Crosslinking agent, dip molding composition, gloves, and manufacturing method thereof for ESG-compliant rubber gloves

Abstract

This invention provides a crosslinking agent that can produce molded articles with excellent fatigue resistance and resistance to tearing. Furthermore, it provides a crosslinking agent that allows a compound solution containing the crosslinking agent and a copolymer elastomer such as X-NBR to mature in a short time of less than 24 hours, enabling the production of molded articles with excellent tensile strength stability. [Solution] A crosslinking agent according to one embodiment of the present invention includes a compound having a structure represented by the following general formula (4). TIFF0007876803000026.tif36170 (In formula (4), X independently represents either a chlorine atom or a hydroxyl group, H x A1 and H x A2 each represents a hydroxy acid residue, but H x A1 and H x This is a hydroxy acid residue with a different structure from A2.

Description

[Technical Field]

[0001] The present invention relates to a crosslinking agent, a dip molding composition, gloves, and a method for producing the same, for ESG-compliant rubber gloves. [Background technology]

[0002] Traditionally, rubber gloves made from synthetic rubber such as carboxy-modified acrylonitrile butadiene rubber (hereinafter also referred to as "X-NBR") using a dip molding method (hereinafter also referred to as "X-NBR gloves") have been widely used as a substitute for natural rubber gloves, which can cause type I allergies.

[0003] X-NBR gloves have traditionally been formed by crosslinking using sulfur compounds such as elemental sulfur (substances composed solely of sulfur atoms, typified by rhombic sulfur represented by chemical formula S8), vulcanization accelerators, and zinc oxide. However, vulcanization accelerators can cause type IV allergies, posing safety concerns for medical applications. Furthermore, the production of X-NBR gloves generates zinc oxide sludge in the wastewater after pre-leaching, requiring costly removal and contributing to environmental pollution. Therefore, in recent years, as an alternative, methods for obtaining X-NBR gloves by aluminum crosslinking without using vulcanization accelerators have been developed.

[0004] Patent Document 1 discloses a crosslinking agent made from a mononuclear aluminum compound as a raw material for obtaining aluminum crosslinked gloves by dip molding.

[0005] Patent Document 2 discloses a crosslinking agent containing a multinuclear aluminum lactate compound. This crosslinking agent has a certain effect in suppressing gelation in the dip molding solution and exhibits stability in mass production processes.

[0006] In addition to aluminum crosslinking agents, other known crosslinking agents include polycarbodiimides and polyvalent epoxy compounds, which are organic crosslinking agents. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2017 / 146238 [Patent Document 2] International Publication No. 2022 / 168831 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the crosslinking agent described in Patent Document 1 is unstable in a basic environment, for example, under a pH of 9.2 to 10.5, and deteriorates over time. As a result, the crosslinking reaction does not proceed uniformly in a solution containing X-NBR.

[0009] In other words, in aluminum crosslinking agents obtained from aluminic acid, aluminum is a single mononuclear compound. Since X-NBR compound solutions typically have a pH between 9.2 and 10.5, the solubility of aluminum compounds in water is significantly reduced. Therefore, when this aluminum crosslinking agent is added to such a solution, the crosslinking agent undergoes rapid changes over time and is extremely unstable. Furthermore, in this crosslinking method, the carboxylic acid of X-NBR coordinates to the mononuclear aluminum, but X-NBR is bulkier than aluminum, and since X-NBR bonds to one aluminum molecule at two locations, it becomes crowded, easily leading to localized stress concentration. Therefore, the resulting gloves have the problem of being easily torn. Furthermore, since mononuclear aluminum is easily extracted by acids and bases, it cannot satisfy environmental regulations.

[0010] Therefore, there is a need for a crosslinking agent that can produce molded articles with excellent fatigue resistance and resistance to tearing.

[0011] The crosslinking agent described in Patent Document 2 is a multinuclear aluminum complex with lactic acid as a ligand, resulting in the presence of terminal aluminum and internal aluminum within the molecule. The internal aluminum has difficulty contacting external substrates, inhibiting its reaction, which slows down the crosslinking site in the crosslinking reaction with X-NBR, and limiting its contribution to crosslinking. Furthermore, aluminum lactate complexes have extremely low reactivity, as evidenced by their use in toothpaste. Therefore, such aluminum complexes with only lactic acid as a ligand become overly stabilized, significantly slowing down the crosslinking reaction with X-NBR. This necessitates a longer maturation time for the compound solution containing this crosslinking agent, leading to lower productivity in rubber production. To increase productivity, heating is essential to promote the elimination of lactic acid residues from the multinuclear aluminum lactate compound and accelerate the exchange reaction involving the carboxylate of X-NBR. This presents challenges such as increased energy costs and difficulty in addressing energy conservation issues.

[0012] Therefore, there is a need for a crosslinking agent that exhibits excellent crosslinking efficiency and can produce molded articles with superior tensile strength stability even after the compound solution containing the crosslinking agent and X-NBR has undergone a maturation period.

[0013] Crosslinking agents using polycarbodiimide are typically expensive, leading to increased costs. In addition, while polycarbodiimide has polyethylene glycol as a side chain to protect the active polycarbodiimide, if drying during crosslinking is insufficient, the polycarbodiimide will hydrolyze, thus restricting manufacturing conditions.

[0014] Crosslinking agents using polyvalent epoxy compounds are difficult to uniformly disperse in X-NBR particles due to their high lipophilicity. Furthermore, their relatively short pot life of approximately 100 hours can lead to quality problems during mass production.

[0015] Therefore, several embodiments of the present invention provide a crosslinking agent that can produce molded articles having excellent fatigue resistance and being resistant to tearing. Furthermore, several embodiments of the present invention provide a crosslinking agent in which a compound solution containing the crosslinking agent and a copolymer elastomer such as X-NBR can be matured in a short time of less than 24 hours and used for dip molding, and which can produce molded articles with excellent tensile strength stability. [Means for solving the problem]

[0016] As a result of diligent research, the inventors have focused on the problems of conventional mononuclear aluminum crosslinking agents, polynuclear aluminum lactate compounds, and other crosslinking agents, namely, lack of stability in a basic environment, low efficiency of the crosslinking reaction due to excessive stabilization of the crosslinking agent, and insufficient reactivity of internal aluminum, and have succeeded in providing a novel crosslinking agent that can solve these problems. The inventors have found that with the novel crosslinking agent containing an aluminum hydroxylate compound, the crosslinking reaction in a crosslinking furnace to obtain dip molded products is unnecessary, thus reducing energy consumption, and that stability and environmental issues are considered because zinc oxide and mononuclear aluminum are not generated in the wastewater. Furthermore, they have found that molded products using this crosslinking agent undergo an unprecedented crosslinking reaction process, resulting in molded products such as gloves with excellent fatigue durability, and molded products such as gloves that can be matured in a short time of less than 24 hours and have excellent tensile strength stability. This aluminum hydroxylate compound can be made from polyaluminum chloride (PAC), which is inexpensive and widely used in water treatment and other applications.

[0017] In other words, the present invention is as follows. [1] A crosslinking agent comprising a compound having a structure represented by the following general formula (4). [ka] (In formula (4), X independently represents either a chlorine atom or a hydroxyl group, H x A1 and H x A2 each represents a hydroxy acid residue, but H x A1 and Hx It is a hydroxy acid residue having a structure different from A2.)

[0018] [2] A crosslinking agent comprising a compound having a structure represented by the following general formula (4) and an organic acid. [Chemical formula] (In formula (4), each X independently represents a chlorine atom or a hydroxy group, H x A1 and H x A2 each represents a hydroxy acid residue. H x A1 and H x A2 may have the same structure or different structures.)

[0019] [3] The crosslinking agent according to [2], wherein the organic acid is a fatty acid.

[0020] [4] The crosslinking agent according to [2], wherein the organic acid is formic acid, acetic acid or propionic acid.

[0021] [5] The crosslinking agent according to any one of [2] to [4], wherein H x A1 and H x A2 are hydroxy acid residues having different structures.

[0022] [6] The crosslinking agent according to any one of [1] to [5], wherein H x A1 is a lactic acid residue, a methyl lactic acid residue, a thioctic acid residue or a citric acid residue.

[0023] [7] The crosslinking agent according to any one of [1] to [6], wherein H x A2 is a glycolic acid residue, a malic acid residue, a citric acid residue, a methyl lactic acid residue, a DL-mandelic acid residue, an L-ascorbic acid residue, a thioglycolic acid residue or a thioctic acid residue.

[0024] [8] The crosslinking agent according to any one of [1] to [7], which is an aqueous solution having a pH of 7.5 or more and 8.4 or less.

[0025] [9] A crosslinking agent described in any one of [1] to [8], used in dip molding.

[0026] A composition comprising a crosslinking agent described in any one of

[10] [1] to [9], a copolymer elastomer, a pH adjuster, and water, The copolymer elastomer comprises structural units derived from (meth)acrylonitrile and ethylenically It contains structural units derived from unsaturated carboxylic acids and structural units derived from butadiene, A dip molding composition having a pH of 8.5 to 10.5.

[0027]

[11] The dip molding composition according to

[10] , which does not contain elemental sulfur and zinc oxide.

[0028]

[12] The dip molding composition according to

[10] or

[11] , wherein the content of the crosslinking agent is 0.1 parts by mass or more and 1.5 parts by mass or less in terms of aluminum oxide, per 100 parts by mass of the copolymer elastomer.

[0029] A glove that is a molded body of a dip molding composition described in any one of

[13]

[10] to

[12] .

[0030] A method for producing a crosslinking agent as described in

[14] [1], A step to obtain a solution containing a hydroxy salt, A step to obtain a solution containing polyaluminum chloride, A step of mixing the solution containing the polyaluminum chloride with the solution containing the hydroxy salt, A method for producing a crosslinking agent, including the crosslinking agent.

[0031] A method for producing a crosslinking agent as described in

[15] [2], A step to obtain a solution containing a hydroxy salt, A step to obtain a solution containing fatty acids, A step to obtain a solution containing polyaluminum chloride, A step of mixing the solution containing the polyaluminum chloride, the solution containing the fatty acid, and the solution containing the hydroxy salt, A method for producing a crosslinking agent, including the crosslinking agent.

[0032]

[16] The method for producing a crosslinking agent according to

[14] or

[15] , wherein the calcium ion content in the polyaluminum chloride is less than 500 ppm by mass with respect to the total amount of the polyaluminum chloride.

[0033]

[17] A method for producing a crosslinking agent according to any one of

[14] to

[16] , wherein the hydroxy salt comprises a first hydroxy salt selected from lactic acid, methyllactic acid, thiolactic acid and citric acid, and a second hydroxy salt selected from glycolic acid, malic acid, citric acid, DL-mandelic acid, L-ascorbic acid, thioglycolic acid and thiolactic acid.

[0034]

[18] The method for producing a crosslinking agent according to

[17] , wherein the molar ratio (B / A) of the second hydroxyate (B) to the first hydroxyate (A) in the solution containing the hydroxyate is 5 / 95 or more and 95 / 5 or less.

[0035]

[19] The molar ratio (D / C) of the hydroxy acid salt (D) to the aluminum atoms (C) of the polyaluminum chloride is 0.5 or more and 2.0 or less, a method for producing a crosslinking agent according to any one of

[14] to

[18] .

[0036] A method for manufacturing gloves as described in

[20]

[13] , (1) A coagulant application step in which a coagulant is applied to a glove molding die to obtain a mold or former, (2) A maturation step in which the composition is stirred to obtain a dipping liquid, (3) Immerse the mold or the former in the dipping solution, and A dipping step in which a film is formed on the former, (4) A gelling step to obtain a pre-dried film-forming crosslinked film by gelling the film, (5) A leaching step to remove impurities from the crosslinked film to obtain the glove precursor 1, (6) A beading step to produce a bead on the cuff portion of the glove precursor 1 to obtain a glove precursor 2 having a bead, (7) A drying step in which the glove precursor 2 is heated and dried to obtain a molded glove, A method for manufacturing gloves, including the method described above. [Effects of the Invention]

[0037] The novel crosslinking agent containing the hydroxy acid aluminum compound of the present invention has the following effects.

[0038] The crosslinking agent of the present invention does not require a heating-based processing reaction step to obtain molded products such as gloves, thus significantly reducing energy consumption in the manufacturing process. Furthermore, the crosslinking agent of the present invention can be manufactured using raw materials that do not burden the human body or the environment, such as polyaluminum chloride (PAC), which is inexpensive and widely used in water treatment and other applications, or lactic acid, which is abundant in nature.

[0039] Furthermore, because no vulcanization accelerators or zinc oxide are used, zinc oxide sludge and aluminum hydroxide gel (derived from mononuclear aluminum) do not form as residues in the wastewater, thus reducing the environmental impact.

[0040] Since the crosslinking agent of the present invention does not contain a vulcanization accelerator, the risk of type IV allergy caused by vulcanization accelerators can be significantly reduced. Therefore, it is possible to provide molded articles such as gloves that are safer, especially in products where contact with the human body is unavoidable, such as medical gloves. Furthermore, because the crosslinking agent of the present invention has appropriate stability in the compound solution, it is possible to manufacture molded articles in which the compound solution containing the crosslinking agent and X-NBR exhibits excellent tensile strength stability even during short to long maturation periods.

[0041] Several embodiments of molded articles using the crosslinking agent of the present invention undergo a unique crosslinking reaction process different from that of the prior art, thereby achieving excellent fatigue durability. Furthermore, because several embodiments of molded articles using the crosslinking agent of the present invention undergo a unique crosslinking reaction process different from that of the prior art, compounds with a maturation time of less than 24 hours can be mass-produced, and even when using a compound solution that has undergone a maturation period of 5 days, it is possible to achieve excellent tensile strength with superior stability. This makes it possible to provide stable quality, especially for products (molded articles) that require high physical properties, such as medical gloves and industrial gloves. In addition, since the crosslinking process is completed in the solution, the efficiency of the manufacturing process is improved, and it can also contribute to reducing manufacturing costs. [Brief explanation of the drawing]

[0042] [Figure 1] Figure 1 shows the mass spectrum obtained by electrospray ionization mass spectrometry of a precipitate obtained using an aqueous solution of polyaluminum chloride with a basicity of approximately 50%. [Figure 2] Figure 2 shows the aluminum NMR spectrum of a mononuclear aluminum lactate compound in which three molecules of lactate are coordinated to aluminum. [Figure 3] Figure 3 shows the aluminum NMR spectrum of aluminum lactate obtained as a precipitate. [Modes for carrying out the invention]

[0043] The following describes embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"): This will be explained in detail. Note that the following embodiments are illustrative examples for explaining the present invention, and the present invention is not limited to these embodiments.

