Preparation method for rubber graft polymer

Abstract

A preparation method for a rubber graft polymer, comprising: subjecting rubber latex, a first monomer, a first chain transfer agent, an activator, a first emulsifier and a first initiator to a first reaction to obtain a first product containing a polymer from the first monomer; subjecting the first product, a second monomer, a second chain transfer agent and a second initiator to a second reaction to obtain a second product; and adding a third initiator into the second product to carry out a third reaction, wherein the solubility parameters of the first monomer and rubber contained in the rubber latex are different, the solubility parameters of the second monomer and the polymer from the first monomer are different, the mass ratio of the second monomer to the second initiator is 110-150:1, and the concentration of the second initiator is 50-85 wt%. The preparation method does not affect the grafting density outside rubber particles while reducing internal grafting and secondary cross-linking inside the rubber particles in the preparation process, and can significantly improve the toughening performance of the rubber graft polymer.

Description

Preparation method of rubber grafted polymer

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202311145423.8 filed on September 6, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of polymer chemical industry, in particular to a method for preparing a rubber grafted polymer. Background Art

[0004] Rubber toughening involves blending a small amount of rubber with a rigid polymer to increase the material's toughness. Both thermoplastic and thermosetting resins can be toughened with rubber. During the rubber-toughening process, cavities are first formed within the rubber particles, weakening their resistance to deformation. This allows them to induce yielding in the matrix under low stress conditions, allowing the matrix surrounding the cavitated rubber particles to deform via various mechanisms. The larger the rubber particle size, the lower the elastic modulus of the rubber, the more susceptible the rubber particles are to cavitation, and the better the mechanical properties of the rubber-toughened resin.

[0005] The compatibility of the rubber used to toughen resins is often poor. To improve the dispersion of the rubber in the resin, a layer of polymer with the same or similar composition as the resin needs to be grafted onto the rubber surface, forming a toughened rubber graft polymer with a "core-shell" structure. However, in the production of these polymers, to ensure sufficient grafting capacity and good dispersion of the toughened rubber in the resin, excessive amounts of grafting monomer and initiator are often added. This partially infiltrates the rubber particles, triggering secondary crosslinking and "internal grafting" of the monomer, increasing the elastic modulus of the rubber, making it more difficult to cavitate, and reducing the toughening properties of the rubber. While reducing the initiator dosage and continuously or semi-continuously adding monomer and initiator can reduce the elastic modulus of the toughened rubber to a certain extent, it also affects the graft density of the rubber outer layer, hindering the dispersion of the rubber in the resin.

[0006] When producing toughened rubber graft polymers with a core-shell structure, the challenge is to minimize internal grafting and secondary crosslinking within the rubber particles while maintaining the density of external grafts and improving the toughening properties of the rubber. Therefore, developing a method for grafting rubber polymers to address this issue is of great significance.

[0007] Summary of the Invention

[0008] The purpose of the present invention is to solve the problems of excessive grafting amount and secondary crosslinking in rubber particles, which are often present in toughened rubber graft polymers with a "core-shell" structure, while avoiding the problem of affecting the grafting density of the rubber outer layer, and to provide a method for preparing a rubber graft polymer.

[0009] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a rubber graft polymer, wherein the method comprises:

[0010] (1) subjecting a rubber latex, a monomer 1, a chain transfer agent 1, an activator, an emulsifier 1, and an initiator 1 to a first reaction to obtain a first product containing a polymer derived from the monomer 1;

[0011] (2) subjecting the first product, monomer 2, chain transfer agent 2, and initiator 2 to a second reaction to obtain a second product;

[0012] (3) adding initiator 3 to the second product to carry out a third reaction to obtain the rubber graft polymer;

[0013] wherein the monomer 1 has a different solubility parameter from the rubber contained in the rubber latex;

[0014] Monomer 2 has a different solubility parameter than the polymer from monomer 1;

[0015] The mass ratio of monomer 2 to initiator 2 is 110-150:1; the concentration of initiator 2 is 50-85 wt%.

[0016] The present invention also provides a rubber graft polymer prepared by the above preparation method, wherein the polymer has a core-shell structure;

[0017] Wherein, the weight ratio of shell to core in the polymer is 0.43-0.46:1;

[0018] The impact strength of the polymer is 20-25 kJ / m 2 , the tensile elongation at break is 20-30%.

[0019] Through the above-mentioned technical solution, the present invention achieves uniform coverage of the rubber particle surface through grafting during the initial grafting reaction, with a certain degree of mass transfer resistance to the monomer and initiator. Furthermore, by reducing the concentrations of the shell monomer and initiator forming the outer graft layer, the driving force for mass transfer between the graft layer and the rubber particles is reduced, allowing the shell monomer and initiator to concentrate primarily on the rubber particle surface for polymerization. Testing of the grafted rubber polymer produced by the present invention for grafting efficiency and mechanical properties demonstrated that while reducing grafting and secondary crosslinking within the rubber particles, the grafting density on the outer surface of the rubber particles was not affected. This significantly enhances the toughening properties of the grafted rubber polymer, breaking the "rigidity-toughness" trade-off and comprehensively improving the product's mechanical properties.

