JP7166336B2 - Statistical Copolymer Latex, Uses Thereof, and Method for Producing Polymer Latex - Google Patents

Description

The present invention relates to statistical copolymer latexes and their uses, as well as to methods of making polymer latexes.

In order to improve the heat resistance of chloroprene polymer latex, a method of adding an anti-aging agent has long been used as a general method (see, for example, Patent Document 1).

Many anti-aging agents are solid at room temperature, and the method of addition requires some ingenuity. Specific addition methods include (1) a method of direct addition, (2) a method of adding as an aqueous dispersion using a surfactant, and (3) a method of dissolving in an organic solvent and then adding. The method is known as prior art (see Patent Document 2).

For example, in Patent Literature 1 and Patent Literature 3, the anti-aging agent is added using the method (2) of adding an aqueous dispersion using a surfactant. This method is the most common addition method for the anti-aging agent and the addition method in the production method of the chloroprene polymer latex from the viewpoint of simplicity and the like.

Further, in Patent Document 4, in the production of rubber latex, the above (2) method of adding as an aqueous dispersion using a surfactant and the above (3) method of adding after dissolving in an organic solvent are combined. , describes the technique of adding anti-aging agents.

JP-A-48-178 JP-A-2000-256512 JP 2007-270057 A WO2008/117620

As described above, in the production of rubber latex, generally three methods are used for adding anti-aging agents. or (2) a method of adding as an aqueous dispersion using a surfactant.

However, in the method (1) of direct addition, when the anti-aging agent is water-insoluble, it cannot be dispersed or dissolved in the latex, resulting in precipitation and sedimentation as aggregates.

In addition, in the method (2) of adding an aqueous dispersion using a surfactant, the water-insoluble anti-aging agent, which is the problem of (1) above, can also be added to the latex. If there is a large difference between the particle size of the dispersion and the particle size of the latex, the anti-aging agent in the latex will have poor dispersion stability in water, resulting in the problem of separation between the latex and the anti-aging agent. In addition, the sedimentation speed of particles in latex is proportional to the square of the particle size and inversely proportional to the viscosity according to Stokes' law. , there was a problem that a large amount of the anti-aging agent would settle.

Thus, when the anti-aging agent precipitates in the latex, there is a problem that physical properties such as elongation at break in the heat resistance test of the obtained film are deteriorated.

Therefore, the main object of the present invention is to provide a technique for improving the dispersion stability of an antioxidant in a chloroprene polymer latex and improving the heat resistance when the chloroprene polymer latex is dried. .

That is, the present invention is as follows.
(1) A statistical copolymer latex containing chloroprene monomer units and unsaturated nitrile monomer units, wherein the unsaturated nitrile monomer unit content is 5 to 20% by mass,
The statistical copolymer latex is diluted with a tetrahydrofuran solution, and the content of the antioxidant measured by gas chromatography is 1.0 to 6.0% by mass with respect to 100% by mass of the statistical copolymer latex. and the ratio of antioxidant concentration in the liquid surface sampling liquid and the bottom sampling liquid after centrifuging the statistical copolymer latex at 14000 rpm for 20 minutes (liquid surface sampling liquid / bottom sampling liquid) is between 0.6 and 1.2.
(2) The polymer obtained by drying the statistical copolymer latex at room temperature has an elongation at break of 500% or more after heat treatment at 140°C for 24 hours, measured according to JIS K6251. A statistical copolymer latex as described in .
(3) RFL film obtained by drying the RFL adhesive of resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) using the statistical copolymer latex at room temperature The statistical copolymer latex according to (1) or (2), which has a breaking elongation of 150% or more after heat treatment at 140° C. for 24 hours, measured according to JIS K6251.
(4) The statistical copolymer latex according to any one of (1) to (3), wherein the antioxidant is an aromatic secondary amine antioxidant.
(5) The statistical copolymer latex according to any one of (1) to (4), which has a volatile organic solvent content of 200 ppm or less.
(6) Volume change rate (ΔV) and weight change after immersion in engine oil at 140° C. for 72 hours, measured in accordance with JIS K6258, for the polymer obtained by drying the statistical copolymer latex at room temperature. A statistical copolymer latex according to any one of (1) to (5) having a modulus (ΔW) value in the range of −10 to +10%.
(7) RFL film obtained by drying the RFL adhesive of resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) using the statistical copolymer latex at room temperature was measured in accordance with JIS K6258, the volume change rate (ΔV) and weight change rate (ΔW) after immersion in engine oil at 140 ° C. for 72 hours are in the range of -10 to +10%, (1 The statistical copolymer latex of any one of ) through (6).
(8) The statistical copolymer latex of any one of (1) to (7) for use in RFL adhesives, dip products, adhesives, or films.
(9) RFL adhesives, dipping products, adhesives or films using the statistical copolymer latex of any one of (1) to (7).
(10) a polymerization step of performing emulsion polymerization using at least chloroprene monomer units;
An antiaging agent addition step of adding an aqueous emulsion of an organic solvent solution containing an antiaging agent;
A method for producing a polymer latex comprising
The anti-aging agent is added substantially by means of a water emulsion,
The polymer latex is diluted in a tetrahydrofuran solution, and the content of the antioxidant measured by gas chromatography is 1.0 to 6.0% by mass with respect to 100% by mass of the polymer latex, and the polymer After centrifuging the latex at 14,000 rpm for 20 minutes, the concentration ratio of the anti-aging agent in the liquid surface sampling solution and the bottom surface sampling solution (liquid surface sampling solution/bottom sampling solution) is 0.6 to 1.2. , a method for producing a polymer latex. (11) The method for producing a polymer latex according to (10), wherein an aqueous emulsion obtained by mixing an organic solvent solution containing an antioxidant, a polymerization inhibitor, and an aqueous surfactant solution is added at the time of stopping the emulsion polymerization reaction.
(12) The method for producing a polymer latex according to (10) or (11), comprising an organic solvent removing step of removing the organic solvent after the antioxidant adding step.
(13) The polymer latex according to any one of (10) to (12), wherein emulsion polymerization is performed using chloroprene monomer units and unsaturated nitrile monomer units in the polymerization step. Production method.
(14) The method for producing a polymer latex according to (13), wherein in the polymerization step, the chloroprene monomer is added continuously or intermittently 10 times or more after initiation of the polymerization reaction.
(15) a polymerization step of performing emulsion polymerization using a chloroprene monomer unit and an unsaturated nitrile monomer unit;
A step of adding an aqueous emulsion obtained by mixing an organic solvent solution containing an aromatic secondary amine anti-aging agent, a polymerization inhibitor, and an aqueous surfactant solution at the time of stopping the polymerization reaction;
and removing the organic solvent;
The anti-aging agent is obtained by a method in which it is added substantially with a water emulsion,
A statistical copolymer latex having an unsaturated nitrile monomer unit content of 5 to 20% by weight.
In this specification, room temperature means 23° C. unless otherwise specified.

That is, in the present invention, first, a chloroprene monomer unit and an unsaturated nitrile monomer unit having an unsaturated nitrile monomer unit content of 5 to 20% by mass, preferably 6 to 17% by mass, are combined. A statistical copolymer latex comprising
The statistical copolymer latex is diluted with a tetrahydrofuran solution, and the content of the anti-aging agent measured by gas chromatography is 1.0 to 6.0 with respect to 100% by mass of the statistical copolymer latex. % by mass, preferably 1.0 to 4.5% by mass, antiaging agent in the liquid surface sampling liquid and the bottom sampling liquid after centrifuging the statistical copolymer latex at 14000 rpm for 20 minutes Provide a statistical copolymer latex having a concentration ratio (top sampling liquid/bottom sampling liquid) of 0.6 to 1.2.
The statistical copolymer latex according to the present invention is a polymer obtained by drying the statistical copolymer latex at room temperature. It can be 500% or more.
The statistical copolymer latex according to the present invention is an RFL adhesive of resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) using the statistical copolymer latex The breaking elongation after heat treatment at 140 ° C. for 24 hours measured according to JIS K6251 of the RFL film obtained by drying at room temperature can be 150% or more.
In the present invention, an aromatic secondary amine antiaging agent can be used as the antiaging agent.
The statistical copolymer latex according to the present invention can have a volatile organic solvent content of 200 ppm or less.
The statistical copolymer latex according to the present invention is a polymer obtained by drying the statistical copolymer latex at room temperature, measured in accordance with JIS K6258, after immersion in engine oil at 140 ° C. for 72 hours. The values of volume change rate (ΔV) and weight change rate (ΔW) can be in the range of -10 to +10%, preferably in the range of -5 to +5%.
The statistical copolymer latex according to the present invention is an RFL adhesive of resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) using the statistical copolymer latex The RFL film obtained by drying at room temperature was measured in accordance with JIS K6258, and the volume change rate (ΔV) and weight change rate (ΔW) after immersion in engine oil for 72 hours at 140 ° C. The values were -10 to It can be in the range of +10%, preferably in the range of -5 to +5%.