[0044] [Crosslinking agent A] A crosslinking agent A according to one embodiment of the present invention includes a compound having a structure represented by the following general formula (1). [ka] (In formula (1), m represents an integer from 0 to 18, X independently represents a chlorine atom or a hydroxyl group, Y independently represents a chlorine atom, a hydroxyl group, or a hydroxy acid residue, H x A1 and H x A2 each represents a hydroxy acid residue, but H x A1 and H x This is a hydroxy acid residue with a different structure from A2.

[0045] The aluminum hydroxy acid chloride compound (hereinafter also simply referred to as "HAC") having the structure represented by the above general formula (1) according to this embodiment is polyaluminum chloride ([Al2(OH) n Cl 6-n ] m , where 1≦n≦5 and 1≦m≦10.Hereafter also simply referred to as "PAC") has as its basic framework and exists in a range from a dinuclear structure having 2 aluminum atoms to a deciduous structure having 20 aluminum atoms.Among these, it is preferable that it has a dinuclear structure, that is, that m basic frameworks containing two aluminum atoms are assembled.Also, the coordination number of aluminum in aluminum complexes is mainly 6.That is, in the above general formula (1), it is preferable that m is 0.HAC exhibits high stability in solution because the hydroxy acid residue coordinates to aluminum, so crosslinking in solution can be suitably achieved.Also, the aluminum in HAC is chloride ion (Cl - When the leaving group is retained, it tends to efficiently form a coordinate bond with the carboxylic acid-modified group of X-NBR.

[0046] By using crosslinking agents containing HACs, a process that does not require a heating furnace for the crosslinking reaction becomes possible, and the crosslinking process is completed in solution, making it possible to achieve improved manufacturing efficiency, cost reduction, and reduced environmental impact simultaneously. In other words, manufacturing processes using crosslinking agents eliminate the need for the heating furnace that was conventionally required for the crosslinking reaction, thereby reducing energy consumption and carbon dioxide emissions.

[0047] Furthermore, since the crosslinking process is completed in solution, it becomes possible to form a uniform crosslinked structure.

[0048] Furthermore, according to the crosslinking agent A of this embodiment, since elemental sulfur, vulcanization accelerators, zinc oxide, etc. are not used in the crosslinking reaction, the risk of developing type IV allergies is reduced, and it can also contribute to reducing the environmental burden. In the present invention, "elemental sulfur" refers to rhombic sulfur or monoclinic sulfur that exists as an eight-membered cyclic molecule at room temperature.

[0049] According to the crosslinking agent A of this embodiment, molded articles can be suitably manufactured by dip molding while taking into consideration energy and environmental issues. The crosslinking agent of this embodiment is H x A1 and H x The structure represented by the general formula (1) above is a hydroxy acid residue having a different structure from A2. Because it contains a compound having [specific characteristic], the steric hindrance caused by hydroxy acid residues in the crosslinking reaction with X-NBR is mitigated. This improves the crosslinking efficiency, allowing the crosslinking reaction to proceed during the maturation process, and enabling the material to be used for dip molding within 24 hours of maturation.

[0050] The crosslinking reaction between crosslinking agent A and X-NBR is thought to proceed as shown in equations (2) and (3) below, for example. In equations (2) and (3) below, crosslinking agent A is m=0 in the general formula (1) above, and H x A1 is a lactate residue, H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This includes compounds having a structure in which X, which is bonded to the Al atom that is bonded to A2, is a hydroxyl group.

[0051] As shown in formula (2) below, when crosslinking agent A is introduced to X-NBR, the aluminum hydroxylate compound, which can move freely in the solution, is thought to rapidly bond with the carboxylate of X-NBR1 while removing good leaving groups such as chlorine. On the other hand, as shown in formula (3) below, the aluminum hydroxylate compound bonded to X-NBR1 as a pendant is unable to move freely in the solution and is thought to require time in the crosslinking reaction with X-NBR2. At this time, H in the aluminum hydroxylate compound x The steric hindrance of A2 significantly affects the crosslinking reaction rate with X-NBR2, and it is thought that the reaction proceeds more rapidly when a glycolic acid residue has less steric hindrance compared to a lactate residue with greater steric hindrance. Therefore, the crosslinking agent A in this embodiment is H x A1 and H x By including a compound having the structure represented by the above general formula (1), which is a hydroxy acid residue having a different structure from A2, the crosslinking efficiency is improved, and it is presumed that the compound solution containing crosslinking agent A and X-NBR can be matured in a short time of less than 24 hours, and a molded article with excellent tensile strength stability can be produced.

[0052] [ka]

[0053] [ka]

[0054] The aluminum concentration (in terms of Al2O3) in crosslinking agent A is preferably 1% to 15% by mass, more preferably 3% to 10% by mass, and 5% to 8% by mass. That is even more preferable.

[0055] Next, we will explain the aluminum hydroxylate compound contained in crosslinking agent A, and then provide a detailed description of the crosslinking agent.

[0056] [Aluminum hydroxylate compounds] HAC is a compound having a structure represented by the following general formula (1). [ka] (In formula (1), m represents an integer from 0 to 18, X independently represents a chlorine atom or a hydroxyl group, Y independently represents a chlorine atom, a hydroxyl group, or a hydroxy acid residue, H x A1 and H x A2 each represents a hydroxy acid residue, but H x A1 and H x This is a hydroxy acid residue with a different structure from A2. Note that when m=0, it becomes a compound with the structure represented by formula (4) described later, and is an aluminum hydroxy acid compound with an aluminum dinucleus as its basic structure.

[0057] H is a hydroxy acid residue x A1 and H x Examples of A2 include glycolic acid residues, lactic acid residues, methyl lactic acid residues, thio lactic acid residues, tartaric acid residues, citrate residues, salicylic acid residues, DL-mandelic acid residues, L-ascorbic acid residues, thioglycolic acid residues, malic acid residues, hydroxybutyrate residues, tartronic acid residues, glyceric acid residues, citramalic acid residues, isocitrate residues, leucic acid residues, mevalonic acid residues, pantoic acid residues, ricinoleic acid residues, ricineradicate residues, cerebronic acid residues, quinic acid residues, shikimic acid residues, gluconic acid residues, and amino acid residues. Examples of amino acid residues include glycine residues, alanine residues, cysteine ​​residues, phenylalanine residues, and glutamic acid residues.

[0058] In the crosslinking agent A according to this embodiment, H x A1 is H x While not particularly limited to hydroxy acid residues having a different structure from A2, lactate residues, methyllactic acid residues, thiolactic acid residues, or citrate residues are preferred. These hydroxy acid residues tend to exhibit superior crosslinking properties of X-NBR due to their good coordination and relatively low steric hindrance. xThe hydroxy acid residue of A1 is more preferably a lactate residue, a methyl lactate residue, or a thio lactate residue, and even more preferably a lactate residue. x From the viewpoint of superior crosslinking properties of X-NBR, it is preferable that the X bonded to the Al atom that bonds with A1 be a chlorine atom.

[0059] H x A2 is H x While not particularly limited to hydroxy acid residues having a different structure from A1, glycolic acid residues, malic acid residues, citrate residues, DL-mandelic acid residues, L-ascorbic acid residues, thioglycolic acid residues, or thiolactic acid residues are preferred. These hydroxy acid residues tend to have better crosslinking properties for X-NBR because they exhibit good coordination and relatively low steric hindrance.

[0060] H x When A2 is a glycolic acid residue, the steric hindrance is particularly small, which tends to result in particularly excellent crosslinking properties for X-NBR.

[0061] H x When A2 is a thioglycolic acid residue or an L-ascorbic acid residue, not only is there good crosslinking ability of X-NBR, but these ligands are reducing agents, which can impart antioxidant properties to the molded product.

[0062] H x If A2 is a lipophilic aromatic hydroxy acid residue such as a DL-mandelic acid residue or a salicylic acid residue, the compatibility between X-NBR particles can be increased, improving the chemical resistance and gas barrier properties of the molded article.

[0063] H x If A2 is a polyvalent carboxylic acid residue such as a citrate residue or a malic acid residue, not only do the hydroxyl group and carboxylate group at the α-position coordinate firmly to the aluminum, but the remaining carboxylic acid group also coordinates to the coordination site of the aluminum depending on the conditions, functioning as a secondary crosslinking site, making it possible to adjust the mechanical properties of the molded article, especially its elongation.

[0064] H x If A2 is an amino acid residue, the molded product properties and the particle interface properties of X-NBR can be adjusted according to the characteristics of various amino acid residues (reducing properties, lipophilicity, diversity of functional groups, etc.). Amino acids have an amino group (-NH2) at the α-position and can form bidentate coordination with a carboxylate group. However, their coordination to aluminum tends to be somewhat weaker compared to α-hydroxy acids such as lactic acid and glycolic acid, but by using them in combination with α-hydroxy acids, stable complex formation is possible even in the alkaline range of pH 7 to 10.

[0065] In the above general formula (1), m represents an integer from 0 to 18, but is preferably an integer from 0 to 10, more preferably an integer from 0 to 6, even more preferably an integer from 0 to 4, particularly preferably an integer from 0 to 2, and most particularly preferably 0. When m is within the above range, the amount of internal aluminum tends to be low and the reactivity is superior. The molecular chains in HAC may be linear or branched.

[0066] In HAC, the ratio A (aluminum atoms:chlorine atoms) of the number of moles of aluminum atoms to the number of moles of chlorine atoms is preferably 1:0.1 or more and 1:1.0 or less, and more preferably 1:0.2 or more and 1:0.6 or less. When the molar ratio is within the above range, the crosslinking reactivity tends to be superior.

[0067] In HAC, the ratio B (aluminum atoms:hydroxy acid residues) of the number of moles of aluminum atoms to the number of moles of hydroxy acid residues is preferably 1:0.5 or more and 1:1.5 or less, more preferably 1:0.7 or more and 1:1.3 or less, and even more preferably 1:0.8 or more and 1:1.2 or less. When the molar ratio B is within the above range, pH stability tends to be superior.

[0068] HAC is a double salt obtained by using PAC as the basic framework and reacting it with, for example, one or more hydroxy salts (hereinafter also simply referred to as "HxA") to PAC.

[0069] Examples of hydroxy salts include potassium hydroxyates, sodium hydroxyates, and ammonium hydroxyates. Specifically, these include potassium glycolate, sodium glycolate, potassium lactate, sodium lactate, potassium methyl lactate, sodium methyl lactate, potassium thio lactate, sodium thio lactate, potassium tartrate, sodium tartrate, potassium citrate, sodium citrate, potassium salicylate, sodium salicylate, potassium DL-mandelate, sodium DL-mandelate, potassium L-ascorbate, sodium L-ascorbate, sodium thioglycolate, potassium thioglycolate, potassium malate, sodium malate, potassium hydroxybutyrate, sodium hydroxybutyrate, potassium tartronate, sodium tartronate, and potassium glycerate. Examples include sodium glycerate, potassium citramarate, sodium citramarate, potassium isocitrate, sodium isocitrate, potassium leucate, sodium leucate, potassium mevalonate, sodium mevalonate, potassium pantoinate, sodium pantoinate, potassium ricinoleate, sodium ricinoleate, potassium ricinelidate, sodium ricinelidate, potassium cerebronate, sodium cerebronate, potassium quinate, sodium quinate, potassium shikimate, sodium shikimate, potassium gluconate, sodium gluconate, and amino acid salts. Among these, the hydroxy salt preferably includes at least one selected from the group consisting of potassium glycolate, sodium glycolate, potassium lactate, sodium lactate, potassium methyl lactate, sodium methyl lactate, potassium thio lactate, sodium thio lactate, potassium malate, sodium malate, potassium citrate, sodium citrate, potassium DL-mandelate, sodium DL-mandelate, potassium L-ascorbate, sodium L-ascorbate, sodium thioglycolate, and potassium thioglycolate, and more preferably includes at least one selected from the group consisting of sodium glycolate and sodium lactate. Furthermore, the hydroxy salt may also preferably include sodium hydroxyate.

[0070] When HAC has a binuclear aluminum salt as its basic framework, the structure of that HAC can be represented, for example, by the following formula (4). [ka] (In formula (4), X independently represents either a chlorine atom or a hydroxyl group, H x A1 and H x A2 each represents a hydroxy acid residue, but H x A1 and H x This is a hydroxy acid residue with a different structure from A2.

[0071] In crosslinking agent A containing HAC of formula (4), the total number of moles (x) of hydroxy acid residues is preferably 1.6 or more and 2.5 or less. When the total number of moles is within the above range, two aluminum atoms can efficiently form coordinate bonds with the hydroxy acid residues, and the compound tends to become more stable.

[0072] In crosslinking agent A containing HAC of formula (4), the hydroxy acid residue (H) relative to the aluminum atom x A1+H x The molar ratio of A2) is preferably 0.5 to 2.0, and more preferably 0.8 to 1.6.

[0073] Because the HAC represented by formula (4) has relatively little coordination of water molecules, even when an alkaline aqueous solution is added to the HAC and the pH exceeds 7, the proton release of the coordinated water is not significant, and crosslinking of aluminum by hydroxyl groups is unlikely to occur.

[0074] When the pH exceeds 9, the carboxylic acid of X-NBR changes to a carboxylate. Since carboxylates are bidentate ligands, they become more stable when coordinated to aluminum. Therefore, the carboxylate substitutes with chloride ions or hydroxyl ions that coordinate to aluminum. Thus, the carboxylate of X-NBR coordinates to HAC. Through this substitution reaction, a structure is formed on aluminum in which a stable five-membered ring complex formed by a hydroxyl acid and a bidentate ligand of the carboxylate derived from X-NBR are coordinated. This structure is aluminum The carboxylate, which satisfies all six coordination requirements for nium and has high electron-donating properties, stabilizes the positive charge of aluminum, resulting in a very stable state.

