Apparatus and method for removing solvent from polyisoprene latex

Abstract

The present invention relates to a method for producing a polymer, and in particular to a device and method for desolvating polyisoprene latex. The device comprises: an atmospheric distillation kettle and an optional vacuum distillation kettle, wherein a gas spraying element and / or a liquid spraying element is arranged on the top of the atmospheric distillation kettle, and each of the atmospheric distillation kettle and the vacuum distillation kettle is provided with a feed inlet, a solvent outlet and a discharge port, and the discharge port of the atmospheric distillation kettle is connected to the feed inlet of the vacuum distillation kettle. The device and method can timely eliminate the foam generated in the distillation, improve the diffusion rate of the solvent, shorten the solvent removal time, and can avoid demulsification as much as possible.

Description

Technical Field

[0001] The present invention relates to a method for producing polymers, and particularly to an apparatus and a method for removing solvents from polyisoprene latex. Background Art

[0002] The microstructure and properties of artificial polyisoprene latex are similar to those of natural latex. Except for a few surfactants and anti-aging agents, it does not contain other non-rubber components, and can better solve problems such as protein allergy and nitrosamine carcinogenesis existing in natural latex. Especially in the medical field, it can completely replace natural latex in aspects such as latex gloves, condoms, medical bandages, medical catheters, foamed cotton pads for makeup, etc.

[0003] In the preparation process of artificial latex, first, an emulsifier is fully mixed with a rubber solution, and then emulsified by mechanical force to obtain a rubber crude emulsion. The content of the solvent in the crude emulsion exceeds 30% by volume, and the excess solvent needs to be removed by distillation. The solvent removal process is the most time-consuming, least efficient, and most lossy process in the production process of artificial latex. Although relevant researchers have proposed various solvent removal methods, a large amount of foam and demulsified gel will be generated due to the high temperature and the evaporation of a large amount of solvent. For example, CN107226916A provides a method for removing solvents from latex. This method continuously passes the crude latex through a concentrator and a thin-film evaporator with a scraper. This method uses a special solvent removal device including a foam eliminator, and although it can effectively remove foam, since it is very easy to cause demulsification of the latex after passing through the thin-film evaporator with a scraper, its practicability is poor.

[0004] Therefore, in the current technology, there are still problems such as difficult solvent removal, easy demulsification, long time consumption, and a large amount of foam, and the production process has low efficiency. Summary of the Invention

[0005] The object of the present invention is to overcome the above problems existing in the prior art, and provide an apparatus and a method for removing solvents from polyisoprene latex. This apparatus and method can timely eliminate the foam generated during distillation, improve the diffusion rate of the solvent, shorten the solvent removal time, and can also avoid demulsification as much as possible.

[0006] To achieve the above object, in a first aspect of the present invention, there is provided an apparatus for removing solvents from polyisoprene latex, the apparatus comprising: an atmospheric distillation kettle and an optional vacuum distillation kettle. A gas spraying element and / or a liquid spraying element is provided at the top of the atmospheric distillation kettle. The atmospheric distillation kettle and the vacuum distillation kettle are each provided with a feed port, a solvent outlet, and a discharge port, and the discharge port of the atmospheric distillation kettle is connected to the feed port of the vacuum distillation kettle.

[0007] In a second aspect of the present invention, there is provided a method for desolventizing polyisoprene latex, the method comprising: subjecting the crude polyisoprene latex without desolventized solvent to atmospheric distillation; and then subjecting the concentrated latex obtained from the atmospheric distillation to optional vacuum distillation; the method further comprising: spraying an inert gas above the liquid surface of the crude latex during the atmospheric distillation.

[0008] By the above technical solutions, the present invention can achieve the following beneficial effects:

[0009] The apparatus and method of the present invention can timely eliminate the foam during the solvent distillation process, improve the transfer rate of the solvent, shorten the desolventization time of the solvent, and can also improve the emulsifying ability of the emulsifier and the stability of the latex, and reduce the demulsification rate. Moreover, the operation of the present invention is simple, the operation cost is low, it will not cause environmental pollution, and the whole process is continuously operated, which is easy to realize automated production and can ensure the stability of the latex quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of an apparatus for desolventizing latex provided by the present invention.

[0011] DESCRIPTION OF THE REFERENCE NUMERALS

[0012] 1 - showerhead-like liquid spraying element; 2 - crude feed inlet of the atmospheric distillation kettle; 3 - heating medium inlet of the atmospheric distillation kettle; 4 - heating medium outlet of the atmospheric distillation kettle; 5 - solvent outlet of the atmospheric distillation kettle; 6 - discharge outlet of the atmospheric distillation kettle; 7 - heating medium inlet of the vacuum distillation kettle; 8 - heating medium outlet of the vacuum distillation kettle; 9 - discharge outlet of the vacuum distillation kettle; 10 - vacuum control system; 11 - solvent outlet of the vacuum distillation kettle; 12 - atmospheric distillation kettle; 13 - vacuum distillation kettle; 14 - feed inlet of the vacuum distillation kettle. DETAILED DESCRIPTION OF THE INVENTION

[0013] The endpoints and any values disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0014] In a first aspect, the present invention provides an apparatus for desolventizing polyisoprene latex, the apparatus comprising: an atmospheric distillation kettle and an optional vacuum distillation kettle, wherein a gas spraying element and / or a liquid spraying element is provided at the top of the atmospheric distillation kettle, and the atmospheric distillation kettle and the vacuum distillation kettle are each provided with a feed inlet, a solvent outlet and a discharge outlet, and the discharge outlet of the atmospheric distillation kettle is connected to the feed inlet of the vacuum distillation kettle.

[0015] Preferably, the liquid spraying element is in the shape of a shower head. The inventor of the present invention found in the research that when the above-mentioned liquid spraying element is used, spraying can be carried out more uniformly, the contact between the sprayed liquid and the materials in the kettle can be increased, and the foam can be better eliminated.

[0016] Preferably, the volume ratio of the atmospheric distillation kettle to the vacuum distillation kettle is 1-20, preferably 5-15, and most preferably 6-9. It can be understood that in the above-mentioned manner, most of the solvent can be removed in the atmospheric distillation kettle. The specific material of the kettle is not particularly limited, for example, it can be stainless steel.

[0017] Preferably, the atmospheric distillation kettle and the vacuum distillation kettle each have a heat exchange jacket. The heat exchange medium inlet of the heat exchange jacket is at the bottom of the heat exchange jacket, and the heat exchange medium outlet is at the top of the heat exchange jacket. The setting of the jacket is more conducive to controlling the distillation temperature in the kettle body.

[0018] According to the present invention, for further convenient operation, preferably, the feed port of the atmospheric distillation kettle is located at the bottom of the kettle body, the solvent outlet is located at the top of the kettle body, and the discharge port is located in the upper middle part of the kettle body. The ratio of the height of the discharge port to the height of the kettle body is 0.5-1, more preferably 0.6-0.9, and most preferably 0.7-0.8. It can be understood that during the distillation process, the solvent is evaporated in the form of steam and leaves the atmospheric distillation kettle from the solvent outlet at the top of the kettle body.

[0019] According to the present invention, for further convenient operation, preferably, the feed port of the vacuum distillation kettle is located at the bottom of the kettle body, the solvent outlet is located at the top of the kettle body, and the discharge port is located in the upper middle part of the kettle body. The ratio of the height of the discharge port to the height of the kettle body is 0.5-1, more preferably 0.6-0.9, and most preferably 0.7-0.8.

[0020] According to the present invention, in order to further improve the solvent transfer rate and shorten the solvent removal time, a stirring unit is respectively arranged in the atmospheric distillation kettle and the vacuum distillation kettle. The stirring unit includes a stirring shaft and at least one stirring paddle vertically arranged on the stirring shaft. The number of stirring paddles is preferably 1-10, more preferably 2-8, and most preferably 3-5. The stirring paddles can be paddle-type stirring paddles evenly distributed on the stirring shaft. It can be understood that the stirring unit can be connected to a motor to drive the stirring unit to stir.

[0021] Among them, the vacuum distillation device can also include a vacuum control system to control the pressure in the vacuum distillation device.

[0022] The second aspect of the present invention provides a method for desolventizing polyisoprene latex, which method comprises: subjecting the crude polyisoprene latex without desolventized solvent to atmospheric distillation; and then subjecting the concentrated latex obtained from the atmospheric distillation to optional vacuum distillation; the method further comprises: during the atmospheric distillation process, spraying an aqueous inorganic salt solution (or an aqueous solution containing inorganic salt) above the liquid surface of the crude latex.

