A latex composition for dip molding with excellent chemical resistance and dip-molded articles manufactured therefrom.

Abstract

This invention provides a latex composition for dip molding with excellent chemical resistance and durability due to its high gel content and high degree of crosslinking, and a dip-molded product that maintains the excellent tensile strength and elongation of existing nitrile-based latex, while possessing excellent durability and chemical resistance. [Solution] A latex composition for dip molding is provided, comprising a copolymer latex obtained by polymerizing an ethylenically unsaturated nitrile monomer, an isoprene monomer, a butadiene monomer, and an ethylenically unsaturated acid monomer, wherein the content of the butadiene monomer is 5 to 20 parts by weight based on 100 parts by weight of the total sum of the isoprene monomer and the butadiene monomer, and the gel content of the copolymer latex is 40 to 90%.

Description

Technical Field

[0001] This specification relates to a latex composition for dip molding having excellent chemical resistance and a dip molded article manufactured therefrom. This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0149594, filed with the Korean Intellectual Property Office on October 29, 2024, the entire contents of which are incorporated herein by reference.

Background Art

[0002] Conventionally, the main raw material of gloves used for medical, agricultural and livestock product processing or industrial purposes was natural rubber latex. However, when using gloves manufactured from natural rubber latex, the problem that users of the gloves suffered from contact allergic diseases frequently occurred due to the proteins contained in the natural rubber latex. In contrast, attempts have been made to manufacture gloves by applying synthetic rubber latex that does not contain proteins, such as nitrile copolymer latex. Nitrile copolymer latex gloves are superior in mechanical strength compared to natural rubber latex gloves, and there is a tendency for demand to increase in the medical or food fields where frequent contact with sharp objects occurs. With the increasing use of nitrile copolymer latex, the need to improve the quality of dip molded articles has increased. Along with this, attempts have been made to improve the durability such as tensile strength and elongation rate of dip molded articles manufactured from latex for dip molding. However, despite such attempts to improve mechanical properties, cases where human life accidents occurred due to damage to dip molded articles or the desired objectives could not be achieved have continued to appear. In particular, molded articles used for the purpose of protecting the human body against chemical reactions, etc. need to have chemical resistance to maintain their shape stably without deformation in various solvents such as acetone and n-hexane, which are organic solvents. Thus, there is a need for the development of a technology for manufacturing dip molded articles having excellent durability and chemical resistance while maintaining the excellent tensile strength and elongation rate of existing nitrile latex. [Overview of the project] [Problems that the invention aims to solve]

[0003] The provisions described herein are intended to solve the problems of the prior art described above, and one of the objectives of this specification is to provide a latex composition for dip molding that has excellent chemical resistance and durability due to its high gel content and high degree of crosslinking. [Means for solving the problem]

[0004] In one aspect, a latex composition for dip molding is provided, comprising a copolymer latex polymerized from an ethylenically unsaturated nitrile monomer, an isoprene monomer, a butadiene monomer, and an ethylenically unsaturated acid monomer, wherein the content of the butadiene monomer is 5 to 20 parts by weight based on 100 parts by weight of the total sum of the isoprene monomer and the butadiene monomer, and the gel content of the copolymer latex is 40 to 90%.

[0005] In one embodiment, the ethylenically unsaturated nitrile monomer may be one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, α-cyanoethylacrylonitrile, and two or more combinations thereof.

[0006] In one embodiment, the ethylenically unsaturated acid monomer may be one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, citraconic anhydride, styrene sulfonic acid, monobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate, and two or more combinations thereof.

[0007] In one embodiment, the copolymer latex may contain 1 to 55 parts by weight of the ethylenically unsaturated nitrile monomer, 65 to 80 parts by weight of the isoprene monomer, 1 to 10 parts by weight of the butadiene monomer, and 1.5 to 6.0 parts by weight of the ethylenically unsaturated acid monomer.

[0008] In one embodiment, the deformation ratio of a dip-molded article produced with the dip-molding latex composition may be 50% or less, as represented by the following formula 1: [Formula 1] (Deformation ratio) = (ab) / a*100. (In Equation 1, a represents the weight (g) measured after manufacturing a dip-molded product with a width of 30 mm, a length of 135 mm, and a thickness of 0.06-0.09 mm, and b represents the weight measured after immersing the manufactured dip-molded product in 80 ml of solvent and stirring at room temperature for 4 hours.)

[0009] In one embodiment, the solvent may be one selected from the group consisting of acetone, ethanol, isopropyl alcohol, methyl ethyl ketone, n-heptane, and toluene. In another aspect, a dip-molded article is provided, manufactured from the dip-molding latex composition.

