Latex composition for dip molding having excellent chemical resistance and dip molded article prepared therefrom

Abstract

The present invention provides a latex composition for dip molding having excellent chemical resistance and a dip molded article prepared therefrom, the latex composition for dip molding according to an embodiment of the present invention comprising a copolymer latex polymerized from an ethylenically unsaturated nitrile monomer, an isoprene monomer, a butadiene monomer, and an ethylenically unsaturated acid monomer, based on 100 parts by weight of the sum of the isoprene monomer and the butadiene monomer, the content of the butadiene monomer is 5-20 parts by weight, and the gel content of the copolymer latex is 40-90%.

Description

Technical Field

[0001] This specification relates to latex compositions for dip molding with excellent chemical resistance and dip-molded articles prepared therefrom. Background Technology

[0002] Traditionally, gloves used in medical, agricultural, and industrial applications have primarily been made from natural rubber latex. However, due to the proteins contained in natural rubber latex, users often experience contact irritation and allergic reactions when using gloves made from it. Therefore, efforts have been made to manufacture gloves using protein-free synthetic rubber latexes, such as nitrile copolymer latex. Nitrile copolymer latex gloves offer superior mechanical strength compared to natural rubber latex gloves, leading to increasing demand in the medical and food industries where frequent contact with sharp objects is common.

[0003] With the increasing use of nitrile copolymer latexes, the demand for improved quality of dip-molded products has also increased. Therefore, attempts have been made to improve the durability of dip-molded products prepared from dip-molding latexes, such as tensile strength and elongation. However, despite these attempts to improve mechanical properties, there have been continuous incidents of fatal accidents or failure to achieve the desired results due to damage to dip-molded products.

[0004] In particular, molded articles intended for human protection against chemical reactions require chemical resistance to maintain their shape stably without deformation in various solvents such as acetone and n-hexane, which are organic solvents. There is an urgent need to develop technologies for preparing dip-molded articles that possess such chemical resistance while retaining the excellent tensile strength and elongation inherent in traditional nitrile latexes, exhibiting superior durability and chemical resistance. Summary of the Invention

[0005] The technical problem to be solved The contents of this specification are intended to solve the problems of the prior art described above. One object of this specification is to provide a latex composition for impregnation molding with high gel content and high cross-linking degree, and excellent chemical resistance and durability.

[0006] Technical solutions to solve technical problems According to one method, a latex composition for impregnation molding is provided, comprising a copolymer latex polymerized from an ethylene unsaturated nitrile monomer, an isoprene monomer, a butadiene monomer, and an ethylene 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 sum of the isoprene monomer and the butadiene monomer, and the gel content of the copolymer latex is 40 to 90%.

[0007] In one embodiment, the vinyl unsaturated nitrile monomer may be selected from the group consisting of acrylonitrile, methacrylonitrile, fumaric acid, α-chloronitrile, α-cyanoethyl acrylonitrile, and combinations of two or more thereof.

[0008] In one embodiment, the vinyl unsaturated acid monomer may be 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 combinations of two or more thereof.

[0009] In one embodiment, the copolymer latex may contain 1 to 55 parts by weight of the vinyl 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 vinyl unsaturated acid monomer.

[0010] In one embodiment, the deformation rate of the dip-molded article prepared from the dip-molding latex composition, as represented by Formula 1, can be 50% or less: Formula 1 (Deformation rate) = (ab) / a * 100 In Formula 1, a represents the weight (g) measured after preparing an impregnated molded article 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 prepared impregnated molded article in 80 ml of solvent and stirring at room temperature for 4 hours.

[0011] In one embodiment, the solvent may be selected from the group consisting of acetone, ethanol, isopropanol, methyl ethyl ketone, n-heptane, and toluene.

[0012] According to another approach, an impregnation-molded article is provided, which is prepared from the impregnation-molding latex composition.

[0013] In one embodiment, the impregnated molded article may be a surgical glove, medical glove, agricultural and livestock processing glove, industrial glove, condom, cosmetic material, catheter, or health care molded article.

[0014] Invention Effects The latex composition for impregnation molding according to one aspect of this specification has excellent mechanical properties such as elongation due to its high gel content and high degree of crosslinking, and can also have excellent chemical resistance.

