Multi-shell structured acrylate-styrene-acrylonitrile copolymers and methods of making

Abstract

The present application provides a kind of multiple core-shell structure acrylate-styrene-acrylonitrile copolymer emulsion, glue powder and acrylonitrile-styrene-acrylate resin and its preparation method.The multiple core-shell structure acrylate-styrene-acrylonitrile copolymer emulsion of the present application is characterized in that the multiple core-shell structure acrylate-styrene-acrylonitrile copolymer emulsion includes multiple core-shell structure acrylate-styrene-acrylonitrile copolymer particles, and the multiple core-shell structure acrylate-styrene-acrylonitrile copolymer particles are composed of PBA core, PBA core layer and PBA-g-SAN shell layer from inside to outside.Using the method of the present application, a kind of acrylate-styrene-acrylonitrile copolymer with good surface gloss and rigid balance can be prepared.

Description

Technical Field

[0001] This invention belongs to the field of resin synthesis technology, specifically relating to a multi-core-shell structured acrylate-styrene-acrylonitrile graft copolymer and its semi-continuous seed emulsion polymerization preparation method. Background Technology

[0002] Generally, acrylonitrile-butadiene-styrene (ABS) resin is suitable for various fields such as automobiles, industrial and office electronics, home electronics, toys, and stationery due to its good impact resistance and processing properties. However, because butadiene rubber has a double bond structure, ABS resin is easily oxidized by oxygen, ultraviolet light, light, and heat when used as an impact modifier. When used as an external material, the resin surface will degrade in color and its performance will deteriorate, resulting in a decline in the appearance quality of products and parts. This greatly limits the exterior applications of ABS resin, and even when used as an interior material, discoloration will occur, failing to meet the actual needs of customers.

[0003] In contrast, acrylate-styrene-acrylonitrile (ASA) resin, which uses acrylic rubber instead of butadiene, improves the resin's weather resistance and chemical resistance while also enhancing the product's physical properties and appearance. The biggest difference between ASA resin and ABS resin is that the rubber phase molecular chain of ASA resin lacks double bonds, significantly improving its weather resistance and overcoming the drawbacks of ABS resin, such as a significant decrease in mechanical strength after long-term outdoor exposure and yellowing of products due to aging and degradation.

[0004] ASA resin's properties fall in the middle among engineering plastics such as ABS, PVC, PC, PP, PET, and PBT. Coupled with its excellent aging resistance, it can replace traditional materials like ABS, PVC, acrylic resin, PC, fiber-reinforced plastics, iron, copper, and aluminum in many applications. It is widely used in automotive interior and exterior parts, household appliance housings, agricultural machinery covers, industrial products, leisure products, and building materials. Another important use of ASA resin is as a toughening and weather-resistant modifier for various resins and plastics, and its applications are also very extensive.

[0005] Patent reports describe ASA resin synthesis methods including bulk method, suspension method, bulk suspension method, emulsion suspension method, and emulsion grafting blending method, but only the emulsion grafting blending method has been industrialized.

[0006] The preparation of ASA resin via emulsion grafting blending mostly employs a stepwise polymerization process: first, emulsion polymerization is used to synthesize a seed latex, while simultaneously using a crosslinking agent to achieve a suitable degree of crosslinking. Then, depending on the specific process, nucleation is further performed on the seed latex. Finally, shell monomers and initiators are added dropwise to initiate grafting, or other monomers and initiators are directly added to the seed latex to initiate the grafting reaction and form a shell, thus preparing a polymer with a core-shell structure. Compared to the polybutadiene structure in ABS, its elastic acrylate rubber core does not contain double bonds, resulting in 10 times higher outdoor weather resistance than ABS resin. Therefore, it has unique performance advantages as a substitute for ABS resin in applications requiring weather resistance. However, due to the lack of double bonds in its rubber core, there are technical problems such as insufficient grafting rate, which can easily lead to unstable performance, low impact strength, and poor dyeability.

[0007] Based on domestic and international literature and patent reports, the synthesis of ASA resin mainly involves the following pathways:

[0008] (1) One-step technology: Deionized water, emulsifier, acrylate soft monomers and crosslinking agents are added to the reactor, and an initiator aqueous solution is added under nitrogen protection and reacted for 3-5 hours to obtain acrylate latex (hereinafter referred to as PBA) for grafting with monomers such as styrene and acrylonitrile. If the commonly used anionic emulsifier is used, the particle size of the rubber phase obtained by this method is usually within 70-130nm. The impact toughness of the ASA resin obtained by direct grafting is insufficient, and the application field is limited. If a nonionic or nonionic and ionic emulsifier compound system is used alone, a rubber phase with a particle size of 180-500nm can be obtained. The impact toughness of the grafted ASA resin is relatively high, but the grafted emulsion coagulation and demulsification are incomplete, the coagulant consumption is high, the COD and BOD content of the production wastewater is high, and the biochemical and physicochemical treatment costs of the wastewater are high.

[0009] (2) Seed enlargement technology: The small-particle-size PBA latex synthesized in one step using the above-mentioned ionic emulsifier is further enlarged by adding emulsifier, initiator, and crosslinking agent, and then adding acrylate soft monomers under nitrogen protection. This process yields larger-particle-size PBA latex suitable for grafting with monomers such as styrene and acrylonitrile, with an average particle size of 180-700 nm. Although this technology is commonly used in industrialization, and each company's patented technology has its own characteristics, none of them have disclosed the core technology. Therefore, this technology remains a hot topic in the current industrialization research of ASA resin.

[0010] (3) Large and small particle size blending method: The small particle size PBA latex (A) synthesized by method 1 and the large particle size PBA latex (B) synthesized by method 2 are blended in a certain proportion to obtain a mixed latex (C). C is used as the PBA latex for grafting with styrene and acrylonitrile monomers; or A and B are grafted with styrene and acrylonitrile monomers respectively to obtain two ASA resins with different particle sizes, and then ASA resins with large and small particle sizes are prepared by blending in different proportions. Using the synergistic effect of different particle size blends to improve and enhance material properties, especially to balance the impact toughness and rigidity of materials, is a commonly used technique and method by professionals familiar with the toughening theory of core-shell structures. It has good practical effects, but its innovation is insufficient.

[0011] (4) Copolymer PBA latex synthesis method: Deionized water, emulsifier, crosslinking agent, acrylate soft monomers and a small amount of second and third monomers (generally less than 10%) are added to the reactor. Under nitrogen protection, an initiator is added. Through methods similar to (1), (2) or (3), copolymer PBA latex grafted with styrene and acrylonitrile monomers is obtained. The second and third monomers can be one or a combination of two of styrene, acrylonitrile and acrylate monomers. These monomers have certain effects on improving product appearance, increasing grafting rate, improving impact performance and processing performance. However, when improving a certain performance, other performance aspects of ASA resin are often sacrificed. For example, using styrene or methyl methacrylate as comonomers of PBA can improve the surface gloss of ASA resin and improve its processability, but at the cost of reduced impact performance. Using a small amount of isoprene or butadiene monomers for copolymerization can improve impact strength, especially low-temperature impact, but sacrifices some weather resistance.

[0012] (5) Synthesis of PBA latex containing cross-linked styrene or styrene-acrylonitrile copolymer cores: Deionized water, emulsifier, and styrene monomer are added to a reactor, and an initiator is added under nitrogen protection to react and obtain cross-linked styrene (PS) or styrene-acrylonitrile (SAN) copolymer latex. Using this as a seed, deionized water, emulsifier, cross-linking agent, and acrylate soft monomers are added, and an initiator is added under nitrogen protection to react and obtain PBA latex containing cross-linked polystyrene or styrene-acrylonitrile copolymer cores for grafting with monomers such as styrene and acrylonitrile. However, this method has the disadvantage of insufficient compatibility between the cross-linked styrene or styrene-acrylonitrile copolymer cores and the expanded PBA layer, resulting in insufficient impact performance of the final product. Furthermore, the cross-linked PS and SAN are prone to gel points due to poor plasticization during molding.

[0013] (6) Special ASA resin grafted with styrene and acrylonitrile onto silicone-acrylic rubber: The addition of modifiers to the resin can impart impact resistance, heat resistance and flame retardancy to the resin, and better solve the technical problems of poor surface gloss and dyeability of ASA resin. However, the polysiloxane content of this graft copolymer is more than 60%, and its manufacturing cost is much higher than that of PBA structure ASA resin. Therefore, its application is limited to very limited special requirements. The inventors call the core-shell structure resin obtained by grafting styrene and acrylonitrile monomers onto the silicone-acrylic rubber phase a special ASA resin. This is for the same reason as the initial classification of the acrylate-styrene-acrylonitrile core-shell structure resin (ASA resin) into weather-resistant ABS resin. On the one hand, its structure is similar to that of ASA resin, and it has good weather resistance. Moreover, it is relatively niche compared to ABS and ASA resin, so there is no need to establish a new material classification.

[0014] (7) Modification of ASA resin with organosiloxane monomers: This method is similar to the processes in (1) and (2), except that a small amount of reactive vinyl organosiloxane monomers (silicone oil) is added to the seed diameter expansion formulation to modify the PBA core through silicone copolymerization. This technique can improve grafting efficiency and increase the surface gloss and impact strength of ASA resin. However, because the alkoxy groups in the organosilicon molecular structure are easily hydrolyzed to generate hydroxyl groups during polymerization, cross-linking reactions can occur between hydroxyl groups to generate gels. The more alkoxy groups are added, the greater the probability of cross-linking reactions due to collisions between hydrolyzed groups, resulting in more gels being generated, which prevents the emulsion polymerization reaction from proceeding. Therefore, the amount added should not be too much, and the polymerization process also needs to be coordinated with pH adjustment to control the occurrence of organosilicon hydrolysis reactions in order to ensure the stability of the emulsion polymerization process. By grafting styrene and acrylonitrile onto the molecular chain of silicon-modified butyl acrylate emulsion (Si-PBA), a core-shell structured Si-O-Si organic-inorganic hybrid organosilicon-modified acrylate-styrene-acrylonitrile (Si-ASA) graft polymer is prepared. This can form a three-dimensional network crosslink in the molecule and improve the poor high-temperature resistance and low-temperature elasticity of PBA rubber.

[0015] (8) Latex (polymer) agglomeration method: Small-particle-size PBA latex and agglomerated latex are synthesized separately. The agglomerated latex is usually a copolymer latex of BA (butyl acrylate) and AA (acrylic acid). Then, the small-particle-size PBA latex is agglomerated with the agglomerated latex to obtain large-particle-size PBA latex with a particle size greater than 200 nm. Then, it is grafted with styrene and acrylonitrile monomers to obtain ASA resin. This method has high production efficiency, but the stability of the agglomerated system deteriorates with the increase of PBA latex particle size. In order to ensure the stability of the latex after agglomeration, the particle size of PBA cannot be increased too much, and often the ideal ASA resin properties, especially impact strength, cannot be obtained.

[0016] Therefore, how to provide an acrylate-styrene-acrylonitrile copolymer that can be economically and industrially produced, has a balance of rigidity and toughness, is easy to control in terms of particle size, and has a good appearance has always been a research interest in the industry. Summary of the Invention

[0017] To achieve the above objectives, the present invention provides a multi-core-shell structured acrylate-styrene-acrylonitrile graft copolymer and an industrially applicable semi-continuous seed method for its preparation.

[0018] Specifically, one aspect of the present invention provides a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion, the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion comprising multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles, the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles being composed of a PBA core, a PBA core layer and a PBA-g-SAN shell layer from the inside out;

[0019] The PBA core comprises an inner PBA core and an outer PBA core layer. The inner PBA core contains the reaction product of alkyl acrylate soft monomers and a crosslinking agent. The outer PBA core layer contains the reaction product of alkyl acrylate soft monomers and a crosslinking agent. The weight of the alkyl acrylate soft monomers in the inner PBA core accounts for 10%-30% of the total weight of the alkyl acrylate soft monomers in the PBA core.

