A butyronitrile emulsion, its preparation method and application

Abstract

The application discloses a kind of butyronitrile emulsion and its preparation method and application, belong to daily chemical rubber technical field.It is specific that the butyronitrile emulsion of the application includes the following components: butyronitrile latex 90-110 parts;Emulsifier 0.1-1.2 parts;Acid-base regulator 0.5-2.5 parts;Zinc oxide 1.0-3.0 parts;Vulcanization package 3.4-5.4 parts;Wherein vulcanization package is composed of sulfur and accelerator, and the weight ratio of sulfur and accelerator is 1.5-2.5;The accelerator is selected from zinc salt accelerator.The butyronitrile emulsion and preparation method of the application can realize the rapid vulcanization crosslinking of rubber under low temperature conditions, and has good mechanical properties and appearance, and can be used for preparing gloves.

Description

Technical Field

[0001] This invention belongs to the field of daily chemical rubber technology, and particularly relates to a nitrile emulsion, its preparation method and application. Background Technology

[0002] Nitrile latex impregnation molding mostly uses a sulfur vulcanization system. On the one hand, sulfur is inexpensive and easily dispersed in latex; on the other hand, this system has a long processing window and can be stored at room temperature for a long time. Sulfur vulcanization molding can be achieved by heating.

[0003] Because sulfur vulcanizing agents require high temperatures during processing to bring sulfur to its melting point and create more activated sulfur sites, the crosslinking density of the vulcanizate can be increased, thus improving vulcanization efficiency. Alternatively, increasing the vulcanization time can increase the crosslinking opportunities of the activated sulfur sites in the vulcanizate, thereby increasing the crosslinking density of sulfur. However, given current mass production requirements, this method is difficult to implement, has a low upper limit, and cannot achieve the goal of high speed, high yield, and low carbon emissions.

[0004] Article 1009-797X(2021)02-0006-04, "Research on Improving the Crosslinking Density of Nitrile Gloves", discloses a research method to improve the crosslinking density of nitrile rubber. The method involves increasing the temperature, time, and amount of accelerator. However, this method does not solve the problem of achieving rapid crosslinking of nitrile latex under low temperature and short time conditions. Furthermore, after the amount of a single component is increased to saturation, blooming occurs, and the physical and mechanical properties of the material are reduced.

[0005] Therefore, the existing technology lacks a method for preparing nitrile emulsions and rubber products that can achieve rapid vulcanization and crosslinking of rubber under low temperature conditions and have good mechanical properties and appearance. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned technical defects and provide a nitrile emulsion that can achieve rapid vulcanization and crosslinking of rubber under low temperature and short time conditions, and has good mechanical properties and appearance.

[0007] Another object of the present invention is to provide a preparation process for the nitrile emulsion and the rubber article.

[0008] Another object of the present invention is to provide the application of the above-mentioned nitrile emulsion.

[0009] This invention is achieved through the following technical solution:

[0010] A nitrile emulsion, comprising the following components by weight:

[0011] 90-110 parts of nitrile latex;

[0012] Emulsifier 0.1-1.2 parts;

[0013] Acid-base regulator: 0.5-2.5 parts;

[0014] Zinc oxide 1.0-3.0 parts;

[0015] Vulcanizing package: 3.4-5.4 parts;

[0016] The weight parts of the nitrile latex are the same as the weight parts of the dry rubber;

[0017] The vulcanizing bag is composed of sulfur and an accelerator, with the weight ratio of sulfur to accelerator being (1.5-2.5):1.

[0018] The accelerator is selected from zinc salt accelerators.

[0019] Preferably, the nitrile latex is selected from carboxylated nitrile latex.

[0020] More preferably, the nitrile latex is selected from butadiene-acrylonitrile and methacrylic acid terpolymer latex.

[0021] This invention can increase the actual amount of sulfur participating in the reaction by limiting the weight ratio range of sulfur to accelerator, thereby increasing the crosslinking reaction rate.

[0022] The proportion of activated sulfur in a single sulfur molecule is relatively low, at 7%-10%. Adding a specific ratio of accelerator can lower the activation energy and act as an activator. The accelerator has 5-6 sites participating in the reaction. When there are enough sites, increasing the amount of activated sulfur will increase the proportion of sulfur participating in the reaction and will positively promote the sulfurization reaction.

[0023] Furthermore, nitrile rubber is a rubber latex obtained by emulsion copolymerization of butadiene, acrylonitrile, and methacrylic acid. It contains hydrophilic, strongly polar carboxyl groups on the main molecular chain, which makes the latex easy to crosslink. It can also react with divalent metal oxides or their salts to form ionic crosslinking bonds.