[0075] Furthermore, the aluminum atoms are linked by Al-(OH)2-Al bonds via hydroxyl groups, and this stable coordination structure forms a cross-linking structure with X-NBR. Thus, it is hypothesized that the stable five-membered ring complex formed by the hydroxy acid residues and the carboxylate derived from X-NBR bond to the aluminum at its center, achieving an extremely stable cross-linking structure in solution.

[0076] As an example of such a crosslinking structure, we hypothesize the following, where a dinuclear aluminum hydroxy acid chloride compound having lactate and glycolic acid residues as hydroxy acid residues coordinately bonded to the carboxylate of X-NBR.

[0077] [ka]

[0078] (Polyaluminum chloride) The basic structure of HAC is PAC, which is [Al2(OH) n Cl 6-n ] m (where 1 ≤ n ≤ 5 and 1 ≤ m ≤ 10.) It has a prepolymer structure represented by the chemical formula, and contains hydroxyl groups (-OH) and chloride ions (Cl - It is a polymeric complex in which multiple aluminum atoms are crosslinked via a rifling agent. This PAC is inexpensive, widely used in water treatment and other applications, and is a raw material that has no burden on the human body or the environment.

[0079] When PAC is dissolved in water, a structure is formed in which water molecules (H2O) coordinate to all coordination sites except the OH group and Cl group. By adding a hydroxy acid salt, the chloride ion in PAC is removed and replaced by the carboxylate group (-COO) of the hydroxy acid. - The hydroxyl group (-OH) in the hydroxy acid coordinates to the aluminum. Additionally, the alcoholic hydroxyl group (-OH) in the hydroxy acid also coordinates to the aluminum, causing the polymer structure to cleave and a more stable aluminum polynuclear complex to be formed.

[0080] The number of nuclei (number of Al atoms) in the aluminum polynuclear complex largely depends on the basicity of the raw material PAC. The basicity percentage is expressed as n / 6 (%). In this embodiment, the basicity of the raw material PAC is preferably 40% to 85%. This is because, normally, chloride ions play an important role after hydroxy acid residues coordinate to aluminum, so as the basicity percentage increases, the amount of chloride decreases, affecting the reactivity. Note that aluminum chloride (derived from AlCl3), which has a basicity of 0%, does not have a hydroxyl group, so it easily forms a mononuclear aluminum complex in reaction with hydroxy acids.

[0081] When the basicity of PAC is 60% or less, preferably 40% to 60%, the Al-(μ-OH)-Al bridged structure is relatively short, and complexes with a low number of nuclei, mainly dinuclear complexes (Al2 type), tend to be formed. On the other hand, when the basicity is greater than 60%, preferably 70% to 85%, In the case below, the Al-(μ-OH)-Al network tends to expand, and a multinuclear complex with three or more nuclei, in which more Al atoms are linked, tends to be formed.

[0082] As an example, a PAC with a basicity of 50% is represented by formula (6) below. Typically, PAC is expressed by formula (6).

[0083] [ka]

[0084] The dinuclear structure of PAC is more stable under acidic conditions (e.g., pH 5 to 6), and within this pH range, PAC tends to be uniformly dispersed in aqueous solutions and exhibit its maximum function as a flocculant.

[0085] In a basic environment with a pH of 7 or higher, the stability of PAC decreases, and the dinuclear structure decomposes to form aluminum hydroxide. This aluminum hydroxide becomes gel-like and precipitates in solution. This gelation is presumed to be due to the following reaction mechanism.

[0086] When an alkaline aqueous solution is added to a PAC aqueous solution, the 6-coordinate environment of aluminum changes, and the following reaction proceeds. Aluminum in PAC forms some of the coordination sites with hydroxyl ions (OH) - ) and chloride ions (Cl - ) occupies the coordination site, and water molecules (H2O) coordinate to the remaining coordination site. When an alkaline aqueous solution is added in this state, the high positive charge of aluminum causes the water molecules to contract protons (H + It releases hydroxyl ions, which increase the amount of hydroxyl ions around the aluminum.

[0087] As the alkaline aqueous solution is added, chloride ions dissociate from their electrostatic bonds and are released into the solution. In particular, when the pH reaches near neutral (about 7), hydroxyl ions form cross-links between aluminum atoms, and the chloride ions are almost completely released. As this reaction progresses, the aluminum becomes multinucleated, and finally, when the pH exceeds 7, Al-O-Al bonds are formed by dehydration condensation, and an aluminum hydroxide gel is produced.

[0088] Thus, the main reason why PAC gels in a basic environment is the disruption of the balance between chloride ions and hydroxyl ions that stabilize the dinuclear structure. For this reason, to effectively use PAC, it is preferable to maintain the reaction conditions at a pH of 6.5 or lower. At pH 8 or higher, gelation becomes more pronounced, and it becomes difficult to maintain the homogeneity of the solution. To maintain the homogeneity of the solution, that is, to dissolve the dinuclear aluminum complex in water, it is effective to add an appropriate ligand that stabilizes the dinuclear structure.

[0089] Commercially available PACs can be used. Examples of such commercially available products include PAC N003 (product name) manufactured by HENAN TAIRAN WATER PURIFICATION MATERIAL CO. LTD, PAC (product name) manufactured by SHANDONG YURUN CHEMICAL CO., LTD, and PAC manufactured by Asada Chemical Industries, Ltd. One example is PAC#100P (product name).

[0090] A suitable ligand for dissolving a dinuclear aluminum complex in water to obtain a homogeneous solution is a hydroxycarboxylic acid. Adding this hydroxycarboxylic acid to the PAC solution To obtain HAC, it is effective to add an appropriate ligand that stabilizes the dinuclear structure. Since the aluminum hydroxy acid salt compound is more stable and has better compatibility with X-NBR raw materials, the crosslinking agent is preferably an aqueous solution with a pH of 7.5 to 8.4. When the pH is within the above range, the coordination bond between the hydroxy acid residue and the aluminum atom is maintained. Furthermore, at a pH of 9.0 or lower, preferably 8.4 or lower, it shows long-term stability and tends not to decompose or precipitate during storage.

[0091] Crosslinking agent A is preferably used in dip molding from the viewpoint of enjoying the effects of the present invention more fully. Crosslinking agent A is preferably applied to the X-NBR dip molding composition described later. In that case, the aqueous solution of crosslinking agent A may be adjusted to a pH range of 9.0 to 10.5. Within this range, it exhibits higher crosslinking reactivity.

[0092] In crosslinking reactions in solutions containing X-NBR, crosslinking agent A tends to be more effective under conditions of pH 9.0 to 10.5. Within this pH range, the hydroxy acid residue stabilizes the aluminum atom, maintaining the chloride ion bond. Furthermore, the chloride ion functions as an excellent leaving group, and the carboxylate (-COO) of X-NBR is bonded. - By efficiently reacting with crosslinking agent A, X-NBR forms a uniform crosslinked structure. Furthermore, the crosslinking agent maintains stability, allowing for long-term storage.

[0093] The crosslinking reaction proceeds as follows, for example, as shown in formulas (7) and (8) below. Note that in the crosslinking reaction shown in formulas (7) and (8) below, H is used as the hydroxy acid residue. x A1 and H xThis is an example of a crosslinking agent containing a dinuclear aluminum hydroxylate compound having A2.

[0094] [ka]

[0095] [ka]

[0096] The carboxylate of the hydroxy acid residue of crosslinking agent A coordinates to aluminum, and at the same time, the lone pair of electrons on the oxygen of the hydroxyl group (-OH group) of the hydroxy acid residue is donated to the aluminum. As a result, the trivalent aluminum cation is further neutralized, and a stable structure can be achieved even at pH levels above 8.0. This increases the coordination bonding ability of chloride ions. In the case of aluminum cations, X can be not only chloride ions, but also hydroxides. Ion (OH) - Even if hydroxide ions are coordinated, these hydroxide ions can also exchange with the carboxylate of X-NBR, allowing the carboxylate to coordinate to aluminum. In alkaline environments with a pH of 8.0 or higher, there are many hydroxide ions, but the reaction proceeds because the coordination of carboxylate to aluminum is thermally stable.

[0097] Under these conditions, the carboxylic acid of X-NBR sequentially converts to carboxylate (-COO) at pH 9.0 or higher. - However, since carboxylates have higher coordination bonding ability than chloride ions, aluminum forms coordination bonds with both the carboxylate of the hydroxy acid residue and the carboxylate of X-NBR. Because this structure is energetically stable, the reaction with the carboxylate of X-NBR proceeds easily even in solution. Therefore, the crosslinking reaction of X-NBR with a crosslinking agent proceeds easily simply by raising the pH.

[0098] When adding crosslinking agent A, the pH of the X-NBR solution must be 9.0 or lower, preferably 8.5 or lower. In an alkaline solution with a pH within the above range, the carboxylic acid-modified group of X-NBR is in the form of carboxylic acid (-COOH), and the crosslinking agent is added to the X-NBR solution in this state. Since the crosslinking agent has low reactivity with carboxylic acid, the pH should be 9.0 or lower during the homogenization process.

[0099] After thoroughly homogenizing the composition to which crosslinking agent A has been added, an alkaline aqueous solution is slowly added to raise the pH to a predetermined range. The predetermined pH range is between 9.0 and 10.5. Under these conditions, the crosslinking agent is based on aluminum hydroxylate and converts stable aluminum into chloride ions (Cl - The carboxylate of X-NBR is eliminated, and the carboxylate of X-NBR and the aluminum of the crosslinking agent form a coordinate bond. This crosslinking reaction proceeds in solution, forming a uniform crosslinked structure. The crosslinking reaction with the carboxylate of X-NBR takes approximately 10 to 24 hours, although this varies depending on the concentration of crosslinking agent A. However, the crosslinking time can be shortened by heating the compound to approximately 50°C.

[0100] Subsequently, the film is formed using a standard dip molding process. This film is already crosslinked and requires no heating; simply drying it provides sufficient mechanical strength and fatigue resistance in artificial sweat. Due to these properties, the film can be widely used in medical and industrial applications.

[0101] Molded articles using crosslinking agent A exhibit diverse properties depending on the grade of X-NBR used. For example, disposable rubber gloves with an average film thickness of approximately 60 μm have the following properties: the tensile strength of the rubber gloves is 18 MPa or higher, and the elongation is 550% or higher. Furthermore, the rubber gloves do not cause type IV allergies and are safe.

[0102] Crosslinking agent A is widely applicable to medical gloves, industrial gloves, and other rubber products. Furthermore, because it does not require a heating process, it significantly contributes to reducing energy consumption and environmental impact.

[0103] [Crosslinking agent B] The crosslinking agent B according to one embodiment of the present invention comprises a compound having a structure represented by the following general formula (1) and an organic acid. [ka] (In formula (1), m represents an integer from 0 to 18, X independently represents a chlorine atom or a hydroxyl group, Y independently represents a chlorine atom, a hydroxyl group, or a hydroxy acid residue, H x A1 and H x A2 represents a hydroxy acid residue. x A1 and H x A2 may have the same structure or a different structure. Note that when m=0, the compound will have the structure represented by formula (4) above, and will be an aluminum hydroxyate compound with an aluminum dinucleus as its basic structure.

[0104] The crosslinking agent B according to this embodiment can be the same as the crosslinking agent A described above, except that it contains an organic acid.

[0105] The crosslinking agent B according to this embodiment contains a compound having the structure represented by the general formula (1) above, H x A1 and H x This is the same as the aluminum hydroxylate compound described above, except that it may be a hydroxy acid residue having the same structure as A2.

[0106] H x A1 and H x A2 is a hydroxy acid residue that has the same structure as H x A1 and H x A2 and H are both lactate residues, or x A1 and H x Examples include cases where both A2 and H are glycolic acid residues. If crosslinking agent B is present in this embodiment, then H xA1 and H x Even hydroxy acid residues that have the same structure as A2 exhibit superior fatigue resistance.

[0107] The crosslinking agent B according to this embodiment contains a compound having the structure represented by the general formula (1), similar to the aluminum hydroxylate compound described above, H x A1 and H x The hydroxy acid residue may have a different structure from A2. In this case, it tends to have better fatigue resistance and tensile strength.

[0108] The organic acid contained in the crosslinking agent B according to this embodiment is not particularly limited, but examples include fatty acids such as formic acid, acetic acid, and propionic acid, hydroxy acids corresponding to the hydroxy acid residues mentioned above, and salts thereof. The organic acid may be used alone or in combination of two or more. The organic acid is preferably formic acid, acetic acid, or propionic acid. Using these organic acids tends to result in superior fatigue durability of the molded article.

[0109] The content of organic acids is not particularly limited, but is preferably 1% to 15% by mass, more preferably 3% to 10% by mass, and even more preferably 5% to 8% by mass, based on the total mass of the crosslinking agent B.

[0110] The crosslinking agent B according to this embodiment may include a compound having a structure represented by the following general formula (1)'. [ka] (In formula (1)', m represents an integer from 0 to 18, X independently represents a chlorine atom, a hydroxyl group, or an organic acid residue, Y independently represents a chlorine atom, a hydroxyl group, an organic acid residue, or a hydroxy acid residue, H x A1 and H x A2 represents a hydroxy acid residue. x A1 and H xA2 may have the same structure or a different structure. Note that when m=0, the compound will have the structure represented by formula (2)' below, and will be an aluminum hydroxyate compound with an aluminum dinucleus as its basic structure. [ka]

[0111] Compounds having the structure represented by general formula (1)' are the same as compounds having the structure represented by general formula (1) above, except that water (H2O) is not coordinated to each Al, and organic acid residues can be selected for X and Y. Examples of organic acid residues include fatty acid residues and the hydroxy acid residues mentioned above. Other examples of organic acid residues include formic acid residues, acetic acid residues, and propionic acid residues. Preferably, the organic acid residue is one or more selected from formic acid residues, acetic acid residues, and propionic acid residues, and more preferably formic acid residues, acetic acid residues, or propionic acid residues.

[0112] When X and Y in a compound having the structure represented by general formula (1)' are organic acid residues, the coordination exchange reaction with the carboxylate group of X-NBR is promoted, enabling crosslinking in a shorter time and potentially resulting in superior fatigue durability of the molded article. Since the organic acid residues and the carboxylate group of X-NBR have similar structures, this coordination exchange reaction is considerably more advantageous than other cases.

