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] This invention relates to a composition for use as a coagulant for rubber latex. [Background technology]

[0002] Molded products such as rubber gloves, rubber balloons, and rubber sacks are manufactured by dip molding of rubber such as nitrile rubber (NBR) or natural rubber (NR). Dip molding is a molding technique in which a mold that will form the shape of the molded product is immersed in a coagulant composition containing a coagulant such as an inorganic acid salt and a release agent, the coagulant and release agent are attached to the surface of the mold, and then the mold is 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 molded product made of rubber (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 05-247266 [Overview of the project] [Problems that the invention aims to solve]

[0004] From the perspective of reducing the cost of molded products, attempts have been made to make them thinner and lighter. However, thinning the walls may result in insufficient strength in certain areas, potentially leading to product defects. To prevent this, it is conceivable to suppress the occurrence of unevenness in molded products by applying a thin, uniform layer of solidifying agent to the surface of the mold. However, conventional solidifying agent compositions have room for improvement in terms of applying a thin, uniform layer of solidifying agent to the surface of the mold.

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

[0006] The present invention A rubber latex coagulant composition for addition to coagulants used in rubber dip molding, 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 condition 1 below, and a dynamic surface tension of 27 mN / m or more and 40 mN / m or less when measured under condition 2 below. <Condition 1> Measurement target for dynamic surface tension: A mixture obtained by mixing 100 parts by mass of a 20% by mass calcium nitrate aqueous solution with the rubber latex coagulant composition such that the amount of surfactant (a) contained in the rubber latex coagulant composition is 0.2 parts by mass. Temperature: 50℃ Surface life: 100 milliseconds <Condition 2> Target for measurement of dynamic surface tension: The aforementioned mixed liquid Temperature: 50℃ Surface life: 1000 milliseconds [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a rubber latex coagulant composition that can be thinly and uniformly applied to the surface of a mold. [Modes for carrying out the invention]

[0008] <Composition for rubber latex coagulant> The rubber latex coagulant composition of this embodiment is a rubber latex coagulant composition for addition to a coagulant used in rubber dip molding, 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 condition 1 below, and a dynamic surface tension of 27 mN / m or more and 40 mN / m or less when measured under condition 2 below. <Condition 1> Measurement target for dynamic surface tension: A mixture obtained by mixing 100 parts by mass of a 20% by mass calcium nitrate aqueous solution with the rubber latex coagulant composition such that the amount of surfactant (a) contained in the rubber latex coagulant composition is 0.2 parts by mass. Temperature: 50℃ Surface life: 100 milliseconds <Condition 2> Target for measurement of dynamic surface tension: The aforementioned mixed liquid Temperature: 50℃ Surface life: 1000 milliseconds

[0009] Rubber dip molding is a molding technique in which a mold, which will be the basis for the shape of the molded product, is immersed in a coagulant composition containing a coagulant, the coagulant composition is attached to the surface of the mold, and then the mold is 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 in the coagulant composition on the surface of the mold, thereby obtaining a rubber molded product. The rubber latex coagulant composition of this embodiment is used to be added to the coagulant used in the rubber dip molding. According to the rubber latex coagulant composition of this embodiment, the coagulant composition can be attached thinly and uniformly to the surface of the mold. The reason why the rubber latex coagulant composition of this embodiment has such an effect is not clear, but it 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, measured under specific conditions, and a dynamic surface tension of 27 mN / m to 40 mN / m at a surface life of 1000 milliseconds. It is presumed that having such a combination of dynamic surface tensions allows for a shorter immersion time of the mold in the coagulant composition, reducing the amount of coagulant composition adhering to it, thus enabling thinner rubber films, and also suppressing the occurrence of unevenness in rubber molded products by allowing the coagulant composition to adhere uniformly to the mold.

