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WO2023048601A1 - Latex de butadiène-nitrile, composition de latex pour moulage par immersion et article moulé par immersion - Google Patents

Latex de butadiène-nitrile, composition de latex pour moulage par immersion et article moulé par immersion Download PDF

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Publication number
WO2023048601A1
WO2023048601A1 PCT/RU2022/050301 RU2022050301W WO2023048601A1 WO 2023048601 A1 WO2023048601 A1 WO 2023048601A1 RU 2022050301 W RU2022050301 W RU 2022050301W WO 2023048601 A1 WO2023048601 A1 WO 2023048601A1
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WIPO (PCT)
Prior art keywords
latex
butadiene
dip
nitrile
monomer
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PCT/RU2022/050301
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English (en)
Inventor
Ludmila Andreevna KORYSTINA
Sergej Viktorovich BAGRYASHOV
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Sibur Holding PJSC
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Sibur Holding PJSC
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Priority claimed from RU2021128244A external-priority patent/RU2776174C1/ru
Application filed by Sibur Holding PJSC filed Critical Sibur Holding PJSC
Publication of WO2023048601A1 publication Critical patent/WO2023048601A1/fr
Priority to ZA2024/01942A priority Critical patent/ZA202401942B/en
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/02—Direct processing of dispersions, e.g. latex, to articles
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B42/00—Surgical gloves; Finger-stalls specially adapted for surgery; Devices for handling or treatment thereof
    • A61B42/10—Surgical gloves
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2309/00—Characterised by the use of homopolymers or copolymers of conjugated diene hydrocarbons
    • C08J2309/02—Copolymers with acrylonitrile
    • C08J2309/04—Latex

Definitions

  • the present invention relates to a butadiene nitrile latex, preferably carboxylated butadiene nitrile latex, suitable for manufacturing of dip-molded articles, in particular for production of latex gloves for industrial and medical purpose.
  • the present invention also relates to a composition based on butadiene nitrile latex for dip-molding and to dip-molded articles produced using such a composition.
  • the process of manufacturing a dip-molded articles comprises the dipping a ceramic or other mold having the required shape of a finished product into a latex composition.
  • a mold is placed in sequential order into a bath comprising salt solution, and then into a latex with subsequent coagulation of latex globules under the influence of cations of the mentioned above salt.
  • Such a method is used, for example, in the manufacture of gloves for medical purpose.
  • the gloves for technical purpose can be textile or unsupported.
  • the textile gloves can be dipped directly into a latex without or with the prior dipping into a coagulant.
  • the nature of a latex has a significant influence on the properties of articles produced with the method of dip-molding.
  • the dip-molded articles can be produced of butadiene-nitrile latex, but in cases where it is required to ensure better physical and mechanical parameters (strength, elasticity, etc.), the carboxylated butadienenitrile latexes are used.
  • the gloves for medical purpose are usually made based on natural or carboxylated butadiene nitrile latex.
  • the gloves of natural latex are produced ever less and more rarely: they can cause allergies, and the availability of natural latex depends on the yield of Hevea plantations.
  • the gloves based on the carboxylated butadiene nitrile latex have similar physical and mechanical properties to natural latex, but without the disadvantages mentioned above. In addition, such gloves have improved oil and gas resistance.
  • latexes used for the production of dip- molded articles should have high aggregative stability, but at the same time easily coagulate under the action of 2-3 valent electrolytes with the formation of a durable and elastic film.
  • latex films produced with the dipmolding method, in particular by ion deposition are subject to requirements to maintain an uncolored, light film lacking the stickiness.
  • a glove for medical purpose made of nitrile butadiene latex should be colorless, thin, durable, elastic, provide the tactile sensitivity, have no residual stickiness, and no external defects in the form of runovers, bubbles, and cracks.
  • One of the methods of latex production is the emulsion copolymerization, which is carried out in a complex multicomponent microheterogeneous system, the control and monitoring of which is difficult to implement in practice. Because of this fact, the identification of a degree of influence on achieving the required properties of the product being made (monomer phase composition, emulsifiers, chain-terminating agents, initiators, electrolytes, etc.), individual reagents as well as groups of reagents of different purposes, their amounts and conditions of introduction into the system, is of particular importance.
  • the patent EP2457933 describes an adhesive composition for making belts comprising a latex of highly saturated nitrile rubber providing high oil resistance and good adhesive properties, wherein the content of the tetrahydrofuran insoluble fraction is indicated as one of the latex characteristics, according to the invention, it is from 30 to 70 wt%.
  • the authors of the invention claim that if the tetrahydrofuran insoluble fraction is too small, when forming the adhesive layer by curing the adhesive composition, the obtained adhesive layer deteriorates in oil resistance and the composite obtained by use of the adhesive composition degrades in oil resistance as well.
  • the average particle size of the latex is preferably 0.01 to 0.5 um, and the concentration of solids in the latex is preferably not more than 50 wt%.
  • the patent does not disclose the influence of these indicators and molecular weight characteristics on the physical and mechanical properties, as well as on the properties of dip-molded latex articles.
  • the patent EP3124512 discloses the highly saturated nitrile rubber latex and adhesive compositions based thereon used in belt production. Said latex is characterized, among others, by a content of a chloroform -soluble polymer with a weighted average molecular weight in the range of 100,000 or less. According to the present invention, if the value of a weight average molecular weight of the solubles in chloroform is too high, the produced adhesive layer ends up deteriorating in stretchability.
  • the weight average molecular weight of the solubles in chloroform can, for example, be found by making the highly saturated nitrile rubber dissolve in chloroform and measuring the solubles of the obtained solution using gel permeation chromatography (GPC). Note that, the molecular weight distribution (Mw/Mn) of the solubles in chloroform is not particularly limited, but is preferably 2 to 100.
  • the patent does not disclose the effect of solubility values in other solvents, in particular, methyl ethyl ketone, on latex properties, or the effect of other parameters, including latex particle size and molecular weight characteristics, on the properties of dip-molded articles.
  • the patent US 10000868 discloses a highly saturated nitrile rubber latex for belts which, among others, is characterized by a content of the tetrahydrofuran insoluble fraction of 30 wt% or more. More specifically, the tetrahydrofuran insoluble fraction is preferably 35 wt% to 95 wt%, more preferably 45 wt% to 90 wt%, and even more preferably 50 wt% to 80 wt%. The authors of the present invention point out that a too small tetrahydrofuran insoluble fraction will deteriorate the oil resistance of coatings.
  • the average particle size of the latex is preferably 0.01 to 0.5 pm, a solid content concentration of the latex is preferably not more than 50 wt%.
  • the patent lacks the disclosure of the influence of the above parameters as well as molecular weight characteristics on physical and mechanical properties, and also on the properties of dip-molded latex articles.
  • the patent US 10907002 describes a copolymeric latex of a conjugated diene monomer unit, an etbylenically unsaturated nitrile monomer unit, and an etbylenically unsaturated acid monomer unit used for making industrial gloves, wherein said number average particle size of the copolymer contained in the copolymer latex is preferably 60 to 300 nm, has an average copolymer particle size of from 60 to 300 nm, an insoluble content in methyl ethyl ketone of 70 wt% or less, and a certain swelling degree in methyl ethyl ketone.
