Carboxylic acid-modified nitrile-based copolymer latex, preparation method therefor, latex composition for dip molding comprising same, and molded article

Abstract

The present invention relates to a carboxylic acid-modified nitrile-based copolymer latex having improved latex stability and enhanced workability during the manufacture of a dip-molded article; a preparation method therefor; a latex for dip molding comprising same; and a molded article molded from the latex for dip molding to have improved wearing comfort and tensile properties, wherein the carboxylic acid-modified nitrile-based copolymer latex comprises: 100 parts by weight of monomer units; and 0.5 to 1.0 parts by weight of reactive emulsifier units relative to 100 parts by weight of the monomer units, and has a particle size of 150 nm to 450 nm, as measured by dynamic light scattering analysis.

Description

Carbonic acid-modified nitrile copolymer latex, method for producing the same, latex composition for dip molding and molded article comprising the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0047523, filed April 8, 2024, the entire disclosure of which is incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a carboxylic acid-modified nitrile copolymer latex having improved latex stability and improved workability in the manufacture of dip-molded products, a method for manufacturing the same, a latex for dip-molding comprising the same, and a molded product having improved wearability and tensile properties molded from the latex for dip-molding.

[0005]

[0006] Traditionally, natural rubber was primarily used as a raw material for industrial, medical, and food-grade gloves, as well as products requiring flexibility such as balloons and condoms. However, due to the side effect of natural rubber causing serious protein allergies in some users, nitrile rubber is increasingly replacing natural rubber. Nitrile rubber boasts high chemical resistance and is widely used in work gloves, particularly those used by users handling organic solvents, as well as in medical and food-grade gloves.

[0007] In addition, due to the unstable supply and demand of natural rubber, many glove manufacturing companies are converting their natural rubber glove production lines to nitrile rubber glove production lines, and as awareness of safety increases, the use of disposable gloves manufactured from nitrile rubber is continuously increasing.

[0008] These nitrile rubber gloves are typically manufactured using dip molding latex. However, if the stability of the dip molding latex is low, coagulation may occur. This coagulation increases the defect rate of the final dip molded product, leading to reduced productivity. In severe cases, dip molding itself may become impossible.

[0009] In particular, when temperatures drop below freezing, such as in winter, the stability of dip molding latex deteriorates rapidly, leading to an increase in the formation of coagulation and sedimentation in stored dip molding latex. Therefore, there is a need for measures to improve the storage stability and low-temperature stability of dip molding latex.

[0010] Meanwhile, latex for dip molding is generally manufactured through emulsion polymerization, and emulsifiers are essential for polymerization stability. Consequently, a significant amount of emulsifier remains in the latex, which can cause foaming problems in the resulting dip molded product. To suppress foaming caused by emulsifier residue in the final dip molded product, the leaching process is being strengthened, but this process consumes a lot of water. However, it is difficult to reduce the amount of emulsifier to ensure the polymerization stability of dip molding latex, and even if polymerization stability is secured while reducing the amount of emulsifier, there is a problem that the workability of manufacturing molded products (reduction of syneresis time) is seriously reduced.

[0011] Therefore, a method is required that can reduce the content of emulsifier contained in latex for dip molding while also improving the stability and workability of the latex.

[0012] [Prior Art Literature]

[0013] [Patent Document]

[0014] (Patent Document 1) KR 10-1775798 B1 (August 31, 2017)

[0015]

[0016] The present invention has been devised to solve the problems of the above-mentioned prior art, and aims to provide a carboxylic acid-modified nitrile copolymer latex having excellent stability and molded product manufacturing workability while having a reduced emulsifier content.

[0017] In addition, the present invention aims to provide a method for producing the carboxylic acid-modified nitrile copolymer latex.

[0018] In addition, the present invention aims to provide a latex composition for dip molding comprising the above-described carboxylic acid-modified nitrile copolymer latex.

[0019] In addition, the present invention aims to provide a molded product having excellent manufacturing workability, excellent tensile properties, and suppressed foaming, molded from the latex composition for deep molding.

[0020]

[0021] In order to solve the above problem, the present invention provides a carboxylic acid-modified nitrile copolymer latex, a method for producing the same, a latex composition for dip molding comprising the same, and a molded product.

[0022] (1) The present invention provides a carboxylic acid-modified nitrile copolymer latex comprising 100 parts by weight of a monomer unit; and 0.5 to 1.0 parts by weight of a reactive emulsifier unit relative to 100 parts by weight of the monomer unit, and having a particle size of 150 nm to 450 nm as measured by a dynamic light scattering analysis method, wherein the monomer unit comprises a conjugated diene monomer unit; an ethylenically unsaturated nitrile monomer unit; and an ethylenically unsaturated acid monomer unit, and the reactive emulsifier is at least one selected from the group consisting of sodium 2-methyl-2-propene-1-sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1 sulfonate, and sodium 11-methacryloyl undecane-1-yl-sulfate.

[0023] (2) The present invention provides a carboxylic acid-modified nitrile copolymer latex in the above (1), wherein the particle size of the carboxylic acid-modified nitrile copolymer is 200 nm to 350 nm.

[0024] (3) The present invention provides a carboxylic acid-modified nitrile copolymer latex, wherein the carboxylic acid-modified nitrile copolymer according to (1) or (2) above comprises 40 to 75 wt% of a conjugated diene monomer unit; 10 to 45 wt% of an ethylenically unsaturated nitrile monomer unit; and 1 to 15 wt% of an ethylenically unsaturated acid monomer unit.

[0025] (4) The present invention provides a carboxylic acid-modified nitrile copolymer latex, wherein the reactive emulsifier is sodium 2-methyl-2-propene-1-sulfonate, in any one of the above (1) to (3).

[0026] (5) The present invention provides a carboxylic acid-modified nitrile copolymer latex according to any one of the above (1) to (4), wherein the carboxylic acid-modified nitrile copolymer has a weight average molecular weight of 100,000 g / mol or more and 200,000 g / mol or less.

[0027] (6) The present invention provides a method for producing a carboxylic acid-modified nitrile copolymer latex according to any one of (1) to (5), comprising the steps of: introducing a monomer mixture including a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, and an ethylenically unsaturated acid monomer, and a reactive emulsifier into a reactor and polymerizing the mixture to produce a first polymer latex; and a step (S2) of aging the first polymer latex at a temperature of 60°C to 70°C for 12 to 36 hours, wherein the reactive emulsifier is introduced in an amount of 0.5 to 1.0 parts by weight based on 100 parts by weight of the monomer mixture.