[0010] In one embodiment, the dip-molded product may be a surgical glove, a medical glove, a glove for processing agricultural and livestock products, an industrial glove, a condom, a cosmetic material, a catheter, or a molded product for healthcare. [Effects of the Invention]

[0011] The latex composition for dip molding described herein, in one aspect, has a high gel content and a high degree of crosslinking, and therefore possesses excellent mechanical properties such as elongation, and can also have excellent chemical resistance. Furthermore, dip-molded articles according to another aspect of this specification offer excellent chemical resistance and durability, making them applicable to a wide range of fields, including surgical gloves, medical gloves, gloves for processing agricultural and livestock products, industrial gloves, condoms, cosmetic materials, catheters, and molded articles for healthcare. The effects of one aspect of this specification should be understood to include all effects that can be inferred from the detailed description or claims herein, not limited to those described above. [Modes for carrying out the invention]

[0012] The following describes one aspect of this specification based on specific examples. However, the provisions of this specification may be embodied in various different forms and are therefore not limited to the examples described herein. Throughout the specification, when a part is said to be “connected” to another part, this includes not only cases where they are “directly connected” but also cases where they are “indirectly connected” through other components in between. Also, when a part is said to “include” a certain component, this does not exclude other components unless otherwise stated, but rather means that it may further include other components. When a range of numerical values ​​is described herein, unless the specific range is otherwise specified, the value shall have the precision of significant figures provided in accordance with the standard rules of chemistry for significant figures. For example, 10 includes the range from 5.0 to 14.9, and the figure 10.0 includes the range from 9.50 to 10.49. latex composition for dip molding

[0013] One aspect of the latex compositions for dip molding described herein includes copolymer latex obtained by polymerizing ethylenically unsaturated nitrile monomers, isoprene monomers, butadiene monomers, and ethylenically unsaturated acid monomers. Among the copolymer latexes produced by polymerizing ethylenically unsaturated nitrile monomers, conjugated diene monomers, and ethylenically unsaturated acid monomers, the most widely known is nitrile-isoprene (NI) copolymer latex. Nitrile-isoprene copolymer latex exhibits high elongation, low modulus, excellent mechanical properties, and high durability. However, such nitrile-isoprene copolymer latex lacks some of the chemical resistance necessary for use in latex gloves used in laboratories and other environments involving chemical reactions. Chemical resistance refers to the property of maintaining its shape and properties without dissolving or deforming in various organic solvents. In order to impart chemical resistance to existing nitrile-isoprene copolymer latex, the inventors conducted numerous experiments and confirmed that by utilizing butadiene in addition to isoprene as a conjugated diene monomer, it is possible to obtain a dip-molding latex with high gel content, excellent durability, and chemical resistance, thus completing the present invention.

[0014] In the dip molding latex composition of the present invention, the content of the butadiene monomer is 5 to 20 parts by weight, preferably 7 to 19.5 parts by weight, more preferably 8 to 19 parts by weight, even more preferably 10 to 18.5 parts by weight, and most preferably more than 10 parts by weight and less than 18.5 parts by weight, based on 100 parts by weight of the total sum of the isoprene monomer and the butadiene monomer, but is not limited thereto. For example, the content of the butadiene monomer may be 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 9.5 parts by weight, 10 parts by weight, 10.5 parts by weight, 11 parts by weight, 11.5 parts by weight, 12 parts by weight, 12.5 parts by weight, 13 parts by weight, 13.5 parts by weight, 14 parts by weight, 14.5 parts by weight, 15 parts by weight, 15.5 parts by weight, 16 parts by weight, 16.5 parts by weight, 17 parts by weight, 17.5 parts by weight, 18 parts by weight, 18.5 parts by weight, 19 parts by weight, 19.5 parts by weight, 20 parts by weight, or a value between two of these values, based on a total of 100 parts by weight of the isoprene monomer and butadiene monomer. If the content of the butadiene monomer satisfies the range based on a total of 100 parts by weight of the isoprene monomer and butadiene monomer, the gel content of the manufactured copolymer latex may be high, resulting in a high degree of crosslinking, and consequently, the chemical resistance of the manufactured dip-molded article to solvents may be excellent.

[0015] In the dip molding latex composition of the present invention, the gel content of the copolymer latex is 40 to 90%, preferably 40 to 80%, more preferably 48 to 75%, and most preferably 50 to 70%, but is not limited thereto. For example, the gel content of the copolymer latex may be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, or a value between two of these values. In the copolymer latex, a higher gel content means a greater number of crosslinks. If the gel content of the copolymer latex exceeds the range, the mechanical properties of the dip-molding latex produced may deteriorate due to excessive aggregation. If it is below the range, it may easily deform due to shear force during dip molding, potentially deteriorating the mechanical properties of the dip-molding latex produced, and furthermore, a low degree of crosslinking may occur, which may result in poor chemical resistance of the dip-molded product to solvents.

