High-transparency weather-resistant PMMA resin toughening agent with core-shell structure and preparation method of PMMA resin toughening agent

Abstract

The invention belongs to the technical field of synthetic resin, and particularly relates to a high-transparency weather-resistant PMMA (polymethyl methacrylate) resin toughening agent with a core-shell structure and a preparation method of the PMMA resin toughening agent. The preparation method comprises the following steps: preparing core-layer latex from an acrylate monomer and a vinyl aromatic monomer through emulsion copolymerization, then preparing a shell layer with the refractive index completely consistent with that of PMMA resin on the surface of the core-layer latex through graft polymerization, and finally preparing the PMMA resin toughening agent with the core-shell structure. The toughening agent can effectively toughen the PMMA resin on the premise that the light transmittance of the PMMA resin is not lower than 85%, so that the elongation at break of the PMMA resin is remarkably improved, and the film drawing requirement of the PMMA resin can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic resins, and in particular relates to a highly transparent weather-resistant core-shell PMMA resin toughening agent and a preparation method thereof. Background Art

[0002] PMMA resin is a material with excellent transparency. It has been widely used in automobile manufacturing and household appliances due to its excellent weather resistance and electrical insulation. During use, the biggest defect of PMMA resin is that its own toughness is poor and it becomes brittle under low temperature conditions. In order to improve the toughness of PMMA resin, researchers have prepared a variety of core-shell toughening agents to toughen PMMA resin. The core-shell toughening agent is essentially a core-shell structured particle with rubber as the core and plastic as the shell. After adding the toughening agent to the PMMA resin, the rubber part of the toughening agent will absorb energy, induce silver streaks or hollowing, and then improve the impact strength of the material.

[0003] Based on the different types of rubber used in core-shell tougheners, PMMA resin tougheners can be roughly divided into two categories, namely, all-acrylate tougheners and non-all-acrylate tougheners. The rubber of all-acrylate tougheners is acrylate rubber, generally a homopolymer or copolymer of butyl acrylate or isooctyl acrylate, and the shell is mostly polymethyl methacrylate. This type of toughener mainly includes ACR and ASA; non-all-acrylate core-shell tougheners can be understood as tougheners containing non-acrylates, such as tougheners with polybutadiene rubber as the rubber phase and ABS with styrene and acrylonitrile copolymer as the shell phase, and MBS with polybutadiene as the core and styrene and methyl methacrylate copolymer as the shell.

[0004] In recent years, there have been many reports on toughening materials with silicone rubber as the core. The above core-shell toughening agents can effectively toughen PMMA resin, and PMMA has excellent gloss and heat resistance after toughening. However, the disadvantage is that after the above toughening agents are blended with PM1MA resin to form a composite material, its transparency will be completely lost and it will turn white. This limits the application of PMMA resin in fields such as liquid crystal displays and automobile dashboards. Therefore, it is particularly important to toughen PMMA resin while ensuring light transmittance.

[0005] In order to ensure the transparency of composite materials, the following requirements must be met in principle: (1) The compatibility of various materials in the composite material should be good and phase separation should not occur; (2) The refractive index of various materials should be as close as possible to reduce the birefringence of light in the material; (3) If an island structure appears in the phase region of the composite material, the size of the island structure should be as small as possible to avoid scattering and diffraction during light propagation.

