Preparation method of core-shell structure polymer

Abstract

The invention relates to the technical field of polymer chemical industry, in particular to a preparation method of a polymer with a core-shell structure. The preparation method comprises the following steps: in the presence of an initiator 1, carrying out first reaction on a core polymer emulsion, a shell monomer 1, a molecular weight regulator 1, an emulsifier 1 and flushing water 1 to obtain a first product; in the presence of an initiator 2, carrying out a second reaction on the first product, a shell monomer 2, a molecular weight regulator 2, an emulsifier 2 and flushing water 2 to obtain a second product; and adding an initiator 3 into the second product, and carrying out a third reaction to obtain the core-shell structure polymer. Wherein the core polymer emulsion contains an emulsifier 3, and the total concentration of the emulsifier 1, the emulsifier 2 and the emulsifier 3 in a water phase of a polymerization system is 0.75-1.5 wt%. By utilizing the preparation method disclosed by the invention, the dosage of the shell monomer in the production process of the core-shell polymer can be reduced, the utilization rate of the shell monomer can be improved, and the generation of by-product coagulum can be inhibited.

Description

Technical Field

[0001] The invention relates to the technical field of polymer chemical industry, and in particular to a method for preparing a core-shell structure polymer. Background Art

[0002] Core-shell polymer refers to particles with polymer A as the core and polymer B as the shell. Polymer A and polymer B can be produced by homopolymerization of one monomer or copolymerization of several monomers with different properties. A series of latex particles with different functions are obtained by combining core and shell polymers with different properties. Most of the core-shell polymers are mainly used in toughening brittle materials, such as MBS (methyl methacrylate, butadiene, styrene terpolymer) toughening PVC, GABS (terpolymer of styrene, acrylonitrile and butadiene) toughening SAN, etc.

[0003] Seed emulsion polymerization technology is the main method for producing core-shell polymers. Its basic process is: first, use ordinary emulsion polymerization to form core polymer particles (called seed emulsion), and then carry out seed emulsion polymerization: under appropriate polymerization conditions, shell monomers are added to the seed emulsion in a certain way, so that the shell monomers undergo polymerization reaction on the "core" surface, and polymer particles with core-shell structure can be obtained. Part of the added shell monomers enters the "core polymer" latex particles to form a "shell layer", and the other part forms free shell monomer polymers. This part of the polymer does not play any role in the formation of the core-shell polymer structure, reducing the utilization rate of the shell monomers.

[0004] At present, in order to avoid an increase in the production of free shell monomer polymers due to excessively high shell monomer concentration in the polymerization system, in the production of core-shell polymers, shell monomers are generally added continuously or semi-continuously: a portion of the monomers are added first, and then the remaining monomers are continuously added to the reactor after a period of reaction. However, there are the following disadvantages: while the reaction rate of the shell monomers in the latex particles increases, the concentration of the outer shell monomers of the latex particles will also decrease as the reaction rate increases, which will not only reduce the driving force for mass transfer inside and outside the latex particles, but also accelerate the production of free shell monomer polymers, resulting in a decrease in the utilization rate of the shell monomers. Therefore, the utilization rate of the shell monomers cannot be further improved.

[0005] Therefore, in the production of core-shell polymers, it is of great significance to study a method that can improve the utilization rate of shell monomers. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of large output of free shell monomer polymers and low shell monomer utilization in the production of core-shell polymers in the prior art, and to provide a core-shell structure polymer and a preparation method thereof.

[0007] In order to achieve the above object, the present invention provides a polymerization method of a core-shell structure polymer, wherein the method comprises:

[0008] (1) in the presence of an initiator 1, reacting the core polymer emulsion with a shell monomer 1, a molecular weight regulator 1, an emulsifier 1 and flushing water 1 to obtain a first product;

[0009] (2) in the presence of an initiator 2, subjecting the first product to a second reaction with a shell monomer 2, a molecular weight regulator 2, an emulsifier 2 and flushing water 2 to obtain a second product;

[0010] (3) adding initiator 3 to the second product to carry out a third reaction to obtain the core-shell structure polymer;

[0011] or,

[0012] (I) mixing the core polymer emulsion with an emulsifier 1 and flushing water 1 to obtain a mixed material;

[0013] (II) reacting the mixture with a shell monomer 4, a molecular weight regulator 4, an emulsifier 2 and flushing water 2 in the presence of an initiator 4 to obtain a product 1;

[0014] (III) adding initiator 3 to the product-1 to carry out reaction-2 to obtain the core-shell structure polymer;

[0015] Wherein, the core polymer emulsion contains emulsifier 3;

[0016] Wherein, in the polymerization method, the total concentration of emulsifier 1, emulsifier 2 and emulsifier 3 in the aqueous phase of the polymerization system is 0.75-1.5wt%.

