Process for the preparation of high stability nitrile latex gloves

Abstract

The application provides a preparation method of high-stability butyronitrile latex gloves, and belongs to the technical field of glove preparation, and comprises the following steps: after acid washing, water washing, alkali washing and cleaning of a ceramic hand mold, a release agent is coated on the ceramic hand mold and dried; butyronitrile latex, an anti-freezing agent, an elasticity regulator and a vulcanization system additive are mixed, and a pre-vulcanized latex is prepared through a temperature-controllable grinding device; the treated hand mold is gradiently dipped in the pre-vulcanized latex for multiple times, and low-temperature pre-drying is performed after each dipping; the hand mold after dipping is sequentially subjected to low-temperature section vulcanization, medium-temperature section vulcanization and high-temperature section vulcanization under the condition that the humidity of the vulcanization environment is controlled, and a vulcanized glove is prepared; and the vulcanized glove coated with a special coating is placed in a low-temperature environment for static curing, and finally, demolding is completed to prepare the glove. The preparation method of the high-stability butyronitrile latex glove can effectively ensure the stability of the adhesion between the special coating and the glue layer, prolong the service life of the glove, and thus meet the demand for long-time use in special environments.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of glove preparation, and more particularly relates to a preparation method of high-stability nitrile latex gloves. BACKGROUND

[0002] Nitrile latex gloves are widely used in low-temperature storage, cold-chain logistics, polar operation and other scenarios due to their good oil resistance, wear resistance and chemical stability. However, when conventional nitrile latex gloves are used in low-temperature environments (usually below -10℃), the molecular chain movement of the glue layer is easily restricted due to low temperature, resulting in problems such as decreased elasticity and increased brittleness. Repeated wearing or stress can easily cause the gloves to freeze and crack, not only shortening the service life of the gloves, but also possibly losing the protective function due to damage, which poses a safety hazard to the user.

[0003] Traditional methods for improving the low-temperature performance of gloves mainly involve adding a single antifreeze agent (such as glycerol or ethylene glycol) to the latex. However, these methods have obvious limitations. On the one hand, a single antifreeze agent cannot effectively lower the overall freezing point of the latex, and uneven dispersion can lead to differences in local antifreeze performance, still unable to avoid low-temperature cracking. On the other hand, the entire glove preparation process is not optimized, such as incomplete pretreatment of the glove former leading to uneven glue layer adhesion, and improper temperature control during vulcanization leading to internal stress, further increasing the risk of cracking at low temperatures.

[0004] In addition, some solutions attempt to coat a special coating on the surface of the glove, but the coating has poor adhesion to the glue layer and can easily peel off in special environments. Moreover, the coating liquid has low recycling rate, increasing production costs. Therefore, how to optimize the entire process to achieve uniform dispersion of the antifreeze agent, stable glue layer structure, and tight adhesion of the coating, and prepare nitrile latex gloves that can adapt to low-temperature environments for a long time and have excellent freeze-cracking resistance, has become a key problem that needs to be solved in the current glove preparation technology field. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of high-stability nitrile latex gloves, aiming to solve the problem of unstable glove structure in low-temperature conditions and poor freeze-cracking resistance.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is to provide a preparation method of high-stability nitrile latex gloves, comprising:

[0007] After the ceramic former is sequentially subjected to acid washing, water washing, alkali washing and cleaning, a low-temperature adapted release agent is coated and dried;

[0008] The nitrile latex, antifreeze agent, elasticity regulator and vulcanization system additive are mixed and ground and dispersed by a temperature controllable grinding device to obtain a pre-vulcanized latex;

[0009] The processed hand mold is gradiently dipped in the pre-vulcanized latex for multiple times, and low-temperature pre-drying is performed after each dipping;

[0010] The dipped hand mold is sequentially subjected to low-temperature, medium-temperature and high-temperature vulcanization treatment under the condition of controlling the humidity of the vulcanization environment to obtain a vulcanized glove;

[0011] The vulcanized glove is dipped in a special coating liquid, and after natural drop, low-temperature pre-curing is performed; the vulcanized glove coated with the special coating is placed in a low-temperature environment for static curing, and finally demolding is completed to prepare.

