Crosslinking agent for esg-aligned rubber glove, composition for dip molding, glove, and method for producing same

Abstract

Provided is a crosslinking agent that is capable of producing a molded body that has excellent fatigue durability and that hardly breaks. Also provided is a crosslinking agent that causes a compound solution containing the crosslinking agent and a copolymerized elastomer such as X-NBR to age in a short period of time of 24 hours or less, and that is capable of producing a molded body that exhibits excellent stability in tensile strength.　A crosslinking agent according to one embodiment of the present invention contains a compound having a structure represented by general formula (4). (In formula (4), each X independently represents a chlorine atom or a hydroxy group, HxA1 and HxA2 each represent a hydroxy acid residue, and HxA1 and HxA2 are hydroxy acid residues having different structures.)

Description

Crosslinking agent, dip molding composition, gloves, and method for manufacturing the same for ESG-compliant rubber gloves.

[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.

[0002] Traditionally, rubber gloves made from synthetic rubber such as carboxy-modified acrylonitrile butadiene rubber (hereinafter also referred to as "X-NBR") by dip molding (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 contain elemental sulfur (chemical formula S ８ Traditionally, X-NBR gloves were formed by crosslinking using sulfur compounds (such as rhombic sulfur, which is composed solely of sulfur atoms), 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 significant costs for removal and contributing to environmental pollution. Therefore, in recent years, as an alternative, methods have been developed to obtain X-NBR gloves by aluminum crosslinking without using vulcanization accelerators.

[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 the mass production process.

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

[0007] International Publication No. 2017 / 146238, International Publication No. 2022 / 168831

[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 the 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 mononuclear aluminum, but X-NBR is bulkier than aluminum, and since X-NBR bonds to one aluminum molecule in two places, it becomes crowded and prone to localized stress concentration. As a result, the resulting gloves have the problem of being easily torn. Moreover, 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 detachment 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 excellent 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, some aspects of the present invention provide a crosslinking agent that has excellent fatigue durability and can produce a molded article that is difficult to break. Further, some aspects of the present invention provide a crosslinking agent in which a compound solution containing a crosslinking agent and a copolymer elastomer such as X-NBR can be aged in a short time within 24 hours and can be used for dip molding, and a molded article having excellent stability of tensile strength can be produced.

[0016] As a result of intensive studies, the inventors of the present invention 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 crosslinking reaction due to excessive stabilization of the crosslinking agent, and insufficient reactivity of internal aluminum, and thus have arrived at providing a novel crosslinking agent that can solve these problems. According to the novel crosslinking agent containing a hydroxyaluminum chloride compound, the inventors of the present invention found that the amount of energy used can be reduced because a crosslinking reaction in a crosslinking furnace for obtaining a dip molded product is unnecessary, and not only can stability and environmental problems be considered because zinc oxide and mononuclear aluminum do not occur in the wastewater, but also a molded article using this crosslinking agent has excellent fatigue durability due to undergoing an unprecedented crosslinking reaction process, such as a molded article like a glove, and a molded article like a glove that can be aged in a short time within 24 hours and has excellent stability of tensile strength can be provided. Incidentally, this hydroxyaluminum chloride compound can be made from polyaluminum chloride (PAC), which is inexpensive and widely used in water treatment and the like, as a raw material.

[0017] That is, the present invention is as follows. [1] A crosslinking agent containing a compound having a structure represented by the following general formula (4). (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, but H ｘ A １ and H ｘ A ２ are hydroxy acid residues having different structures.)

[0018] [2] A crosslinking agent comprising a compound having a structure represented by the following general formula (4) and an organic acid. (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. ｘ A １ and H ｘ A ２ This means that the structures may be the same or different.

[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 above H ｘ A １ and H ｘ A ２ A crosslinking agent according to any one of [2] to [4], which is a hydroxy acid residue having a different structure.

[0022] [6] The above H ｘ A １ The crosslinking agent is one of any one of [1] to [5], wherein the crosslinking agent is a lactic acid residue, a methyllactic acid residue, a thiolactic acid residue, or a citrate residue.

[0023] [7] The above H ｘ A ２ The crosslinking agent according to any one of [1] to [6], wherein the crosslinking agent is a glycolic acid residue, malic acid residue, citrate residue, methyllactic acid residue, DL-mandelic acid residue, L-ascorbic acid residue, thioglycolic acid residue, or thiolactic acid residue.

[0024] [8] A crosslinking agent according to any one of [1] to [7], wherein the pH is 7.5 or higher and 8.4 or lower.

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

[0026] A composition comprising a crosslinking agent according to any one of

[10] [1] to [9], a copolymer elastomer, a pH adjusting agent, and water, wherein the copolymer elastomer comprises structural units derived from (meth)acrylonitrile, structural units derived from ethylenically unsaturated carboxylic acid, and structural units derived from butadiene, and the pH is 8.5 or higher and 10.5 or lower, for dip molding.

[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 amount 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 [1], comprising the steps of: obtaining a solution containing a hydroxyate salt; obtaining a solution containing polyaluminum chloride; and mixing the solution containing polyaluminum chloride with the solution containing the hydroxyate salt.

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

[15] [2], comprising the steps of: obtaining a solution containing a hydroxyate; obtaining a solution containing a fatty acid; obtaining a solution containing polyaluminum chloride; and mixing the solution containing polyaluminum chloride, the solution containing the fatty acid, and the solution containing the hydroxyate.

[0032]

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

[14] or

[15] , wherein the basicity of the polyaluminum chloride is 70% or more and 85% or less.

[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 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.

[0035]

[19] The method for producing a crosslinking agent according to any one of

[14] to

[18] , 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.

[0036] A method for manufacturing gloves as described in

[20] and

[13] , comprising: (1) a coagulant application step of applying a coagulant to a glove mold to obtain a mold or former; (2) a maturation step of stirring the composition to obtain a dipping liquid; (3) a dipping step of immersing the mold or former in the dipping liquid to form a film on the mold or former; (4) a gelling step of gelling the film to obtain a pre-dried film-forming crosslinked film; (5) a leaching step of removing impurities from the crosslinked film to obtain a glove precursor 1; (6) a beading step of creating a winding in the cuff portion of the glove precursor 1 to obtain a glove precursor 2 having a winding; and (7) a final drying step of heating and drying the glove precursor 2 to obtain a molded glove.

[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) are less likely to 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 has excellent tensile strength stability even when the maturation period is short or long.

[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 24 hours or less can be mass-produced, and even when using compound solutions that have undergone a relatively long maturation period, excellent tensile strength stability can be achieved. 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.

[0042] Figure 1 shows the mass spectrum obtained by electrospray ionization mass spectrometry of a precipitate using an aqueous solution of polyaluminum chloride with a basicity of approximately 50%. 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 shows the aluminum NMR spectrum of aluminum lactate obtained as a precipitate.

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

[0044] [Crosslinking agent 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). (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 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.)

[0045] The aluminum hydroxylate compound (hereinafter also simply referred to as "HAC") having the structure represented by the general formula (1) above according to this embodiment is polyaluminum chloride ([Al ２ (OH) ｂ Cl ６－ｂ ] ａ, where 1 ≤ b ≤ 5 and 1 ≤ a ≤ 10.Hereafter, also simply referred to as "PAC") has as its basic framework and exists in a range from a dinuclear structure having two 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 ) is retained as a leaving group, it tends to efficiently form a coordinate bond with the carboxylic acid-modified group of X-NBR.

[0046] By using a crosslinking agent containing HAC, a process that does not require a heating furnace for the crosslinking reaction becomes possible, and since the crosslinking process is completed in solution, it is possible to achieve improved manufacturing efficiency, cost reduction, and reduced environmental impact simultaneously. In other words, the manufacturing process using the crosslinking agent eliminates 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 A １ and H ｘ A２ Because it contains a compound having a structure represented by the general formula (1) above, which is a hydroxy acid residue having a different structure from that of the other compound, the steric hindrance caused by the hydroxy acid residue in the crosslinking reaction with X-NBR is mitigated. As a result, the crosslinking efficiency is improved, the crosslinking reaction proceeds during the maturation process, and the compound can be used for dip molding within a maturation time of 24 hours or less.

[0050] The crosslinking reaction between crosslinking agent A and X-NBR is thought to proceed as shown in, for example, the following equations (2) and (3). In the following equations (2) and (3), crosslinking agent A is m=0 in the above general formula (1), and H ｘ A １ is a lactate residue, H ｘ A ２ is a glycolic acid residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ This includes compounds having a structure in which the X bonded to the Al atom 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 A ２ The steric hindrance of the glycolic acid residue significantly affects the crosslinking reaction rate with X-NBR2, and it is thought that the reaction proceeds more rapidly when the glycolic acid residue has less steric hindrance compared to the lactate residue, which has greater steric hindrance. Therefore, the crosslinking agent A in this embodiment is H ｘ A １ and H ｘ A ２By including a compound having the structure represented by the above general formula (1), which is a hydroxy acid residue having a different structure from the other, 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]

[0053]

[0054] Aluminum concentration in crosslinking agent A (Al ２ O ３ The converted amount is preferably 1% by mass or more and 15% by mass or less, more preferably 3% by mass or more and 10% by mass or less, and even more preferably 5% by mass or more and 8% by mass or less.

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

[0056] [Aluminum hydroxy acid chloride compounds] HAC is a compound having a structure represented by the following general formula (1). (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 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. 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 A １ and H ｘ A ２Examples of such residues 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 A １ H ｘ A ２ While not particularly limited to hydroxy acid residues having a different structure from the above, 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. ｘ A １ The hydroxy acid residue is more preferably a lactate residue, a methyl lactate residue, or a thio lactate residue, and even more preferably a lactate residue. ｘ A １ From the viewpoint of superior crosslinking properties of X-NBR, the X bonded to the Al atom is preferably a chlorine atom.

[0059] H ｘ A ２ H ｘ A １ While not particularly limited to hydroxy acid residues having a different structure, 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] Hｘ A ２ When A is a glycolic acid residue, the steric hindrance is particularly small, and thus the crosslinkability of X-NBR tends to be particularly excellent.

[0061] H ｘ A ２ When A is a thioglycolic acid residue or an L-ascorbic acid residue, not only does it have good crosslinkability of X-NBR, but since these ligands are reducing, it is possible to impart antioxidant properties to the molded body.

[0062] H ｘ A ２ When A is an aromatic hydroxy acid residue having lipophilicity such as a DL-mandelic acid residue or a salicylic acid residue, the compatibility between X-NBR particles can be enhanced, and the chemical resistance and gas barrier properties of the molded body can be improved.

[0063] H ｘ A ２ When A is a polyvalent carboxylic acid residue such as a citric acid residue or a malic acid residue, not only do the hydroxy group and carboxylate group at the α-position strongly coordinate to aluminum, but the remaining carboxylic acid groups also coordinate to the coordination sites of aluminum according to the conditions and function as secondary crosslinking points, making it possible to adjust the mechanical properties of the molded body, particularly the elongation property.

