A carboxylated nitrile butadiene latex for high elongation nitrile gloves, its preparation method and application

Abstract

This application relates to a carboxylated nitrile butadiene latex for high elongation nitrile gloves, its preparation method, and its application. The method includes: S1, adding water, an emulsifier, an unsaturated carboxylic acid monomer, and acrylonitrile to a reaction vessel; S2, evacuating the reaction vessel and filling it with an inert gas, then adding butadiene under negative pressure; S3, adding an initiator to the reaction vessel and maintaining the temperature at 25-27°C for 25-30 minutes; S4, adding a first molecular weight regulator to the reaction vessel and initiating the polymerization reaction, adding a second molecular weight regulator when the conversion rate reaches 20-25%, and adding a third molecular weight regulator when the conversion rate reaches 40-45%; S5, gradually increasing the temperature in the reaction vessel until the conversion rate reaches 95% or higher, then ending the polymerization reaction; S6, degassing, purifying, concentrating, and filtering the obtained crude carboxylated nitrile butadiene latex to obtain the carboxylated nitrile butadiene latex. The carboxylated nitrile latex prepared by this method has a narrow molecular weight distribution, which in turn makes the elongation of nitrile gloves as high as 700-750%.

Description

Technical Field

[0001] This application relates to the field of carboxylated nitrile butadiene latex synthesis technology, and in particular to a carboxylated nitrile butadiene latex for high elongation nitrile butadiene gloves, its preparation method, and its application. Background Technology

[0002] Carboxylated nitrile butadiene latex is an aqueous dispersion mainly produced by emulsion polymerization of acrylonitrile, butadiene, and a third monomer containing carboxylic acid, such as acrylic acid and methacrylic acid. It possesses excellent oil resistance, solvent resistance, heat resistance, chemical corrosion resistance, and abrasion resistance. With appropriate modification, it is widely used in thick and thin gloves, lined and unlined gloves, and sealing materials.

[0003] With the rapid development of medical technology and high-performance rubber products both domestically and internationally, disposable examination gloves made from nitrile rubber latex can better adapt to the high elongation development of rubber products. However, in current technology, the molecular weight regulator required in conventional emulsion polymerization preparation is added only once. As a result, examination gloves made from carboxylated nitrile rubber latex prepared by conventional emulsion methods have a low elongation, generally between 400-500%, and their feel is far inferior to that of natural latex.

[0004] Patent CN110615924A discloses a method for preparing carboxylated nitrile butadiene latex for disposable gloves. This latex is made from the following raw materials: 30%-50% butadiene, 10%-25% methacrylic acid, 20%-30% acrylonitrile, 15%-20% nonionic emulsifier, 5%-15% deionized water, 1%-5% catalyst, and 3%-5% antioxidant. This patent provides a method for preparing carboxylated nitrile butadiene latex for disposable gloves using butadiene, methacrylic acid, and acrylonitrile. The method boasts high reaction efficiency and exhibits high strength and low shrinkage. Preheating the catalyst effectively improves reaction efficiency and prevents temperature runaway. The addition of antioxidants further enhances product quality and reduces oxidative damage. This significantly simplifies the process, facilitates control, increases product yield, and promotes widespread use. However, this patent does not address the issue of low elongation in disposable gloves.

[0005] Therefore, there is a need to provide a method for preparing carboxylated nitrile latex that can effectively solve the problem of low elongation in disposable nitrile gloves. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application provides a method for preparing carboxylated nitrile butadiene latex for high elongation nitrile gloves. This method involves adding a molecular weight regulator twice at specific conversion points after the polymerization reaction begins, meaning the regulator is added in three separate additions. This effectively controls the molecular weight distribution and gelation changes of the resulting carboxylated nitrile butadiene latex, resulting in a narrower molecular weight distribution. Consequently, nitrile gloves made from this latex achieve an elongation of 700-750%, while also providing a soft feel similar to natural rubber.

