Rubber sealing element material for security lens and preparation process of rubber sealing element material

Abstract

The invention relates to the technical field of sealing materials, in particular to a rubber sealing element material for a security lens and a preparation process thereof.The preparation process includes the steps that alkali lignin serves as a raw material to prepare alkali lignin nano-particles, then the alkali lignin nano-particles and graphene oxide are assembled together to prepare composite graphene oxide, epoxy chloropropane is used for epoxidizing the composite graphene oxide, then epoxy-amino reaction is utilized, and the rubber sealing element material for the security lens is obtained. Grafting a fluorine-containing diamine compound; the preparation method comprises the following steps: by taking environment-friendly materials oleic acid and 1, 6-hexanediol as raw materials, firstly esterifying to obtain a plasticizer 1, 6-hexanediol oleate, then epoxidizing, and grafting a fluorine-containing diamine compound by utilizing epoxy-amino reaction to generate an oleic acid derivative as a plasticizer; firstly, formic acid-hydrogen peroxide in-situ epoxidation is carried out to synthesize epoxidized ethylene propylene diene monomer as a raw material of ethylene propylene diene monomer.

Description

Technical Field

[0001] The invention relates to the technical field of sealing materials, in particular to a rubber sealing material for a security lens and a preparation process thereof. Background Art

[0002] Security lenses are the eyes of the security industry and an important part of the security system. As the main component of security lenses, the performance of seals directly affects the image clarity and service life of security lenses.

[0003] For example, when the sealing material for security lenses is not waterproof, water droplets condense on the lens in rainy, foggy, snowy and other weather conditions, causing blurred images. In hot weather, because the high temperature resistance and sealing properties of the sealing material for security lenses are limited, oil substances may precipitate from the internal components, making the image blurred. Therefore, developing a sealing material for security lenses that is water-resistant, high-temperature resistant and well-sealed has practical significance and economic value. Summary of the invention

[0004] The object of the present invention is to provide a rubber sealing material for a security lens and a preparation process thereof, so as to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A rubber sealing material for a security lens comprises the following raw materials, measured in parts by weight: 80 parts of composite EPDM rubber, 20 parts of silica gel, 2-5 parts of activator, 12-18 parts of modified graphene oxide, 20-35 parts of plasticizer, 1-3 parts of accelerator and 1-3 parts of vulcanizer; the silica gel is obtained by compounding gas phase silica gel and precipitated silica gel in a mass ratio of 1:1.

[0007] Furthermore, the activator is prepared by mixing zinc oxide, stearic acid and itaconic acid in a mass ratio of 4:1:1.

[0008] Furthermore, the accelerator is one or a combination of 2-mercaptobenzothiazole, N,N'-diphenyl-thiourea, and N-cyclohexyl-2-benzothiazole sulfenamide.

[0009] Furthermore, the composite EPDM rubber is obtained by compounding EPDM rubber and epoxidized EPDM rubber in a mass ratio of 1:1.

[0010] Further, the preparation of epoxidized EPDM rubber comprises the following steps:

[0011] In a nitrogen atmosphere, EPDM rubber and n-hexane are mixed, kept in a water bath at 48-52°C for 10-15 minutes, formic acid and Tween 80 are added, stirred for 10-15 minutes, hydrogen peroxide is added, kept in a temperature range of 7-8 hours, washed with an aqueous sodium carbonate solution, separated, washed with deionized water to neutrality, added to anhydrous ethanol, and dried in a vacuum to obtain epoxidized EPDM rubber;

[0012] Further, the preparation of modified graphene oxide comprises the following steps:

[0013] (1) mixing graphene oxide powder and ultrapure water, ultrasonically treating for 8-10 min, adding a mixed solution of alkali lignin and ultrapure water, adjusting the pH value to 9.9-10.1, centrifuging, vacuum filtering, and drying to obtain composite graphene oxide;

[0014] (2) mixing composite graphene oxide and N,N-dimethylformamide, ultrasonically dispersing, adding potassium fluoride and potassium iodide, stirring for 10-15 minutes, adding epichlorohydrin, heating to 98-102° C. and keeping warm for 14-15 hours, centrifuging, washing, and freeze-drying to obtain epoxidized composite graphene oxide;

[0015] (3) Under a nitrogen atmosphere, the epoxidized composite graphene oxide, the fluorinated diamine compound, and dimethyl sulfoxide are mixed, the temperature is raised to 105-110° C. and kept for 3-4 hours, cooled, washed, and dried to obtain modified graphene oxide.

