Durable latex polymerization composition, latex for dip molding, and dip-molded articles produced therefrom.

Abstract

One example of this specification provides a latex polymerization composition comprising a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, an ethylenically unsaturated acid monomer, an ionic organic compound, and an ionic inorganic compound, wherein the weight ratio of the ionic inorganic compound to the ionic organic compound is 4.7 or higher.

Description

Technical Field

[0001] This specification relates to a composition for latex polymerization having excellent durability, a dip molding latex, and a dip molded article produced therefrom.

Background Art

[0002] Conventionally, the main raw material for gloves used in medical, agricultural and livestock product processing, or industrial applications was natural rubber latex. However, when using gloves made from natural rubber latex, the problem frequently occurred that users of the gloves suffered from contact allergic diseases 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 the demand is increasing in the medical and food fields where frequent contact with sharp objects occurs.

[0003] 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 the tensile strength and elongation rate of dip molded articles produced from dip molding latex. However, despite such attempts to improve mechanical properties, cases where human life accidents occurred due to damage to dip molded articles or the desired purpose could not be achieved have continued to appear.

[0004] This is because when in contact with body fluids such as human skin or sweat, which is weakly acidic during actual use of the molded article, the physical properties of the molded article deteriorate. The conventional mechanical properties of tensile strength and elongation rate are measured under normal temperature air, and if these properties are excellent, the durability before use of the dip molded article can be guaranteed, but there are cases where the durability under actual use conditions is poor. Therefore, there is a demand for the development of a technology for manufacturing dip molded articles having excellent durability under actual use conditions.

[0005] Furthermore, there is increasing demand for high-solids latex for dip molding that exhibits excellent quality even in small quantities. However, when conventional dip molding latex is concentrated to increase its solids content, there is a problem in that the viscosity increases sharply above a certain content due to a decrease in particle stability. In addition, dip molding latex generally contains particulate polymers with an average particle size of around 800 Å, but when these are concentrated or enlarged through chemical treatment to improve the quality of the latex, there is a problem in that the stability of the latex decreases sharply.

[0006] Therefore, there is a need to develop dip molding latex and dip molded products that simultaneously satisfy the trade-off relationships of high solids content, large particle size, and low viscosity, while also possessing excellent durability in actual use. [Overview of the project] [Problems that the invention aims to solve]

[0007] The provisions described herein are intended to solve the problems of the prior art described above, and one objective of this specification is to provide a latex for dip molding that has excellent stability, large particle size, high solid content and low viscosity characteristics, and a polymerization composition for producing the same.

[0008] Another objective of this specification is to provide dip-molded articles with excellent durability in practical use. [Means for solving the problem]

[0009] In one aspect, the present invention provides a latex polymerization composition comprising a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, an ethylenically unsaturated acid monomer, an ionic organic compound, and an ionic inorganic compound, wherein the weight ratio of the ionic inorganic compound to the ionic organic compound is 4.7 or higher.

[0010] In one embodiment, the conjugated diene monomer may be one selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, 2-chloro-1,3-butadiene, 3-butyl-1,3-octadiene, octadiene, and two or more combinations thereof.

[0011] 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.

[0012] 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.

[0013] In one embodiment, the ionic organic compound may be one selected from the group consisting of ethylenediaminetetraacetic acid (EDTA) or its sodium salt, ethylene glycoltetraacetic acid (EGTA) or its sodium salt, nitrilotriacetic acid (NTA) or its sodium salt, iminodiacetic acid (IDA) or its sodium salt, quinolinic acid (QNA) or its sodium salt, and two or more combinations thereof.

[0014] In one embodiment, the ionic inorganic compound is potassium sulfate (K2SO4), sodium carbonate (Na2CO3), sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), sodium nitrate (NaNO3), potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), magnesium nitrate (Mg(NO3)2), sodium sulfate (Na2SO4), calcium sulfate (CaSO4), magnesium sulfate (MgSO4), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), water It may be one selected from the group consisting of magnesium oxide (Mg(OH)2), sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), potassium carbonate (K2CO3), sodium bisulfite (NaHSO4), potassium bisulfite (KHSO4), sodium pyrophosphate (Na4P2O7), potassium pyrophosphate (K4P2O7), trisodium phosphate (Na3PO4), tripotassium phosphate (K3PO4), monosodium hydrogen phosphate (Na2HPO4), monopotassium hydrogen phosphate (K2HPO4), and two or more combinations of these.