[0017] Through the above technical scheme, the present invention dynamically adjusts the amount of emulsifier used in the polymerization process, so that the emulsifier concentration in the polymerization system is 0.75-1.50wt%, so that the emulsifier concentration on the surface of the core polymer latex particles is kept at a low level, and the stability of the emulsion polymerization system can be maintained while reducing the mass transfer resistance of the oil-water interface, and there will be no excessive coagulant generation. In the core-shell structure polymer prepared by the method of the present invention, the percentage (GD%) of the shell polymer to the weight of the core polymer is high (44-47%), and the utilization rate of the shell monomer is also correspondingly improved (65-78%). In addition, the generation of by-product coagulants can be suppressed, and the content of coagulants in the latex obtained after the reaction (S%) is reduced to 0.08%. It can be seen that the preparation method of the present invention can reduce the amount of shell monomers used in the production process of core-shell polymers, improve the utilization rate of shell monomers, and suppress the generation of by-product coagulants.

[0018] The preparation method of the invention is applicable to the production process of core-shell polymers in which the shell monomers are added in batches, semi-continuously and continuously. DETAILED DESCRIPTION

[0019] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0020] The specific implementation of the present invention is described in detail below in conjunction with the table. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0021] The present invention provides a method for polymerizing a core-shell structure polymer, wherein the method may be scheme 1, comprising:

[0022] (1) in the presence of an initiator 1, reacting the core polymer emulsion with a shell monomer 1, a molecular weight regulator 1, an emulsifier 1 and flushing water 1 to obtain a first product;

[0023] (2) in the presence of an initiator 2, subjecting the first product to a second reaction with a shell monomer 2, a molecular weight regulator 2, an emulsifier 2 and flushing water 2 to obtain a second product;

[0024] (3) adding initiator 3 to the second product to carry out a third reaction to obtain the core-shell structure polymer;

[0025] Wherein, the core polymer emulsion contains emulsifier 3;

[0026] Wherein, in the polymerization method, the total concentration of emulsifier 1, emulsifier 2 and emulsifier 3 in the aqueous phase of the polymerization system is 0.75-1.5wt%.

[0027] According to the present invention, the emulsifier and flushing water can be added synchronously with the shell monomer or asynchronously, and the flushing water and emulsifier can be added in batches or continuously. When the emulsifier and flushing water are added asynchronously with the shell monomer, the flushing water and the emulsifier can be added synchronously or asynchronously. The present invention dynamically adjusts the amount of emulsifier used in the polymerization process so that the emulsifier concentration in the polymerization system is 0.75-1.50wt%, so that the emulsifier concentration on the surface of the core polymer latex particles is maintained at a low level, thereby reducing the mass transfer resistance at the oil-water interface while maintaining the stability of the emulsion polymerization system without excessive coagulant generation.

[0028] According to the present invention, when producing core-shell structure polymers, in order to maintain the stability of the system during the polymerization process, it is necessary to add a certain amount of emulsifier to the core polymer emulsion; at the same time, in order to enable the shell monomer to break through the oil / water interface layer formed by the emulsifier during the polymerization process and enter the core polymer latex particles, preferably, in the polymerization method, the mass ratio of the emulsifier 1 to the flushing water 1 is 1:300-9000; the mass ratio of the emulsifier 2 to the flushing water 2 is 1:150-350; the mass ratio of the emulsifier 1 to the emulsifier 2 is 1:0.5-5.

[0029] According to the present invention, in order to improve the mass transfer efficiency of the monomer and reduce the amount of free shell monomer polymer generated, preferably, in step (1), the mass ratio of the core polymer emulsion, shell monomer 1, molecular weight regulator 1, emulsifier 1, initiator 1 and flushing water 1 is (450-6000): (50-550): (0.5-10): 1: (0.2-4): (300-9000).

[0030] In step (2), the mass ratio of the first product, shell monomer 2, molecular weight regulator 2, emulsifier 2 (dry basis), initiator 2 and flushing water 2 is (800-1200): (100-180): (0.5-1): 1: (0.6-1.2): (150-350).

[0031] According to the present invention, as long as the concentration of the emulsifier in the reaction system is within the range of 0.75-1.5wt%, the stability of the system during the polymerization process is guaranteed and the shell monomer breaks through the oil / water interface layer formed by the emulsifier, in step (2), the mixture of the shell monomer 2 and the molecular weight regulator 2, the flushing water 2, and the emulsifier 2 can be added simultaneously or asynchronously.

[0032] In some embodiments of the present invention, in step (2) of embodiments 1-5, the mixture of the shell monomer 2 and the molecular weight regulator 2, the flushing water 2, and the emulsifier 2 are added simultaneously; in step (2) of embodiments 6-8, the mixture of the shell monomer 2 and the molecular weight regulator 2, the flushing water 2, and the emulsifier 2 are not added simultaneously.

[0033] The flushing water 2 and the emulsifier 2 are added in batches or continuously.

[0034] According to the present invention, in order to make the concentration range of the emulsifier in the reaction system be 0.75-1.5wt%, preferably, in step (2), after the mixture of the shell monomer 2 and the molecular weight regulator 2 is mixed with the flushing water 2, the emulsifier 2 is continuously added separately. Specifically, the mixed solution containing the shell monomer 2, the molecular weight regulator 2 and the flushing water 2, and the emulsifier 2 are added to the reactor at a constant flow rate within 100-200 minutes.

[0035] In some embodiments of the present invention, the mixed solution and the emulsifier 2 are continuously added to the reactor at a constant flow rate within 120 minutes.

