Two-component curable adhesive

Abstract

Provided is a two-component curable adhesive capable of exhibiting good adhesive strength while using an unmodified chloroprene rubber (chloroprene polymer). According to one aspect of the present invention, provided is a two-component curable adhesive used by mixing a first liquid and a second liquid, wherein the first liquid contains a chloroprene polymer and an amine catalyst and has a nitrogen content of 0.003-0.2 mass%, and the second liquid contains a polyisocyanate.

Description

Two-component curable adhesive

[0001] The present invention relates to a two-component curable adhesive.

[0002] As a two-component curable adhesive, chloroprene rubber-based adhesives are widely used in various applications (see Patent Document 1). The chloroprene rubber-based adhesive described in Patent Document 1 has a main component (A) containing carboxyl-modified chloroprene rubber and a curing agent (B) containing a metal oxide, a rubber or thermoplastic resin having a solubility parameter of 7.55, and an isocyanate compound. Carboxyl-modified chloroprene rubber is obtained by copolymerization or graft polymerization of 2-chloro-1,3-butadiene and a carboxyl group-containing monomer.

[0003] Japanese Patent Application Laid-Open No. 2016-69430

[0004] In view of the above circumstances, the present invention aims to provide a two-component curable adhesive that can exhibit sufficient adhesive strength while using unmodified chloroprene rubber (chloroprene polymer).

[0005] According to one aspect of the present invention, there is provided a two-component curable adhesive that is used by mixing a first liquid and a second liquid, wherein the first liquid contains a chloroprene polymer and an amine-based catalyst and has a nitrogen content of 0.003% by mass or more and 0.2% by mass or less, and the second liquid contains a polyisocyanate.

[0006] According to such an aspect, sufficient adhesive strength can be exhibited while using an unmodified chloroprene polymer.

[0007] The following describes embodiments of a two-component curing adhesive. The various features shown in the embodiments below can be combined with each other. In this specification, unless otherwise specified, the content of Y in X (mass% or mol%) refers to the amount of Y when the total amount of X is 100% by mass or mol%. The two-component curing adhesive of this embodiment is a solvent-based adhesive used by mixing a first liquid (main component) and a second liquid (curing agent). The first liquid contains a chloroprene polymer and an amine-based catalyst, and the second liquid contains a polyisocyanate. With this configuration, a crosslinking reaction proceeds between the hydroxyl groups of the chloroprene polymer and the isocyanate groups of the polyisocyanate (urethane bonds are formed), and the chloroprene polymer hardens. The following describes each component (liquid).

[0008] <First Solution> The first solution contains a chloroprene polymer and an amine-based catalyst. <<Chloroprene Polymer>> The chloroprene polymer is a homopolymer of 2-chloro-1,3-butadiene (hereinafter also referred to as "chloroprene"), or a copolymer of chloroprene and a monomer copolymerizable with chloroprene. Examples of monomers copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, sulfur, methacrylic acid or its esters, acrylic acid or its esters, etc. These monomers may be used individually or in combination of two or more. When using monomers copolymerizable with chloroprene, the amount added is preferably 0.01 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the total amount of monomers.

[0009] Chloroprene polymers can be obtained as latex, for example, by emulsion polymerization of the above-mentioned monomers in water in the presence of an emulsifier and / or dispersant, and then stopping the polymerization reaction by adding a polymerization inhibitor when the desired polymerization rate is reached. Unreacted monomers can be removed from the chloroprene polymer latex obtained in this way by methods such as steam flashing or concentration. The emulsifier and / or dispersant can be any anionic compound, nonionic compound, cationic compound, etc. that can be used for emulsion polymerization of chloroprene, and is not particularly limited. Anionic compounds include carboxylic acid type compounds and sulfate ester type compounds, and specific examples include alkali metal salts of rosinic acid, alkyl sulfonates having 8 to 20 carbon atoms, alkylaryl sulfates, and condensates of sodium naphthalene sulfonate and formaldehyde.

[0010] Specific examples of nonionic compounds include, for example, polyvinyl alcohol or its copolymers (e.g., copolymers with acrylamide), polyvinyl ether or its copolymers (e.g., copolymers with maleic acid), polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, sorbitan fatty acid esters, and polyoxyethylene fatty acid esters. Cationic compounds include aliphatic amine salts and aliphatic quaternary ammonium salts, and specific examples of these include, for example, octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, and dilauryldimethylammonium chloride. Among these, it is preferable to use alkali metal salts of rosinic acid as emulsifiers and / or dispersants.

[0011] The amount of emulsifier and / or dispersant (particularly alkali metal salt of rosinic acid) added during emulsion polymerization is preferably 0.5 parts by mass to 20 parts by mass per 100 parts by mass of the total initial monomers. By setting the amount of emulsifier and / or dispersant within the above range, the emulsifying power can be sufficiently exerted, and foaming of the polymerization solution during emulsion polymerization can be suitably prevented or suppressed. The conditions for emulsion polymerization are not particularly limited, but for example, by arbitrarily selecting the polymerization temperature, polymerization initiator, chain transfer agent, polymerization arrester, polymerization rate, etc., it is possible to control the molecular weight, molecular weight distribution, molecular end structure, and crystallization rate. The polymerization temperature is preferably set to 5°C to 50°C in order to carry out emulsion polymerization smoothly.