The statistical copolymer latex according to the invention can be used in RFL adhesives, dip products, adhesives, or films.

In the present invention, next, a polymerization step of performing emulsion polymerization using at least chloroprene monomer units;
An antiaging agent addition step of adding an aqueous emulsion of an organic solvent solution containing an antiaging agent;
A method for producing a polymer latex comprising
The anti-aging agent is added substantially by means of a water emulsion,
The polymer latex is diluted with a tetrahydrofuran solution, and the content of the antioxidant measured by gas chromatography is 1.0 to 6.0% by mass with respect to 100% by mass of the polymer latex, and the polymer After centrifuging the latex at 14,000 rpm for 20 minutes, the concentration ratio of the anti-aging agent in the liquid surface sampling solution and the bottom surface sampling solution (liquid surface sampling solution/bottom sampling solution) is 0.6 to 1.2. provides a method for making a polymer latex.
In the method for producing a polymer latex according to the present invention, a water emulsion obtained by mixing an organic solvent solution containing an antioxidant, a polymerization inhibitor, and an aqueous surfactant solution can be added at the time of stopping the emulsion polymerization reaction.
In the method for producing a polymer latex according to the present invention, an organic solvent removing step of removing the organic solvent can be performed after the antioxidant adding step.
In the method for producing a polymer latex according to the present invention, emulsion polymerization using chloroprene monomer units and unsaturated nitrile monomer units can be carried out in the polymerization step.
In this case, in the polymerization step, the chloroprene monomer can be added continuously or intermittently 10 times or more after initiation of the polymerization reaction.

In the present invention, furthermore, a polymerization step in which emulsion polymerization is performed using chloroprene monomer units and unsaturated nitrile monomer units, and a chloroprene monomer is continuously added or intermittently added 10 times or more after the initiation of the polymerization reaction. process and
A step of adding an aqueous emulsion obtained by mixing an organic solvent solution containing an aromatic secondary amine anti-aging agent, a polymerization inhibitor, and an aqueous surfactant solution at the time of stopping the polymerization reaction;
and removing the organic solvent;
The anti-aging agent is obtained by a method in which it is added substantially with a water emulsion,
A statistical copolymer latex is provided having an unsaturated nitrile monomer unit content of 5 to 20% by weight.

In the present invention, "JIS" means Japanese Industrial Standards.

In the present invention, "statistical copolymers" are defined as those described in J. Am. C. By Bernoulli's statistical model, as described in Randall, POLYMER SEQUENCE DETERMINATION, Carbon-13 NMR Method, Academic Press, New York, 1977, pp. 71-78, or by a first- or second-order Markov statistical model, It means that it is a copolymer that can describe the monomer chain distribution. In addition, the statistical copolymer containing chloroprene monomer units and unsaturated nitrile monomer units of the present embodiment is not particularly limited, but when composed of binary monomers, In the following Mayo-Lewis formula (I), regarding the reactivity ratios r ₁ and r ₂ when the chloroprene monomer is M1, r ₁ is in the range of 0.3 to 3000, and r ₂ is in the range of 1×10 −5 to It can range from 3.0. From a further viewpoint, the "statistical copolymer" in the present invention is a copolymer obtained by radical polymerization using a plurality of types of monomers. This "statistical copolymer" is a concept that includes substantially random copolymers.

ADVANTAGE OF THE INVENTION According to this invention, the dispersion stability of the antioxidant in a chloroprene polymer latex can be improved, and the heat resistance at the time of drying this chloroprene polymer latex can be improved.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated in detail. In addition, this invention is not limited to embodiment described below.

<Statistical Copolymer Latex>
The statistical copolymer latex of this embodiment is a statistical copolymer latex containing chloroprene monomer units and unsaturated nitrile monomer units.

The unsaturated nitrile content of the statistical copolymer latex is 5-20% by weight, preferably 6-17% by weight. Within this range, a statistical copolymer suitable for obtaining a rubber having practically useful oil resistance, mechanical strength and low-temperature properties as a rubber can be obtained. If the unsaturated nitrile content is lower than this range, the oil resistance may be insufficient, and if it is higher than this range, the mechanical strength of the rubber may be lowered, or low-temperature properties such as low-temperature compression set may be lowered.

Although the molecular structure of the statistical copolymer is not particularly limited, the toluene-insoluble content is preferably in the range of 50 to 100% by mass. By making it 50% by mass or more, it is possible to prevent a decrease in mechanical strength when the latex is dried.

Examples of the statistical copolymer latex of the present embodiment include chloroprene-acrylonitrile statistical copolymer latex, chloroprene-methacrylonitrile statistical copolymer latex, chloroprene-ethacrylonitrile statistical copolymer latex, chloroprene -Phenyl acrylonitrile statistical copolymer latex and the like. Among these, chloroprene-acrylonitrile statistical copolymer latex is preferred from the viewpoint of ease of production, oil resistance and mechanical strength.

The statistical copolymer latex according to the present embodiment is diluted with a tetrahydrofuran solution, and the content of the antioxidant measured by gas chromatography is 1.0 to 1.0 with respect to 100% by mass of the statistical copolymer latex. 6.0% by mass, preferably 1.0 to 4.5% by mass, in the liquid surface sampling liquid and the bottom sampling liquid after centrifuging the statistical copolymer latex at 14000 rpm for 20 minutes The antioxidant concentration ratio (liquid surface sampling liquid/bottom sampling liquid) is 0.6 to 1.2.

In the statistical copolymer latex according to the present embodiment, since the ratio of the antioxidant concentration in the liquid surface sampling liquid and the bottom sampling liquid is within this range, the dispersion of the antioxidant in the statistical copolymer latex Good properties. As a result, the heat resistance when drying the statistical copolymer latex can be improved.

Specifically, the statistical copolymer latex according to the present embodiment is a polymer obtained by drying it at room temperature. It is 500% or more, and the heat resistance when made into a film is very high.

In addition, the statistical copolymer latex according to the present embodiment uses the resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) RFL adhesive dried at room temperature. The breaking elongation after heat treatment at 140° C. for 24 hours measured in accordance with JIS K6251 of the RFL film obtained is 150% or more, and the heat resistance when made into an RFL film is also very high.

Furthermore, the statistical copolymer latex according to the present embodiment is a polymer obtained by drying it at room temperature, and the volume change rate after immersion in engine oil at 140 ° C. for 72 hours, which is measured in accordance with JIS K6258. (ΔV) and weight change rate (ΔW) are in the range of -10 to +10%, preferably -5 to +5%, and the oil resistance of the film is very high.

In addition, the statistical copolymer latex according to the present embodiment is a resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) RFL adhesive using this at room temperature. The RFL film obtained by drying was measured in accordance with JIS K6258, and the volume change rate (ΔV) and weight change rate (ΔW) after immersion in engine oil for 72 hours at 140 ° C. are -10 to +10%. is within the range of, preferably within the range of -5 to +5%, and the oil resistance when made into an RFL film is also very high.

As antiaging agents that can be used in the present embodiment, one or more known antiaging agents can be freely selected and used as long as the effects of the present technology are not impaired. Examples thereof include phenol-based and imidazole-based antioxidants. Among these, it is particularly preferable to use an aromatic secondary amine anti-aging agent in the present embodiment. The aromatic secondary amine-based antiaging agent that can be used in the present embodiment is also one or more known aromatic secondary amine-based antiaging agents, as long as it does not impair the effects of the present technology. For example, N-phenyl-1-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4′-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonyl amido)diphenylamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl- N'-(1,3-dimethylbutyl)-p-phenylenediamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, and the like.

The statistical copolymer latex according to the present embodiment preferably has a volatile organic solvent content of 200 ppm or less. By keeping the content of the volatile organic solvent within this range, it is possible to prevent adverse effects on the human body and reduce the environmental load.

<Application of statistical copolymer latex>
The statistical copolymer latex according to the present embodiment can be suitably used for RFL adhesives, dipped products, adhesives, or films by utilizing its high heat resistance and the like. In addition, the statistical copolymer latex according to the present embodiment is a statistical copolymer obtained after adjusting the pH and subjecting it to a statistical copolymer through conventional steps such as freezing and coagulation, washing with water, and drying with hot air. The polymer is preferably used as a material for rubber products such as power transmission belts, conveyor belts, air springs, seals, packings, vibration-proof materials, hoses, rubber rolls, wipers, boots, rubber-coated fabrics, sponge products, and rubber linings. can do.

(RFL adhesive, adhesive)
Chloroprene polymer latex is used as an RFL adhesive for surface treatment by immersing reinforcing fibers in order to improve adhesion to rubber. In belt applications, where reinforcing fibers are used, excellent durability is required in addition to adhesiveness, and there is a high demand for mechanical strength, oil resistance, and heat resistance. Therefore, the development of a chloroprene polymer latex exhibiting even better mechanical strength, oil resistance and heat resistance is desired. In addition, chloroprene polymer latex is used as an adhesive for a wide range of materials, such as civil engineering and construction, plywood, furniture, shoes, wet suits, and automotive interior materials, due to its contact properties and excellent initial adhesive strength. Among these, the demand for one-liquid type adhesives for polyurethane foams, which are widely used as materials for furniture and automobile interior materials, is expanding significantly. Especially for automobile interior materials, the development of chloroprene polymer latexes having excellent heat resistance that can withstand temperature rises in automobile cabins is desired.

