阅读说明：本技术 一种低蛋白天然浓缩胶乳的制备方法 (Preparation method of low-protein natural concentrated latex ) 是由 谭海生 汪志芬 李建斌 于 2020-05-26 设计创作，主要内容包括：本发明公开一种低蛋白天然浓缩胶乳的制备方法,包括以下步骤：S1、制备氧化聚乙烯醇：将聚乙烯醇配制为溶液,然后滴加Fe～(2+)和过量的H-(2)O-(2)进行反应,得氧化聚乙烯醇；S2、将所述氧化聚乙烯醇加入天然胶乳中进行搅拌,直至所述天然胶乳中蛋白质的氨基与所述氧化聚乙烯醇中的醛基充分反应,然后离心浓缩,即可获得低蛋白天然浓缩胶乳。本发明提供的制备方法可以降低胶乳的蛋白质含量。操作简单易行,采用该方法制备的浓缩天然胶乳产品质量稳定,可直接用常规的生产方法生产胶乳海绵和医用外科手术手套、医用导管、检查手套等辅助医疗器械以及计生用品避孕套和电工手套等天然胶乳制品。(The invention discloses a preparation method of low-protein natural concentrated latex, which comprises the following steps: s1, preparation of oxidized polyvinyl alcohol: preparing polyvinyl alcohol into solution, and then dropwise adding Fe 2+ And an excess of H 2 O 2 Reacting to obtain oxidized polyvinyl alcohol; s2, adding the oxidized polyvinyl alcohol into natural latex, stirring until amino of protein in the natural latex and aldehyde group in the oxidized polyvinyl alcohol fully react, and then centrifuging and concentrating to obtain the low-protein natural concentrated latex. The preparation method provided by the invention can reduce the protein content of the latex. The operation is simple and easy, the concentrated natural latex product prepared by the method has stable quality, and the latex sponge, the medical surgical gloves, the medical catheters, the examination gloves and other auxiliary medical services can be directly produced by the conventional production methodTherapeutic equipment, birth control article condoms, electrician gloves and other natural rubber latex products.)

1. A method for preparing low-protein natural concentrated latex is characterized by comprising the following steps:

s1, preparation of oxidized polyvinyl alcohol:

preparing polyvinyl alcohol into solution, and then dropwise adding Fe²⁺And an excess of H₂O₂Reacting to obtain oxidized polyvinyl alcohol;

s2, adding the oxidized polyvinyl alcohol into natural latex, stirring until amino of protein in the natural latex and aldehyde group in the oxidized polyvinyl alcohol fully react, and then centrifuging and concentrating to obtain the low-protein natural concentrated latex.

2. The method according to claim 1, wherein the solution of S1 is prepared by dissolving the polyvinyl alcohol in water at 90-100 deg.C, and cooling to 50-60 deg.C.

3. The method according to claim 1, wherein the H in S1₂O₂The addition amount of (A) is 1-5 wt% of the polyvinyl alcohol, and the Fe²⁺In the amount of said H₂O₂1-6 wt% of.

4. The method according to claim 1, wherein the concentration of the solution in S1 is 8 to 12 wt%, and the reaction time is 0.5 to 24 hours.

5. The method according to any one of claims 1 to 4, wherein sodium formaldehyde sulfoxylate is further added to the oxidized polyvinyl alcohol in S1 to convert Fe³⁺Reduction to Fe²⁺。

6. The method according to claim 5, wherein the sodium formaldehyde sulfoxylate is added in an amount corresponding to the amount of Fe in S1²⁺The mass ratio of (A) to (B) is 5-20: 1.

7. The preparation method according to claim 1, wherein a stabilizer is further added in the natural latex in S2, and the stabilizer is one or more of caustic alkali, ammonium laurate, sodium dodecyl sulfate or ammonia water.

8. The method according to claim 1, wherein the oxidized polyvinyl alcohol in S2 is used in an amount of 1 to 20 wt% based on the absolute dry weight of the natural rubber latex.

9. The preparation method according to claim 1, wherein the standard of sufficient reaction in S2 is that the nitrogen content in the natural latex is less than 0.12 wt%, and the time of sufficient reaction is 0.5-24 h.

10. The method according to claim 1, wherein a latex preservative is further added to the low-protein natural concentrated latex, and the latex preservative is a complex of ammonia, tetramethylthiuram disulfide, and zinc oxide.