[0012] Examples of initiators include persulfates such as potassium persulfate and organic peroxides such as tert-butyl hydroperoxide. Examples of chain transfer agents include long-chain alkyl mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan, dialkylxanthogen disulfides such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide, and iodoform. Examples of polymerization inhibitors include 2,6-tert-butyl-4-methylphenol, phenothiazine, and hydroxyamine. The final polymerization rate is not particularly limited, but can be arbitrarily adjusted within the range of 70% to 100% or more.

[0013] According to this manufacturing method, the microstructure of the chloroprene polymer can be controlled more precisely by precisely adjusting the manufacturing conditions of the chloroprene polymer, for example, the amount of alkali metal salt of rosinic acid added during polymerization. Furthermore, by omitting the heating step, reducing the heating temperature, or shortening the heating time, it is possible to suppress an excessive increase in 1,2-OH rearrangement structures. In other words, the hydroxyl group content in the manufactured chloroprene polymer can be adjusted by such control. The hydroxyl group content in the chloroprene polymer is not particularly limited, but can be set to approximately 0.005 mol% or more and 0.1 mol% or less. With the two-component curing adhesive of this embodiment, regardless of the hydroxyl group content in the chloroprene polymer, the crosslinking reaction can proceed smoothly and sufficiently, allowing for suitable curing.

[0014] The degree of crystallinity of the chloroprene polymer is preferably 15% to 30%, more preferably 17.5% to 27.5%, and even more preferably 20% to 25%. Here, the degree of crystallinity correlates with the crystallization rate, and chloroprene polymers having the above-mentioned degree of crystallinity have a sufficiently fast crystallization rate. By using a chloroprene polymer with such a fast crystallization rate, the mechanical strength and adhesive strength of the cured product of a two-component curing adhesive can be increased. In this specification, the degree of crystallinity is determined by measuring the polymer density in accordance with Method A specified in JIS K 6268:1998 (ISO 2781:1988) to identify the crystalline and amorphous regions, and then determining it as the ratio of the mass of the crystalline region to the total mass of the chloroprene polymer.

[0015] The Mooney viscosity of the chloroprene polymer at 100°C is preferably 30 to 80, more preferably 35 to 70, and even more preferably 40 to 60. By using a chloroprene polymer having such an appropriate Mooney viscosity, the workability when applying a two-component curing adhesive (a mixture of the first and second liquids) and the wettability to the adherend can be improved. Furthermore, the handling of the chloroprene polymer when preparing the first liquid can also be improved. In this specification, Mooney viscosity is a value measured in accordance with JIS K 6300-1:2013.

[0016] The number-average molecular weight (Mn) of the chloroprene polymer is preferably between 150,000 and 350,000, more preferably between 180,000 and 320,000, and even more preferably between 210,000 and 290,000. Chloroprene polymers having such a number-average molecular weight are easy to handle when preparing the first liquid (two-component curing adhesive). The molecular weight distribution (Mw / Mn), expressed as the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), is preferably between 1.3 and 6, more preferably between 1.6 and 5, and even more preferably between 1.9 and 4. By setting the molecular weight distribution of the chloroprene polymer within this range, the physical properties of the cured product of the two-component curing adhesive are improved. In this specification, the number-average molecular weight and weight-average molecular weight are values ​​obtained by measuring by gel permeation chromatography (GPC) and converting them to polystyrene equivalents.

[0017] <<Amine-based catalysts>> Amine-based catalysts have the function of activating the isocyanate groups of the curing agent (polyisocyanate) and promoting the crosslinking reaction between the hydroxyl groups of the chloroprene polymer and the isocyanate groups of the polyisocyanate. Primary amines, secondary amines, or tertiary amines can be used as amine-based catalysts, and these can also be used in combination. Examples of primary amines include acetamide, aniline, amylamine, allylamine, isobutylamine, monoisopropanolamine (MIPA), isopropylamine, 2-ethylhexylamine, ethylenediamine, cyclohexylamine, o-toluidine, 2-butylamine, t-butylamine, propylenediamine, heptylamine, monoethanolamine, monoethylamine, mono-n-butylamine, and monomethylamine. These can be used individually or in combination of two or more.

[0018] Examples of secondary amines include diisopropanolamine (DIPA), N-ethylethanolamine, caprolactam, o-chloroaniline, diamylamine, diisobutylamine, diisopropylamine, diethanolamine, diethylamine, diethylenetriamine, dioctylamine, dicyclohexylamine, diphenylamine, di-n-butylamine, dimethylamine, piperidine, 4-pipecolin, piperazine, pyrrolidine, 2-pyrrolidone, N-butylethanolamine, N-methylformamide, and morpholine. These may be used individually or in combination of two or more.

[0019] Examples of tertiary amines include triethylamine, trioctylamine, tri-n-butylamine, tripropylamine, trialkylamines such as didecylmonomethylamine, triethanolamine, triisopropanolamine, trialcanolamines such as triisopropanolamine, triallylamine, N-ethylmorpholine, didecylmonomethylamine, diisopropylethylamine, N,N-diethylaniline, diethylbenzylamine, N,N-dibutylaniline, N,N-dibutylethanolamine, N,N-dimethylaniline, and N,N-dimethylformamide. These may be used individually or in combination of two or more.