[0020] The PBA core layer comprises a PBA inner core layer and a PBA outer core layer. The PBA inner core layer contains the reaction product of alkyl acrylate soft monomers and a crosslinking agent. The PBA outer core layer contains the reaction product of alkyl acrylate soft monomers, comonomers, crosslinking agents, and grafting agents. The comonomers contain one or more selected from aromatic vinyl monomers, vinyl cyanide monomers, and acrylate hard monomers. The weight of the alkyl acrylate soft monomers in the PBA inner core layer accounts for 5%-10% of the total weight of the alkyl acrylate soft monomers in the PBA core layer.

[0021] The PBA-g-SAN shell layer includes a PBA-g-SAN inner shell layer and a PBA-g-SAN outer shell layer. The PBA-g-SAN inner shell layer contains reaction products of shell-layer mixed monomers, and the PBA-g-SAN outer shell layer contains reaction products of shell-layer mixed monomers. The shell-layer mixed monomers include one or more and optionally acrylate monomers selected from aromatic vinyl monomers and vinyl cyanide monomers. The weight of the shell-layer mixed monomers in the PBA-g-SAN inner shell layer accounts for 10%-40% of the total weight of the shell-layer mixed monomers in the PBA-g-SAN shell layer.

[0022] In one or more embodiments, the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion has one or more of the following characteristics:

[0023] The weight of the crosslinking agent in the PBA core accounts for 30%-60% of the total weight of the crosslinking agent in the PBA core;

[0024] The total weight of alkyl acrylate soft monomers in the PBA core accounts for 97%-99.8% of the dry matter weight of the PBA core;

[0025] The total weight of the crosslinking agent in the PBA core is 0.2%-2% of the total weight of the alkyl acrylate soft monomers in the PBA core;

[0026] The alkyl acrylate soft monomer is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate, preferably selected from one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate, more preferably butyl acrylate.

[0027] The crosslinking agent is selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate and diallyl maleate, preferably ethylene glycol dimethacrylate;

[0028] The cross-linking degree of the PBA inner core is greater than that of the PBA outer core layer;

[0029] The PBA core has a particle size of 70-130 nm;

[0030] The PBA core has a gel content of ≥90%.

[0031] In one or more embodiments, the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion has one or more of the following characteristics:

[0032] The crosslinking agent in the PBA core layer accounts for 10%-30% of the total weight of the crosslinking agent in the PBA core layer;

[0033] The total weight of alkyl acrylate soft monomers in the PBA core layer accounts for 85%-90% of the total dry matter weight of the PBA core and the PBA core layer.

[0034] The dry weight of the PBA core is 1.5%-3.0% of the total weight of the acrylate soft monomers in the PBA core layer;

[0035] The weight of the comonomer in the PBA core layer is 2%-10% of the total weight of the alkyl acrylate soft monomer and comonomer in the PBA core layer.

[0036] The weight of the crosslinking agent in the PBA core layer is 0.2%-2% of the total weight of the alkyl acrylate soft monomers and comonomers in the PBA core layer;

[0037] The grafting agent in the PBA core layer accounts for 0.1%-0.6% of the total weight of the alkyl acrylate soft monomers and comonomers in the PBA core layer.

[0038] The alkyl acrylate soft monomer is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate, preferably selected from one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate, more preferably butyl acrylate.

[0039] The crosslinking agent is selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate and diallyl maleate, preferably ethylene glycol dimethacrylate;

[0040] The initiator is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate, cumene hydroperoxide, dicumene hydroperoxide, benzoyl peroxide, and dicarbonate peroxide, preferably potassium persulfate or cumene hydroperoxide;

[0041] The comonomer comprises one or more selected from aromatic vinyl monomers and vinyl cyanide monomers, and optionally acrylate hard monomers;

[0042] The aromatic vinyl monomer is selected from one or both of styrene and α-methylstyrene, preferably styrene;

[0043] The vinyl cyanide monomer is selected from one or both of acrylonitrile and methacrylonitrile, preferably acrylonitrile;

[0044] The acrylate hard monomer is methyl methacrylate;

[0045] The grafting agent is allyl methacrylate;

[0046] The outer core layer of the PBA contains double bonds that can be grafted;

[0047] The degree of crosslinking of the PBA core layer is greater than the degree of crosslinking of the PBA outer core layer;

[0048] The degree of crosslinking of the PBA core layer and the degree of crosslinking of the PBA outer core layer are both less than the degree of crosslinking of the PBA core.

[0049] The particle size of the PBA core, which is composed of the PBA core and the PBA core layer, is 150-600 nm.

[0050] The PBA core, which consists of the PBA core and the PBA core layer, has a gel content of ≥80%, preferably 80%-90%.

[0051] In one or more embodiments, the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion has one or more of the following characteristics:

[0052] The dry weight of the PBA core, which consists of the PBA core and the PBA core layer, is 40%-60% of the total weight of the shell-mixed monomers in the PBA-g-SAN shell layer.

[0053] The shell-mixed monomers comprise aromatic vinyl monomers, vinyl cyanide monomers, and optionally acrylate monomers;

[0054] The aromatic vinyl monomer is selected from one or both of styrene and α-methylstyrene, preferably styrene;

[0055] The vinyl cyanide monomer is selected from one or both of acrylonitrile and methacrylonitrile, preferably acrylonitrile;

[0056] The acrylate monomers include hard acrylate monomers, and the hard acrylate monomers are preferably methyl methacrylate;

[0057] The grafting rate of the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles is ≥40%;

[0058] The particle size of the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles is 190-700 nm.

[0059] The gel content of the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles is 60%-75%.

[0060] The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder of the present invention can be prepared by the method described in any of the embodiments herein.

[0061] Another aspect of the present invention provides a method for preparing a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion, characterized in that the method comprises the following steps:

[0062] (1) Preparation of PBA core emulsion: First, a portion of alkyl acrylate soft monomers is polymerized in the presence of an initiator, a crosslinking agent, an emulsifier and water to obtain a PBA inner core emulsion. Then, a mixture containing the remaining alkyl acrylate soft monomers, a crosslinking agent and an initiator is continuously added to the PBA inner core emulsion for polymerization to form a PBA outer core layer on the surface of the PBA inner core, thus obtaining a PBA core emulsion. The weight of the alkyl acrylate soft monomers added when preparing the PBA inner core emulsion accounts for 10%-30% of the total weight of the alkyl acrylate soft monomers added when preparing the PBA core emulsion.

[0063] (2) Preparation of PBA core emulsion: First, a portion of alkyl acrylate soft monomers are polymerized in the presence of PBA core emulsion, initiator and crosslinking agent to form PBA core layer on the surface of PBA outer core, thus obtaining PBA core emulsion. Then, a pre-emulsion containing the remaining alkyl acrylate soft monomers, comonomers, crosslinking agent, grafting agent, initiator and emulsifier is continuously added to PBA core emulsion for polymerization to form PBA outer core layer on the surface of PBA core, thus obtaining PBA core emulsion. The weight of alkyl acrylate soft monomers added when preparing PBA core emulsion accounts for 5%-10% of the total weight of alkyl acrylate soft monomers added when preparing PBA core emulsion. The comonomers include one or more selected from aromatic vinyl monomers, vinyl cyanide monomers and acrylate hard monomers.

[0064] (3) Preparation of PBA-g-SAN shell emulsion: First, a portion of the shell-layer mixed monomers are polymerized in the presence of PBA core emulsion and initiator to form a PBA-g-SAN inner shell layer on the surface of the PBA outer core, thus obtaining a PBA-g-SAN inner shell emulsion. Then, a pre-emulsion containing the remaining shell-layer mixed monomers, initiator and emulsifier is continuously added to the PBA-g-SAN inner shell emulsion for polymerization, thus forming a PBA-g-SAN outer shell layer on the surface of the PBA-g-SAN inner shell, thus obtaining a PBA-g-SAN shell emulsion, namely the multi-core-shell structure acrylate-styrene-acrylonitrile copolymer emulsion. The weight of the shell-layer mixed monomers added when preparing the PBA-g-SAN inner shell emulsion accounts for 10%-40% of the total weight of the shell-layer mixed monomers added when preparing the PBA-g-SAN shell emulsion. The shell-layer mixed monomers include one or more of aromatic vinyl monomers and vinyl cyanide monomers and optionally acrylate monomers.

[0065] In one or more embodiments, step (1) has one or more of the following characteristics:

[0066] In step (1), the weight of the initiator added during the preparation of the PBA core emulsion accounts for 10%-30% of the total weight of the initiator added during the preparation of the PBA core emulsion;

[0067] In step (1), the weight of the crosslinking agent added during the preparation of the PBA core emulsion accounts for 30%-60% of the total weight of the crosslinking agent added during the preparation of the PBA core emulsion;

[0068] The total weight of alkyl acrylate soft monomers added during the preparation of PBA core emulsion accounts for 97%-99.8% of the dry matter weight of the PBA core emulsion.

[0069] The total weight of the crosslinking agent added during the preparation of PBA core emulsion is 0.2%-2% of the total weight of the alkyl acrylate soft monomers;

[0070] The alkyl acrylate soft monomer is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate, preferably selected from one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate, more preferably butyl acrylate.

[0071] The crosslinking agent is selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate and diallyl maleate, preferably ethylene glycol dimethacrylate;

[0072] The emulsifier is selected from one or more of alkyl aryl ether sulfates, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and alkyl diphenyl ether disulfonates, preferably selected from one or two of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate;

[0073] The initiator is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate, cumene hydroperoxide, dicumene hydroperoxide, benzoyl peroxide, and dicarbonate peroxide, preferably potassium persulfate;

[0074] In step (1), the reaction system for preparing the PBA core emulsion also contains one or more of the following: complexing agents, electrolytes, and pH buffers.

[0075] When preparing the PBA core emulsion, the reaction temperature is 60-75℃, the reaction time for preparing the PBA inner core emulsion is 0.5-1.0h, and the time for continuously adding the mixture is 2.0-4.5h.

[0076] The cross-linking degree of the PBA inner core is greater than that of the PBA outer core layer;

[0077] The PBA core has a particle size of 70-130 nm;

[0078] The PBA core has a gel content of ≥90%.

[0079] In one or more embodiments, step (2) has one or more of the following characteristics:

[0080] In step (2), the weight of the initiator added during the preparation of the PBA core emulsion accounts for 15%-20% of the total weight of the initiator added during the preparation of the PBA core emulsion;

[0081] In step (2), the weight of the crosslinking agent added during the preparation of the PBA core emulsion accounts for 10%-30% of the total weight of the crosslinking agent added during the preparation of the PBA core emulsion;

[0082] The total weight of alkyl acrylate soft monomers added during the preparation of PBA core emulsion accounts for 85%-90% of the dry matter weight of the PBA core emulsion;

[0083] The dry weight of the PBA core emulsion added during the preparation of the PBA core emulsion is 1.5%-3.0% of the total weight of the acrylate soft monomers added during the preparation of the PBA core emulsion.

[0084] The weight of the comonomer added during the preparation of PBA core emulsion is 2%-10% of the total weight of the alkyl acrylate soft monomer and the comonomer;

[0085] The weight of the crosslinking agent added during the preparation of PBA core emulsion is 0.2%-2% of the total weight of the alkyl acrylate soft monomer and comonomer;

[0086] The grafting agent added during the preparation of PBA core emulsion is 0.1%-0.6% of the total weight of the alkyl acrylate soft monomer and comonomer;

[0087] The alkyl acrylate soft monomer is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate, preferably selected from one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate, more preferably butyl acrylate.