[0015] Furthermore, the dip-molded articles according to another method of this specification, due to their excellent chemical resistance and durability, can be applied to a variety of fields such as surgical gloves, medical gloves, gloves for processing agricultural and livestock products, industrial gloves, condoms, cosmetic materials, catheters, and health care molded articles.

[0016] The effects of one aspect of this specification are not limited to those described above, and should be understood to include all effects inferred from the detailed description of this specification or the structure of the invention as set forth in the appended claims. Detailed Implementation

[0017] In the following description, one manner of this specification will be illustrated with reference to specific examples. However, the contents of this specification can be implemented in many different forms and are not limited to the embodiments described herein.

[0018] Throughout the specification, when describing a component as "connected" to another component, it includes not only the case of "direct connection" but also the case of "connection with other components in between". Furthermore, when a component is referred to as "including (or containing)" a component, unless otherwise expressly stated, it supersedes the exclusion of any other component, which may indicate that a component may further include other components.

[0019] In this specification, when describing a range of numerical values, unless otherwise specified, these values ​​have the precision of significant figures provided by the standard rules in chemistry for significant figures. For example, 10 includes a range of 5.0 to 14.9, while the number 10.0 includes a range of 9.50 to 10.49.

[0020] Latex composition for dip molding According to one aspect of this specification, an impregnation molding latex composition comprises a copolymer latex polymerized from vinyl unsaturated nitrile monomers, isoprene monomers, butadiene monomers, and vinyl unsaturated acid monomers.

[0021] Among the copolymer latexes conventionally used, which are polymers of vinyl unsaturated nitrile monomers, conjugated diene monomers, and vinyl unsaturated acid monomers, the most well-known is nitrile-isoprene (NI) copolymer latex. NI copolymer latex exhibits high elongation and low elastic modulus, thus possessing excellent mechanical properties and high durability. However, when such NI copolymer latex is used as latex gloves in laboratories or other environments where chemical reactions occur during experiments, its required chemical resistance is somewhat insufficient. Chemical resistance refers to the property of not being dissolved or deformed in various organic solvents, but rather maintaining its original shape and physical properties. To impart chemical resistance to conventional NI copolymer latex, the inventors conducted continuous experiments and confirmed that when butadiene is used as a conjugated diene monomer in addition to isoprene, a latex for impregnation molding with high gel content, excellent durability, and guaranteed chemical resistance can be obtained, thus completing the present invention.

[0022] In the latex composition for impregnation molding of the present invention, based on the total amount of the isoprene monomer and the butadiene monomer in 100 parts by weight, the content of the butadiene monomer can be 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 greater than 10 parts by weight and less than 18.5 parts by weight, but is not limited thereto. For example, based on the total of 100 parts by weight of the isoprene monomer and the butadiene monomer, the content of the butadiene monomer can 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 100 parts by weight of the sum of the isoprene monomer and the butadiene monomer, if the content of the butadiene monomer meets the specified range, the prepared copolymer latex will form a high gel content, thereby exhibiting a high degree of crosslinking. As a result, the prepared impregnated molded article can exhibit excellent chemical resistance to solvents.

[0023] In the latex composition for impregnation molding of the present invention, the gel content of the copolymer latex can be 40-90%, preferably 40-80%, more preferably 48-75%, and most preferably 50-70%, but is not limited thereto. For example, the gel content of the copolymer latex can 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 values ​​between two of these. In the copolymer latex, a higher gel content indicates more cross-linking bonds. If the gel content of the copolymer latex is greater than the specified range, the mechanical properties of the prepared latex for impregnation molding may be reduced due to excessive aggregation. If it is less than the specified range, it is prone to deformation due to shear force during impregnation molding, which may reduce the mechanical properties of the prepared latex for impregnation molding and may result in a lower degree of crosslinking, which may lead to poorer chemical resistance of the prepared impregnated molded article to solvents.

[0024] The vinyl unsaturated nitrile monomer may be selected from the group consisting of acrylonitrile, methacrylonitrile, fumaric acid, α-chloronitrile, α-cyanoethyl acrylonitrile, and combinations thereof, but is not limited thereto. In copolymers of latex for dip molding, the structure derived from the vinyl unsaturated nitrile monomer can improve the strength and chemical resistance of the dip-molded article.

[0025] The vinyl unsaturated acid monomer may be 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 combinations thereof, but is not limited thereto. In copolymers of latex for dip molding, the structure derived from the vinyl unsaturated acid monomer can improve the mechanical properties of the dip-molded article by forming a cross-linked structure.

