BR-g-MAH, vulcanized rubber composition with metal adhesion, and method for improving rubber and metal adhesion

Abstract

The invention discloses BR-g-MAH, a vulcanized rubber composition with metal adhesiveness and a method for improving the adhesiveness of rubber and metal. The BR-g-MAH is prepared by the following steps: adding preparation raw materials including butadiene rubber and maleic anhydride into an internal mixer, and plastifying to obtain the BR-g-MAH. The invention provides a vulcanized rubber composition with metal adhesiveness. The vulcanized rubber composition is prepared from masterbatch, BR-g-MAH, sulfur, a vulcanization accelerator and a scorch retarder. The invention provides a method for improving adhesiveness of rubber and metal. The method comprises the steps that 1, activation pretreatment is conducted on the surface of the metal; 2, taking the raw material components according to the formula of the vulcanized rubber composition, mixing on a double-roller open mill, and discharging to obtain rubber sheets; 3, the activated metal and the rubber sheet are subjected to hot pressing vulcanization, and the vulcanized rubber-metal compound is obtained. According to the invention, the bonding of metal and rubber can be realized under the condition of no other bonding agent.

Description

Technical Field

[0001] The present invention relates to the technical field of metal-rubber bonding, and in particular to a BR-g-MAH, a vulcanized rubber composition with metal bonding, and a method for improving the bonding between rubber and metal. Background Art

[0002] Poor adhesion between rubber and metal is a common problem in the industry. Because rubber is generally non-polar and metal is polar, the interfacial forces between the two are generally weak. Therefore, improving the interfacial adhesion between rubber and metals (such as cast iron) is a pressing technical challenge. Summary of the Invention

[0003] The present invention aims to provide a BR-g-MAH, a vulcanized rubber composition having metal adhesion, and a method for improving the adhesion between the vulcanized rubber and metal. The present invention has a simple process, is environmentally friendly, has low cost, does not involve a cross-linking reaction, and can achieve adhesion between metal and rubber without other adhesives.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a BR-g-MAH, which is prepared by the following steps: adding the preparation raw materials into an internal mixer for plasticizing, the temperature in the internal mixer is 50-110°C, the rotation speed is 40-60rpm, and the plasticizing time is 5-15min to obtain BR-g-MAH; the preparation raw materials include butadiene rubber (BR) and maleic anhydride (MAH), and the mass ratio of butadiene rubber (BR) to maleic anhydride is 100:1-5.

[0006] Cis-1,4-butadiene rubber may be more likely to be grafted because it contains a double bond, but it is also more likely to be cross-linked. If you are not careful, the peroxide initiator will cause cross-linking to be formed between the rubber macromolecular chains. And MAH is a monomer that is difficult to self-polymerize, and a free radical can only cause a few MAH monomers to carry out grafting reaction. Therefore, how to avoid self-crosslinking of cis-1,4-butadiene rubber and improve grafting rate and grafting efficiency is a difficult problem for preparing BR-g-MAH. Plastication is a common method for reducing rubber molecular weight, which is essentially to tear off the molecular chain by force chemistry to form free radicals, but due to the presence of oxygen, rubber cross-linking is usually not caused. The present invention utilizes the principle of force chemistry, utilizes strong shear force to disconnect the BR macromolecular chain to form free radicals, and the cis double bond in the BR macromolecular chain can be converted into a trans double bond, and during the cis-trans isomerization conversion, the π bond of the double bond can be disconnected, forming an intermediate state with two free radicals, and the free radical can cause the double bond of maleic anhydride to carry out grafting reaction. Changing the formula (MAH / BR mass ratio) and process (mechanical chemical intensity, time, temperature) can change the grafting rate and grafting efficiency.

[0007] In the present application, the mass ratio of the butadiene rubber (BR) and maleic anhydride in the preparation raw material is 100:1-5, for example, 100:1, 100:2, 100:3, 100:4, 100:5, etc., and preferably, the mass ratio of the butadiene rubber (BR) and maleic anhydride (MAH) is 100:1.

[0008] In the present application, the temperature in the internal mixer is 50-110℃, for example, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, etc., and preferably, the temperature in the internal mixer is 50-90℃, and more preferably, 50℃. The plasticating time in the internal mixer is 5-15min, for example, 5min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 15min, etc., and preferably, 8-12min, and more preferably, 10min.

