Adhesive promoter for silicone rubber and its preparation method

Abstract

The present invention provides an adhesiveness promoter for silicone rubber and a preparation method thereof. The adhesiveness promoter for silicone rubber has a structure shown in Formula 1 or Formula 2: wherein R x is at least one of, R5, R6, R7, and R8 are each independently selected from H or methoxy, and at most only one of R5, R6, R7, and R8 is methoxy; n is 100 - 1000. In the structure of the adhesiveness promoter for silicone rubber of the present invention, the vinyl group and the active group are respectively located at both ends of the polysiloxane chain, and the molecular weight is relatively high. It can effectively cause the end containing the active group to migrate to the interface between the silicone rubber and the substrate due to poor compatibility, and the end containing the vinyl group reacts with the silicone rubber. The purpose of selectively bonding one or several substrates can also be achieved by adjusting the type of the active group, thereby enhancing the bonding effect between the silicone rubber and various substrates.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicone rubber, and particularly relates to a tackifier for silicone rubber and a preparation method thereof. Background Art

[0002] Silicone rubber has excellent properties such as high and low temperature resistance, weather resistance, electrical insulation, and physiological inertness, and plays an increasingly important role in national production and people's lives. However, due to the low surface tension and surface energy of silicone rubber, its adhesion to other materials is poor, which limits its application. To improve the adhesion between silicone rubber and substrates, tackifiers with specific functional groups are usually added to silicone rubber. This method is simple to operate and easy to control. Only the corresponding tackifier molecules need to be synthesized and then mixed during the rubber mixing process. The main mechanism for the tackifier to promote the adhesion between silicone rubber and substrates is as follows: the tackifier molecules have poor compatibility with silicone rubber, and they will migrate to the interface between silicone rubber and substrates during the vulcanization process of silicone rubber. At the same time, the molecular structure contains groups that can interact or even chemically react with silicone rubber and substrates respectively, playing a role in connecting silicone rubber and substrates, thus forming an adhesion.

[0003] However, currently existing tackifiers mainly have three problems: (1) The migration of tackifier molecules during the vulcanization process of silicone rubber is random, and their reactions with silicone rubber and substrates are also random. The distribution of active groups on the adhesive molecular chain is also random, and silicone rubber and substrates cannot form a completely fitting interface. Therefore, there are significant batch differences in their tackifying effect on silicone rubber and substrates; (2) Currently, only the tackifiers that improve the adhesion between silicone rubber and PC are relatively mature on the market, and there are relatively few tackifiers that have a tackifying effect on other materials (such as plastics like PA, ABS, PP, etc.); (3) Currently, the existing tackifiers have poor universality in some occasions where multiple substrates need to be adhered simultaneously, but have poor selectivity in some occasions where there are multiple substrates but only a single variety of substrate needs to be adhered. For example, some tackifiers for adhering PC will also adhere to metals. If the molding process requires the use of metal molds, it is easy to cause the problem of mold sticking.

[0004] Therefore, there is an urgent need for a tackifier for silicone rubber and a preparation method thereof to solve the deficiencies of the prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a tackifier for silicone rubber, which can enhance the adhesion effect between silicone rubber and various substrates.

[0006] Another purpose of the present invention is to provide a preparation method for the tackifier for silicone rubber. Through this preparation method, the above-mentioned tackifier for silicone rubber that can enhance the adhesion effect between silicone rubber and various substrates can be obtained.

[0007] To achieve the above object, the present invention provides a tackifier for silicone rubber, having a structure shown in Formula 1 or Formula 2:

[0008]

[0009] where R x is at least one of

[0010] R5, R6, R7, R8 are each independently selected from H or methoxy, and at most one of R5, R6, R7, R8 is methoxy; n is 100 to 1000.

[0011] Compared with the prior art, one end of the structure of the tackifier for silicone rubber of the present invention is vinyl, and the other end is a branched structure formed by 3 or 3m active groups R x In this structure, the vinyl and the active groups that react with the silicone rubber and the substrate are respectively located at both ends of the polysiloxane chain, and the molecular weight is relatively high, which can effectively cause the end containing the active groups to migrate to the interface between the silicone rubber and the substrate due to poor compatibility, and the end containing vinyl reacts with the silicone rubber, thereby improving the stable adhesion between the silicone rubber and the substrate; the purpose of selectively adhering to one or several substrates can also be achieved by adjusting the type of the active groups, thereby enhancing the adhesion effect between the silicone rubber and various substrates.