[0088] The crosslinking agent is selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate and diallyl maleate, preferably ethylene glycol dimethacrylate;

[0089] The emulsifier is selected from one or more of alkyl aryl ether sulfates, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and alkyl diphenyl ether disulfonates, preferably selected from one or two of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate;

[0090] The initiator is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate, cumene hydroperoxide, dicumene hydroperoxide, benzoyl peroxide, and dicarbonate peroxide, preferably potassium persulfate or cumene hydroperoxide;

[0091] The comonomer comprises one or more selected from aromatic vinyl monomers and vinyl cyanide monomers, and optionally acrylate hard monomers;

[0092] The aromatic vinyl monomer is selected from one or both of styrene and α-methylstyrene, preferably styrene;

[0093] The vinyl cyanide monomer is selected from one or both of acrylonitrile and methacrylonitrile, preferably acrylonitrile;

[0094] The acrylate hard monomer is methyl methacrylate;

[0095] The grafting agent is allyl methacrylate;

[0096] In step (2), the reaction system for preparing the PBA core emulsion also contains one or more of the following: grafting agent, complexing agent, electrolyte, and pH buffer.

[0097] When preparing PBA core emulsion, the reaction temperature is 70-85℃, the reaction time for preparing PBA core emulsion is 0.5-1.0h, the time for continuously adding the mixture is 3-4.5h, and the reaction continues for 1-2h after the mixture is added.

[0098] The outer core layer of the PBA contains double bonds that can be grafted;

[0099] The degree of crosslinking of the PBA core layer is greater than the degree of crosslinking of the PBA outer core layer;

[0100] The degree of crosslinking of the PBA core layer and the degree of crosslinking of the PBA outer core layer are both less than the degree of crosslinking of the PBA core.

[0101] The particle size of the PBA core is 150-600 nm;

[0102] The PBA core has a gel content of ≥80%, preferably 80%-90%.

[0103] In one or more embodiments, step (3) has one or more of the following features:

[0104] In step (3), the weight of the initiator added during the preparation of the PBA-g-SAN inner shell emulsion accounts for 10%-40% of the total weight of the initiator added during the preparation of the PBA-g-SAN shell emulsion;

[0105] The dry weight of the PBA core emulsion added during the preparation of the PBA-g-SAN shell emulsion is 40%-60% of the total weight of the shell-shell mixed monomers added during the preparation of the PBA-g-SAN shell emulsion.

[0106] The initiator is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate, cumene hydroperoxide, dicumene hydroperoxide, benzoyl peroxide, and dicarbonate peroxide, preferably cumene hydroperoxide;

[0107] The emulsifier is one or more of alkyl aryl ether sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and alkyl diphenyl ether disulfonate, preferably selected from one or two of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate;

[0108] The shell-mixed monomers comprise aromatic vinyl monomers, vinyl cyanide monomers, and optionally acrylate monomers;

[0109] The aromatic vinyl monomer is selected from one or both of styrene and α-methylstyrene, preferably styrene;

[0110] The vinyl cyanide monomer is selected from one or both of acrylonitrile and methacrylonitrile, preferably acrylonitrile;

[0111] The acrylate monomers include hard acrylate monomers, and the hard acrylate monomers are preferably methyl methacrylate;

[0112] In step (3), the reaction system for preparing the PBA-g-SAN inner shell emulsion also contains one or more of the following: complexing agents, electrolytes, pH buffers, emulsifiers, and reducing agents.

[0113] In step (3), the materials continuously added during the preparation of the PBA-g-SAN shell emulsion also include a molecular weight regulator and / or a pH buffer, wherein the molecular weight regulator is selected from one or more of tert-dodecyl mercaptan, n-dodecyl mercaptan and n-octyl mercaptan, preferably tert-dodecyl mercaptan;

[0114] The reaction temperature for preparing the PBA-g-SAN shell emulsion is 65-80℃, the reaction time for preparing the PBA-g-SAN inner shell emulsion is 0.5-1.0h, the time for continuously adding the mixture is 3.0-4.5h, and the reaction continues for 1-2h after the mixture is added.

[0115] The grafting rate of the PBA-g-SAN shell is ≥40%;

[0116] The particle size of the PBA-g-SAN shell is 190-700 nm;

[0117] The PBA-g-SAN shell has a gel content of 60%-75%.

[0118] The present invention also provides a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion prepared by the method described in any embodiment herein.

[0119] Another aspect of the present invention provides a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder, wherein the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer is prepared from a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in any embodiment herein.

[0120] In one or more embodiments, the multi-core-shell structure acrylate-styrene-acrylonitrile copolymer powder is prepared by the following method: the multi-core-shell structure acrylate-styrene-acrylonitrile copolymer emulsion is coagulated, and after the emulsion is completely demulsified, it is matured to obtain flocculents. After solid-liquid separation and drying, the multi-core-shell structure acrylate-styrene-acrylonitrile copolymer powder is obtained.

[0121] In one or more embodiments, the core-shell structured acrylate-styrene-acrylonitrile copolymer powder is prepared by the following method: The core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion is heated to 75-85°C, and then, based on 100 parts by weight of the dry weight of the core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion, 3-6 parts by weight of a salt solution (dry weight) are added dropwise to cause coagulation of the core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion. The solid content of the coagulation system is adjusted to 15wt%-30wt%. After the core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion is completely demulsified, the temperature is raised to 90-100°C and matured for 25-35 minutes to obtain flocculants. The flocculants are subjected to solid-liquid separation and dried at 60-70°C to obtain the core-shell structured acrylate-styrene-acrylonitrile copolymer powder.

[0122] Another aspect of the present invention provides an acrylate-styrene-acrylonitrile resin, said acrylate-styrene-acrylonitrile resin being prepared from a blend comprising a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder as described in any embodiment herein and a styrene-acrylonitrile resin.

[0123] In one or more embodiments, the acrylate-styrene-acrylonitrile resin is obtained by granulation of a blend comprising the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder and styrene-acrylonitrile resin via a twin-screw extruder at 180-240°C. Attached Figure Description

[0124] Figure 1This is a schematic diagram of the structure of the PBA core of the present invention. Figure 1 In the diagram, 1 represents the inner core of PBA, and 2 represents the outer core layer of PBA.

[0125] Figure 2 This is a schematic diagram of the structure of the PBA core of the present invention. Figure 2 In the diagram, 1 is the PBA inner core, 2 is the PBA outer core layer, 3 is the PBA inner core layer, and 4 is the PBA outer core layer.

[0126] Figure 3 This is a schematic diagram of the structure of the PBA-g-SAN shell of the present invention. Figure 3 In the diagram, 1 is the PBA inner core, 2 is the PBA outer core layer, 3 is the PBA core layer, 4 is the PBA outer core layer, 5 is the PBA-g-SAN inner shell layer, and 6 is the PBA-g-SAN outer shell layer.

[0127] Figure 4 This is a schematic diagram of the process for preparing the PBA-g-SAN shell emulsion according to the present invention. Detailed Implementation

[0128] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0129] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0130] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0131] In this document, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0132] Unless otherwise specified, percentage refers to mass percentage, proportion refers to mass ratio, and part refers to weight part.

[0133] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0134] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0135] In this invention, unless otherwise specified, particle size refers to the volume average particle size measured using a laser particle size analyzer.

[0136] This invention first prepares a PBA core emulsion using a semi-continuous polymerization method, then prepares a PBA core emulsion using a semi-continuous polymerization method, and finally prepares a PBA-g-SAN shell emulsion using a semi-continuous method. In this invention, the PBA-g-SAN shell emulsion is a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion.

[0137] In this invention, semi-continuous polymerization refers to first adding a portion of the raw materials to the reaction system at once for batch polymerization, and then continuously adding the remaining raw materials to the reaction system for polymerization.

[0138] In this invention, when preparing the PBA core emulsion, a PBA inner core is first obtained through intermittent polymerization, and then a PBA outer core layer is formed on the surface of the PBA inner core through continuous polymerization to obtain the PBA core. In this invention, the PBA core includes a PBA inner core and a PBA outer core layer.

[0139] In this invention, when preparing the PBA core emulsion, a PBA core layer is first formed on the surface of a PBA core through intermittent polymerization to obtain the PBA core, and then a PBA outer core layer is formed on the surface of the PBA core through continuous polymerization to obtain the PBA core. In this invention, the PBA core includes a PBA core and a PBA core layer, and the PBA core itself includes a PBA core, a PBA core layer, and a PBA outer core layer.

[0140] In this invention, when preparing the PBA shell emulsion, an inner shell layer of PBA is first formed on the surface of the PBA core through intermittent polymerization to obtain the PBA inner shell. Then, an outer shell layer of PBA is formed on the surface of the inner shell through continuous polymerization to obtain the PBA shell. In this invention, the PBA inner shell includes a PBA core and an inner shell layer of PBA, and the PBA shell includes a PBA core, an inner shell layer of PBA, and an outer shell layer of PBA.

[0141] The PBA-g-SAN shell emulsion of this invention, after coagulation, maturation, solid-liquid separation, and drying, yields a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder (ASA powder). The ASA powder, blended with SAN resin and optional additives, is then extruded and granulated to obtain acrylate-styrene-acrylonitrile resin (ASA resin).

[0142] In some embodiments, the method for preparing the multi-core-shell structured acrylate-styrene-acrylonitrile graft copolymer of the present invention includes the following steps:

[0143] (1) Preparation of core-shell seed core emulsion (PBA core emulsion): In the presence of emulsifier and crosslinking agent, alkyl acrylate soft monomers are added semi-continuously and polymerized to obtain PBA core emulsion;

[0144] (2) Preparation of core-shell seed emulsion (PBA core emulsion): In the presence of PBA core emulsion, pre-emulsified alkyl acrylate soft monomers and other copolymerizable monomers (comonomers), crosslinking agents and grafting agents are added semi-continuously, and polymerized to obtain PBA core emulsion;

[0145] (3) Preparation of core-shell structure seed shell emulsion (abbreviated as PBA-g-SAN shell emulsion): In the presence of PBA core emulsion, pre-emulsified shell layer mixed monomers (including one or more selected from aromatic vinyl monomers and vinyl cyanide monomers and optional acrylate monomers) are added semi-continuously, and polymerized to obtain PBA-g-SAN shell emulsion (emulsion of PBA-g-SAN copolymer with multiple core-shell structure).

[0146] (4) Preparation of multi-core-shell structure acrylate-styrene-acrylonitrile copolymer powder (hereinafter referred to as ASA powder): Heat the PBA-g-SAN shell emulsion to 75-85℃, for example 80℃, and then add 3-6 parts by weight of salt solution based on 100 parts by weight of the dry weight of the multi-core-shell structure acrylate-styrene-acrylonitrile copolymer emulsion for coagulation. Adjust the solid content of the coagulation system to 15wt%-30wt%. After the PBA-g-SAN shell emulsion is completely demulsified, heat it to 90-100℃, for example 95℃, and mature it for 25-35 minutes, for example 30 minutes to obtain flocculents. Then centrifuge the flocculents and dry them at 60-70℃ until the moisture content is <1% to obtain ASA powder.

[0147] (5) Preparation of ASA resin: The total weight of the resin is 100 parts. 25-50 parts of ASA rubber powder, 50-75 parts of commercial grade SAN resin and optional additives (e.g., 0.2-0.5 parts of antioxidant and 0.2-0.5 parts of lubricant) are mixed and then granulated by twin-screw extruder at 180-240°C to obtain ASA resin.

[0148] In step (1), semi-continuous addition means that 10%-30% of the total weight of alkyl acrylate soft monomers required in step (1), 10%-30% of the total weight of initiator required in step (1), and 30%-60% of the total weight of crosslinking agent required in step (1) are added at once. The mixture is heated to the reaction temperature in the presence of an emulsifier and subjected to intermittent polymerization to obtain the PBA inner core emulsion. Subsequently, the remaining initiator, crosslinking agent and alkyl acrylate soft monomers are added continuously to polymerize and obtain the PBA outer core emulsion.

