CN117957281A

CN117957281A - Composition for dip molding, glove, and method for producing composition for dip molding and glove

Info

Publication number: CN117957281A
Application number: CN202380013676.1A
Authority: CN
Inventors: 池田佳祐; 星野沙也华; 金森航; 松井正裕; 武内大和; 洼野有悟; 榎本宪秀
Original assignee: Midori Anzen Co Ltd
Current assignee: Midori Anzen Co Ltd
Priority date: 2022-05-09
Filing date: 2023-05-08
Publication date: 2024-04-30

Abstract

A composition for non-sulfur crosslinked dip molding comprising a carboxylated diene rubber elastomer, a crosslinking agent comprising at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent, an antioxidant comprising at least one compound having a phenol structure and a sulfur atom, and water, wherein the content of the at least one compound is 0.05 to 4 parts by weight relative to 100 parts by weight of the elastomer.

Description

Composition for dip molding, glove, and method for producing composition for dip molding and glove

Technical Field

The present disclosure relates to a composition for dip molding and a glove, and a method for producing the composition for dip molding and the glove.

Background

Rubber gloves are widely used in various industrial fields, medical fields, and the like. The rubber glove elastomer uses natural latex and synthetic latex. Among them are diene rubbers such as Natural Rubber (NR), polyisoprene rubber (IR), chloroprene Rubber (CR), styrene Butadiene Rubber (SBR), nitrile Butadiene Rubber (NBR), and carboxylated acrylonitrile butadiene rubber (XNBR), and gloves produced by dip molding by crosslinking these elastomers with sulfur and a vulcanization accelerator. Among them, the most used among the conventional gloves is a glove in which a double bond of butadiene in XNBR is vulcanized and carboxyl groups are crosslinked with zinc oxide.

However, these sulfur crosslinked gloves have the following problems: in the case of natural rubber, the protein contained therein causes type I allergy, and in the case of synthetic latex, the vulcanization accelerator added during vulcanization causes type IV allergy.

Therefore, so-called accelerator-free gloves without a vulcanization accelerator have been developed using carboxylated diene rubbers and utilizing non-sulfur-based crosslinking. In this regard, there are the following methods: a method of crosslinking carboxyl groups of the carboxylated diene rubber with an organic crosslinking agent or a metal crosslinking agent; a method of blending a crosslinkable organic compound in the polymerization, namely, self-crosslinking the latex. Examples of gloves that have been practically put into practical use include polycarbodiimide crosslinked gloves, epoxy crosslinked gloves, aluminum crosslinked gloves, and several types of self-crosslinked gloves. These are manufactured by an anode adhesion impregnation method, a so-called dip molding method. Conventionally, there are various methods such as peroxide crosslinking among non-sulfur crosslinking, but it is not suitable to manufacture a glove by dip molding.

In order to prevent the aging of these rubber gloves, antioxidants are used in consideration of the kind, safety to the human body, deteriorated environment, and manufacturing method. In rubber gloves, a phenol-based primary antioxidant having low contamination, particularly a hindered phenol-based primary antioxidant such as wingbay (registered trademark), is generally used. From the viewpoint of pollution, an amine-based antioxidant is not used.

Patent document 1 discloses an example of using a hindered phenol antioxidant of wingstage (registered trademark) for sulfur crosslinking.

Patent document 2 proposes a method for producing a glove, in which a latex composition containing a carboxyl group-containing conjugated diene rubber, an aluminum crosslinking agent, and a hindered phenol based anti-aging agent, and no accelerator, are dip-molded to prepare a radiation irradiation step. Patent document 2 proposes that the content of the hindered phenol based anti-aging agent is 0.5 wt% or more and 7.0 wt% or less.

Patent document 3 discloses an accelerator-free glove obtained by crosslinking carboxylated acrylonitrile butadiene with polycarbodiimide. In patent document 3, a phenol-based antioxidant is used, which is a product of a butylation reaction between p-cresol and cyclopentadiene (BPC) and 2,2' -methylenebis (4-methyl-6-butylphenol) (MBPC).

Patent document 4 discloses accelerator-free gloves obtained by crosslinking carboxylated acrylonitrile butadiene with an epoxy crosslinking agent. In patent document 4, as the antioxidant, a hindered phenol type antioxidant, for example, wingbay (registered trademark) L can be used.

Non-patent document 1 describes a conventional method for producing a carboxylated diene rubber glove by vulcanization, and describes that a non-polluting phenol compound is used as an anti-aging agent in a large amount. (cf. Page 2, 3.2.4)

Non-patent document 2 describes the development of nitrile gloves that do not use a vulcanization accelerator.

Prior art literature

Patent document 1: japanese patent application laid-open No. 11-509873

Patent document 2: international publication No. 2020/066835

Patent document 3: japanese patent laid-open publication No. 2017-213914

Patent document 4: international publication No. 2019/102985

Non-patent document 1: the red feather thoroughly states that "method for producing rubber glove and market trend", 2015, journal of Japanese rubber society, volume 88, no. 9

Non-patent document 2: "development of nitrile gloves without vulcanization accelerators", year 2016, production and technology, volume 68, no. 4

Disclosure of Invention

The rubber glove was subjected to an aging test based on ASTM D6319 (standard specification for nitrile test glove for medical use) to ensure the quality of the deteriorated rubber. Specifically, the tensile strength after aging at 70℃for 168 hours under the temperature condition is 14MPa or more and the elongation is 400% or more. (refer to ASTM D6319, page 2, item 7.5.2Accelarated Aging)

It is considered that the quality of the rubber glove can be maintained for about three years by satisfying the criterion. The accelerator-free gloves in actual use at present are sold on the basis of meeting the standard.

Conventionally, rubber gloves are usually powder-coated gloves having powder on the inner side of the glove in order to facilitate wearing of the glove. However, since the powder is particularly harmful to medical gloves, the surface of the glove is subjected to a chlorine treatment in an in-line process after molding the glove on a glove mold, and the glove is subjected to a treatment for removing a sticky feeling. If the glove is taken off from the hand mould on the basis of this, and turned inside out, the chlorine treated surface will be located inside the glove.

In addition, in the case of glove for clean room, chlorine treatment is performed off-line in order to further smooth the glove surface, reduce dust generation, and avoid elution transfer of metal from the glove surface to the article being handled.

The development of the present disclosure has been started from a study on solving the problem that aluminum crosslinked gloves for clean rooms, which are accelerator-free gloves, develop browning after several months of production. It is also known that the same problems occur with epoxy crosslinked gloves and polycarbodiimide crosslinked gloves.

The present disclosure has been made in view of the problems of such non-sulfur crosslinked gloves. Further, an object of the present disclosure is to provide a glove capable of suppressing at least one of a decrease in mechanical properties such as tensile strength and elongation with time and occurrence of yellowing, a composition for dip molding used for producing the glove, a composition for dip molding, and a method for producing the glove.

The composition for non-sulfur crosslinked dip molding according to the aspect of the present disclosure contains a carboxylated diene rubber elastomer, a crosslinking agent containing at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent, an antioxidant containing at least one compound having a phenol structure and a sulfur atom, and water, and the content of the at least one compound is 0.05 to 4 parts by weight per 100 parts by weight of the elastomer.

The carboxylated diene rubber elastomer may be an elastomer in which the polymer main chain contains structural units derived from (meth) acrylonitrile, structural units derived from an unsaturated carboxylic acid, and structural units derived from butadiene.

The at least one compound may include at least one compound having a phenol structure and at least one selected from the group consisting of a thioether structure, a polysulfide structure, and a thiol structure.

The at least one compound may include at least one compound having a phenol structure, and a thioether structure or polysulfide structure.

The at least one compound may include a compound having both a phenol structure and a sulfur atom in the same molecule.

The above at least one compound may include two or more compounds of a compound having a phenol structure and a compound having a sulfur atom.

The organic crosslinking agent may contain at least one of polycarbodiimide and an epoxy compound.

The divalent or more metal crosslinking agent may contain at least one of a zinc compound and an aluminum compound.

A method for producing a composition for non-sulfur crosslinked dip molding according to another aspect of the present disclosure includes: a step of mixing a carboxylated diene rubber elastomer, a crosslinking agent containing at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent, and an antioxidant containing at least one compound having a phenol structure and a sulfur atom, wherein the content of the at least one compound is 0.05 to 4 parts by weight per 100 parts by weight of the elastomer, and the at least one compound is added to the elastomer in the form of a dispersion dispersed in an aqueous solvent.

A glove according to another aspect of the present disclosure includes: the non-sulfur crosslinked elastomer is a carboxylated diene rubber elastomer, a crosslinking agent containing at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent, and an antioxidant containing at least one compound having a phenol structure and a sulfur atom dispersed in the non-sulfur crosslinked elastomer, and the content of the at least one compound is 0.05 to 4 parts by weight per 100 parts by weight of the non-sulfur crosslinked elastomer.

The carboxylated diene rubber elastomer may be a non-sulfur crosslinked elastomer in which the polymer main chain contains structural units derived from (meth) acrylonitrile, structural units derived from an unsaturated carboxylic acid, and structural units derived from butadiene.

Another embodiment of the present disclosure relates to a method for manufacturing a glove, including a step of dip-molding a glove with a composition for dip-molding.

Drawings

Fig. 1 is a diagram showing an example of a representative yellowing mechanism caused by dibutylhydroxytoluene (BHT) as an antioxidant.

FIG. 2 is a graph showing the relationship between the heating time and the color difference of the test pieces in examples 1 to 4 and comparative examples 1 to 5.

Fig. 3 is a graph showing the relationship between the heating time and the color difference of the test pieces according to examples 5 to 10 and comparative example 6.

Fig. 4 is a graph showing the relationship between the heating time and the elongation at break of the test pieces according to examples 5 to 10 and comparative example 6.

FIG. 5 is a graph showing the relationship between the chlorine treatment time and the tensile strength at break of the glove of example 11 and comparative example 7.

Detailed Description

As described above, the development of the present disclosure has been started from the study of solving the problem that the aluminum crosslinked glove for clean room of the accelerator-free glove turns brown after several months of production. Further, when an off-line chlorine treatment is performed to use the polycarbodiimide crosslinked glove in a clean room, there is a problem that cracks occur in the glove film during the treatment. In order to solve this problem, trial and error searching is performed on the treatment conditions after the on-line and off-line chlorine treatment of the glove, in particular, the conditions of washing with water, neutralization, reducing agent and the like. It is also known that such problems do not occur so much in vulcanized gloves. As a result, it was found that these phenomena are mainly common to non-sulfur crosslinked gloves (accelerator-free gloves).