[0020] The invention is applicable to intermittent and continuous emulsion graft polymerization processes, and is particularly applicable to production processes in which graft monomers are added in batches or in batch-continuously. DETAILED DESCRIPTION

[0021] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0022] The following is a detailed description of the specific embodiments of the present invention in conjunction with the table. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0023] A first aspect of the present invention provides a method for preparing a rubber graft polymer, wherein the method comprises:

[0024] (1) subjecting a rubber latex, a monomer 1, a chain transfer agent 1, an activator, an emulsifier 1, and an initiator 1 to a first reaction to obtain a first product containing a polymer derived from the monomer 1;

[0025] (2) subjecting the first product, monomer 2, chain transfer agent 2, and initiator 2 to a second reaction to obtain a second product;

[0026] (3) adding initiator 3 to the second product to carry out a third reaction to obtain the rubber graft polymer;

[0027] wherein the monomer 1 has a different solubility parameter from the rubber contained in the rubber latex;

[0028] Monomer 2 has a different solubility parameter than the polymer from monomer 1;

[0029] The mass ratio of monomer 2 to initiator 2 is 110-150:1; the concentration of initiator 2 is 50-85 wt %.

[0030] 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 value that can characterize the strength of the interaction between liquid molecules, between liquid molecules and polymers, and between polymers.

[0031] By calculating the solubility parameter of a polymer and comparing it with the solubility parameter 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 solvent are, the higher the solubility of the polymer; conversely, the greater the difference in solubility parameters between the polymer and solvent, the lower the solubility of the polymer.

[0032] 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 the rubber, is grafted onto the surface of the rubber particles to form a polymer that is evenly covered and has a certain mass transfer resistance to the monomer and initiator, forming an inner graft layer composed of the polymer derived from monomer 1. Subsequently, monomer 2, whose solubility parameter is different from that of the polymer derived from monomer 1, is added to the reaction system. Monomer 2 is less likely to pass through the inner graft layer and reach the rubber surface, so that monomer 2 and the initiator are primarily concentrated on the rubber particle surface for polymerization. This reduces grafting and secondary crosslinking within the rubber particles while maintaining the graft density outside the rubber particles. Furthermore, the solubility parameter of monomer 2 is between that of the rubber and that of the rigid resin to be toughened, which facilitates the desirability between the toughened rubber and the rigid resin, thereby improving the dispersion of the rubber in the resin.

[0033] According to the present invention, in order to further reduce the mass transfer driving force between the graft layer and the rubber particles, so that the monomer 2 and the initiator are mainly concentrated on the surface of the rubber particles, and at the same time avoid the mass transfer rate of the monomer 2 being too low, the copolymerization probability during the mass transfer process is increased, resulting in a decrease in the toughened rubber grafting rate and a decrease in the dispersibility of the product in the resin, the mass ratio of the monomer 2 to the initiator 2 in step (2) is controlled within the range of 110-150:1, and the concentration of the initiator 2 is controlled to 50-85wt%.

[0034] According to the present invention, in order to improve the compatibility between the toughened rubber and different resins, when modifying the rubber, graft polymerization with different types of monomers 1 and / or monomers 2 is selected. In order to significantly improve the toughening properties of various rubber graft polymers, preferably, in step (2), the mixed solution of the monomer 2 and the chain transfer agent 2 and the initiator 2 can be mixed and added, or they can be added separately.

[0035] According to the present invention, in order to reduce the initiator from passing through the inner graft layer, reduce the initiator concentration in the graft layer, avoid secondary crosslinking of the rubber due to the presence of excessive initiator, and improve the mechanical properties of the obtained rubber graft polymer, preferably, in step (2), the mixed solution of the monomer 2 and the chain transfer agent 2 is mixed with the initiator 2 and then added.

[0036] Preferably, the mixed solution of the monomer 2 and the chain transfer agent 2 is mixed with the initiator 2 and then added continuously.

[0037] Preferably, the mixed solution of the monomer 2 and the chain transfer agent 2 is mixed with the initiator 2 and then added in batches.

[0038] According to the present invention, depending on the actual application of the toughened rubber, the rubber will be grafted with different types of monomers 1 and / or monomers 2. In order to make the various rubber graft polymers obtained have higher toughening properties, preferably, the mixture of the monomer 2 and the chain transfer agent 2 and the initiator 2 are added separately. In other words, the mixture of the monomer 2 and the chain transfer agent 2 and the initiator 2 are not mixed but added separately.

