Synthesis process of high-solid-content styrene-butadiene latex

Abstract

The invention provides a high-solid-content styrene-butadiene latex synthesis process which comprises the following steps: (1) mixing and shearing butadiene, styrene, vinyl amide and a polyfunctional group crosslinking monomer to prepare a mixed monomer; (2) adding deionized water, an emulsifier and a mixed monomer accounting for 30-60% of the total weight into the reaction kettle, vacuumizing, adding an initiator at the temperature of 5-15 DEG C, reacting for 1-1.5 hours, dropwise adding the rest of the mixed monomer for 6-10 hours, and after dropwise adding, carrying out polymerization reaction at the temperature of 40-60 DEG C for 3-4 hours to obtain the low-solid-content styrene-butadiene latex; and (3) adding an auxiliary agent inorganic salt and an organic concentrating agent into the low-solid-content styrene-butadiene latex, carrying out flash evaporation, and treating by a stripping tower to obtain the high-solid-content styrene-butadiene latex. While the solid content of the latex is increased, the viscosity of polymer emulsion, the size of latex particles, the particle size interval distribution and the like can be effectively controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of latex synthesis, and particularly relates to a process for synthesizing styrene-butadiene latex with high solid content. Background Art

[0002] Styrene-butadiene latex with high solid content is an important industrial raw material, which is widely used in fields such as coatings, adhesives, and sizing agents. Its preparation process involves a series of chemical reactions and fine process control. At present, there are various methods for preparing styrene-butadiene latex with high solid content.

[0003] For example, the invention patent with the application number CN200510082910.X discloses a preparation technology for a new type of carboxylated styrene-butadiene latex. This invention uses aliphatic conjugated dienes and aromatic vinyl compounds as main monomers, and adds vinyl unsaturated carboxylic acids with C3-C5 for modification; the emulsifier includes anionic and non-ionic emulsifiers, uses persulfate as an initiator, and alkyl mercaptans as a molecular weight regulator, and synthesizes a new type of carboxylated styrene-butadiene latex through a batch feeding method. This latex has high surface tension and low particle size. The invention patent with the application number CN200610091157.5 discloses a preparation method for a new type of latex. This technology studies the method for synthesizing carboxylated styrene-butadiene latex by a seed polymerization process, as well as the influence of different functional monomer groups on the latex properties. The carboxylated styrene-butadiene latex synthesized by this method has wide application properties. The invention patent with the application number CN201810384802.5 discloses a carboxylated styrene-butadiene latex and its preparation method and application. It adds raw materials including butadiene, styrene, acrylic acid, etc. into a reaction kettle, and finally obtains carboxylated styrene-butadiene latex with high solid content and small particle size through a series of temperature control and reaction steps. The styrene-butadiene latex prepared by the above synthesis technology has a solid content between 60% and 65%, and it is difficult to achieve a solid content above 67%.

[0004] Currently, when preparing styrene-butadiene latex with high solid content, generally a two-step method is used to synthesize styrene-butadiene latex. In the first step, low-temperature emulsion polymerization is used for preparation. Generally, the obtained styrene-butadiene latex has a solid content below 30%, and the highest does not exceed 40%, and large particle size polymers are prepared; in the second step, a method of concentrating and removing part of the water, or adding monomers and other auxiliaries for polymerization reaction is used to prepare a latex with high solid content and low viscosity. This method involves synthesizing styrene-butadiene latex with large particle size and a concentration process. Summary of the Invention

[0005] The purpose of the present invention is to provide a process for synthesizing styrene-butadiene latex with high solid content, which can effectively control the viscosity of the polymer latex, the size of the latex particles, and the particle size range distribution, etc. while increasing the solid content of the latex.

[0006] To achieve the above object, the present invention is realized by the following technical solutions: A synthetic process for high solid content styrene-butadiene latex, comprising the following steps: (1) Mix and shear butadiene, styrene, vinyl amide, and multi-functional cross-linking monomer to prepare a mixed monomer; (2) Then add deionized water, emulsifier, and 30 - 60% of the total weight of the mixed monomer to the reaction kettle, evacuate, and add an initiator at 5 - 15°C. After reacting for 1 - 1.5 hours, add the remaining mixed monomer dropwise over 6 - 10 hours. After the dropwise addition is completed, carry out a polymerization reaction at 40 - 60°C for 3 - 4 hours to obtain a low solid content styrene-butadiene latex; (3) Add an auxiliary inorganic salt and an organic concentrate to the low solid content styrene-butadiene latex, then carry out flash evaporation, and then treat it in a stripping tower to obtain a high solid content styrene-butadiene latex.