The statistical copolymer latex of this embodiment can enhance the heat resistance of the adhesive. This makes it possible to produce RFL adhesives and adhesives that are superior to conventional chloroprene polymer latexes.

(immersion product)
Rubber latex, including natural rubber and synthetic rubbers such as chloroprene polymer, isoprene rubber, and nitrile butadiene rubber, is dip molded into medical surgical gloves, examination gloves, industrial gloves, balloons, catheters, rubber boots, reinforcing fabrics, etc. Used as a raw material for products. In order to avoid the problem of shock symptoms (anaphylaxis) caused by allergies to natural rubber, chloroprene polymer, isoprene rubber, and nitrile-butadiene rubber are used especially in rubber latex for medical surgical gloves, examination gloves, industrial gloves, and household gloves. , etc. are preferred. Among them, the chloroprene polymer has excellent balance of flexibility and mechanical strength and exhibits high chemical resistance, so that it is used for industrial gloves with resistance to various chemicals. In recent years, the demand for chemical-resistant gloves that can withstand use in high-temperature and low-temperature environments has increased, and the development of chloroprene polymer latex with superior heat resistance is desired.

The statistical copolymer latex of the present embodiments can enhance the heat resistance of dipped products. As a result, it is possible to manufacture industrial gloves that can withstand use in a high-temperature environment, which has been difficult with conventional CR.

(Transmission belts and conveyor belts)
Examples of transmission belts and conveyor belts include flat belts, conveyor belts, timing belts, V-belts, ribbed belts, round belts, and the like. The statistical copolymer of this embodiment can enhance the mechanical strength, oil resistance, bending fatigue resistance, and heat resistance of power transmission belts and conveyor belts. As a result, it is possible to manufacture a belt that can withstand use in an environment exposed to splashed oil or in a high-temperature environment, which has been difficult with conventional materials.

(air spring)
An air spring is a spring device that utilizes the elasticity of compressed air, and is used in air suspensions of automobiles, buses, trucks, and the like. The statistical copolymer of this embodiment can improve the mechanical strength, oil resistance, endurance fatigue resistance, settling resistance (low compression set), and heat resistance of the air spring. As a result, it is possible to manufacture an air spring that can withstand use in an environment with a lot of oil stains and in a high-temperature environment, which has been difficult with conventional materials.

(seal and packing)
Seals are parts of machinery and equipment that prevent leaks of liquids and gases, rainwater, dust, and other dirt and foreign matter from entering the interior. There are packings used for moving parts. For gaskets whose sealing portions are fixed with bolts or the like, various materials are used depending on the purpose, as opposed to soft gaskets such as O-rings and rubber sheets. Packings are also used for shafts of pumps and motors, rotating parts such as the movable parts of valves, reciprocating parts such as pistons, connecting parts of couplers, water shut-off parts of faucets, and the like. The statistical copolymer of this embodiment can enhance the mechanical strength and oil resistance of the seal. This makes it possible to manufacture seals for non-polar fluids such as engine oil and gear oil, which were difficult with conventional materials. In addition to the above, the statistical copolymer of this embodiment also has good sag resistance (low compression set) and heat resistance, so it can be used for a long time and in a high temperature environment. The shape is hard to change and good sealing performance can be obtained. Sag resistance (low compression set), especially at low and high temperatures, is important for this application.

(anti-vibration material)
Anti-vibration materials are rubbers that prevent transmission and spread of vibrations. Specifically, they are torsional dampers and engine mounts that absorb vibrations and prevent noise when the engines of automobiles and other vehicles are running. , muffler hangers, etc. The statistical copolymer of this embodiment can improve the mechanical strength, oil resistance, bending fatigue resistance, and heat resistance of the vibration-damping material. As a result, it is possible to manufacture anti-vibration rubber that can withstand use in oil-spattering environments and high-temperature environments, which has been difficult with conventional materials.

(hose)
A hose is a bendable tube, and specific examples include high/low pressure hoses for water, oil, air, steam, and hydraulic pressure. The statistical copolymer of this embodiment can increase the mechanical strength, oil resistance, sag resistance (low compression set), and heat resistance of the hose. As a result, it is possible to manufacture hoses that are in direct contact with non-polar fluids and hoses that can withstand use in high-temperature environments, which were difficult with conventional materials.

(rubber roll)
A rubber roll is a roll manufactured by adhesively coating a metal core such as an iron core with rubber. There are rubber rolls that meet the required characteristics of various applications such as food processing and food processing. When manufacturing industrial materials and products for iron and paper manufacturing, they are used in an environment where oil adheres. May be exposed to alkali. The statistical copolymer of this embodiment can improve the mechanical strength, oil resistance, settling resistance (low compression set), and heat resistance of the rubber roll. As a result, it is possible to manufacture a rubber roll that can withstand use in an oil-adhering environment or in a high-temperature environment, which has been difficult with conventional CR.

(wiper)
Wipers are specifically used for windshields and rear windows of automobiles, trains, aircraft, ships, construction machines, and the like. The statistical copolymer of this embodiment can increase the mechanical strength, oil resistance, endurance fatigue resistance, sag resistance (low compression set), and heat resistance of the wiper. As a result, it is possible to manufacture a wiper that can withstand use in an environment with a lot of oil stains and in a high-temperature environment, which was difficult with conventional materials.

(boots)
A boot is a bellows-shaped member whose outer diameter gradually increases from one end to the other end. Boots for joint covers (dust cover boots), boots for rack and pinion gears, etc. The statistical copolymer of this embodiment can enhance the mechanical strength, oil resistance, and endurance fatigue resistance of the boot. This makes it possible to manufacture a boot that is more reliable against non-polar liquids such as oil and grease contained therein than conventional materials. In addition, since the statistical copolymer of the present embodiment is excellent in sag resistance (low compression set resistance) and heat resistance, it can be deformation is unlikely to occur.

(Rubber coated cloth)
Rubber-coated fabric is a composite material of rubber and cloth fabric (fiber), which is made by bonding rubber to cloth. Specifically, it is widely used for rubber boats and tent materials, clothing such as raincoats, waterproof sheets for construction, and cushioning materials. used. The statistical copolymer of this embodiment can enhance the mechanical strength, oil resistance, and heat resistance of the rubberized fabric. As a result, it is possible to manufacture a rubber-coated fabric that can withstand use in an oil-spattering environment or in a high-temperature environment, which has been difficult with conventional materials.

(sponge product)
A sponge is a porous material with a myriad of fine pores inside, and specific examples include vibration-isolating members, sponge sealing parts, wet suits, shoes, and the like. The statistical copolymer of this embodiment can enhance the mechanical strength, oil resistance, and heat resistance of sponge products. As a result, it is possible to manufacture a sponge product that is resistant to swelling, deformation and discoloration due to oil, which has been difficult with conventional materials, and that can withstand use in high-temperature environments.

(rubber lining)
Rubber linings are used to prevent corrosion of metals by adhering rubber sheets to the metal surfaces of pipes, tanks, and the like. Rubber linings are also used where electrical resistance, abrasion resistance, and heat resistance are required. The statistical copolymer of this embodiment can improve oil resistance and heat resistance as a rubber lining. This makes it possible to prevent corrosion of pipes and tanks by oil, which was difficult with conventional materials.

<Method for producing polymer latex>
The method for producing a polymer latex according to the present embodiment is a method of performing at least (1) a polymerization step and (2) an antioxidant addition step. In addition, (3) the organic solvent removal step and other steps generally used in the production method of polymer latex can also be carried out. Each step will be described in detail below.

(1) Polymerization step In the polymerization step, emulsion polymerization is carried out using at least 2-chloro-1,3-butadiene (hereinafter abbreviated as “chloroprene”) monomer units. More specifically, in this polymerization step, homopolymerization of chloroprene or copolymerization of chloroprene and one or more copolymerizable monomers is performed.