[0020] Among these, amine-based catalysts are preferably those containing a tertiary amine (particularly a tertiary amine alone). Primary and secondary amines, depending on the type of substituent and molecular weight, tend to function preferentially as antioxidants (see below) rather than catalysts, and may undergo alteration through reaction with radicals, etc., potentially causing discoloration of the cured product of the two-component curing adhesive. Furthermore, primary and secondary amines, depending on the type of substituent and molecular weight, may have high reactivity with polyisocyanates, potentially reducing the reaction sites of polyisocyanates when the first and second liquids are mixed. In contrast, tertiary amines can effectively function as catalysts while preventing or suppressing the above problems.

[0021] Furthermore, it is preferable that the tertiary amine does not have hydroxyl groups at its molecular ends. If the tertiary amine does not have hydroxyl groups at its molecular ends, it will not react with the polyisocyanate, or its reactivity will be poor. Therefore, when the first and second solutions are mixed, there is little risk of reducing the reaction site of the polyisocyanate. For this reason, the tertiary amine can exhibit its catalytic function more effectively. It is preferable that the tertiary amine is a trialkylamine as described above. Trialkylamines, in particular, have poor reactivity with polyisocyanates, and therefore can exhibit their catalytic function very well.

[0022] The nitrogen content in the first solution is approximately 0.003% by mass or more and 0.2% by mass or less, preferably approximately 0.005% by mass or more and 0.19% by mass or less, more preferably approximately 0.007% by mass or more and 0.18% by mass or less, even more preferably approximately 0.008% by mass or more and 0.17% by mass or less, particularly preferably approximately 0.009% by mass or more and 0.16% by mass or less, and most preferably approximately 0.01% by mass or more and 0.15% by mass or less. Here, the nitrogen content in the first solution accurately reflects the content of the amine-based catalyst in the first solution. Therefore, if the nitrogen content in the first solution is within the above range, it can be determined that there is a sufficient amount of amine-based catalyst in the first solution to smoothly carry out the crosslinking reaction between the chloroprene polymer and the polyisocyanate. In this specification, the nitrogen content in the first solution is measured by elemental analysis in accordance with the Dumas method specified in JIS K 6451-1:2016.

[0023] Similarly, if the amine value of the amine catalyst is A [mgKOH / g] and the amount of amine catalyst used per 100 parts by mass of chloroprene polymer is B [parts by mass], then the product of A and B (A × B) is preferably about 60 to 5500, more preferably about 120 to 5000, even more preferably about 240 to 4500, particularly preferably about 360 to 4000, and most preferably about 480 to 3500. In this specification, the amine value is measured in accordance with ASTM D2074-07:2019. The specific amount of amine catalyst used is preferably about 0.2 parts by mass to 30 parts by mass per 100 parts by mass of chloroprene polymer, more preferably about 0.4 parts by mass to 20 parts by mass, even more preferably about 0.6 parts by mass to 10 parts by mass, and particularly preferably about 0.8 parts by mass to 5 parts by mass. By using this amount of amine-based catalyst, the crosslinking reaction between chloroprene polymer and polyisocyanate can be facilitated.

[0024] <<Organic Solvent>> The organic solvent used in the first liquid is preferably selected considering its solubility for the chloroprene polymer. Specific examples of organic solvents include toluene, xylene, acetone, methyl ethyl ketone (MEK), ethyl acetate, butyl acetate, cyclohexane, dichloromethane, tetrahydrofuran (THF), and N-methyl-2-pyrrolidone (NMP). These organic solvents may be used individually or in combination of two or more. The amount of organic solvent used is preferably about 150 parts by mass to 1900 parts by mass, and more preferably about 200 parts by mass to 1000 parts by mass, per 100 parts by mass of chloroprene polymer. In this case, the viscosity and solid content concentration of the two-component curing adhesive become appropriate, improving its coatability and enhancing the adhesive strength of the cured product.

[0025] <<Acid Acceptor>> The first liquid preferably contains an acid acceptor. Chloroprene polymer has the property of undergoing a dehydrochlorination reaction over time when exposed to sunlight or stored at high temperatures for a long period of time. The acid acceptor plays the role of accepting the generated hydrochloric acid. Therefore, by incorporating an acid acceptor, the storage stability of the first liquid can be improved and discoloration can be suppressed. The acid acceptor is not particularly limited, but examples include zinc oxide, magnesium oxide, calcium oxide, and aluminum oxide. These compounds may be used individually or in combination of two or more. The content of the acid acceptor is preferably 0.05 parts by mass to about 10 parts by mass per 100 parts by mass of chloroprene polymer. By including an acid acceptor within this range, the storage stability of the first liquid can be further improved, and discoloration of the cured product of the two-component curing adhesive can be suppressed. In addition, the cured product of the two-component curing adhesive can exhibit sufficiently high adhesive strength.