[0007] The polymerization process of the present invention adopts an oxidation-reduction system and carries out low-temperature emulsion polymerization at 5 - 15°C, which can achieve a latex with high molecular weight and endow it with high elastic modulus performance. During polymerization, water is used as the medium, butadiene and styrene are the main monomers, supplemented by vinyl amide and multi-functional cross-linking monomer, and excellent emulsifiers and other additives are selected to produce styrene-butadiene latex. The inorganic salt added in step (3) plays a role in controlling the particle size, and the organic concentrate plays a role in controlling the molecular weight distribution and surface tension. And the flash evaporation principle can be used to effectively increase the latex content.

[0008] Preferably, in step (1), the mass ratio of butadiene, styrene, vinyl amide, and multi-functional cross-linking monomer is 220 - 280:80 - 180:0.8 - 2.5:0.8 - 6.0.

[0009] Preferably, in step (2), when adding 30 - 60% of the total weight of the mixed monomer, a molecular weight regulator is also added; the molecular weight regulator is one or more of dodecyl mercaptan and mercapto monomer; In step (2), after the polymerization reaction at 40 - 60°C for 3 - 4 hours, a pH regulator is added, and the pH regulator is a sodium hydroxide solution with a mass fraction of 20%.

[0010] Preferably, based on 1000 parts by weight of the total raw materials, the styrene-butadiene latex comprises the following raw materials in parts by weight: 220 - 280 parts of butadiene, 80 - 180 parts of styrene, 0.8 - 2.5 parts of vinyl amide, 0.8 - 6.0 parts of multi-functional cross-linking monomer, 0.8 - 1.5 parts of emulsifier, 4 - 6 parts of initiator, 2 - 6 parts of molecular weight regulator, 30 - 50 parts of pH regulator, and the balance is deionized water.

[0011] Preferably, the vinyl amide is one or more of acrylamide, N-methylol acrylamide, diacetone acrylamide; the multi-functional cross-linking monomer is one or two of ethylene glycol dimethacrylate, triallyl cyanurate, polyethylene glycol dimethacrylate; the emulsifier is one or more of oleic acid soap, sodium dodecyl benzene sulfonate; the initiator is one or more of sodium persulfate, ammonium persulfate, potassium persulfate.

[0012] Preferably, in step (1), the purity of butadiene > 99%, and the purity of styrene > 99.6%; the butadiene and styrene are the butadiene and styrene after being washed with a 10 - 15% NaOH aqueous solution by mass fraction to remove the contained polymerization inhibitors.

[0013] Preferably, in step (3), the auxiliary inorganic salt is a 10% calcium chloride solution by mass fraction; The preparation method of the organic concentrate includes the following steps: After mixing styrene, butadiene, functional monomer, emulsifier, co-stabilizer and deionized water, mechanically stir and pre-emulsify for 60 minutes, and then ultrasonically homogenize for 120 - 140 seconds in an ice-water bath to obtain the organic concentrate; The functional monomer is TEGDMA, accounting for 0.2% of the total amount of styrene and butadiene; the emulsifier is sodium dodecyl benzene sulfonate, accounting for 0.8% of the total amount of styrene and butadiene; the co-stabilizer is fatty alcohol polyoxyethylene ether, accounting for 2.0% of the total amount of styrene and butadiene; the mass ratio of the total amount of styrene and butadiene to deionized water is 300 - 460:500 - 600; the mass ratio of styrene to butadiene is 220 - 280:80 - 180; The addition amount of the auxiliary inorganic salt is 0.1 - 5% of the mass of the low solid content styrene-butadiene rubber latex; the addition amount of the organic concentrate is 4 - 20% of the mass of the low solid content styrene-butadiene rubber latex.

[0014] Preferably, in step (3), during the flash evaporation, the temperature is 22 - 28 °C, the pressure is 0.02 - 0.04 MPa, and the time is 7 - 16 hours.

