A nitrile glove and a method of making the same

Abstract

The present application relates to a kind of nitrile glove and its preparation method.The nitrile glove includes outer layer and inner layer, the outer layer is prepared by first nitrile emulsion, the inner layer is prepared by second nitrile emulsion.The nitrile composition is prepared nitrile glove, and no chlorine water hardening treatment is needed to be carried out to be smooth demoulding, no chlorine residue, and the nitrile glove obtained not only maintains good tensile strength and elongation, but also pinhole rate is not promoted, meets the product requirement of qualified quality.

Description

Technical Field

[0001] This invention relates to the field of nitrile materials technology, and more specifically, to a nitrile glove and its preparation method. Background Technology

[0002] Most nitrile gloves currently sold on the market are made by first impregnating the gloves with a coagulant, then with nitrile emulsion, and finally heating and vulcanizing them. The vulcanized rubber has high adhesion, requiring the gloves to be flipped over and pulled apart during demolding. During this process, the side in contact with the mold contains a release agent in the coagulant (which becomes the coagulant after drying), making separation easier. However, the side not in contact with the mold lacks this coagulant, and the highly adhesive rubber overlaps, causing them to stick together and hindering automated demolding. To address this, most manufacturers currently soak the gloves in chlorine water before demolding for hardening, ensuring smooth release. The side not in contact with the mold becomes the inner side of the nitrile glove after demolding. Because this side has been treated with chlorine water, some chlorine residue remains, which can be harmful to human skin with prolonged contact, easily causing skin allergies and limiting its usability in certain environments. Existing technology provides a method for reducing the chlorine content of nitrile gloves by reducing the number of chlorine washes, but the resulting nitrile gloves still contain a certain amount of chlorine. Furthermore, the large-scale use of chlorine water is detrimental to the safety of production workers. To reduce the residual chlorine content in the gloves, they need to be washed with a large amount of water, increasing the production process and cycle time, and raising the cost of subsequent wastewater treatment.

[0003] Therefore, technical efforts are needed to address the issue of chlorine residue in nitrile gloves. Summary of the Invention

[0004] The primary objective of this invention is to overcome the chlorine residue problem present in existing nitrile gloves and to provide nitrile gloves that can be easily demolded without chlorine hardening treatment and leave no chlorine residue. Furthermore, the resulting nitrile gloves not only maintain excellent tensile strength and elongation but also retain a low pinhole rate, meeting the requirements for qualified quality products.

[0005] A further object of the present invention is to provide a method for preparing the above-mentioned nitrile gloves.

[0006] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0007] A nitrile glove includes an outer layer and an inner layer, the outer layer being prepared from a first nitrile emulsion and the inner layer being prepared from a second nitrile emulsion;

[0008] The first nitrile emulsion comprises the following components in parts by weight:

[0009] 100 parts of nitrile latex, 0.5-1.5 parts of emulsifier, 1.0-2.5 parts of pH adjuster, 0.01-0.1 parts of anti-slip agent, 1.0-2.0 parts of sulfur, 3.0-5.0 parts of zinc oxide, 0.8-2.0 parts of accelerator, 45-140 parts of deionized water, and 1.7-3.6 parts of other additives;

[0010] The second nitrile emulsion comprises the following components in parts by weight:

[0011] The composition includes: 100 parts nitrile latex, 0.5-1.5 parts emulsifier, 1.0-2.5 parts pH adjuster, 0.01-0.1 parts anti-slip agent, 1.0-2.0 parts secondary sulfur, 3.0-5.0 parts secondary zinc oxide, 0.8-2.0 parts accelerator, 1.0-3.0 parts release agent, 5.0-8.0 parts plasticizer, 2.0-5.0 parts anti-sticking and slip agent, 0.5-1.5 parts inorganic filler, 45-140 parts deionized water, and 2.5-5.0 parts other additives.

[0012] The average particle size of the release agent is ≤8μm.