[0006] At present, there are many literature reports on transparent PMMA toughening at home and abroad, but the detailed preparation method of transparent PMMA resin toughening is not fully disclosed. For example, patent CN 103421265 A reports a transparent PMMA toughening agent, which is prepared by compounding MAAS rubber elastomer, core-shell structure toughening agent and antioxidant according to a certain proportion, but does not disclose the specific composition of MAAS and the preparation method of the core-shell toughening agent; patent CN 116333440 A discloses a PMMA alloy material and its preparation method and application. The modifier for toughening PMMA is methyl methacrylate-butadiene-styrene (MBS) toughening agent, with a specific grade of M-210. The specific preparation method of the toughening agent is not disclosed. In addition, the polybutadiene contained in the MBS component contains a large number of unsaturated double bonds, which makes its weather resistance poor, thus further limiting the use of PMMA-based materials outdoors; Patent CN117801449A discloses a light-diffusing, high-heat-resistant, high-toughness, high-gloss spray-free ASA / PMMA composite material and its preparation method. The transmittance of the prepared PMMA-based composite material exceeds 80%, but the specific synthesis method and source of the ASA toughening agent are not described. Summary of the invention

[0007] In view of this, the present invention provides a highly transparent weather-resistant core-shell PMMA resin toughening agent and a preparation method thereof.

[0008] It should be noted that, by comparing the existing disclosed technical methods, it can be seen that the preparation method and specific composition of the transparent PMMA resin toughening agent are not disclosed in the prior art reports. In view of this, the present invention combines the emulsion polymerization technology and the graft polymerization process, and prepares a highly transparent PMMA resin toughening agent by matching the refractive index of the core-shell toughening agent and the PMMA resin, thereby realizing the preparation of a high-toughness, high-transparency PMMA resin-based composite material. Its technical feature is that the prepared toughening agent contains a multi-layer (2 layers or more) core-shell structure, does not contain an unsaturated double bond structure in the composition, and has good weather resistance.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] The first technical purpose of the present invention is to provide a highly transparent and weather-resistant core-shell PMMA resin toughening agent, which is prepared by emulsion copolymerization of acrylic ester monomers and vinyl aromatic monomers into a core layer latex, and then using graft polymerization to prepare a shell layer on the surface of the core layer latex that is completely consistent with the refractive index of the PMMA resin, and finally preparing a core-shell PMMA resin toughening agent.

[0011] It is worth noting that the present invention adopts an emulsion copolymerization method to prepare elastomer particles with a refractive index similar to that of PMMA resin and without unsaturated double bonds, and then constructs a core-shell structure on its surface to enhance the compatibility with PMMA resin, and finally prepares a core-shell toughening agent through flocculation and demulsification.

[0012] The second technical purpose of the present invention is to provide a method for preparing the highly transparent weather-resistant core-shell PMMA resin toughening agent as described above.

[0013] A method for preparing a highly transparent weather-resistant core-shell PMMA resin toughening agent, the specific steps are as follows:

[0014] (1) After the negative pressure is evacuated from the reactor, 1-5 parts of an emulsifier, 0-5 parts of an electrolyte, and 100-300 parts of water are added, and after the temperature is raised, 0.1-5 parts of an initiator, 0-3 parts of a reducing agent, 95-100 parts of a polymerizable monomer A, and 0.1-5 parts of a cross-linking agent are added to react to obtain a core layer latex;

[0015] (2) taking 100 parts (dry basis) of the core layer latex prepared in step (1) and placing it in a reaction kettle, adding 0.1-3 parts of an initiator, 1-5 parts of a reducing agent, and 200-300 parts of water, heating the reaction vessel, and dropwise adding 50-150 parts of a polymerization monomer B, heating the reaction vessel to obtain a core-shell toughening agent latex;

[0016] (3) adding 2-5% by mass of calcium chloride or magnesium sulfate to the core-shell toughening agent latex obtained in step (2) for flocculation; after flocculation, centrifugal dehydration and drying are performed to obtain the highly transparent and weather-resistant core-shell PMMA resin toughening agent.

