CN110561795A - Method for preventing natural latex product from blooming - Google Patents
Method for preventing natural latex product from blooming Download PDFInfo
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- CN110561795A CN110561795A CN201910745830.XA CN201910745830A CN110561795A CN 110561795 A CN110561795 A CN 110561795A CN 201910745830 A CN201910745830 A CN 201910745830A CN 110561795 A CN110561795 A CN 110561795A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
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Abstract
The invention relates to a method for preventing natural latex products from blooming, which comprises the steps of sealing the natural latex products and placing the natural latex products in a dark environment after the natural latex products are prepared. The method keeps the moisture in the adhesive film of the natural latex product, the product is softer, the compounding agent effectively reacts completely, the adhesive film performance of the natural latex product is improved (such as waterproof oil, wear resistance and aging resistance), the residual amount is reduced, and the problem of blooming is relieved. The release of the blooming phenomenon and the more complete reaction of the compounding agent can make the adhesive film of the natural latex product more resistant to moisture and the invasion of external destructive factors. After the treatment by the method, a layer of compact and stable hydrophobic film is generated on the surface of the rubber film of the natural latex glove, and the hydrophobic film can prevent the migration of the compounding agent in the rubber surface of the natural latex product and prevent the entry of external destructive factors, so that the rubber film of the natural latex product forms a closed system, thereby achieving the purpose of preventing the blooming.
Description
Technical Field
The invention relates to a production process of a latex product, in particular to a method for preventing natural latex products from blooming.
Background
Natural latex is derived from the natural rubber tree and consists of spherical particles with a particle size of 0.02-2 μm. The natural latex has active structure and more complex components. The range of applications for natural rubber latex is extremely large, but almost all natural rubber latex products produced using natural rubber latex exhibit severe surface whitening, i.e., blooming. The blooming phenomenon refers to that some small molecular compounds (various accessory ingredients) in the latex formula are migrated and precipitated on the surface of the latex product or semi-finished product to form a layer of exudate similar to white frost and attached to the surface of the latex semi-finished product or vulcanized product. This phenomenon seriously affects the appearance, performance and other product qualities of natural latex products, and even more, causes delayed skin allergy of users, and causes skin itch and eruption of users. Therefore, the problem of blooming of the natural latex product is solved, and the significance of improving the quality of the natural latex product is great.
There are some related researches and discussions in the prior art, which are summarized as follows: (1) the non-rubber components of the article are removed as much as possible prior to vulcanization, such as: the centrifugal and water soaking of the product to be vulcanized are adopted. The disadvantages of this approach are: the anti-blooming effect is poor, the process steps are increased and the cost is increased. (2) Surface protection, which includes two types: a. adding paraffin: most commonly, paraffin is added into the formula, but the paraffin can only be used as a protective agent under static conditions, and is extremely unfavorable for emulsion products under dynamic conditions; in addition, the paraffin is greatly influenced by the environmental temperature, and after the paraffin is precipitated on the surface of vulcanized rubber, the surface of a product loses luster, so that the paraffin is unfavorable for some latex products requiring attractive appearance. b. Applying an antifrost agent: although the frost prevention effect is very obvious, the method has the following requirements in combination with the actual production process and the product requirements: the frost prevention agent can play a role in obvious frost prevention, the process is simple, and the material price is low; the appearance and the original performance of the natural latex product cannot be influenced; the antifrost agent can be stably present on the surface of the latex product. It is due to these limitations that this method has not been practically implemented and applied in practical production. (3) Changing the vulcanization mode: a. irradiation vulcanization: however, the irradiated rubber is restricted by various factors, so that the irradiated rubber is difficult to be used on a large scale in production. b. By improving the vulcanization method, the surplus easy-to-spray sulfur vulcanization system (vulcanizing agent) is not left, the strength of a cross-linking bond is enhanced, the solvent vulcanized rubber is firmer, the vulcanization reversion is eliminated, and the latex product can be sprayed in a frostless manner. However, there are many black impurities on the surface of such products and the performance of the latex products is reduced. (4) The content and the type of the compounding ingredients are adjusted, so that no excessive compounding ingredients in a latex system can be sprayed. The disadvantages are: because the conditions such as the prior art conditions, the raw material performance, the storage environment and the like are diverse, the mode cannot adapt to and meet the diverse conditions, and the frost prevention effect is poor. (5) Adsorption: the addition of an auxiliary agent with strong adsorbability to adsorb redundant compounding agents has the disadvantages that the auxiliary agent is difficult to screen, high in cost, difficult to adapt to and meet variable conditions, and the problem of blooming cannot be fundamentally solved.