[0015] In one embodiment, the composition may contain 30 to 98 parts by weight of a conjugated diene monomer, 1 to 55 parts by weight of an ethylenically unsaturated nitrile monomer, and 0.001 to 20 parts by weight of an ethylenically unsaturated acid monomer.

[0016] In one embodiment, the composition may further comprise water, an emulsifier, a polymerization initiator, and a molecular weight modifier.

[0017] In another aspect, the present invention provides a latex for dip molding comprising a copolymer derived from the latex polymerization composition.

[0018] In another aspect, the present invention provides a dip-molded product manufactured from the dip-molding latex.

[0019] 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 health management. [Effects of the Invention]

[0020] The latex polymerization compositions according to one aspect of this specification have high ionic conductivity and can improve polymer stability during latex polymerization. Consequently, the dip molding latex according to the other aspect of this specification can simultaneously satisfy the trade-offs of high solids content, large particle size, and low viscosity.

[0021] Furthermore, dip-molded articles according to yet another aspect of this specification offer excellent durability in practical use and can be applied 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.

[0022] 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 of this specification, not limited to those described above. [Modes for carrying out the invention]

[0023] The following will explain 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.

[0024] 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. Furthermore, 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.

[0025] When a numerical value range is described in this specification, unless the specific range is described separately, the value has the precision of significant figures provided according to the standard rules in chemistry for significant figures. For example, 10 includes the range from 5.0 to 14.9, and the number 10.0 includes the range from 9.50 to 10.49.

[0026] Composition for latex polymerization

[0027] The composition for latex polymerization according to one aspect of this specification includes a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, an ethylenically unsaturated acid monomer, an ionic organic compound, and an ionic inorganic compound.

[0028] The ionic organic compound and the ionic inorganic compound can improve the ionic conductivity of the composition to improve the stability of the latex and can form a copolymer with a large particle size of 1,000 Å or more. Further, the latex containing the copolymer derived from the composition maintains a low viscosity even at a high solid content of 50% by weight or more, and can simultaneously satisfy high solid content, large particle size, and low viscosity, which are in a trade-off relationship.

[0029] The weight ratio of the ionic inorganic compound to the ionic organic compound can be 4.7 or more. For example, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, a range between two of these values, or one of these values or more. If the weight ratio of the ionic inorganic compound to the ionic organic compound is less than the above range, the polymerization reaction rate may decrease and the final conversion rate may become low. As the amount of residual unreacted monomer increases, the mechanical properties and practical use durability of the dip-molded product produced therefrom may decrease rapidly. On the other hand, in the present invention, since the larger the weight ratio of the ionic inorganic compound to the organic compound, the more advantageous it is for the mechanical properties and practical use durability of the dip-molded product, the upper limit is not particularly limited, but it can be limited to 5.9 or less in consideration of the possibility of spoilage during long-term storage of the latex.

[0030] The conjugated diene monomer may be, but is not limited to, one selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, 2-chloro-1,3-butadiene, 3-butyl-1,3-octadiene, octadiene, and two or more combinations thereof. In a copolymer of latex for dip molding, the structure derived from the conjugated diene monomer can impart flexibility to the dip-molded article.

[0031] 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.

[0032] 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.

[0033] The ionic organic compound and the ionic inorganic compound improve the stability of the copolymer during polymerization of the latex polymerization composition and suppress latex aggregation even after polymerization.

[0034] The aforementioned ionic organic compound may be one selected from the group consisting of ethylenediaminetetraacetic acid (EDTA) or its sodium salt, ethylene glycoltetraacetic acid (EGTA) or its sodium salt, nitrilotriacetic acid (NTA) or its sodium salt, iminodiacetic acid (IDA) or its sodium salt, quinolinic acid (QNA) or its sodium salt, and two or more combinations thereof. For example, it may be ethylenediaminetetraacetic acid (EDTA), but is not limited thereto.

