Toughening agent for polycarbonate as well as preparation method and application of toughening agent

Abstract

The invention belongs to the technical field of toughening agents for polycarbonate, and particularly relates to a toughening agent for polycarbonate as well as a preparation method and application of the toughening agent. The preparation method comprises the following steps: mixing alkyl acrylate, a cross-linking agent, an emulsifier and deionized water to obtain a monomer pre-emulsion; polymerizing under the action of an initiator; adding dibutyl maleate, alkyl methacrylate, alkyl acrylate and an emulsifier into the system, and polymerizing under the action of an initiator to obtain an emulsion A; mixing and stirring dibutyl maleate, the prepared emulsion A, alkyl acrylate, a cross-linking agent, an emulsifier and deionized water, and pre-emulsifying to obtain a pre-emulsion; polymerizing under the action of an initiator; continuously adding dibutyl maleate, alkyl methacrylate and an emulsifier into the system, and polymerizing under the action of an initiator to obtain an emulsion B; the impact property, the tensile strength and the elongation at break of the polycarbonate blend added with the toughening agent are improved, and meanwhile, the weather resistance of the polycarbonate blend is good.

Description

Technical Field

[0001] The invention belongs to the technical field of toughening agents for polycarbonate, and in particular relates to a toughening agent for polycarbonate and a preparation method and application thereof. Background Art

[0002] Polycarbonate is a high-performance polymer containing a carbonate group. According to its functional group, polycarbonate is divided into aliphatic-aromatic, aliphatic, aromatic and other types of polycarbonates.

[0003] In practical applications, due to the poor mechanical properties of aliphatic-aromatic polycarbonates and aliphatic polycarbonates, only bisphenol A type polycarbonate was finally industrialized. Bisphenol A type polycarbonate has a benzene ring and a carbonate structure, which causes the rigidity of the molecular chain to be very large. Due to the special structure of this type of polycarbonate, it is determined that it has excellent mechanical properties, heat resistance, transparency and electrical insulation, and is widely used in the fields of automobiles, electronic appliances, optical instruments, medical equipment, etc. However, the rigidity of polycarbonate is too high, and it is easy to break when subjected to impact or stress, which limits its application in some aspects. Therefore, it is particularly important to toughen polycarbonate.

[0004] At present, the commonly used polycarbonate tougheners on the market are methyl methacrylate-butadiene-styrene terpolymer (MBS) and core-shell tougheners with silica as the core. The core-shell toughener with silica as the core is not as tough as polymer elastomers because the core layer is silica. Although methyl methacrylate-butadiene-styrene terpolymer (MBS) has a certain effect of improving impact and tensile properties, it has poor weather resistance and is expensive.

[0005] In view of this, how to further study and prepare polycarbonate toughening agents with excellent toughening effect and comprehensive performance is a direction worthy of research. Summary of the invention

[0006] The purpose of the present invention is to provide a toughening agent for polycarbonate and a preparation method and application thereof in view of some problems existing in the existing polycarbonate toughening agents; the toughening agent of the present invention has good compatibility with polycarbonate due to the ester substance on the surface layer and the introduction of dibutyl maleate into the formula, which can further improve the grafting efficiency of the flexible unit on the main chain, and finally can significantly improve the impact strength, tensile properties and weather resistance of the polycarbonate toughened product.

[0007] In order to solve the above technical problems, the technical solution provided by the present invention is: In a first aspect, a method for preparing a toughening agent for polycarbonate is provided, comprising the following steps: a) Seed polymerization 1: Mix alkyl acrylate, crosslinking agent, emulsifier and deionized water, and obtain monomer pre-emulsification by pre-emulsification; heat the system to 60-70°C (for example, 62°C, 64°C, 65°C, 68°C), and carry out polymerization reaction under the action of initiator (such as peroxide); (core layer seed monomer polymerization) b) Seed polymerization II: Continue to add dibutyl maleate, alkyl methacrylate, alkyl acrylate, and emulsifier into the system and mix and stir, raise the temperature of the system to 70-80°C (for example, 72°C, 74°C, 75°C, 76°C, 78°C), and carry out polymerization reaction under the action of an initiator (such as peroxide) to obtain emulsion A; (shell seed monomer polymerization) c) Core layer polymerization: dibutyl maleate, emulsion A prepared in the above step, alkyl acrylate, crosslinking agent, emulsifier and deionized water are mixed and stirred, and pre-emulsified to obtain a pre-emulsion; the system is heated to 60-70°C (for example, 62°C, 64°C, 65°C, 68°C), and a polymerization reaction is carried out under the action of an initiator (such as peroxide); d) Shell polymerization: continue to add dibutyl maleate, alkyl methacrylate and emulsifier into the system and mix and stir, raise the temperature of the system to 70-80°C (for example, 72°C, 74°C, 75°C, 76°C, 78°C), and carry out polymerization reaction under the action of an initiator (such as peroxide) to obtain emulsion B; e) Drying: The emulsion B prepared in the above step is spray-dried to obtain a powder of the toughening agent for polycarbonate.