[0028] (7) The present invention provides a latex composition for dip molding comprising a carboxylic acid-modified nitrile copolymer latex according to any one of (1) to (5) above.

[0029] (8) The present invention provides a molded product including a layer derived from a latex composition for deep molding according to (7) above.

[0030]

[0031] The carboxylic acid-modified nitrile copolymer latex according to the present invention has excellent latex stability by including a carboxylic acid-modified nitrile copolymer having a large particle size while having a reduced emulsifier content, and can be included in a latex composition for dip molding to provide excellent workability in the production of molded products.

[0032] In addition, a molded product according to the present invention can be molded from the latex composition for deep molding, and thus has low bubble generation and excellent tensile properties.

[0033]

[0034] The following drawings attached to this specification illustrate specific embodiments of the present invention, and serve to further understand the technical idea of ​​the present invention together with the contents of the invention described above, and therefore the present invention should not be interpreted as being limited to matters described in such drawings.

[0035] Figure 1 is a graph showing changes in particle size during the aging process when producing carboxylic acid-modified nitrile copolymer latex in Examples 1 to 8 and Comparative Examples 1 to 7.

[0036] Figure 2 is a photograph of the film surface of a deep-molded product manufactured in Example 1.

[0037] Figure 3 is a photograph of the film surface of a deep-molded product manufactured in Example 2.

[0038] Figure 4 is a photograph of the film surface of a deep-molded product manufactured in Example 3.

[0039] Figure 5 is a photograph of the film surface of a deep-molded product manufactured in Example 4.

[0040] Figure 6 is a photograph of the film surface of a deep-molded product manufactured in Example 5.

[0041] Figure 7 is a photograph of the film surface of a deep-molded product manufactured in Example 6.

[0042] Figure 8 is a photograph of the film surface of a deep-molded product manufactured in Example 7.

[0043] Figure 9 is a photograph of the film surface of a deep-molded product manufactured in Example 8.

[0044] Figure 10 is a photograph of the film surface of a deep-molded product manufactured in Comparative Example 1.

[0045] Figure 11 is a photograph of the film surface of a deep-molded product manufactured in Comparative Example 2.

[0046] Figure 12 is a photograph of the film surface of the deep-molded product manufactured in Comparative Example 3.

[0047] Figure 13 is a photograph of the film surface of a deep-molded product manufactured in Comparative Example 4.

[0048] Figure 14 is a photograph of the film surface of the deep-molded product manufactured in Comparative Example 5.

[0049] Figure 15 is a photograph of the film surface of the deep-molded product manufactured in Comparative Example 6.

[0050] Figure 16 is a photograph of the film surface of the deep-molded product manufactured in Comparative Example 7.

[0051]

[0052] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0053] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0054] Definition of terms

[0055] In the present invention, the term 'monomer unit' may indicate a component, structure, or substance itself derived from a monomer, and as a specific example, may mean a repeating unit formed within a polymer by a monomer introduced during polymerization of the polymer and participating in the polymerization reaction.

[0056] In the present invention, the term 'polymer' may mean both a homopolymer formed by polymerization from one type of monomer and a copolymer formed by copolymerization from two types of monomers.

[0057] In the present invention, the terms 'latex' and 'emulsion' may mean that a polymer or copolymer polymerized by polymerization exists in a form dispersed in water, and as a specific example, may mean that fine particles of a rubber-like polymer or a rubber-like copolymer polymerized by emulsion polymerization exist in a colloidal state dispersed in a solvent (water), and in the present invention, 'latex' and 'emulsion' may be used interchangeably.

[0058] The term 'composition' as used in the present invention includes a mixture of materials comprising the composition as well as reaction products and decomposition products formed from the materials of the composition.

[0059] In the present invention, the term 'derived layer' may refer to a layer formed from a polymer or copolymer, and as a specific example, may refer to a layer formed from a polymer or copolymer by attaching, fixing, and / or polymerizing the polymer or copolymer on a dip mold during the manufacture of a dip molded product.

[0060]

[0061] Carbonic acid modified nitrile copolymer latex

[0062] The present invention provides a carboxylic acid-modified nitrile copolymer latex that has excellent latex stability while having a reduced emulsifier content and can improve workability in manufacturing a molded product of the latex composition when applied to a latex composition for dip molding.

[0063] According to one embodiment of the present invention, a carboxylic acid-modified nitrile copolymer latex comprises 100 parts by weight of a monomer unit; and 0.5 to 1.0 parts by weight of a reactive emulsifier unit based on 100 parts by weight of the monomer unit, and a carboxylic acid-modified nitrile copolymer having a particle size of 150 nm to 450 nm as measured by a dynamic light scattering analysis method, wherein the monomer unit comprises a conjugated diene monomer unit; an ethylenically unsaturated nitrile monomer unit; and an ethylenically unsaturated acid monomer unit, and the reactive emulsifier may be at least one selected from the group consisting of sodium 2-methyl-2-propene-1-sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1 sulfonate, and sodium 11-methacryloyl undecane-1-yl-sulfate.

[0064]

[0065] In general, the carboxylic acid-modified nitrile copolymer latex that constitutes the latex composition for dip molding is manufactured by emulsion polymerization, and in emulsion polymerization, an emulsifier is essential to lower the interfacial tension between the monomer and the liquid phase to create a stable dispersion, dissolution, and emulsification state between the reaction phase and the continuous phase, provide micelle reaction sites necessary for polymerization through micelle formation, and stabilize the polymer latex emulsion.

[0066] These emulsifiers are typically ionic, low molecular weight emulsifiers such as nonionic, anionic, and cationic. However, these ionic, low molecular weight emulsifiers do not chemically bond with polymers, which adversely affect the properties of the molded product. Specifically, the emulsifier moves from the coagulated latex phase during the manufacture of the molded product to the surface or adhesive interface, easily causing phase separation. In addition, since the emulsifier is highly soluble in water, when the phase-separated emulsifier comes into contact with water, it desorbs, creating flow marks on the surface of the molded product or generating bubbles, which causes quality problems.

[0067] To suppress foaming caused by emulsifier residue in final dip-molded products, the leaching process is being strengthened. However, this process consumes a significant amount of water. However, reducing the amount of emulsifier is difficult to achieve polymerization stability. Even if polymerization stability is secured by reducing the amount of emulsifier, the manufacturing workability (reduced syneresis time) of the molded product is severely reduced.