The reason why the yellowing with time of the non-sulfur crosslinked glove is greater than that of the sulfur crosslinked glove was examined, and it was found that the non-sulfur crosslinked glove was more susceptible to oxidative deterioration than the sulfur crosslinked glove. One reason for this phenomenon is considered to be that polysulfide portions used in crosslinking are oxidized instead of the main chain in sulfur crosslinked gloves, suppressing oxidative deterioration of the rubber glove itself. In addition, it is considered that the vulcanization accelerator itself has a function as an antioxidant in sulfur crosslinked gloves. On the other hand, the non-sulfur crosslinked glove does not contain polysulfide for crosslinking and does not contain a vulcanization accelerator, and therefore does not have the above-described antioxidant function.

Oxidative degradation of rubber generally proceeds as follows: free radicals are generated by oxygen in the air, and cause a chain reaction and generate peroxide. In order to prevent the oxidative deterioration of the rubber, it is necessary to suppress radical chain reaction and decompose peroxide. Compounds containing phenol structures are capable of forming stable free radicals to inhibit chain reactions. In addition, compounds containing sulfur atoms are capable of decomposing peroxides. In the case of sulfur crosslinking using a sulfur-containing compound or a vulcanization accelerator containing a sulfur atom in the crosslinking treatment, both of the above-mentioned oxidative deterioration can be suppressed by adding an antioxidant having a phenol structure. However, in the case where a compound containing a sulfur atom is not used in the crosslinking treatment, the peroxide cannot be decomposed even if the radical chain reaction can be suppressed. An example of a representative yellowing mechanism caused by dibutylhydroxytoluene (BHT) as a representative antioxidant is shown in fig. 1. When only a compound having a phenol structure that inhibits radical chain reaction is used, oxidative deterioration and discoloration of rubber cannot be effectively prevented because there is no compound that decomposes peroxide.

Therefore, it has been found that the use of an antioxidant having a radical chain reaction suppressing function and a peroxide decomposing function in a predetermined ratio can suppress the yellowing of gloves with time. The inhibition of radical chain reaction and the performance of decomposition of peroxide are effective, for example, in stopping the stepwise reaction shown in fig. 1, and particularly effective in preventing oxidative deterioration and discoloration of rubber. By the same mechanism as described above, it is considered that the use of the antioxidant suppresses the deterioration of the mechanical properties with time.

Thus, the rubber glove is subjected to chlorine treatment on-line and off-line as needed. Particularly, chlorine treatment is important for rubber gloves used in environments where dust and garbage components are not favored, such as clean rooms. Chlorine is dissolved in water to produce hypochlorous acid (HClO) and hydrochloric acid (HCl) as shown in the reaction formula Cl ₂+H₂ O→HClO+HCl. Hypochlorous acid oxidizes the nitrile rubber locally, reducing tackiness. On the other hand, hydrochloric acid converts the poorly soluble metal salts and metal oxides on the glove surface into metal chlorides. The metal chloride is generally soluble in water and can be removed from the glove surface by washing with water such as ion-exchanged water. In addition, in the in-line chlorine treatment of the rubber glove, the adhesiveness inside the glove is reduced and the glove is cured, so that the smoothness and the donning property of the glove can be improved.

In the off-line chlorine treatment, the glove is turned inside out when removed from the impregnation die, and therefore, the surface of the glove is washed with deionized water in the subsequent step by reducing the adhesiveness of the outside of the glove, adjusting the gripping property, and simultaneously converting the metal compound into a metal chloride soluble in water by HCl. After this treatment, chlorine is reduced and neutralized by sodium thiosulfate as a reducing agent and KOH, sodium carbonate as an alkaline agent.

The chlorine component used in the chlorine treatment remains in the rubber glove even after the final reduction and neutralization treatment, and causes the rubber glove to deteriorate. Chlorine radicals generated from derivatives such as chlorine and hypochlorous acid remove allylic hydrogen in nitrile rubber, and allylic radical species are generated in the latex backbone. The radical reacts with oxygen, so that peroxide radicals (R-OO. Cndot.) are generated in the same manner as oxidative aging caused by oxygen, and the peroxide radicals cause radical chain reaction, so that aging of rubber gloves proceeds. In this way, the generation of radicals by chlorine species remaining in the glove due to chlorine treatment has an effect of aging the rubber glove, similar to the oxygen in the air. Therefore, in order to suppress the deterioration and the aging of the rubber glove due to the residual chlorine, it is important to prevent both the radical chain reaction and the oxidation reaction due to the peroxide accompanying the radical chain reaction, as in the case of the aging due to oxygen. The dip molding composition and the method for producing the same according to the present embodiment, and the glove and the method for producing the same will be described in detail below.

[ Composition for dip Molding ]

The dip molding composition according to the present embodiment is used as a dip liquid as a glove material. The composition for dip molding contains an elastomer, a crosslinking agent, an antioxidant and water. Each component is described in detail below.

Elastomer >

The present disclosure relates to elastomers targeted to carboxylated diene rubber elastomers. The carboxylated diene rubber is a synthetic latex, and is obtained by carboxylating at least one selected from the group consisting of polyisoprene rubber (IR), chloroprene Rubber (CR), styrene Butadiene Rubber (SBR) and Nitrile Butadiene Rubber (NBR). These are all materials used for manufacturing gloves by conventional dip molding with sulfur and a vulcanization accelerator. Carboxylated diene rubber elastomers may be produced by polymerizing conjugated diene monomers and carboxylating the modified conjugated diene monomers. The conjugated diene monomer is preferably a conjugated diene monomer having 4 to 6 carbon atoms such as 1, 3-butadiene, isoprene, 2, 3-dimethyl-1, 3-butadiene, 1, 3-pentadiene, chloroprene and the like, more preferably 1, 3-butadiene and isoprene, and particularly preferably 1, 3-butadiene. The conjugated diene monomer may be used alone or in combination of two or more.

In this embodiment, a carboxylated acrylonitrile butadiene rubber (XNBR) that is most used in gloves is specifically described as an example of the carboxylated diene rubber elastomer. Carboxylated diene rubber elastomers, for example, the polymer backbone may contain structural units derived from (meth) acrylonitrile, structural units derived from an unsaturated carboxylic acid, and structural units derived from butadiene. (meth) acrylonitrile is a concept including both acrylonitrile and methacrylonitrile.

In the elastomer, the structural unit derived from (meth) acrylonitrile may be 20 to 40% by weight. That is, the (meth) acrylonitrile residue in the elastomer may be 20 to 40% by weight. By setting the structural unit derived from (meth) acrylonitrile to 20 wt% or more, the strength and chemical resistance of the glove can be improved. In addition, the glove can be made soft by setting the structural unit derived from (meth) acrylonitrile to 40 wt% or less. The structural unit derived from (meth) acrylonitrile may be 25% by weight or more and may be 30% by weight or more.

The structural units derived from unsaturated carboxylic acids in the elastomer may be 1 to 10% by weight. That is, the unsaturated carboxylic acid residue in the elastomer may be 1 to 10% by weight. By setting the amount of the structural unit derived from the unsaturated carboxylic acid to 1 to 10% by weight, a moderately crosslinked structure can be formed, and the physical properties of the glove can be maintained well. The structural unit derived from the unsaturated carboxylic acid may be 4% by weight or more. In addition, the structural unit derived from the unsaturated carboxylic acid may be 6% by weight or less. The unsaturated carboxylic acid is not particularly limited, and may be a monocarboxylic acid or a polycarboxylic acid. The unsaturated carboxylic acid may be acrylic acid, methacrylic acid, crotonic acid, maleic acid or fumaric acid. Among them, acrylic acid or methacrylic acid is preferable.

In the elastomer, the structural unit derived from butadiene may be 50 to 75% by weight. That is, the butadiene residue in the elastomer may be 50 to 75 wt%. The flexibility of the glove can be improved by setting the structural unit derived from butadiene to 50 wt% or more. The structural unit derived from butadiene may be 60% by weight or more. The structural unit derived from butadiene may be a structural unit derived from 1, 3-butadiene.

The polymer main chain may further contain a structural unit derived from another polymerizable monomer in addition to the structural unit derived from (meth) acrylonitrile, the structural unit derived from an unsaturated carboxylic acid and the structural unit derived from butadiene. The structural unit derived from another polymerizable monomer in the elastomer may be 30% by weight or less, may be 20% by weight or less, and may be 15% by weight or less.

The ratio of the structural units can be easily determined from the weight ratio (solid content ratio) of the raw materials used for producing the elastomer.

The other polymerizable monomer may contain at least one of a self-crosslinkable compound and a non-self-crosslinkable compound. The self-crosslinkable compound means a polymerizable compound contained in the polymer chain of the elastomer, and is a monomer having a functional group capable of forming intramolecular crosslinking or intermolecular crosslinking (hereinafter also simply referred to as "crosslinking"). That is, the self-crosslinkable compound is a compound (polymerizable monomer) having a polymerizable unsaturated bond (polymerizable unsaturated bond) and 1 or more functional groups capable of forming a crosslinking bond. The polymerizable monomer may be a monofunctional monomer having one of these specific functional groups, or may be a polyfunctional monomer having two or more functional groups. The polyfunctional monomer may have the same or different functional groups. As the formed cross-linking bond, a bond generated by a separation reaction or substitution reaction between the carboxyl group of the unsaturated carboxylic acid and the functional group of the polymerizable monomer or between the functional groups of the polymerizable monomer, such as an ester bond, an amide bond, an imide bond, or a vinyl bond, is generated.

Examples of the self-crosslinkable compound include 2-hydroxyalkyl (meth) acrylate, N-methylolacrylamide, 4-hydroxybutyl acrylate glycidyl ether, 2-isocyanatoethyl methacrylate, 3-glycidoxypropyl methoxysilane, 2- (3, 4-epoxycyclohexyl) ethylmethoxysilane, vinylmethoxysilane, vinylethoxysilane, vinyltris (2-methoxyethoxy) silane, N-allylacrylamide, glycerol triacrylate, trimethylpropane triacrylate, N- (1, 1-dimethyl-3-oxobutyl) acrylamide (diacetone acrylamide), N- (isobutoxymethyl) acrylamide, N-hydroxymethyl diacetone acrylamide, N-formyl-N' -acryloylmethylenediamine, 2-carboxyethyl (meth) acrylate, and mono (2- (meth) acryloyloxyethyl) succinate. Examples of the 2-hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate.