[0012] In a possible implementation, the sequentially performing acid washing, water washing, alkali washing and cleaning on the ceramic hand mold comprises:

[0013] The acid washing of the hand mold is performed by a nitric acid solution and citric acid; the alkali washing is performed by a potassium hydroxide solution and laundry detergent;

[0014] After the hand mold is cleaned in hot water, the hand mold is inclined and recoated with the low-temperature adapted demolding agent by blowing.

[0015] In a possible implementation, the coating of the low-temperature adapted demolding agent and drying after the sequentially performing acid washing, water washing, alkali washing and cleaning on the ceramic hand mold comprises:

[0016] Glycerol is added in the demolding agent; the amount of the demolding agent is controlled by the weight difference before and after the coating of the hand mold.

[0017] In a possible implementation, the gradiently dipping of the processed hand mold in the pre-vulcanized latex for multiple times comprises:

[0018] A vertical baffle is arranged in the dipping tank of the gradient dipping and molding unit, and the bottom of the baffle is designed as a sawtooth shape; the height of the baffle is adjusted by a clamping groove.

[0019] In a possible implementation, the mixing of the butyronitrile latex, antifreeze, elasticity adjusting agent and vulcanization system auxiliary agent comprises:

[0020] The antifreeze of the pre-vulcanized latex preparation unit is a compound of propylene glycol and glycerol, and urea is added; the elasticity adjusting agent is hydrogenated butyronitrile rubber powder, which is pre-wetted by low-concentration butyronitrile latex, and a small amount of deionized water is added intermittently during the grinding time.

[0021] In a possible implementation, the pre-vulcanized latex prepared by the temperature controllable grinding device comprises:

[0022] The temperature controllable grinding device is provided with a metal filter screen and a nylon screen cloth, and the stirring is stopped for 1-2 minutes every 30 minutes during the grinding process, the stirring speed is 50-80 r / min, if the latex appears stratification after standing for 5 minutes, the grinding time is prolonged by 15-20 minutes.

[0023] In a possible implementation, the low-temperature pre-drying after each dipping of the pre-vulcanized latex includes:

[0024] The gradient dipping forming unit dips three times, the first time is slow pulling, the second time is medium speed pulling, and the third time is fast pulling; the low-temperature pre-drying is provided with a layered partition in the oven.

[0025] In a possible implementation, the vulcanized gloves are obtained by sequentially performing low-temperature, medium-temperature and high-temperature vulcanization treatment on the dipped gloves in a controlled vulcanization environment humidity.

[0026] The low-temperature section vulcanization unit is provided with a partition in the oven to form a physical partition; an open container containing saturated salt solution is placed in the vulcanization environment.

[0027] In a possible implementation, the special coating liquid is added to the vulcanized gloves.

[0028] A low-molecular-weight polyvinyl alcohol is added to the special coating liquid; a tilted receiving tray is placed below when the coating liquid naturally drips, and the recovered coating liquid is filtered and reused.

[0029] In a possible implementation, the low-temperature pre-curing after the natural dripping includes:

[0030] A plurality of partitions are provided in the low-temperature freezer, so that each layer of the vulcanized gloves is kept at a distance of 5-8 cm; the vulcanized gloves are checked every 2 hours during the curing process.

[0031] When the frost covers more than 30% of the surface area of the gloves, it is considered that the frost is too much, and the freezer sealing strip needs to be adjusted in time to ensure good sealing of the freezer.