[0023] It can be understood that the crude latex refers to the latex that has not been desolventized after emulsification and homogenization.

[0024] The inventors of the present invention found in their research that during the atmospheric distillation process, spraying an aqueous inorganic salt solution above the liquid surface of the crude latex can strengthen the emulsifying performance of the emulsifier, reduce the gel loss during the distillation process, and can also timely eliminate the foam generated during the distillation, improve the diffusion efficiency of the solvent, and shorten the desolventization time of the solvent.

[0025] The inventors of the present invention further found in their research that by using the above-mentioned atmospheric distillation, most of the solvent in the crude latex can be removed. And whether to perform vacuum distillation to further remove a small amount of residual solvent can be selected according to the requirements of the product.

[0026] According to the present invention, preferably, the spraying amount of the aqueous inorganic salt solution is 0.001 - 1 L, more preferably 0.002 - 0.1 L, and most preferably 0.01 - 0.02 L relative to each liter of the crude latex. The inventors of the present invention found in their research that when the above-mentioned volume ratio is satisfied, the purpose of timely eliminating the foam generated during the distillation, improving the solvent transfer rate, and shortening the solvent desolventization time can be achieved without introducing too much water. According to the present invention, the method can be carried out continuously, the crude latex is fed in a continuous manner, the aqueous inorganic salt solution is sprayed in a continuous manner, and the ratio between the feeding speed of the crude latex and the spraying speed of the aqueous inorganic salt solution is preferably 1 - 1000:1, more preferably 10 - 500:1, and most preferably 50 - 100:1.

[0027] According to the present invention, the inorganic salt only needs to be non-toxic and does not react with the crude latex, but preferably, the inorganic salt is a strong electrolyte salt, and more preferably, the inorganic salt is at least one of NaCl, KCl, Na2SO4, and K2SO4. During the atmospheric distillation process, selecting the above-mentioned inorganic salt can further strengthen the emulsifying performance of the emulsifier and further reduce the gel loss during the distillation.

[0028] According to the present invention, preferably, the mass concentration of the inorganic salt in the aqueous inorganic salt solution is 0.1% - 50%, preferably 5% - 30%, and most preferably 10% - 20%.

[0029] According to the present invention, preferably, the temperature of the inorganic salt aqueous solution is 0°C - 100°C, more preferably 10°C - 50°C, and most preferably 20°C - 30°C. It can be understood that during the atmospheric distillation process, the temperature of the material is relatively high. The inventors of the present invention found in the research that when the temperature of the inorganic salt aqueous solution meets the above requirements, it can not only break the foam in the kettle body and release the solvent vapor in the foam in a timely manner, but also prevent the solvent vapor from instantaneously condensing due to the low temperature of the inorganic salt aqueous solution, which is convenient for solvent evaporation. Moreover, the normal-temperature aqueous solution eliminates the operations of heating or condensation. Especially when the temperature of the inorganic salt aqueous solution is 20°C - 30°C, its temperature is close to room temperature, eliminating the operations of heating or condensation and saving energy consumption.

[0030] According to the present invention, preferably, the pH value of the inorganic salt aqueous solution is adjusted by an inorganic base, and the inorganic base is preferably at least one of NaOH and KOH.

[0031] According to the present invention, preferably, the pH value of the inorganic salt aqueous solution is controlled at 9 - 14, more preferably 10 - 13.5, and most preferably 11 - 13.

[0032] According to the present invention, preferably, the conditions of the atmospheric distillation enable the solvent removed by the atmospheric distillation to account for 80 vol% - 99 vol% of the total amount of the solvent in the crude latex, more preferably 90 vol% - 97 vol%, and most preferably 92 vol% - 95 vol%. It can be understood that generally, the longer the residence time of the material in the atmospheric distillation kettle, the more solvent is removed. To achieve the above solvent removal amount, the residence time is generally 1 - 20 h, or 5 - 15 h, or 6 - 10 h to complete the atmospheric distillation.

[0033] According to the present invention, preferably, the conditions of the vacuum distillation enable the solvent removed by the vacuum distillation to account for 1 vol% - 20 vol% of the total amount of the solvent in the crude latex, more preferably 3 vol% - 10 vol%, and most preferably 5 vol% - 8 vol%. To achieve the above solvent removal amount, the residence time is generally 0.2 h - 4 h, or 0.5 h - 3 h, or 1 - 2.4 h to complete the vacuum distillation.

[0034] According to the present invention, preferably, the difference between the temperature of the atmospheric distillation and the boiling point of the solvent in the crude latex is 0°C - 20°C, more preferably 3°C - 15°C, and most preferably 5°C - 10°C. It can be understood that the temperature of the atmospheric distillation is higher than the boiling point of the solvent in the crude latex. The inventors of the present invention further found in the research that when meeting the above range, the solvent can be evaporated faster, shortening the solvent evaporation time, and preventing the material from boiling violently, and the operation is relatively safe.

[0035] According to the present invention, preferably, the pressure of the vacuum distillation is 0.05 MPa - 0.0001 MPa, more preferably 0.01 MPa - 0.001 MPa, and most preferably 0.008 MPa - 0.003 MPa. The inventors of the present invention further found in the research that within the above range, it is more conducive to the removal of the remaining solvent. And a vacuum control system can be set in the vacuum distillation device to control the pressure.

[0036] According to the present invention, in order to further remove the remaining solvent in the material after atmospheric distillation, preferably, the difference between the temperature of the vacuum distillation and the boiling point of the solvent in the crude latex is 0 °C - 20 °C, more preferably 2 °C - 15 °C, and most preferably 3 °C - 10 °C.

[0037] According to the present invention, preferably, the stirring speeds of the atmospheric distillation and the vacuum distillation are each independently 100 rpm - 2000 rpm, more preferably 300 rpm - 1600 rpm, and most preferably 600 rpm - 1200 rpm. The inventors of the present invention found in the research that within the above range, not only can the latex material be completely turbulent, improving the transmission rate of the solvent and shortening the distillation time, but also the free emulsifier in the material can be combined with the demulsified rubber molecules faster to form new latex particles, reducing demulsification.

[0038] According to the present invention, preferably, the volume content of the solvent in the crude latex is 30% - 70%, more preferably 40% - 55%, and most preferably 42% - 50%.

[0039] According to the present invention, preferably, the weight content of polyisoprene in the crude latex is 2% - 10%, more preferably 3% - 8%, and most preferably 4% - 6%.

[0040] According to the present invention, preferably, the weight content of the emulsifier in the crude latex is 0.5% - 10%, more preferably 1% - 5%, and most preferably 1.5% - 4%.

[0041] According to the present invention, preferably, the solvent in the crude latex is a saturated aliphatic hydrocarbon and / or an alicyclic hydrocarbon, more preferably at least one of n - hexane, cyclohexane, methylcyclopentane, n - heptane, n - pentane, and cyclopentane.

[0042] According to the present invention, preferably, the number - average molecular weight of the polyisoprene in the crude latex is 10,000 - 1,000,000 g / mol, more preferably 100,000 - 500,000 g / mol, and most preferably 200,000 - 350,000 g / mol.

[0043] Among them, there is no particular limitation on the specific substance of the emulsifier, and the method of the present invention has a wide application scope. Preferably, however, the emulsifier in the crude latex is an anionic emulsifier and / or a non-ionic emulsifier. Among them, the anionic emulsifier can be a fatty acid salt, alkylbenzene sulfonate, or alkyl sulfate ester salt of C12-C30, such as the sodium alkylbenzene sulfonate series, oleate series, laurate series, rosin acid salt series, and linoleate series, etc.; the non-ionic emulsifier can be an ether, alcohol, or ester emulsifier between C8-C24, such as fatty alcohol polyoxyethylene ether, SPAN series, Tween series, and Tween series, etc.

[0044] According to the present invention, among them, the atmospheric distillation and vacuum distillation can be carried out in the same kettle or separately in different kettles. However, for more convenient operation, preferably, the method is carried out in the device as described in the first aspect of the present invention. The atmospheric distillation is carried out in an atmospheric distillation kettle, and the vacuum distillation is carried out in a vacuum distillation kettle. The atmospheric distillation kettle and the vacuum distillation kettle are each provided with a feed port, a solvent outlet, and a discharge port, and the discharge port of the atmospheric distillation kettle is connected to the feed port of the vacuum distillation kettle.

