Latex composition for dip molding, method for preparing the same, and molded product

Abstract

This invention relates to a latex composition for dip molding, which has improved latex stability and reduced foam generation, a method for preparing the composition, and a molded product formed therefrom with improved wearing comfort. The invention provides a latex composition for dip molding comprising a first carboxylic acid-modified nitrile copolymer latex and a second carboxylic acid-modified nitrile copolymer latex, wherein the first carboxylic acid-modified nitrile copolymer latex comprises a first carboxylic acid-modified nitrile copolymer, and the second carboxylic acid-modified nitrile copolymer latex comprises a second carboxylic acid-modified nitrile copolymer, wherein the first carboxylic acid-modified nitrile copolymer latex and the second carboxylic acid-modified nitrile copolymer latex have a weight ratio of 1:0.6 to 1.5 based on the solid content of each latex, a method for preparing the latex composition, and a molded product formed therefrom.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0050163, filed on April 15, 2024, the entire contents of which are incorporated herein by reference as a part of this specification.

[0003] This invention relates to a latex composition for impregnation molding that has improved latex stability and reduced foam generation, a method for preparing the latex composition, and molded products formed from the latex composition that have improved wearing comfort. Background Technology

[0004] In the past, natural rubber was primarily used as a raw material for industrial, medical, and food gloves, as well as products requiring elasticity such as balloons and condoms. However, due to the severe protein allergy side effects caused by natural rubber in some users, nitrile rubber is replacing it. Nitrile rubber has high chemical resistance and is widely used in work gloves for users handling organic solvents, as well as in medical and food gloves.

[0005] In addition, due to the unstable supply and demand of natural rubber, many glove manufacturing companies have recently converted their natural rubber glove production lines to nitrile rubber glove production lines, and with increasing safety awareness, the use of disposable gloves made of nitrile rubber continues to increase.

[0006] Acrylic rubber gloves are typically manufactured from dip-molding latex. In this process, if the latex has low stability, it can solidify, increasing the defect rate of the final dip-molded product, leading to reduced productivity, and in severe cases, making dip-molding impossible.

[0007] In particular, when the temperature drops below zero, such as in winter, the stability of latex for impregnation molding decreases sharply, resulting in increased coagulation and precipitation in the stored latex. Therefore, a method is needed to improve the storage stability and low-temperature stability of latex for impregnation molding.

[0008] Meanwhile, latex for dip molding is typically prepared through emulsion polymerization. Emulsifiers are essential for polymerization stability, and a significant amount of emulsifier residue remains in the latex, leading to foaming problems in the resulting dip-molded products. Therefore, to suppress foaming caused by emulsifier residue in the final dip-molded product, the leaching process is strengthened, but this process consumes a large amount of water. However, reducing the amount of emulsifier to ensure the polymerization stability of the latex for dip molding is difficult. Even if the amount of emulsifier is reduced while ensuring polymerization stability, the processability of the molded product (shortened dehydration shrinkage time) is severely reduced.

[0009] Therefore, there is a need for a method that improves the stability and processability of latex while reducing the emulsifier content in latex used for impregnation molding.

[0010] [Existing Technical Documents]

[0011] [Patent Literature]

[0012] (Patent Document 1) KR 10-1775798 B1 (2017.08.31) Summary of the Invention

[0013] Technical issues

[0014] The present invention aims to solve the problems of the prior art and to provide a latex composition for impregnation molding that can provide molded products with excellent stability and improved surface properties while having a reduced emulsifier content.

[0015] Furthermore, the object of the present invention is to provide a method for preparing a latex composition for impregnation molding.

[0016] In addition, the object of the present invention is to provide a molded product formed from the impregnation molding latex composition, which has excellent manufacturability, excellent surface properties and suppresses foam generation.

[0017] Technical solution

[0018] To address these issues, the present invention provides a latex composition for impregnation molding, a method for preparing the same, and a molded product thereof.

[0019] (1) The present invention provides a latex composition for impregnation molding, the latex composition comprising: a first carboxylic acid modified nitrile copolymer latex, which comprises a first carboxylic acid modified nitrile copolymer, the first carboxylic acid modified nitrile copolymer comprising a first conjugated diene monomer unit, a first olefinically unsaturated nitrile monomer unit and a first olefinically unsaturated acid monomer unit; and a second carboxylic acid modified nitrile copolymer latex, which comprises a second carboxylic acid modified nitrile copolymer, the second carboxylic acid modified nitrile copolymer comprising a second conjugated diene monomer unit, a second olefinically unsaturated nitrile monomer unit, a second olefinically unsaturated acid monomer unit and a reactive emulsifier unit, wherein, based on the solid content of each latex, the weight ratio of the first carboxylic acid modified nitrile copolymer latex to the second carboxylic acid modified nitrile copolymer latex is 1:0.6 to 1.5.

[0020] (2) The present invention provides a latex composition for impregnation molding according to (1), wherein the weight ratio of the first carboxylic acid modified nitrile copolymer latex to the second carboxylic acid modified nitrile copolymer latex is 1:0.6 to 1 based on the solid content of each latex.

[0021] (3) The present invention provides a latex composition for impregnation molding according to (1) or (2), wherein the first carboxylic acid modified nitrile copolymer comprises 40% to 75% by weight of a first conjugated diene monomer unit, 20% to 50% by weight of a first olefinically unsaturated nitrile monomer unit and 0.1% to 10% by weight of a first olefinically unsaturated acid monomer unit.

[0022] (4) The present invention provides a latex composition for impregnation molding according to any one of (1) to (3), wherein the second carboxylic acid modified nitrile copolymer comprises 3% to 5% by weight of reactive emulsifier units.

[0023] (5) The present invention provides a latex composition for impregnation molding according to any one of (1) to (4), wherein the second carboxylic acid modified nitrile copolymer comprises 35% to 75% by weight of a second conjugated diene monomer unit, 20% to 50% by weight of a second olefinically unsaturated nitrile monomer unit, 0.1% to 10% by weight of a second olefinically unsaturated acid monomer unit, and 3% to 5% by weight of a reactive emulsifier unit.

[0024] (6) The present invention provides a latex composition for impregnation molding according to any one of (1) to (5), wherein the reactive emulsifier is one or more selected from sodium 2-methyl-2-propene-1-sulfonate, sodium allyloxyhydroxypropyl sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1-sulfonate, sodium 11-methacryloyl undecane-1-yl sulfate and sodium 11-crotonyl undecane-1-yl sulfate.

[0025] (7) The present invention provides a method for preparing a latex composition for impregnation molding, the method comprising the step of mixing a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex at a weight ratio of 1:0.6 to 1.5 based on the solid content of each latex, wherein the first carboxylic acid modified nitrile copolymer latex comprises a first carboxylic acid modified nitrile copolymer, the first carboxylic acid modified nitrile copolymer comprising a first conjugated diene monomer unit, a first olefinically unsaturated nitrile monomer unit and a first olefinically unsaturated acid monomer unit, the second carboxylic acid modified nitrile copolymer latex comprises a second carboxylic acid modified nitrile copolymer, the second carboxylic acid modified nitrile copolymer comprising a second conjugated diene monomer unit, a second olefinically unsaturated nitrile monomer unit, a second olefinically unsaturated acid monomer unit and a reactive emulsifier unit.

[0026] (8) The present invention provides a method for preparing a latex composition for impregnation molding according to (7), wherein, based on the solid content of each latex, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex are mixed in a weight ratio of 1:0.6 to 1.0.

[0027] (9) The present invention provides a method for preparing a latex composition for impregnation molding according to (7) or (8), wherein the first carboxylic acid modified nitrile copolymer latex is prepared by emulsion polymerization of a first conjugated diene monomer, a first olefinically unsaturated nitrile monomer and a first olefinically unsaturated acid monomer in a solvent.