[0039] More preferably, the mixed solution of the monomer 2 and the chain transfer agent 2 is added separately from the initiator 2 and simultaneously.

[0040] More preferably, the mixed solution of the monomer 2 and the chain transfer agent 2 is added separately from the initiator 2 and asynchronously.

[0041] Preferably, in order to reduce the concentration of monomers in the latex particles, improve the selectivity of graft polymerization, and avoid excessive monomers and initiators passing through the graft layer, so as to improve the mechanical properties of the product, the monomer addition time can be appropriately extended. At the same time, it is avoided that the monomer concentration in the latex particles is too low due to the addition time is too long, and the monomers and initiators stay in the graft layer for too long, which may cause the monomers to copolymerize and reduce the product performance. Preferably, in step (2), when adding after mixing, the mixture of monomer 2 and chain transfer agent 2 is continuously added for 100-150 minutes after mixing with initiator 2.

[0042] Preferably, in step (2), when adding separately, the mixture of the monomer 2 and the chain transfer agent 2 and the initiator 2 are added separately and simultaneously for a time period of 100-150 minutes.

[0043] 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, the monomer 1 and the monomer 2 are each independently selected from at least one of acrylonitrile, styrene, α-methylstyrene, methyl methacrylate and methyl acrylate;

[0044] Preferably, the mass ratio of monomer-1 to monomer-2 is 1-5:2-10.

[0045] 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.

[0046] Further preferably, the rubber latex is selected from at least one of polybutadiene latex, polybutadiene styrene latex, and polybutyl acrylate latex.

[0047] According to the present invention, in order to reduce the length of the internal and external grafted molecular chains in the first reaction stage, reduce the elastic modulus, and increase the external grafting density; at the same time, reduce the length of the external grafted chain to avoid the poor compatibility of the grafted polymer with the toughening resin caused by excessive grafting, preferably, the chain transfer agent 1 and the chain transfer agent 2 are each independently selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan.

[0048] According to the present invention, in order to improve the stability of the reaction system and regulate the amount of monomers entering the latex particles, preferably, the emulsifier 1 and the emulsifier 2 are each independently selected from at least one of potassium disproportionate rosin acid, potassium fatty acid, potassium oleate, sodium butylnaphthalene sulfonate and sodium alkyl sulfate.

[0049] According to the present invention, in order to make the monomers react inside the latex particles, effectively reduce the amount of polymer produced outside the latex particles, and at the same time maintain the stability of the polymerization rate during the reaction, preferably, the activator is selected from a reducing sugar-sodium pyrophosphate-ferrous sulfate activation system and / or a sodium formaldehyde sulfoxylate-EDTA-4Na-ferrous sulfate activation system.

[0050] According to the present invention, in order to make the polymerization reaction proceed smoothly and obtain the 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-menthane hydroperoxide, methylcyclohexane hydroperoxide, p-methylisopropylbenzene hydroperoxide and tetralin hydroperoxide.

[0051] According to the present invention, in order to effectively control the amount of monomers entering the interior of the rubber particles and remaining outside, balance the amount of internal and external grafting of the rubber, and enable the grafted rubber to take into account both the elastic modulus and the dispersion, preferably, in step (1), the mass ratio of the rubber latex, 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.

[0052] 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.

[0053] According to the present invention, in order to make the polymerization reaction proceed well and obtain a rubber graft polymer with greatly improved mechanical properties, preferably, the temperature of the first reaction is 40-60° C. and the time is 50-70 min;

[0054] And / or, the temperature of the second reaction is 60-78° C., and the time is 100-120 min.

[0055] And / or, the temperature of the third reaction is 75-80° C., and the time is 15-30 min.

[0056] 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; the temperature of the third reaction is 76° C. and the time is 20 min.

[0057] The present invention can reduce the grafting and secondary cross-linking inside the rubber particles without affecting the grafting density outside the rubber particles, can significantly improve the toughening performance of the rubber grafted polymer, break the "rigidity" balance limitation, and comprehensively improve the mechanical properties of the product.

[0058] The present invention also provides a rubber graft polymer prepared by the above preparation method, wherein the polymer has a core-shell structure;

[0059] Wherein, the weight ratio of shell to core in the polymer is 0.43-0.46:1;

[0060] The impact strength of the polymer is 20-25 kJ / m 2 , the tensile elongation at break is 20-30%.

