Process for the preparation of rubber graft polymers

Abstract

The present application relates to the technical field of high polymer chemical industry, in particular to a preparation method of rubber graft polymer. The preparation method comprises: (1) performing first reaction on rubber emulsion, monomer 1, chain transfer agent 1, activator, emulsifier 1 and initiator 1 to obtain first product containing polymer from monomer 1; (2) performing second reaction on the first product, monomer 2, chain transfer agent 2 and initiator 2 to obtain second product; (3) adding initiator 3 to the second product to perform third reaction to obtain the rubber graft polymer; wherein the solubility parameter of monomer 1 is different from that of rubber contained in the rubber emulsion; the solubility parameter of monomer 2 is different from that of polymer from monomer 1. Through the technical scheme of the present application, the rubber graft polymer can significantly improve the toughening performance while reducing the in-grafting and secondary cross-linking of rubber particles in the preparation process without affecting the grafting density on the outside of rubber particles.

Description

Technical Field

[0001] This invention relates to the field of polymer chemical technology, and more specifically to a method for preparing a rubber-grafted polymer. Background Technology

[0002] Rubber toughening involves blending a small amount of rubber with a rigid polymer to improve the toughness of the material. Both thermoplastic and thermosetting resins can be toughened using rubber. During the rubber toughening process, cavities first form within the rubber particles to reduce their resistance to deformation, allowing them to yield to the matrix under lower stress. This allows the matrix surrounding the cavitated rubber particles to deform through various mechanisms. Larger rubber particle sizes result in lower elastic moduli, easier cavitation, and better mechanical properties of the toughened resin.

[0003] Rubber used in toughening resins often has poor compatibility with the resin. To improve the dispersibility of rubber in the resin, a polymer with the same or similar composition as the resin needs to be grafted onto the rubber surface, forming a "core-shell" structure toughening rubber graft polymer. However, during the production of these polymers, to ensure sufficient grafting and good dispersion of the toughening rubber in the resin, excessive amounts of graft monomers and initiators are often added. Both partially enter the rubber particles, initiating secondary cross-linking and "internal grafting" of the monomers, increasing the elastic modulus of the rubber, increasing the difficulty of cavitation, and reducing the toughening performance. While reducing the amount of initiator and adding monomers and initiators continuously or semi-continuously can reduce the elastic modulus of the toughening rubber to some extent, it affects the grafting density of the outer layer of the rubber, which is detrimental to the dispersion of the rubber in the resin.

[0004] In the production of core-shell structured toughened rubber grafted polymers, how to reduce internal grafting and secondary crosslinking of rubber particles while ensuring that the external grafting density remains unaffected, and thus improve the toughening properties of the rubber, is a pressing problem to be solved. Therefore, researching a method for developing rubber grafted polymers to address these issues is of great significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of excessive grafting amount and secondary crosslinking in rubber particles during the production of core-shell structured toughened rubber grafted polymers, while avoiding the impact on the grafting density of the outer layer of rubber, and to provide a method for preparing rubber grafted polymers.

[0006] To achieve the above objectives, the present invention provides a method for preparing a rubber-grafted polymer, wherein the method includes:

[0007] (1) A first reaction is carried out on rubber latex, monomer 1, chain transfer agent 1, activator, emulsifier 1 and initiator 1 to obtain a first product containing a polymer from monomer 1;

[0008] (2) The first product, monomer 2, chain transfer agent 2 and initiator 2 are subjected to a second reaction to obtain the second product;

[0009] (3) Initiator 3 is added to the second product to carry out a third reaction to obtain the rubber graft polymer;

[0010] Wherein, the solubility parameter of monomer 1 is different from that of the rubber contained in the rubber emulsion;

[0011] Monomer 2 has a different solubility parameter than the polymer derived from monomer 1.

[0012] The present invention also provides a rubber graft polymer prepared by the above preparation method, wherein the polymer has a core-shell structure;

[0013] The weight ratio of the shell to the core in the polymer is 0.43-0.46:1;

[0014] The impact strength of the polymer is 20-25 kJ / m. 2 The elongation at break is 20-30%.

[0015] Through the above technical solution, this invention obtains a polymer with uniform coverage and certain mass transfer resistance to monomers and initiators on the surface of rubber particles during the initial stage of the grafting reaction. By reducing the concentration of shell monomers and initiators forming the outer graft layer, the mass transfer driving force between the graft layer and the rubber particles is reduced, allowing the shell monomers and initiators to concentrate mainly on the surface of the rubber particles for polymerization. Grafting efficiency and mechanical property tests of the rubber graft polymer obtained by this invention show that it can significantly improve the toughening properties of the rubber graft polymer without affecting the grafting density on the outer side of the rubber particles, while reducing internal grafting and secondary crosslinking within the rubber particles, thus breaking the "rigid-toughness" balance limitation and comprehensively improving the mechanical properties of the product.

[0016] This invention is applicable to both batch and continuous emulsion graft polymerization processes, and is particularly suitable for production processes in which graft monomers are added in batches or batch-continuously. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The following detailed description of specific embodiments of the present invention, in conjunction with tables, is provided. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0019] This invention provides a method for preparing a rubber-grafted polymer, wherein the method includes:

[0020] (1) A first reaction is carried out on rubber latex, monomer 1, chain transfer agent 1, activator, emulsifier 1 and initiator 1 to obtain a first product containing a polymer from monomer 1;

[0021] (2) The first product, monomer 2, chain transfer agent 2 and initiator 2 are subjected to a second reaction to obtain the second product;

[0022] (3) Initiator 3 is added to the second product to carry out a third reaction to obtain the rubber graft polymer;

[0023] Wherein, the solubility parameter of monomer 1 is different from that of the rubber contained in the rubber emulsion;

[0024] Monomer 2 has a different solubility parameter than the polymer derived from monomer 1.