[0028] (10) The present invention provides a method for preparing a latex composition for impregnation molding according to any one of (7) to (9), wherein the second carboxylic acid modified nitrile copolymer latex is prepared by the following steps: (S1) introducing the reactive emulsifier and the second olefinic unsaturated acid monomer into a reactor and initiating polymerization to prepare a first polymer latex comprising a first polymer; and (S2) introducing the second conjugated diene monomer, the second olefinic unsaturated nitrile monomer and the second olefinic unsaturated acid monomer into the first polymer latex and polymerizing it.

[0029] (11) The present invention provides a method for preparing a latex composition for impregnation molding according to (10), wherein the reactive emulsifier is added at 3% to 5% by weight based on 100% by weight of total polymerization product, and the polymerization product comprises a second conjugated diene monomer, a second olefinically unsaturated nitrile monomer, a second olefinically unsaturated acid monomer and a reactive emulsifier.

[0030] (12) The present invention provides a method for preparing a latex composition for impregnation molding according to any one of (7) to (11), wherein the reactive emulsifier is one or more selected from sodium 2-methyl-2-propene-1-sulfonate, sodium allyloxyhydroxypropyl sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1-sulfonate, sodium 11-methacryloyl undecane-1-yl sulfate and sodium 11-crotonyl undecane-1-yl sulfate.

[0031] (13) The present invention provides a molded product comprising a layer of latex composition for impregnation molding according to any one of (1) to (6).

[0032] Beneficial effects

[0033] The latex composition for impregnation molding according to the present invention comprises a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex comprising a second carboxylic acid modified nitrile copolymer containing a reactive emulsifier unit, and can exhibit excellent latex stability and processability in the manufacture of molded products while having a reduced emulsifier content.

[0034] Furthermore, the molded products according to the present invention can be molded from the said impregnation molding latex composition and have low foam generation and excellent surface and tensile properties. Detailed Implementation

[0035] The invention will be described in more detail below to aid in understanding it.

[0036] The words or terms used in this specification and claims should not be construed as having the meanings defined in common dictionaries. Based on the principle that inventors can appropriately define the meanings of words to best interpret the invention, the words or terms should be interpreted as having meanings consistent with their meanings in the technical concept of the invention.

[0037] Definition of terminology

[0038] In this invention, the term "monomer unit" may refer to a component or structure derived from a monomer, or the material itself, particularly a repeating unit formed in the polymer during polymerization via the participation of injected monomers.

[0039] In this invention, the term "polymer" can include homopolymers formed by polymerization of one monomer and copolymers formed by copolymerization of two monomers.

[0040] In this invention, the terms "latex" and "emulsion" can refer to polymers or copolymers polymerized by polymerization that exist in a form dispersed in water. As a specific example, they can refer to fine particles of rubber-like polymers or rubber-like copolymers polymerized by emulsion polymerization that exist in a colloidal state dispersed in a solvent (water). In this invention, "latex" and "emulsion" can be used interchangeably.

[0041] The term "composition" as used in this invention includes mixtures of materials comprising the corresponding composition, as well as reaction products and decomposition products formed from the materials of the corresponding composition.

[0042] In this invention, the term "derived layer" can refer to a layer formed of a polymer or copolymer. As a specific example, it can refer to a layer formed of a polymer or copolymer by attaching, fixing and / or polymerizing the polymer or copolymer onto an impregnation frame during the manufacture of an impregnation-molded product.

[0043] Latex composition for dip molding

[0044] The present invention provides a latex composition for impregnation molding, which has excellent latex stability and processability in the manufacture of molded products while having a reduced emulsifier content.

[0045] According to one embodiment of the present invention, a latex composition for impregnation molding comprises: a first carboxylic acid modified nitrile copolymer latex, comprising a first carboxylic acid modified nitrile copolymer, the first carboxylic acid modified nitrile copolymer comprising a first conjugated diene monomer unit, a first olefinically unsaturated nitrile monomer unit, and a first olefinically unsaturated acid monomer unit; and a second carboxylic acid modified nitrile copolymer latex, comprising a second carboxylic acid modified nitrile copolymer, the second carboxylic acid modified nitrile copolymer comprising a second conjugated diene monomer unit, a second olefinically unsaturated nitrile monomer unit, a second olefinically unsaturated acid monomer unit, and a reactive emulsifier unit, wherein, based on the solid content, the weight ratio of the first carboxylic acid modified nitrile copolymer latex to the second carboxylic acid modified nitrile copolymer latex can be from 1:0.6 to 1.5.

[0046] Typically, carboxylic acid-modified nitrile copolymer latexes constituting latex compositions for impregnation molding are prepared by emulsion polymerization. In emulsion polymerization, emulsifiers are essential for reducing the interfacial tension between the monomer and the liquid phase to form a stable dispersion, dissolution, and emulsification state between the reactive phase and the continuous phase, for providing micellar reaction sites required for polymerization through micellar formation, and for stabilizing the polymer latex emulsion.

[0047] Emulsifiers are typically nonionic, while ionic emulsifiers include anionic and cationic emulsifiers, or low molecular weight emulsifiers. Ionic and low molecular weight emulsifiers do not chemically bind to the polymer, thus adversely affecting the performance of the molded product. Specifically, during the manufacturing process, emulsifiers migrate from the coagulated latex phase to the surface or adhesive interface, easily leading to phase separation. Because emulsifiers are highly soluble in water, when the phase-separated emulsifier comes into contact with water, it desorbs and causes scratches (flow marks) or foaming on the surface of the molded product, resulting in quality problems.

[0048] However, according to one embodiment of the present invention, the latex composition for dip molding is prepared by using a first carboxylic acid modified nitrile copolymer latex and a reactive emulsifier instead of the aforementioned ionic and low molecular weight emulsifiers, and contains a second carboxylic acid modified nitrile copolymer latex containing reactive emulsifier units in a controlled proportion, thereby reducing the residual amount of ionic and low molecular weight emulsifiers while still having excellent latex stability, and simultaneously providing dip-molded products with excellent surface properties and tensile properties as well as suppressed foaming.

[0049] In the following description, according to one embodiment of the present invention, a latex composition for impregnation molding is specifically described.

[0050] Primary carboxylic acid modified nitrile copolymer latex

[0051] According to one embodiment of the present invention, the first carboxylic acid-modified nitrile copolymer latex can be in a latex state in which the first carboxylic acid-modified nitrile copolymer is dispersed in a solvent, which can be an aqueous solvent. As a specific example, the aqueous solvent can be water, and the water can be ion-exchanged water or distilled water.

[0052] According to one embodiment of the present invention, the first carboxylic acid modified nitrile copolymer may comprise a first conjugated diene monomer unit, a first olefinically unsaturated nitrile monomer unit, and a first olefinically unsaturated acid monomer unit.

[0053] According to one embodiment of the present invention, the first conjugated diene monomer for forming the first carboxylic acid modified nitrile copolymer may be one or more selected from 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and isoprene, specifically, 1,3-butadiene or isoprene, more specifically, 1,3-butadiene.

[0054] According to one embodiment of the present invention, the first carboxylic acid modified nitrile copolymer may contain 40% to 75% by weight, 45% to 70% by weight, or 50% to 70% by weight of repeating units from a first conjugated diene monomer, and within this range, a molded product formed from an impregnation molding latex composition comprising a carboxylic acid modified nitrile copolymer latex containing the first carboxylic acid modified nitrile copolymer has excellent flexibility and wearing comfort as well as excellent oil resistance and tensile strength.

[0055] According to one embodiment of the present invention, the first olefinically unsaturated nitrile monomer of the first olefinically unsaturated nitrile monomer unit forming the first carboxylic acid modified nitrile copolymer may be one or more selected from acrylonitrile, methacrylonitrile, fumaric acid, α-chloronitrile and α-cyanoethyl acrylonitrile, specifically acrylonitrile and methacrylonitrile, more specifically acrylonitrile.

[0056] According to one embodiment of the present invention, the carboxylic acid modified nitrile copolymer may contain 20% to 50% by weight, 20% to 45% by weight, or 25% to 40% by weight of a first olefinically unsaturated nitrile monomer unit, and within this range, a molded product formed from an impregnation molding latex composition comprising a first carboxylic acid modified nitrile copolymer latex composition has excellent flexibility and wearing comfort as well as excellent oil resistance and tensile strength.