[0061] The present invention uses a dynamic light scattering (DLS) particle size analyzer to test the particle size of the raw material PB rubber and the particle size D of the prepared rubber graft polymer after being dispersed by the solvent. 50 The glass transition temperatures of the PB rubber and the rubber grafted polymer in the comparative example and the embodiment were tested using a dynamic thermodynamic analyzer (DMA). The glass transition temperature difference ΔTg before and after the PB rubber grafting was calculated. The test results are as follows: the rubber grafted polymer as a toughening material after being dispersed in the solvent has a glass transition temperature of ΔTg. 50 ≤2.0 times the particle size of the rubber graft polymer, indicating that the rubber graft polymer prepared by the present invention has good compatibility with the resin and has no obvious agglomeration tendency. Therefore, the D value of the rubber graft polymer used as a toughening material for resin toughening is 50 The closer to the particle size of the grafted rubber particles is to the completely dispersed state; the glass transition temperature difference ΔTg before and after the PB rubber grafting represents the change in the elastic modulus before and after the rubber grafting. The smaller the change in the elastic modulus, the better the rubber toughening.

[0062] The rubber grafted polymer in the present 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 a "soft" monomer; 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 conducive to the dispersion of the toughening rubber in the rigid resin.

[0063] The present invention will be described in detail below through examples.

[0064] In the following examples and comparative examples, the evaluation method of the toughened rubber grafting amount and the mechanical properties of the final product is as follows:

[0065] 1. Test method for the grafting amount of toughened rubber monomer and the utilization rate of shell monomer:

[0066] Weigh a certain amount of core-shell polymer powder (taking ABS high-rubber powder as an example) and record it as m g0 , placed in a special test tube and dissolved in acetone, shaken for 24 hours and separated in a centrifuge at a centrifugal speed of 10000r / min and a centrifugal time of 0.5h. After the centrifugal separation is completed, the clear liquid in the test tube is poured out, and then an appropriate amount of acetone is added and the above experiment is repeated. The final precipitate is a core-shell polymer. The precipitate is dried to a constant weight and weighed, and the weight is 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.

[0067] in:

[0068] GD%—the percentage of shell polymer to core polymer weight, wt%;

[0069] m g0 —Weigh the weight of the toughened rubber graft powder, g;

[0070] m g1 —The weight of the dried product after centrifugation, g;

[0071] A%—content of core polymer in toughened rubber graft powder, wt%.

[0072] The shell utilization rate of the shell monomer is calculated by formula (2).

[0073] in:

[0074] GE%—the percentage of monomers forming the core-shell polymer in the total amount of shell monomers, wt%;

[0075] m g0 —Weigh the weight of the toughened rubber graft powder, g;

[0076] m g1 —The weight of the dried product after centrifugation, g;

[0077] A%—content of core polymer in toughened rubber graft powder, wt%.

[0078] 2. Test methods for rubber particle size and glass transition temperature in products

[0079] (1) Particle size of rubber particles in the product

[0080] 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 the DSL dynamic scattering laser particle size analyzer to measure the median particle size D of the rubber dispersed in the sample. 50 , μm.

[0081] (2) Glass transition temperature test of rubber phase in product

[0082] The glass transition temperature (Tg) of the rubber in the product was measured using a dynamic thermomechanical analyzer (DTA) using a three-point bending fixture with a specimen size of 80 mm × 10 mm × 4 mm. Temperature sweeps were performed at a fixed frequency of 1 Hz over a temperature range of -110 to 30°C, with a heating rate of 10°C / min. The peak value of the ratio of the loss modulus to the storage modulus during the heating process was recorded as the glass transition temperature (Tg) of the rubber in the product.

[0083] 3. Preparation of product test specimens and evaluation methods of mechanical properties

[0084] The toughened rubber graft polymer powder and acrylonitrile-styrene copolymer (SAN resin, a commercial product with the brand number 2437 from Jilin Petrochemical Company of PetroChina) were blended and granulated in a weight ratio of 25 / 75. The mechanical properties of the product were tested according to the method specified in Table 1.

[0085] Table 1

[0086] For ABS graft polymerization with PB as toughening rubber and AN and St as grafting 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) The solubility parameter δ SAN =9.6, with the increase of AN% in SAN, the solubility parameter gradually increases.

[0087] Example 1

[0088] (1) 3120 kg of polybutadiene (PB) rubber emulsion with a solid content of 57.70% and an average particle size of 300 nm of latex particles, 105.24 kg of monomers of acrylonitrile (AN) and 195.45 kg of styrene (St), 5.811 kg of a chain transfer agent of tert-dodecyl mercaptan (TDDM), 174 kg of an activator (glucose: 2.888 wt %, sodium pyrophosphate: 2.299 wt %, ferrous sulfate: 0.046 wt %, water: 94.767 wt %), 306 kg of an emulsifier of potassium disproportionate rosinate solution (solid content: 1.96%), and 1105.86 kg of flushing water were added into a reactor, the contents in the reactor were heated to 40° C., 2.232 kg of an initiator of cumene hydroperoxide (CHP, purity ≥80%) were added, and a first reaction was carried out for 60 min, at which time the temperature in the reactor reached 60° C., to obtain a first product;

[0089] (2) After mixing 234.48 kg of AN, 667.58 kg of St and 3.53 kg of TDDM, the temperature in the kettle was maintained at 60 ° C. The resulting mixture was continuously added to the reactor at a constant flow rate within 110 min. At the same time, 8.02 kg of initiator CHP was added to the reactor separately within the same time to carry out the second reaction. After the reaction, the temperature in the kettle rose to 76 ° C to obtain the second product;

[0090] (3) The temperature in the kettle was maintained at 76° C., 3.19 kg of initiator CHP was added, and the third reaction was carried out for 20 min to obtain rubber graft polymer 1.