[0026] The copolymer latex may contain 1 to 55 parts by weight of the vinyl 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 vinyl unsaturated acid monomer, but is not limited thereto.

[0027] For example, the content of the vinyl unsaturated nitrile monomer in the copolymer latex can 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 content of the vinyl unsaturated nitrile monomer is less than the range, the chemical resistance or mechanical strength of the impregnated molded article may be reduced; if it is greater than the range, the usability may be reduced due to the reduced elongation of the impregnated molded article.

[0028] For example, the isoprene monomer content of the copolymer latex can 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 such values. If the isoprene monomer content is less than the range, the impregnated molded article may suffer from poor wearing comfort due to excessive hardening; if it is greater than the range, the durability and chemical resistance of the impregnated molded article may be reduced.

[0029] 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 two of these. If the butadiene monomer content is less than the range, the gel content will decrease due to the reduced degree of crosslinking of the latex, which may result in poorer chemical resistance. If the content is greater than the range, the durability and chemical resistance of the impregnated molded article may decrease.

[0030] For example, the content of vinyl unsaturated acid monomers in 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 two of these. If the content of vinyl unsaturated acid monomers is less than the range, the tensile strength of the dip-molded article may decrease; if it is greater than the range, the wearing comfort may be worse due to excessive hardening of the dip-molded article.

[0031] The weight percentage of butadiene monomer relative to the isoprene monomer can be 0.15 to 0.7, most preferably 0.2 to 0.65, but is not limited thereto. If the weight percentage of butadiene monomer relative to the isoprene monomer deviates from the range, the durability and chemical resistance of the impregnated molded article prepared from the composition may be reduced.

[0032] The weight percentage of isoprene relative to the vinyl unsaturated nitrile monomer can be 2.1 to 3.5. If the weight percentage of isoprene relative to the vinyl unsaturated nitrile monomer deviates from this range, the durability and chemical resistance of the impregnated molded article prepared from the composition may be reduced.

[0033] The weight percentage of the vinyl unsaturated acid monomer relative to the vinyl unsaturated nitrile monomer can be 0.1 to 0.4. If the weight percentage of the vinyl unsaturated acid monomer relative to the vinyl unsaturated nitrile monomer deviates from this range, the durability and chemical resistance of the impregnated molded article prepared from the composition may be reduced.

[0034] In this specification, "total monomers" refers to the sum of the isoprene monomer, the butadiene monomer, the vinyl unsaturated nitrile monomer, and the vinyl unsaturated acid monomer. However, the latex composition for impregnation molding may also contain polymerizable monomers other than the aforementioned isoprene monomer, butadiene monomer, vinyl unsaturated nitrile monomer, and vinyl unsaturated acid monomer. In this case, "total monomers" also includes the polymerizable monomers.

[0035] The composition may also contain water, emulsifier, polymerization initiator, and molecular weight regulator.

[0036] Based on 100 parts by weight of the total amount of the monomers, the water content can be 75 to 150 parts by weight, 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 less than the specified range, the preparation of the molded article may be difficult due to an excessive increase in viscosity during polymerization; if it is greater than the specified range, the solid content may be excessively reduced. The ionic conductivity of the water can be less than 5 μs / cm, less than 2.5 μs / cm, or less than 1 μs / cm. For example, the water can be ion-exchanged water, ultrapure water, or purified water. If water with high ionic conductivity is used, it may contain impurities that adversely affect the polymerization stability or the stability of the latex.

[0037] The emulsifier may be anionic, nonionic, cationic, or amphoteric surfactants. For example, as an anionic surfactant, one or more of the group consisting of alkylbenzene sulfonates, aliphatic sulfonates, sulfates of higher alcohols, α-olefin sulfonates, and alkyl ether sulfates may be used, but the group is not limited thereto. Based on 100 parts by weight of the total monomers, the emulsifier may be added in amounts of 0.8 to 8 parts by weight.

