Polyisoprene latex and method for its preparation

Abstract

This invention relates to the field of polymer materials and their preparation, and discloses a polyisoprene latex and its preparation method. The method includes: (1) mixing dry polyisoprene rubber with a nonionic emulsifier solution for pre-emulsification; and (2) sequentially pre-mixing and emulsifying the mixture obtained in step (1) with an anionic emulsifier. This method can maximize the emulsifying ability of the emulsifier, reduce the viscosity of the latex mixture, and minimize the loss of rubber molecular weight. The polyisoprene latex prepared by this method exhibits high mechanical properties, high mechanical stability, and good film-forming properties.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and their preparation, specifically to a polyisoprene latex and its preparation method. Background Technology

[0002] The microstructure and properties of synthetic polyisoprene latex are similar to those of natural latex. Apart from containing a few surfactants and antioxidants, it does not contain other non-rubber components. It can effectively solve the problems of protein allergies and nitrosamine carcinogenicity that exist in natural latex. Especially in the medical field, it can completely replace natural latex in applications such as latex gloves, condoms, medical bandages, medical catheters, and foamed cotton pads.

[0003] Numerous research reports on polyisoprene latex exist both domestically and internationally. CN102936346A discloses a method for directly preparing isoprene latex from a latex solution, wherein the emulsification of the polyisoprene latex solution involves directly emulsifying the polyisoprene latex solution prepared in step one with an aqueous emulsifier using a high-speed shearing method. US2009 / 0281211A1 discloses a method for preparing synthetic latex, which uses rosin acid soap-based emulsifiers and a high-speed shearing method to obtain latex products.

[0004] However, the currently reported methods for preparing synthetic latex have a significant drawback: during the emulsification process, the molecular weight of the latex is significantly reduced due to mechanical forces, which affects the film-forming properties of the latex and the mechanical properties of the latex products. Furthermore, the emulsifier does not encapsulate the latex particles sufficiently, leading to unstable performance of the latex during storage and transportation. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems of the prior art and provide a polyisoprene latex and its preparation method. This method can maximize the emulsifying ability of the emulsifier, reduce the viscosity of the latex mixture, and reduce the loss of rubber molecular weight. The polyisoprene latex prepared by this method has a high molecular weight and high mechanical properties, high mechanical stability, and good film-forming properties.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for preparing polyisoprene latex, the method comprising:

[0007] (1) Pre-emulsify the polyisoprene dry adhesive by mixing it with a nonionic emulsifier solution;

[0008] (2) The mixture obtained in step (1) is premixed and emulsified with an anionic emulsifier in sequence.

[0009] A second aspect of the present invention provides a polyisoprene latex prepared by the method described above.

[0010] The method of this invention can maximize the emulsifying ability of the emulsifier, reduce the viscosity of the latex mixture, and reduce the loss of rubber molecular weight. The polyisoprene latex prepared by this method has high mechanical properties, high mechanical stability, and good film-forming properties, making it suitable for the high-end medical industry. Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] In this invention, "film tensile strength" refers to the tensile strength of the rubber obtained after latex demulsification, and "film elongation at break" refers to the elongation at break of the rubber obtained after latex demulsification. If polyisoprene latex has high mechanical properties, it generally has good film-forming properties.

[0013] In a first aspect, the present invention provides a method for preparing polyisoprene latex, the method comprising:

[0014] (1) Pre-emulsify the polyisoprene dry adhesive by mixing it with a nonionic emulsifier solution;

[0015] (2) The mixture obtained in step (1) is premixed and emulsified with an anionic emulsifier in sequence.

[0016] The inventors of this invention discovered in their research that dissolving polyisoprene dry rubber in a nonionic emulsifier solution first allows the polyisoprene and nonionic emulsifier to be more evenly dispersed and better bonded. Simultaneously, the presence of the aqueous solution further weakens the interaction forces between rubber molecular chains, resulting in less chain breakage during subsequent emulsification. This effectively protects the rubber molecular chains, reduces molecular weight loss, and maximizes the emulsifying ability of the emulsifier. By sequentially performing pre-emulsification, premixing, and emulsification, a polyisoprene latex with higher molecular weight, superior mechanical properties, higher mechanical stability, and better film-forming properties can be obtained.

[0017] According to the present invention, in order to further enhance the emulsifying ability of the nonionic emulsifier, better protect the rubber molecular chains, and reduce the loss of molecular weight, preferably, the mass amount of the nonionic emulsifier in the nonionic 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%.