[0045] The present invention does not particularly limit the preparation method of the crude latex, and the method in CN109929123A can be adopted. However, according to a preferred embodiment of the present invention, the method for preparing polyisoprene latex (crude latex) includes the following steps. This preferred embodiment can give full play to the emulsifying ability of the emulsifier as much as possible, reduce the viscosity of the latex mixture, reduce the loss of rubber molecular weight, and the prepared crude latex has a higher molecular weight and has higher mechanical properties, higher mechanical stability, and better film-forming properties.

[0046] (1) Mix the polyisoprene dry rubber with the non-ionic emulsifier solution for pre-emulsification;

[0047] (2) Pre-mix and emulsify the mixture obtained in step (1) with the anionic emulsifier in sequence.

[0048] The inventors of the present invention found in the research that dissolving the polyisoprene dry rubber in the non-ionic emulsifier solution first can make the polyisoprene and the non-ionic emulsifier disperse more uniformly together and combine better. At the same time, due to the presence of the aqueous solution, the intermolecular forces between the rubber molecular chains are better weakened, so that fewer rubber molecular chains are broken during the subsequent emulsification, the rubber molecular chains can be better protected, the loss of molecular weight is reduced, and the emulsifying ability of the emulsifier is exerted as much as possible. Then, pre-emulsification, pre-mixing, and emulsification are carried out in sequence, and polyisoprene latex with a higher molecular weight, higher mechanical properties, higher mechanical stability, and better film-forming properties can be obtained.

[0049] According to the present invention, in order to further exert the emulsifying ability of the non-ionic emulsifier, better protect the rubber molecular chain, and reduce the loss of molecular weight, preferably, the mass dosage of the non-ionic emulsifier in the non-ionic emulsifier solution is 0.5%-5% of the mass of the polyisoprene dry rubber, more preferably 0.8%-3%, and most preferably 1%-2.5%.

[0050] According to the present invention, in order to further exert the emulsifying ability of the emulsifier, preferably, the mass dosage of the anionic emulsifier is 5%-50% of the mass of the polyisoprene dry rubber, more preferably 8%-40%, and more preferably 10%-30%.

[0051] According to the present invention, preferably, in the polyisoprene of the polyisoprene dry rubber, the content of the cis-1,4-polyisoprene structure is not less than 95% by mass, and the number-average molecular weight of the polyisoprene in the polyisoprene dry rubber is 150,000-400,000 g / mol, more preferably 180,000-300,000 g / mol, and most preferably 200,000-230,000 g / mol. Among them, the synthesis method of the polyisoprene is not particularly limited, and it can be prepared by rare earth catalysis, for example. When the above-mentioned range is satisfied, especially the content range of the cis-1,4-polyisoprene structure, it can further ensure that the prepared polyisoprene latex has a high tensile strength of the rubber film and an elongation at break of the rubber film.

[0052] According to the present invention, preferably, in the non-ionic emulsifier solution, the mass concentration of the non-ionic emulsifier is 0.01%-1%, more preferably 0.12%-0.5%, and most preferably 0.15%-0.4%.

[0053] According to the present invention, in order to further exert the emulsifying ability of the non-ionic emulsifier, better protect the rubber molecular chain, and reduce the loss of molecular weight, preferably, the non-ionic emulsifier is at least one of ethers of C8-C24, alcohols of C8-C24, and esters of C8-C24, preferably at least one of fatty alcohol polyoxyethylene ethers, Spans, and Tweens, and more preferably sorbitan monooleate (for example, commercially available Span-80, i.e., SPAN-80) and / or polyoxyethylene sorbitan ether monostearate (for example, commercially available Tween-61, i.e., Tween-61).

[0054] According to the present invention, the solvent in the non-ionic emulsifier solution is not particularly limited as long as it can ensure the dissolution of the polyisoprene dry rubber. However, considering price, environmental protection, and subsequent removal, the solvent is preferably at least one of n-hexane, cyclohexane, methylcyclopentane, n-heptane, n-pentane, and cyclopentane.

[0055] According to the present invention, the conditions for pre-emulsification are not particularly limited as long as the mixture obtained after pre-emulsification is homogeneous and transparent. Preferably, however, the temperature for pre-emulsification is 10°C - 80°C, more preferably 20°C - 70°C, and even more preferably 30°C - 60°C; the time for pre-emulsification is 1 h - 24 h, more preferably 2 h - 15 h, and most preferably 3 - 10 h; the pre-emulsification is carried out under stirring conditions, and the rotation speed of the stirring is 100 rpm - 2000 rpm, more preferably 500 rpm - 1500 rpm, and even more preferably 700 rpm - 1000 rpm. Within the above ranges, especially within the temperature range, it can be further ensured that the polyisoprene dry rubber is completely dissolved as much as possible. And, in order to further ensure the dissolution of the polyisoprene dry rubber as much as possible, the polyisoprene dry rubber can be first cut into small pieces and then pre-emulsified. For example, a non-ionic emulsifier is added to a container containing a solvent, stirred until dissolved, and then the polyisoprene dry rubber is cut into small pieces and added to the above container.

[0056] According to the present invention, preferably, the anionic emulsifier is used in the form of an aqueous solution of the anionic emulsifier, and in the aqueous solution of the anionic emulsifier, the mass concentration of the anionic emulsifier is 0.1% - 10%, more preferably 1.2% - 5%, and most preferably 1.5% - 4%.

[0057] According to the present invention, in order to further exert the emulsifying ability of the emulsifier, preferably, the pH value of the aqueous solution of the anionic emulsifier is 9 - 15, more preferably 10 - 14, and most preferably 11 - 13. Among them, the pH value can be controlled by using an inorganic base, such as KOH and / or NaOH.

[0058] According to the present invention, in order to further exert the emulsifying ability of the emulsifier, preferably, the anionic emulsifier is at least one of fatty acid salts of C12 - C30, alkylbenzene sulfonates of C12 - C30, and alkyl sulfates of C12 - C30, more preferably at least one of sodium alkylbenzene sulfonate, oleate, laurate, rosin acid salt, and linolenate, and even more preferably at least one of sodium dodecylbenzene sulfonate and potassium disproportionated rosin.

[0059] According to the present invention, preferably, the premixing method includes: adding an aqueous solution of an anionic emulsifier to the mixture. Based on the volume of the aqueous solution of the anionic emulsifier, the addition rate of the aqueous solution of the anionic emulsifier is 1% by volume / min - 50% by volume / min, more preferably 2% by volume / min - 20% by volume / min, and most preferably 3% by volume / min - 10% by volume / min; the premixing is carried out under stirring conditions, and the stirring speed is 100 rpm - 3000 rpm, more preferably 300 rpm - 2000 rpm, and most preferably 500 rpm - 1000 rpm; the temperature of the premixing is 10°C - 80°C, more preferably 20°C - 70°C, and more preferably 30°C - 60°C. It can be understood that if the volume of the aqueous solution of the anionic emulsifier is 1000 ml, when added at an addition rate of 5% by volume / min, 50 ml (i.e., 1000 ml * 5%) of the aqueous solution of the anionic emulsifier is added per minute. Among them, the temperature of the premixing can be achieved by controlling the temperature of the aqueous solution of the anionic emulsifier. The inventors of the present invention also found in the research that as the addition amount of the aqueous solution of the anionic emulsifier increases, the material first forms a W / O (water-in-oil) emulsion and then gradually transforms into an O / W (oil-in-water) emulsion; and when the ranges as described above are satisfied, especially the addition rate range of the aqueous solution of the anionic emulsifier, the stability of the latex can be further increased.

[0060] According to the present invention, preferably, the emulsification method is mechanical emulsification, and the stirring speed of the mechanical emulsification is 1000 rpm - 10000 rpm, more preferably 2500 rpm - 8000 rpm, and most preferably 3500 rpm - 7000 rpm.

[0061] According to the present invention, preferably, the emulsification time is 2 min - 30 min, more preferably 5 min - 20 min, and most preferably 7 min - 15 min.

[0062] According to the present invention, preferably, the emulsification temperature is 10°C - 60°C, more preferably 20°C - 55°C, and more preferably 30°C - 50°C.

[0063] The inventors of the present invention found that when the rotation speed, temperature, and time ranges as described above are satisfied, better emulsification can be achieved.

[0064] The method of the present invention may further include removing the solvent from the emulsified product, and the solvent removal can be carried out in a conventional manner, which will not be elaborated here.