[0038] The polymerization initiator may be a free radical initiator. For example, the free radical initiator may be 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 tert-butyl peroxide, cumene hydrogen peroxide, p-menthane hydrogen peroxide, di-tert-butyl peroxide, tert-butylcumyl peroxide, acetyl peroxide, isobutyl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanol peroxide, and tert-butyl isobutyrate peroxide; or one or more azo initiators selected from the group consisting of azobisisobutyronitrile, azobis-2,4-dimethylpentanonitrile, azobiscyclohexanenitrile, and methyl azobisisobutyrate, but not limited thereto. Based on 100 parts by weight of the total monomers, the polymerization initiator may be added in amounts of 0.01 to 1.5 parts by weight.

[0039] The molecular weight regulator may be a thiol such as α-methylstyrene dimer, tert-dodecylthiol, n-dodecylthiol, or octylthiol; a halogenated hydrocarbon such as carbon tetrachloride, dichloromethane, or dibromomethane; or a sulfur-containing compound such as tetraethylthiuram disulfide, dipentamethylenethiuram disulfide, or diisopropylxanthionic acid disulfide, but is not limited thereto. Based on 100 parts by weight of the total amount of the monomers, the content of the molecular weight regulator may be 0.1 to 1 part by weight. For example, the amount can 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 regulator is less than the range, the latex stability may be reduced; if it is greater than the range, the mechanical properties may deteriorate or the chemical resistance may be reduced.

[0040] The average particle size of the copolymer latex can be 1000~3000. For example, it can be 1000. 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200 2250 2300 2350 2400 2450 2500 2550 2600 2650 2700 2750 2800 2850 2900 2950 3000 Or a range between two of their values. The copolymer latex can be prepared by copolymerizing two types of conjugated diene monomers, ensuring its stability and maintaining a high gel content, thereby giving it excellent chemical resistance to solvents.

[0041] The viscosity of the copolymer latex at 25°C can be 50~2500 cps, for example, it can be 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, 750 cps, 775 cps, 800 cps, 825 cps. The viscosity of the copolymer latex may be 850 cps, 875 cps, 900 cps, 925 cps, 950 cps, 975 cps, 1000 cps, 1100 cps, 1200 cps, 1300 cps, 1400 cps, 1500 cps, 1600 cps, 1700 cps, 1800 cps, 1900 cps, 2000 cps, 2100 cps, 2200 cps, 2300 cps, 2400 cps, 2500 cps, or a range of two of these values. If the viscosity of the copolymer latex deviates from the range described above, preparation may be substantially impossible, or dip molding may be difficult.

[0042] The solids content of the copolymer latex can be 45-65% by weight, for example, 45% by weight, 47.5% by weight, 50% by weight, 52.5% by weight, 55% by weight, 57.5% by weight, 60% by weight, 62.5% by weight, 65% by weight, or a range between two of these values. If the solids content of the copolymer latex deviates from the range, the aforementioned stability improvement effect is not needed, or latex aggregation may occur.

[0043] The copolymer latex is characterized in that measurements are taken at pH values ​​between 8.0 and 10.0, for example, at pH values ​​of 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. When the pH of the latex is adjusted by additives, the solids content and average particle size may change, but the copolymer latex can simultaneously meet the aforementioned requirements for average particle size, solids content, and viscosity within the pH range.

[0044] The latex used for impregnation molding may further contain one or more additives selected from the group consisting of chelating agents, dispersants, pH adjusters, oxygen absorbers, particle size modifiers, antioxidants, and oxygen scavengers. These additives may use structural elements known in the art and may be added before or after the polymerization of the copolymer.

[0045] Preparation method of latex for dip molding Another method for preparing a latex for dip molding according to this specification may include: (a) preparing a monomer mixture comprising isoprene monomer, butadiene monomer, vinyl unsaturated nitrile monomer and vinyl unsaturated acid monomer; (b) adding an emulsifier and water to the monomer mixture; and (c) adding a polymerization initiator and preparing a latex for dip molding.

[0046] Step (a) is a step of preparing a monomer mixture comprising isoprene monomer, butadiene monomer, vinyl unsaturated nitrile monomer and vinyl unsaturated acid monomer as monomers constituting the carboxylic acid modified nitrile copolymer, which can be performed under a nitrogen atmosphere.

[0047] Steps (b) and (c) are steps of adding additives and water to prepare the aforementioned copolymer latex. In step (b), a molecular weight regulator may also be added.

[0048] The polymerization in step (c) can be performed at temperatures ranging from 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 between two of these temperatures, but is not limited thereto, and the polymerization temperature can be adjusted according to the target conversion rate.