[0017] Optionally, in steps (1) and (2), the initiator is a peroxide or persulfate initiator, specifically including potassium persulfate, ammonium persulfate, cumene hydroperoxide or potassium benzoyl peroxide; the reducing agent is one or more of sodium bisulfite, ferrous sulfate and EDTA or sodium pyrophosphate chelating solution, bleaching powder, sodium disulfate, monobasic sugar (glucose or fructose) mixed. It is worth noting that the initiator selection at this stage can be selected separately from the initiator with a 10 half-life temperature lower than the reaction temperature. At this time, the reducing agent in the system can be added without or in a trace amount. If potassium persulfate is selected for initiation, the amount of reducing agent added can be selected to be 0; if the added initiator has a high 10 half-life temperature, it is necessary to add a reducing agent so that the initiator and the reducing agent form a redox system to lower the initiation temperature.

[0018] Furthermore, the initiator is cumene hydroperoxide, and the reducing agent is a chelating solution of ferrous sulfate and EDTA or sodium pyrophosphate and monobasic sugar or bleaching powder.

[0019] Optionally, in step (1), the polymerizable monomer A is composed of acrylic acid ester and vinyl aromatic compound in a mass ratio of 80-90:10:20, preferably 80-85:15:20; wherein the polymerizable monomer can be added in a one-time rapid addition or in a continuous dropwise manner; the acrylic acid ester is one or a mixture of butyl acrylate, isooctyl acrylate, and ethyl acrylate, and the vinyl aromatic compound is one or a mixture of styrene and a-methylstyrene;

[0020] The emulsifier is one or a mixture of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, fatty acid potassium, potassium disproportionated rosin acid, potassium oleate, and OP-10;

[0021] The electrolyte is an alkaline salt or a neutral salt; the alkaline salt includes sodium carbonate, potassium carbonate or sodium bicarbonate, and the neutral salt includes potassium chloride or sodium chloride;

[0022] The crosslinking agent is one of divinylbenzene, ethylene glycol dimethacrylate, allyl methacrylate, triallyl isocyanurate, triallyl tripolyhydroxide, dicyclopentene acrylate, and maleic anhydride diallyl ester, or a mixture of the two or more thereof.

[0023] Furthermore, in the step (1), the heating and reaction temperatures are both 40-85° C., and the reaction time is 1-8 h.

[0024] Optionally, in step (2), the polymerizable monomer B is one or a mixture of methyl methacrylate and ethyl acrylate.

[0025] Furthermore, in step (2), the temperature of dropping the polymerized monomer B after heating is 40-75°C, and the dropping time is 1-5 hours; the reaction temperature is 80-85°C, and the time is 0.5-1 hour. After the polymerized monomer B constructs a shell layer, its refractive index is exactly the same as that of the PMMA resin, and the shell layer can be evenly dispersed with the PMMA resin, ensuring the dispersion of the toughening agent in the matrix resin while avoiding the birefringence phenomenon, thereby improving its toughness without affecting the transparency.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention prepares a core layer latex by emulsion copolymerization of acrylic acid ester monomers and vinyl aromatic monomers, and then prepares a shell layer on the surface of the core layer latex by graft polymerization, which is completely consistent with the refractive index of PMMA resin, and finally prepares a core-shell structure PMMA resin toughening agent. The toughening agent can effectively toughen the PMMA resin under the premise of ensuring that the PMMA resin transmittance is not less than 85%, not only significantly improving the elongation at break of the PMMA resin, but also meeting the film drawing requirements of the PMMA resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0029] Figure 1 3 is the stress-strain curve of the toughened PMMA resin and the pure PMMA resin in Example 3 of the present invention. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0032] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0033] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0034] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present application.

[0035] The invention discloses a highly transparent weather-resistant core-shell structure PMMA resin toughening agent and a preparation method thereof.

[0036] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0037] It should be noted that the experimental drugs used in the following examples are all analytically pure and there is no difference between products from different manufacturers.