[0091] Example 2

[0092] The method of Example 1 was followed, except that in step (1), the amount of AN added was 120.28 kg, the amount of St added was 180.41 kg, the amount of TDDM added was 6.127 kg, and the amount of CHP added was 2.353 kg; and in step (2), the amount of AN added was 219.44 kg, the amount of St added was 682.61 kg, the amount of TDDM added was 3.46 kg, and the amount of CHP added was 7.86 kg, to obtain a rubber graft polymer 2.

[0093] Example 3

[0094] The method of Example 1 was followed, except that in step (1), the amount of AN added was 126.29 kg, the amount of St added was 234.54 kg, the amount of TDDM added was 6.973 kg, and the amount of CHP added was 2.678 kg; and in step (2), the amount of AN added was 213.43 kg, the amount of St added was 628.49 kg, the amount of TDDM added was 3.27 kg, and the amount of CHP added was 7.43 kg, to obtain a rubber graft polymer 3.

[0095] Example 4

[0096] The method of Example 1 was followed, 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 were mixed and continuously added to the reactor at a constant flow rate over 110 min to obtain rubber graft polymer 4.

[0097] Example 5

[0098] The method of Example 1 was followed, 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 rosin acid solution (solid content: 1.96%) were mixed to form a pre-emulsified monomer, which was then continuously added to the reactor at a constant flow rate over 110 min to obtain rubber grafted polymer 5.

[0099] Example 6

[0100] The method of Example 1 was followed, except that in step (2), 234.48 kg of AN, 667.58 kg of St, and 3.53 kg of TDDM were mixed and continuously added to the reactor at a constant flow rate over 140 min. At the same time, 8.02 kg of initiator CHP was separately added to the reactor over the same period of time to carry out a second reaction to obtain rubber grafted polymer 6.

[0101] Example 7

[0102] The method of Example 1 was followed, except that in step (2), 234.48 kg of AN, 667.58 kg of St, and 3.53 kg of TDDM were mixed and continuously added to the reactor at a constant flow rate over 170 min. At the same time, 8.02 kg of initiator CHP was separately added to the reactor over the same period of time to carry out a second reaction to obtain rubber grafted polymer 7.

[0103] Example 8

[0104] The method of Example 1 was followed, except that in step (2), after the start of the second reaction, 2.479 kg of initiator CHP was added at a constant flow rate within 0-40 min; 2.625 kg of initiator CHP was added at a constant flow rate within 40-80 min; and 2.078 kg of initiator CHP was added at a constant flow rate within 80-110 min to obtain rubber graft polymer 8.

[0105] Example 9

[0106] The method of Example 1 was followed, except that in step (2), after the start of the second reaction, a mixture of 90.21 kg of AN, 210.48 kg of St, 1.234 kg of TDDM and 2.804 kg of initiator CHP was continuously added at a constant flow rate within 0-40 min; a mixture of 78.16 kg of AN, 222.53 kg of St, 1.177 kg of TDDM and 2.675 kg of initiator CHP was continuously added at a constant flow rate within 40-80 min; and a mixture of 66.11 kg of AN, 234.57 kg of St, 1.120 kg of TDDM and 2.546 kg of initiator CHP was continuously added at a constant flow rate within 80-110 min to obtain rubber graft polymer 9.

[0107] Example 10

[0108] The method of Example 1 was followed, except that in step (2), after the start of the second reaction, at the 0th minute, a mixture of 85.26 kg of AN, 242.76 kg of St, 1.28 kg of TDDM, and 2.92 kg of CHP was added all at once; at the 40th minute, a mixture of 85.26 kg of AN, 242.76 kg of St, 1.28 kg of TDDM, and 2.92 kg of CHP was added all at once; and at the 80th minute, a mixture of 63.95 kg of AN, 182.07 kg of St, 0.96 kg of TDDM, and 2.19 kg of CHP was added all at once to obtain a rubber graft polymer 10.