[0149] The structure of the PBA chip is as follows Figure 1 As shown, the PBA core consists of a highly cross-linked PBA inner core and a PBA outer core layer. The particle size of the PBA core is controlled between 70-130 nm, the gel content of the PBA core is ≥90%, and the cross-linking degree of the PBA inner core is greater than that of the PBA outer core layer.

[0150] In step (2), semi-continuous addition refers to the following steps: in the presence of the PBA core emulsion, a pre-emulsified mixture containing 5-10% by weight of the total weight of the alkyl acrylate soft monomers required in step (2), 15-20% by weight of the initiator required in step (2), and 10%-30% (e.g., 20%) by weight of the crosslinking agent required in step (2) is added at once. The mixture is heated to the reaction temperature and intermittently polymerized for 0.5-1.0 hours to obtain the PBA core emulsion. Then, the remaining fully pre-emulsified mixture containing alkyl acrylate soft monomers, other copolymerizable monomers (i.e., comonomers), crosslinking agent, and grafting agent is continuously added to polymerize and obtain the PBA outer core emulsion.

[0151] The structure of the PBA core is as follows: Figure 2 . Figure 2 In the diagram, 1+2 is a cross-linked PBA core, 3 is a cross-linked PBA inner core layer, and 4 is a cross-linked PBA outer core layer with reserved grafted double bonds. The particle size of the PBA core (1+2+3+4) is 150-600 nm, the gel content of the PBA core is ≥80%, and the degree of cross-linking of the PBA inner core layer is greater than that of the PBA outer core layer, but preferably both are less than the degree of cross-linking of the PBA core.

[0152] The PBA core of the present invention is formed by semi-continuously grafting pre-emulsified acrylate soft monomers, crosslinking agents, grafting agents, and one or more of copolymerizable aromatic vinyl monomers, vinyl cyanide monomers, and acrylate hard monomers onto a PBA core with a gel content of ≥90%, thereby forming a PBA core that contains both a crosslinked structure and reserved grafted double bonds.

[0153] This invention uses different amounts of PBA core emulsion as seeds, and through a diameter expansion reaction, a series of PBA core emulsions with different particle sizes and narrow dispersions can be obtained. The particle size of these core emulsions is increased to 150-600 nm. After the diameter expansion reaction, the gel content of the PBA core is preferably between 80% and 90%, and the crosslinking degree of the PBA core is greater than that of the PBA outer core layer. In principle, it is preferable that the crosslinking degree of both the PBA core layer and the outer core layer is less than that of the PBA core.

[0154] The core structure of this invention, which features alternating soft and hard phases, different degrees of crosslinking, and pre-designed grafting sites, is highly beneficial for improving the subsequent shell grafting rate and achieving a balance between rigidity and toughness in acrylate-styrene-acrylonitrile resin.

[0155] In other words, in this invention, the cross-linked PBA core provides hydrophobicity and the necessary elasticity and hardness, ensuring that the acrylate-styrene-acrylonitrile graft copolymer can easily maintain an intact core-shell structure during shell grafting, avoiding abnormal microphase structures caused by grafting inversion, which would lead to a decrease in the impact strength and surface gloss of the ASA resin.

[0156] The choice of comonomer for the core structure is also very important, depending on the requirements of the application: aromatic monomers such as styrene can improve the processing fluidity of the resin; vinyl cyanide monomers such as acrylonitrile can improve the dyeability of the resin, increase the intermolecular forces of the resin, improve the impact toughness of the resin, and improve the oil and chemical resistance; acrylate hard monomers such as methyl methacrylate can improve the dyeability of the resin, improve the surface gloss, etc., and can further improve the alloy compatibility in alloy systems such as PMMA / ASA and PC / ASA.

[0157] In step (3), semi-continuous addition refers to the following steps: First, in the presence of the PBA core emulsion, a pre-emulsified mixture containing 10%-40% of the total weight of the shell-mixed monomers required in step (3) and 10%-40% of the total weight of the initiator required in step (3) is added at once. The mixture is then heated to a set reaction temperature and intermittently polymerized for 0.5-1.0 hours to obtain the PBA-g-SAN inner shell. Then, a pre-emulsified mixture containing the remaining shell-mixed monomers, initiator, and optional regulator is continuously added, and polymerized to obtain the PBA-g-SAN outer shell. Based on 100 parts by weight of the dry weight of the PBA-g-SAN core emulsion, the total weight of the shell-mixed monomers added in step (3) is 40-60 parts by weight. When a regulator is added in step (3), the weight of the regulator is preferably 20%-30% of the total weight of the shell-mixed monomers added in step (3).

[0158] The grafted SAN shell in step (3) effectively protects the PBA core, which is the rubber phase, and largely avoids changes in the appearance of the product caused by stress deformation during processing. At the same time, the rubber particles with this core-shell structure have good stress absorption and impact buffering capabilities, giving ASA resin good toughness, processability and compatibility when used as a material.

[0159] This invention selects PBA core emulsions of different particle sizes as seeds. After the reaction in step (3), a series of PBA-g-SAN shell emulsions with different particle sizes between 190-700 nm can be obtained. The grafting rate of the core-shell structure PBA-g-SAN shell is usually not less than 40%, with sufficient grafting layer thickness. After grafting, the particle size increases by 40-100 nm, and the gel content of the PBA-g-SAN shell is between 60%-75%.

[0160] In this invention, steps (1), (2), and (3) all employ a semi-continuous seed emulsion polymerization process to control other properties such as reaction rate, particle size distribution, particle morphology, and degree of crosslinking of the resulting latex, all of which have yielded very beneficial results. Figure 4 A schematic diagram of the polymerization process in steps (1), (2), and (3) is given.

[0161] In step (1), the alkyl acrylate soft monomer can be selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, and isooctyl acrylate, preferably one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, and isooctyl acrylate, and more preferably butyl acrylate. The weight of the alkyl acrylate soft monomer used in step (1) is preferably 97%-99.8% of the total dry matter weight of the core emulsion.

[0162] In step (2), the alkyl acrylate soft monomer is preferably n-butyl acrylate. The amount of alkyl acrylate soft monomer used is preferably 90%-98% of the total mass of the PBA core emulsion monomers. The copolymerizable monomer can be selected from one or more of styrene, acrylonitrile, methacrylonitrile, methyl methacrylate, etc., preferably styrene or acrylonitrile. The amount of copolymerizable monomer used is preferably 2%-10% of the total weight of the PBA core emulsion monomers.

[0163] In this invention, the crosslinking agent can be selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate, diallyl maleate, etc. In steps (1) and (2), the amount of crosslinking agent used is preferably 0.2%-2% of the total weight of the reactants.

[0164] In step (1), the crosslinking agent used to prepare the PBA inner core and the PBA outer core layer is preferably ethylene glycol dimethacrylate. Preferably, the concentration of the crosslinking agent in the PBA inner core is greater than the concentration of the crosslinking agent in the PBA outer core layer.

[0165] In step (2), the crosslinking agent used to prepare the PBA core layer and the PBA outer core layer is preferably ethylene glycol dimethacrylate.

[0166] In step (2), the grafting agent is preferably allyl methacrylate. The amount of grafting agent used is preferably 0.1%-0.6% of the total weight of the reacting monomers.

[0167] In step (3), the aromatic vinyl monomer is preferably styrene or α-methylstyrene, and the vinyl cyanide monomer is preferably acrylonitrile or methacrylonitrile.

[0168] In step (3), the amount of PBA core emulsion is preferably 40%-60% of the dry weight of PBA-g-SAN shell emulsion, the aromatic vinyl monomer is preferably styrene, the amount of aromatic vinyl monomer is preferably 30%-45% of the dry weight of PBA-g-SAN shell emulsion, the vinyl cyanide monomer is preferably acrylonitrile, and the amount of vinyl cyanide monomer is preferably 10%-15% of the dry weight of PBA-g-SAN shell emulsion.

[0169] The emulsifier used in steps (1), (2), and (3) can be selected from one or more of alkyl aryl ether sulfates, sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (DBS), and alkyl diphenyl ether disulfonate, preferably sodium dodecyl sulfate (SDS) or sodium dodecylbenzene sulfonate (DBS). Preferably, the same emulsifier is used in steps (1), (2), and (3), for example, SDS or DBS is used in all of them.

[0170] The initiator used in steps (1), (2), and (3) can be selected from one or more of sodium persulfate (NaPS), potassium persulfate (KPS), ammonium persulfate (APS), cumene hydroperoxide (CHP), dicumene hydroperoxide (DCP), benzoyl peroxide (BPO), and ethylenediol peroxide (EHP). The initiator used in step (1) is preferably KPS. The initiator used in step (2) is preferably KPS or CHP. The initiator used in step (3) is preferably CHP. This invention does not particularly limit the amount of initiator used.

[0171] Preferably, the initiation system used varies depending on the reaction stage of the invention: in the first stage, the PBA core emulsion preparation stage, a water-soluble potassium persulfate initiation system is used; in the second stage, the PBA core emulsion preparation stage, both water-soluble and oil-soluble initiation systems have equal reaction efficiency; however, in the third stage, the PBA-g-SAN shell emulsion preparation stage, an oil-soluble initiation system has higher grafting efficiency. It is particularly noteworthy that the water-soluble initiation system requires a higher reaction temperature than the oil-soluble system within the same reaction time (to maintain consistent reaction kinetics).

[0172] In this invention, no molecular weight regulator is required during polymerization in steps (1) and (2). In step (3), a molecular weight regulator may or may not be used, but its use is recommended. The molecular weight regulator can be selected from one or more of tert-dodecyl mercaptan, n-dodecyl mercaptan, and n-octyl mercaptan, with tert-dodecyl mercaptan being preferred. This invention does not particularly limit the specific type and amount of the molecular weight regulator.

[0173] In step (4), monovalent, divalent, and trivalent salts can be selected as coagulants, such as one or more of sodium chloride, potassium chloride, magnesium sulfate, calcium chloride, and aluminum chloride. The preferred amount of coagulant is 3-6% of the weight of the acrylate-styrene-acrylonitrile copolymer.

[0174] Preferably, the soft monomer used in steps (1) and (2) is n-butyl acrylate, the crosslinking agent is ethylene glycol dimethacrylate, and the grafting agent is allyl methacrylate.

[0175] Preferably, the comonomer used in step (2) is styrene and / or acrylonitrile.

[0176] Preferably, the aromatic vinyl monomer used in step (3) is styrene and the vinyl cyanide monomer is acrylonitrile.

[0177] Preferably, the emulsifier used in steps (1), (2), and (3) is sodium dodecyl sulfate or sodium dodecylbenzene sulfonate.

[0178] Preferably, the initiator used in step (1) is KPS, the initiator used in step (2) is KPS or CHP system, and the initiator used in step (3) is KPS or / CHP system, more preferably CHP system.

[0179] Preferably, the molecular weight regulator used in step (3) is tert-dodecyl mercaptan.

[0180] In some implementation schemes, during step (1) of the intermittent polymerization, after adding the raw materials, stirring is started at a speed of 150-300 rpm for 10-20 minutes, and then the temperature is increased to 60-75℃ at a rate of 1-2℃ / min for 0.5-1.0 hours. Then the outer core material is continuously added for 2.0-4.5 hours, and the reaction is stopped when the reaction conversion rate is greater than 98.0%.

[0181] In some implementation schemes, during step (2) of the intermittent polymerization, after adding the raw materials, premixing is performed at a stirring speed of 150-300 rpm for 10-20 minutes, followed by heating to 70-85℃ at a rate of 1-2℃ / min and reacting for 0.5-1.0 hours. Then, the outer core material is continuously added for 3-4.5 hours. After the addition is completed, the reaction continues for 1-2 hours. The reaction ends when the conversion rate reaches 98-99.5%.

