Sulfur copolymerized chloroprene latex composition and method for producing same, and modified asphalt emulsion composition containing sulfur copolymerized chloroprene latex composition and method for producing same

Abstract

The present invention provides a sulfur-copolymerized chloroprene latex composition, a method for producing the same, and a modified asphalt emulsion composition, the sulfur-copolymerized chloroprene latex composition comprising a sulfur-copolymerized chloroprene latex, a nonionic surfactant, and a monoacid, the pKa of the monoacid being 4.0-6.0.

Description

Technical Field

[0001] The present invention relates to a sulfur-copolymerized chloroprene rubber latex composition, a method for producing the same, and a modified asphalt emulsion composition containing the sulfur-copolymerized chloroprene rubber latex composition and a method for producing the same. Background Art

[0002] Roads paved with asphalt materials deteriorate and harden during use due to exposure to sunlight, wind, and rain, resulting in the formation of fine cracks. If rainwater penetrates through these cracks and reaches between the asphalt pavement and the underlying roadbed, it may cause the asphalt pavement to peel off from that location. In addition, during the use of the asphalt pavement, the aggregates (crushed stones) contained in the pavement flake off, resulting in a rough pavement surface.

[0003] As a process method for repairing such deteriorated asphalt pavements, there is a chip seal process method. The chip seal process method is a process method in which an asphalt emulsion is spread on an existing asphalt pavement, followed by spreading aggregates and rolling.

[0004] For the asphalt emulsion used in the chip seal process method, in order to impart grip to the aggregates, an operation of adding a polymer having rubber elasticity as a modifier is usually carried out.

[0005] For example, in Patent Document 1, styrene / butadiene / styrene (SBS), styrene-butadiene rubber (SBR), chloroprene rubber latex, and natural rubber are disclosed as modifiers, and in particular, chloroprene rubber latex is disclosed.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: U.S. Patent No. 5180428 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] However, the grip on the aggregates of the asphalt emulsion containing the modifier disclosed in Patent Document 1 is still insufficient, and it is desired to further improve the grip on the aggregates. The strength of the dry film obtained from the sulfur-copolymerized chloroprene rubber latex is also likely to decrease. Therefore, it is desired to maintain the dry film strength at a high level over a long period of time.

[0011] An object to be solved by one embodiment of the present invention is to provide a sulfur-copolymerized chloroprene rubber latex composition and a method for producing the same, the sulfur-copolymerized chloroprene rubber latex composition having excellent aggregate graspability when forming a layered structure containing the sulfur-copolymerized chloroprene rubber latex composition and excellent storage stability in a film state. Another object to be solved by other embodiments of the present invention is to provide a modified asphalt emulsion composition having excellent aggregate graspability and a method for producing the same.

[0012] Means for Solving the Problem

[0013] The means for solving the above problems include the following.

[0014] <1>A method for producing a sulfur-copolymerized chloroprene rubber latex composition, comprising the following steps:

[0015] A polymerization step of polymerizing a chloroprene monomer and sulfur to obtain a sulfur-copolymerized chloroprene rubber latex; and

[0016] A mixing step of mixing the sulfur-copolymerized chloroprene rubber latex and a monobasic acid having a pKa of 4.0 to 6.0,

[0017] In at least one of the polymerization step and the mixing step, the sulfur-copolymerized chloroprene rubber latex and a nonionic surfactant are mixed.

[0018] <2>The method for producing a sulfur-copolymerized chloroprene rubber latex composition according to <1>, wherein the nonionic surfactant contains a polyoxyalkylene structure.

[0019] <3>The method for producing a sulfur-copolymerized chloroprene rubber latex composition according to <1> or <2>, wherein the monobasic acid is acetic acid.

[0020] <4>A method for producing a modified asphalt emulsion composition, comprising a step of obtaining a composition containing a sulfur-copolymerized chloroprene rubber latex composition and asphalt, the sulfur-copolymerized chloroprene rubber latex composition being obtained by the method for producing a sulfur-copolymerized chloroprene rubber latex composition according to <1> or <2>.

[0021] <5>A sulfur-copolymerized chloroprene rubber latex composition, comprising a sulfur-copolymerized chloroprene rubber latex, a nonionic surfactant, and a monobasic acid,

[0022] The monobasic acid has a pKa of 4.0 to 6.0.

[0023] <6>The sulfur-copolymerized chloroprene rubber latex composition according to <5>, wherein the nonionic surfactant contains a polyoxyalkylene structure.

[0024] <7>The sulfur-copolymerized chloroprene rubber latex composition according to <5> or <6>, wherein the monobasic acid is acetic acid.

[0025] <8>A modified asphalt emulsion composition containing the sulfur-copolymerized chloroprene rubber latex composition according to any one of <5> to <7> and asphalt.

[0026] <9>The modified asphalt emulsion composition according to <8>, further containing sand and aggregate.

[0027] <10>The modified asphalt emulsion composition according to <8> or <9>, which is a modified asphalt composite material.

[0028] Advantages of the Invention

[0029] According to one embodiment of the present invention, a sulfur-copolymerized chloroprene rubber latex composition and a method for producing the same can be provided. The sulfur-copolymerized chloroprene rubber latex composition has excellent aggregate graspability when forming a layered structure containing the sulfur-copolymerized chloroprene rubber latex composition, and excellent storage stability in a film state.

[0030] In addition, according to other embodiments of the present invention, a modified asphalt emulsion composition having excellent aggregate graspability and a method for producing the same can be provided. Detailed Embodiments

[0031] Hereinafter, the content of the present invention will be described in detail. The description of the content of the constituent elements described below is sometimes based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0032] In this specification, "~" indicating a numerical range is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value.

[0033] In this specification, "~" indicating a numerical range means that: unless otherwise specified, the units described before and after it represent the same unit.