  • a certain content of insoluble substances and a certain swelling degree of the film effectively suppressing the occurrence of cracks in a rubber layer.
  • the patent does not disclose requirements for the molecular weight characteristics that provide the required physical and mechanical properties of materials for making articles, in particular medical dip-molded latex gloves.
  • the application JPH09316131 describes a copolymer latex used to make coating paper compositions.
  • Said latex based on aliphatic conjugated diene, unsaturated acid monomer and another copolymerizable monomer satisfies the following conditions:
  • XY/Z > 28000-8*(X-70)*2, where X is the gel fraction (wt%), Y is the weight average molecular weight of tetrahydrofuran-soluble matter, and Z is the latex the average particle diameter (nm).
  • the specified latex provides an excellent balance between adhesive strength and resistance to bubble formation.
  • the application discloses the use of a parameter connecting various characteristics of the polymer and use thereof in the production of coated paper compositions, but it does not disclose the requirements for the characteristics providing the use of the claimed latexes for manufacture of dip -molded articles.
  • the object of the present invention is to provide butadiene nitrile carboxylated latexes and compositions based on them having a set of properties required for the use as starting materials for manufacturing the dip-molded articles, in particular the latex gloves for industrial and medical purpose.
  • the authors of the present invention have unexpectedly found that the specified technical result is achieved under conditions when the latex is produced, which has such a set of specific properties that the numerical value of the parameter determined based on them, should be within a certain range of values.
  • the subject matter of the present invention is a latex for manufacture of the dip- molded articles, comprising the structural units formed from at least one monomer which is conjugated diene, at least one ethylene unsaturated monomer comprising a nitrile group, and at least one monomer which is an unsaturated carboxylic acid, where the value of the solubility index (A), calculated by the formula
  • p is the polymer solubility in methyl ethyl ketone (wt%)
  • S - latex particle size (nm) S - latex particle size (nm)
  • M w is weight average molecular weight of the tetrahydrofuran-soluble fraction of butadiene-nitrile latex (g/mol)
  • the polydispersity value of latex polymer M w /M n is from 2.0 to 5.0, preferably from 2.0 to 4.0, more preferably from 2.0 to 3.5.
  • composition for dip-molding comprising the latex according to the present invention and at least one curing agent.
  • compositions for making the dip-molded articles comprising 96-97 wt% per the dry matter of the latex according to the present invention, 3.0-3.6 wt% of at least one curing agent, optionally 0.2-0.3 wt% of fatty alcohol ether sulphate salt and 0.1 -0.2 wt% of antioxidant per the total weight of composition dry matter in 100%.
  • Another subject matter of the present invention is a dip-molded article based on latex or composition according to the present invention, in particular, the article is a glove.
  • Another subject matter of the present invention is the use of a latex according to the present invention to produce the dip-molded articles, in particular gloves. Detailed description of the invention
  • a latex for manufacturing the dip- molded articles comprising the structural units formed from at least one monomer which is conjugated diene, at least one ethylene unsaturated monomer comprising a nitrile group, and at least one monomer which is an unsaturated carboxylic acid, wherein the value of the solubility index (A), calculated by the formula
  • p is the polymer solubility in methyl ethyl ketone (wt%)
  • S - latex particle size nm
  • M n number-average molecular weight of the tetrahydrofuran-soluble fraction of butadiene-nitrile latex
  • M w is weight average molecular weight of the tetrahydrofuran-soluble fraction of a butadiene-nitrile latex (g/mol)
  • the polydispersity value of a latex polymer M w /M n is from 2.0 to 5.0.
  • a latex polymer in the context of the present invention is the product of monomer copolymerization separated from the latex and purified from the components of the reaction mixture.
  • a monomer mixture in the context of the present invention is the total amount of all monomers used to produce a latex.
  • the technical result of the present invention is to produce a latex having elasticity of crude gel no less than 1 ,000%, sufficient to provide required physical and mechanical properties of a cured film, at that the latex has high resistance to mechanical impacts (absence of coagulum), limited resistance to electrolytes action, as well as required dynamic viscosity (more than 30 cPs), which allow to consider this latex as an ideal material for manufacturing the dip-molded articles.
  • the films made of such a latex have no defects (overlaps, perforations, cracks), are characterized by high values of physical and mechanical parameters: when combined (salt and sulfur) curing is performed, the strength of latex films is not less than 30 mPa in combination with relative elongation of not less than 500%; produced films are thin, durable and transparent.
  • the elasticity of a crude latex polymer gel is a particularly important characteristic determining the quality of latex films formed by dip-molding, in particular ion deposition, which demonstrates, on the one hand, the effectiveness of coalescence (interpenetration) of latex globules during the process of dip-molding, that is, the presence of defects in the film, and, on the other hand, the elasticity parameters of the crude gel can be used to judge about the relative elongation of a cured latex film.
  • the elasticity of crude gel should be no less than 1,000%.
  • the elasticity of the crude gel depends on the emulsion copolymerization process conditions during the production of a butadiene nitrile latex.
  • solubility index A should be within the range of 0.5-22, preferably within the range of 1.0-15, most preferably within the range of 1.0-10. It is noted that at values of solubility index A outside the specified range, the cured latex films do not provide the level of physical and mechanical parameters required by ASTM D 6319.
  • the solubility index is calculated based on the polymer solubility in methyl ethyl ketone (MEK), latex particle size, and polymer molecular weight characteristics, where each of these indicators also has an effect on the properties of the latex and products based on it.
  • MEK methyl ethyl ketone
  • the solubility of butadiene-nitrile polymer in methyl ethyl ketone (MEK) is an indicator characterizing the polymer cross-linking, that is the number of cross-links formed: the more the solubility, the less the number of cross-units and the less the polymer is cross-linked.
  • a butadiene nitrile polymer with high MEK solubility value and low crosslinking value has high elastic properties.
  • the films made of such a polymer have high physical and mechanical properties, in particular high strength and elasticity as well as low modulus at 500% elongation.
  • a glove manufactured with such a latex provides a comfortable tactile sensation when wearing it.
  • a polymer with high solubility value in MEK has a high rate of syneresis (spontaneous compaction of the latex gel structure with sulfur release), which, in turn, can result in defects in the polymer film, its shrinkage and lowering of its physical and mechanical properties.
  • a butadiene nitrile polymer with low MEK solubility value and high cross-linking is characterized by slower syneresis, which can result in an improvement in the structure of a latex film being formed.
  • the high cross- linking value of the polymer causes its reduced elasticity as well as deterioration of the quality of the formed films - decrease of their strength and elasticity and increase in modulus at 500% elongation, resulting in the decrease in the tactile sensations comfort when working in gloves.
  • the formation of films from a polymer with low solubility value creates a risk of cracking, and in extreme cases, the films may not form at all.
  • solubility in MEK within the scope of the present invention are 30-100 wt%, more preferred are 35-80 wt%, most preferred are 40-70 wt%.