The non-self-crosslinkable compound is a compound having polymerizability but not crosslinkability. Examples of the non-self-crosslinkable compound include an aromatic vinyl monomer, an ethylenically unsaturated carboxylic acid amide, an ethylenically unsaturated carboxylic acid alkyl ester monomer, and vinyl acetate. Examples of the aromatic vinyl monomer include styrene, α -methylstyrene, and dimethylstyrene. Examples of the ethylenically unsaturated carboxylic acid amide include (meth) acrylamide and N, N-dimethylacrylamide. Examples of the ethylenically unsaturated carboxylic acid alkyl ester monomer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. These may be used alone or in combination. In the present specification, (meth) acrylic acid is a concept including acrylic acid and methacrylic acid.

The elastomer may contain a polyfunctional organic compound having no polymerizable functional group, having two or more functional groups in the molecule, and crosslinking the polymer chain by this. The organic crosslinking agent is not particularly limited as long as it is a polyfunctional organic compound that is non-polymerizable (i.e., does not have a polymerizable unsaturated bond) and is blended in advance into the elastomer at the time of polymerization.

The elastomer can be obtained by emulsion polymerization using a polymerizable monomer containing (meth) acrylonitrile, an unsaturated carboxylic acid and butadiene, by a conventional method, using a polymerization liquid containing an emulsifier, a polymerization initiator, a molecular weight regulator, water and the like. The solid content of the polymerization liquid is preferably 30 to 60 wt%, more preferably 35 to 55 wt%. The emulsion polymerization liquid after the synthesis of the elastomer can be directly used as an elastomer component of the impregnating composition.

The emulsifier is used as a surfactant and has a hydrophobic group and a hydrophilic group. Examples of the emulsifier include anionic surfactants such as dodecylbenzene sulfonate and aliphatic sulfonate, and nonionic surfactants such as polyethylene glycol alkyl ether and polyethylene glycol alkyl ester. Among them, the emulsifier preferably contains an anionic surfactant.

The polymerization initiator is not particularly limited as long as it is a radical initiator, and examples thereof include: inorganic peroxides such as ammonium persulfate and potassium perphosphate, organic peroxides such as t-butyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, t-butylcumyl peroxide, benzoyl peroxide, 3, 5-trimethylhexanoyl peroxide and t-butylperoxyisobutyrate, and azo compounds such as azobisisobutyronitrile, azobis-2, 4-dimethylvaleronitrile, azobicyclocapronitrile and azobisisobutyrate.

Examples of the molecular weight regulator include thiols such as t-dodecyl mercaptan and n-dodecyl mercaptan, and halogenated hydrocarbons such as carbon tetrachloride, methylene chloride and dibromomethane. The molecular weight regulator preferably contains thiols such as tertiary dodecyl mercaptan and n-dodecyl mercaptan.

The latex contains water and an elastomer as solid components. The latex is an emulsion of particles in which a film in which an emulsifier is dispersed surrounds elastomer particles. The outside of the membrane is hydrophilic, and the inside of the membrane is hydrophobic. Within the particle, the carboxyl groups are oriented towards the inside of the film.

In the dip molding composition, the elastomer may be particles. The average particle diameter of the elastomer may be about 50nm to 250 nm. By setting the average particle diameter to 50nm or more, the specific surface area increases, and inter-particle crosslinking increases. In addition, by setting the average particle diameter to 250nm or less, the slurry separation can be reduced. In the present specification, unless otherwise specified, the value of the "average particle diameter" is calculated as an average value of particle diameters of particles observed in several to several tens of fields of view by using observation means such as a Scanning Electron Microscope (SEM) or a Transmission Electron Microscope (TEM).

The content of the elastomer in the composition for dip molding may be 15% by weight or more and may be 18% by weight or more. The content of the elastomer in the composition for dip molding may be 35% by weight or less and may be 30% by weight or less.

< Crosslinker >

The crosslinking agent consists essentially of a non-sulfur-based crosslinking agent. That is, the dip molding composition contains substantially no sulfur compound as a sulfur crosslinking agent and a vulcanization accelerator. The content of each of the sulfur crosslinking agent and the vulcanization accelerator contained in the dip molding composition may be, for example, less than 1% by weight, and may be less than 0.1% by weight. The sulfur crosslinking agent may be polysulfide or the like. Examples of the crosslinking accelerator include a dithiocarbamate-based vulcanization accelerator such as a dithiocarbamate, a thiuram-based vulcanization accelerator such as tetramethylthiuram disulfide (TMTD), a thiazole-based crosslinking accelerator such as Mercaptobenzothiazole (MBT), a sulfenamide-based crosslinking accelerator, a guanidine-based crosslinking accelerator, and a thiourea-based crosslinking accelerator.

Examples of the non-sulfur crosslinking structure include crosslinking between carboxyl groups crosslinked by a non-sulfur crosslinking agent. The non-sulfur-based crosslinking agent may contain at least one of an organic crosslinking agent and a metal crosslinking agent. Such a crosslinking agent can crosslink carboxyl groups with each other by reacting with the carboxyl groups. The organic crosslinking agent may contain at least one of polycarbodiimide and polyepoxide. The metal crosslinking agent is as follows.

(Polycarbodiimide)

Polycarbodiimide is a compound having a plurality of carbodiimide groups (-n=c=n-). The carbodiimide groups can crosslink carboxyl groups with each other by reacting with carboxyl groups of the elastomer. Polycarbodiimide can be obtained by decarbonated condensation of diisocyanate. The number of carbodiimide functional groups (degree of polymerization) per 1 molecule of polycarbodiimide may be 4 to 20. By setting the polymerization degree to 4 or more, the carboxyl groups of the elastomer can be crosslinked at a plurality of points, and the fatigue durability can be expected to be improved as compared with the case of crosslinking at 2 points. The polymerization degree may be 5 or more, or 9 or more.

The diisocyanate used in the polycarbodiimide synthesis may contain at least one selected from the group consisting of aromatic diisocyanate, aliphatic diisocyanate, and alicyclic diisocyanate. From the viewpoint of weather resistance, the diisocyanate is preferably an aliphatic diisocyanate or a cycloaliphatic diisocyanate. The diisocyanate may contain at least one selected from the group consisting of 1, 5-naphthylene diisocyanate, 4-diphenylmethane diisocyanate, 4-diphenyldimethylmethane diisocyanate, 1, 3-phenylene diisocyanate, 1, 4-phenylene diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, hexamethylene diisocyanate, cyclohexane-1, 4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4, 4' -diisocyanate, methylcyclohexane diisocyanate, and tetramethylxylylene diisocyanate.

The polycarbodiimide may be a compound having isocyanate residues at both ends, which is obtained by decarbonation condensation of a diisocyanate. In order to inhibit the reaction of carbodiimide groups with water, a hydrophilic segment represented by R ¹-O-(CH₂-CHR²-O-)_n- H (wherein R ¹ is an alkyl group having 1 to 4 carbon atoms, R ² is a hydrogen atom or a methyl group, and n is an integer of 5 to 30) may be added to at least a part of the terminal isocyanate residue. The hydrophilic segment may be attached to both ends of the polycarbodiimide or may be attached to only one end. The polycarbodiimide may also be a mixture of a polycarbodiimide having a hydrophilic segment and a polycarbodiimide having no hydrophilic segment. The polycarbodiimide having a hydrophilic segment effectively forms a micelle (micelle) in water, and the highly reactive polycarbodiimide moiety is located in the micelle, so that the reaction with water can be suppressed.

The end of the polycarbodiimide to which no hydrophilic segment is added may be blocked with a blocking agent represented by (R ³)₂N-R⁴ -OH) (wherein R ³ is an alkyl group having 6 or less carbon atoms, and R ⁴ is an alkylene group having 1 to 10 carbon atoms or a polyoxyalkylene group). R ³ is preferably an alkyl group having 4 or less carbon atoms from the viewpoint of availability.

The content of polycarbodiimide in the composition for dip molding may be more than 0.2% by weight and not more than 4.0% by weight relative to the solid content in the composition for dip molding. If the content of polycarbodiimide exceeds 0.2% by weight, it is possible to have high fatigue durability exceeding that of sulfur-crosslinked gloves. If the content of polycarbodiimide is 4.0 wt% or less, profitability is good. The content of polycarbodiimide may be 0.3% by weight or more. The content of polycarbodiimide may be 2.5 wt% or less, or 2.0 wt% or less.

The average particle diameter of the polycarbodiimide colloidal particles is preferably 5 to 30nm.

The average particle diameter of the polycarbodiimide colloidal particles is an average value of particle diameters of respective colloidal particles formed of polycarbodiimide, as measured by a dynamic light scattering method under the following conditions.

Measurement device: zetasizer Nano ZS (Malvern system)

Light source: he-Ne (40 mW) 633nm

Measuring temperature: 25 DEG C

Viscosity of the dispersion medium: 0.887cP (value of Water used)

Refractive index of dispersion medium: 1.33 (value using Water)

Sample preparation: diluting with ion exchange water 100 times

The polycarbodiimide may have a polymerization degree of 5 or more and an average particle diameter of 30nm or less. In this case, it is expected that a cured film having high fatigue durability can be produced even when a certain period of time or more has elapsed after the preparation of the composition for dip molding.

(Polyepoxy crosslinking agent)

The polyepoxy crosslinking agent contains an epoxy compound having an epoxy group. The 1-molecule polyepoxide has more than 2 epoxy groups. In addition, 1 molecule of the polyepoxide may have 3 or more epoxy groups. The epoxy compound has 3 or more epoxy groups, so that crosslinking between the elastomer molecules increases, and fatigue durability can be improved. In addition, even when one epoxy group is deactivated, the remaining epoxy group can be used for crosslinking, and therefore, the elastomer can be effectively crosslinked. This can reduce the amount of polyepoxide added. The upper limit of the number of epoxy groups in the polyepoxide is not particularly limited, and the number of epoxy groups may be 8 or less. The epoxy compound may or may not have an aromatic ring.

From the viewpoint of fatigue durability, the average epoxy number of the polyepoxide crosslinking agent is preferably more than 2.0, more preferably 2.3 or more, and still more preferably 2.5 or more. The average number of epoxy groups is determined by GPC (gel permeation chromatography) of each epoxy compound contained in the epoxy crosslinking agent. Then, the number of epoxy groups obtained by multiplying the number of epoxy groups in 1 molecule of each polyepoxide by the number of moles of the epoxy compound is obtained for each polyepoxide, and the total of these epoxy groups is divided by the total number of moles of all polyepoxides contained in the polyepoxide crosslinking agent.