[0016] The ethylenically unsaturated nitrile monomer may be, but is not limited to, one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, α-cyanoethylacrylonitrile, and two or more combinations thereof. In a copolymer of latex for dip molding, the structure derived from the ethylenically unsaturated nitrile monomer can improve the strength and chemical resistance of the dip-molded article. The ethylenically unsaturated acid monomer may be, but is not limited to, one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, citraconic anhydride, styrene sulfonic acid, monobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate, and two or more combinations thereof. In a copolymer of latex for dip molding, the structure derived from the ethylenically unsaturated acid monomer can form a crosslinked structure and improve the mechanical properties of the dip-molded product. The copolymer latex may, but is not limited to, contain 1 to 55 parts by weight of the ethylenically unsaturated nitrile monomer, 65 to 80 parts by weight of the isoprene monomer, 1 to 10 parts by weight of the butadiene monomer, and 1.5 to 6.0 parts by weight of the ethylenically unsaturated acid monomer.

[0017] For example, the ethylenically unsaturated nitrile monomer content of the copolymer latex may be 1 part by weight, 2.5 parts by weight, 5 parts by weight, 7.5 parts by weight, 10 parts by weight, 12.5 parts by weight, 15 parts by weight, 17.5 parts by weight, 20 parts by weight, 22.5 parts by weight, 25 parts by weight, 27.5 parts by weight, 30 parts by weight, 32.5 parts by weight, 35 parts by weight, 37.5 parts by weight, 40 parts by weight, 42.5 parts by weight, 45 parts by weight, 47.5 parts by weight, 50 parts by weight, 52.5 parts by weight, 55 parts by weight, or a value between two of these values. If the ethylenically unsaturated nitrile monomer content is below the range, the chemical resistance or mechanical strength of the dip-molded article may decrease, and if it exceeds the range, the elongation of the dip-molded article may decrease, reducing its usability.

[0018] For example, the isoprene monomer content of the copolymer latex may be 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, or a value between two of these values. If the isoprene monomer content is below the above range, the dip-molded article may harden excessively, resulting in poor wearability. If it exceeds the above range, the durability and chemical resistance of the dip-molded article may decrease.

[0019] For example, the butadiene monomer content of the copolymer latex can be 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 9.5 parts by weight, 10 parts by weight, or a value between any two of these. If the butadiene monomer content is less than the above range, the crosslinking degree of the latex decreases and the gel content decreases, and the chemical resistance may deteriorate. If it exceeds the above range, the durability and chemical resistance of the dip-molded product may decrease.

[0020] For example, the ethylenically unsaturated acid monomer content of the copolymer latex can be 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, or a value between any two of these. If the ethylenically unsaturated acid monomer content is less than the above range, the tensile strength of the dip-molded product may decrease. If it exceeds the above range, the dip-molded product may be overly cured and the wearing comfort may deteriorate.

[0021] The weight ratio of the butadiene monomer to the isoprene monomer can be 0.15 to 0.7, and most preferably can be 0.2 to 0.65, but is not limited thereto. If the weight ratio of the butadiene monomer to the isoprene monomer is outside the above range, the durability and chemical resistance of the dip-molded product produced from the composition may decrease.

[0022] The weight ratio of the isoprene to the ethylenically unsaturated nitrile monomer can be 2.1 to 3.5. If the weight ratio of the isoprene to the ethylenically unsaturated nitrile monomer is outside the above range, the durability and chemical resistance of the dip-molded product produced from the composition may decrease.

[0023] The weight ratio of the ethylenically unsaturated acid monomer to the ethylenically unsaturated nitrile monomer may be between 0.1 and 0.4. If the weight ratio of the ethylenically unsaturated acid monomer to the ethylenically unsaturated nitrile monomer falls outside this range, the durability and chemical resistance of the dip-molded article produced from the composition may decrease.

[0024] In this specification, "total monomers" means the sum of the isoprene monomer, the butadiene monomer, the ethylenically unsaturated nitrile monomer, and the ethylenically unsaturated acid monomer. However, the dip molding latex composition may further contain polymerizable monomers other than the isoprene monomer, butadiene monomer, ethylenically unsaturated nitrile monomer, and ethylenically unsaturated acid monomer described above, in which case "total monomers" further includes the polymerizable monomers.