[0032] The preparation method of the high-stability nitrile rubber latex glove has the beneficial effect that, compared with the prior art, the preparation method of the high-stability nitrile rubber latex glove comprises the following steps: first, a ceramic hand mold is sequentially subjected to acid washing, water washing, alkali washing and cleaning, and then a low-temperature matched release agent is coated on the ceramic hand mold and dried; a pre-vulcanized latex is prepared by mixing nitrile rubber latex, an anti-freezing agent, an elasticity adjusting agent and a vulcanization system aid, and then the pre-vulcanized latex is dispersed and ground by a temperature-controllable grinding device; the hand mold is gradiently dipped in the pre-vulcanized latex for multiple times, and low-temperature pre-drying is performed after each dipping; the hand mold after dipping is sequentially subjected to vulcanization treatment in a low-temperature section, a medium-temperature section and a high-temperature section under the condition of controlling the humidity of a vulcanization environment, so as to prepare a vulcanized glove; the vulcanized glove is dipped in a special coating liquid, and then natural drop is performed, and low-temperature pre-curing is performed; the vulcanized glove coated with the special coating is placed in a low-temperature environment for static curing, and finally, demolding is completed to prepare the glove. The glove prepared by the method can effectively ensure the stability of the adhesion between the special coating and the glue layer, prolong the service life of the glove, and thus meet the demand for long-time use in a special environment. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0034] Figure 1 The flow chart of the preparation method of the high-stability nitrile rubber latex glove provided by the present application. DETAILED DESCRIPTION

[0035] In order to make the technical problems to be solved by the present application, the technical solutions and beneficial effects more clearly, the following will be further described in detail by combining with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0036] Please refer to Figure 1 The preparation method of the high-stability nitrile rubber latex glove provided by the present application will be described. The preparation method of the high-stability nitrile rubber latex glove comprises the following steps:

[0037] After the ceramic hand mold is sequentially subjected to acid washing, water washing, alkali washing and cleaning, a low-temperature matched release agent is coated on the ceramic hand mold and dried.

[0038] The nitrile rubber latex, the anti-freezing agent, the elasticity adjusting agent and the vulcanization system aid are mixed, and a pre-vulcanized latex is prepared by a temperature-controllable grinding device.

[0039] The treated hand mold is gradiently dipped in pre-vulcanized latex for multiple times, and low-temperature pre-drying is performed after each dipping; the hand mold after dipping is subjected to vulcanization treatment in a low-temperature section, a medium-temperature section and a high-temperature section in sequence under the condition of controlling the humidity of the vulcanization environment to obtain a vulcanized glove.

[0040] The vulcanized glove is dipped in a special coating liquid, and low-temperature pre-curing is performed after natural drop; the vulcanized glove coated with the special coating is placed in a low-temperature environment for static curing, and finally demolding is completed to prepare.

[0041] In an embodiment of the present application, the specific steps of the processing are as follows: first, acid washing is performed using a nitric acid solution and a citric acid mixed solution to remove the surface oxidation layer and metal impurities, then water washing is performed to remove residual acid solution, then alkali washing is performed using a potassium hydroxide solution and a washing powder mixed solution to remove oil stains and organic residues, then hot water washing is performed at 60-80 DEG C to finally place the hand mold in an inclined position and remove the surface moisture by blowing with a fan, complete the pre-treatment, coat the low-temperature adapted demolding agent and dry, wherein the pre-treatment is acid washing, water washing, alkali washing and cleaning in sequence.

[0042] The method for preparing the high-stability nitrile rubber latex glove has the following beneficial effects compared with the prior art: after the ceramic hand mold is sequentially subjected to acid washing, water washing, alkali washing and cleaning, a low-temperature adapted demolding agent is coated and dried. The pre-vulcanized latex is prepared by mixing nitrile rubber latex, anti-freezing agent, elastic adjusting agent and vulcanization system additives, and then is ground and dispersed by a temperature controllable grinding device. The treated hand mold is gradiently dipped in pre-vulcanized latex for multiple times, and low-temperature pre-drying is performed after each dipping. The hand mold after dipping is subjected to vulcanization treatment in a low-temperature section, a medium-temperature section and a high-temperature section in sequence under the condition of controlling the humidity of the vulcanization environment to obtain a vulcanized glove. The vulcanized glove is dipped in a special coating liquid, and low-temperature pre-curing is performed after natural drop; the vulcanized glove coated with the special coating is placed in a low-temperature environment for static curing, and finally demolding is completed to prepare. The glove prepared by the method provided in the present application can effectively ensure the stability of the adhesion of the special coating and the glue layer, prolong the service life of the glove, and thus meet the demand for long-time use in special environments.