[0065] The present invention also provides a polyisoprene latex prepared by the method as described above.

[0066] According to the present invention, preferably, the number-average molecular weight of the polyisoprene latex is 150,000 - 400,000 g / mol, more preferably 180,000 - 300,000 g / mol, and most preferably 200,000 - 230,000 g / mol.

[0067] According to the present invention, preferably, the particle size of the polyisoprene latex is 100 nm - 2000 nm, more preferably 200 - 1500 nm, and most preferably 300 - 1200 nm.

[0068] According to the present invention, preferably, the tensile strength of the polyisoprene latex is 15 MPa - 30 MPa, more preferably 18 MPa - 25 MPa, and most preferably 20 MPa - 22 MPa.

[0069] According to the present invention, preferably, the elongation at break of the polyisoprene latex is 700% - 1500%, more preferably 900% - 1300%, and most preferably 1000% - 1200%.

[0070] According to the present invention, the mass concentration of polyisoprene in the polyisoprene latex is 40 - 80% by mass, more preferably 50 - 70% by mass, and even more preferably 55 - 65% by mass.

[0071] The present invention will be described in detail below through examples.

[0072] In the following examples and comparative examples, unless otherwise specified, the following-described apparatus is used to remove the organic solvent from the crude latex:

[0073] As Figure 1 shown, the apparatus includes an atmospheric distillation kettle 12 and a vacuum distillation kettle 13.

[0074] The volume of the atmospheric distillation kettle is 200 L (the volume below the horizontal plane of the discharge port, i.e., the effective volume of the kettle). The height of the atmospheric distillation kettle 12 is 1 m, and it is provided with an atmospheric distillation kettle feed port 2 at the bottom of the kettle body, an atmospheric distillation kettle solvent outlet 5 at the top of the kettle body, and an atmospheric distillation kettle discharge port 6 at the upper middle part of the kettle body with a height of 0.7 m. A showerhead-shaped liquid spraying element is provided at the top of the atmospheric distillation kettle.

[0075] The volume of the vacuum distillation kettle 13 is 30 L (the volume below the horizontal plane of the discharge port, i.e., the effective volume of the kettle) and the height is 0.56 m. The vacuum distillation kettle 13 is provided with a vacuum distillation kettle feed port 14 at the bottom of the kettle body, a vacuum distillation kettle solvent outlet 11 at the top of the kettle body, and a vacuum distillation kettle discharge port 9 at the upper middle part of the kettle body with a height of 0.4 m.

[0076] The outlet 6 of the atmospheric distillation still is connected to the inlet 14 of the vacuum distillation still. Moreover, both the atmospheric distillation still and the vacuum distillation still are each equipped with a heat exchange jacket. The heat exchange medium inlet of the heat exchange jacket is at the bottom of the heat exchange jacket, and the heat exchange medium outlet is at the top of the heat exchange jacket. The heating medium of the atmospheric distillation still 12 enters from the inlet 3 of the heating medium of the atmospheric distillation still and exits from the outlet 4 of the heating medium of the atmospheric distillation still; the heating medium of the vacuum distillation still 14 enters from the inlet 7 of the heating medium of the vacuum distillation still and exits from the outlet 8 of the heating medium of the vacuum distillation still.

[0077] A stirring unit is respectively arranged in the atmospheric distillation still and the vacuum distillation still. The stirring unit includes a stirring shaft and three stirring paddles arranged vertically and fixed on the stirring shaft (the three stirring paddles are equally spaced).

[0078] Among them, a switching valve is installed on each material pipeline for transporting materials to facilitate controlling the on-off of the material pipeline. And a flow meter is provided on the material pipeline. Moreover, steam is introduced into the jackets of the atmospheric distillation still 12 and the vacuum distillation still 13 to control the atmospheric distillation still 12 and the vacuum distillation still 13 at their respective required temperatures.

[0079] In the following examples and comparative examples, the following method is used to calculate the residual solvent amount and gel loss ratio in the latex products after atmospheric distillation and vacuum distillation:

[0080] Calculation method for the residual solvent amount of latex: Take the material, demulsify it with anhydrous ethanol, then repeatedly rinse the surface moisture with anhydrous ethanol, air-dry it at room temperature for 5 h to remove the surface anhydrous ethanol and then dry it (the drying temperature is 75 ± 2 °C and the time is 12 h). According to the calculation formula w = [(m0 - m1) / m0] × 10 6 , where w is the residual solvent amount, ppm; m0 is the mass of the rubber particles after air-drying; m1 is the mass of the rubber particles after drying. The residual solvent amount of the latex is obtained.

[0081] Calculation method for the gel loss ratio: Take the material, pass it through a 200-mesh filter sieve, repeatedly rinse the filtered coagulum and then put it into an oven to dry (the drying temperature is 75 ± 2 °C and the time is 12 h). According to the calculation formula j = [m1 / (m0 × p + m1)] × 100, where j is the gel loss ratio; m0 is the mass of the dilute latex before drying, in g; m1 is the mass of the gel after drying, in g; p is the mass percentage of latex in the dilute latex before drying. The gel loss ratio during the distillation of the crude latex is obtained.

[0082] Example 1

[0083] In the crude latex: It contains 50 vol% of the solvent n-hexane (the boiling point of n-hexane is 69 °C); the content of polyisoprene is 5 wt%, and the number average molecular weight is 200,000 g / mol; the emulsifier is a mixture of the anionic emulsifier sodium dodecylbenzenesulfonate and potassium disproportionated rosin, with a content of 4 wt%.

[0084] Steam is introduced to maintain the temperature of the atmospheric distillation still at 77 °C. The stirring unit is started in the atmospheric distillation still at a rotation speed of 1000 rpm, and crude latex is added to the atmospheric distillation still at a rate of 40 L / h. In the atmospheric distillation still, an aqueous NaCl solution with a mass concentration of 15% is sprayed above the liquid surface of the crude latex at a spraying rate of 0.5 L / h. The temperature of the aqueous solution is 25 °C, and the pH value of the aqueous solution adjusted with NaOH is 12. The crude latex stays in the atmospheric distillation still until, after atmospheric distillation, the remaining solvent in the material accounts for 8% by volume of the total solvent in the original crude latex. At this time, the residence time of the crude latex in the atmospheric distillation still is 6.7 h, and it is measured that the gel loss ratio of the material after atmospheric distillation is 3%.

[0085] The material flowing out of the atmospheric distillation still is introduced into the vacuum distillation still at a rate of 21 L / h. The temperature in the vacuum distillation still is maintained at 77 °C by steam, the pressure in the still is controlled at 0.005 MPa, and the rotation speed is 1000 rpm. The crude latex stays in the vacuum distillation still until, after vacuum distillation, the remaining solvent in the material accounts for 0.4% by volume of the total solvent in the original crude latex. At this time, the residence time of the material in the vacuum distillation still is 1.5 h, and it is measured that the gel loss ratio after vacuum distillation is 0%.

[0086] Example 2

[0087] In the crude latex: it contains 42% by volume of the solvent n-hexane (the boiling point of n-hexane is 69 °C); the content of polyisoprene is 4% by weight, and the number average molecular weight is 310,000 g / mol; the emulsifier is potassium disproportionated rosin with a content of 1.5% by weight.

[0088] Steam is introduced to maintain the temperature of the atmospheric distillation still at 74 °C. The stirring unit is started in the atmospheric distillation still at a rotation speed of 600 rpm, and crude latex is added to the atmospheric distillation still at a rate of 42 L / h. In the atmospheric distillation still, an aqueous KCl solution with a mass concentration of 20% is sprayed above the liquid surface of the crude latex at a spraying rate of 0.84 L / h. The temperature of the aqueous solution is 30 °C, and the pH value of the aqueous solution adjusted with KOH is 11. The crude latex stays in the atmospheric distillation still until, after atmospheric distillation, the remaining solvent in the material accounts for 6% by volume of the total solvent in the original crude latex. At this time, the residence time of the crude latex in the atmospheric distillation still is 6 h, and it is measured that the gel loss ratio of the material after atmospheric distillation is 2.5%.

[0089] The material flowing out of the atmospheric distillation still is introduced into the vacuum distillation still at a flow rate of 32.6 L / h. The temperature in the vacuum distillation still is maintained at 79 °C by steam, the pressure in the still is controlled at 0.003 MPa, and the rotation speed is 1200 rpm. The crude latex stays in the vacuum distillation still. After vacuum distillation, the remaining solvent in the material accounts for 0.4% by volume of the total solvent in the original crude latex. At this time, the residence time of the material in the vacuum distillation still is 1 h, and the gel loss ratio after vacuum distillation is tested to be 0%.