[0011] From the perspective of thinly and uniformly adhering the coagulant composition to the surface of the mold to achieve thinning of the rubber molded product, the dynamic surface tension measured under the conditions of Condition 1 is 29 mN / m or more, preferably 30 mN / m or more, more preferably 31 mN / m or more, still more preferably 32 mN / m. And from the same perspective, it is 45 mN / m or less, preferably 43 mN / m or less, more preferably 42 mN / m or less, still more preferably 41 mN / m or less, even more preferably 40 mN / m or less. More specifically, the dynamic surface tension measured under the conditions of Condition 1 is 29 mN / m or more and 45 mN / m or less from the perspective of thinly and uniformly adhering the coagulant composition to the surface of the mold to achieve thinning of the rubber molded product, preferably 30 mN / m or more and 43 mN / m or less. And from the above perspective and in addition, from the perspective of enhancing the uniformity of the mold release agent contained in the coagulant composition to uniformly apply the mold release agent to the mold and prevent uneven distribution of the coagulant, it is more preferably 31 mN / m or more and 42 mN / m or less, still more preferably 32 mN / m or more and 41 mN / m or less, even more preferably 32 mN / m or more and 40 mN / m or less.

[0012] The measurement procedure for the dynamic surface tension under the conditions of Condition 1 is as follows. [Measurement Method for Dynamic Surface Tension under the Conditions of Condition 1] Mix calcium nitrate tetrahydrate and ion-exchanged water in an amount such that the concentration of calcium nitrate is 20% by mass to obtain a 20% by mass calcium nitrate aqueous solution. Mix the composition for rubber latex coagulant so that the content of surfactant (a) contained in the composition for rubber latex coagulant is 0.2 parts by mass with respect to 100 parts by mass of the 20% by mass calcium nitrate aqueous solution, and stir at room temperature for 5 hours to obtain a mixed solution. After allowing the obtained mixed solution to stand at 50°C for 2 hours, measure the dynamic surface tension with a bubble pressure type dynamic surface tension meter (for example, manufactured by KRUSS, trade name BP100) at a liquid temperature of 50°C and a surface lifetime of 100 milliseconds.

[0013] From the perspective of thinly adhering the coagulant composition to the surface of the mold to achieve thinning of the rubber molded product, the dynamic surface tension measured under the conditions of Condition 2 is 27 mN / m or more, preferably 28 mN / m or more, more preferably 29 mN / m or more, and from the same perspective, it is 40 mN / m or less, preferably 39 mN / m or less, more preferably 38 mN / m or less, still more preferably 37 mN / m or less, and even more preferably 36 mN / m or less. More specifically, the dynamic surface tension measured under the conditions of Condition 2 is 27 mN / m or more and 40 mN / m or less from the perspective of thinly and uniformly adhering the coagulant composition to the surface of the mold to achieve thinning of the rubber molded product, preferably 28 mN / m or more and 39 mN / m or less, and from the above perspective and in addition, from the perspective of enhancing the uniformity of the mold release agent contained in the coagulant composition and uniformly applying the mold release agent to the mold to prevent uneven distribution of the coagulant, it is more preferably 29 mN / m or more and 38 mN / m or less, still more preferably 29 mN / m or more and 37 mN / m or less, and even more preferably 29 mN / m or more and 36 mN / m or less.

[0014] The measurement procedure for the dynamic surface tension under the conditions of Condition 2 is as follows. [Measurement Method for Dynamic Surface Tension under the Conditions of Condition 2] Using the same mixed solution as that used in the measurement of the dynamic surface tension under the conditions of Condition 1, measure the dynamic surface tension with a surface life of 1000 milliseconds at a liquid temperature of 50 °C using the same bubble pressure type dynamic surface tension meter as that used in the measurement under the conditions of Condition 1.

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

[0016] From the perspective of thinly and uniformly adhering the coagulant composition to the surface of the mold to achieve thinning of the rubber molded product and ensuring storage stability under low-temperature environments, the surfactant (a) preferably contains a nonionic surfactant (1) represented by the following general formula (1). R1 O-(AO)nH (1) (In general formula (1), R 1 (where is a linear or branched aliphatic hydrocarbon group having 9 to 16 carbon atoms, AO is an alkylene oxy group having 2 to 4 carbon atoms, and n represents the average number of moles of AO added, which is between 10 and 20.)

[0017] The manufacture of rubber products by dip molding is carried out in a wide range of environments, from cold to warm climates. However, if conventional coagulant compositions are stored in cold climates at low temperatures (e.g., below 0°C), their fluidity decreases, making it impossible to mix them in the required amount, which may lead to a decrease in the performance of the rubber products. In contrast, if the surfactant (a) contained in the rubber latex coagulant composition of this embodiment contains a nonionic surfactant (1), its structure allows it to maintain fluidity even at low temperatures.