[0109] Example 11

[0110] The method of Example 10 was followed, except that in step (2), after the start of the second reaction, at the 0th minute, a mixture of 90.21 kg of AN, 210.48 kg of St, 1.234 kg of TDDM and 2.804 kg of CHP was added all at once; at the 40th minute, a mixture of 78.16 kg of AN, 222.53 kg of St, 1.177 kg of TDDM and 2.675 kg of CHP was added all at once; and at the 80th minute, a mixture of 66.11 kg of AN, 234.57 kg of St, 1.120 kg of TDDM and 2.546 kg of CHP was added all at once to obtain the rubber graft polymer 11.

[0111] Example 12

[0112] The method of Example 11 was followed, except that in step (2), after the start of the second reaction, at 0 min, the amount of CHP added was 2.383 kg; at 40 min, the amount of CHP added was 2.408 kg; at 80 min, the amount of CHP added was 2.419 kg, to obtain a rubber grafted polymer 12.

[0113] Example 13

[0114] The method of Example 1 was followed, except that in step (1), 180.41 g of methyl acrylate was added instead of 105.24 kg of AN and 195.45 kg of St; the amount of TDDM added was 3.002 kg, and the amount of CHP added was 1.153 kg; in step (2), the amount of AN added was 286.25 kg, the amount of St added was 736.08 kg, the amount of TDDM added was 4.099 kg, and the amount of CHP added was 9.315 kg, to obtain rubber graft polymer 13.

[0115] Comparative Example 1

[0116] The method of Example 1 was followed, 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; and in step (2), the amount of AN added was 255.47 kg, the amount of St added was 646.58 kg, the amount of TDDM added was 3.63 kg, and the amount of CHP added was 8.25 kg, to obtain a rubber graft polymer 14.

[0117] Comparative Example 2

[0118] The method of Example 1 was followed, 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 start of the second reaction, at the 0th minute, 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 the 40th minute, 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; and at the 80th minute, 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. To obtain rubber graft polymer 15.

[0119] Test Case

[0120] The polymer emulsions obtained in the above examples and comparative examples were demulsified using an acidic coagulant (98% concentrated sulfuric acid), washed, dehydrated, and dried to obtain a rubber graft polymer powder. The grafting amounts of the obtained rubber graft polymers were obtained using equations (1) and (2), respectively: GD% and GE%. The results are shown in Table 2:

[0121] Table 2

[0122] The particle size of the raw material PB rubber in the comparative example and the embodiment and the particle size D of the obtained rubber graft polymer after being dispersed by the solvent were respectively measured by dynamic light scattering (DLS) particle size analyzer. 50 The glass transition temperatures of the PB rubber and the rubber grafted polymer in the comparative example and the embodiment were tested using a dynamic thermodynamic analyzer (DMA), and the glass transition temperature difference ΔTg before and after the PB rubber grafting was calculated. The results are shown in Table 3:

[0123] Table 3

[0124] The mechanical properties of the product were tested according to the method specified in Table 1. The results are shown in Table 4:

[0125] Table 4

[0126] As can be seen from Tables 2 and 3, by using the method proposed in this application, by adjusting the monomer composition in each reaction stage, the amount of initiator used, and the monomer addition time in the second reaction stage, a layer of polymer that has a certain mass transfer resistance to the monomer and initiator is covered on the rubber particles, while reducing the mass transfer of monomer and initiator in the rubber particles, ensuring that the outer layer grafting density is not affected.

[0127] Comparing Comparative Example 1 with Examples 1-3, as the AN% of the first reaction monomer increases, the PB grafting rate (GD) and the grafting efficiency (GE) of the monomer decrease slightly. Compared with increasing the AN% of the first reaction monomer, increasing the amount of the first reaction monomer has a relatively small effect on the grafting rate. After adjusting the AN% and amount of the first reaction monomer, the glass transition temperature drop ΔTg of the rubber before and after grafting is reduced from 4.0°C to 2.2°C, and the median particle size D of the rubber in the product is reduced. 50 Increasing from 448nm to 481nm, the mechanical properties of the product have been improved, the impact strength has been increased from 21.18kJ / ㎡ to 22.80kJ / ㎡, the tensile elongation at break has been increased from 18.5% to 22.5%; other mechanical performance indicators have also been improved to varying degrees, and the toughness of the product has been significantly improved.

[0128] Comparing Examples 1, 4, and 5, compared with adding CHP alone, mixing CHP with the monomer or pre-emulsifying the two before adding to the reaction system can reduce the rate at which CHP enters the latex particles, reduce the concentration of CHP in the graft layer, and avoid secondary crosslinking of PB due to the presence of excessive CHP. The glass transition temperature difference ΔTg before and after rubber grafting is reduced from 2.2-2.4°C to 1.1-1.3°C. Adjusting the CHP addition method will not adversely affect the PB grafting rate and monomer grafting efficiency. The median particle size D of the rubber particles in the product is 1.5-2.0°C. 50 Maintained at 477-480nm; due to the reduction of the rubber's glass transition temperature, the product's impact strength is improved. By pre-emulsifying the initiator and monomer and then adding them continuously, the impact strength can reach 23.83kJ / ㎡, the tensile elongation at break reaches 25.4%, and the tensile strength reaches 43.5MPa, significantly improving the product's mechanical properties.