[0090] Example 3

[0091] In the crude latex: it contains 50% by volume of the solvent n-hexane (the boiling point of n-hexane is 69 °C); the content of polyisoprene is 6% by weight, and the number average molecular weight is 350,000 g / mol; the emulsifier is sodium dodecylbenzenesulfonate, and the total content of the emulsifier is 3% by weight.

[0092] Steam is introduced to maintain the temperature of the atmospheric distillation still at 79 °C. The stirring unit is started in the atmospheric distillation still, and the rotation speed is 1200 rpm. The crude latex is added to the atmospheric distillation still at a speed of 28 L / h. In the atmospheric distillation still, an aqueous solution of Na2SO4 with a mass concentration of 10% is sprayed above the liquid level of the crude latex, the spraying rate is 0.28 L / h, the temperature of the aqueous solution is 20 °C, and the pH value of the aqueous solution adjusted with NaOH is 13. The crude latex stays in the atmospheric distillation still. After atmospheric distillation, the remaining solvent in the material accounts for 5% by volume of the total solvent in the original crude latex. At this time, the residence time of the crude latex in the atmospheric distillation still is 9.9 h, and the gel loss ratio of the material after atmospheric distillation is tested to be 3.5%.

[0093] The material flowing out of the atmospheric distillation still is introduced into the vacuum distillation still at a flow rate of 12.6 L / h. The temperature in the vacuum distillation still is maintained at 72 °C by steam, the pressure in the still is controlled at 0.008 MPa, and the rotation speed is 600 rpm. The crude latex stays in the vacuum distillation still. After vacuum distillation, the remaining solvent in the material accounts for 0.1% by volume of the total solvent in the original crude latex. At this time, the residence time of the material in the vacuum distillation still is 2.4 h, and the gel loss ratio after vacuum distillation is tested to be 0.1%.

[0094] Example 4

[0095] In the crude latex: it contains 48% by volume of the solvent n-hexane (the boiling point of n-hexane is 69 °C); the content of polyisoprene is 5% by weight, and the number average molecular weight is 250,000 g / mol; the emulsifier is potassium disproportionated rosin, and the content is 4% by weight.

[0096] Steam is introduced to maintain the temperature of the atmospheric distillation kettle at 75 °C. The stirring unit is started in the atmospheric distillation kettle at a rotational speed of 800 rpm. The crude latex is added to the atmospheric distillation kettle at a rate of 35 L / h. In the atmospheric distillation kettle, an aqueous solution of K2SO4 with a mass concentration of 14% is sprayed above the liquid level of the crude latex at a spraying rate of 0.5 L / h. The temperature of the aqueous solution is 27 °C, and the pH value of the aqueous solution adjusted with KOH is 12.5. The crude latex stays in the atmospheric distillation kettle until, after atmospheric distillation, the remaining solvent in the material accounts for 7% by volume of the total solvent in the original crude latex. At this time, the residence time of the crude latex in the atmospheric distillation kettle is 7.5 h, and it is measured that the gel loss ratio of the material after atmospheric distillation is 3.5%.

[0097] The material flowing out of the atmospheric distillation kettle is introduced into the vacuum distillation kettle at a rate of 18 L / h. The temperature in the vacuum distillation kettle is maintained at 78 °C by steam, the pressure in the kettle is controlled at 0.004 MPa, and the rotational speed is 800 rpm. The crude latex stays in the vacuum distillation kettle until, after vacuum distillation, the remaining solvent in the material accounts for 0.2% by volume of the total solvent in the original crude latex. At this time, the residence time of the material in the vacuum distillation kettle is 1.7 h, and it is measured that the gel loss ratio after vacuum distillation is 0%.

[0098] Example 5

[0099] In the crude latex: the solvent n-hexane (boiling point of n-hexane is 69 °C) has a content of 55% by volume; the content of polyisoprene is 3% by weight, and the number average molecular weight is 100,000 g / mol; the emulsifier is polyoxyethylene sorbitan monostearate with a content of 1% by weight.

[0100] Steam is introduced to maintain the temperature of the atmospheric distillation kettle at 72 °C. The stirring unit is started in the atmospheric distillation kettle at a rotational speed of 300 rpm. The crude latex is added to the atmospheric distillation kettle at a rate of 35 L / h. In the atmospheric distillation kettle, an aqueous solution of K2SO4 with a mass concentration of 30% is sprayed above the liquid level of the crude latex at a spraying rate of 0.07 L / h. The temperature of the aqueous solution is 50 °C, and the pH value of the aqueous solution adjusted with KOH is 13.5. The crude latex stays in the atmospheric distillation kettle until, after atmospheric distillation, the remaining solvent in the material accounts for 10% by volume of the total solvent in the original crude latex. At this time, the residence time of the crude latex in the atmospheric distillation kettle is 7.6 h, and it is measured that the gel loss ratio of the material after atmospheric distillation is 3%.

[0101] The material flowing out of the atmospheric distillation kettle is introduced into the vacuum distillation kettle at a flow rate of 16 L / h. The temperature in the vacuum distillation kettle is maintained at 71 °C by steam, the pressure in the kettle is controlled at 0.01 MPa, and the rotation speed is 1600 rpm. The crude latex stays in the vacuum distillation kettle. After vacuum distillation, the remaining solvent in the material accounts for 7.5 vol% of the total solvent in the original crude latex. At this time, the residence time of the material in the vacuum distillation kettle is 1.86 h, and the gel loss ratio after vacuum distillation is measured to be 0.1%.

[0102] Example 6

[0103] In the crude latex: it contains 40 vol% of the solvent n-hexane (the boiling point of n-hexane is 69 °C); the content of polyisoprene is 8 wt%, and the number average molecular weight is 500,000 g / mol; the emulsifier is potassium disproportionated rosin, and the content is 5 wt%.

[0104] Steam is introduced to maintain the temperature of the atmospheric distillation kettle at 84 °C. The stirring unit is started in the atmospheric distillation kettle, and the rotation speed is 1600 rpm. The crude latex is added to the atmospheric distillation kettle at a rate of 35 L / h. In the atmospheric distillation kettle, an aqueous solution of K2SO4 with a mass concentration of 5% is sprayed above the liquid level of the crude latex, the spraying rate is 3.5 L / h, the temperature of the aqueous solution is 10 °C, and the pH value of the aqueous solution adjusted with KOH is 10. The crude latex stays in the atmospheric distillation kettle. After atmospheric distillation, the remaining solvent in the material accounts for 3 vol% of the total solvent in the original crude latex. At this time, the residence time of the crude latex in the atmospheric distillation kettle is 7 h, and the gel loss ratio of the material after atmospheric distillation is measured to be 2.9%.

[0105] The material flowing out of the atmospheric distillation kettle is introduced into the vacuum distillation kettle at a flow rate of 16 L / h. The temperature in the vacuum distillation kettle is maintained at 84 °C by steam, the pressure in the kettle is controlled at 0.001 MPa, and the rotation speed is 300 rpm. The crude latex stays in the vacuum distillation kettle. After vacuum distillation, the remaining solvent in the material accounts for 0.2 vol% of the total solvent in the original crude latex. At this time, the residence time of the material in the vacuum distillation kettle is 1.1 h, and the gel loss ratio after vacuum distillation is measured to be 0%.

[0106] Example 7

[0107] The organic solvent is removed according to the method of Example 3, except that an aqueous solution of Na2SO4 with a mass concentration of 0.1% is sprayed above the liquid level of the crude latex, the spraying rate is 0.028 L / h, the temperature of the aqueous solution is 0 °C, and the pH value of the aqueous solution adjusted with NaOH is 9. After the crude latex stays in the atmospheric distillation kettle for 9.9 h, a sample in the atmospheric distillation kettle is taken and tested. It is found that the remaining solvent in the material accounts for 6 vol% of the total solvent in the original crude latex, and the gel loss ratio is 4%.

[0108] The material that has stayed in the atmospheric distillation kettle for 9.9 h is fed into the vacuum distillation kettle. After the material has stayed in the vacuum distillation kettle for 2.4 h, the vacuum distillation is stopped. A sample is taken and tested, and it is found that the remaining solvent in the material accounts for 0.3% by volume of the total solvent in the original crude latex, and the gel loss ratio is 0.2%.

