimethylsiloxy)silyl]propyl methacrylate; acrylate functional carbosilane molecules; methacrylate functional carbosilane molecules; dipentaerythritol pentaacrylate; ethoxylated pentaerythritol tetraacrylate; ditrimethylolpropane tetraacrylate; pentaerythritol triacrylate; trimethylolpropane triacrylate; ethoxylated trimethylolpropane triacrylate; or a mixture thereof. In addition, the amount of the organic acrylate may be about 0.8 to 3.6 weight percent relative to the weight of the liquid silicone rubber matrix.

[0042] The organic peroxide curing agent can be selected from dibenzoyl peroxide, tert-butyl perbenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane, bis(2,4-dichlorobenzoyl)peroxide, di-tert-butyl peroxide, and mixtures thereof. In addition, the amount of the organic peroxide can be about 0.4 to 1.8 weight percent relative to the weight of the liquid silicone rubber matrix.

[0043] The platinum-based complex curing agent can be selected from platinum black, platinum chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and an olefin, or bisacetoacetate platinum. In addition, the amount of the platinum-based complex can be about 0.5 to 1000 parts per million relative to the weight of the liquid silicone rubber matrix.

[0044] The present invention also provides a method for improving the bonding strength of liquid silicone rubber with the above-mentioned modifier. The method includes providing a liquid silicone rubber formed from a commercially available liquid silicone rubber resin, and introducing an adjustable amount of the modifier of claim 1 into the liquid silicone rubber through a metering unit for pigments or additives of a liquid silicone rubber processor at a temperature of 50 degrees Celsius. 20 degrees Celsius to 30 degrees Celsius, and a pressure of 0.3 MPa to 0.6 MPa. It should be noted that by adjusting the amount of the modifier, the bonding strength of the enhanced liquid silicone rubber can be adjusted. The amount of the modifier can be less than 8 percent weight of the liquid silicone rubber base. Compared with the curing time of the unmodified liquid silicone rubber, the method also increases the curing time by only less than 10%.

[0045] According to ASTM D3163 (Standard Test Method for Strength of Bonded Rigid Plastic Lap Shear Joints by Tensile Load), the shear strength of the liquid silicone rubber after adding at least 6 weight percent of the modifier to the liquid silicone rubber base in the above manner will be increased to at least 0.56 MPa.

[0046] Advantageously, the use of the modifier of the present invention can be applied to commercially available liquid silicone rubber resins. By providing a selected amount of the modifier (as detailed in the examples below), a liquid silicone rubber product having a specific bonding strength can be produced. In this way, small batches of silicone products having different selected bonding strengths can be manufactured.

[0047] Example 1: Testing the bonding effect of multifunctional self-adhesive modifier - liquid silicone rubber (FC LR3038)

[0048] In order to test the degree of reinforcement of the added modifier, commercially available liquid silicone rubber FC LR3038 was selected and used to produce reinforced liquid silicone rubber, the method was as described in paragraph

[0043] above, and the shear strength test was carried out according to ASTM D3163 standard (Standard test method for determining the strength of bonded rigid plastic lap shear joints by tensile loading).

[0049] The above test results are listed in Table 1 below. Table 1: Testing the bonding effect of multifunctional self-adhesive modifier - liquid silicone rubber (FC LR3038)

[0050] As a comparative example, the curing time of the unmodified liquid silicone rubber FC LR3038 is 5 minutes at a curing temperature of 160 degrees Celsius; the curing time is 4 hours at a temperature of 200 degrees Celsius.

[0051] Example 2: Cost calculation for making multifunctional self-adhesive modifier - liquid silicone rubber (FCLR3038)

[0052] The additional material cost of producing the reinforced liquid silicone rubber using the multifunctional self-adhesive modifier in Example 1 is calculated and listed in Table 2 below. Table 2: Cost calculation for making multifunctional self-adhesive modifier - liquid silicone rubber (FC LR3038)

[0053] Example 3: Testing the bonding effect of multifunctional self-adhesive modifier - liquid silicone rubber (NPCHN2003)

[0054] In order to test the degree of reinforcement of the added modifier, commercially available liquid silicone rubber NP CHN2003 was selected and used to produce reinforced liquid silicone rubber, the method was as described in paragraph

[0043] above, and the shear strength test was carried out according to ASTM D3163 standard (Standard test method for determining the strength of bonded rigid plastic lap shear joints by tensile load).

[0055] The above test results are listed in Table 3 below. Table 3: Test of the bonding effect of multifunctional self-adhesive modifier - liquid silicone rubber (NP CHN2003)

[0056] As a comparison and control, the curing time of the unmodified liquid silicone rubber NP CHN2003 is 10 minutes and the curing temperature is 120 degrees Celsius.

