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

Abstract

The present invention relates to a latex composition for dip molding having improved latex stability, a method for preparing the same, and a molded product molded therefrom and having improved wearing feel and tensile properties. There is provided a latex composition for dip molding comprising: a first carboxylic acid modified nitrile-based copolymer latex comprising a first carboxylic acid modified nitrile-based copolymer; and a second carboxylic acid-modified nitrile-based copolymer latex containing a second carboxylic acid-modified nitrile-based copolymer and a basic water-soluble resin unit wherein the basic water-soluble resin comprises a conjugated diene monomer unit, an ethylenically unsaturated nitrile-based monomer unit, and an ethylenically unsaturated acid monomer unit, a method for preparing the same, and a molded product molded therefrom.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0015242, filed on January 31, 2024, the entire contents of which are hereby incorporated in this document as a part of the specification.

[0003] The present invention relates to a latex composition for impregnation molding with improved latex stability, a method for preparing said latex composition, and a molded product molded therefrom having improved wearing comfort and tensile properties. Background Technology

[0004] Previously, natural rubber was primarily used as a raw material for industrial, medical, and food gloves, as well as for 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 are currently converting 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 is constantly increasing.

[0006] Acrylic rubber gloves are typically manufactured by dip molding from latex used for dip molding. In this process, if the latex used for dip molding has low stability and coagulation occurs, coagulation increases 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 used for dip molding decreases rapidly, resulting in an increase in coagulation and sedimentation in stored dip molding latex. Therefore, there is a need to improve methods for the storage stability and low-temperature stability of latex used for dip molding.

[0008] Meanwhile, latex used for dip molding is typically prepared via emulsion polymerization. Emulsifiers are essential for polymerization stability, and a significant amount of emulsifier remains in the latex, leading to foaming problems in the resulting dip-molded products. Therefore, the leaching process has been intensified to suppress foaming caused by emulsifier residues in the final dip-molded product; however, this process consumes a large amount of water. Furthermore, it is difficult to reduce the amount of emulsifier to ensure the polymerization stability of the latex used for dip molding. Even if polymerization stability is maintained while reducing the amount of emulsifier, there is a significant decrease in the processing performance (reduced dehydration shrinkage time) of the molded products.

[0009] Therefore, there is a need for methods to improve the stability and processing performance of latexes while reducing the emulsifier content in latexes used for dip 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 address the problems of the prior art and to provide a latex composition for dip molding that has excellent stability and manufacturing and processing properties of molded products, while having a reduced emulsifier content.

[0015] Furthermore, the present invention aims to provide a method for preparing a latex composition for dip molding.

[0016] Furthermore, the present invention aims to provide a molded product molded from the latex composition for impregnation molding, exhibiting excellent manufacturing and processing properties, excellent tensile properties, and suppressed foaming.

[0017] Technical solution

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

[0019] (1) The present invention provides a latex composition for impregnation molding, the latex composition comprising: 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 and a second olefinically unsaturated nitrile monomer unit, and an alkaline water-soluble resin unit, wherein the alkaline water-soluble resin comprises a third conjugated diene monomer unit, a third olefinically unsaturated nitrile monomer unit and a third olefinically unsaturated acid monomer unit.

[0020] (2) The present invention provides a latex composition for dip molding according to (1) above, wherein the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex have a weight ratio of 1.00:0.20 to 1.25.

[0021] (3) The present invention provides a latex composition for dip molding according to (1) or (2) above, wherein the first carboxylic acid modified nitrile copolymer comprises: 35% to 78% 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 dip molding according to any one of (1) to (3) above, wherein the second carboxylic acid modified nitrile copolymer comprises: 60% to 80% by weight of a second conjugated diene monomer unit; and 20% to 40% by weight of a second olefin unsaturated nitrile monomer unit.

[0023] (5) The present invention provides a latex composition for dip molding according to any one of (1) to (4) above, wherein the second carboxylic acid modified nitrile copolymer latex comprises 5 to 25 parts by weight of an alkaline water-soluble resin unit relative to 100 parts by weight of the second carboxylic acid modified nitrile copolymer.

[0024] (6) The present invention provides a latex composition for impregnation molding according to any one of (1) to (5) above, wherein the alkaline water-soluble resin comprises: 40% to 75% by weight of a third conjugated diene monomer unit; 10% to 50% by weight of a third olefinically unsaturated nitrile monomer unit; and 10% to 50% by weight of a third olefinically unsaturated acid monomer unit.

[0025] (7) The present invention provides a latex composition for dip molding according to any one of (1) to (6) above, wherein the second carboxylic acid modified nitrile copolymer latex has a micelle form, the micelles being formed of alkaline water-soluble resin units, and the micelles comprising the second carboxylic acid modified nitrile copolymer therein.

[0026] (8) The present invention provides a latex composition for dip molding according to any one of (1) to (7) above, which contains 1.5 to 2.5 parts by weight of emulsifier relative to a total solid content of 100 parts by weight.

[0027] (9) The present invention provides a method for preparing a latex composition for impregnation molding, the method comprising: mixing a first carboxylic acid modified nitrile copolymer latex with 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, 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 and a second olefinically unsaturated nitrile monomer unit, and an alkaline water-soluble resin unit, and the second carboxylic acid modified nitrile copolymer latex is prepared by mixing a second conjugated diene monomer, a second olefinically unsaturated nitrile monomer and an alkaline water-soluble resin solution, and performing emulsion polymerization on the mixture.

[0028] (10) The present invention provides a method for preparing a latex composition for dip molding according to (9) above, wherein a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex are mixed in a weight ratio of 1.00:0.20 to 1.25.

[0029] (11) The present invention provides a method for preparing a latex composition for impregnation molding according to (9) or (10) above, wherein the alkaline water-soluble resin solution is used in an amount of 5 to 25 parts by weight, based on the solid content, relative to the total amount of the second conjugated diene monomer and the second olefinically unsaturated nitrile monomer, in 100 parts by weight.

[0030] (12) The present invention provides a method for preparing a latex composition for impregnation molding according to any one of (9) to (11) above, wherein an alkaline water-soluble resin solution is injected at least twice before and after initiating emulsion polymerization.

[0031] (13) The present invention provides a method for preparing a latex composition for impregnation molding according to any one of (9) to (12) above, wherein an alkaline water-soluble resin solution is first injected before initiating emulsion polymerization, and an alkaline water-soluble resin solution is injected a second time after initiating emulsion polymerization, and the second injection is performed continuously in the range of 30% to 70% polymerization conversion.

[0032] (14) The present invention provides a method for preparing a latex composition for dip molding according to (13) above, wherein the alkaline water-soluble resin solution in the first injection and the alkaline water-soluble resin solution in the second injection have a weight ratio of 1:0.2 to 1 based on the solid content.

[0033] (15) The present invention provides a method for preparing a latex composition for impregnation molding according to any one of (8) to (13) above, wherein the alkaline water-soluble resin solution is prepared by a preparation method comprising the steps of: emulsion polymerization of a third conjugated diene monomer, a third olefinically unsaturated nitrile monomer and a third olefinically unsaturated acid monomer in a solvent to prepare a polymer latex; and injecting a pH adjuster into the polymer latex.

[0034] (16) The present invention provides a method for preparing a latex composition for impregnation molding according to any one of (9) to (15) above, wherein the alkaline water-soluble resin solution has a pH of 7.0 to 10.0 at 25°C.

[0035] (17) The present invention provides a method for preparing a latex composition for impregnation molding according to any one of (9) to (16) above, wherein the first carboxylic acid modified nitrile copolymer latex is prepared by emulsion polymerization in a solvent of a first conjugated diene monomer; a first olefinically unsaturated nitrile monomer; and a first olefinically unsaturated acid monomer.

[0036] (18) The present invention provides a molded product comprising a layer of a latex composition for impregnation molding according to any one of (1) to (8) above.

[0037] Beneficial effects

[0038] The latex composition for dip molding according to the present invention comprises a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex containing an alkaline water-soluble resin unit, and may have a reduced emulsifier content, while exhibiting excellent latex stability and processing performance in the production of molded products.