[0043] The ceramic hand mold is sequentially subjected to acid washing, water washing, alkali washing and hot water cleaning, and then a low-temperature adapted demolding agent is coated and dried; this unit is the basis for ensuring uniform adhesion of the glue layer, the surface oxidation layer, oil stains and residual impurities are removed through multiple cleaning, the adhesion of the glue layer is prevented from being affected by impurities, and the low-temperature adapted demolding agent is designed for a low-temperature scene to prevent the glue layer from being damaged due to low-temperature embrittlement during demolding.

[0044] Low-temperature adaptive pre-vulcanized latex preparation unit: the butyronitrile latex is mixed with antifreeze, elastic adjuster, vulcanization system aid, and is ground and dispersed through a temperature-controllable grinding device to obtain pre-vulcanized latex; this unit is the core of improving the low-temperature performance of gloves, the antifreeze solves the problem of ice formation of the rubber layer at low temperature, the elastic adjuster maintains the elastic recovery ability at low temperature, and the temperature-controllable grinding ensures uniform dispersion of the aid and avoids local performance deviation.

[0045] Gradient dipping and molding unit: the pretreated hand mold is dipped in the pre-vulcanized latex for multiple times, and low-temperature pre-drying is performed after each dipping; this unit controls the thickness and structure of the rubber layer through “multiple dipping + segmented drying” to avoid internal stress generated when a single thick rubber layer is dried and to reduce the risk of cracking at low temperature, and the gradient dipping can form a rubber layer structure with coordinated performance of the inner and outer layers.

[0046] Low-temperature segmented vulcanization unit: the dipped hand mold is sequentially subjected to low-temperature, medium-temperature and high-temperature vulcanization treatment, and the humidity of the vulcanization environment is controlled; this unit realizes gradual formation of the crosslinked structure of the rubber layer through segmented temperature rising, avoids overcrosslinking or unevenness caused by a single high temperature, and the humidity control prevents the rubber layer from being dried and cracked due to rapid water loss during the vulcanization process.

[0047] Special coating treatment unit: the vulcanized gloves are dipped in a special coating liquid, and low-temperature pre-curing is performed after natural dripping; this unit adds “secondary antifreeze protection” to the gloves, the coating forms a protective film on the surface of the rubber layer, further isolates the low-temperature influence, and the low-temperature pre-curing ensures that the coating is closely combined with the rubber layer to avoid falling off.

[0048] Low-temperature performance curing unit: the gloves coated with the special coating are placed in a low-temperature environment for static curing, and finally demolding inspection is performed; this unit simulates the actual low-temperature use scenario, promotes the performance stability of the rubber layer and the coating, ensures that the gloves can directly adapt to the low-temperature environment after leaving the factory, and the demolding inspection screens out unqualified products such as cracking of the rubber layer and falling off of the coating.

[0049] In some embodiments of the method for preparing the high-stability butyronitrile latex glove provided in the application, the ceramic hand mold is sequentially subjected to acid washing, water washing, alkali washing and cleaning, which comprises:

[0050] The acid washing of the hand mold is performed through a nitric acid solution and citric acid; the alkali washing is performed through a potassium hydroxide solution and laundry detergent.

[0051] After the hand mold is cleaned in hot water, it is inclined and coated with a low-temperature adaptive release agent through blowing.

[0052] Food-grade citric acid is added in the acid washing, which utilizes the complexation of citric acid to specifically remove metal impurities (such as iron and calcium) remaining on the surface of the hand mold, avoids the problem that the residual metal impurities after traditional single acid washing cause pitting and decreased adhesion of the rubber layer, and the food-grade citric acid has high safety and does not introduce harmful pollutants.

[0053] Adding industrial-grade laundry detergent to alkaline washing utilizes the surface-active components of the detergent to enhance foam stability and improve the emulsification effect on stubborn oil stains on the surface of hand molds after long-term use. Compared with simple alkaline washing, it can reduce the alkaline washing time and reduce the concentration of alkali solution, thus avoiding excessive corrosion of the hand molds.

[0054] The combination of "tilting + fan blowing" after hot water washing can quickly remove residual moisture from the micropores of the hand mold (especially dead corners such as finger gaps and fingertips) compared to natural air drying. This prevents uneven film formation caused by moisture mixing with the release agent during subsequent application of the release agent, ensuring that the release agent forms a continuous and uniform protective film on the hand surface.

