A kind of vinyl silane controllable grafted emulsion polystyrene butadiene rubber and preparation method

Abstract

The present invention relates to a vinyl silane controllable grafted latex polystyrene butadiene rubber (SBR) and a preparation method. First, an emulsifier and N-bromosuccinimide are added to SBR latex, and the mixture is reacted under a nitrogen atmosphere, with stirring to obtain brominated SBR latex. Then, a vinyl silane coupling agent, a catalyst, and a ligand are sequentially added to the brominated SBR latex, and the mixture is reacted under a nitrogen atmosphere, with stirring, and with activation of a reducing agent to prepare grafted SBR. The grafted SBR prepared using the method of the present invention has the advantages of controllable graft chain length, uniform length, and controllable graft density. The grafted vinyl silane can better achieve uniform distribution of silica in the rubber, construct an efficient filler network, reduce the Payne effect, and ultimately achieve effective reinforcement of the SBR by silica.

Description

Technical Field

[0001] The present invention belongs to a grafting modification method for emulsion-polymerized styrene-butadiene rubber, and relates to a vinyl-based silane controllably grafted emulsion-polymerized styrene-butadiene rubber and a preparation method thereof, in particular to a method for preparing the vinyl-based silane controllably grafted emulsion-polymerized styrene-butadiene rubber based on the principle of electron-activated regenerative atom transfer radical polymerization. Background Art

[0002] Graft modification of styrene-butadiene rubber involves the grafting of diene polymers, using double bonds and allylic hydrogen atoms as grafting sites. Through graft polymerization, polar and non-polar groups or segments can be bonded together with highly elastic segments, thereby endowing styrene-butadiene rubber with numerous unique properties. With the continued deepening and expansion of research in fields such as biomedicine, materials science, and aerospace in recent years, higher performance requirements for polymers have been placed. Atom transfer radical polymerization has been introduced into graft modification, enabling greater control over graft density, grafted side chain length, and the distance between adjacent grafting sites, resulting in the production of precisely structured grafted polymers.

[0003] The document "Xueying Huang, Mary J. Wirth. Sustainable, Surface-Initiated Radical Polymerization on Porous Silica[J]. Analytical Chemistry, 1997, 69(22): 4577-4580." first introduced the atom transfer radical polymerization (ATRP) method into the field of graft polymerization. They self-assembled 1-trichlorosilyl-2-o-p-chloromethylphenylethane on the surface of silicon material and used CuCl / bpy as a catalytic system to initiate the graft polymerization of acrylamide.

[0004] CN102167782.A introduces a method for preparing natural rubber graft copolymers in solution using atom transfer radical polymerization. However, this reaction not only has strict requirements on the polymerization system, but also requires a large amount of low-valent transition metal catalysts. After the polymerization is completed, these transition metal catalysts will remain in the polymer.

[0005] Currently, most reports on the use of the ATRP method for grafting modification of rubber are carried out in solution and the monomers used are styrene and methyl methacrylate. The reaction in solution requires the use of toxic solvents such as tetrahydrofuran and toluene, which limits its application. In addition, the interaction between styrene-butadiene rubber grafted with styrene and methyl methacrylate and silica is weak, making it impossible to achieve effective reinforcement of styrene-butadiene rubber by silica. Summary of the Invention

[0006] Technical problems to be solved

[0007] To overcome the shortcomings of the prior art, the present invention provides a method for preparing vinyl silane controlled grafted styrene-butadiene rubber (SBR) in an emulsion based on the principle of electron-activated regenerative atom transfer radical polymerization (ARGET ATRP). This method allows for the preparation of SBR with controllable grafting of vinyl silanes in an emulsion, with uniform graft chain length and controlled graft density.

[0008] Technical Solution

[0009] A vinyl silane controllable grafted latex polystyrene butadiene rubber, characterized in that the components are: based on 100 parts by mass of the latex polystyrene butadiene rubber, parts of surfactant, parts of N-bromosuccinimide and The invention relates to a method for preparing a vinyl silane coupling agent; utilizing the Wohl-Ziegler reaction, through the reaction of styrene-butadiene rubber (SBR) with N-bromosuccinimide (NBS), introducing a side group with an ATRP-active bromine atom as a macroinitiator at the allyl position of the SBR molecular chain, and then grafting a polymer chain at the allyl position of the SBR molecular chain through ARGET ATRP.

[0010] The density of the grafted polymer chain is controlled by using SBR macroinitiators with different bromine atom loadings, and the length and uniformity of the grafted chains are controlled by the reaction conditions.