[0013] The inventors of this invention further discovered that by using a first nitrile butadiene emulsion without adding a release agent, and a second nitrile butadiene emulsion with a certain amount of release agent and controlling the average particle size of the release agent, the nitrile gloves prepared from the first and second nitrile butadiene emulsions can be easily demolded without chlorination, exhibiting a smaller decrease in tensile strength and elongation, and no increase in pinhole rate. This is because controlling the average particle size of the release agent in the second nitrile butadiene emulsion to be small (average particle size ≤ 8 μm) facilitates a denser adhesive layer after drying, maintaining better toughness and strength. Furthermore, it promotes better fusion between the adhesive layer formed after drying the second and first nitrile butadiene emulsions, achieving the density of conventional nitrile gloves (i.e., nitrile gloves prepared from nitrile butadiene emulsions without release agents), thus eliminating the problem of increased pinhole rate. The addition of plasticizers and inorganic fillers further enhances the tensile strength and elongation of the gloves, ensuring that the resulting glove product meets quality requirements. In addition, since the second nitrile emulsion contains a separating agent and an anti-sticking and slip agent, it can be easily flipped and demolded without the need for chlorine water hardening treatment during preparation, which solves the problem of chlorine residue in nitrile gloves and reduces production costs.

[0014] If the average particle size of the release agent in the second nitrile emulsion is >8μm (for example, the average particle size is 10μm), the nitrile gloves can be easily demolded without chlorine water hardening treatment. However, the resulting nitrile gloves fail the pinhole test and have significantly reduced tensile strength and elongation at break.

[0015] The nitrile gloves of this invention can be easily demolded without chlorine hardening treatment, leaving no chlorine residue. Furthermore, the resulting nitrile gloves not only maintain excellent tensile strength and elongation, but also retain a low pinhole rate, meeting the requirements for qualified quality products.

[0016] It should be understood that the nitrile gloves are only finished after being dipped in emulsion twice and then turned over and demolded. When turning over and demolding, the rubber needs to be turned over. Therefore, the layer that is in contact with the mold during dipping becomes the outer layer of the finished product after turning over and demolding, while the layer that is not in contact with the mold during dipping becomes the inner layer of the finished product after turning over and demolding. In this invention, the outer layer refers to the outer layer of the finished nitrile glove, and the inner layer refers to the inner layer of the finished nitrile glove.

[0017] Preferably, the average particle size of the release agent is 3 to 6 μm.

[0018] By selecting a release agent within this average particle size range, the resulting nitrile gloves exhibit better tensile strength, tensile power, and elongation at break.

[0019] Preferably, the separating agent is at least one of calcium stearate or magnesium stearate.

[0020] Sulfur (first sulfur and second sulfur) and zinc oxide (first zinc oxide and second zinc oxide) commonly used in this field can be used in this invention.

[0021] The average particle size of the first sulfur and the first zinc oxide does not need to be specifically limited. The resulting nitrile gloves do not require chlorine water hardening treatment and can be easily demolded. They can maintain good tensile strength and elongation, and the pinhole rate is kept at a low level.

[0022] Preferably, the average particle size of the second sulfur is 6–9 μm.

[0023] Using second sulfur within this average particle size range, the resulting nitrile gloves exhibit better tensile strength, tensile power, and elongation at break.

[0024] Preferably, the average particle size of the second zinc oxide is 1.5 to 2.5 μm.

[0025] By selecting the second zinc oxide within this average particle size range, the resulting nitrile gloves exhibit better tensile strength, tensile power, and elongation at break.

[0026] Commonly used nitrile latex, emulsifiers, pH adjusters, anti-slip agents, accelerators, plasticizers, anti-sticking and slip agents, and inorganic fillers in this invention can all be used.

[0027] Preferably, the mass fraction of acrylonitrile in the nitrile latex is 23-28%.

[0028] The nitrile latex selected within this acrylonitrile mass fraction range produces nitrile gloves with better tensile strength, elongation at break, and lower pinhole rate.

[0029] Preferably, the emulsifier is at least one of dodecylbenzenesulfonic acid and / or polyoxyethylene sorbitan fatty acid ester.

[0030] Preferably, the pH adjuster is at least one of potassium hydroxide solution or ammonia water.

[0031] Preferably, the anti-popping agent is an organosilicon anti-popping agent, such as polydimethylsiloxane or ethylene glycol siloxane.

[0032] Preferably, the accelerator is composed of EZ accelerator and BZ accelerator, and the mass ratio of EZ accelerator to BZ accelerator is 1:(0.4~2.5).