[0182] In some implementation schemes, in step (3), during intermittent polymerization, after adding the raw material, the mixture is stirred and emulsified at a stirring speed of 150-200 rpm for 10-20 minutes, and then heated to 65-80℃ at a speed of 1-2℃ / min, and the reaction is maintained for 0.5-1.0 hours; then the outer shell material is continuously added for 3-4.5 hours, and the reaction continues for 1-2 hours after the addition is completed. The reaction ends when the conversion rate is greater than 98.0%.

[0183] Preferably, the coagulant used in step (4) is magnesium sulfate or calcium chloride.

[0184] The SAN resin used in this invention can be any commercially available SAN resin. It can be freely selected according to the actual formulation design requirements.

[0185] In this invention, buffers, reducing agents, complexing agents, pH adjusters and other chemicals may be added to the polymerization formulations in steps (1), (2) and (3). Antioxidants, heat stabilizers and other additives may also be used in step (4). Antioxidants, lubricants, ultraviolet absorbers, colorants and other additives may also be used in step (5).

[0186] In order to control the particle size of the core and achieve a single particle size distribution, this invention adopts a multi-step semi-continuous seed emulsion polymerization process. By controlling the amount of emulsifier and initiator, the monomer feeding method, etc., the particle size and particle size distribution of the core-shell latex particles can be controlled.

[0187] To control the degree of crosslinking in the core layer, this invention adds a small amount of multifunctional monomers as crosslinking agents to the core layer monomers. The double bonds in these multifunctional monomers are highly reactive and can copolymerize with the core layer monomers, achieving appropriate crosslinking of the core layer monomers. A certain degree of crosslinking can function as an elastic material, absorbing impact energy and increasing impact strength, while also improving surface gloss.

[0188] This invention achieves a high grafting rate of shell graft copolymerization through the unique multi-core-shell structure design of ASA adhesive powder, matched with a unique synthesis process and polymerization formula, thereby achieving a balance between rigidity and toughness in ASA materials.

[0189] The present invention has the following beneficial effects:

[0190] 1. This invention uses a multi-step semi-continuous emulsion synthesis process to prepare a six-core-shell structured acrylate-styrene-acrylonitrile graft copolymer, which effectively controls the reaction rate, making the reaction process stable and controllable, and easy to industrialize.

[0191] 2. The present invention employs a specially designed core structure with alternating soft and hard phases, different interlayer crosslinking degrees, different comonomer selections, and preset grafting sites to improve the grafting rate, thereby enhancing the mechanical properties of the acrylate-styrene-acrylonitrile graft copolymer.

[0192] 3. This invention utilizes the relative hydrophobicity and necessary elasticity and hardness provided by the cross-linked PBA core, and by adjusting the molecular weight of the ASA copolymer in the grafted shell layer to obtain a relatively hydrophilic copolymer as the shell layer, it ensures that the shell layer can easily and naturally adhere to the outside of the core during grafting, forming a relatively complete core-shell structure, avoiding grafting inversion, and achieving a good balance of impact strength, surface gloss, and processing performance of ASA resin.

[0193] 4. This invention employs a multi-step semi-continuous emulsion synthesis process to achieve designable control of the rubber phase particle size, thus solving the differentiated requirements for ASA resin particle size in application stages.

[0194] The present invention will be described below by way of specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the scope of the invention. The methods, reagents, and materials used in the embodiments are conventional methods, reagents, and materials in the art, unless otherwise stated. The raw material compounds in the embodiments are all commercially available.

[0195] The analytical characterization methods used in Preparation Examples 1-5 are as follows:

[0196] I. Determination of Emulsion Solid Content (S)

[0197] Take 1.5-2.0g (W1) of latex sample and place it on aluminum foil. Dry it with an infrared lamp to a constant weight (W2). The net weight of the aluminum foil is W0. Calculate the solid content (S) according to formula (1):

[0198] S = [(W2 - W0) / (W1 - W0)] 100% (1)

[0199] II. Determination of gel content (X)

[0200] The gel content reflects the degree of cross-linking of latex; the higher the gel content, the higher the degree of cross-linking. Take an appropriate amount of latex for flocculation, then separate the flocculent, wash thoroughly with ethanol, dry, and weigh a quantitative sample. Place the sample in toluene and shake at 40°C for 8 hours. Separate the sample, wash thoroughly with ethanol, dry, and weigh. Calculate the gel content (X) according to formula (2):

[0201] X = {[(Swelled gel dry weight (g)] / Sample weight (g)} 100% (2)

[0202] III. Determination of Particle Size (R) and Distribution Index (PDI)

[0203] Particle size and distribution of latex are important parameters of polymer emulsions. These were tested using a 90 PLUS laser particle size analyzer manufactured by Brookhaven, Inc. (USA). During testing, a small drop of the latex to be tested was added to the sample cell and diluted approximately 1000 times with deionized water. The conductivity of the sample was adjusted to be between 100 and 800 kcps, or the transmittance to be >80%. Each sample was tested in triplicate, and the average value was taken.

[0204] IV. Emulsion pH Measurement

[0205] The pH value of the system was measured using a PH-2C precision digital pH meter.

[0206] 5. Determination of emulsion precipitates

[0207] After polymerization, the precipitates in the latex were filtered through a 100-mesh stainless steel mesh, and the precipitates from the agitator and inner wall of the reactor were collected simultaneously. These precipitates were then dried in an oven and the results were calculated.

[0208] VI. Determination of Reaction Conversion Rate

[0209] The reaction conversion rate was determined by gravimetric method and calculated according to formula (3):

[0210] Conversion rate = [Weight of monomers reacting (g) / Total weight of monomers (g)] 100% (3)

[0211] VII. Determination of Grafting Efficiency

[0212] Take 1.5g of the sample and place it in an Erlenmeyer flask. Reflux with 150ml of acetone at its boiling point for 2-3 hours. Transfer the sample completely to a centrifuge tube and centrifuge at 15000rpm to separate the insoluble matter. Dry the sample and weigh it. Combined with the polymerization formulation, calculate the grafting efficiency of each sample using formula (4):

[0213] Grafting efficiency = [Mass of grafted monomers / (Mass of grafted monomers + Mass of grafted monomer homopolymer)] 100%. (4)

[0214] Wherein the mass of the grafted monomer = sample weight - polymer weight grafted onto the PBA core.

[0215] 8. Rotational viscosity

[0216] When using a rotational viscometer, operate it according to its operating procedures.

[0217] Preparation Example 1: Preparation of PBA core emulsion by semi-continuous seed emulsion polymerization

[0218] According to the formula in Table 1, the raw materials for synthesizing the inner core are first added to the reactor: deionized water, emulsifier (SDS or DBS), complexing agent (TSPP), electrolyte (KCl), pH buffer (NaHCO3), acrylate soft monomer (butyl acrylate), initiator (potassium persulfate) and crosslinking agent (ethylene glycol dimethacrylate). Stirring is started at 200 rpm, emulsification is carried out for 15 minutes, and then the temperature is increased to 70℃ at 1.5℃ / min, and the reaction is carried out for 1.0 hour.

[0219] Subsequently, the raw materials for synthesizing the outer core layer were continuously added: a mixture of soft monomers (butyl acrylate and optional isooctyl acrylate), initiator (potassium persulfate) and crosslinking agent (ethylene glycol dimethacrylate). The addition time was 3.5 hours. The reaction was terminated when the reaction conversion rate was greater than 98.0%. The particle size, particle size distribution index, gel content, amount of gel (precipitate content), pH value, viscosity and solid content of the PBA core emulsion prepared were analyzed.

[0220] The formulation and analysis results of the PBA core emulsion are shown in Table 1.

[0221] Table 1: Formulation and Analytical Results of PBA Core Emulsion Preparation

[0222]

[0223] Examples 1, 2, and 3 demonstrate that the core emulsion prepared according to the technology of this invention is actually a core-shell structure PBA core emulsion with an inner core as the core and an outer core layer as the shell. Since the inner core monomer uses a higher proportion of the crosslinking agent ethylene glycol dimethacrylate than the outer core layer monomer, theoretically, the crosslinking degree of the inner core of the core emulsion is greater than that of the outer core layer. Furthermore, from a process perspective, the inner core can be considered the seed of the outer core.

[0224] The results of Examples 1, 2, and 3, and Comparative Example 1, also indicate that while reducing the amount of emulsifier to 0.5% (relative to the total mass of acrylate soft monomers) can increase the particle size of the core emulsion, the increase is very limited. Furthermore, the particle size distribution becomes larger, and the amount of reaction precipitates increases, both of which are undesirable trends. Therefore, this invention does not support excessively reducing the amount of emulsifier to increase the particle size of the core emulsion, and considers an emulsifier amount of 0.8-1.0% (relative to the total mass of acrylate soft monomers) to be necessary for the synthesis of the core emulsion.

[0225] The core structures of Examples 1, 2, and 3 all have a gel content greater than 90%, and their particle size distribution is very narrow. The distribution index (PDI) is 0.011, 0.009, and 0.015, respectively, corresponding to particle sizes of 92 nm, 87 nm, and 89 nm. The rotational viscosity is less than 20 centipoise, and the amount of gelation is less than 0.01%. Therefore, the latex itself is very stable.

[0226] Preparation Example 2: Preparation of PBA core emulsion by semi-continuous emulsion polymerization

[0227] According to the formulation in Table 2, the raw materials for synthesizing the core were first added to the reactor: PBA core emulsion of Example 1, 2 or 3, acrylate soft monomers (butyl acrylate or isooctyl acrylate), initiator (potassium persulfate), grafting agent (allyl methacrylate), crosslinking agent (ethylene glycol dimethacrylate), deionized water, complexing agent (TSPP), electrolyte (KCl), and pH buffer (NaHCO3). The mixture was premixed, stirred at 200 rpm for 15 minutes, and then heated to 75°C at 1.5°C / min for 1.0 hour.

[0228] Then, the outer core layer raw materials are continuously added: a mixture of fully pre-emulsified acrylate soft monomers (butyl acrylate and optional isooctyl acrylate), other copolymerizable monomers (styrene or acrylonitrile), deionized water, crosslinking agent (ethylene glycol dimethacrylate), grafting agent (allyl methacrylate), initiator (potassium persulfate), and emulsifier (SDS). The continuous feeding time is 3.5 hours, and the reaction continues for 1.5 hours after the addition is completed. The reaction is stopped when the conversion rate is between 98% and 99.5%. The particle size, particle size fraction index, gel content, gelation amount, pH value, viscosity, and solid content of the PBA core emulsion are analyzed, and the theoretical value of the core emulsion particle size is calculated.

[0229] The formulation and analysis results of PBA nuclear emulsion preparation are shown in Table 2.

[0230] Table 2: Formulation and Analytical Results of PBA Nuclear Emulsion Preparation

[0231]

[0232] Examples 4-11 demonstrate that using the PBA core emulsions from Examples 1, 2, and 3 as seeds, a core-shell structured PBA core emulsion can be prepared using semi-continuous emulsion polymerization technology. Furthermore, as the amount of PBA core emulsion decreases, the particle size of the PBA core emulsion can be precisely controlled to increase to the required PBA core emulsion particle size. The experimental results also reproduce the calculated particle size values ​​well, proving that the PBA emulsion diameter expansion synthesis route is successful.

[0233] Examples 4-11 show that it is feasible to prepare PBA core emulsions with particle sizes of 150-500 nm using any core emulsion with a particle size of 70-130 nm, as long as its amount, on a dry basis, is 1.5%-3.0% of the total weight of the acrylate soft monomers added during core layer preparation. However, for PBA core emulsions with particle sizes above 500 nm, using a PBA core emulsion with a particle size of 70-130 nm as a seed emulsion results in poor stability of actual particle size control during polymerization due to the insufficient amount of PBA core emulsion required.