[0025] The composition may further comprise water, an emulsifier, a polymerization initiator, and a molecular weight modifier. The water content may be 75 to 150 parts by weight based on 100 parts by weight of the total monomers, for example, 75 parts by weight, 77.5 parts by weight, 80 parts by weight, 82.5 parts by weight, 85 parts by weight, 87.5 parts by weight, 90 parts by weight, 92.5 parts by weight, 95 parts by weight, 97.5 parts by weight, 100 parts by weight, 102.5 parts by weight, 105 parts by weight, 107.5 parts by weight, 110 parts by weight, 112.5 parts by weight, 115 parts by weight, 117.5 parts by weight, 120 parts by weight, 122.5 parts by weight, 125 parts by weight, 127.5 parts by weight, 130 parts by weight, 132.5 parts by weight, 135 parts by weight, 137.5 parts by weight, 140 parts by weight, 142.5 parts by weight, 145 parts by weight, 147.5 parts by weight, 150 parts by weight, or a value between two of these values. If the water content is below the range, the viscosity during polymerization may increase excessively, making it difficult to manufacture molded articles. If it exceeds the range, the solid content may become excessively low. The water may have an ionic conductivity of 5 μS / cm or less, 2.5 μS / cm or less, or 1 μS / cm or less. For example, the water may be deionized water, ultrapure water, or purified water. Using water with high ionic conductivity may result in the presence of impurities that adversely affect polymerization stability or latex stability.

[0026] The emulsifier may be an anionic surfactant, a nonionic surfactant, a cationic surfactant, or an amphoteric surfactant. For example, one or more anionic surfactants selected from the group consisting of alkylbenzene sulfonates, aliphatic sulfonates, sulfate esters of higher alcohols, α-olefin sulfonates, and alkyl ether sulfate esters may be used, but are not limited thereto. The emulsifier may be added in an amount of 0.8 to 8 parts by weight based on 100 parts by weight of the total monomers.

[0027] The polymerization initiator may be a radical initiator. The radical initiator may be, for example, an inorganic peroxide selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, potassium superphosphate, and hydrogen peroxide; an organic peroxide selected from the group consisting of t-butyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanol peroxide, and t-butyl peroxyisobutyrate; or one or more azo initiators selected from the group consisting of azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonilate, and azobisisobutyrate (butylate)methyl. The polymerization initiator may be added in an amount of 0.01 to 1.5 parts by weight based on 100 parts by weight of the total monomers.

[0028] The molecular weight modifier may be, but is not limited to, α-methylstyrene dimer, t-dodecyl mercaptan, n-dodecyl mercaptan, octyl mercaptan, and other mercaptans; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, and methylene bromide; or sulfur-containing compounds such as tetraethyl thiuram disulfide, dipentamethylenethiuram disulfide, and diisopropyl xanthogen disulfide. The content of the molecular weight modifier may be 0.1 to 1 part by weight based on 100 parts by weight of the total monomers. For example, the amount may be 0.1 parts by weight, 0.15 parts by weight, 0.2 parts by weight, 0.25 parts by weight, 0.3 parts by weight, 0.35 parts by weight, 0.4 parts by weight, 0.45 parts by weight, 0.5 parts by weight, 0.55 parts by weight, 0.6 parts by weight, 0.65 parts by weight, 0.7 parts by weight, 0.75 parts by weight, 0.8 parts by weight, 0.85 parts by weight, 0.9 parts by weight, 0.95 parts by weight, 1 part by weight, or a value between two of these values. If the content of the molecular weight modifier is below the above range, the latex stability may decrease, and if it exceeds the above range, the mechanical properties may deteriorate or the chemical resistance may decrease.

[0029] The average particle size of the copolymer latex may be 1,000 to 3,000 Å. For example, 1,000 Å, 1,050 Å, 1,100 Å, 1,150 Å, 1,200 Å, 1,250 Å, 1,300 Å, 1,350 Å, 1,400 Å, 1,450 Å, 1,500 Å, 1,550 Å, 1,600 Å, 1,650 Å, 1,700 Å, 1,750 Å, 1,800 Å, 1,850 Å, 1,900 Å, 1,950 Å, 2,000 Å, 2,050 Å, 2,100 Å, 2,150 Å, 2,200 Å, 2,250 Å, 2,300 Å, 2,350 Å, 2,400 Å, 2,450 The values ​​may be Å, 2,500 Å, 2,550 Å, 2,600 Å, 2,650 Å, 2,700 Å, 2,750 Å, 2,800 Å, 2,850 Å, 2,900 Å, 2,950 Å, 3,000 Å, or a range between two of these values. The copolymer latex can be manufactured by copolymerizing two types of conjugated diene monomers, thereby ensuring stability, maintaining a high gel content, and exhibiting excellent chemical resistance to solvents.