[0034] In this specification, a combination of two or more preferred modes is a more preferred mode.

[0035] Hereinafter, the present invention will be described in detail.

[0036] <Sulfur-Copolymerized Chloroprene Rubber Latex Composition>

[0037] The sulfur-copolymerized chloroprene rubber latex composition of the present invention contains a sulfur-copolymerized chloroprene rubber latex, a nonionic surfactant, and a monobasic acid, and the pKa of the monobasic acid is 4.0 to 6.0.

[0038] Since the sulfur copolymerized chloroprene rubber latex composition has the above constitution, the resulting asphalt emulsion composition is excellent in storage stability and aggregate retention. Although the reason is not clear, it is presumed to be as follows.

[0039] The inventors of the present application conducted research and as a result, it is presumed that by including a nonionic surfactant (for example, polyethylene oxide alkyl ether) and a monobasic acid having a pKa of 4.0 to 6.0 in the sulfur copolymerized chloroprene rubber latex composition, compared with the conventional sulfur copolymerized chloroprene rubber latex composition containing only a nonionic surfactant, the physical property change of the sulfur copolymerized chloroprene rubber latex composition is suppressed, and thus, the storage stability in the film state is excellent. In addition, it is presumed that the aggregate retention of the modified asphalt emulsion composition containing this composition is also excellent, and the performance as an asphalt emulsion modifier can be exhibited for a long time.

[0040] Hereinafter, the details of the sulfur copolymerized chloroprene rubber latex composition will be described.

[0041] <<Sulfur Copolymerized Chloroprene Rubber Latex>>

[0042] The sulfur copolymerized chloroprene rubber latex can be obtained by copolymerizing 2-chloro-1,3-butadiene monomer (hereinafter, also referred to as "chloroprene monomer") in the presence of sulfur and water, or by copolymerizing in the presence of a chloroprene monomer, a monomer copolymerizable with the chloroprene monomer, sulfur, and water.

[0043] As the monomer copolymerizable with the chloroprene monomer, as long as it does not hinder the object of the present invention, there is no particular limitation, and examples thereof include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, styrene, acrylonitrile, acrylic acid and its esters, and methacrylic acid and its esters. Among them, as the monomer copolymerizable with the chloroprene monomer, 2,3-dichloro-1,3-butadiene and 1-chloro-1,3-butadiene are preferred, and 2,3-dichloro-1,3-butadiene is more preferred.

[0044] As the content of the monomer copolymerizable with the chloroprene monomer, relative to 100 parts by mass of 2-chloro-1,3-butadiene (chloroprene), the range of 0 to 20 parts by mass is preferred.

[0045] The monomer copolymerizable with the chloroprene monomer may be a single kind or two or more kinds may be used in combination. By setting the content of the monomer copolymerizable with the chloroprene monomer in the range of 0 to 20 parts by mass relative to 100 parts by mass of 2-chloro-1,3-butadiene (chloroprene), good tensile strength can be maintained.

[0046] The solid content ratio of the sulfur copolymerized chloroprene rubber latex is preferably 0 to 60% by mass, more preferably 20 to 50% by mass. The sulfur copolymerized chloroprene rubber may be a single type or two or more types may be used in combination.

[0047] <<Sulfur>>

[0048] As the sulfur copolymerized with the above-mentioned chloroprene monomer, there is no particular limitation as long as it is substantially composed of only sulfur atoms and can be used as an elemental sulfur for use in crosslinking agents for crosslinking various rubbers. As the above-mentioned sulfur, elemental sulfur that acts on the carbon-carbon double bond portion in the monomer unit of the conjugated diene is preferred. The form of sulfur is not particularly limited, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. The shape of sulfur is not particularly limited, and it may be cyclic or chain-like.

[0049] <<Gel content>>

[0050] From the viewpoint of excellent aggregate graspability, the gel content in the sulfur copolymerized chloroprene rubber latex composition is preferably 0 to 90% by mass, more preferably 5 to 85% by mass, and further preferably 15 to 75% by mass.

[0051] The gel content can be determined as the content of the sulfur copolymerized chloroprene rubber latex insoluble in tetrahydrofuran (hereinafter, also referred to as "tetrahydrofuran-insoluble component"). The tetrahydrofuran-insoluble component can be determined by the measurement method described in the following examples.

[0052] From the viewpoint of more excellent aggregate graspability when forming a layered structure, the content of sulfur in the sulfur copolymerized chloroprene rubber latex is preferably 0.01 to 5.0% by mass, more preferably 0.05 to 0.6% by mass, and further preferably 0.1 to 0.5% by mass, relative to the total mass of the sulfur copolymerized chloroprene rubber latex.

[0053] 〔Method for producing sulfur copolymerized chloroprene rubber latex〕

[0054] The method for copolymerizing a chloroprene monomer with sulfur (method for producing a sulfur copolymerized chloroprene rubber latex) is not particularly limited, but emulsion polymerization is preferred, and aqueous emulsion polymerization is particularly more preferred industrially.

[0055] As the emulsifier for emulsion polymerization, anionic surfactants, nonionic surfactants, and compounds that act as protective colloids such as polyvinyl alcohol are preferred. Among them, as the emulsifier for emulsion polymerization, anionic surfactants are preferred.

[0056] Specific examples of the anionic surfactant include rosin acid soap, sodium salt of naphthalene sulfonic acid condensate, sodium salt of dodecylbenzenesulfonic acid, sodium salt of dodecyl sulfate, etc.

[0057] Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, etc.

[0058] When using rosin acid soap as an emulsifier, the amount of rosin acid soap used, in terms of the converted amount of rosin acid, is preferably 3 to 8 parts by mass, more preferably 3 to 5 parts by mass, relative to 100 parts by mass of 2-chloro-1,3-butadiene (chloroprene) or the total of 100 parts by mass of chloroprene monomer and monomers copolymerizable with the chloroprene monomer.