[0036] According to the present invention, in order to improve the utilization rate of the shell monomer, preferably, in step (2), the mixed solution of the shell monomer 2 and the molecular weight regulator 2, the flushing water 2, and the emulsifier 2 are not added synchronously.

[0037] Further preferably, when adding asynchronously, in step (2), the mixture of the shell monomer 2 and the molecular weight regulator 2 is added continuously.

[0038] Further preferably, in step (2), the flushing water 2 and the emulsifier 2 are added in batches synchronously, or the flushing water 2 and the emulsifier 2 are added in batches asynchronously. The amounts of the flushing water 2 and the emulsifier 2 added in batches may be equal or unequal. For example, the flushing water 2 and the emulsifier 2 are added in a set amount within a set time period and at a set time interval.

[0039] According to the present invention, in order to obtain a lower oil-water interface mass transfer resistance while ensuring the stability of the emulsion reaction system, preferably, the emulsifier 1 and the emulsifier 2 are each independently selected from at least one of anionic emulsifiers, cationic emulsifiers and nonionic emulsifiers.

[0040] Among them, anionic emulsifiers include fatty acid potassium, potassium oleate, potassium disproportionate rosin acid and sodium butyl naphthalene sulfonate;

[0041] Among them, cationic emulsifiers include dodecyl ammonium chloride and cetyl trimethyl ammonium bromide;

[0042] Among them, nonionic emulsifiers include alkylphenol polyoxyethylene ether type, polysorbate type and sorbitan monofatty acid ester type.

[0043] According to the present invention, in order to make the density of the outer graft layer of the core polymer higher, preferably, the molecular weight regulator 1 and the molecular weight regulator 2 are each independently selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan.

[0044] According to the present invention, in order to obtain a higher conversion rate at a lower reaction temperature, preferably, the initiator 1, initiator 2 and initiator 3 are each independently selected from at least one of tert-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, methylcyclohexane hydroperoxide, p-methylcumene hydroperoxide, cumene and tetralin hydroperoxide.

[0045] According to the present invention, in order to enable the core-shell polymer to toughen more brittle materials, preferably, the shell monomer 1 and the shell monomer 2 are each independently selected from at least one of acrylonitrile, styrene, α-methylstyrene and methyl methacrylate.

[0046] According to the present invention, in order to obtain a lower glass transition temperature of the core-shell polymer so that the toughened brittle material can maintain high toughness even at low temperatures, preferably, the core polymer is selected from at least one of polybutadiene, polybutadiene-styrene and polybutyl acrylate.

[0047] According to the use of the core-shell structure polymer obtained, the method further comprises: performing coagulation, aging and dehydration treatment after the third reaction.

[0048] According to the present invention, in order to make the polymerization reaction proceed better, preferably, the temperature of the first reaction is 35-60° C. and the time is 50-65 min.

[0049] Preferably, the temperature of the second reaction is 50-80°C and the time is 100-200 min.

[0050] Preferably, the temperature of the third reaction is 60-80° 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 56°C or 57°C and the time is 120 min; the temperature of the third reaction is 76°C or 75°C and the time is 20 min.

[0052] The present invention provides a method for polymerizing a core-shell structure polymer, wherein the method may be scheme 2, comprising:

[0053] (I) mixing the core polymer emulsion with an emulsifier 1 and flushing water 1 to obtain a mixed material;

[0054] (II) reacting the mixture with a shell monomer 4, a molecular weight regulator 4, an emulsifier 2 and flushing water 2 in the presence of an initiator 4 to obtain a product 1;

[0055] (III) adding initiator 3 to the product-1 to carry out reaction-2 to obtain the core-shell structure polymer;

[0056] Wherein, the core polymer emulsion contains emulsifier 3;

[0057] Wherein, in the polymerization method, the total concentration of emulsifier 1, emulsifier 2 and emulsifier 3 in the aqueous phase of the polymerization system is 0.75-1.5wt%.

[0058] According to the present invention, the emulsifier and the flushing water can be added synchronously with the shell monomer or asynchronously, and the flushing water and the emulsifier can be added in batches or continuously. When the emulsifier and the flushing water are added asynchronously with the shell monomer, the flushing water and the emulsifier can be added synchronously or asynchronously. The present invention dynamically adjusts the amount of the emulsifier used in the polymerization process so that the emulsifier concentration in the polymerization system is 0.75-1.50wt%, so that the emulsifier concentration on the surface of the core polymer latex particles is maintained at a low level, and the mass transfer resistance at the oil-water interface can be reduced while maintaining the stability of the emulsion polymerization system, and no excessive coagulants will be generated.

[0059] According to the present invention, when producing core-shell structure polymers, in order to maintain the stability of the system during the polymerization process, it is necessary to add a certain amount of emulsifier to the core polymer emulsion; at the same time, in order to enable the shell monomer to break through the oil / water interface layer formed by the emulsifier during the polymerization process and enter the core polymer latex particles, preferably, in the polymerization method, the mass ratio of the emulsifier 1 to the flushing water 1 is 1:300-9000; the mass ratio of the emulsifier 2 to the flushing water 2 is 1:150-350; the mass ratio of the emulsifier 1 to the emulsifier 2 is 1:0.5-5.