[0113] In this case, the crosslinking reaction proceeds as shown in formula (9) below, for example. In formula (9) below, the crosslinking agent is a compound having a structure represented by formula (2)' of the above general formula (1)' where m=0, and H x A1 is a lactate residue, H x This includes compounds having a structure in which A2 is a glycolic acid residue and X are acetic acid residues.

[0114] As shown in formula (9) below, the coordination exchange reaction with the carboxylate group of X-NBR is promoted in aluminum hydroxy acid chloride compounds to which an acetate residue is coordinated, for example, by the elimination of K(CH3COO). Therefore, it is presumed that if the crosslinking agent B according to this embodiment contains a compound having a structure represented by general formula (1)' in which X and Y are fatty acid residues, crosslinking can be formed in a shorter time, and the fatigue durability of the molded article may be superior.

[0115] [ka]

[0116] [Method for producing crosslinking agent A] A method for producing a crosslinking agent A according to one embodiment of the present invention includes the steps of: obtaining a solution containing a hydroxy salt; obtaining a solution containing polyaluminum chloride; and mixing the solution containing polyaluminum chloride with the solution containing a hydroxy salt. By going through such steps, HAC can be suitably produced. Each step will be described below.

[0117] (Step to obtain a solution containing hydroxy salts) A solution containing a hydroxy salt will be referred to here as a drop solution. The solution containing the hydroxy salt may be basic, and can be prepared to be basic using an aqueous solution of an alkaline compound such as sodium hydroxide, potassium hydroxide, or ammonia. Among these, an aqueous solution of sodium hydroxide is preferred. Furthermore, the solution containing the hydroxy salt may be prepared, for example, at room temperature, or by heating it to a temperature between 30°C and 50°C.

[0118] For hydroxy salts, refer to the above. Hydroxy salts may be used alone or in combination of two or more. When two or more hydroxy salts are used in combination, it is preferable to include a first hydroxy salt selected from lactic acid, methyllactic acid, thiolactic acid, and citric acid, and a second hydroxy salt selected from glycolic acid, malic acid, citric acid, DL-mandelic acid, L-ascorbic acid, thioglycolic acid, and thiolactic acid. The inclusion of these hydroxy salts tends to result in superior fatigue durability of the molded article. Furthermore, the compound solution containing the crosslinking agent and X-NBR tends to mature in a short time of 24 hours or less and exhibit superior tensile strength stability.

[0119] In a solution containing a hydroxyate salt, the molar ratio (B / A) of the second hydroxyate salt (B) to the first hydroxyate salt (A) is preferably 5 / 95 or more and 95 / 5 or less, more preferably 30 / 70 or more and 70 / 30 or less, even more preferably 40 / 60 or more and 60 / 40 or less, and particularly preferably 45 / 55 or more and 55 / 45 or less. When the molar ratio (B / A) is within the above range, the fatigue durability of the molded article tends to be superior. Furthermore, the compound solution containing the crosslinking agent and X-NBR can be matured in a short time of 24 hours or less and used for dip molding, and tends to produce a molded article with excellent tensile strength stability.

[0120] The hydroxy salt content is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 45% by mass or less, even more preferably 15% by mass or more and 40% by mass or less, particularly preferably 15% by mass or more and 35% by mass or less, and most particularly preferably 20% by mass or more and 30% by mass or less, based on the total mass of the solution.

[0121] The alkali compound content is preferably between 1% by mass and 20% by mass relative to the total mass of the solution. Furthermore, 3% by mass or more and 15% by mass or less is more preferable, and 5% by mass or more and 10% by mass or less is even more preferable.

[0122] Multiple steps are taken to obtain a solution containing a hydroxy salt, thereby obtaining a solution containing multiple hydroxy salts.

[0123] (Step to obtain a solution containing polyaluminum chloride) Here, the solution containing polyaluminum chloride will be referred to as the bottom solution. The solution containing polyaluminum chloride can be prepared, for example, by dissolving PAC (polyaluminum chloride) in water heated to a temperature of 40°C to 80°C (preferably 60°C to 80°C). To ensure suitable mixing with the drop solution, it is preferable to continue heating the bottom aqueous solution at a temperature of 40°C to 80°C (preferably 60°C to 80°C). For PAC, please refer to the above information.

[0124] The aluminum concentration (in terms of Al2O3) in a solution containing polyaluminum chloride is preferably 15% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 45% by mass or less.

[0125] The calcium ion content in the polyaluminum chloride is preferably less than 500 ppm by mass relative to the total amount of polyaluminum chloride. When the calcium ion content is less than 500 ppm by mass, aggregation of the copolymerized elastomer can be suppressed when the crosslinking agent is used in the dip molding composition described later.

[0126] (Mixing process) In the mixing step, a solution containing polyaluminum chloride (drop solution) and a solution containing hydroxy salt (bottom solution) are mixed. A mixture is obtained by mixing the drop solution and the bottom aqueous solution. One mixing method is to add the drop solution to the bottom solution, which has been heated to between 60°C and 80°C, and then stir.

[0127] When adding the solution, it is preferable that the molar ratio of the hydroxyate salt contained in the drop solution to the molar amount of aluminum in the PAC contained in the bottom solution be in the range of 0.5 to 2.0.

[0128] When adding the drop solution to the bottom solution, it is preferable to gradually add the entire amount of the drop solution over a period of time of preferably 10 minutes to 60 minutes, more preferably 20 minutes to 50 minutes, and even more preferably 25 minutes to 35 minutes.

[0129] When adding multiple drop solutions, it is preferable to add each drop solution according to the time specified above.

[0130] The molar ratio (D / C) of hydroxy acid salts (D) to aluminum atoms (C) in polyaluminum chloride is preferably 0.5 to 2.0, and more preferably 0.8 to 1.6. When the molar ratio (D / C) is within the above range, the fatigue durability of the molded article tends to be superior. Furthermore, the compound solution containing the crosslinking agent and X-NBR can be matured in a short time of 24 hours or less and used for dip molding, and tends to produce a molded article with excellent tensile strength stability.

[0131] The stirring time after addition is usually between 30 and 120 minutes, taking into account the reaction time. Since the pH gradually increases during the reaction, it is preferable to maintain the pH at 7 or below, preferably on the acidic side. Maintaining the pH on the acidic side prevents the aluminum from gelling during the reaction. PAC can be cleaved by hydroxy acid salts, allowing it to complete coordination with hydroxy acids while maintaining its dinuclear structure as the basic framework.

[0132] (pH adjustment process) The method for producing the crosslinking agent according to this embodiment may include a pH adjustment step. By adjusting the pH of the mixed solution of the drop solution and the bottom solution, an aluminum hydroxylate compound can be preferably obtained in an aqueous solution.

[0133] The pH is preferably adjusted to 7.5 or more and 8.4 or less. As the adjustment of the pH, for example, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, and aqueous ammonia can be used. As the preparation of the pH, it is preferable to use an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution. When adjusting the pH, it is usually carried out at room temperature.

[0134] (Method for identifying aluminum hydroxyacid chloride compound) The obtained PAC can be identified by a known method. Such methods include, for example, 27 Al-NMR (nuclear magnetic resonance), 13 C-NMR, mass spectrometry, osmotic pressure method, ICP-AES (inductively coupled plasma atomic emission spectrometry), and FT-IR (Fourier transform infrared spectroscopy).

[0135] [Method for manufacturing crosslinking agent B] The method for manufacturing crosslinking agent B according to an embodiment of the present invention includes a step of obtaining a solution containing hydroxyacid salt, a step of obtaining a solution containing fatty acid, a step of obtaining a solution containing polyaluminum chloride, and a step of mixing the solution containing polyaluminum chloride, the solution containing the fatty acid, and the solution containing hydroxyacid salt.

[0136] In the method for manufacturing crosslinking agent B according to this embodiment, except for the step of obtaining a solution containing fatty acid, it can be the same as the method for manufacturing crosslinking agent A described above.

[0137] (Step of obtaining a solution containing fatty acid) The solution containing fatty acid is also referred to as a drop solution. The solution containing fatty acid may be basic, and for example, it can be prepared to be basic using an aqueous solution of an alkali compound such as sodium hydroxide, potassium hydroxide, ammonia, etc. Among these, it is preferable to use an aqueous sodium hydroxide solution. Also, the solution containing fatty acid may be prepared, for example, at room temperature, or may be prepared by heating at 30°C or more and 50°C or less. For fatty acids, refer to the above.

[0138] The fatty acid content is preferably 10% to 40% by mass, more preferably 15% to 35% by mass, and even more preferably 20% to 30% by mass, relative to the total mass of the solution.

[0139] The alkali compound content is preferably 1% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less, relative to the total mass of the solution.

[0140] Furthermore, for long-term storage, it is desirable to add a preservative to both crosslinking agent A and crosslinking agent B of the present invention to prevent spoilage by microorganisms and bacteria. Suitable preservatives include those used in food additives and cosmetics. For example, it is preferable to add potassium sorbate at a concentration of approximately 0.05% to 0.5% by mass relative to the total amount of crosslinking agent and to store the product at a pH of 6.0 to 6.5. Under these storage conditions, long-term storage of approximately six months to one year becomes possible.

[0141] Furthermore, it has been confirmed that the addition of preservatives such as potassium sorbate does not affect the performance of the crosslinking agent in any way.

[0142] Furthermore, when using a crosslinking agent solution stored in this manner, it is preferable to adjust the pH to approximately 7.0 to 9.0 using an alkaline solution such as NaOH, KOH, or ammonia before use.

[0143] [Composition for dip molding] A dip molding composition according to one embodiment of the present invention (hereinafter also simply referred to as "the composition") comprises the crosslinking agent described above, a copolymer elastomer, a pH adjusting agent, and water, wherein the copolymer elastomer comprises a constituent unit derived from (meth)acrylonitrile, a constituent unit derived from an ethylenically unsaturated carboxylic acid, and a constituent unit derived from butadiene, and the pH of the composition is 8.5 or higher and 10.5 or lower.

[0144] The composition serves as a raw material for manufacturing film-shaped molded products using a dipping solution.

[0145] The composition preferably contains substantially no elemental sulfur and zinc oxide. Because the composition does not contain elemental sulfur for crosslinking, a vulcanization accelerator, and zinc oxide for crosslinking, the risk of developing type IV allergies is reduced, and it can also contribute to reducing the environmental burden. In this specification, "substantially free of elemental sulfur and zinc oxide" means, for example, that the amount of elemental sulfur for crosslinking in the composition is 0.3% by mass or less, and the amount of zinc oxide for crosslinking in the composition is 0.2% by mass or less.

[0146] In the composition, the content of the crosslinking agent described above is preferably 0.1 parts by mass to 1.5 parts by mass, and more preferably 0.2 parts by mass to 0.8 parts by mass, in terms of aluminum oxide, per 100 parts by mass of copolymer elastomer. When the crosslinking agent content is within the above range, the tensile strength and elongation tend to be superior.

[0147] The molded body of the composition is preferably a glove.

[0148] (Copolymer elastomer) Copolymerized elastomers include, for example, carboxylic acid-modified elastomers. As copolymerized elastomers, various elastomers containing NBR (nitrile butadiene rubber) can also be used. It is preferable to use X-NBR (carboxylate-modified nitrile butadiene rubber) as the carboxylic acid-modified elastomer.

[0149] The composition contains a latex, which is an aqueous dispersion in which particles of a copolymerized elastomer compound are dispersed in water. In this embodiment, it is preferable to contain an X-NBR latex in which X-NBR particles containing X-NBR molecules are dispersed in water.

[0150] The copolymer elastomer consists of copolymer particles containing 20.0% to 40.0% by mass of structural units derived from (meth)acrylonitrile (acrylonitrile or methacrylonitrile), 1.5% to 6.0% by mass of structural units derived from ethylenically unsaturated carboxylic acid, and 59.0% to 78.5% by mass of structural units derived from butadiene, and water. The copolymer elastomer is used as X-NBR latex. The polymerization composition of X-NBR may also contain monomers for self-crosslinking.

[0151] X-NBR latex is preferably manufactured by emulsion polymerization. In this case, the X-NBR particles contained in the X-NBR latex are X-NBR and dodecylbenzenesulfonic acid The copolymer is surrounded by a surfactant such as sodium, forming particles.

[0152] When X-NBR is used as a copolymer elastomer, the basic physical properties of X-NBR latex and molded articles using it can be altered by varying the composition ratio of structural units, the polymerization temperature during emulsion polymerization, the amount of polymerization initiators such as ammonium persulfate (which are radical initiators), the amount of modifiers such as tert-dodecyl mercaptan, and the polymerization conversion rate. The functions of each structural unit in the X-NBR molecule are as follows: acrylonitrile provides strength and chemical resistance to the molded article, while butadiene provides rubber-like softness. Ethylene-unsaturated carboxylic acids are used for interparticle crosslinking with zinc oxide, aluminum crosslinking agents, and water-soluble crosslinking agents. However, if the amount of ethylenically unsaturated carboxylic acid is too high compared to the aforementioned composition ratio range, the molded article tends to become hard and difficult to stretch. Each of these components can be suitably used as long as it is within the aforementioned composition ratio range of structural units. Examples of ethylenically unsaturated carboxylic acids include acrylic acid and methacrylic acid, with methacrylic acid being preferred.

[0153] By further incorporating unsaturated carboxylic acid amides such as (meth)acrylamide and N,N'-dimethylacrylamide into X-NBR latex in a structural unit content of 1% to 3% by mass, the molded article can be given physical properties such as flexibility and strength.

[0154] While the pH of this X-NBR latex is typically between 8.0 and 8.3, in dip molding compositions, the overall pH is adjusted to between 8.5 and 10.5. At pH levels between 8.0 and 8.3, the carboxyl groups (-COOH) of X-NBR are located at and near the interface of the X-NBR particles. In contrast, by increasing the pH further, the carboxyl groups of X-NBR become carboxylates (-COOH). - This allows the particles to be oriented outwards as a carboxylate (-COO). This action enables interparticle crosslinking with a crosslinking agent containing HAC. Carboxylate (-COO) oriented between X-NBR particles - ) is pH-dependent; as alkalinity increases, the carboxylate content increases, which promotes the crosslinking reaction by the crosslinking agent, thereby increasing the strength and modulus of the rubber gloves.