[0068] In addition, in order to improve the problems caused by the use of the above ionic, low-molecular-weight emulsifier, a reactive emulsifier containing an allyl group as a functional group that reacts with a polymer chain is used. However, the allyl group-containing reactive emulsifier has low reactivity with the polymer chain, so the chemical bonding rate with the polymer chain may be low, and there is a problem that the degree of foaming on the surface of the molded product increases due to the long alkyl chain and sulfonate group in the reactive emulsifier remaining in the latex separately from the polymer chain.

[0069] However, the carboxylic acid-modified nitrile copolymer latex according to one embodiment of the present invention uses a reactive emulsifier containing an alkyl-substituted vinyl group in which an alkyl group is substituted at a double bond participating in a radical reaction without using the above-mentioned ionic, low-molecular-weight emulsifier, and is manufactured through a particle enlargement step, thereby providing a latex composition for dip molding with excellent latex stability and improved workability in manufacturing a molded product.

[0070]

[0071] Hereinafter, a carboxylic acid modified nitrile copolymer latex according to one embodiment of the present invention will be described in more detail.

[0072] According to one embodiment of the present invention, the carboxylic acid-modified nitrile copolymer latex may be a latex in which the carboxylic acid-modified nitrile copolymer is dispersed in a solvent, and the solvent may be an aqueous solvent. As a specific example, the aqueous solvent may be water, and the water may be ion-exchanged water or distilled water.

[0073] According to one embodiment of the present invention, the carboxylic acid-modified nitrile copolymer latex is manufactured by emulsion polymerization in the presence of a reactive emulsifier without using an ionic, low-molecular-weight emulsifier, and the reactive emulsifier may form a chemical bond with a polymer chain formed by a monomer. Accordingly, a latex composition for dip molding according to one embodiment of the present invention, which includes the carboxylic acid-modified nitrile copolymer latex, has excellent latex stability without including an ionic, low-molecular-weight emulsifier, and a molded product manufactured therefrom may have excellent surface properties.

[0074] Meanwhile, in the present invention, the term 'reactive emulsifier unit' may indicate a component, structure, or substance itself derived from a reactive emulsifier, and as a specific example, may mean a unit (part) formed by a reactive emulsifier introduced during polymerization participating in a polymerization reaction and chemically bonding with a polymer chain.

[0075]

[0076] According to one embodiment of the present invention, the carboxylic acid-modified nitrile copolymer includes a conjugated diene monomer unit; an ethylenically unsaturated nitrile monomer unit; an ethylenically unsaturated acid monomer unit, and a reactive emulsifier unit.

[0077] In addition, according to one embodiment of the present invention, the carboxylic acid-modified nitrile-based copolymer may include 0.5 to 1.0 parts by weight of a reactive emulsifier unit based on 100 parts by weight of the total amount of monomer units. When the above range is satisfied, the latex stability of the carboxylic acid-modified nitrile-based copolymer latex including the same may be excellent. In addition, when the amount of the reactive emulsifier unit in the carboxylic acid-modified nitrile-based copolymer is less than the above-mentioned range, the functional group that provides stability to the latex particles in the copolymer main chain is insufficient, so that the stability of the particles is reduced, and the particle size may not be sufficient, so that the workability may not be good when manufacturing a molded product. On the contrary, when the amount of the reactive emulsifier unit in the carboxylic acid-modified nitrile-based copolymer is more than the above-mentioned range, the particle overgrowth may occur due to excessive sulfonation of the latex particles, which may rather worsen the latex stability.

[0078]

[0079] The above reactive emulsifier may be at least one selected from the group consisting of sodium 2-methyl-2-propene-1-sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1 sulfonate, and sodium 11-methacryloyl undecan-1-yl sulfate, and specifically may be sodium 2-methyl-2-propene-1-sulfonate.

[0080]

[0081] According to one embodiment of the present invention, the conjugated diene monomer for forming the conjugated diene monomer unit of the carboxylic acid-modified nitrile copolymer may be at least one selected from the group consisting of 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, and isoprene, and as a specific example, it may be 1,3-butadiene or isoprene, and as a more specific example, it may be 1,3-butadiene.

[0082] According to one embodiment of the present invention, the carboxylic acid-modified nitrile-based copolymer may contain 40 wt% to 75 wt%, 45 wt% to 70 wt%, or 50 wt% to 70 wt% of the conjugated diene-based monomer unit, and within this range, a molded product molded from a latex composition for dip molding comprising a carboxylic acid-modified nitrile-based copolymer latex including the carboxylic acid-modified nitrile-based copolymer has excellent flexibility and wearability, and has excellent oil resistance and tensile strength.

[0083] According to one embodiment of the present invention, the ethylenically unsaturated nitrile monomer forming the ethylenically unsaturated nitrile monomer unit of the carboxylic acid-modified nitrile copolymer may be at least one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, and α-cyano ethyl acrylonitrile, and as a specific example, may be acrylonitrile and methacrylonitrile, and as a more specific example, may be acrylonitrile.

[0084] According to one embodiment of the present invention, the carboxylic acid-modified nitrile-based copolymer may contain 10 wt% to 45 wt%, 15 wt% to 40 wt%, or 20 wt% to 35 wt% of the ethylenically unsaturated nitrile-based monomer unit, and a molded product molded from a latex composition for dip molding including the carboxylic acid-modified nitrile-based copolymer latex containing the same within this range is flexible and has excellent wearability, and has excellent oil resistance and tensile strength.

[0085] According to one embodiment of the present invention, the ethylenically unsaturated acid monomer forming the ethylenically unsaturated acid monomer unit of the carboxylic acid-modified nitrile copolymer may be at least one selected from the group consisting of ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid; polycarboxylic anhydrides such as maleic anhydride and citraconic anhydride; ethylenically unsaturated sulfonic acid monomers such as styrene sulfonic acid; and ethylenically unsaturated polycarboxylic acid partial ester monomers such as monobutyl fumarate, monobutyl maleate, and mono-2-hydroxypropyl maleate, and as a more specific example, it may be at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid, and as a more specific example, it may be methacrylic acid. Additionally, the above ethylenically unsaturated acid monomer can be used in the form of a salt, such as an alkali metal salt or an ammonium salt, during polymerization.

[0086] According to one embodiment of the present invention, the carboxylic acid-modified nitrile copolymer may contain 1 wt% to 15 wt%, 1 wt% to 10 wt%, or 1 wt% to 8 wt% of the ethylenically unsaturated acid monomer unit, and within this range, a molded product molded from a latex composition for dip molding comprising a carboxylic acid-modified nitrile copolymer latex including the carboxylic acid-modified nitrile copolymer has the effect of being flexible, having excellent wearability, and having excellent tensile strength.

