Underwater adhesive

Abstract

This invention provides an underwater adhesive that improves adhesion, adhesive strength, adsorption, underwater application, and conformability. [Solution] This invention relates to an underwater adhesive comprising a silicate binder and sericin.

Description

[Technical Field]

[0001] This invention relates to an underwater adhesive. [Background technology]

[0002] Conventionally, underwater adhesives have been used for repairing drainage pipes, sewer pipes, etc., placed underwater or on the water surface, and for attaching larvae that hatch from coral eggs laid underwater to substrates for the conservation and regeneration of coral reefs. Underwater adhesives are used in such a wide range of applications (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 7193814 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, since underwater adhesives are used in underwater environments where adhesion is hindered, further performance improvements are expected. Typical improvements in performance include increasing adhesion and adhesive strength, as well as greatly improving adsorption, underwater application, and conformability.

[0005] This invention was made to meet such expectations and aims to provide an underwater adhesive that improves adhesion, adhesive strength, adsorption, underwater application, and conformability. [Means for solving the problem]

[0006] (1) An underwater adhesive according to an embodiment for achieving the above objective comprises a silicate binder and sericin. (2) An underwater adhesive according to another embodiment preferably further comprises a sacrificial agent having two or more hydrolyzable groups in one molecule of silane or a partially hydrolyzed condensate of said silane. (3) An underwater adhesive according to another embodiment preferably further comprises a thickening agent. (4) In an underwater adhesive according to another embodiment, the silicate binder is preferably a silane compound having at least a hydrolyzable alkoxy group. (5) In an underwater adhesive according to another embodiment, the thickener is preferably a cellulose derivative. (6) In an underwater adhesive according to another embodiment, preferably, the sericin contains at least 40 mol% of amino acids having a hydroxyl group and 42 mol% or more of amino acids having a polar side chain in its amino acid composition. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an underwater adhesive that improves adhesion, adhesive strength, adsorption, underwater application, and conformability. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows a state in which a long, slender rod-shaped member is inserted into the underwater adhesive of Example 1, which is placed in water, and the rod-shaped member is tilted 90 degrees to the left. [Figure 2] Figure 2 shows a state in which a long, slender rod-shaped member is inserted into the underwater adhesive of Example 2, which is placed in water, and the rod-shaped member is tilted 90 degrees to the right. [Figure 3] Figure 3 shows the adhesive state of the laminate when the laminate, which was laminated using the underwater adhesive of Example 1, was left in water for 30 minutes and then removed and the top layer of the laminate was lifted. [Figure 4] Figure 4 shows the adhesive state of the laminate when the laminated material, which was laminated using the underwater adhesive in Example 1, was left in water for 1 hour, and then removed and the top layer of the laminate was lifted. [Figure 5]FIG. 5 shows the states of the bonded portions after rupture of the underwater adhesive of Example 3 at 30 minutes (5A), 1 hour (5B), and 1 week (5C) after rupture, and the states of the bonded portions after rupture of the underwater adhesive of Comparative Example 2 at 30 minutes (5D), 1 hour (5E), and 1 week (5F) after rupture, respectively.

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below do not limit the invention according to each claim of the claims. Also, not all of the elements and combinations thereof described in the embodiments are essential for the solution means of the present invention.

[0010] The underwater adhesive according to this embodiment contains a silicate binder and sericin. The underwater adhesive preferably further contains a sacrificial agent containing a silane having two or more hydrolyzable groups in one molecule or a partial hydrolyzate condensate of the silane, and more preferably further contains a thickener. The silicate binder is preferably a silane compound having at least a hydrolyzable group of an alkoxy group. The thickener is preferably a methylcellulose type.

[0011] The underwater adhesive mainly contains, for example, the following components.

[0012] (1-1) Silicate binder The silicate binder (which may be simply referred to as silicate) used in the embodiment is a silane compound having a hydrolyzable group of an alkoxy group. Examples of the silane compound include compounds represented by the following chemical formula (1).

