Polybutadiene latex, preparation method thereof and transparent ABS (Acrylonitrile Butadiene Styrene) resin

Abstract

The invention discloses polybutadiene latex, a preparation method thereof and transparent ABS (Acrylonitrile Butadiene Styrene) resin. In the preparation process of the polybutadiene latex, the emulsifier is additionally added at a relatively high conversion rate to promote the reaction to generate part of latex particles with small particle sizes. When the latex prepared by the method is used for further preparing the transparent ABS resin, since the latex with the particle size of 30-70nm has a rayleigh scattering effect to a certain extent, a small amount of blue light can be scattered, so that the yellow index of the resin is reduced, and the prepared transparent ABS has better hue.

Description

Technical Field

[0001] This invention discloses a method for preparing polybutadiene latex, which belongs to the field of ABS resin materials. Background Technology

[0002] Transparent ABS is a differentiated product of ABS. The emulsion grafting-bulk blending method for transparent ABS involves introducing a fourth monomer, MMA, for copolymerization. This controls the refractive index of the two resin phases to be consistent, thereby achieving light transmission. For example, patent CN101336255A mentions that the refractive index difference between the continuous phase and the dispersed phase needs to be controlled to <0.002. Transparent ABS has a higher market share in household appliances, toys, and other fields because it has better processability, chemical resistance, dimensional stability, and product yield compared to other materials (PC, PMMA, PETG).

[0003] In downstream applications, it is generally desirable for transparent ABS to have good optical properties (transmittance, haze) while also having an extremely low yellowness index, so as to facilitate color matching and appearance control of the parts.

[0004] Since general-purpose ABS resin is an opaque material, its yellow index has no significant impact on the manufacturing process, and downstream users usually do not have strict requirements for this indicator. However, for transparent ABS that is translucent, the yellow index becomes an indicator that must be strictly controlled.

[0005] In the industry, yellow index control is typically achieved by controlling the content of polymerization inhibitors in raw materials, improving the airtightness of the reaction system, reducing the thermal history of the resin, and adding additional antioxidants in each process. Even after implementing these methods, colorants are still added to further reduce the resin's yellow index. For transparent ABS resin, the addition of additional materials (colorants or antioxidants) will affect the resin's light transmittance and haze to varying degrees; these are compromise solutions for controlling the yellow index in existing processes.

[0006] It has been noted that existing technologies have methods for preparing polybutadiene / styrene-butadiene latex with different particle size distributions. For example, patents CN114031720A and CN1760222A both mention methods for preparing small-particle-size latex. The essence of this method is to overcome the limitations of the emulsion polymerization mechanism by first preparing small-particle-size latex and then using pressure agglomeration, chemical agglomeration, and polymer agglomeration to obtain large-particle-size latex of 300nm-500nm, thereby improving the efficiency of the process. Although the above methods can prepare latex with dual-distribution particle sizes, the latex particle size distribution is usually extremely wide. The presence of ultra-large particle-size latex >600nm will significantly increase the resin haze, making it impossible to prepare transparent ABS resin with excellent optical properties.

[0007] Patent CN110204656A mentions adding alkaline substances such as emulsifiers after the reaction has reached a certain extent. The purpose is to adjust the pH value of the reaction system, improve the stability of the emulsion, and avoid slag formation. However, this method cannot directly prepare latex with dual particle size distribution in a single reaction. Patent CN113544171A uses multiple additions of molecular weight regulators, diene monomers, initiators, and emulsifiers at different conversion rates. The purpose is to increase the reaction conversion rate by continuously adding initiators, and at the same time, to increase the proportion of small particle size in the latex particle size distribution by adding emulsifiers multiple times, thereby improving the gloss of the resin. However, in actual use, the particle size distribution of the latex still widens after multiple additions of emulsifiers, resulting in poor haze in the preparation of transparent ABS.

[0008] Therefore, a method is needed to fundamentally reduce the yellow index of transparent ABS resin without compromising the product's optical performance. Summary of the Invention

[0009] The purpose of this invention is to provide a polybutadiene latex and its preparation method, a transparent ABS resin. The prepared polybutadiene latex can be further used to prepare transparent ABS resin, and the finished transparent ABS has a lower yellow index and better optical properties.

[0010] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0011] A method for preparing polybutadiene latex, comprising the following steps:

[0012] (1) Deionized water, emulsifier-1, butadiene, electrolyte, chain transfer agent and initiator are added to the reactor to carry out emulsion polymerization reaction.

[0013] (2) When the reaction reaches a certain level, add emulsifier-2. When the conversion rate reaches 92% or more (e.g., 92-94%), remove the unreacted butadiene to obtain polybutadiene latex.