[0059] If the amount of rosin acid soap used is 3 parts by mass or more, good emulsification can be achieved, good control of polymerization heat generation can be obtained, generation of agglomerates can be suppressed, and good product appearance can be obtained.

[0060] By adding a dispersant such as naphthalene sulfonate and formaldehyde condensate in the copolymerization reaction of chloroprene monomer and sulfur, the above problems can be suppressed even in a system emulsified with 3 parts by mass or less of rosin acid.

[0061] As the polymerization initiator, ordinary radical polymerization initiators can be used. For example, in the case of emulsion polymerization, as the radical polymerization initiator, ordinary organic or inorganic peroxides such as benzoyl peroxide, potassium persulfate, ammonium persulfate, and azo compounds such as azobisisobutyronitrile can be used. Promoters such as anthraquinone sulfonate, potassium sulfite, and sodium sulfite can be suitably used together with the radical polymerization initiator.

[0062] Generally, in the production of sulfur-copolymerized chloroprene latex, for the purpose of obtaining a copolymer with a desired molecular weight and distribution, a molecular weight regulator (chain transfer agent) can also be used during polymerization.

[0063] There is no particular limitation on the chain transfer agent. Examples include dialkylxanthogen disulfides represented by O,O-diisopropyl dithiobis(thiocarbonate), and alkyl mercaptans represented by dodecyl mercaptan.

[0064] The chain transfer agent can be a single type or a combination of two or more types.

[0065] Generally, in the production of sulfur-copolymerized chloroprene latex, for the purpose of obtaining a polymer with a desired molecular weight and distribution, at the time point when the specified polymerization rate is reached, a polymerization terminator is added to stop the reaction. There is no particular limitation on the polymerization terminator, and commonly used terminators such as phenothiazine, p-tert-butylcatechol, hydroquinone, hydroquinone monomethyl ether, and diethylhydroxylamine can be used.

[0066] In the method for manufacturing a sulfur-copolymerized chloroprene latex, with respect to 100 parts by mass of 2-chloro-1,3-butadiene (chloroprene) or a total of 100 parts by mass of chloroprene and a monomer copolymerizable with the chloroprene monomer, the compounding amount of sulfur is preferably 0.01 to 5.0 parts by mass, more preferably 0.05 to 0.6 parts by mass, and still more preferably 0.1 to 0.5 parts by mass.

[0067] When the compounding amount of sulfur is 0.01 parts by mass or more, the crosslinking reactivity of the sulfur-copolymerized chloroprene latex is improved. If 5.0 parts by mass or less is added, the polymerization reaction is not hindered, and a good polymerization conversion rate can be obtained.

[0068] It should be noted that the sulfur used in the reaction is the sulfur in which all the sulfur used for compounding remains in the sulfur-copolymerized chloroprene latex.

[0069] <<Monobasic acid>>

[0070] The sulfur-copolymerized chloroprene latex composition contains a monobasic acid having a pKa of 4.0 to 6.0.

[0071] pKa represents the acid dissociation constant (pKa) in an aqueous solution. For example, it is described in the Chemical Handbook (II) (Revised 4th Edition, 1993, edited by the Chemical Society of Japan, Maruzen Co., Ltd.). The lower the value of the acid dissociation constant pKa, the stronger the acid strength. When the above pKa is not described in the above Chemical Handbook, it is the theoretical value of the value in water at 25°C.

[0072] A monobasic acid is an acid that ionizes to release one hydrogen ion from one molecule.

[0073] Examples of the monobasic acid having a pKa of 4.0 to 6.0 include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, etc. Among them, as a monocarboxylic acid, acetic acid is preferred.

[0074] The pKa of the monobasic acid is 4.0 to 6.0, preferably 4.0 to 5.0.

[0075] <<Nonionic surfactant>>

[0076] The sulfur-copolymerized chloroprene latex composition contains a nonionic surfactant.

[0077] The nonionic surfactant is not particularly limited, and examples include polyoxyethylene alkyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, etc. Among them, as the nonionic surfactant, a nonionic surfactant containing a polyalkylene oxide structure is preferred, and polyoxyethylene alkyl ether is more preferred.

[0078] As the polyoxyethylene alkyl ether, there is no particular limitation, and examples thereof include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene myristyl ether, polyoxyethylene octyldodecyl ether, polyalkylene oxide alkyl ether, polyoxyphenylene stilbenized phenyl ether, polyoxyethylene tribenzylphenyl ether, polyalkylene oxide alkenyl ether, polyoxyethylene nonylphenyl ether, etc.

[0079] The nonionic surfactant can be synthesized or can be a commercially available product.

[0080] As commercially available products, examples include Emulgen (registered trademark) 102KG, 103, 104P, 105, 106, 108, 109P, 120, 123P, 130K, 147, 150, 210P, 220, 306P, 320P, 350, 404, 408, 409PV, 420, 430, 705, 707, 709, 1108, 1118S-70, 1135S-70, 1150S-60, 4085, 2020G-HA, 2025G, LS-106, LS-110, LS-114, MS-110, A-60, A-90, B-66, A-500, PP-290, Latemul (registered trademark) PD-420, PD-430, PD-430S, PD450, Leodol (registered trademark) SP-L10, SP-P10, SP^S10V, SP-S20, SP-S30V, SP-O10V, SP-O30V, AS-10V, AO-10V, AO-15V, TW-L120, TW-L106, TW-P120, TW-S120V, TW-S106V, TW-S320V, TW-O120V, TW-O106V, TW-O320V, TW-IS399C, Super TW-L120, 430V, 440V, 460V, MS-50, MS-60, MO-60, MS-165V, Emazol (registered trademark) L-10V, P-10V, S-10V, O-10V, Emanon 1112, 3199V, 3299V, 3299RV, 4110, CH-25, CH-40, CH-60(K), CH-80, Amite (registered trademark) 102, 105, 105A, 302, 320, Aminon (registered trademark) PK-02S, L-02, Homogenol (registered trademark) L-95 (the above are manufactured by Kao Corporation).