[0015] Preferably, in step (3), when being treated in the styrene stripping tower: the styrene-butadiene rubber latex after flash evaporation enters the upper part of the styrene stripping tower, the bottom of the tower is directly heated with steam, styrene and water vapor come out from the top of the tower, and after condensation, water and styrene are separated, and the styrene is recycled.

[0016] Preferably, in step (3), the solid content of the high solid content styrene-butadiene rubber latex is 68 - 70%.

[0017] The beneficial effects of the present invention are as follows: The present invention aims to provide a synthetic process for high-solid-content styrene-butadiene latex, which can effectively control the viscosity of the polymer emulsion, the size of the latex particles, and the particle size range distribution while increasing the solid content of the latex. Detailed implementation manners

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] Example 1: A synthetic process for high-solid-content styrene-butadiene latex includes the following steps: (1) Mix and shear butadiene, styrene, acrylamide, and ethylene glycol dimethacrylate monomers to prepare a mixed monomer; The purity of the above-mentioned butadiene > 99%, and the purity of styrene > 99.6%; butadiene and styrene are the butadiene and styrene after being washed with a 10% NaOH aqueous solution by mass fraction to remove the contained polymerization inhibitors.

[0020] (2) Then add deionized water, oleic acid soap, dodecyl mercaptan, and 40% of the total weight of the mixed monomer to the reaction kettle, evacuate, and add sodium persulfate at 7°C. After reacting for 1 hour, add the remaining mixed monomer dropwise. The dropping time is 10 hours. After the dropping is completed, carry out a polymerization reaction at 50°C for 4 hours, and then add a pH regulator (a 20% sodium hydroxide solution by mass fraction) to obtain a low-solid-content styrene-butadiene latex; Based on 1000 parts by weight of the total raw materials, the low-solid-content styrene-butadiene latex includes the following raw materials in parts by weight: 280 parts of butadiene, 120 parts of styrene, 0.8 part of acrylamide, 1.5 parts of ethylene glycol dimethacrylate, 1.5 parts of oleic acid soap, 4.5 parts of sodium persulfate, 2.0 parts of dodecyl mercaptan, 30 parts of pH regulator, and the balance is deionized water.

[0021] (3) Add an auxiliary agent inorganic salt (a 10% calcium chloride solution by mass fraction) of 0.5% of its mass and an organic concentrate of 15% of its mass to the low-solid-content styrene-butadiene latex at 40°C, and then carry out flash evaporation using a flash evaporator. The operating conditions of the flash evaporator are 25°C and a pressure of 0.02 - 0.04 MPa, and the flash evaporation time is 10 hours; the styrene-butadiene latex obtained after flash evaporation is then treated by a styrene stripping column to obtain a high-solid-content styrene-butadiene latex; Among them, the preparation method of the organic concentrate includes the following steps: After mixing styrene, butadiene, TEGDMA, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether and deionized water, mechanically stir and pre-emulsify for 60 minutes, and then ultrasonically homogenize for 120 seconds in an ice-water bath to obtain the organic concentrate; among them, TEGDMA accounts for 0.2% of the total amount of styrene and butadiene; sodium dodecylbenzenesulfonate accounts for 0.8% of the total amount of styrene and butadiene; fatty alcohol polyoxyethylene ether accounts for 2.0% of the total amount of styrene and butadiene; the mass ratio of the total amount of styrene and butadiene to deionized water is 400:500; the mass ratio of styrene and butadiene is 280:120.

[0022] When being treated in the styrene stripping column, the styrene-butadiene latex after flash evaporation enters the upper part of the styrene stripping column, and the bottom of the column is directly heated by steam. Styrene and water vapor come out from the top of the column. After condensation, water and styrene are separated, and the styrene is recycled.

[0023] Example 2: A synthetic process for high-solid-content styrene-butadiene latex includes the following steps: (1) Mix and shear butadiene, styrene, diacetone acrylamide, and ethylene glycol dimethacrylate to make a mixed monomer; The above-mentioned butadiene purity > 99%, styrene purity > 99.6%; butadiene and styrene are the butadiene and styrene after being washed with a 10% NaOH aqueous solution by mass fraction to remove the contained polymerization inhibitors.