In summary, the above processes are complex, but modify or change the formulation composition, the vulcanization process conditions and the surface of the final product of the natural rubber latex product to a greater or lesser extent, so as to alleviate the blooming phenomenon of the rubber latex product to a certain extent, but at the same time sacrifice the performance or appearance of the rubber latex product to a greater or lesser extent, resulting in the failure of the product to meet the relevant production standards and requirements.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms part of the prior art that is already known to a person skilled in the art.
Disclosure of Invention
Technical problem to be solved
In order to solve the above problems in the prior art, the present invention provides a method for preventing natural latex products from blooming, which does not change the formulation composition, vulcanization process conditions and surface frost prevention, and the natural latex products are prepared by the original latex formulation and production process, and then the treatment of the method of the present invention is performed, so as to maintain the moisture in the latex products, further completely react the compounding agents, reduce the residual amount of the compounding agents in the latex products, and form a layer of hydrophobic film on the surface of the latex products, so as to block the migration of the compounding agents in the latex products and the entrance of external environmental factors, thereby achieving the purpose of preventing natural latex products from blooming.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
A method of preventing blooming of a natural latex article, the method comprising: after the natural latex product is prepared, the natural latex product is sealed and placed in a dark environment for treatment.
Preferably, the sealing is performed by sealing the natural latex product using at least one of a sealed container, a sealed bag, a sealing film and a plastic sealing film.
Preferably, the light-protected environment is preferably a dark environment. Compared with the light environment, the dark environment can prevent the rapid evaporation and loss of water in the natural latex product, prevent the compounding agent from fast migrating to the surface of the product and weaken various properties (such as water resistance, oil resistance, wear resistance and the like) of the natural latex product. The treatment effect in the dark environment (the dark environment is the environment without light but without completely shielding light) is between the dark environment and the light environment.
Preferably, the sealed bag is a valve bag.
preferably, the sealing film is a preservative film, and the preservative film wraps or covers the surface of the natural latex product.
Preferably, the preservative film is one of PE (polyethylene), PVDC (polyvinylidene chloride) and PVC (polyvinyl chloride) film.
Preferably, the natural latex product is not suitable to be exposed to the air for too long time after being vulcanized, preferably within 30min, so as to prevent the factors such as oxygen, ozone, moisture and the like in the air which promote the occurrence of frost from damaging the rubber surface of the natural latex; then sealing and placing; the environment temperature of the standing treatment is 25-60 ℃, and the standing treatment time is 2-72 h. The purpose of this standing temperature range (25-60 ℃) is to promote further reaction of the excess complexing agent and the production of a surface hydrophobic film. On the contrary, if the temperature is too high, the natural latex product is easy to be over-vulcanized, the performance of the product is influenced, meanwhile, the moisture in the latex film is easy to volatilize, the formation of a hydrophobic film is not facilitated, and if the temperature is too low, the reaction activity is low, the treatment time is longer, and the efficiency is reduced.
