Composition for rubber latex coagulant

Abstract

To provide a composition for a rubber latex coagulant which is excellent in storage stability in a low-temperature environment and can be thinly and uniformly attached to the surface of a mold.SOLUTION: A composition for a rubber latex coagulant to be added to a coagulant for use in dip-forming of rubber, wherein the composition for a rubber latex coagulant has dynamic surface tensions of 29mN / m or more and 45mN / m or less at 100 milliseconds and 27mN / m or more and 40mN / m or less at 1000 milliseconds.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber latex coagulant composition. [Background technology]

[0002] Molded articles such as rubber gloves, rubber balloons, and rubber sacks are produced by dip molding of rubber such as nitrile rubber (NBR) and natural rubber (NR). The dip molding is a molding technique in which a mold, which is the basis for the shape of the molded article, is immersed in a coagulant composition containing a coagulant such as a salt of an inorganic acid and a mold release agent, and the coagulant and mold release agent are attached to the surface of the mold. The mold is then immersed in a rubber latex layer-forming composition containing rubber, and the rubber in the rubber latex layer-forming composition is salted out onto the surface of the mold by the coagulant on the surface of the mold, thereby obtaining a rubber molded article (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 05-247266 Summary of the Invention [Problem to be solved by the invention]

[0004] From the viewpoint of reducing the cost of molded products, attempts have been made to reduce the thickness and weight of such molded products. However, thinning the wall thickness can result in insufficient strength in some areas, which can lead to product defects. To prevent this, it is thought that the occurrence of unevenness in the molded product can be suppressed by thinly and uniformly applying a coagulant to the surface of the mold. However, conventional coagulant compositions have room for improvement in terms of thinly and uniformly applying the coagulant to the surface of the mold.

[0005] The present invention provides a rubber latex coagulant composition that can be applied thinly and uniformly to the surface of a molding die. [Means for solving the problem]

[0006] The present invention provides A rubber latex coagulant composition for addition to a coagulant used in rubber dip molding, comprising: The rubber latex coagulant composition contains a surfactant (a), The rubber latex coagulant composition has a dynamic surface tension of 29 mN / m or more and 45 mN / m or less when measured under the following condition 1, and a dynamic surface tension of 27 mN / m or more and 40 mN / m or less when measured under the following condition 2. <Condition 1> Measurement target of dynamic surface tension: A mixture obtained by mixing a rubber latex coagulant composition with 100 parts by mass of a 20% by mass calcium nitrate aqueous solution so that the content of surfactant (a) contained in the rubber latex coagulant composition is 0.2 parts by mass. Temperature: 50℃ Surface life: 100 ms <Condition 2> Dynamic surface tension measurement object: the above-mentioned mixed liquid Temperature: 50℃ Surface life: 1000 ms [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a rubber latex coagulant composition that can be applied thinly and uniformly to the surface of a molding die. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Rubber latex coagulant composition> The rubber latex coagulant composition of the present embodiment is a rubber latex coagulant composition to be added to a coagulant used in dip molding of rubber, The rubber latex coagulant composition contains a surfactant (a), The rubber latex coagulant composition has a dynamic surface tension of 29 mN / m or more and 45 mN / m or less when measured under the following condition 1, and a dynamic surface tension of 27 mN / m or more and 40 mN / m or less when measured under the following condition 2. <Condition 1> Measurement target of dynamic surface tension: A mixture obtained by mixing a rubber latex coagulant composition with 100 parts by mass of a 20% by mass calcium nitrate aqueous solution so that the content of surfactant (a) contained in the rubber latex coagulant composition is 0.2 parts by mass. Temperature: 50℃ Surface life: 100 ms <Condition 2> Dynamic surface tension measurement object: the above-mentioned mixed liquid Temperature: 50℃ Surface life: 1000 ms

[0009] Rubber dip molding is a molding technique in which a mold, which is the basis for the shape of a molded product, is immersed in a coagulant composition containing a coagulant, and the coagulant composition is adhered to the surface of the mold. The mold is then immersed in a rubber latex layer-forming composition containing rubber, and the coagulant in the coagulant composition on the surface of the mold causes the rubber in the rubber latex layer-forming composition to salt out onto the mold surface, resulting in a rubber molded product. The rubber latex coagulant composition of this embodiment is used to add to the coagulant used in the rubber dip molding. The rubber latex coagulant composition of this embodiment allows the coagulant composition to be applied thinly and uniformly to the surface of the mold. The reason why the rubber latex coagulant composition of this embodiment exhibits such an effect is unclear, but is presumed to be as follows.

[0010] The rubber latex coagulant composition of this embodiment has a dynamic surface tension of 29 mN / m to 45 mN / m at a surface life of 100 milliseconds, and a dynamic surface tension of 27 mN / m to 40 mN / m at a surface life of 1000 milliseconds, measured under specific conditions. It is presumed that such a combination of dynamic surface tensions shortens the time for immersing the molding die in the coagulant composition, reducing the amount of coagulant composition adhered, resulting in a thinner rubber film, and also allows the coagulant composition to adhere uniformly to the molding die, thereby suppressing the occurrence of mottling in the rubber molded product.