[0129] Comparing Examples 1, 6, and 7, by extending the monomer addition time, the monomer concentration in the latex particles can be reduced. On the one hand, a high PB / monomer ratio will improve the selectivity of graft polymerization. On the other hand, it can also prevent excessive monomers and CHP from entering and breaking through the inner graft layer. The glass transition temperature difference ΔTg before and after rubber grafting is further reduced from 2.4°C to 0.8°C, thereby improving the mechanical properties of the product. However, if the addition time is too long, the monomer concentration in the latex particles is too low. At the same time, the monomer and CHP will stay in the graft layer for too long, which will trigger the copolymerization of the monomers, which will in turn reduce the PB grafting rate and make the median particle size D of the rubber particles in the product 50 When increasing from 462nm to 520nm, product performance has declined.

[0130] Comparing Examples 1 and 8, CHP is added in stages during the second reaction. At the beginning of the second reaction, the graft layer is relatively thin, and the monomer and initiator can still quickly pass through the graft layer to reach the surface of the latex particles and penetrate into the interior of the latex particles. Properly reducing the amount of initiator can avoid excessive CHP entering the interior of the latex particles due to the graft layer being too thin or poorly uniform in the first reaction; as the second reaction proceeds, the thickness of the PB outer layer polymer gradually increases, and the monomer and initiator need a longer time to reach the PB surface. At this time, it is necessary to appropriately increase the amount of CHP to shorten the time it takes for CHP to reach the PB, so as to avoid the initiator monomer copolymerization due to CHP staying in the outer graft layer for too long, which significantly affects the PB grafting rate. Compared with Example 1, the PB grafting rate of Example 8 is slightly lower, but the glass transition temperature difference ΔTg before and after rubber grafting is equal to 1.0°C, and the median particle size D of the rubber particles in the product is 1.0°C. 50 It is still less than 500nm, and the product has good mechanical properties.

[0131] Comparing Examples 1 and 9, without changing the total amount of AN and St, different AN% of grafting monomers are used in each period of the second reaction. As the reaction proceeds, the AN% of the added grafting monomers gradually decreases, and the amounts of CHP and TDDM are adjusted according to the molar amount of the grafting monomers. At the end of the first reaction, some exposure will inevitably occur on the surface of PB; continuing to use monomers with high AN% at the beginning of the second reaction can "repair" to a certain extent, avoiding excessive monomers and initiators from entering the PB, so that the glass transition temperature difference ΔTg before and after rubber grafting in the final product is not higher than 1.0°C. As the reaction proceeds, a grafting layer with gradually decreasing AN% will be formed on the outside of PB, resulting in a gradual extension of the time required for the subsequently added monomers to reach the PB surface, a reduction in the PB grafting rate and monomer grafting efficiency, and a decrease in the median particle size D of the rubber particles in the product. 50 Due to the poor grafting effect, a small amount of grafted rubber particles agglomerate to form a small number of rubber agglomerated particles with a particle size of 0.8-1.5μm. These micro-agglomerated particles 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 product's impact strength and tensile elongation at break are improved.

[0132] Comparing Comparative Example 2 and Example 10, when ABS graft polymerization is carried out by adopting the staged feeding method, by increasing the AN% of the first feeding monomer, the PB grafting rate and monomer grafting efficiency can also be increased while improving the mechanical properties of the product.

[0133] Comparing Examples 10 and 11, in the second reaction stage, when ABS graft polymerization is carried out by adopting a staged batch feeding method, by adjusting the monomer composition in each period of the second reaction stage and adjusting the amount of initiator and chain transfer agent in proportion to the molar amount of the monomer, not only the coverage of the grafted polymer outside the PB can be improved, but also excessive monomer can be prevented from entering the PB. The glass transition temperature difference ΔTg of the rubber before and after grafting in the product is less than 1.5°C. However, a graft layer with gradually decreasing AN% will be formed on the outside of the PB, resulting in a gradual increase in the time required for the subsequently added monomer to reach the PB surface, a decrease in the PB grafting rate and monomer grafting efficiency, and a decrease in the particle size D of the rubber particles in the product. 50 There is a slight increase, but the product's impact strength and tensile elongation at break have been improved.