[0033] Within this mass ratio range, the resulting nitrile gloves exhibit better tensile strength, tensile power, and elongation at break.

[0034] Preferably, the plasticizer is at least one of dioctyl terephthalate, dioctyl adipate, or dioctyl phthalate.

[0035] Preferably, the anti-sticking and slip agent is at least one of stearamide or stearamide.

[0036] Preferably, the inorganic filler is at least one of silica, calcium carbonate, silicate, or kaolin.

[0037] Preferably, the average particle size of the inorganic filler is 1–3 μm.

[0038] By selecting inorganic fillers within this average particle size range, the resulting nitrile gloves exhibit better tensile strength, elongation at break, and lower pinhole rate.

[0039] Preferably, the other additives are at least one of color powder or anti-aging agent.

[0040] More preferably, the pigment is titanium dioxide.

[0041] More preferably, the anti-aging agent is at least one of styrene, phenol, and / or p-phenylenediamine.

[0042] The preparation method of the above-mentioned nitrile gloves includes the following steps:

[0043] S1. Mix nitrile latex, emulsifier, pH adjuster, anti-slip agent, first sulfur, first zinc oxide, accelerator and other additives, stir, add water, mix well, and the first nitrile emulsion is obtained.

[0044] S2. Mix nitrile latex, emulsifier, pH adjuster, anti-slip agent, second sulfur, second zinc oxide, release agent, plasticizer, anti-sticking and slip agent, accelerator, inorganic filler and other additives, stir, add water, mix well to obtain the second nitrile latex.

[0045] S3. The hand mold is immersed in the coagulation liquid for the first time, removed and dried for the first time, then immersed in the first nitrile emulsion for the second time, removed and dried for the second time to form the outer layer, then immersed in the second nitrile emulsion for the third time, removed and dried for the third time to form the outer layer, and then demolded to obtain the nitrile glove.

[0046] Preferably, the stirring process in step S1 is as follows: stirring with a 30 Hz stirring motor for 16 to 22 hours.

[0047] Preferably, the stirring process in step S2 is as follows: stirring with a 30 Hz stirring motor for 16 to 22 hours.

[0048] Preferably, the temperature of the first immersion in step S3 is 50-60°C, and the immersion time is 2-6 seconds.

[0049] Preferably, the temperature of the first drying in step S3 is 70-100°C and the time is 280-320 seconds.

[0050] Preferably, the temperature of the second immersion in step S3 is 25-34°C, and the immersion time is 2-10 seconds.

[0051] Preferably, the temperature of the second drying in step S3 is 70-120°C and the time is 120-140 seconds.

[0052] Preferably, the temperature of the third immersion in step S3 is 25-34°C, and the immersion time is 2-10 seconds.

[0053] Preferably, the temperature of the third drying in step S3 is 70-120°C and the time is 90-110 seconds.

[0054] Compared with the prior art, the beneficial effects of the present invention are:

[0055] The nitrile butadiene gloves prepared using the nitrile butadiene composition of the present invention can be easily demolded without chlorine curing treatment, leaving no chlorine residue and avoiding skin allergies caused by residual chlorine when using the gloves. Furthermore, the resulting nitrile butadiene gloves not only maintain excellent tensile strength and elongation, but also retain a low pinhole rate, meeting the requirements for qualified quality products. Detailed Implementation

[0056] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0057] The reagents used in the various embodiments and comparative examples of this invention are described below:

[0058] Nitrile latex #1: KNL834, Kumho, South Korea, with an acrylonitrile mass fraction of 28%;

[0059] Nitrile latex 2#: XNBRL-730, Hualan, with an acrylonitrile mass fraction of 25%;

[0060] Nitrile latex #3: QD-1001, Qixiang Tengda, with an acrylonitrile mass fraction of 23%;

[0061] Nitrile latex #4: LG NL105, Yongxing, with an acrylonitrile mass fraction of 20%;

[0062] Sulfur (unground): Commercially available, with an average particle size of 15μm. Sulfur with different average particle sizes is obtained by grinding in a ball mill for different times.