Technical Field

The invention relates to the technical field of natural latex concentration, in particular to a preparation method of low-protein natural concentrated latex.

Background

Because of its good biocompatibility and processability, natural rubber latex is widely used in the production of auxiliary medical devices such as surgical gloves, medical catheters, examination gloves, etc., or birth control products such as condoms, etc. Fresh natural latex contains about 1-2% protein by weight of the total latex weight, while concentrated natural latex contains 1.5-3.5% protein by weight, and the product still contains a considerable amount of soluble protein after the processing procedures of dipping, leaching, vulcanizing, washing and the like. Some doctors and patients may develop contact allergy such as dermatitis even when they contact the medical latex containing soluble protein, and severe patients may develop anaphylactic shock. Studies have shown that the major cause of allergic reactions is the soluble protein remaining in natural latex products. Therefore, the reduction of the protein content in the natural latex raw material can reduce the anaphylactic risk of medical latex products from a production source, and meanwhile, the natural latex with low protein content has low water absorption property and can be used for producing products with higher requirements on water absorption property and insulating property.

At present, the production method of low-protein concentrated natural latex mainly comprises the following steps: (1) firstly, decomposing protein in fresh latex by protease, and then removing the protein by a centrifugal or leaching method in the process of centrifugal concentration or product production; (2) removing soluble protein in the natural latex by adopting a multi-centrifugation method; (3) by usingVulcanizing latex by radiation such as ray or electron beam, decomposing protein, and diluting and centrifuging or leaching the latex to remove protein; (4) the protein in the natural latex is adsorbed and separated by urea or surfactant.

The methods have the advantages and the disadvantages, for example, the protease hydrolysis method needs heating reaction, the equipment investment is large, and the cost is high; the non-rubber substances which are beneficial to the performance of the product are easy to run off along with the product after multiple times of centrifugation, so that the performance of the product is reduced; the strength of the product prepared by adopting dialdehyde starch, urea or surfactant and the like is insufficient.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a preparation method of low-protein natural concentrated latex, which can obtain the low-protein natural concentrated latex, has low cost and simple and easy operation, and the prepared concentrated natural latex has stable quality and good reinforcing effect and can be directly used for producing natural latex products.

In order to achieve the above purpose, the invention provides the following technical scheme:

a method for preparing low-protein natural concentrated latex comprises the following steps:

s1, preparation of oxidized polyvinyl alcohol:

preparing polyvinyl alcohol into solution, and then dropwise adding Fe²⁺And an excess of H₂O₂Reacting to obtain oxidized polyvinyl alcohol;

s2, adding the oxidized polyvinyl alcohol into natural latex, stirring until amino of protein in the natural latex and aldehyde group in the oxidized polyvinyl alcohol fully react, and then centrifuging and concentrating to obtain the low-protein natural concentrated latex.

Firstly, polyvinyl alcohol is modified, and Fe is added into a solution of the polyvinyl alcohol²⁺And an excess of H₂O₂，Fe²⁺Capable of catalyzing H₂O₂The hydroxyl in the polyvinyl alcohol is oxidized into aldehyde group, and simultaneously, the polyvinyl alcohol molecule is broken, the molecular weight of the polyvinyl alcohol is reduced, the phenomenon that the natural latex is thickened by the high molecular weight polyvinyl alcohol is avoided, and the generated aldehyde group can perform a cross-linking reaction with the amino of the protein in the natural latex, so that the protein content in the latex is reduced.

As an implementable mode, the solution in S1 is prepared by adding the polyvinyl alcohol into water with the temperature of 90-100 ℃ for dissolution, and then cooling to the temperature of 50-60 ℃ for standby.

As an implementable mode, the H in S1₂O₂The addition amount of (A) is 1-5 wt% of the polyvinyl alcohol, and the Fe²⁺In the amount of said H₂O₂1-6 wt% of.

In this application Fe²⁺As a catalyst which can accelerate H₂O₂Oxidizing hydroxy group in polyvinyl alcohol to aldehyde group, adding oxidantWhen the amount is 1-5 wt% of polyvinyl alcohol, it can completely oxidize the hydroxyl in polyvinyl alcohol into aldehyde group, and at the same time make polyvinyl alcohol molecule chain-break to form low-molecular weight polymer.

As a practical way, the concentration of the solution in S1 is 8-12 wt%, and the reaction time is 0.5-24 h.

