2-Cyanoacrylate adhesive composition

Abstract

The present invention provides a 2-cyanoacrylate adhesive composition that can suppress the decrease in curing rate for aluminum during storage. [Solution] A 2-cyanoacrylate adhesive composition having a content of trialkyl phosphate with an alkyl group having 1 to 4 carbon atoms in the alkyl group of 700 ppm by mass or less.

Description

Technical Field

[0001] The present disclosure relates to a 2-cyanoacrylate-based adhesive composition.

Background Art

[0002] Due to the specific anionic polymerization property of 2-cyanoacrylate ester, which is the main component of the 2-cyanoacrylate-based adhesive composition, polymerization is initiated by weak anions such as a small amount of moisture adhering to the surface of the adherend, and various materials can be firmly joined in a short time. Therefore, it is used as a so-called instant adhesive in a wide range of fields such as industrial, medical, and household applications.

[0003] Although the 2-cyanoacrylate-based adhesive composition is excellent in the property of firmly joining various materials in a short time (hereinafter referred to as "instant adhesiveness"), the quality may deteriorate, for example, the adhesive strength and the curing rate may decrease during storage. For the purpose of improving the storage stability of the 2-cyanoacrylate-based adhesive composition, for example, Patent Document 1 describes a 2-cyanoacrylate-based adhesive composition characterized by containing (B) sulfur dioxide (SO2) in an amount of 0.001 to 0.01 parts by weight and (C) trifluoromethanesulfonic acid in an amount of 0.0001 to 0.01 parts by weight with respect to 100 parts by weight of (A) 2-cyanoacrylate. Further, Patent Document 2 describes a photocurable adhesive composition containing a Group 8 transition metal metallocene compound and a 2-cyanoacrylate compound and not containing a compound having a benzoquinone structure or having a content of a compound having a benzoquinone structure exceeding 0 ppm and less than 4 ppm.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] While Patent Document 1 describes that the stability of a 2-cyanoacrylate-based instant adhesive is improved when a glass container is used, the stability for materials other than glass has not been investigated. Furthermore, while Patent Document 2 describes that the storage stability of a photocurable adhesive composition can be improved by reducing the content of compounds having a benzoquinone structure that are mixed in as impurities during the manufacturing process of the 2-cyanoacrylate compound, the effect has only been confirmed for photocurable adhesive compositions. In 2-cyanoacrylate-based adhesive compositions, including non-photocurable ones, the components other than compounds having a benzoquinone structure that affect storage stability have not yet been clarified.

[0006] This disclosure has been made in view of the above-mentioned problems and aims to provide a 2-cyanoacrylate adhesive composition that can suppress the decrease in the curing rate of aluminum during storage. [Means for solving the problem]

[0007] As a result of diligent research, the present inventors have found that by limiting the amount of trialkyl phosphate containing alkyl groups with 1 to 4 carbon atoms in a 2-cyanoacrylate adhesive composition to a predetermined amount or less, the decrease in the curing rate for aluminum after storage is suppressed, leading to the completion of this disclosure.

[0008] In other words, the 2-cyanoacrylate adhesive composition relating to this disclosure is as follows: 1. A 2-cyanoacrylate adhesive composition having a trialkyl phosphate content of 700 ppm by mass or less, wherein the alkyl group has 1 to 4 carbon atoms. 2. The 2-cyanoacrylate adhesive composition described in 1. above, wherein the content of the above trialkyl phosphate is 50 ppm by mass or less. 3. The 2-cyanoacrylate adhesive composition according to 1. or 2. above, wherein the trialkyl phosphate is triethyl phosphate. 4. A 2-cyanoacrylate adhesive composition for use with aluminum, as described in any of items 1 to 3 above. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a 2-cyanoacrylate adhesive composition that can suppress the decrease in the curing rate of aluminum during storage. [Modes for carrying out the invention]

[0010] One embodiment of this disclosure is described below, but this disclosure is not limited to this embodiment.

[0011] <2-Cyanoacrylate-based adhesive composition> The 2-cyanoacrylate adhesive composition of this disclosure (hereinafter also simply referred to as "the composition") is characterized in that the content of trialkyl phosphate with an alkyl group having 1 to 4 carbon atoms is 700 ppm by mass or less. The matters that define this disclosure will be described in detail below.