[0013]

Chemical formula

[0014] In formula (1), R

[0014] , , , 2 , , , , , , , 1 , ,

[0013] , , R <> 2 , R3 and R 4 are each independently an alkyl group having 1 to 4 carbon atoms, and s is an integer of 1 to 100. The alkyl group having 1 to 4 carbon atoms may be linear or branched, and specifically, examples thereof include a methyl group, an ethyl group, a propyl group, and a butyl group. s is preferably 1 to 50, more preferably 1 to 25, and even more preferably 1 to 10.

[0015] The hydrolyzable silane compound is a silane compound having a hydrolyzable group such as an alkoxy group, an alkoxyalkoxy group, an acyloxy group, an aryloxy group, an aminoxy group, an amide group, a ketoxime group, an isocyanate group, or a halogen atom.

[0016] Among the above, an alkoxysilane compound is preferably used. Examples of the alkyl group of the alkoxy group (-OR) include lower alkyl groups such as a methyl group, an ethyl ethylyl group, a propyl group, and a butyl group. Depending on the number of hydrolyzable groups, 1- to 4-functional ones are known.

[0017] Representative examples of the alkoxysilane compound include dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), tetramethoxysilane (TMOS), dimethyldiethoxysilane (DMDES), methyltriethoxysilane (MTES), tetraethoxysilane (TEOS), vinyltrimethoxysilane, and the like.

[0018] The multimer of the hydrolyzable silane compound is obtained by condensing and polymerizing (oligomerizing) the above monomers. In this reaction, first, a silanol group (-Si-OH) is formed by hydrolysis of the alkoxy group. At the same time, alcohol (R-OH) is generated. Next, a siloxane bond (-Si-O-Si-O-) is formed by (dehydration) condensation of the silanol group, and this condensation is repeated to form a siloxane oligomer. As the multimer of the alkoxysilane compound, from the aspects of hydrolysis and condensability of the alkoxy group, a multimer of tetramethoxysilane in which R is a methyl group or a multimer of tetraethoxysilane in which R is an ethyl group is preferable.

[0019] In the present invention, a partially hydrolyzed condensate of tetramethoxysilane (a partially hydrolyzed oligomer of tetramethoxysilane) is used as the silicate compound, and known commercially available products can be used.

[0020] (1-2) Sericin Silkworm cocoons are composed of two types of proteins, "fibroin" and "sericin," in a ratio of approximately 4:1. Fibroin is a fibrous protein, while sericin is a paste-like protein. Sericin can be obtained, for example, from wastewater in the silk refining process, and has a weight-average molecular weight (MW) of 65,000 to 400,000, containing serine, glycine, aspartic acid, and threonine. In this embodiment, it is preferable that the sericin has at least the following three characteristics. Table 1 below shows the main amino acid composition and physical properties of the sericin used in the examples described later. The following content percentages (mol%) are values ​​when the total amino acid composition in the sericin used (for example, sericin powder or hydrolyzed sericin, etc., described later; the same applies hereafter in this paragraph) is set to 100 mol%. In this embodiment, it is sufficient that the content percentage is equal to or greater than the following value for the entire sericin used, and it is not necessary for all individual protein molecules or peptide molecules contained in the sericin used to have a content percentage equal to or greater than the following value. For example, when examining the amino acid composition (amount of substance) of the entire sericin powder used, it is sufficient that the content percentage of the following amino acids relative to the total amino acids is equal to or greater than the following value. • Contains 40 mol% or more of amino acids with a hydroxyl group in its amino acid composition. • Contains 42 mol% or more of amino acids with polar side chains in its amino acid composition. • The amino acid has a bulky side chain. [Table 1] The amount of sericin is preferably in the range of 90 to 200 parts by mass per 100 parts by mass of component (1-1), more preferably in the range of 92 to 170 parts by mass, and even more preferably in the range of 95 to 125 parts by mass.

