JP6233115B2 - How to remove scale - Google Patents

Description

 The present invention relates to a method for removing scale adhered to a container used in a process from production of latex to unloading.

 In conventional latex production methods, agglomerates called scales sometimes adhere to and deposit on the polymerization vessel. If scale adheres to the polymerization vessel and accumulates, it may cause a decrease in latex productivity due to an increase in reaction time due to a decrease in the heat transfer performance of the polymerization vessel, removal of the attached scale, or reduction in actual operation time due to cleaning operations, etc. There was. Further, when the latex is concentrated or stored, the adhesion of the scale to the container used has been a problem.

 In Patent Document 1 (Japanese Patent Laid-Open No. 10-101708), the scale is removed by injecting a cleaning liquid in which a predetermined amount of a polymer or the like is dissolved in water at a high pressure.

 However, in the scale removal method described in Patent Document 1, since it is necessary to prepare a cleaning liquid and perform high-pressure cleaning, capital investment is required and labor is required, which may reduce latex productivity. It was.

JP-A-10-101708

 The present invention has been made in view of the above-described conventional technology, and an object thereof is to provide a method for easily removing scales by a simple method.

 As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by adopting a process of blending a polar low molecular compound with latex in the scale removal method. The present invention has been completed based on the above.

The gist of the present invention for solving the above problems is as follows.
[1] A method for removing a scale, comprising a step of blending a polar low molecular weight compound with latex.

[2] A method for removing scales adhering to a container used in a process from production of latex to unloading,
A method for removing scale, comprising a step of blending a polar low molecular weight compound with latex.

[3] The scale removing method according to [2], wherein the container is a polymerization container, a concentration container, or a storage container.

[4] The scale removing method according to [2] or [3], including a step of adding water to the container after discharging the latex and stirring.

[5] The scale removing method according to any one of [1] to [4], wherein the blending amount of the polar low molecular compound is 0.05 parts by weight or more with respect to 100 parts by weight of the solid content of the latex.

[6] The scale removing method according to any one of [1] to [5], wherein the molecular weight of the polar low molecular weight compound is 30 to 1000.

[7] The scale removing method according to any one of [1] to [6], wherein the polar low molecular weight compound is urea.

 According to the method for removing a scale according to the present invention, the scale can be easily dispersed in water by employing the step of blending a polar low molecular weight compound into the latex, so that the scale can be easily removed.

Step of Blending Polar Low Molecular Compound with Latex The method for removing a scale according to the present invention includes a step of blending a polar low molecular compound with latex. More specifically, the method for removing scale according to the present invention is a method for removing scale attached to a container used in a process from the production of latex to carrying it out, and a step of adding a polar low molecular compound to latex. It is characterized by including.

 By adding a polar low molecular weight compound to the latex, it becomes easy to remove the scale attached to the container used in the process from the production of the latex to the carrying out. This is probably because the polar low molecular weight compound blended in the latex is also contained in the scale, and as a result, the dispersibility of the scale in water is improved. In addition, by adding a polar low molecular weight compound to latex, aggregation of latex can be suppressed and generation of scale can be reduced. As a result, latex productivity can be improved.

 The container used in the process from the production of the latex to the unloading is not particularly limited, and examples thereof include a polymerization container used for producing the latex, a concentration container used for concentrating the latex, and a storage container for storing the latex. . Scales are particularly likely to adhere to these containers, but according to the scale removal method of the present invention, scales can be easily and easily removed.

(latex)
The latex in the present invention is not particularly limited, and examples thereof include diene polymer particle aqueous dispersion, acrylic polymer particle aqueous dispersion, fluorine polymer particle aqueous dispersion, and silicone polymer particle aqueous dispersion. It is done.

The diene polymer particle aqueous dispersion is an aqueous dispersion of a polymer (diene polymer) containing a monomer unit obtained by polymerizing a conjugated diene such as butadiene or isoprene. The proportion of monomer units obtained by polymerizing conjugated diene in the diene polymer is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 60% by weight or more.
In the present invention, the monomer unit means a structural unit in a polymer formed by polymerizing the monomer.

 Diene polymers include conjugated diene homopolymers; copolymers of different types of conjugated dienes; copolymers with other monomers copolymerizable with conjugated dienes; and their hydrogenated products. Can be mentioned.

 Examples of the conjugated diene include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, and 2-chloro-1. 1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, and the like.