[0035] The aforementioned ionic inorganic compounds are potassium sulfate (K2SO4), sodium carbonate (Na2CO3), sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), sodium nitrate (NaNO3), potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), magnesium nitrate (Mg(NO3)2), sodium sulfate (Na2SO4), calcium sulfate (CaSO4), magnesium sulfate (MgSO4), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), and bicarbonate. It may be one selected from the group consisting of sodium (NaHCO3), potassium bicarbonate (KHCO3), potassium carbonate (K2CO3), sodium bisulfite (NaHSO4), potassium bisulfite (KHSO4), sodium pyrophosphate (Na4P2O7), potassium pyrophosphate (K4P2O7), trisodium phosphate (Na3PO4), tripotassium phosphate (K3PO4), monosodium hydrogen phosphate (Na2HPO4), monopotassium hydrogen phosphate (K2HPO4), and two or more combinations of these, for example, a combination of potassium sulfate and sodium carbonate, but not limited thereto.

[0036] The composition may, but is not limited to, contain 30 to 98 parts by weight of a conjugated diene monomer, 1 to 55 parts by weight of an ethylenically unsaturated nitrile monomer, and 0.001 to 20 parts by weight of an ethylenically unsaturated acid monomer.

[0037] For example, the conjugated diene monomer content of the composition may be 30 parts by weight, 32 parts by weight, 34 parts by weight, 36 parts by weight, 38 parts by weight, 40 parts by weight, 42 parts by weight, 44 parts by weight, 46 parts by weight, 48 parts by weight, 50 parts by weight, 52 parts by weight, 54 parts by weight, 56 parts by weight, 58 parts by weight, 60 parts by weight, 62 parts by weight, 64 parts by weight, 66 parts by weight, 68 parts by weight, 70 parts by weight, 72 parts by weight, 74 parts by weight, 76 parts by weight, 78 parts by weight, 80 parts by weight, 82 parts by weight, 84 parts by weight, 86 parts by weight, 88 parts by weight, 90 parts by weight, 92 parts by weight, 94 parts by weight, 96 parts by weight, 98 parts by weight, or in a range between two of these values. If the conjugated diene monomer content is below the aforementioned range, the dip-molded product may harden excessively, resulting in poor wearability. If it exceeds the aforementioned range, the durability or chemical resistance of the dip-molded product may decrease.

[0038] The ethylenically unsaturated nitrile monomer content of the composition 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 in a range between two of these values. If the ethylenically unsaturated nitrile monomer content is below the above range, the chemical resistance or mechanical strength of the dip molded article may decrease, and if it exceeds the above range, the elongation of the dip molded article may decrease, reducing its usability.

[0039] The ethylenically unsaturated acid monomer content of the above composition is 0.001 parts by weight, 0.5 parts by weight, 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, 10.5 parts by weight. The content may be 10 parts, 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 range between two of these values. If the ethylenically unsaturated acid monomer content is below the above range, the tensile strength of the dip molded article may decrease, and if it exceeds the above range, the dip molded article may harden excessively, resulting in poor wearability.

[0040] The aforementioned conjugated diene monomer may include isoprene. For example, the aforementioned conjugated diene monomer may include isoprene and one or more conjugated diene monomers other than isoprene.

[0041] The conjugated diene monomer may, but is not limited to, 29 to 97 parts by weight of isoprene and 1 to 50 parts by weight of a conjugated diene monomer other than isoprene. For example, the isoprene content may be 29, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97, or between two of these values. If the isoprene content is below this range, the durability of the dip-molded article produced from the composition may decrease.

[0042] The weight ratio of isoprene to the ethylenically unsaturated nitrile monomer may be between 1.0 and 3.5. If the weight ratio of isoprene to the ethylenically unsaturated nitrile monomer falls outside this range, the durability of the dip-molded article produced from the composition may decrease.

[0043] 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 of the dip-molded article produced from the composition may decrease.