Atypical, the environmental temperature in the process of placing and processing is 25-30 deg.C, 30-35 deg.C, 35-40 deg.C, 40-45 deg.C, 45-50 deg.C, 50-55 deg.C or 55-60 deg.C.
the standing treatment time is 2-8 hours, 8-10 hours, 10-15 hours, 15-20 hours, 20-25 hours, 25-30 hours, 30-35 hours, 35-40 hours, 45-50 hours, 50-55 hours, 55-60 hours, 60-65 hours, 65-70 hours or 70-72 hours. In theory, the time for the leaving treatment should be extended as the ambient temperature is lower, whereas the time for the leaving treatment can be shortened as the ambient temperature is higher. The purpose is mainly to ensure that the compounding ingredients in the adhesive film of the natural latex product are further reacted completely. The proper heating temperature can promote the vulcanization reaction speed of the compounding agent and the latex, but the excessive temperature can cause the over-vulcanization of the rubber film of the natural latex product, influence the performance of the product, rapid evaporation and loss of water, be not beneficial to the formation of a hydrophobic film on the surface of the rubber film of the glove and also cause the rubber film of the natural latex product to be stiff.
Preferably, the natural latex article is prepared using a latex size formulation comprising: 100 parts of natural latex, 0.5-1.5 parts of vulcanizing agent, 0.6-1.2 parts of anti-aging agent, 0.8-1.2 parts of activating agent, 0.2-0.6 part of accelerating agent and 0.2-0.5 part of stabilizing agent.
Preferably, the natural latex product is prepared from the following raw materials in parts by weight: 100 parts of natural latex, 0.5-1.5 parts of vulcanizing agent sulfur, 0.4-0.6 part of anti-aging agent 2, 6-di-tert-butyl-p-cresol, 0.2-0.6 part of anti-aging agent 2,2' -methylene bis- (4-methyl-6-tert-butylphenol), 0.8-1.2 parts of activator ZnO, 0.2-0.6 part of promoter zinc diethyldithiocarbamate and 0.2-0.5 part of stabilizer KOH.
Preferably, the basic preparation process steps of the natural latex product comprise: pre-vulcanizing: taking natural latex and at least one compounding agent required by preparing a latex product according to parts by weight for prevulcanization; molding and further vulcanizing.
Preferably, after the natural latex product is placed in the sealed container or sealed bag, the sealed bag or sealed container is evacuated. Preferably, the volume of the sealed container is not too large, so that the natural latex product can be just contained. If the volume of the sealed container is too large relative to the natural latex product, the loss of water in the glue film of the natural latex product is accelerated under the vacuum condition, which is not favorable for the further reaction of the compounding agent in the glue film.
Preferably, the ambient humidity during the placement process is 35-90% RH. It should be noted that, since the natural latex product is already wrapped by a sealed container, a self-sealing bag, a sealing film or a plastic film, and is already in an isolated state from the outside, the influence of the environmental humidity on the natural latex product is not great. However, for further insurance, the preferred ambient humidity should not be too low or too high.
Specifically, when the ambient humidity is too low, the loss of water in the natural latex product is accelerated more or less, which is not favorable for the compounding agent to generate more sufficient vulcanization reaction in the natural latex product; when the ambient humidity is too high, the surface humidity of the natural latex product may be too high, which is not favorable for the balance of the dry humidity inside the natural latex product, and the moisture may also promote the migration of the compounding agent inside the natural latex product.
(III) advantageous effects
The invention has the beneficial effects that:
On the premise of not changing the formula composition and production process of the latex rubber material of the natural latex product, after the natural latex product is prepared, a physical treatment method is used, the obtained natural latex product is sealed and placed away from light, and particularly, a self-sealing plastic bag or a preservative film is used for wrapping/covering the rubber film of the natural latex product, so that the volatilization of water in the rubber film of the natural latex product is reduced, the rubber film is softer, the reaction of the compounding agent in the rubber film is promoted to be further completed in the placement treatment process, and the content of the redundant compounding agent in the rubber film is reduced, so that the phenomenon of frost spraying is relieved.
The inventor also finds that a compact and stable hydrophobic film can be formed on the surface of the rubber surface of the natural latex product by the treatment of the method, and the hydrophobic film can prevent the migration of the compounding agent in the rubber surface of the natural latex product, block the entering of external destructive factors (moisture), and enable the rubber film of the natural latex product to form a closed system, thereby achieving the purpose of preventing the natural latex product from frosting.