[0026] For example, methods for producing zinc oxide include the indirect method, in which metallic zinc is vaporized to generate zinc vapor, which is then oxidized to produce zinc oxide; the direct method, in which zinc is vaporized while reducing zinc from zinc ore to generate zinc vapor, which is then oxidized to produce zinc oxide; and the wet method, in which zinc carbonate is produced in an aqueous phase and then calcined. Here, the powder characteristics such as particle size, surface area, and particle shape differ depending on the manufacturing method, but any zinc oxide can be used. The particle shape can be amorphous, porous, fine particles, spherical, flaky, needle-shaped, or tetrapod-shaped. Furthermore, it is possible to improve the adhesive strength of the cured product of the two-component curing adhesive by surface treating the acid acceptor with a silane coupling agent, titanate-based coupling agent, or aluminum-based coupling agent before mixing it into the first liquid.

[0027] <<Anti-aging agent>> The first solution may contain an anti-aging agent. By including an anti-aging agent, the deterioration of the crosslinked product of the chloroprene polymer and polyisocyanate (cured product of a two-component curing adhesive) can be prevented or suppressed. As the anti-aging agent, at least one selected from the group consisting of amine-based anti-aging agents, phenol-based anti-aging agents, sulfur-based anti-aging agents, and phosphorus-based anti-aging agents can be used. Examples of amine-based anti-aging agents include 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, p-(p-toluenesulfonylamide)diphenylamine, and N-isopropyl-N'-p-phenylenediamine.

[0028] Examples of phenolic antioxidants include 2,2'-methylenebis(4-methyl-6-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol). Examples of sulfur-based antioxidants include 2-mercaptobenzimidazole and 2-mercaptomethylbenzimidazole. Examples of phosphorus-based antioxidants include tris(nonylphenyl)phosphite.

[0029] The amount of antioxidant used is preferably 0.2 parts by mass or more and 8 parts by mass or less per 100 parts by mass of chloroprene polymer, more preferably 0.4 parts by mass or more and 6 parts by mass or less, even more preferably 0.6 parts by mass or more and 4 parts by mass or less, particularly preferably 0.8 parts by mass or more and 3 parts by mass or less, and most preferably 1 part by mass or more and 2 parts by mass or less. By setting the content of the antioxidant per 100 parts by mass of chloroprene polymer within the above range, it is possible to improve the mechanical properties while suppressing the deterioration of the crosslinked product between the chloroprene polymer and the polyisocyanate.

[0030] <<Tackifying Resin>> The first liquid may contain a tackifying resin. By including a tackifying resin, the adhesive strength of the cured product of a two-component curing adhesive can be improved by increasing the tackiness (tack) immediately after preparing a mixture of the first and second liquids and applying it to the adherend. The tackifying resin is a resin that can be used in the field of solvent-based adhesives, and its type is not particularly limited. Specific examples of tackifying resins include, for example, rosin resin, rosin ester resin, hydrogenated rosin resin, polymerized rosin resin, α-pinene resin, β-pinene resin, terpene phenol resin, C5 fraction petroleum resin, C9 fraction petroleum resin, C5 / C9 fraction petroleum resin, DCPD petroleum resin, alkylphenol resin, xylene resin, coumarone resin, coumarone indene resin, etc. For example, when used for bonding the soles or parts of footwear, a resin with a softening point of about 80°C to 150°C is preferred, taking into consideration the heat-resistant adhesive strength.

[0031] The amount of tackifying resin used is preferably 5 to 100 parts by mass, and more preferably 20 to 80 parts by mass, per 100 parts by mass of chloroprene polymer. By using tackifying resin within this range, it is possible to improve both the initial adhesive strength and the normal adhesive strength of the two-component curing adhesive.

[0032] <Second Solution> The second solution contains polyisocyanate. By using polyisocyanate, the rate of the crosslinking reaction with chloroprene polymer can be increased, and sufficient adhesive strength can be achieved in the cured product of the two-component curing adhesive. <<Polyisocyanate>> Polyisocyanate is a compound having two or more isocyanate groups. Examples of polyisocyanates include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, or their adducts, isocyanurates, biuretes, polymers (homopolymers), etc.

[0033] Aromatic polyisocyanates are not particularly limited, but examples include 1,3-phenylenediisocyanate, 4,4'-diphenyldiisocyanate, 1,4-phenylenediisocyanate, 4,4'-diphenylmethanediisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, 4,4'-toluidinediisocyanate, 2,4,6-triisocyanatetoluene, 1,3,5-triisocyanatebenzene, dianisidinediisocyanate, 4,4'-diphenyletherdiisocyanate, 4,4',4''-triphenylmethanetriisocyanate, tris(p-isocyanatophenyl)thiophosphate, tris(4-isocyanatophenyl)methane, and polymethylene polyphenyl polyisocyanate.

[0034] The aliphatic polyisocyanates are not particularly limited, but examples include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate. Alicyclic polyisocyanates are not particularly limited, but examples include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), toluene diisocyanate, and the like.

[0035] Among these, the polyisocyanate is preferably an aromatic polyisocyanate or an alicyclic polyisocyanate, and more preferably contains at least one selected from the group consisting of tris(p-isocyanatophenyl)thiophosphate, a homopolymer of toluene diisocyanate, tris(4-isocyanatophenyl)methane, and polymethylene polyphenyl polyisocyanate. By using these polyisocyanates, the adhesive strength of the cured product of the two-component curing adhesive can be improved. The amount of polyisocyanate used is preferably about 1 to 10 parts by mass, and more preferably about 3 to 8 parts by mass, per 100 parts by mass of chloroprene polymer. In this case, the necessary and sufficient adhesive strength is exhibited in the cured product of the two-component curing adhesive.