[0024] The reaction rate can also be controlled by adjusting the number of vulcanizing packets.

[0025] Traditional formulations using high sulfur and low accelerator content require prolonged vulcanization at room temperature. The latex contains a relatively excessive amount of carboxyl groups, most of which do not participate in the reaction. Traditional formulations also result in long processing cycles and low production capacity. In contrast, the nitrile latex provided by this invention fully utilizes the carboxyl groups and accelerators in the latex, effectively increasing the vulcanization reaction rate.

[0026] Zinc salt accelerators have low activation energy, requiring only 100℃ for activation. They also have shorter scorch times, which facilitates rapid impregnation, faster dehydration and condensation, a denser film structure, faster heating and evaporation efficiency, and faster thermal vulcanization.

[0027] Preferably, the nitrile emulsion comprises, by weight, the following components:

[0028] 95-105 parts of nitrile latex;

[0029] Emulsifier 0.3-1.0 parts;

[0030] Acid-base regulator 1.0-2.0 parts;

[0031] Zinc oxide 1.5-2.5 parts;

[0032] Vulcanizing package 3.4-4.5 parts.

[0033] Preferably, the acrylonitrile content in the nitrile latex is 23%-27% by mass.

[0034] Preferably, the content of carboxyl groups in the nitrile latex accounts for 1-7 wt% of the dry weight of the nitrile latex.

[0035] Preferably, the emulsifier is selected from at least one of sodium dodecylbenzenesulfonate, ammonium dodecyl sulfate, sodium dodecyl sulfate, or sodium secondary alkyl sulfonate.

[0036] Preferably, the acid-base regulator is selected from potassium hydroxide.

[0037] Preferably, the sulfur is selected from elemental sulfur.

[0038] Preferably, the zinc salt accelerator is selected from at least two of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, or zinc diisobutyldithiocarbamate.

[0039] More preferably, the zinc salt accelerator is selected from a mixture of zinc diethyldithiocarbamate and zinc diisobutyldithiocarbamate; the mass ratio of zinc diethyldithiocarbamate to zinc diisobutyldithiocarbamate is (1-2):(1-2).

[0040] Dithiocarbamate accelerators contain two promoting groups and two activating groups, along with highly reactive and easily broken strong polar sulfur-zinc bonds. In the vulcanization reaction, they have 3-4 times more activation sites than ordinary accelerators. Adding a matching amount of sulfur can significantly increase the vulcanization speed. The easily broken strong polar sulfur-zinc bonds lower the activation energy, accelerate bond opening, and shorten scorch time, allowing for rapid formation of monosulfide and polysulfide bonds, thus creating a dense cross-linked rubber network.

[0041] This invention also provides a method for preparing a rubber product, comprising the following steps:

[0042] S1: Weigh each component according to the weight parts, stir for no less than 20 hours, and then add deionized water to prepare nitrile latex of the required concentration for later use;

[0043] S2: Prepare a release liquid, wherein the release liquid comprises, by weight fraction, 10-30 parts of coagulant, 1-3 parts of release agent, and 67-89 parts of deionized water; the components are weighed by weight and mixed evenly after stirring; the coagulant is selected from at least one of calcium nitrate, magnesium nitrate, and calcium chloride, and the release agent is selected from at least one of calcium stearate, sodium stearate, and zinc stearate.

[0044] S3: Clean the mold with acid and alkali and dry it; after drying, immerse the mold in the release solution of S2, take it out and rotate it to dry;

[0045] S4: After the release agent has dried, the mold is immersed in the nitrile latex diluted in S1, then removed and rotated to dry; the mold is then immersed in the nitrile latex diluted in S1 again, and removed and rotated to dry a second time.

[0046] S5: After drying, the molds are filtered with clean water, hot vulcanized, demolded, and packaged.

[0047] Preferably, in step S1, the acid-base regulator is added in the form of a solution with a concentration of 0.5-4.0 wt%.

[0048] Preferably, in step S1, zinc oxide is added in the form of an emulsified zinc oxide emulsion.

[0049] Preferably, in step S1, the vulcanizing package is added in the form of a mixture of sulfur and accelerator. The mixture is prepared by mixing and grinding the sulfur and accelerator to achieve a stable suspension mixture state.

[0050] Preferably, the solid content of the nitrile emulsion diluted with deionized water in step S1 is 10-40 wt%.

[0051] Preferably, the optimal processing window for the nitrile latex described in S1 is 20 to 40 hours.

[0052] Accelerators, zinc oxide, and sulfur first generate polysulfide compounds for the accelerators, which then react with rubber molecules to form rubber thiols. The rubber thiols then undergo cross-linking reactions with rubber molecules or with themselves, and finally undergo rearrangement, shortening, and main chain modification to form vulcanized rubber.