[0011] The rubber latex coagulant composition of this embodiment has a dynamic surface tension measured under the condition 1 described above of 29 mN / m or more, preferably 30 mN / m or more, more preferably 31 mN / m or more, and even more preferably 32 mN / m, from the viewpoint of thinning the wall of a rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of a molding die, and from the same viewpoint, the dynamic surface tension is 45 mN / m or less, preferably 43 mN / m or less, more preferably 42 mN / m or less, even more preferably 41 mN / m or less, and still even more preferably 40 mN / m or less. More specifically, the dynamic surface tension measured under the condition 1 is from 29 mN / m to 45 mN / m, preferably from 30 mN / m to 43 mN / m, from the viewpoint of thinning the rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of the mold. From the viewpoints mentioned above and in addition to the viewpoint of increasing the uniformity of the release agent contained in the coagulant composition, uniformly applying the release agent to the mold, and preventing uneven distribution of the coagulant, the dynamic surface tension is more preferably from 31 mN / m to 42 mN / m, even more preferably from 32 mN / m to 41 mN / m, and still more preferably from 32 mN / m to 40 mN / m.

[0012] The procedure for measuring the dynamic surface tension under the condition 1 is as follows. [Method for measuring dynamic surface tension under condition 1] A 20% by weight calcium nitrate aqueous solution was prepared by mixing calcium nitrate tetrahydrate with ion-exchanged water in an amount to give a calcium nitrate concentration of 20% by weight, and then a rubber latex coagulant composition was added to the 20% calcium nitrate aqueous solution so that the content of surfactant (a) in the rubber latex coagulant composition was 0.2 parts by weight per 100 parts by weight of the 20% calcium nitrate aqueous solution. The mixture was stirred at room temperature for 5 hours to obtain a mixed solution. After allowing the mixed solution to stand at 50°C for 2 hours, the dynamic surface tension was measured at a liquid temperature of 50°C with a surface life of 100 milliseconds using a bubble pressure dynamic surface tensiometer (e.g., KRUSS, product name BP100).

[0013] The rubber latex coagulant composition of this embodiment has a dynamic surface tension measured under the conditions of Condition 2 above of 27 mN / m or more, preferably 28 mN / m or more, and more preferably 29 mN / m or more, from the viewpoint of thinning the wall of a rubber molded product by thinly adhering the coagulant composition to the surface of a molding die, and from the same viewpoint, the dynamic surface tension is 40 mN / m or less, preferably 39 mN / m or less, more preferably 38 mN / m or less, even more preferably 37 mN / m or less, and still more preferably 36 mN / m or less. More specifically, the dynamic surface tension measured under the condition 2 is from 27 mN / m to 40 mN / m, preferably from 28 mN / m to 39 mN / m, from the viewpoint of thinning the rubber molded product by thinning the wall of the rubber molded product by uniformly adhering the coagulant composition to the surface of the mold. From the viewpoints mentioned above and in addition to the viewpoint of increasing the uniformity of the release agent contained in the coagulant composition, uniformly applying the release agent to the mold, and preventing uneven distribution of the coagulant, the dynamic surface tension is more preferably from 29 mN / m to 38 mN / m, even more preferably from 29 mN / m to 37 mN / m, and still more preferably from 29 mN / m to 36 mN / m.

[0014] The procedure for measuring the dynamic surface tension under the condition 2 is as follows. [Method for measuring dynamic surface tension under condition 2] Using the same mixed liquid as used in the dynamic surface tension measurement under Condition 1 above, measure the dynamic surface tension at a liquid temperature of 50°C with the same bubble pressure type dynamic surface tensiometer as used in the measurement under Condition 1 above, and with a surface life of 1000 milliseconds.

[0015] The surfactant (a) includes all surfactants contained in the rubber latex coagulant composition of the present embodiment.

[0016] The surfactant (a) preferably contains a nonionic surfactant (1) represented by the following general formula (1), from the viewpoint of achieving thin-walled rubber molded articles by thinly and uniformly adhering the coagulant composition to the surface of the mold, and from the viewpoint of ensuring storage stability in low-temperature environments. R1 O-(AO)nH (1) (In general formula (1), R 1 is a linear or branched aliphatic hydrocarbon group having from 9 to 16 carbon atoms, AO is an alkyleneoxy group having from 2 to 4 carbon atoms, and n represents the average number of moles of AO added, which is a number of from 10 to 20.

[0017] The production of rubber products by dip molding is carried out in a wide range of environments, from cold to warm regions, but when conventional coagulant compositions are stored in low-temperature environments in cold regions (for example, below 0°C), their fluidity decreases, making it impossible to blend them in the required amount, which may result in a deterioration in the performance of the rubber product.In contrast, when the surfactant (a) contained in the rubber latex coagulant composition of this embodiment contains a nonionic surfactant (1), its structure allows the composition to maintain fluidity even at low temperatures.