[0057] According to one embodiment of the present invention, the first olefinically unsaturated acid monomer forming the first carboxylic acid-modified nitrile copolymer may be one or more selected from olefinically unsaturated monomers containing acidic groups such as carboxyl groups, sulfonic acid groups, and anhydride groups, specifically olefinically 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; olefinically unsaturated sulfonic acid monomers such as styrene sulfonic acid; olefinically unsaturated polycarboxylic acid ester monomers such as monobutyl fumarate, monobutyl maleate, and mono-2-hydroxypropyl maleate, more specifically, one or more selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid, and even more specifically, methacrylic acid. During polymerization, the first olefinically unsaturated acid monomer may be used in the form of a salt, such as an alkali metal salt or an ammonium salt.

[0058] According to one embodiment of the present invention, the first carboxylic acid modified nitrile copolymer may contain 0.1% to 10% by weight, 0.5% to 9% by weight, or 1% to 8% by weight of the first olefinic unsaturated acid monomer unit. Within this range, the molded product formed from the latex composition for impregnation molding containing the first carboxylic acid modified nitrile copolymer latex has the effects of excellent flexibility, excellent wearing comfort, and excellent tensile strength.

[0059] Second carboxylic acid modified nitrile copolymer latex

[0060] According to one embodiment of the present invention, the second carboxylic acid-modified nitrile copolymer latex can be in a latex state in which the second carboxylic acid-modified nitrile copolymer is dispersed in a solvent, and the solvent can be an aqueous solvent. As a specific example, the aqueous solvent can be water, and the water can be ion-exchanged water or distilled water.

[0061] According to one embodiment of the present invention, the second carboxylic acid modified nitrile copolymer latex may comprise a second conjugated diene monomer unit, a second olefinically unsaturated nitrile monomer unit, a second olefinically unsaturated acid monomer unit, and a reactive emulsifier unit.

[0062] According to one embodiment of the present invention, a second carboxylic acid-modified nitrile copolymer latex can be prepared by emulsion polymerization in the presence of a reactive emulsifier without the use of ionic and low molecular weight emulsifiers, wherein the reactive emulsifier can form chemical bonds with polymer chains formed from monomers. Therefore, a latex composition for impregnation molding according to one embodiment of the present invention, comprising a predetermined ratio of a second carboxylic acid-modified nitrile copolymer latex and a first carboxylic acid-modified nitrile copolymer latex, can exhibit excellent latex stability while containing reduced ionic and low molecular weight emulsifiers, and the molded product manufactured can have excellent surface properties.

[0063] Meanwhile, in this invention, the term "reactive emulsifier unit" can refer to a component or structure or substance from a reactive emulsifier, and as a specific example, it can refer to a unit (part) formed by a reactive emulsifier introduced during polymerization participating in the polymerization reaction and chemically bonding with the polymer chain.

[0064] Furthermore, according to one embodiment of the invention, the second carboxylic acid modified nitrile copolymer may contain 3% to 5% by weight of reactive emulsifier units, and in this case, the latex stability of the second carboxylic acid modified nitrile copolymer latex containing it may be excellent.

[0065] The reactive emulsifier may be one or more selected from sodium 2-methyl-2-propene-1-sulfonate, sodium allyloxyhydroxypropyl sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1-sulfonate, sodium 11-methacryloyl undecane-1-yl sulfate and sodium 11-crotonyl undecane-1-yl sulfate, and specifically sodium 2-methyl-2-propene-1-sulfonate.

[0066] According to one embodiment of the present invention, the second conjugated diene monomer of the second conjugated diene monomer unit used to form the second carboxylic acid modified nitrile copolymer can be the same as the first conjugated diene monomer of the first conjugated diene monomer unit used to form the first carboxylic acid modified nitrile copolymer described above; specifically, the second conjugated diene monomer can be one or more selected from 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, and isoprene, specifically 1,3-butadiene or isoprene, more specifically 1,3-butadiene. In this case, the second conjugated diene monomer of the second conjugated diene monomer unit used to form the second carboxylic acid modified nitrile copolymer can be the same as or different from the first conjugated diene monomer of the first conjugated diene monomer unit used to form the first carboxylic acid modified nitrile copolymer.

[0067] According to one embodiment of the present invention, the second carboxylic acid modified nitrile copolymer may contain 35% to 75% by weight, 40% to 70% by weight, or 45% to 70% by weight of a second conjugated diene monomer unit, and within this range, the molded product formed from the latex composition for impregnation molding containing the second carboxylic acid modified nitrile copolymer latex is flexible and has excellent wearing comfort, while also having excellent oil resistance and tensile strength.

[0068] According to one embodiment of the present invention, the second unsaturated nitrile monomer of the second olefinically unsaturated nitrile monomer unit used to form the second carboxylic acid modified nitrile copolymer can be the same as the first olefinically unsaturated nitrile monomer of the first olefinically unsaturated nitrile monomer unit used to form the first carboxylic acid modified nitrile copolymer latex. Specifically, the second olefinically unsaturated nitrile monomer can be one or more selected from acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, and α-cyanoethyl acrylonitrile, specifically acrylonitrile and methacrylonitrile, more specifically acrylonitrile. In this case, the second olefinically unsaturated nitrile monomer of the second olefinically unsaturated nitrile monomer unit used to form the second carboxylic acid modified nitrile copolymer latex can be the same as or different from the first olefinically unsaturated nitrile monomer of the first olefinically unsaturated nitrile monomer unit used to form the first carboxylic acid modified nitrile copolymer.

[0069] According to one embodiment of the present invention, the second carboxylic acid modified nitrile copolymer may contain 20% to 50% by weight, 20% to 45% by weight, or 20% to 40% by weight of a second olefinically unsaturated nitrile monomer unit, and within this range, the molded product formed from the latex composition for impregnation molding containing the second carboxylic acid modified nitrile copolymer latex is flexible and has excellent wearing comfort, while also having excellent oil resistance and tensile strength.

[0070] According to one embodiment of the present invention, the second olefinically unsaturated acid monomer forming the second olefinically unsaturated acid monomer unit of the second carboxylic acid modified nitrile copolymer can be the same as the first olefinically unsaturated acid monomer unit forming the first carboxylic acid modified nitrile copolymer latex. Specifically, the second olefinically unsaturated acid monomer can be selected from olefinically 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; olefinically unsaturated sulfonic acid monomers, such as styrene sulfonic acid; and olefinically unsaturated polycarboxylic acid ester monomers, such as monobutyl fumarate, monobutyl maleate, and mono-2-hydroxypropyl maleate, or more specifically, it can be selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid, or more specifically, it can be selected from one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid, or more specifically, methacrylic acid. Furthermore, during polymerization, the second olefinically unsaturated acid monomer can be used in the form of a salt, such as an alkali metal salt or an ammonium salt. In this case, the second olefinically unsaturated acid monomer used to form the second carboxylic acid modified nitrile copolymer latex can be the same as or different from the first olefinically unsaturated acid monomer used to form the first carboxylic acid modified nitrile copolymer.

[0071] According to one embodiment of the present invention, the second carboxylic acid modified nitrile copolymer may contain 0.1% to 10% by weight, 0.5% to 9% by weight, or 1% to 8% by weight of a second olefinic unsaturated acid monomer unit. Within this range, molded products formed from an impregnation molding latex composition comprising a first carboxylic acid modified nitrile copolymer latex containing a first carboxylic acid modified nitrile copolymer have excellent flexibility, wearability, and tensile strength.

[0072] Latex composition for dip molding

[0073] According to one embodiment of the present invention, a latex composition for dip molding is used for dip molding and comprises a first carboxylic acid-modified nitrile copolymer latex and a second carboxylic acid-modified nitrile copolymer latex, wherein the first carboxylic acid-modified nitrile copolymer latex and the second carboxylic acid-modified nitrile copolymer latex can have a weight ratio of 1:0.6 to 1.5 and a weight ratio of 1:0.6 to 1.0. When the weight ratio is within this range, the residual amount of ionic and low molecular weight emulsifiers in the latex composition for dip molding is reduced, while the latex stability is excellent, resulting in excellent processability of the molded product, and the molded product has excellent surface properties and tensile properties, while suppressing foam formation.