[0038] Example 1

[0039] (1) After the reactor is evacuated from negative pressure, 1 kg of sodium dodecyl sulfate as an emulsifier, 0.5 kg of potassium carbonate as an electrolyte, and 100 kg of water are added in sequence; then the stirring device is turned on, and after the temperature of the reactor is raised to 40° C., 0.5 kg of cumene hydroperoxide as an initiator and 0.3 kg of sodium disulfate as a reducing agent are added; 90 kg of butyl acrylate and 10 kg of styrene and 0.2 kg of divinylbenzene as a cross-linking agent are added as a polymerization monomer A; the polymerization monomer can be added in a one-time rapid manner, and the temperature of the reactor is maintained constant. The reaction is carried out for 1 hour to obtain a core layer latex;

[0040] (2) taking 100 kg of the core latex prepared in step (1), adding 0.5 kg of initiator cumene hydroperoxide, reducing agent solution (ferrous sulfate / sodium pyrophosphate / glucose mass ratio is 0.01 / 0.6 / 0.8), and 200 kg of water, heating to 65° C., and then dripping 50 kg of polymerization monomer B methyl methacrylate, the dripping time is controlled within 1 hour, and after the dripping is completed, heating to 80° C. and keeping warm for 1 hour to obtain the core-shell toughening agent latex;

[0041] (3) Adding 2% by mass of calcium chloride to the obtained core-shell toughening agent latex for flocculation, centrifugally dehydrating the obtained core-shell toughening agent after flocculation, and drying the obtained core-shell toughening agent to obtain the core-shell toughening agent.

[0042] Example 2

[0043] (1) After the reactor is evacuated from negative pressure, 1 kg of emulsifier sodium dodecylbenzene sulfonate and 0.5 kg of sodium dodecyl sulfonate; 0.2 kg of electrolyte sodium carbonate and 0.8 kg of sodium bicarbonate; and 300 kg of water are added in sequence; then the stirring device is turned on, and after the temperature of the reactor is raised to 85° C., 1 kg of initiator potassium persulfate and 0 kg of reducing agent are added; 80 kg of polymerizable monomer A containing 20 kg of isooctyl acrylate and 20 kg of styrene and 0.2 kg of crosslinking agent ethylene glycol dimethacrylate are added; wherein the polymerizable monomer is added by continuous dropwise addition, the temperature of the reactor is maintained constant, and the reaction is carried out for 8 hours to obtain the core layer latex.

[0044] (2) Take 100 kg of the dry base of the core latex prepared in step (1), add 0.5 kg of initiator cumene hydroperoxide, a reducing agent solution (ferrous sulfate / EDTA / bleaching powder mass ratio is 0.01 / 0.6 / 0.8), and 100 kg of water, then heat it to 40° C., and start dripping 100 kg of polymerization monomer B methyl methacrylate. The dripping time is controlled within 5 hours. After the dripping is completed, heat it to 80° C. and keep it warm for 1 hour to obtain the core-shell toughening agent latex.

[0045] (3) Adding 5% by weight of magnesium sulfate to the obtained core-shell toughening agent latex for flocculation, centrifugally dehydrating the obtained core-shell toughening agent after flocculation, and drying the obtained core-shell toughening agent to obtain the core-shell toughening agent.

[0046] Example 3

[0047] (1) After the reactor is evacuated from negative pressure, 0.5 kg of fatty acid potassium and 1 kg of disproportionated rosin acid potassium are added in sequence; 0.5 kg of potassium chloride and 0.5 kg of sodium chloride are added as electrolytes; and 200 kg of water is added in sequence; then the stirring device is turned on, and after the temperature of the reactor is raised to 65° C., 1 kg of ammonium persulfate as an initiator and 1 kg of sodium bisulfite as a reducing agent are added; 82 kg of butyl acrylate, 18 kg of styrene and 0.5 kg of allyl methacrylate are added as polymerization monomers A; the polymerization monomers are added by continuous dropwise addition, and the temperature of the reactor is maintained constant. The reaction is carried out for 3 hours to obtain a core layer latex.