[0109] Example 8

[0110] Remove the organic solvent according to the method of Example 3, except that the showerhead-shaped liquid spraying element is replaced with a tap water pipe.

[0111] After the crude latex has stayed in the atmospheric distillation kettle for 9.9 h, a sample is taken from the atmospheric distillation kettle and tested. It is found that the remaining solvent in the material accounts for 11% by volume of the total solvent in the original crude latex, and the gel loss ratio is 8%.

[0112] The material that has stayed in the atmospheric distillation kettle for 9.9 h is fed into the vacuum distillation kettle. After the material has stayed in the vacuum distillation kettle for 2.4 h, the vacuum distillation is stopped. A sample is taken and tested, and it is found that the remaining solvent in the material accounts for 3% by volume of the total solvent in the original crude latex, and the gel loss ratio is 1.5%.

[0113] Comparative Example 1

[0114] Remove the organic solvent according to the method of Example 1, except that the aqueous inorganic salt solution is not sprayed in the atmospheric distillation kettle. After the crude latex has stayed in the atmospheric distillation kettle for 6.7 h, a sample is taken from the atmospheric distillation kettle and tested. It is found that the remaining solvent in the material accounts for 22% by volume of the total solvent in the original crude latex, and the gel loss ratio is 8%.

[0115] The material that has stayed in the atmospheric distillation kettle for 6.7 h is fed into the vacuum distillation kettle. After the material has stayed in the vacuum distillation kettle for 1.5 h, a sample is taken and tested, and it is found that the remaining solvent in the material accounts for 4% by volume of the total solvent in the original crude latex, and the gel loss ratio is 1%.

[0116] Comparative Example 2

[0117] Remove the organic solvent according to the method of Example 2, except that the aqueous inorganic salt solution is not sprayed in the atmospheric distillation kettle. After the crude latex has stayed in the atmospheric distillation kettle for 6 h, a sample is taken from the atmospheric distillation kettle and tested. It is found that the remaining solvent in the material accounts for 26% by volume of the total solvent in the original crude latex, and the gel loss ratio is 7.5%.

[0118] The material that has stayed in the atmospheric distillation kettle for 6 h is fed into the vacuum distillation kettle. After the material has stayed in the vacuum distillation kettle for 1 h, a sample is taken and tested, and it is found that the remaining solvent in the material accounts for 4% by volume of the total solvent in the original crude latex, and the gel loss ratio is 1%.

[0119] Comparative Example 3

[0120] The organic solvent was removed according to the method of Example 3, except that the aqueous inorganic salt solution was not sprayed into the atmospheric distillation kettle. After the crude latex stayed in the atmospheric distillation kettle for 9.9 h, a sample in the atmospheric distillation kettle was taken and tested. It was found that the remaining solvent in the material accounted for 15% by volume of the total solvent in the original crude latex, and the gel loss ratio was 12%.

[0121] The material that had stayed in the atmospheric distillation kettle for 9.9 h was fed into the vacuum distillation kettle. After the material stayed in the vacuum distillation kettle for 2.4 h, a sample was taken and tested. It was found that the remaining solvent in the material accounted for 1% by volume of the total solvent in the original crude latex, and the gel loss ratio was 2%.

[0122] Comparative Example 4

[0123] The organic solvent was removed according to the method of Example 4, except that the aqueous inorganic salt solution was not sprayed into the atmospheric distillation kettle. After the crude latex stayed in the atmospheric distillation kettle for 7.5 h, a sample in the atmospheric distillation kettle was taken and tested. It was found that the remaining solvent in the material accounted for 18% by volume of the total solvent in the original crude latex, and the gel loss ratio was 10%.

[0124] The material that had stayed in the atmospheric distillation kettle for 7.5 h was fed into the vacuum distillation kettle. After the material stayed in the vacuum distillation kettle for 1.7 h, a sample was taken and tested. It was found that the remaining solvent in the material accounted for 2% by volume of the total solvent in the original crude latex, and the gel loss ratio was 1.5%.

[0125] It can be seen from the above examples and comparative examples that for Examples 1-8 adopting the technical solution of the present invention, better solvent removal effect can be obtained in a shorter time, the solvent removal time is shortened, and the gel loss ratio is lower, that is, demulsification is significantly reduced. Among them, Examples 1-4 have better effects.

[0126] In the following examples,

[0127] SPAN-80, the component is sorbitan monooleate;

[0128] Tween-61, the component is polyoxyethylene sorbitan monostearate;

[0129] Mooney 70 rubber, the component is polyisoprene, in which the content of cis-1,4-polyisoprene structure is not less than 95% by mass, and the number-average molecular weight is 220,000 g / mol,

[0130] The test method for the molecular weight of the latex is: first dry the latex and then determine it by gel permeation liquid chromatography (GPC);

[0131] The latex particle size was tested using a Malvern nano particle size and Zeta potential analyzer;

[0132] The pH value of the emulsifier was tested using an S475-LRF multi-functional pH meter;

[0133] The mass concentration of polyisoprene in the polyisoprene latex was tested by thermogravimetric method;

[0134] The test method for the tensile strength of the rubber film was GB / T528 - 1998;

[0135] The test method for the elongation at break of the rubber film was GB / T528 - 1998;

[0136] The test method for the storage stability of the latex was to let it stand still and observe. The longer the storage stability time of the latex, the better the mechanical stability.

[0137] Example 9

[0138] 500 g of n - hexane solvent was pressured into a 2 - L glass kettle with a jacket. 0.75 g of non - ionic emulsifier SPAN - 80 was added to the glass kettle and stirred until completely dissolved, that is, the solution looked homogeneous and transparent to the naked eye. 56 g of Mooney 70 rubber was weighed and cut into small pieces and then added to the above - mentioned glass kettle for pre - emulsification. The stirring speed for pre - emulsification was 800 rpm. The temperature of the pre - emulsification was heated to 60 °C by the water bath in the jacket of the glass kettle. After stirring for 3 h, the substances in the kettle formed a homogeneous and transparent latex.

[0139] 550 g of deionized water was added to a beaker. 11 g of sodium dodecylbenzenesulfonate was weighed and added to the beaker. The beaker was placed on a flat heater and heated, and continuously stirred with a glass rod until the emulsifier was completely dissolved. A little KOH was added to adjust the pH value to 11.2. The temperature of the solution was controlled at 50 °C. This emulsifier solution was slowly added to the above - mentioned glass kettle for premixing. The addition time was 20 min, and the stirring speed during addition was controlled at 500 rpm. After all additions were completed, the stirring speed was increased to 5000 rpm for emulsification, and stirred at 50 °C for 10 min to obtain crude polyisoprene latex. The crude latex in the kettle was desolventized and concentrated to obtain a stable polyisoprene latex with a concentration of 60 wt%.

[0140] Example 10

[0141] 500 g of n - hexane solvent was pressured into a 2 - L glass kettle with a jacket. 1 g of non - ionic emulsifier Tween - 61 was added to the glass kettle and stirred until completely dissolved, that is, the solution looked homogeneous and transparent to the naked eye. 68 g of Mooney 70 rubber was weighed and cut into small pieces and then added to the above - mentioned glass kettle for pre - emulsification. The stirring speed for pre - emulsification was 700 rpm. The temperature of the pre - emulsification was heated to 30 °C by the water bath in the jacket of the glass kettle. After stirring for 8 h, the substances in the kettle formed a homogeneous and transparent latex.

[0142] Add 660 g of deionized water to a beaker, weigh 20.4 g of potassium disproportionated rosin and add it to the beaker. Place the beaker on a flat heating instrument and heat it while continuously stirring with a glass rod until the emulsifier is completely dissolved. Add a little KOH to adjust the pH value to 12.3. Control the solution temperature at 30 °C, slowly add this emulsifier solution to the above-mentioned glass kettle for premixing, with an addition time of 33 min, and control the stirring speed at 700 rpm during the addition. After all the addition is completed, increase the stirring speed to 3500 rpm for emulsification, and stir at 30 °C for 12 min to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the kettle and concentrate it to obtain a stable polyisoprene latex with a concentration of 55 wt%.