[0074] 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.

[0075] According to one embodiment of the invention, the crosslinking agent composition can be used to form a crosslinked portion from the crosslinking agent through a crosslinking reaction of a carboxylic acid-modified nitrile copolymer.

[0076] According to one embodiment of the present invention, the crosslinking agent composition may contain a vulcanizing agent and a vulcanization accelerator, more specifically, it may contain a vulcanizing agent, a vulcanization accelerator, and zinc oxide.

[0077] According to one embodiment of the invention, the vulcanizing agent is used to vulcanize the latex composition for impregnation molding. It can be sulfur, and specific examples include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur. Based on the total content (in solids) of the first carboxylic acid-modified nitrile copolymer latex and the second carboxylic acid-modified nitrile copolymer latex in 100 parts by weight of the latex composition for impregnation molding, the content of the vulcanizing agent can be from 0.1 parts by weight to 10 parts by weight or from 1 part by weight to 5 parts by weight, within which excellent vulcanization crosslinking ability can be effectively achieved.

[0078] According to one embodiment of the invention, the vulcanization accelerator may be one or more selected from 2-mercaptobenzothiazole (MBT), 2,2-dithiodibenzothiazole-2-sulfenamide (MBTS), N-cyclohexylbenzothiazole-2-sulfenamide (CBS), 2-morpholinothiobenzothiazole (MBS), tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), zinc diethyldithiocarbamate (ZDEC), and zinc di-n-butyldithiocarbamate (ZDBC). Based on the total content (in solids) of the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex in 100 parts by weight of the latex composition for impregnation molding, the content of the vulcanization accelerator may be from 0.1 parts by weight to 10 parts by weight or from 0.5 parts by weight to 5 parts by weight, within which excellent crosslinking ability by vulcanization is effective.

[0079] According to one embodiment of the invention, zinc oxide can be a crosslinking agent that forms crosslinked portions by ionic bonding with the carboxyl groups of the carboxylic acid-modified nitrile copolymer in the latex composition for impregnation molding, thereby forming crosslinked portions within or between the carboxylic acid-modified nitrile copolymers. Based on the total content (in solids) of the first carboxylic acid-modified nitrile copolymer latex and the second carboxylic acid-modified nitrile copolymer latex in 100 parts by weight of the latex composition for impregnation molding, the content of zinc oxide can be from 0.1 parts by weight to 5 parts by weight or from 0.5 parts by weight to 4 parts by weight. Within this range, excellent crosslinking ability, excellent latex stability, and excellent tensile strength and flexibility of the molded product are achieved.

[0080] According to one embodiment of the present invention, the latex composition for impregnation molding can have a solid content (concentration) of 5% to 40% by weight, 8% to 35% by weight, or 10% to 33% by weight, within which the latex delivery efficiency is excellent and the increase in latex viscosity can be prevented, thereby providing excellent storage stability.

[0081] According to one embodiment of the present invention, the latex composition for dip molding can have a pH of 8 to 12, 9 to 11, or 9.5 to 10.5 at 25°C, within which excellent processing performance and productivity can be obtained when manufacturing dip-molded products. The pH of the latex composition for dip molding can be adjusted by adding the aforementioned pH adjuster.

[0082] According to one embodiment of the present invention, the latex composition for impregnation molding may further include additives as needed, such as pigments including titanium dioxide, fillers including silica, thickeners, pH adjusters, etc.

[0083] Method for preparing latex compositions for impregnation molding

[0084] This invention provides a method for preparing a latex composition for impregnation molding.

[0085] A method for preparing a latex for impregnation molding according to one embodiment of the present invention includes the following mixing steps: a first carboxylic acid modified nitrile copolymer latex comprising a first carboxylic acid modified nitrile copolymer, the first carboxylic acid modified nitrile copolymer comprising a first conjugated diene monomer unit, a first olefinically unsaturated nitrile monomer unit and a first olefinically unsaturated acid monomer unit; and a second carboxylic acid modified nitrile copolymer latex comprising a second carboxylic acid modified nitrile copolymer, the second carboxylic acid modified nitrile copolymer comprising a second conjugated diene monomer unit, a second olefinically unsaturated nitrile monomer unit, a second olefinically unsaturated acid monomer unit and a reactive emulsifier unit, wherein the weight ratio is from 1:0.6 to 1.5 based on the solid content of each latex.

[0086] Meanwhile, the nitrile copolymer latex modified with the first carboxylic acid and the nitrile copolymer latex modified with the second carboxylic acid can be prepared by common emulsion polymerization, which will be described in more detail below.

[0087] Method for preparing nitrile copolymer latex modified with primary carboxylic acid

[0088] According to one embodiment of the present invention, a first carboxylic acid modified nitrile copolymer latex can be prepared by emulsion polymerization of a first conjugated diene monomer, a first olefinically unsaturated nitrile monomer and a first olefinically unsaturated acid monomer in a solvent, wherein the amount of each monomer used can be appropriately adjusted to allow each monomer unit to satisfy the above-mentioned range in the first carboxylic acid modified nitrile copolymer latex.

[0089] According to one embodiment of the present invention, the solvent, the first conjugated diene monomer, the first olefinically unsaturated nitrile monomer, and the first olefinically unsaturated acid monomer may be the same as those described above.

[0090] Specifically, the first carboxylic acid modified nitrile copolymer latex can be prepared by emulsion polymerization of 40% to 75% by weight of a first conjugated diene monomer, 20% to 50% by weight of a first olefinically unsaturated nitrile monomer, and 0.1% to 10% by weight of a first olefinically unsaturated acid monomer in a solvent.

[0091] According to one embodiment of the present invention, emulsion polymerization can be carried out in the presence of one or more additives selected from emulsifiers, molecular weight regulators and polymerization initiators. The emulsifier may be one or more selected from anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants, specifically one or more anionic surfactants selected from alkylbenzene sulfonates, aliphatic sulfonates, higher alcohol sulfates, α-olefin sulfonates and alkyl ether sulfates.

[0092] According to one embodiment of the present invention, in the emulsion polymerization for preparing a first carboxylic acid modified nitrile copolymer latex, an emulsifier may be used in an amount of 1.0 to 5.0 parts by weight based on 100 parts by weight of total monomer content. Specifically, the emulsifier may be injected in an amount of more than 1.0 parts by weight, more than 1.5 parts by weight, more than 2.0 parts by weight, or more than 2.5 parts by weight, and may further be injected in an amount of less than 5.0 parts by weight, less than 4.5 parts by weight, less than 4.0 parts by weight, less than 3.5 parts by weight, less than 3.0 parts by weight, or less than 2.5 parts by weight, within which the polymerization stability can be further improved.

[0093] According to one embodiment of the present invention, the emulsion polymerization for preparing a first carboxylic acid modified nitrile copolymer latex can be carried out in the presence of a molecular weight regulator, which may be selected from α-methylstyrene dimer; thiols, such as tert-dodecyl mercaptan, n-dodecyl mercaptan and octyl mercaptan; halogenated hydrocarbons, such as carbon tetrachloride, dichloromethane and dibromomethane; and sulfur-containing compounds, such as tetraethylthiuram disulfide, dipentylthiuram disulfide and diisopropyl xanthate disulfide, and a specific example thereof may be tert-dodecyl mercaptan.

[0094] According to one embodiment of the present invention, the emulsion polymerization for preparing a first carboxylic acid modified nitrile copolymer latex can be carried out by adding 0.8 to 8.0 parts by weight of a molecular weight regulator based on 100 parts by weight of total monomer content. Specifically, it can be added in amounts 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. Further, it can be added in amounts of less than 8.0 parts by weight, less than 7.5 parts by weight, less than 7.0 parts by weight, less than 6.5 parts by weight, less than 6.0 parts by weight, less than 5.5 parts by weight, less than 5.0 parts by weight, less than 4.5 parts by weight, less than 4.0 parts by weight, or less than 3.5 parts by weight. Within this range, the molecular weight of the polymer can be appropriately controlled, preventing a decrease in latex stability due to increased viscosity, while improving the entanglement between the polymer and the carboxylic acid modified nitrile copolymer, thereby further improving the mechanical properties, such as tensile properties, of the molded product formed from the latex composition for impregnation molding.