[0234] In Examples 12 and 13 of this invention, a secondary seeding method is used. The core emulsion with a theoretically calculated particle size of 313 nm from Example 5 is used as the seed (considered as a PBA core emulsion with a particle size of 313 nm). When 3% and 2.8% of the total weight of the acrylate soft monomers added during core layer preparation are taken respectively (on a dry basis), PBA core emulsions with particle sizes of 570 nm and 628 nm can be obtained. It is easy to understand that further reducing the amount of this seed emulsion can yield PBA core emulsions with larger particle sizes.

[0235] The core emulsion prepared according to the technology of this invention can also be interpreted as a core-shell structure PBA core emulsion with a PBA core emulsion as the core and an inner core layer and an outer core layer as the shell. Meanwhile, the core layer monomers use a higher proportion of the crosslinking agent ethylene glycol dimethacrylate and a lower proportion of the grafting agent allyl methacrylate than the outer core layer monomers. Therefore, theoretically, the crosslinking degree of the core layer in the designed core emulsion is greater than that of the outer core layer, and the number of grafting active sites reserved in the outer core layer is also much greater than that in the core layer.

[0236] The PBA core emulsions in Examples 4-13 all had a structural gel content greater than 80%, a very narrow particle size distribution, and a distribution index (PDI) between 0.008 and 0.084. The particle size of the PBA core emulsions prepared in this invention also closely matches the calculated particle size values. Furthermore, the rotational viscosity of all examples was less than 10 centipoise, the amount of gelation was less than 0.01%, and the latex pH was between 7 and 0.5. The PBA core emulsions themselves are very stable and easily industrialized.

[0237] It is worth mentioning that the preferred alkyl acrylate soft monomers are n-butyl acrylate (BA) and isooctyl acrylate (2-EHA), with isooctyl acrylate (2-EHA) being the preferred choice. However, n-butyl acrylate (BA) is readily available and inexpensive, offering better cost-effectiveness.

[0238] In the examples, the potassium persulfate (KPS) water-soluble initiator system used to prepare the PBA core emulsion can be completely replaced by the cumene hydroperoxide (CHP) oil-soluble redox system. This is well known to all professionals familiar with emulsion polymerization technology. The inventors will not list more examples. It should be noted that more chemicals are used and the reaction temperature is lower than that of the KPS system.

[0239] Preparation Example 3: Preparation of PBA-g-SAN shell emulsion by semi-continuous emulsion polymerization:

[0240] According to the formulation in Table 3, the raw materials for preparing the inner shell were first added to the reactor: the PBA core latex obtained in Preparation Example 2, the shell mixed monomers (styrene and acrylonitrile and optional methyl methacrylate), the inner shell initiator (CHP), deionized water, complexing agent (EDTA), electrolyte (KCl), pH buffer (NaHCO3), emulsifier (SDS), and reducing agent (sodium formaldehyde sulfoxylate SFS and ferrous sulfate) were premixed and stirred at 200 rpm for 15 minutes. Then, the temperature was increased to 70°C at 1.5°C / min and the reaction was maintained for 1.0 hour to obtain the PBA-g-SAN inner shell.

[0241] Then, the raw materials for the outer shell layer were continuously added: a mixture of pre-emulsified aromatic vinyl monomers (styrene), vinyl cyanide monomers (acrylonitrile), optional acrylate monomers (methyl methacrylate), deionized water, initiator (CHP), conditioner (TDM), pH buffer (NaHCO3), and emulsifier (SDS). The continuous feeding time was 3.5 hours, and after the addition was completed, the reaction continued for 2 hours. The reaction was stopped when the conversion rate was greater than 98.0%, thus obtaining the PBA-g-SAN shell. The particle size, particle size fraction index, grafting efficiency, gel content, gelation amount, pH value, viscosity, and solid content of the PBA-g-SAN shell emulsion were analyzed.

[0242] The formulation and analytical results of the PBA-g-SAN shell emulsion preparation are shown in Table 3.

[0243] Table 3: Formulation and Analytical Results of PBA-g-SAN Shell Emulsion Preparation

[0244]

[0245]

[0246]

[0247] In Table 3, the solid content of the nuclear emulsion in Examples 4-13 is uniformly calculated as 40%. For example, adding 50 parts by weight of dry nuclear emulsion means that the actual added nuclear emulsion is 125 parts by weight (including 50 parts by weight of dry nuclear emulsion and 75 parts by weight of water contained in the nuclear emulsion).

[0248] The results of Examples 14-26 show that using the PBA core emulsion from Examples 4-13 as the rubber phase, and utilizing the grafting active sites reserved in its core layer, a semi-continuous emulsion polymerization technique can effectively graft mixed monomers onto the upper shell layer to prepare a PBA-g-SAN shell emulsion with a core-shell structure. Furthermore, the method of this invention exhibits very stable polymerization processes when the dry weight of the PBA core emulsion is 40-60 parts by weight (the sum of the dry weight of the PBA core emulsion added during the preparation of the inner shell and the total mass of the monomers added during the preparation of the shell layer is recorded as 100 parts by weight) and the particle size is within the range of 160-650 nm, with the grafting of mixed monomers onto the shell layer. The polymerization precipitates are all less than 0.2%, and the grafting efficiency is greater than 40%, indicating a very promising prospect for industrialization.

[0249] Examples 14-26 also demonstrate that by using a 150-320 nm PBA core emulsion as the base latex and grafting shell-layer mixed monomers to form a PBA-g-SAN shell emulsion structure, the corresponding emulsion particle size can be further increased in a controlled manner to 200-750 nm, with a very narrow distribution. This provides a method and approach for preparing multi-grade ASA resins with different particle sizes and bimodal or multimodal structures.

[0250] The PBA-g-SAN shell emulsion prepared according to the technology of this invention can be understood as a multi-core-shell structure PBA-g-SAN emulsion with a PBA core emulsion as the core and SAN grafted onto the inner and outer shell layers as the shell. This multi-core-shell structure design at the molecular level is highly beneficial for improving the balance of stiffness and toughness of ASA resin and optimizing the resin's surface properties, which will be further illustrated in the following examples.

[0251] This invention also specifically uses a molecular weight regulator in the outer shell monomer, primarily to improve the processability of the ASA resin. This invention believes that whether or not a molecular weight regulator is used in step (3) depends on the specific application of the ASA resin. When it is desirable to improve the material's processing flow properties, adding a molecular weight regulator during the polymerization stage is more effective, and compared to adding a lubricant or a more fluid continuous phase resin during the blending stage, the risk in product manufacturing is lower. For example, improper or excessive addition of lubricant can easily cause pigment migration, and improper or excessive selection of the continuous phase resin can lead to a decrease in thermal stability.

[0252] The structural gel content of the PBA-g-SAN shell emulsions in Examples 14-26 was reduced to between 60-80%, which ensures that the ASA resin has sufficient impact strength and rigidity while providing the necessary ductility, so that the resin can meet more performance requirements in injection molding, extrusion, blow molding and other processing applications.

[0253] The rotational viscosity of the PBA-g-SAN shell emulsions prepared in this invention is less than 8 centipoise, which is further reduced compared to the PBA core emulsion. This is a result of the increased latex particle size after grafting shell monomers onto the PBA core phase, which is beneficial for mass and heat transfer processes and is also advantageous for industrial implementation.

[0254] In step (3) of this invention, a potassium persulfate (KPS) water-soluble initiator system can be used instead of the cumene hydroperoxide (CHP) oil-soluble redox system in the embodiments of this invention. However, since experimental results show that the grafting efficiency of the CHP system is better than that of the KPS system, this invention only lists the more optimized CHP system embodiments.

[0255] Preparation Example 4: Preparation of PBA-g-SAN copolymer powder with multiple core-shell structure

[0256] The PBA-g-SAN shell emulsions prepared in Examples 14-26 of Preparation Example 3 were heated to 80°C, and then 3-6 parts by weight of salt solution (relative to 100 parts by weight of dry matter of PBA-g-SAN shell emulsion) were added dropwise to coagulate. The solid content of the coagulation system was adjusted to 15%-30%. After the PBA-g-SAN emulsion was completely demulsified, the temperature was raised to 95°C and matured for 30 minutes. The flocculants were then separated by centrifugation and dried at 60-70°C until the moisture content was <1%.

[0257] The obtained PBA-g-SAN grafted adhesive powders are respectively designated as Examples 14N, 15N, 16N, 17N, 18N, 19N, 20N, 21N, 22N, 23N, 24N, 25N, and 26N, corresponding to Examples 14-26. Finally, the bulk density (g / cm³) of these examples was analyzed. 3 The results are shown in Table 4.

[0258] Table 4: Bulk Density of PBA-g-SAN Copolymer Powder

[0259]

[0260] The experimental results in Table 4 show that when the particle size of PBA-g-SAN latex is small, the particles aggregated under the same conditions have higher hardness and corresponding higher bulk density. This is because the small particle size and large surface area of ​​PBA cores are conducive to the grafting of SAN with higher density (Examples 19N, 20N, 21N).

[0261] Experimental data also show that the larger the particle size, the less coagulant is needed for the latex. This is because the larger the particle size, the worse the stability of the emulsion, and the easier it is to coagulate and break the emulsion. However, the particle size distribution after coagulation will be wider. Therefore, when the latex particle size is large, the bulk density of the rubber powder decreases with the increase of particle size (Examples 24N, 25N, 26N).

[0262] The analysis also revealed that when the amount of adhesive powder was relatively low, the bulk density was also high. This was mainly due to the increased proportion of SAN with higher density (Examples 16N, 17N, 18N).

[0263] Preparation Example 5: Preparation and Performance Testing of ASA Resin

[0264] The PBA-g-SAN rubber powder from Preparation Example 4 or commercially available rubber powder (Japan UMG ASA rubber powder 600N or Korea Kumho Petrochemical ASA rubber powder XC500A), commercial-grade SAN resin (China Formosa Chemicals & Fibre bulk SAN resin AS2200), antioxidants (1076 and 168), lubricant (ethylene bis-stearimide EBS), and silicone oil were blended and then granulated at 180-240℃ using a twin-screw extruder to obtain ASA resins with different properties. The preparation formulations are shown in Tables 5 and 6.

[0265] The analytical testing standards or methods used in preparation Example 5 are as follows, and the test results are shown in Tables 5 and 6:

[0266] 1. IZOD impact strength (J / m): The specimen thickness is 1 / 8″, and the measurement is performed according to ASTM D256 standard.

[0267] 2. Melt flow index (MI, g / 10min): Tested according to ASTM D1238 standard, under the conditions of 220℃, 10kg load, and 10 minutes.

[0268] 3. Tensile strength (MPa): Tested according to ASTM D638 standard.

[0269] 4. Colorimetric measurement: Use a whiteness meter to measure the L, a, and b values ​​according to the CIE Lab method.

[0270] 5. Gloss (°): According to ASTM D528 standard, the gloss meter takes data at a 60° angle.

[0271] Table 5: ASA Resin Blending Formulations and Performance Test Results

[0272]

[0273] Table 6: ASA Resin Formulation and Performance Test Results

[0274]

[0275] 600N: UMG ASA adhesive powder from Japan, 60% adhesive content;

[0276] XC500A: ASA adhesive powder from Kumho Petrochemical, South Korea, with an adhesive content of 50%.

[0277] Examples 27-43 use 40%-60% of PBA-g-SAN adhesive powder of different particle sizes, different amounts of adhesive, and different core-shell structures of the present invention, blended with 60%-40% of Formosa Plastics AS2200 bulk resin, add necessary additives, and analyze the physical properties of the resin obtained by injection molding after plasticizing and granulation by twin-screw extrusion. The results are compared with two representative ASA adhesive powders widely recognized in the market: Japan's UMG600N and South Korea's Kumho Petrochemical's AX500A.