[0009] Since MAH is relatively easy to copolymerize with vinyl monomers and graft onto the BR molecular chain, the use of vinyl monomers can effectively increase the grafting rate of MAH, so in one embodiment, the preparation raw material further comprises a vinyl monomer, the vinyl monomer is styrene or acrylate or acrylic acid salt, and the mass ratio of the butadiene rubber to the vinyl monomer is 100:1-5, for example, 100:1, 100:2, 100:3, 100:4, 100:5, etc. As a preferred embodiment, the vinyl monomer is zinc acrylate (ZDA), which is an acrylate salt, and each ZDA molecule has two double bonds, which can copolymerize with MAH. In this case, the temperature in the internal mixer is 90-110℃, and more preferably, 110℃. As a further preferred embodiment, the mass ratio of the zinc acrylate to the butadiene rubber is 1:100.

[0010] In a second aspect, the present application provides a vulcanized rubber composition with metal adhesion, comprising a masterbatch, the BR-g-MAH of the first aspect, sulfur, a vulcanization accelerator and an anti-scorching agent; wherein the mass ratio of the masterbatch, the BR-g-MAH, the sulfur, the vulcanization accelerator and the anti-scorching agent is 100:60-70:1-2:0.5-1.5:0.1-0.3; and the masterbatch comprises natural rubber (NR), styrene-butadiene rubber (SBR) and butadiene rubber (BR).

[0011] As a preferred embodiment, the mass ratio of the masterbatch, the BR-g-MAH, the sulfur, the vulcanization accelerator and the anti-scorching agent is 100:64-69:1.2-1.6:0.7-1.2:0.1-0.2.

[0012] Preferably, the vulcanization accelerator is a combination of N-tert-butyl-2-benzothiazole sulfenamide (TBBS) and N-cyclohexyl-2-benzothiazole sulfenamide (CBS), and the scorch retarder is N-cyclohexylthiophthalimide (CTP); the masterbatch, BR-g-MAH, sulfur, N-tert-butyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide, N The mass ratio of -cyclohexylthiophthalimide is 100:60-70:1-2:0.3-0.6:0.4-0.8:0.1-0.3; more preferably 100:64-69:1.2-1.6:0.3-0.5:0.4-0.7:0.1-0.2; further preferably 100:66.67:1.43:0.46:0.53:0.15.

[0013] Preferably, in the masterbatch, the mass percentage contents of natural rubber (NR), styrene-butadiene rubber (SBR) and butadiene rubber (BR) are 15-25%, 5-15%, 30-40%, more preferably 18-22%, 8-10%, 32-36%, respectively.

[0014] Preferably, the masterbatch further contains carbon black, stearic acid (SA), ZnO, protective wax, leveling agent, process oil and antioxidant. Further preferably, in the masterbatch, the mass percentage contents of carbon black, stearic acid (SA), ZnO, protective wax, leveling agent, process oil and antioxidant are 20-30%, 0.5-1.5%, 1.5-3.0%, 1.0-2.5%, 1.0-2.5%, 0.8-1.5% and 2.0-3.0%, respectively, and more preferably 24-26%, 0.8-1.2%, 2.0-2.5%, 1.5-2.0%, 1.5-2.0%, 1.0-1.5% and 2.2-2.7%, respectively.

[0015] In the present invention, the protective wax, leveler, process oil and antioxidant may be conventional protective wax, leveler, process oil and antioxidant used for masterbatch.

[0016] The present invention adds BR-g-MAH to a vulcanized rubber composition. After BR is grafted with MAH, the originally non-polar BR becomes polar due to the MAH. MAH can react with hydroxyl groups on the metal surface (forming ester bonds) or modified active amine groups (forming amide bonds) or epoxy groups (forming ester bonds), thereby imparting metal adhesion to the vulcanized rubber and achieving strong adhesion to the metal. At the same time, the BR in the BR-g-MAH has excellent compatibility with rubbers such as NR in the masterbatch, and can react with sulfur and bond to the metal during the co-vulcanization process.

[0017] In a third aspect, the present application provides a method for improving the adhesion between rubber and metal, comprising the following steps:

[0018] Step 1: activating the surface of the metal to modify the surface with siloxane having terminal active amine group or epoxy group;

[0019] Step 2: obtaining masterbatch containing natural rubber (NR), styrene-butadiene rubber (SBR) and butadiene rubber (BR) by plasticating and mixing on an internal mixer; then weighing the raw material components according to the formulation of the vulcanized rubber composition with metal adhesion of the second aspect, mixing on a two-roll open mill, and finally sheeting to obtain rubber sheet;

[0020] Step 3: hot pressing and vulcanizing the activated metal of Step 1 and the rubber sheet obtained in Step 2 on a flat vulcanizing machine to obtain a vulcanized rubber-metal composite.