[0011] The surfactant includes, but is not limited to, sodium lauryl sulfate (SDS), sodium lauryl sulfonate, polyoxyethylene oleyl ether, alkylphenol polyoxyethylene ether, or polyoxyethylene sorbitan laurate.

[0012] The vinyl silane coupling agent includes but is not limited to: one or more of y-methacryloxypropyltrimethoxysilane MPS, vinyl triethoxysilane VTES, vinyl trimethoxysilane VTMS, vinyl tri(β-methoxyethoxy) silane, vinyl trimethylsilane VTS, dimethylethoxyvinylsilane, vinyl triacetoxysilane, vinyl tributanoximosilane, vinyl triisopropoxysilane, vinyl trimethoxysilane oligomer, tris(trimethylsiloxy)methacryloxypropyl silane MPTS

[0013] The vinyl silane coupling agent is preferably one or more of vinyl triethoxysilane, vinyl trimethoxysilane, and γ-methacryloxypropyl trimethoxysilane MPS.

[0014] A method for the controllable grafting of vinyl silane onto emulsion-polymerized styrene-butadiene rubber, characterized by the following steps:

[0015] Step 1: Add part of surfactant to emulsion polystyrene butadiene rubber latex, ultrasonically disperse for 0.5h and mix evenly, then in nitrogen atmosphere, Add while stirring parts of N-bromosuccinimide, react Obtain SBR-Br macroinitiator;

[0016] Step 2: Stir the SBR-Br macroinitiator under nitrogen atmosphere for 1 hour to remove oxygen from the latex, and then add Vinyl silane coupling agent, The reaction flask was immersed in an oil bath set to the reaction temperature and nitrogen atmosphere was added. The reducing agent is added, and the grafted styrene-butadiene rubber is prepared by stirring and reacting under the activation of the reducing agent.

[0017] The catalyst is a bromide of a transition metal.

[0018] Copper bromide is preferred.

[0019] The ligand includes, but is not limited to, a bipyridine ligand, a diamine ligand, a terpyridine ligand, a triamine ligand or a mixed ligand.

[0020] The ligand can be a dipyridine ligand (a substituent of bpy, such as dHbpy and dNbpy), a diamine ligand (such as TMEDA), a terpyridine ligand (a substituent of tpy, such as tNtpy), a triamine ligand, a mixed ligand (such as BPMDA, NPPMI and NOPMI), etc., preferably dNbpy.

[0021] The reducing agent includes, but is not limited to, ascorbic acid, phenylhydrazine, glucose, nitrogen-based ligands or metallic copper.

[0022] Ascorbic acid is preferred.

[0023] Beneficial effects

[0024] The present invention provides a vinyl silane controllable grafted emulsion polystyrene butadiene rubber and a preparation method thereof. First, an emulsifier and N-bromosuccinimide are added to the styrene butadiene rubber latex, and the emulsifier and N-bromosuccinimide are added to the styrene butadiene rubber latex. and stirring to obtain brominated styrene butadiene rubber latex, and then adding vinyl silane coupling agent, catalyst and ligand to brominated styrene butadiene rubber latex in sequence, and reacting under nitrogen atmosphere, Grafted styrene-butadiene rubber is prepared by reacting under stirring and activation with a reducing agent. The grafted styrene-butadiene rubber prepared using the method of the present invention has the advantages of controllable graft chain length, uniform length, and controllable graft density. The grafted vinyl silane can better achieve uniform distribution of silica in the rubber, build an efficient filler network, reduce the Payne effect, and ultimately achieve effective reinforcement of the styrene-butadiene rubber by silica.

[0025] The advantages of the present invention are as follows:

[0026] First, compared to existing technologies, this invention achieves controlled grafting of rubber directly in emulsion, rather than in toxic solvents such as toluene, tetrahydrofuran, and xylene. This modification yields a new type of styrene-butadiene rubber graft copolymer with controllable graft chain length and density, resulting in an unrestricted and environmentally friendly reaction.

[0027] Second: Compared with patent CN102167782.A, the present invention has simple reaction conditions and is easy to operate. By adding an excess reducing agent, the amount of transition metal catalyst used is greatly reduced, and the residual amount of transition metal in the polymer is greatly reduced. At the same time, trace amounts of oxygen will not affect the reaction.