[0044] In this specification, "total monomers" means the sum of the conjugated diene monomers, the ethylenically unsaturated nitrile monomers, and the ethylenically unsaturated acid monomers. However, the latex polymerization composition may further contain polymerizable monomers other than the aforementioned conjugated diene monomers, ethylenically unsaturated nitrile monomers, and ethylenically unsaturated acid monomers, in which case "total monomers" further includes the polymerizable monomers.

[0045] The total content of the ionic organic compound and the ionic inorganic compound may vary depending on the monomer composition ratio and the type of ionic compound. The total content of the ionic organic compound and the ionic inorganic compound may be 0.1 to 0.6 parts by weight based on 100 parts by weight of the total monomers. For example, 0.1 parts by weight, 0.11 parts by weight, 0.12 parts by weight, 0.13 parts by weight, 0.14 parts by weight, 0.15 parts by weight, 0.16 parts by weight, 0.17 parts by weight, 0.18 parts by weight, 0.19 parts by weight, 0.2 parts by weight, 0.21 parts by weight, 0.22 parts by weight, 0.23 parts by weight, 0.24 parts by weight, 0.25 parts by weight, 0.26 parts by weight, 0.27 parts by weight, 0.28 parts by weight, 0.29 parts by weight, 0.3 parts by weight, 0.31 parts by weight, 0.32 parts by weight, 0.33 parts by weight, 0.34 parts by weight, 0.35 parts by weight, 0.36 parts by weight The amount may be 0.37 parts by weight, 0.38 parts by weight, 0.39 parts by weight, 0.4 parts by weight, 0.41 parts by weight, 0.42 parts by weight, 0.43 parts by weight, 0.44 parts by weight, 0.45 parts by weight, 0.46 parts by weight, 0.47 parts by weight, 0.48 parts by weight, 0.49 parts by weight, 0.5 parts by weight, 0.51 parts by weight, 0.52 parts by weight, 0.53 parts by weight, 0.54 parts by weight, 0.55 parts by weight, 0.56 parts by weight, 0.57 parts by weight, 0.58 parts by weight, 0.59 parts by weight, 0.6 parts by weight, or a range between two of these values. If the total content of ionic organic compounds and ionic inorganic compounds is less than the above range, the ionic conductivity of the composition may decrease, the stability of the latex may decrease, the particle size of the latex may decrease due to a high polymerization reaction rate, the viscosity may increase, and it may become difficult to store the product and control the heat of reaction. If the total content of ionic organic compounds and ionic inorganic compounds exceeds the aforementioned range, the polymerization reaction rate may decrease, resulting in a lower final conversion rate, which may reduce the mechanical properties and practical durability of the dip-molded articles produced therefrom.

[0046] The ionic conductivity of the composition may be 250 μs / cm or higher. For example, 250 μs / cm, 255 μs / cm, 260 μs / cm, 265 μs / cm, 270 μs / cm, 275 μs / cm, 280 μs / cm, 285 μs / cm, 290 μs / cm, 295 μs / cm, 300 μs / cm, 305 μs / cm, 310 μs / cm, 315 μs / cm, 320 μs / cm, 325 μs / cm, 330 μs / cm, 33 The ionic conductivity may be 5 μs / cm, 340 μs / cm, 345 μs / cm, 350 μs / cm, 355 μs / cm, 360 μs / cm, 365 μs / cm, 370 μs / cm, 375 μs / cm, 380 μs / cm, 385 μs / cm, 390 μs / cm, 395 μs / cm, 400 μs / cm, or within a range between two of these values, or greater than or equal to one of these values. If the ionic conductivity of the composition is below the above range, the stability of the polymerized latex may decrease, and the viscosity may increase rapidly when the solid content is concentrated.

[0047] The ionic conductivity of the composition may be 10 ms / cm or less, 5 ms / cm or less, or 1 ms / cm or less, but is not limited thereto. If the ionic conductivity of the composition is excessively high, the amount of components unnecessary for polymerization may increase, which may reduce the stability of the latex.