[0007] Therefore, the first aspect of this application provides a method for preparing carboxylated nitrile latex for high elongation nitrile gloves, the method comprising the following steps:

[0008] S1, add water, emulsifier, unsaturated carboxylic acid monomer and acrylonitrile to the reactor and mix;

[0009] S2, the reactor is evacuated and filled with inert gas, butadiene is added to the reactor under negative pressure, and the mixture is mixed again;

[0010] S3, add sodium persulfate aqueous solution and sodium bisulfite aqueous solution to the reaction vessel, and maintain the temperature inside the reaction vessel at 25-27°C for 25-30 minutes;

[0011] S4, after adding the first molecular weight regulator into the reactor, the polymerization reaction begins. When the conversion rate reaches 20-25%, the second molecular weight regulator is added and the polymerization reaction continues. When the conversion rate reaches 40-45%, the third molecular weight regulator is added and the polymerization reaction continues.

[0012] S5, the temperature inside the reactor is increased in stages, and the polymerization reaction is ended when the conversion rate reaches more than 95% to obtain crude carboxylated butadiene-acrylonitrile latex.

[0013] S6, the crude carboxylated nitrile butadiene latex is degassed, purified, concentrated, and filtered to obtain the high elongation nitrile butadiene glove carboxylated nitrile butadiene latex.

[0014] In the preparation method of carboxylated nitrile butadiene latex described in this application, the molecular weight regulator is added in three batches. The first batch is added before the start of the polymerization reaction, and the latter two batches are added at specific conversion points. The first addition occurs when the conversion rate reaches 20-25%. At this point, the added molecular weight regulator helps regulate the average molecular weight of the synthesized carboxylated nitrile butadiene latex, preventing excessive grafting and thus avoiding an excessively large average molecular weight. The second addition occurs when the conversion rate reaches 40-45%. At this point, the added molecular weight regulator helps regulate the molecular weight distribution of the synthesized carboxylated nitrile butadiene latex, resulting in a narrower molecular weight distribution. Gel permeation chromatography was used to determine the molecular weight distribution, and the molecular weight distribution index was found to be controlled between 1.1 and 1.5. In contrast, a preparation method that adds the molecular weight regulator all at once would result in a molecular weight distribution index as high as 2.1 or even higher, leading to an excessively wide molecular weight distribution. When the carboxylated nitrile butadiene latex synthesized in this application is used to prepare disposable nitrile butadiene gloves, due to its narrow molecular weight distribution, the vulcanization time of the carboxylated nitrile butadiene latex is shorter and the vulcanization effect is better, which in turn makes the nitrile gloves have excellent performance, high elongation (700-750%), and soft feel, similar to natural rubber.

[0015] Furthermore, in the method described in this application, after adding the initiator (sodium persulfate and sodium bisulfite), the reaction system is maintained at 25–27°C for 25–30 minutes. This allows the material to have an initial reaction stage, generating some latex nuclei. These latex nuclei are similar to seed latex, are active, and can control the particle size in the early stages of polymerization, resulting in a uniform particle size distribution of the prepared carboxylated nitrile butadiene latex. This helps to further improve the overall performance of nitrile gloves made from this carboxylated nitrile butadiene latex. However, the number of latex nuclei generated during the preparation process cannot be too large, and the particle size cannot be too large (the particle size needs to be maintained at 20–50 nm). Therefore, it is necessary to maintain the temperature of the reaction system at 25–27°C to maintain a low polymerization rate, and the reaction time also needs to be controlled at 25–30 minutes.

[0016] It should be noted that, in the method described in this application, the temperature inside the reactor needs to be maintained at around 25°C before adding the molecular weight regulator to avoid premature polymerization and affecting the subsequent molecular weight control.

[0017] In some embodiments, the proportions of the preparation raw materials added to the reaction vessel by weight are as follows: 120-140 parts water, 3-10 parts emulsifier, 4-10 parts unsaturated carboxylic acid monomer, 25-35 parts acrylonitrile, 55-70 parts butadiene, 0.2-0.6 parts sodium persulfate aqueous solution, 0.05-0.1 parts sodium bisulfite aqueous solution, 0.1-0.2 parts first molecular weight regulator, 0.1-0.2 parts second molecular weight regulator, and 0.1-0.2 parts third molecular weight regulator;

[0018] The sodium persulfate aqueous solution contains 3-5 wt% sodium persulfate, and the sodium bisulfite aqueous solution contains 0.8-1.2 wt% sodium bisulfite.

[0019] By controlling the weight proportions of each raw material within the above-mentioned range, this application facilitates the smooth progress of the polymerization reaction and also helps to improve the molecular weight distribution of the synthesized carboxylated nitrile latex, resulting in a narrower molecular weight distribution.

