Chloroprene-based latex product, and method for producing chloroprene-based latex product

Abstract

Provided is a chloroprene-based latex product capable of reducing the occurrence of aggregates during storage and / or transport, which has been difficult with conventional chloroprene-based latex products.　The present invention provides a chloroprene-based latex product comprising a container and chloroprene-based latex filled in the container, wherein at least part of the inner surface of the container is composed of a resin, and the filling amount of the chloroprene-based latex is 90-100% relative to the maximum filling capacity of the container.

Description

Chloroprene-based latex products, and methods for manufacturing chloroprene-based latex products

[0001] This invention relates to chloroprene-based latex products and methods for producing chloroprene-based latex products.

[0002] Chloroprene latex containing chloroprene polymers exhibits excellent mechanical properties, ozone resistance, and chemical resistance, and these properties are utilized in a wide range of fields, including automotive parts, adhesives, and various industrial rubber parts. For example, Patent Document 1 discloses a method for producing chloroprene polymers, in which chloroprene or monomers copolymerizable with chloroprene are polymerized in an aqueous medium in the presence of a surfactant, wherein the surfactant is added at a concentration below the critical micelle concentration (CMC).

[0003] WO2011 / 004860

[0004] However, conventional chloroprene-based latex products sometimes developed aggregates during storage or transportation.

[0005] This invention has been made in view of these circumstances, and provides a chloroprene-based latex product that can reduce the generation of aggregates during storage and / or transportation, which has been difficult with conventional chloroprene-based latex products.

[0006] The present invention provides a chloroprene latex product comprising a container and chloroprene latex filled in the container, wherein at least a portion of the inner surface of the container is made of resin, and the amount of chloroprene latex filled is 90 to 100% of the maximum filling amount of the container.

[0007] Through diligent research, the inventors discovered that by adjusting the container material and filling rate of chloroprene-based latex products, it is possible to create chloroprene-based latex products that can reduce the generation of aggregates during storage and / or transportation, thus completing the present invention.

[0008] The following are examples of various embodiments of the present invention. The embodiments shown below can be combined with each other. [1] A chloroprene latex product comprising a container and chloroprene latex filled in the container, wherein at least a portion of the inner surface of the container is made of resin, and the amount of chloroprene latex filling is 90 to 100% of the maximum filling amount of the container. [2] The chloroprene latex product according to [1], wherein the container is a blow-molded container, and the resin comprises high-density polyethylene. [3] The chloroprene latex product according to [1] or [2], further comprising an outer frame for housing the container. [4] The chloroprene latex product according to any one of [1] to [3], wherein the container comprises a filling port and a cap capable of sealing the filling port, the filling port is provided on the upper surface of the container, the cap is removable, and gas can be vented from the container when the cap is attached to the filling port. [5] A chloroprene latex product according to any one of [1] to [4], wherein, after storage at 23°C for 3 days, the chloroprene latex is removed from the container and filtered through an 80-mesh wire mesh, and the mass of solids remaining on the wire mesh is 0.0300% by mass or less relative to 100% by mass of the chloroprene latex. [6] A chloroprene latex product according to any one of [1] to [5], wherein the chloroprene latex has a solid content concentration of 35.0 to 70.0% by mass. [7] A chloroprene latex product according to any one of [1] to [6], wherein the viscosity of the chloroprene latex, measured with a B-type viscometer at 23°C, is 5 to 1500 mPa·s. [8] A method for manufacturing a chloroprene latex product, comprising a filling step of filling a container with the chloroprene latex product, wherein in the filling step, the container is filled with chloroprene latex to 90-100% of its maximum filling capacity, and the container is composed of resin in at least a portion of its inner surface.

[0009] According to the chloroprene-based latex product of the present invention, the generation of aggregates during storage and / or transportation can be reduced by adjusting the material and filling rate of the container in the chloroprene-based latex product. Because the amount of aggregates generated during storage and / or transportation is small according to the chloroprene-based latex product of the present invention, aggregate removal processes such as filtration can be shortened, simplified, or omitted, thereby reducing manufacturing costs and manufacturing time.

[0010] Figure 1 is a schematic diagram of a chloroprene-based latex product according to one embodiment of the present invention. Figure 2 is a schematic diagram of a chloroprene-based latex product according to one embodiment of the present invention.