[0025] The solubility parameter of a substance is defined as the square root of the cohesive energy per unit volume of the substance. It is a parameter that can characterize the strength of interactions between liquid molecules, between liquid molecules and polymers, and between polymers.

[0026] By calculating the solubility parameters of the polymer and comparing them with the solubility parameters of the solvent, the degree of solubility between the polymer and the solvent can be quantitatively characterized. The closer the solubility parameters of the polymer and the solvent are, the higher the degree of solubility of the polymer; conversely, the greater the difference between the solubility parameters of the polymer and the solvent, the lower the degree of solubility of the polymer.

[0027] According to the preparation method of the present invention, in the initial stage of the grafting reaction, monomer 1, whose solubility parameter is different from that of rubber, is used to graft onto the surface of rubber particles to obtain a polymer that is uniformly covered and has a certain mass transfer resistance to the monomer and initiator, forming an inner graft layer composed of polymer from monomer 1. Next, monomer 2, whose solubility parameter is different from that of the polymer from monomer 1, is added to the reaction system. Monomer 2 does not easily penetrate the inner graft layer to reach the rubber surface, allowing monomer 2 and the initiator to mainly concentrate on the surface of the rubber particles for polymerization. This reduces internal grafting and secondary crosslinking of the rubber particles without affecting the grafting density on the outer side of the rubber particles. Furthermore, the solubility parameter of monomer 2 is between that of rubber and the solubility parameter of the rigid resin to be toughened, which is beneficial for promoting the compatibility between the toughened rubber and the rigid resin, thereby improving the dispersion of the rubber in the resin.

[0028] According to the present invention, in order to further reduce the mass transfer driving force between the grafted layer and the rubber particles, so that monomer 2 and initiator are mainly concentrated on the surface of the rubber particles, and at the same time avoid the mass transfer rate of monomer 2 being too low, increasing the copolymerization probability during the mass transfer process, resulting in a decrease in the grafting rate of the toughened rubber, and a decrease in the dispersibility of the product in the resin, preferably, in step (2), the mass ratio of monomer 2 to initiator 2 is 110-150:1; the concentration of initiator 2 is 50-85wt%.

[0029] According to the present invention, in order to improve the compatibility between toughened rubber and different resins, when modifying rubber, graft polymerization with different types of monomer 1 and / or monomer 2 is selected. In order to significantly improve the toughening properties of various rubber graft polymers, preferably, in step (2), the mixture of monomer 2 and chain transfer agent 2 and initiator 2 can be added after mixing, or they can be added separately.

[0030] According to the present invention, in order to reduce the initiator penetration through the inner graft layer, reduce the initiator concentration in the graft layer, avoid secondary crosslinking of rubber due to excessive initiator, and improve the mechanical properties of the obtained rubber graft polymer, preferably, in step (2), the mixture of monomer 2 and chain transfer agent 2 is mixed with initiator 2 and then added.

[0031] Preferably, the mixture of monomer 2 and chain transfer agent 2 is added continuously after being mixed with initiator 2.

[0032] Preferably, the mixture of monomer 2 and chain transfer agent 2 is added in batches after being mixed with initiator 2.

[0033] According to the present invention, depending on the actual application of toughened rubber, the rubber will be grafted with different types of monomer 1 and / or monomer 2. In order to obtain various rubber graft polymers with high toughening properties, preferably, the mixture of monomer 2 and chain transfer agent 2 and initiator 2 are added separately. In other words, the mixture of monomer 2 and chain transfer agent 2 and initiator 2 are not mixed but added separately.

[0034] More preferably, the mixture of monomer 2 and chain transfer agent 2 is added separately from and simultaneously with initiator 2.

[0035] More preferably, the mixture of monomer 2 and chain transfer agent 2 is added separately from and at different times than the initiator 2.

[0036] Preferably, in order to reduce the concentration of monomers in latex particles, improve the selectivity of graft polymerization, and avoid excessive monomers and initiators passing through the graft layer to improve the mechanical properties of the product, the monomer dripping time can be appropriately extended. At the same time, it is necessary to avoid the monomer concentration in the latex particles being too low due to excessive dripping time, and also to avoid the monomers and initiators staying in the graft layer for too long, which may cause copolymerization of monomers and reduce product performance. Preferably, in step (2), when adding the mixture after mixing, the mixture of monomer 2 and chain transfer agent 2, after mixing with initiator 2, is continuously added for 100-150 minutes.

[0037] Preferably, in step (2), when the monomer 2 and chain transfer agent 2 are added separately and synchronously, the time is 100-150 min.

[0038] According to the preparation method of the present invention, in order to make the obtained rubber graft polymer have a good toughening effect on various resins, preferably, monomer 1 and monomer 2 are each independently selected from at least one of acrylonitrile, styrene, α-methylstyrene, methyl methacrylate and methyl acrylate.

[0039] Preferably, the mass ratio of monomer-1 to monomer-2 is 1-5:2-10.

[0040] Preferably, the solid content of the rubber latex is 45-60%, and the average particle size of the latex particles contained in the rubber latex is 100-800 nm.

[0041] More preferably, the rubber latex is selected from at least one of polybutadiene latex, polybutadiene styrene latex, and polybutyl acrylate latex.

[0042] According to the present invention, in order to reduce the length of the inner and outer grafted molecular chains in the first reaction stage, reduce the elastic modulus, and increase the outer graft density; at the same time, to reduce the length of the outer grafted chains and avoid the grafted polymer from becoming less compatible with the toughening resin due to excessive grafting, preferably, the chain transfer agent 1 and chain transfer agent 2 are each independently selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan.