[0016] Furthermore, the plasticizer is an oleic acid derivative.

[0017] Further, the preparation of oleic acid derivatives comprises the following steps:

[0018] 1) Under a nitrogen atmosphere, oleic acid and 1,6-hexanediol are mixed, concentrated sulfuric acid is added, the temperature is raised to 128-132°C and kept warm for 7-8 hours, the solution is washed with sodium bicarbonate until neutral, washed with water, and allowed to stand to obtain 1,6-hexanediol oleate; 1,6-hexanediol oleate, hydrogen peroxide solution, formic acid, and concentrated sulfuric acid are mixed, stirred at 58-62°C for 7-8 hours, washed with deionized water until neutral, and rotary evaporated to obtain epoxy 1,6-hexanediol oleate;

[0019] 2) In a nitrogen atmosphere, epoxy 1,6-hexanediol oleate, a fluorinated diamine compound and dimethyl sulfoxide are mixed, heated to 100-105° C. and kept warm for 4-5 hours, cooled, washed and dried to obtain an oleic acid derivative.

[0020] Further, the preparation of the fluorine-containing diamine compound comprises the following steps:

[0021] Under a nitrogen atmosphere, p-trifluoromethylbenzaldehyde and 2,6-dimethylaniline are mixed, heated to 78-82°C, hydrochloric acid solution is added, heated to 148-152°C and kept warm for 23-24 hours, cooled, sodium hydroxide solution is added, extracted with dichloromethane for 3-5 times, washed with deionized water and saturated sodium chloride solution for 3-5 times, rotary evaporated, poured into methanol for precipitation, filtered, washed and dried to obtain a fluorine-containing diamine compound.

[0022] Furthermore, a preparation process of a rubber sealing material for a security lens comprises the following steps: putting composite EPDM rubber and silicone into an internal mixer, then sequentially adding modified graphene oxide, an activator, and a plasticizer, mixing, degumming, transferring to an open mixer, adding a vulcanizer and an accelerator, filtering, standing, and vulcanizing to obtain a rubber sealing material for a security lens.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The invention provides a rubber sealing material for a security lens and a preparation process thereof. By optimizing component composition and process design, a sealing material with good sealing performance, good water resistance, high temperature resistance and aging resistance is prepared, which meets the requirements of the security lens for the sealing material.

[0025] In the present invention, graphene oxide is selected as a reinforcing agent, lignin is selected as an antioxidant, alkali lignin is used as a raw material to prepare alkali lignin nanoparticles, and then the alkali lignin nanoparticles are co-assembled with graphene oxide to prepare composite graphene oxide. In order to improve the uniformity of dispersion of the composite graphene oxide in a rubber matrix, the composite graphene oxide is modified by first epoxidizing it with epichlorohydrin, and then grafting a fluorine-containing diamine compound by epoxy-amino reaction, wherein the fluorine-containing diamine compound is prepared with p-trifluoromethylbenzaldehyde and 2,6-dimethylaniline as raw materials, and fluorine element is introduced to improve its water resistance and thermal stability. At the same time, the introduction of multiple active sites on the modified graphene oxide helps to improve its interface compatibility with the rubber matrix, so that the graphene oxide and lignin are firmly attached to the sealing material, and the durability of its use is improved.

[0026] Most of the current chemical plasticizers have the problems of high cost, poor migration resistance, and being unfriendly to the environment. In the present invention, environmentally friendly materials oleic acid and 1,6-hexanediol are used as raw materials, and the plasticizer 1,6-hexanediol oleate is first esterified, then epoxidized, and then the epoxy-amino reaction is used to graft the fluorinated diamine compound to generate an oleic acid derivative with good water resistance and high thermal stability as a plasticizer, thereby greatly improving the various properties of the sealing material.