[0081] <Method for manufacturing sulfur copolymerized chloroprene rubber latex composition>

[0082] The method for manufacturing the sulfur copolymerized chloroprene rubber latex composition includes the following steps:

[0083] A polymerization step of polymerizing a chloroprene monomer and sulfur to obtain a sulfur-copolymerized chloroprene latex (hereinafter, also simply referred to as "polymerization step"); and

[0084] A mixing step of mixing the above sulfur-copolymerized chloroprene latex and a monobasic acid having a pKa of 4.0 to 6.0 (hereinafter, also simply referred to as "mixing step"),

[0085] In at least one of the above polymerization step and mixing step, the sulfur-copolymerized chloroprene latex and a nonionic surfactant are mixed.

[0086] The sulfur-copolymerized chloroprene latex composition obtained by the method for producing a sulfur-copolymerized chloroprene latex composition including the above steps has excellent storage stability, and also has excellent aggregate holdability when forming a layered structure containing an asphalt emulsion composition containing the composition.

[0087] <<Polymerization step>>

[0088] The polymerization step is synonymous with the method for producing the above sulfur-copolymerized chloroprene latex, and the preferred mode is the same. It should be noted that in the polymerization step, a mode of mixing a nonionic surfactant after polymerizing a chloroprene monomer and sulfur is also included.

[0089] <<Mixing step>>

[0090] The mixing step is a step of mixing the above sulfur-copolymerized chloroprene latex and a monobasic acid having a pKa of 4.0 to 6.0.

[0091] The sulfur-copolymerized chloroprene latex and the monobasic acid used in the mixing step are synonymous with the sulfur-copolymerized chloroprene latex and the monobasic acid in the above sulfur-copolymerized chloroprene latex composition, and the preferred mode is the same.

[0092] As the sulfur-copolymerized chloroprene latex used in the mixing step, in addition to the sulfur-copolymerized chloroprene latex obtained through the sulfur-copolymerized chloroprene latex preparation step, a sulfur-copolymerized chloroprene latex prepared at other places can also be used, and a commercially available sulfur-copolymerized chloroprene latex can also be used.

[0093] A method for producing a sulfur-copolymerized chloroprene latex composition, in which in at least one of the above polymerization step and mixing step, the sulfur-copolymerized chloroprene latex and a nonionic surfactant are mixed.

[0094] From the viewpoint that the storage stability of the obtained sulfur-copolymerized chloroprene rubber latex composition is more excellent, in the method for producing a sulfur-copolymerized chloroprene rubber latex composition, it is preferable to mix the sulfur-copolymerized chloroprene rubber latex and a nonionic surfactant before mixing the sulfur-copolymerized chloroprene rubber latex and a monobasic acid. More preferably, the chloroprene monomer is polymerized with sulfur through a polymerization step, and the obtained sulfur-copolymerized chloroprene rubber latex and a nonionic surfactant are mixed.

[0095] The nonionic surfactant is synonymous with the nonionic surfactant contained in the above sulfur-copolymerized chloroprene rubber latex composition, and the preferred mode is the same.

[0096] As the mixing method of each component in the mixing step and the mixing method of the above sulfur-copolymerized chloroprene rubber latex and a nonionic surfactant, there is no particular limitation, and a known mixing method can be adopted.

[0097] The method for producing a sulfur-copolymerized chloroprene rubber latex composition may further include steps other than the above polymerization step and mixing step (hereinafter, also referred to as "other steps").

[0098] As other steps, there can be mentioned a step of purifying the sulfur-copolymerized chloroprene rubber latex obtained in the polymerization step, etc.

[0099] <Modified asphalt emulsion composition>

[0100] The modified asphalt emulsion composition preferably contains a sulfur-copolymerized chloroprene rubber latex composition and asphalt, and more preferably contains a sulfur-copolymerized chloroprene rubber latex composition, asphalt and water.

[0101] <<Asphalt>>

[0102] As the asphalt, there is no particular limitation, and known common asphalts can be used. As the asphalt, there can be mentioned, for example, straight-run asphalt, blown asphalt, semi-blown asphalt, natural asphalt, modified asphalt, solvent-deasphalted asphalt, tar, asphalt materials such as asphalt, heavy oil A, heavy oil B and heavy oil C.

[0103] As the content rate of the asphalt, based on 100% by mass of the solid content of the modified asphalt emulsion composition, it is preferably 50 to 99.9% by mass, more preferably 83 to 99% by mass, and further preferably 89 to 99% by mass.

[0104] In addition, as the content rate of the asphalt, based on 100% by mass of the modified asphalt emulsion composition, it is preferably 30 to 74% by mass, more preferably 40 to 72% by mass, and further preferably 50 to 70% by mass.

[0105] The asphalt can be a single type, or two or more types can be used in combination.

[0106] With respect to 100 parts by mass of the solid component of asphalt, the content of the solid component of the sulfur copolymerized chloroprene latex is preferably 0.5 to 20 parts by mass, more preferably 1.0 to 10 parts by mass, and still more preferably 2.0 to 5.0 parts by mass.

[0107] <<Water>>

[0108] The water is not particularly limited, and examples thereof include industrial water, tap water, ion-exchanged water, pure water, and the like.

[0109] With respect to 100 parts by mass of the solid component of the modified asphalt emulsion composition, the content of water is preferably 25 to 400 parts by mass, more preferably 35 to 230 parts by mass, and still more preferably 40 to 150 parts by mass.