 Examples of the other copolymerizable monomers include α, β-unsaturated nitrile compounds such as (meth) acrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile; (meth) acrylic acid, itaconic acid, fumaric acid, etc. Unsaturated carboxylic acids: aromatics such as styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene, divinylbenzene Vinyl monomers; olefins such as ethylene and propylene; halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; methyl vinyl ether, ethyl Vinyl ether, butyl vinyl Vinyl ethers such as ruether; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; heterocyclic-containing vinyl compounds such as N-vinylpyrrolidone, vinylpyridine, and vinylimidazole; (Meth) acrylic acid ester compounds such as methyl acrylate; hydroxyalkyl group-containing compounds such as β-hydroxyethyl (meth) acrylate; (meth) acrylamide, N-methylol (meth) acrylamide, acrylamide-2-methylpropane Examples include amide monomers such as sulfonic acid. In addition, as for the conjugated diene and the other copolymerizable monomer, one type may be used alone, or two or more types may be used in combination at any ratio. Moreover, in this specification, (meth) acryl includes both acryl and methacryl.

 Specific examples of the diene polymer include styrene / butadiene copolymer (SBR), styrene / isoprene copolymer (SIR), isobutylene / isoprene copolymer (butyl rubber), ethylene / propylene / diene copolymer, acrylonitrile. -Butadiene copolymer (NBR), hydrogenated SBR, hydrogenated NBR and the like. These polymers can be used alone or in combination of two or more.

The acrylic polymer particle aqueous dispersion is a general formula (1): CH ₂ = CR ¹ —COOR ² (wherein R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group or a cycloalkyl group). .) Is an aqueous dispersion of a polymer (acrylic polymer) containing a monomer unit derived from a compound represented by the formula (hereinafter sometimes referred to as “(meth) acrylic ester compound”). The ratio of the monomer unit derived from the (meth) acrylic acid ester compound in the acrylic polymer is preferably 40% by weight or more, more preferably 50% by weight or more, and further preferably 60% by weight or more.

 Specific examples of the (meth) acrylic acid ester compound include ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, T-butyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, Examples include stearyl (meth) acrylate.

 Acrylic polymers include homopolymers of (meth) acrylic acid ester compounds; copolymers of different types of (meth) acrylic acid ester compounds; other monomers copolymerizable with (meth) acrylic acid ester compounds. And a copolymer with a monomer.

 Examples of the other copolymerizable monomers include α, β-unsaturated nitrile compounds such as (meth) acrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile; (meth) acrylic acid, itaconic acid, fumaric acid, etc. Unsaturated carboxylic acids; carboxylic acid esters having two or more carbon-carbon double bonds such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate; Unsaturated esters containing fluorine in the side chain such as octylethyl (meth) acrylate; styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxy Methyl Stille , Α-methylstyrene, aromatic vinyl monomers such as divinylbenzene; amide monomers such as (meth) acrylamide, N-methylol (meth) acrylamide, acrylamide-2-methylpropanesulfonic acid; ethylene, propylene, etc. Olefins; diene monomers such as butadiene and isoprene; halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; Vinyl ethers such as ethyl vinyl ether and butyl vinyl ether; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; N-vinyl pyrrolidone, vinyl pyridine and vinyl imi Heterocycle-containing vinyl compounds such as tetrazole; glycidyl ethers such as allyl glycidyl ether; and glycidyl esters such as glycidyl (meth) acrylate. In addition, the compound represented by General formula (1) and the other monomer which can be copolymerized may be used individually by 1 type, respectively, and may combine 2 or more types by arbitrary ratios, respectively.

 The aqueous dispersion of fluoropolymer particles is an aqueous dispersion of a polymer (fluorine polymer) containing a monomer unit obtained by polymerizing a fluorine-containing monomer. The ratio of the monomer unit obtained by polymerizing the fluorine-containing monomer in the fluoropolymer is preferably 70% by weight or more, more preferably 80% by weight or more.

 Fluoropolymers include homopolymers of fluorine-containing monomers; copolymers of different types of fluorine-containing monomers; copolymerization with other monomers copolymerizable with fluorine-containing monomers Examples include coalescence.

 Examples of the fluorine-containing monomer include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, vinyl trifluoride chloride, vinyl fluoride, and perfluoroalkyl vinyl ether.

 Examples of the other copolymerizable monomers include olefins such as ethylene, propylene, and 1-butene; aromatic vinyl monomers such as styrene, α-methylstyrene, t-butylstyrene, vinyltoluene, and chlorostyrene. Α, β-unsaturated nitrile compounds such as (meth) acrylonitrile; (meth) acrylic acid ester compounds such as methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; ) Amide monomers such as acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide; Unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, fumaric acid, crotonic acid and maleic acid ; Contains epoxy groups such as allyl glycidyl ether and glycidyl (meth) acrylate Unsaturated compound; amino group-containing unsaturated compound such as (meth) acryldimethylaminoethyl, diethylaminoethyl (meth) acrylate; sulfonic acid group-containing unsaturation such as styrene sulfonic acid, vinyl sulfonic acid, (meth) allyl sulfonic acid Saturated compound; sulfate group-containing unsaturated compound such as 3-allyloxy-2-hydroxypropanesulfuric acid; phosphate group such as (meth) acrylic acid-3-chloro-2-phosphate, 3-allyloxy-2-hydroxypropanephosphate And unsaturated compounds.