The polyepoxide compound may include at least one selected from the group consisting of polyglycidyl ether, polyglycidyl amine, polyglycidyl ester, epoxidized polybutadiene, and epoxidized soybean oil.

The polyglycidyl ether may be at least one selected from the group consisting of diglycidyl ether, triglycidyl ether, tetraglycidyl ether, pentaglycidyl ether, hexaglycidyl ether, heptaglycidyl ether and octaglycidyl ether. The triglycidyl ether may include at least one selected from the group consisting of glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol triglycidyl ether, pentaerythritol triglycidyl ether and diglycerol triglycidyl ether. The tetraglycidyl ether may contain at least one selected from the group consisting of sorbitol tetraglycidyl ether and pentaerythritol tetraglycidyl ether. Among them, the polyepoxide compound preferably contains at least one selected from the group consisting of glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol triglycidyl ether, diglycerol triglycidyl ether and pentaerythritol tetraglycidyl ether.

The amount of the polyepoxy crosslinking agent added is also dependent on the number and purity of epoxy groups in 1 molecule of the epoxy compound, but may be 0.1 parts by weight or more, 0.4 parts by weight or more, or 0.5 parts by weight or more based on 100 parts by weight of the elastomer, from the viewpoint of introducing a sufficient crosslinking structure between the elastomers to ensure fatigue durability. From the viewpoint of improving the properties of the elastomer, the amount of the polyepoxide crosslinking agent added to the dip-molding composition may be 5 parts by weight or less, 1.0 parts by weight or less, or 0.7 parts by weight or less, based on 100 parts by weight of the elastomer.

The amount of the polyepoxide to be added may be 0.05 parts by weight or more, 0.2 parts by weight or more, or 0.25 parts by weight or more based on 100 parts by weight of the elastomer, although the amount of epoxy groups in the polyepoxide to be added depends on the number and purity of epoxy groups in the polyepoxide 1 molecule from the viewpoint of introducing a sufficient crosslinked structure between the elastomers to ensure fatigue durability. From the viewpoint of improving the properties of the elastomer, the upper limit of the amount of the polyepoxide crosslinking agent to be added to the dip-molding composition may be 2.5 parts by weight or less, 0.5 parts by weight or less, or 0.35 parts by weight or less, based on 100 parts by weight of the elastomer.

The water solubility of the polyepoxide cross-linking agent may be 10-70%. When the water solubility is 10% or more, the solubility in water and XNBR is improved, and the productivity is improved. A composition for dip molding having a pot life excellent in mass productivity can be obtained. When the water solubility is 70% or less, a composition for dip molding having a pot life excellent in mass productivity can be obtained.

Method for measuring water solubility

1. 25.0G of polyepoxide cross-linker was weighed precisely in a beaker and 225g of water (25 ℃ C.) was added.

2. After vigorously stirring and mixing at room temperature (23 ℃ C..+ -. 2 ℃ C.) for 15 minutes, the mixture was allowed to stand for 1 hour.

3. The volume (mL) of oil precipitated at the bottom of the beaker was determined.

4. The water solubility was calculated by the following formula.

Water solubility (%) = (25.0 (g) - (volume of oil (mL) ×density of polyepoxy crosslinker (g/mL))/25.0×100

The MIBK (methyl isobutyl ketone)/water distribution ratio of the polyepoxide crosslinking agent may be 27% or more. The use of a polyepoxy crosslinking agent having a MIBK/water partition ratio of 27% or more makes it easy for the polyepoxy crosslinking agent to enter the lipophilic region in XNBR particles, thereby inhibiting the polyepoxy crosslinking agent from being deactivated. Thus, a composition for dip molding having a pot life of 3 days or more can be obtained. The MIBK/water distribution ratio is preferably 30% or more, more preferably 50% or more, and still more preferably 70% or more. On the other hand, in the case of a polyepoxy crosslinking agent or the like having a MIBK/water distribution ratio of 27% or more and less than 30%, the polyepoxy crosslinking agent is also preferably 1.0 part by weight or more relative to 100 parts by weight of the elastomer.

MIBK/water distribution can be determined as follows.

First, about 5.0g of water, about 5.0gMIBK g of polyepoxide cross-linker, about 0.5g were weighed accurately into the test tube. The weight of MIBK was set to M (g) and the weight of polyepoxide crosslinking agent was set to E (g). The mixture was stirred and mixed at 23.+ -. 2 ℃ for 3 minutes, and then centrifuged at 1.0X10 ³ G for 10 minutes to separate the mixture into an aqueous layer and a MIBK layer. Next, the weight of the MIBK layer was measured and taken as ML (g).

MIBK/Water partition Rate (%) = (ML (g) -M (g))/E (g). Times.100

In the present specification, the measurement method of the MIBK/water distribution ratio is based on the weight measurement of water and MIBK, and since MIBK dissolves some water, as an experimental value, it is assumed that it is used as a reference because it is measured on the same basis.

The dip molding composition may contain a polyepoxy crosslinking agent and a dispersant. In the dip molding composition, the weight ratio of the polyepoxy crosslinking agent to the dispersant is preferably polyepoxy crosslinking agent/dispersant=1:4 to 1:1.

The dispersant is preferably 1 or more selected from the group consisting of monohydric lower alcohols, glycols, ethers, and esters. Examples of the monohydric lower alcohol include methanol and ethanol. As the diol, HO- (CH ₂CHR¹-O)_n1-H(R¹ represents hydrogen or methyl group) and n1 represents an integer of 1 to 3 may be mentioned. Specific examples of the diol include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and tripropylene glycol. Examples of the ether include R ²O-(CH₂CHR¹-O)_n2-R³(R¹ represents hydrogen or methyl, R ² represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, R ³ represents hydrogen or an aliphatic hydrocarbon group having 1 to 3 carbon atoms, and n2 represents an integer of 0 to 3). Specific examples of the ether include glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and triethylene glycol dimethyl ether. As the ester, R ²O-(CH₂CHR¹-O)_n3-(C＝O)-CH₃(R¹ represents hydrogen or methyl, R ² represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n3 represents an integer of 0 to 3). Examples of the ester include diethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate. These may be used alone or in combination of two or more. The dispersant may be used without being mixed with water in advance. The dispersant is preferably a monohydric lower alcohol. In addition, methanol, ethanol, diethylene glycol are also preferably used as the dispersant. Diethylene glycol is preferably used as the dispersant from the viewpoints of volatility and ignition. Furthermore, it is presumed that: diethylene glycol has a glycol group and an ether structure having high hydrophilicity, and contains a hydrocarbon structure having lipophilicity, and is easily dissolved in water and an elastomer, and thus is suitable.

(Metal crosslinker)

The metal cross-linking agent forms a cross-link with the carboxyl groups of the XNBR via ionic bonds. The metal crosslinking agent may contain a polyvalent metal compound having a metal of 2 or more valences. Examples of the metal having a valence of 2 or more include magnesium, aluminum, calcium, titanium, chromium, iron, cobalt, zinc, zirconium, tin, and lead. The metal crosslinking agent may contain at least one of a zinc compound and an aluminum compound. By using such a metal crosslinking agent, improvement of the tensile strength of the glove, suppression of swelling in artificial sweat, improvement of the impermeability to organic solvents, and the like can be expected.

Examples of the zinc compound include zinc oxide and zinc hydroxide. Among them, zinc oxide is often used. The amount of zinc oxide to be added may be 0.2 to 4.0 parts by weight based on the total amount of the solid components of the composition for dip molding. Thereby improving the tensile strength of the glove. The amount of zinc oxide added may be 0.8 parts by weight or more. The amount of zinc oxide added may be 1.5 parts by weight or less.

The aluminum compound may contain aluminum hydroxy acid or aluminate. Examples of the aluminum hydroxy acid include aluminum citrate and aluminum lactate. Examples of the aluminate include sodium aluminate and potassium aluminate. When aluminate is used, the dip molding composition may contain a stabilizer. As the stabilizer, alcohol compounds, hydroxycarboxylic acids, and hydroxycarboxylic acid salts can be used. Examples of the alcohol compound include sugar alcohols such as sorbitol, saccharides such as glucose, and polyhydric alcohols such as glycerin and ethylene glycol. Examples of the hydroxycarboxylic acid include a diol, citric acid, malic acid, and lactic acid. Examples of the hydroxycarboxylic acid salt include metal salts of the hydroxycarboxylic acid described above.

In the dip molding composition, the aluminum compound may be present as an aluminum complex ion such as a tetrahydroxyaluminate ion ([ Al (OH) ₄]^-). The aluminum complex ion is changed to Al (OH) ₃ in the leaching step S5 described later, for example, and Al ³⁺ is formed in the curing step S8, and is bonded to the carboxyl ion to form a cross-link. The amount of the aluminum compound added is preferably 0.2 to 1.5 parts by weight in terms of aluminum oxide (Al ₂O₃) relative to the total amount of the solid content of the composition for dip molding.

The metal crosslinking agent may comprise a zinc compound and an aluminum compound. This eases the curing of the glove, and a glove excellent in extensibility can be obtained. The total amount of the zinc compound and the aluminum compound is preferably 0.7 to 2.3 parts by weight based on the total amount of the solid components of the composition for dip molding. The ratio of zinc oxide to aluminum compound (in terms of Al ₂O₃) is preferably ZnO: al ₂O₃ =1:0.6 to 1:1.2.

< Antioxidant >

The composition for dip molding contains an antioxidant comprising at least one compound having a phenol structure and a sulfur atom. The at least one compound may include at least one compound having a phenol structure and at least one selected from the group consisting of a thioether structure, a polysulfide structure, and a thiol structure. The at least one compound may include at least one compound having a phenol structure, and a thioether structure or polysulfide structure. The at least one compound may include a compound having both a phenol structure and a sulfur atom in the same molecule or two or more compounds including a compound having a phenol structure and a compound having a sulfur atom. The at least one compound may include a compound having both a phenol structure and a sulfur atom in the same molecule and include at least either one of a compound having a phenol structure and a compound having a sulfur atom. The at least one compound may have only one phenol structure or may have a plurality of phenol structures. In addition, at least one compound may have only one sulfur atom or may have a plurality of sulfur atoms. The content of the at least one compound is 0.05 to 4 parts by weight relative to 100 parts by weight of the elastomer. By setting the content of the above-mentioned compound to 0.05 parts by weight or more, at least one of a decrease in mechanical properties with time and yellowing can be suppressed. Further, by setting the content of the above-mentioned compound to 4 parts by weight or less, a glove having a soft texture can be produced. The content of the at least one compound may be 0.1 to 2 parts by weight with respect to 100 parts by weight of the elastomer.