[0055] In some embodiments of the method for preparing high-stability nitrile latex gloves provided in this application, coating with a low-temperature-compatible release agent and drying after processing includes:

[0056] Add glycerin to the release agent; control the amount of release agent used by measuring the weight difference before and after applying the release agent to the mold.

[0057] Adding glycerin to the mold release agent utilizes its flexibility to improve the crack resistance of the mold release agent film. Traditional polyethylene glycol mold release agents have a brittle film after drying and are prone to cracking at low temperatures. Adding a small amount of glycerin can make the film softer. At the same time, glycerin has good compatibility with polyethylene glycol and will not affect the mold release effect.

[0058] By controlling the amount of release agent by "weight difference", compared with the traditional "visual judgment of thickness", the amount of release agent can be precisely controlled (e.g., each hand mold increases in weight by 0.5-0.8g, corresponding to a film thickness of 0.02-0.03mm). This avoids the problem of insufficient release agent causing demolding difficulties and damage to the adhesive layer, or excessive release agent causing release agent residue on the glove surface, which affects subsequent use (e.g., in medical settings, residual release agent may affect the protective effect).

[0059] After coating, hot air drying can shorten the drying time (5-8 minutes) compared to natural drying. Hot air also ensures that the release agent forms a uniform film on the glove surface, avoiding uneven film formation caused by changes in ambient humidity during natural drying.

[0060] In some embodiments of the method for preparing high-stability nitrile latex gloves provided in this application, the treated hand mold is subjected to multiple gradient impregnations with pre-vulcanized latex, including:

[0061] A vertical baffle is installed in the impregnation tank of the gradient impregnation molding unit. The bottom of the baffle is designed to be serrated. The height of the baffle is adjusted by a slot.

[0062] The vertical baffle bottom is designed in a zigzag shape. Compared with the traditional flat baffle, the zigzag structure can reduce the glue liquid fluctuation, generate a small vortex through the gap between the zigzags, promote the circulation and updating of the glue liquid in the glue dipping tank, avoid the decrease of the local glue liquid concentration in the tank after repeated dipping of the hand mold (for example, the concentration of the glue liquid around the hand mold decreases due to adhesion), and ensure that the glue liquid concentration is consistent and the glue layer thickness is uniform during each dipping.

[0063] The height of the baffle is adjusted through the clamping groove to adapt to the consumption of the glue liquid during the dipping process: as the dipping frequency increases, the liquid level in the tank will gradually decrease, and the height of the baffle is quickly adjusted through the clamping groove (always 1-2 cm lower than the liquid level), so that the glue liquid does not need to be frequently added during the production process, the production efficiency is improved, and the failure of the baffle due to the decrease of the liquid level (for example, the baffle cannot block the fluctuation when it is higher than the liquid level) is avoided.

[0064] In some embodiments of the preparation method of the high-stability nitrile latex glove provided in the application, the mixing of the nitrile latex, the antifreeze, the elasticity regulator and the vulcanization system additive includes:

[0065] The antifreeze of the pre-vulcanized latex preparation unit is a compound of propylene glycol and glycerol, and urea is added; the elasticity regulator hydrogenated nitrile rubber powder is pre-wetted with low-concentration nitrile latex, and a small amount of deionized water is added intermittently during the grinding time.

[0066] The addition of urea in the antifreeze utilizes the characteristic that urea molecules can form hydrogen bonds with water molecules to further lower the freezing point of the latex with propylene glycol and glycerol. In addition, urea is low in cost, easy to obtain, more suitable for mass production requirements of enterprises compared with the addition of high-end antifreeze, and has good compatibility with nitrile latex, which does not affect the mechanical properties of the glue layer.

[0067] The pre-wetting of the elasticity regulator hydrogenated nitrile rubber powder with low-concentration nitrile latex is to solve the problem of easy agglomeration when dry powder is directly added. The surface of the rubber powder after pre-wetting is attached with a layer of latex film, which can avoid the mutual adhesion of rubber powder particles to form large agglomerates during the grinding process, ensure uniform dispersion of the rubber powder in the latex, and fully play the role of the elasticity regulator.