  • the latex particle size can be within a very wide range. An increase in particle size results in a reduction of dynamic viscosity, decrease in transparency of a latex film, while a decrease in particle size results in an increase in viscosity and a decrease in its resistance to mechanical impacts, as well as a greater polymer loss due to the surface film formation.
  • the size of latex parts affects the nature of film formation, that is, the homogeneity of the latex film and the presence of defects in it.
  • latex particle size is influenced by the nature and dosage of the emulsifier, initiator, ratio of the monomer phase to the aqueous phase and many other factors.
  • the preferred range of latex particle size is 70 to 160 nm, more preferably 70 to 140 nm, most preferably 70 to 120 nm.
  • the values of the polymer molecular weights are also important for achieving the technical result according to the present invention.
  • increasing the values of M w and M n results in improving the strength properties of the latex film
  • reducing M w and M n results in decreasing the strength while maintaining the elasticity of latex film articles having low thickness and low weight, and increasing the modulus values at 300% and 500% elongation, which impairs the tactile sensations comfort when wearing the dip-molded gloves.
  • M w is from 50,000 to 250,000
  • Mn is from 25,000 to 80,000
  • M w 80,000- 200,000
  • M n 35,000-70,000.
  • the polydispersity value of the M w /M n latex is from 2.0 to 5.0, preferably the polydispersity value is from 2.0 to 4.0, most preferably from 2.0 to 3.5.
  • the polydispersity value below 2.0 results in deterioration of polymer elastic properties and is not typical for elastomers produced by polymerization in emulsion.
  • polydispersity value above 5.0 an increase of modulus at 300% and 500% stretching occurs, which reduces the comfort of the glove during operation.
  • the butadiene-nitrile latexes are aqueous dispersions of copolymers of conjugated dienes and ethylene unsaturated monomers comprising a nitrile group, such as acrylic acid nitrile (AAN), produced by the polymerization in emulsion.
  • AAN acrylic acid nitrile
  • the butadiene-nitrile latexes comprise other monomers as well.
  • Conjugated dienes from which latexes are derived may include 1,3 -butadiene, 2-chloro-l,3-butadiene and 2-methyl-l,3-butadiene, 2,3-dimethyl-l,3-butadiene, 1,3- pentadiene, 2-methyl-3-ethyl-l,3-butadiene, 3-methyl-l,3-pentadiene, 2-methyl-3- ethyl- 1,3 -pentadiene, 1,3 -hexadiene, 2-methyl-l,3-hexadiene, 1,3-heptadiene, 3- methyl-l,3-heptadiene, 1,3-octadiene, 3-butyl-l,3-octadiene, 3,4-dimethyl-l,3- hexadiene, 4,5-diethyl-l,3-octadiene, phenyl-l,3-butadiene, 2, 3
  • Preferred conjugated dienes are 1,3 -butadiene, 2-methyl-l,3-butadiene, and 1,3- pentadiene.
  • the most preferred conjugated diene is 1,3 -butadiene.
  • the content of monomer that is conjugated diene in the butadiene nitrile carboxylated latex depends on the further use of the latex and can be at any amount.
  • the amount of conjugated diene monomer being introduced is typically within the range of 50 wt% to 85 wt%, preferably 60 to 75 wt%, most preferably 63 to 70 wt% per 100 wt% of a monomer mixture.
  • Acrylic acid nitrile is used as a co-monomer for latex production, but other ethylene unsaturated monomers comprising a nitrile group can also be used, the presence of which provides low solubility value of the polymer in non-polar solvents such as liquid hydrocarbons and petroleum oils. It is also known that the nitrile - comprising monomer gives the latex film the necessary strength properties. Acrylonitrile, methacrylonitrile, a-cyano-ethyl acrylonitrile, and fumaronitrile can be used as ethylene unsaturated monomers comprising the nitrile group. Acrylic acid nitrile is the most preferred variant.
  • the content of at least one ethylene unsaturated monomer comprising a nitrile group for the purpose of preparation of butadiene nitrile carboxylated latexes depends on the further use of the latex and can be at any amount.
  • the amount of at least one ethylene unsaturated monomer comprising a nitrile group is typically from 10 to 45 wt%, preferably from 15 to 40 wt%, more preferably from 25 to 35 wt% per 100 wt% of a monomer mixture.
  • the latexes used to produce film products by ionic deposition preferably comprise a carboxylating agent of the type of unsaturated carboxylic acids, as the presence of carboxyl group in the polymer phase allows for more efficient combined curing of a latex film, since, on the one hand, ionic deposition causes the polymer cross-linking due to the interaction between copolymer carboxyl groups and electrolyte coagulant cation deposited on a mold conforming to an article. On the other hand, the chemical bonds being formed in the polymer matrix in the presence of curing agents.
  • Carboxyl-comprising polymers in ion deposition behave like polymer electrolytes whose reactivity depends on the degree of dissociation of carboxyl groups and increases with increasing pH value.
  • carboxylating agents in the monomer composition results in a decrease in the butadiene content in the reaction mixture and a decrease in the hard-to-remove high-boiling byproducts in the dispersion phase from the latexes at the degassing stage.
  • the carboxylating agent contained in the monomer mixture is selected from the group of ethylene unsaturated carboxylic acids.
  • alpha(methylene)carboxyl-comprising acids or mixtures thereof such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid or mixtures thereof, are used as carboxylating agents.
  • Acrylic or methacrylic acids are preferred carboxylating agents.
  • MAK methacrylic acid
  • the content of a monomer based on unsaturated carboxylic acids in glove latex is from 2 to 10 wt%, preferably from 2 to 7 wt%, most preferably 3 to 7 wt% per 100 wt% of a monomer mixture.
  • various functional additives introduced into the monomer mixture during the emulsion polymerization process may be present in the latex composition and determined by suitable means.
  • Such compounds include, in particular, emulsifiers, initiators, chain-terminating agents, defoamers and other additives involved in the polymerization process.
  • Surfactants of various nature like anionic, nonionic, cationic and amphoteric ones can be used as emulsifiers in the synthesis of carboxylated latexes for use in the manufacture of articles with the ion deposition method.
  • the anionic emulsifiers contained in the butadiene nitrile carboxylated latex are generally alkyl(aryl)sulfonic acid salts selected from the group of alkylbenzene sulfonates, aliphatic sulfonates, olefin sulfonates, and alkyl sulfuric acid salts - alkyl sulfates.
  • various co-emulsifiers in particular non-ionic ethylene oxide compounds with fatty alcohols such as lauryl, myristin, cetyl, stearin and olein alcohols, may additionally be present in the latex.
  • the latex comprises emulsifiers from the group of alkylbenzene sulfonates and alkyl sulfates of alkali metals.
  • the most preferred anionic emulsifier is sodium alkylbenzene sulfonate, which can be either an individual compound, such as dodecylbenzene sulfonate, or a mixture of homologues of different molecular weight, preferably with an alkyl radical length from CIO to Cl 8.