The invention uses physical treatment means for the first time, and achieves the technical effect of preventing the natural latex product from blooming under the conditions of not changing the latex rubber compound formula and preparation process conditions of the natural latex product and not coating surface antifrost agent; the method does not change the original performance and appearance of the natural latex product, is simple to operate and low in cost, does not need to use special treatment agents or purchase treatment equipment, and is suitable for practical production and application.
Drawings
FIG. 1 is a macro-contrast view of natural latex gloves treated without the method of the present invention, natural latex gloves treated with a wrap seal, and natural latex gloves treated with a valve bag seal, respectively, after being air-cured for 3 months.
FIG. 2 is a graph showing the comparison of the total surface reflection infrared of natural latex gloves processed without the method of the present invention, natural latex gloves processed with a self-sealing bag, and natural latex gloves processed with a wrap film.
FIG. 3 is a graph showing a comparison of the thermal weight loss of the latex films of natural latex gloves not treated by the process of the present invention and natural latex gloves treated by the process of the present invention.
FIG. 4 is a graph comparing the contact angle of the surface of a natural rubber latex glove treated without the method of the present invention, a natural rubber latex glove treated with a self-sealing bag, and a natural rubber latex glove treated with a wrap film with a water drop.
FIG. 5 is a graph showing the contact angle between the surface of a natural latex glove treated without the method of the present invention and a water drop after the natural latex glove treated with a self-sealing bag and the natural latex glove treated with a wrap film were respectively air-dried for 3 days.
FIG. 6 is an SEM image (scale 1 μm) of the surface of a natural rubber latex glove treated without the method of the present invention, a natural rubber latex glove treated with a valve bag according to the method of the present invention, and a natural rubber latex glove treated with a preservative film according to the method of the present invention, respectively, after being air-cured for 15 days.
FIG. 7 is an SEM image (scale 1 μm) of the surface of a natural rubber latex glove treated without the method of the present invention, a natural rubber latex glove treated with a valve bag according to the method of the present invention, and a natural rubber latex glove treated with a preservative film according to the method of the present invention, respectively, after being air-dried for 3 months.
Detailed Description
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
the innovation of the invention is mainly as follows: on the premise of not changing the sizing formula and production process of the natural latex product, the physical method is used for realizing the anti-blooming treatment on the surface of the product for the first time. Namely: the surface of the natural latex product adhesive film is tightly wrapped by the sealing bag or the preservative film, so that the volatilization of water in the adhesive film is reduced, and the adhesive film is softer. More importantly, through the treatment, the further reaction of the compounding ingredients in the natural latex product is promoted, the content of the redundant compounding ingredients is reduced, and the blooming is less. Even more surprisingly, the natural latex products treated by the above process proved to be: a layer of compact and stable hydrophobic film is also formed on the surface of the natural latex product, and the hydrophobic film enables the glue film of the natural latex product to form a closed system, and prevents the migration of the compounding agent and the entrance of external destructive factors, thereby achieving the purpose of preventing the natural latex product from blooming.
the invention specifically comprises the following steps: placing the vulcanized natural latex gloves at room temperature for 0-30min, and then placing in a self-sealing bag, or tightly wrapping with preservative film, and placing in a dark environment for 2-72h, wherein the temperature is kept at 25-60 deg.C. Experiments prove that the natural latex product which does not bloom for more than one year is prepared by the simple treatment method. The method of the present invention is applicable to any natural latex article, such as natural latex gloves and the like.
To further illustrate the features and technical effects of the present invention, the following description is given with reference to specific examples of "natural latex gloves" and experimental results.
Wherein the latex formulation of the natural latex glove comprises: 100 parts of natural latex, 0.5-1.5 parts of vulcanizing agent, 0.6-1.2 parts of anti-aging agent, 0.8-1.2 parts of activating agent, 0.2-0.6 part of accelerating agent and 0.2-0.5 part of stabilizing agent.