[0012] Preferably, n of the present invention is 300 to 1000. When n is 300 to 1000, the molecular weight of the tackifier for silicone rubber is relatively high, so it can play a role in connecting the two when the silicone rubber and the substrate do not fit well.

[0013] To achieve the above object, the present invention also provides a preparation method of a tackifier for silicone rubber, and the steps include:

[0014] (1) Mix terminal vinyl polysiloxane, trimethoxyhydrogensilane, a first catalyst, and toluene, and obtain a first reaction mixture after heating and reacting;

[0015] (2) Mix the first reaction mixture, esters, and active substances, and obtain the structure shown in Formula 1 after heating and reacting; or mix the first reaction mixture, trimethoxyhydrogensilane, and a second catalyst, and obtain a second reaction mixture after heating and reacting, and then heat and react the second reaction mixture, esters, and active substances to obtain the structure shown in Formula 2; the terminal vinyl polysiloxane has a structure shown in Formula 3:

[0016] where n is 100 to 1000;

[0017] The active substance is at least one of them, where R5, R6, R7, and R8 are each independently selected from H or methoxy, and at most only one of R5, R6, R7, and R8 is methoxy.

[0018] Compared with the prior art, the present invention uses vinyl-terminated polysiloxane as the basic raw material, and by controlling the reaction conditions, trimethoxysilane is made to react only with the vinyl group at one end, obtaining a vinyl silicone oil with an asymmetric structure in which one end of the molecular chain is a vinyl group and the other end is 3 or 3m trimethoxysilyl groups. Then, by controlling the reaction conditions, one or more molecules with active groups are introduced to form a tackifier for silicone rubber through transesterification reaction. Therefore, in the molecular structure of the tackifier for silicone rubber prepared by the preparation method of the present invention, the vinyl group and the active group that react with the silicone rubber and the substrate are respectively located at both ends of the polysiloxane chain, and the molecular weight is relatively high. The end containing the active group can effectively migrate to the interface between the silicone rubber and the substrate due to poor compatibility, and the end containing the vinyl group reacts with the silicone rubber, thereby improving the stable adhesion between the silicone rubber and the substrate. At the same time, the preparation method of the present invention can also introduce various active groups by controlling the reaction conditions to achieve the purpose of simultaneously bonding multiple substrates, or can achieve the purpose of selectively bonding one or several substrates by screening suitable active groups. In addition, the preparation method of the present invention uses vinyl-terminated polysiloxane with a wider molecular weight adjustment range as the basic raw material, and polysiloxane with different molecular weights can be used according to different requirements, with a wider application range.

[0019] Preferably, the first catalyst of the present invention is a Karstedt catalyst at 3000 ppm.

[0020] Preferably, the second catalyst of the present invention is tris(pentafluorophenyl)boron catalyst.

[0021] Preferably, the ester of the present invention is n-butyl titanate.

[0022] Preferably, in step (1) of the present invention, the temperature of the heating reaction is 78 - 82 °C, and the time of the heating reaction is 5.5 - 6.5 hours.

[0023] Preferably, step (1) of the present invention includes first mixing vinyl-terminated polysiloxane, the first catalyst, and toluene, adding trimethoxysilane dropwise under stirring conditions, and then obtaining a first reaction mixture after heating reaction.

[0024] Preferably, step (2) of the present invention includes mixing the first reaction mixture, the ester, and the active substance, reacting at 78 - 82 °C for 3.5 - 4.5 hours, and obtaining the structure shown in formula 1 after vacuum distillation.

[0025] Preferably, step (2) of the present invention includes mixing the first reaction mixture, trimethoxysilane, and the second catalyst, heating to 58 - 62°C under a nitrogen atmosphere, reacting for 25 - 35 minutes, and obtaining a second reaction mixture after vacuum distillation.

[0026] Preferably, step (2) of the present invention further includes reacting the second reaction mixture, esters, and active substances at 78 - 82°C for 3.5 - 4.5 hours, and obtaining the structure shown in Formula 2 after vacuum distillation. Detailed Embodiments

[0027] To better illustrate the object, technical solution, and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following embodiments are further explanatory descriptions of the present invention and should not be regarded as limitations to the present invention.