Examples of the monomer copolymerizable with chloroprene in the present embodiment include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, styrene, methyl methacrylate, Ethyl methacrylate, propyl methacrylate (all isomers), butyl methacrylate (all isomers), 2-ethylhexyl methacrylate, isobornyl methacrylate, methacrylic acid, benzyl methacrylate, phthalate , ethyl acrylate, propyl acrylate (all isomers), butyl acrylate (all isomers), 2-ethylhexyl acrylate, isobornyl acrylate, acrylic acid, benzyl acrylate, phenyl acrylate acid, styrene, and glycidyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate (all isomers), hydroxybutyl methacrylate (all isomers), N,N-dimethylaminoethyl methacrylate salt, N,N-diethylaminoethyl methacrylate, triethylene glycol methacrylate, itaconic anhydride, itaconic acid, glycidyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate (all isomers), Hydroxybutyl acrylate (all isomers), N,N-dimethylaminoethyl acrylate, N,N-ethylaminoethyl acrylate, triethylene glycol acrylate, methacrylamide, N-methylacrylamide, N , N-dimethylacrylamide, N-tert-butyl methacrylamide, Nn-butyl methacrylamide, N-methylol methacrylamide, N-ethylol methacrylamide, N-tert-butyl acrylamide, Nn-butyl Acrylamide, N-methylolacrylamide, N-ethylolacrylamide, vinylbenzoic acid (all isomers), diethylaminositylene (all isomers), alpha-ethylvinylbenzoic acid (all isomers), diethylamino alpha-methylstyrene (all isomers) isomer), p-vinylbenzenesulfonic acid, p-vinylbenzenesulfone sodium salt, trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, tributoxysilylpropyl methacrylate, dimethoxymethylsilylpropyl methacrylate, Diethoxymethylsilylpropyl methacrylate, Dibutoxymethylsilylpropyl methacrylate phosphate, diisopropoxymethylsilylpropyl methacrylate, dimethoxysilylpropyl methacrylate, diethoxysilylpropyl methacrylate, dibutoxysilylpropyl methacrylate, diisopropoxysilylpropyl methacrylate, trimethoxysilylpropyl Acrylate, triethoxysilylpropyl acrylate, tributoxysilylpropyl acrylate, dimethoxymethylsilylpropyl acrylate, diethoxymethylsilylpropyl acrylate, dibutoxymethylsilylpropyl acrylate, diisopropoxymethyl Silylpropyl acrylate, dimethoxysilylpropyl acrylate, diethoxysilylpropyl acrylate, dibutoxysilylpropyl acrylate, diisopropoxysilylpropyl acrylate, vinyl acetate, vinyl butyrate, vinyl benzoate, vinyl chloride , vinyl fluoride, vinyl bromide, maleic anhydride, N-phenylmaleimide, N-butylmaleimide, N-vinylpyrrolidone, N-vinylcarbazole, ethylene, propylene, unsaturated nitrile monomers (acrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile, etc.).

The polymerization method is not particularly limited, but the raw material monomers may be polymerized by a generally used emulsion polymerization method in the presence of a surfactant, a polymerization initiator, a molecular weight modifier, and the like.

Surfactants (emulsifying/dispersing agents) that can be used in the present embodiment are not particularly limited as long as they do not impair the effects of the present technology. Various types such as cationic type can be used. From the viewpoint of the stability of the resulting latex, anionic surfactants are preferred, such as rosinates, alkylsulfonate salts having 8 to 20 carbon atoms, alkylsulfate salts, alkylarylsulfate salts, sodium naphthalenesulfonate and formaldehyde. and sodium alkyldiphenyl ether disulfonate. Among anionic surfactants, it is particularly preferable to use an alkali metal rosinate because the stability of the latex is excellent. Rosin acid is a mixture of resin acids, fatty acids and the like. Resin acids include abietic acid, neoabietic acid, parastric acid, pimaric acid, isopimaric acid, dehydroabietic acid, dihydropimaric acid, dihydroisopimaric acid, secodehydroabietic acid, dihydroabietic acid, etc. Fatty acids include , oleic acid, and linoleic acid. These component compositions are classified into gum rosin, wood rosin, and tall rosin, and vary depending on the method of extracting rosin, the production area and tree species of pine, distillation and refining, and disproportionation (disproportionation) reaction. not. Considering emulsion stability and ease of handling, sodium salt or potassium salt is preferably used.

The amount of the surfactant to be added is preferably 0.2 to 20 parts by mass, more preferably 2 to 10 parts by mass, based on 100 parts by mass of the chloroprene monomer and other monomers. By making it 0.2 parts by mass or more, the monomer can be sufficiently emulsified, and by making it 20 parts by mass or less, it is possible to prevent the surfactant from blooming on the surface of the resulting film.

As the polymerization initiator that can be used in the present embodiment, one or more known polymerization initiators can be freely used as long as the effect of the present technology is not impaired. For example, potassium persulfate, ammonium persulfate, benzoyl peroxide, sodium persulfate, hydrogen peroxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyoctoate, t-butyl peroxyneodecanoate, t - butyl peroxyisobutyrate, t-amyl peroxypivalate, t-butyl peroxypivalate, di-isopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, dicumyl peroxide, dibenzoyl peroxide, dilauroyl peroxide, potassium peroxydisulfate, Organic peroxides such as ammonium peroxydisulfate, di-t-butyl hyponitrite, dicumyl hyponitrite, 2,2-azobis(isobutyronitrile), 2,2'-azobis(2-cyano-2-butane ), dimethyl 2,2′-azobisdimethyl isobutyrate, 4,4′-azobis(4-cyanopentanoic acid), 1,1′-azobis(cyclohexanecarbonitrile), 2-(t-butylazo)-2 -cyanopropane, 2,2'-azobis[2-methyl-N-(1,1)-bis(hydroxymethyl)-2-hydroxyethyl]propionamide, 2,2'-azobis[2-methyl-N- hydroxyethyl)]-propionamide, 2,2′-azobis(N,N′-dimethyleneisobutyramidine) dihydrochloride, 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis( N,N'-dimethylene isobutylamine), 2,2'-azobis (2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide), 2,2'-azobis (2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide, 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2-azobis (isobutylamido) dihydrate), 2,2′-azobis(2,2,4-trimethylpentane), 2,2′-azobis(2-methylpropane) and other azo initiators.

A polymerization co-catalyst can also be used in the emulsion polymerization. The polymerization co-catalyst that can be used in the present embodiment is not particularly limited as long as it does not impair the effects of the present invention, and one or more known polymerization co-catalysts can be freely used. For example, L-ascorbic acid, tartaric acid, sodium bisulfite, zinc- or sodium-formaldehyde-sulfoxylate longalite, formdiaminesulfinic acid, glucose, formalin, anthraquinone sodium β-sulfonate, ferrous sulfate, copper sulfate, sodium bisulfite, thiourea and the like.

In the production method of this embodiment, a chain transfer agent can be used to control the molecular weight. The chain transfer agent that can be used in the present embodiment is not particularly limited as long as it does not impair the effects of the present invention, and one or more known chain transfer agents can be freely used. For example, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl mercaptan and other long-chain alkyl mercaptans, xanthogen compounds such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide, iodoform, benzyl 1-pyrrole dithiocarbamate (also known as benzyl 1-pyrrole carbodithioate), 1-benzyl-N,N-dimethyl-4-aminodithiobenzoate, 1-benzyl-4-methoxydithiobenzoate, 1-phenylethylimidazole dithiocarbamate (also known as 1-phenylethylimidazole carbodithioate), benzyl -1-(2-pyrrolidinone)dithiocarbamate (aka benzyl-1-(2-pyrrolidinone)carbodithioate), benzylphthalimidyldithiocarbamate (aka benzylphthalimidylcarbodithioate), 2-cyanoprop-2-yl -1-pyrrole dithiocarbamate (also known as 2-cyanoprop-2-yl-1-pyrrole carbodithioate), 2-cyanobut-2-yl-1-pyrrole dithiocarbamate (also known as 2-cyanobut-2-yl-1-pyrrole carbodithioate), benzyl-1-imidazole dithiocarbamate (also known as benzyl-1-imidazole carbodithioate), 2-cyanoprop-2-yl-N,N-dimethyldithiocarbamate, benzyl-N,N-diethyldithiocarbamate, Cyanomethyl-1-(2-pyrrolidone)dithiocarbamate, 2-(ethoxycarbonylbenzyl)prop-2-yl-N,N-diethyldithiocarbamate, benzyldithioate, 1-phenylethyldithiobenzoate, 2-phenylprop-2 -yl dithiobenzoate, 1-acetic acid-1-yl-ethyldithiobenzoate, 1-(4-methoxyphenyl)ethyldithiobenzoate, benzyldithioacetate, ethoxycarbonylmethyldithioacetate, 2-(ethoxycarbonyl)prop-2- yl dithiobenzoate, 2-cyanoprop-2-yl dithiobenzoate, dithiobenzoate, tert-butyl dithiobenzoate, 2,4,4-trimethylpent-2-yl dithiobenzoate, 2-(4-chlorophenyl)-prop-2- yldithiobenzoate, 3-vinylbenzyldithiobenzoate, 4-vinylbenzyldithiobenzoate, benzyldiethoxyphosphide Nyldithioformate, tert-butyl trithioperbenzoate, 2-phenylprop-2-yl-4-chlorodithiobenzoate, naphthalene-1-carboxylic acid-1-methyl-1-phenyl-ethyl ester, 4-cyano-4 -methyl-4-thiobenzylsulfanylbutyric acid, dibenzyltetrathioterephthalate, carboxymethyldithiobenzoate, poly(ethylene oxide) with dithiobenzoate end groups, 4-cyano-4-methyl-4-thiobenzylsulfanylbutyric acid end groups. poly(ethylene oxide), 2-[(2-phenylethanethiol)sulfanyl]propanoic acid, 2-[(2-phenylethanethiol)sulfanyl]succinic acid, 3,5-dimethyl-1H-pyrazole- 1-carbodithioate potassium, cyanomethyl-3,5-dimethyl-1H-pyrazole-1-carbodithioate, cyanomethylmethyl-(phenyl)dithiocarbamate, benzyl-4-chlorodithiobenzoate, phenylmethyl-4-chlorodithiobenzoate , 4-nitrobenzyl-4-chlorodithiobenzoate, phenylprop-2-yl-4-chlorodithiobenzoate, 1-cyano-1-methylethyl-4-chlorodithiobenzoate, 3-chloro-2-butenyl-4- Chlorodithiobenzoate, 2-chloro-2-butenyldithiobenzoate, benzyldithioacetate, 3-chloro-2-butenyl-1H pyrrole-1-dithiocarboxylic acid, 2-cyanobutane-2-yl 4-chloro-3,5 -dimethyl-1H-pyrazole-1-carbodithioate, cyanomethylmethyl(phenyl)carbamodithioate, 2-cyano-2-propyldodecyltrithiocarbonate, dibenzyltrithiocarbonate, butylbenzyltrithiocarbonate , 2-[[(butylthio)thioxomethyl]thio]propionic acid, 2-[[(dodecylthio)thioxomethyl]thio]propionic acid, 2-[[(butylthio)thioxomethyl]thio]succinic acid, 2-[[(dodecylthio) thioxomethyl]thio]succinic acid, 2-[[(dodecylthio)thioxomethyl]thio]-2-methylpropionic acid, 2,2′-[carbonothioylbis(thio)]bis[2-methylpropionic acid], 2- Amino-1-methyl-2-oxoethylbutyltrithiocarbonate, benzyl 2-[(2-hydroxyethyl)amino]-1-methyl-2- oxoethyltrithiocarbonate, 3-[[[(tert-butyl)thio]thioxomethyl]thio]propionic acid, cyanomethyldodecyltrithiocarbonate, diethylaminobenzyltrithiocarbonate, dibutylaminobenzyltrithiocarbonate, etc. Known chain transfer agents such as thiocarbonyl compounds can be used.