 Specific examples of the fluoropolymer include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Examples thereof include polyvinyl fluoride and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. These polymers can be used alone or in combination of two or more.

 The silicone polymer particle aqueous dispersion is an aqueous dispersion of a silicone polymer such as silicone rubber, fluorosilicone rubber or polyimide silicone.

 The latex in the present invention can be produced, for example, by emulsion polymerization of a mixture of the above monomers in water. The method for mixing the monomers is not particularly limited, and examples thereof include a method using a mixing apparatus such as a stirring type, a shaking type, and a rotary type. In addition, a method using a dispersion kneader such as a homogenizer, a ball mill, a sand mill, a roll mill, a planetary mixer, and a planetary kneader can be used. The method for emulsion polymerization is not particularly limited, and a conventionally known emulsion polymerization method may be employed.

 Examples of the polymerization initiator used for emulsion polymerization include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; t-butyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide Organic peroxides such as oxide and t-butylperoxyisobutyrate; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, etc. Is . These polymerization initiators can be used alone or in combination of two or more. The peroxide initiator can also be used as a redox polymerization initiator in combination with a reducing agent such as sodium bisulfite.

 Moreover, you may use a chain transfer agent at the time of emulsion polymerization. Examples of the chain transfer agent include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan; dimethylxanthogen disulfide, diisopropylxanthogendi Xanthogen compounds such as sulfides; thiuram compounds such as terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide; phenols such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol Compounds; allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, carbon tetrabromide; thioglycolic acid, Oringo acid, 2-ethylhexyl thioglycolate, diphenylethylene, etc. α- methylstyrene dimer. These chain transfer agents can be used alone or in combination of two or more.

 The surfactant used for the emulsion polymerization is not particularly limited, and may be any of an anionic surfactant, a nonionic surfactant, and a cationic surfactant. These surfactants may be used individually by 1 type, and may be used in combination of 2 or more type.

 Specific examples of anionic surfactants include fatty acid salts such as sodium myristate, potassium palmitate, sodium oleate, and potassium linolenate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; higher alcohol sulfates; alkyls Examples thereof include sulfosuccinate; rosinate and the like.

 Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester, and the like.

 Specific examples of the cationic surfactant include alkyltrimethylammonium chloride, dialkylammonium chloride, and benzylammonium chloride.

 A known dispersant, thickener, anti-aging agent, antifoaming agent, antiseptic, antibacterial agent, anti-blistering agent and the like can be added to the latex as necessary.

 The solid content concentration of the latex is preferably 10 to 60% by weight, more preferably 30 to 55% by weight.

Polar low molecular compound The polar low molecular compound in the present invention is not particularly limited as long as it is a low molecular compound having a polar group.
As the polar low molecular weight compound, a polar low molecular weight organic compound is preferable.
Moreover, as a polar low molecular weight organic compound, a water-soluble polar low molecular weight organic compound is preferable.
The polar group is preferably a hydroxyl group, an amino group or an amide group, and more preferably an amino group. Moreover, the molecular weight of the polar low molecular weight compound is preferably 30 to 1000, more preferably 40 to 500, and still more preferably 50 to 200. By adding such a polar low molecular weight compound to the latex, the generated scale contains the polar low molecular weight compound, the dispersibility of the scale in water is improved, and the scale can be easily removed.

 As specific examples of the polar low molecular weight compound, urea, monoethylene glycol, diethylene glycol, tetraethylene glycol and the like are particularly preferable, and urea is most preferable.

 The blending amount of the polar low molecular weight compound is preferably 0.05 parts by weight or more, more preferably 0.05 to 20 parts by weight, still more preferably 0.5 to 15 parts by weight with respect to 100 parts by weight of the solid content of the latex. Particularly preferred is 2 to 15 parts by weight. By setting the blending amount of the polar low molecular weight compound within the above range, it is possible to improve the scale removal rate and the finally obtained rubber tensile strength. The removal rate of scale and the tensile strength of rubber can be measured by the methods described in Examples.