[0018] In the general formula (1), R 1 is a straight-chain or branched-chain aliphatic hydrocarbon group, preferably a straight-chain or branched-chain alkyl group, from the viewpoint of achieving a thin wall of a rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of the mold, and from the viewpoint of ensuring storage stability in a low-temperature environment.

[0019] In the general formula (1), R 1 The carbon number of the coagulant composition is preferably 9 or more, more preferably 10 or more, and even more preferably 12 or more, from the viewpoint of thinning the wall of a rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of a molding die, and from the viewpoint of ensuring storage stability in a low-temperature environment; and from the same viewpoint, the carbon number is preferably 16 or less, more preferably 14 or less.

[0020] In the general formula (1), AO is preferably an alkyleneoxy group having 2 to 4 carbon atoms, more preferably an alkyleneoxy group having 2 to 3 carbon atoms, from the viewpoint of achieving a thin wall of a rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of a molding die, and from the viewpoint of ensuring storage stability in a low-temperature environment.

[0021] In the general formula (1), n ​​is preferably 10 or more, more preferably 13 or more, and even more preferably 14 or more from the viewpoint of achieving a thin walled rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of the mold, and from the viewpoint of ensuring storage stability in a low-temperature environment; and from the same viewpoint, n is preferably a number of 20 or less, more preferably 18 or less, and even more preferably 16 or less.

[0022] The surfactant (a) preferably contains a nonionic surfactant (2) represented by the following general formula (2), from the viewpoint of achieving thin-walled rubber molded articles by thinly and uniformly adhering the coagulant composition to the surface of the mold, and from the viewpoint of ensuring storage stability in low-temperature environments. R 2 O-(AO)mH (2) (In general formula (2), R 2 is a linear or branched aliphatic hydrocarbon group having from 8 to 15 carbon atoms, AO is an alkyleneoxy group having from 2 to 4 carbon atoms, and m represents the average number of moles of AO added, which is a number of from 6 to 9.

[0023] When the surfactant (a) contained in the rubber latex coagulant composition of the present embodiment contains the nonionic surfactant (2), the fluidity can be maintained even at low temperatures due to its structure.

[0024] In the general formula (2), R 2 is a straight-chain or branched-chain aliphatic hydrocarbon group from the viewpoint of achieving a thin wall thickness of the rubber molded article by thinly and uniformly adhering the coagulant composition to the surface of the mold.

[0025] In the general formula (2), R 2 The carbon number of the coagulant composition is preferably 8 or more, more preferably 10 or more, from the viewpoint of thinning the wall of a rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of a molding die, and from the viewpoint of ensuring storage stability in a low-temperature environment; and from the same viewpoint, the carbon number is preferably 15 or less, more preferably 14 or less, and even more preferably 12 or less.

[0026] In the general formula (2), AO is preferably an alkyleneoxy group having 2 to 4 carbon atoms, more preferably an alkyleneoxy group having 2 to 3 carbon atoms, and even more preferably an alkyleneoxy group having 2 carbon atoms, from the viewpoint of achieving a thin wall of a rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of a molding die, and from the viewpoint of ensuring storage stability in a low-temperature environment.

[0027] In the general formula (2), m is preferably 6 or more, more preferably 8 or more, from the viewpoint of achieving a thin walled rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of the mold, and from the viewpoint of ensuring storage stability in a low-temperature environment, and from the same viewpoint, it is preferably 9 or less.

[0028] The surfactant (a) in the rubber latex coagulant composition of the present embodiment preferably contains the nonionic surfactant (1) and the nonionic surfactant (2).

[0029] When the surfactant (a) contains the nonionic surfactant (1) and the nonionic surfactant (2), the mass ratio of the nonionic surfactant (1) to the nonionic surfactant (2) in the surfactant (a) (mass of the nonionic surfactant (1): mass of the nonionic surfactant (2)) is preferably 100:0 to 20:80, more preferably 100:0 to 30:70, even more preferably 100:0 to 40:60, still more preferably 100:0 to 50:50, still more preferably 100:0 to 60:40, still more preferably 100:0 to 70:30, still more preferably 100:0 to 80:20, still more preferably 100:0 to 90:10, and still more preferably 100:0, from the viewpoint of achieving a thin walled rubber molded article by thinly and uniformly adhering the coagulant composition to the surface of the molding die.

[0030] In the rubber latex coagulant composition of the present embodiment, the total content of the nonionic surfactant (1) and the nonionic surfactant (2) in the surfactant (a) is preferably 90% by mass or more, more preferably 100% by mass, from the viewpoint of achieving a thin walled rubber molded product by thinly and uniformly adhering the coagulant composition to the surface of a molding die and ensuring storage stability in a low-temperature environment.