[0110] The modified asphalt emulsion composition may contain a surfactant. As the surfactant, for example, at least one surfactant selected from cationic surfactants and nonionic surfactants can be mentioned. Among them, as the surfactant, a cationic surfactant is preferred.

[0111] As the cationic surfactant, for example, a mixture of an amine and an acid can be mentioned. As the amine, primary amines, secondary amines, tertiary amines, aliphatic diamines, etc. can be mentioned. Among them, as the amine, amines having an alkyl group are further preferred.

[0112] As the primary amine, laurylamine, myristylamine, 1-amino-3-undecyloxy-propane, cetylamine, stearylamine, oleylamine, behenylamine, etc. can be mentioned. Alternatively, as the primary amine, compounds obtained by substituting the hydroxyl group of coconut oil, soybean oil, beef tallow, hardened beef tallow, etc. with an amino group can also be mentioned.

[0113] As the tertiary amine, dimethyllaurylamine, dimethylstearylamine, dimethylmyristylamine, compounds obtained by substituting the hydroxyl group of coconut oil, hardened beef tallow, etc. with a dimethylamino group can be mentioned.

[0114] It should be noted that the compound obtained by substituting the hydroxyl group of hardened beef tallow with a dimethylamino group is also called dimethyl hardened beef tallow amine.

[0115] As the above acid, hydrochloric acid is preferred.

[0116] As the nonionic surfactant, the compounds described in the production method of the sulfur copolymerized chloroprene latex can be used.

[0117] The modified asphalt emulsion composition may further contain components other than the above sulfur copolymerized chloroprene latex, asphalt, surfactant, and water (hereinafter, also referred to as "other components").

[0118] As other components, for example, for the stabilization of emulsification, salts such as calcium chloride, film-forming agents, thickening stabilizers, retarders, sand, aggregates, etc. can be cited.

[0119] By making the modified asphalt emulsion composition further contain sand, gravel and aggregates, it can be suitably used as a modified asphalt composite material.

[0120] From the viewpoint of excellent aggregate graspability, the multiple stress creep recovery: MSCR (multiple stress creep recovery) of the asphalt emulsion composition depends on the solid content of the sulfur copolymerized chloroprene latex in the modified asphalt emulsion composition, but is preferably 20 to 95%, more preferably 20 to 80%, further preferably 20 to 60%, and particularly preferably 20 to 40%.

[0121] The MSCR of the modified asphalt emulsion composition can be determined by the method described in the following examples.

[0122] 〔Manufacturing method of modified asphalt emulsion composition〕

[0123] The manufacturing method of the modified asphalt emulsion composition preferably includes the step of obtaining a composition containing the sulfur copolymerized chloroprene latex composition obtained by the manufacturing method of the above sulfur copolymerized chloroprene latex composition and asphalt, and includes the step of adding and / or mixing the sulfur copolymerized chloroprene latex and asphalt, and more preferably includes the step of mixing the sulfur copolymerized chloroprene latex and the asphalt emulsion. In the manufacturing method of the modified asphalt emulsion composition, the asphalt is preferably asphalt particles.

[0124] In addition, the manufacturing method of the modified asphalt emulsion composition preferably includes the following steps (hereinafter, also referred to as "sulfur copolymerized chloroprene latex preparation step"): Polymerize the chloroprene monomer in the presence of 0.05 to 0.60 parts by mass of sulfur and water with respect to 100 parts by mass of the above chloroprene monomer to obtain the above sulfur copolymerized chloroprene latex.

[0125] The manufacturing method of the modified asphalt emulsion composition preferably includes the step of adding asphalt, surfactant and water (hereinafter, also referred to as "asphalt emulsion formation step").

[0126] In the asphalt emulsion formation step, the order of adding asphalt, surfactant and water is not particularly limited as long as an asphalt emulsion is formed. They can be added separately or simultaneously. For example, various surfactants can be added to the asphalt and then mixed with water to form an asphalt emulsion.

[0127] In addition, the order can also be set to add the surfactant and water first and then add the asphalt.

[0128] As a method for mixing sulfur - copolymerized chloroprene rubber latex with asphalt, surfactant, and water, there is no particular limitation, and various known methods can be cited. For example, methods of mixing using a defoaming kneader, dry ball mill, dry bead mill, blade - type planetary mixer, container - rotating type planetary mixer, grinder, mortar, homogenizer, colloid mill, etc. Among them, as the mixing method, a method of emulsifying using a homogenizer or a colloid mill is desirable.

[0129] The method for manufacturing the modified asphalt emulsion composition may include a step of adding the above - mentioned other components as needed. In addition, for example, after the step of preparing the sulfur - copolymerized chloroprene rubber latex, a step of adjusting the pH may be included.

[0130] The pH of the sulfur - copolymerized chloroprene rubber latex composition after the step of adjusting the pH is preferably from 1.0 to 4.5, more preferably from 1.5 to 3.5.

[0131] There is no particular limitation on the pH regulator used in the step of adjusting the pH, and known pH regulators can be used.

[0132] The modified asphalt emulsion composition is preferably an asphalt emulsion composition manufactured by the above - mentioned method for manufacturing the asphalt emulsion composition.

[0133] It is presumed that in the composition obtained by the method for manufacturing the modified asphalt emulsion composition, that is, the composition obtained by adding and / or mixing sulfur - copolymerized chloroprene rubber latex and asphalt, an island - like structure is formed in which chloroprene is the continuous phase.

[0134] From the viewpoint of excellent aggregate retention, the modified asphalt emulsion composition can be suitably used for road paving. As a method for road paving, for example, the chip seal process method can be cited, and a method of successively overlapping the asphalt emulsion composition and aggregate on the surface side of the road and then rolling can be cited.