[0024] (2) Then add deionized water, emulsifier, dodecyl mercaptan and 40% of the total weight of the mixed monomer to the reaction kettle, evacuate, and add sodium persulfate at 7°C. After reacting for 1 hour, add the remaining mixed monomer dropwise. The dropping time is 10 hours. After the dropping is completed, carry out a polymerization reaction at 50°C for 4 hours, and then add a pH regulator (a 20% sodium hydroxide solution by mass fraction) to obtain a low-solid-content styrene-butadiene latex; Based on 1000 parts by weight of the total raw materials, the low-solid-content styrene-butadiene latex includes the following raw materials in parts by weight: 280 parts of butadiene, 120 parts of styrene, 1.25 parts of diacetone acrylamide, 1.5 parts of ethylene glycol dimethacrylate, 1.5 parts of emulsifier, 4.5 parts of sodium persulfate, 4 parts of dodecyl mercaptan, 30 parts of pH regulator, and the balance is deionized water. The emulsifier is oleic acid soap and sodium dodecylbenzenesulfonate with a mass ratio of 1:0.8.

[0025] (3) Add 1.0% of the auxiliary agent inorganic salt (calcium chloride solution with a mass fraction of 10%) and 15% of the organic concentrate by mass of the low solid content styrene-butadiene latex at 40°C, and then perform flash evaporation using a flash evaporator. The operating conditions of the flash evaporator are 25°C, a pressure of 0.02 - 0.04 MPa, and the flash evaporation time is 10 hours; the styrene-butadiene latex obtained after flash evaporation is further treated in a styrene stripping tower to obtain a high solid content styrene-butadiene latex; Among them, the preparation method of the organic concentrate includes the following steps: Mix styrene, butadiene, TEGDMA, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, and deionized water, and then mechanically stir and pre-emulsify for 60 minutes, and then perform ultrasonic homogenization for 120 seconds in an ice-water bath to obtain the organic concentrate; among them, TEGDMA accounts for 0.2% of the total amount of styrene and butadiene; sodium dodecylbenzenesulfonate accounts for 0.8% of the total amount of styrene and butadiene; fatty alcohol polyoxyethylene ether accounts for 2.0% of the total amount of styrene and butadiene; the mass ratio of the total amount of styrene and butadiene to deionized water is 400:500; the mass ratio of styrene and butadiene is 280:120.

[0026] When being treated in the styrene stripping tower, the styrene-butadiene latex after flash evaporation enters the upper part of the styrene stripping tower, and the bottom of the tower is directly heated by steam. Styrene and water vapor come out from the top of the tower. After condensation, water and styrene are separated, and the styrene is recycled.

[0027] Example 3: A synthesis process of high solid content styrene-butadiene latex, including the following steps: (1) Mix and shear butadiene, styrene, diacetone acrylamide, and triallyl ureidoformate to make a mixed monomer; The above-mentioned butadiene has a purity > 99%, and styrene has a purity > 99.6%; butadiene and styrene are the butadiene and styrene after being washed with a 10% NaOH aqueous solution by mass fraction to remove the contained polymerization inhibitors.

[0028] (2) Then add deionized water, emulsifier, dodecyl mercaptan, and 30% of the total weight of the mixed monomer to the reaction kettle, evacuate, and add sodium persulfate at 10°C. After reacting for 1.2 hours, add the remaining mixed monomer dropwise. The dropping time is 10 hours. After the dropping is completed, carry out a polymerization reaction at 50°C for 4 hours, and then add a pH regulator (sodium hydroxide solution with a mass fraction of 20%) to obtain a low solid content styrene-butadiene latex; Based on 1000 parts by weight of the total raw materials, the low solid content styrene-butadiene latex comprises the following raw materials in parts by weight: 240 parts of butadiene, 160 parts of styrene, 1.5 parts of diacetone acrylamide, 1.2 parts of triallyl ureate, 1.2 parts of emulsifier, 4 parts of sodium persulfate, 5 parts of dodecyl mercaptan, 40 parts of pH regulator, and the balance is deionized water; the emulsifier is a soap of oleic acid and sodium dodecylbenzenesulfonate with a mass ratio of 1:0.8.