[0027] In order to reduce the usage content of the vulcanizing agent in the present invention, the epoxidized EPDM rubber is first synthesized as the raw material of the EPDM rubber by in-situ epoxidation with formic acid-hydrogen peroxide, and a cross-linked network structure containing ester bonds is constructed with an activator, modified graphene oxide and a plasticizer based on the reaction of epoxy with amino groups and carboxyl groups. At the same time, the addition of zinc oxide in the activator can activate the epoxy group, effectively improve its cross-linking efficiency and cross-linking density, thereby improving various properties of the sealing material. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that if the embodiments of the present invention involve directional indications such as up, down, left, right, front, and back, the directional indication is only used to explain a specific posture such as the relative position relationship between the components, the movement status, etc. If the specific posture changes, the directional indication will also change accordingly. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0030] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0031] Embodiment 1: A preparation process of a rubber sealing material for a security lens, comprising the following steps: putting composite EPDM rubber and silica gel into an internal mixer, then sequentially adding modified graphene oxide, an activator, and a plasticizer, mixing, removing the glue, transferring to an open mixer, adding a vulcanizing agent and an accelerator, filtering, standing, and vulcanizing to obtain a rubber sealing material for a security lens;

[0032] The raw material composition of the sealing material is as follows, in parts by weight: 80 parts of composite EPDM rubber, 20 parts of silica gel, 2 parts of activator, 12 parts of modified graphene oxide, 20 parts of plasticizer, 1 part of accelerator, and 1 part of vulcanizer; the silica gel is obtained by compounding gas phase silica gel and precipitated silica gel in a mass ratio of 1:1;

[0033] The activator is prepared by mixing zinc oxide, stearic acid and itaconic acid in a mass ratio of 4:1:1;

[0034] The accelerator is 2-mercaptobenzothiazole;

[0035] The composite EPDM rubber is obtained by compounding EPDM rubber and epoxidized EPDM rubber in a mass ratio of 1:1;

[0036] The preparation of the epoxidized EPDM rubber comprises the following steps:

[0037] Under nitrogen atmosphere, 30 g of EPDM rubber and 500 mL of n-hexane were mixed, kept warm in a 48°C water bath for 15 min, 0.6 g of formic acid and 1.5 g of Tween 80 were added, stirred for 10 min, 5.1 g of hydrogen peroxide was added, kept warm for 7 h, washed with sodium carbonate aqueous solution, separated, washed with deionized water to neutrality, added to 1 L of anhydrous ethanol, and vacuum dried to obtain epoxidized EPDM rubber;

[0038] The preparation of the modified graphene oxide comprises the following steps:

[0039] (1) 0.2 g of graphene oxide powder and 150 mL of ultrapure water were mixed, ultrasonically treated for 8 min, 2 g of alkali lignin and 50 mL of ultrapure water were added, the pH value was adjusted to 9.9, centrifuged, vacuum filtered, and dried to obtain composite graphene oxide;

[0040] (2) 0.2 g of composite graphene oxide and 100 mL of N,N-dimethylformamide were mixed, ultrasonically dispersed, 37.6 g of potassium fluoride and 5 g of potassium iodide were added, stirred for 10 min, 20 mL of epichlorohydrin was added, the temperature was raised to 98 ° C and kept warm for 15 h, centrifuged, washed, and freeze-dried to obtain epoxidized composite graphene oxide;

[0041] (3) Under a nitrogen atmosphere, 5.3 g of epoxidized composite graphene oxide, 2.2 g of a fluorinated diamine compound, and 100 mL of dimethyl sulfoxide were mixed, the temperature was raised to 105° C. and kept for 4 h, cooled, washed, and dried to obtain modified graphene oxide;

[0042] The plasticizer is an oleic acid derivative, and the preparation comprises the following steps:

[0043] 1) Under a nitrogen atmosphere, 2.1 g of oleic acid and 5.9 g of 1,6-hexanediol were mixed, 0.03 g of concentrated sulfuric acid was added, the temperature was raised to 128°C and kept warm for 8 h, the solution was washed with sodium bicarbonate until neutral, washed with water, and allowed to stand to obtain 1,6-hexanediol oleate; 0.6 g of 1,6-hexanediol oleate, 0.4 g of a 30% hydrogen peroxide solution, 0.09 g of formic acid, and 6 mg of concentrated sulfuric acid were mixed, stirred at 58°C for 8 h, washed with deionized water until neutral, and rotary evaporated to obtain epoxy 1,6-hexanediol oleate;