[0008] According to the preparation method provided by the present invention, in steps a) to d), there is no special regulation on the polymerization time. For example, the polymerization time in steps a) to d) can be independently 1-6 hours, such as 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, preferably 3-4 hours.

[0009] According to the preparation method provided by the present invention, in some embodiments, the number of carbon atoms in the alkyl group of the alkyl acrylate is 1-8 (e.g., 2, 3, 4, 5, 6, 7). The alkyl acrylate can be, for example but not limited to, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isopropyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-hexyl acrylate, n-heptyl acrylate, etc.

[0010] In some embodiments, the number of carbon atoms in the alkyl group of the methacrylate is 1-8 (e.g., 2, 3, 4, 5, 6, 7). The methacrylate alkyl ester may be, for example but not limited to, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, and n-heptyl methacrylate.

[0011] In some embodiments, the crosslinking agent is selected from one or more of divinylbenzene, allyl methacrylate, and 1,4-butanediol dimethacrylate.

[0012] In some embodiments, the emulsifier is an anionic emulsifier, preferably one or two selected from sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

[0013] In some embodiments, the initiator is a peroxide initiator, preferably one or more of potassium persulfate, ammonium persulfate, dibenzoyl peroxide and dicumyl peroxide.

[0014] According to the preparation method provided by the present invention, in some embodiments, the seed polymerization comprises the following components, based on 100 parts by total weight of each component: 21-33 parts of alkyl acrylate, for example, 22 parts, 24 parts, 25 parts, 26 parts, 28 parts, 30 parts, 32 parts, 0.4-0.7 parts of a crosslinking agent, for example, 0.45 parts, 0.5 parts, 0.55 parts, 0.6 parts, 0.65 parts, 0.2-0.4 parts of emulsifier, for example, 0.25 parts, 0.28 parts, 0.3 parts, 0.32 parts, 0.35 parts, 0.38 parts, 66-78 parts of deionized water, for example, 67 parts, 68 parts, 70 parts, 72 parts, 74 parts, 75 parts, 76 parts.

[0015] In some embodiments, in the seed polymerization, the amount of the initiator used is 0.06-0.20wt% (e.g., 0.08wt%, 0.09wt%, 0.1wt%, 0.12wt%, 0.13wt%, 0.14wt%, 0.16wt%, 0.18wt%), preferably 0.1-0.15wt%, based on the weight of the monomer.

[0016] In some embodiments, the seed polymerization method 2 includes the following components, based on 100 parts by total weight of each component: 5-20 parts (preferably 9-14 parts) of dibutyl maleate, for example, 6 parts, 8 parts, 9 parts, 10 parts, 12 parts, 14 parts, 15 parts, 18 parts, 62-90 parts of alkyl methacrylate, for example, 63 parts, 64 parts, 65 parts, 68 parts, 70 parts, 72 parts, 75 parts, 78 parts, 80 parts, 85 parts, 88 parts, 4-20 parts of alkyl acrylate, for example, 5 parts, 6 parts, 8 parts, 9 parts, 10 parts, 12 parts, 14 parts, 15 parts, 18 parts, 0.7-1.2 parts of emulsifier, for example, 0.75 parts, 0.8 parts, 0.85 parts, 0.9 parts, 0.95 parts, 1.0 parts, 1.1 parts, 1.15 parts.

[0017] In some embodiments, in the seed polymerization 2, the amount of the initiator used is 0.03-0.20wt% (for example, 0.05wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.10wt%, 0.12wt%, 0.14wt%, 0.15wt%, 0.18wt%), preferably 0.06-0.17wt%, based on the weight of the monomer.

[0018] In some embodiments, the core layer polymerization includes the following components based on 100 parts by total weight of each component: 5-20 parts (preferably 9-15 parts) of dibutyl maleate, for example, 6 parts, 8 parts, 9 parts, 10 parts, 12 parts, 15 parts, 18 parts, 1.5-2.4 parts of emulsion A, for example, 1.55 parts, 1.6 parts, 1.8 parts, 2.0 parts, 2.1 parts, 2.2 parts, 2.3 parts, 10-25 parts of alkyl acrylate, for example, 12 parts, 14 parts, 15 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 0.2-0.4 parts of a crosslinking agent, for example, 0.25 parts, 0.26 parts, 0.28 parts, 0.3 parts, 0.32 parts, 0.35 parts, 0.38 parts, 0.1-0.3 parts of emulsifier, for example, 0.15 parts, 0.18 parts, 0.2 parts, 0.22 parts, 0.25 parts, 0.28 parts, 55-80 parts of deionized water, for example, 56 parts, 60 parts, 65 parts, 70 parts, 75 parts.