[0021] In an embodiment, the metal is cast iron sheet. As a preferred, the specific operation of Step 1 is as follows: the metal is immersed in NaOH aqueous solution, washed with water, dried, then the dried metal is immersed in a solution of siloxane having terminal active amine group or epoxy group, then washed and dried to obtain the activated metal.

[0022] As a further preferred, the siloxane having terminal active amine group is γ-aminopropyl triethoxysilane (KH550), and the dried metal is immersed in 5-10 wt% γ-aminopropyl triethoxysilane (KH550) aqueous solution for 30-40 min.

[0023] As a preferred, in Step 2, the masterbatch is obtained by the following operation on the internal mixer: natural rubber (NR), styrene-butadiene rubber (SBR) and butadiene rubber (BR) are put into the internal mixer for plasticating for 4-6 min, then carbon black and stearic acid (SA) are put in for further mixing for 3-4 min, then ZnO, protective wax, uniformizing agent, operating oil and antioxidant are put in for further mixing for 3-4 min, then the rubber is discharged to obtain the masterbatch; the mixing process parameters of the internal mixer are 90-110℃ and 40-60 rpm.

[0024] As a preferred, in Step 2, the rubber sheet is obtained by the following operation on the two-roll open mill: the BR-g-MAH and the masterbatch are mixed on the two-roll open mill in proportion for 2-3 min to make them wrap the roll; then vulcanization accelerator and anti-scorching agent are added for further mixing to make the additives uniformly dispersed; then sulfur is added for further mixing, and the rubber is passed through the mill 4-6 times and wrapped 6-8 times; finally, the rubber sheet is obtained by sheeting at a certain roll gap; wherein the rotation speed of the front and rear rolls of the two-roll open mill is (12-14) / (10-12) rpm, the temperature of the front and rear rolls is (50-60) / (50-60)℃, and the sheeting roll gap is 0.5-0.7 mm.

[0025] As preferred, in step 3, the vulcanization temperature in the flat vulcanization machine is 150-160℃, the preheating time is 2-4min, the pre-pressing time is 3-5min, the full-pressing time is 5-7min, the cooling time is 3-5min, and the pressure is 60-80bar.

[0026] The method for improving the adhesion of vulcanized rubber and metal according to the present application can realize the adhesion of metal and vulcanized rubber without using other adhesives.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] (1) The present application uses a mechanochemical method to prepare the grafted polymer BR-g-MAH, does not use organic solvents, is friendly to the environment, has mild reaction conditions, and is simple to operate; can greatly reduce the crosslinking reaction of BR in the MAH grafting process; and can effectively improve the grafting rate and grafting efficiency of MAH.

[0029] (2) The present application adds a vinyl monomer to the raw material for preparing the grafted polymer BR-g-MAH, increases the grafting rate of MAH through the principle that MAH and the vinyl monomer are easily copolymerized.

[0030] (3) The present application can realize the adhesion of metal and vulcanized rubber without using other adhesives. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic diagram of the adhesive film prepared by the present application for bonding metal and rubber.

[0032] Figure 2 is a schematic diagram of the principle of BR grafting MAH and ZDA in the present application.

[0033] Figure 3 is the FT-IR diagram of pure BR and BR after mechanochemical grafting in Example 8, wherein the peak at 1780cm -1 is the absorption peak of the carbonyl group in anhydride; the peak at 1697cm -1 is the absorption peak of hydrogen bonding of carboxylic acid; and the peak near 1600cm -1 is the non-anti-stretching vibration absorption peak of C-O in carboxylate. DETAILED DESCRIPTION

[0034] The present application will be further described below in conjunction with specific embodiments, but the scope of protection of the present application is not limited thereto:

[0035] In the examples of the present invention, if the specific conditions are not specified, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are conventional products that can be obtained by conventional techniques or purchased commercially.

[0036] In the present embodiment, the cis-1,4-butadiene rubber is BR9000, wherein the cis-1,4 structure accounts for 97.5%, the trans-1,4 structure accounts for 1.3%, and the 1,2-structure accounts for 1.3%. The number average molecular weight is 50,000-70,000, and the polydispersity coefficient is 4-6. The natural rubber (NR) is SVR 3L. The styrene-butadiene rubber (SBR) is SBR 1502.

[0037] The formula of the masterbatch used in the examples of the present invention is shown in Table 1. The preparation method is as follows: natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR) are placed in an internal mixer and masticated for 5 minutes. Carbon black N330 and stearic acid (SA) are then added and mixed for 3 minutes. ZnO, protective wax RW287 (Reba Chemical), leveling agent GS-103A (Yixing Xinghongsheng New Material Technology Co., Ltd.), operating oil FX8030 (Taizhou Yihu Trading Co., Ltd.), and antioxidant 4020 are then added and mixed for 3 minutes. The masterbatch is then discharged and set aside. The internal mixer mixing process parameters are 100°C and 60 rpm.