[0044] 2) Under a nitrogen atmosphere, 0.8 g of epoxy 1,6-hexanediol oleate, 0.5 g of a fluorinated diamine compound, and 20 mL of dimethyl sulfoxide were mixed, the temperature was raised to 100° C. and kept for 5 h, cooled, washed, and dried to obtain an oleic acid derivative;

[0045] The preparation of the fluorine-containing diamine compound comprises the following steps:

[0046] Under a nitrogen atmosphere, 0.05 mol of p-trifluoromethylbenzaldehyde and 0.35 mol of 2,6-dimethylaniline were mixed, the temperature was raised to 78°C, 2 mL of a 37% hydrochloric acid solution was added, the temperature was raised to 148°C and kept warm for 24 hours, cooled, 12.5 mL of a 10% sodium hydroxide solution was added, and the mixture was extracted 3 times with 10 mL of dichloromethane, washed 3 times with deionized water and a saturated sodium chloride solution in turn, rotary evaporated, poured into methanol for precipitation, filtered, washed, and dried to obtain a fluorinated diamine compound.

[0047] Embodiment 2: A preparation process of a rubber sealing material for a security lens, comprising the following steps: putting a composite EPDM rubber into an internal mixer, then sequentially adding modified graphene oxide, an activator, and a plasticizer, mixing, removing the rubber, transferring to an open mixer, adding a vulcanizing agent and an accelerator, filtering, standing, and vulcanizing to obtain a rubber sealing material for a security lens;

[0048] The raw material composition of the sealing material is as follows, in parts by weight: 80 parts of composite EPDM rubber, 20 parts of silica gel, 3 parts of activator, 16 parts of modified graphene oxide, 29 parts of plasticizer, 2 parts of accelerator, and 2 parts of vulcanizer; the silica gel is obtained by compounding gas phase silica gel and precipitated silica gel in a mass ratio of 1:1;

[0049] The activator is prepared by mixing zinc oxide, stearic acid and itaconic acid in a mass ratio of 4:1:1;

[0050] The accelerator is 2-mercaptobenzothiazole;

[0051] The composite EPDM rubber is obtained by compounding EPDM rubber and epoxidized EPDM rubber in a mass ratio of 1:1;

[0052] The preparation of the epoxidized EPDM rubber comprises the following steps:

[0053] Under nitrogen atmosphere, 30 g of EPDM rubber and 500 mL of n-hexane were mixed, kept warm in a 50°C water bath for 12 min, 0.6 g of formic acid and 1.5 g of Tween 80 were added, stirred for 13 min, 5.1 g of hydrogen peroxide was added, kept warm for 7.5 h, washed with sodium carbonate aqueous solution, separated, washed with deionized water to neutrality, added to 1 L of anhydrous ethanol, and vacuum dried to obtain epoxidized EPDM rubber;

[0054] The preparation of the modified graphene oxide comprises the following steps:

[0055] (1) 0.2 g of graphene oxide powder and 150 mL of ultrapure water were mixed, ultrasonically treated for 9 min, 2 g of alkali lignin and 50 mL of ultrapure water were added, the pH value was adjusted to 10, centrifuged, vacuum filtered, and dried to obtain composite graphene oxide;

[0056] (2) 0.2 g of composite graphene oxide and 100 mL of N,N-dimethylformamide were mixed, ultrasonically dispersed, 37.6 g of potassium fluoride and 5 g of potassium iodide were added, stirred for 13 min, 20 mL of epichlorohydrin was added, the temperature was raised to 100 ° C and kept for 14.5 h, centrifuged, washed, and freeze-dried to obtain epoxidized composite graphene oxide;

[0057] (3) Under a nitrogen atmosphere, 5.3 g of epoxidized composite graphene oxide, 2.2 g of a fluorinated diamine compound, and 100 mL of dimethyl sulfoxide were mixed, the temperature was raised to 108° C. and kept for 3.5 h, cooled, washed, and dried to obtain modified graphene oxide.