As a practical way, sodium formaldehyde sulfoxylate is further added into the oxidized polyvinyl alcohol in S1 to react Fe generated in the reaction process³⁺Reduction to Fe²⁺。

The addition of sodium formaldehyde sulfoxylate to the oxidized polyvinyl alcohol of the present application can result in Fe³⁺Reduction to Fe²⁺Thereby making Fe possible²⁺Can be recycled to reduce Fe²⁺The amount of (2) reduces the amount of residual iron in the latex product, thereby improving the aging resistance of the rubber product.

As an embodiment, the addition amount of the sodium formaldehyde sulfoxylate and the Fe are²⁺The mass ratio of (A) to (B) is 5-20: 1.

In an implementation manner, the natural latex in S2 is further added with a stabilizer, and the stabilizer is one or more of caustic alkali, ammonium laurate, sodium dodecyl sulfate and ammonia water.

As a practical way, the amount of the oxidized polyvinyl alcohol in S2 is 1 to 20 wt% based on the oven-dried amount of the natural rubber latex.

As a practical manner, the criterion of the sufficient reaction in S2 is that the nitrogen content in the natural latex is less than 0.12 wt%, and the time of the sufficient reaction is 0.5 to 24 hours. At this time, the amino group of the protein in the latex can be sufficiently reacted with the aldehyde group in the oxidized polyvinyl alcohol, thereby reducing the protein content in the latex.

In an embodiment, the low-protein natural concentrated latex is further added with a latex preservative, wherein the latex preservative is ammonia, a compound of tetramethylthiuram disulfide and zinc oxide, formaldehyde, sodium sulfite, a mixture of formaldehyde and ammonia, a mixture of hydroxylamine and ammonia, sodium carbonate or urea.

The natural latex is a viscous milky white liquid, looks like milk, is a milky aqueous dispersion of rubber particles in a near-neutral medium, increases the acidity of the latex due to the action of oxygen and microorganisms in the air, can be naturally coagulated within 2 to 12 hours, and needs to be added with a certain amount of protective agent to prevent the natural coagulation. The natural rubber latex of the present invention is provided by Hainan rubber group Co. The natural latex is characterized by high elasticity, good film-forming property during bonding and rich flexibility of the adhesive film, so that the adhesive film has excellent flexing resistance, shock resistance and creep resistance, and is widely applied to various fields of industry, agriculture, national defense, traffic, medical treatment and health care and the like. The sponge product prepared from the natural latex has the advantages of light weight, large volume, environmental protection, excellent buffering performance, high elasticity, special comfortable touch feeling, quick recovery after deformation, creep resistance and permanent deformation resistance, excellent buffering and pressure reducing performance, compression fatigue resistance and the like.

Sodium formaldehyde sulfoxylate (also known as sodium formaldehyde sulfoxylate dihydrate, sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate dihydrate, sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate dihydrate, sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate dihydrate, sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate dihydrate, sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate dihydrate, sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate dihydrate, sodium formaldehyde-sodium hydrogen sulfate dihydrate, sodium formaldehyde sulfoxylate-sodium hydrogen sulfate dihydrate, sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate dihydrate, or sodium formaldehyde sulfoxylate-sodium hydrogen sulfate dihydrate, sodium formaldehyde-sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate, sodium formaldehyde sulfoxylate-sodium hydrogen sulfate, sodium formaldehyde-sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate, sodium hydrogen sulfate, sodium formaldehyde sulfoxylate-sodium formaldehyde sulfoxylate, or ronylate-sodium formaldehyde sulfoxylate-sodium formaldehyde sulfox₃NaO₃S·2H₂O；HOCH₂SO₂Na·2H₂O, the water solution of which is stable at normal temperature and decomposes at high temperature; the melting point is about 65 ℃, the water solubility is high, the ethanol solubility is low, and the decomposition can be rapidly realized when meeting acid; the solution is neutral and has strong reducibility.

The latex stabilizer is a multi-series surface active chemical substance, and is a substance which can increase the surface charge, the protective layer and the hydration degree of latex particles and avoid the early gel precipitation of latex or matched latex in the processes of storage, mechanical operation and matching with auxiliary agents. The multi-series surface active compound has larger hydrophilicity, and can form a layer of shell loosely combined with water on the surface of colloidal particles through the polar-nonpolar structural characteristics after being added into latex, so that the rubber particles are not easily influenced by external factors, the viscosity of an aqueous solution is increased, and the effect of protecting colloid is achieved. Mainly comprises casein, gelatin, sulfate, sulfonate, carboxylate, condensate of ethylene oxide and fatty alcohol, etc. In addition, many basic antigelling agents also fall within the category of latex stabilizers.