[0011] Embodiments of the present invention will be described below with reference to the drawings. The features shown in the embodiments below can be combined with each other. Furthermore, each feature constitutes an independent invention. In addition, any element not specified in the claims in the embodiments below is an optional element and can be omitted. Any number of zeros (for example, one or two) may be added to the end of the numerical values ​​disclosed in the following description. For example, one or two zeros may be added after "1.4" to make it "1.40" or "1.400".

[0012] 1. Chloroprene-based latex product The chloroprene-based latex product according to the present invention comprises a container and chloroprene-based latex filled in the container, wherein at least a portion of the inner surface of the container is made of resin, and the amount of chloroprene-based latex filled is 90 to 100% of the maximum filling amount of the container. Conventionally, chloroprene-based latex products sometimes produced aggregates during storage or transportation. One of the causes of aggregate formation is the formation of a drying film. It is presumed that the drying film is formed at the interface between the chloroprene-based latex and air, when water evaporates from the chloroprene-based latex, causing the chloroprene-based latex to concentrate and solidify locally. It is also presumed that it may be formed when the chloroprene-based latex adheres to the upper wall surface of the container due to shaking during transportation, and the attached latex dries. According to the present invention, by defining the structure of the container for the chloroprene-based latex product and the filling rate of the container, the formation of aggregates during transportation and / or storage can be reduced.

[0013] 1.1 Container Hereinafter, a chloroprene-based latex product 100 according to one embodiment of the present invention will be described with reference to Figure 1. Figure 1 shows a chloroprene-based latex product 100 according to one embodiment of the present invention, and the chloroprene-based latex product 100 comprises a container 10 and chloroprene-based latex 20 filled in the container 10.

[0014] At least a portion of the inner surface 11 of the container 10 according to the present invention is made of resin. In the container 10 according to one embodiment of the present invention, it is preferable that at least a portion of the inner surface of the container that comes into contact with the chloroprene latex 20 is made of resin, and that the inner surface of the upper part of the container 10 is made of resin. For example, when the volume of the container is 100 volume%, it is preferable that the upper 10 volume% or more of the inner surface is made of resin, for example, it is preferable that the upper 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 volume% or more of the inner surface is made of resin, and it may be within the range of any two of the values ​​exemplified here. In the container according to one embodiment of the present invention, the entire inner surface of the container may be made of resin. The reason why using resin as the material constituting the inner surface of the container can reduce the generation of aggregates during transport and / or storage is not clear, but it is presumed that chloroprene latex has lower wettability to resin than other materials such as glass. That is, even if the container is shaken and chloroprene latex adheres to the wall surface, it is thought that the latex does not spread thinly easily and does not dry easily.

[0015] The inner surface 11 of the container 10 preferably contains a material with a surface energy lower than the surface tension of chloroprene latex, and is preferably composed of a material with a surface energy lower than the surface tension of chloroprene latex. The material constituting the inner surface 11 of the container 10 preferably has a surface energy of 60 mN / m or less, and more preferably 35 mN / m or less. The surface energy of the resin is, for example, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 mN / m, and may be within the range of any two of the values ​​exemplified here. As an example, the surface energy of glass is 200 to 300 mN / m, and the surface energy of polyethylene is 31 mN / m. The surface energy of glass can be determined by the drop method (contact angle method) using a contact angle meter (for example, DM-301, manufactured by Kyowa Interface Chemical Co., Ltd.) with a test liquid whose surface tension value is known, and the measurement conditions can be 23°C. The surface tension of chloroprene latex can be 20 to 60 mN / m, and preferably 30 to 40 mN / m. For example, the surface tension of chloroprene latex may be 20, 25, 30, 35, 40, 45, 50, 55, or 60 mN / m, and may be within the range of any two of the values ​​exemplified here. Chloroprene latex has a higher surface energy than chloroprene latex, and it is presumed that materials with a particularly large difference in surface energy will wet well and spread thinly on wall surfaces. The surface tension of chloroprene latex can be determined by the suspension drop method using a contact angle meter (for example, DM-301, manufactured by Kyowa Interface Chemical Co., Ltd.), and the measurement conditions can be 7.5 μL of liquid used and 20°C.