[0095] According to one embodiment of the present invention, the emulsion polymerization for preparing a first carboxylic acid modified nitrile copolymer latex can be initiated by injecting a polymerization initiator, which can be a free radical initiator, specifically selected from inorganic peroxides, such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium superphosphate, and hydrogen peroxide; organic peroxides, such as tert-butyl peroxide, cumene hydrogen peroxide, p-menthane hydrogen peroxide, di-tert-butyl peroxide, tert-butylisocumene peroxide, acetyl peroxide, isobutyl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanol peroxide, and tert-butyl peroxyisobutyrate; and nitrogen compounds, such as one or more of azobisisobutyronitrile, azobis-2,4-dimethylpentanonitrile, azobiscyclohexylformitrile, and methyl azobisisobutyrate, specifically examples of which can be inorganic peroxides, and more specifically examples of which can be persulfates.

[0096] According to one embodiment of the present invention, the emulsion polymerization for preparing a first carboxylic acid modified nitrile copolymer latex can be carried out by adding 0.01 to 2.0 parts by weight of polymerization initiator based on 100 parts by weight of total monomer content. Specifically, it can be added in amounts 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 less than 2.0 parts by weight, less than 1.9 parts by weight, less than 1.8 parts by weight, less than 1.7 parts by weight, less than 1.6 parts by weight, less than 1.5 parts by weight, less than 1.4 parts by weight, less than 1.3 parts by weight, less than 1.2 parts by weight, less than 1.1 parts by weight, or less than 1.0 parts by weight, within which the polymerization rate can be maintained at an appropriate level.

[0097] Furthermore, according to one embodiment of the invention, after emulsion polymerization, a deodorization step may be performed as needed to remove unreacted monomers and residual components.

[0098] Method for preparing nitrile copolymer latex modified with second carboxylic acid

[0099] According to one embodiment of the present invention, the second carboxylic acid modified nitrile copolymer latex can be prepared by emulsion polymerization of a second conjugated diene monomer, a second olefinically unsaturated nitrile monomer, and a second olefinically unsaturated acid monomer in a solvent in the presence of a reactive emulsifier.

[0100] According to one embodiment of the present invention, the solvent, the second conjugated diene monomer, the second olefinically unsaturated nitrile monomer, the second olefinically unsaturated acid monomer, and the reactive emulsifier may be the same as those described above.

[0101] Specifically, the second carboxylic acid modified nitrile copolymer latex can be prepared by including the following steps: (S1) introducing a reactive emulsifier and a second olefinic unsaturated acid monomer into a reactor and initiating polymerization to prepare a first polymer latex containing a first polymer; and (S2) introducing a second conjugated diene monomer, a second olefinic unsaturated nitrile monomer, and a second olefinic unsaturated acid monomer into the first polymer latex and polymerizing it.

[0102] According to one embodiment of the invention, the preparation method includes, during the preparation of a second carboxylic acid modified nitrile copolymer latex, prepolymerizing a reactive emulsifier and a second olefinically unsaturated acid monomer, such that the reactive emulsifier and the second olefinically unsaturated acid monomer react to form micelles having a hydrophobic portion of the reactive emulsifier similar to that of a conventional emulsifier and a hydrophilic portion of the ionized second olefinically unsaturated acid monomer, thereby enabling the polymerization reaction to proceed stably and readily.

[0103] Based on 100% by weight of the total polymerization product, the amount of reactive emulsifier added can be from 3% to 5% by weight, and the polymerization product can contain a second conjugated diene monomer, a second olefin unsaturated nitrile monomer, a second olefin unsaturated acid monomer, and a reactive emulsifier.

[0104] According to one embodiment of the invention, polymerization can be carried out without the use of any emulsifier other than a reactive emulsifier, and if desired, in the presence of one or more additives selected from molecular weight regulators and polymerization initiators.

[0105] According to one embodiment of the present invention, the molecular weight regulator and polymerization initiator may be the same as those described above.

[0106] According to one embodiment of the present invention, the polymerization for preparing a second carboxylic acid-modified nitrile copolymer latex can be carried out by adding 0.8 to 8.0 parts by weight of a molecular weight regulator based on 100 parts by weight of total monomer content. Specifically, this is done in amounts 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 less than 8.5 parts by weight, less than 8.0 parts by weight, less than 7.5 parts by weight, less than 7.0 parts by weight, less than 6.5 parts by weight, less than 6.0 parts by weight, less than 5.5 parts by weight, less than 5.0 parts by weight, less than 4.5 parts by weight, or less than 4.0 parts by weight. Within this range, the molecular weight of the polymer can be appropriately adjusted, and the latex stability can be prevented from deteriorating due to increased viscosity.

[0107] According to one embodiment of the present invention, the polymerization for preparing a second carboxylic acid modified nitrile copolymer latex can be carried out by adding 0.01 to 2.0 parts by weight of a polymerization initiator based on 100 parts by weight of total monomer content. Specifically, the initiator is added in amounts 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 amounts of less than 2.0 parts by weight, less than 1.9 parts by weight, less than 1.8 parts by weight, less than 1.7 parts by weight, less than 1.6 parts by weight, less than 1.5 parts by weight, less than 1.4 parts by weight, less than 1.3 parts by weight, less than 1.2 parts by weight, less than 1.1 parts by weight, or less than 1.0 parts by weight. Within this range, the polymerization rate can be maintained at an appropriate level.

[0108] Furthermore, according to one embodiment of the invention, after polymerization, a deodorization step can be performed as needed to remove unreacted monomers and residual components.

[0109] Molded products

[0110] The present invention provides an impregnation-molded product manufactured by impregnating the impregnation-molding latex composition.

[0111] According to one embodiment of the invention, the molded product may include a layer from the dip-molding latex composition. The molded product may be a dip-molded product manufactured by dip-molding with the dip-molding latex composition, and may be a molded product comprising a layer from the dip-molding latex composition formed by dip-molding with the dip-molding latex composition. A method for manufacturing a molded product may include a direct dip-molding method, anodizing dip-molding method, Teague adhesive dip-molding method, etc., and specifically, a step of dip-molding with the dip-molding latex composition by anodizing dip-molding method, in which case it has the advantage of obtaining a dip-molded product with uniform thickness.

[0112] According to one embodiment of the present invention, the method for manufacturing a molded product includes: a step of attaching a coagulant to an impregnation mold frame (S100); a step of immersing the impregnation mold frame with the attached coagulant into an impregnation molding latex composition to form a layer from the impregnation molding latex composition, i.e., an impregnation molding layer (S200); and a step of heating the impregnation molding layer to crosslink the impregnation molding latex composition (S300).

[0113] According to one embodiment of the invention, step (S100) involves immersing the impregnation mold frame in a coagulant solution to adhere the coagulant to the surface of the impregnation mold frame, thereby forming a coagulant within the impregnation mold frame. The coagulant solution is a solution in which the coagulant is dissolved in water, alcohol, or a mixture thereof. Based on the total content of the coagulant solution, the content of the coagulant in the solution can be from 5% to 75% by weight, 5% to 50% by weight, or 10% to 40% by weight. The coagulant can be selected from 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, specifically, calcium chloride or calcium nitrate. Furthermore, according to one embodiment of the present invention, step (S100) may further include attaching a coagulant to the impregnation mold frame, immersing the impregnation mold frame in the coagulant solution for more than 5 seconds, removing the impregnation mold frame, and drying it at 50°C to 150°C.