[0087]

[0088] According to one embodiment of the present invention, the carboxylic acid-modified nitrile copolymer may have a particle size of 150 nm or more and 450 nm or less, or 200 nm or more and 350 nm or less. In this case, there is an effect of improving the workability of a latex composition for dip molding comprising a carboxylic acid-modified nitrile copolymer latex including the carboxylic acid-modified nitrile copolymer.

[0089] In addition, the above-mentioned carboxylic acid-modified nitrile copolymer may have a weight average molecular weight of 100,000 g / mol or more and 200,000 g / mol or less.

[0090]

[0091] Method for producing carboxylic acid-modified nitrile copolymer latex

[0092] The present invention provides a method for producing the above-described carboxylic acid-modified nitrile copolymer latex.

[0093] According to one embodiment of the present invention, the method for producing the carboxylic acid-modified nitrile copolymer latex includes a step (S1) of introducing a monomer mixture including a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, and an ethylenically unsaturated acid monomer, and a reactive emulsifier into a reactor and polymerizing the mixture to produce a first polymer latex; and a step (S2) of aging the first polymer latex at a temperature of 60°C to 70°C for 12 to 36 hours, wherein the reactive emulsifier is introduced in an amount of 0.5 to 1.0 parts by weight based on 100 parts by weight of the monomer mixture.

[0094] Here, the amount of each monomer used can be appropriately adjusted so that each monomer unit can satisfy the above-mentioned range in the levonic acid-modified nitrile copolymer latex.

[0095] According to one embodiment of the present invention, the conjugated diene monomer, the ethylenically unsaturated nitrile monomer, the ethylenically unsaturated acid monomer, and the reactive emulsifier may be the same as those described above.

[0096]

[0097] Hereinafter, a method for manufacturing the carboxylic acid-modified nitrile copolymer latex according to one embodiment of the present invention will be described in detail step by step.

[0098] (S1) Step

[0099] The above step (S1) is a step for producing a first polymer latex including a carboxylic acid-modified nitrile copolymer by polymerizing a monomer in the presence of a reactive emulsifier, and can be performed by introducing a monomer mixture including a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, and an ethylenically unsaturated acid monomer and a reactive emulsifier into a reactor in a solvent and performing emulsion polymerization.

[0100] At this time, the reactive emulsifier can be added in an amount of 0.5 to 1.0 parts by weight based on 100 parts by weight of the monomer mixture.

[0101] According to one embodiment of the present invention, the emulsion polymerization may be carried out in the presence of at least one additive selected from an emulsifier, a molecular weight regulator, and a polymerization initiator, and the emulsifier may be at least one selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, and as a specific example, may be at least one anionic surfactant selected from the group consisting of alkylbenzene sulfonates, aliphatic sulfonates, higher alcohol sulfate ester salts, α-olefin sulfonates, and alkyl ether sulfate ester salts.

[0102] According to one embodiment of the present invention, in the emulsion polymerization for producing the carboxylic acid-modified nitrile copolymer latex, the emulsifier can be used in an amount of 1.0 to 5.0 parts by weight based on 100 parts by weight of the total monomer content, and as a specific example, the emulsifier can be introduced in an amount of 1.0 parts by weight or more, 1.5 parts by weight or more, 2.0 parts by weight or more, or 2.5 parts by weight or more, and further, the emulsifier can be introduced in an amount of 5.0 parts by weight or less, 4.5 parts by weight or less, 4.0 parts by weight or less, 3.5 parts by weight or less, 3.0 parts by weight or less, or 2.5 parts by weight or less, and within this range, the polymerization stability can be further improved.

[0103] According to one embodiment of the present invention, the molecular weight modifier may be at least one selected from the group consisting of α-methylstyrene dimer; mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and octyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, and methylene bromide; and sulfur-containing compounds such as tetraethyl thiuram disulfide, dipentamethylene thiuram disulfide, and diisopropylxanthogen disulfide, and a specific example thereof may be t-dodecyl mercaptan.

[0104] According to one embodiment of the present invention, the emulsion polymerization for producing the carboxylic acid-modified nitrile copolymer latex can be carried out by adding a molecular weight modifier in an amount of 0.8 parts by weight or more and 8.0 parts by weight or less based on 100 parts by weight of the total monomer content, and for specific examples, it can be carried out by adding a content of 0.8 parts by weight or more, 0.9 parts by weight or more, 1.0 parts by weight or more, 1.5 parts by weight or more, 2.0 parts by weight or more, 2.5 parts by weight or more, 3.0 parts by weight or more, or 3.5 parts by weight or more, and further, it can be carried out by adding a content of 8.0 parts by weight or less, 7.5 parts by weight or less, 7.0 parts by weight or less, 6.5 parts by weight or less, 6.0 parts by weight or less, 5.5 parts by weight or less, 5.0 parts by weight or less, 4.5 parts by weight or less, 4.0 parts by weight or less, or 3.5 parts by weight or less, and within this range, the molecular weight of the polymer can be appropriately adjusted. By controlling the latex composition for dip molding, it is possible to prevent the latex stability from being reduced due to an increase in viscosity, and at the same time, to further improve the mechanical properties, such as tensile properties, of a molded product molded from the latex composition for dip molding.

[0105] According to one embodiment of the present invention, the polymerization initiator may be a radical initiator, and specific examples thereof include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; organic peroxides such as t-butyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanol peroxide, and t-butyl peroxy isobutyrate; It may be at least one selected from the group consisting of nitrogen compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, and azobisisobutyric acid methyl, and a specific example thereof may be an inorganic peroxide, and a more specific example thereof may be a persulfate.

[0106] According to one embodiment of the present invention, the emulsion polymerization for producing the carboxylic acid-modified nitrile copolymer latex can be carried out by adding a polymerization initiator in an amount of 0.01 parts by weight or more and 2.0 parts by weight or less based on 100 parts by weight of the total monomer content, and for specific examples, the polymerization initiator can be added in an amount of 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, 0.5 parts by weight or more, 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, or 1.0 parts by weight or more, and further, the polymerization initiator can be added in an amount of 2.0 parts by weight or less, 1.9 parts by weight or less, 1.8 parts by weight or less, 1.7 parts by weight or less, 1.6 parts by weight or less, 1.5 parts by weight or less, 1.4 parts by weight or less, or 1.3 parts by weight. The polymerization can be carried out by adding the amount of 1.2 parts by weight or less, 1.1 parts by weight or less, or 1.0 parts by weight or less, and the polymerization speed can be maintained at an appropriate level within this range.

[0107]

[0108] Additionally, according to one embodiment of the present invention, a deodorizing step may be performed to remove unreacted monomers and residual components as needed after the emulsion polymerization.