[0048] The composition may further comprise water, an emulsifier, a polymerization initiator, and a molecular weight modifier.

[0049] 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 in the range between two of these values. If the water content is below the aforementioned range, the viscosity during polymerization may increase excessively, making it difficult to manufacture molded articles. If it exceeds the aforementioned 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.

[0050] The emulsifier may be an anionic surfactant, a nonionic surfactant, a cationic surfactant, or an amphoteric surfactant. For example, as an anionic surfactant, one or more 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 is not limited thereto. The emulsifier may be used in amounts of 0.8 to 8 parts by weight based on 100 parts by weight of the total monomers.

[0051] 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 used in amounts of 0.01 to 1.5 parts by weight based on 100 parts by weight of the total monomers.

[0052] 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 range between two of these values. If the content of the molecular weight modifier is below the above range, gel formation may occur and latex stability may decrease, and if it exceeds the above range, in addition to poor tensile strength and reduced stress retention rate, practical durability may decrease.

[0053] latex for dip molding

[0054] The latex for dip molding according to another aspect of this specification may include copolymers derived from the latex polymerization compositions described above.

[0055] The average particle size of the copolymer can 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. The particle size may be 2,100 Å, 2,150 Å, 2,200 Å, 2,250 Å, 2,300 Å, 2,350 Å, 2,400 Å, 2,450 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 latex for dip molding can be produced by polymerizing a composition containing ionic organic compounds and ionic inorganic compounds, thereby increasing the particle size of the copolymer while minimizing the decrease in stability. Furthermore, the latex may have a lower oligomer content and better stability.

[0056] The magnitude (absolute value) of the zeta potential of the dip molding latex may be 60 mV or higher, 62.5 mV or higher, 65 mV or higher, 67.5 mV or higher, or 70 mV or higher. Latex satisfying these conditions exhibits excellent stability and can suppress viscosity increase even when concentrated to a high solid content of 50% by weight or more.

[0057] The viscosity of the dip molding 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, 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, 75 The viscosity may be 0 cps, 775 cps, 800 cps, 825 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. Latex with a viscosity outside this range may be practically impossible to manufacture or difficult to dip mold.

[0058] The solid content of the latex for dip molding can be 50 to 65% by weight, for example, 50%, 52.5%, 55%, 57.5%, 60%, 62.5%, 65%, or in the range between two of these values. If the solid content falls outside this range, the aforementioned effect of stability improvement may become unnecessary, or aggregation of the latex may occur.

[0059] The characteristics of the dip molding latex are that it may be measured at pH 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. Although the solid content and average particle size may change when the pH of the latex is adjusted through additives, the dip molding latex can simultaneously satisfy the aforementioned average particle size, solid content, and viscosity requirements within the pH range.

[0060] The latex for dip molding 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.

[0061] The aforementioned latex for dip molding simultaneously satisfies low viscosity, high solids content, and large particle size, resulting in excellent stability of the latex itself. Therefore, it is possible to prevent deterioration of the quality of dip-molded products even when subjected to external impact or stored for long periods.

[0062] Method for manufacturing latex for dip molding

[0063] A method for producing latex for dip molding according to another aspect of this specification may include: (a) preparing a monomer mixture comprising a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, and an ethylenically unsaturated acid monomer; (b) adding an ionic organic compound, an ionic inorganic compound, an emulsifier, and water to the monomer mixture; and (c) adding a polymerization initiator to produce latex for dip molding.

[0064] The weight ratio of the ionic inorganic compound to the ionic organic compound introduced in step (b) above may be 4.7 or greater.

[0065] Step (a) above is a step in which a monomer mixture is prepared, which includes a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, and an ethylenically unsaturated acid monomer, which are monomers constituting a carboxylic acid-modified nitrile copolymer, and can be carried out under a nitrogen atmosphere.

[0066] Step (b) is a step in which an ionic compound is added to produce the latex polymerization composition described above. A molecular weight modifier may be further added in step (b).

[0067] 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 can be adjusted according to the target conversion rate.

[0068] 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 time between two of these hours.

[0069] The aforementioned step (c) may further include a step of adding a polymerization inhibitor to stop polymerization.