[0068] The intermittent addition of a small amount of deionized water during the grinding time is to control the viscosity of the latex. The latex may be slightly heated due to mechanical friction during the grinding process, which may cause water evaporation and viscosity increase. Intermittent water addition can maintain the stable viscosity of the latex, ensure the normal operation of the grinding device, and avoid uneven dispersion of the additives due to high viscosity.

[0069] In some embodiments of the preparation method of the high-stability nitrile latex glove provided in the application, the pre-vulcanized latex prepared by the temperature-controllable grinding device includes:

[0070] The feeding port of the temperature-controllable grinding device is provided with a metal filter screen and a nylon screen cloth, and the stirring is stopped for 1-2 minutes every 30 minutes during the grinding process, and the stirring speed is 50-80 r / min, if the latex appears stratification after standing for 5 minutes, the grinding time is prolonged by 15-20 minutes.

[0071] The feeding port is provided with a double-layer filtering structure of "metal filter screen + nylon screen cloth", the metal filter screen (60-80 meshes) is used to intercept larger impurity particles (such as rubber scraps, packaging residues, etc.) in the latex raw materials, and the nylon screen cloth (80-100 meshes) further intercepts fine impurities (such as additive agglomerate particles) that cannot be filtered by the metal filter screen by using its flexible characteristics, and the nylon screen cloth is easy to clean and can be reused, thereby reducing the filtering cost.

[0072] The manual stirring during the interval shutdown in the grinding process is to intuitively observe the latex state (such as whether stratification or particle feeling occurs) by manual observation, which is more suitable for the production conditions of small and medium-sized enterprises compared with relying on automatic detection equipment, if the latex stratification (which is mainly caused by the density difference of additives) is found, the grinding time is prolonged, and the stratified components can be mixed uniformly again through mechanical action, so that the overall dispersion effect of the latex is ensured.

[0073] In some embodiments of the preparation method of the high-stability nitrile latex glove provided in the application, the treated former is gradiently dipped in the presulfurized latex for multiple times, and low-temperature pre-drying is performed after each dipping.

[0074] The gradient dipping forming unit dips for three times, the first time is slow pulling, the second time is medium-speed pulling, and the third time is fast pulling; and the layered partition is arranged in the oven during the low-temperature pre-drying.

[0075] The three times of dipping adopt the pulling speed gradient of "slow-medium-fast", the first time of slow pulling (5-8 cm / s) can make the latex adhere to the surface of the former, especially the parts such as the finger joints and the fingertips, so as to avoid missed coating; the second time of medium-speed pulling (8-10 cm / s) can control the thickness of the glue layer to prevent excessive accumulation of glue solution; and the third time of fast pulling (10-12 cm / s) can reduce the dripping of the glue solution, help the glue layer to be quickly shaped, and compared with the fixed speed pulling, the thickness uniformity of the glue layer can be significantly improved.

[0076] The layered partition is arranged in the oven, in order to avoid the poor local ventilation caused by the stacking of the former - when the traditional drying is performed without the partition, the lower former is easily blocked by the upper former, so that the drying speed is inconsistent, and the local glue layer appears to be sticky, the layered partition can ensure that the hot air circulation around each former is uniform, and the surface of the glue layer after each drying is ensured to be non-sticky and wrinkle-free.

[0077] In some embodiments of the method for preparing the high-stability butyronitrile latex glove provided in the application, the dipping of the former into the glue solution includes:

[0078] The low-temperature sub-section vulcanization unit is physically divided by installing a partition in the oven; an open container containing saturated salt solution is placed in the vulcanization environment.

[0079] The physical division by installing a partition in the oven is achieved by simply modifying the physical structure, which divides the oven into three independent areas, i.e., a low-temperature section, a medium-temperature section, and a high-temperature section. Compared with the traditional whole oven, the temperature fluctuation of the former when moving between different temperature sections can be reduced (e.g., heat loss in the low-temperature section and heat intrusion in the high-temperature section), the temperature stability of each vulcanization stage can be ensured, and uneven crosslinking of the glue layer caused by temperature fluctuation can be avoided.