[0060] According to the present invention, in order to obtain a lower oil-water interface mass transfer resistance, preferably, in step (I), the mass ratio of the core polymer emulsion, the emulsifier 1 and the flushing water 1 is (5000-6000):1:(4000-5000);

[0061] Preferably, in step (II), the mass ratio of the first material, shell monomer 4, molecular weight regulator 4, emulsifier 2 (dry basis), initiator 4 and flushing water 2 is (400-550): (100-250): (1-1.5): 1: (1-2.5): (150-350).

[0062] According to the present invention, as long as the concentration of the emulsifier in the reaction system is in the range of 0.75-1.5wt%, the stability of the system during the polymerization process is guaranteed and the shell monomer breaks through the oil / water interface layer formed by the emulsifier. Preferably, in step (II), the mixture of the shell monomer 4 and the molecular weight regulator 4, the flushing water 2, and the emulsifier 2 can be added simultaneously or asynchronously.

[0063] Preferably, in step (II), when adding simultaneously, the mixed solution of the shell monomer 4 and the molecular weight regulator 4 is mixed with the flushing water 2, and then continuously added with the emulsifier 2. Specifically, the mixed solution containing the shell monomer 4, the molecular weight regulator 4 and the flushing water 2, and the emulsifier 2 are added to the reactor at a constant flow rate within 100-200 minutes.

[0064] In some embodiments of the present invention, the mixed solution and emulsifier 2 are added to the reactor at a constant flow rate within 180 minutes.

[0065] According to the present invention, in order to improve the utilization rate of the shell monomer, preferably, in the step (II), the mixed solution of the shell monomer 4 and the molecular weight regulator 4, the flushing water 2, and the emulsifier 2 are not added synchronously.

[0066] Further preferably, in step (II), when adding asynchronously, the mixture of the shell monomer 4 and the molecular weight regulator 4 is added continuously.

[0067] Preferably, in step (II), the flushing water 2 and the emulsifier 2 can be added in batches synchronously or asynchronously, and the amounts of the flushing water 2 and the emulsifier 2 added in batches can be equal or unequal. For example, the flushing water 2 and the emulsifier 2 are added in a set amount within a set time period and at a set time interval.

[0068] In some embodiments of the present invention, when the flushing water 2 and the emulsifier 2 are added in batches, the number of batches is 2, 3 or 4 respectively.

[0069] According to the present invention, in order to obtain a lower oil-water interface mass transfer resistance while ensuring the stability of the emulsion reaction system, preferably, the emulsifier 1 and the emulsifier 2 are each independently selected from at least one of anionic emulsifiers, cationic emulsifiers and nonionic emulsifiers.

[0070] Among them, anionic emulsifiers include fatty acid potassium, potassium oleate, potassium disproportionate rosin acid and sodium butyl naphthalene sulfonate;

[0071] Among them, cationic emulsifiers include dodecyl ammonium chloride and cetyl trimethyl ammonium bromide;

[0072] Among them, nonionic emulsifiers include alkylphenol polyoxyethylene ether type, polysorbate type and sorbitan monofatty acid ester type.

[0073] According to the present invention, in order to make the density of the outer graft layer of the core polymer higher, preferably, the molecular weight regulator 4 is selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan.

[0074] According to the present invention, in order to obtain a higher conversion rate at a lower reaction temperature, preferably, the initiator 3 and the initiator 4 are each independently selected from at least one of tert-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, methylcyclohexane hydroperoxide, p-methylcumene hydroperoxide, cumene and tetralin hydroperoxide.

[0075] According to the present invention, in order to enable the core-shell polymer to toughen more brittle materials, preferably, the shell monomer 4 is selected from at least one of acrylonitrile, styrene, α-methylstyrene and methyl methacrylate.

[0076] According to the present invention, in order to obtain a lower glass transition temperature of the core-shell polymer, preferably, the core polymer is selected from at least one of polybutadiene, polybutadiene-styrene and polybutyl acrylate.

[0077] According to the use of the obtained core-shell structure polymer, the method further comprises: performing coagulation, aging and dehydration treatment after the step (3).

[0078] According to the present invention, in order to make the polymerization reaction proceed better, preferably, the temperature of the reaction-1 is 40-75° C. and the time is 100-200 min.

[0079] Preferably, the temperature of reaction-2 is 75-80°C and the time is 15-30 minutes.

[0080] In some embodiments of the present invention, the temperature of reaction-1 is 40° C. and the time is 180 min; the temperature of reaction-2 is 76° C. and the time is 20 min.

[0081] By utilizing the preparation method of the present invention, the amount of shell monomers used in the production process of core-shell polymers can be reduced, the utilization rate of shell monomers can be improved, and the generation of by-product coagulants can be inhibited.

[0082] The preparation method of the invention is applicable to the production process of core-shell polymers in which the shell monomers are added in batches, semi-continuously and continuously.

[0083] According to the use of the core-shell structure polymer obtained, the method further comprises: performing coagulation, aging and dehydration treatment after the reaction-2.

[0084] The present invention also provides a core-shell structure polymer prepared by the method, wherein the weight ratio of the shell to the core of the polymer is 0.44-0.48:1.