  • the emulsifiers of butadiene nitrile carboxylated latex are present in doses from 1.0 to 10 wt%, the preferred emulsifier dosage range is 0.8 to 8.0 wt%, the most preferred range is from 1.5 to 6.0 wt% per 100 wt% of the monomers comprising the carboxylated copolymer.
  • elements of the redox initiating system may be present in a latex composition, whereby transition metal salts such as iron, cobalt or nickel in combination with a suitable complexing agent such as sodium ethylenediaminetetraacetate, sodium nitrile triacetate, trisodium phosphate or tetrapotassium diphosphate, may be additionally determined.
  • transition metal salts such as iron, cobalt or nickel
  • a suitable complexing agent such as sodium ethylenediaminetetraacetate, sodium nitrile triacetate, trisodium phosphate or tetrapotassium diphosphate
  • the latex also contains polymerization initiators such as peroxo- and azocompounds.
  • Peroxy compounds include hydrogen peroxide, peroxodisulfates, peroxodiphosphates, hydroperoxides, peracids, peracid esters, peracid anhydrides, and peroxides with two organic residues.
  • Sodium, potassium and ammonium salts can be used as salts of persulfuric acid and perphosphoric acid.
  • Suitable organic hydroperoxides are, for example, tretbutylhydroperoxide, cumene hydroperoxide and p-mentangydroperoxide.
  • Dibenzoylperoxide, 2,4, -dichlorobenzoylperoxide, ditertbutylperoxide, dicumyl peroxide, tertbutylperbenzoate, tertbutylperacetate, etc. are suitable peroxides with two organic residues.
  • Azo-bis-isobutyronitrile, azo-bis- valeronitrile, and azo-bis-cyclohexannitrile are suitable azo- compounds.
  • the amount of an initiator of hydroperoxide type may be from 0.01 to 0.5 wt% per 100 wt% of a monomer mixture, preferably from 0.02 to 0.3 wt%, most preferably from 0.02 to 0.2 wt%.
  • the amount of an initiator of persulfate type may be from 0.1 to 1.5 wt% per 100 wt% of a monomer mixture, preferably from 0.15 to 1.0 wt%, most preferably from 0.15 to 0.6 wt%.
  • Preferred redox initiating systems are, for example: 1) potassium peroxodisulfate in combination with triethanolamine, 2) ammonium peroxodiphosphate in combination with sodium metabisulfite (Na2S20s), 3) p- menthane hydroperoxide/sodium formaldehyde sulfoxylate (rongalite C) in combination with divalent iron sulfate (FeSO. ⁇ ), sodium ethylenediamine acetate and trisodium phosphate; 4) cumene hydroperoxide/sodium formaldehyde sulfoxylate in combination with divalent iron sulfate (FeSO. ⁇ ) and complexing agent sodium ethylenediaminoacetate and trisodium phosphate buffer.
  • the mole amount of the reducing agent is between 50-500% per mole amount of the initiator used and is 0.015-0.02 wt%.
  • the amount of complexing agent depends on the amount of transition metal used and is usually equimolar to it.
  • the latex is produced in the presence of a chain-terminating agent typical for polymerization in emulsion.
  • the chain-terminating agents can represent, in particular, organic thiocompounds which are selected from a series of compounds such as n-hexylmercaptan, n-octylmercaptan, n-dodecylmercaptan, tert-dodecylmercaptan, n- hexadecylmercaptan, n-tetradecylmercaptan, tert-tetradecylmercaptan, as well as xanthogendisulfides, in particular such as dimethylxanthogendisulfide, diethylxanthogendisulfide and diisopropylxanthogendisulfide, thiuram disulfides - tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide; halogenated hydrocarbons such as chloroform, carbon
  • Tertiary dodecyl mercaptan is the most common and commonly available chainterminating agent.
  • All of the listed chain-terminating agents may be present individually or in various combinations (two or more) in total amounts up to 1.0 wt%, in particular from 0.1 to 1.0 wt% per 100 wt% of a monomer mixture, preferably from 0.15 to 1.0 wt%, most preferably from 0.18 to 0.8. If a content of the chain-terminating agent is less than the indicated range per 100 wt%, the physical and mechanical properties of the dip-molded articles will be significantly lower, and if a dosage of the chainterminating agent exceeds the indicated range, the stability of the colloidal system during synthesis process will decrease, resulting in coagulum formation.
  • the buffers are used to ensure pH stability during the synthesis process, which can be detected in the latex composition.
  • Phosphates and pyrophosphates of alkali metals such as trisodium phosphate, sodium pyrophosphate, are used as such substances.
  • the amount of buffer is 0.01 to 1.0 wt% per 100 wt% of the monomer mixture, preferably 0.2 to 0.8 wt%, most preferably 0.3 to 0.6 wt%.
  • a latex may comprise pH-regulating additives, anti-ageing agents, antiseptics preventing the growth of fungi and bacteria in the aquatic environment, etc., introduction of which is possible during latex synthesis and conditioning, as well as foam suppressants, including silicone oligomers emulsions, as well as mineral oils, alcohols, esters, alkylaminosulfonates in doses from 0,02 vol%.
  • the films made of latex have no defects (overlaps, perforations, cracks) and have high physical and mechanical parameters: during combined (salt and sulfur) curing the strength of latex films is at least 30 mPa combined with relative elongation of at least 500%; the produced films are thin, strong and transparent.
  • a process of butadiene nitrile latex production comprises the copolymerization and can be carried out in a semi -batch mode, where monomers and other reagents are gradually introduced into a reactor at a certain rate, but the unloading of the finished latex is carried out in a single step.
  • the latex production can also be carried out in a batch mode, with simultaneous introduction of initial reagents into the reactor followed by the unloading of the resulting latex after copolymerization. Also, the latex production can be carried out in a continuous mode: the polymerization process is performed in a cascade of reactors connected in series, wherein the copolymerization is performed in several reactors, with the reagent flows moving at the same rate. The resulting latex comes out from the cascade of reactors at the same rate.
  • the reactor for performing the reaction can be a perfect mixing reactor or displacement reactor.
  • the copolymerization process can be carried out using a seed, where various monomers can be used for the synthesis of the seed latex, including the monomers the same as or different from those used in the basic synthesis, as well as inorganic pigments, such as silicone dioxide of any origin.
  • the latex seed can be synthesized in situ directly in the polymerization vessel prior to the basic reaction or pre-synthesized in a separate vessel and then fed into the reaction zone in a required amount.
  • the dosage of the seed latex may be from 0.01 to 15 wt% per the total amount of monomers, preferably from 1 to 10 wt%, most preferably from 2 to 5 wt%, and the particle size of the seed latex may be, without limitation, 10-90 nm, preferably 20-80 nm, most preferably 30-70 nm.
  • the monomers that can be used for the synthesis of a seed latex are ethylene unsaturated monomer either as a single monomer or mixed with other ethylene unsaturated monomers or conjugated dienes.
  • the ethylene unsaturated monomers for the seed latex are selected from nitriles: acrylonitrile, methacrylonitrile, a-cyano-ethyl-acrylonitrile, and fumaronitrile.