[0080] The open container containing saturated salt solution is used to precisely control the humidity of the vulcanization environment by utilizing the humidity stability of the saturated salt solution (e.g., a saturated magnesium nitrate solution can maintain a relative humidity of 40-50%). Compared with simply containing water (the humidity easily fluctuates with temperature), the humidity of the vulcanization environment can be precisely controlled to prevent the glue layer from drying out too quickly due to excessively low humidity, causing cracking, or the vulcanization time from being prolonged due to excessively high humidity.

[0081] In some embodiments of the method for preparing the high-stability butyronitrile latex glove provided in the application, the dipping of the vulcanized glove into the special coating liquid includes:

[0082] A low-molecular-weight polyvinyl alcohol is added to the special coating liquid; a tilted receiving tray is placed below the natural drop to recycle the coating liquid after filtration and reuse.

[0083] The addition of low-molecular-weight polyvinyl alcohol to the coating liquid utilizes the excellent film-forming property of polyvinyl alcohol to assist the formation of a continuous and complete protective film for the polyurethane coating, thereby improving the adhesion between the coating and the glue layer. Compared with high-end additives such as silane coupling agents, low-molecular-weight polyvinyl alcohol has low cost, good solubility, and can enhance the low-temperature toughness of the coating, preventing the coating from being brittle at low temperatures.

[0084] The placement of a tilted receiving tray below to recycle the coating liquid is to reduce raw material waste. The special coating liquid (e.g., polyurethane emulsion) is relatively expensive, and after simple filtration (removal of impurities and sludge), it can be reused for dipping, reducing the raw material cost of the enterprise. At the same time, the tilted receiving tray can prevent the coating liquid from accumulating and deteriorating in the tray.

[0085] The pre-curing in a low-temperature environment is to quickly lock the coating morphology, prevent the coating from flowing due to excessively high temperature after natural dropping, and ensure uniform coating thickness to play a stable anti-freezing role.

[0086] In some embodiments of the method for preparing the high-stability nitrile latex glove provided in the present application, the low-temperature pre-curing after natural drop is performed by:

[0087] In the low-temperature freezer, multiple partitions are arranged to keep a distance of 5-8 cm between each layer of vulcanized gloves; during the curing process, the gloves are checked every 2 hours to determine whether there is "too much" frost by the area covered by the frost. When the frost covers more than 30% of the surface area of the gloves, it is considered that there is too much frost, and the sealing strip of the freezer needs to be adjusted in time to ensure good sealing of the freezer.

[0088] In the low-temperature freezer, multiple partitions are arranged to keep a distance between each layer of vulcanized gloves; during the curing process, the gloves are checked at intervals, and if there is too much frost on the surface, the sealing of the freezer is adjusted.

[0089] The multiple partitions in the low-temperature freezer are arranged to keep a distance between the gloves, in order to avoid the gloves being squeezed by stacking. When the gloves are stacked in the traditional curing method, the rubber layer at the contact part is easily deformed due to squeezing, and the cold air cannot circulate, resulting in uneven local temperature, affecting the performance stability. The distance setting (5-8 cm) can ensure that each glove is in a uniform low-temperature environment, and the curing effect is consistent.

[0090] Checking at intervals and adjusting the sealing according to the frost is to use the amount of "frost" to intuitively judge the sealing of the freezer. If there is too much frost on the surface of the gloves, it means that the freezer has air leakage (external moisture enters and condenses into frost), causing internal temperature fluctuations. Adjusting the sealing (such as replacing the sealing strip and checking the door buckle) can maintain a stable low-temperature environment and avoid the decrease of the bonding force between the rubber layer and the coating due to temperature fluctuations.