[0030] The viscosity of the copolymer latex at 25° C. is 50 to 2,500 cps, for example, 50 cps, 75 cps, 100 cps, 125 cps, 150 cps, 175 cps, 200 cps, 225 cps, 250 cps, 275 cps, 300 cps, 325 cps, 350 cps, 375 cps, 400 cps. cps, 425 cps, 450 cps, 475 cps, 500 cps, 525 cps, 550 cps, 575 cps, 600 cps, 625 cps, 650 cps, 675 cps, 700 cps, 725 cps, 750 cps, 775 cps, 800 cps, 825 The viscosity may be cps, 850 cps, 875 cps, 900 cps, 925 cps, 950 cps, 975 cps, 1,000 cps, 1,100 cps, 1,200 cps, 1,300 cps, 1,400 cps, 1,500 cps, 1,600 cps, 1,700 cps, 1,800 cps, 1,900 cps, 2,000 cps, 2,100 cps, 2,200 cps, 2,300 cps, 2,400 cps, 2,500 cps, or a range between two of these values. If the viscosity of the copolymer latex falls outside this range, it may become substantially impossible to manufacture or difficult to dip mold.

[0031] The solid content of the copolymer latex may be 45 to 65% by weight, for example, 45%, 47.5%, 50%, 52.5%, 55%, 57.5%, 60%, 62.5%, 65%, or any two of these values. If the solid content of the copolymer latex falls outside this range, the aforementioned effect of stability improvement may become unnecessary, or aggregation of the latex may occur.

[0032] The characteristics of the copolymer latex may be measured at a pH of 8.0 to 10.0, for example, at pH 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, and 10.0. Adjusting the pH of the latex through additives may change the solid content and average particle size, but the copolymer latex can simultaneously satisfy the aforementioned average particle size, solid content, and viscosity requirements within the pH range.

[0033] The dip molding latex composition may further contain one or more additives selected from the group consisting of chelating agents, dispersants, pH adjusters, oxygen scavengers, particle size adjusters, antioxidants, and oxygen scavengers. These additives may be in configurations known in the industry and may be added before or after polymerization of the copolymer.

[0034] Method for manufacturing latex for dip molding A method for producing latex for dip molding according to another aspect of this specification may include: (a) preparing a monomer mixture comprising isoprene monomer, butadiene monomer, ethylenically unsaturated nitrile monomer and ethylenically unsaturated acid monomer; (b) adding an emulsifier and water to the monomer mixture; and (c) adding a polymerization initiator to produce latex for dip molding.

[0035] Step (a) above is a step in which a monomer mixture is prepared, which includes isoprene monomer, butadiene monomer, ethylenically unsaturated nitrile monomer and ethylenically unsaturated acid monomer, which are monomers constituting a carboxylic acid-modified nitrile copolymer, and can be carried out under a nitrogen atmosphere.

[0036] Steps (b) and (c) above are steps in which additives and water are added to produce the copolymer latex described above. A molecular weight modifier may be further added in step (b).

[0037] The polymerization in step (c) above may be carried out at 10 to 90°C, for example, at 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or at a temperature between two of these temperatures, but is not limited thereto, and the polymerization temperature may be adjusted according to the target conversion rate.

[0038] The polymerization in step (c) above may take place over 2 to 24 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, or any two of these hours, but is not limited thereto.

[0039] The aforementioned step (c) may further include a step of adding a polymerization inhibitor to stop polymerization. The polymerization inhibitor may be one selected from the group consisting of sodium hydroxide, hydroxylamine, hydroxyamine sulfate, diethylhydroxyamine, hydroxyamine sulfonic acid and its alkali metal ions, sodium dimethyldithiocarbamate, hydroquinone derivatives, aromatic hydroxydithiocarboxylic acids such as hydroxydiethylbenzenedithiocarboxylic acid and hydroxydibutylbenzenedithiocarboxylic acid, and two or more combinations thereof. The polymerization inhibitor content may be 0.02 to 1.5 parts by weight per 100 parts by weight of the monomer mixture. In step (c) above, the final conversion rate of the polymerization reaction may be 92% or higher. For example, it may be 92% or higher, 93% or higher, 94% or higher, 95% or higher, 96% or higher, 97% or higher, or 98% or higher, but is not limited to these. If the conversion rate is below the above range, the amount of residual unreacted monomers will increase, and the mechanical properties and practical durability of the dip molded article produced therefrom may decrease. Furthermore, the raw materials and their contents used in the aforementioned manufacturing method are as described above.