[0039] Furthermore, the molded products according to the present invention can be molded from a latex composition for dip molding and have low foam generation and excellent tensile properties. Detailed Implementation

[0040] The invention will be described in more detail below to aid in understanding it.

[0041] 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.

[0042] Definition of terminology

[0043] 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 a polymer through the participation of a monomer injected during the polymerization of the polymer in a polymerization reaction.

[0044] In this invention, the term "polymer" can include homopolymers formed by polymerization of one type of monomers and copolymers formed by copolymerization of two types of monomers.

[0045] 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, and as a specific example, they can refer to fine particles of rubbery polymers or rubbery 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.

[0046] The term "composition" as used in this invention includes materials comprising the corresponding composition and mixtures of reaction products and decomposition products formed from the materials of the corresponding composition.

[0047] In this invention, the term "layer from" can refer to a layer formed of a polymer or copolymer, and 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 molded frame during the manufacture of an impregnation molded product.

[0048] Latex composition for dip molding

[0049] This invention provides a latex composition for impregnation molding that exhibits excellent latex stability and processing performance in the manufacture of molded products, while also having a reduced emulsifier content.

[0050] According to an embodiment of the present invention, a latex composition for impregnation molding comprises a first carboxylic acid-modified nitrile copolymer latex containing 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 containing 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; and an alkaline water-soluble resin unit, wherein the alkaline water-soluble resin may comprise a third conjugated diene monomer unit, a third olefinically unsaturated nitrile monomer unit, and a third olefinically unsaturated acid monomer unit.

[0051] According to an embodiment of the present invention, the alkaline water-soluble resin (ASR; alkali-soluble resin) may be an alkali-soluble polymer composition or an alkali-soluble emulsion polymer.

[0052] Typically, carboxylic acid-modified nitrile copolymer latexes constituting latex compositions for dip molding are prepared via emulsion polymerization. In this process, emulsifiers are essential for polymerization stability, and significant amounts of emulsifier remain in the latex. This leads to foaming problems in dip-molded products obtained from latex compositions containing emulsifiers for dip molding. Therefore, the leaching process is intensified to suppress foaming caused by emulsifier residues in the final dip-molded product, but this process consumes a large amount of water. However, it is difficult to reduce the amount of emulsifier for polymerization stability, and even if polymerization stability is ensured by reducing the amount of emulsifier, there is a problem of severely reduced manufacturing and processing properties of the molded product (reduced dehydration shrinkage time).

[0053] However, the latex composition for impregnation molding according to embodiments of the present invention comprises a first carboxylic acid-modified nitrile copolymer latex and a second carboxylic acid-modified nitrile copolymer latex prepared by emulsifying an alkaline water-soluble resin solution with conjugated diene monomers and olefinically unsaturated nitrile monomers, thereby having a reduced amount of residual emulsifier and excellent processing properties in the manufacture of molded products.

[0054] Hereinafter, a latex composition for dip molding according to an embodiment of the present invention will be specifically described by dividing it into constituent components.

[0055] First carboxylic acid modified nitrile copolymer latex

[0056] According to an 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, 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.

[0057] According to an embodiment of the present invention, the first carboxylic acid modified nitrile copolymer may include a first conjugated diene monomer unit, a first olefinically unsaturated nitrile monomer unit, and a first olefinically unsaturated acid monomer unit.

[0058] According to an embodiment of the present invention, the first conjugated dienyl monomer of the first conjugated dienyl monomer unit used to form 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.

[0059] According to an embodiment of the present invention, the first carboxylic acid modified nitrile copolymer may contain 35% to 78% by weight, 40% to 75% by weight, or 45% to 70% by weight of repeating units from the first conjugated diene monomer, and within this range, a molded product molded from a latex composition for impregnation molding comprising a carboxylic acid modified nitrile copolymer latex containing the first carboxylic acid modified nitrile copolymer has the effect of being flexible and having excellent wearing comfort, as well as excellent oil resistance and tensile strength.

[0060] According to an 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 nitrile, α-chloronitrile and α-cyanoethyl acrylonitrile, specifically acrylonitrile and methacrylonitrile, more specifically acrylonitrile.

[0061] According to an embodiment of the present invention, the first carboxylic acid modified nitrile copolymer may include 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 molded from a latex composition for impregnation molding comprising a first carboxylic acid modified nitrile copolymer latex containing the first carboxylic acid modified nitrile copolymer has the effect of being flexible and having excellent wearing comfort, as well as excellent oil resistance and tensile strength.

[0062] According to embodiments of the present invention, the first olefinically unsaturated acid monomer forming the first olefinically unsaturated acid monomer unit of the first carboxylic acid modified nitrile copolymer can be selected from one or more of the following: 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 selected from one or more of 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 can be used in the form of a salt such as an alkali metal salt or an ammonium salt.

[0063] According to an embodiment of the present invention, the first carboxylic acid modified nitrile copolymer may include 0.1% to 10% by weight, 0.5% to 9% by weight, or 1% to 8% by weight of a first olefinic unsaturated acid monomer unit, and within this range, a molded product molded from a latex composition for impregnation molding comprising a first carboxylic acid modified nitrile copolymer latex containing the first carboxylic acid modified nitrile copolymer has the effect of being flexible, having excellent wearability, and simultaneously having excellent tensile strength.

[0064] Second carboxylic acid modified nitrile copolymer latex

[0065] According to an embodiment of the present invention, the second carboxylic acid-modified nitrile copolymer latex can be a latex state in which the second carboxylic acid-modified nitrile copolymer and the alkaline water-soluble resin unit are 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.

[0066] According to an embodiment of the present invention, the second carboxylic acid modified nitrile copolymer latex may include a second carboxylic acid modified nitrile copolymer, wherein the second carboxylic acid modified nitrile copolymer includes a second conjugated diene monomer unit and a second olefinically unsaturated nitrile monomer unit, as well as an alkaline water-soluble resin unit.

[0067] According to an embodiment of the present invention, the second carboxylic acid-modified nitrile copolymer latex has a micelle form, the micelles being formed from alkaline water-soluble resin units, and the micelles may contain within the micelles a second carboxylic acid-modified nitrile copolymer containing a second conjugated diene monomer unit and a second olefinically unsaturated nitrile monomer unit. Specifically, the alkaline water-soluble resin contained in the second carboxylic acid-modified nitrile copolymer latex is a polymerization product of a hydrophilic olefinically unsaturated acid monomer, a hydrophobic conjugated diene monomer, and an olefinically unsaturated nitrile monomer, and the alkaline water-soluble resin dissolves in an alkaline aqueous solution when the olefinically unsaturated acid is ionized at pH 7 or higher. Therefore, when preparing the second carboxylic acid-modified nitrile copolymer, the hydrophobic conjugated diene monomer and the olefinically unsaturated nitrile monomer are mixed with an alkaline water-soluble resin solution, and the hydrophobic portion of the alkaline water-soluble resin is distributed in the hydrophobic monomer, while the hydrophilic portion—the ionized olefinically unsaturated acid—is distributed in the aqueous phase, thereby forming a micelle form similar to a general emulsifier.

[0068] Due to the properties of the alkaline water-soluble resin, the second carboxylic acid-modified nitrile copolymer according to embodiments of the present invention can be readily polymerized without a general emulsifier or with a very small amount of emulsifier, since the alkaline water-soluble resin acts as an emulsifier.

[0069] Furthermore, according to embodiments of the present invention, the "alkaline water-soluble resin unit" may represent a component or structure derived from an alkaline water-soluble resin, or the material itself, and as an embodiment, it may be an alkaline water-soluble resin dispersed together with a second carboxylic acid-modified nitrile copolymer in a second carboxylic acid-modified nitrile copolymer latex. In another embodiment, the alkaline water-soluble resin may act as a reactive polymer emulsifier and may participate in the polymerization reaction together with a second conjugated diene monomer and a second olefinically unsaturated nitrile monomer constituting the second carboxylic acid-modified nitrile copolymer to form chemical bonds and / or strong physical bonds with the polymer chain. In this case, the alkaline water-soluble resin unit may include a unit (part) comprising a component or structure derived from an alkaline water-soluble resin that forms chemical bonds and / or physical bonds with the polymer chain.