[0114] According to one embodiment of the present invention, step (S200) may be: immersing an impregnation mold frame coated with a coagulant into the latex composition for impregnation molding of the present invention to form an impregnation molding layer, and removing the impregnation mold frame to form an impregnation molding layer on the impregnation mold frame. Furthermore, according to one embodiment of the present invention, step (S200) may involve immersion for more than 5 seconds to form an impregnation molding layer on the impregnation mold frame.

[0115] According to one embodiment of the invention, step (S300) may be a step of heating the dip-molding layer formed on the dip-molding mold frame to evaporate the liquid component and crosslink and cure the dip-molding latex composition to obtain a dip-molded product. In this case, if the dip-molding latex composition according to the invention is used, crosslinking through vulcanization and / or ionic bonding of the crosslinking agent composition contained in the dip-molding latex composition can be performed. Furthermore, according to one embodiment of the invention, the heating may be performed by a first heating at 70°C to 150°C for 1 minute to 10 minutes, followed by a second heating at 100°C to 180°C for 5 minutes to 30 minutes. In this case, after the first heating and before the second heating, a dipping process may be further included by immersion in water or warm water for 10 seconds to 10 minutes.

[0116] According to one embodiment of the present invention, the molded product can be a glove, including surgical gloves, examination gloves, industrial gloves and household gloves, condoms, catheters or health care products.

[0117] Embodiments of the present invention will be described in detail below to enable those skilled in the art to readily implement the invention. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0118] Examples and Comparative Examples

[0119] Preparation Example 1: Preparation of Nitrile Copolymer Latex Modified with Primary Carboxylic Acid

[0120] A 10L high-pressure reactor equipped with a thermometer, cooler, nitrogen inlet, and inlet capable of continuously injecting monomers, emulsifiers, and polymerization initiators was used. After purging the 10L high-pressure reactor with nitrogen, 27 wt% acrylonitrile, 67 wt% 1,3-butadiene, and 6 wt% methacrylic acid were injected. Based on a monomer mixture of 100 parts by weight consisting of acrylonitrile, 1,3-butadiene, and methacrylic acid, 3.0 parts by weight sodium alkylbenzene sulfonate as an emulsifier, 0.7 parts by weight tert-dodecyl mercaptan as a molecular weight regulator, and 150 parts by weight deionized water were injected, and the internal temperature of the reactor was raised to 40°C. After heating, 1.0 part by weight potassium persulfate was added as a polymerization initiator to initiate polymerization. When the polymerization conversion rate reached 95%, 1.0 part by weight sodium dimethyl dithiocarbamate was added to terminate the polymerization, thereby preparing a polymer latex containing the polymer. Subsequently, potassium hydroxide was added to the polymer latex to adjust the pH to 8.5 at 25°C, and a deodorization process was performed to remove unreacted monomers, thereby obtaining a first carboxylic acid modified nitrile copolymer latex (solid content of 45% by weight, average particle size of 120nm).

[0121] Preparation Example 2: Preparation of Nitrile Copolymer Latex A Modified with Second Carboxylic Acid

[0122] A 10L high-pressure reactor equipped with a thermometer, cooler, nitrogen inlet, and inlet capable of continuously injecting monomers, emulsifiers, and polymerization initiators was used. After purging the 10L high-pressure reactor with nitrogen, 3% by weight of sodium 2-methyl-2-propene-1-sulfonate as a reactive emulsifier, 1.5% by weight of methacrylic acid, and 150 parts by weight of deionized water were added to raise the internal temperature of the reactor to 65°C, and 1.2% by weight of potassium persulfate as a polymerization initiator was added to initiate polymerization. After 2 hours of polymerization, 26% by weight of acrylonitrile, 3.5% by weight of methacrylic acid, 66% by weight of 1,3-butadiene, and 0.55 parts by weight of tert-dodecyl mercaptan as a molecular weight regulator were added, and an additional 0.25 parts by weight of potassium persulfate was added while polymerization continued. Here, the weight parts of emulsifier, polymerization initiator, and molecular weight regulator are based on 100 parts by weight of the polymerization reactant containing acrylonitrile, 1,3-butadiene, methacrylic acid, and reactive emulsifier. When the polymerization conversion rate is 95%, potassium hydroxide is added to adjust the pH to 5.5 at 25°C, and a deodorization process is carried out to remove unreacted monomers, thereby obtaining the second carboxylic acid modified nitrile copolymer latex A (solid content 35 wt%, average particle size 280.2 nm).

[0123] Preparation Example 3: Preparation of Nitrile Copolymer Latex B Modified with Second Carboxylic Acid

[0124] A 10L high-pressure reactor equipped with a thermometer, cooler, nitrogen inlet, and inlet capable of continuously injecting monomers, emulsifiers, and polymerization initiators was used. After purging the 10L high-pressure reactor with nitrogen, 5% by weight of sodium 2-methyl-2-propene-1-sulfonate as a reactive emulsifier, 3.0% by weight of methacrylic acid, and 150 parts by weight of deionized water were added to raise the internal temperature of the reactor to 65°C, and 1.2 parts by weight of potassium persulfate as a polymerization initiator were added to initiate polymerization. After 2 hours of polymerization, 26% by weight of acrylonitrile, 2.0% by weight of methacrylic acid, 64% by weight of 1,3-butadiene, and 0.55 parts by weight of tert-dodecyl mercaptan as a molecular weight regulator were added, and an additional 0.25 parts by weight of potassium persulfate was added while polymerization continued. Here, the weight parts of emulsifier, polymerization initiator, and molecular weight regulator are based on 100 parts by weight of the polymerization reactant containing acrylonitrile, 1,3-butadiene, methacrylic acid, and reactive emulsifier. When the polymerization conversion rate is 85%, potassium hydroxide is added to adjust the pH to 5.4 at 25°C, and a deodorization process is carried out to remove unreacted monomers, thereby obtaining the second carboxylic acid modified nitrile copolymer latex B (solid content 35 wt%, average particle size 239.4 nm).

[0125] Preparation Example 4: Preparation of Nitrile Copolymer Latex C Modified with Second Carboxylic Acid

[0126] A 10L high-pressure reactor equipped with a thermometer, cooler, nitrogen inlet, and inlet capable of continuously injecting monomers, emulsifiers, and polymerization initiators was used. After purging the 10L high-pressure reactor with nitrogen, 3% by weight of sodium allyl hydroxypropyl sulfonate as a reactive emulsifier, 1.5% by weight of methacrylic acid, and 150 parts by weight of deionized water were added to raise the internal temperature of the reactor to 65°C, and 1.2 parts by weight of potassium persulfate as a polymerization initiator were added to initiate polymerization. After 2 hours of polymerization, 26% by weight of acrylonitrile, 3.5% by weight of methacrylic acid, 66% by weight of 1,3-butadiene, and 0.55 parts by weight of tert-dodecyl mercaptan as a molecular weight regulator were added, and an additional 0.25 parts by weight of potassium persulfate was added while polymerization continued. Here, the weight parts of emulsifier, polymerization initiator, and molecular weight regulator are based on 100 parts by weight of the polymerization reactant containing acrylonitrile, 1,3-butadiene, methacrylic acid, and reactive emulsifier. When the polymerization conversion rate is 95%, potassium hydroxide is added to adjust the pH to 5.5 at 25°C, and a deodorization process is carried out to remove unreacted monomers, thereby obtaining the second carboxylic acid modified nitrile copolymer latex C (solid content 35 wt%, average particle size 290.3 nm).