[0155] For example, in mass production such as glove manufacturing, the composition needs to be stable under alkaline conditions with a pH of 8.5 to 10.5 for approximately 3 to 5 days. HAC is characterized by its stable use, unlike crosslinking agents that generally use aluminum, which tend to gel under alkaline conditions.

[0156] Unlike conventional metal crosslinking agents such as zinc, which are used in combination with other covalent crosslinking methods, HAC allows for the production of molded articles, such as gloves, solely through crosslinking with this compound. In this embodiment, since the gloves produced by dip molding using the crosslinking agent primarily involve crosslinking between X-NBR particles, other organic crosslinking agents capable of intraparticle covalent bonding may be used in combination.

[0157] (pH adjuster) Examples of pH adjusting agents include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and ammonium compounds such as ammonium hydroxide. Preferably, aqueous potassium hydroxide solution and aqueous ammonia solution are used as pH adjusting agents. It is preferable to add the pH adjusting agent so that the pH of the composition is adjusted to a range of 8.5 to 10.5.

[0158] (optional ingredient) For example, in the manufacture of gloves, the composition may typically contain optional components such as dispersants, antioxidants, and pigments in addition to the components mentioned above.

[0159] Examples of dispersants include anionic surfactants such as sulfonates. Examples of antioxidants include hindered phenols. Examples of pigments include titanium dioxide.

[0160] [Method for manufacturing molded articles and gloves using the composition] A method for manufacturing a molded article by dip molding (dipping method) using the above-described dip molding composition will be explained using a typical example of a glove manufacturing method. The glove of this embodiment is formed by molding a constituent material containing the above-described dip molding composition.

[0161] In this embodiment, the manufacturing process for gloves, which are molded bodies of the above-described dip molding composition, includes the following steps. The glove manufacturing process is, (1) A process of applying a coagulant to a glove mold to obtain a mold or former (a process of applying a coagulant to a glove mold), (2) A maturation step in which the composition is stirred to obtain a dipping solution (a step in which a composition for dipping and stirring is prepared), (3) A dipping step (a step of immersing a glove mold in a dip molding composition) in which the mold or former is immersed in the dip liquid to form a film on the mold or former, (4) A gelling step to obtain a pre-dried crosslinked film by gelling the film (a step of pre-drying the film formed on the glove mold to create a crosslinked film precursor), (5) A leaching step to remove impurities from the crosslinked film to obtain the glove precursor 1 (a step to remove impurities from the crosslinked film formed on the glove molding die), (6) A beading step to create a bead on the cuff portion of the glove precursor 1 to obtain a glove precursor 2 having a bead (a step to create a bead on the cuff portion of the glove), (7) The process includes a drying step (a step of heating and drying at a temperature necessary for the crosslinking reaction) in which the glove precursor 2 is heated and dried to obtain a molded glove. Steps (3) through (7) shall be carried out in the order described above.

[0162] Furthermore, the following step (6') may be optionally included between step (6) and step (7). (6') Pre-drying process (a process in which glove precursor 2 is heated and dried at a lower temperature than the main drying process).

[0163] Furthermore, the aforementioned manufacturing method also includes a method for manufacturing gloves by so-called double dipping, in which steps (3) and (4) described above are each repeated twice.

[0164] In this specification, a film-forming crosslinked film refers to a film composed of elastomers aggregated on a glove mold by a coagulant in the dipping process, and which has been partially gelled by the dispersion of calcium in the gelling process, prior to the final drying.

[0165] The following provides a detailed explanation of each step. (1) Coagulant application process (a) The coagulant application process involves applying a mold or former (glove mold) to a mold and gelling agent, Ca 2+This step involves immersing the mold or former in a coagulant solution containing ions in an amount of 5% to 40% by mass, preferably 8% to 35% by mass. The time for applying the coagulant to the surface of the mold or former is determined as appropriate, usually between 10 and 20 seconds. Calcium nitrate or chloride is used as the coagulant. Other inorganic salts that have the effect of precipitating elastomers may also be used. Among these, calcium nitrate is preferred. This coagulant is usually used as an aqueous solution containing 5% to 40% by mass. It can be done.

[0166] Furthermore, the solution containing the coagulant preferably contains approximately 0.5% to 2% by mass, for example, about 1% by mass, of potassium stearate, calcium stearate, mineral oil, or ester-based oil as a release agent.

[0167] (b) Place the mold or former coated with the coagulant solution into an oven at a temperature of approximately 50°C to 140°C for 30 seconds to 3 minutes to allow the coagulant to adhere to the entire or partial surface of the glove mold. It should be noted that the surface temperature of the glove mold after drying will be around 60°C, which will affect subsequent reactions.

[0168] (c) Calcium not only functions as a coagulant to form a film on the surface of the glove mold, but also contributes to the crosslinking function of a significant portion of the final glove. However, calcium alone has weak binding strength and is prone to cracking due to immersion in artificial sweat solution or stress loading. In this crosslinking technology, the crosslinking agent containing aluminum hydroxylate of this embodiment is bound to the carboxylate of X-NBR in the compound solution, making it possible to reduce the binding of calcium to X-NBR.

[0169] (2) Maturation process (a) The maturation process is a process of preparing a dip molding composition and dispersing it uniformly while stirring.

[0170] (b) In a typical X-NBR manufacturing process, sulfur, vulcanization accelerator, zinc oxide, pigment, and antioxidant are added and diluted to a predetermined concentration. At the same time, an alkali adjusting agent such as potassium hydroxide aqueous solution or ammonia aqueous solution is added to adjust the pH to 9.2-10.2, thereby creating a uniform dip molding solution.

[0171] However, this embodiment incorporates significant improvements to the conventional manufacturing process. Pigments, antioxidants, and other additives can be used as before, but elemental sulfur for crosslinking, vulcanization accelerators, and zinc oxide for crosslinking are not added. In this embodiment, the order of the steps is very important because the crosslinking reaction proceeds during the preparation of the compound solution. Additives such as pigments and antioxidants can be added in the conventional way, but the addition of HAC (diluted to 4% by mass or less, preferably 3% by mass or less, in terms of aluminum oxide) is done before pH adjustment. The initial pH of X-NBR is usually around 8.0 to 8.6, and at this stage, the carboxylic acid has not yet dissociated into carboxylate. HAC is added in this state. X-NBR is shipped from the manufacturer at a concentration of 45% by mass, so it can be used as is, but if possible, it should be diluted to about 35% by mass beforehand, and HAC adjusted to 0.5% to 4% by mass in terms of aluminum oxide is added to create a homogeneous solution.

[0172] It is important to slowly add the alkali adjusting agent to the X-NBR solution with added HAC while stirring thoroughly. In this step, the aluminum in HAC and the carboxylic acid in X-NBR coordinate bond, and the crosslinking reaction proceeds sequentially. The alkali adjusting agent should be added over a period of 30 minutes to 5 hours. If the addition rate is too fast, localized crosslinking reactions may occur, and there is a risk of clump formation. Such clumps can cause non-uniformity during film formation, so caution is necessary.

[0173] Furthermore, if aggregates are observed in the dip solution after the addition of HAC, it is preferable to further dilute the HAC and adjust the amount of aluminum in the diluted solution to approximately 0.5% by mass or more and 1.0% by mass or less, in terms of aluminum oxide.

[0174] (c) The aluminum crosslinking agent for dip molding usually has a pH of around 4, but to prevent the latex from experiencing acid shock, it is necessary to adjust the pH beforehand to around 7 to 9 using a pH adjusting agent such as an aqueous sodium hydroxide solution or ammonia solution. At this time, the aluminum crosslinking agent for dip molding is stable without gelling.

[0175] (3) Dipping process The dipping process involves pouring the dip molding composition (dip liquid) prepared in the maturation process into a dip tank, and immersing the mold or former, which has been coated with a coagulant and dried in the coagulant application process, into the dip tank for typically 1 second to 60 seconds under temperature conditions of 25°C to 35°C. In this process, the elastomer contained in the dip molding composition aggregates on the surface of the mold or former due to the calcium ions contained in the coagulant, forming a film. At this time, HAC is strongly bonded to the carboxyl groups of the latex.

[0176] (4) Gering process The gelling process is a process of gelling the film to obtain a pre-dried, cross-linked film. Typically, this is done by heating the film in a gelling oven to around 40°C to 110°C. The heating time is usually between 1 and 3 minutes. Alternatively, since the mold or former already has a certain temperature, and the ambient temperature in the factory is around 30°C to 50°C, the film may be left at this temperature for a certain period of time. The gelling process aims to disperse calcium in the cross-linked film simultaneously with gelation. This is because calcium crosslinks constitute a significant portion of the final glove's properties and form the basis of its physical characteristics.

[0177] (5) Reaching process (a) The leaching process is a process in which excess chemicals and impurities such as calcium deposited on the surface of the cross-linked film that would interfere with subsequent curing are washed off with water to obtain glove precursor 1. Typically, the mold or former is immersed in warm water at 30°C to 70°C for about 1 minute to 4 minutes.

[0178] (b) In this process as well, HAC is firmly bound to the X-NBR particles and is therefore not removed by washing.

[0179] (6) Beading process This step involves rolling up the cuff end of the glove formed from glove precursor 1 after the leaching process to create a ring of appropriate thickness, reinforcing it, and obtaining glove precursor 2. Performing this step in a wet state after the leaching process results in good adhesion of the rolled portion.

[0180] (6') Pre-drying process (a) After the beading step, the glove precursor 2 formed into the glove shape is heated and dried at a lower temperature than the subsequent main drying step. Typically, this step involves heating and drying at 60°C to 90°C for 30 seconds to 5 minutes. If the main drying step is performed at a high temperature without going through the pre-drying step, the moisture will evaporate rapidly, causing blister-like bumps on the glove and impairing its quality. However, it is also possible to proceed directly to the main drying step without going through this pre-drying step.

[0181] (b) Although the temperature may be raised to the final temperature of this drying process without going through this process, if drying is performed in multiple drying ovens and the temperature of the first drying oven is slightly lower, this first drying process is considered a pre-drying process.

[0182] (7) Main drying process (a) This drying step involves heating the glove precursor 2 formed into the glove shape described above, and finally drying it to obtain a molded glove. The heating temperature and time are preferably selected appropriately from the temperature required to cause the crosslinking reaction and drying. For example, the molded glove of this embodiment can be dried by heating at 50°C to 70°C for about 15 minutes to 30 minutes. (b) In this final drying process, the moisture contained in the film is removed, and the glove is completed. Note that the chloride ions that were coordinated to aluminum in the HAC in the compand solution undergo ligand exchange with the carboxylates of the X-NBR particles. The carboxylates of the X-NBR particles are coordinated to aluminum, and crosslinking does not proceed in this process. At the same time, the binding of potassium (K) and calcium (Ca) to the carboxylates of the X-NBR particles, which weaken the physical properties of the glove, is also suppressed.

[0183] (8) Double dipping Regarding the method for manufacturing gloves, the above description was about the so-called single dipping. In contrast, the dipping process and the gelling process may be performed two or more times, which is usually referred to as double dipping. Double dipping is carried out for the purpose of preventing the generation of pinholes, etc., when manufacturing thick gloves (with a film thickness of about 200 μm or more and 300 μm or less) or in the manufacturing method of thin gloves.

[0184] As a point to note in double dipping, in the second dipping process, in order to aggregate the X-NBR particles, it is preferable to spend sufficient time in the gelling process in the first gelling process to deposit calcium sufficiently on the film surface. <(

[0185] 〔Crosslinked product using the composition〕 The molded product manufactured by the above manufacturing method can be used in various forms. For example, it can be suitably used for gloves. Hereinafter, gloves, particularly X-NBR gloves crosslinked with X-NBR, will be described, but it can also be applied to molded products other than gloves.

[0186] Since the particle size of X-NBR particles is about one-tenth that of natural rubber particles, when X-NBR particles are laminated by dip molding to form a film, theoretically, it is possible to achieve approximately 100 times more interparticle bonding (crosslinking) within a single region compared to a film formed by laminating natural rubber particles. Therefore, the quality of X-NBR interparticle bonding is extremely important for the film properties of X-NBR gloves. The carboxylic acid present in X-NBR contributes to this interparticle bonding (crosslinking), and the carboxylate (-COO) interacts with the metal ions of divalent metals. - The main linkage is the metal ion bond formed from ).

[0187] Therefore, conventional X-NBR gloves typically covalently bond particles together using elemental sulfur, a vulcanization accelerator, a self-crosslinking compound, or an organic crosslinking agent, and then use zinc oxide to create interparticle ionic bonds. Regarding aluminum crosslinking, various X-NBR gloves have been proposed that overcome its instability and replace zinc oxide with this interparticle crosslinking method. The gloves manufactured using the crosslinking agent containing HAC in this embodiment overcome the weaknesses of gloves manufactured using other conventional crosslinking agents containing aluminum compounds, and further improve the overall physical properties of the gloves.

[0188] The following describes the physical properties of the gloves of this embodiment using a crosslinking agent containing HAC. Regarding tensile strength, conventional X-NBR gloves maintained it through zinc crosslinking, but the gloves of this embodiment, due to their strong bonding, can achieve strength equivalent to or greater than that of zinc with a smaller amount of zinc.

[0189] Furthermore, comparing the calcium, zinc, and aluminum that constitute the interparticle crosslinks in the X-NBR gloves, aluminum hardly dissolves even in artificial sweat. Therefore, the gloves of this embodiment have the characteristic of exhibiting the least decrease in tensile strength even when used by a person.

[0190] Furthermore, regarding the elongation and softness of the gloves, conventional aluminum crosslinking, due to its strong bonding, is characterized by being harder and less stretchable compared to other crosslinking agents. In contrast, HAC has one X-NBR carboxylate bonded to each of the two aluminum cores, so there is no stress concentration due to the crosslinking of two X-NBR carboxylates on a single aluminum core. Therefore, the gloves are highly stretchable and soft.