[0019] In some embodiments, in the core layer polymerization, the amount of the initiator used is 0.02-0.10 wt% (eg, 0.03 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.09 wt%), preferably 0.04-0.08 wt%, based on the weight of the monomer.

[0020] In some embodiments, the shell polymerization includes the following components, based on 100 parts by total weight of each component: 9-20 parts of dibutyl maleate, for example, 10 parts, 12 parts, 14 parts, 15 parts, 18 parts, 80-90 parts of alkyl methacrylate, for example, 82 parts, 84 parts, 85 parts, 86 parts, 88 parts, 0.2-0.5 parts of emulsifier, for example, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts.

[0021] In some embodiments, in the shell polymerization, the amount of the initiator used is 0.1-1.0 wt% (eg, 0.2 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.8 wt%), preferably 0.36-0.78 wt%, based on the weight of the monomers.

[0022] In a second aspect, a toughening agent prepared by the preparation method as described above is provided.

[0023] According to the toughening agent provided by the present invention, in some embodiments, the latex particle size of the toughening agent for polycarbonate can be 150-300nm (for example, 160nm, 180nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 262nm, 264nm, 265nm, 268nm, 270nm, 272nm, 274nm, 275nm, 278nm, 280nm, 285nm, 290nm, 295nm), preferably 200-300nm, more preferably 250-300nm, and the latex particle size dispersion index can be 0.002-0.01 (for example, 0.003, 0.004, 0.005, 0.006, 0.008, 0.009).

[0024] In the third aspect, a use of the toughening agent prepared by the preparation method described above in polycarbonate is provided. In the present invention, the operation steps and process conditions for using the toughening agent in polycarbonate can be conventionally selected in the art and will not be described in detail here.

[0025] In the present invention, the pre-emulsification operation process can make the reaction of the polymerization system more stable, and the obtained product particle size is uniform, which is helpful to improve the toughening effect of the toughening agent; and the addition of dibutyl maleate in the formula can effectively increase the flexible units in the polymer side chains and improve its energy absorption effect, thereby achieving better toughening effect and purpose; and the amount of emulsifier and initiator is controlled within a suitable range, which is conducive to the smooth progress of the polymerization process and reduces the output of by-products. While controlling the particle size within a suitable range, the particle size can be further increased, thereby improving the toughening effect. The toughening agent absorbs energy by inducing silver streaks and shear bands. When its particle size is small (<100nm), it cannot effectively induce sufficient silver streaks and shear bands, resulting in limited improvement in impact strength. If its particle size (>400nm) is too large, it will lead to excessive stress concentration, causing early fracture and even reducing toughness. The particle size distribution of the toughening agent latex particles obtained by the present invention is uniform and the particle size range is 150-300nm. When the particle size is within a certain range (such as 100-300nm), the larger the particle size, the more uniform stress concentration points can be formed in the matrix, which effectively triggers the energy absorption mechanism and significantly improves the impact strength of the resin.

[0026] Compared with the prior art, the technical solution of the present invention can achieve at least the following beneficial effects: The toughening agent of the present invention can be smoothly carried out during the polymerization process, reduce the generation of by-products, increase the particle size of latex particles to a certain extent, ensure the uniformity of the particle size of the product, and help improve the toughening effect of the toughening agent; after the toughening agent of the present invention is added and applied to polycarbonate, the impact performance, tensile strength and elongation at break of the polycarbonate blend are all improved, and in addition, the polycarbonate blend product can achieve excellent toughening while maintaining good weather resistance. DETAILED DESCRIPTION

[0027] In order to understand the technical features and content of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. For those who do not specify specific conditions in the embodiments, they are carried out according to normal conditions or the conditions recommended by the manufacturer.