[0020] In this application, the added butadiene is de-resisted butadiene, and the added sodium persulfate aqueous solution and sodium bisulfite aqueous solution are initiators.

[0021] In some embodiments, the emulsifier includes anionic emulsifiers and nonionic emulsifiers, and the mass ratio of the anionic emulsifier to the nonionic emulsifier is (3-5):1.

[0022] In this application, the emulsifier includes both anionic and nonionic emulsifiers. Anionic emulsifiers have better emulsification effects, but they are more sensitive to pH value and inorganic ion concentration, resulting in poor emulsion stability. Nonionic emulsifiers mainly rely on the steric hindrance generated by the hydration layer to maintain emulsion stability, effectively improving emulsion stability while increasing the stability of the polymerization process. This application achieves better emulsification effect through the synergistic effect of anionic and nonionic emulsifiers. Furthermore, controlling the mass ratio of anionic to nonionic emulsifiers at (3-5):1 helps to further improve the emulsification effect.

[0023] In some embodiments, the anionic emulsifier is selected from at least one of sodium alkyl sulfonate, sodium alkylbenzene sulfonate, and sodium alkyl diphenyl ether disulfonate; the nonionic emulsifier is isotridecyl ether.

[0024] In some preferred embodiments, the anionic emulsifier sodium dodecylbenzenesulfonate and sodium dodecyl diphenyl ether disulfonate are a mixture, and the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl diphenyl ether disulfonate in the mixture is (2-6):1.

[0025] In some preferred embodiments, the emulsifier comprises, by weight, 2 to 6 parts of sodium dodecylbenzenesulfonate, 1 to 4 parts of sodium dodecyl diphenyl ether disulfonate, and 0.75 to 2.5 parts of isotridecyl ether; and the mass ratio of anionic emulsifier to nonionic emulsifier is (3 to 5):1, and the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl diphenyl ether disulfonate is (2 to 6):1.

[0026] This application utilizes isomeric tridecyl alcohol ether as a nonionic emulsifier and combines it with anionic emulsifiers (sodium dodecylbenzenesulfonate and sodium dodecyl diphenyl ether disulfonate) to achieve good emulsification and high stability of the emulsion during polymerization.

[0027] In some embodiments, the first molecular weight regulator, the second molecular weight regulator, and the third molecular weight regulator are the same, all being a mixture of tert-dodecyl mercaptan and n-dodecyl mercaptan acetate.

[0028] In this application, the molecular weight regulator added in all three batches is the same: a mixture of tert-dodecyl mercaptan and n-dodecyl mercaptan acetate. The molecular weight regulator added in this application includes both thiols and thiol derivatives. The synergistic effect of tert-dodecyl mercaptan and n-dodecyl mercaptan acetate helps to narrow the molecular weight distribution of the synthesized carboxylated nitrile butadiene latex. Furthermore, since tert-dodecyl mercaptan has a strong odor, using only it as a molecular weight regulator would result in a very strong odor in the synthesized carboxylated nitrile butadiene latex. However, by using n-dodecyl mercaptan acetate to replace a portion of the tert-dodecyl mercaptan, the thiol derivative not only plays a role in molecular weight regulation but also significantly reduces the odor of the resulting latex.

[0029] In some embodiments, the mass ratio of tert-dodecyl mercaptan to dodecyl mercaptan acetate in the mixture is (4-6):1.

[0030] In some preferred embodiments, the mass ratio of tert-dodecyl mercaptan to dodecyl mercaptan acetate in the mixture is 5:1.

[0031] This application improves the molecular weight regulation of carboxylated nitrile latex by controlling the mass ratio of tert-dodecyl mercaptan to dodecyl mercaptan acetate in the molecular weight regulator within the above-mentioned range, resulting in a narrower molecular weight distribution of the synthesized carboxylated nitrile latex.

[0032] In this application, the specific type of unsaturated carboxylic acid monomer used in the prepared raw materials is not explicitly limited, and those skilled in the art can make conventional selections as needed. In some embodiments, the unsaturated carboxylic acid monomer may be selected from at least one of acrylic acid, methacrylic acid, itaconic acid, and maleic acid. In some more specific embodiments, the unsaturated carboxylic acid monomer is methacrylic acid and itaconic acid.