[0053] Preferably, the acid-base cleaning temperature in S3 is 40-70℃, the acid ion concentration is 1-6wt%, and the base ion concentration is 3-8wt%.

[0054] Preferably, the temperature of the release liquid in S3 is 50-70℃, and the drying temperature is 60-100℃.

[0055] Preferably, the temperature of the nitrile latex in S4 is 25-35℃, and the drying temperature is 60-100℃.

[0056] Preferably, the vulcanization temperature in S5 is 80-100℃, and the vulcanization time is 10 to 15 minutes.

[0057] The present invention also provides a rubber product prepared using the above-mentioned nitrile emulsion.

[0058] Preferably, the rubber product is a glove.

[0059] Compared with the prior art, the present invention has the following advantages:

[0060] Traditional nitrile rubber latex impregnation molding requires 25-40 minutes of hot vulcanization. The nitrile rubber latex and its preparation method provided by this invention achieve rapid vulcanization and crosslinking of nitrile rubber latex at 100℃ for only 15 minutes, resulting in excellent mechanical and appearance properties. This significantly shortens the cycle time for preparing nitrile rubber products from nitrile rubber latex, doubles production efficiency, and reduces energy consumption by 30%, thereby reducing substantial costs in the production process. Detailed Implementation

[0061] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0062] Sources of raw materials used in this invention:

[0063] Nitrile latex 1: LG NL105, with carboxyl content accounting for 1-2 wt% of dry rubber weight, Ningbo LG Yongxing Chemical Co., Ltd.

[0064] Emulsifier: LAS-30, sodium dodecylbenzenesulfonate, Jiangsu Qingting Detergent Co., Ltd.

[0065] Acid-base regulator: KOH, Huarong Chemical (Chengdu) Co., Ltd., added in the form of a 2wt% diluted solution.

[0066] Zinc oxide (ZnO), Guangzhou Lixin Trading Co., Ltd.

[0067] Accelerator 1: Zinc diethyldithiocarbamate (ZDEC) Guangzhou Lixin Trading Co., Ltd.

[0068] Accelerator 2: Zinc diisobutyl dithiocarbamate ZDIBC Guangzhou Lixin Trading Co., Ltd.

[0069] Accelerator 3: Tetramethylthiuram disulfide TMTD, Guangzhou Lixin Trading Co., Ltd.

[0070] Sulfur: S Guangzhou Lixin Trading Co., Ltd.

[0071] Calcium nitrate: Jiaocheng County Sanxi Chemical Co., Ltd.

[0072] Calcium stearate: MAXCO B101, Guangzhou Murphy Environmental Protection Technology Co., Ltd.

[0073] Test methods:

[0074] Tensile strength: According to the ASTM D5034-2017 standard method, the sample was uniformly cut into dumbbell shapes with a length of 115 mm and a width of 6 mm. The standard temperature for the test was 23±2℃, the relative humidity was maintained at 50±5%, and the test was carried out on a motor-driven machine with a constant speed of 500±50 mm / min, with a distance of at least 750 mm.

[0075] Elongation at break: according to ASTM D5034-2017 standard method. Thirteen samples were cut using a standard cutter, and the average value was taken.

[0076] Vulcanization rate: Following the method outlined in GB / T 25268-2010 "Guide to the Use of Rubber Vulcanizers," the rubber compound was prepared into dry blocks. A 6g-8g sample was placed in the vulcanizer, and the test conditions were 100℃ for 60 minutes. T90 represents the vulcanization time at which the rubber compound reaches its optimal performance state, also known as the optimal vulcanization time in the process. T90 = [ML + (MH - ML) x 90%] corresponds to this time. Conventionally, the optimal vulcanization time also refers to the time slightly before the tensile strength reaches its maximum. Because rubber products continue to vulcanize during storage, in actual production, complete vulcanization is not required; reaching the product's performance is sufficient. This saves costs and extends product lifespan. T70 is the vulcanization time at which nitrile rubber products reach their performance in actual production. T70 = [ML + (MH - ML) x 70%].

[0077] Appearance test: After being placed at room temperature for 30 days, observe and compare the presence or absence of blooming under fluorescent light.

[0078] Preparation methods of the embodiments and comparative examples in this invention:

[0079] S1: Weigh each component according to the weight parts, stir for 20 hours, and then add deionized water to dilute to a nitrile emulsion solid content of 40 wt%;

[0080] S2: Prepare a release liquid, which, by weight fraction, comprises 20 parts of coagulant, 2 parts of release agent, and 80 parts of deionized water. The components are weighed by weight and mixed evenly after stirring. The coagulant is selected from calcium nitrate, and the release agent is selected from calcium stearate.