Optionally, the non-blooming natural latex product is prepared from the following raw materials in parts by weight: 100 parts of natural latex, 0.5-1.5 parts of vulcanizing agent sulfur, 0.4-0.6 part of anti-aging agent 2, 6-di-tert-butyl-p-cresol, 0.2-0.6 part of anti-aging agent 2,2' -methylene bis- (4-methyl-6-tert-butylphenol), 0.8-1.2 parts of activator ZnO, 0.2-0.6 part of promoter zinc diethyldithiocarbamate and 0.2-0.5 part of stabilizer KOH.
Specifically, the preparation method comprises the following steps:
(1) Pre-vulcanizing: putting natural latex, a vulcanizing agent, an anti-aging agent and an accelerator in parts by weight into a vulcanizing tank, slowly heating to 50-70 ℃ within 1-3h for prevulcanization, then preserving heat for 1-3h, cooling to 25-35 ℃, adding an activating agent and a stabilizing agent, uniformly stirring, standing for 30-60h to obtain prevulcanized latex, and adjusting the concentration of the prevulcanized latex to 50-65 wt% by using ammonia water;
(2) Molding: adopting a casting method, an impregnation method or an extrusion method:
The casting method comprises the following steps: pouring the natural latex into a mold, standing at normal temperature for 12-24h, then placing in an oven at 40-60 ℃, and demolding;
The impregnation method comprises the following steps: placing the dipping mold in an oven until the surface temperature is 55-65 ℃, dipping the dipping mold with a coagulant, throwing off the excess coagulant, continuing heating until the surface temperature is 45-55 ℃, dipping the natural latex compound, and airing at room temperature;
The extrusion method comprises the following steps: extruding the natural latex compound from a nozzle of a capillary at a certain speed by means of compressed air or static pressure, forming a glue thread by coagulant gel, placing the glue thread in an oven at 45-55 ℃ after 12-24h at normal temperature;
(3) And (3) vulcanization: and (3) putting the formed adhesive film into an oven at 100-120 ℃ for vulcanization, wherein the vulcanization time is 40-60min, and thus obtaining the natural latex product.
the natural rubber latex gloves used in all of the following examples were prepared in accordance with the above-described method. It is claimed that the present invention is not limited to the field of natural latex glove manufacturing, which is a conventional process in the field of natural latex article manufacturing.
Example 1
3 samples of the same batch of natural latex gloves which have just been vulcanized are collected from a vulcanization workshop of the natural latex gloves, and after the natural latex gloves are respectively placed for 1min in a laboratory, the treatment is started to carry out the treatment of the method of the invention on two gloves. One glove is unfolded and put into a self-sealing bag (a plastic bag with a sealing zipper and good sealing performance) to be sealed, the other glove is completely wrapped and sealed on the surface of the glove by a PE preservative film, and the third glove sample is not subjected to the treatment. The three gloves were spread in a dark box (60cm x 100cm x 30cm) of a laboratory, kept at 25 ℃ and left for 3 days, and then taken out. Then, the valve bags and the preservative films were removed, respectively, to obtain 3 comparative samples. And 3 comparative samples are placed on a window sill with visible sunlight in the south direction indoors for airing for 3 months and then observed.
as shown in fig. 1, the leftmost glove sample of natural latex was not sealed, the middle glove sample was wrapped with PE wrap and sealed, and the right glove sample was sealed with a self-sealing bag. From the observation results of fig. 1, it is understood that the glove samples without the sealing treatment on the left side have whitish surface color (blooming), while the glove samples on the middle and right sides still maintain the original glove color and have no whitish appearance (blooming does not occur).
Example 2
3 samples of the same batch of natural latex gloves which are just vulcanized are collected from a vulcanization workshop of the natural latex gloves, and after the natural latex gloves are respectively placed for 1min in a laboratory, the treatment is started to carry out the treatment of the method of the invention on two gloves. One glove is unfolded and put into a self-sealing bag (a plastic bag with a sealing zipper and good sealing performance) to be sealed, the other glove is completely wrapped and sealed on the surface of the glove by a PE preservative film, and the third glove sample is not subjected to the treatment. The three gloves were spread in a dark box (60cm x 100cm x 30cm) of a laboratory, kept at 40 ℃ and left for 2 days, and then taken out. Then, the valve bags and the preservative films are respectively removed, and 3 glove samples to be tested are obtained. The surfaces of these 3 glove samples were scanned for total reflection infrared analysis. The results are shown in FIG. 2. As can be seen from the peak spectrum of FIG. 2, the sealed glove sample is wrapped by the PE preservative film, and the surface of the glove sample is 1738cm-1A new absorption peak appears. It can be confirmed that the wrapping of the sealed glove surface with PE wrap creates new chemical structural features.