[0033] In some implementations, the staged heating procedure in step S5 is as follows:

[0034] When the conversion rate reaches 70-75%, the temperature inside the reactor is raised to 30-35°C.

[0035] When the conversion rate reaches 85-90%, the temperature inside the reactor is raised to 40-45°C.

[0036] Since the polymerization rate slows down in the later stages of the polymerization reaction, in order to further improve the conversion rate, this application adopts a staged heating method in the later stages of the polymerization reaction to gradually increase the temperature inside the reactor, thereby further improving the conversion rate.

[0037] The “conversion rate” in this application is the theoretical conversion rate, which is calculated by testing the polymer solid content and the theoretical solid content.

[0038] This application does not explicitly limit the type of inert gas introduced in step S2; those skilled in the art can make conventional selections as needed. In some specific embodiments, the inert gas may be nitrogen, etc.

[0039] In this application, in step S2, the operation of evacuating the reactor and filling it with inert gas can be repeated 3 to 5 times, and the pressure inside the reactor can be -0.095 to -0.10 MPa.

[0040] In step S6 of this application, degassing and purification can be achieved by adding defoamer and ammonia to the crude carboxylated nitrile latex.

[0041] The second aspect of this application provides a carboxylated nitrile latex for high elongation nitrile gloves prepared by the method described in the first aspect of this application.

[0042] The method described in this application adds a molecular weight regulator twice at a specific conversion point after the polymerization reaction begins, that is, the molecular weight regulator is added three times in total. This can effectively control the molecular weight distribution and gelation changes of the obtained carboxylated nitrile latex, making the molecular weight distribution of the carboxylated nitrile latex narrow, which helps to improve the elongation of nitrile gloves.

[0043] The third aspect of this application provides a disposable nitrile glove, wherein the raw materials for preparing the disposable nitrile glove contain carboxylated nitrile latex for high elongation nitrile gloves prepared by the method described in the first aspect of this application.

[0044] Because the carboxylated nitrile latex prepared by the method described in this application has a narrow molecular weight distribution, when the carboxylated nitrile latex is used to prepare disposable nitrile gloves, the vulcanization time of the carboxylated nitrile latex is shorter and the vulcanization effect is better, which makes the nitrile gloves have excellent performance, high elongation (700-750%), and soft feel (similar to natural rubber), with good application prospects.

[0045] In some embodiments, the raw materials for preparing the disposable nitrile gloves, by weight, include the following components:

[0046] It should be noted that the weight parts of the high elongation nitrile gloves using carboxylated nitrile latex described in this application are based on their dry weight.

[0047] In this application, both zinc dibutyldithiocarbamate and zinc diethyldithiocarbamate are accelerators, wherein zinc dibutyldithiocarbamate is also known as accelerator BZ and zinc diethyldithiocarbamate is also known as accelerator EZ.

[0048] This application does not specify the specific type of antioxidant; any antioxidant sold on the market may be used.

[0049] In this application, the method for preparing the disposable nitrile gloves is a conventional method in the art.

[0050] The beneficial technical effects of this application are as follows: In the preparation method of carboxylated nitrile butadiene latex provided in this application, the molecular weight regulator is added in three batches. The first batch is added before the start of the polymerization reaction, and the latter two batches are added at specific conversion points. This effectively controls the molecular weight distribution and gelation changes of the obtained carboxylated nitrile butadiene latex, resulting in a narrow molecular weight distribution and a molecular weight distribution index controlled between 1.1 and 1.5. When the carboxylated nitrile butadiene latex synthesized in this application is used to prepare disposable nitrile butadiene gloves, due to the narrow molecular weight distribution, the vulcanization time is shorter and the vulcanization effect is better. This results in excellent performance of the nitrile gloves, with a high elongation of 700-750%, and a soft feel similar to natural rubber, showing good application prospects. Attached Figure Description

[0051] Figure 1 This is a diagram of the synthesis apparatus used in Example 1 of this application to prepare carboxylated nitrile butadiene latex for high elongation nitrile gloves. Detailed Implementation

[0052] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0053] Example 1: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0054] The synthesis apparatus used in the preparation process of this embodiment is shown in the figure below. Figure 1 As shown, the specific synthesis steps are as follows:

[0055] Step 1: Add 145 parts of pure water, 4 parts of sodium dodecylbenzenesulfonate, 2 parts of sodium dodecyl diphenyl ether disulfonate, 1.5 parts of isotridecyl ether, 3 parts of methacrylic acid, 2 parts of itaconic acid, and 25 parts of acrylonitrile to the reaction vessel. Start stirring, heat, and maintain at 25°C. The mass ratio of anionic surfactant (sodium dodecylbenzenesulfonate and sodium dodecyl diphenyl ether disulfonate) to nonionic surfactant (isotridecyl ether) in the emulsifier is 4:1, and the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl diphenyl ether disulfonate is 3:1.