[0036] The organic solvent used in the second liquid is preferably selected considering the solubility of the polyisocyanate. Specific examples of organic solvents include toluene, xylene, acetone, methyl ethyl ketone (MEK), ethyl acetate, butyl acetate, cyclohexane, dichloromethane, tetrahydrofuran (THF), and N-methyl-2-pyrrolidone (NMP). These organic solvents may be used individually or in combination of two or more. Depending on the application and required performance, the two-component curing adhesive (first liquid and / or second liquid) may optionally contain processing aids, plasticizers, thickeners, vulcanization accelerators, fillers (reinforcements), pigments, colorants, antioxidants, UV absorbers, fungicides, preservatives, antibacterial agents, rust inhibitors, polymers other than chloroprene polymer, etc.

[0037] <<Processing Aid>> The processing aid preferably contains at least one selected from the group consisting of fatty acids such as stearic acid, fatty acid metal salts such as zinc stearate, and fatty acid amides such as stearic acid amide, and more preferably contains at least one selected from the group consisting of fatty acids and fatty acid metal salts. This improves the applicability of the two-component curing adhesive (a mixture of the first and second liquids). The amount of processing aid used is preferably 0.1 parts by mass to 5 parts by mass, more preferably 0.2 parts by mass to 4 parts by mass, and even more preferably 0.3 parts by mass to 3 parts by mass, per 100 parts by mass of chloroprene polymer. By using the processing aid in the above range of content, the balance between the applicability of the two-component curing adhesive (a mixture of the first and second liquids) and the mechanical properties of the cured product can be improved.

[0038] <<Plasticizer>> The plasticizer may include, for example, at least one selected from the group consisting of aliphatic dibasic acid plasticizers, ester plasticizers such as epoxy plasticizers, and process oils such as aromatic process oils, naphthenic process oils, and paraffinic process oils. The plasticizer preferably includes an aliphatic dibasic acid plasticizer, more preferably at least one selected from the group consisting of dioctyl sebacate, dioctyl azelaate, dioctyl adipate, diisononyl adipate, and diisodecyl adipate, and even more preferably dioctyl sebacate. The plasticizer also preferably includes a process oil, and more preferably at least one selected from the group consisting of aromatic process oils and naphthenic process oils. The amount of plasticizer used is preferably about 3 to 30 parts by mass, more preferably about 4 to 25 parts by mass, and even more preferably about 5 to 20 parts by mass, per 100 parts by mass of chloroprene polymer. By using a plasticizer in the above-mentioned range, it is possible to improve the balance between the applicability of a two-component curing adhesive (a mixture of the first and second components) and the mechanical properties of its cured product.

[0039] The amount of the second liquid used is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 3 to 6 parts by mass, per 100 parts by mass of the first liquid. The solid content (polyisocyanate) in the second liquid is not particularly limited, but is preferably 20% to 40% by mass, and more preferably 25% to 35% by mass. By using the second liquid in the above ratio, the crosslinking reaction between the chloroprene polymer and the polyisocyanate can be carried out more smoothly and reliably while preventing a shortening of the pot life.

[0040] <Physical Properties of Two-Component Curing Adhesives> In accordance with JIS K 6854-3:1999 (ISO 11339:1993), the initial adhesive strength of two-component curing adhesives, measured by a T-type peel test after a standing period of 3 hours, is preferably about 1 N / mm or more, more preferably about 1.3 N / mm or more, and even more preferably about 1.6 N / mm or more. The upper limit of the initial adhesive strength after a standing period of 3 hours is not particularly limited, but is about 2.5 N / mm. Therefore, the initial adhesive strength after a standing period of 3 hours can be, for example, between 1 N / mm and 2.5 N / mm. The cured product of such a two-component curing adhesive can be judged to have excellent adhesive strength.

[0041] Furthermore, in accordance with JIS K 6854-3:1999 (ISO 11339:1993), the initial adhesive strength of the two-component curing adhesive, measured by a T-type peel test after a standing period of one day, is preferably around 5 N / mm or more, more preferably around 6 N / mm or more, even more preferably around 7 N / mm or more, and particularly preferably around 8 N / mm or more. The upper limit of the initial adhesive strength after a standing period of one day is not particularly limited, but is approximately 10 N / mm. Therefore, the initial adhesive strength after a standing period of one day can be, for example, between 5 N / mm and 10 N / mm. The cured product of such a two-component curing adhesive can also be judged to have excellent adhesive strength.

[0042] The two-component curing adhesive preferably has a pot life of 20 minutes or more at 25°C, measured in accordance with JIS K 6870:2008, more preferably 25 minutes or more, even more preferably 30 minutes or more, particularly preferably 35 minutes or more, and most preferably 40 minutes or more. The upper limit of the pot life is not particularly limited, but is approximately 80 minutes. Therefore, the pot life can be, for example, between 20 minutes and 80 minutes. Such a two-component curing adhesive prevents the curing time from becoming extremely long while also providing good handling of the mixture of the first and second components.