[0134] Comparing Examples 11 and 12, when ABS graft polymerization was carried out using a staged batch feeding method, by adjusting the second reaction stage, while reducing the AN% of the monomer added in each period, the amount of initiator was further gradually reduced. This can further prevent excessive initiator from entering the PB, and the glass transition temperature difference ΔTg before and after rubber grafting is reduced to 1.2°C. However, due to the reduction in the amount of initiator outside the PB, the grafting rate and monomer grafting efficiency decreased, and the median particle size D of the rubber particles in the product was 1.2°C. 50At the same time, during the blending process of the grafted powder and SAN, the rubber particles undergo a certain degree of agglomeration, forming a small amount of micro-agglomerated particles that can form a synergistic toughening effect with the rubber particles of normal particle size, thereby improving the product's impact strength and tensile elongation at break.

[0135] Comparing Comparative Example 1 and Example 13, by adding methyl methacrylate with a higher solubility parameter in the first reaction, the grafting rate of PB is slightly reduced, the glass transition temperature difference ΔTg before and after rubber grafting is reduced to 1.0°C, and the rubber particle size D is 50 The thickness also reaches 530nm, but the mechanical properties of the product are improved, and the impact strength is increased from 21.18kJ / ㎡ to 22.25kJ / m 2 The tensile elongation at break was increased from 18.5% to a maximum of 21.5%, and other mechanical performance indicators were also improved to varying degrees, and the toughness of the product was significantly improved.

[0136] It can be seen from the above examples and comparative examples that the present invention can reduce grafting and secondary crosslinking within rubber particles and lower the glass transition temperature of the rubber phase without affecting the grafting density outside the rubber particles, thereby maintaining good dispersion of the rubber phase in the rigid polymer. At least 50% of the rubber particles can exist 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, significantly improving the toughening properties of the ABS grafted powder, breaking the "rigidity-toughness" balance limitation, and comprehensively improving the mechanical properties of the product.

[0137] The present invention is applicable to intermittent and continuous emulsion graft polymerization processes, and is particularly applicable to production processes in which graft monomers are added in batches or in batch / continuously.

[0138] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a rubber graft polymer, characterized in that: The method comprises: (1) subjecting a rubber latex, a monomer 1, a chain transfer agent 1, an activator, an emulsifier 1 and an initiator 1 to a first reaction to obtain a first product containing a polymer derived from the monomer 1; (2) subjecting the first product, monomer 2, chain transfer agent 2 and initiator 2 to a second reaction to obtain a second product; (3) adding initiator 3 to the second product to carry out a third reaction to obtain the rubber graft polymer; Wherein, the solubility parameter of the monomer 1 is different from that of the rubber contained in the rubber latex; Monomer 2 has a different solubility parameter than the polymer from monomer 1; The mass ratio of monomer 2 to initiator 2 is 110-150:1; the concentration of initiator 2 is 50-85wt%.

2. The preparation method according to claim 1, wherein In step (2), the mixed solution of the monomer 2 and the chain transfer agent 2 is mixed with the initiator 2 and then added; Alternatively, the mixed solution of the monomer 2 and the chain transfer agent 2 and the initiator 2 are added separately.

3. The preparation method according to claim 2, wherein In step (2), when adding after mixing, the mixed solution of the monomer 2 and the chain transfer agent 2 is mixed with the initiator 2 and then added in batches or continuously; And / or, when adding separately, the mixed solution of the monomer 2 and the chain transfer agent 2 is added synchronously with the initiator 2, or the mixed solution of the monomer 2 and the chain transfer agent 2 is added asynchronously with the initiator 2.

4. The preparation method according to claim 2 or 3, wherein In step (2), during the post-mixing addition, the mixed solution of the monomer 2 and the chain transfer agent 2, the initiator 2 and the emulsifier 2 are mixed.

5. The preparation method according to claim 3, wherein: When adding after mixing, the continuous adding time is 100-150min; And / or, when adding separately, the time of adding simultaneously is 100-150 minutes.

6. The preparation method according to claim 1 or 2, wherein: The monomer 1 and the monomer 2 are each independently selected from at least one of acrylonitrile, styrene, α-methylstyrene, methyl methacrylate and methyl acrylate; And / or, the mass ratio of monomer-1 to monomer-2 is 1-5:2-10.

7. The preparation method according to any one of claims 1 to 6, 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 100-800nm; Wherein, the rubber latex is selected from at least one of polybutadiene latex, polybutadiene styrene latex and polybutyl acrylate latex.

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

9. The preparation method according to claim 4, wherein: The emulsifier 2 is selected from at least one of potassium disproportionate rosin acid, potassium fatty acid, potassium oleate, sodium butylnaphthalene sulfonate and sodium alkyl sulfate.

10. The preparation method according to any one of claims 1 to 9, wherein: 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; And / or, 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.

11. The preparation method according to any one of claims 1 to 10, wherein: The temperature of the first reaction is 40-60°C and the time is 50-70min; And / or, the temperature of the second reaction is 60-78°C and the time is 100-120min; And / or, the temperature of the third reaction is 78-80° C. and the time is 15-30 min.

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