[0091] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of high stability nitrile latex gloves, characterized in that, include: After sequentially acid washing, water washing, alkali washing and cleaning, the ceramic hand mold is coated with a low-temperature suitable release agent and dried. Pre-vulcanized latex is prepared by mixing nitrile latex, antifreeze, elastic modifier and vulcanization system additives and grinding and dispersing them by a temperature-controlled grinding device. The pre-vulcanized latex was repeatedly and gradient-impregnated after each impregnation, and then pre-dried at low temperature. The impregnated hand mold was then subjected to vulcanization treatment in a low-temperature section, a medium-temperature section, and a high-temperature section under controlled humidity conditions to obtain vulcanized gloves. The vulcanized gloves are immersed in a special coating liquid, allowed to drip naturally, and then pre-cured at low temperature. The vulcanized gloves coated with the special coating are placed in a low-temperature environment for static curing, and finally demolded to complete the preparation. The step of repeatedly and gradually impregnating the pre-vulcanized latex with the treated hand mold, followed by low-temperature pre-drying after each impregnation, includes: The gradient dip molding unit dips in the resin three times: first, a slow lift; second, a medium-speed lift; and third, a fast lift. During low-temperature pre-drying, layered partitions are installed inside the oven. The process of producing vulcanized gloves by sequentially subjecting the impregnated hand mold to vulcanization in a low-temperature, medium-temperature, and high-temperature zone under controlled humidity conditions includes: The low-temperature segmented vulcanization unit is equipped with partitions inside the oven to form physical partitions; an open container filled with saturated salt solution is placed in the vulcanization environment.

2. The process for the preparation of high stability nitrile latex gloves as claimed in claim 1, wherein, The process of sequentially acid washing, water washing, alkaline washing, and cleaning of the ceramic hand mold includes: The hand mold was acid-washed using nitric acid solution and citric acid; and alkaline-washed using potassium hydroxide solution and laundry detergent. After the hand mold is washed with hot water, it is tilted and then coated with the low-temperature-compatible release agent by blowing.

3. The process for the preparation of high stability nitrile latex gloves as claimed in claim 1, wherein, The process of sequentially acid-washing, water-washing, alkali-washing, and cleaning the ceramic hand mold, followed by coating with a low-temperature suitable release agent and drying, includes: Glycerin is added to the release agent; the amount of release agent used is controlled by the weight difference before and after the hand mold is coated.

4. The process for preparing high stability nitrile latex gloves as claimed in claim 1, wherein, The step of repeatedly and gradually impregnating the treated hand mold with the pre-vulcanized latex includes: A vertical baffle is provided in the impregnation tank of the gradient impregnation molding unit. The bottom of the baffle is designed to be serrated. The height of the baffle is adjusted by a slot.

5. The process for preparing high stability nitrile latex gloves as claimed in claim 1, wherein, The mixing of nitrile latex, antifreeze agent, elastic modifier and vulcanization system additives includes: The antifreeze agent in the pre-vulcanized latex preparation unit is a compound of propylene glycol and glycerin, and urea is added; the elastic modifier hydrogenated nitrile rubber powder is pre-wetted with low-concentration nitrile latex, and a small amount of deionized water is added intermittently during grinding.

6. The process for preparing high stability nitrile latex gloves as claimed in claim 1, wherein, The pre-vulcanized latex obtained by grinding and dispersing using a temperature-controlled grinding device includes: The feed inlet of the temperature-controlled grinding device is equipped with a metal filter and a nylon screen. During the grinding process, the machine is stopped and stirred for 1-2 minutes every 30 minutes, with a stirring speed of 50-80 r / min. If the latex shows stratification after standing for 5 minutes, the grinding time is extended by 15-20 minutes.

7. The process for preparing high stability nitrile latex gloves as claimed in claim 1, wherein, The special coating liquid used to impregnate the vulcanized gloves includes: Low molecular weight polyvinyl alcohol is added to the special coating liquid; when it drips naturally, an inclined receiving tray is placed below to filter and reuse the recovered coating liquid.

8. The process for preparing high stability nitrile latex gloves as claimed in claim 1, wherein, The low-temperature pre-curing following natural dripping includes: In the low temperature freezer set up multiple layers of partitions, so that each layer of the gloves keep 5-8 cm apart; solidification process every 2 hours to see once; When the frost cover gloves surface area more than 30% is considered too much frost, need to adjust the freezer seal bar in time to ensure good sealing of the freezer.

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