[0043] The use conditions of the two-component curable adhesive as described above are not particularly limited. Examples of the adherend include metals, wood, concrete, rubber, fiber cloth, ceramics, and the like. For example, in footwear, it can be used for bonding fabrics (knitted, woven, or non-woven fabrics made of nylon, polyester, cotton, etc.), natural leathers (cowhide, kangaroo leather, etc.), artificial leathers (polyurethane, polyvinyl chloride resin, etc.), vulcanized rubbers (styrene-butadiene rubber (SBR), chloroprene rubber (CR), isoprene rubber (IR), butyl rubber (IIR), nitrile rubber (NBR), butadiene rubber (BR)), resins (foams or non-foams made of polyurethane or ethylene-vinyl acetate copolymer, etc.).

[0044] The method and device specifications for applying the mixture of the first liquid and the second liquid to the adherend are also not particularly limited. Specifically, examples of the method for applying the mixture include the curtain flow coater method, bar coater method, roll coater method, spray method, etc. Also, the roll coater method includes the gravure roll coater method, reverse gravure coater method, etc. The method can be selected according to the purpose of applying the mixture, etc. For example, when uniformly applying the mixture to the surface of the adherend, the operation by the spray method is preferable, and when applying to a part with a small coating area (small adherend) such as a small part, manual work with a brush is preferable. The crimping operation after overlapping the two adherends may be either a hot press or a normal temperature press. The crimping device, crimping conditions, and press pressure at this time are also not particularly limited. Also, the adhesion between the two adherends and the mixture may be performed by integral molding adhesion.

[0045] Further, it may be provided in each of the aspects described below.

[0046] (1) A two-component curable adhesive that uses a mixture of a first liquid and a second liquid, wherein the first liquid contains a chloroprene polymer and an amine-based catalyst, and the nitrogen content is 0.003% by mass or more and 0.2% by mass or less, and the second liquid contains a polyisocyanate.

[0047] (2) The two-component curable adhesive according to (1) above, wherein the amine-based catalyst contains a tertiary amine.

[0048] (3) In the two-component curable adhesive according to (2) above, the tertiary amine is a two-component curable adhesive that does not have a hydroxyl group at the molecular end.

[0049] (4) In the two-component curable adhesive according to (2) or (3) above, the tertiary amine is a trialkylamine, which is a two-component curable adhesive.

[0050] (5) In the two-component curable adhesive according to any one of (1) to (4) above, the amount of the amine-based catalyst used is 0.2 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the chloroprene polymer, which is a two-component curable adhesive.

[0051] (6) In the two-component curable adhesive according to any one of (1) to (5) above, the crystallinity of the chloroprene polymer is 15% or more and 30% or less, which is a two-component curable adhesive.

[0052] (7) In the two-component curable adhesive according to any one of (1) to (6) above, the Mooney viscosity of the chloroprene polymer at 100 ° C is 30 or more and 80 or less, which is a two-component curable adhesive.

[0053] (8) In the two-component curable adhesive according to any one of (1) to (7) above, the polyisocyanate contains at least one selected from the group consisting of tris(p-isocyanatophenyl) thiophosphate, a homopolymer of toluene diisocyanate, tris(4-isocyanatophenyl) methane, and polymethylene polyphenyl polyisocyanate, which is a two-component curable adhesive.

[0054] (9) In the two-component curable adhesive according to any one of (1) to (8) above, the amount of the second liquid used is 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the first liquid, which is a two-component curable adhesive.

[0055] (10) In the two-component curable adhesive according to any one of (1) to (9) above, the initial adhesive strength measured by the T-peel test after a standing time of 3 hours in accordance with JIS K 6854-3:1999 is 1 N / mm or more, which is a two-component curable adhesive.

[0056] (11) A two-component curing adhesive as described in any one of (1) to (10) above, wherein the initial adhesive strength measured by a T-type peel test after a standing period of 1 day in accordance with JIS K 6854-3:1999 is 5 N / mm or more.

[0057] (12) A two-component curing adhesive as described in any one of (1) to (11) above, wherein the pot life at 25°C, as measured in accordance with JIS K 6870:2008, is 20 minutes or more. Of course, this is not limited to this.

[0058] Finally, while various embodiments relating to this disclosure have been described, these are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0059] The following will provide a more detailed explanation of two-component curing adhesives using the following examples and comparative examples, but these are not limited to the following examples.

[0060] 1. Preparation of raw materials and chloroprene polymer The chloroprene polymer was manufactured as follows: First, in a reactor with an internal volume of 10 liters, 110 parts by mass of water, 4 parts by mass of sodium rosin acid, 0.7 parts by mass of sodium hydroxide, 0.4 parts by mass of sodium formaldehyde naphthalene sulfonic acid condensate, and 0.5 parts by mass of sodium sulfite were charged under a nitrogen atmosphere. After these were dissolved, 100 parts by mass of chloroprene and 0.25 parts by mass of n-dodecyl mercaptan were added while stirring.

[0061] Next, 0.1 parts by mass of potassium persulfate was used as a polymerization initiator, and polymerization was carried out at 10°C under a nitrogen atmosphere. When the final polymerization rate reached 70%, a phenothiazine emulsion was added to stop the polymerization. Unreacted monomers were removed under reduced pressure to obtain a chloroprene polymer latex. This latex was freeze-dried to obtain the chloroprene polymer. The obtained chloroprene polymer had a Mooney viscosity MS (2 + 2.5) at 100°C of 48, a degree of crystallinity of 22.5%, a number-average molecular weight (Mn) of 274,000, and a molecular weight distribution (Mw / Mn) of 2. The chloroprene polymer was analyzed by nuclear magnetic resonance spectroscopy in a deuterated chloroform solution. １ Confirmation by 1H-NMR revealed the presence of a hydroxyl group.