[0031] The rubber latex coagulant composition of this embodiment preferably contains a water-soluble organic solvent and / or water from the viewpoint of achieving a thin, uniform coating of the coagulant composition on the surface of a mold to produce a thin rubber molded product. In this specification, a water-soluble organic solvent refers to an organic solvent that can be mixed with water in any ratio. When the rubber latex coagulant composition of this embodiment contains a water-soluble organic solvent, the effect of controlling the dynamic surface tension of the rubber latex coagulant composition within the above range is further enhanced, allowing the coagulant composition to be applied more uniformly to the mold. Furthermore, the uniformity of the release agent contained in the coagulant composition is improved, allowing the release agent to be applied uniformly to the mold, preventing uneven distribution of the coagulant. This further suppresses uneven rubber film thickness, i.e., the occurrence of spots.

[0032] From the viewpoint of achieving a thin-walled rubber molded product by uniformly adhering the mold release agent to the mold and preventing uneven distribution of the coagulant, the water-soluble organic solvent preferably contains at least one selected from the group consisting of alkylene glycol, polyalkylene glycol, and alkylene glycol monoalkyl ether, more preferably an alkylene glycol monoalkyl ether.

[0033] The alkylene glycol is preferably at least one selected from the group consisting of ethylene glycol and propylene glycol.

[0034] The polyalkylene glycol is preferably at least one selected from the group consisting of diethylene glycol, triethylene glycol, polyethylene glycol with a sequence number of 4 or more, dipropylene glycol, tripropylene glycol, and polypropylene glycol with a sequence number of 4 or more.

[0035] The alkylene glycol monoalkyl ether preferably contains a water-soluble organic solvent represented by the following general formula (3), from the viewpoint of achieving thin-walled rubber molded articles by uniformly adhering the release agent to the molding die and preventing uneven distribution of the coagulant: CH3-(CH2) p -O-(R 3 O) q -H (3) (wherein p is preferably an integer of 1 to 5, more preferably an integer of 1 to 3; q is preferably an integer of 1 to 5, more preferably an integer of 1 or 2; R 3 is preferably an ethyl group or a propyl group, more preferably a propyl group.

[0036] Examples of alkylene glycol monoalkyl ethers include one or more selected from the group consisting of ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol mono-n-butyl ether, and among these, one or more selected from the group consisting of ethylene glycol mono-n-butyl ether and diethylene glycol monoethyl ether are preferred.

[0037] From the viewpoint of achieving a thin-walled rubber molded article by uniformly adhering the mold release agent to the mold and preventing uneven distribution of the coagulant, the water-soluble organic solvent is more preferably at least one selected from propylene glycol, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether.

[0038] When the rubber latex coagulant composition of the present embodiment contains a water-soluble organic solvent, the content of the water-soluble organic solvent A, which is at least one selected from ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycols with a sequence number of 4 or more, dipropylene glycol, tripropylene glycol, polypropylene glycols with a sequence number of 4 or more, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol mono-n-butyl ether, in the water-soluble organic solvent is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. Among these, the content of water-soluble organic solvent A, which is at least one selected from propylene glycol, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether, in the water-soluble organic solvent contained in the rubber latex coagulant composition is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0039] The content of the surfactant (a) in the rubber latex coagulant composition of the present embodiment is preferably 40% by mass or more, more preferably 50% by mass or more, from the viewpoint of thinning the wall of a rubber molded product by thinly and uniformly adhering the coagulant in the coagulant composition to the surface of the mold, and from the same viewpoint, it is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0040] The content of the water-soluble organic solvent in the rubber latex coagulant composition of the present embodiment is preferably 0% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and still more preferably 15% by mass or more, from the viewpoint of achieving a thin walled rubber molded product by thinly and uniformly adhering the coagulant in the coagulant composition to the surface of the mold, and from the viewpoint of ensuring storage stability in a low-temperature environment; and from the same viewpoints, it is preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less.

[0041] The water content in the rubber latex coagulant composition of the present embodiment is preferably 0% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of improving storage stability in a low-temperature environment, and is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less, from the viewpoint of thinning the wall of a rubber molded product by thinly and uniformly adhering the coagulant in the coagulant composition to the surface of a molding die.

[0042] The rubber latex coagulant composition may contain a thickener, a wetting agent, a defoaming agent, a pH adjuster, an antioxidant, a preservative, an antibacterial agent, etc., as long as the effects of the present invention are not essentially impaired.

[0043] <Rubber latex coagulant composition> The rubber latex coagulant composition of this embodiment contains the rubber latex coagulant composition and a coagulant. The rubber latex coagulant composition of this embodiment can be used to adhere the coagulant in the rubber latex coagulant composition to the surface of the molding die by immersing the molding die in a rubber latex layer-forming composition containing rubber latex before a rubber layer-forming step of forming a rubber layer on the surface of the molding die. Therefore, the rubber latex coagulant composition of this embodiment is substantially free of the rubber latex contained in the rubber latex layer-forming composition.

[0044] When the molding die is immersed in the rubber latex coagulant composition of this embodiment, the coagulant can be applied thinly and uniformly to the surface of the molding die. Therefore, when the molding die is subsequently immersed in a dip-forming composition containing rubber latex, the rubber layer formed on the surface of the molding die can be made thinner and the occurrence of unevenness can be suppressed.