Example 3
2 samples of the same batch of natural latex gloves which are just vulcanized are collected from a vulcanization workshop of the natural latex gloves, and after the samples are respectively placed for 1min in a laboratory, the treatment is started to carry out the treatment of the method on 1 glove.
The glove surface is completely wrapped and sealed by a PVC preservative film, and the other glove sample is not subjected to the treatment. The 2 gloves were spread in a laboratory dark box (60cm 100cm 30cm) at 35 deg.C, and left to stand for 60 h. And removing the preservative film on the surface of the glove to obtain 2 glove samples to be tested. The thermo-gravimetric analysis was performed on the film surface of these 2 glove samples. As shown in fig. 3, the water content in the surface adhesive film of the glove wrapped and sealed by the PVC preservative film is higher, which is beneficial to promoting the fluidity and the reactivity of the compounding agent in the glove adhesive film, and promoting the more complete vulcanization reaction of the compounding agent in the adhesive film, thereby reducing the residual amount and the migration of the redundant compounding, and alleviating the blooming phenomenon.
Example 4
3 samples of the same batch of natural latex gloves which are just vulcanized are collected from a vulcanization workshop of the natural latex gloves, and after the natural latex gloves are respectively placed for 1min in a laboratory, the treatment is started to carry out the treatment of the method of the invention on two gloves. Before treatment, a flat adhesive film was cut from any glove sample, a drop of pure water was dropped on the surface of the adhesive film, and the water contact angle was measured and recorded under a microscope using a contact angle measuring instrument.
The treatment process is as follows:
One glove is unfolded and put into a self-sealing bag (a plastic bag with a sealing zipper and good sealing performance) to be sealed, the other glove is completely wrapped and sealed on the surface of the glove by adopting a PVDC preservative film, and the third glove sample is not subjected to the treatment. The three gloves were spread in a laboratory dark box (60cm 100cm 30cm) at 45 deg.C, and left to stand for 36 h. Then, the valve bags and the preservative films are respectively removed, and 3 glove samples to be tested are obtained. And respectively intercepting a flat adhesive film on the 3 samples to be measured, respectively dripping a drop of pure water on the surface of the adhesive film, and measuring the water contact angle by using a contact angle measuring instrument under a microscope. The results are shown in FIG. 4.
As can be seen from fig. 4, the contact angles between the surfaces of the adhesive films of the two gloves and water are consistent and both are 78 degrees in the glove samples without sealing treatment and the glove samples before treatment; the contact angle of the glove which is subjected to the sealing treatment of the self-sealing bag, the sealing treatment of the safety film and the placing treatment in the dark box is obviously increased to 90 degrees and 100 degrees. It can be seen that the contact angle of the surface of the natural rubber latex glove with water is not changed obviously when the glove is placed in a dark environment and at the same temperature without sealing. Therefore, both a self-sealing bag and a wrap-around wrap seal are necessary. However, after the glove is wrapped and sealed, in order to prevent the moisture from evaporating from the adhesive film on the surface of the glove too quickly, the preferable scheme is to wrap the glove in a sealing way and then to perform standing treatment in a dark environment.
the experimental results of this example show that the contact angle with water of the glove surface treated by the method of the present invention is significantly increased, indicating that the surface of the latex film of the natural latex glove is changed from weak hydrophilic to hydrophobic.