[0018] According to the present invention, in order to further enhance the emulsifying ability of the emulsifier, preferably, the mass amount of the anionic emulsifier is 5%-50% of the mass of the polyisoprene dry adhesive, more preferably 8%-40%, and even more preferably 10%-30%.

[0019] According to the present invention, preferably, the content of cis-1,4-polyisoprene structure in the polyisoprene dry adhesive is not less than 95% by mass, and the number average molecular weight of polyisoprene in the polyisoprene dry adhesive is 150,000-400,000 g / mol, more preferably 180,000-300,000 g / mol, and most preferably 200,000-230,000 g / mol. The synthesis method of the polyisoprene is not particularly limited; for example, it can be prepared by rare earth catalysis. Meeting the above-mentioned ranges, especially the content range of cis-1,4-polyisoprene structure, further ensures that the prepared polyisoprene latex has high film tensile strength and film elongation at break.

[0020] According to the present invention, preferably, the mass concentration of the nonionic emulsifier in the nonionic emulsifier solution is 0.01%-1%, more preferably 0.12%-0.5%, and most preferably 0.15%-0.4%.

[0021] According to the present invention, in order to further enhance the emulsifying ability of the nonionic emulsifier, better protect the rubber molecular chains, and reduce the loss of molecular weight, the nonionic emulsifier is preferably at least one of C8-C24 ethers, C8-C24 alcohols, and C8-C24 esters, preferably at least one of fatty alcohol polyoxyethylene ether, Span, and Tween, more preferably sorbitan monooleate (e.g., commercially available Span-80) and / or polyoxyethylene sorbitan monostearate (e.g., commercially available Tween-61).

[0022] According to the present invention, the solvent in the nonionic emulsifier solution is not particularly limited, as long as it can dissolve the polyisoprene dry glue. However, considering the price, environmental protection and subsequent removal, the solvent is preferably at least one of n-hexane, cyclohexane, methylcyclopentane, n-heptane, n-pentane and cyclopentane.

[0023] According to the present invention, the pre-emulsification conditions are not particularly limited, as long as the mixture obtained after pre-emulsification is uniformly transparent. However, preferably, the pre-emulsification temperature is 10℃-80℃, more preferably 20℃-70℃, and even more preferably 30℃-60℃; the pre-emulsification time is 1h-24h, more preferably 2h-15h, and most preferably 3-10h; the pre-emulsification is carried out under stirring conditions, with a stirring speed of 100rpm-2000rpm, more preferably 500rpm-1500rpm, and even more preferably 700rpm-1000rpm. Within the above ranges, especially the temperature range, it is possible to further ensure that the polyisoprene dry adhesive dissolves as completely as possible. Furthermore, to further ensure that the polyisoprene dry adhesive dissolves as much as possible, the polyisoprene dry adhesive can be cut into small pieces before pre-emulsification. For example, add a nonionic emulsifier to a container containing a solvent, stir until dissolved, and then cut the polyisoprene dry glue into small pieces and add them to the container.

[0024] According to the present invention, preferably, the anionic emulsifier is used in the form of an aqueous solution of anionic emulsifier, wherein the mass concentration of the anionic emulsifier in the aqueous solution is 0.1%-10%, more preferably 1.2%-5%, and most preferably 1.5%-4%.

[0025] According to the present invention, in order to further enhance 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. The pH value can be controlled by using an inorganic base, such as KOH and / or NaOH.

[0026] According to the present invention, in order to further enhance the emulsifying ability of the emulsifier, preferably, the anionic emulsifier is at least one of C12-C30 fatty acid salts, C12-C30 alkylbenzene sulfonates and C12-C30 alkyl sulfate esters, more preferably at least one of sodium alkylbenzene sulfonate, oleate, laurate, rosinate and linoleate, and even more preferably at least one of sodium dodecylbenzene sulfonate and potassium disproportionated rosinate.