[0056] Step 2: Vacuum the reactor and purge it with nitrogen four times. Finally, maintain the reactor under negative pressure (internal pressure -0.095MPa). Add 70 parts of butadiene that has undergone de-inhibition treatment to the reactor, start stirring, and premix for 10 minutes.

[0057] Step 3: Add 0.35 parts of sodium persulfate aqueous solution to the reactor. After 10 minutes, add 0.08 parts of sodium bisulfite aqueous solution. Maintain the temperature inside the reactor at 25°C. When the reaction temperature shows a significant upward trend, immediately control the jacket temperature to maintain the reactor temperature at 25°C for 30 minutes. The sodium persulfate aqueous solution contains 4.0 wt% sodium persulfate, and the sodium bisulfite aqueous solution contains 1.0 wt% sodium bisulfite.

[0058] Step 4: Add 0.18 parts of molecular weight regulator to the reactor and start timing the reaction. The molecular weight regulator contains 0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate, with a mass ratio of 5:1. Calculate the theoretical conversion rate by testing the polymer solid content and theoretical solid content. When the conversion rate reaches 20%, add another 0.18 parts of molecular weight regulator (0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate); when the conversion rate reaches 40%, add another 0.18 parts of molecular weight regulator (0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate).

[0059] Step 5: When the conversion rate reaches 70%, the temperature inside the reactor is increased to 35°C; when the conversion rate reaches 85%, the temperature inside the reactor is increased to 45°C; when the conversion rate reaches 95%, the polymerization reaction is terminated to obtain crude carboxylated nitrile latex.

[0060] Step 6: Add defoamer and ammonia to the crude carboxylated nitrile latex for degassing and purification, then concentrate it until the solid content reaches 45%, and filter out the finished product, which is the high elongation nitrile glove carboxylated nitrile latex.

[0061] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.22.

[0062] Example 2: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0063] The preparation process is basically the same as in Example 1, except that the added emulsifier contains 3 parts sodium dodecylbenzenesulfonate, 3 parts dodecyl diphenyl ether disulfonic acid, and 1.5 parts isomeric tridecyl alcohol ether. The mass ratio of anionic surfactant to nonionic surfactant in the emulsifier is 4:1, and the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl diphenyl ether disulfonic acid salt is 1:1.

[0064] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.26.

[0065] Example 3: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0066] The preparation process is basically the same as in Example 1, except that the added emulsifier contains 3.75 parts sodium dodecylbenzenesulfonate, 1.25 parts dodecyl diphenyl ether disulfonic acid, and 2.5 parts isotridecyl ether. The mass ratio of anionic surfactant to nonionic surfactant in the emulsifier is 2:1, and the mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl diphenyl ether disulfonic acid salt is 3:1.

[0067] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.27.

[0068] Example 4: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0069] The preparation process is basically the same as in Example 1, except that the added emulsifier contains 5.625 parts sodium dodecylbenzenesulfonate, 1.875 parts dodecyl diphenyl ether disulfonic acid, and 0 parts isomeric tridecyl alcohol ether. The mass ratio of sodium dodecylbenzenesulfonate to sodium dodecyl diphenyl ether disulfonic acid salt in the emulsifier is 3:1.

[0070] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.32.

[0071] Example 5: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0072] The preparation process is basically the same as in Example 1, except that the nonionic surfactant in the added emulsifier is isomeric decaol ether.

[0073] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.29.

[0074] Example 6: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0075] The preparation process is basically the same as in Example 1, except that in step 4, the molecular weight regulator added in the three batches contains 0.135 parts of tert-dodecyl mercaptan and 0.045 parts of n-dodecyl mercaptan acetate, and the mass ratio of tert-dodecyl mercaptan to n-dodecyl mercaptan acetate is 3:1.