[0028] <Source of raw materials> Methyl methacrylate: Lihua Yilijin Refining and Chemical Co., Ltd., industrial grade; Ethyl methacrylate: Shandong Derui Polymer Materials Co., Ltd., industrial grade; Ethyl acrylate: Shandong Derui Polymer Materials Co., Ltd., industrial grade; n-Butyl acrylate, Shandong Kaitai Petrochemical Acrylic Acid Co., Ltd., industrial grade; Butyl methacrylate: Shandong Hefeng Chemical Co., Ltd., industrial pure; Potassium persulfate: Yatai Electrochemical Co., Ltd., industrial grade; Ammonium persulfate: Shandong Sanju Chemical Technology Co., Ltd., industrial pure; Dicumyl peroxide: Anhui Xiangyun Rubber & Plastic Co., Ltd. Dibenzoyl peroxide: Dongying Jinghai Chemical Co., Ltd.; Sodium dodecylbenzene sulfonate (emulsifier): Jiangsu Qingting Detergent Co., Ltd.; Divinylbenzene: Jiangsu Evergreen New Materials Technology Co., Ltd.; 1,4-Butanediol dimethacrylate: Jining Chemical Technology Co., Ltd.; Allyl methacrylate: Tai'an Jiangzhou Biotechnology Co., Ltd.; Dibutyl maleate: Shandong Yuanli Chemical Co., Ltd.; Polycarbonate, LG Chem, South Korea.

[0029] <Test Method> Izod beam notch impact: unit: KJ / m 2 , the testing standard is GB / T1843-2008; Tensile strength: unit is MPa, testing standard is GB / T1040-2006; Elongation at break: unit: %, testing standard: GB / T1040-2006; Weather resistance test: Place 2mm impact notch specimens with a size of 10×80 cm in a constant temperature and humidity chamber under lighting conditions at a temperature of 85°C and a humidity of 85% for 4 weeks, and take out a group of samples every week for impact performance testing.

[0030] In the present invention, a method for preparing a toughening agent for polycarbonate having a toughening effect can be specifically implemented as follows: a) adding alkyl acrylate, crosslinking agent, emulsifier and deionized water into a reaction kettle in a weight ratio of (21-33): (0.4-0.7): (0.2-0.4): (66-78), stirring and mixing them evenly to obtain a monomer pre-emulsion; heating the system to 60°C, introducing nitrogen into the bottom of the reaction kettle, adding the prepared initiator solvent, wherein the amount of the initiator added is 0.1-0.15wt% of the weight percentage of the monomer, controlling the reaction temperature between 60°C and 70°C, and carrying out the polymerization reaction for 3-4h; b) Then, dibutyl maleate, alkyl methacrylate, alkyl acrylate, emulsifier and peroxide are added to the system in a weight ratio of (5-20): (62-90): (4-20): (0.7-1.2): (0.08-0.12), and stirred to mix them evenly; the system is heated and the reaction temperature is controlled at 70-80°C, and the reaction is continued for 3-4 hours and then ripened to obtain emulsion A; c) adding dibutyl maleate, emulsion A prepared as above, alkyl acrylate, crosslinking agent, emulsifier and deionized water into a reaction kettle in a weight ratio of (5-20): (1.5-2.4): (10-25): (0.2-0.4): (0.1-0.3): (55-80), stirring and mixing them evenly to obtain a pre-emulsion; heating the system to 50° C., introducing nitrogen into the bottom of the reaction kettle, adding the prepared initiator solvent, wherein the amount of the initiator added is 0.04-0.08wt% of the weight percentage of the monomer, heating the system and controlling the reaction temperature between 60° C. and 70° C., and carrying out polymerization reaction for 3-4 hours; d) After that, dibutyl maleate, alkyl methacrylate, emulsifier and peroxide are added into the system in a weight ratio of (9-20):(80-90):(0.2-0.5):(0.4-0.7), and stirred to mix them evenly. The reaction temperature is controlled at 70-80°C, and the polymerization reaction is continued for 3-4 hours and then matured to obtain emulsion B.

[0031] The prepared emulsion B is spray-dried to obtain a toughening agent powder for polycarbonate.

[0032] Example Embodiment 1: The preparation method of a toughening agent for polycarbonate comprises the following steps: a) In a 1-ton reactor, 155 kg of n-butyl acrylate, 3.11 kg of divinylbenzene, 1.56 kg of sodium dodecylbenzene sulfonate and 421 kg of deionized water were added in sequence, and stirring was started to mix them evenly to obtain a monomer pre-emulsion; the system was heated to 60°C, nitrogen was introduced into the bottom of the reactor, 0.16 kg of diisopropylbenzene peroxide was added, the reaction temperature was controlled at 65°C, and the polymerization reaction was carried out for 3.5 hours; b) 13.65 kg of dibutyl maleate, 92 kg of ethyl methacrylate, 11 kg of n-butyl acrylate, 1 kg of sodium dodecylbenzene sulfonate and 0.1 kg of diisopropylbenzene peroxide were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 3 hours, and then ripened to obtain emulsion A.