[0143] Example 11

[0144] Press 500 g of n-hexane solvent into a 2 L glass kettle with a jacket, add 1.5 g of non-ionic emulsifier SPAN-80 to the glass kettle, and stir until completely dissolved, that is, the solution looks homogeneous and transparent to the naked eye. Weigh 75 g of Mooney 70 rubber, cut it into small pieces and add it to the above-mentioned glass kettle for pre-emulsification. The stirring speed for pre-emulsification is 1000 rpm. Heat the jacket of the glass kettle with a water bath to make the temperature of pre-emulsification 40 °C. After stirring for 10 h, the substances in the kettle form a homogeneous and transparent colloidal solution.

[0145] Add 435 g of deionized water to a beaker, weigh 18.2 g of potassium disproportionated rosin and add it to the beaker. Place the beaker on a flat heating instrument and heat it while continuously stirring with a glass rod until the emulsifier is completely dissolved. Add a little KOH to adjust the pH value to 13. Control the solution temperature at 40 °C, slowly add this emulsifier solution to the above-mentioned glass kettle, with an addition time of 10 min, and control the stirring speed at 1000 rpm during the addition. After all the addition is completed, increase the stirring speed to 7000 rpm for emulsification, and stir at 40 °C for 15 min to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the kettle and concentrate it to obtain a stable polyisoprene latex with a concentration of 65 wt%.

[0146] Example 12

[0147] Press 500 g of n-hexane solvent into a 2 L glass kettle with a jacket, add 2 g of non-ionic emulsifier Tween-61 to the glass kettle, and stir until completely dissolved, that is, the solution looks homogeneous and transparent to the naked eye. Weigh 88 g of Mooney 70 rubber, cut it into small pieces and add it to the above-mentioned glass kettle for pre-emulsification. The stirring speed for pre-emulsification is 900 rpm. Heat the jacket of the glass kettle with a water bath to make the temperature of pre-emulsification 45 °C. After stirring for 5 h, the substances in the kettle form a homogeneous and transparent colloidal solution.

[0148] Add 580 g of deionized water to a beaker, weigh 21 g of sodium dodecylbenzenesulfonate and add it to the beaker. Place the beaker on a flat heating instrument and heat it, and continuously stir with a glass rod until the emulsifier is completely dissolved. Add a little KOH to adjust the pH value to 12.5. The temperature of the solution is measured by a thermometer to be 60 °C. Slowly add this emulsifier solution to the above glass kettle for premixing, with an addition time of 15 min, and the stirring speed during addition is controlled at 800 rpm. After all the addition is completed, increase the stirring speed to 6000 rpm for emulsification, and stir at 50 °C for 7 min to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the kettle and concentrate it to obtain a stable polyisoprene latex with a concentration of 63 wt%.

[0149] Example 13

[0150] Press 500 g of n-hexane solvent into a 2 L glass kettle with a jacket. Add 0.5 g of non-ionic emulsifier SPAN-80 to the glass kettle and stir until it is completely dissolved, that is, the solution looks homogeneous and transparent to the naked eye. Weigh 56 g of Mooney 70 rubber, cut it into small pieces and add it to the above glass kettle for pre-emulsification. The stirring speed for pre-emulsification is 500 rpm. The temperature of the pre-emulsification is controlled at 20 °C by heating the water bath in the jacket of the glass kettle. After stirring for 15 h, the substances in the kettle form a homogeneous and transparent latex.

[0151] Add 550 g of deionized water to a beaker, weigh 8.4 g of sodium dodecylbenzenesulfonate and add it to the beaker. Place the beaker on a flat heating instrument and heat it, and continuously stir with a glass rod until the emulsifier is completely dissolved. Add a little KOH to adjust the pH value to 10. Control the solution temperature at 20 °C. Slowly add this emulsifier solution to the above glass kettle for premixing, with an addition time of 50 min, and the stirring speed during addition is controlled at 300 rpm. After all the addition is completed, increase the stirring speed to 2500 rpm for emulsification, and stir at 20 °C for 5 min to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the kettle and concentrate it to obtain a stable polyisoprene latex with a concentration of 62 wt%.

[0152] Example 14

[0153] Press 500 g of n-hexane solvent into a 2 L glass kettle with a jacket. Add 1.68 g of non-ionic emulsifier SPAN-80 to the glass kettle and stir until it is completely dissolved, that is, the solution looks homogeneous and transparent to the naked eye. Weigh 56 g of Mooney 70 rubber, cut it into small pieces and add it to the above glass kettle for pre-emulsification. The stirring speed for pre-emulsification is 1500 rpm. The temperature of the pre-emulsification is controlled at 70 °C by heating the water bath in the jacket of the glass kettle. After stirring for 2 h, the substances in the kettle form a homogeneous and transparent latex.

[0154] Add 550 g of deionized water to a beaker, weigh 22.4 g of sodium dodecylbenzenesulfonate and add it to the beaker. Place the beaker on a flat heating instrument and heat it, and continuously stir with a glass rod until the emulsifier is completely dissolved. Add a little KOH to adjust the pH value to 14. Control the solution temperature at 70 °C, slowly add this emulsifier solution to the above-mentioned glass kettle for premixing, with an addition time of 5 min, and control the stirring speed at 2000 rpm during the addition. After all the addition is completed, increase the stirring speed to 8000 rpm for emulsification, and stir at 55 °C for 20 min to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the kettle and concentrate it to obtain a stable polyisoprene latex with a concentration of 61 wt%.

[0155] Example 15

[0156] Prepare polyisoprene latex according to the method of Example 9, except that instead of directly adding the non-ionic emulsifier SPAN-80 to the n-hexane solvent, 0.75 g of the non-ionic emulsifier SPAN-80 is added simultaneously when adding sodium dodecylbenzenesulfonate to deionized water.

[0157] Example 16

[0158] Prepare polyisoprene latex according to the method of Example 10, except that instead of directly adding the non-ionic emulsifier Tween-61 to the n-hexane solvent, 1 g of the non-ionic emulsifier Tween-61 is added simultaneously when adding potassium disproportionated rosin to deionized water.

[0159] Example 17

[0160] Prepare polyisoprene latex according to the method of Example 11, except that instead of directly adding the non-ionic emulsifier SPAN-8 to the n-hexane solvent, 1.5 g of the non-ionic emulsifier SPAN-8 is added simultaneously when adding potassium disproportionated rosin to deionized water.

[0161] Example 18

[0162] Prepare polyisoprene latex according to the method of Example 12, except that instead of directly adding the non-ionic emulsifier Tween-61 to the n-hexane solvent, 2 g of the non-ionic emulsifier Tween-61 is added simultaneously when adding sodium dodecylbenzenesulfonate to deionized water.

[0163] Test Example

[0164] For the latexes prepared in Examples 9 - 18, test the latex particle size, tensile strength of the rubber film, molecular weight and storage stability of the latex, and the results are shown in Table 1.

[0165] Table 1

[0166]

[0167]

[0168] As can be seen from the above results, the polyisoprene latex prepared by Examples 9-18 adopting the technical solution of the present invention has a relatively high molecular weight, a relatively high elongation at break and tensile strength of the rubber film, has relatively high mechanical properties and good film-forming properties, and has relatively high mechanical stability.

[0169] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for desolventizing polyisoprene latex, characterized in that, The method includes: (1) Mixing polyisoprene dry rubber with a nonionic emulsifier solution for pre-emulsification; (2) Pre-mixing and emulsifying the mixture obtained in step (1) with an anionic emulsifier in sequence to obtain a polyisoprene crude latex; (3) Subjecting the polyisoprene crude latex without removing the solvent to atmospheric distillation; then subjecting the concentrated latex obtained by atmospheric distillation to vacuum distillation; In the non-ionic emulsifier solution, the non-ionic emulsifier is selected from at least one of ethers of C8-C 24 , alcohols of C8-C 24 , and esters of C8-C 24 ; the mass dosage of the non-ionic emulsifier is 0.5%-5% of the mass of the polyisoprene dry rubber; The anionic emulsifier is selected from at least one of fatty acid salts of C 12 -C 30 , alkylbenzene sulfonates of C 12 -C 30 , and alkyl sulfate salts of C 12 -C 30 ; the mass dosage of the anionic emulsifier is 5%-50% of the mass of the polyisoprene dry rubber; The method further includes spraying an inorganic salt aqueous solution above the liquid surface during the atmospheric distillation.

2. The method according to claim 1, wherein The spraying amount of the inorganic salt aqueous solution is 0.001 - 1 L relative to each liter of the crude latex; and / or, the inorganic salt is a strong electrolyte salt; and / or, the mass concentration of the inorganic salt in the inorganic salt aqueous solution is 0.1% - 50%; and / or, the temperature of the inorganic salt aqueous solution is 0°C - 100°C; and / or, the pH value of the inorganic salt aqueous solution is regulated using an inorganic base; and / or, the pH value of the inorganic salt aqueous solution is controlled at 9 - 14.