[0027] According to the present invention, preferably, the premixing method includes: adding an aqueous anionic emulsifier to the mixture, wherein the addition rate of the aqueous anionic emulsifier is 1 volume% / min to 50 volume% / min, more preferably 2 volume% / min to 20 volume% / min, and most preferably 3 volume% / min to 10 volume% / min, based on the volume of the aqueous anionic emulsifier; the premixing is carried out under stirring conditions, with a stirring speed of 100 rpm to 3000 rpm, more preferably 300 rpm to 2000 rpm, and most preferably 500 rpm to 1000 rpm; the premixing temperature is 10℃ to 80℃, more preferably 20℃ to 70℃, and even more preferably 30℃ to 60℃. It is understood that if the volume of the aqueous anionic emulsifier is 1000 ml, when added at an addition rate of 5 volume% / min, 50 ml (i.e., 1000 ml * 5%) of the aqueous anionic emulsifier is added per minute. The premixing temperature can be achieved by controlling the temperature of the aqueous anionic emulsifier. The inventors of this invention also discovered in their research that, with the increase of the amount of anionic emulsifier aqueous solution added, the material first forms a W / O type (water-in-oil) emulsion, and then gradually transforms into an O / W type (oil-in-water) emulsion; and, when the ranges described above, especially the range of the addition rate of the anionic emulsifier aqueous solution, are met, the stability of the latex can be further increased.

[0028] According to the present invention, preferably, the emulsification method is mechanical emulsification, and the stirring speed of the mechanical emulsification is 1000rpm-10000rpm, more preferably 2500rpm-8000rpm, and most preferably 3500rpm-7000rpm.

[0029] 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.

[0030] According to the present invention, preferably, the emulsification temperature is 10℃-60℃, more preferably 20℃-55℃, and even more preferably 30℃-50℃.

[0031] The inventors of this invention have discovered that emulsification can be achieved better when the rotation speed, temperature, and time range described above are met.

[0032] The method of the present invention may further include removing the solvent from the emulsified product. The solvent removal can be carried out in a conventional manner, which will not be described in detail here.

[0033] Secondly, the present invention provides a polyisoprene latex prepared by the method described above.

[0034] 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.

[0035] According to the present invention, preferably, the particle size of the polyisoprene latex is 100nm-2000nm, more preferably 200-1500nm, and most preferably 300-1200nm.

[0036] According to the present invention, preferably, the tensile strength of the polyisoprene latex is 15MPa-30MPa, more preferably 18MPa-25MPa, and most preferably 20MPa-22MPa.

[0037] 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%.

[0038] 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.

[0039] According to a particularly preferred embodiment of the present invention, polyisoprene latex is prepared by the following method:

[0040] Hexane solvent is injected into a jacketed glass reactor. The nonionic emulsifier Tween-61 is then added to the reactor, ensuring the nonionic emulsifier concentration in the solution is 0.35-0.4% by mass. The mixture is stirred until completely dissolved. Polyisoprene dry adhesive with a number-average molecular weight of 200,000-230,000 g / mol is weighed, cut into small pieces, and added to the reactor. The amount of polyisoprene dry adhesive used is such that the nonionic emulsifier in the solution is 2.1-2.4% of the mass of the polyisoprene dry adhesive. Pre-emulsification is performed at a stirring speed of 850-950 rpm. The pre-emulsification temperature is maintained at 45-55°C by a water bath in the jacket of the glass reactor, and the mixture is stirred for 5-7 hours.

[0041] Add deionized water to a beaker, weigh out sodium dodecylbenzenesulfonate and add it to the beaker. Heat the beaker and stir continuously with a glass rod until the emulsifier is completely dissolved. Add a small amount of KOH to adjust the pH to 12.5-12.8 to prepare a 3.6-4% (w / w) dodecylbenzenesulfonic acid solution. Control the solution temperature at 55-60℃ and slowly add the emulsifier solution to the glass reactor for premixing over 14-16 minutes, while maintaining a stirring speed of 800-900 rpm. After all the emulsifier has been added, increase the stirring speed to 5500-6000 rpm for emulsification. Stir at 45-50℃ for 7-9 minutes to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the reactor and concentrate it to obtain a 61-64 wt% polyisoprene latex.

[0042] The present invention will be described in detail below through embodiments. In the following embodiments,

[0043] SPAN-80 contains dehydrated sorbitan monooleate.

[0044] Tween-61 is composed of polyoxyethylene sorbitan monostearate.

[0045] Mooney 70 rubber is composed of polyisoprene, wherein 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.

[0046] The method for testing the molecular weight of latex is as follows: first, dry the latex, and then determine it using gel permeation liquid chromatography (GPC).

[0047] Latex particle size was measured using a Malvern nanoparticle size and Zeta potential analyzer.

[0048] The pH value of the emulsifier was tested using an S475-LRF multi-functional pH meter.