[0076] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.40.

[0077] Example 7: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0078] The preparation process is basically the same as in Example 1, except that in step 4, the molecular weight regulator added in the three batches contains 0.16 parts of tert-dodecyl mercaptan and 0.02 parts of n-dodecyl mercaptan acetate, and the mass ratio of tert-dodecyl mercaptan to n-dodecyl mercaptan acetate is 8:1.

[0079] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.35.

[0080] Example 8: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0081] The preparation process is basically the same as in Example 1, except that in step 4, the molecular weight regulator added in all three batches is 0.18 parts of tert-dodecyl mercaptan.

[0082] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.43.

[0083] Example 9: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0084] The preparation process is basically the same as in Example 1, except that in step 4, the molecular weight regulator added in all three batches is 0.12 parts, of which 0.1 parts are tert-dodecyl mercaptan and 0.02 parts are n-dodecyl mercaptan acetate. The mass ratio of tert-dodecyl mercaptan to n-dodecyl mercaptan acetate is 5:1.

[0085] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.37.

[0086] Example 10: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0087] The preparation process is basically the same as in Example 1, except that step 4 is as follows:

[0088] Add 0.18 parts of molecular weight regulator to the reactor and start timing the reaction. The molecular weight regulator contains 0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate, with a mass ratio of 5:1. The theoretical conversion rate is calculated by testing the polymer solid content and theoretical solid content. When the conversion rate reaches 25%, add another 0.18 parts of molecular weight regulator (0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate); when the conversion rate reaches 45%, add another 0.18 parts of molecular weight regulator (0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate).

[0089] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.21.

[0090] Example 11: Preparation of carboxylated nitrile butadiene latex for high elongation nitrile gloves

[0091] The preparation process is basically the same as in Example 1, except that step 5 is as follows:

[0092] When the conversion rate reaches 75%, the temperature inside the reactor is increased to 30°C; when the conversion rate reaches 90%, the temperature inside the reactor is increased to 40°C; when the conversion rate reaches 95%, the polymerization reaction is terminated to obtain crude carboxylated nitrile latex.

[0093] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.25.

[0094] Comparative Example 1: Preparation of Carboxylated Acrylonitrile Latex for High Elongation Acrylonitrile Gloves

[0095] The preparation process is basically the same as in Example 1, except that step 3 is as follows:

[0096] Add 0.35 parts of sodium persulfate aqueous solution to the reaction vessel, and after 10 minutes, add 0.08 parts of sodium bisulfite aqueous solution. The sodium persulfate aqueous solution contains 4.0 wt% sodium persulfate, and the sodium bisulfite aqueous solution contains 1.0 wt% sodium bisulfite.

[0097] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.49.

[0098] Comparative Example 2: Preparation of Carboxylated Acrylonitrile Latex for High Elongation Acrylonitrile Gloves

[0099] The preparation process is basically the same as in Example 1, except that step 4 is as follows:

[0100] Add 0.18 parts of molecular weight regulator to the reactor and start timing the reaction. The molecular weight regulator contains 0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate, with a mass ratio of 5:1. The theoretical conversion rate is calculated by testing the polymer solid content and theoretical solid content. When the conversion rate reaches 35%, add another 0.18 parts of molecular weight regulator (0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate); when the conversion rate reaches 55%, add another 0.18 parts of molecular weight regulator (0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate).

[0101] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.77.

[0102] Comparative Example 3: Preparation of Carboxylated Acrylonitrile Latex for High Elongation Acrylonitrile Gloves

[0103] The preparation process is basically the same as in Example 1, except that step 4 is as follows:

[0104] Add 0.18 parts of molecular weight regulator to the reactor and start timing the reaction. The molecular weight regulator contains 0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate, with a mass ratio of 5:1. The theoretical conversion rate is calculated by testing the polymer solid content and theoretical solid content. When the conversion rate reaches 10%, add another 0.18 parts of molecular weight regulator (0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate); when the conversion rate reaches 30%, add another 0.18 parts of molecular weight regulator (0.15 parts of tert-dodecyl mercaptan and 0.03 parts of n-dodecyl mercaptan acetate).

[0105] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 1.82.