The compound having both a phenol structure and a sulfur atom in the same molecule or the compound having a phenol structure is a compound including a phenol compound. The compound having a phenol structure may include at least one phenol compound selected from the group consisting of hindered phenol compounds, semi-hindered phenol compounds, and less-hindered phenol compounds. The hindered phenol compound is a phenol compound having a bulky substituent at both ortho positions to the para-hydroxyl group of the phenol structure. A semi-hindered phenol compound is a phenol compound having a bulky substituent at one ortho position to the hydroxyl group of the phenol structure and a less bulky substituent at the other ortho position. The less hindered phenol compound is a less hindered phenol compound having a bulky substituent at one ortho position to the hydroxyl group of the phenol structure and hydrogen at the other ortho position. Examples of the bulky substituent include a substituent having a tertiary carbon, and the substituent is represented by a tert-butyl group. Examples of the substituent having a small volume include a substituent having a primary carbon, and a methyl group is typical.

The compound having both a phenol structure and a sulfur atom in the same molecule may be a compound having both a phenol structure and at least one selected from the group consisting of a thioether structure, a polysulfide structure, and a thiol structure in the same molecule. The above-mentioned compounds may have only one phenol structure or may have a plurality of phenol structures in the same molecule. The compound having both a phenol structure and a sulfur atom in the same molecule may contain, for example, at least one selected from the group consisting of 2-methyl-4, 6-bis [ (octylthio) methyl ] phenol (CAS number: 110553-27-0), 2, 4-bis (n-octylthio) -6- (4-hydroxy-3, 5-di-t-butylanilino) -1,3, 5-triazine (CAS number: 991-84-4), 2 '-thiodiethylbis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] (CAS number: 41484-35-9), 4' -thiobis (3-methyl-6-t-butylphenol) (CAS number: 96-69-5).

The content of the compound having both a phenol structure and a sulfur atom in the same molecule may be 0.05 to 4 parts by weight with respect to 100 parts by weight of the elastomer. By setting the content of the above-mentioned compound to 0.05 parts by weight or more, at least one of a decrease in mechanical properties with time and yellowing can be suppressed. Further, by setting the content of the above-mentioned compound to 4 parts by weight or less, a glove having a soft texture can be produced. The content of the compound having both a phenol structure and a sulfur atom in the same molecule may be 0.1 to 2 parts by weight relative to 100 parts by weight of the elastomer.

The compound having a phenol structure may contain a compound selected from the group consisting of a butylated reaction product of p-cresol with dicyclopentadiene and isobutylene (CAS No. 68610-51-5), tris- (3, 5-di-t-butyl-4-hydroxybenzyl) isocyanurate (CAS No. 27676-62-6), 4' -butylidenebis (6-t-butyl-3-methylphenol) (CAS No. 85-60-9), n-octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate (CAS No. 2082-79-3), pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] (CAS No. 6683-19-8), 2, 6-di-t-butyl-4-methylphenol (CAS No. 128-37-0), 2, 6-di-t-butylphenol (CAS No. 128-39-2), 2, 6-di-t-butyl-4-hydroxymethylphenol (CAS No. 88-26-6), 2, 4-dimethyl-6-t-butylphenol (18-butylphenol) (CAS No. 18-9-5), and (CAS No. 16-13-5-t-butylphenol) (CAS No. 16-9-7-0) At least one of the group consisting of 2,2' -methylenebis (4-ethyl-6-tert-butylphenol) (CAS number: 88-24-4), 1, 6-hexanediol-bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] (CAS number: 35074-77-2), 1,3, 5-trimethyl-2, 4, 6-tris- (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene (CAS number: 1709-70-2), triethylene glycol-bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate ] (CAS number: 36443-68-2), 3-tert-butyl-4-hydroxyanisole (CAS number: 121-00-6), 1, 3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane (CAS number: 1843-03-4), 3, 9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] -1, 1-dimethyl ] -2, 1-diethyl ] -2, 10, 5-tetraoxa-1, 90498-1, 5-tetraoxa-1-oxa-1, 341-oxa-2. The compound having a phenol structure may be free of a compound having both a phenol structure and a sulfur atom in the same molecule. The compound having a phenol structure may have only one phenol structure or may have a plurality of phenol structures in the same molecule.

The content of the compound having a phenol structure may be 0.01 to 2 parts by weight relative to 100 parts by weight of the elastomer. By setting the content of the compound having a phenol structure to 0.01 part by weight or more, at least one of a decrease in mechanical properties with time and yellowing can be suppressed. Further, by setting the content of the compound having a phenol structure to 2 parts by weight or less, a glove having a soft texture can be produced.

The compound having a sulfur atom may be a compound having at least one selected from the group consisting of a thioether structure, a polysulfide structure, and a thiol structure. The compound having a sulfur atom may be a compound having a sulfide structure or a polysulfide structure. The compound having a sulfur atom may contain at least one selected from the group consisting of dilauryl 3,3' -thiodipropionate (CAS number: 123-28-4), dimyristyl 3,3' -thiodipropionate (CAS number: 16545-54-3), 3-laurylthiopropionic acid (CAS number: 1462-52-8), distearyl 3,3' -thiodipropionate (CAS number: 693-36-7), 3' -thiodipropionate (CAS number: 111-17-1), ditridecyl) -3,3' -thiodipropionate (CAS number: 10595-72-9), tetrakis [ methylene-3- (dodecylthio) propionate ] methane (CAS number: 29598-76-3), thiobis (2-tert-butyl-5-methyl-4, 1-phenylene) bis (3- (dodecylthio) propionate) (CAS number: 66534-05-2). The compound having a sulfur atom may be free of a compound having both a phenol structure and a sulfur atom in the same molecule. The compound having a sulfur atom may have only one sulfur atom or may have a plurality of sulfur atoms in the same molecule.

The content of the compound having a sulfur atom may be 0.01 to 2 parts by weight relative to 100 parts by weight of the elastomer. By setting the content of the compound having a sulfur atom to 0.01 part by weight or more, at least one of a decrease in mechanical properties with time and yellowing can be suppressed. Further, by setting the content of the compound having a sulfur atom to 2 parts by weight or less, a glove having a soft texture can be produced.

The content of the compound having a sulfur atom may be more than the content of the compound having a phenol structure in terms of weight ratio. In addition, the content of the compound having a sulfur atom may also be smaller than the content of the compound having a phenol structure in terms of weight ratio. Further, the content of the compound having a sulfur atom may be the same as the content of the compound having a phenol structure in terms of weight ratio. The content of the compound having a sulfur atom is preferably 2 times or more and 4 times or less with respect to the content of the compound having a phenol structure in terms of weight ratio.

It is to be noted that at least one compound preferably contains a compound having both a phenol structure and a sulfur atom in the same molecule. Compounds having a phenol structure typically react with free radicals to form phenoxy radicals. The phenoxy radical is stabilized by the presence of a bulky substituent represented by t-butyl group in the adjacent ortho position, and suppresses radical chain reaction which causes rubber deterioration. However, if the phenoxy radical reacts further, a quinone compound is produced. If a quinone compound is produced, the composition may be yellow to brown in color even if the compound itself having a phenol structure is usually colorless. In the formulation of adding both the compound having a phenol structure and the compound having a sulfur atom, when oxidative degradation proceeds, the compound having a phenol structure itself changes color. On the other hand, in the case of a compound having both a phenol structure and a sulfur atom, the sulfur atom can be caused to decompose the peroxide compound, thereby suppressing further reaction of phenoxy radicals. It is considered that the oxidation degradation inhibition can prevent the self-modification, and thus further inhibit yellowing effect can be obtained.

< Other optional Components >

The dip molding composition may further contain, in addition to the elastomer, the crosslinking agent, the antioxidant, and water, a pH adjuster, a humectant, a dispersant, a pigment, a chelating agent, and the like as other optional components.

As the pH adjuster, potassium hydroxide is generally used. The amount of potassium hydroxide used is usually 0.1 to 2.0 parts by weight based on 100 parts by weight of the composition for dip molding. As the humectant, polyhydric alcohols can be exemplified, and among them, 2-or 3-membered compounds are preferably used. The humectant may be used in an amount of about 1.0 to 5.0 parts by weight per 100 parts by weight of the elastomer. The dispersant is preferably an anionic surfactant, and examples thereof include carboxylate, sulfonate, phosphate, polyphosphate, high-molecular alkyl allyl sulfonate, high-molecular sulfonated naphthalene, and high-molecular naphthalene/formaldehyde polycondensate, and sulfonate is preferably used. The dispersant is preferably about 0.5 to 2.0 parts by weight per 100 parts by weight of the elastomer in the composition for dip molding. As the pigment, titanium dioxide or the like is used. As the chelating agent, sodium ethylenediamine tetraacetate and the like can be used.

As described above, the non-sulfur crosslinked dip molding composition according to the present embodiment contains the carboxylated diene rubber elastomer, the crosslinking agent containing at least one of the organic crosslinking agent and the divalent or more metal crosslinking agent, the antioxidant, and water. The carboxylated diene rubber elastomer polymer backbone may contain structural units derived from (meth) acrylonitrile, structural units derived from an unsaturated carboxylic acid, and structural units derived from butadiene. The antioxidant contains at least one compound having a phenol structure and a sulfur atom. The content of the at least one compound is 0.05 to 4 parts by weight relative to 100 parts by weight of the elastomer. According to the dip molding composition of the present embodiment, a glove in which at least one of deterioration of mechanical properties with time and yellowing can be suppressed can be formed.

[ Method for producing composition for dip Molding ]

Next, a method for producing the non-sulfur crosslinked dip molding composition according to the present embodiment will be described. The method for producing the composition for dip molding comprises a step of mixing the carboxylated diene rubber elastomer, the crosslinking agent and the antioxidant. The carboxylated diene rubber elastomer polymer backbone may contain structural units derived from (meth) acrylonitrile, structural units derived from an unsaturated carboxylic acid, and structural units derived from butadiene. The crosslinking agent contains at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent. The antioxidant contains at least one compound having a phenol structure and a sulfur atom. The content of the at least one compound is 0.05 to 4 parts by weight relative to 100 parts by weight of the elastomer. According to the method for producing the composition for dip molding of the present embodiment, the composition for dip molding can be produced. The details of the materials used and the amounts added are the same as those described above, and therefore, the description thereof is omitted.