 The method of blending the polar low molecular weight compound with the latex is not particularly limited. For example, a method using a mixing device such as a stirring type, a shaking type, and a rotary type, a homogenizer, a ball mill, a sand mill, a roll mill, a planetary mixer, Examples thereof include a method using a dispersion kneader such as a planetary kneader. Moreover, when adding a polar low molecular compound to a polymerization container, the whole quantity of a polar low molecular compound may be added to a container previously, and you may add sequentially.

Step of adding water to the container after discharging the latex and stirring the method The scale removing method according to the present invention includes a step of adding water to the container after discharging the latex and stirring, in addition to the above steps. Is preferred. By adding a polar low molecular weight compound to the latex, the polar low molecular weight compound is finely dispersed in the scale, so that the scale is easily dispersed in water. As a result, the scale can be easily removed by a simple process of putting water into the container after discharging the latex and stirring it. Therefore, the scale can be removed by a simple process as compared with a method of removing the scale by a process such as high-pressure washing, and latex productivity can be improved.

 The time and temperature required for stirring are not particularly limited and can be arbitrarily selected according to the stirring method and the amount of water, but the stirring time is preferably 10 to 300 minutes, more preferably 30 to 180 minutes. The temperature is preferably 10 to 90 ° C, more preferably 20 to 80 ° C.

 The stirring method is not particularly limited, and for example, a device such as a stirrer can be used.

 Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In the examples, parts and% are based on weight unless otherwise specified. In Examples and Comparative Examples, the following evaluation was performed. In the following evaluation, the latex mixture refers to a mixture of latex and a polar low molecular weight compound. In the comparative example, since the polar low molecular compound was not blended in the latex, the following evaluation was performed using the latex.

<Rubber removal rate>
A latex mixture corresponding to 8 g in terms of rubber amount was put as a test specimen in a stainless steel 2 L container. Thereafter, the latex mixture was left to dry at a constant temperature and humidity of 20 ° C. and a relative humidity of 60% until the solid content concentration reached 95% or more, and rubber was adhered to the container.

 1 L of deionized water was added to the container and stirred for 1 hour using a stirrer.

 The mixture of the above deionized water and the adhered rubber removed from the container was filtered through a 325 mesh wire mesh, and then the wire mesh was dried at 100 ° C. for 3 hours, and the weight of the dry rubber on the wire mesh was measured.

The removal rate of the attached rubber (scale) was calculated by the following formula.
Removal rate of adhered rubber [%] = (weight of dry rubber / total amount of rubber of test specimen (8 g)) × 100

<Tensile strength>
(1) Preparation of test piece The latex mixture was dried at a constant temperature and humidity of 20% and a relative humidity of 60% until the solids concentration became 95% or more so that the thickness would be 1 mm. Heat treatment was performed for a minute.

 Thereafter, the dried body (rubber) of the latex mixture obtained above was punched into a dumbbell shape in accordance with JIS K-6251-2 (L = 60) to prepare a test piece.

(2) Measuring method of breaking strength (TB) The above-mentioned test piece is pulled at INSTRON 3343 manufactured by Instron Japan Company Limited at a tensile speed of 500 mm / min, the breaking strength (TB) is measured, and the tensile strength of the rubber did. In addition, the higher the tensile strength, the more preferable, and the comparative example was standardized as 100 for each type of latex.

(Examples 1-15 and Comparative Examples 1-3)
As latex, SBR latex (Nippon Zeon Nipol 2518FSH, solid concentration 40.5%), NBR latex (Nippon Zeon Nipol LX552, solid concentration 43.2%), acrylic polymer latex (Nihon Zeon Nipol LX811H) , Solid content concentration 50.0%).

To 100 parts of the latex solids described in Tables 1 to 3 below, urea is added as a polar low molecular weight compound in the amount shown in Tables 1 to 3, and then deionized water is added to form a solid. The partial concentration was adjusted to 40%, and the mixture was mixed using a stirrer so as not to generate agglomerates to obtain a latex mixture.
Said evaluation was performed about the obtained latex mixture.

 From the above Tables 1 to 3, the scale removal method (Example 1) having a step of blending a polar low molecular weight compound with latex as compared with the case where no polar low molecular weight compound is blended with latex (Comparative Examples 1 to 3). It can be seen that ˜15) is excellent in the removal rate of the adhered rubber (scale). Therefore, it turns out that productivity of latex can be improved by a simple method.

Claims (3)

A method of removing scales attached to a container used in a process from production of latex to unloading,
Adding urea to latex ;
A method for removing scales, comprising a step of adding water to a container after discharging latex and stirring . The scale removal method according to claim 1 , wherein the container is a polymerization container, a concentration container, or a storage container. The method for removing a scale according to claim 1 or 2 , wherein the compounding amount of urea is 0.05 parts by weight or more with respect to 100 parts by weight of the solid content of the latex.