[0058] The plasticizer is an oleic acid derivative, and the preparation comprises the following steps:

[0059] 1) Under a nitrogen atmosphere, 2.1 g of oleic acid and 5.9 g of 1,6-hexanediol were mixed, 0.03 g of concentrated sulfuric acid was added, the temperature was raised to 130° C. and kept warm for 7.5 h, the solution was washed with sodium bicarbonate until neutral, washed with water, and allowed to stand to obtain 1,6-hexanediol oleate; 0.6 g of 1,6-hexanediol oleate, 0.4 g of a 30% hydrogen peroxide solution, 0.09 g of formic acid, and 6 mg of concentrated sulfuric acid were mixed, stirred at 60° C. for 7.5 h, washed with deionized water until neutral, and rotary evaporated to obtain epoxy 1,6-hexanediol oleate;

[0060] 2) Under a nitrogen atmosphere, 0.8 g of epoxy 1,6-hexanediol oleate, 0.5 g of a fluorinated diamine compound, and 20 mL of dimethyl sulfoxide were mixed, the temperature was raised to 103° C. and kept for 4.5 h, cooled, washed, and dried to obtain an oleic acid derivative;

[0061] The preparation of the fluorine-containing diamine compound comprises the following steps:

[0062] Under a nitrogen atmosphere, 0.05 mol of p-trifluoromethylbenzaldehyde and 0.35 mol of 2,6-dimethylaniline were mixed, the temperature was raised to 80°C, 2 mL of a 37% hydrochloric acid solution was added, the temperature was raised to 150°C and kept warm for 23.5 h, cooled, 12.5 mL of a 10% sodium hydroxide solution was added, and the mixture was extracted 4 times with 10 mL of dichloromethane, washed 4 times with deionized water and a saturated sodium chloride solution in turn, rotary evaporated, poured into methanol for precipitation, filtered, washed, and dried to obtain a fluorinated diamine compound.

[0063] Embodiment 3: A preparation process of a rubber sealing material for a security lens, comprising the following steps: putting a composite EPDM rubber into an internal mixer, then sequentially adding modified graphene oxide, an activator, and a plasticizer, mixing, removing the rubber, transferring to an open mixer, adding a vulcanizing agent and an accelerator, filtering, standing, and vulcanizing to obtain a rubber sealing material for a security lens;

[0064] The raw material composition of the sealing material is as follows, in parts by weight: 80 parts of composite EPDM rubber, 20 parts of silica gel, 5 parts of activator, 18 parts of modified graphene oxide, 35 parts of plasticizer, 3 parts of accelerator, and 3 parts of vulcanizer; the silica gel is obtained by compounding gas phase silica gel and precipitated silica gel in a mass ratio of 1:1;

[0065] The activator is prepared by mixing zinc oxide, stearic acid and itaconic acid in a mass ratio of 4:1:1;

[0066] The accelerator is 2-mercaptobenzothiazole;

[0067] The composite EPDM rubber is obtained by compounding EPDM rubber and epoxidized EPDM rubber in a mass ratio of 1:1;

[0068] The preparation of the epoxidized EPDM rubber comprises the following steps:

[0069] Under nitrogen atmosphere, 30 g of EPDM rubber and 500 mL of n-hexane were mixed, kept warm in a 52°C water bath for 10 min, 0.6 g of formic acid and 1.5 g of Tween 80 were added, stirred for 15 min, 5.1 g of hydrogen peroxide was added, kept warm for 8 h, washed with sodium carbonate aqueous solution, separated, washed with deionized water to neutrality, added to 1 L of anhydrous ethanol, and vacuum dried to obtain epoxidized EPDM rubber;

[0070] The preparation of the modified graphene oxide comprises the following steps:

[0071] (1) 0.2 g of graphene oxide powder and 150 mL of ultrapure water were mixed, ultrasonically treated for 10 min, 2 g of alkali lignin and 50 mL of ultrapure water were added, the pH value was adjusted to 10.1, centrifuged, vacuum filtered, and dried to obtain composite graphene oxide;

[0072] (2) 0.2 g of composite graphene oxide and 100 mL of N,N-dimethylformamide were mixed, ultrasonically dispersed, 37.6 g of potassium fluoride and 5 g of potassium iodide were added, stirred for 15 min, 20 mL of epichlorohydrin was added, the temperature was raised to 102 ° C and kept warm for 14 h, centrifuged, washed, and freeze-dried to obtain epoxidized composite graphene oxide;