[0021] The sericin used in this embodiment may be in powder form (referred to as sericin powder), or it may be extracted from silkworm cocoons by known methods such as hydrolysis (hereinafter also referred to as hydrolyzed sericin) and used as is. When sericin powder is used, the particle size of the powder is preferably 5 to 500 μm, more preferably 7 to 400 μm, and even more preferably 10 to 300 μm. Furthermore, the weight-average molecular weight of the sericin (sericin powder and / or hydrolyzed sericin) used in this embodiment is preferably 50,000 or more, more preferably 60,000 to 300,000, even more preferably 80,000 to 300,000, and particularly preferably 100,000 to 300,000.

[0022] The sericin used in this embodiment preferably contains 40-50 mol% and more preferably 40-45 mol% of amino acids having a hydroxyl group (such as serine and threonine) in its amino acid composition. It also preferably contains 42-80 mol% and more preferably 45-70 mol% of amino acids having polar side chains (regardless of whether they have an electric charge; such as serine, threonine, cysteine, asparagine, glutamine, aspartic acid, glutamic acid, arginine, lysine, histidine, etc.) in its amino acid composition.

[0023] Furthermore, fibroin may be used instead of sericin as a component of the underwater adhesive of the present invention. The fibroin may be in powder form (hereinafter referred to as fibroin powder in this paragraph), for example. When using fibroin powder, it is necessary to add a hydrophilic additive to enhance the overall hydrophilicity of the adhesive. Examples of such additives include calcium carbonate, preferably heavy calcium carbonate or precipitated (light) calcium carbonate. The amount of such additive is preferably 5 parts by mass per 100 parts by mass of component (1-1).

[0024] (1-3) Thickening agents As a thickening agent, for example, cellulose derivatives such as methylcellulose, ethylcellulose, methylhydroxypropylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, nitrocellulose, sodium cellulose sulfate, sodium carboxymethylcellulose, crystalline cellulose, cationized cellulose, and cellulose powder can be used. Among these, methylcellulose and carboxymethylcellulose are preferred. The amount of thickener added is preferably in the range of 0 to 10 parts by mass per 100 parts by mass of component (1-1), more preferably in the range of 0 to 7 parts by mass, and even more preferably in the range of 0 to 5 parts by mass.

[0025] (1-4) Sacrificial Agent As the sacrificial agent, a silane having two or more, preferably three or more, hydrolyzable groups in one molecule, or a partially hydrolyzed condensate of said silane can be used. Examples of hydrolyzable groups include alkoxy groups (methoxy group, ethoxy group, butoxy group, etc.), ketoxime groups (dimethylketoxime group, methylethylketoxime group, etc.), acyloxy groups (acetoxy group, etc.), alkenyloxy groups (isopropenyloxy group, isobutenyloxy group, etc.), amino groups (N-butylamino group, N,N-diethylamino group, etc.), and amide groups (N-methylacetamide group, etc.). Among these, alkoxy groups, ketoxime groups, acyloxy groups, and alkenyloxy groups are preferred. Tetraethoxysilane or tetramethoxysilane can be exemplified as preferred sacrificial agents. The amount of sacrificial agent is preferably in the range of 0 to 10 parts by mass per 100 parts by mass of component (1-1), more preferably in the range of 0.1 to 7 parts by mass, and even more preferably in the range of 1 to 5 parts by mass. [Examples]

[0026] Next, embodiments of the present invention will be described in comparison with comparative examples. However, the present invention is not limited to the embodiments described below.

[0027] (1) Adhesion test of underwater adhesive with sacrificial agent 1. Materials for underwater adhesives • Methyl silicate (manufactured by Mitsubishi Chemical Corporation, product code: MS51), a silane compound having a hydrolyzable alkoxy group. • Sericin powder (manufactured by Nagasuna Mayu Co., Ltd., product name: N-Sericin, weight-average molecular weight: approximately 200,000, particle size: 10-300 μm) • Thickening agent (methylcellulose: manufactured by Shin-Etsu Chemical Co., Ltd., product number: hi-Metholose (registered trademark) mortar admixture for plastering) • Sacrificial agent (silane coupling agent: manufactured by Shin-Etsu Chemical Co., Ltd., product number: KBM-1003) Titanium diisopropoxybis(ethylacetoacetate): (Manufactured by Matsumoto Fine Chemical Co., Ltd., product code: TC-750) • Heavy calcium carbonate (manufactured by Maruo Calcium Co., Ltd., product name: Super S) Titanium diisopropoxybis and heavy calcium carbonate are included in the comparative examples described later.