[0018] In the above general formula (1), R 1 From the viewpoint of achieving thin-walled rubber molded products 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, the coagulant is a linear or branched aliphatic hydrocarbon group, preferably a linear or branched alkyl group.

[0019] In the above general formula (1), R 1 From the viewpoint of achieving thin-walled rubber molded products 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, the carbon number is preferably 9 or more, more preferably 10 or more, even more preferably 12 or more, and from the same viewpoint, preferably 16 or less, more preferably 14 or less.

[0020] In the general formula (1) above, AO is preferably an alkylene oxy group having 2 to 4 carbon atoms, more preferably an alkylene oxy group having 2 to 3 carbon atoms, from the viewpoint of achieving thin-walled rubber molded products 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.

[0021] In the general formula (1) above, n is preferably 10 or more, more preferably 13 or more, and even more preferably 14 or more, from the viewpoint of achieving thin-walled rubber molded products 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. Similarly, it is preferably 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 products 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 (where is a linear or branched aliphatic hydrocarbon group having 8 to 15 carbon atoms, AO is an alkylene oxy group having 2 to 4 carbon atoms, and m represents the average number of moles of AO added, which is between 6 and 9.)

[0023] If the surfactant (a) contained in the rubber latex coagulant composition of this embodiment contains a nonionic surfactant (2), its structure allows it to maintain fluidity even at low temperatures.

[0024] In the above general formula (2), R 2 This refers to a linear or branched aliphatic hydrocarbon group, from the viewpoint of achieving thin-walled rubber molded products by thinly and uniformly adhering the coagulant composition to the surface of the mold.

[0025] In the above general formula (2), R 2 From the viewpoint of achieving thin-walled rubber molded products 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, the carbon number is preferably 8 or more, more preferably 10 or more, and from the same viewpoint, preferably 15 or less, more preferably 14 or less, and even more preferably 12 or less.

[0026] In the general formula (2) above, AO is preferably an alkylene oxy group having 2 to 4 carbon atoms, more preferably an alkylene oxy group having 2 to 3 carbon atoms, and even more preferably an alkylene oxy group having 2 carbon atoms, from the viewpoint of achieving thin-walled rubber molded products 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.

[0027] In the general formula (2) described above, m is preferably 6 or more, more preferably 8 or more, from the viewpoint of achieving thin-walled rubber molded products 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, and from the same viewpoint, preferably 9 or less.

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

[0029] If 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, even more preferably 100:0 to 50:50, even more preferably 100:0 to 60:40, even more preferably 100:0 to 70:30, even more preferably 100:0 to 80:20, even more preferably 100:0 to 90:10, and even more preferably 100:0.

[0030] In the rubber latex coagulant composition of this 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 thin-walled rubber molded products 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.

[0031] The rubber latex coagulant composition of this embodiment preferably contains a water-soluble organic solvent and / or water, from the viewpoint of achieving thin-walled rubber molded products by thinly and uniformly adhering the coagulant composition to the surface of the mold. In this specification, a water-soluble organic solvent means an organic solvent that can be mixed with water in any proportion. When the rubber latex coagulant composition of this embodiment contains a water-soluble organic solvent, the effect of setting the dynamic surface tension of the rubber latex coagulant composition within the aforementioned 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 increased, allowing the release agent to be applied uniformly to the mold, thereby preventing uneven distribution of the coagulant. This further suppresses the occurrence of unevenness in rubber film thickness, i.e., mottling.

[0032] The aforementioned water-soluble organic solvent preferably contains one or more selected from the group consisting of alkylene glycol, polyalkylene glycol, and alkylene glycol monoalkyl ether, and more preferably alkylene glycol monoalkyl ether, from the viewpoint of uniformly adhering the release agent to the mold and preventing uneven distribution of the coagulant, thereby enabling the thinning of rubber molded products.

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

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

[0035] From the perspective of realizing the thinning of rubber molded products by uniformly adhering a mold release agent to the mold and preventing uneven distribution of the coagulant, it is preferable to contain a water-soluble organic solvent represented by the following general formula (3). CH3-(CH2) p -O-(R 3 O) q -H (3) (In the formula, 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, and R 3 is preferably an ethyl group or a propyl group, more preferably a propyl group.)