[0073] (3) Under a nitrogen atmosphere, 5.3 g of epoxidized composite graphene oxide, 2.2 g of a fluorinated diamine compound, and 100 mL of dimethyl sulfoxide were mixed, the temperature was raised to 110° C. and kept for 3 h, cooled, washed, and dried to obtain modified graphene oxide;

[0074] The plasticizer is an oleic acid derivative, and the preparation comprises the following steps:

[0075] 1) Under a nitrogen atmosphere, 2.1 g of oleic acid and 5.9 g of 1,6-hexanediol were mixed, 0.03 g of concentrated sulfuric acid was added, the temperature was raised to 132° C. and kept warm for 7 h, the solution was washed with sodium bicarbonate until neutral, washed with water, and allowed to stand to obtain 1,6-hexanediol oleate; 0.6 g of 1,6-hexanediol oleate, 0.4 g of a 30% hydrogen peroxide solution, 0.09 g of formic acid, and 6 mg of concentrated sulfuric acid were mixed, stirred at 62° C. for 7 h, washed with deionized water until neutral, and rotary evaporated to obtain epoxy 1,6-hexanediol oleate;

[0076] 2) Under a nitrogen atmosphere, 0.8 g of epoxy 1,6-hexanediol oleate, 0.5 g of a fluorinated diamine compound, and 20 mL of dimethyl sulfoxide were mixed, the temperature was raised to 105° C. and kept for 4 h, cooled, washed, and dried to obtain an oleic acid derivative;

[0077] The preparation of the fluorine-containing diamine compound comprises the following steps:

[0078] Under a nitrogen atmosphere, 0.05 mol of p-trifluoromethylbenzaldehyde and 0.35 mol of 2,6-dimethylaniline were mixed, the temperature was raised to 82°C, 2 mL of a 37% hydrochloric acid solution was added, the temperature was raised to 152°C and kept warm for 23 h, cooled, 12.5 mL of a 10% sodium hydroxide solution was added, extracted with 10 mL of dichloromethane for 5 times, washed with deionized water and a saturated sodium chloride solution for 5 times, rotary evaporated, poured into methanol for precipitation, filtered, washed, and dried to obtain a fluorinated diamine compound.

[0079] Comparative Example 1: Taking Example 3 as the control group, the modified graphene oxide was replaced by graphene oxide, and the other processes were normal.

[0080] Comparative Example 2: Using Example 3 as a control group, dioctyl phthalate (D109648: Aladdin reagent) was used to replace the oleic acid derivative, and the other processes were normal.

[0081] Comparative Example 3: Example 3 was used as the control group, epoxidized EPDM rubber was not prepared, and other processes were normal.

[0082] In the embodiments and comparative examples, the vulcanization working conditions are: temperature of 175° C. and time of 240 s.

[0083] Sources of raw materials used (for demonstration purposes only):

[0084] EPDM rubber 5467C: Alanxin; fumed silica gel TY171-70, precipitated silica gel TY371-70: Xin'an Tianyu Silicone Co., Ltd.; curing agent C-14: Dawei Technology; alkali lignin 471003: Sigma-Aldrich (Shanghai) Trading Co., Ltd.; zinc oxide Z111836, stearic acid S754992, itaconic acid I106140, 2-mercaptobenzothiazole M104864, Tween 80T434510, graphene oxide powder G139803, N, N-Dimethylformamide D111999, epichlorohydrin E108182, dimethyl sulfoxide D103274, oleic acid O108484, 1,6-hexanediol H103708, p-trifluoromethylbenzaldehyde T106647, 2,6-dimethylaniline D105633: Aladdin reagent; hydrochloric acid, sodium hydroxide, dichloromethane, sodium chloride, methanol, n-hexane, formic acid, sodium carbonate, ethanol, potassium fluoride, potassium iodide, hydrogen peroxide, formic acid, concentrated sulfuric acid, sodium bicarbonate, analytical grade: Sinopharm Group reagent.