[0049] The aggregation in step (c) can be performed for 2 to 24 hours, for example, for 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 values, but is not limited to this.

[0050] Step (c) may also include the step of adding a polymerization terminator and terminating the polymerization.

[0051] The polymerization terminator may be selected from the group consisting of sodium hydroxide, hydroxylamine, hydroxylamine sulfate, diethylhydroxylamine, hydroxylamine sulfonic acid and its alkali metal ions, sodium dimethyl dithiocarbamate, hydroquinone derivatives, hydroxydiethylphenyl dithiocarboxylic acid, hydroxydibutylphenyl dithiocarboxylic acid, and other aromatic hydroxydithiocarboxylic acids, as well as combinations of two or more of them. The content of the polymerization terminator may be 0.02 to 1.5 parts by weight relative to 100 parts by weight of the monomer mixture.

[0052] In step (c), the final conversion rate of the polymerization reaction can be 92% or higher. For example, it can 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 thereto. If the conversion rate is less than the range described above, the mechanical properties and actual service durability of the impregnated molded articles prepared therefrom may decrease as the amount of residual unreacted monomers increases.

[0053] In addition, the raw materials and their contents used in the preparation method are as described above.

[0054] Dipping molded products According to another embodiment of this specification, an impregnation-molded article can be prepared from the aforementioned latex composition for impregnation molding.

[0055] Based on 100 parts by weight of the latex for impregnation molding, 1 to 2 parts by weight of sulfur, 1.5 to 4 parts by weight of crosslinking agent and 0.3 to 1.5 parts by weight of sulfurizing accelerator can be added to the aforementioned latex for impregnation molding before impregnation molding to prepare the impregnated molded article, but it is not limited thereto.

[0056] The sulfur can form a cross-linked structure by reacting with structures derived from the conjugated diene monomers. When the isoprene and butadiene monomers are added within the specified weight range, shrinkage of the molded article caused by syneresis during sulfur addition can be suppressed. The sulfur content can 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 values ​​between two of these. If the sulfur content is less than the specified range, mechanical properties such as tensile strength and chemical resistance may decrease; if it is greater than the specified range, it may cause allergic reactions in users.

[0057] The crosslinking agent can form a crosslinked structure by forming ionic bonds with a structure derived from the vinyl unsaturated acid. The crosslinking agent can be one or more selected from the group consisting of zinc oxide or titanium oxide. For example, the content of the crosslinking agent can 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 less than the range, durability and chemical resistance may decrease; if it is greater than the range, tensile strength may decrease.

[0058] The dip-molded article can be dip-molded by adding an aqueous potassium hydroxide solution to the dip-molding latex to adjust the solid content, but is not limited to this.

[0059] The tensile strength of the impregnated molded article can be 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, but is not limited to these. Higher tensile strength results in higher durability during storage, but other mechanical properties such as elongation may decrease.

[0060] The elongation of the dip-molded article can be 600% or more, 650% or more, 700% or more, 750% or more, 800% or more, 850% or more, or 900% or more, but is not limited to these values. Higher elongation results in better wearing comfort, but there may be a trade-off with other mechanical properties.

[0061] The deformation rate test result of the impregnated molded article according to the following chemical resistance test method is 50% or less, which indicates that it does not dissolve in a variety of organic solvents or deform in structure, and has excellent durability and high quality. For example, the deformation rate test result of the impregnated molded article can be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

[0062] Chemical resistance test methods After preparing an impregnated molded article with a width of 30 mm, a length of 135 mm, and a thickness of 0.06~0.09 mm, when the initially measured weight is referred to as a (in g), and the weight of the prepared impregnated molded article after immersing it in 80 ml of solvent and stirring at room temperature for 4 hours is referred to as b (in g), the deformation rate calculated by the following formula 1 is as described above and is less than 50%.

[0063] Formula 1 (Deformation rate) = (ab) / a*100.

[0064] The chemical resistance test method confirms whether deformation or weight increase occurs due to the solvent by verifying the weight change of the sample when it is immersed in an organic solvent that is likely to be exposed to it during actual use. The chemical resistance of the immersed molded article can be measured under the actual use conditions of the molded article.