[0036] Examples of the alkylene glycol monoalkyl ether 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. Among these, one or more selected from the group consisting of ethylene glycol mono-n-butyl ether and diethylene glycol monoethyl ether are preferable.

[0037] From the perspective of realizing the thinning of rubber molded products by uniformly adhering a mold release agent to the mold and preventing uneven distribution of the coagulant, one or more 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 are more preferable.

[0038] When the rubber latex coagulant composition of this embodiment contains a water-soluble organic solvent, the content of the water-soluble organic solvent A 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 this embodiment is preferably 40% by mass or more, more preferably 50% by mass or more, from the viewpoint of thinning the 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, 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 this embodiment is preferably 0% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of achieving thin-walled rubber molded products 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 low-temperature environments. From the same viewpoint, it is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0041] The water content in the rubber latex coagulant composition of this 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 low-temperature environments, and from the viewpoint of thinning the rubber molded product by thinly and uniformly adhering the coagulant in the coagulant composition to the surface of the mold, it is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0042] The rubber latex coagulant composition may contain thickeners, wetting agents, defoaming agents, pH adjusters, antioxidants, preservatives, antibacterial agents, etc., as long as they do not essentially impair the effects of the present invention.

[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 immerse the mold in a rubber latex layer-forming composition containing rubber latex before the rubber layer-forming step in which a rubber layer is formed on the surface of the mold, thereby allowing the coagulant in the rubber latex coagulant composition to adhere to the surface of the mold. Therefore, the rubber latex coagulant composition of this embodiment substantially does not contain the rubber latex contained in the rubber latex layer-forming composition.

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

[0045] The aforementioned coagulant causes salting out and solidifying the rubber contained in the rubber latex layer forming composition, and is not particularly limited as long as it is one that is normally 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, from the viewpoint of achieving thin-walled rubber molded products, salts of inorganic acids are preferred, 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 are more preferred, and one or more selected from calcium chloride and calcium nitrate are even more preferred. The aforementioned coagulant can be used in combination of one or two or more types.

[0046] The amount of the rubber latex coagulant composition blended into 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 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, preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, even more preferably 1% by mass or less, and 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 achieving thin-walled rubber molded articles, and from the same viewpoint, preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0048] The mass ratio of the amount of the rubber latex coagulant composition to the amount of the coagulant in the rubber latex coagulant composition (amount of rubber latex coagulant composition / amount 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 even more preferably 0.01 or more, from the viewpoint of thinly and uniformly adhering the coagulant in the coagulant composition to the surface of the mold to achieve thin-walled rubber molded products, and from the same viewpoint, 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 even 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 water-soluble organic solvents that may be included in the rubber latex coagulant composition include lower alcohols such as methanol, ethanol, and isopropanol; acetone; and water-soluble organic solvents introduced from the rubber latex coagulant composition of this embodiment.

[0050] The rubber latex coagulant composition preferably contains one or more selected from release agents, thickeners, wetting agents, defoaming agents, pH adjusters, anti-aging agents, preservatives, and antibacterial agents.

[0051] Preferred release agents include fatty acid salts, mineral oils, or ester oils. Preferred examples of fatty acid salts include stearates, with one or more selected from sodium stearate, potassium stearate, magnesium stearate, and calcium stearate being more preferred.

[0052] The content of the release agent in the rubber latex coagulant composition of this 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 mold and improving the uniform adhesion of the coagulant in the mold to achieve thinner rubber molded products. Similarly, it is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0053] <Dip molding method> The dip molding method of this embodiment is A molding die is immersed in the rubber latex coagulant composition and the rubber latex coagulant composition containing the coagulant, thereby adhering at least the coagulant to the surface of the molding die, and The process includes a rubber layer formation step in which the mold, on which the coagulant is attached to the surface, is immersed in a rubber latex layer forming composition containing rubber latex to form a rubber layer on the surface of the mold.

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

[0055] The rubber latex layer-forming composition contains rubber latex. The rubber used to form the rubber latex is not particularly limited, but a conjugated diene polymer is preferred. A conjugated diene polymer is a polymer having units derived from a conjugated diene monomer, and examples 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 mold to which the coagulant has been applied, obtained in the coagulant application 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 mold, thereby forming a rubber layer on the surface of the mold.