[0064] H ｘ A ２ When A is an amino acid residue, according to the characteristics of various amino acid residues (reductivity, lipophilicity, diversity of functional groups, etc.), the properties of the molded body and the particle interface properties of X-NBR can be adjusted. Note that an amino acid has an amino group (-NH ２ ) at the α-position and can form a bidentate coordination together with the carboxylate group. However, compared with α-hydroxy acids such as lactic acid and glycolic acid, the coordination to aluminum tends to be slightly weaker, but by using it in combination with α-hydroxy acids, stable complex formation is possible even in the alkaline region 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 moles of aluminum atoms to 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 reacting PAC, for example, with one or more hydroxy salts (hereinafter also simply referred to as "HxA"), using PAC as the basic framework.

[0069] Examples of hydroxy salts include potassium hydroxyate, sodium hydroxyate, and ammonium hydroxyate. Specifically, 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, tartron Examples include sodium phosphate, potassium glycerate, 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 the basic skeleton, the structure of the HAC is represented by, for example, the following formula (4). (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, but H ｘ A １ and H ｘ A ２ have different structures of hydroxy acid residues.)

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

[0072] In the crosslinking agent A containing HAC of formula (4), the molar ratio of the hydroxy acid residues (H ｘ A １ + H ｘ A ２ ) to the aluminum atom is preferably 0.5 or more and 2.0 or less, and more preferably 0.8 or more and 1.6 or less.

[0073] Since the HAC represented by formula (4) has relatively few coordinated 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 the crosslinking of aluminum by the hydroxy group is also difficult 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 the hydroxyl acid and the bidentate ligand of the carboxylate derived from X-NBR are coordinated. This structure satisfies all six coordination requirements for aluminum, and the highly electron-donating carboxylate stabilizes the positive charge of aluminum, resulting in a very stable state.

[0075] Furthermore, aluminum atoms can interact with each other via hydroxyl groups, such as Al-(OH) ２ The molecules are linked by an Al bond, 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 residue and the carboxylate derived from X-NBR bond to the aluminum 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 coordinates to the carboxylate of X-NBR.

[0077]

[0078] (Polyaluminum chloride) PAC, the basic framework of HAC, is [Al ２ (OH) ｂ Cl ６－ｂ ] a (where 1 ≤ b ≤ 5 and 1 ≤ a ≤ 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, water molecules (H) are present in the coordination sites other than the OH group and Cl group. ２ The structure becomes one in which O) coordinates. By adding a hydroxy acid salt here, the chloride ion in PAC is removed and replaced by the carboxylate group (-COO) of the hydroxy acid. － The hydroxyl group (-OH) in the hydroxyl acid coordinates to the aluminum. Additionally, the alcoholic hydroxyl group (-OH) in the hydroxyl 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 an aluminum polynuclear complex largely depends on the basicity of the raw material PAC. The basicity ratio is expressed as b / 6 (%). In this embodiment, the basicity of the raw material PAC is preferably 40% to 85%. This is because, normally, after the hydroxy acid residue coordinates to aluminum, chloride ions play an important role, and as the basicity ratio increases, the amount of chloride decreases, affecting the reactivity. Note that aluminum chloride (AlCl) has a basicity of 0%. ３ (Origin) Because it does not have a hydroxyl group, it readily forms mononuclear aluminum complexes in reactions 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 mainly a dinuclear complex (Al ２ Low-nuclear complexes, primarily of the (μ-OH) type, tend to form. On the other hand, when the basicity exceeds 60%, preferably between 70% and 85%, the Al-(μ-OH)-Al network tends to expand, and multinuclear complexes with three or more nuclei, in which more Al atoms are linked, tend to form.

[0082] The polyaluminum chloride PAC N003 (PAC), described later, has a basicity of 40% to 60%. Aqueous solutions of PAC with such basicity generally exhibit strong acidity (for example, pH 2 or lower). Under such strongly acidic conditions, even when a hydroxy acid is used as an alkali metal salt such as sodium hydroxyate, the weak alkalinity exhibited by the hydroxyate is immediately neutralized in the PAC aqueous solution. Therefore, the carboxylate group of the hydroxy acid can efficiently coordinate to the aluminum in PAC even under such strongly acidic conditions, forming an appropriate aluminum hydroxyate complex. Furthermore, even when sodium hydroxyate is added to PAC in an equivalent amount of aluminum, the aqueous solution remains strongly acidic. Therefore, when adjusting it to a predetermined pH, for example around pH 7.5, the pH can be easily controlled by adding an aqueous sodium hydroxide solution.

[0083] In this case, the total molar amount of sodium hydroxyate salt and sodium hydroxide added for pH adjustment is preferably approximately 1.8 to 2.5 in molar ratio with respect to the aluminum atoms contained in the PAC. Within this range, the hydroxy acid residues coordinate appropriately with the aluminum in the PAC, and a stable aluminum hydroxyate compound with a dinuclear structure as its basic framework can be obtained.

[0084] Furthermore, when using hydroxy acids containing polycarboxylic acids such as citric acid, sodium hydroxide is required to neutralize the remaining carboxyl groups in addition to the carboxylate that coordinates to aluminum. Therefore, the total molar amount of hydroxy acid salt and sodium hydroxide is appropriately adjusted within the above range depending on the structure of the hydroxy acid used.

[0085] On the other hand, highly basic PACs (e.g., Al) have a basicity of 70% or more, especially 80% or more. ２ (OH) ５In the case of Cl, the aqueous solution has a pH of 3 to 4, which is higher than that of PAC with a basicity of 40% to 60%. When sodium hydroxyate is added to such a highly basic PAC, a region with a pH of 6 or higher is easily instantaneously formed in the solution, depending on the local concentration of sodium hydroxyate. As a result, the hydroxylation reaction of aluminum proceeds rapidly, and Al(OH) ３ A gel may form. Such gelation inhibits the complex formation reaction of the present invention, which involves coordinating hydroxy acid residues while maintaining the multinuclear skeleton of PAC, and causes an increase in the amount of aluminum that does not function as the desired aluminum hydroxy acid complex.

[0086] Therefore, when producing aluminum hydroxy acid chloride compounds using highly basic PAC as a raw material, it is preferable to add the hydroxy acid as a free hydroxy acid rather than as an alkali metal salt. By using the hydroxy acid as a free acid, the occurrence of locally high pH is suppressed, and excessive hydrolysis and gelation of aluminum can be prevented. As a result, it becomes possible to stably obtain the aluminum hydroxy acid chloride compound according to the present invention, in which the hydroxy acid residue is appropriately coordinated while maintaining the aluminum dinuclear structure.

[0087] Furthermore, when a hydroxy acid is used as a free acid, the acidity of the entire PAC solution is maintained, so a relatively small amount of aqueous sodium hydroxide solution added later for pH adjustment is sufficient. Therefore, an aqueous solution of aluminum hydroxy acid chloride compound adjusted to a pH range of 7.5 to 8.4 exhibits long-term stability without gelation and can be preferably used as a crosslinking agent according to the present invention.

[0088] Furthermore, there are several commercially available highly basic polyaluminum chlorides with a basicity of 75% to 90% and a high atomic ratio of aluminum atoms to chlorine atoms (Al / Cl). As an example of such highly basic polyaluminum chloride, the manufacturer's specifications list it as Aluminum Chlorohydrate (hereinafter also referred to as "ACH"), with the chemical formula Al ２ (OH) ５ Cl・2H ２Products are described that have oxygen (O) as the basic framework, a basicity of 75% to 90%, and an atomic ratio of aluminum atoms to chlorine atoms (Al / Cl) of 1.9 / 1 to 2.1 / 1. Such highly basic polyaluminum chloride has a relatively large number of hydroxyl groups (-OH) and a small number of chlorine atoms in the PAC, which makes it easy for the hydrolysis of aluminum polynuclides to proceed in solution.

[0089] In highly basic polyaluminum chloride, which has a basicity of 75% to 90% and a high atomic ratio of aluminum atoms to chlorine atoms (Al / Cl), the stabilization of the dinuclear structure by chloride ions is relatively weak. Therefore, when weakly alkaline conditions are locally formed, the coordination water around the aluminum is easily deprotonated, forming Al-(OH) ２ - Al-type crosslinking proceeds rapidly. As a result, an aluminum hydroxide-like gel is easily formed while maintaining a multinuclear structure. In particular, when a hydroxy acid is added as an alkali metal salt, a momentary local alkaline environment is easily created around the addition point, which promotes the hydrolysis of aluminum and may form an insoluble gel. Therefore, the coordination of the hydroxy acid residue to aluminum does not proceed sufficiently, and it may be difficult to form an aluminum hydroxy acid complex based on the dinuclear structure intended by the present invention.

[0090] From the above points, it is important to add hydroxy acids as free hydroxy acids rather than alkali metal salts to highly basic polyaluminum chloride with a basicity of 75% to 90% and an Al / Cl atomic ratio of 1.9 to 2.1. By using free acids, the rise in local pH upon addition is suppressed, making excessive hydrolysis and gelation of the aluminum species less likely. As a result, the aluminum in highly basic polyaluminum chloride is retained in the solution, and the hydroxy acid residues coordinate efficiently as bidentate ligands, thereby stably forming the dinuclear hydroxy acid aluminum complex targeted by this invention.

[0091] Furthermore, because it is a highly basic aluminum chloride, the initial solution already has a pH of 3 to 5, and even when a hydroxy acid is added as a free acid, the overall solution maintains a relatively weak acidity. For this reason, a relatively small amount of aqueous sodium hydroxide solution is sufficient for pH adjustment, and the desired pH can be easily adjusted to the range of 7.5 to 8.4. Moreover, gelation is less likely to occur during the pH adjustment process, and coordination bonding between the hydroxy acid residue and aluminum proceeds uniformly, resulting in an aluminum hydroxy acid chloride compound that exhibits long-term stability in solution.

[0092] Thus, even when using highly basic PACs such as ACH as described above, by appropriately adding hydroxy acids as free acids and suppressing the localization of weak alkalinity, aluminum hydroxy acid chloride complexes with an aluminum dinuclear structure as the basic framework can be stably produced. As a result, the aluminum species to which the hydroxy acid residues are coordinated efficiently exchange coordination with the carboxylate groups of X-NBR, forming a uniform and strong interparticle crosslinking structure, which tends to improve the tensile strength and fatigue durability of the molded article.

[0093] Here, as the basicity of PAC increases and the number of multinuclear structures with three or more nuclei increases, it may exhibit properties different from those of a dinuclear compound. That is, when highly basic polyaluminum chloride is used, multinuclear aluminum hydroxyate complexes with three or more nuclei may be formed. In such multinuclear aluminum hydroxyate complexes, only the aluminum located at both ends is reactive, and the aluminum located in the middle is strongly bound to the adjacent aluminum by μ-OH crosslinking. Therefore, it is presumed that it is difficult for it to coordinate with the carboxylate of X-NBR even in coordination exchange by hydroxy acid residues.