[0085] Performance test: The sealing materials prepared in the embodiments and comparative examples were tested:

[0086] Water absorption test: Place a 5g sample in a constant temperature and humidity chamber (temperature 55°C, humidity 93%) and calculate the water absorption of the sample after 96 hours;

[0087] Compression test: keep the sample at 140℃ for 2h, put the sample into the compression deformation device (compression amount is 33.3%), keep the compression deformation device at 105℃ for 96h, take it out and place it for 30min to test the size of the sample, compression deformation = (h1-h2) / (h1-hs), where h1 is the initial sample size height, h2 is the sample height after the test, hs is the limiter height, which is 0.94cm, and the compression deformation is less than or equal to 30% to pass, otherwise it is unqualified;

[0088] Oil bleed test: put the oil absorbing paper and the sample into the compression deformation device (compression amount is 40%), keep the compression deformation device at 105℃ for 3h, then take out the sample to observe whether there is oil on the oil absorbing paper, if there is no oil, it is qualified, otherwise it is unqualified; the results are shown in Table 1;

[0089] Table 1

[0090] Water absorption (%) Compression test Oil leakage test Example 1 0.092 qualified qualified Example 2 0.091 qualified qualified Example 3 0.090 qualified qualified Comparative Example 1 0.123 Failure Failure Comparative Example 2 0.135 Failure Failure Comparative Example 3 0.126 Failure Failure

[0091] The invention provides a rubber sealing material for a security lens and a preparation process thereof. By optimizing component composition and process design, a sealing material with good sealing performance, good water resistance, high temperature resistance and aging resistance is prepared, which meets the requirements of the security lens for the sealing material.

[0092] By comparing Example 3 with Comparative Example 1, it can be seen that graphene oxide is selected as a reinforcing agent, lignin is selected as an antioxidant, and alkali lignin nanoparticles are prepared using alkali lignin as a raw material, and then co-assembled with graphene oxide to prepare composite graphene oxide. In order to improve the uniformity of dispersion of the composite graphene oxide in the rubber matrix, the composite graphene oxide is modified by first epoxidizing it with epichlorohydrin, and then utilizing the epoxy=amino reaction to graft a fluorine-containing diamine compound, wherein the fluorine-containing diamine compound is prepared using trifluoromethylbenzaldehyde and 2,6=dimethylaniline as raw materials, and the fluorine element is introduced to improve its water resistance and thermal stability. At the same time, the introduction of multiple active sites on the modified graphene oxide helps to improve its interfacial compatibility with the rubber matrix, so that the graphene oxide and lignin are firmly attached to the sealing material, thereby improving its durability in use.

[0093] By comparing Example 3 with Comparative Example 2, it can be seen that most of the current chemical plasticizers have the problems of high cost, poor migration resistance, and being unfriendly to the environment. In the present invention, environmentally friendly materials oleic acid and 1,6-hexanediol are used as raw materials, and the plasticizer 1,6-hexanediol oleate is first esterified and then epoxidized. Then, the epoxy-amino reaction is used to graft the fluorinated diamine compound to generate an oleic acid derivative with good water resistance and high thermal stability as a plasticizer, thereby greatly improving the various performances of the seal.

[0094] By comparing Example 3 with Comparative Example 3, it can be seen that in order to reduce the content of vulcanizing agent used in the present invention, epoxidized EPDM rubber is first synthesized as the raw material of EPDM rubber by in-situ epoxidation with formic acid-hydrogen peroxide, and a cross-linked network structure containing ester bonds is constructed with an activator, modified graphene oxide and a plasticizer based on the reaction of epoxy with amino and carboxyl groups. At the same time, the addition of zinc oxide in the activator can activate the epoxy group, effectively improve its crosslinking efficiency and crosslinking density, thereby improving various performances of the seal.

[0095] The above descriptions are only embodiments of the present invention and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the present invention specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A rubber sealing material for a security lens, characterized in that: The raw material composition of the sealing material is as follows, in parts by weight: 80 parts of composite EPDM rubber, 20 parts of silica gel, 2-5 parts of activator, 12-18 parts of modified graphene oxide, 20-35 parts of plasticizer, 1-3 parts of accelerator, and 1-3 parts of vulcanizer; the silica gel is obtained by compounding gas phase silica gel and precipitated silica gel in a mass ratio of 1:

1.

2. The rubber sealing material for security lens according to claim 1, characterized in that: The activator is prepared by mixing zinc oxide, stearic acid and itaconic acid in a mass ratio of 4:1:

1.