[0063] First sulfur: Unground sulfur with an average particle size of 15μm;

[0064] Second sulfur No. 1: Grinding time is 150 min, and the average particle size is 6 μm;

[0065] Second sulfur #2: Grinding time is 120 min, average particle size is 8 μm;

[0066] Second sulfur #3: Grinding time is 90 min, and the average particle size is 9 μm;

[0067] Second sulfur #4: Unground sulfur with an average particle size of 15μm;

[0068] Zinc oxide (unground): Commercially available, with an average particle size of 5μm. Zinc oxide with different average particle sizes is obtained after being ground in a ball mill for different times.

[0069] First type of zinc oxide: Unground zinc oxide with an average particle size of 5 μm.

[0070] Second zinc oxide #1: grinding time is 160 min, average particle size is 1.5 μm;

[0071] Second zinc oxide #2: grinding time is 140 min, average particle size is 2 μm;

[0072] Second zinc oxide #3: grinding time is 100 min, average particle size is 2.5 μm;

[0073] Second zinc oxide #4: Unground zinc oxide with an average particle size of 5μm;

[0074] Release agent (unground): Calcium stearate, commercially available, with an average particle size of 16μm. Release agents with different average particle sizes were obtained after being ground in a ball mill for different times.

[0075] Separator 1: Grinding time is 180 min, average particle size is 3 μm;

[0076] Separator 2: Grinding time is 150 min, and the average particle size is 4 μm;

[0077] Separator 3: Grinding time is 120 min, and the average particle size is 6 μm;

[0078] Separator 4: Grinding time is 80 min, and the average particle size is 8 μm;

[0079] Separator 5: Grinding time is 50 min, and the average particle size is 10 μm.

[0080] Inorganic filler: Calcium carbonate, commercially available, with an average particle size of 10μm. Inorganic fillers with different average particle sizes are obtained by grinding in a ball mill for different times.

[0081] Inorganic filler #1: grinding time is 160 min, average particle size is 1 μm;

[0082] Inorganic filler #2: grinding time is 130 min, average particle size is 2 μm;

[0083] Inorganic filler #3: grinding time is 90 min, average particle size is 3 μm;

[0084] Inorganic filler #4: grinding time is 60 min, average particle size is 5 μm;

[0085] Accelerator 1#: Zinc diethyldithiocarbamate dispersion, EZ accelerator, commercially available;

[0086] Accelerator 2#: Zinc butyl dithiocarbamate dispersion, BZ accelerator, commercially available;

[0087] Emulsifier: Sodium dodecylbenzenesulfonate, commercially available;

[0088] Acid-base regulator: potassium hydroxide solution, mass concentration of 2%.

[0089] Anti-splatter agent: Polydimethylsiloxane, commercially available;

[0090] Plasticizer: Dioctyl terephthalate, commercially available;

[0091] Anti-sticking and slip agent: stearamide, commercially available;

[0092] Pigment: Titanium white, commercially available;

[0093] Anti-aging agent: styrene-phenol, commercially available;

[0094] Wetting agent: Ethoxylated wetting agent, commercially available.

[0095] Unless otherwise specified, all components used in the parallel embodiments and comparative examples are the same commercially available products.

[0096] The preparation processes of the nitrile butadiene gloves of the various embodiments and comparative examples of the present invention are as follows:

[0097] 1. Preparation of the first nitrile latex: Nitrile latex, emulsifier, potassium hydroxide, anti-slip agent, first sulfur, first zinc oxide, accelerator, colorant and antioxidant are mixed to form a nitrile latex emulsion. The mixture is stirred for 20 hours with a 30 Hz stirring motor. Then deionized water is added and mixed evenly to obtain the first nitrile latex emulsion, which is placed in a glue tank for later use.

[0098] 2. Preparation of the second nitrile latex: Nitrile latex, emulsifier, potassium hydroxide, anti-slip agent, sulfur, zinc oxide, accelerator, colorant, antioxidant, release agent, plasticizer, anti-sticking and slip agent, and inorganic filler are mixed to form a high-efficiency nitrile latex emulsion. The mixture is stirred for 20 hours with a 30 Hz stirring motor, and then deionized water is added and mixed evenly to obtain the second nitrile latex emulsion, which is then placed in the glue tank for later use.