[0057] The aforementioned dip molding method can produce molded articles using a known dip molding process, except that the rubber latex coagulant composition used to adhere the coagulant to the surface of the mold contains the rubber latex coagulant composition. [Examples]

[0058] <Preparation of surfactants, etc.> [Synthesis Example 1 (Synthesis of Surfactant (a)1)] 200 g (1.075 mol) of Calcol 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 placed in a 2 L autoclave equipped with a stirrer, thermometer, and alkylene oxide inlet tube. After purging with nitrogen, the mixture was dehydrated at 110°C and -0.101 MPa for 1 hour. Subsequently, 612 g (13.91 mol) of ethylene oxide was fed and added at an initial nitrogen pressure of 0.005 MPa and 155 ± 5°C. Then, 1.2 g (0.02 mol) of acetic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to neutralize the mixture and obtain surfactant (a)1 described below.

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

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

[0061] [Synthesis Example 4 (Synthesis of Surfactant (a)4)] The synthesis was carried out using the same method as in Preparation Example 1, except that 287 g (1.075 mol) of Calcol 8688 (a mixture of C16 and C18 alcohols manufactured by Kao Corporation) was added instead of 200 g of Calcol 2098, and 12 mol of ethylene oxide was added instead of 13.91 mol, to obtain the following surfactant (a)4.

[0062] [Synthesis Example 5 (Synthesis of Surfactant (a) 5)] The synthesis was carried out using the same method as in Preparation Example 1, except that 185 g (1.075 mol) of Exal 11 (Isoundecanol, manufactured by ExxonMobil) was added instead of 200 g of Calcol 2098, and 8 mol of ethylene oxide was added instead of 13.91 mol, to obtain the following surfactant (a)5.

[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 with 12 to 14 carbon atoms) was used as is without any special purification.

[0064] The structures of surfactants 1 to 6 are shown below. The numbers in brackets [] represent 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 deionized water were added and stirred until uniformly dissolved at room temperature to obtain rubber latex coagulant composition A1 according to Example 1, which contains surfactant (a)1.

[0066] [Examples 2-18, and Comparative Examples 1 and 2] Each component was blended in the amounts listed in Table 1 and stirred until uniformly dissolved at room temperature 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.) and 1424 g of deionized water were mixed and uniformly dissolved to obtain a 20% by mass aqueous solution of calcium nitrate. Composition A1 for rubber latex coagulant was mixed with 100 parts by mass of the obtained 20% by mass aqueous solution of calcium nitrate so that the surfactant (a)1 amounted to 0.2 parts by mass, and the mixture was stirred at room temperature for 5 hours to obtain a mixture of composition A1 for rubber latex coagulant and 20% by mass aqueous solution of calcium nitrate.

[0068] [Preparation of a mixture of rubber latex coagulant compositions A2-A20 and a 20% by mass calcium nitrate aqueous solution] A mixture of each of the rubber latex coagulant compositions A2 to A20 with a 20% by mass calcium nitrate aqueous solution was obtained using the same procedure.

[0069] (Measurement of dynamic surface tension) After allowing the mixture of the obtained rubber latex coagulant compositions A1 to A20 and a 20% by mass aqueous solution of calcium nitrate to stand at 50°C for 2 hours, the dynamic surface tension at a liquid temperature of 50°C was measured at a surface lifetime of 100 milliseconds (<Condition 1>) and a surface lifetime of 1000 milliseconds (<Condition 2>) using a bubble pressure dynamic surface tensimeter (KRUSS, product name BP100). The results are shown in Table 1.

[0070] <Rating> [Evaluation of low-temperature stability] Rubber latex coagulant compositions A1 to A20 were placed in Maruemu Co., Ltd. screw tubes No. 8 (transparent) and stored in a constant temperature bath (AS ONE Co., Ltd., KMH-050) set to -10°C. After 7 days, they were removed, and the screw tubes were tilted 90°C to check for the presence or absence of fluidity of the rubber latex coagulant compositions according to each example and comparative example, thereby evaluating their low-temperature stability.