[0070] The polymerization inhibitor may be one selected from the group consisting of 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 combinations of two or more of these. The polymerization inhibitor content may be 0.02 to 1.5 parts by weight per 100 parts by weight of the monomer mixture.

[0071] 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 increases, which may reduce the mechanical properties and practical durability of the dip molded article produced therefrom.

[0072] Furthermore, the raw materials and their contents used in the aforementioned manufacturing method are as described above.

[0073] Dip-molded products

[0074] Dip-molded articles according to yet another aspect of this specification may be manufactured from the dip-molding latex described above.

[0075] The aforementioned dip-molded article may be, but is not limited to, a product manufactured by dip-molding after adding 1 to 2 parts by weight of sulfur, 0.1 to 1 part by weight of zinc oxide, and 0.3 to 1.5 parts by weight of vulcanization accelerator to the aforementioned dip-molding latex based on 100 parts by weight of the dip-molding latex.

[0076] The sulfur can react with the structure derived from the conjugated diene monomer to form a cross-linked structure. Adding ionic organic compounds and ionic inorganic compounds in the aforementioned weight ratio range can suppress shrinkage of the molded article due to syneresis during vulcanization. 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 range between two of these values. If the sulfur content is below the range, mechanical properties such as tensile strength and durability in actual use may decrease, and if it exceeds the range, it may induce an allergic reaction in the user.

[0077] The zinc oxide can form a cross-linked structure by forming ionic bonds with the structure derived from the ethylenically unsaturated acid. Furthermore, by adding ionic organic compounds and ionic inorganic compounds in the aforementioned weight ratio range, the strength of the ionic bonds can be improved, thereby enhancing durability. The content of the zinc oxide may be, for example, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, or a range between two of these values. If the zinc oxide content is below the above range, the durability in actual use may decrease, and if it exceeds the above range, the tensile strength may decrease.

[0078] 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.

[0079] 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 durability during storage, but other mechanical properties such as elongation may decrease.

[0080] The elongation rate 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.

[0081] The durability test results of the dip-molded product according to the following durability test method are 60 minutes or more, demonstrating high quality with excellent durability in actual use. For example, the durability test results of the dip-molded product may be 60 minutes or more, 90 minutes or more, 120 minutes or more, 150 minutes or more, 180 minutes or more, 210 minutes or more, or 240 minutes or more.

[0082] [Durability Testing Method]

[0083] A dip-molded product measuring 30 mm in width, 135 mm in length, and 0.06 to 0.08 mm in thickness was stretched 20% in the length direction and immersed in a pH 4.0 to 4.3 solution at 35°C. The product was stretched for 10 seconds to achieve a lengthwise elongation of 50%, fixed for 2 seconds, and then relaxed for 10 seconds to achieve a lengthwise elongation of 20%. This process was repeated, and the time it took for the product to break was measured.

[0084] The aforementioned durability test method involves repeatedly stretching and relaxing the dip-molded product in a solution at 35°C and pH 4.0-4.3, conditions similar to those of skin and bodily fluids that are likely to come into contact with the product during actual use, and confirming whether the test piece can be damaged. For example, if the molded product is a glove, the test method can simulate the situation in which the molded product repeatedly stretches and relaxes in response to finger movements, thereby measuring the durability of the dip-molded product under actual use conditions.

[0085] 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 health management. For example, the aforementioned 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.

[0086] 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 concrete examples of this specification that are not explicitly presented below will be described specifically in the relevant sections.