[0094] Therefore, the positions in which X-NBR reacts with the multinuclear complex crosslinking agent to form coordinate bonds are mainly limited to both ends of the multinuclear complex. In other words, because the multinuclear complex has a relatively large molecular length, the distance between crosslinking points formed on X-NBR becomes longer, and it is thought that stress concentration in the entire crosslinking network is reduced. As a result, internal stress in the molded article is relaxed, the rubber elasticity (modulus) decreases, and the flexibility is improved.

[0095] Therefore, when the basicity of PAC is in the range of 40-60%, dinuclear structures are mainly formed, resulting in high crosslinking reactivity with X-NBR, making it suitable for applications requiring high strength and durability. On the other hand, in highly basic PAC with a basicity exceeding 60%, although there is a tendency for the number of trinuclear or more multinuclear structures to increase, the dinuclear structure does not completely disappear, and a certain amount of dinuclear aluminum complexes remains.

[0096] In this invention, this dinuclear aluminum complex is the reaction center that can efficiently exchange coordination with the carboxylate group of X-NBR, and as long as the dinuclear group is present, it functions effectively as a crosslinking agent of the present invention, even when a highly basic PAC is used as a raw material. Furthermore, by changing the abundance ratio of polynuclei depending on the basicity, the distance between crosslinking points and the distribution of internal stress can be adjusted, and in some cases the flexibility and modulus of the molded article can be controlled. In other words, by appropriately utilizing the ratio of dinuclear and polynuclear groups generated according to the basicity of PAC, it is possible to adjust the physical properties of the X-NBR molded article according to the application.

[0097] Furthermore, the fact that dinuclear aluminum complexes can be formed even when highly basic PAC is used as a raw material is consistent with well-known knowledge in PAC chemistry. In other words, even in PAC where multinucleation has progressed, Al remains relatively thermodynamically stable in solution. ２ It is believed that a certain proportion of (so-called dinuclear) structures exist, and these two nuclei are the most reactive to ligand exchange. In particular, when hydroxy acid residues are introduced, the aluminum atoms located at both ends of the multinucleus preferentially undergo ligand exchange, and it is known that a portion of the multinuclear structure is converted to a dinuclear structure through complexation with the hydroxy acid residues. From this, it is presumed that even when using PAC with high basicity, a dinuclear aluminum hydroxyate complex is formed under reaction conditions, and this can function as a reaction center that undergoes a coordination exchange reaction with the carboxylate group of X-NBR.

[0098] As an example, PAC with a basicity of 50% is represented by the following formula (6). Typically, PAC is expressed by formula (6).

[0099]

[0100] 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.

[0101] 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.

[0102] When an alkaline aqueous solution is added to a PAC aqueous solution, the six-coordinate environment of aluminum changes, and the following reaction proceeds: Aluminum in PAC forms some of its coordination sites with hydroxyl ions (OH) － ) and chloride ions (Cl － ) occupies the remaining coordination site, and water molecules (H ２ O) is coordinated. When an alkaline aqueous solution is added in this state, the high positive charge of aluminum causes the water molecules to become protons (H). ＋ It releases hydroxyl ions, which increase the amount of hydroxyl ions around the aluminum.

[0103] 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.

[0104] 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.

[0105] Commercially available PAC products 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 PAC #100P (product name) manufactured by Asada Chemical Industries, Ltd.

[0106] A suitable ligand for dissolving a dinuclear aluminum complex in water to obtain a homogeneous solution is a hydroxycarboxylic acid. To obtain HAC by adding this hydroxycarboxylic acid to a PAC solution, it is effective to add a suitable ligand that stabilizes the dinuclear structure. From the viewpoint of making the hydroxy acid aluminum compound more stable and allowing it to fully exhibit crosslinking reactivity with X-NBR, the crosslinking agent is preferably an aqueous solution with a pH of 7.5 to 8.4. If 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, long-term stability is observed, and decomposition and precipitation during storage tend not to occur.

[0107] On the other hand, although the aluminum hydroxylate compound is stabilized in aqueous solution by the coordination of hydroxy acid residues, if stored for a long period, hydrolysis may gradually proceed depending on the storage conditions, and some of it may aggregate or gel. In addition, microbial growth may occur under neutral to weakly alkaline conditions.

[0108] Therefore, when storing the crosslinking agent according to the present invention for a long period of time, it is preferable to store it under weakly acidic conditions with a pH of 6.0 to 6.5. Under such pH conditions, hydrolysis and aggregation of the hydroxy acid aluminum compound are further suppressed, and the stability during storage tends to be further improved.

[0109] Furthermore, from the viewpoint of further enhancing storage stability, preservatives such as potassium sorbate and sodium sorbate may be added to the crosslinking agent. In this case as well, it is preferable to maintain the pH of the crosslinking agent solution within the range of 6.0 to 6.5.

[0110] 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.

[0111] Furthermore, even if the crosslinking agent has been stored under weakly acidic conditions as described above, it can be made suitable for the crosslinking reaction with X-NBR by raising the pH using an alkaline agent such as an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, or aqueous ammonia before use.

[0112] From the viewpoint of the progress of the crosslinking reaction, it is preferable that the pH of the composition after adding the crosslinking agent be 9.0 or higher. However, when incorporating the crosslinking agent into X-NBR latex, it is preferable to add the crosslinking agent after adjusting its pH to a range close to that of the X-NBR latex in order to prevent aggregation and heterogeneity of the latex due to local pH differences. After in this manner, the crosslinking reaction can be carried out without aggregation by raising the overall pH with an alkaline agent.

[0113] Thus, the crosslinking agent according to the present invention has the characteristic of being able to design the pH conditions during storage separately from the pH conditions during compounding and crosslinking reaction, thereby achieving both storage stability, compounding stability, and crosslinking reactivity during use.

[0114] 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, hydroxy acid residues stabilize 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 (), X-NBR forms a uniform crosslinked structure via crosslinking agent A. Furthermore, the crosslinking agent maintains stability and allows for long-term storage.

[0115] 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 A １ and H ｘ This is an example of a crosslinking agent containing a dinuclear aluminum hydroxylate compound having A2.

[0116]

[0117]

[0118] 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 maintained even when the pH exceeds 8.0. Consequently, the chloride ion can maintain its coordinated state with aluminum and can also function as a leaving group. In the case of the aluminum cation, X can be not only a chloride ion, but also a hydroxide ion (OH). － ) may also be coordinated, and this hydroxide ion can 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.

[0119] Under these conditions, the carboxylic acid of X-NBR is sequentially converted 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. This structure is also energetically stable, so the reaction with the carboxylate of X-NBR proceeds easily even in solution. For this reason, the crosslinking reaction of X-NBR with a crosslinking agent proceeds easily simply by raising the pH.

[0120] 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.

[0121] 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 9.0 to 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 crosslinking agent form a coordination 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.

[0122] The reason for adding crosslinking agent A to the X-NBR solution under conditions of pH 9 or lower is based on the pH-dependent orientation behavior of the carboxyl groups contained in X-NBR. The carboxyl groups in X-NBR ionize as the pH increases to form carboxylates (-COO － ) and also tend to orient outwards from the particle interface. On the other hand, under conditions of pH 9 or lower, the ionization and outward orientation of carboxyl groups are limited, and a high proportion remain near the particle surface.

[0123] Therefore, when crosslinking agent A is added at a pH of 9 or lower, the reaction between the aluminum in the crosslinking agent and the carboxylate of X-NBR does not proceed excessively immediately after addition, allowing crosslinking agent A to be uniformly dispersed in the latex. Subsequently, when the pH is increased by adding an alkaline aqueous solution, the carboxyl groups of X-NBR sequentially become carboxylates and orient themselves outward from the particles, so the coordination bond reaction with crosslinking agent A proceeds uniformly throughout the entire system. As a result, a uniform interparticle crosslinking structure can be formed without localized aggregation.

[0124] 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.

[0125] 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 about 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.

[0126] 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.

[0127] [Crosslinking agent B] 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. (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 A １ and H ｘ A ２ H represents a hydroxy acid residue. ｘ A １ and Hｘ A ２ This means the structures may be the same or different. 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.

[0128] 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.

[0129] The crosslinking agent B according to this embodiment contains a compound having the structure represented by the general formula (1) above, H ｘ A １ and H ｘ A ２ This is similar to the aluminum hydroxy acid salt compounds described above, except that the residues may have the same structure as the hydroxy acid residues.

[0130] H ｘ A １ and H ｘ A ２ For two hydroxy acid residues to have the same structure, for example, H ｘ A １ and H ｘ A ２ Both are lactate residues, or H ｘ A １ and H ｘ A ２ Examples include cases where both are glycolic acid residues. If crosslinking agent B is present in this embodiment, then H ｘ A １ and H ｘ A ２ Even though they are hydroxy acid residues with the same structure, they exhibit excellent fatigue resistance.

[0131] The crosslinking agent B according to this embodiment contains a compound having the structure represented by the general formula (1), similar to the aluminum hydroxy acid salt compound described above, H ｘ A １ and H ｘ A ２ The hydroxy acid residue may have a different structure. In this case, it tends to have better fatigue resistance and tensile strength.

[0132] 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 two or more may be used in combination. The organic acid is preferably formic acid, acetic acid, or propionic acid. When these organic acids are used, the fatigue durability of the molded article tends to be superior.

[0133] 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.

[0134] The crosslinking agent B according to this embodiment may include a compound having a structure represented by the following general formula (1)'. (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 A １ and H ｘ A ２ H represents a hydroxy acid residue. ｘ A １ and H ｘ A ２ This means the structures may be the same or different. Note that when m = 0, the compound has the structure represented by formula (2)' below, and is an aluminum hydroxyate compound with an aluminum dinucleus as its basic structure.

[0135] Compounds having the structure represented by general formula (1)' are those in which water (H) is present in each Al. ２The compound is similar to the compound having the structure represented by the general formula (1) above, except that O) is not coordinated 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.

[0136] 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.

[0137] 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 general formula (1)' above, where m = 0, and H ｘ A １ is a lactate residue, H ｘ A ２ This includes compounds having a structure in which is a glycolic acid residue and X is an acetate residue.

[0138] As shown in formula (9) below, an aluminum hydroxylate compound to which an acetate residue is coordinated is, for example, K(CH ３ The elimination of COO promotes the coordination exchange reaction with the carboxylate group of X-NBR. 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.

[0139]

[0140] [Method for producing crosslinking agent A] A method for producing 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 and the solution containing a hydroxy salt. By going through such steps, HAC can be suitably produced. Each step will be described below.

[0141] (Step to obtain a solution containing hydroxy salts) The solution containing hydroxy salts will be referred to here as a drop solution. The solution containing hydroxy salts 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, the use of an aqueous solution of sodium hydroxide is preferred. The solution containing hydroxy salts may also be prepared, for example, at room temperature, or by heating it to a temperature between 30°C and 50°C.

[0142] For hydroxy salts, refer to the above. Hydroxy salts may be used alone, or two or more may be used in combination. 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. Including these hydroxy salts tends to improve the 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 exhibits superior tensile strength stability.