Since moisture is an important factor causing blooming of the natural latex product during use of the natural latex product, migration of the hydrophilic compounding agent is promoted by the invasion of external factors such as moisture. Therefore, if the surface of the natural latex glove has higher hydrophobicity, the moisture adhesion can be reduced, and the prevention of the blooming phenomenon of the natural latex product can be greatly improved. Conversely, the more hydrophilic the surface of the latex article, the more blooming it will result. In combination with example 2, it can be seen that a dense hydrophobic film is indeed formed on the surface of the latex film of the natural rubber latex product by the treatment of the method of the present invention.
Example 5
The 3 samples obtained in example 4, namely one of the self-sealing bags, were sealed in a dark box at 45 ℃ for 36 hours, the other was wrapped and sealed with PVDC preservative film and was also placed in a dark box at 45 ℃ for 36 hours, and the third was not wrapped and sealed but was also placed in a dark box at 45 ℃ for 36 hours.
And (3) placing the glove samples on a south windowsill with visible sunlight in a laboratory, airing for 3 days, and then measuring the water contact angle. The results are shown in FIG. 5.
As can be seen from FIG. 5, after 3 days of drying, the water contact angle of the glove sample without sealing treatment was 57 ° due to the occurrence of blooming, which was reduced by 20 ° compared to that before drying. After 3 days of drying, the hydrophilicity of the surface of the glove sample without sealing treatment is enhanced, and the enhanced hydrophilicity can aggravate the blooming.
On the contrary, the water contact angle of the glove samples sealed by the PVDC preservative film wrapping and the valve bag is not obviously reduced although the glove samples are also dried for 3 days. The valve bag is filled with a sealed glove sample, the water contact angle of the valve bag is not reduced, but the valve bag is enlarged again, and the hydrophobicity of the valve bag is enhanced again. The PVDC preservative film wrapped the sealed glove sample with a small reduction in water contact angle, but still a much larger contact angle than the unsealed glove sample. The results were similar after the 3 samples were left to air for 15 days.
Example 6
3 samples of the same batch of natural latex gloves which are just vulcanized are collected from a vulcanization workshop of the natural latex gloves, and after the natural latex gloves are respectively placed for 1min in a laboratory, the treatment is started to carry out the treatment of the method of the invention on two gloves. One glove is unfolded and put into a self-sealing bag (a plastic bag with a sealing zipper and good sealing performance) to be sealed, the other glove is completely wrapped and sealed on the surface of the glove by adopting a PVC preservative film, and the third glove sample is not subjected to the treatment. The three gloves were spread in a laboratory dark box (60cm x 100cm x 30cm) at 60 deg.C, left to stand for 4h, and then taken out. Then, the valve bags and the preservative films are respectively removed, and 3 glove samples to be tested are obtained.
3 samples to be tested are placed on a south sunny balcony of a laboratory for airing for 15 days, and SEM scanning is carried out on the surfaces of the 3 glove samples, so that the result shown in figure 6 is obtained.
The experiment proves that: the surface of the glove sample which is not subjected to sealing treatment is aged, and a large number of holes appear; and the sealed glove samples are contained in the self-sealing bag and wrapped by the PVC preservative film, so that no hole is formed on the surface of the adhesive film. Wherein the surfaces of the sealed glove samples contained in the self-sealing bags are very flat and smooth and have consistent colors. The surface of the sample wrapped and sealed by the preservative film is flat and smooth, but has light-colored spots. It may be that the wrap seal of the wrap is not tight enough. In combination with the water contact angle data of example 5, it can be determined that the natural latex glove treated by the method of the present invention has a covering film formed on the surface of the rubber film, and the covering film is determined to be a hydrophobic film.
Example 7
The 3 glove samples to be tested obtained in example 6 were further dried in the sun for 3 months, and then SEM scanning was performed on the surfaces of the 3 glove samples to obtain the results shown in fig. 7.
Compared with the experimental result of example 6, the glove sample without sealing treatment has more holes on the surface of the adhesive film, and the aging damage is serious. The glove sample subjected to the sealing treatment of the self-sealing bag or the preservative film has the advantages that the surface change of the rubber film is small, the hydrophobic film is not damaged, the rubber film of the natural latex product is effectively protected, and the change is mutually verified with the measurement result of the contact angle.