[0191] Furthermore, in terms of fatigue resistance, the gloves of this embodiment are superior to those manufactured using other aluminum crosslinking agents and conventional X-NBR. Regarding fatigue durability, X-NBR gloves made with organic crosslinking agents that form covalent bonds are generally good because they are less prone to tearing. However, X-NBR gloves made with HAC are considered to have good fatigue durability because they are less prone to tearing due to strong bonds formed by interparticle bonding (crosslinking).

[0192] Furthermore, the stress retention rate of the gloves in this embodiment is significantly higher than that of conventional gloves made with sulfur vulcanization and zinc crosslinking. This is thought to be because the aluminum atoms firmly bond the X-NBR particles together, causing the X-NBR particles to cluster together like natural rubber particles, thereby restoring the rubber elasticity that was absent in conventional X-NBR gloves. In contrast, conventional X-NBR gloves use zinc as the interparticle crosslinking material, but the bonding strength of the zinc crosslinks is relatively weak. When tensile stress is applied, they break and recombine in an elongated state, which causes a decrease in stress retention.

[0193] In addition, regarding organic solvent impermeability, aluminum crosslinking, such as in the gloves of this embodiment, is generally superior to zinc crosslinking. While the physical properties of the gloves are also influenced by the properties of the X-NBR latex, the above describes the characteristics of the physical properties brought about by crosslinking with HAC. The gloves of this embodiment can be made without having internal cross-linking of particles. Furthermore, by using an internal cross-linking agent in combination or by changing the properties of X-NBR latex, gloves with changed physical properties can be made.

[0194] Since the gloves of this embodiment are not vulcanized with sulfur as in the prior art, they are accelerator-free gloves and there is no concern about type IV allergy. In addition, since aluminum has low toxicity in the gloves of this embodiment, even if it is discharged in the leaching process, there will be no problem with wastewater treatment as in the case of zinc oxide, which is a heavy metal. Also, in the gloves of this embodiment, aluminum is less likely to elute in food gloves for which the upper limit of zinc elution amount is determined under the Food Hygiene Law, and in clean room gloves that dislike the elution of metals such as zinc, metal salts, and anions and their transfer to semiconductors, so it is optimal.

Examples

[0195] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0196] [Cross-linking agent for dip molding] [[ID=I9]]〔Measurement method〕 (1) NMR measurement Using the aqueous solutions obtained in the examples and comparative examples, regarding the structure of the aluminum hydroxyacid chloride compound, under the following conditions, 27 Al-NMR measurement, and 13 C-NMR measurement were each performed. All measurements were performed by the single pulse method.

[0197] ([[ID = 34]] 27 Al-NMR measurement) Measuring device: Nuclear magnetic resonance device JNM-ECS400 (trade name, manufactured by JEOL Ltd.) Magnetic field strength: 9.40 T (400 MHz) Resonance frequency: 104.17 MHz External standard: 1 mol / L aqueous solution of aluminum nitrate Solvent: Heavy water (D2O) Measured temperature: 30°C For the preparation of the locking solvent (heavy water), a coaxial tube manufactured by Shigemi Co., Ltd. was used.

[0198] ( 13 C-NMR measurement) Measuring device: Nuclear magnetic resonance device AVANCE NEO (trade name, manufactured by Bruker) Magnetic field strength: 700 MHz Solvent: Heavy water (D2O) Internal standard: TMS Measured temperature: 30°C The adjustment with the locking solvent (heavy water) was carried out using a coaxial tube manufactured by Shigemi Co., Ltd.

[0199] (2) Mass spectrometry Using the aqueous solution obtained by diluting the aqueous solutions obtained in the examples and comparative examples 20-fold, mass spectrometry was performed on the structure of the aluminum hydroxyacid chloride compound under the following conditions. (Mass spectrometry) Measuring device: Quadrupole hybrid mass spectrometer Q Exactive (registered trademark) Plus (manufactured by Thermo Fisher Scientific) Ionization: nano-ESI (electrospray ionization) method Ion source: TriVersa NanoMate (registered trademark) MS detection: Full scan (positive ion, m / z: 80 - 1200) Gas pressure: N2 0.3 psi Voltage during spraying: 1.8 kV

[0200] (3) pH measurement The pH of the aqueous solutions obtained in the examples and comparative examples was measured using a pH meter.

[0201] (4) Measurement of aluminum concentration The aluminum concentration (mass %) in the crosslinking agent for dip molding obtained in the examples and comparative examples was measured by high-frequency inductively coupled plasma (ICP) emission spectroscopy to measure the aluminum content, and calculated as aluminum oxide (in terms of Al2O3) from that value.

[0202] [Structural analysis] In a 200mL glass container, add a sodium lactate aqueous solution (concentration: 60%), Haihang Industry A drop solution was obtained by adding 35.3 g of (manufactured by Co. Ltd.) and 50.0 g of deionized water, and stirring at room temperature (27°C) for 0.1 hours.

[0203] In a 200 mL glass container, 30.0 g of an aqueous solution of polyaluminum chloride with a basicity of approximately 50% (details will be described later) and 40.0 g of deionized water were added, and the mixture was stirred at 70°C to 80°C for 30 minutes to obtain the bottom solution.

[0204] While heating the above bottom solution to 70°C or higher and 80°C or lower, the above mud is added to the bottom solution while stirring. The entire volume of the drop solution was gradually added over approximately 30 minutes, and the mixture was stirred for 60 minutes at a temperature between 70°C and 80°C. Then, another drop solution was gradually added over approximately 30 minutes, and the mixture was stirred for 60 minutes at a temperature between 70°C and 80°C, and slowly cooled to room temperature. When sodium hydroxide aqueous solution (concentration: 48%, manufactured by R&M Chemicals Sdn. Bhd.) was added to this aqueous solution to adjust the pH to between 7.5 and 8.0, a precipitate was formed. The aluminum concentration of the PAC charged in the bottom solution was 17% by mass according to ICP-AES. The number of moles of aluminum was calculated from this, and the ratio of the number of moles of sodium lactate added as the drop solution to aluminum was sodium lactate / aluminum: 2.

[0205] Electrospray ionization mass spectrometry (ESI-MS) was performed on the above precipitate. The obtained mass spectrum is shown in Figure 1. According to Figure 1, the precipitate is a complex in which the main component is a molecule with a molecular weight of approximately 421.25, and a minor component is a fragment with a molecular weight of 422.25.

[0206] Table 1 below summarizes the calculated molecular weights of various aluminum lactate complexes, ranging from mononuclear to trinuclear. Note that in Table 1, the coordination number of aluminum is standardized to 6. According to Table 1, mononuclear aluminum complexes have molecular weights of 200-300, dinuclear aluminum complexes have molecular weights of 250-450, and trinuclear aluminum complexes have molecular weights of 500-700.

[0207] [Table 1]

[0208] Therefore, the above precipitates, which are complexes with fragments of molecular weight 421.25 and 422.25, are presumed to have a dinuclear aluminum complex as their basic structure, with lactic acid residues coordinating 2-equally to aluminum. Thus, it was found that aluminum hydroxy acid chloride compounds prepared using polyaluminum chloride with a basicity of approximately 50% have a dinuclear aluminum complex as their basic structure.

[0209] [Aluminum NMR Analysis] Nuclear magnetic resonance spectroscopy (NMR) of aluminum-27 is an effective method for analyzing the state of aluminum in a material. In the aluminum compound according to the present invention, aluminum atoms are bonded to oxygen atoms such as hydroxyl groups and oxygen atoms. When the chemical shift value of aluminum bonded to such oxygen is approximately -30 to -40, it is known that aluminum has a 6-coordinate structure (Reference 1: Mohamed Haouas, Francis Taulelle, Charlotte Martineau, Progress in Nuclear Magnetic Resonance Spectroscopy 94-95 (2016) 11-36). Figure 2 shows the aluminum NMR spectrum of a commercially available mononuclear aluminum lactate compound in which three molecules of lactate are coordinated to aluminum. In this mononuclear aluminum lactate, it has been elucidated that lactate is bidentate coordinated with a carboxylate group and a hydroxyl group, and aluminum adopts a 6-coordinate structure (Reference 2: G. Giorgio Bombi, Benedetto Corain, Abdiqafar A. Sheikh-Osman, Inorganica Chimic (a Acta, 171 (1990) 79-83.) In this NMR spectrum, a spectrum with a peak at a chemical shift value of 15.9 was observed, confirming that aluminum has a 6-coordinate structure. On the other hand, in the aluminum NMR of the aluminum lactate obtained as a precipitate (Figure 3), a spectrum with a peak at a chemical shift value of 26.3 was observed. From this chemical shift region, it can be seen that this aluminum lactate complex is a complex with 6-coordinate aluminum as shown in the compound having the structure represented by formula (4) above. However, the chemical shift value of the peak differs from that of mononuclear aluminum lactate by 10 ppm. In general, in 6-coordinate aluminum, it is thought that the chemical shift value increases significantly as the number of aluminum atoms in the aluminum core increases, i.e., as it becomes multinuclear. That is, the aluminum lactate obtained as a precipitate is thought to be a complex with two or more aluminum atoms in the 6-coordinate aluminum core. As discussed above, it is reasonable to assume that the number of aluminum atoms is 2, so the aluminum lactate obtained as a precipitate is thought to be a complex in which two 6-coordinate aluminum atoms are bonded by oxygen atoms such as hydroxyl groups.

[0210] The aluminum hydroxycarboxylate complex according to the present invention reacts with the carboxylic acid portion of X-NBR, thereby crosslinking the X-NBR. The dinuclear aluminum lactate complex obtained as a precipitate can be considered a model reaction for this crosslinking reaction and a model complex for the aluminum complex during crosslinking. In other words, the aluminum hydroxycarboxylate according to the present invention is a complex having a basic structure with two aluminum atoms in a 6-coordinate aluminum configuration, such as the aluminum lactate precipitate obtained above, that crosslinks the X-NBR. The aluminum hydroxycarboxylate according to one embodiment of the present invention is thought to be formed by the aggregation of a certain number of complexes with two 6-coordinate aluminum atoms as the basic structure, but the aggregation state is resolved by reaction with the carboxylic acid, and a dinuclear aluminum complex, which is the basic structure, is formed. It is thought that a similar reaction proceeds during the crosslinking of X-NBR.

[0211] The structure of the aluminum lactate compound obtained as the precipitate is estimated to be as follows. Note that "Lact" represents a lactate residue. [ka]

[0212] [Preparation of crosslinking agent for dip molding] [Example A1] (Preparation of A1 in Drop Solution 1) In a 200mL glass container, add a sodium lactate aqueous solution (concentration: 60%), Haihang Industry 24.7 g of (manufactured by Co. Ltd.), 5.8 g of sodium glycolate (98% by mass, solid), and 50.0 g of deionized water were added and stirred at room temperature (27°C) for 0.1 hours to obtain A1 of drop solution 1.

[0213] (Preparation of bottom solution A1) In a 200 mL glass container, add an aqueous solution of polyaluminum chloride (PAC (High Purity Polyaluminium Chloride), N003 (abbreviation), [Al2(OH) 2OH], manufactured by HENAN TAIRAN WATER PURIFICATION MATERIAL CO. LTD. n ·Cl 6-n ] m (However, add 30.0g of 1≦n≦5, m≦10) and 40.0g of deionized water, and stir for 30 minutes at 70℃ to 80℃. This process yielded bottom solution A1. The aluminum content of PAC N003 was 17% by weight, the chlorine content was 30%, and the molar ratio of aluminum atoms to chlorine atoms was 1.5 moles of chlorine atoms per mole of aluminum atoms. Furthermore, the basicity of PAC N003 is in the range of 45% to 50% according to the catalog values.

[0214] (Preparation of crosslinking agent A1 for dip molding) Subsequently, while heating bottom solution A1 at 70°C to 80°C, the entire volume of drop solution A1 was gradually added to bottom solution A1 over approximately 30 minutes, and the mixture was further stirred at 70°C to 80°C for 60 minutes. After that, a clear aqueous solution was obtained by slowly cooling to room temperature. To this aqueous solution, 19.22 g of sodium hydroxide aqueous solution (concentration: 48%, manufactured by R&M Chemicals Sdn.Bhd.) was added to adjust the pH to 7.5 to 8.0 to obtain an aqueous solution.

[0215] Regarding this aqueous solution, the above 27 Al-NMR, mass spectrometry, degree of polymerization, pH, and aluminum concentration were measured. These results confirmed the presence of an aqueous solution containing an aluminum hydroxylate compound, and this aqueous solution was designated as dip molding crosslinking agent A1. The aluminum concentration (in terms of Al2O3) was 6.5% by mass. In general formula (1), the aluminum hydroxylate compound has m=0 and H x A1 is a lactate residue, H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This compound has a structure in which the X bonded to the Al atom that is bonded to A2 is a hydroxyl group.

[0216] [Examples A2 to A7, Comparative Examples A1 to A2] (Preparation of A2-A9 of Drop Solution 1) Except for changing the amounts of sodium hydroxide aqueous solution (concentration: 48%), sodium lactate aqueous solution (concentration: 60%), sodium glycolate (98% by mass, solid), and deionized water to the amounts listed in Table 2, drop solutions A2 to A9 were obtained by preparing them in the same manner as drop solution A1 in Example A1.

[0217] (Preparation of Drop Solution 2, A3-A6) Drop solutions A3 to A6 were obtained by preparing them in the same manner as the preparation of drop solution A1 in Example A1, except that the amounts of L-ascorbic acid, sodium thioglycolate, thiolactic acid, citric acid, sodium hydroxide aqueous solution (concentration: 48%), and deionized water were changed to the amounts shown in Table 2.

[0218] (Preparation of bottom solutions A2-A9) Bottom solutions A2 to A9 were obtained by preparing them in the same manner as bottom solution A1 in Example A1. Note that bottom solutions A2 to A6, A8, and A9 are the same solution as bottom solution A1.

[0219] (Preparation of crosslinking agents A2, A7-A9 for dip molding) As shown in Table 2, dip molding crosslinking agents A2, A7-A9 were obtained by preparing them in the same manner as the preparation of dip molding crosslinking agent A1 in Example A1, except that A2, A7-A9 of drop solution 1 were used instead of A1 of drop solution 1, A2, A7-A9 of bottom solution 1 were used instead of bottom solution A1, and the amount of sodium hydroxide aqueous solution was changed to the amount shown in Table 2.