[0065] The solvent used in the chemical resistance test can be selected from one of the group consisting of acetone, ethanol, isopropanol, methyl ethyl ketone, n-heptane, and toluene. In particular, dip-molded articles prepared from the latex composition for dip molding of the present invention exhibit a low deformation rate due to hydrophilic organic solvents such as ethanol and isopropanol, thus avoiding swelling and ensuring that their physical properties are not degraded even under prolonged operation, thereby increasing the ease of operation for the worker.

[0066] When the solvent used in the chemical resistance test is acetone, the deformation rate calculated by Formula 1 can 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.

[0067] The impregnated molded article can be a surgical glove, medical glove, agricultural or livestock processing glove, industrial glove, condom, cosmetic material, catheter, or health care molded article, but is not limited thereto. For example, the impregnated molded article can be a surgical glove or other medical glove, an industrial glove such as a chemical handling glove, or a cosmetic material such as a powder puff.

[0068] The embodiments of this specification will now be described in more detail. However, the experimental results below are merely representative of those described in the embodiments, and the embodiments should not be construed as narrowing or limiting the scope and content of this specification. The effects of various implementations of this specification not explicitly mentioned below are specifically described in the corresponding sections.

[0069] Examples and Comparative Examples A 5L high-pressure reactor equipped with a stirrer, thermometer, cooler, and nitrogen inlet was prepared and configured to continuously add monomers, emulsifiers, polymerization initiators, and other components. Water with a conductivity of less than 1 μs / cm was prepared as ion-exchange water. After purging the reactor with nitrogen, a monomer mixture of isoprene (IP), 1,3-butadiene (BD), acrylonitrile (AN), and methacrylic acid (MAA) was added according to the weights shown in Table 1 below, based on the total weight of the monomer mixture. Then, relative to 100 parts by weight of the monomer mixture, 0.5 parts by weight of t-dodecyl mercaptan (TDDM) as a molecular weight regulator, 2 parts by weight of sodium alkylbenzene sulfonate as an emulsifier, and 120 parts by weight of ion-exchange water were added to the reactor to prepare a latex composition for impregnation molding. After heating the reactor to 40°C, 0.3 parts by weight of sodium persulfate as a polymerization initiator were added. Polymerization was carried out for 12 hours, and when the conversion rate reached approximately 98%, 0.9 parts by weight of sodium hydroxide was added to terminate the polymerization reaction. Then, unreacted monomers were removed through a deodorization process, and ammonia, antioxidants, and defoamers were added to obtain a copolymer latex with a solids concentration of 45-55% and a pH of 8.6-9.0.

[0070] Table 1

[0071] Experimental Example 1: Evaluation of Gel Content The gel content of the copolymer latex obtained in the embodiments and comparative examples was measured by the following method and recorded in Table 2.

[0072] Add 5 g of each copolymer latex prepared according to Examples 1 to 8 and Comparative Examples 1 to 4 to 200 mL of isopropanol while stirring, and allow to solidify. Filter the solidified material through a 120-mesh metal mesh, dry it in a constant-temperature vacuum desiccator at 50±2°C and 750±10 mmHg for 1 hour, and then allow it to cool to room temperature in the desiccator. Weigh 0.25–0.35 g of the dried sample accurately to a unit of 0.1 mg (W). i The sample was transferred to an Erlenmeyer flask, and 100 mL of methyl ethyl ketone (MEK) was added. The mixture was stirred for 2 hours. The sample was then filtered completely through filter paper. 20 mL of the filtrate was heated to evaporate the methyl ethyl ketone, cooled to room temperature in a desiccator, and then weighed accurately to an accuracy of 0.1 mg (W). f The gel content in the sample is measured according to Formula 2 below, and the two average values ​​are calculated to one decimal place.

[0073] Formula 2

[0074] Table 2

[0075] Referring to Table 2, in Examples 1 to 8, a gel content of over 40% was observed, resulting in excellent cross-linking. In Comparative Example 1, which did not contain butadiene monomer, the gel content was 0%, resulting in no cross-linking at all. In Comparative Examples 2 to 4, where the butadiene monomer content did not exceed 5 parts by weight of 100 parts by weight of the entire conjugated diene monomer, the gel content was less than 20%, resulting in insufficient cross-linking.

