Hot-melt adhesive

Abstract

Provided is a hot-melt adhesive having high sustainability and excellent adhesiveness.　The hot-melt adhesive contains a β-1,3-glucan derivative and, when applied to a wood piece, has compressive shear bonding strength in a specific range.

Description

Hot melt adhesive

[0001] The present invention relates to a hot melt adhesive and a method for producing the hot melt adhesive.

[0002] Hot melt adhesives are adhesives that use thermoplastic polymers that are solid at room temperature and liquid at high temperatures, and utilize a cycle of heating, melting, and cooling to solidify to bond a variety of materials, including plastics, metals, wood-based materials, paper, painted surfaces, etc. Hot melt adhesives are widely used industrially because they are highly safe as they do not contain volatile solvents and have excellent properties such as not shrinking when drying.

[0003] Hot melt adhesives are generally made from petroleum-based resins such as ethylene vinyl acetate copolymer (EVA), olefin, synthetic rubber, polyamide, and polyester. However, petroleum-based resins have a large environmental impact and are fossil-based resins that are feared to be depleted in the near future. Therefore, there is a need for hot melt adhesives that use highly sustainable raw materials to replace petroleum-based resins.

[0004] Patent Document 1 describes an adhesive and pressure-sensitive adhesive made from a derivative of paramylon, a naturally occurring biomass resource. This adhesive and pressure-sensitive adhesive is particularly useful for bonding or adhering plastic materials such as polyethylene terephthalate.

[0005] Japanese Patent Application Laid-Open No. 2018-154723

[0006] An object of the present invention is to provide a hot melt adhesive that is highly sustainable and has excellent adhesive properties.

[0007] That is, the present invention provides the following aspects: [1] A compound represented by the following formula (I): [In formula (I), R １ are each independently hydrogen or —COR １ is an acyl group represented by R １ is a hydrocarbon group, and n is a natural number. １The β-1,3-glucan derivative has a structure represented by the formula: ２ A hot melt adhesive as described above. <Condition 1> A piece of wood measuring 30 mm in length, 25 mm in width, and 10 mm in thickness is used as the adherend. Two pieces of the adherend are sandwiched between a piece of the hot melt adhesive measuring 25 mm in length, 25 mm in width, and 0.1 mm in thickness, overlapped with the fibers aligned, and hot pressed at a temperature of 190°C, a pressure of 1 MPa, and for 20 minutes, and then bonded by cooling to room temperature while maintaining the pressing pressure of 1 MPa to obtain a test piece. The test piece is measured for compressive shear adhesive strength (N / mm) using the adhesive compressive shear adhesive strength test method according to JIS K6852. ２ [2] The hot melt adhesive according to [1], which has a softening temperature of 90°C or higher. [3] The hot melt adhesive according to [1] or [2], which has a 5% weight loss temperature of 250°C or higher. [4] R １ [5] The hot melt adhesive according to any one of [1] to [3], wherein R is a C5-C15 alkyl group. １ [6] The hot melt adhesive according to any one of [1] to [4], wherein R is a C5-C11 alkyl group. １ [7] The hot melt adhesive according to any one of [1] to [6], wherein the acyl group substitution degree of the β-1,3-glucan derivative is 1.00 to 2.90. [8] The compressive shear adhesive strength after readhesion measured under the following condition 2 is 1.0 N / mm ２ The hot melt adhesive according to any one of [1] to [7], wherein the adhesive strength is measured by heating the test piece to separate the two adherends, and then the adhesive surfaces of the two separated adherends are re-placed and hot-pressed at a temperature of 190°C, a pressure of 1 MPa, and a time of 20 minutes. The adhesive is then re-adhered by cooling to room temperature while maintaining the pressure of 1 MPa, to obtain a re-adhesion test piece. The re-adhesion test piece is subjected to a compressive shear bond strength test method for adhesives according to JIS K6852 to measure the compressive shear bond strength (N / mm ２[9] A method for producing a hot melt adhesive according to any one of [1] to [8], comprising converting hydrogen of at least one hydroxy group in at least one glucose unit of the β-1,3-glucan to -COR １ (R １

[10] A method for bonding a first adherend to a second adherend, comprising applying the hot melt adhesive according to any one of [1] to [8] between the first adherend and the second adherend.