[0087] Examples and Comparative Examples

[0088] A 1 L high-pressure reactor was prepared, equipped with a stirrer, thermometer, cooler, and nitrogen gas inlet, and configured to allow continuous input 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 consisting of 40 wt% isoprene (IP), 25 wt% 1,3-butadiene (BD), 30 wt% acrylonitrile (AN), and 5 wt% methacrylic acid (MAA) was added based on the total weight of the monomer mixture. Subsequently, to 100 parts by weight of the monomer mixture, ethylenediaminetetraacetic acid (EDTA), an ionic organic compound; potassium sulfate (K2SO4) and sodium carbonate (Na2CO3), ionic inorganic compounds; 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 the reactor to produce a latex polymerization composition. After raising the temperature of the reactor to approximately 40°C, 0.3 parts by weight of potassium persulfate was added as a polymerization initiator. After polymerization for 12 hours, 0.9 parts by weight of sodium hydroxide was added to stop the polymerization reaction. Then, unreacted monomers and other contaminants were removed through a deodorization process, and ammonia water, antioxidants, defoamers, etc. were added to obtain a carboxylic acid-modified nitrile copolymer latex with a pH of 8.5.

[0089] The content of the ionic compounds used in each example and comparative example, and their weight ratios, are shown in Table 1 below.

[0090] [Table 1]

[0091] Experimental Example 1

[0092] The final conversion rate, initial conversion rate (after 2 hours of polymerization), average particle size, ionic conductivity, solid content, viscosity at 25°C, and zeta potential of the carboxylic acid-modified nitrile copolymer latex obtained in the above examples and comparative examples were measured and are shown in Table 2 below.

[0093] -Average particle size (Å): Measured using dynamic laser light scattering with Nanotrac 150.

[0094] - Ionic conductivity (μs / cm): Ionic conductivity was determined by measuring resistance using a two-electrode electrochemical impedance spectrometer (EIS) and then using the Nyquist graphing method. Resistance was measured under conditions of frequency 60 Hz to 1 kHz, current 10.0 mV, and voltage range ±10 V. Ionic conductivity was measured after correction with standard solutions within the expected range. Graphite electrodes were used as electrodes. Ionic conductivity values ​​corrected to 25°C were used.

[0095] Viscosity at -25°C (cps): Measured using a Brookfield viscometer with a spindle of 62 and 100 rpm.

[0096] - Zeta potential (mV): The zeta potential was measured at 25°C using a Malvern Zetasizer instrument.

[0097] [Table 2]

[0098] Referring to Table 2 above, in Examples 1 to 3, high conversion rates were observed in all cases, and the ionic conductivity was higher than that of Comparative Example 3, which did not contain an ionic compound. A large zeta potential, which indicates the electrical stability of the latex particles, was also measured. Furthermore, the latexes of Examples 1 to 3 exhibited low viscosity while achieving large particle sizes of 1,000 Å or more and high solid content of 50% by weight or more.

[0099] In Comparative Examples 1 and 2, the ionic conductivity was higher and the zeta potential was larger compared to the latex of Comparative Example 3, which did not contain an ionic compound. They also exhibited similar physical properties to Examples 1 to 3, achieving a large particle size of 1,000 Å or more and a high solids content of 50% by weight or more, while maintaining low viscosity. However, the reaction rate was slow, the initial conversion rate was lower than in the examples, the final conversion rate was low, and it was confirmed that a relatively large amount of unreacted monomers remained even after polymerization was complete.

[0100] The latex of Comparative Example 3, which did not contain an ionic compound, was measured to have a relatively small zeta potential, and its low stability made it difficult to simultaneously achieve large particle size, high solid content, and low viscosity. Furthermore, the reaction rate was fast, the particle size was small, and the viscosity was high, making it difficult to control product storage and reaction heat. In particular, the latex of Comparative Example 3, which had a small particle size, had the problem of a sharp increase in viscosity when the solid content was increased through concentration.

[0101] Manufacturing example

[0102] To 100 parts by weight of each carboxylic acid-modified nitrile copolymer latex produced according to the above examples and comparative examples, 1.8 parts by weight of sulfur (S), 0.7 parts by weight of zinc oxide (ZnO), and 1.2 parts by weight of zinc dibutyldithiocarbamate (ZDBC) as a vulcanization accelerator were added. Subsequently, a 4% potassium hydroxide aqueous solution and secondary distilled water were added to produce a dip molding latex composition with a solid content of 20% and a pH of 10.0.

[0103] Experimental Example 2

[0104] Rectangular test specimens measuring 30 mm in width, 135 mm in length, and 0.072 to 0.074 mm in thickness were prepared using each of the dip-molding latex compositions produced according to the above manufacturing examples, and the durability of the test specimens was evaluated. The results are shown in Table 3 below.