[0076] Preparation Example Relative to 100 parts by weight of each copolymer latex prepared according to the embodiments 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 oxide (TiO2), and 1.0 part by weight of zinc dibutyldithiocarbamate (ZDBC) as a sulfurization accelerator were added. Then, the mixture was heated to 120-150°C and a sulfurization reaction was carried out. After adding double-distilled water and removing residues at 50°C for 2 minutes, a latex composition for impregnation molding with a solids concentration of 45% and a pH of 8.5 was prepared.

[0077] Experimental Example 2: Evaluation of Chemical Resistance Rectangular samples with a width of 30 mm, a length of 135 mm, and a thickness of 0.080–0.089 mm were prepared from the various latex compositions for impregnation molding prepared according to the preparation examples described above, and the chemical resistance of the samples was evaluated. The results are shown in Tables 3 to 5 below. Table 3 shows the experimental results using acetone as a solvent, Table 4 shows the experimental results using ethanol as a solvent, and Table 5 shows the experimental results using methyl ethyl ketone as a solvent.

[0078] The initial weight of the prepared impregnated molded article was measured and recorded (a (in g)). After immersing the prepared impregnated molded article in 80 ml of solvent and stirring at room temperature for 4 hours, the swollen molded article was removed with small tweezers, and the solvent adhering to the surface was physically removed. Its weight was then measured and recorded (b (in g)). Then, the deformation rate was calculated using Equation 1 above and is shown in Tables 3 to 5.

[0079] Table 3

[0080] Table 4

[0081] Table 5

[0082] Referring to Tables 3 to 5, the samples prepared using the latex of Examples 1 to 8 exhibited superior chemical resistance compared to the samples prepared using the latex of Comparative Examples 1 to 4. In this invention, by adjusting the butadiene monomer content to 5-20 parts by weight (based on the total of 100 parts by weight of isoprene monomer and butadiene monomer) to achieve a higher degree of crosslinking, it was confirmed that a high gel content resulted in a low deformation rate. In particular, for ketones and ethanol used in various chemical reactions, such as acetone and ethanol, it was confirmed that the examples exhibited significantly superior chemical resistance compared to the comparative examples. On the other hand, in the case of the sample prepared using the latex of Comparative Example 3, it exhibited a deformation rate of over 50% in all solvents, thus confirming its insufficient chemical resistance in organic solvents.

[0083] The descriptions in this specification are merely illustrative. Anyone skilled in the art will understand that other specific forms can be easily derived without altering the technical concept or essential features of this specification. Therefore, it should be understood that the embodiments described above are merely illustrative in various respects and are not limited thereto. For example, the structural components described as a single type can also be implemented separately, and similarly, the structural components described separately can also be implemented in a combined form.

[0084] The scope of this specification is defined by the appended claims, not by the detailed description described herein, and all variations or modifications derived from the meaning, scope and equivalent concepts of the appended claims shall be interpreted as including within the scope of this specification.

Claims

1. A latex composition for impregnation molding, comprising a copolymer latex polymerized from an ethylene-unsaturated nitrile monomer, an isoprene monomer, a butadiene monomer, and an ethylene-unsaturated acid monomer, wherein, Based on the total amount of the isoprene monomer and the butadiene monomer in 100 parts by weight, the content of the butadiene monomer is 5 to 20 parts by weight. The copolymer latex has a gel content of 40-90%.

2. The latex composition for impregnation molding according to claim 1, wherein, The vinyl unsaturated nitrile monomer is selected from the group consisting of acrylonitrile, methacrylonitrile, fumaric acid, α-chloronitrile, α-cyanoethyl acrylonitrile, and combinations of two or more of them.

3. The latex composition for impregnation molding according to claim 1, wherein, The vinyl unsaturated acid monomer is 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 combinations of two or more thereof.

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

5. The latex composition for impregnation molding according to claim 1, wherein, The deformation rate of the dip-molded article prepared from the latex composition for dip molding, as expressed by Formula 1, is 50% or less: Formula 1 (Deformation rate) = (ab) / a * 100 In Formula 1, a represents the weight measured after preparing an impregnated molded article with a width of 30 mm, a length of 135 mm, and a thickness of 0.06~0.09 mm, in g; b represents the weight measured after immersing the prepared impregnated molded article in 80 ml of solvent and stirring at room temperature for 4 hours, in g.

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

7. An dip-molded article prepared 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 impregnated molded articles are surgical gloves, medical gloves, agricultural and livestock processing gloves, industrial gloves, condoms, cosmetic materials, catheters, or health care molded articles.

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