[0085] In the present invention, the core polymer, monomer and water are formulated to form an emulsion under the action of an emulsifier, and polymerization is carried out therein. The polymerization system is mainly composed of the polymer, monomer, water, emulsifier and initiator, wherein the aqueous phase in the polymerization system includes water, emulsifier and various water-soluble additives, including but not limited to initiator.

[0086] In the present invention, the core in the core-shell polymer is a particle used to toughen the rigid polymer, which is usually a polymer with a lower elastic modulus polymerized from a "soft" monomer; the shell in the core-shell polymer is a polymer with a solubility parameter similar to that of the rigid polymer to be toughened and has a certain compatibility.

[0087] The present invention will be described in detail below through examples.

[0088] In the following examples and comparative examples, the percentage of shell polymer to core polymer weight (shell / core), the utilization of shell monomers and the evaluation method of the coagulant content in the latex are:

[0089] 1. Test method for shell / core and shell monomer utilization:

[0090] Weigh a certain amount of core-shell polymer powder (taking ABS high-rubber powder as an example) and record it as m g0 , put it in a special test tube and dissolve it in acetone, shake it for 24 hours and separate it in a centrifuge, the centrifugal speed is 10000r / min, and the centrifugal time is 0.5h. After the centrifugal separation, pour out the clear liquid in the test tube, then add an appropriate amount of acetone and repeat the above experiment. 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 Represented by, and based on the content of core polymer in the core-shell polymer powder, the "shell / core" ratio of the core-shell polymer is calculated by formula (1).

[0091]

[0092] in:

[0093] GD%—the percentage of the weight of the shell polymer to the weight of the core polymer (shell / core), wt%;

[0094] m g0 —Weigh the weight of the core-shell polymer powder, g;

[0095] m g1 —The weight of the dried product after centrifugation, g;

[0096] A%—content of core polymer in core-shell polymer, wt%.

[0097] The shell utilization rate of the shell monomer is calculated by formula (2).

[0098]

[0099] in:

[0100] GE%—the percentage of monomers forming core-shell polymers in the total amount of shell monomers, wt%;

[0101] m g0 —Weigh the weight of the core-shell polymer powder, g;

[0102] m g1 —The weight of the dried product after centrifugation, g;

[0103] A%—core polymer content in core-shell polymer powder, wt%.

[0104] 2. Evaluation method of coagulant content in latex

[0105] (1) Weighing 1000 g of polymer latex, cooling it to room temperature, and filtering it using a 150-mesh stainless steel filter with a weight of M0 (g);

[0106] (2) Use a large amount of desalted water to rinse the filter residue until the rinse water becomes transparent;

[0107] (3) Place the filter in a vacuum oven at 80°C and dry until constant weight is obtained, recorded as M1 (g);

[0108] (4) The coagulant content S in the latex is recorded as:

[0109]

[0110] Example 1

[0111] (1) Adding 1135 kg of polybutadiene (PB) latex having a polybutadiene (PB) content of 58.15%, 110 kg of a shell monomer composed of acrylonitrile (AN) and styrene (St), 2.0 kg of a molecular weight regulator (TDDM), 2.058 kg of an emulsifier potassium disproportionate rosin acid, and 689.94 kg of flushing water into a reaction kettle, heating the contents in the kettle to 40° C., adding 0.6 g of an initiator, and carrying out a first reaction for 60 min, at which time the temperature in the kettle rises to 56° C., to obtain a first product;

[0112] (2) 330 kg of shell monomer, 1.33 kg of TDDM, 2.058 kg of potassium disproportionate rosin acid and 689.94 kg of flushing water were mixed, and the temperature in the kettle was kept at 56° C. The obtained mixed solution was continuously added to the reactor at a constant flow rate within 120 minutes. 2.42 kg of initiator was added to the reactor at a constant flow rate within the same time, and a second reaction was carried out. After the reaction, the temperature in the kettle was raised to 76° C. to obtain a second product;

[0113] (3) The temperature in the kettle was maintained at 76° C., 0.95 kg of initiator was added, and an aging reaction was carried out for 20 min to obtain a core-shell structure polymer 1.

[0114] Example 2

[0115] The method of Example 1 is followed, except that in step (1), the amount of potassium disproportionate rosin acid added is 0.8232 kg, and the amount of rinsing water added is 628.18 kg; in step (2), the amount of potassium disproportionate rosin acid added is 3.293 kg, and the amount of rinsing water added is 751.71 kg, to obtain a core-shell structure polymer 2.

[0116] Example 3

[0117] The method of Example 1 is followed, except that in step (1), the amount of potassium disproportionate rosin acid added is 0.5058 kg, and the amount of rinsing water added is 597.29 kg; in step (2), the amount of potassium disproportionate rosin acid added is 2.2638 kg, and the amount of rinsing water added is 700.236 kg, to obtain a core-shell structure polymer 3.

[0118] Example 4

[0119] The method of Example 3 was followed, except that the amount of flushing water used in step (1) was 1042.14 kg and in step (2) was 234.8 kg, to obtain a core-shell structure polymer 4.