[0014] As a preferred embodiment, the mass fractions of the raw materials used in the method are as follows:

[0015]

[0016] The initiator is 0.2-0.6 parts, preferably 0.3-0.5 parts;

[0017] 50-150 parts deionized water, preferably 70-100 parts;

[0018] Emulsifier-2: 0.1-0.7 parts, preferably 0.3-0.5 parts.

[0019] As a preferred embodiment, the emulsifier of the present invention is selected from one or more of the potassium or sodium salts of disproportionated rosin acid, oleic acid, linoleic acid, stearic acid, and dodecylbenzenesulfonic acid.

[0020] As a preferred embodiment, the electrolyte is selected from one or more of sodium carbonate, potassium carbonate, sodium chloride, potassium phosphate, and sodium sulfite.

[0021] As a preferred embodiment, the chain transfer agent is selected from one or more of tert-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and n-octadecyl mercaptan.

[0022] As a preferred embodiment, the initiator may be one or more of sodium persulfate, potassium persulfate, cumene hydroperoxide, and tert-butyl hydroperoxide.

[0023] As a preferred embodiment, the polymerization reaction temperature of the present invention is 60℃-85℃, preferably 65℃-80℃.

[0024] As a preferred embodiment, the emulsifier-2 of the present invention is added when the reaction conversion rate reaches 70-90%, preferably 75-85%.

[0025] As a preferred embodiment, the method for removing unreacted butadiene described in this invention can be achieved by means of flash evaporation, stripping, etc.

[0026] The polybutadiene latex prepared by the method of the present invention has a typical bimodal particle size distribution, wherein the volume ratio of small particle size latex of 30nm-70nm to large particle size latex of 200-400nm is (1-5):(95-99). Based on the sum of the two, it can be further grafted and polymerized to prepare transparent ABS powder, which can then be used to prepare transparent ABS resin.

[0027] The present invention also relates to a transparent ABS resin, which is prepared using the above-mentioned polybutadiene latex.

[0028] The beneficial effects of this invention are as follows: by adding an extra emulsifier at a specific reaction conversion rate, the reaction is promoted to nucleate twice, forming a portion of small-particle latex with a particle size of 30nm-70nm. After this portion of small-particle latex is further prepared into transparent ABS, it can scatter a small amount of short-wavelength blue light due to the Rayleigh scattering effect. Thus, without affecting the light transmittance of the part, the transparent ABS resin part appears slightly blue, fundamentally covering the yellowing of the resin and reducing the yellow index of the resin. Detailed Implementation

[0029] The following embodiments will further illustrate the solutions provided by the present invention, but the present invention is not limited to the listed embodiments, and should also include any other known modifications within the scope of the claims of the present invention.

[0030] Test method:

[0031] Latex particle size: 1g of latex was mixed with 100g of deionized water, and the average particle size, particle size distribution, and the proportion of particles with a diameter of 30nm-100nm were measured using a Malvern Mastersizer laser particle size analyzer according to the dynamic laser scattering method.

[0032] The prepared latex needs to be grafted with MMA, acrylonitrile, and styrene to produce transparent ABS powder, which is then blended with MSAN (1.515 refractive index) in a fixed ratio to obtain transparent ABS resin for performance testing. The preparation process is as follows:

[0033] Latex grafting: Take 100 parts of polybutadiene latex emulsion, add 0.001 parts of FeSO4, stir evenly, and gradually heat the reaction system to 70°C. Then, gradually add 0.1 parts of cumene hydroperoxide, 12.2 parts of MMA, 3.1 parts of styrene, 1 part of acrylonitrile, 0.2 parts of tert-dodecyl mercaptan, 0.3 parts of potassium oleate, and 10 parts of deionized water. The continuous addition time is 3 hours. After the addition is completed, continue the reaction for 3 hours to obtain grafted latex emulsion with a grafting rate of about 40%.

[0034] Coagulation / Drying: 100 parts of the above-obtained grafted latex emulsion were added to a reaction vessel and heated to 95°C. 1.2 parts of H2SO4 and 40 parts of deionized water were gradually added to the emulsion. The temperature was maintained and the mixture was stirred uniformly for 1 hour. The resulting coagulated emulsion was filtered through a 200-mesh stainless steel filter cloth to obtain a moist transparent ABS powder. The powder was then fluidized and dried in a fluidized bed dryer at 60°C for 1 hour to obtain a transparent ABS powder with a moisture content of <1%.

[0035] Blending: Using a twin-screw extruder at 200-220℃, LG XT500 is used as the MSAN phase for blending. The mixture is blended at a ratio of XT500 to the above transparent ABS powder = 75 / 25. After cooling and granulation, transparent ABS resin particles are obtained.