[0045] The coagulant salts out and coagulates the rubber contained in the rubber latex layer-forming composition, and is not particularly limited as long as it is one commonly used in dip molding. Examples of suitable coagulants include one or more selected from the group consisting of barium chloride, calcium chloride, magnesium chloride, zinc chloride, aluminum chloride, barium nitrate, calcium nitrate, zinc nitrate, barium acetate, calcium acetate, zinc acetate, calcium sulfate, magnesium sulfate, and aluminum sulfate. Among these, salts of inorganic acids are preferred from the viewpoint of achieving thin-walled rubber molded products, with one or more selected from the group consisting of barium chloride, calcium chloride, magnesium chloride, zinc chloride, aluminum chloride, barium nitrate, calcium nitrate, zinc nitrate, calcium sulfate, magnesium sulfate, and aluminum sulfate being more preferred, and one or more selected from calcium chloride and calcium nitrate being even more preferred. The coagulants can be used alone or in combination.

[0046] The amount of the rubber latex coagulant composition in the rubber latex coagulant composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, from the viewpoint of thinning the wall of a rubber molded product by thinly and uniformly adhering the coagulant in the coagulant composition to the surface of the mold, and from the same viewpoint, is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, still even more preferably 1% by mass or less, and even even more preferably 0.6% by mass or less.

[0047] The content of the coagulant in the rubber latex coagulant composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of realizing a thin-walled rubber molded product; and from the same viewpoint, it is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, and still more preferably 20% by mass or less.

[0048] The mass ratio of the amount of the rubber latex coagulant composition to the content of the coagulant in the rubber latex coagulant composition (amount of rubber latex coagulant composition / content of coagulant) is preferably 0.0001 or more, more preferably 0.001 or more, even more preferably 0.002 or more, even more preferably 0.005 or more, and still more preferably 0.01 or more, from the viewpoint of thinning the wall of a rubber molded product by thinly and uniformly adhering the coagulant in the coagulant composition to the surface of a molding die; and from the same viewpoint, it is preferably 1 or less, more preferably 0.5 or less, even more preferably 0.1 or less, even more preferably 0.08 or less, and still more preferably 0.05 or less.

[0049] The rubber latex coagulant composition preferably contains a water-soluble organic solvent and / or water from the viewpoint of improving the dispersibility of the rubber latex coagulant composition and the coagulant in the rubber latex coagulant composition. Examples of the water-soluble organic solvent that can be contained in the rubber latex coagulant composition include lower alcohols such as methanol, ethanol, and isopropanol; acetone; and the water-soluble organic solvent brought in from the rubber latex coagulant composition of this embodiment.

[0050] The rubber latex coagulant composition preferably contains at least one selected from a release agent, a thickener, a wetting agent, an antifoaming agent, a pH adjuster, an antioxidant, a preservative, and an antibacterial agent.

[0051] The release agent is preferably a fatty acid salt, a mineral oil, or an ester oil. A preferred example of the fatty acid salt is a stearate, and more preferably one or more selected from the group consisting of sodium stearate, potassium stearate, magnesium stearate, and calcium stearate.

[0052] The content of the release agent in the rubber latex coagulant composition of the present embodiment is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, from the viewpoint of preventing uneven distribution of the release agent in the molding die and increasing uniform adhesion of the coagulant in the molding die to realize thin-walled rubber molded products, and from the same viewpoint, it is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and further more preferably 1% by mass or less.

[0053] <Dip molding method> The dip-forming method of the present embodiment includes: a coagulant-attaching step of immersing a molding die in the rubber latex coagulant composition containing the rubber latex coagulant composition and a coagulant to attach at least the coagulant to the surface of the molding die; and The method includes a rubber layer forming step of immersing the molding die having the coagulant adhered to its surface in a rubber latex layer forming composition containing rubber latex to form a rubber layer on the surface of the molding die.

[0054] The mold is a mold used for dip molding that has a shape corresponding to the desired three-dimensional shape, and any mold that is used for known dip molding can be used without any particular limitation.

[0055] The rubber latex layer-forming composition contains rubber latex. The rubber forming the rubber latex is not particularly limited, but a conjugated diene polymer is preferred. The conjugated diene polymer is a polymer having units derived from a conjugated diene monomer, and examples thereof include nitrile rubber (NBR), natural rubber (NR), styrene-butadiene rubber (SBR), synthetic polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-isoprene copolymer rubber, and styrene-isoprene-styrene copolymer rubber.

[0056] By immersing the molding die to which the coagulant has been attached, obtained in the coagulant attachment step, in a rubber latex layer-forming composition containing rubber latex, the rubber in the rubber latex layer-forming composition is salted out by the coagulant on the surface of the molding die, and a rubber layer can be formed on the surface of the molding die.