[0038] Table 1. Masterbatch formula

[0039]

[0040]

[0041] Example 1

[0042] Calculated by mass, the BR-g-MAH contains 100 parts of BR and 1 part of MAH.

[0043] Calculated by mass, the film contains 100 parts of masterbatch, 66.67 parts of BR-g-MAH, 0.46 parts of TBBS, 0.53 parts of CBS, 0.15 parts of CTP, and 1.43 parts of sulfur.

[0044] Preparation of BR-g-MAH: BR and MAH were weighed according to the formula, and all raw materials were directly put into an internal mixer for plastication at a temperature of 50°C, a speed of 40 rpm, and a plastication time of 10 min. MAH was grafted onto the BR molecular chain to obtain BR-g-MAH.

[0045] Preparation of the adhesive sheet: BR-g-MAH and masterbatch were mixed in proportion on a two-roll mill (LRM-S-150 / 3E, Lab Tech, USA) for 2-3 minutes to allow the rolls to wrap. The accelerators TBBS, CBS, and CTP (all commercially available) were then added and mixing continued to evenly disperse the additives. Sulfur (commercially available) was then added and mixing continued for 7 minutes. The sheet was thinned five times and triangularly wrapped seven times, and then stably discharged at a roll gap of 0.6 mm. The front and rear rolls of the two-roll mill rotated at 12 / 10 rpm, the front and rear roll temperatures were 60 / 55°C, and the sheeting roll gap was 0.6 mm.

[0046] Modification of cast iron sheets: The cast iron sheets were immersed in a 5 wt % NaOH aqueous solution for 10 min, rinsed with water, and dried at 60°C in a forced air drying oven (GZX-9076MBE, Shanghai Boxun Industrial Co., Ltd.) for 20 min. The dried cast iron sheets were then immersed in a 5 wt % KH 550 aqueous solution for 30 min, rinsed with ethanol, and dried at 60°C for 20 min.

[0047] Preparation of peeling specimens: The modified cast iron sheet and adhesive film were co-vulcanized using a flat plate vulcanizer (LP-S-50, Lab Tech, USA) at a vulcanization temperature of 150°C, a preheating time of 3 min, a pre-pressing time of 3 min, a full pressing time of 5 min, a cooling time of 3 min, and a pressure of 70 bar.

[0048] The prepared peeling specimens were subjected to a peeling strength test according to GB / T 7760-2003 to measure the peeling strength.

[0049] Example 2

[0050] Other steps were the same as those in Example 1, except that the amount of MAH added during the preparation of BR-g-MAH was increased from 1 part to 3 parts.

[0051] Example 3

[0052] Other steps were the same as those in Example 1, except that the amount of MAH added during the preparation of BR-g-MAH was increased from 1 part to 5 parts.

[0053] Example 4

[0054] Other steps were the same as those in Example 1, except that the internal mixer temperature during the preparation of BR-g-MAH was changed to 70°C.

[0055] Example 5

[0056] Other steps were the same as in Example 1, except that the internal mixer temperature during the preparation of BR-g-MAH was changed to 90°C.

[0057] Example 6

[0058] Other steps were the same as those in Example 1, except that the internal mixer speed during the preparation of BR-g-MAH was changed to 50 rpm.

[0059] Example 7

[0060] Other steps were the same as those in Example 1, except that the internal mixer speed during the preparation of BR-g-MAH was changed to 60 rpm.

[0061] Example 8

[0062] The other steps were the same as in Example 1, but 1 part of ZDA was added during the preparation of BR-g-MAH, and the internal mixer temperature during the preparation of BR-g-MAH was changed to 110°C.

[0063] Example 9

[0064] Other steps were the same as those in Example 8, except that the amount of ZDA added during the preparation of BR-g-MAH was increased from 1 part to 3 parts.

[0065] Example 10

[0066] Other steps were the same as those in Example 8, except that the amount of ZDA added during the preparation of BR-g-MAH was increased from 1 part to 5 parts.

[0067] Comparative Example 1

[0068] The other steps were the same as those in Example 1, but without adding MAH, that is, without carrying out the grafting reaction on BR.

[0069] Comparative Example 2

[0070] Other aspects are the same as those in Example 1, except that the cast iron sheet is not subjected to surface modification.

[0071] Comparative Example 3

[0072] The grafting was performed using a melt method. Calculated by weight, the BR-g-MAH contained 100 parts of BR, 1 part of MAH, and 0.3 parts of DCP.