[0220] (Preparation of crosslinking agents A3-A6 for dip molding) As shown in Table 2, each of A3 to A6 of Drop Solution 1 was used instead of A1 of Drop Solution 1, and each of A3 to A6 of Bottom Solution 1 was used instead of A1 of Bottom Solution 1.

[0221] Furthermore, while heating bottom solutions A3 to A6 to 70°C or higher and 80°C or lower, the bottom solution during stirring... After gradually adding the entire contents of Drop Solution 1 (A3-A6) to liquids A3-A6 over approximately 30 minutes, the mixture was heated at a temperature between 70°C and 80°C while gradually adding the entire contents of Drop Solution 2 (A3-A6) over approximately 30 minutes, and the mixture was further stirred at a temperature between 70°C and 80°C for 60 minutes.

[0222] Except for these changes, dip molding crosslinking agents A3 to A6 were obtained by preparing them in the same manner as the preparation of dip molding crosslinking agent A1 in Example A1.

[0223] Table 2 shows the aluminum concentration (in Al2O3 equivalent) contained in each of the dip molding crosslinking agents A2 to A9.

[0224] Furthermore, by using a 1L flask instead of a 200mL glass container and scaling up the content ratio of each component by five times, each of the dip molding crosslinking agents A1 to A9 could also be obtained in the same manner as described above.

[0225] The aluminum hydroxylate compound contained in dip molding crosslinking agent A2 has m=0 and H in general formula (1). x A1 is a lactate residue, H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This compound has a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 6.8% by mass.

[0226] The aluminum hydroxyate compound contained in dip molding crosslinking agent A3 is, in general formula (1), m=0, H x A1 is a lactate residue, H x A2 is an L-ascorbic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This compound has a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 6.4% by mass.

[0227] The aluminum hydroxyate compound contained in dip molding crosslinking agent A4 has m=0 and H in general formula (1). x A1 is a lactate residue, H x A2 is a thioglycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, Hx This compound has a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 6.4% by mass.

[0228] The aluminum hydroxyate compound contained in dip molding crosslinking agent A5 has m=0 and H in general formula (1). x A1 is a lactate residue, H x A2 is a thiolactate residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This compound has a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 6.4% by mass.

[0229] The aluminum hydroxyate compound contained in dip molding crosslinking agent A6 has m=0 and H in general formula (1). x A1 is a glycolic acid residue, H x A2 is a citrate residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This compound has a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 5.4% by mass.

[0230] The aluminum hydroxyate compound contained in dip molding crosslinking agent A7 has m=0 and H in general formula (1). x A1 is a lactate residue, H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This compound has a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 8.0% by mass.

[0231] The aluminum hydroxyate compound contained in dip molding crosslinking agent A8 has m=0 and H in general formula (1). x A1 and H x A2 are both lactate residues, H xX, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This compound has a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 6.4% by mass.

[0232] The aluminum hydroxyate compound contained in dip molding crosslinking agent A9 has m=0 and H in general formula (1). x A1 and H x A2 are both glycolic acid residues, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x This compound has a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 6.9% by mass.

[0233] [Table 2]

[0234] [Preparation of crosslinking agent for dip molding] [Example B1] (Preparation of B1 in drop solution 1) In a 200mL glass container, add a sodium lactate aqueous solution (concentration: 60%), Haihang Industry 35.3g of (manufactured by Co. Ltd.) and 30.0g of deionized water were added and stirred at room temperature (27°C) for 0.1 hours to obtain B1 of drop solution 1.

[0235] (Preparation of B1 in drop solution 2) In a 200 mL glass container, 11.4 g of acetic acid, 15.7 g of sodium hydroxide aqueous solution (concentration: 48%, manufactured by R&M Chemicals Sdn. Bhd.), and 20.0 g of deionized water were added and stirred at room temperature (27°C) for 0.1 hours to obtain drop solution B1 of 2.

[0236] (Preparation of bottom solution B1) In a 200 mL glass container, add an aqueous solution of polyaluminum chloride (PAC (High Purity Polyaluminium Chloride), N003 (abbreviation), [Al2(OH) 2OH], manufactured by HENAN TAIRAN WATER PURIFICATION MATERIAL CO. LTD. n ·Cl 6-n ] m However, 30.0 g of (1 ≤ n ≤ 5, m ≤ 10) and 40.0 g of deionized water were added and stirred at 70°C to 80°C for 30 minutes to obtain bottom solution B1.

[0237] (Preparation of crosslinking agent B1 for dip molding) Subsequently, while heating bottom solution B1 at 70°C to 80°C, the entire contents of drop solution 1 (B1) were gradually added to bottom solution A1, which was being stirred, over approximately 30 minutes. Then, while heating at 70°C to 80°C, the entire contents of drop solution 2 (B1) were further added over approximately 30 minutes, and the mixture was stirred for another 30 minutes at 70°C to 80°C. After that, a clear aqueous solution was obtained by slowly cooling to room temperature. To this aqueous solution, 17.26 g of sodium hydroxide aqueous solution (concentration: 48%, manufactured by R&M Chemicals Sdn.Bhd.) was added to adjust the pH to 7.5 to 8.0 to obtain an aqueous solution.

[0238] Regarding this aqueous solution, the above 27 Al-NMR, mass spectrometry, pH, and aluminum concentration were measured, respectively. These results confirmed that the solution contained an aluminum hydroxylate compound, and this solution was designated as dip molding crosslinking agent B1. Dip molding crosslinking agent B1 contains acetic acid and, in general formula (1), m=0, H x A1 and H x A2 is a lactate residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x The compound contains a structure in which X, bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 5.5% by mass.

[0239] [Examples B2-B4, Comparative Examples B1-B4] (Preparation of B2-B8 in Drop Solution 1) Except for changing the amounts of sodium lactate aqueous solution, sodium glycolate (98% by mass, solid), and deionized water to the amounts shown in Table 3, each of the drop solutions B2 to B8 was prepared in the same manner as the preparation of drop solution B1 in Example B1.

[0240] (Preparation of B2-B4 in Drop Solution 2) Except for changing the amount of acetic acid to the amount shown in Table 3, each of the drop solutions B2 to B4 was obtained by preparing them in the same manner as the preparation of drop solution B1 in Example B1.

[0241] (Preparation of bottom solutions B2-B8) Bottom solutions B2 to B8 were obtained by preparing them in the same manner as bottom solution B1 in Example B1. Note that bottom solutions B2 to B8 are the same solution as bottom solution B1.

[0242] (Preparation of crosslinking agents B2-B4 for dip molding) As shown in Table 3, dip molding crosslinking agents B2 to B4 were obtained by preparing them in the same manner as the preparation of dip molding crosslinking agent B1 in Example B1, except that B2 to B4 of drop solution 1 were used instead of B1 of drop solution 1, B2 to B4 of drop solution 2 were used instead of B1 of drop solution 2, B2 to B4 of bottom solution were used instead of bottom solution B1, and the amount of sodium hydroxide aqueous solution was changed to the amount shown in Table 3.

[0243] (Preparation of crosslinking agents B5-B8 for dip molding) As shown in Table 3, dip molding crosslinking agents B5 to B8 were obtained by preparing them in the same manner as the preparation of dip molding crosslinking agent B1 in Example B1, except that B5 to B8 of drop solution 1 were used instead of B1 of drop solution 1, drop solution 2 was not added, B5 to B8 of bottom solution were used instead of bottom solution B1, and the amount of sodium hydroxide aqueous solution was changed to the amount shown in Table 3.

[0244] Table 3 shows the aluminum concentrations (in Al2O3 equivalent) contained in each of the dip molding crosslinking agents B2 to B8.

[0245] The crosslinking agent B2 for dip molding is acetic acid and, in general formula (1), m=0, H x A1 is a lactate residue, H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x The compound contains a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 5.6% by mass.

[0246] The dip molding crosslinking agent B3 is acetic acid and, in general formula (1), m=0, H x A1 is a lactate residue, H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x The compound contains a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 5.7% by mass.

[0247] The dip molding crosslinking agent B4 is acetic acid and, in general formula (1), m=0, H x A1 and H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H xThe compound contains a structure in which X, which is bonded to the Al atom bonded to A2, is a hydroxyl group. The aluminum concentration (in terms of Al2O3) was 6.0% by mass.

[0248] The crosslinking agent B5 for dip molding is in general formula (1) where m=0, H x A1 and H x A2 is a lactate residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x The compound contains a structure in which X, bonded to the Al atom bonded to A2, is a hydroxyl group, but does not contain acetic acid. The aluminum concentration (in terms of Al2O3) was 6.4% by mass.

[0249] The crosslinking agent B6 for dip molding is defined in general formula (1) as m=0, H x A1 is a lactate residue, H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x The compound contains a structure in which X, bonded to the Al atom bonded to A2, is a hydroxyl group, but does not contain acetic acid. The aluminum concentration (in terms of Al2O3) was 6.5% by mass.

[0250] The dip molding crosslinking agent B7 is in general formula (1) m=0, H x A1 is a lactate residue, H x A 2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H x The compound contains a structure in which X, bonded to the Al atom bonded to A2, is a hydroxyl group, but does not contain acetic acid. The aluminum concentration (in terms of Al2O3) was 6.8% by mass.

[0251] The crosslinking agent B8 for dip molding is defined in general formula (1) as m=0, H x A1 and H x A2 is a glycolic acid residue, H x X, which is bonded to the Al atom that bonds to A1, is a chlorine atom, H xThe compound contains a structure in which X, bonded to the Al atom bonded to A2, is a hydroxyl group, but does not contain acetic acid. The aluminum concentration (in terms of Al2O3) was 6.9% by mass.

[0252] [Table 3]

[0253] [Example C1] Dip molding and physical property measurement The usefulness of a crosslinking agent for dip molding was investigated using KNL-834 (trade name), a nitrile rubber glove emulsion (X-NBR (butadiene-acrylonitrile-methacrylic acid copolymer emulsion)) from Kumho Petrochemical Co., Ltd.

[0254] First, 4.5 kg of KNL-834 was weighed and filtered. Separately, 155.8 g of the dip molding crosslinking agent A1 obtained in Example A1 was diluted with 6.85 kg of deionized water. The diluted crosslinking agent was slowly added to the KNL-834 and then held while stirring for 30 minutes. Next, 1200 g of 3% potassium hydroxide aqueous solution was slowly added to the solution to prepare the dip compound solution.

[0255] The compound solution was prepared by stirring and allowing it to mature for one day, two days, or three days, and each was used for dip molding in the dipping test.

[0256] (Dipping test) 325 g of a release agent (Budget Champ CTF 3B-G2 (trade name), solid content concentration 40% by mass) was diluted with 1000 g of pre-weighed water to prepare a release agent dispersion. Separately, 5.2 g of a wetting agent (Triton-X) was dissolved in 100 g of water until clear to prepare a wetting agent solution. Next, 1536 g of calcium nitrate was dissolved in 3000 g of water, and while stirring, the previously prepared release agent dispersion and wetting agent solution were added to the calcium nitrate aqueous solution. Then, the remaining water (approximately 533 g) was added so that the calcium nitrate had a solid content concentration of 13% by mass as an anhydrous substance, and the release agent had a solid content concentration of 2.0% by mass, to prepare a total coagulation solution weighing 6500 g.

[0257] The resulting solidified solution was heated to approximately 50°C while being stirred, filtered through a 200-mesh nylon filter, and then placed in an immersion container. A ceramic hand mold (a medical examination hand mold manufactured by Shinko Ceramics Malaysia), which had been washed and heated to 60°C, was inserted fingertip first. After the tip touched the surface of the solidified solution, it was inserted over 4 seconds, held in that position for 4 seconds, and then withdrawn over 3 seconds. The solidified solution adhering to the surface of the hand mold was quickly shaken off, and the surface of the hand mold was dried. The dried hand mold was then heated to 60°C and stored.

[0258] Subsequently, when the surface temperature of the hand mold reached approximately 60°C, it was immersed for 1 second in dipping compound solution A1 with a maturation period of 1 day, 2 days, or 3 days, held in that position for 3 seconds, and then removed for 1 second. An X-NBR film was deposited on the surface of the hand mold. To gel the deposited film, it was placed in an oven heated to 100°C for 1 minute, and then immersed in 60°C warm water for 30 seconds as a leaching process.

[0259] After the leaching process was completed, the cuff of the glove, formed from the deposited film, was rolled up to create a ring and reinforced. It was then dried at a drying temperature of 110°C for 18 minutes.

[0260] After drying and returning to room temperature, the film was released from the hand mold surface, yielding nitrile gloves with an average thickness of 60 μm for each of the dipping compound solutions A1 with a maturation period of 1 day or 3 days.

[0261] [Example C2] Except for using dip molding crosslinking agent A2 obtained in Example A2 instead of dip molding crosslinking agent A1 obtained in Example A1, the process was carried out in the same manner as in Example C1, with a maturation period of 1 day or Nitrile gloves were obtained for each of the three-day curing compound solutions A2 for dipping.

[0262] [Example C3] Nitrile gloves were obtained for each of the dip compound solutions A3 with a curing period of 1 day or 3 days, in the same manner as in Example C1, except that the dip molding crosslinking agent A3 obtained in Example A3 was used instead of the dip molding crosslinking agent A1 obtained in Example A1.

[0263] [Example C4] Nitrile gloves were obtained for each of the dip compound solutions A4 with a curing period of 1 day or 2 days, in the same manner as in Example C1, except that the dip molding crosslinking agent A4 obtained in Example A4 was used instead of the dip molding crosslinking agent A1 obtained in Example A1.

[0264] [Example C5] Nitrile gloves were obtained for each of the dip compound solutions A5 with a curing period of 1 day or 2 days, in the same manner as in Example C1, except that the dip molding crosslinking agent A5 obtained in Example A5 was used instead of the dip molding crosslinking agent A1 obtained in Example A1.

[0265] [Example C6] Nitrile gloves were obtained for each of the dip compound solutions A6 with a curing period of 1 day or 3 days, in the same manner as in Example C1, except that the dip molding crosslinking agent A6 obtained in Example A6 was used instead of the dip molding crosslinking agent A1 obtained in Example A1.