[0143] 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 molded article tends to have superior fatigue durability. 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.

[0144] 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, relative to the total mass of the solution.

[0145] The content of the alkaline compound is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and even more preferably 5% by mass or more and 10% by mass or less, relative to the total mass of the solution.

[0146] Multiple steps are taken to obtain a solution containing a hydroxy salt, thereby obtaining a solution containing multiple hydroxy salts.

[0147] (Step to obtain a solution containing polyaluminum chloride) The solution containing polyaluminum chloride will be referred to here as the bottom solution. The solution containing polyaluminum chloride can be prepared, for example, by dissolving PAC (polyaluminum chloride) in water heated to 40°C to 80°C (preferably 60°C to 80°C). In order to mix well with the drop solution, it is preferable to continue heating the bottom aqueous solution to 40°C to 80°C (preferably 60°C to 80°C). Refer to the above for PAC.

[0148] Aluminum concentration (Al) in a solution containing polyaluminum chloride ２ O ３The converted amount 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.

[0149] The calcium ion content in 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.

[0150] (Mixing process) In the mixing process, a solution containing polyaluminum chloride (bottom solution) and a solution containing hydroxy salt (drop 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 60°C or higher and 80°C or lower, and then stir.

[0151] 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.

[0152] 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.

[0153] When adding multiple drop solutions, it is preferable to add each drop solution according to the time specified above.

[0154] 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.

[0155] The stirring time after addition is usually between 30 and 120 minutes, taking into account the reaction time. Since the pH gradually rises during the reaction, it is preferable to maintain the pH at 7 or below, preferably on the acidic side. By maintaining the pH on the acidic side, the aluminum during the reaction does not gel, the PAC is cleaved by the hydroxy salt, and coordination with the hydroxy acid can be completed while maintaining the dinuclear body as the basic framework.

[0156] (pH adjustment step) 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.

[0157] The pH is preferably adjusted to between 7.5 and 8.4. For pH adjustment, for example, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, and an aqueous ammonia solution can be used. For pH adjustment, it is preferable to use an aqueous solution of sodium hydroxide or potassium hydroxide. pH adjustment is usually carried out at room temperature.

[0158] (Method for identifying aluminum hydroxylate compounds) The obtained PAC can be identified by known methods. For example, ２７ Al-NMR (nuclear magnetic resonance), １３ Examples include C-NMR, mass spectrometry, osmotic spectroscopy, ICP-AES (inductively coupled plasma emission spectroscopy), and FT-IR (Fourier transform infrared spectroscopy).

[0159] [Method for producing crosslinking agent B] A method for producing crosslinking agent B according to one embodiment of the present invention includes the steps of: obtaining a solution containing a hydroxyate; obtaining a solution containing a fatty acid; obtaining a solution containing polyaluminum chloride; and mixing the solution containing polyaluminum chloride, the solution containing the fatty acid, and the solution containing the hydroxyate.

[0160] In the method for producing the crosslinking agent B according to this embodiment, the method is the same as the method for producing the crosslinking agent A described above, except for the step of obtaining a solution containing fatty acids.

[0161] (Step to obtain a solution containing fatty acids) A solution containing fatty acids is also called a drop solution. The solution containing fatty acids 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, the use of an aqueous solution of sodium hydroxide is preferred. The solution containing fatty acids may be prepared, for example, at room temperature, or by heating at a temperature between 30°C and 50°C. Refer to the above for information on fatty acids.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] Furthermore, if the carboxylated nitrile rubber latex (X-NBR) is an alkaline emulsion with a pH of 7.5 to 8.0, the crosslinking reaction using the crosslinking agent can be promoted by diluting crosslinking agent A or crosslinking agent B of the present invention, which has been stored at a pH of 6.0 to 6.5, with water and adding it to the X-NBR latex, thereby shifting the pH of the entire system to the alkaline side without adding an external alkaline solution.

[0168] [Composition for dip molding] A composition for dip molding 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 more and 10.5 or less.

[0169] The composition serves as a raw material for manufacturing film-shaped molded products using a dipping solution.

[0170] 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.

[0171] 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 content of the crosslinking agent is within the above range, the tensile strength and elongation tend to be superior.

[0172] The molded body of the composition is preferably a glove.

[0173] (Copolymerized Elastomer) Copolymerized elastomers include, for example, carboxylic acid-modified elastomers. As copolymerized elastomers, elastomers containing various NBRs (nitrile butadiene rubbers) can also be used. It is preferable to use X-NBR (carboxylate-modified nitrile butadiene rubber) as the carboxylic acid-modified elastomer.

[0174] 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.

[0175] 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.

[0176] X-NBR latex is preferably produced by emulsion polymerization. In this case, the X-NBR particles contained in the X-NBR latex are formed when the X-NBR is surrounded by a surfactant such as sodium dodecylbenzenesulfonate to form particles.

[0177] 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 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.

[0178] 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.

[0179] The pH of this X-NBR latex is usually between 8.0 and 8.3, but in dip molding compositions, the overall pH is adjusted to between 8.5 and 10.5. The carboxyl groups (-COOH) of X-NBR are located at and near the interface of the X-NBR particles at a pH of 8.0 to 8.3. 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.

[0180] 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.

[0181] 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 also be used in combination.

[0182] (pH adjuster) Examples of pH adjusters 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 adjusters. It is preferable to add the pH adjuster so that the pH of the composition is adjusted to a range of 8.5 to 10.5.

[0183] (Optional components) The composition may, for example, in the manufacture of gloves, typically contain optional components such as dispersants, antioxidants, and pigments in addition to the components listed above.

[0184] Examples of dispersants include anionic surfactants such as sulfonates. Examples of antioxidants include hindered phenols. Examples of pigments include titanium dioxide.

[0185] [Method for Manufacturing Molded Articles and Gloves Using the Composition] A method for manufacturing molded articles by dip molding (dipping method) using the above-described dip molding composition will be explained in accordance with a typical example of a glove manufacturing method. In this embodiment, the step of removing the molded article from the mold or former after the drying step may be included. The gloves of this embodiment are formed by molding a constituent material containing the above-described dip molding composition.

[0186] In this embodiment, the manufacturing process for gloves, which are molded bodies of the above-mentioned dip molding composition, includes the following steps. The glove manufacturing process includes: (1) a coagulant application step (a step of applying a coagulant to a glove mold to obtain a mold or former by applying a coagulant to the glove mold); (2) a maturation step (a step of preparing and stirring a composition for dip molding) by stirring the composition to obtain a dipping solution; (3) a dipping step (a step of immersing the glove mold in the composition for dip molding) by immersing the mold or former in the dipping solution to form a film on the mold or former; (4) a gelling step (a step of pre-drying the film formed on the glove mold to create a cross-linked film precursor) by gelling the film to obtain a pre-dried cross-linked film; (5) a leaching step (a step of removing impurities from the cross-linked film formed on the glove mold) by removing impurities from the cross-linked film to obtain a glove precursor 1; and (6) a beading step (a step of creating a bead on the cuff portion of the glove to obtain a glove precursor 2 having a bead. (7) A drying step (a step of heating and drying at a temperature necessary for the crosslinking reaction) is performed to obtain a molded glove by heating and drying the glove precursor 2. Steps (3) to (7) are performed in the order described above.

[0187] The following step (6') may be optionally included between step (6) and step (7): (6') Pre-drying step (a step of heating and drying the glove precursor 2 at a lower temperature than the main drying step).

[0188] 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.

[0189] 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.

[0190] The following describes the process in detail. (1) Coagulant application process (a) In the coagulant application process, the mold or former (glove molding mold) is coated with Ca as a coagulant and gelling agent. 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, and is 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.

[0191] 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.

[0192] (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.

[0193] (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.

[0194] (2) Maturation process (a) The maturation process is a process of preparing a dip molding composition and dispersing it uniformly while stirring.

[0195] (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 to 10.2, thereby creating a uniform dip molding solution.

[0196] 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.

[0197] 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.

[0198] Furthermore, if aggregates are observed in the dip solution after the addition of HAC, it is preferable to further dilute the HAC so that the amount of aluminum in the diluted solution is approximately 0.5% by mass or more and 1.0% by mass or less, in terms of aluminum oxide.

[0199] (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.

[0200] (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 had the coagulant applied and dried in the coagulant application process described above, into the dip tank for a period of 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.

[0201] (4) Gerring process The gelling process is a process in which the film is gelled to obtain a pre-dried cross-linked film. Typically, it is heated in a gelling oven to around 40°C to 110°C. The heating time is usually between 1 minute 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, it may be left at this temperature for a certain period of time. The gelling process has the purpose of dispersing calcium in the cross-linked film at the same time as gelling. This is because calcium crosslinks make up a considerable number of crosslinks in the final gloves and form the basis of the glove's physical properties.

[0202] (5) Leaching process (a) The leaching process is a process in which excess chemicals and impurities such as calcium precipitated on the surface of the cross-linked film that would interfere with subsequent curing are washed off with water to obtain glove precursor 1. Normally, the mold or former is immersed in warm water at 30°C to 70°C for about 1 minute to 4 minutes.

[0203] (b) In this process as well, HAC is firmly bound to the X-NBR particles and is therefore not removed by washing with water.

[0204] (6) Beading process This process involves rolling up the cuff end of the glove formed from the glove precursor 1 after the leaching process to create a ring of appropriate thickness, reinforcing it, and obtaining glove precursor 2. Performing this process in a wet state after the leaching process results in good adhesion of the rolled portion.

[0205] (6') Pre-drying step (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, in this step, heating and drying are carried out at a temperature of 60°C to 90°C for 30 seconds to 5 minutes. If the main drying step is carried out at a high temperature without going through the pre-drying step, the moisture will evaporate rapidly, and blister-like protrusions may form on the glove, impairing its quality. However, it is also possible to proceed to the main drying step without going through this step.

[0206] (b) Although the temperature may be raised to the final temperature of the 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.

[0207] (7) Main drying process (a) This drying process involves heating the glove precursor 2 formed into the glove shape described above, and finally drying it to obtain a molded body that can withstand demolding. The heating temperature and time are preferably selected appropriately from the temperature required to cause the crosslinking reaction and drying. For example, the molded body of this embodiment can be dried by heating at 50°C to 70°C for about 15 minutes to 30 minutes. (b) In this drying process, the moisture contained in the film is removed, and the molded body becomes a state in which it has mechanical strength that can be subjected to the demolding process. The chloride ions that were coordinately bonded to the aluminum of HAC in the compound solution undergo ligand exchange with the carboxylate of the X-NBR particles, and the carboxylate of the X-NBR particles is coordinately bonded to the aluminum, so crosslinking does not proceed in this process. At the same time, the bonding of potassium (K) and calcium (Ca) to the carboxylate of the X-NBR particles, which weakens the glove properties, is also suppressed.