[0036] Impact performance test: ABS resin chips obtained by blending were used for sample preparation and impact performance testing according to GB / T1043 rigid plastics simply supported beam impact test method.

[0037] Transmittance / Haze: The transmittance / haze index of a 3.2mm transparent ABS optical sample was tested using a transmittance / haze tester according to ASTM D1003.

[0038] Yellow Index (YI): Hue analysis was performed using a HunterLab UltraScan VIS colorimeter according to ASTM E313 [D65 / 10] method. Transmission mode was used during the test. After instrument calibration, a 3.2mm transparent ABS optical sample was placed on the sample holder, and the test was conducted three times, with the average value taken.

[0039] Example 1

[0040] 1.1 parts potassium oleate, 1.1 parts potassium disproportionated rosinate, 100 parts butadiene, 1.0 part potassium carbonate, 0.4 parts tert-dodecyl mercaptan (TDM), and 70 parts deionized water were added to a reactor and heated to 70°C. 0.35 parts potassium persulfate were added to initiate the emulsion polymerization reaction. After 20 hours of reaction, the butadiene conversion rate in the reactor was 74.5%. 0.4 parts potassium disproportionated rosinate were added, and the reaction was continued for another 8 hours. After that, the butadiene conversion rate in the reactor was 93.5%. The reaction was stopped, and unreacted butadiene was removed by vacuum flash evaporation to obtain a polybutadiene latex with a latex particle size of 292 nm. The volume ratio of 30-70 nm small particle size polybutadiene latex to 200 nm-400 nm large particle size polybutadiene latex was 1.52:98.48.

[0041] The aforementioned method is used to further prepare the above-mentioned latex into grafted latex emulsion, transparent ABS grafted adhesive powder, and transparent ABS resin in sequence.

[0042] The impact strength of the prepared transparent ABS resin, tested using the aforementioned analytical method, was 144 J / m. The 3.2 mm transparent ABS optical plate had a light transmittance of 90.1%, a haze of 2.5%, and a yellow index (YI) value of -1.2.

[0043] Example 2

[0044] 0.6 parts potassium stearate, 1.1 parts potassium disproportionated rosinate, 100 parts butadiene, 0.5 parts potassium phosphate, 0.6 parts n-octyl mercaptan, and 60 parts deionized water were added to a reactor and heated to 75°C. 0.6 parts tert-butyl hydroperoxide were added to initiate the emulsion polymerization reaction. After 26 hours of reaction, the butadiene conversion rate in the reactor was 72.7%. 0.1 parts potassium disproportionated rosinate were added, and the reaction was continued for another 11 hours. After that, the butadiene conversion rate in the reactor was 92.3%. The reaction was stopped, and unreacted butadiene was removed by vacuum flash evaporation to obtain a polybutadiene latex with a latex particle size of 327 nm. The volume ratio of 30-70 nm small-particle-size polybutadiene latex to 200 nm-400 nm large-particle-size polybutadiene latex was 1.26:98.74.

[0045] The aforementioned method is used to further prepare the above-mentioned latex into grafted latex emulsion, transparent ABS grafted adhesive powder, and transparent ABS resin in sequence.

[0046] The impact strength of the prepared transparent ABS resin, tested using the aforementioned analytical method, was 154 J / m. The 3.2 mm transparent ABS optical plate had a light transmittance of 89.8%, a haze of 2.7%, and a yellow index (YI) value of 0.3.

[0047] Example 3

[0048] Two parts of sodium linoleate, 100 parts of butadiene, 1.2 parts of sodium sulfite, 0.5 parts of n-dodecyl mercaptan, and 100 parts of deionized water were added to a reactor and heated to 80°C. 0.2 parts of cumene hydroperoxide were added to initiate the emulsion polymerization reaction. After 17 hours of reaction, the butadiene conversion rate in the reactor was 80.3%. 0.3 parts of potassium stearate were added, and the reaction was continued for another 6 hours. After that, the butadiene conversion rate in the reactor was 93.1%. The reaction was stopped, and unreacted butadiene was removed by vacuum flash evaporation to obtain a polybutadiene latex with a latex particle size of 261 nm. The volume ratio of 30-70 nm small-particle-size polybutadiene latex to 200 nm-400 nm large-particle-size polybutadiene latex was 2.14:97.86.

[0049] The aforementioned method is used to further prepare the above-mentioned latex into grafted latex emulsion, transparent ABS grafted adhesive powder, and transparent ABS resin in sequence.

[0050] The impact strength of the prepared transparent ABS resin, tested using the aforementioned analytical method, was 131 J / m. The 3.2 mm transparent ABS optical plate had a light transmittance of 90.3%, a haze of 2.3%, and a yellow index (YI) value of -1.7.