[0071] [Evaluation of coating properties] A mixture of rubber latex coagulant compositions A1-A20 and 20% by mass calcium nitrate, used for the measurement of the dynamic surface tension, was allowed to stand at 50°C for 2 hours. Then, 5 μl of the mixture was dropped onto the center of a glass slide (AS ONE, MICROSCOPE SLIDES 25mm x 75mm), 18 mm below the top edge. The mixture was then coated using a bar coater No. 3 (theoretical coating thickness 6.87 μm, theoretical coating thickness after drying 1.4 μm) at room temperature (23°C) and dried in an 80°C constant temperature bath (Tokyo Rikakikai Co., Ltd., NDO-520). The area of ​​the coated portion was analyzed using ImageJ (free software). The coating area ratio was calculated from the calculated area of ​​the coated portion and the theoretical coating area value obtained by dividing the volume of the dropped droplet by the theoretical coating thickness. When the coating area ratio is greater than 50%, a thin layer of the coagulant (calcium nitrate) can be applied to the surface of the mold. When the coating area ratio is less than 75%, the coagulant can be applied to the surface of the mold at a thickness that does not make the rubber thickness of the molded product too thin. When the coating area ratio is less than 65%, the coagulant can be applied to the surface of the mold at 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 to A20, each containing 0.2 parts by mass of surfactant (a) per 100 parts by mass of 20% calcium nitrate aqueous solution, and 0.23 parts of potassium stearate (manufactured by Kanto Chemical Co., Ltd.) in an amount equivalent to 0.2 parts by mass of stearate anionic component per 100 parts by mass of 20% calcium nitrate aqueous solution, were stirred at room temperature for 0.5 hours using a magnetic stirrer in a Maruemu screw tube No. 8 (transparent), and then allowed to stand at 50°C for 2 hours to obtain a dispersion of stearate. The obtained dispersion was diluted five-fold with a 20% calcium nitrate aqueous solution that had been heated to 50°C, and the average particle size of the stearate was measured using a particle size / molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd., product name: ELSZ-1000ZS). The measurement and analysis method used was the cumulant average particle size obtained by accumulating 70 measurements. The smaller the average particle size of the stearate, the more uniformly the release agent can be applied to the mold, preventing uneven distribution of the coagulant and enabling 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 results of each evaluation are shown in Table 1.

[0074] [Table 1]

Claims

1. A rubber latex coagulant composition for addition to coagulants used in rubber dip molding, The rubber latex coagulant composition contains surfactant (a), The surfactant (a) contains a nonionic surfactant (1) represented by the following general formula (1), A rubber latex coagulant composition wherein the dynamic surface tension of the rubber latex coagulant composition measured under the following condition 1 is 29 mN / m or more and 45 mN / m or less, and the dynamic surface tension of the rubber latex coagulant composition measured under the following condition 2 is 27 mN / m or more and 40 mN / m or less. R １ --(AO).. (1) (In general formula (1), R １ (where is a linear or branched aliphatic hydrocarbon group having 9 to 16 carbon atoms, AO is an alkylene oxy group having 2 to 4 carbon atoms, and n represents the average number of moles of AO added, which is between 10 and 20.) <Condition 1> Measurement target for 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, such that the amount of surfactant (a) contained in the rubber latex coagulant composition is 0.2 parts by mass. Temperature: 50℃ Surface life: 100 milliseconds <Condition 2> Target for measurement of dynamic surface tension: the aforementioned mixed liquid Temperature: 50℃ Surface life: 1000 milliseconds

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 (where is a linear or branched aliphatic hydrocarbon group having 8 to 15 carbon atoms, AO is an alkylene oxy group having 2 to 4 carbon atoms, and m represents the average number of moles of AO added, which is between 6 and 9.)

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

80.

4. 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. 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.

5. The rubber latex coagulant composition according to claim 4, wherein the water-soluble organic solvent contains one or more selected from alkylene glycol and alkylene glycol monoalkyl ether.

6. The rubber latex coagulant composition according to claim 5, wherein the water-soluble organic solvent contains one or more selected from alkylene glycol monoalkyl ethers.

7. The rubber latex coagulant composition according to claim 6, 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) (In the formula, p is an integer from 1 to 5, q is an integer from 1 to 5, R ３ (This is an ethyl group or a propyl group.)

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

9. A rubber latex coagulant composition according to any one of claims 1 to 8, and a rubber latex coagulant composition containing a coagulant.

10. The rubber latex coagulant composition according to claim 9, wherein the coagulant contains a salt of an inorganic acid.

11. The rubber latex coagulant composition according to claim 10, wherein the salt of the inorganic acid is 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.

12. The rubber latex coagulant composition according to claim 9, further containing a release agent.

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