[0208] (8) Regarding the manufacturing method of double-dipped gloves, the above explanation described so-called single-dipping. In contrast, the dipping process and the gelling process may be performed two or more times, and this is usually called double-dipping. Double-dipping is performed when manufacturing thick gloves (film thickness of approximately 200 μm to 300 μm) and also in the manufacturing method of thin gloves for purposes such as preventing the formation of pinholes.

[0209] One important point to note regarding double dipping is that, in order to aggregate the X-NBR particles in the second dipping step, it is preferable to allow sufficient time in the first gelling step to allow calcium to precipitate sufficiently on the film surface.

[0210] In either case, the final gloves are obtained by removing the molded body from the mold or former after this drying process.

[0211] [Crosslinked articles using the composition] The molded articles produced by the manufacturing method described above can be used in various forms, but are preferably used for gloves, for example. The following description will focus on gloves, particularly X-NBR gloves made by crosslinking X-NBR, but the composition can also be applied to molded articles other than gloves.

[0212] 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 interparticle bonding of X-NBR particles 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 ).

[0213] 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 HAC-containing crosslinking agent of this embodiment overcome the weaknesses of gloves manufactured using other conventional aluminum compound-containing crosslinking agents and further improve the overall physical properties of the gloves.

[0214] 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.

[0215] 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 having the least decrease in tensile strength even when used by a person.

[0216] 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 two X-NBR carboxylate crosslinks on a single aluminum core. Therefore, the gloves are characterized by being highly stretchable and soft.

[0217] Furthermore, in terms of fatigue durability, the gloves of this embodiment are superior to those manufactured using other aluminum crosslinking agents and conventional X-NBR. Generally, X-NBR gloves made with organic crosslinking agents that form covalent bonds are superior in terms of fatigue durability because they are less prone to tearing. However, we believe that X-NBR gloves made with HAC have superior fatigue durability because they are less prone to tearing due to strong bonds formed by interparticle bonding (crosslinking).

[0218] 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 crosslinking is relatively weak. When tensile stress is applied, it breaks and recombines in an elongated state, which lowers the stress retention rate.

[0219] In addition, regarding organic solvent impermeability, aluminum crosslinking, as seen in the gloves of this embodiment, is generally superior to zinc crosslinking. The physical properties of the gloves are also influenced by the properties of the X-NBR latex, but the above describes the characteristics of the physical properties brought about by crosslinking with HAC. The gloves of this embodiment can be made without intraparticle crosslinking, but gloves with altered physical properties can be made by further using an intraparticle crosslinking agent or by changing the properties of the X-NBR latex.

[0220] The gloves of this embodiment are accelerator-free gloves because they are not sulfur-vulcanized as in conventional gloves, eliminating concerns about type IV allergies. Furthermore, because aluminum in these gloves is low-toxicity, even if discharged during the leaching process, they do not cause wastewater treatment problems like those associated with heavy metals such as zinc oxide. Moreover, these gloves are ideal for food-grade gloves, where the upper limit of zinc leaching is regulated under the Food Sanitation Law, and for cleanroom gloves, where the leaching of metals such as zinc, metal salts, and anions and their transfer to semiconductors is undesirable, as aluminum does not leach easily.

[0221] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0222] [Crosslinking agent for dip molding] [Measurement method] (1) Using the aqueous solutions obtained in the NMR measurement examples and comparative examples, the structure of the aluminum hydroxy acid salt compound was determined under the following conditions: ２７ Al-NMR measurement, and１３ C-NMR measurements were performed on each sample. All measurements were performed using the single-pulse method.

[0223] ( ２７ Al-NMR measurement) Measuring device: Nuclear magnetic resonance device JNM-ECS400 (trade name, manufactured by JEOL Ltd.) Magnetic field strength: 9.40T (400MHz) Resonance frequency: 104.17MHz External standard: 1 mol / L aluminum nitrate aqueous solution Solvent: Heavy water (D ２ O) Measurement temperature: 30°C. A coaxial tube manufactured by Shigemi Co., Ltd. was used to prepare the locking solvent (heavy water).

[0224] ( 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 (D ２ O) Internal standard: TMS. Measurement temperature: 30°C. Note that the adjustment with the locking solvent (heavy water) was performed using a coaxial tube manufactured by Shigemi Co., Ltd.

[0225] (2) Mass spectrometry The structure of the aluminum hydroxylate compound was determined by mass spectrometry using aqueous solutions obtained by diluting the aqueous solutions obtained in the mass spectrometry examples and comparative examples 20 times under the following conditions. (Mass spectrometry) Measurement device: Quadrupole hybrid mass spectrometer Q Exactive® Plus (manufactured by Thermo Fisher Scientific) Ionization: nano-ESI (electrospray ionization) method Ion source: TriVersa NanoMate® MS detection: Full scan (positive ions, m / z: 80-1200) Gas pressure: N ２ Voltage during 0.3 psi spray: 1.8 kV

[0226] (3) pH measurement The pH of the aqueous solutions obtained in the examples and comparative examples was measured using a pH meter.

[0227] (4) The aluminum concentration (mass%) contained in the dip molding crosslinking agent obtained in the measurement examples and comparative examples was determined by measuring the aluminum content using high-frequency inductively coupled plasma (ICP) emission spectroscopy, and from that value, the aluminum oxide (Al ２ O３ It was calculated as (converted).

[0228] [Structural Analysis] A drop solution was obtained by adding 35.3 g of sodium lactate aqueous solution (concentration: 60%, manufactured by Haihang Industry Co. Ltd.) and 50.0 g of deionized water to a 200 mL glass container and stirring at room temperature (27°C) for 0.1 hours.

[0229] 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.

[0230] While heating the bottom solution above at 70°C to 80°C, the entire amount of the drop solution was gradually added to the stirring bottom solution over approximately 30 minutes, and the mixture was further stirred at 70°C to 80°C for 60 minutes. Subsequently, another drop solution was gradually added over approximately 30 minutes, the mixture was stirred at 70°C to 80°C for 60 minutes, and then slowly cooled to room temperature. When a sodium hydroxide aqueous solution (concentration: 48%, manufactured by R&M Chemicals Sdn.Bhd.) was added to this aqueous solution to adjust the pH to 7.5 to 8.0, a precipitate was formed. The aluminum concentration of the PAC charged into the bottom solution was 17% by mass according to ICP-AES, and the number of moles of aluminum was calculated from this. The ratio of the number of moles of sodium lactate added as the drop solution to the number of moles of aluminum was sodium lactate / aluminum 2.

[0231] 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.

[0232] 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.

[0233]

[0234] Therefore, the above precipitates, which are complexes with fragments having molecular weights of 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.

[0235] [Aluminum NMR Analysis] Nuclear magnetic resonance spectroscopy of aluminum-27 is an effective method for analyzing the state of aluminum in a substance. In the aluminum compound according to the present invention, aluminum atoms are bonded to oxygen 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 revealed that lactic acid is bidentately coordinated with a carboxylate group and a hydroxyl group, and aluminum adopts a hexa-coordinate structure (Reference 2: G. Giorgio Bombi, Benedetto Corain, Abdiqafar A. Sheikh-Osman, Inorganica Chimica 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 hexa-coordinate structure. On the other hand, in the aluminum NMR of the aluminum lactate obtained as the 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 hexa-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, it is believed that in 6-coordinate aluminum, the chemical shift value increases significantly as the number of aluminum atoms forming the aluminum core increases, i.e., as the nucleus becomes more multinucleated. In other words, the aluminum lactate obtained as the precipitate is considered to be a complex with 6-coordinate aluminum cores containing two or more aluminum atoms.As discussed above, it is reasonable to assume that the number of aluminum atoms is 2. Therefore, the aluminum lactate obtained as the precipitate is considered to be a complex in which two aluminum atoms in a 6-coordinate state are bonded together by oxygen atoms such as hydroxyl groups.

[0236] 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 at the time of 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 obtained as a precipitate, 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.

[0237] The structure of the aluminum lactate compound obtained as the precipitate is estimated to be as follows. Note that "Lact" represents a lactate residue.

[0238] [Preparation of Crosslinking Agent for Dip Molding] [Example A1] (Preparation of A1 of Drop Solution 1) 24.7 g of aqueous sodium lactate solution (concentration: 60%, manufactured by Haihang Industry Co. Ltd.), 5.8 g of sodium glycolate (98% by mass, solid), and 50.0 g of deionized water were added to a 200 mL glass container and stirred at room temperature (27°C) for 0.1 hours to obtain A1 of Drop Solution 1.

[0239] (Preparation of bottom solution A1) In a 200 mL glass container, combine the following: aqueous solution of polyaluminium chloride (PAC (High Purity Polyaluminium Chloride), No. 003 (abbreviation), manufactured by HENAN TAIRAN WATER PURIFICATION MATERIAL CO. LTD, [Al ２(OH) ｂ ・Cl ６－ｂ ] ａ (where 1 ≤ b ≤ 5, a ≤ 10) 30.0 g and 40.0 g of deionized water were added and stirred at 70°C to 80°C for 30 minutes to obtain 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. The basicity of PAC N003 is in the range of 45% to 50% according to the catalog value.

[0240] (Preparation of dip molding crosslinking agent A1) Then, while heating bottom solution A1 at 70°C to 80°C, the entire amount 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.

[0241] Regarding this aqueous solution, the above ２７ Al-NMR, mass spectrometry, degree of polymerization, pH, and aluminum concentration were measured. Based on these results, it was confirmed that the solution contained an aluminum hydroxylate compound, and this solution was designated as dip molding crosslinking agent A1. Note that the aluminum concentration (Al ２ O ３ The converted amount was 6.5% by mass. In general formula (1), the aluminum hydroxy acid salt compound is represented by m=0, H ｘ A １ is a lactate residue, H ｘ A ２ is a glycolic acid residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ This compound has a structure in which the X bonded to the Al atom is a hydroxyl group.

[0242] [Examples A2 to A7, Comparative Examples A1 to A2] (Preparation of A2 to A9 of Drop Solution 1) Each of A2 to A9 of Drop Solution 1 was obtained by preparing it in the same manner as the preparation of A1 of Drop Solution 1 in Example A1, except that the blending amounts of an aqueous sodium hydroxide solution (concentration: 48%), an aqueous sodium lactate solution (concentration: 60%), sodium glycolate (98% by mass, solid), and ion-exchanged water were changed to the blending amounts shown in Table 2.

[0243] (Preparation of A3 to A6 of Drop Solution 2) Each of A3 to A6 of Drop Solution 2 was obtained by preparing it in the same manner as the preparation of A1 of Drop Solution 1 in Example A1, except that the blending amounts of L-ascorbic acid, sodium thioglycolate, thiolactic acid, citric acid, an aqueous sodium hydroxide solution (concentration: 48%), and ion-exchanged water were changed to the blending amounts shown in Table 2.

[0244] (Preparation of Bottom Solutions A2 to A9) Each of Bottom Solutions A2 to A9 was obtained by preparing it in the same manner as the preparation of Bottom Solution A1 in Example A1. Note that Bottom Solutions A2 to A6, A8, and A9 are the same solutions as Bottom Solution A1.