[0048] (2) Take 100 kg of the dry base of the core latex prepared in step (1), add 0.5 kg of initiator cumene hydroperoxide, a reducing agent solution (ferrous sulfate / EDTA / bleaching powder mass ratio is 0.01 / 0.6 / 0.8), and 100 kg of water, then heat it to 60° C., and start dripping 90 kg of polymerization monomer B methyl methacrylate and 10 kg of ethyl acrylate. The dripping time is controlled within 3 hours. After the dripping is completed, heat it to 85° C. and keep it warm for 1 hour to obtain the core-shell toughening agent latex.

[0049] (3) adding 5% by mass of magnesium sulfate to the obtained core-shell toughening agent latex for flocculation, centrifugally dehydrating the obtained core-shell toughening agent after flocculation, and drying the obtained core-shell toughening agent to obtain the core-shell toughening agent.

[0050] Example 4

[0051] (1) After the reactor is evacuated from negative pressure, 1 kg of potassium oleate and 1 kg of OP10 emulsifiers, 0.5 kg of potassium chloride and 0.5 kg of sodium chloride electrolytes, and 200 kg of water are added in sequence; then the stirring device is turned on, and after the temperature of the reactor is raised to 70° C., 1 kg of benzoyl peroxide initiator and 1 kg of bleaching agent are added; 82 kg of butyl acrylate and 18 kg of styrene, 0.2 kg of triallyl isocyanurate, and 0.3 kg of triallyl tripolyacrylate are added to the polymerization monomer A; the polymerization monomer is added by continuous dropwise addition, the temperature of the reactor is maintained constant, and the reaction is carried out for 3 hours to obtain the core layer latex.

[0052] (2) Take 100 kg of the dry base of the core latex prepared in step (1), add 1 kg of initiator cumene hydroperoxide, a reducing agent solution (ferrous sulfate / EDTA / bleaching powder mass ratio is 0.01 / 0.6 / 0.8), and 100 kg of water, then heat it to 65° C., and start dripping 90 kg of polymerization monomer B methyl methacrylate and 10 kg of ethyl acrylate. The dripping time is controlled within 3 hours. After the dripping is completed, heat it to 85° C. and keep it warm for 1 hour to obtain the core-shell toughening agent latex.

[0053] (3) adding 5% by mass of magnesium sulfate to the obtained core-shell toughening agent latex for flocculation, centrifugally dehydrating the obtained core-shell toughening agent after flocculation, and drying the obtained core-shell toughening agent to obtain the core-shell toughening agent.

[0054] Example 5

[0055] (1) After the reactor is evacuated from negative pressure, 1 kg of potassium oleate and 1 kg of OP10 emulsifiers, 0.5 kg of potassium chloride and 0.5 kg of sodium chloride electrolytes, and 200 kg of water are added in sequence; then the stirring device is turned on, and after the temperature of the reactor is raised to 70° C., 1 kg of potassium persulfate initiator and 0 kg of reducing agent are added; 82 kg of butyl acrylate, 18 kg of a-methylstyrene, 2 kg of dicyclopentene acrylate, and 0.5 kg of maleic anhydride diallyl ester are added to the reactor; the polymerization monomers are added by continuous dropwise addition, and the temperature of the reactor is maintained constant. The reaction is carried out for 2 hours to obtain the core layer latex.

[0056] (2) Take 100 kg of the dry base of the core latex prepared in step (1), add 1 kg of initiator isopropyl benzene hydroperoxide, a reducing agent solution (ferrous sulfate / EDTA / fructose mass ratio is 0.01 / 0.6 / 0.8), and 100 kg of water, then heat it to 65° C., and start dripping 80 kg of polymerization monomer B methyl methacrylate and 20 kg of ethyl acrylate. The dripping time is controlled within 3 hours. After the dripping is completed, heat it to 85° C. and keep it warm for 1 hour to obtain the core-shell toughening agent latex.

[0057] (3) adding 5% by mass of magnesium sulfate to the obtained core-shell toughening agent latex for flocculation, centrifugally dehydrating the obtained core-shell toughening agent after flocculation, and drying the obtained core-shell toughening agent to obtain the core-shell toughening agent.