[0028] Example 1

[0029] This example provides a tackifier for silicone rubber, having the following structural formula:

[0030]

[0031] The preparation method of the tackifier for silicone rubber in this example includes the following steps:

[0032] (1) Load 600 g of vinyl-terminated polysiloxane with a number average molecular weight of 40,000, 0.6 g of 3000 ppm Karstedt catalyst, and 300 g of toluene into a 1000 mL three-necked flask. Gradually add 2.16 g of trimethoxysilane dropwise under stirring conditions. After the addition is complete, heat to 80°C and react for 6 hours. After vacuum distillation, 570 g of the first reaction mixture is obtained;

[0033] (2) Load 100 g of the first reaction mixture, 1.6 g of 2-methoxy-4-methylphenol, and 0.2 g of tetrabutyl titanate into a 500 mL three-necked flask, react at 80°C for 4 hours, and obtain 92 g of the tackifier for silicone rubber after vacuum distillation;

[0034] The reaction route of the tackifier for silicone rubber in this example is as follows:

[0035]

[0036] Example 2

[0037] This example provides a tackifier for silicone rubber, having the following structural formula:

[0038]

[0039] The preparation method of the tackifier for silicone rubber in this example includes the following steps:

[0040] (1) Charge 600 g of vinyl-terminated polysiloxane with a number-average molecular weight of 40,000, 0.6 g of 3000 ppm of Karstedt's catalyst, and 300 g of toluene into a 1000 mL three-necked flask. While stirring, gradually add 2.16 g of trimethoxysilane dropwise. After the addition is complete, heat to 80 °C and react for 6 hours. After vacuum distillation, 570 g of the first reaction mixture is obtained;

[0041] (2) Charge 100 g of the first reaction mixture, 3.5 g of trimethoxysilane, and 14.8 mg of tris(pentafluorophenyl)borane into a 500 mL three-necked flask. Heat to 60 °C under a nitrogen atmosphere and react for 30 minutes. After vacuum distillation, 82 g of the second reaction mixture is obtained. Then, charge 50 g of the second reaction mixture, 2.4 g of 2-methoxy-4-methylphenol, and 0.1 g of n-butyl titanate into a 500 mL three-necked flask. React at 80 °C for 4 hours. After vacuum distillation, 43 g of the tackifier for silicone rubber is obtained;

[0042] The reaction route of the tackifier for silicone rubber in this example is as follows:

[0043]

[0044] Example 3

[0045] This example provides a tackifier for silicone rubber with the following structural formula:

[0046]

[0047] The preparation method of the tackifier for silicone rubber in this example includes the following steps:

[0048] (1) Charge 600 g of vinyl-terminated polysiloxane with a number-average molecular weight of 40,000, 0.6 g of 3000 ppm of Karstedt's catalyst, and 300 g of toluene into a 1000 mL three-necked flask. While stirring, gradually add 2.16 g of trimethoxysilane dropwise. After the addition is complete, heat to 80 °C and react for 6 hours. After vacuum distillation, 570 g of the first reaction mixture is obtained;

[0049] (2) Charge 100 g of the first reaction mixture, 2.1 g of the active substance with the structure of formula 4, and 0.2 g of n-butyl titanate into a 500 mL three-necked flask. React at 80 °C for 4 hours. After vacuum distillation, 90 g of the tackifier for silicone rubber is obtained;

[0050] The reaction route of the tackifier for silicone rubber in this example is as follows:

[0051]

[0052] Example 4

[0053] This embodiment provides a tackifier for silicone rubber, which has the following structural formula:

[0054]

[0055] The preparation method of the tackifier for silicone rubber in this embodiment includes the following steps:

[0056] (1) Load 600 g of vinyl-terminated polysiloxane with a number-average molecular weight of 40,000, 0.6 g of 3000 ppm Karstedt's catalyst, and 300 g of toluene into a 1000 mL three-necked flask. Dropwise add 2.16 g of trimethoxyhydroxysilane under stirring conditions. After the dropping is complete, heat to 80 °C and react for 6 hours. After vacuum distillation, 570 g of the first reaction mixture is obtained;

[0057] (2) Load 100 g of the first reaction mixture, 3.5 g of trimethoxyhydroxysilane, and 14.8 mg of tris(pentafluorophenyl)borane into a 500 mL three-necked flask. Heat to 60 °C under a nitrogen atmosphere and react for 30 minutes. After vacuum distillation, 87 g of the second reaction mixture is obtained. Then, load 50 g of the second reaction mixture, 3 g of the active substance with the structure of formula 4, and 0.1 g of n-butyl titanate into a 500 mL three-necked flask. React at 80 °C for 4 hours. After vacuum distillation, 46 g of the tackifier for silicone rubber is obtained;