[0040] Dip-molded products Dip-molded articles according to yet another aspect of this specification may be manufactured from the dip-molding latex compositions described above. The aforementioned dip-molded product may be, but is not limited to, a product manufactured by dip-molding after adding 1 to 2 parts by weight of sulfur, 1.5 to 4 parts by weight of a crosslinking agent, and 0.3 to 1.5 parts by weight of a vulcanization accelerator to the aforementioned dip-molding latex, based on 100 parts by weight of the dip-molding latex. The sulfur can react with the structure derived from the conjugated diene monomer to form a cross-linked structure. When the isoprene monomer and butadiene monomer are added in the weight ratio range, shrinkage of the molded article due to syneresis during vulcanization can be suppressed. The sulfur content may be, for example, 1 part by weight, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, 1.4 parts by weight, 1.5 parts by weight, 1.6 parts by weight, 1.7 parts by weight, 1.8 parts by weight, 1.9 parts by weight, 2 parts by weight, or a value between two of these values. If the sulfur content is below the range, mechanical properties such as tensile strength and chemical resistance may decrease, and if it exceeds the range, it may induce an allergic reaction in the user.

[0041] The crosslinking agent can form a crosslinked structure by forming ionic bonds with the structure derived from the ethylenically unsaturated acid. The crosslinking agent may be one or more selected from the group consisting of zinc oxide or titanium oxide. For example, the content of the crosslinking agent may be 1.5 parts by weight, 1.6 parts by weight, 1.7 parts by weight, 1.8 parts by weight, 1.9 parts by weight, 2.0 parts by weight, 2.1 parts by weight, 2.2 parts by weight, 2.3 parts by weight, 2.4 parts by weight, 2.5 parts by weight, 2.6 parts by weight, 2.7 parts by weight, 2.8 parts by weight, 2.9 parts by weight, 3.0 parts by weight, 3.1 parts by weight, 3.2 parts by weight, 3.3 parts by weight, 3.4 parts by weight, 3.5 parts by weight, 3.6 parts by weight, 3.7 parts by weight, 3.8 parts by weight, 3.9 parts by weight, 4.0 parts by weight, or a value between two of these values. If the content of the crosslinking agent is below the above range, durability and chemical resistance may decrease, and if it exceeds the above range, tensile strength may decrease.

[0042] The dip-molded article may, but is not limited to, a product obtained by dip-molding after adjusting the solid content by adding an aqueous potassium hydroxide solution to the dip-molding latex.

[0043] The tensile strength of the dip-molded product may be, but is not limited to, 3 MPa or higher, 5 MPa or higher, 7 MPa or higher, 9 MPa or higher, 11 MPa or higher, 13 MPa or higher, 15 MPa or higher, 20 MPa or higher, 25 MPa or higher, 30 MPa or higher, or 35 MPa or higher. Higher tensile strength improves storage durability, but other mechanical properties such as elongation may decrease.

[0044] The elongation of the dip-molded product may be, but is not limited to, 600% or more, 650% or more, 700% or more, 750% or more, 800% or more, 850% or more, or 900% or more. A higher elongation rate improves wearability and other properties, but there may be a trade-off relationship with other mechanical properties.

[0045] The deformation rate test results of the aforementioned dip-molded product using the following chemical resistance test method are 50% or less, indicating that it does not dissolve in various organic solvents or undergo structural deformation, thus demonstrating high quality and excellent durability. For example, the deformation rate test results of the aforementioned dip-molded product may be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

[0046] [Chemical Resistance Test Method] After manufacturing a dip-molded product with a width of 30 mm, a length of 135 mm, and a thickness of 0.06 to 0.09 mm, let a (g) be the initial weight measured. Then, let b (g) be the weight measured after immersing the manufactured dip-molded product in 80 ml of solvent and stirring at room temperature for 4 hours. The deformation rate calculated using the following formula 1 may be 50% or less, as described above. [Formula 1] (Deformation ratio) = (ab) / a*100. The aforementioned chemical resistance test method involves observing the weight change of a test specimen when it is immersed for a long period of time in an organic solvent that is highly likely to come into contact with the dip-molded product during actual use, and confirming whether or not it deforms or increases in weight due to the solvent. This method allows for the measurement of the chemical resistance of the dip-molded product under actual use conditions.

[0047] The solvent used in the aforementioned chemical resistance test may be one selected from the group consisting of acetone, ethanol, isopropyl alcohol, methyl ethyl ketone, n-heptane, and toluene. In particular, dip-molded articles produced from the dip-molding latex composition of the present invention exhibit a low rate of deformation when exposed to hydrophilic organic solvents such as ethanol and isopropyl alcohol, and do not undergo the swelling phenomenon. Furthermore, their physical properties do not deteriorate even after prolonged use, thus increasing the ease of use for the worker.