[0099] 3. Preparation of nitrile gloves

[0100] 3.1 The hand mold is subjected to pickling, first water washing, first alkaline washing, second water washing, second alkaline washing, brush cleaning, third water washing, and drying;

[0101] 3.2. After drying, immerse the hand mold in a 55°C solidification liquid for 4 seconds, remove it, and dry it by rotation at 85°C.

[0102] 3.3. Immerse the hand mold in the first nitrile emulsion at 30°C for 6 seconds, remove it, and dry the hand mold by rotation at 90°C to form the outer layer;

[0103] 3.4. Immerse the hand mold in the second nitrile emulsion at 30°C for a second time for 6 seconds. Remove the hand mold and dry it by rotation at 90°C to form the inner layer.

[0104] 3.5. After drying, the film is rolled, filtered, dehumidified, vulcanized, filtered again, impregnated with anti-sticking chelating agent, dried, demolded, counted, and packaged.

[0105] The coagulation solution is formulated as follows: by weight, 12-18 parts calcium nitrate, 0.1 parts wetting agent, 0.9 parts separating agent, and 84 parts deionized water. The ratio of the first and second nitrile butadiene emulsions can be adjusted by changing the calcium nitrate concentration in the coagulation solution. The second nitrile butadiene emulsion does not come into contact with the coagulant (which becomes the coagulant after drying), therefore its quality is relatively stable. The first nitrile butadiene emulsion comes into contact with the coagulant; a higher calcium nitrate concentration in the coagulation solution results in a larger outer layer formed by the first nitrile butadiene emulsion, while a lower calcium nitrate concentration results in a smaller outer layer formed by the first nitrile butadiene emulsion.

[0106] The nitrile compositions provided in the various embodiments and comparative examples of this invention were used to prepare nitrile gloves, and their performance was determined according to the following test methods:

[0107] Tensile strength: According to the standard method of BS EN 455-2:2009, the tensile strength is required to be ≥6N;

[0108] Tensile strength: According to the standard method of BS EN 455-2:2009, the tensile strength is required to be ≥14MPa;

[0109] Elongation at break: According to the standard method of BS EN 455-2:2009, the elongation at break is required to be ≥500%;

[0110] Pinhole test: According to the BS EN 455-1:2020 standard method, the AQL is required to be ≤1.5.

[0111] Example 1

[0112] Examples 1-25 provide a series of formulations for the outer layer (formed from a first nitrile emulsion) and inner layer (formed from a second nitrile emulsion) of nitrile gloves. The first and second nitrile emulsions are prepared according to the formulations and then nitrile gloves are made.

[0113] Table 1. Formulations (parts by weight) of nitrile gloves in Examples 1-10

[0114]

[0115] Table 2. Formulations (parts by weight) of nitrile gloves in Examples 11-19

[0116]

[0117]

[0118] Table 3. Formulations (parts by weight) of nitrile gloves in Examples 20-25

[0119]

[0120]

[0121] Comparative Example 1

[0122] This comparative example provides a nitrile glove, which differs from Example 1 in that the release agent 1# in the second nitrile emulsion is replaced with release agent 5#.

[0123] Comparative Example 2

[0124] This comparative example provides a nitrile glove, which differs from Example 1 in that: 2.0 parts of release agent 1# are added to the first nitrile emulsion.

[0125] Comparative Example 3

[0126] This comparative example provides a nitrile glove, which differs from Example 1 in that: 2.0 parts of release agent 1# are added to the first nitrile emulsion, while no release agent 1# is added to the second nitrile emulsion.

[0127] The performance of the nitrile gloves prepared in each embodiment and comparative example was determined according to the test methods mentioned above, and the test results are shown in Table 4.

[0128] Table 4. Performance test results of nitrile gloves prepared in each example and comparative example.