[0016] The resin preferably contains at least one selected from the group consisting of polyethylene, EVOH (ethylene-vinyl alcohol copolymer), ethylene-propylene copolymer, ethylene-1-butene copolymer, and ethylene-1-hexene copolymer, and preferably contains polyethylene. The resin preferably contains high-density polyethylene. The high-density polyethylene has a density of 0.940 g / cm³ at 23°C. ３ The above refers to polyethylene, and high-density polyethylene has a density of 0.940 to 0.970 g / cm³.３ It is preferable that the material is polyethylene. The density of high-density polyethylene can be measured by the water displacement method based on JIS K 7112. The resin preferably contains high molecular weight polyethylene. The high molecular weight polyethylene can have an MFR (melt mass flow rate) of less than 0.10 g / 10 min, measured at 190°C and 21.6 kg, and can be between 0.03 and 0.08 g / 10 min. The MFR of polyethylene is, for example, less than 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 g / 10 min or 0.1 g / 10 min, and may be within the range of any two of the values ​​exemplified here. The MFR of high-density polyethylene can be measured based on JIS K 7210-1. The resin according to one embodiment of the present invention preferably contains high-density high molecular weight polyethylene. Furthermore, the resin according to one embodiment of the present invention preferably contains high-density ultra-high molecular weight polyethylene. The resin according to one embodiment of the present invention preferably contains polyethylene with a weight-average molecular weight of 1 million or more, as measured by gel permeation chromatography or the like. The weight-average molecular weight of polyethylene is, for example, 1 million, 2 million, 3 million, 4 million, 5 million, 6 million, 7 million, 8 million, 9 million, or 10 million, and may be within the range of any two of the values ​​exemplified herein. The container may have a single-layer structure or a multilayer structure. If the container has a multilayer structure, it is preferable that at least the innermost layer in contact with the chloroprene latex contains and is composed of the above-mentioned resin. The multilayer container may be made up of layers of different resins stacked together, and may include adhesive layers or barrier layers.

[0017] The container according to one embodiment of the present invention is preferably a resin molded product. The molding method is not particularly limited, but the container according to one embodiment of the present invention can be an injection molded container, a blow molded container, etc., and is preferably a blow molded container.

[0018] The container capacity (maximum filling volume) is not specifically defined, but as an example, it can be 1 to 2000 L, for example, 1, 10, 100, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 2000 L, and may be within the range of any two of the values ​​exemplified here. The inner bottom surface area of ​​the container is not specifically limited, but as an example, it can be 100 to 20000 cm². ２ For example, 10, 100, 1000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 20000 cm ２ The dimensions may be within the range of any two of the values ​​exemplified here. The height of the inner surface of the container (inner height of the body) is not particularly limited, but as an example, it can be 10 to 200 cm, for example, 10, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 200 cm, and may be within the range of any two of the values ​​exemplified here. The thickness of the container is not particularly limited, but as an example, the thickness of the thinnest part may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mm, and may be within the range of any two of the values ​​exemplified here.

[0019] A container 10 according to one embodiment of the present invention may be provided with a filling port 12 and a cap 13 capable of sealing the filling port 12. The filling port 12 is preferably provided on the upper surface of the container. The diameter (inner diameter) of the filling port 12 is, for example, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500 mm, and may be within the range of any two of the values ​​exemplified here. The cap 13 is preferably removable. Furthermore, the cap 13 is preferably equipped with a gas venting means 14, allowing for gas venting from the container while the cap 13 is attached to the filling port 12. With the above configuration, the chloroprene latex product according to one embodiment of the present invention can maintain a slight pressure in the gas phase during storage and / or transport, easily take in outside air when discharging the chloroprene latex from the container, prevent liquid from splashing out, and achieve a higher filling rate compared to conventional methods.

[0020] The container 10 may also be equipped with an outlet 15 at the bottom of the container for discharging chloroprene latex. The diameter (inner diameter) of the outlet 15 may be, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150 mm, and may be within the range of any two of the values ​​exemplified here. An outlet valve 16 may also be attached to the outlet 15. The outlet valve 16 may be of the piston type or the ball type. The container 10 may also be provided with a trap mechanism (not shown) on the inner surface of the upper part of the container body or the ceiling part (the inner surface at the position corresponding to the gas phase) that can capture aggregates and prevent their transfer to chloroprene latex. This trap mechanism may be composed of, for example, a three-dimensional mesh structure, a sheet material having a surface roughened to have a surface roughness greater than the surface roughness of the inner surface of the container, etc.