[0028] Third: The new variety of Si-O bond grafted modified styrene-butadiene rubber with a microphase separation structure prepared by the present invention solves the problem of easy agglomeration when adding white carbon black through the subsequent mixing method, and further improves the reinforcing effect of white carbon black on styrene-butadiene rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The infrared spectrum and NMR images of brominated styrene butadiene rubber in Example 1 are shown in Figure A. The infrared spectrum before and after the bromination reaction is compared. -1 and 816cm -1 A new absorption peak corresponding to C-Br appeared at 1640 cm -1 The absence of a significant shift in the C=C double bond peak at , indicating that the bromination reaction did not destroy the C=C. Figure B compares the NMR spectra before and after the bromination reaction. The SBR allylic hydrogen peak is located around 1.8 ppm. After bromination, this hydrogen shift peak shifts to around 3.5 ppm, indicating that the bromination reaction occurs at the allylic position of the SBR. Therefore, reaction conditions can be used to control the active site of the macroinitiator, thereby controlling the grafting density and location of the grafted chains.

[0030] Figure 2 For the grafting reaction in Example 1 Infrared spectrum of 4h after 1726cm -1A new characteristic peak appears, which is the stretching vibration absorption peak of the C=O group in the silane coupling agent MPS, at 1096 cm -1 New characteristic peaks appear, which are the antisymmetric stretching vibration absorption peaks of Si-O-Si in the silane coupling agent MPS. These all indicate that MPS has been successfully grafted onto the SBR molecular chain. Moreover, the peak intensity gradually increases with the increase of polymerization reaction time, while the intensity of the characteristic absorption peak gradually weakens. This is because the molecular chain of the grafted monomer is growing and the molecular weight is increasing with the extension of polymerization time. To a certain extent, this proves that the reaction has certain "activity" / controllable characteristics.

[0031] Figure 3 The figure shows the molecular weight change of the graft copolymer during the grafting of VTS onto styrene-butadiene rubber (SBR) in Example 2. As shown in the figure, the molecular weight of the grafted polymer increases linearly with increasing reaction time, and the resulting grafted polymer has a relatively narrow molecular weight distribution. The GPC curve of the grafted polymer shows that as reaction time increases, the GPC curve shifts toward higher molecular weight while maintaining a relatively good normal distribution. This indicates that during the graft polymerization of VTS onto SBR, the free radical concentration in the system remains constant, resulting in a controlled polymerization. By adjusting the ratio of monomer to macroinitiator or controlling the reaction time, grafted polymers with controllable graft chain molecular weight can be obtained.

[0032] Figure 4 The reaction kinetics curves of Example 6 and Example 1 are compared. A is Example 6. It can be seen from the figure that the traditional graft polymerization method has the mechanism characteristics of slow initiation, rapid growth, and rapid termination, and it is impossible to control the graft structure, graft chain length, etc. B is the reaction kinetics curve of Example 1. It can be seen from the figure that there is a good linear correlation between ln(M0 / M)-t throughout the polymerization process. This shows that the active center has not been destroyed during the silane graft polymerization process initiated by SBR-Br, the free radical concentration in the system remains constant, the active free radicals can effectively initiate and grow, and the graft polymerization process meets the "active" characteristic. By adjusting the ratio of monomer to macromolecular initiator or controlling the reaction time, a graft polymer with controllable graft chain length can be obtained.

[0033] Figure 5 3 are stress-strain curves of Example 6 and Example 1. A is Example 6. It can be seen from the figure that the breaking elongation of the styrene-butadiene rubber material obtained by the traditional graft polymerization method is 586.69%, the tensile breaking stress is 2.67 MPa, and the tensile strength is 3.29 MPa. B is the stress-strain curve of Example 1. Its breaking elongation is 669.53%, the tensile breaking stress is 3.71 MPa, and the tensile strength is 3.88 MPa. By comparison, it can be seen that the mechanical properties of the material obtained in Example 1 are much better than those in Example 6.

[0034] Figure 6 The atomic force microscope phase images of unmodified styrene-butadiene rubber and Example 1 and Example 2 are shown. It can be clearly seen from the figure that Example 1 and Example 2 have obvious ordered microphase separation morphology. This is due to the incompatibility between the styrene-butadiene rubber component and the silane coupling agent component of the graft chain. This microphase separation morphology is conducive to a more uniform dispersion of silica in the styrene-butadiene rubber matrix. DETAILED DESCRIPTION

[0035] The present invention will now be further described with reference to the embodiments and accompanying drawings:

[0036] In order to illustrate the effects of the present invention, the present invention will be further described in detail with reference to examples, but the present invention is not limited to these examples.