[0043] According to the present invention, in order to improve the stability of the reaction system and control the amount of monomer entering the latex particles, preferably, the emulsifier 1 and the emulsifier 2 are each independently selected from at least one of potassium disproportionated rosinate, potassium fatty acid, potassium oleate, sodium butylnaphthalene sulfonate and sodium alkyl sulfate.

[0044] According to the present invention, in order to enable the monomer to react inside the latex particles, effectively reduce the amount of polymer generated outside the latex particles, and maintain the stability of the polymerization rate during the reaction, the activator is preferably selected from the reducing sugar-sodium pyrophosphate-ferrous sulfate activation system and / or formaldehyde sodium hyposulfite-EDTA-4Na-ferrous sulfate activation system.

[0045] According to the present invention, in order to facilitate the polymerization reaction and obtain a rubber graft polymer that meets the requirements, preferably, the initiator 1, initiator 2 and initiator 3 are each independently selected from at least one of cumene hydroperoxide, tert-butyl hydroperoxide, p-menthol hydroperoxide, methylcyclohexane hydroperoxide, p-methyl cumene hydroperoxide, and tetrahydronaphthalene hydroperoxide.

[0046] According to the present invention, in order to effectively control the amount of monomers entering the interior of the rubber particles and remaining on the exterior, balance the amount of internal and external grafting of the rubber, and enable the grafted rubber to take into account both elastic modulus and dispersion, preferably, in step (1), the mass ratio of the rubber emulsion, monomer 1, chain transfer agent 1, activator, emulsifier and initiator 1 is 1100-1500:120-150:2-5:50-100:100-150:0.5-1.5.

[0047] Preferably, in step (2), the mass ratio of the first product, monomer-2, chain transfer agent-2, and initiator-2 is 1500-2000:0.5-1.5:1:1-3.

[0048] According to the present invention, in order to ensure that the polymerization reaction proceeds well and to obtain a rubber graft polymer with significantly improved mechanical properties, preferably, the temperature of the first reaction is 40-60°C and the time is 50-70 min.

[0049] And / or, the temperature of the second reaction is 60-78°C and the time is 100-120 min.

[0050] And / or, the temperature of the third reaction is 75-80°C and the time is 15-30 min.

[0051] In some embodiments of the present invention, the temperature of the first reaction is 40°C and the time is 60 min; the temperature of the second reaction is 60°C and the time is 110 min; and the temperature of the third reaction is 76°C and the time is 20 min.

[0052] This invention can reduce the internal grafting and secondary crosslinking of rubber particles without affecting the external grafting density of rubber particles, thereby significantly improving the toughening properties of rubber grafted polymers, breaking the "rigidity and toughness" balance limitation, and comprehensively improving the mechanical properties of products.

[0053] The present invention also provides a rubber graft polymer prepared by the above preparation method, wherein the polymer has a core-shell structure;

[0054] The weight ratio of the shell to the core in the polymer is 0.43-0.46:1;

[0055] The impact strength of the polymer is 20-25 kJ / m. 2 The elongation at break is 20-30%.

[0056] This invention utilizes a dynamic light scattering (DLS) particle size analyzer to test the particle size (D50) of the raw PB rubber and the obtained rubber-grafted polymer after solvent dispersion. A dynamic thermodynamic analyzer (DMA) is used to test the glass transition temperature (Tg) of the PB rubber and the rubber-grafted polymer in the comparative and examples. The glass transition temperature difference (ΔTg) before and after PB rubber grafting is calculated. The test results show that the D50 of the rubber-grafted polymer dispersed in the solvent as a toughening material is ≤ 2.0 times the particle size of the rubber-grafted polymer. This indicates that the rubber-grafted polymer obtained in this invention has good compatibility with the resin and no obvious agglomeration tendency. Therefore, the closer the D50 of the rubber-grafted polymer used as a toughening material for resin toughening is to the particle size of the fully dispersed grafted rubber particles, the better. The glass transition temperature difference (ΔTg) before and after PB rubber grafting characterizes the change in elastic modulus before and after rubber grafting; the smaller the change in elastic modulus, the better the rubber toughening.

[0057] The rubber graft polymer of this invention has a core-shell structure, wherein the core is a particle used to toughen the rigid polymer, which is usually a polymer with a low elastic modulus polymerized from "soft" monomers; the solubility parameter of the polymer constituting the shell structure is between the solubility parameter of the toughening rubber and the solubility parameter of the rigid resin to be toughened, which plays a role in improving the compatibility between the toughening rubber and the rigid resin and is beneficial to the dispersion of the toughening rubber in the rigid resin.

[0058] The present invention will be described in detail below through embodiments.

[0059] The following examples and comparative examples illustrate the evaluation methods for the amount of toughened rubber grafted and the mechanical properties of the final product:

[0060] 1. Test methods for the grafting amount of toughening rubber monomers and the utilization rate of shell monomers:

[0061] Weigh out a certain amount of core-shell polymer powder (taking ABS high-resin powder as an example) and record it as m. g0 The solution was dissolved in acetone in a special test tube, shaken for 24 hours, and then separated using a centrifuge at 10000 r / min for 0.5 hours. After centrifugation, the supernatant in the test tube was poured off, and an appropriate amount of acetone was added to repeat the experiment. The final precipitate was a core-shell polymer. The precipitate was dried to constant weight and then weighed, expressed as m. g1 The shell / core ratio of the core-shell polymer is calculated by formula (1) based on the content of the core polymer in the core-shell polymer powder.

[0062]

[0063] in:

[0064] GD% — Percentage of shell polymer to core polymer by weight, wt%.