[0021] 1.2 Outer frame, pad, pallet A chloroprene-based latex product according to one embodiment of the present invention may further comprise an outer frame for housing a container. A chloroprene-based latex product according to one embodiment of the present invention may have a shock-absorbing pad between the container and the outer frame. For example, the outer frame may be made of metal, and the pad may be made of resin. With the above configuration, shaking during storage and / or transport can be reduced, and the generation of aggregates due to the dried film can be further reduced.

[0022] A chloroprene-based latex product according to one embodiment of the present invention may have a pallet at the bottom of the container. For example, the pallet can be a hybrid type comprising a frame made of metal pipes and columns made of resin, and can be handled by inserting a forklift or hand fork from all four sides.

[0023] Hereinafter, a chloroprene-based latex product 100 according to one embodiment of the present invention will be described with reference to Figure 2. Figure 2 shows a chloroprene-based latex product 100 according to one embodiment of the present invention, which comprises a container 10 and chloroprene-based latex 20 filled in the container 10. The chloroprene-based latex product 100 comprises an outer frame 30 for housing the container. The chloroprene-based latex product 100 also comprises a pallet 40 at the bottom of the container. The outer frame 30 and the pallet 40 may be integrated. Furthermore, the chloroprene-based latex product 100 has a pad 50 between the container 10 and the outer frame 30 that can mitigate impact from the bottom side.

[0024] 1.3 Chloroprene-based latex The chloroprene-based latex according to the present invention comprises a chloroprene polymer. The chloroprene-based latex according to one embodiment of the present invention comprises a chloroprene polymer, water, and an emulsifier.

[0025] 1.3.1 Chloroprene-based polymers The chloroprene-based polymers according to the present invention refer to polymers containing monomer units (monomer units = structural units) derived from 2-chloro-1,3-butadiene (hereinafter also referred to as chloroprene). Examples of chloroprene-based polymers include chloroprene homopolymers and chloroprene copolymers (polymers of chloroprene and monomers copolymerizable with chloroprene). The polymer structure of chloroprene-based polymers is not particularly limited.

[0026] Note that 2-chloro-1,3-butadiene may contain small amounts of 1-chloro-1,3-butadiene as an impurity. Such 2-chloro-1,3-butadiene containing small amounts of 1-chloro-1,3-butadiene can also be used as the chloroprene monomer in this embodiment.

[0027] A chloroprene polymer according to one embodiment of the present invention may also have monomer units derived from monomers other than chloroprene monomers. Examples of monomers other than chloroprene monomers are not particularly limited as long as they can copolymerize with chloroprene monomers, but include esters of (meth)acrylic acid (methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.), hydroxyalkyl (meth)acrylates (2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.), unsaturated nitriles (acrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile, etc.), 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, sulfur, and the like.

[0028] The chloroprene polymer according to one embodiment of the present invention preferably contains 70 to 100% by mass of chloroprene monomer units when the chloroprene polymer is considered to be 100% by mass. The content of chloroprene monomer units in the chloroprene polymer may be, for example, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within the range of any two of the values ​​exemplified herein. By setting the content of chloroprene monomer units within the above numerical range, it is possible to obtain a latex that has characteristics derived from chloroprene (such as adhesive strength when used as an adhesive composition, or mechanical properties when used as a molded article).

[0029] The chloroprene latex according to one embodiment of the present invention may contain 0 to 30% by mass of other monomer units other than chloroprene monomer units, when the chloroprene polymer contained in the chloroprene latex is considered to be 100% by mass. The content of other monomer units may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% by mass, and may be within the range of any two of the values ​​exemplified here.

[0030] The chloroprene latex according to one embodiment of the present invention may contain one or more chloroprene polymers. The chloroprene latex according to one embodiment of the present invention may also contain one chloroprene polymer. When the chloroprene latex according to one embodiment of the present invention contains two or more chloroprene polymers, it is preferable that the content rate based on the total amount of each monomer unit contained in the two or more chloroprene polymers is within the above numerical range, relative to 100% by mass of the total of the two or more chloroprene polymers contained in the chloroprene latex.

[0031] The chloroprene-based polymer contained in the chloroprene-based polymer according to the present invention (such as a homopolymer of chloroprene, a copolymer of chloroprene, etc.) may be a sulfur-modified chloroprene polymer, a mercaptan-modified chloroprene polymer, a xanthate-modified chloroprene polymer, a dithiocarbonate-based chloroprene polymer, a trithiocarbonate-based chloroprene polymer, a carbamate-based chloroprene polymer, etc.