[0057] The dip molding method can produce a molded product by utilizing the process of a known dip molding method, except that the rubber latex coagulant composition for adhering the coagulant to the surface of the molding die contains the rubber latex coagulant composition. [Example]

[0058] <Preparation of surfactants, etc.> [Synthesis Example 1 (Synthesis of Surfactant (a)1)] 200 g (1.075 mol) of Kalcol 2098 (lauryl alcohol, manufactured by Kao Corporation) and 1.4 g (0.022 mol) of 86% potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were charged into a 2 L autoclave equipped with a stirrer, thermometer, and alkylene oxide inlet tube. After purging with nitrogen, the autoclave was dehydrated at 110 °C and -0.101 MPa for 1 hour. Subsequently, 612 g (13.91 mol) of ethylene oxide was added at an initial nitrogen pressure of 0.005 MPa and 155 ± 5 °C. Subsequently, 1.2 g (0.02 mol) of acetic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to neutralize the mixture, yielding the following surfactant (a)1.

[0059] [Synthesis Example 2 (Synthesis of Surfactant (a)2)] The synthesis was carried out in the same manner as in Preparation Example 1, except that 210 g (1.075 mol) of Kalcol 2463 (a mixture of C12, C14, and C16 alcohols manufactured by Kao Corporation) was fed and added instead of 200 g of Kalcol 2098, and 22 mol of ethylene oxide was fed and added instead of 13.91 mol, to obtain the following surfactant (a) 2.

[0060] [Synthesis Example 3 (Synthesis of surfactant (a)3)] 200 g (1.02 mol) of Kalcol 2463 (Kao Corporation) and 1.3 g (0.02 mol) of 86% KOH were charged into a 2 L autoclave equipped with a stirrer, thermometer, and alkylene oxide inlet tube. After purging with nitrogen, the autoclave was dehydrated at 110 °C and -0.101 MPa for 1 hour. Subsequently, 359 g (8.16 mol) of ethylene oxide was added at 155 ± 5 °C with an initial nitrogen pressure of 0.005 MPa. Subsequently, 118 g (2.04 mol) of propylene oxide (Fujifilm Wako Pure Chemical Industries, Ltd.) was added at 125 °C ± 5 °C, followed by 359 g (8.16 mol) of ethylene oxide at 155 ± 5 °C. Subsequently, 1.2 g (0.02 mol) of acetic acid was added for neutralization to obtain the following surfactant (a) 3.

[0061] [Synthesis Example 4 (Synthesis of Surfactant (a) 4)] Surfactant (a) 4 below was obtained by synthesis in the same manner as in Preparation Example 1, except that 287 g (1.075 mol) of Kalcol 8688 (a mixture of C16 alcohol and C18 alcohol, manufactured by Kao Corporation) was fed and added instead of 200 g of Kalcol 2098, and 12 mol of ethylene oxide was fed and added instead of 13.91 mol.

[0062] [Synthesis Example 5 (Synthesis of Surfactant (a) 5)] The same synthesis procedure as in Preparation Example 1 was repeated, except that 185 g (1.075 mol) of Exxal 11 (isoundecanol, manufactured by ExxonMobil) was fed and added instead of 200 g of Kalcol 2098, and 8 mol of ethylene oxide was fed and added instead of 13.91 mol, to obtain surfactant (a) 5 below.

[0063] [Surfactant (a)6] Softanol 90 (manufactured by Nippon Shokubai Co., Ltd., a product in which 9 moles of ethylene oxide are added to a linear secondary alcohol having 12 to 14 carbon atoms) was used as is without any particular purification.

[0064] The structures of the surfactants 1 to 6 are shown below, where the number in brackets is the average number of moles of alkylene oxide added. Surfactant (a) 1: Polyoxyethylene

[13] alkyl (C12) ether Surfactant (a) 2: Polyoxyethylene

[22] alkyl (C12-C14) ether Surfactant (a) 3: Polyoxyethylene

[16] polyoxypropylene [2] alkyl (C12-C14) ether Surfactant (a) 4: Polyoxyethylene

[12] alkyl (C16-C18) ether Surfactant (a) 5: Polyoxyethylene [8] branched alkyl (C11) ether Surfactant (a) 6: Polyoxyethylene [9] alkyl (C12) ether

[0065] <Examples and Comparative Examples> Example 1 50 g of the surfactant (a)1, 15 g of diethylene glycol-n-monobutyl ether (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 35 g of ion-exchanged water were added and stirred at room temperature until uniformly dissolved, thereby obtaining a rubber latex coagulant composition A1 according to Example 1 containing surfactant (a)1.

[0066] [Examples 2 to 18 and Comparative Examples 1 and 2] Each component was blended in the blending amount shown in Table 1 and stirred at room temperature until uniformly dissolved, to obtain rubber latex coagulant compositions A2 to A18 according to Examples 2 to 18 and rubber latex coagulant compositions A19 and A20 according to Comparative Examples 1 and 2, respectively.

[0067] [Measurement of dynamic surface tension] [Preparation of a Mixture of Rubber Latex Coagulant Composition A1 and 20% by Mass Calcium Nitrate Aqueous Solution] 576 g of calcium nitrate tetrahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with 1,424 g of ion-exchanged water and dissolved uniformly to obtain a 20% by mass aqueous calcium nitrate solution. 100 parts of the obtained 20% by mass aqueous calcium nitrate solution were mixed with surfactant (a)1 at 0.2 parts by mass and further stirred at room temperature for 5 hours to obtain a mixed solution of rubber latex coagulant composition A1 and 20% by mass aqueous calcium nitrate solution.