[0033] c) 81 kg of dibutyl maleate, 12.73 kg of emulsion A prepared in the above step, 134 kg of n-butyl acrylate, 1.72 kg of divinylbenzene, 1.17 kg of sodium dodecylbenzene sulfonate and 414 kg of deionized water were added to a 1-ton reactor, and stirred to mix them evenly to obtain a pre-emulsion; the system was heated to 50° C., nitrogen was introduced into the bottom of the reactor, 0.11 kg of diisopropylbenzene peroxide was added, the reaction temperature was controlled at about 65° C., and the polymerization reaction was carried out for 3 hours; d) 9 kg of dibutyl maleate, 41 kg of ethyl methacrylate, 0.19 kg of sodium dodecylbenzene sulfonate and 0.3 kg of diisopropylbenzene peroxide were added to the system, the reaction temperature was controlled at 75°C, the reaction was continued for 4 hours and then matured to obtain emulsion B with a monomer conversion rate of 97.98%.

[0034] The prepared emulsion B is spray-dried to obtain a toughening agent powder for polycarbonate.

[0035] Embodiment 2: The preparation method of a toughening agent for polycarbonate comprises the following steps: a) In a 1-ton reactor, 160 kg of ethyl acrylate, 3 kg of 1,4-butanediol dimethacrylate, 1.3 kg of sodium dodecylbenzene sulfonate, and 400 kg of deionized water were added in sequence, and stirring was started to mix them evenly to obtain a monomer pre-emulsion; the system was heated to 50°C, nitrogen was introduced into the bottom of the reactor, 0.18 kg of ammonium persulfate was added, the reaction temperature was controlled at 60°C, and the polymerization reaction was carried out for 3.5 hours; b) 13.65 kg of dibutyl maleate, 92 kg of methyl methacrylate, 11 kg of ethyl acrylate, 1 kg of sodium dodecylbenzene sulfonate and 0.1 kg of ammonium persulfate were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 3 hours, and then ripened to obtain emulsion A.

[0036] c) 81 kg of dibutyl maleate, 12.73 kg of emulsion A prepared in the above step, 134 kg of ethyl acrylate, 1.72 kg of 1,4-butanediol dimethacrylate, 1.17 kg of sodium dodecylbenzene sulfonate, and 414 kg of deionized water were added to a 1-ton reactor, and stirred to mix them evenly to obtain a pre-emulsion; the system was heated to 50° C., nitrogen was introduced into the bottom of the reactor, 0.11 kg of ammonium persulfate was added, the reaction temperature was controlled at about 65° C., and the polymerization reaction was carried out for 3 hours; d) 9 kg of dibutyl maleate, 41 kg of methyl methacrylate, 0.19 kg of sodium dodecylbenzene sulfonate and 0.3 kg of ammonium persulfate were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 4 hours and then matured to obtain emulsion B with a monomer conversion rate of 98.25%.

[0037] The prepared emulsion B is spray-dried to obtain a toughening agent powder for polycarbonate.

[0038] Example 3 The preparation method of a toughening agent for polycarbonate comprises the following steps: a) In a 1-ton reactor, 160 kg of n-butyl acrylate, 3 kg of allyl methacrylate, 1.3 kg of sodium dodecylbenzene sulfonate, and 400 kg of deionized water were added in sequence, and stirring was started to mix them evenly to obtain a monomer pre-emulsion; the system was heated to 50°C, nitrogen was introduced into the bottom of the reactor, 0.16 kg of potassium persulfate was added, the reaction temperature was controlled at 60°C, and the polymerization reaction was carried out for 3.5 hours; b) 18 kg of dibutyl maleate, 100 kg of methyl methacrylate, 12 kg of n-butyl acrylate, 1 kg of sodium dodecylbenzene sulfonate and 0.1 kg of potassium persulfate were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 3 hours, and then ripened to obtain emulsion A.

[0039] c) 81 kg of dibutyl maleate, 12.73 kg of emulsion A prepared in the above step, 134 kg of n-butyl acrylate, 1.72 kg of allyl methacrylate, 1.17 kg of sodium dodecylbenzene sulfonate and 414 kg of deionized water were added to a 1-ton reactor, and stirred to mix them evenly to obtain a pre-emulsion; the system was heated to 50° C., nitrogen was introduced into the bottom of the reactor, 0.11 kg of potassium persulfate was added, the reaction temperature was controlled at about 65° C., and the polymerization reaction was carried out for 3 hours; d) 9 kg of dibutyl maleate, 41 kg of methyl methacrylate, 0.19 kg of sodium dodecylbenzene sulfonate and 0.3 kg of potassium persulfate were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 4 hours and then matured to obtain emulsion B with a monomer conversion rate of 97.31%.