[0127] Preparation Example 5: Preparation of Nitrile Copolymer Latex D Modified with Second Carboxylic Acid

[0128] A 10L high-pressure reactor equipped with a thermometer, cooler, nitrogen inlet, and inlet capable of continuously injecting monomers, emulsifiers, and polymerization initiators was used. After purging the 10L high-pressure reactor with nitrogen, 3% by weight of sodium 2-hydroxy-3-(methacryloyloxy)propane-1-sulfonate as a reactive emulsifier, 1.5% by weight of methacrylic acid, and 150 parts by weight of deionized water were added to raise the internal temperature of the reactor to 65°C. 1.2 parts by weight of potassium persulfate as a polymerization initiator were then added to initiate polymerization. After 2 hours of polymerization, 26% by weight of acrylonitrile, 3.5% by weight of methacrylic acid, 66% by weight of 1,3-butadiene, and 0.55 parts by weight of tert-dodecyl mercaptan as a molecular weight regulator were added, and an additional 0.25 parts by weight of potassium persulfate was added while polymerization continued. Here, the weight parts of emulsifier, polymerization initiator, and molecular weight regulator are based on 100 parts by weight of a polymerization reactant containing acrylonitrile, 1,3-butadiene, methacrylic acid, and a reactive emulsifier. When the polymerization conversion rate is 95%, potassium hydroxide is added to adjust the pH to 5.5 at 25°C, and a deodorization process is performed to remove unreacted monomers, thereby obtaining a second carboxylic acid modified nitrile copolymer latex D (solid content 35 wt%, average particle size 271.6 nm).

[0129] Example 1

[0130] <Preparation of Latex Compositions for Impregnation Molding>

[0131] 1.2 parts by weight of a 3% potassium hydroxide aqueous solution, 1.2 parts by weight of a vulcanizing agent (Akron dispersions, BOSTEX 378), 0.7 parts by weight of a vulcanization accelerator (Akron dispersions, BOSTEX 497B), 1.0 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 a total of 100 parts by weight (based on solid content) of the first carboxylic acid modified nitrile copolymer latex prepared in Preparation Example 1 and the second carboxylic acid modified nitrile copolymer latex A prepared in Preparation Example 2 to prepare a latex composition for impregnation molding with a solid content of 25% by weight. Ammonia was added to prepare a latex composition for impregnation molding with a pH of 10 at 25°C. In this case, based on the solid content of each latex, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex are mixed at a weight ratio of 60:40 (1.5:1).

[0132] <Manufacturing of Dip-Molded Products>

[0133] A coagulant solution was prepared by mixing 18% by weight of calcium nitrate, 81.9% by weight of water, and 0.1% by weight of 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 mold.

[0134] Then, the hand-shaped mold coated with the coagulant is immersed in the obtained latex composition for dip molding for 10 seconds, removed, dried at 80°C for 2 minutes, and then immersed in water for 30 seconds. Next, after crosslinking the mold at 110°C for 20 minutes, the crosslinked dip molding layer is peeled off from the hand-shaped mold to obtain a glove-shaped dip-molded product.

[0135] Example 2

[0136] Except that, when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex A in Example 1 are mixed at a weight ratio of 50:50 (1:1) based on the latex solid content, the latex composition for impregnation molding is prepared using the same steps as in Example 1, and the impregnation molding product is obtained using the composition.

[0137] Example 3

[0138] Except that when preparing the latex composition for impregnation molding, the second carboxylic acid modified nitrile copolymer latex A in Example 1 is replaced with the second carboxylic acid modified nitrile copolymer latex B prepared in Preparation Example 2, and they are mixed at a weight ratio of 60:40 (1.5:1), the latex composition for impregnation molding is prepared using the same steps as in Example 1, and the impregnation molding product is obtained using it.

[0139] Example 4

[0140] Except that when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex B in Example 3 are mixed at a weight ratio of 50:50 (1:1), the latex composition for impregnation molding is prepared using the same steps as in Example 3, and the impregnation molding product is obtained using the composition.

[0141] Example 5

[0142] Except that, when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex A in Example 1 are mixed at a weight ratio of 40:60, the latex composition for impregnation molding is prepared using the same steps as in Example 1, and the impregnation molding product is obtained using the composition.

[0143] Example 6

[0144] Except that, when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex C in Example 1 are mixed at a weight ratio of 60:40, the latex composition for impregnation molding is prepared using the same steps as in Example 1, and the impregnation molding product is obtained using the composition.

[0145] Example 7

[0146] Except that, when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex D in Example 1 are mixed at a weight ratio of 60:40, the latex composition for impregnation molding is prepared using the same steps as in Example 1, and the impregnation molding product is obtained using the composition.

[0147] Comparative Example 1

[0148] Except that in Example 1, instead of mixing the second carboxylic acid-modified nitrile copolymer latex, 100 parts by weight of the first carboxylic acid-modified nitrile copolymer latex were used, the latex composition for impregnation molding was prepared using the same steps as in Example 1, and the impregnation-molded product was obtained using it.

[0149] Comparative Example 2

[0150] Except that, when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex A in Example 1 are mixed at a weight ratio of 70:30 based on solid content, the latex composition for impregnation molding is prepared using the same steps as in Example 1, and the impregnation molding product is obtained using the composition.

[0151] Comparative Example 3

[0152] Except that, when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex A of Example 1 are mixed at a weight ratio of 30:70 based on the solid content of each latex, the same steps as in Example 1 are used to prepare the latex composition for impregnation molding, and the impregnation molding product is obtained using the composition.

[0153] Comparative Example 4

[0154] Except that, when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex B in Example 3 are mixed at a weight ratio of 70:30 based on the solid content of each latex, the same steps as in Example 3 are used to prepare the latex composition for impregnation molding, and the impregnation molding product is obtained using the composition.

[0155] Comparative Example 5

[0156] Except that, when preparing the latex composition for impregnation molding, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex B in Example 3 are mixed at a weight ratio of 30:70 based on the solid content of each latex, the same steps as in Example 3 are used to prepare the latex composition for impregnation molding, and the impregnation molding product is obtained using the composition.

[0157] Experimental Example 1

[0158] The latex stability of the latex compositions for impregnation molding prepared in Examples 1 to 7 and Comparative Examples 1 to 5 was measured, and the results are shown in Table 1 below.

[0159] Latex stability was determined by the total coagulated content and the amount of reactor fouling generated.

[0160] The total coagulation content was measured by filtering each composition through a #200 mesh sieve and measuring the weight of the filtered coagulation. The lower the weight, the better the latex stability.

[0161] The amount of scale generated in the reactor is evaluated by scoring the amount of scale generated in the vessel on a 10-point scale after manufacturing the dip-molded product, with higher scores being better. In this case, a completely clean reactor is awarded 10 points, a reactor with fine rings at the interface is awarded 9 points, a reactor covered with scale is awarded 5 points, a reactor with scale causing difficulties in manufacturing the next dip-molded product is awarded 2 points, and a reactor with complete latex stability is awarded 0 points.

[0162] [Table 1]

[0163] As shown in Table 1 above, it was confirmed that compared with Comparative Examples 1 to 5, the latex for impregnation molding in Examples 1 to 7 significantly reduced the total solids content to approximately 13% to 38% while maintaining reactor fouling at a similar level. Here, Comparative Example 1 did not contain the second carboxylic acid-modified nitrile copolymer latex proposed in this invention, and although Comparative Examples 2 to 5 contained first carboxylic acid-modified nitrile copolymer latex and second carboxylic acid-modified nitrile copolymer latex, the proportions deviated from those proposed in this invention. Based on the above results, it was confirmed that the latex composition for impregnation molding according to the present invention, by containing first carboxylic acid-modified copolymer latex and second carboxylic acid-modified copolymer latex, and simultaneously controlling the ratio of the first carboxylic acid-modified copolymer latex to the second carboxylic acid-modified copolymer latex, exhibits excellent latex stability.

[0164] Experimental Example 2

[0165] The processability of the latex compositions for impregnation molding prepared in Examples 1 to 7 and Comparative Examples 1 to 5, as well as the tensile strength, elongation, 500% modulus and degree of foaming of the impregnated products were measured, and the results are shown in Table 2 below.

[0166] (1) Impregnation molding processability

[0167] The processability of dip molding is evaluated by flow marks.

[0168] The degree of flow marks on each of the 10 dip-molded products was visually observed and evaluated using a 10-point scale. The evaluation criteria were as follows: 10 points for 0 visually confirmed flow marks within a 2cm×2cm area, 9 points for 1 flow mark, 8 points for 2 flow marks, 7 points for 3 flow marks, 6 points for 4 to 5 flow marks, 5 points for 6 to 7 flow marks, 4 points for 8 to 10 flow marks, 3 points for 11 to 12 flow marks, 2 points for 13 to 14 flow marks, and 1 point for more than 15 flow marks.