[0120] Example 5

[0121] The method of Example 3 was followed, except that the amount of flushing water used in step (1) was 1419.09 kg and in step (2) was 348.04 kg. The theoretical solid content of the latex was 37.09%, and a core-shell structure polymer 5 was obtained.

[0122] Example 6

[0123] (1) 1135 kg of polybutadiene (PB) latex having a polybutadiene (PB) content of 58.15%, 110 kg of a shell monomer composed of acrylonitrile (AN) and styrene (St), 2.0 kg of a molecular weight regulator (TDDM), 0.2058 kg of an emulsifier potassium disproportionate rosin acid, and 1419.09 kg of flushing water were added to a reaction kettle, the temperature of the materials in the kettle was raised to 40° C., 0.6 g of an initiator was added, and a first reaction was carried out. The reaction lasted for 60 min, at which time the temperature in the kettle was raised to 57° C., and a first product was obtained;

[0124] (2) 330 kg of shell monomer was mixed with 1.33 kg of TDDM, the temperature in the kettle was kept at 56° C., the obtained mixed solution was continuously added to the reactor at a constant flow rate within 120 min, and 2.42 kg of initiator was added to the reactor at a constant flow rate within the same time, and a second reaction lasting 120 min was carried out. After the reaction, the temperature in the kettle was raised to 75° C. to obtain a second product; wherein 2.26 kg of potassium disproportionate rosinate was diluted to 350.3 kg with 348.04 kg of flushing water, 175.15 kg of the diluted solution was added to the reactor at the beginning of the second reaction, and another 175.15 kg was added after the second reaction was carried out for 40 min;

[0125] (3) The temperature in the kettle was maintained at 75° C., 0.95 kg of initiator was added, and an aging reaction was carried out for 20 min to obtain a core-shell structure polymer 6.

[0126] Example 7

[0127] The method of Example 6 is followed, except that in step (2), 35.03 kg of the diluted 350.3 kg potassium disproportionate rosin acid solution is added to the reactor at the beginning of the second reaction, and 70.06 kg, 105.09 kg and 140.12 kg are added in sequence every 25 minutes after the start of the second reaction to obtain a core-shell structure polymer 7.

[0128] Example 8

[0129] The method of Example 6 is followed, except that in step (2), 348.04 kg of flushing water and 2.26 kg of potassium disproportionate rosin acid are added according to the method shown in Table 1 to obtain a core-shell structure polymer 8.

[0130] Table 1

[0131] Second reaction time / min 0 30 60 90 120 Flushing water / kg 78.27 116.02 116.02 37.75 0 Potassium disproportionate rosin acid / kg 0 0.7546 0.7546 0.7546 0

[0132] Example 9

[0133] (1) adding 1135 kg of polybutadiene (PB) latex having a PB content of 58.15%, 0.2058 kg of potassium disproportionate rosinate as an emulsifier, and 949.49 kg of flushing water into a reaction kettle to obtain a mixed material;

[0134] (2) 440 kg of shell monomer, 2.33 kg of TDDM, 2.058 kg of potassium disproportionate rosin acid and 689.94 kg of flushing water were mixed, the temperature in the kettle was raised to 40° C., the obtained mixed solution was continuously added to the reactor at a constant flow rate within 180 min, and 3.02 kg of initiator was added to the reactor at a constant flow rate within the same time, and the reaction was carried out for 180 min-1. After the reaction, the temperature in the kettle was raised to 76° C. to obtain product-1;

[0135] (3) The temperature in the kettle was maintained at 76° C., 0.95 kg of initiator was added, and reaction-2 was carried out for 20 min to obtain a core-shell structure polymer I.

[0136] Example 10

[0137] The method of Example 9 is followed, except that in step (1), the amount of potassium disproportionate added is 0.2058 kg, and the amount of flushing water used is 949.49 kg; in step (2), the amount of potassium disproportionate added is 2.26 kg, and the amount of flushing water used is 463.55 kg, to obtain a core-shell structure polymer II.

[0138] Embodiment 11

[0139] The method of Example 9 was followed, except that in step (2), 463.55 kg of flushing water and 2.26 kg of potassium disproportionate rosin acid were added as shown in Table 2 to obtain a core-shell structure polymer III.

[0140] Table 2

[0141]

[0142] Example 12

[0143] The method of Example 9 was followed, except that 1419.09 kg of flushing water was added in step 1, and the theoretical solid content of the latex was 37.09 wt %, to obtain a core-shell structure polymer IV.

[0144] Embodiment 13

[0145] The method of Example 1 is followed, except that in steps (1) and (2), 0.1295 kg of a composite emulsifier (solid content 0.37 wt%, of which potassium disproportionate rosin acid accounts for 78 wt%, potassium fatty acid accounts for 14 wt%, and sodium butylnaphthalene sulfonate accounts for 8 wt%) is used to replace potassium disproportionate rosin acid to obtain a core-shell structure polymer 13.

[0146] Embodiment 14

[0147] The method of Example 1 is followed, except that in steps (1) and (2), 0.111 kg of a composite emulsifier (solid content 0.37%, of which potassium disproportionate rosin acid accounts for 76%, potassium fatty acid accounts for 20wt%, and non-ionic emulsifier OP-30 accounts for 4wt%) is used instead of potassium disproportionate rosin acid to obtain a core-shell structure polymer 14.