[0032] The weight average molecular weight (Mw) of the chloroprene-based polymer is, for example, 10×10 ３ g / mol, 50×10 ３ g / mol, 100×10 ３ g / mol, 300×10 ３ g / mol, 400×10 ３ g / mol, 450×10 ３ g / mol, 500×10 ３ g / mol, 800×10 ３ g / mol, 1000×10 ３ g / mol, 2000×10 ３ g / mol, 3000×10 ３ g / mol, 5000×10 ３ g / mol, and may also be within the range between any two of the values exemplified here.

[0033] The number average molecular weight (Mn) of the chloroprene-based polymer is, for example, 1×10 ３ g / mol, 5×10 ３ g / mol, 10×10 ３ g / mol, 50×10 ３ g / mol, 100×10 ３ g / mol, 130×10 ３ g / mol, 200×10 ３ g / mol, 300×10 ３ g / mol, 500×10 ３ g / mol, 800×10​​​​​​The molecular weight distribution (Mw / Mn) of the chloroprene-based polymer is 1.0, 1.5, 2.0, 2.5, 3.0, 3.2, 3.4, 3.5, 3.8, 4.0, 5.0, 8.0, 10, and it may also be within the range between any two of the values exemplified herein.

[0035] The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the chloroprene-based polymer can be measured by gel permeation chromatography (GPC) and obtained by converting to polystyrene. Specifically, it can be measured by the following method. Apparatus name: HLC-8320 (manufactured by Tosoh Corporation) Column: Three TSKgel GMHHHR-H columns in series Temperature: 40 °C Detection: Differential refractive index Solvent: Tetrahydrofuran Calibration curve: Prepared using standard polystyrene (PS)

[0036] 1.3.2 Emulsifier The chloroprene-based latex according to one embodiment of the present invention contains an emulsifier. The emulsifier preferably contains rosin acid and / or rosin acid salt. The emulsifier can also contain emulsifiers and dispersants other than rosin acid and rosin acid salt. As emulsifiers and dispersants other than rosin acid and rosin acid salt, cationic, anionic, and nonionic emulsifiers and dispersants can be used. In one embodiment of the present invention, as the emulsifier, it can contain rosin acid and / or rosin acid salt and anionic emulsifiers and dispersants. From the viewpoint of stabilizing the chloroprene-based latex when adding a pH adjuster, it is preferable to use sulfate-based or sulfonate-based anionic emulsifiers and dispersants in combination as the anionic emulsifiers and dispersants. Specifically, examples include alkyl sulfonates having 8 to 20 carbon atoms, alkyl aryl sulfates, condensates of sodium β-naphthalene sulfonate and formaldehyde, and sodium alkyl diphenyl ether disulfonate.

[0037] The content of the emulsifier with respect to 100 parts by mass of the chloroprene-based polymer can be 0.5 to 8.0 parts by mass. The content of the emulsifier is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0 parts by mass, and it may also be within the range between any two of the values exemplified herein.

[0038] The chloroprene latex according to one embodiment of the present invention may contain water as a solvent, and the solid content concentration may be 35.0 to 70.0% by mass. The solid content concentration may be, for example, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0, 65.0, or 70.0% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0039] The viscosity of the chloroprene latex according to one embodiment of the present invention, as measured with a B-type viscometer at 23°C, can be 5 to 1500 mPa·s. The viscosity can be, for example, 5, 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, or 1500 mPa·s, and may be within the range of any two of the values ​​exemplified here. The viscosity can be measured by the method described in the examples.

[0040] The toluene-insoluble content of the chloroprene latex according to one embodiment of the present invention can be 0 to 100%. The toluene-insoluble content may be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100%, and may be within the range of any two of the values ​​exemplified herein. The toluene-insoluble content can be measured by the method described in the examples.

[0041] The pH of the chloroprene latex according to one embodiment of the present invention can be 11.5 to 13.5. The pH can be, for example, 11.5, 11.6, 11.7, 11.8, 11.9, 12, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13, 13.1, 13.2, 13.3, 13.4, or 13.5, and may be within the range of any two of the values ​​exemplified here.