[0109]

[0110] (S2) Step

[0111] The above step (S2) is a step for enlarging the particles of the carboxylic acid-modified nitrile copolymer manufactured by the above emulsion polymerization, and can be performed by aging the first polymer latex manufactured above at a temperature of 60°C to 70°C for 12 to 36 hours.

[0112] Here, the aging means allowing the first polymer latex to stand under the above conditions.

[0113]

[0114] Latex composition for deep molding

[0115] The present invention provides a latex composition for dip molding that has excellent latex stability and workability in manufacturing molded products while having a reduced emulsifier content.

[0116] The latex composition for dip molding according to one embodiment of the present invention is for performing dip molding and includes the carboxylic acid-modified nitrile copolymer latex, and thus has excellent latex stability, excellent workability in manufacturing molded products, and excellent tensile properties.

[0117]

[0118] According to one embodiment of the present invention, the latex composition for dip molding may include a crosslinking agent composition for controlling pH and inducing crosslinking during dip molding.

[0119] According to one embodiment of the present invention, the crosslinking agent composition may be for forming a crosslinking unit derived from the crosslinking agent through a crosslinking reaction for a carboxylic acid-modified nitrile-based copolymer.

[0120] According to one embodiment of the present invention, the crosslinking composition may include a vulcanizing agent and a vulcanizing accelerator, and more specifically, may include a vulcanizing agent, a vulcanizing accelerator, and zinc oxide.

[0121] According to one embodiment of the present invention, the vulcanizing agent is for vulcanizing the latex composition for dip molding, and may be sulfur, and specific examples thereof include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur. The content of the vulcanizing agent may be 0.1 to 10 parts by weight, or 1 to 5 parts by weight, based on 100 parts by weight (based on solid content) of the total content of the first and second carboxylic acid-modified nitrile-based copolymer latexes in the latex composition for dip molding, and within this range, excellent crosslinking ability by vulcanization is effective.

[0122] According to one embodiment of the present invention, the vulcanization accelerator is 2-mercaptobenzothiazole (MBT, 2-mercaptobenzothiazole), 2,2-dithiobisbenzothiazole-2-sulfenamide (MBTS, 2,2-dithiobisbenzothiazole-2-sulfenamide), N-cyclohexylbenzothiasole-2-sulfenamide (CBS, N-cyclohexylbenzothiasole-2-sulfenamide), 2-morpholinothiobenzothiazole (MBS, 2-morpholinothiobenzothiazole), tetramethylthiuram monosulfide (TMTM, tetramethylthiuram monosulfide), tetramethylthiuram disulfide (TMTD, tetramethylthiuram disulfide), zinc diethyldithiocarbamate (ZDEC, zinc diethyldithiocarbamate), zinc di-n-butyldithiocarbamate (ZDBC, zinc The vulcanization accelerator may be at least one selected from the group consisting of di-n-butyldithiocarbamate, diphenylguanidine (DPG), and di-o-tolylguanidine. The content of the vulcanization accelerator may be 0.1 to 10 parts by weight, or 0.5 to 5 parts by weight, based on 100 parts by weight (based on solid content) of the total content of the first and second carboxylic acid-modified nitrile-based copolymer latexes in the latex composition for dip molding, and within this range, excellent crosslinking ability by vulcanization is effective.

[0123] According to one embodiment of the present invention, the zinc oxide may be a crosslinking agent for forming a crosslinked portion through an ionic bond within the carboxylic acid-modified nitrile-based copolymer or between carboxylic acid-modified nitrile-based copolymers by performing an ionic bond with a carboxyl group of the carboxylic acid-modified nitrile-based copolymer in the latex composition for dip molding. The content of the zinc oxide may be 0.1 to 5 parts by weight, or 0.5 to 4 parts by weight, based on 100 parts by weight (based on solid content) of the total content of the first and second carboxylic acid-modified nitrile-based copolymer latexes in the latex composition for dip molding, and within this range, the crosslinking ability is excellent, the latex stability is excellent, and the tensile strength and flexibility of the manufactured product are excellent.

[0124] According to one embodiment of the present invention, the latex composition for dip molding may have a solid content (concentration) of 5 wt% to 40 wt%, 8 wt% to 35 wt%, or 10 wt% to 33 wt%, and within this range, the latex transport efficiency is excellent, and the latex viscosity is prevented from increasing, resulting in excellent storage stability.

[0125] According to one embodiment of the present invention, the latex composition for dip molding may have a pH of 8 to 12, 9 to 11, or 9.5 to 10.5 at 25°C, and within this range, excellent processability and productivity are achieved when manufacturing a dip molded product. The pH of the latex composition for dip molding may be adjusted by adding the pH adjusting agent described above.

[0126] According to one embodiment of the present invention, the latex composition for dip molding may further include additives such as pigments such as titanium dioxide, fillers such as silica, thickeners, pH regulators, etc., as needed.

[0127]

[0128] molded products

[0129] The present invention provides a dip-molded product manufactured by dip-molding the latex composition for dip-molding.

[0130] According to one embodiment of the present invention, the molded article may include a layer derived from a latex composition for dip molding. The molded article may be a dip molded article manufactured by dip molding the latex composition for dip molding, and may be a molded article including a layer derived from a latex composition for dip molding formed from the latex composition for dip molding by dip molding. A molded article manufacturing method for molding the molded article may include a step of immersing the latex composition for dip molding by a direct immersion method, an anodic adhesion immersion method, a Teague adhesion immersion method, or the like, and as a specific example, it may be performed by an anodic adhesion immersion method, in which case there is an advantage of being able to obtain a dip molded article having a uniform thickness.

[0131] According to one embodiment of the present invention, the method for manufacturing a molded product may include a step of attaching a coagulant to a dip mold (S100); a step of immersing the dip mold with the coagulant attached into a latex composition for dip molding to form a layer derived from the latex composition for dip molding, i.e., a dip molding layer (S200); and a step of heating the dip molding layer to crosslink the latex composition for dip molding (S300).