[0106] Comparative Example 4: Preparation of Carboxylated Acrylonitrile Latex for High Elongation Acrylonitrile Gloves

[0107] The preparation process is basically the same as in Example 1, except that step 4 is as follows:

[0108] Add 0.54 parts of a molecular weight regulator to the reaction vessel and start timing the reaction. The molecular weight regulator contains 0.45 parts of tert-dodecyl mercaptan and 0.09 parts of n-dodecyl mercaptan acetate, with a mass ratio of 5:1 between tert-dodecyl mercaptan and n-dodecyl mercaptan acetate.

[0109] The molecular weight distribution was determined by gel permeation chromatography, and the molecular weight distribution index of the prepared carboxylated nitrile latex for high elongation nitrile gloves was 2.30.

[0110] Application Example 1: Preparation of disposable nitrile gloves. The raw materials for preparing disposable nitrile gloves are as follows (by weight):

[0111] The high elongation nitrile glove carboxylated nitrile latex prepared in Example 1 (on dry weight): 100 parts; sulfur: 1.5 parts; zinc oxide: 0.65 parts; BZ (zinc dibutyl dithiocarbamate): 0.5 parts; EZ (zinc diethyl dithiocarbamate): 0.3 parts; antioxidant: 0.01 parts.

[0112] Preparation method: After stirring and mixing the raw materials, add 100 parts of deionized water and mix evenly to prepare a nitrile emulsion for later use. Dry the glove mold impregnated with the coagulant by rotation at 85°C, then immerse it in the prepared nitrile emulsion for 10 seconds. After removal, dry it by rotation at 90°C. The dried film is then subjected to edge rolling, leaching, dehumidification, vulcanization, post-leaching, impregnation with an anti-sticking chelating agent, drying, demolding, counting, and packaging to obtain disposable nitrile gloves.

[0113] Application Example 2-11: Preparation of Disposable Nitrile Gloves

[0114] The preparation process is basically the same as in Application Example 1, except that the high elongation nitrile glove carboxylated nitrile latex prepared in Example 1 is replaced with the high elongation nitrile glove carboxylated nitrile latex prepared in Examples 2-11.

[0115] Comparative Application Examples 1-4: Preparation of Disposable Nitrile Gloves

[0116] The preparation process is basically the same as in Application Example 1, except that the high elongation nitrile glove carboxylated nitrile latex prepared in Comparative Examples 1-4 is used instead of the high elongation nitrile glove carboxylated nitrile latex prepared in Example 1.

[0117] Test Example 1

[0118] The tensile strength and elongation of disposable nitrile gloves prepared according to Case 1-11 and Comparative Application Example 1-4 were tested. The test method was in accordance with ASTM D 412-1998A, and the average thickness of the disposable nitrile glove test piece was 0.07 mm. The test results are shown in Table 1.

[0119] Table 1

[0120] Tensile strength (MPa) Elongation (%) Application Example 1 30 727 Application Example 2 28 721 Application Example 3 27 717 Application Example 4 25 702 Application Example 5 26 715 Application Example 6 21 711 Application Example 7 24 707 Application Example 8 20 700 Application Example 9 23 704 Application Example 10 30 730 Application Example 11 28 723 Comparative Application Example 1 18 681 Comparative Application Example 2 15 635 Comparative Application Example 3 14 622 Comparative Application Example 4 11 531

[0121] As can be seen from the test results in Table 1, compared with Comparative Application Examples 1-4, the high elongation nitrile glove carboxylated nitrile latex prepared in Application Examples 1-11 has better tensile strength and elongation. The tensile strength of the high elongation nitrile glove carboxylated nitrile latex prepared in Application Examples 1-11 is 20-30 MPa, and the elongation is 700-730%.

[0122] The test results from Application Examples 1 and 10 and Comparative Application Examples 2-4 show that, compared to Comparative Application Example 1 where the molecular weight regulator was added all at once, adding the molecular weight regulator in batches can significantly improve the elongation of disposable nitrile gloves. Furthermore, when the molecular weight regulator is added twice at a conversion rate of 20-25% and 40-45%, respectively, the molecular weight distribution of carboxylated nitrile latex becomes narrower, resulting in higher elongation of disposable nitrile gloves, as well as higher tensile strength.

[0123] The test results from Application Examples 1-5 show that the emulsifier added during the preparation process also affects the molecular weight distribution of carboxylated nitrile latex, which in turn affects the elongation of disposable nitrile gloves.