[0029] (3) Add 1.0% of an auxiliary inorganic salt (a 10% calcium chloride solution by mass fraction) and 15% of an organic concentrate by its mass to the low solid content styrene-butadiene latex at 40 °C, and then perform flash evaporation using a flash evaporator. The operating conditions of the flash evaporator are 25 °C and a pressure of 0.02 - 0.04 MPa, and the flash evaporation time is 12 hours; subject the styrene-butadiene latex obtained after flash evaporation to treatment in a styrene stripping column to obtain a high solid content styrene-butadiene latex; Among them, the preparation method of the organic concentrate includes the following steps: Mix styrene, butadiene, TEGDMA, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, and deionized water, and then perform mechanical stirring for pre-emulsification for 60 minutes, and then perform ultrasonic homogenization for 140 seconds in an ice-water bath to obtain the organic concentrate; among them, TEGDMA accounts for 0.2% of the total amount of styrene and butadiene; sodium dodecylbenzenesulfonate accounts for 0.8% of the total amount of styrene and butadiene; fatty alcohol polyoxyethylene ether accounts for 2.0% of the total amount of styrene and butadiene; the mass ratio of the total amount of styrene and butadiene to deionized water is 400:600; the mass ratio of styrene to butadiene is 240:160.

[0030] When being treated in the styrene stripping column, the styrene-butadiene latex after flash evaporation enters the upper part of the styrene stripping column, and the bottom of the column is directly heated with steam. Styrene and water vapor come out from the top of the column. After condensation, water and styrene are separated, and the styrene is recycled.

[0031] Example 4: A synthesis process of high solid content styrene-butadiene latex, comprising the following steps: (1) Mix and shear butadiene, styrene, acrylamide, N-methylol acrylamide, and triallyl ureate to form a mixed monomer; The above-mentioned butadiene has a purity > 99%, and styrene has a purity > 99.6%; butadiene and styrene are the butadiene and styrene after being washed with a 10% NaOH aqueous solution by mass fraction to remove the contained polymerization inhibitors.

[0032] (2) Then, deionized water, an emulsifier, dodecyl mercaptan, and 30% of the total weight of the mixed monomers were added to the reaction kettle. The mixture was evacuated, and sodium persulfate was added at 10°C. After reacting for 1.2 hours, the remaining mixed monomers were added dropwise over a period of 10 hours. After the addition was complete, the polymerization reaction was carried out at 50°C for 4 hours. Then, a pH regulator (a 20% sodium hydroxide solution by mass fraction) was added to obtain a low solids content styrene-butadiene latex. Based on 1000 parts by weight of the total raw materials, the low solids content styrene-butadiene latex comprises the following raw materials in parts by weight: 240 parts of butadiene, 160 parts of styrene, 0.6 part of acrylamide, 0.6 part of N-methylolacrylamide, 0.8 part of triallyl ureidoglycolate, 1.2 parts of emulsifier, 4 parts of sodium persulfate, 5 parts of dodecyl mercaptan, 40 parts of pH regulator, and the balance being deionized water; the emulsifier is a soap of oleic acid and sodium dodecylbenzenesulfonate with a mass ratio of 1:2.

[0033] (3) The low solids content styrene-butadiene latex was added with 1.0% of its mass of an auxiliary inorganic salt (a 10% calcium chloride solution by mass fraction) and 15% of its mass of an organic concentrate at 40°C. Then, flash evaporation was carried out using a flash evaporator. The operating conditions of the flash evaporator were 25°C and a pressure of 0.02 - 0.04 MPa, and the flash evaporation time was 12 hours; the styrene-butadiene latex obtained after flash evaporation was further treated in a styrene stripping column to obtain a high solids content styrene-butadiene latex. Among them, the preparation method of the organic concentrate includes the following steps: Styrene, butadiene, TEGDMA, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, and deionized water were mixed and mechanically stirred for pre-emulsification for 60 minutes, and then ultrasonically homogenized for 140 seconds in an ice-water bath to obtain the organic concentrate; among them, TEGDMA accounts for 0.2% of the total amount of styrene and butadiene; sodium dodecylbenzenesulfonate accounts for 0.8% of the total amount of styrene and butadiene; fatty alcohol polyoxyethylene ether accounts for 2.0% of the total amount of styrene and butadiene; the mass ratio of the total amount of styrene and butadiene to deionized water is 400:500; the mass ratio of styrene to butadiene is 240:160.

[0034] When being treated in the styrene stripping column, the styrene-butadiene latex after flash evaporation enters the upper part of the styrene stripping column, and the bottom of the column is directly heated with steam. Styrene and steam come out from the top of the column. After condensation, water and styrene are separated, and styrene is recycled.