[0062] - Amine catalysts: Triethylamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade), Didecyl monomethylamine (manufactured by Kao Corporation, "Farmin M2-1095") - Other catalysts: Potassium stearate (manufactured by NOF Corporation, "Nonsal SK-1"), Iron(II) chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako First Grade)

[0063] - Acid acceptors: Magnesium oxide (manufactured by Kyowa Chemical Industry Co., Ltd., "Kyowa Mag 150"), Zinc oxide (manufactured by Sakai Co., Ltd., "Zinc Oxide Type 2") - Anti-aging agent: 2,6-di-tert-butyl-p-cresol (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Nocrac 200")

[0064] - Polyisocyanate tris(p-isocyanatophenyl) thiophosphate 27% by mass / ethyl acetate 73% by mass (manufactured by Sumika Covestro Urethane Co., Ltd., "Desmodule RFE") - Toluene diisocyanate homopolymer mixture 35% by mass / ethyl acetate 65% by mass (manufactured by Sumika Covestro Urethane Co., Ltd., "Desmodule RC")

[0065] 2. Preparation of a two-component curing adhesive (Example 1) - The first solution was prepared by stirring 100 parts by mass of chloroprene polymer, 4 parts by mass of magnesium oxide, 5 parts by mass of zinc oxide, 2 parts by mass of 2,6-di-tert-butyl-p-cresol, 510 parts by mass of toluene, and 1 part by mass of triethylamine in a ball mill for 2 days. - The second solution was prepared by using tris(p-isocyanatophenyl)thiophosphate / ethyl acetate as the second solution. The amount of the second solution used was 3 parts by mass per 100 parts by mass of the first solution.

[0066] (Example 2) - The first solution was prepared in the same manner as in Example 1, except that 1 part by mass of triethylamine in the first solution was changed to 5 parts by mass of triethylamine. - The second solution was prepared in the same manner as in Example 1.

[0067] (Example 3) - The first solution was prepared in the same manner as in Example 1, except that 1 part by mass of triethylamine in the first solution was replaced with 1 part by mass of didecyl monomethylamine. - The second solution was prepared in the same manner as in Example 1.

[0068] (Example 4) - The first solution was prepared in the same manner as in Example 1, except that 1 part by mass of triethylamine in the first solution was replaced with 20 parts by mass of didecyl monomethylamine. - The second solution was prepared in the same manner as in Example 1.

[0069] (Example 5) - The first solution was the same as in Example 1. - For the second solution, a homopolymer mixture of toluene diisocyanate / ethyl acetate was used. The amount of the second solution used was 3 parts by mass per 100 parts by mass of the first solution.

[0070] (Comparative Example 1) - The first solution was prepared in the same manner as in Example 1, except that the use of 1 part by mass of triethylamine in the first solution was omitted. - The second solution was prepared in the same manner as in Example 1.

[0071] (Comparative Example 2) The first solution was prepared in the same manner as in Example 1, except that 1 part by mass of triethylamine in the first solution was replaced with 0.1 parts by mass of triethylamine. The second solution was prepared in the same manner as in Example 1.

[0072] (Comparative Example 3) - The first solution was prepared in the same manner as in Example 1, except that 1 part by mass of triethylamine in the first solution was replaced with 10 parts by mass of triethylamine. - The second solution was prepared in the same manner as in Example 1.

[0073] (Comparative Example 4) - The first solution was prepared in the same manner as in Example 1, except that 1 part by mass of triethylamine in the first solution was replaced with 5 parts by mass of potassium stearate. - The second solution was prepared in the same manner as in Example 1.

[0074] (Comparative Example 5) - The first solution was prepared in the same manner as in Example 1, except that 1 part by mass of triethylamine in the first solution was replaced with 5 parts by mass of iron(II) chloride. - The second solution was prepared in the same manner as in Example 1.

[0075] 3. Measurement and Evaluation 3-1. Measurement of Mooney Viscosity of Chloroprene Polymer The Mooney viscosity of chloroprene polymer at 100°C was measured in accordance with JIS K 6300-1:2013. The measurement samples were prepared in accordance with "5.3.1 Sampling and Preparation of Test Specimens, 2.2) Roll Passing Method" of JIS K-6300-1:2013. The measurement was performed using a Mooney viscometer (Shimadzu Corporation, "SMV-300") with an S-type rotor. The measurement conditions were a test temperature of 100°C, a preheating time of 2 minutes, a test time of 2.5 minutes, and a die sealing force of 11.5 kN. This yielded the Mooney viscosity MS(2+2.5) at 100°C.

[0076] 3-2. Measurement of the Crystallinity of Chloroprene Polymer First, the density of the chloroprene polymer was measured in accordance with Method A specified in JIS K 6268:1998 to identify the crystalline region (density 1.353) and the amorphous region (density 1.230). Then, the ratio (%) of the mass of the crystalline region to the total mass of the chloroprene polymer was calculated and expressed as the degree of crystallinity (%) of the chloroprene polymer.