[0245] (Preparation of Crosslinking Agents A2, A7 to A9 for Dip Molding) Each of Crosslinking Agents A2, A7 to A9 for Dip Molding was obtained by preparing it in the same manner as the preparation of Crosslinking Agent A1 for Dip Molding in Example A1, except that each of A2, A7 to A9 of Drop Solution 1 was used instead of A1 of Drop Solution 1, each of A2, A7 to A9 of Bottom Solution was used instead of Bottom Solution A1, and the blending amount of the aqueous sodium hydroxide solution was changed to the blending amount shown in Table 2.

[0246] (Preparation of Crosslinking Agents A3 to 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 was used instead of Bottom Solution A1.

[0247] Furthermore, while heating bottom solutions A3 to A6 at 70°C to 80°C, the entire contents of drop solution 1 A3 to A6 were gradually added to the stirred bottom solutions A3 to A6 over approximately 30 minutes. Then, while heating at 70°C to 80°C, the entire contents of drop solution 2 A3 to A6 were further added over approximately 30 minutes, and the mixture was stirred for another 60 minutes at 70°C to 80°C.

[0248] 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.

[0249] Table 2 shows the aluminum concentration (Al) contained in dip molding crosslinking agents A2 to A9. ２ O ３ The conversions are shown below.

[0250] Furthermore, by using a 1 L flask instead of a 200 mL 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.

[0251] The aluminum hydroxylate compound contained in dip molding crosslinking agent A2 is, in general formula (1), m = 0, H ｘ A １ is a lactate residue, H ｘ A ２ is a glycolic acid residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It is a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 6.8% by mass.

[0252] The aluminum hydroxyate compound contained in dip molding crosslinking agent A3 is, in general formula (1), m = 0, H ｘ A １ is a lactate residue, H ｘ A ２ This is an L-ascorbic acid residue, H ｘ A １X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It is a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 6.4% by mass.

[0253] The aluminum hydroxyate compound contained in dip molding crosslinking agent A4 is, in general formula (1), m=0, H ｘ A １ is a lactate residue, H ｘ A ２ is a thioglycolic acid residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It is a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 6.4% by mass.

[0254] The aluminum hydroxyate compound contained in dip molding crosslinking agent A5 is, in general formula (1), m=0, H ｘ A １ is a lactate residue, H ｘ A ２ is a thiolactate residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It is a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 6.4% by mass.

[0255] The aluminum hydroxyate compound contained in dip molding crosslinking agent A6 is, in general formula (1), m = 0, H ｘ A １ is a glycolic acid residue, H ｘ A ２ is a citrate residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A２ It is a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 5.4% by mass.

[0256] The aluminum hydroxyate compound contained in dip molding crosslinking agent A7 has m=0 and H in general formula (1). ｘ A １ is a lactate residue, H ｘ A ２ is a glycolic acid residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It is a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 8.0% by mass.

[0257] The aluminum hydroxyate compound contained in dip molding crosslinking agent A8 is, in general formula (1), m = 0, H ｘ A １ and H ｘ A ２ Both are lactate residues, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It is a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 6.4% by mass.

[0258] The aluminum hydroxyate compound contained in dip molding crosslinking agent A9 is, in general formula (1), m = 0, H ｘ A １ and H ｘ A ２ Both are glycolic acid residues, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２It is a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 6.9% by mass.

[0259]

[0260] [Preparation of Crosslinking Agent for Dip Molding] [Example B1] (Preparation of B1 of Drop Solution 1) 35.3 g of sodium lactate aqueous solution (concentration: 60%, manufactured by Haihang Industry Co. Ltd.) and 30.0 g of deionized water were added to a 200 mL glass container and stirred at room temperature (27°C) for 0.1 hours to obtain B1 of Drop Solution 1.

[0261] (Preparation of B1 of 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 B1 of Drop Solution 2.

[0262] (Preparation of bottom solution B1) In a 200 mL glass container, combine the following: aqueous solution of polyaluminum chloride (PAC (High Purity Polyaluminium Chloride), No. 003 (abbreviation), manufactured by HENAN TAIRAN WATER PURIFICATION MATERIAL CO. LTD, [Al ２ (OH) ｂ ・Cl ６－ｂ ] ａ (However, 30.0 g of 1 ≤ b ≤ 5, a ≤ 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.

[0263] (Preparation of dip molding crosslinking agent B1) Then, while heating bottom solution B1 at 70°C to 80°C, the entire amount of B1 from drop solution 1 was 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 amount of B1 from drop solution 2 was further gradually 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.

[0264] Regarding this aqueous solution, the above ２７ Al-NMR, mass spectrometry, pH, and aluminum concentration were measured. 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 A １ and H ｘ A ２ is a lactate residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It includes a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 5.5% by mass.

[0265] [Examples B2-B4, Comparative Examples B1-B4] (Preparation of Drop Solution 1 B2-B8) Drop Solution 1 B2-B8 were obtained in the same manner as the preparation of Drop Solution 1 B1 in Example B1, except that the amounts of sodium lactate aqueous solution, sodium glycolate (98% by mass, solid), and deionized water were changed to the amounts shown in Table 3.

[0266] (Preparation of Drop Solution 2 B2 to B4) Drop Solution 2 B2 to B4 were obtained by preparing them in the same manner as the preparation of Drop Solution 2 B1 in Example B1, except that the amount of acetic acid was changed to the amount shown in Table 3.

[0267] (Preparation of bottom solutions B2 to 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.

[0268] (Preparation of dip molding crosslinking agents B2 to B4) As shown in Table 3, dip molding crosslinking agents B2 to B4 were obtained 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.

[0269] (Preparation of dip molding crosslinking agents B5 to B8) As shown in Table 3, dip molding crosslinking agents B5 to B8 were obtained 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, bottom solution B5 to B8 were used instead of bottom solution B1, and the amount of sodium hydroxide aqueous solution was changed to the amount shown in Table 3.

[0270] Table 3 shows the aluminum concentration (Al) contained in dip molding crosslinking agents B2 to B8. ２ O ３ The conversions are shown below.

[0271] The crosslinking agent B2 for dip molding is acetic acid and, in general formula (1), m=0, H ｘ A １ is a lactate residue, H ｘ A ２ is a glycolic acid residue, H ｘ A １X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It includes a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 5.6% by mass.

[0272] The dip molding crosslinking agent B3 is acetic acid and, in general formula (1), m=0, H ｘ A １ is a lactate residue, H ｘ A ２ is a glycolic acid residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It includes a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 5.7% by mass.

[0273] The dip molding crosslinking agent B4 is acetic acid and, in general formula (1), m=0, H ｘ A １ and H ｘ A ２ is a glycolic acid residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It includes a compound having a structure in which X, which is bonded to the Al atom, is a hydroxyl group. Aluminum concentration (Al ２ O ３ The converted value was 6.0% by mass.

[0274] The crosslinking agent B5 for dip molding is in general formula (1) m=0, H ｘ A １ and H ｘ A ２ is a lactate residue, H ｘ A １ X, which bonds to the Al atom, is a chlorine atom, H ｘ A ２ It contains compounds having a structure in which X, which is bonded to the Al atom, is a hydroxyl group, but does not contain acetic acid. Aluminum concentration (Al２ O ３ The conversion) was 6.4% by mass.

[0275] The crosslinking agent B6 for dip molding has, in the general formula (1), m = 0, H ｘ A １ is a lactic acid residue, H ｘ A ２ is a glycolic acid residue, H ｘ A １ X bonded to the Al atom bonded to is a chlorine atom, H ｘ A ２ and a compound having a structure in which X bonded to the Al atom bonded to is a hydroxy group, and does not contain acetic acid. The aluminum concentration (Al ２ O ３ The conversion) was 6.5% by mass.

[0276] The crosslinking agent B7 for dip molding has, in the general formula (1), m = 0, H ｘ A １ is a lactic acid residue, H ｘ A ２ is a glycolic acid residue, H ｘ A １ X bonded to the Al atom bonded to is a chlorine atom, H ｘ A ２ and a compound having a structure in which X bonded to the Al atom bonded to is a hydroxy group, and does not contain acetic acid. The aluminum concentration (Al ２ O ３ The conversion) was 6.8% by mass.

[0277] The crosslinking agent B8 for dip molding has, in the general formula (1), m = 0, H ｘ A １ and H ｘ A ２ are glycolic acid residues, H ｘ A １ X bonded to the Al atom bonded to is a chlorine atom, H ｘ A ２ and a compound having a structure in which X bonded to the Al atom bonded to is a hydroxy group, and does not contain acetic acid. The aluminum concentration (Al ２ O ３ The conversion) was 6.9% by mass.

[0278]

[0279] [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.

[0280] 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.

[0281] The compound solution was prepared by stirring and then aging it for one day, two days, or three days. Each of these solutions was then used for dip molding in the dipping test.

[0282] (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 water that had been weighed in advance 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 added to the calcium nitrate aqueous solution while stirring. 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 solidification solution weighing 6500 g.

[0283] 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.

[0284] 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 state for 3 seconds, and then removed for 1 second. An X-NBR film was formed on the surface of the hand mold. To gel the 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.

[0285] After the leaching process was completed, the cuff end of the glove, formed from the thin film, was rolled up to create a ring and reinforced. Then, it was dried at a drying temperature of 110°C for 18 minutes.

[0286] 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.

[0287] [Example C2] Nitrile gloves were obtained for each of the dip compound solutions A2 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 A2 obtained in Example A2 was used instead of the dip molding crosslinking agent A1 obtained in Example A1.

[0288] [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.

[0289] [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.

[0290] [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.

[0291] [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.

[0292] [Comparative Example C1] Nitrile gloves for 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 dip molding crosslinking agent A8 obtained in Comparative Example A1 was used instead of dip molding crosslinking agent A1 obtained in Example A1.

[0293] [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 the dip molding crosslinking agent A9 obtained in Comparative Example A2 was used instead of the dip molding crosslinking agent A1 obtained in Example A1.

[0294] [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.

[0295] [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.

[0296] [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.

[0297] [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.

[0298] [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.

[0299] [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.

[0300] [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.

[0301] [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.

[0302] [Physical Property Tests] Various physical property tests were performed using the nitrile gloves obtained above. For the nitrile gloves of Examples C1 to C6 and Comparative Examples C1 and C2, gloves that had been aged by being stored at 100°C for 22 hours after manufacturing were used for the physical property tests. For the nitrile gloves of Examples D1 to D4 and Comparative Examples D1 to D4, both gloves that had been aged by being stored at 100°C for 22 hours after manufacturing and gloves that had not undergone the above aging process were prepared. For the nitrile gloves of Examples D1 to D4 and Comparative Examples D1 to 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.

[0303] (1) Tensile strength, tensile elongation, and modulus The tensile strength (MPa), tensile elongation (%), and modulus (MPa) were measured using each of the nitrile gloves obtained above, in accordance with ASTM D412. Specifically, the molded bodies were punched out using a DieC manufactured by Dumbbell, and test specimens were prepared. These test specimens were measured using an A&D STA-1225 universal tester (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).