[0040] The prepared emulsion B is spray-dried to obtain a toughening agent powder for polycarbonate.

[0041] Embodiment 4: The preparation method of a toughening agent for polycarbonate comprises the following steps: a) In a 1-ton reactor, 160 kg of n-butyl acrylate, 3 kg of divinylbenzene, 1.3 kg of sodium dodecylbenzene sulfonate and 400 kg of deionized water were added in sequence, and stirring was started to mix them evenly to obtain a monomer pre-emulsion; the system was heated to 50°C, nitrogen was introduced into the bottom of the reactor, 0.16 kg of potassium persulfate was added, the reaction temperature was controlled at 60°C, and the polymerization reaction was carried out for 3.5 hours; b) 18 kg of dibutyl maleate, 100 kg of butyl methacrylate, 12 kg of n-butyl acrylate, 1 kg of sodium dodecylbenzene sulfonate and 0.1 kg of potassium persulfate were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 3 hours, and then ripened to obtain emulsion A.

[0042] c) 90 kg of dibutyl maleate, 12.73 kg of emulsion A prepared in the above step, 124 kg of n-butyl acrylate, 1.72 kg of divinylbenzene, 1 kg of sodium dodecylbenzene sulfonate, and 414 kg of deionized water were added to a 1-ton reactor, and stirred to mix them evenly to obtain a pre-emulsion; the system was heated to 50° C., nitrogen was introduced into the bottom of the reactor, 0.11 kg of potassium persulfate was added, the reaction temperature was controlled at about 65° C., and the polymerization reaction was carried out for 3 hours; d) 9 kg of dibutyl maleate, 41 kg of butyl methacrylate, 0.19 kg of sodium dodecylbenzene sulfonate and 0.3 kg of potassium persulfate were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 4 hours and then matured to obtain emulsion B with a monomer conversion rate of 97.20%.

[0043] The prepared emulsion B is spray-dried to obtain a toughening agent powder for polycarbonate.

[0044] Embodiment 5: The preparation method of a toughening agent for polycarbonate comprises the following steps: a) In a 1-ton reactor, 155 kg of n-butyl acrylate, 3 kg of divinylbenzene, 1.3 kg of sodium dodecyl sulfate, and 400 kg of deionized water were added in sequence, and stirring was started to mix them evenly to obtain a monomer pre-emulsion; the system was heated to 50°C, nitrogen was introduced into the bottom of the reactor, 0.2 kg of dibenzoyl peroxide was added, the reaction temperature was controlled at 60°C, and the polymerization reaction was carried out for 3.5 hours; b) 18 kg of dibutyl maleate, 100 kg of methyl methacrylate, 12 kg of n-butyl acrylate, 1 kg of sodium dodecyl sulfate and 0.1 kg of dibenzoyl peroxide were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 3 hours, and then ripened to obtain emulsion A.

[0045] c) 90 kg of dibutyl maleate, 12.73 kg of emulsion A, 124 kg of n-butyl acrylate, 1.72 kg of divinylbenzene, 1 kg of sodium dodecyl sulfate and 414 kg of deionized water were added to a 1-ton reactor, and stirred to mix them evenly to obtain a pre-emulsion; the system was heated to 50° C., nitrogen was introduced into the bottom of the reactor, 0.17 kg of dibenzoyl peroxide was added, the reaction temperature was controlled at about 65° C., and the polymerization reaction was carried out for 3 hours; d) 5 kg of dibutyl maleate, 45 kg of methyl methacrylate, 0.19 kg of sodium dodecyl sulfate and 0.3 kg of dibenzoyl peroxide were added to the system, the reaction temperature was controlled at 70°C, and the reaction was continued for 3.5 hours and then matured to obtain emulsion B with a monomer conversion rate of 98.21%.

[0046] The prepared emulsion B is spray-dried to obtain a toughening agent powder for polycarbonate.

[0047] Comparative Example 1: The preparation method of a toughening agent for polycarbonate comprises the following steps: a) In a 1-ton reactor, 155 kg of n-butyl acrylate, 3.28 kg of allyl methacrylate, 1.77 kg of sodium dodecylbenzene sulfonate and 500 kg of deionized water were added in sequence, and stirring was started to mix them evenly to obtain a monomer pre-emulsion; the system was heated to 50°C, nitrogen was introduced into the bottom of the reactor, 0.2 kg of potassium persulfate was added, the reaction temperature was controlled at 60°C, and the polymerization reaction was carried out for 3 hours; b) 105.65 kg of methyl methacrylate, 11 kg of n-butyl acrylate, 1 kg of sodium dodecylbenzene sulfonate and 0.15 kg of potassium persulfate were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 3 hours, and then ripened to obtain emulsion A with a monomer conversion rate of 97.11%.