[0129]

[0130]

[0131] Table 4 shows that the nitrile gloves prepared from the nitrile compositions in Examples 1-25 can be easily demolded without chlorine curing, and the pinhole test meets the requirement of AQL≤1.5, exhibiting good tensile strength, elongation at break, and tensile strength. In Comparative Example 1, the second nitrile emulsion contained release agent 5#, which had a relatively large average particle size (10 μm). The nitrile gloves could be easily demolded without chlorine curing, but the pinhole test of the final nitrile gloves was unsatisfactory. In Comparative Example 2, release agent 1# was also added to the first nitrile emulsion. The nitrile gloves could be easily demolded without chlorine curing, but the pinhole test of the final nitrile gloves was unsatisfactory. In Comparative Example 3, 2.0 parts of release agent 1# were added to the first nitrile emulsion, but no release agent 1# was added to the second nitrile emulsion. The final nitrile gloves could not be easily demolded without chlorine curing, and the pinhole test was unsatisfactory.

[0132] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A nitrile glove characterized in that, The outer layer is prepared from a first nitrile emulsion, and the inner layer is prepared from a second nitrile emulsion. The first nitrile emulsion comprises the following components in parts by weight: 100 parts of nitrile latex, 0.5-1.5 parts of emulsifier, 1.0-2.5 parts of pH regulator, 0.01-0.1 parts of anti-plaster agent, 1.0-2.0 parts of first sulfur, 3.0-5.0 parts of first zinc oxide, 0.8-2.0 parts of accelerator, 45-140 parts of deionized water, and 1.7-3.6 parts of other additives; The second nitrile emulsion comprises the following components in parts by weight: 100 parts of nitrile latex, 0.5-1.5 parts of emulsifier, 1.0-2.5 parts of pH regulator, 0.01-0.1 parts of anti-plaster agent, 1.0-2.0 parts of first sulfur, 3.0-5.0 parts of first zinc oxide, 0.8-2.0 parts of accelerator, 45-140 parts of deionized water, and 1.7-3.6 parts of other additives; The average particle size of the anti-plaster agent is ≤8 μm. The first nitrile emulsion does not contain an anti-plaster agent.

2. The nitrile glove of claim 1, wherein, The average particle size of the anti-plaster agent is 3-6 μm.

3. The nitrile glove of claim 1, wherein, The average particle size of the second sulfur is 6-9 μm.

4. The nitrile glove of claim 1, wherein, The mass fraction of acrylonitrile in the nitrile latex is 23-28%.

5. The nitrile glove of claim 1, wherein, The accelerator is composed of EZ accelerator and BZ accelerator, and the mass ratio of EZ accelerator to BZ accelerator is 1: (0.4-2.5).

6. The nitrile glove of claim 1, wherein, The average particle size of the inorganic filler is 1-3 μm.

7. The nitrile glove of claim 1, wherein, The mass ratio of the inner layer to the outer layer is 1: (0.38-0.47).

8. The nitrile glove of claim 1, wherein, The emulsifier is at least one of dodecylbenzenesulfonic acid and polyoxyethylene sorbitan fatty acid ester; the pH regulator is at least one of potassium hydroxide solution and ammonia water; the anti-plaster agent is a silicone-based anti-plaster agent; the plasticizer is at least one of dioctyl terephthalate, dioctyl adipate, or dioctyl phthalate; the anti-stick slip agent is at least one of stearamide and stearic acid amide; and the inorganic filler is at least one of white carbon black, calcium carbonate, silicate, or kaolin.

9. The nitrile glove of claim 1, wherein, The other additive is at least one of toner and anti-aging agent.

10. A process for the production of nitrile gloves as claimed in any one of claims 1 to 9, characterised in that, The method comprises the following steps: S1. mixing nitrile latex, emulsifier, pH regulator, anti-plaster agent, first sulfur, first zinc oxide, accelerator, and other additives, stirring, then adding water and mixing uniformly to obtain the first nitrile emulsion; S2. mixing nitrile latex, emulsifier, pH regulator, anti-plaster agent, second sulfur, second zinc oxide, anti-plaster agent, plasticizer, anti-stick slip agent, accelerator, inorganic filler, and other additives, stirring, then adding water and mixing uniformly to obtain the second nitrile emulsion; S3. immersing a hand mold in a coagulation solution for the first time, taking out and drying for the first time, then immersing the hand mold in the first nitrile emulsion for the second time, taking out and drying for the second time to form an outer layer, then immersing the hand mold in the second nitrile emulsion for the third time, taking out and drying for the third time to form an inner layer, and demolding to obtain the nitrile glove.

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