[0037] 1. Analysis Method

[0038] Infrared spectrum testing method: After coagulation, the modified SBR latex contains some silane coupling agent homopolymer, a small amount of silane coupling agent hydrolysis products, and unreacted silane coupling agent monomer. These products are removed by Soxhlet extraction. Acetone is used as the extraction solvent for 24 hours to remove unreacted monomer and silane coupling agent autopolymerization and autohydrolysis products. SBR and graft-modified SBR are insoluble in acetone. The composition of the grafted product was analyzed using a Bruker Tensor 27 infrared spectrometer in total reflectance mode (ATR-FT-IR).

[0039] Molecular weight and molecular weight distribution test method: After Soxhlet extraction of the grafted copolymer, its relative molecular mass and molecular weight distribution were determined using a Waters 1515 gel permeation chromatography (GPC) instrument. The column temperature was 25°C, tetrahydrofuran was used as the eluent, the flow rate was 1 mL / min, and monodisperse polystyrene was used as the calibration standard.

[0040] The microphase separation morphology of the graft copolymer was characterized using atomic force microscopy: first, a 0.5% toluene solution of the graft copolymer was prepared, and then the above-mentioned graft copolymer was dropped onto a clean silicon wafer. After drying, the surface morphology of the graft copolymer was detected using a Seiko SPI3800-SPA-400 atomic force microscope in tapping mode. The elastic modulus of the probe was 1.6 N / m.

[0041] Example 1

[0042] 100.0000g of styrene butadiene latex was weighed and added with 2.0000g of SDS and ultrasonically dispersed uniformly. Then, 0.4000g of NBS brominated styrene butadiene latex was added under nitrogen atmosphere at 70°C and stirred to prepare the initiator for ATRP reaction. The brominated styrene butadiene latex was then stirred under nitrogen atmosphere for 1h to remove oxygen from the latex. Then, 0.0010g of copper bromide (CuBr 2) , 0.0010g 4,4'-dinonyl-2,22-bipyridine (dNbpy), and 3.0000g methacryloyloxypropyltrimethoxysilane (MPS). The reaction flask was immersed in an oil bath set at 75°C. Activated with 0.0010g ascorbic acid, the reaction was stirred under a nitrogen atmosphere for 12 hours to prepare grafted styrene-butadiene rubber. After the reaction, methanol was added to break the emulsion and remove the CuBr2 and dNbpy. The mixture was then coagulated and dried. After Soxhlet extraction, the composition and structure of the grafted polymer were analyzed using ATR-FT-IR, and the relative molecular mass and molecular weight distribution were determined using GPC.

[0043] Example 2

[0044] 100.0000g of styrene butadiene latex was weighed and added with 2.0000g of SDS and ultrasonically dispersed uniformly. Then, 0.4000g of NBS brominated styrene butadiene latex was added under nitrogen atmosphere at 70°C and stirred to prepare the initiator for ATRP reaction. The brominated styrene butadiene latex was then stirred under nitrogen atmosphere for 1h to remove oxygen from the latex. Then, 0.0010g of copper bromide (CuBr 2) , 0.0010g 4,4'-dinonyl-2,22-bipyridine (dNbpy) and 3.0000g vinyltrimethylsilane (VTS), immerse the reaction bottle in an oil bath preset to 75°C, activate with 0.0010g ascorbic acid, and stir the reaction for 12h in a nitrogen atmosphere to prepare grafted styrene-butadiene rubber. After the reaction, methanol is added to break the emulsion and remove CuBr2 and dNbpy, condense and dry. After Soxhlet extraction, the composition and structure of the grafted polymer are analyzed using ATR-FT-IR, and its relative molecular mass and molecular weight distribution are determined using GPC.

[0045] Example 3

[0046] 100.0000g of styrene butadiene latex was weighed and added with 2.0000g of polyoxyethylene (20) oleyl ether (Brij98) and ultrasonically dispersed uniformly. Then, 0.4000g of NBS brominated styrene butadiene latex was added under nitrogen atmosphere at 70°C and stirred to prepare the initiator for ATRP reaction. The brominated styrene butadiene latex was then stirred under nitrogen atmosphere for 1h to remove oxygen from the latex. Then, 0.0010g of copper bromide (CuBr 2), 0.0010g 4,4'-dinonyl-2,22-bipyridine (dNbpy), and 3.0000g methacryloyloxypropyltrimethoxysilane (MPS). The reaction flask was immersed in an oil bath set at 75°C. Activated with 0.0010g ascorbic acid, the reaction was stirred under a nitrogen atmosphere for 12 hours to prepare grafted styrene-butadiene rubber. After the reaction, methanol was added to break the emulsion and remove the CuBr2 and dNbpy. The mixture was then coagulated and dried. After Soxhlet extraction, the composition and structure of the grafted polymer were analyzed using ATR-FT-IR, and the relative molecular mass and molecular weight distribution were determined using GPC.