[0068] [Preparation of Mixtures of Rubber Latex Coagulant Compositions A2 to A20 and 20% by Mass Calcium Nitrate Aqueous Solution] A mixed solution with a 20% by mass aqueous solution of calcium nitrate was obtained for each of the rubber latex coagulant compositions A2 to A20 in the same manner.

[0069] (Measurement of dynamic surface tension) The resulting mixtures of rubber latex coagulant compositions A1 to A20 and 20% by mass aqueous calcium nitrate solution were allowed to stand at 50°C for 2 hours, and then the dynamic surface tensions were measured at a liquid temperature of 50°C with a surface life of 100 milliseconds (<Condition 1>) and a surface life of 1000 milliseconds (<Condition 2>) using a bubble pressure dynamic surface tensiometer (manufactured by KRUSS, product name BP100). The results are shown in Table 1.

[0070] <Evaluation> [Evaluation of low temperature stability] The rubber latex coagulant compositions A1 to A20 were placed in Maruemu's No. 8 screw tube (transparent), and stored in a thermostatic bath (AS ONE, KMH-050) set at -10°C. After 7 days, they were removed and the screw tube was tilted 90° to check the fluidity of the rubber latex coagulant compositions of each example and comparative example, thereby evaluating their low-temperature stability.

[0071] [Evaluation of Coatability] The mixture of rubber latex coagulant compositions A1 to A20 and 20% by weight calcium nitrate used in the dynamic surface tension measurements was allowed to stand at 50°C for 2 hours, after which 5 μl was dropped onto the center of a glass slide (25 mm x 75 mm, MICROSCOPE SLIDES, manufactured by AS ONE Corporation) 18 mm below the top edge. The slide was coated at room temperature (23°C) using a No. 3 bar coater (theoretical coating thickness: 6.87 μm, theoretical dry thickness: 1.4 μm) and then dried in an 80°C thermostatic oven (NDO-520, manufactured by Tokyo Rikakikai Co., Ltd.). The coated area was analyzed using ImageJ (free software). The coated area ratio was calculated from the calculated coated area and the theoretical coating area value obtained by dividing the volume of the dropped droplet by the theoretical coating thickness. If the coating area ratio is greater than 50%, the coagulant (calcium nitrate) can be thinly adhered to the surface of the mold, and if the coating area ratio is less than 75%, the coagulant can be adhered to the surface of the mold to a thickness that does not make the rubber thickness of the rubber molded product too thin.If the coating area ratio is less than 65%, the coagulant can be adhered to the surface of the mold to a thickness that does not make the rubber thickness too thin, which is preferable.

[0072] [Measurement of average particle size of stearate] Rubber latex coagulant compositions A1-A20, each containing 0.2 parts by weight of surfactant (a) per 100 parts by weight of 20% by weight calcium nitrate aqueous solution, and 0.23 parts of potassium stearate (Kanto Chemical Co., Ltd.) in an amount that resulted in 0.2 parts by weight of stearic acid anion component per 100 parts by weight of 20% by weight calcium nitrate aqueous solution, were mixed in a Maruemu Co., Ltd. No. 8 (transparent) screw tube using a magnetic stirrer at room temperature for 0.5 hours and then allowed to stand at 50°C for 2 hours to obtain a stearate dispersion. The resulting dispersion was diluted 5-fold with 20% by weight calcium nitrate aqueous solution that had been preheated to 50°C, and the average particle size of the stearate was measured using a particle size / molecular weight measurement system (Otsuka Electronics Co., Ltd., product name: ELSZ-1000ZS). The measurement and analysis method used was the cumulant average particle size measured 70 times. The smaller the average particle size of the stearate, the more uniformly the release agent can be adhered to the molding die, preventing uneven distribution of the coagulant and enabling the production of thinner rubber molded products, which is preferable. Specifically, the average particle size of the stearate measured under the above conditions is preferably 250 nm or less, more preferably 200 nm or less, even more preferably 180 nm or less, and even more preferably 170 nm or less.

[0073] The evaluation results are shown in Table 1.

[0074] [Table 1]

Claims

1. A rubber latex coagulant composition for addition to a coagulant used in rubber dip molding, comprising: The rubber latex coagulant composition contains a surfactant (a), The rubber latex coagulant composition has a dynamic surface tension of 29 mN / m or more and 45 mN / m or less when measured under the following condition 1, and a dynamic surface tension of 27 mN / m or more and 40 mN / m or less when measured under the following condition 2. <Condition 1> Measurement target of dynamic surface tension: A mixture obtained by mixing a rubber latex coagulant composition with 100 parts by mass of a 20% by mass aqueous solution of calcium nitrate so that the content of surfactant (a) contained in the rubber latex coagulant composition is 0.2 parts by mass. Temperature: 50℃ Surface life: 100 ms <Condition 2> Dynamic surface tension measurement object: the above-mentioned mixed liquid Temperature: 50℃ Surface life: 1000 milliseconds

2. 2. The rubber latex coagulant composition according to claim 1, wherein the surfactant (a) contains a nonionic surfactant (1) represented by the following general formula (1): R １ --(AO).. (1) (In general formula (1), R １ is a linear or branched aliphatic hydrocarbon group having from 9 to 16 carbon atoms, AO is an alkyleneoxy group having from 2 to 4 carbon atoms, and n represents the average number of moles of AO added, which is a number of from 10 to 20.