[0278] Test data from Examples 27-43 show that the impact strength of ASA resin is closely related to the particle size of the PBA core emulsion. Impact strength increases with increasing PBA core particle size, but peaks around 500 nm. Further increases in particle size lead to a decrease in impact strength (Examples 41, 42, and 43), which aligns with the basic theory of rubber toughening. Example 37, with its relatively low impact strength due to the PBA particle size of only 166 nm, follows the same principle. When the PBA particle size exceeds 500 nm, the grafted particle size increases to over 600 nm, causing a decrease in material rigidity and gloss. This undoubtedly provides another material option for applications requiring matte finish.

[0279] Experiments have also shown that blending ASA powder with different particle sizes, SAN resins with different molecular weights and nitrile contents, styrene polymers containing a third monomer, reactive resins, PC, PMMA, etc., in different proportions has yielded many beneficial results in terms of performance and appearance. These will not be elaborated here, as this is knowledge familiar to engineering technicians who are familiar with modified materials.

[0280] Examples 27-38 (except Example 37) have better mechanical properties than Comparative Examples 2, 3, 4, 5, 6, and 7. Their gloss and whiteness are comparable to Japanese UMG600N and far superior to Korean Kumho Petrochemical's AX500A. Their processing performance is comparable to UMG600N and also superior to AX500A.

[0281] Since the rubber content, particle size, and resin blending formulation of the ASA rubber powder obtained in Examples 30, 31, and 32 are equivalent to or consistent with those of Comparative Examples 5, 6, and 7, the following results were obtained by comparing the performance data of Examples 30, 31, and 32 with those of Comparative Examples 5, 6, and 7: Tensile strength (41.7, 40.6, 40.3), impact strength (171.2, 187.5, 215.2), gloss (85.2, 83.6, 83.4), L value (93.2, 93.0, 92.1), and b value (11.6, 12.4, ...) of the ASA resin obtained in this invention. 12.7), melt index (17.7, 16.6, 15.7); compared with the ASA resin prepared from AX500A adhesive powder, the tensile strength (36.2, 36.1, 35.3), impact strength (154.2, 167.2, 183.3), gloss (70.5, 68.7, 67.9), L value (91.0, 91.2, 90.5), b value (13.5, 14.6, 14.7), and melt index (10.2, 9.8, 8.5) of the present invention are excellent in all aspects. It is not difficult to conclude that the grafted ASA adhesive powder prepared by the present invention has better rigidity-toughness balance than AX500A, higher resin surface gloss, whiter appearance, and excellent processing performance. Compared with AX500A adhesive powder, the ASA adhesive powder of the present invention is more likely to produce an acrylate-styrene-acrylonitrile copolymer with good surface gloss and rigidity-toughness balance.

[0282] Similarly, since the ASA rubber powder obtained in Examples 33, 34, and 35 has the same or identical rubber content, particle size, and resin blending formulation as Comparative Examples 2, 3, and 4, a comparison of their performance data reveals that the ASA resin obtained by this invention has the following tensile strength (40.2, 40.1, 39.8), impact strength (137.0, 158.2, 175.7), gloss (83.5, 82.6, 81.3), L value (93.1, 94.0, 92.7), and b value (12.0, 11.3, 11.1). The melt indexes are 16.9, 15.8, and 15.3. Comparisons are made between the ASA resin prepared from UMG600N adhesive powder and the following parameters: tensile strength (39.0, 39.1, 38.0), impact strength (120.2, 139.0, 157.3), gloss (84.3, 82.4, 81.2), L-value (93.2, 93.0, 93.4), b-value (11.7, 12.3, 12.6), and melt index (16.8, 15.4, 14.3). It can be seen that the grafted ASA adhesive powder prepared by this invention has similar rigidity to UMG600N, but the resin prepared from the adhesive powder of this invention has a significant advantage in toughness. While the surface gloss and appearance of the resin are comparable, the product of this invention has a higher melt index and better processing performance.

[0283] The above embodiments fully illustrate the technology of the present invention, which can produce an acrylate-styrene-acrylonitrile copolymer with good surface gloss and a balance of rigidity and toughness.

[0284] The above description of the disclosed embodiments is intended to enable those skilled in the art to use or implement this technology, promote the industrialization of ASA resin in China, and research and develop ASA resin products comparable to ABS resin. However, based on the principles, novelty, and spirit of this invention, modifications can be easily made to the embodiments of the invention. All changes, modifications, and breakdowns made according to specific examples are within the scope of protection of the claims of this patent.

Claims

1. A multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion, characterized in that, The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion includes multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles, which are composed of a PBA core, a PBA core layer, and a PBA-g-SAN shell layer from the inside out. The PBA core comprises an inner PBA core and an outer PBA core layer. The inner PBA core contains the reaction product of alkyl acrylate soft monomers and a crosslinking agent. The outer PBA core layer contains the reaction product of alkyl acrylate soft monomers and a crosslinking agent. The weight of the alkyl acrylate soft monomers in the inner PBA core accounts for 10%-30% of the total weight of the alkyl acrylate soft monomers in the PBA core. The PBA core layer comprises a PBA inner core layer and a PBA outer core layer. The PBA inner core layer contains the reaction product of alkyl acrylate soft monomers and a crosslinking agent. The PBA outer core layer contains the reaction product of alkyl acrylate soft monomers, comonomers, crosslinking agents, and grafting agents. The weight of the alkyl acrylate soft monomers in the PBA inner core layer accounts for 5%-10% of the total weight of the alkyl acrylate soft monomers in the PBA core layer. The comonomers contain one or more, and optionally, hard acrylate monomers selected from aromatic vinyl monomers and vinyl cyanide monomers. The PBA-g-SAN shell comprises a PBA-g-SAN inner shell and a PBA-g-SAN outer shell. The PBA-g-SAN inner shell contains reaction products of shell-mixed monomers, and the PBA-g-SAN outer shell contains reaction products of shell-mixed monomers. The shell-mixed monomers include one or more and optionally acrylate monomers selected from aromatic vinyl monomers and vinyl cyanide monomers. The weight of the shell-mixed monomers in the PBA-g-SAN inner shell accounts for 10%-40% of the total weight of the shell-mixed monomers in the PBA-g-SAN shell. Wherein, the degree of crosslinking of the PBA inner core is greater than the degree of crosslinking of the PBA outer core layer; the degree of crosslinking of the PBA inner core layer is greater than the degree of crosslinking of the PBA outer core layer; and the degree of crosslinking of both the PBA inner core layer and the PBA outer core layer is less than the degree of crosslinking of the PBA core. The PBA core has a gel content of ≥90%; The PBA core, which consists of the PBA core and the PBA core layer, has a gel content of 80%-90%. The gel content of the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles is 60%-75%.

2. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 1, characterized in that, The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion has one or more of the following characteristics: The weight of the crosslinking agent in the PBA core accounts for 30%-60% of the total weight of the crosslinking agent in the PBA core; The total weight of alkyl acrylate soft monomers in the PBA core accounts for 97%-99.8% of the dry matter weight of the PBA core; The total weight of the crosslinking agent in the PBA core is 0.2%-2% of the total weight of the alkyl acrylate soft monomers in the PBA core; The alkyl acrylate soft monomer in the PBA core is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, and isooctyl acrylate. The crosslinking agent in the PBA core is selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate, and diallyl maleate. The PBA core has a particle size of 70-130 nm.

3. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 2, characterized in that, The alkyl acrylate soft monomers in the PBA core are each independently selected from one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, and isooctyl acrylate.

4. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 2, characterized in that, The alkyl acrylate soft monomer in the PBA core is butyl acrylate.

5. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 2, characterized in that, The crosslinking agent in the PBA core is ethylene glycol dimethacrylate.

6. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 1, characterized in that, The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion has one or more of the following characteristics: The crosslinking agent in the PBA core layer accounts for 10%-30% of the total weight of the crosslinking agent in the PBA core layer; The total weight of alkyl acrylate soft monomers in the PBA core layer accounts for 85%-90% of the total dry matter weight of the PBA core and the PBA core layer. The dry weight of the PBA core is 1.5%-3.0% of the total weight of the acrylate soft monomers in the PBA core layer; The weight of the comonomer in the PBA core layer is 2%-10% of the total weight of the alkyl acrylate soft monomer and comonomer in the PBA core layer. The weight of the crosslinking agent in the PBA core layer is 0.2%-2% of the total weight of the alkyl acrylate soft monomers and comonomers in the PBA core layer; The grafting agent in the PBA core layer accounts for 0.1%-0.6% of the total weight of the alkyl acrylate soft monomers and comonomers in the PBA core layer. The alkyl acrylate soft monomer in the PBA core layer is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, and isooctyl acrylate. The crosslinking agent in the PBA core layer is selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate, and diallyl maleate. The aromatic vinyl monomer in the comonomer is selected from one or both of styrene and α-methylstyrene; The vinyl cyanate monomer in the comonomer is selected from one or both of acrylonitrile and methacrylonitrile; The acrylate hard monomer in the comonomer is methyl methacrylate; The grafting agent in the outer core layer of the PBA is allyl methacrylate. The outer core layer of the PBA contains double bonds that can be grafted; The particle size of the PBA core, which consists of the PBA core and the PBA core layer, is 150-600 nm.

7. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 6, characterized in that, The alkyl acrylate soft monomer in the PBA core layer is selected from one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, and isooctyl acrylate.

8. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 6, characterized in that, The alkyl acrylate soft monomer in the PBA core layer is butyl acrylate.

9. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 6, characterized in that, The crosslinking agent in the PBA core layer is ethylene glycol dimethacrylate.

10. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 6, characterized in that, The aromatic vinyl monomer in the copolymer is styrene.

11. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 6, characterized in that, The vinyl cyanide monomer in the comonomer is acrylonitrile.

12. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 1, characterized in that, The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion has one or more of the following characteristics: The dry weight of the PBA core, which consists of the PBA core and the PBA core layer, is 40%-60% of the total weight of the shell-mixed monomers in the PBA-g-SAN shell. The shell-mixed monomers comprise aromatic vinyl monomers, vinyl cyanide monomers, and optionally acrylate monomers; The aromatic vinyl monomers in the shell-mixed monomers are selected from one or both of styrene and α-methylstyrene; The vinyl cyanate monomer in the shell-mixed monomer is selected from one or both of acrylonitrile and methacrylonitrile; The acrylate monomers in the shell-mixed monomers include hard acrylate monomers; The grafting rate of the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles is ≥40%; The particle size of the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer particles is 190-700 nm.

13. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 12, characterized in that, The aromatic vinyl monomer in the shell-mixed monomer is styrene.

14. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 12, characterized in that, The vinyl cyanide monomer in the shell-mixed monomer is acrylonitrile.

15. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion as described in claim 12, characterized in that, The acrylate hard monomer in the shell-mixed monomer is methyl methacrylate.