[0051] Example 4

[0052] 1.2 parts sodium dodecylbenzenesulfonate, 1.2 parts potassium oleate, 100 parts butadiene, 1.4 parts sodium carbonate, 0.7 parts n-octadecyl mercaptan, and 130 parts deionized water were added to a reactor and heated to 65°C. 0.4 parts sodium persulfate were added to initiate the emulsion polymerization reaction. After 16 hours of reaction, the butadiene conversion rate in the reactor was 87.9%. 0.7 parts potassium oleate were added, and the reaction was continued for another 6 hours. After that, the butadiene conversion rate in the reactor was 92.7%. The reaction was stopped, and unreacted butadiene was removed by vacuum flash evaporation to obtain a polybutadiene latex with a latex particle size of 252 nm. The volume ratio of 30-70 nm small particle size polybutadiene latex to 200 nm-400 nm large particle size polybutadiene latex was 3.93:96.07.

[0053] The aforementioned method is used to further prepare the above-mentioned latex into grafted latex emulsion, transparent ABS grafted adhesive powder, and transparent ABS resin in sequence.

[0054] The impact strength of the prepared transparent ABS resin, tested using the aforementioned analytical method, was 123 J / m. The 3.2 mm transparent ABS optical plate had a light transmittance of 90.5%, a haze of 2.1%, and a yellow index (YI) value of -2.1.

[0055] Comparative Example 1

[0056] 1.1 parts potassium oleate, 1.1 parts potassium disproportionated rosinate, 100 parts butadiene, 1.0 part potassium carbonate, 0.4 parts tert-dodecyl mercaptan (TDM), and 70 parts deionized water were added to a reactor and heated to 70°C. 0.35 parts potassium persulfate were added to initiate the emulsion polymerization reaction. After 28 hours of reaction, the butadiene conversion rate in the reactor was 92.7%. The reaction was stopped, and unreacted butadiene was removed by vacuum flash evaporation to obtain a polybutadiene latex with a latex particle size of 307 nm. The volume ratio of 30-70 nm small-particle-size polybutadiene latex to 200 nm-400 nm large-particle-size polybutadiene latex was 0.08:99.92.

[0057] The aforementioned method is used to further prepare the above-mentioned latex into grafted latex emulsion, transparent ABS grafted adhesive powder, and transparent ABS resin in sequence.

[0058] The impact strength of the prepared transparent ABS resin, tested using the aforementioned analytical method, was 147 J / m. The 3.2 mm transparent ABS optical plate had a light transmittance of 89.6%, a haze of 3.1%, and a yellowness index (YI) of 7.4.

[0059] Finally, it should be noted that the above embodiments are only used to describe preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that various modifications and improvements made to the technical solutions of the present invention by means of modifications or equivalent substitutions should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing polybutadiene latex, comprising the following steps: (1) Deionized water, emulsifier-1, butadiene, electrolyte, chain transfer agent and initiator are added to the reactor to carry out emulsion polymerization reaction. (2) When the reaction reaches a certain level, add emulsifier-2. When the conversion rate reaches 92% or more (e.g., 92-94%), remove the unreacted butadiene to obtain polybutadiene latex.

2. The method according to claim 1, characterized in that, The mass fractions of the raw materials used are as follows:

3. The method according to claim 1 or 2, characterized in that, The emulsifier is selected from one or more of the potassium or sodium salts of disproportionated rosin acid, oleic acid, linoleic acid, stearic acid, and dodecylbenzenesulfonic acid.

4. The method according to any one of claims 1-3, characterized in that, The electrolyte is selected from one or more of sodium carbonate, potassium carbonate, sodium chloride, potassium phosphate, and sodium sulfite.

5. The method according to any one of claims 1-4, characterized in that, The chain transfer agent is selected from one or more of tert-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and n-octadecyl mercaptan.

6. The method according to any one of claims 1-5, characterized in that, The initiator can be one or more of sodium persulfate, potassium persulfate, cumene hydroperoxide, and tert-butyl hydroperoxide.

7. The method according to any one of claims 1-6, characterized in that, The polymerization reaction temperature is 60℃-85℃, preferably 65℃-80℃.

8. The method according to any one of claims 1-7, characterized in that, The emulsifier-2 is added when the reaction conversion rate reaches 70-90%, preferably 75-85%.

9. A polybutadiene latex prepared according to any one of claims 1-8, characterized in that, The polybutadiene latex has a bimodal particle size distribution, wherein the volume ratio of the 30nm-70nm small particle size latex to the 200-400nm large particle size latex is (1-5):(95-99), based on the sum of the two.

10. A transparent ABS resin, prepared using polybutadiene latex prepared by the method described in any one of claims 1-9.

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