[0081] S3: After the production line equipment has been verified to be in good working order, the mold is cleaned and dried under the conditions of 70°C, acid ion concentration of 5% and alkali ion concentration of 5%; the mold is then immersed in a 60°C release solution and taken out to be rotated and dried at 80°C.

[0082] S4: Immerse the mold in 30℃ nitrile latex, remove and dry at 80℃ by rotation; immerse the mold in nitrile latex again, remove and dry at 80℃ by rotation a second time;

[0083] S5: The mold is filtered with clean water, hot vulcanized at 100℃ for 15 minutes, demolded, and packaged.

[0084] Table 1. Weight parts of each component of nitrile emulsions in Examples 1-9 and their test results.

[0085]

[0086] Examples 2-5 increased the amount of vulcanizing bag added when the weight ratio of accelerator to sulfur was 2.

[0087] In Examples 6-8, the weight ratio of accelerator to sulfur was gradually increased while the amount of vulcanizing bag added was 4.2.

[0088] As can be seen from Examples 1-9, the rubber products prepared by the nitrile emulsion provided by the present invention have a breaking force ≥6N, a tensile strength ≥32MPa, and an elongation at break ≥500%.

[0089] Table 2. Weight parts of each component and test results of nitrile emulsions in Comparative Examples 1-6

[0090]

[0091] Comparative Examples 1 and 2 show that a low weight ratio of accelerator to sulfur will lead to an increase in vulcanization time, and both a low and high weight ratio of accelerator to sulfur will result in blooming on the surface.

[0092] Comparative Examples 3 and 4 show that both too low and too high amounts of vulcanizing bag will increase the vulcanization time, and too high amounts of vulcanizing bag will cause blooming on the surface.

[0093] Comparative Examples 5 and 6 show that using non-zinc salt accelerators significantly increases the vulcanization time.

Claims

1. A nitrile emulsion, characterized in that, By weight, it includes the following components: 90-110 parts of nitrile latex; Emulsifier 0.1-1.2 parts; Acid-base regulator: 0.5-2.5 parts; Zinc oxide 1.0-3.0 parts; Vulcanizing package: 3.4-5.4 parts; The weight parts of the nitrile latex are the same as the weight parts of the dry rubber; The vulcanizing bag consists of sulfur and an accelerator, with the weight ratio of accelerator to sulfur being (1.5-2.5):

1. The accelerator is selected from zinc salt accelerators; The zinc salt accelerator is selected from at least two of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, or zinc diisobutyldithiocarbamate.

2. The nitrile emulsion according to claim 1, characterized in that, The carboxyl group content in the nitrile latex accounts for 1-7 wt% of the dry weight of the nitrile latex.

3. The nitrile emulsion according to claim 1, characterized in that, The emulsifier is selected from at least one of sodium dodecylbenzenesulfonate, ammonium dodecyl sulfate, sodium dodecyl sulfate, or sodium secondary alkyl sulfonate.

4. The nitrile emulsion according to claim 1, characterized in that, The acid-base regulator is selected from potassium hydroxide.

5. The nitrile emulsion according to claim 1, characterized in that, The zinc salt accelerator is selected from a mixture of zinc diethyldithiocarbamate and zinc diisobutyldithiocarbamate.

6. A method for preparing a rubber product, characterized in that, Includes the following steps: S1: Weigh out the components of the nitrile emulsion according to any one of claims 1-5 by weight, stir thoroughly, and then dilute for later use; S2: Prepare the release solution for later use; S3: Clean and dry the mold; After drying, the mold is immersed in the release liquid S2, then removed and dried again. S4: Immerse the mold after the release liquid has dried into the nitrile emulsion diluted in S1, remove and dry; immerse the mold again into the nitrile emulsion diluted in S1, remove and dry a second time; S5: After drying, the mold undergoes leaching, hot vulcanization, demolding, and packaging to obtain the rubber product.

7. The method for preparing rubber products according to claim 6, characterized in that, In step S1, the acid-base regulator is added in the form of a solution with a concentration of 0.5-4.0 wt%.

8. The method for preparing rubber products according to claim 6, characterized in that, In step S1, zinc oxide is added in the form of an emulsified zinc oxide emulsion.

9. The method for preparing rubber products according to claim 6, characterized in that, In step S1, the vulcanizing package is added in the form of a mixture of sulfur and accelerator. The mixture is prepared by mixing and grinding the sulfur and accelerator to achieve a stable suspension mixture.

10. A rubber product, characterized in that, It is prepared using the nitrile emulsion according to any one of claims 1-5.

11. A rubber product according to claim 10, characterized in that, The rubber product in question is a glove.

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