[0042] As described above, conventional chloroprene-based latex products may develop aggregates during storage or transportation, and this problem is particularly pronounced when the solid content is high or the viscosity is high. According to the chloroprene-based latex product according to one embodiment of the present invention, for example, even with latex that has a relatively high solid content, viscosity, and toluene-insoluble content, the generation of aggregates during storage and / or transportation can be reduced. Furthermore, according to the chloroprene-based latex product according to one embodiment of the present invention, for example, even with latex that has a relatively low pH, or with latex that has a relatively low pH and uses an anionic emulsifier, the generation of aggregates during storage and / or transportation can be reduced.

[0043] The chloroprene-based latex according to the present invention is not particularly limited in its applications and can be used in known applications such as adhesives, dipping molded articles, and vulcanized molded articles.

[0044] 1.3.3 Method for Producing Chloroprene-Based Latex The method for producing chloroprene-based latex according to the present invention is not particularly limited, but can be obtained, for example, by the following method. A method for producing chloroprene-based latex according to one embodiment of the present invention may include a polymerization step in which raw material monomers containing chloroprene are polymerized to obtain chloroprene-based latex.

[0045] When producing chloroprene polymers, the raw material monomers can be polymerized by polymerization methods such as emulsion polymerization, solution polymerization, suspension polymerization, and bulk polymerization. Among these polymerization methods, emulsion polymerization is preferred because it offers various advantages, such as ease of control, ease of extracting the polymer from the polymerization completion solution, and a relatively fast polymerization rate.

[0046] Emulsion polymerization is a type of radical polymerization in which raw material monomers are added to a reaction vessel along with a chain transfer agent, water, alkali (e.g., metal hydroxides such as potassium hydroxide and sodium hydroxide), emulsifier (dispersant), reducing agent (e.g., sodium bisulfite), polymerization initiator, etc., and polymerization is carried out.

[0047] In the polymerization process, the raw material monomers include chloroprene and may also include other monomers copolymerizable with chloroprene. Other monomers copolymerizable with chloroprene are as described above. It is preferable to adjust the type and amount of each monomer used so that the type and content of each monomer unit in the resulting polymer fall within the numerical ranges described above.

[0048] The types of emulsifiers used in emulsion polymerization are as described above. The amount of emulsifier added per 100 parts by mass of raw material monomer is, for example, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, or 8.0 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0049] As polymerization initiators, potassium persulfate, benzoyl peroxide, ammonium persulfate, and hydrogen peroxide, which are commonly used in radical polymerization, can be used.

[0050] In the polymerization process, a chain transfer agent can also be used. The type of chain transfer agent is not particularly limited, and known chain transfer agents commonly used in the emulsion polymerization of chloroprene can be used, such as long-chain alkyl mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan, dialkyl xanthogen disulfides such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide, and iodoform. Long-chain alkyl mercaptans are preferred as the chain transfer agent, and n-dodecyl mercaptan is more preferred. The amount of chain transfer agent added can be adjusted according to the desired weight-average molecular weight, and as an example, it can be 0.01 to 10 parts by mass per 100 parts by mass of the raw material monomer.

[0051] The polymerization temperature is preferably within the range of 5 to 55°C. A temperature of 5°C or higher makes the emulsion less likely to freeze, while a temperature of 55°C or lower prevents evaporation and boiling of the chloroprene monomer.

[0052] The polymerization conversion rate is preferably in the range of 50 to 95%. The polymerization reaction is stopped by adding a polymerization inhibitor. If the polymerization conversion rate is 50% or higher, the toluene-insoluble content tends to increase, and the resulting immersion molded article tends to have a higher tensile strength at break. This is also advantageous from the standpoint of production costs. If the polymerization conversion rate is less than 95%, a decrease in polymerization reactivity due to a reduction in unreacted monomers can be avoided, thus preventing a decrease in productivity.

[0053] Examples of polymerization inhibitors include diethylhydroxylamine, thiodiphenylamine, 4-tert-butylcatechol, and 2,2'-methylenebis-4-methyl-6-tert-butylphenol. Unreacted monomers after emulsion polymerization can be removed by conventional methods such as vacuum distillation.

[0054] Furthermore, the chloroprene-based latex obtained by the manufacturing method of one embodiment of the present invention may optionally contain freeze stabilizers, emulsifying stabilizers, viscosity modifiers, antioxidants, preservatives, etc., after polymerization, to the extent that they do not impair the effects of the present invention.