[0028] 2. Experimental Method (Example 1) A mixture (underwater adhesive) was obtained by mixing 20g of methyl silicate, 20g of sericin powder, and 2g of silane coupling agent. The mixture (underwater adhesive) was then left to stand in a container (water tank) filled with tap water, and its adsorption, underwater application, and conformability (spreadability) were evaluated. Furthermore, multiple mortar test pieces were prepared, and the above-mentioned mixture was applied between two adjacent test pieces. These mortar test pieces were then placed in a container (water tank) filled with tap water for a predetermined time. After the predetermined time had elapsed, the test pieces were removed from the container, and their adhesion (rapid hardening) was evaluated. Furthermore, multiple mortar test pieces were prepared, and the above-mentioned mixture was applied between two adjacent test pieces. These mortar test pieces were then placed in a container (water tank) filled with tap water, and after one week, the test pieces were removed from the container and their adhesive strength was evaluated. <Adsorption> Immediately after preparing the mixture, it was applied to the mortar, which was the substrate, and left to stand in water. The adsorption force was evaluated by observing whether or not the mixture was adsorbed onto the mortar in the water. <Applicability underwater> We observed whether the mixture could be applied to the substrate in water and evaluated its applicability in water. <Followability (spreadability)> A long, slender rod-shaped member was inserted into a mixture that had been left to rest in water, and the rod-shaped member was tilted to the left and right by predetermined angles. The maximum tilt angle for each direction was measured to evaluate its conformability (extendability). <Adhesiveness (quick curing)> Adhesion was evaluated by preparing seven mortar test pieces (size: 50mm x 50mm x 10mm), applying underwater adhesive between each test piece and adjacent pieces, and then leaving them in water for 30 minutes before removing the test pieces from the container and evaluating their adhesion. Additionally, the adhesion (rapid hardening) was evaluated by leaving the test pieces in a container (water tank) for 1 hour before removing them from the container. <Adhesive strength (adhesive strength)> To measure adhesive strength, two mortar test pieces were prepared. A water-based adhesive was placed between the two mortar test pieces (approximately 10 mm apart) to bond them together. These were then placed in a constant temperature and humidity chamber (50 RH) for one week (at ambient temperature of 23°C). After this, the mortar test pieces were removed from the chamber. The adhesive strength was then measured using a tensile testing machine (tensile speed: 50 mm / min). The tensile test was performed perpendicular to the bonding surface between the mortar test pieces. This measurement was repeated a total of four times, and the average adhesive strength (N / mm²) was calculated. 2 The adhesive strength was evaluated by calculating the coefficient of adhesion. (Example 2) A mixture was prepared by mixing 20 g of methyl silicate, 15 g of sericin powder, 5 g of methylcellulose, and 2 g of silane coupling agent. The adsorption, water coating, conformability, adhesion, and adhesive strength of this mixture were evaluated in the same manner as in Example 1. (Comparative Example 1) A mixture was prepared by mixing 10 g of methyl silicate, 1 g of silane coupling agent, 56 g of heavy calcium carbonate, and 0.1 g of diisopropoxybis(ethylacetoacetate) titanium. The adsorption, water coating, conformability, adhesion, and adhesive strength of this mixture were evaluated using the same method as in Example 1.

[0029] 3. Experimental Results Table 2 below shows the experimental results for Example 1, Example 2, and Comparative Example 1. Figure 1 shows a long, slender rod-shaped member inserted into the underwater adhesive of Example 1, which was left submerged in water, and the rod-shaped member tilted 90 degrees to the left. Figure 2 shows a long, slender rod-shaped member inserted into the underwater adhesive of Example 2, which was left submerged in water, and the rod-shaped member tilted 90 degrees to the right. Figure 3 shows the adhesion state of the laminate when the laminate, which was laminated using the underwater adhesive of Example 1, was left submerged in water for 30 minutes and then removed, and the top layer of the laminate was lifted. Figure 4 shows the adhesion state of the laminate when the laminate, which was laminated using the underwater adhesive of Example 1, was left submerged in water for 1 hour and then removed, and the top layer of the laminate was lifted.