[0135] In the chip seal process method, it can be a single layer (seal coat) obtained by forming a layer of the asphalt emulsion composition and a layer of the aggregate respectively, or a multi - layer (protective coating) obtained by laminating these single layers.

[0136] From the viewpoint of excellent aggregate retention, in addition to being applicable to the chip seal process method, the above - mentioned modified asphalt emulsion composition can also be applied to scrub seal, bond coat, binder for subgrade, process methods including on - road subgrade recycling process method and Cold In - place Recycling process method, etc.

[0137] Examples

[0138] Examples and comparative examples are given below to illustrate the present invention, but the present invention is not limited by any of the following examples.

[0139] <Manufacture of Asphalt Emulsion>

[0140] 3.50 kg of pure water heated to 80°C was charged into a container with an internal volume of 5 L, and 24 g of dimethyl cured tallow amine (manufactured by NOF Corporation, product name: Nissan Amine (registered trademark) ABT) as a surfactant, 19 g of 35 mass% hydrochloric acid (manufactured by Kanto Chemical Co., Inc.), and 14 g of calcium chloride (manufactured by Kanto Chemical Co., Inc.) were added to prepare an aqueous surfactant solution. Using a colloid mill (manufactured by IKA JAPAN Co., Ltd., product name: MagicLAB (registered trademark) XP), the aqueous surfactant solution and 6.50 kg of straight-run asphalt (manufactured by Showa Bitumen Kogyo Co., Ltd., product name: SA120 - 150) heated and melted at 140°C were emulsified at an asphalt emulsion production rate of 0.5 L / minute to obtain an asphalt emulsion having a solid content ratio of 65 mass%.

[0141] (Production Example 1)

[0142] <Manufacture of Sulfur Copolymerized Chloroprene Latex>

[0143] 1.00 kg (100 mass parts) of 2-chloro-1,3-butadiene (chloroprene) (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.93 kg of pure water, 34 g of rosin acid (manufactured by Arakawa Chemical Industries, Ltd., rosin HTR), 1.0 g of sulfur (0.10 mass parts), 1.5 g of O,O-diisopropyl dithiobis(thiocarbonate) (manufactured by Sanshin Chemical Industry Co., Ltd.), 5.9 g of potassium hydroxide, 4.9 g of sodium hydroxide, and 0.44 mg of copper sulfate were charged into a reactor and emulsified. After making rosin acid into rosin acid soap (a mixture of potassium rosin and sodium rosin), potassium persulfate was used as an initiator, and polymerization was carried out under a nitrogen atmosphere at an initial polymerization temperature of 40°C. When the polymerization conversion rate reached 90%, the temperature was raised to 45°C and polymerization was continued. Polymerization was stopped when the polymerization conversion rate was confirmed to be 95%.

[0144] Subsequently, unreacted monomers were removed by steam distillation, 10 g of diethanolamine (manufactured by Nippon Shokubai Co., Ltd.) and 30 g of a 70% aqueous solution of polyoxyethylene alkyl ether as a nonionic surfactant (manufactured by Kao Corporation, product name: Emulgen 1118S - 70) were added and mixed to obtain a sulfur copolymerized chloroprene latex having a solid content ratio of 48.0 mass% and a gel content ratio of 30 mass%. It should be noted that the gel content ratio was determined by the method described later.

[0145] [Example 1]

[0146] <<Manufacture of Sulfur Copolymerized Chloroprene Latex Composition>>

[0147] For 100 g of the sulfur-copolymerized chloroprene latex synthesized in Production Example 1, 0.77 g of acetic acid (manufactured by Kanto Chemical Co., Inc.) was added and mixed, and the pH was adjusted to 7.0 to obtain a sulfur-copolymerized chloroprene latex composition.

[0148] <<Production of Asphalt Emulsion Composition>>

[0149] To 40 g of the asphalt emulsion (solid content rate: 65% by mass) prepared above and heated to 60°C, 1.63 g of the product obtained by adding 0.5 g of 35% by mass hydrochloric acid (manufactured by Kanto Chemical Co., Inc.) to the sulfur-copolymerized chloroprene latex composition whose pH had been adjusted to 7.0 above to adjust the pH to 2.0 was added and mixed to obtain an asphalt emulsion composition.

[0150] It should be noted that the addition amount of the sulfur-copolymerized chloroprene latex was determined such that the solid content in the sulfur-copolymerized chloroprene latex was 3 parts by mass when the solid content in the asphalt emulsion was 100 parts by mass.

[0151] Specifically, the addition amount of the sulfur-copolymerized chloroprene latex was calculated based on the following formula.

[0152] Addition amount of sulfur-copolymerized chloroprene latex = Amount of asphalt emulsion (40 g) × (Solid content rate of asphalt emulsion) × (3 parts by mass / 100 parts by mass) ÷ (Solid content rate of sulfur-copolymerized chloroprene latex)

[0153] It should be noted that hydrochloric acid is sometimes used for pH adjustment after the sulfur-copolymerized chloroprene latex is prepared, but hydrochloric acid volatilizes under the conditions for measuring the solid content rate, and thus does not affect the solid content rate.

[0154] <Gel Content Rate of Sulfur-Copolymerized Chloroprene Latex (Tetrahydrofuran-Insoluble Component)>

[0155] The gel content rate of the sulfur-copolymerized chloroprene latex was determined as the content rate (tetrahydrofuran-insoluble component) of the sulfur-copolymerized chloroprene latex that is insoluble in tetrahydrofuran (THF).

[0156] 0.5 g of the sulfur-copolymerized chloroprene latex synthesized in Production Example 1 above (in the above latex, the water content was in the range of 40% to 65% by mass) was dropped into 100 mL of tetrahydrofuran, shaken overnight, and then the THF solution was separated using a centrifuge to extract the THF-soluble phase of the supernatant.