3. The method according to claim 2, wherein The spraying amount of the inorganic salt aqueous solution is 0.002 - 0.1 L relative to each liter of the crude latex; and / or, the inorganic salt is at least one of NaCl, KCl, Na2SO4, and K2SO4; and / or, the mass concentration of the inorganic salt in the inorganic salt aqueous solution is 5% - 30%; and / or, the temperature of the inorganic salt aqueous solution is 10°C - 50°C; and / or, the inorganic base is at least one of NaOH and KOH; and / or, the pH value of the inorganic salt aqueous solution is controlled at 10 - 13.

5.

4. The method according to claim 3, wherein The spraying amount of the inorganic salt aqueous solution is 0.01 - 0.02 L relative to each liter of the crude latex; and / or, the mass concentration of the inorganic salt in the inorganic salt aqueous solution is 10% - 20%; and / or, the temperature of the inorganic salt aqueous solution is 20°C - 30°C; and / or, the pH value of the inorganic salt aqueous solution is controlled at 11 - 13.

5. The method according to any one of claims 1-4, wherein, The conditions of the atmospheric distillation are such that the solvent removed by the atmospheric distillation accounts for 80 vol% - 99 vol% of the total amount of the solvent in the crude latex; and / or, the conditions of the vacuum distillation are such that the solvent removed by the vacuum distillation accounts for 1 vol% - 20 vol% of the total amount of the solvent in the crude latex.

6. The method according to claim 5, wherein The conditions of the atmospheric distillation are such that the solvent removed by the atmospheric distillation accounts for 90 vol% - 97 vol% of the total amount of the solvent in the crude latex; and / or, the conditions of the vacuum distillation are such that the solvent removed by the vacuum distillation accounts for 3 vol% - 10 vol% of the total amount of the solvent in the crude latex.

7. The method according to claim 6, wherein, The conditions of the atmospheric distillation are such that the solvent removed by the atmospheric distillation accounts for 92 vol% - 95 vol% of the total amount of the solvent in the crude latex; and / or, the conditions of the vacuum distillation are such that the solvent removed by the vacuum distillation accounts for 5 vol% - 8 vol% of the total amount of the solvent in the crude latex.

8. The method according to any one of claims 1-4, 6 and 7, wherein, The difference between the temperature of the atmospheric distillation and the boiling point of the solvent in the crude latex is 0°C - 20°C; and / or, the pressure of the vacuum distillation is 0.05 MPa - 0.0001 MPa; and / or, the difference between the temperature of the vacuum distillation and the boiling point of the solvent in the crude latex is 0°C - 20°C; and / or, the stirring speeds of the atmospheric distillation and the vacuum distillation are each independently 100 rpm - 2000 rpm.

9. The method according to claim 8, wherein The difference between the temperature of atmospheric distillation and the boiling point of the solvent in the crude latex is 3°C - 15°C; and / or, the pressure of the vacuum distillation is 0.01 MPa - 0.001 MPa; and / or, the difference between the temperature of the vacuum distillation and the boiling point of the solvent in the crude latex is 2°C - 15°C; and / or, the stirring speeds of the atmospheric distillation and the vacuum distillation are each independently 300 rpm - 1600 rpm.

10. The method according to claim 9, wherein, The difference between the temperature of atmospheric distillation and the boiling point of the solvent in the crude latex is 5°C - 10°C; and / or, the pressure of the vacuum distillation is 0.008 MPa - 0.003 MPa; and / or, the difference between the temperature of the vacuum distillation and the boiling point of the solvent in the crude latex is 3°C - 10°C; and / or, the stirring speeds of the atmospheric distillation and the vacuum distillation are each independently 600 rpm - 1200 rpm.

11. The method according to any one of claims 1-4, 6, 7, 9 and 10, wherein, The volume content of the solvent in the crude latex is 30% - 70%; and / or, the weight content of polyisoprene in the crude latex is 2% - 10%; and / or, the weight content of the emulsifier in the crude latex is 0.5% - 10%.

12. The method according to claim 11, wherein, The volume content of the solvent in the crude latex is 40% - 55%; and / or, the weight content of polyisoprene in the crude latex is 3% - 8%; and / or, the weight content of the emulsifier in the crude latex is 1% - 5%.

13. The method according to claim 12, wherein, The volume content of the solvent in the crude latex is 42% - 50%; and / or, the weight content of polyisoprene in the crude latex is 4% - 6%; and / or, the weight content of the emulsifier in the crude latex is 1.5% - 4%.

14. The method according to any one of claims 1-4, 6, 7, 9, 10, 12, and 13, wherein, The solvent in the crude latex is a saturated aliphatic hydrocarbon and / or an alicyclic hydrocarbon; and / or, the number-average molecular weight of polyisoprene in the crude latex is 10,000 - 1,000,000 g / mol.

15. The method according to claim 14, wherein The solvent in the crude latex is at least one of n-hexane, cyclohexane, methylcyclopentane, n-heptane, n-pentane, and cyclopentane; and / or, the number-average molecular weight of polyisoprene in the crude latex is 100,000 - 500,000 g / mol.

16. The method according to claim 15, wherein, The number-average molecular weight of polyisoprene in the crude latex is 200,000 - 350,000 g / mol.

17. The method according to any one of claims 1-4, 6, 7, 9, 10, 12, 13, 15 and 16, wherein, The emulsifier in the crude latex is an anionic emulsifier and / or a nonionic emulsifier.

18. The method according to any one of claims 1-4, 6, 7, 9, 10, 12, 13, 15 and 16, wherein, The method is carried out in a device for solvent removal from polyisoprene latex. The atmospheric distillation is carried out in an atmospheric distillation kettle, and the vacuum distillation is carried out in a vacuum distillation kettle. The device includes: an atmospheric distillation kettle and a vacuum distillation kettle. An inorganic salt solution spraying element is arranged at the top of the atmospheric distillation kettle. The atmospheric distillation kettle and the vacuum distillation kettle are each provided with a feed inlet, a solvent outlet, and a discharge outlet. The discharge outlet of the atmospheric distillation kettle is connected to the feed inlet of the vacuum distillation kettle.

19. The method according to claim 18, wherein, The inorganic salt solution spraying element is in the shape of a shower head; and / or, the volume ratio of the atmospheric distillation kettle to the vacuum distillation kettle is 1 - 20; and / or, the atmospheric distillation kettle and the vacuum distillation kettle each have a heat exchange jacket. The heat exchange medium inlet of the heat exchange jacket is at the bottom of the heat exchange jacket, and the heat exchange medium outlet is at the top of the heat exchange jacket; And / or, the feed inlet of the atmospheric distillation kettle is located at the bottom of the kettle body, the solvent outlet is located at the top of the kettle body, the discharge outlet is located in the upper middle part of the kettle body, and the ratio of the height of the discharge outlet to the height of the kettle body is 0.5 - 1; And / or, the feed inlet of the vacuum distillation kettle is located at the bottom of the kettle body, the solvent outlet is located at the top of the kettle body, the discharge outlet is located in the upper middle part of the kettle body, and the ratio of the height of the discharge outlet to the height of the kettle body is 0.5 - 1; And / or, a stirring unit is respectively arranged in the atmospheric distillation kettle and the vacuum distillation kettle, the stirring unit includes a stirring shaft and at least one stirring paddle vertically arranged and fixed on the stirring shaft, and the number of the stirring paddles is 1 - 10.

20. The method according to claim 19, wherein, The volume ratio of the atmospheric distillation kettle to the vacuum distillation kettle is 5 - 15; And / or, the ratio of the height of the discharge outlet to the height of the kettle body is 0.6 - 0.9; And / or, the ratio of the height of the discharge outlet to the height of the kettle body is 0.6 - 0.9; And / or, the number of the stirring paddles is 2 - 8.

21. The method according to claim 20, wherein, The volume ratio of the atmospheric distillation kettle to the vacuum distillation kettle is 6 - 9; And / or, the ratio of the height of the discharge outlet to the height of the kettle body is 0.7 - 0.8; And / or, the ratio of the height of the discharge outlet to the height of the kettle body is 0.7 - 0.8; And / or, the number of the stirring paddles is 3 - 5.

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