[0049] The mass concentration of polyisoprene in polyisoprene latex was determined by thermogravimetric analysis.

[0050] The test method for the tensile strength of the adhesive film is GB / T528-1998;

[0051] The test method for elongation at break of adhesive film is GB / T528-1998;

[0052] The test method for latex storage stability is to let it stand and observe it. The longer the storage stability time of latex, the better its mechanical stability.

[0053] Example 1

[0054] 500g of n-hexane solvent was injected into a 2L jacketed glass reactor. 0.75g of nonionic emulsifier SPAN-80 was added to the reactor and stirred until completely dissolved, resulting in a homogeneous and transparent solution. 56g of Mooney 70 rubber was weighed, cut into small pieces, and added to the reactor for pre-emulsification. The stirring speed during pre-emulsification was 800 rpm. The reactor was heated in a water bath within the jacket to maintain a pre-emulsification temperature of 60°C. After stirring for 3 hours, a homogeneous and transparent gel-like solution was formed in the reactor.

[0055] Add 550g of deionized water to a beaker, then weigh out 11g of sodium dodecylbenzenesulfonate and add it to the beaker. Heat the beaker on a plate heat exchanger and stir continuously with a glass rod until the emulsifier is completely dissolved. Add a small amount of KOH to adjust the pH to 11.2. Maintain the solution temperature at 50℃. Slowly add the emulsifier solution to the aforementioned glass reactor for premixing over 20 minutes, maintaining a stirring speed of 500 rpm during addition. After all the solution has been added, increase the stirring speed to 5000 rpm for emulsification. Stir at 50℃ for 10 minutes to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the reactor and concentrate it to obtain a stable polyisoprene latex with a concentration of 60 wt%.

[0056] Example 2

[0057] 500g of n-hexane solvent was injected into a 2L jacketed glass reactor. 1g of nonionic emulsifier Tween-61 was added to the reactor and stirred until completely dissolved, resulting in a homogeneous and transparent solution. 68g of Mooney 70 rubber was weighed, cut into small pieces, and added to the reactor for pre-emulsification. The stirring speed during pre-emulsification was 700 rpm. The reactor was heated in a water bath within the jacket to maintain a pre-emulsification temperature of 30°C. After stirring for 8 hours, a homogeneous and transparent gel-like solution was formed in the reactor.

[0058] Add 660g of deionized water to a beaker, then weigh out 20.4g of potassium disproportionated rosinate and add it to the beaker. Heat the beaker on a plate heat exchanger and stir continuously with a glass rod until the emulsifier is completely dissolved. Add a small amount of KOH to adjust the pH to 12.3. Maintain the solution temperature at 30℃. Slowly add the emulsifier solution to the aforementioned glass reactor for premixing over 33 minutes, while maintaining a stirring speed of 700 rpm during addition. After all the emulsifier has been added, increase the stirring speed to 3500 rpm for emulsification. Stir at 30℃ for 12 minutes to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the reactor and concentrate it to obtain a stable polyisoprene latex with a concentration of 55 wt%.

[0059] Example 3

[0060] 500g of n-hexane solvent was injected into a 2L jacketed glass reactor. 1.5g of nonionic emulsifier SPAN-80 was added to the reactor and stirred until completely dissolved, resulting in a homogeneous and transparent solution. 75g of Mooney 70 rubber was weighed, cut into small pieces, and added to the reactor for pre-emulsification. The stirring speed during pre-emulsification was 1000rpm. The reactor was heated in a water bath within the jacket to maintain a pre-emulsification temperature of 40℃. After stirring for 10 hours, a homogeneous and transparent gel-like solution was formed in the reactor.

[0061] Add 435g of deionized water to a beaker, then weigh out 18.2g of potassium disproportionated rosinate and add it to the beaker. Heat the beaker on a plate heat exchanger and stir continuously with a glass rod until the emulsifier is completely dissolved. Add a small amount of KOH to adjust the pH to 13. Maintain the solution temperature at 40℃ and slowly add the emulsifier solution to the glass reactor over 10 minutes, stirring at 1000 rpm. After all the solution has been added, increase the stirring speed to 7000 rpm for emulsification. Stir at 40℃ for 15 minutes to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the reactor and concentrate it to obtain a stable polyisoprene latex with a concentration of 65 wt%.