[0030] [Table 2]

[0031] (Example 1) <Adsorption> The adsorption performance was evaluated on a three-level scale: A, B, and C. In Table 2, A is defined as good adsorption, B as insufficient adsorption, and C as no adsorption. As shown in Table 2, the adsorption performance was good (A: see Table 2 and Figure 1). <Applicability underwater> The underwater coating performance was evaluated on a three-point scale: A for good underwater coating performance, B for insufficient underwater coating performance, and C for no underwater coating performance (see Table 2). Underwater coating performance was good (A: see Table 2, Figure 1). <Followability> The evaluation was expressed on a three-level scale: A, B, and C. In Table 2, A was defined as good tracking performance, B as insufficient tracking performance, and C as no tracking performance. The maximum tilt angle was 90 degrees to the left and right (see Figures 1 and 2). As shown in Table 2, the tracking performance was good (A: Table 2). <Adhesion, adhesive strength> Regarding adhesion, when the top layer of the laminated mortar was lifted after 30 minutes, the laminated structure did not separate and fall, indicating good adhesion (see Figure 3). Furthermore, when the top layer of the laminated mortar was lifted after 1 hour, the laminated structure did not separate and fall, indicating good adhesion (see Figure 4). The average adhesive strength is 0.13 (N / mm²). 2 ) and had sufficient adhesive strength for use underwater.

[0032] (Example 2) <Adsorption> As shown in Table 2, the adsorption properties were good. <Applicability underwater> The coating properties underwater were good (A: Table 2). <Followability> The maximum tilt angle was 10 degrees to the left and right, and the tracking performance was average (see B: Table 2, Figure 1). <Adhesion, adhesive strength> Regarding adhesion, when the top layer of the laminated mortar was lifted after 30 minutes, it did not fall off, indicating good adhesion. Furthermore, when the top layer of the laminated mortar was lifted after 1 hour, it also did not fall off, demonstrating good adhesion. The average adhesive strength is 0.06 (N / mm²). 2 ) and had sufficient adhesive strength for use underwater.

[0033] (Comparative Example 1) <Adsorption> It did not have sufficient adhesive properties to be applied to mortar (C: Table 2). <Applicability underwater> Underwater application was not possible (C: Table 2). <Followability> The maximum tilt angle was 10 degrees to the left and 20 degrees to the right. As shown in Table 2, the tracking performance was average (B: Table 2). <Adhesion, adhesive strength> Regarding adhesion, when the top layer of the laminated mortar was lifted 30 minutes after bonding, some of the laminated mortar fell off. When the top layer of the laminated mortar was lifted 1 hour later, no material fell off. The average adhesive strength is 0.15 (N / mm²). 2 ) and had sufficient adhesive strength for use underwater.

[0034] 4. Summary Examples 1 and 2, which contained sericin, showed superior adsorption, water coating properties, and conformability compared to Comparative Example 1, which did not contain sericin, and also yielded good results in terms of adhesion and adhesive strength.

[0035] (2) Adhesion test of underwater adhesive without sacrificial agent 1. Materials for underwater adhesives The methyl silicate and sericin powder used were the same as those described in (1) above.

[0036] 2. Experimental Method (Example 3) A mixture (aquatic adhesive) was obtained by mixing 10g of methyl silicate and 10g of sericin powder.

[0037] Furthermore, multiple mortar test pieces were prepared, and the above-mentioned mixture was applied and bonded between two adjacent test pieces. The bonded mortar test pieces were then placed in a container (water tank) filled with tap water, and the test pieces were removed from the container after 30 minutes, 1 hour, or 1 week. The adhesive strength was evaluated for each removed test piece. The condition of the broken bonded area was also visually evaluated. The detailed methods for each evaluation will be described later.