[0048] When the solvent used in the chemical resistance test is acetone, the deformation rate calculated through Formula 1 may be 50% or less, preferably 40% or less, more preferably 30% or less, and even more preferably 25% or less, but is not limited thereto.

[0049] The aforementioned dip-molded product may, but is not limited to, surgical gloves, medical gloves, gloves for processing agricultural and livestock products, industrial gloves, condoms, cosmetic materials, catheters, or molded products for healthcare. For example, the dip-molded product may be surgical gloves or other medical gloves, industrial gloves such as gloves for handling chemicals, or cosmetic materials such as puffs.

[0050] The following describes the examples of this specification in more detail. However, the following experimental results represent only representative results from the aforementioned examples, and the scope and content of this specification should not be narrowed or limited by these examples. The effects of various embodiments of this specification that are not explicitly presented below should be described specifically in the relevant sections.

[0051] Examples and Comparative Examples A 5 L high-pressure reactor was prepared, equipped with a stirrer, thermometer, cooler, and nitrogen gas inlet, and configured to allow continuous addition of each component, such as monomers, emulsifiers, and polymerization initiators. Deionized water with a conductivity of 1 μS / cm or less was prepared. After purging the reactor with nitrogen, a monomer mixture was added, consisting of isoprene (IP), 1,3-butadiene (BD), acrylonitrile (AN), and methacrylic acid (MAA) mixed in the weights listed in Table 1 below, based on the total weight of the monomer mixture. Subsequently, 0.5 parts by weight of t-dodecyl mercaptan (TDDM) as a molecular weight modifier, 2 parts by weight of sodium alkylbenzene sulfonate as an emulsifier, and 120 parts by weight of deionized water were added to 100 parts by weight of the monomer mixture in the reactor to produce a latex composition for dip molding. After raising the temperature of the reactor to 40°C, 0.3 parts by weight of sodium persulfate was added as a polymerization initiator. Polymerization was carried out for 12 hours until the conversion rate reached approximately 98%, at which point 0.9 parts by weight of sodium hydroxide was added to stop the polymerization reaction. After that, unreacted monomers and other impurities were removed through a deodorization process, and ammonia water, antioxidants, defoamers, etc. were added to obtain a copolymer latex with a solid content of 45-55% and a pH of 8.6-9.0. [Table 1] Experimental Example 1: Gel Content Evaluation The gel content of the copolymer latex obtained in the above examples and comparative examples was measured by the following method and recorded in Table 2.

[0052] 5 g of each copolymer latex prepared according to Examples 1 to 8 and Comparative Examples 1 to 4 was added to 200 mL of isopropyl alcohol while stirring, and allowed to solidify. The solidified material was filtered through a 120-mesh wire mesh, dried in a constant temperature vacuum dryer at 50±2°C and 750±10 mmHg for 1 hour, and then left to room temperature in a desiccator. 0.25 to 0.35 g of the dried sample was accurately weighed (Wi) to an accuracy of 0.1 mg and placed in an Erlenmeyer flask. 100 mL of methyl ethyl ketone (MEK) was added, and the mixture was stirred for 2 hours. The entire sample was then filtered through filter paper. 20 mL of the filtrate was heated to evaporate the methyl ethyl ketone, then allowed to cool to room temperature in a desiccator, and accurately weighed (Wf) to an accuracy of 0.1 mg. The gel content in the sample was measured according to the following formula 2, and the average of the two values ​​was calculated to one decimal place. [Formula 2] Gel content (%) = 100 - (W f × 5 / W i ) × 100 [Table 2] Referring to Table 2 above, in Examples 1 to 8, a gel content of 40% or more was observed in all cases, indicating excellent cross-linking formation. In Comparative Example 1, which did not contain butadiene monomer, the gel content was 0%, indicating that no cross-linking was formed at all. In Comparative Examples 2 to 4, where the butadiene monomer did not exceed 5 parts by weight based on 100 parts by weight of the total conjugated diene monomer, the gel content was low at 20% or less, indicating that insufficient cross-linking was formed.

[0053] Manufacturing example To 100 parts by weight of each copolymer latex prepared according to the above examples and comparative examples, 1.0 part by weight of sulfur (S), 0.7 parts by weight of zinc oxide (ZnO), 1.0 part by weight of titanium dioxide (TiO2), and 1.0 part by weight of zinc dibutyldithiocarbamate (ZDBC) as a vulcanization accelerator were added. The temperature was then raised to 120-150°C to allow the vulcanization reaction to proceed, and after adding secondary distilled water and removing the residue at 50°C for 2 minutes, a dip molding latex composition with a solid content of 45% and a pH of 8.5 was prepared.