[0058] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the following comparative examples are used to further illustrate the technical features disclosed in the present invention, but they should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above invention content without inventive work are also considered to fall within the scope of protection of the present invention.

[0059] Comparative Example 1

[0060] (1) After the reactor is evacuated from negative pressure, 1 kg of sodium dodecyl sulfate as an emulsifier, 0.5 kg of potassium carbonate as an electrolyte, and 100 kg of water are added in sequence; then the stirring device is turned on, and after the temperature of the reactor is raised to 40° C., 0.5 kg of cumene hydroperoxide as an initiator and 0.3 kg of sodium disulfate as a reducing agent are added; 100 kg of butyl acrylate and 0.2 kg of divinylbenzene as a cross-linking agent are added to the polymerization monomer A; the polymerization monomer can be added in a one-time rapid manner, and the temperature of the reactor is maintained constant. The reaction is carried out for 1 hour to obtain the core layer latex;

[0061] (2) taking 100 kg of the core latex prepared in step (1), adding 0.5 kg of initiator cumene hydroperoxide, reducing agent solution (ferrous sulfate / sodium pyrophosphate / glucose mass ratio is 0.01 / 0.6 / 0.8), and 200 kg of water, heating to 65° C., and then dripping 50 kg of polymerization monomer B methyl methacrylate, the dripping time is controlled within 1 hour, and after the dripping is completed, heating to 80° C. and keeping warm for 1 hour to obtain the core-shell toughening agent latex;

[0062] (3) Adding 2% by mass of calcium chloride to the obtained core-shell toughening agent latex for flocculation, centrifugally dehydrating the obtained core-shell toughening agent after flocculation, and drying the obtained core-shell toughening agent to obtain the core-shell toughening agent.

[0063] Comparative Example 2

[0064] (1) After the reactor is evacuated from negative pressure, 1 kg of emulsifier sodium dodecylbenzene sulfonate and 0.5 kg of sodium dodecyl sulfonate; 0.2 kg of electrolyte sodium carbonate and 0.8 kg of sodium bicarbonate; and 300 kg of water are added in sequence; then the stirring device is turned on, and after the temperature of the reactor is raised to 85° C., 1 kg of initiator potassium persulfate and 0 kg of reducing agent are added; 100 kg of styrene and 0.2 kg of cross-linking agent ethylene glycol dimethacrylate are added to the polymerization monomer A; the polymerization monomer is added by continuous dropwise addition, and the temperature of the reactor is maintained constant. The reaction is carried out for 8 hours to obtain the core layer latex;

[0065] (2) taking 100 kg of the core latex prepared in step (1), adding 0.5 kg of initiator cumene hydroperoxide, reducing agent solution (ferrous sulfate / EDTA / diaobai block mass ratio of 0.01 / 0.6 / 0.8), 100 parts of water, heating to 40° C., and starting to drip 100 kg of polymerization monomer B methyl methacrylate, the dripping time is controlled within 5 hours, and after the dripping is completed, heating to 80° C. and keeping warm for 1 hour to obtain the core-shell toughening agent latex;

[0066] (3) Adding 5% by weight of magnesium sulfate to the obtained core-shell toughening agent latex for flocculation, centrifugally dehydrating the obtained core-shell toughening agent after flocculation, and drying the obtained core-shell toughening agent to obtain the core-shell toughening agent.