[0055] 1.4 Filling Conditions The chloroprene latex product according to the present invention has a chloroprene latex filling amount of 90 to 100% (volume %) of the maximum filling amount of the container. The chloroprene latex filling amount may be, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100%, and may be within the range of any two of the values ​​exemplified herein.

[0056] As described above, conventional chloroprene latex products may develop aggregates during storage or transportation, and one of the causes of aggregate formation is the formation of a dry film. The chloroprene latex product according to the present invention defines the material constituting the inner surface of the container and defines the filling rate of chloroprene latex inside the container, i.e., the volume of the gas phase, thereby reducing the dry film that forms at the interface between chloroprene latex and air, and the dry film that forms on the upper wall of the container, and thus suppressing the formation of aggregates.

[0057] The gas phase inside the container of the chloroprene-based latex product according to one embodiment of the present invention can be air, an inert gas, or an air atmosphere. The gas phase inside the container can be under a slight pressure higher than atmospheric pressure.

[0058] 1.5 Characteristics of Chloroprene-based Latex Products In one embodiment of the present invention, when the chloroprene-based latex product is stored at 23°C for 3 days, the chloroprene-based latex is removed from the container and filtered through an 80-mesh wire mesh. Preferably, the mass of the solids remaining on the wire mesh is 0.0300% by mass or less relative to 100% by mass of the chloroprene-based latex. The amount of aggregates after 3 days of storage can be determined by the method described in the examples. The amount of aggregates after 3 days of storage may be, for example, 0, 0.0050, 0.0100, 0.0150, 0.0200, 0.0250, or 0.0300% by mass, and may be within the range of any two of the values ​​exemplified here.

[0059] The amount of aggregates measured after three days under the specific conditions described above can serve as an indicator of the extent to which aggregates will occur when chloroprene latex products are stored for extended periods or when they are transported while being shaken. A chloroprene latex product according to one embodiment of the present invention can be made less prone to aggregate formation during longer storage or transport by adjusting the properties of the chloroprene latex to be filled (e.g., solid content concentration, viscosity, toluene insoluble content, etc.) and the container configuration so that the amount of aggregates measured after three days under the specific conditions described above falls within the above numerical range. The storage period for chloroprene latex products is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 months, and may be within the range of any two of the values ​​exemplified here.

[0060] 2. Method for Manufacturing Chloroprene-Based Latex Products The method for manufacturing chloroprene-based latex products according to one embodiment of the present invention includes a filling step of filling a container with chloroprene-based latex products, wherein the container is filled with chloroprene-based latex to 90-100% of its maximum filling capacity. The container is also made of resin, at least a portion of its inner surface. According to the method for manufacturing chloroprene-based latex products of the present invention, by adjusting the material of the container and the filling rate in the chloroprene-based latex product, it is possible to obtain a chloroprene-based latex product that can reduce the generation of aggregates during storage and / or transportation.

[0061] The chloroprene-based latex product according to one embodiment of the present invention is preferably stored and / or transported at 35°C or below. The storage and / or transport temperature may be, for example, 5, 10, 15, 20, 25, 30, or 35°C, and may be within the range of any two of the values ​​exemplified herein. The storage and transport method for the chloroprene-based latex product according to one embodiment of the present invention may involve storing the chloroprene-based latex product at a temperature within the above range for three days or more.

[0062] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0063] (Example 1) Chloroprene latex A containing a chloroprene polymer was filled to 90% in a high-density, high-molecular-weight polyethylene container (mouth inner diameter 45.5 mm, outer diameter 79.5 mm, total height 151 mm, capacity 500 mL) and shaken vertically 10 cm back and forth 10 times. It was then stored at 23°C for 3 days. The container was rotated once vertically (one rotation in a vertical plane) once a day before observation.

[0064] Chloroprene latex A had a solid content concentration of 55.0% by mass relative to 100% by mass of chloroprene latex, a viscosity of 30 mPa·s, a toluene-insoluble content of 19%, and a pH of 12.7. The solid content concentration was measured by the following method: 2-3 g of chloroprene polymer latex filtered through a wire mesh was placed in an aluminum cup (Toyo Aluminum Asagao Large Case, top diameter Φ70 mm × height H23 mm × bottom diameter Φ44 mm). The latex sample was spread evenly across the bottom of the cup and dried for 1 hour at 125°C. When C g of chloroprene polymer latex is denoted as the amount of chloroprene polymer latex and D g is the mass after drying for 1 hour at 125°C, the concentration can be expressed as D / C × 100 (%).