[0105] - Durability: A pH 4 solution was prepared using citric acid and maintained at 35°C. A rectangular test specimen was immersed in the solution with its length stretched by 20%. The specimen was stretched to 50% for 10 seconds, held for 2 seconds, and then relaxed to 20% for 10 seconds. This process was repeated, and the time it took for the specimen to break was measured.

[0106] [Table 3]

[0107] Referring to Table 3 above, the test specimens manufactured using the latex of Examples 1 to 3 showed superior durability in actual use compared to the test specimens manufactured using the latex of Comparative Examples 1 to 3. In particular, the test specimens manufactured using the latex of Comparative Example 1 or 2 broke within one hour, confirming insufficient durability in actual use.

[0108] 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.

[0109] 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, as well as the concept of equivalents thereof, should be construed as being included within the scope of this specification.

Claims

1. It includes conjugated diene monomers, ethylenically unsaturated nitrile monomers, ethylenically unsaturated acid monomers, ionic organic compounds, and ionic inorganic compounds. A latex polymerization composition wherein the weight ratio of the ionic inorganic compound to the ionic organic compound is 4.7 or more.

2. The latex polymerization composition according to claim 1, wherein the conjugated diene monomer is selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, 2-chloro-1,3-butadiene, 3-butyl-1,3-octadiene, octadiene, and two or more combinations thereof.

3. The latex polymerization composition according to claim 1, wherein 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.

4. The latex polymerization composition 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, styrene sulfonic acid, monobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate, and two or more combinations thereof.

5. The latex polymerization composition according to claim 1, wherein the ionic organic compound is one selected from the group consisting of ethylenediaminetetraacetic acid (EDTA) or its sodium salt, ethylene glycoltetraacetic acid (EGTA) or its sodium salt, nitrilotriacetic acid (NTA) or its sodium salt, iminodiacetic acid (IDA) or its sodium salt, quinolinic acid (QNA) or its sodium salt, and two or more combinations thereof.

6. The ionic inorganic compound is potassium sulfate (K ２ SO ４ ), sodium carbonate (Na ２ CO ３ ), sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl ２ ), magnesium chloride (MgCl ２ ), sodium nitrate (NaNO ３ ), potassium nitrate (KNO ３ ), calcium nitrate (Ca(NO ３ ) ２ ), magnesium nitrate (Mg(NO ３ ) ２ ), sodium sulfate (Na ２ SO ４ ), calcium sulfate (CaSO ４ ), magnesium sulfate (MgSO ４ ), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH) ２ ), magnesium hydroxide (Mg(OH) ２ ), sodium hydrogen carbonate (NaHCO ３ ), potassium hydrogen carbonate (KHCO ３ ), potassium carbonate (K ２ CO ３ ), sodium hydrogen sulfite (NaHSO ４ ), potassium bisulfite (KHSO ４ ), sodium pyrophosphate (Na ４ P ２ O ７ ), potassium pyrophosphate (K ４ P ２ O ７ ), trisodium phosphate (Na ３ PO ４ ), tripotassium phosphate (K ３ PO ４ ), disodium hydrogen phosphate (Na ２ HPO ４ ), dipotassium hydrogen phosphate (K ２ HPO ４ ), and is one selected from the group consisting of combinations of two or more of these, the latex polymerization composition according to claim 1.

7. The latex polymerization composition according to claim 1, comprising 30 to 98 parts by weight of a conjugated diene monomer, 1 to 55 parts by weight of an ethylenically unsaturated nitrile monomer, and 0.001 to 20 parts by weight of an ethylenically unsaturated acid monomer.

8. The latex polymerization composition according to claim 1, further comprising water, an emulsifier, a polymerization initiator, and a molecular weight modifier.

9. A latex for dip molding comprising a copolymer derived from the latex polymerization composition of claim 1.

10. A dip-molded article manufactured from the dip-molding latex of claim 9.

11. The dip-molded article according to claim 10, 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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