[0157] The extracted soluble phase was heated to 100°C, and tetrahydrofuran was evaporated and dried over 1 hour to calculate the mass of the sulfur-copolymerized chloroprene latex dissolved in the THF-soluble phase.

[0158] Then, the content of the sulfur-copolymerized chloroprene latex insoluble in tetrahydrofuran (tetrahydrofuran insoluble component) was calculated by subtracting the mass of the sulfur-copolymerized chloroprene latex dissolved in THF from the mass of the sulfur-copolymerized chloroprene in the sulfur-copolymerized chloroprene latex and further dividing the mass by the mass of the sulfur-copolymerized chloroprene in the sulfur-copolymerized chloroprene latex. The results are shown in Table 1.

[0159] <Solid content>

[0160] The value obtained by multiplying the mass of 1 g of the sulfur-copolymerized chloroprene latex after drying at 141° C. for 30 minutes by 100 is referred to as the solid content. This value is also referred to as solid content.

[0161] 〔evaluate〕

[0162] <Aggregate control>

[0163] In the evaluation of aggregate controllability, multiple stress creep recovery (MSCR) was measured in accordance with AASHTO (America Association of State Highway and Transportation Officials) T350-14 and evaluated as an index of aggregate controllability.

[0164] Specifically, a rheometer (MCR301 manufactured by Anton Paar) was used for the measurement, and a parallel plate having a diameter of 25 mm as specified in JIS K7244-10:2005 was used as a measurement jig.

[0165] <<MSCR测定用样品的调制> >

[0166] 40 g of the asphalt emulsion composition prepared above was injected into a silicone barrel with a bottom area of ​​216 mm × 175 mm and a depth of 40 mm so that it spread throughout the barrel. Then, after drying at 23°C for 24 hours, it was dried in an oven at 60°C for 24 hours to obtain a sample for multiple stress creep recovery (MSCR) measurement.

[0167] <<Measurement>>

[0168] The rheometer was set to 64° C. and the temperature was sufficiently adjusted. Then, about 1.0 g of the sample for MSCR measurement prepared above was installed, and the excess sample was removed before measurement.

[0169] The measurement was performed by the following steps.

[0170] (1) Record the deformation (A) before stress is applied.

[0171] (2) Apply a stress of 3.2 kPa for 1 second and record the amount of deformation (B) at this time.

[0172] (3) After stopping the application of stress, wait for 9 seconds (during which time the sample will return to its original state due to rubber elasticity), and record the amount of deformation (C) after 9 seconds.

[0173] Repeat the procedures (1) to (3) above for 10 cycles.

[0174] In each cycle, calculate the recovery amount of the deformation caused by stress using the following formula.

[0175] (Amount of deformation (B) - Amount of deformation (C)) ÷ (Amount of deformation (B) - Amount of deformation (A)) × 100

[0176] For 10 cycles, calculate the value (recovery amount of the deformation caused by stress) using the above formula respectively, and find the arithmetic mean as the initial value of MSCR.

[0177] Furthermore, the sulfur - copolymerized chloroprene rubber latex is stored in a constant - temperature bath at 38 °C for 3 months. The sample for MSCR measurement is prepared and the MSCR measurement is carried out through the same steps, and the result is obtained as the MSCR after storage at 38 °C for 3 months. The respective results are shown in Table 1.

[0178] When both the initial value of MSCR and the MSCR after storage at 38 °C for 3 months are 22% or more, it can be said that the aggregate grasping property is excellent. In addition, if MSCR is greater than 22%, it can be judged that there is sufficient aggregate grasping property in actual paving.

[0179] In addition, the residual rate of the aggregate grasping property is calculated by the following formula.

[0180] Residual rate of aggregate grasping property (%) = Aggregate grasping property after storage at 38 °C for 3 months ÷ Initial value of aggregate grasping property × 100

[0181] The residual rate of the aggregate grasping property is preferably 90 - 105%. It can be seen that if the residual rate of the aggregate grasping property is within the above range, the change over time is small (i.e., the storage stability is excellent), and it is preferable as a pavement.

[0182] <Storage stability>

[0183] As an index of storage stability, the change rate of the tensile strength at break (Tb) of the dry film obtained by drying the sulfur - copolymerized chloroprene rubber latex composition was adopted.

[0184] The change rate of the dry film strength obtained from the sulfur copolymerized chloroprene rubber latex composition after being treated at 38°C for 3 months with respect to the dry film strength obtained from the sulfur copolymerized chloroprene rubber latex composition just after preparation was used as the degree of denaturation of the polymer (sulfur copolymerized chloroprene) for evaluation.

[0185] <<Tensile strength at break (Tb)>>

[0186] First, 60 g of the sulfur copolymerized chloroprene rubber latex composition prepared above, whose solid content was adjusted to 40% by dilution with water, was charged into a Teflon (registered trademark) container with a bottom area of 120 mm × 260 mm and a depth of 4 mm.

[0187] Next, after drying the above sulfur copolymerized chloroprene rubber latex composition in an environment of 23°C and a relative humidity of 50% for 3 days, the formed dry film was turned over and further dried in an environment of 23°C and a relative humidity of 50% for 3 days. Then it was dried in an oven at 50°C for 30 minutes to obtain a dry film for evaluating the tensile strength at break (hereinafter, also referred to as "Tb").

[0188] The dry film for evaluation was cut into No. 6 dumbbell shape of JIS K6251:2017, and a tensile test was carried out using a tensile tester (UTM-I-2500). The tensile speed was set at 200 mm / min, and the stress at break was defined as Tb, which was used as the initial value of Tb.