[0070] According to embodiments of the present invention, the second conjugated dienyl monomer of the second conjugated dienyl monomer unit used to form the second carboxylic acid modified nitrile copolymer can be the same as that described in the first conjugated dienyl monomer unit used to form the first carboxylic acid modified nitrile copolymer. Specifically, the second conjugated dienyl 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 dienyl monomer of the second conjugated dienyl monomer unit used to form the second carboxylic acid modified nitrile copolymer can be the same as or different from the first conjugated dienyl monomer of the first conjugated dienyl monomer unit used to form the first carboxylic acid modified nitrile copolymer.

[0071] According to an embodiment of the invention, the second carboxylic acid modified nitrile copolymer may comprise 65% to 80% by weight, 65% to 75% by weight, or 65% to 70% by weight of repeating units from the second conjugated diene monomer, and within this range, a molded product molded from a latex composition for impregnation molding comprising a second carboxylic acid modified nitrile copolymer latex containing the second carboxylic acid modified nitrile copolymer is flexible and has excellent wearing comfort, while also exhibiting excellent oil resistance and tensile strength.

[0072] According to embodiments of the present invention, the second olefinically unsaturated nitrile monomer of the second olefinically unsaturated nitrile monomer unit forming the second carboxylic acid-modified nitrile copolymer can be the same as that described in the first olefinically unsaturated nitrile monomer unit used to form the first olefinically unsaturated nitrile monomer unit in the first carboxylic acid-modified nitrile copolymer latex. Specifically, the second olefinically unsaturated nitrile monomer can be one or more selected from acrylonitrile, methacrylonitrile, fumaric nitrile, α-chloronitrile, and α-cyanoethylacrylonitrile, 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.

[0073] According to an embodiment of the present invention, the second carboxylic acid modified nitrile copolymer may include 20% to 40% by weight, 25% to 35% by weight, or 25% to 30% by weight of a second olefinically unsaturated nitrile monomer unit, and within this range, a molded product molded from a latex composition for impregnation molding comprising a second carboxylic acid modified nitrile copolymer latex containing the second carboxylic acid modified nitrile copolymer is flexible and has excellent wearability, while also having excellent oil resistance and tensile strength.

[0074] According to an embodiment of the present invention, the alkaline water-soluble resin forming the alkaline water-soluble resin unit of the second carboxylic acid modified nitrile copolymer may include a third conjugated diene monomer unit, a third olefinically unsaturated nitrile monomer unit, and a third olefinically unsaturated acid monomer unit.

[0075] According to embodiments of the present invention, the alkaline water-soluble resin is characterized by comprising monomer units derived from the same monomers or monomers of the same series as those in the carboxylic acid-modified nitrile copolymer, and thus can act as a stabilizer such as an emulsifier during latex polymerization, allowing the alkaline water-soluble resin to replace or reduce the amount of emulsifier used, while exhibiting excellent polymerization stability, and simultaneously improving the manufacturing and processing properties of molded products comprising a second carboxylic acid-modified nitrile copolymer latex containing the alkaline water-soluble resin for impregnation molding, as well as the mechanical properties of the molded products such as comfort and tensile properties.

[0076] According to an embodiment of the present invention, the third conjugated dienyl monomer of the third conjugated dienyl monomer unit used to form the alkaline water-soluble resin 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. As a specific example, it may be 1,3-butadiene or isoprene. As a more specific example, it may be 1,3-butadiene.

[0077] According to embodiments of the present invention, the third olefinically unsaturated nitrile monomer of the third olefinically unsaturated nitrile monomer unit forming the alkaline water-soluble resin may be one or more selected from acrylonitrile, methacrylonitrile, fumaric acid nitrile, α-chloronitrile and α-cyanoethyl acrylonitrile. As a specific example, it may be acrylonitrile and methacrylonitrile. As a more specific example, it may be acrylonitrile.

[0078] According to embodiments of the present invention, the third olefinically unsaturated acid monomer forming the third olefinically unsaturated acid monomer unit of the basic water-soluble resin can be an olefinically unsaturated monomer containing acidic groups such as carboxyl groups, sulfonic acid groups, and anhydride groups. As a specific example, it can be selected from one or more of the following: 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. More specifically, it can be selected from one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid, and even more specifically, it can be methacrylic acid. The third olefinically unsaturated acid monomer can be used in the polymerization process in the form of a salt such as an alkali metal salt or an ammonium salt.

[0079] According to an embodiment of the present invention, the alkaline water-soluble resin may comprise 40% to 75% by weight of a third conjugated diene monomer unit, 10% to 50% by weight of a third olefinically unsaturated nitrile monomer unit, and 10% to 50% by weight of a third olefinically unsaturated acid monomer unit, and within this range, the glass transition temperature desired by the present invention can be met, thereby maintaining a balance between comfort and tensile properties.

[0080] According to embodiments of the present invention, the alkaline water-soluble resin may include a third conjugated diene monomer unit in an amount of 40% or more, 45% or more, 50% or more, 55% or more, or 60% or more, and may also include a third conjugated diene monomer unit in an amount of 75% or less, 70% or less, 65% or less, or 60% or less. Within this range, the glass transition temperature can be controlled, and the mechanical properties, such as tensile properties, of molded products molded from latex compositions for impregnation molding containing the alkaline water-soluble resin can be improved.

[0081] According to embodiments of the present invention, the alkaline water-soluble resin may include a third olefinically unsaturated nitrile monomer unit in amounts of 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 16% or more, 17% or more, 18% or more, 19% or more, or 20% or more, and may also include a third olefinically unsaturated nitrile monomer unit in amounts of 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 24% or less, 23% or less, 22% or less, 21% or less, or 20% or less. Within this range, the glass transition temperature can be controlled, and the polymerization stability of the latex composition for impregnation molding containing the third olefinically unsaturated nitrile monomer unit can be improved, and the mechanical properties of the molded product molded therefrom, such as comfort and tensile properties, can be improved simultaneously.

[0082] According to embodiments of the present invention, the alkaline water-soluble resin may comprise 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 16% or more, 17% or more, 18% or more, 19% or more, or 20% or more of a third olefinic unsaturated acid monomer unit, and may further comprise 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 24% or less, 23% or less, 22% or less, 21% or less, or 20% or less of a third olefinic unsaturated acid monomer unit. Within this range, the glass transition temperature can be controlled, and the mechanical properties, such as comfort and tensile properties, of molded products molded from latex compositions for impregnation molding containing the third olefinic unsaturated acid monomer units can be improved.

[0083] According to an embodiment of the present invention, the alkaline water-soluble resin may have a weight-average molecular weight of 5,000 g / mol to 50,000 g / mol. As a specific example, the polymer may have a concentration of 5,000 g / mol or greater, 5,500 g / mol or greater, 6,000 g / mol or greater, 6,500 g / mol or greater, 7,000 g / mol or greater, 7,500 g / mol or greater, 8,000 g / mol or greater, 8,500 g / mol or greater, 9,000 g / mol or greater, 9,500 g / mol or greater, 10,000 g / mol or greater, 10,500 g / mol or greater, 11,000 g / mol or greater, 11,500 g / mol or greater, or 12,000 g / mol or greater, and further 50,000 g / mol or less, 49,000 g / mol or less, 48,000 g / mol or less, 47,000 g / mol or less, 46,000 g / mol or less. Weight-average molecular weight of g / mol or less, 45,000 g / mol or less, 40,000 g / mol or less, 35,000 g / mol or less, 30,000 g / mol or less, 25,000 g / mol or less, 20,000 g / mol or less, 15,000 g / mol or less, 14,000 g / mol or less, 13,000 g / mol or less, or 12,000 g / mol or less.

[0084] According to an embodiment of the present invention, the alkaline water-soluble resin may have a glass transition temperature of -34°C to 33°C. As a specific example, the polymer may have a glass transition temperature of -34°C or higher, -33°C or higher, -32°C or higher, -30°C or higher, -29°C or higher, -28°C or higher, -27°C or higher, -26°C or higher, -25°C or higher, -20°C or higher, -15°C or higher, -14°C or higher, -13°C or higher, or -12°C or higher, and 33°C or lower, 32°C or lower, or 31°C. Glass transition temperatures may be 30°C or lower, 29°C or lower, 28°C or lower, 27°C or lower, 26°C or lower, 25°C or lower, 24°C or lower, 23°C or lower, 22°C or lower, 21°C or lower, 20°C or lower, 15°C or lower, 10°C or lower, 5°C or lower, 0°C or lower, -5°C or lower, -10°C or lower, -11°C or lower, or -12°C or lower. In this case, the glass transition temperature can be controlled by the content of each monomer unit of the polymer, especially the content of conjugated diene monomer units, and can be measured using differential scanning calorimetry (DSC).