[0067] Comparative Example 3

[0068] (1) After the reactor is evacuated from negative pressure, 0.5 kg of fatty acid potassium and 1 kg of disproportionated rosin acid potassium are added in sequence; 0.5 kg of potassium chloride and 0.5 kg of sodium chloride are added as electrolytes; and 200 kg of water is added in sequence; then the stirring device is turned on, and after the temperature of the reactor is raised to 65° C., 1 kg of ammonium persulfate as an initiator and 1 kg of sodium bisulfite as a reducing agent are added; and polymerizable monomers A comprising 70 kg of butyl acrylate, 30 kg of styrene and 0.5 kg of allyl methacrylate are added; wherein the polymerizable monomers are added by continuous dropwise addition, and the temperature of the reactor is maintained constant. The reaction is carried out for 3 hours to obtain a core layer latex;

[0069] (2) taking 100 kg of the core latex prepared in step (1), adding 0.5 kg of initiator cumene hydroperoxide, reducing agent solution (ferrous sulfate / EDTA / diaobai block mass ratio of 0.01 / 0.6 / 0.8), and 100 kg of water, heating to 60° C., and then dripping 90 kg of polymerization monomer B methyl methacrylate and 10 kg of ethyl acrylate, the dripping time is controlled within 3 hours, and after the dripping is completed, heating to 85° C. and keeping warm for 1 hour to obtain the core-shell toughening agent latex;

[0070] (3) Adding 5% by weight of magnesium sulfate to the obtained core-shell toughening agent latex for flocculation, centrifugally dehydrating the obtained core-shell toughening agent after flocculation, and drying the obtained core-shell toughening agent to obtain the core-shell toughening agent.

[0071] The core-shell toughening agent obtained above was melt-blended and granulated with PMMA resin at 220°C, and prepared into standard impact specimens according to ASTM D256 standard, and prepared into standard light transmittance and haze test specimens with a thickness of 2 mm according to GB T 2410-2008 standard. The test results are shown in the following table:

[0072] Table 1 Modification effect of toughening agents prepared in Examples and Comparative Examples on PMMA resin

[0073] Impact strength (J / m) Light transmittance (%) Haze(%) Example 1 67 85 9.5 Example 2 48 86 7.4 Example 3 72 89 3.4 Example 4 73 89 2.9 Example 5 66 90 2.9 Comparative Example 1 84 ------ ------ Comparative Example 2 5 ------ ------ Comparative Example 3 23 ------ ------

[0074] It can be seen from the results of the above embodiments and comparative examples that the PMMA resin toughening agent prepared by the present invention can effectively toughen the PMMA resin under the premise of ensuring that the PMMA resin transmittance exceeds 85%. The ratio of acrylate monomers and vinyl aromatic compounds in the core layer latex during the preparation of the toughening agent is the key to determining the transmittance. For example, the difference between comparative example 1 and example 1 is that no vinyl aromatic compounds are added during the preparation of the core layer latex. The result of comparative example 1 is that although the prepared toughening agent can toughen the PMMA resin, it becomes opaque; the difference between comparative example 2 and example 2 is that no acrylate monomers are introduced during the preparation of the core layer latex. The result of comparative example 2 is that the prepared toughening agent cannot toughen the PMMA resin, and the mixed material is opaque; the difference between comparative example 3 and example 3 is that the ratio of acrylate to styrene during the preparation of the core layer is not within the scope of protection of the invention. The toughening effect of the toughening agent prepared in comparative example 3 is poor, and the prepared mixture is opaque.

[0075] In addition, in order to illustrate that the toughened PMMA resin has good tensile properties and can be used to prepare highly transparent PMMA films, Figure 1 The stress-strain curves of Example 3 and pure PMMA resin are shown in FIG. 1. As can be seen from the figure, the elongation at break of the toughened PMMA resin of Example 3 is significantly improved to 15%, which is more than 2 times higher than that of the pure PMMA resin, and the yield strength is greater than 45 MPa.

[0076] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A highly transparent weather-resistant core-shell PMMA resin toughening agent, characterized in that: The core layer latex is prepared by emulsion copolymerization of acrylate monomers and vinyl aromatic monomers, and then a shell layer with a refractive index completely consistent with that of PMMA resin is prepared on the surface of the core layer latex by graft polymerization, and finally a core-shell structure PMMA resin toughening agent is prepared.