[0073] Preparation of BR-g-MAH: BR, MAH, and DCP (all commercially available) were weighed according to the formula and directly placed into a 60 mL internal mixer for plasticization at a temperature of 150°C, a speed of 40 rpm, and a plasticization time of 10 min. MAH was grafted onto the BR molecular chain to obtain BR-g-MAH.

[0074] When this method is used to prepare BR-g-MAH, BR will crosslink rapidly and to a large extent, making subsequent processing difficult.

[0075] Table 2. Peel strength of various strips

[0076]

[0077]

Claims

1. A BR-g-MAH, characterized in that: The BR-g-MAH is prepared by the following steps: adding the raw materials to an internal mixer for plastication, wherein the temperature in the internal mixer is 50-110° C., the rotation speed is 40-60 rpm, and the plastication time is 10 minutes to obtain BR-g-MAH; the raw materials include butadiene rubber and maleic anhydride, and the mass ratio of the butadiene rubber to the maleic anhydride is 100:1-5.

2. The BR-g-MAH according to claim 1, wherein: The mass ratio of the butadiene rubber to maleic anhydride is 100:

1.

3. The BR-g-MAH according to claim 1 or 2, wherein: The temperature in the internal mixer is 50-90°C, preferably 50°C.

4. The BR-g-MAH according to claim 1, wherein: The preparation raw materials also include vinyl monomers, which are styrene or acrylate or acrylate, and the mass ratio of the butadiene rubber to the vinyl monomers is 100:1-5.

5. The BR-g-MAH according to claim 4, wherein: The vinyl monomer is zinc acrylate, and the temperature in the internal mixer is 90-110°C, preferably 110°C.

6. The BR-g-MAH according to claim 5, wherein: The feed mass ratio of the zinc acrylate to the butadiene rubber is 1:

100.

7. A vulcanized rubber composition having metal adhesion, characterized in that: The vulcanized rubber composition with metal adhesion comprises a masterbatch, the BR-g-MAH according to any one of claims 1 to 6, sulfur, a vulcanization accelerator, and a scorch retarder; wherein the mass ratio of the masterbatch, BR-g-MAH, sulfur, vulcanization accelerator, and scorch retarder is 100:60-70:1-2:0.5-1.5:0.1-0.3; the masterbatch comprises natural rubber, styrene-butadiene rubber, and butadiene rubber, preferably in a ratio of 100:64-69:1.2-1.6:0.7-1.2:0.1-0.

2.

8. The vulcanized rubber composition having metal adhesion according to claim 7, wherein: The vulcanization accelerator is a combination of N-tert-butyl-2-benzothiazolesulfenamide and N-cyclohexyl-2-benzothiazolesulfenamide, and the scorch retarder is N-cyclohexylthiophthalimide. The mass ratio of the masterbatch, BR-g-MAH, sulfur, N-tert-butyl-2-benzothiazolesulfenamide, N-cyclohexyl-2-benzothiazolesulfenamide, and N-cyclohexylthiophthalimide is 100:60-70:1-2:0.3-0.6:0.4-0.8:0.1-0.3; preferably 100:64-69:1.2-1.6:0.3-0.5:0.4-0.7:0.1-0.2; more preferably 100:66.67:1.43:0.46:0.53:0.

15.

9. A method for improving the adhesion between rubber and metal, characterized in that: The method comprises the following steps: Step 1: Activate and pretreat the metal surface so that the surface is modified with siloxane containing active amine or epoxy groups at the end; Step 2: first, a masterbatch containing natural rubber, styrene-butadiene rubber and butadiene rubber is obtained by masticating and mixing on an internal mixer; then, raw material components are weighed according to the formula of the vulcanized rubber composition with metal adhesion according to claim 7 or 8, mixed on a two-roll mill, and finally sheeted to obtain a film; Step 3: The metal activated in step 1 and the film obtained in step 2 are hot-pressed and vulcanized on a flat vulcanizer to obtain a vulcanized rubber-metal composite.

10. The method according to claim 9, wherein: In step 2, a film is obtained on a two-roll mill by the following operations: the BR-g-MAH and the masterbatch are mixed in proportion on a two-roll mill for 2-3 minutes to roll them; then a vulcanization accelerator and a scorch retarder are added, and mixing is continued to uniformly disperse the additives; then sulfur is added and mixing is continued, thinning the mixture 4-6 times and triangularly wrapping the mixture 6-8 times; finally, the film is discharged at a certain roller distance to obtain a film; wherein the front and rear roller speeds of the two-roll mill are (12-14) / (10-12) rpm, the front and rear roller temperatures are (50-60) / (50-60)°C, and the discharge roller distance is 0.5-0.7 mm.

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