[0012] (2-cyanoacrylate compound) Examples of 2-cyanoacrylate compounds included in the compositions of this disclosure include compounds represented by the following formula (1). CH2=C(CN)-COOR 1 …(1) (In formula (1), R 1 This represents a saturated or unsaturated linear hydrocarbon group having 1 to 20 carbon atoms that may have a halogen atom or an ether bond, a saturated or unsaturated branched hydrocarbon group having 3 to 20 carbon atoms that may have a halogen atom or an ether bond, a saturated or unsaturated aliphatic cyclic hydrocarbon group having 3 to 20 carbon atoms that may have a halogen atom or an ether bond, or an aromatic hydrocarbon group having 5 to 20 carbon atoms that may have a halogen atom or an ether bond.

[0013] Specific examples of 2-cyanoacrylate compounds include methyl, ethyl, chloroethyl, n-propyl, i-propyl, allyl, propargyl, n-butyl, i-butyl, n-pentyl, n-hexyl, amyl, 2-methyl-3-butenyl, 3-methyl-3-butenyl, 2-pentenyl, 6-chlorohexyl, cyclohexyl, phenyl, tetrahydrofurfuryl, 2-hexenyl, 4-methylpentenyl, 3-methyl-2-cyclohexenyl, norbornyl, heptyl, cyclohexanemethyl, cycloheptyl, 1-methylcyclohexyl, 2-methylcyclohexyl, 3-methyl-cyclohexyl, 2-ethylhexyl, n-octyl, 2-octyl, cyclooctyl, and cyclohexyl groups. Examples of ester compounds that are replaced by a methyl thane group, a 2,3-dimethylcyclohexyl group, an n-nonyl group, an isononyl group, an oxononyl group, an n-decyl group, an isodecyl group, an n-dodecyl group, a 2-methoxyethyl group, a 2-ethoxyethyl group, a 2-ethoxy-2-ethoxyethyl group, a butoxyethoxyethyl group, a 1-(2-methoxy-1-methylethoxy)propyl group, a 2,2,2-trifluoroethyl group, a hexafluoroisopropyl group, a lauryl group, an isotridecyl group, a myristyl group, a cetyl group, a stearyl group, an oleyl group, a behenyl group, a hexyldecyl group, an octyldodecyl group, a benzyl group, a chlorophenyl group, a 2-pentyloxyethyl group, a 2-hexyloxyethyl group, a 2-cyclohexyloxyethyl group, a 2-(2-ethylhexyloxy)ethyl group, or a 2-phenoxyethyl group.

[0014] Among the above, ester compounds are preferred in which the hydrogen atoms in the carboxyl group of 2-cyanoacrylate are replaced by saturated linear hydrocarbon groups having 1 to 10 carbon atoms, which may have ether bonds; saturated branched hydrocarbon groups having 3 to 10 carbon atoms, which may have ether bonds; saturated aliphatic cyclic hydrocarbon groups having 3 to 12 carbon atoms, which may have ether bonds; or aromatic hydrocarbon groups having 6 to 12 carbon atoms. Of these, ester compounds are particularly preferred in which the hydrogen atoms in the carboxyl group of 2-cyanoacrylate are replaced by methyl groups, ethyl groups, n-propyl groups, i-propyl groups, n-butyl groups, i-butyl groups, cyclohexyl groups, phenyl groups, tetrahydrofurfuryl groups, 2-ethylhexyl groups, n-octyl groups, 2-octyl groups, 2-methoxyethyl groups, 2-ethoxyethyl groups, or 1-(2-methoxy-1-methylethoxy)propyl groups. The compositions disclosed herein may contain one 2-cyanoacrylate compound alone, or two or more compounds.

[0015] The total content of the 2-cyanoacrylate compound in the composition of this disclosure is preferably 50% by mass or more, more preferably 60% to 99.9% by mass, and even more preferably 65% ​​to 99.9% by mass, based on the total mass of the composition of this disclosure, from the viewpoint of curing speed, adhesive strength, etc.