[0132] According to one embodiment of the present invention, the step (S100) is a step of immersing the dip mold in a coagulant solution to attach the coagulant to the surface of the dip mold to form a coagulant in the dip mold, wherein the coagulant solution is a solution in which the coagulant is dissolved in water, alcohol, or a mixture thereof, and the content of the coagulant in the coagulant solution may be 5 wt% to 75 wt%, 5 wt% to 50 wt%, or 10 wt% to 40 wt% based on the total content of the coagulant solution. The coagulant may be at least one selected from the group consisting of metal halides such as barium chloride, calcium chloride, magnesium chloride, zinc chloride, and aluminum chloride; nitrates such as barium nitrate, calcium nitrate, and zinc nitrate; acetates such as barium acetate, calcium acetate, and zinc acetate; and sulfates such as calcium sulfate, magnesium sulfate, and aluminum sulfate, and a specific example thereof may be calcium chloride or calcium nitrate. In addition, according to one embodiment of the present invention, the step (S100) may further include a step of immersing the dip mold in a coagulant solution for 5 seconds or more, taking it out, and drying it at 50°C to 150°C to attach a coagulant to the dip mold.

[0133] According to one embodiment of the present invention, the step (S200) may be a step of immersing a dip mold having a coagulant attached thereto in a latex composition for dip molding according to the present invention to form a dip molding layer, and taking it out to form a dip molding layer in the dip molding mold. In addition, according to one embodiment of the present invention, in the step (S200), in order to form a dip molding layer in the dip molding mold, the immersion may be performed for 5 seconds or longer.

[0134] According to one embodiment of the present invention, the step (S300) may be a step of heating a dip molding layer formed in a dip mold to evaporate a liquid component and crosslinking and hardening the latex composition for dip molding in order to obtain a dip molded product. At this time, when the latex composition for dip molding according to the present invention is used, crosslinking by vulcanization and / or ionic bonding of the crosslinking agent composition included in the latex composition for dip molding may be performed. In addition, according to one embodiment of the present invention, the heating may be performed by first heating at 70°C to 150°C for 1 minute to 10 minutes, and then second heating at 100°C to 180°C for 5 minutes to 30 minutes. At this time, after the first heating and before performing the second heating, a leaching process by soaking in water or warm water for 10 seconds to 10 minutes may be further included.

[0135] According to one embodiment of the present invention, the molded product may be a glove, such as a surgical glove, an examination glove, an industrial glove, or a household glove, a condom, a catheter, or a health care product.

[0136]

[0137] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0138]

[0139] Examples and Comparative Examples

[0140] Example 1

[0141] <Manufacture of carboxylic acid-modified nitrile copolymer latex>

[0142] A 10 L high-pressure reactor equipped with a thermometer, a cooler, a nitrogen gas inlet, and an inlet capable of continuously introducing monomers, emulsifiers, and polymerization initiators was used. After the 10 L high-pressure reactor was replaced with nitrogen, 28 wt% of acrylonitrile, 67 wt% of 1,3-butadiene, and 5 wt% of methacrylic acid and 100 wt% of a monomer mixture composed of the acrylonitrile, 1,3-butadiene, and methacrylic acid were introduced, 0.5 wt% of sodium 2-methyl-2-propene-1-sulfonate as a reactive emulsifier, 1.5 wt% of sodium alkylbenzene sulfonate as an emulsifier, 0.7 wt% of t-dodecyl mercaptan as a molecular weight regulator, and 250 wt% of ion-exchanged water were introduced, and the internal temperature of the reactor was raised to 40°C. After the temperature rise was completed, 1.0 part by weight of potassium persulfate as a polymerization initiator was added to initiate polymerization, and when the polymerization conversion rate reached 95%, 1.0 part by weight of sodium dimethyldithiocarbamate was added to stop the polymerization, thereby producing a polymer latex including a polymer. Subsequently, potassium hydroxide was added to the polymer latex to adjust the pH at 25°C to 8.5, and a deodorization process was performed to remove unreacted monomers, thereby producing a first polymer latex.

[0143] The above first polymer latex was aged while stirring in a water bath at 65°C for 24 hours to produce a carboxylic acid-modified nitrile copolymer latex containing a carboxylic acid-modified conjugated diene polymer.

[0144]

[0145] <Manufacture of latex composition for deep molding>

[0146] 1.8 parts by weight of a 3 wt% potassium hydroxide aqueous solution, 1.2 parts by weight of a vulcanizing agent (Akron dispersions, BOSTEX 378), 0.6 parts by weight of a vulcanizing accelerator (Akron dispersions, BOSTEX 497B), 1.2 parts by weight of zinc oxide (Akron dispersions, BOSTEX 422), 1.0 parts by weight of titanium dioxide (Akron dispersions, BOSTEX 497D), and double-distilled water were added to 100 parts by weight of the carboxylic acid-modified nitrile copolymer latex prepared above (based on solid content), thereby preparing a latex composition for dip molding having a solid content of 28 wt%, and ammonia was added to prepare a latex composition for dip molding having a pH of 10 at 25°C.

[0147]

[0148] <Manufacturing of deep-molded products>

[0149] A coagulant solution was prepared by mixing 18 wt% calcium nitrate, 81.9 wt% water, and 0.1 wt% wetting agent (Huntsman Corporation, Australia, product name: Teric 320). A hand-shaped ceramic mold was immersed in the coagulant solution for 10 seconds, removed, and dried at 80°C for 4 minutes to apply the coagulant to the hand-shaped mold.

[0150] Next, a hand-shaped mold coated with a coagulant was immersed in the obtained dip-molding latex composition for 10 seconds, taken out, dried at 80°C for 2 minutes, and leached by immersing in water for 30 seconds. Again, the mold was crosslinked at 110°C for 20 minutes, and the crosslinked dip-molding layer was peeled off from the hand-shaped mold to obtain a glove-shaped dip-molded product.

[0151]

[0152] Example 2

[0153] In the above Example 1, except that 0.6 parts by weight of a reactive emulsifier was added during the production of the carboxylic acid-modified nitrile-based copolymer latex, the same procedure as in Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0154]

[0155] Example 3

[0156] In the above Example 1, except that 0.8 parts by weight of a reactive emulsifier was added during the production of the carboxylic acid-modified nitrile-based copolymer latex, the same procedure as in Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0157]

[0158] Example 4

[0159] In the above Example 1, except that 66.5 wt% of 1,3-butadiene, 5.5 wt% of methacrylic acid, and 0.8 wt% of a reactive emulsifier were added when producing a carboxylic acid-modified nitrile-based copolymer latex, the same procedure as in Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0160]

[0161] Example 5

[0162] In the above Example 1, except that 29 wt% of acrylonitrile, 65.5 wt% of 1,3-butadiene, 5.5 wt% of methacrylic acid, and 1.0 wt% of a reactive emulsifier were added when producing the carboxylic acid-modified nitrile-based copolymer latex, the same procedure as in Example 1 was carried out to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0163]

[0164] Example 6

[0165] In the above Example 1, except that when producing the carboxylic acid-modified nitrile-based copolymer latex, 29 wt% of acrylonitrile, 65 wt% of 1,3-butadiene, 6 wt% of methacrylic acid, and 1.0 wt% of a reactive emulsifier were added, the same procedure as in Example 1 was carried out to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0166]

[0167] Example 7

[0168] In the above Example 1, except that 1.0 part by weight of sodium 2-hydroxy-3-(methacryloyloxy)propane-1-sulfonate was added instead of sodium 2-methyl-2-propene-1-sulfonate as a reactive emulsifier when producing a carboxylic acid-modified nitrile-based copolymer latex, the same procedure as Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0169]

[0170] Example 8

[0171] In the above Example 1, except that 1.0 part by weight of sodium 11-methacryloyl undecan-1-yl sulfate was added instead of sodium 2-methyl-2-propene-1-sulfonate as a reactive emulsifier when producing a carboxylic acid-modified nitrile-based copolymer latex, a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding were produced in the same manner as in Example 1, and a dip molded product was obtained using the same.