The polymerization temperature in the emulsion polymerization is not particularly limited, but is preferably 0 to 59°C, particularly preferably 5 to 55°C. By setting the polymerization temperature to 5° C. or higher, it is possible to further improve the viscosity of the emulsion and the efficiency of the initiator. In addition, since the boiling point of chloroprene at normal pressure is about 59°C, by setting the polymerization temperature to 55°C or less, even if heat is generated due to abnormal polymerization or the like, the reaction solution will bubble because the heat cannot be removed. situation can be avoided. More preferably, by maintaining the polymerization temperature at 30 to 45° C., a polymer having excellent mechanical properties can be obtained.

In the polymerization step, when emulsion polymerization is performed using a chloroprene monomer unit and an unsaturated nitrile monomer unit, the chloroprene monomer can be added continuously or intermittently 10 times or more after the initiation of the polymerization reaction. preferable. Chloroprene has a faster reaction rate than unsaturated nitriles. Therefore, the chloroprene monomer is consumed faster than the unsaturated nitrile monomer in the polymerization system. Large imbalances in the ratio of chloroprene monomers to unsaturated nitrile monomers can reduce the oil resistance of the resulting statistical copolymers. In the production method of the present embodiment, mainly the chloroprene monomer, which has been reduced by the polymerization reaction, is continuously added or intermittently added 10 times or more, so that the chloroprene monomer and the unsaturated nitrile monomer in the polymerization system The ratio of the mers can be kept constant. The statistical copolymer produced by the production method of this embodiment also has excellent mechanical strength.

In the production method of the present embodiment, in the case of intermittent addition of 10 times or more, the amount of the chloroprene monomer added after the start of the polymerization reaction is the total amount of the chloroprene monomer and the unsaturated nitrile monomer. It is preferable to make it 10 mass parts or less with respect to 100 mass parts. In the case of intermittent addition, the addition rate is preferably 2 parts by mass/minute or less. By setting it in such a range, a statistical copolymer excellent in oil resistance and mechanical strength can be obtained. Here, keeping the ratio of the unreacted chloroprene monomer and the unsaturated nitrile monomer constant in the polymerization liquid during the polymerization means that the total amount of the chloroprene monomer and the unsaturated nitrile monomer is That is, the mass ratio of saturated nitrile monomer is preferably within ±10% of the target value. For example, during polymerization, when the mass ratio of the unsaturated nitrile monomer to the sum of the unreacted chloroprene monomer and the unsaturated nitrile monomer in the polymerization solution is maintained at 0.50, it is preferably 0.45 to 0. means to keep it in the .55 range.

In the production method of the present embodiment, the polymerization rate (polymerization conversion rate) is preferably in the range of 60 to 100%. The polymerization reaction is terminated by adding a polymerization inhibitor. By setting the degree of polymerization to 60% or more, the strength of the obtained film can be improved.

The polymerization inhibitor that can be used in the present embodiment is not particularly limited as long as it does not impair the effects of the present invention, and one or more known polymerization inhibitors can be freely used. Examples include thiodiphenylamine, 4-tert-butylcatechol, 2,2-methylenebis-4-methyl-6-tert-butylphenol, and diethylhydroxylamine.

In the production method of the present embodiment, removal and concentration of unreacted monomers may be performed by a known method such as heating under reduced pressure.

In addition, the polymer latex obtained by the production method of the present embodiment may optionally contain a freeze stabilizer, an emulsion stabilizer, a viscosity modifier, an antioxidant, a preservative, etc. after polymerization within a range that does not impede the effects of the present invention. can be added to

(2) Antiaging agent addition step The antiaging agent addition step is a step of adding an aqueous emulsion of an organic solvent solution containing an antiaging agent. In the production method of the present invention, the anti-aging agent is added substantially as an aqueous emulsion. Here, "substantially" means that 70% by mass or more, preferably 95% by mass or more, and most preferably 100% by mass of the total antioxidant is added as a water emulsion.

The organic solvent that can be used in the antioxidant addition step is not particularly limited as long as the effect of the present technology is not impaired, and one or more known organic solvents can be freely used. For example, aromatic hydrocarbon solvents such as benzene, toluene and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene and cyclohexane; aliphatic hydrocarbon solvents such as pentane, hexane and heptane; chloroprene, methylene chloride, chloroform, halogenated hydrocarbon solvents such as ethylene dichloride; ether solvents such as diethyl ether, tetrahydrofuran, tetrahydropyran; and the like.

The amount of the organic solvent used in the anti-aging agent addition step is also not particularly limited as long as the effect of the present technology is not impaired, and can be freely set within a range in which the anti-aging agent to be used can be completely dissolved.

The anti-aging agent that can be used in the anti-aging agent addition step is not particularly limited as long as it does not impair the effects of the present technology, and one or more known anti-aging agents can be freely used. The specific types are the same as those of the anti-aging agent that can be used in the statistical copolymer latex described above, so the description is omitted here.

The amount of the anti-aging agent added in the anti-aging agent addition step is preferably 2.0 to 9.0 parts by mass with respect to the total of 100 parts by mass of the chloroprene monomer and other monomers. By making it 2.0 parts by mass or more, the heat resistance of the obtained film can be improved. By setting the amount to 9.0 parts by mass or less, it is possible to prevent the deterioration of physical properties such as elongation at break due to blooming of the anti-aging agent on the surface of the film obtained.

The surfactant used to emulsify the organic solvent solution containing the anti-aging agent is also not particularly limited as long as the effect of the present technology is not impaired, and one or more known surfactants can be freely used. can. The specific types are the same as the surfactants used in the statistical copolymer latex described above, so the description is omitted here.

The anti-aging agent addition step can be performed after the polymerization step described above, but when the emulsion polymerization reaction is stopped in the polymerization step, the organic solvent solution containing the anti-aging agent, the polymerization inhibitor, and the surfactant aqueous solution are mixed. Adding a water emulsion is more preferred. By adding an organic solvent solution containing an anti-aging agent at the time of stopping polymerization, it is possible to stop the polymerization and disperse the anti-aging agent in the latex at the same time, shortening the manufacturing process and reducing the amount of organic solvent used. be able to.

(3) Organic Solvent Removal Step The organic solvent removal step is a step of removing the organic solvent used for adding the anti-aging agent in the anti-aging addition step. When the termination of the emulsion polymerization reaction and the addition of the aqueous emulsion of the organic solvent solution containing the anti-aging agent are carried out at the same time, the unreacted monomer and the organic solvent can be removed at the same time in this step. By performing the organic solvent removal step, it is possible to prevent the produced polymer latex from adversely affecting the human body and to reduce the environmental load.