[0266] [Comparative Example C1] Nitrile gloves for each of the dip compound solutions A8 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that the dip molding crosslinking agent A8 obtained in Comparative Example A1 was used instead of the dip molding crosslinking agent A1 obtained in Example A1.

[0267] [Comparative Example C2] Nitrile gloves for each of the dip compound solutions A9 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent A9 obtained in Comparative Example A2 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0268] [Example D1] Nitrile gloves for dip compound solution B1 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent B1 obtained in Example B1 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0269] [Example D2] Nitrile gloves for dip compound solution B2 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent B2 obtained in Example B2 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0270] [Example D3] Nitrile gloves for dip compound solution B3 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent B3 obtained in Example B3 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0271] [Example D4] Nitrile gloves for dip compound solution B4 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent B4 obtained in Example B4 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0272] [Comparative Example D1] Nitrile gloves for dip compound solution B5 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent B5 obtained in Comparative Example B1 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0273] [Comparative example D2] Nitrile gloves for dip compound solution B6 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent B6 obtained in Comparative Example B2 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0274] [Comparative Example D3] Nitrile gloves for dip compound solution B7 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent B7 obtained in Comparative Example B3 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0275] [Comparative Example D4] Nitrile gloves for dip compound solution B8 with a curing period of 1 day or 3 days were obtained in the same manner as in Example C1, except that dip molding crosslinking agent B8 obtained in Comparative Example B4 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0276] [Physical property testing] Various physical property tests were performed using the nitrile gloves obtained above. For Examples C1-C6 and Comparative Examples C1 and C2, the nitrile gloves used in the physical property tests were aged for 22 hours at 100°C after manufacturing. For Examples D1-D4 and Comparative Examples D1-D4, both gloves aged for 22 hours at 100°C after manufacturing and gloves without the above aging process were prepared. For the nitrile gloves of Examples D1-D4 and Comparative Examples D1-D4, a dipping compound solution with a 3-day aging period was used for evaluating fatigue durability, while a dipping compound solution with a 1-day aging period was used for evaluations other than fatigue durability.

[0277] (1) Tensile strength, tensile elongation, and modulus Tensile strength (MPa), tensile elongation (%), and modulus (MPa) were measured for each of the nitrile gloves obtained above, in accordance with ASTM D412. Specifically, molded bodies were punched out using a DieC machine manufactured by Dumbbell, Inc., to prepare test specimens. These test specimens were measured using an A&D STA-1225 universal testing machine (product name) at a test speed of 500 mm / min, a chuck distance of 75 mm, and a gauge length of 25 mm. The modulus was measured at 300% modulus (MPa) and 500% modulus (MPa).

[0278] (2) Tensile testing and fatigue durability Tensile tests were performed on each of the nitrile gloves obtained above, and the fatigue endurance (minutes) was further measured for the nitrile gloves of Examples D1-D4 and Comparative Examples D1-D4. Specifically, each nitrile glove was first conditioned at room temperature for 48 hours, and then a test specimen (120 mm in length) conforming to the ASTI EN standard was cut out. As an artificial sweat solution, 20 g of sodium chloride, 17.5 g of ammonium chloride, 17.05 g of lactic acid, and 5.01 g of acetic acid were added to 1 liter of deionized water, and the pH was adjusted to 4.7 with an aqueous sodium hydroxide solution.

[0279] The test specimen (120 mm in length) obtained above was clamped 15 mm from each end using a fixed chuck and a movable chuck, and the portion of the specimen from the bottom up to 60 mm on the fixed chuck side was immersed in the artificial sweat solution obtained above. Next, the movable chuck was moved to the minimum position (relaxed state) where the length of the test specimen was 147 mm (123%). The test specimen was held in this state for 11 seconds. After that, the movable chuck was moved to the maximum position (extended state) where the length of the test specimen was 195 mm (163%), and then moved back to the minimum position (relaxed state) in 1.8 seconds. A cycle test was performed with a total of 12.8 seconds of movement from holding the test specimen in the minimum position to returning to the minimum position via the maximum position as one cycle. Fatigue durability was evaluated by multiplying this 12.8 seconds cycle by the number of cycles until the test specimen fractured (in minutes). Furthermore, the strength at which the test specimen fractured was measured as the tensile strength (FAB, N).

[0280] These measurement results are shown in Tables 4 and 5.

[0281] [Table 4]

[0282] From the results shown in Table 4, H x A1 and H xNitrile gloves using the crosslinking agents according to each of Examples C1 to C5, which contain a compound having a structure represented by general formula (1) that is a hydroxy acid residue with a structure different from A2, matured in a short time of less than 24 hours and exhibited stable tensile strength. Specifically, the nitrile gloves using the crosslinking agents according to each of Examples C1 to C5 showed a tensile strength of 0.90 to 1.13 between the tensile strength after a 3-day maturation period and the tensile strength after a 1-day maturation period (rate of change in tensile strength), indicating that they matured in a short time of less than 24 hours and exhibited stable tensile strength.

[0283] On the other hand, H x A1 and H x Nitrile gloves using the crosslinking agents described in Comparative Examples C1 to C2, which contain a compound having a structure represented by general formula (1) that is a hydroxy acid residue with the same structure as A2, showed unstable tensile strength, with a significant increase after the maturation period. Specifically, the nitrile gloves using the crosslinking agents described in Comparative Examples C1 to C2 showed a tensile strength of 1.29 or higher for a maturation period of 3 days compared to a maturation period of 1 day (rate of change in tensile strength), indicating that maturation was difficult in a short period of less than 24 hours, resulting in a large change in tensile strength.

[0284] Although not shown in Table 4, various physical property tests were also performed for each example without aging (22 hours of storage at 100°C after glove fabrication) (Unaged). The tensile strength of the nitrile gloves using the crosslinking agent according to Example C1 was 27.19 MPa after 1 day of aging and 29.30 MPa after 2 days of aging. Similarly, the tensile strength of the nitrile gloves using the crosslinking agent according to Example C2 was 27.80 MPa after 1 day of aging and 29.92 MPa after 2 days of aging. Thus, even in the Unaged state, aging occurred in a short time of less than 24 hours, and the tensile strength remained stable.

[0285] [Table 5]

[0286] The results shown in Table 5 indicate that compounds having the structure represented by general formula (1) and organic acids are included. The nitrile gloves using the crosslinking agents in each of Examples D1 to D4 exhibited excellent fatigue resistance. Specifically, the nitrile gloves using the crosslinking agents in each of Examples D1 to D4 all had a fatigue resistance of 200 minutes or more, demonstrating excellent fatigue resistance.

[0287] On the other hand, nitrile gloves using the crosslinking agents in Comparative Examples D1 to D4, which did not contain organic acids, exhibited inferior fatigue durability. Specifically, the nitrile gloves using the crosslinking agents in Comparative Examples D1 to D4 all had a fatigue durability of 111 minutes or less, indicating poor fatigue durability.

[0288] Although not shown in Table 5, various physical property tests were also performed for each example with a 2-day aging period. The nitrile gloves using the crosslinking agent in Example D1 had a 300% modulus of 3.88 MPa and a FAB of 6.30 N after a 2-day aging period. From these results, it can be seen that good initial physical properties can be obtained from a 1-day aging period when acetic acid is added.

[0289] On the other hand, the nitrile gloves using the crosslinking agent in Comparative Example D1 had a 300% modulus of 3.26 MPa and a FAB of 6.20 N after a one-day aging period. From these results, it was found that the initial physical properties were low when acetic acid was not added, and that aging was insufficient after a one-day aging period.

[0290] (Low-temperature crosslinking test) A low-temperature crosslinking test was performed using the dip molding crosslinking agent A7 obtained above. Based on the conditions described in Table 6, nitrile gloves according to Example E1 and Example E2 were obtained using the same method as the dip molding described above. The tensile strength, tensile elongation, and modulus of the obtained nitrile gloves were measured in the same manner as above. The measurement results are shown in Table 6.

[0291] [Table 6]

[0292] As shown in Table 6, no difference was observed in the tensile strength, tensile elongation, and modulus measurements between the nitrile gloves according to Example E1, which were manufactured at a drying temperature of 110°C, and the nitrile gloves according to Example E2, which were manufactured at a drying temperature of 60°C. Therefore, it was found that the crosslinking agent according to the present invention can obtain good physical properties even when crosslinked at low temperatures. [Industrial applicability]

[0293] Molded articles obtained from the crosslinking agent containing the aluminum hydroxylate compound of the present invention, such as nitrile gloves, exhibit remarkably excellent fatigue resistance and are soft despite having high tensile strength and tensile elongation. Therefore, the dip molding composition of the present invention is expected to be widely used in the field of rubber molded articles, such as rubber gloves, in the future.

Claims

1. A crosslinking agent comprising a compound having a structure represented by the following general formula (4), The aluminum concentration (in Al₂O₃ equivalent) in the crosslinking agent is 1% by mass or more and 15% by mass or less relative to the total amount of the crosslinking agent. A crosslinking agent used for crosslinking carboxylic acid-modified elastomers. 【Chemistry 1】 (In formula (4), X independently represents a chlorine atom or a hydroxyl group, and H ｘ A １ and H ｘ A ２ Each of these represents a hydroxy acid residue, H ｘ A １ and H ｘ A ２ (This is a hydroxy acid residue with a different structure.)

2. A crosslinking agent comprising a compound having a structure represented by the following general formula (4) and an organic acid, The aforementioned organic acid is formic acid, acetic acid, or propionic acid. The aluminum concentration (in Al₂O₃ equivalent) in the crosslinking agent is 1% by mass or more and 15% by mass or less relative to the total amount of the crosslinking agent. The content of the organic acid is 1% by mass or more and 15% by mass or less relative to the total amount of the crosslinking agent. A crosslinking agent used for crosslinking carboxylic acid-modified elastomers. 【Chemistry 2】 (In formula (4), each X independently represents a chlorine atom or a hydroxy group, and H ｘ A １ and H ｘ A ２ each represent a hydroxy acid residue. H ｘ A １ and H ｘ A ２ may have the same structure or different structures.)

3. The aforementioned H ｘ A １ and H ｘ A ２ The crosslinking agent according to claim 2, wherein the crosslinking agent is a hydroxy acid residue having a different structure from that of the original hydroxy acid residue.

4. The aforementioned H ｘ A １ The crosslinking agent according to claim 1 or claim 2, wherein the crosslinking agent is a lactic acid residue, a methyllactic acid residue, a thiolactic acid residue, or a citrate residue.

5. The aforementioned H ｘ A ２ The crosslinking agent according to claim 1 or claim 2, wherein the crosslinking agent is a glycolic acid residue, a malic acid residue, a citrate residue, a methyllactic acid residue, a DL-mandelic acid residue, a L-ascorbic acid residue, a thioglycolic acid residue, or a thiolactic acid residue.

6. The crosslinking agent according to claim 1 or claim 2, wherein the pH is 7.5 or higher and 8.4 or lower in aqueous solution.

7. A crosslinking agent according to claim 1 or claim 2, used in dip molding.

8. A composition comprising the crosslinking agent according to claim 1 or claim 2, a copolymer elastomer, a pH adjusting agent, and water, The copolymerized elastomer comprises structural units derived from (meth)acrylonitrile, structural units derived from ethylenically unsaturated carboxylic acid, and structural units derived from butadiene. A dip molding composition having a pH of 8.5 to 10.

5.

9. The dip molding composition according to claim 8, which does not contain elemental sulfur or zinc oxide.

10. The dip molding composition according to claim 8, wherein the content of the crosslinking agent is 0.1 parts by mass or more and 1.5 parts by mass or less in terms of aluminum oxide, per 100 parts by mass of the copolymer elastomer.

11. A glove, which is a molded article of the dip molding composition described in claim 8.

12. A method for producing a crosslinking agent according to claim 1, A step to obtain a solution containing a hydroxy salt, A step to obtain a solution containing polyaluminum chloride, A step of mixing the solution containing the polyaluminum chloride with the solution containing the hydroxy salt, A method for producing a crosslinking agent, including the crosslinking agent.

13. A method for producing a crosslinking agent according to claim 2, A step to obtain a solution containing a hydroxy salt, A step of obtaining a solution containing formic acid, acetic acid, or propionic acid, A step to obtain a solution containing polyaluminum chloride, The solution containing the aforementioned aluminum chloride and the solution containing the aforementioned formic acid, acetic acid, or propionic acid A step of mixing the above-mentioned hydroxy salt with a solution containing the above-mentioned hydroxy salt, A method for producing a crosslinking agent, including the crosslinking agent.

14. The method for producing a crosslinking agent according to claim 12 or claim 13, wherein the calcium ion content in the polyaluminum chloride is less than 500 ppm by mass relative to the total amount of the polyaluminum chloride.

15. A method for producing a crosslinking agent according to claim 12 or claim 13, wherein the hydroxy salt comprises a first hydroxy salt selected from lactic acid, methyllactic acid, thiolactic acid, and citric acid, and a second hydroxy salt selected from glycolic acid, malic acid, citric acid, DL-mandelic acid, L-ascorbic acid, thioglycolic acid, and thiolactic acid.

16. The method for producing a crosslinking agent according to claim 15, wherein the molar ratio (B / A) of the second hydroxy salt (B) to the first hydroxy salt (A) in the solution containing the hydroxy salt is 5 / 95 or more and 95 / 5 or less.

17. A method for producing a crosslinking agent according to claim 12 or claim 13, wherein the molar ratio (D / C) of the hydroxy salt (D) to the aluminum atoms (C) of the polyaluminum chloride is 0.5 or more and 2.0 or less.

18. A method for manufacturing gloves according to claim 11, (1) A coagulant application step in which a coagulant is applied to a glove molding die to obtain a mold or former, (2) A maturation step in which the composition is stirred to obtain a dipping liquid, (3) A dipping step of immersing the mold or the former in the dipping liquid to form a film on the mold or the former, (4) A gelling step to obtain a pre-dried film-forming crosslinked film by gelling the film, (5) A leaching step to remove impurities from the crosslinked film to obtain the glove precursor 1, (6) A beading step to produce a winding on the cuff portion of the glove precursor 1 to obtain a glove precursor 2 having a winding, (7) The drying step involves heating and drying the glove precursor 2 to obtain a molded glove, A method for manufacturing gloves, including the method described above.

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