[0065] m g0 —Weigh the toughened rubber graft powder, in grams;

[0066] m g1 —The weight of the product obtained after centrifugation and drying, in grams;

[0067] A% — Content of the core polymer in the toughened rubber graft powder, in wt%.

[0068] The shell utilization rate of the shell unit is calculated using formula (2).

[0069]

[0070] in:

[0071] GE% — The percentage of monomers forming the core-shell polymer relative to the total shell monomers, in wt%.

[0072] m g0 —Weigh the toughened rubber graft powder, in grams;

[0073] m g1 —The weight of the product obtained after centrifugation and drying, in grams;

[0074] A% — Content of the core polymer in the toughened rubber graft powder, in wt%.

[0075] 2. Test methods for rubber particle size and glass transition temperature in the product

[0076] (1) Particle size of rubber particles in the product

[0077] Select a suitable solvent to dissolve the test sample, ensuring that the resin phase in the product is completely dissolved while the rubber phase is dispersed without swelling. Add the dissolved sample to a DSL dynamic scattering laser particle size analyzer to measure the median particle size D50, μm, of the rubber dispersed in the sample.

[0078] (2) Testing the glass transition temperature of the rubber phase in the product

[0079] The glass transition temperature (Tg) of the rubber in the product was tested using a dynamic thermomechanical analyzer. A three-point bending fixture was selected for the test, and the sample size was 80mm × 10mm × 4mm. Temperature scanning was performed at a fixed frequency of 1Hz, with a temperature range of -110 to 30℃ and a heating rate of 10℃ / min. The peak value of the ratio of loss modulus to storage modulus during the heating process was recorded as the glass transition temperature (Tg) of the rubber in the product.

[0080] 3. Preparation of product test strips and methods for evaluating mechanical properties.

[0081] The toughened rubber graft polymer powder was blended with acrylonitrile-styrene copolymer (SAN resin, commercially available product of China Petroleum Jilin Petrochemical Company with brand name 2437) at a weight ratio of 25 / 75 and granulated. The mechanical properties of the product were tested according to the method specified in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] For ABS graft polymerization using PB as the toughening rubber and AN and St as graft monomers, the solubility parameter δ of PB is... PB =8.4, δ of styrene St =9.3, δ of acrylonitrile AN =10.5, δ of cumene hydroperoxide CHP =10.5, δ of polyacrylonitrile (PAN) SAN =12.8, δ of polystyrene (PS) PS =9.05, SAN (75 / 25) solubility parameter δ SAN =9.6, and the solubility parameter gradually increases as the AN% in SAN increases.

[0086] Example 1

[0087] (1) Add 3120 kg of polybutadiene (PB) rubber latex with a solid content of 57.70% and an average particle size of 300 nm, 105.24 kg of acrylonitrile (AN) monomer and 195.45 kg of styrene (St) to the reactor, 5.811 kg of chain transfer agent tert-dodecyl mercaptan (TDDM), 174 kg of activator (glucose: 2.888 wt%, sodium pyrophosphate: 2.299 wt%, ferrous sulfate: 0.046 wt%, water: 94.767 wt%), 306 kg of emulsifier potassium disproportionate solution (solid content of 1.96%), and 1105.86 kg of rinsing water to the reactor. Heat the material in the reactor to 40°C, add 2.232 kg of initiator cumene hydroperoxide (CHP, purity ≥80%), and carry out the first reaction. The reaction time is 60 min. At this time, the temperature in the reactor reaches 60°C, and the first product is obtained.

[0088] (2) After mixing 234.48 kg of AN, 667.58 kg of St and 3.53 kg of TDDM, the temperature inside the reactor was kept at 60°C. The resulting mixture was continuously added to the reactor at a constant flow rate over 110 min. At the same time, 8.02 kg of initiator CHP was added to the reactor separately over the same time to carry out the second reaction. After the reaction, the temperature inside the reactor rose to 76°C, and the second product was obtained.

[0089] (3) Keep the temperature inside the reactor at 76°C, add 3.19 kg of initiator CHP, carry out the third reaction, react for 20 min, and obtain rubber graft polymer 1.

[0090] Example 2

[0091] The method of Example 1 is different in that, in step (1), the amount of AN added is 120.28 kg, the amount of St added is 180.41 kg, the amount of TDDM added is 6.127 kg, and the amount of CHP added is 2.353 kg; in step (2), the amount of AN added is 219.44 kg, the amount of St added is 682.61 kg, the amount of TDDM added is 3.46 kg, and the amount of CHP added is 7.86 kg, so as to obtain rubber graft polymer 2.

[0092] Example 3

[0093] The method of Example 1 is different in that, in step (1), the amount of AN added is 126.29 kg, the amount of St added is 234.54 kg, the amount of TDDM added is 6.973 kg, and the amount of CHP added is 2.678 kg; in step (2), the amount of AN added is 213.43 kg, the amount of St added is 628.49 kg, the amount of TDDM added is 3.27 kg, and the amount of CHP added is 7.43 kg, so as to obtain rubber graft polymer 3.

[0094] Example 4

[0095] The method of Example 1 is different except that in step (2), 234.48 kg of AN, 667.58 kg of St, 3.53 kg of TDDM and 8.02 kg of initiator CHP are mixed and continuously added to the reactor at a constant flow rate over 110 min to obtain rubber graft polymer 4.

[0096] Example 5

[0097] The method of Example 1 is different except that in step (2), 234.48 kg of AN, 667.58 kg of St, 3.53 kg of TDDM, 8.02 kg of initiator CHP, and 306 kg of emulsifier potassium disproportionate solution (solid content of 1.96%) are mixed to form a pre-emulsified monomer, and then continuously added to the reactor at a constant flow rate within 110 min to obtain rubber graft polymer 5.