In the method for producing the composition for dip molding according to the present embodiment, at least one compound having a phenol structure and a sulfur atom may be added to the elastomer in the form of a dispersion dispersed in an aqueous solvent. That is, the antioxidant may be a dispersion. This can improve the dispersibility of at least one compound having a phenol structure and sulfur atoms in the composition for dip molding. The content of at least one compound having a phenol structure and a sulfur atom in the dispersion may be 25 to 75% by weight, and may be 40 to 60% by weight.

[ Gloves ]

Next, a glove according to this embodiment will be described. The glove according to the present embodiment includes a non-sulfur crosslinked elastomer as a carboxylated diene rubber, a crosslinking agent, and an antioxidant. The carboxylated diene rubber elastomer polymer backbone may contain structural units derived from (meth) acrylonitrile, structural units derived from an unsaturated carboxylic acid, and structural units derived from butadiene. The crosslinking agent contains at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent. The antioxidant is dispersed in the non-sulfur crosslinked elastomer. The antioxidant contains at least one compound having a phenol structure and a sulfur atom. The content of the at least one compound is 0.05 to 4 parts by weight relative to 100 parts by weight of the non-sulfur-crosslinked elastomer. According to the glove of the present embodiment, at least one of deterioration of mechanical properties with time and yellowing can be suppressed.

The glove is composed of a cured film formed by curing the composition for dip molding. The composition of the carboxylated diene rubber elastomer (for example, XNBR) of the cured film may be the same as that of the elastomer added to the composition for dip molding.

In addition, in the dip molding composition, the elastomer is crosslinked by a crosslinking agent consisting essentially of a non-sulfur-based crosslinking agent to form a non-sulfur crosslinked elastomer. Specifically, the carboxyl groups of the carboxylated diene rubber elastomer are crosslinked to form a non-sulfur crosslinked elastomer. When polycarbodiimide is used as the crosslinking agent, the non-sulfur crosslinked elastomer has a polycarbodiimide crosslinking structure. When a zinc compound is used as the crosslinking agent, the non-sulfur crosslinked elastomer has a zinc crosslinked structure. When an aluminum compound is used as the crosslinking agent, the non-sulfur crosslinked elastomer has an aluminum crosslinked structure.

The thickness of the glove is, for example, 50 to 100 μm, and can be adjusted according to the purpose, and the glove can be used for medical treatment, food, and clean room applications as a disposable glove without accelerator.

[ Method for producing glove ]

Next, a method for manufacturing a glove according to the present embodiment will be described. The method for manufacturing the glove comprises a step of dip-molding the glove with the composition for dip-molding. According to the method for manufacturing a glove of the present embodiment, the glove can be manufactured.

The dip molding process may include a coagulation liquid adhesion process S1, a stirring process S2, a dipping process S3, a gelation process S4, a leaching process S5, a hemming process S6, a pre-curing process S7, a curing process S8, and an in-line chlorine treatment process S9. Further, in the case of manufacturing the glove for clean room, the off-line chlorine treatment step S10 may be included after the glove is released from the hand mold.

(Coagulation liquid adhesion step S1)

In the coagulation liquid adhesion step S1, a mold or a shaping die (glove shaping die) is immersed in the coagulation liquid. The mold or the molding die to which the solidification liquid is attached may be dried at 50 to 70 ℃ to dry the whole or part of the surface. The time for attaching the solidification liquid to the surface of the mold or the shaping mold is appropriately determined, and may be about 10 to 20 seconds. As the coagulating liquid, for example, an aqueous solution containing preferably 5 to 40% by weight, more preferably 8 to 35% by weight of a coagulating agent such as calcium nitrate or calcium chloride or an inorganic salt having an effect of precipitating an elastomer is used. The solidification liquid preferably contains about 0.5 to 2 wt%, for example about 1 wt%, of potassium stearate, calcium stearate, mineral oil, ester-based oil, or the like as a mold release agent. The coagulating liquid plays a role of coagulating the elastomer in the following impregnation step S3, and calcium ions contained in the coagulating liquid form calcium crosslinks in the cured film.

(Stirring step S2)

The stirring step S2 is a step of stirring the dip-molding composition. The stirring step S2 is also called aging along with the aging step of vulcanization, but in the non-sulfur crosslinked glove, it means a step of stirring the dip molding composition, dispersing, mixing and defoaming the composition as uniformly as possible. In actual mass production, the production is carried out for about 1 to 2 days. In the dipping tanks of the stirring step S2 and the dipping step S3, the pot life (pot life) of the crosslinking agent is about 3 to 5 days in practical use.

(Impregnation step S3)

The dipping step S3 is a step of adhering the composition for dip molding to a mold or a forming die to which the solidification liquid is adhered. In the dipping step S3, the mold or the shaping mold dried in the solidification liquid adhering step S1 may be dipped in the dip molding composition at a dipping liquid temperature of, for example, 10 to 30 seconds and 25 to 40 ℃. In the dipping step S3, the elastomer in the composition for dip molding may be coagulated on the surface of the mold or the shaping mold by calcium ions contained in the coagulating liquid to form a film.

(Gelation step S4)

The gelation step S4 is a step of gelation of the film lifted from the dip-forming composition, and forming the film to a certain extent so as to avoid dissolution of the elastomer in the leaching step S5. The film at this time is referred to as a cured film precursor. Generally, gelation is a step of heating and drying at 100 to 120℃for about 30 to 4 minutes for vulcanized XNBR gloves, and the optimal conditions are set according to the crosslinking agent for non-sulfur crosslinked gloves. For example, in the polycarbodiimide crosslinked glove, when the pH adjustor is a volatile base, the pH adjustor can be at ordinary temperature, and if a humectant is added, the crosslinking agent is deactivated if the temperature is raised. When the pH adjustor is an alkali metal hydroxide, it may be heated to the above temperature, but it is gelled to avoid drying of the cured film precursor.

(Leaching step S5)

The leaching step S5 is a step of washing the cured film precursor attached to the glove molding die with water after the gelation step S4, and removing the excessive water-soluble substance. In the non-sulfur crosslinked glove, particularly in the polycarbodiimide crosslinked glove, when the pH adjuster is a volatile base, the leaching temperature and time are adjusted in this step so as to reduce the amount of substances such as calcium and potassium that interfere with the crosslinking of the polycarbodiimide in the curing step S8 to a certain amount or less.

(Hemming step S6)

The crimping step S6 is a step of crimping the cuff portion of the glove after the completion of the leaching step S5.

(Precuring step S7)

The pre-curing step S7 is a step of drying the mold or the shaping die in an oven at 60 to 90 ℃, more preferably 65 to 80 ℃ for 30 seconds to 10 minutes, for example, after the hemming step S6 and before the curing step S8. By the presence of the pre-curing step S7, it is possible to prevent the glove from being partially inflated, which may occur due to the rapid decrease in moisture in the curing step S8. This step and the subsequent step are sometimes collectively referred to as a curing step.

(Curing Process S8)

The curing step S8 is a step of heating and drying the cured film precursor, and crosslinking the elastomer with a crosslinking agent to obtain a glove formed of the cured film. Heating and drying are generally carried out at a temperature of 100℃to 140℃for 15 minutes to 30 minutes.

(Online chlorine treatment Process S9)

The in-line chlorine treatment step S9 is a step of directly chlorine-treating the cured film on the hand mold produced in the curing step S8, neutralizing and washing the film, and then drying the film. This step is performed as follows.

The surface of the cured film is washed with water, and the chemical agent or the like is removed and dried. The water washing conditions are usually 30 to 80℃and 60 to 80 seconds.

Immersing the cured film in a treatment tank as an aqueous solution having a chlorine concentration of 600ppm to 1200ppm for 5 to 10 seconds, and removing tackiness (tackiness) of the surface of the cured film. The thickness of the cured film surface at this time is slightly reduced.

After the cured film is subjected to chlorine treatment, it is reduced with a reducing agent such as sodium thiosulfate, an alkaline agent such as KOH or sodium carbonate, and neutralized. Even after the above treatment, chlorine remains in the rubber glove.

-Washing the cured film with water and drying.

After the chlorine treatment step S9, the cured film is removed from the hand mold while being turned inside out, thereby obtaining a glove. In this case, the chlorinated side is the inner side when the glove is worn, the glove inner side may be formed as a surface having no tackiness, and the portion of the glove in contact with the hand is smooth, so that a glove in which the hand easily slides in the glove can be obtained.

The common glove is manufactured through the above-mentioned on-line processes S2 to S9.

(Offline chlorine treatment Process S10)

The off-line chlorine treatment step S10 is a step of an off-line method for producing a glove for clean room from a normal glove. In a clean room, in order to reduce dust generation from gloves and prevent elution and transfer of metal from the glove surfaces to products, the glove surfaces are smoothed or impurity metals are removed. The off-line chlorine treatment process S10 is performed by the following steps.

A step of turning the glove inside and outside and removing the glove from the mold, and chlorine-treating the outside of the glove

The glove is placed in a chlorine treatment device, and chlorine water is added to impregnate the glove. The chlorine treatment apparatus includes a horizontally-oriented cylindrical basket, and is configured to process while stirring by placing and rotating a glove in the basket. The chlorine treatment conditions are, for example, as follows.

The glove is pre-washed, immersed in chlorine water with the chlorine concentration of 200-400 ppm for 5-25 minutes, and then is subjected to neutralization treatment. The glove was further washed with water several times, dried and cooled.

-A step of washing the chlorinated glove with pure water

The pure water washing conditions are, for example, as follows.

The glove was washed in ion-exchanged water having a resistivity of 18mΩ·cm or more for about 10 to 20 minutes for about 2 times. The washing steps comprise washing, draining, centrifugal separation and dehydration and drying. As a result, the impurity metal contained on the glove surface forms chloride, and the solubility increases, and is removed by washing with pure water. The chlorine concentration is appropriately set according to the purpose of the clean room. Even after the above treatment, chlorine remains in the rubber glove.

In the above-described production method, the case where the glove molding die is immersed in the composition for immersion molding is described as being carried out only once, and the glove may be produced by immersing it a plurality of times (2 times or 3 times). Such a method is effective for suppressing the occurrence of pinholes, which are feared when the glove thickness is made to be as thin as about 50 μm. Is also an effective means for making thick gloves. In the case of performing the impregnation a plurality of times, the impregnation step S3 and the gelation step S4 may be repeated.

Examples

The present embodiment will be described in further detail with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

Test pieces of examples 1 to 4 and comparative examples 1 to 5 were produced as follows.