The method for removing the organic solvent is not particularly limited as long as the effect of the present technology is not impaired, and one or more known removal methods can be freely used. For example, methods such as vacuum distillation, normal pressure distillation, and steam distillation can be employed. The content of the organic solvent is preferably 200 ppm or less in the latex.

The polymer latex produced by the production method of the present embodiment is diluted with a tetrahydrofuran solution, and the content of the anti-aging agent measured by gas chromatography is 1.0 to 6 with respect to 100% by mass of the polymer latex. .0% by mass, preferably 1.0 to 4.5% by mass, and concentration of anti-aging agent in liquid surface sampling liquid and bottom sampling liquid after centrifuging the polymer latex at 14000 rpm for 20 minutes (liquid surface sampling liquid/bottom sampling liquid) is 0.6 to 1.2. Here, the liquid surface sampling liquid is the latex liquid carefully collected with a syringe from the liquid surface of the centrifuge tube after centrifugation, and the bottom liquid sampling liquid is the latex liquid carefully collected from the bottom of the tube after centrifugation with a syringe. This is the latex liquid collected in

Since the concentration ratio of the anti-aging agent in the surface sampling liquid and the bottom surface sampling liquid is within this range, the dispersibility of the anti-aging agent in the polymer latex produced by the production method of the present embodiment is good. As a result, the heat resistance when the polymer latex is dried can be improved.

Specifically, the polymer latex produced by the production method of the present embodiment is obtained by drying the polymer at room temperature, and the elongation at break after heat treatment at 140° C. for 24 hours measured in accordance with JIS K6251. is 500% or more, and the heat resistance when made into a film is very high.

In addition, the polymer latex produced by the production method of the present embodiment is an RFL adhesive of resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) using this The RFL film obtained by drying at room temperature has a breaking elongation of 150% or more after heat treatment at 140° C. for 24 hours, which is measured according to JIS K6251, and the heat resistance of the RFL film is very high.

The present invention will be described in more detail below based on examples. It should be noted that the examples described below are examples of representative examples of the present invention, and the present invention is not limited to the following examples.

<Production of polymer latex>
[Example 1]
20 parts by mass of chloroprene monomer, 20 parts by mass of acrylonitrile monomer, 150 parts by mass of pure water, disproportionated potassium rosinate (Harima Kasei Co., Ltd. (manufactured by Kao Corporation) 5.0 parts by mass, 0.4 parts by mass of potassium hydroxide, and 1.0 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation). 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40° C. under a nitrogen stream. The partial addition of chloroprene monomer has a specific gravity of 0.989, 0.993, 1.000, 1.007, 1.013, 1.020, 1.026, 1.032, 1.038, 1.042. , 1.046 and 1.050, 5.0 parts by mass were added 12 times in total. When the polymerization rate with respect to the total amount of chloroprene and acrylonitrile reached 82%, an aqueous emulsion of an organic solvent solution containing an antioxidant (polymerization terminating liquid) was added to terminate the polymerization. A water emulsion of an organic solvent solution (polymerization terminating solution) contains 0.1 parts by mass of thiodiphenylamine, 0.1 parts by mass of diethylhydroxylamine, and 4,4'-bis(α, 4.8 parts by mass of α-dimethylbenzyl)diphenylamine was completely dissolved in 9.6 parts by mass of chloroprene as an organic solvent, and 0.2 parts by mass of sodium lauryl sulfate as a surfactant and β-naphthalenesulfonic acid formalin condensate were added. It was prepared by emulsification using 0.2 parts by mass of sodium salt and 4.0 parts by mass of pure water.
Then, the unreacted monomers, organic solvent, etc. were removed by distillation under reduced pressure, and the solid content of the polymer latex was adjusted to 50% by mass.

During the polymerization, the polymerization solution was periodically sampled at least 10 times to measure the unreacted chloroprene monomer and acrylonitrile monomer contained in the polymerization solution. The mass ratio of acrylonitrile monomer to total body was always within ±10% of the target value.

<Recovery of copolymer by freeze-drying>
After freezing 12 g of the polymer latex prepared above at −30° C. for 3 hours or more, it was dried at room temperature of 23° C. for 16 hours or more using a vacuum dryer to obtain a solid copolymer.

<Measurement of amount of monomer in polymerization liquid>
1.0 g of the polymerization liquid sampled in a 25 ml volumetric flask was weighed, diluted with tetrahydrofuran to 25 ml, and stirred to obtain a sample. Measurement was performed by a conventional quantitative analysis method using a gas chromatograph and a calibration curve. (same below).
(Gas chromatograph measurement conditions)
Gas chromatography was performed under the following measurement conditions.
・ Apparatus: GC-2010 (manufactured by Shimadzu Corporation)
・ Column used: DB-1, 0.25 mm × 60 m
・Carrier gas: Helium ・Column temperature: Increased from 50°C to 100°C at 5°C/min ・Inlet temperature: 270°C
・Detector: FID
・Detector temperature: 300°C
・Injection volume: 1 μL

The polymerization rate from the start of polymerization of the chloroprene-acrylonitrile statistical copolymer to a certain time was calculated from the dry weight (solid content concentration, hereinafter the same) by heating and air-drying the chloroprene-acrylonitrile statistical copolymer latex. . Specifically, it was calculated from the following general formula (II). The dry weight during polymerization was obtained by adding a small amount of polymerization inhibitor to the latex which does not affect the dry weight. In the formula, the solid content concentration is obtained by heating 2 g of the sampled emulsion polymerization liquid at 130 ° C. and removing the solvent (water), volatile chemicals and raw materials, and then removing the volatile content from the weight change before and after heating. concentration (% by mass). The total charged amount and evaporation residue were calculated from the polymerization recipe. The total charged amount is the total amount of raw materials, reagents, and solvent (water) charged into the polymerization vessel from the start of polymerization to a certain time. Evaporation residue means the weight of the chemicals and raw materials charged up to a certain time from the start of polymerization that do not volatilize under conditions of 130° C. and remain as solids together with the polymer. The amount of charged monomer is the sum of the amount of the monomer initially charged in the polymerization vessel and the amount of the monomer added until a certain time from the start of the polymerization. The term "monomer" as used herein means the total amount of the chloroprene monomer and the acrylonitrile monomer.

Polymerization rate [%] = {(total charged amount [g] x solid concentration [mass%]/100) - (evaporation residue [g])}/monomer charged amount [g] x 100 ( II)

[Example 2]
15 parts by mass of chloroprene monomer, 35 parts by mass of acrylonitrile monomer, 200 parts by mass of pure water, disproportionated potassium rosinate (Harima Kasei Co., Ltd. (manufactured by Kao Corporation) 5.0 parts by mass, 0.4 parts by mass of potassium hydroxide, and 1.0 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation). 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40° C. under a nitrogen stream. The partial addition of chloroprene monomer has a specific gravity of 0.981, 0.987, 0.992, 0.997, 1.002, 1.007, 1.012, 1.017, 1.022, 1.027. , 1.032 and 1.037, 5.0 parts by mass were added 12 times in total. When the polymerization rate with respect to the total amount of chloroprene and acrylonitrile reached 77%, an aqueous emulsion of an organic solvent solution containing an antioxidant (polymerization terminating liquid) was added to terminate the polymerization. A water emulsion of an organic solvent solution (polymerization terminating solution) contains 0.1 parts by mass of thiodiphenylamine, 0.1 parts by mass of diethylhydroxylamine, and 4,4'-bis(α, 4.8 parts by mass of α-dimethylbenzyl)diphenylamine was completely dissolved in 9.6 parts by mass of chloroprene as an organic solvent, and 0.2 parts by mass of sodium lauryl sulfate as a surfactant and β-naphthalenesulfonic acid formalin condensate were added. It was prepared by emulsification using 0.2 parts by mass of sodium salt and 4.0 parts by mass of pure water.
Then, the unreacted monomers, organic solvent, etc. were removed by distillation under reduced pressure, and the solid content of the polymer latex was adjusted to 50% by mass.

During the polymerization, the polymerization solution was periodically sampled at least 10 times to measure the unreacted chloroprene monomer and acrylonitrile monomer contained in the polymerization solution. The mass ratio of acrylonitrile monomer to total body was always within ±10% of the target value.

[Examples 3 to 5]
A chloroprene-acrylonitrile statistical copolymer latex was obtained in the same manner as in Example 1, except that the formulations were changed to those shown in Table 1 below. During the polymerization, the polymerization solution was periodically sampled at least 10 times to measure the unreacted chloroprene monomer and acrylonitrile monomer contained in the polymerization solution. The mass ratio of acrylonitrile monomer to total body was always within ±10% of the target value.