[0085] Latex composition for dip molding

[0086] According to an embodiment of the invention, the latex composition for dip molding is used for dip molding and may contain an emulsifier in an amount of 1.5 to 2.5 parts by weight based on 100 parts by weight of total solids content.

[0087] According to embodiments of the present invention, the latex composition for dip molding 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 may have a weight ratio of 1.00:0.20 to 1.25, 1.00:0.25 to 1.00, 1.0:0.3 to 1.0, or 1.0:0.6 to 1.0. If the weight ratio is within this range, the emulsifier content of the latex composition for dip molding is controlled as described above, such that the molding product can have excellent manufacturing processability and tensile properties, while having a reduced emulsifier content.

[0088] According to embodiments of the present invention, the latex composition for dip molding may include a crosslinking agent composition for controlling pH and inducing crosslinking during the dip molding process.

[0089] According to an embodiment of the present 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.

[0090] According to embodiments of the present invention, the crosslinking agent composition may include a vulcanizing agent and a vulcanization accelerator, and more specifically, may include a vulcanizing agent, a vulcanization accelerator, and zinc oxide.

[0091] According to embodiments of the present invention, the vulcanizing agent is used to vulcanize a latex composition for dip molding, and may be sulfur, specific examples of which may include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur. Based on 100 parts by weight (based on solids content) of the total content of the first and second carboxylic acid-modified nitrile copolymer latexes in the latex composition for dip molding, the content of the vulcanizing agent may 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 crosslinking ability is effectively achieved by vulcanization.

[0092] According to embodiments of the present invention, the vulcanization accelerator may be one or more selected from 2-mercaptobenzothiazole (MBT), 2,2-dithiobisbenzothiazole-2-sulfinamide (MBTS), N-cyclohexylbenzothiazole-2-sulfinamide (CBS), 2-morpholinothiobenzothiazole (MBS), tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), zinc diethyldithiocarbamate (ZDEC), and zinc di-n-butyldithiocarbamate (ZDBC). Based on the total content of the first and second carboxylic acid modified nitrile copolymer latexes in 100 parts by weight (based on solids content) 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, and within this range, excellent crosslinking ability by vulcanization is effective.

[0093] According to embodiments of the present invention, zinc oxide can be a crosslinking agent used to form crosslinked portions within or between carboxyl-modified nitrile copolymers by ionic bonding with the carboxyl groups of the carboxyl-modified nitrile copolymers in the latex composition for impregnation molding. Based on 100 parts by weight (based on solids content) of the total content of the first and second carboxyl-modified nitrile copolymer latexes in the latex composition for impregnation molding, the zinc oxide content 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, and within this range, excellent crosslinking ability, excellent latex stability, and excellent tensile strength and flexibility of the molded product are observed.

[0094] According to embodiments 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, and within this range, the latex delivery efficiency is excellent and the increase in latex viscosity is prevented, thereby achieving excellent storage stability.

[0095] According to embodiments 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, and within this range, excellent processing performance and productivity can be achieved when manufacturing dip-molded products. The pH of the latex composition for dip molding can be adjusted by adding the aforementioned pH adjuster.

[0096] According to embodiments 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.

[0097] Method for preparing latex compositions for dip molding

[0098] This invention provides a method for preparing a latex composition for dip molding.

[0099] According to an embodiment of the present invention, a method for preparing a latex for impregnation molding includes the steps of mixing a first carboxylic acid-modified nitrile copolymer latex and a second carboxylic acid-modified nitrile copolymer latex. The first carboxylic acid-modified nitrile copolymer latex 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 containing a second conjugated diene monomer unit, a second olefinically unsaturated nitrile monomer unit, and an alkaline water-soluble resin unit. The second carboxylic acid-modified nitrile copolymer latex can be prepared by mixing the second conjugated diene monomer, the second olefinically unsaturated nitrile monomer, and the alkaline water-soluble resin solution and performing emulsion polymerization.

[0100] According to an embodiment of the present invention, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex can be mixed in a weight ratio of 1.00:0.20 to 1.25, 1.00:0.25 to 1.00, 1.0:0.3 to 1.0, or 1.0:0.6 to 1.0. Within this range, a latex composition for dip molding with excellent molding product manufacturing and processing properties can be obtained while reducing the emulsifier content.

[0101] Meanwhile, the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex can be prepared by common emulsion polymerization, which will be described in more detail below.

[0102] Method for preparing nitrile copolymer latex modified with primary carboxylic acid

[0103] According to an embodiment of the present invention, the 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 such that each monomer unit in the first carboxylic acid modified nitrile copolymer latex can satisfy the above-mentioned range.

[0104] According to an 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.

[0105] Specifically, the first carboxylic acid modified nitrile copolymer latex can be prepared by emulsion polymerization in a solvent of 35% to 78% of a first conjugated diene monomer; 20% to 50% of a first olefinically unsaturated nitrile monomer; and 0.1% to 10% of a first olefinically unsaturated acid monomer.

[0106] According to embodiments 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, and the emulsifier can be one or more selected from anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants, and specifically, one or more anionic surfactants selected from alkylbenzene sulfonates, aliphatic sulfonates, higher alcohol sulfates, α-olefin sulfonates and alkyl ether sulfates.

[0107] According to embodiments of the present invention, in the emulsion polymerization for preparing a first carboxylic acid modified nitrile copolymer latex, the emulsifier may be used in an amount from 1.0 part by weight 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 1.0 part 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, it may be injected 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, polymerization stability may be further improved.

[0108] According to embodiments 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 one or more 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.

[0109] According to embodiments of the present invention, the emulsion polymerization for preparing a first carboxylic acid-modified nitrile copolymer latex can be carried out by adding a molecular weight regulator in an amount of 0.8 to 8.0 parts by weight based on 100 parts by weight of total monomer content, specifically by adding an amount 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 by adding an amount of 8.0 parts by weight or less, 7.5 parts by weight or less, or 7... The molecular weight regulator is added in amounts of 0.0 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. Within this range, the molecular weight of the polymer can be appropriately controlled, preventing the latex stability from decreasing 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 molded from the latex composition used for impregnation molding.

[0110] According to embodiments 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, wherein the polymerization initiator can be a free radical initiator, specifically selected from one or more of the following: inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium superphosphate, and hydrogen peroxide; organic peroxides such as tert-butyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, di-tert-butyl peroxide, tert-butylcumene peroxide, acetyl peroxide, isobutyl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanol peroxide, and tert-butyl peroxyisobutyrate; nitrogen compounds such as azobisisobutyronitrile, azobis-2,4-dimethylpentanonitrile, azobiscyclohexylformitrile, and methyl azobisisobutyrate, and specific examples can be inorganic peroxides, and more specific examples can be persulfates.

[0111] According to embodiments of the present invention, the emulsion polymerization for preparing a first carboxylic acid-modified nitrile copolymer latex can be carried out by adding a polymerization initiator in an amount of 0.01 parts by weight to 2.0 parts by weight based on 100 parts by weight of total monomer content, specifically 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. The polymerization initiator may be added in amounts of 0.8 parts by weight or more, 0.9 parts by weight or more, or 1.0 parts by weight or more, and 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 more, 1.4 parts by weight or less, 1.3 parts by weight or less, 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 rate may be maintained at an appropriate level within this range.

[0112] Furthermore, according to embodiments of the present invention, a deodorization step can be performed as needed after emulsion polymerization to remove unreacted monomers and residual components.

[0113] Method for preparing nitrile copolymer latex modified with second carboxylic acid

[0114] According to an 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 an alkaline water-soluble resin solution in a solvent, wherein the amount of each monomer and the alkaline water-soluble resin solution used can be appropriately adjusted to the extent that each unit in the second carboxylic acid modified nitrile copolymer latex satisfies the above-mentioned range.