[0062] Example 4

[0063] 500g of n-hexane solvent was injected into a 2L jacketed glass reactor. 2g of the nonionic emulsifier Tween-61 was added to the reactor and stirred until completely dissolved, resulting in a homogeneous and transparent solution. 88g of Mooney 70 rubber was weighed, cut into small pieces, and added to the reactor for pre-emulsification. The stirring speed during pre-emulsification was 900rpm. The reactor was heated in a water bath within the jacket to maintain a pre-emulsification temperature of 45℃. After stirring for 5 hours, a homogeneous and transparent gel-like solution was formed in the reactor.

[0064] Add 580g of deionized water to a beaker, then weigh 21g of sodium dodecylbenzenesulfonate and add it to the beaker. Heat the beaker on a plate heat exchanger and stir continuously with a glass rod until the emulsifier is completely dissolved. Add a small amount of KOH to adjust the pH to 12.5. The solution temperature is measured to be 60℃. Slowly add the emulsifier solution to the glass reactor for premixing over 15 minutes, maintaining a stirring speed of 800 rpm during addition. After all the emulsifier has been added, increase the stirring speed to 6000 rpm for emulsification. Stir at 50℃ for 7 minutes to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the reactor and concentrate it to obtain a stable polyisoprene latex with a concentration of 63 wt%.

[0065] Example 5

[0066] 500g of n-hexane solvent was injected into a 2L jacketed glass reactor. 0.5g of nonionic emulsifier SPAN-80 was added to the reactor and stirred until completely dissolved, resulting in a homogeneous and transparent solution. 56g of Mooney 70 rubber was weighed, cut into small pieces, and added to the reactor for pre-emulsification. The stirring speed during pre-emulsification was 500 rpm. The reactor was heated in a water bath within the jacket to maintain a pre-emulsification temperature of 20°C. After stirring for 15 hours, a homogeneous and transparent gel-like solution was formed in the reactor.

[0067] Add 550g of deionized water to a beaker, then weigh out 8.4g of sodium dodecylbenzenesulfonate and add it to the beaker. Heat the beaker on a plate heat exchanger and stir continuously with a glass rod until the emulsifier is completely dissolved. Add a small amount of KOH to adjust the pH to 10. Maintain the solution temperature at 20℃. Slowly add the emulsifier solution to the aforementioned glass reactor for premixing over 50 minutes, maintaining a stirring speed of 300 rpm during addition. After all the emulsifier has been added, increase the stirring speed to 2500 rpm for emulsification. Stir at 20℃ for 5 minutes to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the reactor and concentrate it to obtain a stable polyisoprene latex with a concentration of 62 wt%.

[0068] Example 6

[0069] 500g of n-hexane solvent was injected into a 2L jacketed glass reactor. 1.68g of nonionic emulsifier SPAN-80 was added to the reactor and stirred until completely dissolved, resulting in a homogeneous and transparent solution. 56g of Mooney 70 rubber was weighed, cut into small pieces, and added to the reactor for pre-emulsification. The stirring speed during pre-emulsification was 1500rpm. The reactor was heated in a water bath within the jacket to maintain a pre-emulsification temperature of 70℃. After stirring for 2 hours, a homogeneous and transparent gel-like solution was formed in the reactor.

[0070] Add 550g of deionized water to a beaker, then weigh out 22.4g of sodium dodecylbenzenesulfonate and add it to the beaker. Heat the beaker on a plate heat exchanger and stir continuously with a glass rod until the emulsifier is completely dissolved. Add a small amount of KOH to adjust the pH to 14. Maintain the solution temperature at 70℃. Slowly add the emulsifier solution to the aforementioned glass reactor for premixing over 5 minutes, maintaining a stirring speed of 2000 rpm during addition. After all the emulsifier has been added, increase the stirring speed to 8000 rpm for emulsification. Stir at 55℃ for 20 minutes to obtain crude polyisoprene latex. Remove the solvent from the crude latex in the reactor and concentrate it to obtain a stable polyisoprene latex with a concentration of 61 wt%.

[0071] Comparative Example 1

[0072] Polyisoprene latex was prepared according to the method of Example 1, except that the nonionic emulsifier SPAN-80 was not added directly to the hexane solvent, but 0.75g of nonionic emulsifier SPAN-80 was added simultaneously when sodium dodecylbenzenesulfonate was added to deionized water.

[0073] Comparative Example 2

[0074] Polyisoprene latex was prepared according to the method of Example 2, except that the nonionic emulsifier Tween-61 was not added directly to the hexane solvent, but 1g of nonionic emulsifier Tween-61 was added at the same time as potassium disproportionated rosinate added to deionized water.