[0304] (2) Tensile Test and Fatigue Durability Tensile tests were performed on each of the nitrile gloves obtained above, and the fatigue durability (minutes) was further measured for the nitrile gloves of Examples D1 to D4 and Comparative Examples D1 to 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 ASTM 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.

[0305] 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 bottom 60 mm of the specimen 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).

[0306] These measurement results are shown in Tables 4 and 5.

[0307]

[0308] From the results shown in Table 4, H ｘ A １ and H ｘ A ２Nitrile 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 having a different structure from the above, 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 or more and 1.13 or less for a tensile strength after a 3-day maturation period compared to a tensile strength after a 1-day maturation period, indicating that they matured in a short time of less than 24 hours and exhibited stable tensile strength.

[0309] Meanwhile, H ｘ A １ and H ｘ A ２ Nitrile gloves using the crosslinking agents described in Comparative Examples C1 to C2, which contain compounds having a structure represented by general formula (1) in which hydroxy acid residues have the same structure, 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 3-day maturation period compared to a 1-day maturation period (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.

[0310] Although not shown in Table 4, various physical property tests were also performed for each example without aging (unaged) by storing the gloves at 100°C for 22 hours after manufacturing. For the nitrile gloves using the crosslinking agent according to Example C1, the tensile strength after one day of aging was 27.19 MPa, and after two days of aging was 29.30 MPa. Similarly, for the nitrile gloves using the crosslinking agent according to Example C2, the tensile strength after one day of aging was 27.80 MPa, and after two days of aging was 29.92 MPa. Thus, even in the unaged case, aging occurred in a short time of less than 24 hours, and the tensile strength remained stable.

[0311]

[0312] As shown in Table 5, the nitrile gloves using the crosslinking agents according to each of Examples D1 to D4, which contain compounds having the structure represented by general formula (1) and organic acids, exhibited excellent fatigue resistance. Specifically, the nitrile gloves using the crosslinking agents according to each of Examples D1 to D4 all had a fatigue resistance of 200 minutes or more, demonstrating excellent fatigue resistance.

[0313] On the other hand, the nitrile gloves using the crosslinking agents in Comparative Examples D1 to D4, which did not contain organic acids, exhibited inferior fatigue endurance. Specifically, the nitrile gloves using the crosslinking agents in Comparative Examples D1 to D4 all had a fatigue endurance of 111 minutes or less, indicating poor fatigue endurance.

[0314] 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 according to 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.

[0315] 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.

[0316] (Low-temperature crosslinking test) A low-temperature crosslinking test was conducted 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 by 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.

[0317]

[0318] 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.

[0319] The crosslinking agent according to the present invention has the characteristic of rapidly coordinating with the carboxyl groups of X-NBR in the compound solution and forming an interparticle crosslinked structure while remaining in solution. Therefore, it is possible to obtain a molded article with sufficient tensile strength and modulus by only a low-temperature drying process, without using a high-temperature crosslinking furnace of 110°C or higher, which has been considered essential in conventional X-NBR glove manufacturing. In other words, the crosslinking reaction using the crosslinking agent according to the present invention differs from the conventional method of "proceeding with crosslinking at high temperature after drying" in that it is a "pre-crosslinking process in which the crosslinking reaction is completed in advance in the compound solution," and it is presumed that this is the factor that enables film formation by low-temperature drying.

[0320] To confirm the moldability and physical properties of the crosslinking agent according to the present invention under low-temperature drying conditions, a dipping compound solution prepared in the same manner as in Example C1 was used, except that crosslinking agent A7 obtained in Example A7 was used instead of crosslinking agent A1. Gloves were then produced using a drying condition of 40°C for 8 hours after the beading process. The maturation period of the compound solution was set to 2 days, and Examples F1 and F2 were obtained by changing the amount of crosslinking agent added. The dipping conditions, gelation conditions, leaching conditions, and beading conditions were the same as in Example C1. The amount of crosslinking agent used in Examples F1 and F2, the drying conditions, and the physical properties of the obtained gloves (unaged) are shown in Table 7.

[0321] As shown in Table 7 below, Example F1 exhibited a tensile strength of 28.97 MPa, a tensile elongation of 636%, and a 300% modulus of 3.67 MPa, while Example F2 exhibited a tensile strength of 31.95 MPa and a 300% modulus of 5.90 MPa. Both examples demonstrated sufficient mechanical properties under low-temperature drying conditions of 40°C. These results support the conclusion that the crosslinking agent according to the present invention forms a crosslinked structure with X-NBR in the compound solution beforehand, thus exhibiting high strength and appropriate modulus through a low-temperature drying process alone.

[0322] Furthermore, by using the crosslinking agent according to the present invention, a molding process that does not require a high-temperature crosslinking furnace becomes possible, resulting in significant energy savings and reductions in carbon dioxide emissions compared to conventional manufacturing processes. For this reason, the dip molding composition and crosslinking agent according to the present invention have extremely important industrial value as a sustainable manufacturing technology that is highly compliant with ESG (Environmental, Social, and Governance) requirements for achieving energy conservation and decarbonization.

[0323]

[0324] [Tests using different hydroxy acids] The crosslinking agent according to the present invention can be used in combination with multiple types of hydroxy salts such as lactic acid, glycolic acid, ascorbic acid, citric acid, thioglycolic acid, and thiolactic acid to adjust the coordination environment for the aluminum dinuclear complex, thereby allowing for better control of crosslinking reactivity, ligand exchangeability, and solution stability. To evaluate this feature of the present invention in more detail, drop solutions 1 to 3 were prepared by combining different types of hydroxy salts, as shown in Table 8 below, and these were used to prepare the dip molding crosslinking agents according to Examples G1 to G5 and Comparative Example G1.

[0325] Drop solution 1 was prepared by dissolving lactic acid, citric acid monohydrate, or a combination thereof in deionized water, and adding a 48% by mass sodium hydroxide aqueous solution as needed to create basic conditions. Drop solution 2 was prepared by dissolving ascorbic acid, sodium thioglycolate, citric acid monohydrate, etc., in water, and similarly adjusting the conditions to be basic with a sodium hydroxide aqueous solution. Drop solution 3 was prepared by dissolving sodium thioglycolate in deionized water and was used in Examples G2 to G4. The proportions of each drop solution are shown in Table 8 below, and the design was such that the structure of the final aluminum complex would change by changing the type and ratio of hydroxy acid residues.

[0326] The bottom solution was prepared by adding 30 g of an aqueous solution of polyaluminum chloride (PAC N003) to 40 g of deionized water and stirring at 70-80°C for 30 minutes. Then, drop solution 1 shown in Table 8 was gradually added to the bottom solution over 30 minutes and stirred at 70-80°C for 60 minutes. Drop solutions 2 and 3 were added sequentially in the same manner as needed, and the mixture was stirred again for 60 minutes to form an aluminum hydroxy acid complex in which hydroxy acid residues were coordinated to the aluminum dinuclear skeleton.

[0327] The mixed solution was slowly cooled to room temperature, and the amount of 48% by mass sodium hydroxide aqueous solution shown in Table 8 was added to adjust the pH to a range of 7.5 to 8.0. In all cases, a uniform aqueous solution ranging from clear to pale yellow was obtained. The aluminum concentration (Al) of each crosslinking agent obtained was then calculated. ２ O ３ The converted percentage ranged from 5.0% to 7.2% by mass, and varied depending on the type and ratio of hydroxy acid residues incorporated.

[0328] The crosslinking agents in Examples G1 to G5 all have structures containing multiple types of hydroxy acid residues (such as lactic acid + thioglycolic acid, lactic acid + citric acid, and lactic acid + ascorbic acid), and their coordination environment is significantly different from that of Comparative Example G1 (mainly citric acid).

[0329] When multiple hydroxy acids are combined, the following characteristics are obtained: (i) steric hindrance is dispersed and coordination exchange with aluminum proceeds smoothly; (ii) complex decomposition in the basic region (pH 7.5-8.0) is suppressed; and (iii) substitution reactions with the carboxyl group of X-NBR proceed rapidly.

[0330] From the results above, it was confirmed that, unlike complexes containing only a single hydroxy acid residue (lactic acid or citric acid), the crosslinking agent according to the present invention forms an aluminum hydroxy acid complex having multiple hydroxy acid residues, thereby comprehensively improving solution stability, coordination exchangeability, and crosslinking reactivity. These crosslinking agents are also effective in obtaining molded articles that exhibit sufficient physical properties after low-temperature drying at 40°C, as shown in Examples F1 and F2 above, and further strengthen the pre-crosslinking process of the present invention.

[0331]

[0332] [Examples H1-H4 and Comparative Example H1] Using X-NBR latex HT-108 (solid content 45% by mass) manufactured by Hong Tai (China), dip molding compounds were prepared using the crosslinking agents obtained in Examples G1-G3, G5 and Comparative Example G1, and the physical properties of the resulting molded articles were evaluated.

[0333] Specifically, 5.4 kg of HT-108 was weighed and filtered. Next, the crosslinking agents obtained in Examples G1 to G3, G5, or Comparative Example G1 were weighed in the amounts shown in Table 9 below, and deionized water was added to each to prepare a diluted aqueous solution of the crosslinking agent (total amount 1.215 kg) in which the aluminum oxide concentration was 0.5% by mass relative to the solid content of HT108. This diluted aqueous solution of the crosslinking agent was slowly added to HT-108 and stirred for 30 minutes to disperse uniformly.

[0334] Next, 1.62 kg of 3% by mass potassium hydroxide aqueous solution was added, followed by 1.89 kg of deionized water, and the mixture was stirred until homogeneous to obtain a total compound solution for dip molding with a total volume of 10.12 kg. The compound was allowed to mature for 24 hours. The specific formulations for each example and comparative example are shown in Table 9 below.

[0335] (Dipping Test) The dipping conditions, coagulant solution, wetting agent solution, gelling process, leaching process, and beading process were carried out in the same manner as in Example C1. The glove precursor after film formation was heated and dried in an oven at 90°C for 18 minutes. After drying, it was returned to room temperature and released from the mold to obtain gloves.

[0336] (Aging Treatment and Physical Property Measurement) The obtained gloves were subjected to aging treatment at 100°C for 22 hours in accordance with ASTM D412. Test specimens were prepared after aging, and tensile strength, tensile elongation, 300% modulus, and stress retention rate were measured. The physical property results for Examples H1 to H4 and Comparative Example H1 are shown in Table 9 below.

[0337] (Results and Discussion) As shown in Table 9 below, Examples H1 to H4, which used crosslinking agents containing multiple types of hydroxy acid residues (Examples G1, G2, G3, G5), all showed high tensile strength and appropriate modulus, and also exhibited good stress retention.

[0338] In Example H1, the material exhibited a tensile strength of 26.2 MPa, a tensile elongation of 868%, a 300% modulus of 3 MPa, and a stress retention rate of 53%, demonstrating a good balance between strength and flexibility.