[0172]

[0173] Comparative Example 1

[0174] In the above Example 1, when producing a carboxylic acid-modified nitrile-based copolymer latex, a reactive emulsifier was not added, and 3.0 parts by weight of sodium alkylbenzene sulfonate was added. However, the same procedure as Example 1 was followed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0175]

[0176] Comparative Example 2

[0177] In the above Example 1, except that a reactive emulsifier was not added during the production of the carboxylic acid-modified nitrile-based copolymer latex, the same procedure as in Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0178]

[0179] Comparative Example 3

[0180] In the above Example 1, except that aging was not performed after the deodorizing process when producing the carboxylic acid-modified nitrile-based copolymer latex, the same procedure as in Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0181]

[0182] Comparative Example 4

[0183] In the above Example 1, except that 1.0 part by weight of sodium dodecyl allyl sulfosuccinate was added as a reactive emulsifier when producing the carboxylic acid-modified nitrile-based copolymer latex, the same procedure as Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0184]

[0185] Comparative Example 5

[0186] In the above Example 1, except that 1.0 part by weight of poly(vinylethylene glycol) (Mw: 2400 g / mol) was added as a reactive emulsifier when producing a carboxylic acid-modified nitrile-based copolymer latex, a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding were produced in the same manner as in Example 1, and a dip molded product was obtained using the same.

[0187]

[0188] Comparative Example 6

[0189] In the above Example 1, except that 0.1 part by weight of a reactive emulsifier was added during the production of the carboxylic acid-modified nitrile-based copolymer latex, the same procedure as in Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0190]

[0191] Comparative Example 7

[0192] In the above Example 1, except that 1.5 parts by weight of a reactive emulsifier was added when producing the carboxylic acid-modified nitrile-based copolymer latex, the same procedure as in Example 1 was performed to produce a carboxylic acid-modified nitrile-based copolymer latex and a latex composition for dip molding, and a dip molded product was obtained using the same.

[0193]

[0194] Experimental example

[0195] Experimental Example 1

[0196] The particle size and weight average molecular weight of the carboxylic acid-modified nitrile copolymer latex prepared in Examples 1 to 8 and Comparative Examples 1 to 7 were measured, and the results are shown in Table 1 below.

[0197] (1) Particle size (nm)

[0198] Particle size was measured by sampling a portion of the first polymer latex before aging and the final manufactured carboxylic acid-modified nitrile copolymer latex. Additionally, a portion of the latex was sampled every 5 hours during the aging process to observe changes in particle size, and the results are shown in Figure 1.

[0199] Samples were prepared by diluting 0.08 g of each latex in 40 ml of distilled water, and measured using the NICOMP Nano DLS / ZLS System (Entegris).

[0200]

[0201] (2) Weight average molecular weight (g / mol)

[0202] Each carboxylic acid-modified nitrile copolymer latex was dried in a constant temperature and humidity room (25°C, 50% humidity) for 24 hours to obtain a film, and each obtained film was dissolved in THF (tetrahydrofuran). Only the sol portion dissolved in THF was taken and measured using GPC (Waters 2414 Refractive Index Detector with external column heater, Waters 1515 Isocractic Pump, Waters 717Plus Autosampler).

[0203]

[0204] As confirmed through Table 1 above, it was confirmed that the particle size of the carboxylic acid-modified nitrile copolymer latex of Examples 1 to 8 significantly increased after aging compared to the carboxylic acid-modified nitrile copolymer latex of Comparative Examples 1 to 6.

[0205] Specifically, in Comparative Examples 1 and 2, which did not use a reactive emulsifier during the production of latex, and in Comparative Examples 3 and 4, which used a reactive emulsifier other than the reactive emulsifier suggested in the present invention, there was almost no increase in particle size after aging, whereas in the case of the latexes of Examples 1 to 8, it was confirmed that the particle size increased by about 1.2 to 2.2 times.

[0206] In addition, in Comparative Example 6, in which a reactive emulsifier was used during the manufacture of latex but in an amount less than that suggested by the present invention, the increase in particle size after aging was significantly reduced compared to Examples 1 to 8. On the other hand, in Comparative Example 7, in which a reactive emulsifier was used during the manufacture of latex but in an amount exceeding that suggested by the present invention, the particle size after aging increased similarly to that of the Examples, but due to the excessive presence of the reactive emulsifier in the latex, the tensile strength and elongation were significantly reduced and the bubble area increased, resulting in poor surface properties, as confirmed in Table 2 below.

[0207] Meanwhile, the alkyl-substituted vinyl group (R-CH(=CH2)-)-containing reactive emulsifier used in the present invention has excellent reactivity with monomers when producing a carboxylic acid-modified nitrile-based copolymer, and reacts together to form a chemical bond with the polymer chain (backbone) of the copolymer, thereby imparting anionic properties to the copolymer, thereby providing stability to latex particles. At the same time, the sulfonate group in the reactive emulsifier forms an electronic layer in the latex particles, thereby inducing swelling of the particles, thereby facilitating particle enlargement.

[0208] However, in the case of conventional ionic, low-molecular-weight emulsifiers that are not reactive emulsifiers, they are not introduced into the polymer chain and thus cannot induce the particle swelling and thus cannot exhibit the particle enlargement effect. In the case of reactive emulsifiers with low reactivity, they are not easily introduced into the polymer chain and the electrostatic effect is reduced due to the long alkyl chain or ethylene glycol group in the reactive emulsifier, so the particle enlargement effect is not exhibited.