[0115] According to embodiments of the present invention, the solvent, the second conjugated diene monomer, and the second olefinically unsaturated nitrile monomer may be the same as those described above.

[0116] Specifically, 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 an alkaline water-soluble resin solution in a solvent, wherein the alkaline water-soluble resin solution can be used in an amount of 5 to 25 parts by weight relative to 100 parts by weight of the total amount of the second conjugated diene monomer and the second olefinically unsaturated nitrile monomer, based on the solids content.

[0117] According to an embodiment of the present invention, before initiating emulsion polymerization, an alkaline water-soluble resin solution can be injected in batches together with a second conjugated diene monomer and a second olefinically unsaturated nitrile monomer.

[0118] Furthermore, according to embodiments of the present invention, the alkaline water-soluble resin solution can be injected at least twice, before initiating emulsion polymerization, after initiation, and during polymerization. In another embodiment, the alkaline water-soluble resin solution can be injected for the first time before initiating emulsion polymerization and for the second time after initiating emulsion polymerization, and the second injection can be performed continuously during polymerization conversion of 30% to 70%. In this case, if the alkaline water-soluble resin solution is injected in batches, the total amount of alkaline water-soluble resin solution injected can be from 5 parts by weight to 25 parts by weight, based on the solid content relative to the total amount of 100 parts by weight of conjugated diene monomer and olefin unsaturated nitrile monomer.

[0119] According to embodiments of the present invention, an alkaline water-soluble resin solution can be injected a first time before initiating emulsion polymerization, and a second injection can be performed after initiating emulsion polymerization, with the second injection occurring continuously during a polymerization conversion rate of 30% to 70%. Based on the solids content, the weight ratio of the alkaline water-soluble resin solution during the first injection to that during the second injection can be from 1:0.2 to 1. Furthermore, if the alkaline water-soluble resin solution is injected in batches for emulsion polymerization, there is an effect that can further improve polymerization stability.

[0120] According to an embodiment of the present invention, the polymerization conversion rate can be obtained by collecting a certain amount of sample from the composition undergoing the reaction at certain time intervals, measuring the solid content in the sample, and then calculating it using the following mathematical formula 1.

[0121] [Mathematical Formula 1]

[0122] Polymerization conversion rate (%) = [(Ms - Mo) / (Mp - M'o)] × 100

[0123] In the above mathematical formula 1, Ms is the weight of the dry copolymer, Mo is the sum of the weights of the emulsifier and the polymerization initiator, Mp is the weight of the 100% polymerized copolymer, and M'o is the sum of the weights of the emulsifier and the polymerization initiator.

[0124] According to embodiments of the present invention, the alkaline water-soluble resin solution may have a pH of 7.0 to 10.0 at 25°C. In specific examples, the alkaline water-soluble resin solution may have a pH of 7.0 or higher, 7.1 or higher, 7.2 or higher, 7.3 or higher, 7.4 or higher, 7.5 or higher, 7.6 or higher, 7.7 or higher, 7.8 or higher, 7.9 or higher, or 8.0 or higher and 10.0 or lower, 9.9 or lower, 9.8 or lower, 9.7 or lower, 9.6 or lower, 9.5 or lower, 9.4 or lower, 9.3 or lower, 9.2 or lower, 9.1 or lower, or 9.0 or lower at 25°C, and within this range, the alkaline water-soluble resin solution can more effectively act as a polymerization stabilizer when preparing a second carboxylic acid modified nitrile copolymer latex, thereby improving latex stability.

[0125] According to embodiments of the present invention, emulsion polymerization can be carried out in the absence of an emulsifier, and, if desired, in the presence of one or more additives selected from emulsifiers, molecular weight regulators, and polymerization initiators. Since the alkaline water-soluble resin solution can act as a polymerization stabilizer like an emulsifier, the second carboxylic acid-modified nitrile copolymer latex can be stably polymerized even in the absence of an emulsifier or in the presence of a reduced amount of emulsifier.

[0126] According to embodiments of the present invention, the emulsifier, molecular weight regulator, and polymerization initiator may be the same as those described above.

[0127] According to embodiments of the present invention, if an emulsifier is used in the emulsion polymerization for preparing a second carboxylic acid modified nitrile copolymer latex, the emulsifier can be used in an amount from 0.3 parts by weight to 2.0 parts by weight, based on 100 parts by weight of the monomers constituting the second carboxylic acid modified nitrile copolymer (e.g., the second conjugated diene monomer and the second olefinically unsaturated nitrile monomer) or the total solids content of the second carboxylic acid modified nitrile copolymer. Specifically, the emulsifier can be injected in an amount of 0.3 parts by weight or more, 0.4 parts by weight or more, 0.5 parts by weight or more, or 0.6 parts by weight or more, and can be injected in an amount of 2.0 parts by weight or less, 1.8 parts by weight or less, 1.6 parts by weight or less, 1.4 parts by weight or less, 1.2 parts by weight or less, or 1.0 parts by weight or less, and within this range, the polymerization stability can be further improved.

[0128] According to embodiments of the present invention, the emulsion polymerization for preparing a second carboxylic acid-modified nitrile copolymer latex can be carried out by adding a molecular weight regulator in amounts from 0.8 parts by weight to 8.0 parts by weight based on 100 parts by weight of total monomer content, specifically 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 8.5 parts by weight or less, 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, or 4.0 parts by weight or less. 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.

[0129] According to embodiments of the present invention, the emulsion polymerization for preparing a second carboxylic acid-modified nitrile copolymer latex can be carried out by adding a polymerization initiator in an amount of 0.01 parts by weight to 2.0 parts by weight based on 100 parts by weight of total monomer content, and specifically, 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, or 0.7 parts by weight. The polymerization initiator may be added in amounts of 0.8 parts by weight or more, 0.9 parts by weight or more, or 1.0 parts by weight or more and 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, 1.3 parts by weight or less, 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 rate may be maintained at an appropriate level within this range.

[0130] Furthermore, according to embodiments of the present invention, a deodorization step can be performed as needed after emulsion polymerization to remove unreacted monomers and residual components.

[0131] Meanwhile, according to an embodiment of the present invention, the alkaline water-soluble resin solution can be prepared by a preparation method including the following steps: preparing a polymer latex by emulsion polymerization of a third conjugated diene monomer, a third olefinically unsaturated nitrile monomer and a third olefinically unsaturated acid monomer in a solvent (S10); and adding a pH adjuster to the polymer latex (S20).

[0132] According to embodiments of the present invention, the solvent, the third conjugated diene monomer, the third olefinically unsaturated nitrile monomer, and the third olefinically unsaturated acid monomer can be the same as those described above.

[0133] According to an embodiment of the invention, step (S10) is a step of preparing a polymer latex, which can be carried out by emulsion polymerization, and in this case, the emulsion polymerization can be carried out in the presence of an emulsifier and a molecular weight regulator. Furthermore, the emulsifier and molecular weight regulator can be the same as those described above.

[0134] According to an embodiment of the present invention, the emulsion polymerization in step (S10) can be carried out by adding an emulsifier 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 can be added 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 can be added 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.

[0135] According to an embodiment of the invention, the emulsion polymerization in step (S10) can be carried out by adding a molecular weight regulator in an amount of 0.8 to 8.0 parts by weight based on 100 parts by weight of total monomer content. Specifically, it can be carried out by adding a molecular weight regulator in an amount 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. It can also be carried out by adding a molecular weight regulator in an amount 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. By appropriately adjusting the molecular weight of the polymer within this range, the latex stability can be prevented from deteriorating due to increased viscosity.

[0136] According to an embodiment of the present invention, the emulsion polymerization in step (S10) can be initiated by injecting a polymerization initiator, and the polymerization initiator can be a free radical initiator. In this case, the polymerization initiator can be the same as described above.

[0137] According to an embodiment of the invention, the emulsion polymerization in step (S10) can be carried out by injecting a polymerization initiator in an amount of 0.01 parts by weight to 2.0 parts by weight based on 100 parts by weight of total monomer content. Specifically, it can be carried out by injecting a polymerization initiator 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, or 0. The polymerization initiator can be injected in amounts of 9 parts by weight or more, or 1.0 parts by weight or more, and can also be carried out by injecting in amounts 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, 1.3 parts by weight or less, 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 rate can be maintained at an appropriate level within this range.