[0169] (2) Tensile strength (MPa), elongation (%), 300% modulus (MPa) and 500% modulus (MPa)

[0170] Tensile strength was measured according to ASTM D-412 using dumbbell-shaped specimens prepared from various dip-molded products. Using these specimens, according to ASTM D638, a universal testing machine (UTM) (Instron, model: 4466) was used to stretch the specimen at a beam speed of 500 mm / min, and the point of fracture was measured. The tensile strength was calculated using Equation 2 below and then converted to MPa (1 MPa = 0.10197 kgf / mm²). A higher calculated tensile strength indicates better tensile properties. The fracture force (FAB) at the cut point of the specimen is also shown.

[0171] [Mathematical Expression 2]

[0172] Tensile strength (kgf / mm²) = Load value (kgf) / (thickness (mm) × width (mm))

[0173] Elongation is calculated according to ASTM D638 using a universal testing machine (UTM) (Instron, model 4466) at a beam speed of 500 mm / min, using specimens prepared for tensile strength measurement. The point at which the specimen breaks is measured, and the elongation is calculated according to Equation 3 below. In this case, the higher the calculated elongation, the better the tensile properties.

[0174] [Mathematical Expression 3]

[0175] Elongation (%) = (Length of the specimen after elongation / Length of the specimen before elongation) × 100

[0176] The 300% and 500% moduli are measured according to ASTM D638 using specimens prepared for tensile strength measurement. The measurements are performed using a Universal Testing Machine (UTM) apparatus (Instron, model: 4466) at a beam speed of 500 mm / min. The tensile strength of the 300% and 500% moduli is measured when the specimen is stretched to 3 and 5 times its original length, respectively. In this case, the lower the measured 300% and 500% moduli, the softer and more comfortable the garment will be.

[0177] (3) Degree of foaming (out of 10)

[0178] For each dip-molded product, a dip-dip process was performed 50 times. Water was added to the dip-molded product 8 times. The product was then folded in half and kneaded for 10 seconds to generate foam. The degree of foaming was calculated using the following mathematical formula 4, and evaluated as follows: less than 1% = 10 points, 1% to less than 5% = 9 points, 5% to less than 10% = 8 points, 10% to less than 20% = 7 points, 20% to less than 30% = 6 points, 30% to less than 40% = 5 points, 40% to less than 50% = 4 points, 50% to less than 70% = 3 points, 70% to less than 90% = 2 points, and 90% or more = 1 point. Higher values ​​indicate better performance. In this case, a surface photograph was taken immediately after kneading, and the foam area and the total area of ​​the molded product were obtained using the ImageJ program.

[0179] [Mathematical Expression 4]

[0180] Foaming degree (%) = [Foam area / Total area of ​​molded product] × 100.

[0181] [Table 2]

[0182] As shown in Table 2 above, it was confirmed that the dip-molded products of Examples 1 to 7 had at least the same level of tensile properties as those of Comparative Examples 1 to 5, while their processability was significantly improved.

Claims

1. A latex composition for impregnation molding, said latex composition comprising: A first carboxylic acid-modified nitrile copolymer latex, comprising a first carboxylic acid-modified nitrile copolymer containing a first conjugated diene monomer unit, a first olefinically unsaturated nitrile monomer unit, and a first olefinically unsaturated acid monomer unit; and The second carboxylic acid-modified nitrile copolymer latex comprises a second carboxylic acid-modified nitrile copolymer containing a second conjugated diene monomer unit, a second olefinically unsaturated nitrile monomer unit, a second olefinically unsaturated acid monomer unit, and a reactive emulsifier unit. in, Based on the solid content of each latex, the weight ratio of the first carboxylic acid modified nitrile copolymer latex to the second carboxylic acid modified nitrile copolymer latex is 1:0.6 to 1.

5.

2. The latex composition for impregnation molding according to claim 1, wherein, Based on the solid content of each latex, the weight ratio of the first carboxylic acid modified nitrile copolymer latex to the second carboxylic acid modified nitrile copolymer latex is 1:0.6 to 1.

3. The latex composition for impregnation molding according to claim 1, wherein, The first carboxylic acid modified nitrile copolymer comprises 40% to 75% by weight of the first conjugated diene monomer unit, 20% to 50% by weight of the first olefinically unsaturated nitrile monomer unit, and 0.1% to 10% by weight of the first olefinically unsaturated acid monomer unit.

4. The latex composition for impregnation molding according to claim 1, wherein, The second carboxylic acid-modified nitrile copolymer contains 3% to 5% by weight of the reactive emulsifier unit.

5. The latex composition for impregnation molding according to claim 1, wherein, The second carboxylic acid-modified nitrile copolymer comprises 35% to 75% by weight of the second conjugated diene monomer unit, 20% to 50% by weight of the second olefinically unsaturated nitrile monomer unit, 0.1% to 10% by weight of the second olefinically unsaturated acid monomer unit, and 3% to 5% by weight of the reactive emulsifier unit.

6. The latex composition for impregnation molding according to claim 1, wherein the reactive emulsifier is one or more selected from sodium 2-methyl-2-propen-1-sulfonate, sodium allyloxyhydroxypropyl sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1-sulfonate, sodium 11-methacryloyl undecane-1-yl sulfate, and sodium 11-crotonyl undecane-1-yl sulfate.

7. A method for preparing a latex composition for impregnation molding, the method comprising the following steps: Based on the solids content of each latex, a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex are mixed in a weight ratio of 1:0.6 to 1.

5. The first carboxylic acid modified nitrile copolymer latex comprises a first carboxylic acid modified nitrile copolymer, which comprises a first conjugated diene monomer unit, a first olefinically unsaturated nitrile monomer unit, and a first olefinically unsaturated acid monomer unit. The second carboxylic acid modified nitrile copolymer latex comprises a second carboxylic acid modified nitrile copolymer, which comprises a second conjugated diene monomer unit, a second olefinically unsaturated nitrile monomer unit, a second olefinically unsaturated acid monomer unit, and a reactive emulsifier unit.

8. The method for preparing a latex composition for impregnation molding according to claim 7, wherein the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex are mixed in a weight ratio of 1:0.6 to 1.0 based on the solid content of each latex.

9. The method for preparing a latex composition for impregnation molding according to claim 7, wherein the first carboxylic acid modified nitrile copolymer latex is prepared by emulsion polymerization of the first conjugated diene monomer, the first olefinically unsaturated nitrile monomer and the first olefinically unsaturated acid monomer in a solvent.

10. The method for preparing a latex composition for impregnation molding according to claim 7, wherein the second carboxylic acid-modified nitrile copolymer latex is prepared by the following steps: The step (S1) involves introducing the reactive emulsifier and the second olefinic unsaturated acid monomer into a reactor and initiating polymerization to prepare a first polymer latex comprising the first polymer; and The step (S2) involves introducing the second conjugated diene monomer, the second olefinically unsaturated nitrile monomer, and the second olefinically unsaturated acid monomer into the first polymer latex and polymerizing it.

11. The method for preparing a latex composition for impregnation molding according to claim 10, wherein... Based on 100% by weight of the total polymerization product, the reactive emulsifier is added at 3% to 5% by weight, and The polymerization product comprises the second conjugated diene monomer, the second olefinically unsaturated nitrile monomer, the second olefinically unsaturated acid monomer, and the reactive emulsifier.

12. The method for preparing a latex composition for impregnation molding according to claim 7, wherein the reactive emulsifier is one or more selected from sodium 2-methyl-2-propene-1-sulfonate, sodium allyloxyhydroxypropyl sulfonate, sodium 2-hydroxy-3-(methacryloyloxy)propane-1-sulfonate, sodium 11-methacryloyl undecane-1-yl sulfate, and sodium 11-crotonyl undecane-1-yl sulfate.

13. A molded product comprising a layer from the latex composition for impregnation molding according to claim 1.

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