[0016] (trialkyl phosphate) The composition of this disclosure has a content of trialkyl phosphate with an alkyl group having 1 to 4 carbon atoms in the alkyl group of 700 ppm by mass or less. By limiting the content of trialkyl phosphate with an alkyl group having 1 to 4 carbon atoms in the alkyl group to 700 ppm by mass or less, it is possible to suppress the decrease in the curing rate of the 2-cyanoacrylate adhesive composition with respect to aluminum during storage. The alkyl group of the trialkyl phosphate has 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms, and more preferably 2 carbon atoms (i.e., triethyl phosphate).

[0017] Trialkyl phosphate is presumed to be a compound that混入 as an impurity due to the manufacturing process of the 2-cyanoacrylate compound. That is, the 2-cyanoacrylate compound is generally produced by subjecting cyanoacetate and formaldehyde to a dehydration condensation reaction with a base catalyst and then heating and depolymerizing the condensate obtained by this reaction. In this manufacturing process, a phosphate compound (such as phosphoric acid or diphosphorus pentoxide) may be used as a depolymerization catalyst and / or an anionic polymerization inhibitor. In this case, it is considered that the phosphate compound reacts with the decomposition products generated during polymerization (specifically, alcohols having a structure corresponding to the ester moiety of 2-cyanoacrylate), and the trialkyl phosphate thus produced is contained as an impurity in the product of the 2-cyanoacrylate compound.

[0018] From the viewpoint of suppressing a decrease in the curing rate with respect to aluminum during storage, the content of trialkyl phosphate in the 2-cyanoacrylate-based adhesive composition of the present disclosure is preferably 700 mass ppm or less, more preferably 500 mass ppm or less, still more preferably 300 mass ppm or less, particularly preferably 100 mass ppm or less, and most preferably 50 mass ppm or less. When the content of trialkyl phosphate is 50 mass ppm or less, not only can a decrease in the curing rate with respect to aluminum during storage be suppressed, but it is also possible to improve the initial curing rate.

[0019] It should be noted that the part "混入 as an impurity" in the translation of is a placeholder for the original Japanese word which needs to be accurately filled in according to the specific context. Here it is left as is for the time to emphasize the need for further refinement.The method for reducing the content of trialkyl phosphate in the 2-cyanoacrylate adhesive composition of the present disclosure is not particularly limited. For example, in the case of distillation, as the distillation method, a method of heating a 2-cyanoacrylate compound containing more than a predetermined amount of trialkyl phosphate using a packed distillation column, a plate distillation column, or a rectification column can be mentioned. When purifying using a distillation column, for example, the number of theoretical plates of the distillation column is preferably 3 or more. Also, after manufacturing the 2-cyanoacrylate compound in a kettle, thoroughly cleaning the kettle with an alkaline cleaning agent or the like before manufacturing the 2-cyanoacrylate compound again, and not reusing the solvent used during manufacturing can also suppress the mixing of trialkyl phosphate from the previous batch to the next batch and reduce the content of trialkyl phosphate.

[0020] The content of trialkyl phosphate in the 2-cyanoacrylate adhesive composition of the present disclosure can be measured by gas chromatography.

[0021] (Other components) In the 2-cyanoacrylate adhesive composition of the present disclosure, for the purpose of improving storage stability, anionic polymerization inhibitors such as sulfur dioxide, p-toluenesulfonic acid, methanesulfonic acid, propane sultone, boron trifluoride complex, and radical polymerization inhibitors such as hydroquinone, catechol, pyrogallol can be added. Also, for the purpose of improving the curing rate, curing accelerators such as polyethylene glycol derivatives, crown ethers, calixarenes can be added. Furthermore, thickeners, plasticizers, fillers, elastomers, thixotropic agents, adhesion promoters, crosslinking agents, dyes, fragrances, etc. may be added according to the purpose. The addition amounts of these additives can be appropriately selected within the range that suppresses the decrease in the curing rate with respect to aluminum during storage due to the reduction of trialkyl phosphate of the present disclosure and does not impair the practicality or economy of the adhesive of the present disclosure.

[0022] 4. Bonded products and their manufacturing methods The 2-cyanoacrylate adhesive composition of this disclosure is excellent at suppressing the decrease in curing rate for aluminum during storage, and is therefore suitable for use as an adhesive for joining two parts, at least one of which is made of aluminum, in a manufacturing method for joining two parts. Accordingly, according to this disclosure, a joined product can be manufactured comprising at least a first aluminum part and a second part bonded thereto, wherein the first part and the second part are joined via the 2-cyanoacrylate adhesive composition of this disclosure. In this case, the 2-cyanoacrylate adhesive composition of this disclosure may be bonded directly to the aluminum surface of the first part, or it may be bonded to an aluminum surface that has been pre-primed. The material of the second part is not particularly limited and can be appropriately selected from metal, plastic, rubber, wood, concrete, etc.