[0047] Example 4

[0048] 100.0000g of styrene butadiene latex was weighed and added with 2.0000g of polyoxyethylene (20) oleyl ether (Brij98) and dispersed uniformly by ultrasonication. Then, 0.4000g of NBS brominated styrene butadiene latex was added under nitrogen atmosphere at 70°C and stirred to prepare the initiator for ATRP reaction. The brominated styrene butadiene latex was then stirred under nitrogen atmosphere for 1h to remove oxygen from the latex. Then, 0.0010g of copper bromide (CuBr 2) , 0.0010g tris(2-picolyl)amine (TPMA), and 3.0000g γ-methacryloxypropyltrimethoxysilane (MPS). The reaction flask was immersed in an oil bath preset to 80°C. Activated with 0.0010g ascorbic acid, the reaction was stirred for 12 hours under a nitrogen atmosphere to prepare grafted styrene-butadiene rubber. After the reaction, methanol was added to break the emulsion and remove the CuBr2 and PMDETA. The mixture was then coagulated and dried. After Soxhlet extraction, the composition and structure of the grafted polymer were analyzed using ATR-FT-IR, and the relative molecular mass and molecular weight distribution were determined using GPC.

[0049] Example 5

[0050] 100.0000g of styrene butadiene latex was weighed and added with 2.0000g of polyoxyethylene (20) oleyl ether (Brij98) and ultrasonically dispersed uniformly. Then, 0.4000g of NBS brominated styrene butadiene latex was added under nitrogen atmosphere at 70°C and stirred to prepare the initiator for ATRP reaction. The brominated styrene butadiene latex was then stirred under nitrogen atmosphere for 1h to remove oxygen from the latex. Then, 0.0010g of copper bromide (CuBr 2), 0.0010g tris(2-picolyl)amine (TPMA), and 3.0000g vinyltrimethylsilane were added to the reaction flask, which was immersed in an oil bath preset to 85°C. Under nitrogen atmosphere and with the activation of 0.0010g ascorbic acid, the reaction was stirred for 12 hours to prepare grafted styrene-butadiene rubber. After the reaction, methanol was added to break the emulsion and remove the CuBr2 and PMDETA. The mixture was then coagulated and dried. After Soxhlet extraction, the composition and structure of the grafted polymer were analyzed using ATR-FT-IR, and its relative molecular mass and molecular weight distribution were determined using GPC.

[0051] Example 6

[0052] The traditional graft polymerization method was used to prepare styrene-butadiene rubber graft polymer. 100.0000g of styrene-butadiene rubber latex was weighed and added with 2.0000g of SDS for ultrasonic dispersion. Then, 3.0000g of MPS and 0.01g of free radical initiator were added under nitrogen atmosphere, 70°C and stirring. The reaction was carried out for 12h. After the reaction, methanol was added to break the emulsion, coagulation was performed, and drying was performed.

Claims

1. A method for preparing vinyl silane controlled grafted emulsion polystyrene-butadiene rubber, characterized in that: The preparation steps include: Step 1: Add 2 parts of surfactant to 100 parts of styrene-butadiene latex, ultrasonically disperse for 0.5 h to mix evenly, then add 0.4 parts of N-bromosuccinimide under nitrogen atmosphere at 70°C to 90°C and stir, and react for 8 to 16 h to obtain SBR-Br macroinitiator; Step 2: Stir the SBR-Br macroinitiator under a nitrogen atmosphere for 1 hour to remove oxygen from the latex, then add 3 parts of a vinyl silane coupling agent, 0.001 parts of a catalyst, and 0.001 parts of a ligand in sequence. Immerse the reaction flask in a 75°C oil bath, add 0.001 parts of a reducing agent under a nitrogen atmosphere, and stir to react under the activation of the reducing agent to prepare a grafted styrene-butadiene rubber. After the reaction is completed, methanol is added to break the emulsion and remove CuBr2 and dNbpy, and the rubber is coagulated and dried. The catalyst is copper bromide; The ligand is 4,4'-dinonyl-2,2'-bipyridine or tris(2-pyridylmethyl)amine; The reducing agent is ascorbic acid; The surfactant is polyoxyethylene (20) oleyl ether; The vinyl silane coupling agent is vinyl trimethylsilane or γ-methacryloxypropyl trimethoxysilane.

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