[0035] Example 5: A process for synthesizing a high solids content styrene-butadiene latex, comprising the following steps: (1) Butadiene, styrene, N-methylolacrylamide, and triallyl ureidoglycolate were mixed and sheared to form a mixed monomer. The above-mentioned butadiene has a purity > 99%, and styrene has a purity > 99.6%; the butadiene and styrene are those after being washed with an aqueous NaOH solution with a mass fraction of 10% to remove the contained polymerization inhibitors.

[0036] (2) Then, deionized water, an emulsifier, dodecyl mercaptan, and 35% of the total weight of the mixed monomers are added to the reaction kettle, evacuated, and sodium persulfate is added at 15°C. After reacting for 1.2 hours, the remaining mixed monomers are added dropwise over 10 hours. After the addition is complete, the polymerization reaction is carried out at 50°C for 4 hours, and then a pH regulator (an aqueous sodium hydroxide solution with a mass fraction of 20%) is added to obtain a low-solid-content styrene-butadiene latex. Based on 1000 parts by weight of the total raw materials, the low-solid-content styrene-butadiene latex includes the following raw materials in parts by weight: 220 parts of butadiene, 180 parts of styrene, 2.0 parts of N-methylolacrylamide, 2.0 parts of triallyl ureasulfonic acid, 1.2 parts of emulsifier, 6 parts of sodium persulfate, 6 parts of dodecyl mercaptan, 40 parts of pH regulator, and the balance is deionized water; the emulsifier is a mixture of oleic acid soap and sodium dodecylbenzenesulfonate with a mass ratio of 1:2.

[0037] (3) The low-solid-content styrene-butadiene latex is added with 1.2% of its mass of an auxiliary inorganic salt (a 10% calcium chloride solution) and 15% of its mass of an organic concentrate at 30°C, and then flash evaporation is carried out using a flash evaporator. The operating conditions of the flash evaporator are 28°C and a pressure of 0.02 - 0.04 MPa, and the flash evaporation time is 15 hours; the styrene-butadiene latex obtained after flash evaporation is further treated in a styrene stripping tower to obtain a high-solid-content styrene-butadiene latex. Among them, the preparation method of the organic concentrate includes the following steps: styrene, butadiene, TEGDMA, sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, and deionized water are mixed and mechanically stirred for pre-emulsification for 60 minutes, and then ultrasonically homogenized for 120 seconds in an ice-water bath to obtain the organic concentrate; among them, TEGDMA accounts for 0.2% of the total amount of styrene and butadiene; sodium dodecylbenzenesulfonate accounts for 0.8% of the total amount of styrene and butadiene; fatty alcohol polyoxyethylene ether accounts for 2.0% of the total amount of styrene and butadiene; the mass ratio of the total amount of styrene and butadiene to deionized water is 400:550; the mass ratio of styrene to butadiene is 220:180.

[0038] When being treated in the styrene stripping tower, the styrene-butadiene latex after flash evaporation enters the upper part of the styrene stripping tower, and the bottom of the tower is directly heated with steam. Styrene and water vapor come out from the top of the tower. After condensation, water and styrene are separated, and styrene is recycled.

[0039] Performance test: The properties of the high-solid styrene-butadiene latexes in Examples 1 to 5 were tested. Among them, the solid content detection referred to GB / T 2793-1995, the viscosity and stability tests referred to GB / T 11175-2002, and the yellowing resistance test referred to GB / T 1865-2009. The specific indicators are shown in Table 1.

[0040] Table 1 Performance indicators of high-solid styrene-butadiene latex The above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A high solid content styrene butadiene latex synthesis process, characterized in that: The following steps are involved: (1) mixing and shearing butadiene, styrene, vinyl amide, and a multifunctional cross-linking monomer to prepare a mixed monomer; (2) deionized water, an emulsifier and 30-60% of the total weight of the mixed monomers are then added to the reactor, vacuumized, and an initiator is added at 5-15° C. After reacting for 1-1.5 hours, the remaining mixed monomers are added dropwise for 6-10 hours. After the addition is completed, polymerization is carried out at 40-60° C. for 3-4 hours to obtain a low-solid content styrene-butadiene latex; (3) Adding auxiliary inorganic salt and organic concentrator to the low-solid-content styrene-butadiene latex, and then flash evaporating the latex, and then treating the latex in a stripping tower to obtain a high-solid-content styrene-butadiene latex.