[0138] According to an embodiment of the invention, step (S20) is a step of adjusting the pH of the polymer latex prepared in step (S10), thereby adjusting the pH of the finally obtained alkaline water-soluble resin solution at 25°C to 7.0 to 10.0. In this case, the pH adjuster may be an alkaline compound, specifically including alkaline hydroxide salts and / or ammonia solutions, and more specifically including sodium hydroxide or potassium hydroxide.

[0139] Furthermore, according to an embodiment of the present invention, after step (S20), a deodorization step may be performed as needed to remove unreacted monomers and residual components.

[0140] Molded products

[0141] The present invention provides an dip-molded product manufactured by dip molding a latex composition used for dip molding.

[0142] According to embodiments of the present invention, a molded product may include a layer from a latex composition used for dip molding. The molded product may be an dip-molded product manufactured by dip molding the latex composition used for dip molding, and may be a molded product comprising a layer from the latex composition used for dip molding formed by dip molding from the latex composition used for dip molding. A method for manufacturing the molded product may include the step of immersing the latex composition used for dip molding by direct immersion, anodic adhesive immersion, Teague adhesive immersion, etc., particularly by anodic adhesive immersion, in which case there is the advantage of obtaining a dip-molded product with a uniform thickness.

[0143] According to an embodiment of the present invention, the method for manufacturing the molded product includes the steps of attaching a coagulant to an impregnation mold frame (S100); immersing the impregnation mold frame to which the coagulant is attached in a latex composition for impregnation molding to form a layer from the latex composition for impregnation molding, namely an impregnation molding layer (S200); and heating the impregnation molding layer to crosslink the latex composition for impregnation molding (S300).

[0144] According to an embodiment of the invention, step (S100) involves immersing the immersion mold frame in a coagulant solution to adhere the coagulant to the surface of the immersion mold frame to form a coagulant within the immersion mold frame. 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 solution can be from 5% to 75% by weight, 5% to 50% by weight, or 10% to 40% by weight, based on the total content of the coagulant solution. The coagulant can be one or more 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, particularly calcium chloride or calcium nitrate. Furthermore, according to an embodiment of the present invention, in order to adhere the coagulant to the impregnation mold frame, step (S100) may further include immersing the impregnation mold frame in the coagulant solution for 5 seconds or longer, removing the impregnation mold frame, and drying it at 50°C to 150°C.

[0145] According to an embodiment of the invention, step (S200) may be the step of immersing an impregnation mold frame to which a coagulant is attached in a latex composition for impregnation molding according to the 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 an embodiment of the invention, step (S200) may be performed for 5 seconds or longer to form an impregnation molding layer on the impregnation mold frame.

[0146] According to an embodiment of the invention, step (S300) may be a step of heating the dip molding layer formed on the dip mold frame to evaporate the liquid component and crosslink and harden the latex composition for dip molding to obtain a dip molded product. In this case, if the latex composition for dip molding according to the invention is used, crosslinking can be performed by vulcanization and / or ionic bonding of the crosslinking agent composition contained in the latex composition for dip molding. Furthermore, according to an embodiment of the invention, the heating may be performed by first heating at 70°C to 150°C for 1 minute to 10 minutes and then heating a second time 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 leaching process by immersion in water or warm water for 10 seconds to 10 minutes may be further included.

[0147] According to embodiments of the present invention, the molded product may be gloves (including surgical gloves, examination gloves, industrial gloves, and household gloves), condoms, catheters, or health care products.

[0148] The embodiments of the present invention will now be described in detail 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.

[0149] Examples and Comparative Examples

[0150] Example 1

[0151] <Preparation of nitrile copolymer latex modified with primary carboxylic acid>.

[0152] A 10 L high-pressure reactor, equipped with a thermometer, cooler, nitrogen inlet, and inlet for continuous injection of monomers, emulsifiers, and polymerization initiators, was used. After purging the 10 L high-pressure reactor with nitrogen, 27 wt% acrylonitrile, 67 wt% 1,3-butadiene, 6 wt% methacrylic acid, and a monomer mixture based on 100 parts by weight of acrylonitrile, 1,3-butadiene, and methacrylic acid, 2.8 parts by weight of sodium alkylbenzene sulfonate as emulsifier, 0.7 parts by weight of tert-dodecyl mercaptan as molecular weight regulator, and 150 parts by weight of deionized water were injected, and the internal temperature of the reactor was raised to 40°C. After the temperature rise was complete, 1.0 part by weight of potassium persulfate as a polymerization initiator was added to initiate polymerization, and when the polymerization conversion rate was 95%, 1.0 part by weight of sodium dimethyl dithiocarbamate was added to terminate the polymerization, thereby producing 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 carried out to remove unreacted monomers, thereby obtaining a first carboxylic acid modified nitrile copolymer latex.

[0153] <Preparation of Nitrile-Modified Second Carboxylic Acid Copolymer Latex>

[0154] 1) Preparation of alkaline water-soluble resin solution

[0155] A 10 L high-pressure reactor, equipped with a thermometer, cooler, nitrogen inlet, and inlet for continuous injection of monomers, emulsifiers, and polymerization initiators, was used. After purging the 10 L high-pressure reactor with nitrogen, 20 wt% acrylonitrile, 60 wt% 1,3-butadiene, 20 wt% methacrylic acid, a monomer mixture based on 100 parts by weight of acrylonitrile, 1,3-butadiene, and methacrylic acid, 2.5 parts by weight of sodium alkylbenzene sulfonate as an emulsifier, 4.0 parts by weight of tert-dodecyl mercaptan as a molecular weight regulator, and 250 parts by weight of deionized water were added to raise the internal temperature of the reactor to 40 °C. After heating, 1.0 part by weight of potassium persulfate as a polymerization initiator was added to initiate polymerization. When the polymerization conversion rate reached 95%, potassium hydroxide was added to adjust the pH to 9.5 at 25 °C, and a deodorization process was performed to remove unreacted monomers, thereby obtaining an alkaline water-soluble resin solution.

[0156] 2) Preparation of nitrile copolymer latex modified with second carboxylic acid

[0157] A 10 L high-pressure reactor was used, equipped with a thermometer, cooler, nitrogen inlet, and inlet for continuous injection of monomers, emulsifiers, and polymerization initiators. After purging the 10 L high-pressure reactor with nitrogen, 30 wt% acrylonitrile, 70 wt% 1,3-butadiene, and based on 100 parts by weight of a monomer mixture of acrylonitrile and 1,3-butadiene, 15 parts by weight (based on solids content) of the alkaline water-soluble resin solution prepared above, 0.7 parts by weight of tert-dodecyl mercaptan as a molecular weight regulator, and 150 parts by weight of deionized water were added, and the internal temperature of the reactor was raised to 40°C. After the temperature rise was complete, 1.0 part by weight of potassium permanganate as a polymerization initiator was added to initiate polymerization, and 5 parts by weight (based on solids content) of the alkaline water-soluble resin solution were continuously added during the polymerization conversion process from 30% to 70%. At a polymerization conversion rate of 95%, 1.0 part by weight of sodium dimethyldithiocarbamate was added to terminate the polymerization, thereby preparing a polymer latex containing the polymer. Subsequently, a deodorization process was performed to remove unreacted monomers, thereby obtaining a second carboxylic acid-modified nitrile copolymer latex.

[0158] <Preparation of latex compositions for dip molding>

[0159] To 100 parts by weight (based on solids content) of the first carboxylic acid-modified nitrile copolymer latex and the second carboxylic acid-modified nitrile copolymer latex prepared above, 1.2 parts by weight of a 3% potassium hydroxide aqueous solution, 1.2 parts by weight of a vulcanizing agent (Akron dispersions Co., BOSTEX 378), 0.7 parts by weight of a vulcanization accelerator (Akron dispersions Co., BOSTEX 497B), 1.0 parts by weight of zinc oxide (Akron dispersions Co., BOSTEX 422), 1.0 parts by weight of titanium dioxide (Akron dispersions Co., BOSTEX 497D), and double-distilled water were added to prepare a latex composition for dip molding with a solids content of 25% by weight. Ammonia was added to prepare a latex composition for dip molding with a pH of 10 at 25°C. In this case, the first carboxylic acid-modified nitrile copolymer latex and the second carboxylic acid-modified nitrile copolymer latex were mixed at a weight ratio of 80:20 (4:1).