[0098] Example 6

[0099] The method of Example 1 is different except that in step (2), 234.48 kg of AN, 667.58 kg of St and 3.53 kg of TDDM are mixed and then continuously added to the reactor at a constant flow rate within 140 min. At the same time, 8.02 kg of initiator CHP is added separately to the reactor within the same time to carry out the second reaction and obtain rubber graft polymer 6.

[0100] Example 7

[0101] The method of Example 1 is different except that in step (2), 234.48 kg of AN, 667.58 kg of St and 3.53 kg of TDDM are mixed and then continuously added to the reactor at a constant flow rate within 170 min. At the same time, 8.02 kg of initiator CHP is added separately to the reactor within the same time to carry out the second reaction and obtain rubber graft polymer 7.

[0102] Example 8

[0103] The method of Example 1 is different except that in step (2), after the second reaction begins, 2.479 kg of initiator CHP is added at a constant flow rate within 0-40 min; 2.625 kg of initiator CHP is added at a constant flow rate within 40-80 min; and 2.078 kg of initiator CHP is added at a constant flow rate within 80-110 min to obtain rubber graft polymer 8.

[0104] Example 9

[0105] The method is the same as in Example 1, except that in step (2), after the second reaction begins, a mixture of 90.21 kg of AN, 10.48 kg of St 2, 1.234 kg of TDDM and 2.804 kg of initiator CHP is continuously added at a constant flow rate within 0-40 min; a mixture of 78.16 kg of AN, 222.53 kg of St 2, 1.177 kg of TDDM and 2.675 kg of initiator CHP is continuously added at a constant flow rate within 40-80 min; and a mixture of 66.11 kg of AN, 34.57 kg of St 2, 1.120 kg of TDDM and 2.546 kg of initiator CHP is continuously added at a constant flow rate within 80-110 min to obtain rubber graft polymer 9.

[0106] Example 10

[0107] The method is the same as in Example 1, except that in step (2), after the second reaction begins, at 0 min, a mixture of AN 85.26 kg, St 242.76 kg, TDDM 1.28 kg and CHP 2.92 kg is added all at once; at 40 min, a mixture of AN 85.26 kg, St 242.76 kg, TDDM 1.28 kg and CHP 2.92 kg is added all at once; at 80 min, a mixture of AN 63.95 kg, St 182.07 kg, TDDM 0.96 kg and CHP 2.19 kg is added all at once to obtain rubber graft polymer 10.

[0108] Example 11

[0109] The method of Example 10 is different in that, in step (2), after the second reaction begins, at min 0, a mixture of 90.21 kg of AN, 210.48 kg of St, 1.234 kg of TDDM and 2.804 kg of CHP is added at once; at min 40, a mixture of 78.16 kg of AN, 222.53 kg of St, 1.177 kg of TDDM and 2.675 kg of CHP is added at once; at min 80, a mixture of 66.11 kg of AN, 234.57 kg of St, 1.120 kg of TDDM and 2.546 kg of CHP is added at once to obtain rubber graft polymer 11.

[0110] Example 12

[0111] The method of Example 11 is different except that in step (2), after the second reaction starts, the amount of CHP added is 2.383 kg at 0 min; the amount of CHP added is 2.408 kg at 40 min; and the amount of CHP added is 2.419 kg at 80 min, thus obtaining rubber graft polymer 12.

[0112] Example 13

[0113] The method of Example 1 is different in that, in step (1), 180.41g of methyl acrylate is added instead of 105.24kg of AN and 195.45kg of St; the amount of TDDM added is 3.002kg and the amount of CHP added is 1.153kg; in step (2), the amount of AN added is 286.25kg, the amount of St added is 736.08kg, the amount of TDDM added is 4.099kg, and the amount of CHP added is 9.315kg, to obtain rubber graft polymer 13.

[0114] Comparative Example 1

[0115] The method of Example 1 is different in that, in step (1), the amount of AN added is 84.25 kg, the amount of St added is 216.43 kg, the amount of TDDM added is 5.37 kg, and the amount of CHP added is 2.06 kg; in step (2), the amount of AN added is 255.47 kg, the amount of St added is 646.58 kg, the amount of TDDM added is 3.63 kg, and the amount of CHP added is 8.25 kg, so as to obtain rubber graft polymer 14.

[0116] Comparative Example 2

[0117] The method was followed according to Example 1, except that in step (1), the amount of AN added was 84.25 kg, the amount of St added was 216.43 kg, the amount of TDDM added was 5.37 kg, and the amount of CHP added was 2.06 kg; in step (2), after the second reaction started, at 0 min, 92.9 kg of AN, 325.12 kg of St, 1.32 kg of TDDM, and 3.00 kg of CHP were added all at once; at 40 min, 92.9 kg of AN, 325.12 kg of St, 1.32 kg of TDDM, and 3.00 kg of CHP were added all at once; at 80 min, 69.67 kg of AN, 176.34 kg of St, 0.99 kg of TDDM, and 2.25 kg of CHP were added all at once. Rubber grafted polymer 15 was obtained.

[0118] Test case

[0119] The polymer emulsions obtained in the above examples and comparative examples were demulsified using an acidic coagulant (98% concentrated sulfuric acid), followed by washing, dehydration, and drying to obtain rubber-grafted polymer powder. The grafting amounts of the prepared rubber-grafted polymers, GD% and GE%, were obtained using formulas (1) and (2), respectively, and the results are shown in Table 2.