[0209]

[0210] Through the above results, it can be confirmed that the carboxylic acid-modified nitrile copolymer latex of the present invention is manufactured by emulsion polymerization in the presence of an alkyl-substituted vinyl group-containing reactive emulsifier, and includes a carboxylic acid-modified nitrile copolymer containing a unit derived from the reactive emulsifier in the molecule, thereby exhibiting excellent latex stability and easily expressing particle enlargement, thereby being able to include enlarged particles.

[0211]

[0212] Experimental Example 2

[0213] The tensile properties, dip molding workability, and surface properties (bubble generation) of the latex compositions and molded products for dip molding manufactured in Examples 1 to 8 and Comparative Examples 1 to 7 were measured, and the results are shown in Table 2 and Figures 2 to 16 below.

[0214] (1) Deep forming workability

[0215] Deep molding workability was evaluated by syneresis.

[0216] The dripping phenomenon was measured by the time (in seconds) for water droplets to drip when the film was dried in an oven at 80°C after applying a CaNO3 solution to a cylindrical ceramic mold and then drying it, and dipping it in each latex composition for dip molding. The longer the time (the longer the elapsed time), the better.

[0217]

[0218] (2) Tensile strength (MPa), elongation (%), 300% modulus (MPa) and 500% modulus (MPa)

[0219] Tensile strength was measured by manufacturing dumbbell-shaped test specimens using each deep-molded product in accordance with ASTM D-412. Using these test specimens, a UTM (Universal Testing Machine) device (Instron, Model: 4466) was used in accordance with ASTM D638 to pull the specimen at a crosshead speed of 500 mm / min, and the point where the specimen breaks was measured. The tensile strength was calculated according to the following mathematical formula 1, and then converted to MPa (1 MPa = 0.10197 kgf / mm). 2 ) was performed. At this time, the higher the calculated tensile strength, the better the tensile properties.

[0220] [Mathematical Formula 1]

[0221] Tensile strength (kgf / mm) 2 ) = load value (kgf) / (thickness (mm) × width (mm))

[0222] The elongation was calculated according to the following mathematical formula 2 using a test piece manufactured for the measurement of the above tensile strength, using a Universal Testing Machine (UTM) device (manufactured by Instron, model number: 4466) in accordance with ASTM D638, at a crosshead speed of 500 mm / min, and the point where the test piece breaks was measured. At this time, the higher the calculated elongation, the better the tensile properties.

[0223] [Equation 2]

[0224] Elongation (%) = (length of specimen after elongation / length of specimen before elongation) × 100

[0225] 300% modulus and 500% modulus were measured using a test piece manufactured for the above tensile strength measurement in accordance with ASTM D638, using a Universal Testing Machine (UTM) device (Instron, Model: 4466) at a crosshead speed of 500 mm / min, and when the test piece was stretched 3 times and 5 times its pre-tension length, the 300% modulus and 500% modulus, which are the tensile strengths, were measured. At this time, the lower the measured modulus, the softer and more comfortable it is to wear.

[0226]

[0227] (3) Surface characteristics (bubble formation)

[0228] For each dip-molded product, the leaching process was performed 50 times, water droplets were dropped on the dip-molded product 8 times, the film was rubbed for 10 seconds to generate foam, and the degree of foaming was compared by visual observation and evaluated with a relative score (10-point method), with a higher score indicating better performance. At this time, if no foaming occurred at all on the surface of the dip-molded product when visually confirmed, it was evaluated as 10 points, and based on this, the degree of foaming was relatively compared and evaluated.

[0229] In addition, after dropping water droplets on the deep-molded product 10 times and mixing it, the surface was photographed, and the bubble area was measured using a DeepLearning program. The bubble area (%) was calculated using the following mathematical formula 3. A smaller value indicates better surface properties.

[0230] [Equation 3]

[0231] Foam area (%) = (Foam area / Molded product area) × 100

[0232]

[0233] As confirmed through Table 2 above, Examples 1 to 8 were confirmed to be generally superior in workability, surface properties, and tensile properties compared to Comparative Examples 1 to 7. In particular, the composition for dip molding comprising the carboxylic acid-modified nitrile copolymer latex of Examples 1 to 8 according to an embodiment of the present invention and the molded article manufactured therefrom had overall improved tensile strength and elongation compared to Comparative Examples 1 to 7, while being soft and having an equal or superior wearing comfort. At the same time, the phenomenon of syneresis was greatly reduced, thereby improving workability, and the surface properties were excellent due to reduced foaming.

Claims

1. A carboxylic acid-modified nitrile copolymer comprising 100 parts by weight of a monomer unit; and 0.5 to 1.0 parts by weight of a reactive emulsifier unit relative to 100 parts by weight of the monomer unit, and having a particle size of 150 nm to 450 nm as measured by dynamic light scattering analysis. The above monomer unit includes a conjugated diene monomer unit; an ethylenically unsaturated nitrile monomer unit; and an ethylenically unsaturated acid monomer unit. A carboxylic acid-modified nitrile copolymer latex, wherein the reactive emulsifier is at least one selected from the group consisting of sodium 2-methyl-2-propene-1-sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1 sulfonate, and sodium 11-methacryloyl undecane-1-yl-sulfate.

2. In paragraph 1, A carboxylic acid-modified nitrile copolymer latex having a particle size of 200 nm to 350 nm.

3. In paragraph 1, A carboxylic acid-modified nitrile copolymer latex comprising 40 to 75 wt% of a conjugated diene monomer unit; 10 to 45 wt% of an ethylenically unsaturated nitrile monomer unit; and 1 to 15 wt% of an ethylenically unsaturated acid monomer unit.

4. In paragraph 1, A carboxylic acid modified nitrile copolymer latex wherein the above reactive emulsifier is sodium 2-methyl-2-propene-1-sulfonate.

5. In paragraph 1, The above carboxylic acid modified nitrile copolymer is a carboxylic acid modified nitrile copolymer latex having a weight average molecular weight of 100,000 g / mol or more and 200,000 g / mol or less.

6. A step (S1) of introducing a monomer mixture including a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, and an ethylenically unsaturated acid monomer and a reactive emulsifier into a reactor and polymerizing the mixture to produce a first polymer latex; and A step (S2) of aging the first polymer latex at a temperature of 60°C to 70°C for 12 to 36 hours, A method for producing a carboxylic acid-modified nitrile copolymer latex, wherein the above-mentioned reactive emulsifier is added in an amount of 0.5 to 1.0 parts by weight per 100 parts by weight of a monomer mixture.

7. A latex composition for dip molding comprising a carboxylic acid-modified nitrile copolymer latex according to Article 1.

8. A molded product comprising a layer derived from a latex composition for deep molding according to Article 7.

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