[0160] <Manufacturing dip-molded products>

[0161] 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 allow the coagulant to be applied to the mold.

[0162] Subsequently, the hand-shaped mold to which the coagulant was applied was 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. Again, after crosslinking the mold at 110°C for 20 minutes, the crosslinked dip molding layer was peeled off from the hand-shaped mold to obtain a glove-shaped dip-molded product.

[0163] Example 2

[0164] The same procedure as in Example 1 was performed to prepare a latex composition for dip molding, except that in the preparation of the latex composition for dip molding, a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex were mixed at a weight ratio of 70:30 (about 2.3:1), and the dip molding product was obtained using the latex composition.

[0165] Example 3

[0166] The same procedure as in Example 1 was performed to prepare a latex composition for dip molding, except that in the preparation of the latex composition for dip molding, a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex were mixed at a weight ratio of 60:40 (about 1.5:1), and the dip molding product was obtained using the latex composition.

[0167] Example 4

[0168] The same procedure as in Example 1 was performed to prepare a latex composition for dip molding, except that in the preparation of the latex composition for dip molding, a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex were mixed in a weight ratio of 50:50 (about 1:1), and the dip molding product was obtained using the latex composition.

[0169] Example 5

[0170] The same procedure as in Example 1 was performed to prepare a latex composition for dip molding, except that in the preparation of the latex composition for dip molding, a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex were mixed at a weight ratio of 90:10 (about 9:1), and the dip molding product was obtained using the latex composition.

[0171] Example 6

[0172] The same procedure as in Example 1 was performed to prepare a latex composition for dip molding, except that in the preparation of the latex composition for dip molding, a first carboxylic acid modified nitrile copolymer latex and a second carboxylic acid modified nitrile copolymer latex were mixed at a weight ratio of 40:60 (about 1:1.5), and the dip molding product was obtained using the latex composition.

[0173] Comparative Example 1

[0174] The same procedure as in Example 1 was performed to prepare a latex composition for dip molding, except that the second carboxylic acid modified nitrile copolymer latex was not mixed in the preparation of the latex composition for dip molding, and 100 parts by weight of the first carboxylic acid modified nitrile copolymer latex was used, and the dip molding product was obtained using the latex composition.

[0175] Comparative Example 2

[0176] The same procedure as in Example 1 was performed to prepare a latex composition for dip molding, except that the second carboxylic acid modified nitrile copolymer latex was not mixed in the preparation of the latex composition for dip molding, 100 parts by weight of the first carboxylic acid modified nitrile copolymer latex was used, and 2.2 parts by weight of emulsifier was used in the preparation of the first carboxylic acid modified nitrile copolymer latex, and the dip molding product was obtained using the latex composition.

[0177] Comparative Example 3

[0178] <Preparation of Carboxylic Acid Modified Acrylonitrile Copolymer Latex>

[0179] A 10 L high-pressure reactor, equipped with a thermometer, cooler, nitrogen inlet, and inlet for continuous injection of monomers, emulsifiers, and polymerization initiators, was used. After purging the 10 L high-pressure reactor with nitrogen, 27 wt% acrylonitrile, 67 wt% 1,3-butadiene, 6 wt% methacrylic acid, and a monomer mixture based on 100 parts by weight of acrylonitrile, 1,3-butadiene, and methacrylic acid, 2.8 parts by weight of sodium alkylbenzene sulfonate as emulsifier, 0.7 parts by weight of tert-dodecyl mercaptan as a molecular weight regulator, and 150 parts by weight of deionized water were added, and the internal temperature of the reactor was raised to 40°C. After the temperature rise was complete, 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 dimethyl dithiocarbamate was added to terminate the polymerization, thereby producing 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 carried out to remove unreacted monomers, thereby obtaining a carboxylic acid modified nitrile copolymer latex.

[0180] <Preparation of alkaline water-soluble resin solution>

[0181] A 10 L high-pressure reactor, equipped with a thermometer, cooler, nitrogen inlet, and inlet for continuous injection of monomers, emulsifiers, and polymerization initiators, was used. After purging the 10 L high-pressure reactor with nitrogen, 20 wt% acrylonitrile, 60 wt% 1,3-butadiene, 20 wt% methacrylic acid, and a monomer mixture based on 100 parts by weight of acrylonitrile, 1,3-butadiene, and methacrylic acid, 2.5 parts by weight of sodium alkylbenzene sulfonate as an emulsifier, 4.0 parts by weight of tert-dodecyl mercaptan as a molecular weight regulator, and 250 parts by weight of deionized water were added to raise the internal temperature of the reactor to 40 °C. After heating, 1.0 part by weight of potassium persulfate as a polymerization initiator was added to initiate polymerization. When the polymerization conversion rate reached 95%, potassium hydroxide was added to adjust the pH to 9.5 at 25 °C, and a deodorization process was performed to remove unreacted monomers, thereby obtaining an alkaline water-soluble resin solution.

[0182] <Preparation of latex compositions for dip molding>

[0183] To 100 parts by weight (based on solids content) of the carboxylic acid-modified nitrile copolymer latex prepared above, 5 parts by weight of an alkaline water-soluble resin solution, 1.2 parts by weight of a 3% potassium hydroxide aqueous solution, 1.2 parts by weight of a vulcanizing agent (Akron dispersions Co., BOSTEX 378), 0.7 parts by weight of a vulcanization accelerator (Akron dispersions Co., BOSTEX 497B), 1.0 part by weight of zinc oxide (Akron dispersions Co., BOSTEX 422), 1.0 part by weight of titanium dioxide (Akron dispersions Co., BOSTEX 497D), and double-distilled water were added to prepare a latex composition for dip molding with a solids content of 25% by weight. Ammonia was added to prepare a latex composition for dip molding with a pH of 10 at 25°C. Furthermore, the dip-molded product was obtained by performing the same procedure as in Example 1.

[0184] Comparative Example 4

[0185] The same procedure as Comparative Example 3 was performed to prepare a latex composition for dip molding, except that in the preparation of the latex composition for dip molding, 20 parts by weight of an alkaline water-soluble resin was mixed with 100 parts by weight of a carboxylic acid-modified nitrile copolymer latex, and the latex composition was used to obtain dip-molded articles.

[0186] Test Examples

[0187] Experimental Example 1

[0188] The latex stability and total emulsifier content of the latex compositions for impregnation molding prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were measured, and the results are shown in Table 1 below.

[0189] (1) Latex stability

[0190] Latex stability is determined by the total coagulum content and the amount of reactor fouling generated.

[0191] The total clumping content was determined by filtering each composition through a #200 mesh sieve and measuring the weight of the filtered clumping. A lower weight indicates better latex stability.

[0192] A 10-point scale was used to score the amount of fouling generated in the reactor after polymerization, thus evaluating the amount of fouling in the reactor; a higher score was better. In this case, a completely clean reaction was given 10 points, fine, ribbon-like fouling at the reaction interface was given 9 points, fouling across the entire impeller was given 5 points, fouling that made subsequent polymerization difficult was given 2 points, and complete disruption of latex stability was given 0 points.

[0193] (2) Total emulsifier content

[0194] Total emulsifier content is expressed as the sum of the total emulsifier content added up to the preparation of the latex composition for dip molding.

[0195] [Table 1]

[0196] As shown in Table 1 above, it can be confirmed that Examples 1 to 6 have reduced emulsifier content, but have lower or similar total clumping content and reactor fouling than those of the Comparative Examples. Specifically, compared to Comparative Example 1 (which corresponds to a latex composition for dip molding containing only a first carboxylic acid-modified nitrile copolymer latex), Examples 1 to 6 have a reduced emulsifier content of about 50% to 90%, but exhibit equal or higher levels of latex stability, and it is confirmed that latex stability is significantly improved with reduced or similar emulsifier content compared to Comparative Example 2 (which corresponds to a latex composition for dip molding containing only a carboxylic acid-modified nitrile copolymer latex prepared by reducing the amount of emulsifier used).