[0057] Example 4: Cost calculation for making multifunctional self-adhesive modifier - liquid silicone rubber (NP CHN2003)

[0058] The additional material cost of producing the reinforced liquid silicone rubber using the multifunctional self-adhesive modifier in Example 1 is calculated and listed in Table 4 below. Table 4: Cost calculation for making multifunctional self-adhesive modifier - liquid silicone rubber (NP CHN2003)

[0059] Those skilled in the art will appreciate that, in light of these teachings, alternative embodiments may be implemented without departing from the spirit and scope of the invention as described in the appended claims. The present invention is limited solely by the following claims, which, when considered in conjunction with the above description and drawings, include all such embodiments and modifications.

Claims

1. A self-adhesive silicone rubber composition having adjustable bonding strength to a plastic substrate, comprising: Commercially available ordinary liquid silicone base; and The self-adhesive modifying additive is selected from: A crosslinking agent selected from organosilane, organic acrylate or its derivatives; A curing agent selected from a platinum-based complex, an organic peroxide or a derivative thereof; or any mixture or combination thereof; The mass ratio of the silicone rubber substrate to the self-adhesive modification additive is 100:0.5 to 100:

10. 2 . The silicone rubber according to claim 1 , wherein the plastic substrate is selected from polycarbonate, polybutylene terephthalate, polyetheretherketone or polyphenylsulfone.

3. The silicone rubber composition according to claim 1, characterized in that: The liquid silicone rubber matrix comprises two components, one is an alkenyl-containing organopolysiloxane, and the other is a linear or branched organohydrogenpolysiloxane.

4. The silicone rubber composition according to claim 1, characterized in that: The liquid silicone rubber matrix is ​​selected from food contact grade liquid silicone rubber, non-post-curing liquid silicone rubber or highly transparent liquid silicone rubber.

5. The silicone rubber composition according to claim 1, wherein the organosilane is selected from tetraalkyl orthosilicate, (epoxy-organo)trialkoxysilane or any derivative, copolymer or mixture thereof.

6. The silicone rubber composition according to claim 5, wherein the tetraalkyl orthosilicate has Si(OR 1 )4, where R 1 is a monovalent hydrocarbon selected from the following: A straight or branched alkyl group having equal to or less than 8 carbon atoms; an alkoxy group having 4 or less carbon atoms; or Toluene.

7. The silicone rubber composition according to claim 5, wherein the (epoxy-organic)trialkoxysilane has one of the following chemical formulas: wherein R2 is a divalent hydrocarbon group containing 2 to 4 carbon atoms; R3 and R5 are alkyl groups containing 1 to 3 carbon atoms; and R4 is a divalent alkoxy group consisting of 2 to 4 carbon atoms.

8. The silicone rubber composition according to claim 1, characterized in that: The organic acrylate is selected from ethyl acrylate, butyl acrylate, propyl acrylate, N,N-dimethylacrylamide, methacrylic acid, N-isopropylacrylamide, 2-hydroxyethyl methacrylate, 3-[tris(trimethylsiloxy)silyl]propyl methacrylate, acrylate functional carbosilane molecules, methacrylate functional carbosilane molecules, dipentaerythritol pentaacrylate, ethoxylated pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate; ethoxylated trimethylolpropane triacrylate, or a mixture thereof.

9. The silicone rubber composition according to claim 1, characterized in that: The organic peroxide is selected from dibenzoyl peroxide, tert-butyl perbenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane, bis(2,4-dichlorobenzoyl)peroxide, di-tert-butyl peroxide, or a mixture thereof.

10. The silicone rubber composition according to claim 1, characterized in that: The platinum-based complex is selected from platinum black, platinum chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and an olefin, or bisacetoacetate platinum.

11. A method for improving the bonding strength of liquid silicone rubber using the modifier of claim 1, comprising: Provided is a liquid silicone rubber formed from a commercially available common liquid silicone rubber resin; and introducing an adjustable amount of the modifier of claim 1 into the liquid silicone rubber through a pigment metering unit at a temperature of 20 degrees Celsius to 30 degrees Celsius and a pressure of 0.3 MPa to 0.6 MPa; It is characterized in that the bonding strength of the reinforced liquid silicone rubber can be adjusted by adjusting the amount of the modifier described in claim 1. wherein the amount of the modifier is less than 10 weight percent of the liquid silicone rubber base; and The required curing time is less than 10% longer than that of unmodified liquid silicone rubber.

12. The method according to claim 11, characterized in that The reinforced liquid silicone rubber has a shear strength of at least 0.6 MPa, wherein the added modifier accounts for at most 10 weight percent of the liquid silicone rubber base.

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