[0048] The prepared emulsion A is spray-dried to obtain a toughening agent powder for polycarbonate.

[0049] Comparative Example 2: The preparation method of a toughening agent for polycarbonate comprises the following steps: a) In a 1-ton reactor, 105 kg of n-butyl acrylate, 50 kg of dibutyl maleate, 3.28 kg of allyl methacrylate, 1.77 kg of sodium dodecylbenzene sulfonate, and 500 kg of deionized water were added in sequence, and stirring was started to mix them evenly to obtain a monomer pre-emulsion; the system was heated to 50°C, nitrogen was introduced into the bottom of the reactor, 0.2 kg of potassium persulfate was added, the reaction temperature was controlled at 60°C, and the polymerization reaction was carried out for 3.5 hours; b) 19 kg of dibutyl maleate, 86.65 kg of methyl methacrylate, 11 kg of n-butyl acrylate, 1 kg of sodium dodecylbenzene sulfonate and 0.15 kg of potassium persulfate were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 3 hours, and then ripened to obtain emulsion A with a monomer conversion rate of 97.02%.

[0050] The prepared emulsion A is spray-dried to obtain a toughening agent powder for polycarbonate.

[0051] Comparative Example 3 The preparation method of a toughening agent for polycarbonate comprises the following steps: a) In a 1-ton reactor, 155 kg of n-butyl acrylate, 3 kg of divinylbenzene, 1.3 kg of sodium dodecyl sulfate, and 400 kg of deionized water were added in sequence, and stirring was started to mix them evenly to obtain a monomer pre-emulsion; the system was heated to 50°C, nitrogen was introduced into the bottom of the reactor, 0.22 kg of dibenzoyl peroxide was added, the reaction temperature was controlled at 60°C, and the polymerization reaction was carried out for 3 hours; b) 105 kg of methyl methacrylate, 23 kg of n-butyl acrylate, 1 kg of sodium dodecyl sulfate and 0.2 kg of dibenzoyl peroxide were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 3 hours, and then ripened to obtain emulsion A.

[0052] c) 12.73 kg of emulsion A prepared in the above step, 214 kg of n-butyl acrylate, 1.72 kg of divinylbenzene, 1 kg of sodium dodecyl sulfate and 414 kg of deionized water were added to a 1-ton reactor, and stirred to mix them evenly to obtain a pre-emulsion; the system was heated to 50° C., nitrogen was introduced into the bottom of the reactor, 0.18 kg of dibenzoyl peroxide was added, the reaction temperature was controlled at about 65° C., and the polymerization reaction was carried out for 3 hours; d) 45 kg of methyl methacrylate, 0.19 kg of sodium dodecyl sulfate and 0.35 kg of dibenzoyl peroxide were added to the system, the reaction temperature was controlled at 70°C, the reaction was continued for 4 hours and then matured to obtain emulsion B with a monomer conversion rate of 98.36%.

[0053] The prepared emulsion B is spray-dried to obtain a toughening agent powder for polycarbonate.

[0054] Table 1 Polymerization parameters of toughening agents obtained in various examples and comparative examples

[0055] The toughening agent obtained by the above-mentioned embodiments and comparative examples was tested for its toughening effect on polycarbonate by the following operation and method.

[0056] The toughening agents obtained in the above-mentioned embodiments and comparative examples 1-3 were mixed with pure polycarbonate. The composition of each component in the blend raw material is shown in Table 2. The operation and process conditions for mixing and extrusion granulation are as follows: the raw materials were mixed in a high-speed mixer at 110°C, and then cooled to 44°C before discharging, and then extrusion granulation experiments were performed through an extruder. The extrusion granulation process conditions of the polycarbonate blend are shown in Table 3 below.

[0057] Table 2 Ratio of each component in polycarbonate blend products

[0058] Table 3 Extrusion granulation process conditions of polycarbonate blends

[0059] After granulation, the pellets were dried at 120°C for 4 hours and then injection molded in an injection molding machine; the injection molding process conditions are shown in Table 4 below.

[0060] Table 4 Injection molding process conditions

[0061] According to the above-mentioned testing methods and standards, the toughening agents of various embodiments and comparative examples were tested for impact resistance, weather resistance and tensile properties of polycarbonate products, as shown in Tables 5-7.