3. The rubber sealing material for security lens according to claim 1, characterized in that: The accelerator is one or a combination of 2-mercaptobenzothiazole, N,N'-diphenyl-thiourea, and N-cyclohexyl-2-benzothiazole sulfenamide.

4. The rubber sealing material for security lens according to claim 1, characterized in that: The composite EPDM rubber is obtained by compounding EPDM rubber and epoxidized EPDM rubber in a mass ratio of 1:

1.

5. The rubber sealing material for security lens according to claim 4, characterized in that: The preparation of the epoxidized EPDM rubber comprises the following steps: In a nitrogen atmosphere, EPDM rubber and n-hexane are mixed, kept warm in a water bath at 48-52°C for 10-15 min, formic acid and Tween 80 are added and stirred for 10-15 min, hydrogen peroxide is added, and the mixture is kept warm for 7-8 h, washed with an aqueous sodium carbonate solution, separated, washed with deionized water until neutral, added to anhydrous ethanol, and dried in vacuo to obtain epoxidized EPDM rubber.

6. The rubber sealing material for security lens according to claim 1, characterized in that: The plasticizer is an oleic acid derivative.

7. The rubber sealing material for security lens according to claim 6, characterized in that: The preparation of the oleic acid derivative comprises the following steps: 1) Under a nitrogen atmosphere, oleic acid and 1,6-hexanediol are mixed, concentrated sulfuric acid is added, the temperature is raised to 128-132°C and kept warm for 7-8 hours, the solution is washed with sodium bicarbonate until neutral, washed with water, and allowed to stand to obtain 1,6-hexanediol oleate; 1,6-hexanediol oleate, hydrogen peroxide solution, formic acid, and concentrated sulfuric acid are mixed, stirred at 58-62°C for 7-8 hours, washed with deionized water until neutral, and rotary evaporated to obtain epoxy 1,6-hexanediol oleate; 2) In a nitrogen atmosphere, epoxy 1,6-hexanediol oleate, a fluorinated diamine compound and dimethyl sulfoxide are mixed, heated to 100-105° C. and kept warm for 4-5 hours, cooled, washed and dried to obtain an oleic acid derivative.

8. The rubber sealing material for security lens according to claim 1, characterized in that: The preparation of the modified graphene oxide comprises the following steps: (1) mixing graphene oxide powder and ultrapure water, ultrasonically treating for 8-10 min, adding a mixed solution of alkali lignin and ultrapure water, adjusting the pH value to 9.9-10.1, centrifuging, vacuum filtering, and drying to obtain composite graphene oxide; (2) mixing composite graphene oxide and N,N-dimethylformamide, ultrasonically dispersing, adding potassium fluoride and potassium iodide, stirring for 10-15 minutes, adding epichlorohydrin, heating to 98-102° C. and keeping warm for 14-15 hours, centrifuging, washing, and freeze-drying to obtain epoxidized composite graphene oxide; (3) Under a nitrogen atmosphere, the epoxidized composite graphene oxide, the fluorinated diamine compound, and dimethyl sulfoxide are mixed, the temperature is raised to 105-110° C. and kept for 3-4 hours, cooled, washed, and dried to obtain modified graphene oxide.

9. A rubber sealing material for a security lens according to claim 7 or 8, characterized in that: The preparation of the fluorine-containing diamine compound comprises the following steps: Under a nitrogen atmosphere, p-trifluoromethylbenzaldehyde and 2,6-dimethylaniline are mixed, heated to 78-82°C, hydrochloric acid solution is added, heated to 148-152°C and kept warm for 23-24 hours, cooled, sodium hydroxide solution is added, extracted with dichloromethane for 3-5 times, washed with deionized water and saturated sodium chloride solution for 3-5 times, rotary evaporated, poured into methanol for precipitation, filtered, washed and dried to obtain a fluorine-containing diamine compound.

10. A process for preparing a rubber sealing material for a security lens according to any one of claims 1 to 8, characterized in that: The following steps are involved: The composite EPDM rubber and silica gel are put into an internal mixer, and then the modified graphene oxide, activator and plasticizer are added in sequence, mixed, discharged, transferred to an open mixer, vulcanizer and accelerator are added, filtered, allowed to stand, and vulcanized to obtain a rubber sealing material for security lenses.