16. A method for preparing a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion, characterized in that, The method includes the following steps: (1) Preparation of PBA core emulsion: First, a portion of alkyl acrylate soft monomers is polymerized in the presence of an initiator, a crosslinking agent, an emulsifier and water to obtain a PBA inner core emulsion. Then, a mixture containing the remaining alkyl acrylate soft monomers, a crosslinking agent and an initiator is continuously added to the PBA inner core emulsion for polymerization to form a PBA outer core layer on the surface of the PBA inner core, thus obtaining a PBA core emulsion. The weight of the alkyl acrylate soft monomers added when preparing the PBA inner core emulsion accounts for 10%-30% of the total weight of the alkyl acrylate soft monomers added when preparing the PBA core emulsion. (2) Preparation of PBA core emulsion: First, a portion of alkyl acrylate soft monomers are polymerized in the presence of PBA core emulsion, initiator and crosslinking agent to form PBA core layer on the surface of PBA outer core, thus obtaining PBA core emulsion. Then, a pre-emulsion containing the remaining alkyl acrylate soft monomers, comonomers, crosslinking agent, grafting agent, initiator and emulsifier is continuously added to PBA core emulsion for polymerization to form PBA outer core layer on the surface of PBA core, thus obtaining PBA core emulsion. The weight of alkyl acrylate soft monomers added when preparing PBA core emulsion accounts for 5%-10% of the total weight of alkyl acrylate soft monomers added when preparing PBA core emulsion. The comonomers include one or more selected from aromatic vinyl monomers and vinyl cyanide monomers and optional acrylate hard monomers. (3) Preparation of PBA-g-SAN shell emulsion: First, a portion of the shell-layer mixed monomers are polymerized in the presence of PBA core emulsion and initiator to form PBA-g-SAN inner shell layer on the surface of PBA outer core, thus obtaining PBA-g-SAN inner shell emulsion. Then, a pre-emulsion containing the remaining shell-layer mixed monomers, initiator and emulsifier is continuously added to the PBA-g-SAN inner shell emulsion for polymerization, thus forming PBA-g-SAN outer shell layer on the surface of PBA-g-SAN inner shell, thus obtaining PBA-g-SAN shell emulsion, namely the multi-core-shell structure acrylate-styrene-acrylonitrile copolymer emulsion. The weight of the shell-layer mixed monomers added when preparing PBA-g-SAN inner shell emulsion accounts for 10%-40% of the total weight of the shell-layer mixed monomers added when preparing PBA-g-SAN shell emulsion. The shell-layer mixed monomers include one or more of aromatic vinyl monomers and vinyl cyanide monomers and optional acrylate monomers. Wherein, the crosslinking degree of the PBA inner core is greater than that of the PBA outer core layer, the crosslinking degree of the PBA inner core layer is greater than that of the PBA outer core layer, and the crosslinking degree of both the PBA inner core layer and the PBA outer core layer is less than that of the PBA core. The PBA core has a gel content of ≥90%; The PBA core has a gel content of 80%-90%; The PBA-g-SAN shell has a gel content of 60%-75%.

17. The method as described in claim 16, characterized in that, Step (1) has one or more of the following characteristics: In step (1), the weight of the initiator added during the preparation of the PBA core emulsion accounts for 10%-30% of the total weight of the initiator added during the preparation of the PBA core emulsion; In step (1), the weight of the crosslinking agent added during the preparation of the PBA core emulsion accounts for 30%-60% of the total weight of the crosslinking agent added during the preparation of the PBA core emulsion; The total weight of alkyl acrylate soft monomers added during the preparation of PBA core emulsion accounts for 97%-99.8% of the dry matter weight of the PBA core emulsion. The total weight of the crosslinking agent added during the preparation of PBA core emulsion is 0.2%-2% of the total weight of the alkyl acrylate soft monomers; The alkyl acrylate soft monomer is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, and isooctyl acrylate; The crosslinking agent is selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate, and diallyl maleate. The emulsifier is selected from one or more of alkyl aryl ether sulfates, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and alkyl diphenyl ether disulfonates; The initiator is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate, cumene hydroperoxide, dicumene hydroperoxide, benzoyl peroxide, and dicarbonate peroxide; In step (1), the reaction system for preparing the PBA core emulsion also contains one or more of the following: complexing agents, electrolytes, and pH buffers. When preparing the PBA core emulsion, the reaction temperature is 60-75℃, the reaction time for preparing the PBA inner core emulsion is 0.5-1.0h, and the time for continuously adding the mixture is 2.0-4.5h. The PBA core has a particle size of 70-130 nm.

18. The method as described in claim 17, characterized in that, The alkyl acrylate soft monomer mentioned in step (1) is selected from one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate.

19. The method as described in claim 17, characterized in that, The alkyl acrylate soft monomer mentioned in step (1) is butyl acrylate.

20. The method as described in claim 17, characterized in that, The crosslinking agent mentioned in step (1) is ethylene glycol dimethacrylate.

21. The method as described in claim 17, characterized in that, The emulsifier mentioned in step (1) is selected from one or both of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

22. The method as described in claim 17, characterized in that, The initiator mentioned in step (1) is potassium persulfate.

23. The method as described in claim 16, characterized in that, Step (2) has one or more of the following characteristics: In step (2), the weight of the initiator added during the preparation of the PBA core emulsion accounts for 15%-20% of the total weight of the initiator added during the preparation of the PBA core emulsion; In step (2), the weight of the crosslinking agent added during the preparation of the PBA core emulsion accounts for 10%-30% of the total weight of the crosslinking agent added during the preparation of the PBA core emulsion; The total weight of alkyl acrylate soft monomers added during the preparation of PBA core emulsion accounts for 85%-90% of the dry matter weight of the PBA core emulsion; The dry weight of the PBA core emulsion added during the preparation of the PBA core emulsion is 1.5%-3.0% of the total weight of the acrylate soft monomers added during the preparation of the PBA core emulsion. The weight of the comonomer added during the preparation of PBA core emulsion is 2%-10% of the total weight of the alkyl acrylate soft monomer and the comonomer; The weight of the crosslinking agent added during the preparation of PBA core emulsion is 0.2%-2% of the total weight of the alkyl acrylate soft monomer and comonomer; The grafting agent added during the preparation of PBA core emulsion is 0.1%-0.6% of the total weight of the alkyl acrylate soft monomer and comonomer; The alkyl acrylate soft monomer is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, and isooctyl acrylate; The crosslinking agent is selected from one or more of triallyl cyanurate, divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate, and diallyl maleate. The emulsifier is selected from one or more of alkyl aryl ether sulfates, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and alkyl diphenyl ether disulfonates; The initiator is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate, cumene hydroperoxide, dicumene hydroperoxide, benzoyl peroxide, and dicarbonate peroxide; The aromatic vinyl monomer is selected from one or both of styrene and α-methylstyrene; The vinyl cyanide monomer is selected from one or both of acrylonitrile and methacrylonitrile; The acrylate hard monomer is methyl methacrylate; The grafting agent is allyl methacrylate; In step (2), the reaction system for preparing the PBA core emulsion also contains one or more of the following: grafting agent, complexing agent, electrolyte, and pH buffer. When preparing PBA core emulsion, the reaction temperature is 70-85℃, the reaction time for preparing PBA core emulsion is 0.5-1.0h, the time for continuously adding the mixture is 3-4.5h, and the reaction continues for 1-2h after the mixture is added. The outer core layer of the PBA contains double bonds that can be grafted; The PBA core has a particle size of 150-600 nm.

24. The method as described in claim 23, characterized in that, The alkyl acrylate soft monomer mentioned in step (2) is selected from one or more of butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate and isooctyl acrylate.

25. The method as described in claim 23, characterized in that, The alkyl acrylate soft monomer mentioned in step (2) is butyl acrylate.

26. The method as described in claim 23, characterized in that, The crosslinking agent mentioned in step (2) is ethylene glycol dimethacrylate.

27. The method as described in claim 23, characterized in that, The emulsifier mentioned in step (2) is selected from one or both of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

28. The method as described in claim 23, characterized in that, The initiator mentioned in step (2) is potassium persulfate or cumene hydroperoxide.

29. The method as described in claim 23, characterized in that, The aromatic vinyl monomer mentioned in step (2) is styrene.

30. The method as described in claim 23, characterized in that, The vinyl cyanide monomer mentioned in step (2) is acrylonitrile.

31. The method as described in claim 16, characterized in that, Step (3) has one or more of the following characteristics: In step (3), the weight of the initiator added during the preparation of the PBA-g-SAN inner shell emulsion accounts for 10%-40% of the total weight of the initiator added during the preparation of the PBA-g-SAN shell emulsion; The dry weight of the PBA core emulsion added during the preparation of the PBA-g-SAN shell emulsion is 40%-60% of the total weight of the shell-shell mixed monomers added during the preparation of the PBA-g-SAN shell emulsion. The initiator is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate, cumene hydroperoxide, dicumene hydroperoxide, benzoyl peroxide, and dicarbonate peroxide; The emulsifier is selected from one or more of alkyl aryl ether sulfates, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and alkyl diphenyl ether disulfonates; The shell-mixed monomers comprise aromatic vinyl monomers, vinyl cyanide monomers, and optionally acrylate monomers; The aromatic vinyl monomer is selected from one or both of styrene and α-methylstyrene; The vinyl cyanide monomer is selected from one or both of acrylonitrile and methacrylonitrile; The acrylate monomers include hard acrylate monomers; In step (3), the reaction system for preparing the PBA-g-SAN inner shell emulsion also contains one or more of the following: complexing agents, electrolytes, pH buffers, emulsifiers, and reducing agents. In step (3), the materials continuously added during the preparation of the PBA-g-SAN shell emulsion also include a molecular weight regulator and / or a pH buffer, wherein the molecular weight regulator is selected from one or more of tert-dodecyl mercaptan, n-dodecyl mercaptan and n-octyl mercaptan; The reaction temperature for preparing the PBA-g-SAN shell emulsion is 65-80℃, the reaction time for preparing the PBA-g-SAN inner shell emulsion is 0.5-1.0h, the time for continuously adding the mixture is 3.0-4.5h, and the reaction continues for 1-2h after the mixture is added. The grafting rate of the PBA-g-SAN shell is ≥40%; The particle size of the PBA-g-SAN shell is 190-700 nm.

32. The method as described in claim 31, characterized in that, The initiator mentioned in step (3) is cumene hydroperoxide.

33. The method as described in claim 31, characterized in that, The emulsifier mentioned in step (3) is selected from one or both of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

34. The method as described in claim 31, characterized in that, The aromatic vinyl monomer mentioned in step (3) is styrene.

35. The method as described in claim 31, characterized in that, The vinyl cyanide monomer mentioned in step (3) is acrylonitrile.

36. The method as described in claim 31, characterized in that, The acrylate hard monomer mentioned in step (3) is methyl methacrylate.

37. The method as described in claim 31, characterized in that, The molecular weight regulator added in step (3) when preparing the PBA-g-SAN shell emulsion is tert-dodecyl mercaptan.

38. A multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion prepared by any one of claims 16-37.

39. A multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder, characterized in that, The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder is prepared from the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion according to any one of claims 1-15 and 38.

40. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder as described in claim 39, characterized in that, The core-shell structured acrylate-styrene-acrylonitrile copolymer powder is prepared by the following method: the core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion is coagulated, and after the emulsion is completely demulsified, it is matured to obtain flocculents. After solid-liquid separation and drying, the core-shell structured acrylate-styrene-acrylonitrile copolymer powder is obtained.

41. The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder as described in claim 40, characterized in that, The multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder was prepared by the following method: The core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion is heated to 75-85°C. Then, based on 100 parts by weight of the dry weight of the core-shell structured acrylate-styrene-acrylonitrile copolymer emulsion, 3-6 parts by weight of a salt solution are added dropwise to cause the emulsion to coagulate. The solid content of the coagulation system is adjusted to 15wt%-30wt%. After the emulsion is completely demulsified, the temperature is raised to 90-100°C and matured for 25-35 minutes to obtain flocculants. The flocculants are then subjected to solid-liquid separation and dried at 60-70°C to obtain the core-shell structured acrylate-styrene-acrylonitrile copolymer powder.

42. An acrylate-styrene-acrylonitrile resin, characterized in that, The acrylate-styrene-acrylonitrile resin is prepared from a blend comprising a multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder and a styrene-acrylonitrile resin as described in any one of claims 39-41.

43. The acrylate-styrene-acrylonitrile resin according to claim 42, characterized in that, The acrylate-styrene-acrylonitrile resin is prepared by granulation of a blend containing the multi-core-shell structured acrylate-styrene-acrylonitrile copolymer powder and styrene-acrylonitrile resin using a twin-screw extruder at 180-240°C.

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