  • aromatic ethylene unsaturated compounds can be used such as styrene and a-methyl styrene; as well as unsaturated acrylic carboxylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate and glycidyl methacrylate; ethylene unsaturated amides such as acrylamide, methacrylamide, N,N-dimethylacrylamide and N- methylolacrylamide; vinyl carboxylates such as vinyl acetate; ethylene unsaturated amines such as methylaminoethyl(met)acrylate, dimethylaminoethyl(met)acrylate, 2- vinyl carboxylates such as vinyl a
  • carboxylating agents - ethylene unsaturated acids such as monobasic acids: (meth)acrylic acid and crotonic acid; dibasic acids: maleic acid, fumaric acid, itaconic acid, as well as anhydrides and esters thereof, such as monoesters of dibasic acids (hemi-esters) such as methyl maleate, methylitaconate is acceptable for making a seed latex.
  • the following monomers are preferred for the production of a seed latex: styrene, acrylonitrile, methyl methacrylate, butyl acrylate, 1,3 -butadiene, ethylene unsaturated acid or mixtures thereof.
  • seeds are latexes of copolymers of polystyrene, polybutadiene, carboxylated copolymer latexes based on acrylonitrile, styrene or methyl methacrylate, where ethylene unsaturated acid is present in an amount up to 10 wt% of the total monomer weight.
  • inorganic pigments with a particle size of 50 to 100 nm such as silicon dioxide of any nature, can be used as a seed.
  • anion-active emulsifiers such as sodium lauryl sulfate, fatty acid sulfoether salts, sodium alkylbenzene sulfonate, as well as non-ionic emulsifiers such as oxyethylated fatty alcohols or oxyethylated alkylphenols can be used in the process of producing a seed latex.
  • Sodium lauryl sulfate and/or sodium alkyl benzene sulfonate are preferred.
  • the amount of an emulsifier used in the synthesis of a seed latex is from 1 wt% to 20 wt% per the total amount of monomers, in preferable embodiment from 2 wt% to 10 wt%.
  • the chelating agent sodium ethylenediaminetetraacetate (Trilon B) or inorganic salts such as trisodium phosphate, sodium pyrophosphate, can also be used to produce a seed latex.
  • the producing of a seed latex is carried out in the presence of an initiator and chain-terminating agent, typical for the emulsion polymerization process.
  • the initiator is chosen from water-soluble persulfates, preferably using ammonium or potassium persulfate.
  • the amount of the initiator being used ranges from 0.1 to 10 wt%, preferably from 0.5 to 2 wt% per the total amount of monomers.
  • the most common and widely available chain-terminating agent, mercaptan can be used in amounts of up to 5 wt%, preferably from 0.2 to 2 wt%.
  • a composition can be prepared for making dip-molded film articles.
  • the composition comprises a latex and curing agents.
  • other components can be introduced into the composition, depends on the further use of the latex article.
  • a latex composition comprising 96-97% of a latex per dry matter, 3.0-3.6% of curing agents, 0.2-0.3% of fatty alcohol sulfoether salt or other suitable emulsifier and 0.1 -0.2% of antioxidant per 100% of total dry matter weight of the composition can be prepared to make gloves.
  • Sulfur, zinc oxide, zinc diethyldithiocarbamate, titanium dioxide can be used as curing agents for the composition for film articles.
  • the curing agents are introduced into the latex composition in the form of dispersions in the emulsifier.
  • the emulsifier is chosen from a group of any suitable emulsifiers.
  • Emulsifiers introduced into latex formulations act as stabilizers of the size of dispersed particles and prevent them from agglomeration and precipitation from dispersions.
  • 50% dispersions of each of the curing agents are prepared, where the dosage of the dispersing agent is 1.0-8.0 wt%, preferably 2.0-6.0 wt%, most preferably 3.0-5.0 wt% per 100 wt% of an ingredient being dispersed, higher emulsifier dosages result in unproductive costs, and lower emulsifier dosages do not provide the desired level of aggregative stability of the dispersion. It is also possible to prepare a complex (total) dispersion of curing agents, which also comprises an antioxidant additive.
  • the additives of anti-ageing agents based on phenols, sterically hindered phenols, diphenylamine derivatives, organophosphorus compounds, thioesters, etc. can be introduced into dispersions, main purpose of which is to suppress interaction processes of formed peroxide radicals with unsaturated polymer bonds.
  • antioxidants based on phenols, sterically hindered phenols, diphenylamine derivatives, organophosphorus compounds, thioesters, etc.
  • dispersions main purpose of which is to suppress interaction processes of formed peroxide radicals with unsaturated polymer bonds.
  • the most common antioxidants used to suppress thermo-oxidative degradation are 2,2-methylene-bis(4-methyl-6- butylphenol, 4-methyl-2,6 ditertbutylphenol, 4,6-bis(octylthiomethylphenol)-o-cresol, and others.
  • the antioxidants are introduced into latexes as dispersions in dosages of 0.10-0.50 wt%, preferably 0.20-0.45 wt%, most preferably 0.25-0.45 wt% per latex polymer.
  • the latex composition for film articles is prepared as follows: dispersions of curing agents in aqueous emulsifier solution are introduced in random sequence into the latex, which was distilled and neutralized to a pH value of 8.0-12.0.
  • the most preferred embodiment is the combination of 0.6 wt% of sulfur, 1.5.0 wt% of zinc oxide, 1.0 wt% of titanium dioxide, 1.0 wt% of zinc diethyldithiocarbamate, and 0.2 wt% of an antioxidant.
  • the latex composition for film articles according to the proposed invention has a dry matter weight fraction of 5 to 45%, preferably from 8 to 35%, most preferably from 10 to 33%.
  • the pH value of the latex composition is maintained at 8-12, preferably at 8.0- 10.0, most preferably at 8.0-9.5.
  • the required pH level of the composition is achieved by introducing of neutralizing agents having 1-10% concentration selected from hydroxides of sodium, potassium, ammonia or mixtures thereof.
  • the resulting latex composition is subjected to mature for 24 hours at 20-25°C with periodic careful stirring at interval of 3-5 hours.
  • the dip-molded articles can be made by direct dipping of a mold in the latex composition or with the ion deposition method.
  • the ion deposition method is used, where a mold conforming to an article is dipped into a coagulating electrolyte solution (a), where the electrolyte being deposited on the mold surface, for that, the mold is dipped into the electrolyte solution for 2-5 seconds, followed by the drying at 25°C for 3-5 minutes.
  • the mold with an electrolyte layer (a) is dipped into a latex composition, where polymer gel being deposited on the mold surface for 5 seconds (b), which ensures optimum thickness of the deposited polymer gel (0.05- 0.06 mm) and weight of the obtained product not more than 3.5 grams. After that, the mold with the polymer gel layer is subjected to the heat treatment (c).
  • the coagulating solution is an aqueous or alcohol electrolyte solution, it is also possible to use a mixture of aqueous and alcohol solution as a solvent.
  • the electrolyte concentration in the solution is 5 to 50%, preferably 10 to 40%.