[0120] Table 2

[0121]

[0122] The particle size of the raw material PB rubber in the comparative example and the examples, as well as the particle size D50 of the obtained rubber-grafted polymer after solvent dispersion, were measured using a dynamic light scattering (DLS) particle size analyzer. The glass transition temperature of PB rubber and rubber-grafted polymer in the comparative example and the examples was measured using a dynamic thermodynamic analyzer (DMA). The glass transition temperature difference ΔTg before and after PB rubber grafting was calculated, and the results are shown in Table 3.

[0123] Table 3

[0124]

[0125] The mechanical properties of the product were tested according to the method specified in Table 1, and the results are shown in Table 4:

[0126] Table 4

[0127]

[0128]

[0129] As can be seen from Tables 2 and 3, by using the method proposed in this application, by adjusting the monomer composition of each stage of the reaction, the amount of initiator, and the monomer drop-in time of the second reaction stage, a polymer layer with certain mass transfer resistance to monomers and initiators is coated on the rubber particles. This reduces the mass transfer of monomers and initiators within the rubber particles while ensuring that the outer layer grafting density is not affected.

[0130] Comparing Comparative Example 1 and Examples 1-3, with the increase of the percentage of the first reactant monomer AN%, the grafting rate (GD) and grafting efficiency (GE) of PB decreased slightly. Compared with increasing the percentage of the first reactant monomer AN, increasing the amount of the first reactant monomer had a relatively smaller effect on the grafting rate. After adjusting the percentage and amount of the first reactant monomer AN, the decrease in glass transition temperature ΔTg of the rubber before and after grafting decreased from 4.0℃ to 2.2℃, and the median particle size D of the rubber in the product... 50 The increase from 448nm to 481nm improved the mechanical properties of the product. The impact strength increased from 21.18kJ / ㎡ to a maximum of 22.80kJ / ㎡, the tensile elongation at break increased from 18.5% to a maximum of 22.5%, and other mechanical properties were also improved to varying degrees. The toughness of the product was significantly enhanced.

[0131] Comparing Examples 1, 4, and 5, compared to adding CHP alone, mixing CHP with monomers or pre-emulsifying both before adding them to the reaction system reduces the rate at which CHP enters the latex particles, decreases the concentration of CHP in the grafted layer, and avoids secondary crosslinking of PB due to excessive CHP. The glass transition temperature difference ΔTg before and after rubber grafting decreases from 2.2-2.4℃ to 1.1-1.3℃. Adjusting the CHP addition method does not adversely affect the PB grafting rate and monomer grafting efficiency. The median particle size D of the rubber particles in the product is [not specified]. 50 Maintaining a temperature of 477-480 nm; due to the decrease in the glass transition temperature of the rubber, the impact strength of the product is improved. Continuous dropwise addition of a pre-emulsified mixture of initiator and monomer can achieve an impact strength of 23.83 kJ / m², a tensile elongation at break of 25.4%, and a tensile strength of 43.5 MPa, resulting in a significant improvement in the product's mechanical properties.

[0132] Comparing Examples 1, 6, and 7, extending the monomer dropwise time can reduce the monomer concentration in the latex particles. On one hand, a higher PB / monomer ratio improves the selectivity of graft polymerization; on the other hand, it prevents excessive monomer and CHP from entering the inner graft layer. The glass transition temperature difference ΔTg before and after rubber grafting further decreases from 2.4℃ to 0.8℃, thereby improving the mechanical properties of the product. However, if the dropwise time is too long, the monomer concentration in the latex particles will be too low, and the monomer and CHP will also cause copolymerization due to prolonged residence time in the graft layer, which will reduce the PB grafting rate and decrease the median particle size D of the rubber particles in the product. 50As the process progresses from 462nm to 520nm, product performance decreases.

[0133] Comparing Examples 1 and 8, CHP was added in stages during the second reaction. In the initial stage of the second reaction, the grafted layer was relatively thin, allowing monomers and initiators to quickly penetrate the grafted layer to the surface of the latex particles and infiltrate their interior. Appropriately reducing the amount of initiator prevented excessive CHP from entering the latex particles due to an excessively thin or uneven grafted layer in the first reaction. As the second reaction progressed, the thickness of the outer polymer layer of PB gradually increased, requiring more time for monomers and initiators to reach the PB surface. At this point, the amount of CHP needed to be appropriately increased to shorten the time it took for CHP to reach PB, preventing initiator-monomer copolymerization due to prolonged residence of CHP in the outer grafted layer, which would significantly affect the PB grafting rate. Compared to Example 1, the PB grafting rate in Example 8 was slightly lower, but the glass transition temperature difference ΔTg before and after rubber grafting was equal to 1.0℃, and the median particle size D50 of the rubber particles in the product was still less than 500nm, indicating good mechanical properties.

[0134] Comparing Examples 1 and 9, without changing the total amount of AN and St, different percentages of AN% of grafted monomers were used at different stages of the second reaction. As the reaction proceeded, the AN% of the added grafted monomers gradually decreased, and the amounts of CHP and TDDM were adjusted according to the molar amount of the grafted monomers. At the end of the first reaction, some bare surfaces inevitably remained on the PB surface; using monomers with a high AN% at the beginning of the second reaction could, to some extent, "repair" the surface, preventing excessive monomers and initiators from entering the PB, ensuring that the glass transition temperature difference ΔTg before and after rubber grafting in the final product did not exceed 1.0℃. As the reaction proceeded, a grafted layer with a gradually decreasing AN% formed on the outer surface of the PB, causing the time required for subsequently added monomers to reach the PB surface to gradually increase, reducing the PB grafting rate and monomer grafting efficiency, and resulting in a median particle size D50 of rubber particles in the product exceeding 550nm. Due to the deterioration of the grafting effect, a small number of grafted rubber particles agglomerate, forming a small number of rubber agglomerates with a particle size of 0.8-1.5μm. These micro-agglomerates can make the 400-600nm rubber particles form a bimodal distribution of rubber particle size. By utilizing the synergistic toughening mechanism of large and small particle sizes, the impact strength and tensile elongation at break of the product are improved.