[0023] Examples of the bonded products of this disclosure include laminates formed by overlapping and joining two sheet-like components, and laminates formed by covering and joining a linear component with other components. Examples include articles in which a metal component is attached to a resin molded product. More specifically, examples include printed circuit boards and their laminates, wire harnesses, connectors, insulated wires, etc. [Examples]

[0024] The present disclosure will be described in more detail below based on examples, but the disclosure is not limited thereto. In the following, parts and percentages are based on mass unless otherwise specified.

[0025] 1. Evaluation Method (1) Forced degradation test The 2-cyanoacrylate adhesive compositions obtained in the examples and comparative examples described later were placed in sealed polyethylene containers and stored in a constant temperature room at 60°C for 14 and 28 days. The 2-cyanoacrylate adhesive compositions were removed from the constant temperature room and returned to room temperature, and then subjected to the measurements or evaluations described in (2) to (6) below. (2) Set time for aluminum The set times for aluminum (AL below) after initial and forced degradation tests were measured in accordance with JIS K 6861. The results are shown in Table 1. • AL: Aluminum test piece (material: A1050P, 3.0 x 25 x 50 mm) manufactured by Japan Test Panel Co., Ltd., which has been sandblasted and then degreased with ethanol. (3) Set time for ABS The set times for the following ABS materials, both initial and after forced degradation tests, were measured in accordance with JIS K 6861. The results are shown in Table 2. • ABS: ABS resin rectangular prism test specimen (base 12.7mm x 12.7mm, height 38mm, manufactured by Engineering Test Services Co., Ltd.) (4) Viscosity The viscosity was measured under the following conditions using a TVE-20H viscometer (saltwater / flat plate type, manufactured by Toki Sangyo Co., Ltd.), which is an E-type viscometer (cone plate type viscometer). The results are shown in Table 2. -Measurement conditions- Cone shape: Angle 1°34′, radius 24mm Temperature: 25℃±0.5℃ (5) Acid content The acid content was measured using the following method during the initial and forced degradation tests. The results are shown in Table 2. [1] Place 3 g of the sample into a 200 ml Erlenmeyer flask and weigh it accurately. [2] Dilute this sample by adding 90 ml of reagent-grade acetone. [3] After shaking well, add 3 ml of distilled water. [4] Add a few drops of bromophenol blue solution (Kishida Chemical Co., Ltd.; for pH testing) as an indicator. [5] Using a microburette, add 1 / 100 N NaOH aqueous solution drop by drop until the solution changes color from yellow to blue, at which point the neutralization is complete. (6) Appearance of the liquid The appearance of the liquid was visually evaluated after the initial and forced degradation tests. The results are shown in Table 2.

[0026] 2. Manufacturing of adhesive compositions (Example 1 of preparation of 2-cyanoacrylate compounds) The condensate obtained by dehydration condensation of ethyl cyanoacetate and formaldehyde was depolymerized using phosphorus pentoxide as a depolymerization catalyst (catalyst concentration relative to the condensate was 13 g / L) to obtain crude ethyl-2-cyanoacrylate. Subsequently, distillation using a rectification column was performed to obtain ethyl-2-cyanoacrylate. The content of triethyl phosphate in the ethyl-2-cyanoacrylate was measured by gas chromatography and was found to be below the detection limit (5 ppm), so it was determined to be 0 ppm. (Measurement of triethyl phosphate content by gas chromatography) (1) Measurement conditions for gas chromatograph-mass spectrometer Equipment: Agilent Model 7890 Column: DB-225MS (30m x 0.25mm ID, df: 0.25μm) Temperature conditions: 40°C (5 minutes) - increase at 10°C / minute - 220°C (10 minutes) Inlet temperature: 220℃ Gas flow rate: 1.5 mL / min (constant flow) Split ratio: 20:1 (2) Mass spectrometry conditions Equipment: JMS-Q1000GC K9 model manufactured by JEOL Ltd. Ionization method: EI Ionization current: 200 μA Ionization energy: 70 eV Ion source temperature: 250℃ Detector voltage: -980V Mass range: 29-600 (3) Sample conditions Sample volume: 1 μL Sample preparation method: 0.5 g of the sample was accurately weighed into a volumetric flask, and diluted with an organic solvent / carboxylic acid = 99 / 1 (vol / vol) solution to prepare 5 mL of solution. 10 μL of butyl acetate (internal standard) was added to this solution and mixed until homogenized before being subjected to measurement. Preparation method for quantitative standard samples: Triethyl phosphate reagent was diluted with an organic solvent / carboxylic acid = 99 / 1 (vol / vol) solution to prepare 10 mL each of standard solutions at concentrations of 5, 10, 10, 50, 100, 500, and 1000 ppm. 20 μL of butyl acetate (internal standard) was added to each solution and mixed until homogenized before being subjected to measurement.