  • halides of 2- and 3 -valent metals such as barium chloride, calcium chloride, magnesium chloride, zinc chloride, aluminum chloride, as well as barium, calcium, zinc nitrates; barium, calcium, zinc acetates; calcium, magnesium, aluminum sulfates, may be used. Calcium nitrate and calcium chloride and mixtures thereof are preferred.
  • the process of moisture evaporation and cross-linking of polymer chains in latex film (curing) takes place.
  • the heat treatment generally, is carried out in two stages: the first stage of moisture evaporation is carried out at temperature from 70 to 150° C for 1-20 minutes, and the second - direct curing - at temperature 100-180° C for 5-30 minutes.
  • the determination of a molecular weight of the polymer separated from latex was carried out according to the GOST 33418-2015 using 2 serially connected AGILENT PLGEL MIXED-C columns, 7.5 X 300 MM, 5 pm.
  • Column thermostat temperature was 40 degrees Celsius; eluent was 100% tetrahydrofuran (THF).
  • the injection volume was 100 pl, refractometric detection, detector cell temperature was 40° C, analysis time was 30 min.
  • the column calibration according to polystyrene standards was within the range of 580-482,000.
  • the method is based on dissolving a rubber charge, which was previously separated and dried from latex, in methyl ethyl ketone at 21 ⁇ 3 °C, separation of the gel fraction with a Capron cloth filter K-52 and gravimetric determination of the polymer content in the sol fraction.
  • the produced rubber solution is filtered through a cloth filter K-52 3 into a beaker and 20 cm of the filtered solution is immediately taken into a previously weighed weighting cup.
  • the solution is evaporated using a bath.
  • the weighing cup with dry residue is transferred to a desiccator and dried to constant weight at 105 ⁇ 3°C.
  • the weighing cups with dry residue taken out of the drying oven are kept in a desiccator and weighed, determining the weight of each weighing cup with an accuracy of 0.0002 g.
  • X — - - - , where: m K x 20 mj - weight of the weighing cup with a dry residue, g; mo - weight of the weighing cup, g; m K - weight of the rubber taken for the test, g.
  • a latex sample in amount of at least 500 cm is filtered through a double layer of gauze and poured into a beaker with a diameter of 100 to 150 mm to produce samples by ionic deposition.
  • the latex surface is cleaned from the resulting film with a filter paper.
  • Spatulas are cut from the filters "blue ribbon” or “red ribbon” with a cutting die in accordance with GOST 12580-78. Then they are dipped to the full length in the fixing agent (40% calcium nitrate solution) for 5 seconds, carefully removed and dried for 3 minutes.
  • the drops of fixing agent are removed from the lower end of the spatulas with the filter paper and dipped into latex one by one, making sure that the spatulas do not touch the walls of the beaker.
  • the gel settling time in the latex is 3 min.
  • the spatulas coated with latex raw gel are kept suspended in the air for 5 min.
  • spatula is fixed in the clamps of the tensile machine and the relative elongation at break is determined according to GOST 12580.
  • the results of the individual determinations are calculated with an accuracy of up to three significant digits.
  • the test result is the arithmetic mean of 10 parallel determinations of elasticity, where the acceptable difference between the two most different determinations does not exceed 150%. If the difference between the two most different determinations is more than 150%, these two results are discarded. The number of determinations after discarding shall be not less than 6, otherwise the test shall be repeated.
  • test result is rounded off with 50 % increments and recorded as numbers, for example: 200; 250; 300; 350, etc.
  • This parameter was determined by drying a charge of a latex sample having a certain weight to constant weight according to GOST 25709.
  • the determination of pH value is carried out in accordance with GOST 11604.
  • This parameter was determined in accordance with GOST 20216-74.
  • the appearance of the film was evaluated visually by the presence of defects in the form of cracks, etc.
  • This parameter was determined by coagulum amount in 1 liter of latex after keeping it in a tightly closed container for six months at 25 and 50° C. For that, after expiry of the test period, the latex was filtered through a Capron mesh, the coagulum separated from the latex was washed, and dried to a constant weight at 105°C. The amount of coagulum expressed as a percentage of the total polymer weight in the sample analyzed was considered as a measure of the latex storage stability.
  • Latex viscosity was measured with the Brookfield viscometer according to ISO 2555: 1989.
  • the determination was carried out with a method consisting in manual shaking of a cylinder with a latex and subsequent measurement of foam volume formed in the cylinder. To this end, 10 ml of the latex was placed in a 25 ml measuring cylinder with a diameter of 20 mm, the cylinder was closed and shaken sharply 10 times with constant force, after which the volume of foam formed was determined.
  • This parameter was determined by the coagulum amount in the composition after its periodic stirring for 24 hours.
  • the agents in the form of 50% dispersions were added in the amount of 0.6 wt% of sulfur, 1.5 wt% of zinc oxide, 1.0 wt% of zinc diethyl dithiocarbamate, 1.0 wt% of titanium dioxide per 100 wt% of the polymer.
  • the composition maturation was carried out for 24 hours at 18-22°C with the constant stirring at a rate of 60 rpm. After completion of maturation period, the composition was filtered through a Capron mesh, separated coagulum was washed, and dried to constant weight at 105°C.
  • the amount of coagulum expressed as a percentage of the total polymer weight in the sample being analyzed was considered as a measure of latex resistance to the introduction of curing agent dispersion.
  • This parameter was determined by the amount of coagulum formed by adding a 5% alkaline solution to the latex. To this end, 100 ml of 5% KOH solution was introduced into 1 liter of the latex, previously diluted to a dry residue of 28-32%, at a rate calculated on the basis of 5 ml/min, while stirring at a rate of 60 rpm. After completion of KOH solution feeding period, the latex was filtered through a Capron mesh, the separated coagulum was washed and dried to a constant weight at 105°C. The amount of coagulum expressed as a percentage of the total polymer weight in a sample being analyzed was considered as a measure of latex resistance to the introduction of 5% KOH solution.
  • This parameter was determined organoleptically by finger contact with the cured film. The result was evaluated from 0 to 5, where 0 is no stickiness, 5 is high stickiness.
  • a coagulant mixture for the ionic deposition process was prepared by mixing 40 wt% of calcium nitrate and 60 wt% of water.
  • the 50% dispersions of curing agents were prepared in a ball mill: the sulfur dispersion was prepared for 72 hours by mixing 100 wt% of sulfur, 100 wt% of water and 5 wt% of sodium alkylbenzene sulfonate.
  • the dispersions of titanium dioxide, zinc oxide, and zinc diethyldithiocarbamate were prepared similarly with the only difference that the dispersing period was 24 hours.
  • the latex mixture was prepared by mixing dispersions of curing agents so that the sulfur content was 0.6 wt% of sulfur, 1.0 wt% of titanium dioxide, 1.5 wt% of zinc oxide and 1.0 wt% of zinc diethyldithiocarbamate per 100 wt% of dry matter, pre-diluted to 25% latex concentration at 18-25°C. The mixture was incubated under constant stirring at 60 rpm for 24 hours.
  • a porcelain dipping mold was preheated to 55°C and immersed in a solution of 20% calcium nitrate coagulant for 3 seconds. Then the mold was held in the air for 5 minutes and dipped into the latex mixture (17.3) for 5 seconds. The resulting polymer layer was then air-dried for 5 minutes followed by drying at 80°C for 20 minutes and curing at 110°C for 20 minutes.