[Example 6]
20 parts by mass of chloroprene monomer, 20 parts by mass of acrylonitrile monomer, 150 parts by mass of pure water, disproportionated potassium rosinate (Harima Kasei Co., Ltd. (manufactured by Kao Corporation) 5.0 parts by mass, 0.4 parts by mass of potassium hydroxide, and 1.0 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation). 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40° C. under a nitrogen stream. The partial addition of chloroprene monomer has a specific gravity of 0.989, 0.993, 1.000, 1.007, 1.013, 1.020, 1.026, 1.032, 1.038, 1.042. , 1.046, and 1.050, 5 parts by mass were added for a total of 12 times. When the polymerization rate with respect to the total amount of chloroprene and acrylonitrile reached 82%, an aqueous emulsion of the organic solvent solution was added to terminate the polymerization. A water emulsion of an organic solvent solution is obtained by completely dissolving 0.1 parts by mass of thiodiphenylamine and 0.1 parts by mass of diethylhydroxylamine, which are polymerization terminator, in 0.8 parts by mass of chloroprene, which is an organic solvent, and adding a surfactant. 0.01 parts by mass of sodium lauryl sulfate, 0.01 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate, and 0.4 parts by mass of pure water were emulsified.
Next, after removing and concentrating unreacted monomers and the like and the organic solvent by distillation under reduced pressure to adjust the solid content of the polymer latex to 50% by mass, 4,4'-bis(α,α, which is an anti-aging agent, -Dimethylbenzyl)diphenylamine (4.8 parts by mass) is completely dissolved in 9.6 parts by mass of chloroprene as an organic solvent, and 0.2 parts by mass of sodium lauryl sulfate as a surfactant and sodium of β-naphthalenesulfonic acid formalin condensate are added. An aqueous emulsion of an organic solvent solution containing an anti-aging agent emulsified with 0.2 parts by mass of salt and 4.0 parts by mass of pure water was added. During the polymerization, the polymerization solution was periodically sampled at least 10 times to measure the unreacted chloroprene monomer and acrylonitrile monomer contained in the polymerization solution. The mass ratio of acrylonitrile monomer to total body was always within ±10% of the target value.

[Example 7]
100 parts by mass of chloroprene monomer, 150 parts by mass of pure water, 5.0 parts by mass of disproportionated potassium rosinate (manufactured by Harima Kasei Co., Ltd.), and 0.4 parts by mass of potassium hydroxide and 1.0 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation) were added. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40° C. under a nitrogen stream. When the polymerization rate to chloroprene reached 82%, an aqueous emulsion of an organic solvent solution containing an anti-aging agent (polymerization terminating liquid) was added to terminate the polymerization. A water emulsion of an organic solvent solution (polymerization terminating solution) contains 0.1 parts by mass of thiodiphenylamine, 0.1 parts by mass of diethylhydroxylamine, and 4,4'-bis(α, 4.8 parts by mass of α-dimethylbenzyl)diphenylamine was completely dissolved in 9.6 parts by mass of chloroprene as an organic solvent, and 0.2 parts by mass of sodium lauryl sulfate as a surfactant and β-naphthalenesulfonic acid formalin condensate were added. It was prepared by emulsification using 0.2 parts by mass of sodium salt and 4.0 parts by mass of pure water.
Then, the unreacted monomers, organic solvent, etc. were removed by distillation under reduced pressure, and the solid content of the polymer latex was adjusted to 50% by mass.

[Comparative Example 1]
A chloroprene homopolymer latex was obtained in the same manner as in Example 7, except that the formulation was changed to that shown in Table 2 below.

[Comparative Example 2]
A chloroprene-acrylonitrile statistical copolymer latex was obtained in the same manner as in Example 1, except that the formulation was changed to that shown in Table 2 below.

[Comparative Example 3]
20 parts by mass of chloroprene monomer, 20 parts by mass of acrylonitrile monomer, 150 parts by mass of pure water, disproportionated potassium rosinate (Harima Kasei Co., Ltd. (manufactured by Kao Corporation) 5.0 parts by mass, 0.4 parts by mass of potassium hydroxide, and 1.0 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation). 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40° C. under a nitrogen stream. The partial addition of chloroprene monomer has a specific gravity of 0.989, 0.993, 1.000, 1.007, 1.013, 1.020, 1.026, 1.032, 1.038, 1.042. , 1.046, and 1.050, 5 parts by mass were added for a total of 12 times. When the conversion of the total amount of chloroprene and acrylonitrile reached 81%, an aqueous emulsion of the organic solvent solution was added to terminate the polymerization. A water emulsion of an organic solvent solution is obtained by completely dissolving 0.1 parts by mass of thiodiphenylamine and 0.1 parts by mass of diethylhydroxylamine, which are polymerization terminator, in 0.8 parts by mass of chloroprene, which is an organic solvent, and adding a surfactant. 0.01 parts by mass of sodium lauryl sulfate, 0.01 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate, and 0.4 parts by mass of pure water were emulsified.
Next, unreacted monomers and organic solvents are removed and concentrated by distillation under reduced pressure to adjust the solid content of the polymer latex to 50% by mass. 4.8 parts by mass of anti-aging agent dispersed using 0.2 parts by mass of sodium lauryl sulfate, 0.1 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate and 11.2 parts by mass of pure water A water dispersion was added.
During the polymerization, the polymerization solution was periodically sampled at least 10 times to measure unreacted chloroprene monomer and acrylonitrile monomer contained in the polymerization solution. The mass ratio of acrylonitrile monomer to total monomer was always within ±10% of the target value.

[Comparative Examples 4 and 5]
In the same manner as in Example 1, a chloroprene-acrylonitrile statistical copolymer latex was obtained with the formulation shown in Table 2 below, and in the same manner as in Comparative Example 3, an anti-aging agent aqueous dispersion was added. rice field.

<Measurement of unsaturated nitrile (acrylonitrile) content>
It was determined from the nitrogen atom content measured by an elemental analyzer (Sumigraph 220F: manufactured by Sumika Analysis Center Co., Ltd.) using 100 mg of the polymer obtained by freeze-drying the polymer latex produced above. At this time, minute errors due to nitrogen atoms in polymerization inhibitors and antioxidants were ignored. The electric furnace temperature was set to 900° C. for the reactor, 600° C. for the reduction furnace, 70° C. for the column, and 100° C. for the detector. . A calibration curve was prepared using aspartic acid (10.52%) with a known nitrogen content as a standard substance.

<Measurement of Toluene Insoluble Content>
0.75 g of the solid polymer obtained by freeze-drying the polymer latex prepared above was cut into 2 mm squares, placed in a conical beaker together with 123 g of toluene, and stirred with a magnetic stirrer at about 1 time/second. Dissolve at room temperature 23° C. for 16 hours. After that, the gel content was separated using a 200-mesh wire mesh, dried at 110° C. for 60 minutes, and the weight was measured to calculate the toluene-insoluble content.

<Measurement of Chloroprene Monomer Amount>
About 0.02 g of the polymer latex prepared above was placed in a glass vial, sealed, heated in a head space sampler, and the gas phase portion was injected into a gas chromatograph and measured.
(Gas chromatograph measurement conditions)
Gas chromatography was performed under the following measurement conditions.
・Apparatus: GC-1700 (manufactured by Shimadzu Corporation)
TurboMatrix HS-40 (manufactured by Perkin Elmer)
・ Column used: Pora Plot-U 0.53 mm φ × 25 m (film thickness 20 μm)
Gas chromatograph Vaporization chamber temperature: 180°C
・Column initial temperature: 130°C
・Final temperature: 190℃
・Column heating rate: 2.0°C/min
・Detector: FID
・Detector temperature: 190°C
Headspace sampler ・Injection time: 0.04 min
・Oven temperature: 80℃
・Needle temperature: 120°C
・Transfer temperature: 150°C
・Insulation time: 30min
・Pressurization time: 3.0 min
・Injection amount: Injection of the entire amount

<Measurement of content of antioxidant in polymer latex>
About 1 g of the polymer latex prepared above was weighed, placed in a 25 mL volumetric flask, filled with a tetrahydrofuran solution, and measured by the following gas chromatography method.

<Ratio of Antioxidant Concentration in Liquid Surface Sampling Liquid and Bottom Sampling Liquid>
About 40 g of the polymer latex produced above is placed in a 50 ml tube (made of stainless steel, diameter 35 mm, length 100 mm) of a centrifuge (H-200NR: manufactured by Kokusan Co., Ltd.) and rotated at 14,000 rpm for 20 minutes. After centrifugation at 15° C., 2 g of the latex liquid was carefully sampled with a syringe from the liquid surface of the tube after centrifugation as a liquid surface sampling liquid. Furthermore, as a bottom sampling liquid, 2 g of the latex liquid was carefully sampled with a syringe from the bottom of the tube after centrifugation. About 1 g of the liquid surface sampling liquid and the bottom surface sampling liquid were weighed, placed in a 25 mL volumetric flask, filled up with a tetrahydrofuran solution, and measured by the following gas chromatography method.