2. A method for preparing the highly transparent weather-resistant core-shell PMMA resin toughening agent as claimed in claim 1, characterized in that: The specific steps are as follows: (1) After the negative pressure is evacuated from the reactor, 1-5 parts of an emulsifier, 0-5 parts of an electrolyte, and 100-300 parts of water are added, and after the temperature is raised, 0.1-5 parts of an initiator, 0-3 parts of a reducing agent, 95-100 parts of a polymerizable monomer A, and 0.1-5 parts of a cross-linking agent are added to react to obtain a core layer latex; (2) taking 100 parts (dry basis) of the core layer latex prepared in step (1) and placing it in a reaction kettle, adding 0.1-3 parts of an initiator, 1-5 parts of a reducing agent, and 200-300 parts of water, heating the reaction vessel, and dropwise adding 50-150 parts of a polymerization monomer B, heating the reaction vessel to obtain a core-shell toughening agent latex; (3) adding 2-5% by mass of calcium chloride or magnesium sulfate to the core-shell toughening agent latex obtained in step (2) for flocculation; after flocculation, centrifugal dehydration and drying are performed to obtain the highly transparent and weather-resistant core-shell PMMA resin toughening agent.

3. The method for preparing the highly transparent weather-resistant core-shell PMMA resin toughening agent according to claim 2, characterized in that: In steps (1) and (2), the initiator is a peroxide or persulfate initiator, specifically including potassium persulfate, ammonium persulfate, cumene hydroperoxide or potassium benzoyl peroxide; the reducing agent is one or a mixture of sodium bisulfite, ferrous sulfate and EDTA or sodium pyrophosphate chelate solution, bleaching powder, sodium disulfate, monobasic sugar (glucose or fructose).

4. The method for preparing the highly transparent weather-resistant core-shell PMMA resin toughening agent according to claim 3, characterized in that: The initiator is cumene hydroperoxide, and the reducing agent is ferrous sulfate and EDTA or sodium pyrophosphate chelate solution and monobasic sugar or bleaching block.

5. The method for preparing the highly transparent weather-resistant core-shell PMMA resin toughening agent according to claim 2 or 3, characterized in that: In step (1), the polymerizable monomer A is composed of acrylic acid ester and vinyl aromatic compound in a mass ratio of 80-90:10:20, the acrylic acid ester is one or a mixture of butyl acrylate, isooctyl acrylate, and ethyl acrylate, and the vinyl aromatic compound is one or a mixture of styrene and a-methylstyrene; The emulsifier is one or a mixture of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, fatty acid potassium, potassium disproportionated rosin acid, potassium oleate, and OP-10; The electrolyte is an alkaline salt or a neutral salt; the alkaline salt includes sodium carbonate, potassium carbonate or sodium bicarbonate, and the neutral salt includes potassium chloride or sodium chloride; The crosslinking agent is one of divinylbenzene, ethylene glycol dimethacrylate, allyl methacrylate, triallyl isocyanurate, triallyl tripolyhydroxide, dicyclopentene acrylate, and maleic anhydride diallyl ester, or a mixture of the two or more thereof.

6. The method for preparing the highly transparent weather-resistant core-shell PMMA resin toughening agent according to claim 5, characterized in that: In the step (1), the heating and reaction temperatures are both 40-85° C., and the reaction time is 1-8 hours.

7. The method for preparing the highly transparent weather-resistant core-shell PMMA resin toughening agent according to claim 2 or 3, characterized in that: In step (2), the polymerizable monomer B is one or a mixture of methyl methacrylate and ethyl acrylate.

8. The method for preparing the highly transparent weather-resistant core-shell PMMA resin toughening agent according to claim 7, characterized in that: In step (2), the temperature of adding the polymerizable monomer B after heating is 40-75°C, and the adding time is 1-5 hours; the reaction temperature is 80-85°C, and the time is 0.5-1 hour.

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