[0038] (Comparative Example 2) For the comparative example, underwater adhesive E380 (manufactured by Konishi Corporation) was used. Otherwise, the procedure was the same as in Example 3 above.

[0039] <Adhesive strength (adhesive strength)> For the cohesive force, two mortar test pieces were prepared, and 4 g of the underwater adhesive according to Example 3 or Comparative Example 2 was packed between the two mortar test pieces (interval of about 2 to 3 mm) to bond the test pieces together. Then, it was left standing in a water tank, which was a thermo-hygrostat at 50% RH (underwater), for 30 minutes, 1 hour, or 1 week (outside air temperature of 23°C). After that, the mortar test pieces were taken out of the water tank. And the adhesive force was measured for the mortar test pieces using a tensile testing machine (tensile speed was 50 mm / min). The tensile test was carried out in a direction perpendicular to the bonding surface between the mortar test pieces. The measurement was carried out until the bond between the mortar test pieces was broken. This measurement was carried out three times for each sample in total, and the average adhesive force (N / mm 2 2) was calculated to evaluate the adhesive strength. The evaluation results are shown in Tables 3 to 5.

[0040] <State of the bonding failure location> After the measurement of the above adhesive force (adhesive strength), the broken bonding location was visually confirmed. The confirmation results are shown in Tables 3 to 5 and FIG. 5. The meanings of the notations in the column of "Appearance of the bonding location after breakage" in Tables 3 to 5 are as follows. · Cohesive failure: The failure location was inside the adhesive layer formed between the underwater adhesives. That is, no failure was observed at the interface between the underwater adhesive and the mortar test piece. · Interface peeling: The failure location was at the interface between the underwater adhesive and the mortar test piece. That is, the adhesive layer was peeled off from the mortar test piece.

[0041] 3. Experimental results The experimental results of Example 3 and Comparative Example 2 are shown in Tables 3 to 5 below. FIG. 5 shows the appearances of the bonding locations after breakage of the underwater adhesive of Example 3 at 30 minutes later (5A), 1 hour later (5B), and 1 week later (5C), and the appearances of the bonding locations after breakage of the underwater adhesive of Comparative Example 2 at 30 minutes later (5D), 1 hour later (5E), and 1 week later (5F), respectively.

[0042]

Table 3

[0043] [Table 4]

[0044] [Table 5]

[0045] 4. Summary The underwater adhesive according to Example 3, which contains sericin, showed higher adhesive strength after 30 minutes and 1 hour compared to the underwater adhesive according to Comparative Example 2, suggesting that underwater bonding can be achieved in a shorter time. Furthermore, the average adhesive strength remained at 0.25 N / mm² after one week. 2 The adhesive strength was sufficient for use underwater. Furthermore, when the underwater adhesive of Example 3 was broken, it consistently broke due to cohesive failure rather than interfacial delamination. In other words, no peeling of the adhesive layer from the mortar test piece was observed after breakage. Therefore, the underwater adhesive of Example 3 is less dependent on various conditions caused by the adherend (mortar test piece), such as surface shape, roughness, and contamination, and can reduce variations in adhesive strength, thus being considered to have higher reliability as an adhesive. [Industrial applicability]

[0046] The present invention can be used, for example, as an adhesive member or a sealing member.

Claims

1. An underwater adhesive characterized by containing a silicate binder and sericin.

2. The underwater adhesive according to claim 1, further comprising a sacrificial agent containing a silane having two or more hydrolyzable groups in one molecule, or a partially hydrolyzed condensate of said silane.

3. Further containing a thickening agent, An underwater adhesive according to feature 1 or 2.

4. The silicate binder is a silane compound having at least a hydrolyzable alkoxy group. An underwater adhesive according to feature 1 or 2.

5. The thickening agent is a cellulose derivative. The underwater adhesive according to feature 3.

6. The sericin contains, in its amino acid composition, at least 40 mol% or more of amino acids having a hydroxyl group, and at least 42 mol% or more of amino acids having a polar side chain. An underwater adhesive according to feature 1 or 2.

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