[0197] Furthermore, compared to the examples, Comparative Examples 3 and 4 (which correspond to latex compositions for impregnation molding prepared by mixing an alkaline water-soluble resin solution with a carboxylic acid-modified nitrile copolymer latex) have an increased emulsifier content of about 10% to 200%, but the latex stability is the same or slightly improved.

[0198] Experimental Example 2

[0199] The dip molding processing properties of the latex compositions prepared in Examples 1 to 6 and Comparative Examples 1 to 4 for dip molding, and the tensile strength, elongation, 500% modulus and foaming degree of the dip molded products were measured, and the results are shown in Table 2 below.

[0200] (1) Impregnation molding processing performance

[0201] The processing performance of dip molding is evaluated by dehydration shrinkage and webbing.

[0202] After applying and drying a CaNO3 solution to a cylindrical ceramic mold, and then immersing it in each latex composition used for impregnation molding, dehydration shrinkage was measured by the time (in seconds) it took for the water droplets to fall, which occurred when the film was dried in an oven at 80°C. Longer times (the longer the time elapsed) are better.

[0203] The web formation was measured in seconds by the time it took for the foam film formed on the ring to rupture when a triangular ring was inserted into each latex composition used for molding and then removed. The shorter the time (the less time elapsed), the better.

[0204] (2) Tensile strength (MPa), elongation (%) and 500% modulus (MPa)

[0205] Tensile strength was measured using dumbbell-shaped specimens prepared according to ASTM D-412 for each type of impregnated molded part. Using these specimens, the specimens were stretched at a crosshead speed of 500 mm / min using a Universal Testing Machine (UTM) (Instron Co., model 4466) according to ASTM D638, and the point of fracture was measured. The tensile strength was calculated using mathematical formula 2 below and then converted to MPa (1 MPa = 0.10197 kgf / mm²). 2 At this point, the higher the calculated tensile strength, the better the tensile properties.

[0206] [Mathematical Formula 2]

[0207] Tensile strength (kgf / mm) 2 = Load value (kgf) / (thickness (mm) × width (mm))

[0208] Elongation is calculated as follows: using a specimen manufactured for tensile strength measurement, according to ASTM D638, using a universal testing machine (UTM) (Instron Co., model 4466) at a crosshead speed of 500 mm / min, the point of fracture of the specimen is measured, and the elongation is calculated according to mathematical formula 3 below. In this case, the higher the calculated elongation, the better the tensile properties.

[0209] [Mathematical Formula 3]

[0210] Elongation (%) = (Length of specimen after elongation / Length of specimen before elongation) × 100

[0211] Using specimens manufactured for tensile strength measurement, the 500% modulus was measured using a Universal Testing Machine (UTM) apparatus (Instron Co., model 4466) at a crosshead speed of 500 mm / min, according to ASTM D638. The tensile strength at the 500% modulus was measured when the specimen was stretched five times its original length. In this case, the lower the measured 500% modulus, the softer and more comfortable it is to wear.

[0212] (3) Foam generation rate (%)

[0213] After dripping water eight times onto each dip-molded product, rub them together for 10 seconds to create foam. Immediately afterward, take a picture to obtain an image. Use the ImageJ program to obtain the foam area and total area of ​​the molded products, and calculate using the mathematical formula 4 below. The smaller the number, the better.

[0214] [Mathematical Formula 4]

[0215] Foam generation rate (%) = [Foam area / Total area of ​​molded product] × 100.

[0216] [Table 2]

[0217] As shown in Table 2 above, the dip-molded products of Examples 1 to 6 are confirmed to have significantly improved processing performance and greatly reduced foam generation, while having tensile properties that are at least as good as those of Comparative Examples 1 to 4.

Claims

1. A latex composition for dip molding, said latex composition comprising: A first carboxylic acid-modified nitrile copolymer latex comprising a first carboxylic acid-modified nitrile copolymer, wherein the first carboxylic acid-modified nitrile copolymer comprises: 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 conjugated diene monomer unit and a second olefinically unsaturated nitrile monomer unit, and an alkaline water-soluble resin unit, wherein... The alkaline water-soluble resin comprises a third conjugated diene monomer unit, a third olefinically unsaturated nitrile monomer unit, and a third olefinically unsaturated acid monomer unit.

2. The latex composition for dip molding according to claim 1, wherein the first carboxylic acid modified nitrile copolymer latex and the second carboxylic acid modified nitrile copolymer latex have a weight ratio of 1.00:0.20 to 1.

25.

3. The latex composition for impregnation molding according to claim 1, wherein the first carboxylic acid modified nitrile copolymer comprises: 35% to 78% 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 comprises: 60% to 80% by weight of the second conjugated diene monomer unit; and 20% to 40% by weight of the second olefinically unsaturated nitrile monomer unit.

5. The latex composition for impregnation molding according to claim 1, wherein the second carboxylic acid modified nitrile copolymer latex comprises 5 to 25 parts by weight of the alkaline water-soluble resin unit relative to 100 parts by weight of the second carboxylic acid modified nitrile copolymer.

6. The latex composition for impregnation molding according to claim 1, wherein the alkaline water-soluble resin comprises: 40% to 75% by weight of a third conjugated diene monomer unit; 10% to 50% by weight of a third olefinically unsaturated nitrile monomer unit; and 10% to 50% by weight of a third olefinically unsaturated acid monomer unit.

7. The latex composition for dip molding according to claim 1, wherein... The second carboxylic acid-modified nitrile copolymer latex has a micelle form. The micelles are formed from the alkaline water-soluble resin units, and The micelles contain the second carboxylic acid-modified nitrile copolymer within them.

8. The latex composition for dip molding according to claim 1, comprising 1.5 to 2.5 parts by weight of emulsifier relative to a total solid content of 100 parts by weight.

9. A method for preparing a latex composition for dip molding, the method comprising: The step of mixing a nitrile copolymer latex modified with a first carboxylic acid and a nitrile copolymer latex modified with a second carboxylic acid, wherein 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 includes a second conjugated diene monomer unit and a second olefinically unsaturated nitrile monomer unit, as well as an alkaline water-soluble resin unit. The second carboxylic acid modified nitrile copolymer latex is prepared by mixing a second conjugated diene monomer, a second olefinically unsaturated nitrile monomer, and an alkaline water-soluble resin solution, and then performing emulsion polymerization on the mixture.

10. The method for preparing a latex composition for dip molding according to claim 9, 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 1.00:0.20 to 1.

25.

11. The method for preparing a latex composition for impregnation molding according to claim 9, wherein the alkaline water-soluble resin solution is used in an amount of 5 to 25 parts by weight, based on the solids content, relative to the total amount of 100 parts by weight of the second conjugated diene monomer and the second olefinically unsaturated nitrile monomer.

12. The method for preparing a latex composition for impregnation molding according to claim 9, wherein the alkaline water-soluble resin solution is injected at least twice, before and after initiating emulsion polymerization.

13. The method for preparing a latex composition for dip molding according to claim 9, wherein... An alkaline water-soluble resin solution was injected for the first time before emulsion polymerization was initiated, and a second alkaline water-soluble resin solution was injected after emulsion polymerization was initiated. A second injection is performed consecutively within a polymerization conversion rate range of 30% to 70%.

14. The method for preparing a latex composition for dip molding according to claim 13, wherein the alkaline water-soluble resin solution in the first injection has a weight ratio of 1:0.2 to 1 to the alkaline water-soluble resin solution in the second injection, based on the solids content.

15. The method for preparing a latex composition for impregnation molding according to claim 9, wherein the alkaline water-soluble resin solution is prepared by a preparation method comprising the following steps: The steps of emulsion polymerization of a third conjugated diene monomer, a third olefinically unsaturated nitrile monomer, and a third olefinically unsaturated acid monomer in a solvent to prepare a polymer latex; and The step of injecting a pH adjuster into the polymer latex.

16. The method for preparing a latex composition for impregnation molding according to claim 9, wherein the alkaline water-soluble resin solution has a pH of 7.0 to 10.0 at 25°C.

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

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

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