By the treatment of the method, the compounding agents in the adhesive film of the natural latex product can effectively and completely react, the adhesive film performance (such as waterproof, oil-resistant, wear-resistant, aging-resistant and other performances) of the natural latex product is improved, the residual amount is reduced, and the blooming problem is relieved. The release of the blooming phenomenon and the more complete reaction of the compounding agent can make the adhesive film of the natural latex product more resistant to moisture and the invasion of external destructive factors. In addition, the inventor also unexpectedly finds that a layer of compact and stable hydrophobic film is formed on the surface of the rubber film of the natural latex glove after the treatment of the method, and the hydrophobic film can prevent the migration of a compounding agent in the rubber surface of the natural latex product and block the entering of external destructive factors (moisture), so that the rubber film of the natural latex product is self-formed into a closed system, and the aim of preventing the natural latex product from frosting is fulfilled.
Claims (10)
1. A method of preventing blooming in a natural latex article, the method comprising: after the natural latex product is prepared, the natural latex product is sealed and placed in a dark environment for treatment.
2. the method of claim 1, wherein the sealing is performed by at least one of sealing the natural latex product with a sealed container, a sealed bag, a sealing film, and a plastic film.
3. The method for preventing blooming of natural latex product according to claim 1, wherein the light-protected environment is preferably a dark environment.
4. The method of claim 1, wherein the sealed bag is a self-sealing bag; the sealing film is a preservative film, and the preservative film wraps or covers the surface of the natural latex product.
5. The method of claim 4, wherein the preservative film is one of PE, PVDC and PVC film.
6. The method for preventing natural latex products from blooming according to any one of claims 1 to 5, wherein after the natural latex products are vulcanized, the natural latex products are allowed to stand at normal temperature for 0 to 30min, and then are subjected to sealing and standing treatment; the environment temperature of the standing treatment is 25-60 ℃, and the standing treatment time is 2-72 h.
7. The method of claim 6, wherein the natural latex formulation used in the manufacturing process of the natural latex article comprises: 100 parts of natural latex, 0.5-1.5 parts of vulcanizing agent, 0.6-1.2 parts of anti-aging agent, 0.8-1.2 parts of activating agent, 0.2-0.6 part of accelerating agent and 0.2-0.5 part of stabilizing agent.
8. the method of claim 6, wherein the natural latex article is a cast, dipped or extruded article, and the method comprises the steps of:
S1, pre-vulcanization: putting natural latex, a vulcanizing agent, an anti-aging agent and an accelerator in parts by weight into a vulcanizing tank, slowly heating to 50-70 ℃ within 1-3h for prevulcanization, then preserving heat for 1-3h, cooling to 25-35 ℃, adding an activating agent and a stabilizing agent, uniformly stirring, standing for 30-60h to obtain prevulcanized latex, and adjusting the concentration of the prevulcanized latex to 50-65 wt% by using ammonia water;
S2, molding: adopting a casting method, an impregnation method or an extrusion method:
The casting method comprises the following steps: pouring the natural latex into a mold, standing at normal temperature for 12-24h, then placing in an oven at 40-60 ℃, and demolding;
The impregnation method comprises the following steps: placing the dipping mold in an oven until the surface temperature is 55-65 ℃, dipping the dipping mold with a coagulant, throwing off the excess coagulant, continuing heating until the surface temperature is 45-55 ℃, dipping the natural latex compound, and airing at room temperature;
The extrusion method comprises the following steps: extruding the natural latex compound from a nozzle of a capillary at a certain speed by means of compressed air or static pressure, forming a glue thread by coagulant gel, placing the glue thread in an oven at 45-55 ℃ after 12-24h at normal temperature;
s3, vulcanization: and (3) putting the formed rubber film into an oven at 100-120 ℃ for vulcanization for 40-60min to obtain the natural latex product.
9. The method of claim 1, wherein the sealed container or sealed container is evacuated after the natural latex product is placed in the sealed container or sealed bag.
10. The method of claim 1, wherein the ambient humidity during the placing process is 35-90% RH.
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Application publication date: 20191213 |