[0054] Experimental Example 2: Chemical Resistance Evaluation Rectangular test specimens measuring 30 mm in width, 135 mm in length, and 0.080-0.089 mm in thickness were prepared using each dip-molding latex composition manufactured according to the above manufacturing example, and the chemical resistance of the test specimens was evaluated. The results are shown in Tables 3 to 5 below. Table 3 shows the experimental results using acetone as the solvent, Table 4 shows the experimental results using ethanol as the solvent, and Table 5 shows the experimental results using methyl ethyl ketone as the solvent.

[0055] The initial weight of the dip-molded product was measured and recorded (a(g)). The dip-molded product was then immersed in 80 ml of solvent and stirred at room temperature for 4 hours. After that, the swollen product was removed with tweezers, the solvent adhering to the surface was physically removed, and the weight was measured and recorded (b(g)). Subsequently, the deformation rate was calculated using Equation 1 described above and is shown in Tables 3 to 5. [Table 3] [Table 4] [Table 5] Referring to Tables 3 to 5, the test specimens prepared using the latex of Examples 1 to 8 showed superior chemical resistance compared to the test specimens prepared using the latex of Comparative Examples 1 to 4. In the present invention, the content of butadiene monomer was adjusted to 5 to 20 parts by weight based on 100 parts by weight of the total sum of isoprene monomer and butadiene monomer. It was confirmed that as the degree of crosslinking increased, the gel content increased, and consequently, a lower deformation rate was recorded. In particular, it was confirmed that the latex showed significantly superior chemical resistance compared to the comparative examples to ketones and ethanol, which are used in various chemical reactions, such as acetone and ethanol. On the other hand, the test specimen prepared using the latex of Comparative Example 3 recorded a deformation rate of 50% or more for all solvents, indicating insufficient chemical resistance in organic solvents.

[0056] The descriptions herein, as set forth above, are illustrative, and those with ordinary skill in the art to which any aspect of this specification belongs will understand that the technical ideas and essential features described herein can be readily modified into other specific forms without alteration. Therefore, the embodiments described above should be understood in all respects as illustrative and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

[0057] The scope of this specification is defined by the claims set forth below, and all modifications or alterations derived from the meaning and scope of the claims and the concept of equivalents thereof should be construed as being included within the scope of this specification.

Claims

1. A latex composition for dip molding comprising a copolymer latex obtained by polymerizing an ethylenically unsaturated nitrile monomer, an isoprene monomer, a butadiene monomer, and an ethylenically unsaturated acid monomer, The content of the butadiene monomer is 5 to 20 parts by weight based on 100 parts by weight of the total sum of the isoprene monomer and the butadiene monomer. The gel content of the copolymer latex is 40-90%. Latex composition for dip molding.

2. The ethylenically unsaturated nitrile monomer is one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, α-cyanoethylacrylonitrile, and two or more combinations thereof, as described in claim 1 for dip molding.

3. The latex composition for dip molding according to claim 1, wherein the ethylenically unsaturated acid monomer is one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, citraconic anhydride, styrenesulfonic acid, monobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate, and two or more combinations thereof.

4. The latex composition for dip molding according to claim 1, wherein the copolymer latex comprises 1 to 55 parts by weight of the ethylenically unsaturated nitrile monomer, 65 to 80 parts by weight of the isoprene monomer, 1 to 10 parts by weight of the butadiene monomer, and 1.5 to 6.0 parts by weight of the ethylenically unsaturated acid monomer.

5. In the latex composition for dip molding according to claim 1, The dip-molding latex composition according to claim 1, wherein the deformation rate of the dip-molded article produced with the dip-molding latex composition is 50% or less, as represented by the following formula 1: [Formula 1] (Deformation ratio) = (ab) / a*100. (In Equation 1, a represents the weight (g) measured after manufacturing a dip-molded product with a width of 30 mm, a length of 135 mm, and a thickness of 0.06–0.09 mm, and b represents the weight (g) measured after immersing the manufactured dip-molded product in 80 ml of solvent and stirring at room temperature for 4 hours.)

6. The latex composition for dip molding according to claim 5, wherein the solvent is one selected from the group consisting of acetone, ethanol, isopropyl alcohol, methyl ethyl ketone, n-heptane, and toluene.

7. A dip-molded article manufactured from a latex composition for dip molding according to any one of claims 1 to 6.

8. The dip-molded article according to claim 7, wherein the dip-molded article is a surgical glove, a medical glove, a glove for processing agricultural and livestock products, an industrial glove, a condom, a cosmetic material, a catheter, or a molded article for health management.

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