[0148] Comparative Example 1

[0149] The method of Example 1 is followed, except that the amounts of potassium disproportionate rosin acid and flushing water added in step (1) are 4.116 kg and 205.884 kg, respectively; at the end of the addition of the mixed solution in step (2), 1174 kg of flushing water is added, and the theoretical solid content of the polymer latex is 44.12 wt%, to obtain a core-shell structure polymer 15.

[0150] Comparative Example 2

[0151] The method of Example 9 is followed, except that the amounts of potassium disproportionate rosin acid and flushing water added in step (1) are 4.116 kg and 205.884 kg, respectively; at the end of the addition of the mixed solution in step (2), 1174 kg of flushing water is added, and the theoretical solid content of the polymer latex is 44.12%, thereby obtaining a core-shell structure polymer 16.

[0152] Test Case

[0153] The polymer latex obtained in the above examples and comparative examples was demulsified using an acidic coagulant (acetone), washed, dehydrated and dried, and the shell / core (GD%) and shell monomer utilization (GE%) of the obtained core-shell structure polymer were obtained by formula (1) and (2), respectively; the coagulant content (S%) of the latex in the examples and comparative examples was obtained by formula (3). The results are shown in Table 3:

[0154] Table 3

[0155]

[0156]

[0157] As can be seen from Table 3, by comparing the data of Comparative Example 1 with those of Examples 1-4, without adjusting the solid content of the polymerization system, the method of the present invention is used to increase the amount of flushing water used in the initial stage of the reaction, reduce the concentration of the emulsifier in the system in the initial stage of the polymerization reaction, reduce the resistance of the "oil-water" two-phase interface layer, increase the rate at which the shell monomer enters the latex particles, and shorten its residence time outside the latex particles. Compared with Comparative Example 1, the shell / core ratio is increased from 43.2% to 46.41%, and the corresponding shell monomer utilization rate is increased from 64.8% to 69.6%. However, reducing the amount of emulsifier used will have an adverse effect on the stability of the latex, and the coagulant content in the latex increases from 0.21% to 0.35%.

[0158] Comparing Example 4 with Example 5, without adjusting other reaction conditions, the amount of flushing water in the initial stage of the reaction was increased, and the solid content of the reaction system was reduced from 44.12% to 37%. By increasing the amount of water, the emulsifier concentration was further reduced without reducing the stability of the emulsion, so that the utilization rates of shell / core and shell monomers could be further increased to 46.86% and 69.82%, while the coagulant content in the latex was reduced to 0.08%.

[0159] Compared with Example 4, in the second reaction stage in Example 6, the emulsifier diluted with flushing water is added in batches. Since the emulsifier concentration in the system fluctuates with the addition of the emulsifier, the emulsifier solution is added to the reaction system in two equal batches. This has no obvious effect on the utilization of the shell / core and shell monomers, but can increase the stability of the latex.

[0160] Comparing Example 6 with Examples 7 and 8, as the reaction proceeds, the amount of the emulsifier diluted by the flushing water added step by step in the second reaction stage increases gradually, which can effectively alleviate the adverse effects of emulsifier concentration fluctuations on the utilization of shell / core and shell monomers.

[0161] Compared with Example 6, in the second reaction stage of Example 8, the flushing water and the emulsifier are added separately. In the initial stage of the second reaction, the flushing water is added first, and the emulsifier concentration is reduced as much as possible. As the amount of shell monomer added increases, the stability of the system decreases, and a certain amount of emulsifier is added, and this process is repeated until the second reaction is completed. Using this process, the shell / core and shell monomer utilization rates of the polymer can reach 46.81% and 70.2%.

[0162] Comparing Examples 9-11 with Comparative Example 2, it can be seen that when the monomers are added continuously, the scheme provided in the present application can still improve the utilization rate of the shell / core and shell monomers of the core-shell polymer.

[0163] Comparing Example 1 with Examples 12-13, the use of a composite emulsifier with a lower CMC can reduce the resistance of the oil-water interface layer, improve the mass transfer efficiency of the shell monomer, and increase the utilization of the shell / core and shell monomers of the core-shell polymer while maintaining the stability of the emulsification system and maintaining the coagulant content in the latex.

[0164] It can be seen from the above examples and comparative examples that the method provided by the present application can reduce the amount of emulsifier, reduce the coverage density of the emulsifier on the surface of the latex particles, reduce the mass transfer resistance of the shell monomer, and improve the utilization of the shell / core and shell monomers.

[0165] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for polymerizing a core-shell structure polymer, characterized in that: The method comprises: (1) in the presence of an initiator 1, reacting the core polymer emulsion with a shell monomer 1, a molecular weight regulator 1, an emulsifier 1 and flushing water 1 to obtain a first product; (2) in the presence of an initiator 2, subjecting the first product to a second reaction with a shell monomer 2, a molecular weight regulator 2, an emulsifier 2 and flushing water 2 to obtain a second product; (3) adding initiator 3 to the second product to carry out a third reaction to obtain the core-shell structure polymer; or, (I) mixing the core polymer emulsion with an emulsifier 1 and flushing water 1 to obtain a mixed material; (II) reacting the mixture with a shell monomer 4, a molecular weight regulator 4, an emulsifier 2 and flushing water 2 in the presence of an initiator 4 to obtain a product 1; (III) adding initiator 3 to the product-1 to carry out reaction-2 to obtain the core-shell structure polymer; Wherein, the core polymer emulsion contains emulsifier 3; The total concentration of emulsifier 1, emulsifier 2 and emulsifier 3 in the aqueous phase of the polymerization system is 0.75-1.5 wt %.