(Measurement conditions for gas chromatography)
Gas chromatography was performed under the following measurement conditions.
・Apparatus: GC-2025 (manufactured by Shimadzu Corporation)
・ Column used: DB-5 0.25 mmφ×30 m (thickness 1 μm)
・Column temperature: 325°C constant ・Inlet temperature: 325°C
・Detector temperature: 325°C
・Column flow rate: He 1 mL/min (Split 1:50)
・Injection volume: 1 μL (using an autosampler)

<Production of film>
The polymer latex was poured into a horizontal stainless vat while filtering so that the thickness after drying was about 1.1 mm, and dried at room temperature for 3 days. After that, it was produced by hot pressing at 140° C. for 15 minutes so that the thickness would be about 1.0 mm.

<Preparation of RFL film>
11 g of resorcinol (manufactured by Wako Pure Chemical Industries, Ltd.), 16 g of formaldehyde 37% by mass aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.), 3.0 g of 10% NaOH aqueous solution, and 250 g of pure water were mixed and allowed to stand at room temperature for 20 hours. A mixture of 100 g of pure water, 200 g of polymerized latex, and 5.0 g of 10% NaOH aqueous solution was added to the mixture, and the mixture was allowed to stand at room temperature for 24 hours. This was poured into a horizontal glass plate so as to have a thickness of about 0.2 mm after drying, and dried at room temperature for 3 days.

<Heat resistance evaluation>
For the film and RFL film produced above, the breaking strength and breaking elongation after heat treatment at 140° C. for 24 hours were measured according to JIS K6251.

<Oil resistance evaluation>
For the film and RFL film produced above, the volume change rate (ΔV) and weight change rate (ΔW) after immersion in engine oil (10W-30) for 72 hours at 140° C. were measured according to JIS K6258.

<Results>
The results of Examples 1-7 are shown in Table 1 below, and the results of Comparative Examples 1-5 are shown in Table 2 below.

<Discussion>
Compared to Comparative Example 1 using a chloroprene polymer latex containing no antiaging agent, Example 7 using a chloroprene polymer latex containing an antiaging agent has better heat resistance (particularly elongation at break). I was able to confirm something. In addition, Example 1 using a chloroprene-acrylonitrile statistical copolymer latex containing an antioxidant is better than Comparative Example 2 using a chloroprene-acrylonitrile statistical copolymer latex containing no antioxidant. , it was confirmed that the heat resistance (particularly, elongation at break) was good.

In Comparative Examples 3 to 5 using a chloroprene-acrylonitrile statistical copolymer latex to which an anti-aging agent was added as an aqueous dispersion, the anti-aging agent concentration ratio after centrifugation (liquid surface sampling liquid/bottom sampling liquid) was , was less than 0.6. This means that the anti-aging agent has precipitated. On the other hand, in Example 6 using a chloroprene-acrylonitrile statistical copolymer latex in which the antioxidant was added as a water emulsion of an organic solvent solution, the ratio of the antioxidant concentration after centrifugation (liquid surface sampling liquid/bottom sampling liquid) was in the range of 0.6 to 1.2. This means that the antioxidant is evenly distributed in the latex. It was also confirmed that Example 6 had better heat resistance (especially elongation at break) than Comparative Examples 3-5.

Comparing the examples, Example 1 using a chloroprene-acrylonitrile statistical copolymer latex containing an unsaturated nitrile is better than Example 7 using a chloroprene polymer latex that does not contain an unsaturated nitrile. However, it was confirmed that the oil resistance was good. From this result, it was found that the oil resistance was further improved by using the unsaturated nitrile. The fact that the oil resistance of the films of Examples 1 and 2 was negative in volume change rate (ΔV) and weight change rate (ΔW) means that the surfactant in the film was extracted. It is thought that

Furthermore, compared with Example 5 using a bisphenol-based antioxidant, it was confirmed that Example 1 using an aromatic secondary amine-based antioxidant had better elongation at break, which is heat resistance. did it. From this result, it was found that heat resistance is further improved by using an aromatic secondary amine anti-aging agent.

Even when an emulsified liquid obtained by mixing an organic solvent solution containing an anti-aging agent, a polymerization inhibitor, and an aqueous surfactant solution is added at the time of stopping the polymerization, water containing the anti-aging agent is added after the polymerization step. In Comparative Examples 4 and 5 in which the dispersion liquid was added, precipitation of the anti-aging agent was observed as described above. From these results, it was found that when the step of adding an anti-aging agent-containing aqueous dispersion is performed, the dispersion stability of the anti-aging agent is lowered, and as a result, the heat resistance when the chloroprene polymer latex is dried is lowered. I found out.

Claims (13)

A statistical copolymer latex containing chloroprene monomer units and unsaturated nitrile monomer units, wherein the unsaturated nitrile monomer unit content is 5 to 20% by mass,
The statistical copolymer latex is diluted with a tetrahydrofuran solution, and the content of the antioxidant measured by gas chromatography is 1.0 to 6.0% by mass with respect to 100% by mass of the statistical copolymer latex. and the ratio of antioxidant concentration in the liquid surface sampling liquid and the bottom sampling liquid after centrifuging the statistical copolymer latex at 14000 rpm for 20 minutes (liquid surface sampling liquid / bottom sampling liquid) is 0.6 to 1.2 ,
The antioxidant is N-phenyl-1-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4′-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonylamido)diphenylamine, N , N'-di-2-naphthyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'-(1 ,3-dimethylbutyl)-p-phenylenediamine, and N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, including at least one selected from the group consisting of statistical Copolymer latex. The statistic according to claim 1, wherein the polymer obtained by drying the statistical copolymer latex at room temperature has an elongation at break after heat treatment at 140 ° C. for 24 hours measured in accordance with JISK6251 of 500% or more. Copolymer latex. RFL film obtained by drying the RFL adhesive of resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) using the statistical copolymer latex at room temperature to JISK6251 3. The statistical copolymer latex according to claim 1 or 2, having an elongation at break after heat treatment at 140[deg.] C. for 24 hours, measured in accordance with the standards, of 150% or more. 4. The statistical copolymer latex according to any one of claims 1 to 3 , wherein the content of volatile organic solvents is 200 ppm or less. The volume change rate (ΔV) and weight change rate (ΔW) after immersion in engine oil at 140° C. for 72 hours were measured in accordance with JISK6258 for the polymer obtained by drying the statistical copolymer latex at room temperature. Statistical copolymer latex according to any one of claims 1 to 4 , wherein the value of is in the range of -10 to +10%. An RFL film obtained by drying the RFL adhesive of resorcin (R) / formalin (F) / latex (L) = 10/5/85 (mass ratio) using the statistical copolymer latex at room temperature was prepared according to JIS K6258. Claims 1 to 5 , wherein the volume change rate (ΔV) and weight change rate (ΔW) after immersion in engine oil for 72 hours at 140 ° C. are in the range of -10 to +10%. Statistical copolymer latex according to any one of the preceding claims. 6. A statistical copolymer latex according to any one of claims 1 to 5 for use in RFL adhesives, dip products, adhesives or films. RFL adhesives, dipping products, adhesives or films using the statistical copolymer latex of any one of claims 1-6 . a polymerization step of performing emulsion polymerization using at least a chloroprene monomer ;
An antiaging agent addition step of adding an aqueous emulsion of an organic solvent solution containing an antiaging agent;
A method for producing a polymer latex comprising
Said anti-aging agents are added substantially by means of a water emulsion and include N-phenyl-1-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4′-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonylamido)diphenylamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p- from phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine and N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine including at least one selected from the group consisting of
The polymer latex is diluted in a tetrahydrofuran solution, and the content of the antioxidant measured by gas chromatography is 1.0 to 6.0% by mass with respect to 100% by mass of the polymer latex, and the polymer After centrifuging the latex at 14,000 rpm for 20 minutes, the concentration ratio of the anti-aging agent in the liquid surface sampling solution and the bottom surface sampling solution (liquid surface sampling solution/bottom sampling solution) is 0.6 to 1.2. , a method for producing a polymer latex. When the emulsion polymerization reaction is stopped, a water emulsion obtained by mixing an organic solvent solution containing an antioxidant, a polymerization inhibitor, and an aqueous surfactant solution is added ,
The polymerization inhibitor comprises at least one selected from the group consisting of thiodiphenylamine, 4-tert-butylcatechol, 2,2-methylenebis-4-methyl-6-tert-butylphenol, and diethylhydroxylamine, 9. A method for producing a polymer latex according to 9. The method for producing a polymer latex according to claim 9 or 10 , further comprising an organic solvent removing step of removing the organic solvent after the antioxidant adding step. The method for producing a polymer latex according to any one of claims 9 to 11 , wherein emulsion polymerization using a chloroprene monomer and an unsaturated nitrile monomer is performed in the polymerization step. 13. The method for producing a polymer latex according to claim 12 , wherein in the polymerization step, the chloroprene monomer is continuously added or intermittently added 10 times or more after initiation of the polymerization reaction.