  • This parameter was determined by laser diffraction method using the Microtrac device according to ISO 13320-1.
  • an aqueous phase comprising 110 wt% of deoxygenated and desalinated water, 2.5 wt% of emulsifier (1), sodium alkylbenzene sulfonate (ABS) and 0.4 wt% of trisodium phosphate (TSP), 0.007 wt% of Trilon B complexing agent and 0.0018 wt% of iron sulfate.
  • emulsifier (1) sodium alkylbenzene sulfonate (ABS) and 0.4 wt% of trisodium phosphate (TSP), 0.007 wt% of Trilon B complexing agent and 0.0018 wt% of iron sulfate.
  • ABS sodium alkylbenzene sulfonate
  • TSP trisodium phosphate
  • the apparatus was purged with nitrogen followed by the introduction of a total monomer mixture comprising 65 wt% of butadiene, 30 wt% of acrylic acid nitrile, 5 wt% of methacrylic acid, as well as a tertiary dodecylmercaptan (TDM) chain-terminating agent dissolved in acrylic acid nitrile in the amount of 0.2 wt% and 0.02 wt% of pinane hydroperoxide initiator (PHI) into it.
  • TDM tertiary dodecylmercaptan
  • an initiator emulsion was prepared separately for feeding during the process, consisting of 0.01 wt% of PHI, 0.5 wt% of sodium alkylbenzene sulfonate emulsifier and 5 wt% of water, and an activator solution comprising 0.018 wt% of rongalite in 5 wt% of water.
  • the initiating system and tertiary dodecylmercaptan at 15°C
  • rongalite solution was fed into the reactor, which was considered the starting of the polymerization reaction.
  • each i of the prepared initiator emulsion volume was fed into the apparatus.
  • the latex synthesis was carried out similarly to Example 1 , except that the content of sodium alkylbenzene sulfonate was 2.8 wt%, ratio of the monomer phase components was 73 wt% of butadiene, 25 wt% of acrylic acid nitrile, 2 wt% of methacrylic acid, 0.3 wt% of TDM and 0.015 wt% of PHI, and 0.4 wt% of sodium sulfate.
  • the feeding of initiator emulsion in 0.2 wt% of alkylbenzene sulfonate was carried out at 25% conversion.
  • the polymerization process was carried out at 20°C until the conversion rate of 99.8% was reached within 28 hours. Weight fraction of dry matter in a latex before distillation of residual monomers was 46.8 %.
  • the neutralization of the latex to pH 8.3 was carried out as in Example 1.
  • the latex synthesis was carried out similarly to the Example 1, except that sodium alkyl sulfonate was used as an emulsifier in the amount of 2.2 wt%, the ratio of monomer phase components was 65 wt% of butadiene, 32 wt% of acrylic acid nitrile, 3 wt% of methacrylic acid, 0.3 wt% of TDM and 0.015 wt% of PHI, and 0.2 wt% of sodium pyrophosphate.
  • 0.2 wt% of sodium alkylbenzene sulfonate emulsifier was used to prepare the initiator emulsion.
  • the feeding of an initiator emulsion was carried out at 30% and 60% conversion.
  • the polymerization process was carried out at 24°C until reaching 99% conversion within 30 hours.
  • the weight fraction of dry matter in a latex before distillation of residual monomers was 46,6 %.
  • the latex synthesis was carried out similarly to the Example 1, except that sodium lauryl sulfate was used as an emulsifier in the amount of 2.2 wt%.
  • the ratio of monomer phase components was 67 wt% of butadiene, 30 wt% of acrylic acid nitrile, 3 wt% of methacrylic acid, 0.4 wt% of TDM and 0.015 wt% of PHI, and 0.2 wt% of potassium pyrophosphate.
  • the feed of an initiator emulsion in 0.2 wt% of sodium lauryl sulfate was carried out at conversion rates of 20% and 50%.
  • the polymerization process was carried out at 28 °C until reaching 99 % conversion within 29 hours.
  • the weight fraction of dry matter in a latex before distillation of residual monomers was 46,0%.
  • the latex was neutralized to pH 8.5 with a 10% ammonia solution.
  • the latex synthesis was carried out similarly to the Example 1, except that the content of sodium alkylbenzene sulfonate in the aqueous phase was 2.3 wt%, the ratio of monomer phase components was 50 wt% of butadiene, 45 wt% of acrylic acid nitrile, 5 wt% of methacrylic acid, 0.75 wt% of TDM and 0.015 wt% of PHI, and 0.15 wt% of sodium pyrophosphate.
  • the TDM chain-terminating agent was fed fractionally at 3 points: 0.6 wt% at the beginning of the process and 0.075 wt% each at 25% and 75% conversion.
  • the initiator emulsion To prepare the initiator emulsion, 0.4 wt% of sodium alkylbenzene sulfonate was used. The feed of the initiator emulsion was carried out at 25% and 60% conversion. The polymerization process was carried out at 42°C to the conversion rate of 99.8% for 15 hours. The weight fraction of dry matter in a latex before distillation of residual monomers was 46.9 %, pH value of the latex after neutralization with ammonia was 8.5.
  • the latex synthesis was carried out similarly to Example 1, except that ABS content in the aqueous phase was 2.5 wt%, the ratio of monomer phase components was 60 wt% of butadiene, 33 wt% of acrylic acid nitrile, 7 wt% of methacrylic acid and 0.18 wt% of TDM, 0.015 wt% of PHI, and 0.8 wt% of potassium pyrophosphate.
  • To prepare the initiator emulsion 0.2 wt% sodium alkylbenzene sulfonate was used. The feed of the initiator emulsion was carried out at 30% and 55% conversion. The polymerization process was carried out at 35°C up to 99.8% conversion, weight fraction of dry matter in latex was 47.0%, pH after neutralization with ammonia was 8.0.
  • the latex synthesis was carried out similarly to Example 1 , except that the ABS content in the aqueous phase was 4.0 wt%, the ratio of monomer phase components was 68 wt% of butadiene, 22 wt% of acrylic acid nitrile, 10 wt% of methacrylic acid and 0.18 wt% of TDM, 0.015 wt% of PHI, 0.6 wt% of potassium pyrophosphate.
  • To prepare the initiator emulsion 0.2 wt% of sodium alkylbenzene sulfonate was used. The feed of the initiator emulsion was carried out at 30% and 55% conversion. The polymerization process was carried out at 29°C to the conversion of 99.8% for 28 hours.
  • the weight fraction of dry matter in a latex before distillation of residual monomers was 47.6 %, pH after neutralization was 8.2.
  • the desired latex was produced in a 2-liter steel autoclave equipped with an agitator and a thermostatic jacket.
  • a seed latex (Prescription 1), 90 wt% of water, initiator - 0.6 wt% of potassium persulfate, 0.2 wt% of tetra sodium pyrophosphate, complexing agent - 0.05 wt% of disodium salt of ethylenediaminetetraacetic acid, were loaded.