2. The method according to claim 1, wherein: The mass ratio of the emulsifier 1 to the flushing water 1 is 1:300-9000; and / or, the mass ratio of the emulsifier 2 to the flushing water 2 is 1:150-350; And / or, the mass ratio of the emulsifier 1 to the emulsifier 2 is 1:0.5-5.

3. The method according to claim 1 or 2, wherein: In step (1), the mass ratio of the core polymer emulsion, shell monomer 1, molecular weight regulator 1, emulsifier 1, initiator 1 and flushing water 1 is (450-6000): (50-550): (0.5-10): 1: (0.2-4): (300-9000); And / or, in step (2), the mass ratio of the first product, shell monomer 2, molecular weight regulator 2, emulsifier 2, initiator 2 and flushing water 2 is (800-1200): (100-180): (0.5-1): 1: (0.6-1.2): (150-350).

4. The method according to any one of claims 1 to 3, wherein: In step (2), the mixture of the shell monomer 2 and the molecular weight regulator 2, the flushing water 2, and the emulsifier 2 are added synchronously or asynchronously.

5. The method according to claim 4, wherein: During the synchronous addition, the mixture of the shell monomer 2 and the molecular weight regulator 2 is mixed with the flushing water 2, and then the emulsifier 2 is added continuously; And / or, when adding asynchronously, the mixture of the shell monomer 2 and the molecular weight regulator 2 is added continuously; the flushing water 2 and the emulsifier 2 are added synchronously in batches, or the flushing water 2 and the emulsifier 2 are added asynchronously in batches.

6. The method according to claim 1 or 2, wherein: In step (I), the mass ratio of the core polymer emulsion, emulsifier 1 and flushing water 1 is: (5000-6000):1:(4000-5000); And / or, in step (II), the mass ratio of the mixed material, shell monomer 4, molecular weight regulator 4, emulsifier 2, initiator 4 and flushing water 2 is (400-550): (100-250): (1-1.5): 1: (1-2.5): (150-350).

7. The method according to any one of claims 1, 2 and 6, wherein: In step (II), the mixture of the shell monomer 4 and the molecular weight regulator 4, the flushing water 2, and the emulsifier 2 are added synchronously or asynchronously.

8. The method according to claim 7, wherein: When adding simultaneously, the mixture of the shell monomer 4 and the molecular weight regulator 4 is mixed with the flushing water 2 and then added continuously with the emulsifier 2; And / or, when adding asynchronously, the mixture of the shell monomer 4 and the molecular weight regulator 4 is added continuously; the flushing water 2 and the emulsifier 2 are added synchronously in batches, or the flushing water 2 and the emulsifier 2 are added asynchronously in batches.

9. The method according to any one of claims 1 to 8, wherein: The emulsifier 1 and the emulsifier 2 are each independently selected from at least one of anionic emulsifiers, cationic emulsifiers and nonionic emulsifiers; Among them, anionic emulsifiers include fatty acid potassium, potassium oleate, disproportionated rosin potassium and sodium butylnaphthalene sulfonate; Among them, cationic emulsifiers include dodecyl ammonium chloride and hexadecyl trimethyl ammonium bromide; Among them, nonionic emulsifiers include alkylphenol polyoxyethylene ether type, polysorbate type and sorbitan monofatty acid ester type.

10. The method according to any one of claims 1 to 9, wherein: The molecular weight regulator 1, molecular weight regulator 2 and molecular weight regulator 4 are each independently selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan; and / or, the initiator 1, initiator 2, initiator 3 and initiator 4 are each independently selected from at least one of tert-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, methylcyclohexane hydroperoxide, p-methylcumene hydroperoxide, cumene and tetralin hydroperoxide; and / or, the shell monomer 1, shell monomer 2 and shell monomer 4 are each independently selected from at least one of acrylonitrile, styrene, α-methylstyrene and methyl methacrylate; And / or, the core polymer is selected from at least one of polybutadiene, polybutadiene-styrene and polybutyl acrylate.

11. The method according to any one of claims 1 to 10, wherein: The method further comprises: performing coagulation, aging and dehydration treatments after step (3).

12. The method according to any one of claims 1 to 11, wherein: The solid content of the core polymer emulsion is 56-58 wt %, and the average particle size of the latex particles contained in the core polymer emulsion is 280-350 nm; And / or, the temperature of the first reaction is 35-60°C and the time is 50-65min; And / or, the temperature of the second reaction is 50-80°C and the time is 100-200 min; And / or, the temperature of the third reaction is 60-80°C and the time is 15-30min; And / or, the temperature of reaction-1 is 40-75°C and the time is 100-200min; And / or, the temperature of reaction-2 is 75-80°C and the time is 15-30 minutes.

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