[0062] Table 5 Test data of products obtained from various embodiments and comparative examples

[0063] Table 6 Weather resistance test data of the products obtained in each embodiment and comparative example

[0064] Table 7 Tensile performance test data of the products obtained in each embodiment and comparative example

[0065] Pure polycarbonate products without toughening agent have low impact toughness, weather resistance and elongation at break. After pure polycarbonate is blended with the toughening agent prepared by the present invention, the impact toughness and tensile properties of the product are improved, and its weather resistance is also good. By comparing Examples 1-5 with Comparative Examples 1-3, it can be found that if the obtained toughening agent is a conventional two-layer core-shell structure, or a conventional two-layer core-shell structure with dibutyl maleate component added to the formula, or a four-layer core-shell structure without dibutyl maleate component added to the formula, its performance in various performance indicators is not as good as the performance of the toughening agent with a four-layer core-shell structure obtained in Examples 1-5, indicating that by adopting the technical scheme of the present invention, the polymerization process can be carried out smoothly, the generation of by-products is reduced, the particle size of the obtained toughening agent latex particles is uniform, and the particle size of the latex particles is increased within a suitable particle size range, which better improves its performance. The toughening agent of the present invention is applied to the polycarbonate toughening system, and the impact performance, tensile strength, and elongation at break of the obtained toughened blend resin or product are all improved; at the same time, the toughened blend resin or product has good weather resistance while being toughened, that is, compared with the product modified by the ordinary toughening agent, the product modified by the toughening agent provided by the present invention has improved impact performance, and after experiencing the same weathering conditions, its impact performance is still high.

[0066] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for preparing a toughening agent for polycarbonate, characterized in that: The following steps are involved: a) Seed polymerization 1: Mix and stir alkyl acrylate, crosslinking agent, emulsifier and deionized water, and obtain monomer pre-emulsification; heat the system to 60-70°C, and carry out polymerization reaction under the action of initiator; b) Seed polymerization II: Continue to add dibutyl maleate, alkyl methacrylate, alkyl acrylate and emulsifier into the system and mix and stir, raise the temperature of the system to 70-80°C, and carry out polymerization reaction under the action of the initiator to obtain emulsion A; c) Core layer polymerization: dibutyl maleate, emulsion A prepared in the above step, alkyl acrylate, crosslinking agent, emulsifier and deionized water are mixed and stirred, and pre-emulsified to obtain a pre-emulsion; the system is heated to 60-70°C, and a polymerization reaction is carried out under the action of an initiator; d) Shell polymerization: continue to add dibutyl maleate, alkyl methacrylate and emulsifier into the system and mix and stir, raise the temperature of the system to 70-80°C, and carry out polymerization reaction under the action of the initiator to obtain emulsion B; e) Drying: The emulsion B prepared in the above step is spray-dried to obtain a powder of the toughening agent for polycarbonate.

2. The preparation method according to claim 1, characterized in that: The alkyl group in the alkyl acrylate has 1 to 8 carbon atoms.

3. The preparation method according to claim 1, characterized in that: The alkyl group in the alkyl methacrylate has 1 to 8 carbon atoms.

4. The preparation method according to claim 1, characterized in that: The crosslinking agent is selected from one or more of divinylbenzene, allyl methacrylate and 1,4-butanediol dimethacrylate.

5. The preparation method according to claim 1, characterized in that: The emulsifier is an anionic emulsifier.

6. The preparation method according to claim 1, characterized in that: The initiator is a peroxide initiator.

7. The preparation method according to claim 1, characterized in that: In the seed polymerization, the total weight of each component is 100 parts, including the following components: 21-33 parts of alkyl acrylate, 0.4-0.7 parts of cross-linking agent, 0.2-0.4 parts of emulsifier, 66-78 parts deionized water.

8. The preparation method according to claim 1, characterized in that: In the seed polymerization 2, the total weight of each component is 100 parts, including the following components: 5-20 parts of dibutyl maleate, 62-90 parts of alkyl methacrylate, 4-20 parts of alkyl acrylate, 0.7-1.2 parts of emulsifier.

9. The preparation method according to claim 1, characterized in that: In the core layer polymerization, the total weight of each component is 100 parts, including the following components: 5-20 parts of dibutyl maleate, 1.5-2.4 parts of Emulsion A, 10-25 parts of alkyl acrylate, 0.2-0.4 parts of cross-linking agent, 0.1-0.3 parts of emulsifier, 55-80 parts deionized water.

10. The preparation method according to any one of claims 1 to 9, characterized in that: In the shell polymerization, the total weight of each component is 100 parts, including the following components: 9-20 parts of dibutyl maleate, 80-90 parts of alkyl methacrylate, 0.2-0.5 parts of emulsifier.

11. A toughening agent obtained by the preparation method according to any one of claims 1 to 10.

12. Use of the toughening agent obtained by the preparation method according to any one of claims 1 to 10 in polycarbonate.

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