[0075] Comparative Example 3

[0076] Polyisoprene latex was prepared according to the method of Example 3, except that the nonionic emulsifier SPAN-8 was not added directly to the hexane solvent, but 1.5g of nonionic emulsifier SPAN-8 was added at the same time as potassium disproportionated rosinate added to deionized water.

[0077] Comparative Example 4

[0078] Polyisoprene latex was prepared according to the method of Example 4, except that the nonionic emulsifier Tween-61 was not added directly to the hexane solvent, but 2g of nonionic emulsifier Tween-61 was added simultaneously when sodium dodecylbenzenesulfonate was added to deionized water.

[0079] Test case

[0080] The latexes prepared in Examples 1-6 and Comparative Examples 1-4 were tested for latex particle size, film tensile strength, molecular weight and latex storage stability. The results are shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] The results above show that the polyisoprene latex prepared using the technical solutions of this invention in Examples 1-6 has a high molecular weight, high elongation at break and high tensile strength, and exhibits high mechanical properties, good film-forming properties, and high mechanical stability.

[0085] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing polyisoprene latex, characterized in that, The method includes: (1) Pre-emulsify by mixing polyisoprene dry adhesive with a nonionic emulsifier solution; (2) The mixture obtained in step (1) is premixed and emulsified with an anionic emulsifier in sequence; The polyisoprene in the polyisoprene dry adhesive contains at least 95% by mass of cis-1,4-polyisoprene structure. The nonionic emulsifier is sorbitan monooleate and / or polyoxyethylene sorbitan monostearate. The anionic emulsifier is at least one of sodium dodecylbenzenesulfonate and potassium disproportionate; The amount of nonionic emulsifier in the nonionic emulsifier solution is 0.5%-5% of the mass of the polyisoprene dry adhesive; The amount of the anionic emulsifier used is 5%-50% of the mass of the polyisoprene dry adhesive.

2. The method according to claim 1, wherein, The amount of nonionic emulsifier in the nonionic emulsifier solution is 0.8%-3% of the mass of the polyisoprene dry adhesive; And / or, the amount of the anionic emulsifier used is 8%-40% of the mass of the polyisoprene dry adhesive.

3. The method according to claim 2, wherein, The amount of nonionic emulsifier in the nonionic emulsifier solution is 1%-2.5% of the mass of the polyisoprene dry adhesive; And / or, the amount of the anionic emulsifier used is 10%-30% of the mass of the polyisoprene dry adhesive.

4. The method according to claim 1, wherein, The number-average molecular weight of polyisoprene in the polyisoprene dry adhesive is 150,000-400,000 g / mol.

5. The method according to claim 4, wherein, The number-average molecular weight of polyisoprene in the polyisoprene dry adhesive is 180,000-300,000 g / mol.

6. The method according to claim 5, wherein, The number-average molecular weight of polyisoprene in the polyisoprene dry adhesive is 200,000-230,000 g / mol.

7. The method according to claim 1 or 2, wherein, The nonionic emulsifier solution has a mass concentration of 0.01%-1%.

8. The method according to claim 7, wherein, The nonionic emulsifier solution has a mass concentration of 0.12%-0.5%.

9. The method according to claim 8, wherein, The nonionic emulsifier solution has a mass concentration of 0.15%-0.4%.

10. The method according to claim 1, wherein, The solvent in the nonionic emulsifier solution is selected from saturated aliphatic hydrocarbons and / or alicyclic hydrocarbons.

11. The method according to claim 10, wherein, The solvent in the nonionic emulsifier solution is at least one of n-hexane, cyclohexane, methylcyclopentane, n-heptane, n-pentane, and cyclopentane.

12. The method according to claim 1, wherein, The pre-emulsification temperature is 10℃-80℃; the pre-emulsification time is 1h-24h; The pre-emulsification is carried out under stirring conditions, with the stirring speed being 100 rpm to 2000 rpm.

13. The method according to claim 12, wherein, The pre-emulsification temperature is 20℃-70℃; The pre-emulsification time is 2h-15h; The pre-emulsification is carried out under stirring conditions, with the stirring speed being 500 rpm to 1500 rpm.

14. The method according to claim 13, wherein, The pre-emulsification temperature is 30℃-60℃; The pre-emulsification time is 3-10 hours; The pre-emulsification is carried out under stirring conditions, with the stirring speed being 700 rpm-1000 rpm.