[0135] Comparing Comparative Example 2 and Example 10, when using a segmented feeding method for ABS graft polymerization, increasing the AN% of the initial feeding monomer can also improve the PB grafting rate and monomer grafting efficiency while improving the mechanical properties of the product.

[0136] Comparing Examples 10 and 11, in the second reaction stage, when ABS graft polymerization is carried out using a segmented batch feeding method, by adjusting the monomer composition at each stage of the second reaction stage and adjusting the initiator and chain transfer agent dosages proportionally according to the monomer molar amount, not only can the coverage of the grafted polymer on the PB be improved, but also excessive monomer entering the PB can be avoided. The glass transition temperature difference ΔTg before and after rubber grafting in the product is less than 1.5℃. However, a grafted layer with gradually decreasing AN% will subsequently form on the outside of the PB, causing the time required for subsequently added monomers to reach the PB surface to gradually increase, reducing the PB grafting rate and monomer grafting efficiency, and decreasing the rubber particle size D in the product. 50 There was a slight increase, but the product's impact strength and tensile elongation at break improved.

[0137] Comparing Examples 11 and 12, when using a segmented batch feeding method for ABS graft polymerization, by adjusting the second reaction stage and reducing the AN% of monomers added at each stage, the amount of initiator was further gradually reduced. This further prevented excessive initiator from entering the PB, and the glass transition temperature difference ΔTg before and after rubber grafting was reduced to 1.2℃. However, due to the reduction in the amount of initiator on the outside of the PB, the grafting rate and monomer grafting efficiency decreased, and the median particle size D50 of the rubber particles in the product reached 575nm. At the same time, during the blending process of the grafted powder with SAN, the rubber particles agglomerated to a certain extent, forming a small number of micro-agglomerated particles that could form a synergistic toughening effect of particle size with the normal particle size rubber particles, improving the impact strength and tensile elongation at break of the product.

[0138] Comparing Comparative Example 1 and Example 13, the addition of methyl methacrylate, which has a higher solubility parameter, in the first reaction slightly reduced the grafting rate of PB, decreased the glass transition temperature difference ΔTg before and after rubber grafting to 1.0℃, and the rubber particle size D50 also reached 530nm. However, the mechanical properties of the product were improved, with the impact strength increasing from 21.18kJ / ㎡ to a maximum of 22.25kJ / ㎡, the tensile elongation at break increasing from 18.5% to a maximum of 21.5%, and other mechanical properties also improved to varying degrees. The toughness of the product was significantly improved.

[0139] As can be seen from the above embodiments and comparative examples, the present invention can reduce the internal grafting and secondary crosslinking of rubber particles and lower the glass transition temperature of the rubber phase without affecting the external grafting density of the rubber particles. This allows the rubber phase to maintain good dispersion in the rigid polymer, with at least 50% of the rubber particles existing in a non-agglomerated state. The small amount of rubber particles that agglomerate due to the reduced grafting rate can also work together with the completely dispersed rubber particles to exert a bimodal synergistic toughening effect, which can significantly improve the toughening performance of ABS grafted powder, break the "rigidity and toughness" balance limitation, and comprehensively improve the mechanical properties of the product.

[0140] This invention is applicable to both batch and continuous emulsion graft polymerization processes, and is particularly suitable for production processes in which graft monomers are added in batches or batch / continuously.

[0141] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a rubber-grafted polymer, characterized in that, The method includes: (1) The rubber latex, monomer 1, chain transfer agent 1, activator, emulsifier 1 and initiator 1 are subjected to a first reaction to obtain a first product containing a polymer from monomer 1; (2) The first product, monomer 2, chain transfer agent 2 and initiator 2 are subjected to a second reaction to obtain a second product; (3) Initiator 3 is added to the second product to carry out a third reaction to obtain the rubber graft polymer; Wherein, the solubility parameter of monomer 1 is different from that of the rubber contained in the rubber emulsion; Monomer 2 has a different solubility parameter than the polymer derived from monomer 1; In step (2), the mixture of monomer 2 and chain transfer agent 2 is added after being mixed with initiator 2; In step (2), when the mixture is added after mixing, the mixture of monomer 2 and chain transfer agent 2 is mixed with initiator 2 and then added in batches or continuously. In step (2), when the mixture is added, the mixture of monomer 2 and chain transfer agent 2, initiator 2 and emulsifier 2 are mixed. wherein monomer 1 and monomer 2 are each independently selected from at least one of acrylonitrile, styrene, α-methylstyrene, methyl methacrylate and methyl acrylate; The rubber latex is selected from at least one of polybutadiene latex, polybutadiene styrene latex, and polybutyl acrylate latex; In step (1), the mass ratio of the rubber latex, monomer 1, chain transfer agent 1, activator, emulsifier 1 and initiator 1 is 1100-1500:120-150:2-5:50-100:100-150:1; In step (2), the mass ratio of the first product, monomer 2, chain transfer agent 2, and initiator 2 is 1500-2000:200-300:1:1-3.

2. The preparation method according to claim 1, wherein, In step (2), the mass ratio of monomer 2 to initiator 2 is 110-150:1; the concentration of initiator 2 is 50-85wt%.

3. The preparation method according to claim 1 or 2, wherein, When the mixture is added, the continuous addition time is 100-150 minutes.