  • a monomer mixture consisting of 30 wt% of acrylic acid nitrile, 4 wt% of methacrylic acid, 0.4 wt% of TDM was prepared in a separate reactor equipped with an agitator and a thermostatic jacket.
  • TDM to which 52 wt% of butadiene was introduced after purging the reactor with nitrogen.
  • the reactor with monomers was cooled to 5°C after loading of all ingredients.
  • a mixture of 30 wt% of water and 2.0 wt% of sodium alkylbenzene sulfonate emulsifier was prepared in a separate container.
  • the autoclave comprising water-soluble ingredients and a seed was heated to 30 °C, after that the first monomer mixture was continuously fed into it, and an aqueous solution of the emulsifier was fed in parallel for 5 hours.
  • the polymerization temperature was 40°C.
  • the second part of the monomer mixture consisting of 13 wt% of butadiene, 1 wt% of MAA and 0.4 wt% of TDM was started.
  • the monomer mixture was fed for 5 hours with the parallel dosing of an emulsifier solution mixture.
  • the temperature in the polymerizer was maintained at 38-40° C, polymerization was carried out to a dry residue of 47.4 wt% (99.2% conversion).
  • the latex synthesis was carried out similarly to the Synthesis 8 on a seed (Prescription 2), except that the first monomer mixture comprised 50 wt% of butadiene and 0.5 wt% of TDM, 0.2 wt% of tetra potassium pyrophosphate was used as a buffer and sodium alkylbenzene sulfonate dosage was 3.0 wt%.
  • the second monomer mixture comprised 15 wt% of butadiene.
  • the monomer conversion was 99.1% and the weight fraction of dry matter was 48.0%.
  • the latex synthesis was carried out similarly to the example 8 on a seed (Prescription 3), except e that 0.1 wt% of pinane hydroperoxide was used as well as an initiator and activating complex comprising 0.005 wt% of iron sulfate and 0.05 wt% of rongalite in the presence of 0.8 wt% of trisodium phosphate, and 2.5 wt% of sodium alkyl benzene sulfonate.
  • the monomer conversion was 99.5, weight fraction of latex dry matter was 45.2%.
  • the latex synthesis was carried out similarly to the Example 1, except that content of sodium alkylbenzene sulfonate in the aqueous phase was 6.2 wt%, the ratio of monomer phase components was 60 wt% of butadiene, 33 wt% of acrylic acid nitrile, 7 wt% of methacrylic acid and 1.2 wt% of TDM, 0.02 wt% of PHI, and 0.1 wt% of sodium pyrophosphate.
  • To prepare the initiator emulsion 0.2 wt% sodium alkylbenzene sulfonate and 5 wt% of water were used. The feed of the initiator emulsion was carried out at 30% and 55% conversion. The polymerization process was carried out at 20°C up to conversion rate of 75%, the weight fraction of dry matter in latex was 36.2%, pH after neutralization with ammonia was 8.0.
  • the latex synthesis was performed similarly to the Example 1, except that ABS content in the aqueous phase was 1.8 wt%, the ratio of monomer phase components was 60 wt% butadiene, 33 wt% of acrylic acid nitrile, 7 wt% of methacrylic acid TDM was missing, PHI was 0.025 wt%, and 0.8 wt% of sodium pyrophosphate.
  • To prepare an initiator emulsion 0.2 wt% of sodium alkylbenzene sulfonate and 5 wt% of water were used. The feed of the initiator emulsion was carried out at three points at conversion of 30%, 55% and 90%. The polymerization process was carried out at 40°C up to 100% conversion, the weight fraction of dry matter in latex was 47.8 %, pH value after neutralization with ammonia was 8.0.
  • the latex sample was made by mixing the two samples prepared according the Example 11 and Example 12 in the 1 : 1 ratio per dry matter.
  • the weight fraction of dry matter was 41.3%.
  • the prescriptions and properties of prepared carboxylated butadiene nitrile latexes are presented in the Tables 1 and 4, and the weight fractions of elements in latex films and film properties are presented in the Tables 5 and 6, respectively.
  • latex samples from the Examples 11-13 had lower resistance to the introduction of curing agents and the introduction of 5% KOH solution.
  • the presence of coagulum in the latex was observed for these samples when the dispersion was filtered immediately after synthesis.
  • the latex samples according to the invention are characterized by the values of solubility index A in the range from 0.5 to 22 wt%*nm*mol*g' 1 and polydispersity of latex polymer M w /M n from 2 to 5, are characterized by high level of strength properties of cured latex films.
  • the values of crude gel elasticity are in the optimal range - from 1,000% to 1,600%.
  • the skilled persons know that there is a direct correlation between the raw gel elasticity and the relative elongation of the cured film. With raw gel elasticity values higher than 1,600%, the relative elongation is also very high; products based on such a latex are too soft, sticky, and viscous.
  • the appearance of the crude latex gel according to the present invention is homogeneous; no defects (strokes (coats), cracks, holes, etc.) are noted on the test specimens (spatulas).
  • the specified elasticity values of the crude latex gel according to the present invention demonstrate the high quality of the latex films formed by dipmolding.
  • the stress at 300% elongation for samples of cured films produced from latexes according to the present invention has lower values than for films according to the Comparative examples 11-13, which in turn provides greater comfort and tactile sensitivity when using the gloves.
  • the data presented demonstrate that the proposed technical solution makes it possible to produce films without external defects and increased stickiness.

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Abstract

La présente invention concerne un latex de butadiène-nitrile carboxylé, utilisé pour la fabrication d'articles moulés par immersion, en particulier pour la production de gants en latex à des fins industrielles et médicales. Plus particulièrement, la présente invention concerne un latex pour la fabrication d'articles moulés par immersion, comprenant des motifs structuraux formés à partir d'au moins un monomère qui est un diène conjugué, d'au moins un monomère éthylénique insaturé comprenant un groupe nitrile et d'au moins un monomère qui est un acide carboxylique insaturé, la valeur de l'indice de solubilité (A) calculée par la formule А=100 * p *S /(Mn+Mw) étant comprise entre 0,5 et 22 % en poids*nm*mol*g-1, p représentant la solubilité du polymère dans la méthyléthylcétone (% en poids), S - la taille des particules de latex (nm), Mn - le poids moléculaire moyen en nombre de la fraction du latex de butadiène-nitrile soluble dans le tétrahydrofurane (g/mol), Mw représentant le poids moléculaire moyen en poids de la fraction du latex de butadiène-nitrile soluble dans le tétrahydrofurane (g/mol), la valeur de polydispersité du polymère de latex Mw/Mn étant comprise entre 2,0 et 5,0. La présente invention concerne également une composition de moulage par immersion à base de latex de butadiène-nitrile, un article moulé par immersion et un gant fabriqués à partir de la composition de latex selon la présente invention.
PCT/RU2022/050301 2021-09-27 2022-09-23 Latex de butadiène-nitrile, composition de latex pour moulage par immersion et article moulé par immersion Ceased WO2023048601A1 (fr)

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Citations (8)

* Cited by examiner, † Cited by third party
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