[0189] Furthermore, the dry film for evaluation was stored in a constant temperature bath at 38°C for 3 months, and a tensile test was carried out through the same steps as above. The results are shown in Table 1 as Tb after being stored at 38°C for 3 months.

[0190] In addition, the Tb change rate was calculated by substituting into the following formula.

[0191] Tb change rate (%) = (Tb after being stored at 38°C for 3 months - initial value of Tb) ÷ initial value of Tb × 100

[0192] When the change rate of Tb is greater than -10% and less than or equal to +50%, the denaturation of the polymer during storage is less, so it can be judged that the storage stability is excellent. In addition, if both the initial value of Tb and the value of Tb after being stored at 38°C for 3 months are 5.5 MPa or more, it can be judged that it has sufficient practical performance.

[0193] 〔Comparative Examples 1 - 7〕

[0194] In Comparative Examples 1 to 7, the amounts and types of sulfur, nonionic surfactants, and acids were changed to the amounts described in Table 1, and otherwise, the same operations as in Production Example 1 and Example 1 were carried out to prepare a sulfur copolymerized chloroprene latex, thereby obtaining it. In addition, the same operations as in Example 1 were carried out, and using the prepared sulfur copolymerized chloroprene latex, an asphalt emulsion composition was prepared.

[0195] Using the obtained asphalt emulsion composition, a sample for MSCR measurement was prepared, and the evaluation of aggregate graspability and breaking tensile strength (Tb) was carried out. The results are shown in Table 1.

[0196] In Comparative Example 8, the amounts and types of sulfur, nonionic surfactants, and acids were changed to the amounts described in Table 1, and otherwise, the same operations as in Production Example 1 and Example 1 were carried out to prepare a sulfur copolymerized chloroprene latex, and a sulfur copolymerized chloroprene latex composition was obtained.

[0197]

[0198] In the table, "-" means that the component is not included. In addition, the "-" in the columns of "aggregate graspability" and "breaking tensile strength" in Comparative Example 8 means that in the production of the sulfur copolymerized chloroprene latex composition, rubber aggregates were generated or precipitated when acetic acid was added, and this evaluation could not be carried out.

[0199] "AcOH" in the table means acetic acid, "HCl" means hydrochloric acid, "HNO3" means nitric acid, and "TsOH" means p-toluenesulfonic acid.

[0200] The storage stability of the sulfur copolymerized chloroprene latex composition of Example 1 was significantly improved compared with the sulfur copolymerized chloroprene latex compositions of Comparative Examples 1 to 7 when the latex was stored in a film state for a long time (that is, the denaturation of the polymer during storage was less and the dry film strength did not decrease).

[0201] It was confirmed that both the sulfur copolymerized chloroprene latex composition just prepared and the asphalt emulsion obtained by modifying with the sulfur copolymerized chloroprene latex subjected to heat treatment equivalent to long-term had high aggregate graspability.

[0202] The MSCR of the asphalt emulsion composition containing the sulfur copolymerized chloroprene latex composition of Example 1 was greater than 22% in any case after just being prepared and after being treated at 38 °C for 3 months, indicating excellent aggregate graspability.

[0203] In the sulfur copolymerized chloroprene latex composition and the modified asphalt emulsion composition of Comparative Example 8, rubber aggregates were generated or precipitated when acetic acid was added, and the function as a latex could not be guaranteed, which was inappropriate. Therefore, in Comparative Example 8, MSCR and breaking tensile strength (Tb) could not be measured.

[0204] The asphalt emulsion composition of Example 1 is also excellent in terms of such MSCR and aggregate graspability. Therefore, in addition to chip seal, even when used in scrub seal, bonding layer, binder for roadbed, process methods including in-road subgrade recycling and cold in-place recycling process methods, etc., it can exhibit good performance.

Claims

1. A method for manufacturing a sulfur-copolymerized chloroprene rubber latex composition, which comprises the following steps: A polymerization step of polymerizing a chloroprene monomer and sulfur to obtain a sulfur-copolymerized chloroprene rubber latex; and A mixing step of mixing the sulfur-copolymerized chloroprene rubber latex and a monobasic acid having a pKa of 4.0 to 6.0, In at least one of the polymerization step and the mixing step, the sulfur-copolymerized chloroprene rubber latex and a nonionic surfactant are mixed.

2. The method for manufacturing a sulfur-copolymerized chloroprene rubber latex composition according to claim 1, wherein the nonionic surfactant contains a polyoxyalkylene structure.

3. The method for manufacturing a sulfur-copolymerized chloroprene rubber latex composition according to claim 1 or 2, wherein the monobasic acid is acetic acid.

4. A method for manufacturing a modified asphalt emulsion composition, which comprises a step of obtaining a composition containing a sulfur-copolymerized chloroprene rubber latex composition and asphalt, and the sulfur-copolymerized chloroprene rubber latex composition is obtained by using the method for manufacturing a sulfur-copolymerized chloroprene rubber latex composition according to claim 1 or 2.

5. A sulfur-copolymerized chloroprene rubber latex composition, which comprises a sulfur-copolymerized chloroprene rubber latex, a nonionic surfactant, and a monobasic acid, The pKa of the monobasic acid is 4.0 to 6.

0.

6. The sulfur-copolymerized chloroprene rubber latex composition according to claim 5, wherein the nonionic surfactant contains a polyoxyalkylene structure.

7. The sulfur-copolymerized chloroprene rubber latex composition according to claim 5 or 6, wherein the monobasic acid is acetic acid.

8. A modified asphalt emulsion composition, which contains the sulfur-copolymerized chloroprene rubber latex composition according to claim 5 or 6 and asphalt.

9. The modified asphalt emulsion composition according to claim 8, which further contains sand, gravel, and aggregate.

10. The modified asphalt emulsion composition according to claim 8, which is a modified asphalt composite material.

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