15. The method according to claim 1 or 12, wherein, The anionic emulsifier is used in the form of an aqueous solution of anionic emulsifier, wherein the mass concentration of the anionic emulsifier in the aqueous solution is 0.1%-10%.

16. The method according to claim 15, wherein, The anionic emulsifier aqueous solution has a mass concentration of 1.2%-5%.

17. The method according to claim 16, wherein, The anionic emulsifier aqueous solution has a mass concentration of 1.5%-4%.

18. The method according to claim 15, wherein, The pH value of the anionic emulsifier aqueous solution is 9-15.

19. The method according to claim 18, wherein, The pH value of the anionic emulsifier aqueous solution is 10-14.

20. The method according to claim 19, wherein, The pH value of the anionic emulsifier aqueous solution is 11-13.

21. The method according to claim 15, wherein, The premixing method includes: adding an aqueous solution of an anionic emulsifier to the mixture, wherein the addition rate of the aqueous solution of the anionic emulsifier is 1 volume% / min to 50 volume% / min based on the volume of the aqueous solution; the premixing is carried out under stirring conditions, with a stirring speed of 100 rpm to 3000 rpm; and the premixing temperature is 10℃ to 80℃.

22. The method according to claim 21, wherein, The premixing method includes: adding an aqueous solution of an anionic emulsifier to the mixture, wherein the addition rate of the aqueous solution of the anionic emulsifier is 2% / min to 20% / min based on the volume of the aqueous solution; the premixing is carried out under stirring conditions, with a stirring speed of 300 rpm to 2000 rpm; and the premixing temperature is 20℃ to 70℃.

23. The method according to claim 22, wherein, The premixing method includes: adding an aqueous solution of an anionic emulsifier to the mixture, wherein the addition rate of the aqueous solution of the anionic emulsifier is 3% / min to 10% / min based on the volume of the aqueous solution; the premixing is carried out under stirring conditions, with a stirring speed of 500 rpm to 1000 rpm; and the premixing temperature is 30℃ to 60℃.

24. The method according to claim 1, wherein, The emulsification method is mechanical emulsification, and the stirring speed of the mechanical emulsification is 1000rpm-10000rpm; And / or, the emulsification time is 2 min-30 min; And / or, the emulsification temperature is 10℃-60℃.

25. The method according to claim 24, wherein, The stirring speed for mechanical emulsification is 2500 rpm to 8000 rpm; And / or, the emulsification time is 5 min-20 min; And / or, the emulsification temperature is 20℃-55℃.

26. The method of claim 25, wherein, The stirring speed for mechanical emulsification is 3500 rpm-7000 rpm; And / or, the emulsification time is 7 min-15 min; And / or, the emulsification temperature is 30℃-50℃.

27. The polyisoprene latex prepared by the method of any one of claims 1-26.

28. The polyisoprene latex according to claim 27, wherein, The number-average molecular weight of the polyisoprene latex is 150,000-400,000 g / mol; And / or, the particle size of the polyisoprene latex is 100nm-2000nm; And / or, the tensile strength of the polyisoprene latex is 15MPa-30MPa; And / or, the elongation at break of the polyisoprene latex is 700%-1500%; And / or, the mass concentration of polyisoprene in the polyisoprene latex is 40-80 by mass.

29. The polyisoprene latex according to claim 28, wherein, The number-average molecular weight of the polyisoprene latex is 180,000-300,000 g / mol; And / or, the particle size of the polyisoprene latex is 200-1500 nm; And / or, the tensile strength of the polyisoprene latex is 18MPa-25MPa; And / or, the elongation at break of the polyisoprene latex is 900%-1300%; And / or, the mass concentration of polyisoprene in the polyisoprene latex is 50-70 by mass.

30. The polyisoprene latex according to claim 29, wherein, The number-average molecular weight of the polyisoprene latex is 200,000-230,000 g / mol; And / or, the particle size of the polyisoprene latex is 300-1200 nm; And / or, the tensile strength of the polyisoprene latex is 20MPa-22MPa; And / or, the elongation at break of the polyisoprene latex is 1000%-1200%; And / or, the mass concentration of polyisoprene in the polyisoprene latex is 55-65 by mass.

31. The application of the method according to any one of claims 1-26 in improving the mechanical stability of polyisoprene latex.

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