[0027] (Example 1) The ethyl-2-cyanoacrylate obtained in Production Example 1 was mixed with BF3-methanol complex (polymerization inhibitor) at a concentration of 5 ppm by mass, BF3-diethyl ether complex (polymerization inhibitor) at a concentration of 80 ppm by mass, and Smirizer MDP-S (polymerization inhibitor, the compound below) at a concentration of 1,000 ppm by mass to obtain the 2-cyanoacrylate adhesive composition according to Example 1. (Example 2) 100 ppm by mass of triethyl phosphate was added to the 2-cyanoacrylate adhesive composition according to Example 1 to obtain the 2-cyanoacrylate adhesive composition according to Example 2. (Example 3) 500 ppm by mass of triethyl phosphate was added to the 2-cyanoacrylate adhesive composition according to Example 1 to obtain the 2-cyanoacrylate adhesive composition according to Example 3. (Comparative Example 1) 1000 ppm by mass of triethyl phosphate was added to the 2-cyanoacrylate adhesive composition according to Example 1 to obtain the 2-cyanoacrylate adhesive composition according to Comparative Example 1.

[0028] The set time measurements described above were performed using the 2-cyanoacrylate adhesive compositions obtained in Examples 1-3 and Comparative Example 1. The results are shown in Table 1.

[0029] [Table 1]

[0030] [Table 2]

[0031] As shown in Table 1 above, in the 2-cyanoacrylate adhesive compositions of Examples 1 to 3, in which the trialkyl phosphate content was within the range specified in this disclosure, the set time for AL remained unchanged or its increase was suppressed even after a 28-day forced degradation test. On the other hand, in the 2-cyanoacrylate adhesive composition of Comparative Example 1, in which the trialkyl phosphate content exceeded the range specified in this disclosure, the set time for AL increased significantly and stringing occurred after a 28-day forced degradation test. Furthermore, in particular, the 2-cyanoacrylate adhesive composition of Example 1, which does not contain trialkyl phosphate, had a shorter initial set time for AL and superior initial curing speed for AL compared to the 2-cyanoacrylate adhesive compositions of Examples 2 and 3 and Comparative Example 1, which contain trialkyl phosphate. On the other hand, as shown in Table 2, there were no significant differences in the results regarding set time, viscosity, acid content, and liquid appearance for ABS between Examples 1-3 and Comparative Example 1. In other words, in the composition of this disclosure, by keeping the content of trialkyl phosphate within the range specified in this disclosure, no significant differences were observed in other evaluation items related to storage stability, while it was confirmed that the increase in set time after forced degradation testing was specifically suppressed for AL. [Industrial applicability]

[0032] The 2-cyanoacrylate adhesive composition obtained by this disclosure does not experience a significant decrease in curing speed with respect to aluminum even after storage and is used as an instant adhesive in fields such as household and industrial use.

Claims

1. A 2-cyanoacrylate adhesive composition having a trialkyl phosphate content of 700 ppm by mass or less, wherein the alkyl group has 1 to 4 carbon atoms.

2. The 2-cyanoacrylate adhesive composition according to claim 1, wherein the content of the trialkyl phosphate is 50 ppm by mass or less.

3. The 2-cyanoacrylate adhesive composition according to claim 1, wherein the trialkyl phosphate is triethyl phosphate.

4. A 2-cyanoacrylate adhesive composition according to claim 1, for use with aluminum.

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