Compared with the prior art, the invention has the following beneficial effects:

the low-protein natural concentrated latex provided by the invention is prepared by mixing oxidized polyvinyl alcohol and natural latex, aldehyde groups in the oxidized polyvinyl alcohol and amino groups of proteins in the natural latex are subjected to a cross-linking effect in the mixing process, the molecular weight of the proteins is increased, and the water solubility of the proteins is lost, so that the problem of allergy of the proteins in latex products is solved;

in addition, the invention adds Fe²⁺Catalysis H₂O₂Modifying polyvinyl alcohol, so that hydrogen peroxide can not only oxidize hydroxyl in the polyvinyl alcohol into aldehyde group, but also generate crosslinking action with amino of protein, and also break the molecular chain of the polyvinyl alcohol, thereby reducing the molecular weight of the polyvinyl alcohol, and avoiding the problems that high molecular weight polyvinyl alcohol thickens natural latex, influences the production process of latex products and the performance of products, or coagulates the latex;

secondly, because the oxidized polyvinyl alcohol particles are smaller and can be uniformly dispersed in the natural latex under mechanical stirring after being mixed with the natural latex, and the oxidized polyvinyl alcohol has certain compatibility with the natural latex, when the oxidized polyvinyl alcohol is mixed with the natural latex, the oxidized polyvinyl alcohol can permeate into the particles of the natural latex or occupy the gaps among the rubber particles, or be mechanically adhered or wet-adsorbed on the surface of rubber particles, thereby not only playing the role of chemical crosslinking with protein amino, but also playing the role of physical crosslinking, when the rubber film is stressed, any stressed natural rubber molecular chain can transmit and disperse stress to other natural rubber molecular chains through the oxidized polyvinyl alcohol connected with the rubber film, even if the natural rubber molecular chains are broken, other natural rubber molecular chains can still bear stress through the oxidized polyvinyl alcohol, and the danger and the integral damage cannot be rapidly caused, therefore, the natural latex product can also be reinforced.

In addition, Fe is also added in the preparation of the oxidized polyvinyl alcohol²⁺And sodium formaldehyde sulfoxylate, Fe²⁺Can accelerate the reaction of hydrogen peroxide on polyvinyl alcohol, and sodium formaldehyde sulfoxylate can be used for preparing the polyvinyl alcoholFe produced during the reaction³⁺Reduction to Fe²⁺Thereby making Fe possible²⁺Can be recycled to reduce Fe²⁺The amount of (2) reduces the amount of residual iron in the latex product, thereby improving the aging resistance of the rubber product.

Detailed Description

The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

The invention provides a preparation method of low-protein natural concentrated latex, which comprises the following steps:

s1, preparation of oxidized polyvinyl alcohol:

dissolving polyvinyl alcohol in water, stirring at 90 ℃ to prepare a solution with the mass fraction of 10%, cooling the solution to 50 ℃, adding ferrous sulfate, stirring uniformly, dropwise adding hydrogen peroxide, and reacting for 0.5h to obtain oxidized polyvinyl alcohol.

Wherein, the dosage of the hydrogen peroxide is 10 percent of the mass fraction of the polyvinyl alcohol, and the dosage of the ferrous sulfate is 10 percent of the mass fraction of the hydrogen peroxide.

S2, adding caustic alkali (KOH) into fresh natural latex, uniformly stirring, then adding oxidized polyvinyl alcohol with the mass percentage of 10% of the dry rubber amount of the latex, and stirring for 0.5h to ensure that amino groups of protein in the latex and aldehyde groups in the oxidized polyvinyl alcohol fully react;

and S3, when the nitrogen content in the latex is reduced to 0.12 percent by mass, centrifugally concentrating the latex, and adding ammonia water for storage according to a conventional method to obtain the low-protein natural concentrated latex.

Example 2

The invention provides a preparation method of low-protein natural concentrated latex, which comprises the following steps:

s1, preparation of oxidized polyvinyl alcohol:

dissolving polyvinyl alcohol in water, stirring at 95 ℃ to prepare a solution with the mass fraction of 10%, cooling the solution to 55 ℃, adding ferrous sulfate, stirring uniformly, then dropwise adding hydrogen peroxide, reacting for 12h, adding sodium formaldehyde sulfoxylate, and stirring.