[0058] The reaction route of the tackifier for silicone rubber in this embodiment is as follows:

[0059]

[0060] Example 5

[0061] This embodiment provides a tackifier for silicone rubber, which has the following structural formula:

[0062]

[0063] The preparation method of the tackifier for silicone rubber in this embodiment includes the following steps:

[0064] (1) Load 600 g of vinyl-terminated polysiloxane with a number-average molecular weight of 40,000, 0.6 g of 3000 ppm Karstedt's catalyst, and 300 g of toluene into a 1000 mL three-necked flask. Dropwise add 2.16 g of trimethoxyhydroxysilane under stirring conditions. After the dropping is complete, heat to 80 °C and react for 6 hours. After vacuum distillation, 570 g of the first reaction mixture is obtained;

[0065] (2) 100 g of the first reaction mixture, 3.5 g of trimethoxysilane, and 14.8 mg of tris(pentafluorophenyl)borane were charged into a 500 mL three-necked flask, heated to 60 °C under a nitrogen atmosphere, and reacted for 30 minutes. After vacuum distillation, 85 g of the second reaction mixture was obtained. Then, 50 g of the second reaction mixture, 1.2 g of 2-methoxy-4-methylphenol, 1.5 g of the active substance having the structure of Formula 4, and 0.1 g of tetrabutyl titanate were charged into a 500 mL three-necked flask and reacted at 80 °C for 4 hours. After vacuum distillation, 45 g of the tackifier for silicone rubber was obtained;

[0066] The reaction route of the tackifier for silicone rubber in this example is as follows:

[0067]

[0068] Comparative Example 1

[0069] This comparative example provides a tackifier 1 for silicone rubber. The preparation of the tackifier 1 for silicone rubber includes:

[0070] 100 g of hydrogen-containing silicone oil with a viscosity of 82 cs (hydrogen content: 0.75%), 40 g of 1,6-hexanediol diacrylate (HDDA), and 0.5 g of 3000 ppm of Karstedt's catalyst were mixed in 50 g of toluene and reacted at 80 °C for 6 hours. After vacuum distillation, 115 g of the tackifier 1 for silicone rubber was obtained.

[0071] Comparative Example 2

[0072] This comparative example provides a tackifier 2 for silicone rubber. The preparation of the tackifier 2 for silicone rubber includes:

[0073] 100 g of hydrogen-containing silicone oil with a viscosity of 82 cs (hydrogen content: 0.75%), 20 g of allyl glycidyl ether, and 0.5 g of 3000 ppm of Karstedt's catalyst were mixed in 50 g of toluene and reacted at 80 °C for 6 hours. After vacuum distillation, 98 g of the tackifier 2 for silicone rubber was obtained.

[0074] Comparative Example 3

[0075] This comparative example provides a tackifier 3 for silicone rubber. The preparation of the tackifier 3 for silicone rubber includes:

[0076] 100 g of hydrogen-containing silicone oil with a viscosity of 82 cs (hydrogen content: 0.75%), 20 g of trimethoxyvinylsilane, and 0.5 g of chloroplatinic acid-isopropanol (pt: 1000 ppm) were mixed in 50 g of toluene and reacted at 80 °C for 6 hours. After vacuum distillation, 102 g of the tackifier 3 for silicone rubber was obtained.

[0077] Using the self-made addition-type liquid silicone rubber (A+B components) as the base material, the silicone rubbers prepared in Examples 1-5 and Comparative Examples 1-3 were added to the silicone rubber B component at an addition amount of 2 wt% respectively with a tackifier. The A and B components were fully mixed at a mass ratio of 1:1 and vacuum degassed. The silicone rubber compositions were bonded to polycarbonate substrates (PC), polyamide substrates (PA), and stainless steel respectively, and cured at 130°C for 5 minutes. After curing, the shear strength was tested according to GB / T 13936-2014. The test results are shown in Table 1:

[0078] The steps for preparing the self-made addition-type liquid silicone rubber are as follows:

[0079] A) Put 478 g of the liquid base rubber with the brand number GA-2860BS, 20 g of polyvinyl silicone oil with a viscosity of 1000 cs (vinyl content 5 wt%), and 2 g of a Kaster catalyst at 3000 ppm into a mixer and mix evenly to obtain Component A.