(Production of composition for dip Molding)

300G of latex (Bangkok Synthetics Co., ltd. BST8503S: solid content 45.1%) containing XNBR was placed in a 1L beaker (manufactured by Sugaku Co., ltd., cup diameter: 105 mm. Times. Height: 150 mm). 100g of water was added to the latex to dilute it, and stirring was started. The liquid was previously pH adjusted to 9.5 with 5 wt% aqueous potassium hydroxide. Thereafter, as shown in Table 1, a polyepoxy crosslinking agent (trade name "DENACOL EX-321" manufactured by Nagase ChemteX Co., ltd.) (solid content (epoxy compound content) of 50% by weight, an epoxy equivalent of 141 (g/eq.)), an average epoxy number of 2.7, a MIBK/water distribution ratio of 87%, a zinc oxide (trade name "CZnO-50" manufactured by Farben technology (M) Co., ltd.) (solid content) of 50% by weight), a titanium oxide (trade name "PW-601" manufactured by Farben technology (M) Co., ltd.) (solid content) of 71.4% by weight) as a white pigment, and an antioxidant were added to water so that the solid content concentration was 25%, and the mixture was stirred and mixed for one night to produce a composition for dip molding. The dip-forming composition was continuously stirred in a beaker until use. Table 1 shows the amount of the solid content.

The antioxidants used were as follows.

Antioxidant (Phe 1)

Phe1 dispersion in aqueous solvent

Solid content (Phe 1 content) 50.3 wt%

Phe1: winstay (registered trademark) L (butylation reaction product of p-cresol with dicyclopentadiene and isobutylene: CAS No. 68610-51-5) (Compound having phenol Structure) (refer to the following chemical formula (1))

[ Chemical 1]

Antioxidant (Phe1+Pho)

Dispersions of Phe1 and Pho in aqueous solvents

Solid content (total content of Phe1 and Pho) 48.4 wt%

Phe1: reference is made to the above

Pho: tris (2, 4-di-t-butylphenyl) phosphite: trade name "Irgafos168" manufactured by CAS number 31570-04-4BASF Japanese company (see chemical formula (2) below)

The content of Pho relative to the total of Phe1 and Pho was 75% by weight.

[ Chemical 2]

Antioxidant (Phe1+Sul) 1

Dispersions of Phe1 and Sul in aqueous solvents

Solid content (total content of Phe1 and Sul) 52.8 wt%

Phe1: reference is made to the above

Sul: di (tridecyl) -3,3' -thiodipropionate: CAS No. 10595-72-9 (Compound having a Sulfur atom) trade name "ADEKASTAB AO-503" manufactured by ADEKA Co., ltd. (refer to the following chemical formula (3))

The content of Sul was 75% by weight based on the total of Phe1 and Sul.

[ Chemical 3]

Antioxidant (Phe/Sul)

Phe/Sul dispersion in aqueous solvent

Solid components: (Phe/Sul content) 53.2 wt%

Phe/Sul: 2-methyl-4, 6-bis [ (octylthio) methyl ] phenol: CAS No. 110553-27-0 (a compound having both a phenol structure and a sulfur atom in the same molecule) manufactured by BASF Japanese company under the trade name "Irganox1520L" (see the following chemical formula (4))

[ Chemical 4]

(Preparation of coagulation liquid)

19.6G of release agent was diluted approximately 2-fold using a pre-weighed portion of 30g of water. Then, the diluent of the release agent was slowly added to a liquid obtained by dissolving 0.56g of the surfactant in 42.0g of water. The surfactant used was "technical 320" manufactured by hensmal company (Huntsman Corporation). As the mold release agent, the trade name "S-9" (solid content concentration: 25.46% by weight) manufactured by CRESTAGE INDUSTRY was used. The remaining S-9 in the vessel was rinsed with the remaining water and the total amount thereof was added, followed by stirring for 3 to 4 hours to prepare an S-9 dispersion.

Next, an aqueous calcium nitrate solution obtained by dissolving 143.9g of calcium nitrate tetrahydrate in 153.0g of water was prepared in a 1L beaker (manufactured by Sugaku Co., ltd., cup diameter: 105 mm. Times. Height: 150 mm), and the previously prepared S-9 dispersion was added to the aqueous calcium nitrate solution while stirring. The pH of the solution was adjusted to 8.5 to 9.5 with 5% aqueous ammonia, and water was added so that the final calcium nitrate had a solid content concentration of 20% and S-9 had a solid content of 1.2% as an anhydrate, to obtain 500g of a coagulated liquid. The resulting coagulated liquid was continuously stirred in a 1L beaker until use.

(Production of cured film)

The coagulated liquid thus obtained was stirred and heated to about 50℃and filtered through a 200-mesh nylon filter, and then placed in a dipping vessel. Then, the washed ceramic plate (200×80×3mm, hereinafter referred to as "ceramic plate") heated to 70 ℃ was immersed in a solidification liquid (solidification liquid adhesion step). Specifically, the ceramic plate was immersed in the coagulating liquid for 6 seconds from the front end of the ceramic plate to a position 18cm from the front end of the ceramic plate, and then held in the immersed state for 6 seconds, and lifted up for 6 seconds. Rapidly shaking off the solidification liquid attached to the surface of the ceramic plate, and drying the surface of the ceramic plate. The dried ceramic plate was again heated to 70 ℃ for impregnation into the composition for impregnation molding.

The composition for dip molding was filtered through a 200 mesh nylon filter at room temperature, and then placed in a dip container, and a ceramic plate at 70℃to which the solidification liquid was adhered was immersed in the composition for dip molding. Specifically, the ceramic plate was immersed for 6 seconds, held for 6 seconds, and lifted for 6 seconds. The solution was held in the air until the dip-molding composition was no longer dropped, and the drop of the dip-molding composition attached to the tip was gently shaken off.

The ceramic plate immersed in the composition for dip molding was dried at 23.+ -. 2 ℃ for 30 seconds (gelation step), and washed with warm water at 50 ℃ for 5 minutes (leaching step). Thereafter, the mixture was dried at 70℃for 5 minutes (pre-curing step) and thermally cured at 130℃for 30 minutes (curing step). The resulting cured film (thickness: average 0.08 mm) was peeled off intact from the ceramic plate and stored in an atmosphere of 23.+ -. 2 ℃ and 50%.+ -. 10% humidity before being used for physical property test.

[ Evaluation ]

(Color difference measurement)

The test pieces of examples 1 to 4 and comparative examples 1 to 5 were placed in an oven set at 100℃and taken out after 1 day, after 4 days, after 7 days and after 11 days. Then, a color difference meter (product name "CR-400" manufactured by Konikoku Meida Co., ltd.) was used for the surface of each test piece, based on JIS-Z8730: 2009 gives a color difference (Δe). The color difference was calculated based on the color difference of the test piece on day 0, which was not subjected to the aging treatment.

TABLE 1

As shown in table 1 and fig. 2, the test pieces of examples 1 to 4 were less in color difference before and after aging than the test pieces of comparative examples 1 to 5. From these results, it is seen that the test piece using the antioxidant comprising at least one compound having a phenol structure and a sulfur atom causes less discoloration due to aging than the case of using the compound having a phenol structure alone, and the test piece using the compound having a phenol structure and the phosphite compound in combination. It can be further seen that the test pieces of example 3 and example 4 have less discoloration due to aging than the test pieces of example 1 and example 2. From these results, it was found that an antioxidant containing a compound having both a phenol structure and a sulfur atom in the same molecule was superior to an antioxidant containing two compounds of a compound having a phenol structure and a compound having a sulfur atom.

Next, test pieces of examples 5 to 10 and comparative example 6 were prepared according to the formulations shown in table 2, similarly to the above examples. In this case, BST8503S was replaced with latex (NL 105 made by LG chemical Co., ltd.: solid content (elastomer content) 45 wt%). In addition, a polycarbodiimide-based crosslinking agent (trade name "V-02-L2" manufactured by Niqing textile chemical Co., ltd.: solid content (polycarbodiimide content) of 40.0%, the number of carbodiimide functional groups per 1 molecule: 9.4) was used instead of the polyepoxide crosslinking agent (EX-321: solid content of 50%). The antioxidant (Phe 2), the antioxidant (Phe1+Sul) 1, the antioxidant (Phe1+Sul) 2, and the antioxidant (Phe/Sul) were used. Table 2 shows the amount of the solid content.

Antioxidant (Phe 2)

Phe2 dispersion in aqueous solvent

Solid content (Phe 2 content) 50 wt%

Phe2: winstay (registered trademark) L (butylation reaction product of p-cresol with dicyclopentadiene and isobutylene: CAS No. 68610-51-5) (Compound having phenol Structure)

Antioxidant (Phe1+Sul) 2

Dispersions of Phe1 and Sul in aqueous solvents

Solid content (total content of Phe1 and Sul) 52.8 wt%

Phe1: reference is made to the above

Sul: reference is made to the above

The content of Sul was 50% by weight based on the total of Phe1 and Sul.

[ Evaluation ]

(Color difference measurement)

The color difference was measured in the same manner as described above.

(Elongation at break)

For the test pieces of examples 5 to 10 and comparative example 6, no. 5 dumbbell test pieces of JIS K6251 were cut out, and the elongation at break was measured at a test speed of 500 mm/min, a chuck pitch of 75mm, and a reticle pitch of 25mm using TENSILON universal tensile tester RTC-1310A manufactured by A & D Co. The elongation at break was determined based on the following equation.

Elongation at break (%) =100× (reticle pitch at break in tensile test-reticle pitch before tensile test)/reticle pitch before tensile test

TABLE 2

As shown in table 2 and fig. 3 and 4, it can be seen that the test pieces of examples 5 to 10 have smaller color difference before and after aging and have excellent elongation at break after aging than the test piece of comparative example 6. From these results, it is seen that the test piece using the antioxidant comprising at least one compound having a phenol structure and a sulfur atom is less in discoloration and deterioration in physical properties due to aging as compared with the test piece using the compound having a phenol structure alone. It can be further seen that the test pieces of example 9 and example 10 have less discoloration due to aging and have excellent elongation at break after aging, as compared with the test pieces of example 5 and example 6 and the test pieces of example 7 and example 8. From these results, it was found that an antioxidant containing a compound having both a phenol structure and a sulfur atom in the same molecule was superior to a test piece using an antioxidant containing two compounds of a compound having a phenol structure and a compound having a sulfur atom. It can also be seen that the test pieces of example 5 and example 6 have less discoloration due to aging than the test pieces of example 7 and example 8. From these results, it is preferable that the content of the compound having a sulfur atom is larger than that of the compound having a phenol structure.