[0124] The test results from Application Examples 1 and 6-9 show that the amount and composition of the molecular weight regulator added during the preparation process have a significant impact on the molecular weight distribution of carboxylated nitrile latex, and thus significantly affect the elongation of disposable nitrile gloves.

[0125] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. A process for the preparation of a carboxylated nitrile latex for high elongation nitrile gloves, characterized by, The method comprises the following steps: S1, water, emulsifier, unsaturated carboxylic acid monomer and acrylonitrile are added into a reaction kettle and mixed; S2, the reaction kettle is vacuumized and filled with inert gas, and butadiene is added into the reaction kettle under negative pressure and mixed again; S3, sodium persulfate aqueous solution and sodium bisulfite aqueous solution are added into the reaction kettle, and the temperature in the reaction kettle is maintained at 25-27℃ for 25-30 minutes; S4, the polymerization reaction is started after the first molecular weight regulator is added into the reaction kettle, the second molecular weight regulator is added after the conversion rate reaches 20-25% to continue the polymerization reaction, and the third molecular weight regulator is added after the conversion rate reaches 40-45% to continue the polymerization reaction; S5, the temperature in the reaction kettle is raised in stages, and the polymerization reaction is ended when the conversion rate reaches more than 95% to obtain a carboxyl butyronitrile latex crude product; S6, the carboxyl butyronitrile latex crude product is degassed, purified, concentrated and filtered to prepare the high-elongation carboxyl butyronitrile latex for butyronitrile gloves. The emulsifier comprises an anionic emulsifier and a non-ionic emulsifier, and the mass ratio of the anionic emulsifier to the non-ionic emulsifier is (3-5):1; the anionic emulsifier is a mixture of sodium dodecyl benzene sulfonate and sodium dodecyl diphenyl ether disulfonate, and the mass ratio of sodium dodecyl benzene sulfonate to sodium dodecyl diphenyl ether disulfonate in the mixture is (2-6):1; and the non-ionic emulsifier is isomeric tridecanol ether.

2. The method of claim 1, wherein, The preparation raw materials added into the reaction kettle are as follows in parts by weight: water 120-140 parts, emulsifier 3-10 parts, unsaturated carboxylic acid monomer 4-10 parts, acrylonitrile 25-35 parts, butadiene 55-70 parts, sodium persulfate aqueous solution 0.2-0.6 parts, sodium bisulfite aqueous solution 0.05-0.1 parts, first molecular weight regulator 0.1-0.2 parts, second molecular weight regulator 0.1-0.2 parts, and third molecular weight regulator 0.1-0.2 parts; The content of sodium persulfate in the sodium persulfate aqueous solution is 3-5 wt%, and the content of sodium bisulfite in the sodium bisulfite aqueous solution is 0.8-1.2 wt%.

3. The method according to claim 1 or 2, characterized in that, The first, second and third molecular weight regulators are the same, and all are a mixture of tertiary dodecyl mercaptan and n-dodecyl mercaptan acetate.

4. The method of claim 3, wherein, The mass ratio of tertiary dodecyl mercaptan to n-dodecyl mercaptan acetate in the mixture is (4-6):

1.

5. The method according to claim 1 or 2, characterized in that, In step S5, the procedure of the staged temperature raising is as follows: When the conversion rate reaches 70-75%, the temperature in the reaction kettle is increased to 30-35℃; When the conversion rate reaches 85-90%, the temperature in the reaction kettle is increased to 40-45℃.

6. A high-elongation carboxyl butyronitrile latex for butyronitrile gloves prepared by the method of any one of claims 1-5.

7. A disposable nitrile glove characterized in that, The preparation raw materials of the disposable butyronitrile gloves contain the high-elongation carboxyl butyronitrile latex for butyronitrile gloves prepared by the method of any one of claims 1-5.

8. The disposable nitrile glove of claim 7, wherein, The raw materials for preparing the disposable nitrile glove include the following components in parts by weight: 100 parts of carboxyl nitrile latex for the high elongation nitrile glove; 1.0-1.5 parts of sulfur; 0.5-1.5 parts of zinc oxide; 0.3-0.8 parts of zinc dibutyldithiocarbamate; 0.3-0.8 parts of zinc diethyldithiocarbamate; 0.01-0.05 parts of antioxidant.

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