[0080] B) Put 449.8 g of the liquid base rubber with the brand number GA-2860BS, 20 g of polyvinyl silicone oil with a viscosity of 1000 cs (vinyl content 5 wt%), 30 g of hydrogen-containing silicone oil with a viscosity of 82 cs (hydrogen content about 0.75%), and 0.2 g of ethynylcyclohexanol into a mixer and mix evenly to obtain Component B.

[0081] Table 1

[0082]

[0083] As can be seen from Table 1, the tackifier for the silicone rubbers in Examples 1-5 can enhance the bonding effect between the silicone rubber and various substrates. This is because one end of the structure of the tackifier for the silicone rubber of the present invention is vinyl and the other end is a branched structure formed by 3 or 3m active groups R x In this structure, the vinyl and active groups reacting with the silicone rubber and the substrate are respectively located at both ends of the polysiloxane chain, and the molecular weight is relatively high. It can effectively cause the end containing active groups to migrate to the interface between the silicone rubber and the substrate due to poor compatibility, and the end containing vinyl reacts with the silicone rubber, thereby improving the stable bonding between the silicone rubber and the substrate; the purpose of selectively bonding one or several substrates can also be achieved by adjusting the type of active groups, thereby enhancing the bonding effect between the silicone rubber and various substrates.

[0084] As can be seen from Table 1, the tackifiers for silicone rubber in Comparative Examples 1 to 3 cannot enhance the adhesion effect between silicone rubber and various substrates. This is because Comparative Examples 1 to 3 are hydrogen-containing silicone oil systems, and the molecular weight of hydrogen-containing silicone oil is not high. Therefore, when the silicone rubber and the substrate do not fit well, it cannot play a role in connecting the two; at the same time, most of the functional groups on the tackifiers in Comparative Examples 1 to 3 are single functional groups, or even if there are multiple functional groups, their distribution is disordered. Therefore, the adhesion between silicone rubber and different substrates cannot be precisely controlled.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A tackifier for silicone rubber, characterized in that: Having the structure shown in Formula 1 or Formula 2: where R x for At least one of R5, R6, R7, and R8 are each independently selected from H or methoxy, and at most only one of R5, R6, R7, and R8 is methoxy; n is 100-1000.

2. The tackifier for silicone rubber according to claim 1, wherein n is 300 to 1000.

3. A method for preparing a tackifier for silicone rubber according to claim 1, characterized in that the steps include: (1) mixing vinyl-terminated polysiloxane, trimethoxysilane, a first catalyst, and toluene, and heating the mixture to obtain a first reaction mixture; (2) mixing the first reaction mixture, esters, and active substances, and heating the mixture to obtain the structure shown in Formula 1; or mixing the first reaction mixture, trimethoxysilane, and a second catalyst, and heating the mixture to obtain a second reaction mixture, and then heating the second reaction mixture, esters, and active substances to obtain the structure shown in Formula 2; The vinyl-terminated polysiloxane has a structure shown in Formula 3: Where n is 100 to 1000; The active ingredient is At least one of, wherein R5, R6, R7, and R8 are each independently selected from H or methoxy, and at most only one of R5, R6, R7, and R8 is methoxy.

4. The method for preparing a tackifier for silicone rubber according to claim 3, wherein: The first catalyst is 3000 ppm of KARSTEDT catalyst.

5. The method for preparing a tackifier for silicone rubber according to claim 3, wherein: The second catalyst is tris(pentafluorophenyl)borane catalyst.

6. The method for preparing a tackifier for silicone rubber according to claim 3, wherein: The ester is n-butyl titanate.

7. The method for preparing a tackifier for silicone rubber according to claim 3, wherein: The temperature of the heating reaction in step (1) is 78-82° C., and the time of the heating reaction is 5.5-6.5 hours.

8. The method for preparing a tackifier for silicone rubber according to claim 3, wherein: Step (2) comprises reacting the first reaction mixture, esters, and active substances at 78-82° C. for 3.5-4.5 hours, and then distilling under reduced pressure to obtain the structure shown in Formula 1.

9. The method for preparing a tackifier for silicone rubber according to claim 3, wherein: Step (2) comprises mixing the first reaction mixture, trimethoxysilane and a second catalyst, heating the mixture to 58-62° C. under a nitrogen atmosphere, reacting the mixture for 25-35 minutes, and obtaining a second reaction mixture after vacuum distillation.

10. The method for preparing a tackifier for silicone rubber according to claim 3, wherein: Step (2) comprises reacting the second reaction mixture, esters, and active substances at 78-82° C. for 3.5-4.5 hours, and then distilling under reduced pressure to obtain the structure shown in Formula 2.

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