Wherein the dosage of the hydrogen peroxide is 3 percent of the mass fraction of the polyvinyl alcohol, the dosage of the ferrous sulfate is 3 percent of the weight of the hydrogen peroxide, and the mass ratio of the dosage of the sodium formaldehyde sulfoxylate to the dosage of the ferrous sulfate is 10: 1.

s2, adding ammonium laurate and sodium dodecyl sulfate which are mixed in equal proportion into fresh natural latex, uniformly stirring, then adding oxidized polyvinyl alcohol with the mass percentage of 10% of the dry latex amount, and stirring for 12 hours to enable amino of protein in the latex to fully react with aldehyde groups in the oxidized polyvinyl alcohol;

and S3, when the nitrogen content in the latex is reduced to 0.12 percent by mass, centrifugally concentrating the latex, and adding a mixture of formaldehyde and ammonia for storage according to a conventional method to obtain the low-protein natural concentrated latex.

Example 3

The invention provides a preparation method of low-protein natural concentrated latex, which comprises the following steps:

s1, preparation of oxidized polyvinyl alcohol:

dissolving polyvinyl alcohol in water, stirring at 100 ℃ to prepare a solution with the mass fraction of 10%, cooling the solution to 60 ℃, adding ferrous sulfate, stirring uniformly, then dropwise adding hydrogen peroxide, reacting for 24h, adding sodium formaldehyde sulfoxylate, and stirring.

Wherein the dosage of the hydrogen peroxide is 5 percent of the mass fraction of the polyvinyl alcohol, the dosage of the ferrous sulfate is 6 percent of the mass fraction of the hydrogen peroxide, and the mass ratio of the dosage of the rongalite to the dosage of the ferrous sulfate is 20: 1.

s2, adding ammonia water into fresh natural latex, uniformly stirring, adding oxidized polyvinyl alcohol with the mass percentage of 20% of the dry rubber amount of the latex, and stirring for 24 hours to enable amino groups of proteins in the latex to fully react with aldehyde groups in the oxidized polyvinyl alcohol;

s3, when the nitrogen content in the latex is reduced to 0.12 percent by mass, centrifugally concentrating the latex, and adding a compound of tetramethyl thiuram disulfide and zinc oxide for storage according to a conventional method to obtain the low-protein natural concentrated latex.

The following results were obtained by examining the water-soluble protein elution rate, the tensile strength, and the retention of the tensile strength after hot air aging at 100 ℃ for 24 hours for each of the analysis subjects, using the adhesive film prepared from the concentrated natural latex as a comparative example 1, the adhesive film prepared from the low-protein natural concentrated latex produced by adding dialdehyde starch to the concentrated natural latex as a comparative example 2, and the adhesive films prepared from the comparative examples 1 and 2 and the low-protein natural concentrated latexes of examples 1 to 3 in this application as the analysis subjects:

as can be seen from the above table, the precipitation rates of the water-soluble proteins in the examples 1-3 of the present application are less than or equal to 32.2. mu.g/g, which is lower than the minimum allowable protein content of latex protein sensitization (ASTM, 2005), and the tensile strength of the prepared adhesive film is greater than or equal to 20.3MPa, which is much greater than the tensile strength of the low-protein natural concentrated latex prepared by adding dialdehyde starch, and is also higher than the tensile strength of the concentrated natural latex, the method can be used for preparing the low-protein natural concentrated latex and simultaneously reinforcing the natural latex product, further, as can be seen by comparing example 1 with examples 2 to 3, the aging resistance of examples 2 to 3 is larger than that of example 1, therefore, the addition of the sodium formaldehyde sulfoxylate effectively improves the aging resistance of the low-protein natural concentrated latex; comparative example 1 and comparative example 2 found that the tensile strength retention of example 1 was lower under the same aging conditions because of the addition of Fe²⁺The addition of metal ions reduced the aging resistance, while comparative examples 2 and 3 and comparative example 2 found that the aging resistance of examples 2 and 3 was not reduced by the addition of the metal catalyst Fe²⁺To lowerThe aging resistance of comparative example 2 was low, but rather leveled, because the addition of sodium formaldehyde sulfoxylate reduced the amount of residual iron in the latex product, thereby improving the aging resistance of the rubber product.

In conclusion, the concentrated natural rubber latex prepared by the method has stable quality and good reinforcing effect.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.