Next, test pieces of example 11 and comparative example 7 were prepared as follows, and subjected to chlorine treatment.

(Production of composition for dip Molding)

300G of XNBR-containing latex (NL 151: solid content (elastomer content) 45% by weight, manufactured by LG chemical Co., ltd.) was placed in a 1L beaker (manufactured by Sugaku Co., ltd., cup diameter 105 mm. Times. Height 150 mm). 100g of water was added to the latex to dilute it, and stirring was started. The liquid was previously pH adjusted to 9.9 using 5wt% aqueous potassium hydroxide. Thereafter, as shown in Table 3, a polyepoxide crosslinking agent (DENACOL EX-321: solid content (epoxy compound content) 50% by weight), an aluminum crosslinking agent (polynuclear aluminum lactate compound: solid content (aluminum compound content) 3.6%), titanium oxide (trade name "PW-601" manufactured by Farben technology (M)) as a white pigment (solid content (titanium oxide content) 71.4% by weight), an antioxidant (Phe 3) and the antioxidant (Phe1+Sul) 1 were added, and water was added so that the solid content concentration was 30%, and the mixture was stirred and mixed for one night to produce a composition for dip molding. The dip-forming composition was continuously stirred in a beaker until use. Table 3 shows the amount of the solid content.

Antioxidant (Phe 3): trade name "CVOX-50" manufactured by Farben technology (M) company "

Phe3 dispersion in aqueous solvent

Solid content (Phe 3 content) 52.88 wt%

Phe3: butyl reaction product of p-cresol with dicyclopentadiene and isobutylene: CAS number 68610-51-5 (Compound with phenol Structure)

TABLE 3 Table 3

(Preparation of coagulation liquid)

19.6G of release agent was diluted approximately 2-fold using a pre-weighed portion of 30g of water. Then, a dilution of the release agent was slowly added to a liquid obtained by dissolving 0.56g of the surfactant in 42.0g of water. The surfactant used was "technical 320" manufactured by hensmal company (Huntsman Corporation). As the mold release agent, the trade name "S-9" (solid content: 25.46%) manufactured by CRESTAGE INDUSTRY was used. The remaining S-9 in the vessel was rinsed with the remaining water and the total amount thereof was added, followed by stirring for 3 to 4 hours to prepare an S-9 dispersion.

Next, an aqueous calcium nitrate solution obtained by dissolving 143.9g of calcium nitrate tetrahydrate in 153.0g of water was prepared in a 1L beaker (manufactured by Sugaku Co., ltd., cup diameter: 105 mm. Times. Height: 150 mm), and the previously prepared S-9 dispersion was added to the aqueous calcium nitrate solution while stirring. The pH of the solution was adjusted to 8.5 to 9.5 with 5% aqueous ammonia, and water was added so that the final calcium nitrate was 30% as an anhydrous substance and so that S-9 was 1.2% as a solid concentration, thereby obtaining 500g of a coagulated liquid. The resulting coagulated liquid was continuously stirred in a 1L beaker until use.

(Production of cured film)

The coagulated liquid thus obtained was stirred and heated to about 50℃and filtered through a 200-mesh nylon filter, and then placed in a dipping vessel. Then, the washed ceramic plate (200X 80X 3mm, hereinafter referred to as "ceramic plate") which has been heated to 60℃in advance was immersed in a solidification liquid (solidification liquid adhesion step). Specifically, the ceramic plate was immersed in the coagulating liquid for 10 seconds from the contact of the front end of the ceramic plate with the surface of the coagulating liquid to a position 18cm from the front end of the ceramic plate, and held in the immersed state for 5 seconds, and lifted up for 5 seconds. Rapidly shaking off the solidification liquid attached to the surface of the ceramic plate, and drying the surface of the ceramic plate. The dried ceramic plate was again heated to 60℃to prepare for impregnation into the composition for impregnation molding.

The composition for dip molding was filtered through a 200 mesh nylon filter at room temperature, and then placed in a dip container, and a ceramic plate at 60℃to which the solidification liquid was adhered was immersed in the composition for dip molding. Specifically, the ceramic plate was immersed for 10 seconds, held for 5 seconds, and lifted up for 5 seconds. The solution was held in the air until the dip-molding composition was no longer dropped, and the drop of the dip-molding composition attached to the tip was gently shaken off.

The ceramic plate impregnated with the composition for dip molding was dried at 50℃for 2 minutes (gelation step), and washed with warm water at 50℃for 2 minutes (leaching step). Thereafter, the mixture was dried at 70℃for 5 minutes (pre-curing step) and thermally cured at 130℃for 30 minutes (curing step). After the curing step, the mixture was washed with warm water at 50℃for 2 minutes (post-leaching step).

(Chlorine treatment)

After the post-leaching step, the solution was immersed in chlorine water adjusted to 800ppm for 20 seconds as an in-line chlorine treatment. After that, neutralization treatment was performed with an aqueous solution prepared from sodium carbonate, sodium thiosulfate, hypochlorous acid, washing with water 3 times, and drying in an oven at 70 ℃ for 15 minutes. Then, the glove is taken off from the glove mold and stored at a temperature of about 20 to 35 ℃ for 1 week. Thereafter, the glove was immersed in chlorine water having the concentration shown in table 4 for a predetermined time to perform off-line chlorine treatment. After the glove was taken out of the chlorine water, neutralization treatment was performed with an aqueous solution prepared from sodium carbonate, sodium thiosulfate and hypochlorous acid in the same manner as in the case of the on-line chlorine treatment, the glove was washed with water about 3 times and dried in an oven at 70℃for 15 minutes.

[ Evaluation ]

The thickness of the glove treated with chlorine as described above was measured based on the specifications of ASTM-6319-00. Further, tensile strength at break (TSB) of the chlorine treated glove was measured based on the specifications of ASTM D412. These results are shown in Table 4.

TABLE 4 Table 4

As shown in table 4 and fig. 5, the glove of example 11 had no great effect on tensile strength even when subjected to chlorine treatment. On the other hand, it was found that the glove of comparative example 7 had a tendency that the tensile strength at break was lowered by chlorine treatment. From these results, it can be seen that the resistance to chlorine treatment is also improved due to the antioxidant comprising at least one compound having a phenol structure and a sulfur atom.

The elastomer may generate radicals due to chlorine treatment, and physical properties may be degraded due to the radicals. On the other hand, even when chlorine treatment was performed, the physical properties of the glove of example 11 were not lowered, and it was presumed that radicals generated by chlorine treatment were decomposed. Such a glove is considered to be capable of suppressing at least one of a decline in mechanical properties with time and yellowing with time. Namely, consider that: the non-sulfur crosslinked glove is aged by heat or chlorine treatment faster than the sulfur crosslinked glove, and as a result, the tensile strength, elongation, flexibility, and yellowing of the glove can be suppressed from decreasing with time, so that the glove does not occur during storage before use.

The present application refers to the whole contents of Japanese patent application No. 2022-076972 (application day: 5/9/2022) and Japanese patent application No. 2023-003683 (application day: 13/2023/1).

The present embodiment has been described above, but the present embodiment is not limited to these embodiments, and various modifications are possible within the scope of the present embodiment.

Industrial applicability

According to the present disclosure, it is possible to provide a glove capable of suppressing deterioration of mechanical properties such as tensile strength, elongation, flexibility, and the like with time and yellowing of a glove without an accelerator due to aging by heat and chlorine treatment, a composition for dip molding used for producing the glove, and a composition for dip molding and a method for producing the glove.

Claims

1. A composition for non-sulfur cross-linked dip molding,

The method comprises the following steps:

Carboxylated diene rubber elastomer,

A crosslinking agent comprising at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent,

An antioxidant comprising at least one compound having a phenol structure and a sulfur atom, and

The water is used as the water source,

The content of the at least one compound is 0.05 to 4 parts by weight relative to 100 parts by weight of the elastomer.

2. The composition for dip molding according to claim 1, wherein the carboxylated diene rubber elastomer is an elastomer having a polymer main chain containing a structural unit derived from (meth) acrylonitrile, a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from butadiene.

3. The composition for dip molding according to claim 1 or 2, wherein the at least one compound comprises at least one compound having the phenol structure and at least one selected from the group consisting of a thioether structure, a polysulfide structure, and a thiol structure.

4. The composition for dip molding according to any one of claims 1 to 3, wherein the at least one compound comprises at least one compound having the phenol structure and a thioether structure or polysulfide structure.

5. The composition for dip molding according to any one of claims 1 to 4, wherein the at least one compound comprises a compound having both the phenol structure and the sulfur atom in the same molecule.

6. The composition for dip molding according to any one of claims 1 to 5, wherein the at least one compound comprises two or more compounds of a compound having the phenol structure and a compound having the sulfur atom.

7. The composition for dip molding according to any one of claims 1 to 6, wherein the organic crosslinking agent comprises at least one of polycarbodiimide and an epoxy compound.

8. The composition for dip molding according to any one of claims 1 to 7, wherein the metal crosslinking agent having at least two valences contains at least one of a zinc compound and an aluminum compound.

9. A process for producing a composition for non-sulfur crosslinked dip molding,

Comprising the following steps: a step of mixing a carboxylated diene rubber elastomer, a crosslinking agent containing at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent, and an antioxidant containing at least one compound having a phenol structure and a sulfur atom,

The content of the at least one compound is 0.05 to 4 parts by weight relative to 100 parts by weight of the elastomer,

The at least one compound is added to the elastomer in the form of a dispersion dispersed in an aqueous solvent.

10. The method for producing a composition for dip molding according to claim 9, wherein the carboxylated diene rubber elastomer is an elastomer having a polymer main chain containing a structural unit derived from (meth) acrylonitrile, a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from butadiene.

11. A glove is provided with:

non-sulfur crosslinked elastomer as carboxylated diene rubber elastomer,

A crosslinking agent comprising at least one of an organic crosslinking agent and a divalent or more metal crosslinking agent, and

An antioxidant comprising at least one compound having a phenol structure and a sulfur atom dispersed in the non-sulfur crosslinked elastomer,

The content of the at least one compound is 0.05 to 4 parts by weight relative to 100 parts by weight of the non-sulfur-crosslinked elastomer.

12. The glove of claim 11, the carboxylated diene rubber elastomer being a non-sulfur crosslinked elastomer having a polymer backbone comprising structural units derived from (meth) acrylonitrile, structural units derived from an unsaturated carboxylic acid, and structural units derived from butadiene.

13. A method for producing a glove, comprising the step of dip-molding a glove with the composition for dip-molding according to claim 1 or 2.