2. The high solid content styrene-butadiene latex synthesis process as claimed in claim 1, characterized in that: In step (1), the mass ratio of butadiene, styrene, vinyl amide and multifunctional cross-linking monomer is 220-280: 80-180: 0.8-2.5: 0.8-6.

0.

3. The high solid content styrene-butadiene latex synthesis process as claimed in claim 2, characterized in that: In step (2), when adding 30-60% of the total weight of the mixed monomer, a molecular weight regulator is also added; the molecular weight regulator is one or more of dodecyl mercaptan and mercapto monomer; In step (2), after the polymerization reaction is carried out at 40-60° C. for 3-4 hours, a pH adjuster is added, wherein the pH adjuster is a sodium hydroxide solution with a mass fraction of 20%.

4. The high solid content styrene butadiene latex synthesis process as claimed in claim 3, characterized in that: Based on 1000 parts by weight of the total amount of raw materials, the styrene-butadiene latex includes the following raw materials in parts by weight: 220-280 parts of butadiene, 80-180 parts of styrene, 0.8-2.5 parts of vinylamide, 0.8-6.0 parts of multifunctional cross-linking monomer, 0.8-1.5 parts of emulsifier, 4-6 parts of initiator, 2-6 parts of molecular weight regulator, 30-50 parts of pH regulator, and the balance is deionized water.

5. The high solid content styrene-butadiene latex synthesis process according to claim 1, characterized in that: The vinyl amide is one or more of acrylamide, N-hydroxymethyl acrylamide, and diacetone acrylamide; the multifunctional cross-linking monomer is one or two of ethylene glycol dimethacrylate, triallyl cyanurate, and polyethylene glycol dimethacrylate; the emulsifier is one or more of oleic acid soap and sodium dodecylbenzene sulfonate; and the initiator is one or more of sodium persulfate, ammonium persulfate, and potassium persulfate.

6. The process for synthesizing high solid content styrene-butadiene latex according to any one of claims 1 to 5, characterized in that: In step (1), the purity of butadiene is greater than 99%, and the purity of styrene is greater than 99.6%; the butadiene and styrene are obtained by eluting with a 10-15% by mass NaOH aqueous solution to remove the polymerization inhibitor contained therein.

7. The process for synthesizing high solid content styrene-butadiene latex according to any one of claims 1 to 5, characterized in that: In step (3), the auxiliary inorganic salt is a calcium chloride solution with a mass fraction of 10%; The preparation method of the organic concentrator comprises the following steps: mixing styrene, butadiene, functional monomers, emulsifiers, stabilizers and deionized water, pre-emulsifying by mechanical stirring for 60 minutes, and then homogenizing by ultrasonic wave in an ice water bath for 120 to 140 seconds to obtain the organic concentrator; The functional monomer is TEGDMA, accounting for 0.2% of the total amount of styrene and butadiene; the emulsifier is sodium dodecylbenzene sulfonate, accounting for 0.8% of the total amount of styrene and butadiene; the auxiliary stabilizer is fatty alcohol polyoxyethylene ether, accounting for 2.0% of the total amount of styrene and butadiene; the mass ratio of the total amount of styrene and butadiene to deionized water is 300-460:500-600; the mass ratio of styrene and butadiene is 220~280:80~180; The addition amount of the auxiliary inorganic salt is 0.1-5% of the mass of the low-solid-content styrene-butadiene latex; the addition amount of the organic concentrator is 4-20% of the mass of the low-solid-content styrene-butadiene latex.

8. The process for synthesizing high solid content styrene-butadiene latex according to any one of claims 1 to 5, characterized in that: In step (3), during the flash evaporation, the temperature is 22-28° C., the pressure is 0.02-0.04 MPa, and the time is 7-16 hours.

9. The process for synthesizing high solid content styrene-butadiene latex according to any one of claims 1 to 5, characterized in that: In step (3), when the styrene stripping tower is used for treatment, the styrene-butadiene latex after flash evaporation enters the upper part of the styrene stripping tower, the bottom of the tower is directly heated by steam, and styrene and water vapor come out from the top of the tower. After condensation, water and styrene are separated, and the styrene is recycled.

10. The process for synthesizing high solid content styrene-butadiene latex according to any one of claims 1 to 5, characterized in that: In step (3), the solid content of the high-solid-content styrene-butadiene latex is 68-70%.

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