3. 2. The rubber latex coagulant composition according to claim 1, wherein the surfactant (a) contains a nonionic surfactant (2) represented by the following general formula (2): R ２ O- (A-O) m-H (2) (In general formula (2), R ２ represents a linear or branched aliphatic hydrocarbon group having from 8 to 15 carbon atoms, AO represents an alkyleneoxy group having from 2 to 4 carbon atoms, and m represents the average number of moles of AO added, which is a number of from 6 to 9.

4. 2. The rubber latex coagulant composition according to claim 1, wherein the surfactant (a) contains a nonionic surfactant (1) represented by the following general formula (1) and a nonionic surfactant (2) represented by the following general formula (2): R １ --(AO).. (1) (In general formula (1), R １ is a linear or branched aliphatic hydrocarbon group having from 9 to 16 carbon atoms, AO is an alkyleneoxy group having from 2 to 4 carbon atoms, and n represents the average number of moles of AO added, which is a number of from 10 to 20. R ２ O- (A-O) m-H (2) (In general formula (2), R ２ represents a linear or branched aliphatic hydrocarbon group having from 8 to 15 carbon atoms, AO represents an alkyleneoxy group having from 2 to 4 carbon atoms, and m represents the average number of moles of AO added, which is a number of from 6 to 9.

5. 5. The rubber latex coagulant composition according to claim 4, wherein a mass ratio of the nonionic surfactant (1) to the nonionic surfactant (2) in the surfactant (a) (mass of the nonionic surfactant (1):mass of the nonionic surfactant (2)) is 100:0 to 20:

80.

6. the rubber latex coagulant composition contains a water-soluble organic solvent and / or water, the content of the surfactant (a) in the rubber latex coagulant composition is 40% by mass or more and 70% by mass or less; the content of the water-soluble organic solvent in the rubber latex coagulant composition is 0% by mass or more and 30% by mass or less; 6. The rubber latex coagulant composition according to claim 1, wherein the water content in the rubber latex coagulant composition is 0% by mass or more and 50% by mass or less.

7. The rubber latex coagulant composition according to claim 6, wherein the water-soluble organic solvent contains at least one selected from the group consisting of alkylene glycols and alkylene glycol monoalkyl ethers.

8. The rubber latex coagulant composition according to claim 7, wherein the water-soluble organic solvent contains one or more selected from alkylene glycol monoalkyl ethers.

9. The rubber latex coagulant composition according to claim 8, wherein the water-soluble organic solvent contains a water-soluble organic solvent represented by the following general formula (3): CH ３ -(CH ２ ) ｐ -O-(R ３ O) ｑ -H (3) (wherein p is preferably an integer of 1 to 5, q is preferably an integer of 1 to 5, and R ３ is preferably an ethyl group or a propyl group.

10. 10. The rubber latex coagulant composition according to claim 9, wherein the water-soluble organic solvent contains one or more selected from the group consisting of ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether.

11. A rubber latex coagulant composition for use in dip molding of rubber, comprising: The rubber latex coagulant composition contains a rubber latex coagulant composition and a coagulant, The rubber latex coagulant composition contains a surfactant (a), The rubber latex coagulant composition has a dynamic surface tension of 29 mN / m or more and 45 mN / m or less when measured under the following condition 1, and a dynamic surface tension of 27 mN / m or more and 40 mN / m or less when measured under the following condition 2. <Condition 1> Measurement target of dynamic surface tension: A mixture obtained by mixing a rubber latex coagulant composition with 100 parts by mass of a 20% by mass aqueous solution of calcium nitrate so that the content of surfactant (a) contained in the rubber latex coagulant composition is 0.2 parts by mass. Temperature: 50℃ Surface life: 100 ms <Condition 2> Dynamic surface tension measurement object: the above-mentioned mixed liquid Temperature: 50℃ Surface life: 1000 milliseconds

12. 12. The rubber latex coagulant composition of claim 11, wherein the coagulant comprises a salt of an inorganic acid.

13. 13. The rubber latex coagulant composition according to claim 12, wherein the salt of an inorganic acid is at least one selected from the group consisting of barium chloride, calcium chloride, magnesium chloride, zinc chloride, aluminum chloride, barium nitrate, calcium nitrate, zinc nitrate, calcium sulfate, magnesium sulfate, and aluminum sulfate.

14. The rubber latex coagulant composition according to any one of claims 11 to 13, further comprising a release agent.

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