[0065] Viscosity was measured using a B-type viscometer under the following conditions: Measuring instrument: "VISCOMETER TVB-20L" manufactured by Toki Sangyo Co., Ltd. Spindle / rotor: 2M (19 mm diameter x 7 mm thickness disc) Rotation speed: 30 rpm

[0066] Furthermore, the toluene-insoluble content was measured by the following method. A 0.23 ± 0.01 g test piece was obtained by cutting chloroprene polymer rubber, obtained by freeze-drying chloroprene latex, into a 2 mm square. After placing this test piece in a conical beaker, the test piece was dissolved in 40.2 g of toluene over 16 hours. Subsequently, centrifugation was performed, and the gel component (insoluble content) was separated using a 200 mesh wire mesh. After drying the gel component, the mass of the dried product was measured. The toluene-insoluble content in the chloroprene polymer rubber was calculated using the following formula, where A g is the amount of freeze-dried chloroprene polymer rubber and B g is the amount of gel component (insoluble content) separated from the mixture dissolved in toluene: Toluene-insoluble content (gel component) = B / A × 100 (%)

[0067] The weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of chloroprene polymers can be obtained by measuring them using gel permeation chromatography (GPC) and converting them to polystyrene equivalents. Specifically, the following method was used: Instrument name: HLC-8320 (manufactured by Tosoh Corporation) Column: Three TSKgel GMHHR-H columns in series Temperature: 40°C Detection: Differential refractive index Solvent: Tetrahydrofuran Calibration curve: Prepared using standard polystyrene (PS)

[0068] <Amount of aggregated material after 3 days> After storage for 3 days, the chloroprene latex was removed from the container, filtered through an 80-mesh wire mesh, and the solid remaining on the mesh was dried and its mass measured. The percentage (mass%) of the solid remaining on the wire mesh relative to 100% by mass of chloroprene latex was determined.

[0069] (Examples 2 to 6, Comparative Examples 7 to 11) Chloroprene latex was stored in the same manner as in Example 1, except that the type of chloroprene latex to be filled, the filling rate, the storage temperature, the material of the container, and the storage temperature were changed, and the amount of aggregated material after 3 days was determined. Regarding the material of the container, "poly" refers to a container made of high-density, high-molecular-weight polyethylene, similar to that in Example 1, and "glass" refers to a glass container of a similar shape.

[0070]

[0071] 100: Chloroprene latex product, 10: Container, 11: Inner surface, 12: Filling port, 13: Cap, 14: Degassing means, 15: Discharge port, 16: Discharge valve, 20: Chloroprene latex, 30: Outer frame, 40: Pallet, 50: Pad

Claims

A container and a chloroprene-based latex filled in the container, At least a portion of the inner surface of the container is made of resin. A chloroprene latex product in which the amount of chloroprene latex filled is 90 to 100% of the maximum filling amount of the container. 　 The chloroprene-based latex product according to claim 1, wherein the container is a blow-molded container and the resin comprises high-density polyethylene. 　 The chloroprene-based latex product according to claim 1 or claim 2, further comprising an outer frame for housing the container. 　 The container is equipped with a filling port and a cap capable of sealing the filling port. The filling port is provided on the upper surface of the container. The chloroprene-based latex product according to claim 1 or claim 2, wherein the cap is removable and gas can be released from the container with the cap attached to the filling port. 　 The chloroprene latex product according to claim 1 or claim 2, wherein, after being stored at 23°C for 3 days, the chloroprene latex is removed from the container and filtered through an 80-mesh wire mesh, and the mass of solids remaining on the wire mesh is 0.0300% by mass or less relative to 100% by mass of the chloroprene latex. 　 The chloroprene latex product according to claim 1 or claim 2, wherein the chloroprene latex has a solid content concentration of 35.0 to 70.0% by mass. 　 The chloroprene-based latex product according to claim 1 or claim 2, wherein the chloroprene-based latex has a viscosity of 5 to 1500 mPa·s as measured by a B-type viscometer at 23°C. 　 A method for manufacturing chloroprene latex products, This includes a filling process for filling containers with chloroprene-based latex products. In the filling process, chloroprene latex is filled to 90-100% of the maximum filling capacity of the container. The container has an inner surface that is made of resin, at least a portion of it. A method for manufacturing chloroprene latex products.

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