[0339] Examples H2 and H3 showed high stress retention rates of 64% and 59.8%, respectively, confirming that crosslinking agents using multiple hydroxy acid residues as ligands improve crosslinking uniformity and reactivity.

[0340] In Example H4, the highest value was observed at a tensile strength of 27.5 MPa, clearly demonstrating the strong formation of interparticle crosslinks.

[0341] On the other hand, the crosslinking agent used in Comparative Example G1 in Comparative Example H1 was an aluminum hydroxy acid chloride complex with only citric acid as a ligand, and because the coordinating hydroxy acid residue had a single structure, its crosslinking reactivity was insufficient. As a result, Comparative Example H1 had a low tensile strength of 17 MPa and a 300% modulus of 2.1 MPa, clearly demonstrating the performance difference compared to crosslinking agents having multiple hydroxy acid residues.

[0342]

[0343] [High-Basicity Polyaluminum Chloride Test] Examples of producing aluminum hydroxylate compounds using high-basic aluminum chloride (PAC N004, trade name of HENAN TAIRAN WATER PURIFICATION MATERIAL CO. LTD, equivalent to the above-mentioned ACH) having a basicity of 75% to 90% and an atomic ratio of aluminum atoms to chlorine atoms of 1.9 / 1 to 2.1 / 1 will be described. As shown in Table 10 below, drop solution 1 was prepared by mixing lactic acid and ion-exchanged water, and in Examples I1 to I3, drop solution 2 was prepared by mixing citric acid monohydrate and ion-exchanged water. In Comparative Example I1, citric acid was not used. Separately, a bottom solution was prepared by heating and dissolving PAC N004, and after mixing these solutions, the pH was adjusted with an aqueous sodium hydroxide solution to obtain a dip molding crosslinking agent containing an aluminum hydroxylate compound.

[0344] Drop solution 1 was prepared by mixing 6.8 to 27 g of lactic acid (88% purity by mass) with 30 g of deionized water and stirring at room temperature. Drop solution 2 was obtained by dissolving 14.1 to 42.2 g of citric acid monohydrate (99.5% purity by mass) in 30 g of deionized water. In Comparative Example I1, citric acid was not used, so drop solution 2 was not prepared. Both lactic acid and citric acid can bidentately coordinate to aluminum as hydroxy acid residues, and therefore function as effective ligands for the formation of the aluminum hydroxy acid complex of the present invention.

[0345] As the bottom solution, 30 g of PAC N004 was added to 40 g of deionized water, heated and stirred at 70-80°C to obtain a homogeneous solution. PAC N004 has a high basicity of 75% to 90%, and the solution contains dinuclear aluminum species with three or more nuclei (Al ３ Al ４ Al １３It is known that these multinucleates (etc.) can coexist. The internal aluminum of these multinucleates is constrained by μ-OH crosslinking and is less susceptible to coordination exchange reactions, but the aluminum located at the ends of the multinuclear structure is reactive and preferentially exchanges coordination with lactic acid or citrate residues. In this example as well, it is presumed that a complex aluminum hydroxylate complex is formed that includes a reaction unit (active end portion) corresponding to a dinuclear body while maintaining a multinuclear structure. In other words, even when a high-basicity PAC is used, it is not just a dinuclear body that is formed, but rather a dinuclear reaction unit and a multinuclear structure with three or more nuclei coexist.

[0346] The mixed solution was slowly cooled to room temperature, and the amount of sodium hydroxide aqueous solution (48% by mass) shown in Table 10 was added to adjust the pH to between 7.5 and 8.0. Although PAC N004 is prone to gelation under weakly alkaline conditions, under the conditions of this example, coordination exchange with hydroxy acid residues could be promoted while suppressing a rapid increase in local pH. The resulting solutions were all transparent or pale yellow, and no precipitate was formed. From this, it is presumed that a stable aluminum hydroxy acid acid complex was formed, containing dinuclear reaction units while also having a multinuclear structure of three or more nuclei.

[0347] The aluminum concentration (Al) of the resulting dip molding crosslinking agent ２ O ３ The converted values ​​were 6.2% by mass, 6.7% by mass, and 7.4% by mass for Examples I1 to I3, as shown in Table 10 below, and 10.0% by mass for Comparative Example I1. In other words, even when using high-basicity PAC, by appropriately controlling the ratio of hydroxy acids and the amount of sodium hydroxide added, it was possible to obtain a stable aluminum hydroxy acid complex in which dinuclear reaction units and multinuclear structures of three or more nuclei coexist, and it was confirmed that this complex effectively functions in the crosslinking reaction with X-NBR of the present invention.

[0348]

[0349] For the X-NBR latex, NL129 manufactured by LG Chem (South Korea) was used. 4.5 kg of NL129 latex (45% solid content) was weighed and filtered.

[0350] Next, the amount of aluminum hydroxylate crosslinking agent (crosslinking agent for Example I1) shown in Table 11 was taken and diluted with deionized water to a total volume of 2.025 kg. This diluted crosslinking agent aqueous solution was gradually added to NL129 latex and stirred for 30 minutes after addition. Subsequently, 1.553 kg of 3% by mass potassium hydroxide aqueous solution was added and stirred until homogeneous. After that, 0.36 kg of deionized water was added to form a compound.

[0351] After allowing the resulting compound to stand to remove air bubbles, dip molding was performed. First, a cleaned porcelain hand mold was immersed in an aqueous solution of a coagulant containing calcium salt (concentration 5-20% by mass) to form a coagulant film on the surface of the hand mold, and then dried. Next, the hand mold was preheated (40-70°C) and immersed in the resulting compound at a constant speed to form a film.

[0352] The coating, after immersion, was rapidly gelled by holding it in an environment of 100-120°C for 90-120 seconds.

[0353] Subsequently, the coating was leached in water to remove coagulant residue and soluble components. Then, it was dried at 90°C for 18 minutes to form a uniform film. After drying, the molded body was released from the hand mold to obtain a glove-shaped molded body with an average film thickness of approximately 0.9 mm.

[0354] The fabricated gloves were aged for one day (Day 1) or three days (Day 3), after which their mechanical properties were measured according to ASTM D412 and EN455. The results are shown in Table 11 below.

[0355] Furthermore, the above compound may be used in combination, as needed, with a release agent to provide release properties, a pigment for coloring, an antioxidant, a UV stabilizer, and other additives commonly used by those skilled in the art in latex molding. In addition, commercially available release agents or surfactants can be appropriately added to the aqueous solution of the coagulant to adjust the coagulation and release properties. The presence or absence of these additives and the types used do not hinder the effects of the present invention and can be selected arbitrarily.

[0356] As shown in Table 11 below, even when using highly basic aluminum chloride, the nitrile gloves using the crosslinking agents according to each of Examples J1 to J3, which combine lactic acid and citric acid as hydroxy acids, matured in a short time of less than 24 hours, and their tensile strength was stable. Specifically, the nitrile gloves using the crosslinking agents according to each of Examples J1 to J3 showed a tensile strength of 1.04 or more and 1.07 or less after a 3-day maturation period compared to the tensile strength after a 1-day maturation period, indicating that they matured in a short time of less than 24 hours and their tensile strength was stable.

[0357] On the other hand, nitrile gloves using the crosslinking agent according to Comparative Example J1, which uses only lactic acid as the hydroxy acid, showed unstable tensile strength, with a significant increase after the maturation period. Specifically, the nitrile gloves using the crosslinking agent according to Comparative Example J1 showed a tensile strength of 1.25 after a 3-day maturation period compared to a 1-day maturation period (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. Thus, the significant progression of crosslinking due to maturation suggests that the crosslinking reaction in the compound is excessively delayed. Such delayed crosslinking impairs stability in the manufacturing process and creates problems with the practicality of the compound.

[0358] Furthermore, differences in the basicity of the PAC clearly affected the mechanical properties of the X-NBR molded article. Specifically, when PAC with a basicity of 40-60% was used, the complex mainly formed a dinuclear structure (Al ２The resulting structure, with its relatively close crosslinking points, exhibited high 300% modulus (M300) and 500% modulus (M500), resulting in a molded article with relatively hard elastic properties. In contrast, when a highly basic PAC with a basicity of 75-90%, such as PAC N004, was used, M300 and M500 decreased, and a more flexible molded article was obtained. This is presumed to be because, when a highly basic PAC is used, a multinuclear structure with three or more nuclei coexists in addition to the dinuclear structure, and in this multinuclear structure, the internal aluminum is less likely to undergo coordination exchange, so only the terminal aluminum is substantially involved in the crosslinking reaction, resulting in a longer distance between the crosslinking points formed in the X-NBR. In Examples J1 to J3, M300 was clearly lower compared to Comparative Example J1, demonstrating that the multinuclear aluminum hydroxyate complex derived from highly basic PAC is useful for soft rubber glove applications.

[0359] Furthermore, when lactic acid alone was used as the hydroxy acid (Comparative Example J1), the tensile strength on Day 1 decreased to 20.0 MPa, indicating insufficient initial strength. In contrast, Examples J1 to J3, which combined lactic acid and citric acid, showed sufficient tensile strength of 23 to 27 MPa from Day 1.

[0360] As described above, the type and ratio of hydroxy acids are important for suppressing initial crosslinking and excessive crosslinking during maturation. In particular, it was suggested that lactic acid alone is prone to insufficient strength and rapid crosslinking due to maturation.

[0361]

[0362] 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

A crosslinking agent comprising a compound having a structure represented by the following general formula (4). (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.) 　 A crosslinking agent comprising a compound having a structure represented by the following general formula (4) and an organic acid. (In formula (4), each X independently represents a chlorine atom or a hydroxy group, 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.) 　 The crosslinking agent according to claim 2, wherein the organic acid is a fatty acid. 　 The crosslinking agent according to claim 2, wherein the organic acid is formic acid, acetic acid, or propionic acid. 　 The aforementioned H ｘ A １ and H ｘ A ２ The crosslinking agent according to any one of claims 2 to 4, wherein the crosslinking agent is a hydroxy acid residue having a different structure from the one described above. 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. 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. 　 The crosslinking agent according to claim 1 or claim 2, wherein the pH is an aqueous solution between 7.5 and 8.

4. A crosslinking agent according to claim 1 or claim 2, used in dip molding. 　 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. The dip molding composition according to claim 10, which does not contain elemental sulfur or zinc oxide. 　 The dip molding composition according to claim 10, 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. 　 A glove, which is a molded body of the dip molding composition described in claim 10. 　 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. 　 A method for producing a crosslinking agent according to claim 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. 　 The method for producing a crosslinking agent according to claim 14 or claim 15, wherein the basicity of the polyaluminum chloride is 70% or more and 85% or less. 　 A method for producing a crosslinking agent according to claim 14 or claim 15, 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. 　 The method for producing a crosslinking agent according to claim 17, 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. 　 A method for producing a crosslinking agent according to claim 14 or claim 15, 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. 　 A method for manufacturing gloves according to claim 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) 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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