[0077] 3-3. Measurement of Number-Average Molecular Weight (Mn) and Weight-Average Molecular Weight (Mw) of Chloroprene Polymers The number-average molecular weight and weight-average molecular weight of chloroprene polymers were measured by gel permeation chromatography (GPC) under the following conditions, and the values ​​were determined in polystyrene equivalents. Instrument name: SYSTEM-21 Shodex (manufactured by Showa Denko K.K.) Column: 3 PL gel MIXED-B columns in series Temperature: 40°C Detection: Differential refractive index Solvent: Tetrahydrofuran Concentration: 2% by mass Calibration curve: Created using standard polystyrene (PS) (manufactured by PL Co., Ltd.).

[0078] 3-4. Measurement of Nitrogen Content in Solution 1 The nitrogen content in Solution 1 was measured using a nitrogen analyzer (Sumika Analysis Center Co., Ltd., "Sumigraph 220F") by elemental analysis in accordance with the Dumas method specified in JIS K 6451-1:2016.

[0079] 3-5. Measurement of Initial Adhesion Strength The initial adhesion strength of the two-component curing adhesives in each example and comparative example was measured by a T-type peel test in accordance with JIS K 6854-3:1999. Canvas was used for both adherends. The open time (the time between applying the mixture of the first and second components to the adherends and bonding them together) was set to 30 minutes. This operation was performed in an atmosphere of 23°C and 30% RH humidity. After that, the two were bonded together and bonded by rolling a 10-pound roll back and forth five times. The initial adhesion strength after a standing time (set time) of 3 hours is the adhesion strength after 3 hours in an atmosphere of 23°C and 30% RH humidity after bonding, and the initial adhesion strength after a standing time (set time) of 1 day is the adhesion strength after 1 day in an atmosphere of 23°C and 30% RH after bonding.

[0080] 3-6. Measurement of Pot Life The pot life of the two-component curing adhesives in each example and comparative example was measured at 25°C in accordance with JIS K 6870:2008. Pot life was defined as the time it took for the viscosity of the mixture to reach 1.5 times its initial value after mixing the first and second components.

[0081] The results are shown in Table 1 below.

[0082] The two-component curing adhesives in each example were confirmed to exhibit high adhesive strength at room temperature and in a short time. Furthermore, the two-component curing adhesives in each example had a sufficient pot life and excellent handling properties. In contrast, the two-component curing adhesives in each comparative example were found to either not exhibit sufficient adhesive strength or to have an extremely short pot life.

[0083] Furthermore, even when a primary or secondary amine is used as the amine catalyst, similar good results can be obtained by adjusting the nitrogen content in the first solution to a range of 0.003% by mass or more and 0.2% by mass or less, and evaluating it in the same manner as in the above examples. Moreover, when a chloroprene polymer having hydroxyl groups is used, with a Mooney viscosity MS (2 + 2.5) at 100°C set to a range of 30 or more and 80 or less, and a crystallinity set to a range of 15% or more and 30% or less, and evaluated in the same manner as in the above examples, similar good results can be obtained.

Claims

1. A two-component curing adhesive used by mixing a first liquid and a second liquid, wherein the first liquid contains a chloroprene polymer and an amine-based catalyst, and has a nitrogen content of 0.003% by mass or more and 0.2% by mass or less, and the second liquid contains a polyisocyanate.

2. A two-component curing adhesive according to claim 1, wherein the amine catalyst contains a tertiary amine.

3. A two-component curing adhesive according to claim 2, wherein the tertiary amine does not have hydroxyl groups at the molecular ends.

4. A two-component curable adhesive according to claim 2 or claim 3, wherein the tertiary amine is a trialkylamine.

5. A two-component curing adhesive according to claim 1 or claim 2, wherein the amount of the amine-based catalyst used is 0.2 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the chloroprene polymer.

6. A two-component curing adhesive according to claim 1 or claim 2, wherein the degree of crystallinity of the chloroprene polymer is 15% or more and 30% or less.

7. A two-component curing adhesive according to claim 1 or claim 2, wherein the Mooney viscosity of the chloroprene polymer at 100°C is 30 or more and 80 or less.

8. A two-component curing adhesive according to claim 1 or claim 2, wherein the polyisocyanate comprises at least one selected from the group consisting of tris(p-isocyanatophenyl)thiophosphate, a homopolymer of toluene diisocyanate, tris(4-isocyanatophenyl)methane, and polymethylene polyphenyl polyisocyanate.

9. A two-component curing adhesive according to claim 1 or claim 2, wherein the amount of the second liquid used is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the first liquid.

10. A two-component curing adhesive according to claim 1 or claim 2, wherein the initial adhesive strength measured by a T-type peel test after a standing time of 3 hours in accordance with JIS K 6854-3:1999 is 1 N / mm or more.

11. A two-component curing adhesive according to claim 1 or claim 2, wherein the initial adhesive strength measured by a T-type peel test after a standing period of 1 day in accordance with JIS K 6854-3:1999 is 5 N / mm or more.

12. A two-component curing adhesive according to claim 1 or claim 2, wherein the pot life at 25°C, as measured in accordance with JIS K 6870:2008, is 20 minutes or more.

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