4. The preparation method according to claim 1 or 2, wherein, The mass ratio of monomer 1 to monomer 2 is 1-5:2-10.

5. The preparation method according to claim 1 or 2, wherein, The solid content of the rubber latex is 45-60%, and the average particle size of the latex particles contained in the rubber latex is 100-800 nm.

6. The preparation method according to claim 3, wherein, The solid content of the rubber latex is 45-60%, and the average particle size of the latex particles contained in the rubber latex is 100-800 nm.

7. The preparation method according to claim 4, wherein, The solid content of the rubber latex is 45-60%, and the average particle size of the latex particles contained in the rubber latex is 100-800 nm.

8. The preparation method according to any one of claims 1, 2, 6, and 7, wherein, The chain transfer agent 1 and chain transfer agent 2 are each independently selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan; And / or, the emulsifier 1 is selected from at least one of potassium disproportionated rosinate, potassium fatty acid, potassium oleate, sodium butylnaphthalene sulfonate, and sodium alkyl sulfate; And / or, the activator is selected from the reducing sugar-sodium pyrophosphate-ferrous sulfate activation system and / or formaldehyde sodium hyposulfite-EDTA-4Na-ferrous sulfate activation system; And / or, each of the initiators 1, 2 and 3 is independently selected from at least one of cumene hydroperoxide, tert-butyl hydroperoxide, p-menthane hydroperoxide, methylcyclohexane hydroperoxide and tetrahydronaphthalene hydroperoxide.

9. The preparation method according to claim 3, wherein, The chain transfer agent 1 and chain transfer agent 2 are each independently selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan; And / or, the emulsifier 1 is selected from at least one of potassium disproportionated rosinate, potassium fatty acid, potassium oleate, sodium butylnaphthalene sulfonate, and sodium alkyl sulfate; And / or, the activator is selected from the reducing sugar-sodium pyrophosphate-ferrous sulfate activation system and / or formaldehyde sodium hyposulfite-EDTA-4Na-ferrous sulfate activation system; And / or, each of the initiators 1, 2 and 3 is independently selected from at least one of cumene hydroperoxide, tert-butyl hydroperoxide, p-menthane hydroperoxide, methylcyclohexane hydroperoxide and tetrahydronaphthalene hydroperoxide.

10. The preparation method according to claim 4, wherein, The chain transfer agent 1 and chain transfer agent 2 are each independently selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan; And / or, the emulsifier 1 is selected from at least one of potassium disproportionated rosinate, potassium fatty acid, potassium oleate, sodium butylnaphthalene sulfonate, and sodium alkyl sulfate; And / or, the activator is selected from the reducing sugar-sodium pyrophosphate-ferrous sulfate activation system and / or formaldehyde sodium hyposulfite-EDTA-4Na-ferrous sulfate activation system; And / or, each of the initiators 1, 2 and 3 is independently selected from at least one of cumene hydroperoxide, tert-butyl hydroperoxide, p-menthane hydroperoxide, methylcyclohexane hydroperoxide and tetrahydronaphthalene hydroperoxide.

11. The preparation method according to claim 5, wherein, The chain transfer agent 1 and chain transfer agent 2 are each independently selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan; And / or, the emulsifier 1 is selected from at least one of potassium disproportionated rosinate, potassium fatty acid, potassium oleate, sodium butylnaphthalene sulfonate, and sodium alkyl sulfate; And / or, the activator is selected from the reducing sugar-sodium pyrophosphate-ferrous sulfate activation system and / or formaldehyde sodium hyposulfite-EDTA-4Na-ferrous sulfate activation system; And / or, each of the initiators 1, 2 and 3 is independently selected from at least one of cumene hydroperoxide, tert-butyl hydroperoxide, p-menthane hydroperoxide, methylcyclohexane hydroperoxide and tetrahydronaphthalene hydroperoxide.

12. The preparation method according to claim 1 or 2, wherein, The emulsifier 2 is selected from at least one of potassium disproportionated rosinate, potassium fatty acid, potassium oleate, sodium butylnaphthalene sulfonate, and sodium alkyl sulfate.

13. The preparation method according to any one of claims 1, 2, 6, 7, 9-11, wherein, The temperature of the first reaction is 40-60℃, and the time is 50-70 min; And / or, the temperature of the second reaction is 60-78°C and the time is 100-120 min; And / or, the temperature of the third reaction is 78-80°C and the time is 15-30 min.

14. The preparation method according to claim 3, wherein, The temperature of the first reaction is 40-60℃, and the time is 50-70 min; And / or, the temperature of the second reaction is 60-78°C and the time is 100-120 min; And / or, the temperature of the third reaction is 78-80°C and the time is 15-30 min.

15. The preparation method according to claim 4, wherein, The temperature of the first reaction is 40-60℃, and the time is 50-70 min; And / or, the temperature of the second reaction is 60-78°C and the time is 100-120 min; And / or, the temperature of the third reaction is 78-80°C and the time is 15-30 min.

16. The preparation method according to claim 5, wherein, The temperature of the first reaction is 40-60℃, and the time is 50-70 min; And / or, the temperature of the second reaction is 60-78°C and the time is 100-120 min; And / or, the temperature of the third reaction is 78-80°C and the time is 15-30 min.

17. The preparation method according to claim 8, wherein, The temperature of the first reaction is 40-60℃, and the time is 50-70 min; And / or, the temperature of the second reaction is 60-78°C and the time is 100-120 min; And / or, the temperature of the third reaction is 78-80°C and the time is 15-30 min.

18. The preparation method according to claim 12, wherein, The temperature of the first reaction is 40-60℃, and the time is 50-70 min; And / or, the temperature of the second reaction is 60-78°C and the time is 100-120 min; And / or, the temperature of the third reaction is 78-80°C and the time is 15-30 min.

Images