[11] The method according to

[10] , wherein the first adherend and the second adherend are wood-based materials.

[12] A method for bonding a first adherend to a second adherend, comprising: heat-separating the first adherend and the second adherend bonded by the method according to

[10] or

[11] ; and re-adhering the first adherend and the second adherend using the hot melt adhesive remaining on the bonding surface of the first adherend and / or the bonding surface of the second adherend.

[13] A hot melt adhesive according to any one of [1] to [8] for use in bonding wood-based materials.

[14] Use of the hot melt adhesive according to any one of [1] to [8] in bonding wood-based materials.

[0008] The present invention can provide a hot melt adhesive that is highly sustainable and has excellent adhesive properties.

[0009] [Explanation of Terms] "β-1,3-glucan" is a polysaccharide formed by the polymerization of glucose through β-1,3 bonds. β-1,3-glucan may be derived from a living organism or may be a synthetic product. From the viewpoint of reducing environmental impact, a living organism is preferred, and a plant-derived product is more preferred. In particular, from the viewpoint of ease of isolation and purification of β-1,3-glucan, β-1,3-glucan isolated from microalgae that synthesize β-1,3-glucan intracellularly is preferred. As microalgae, the genus Euglena (Japanese name: Midorimushi) is preferred, and Euglena gracilis is more preferred. The genus Euglena is easy to cultivate, has a rapid growth cycle, and accumulates large amounts of β-1,3-glucan particles intracellularly as a photosynthetic product. Furthermore, β-1,3-glucan can be easily isolated from microalgae using standard methods. The β-1,3-glucan produced by Euglena is also called paramylon.

[0010] A "β-1,3-glucan derivative" is typically a compound in which the hydrogen atom of at least one hydroxy group in at least one glucose unit of a β-1,3-glucan is substituted with a functional group such as an acyl group. β-1,3-glucan derivatives can be prepared according to standard methods. Specific examples of such methods are described below.

[0011] "Adhesion" is the state or state of joining together of similar or dissimilar things. "To adhere" is to bring about adhesion. "Adhesive" is a substance used to bond. "Adhesion" is the property of bringing about adhesion.

[0012] "Adhesion" is a phenomenon commonly seen in highly viscous liquids, whereby they adhere with only slight pressure applied for a short period of time without undergoing a change in state. "To stick" is to cause adhesion. "Adhesive" is a substance used to cause adhesion. "Adhesion" is the property of causing adhesion.

[0013] "Hot melt adhesives" are adhesives that use thermoplastic polymers that become solid at room temperature and liquid at high temperatures, and use a cycle of heating, melting, and cooling to solidify to bond a variety of materials, including plastics, metals, wood-based materials, paper, and painted surfaces.Hot melt adhesives are widely used industrially because they are highly safe as they do not contain volatile solvents and have excellent properties such as not shrinking when drying.

[0014] "Wood-based materials" are materials made from wood or bamboo. The wood may be either softwood or hardwood. Wood-based materials may also be materials made from wood or bamboo that have been processed into boards, chips, or fibers and then reconstituted, such as plywood, particle board, or fiberboard, or recycled materials thereof.

[0015] In the present disclosure, any numerical range described using the expressions "from" or "to" includes the upper and lower limits, respectively. For example, the description "A to B" or "A to B" using numerical values ​​A and B means A or more and B or less. Furthermore, the descriptions "A to B," "A to B," or "A or more and B or less" independently include both "A or more is preferred" and "B or less is preferred." When multiple numerical ranges are described for a specific parameter in the present disclosure, any upper and lower limits of each numerical range can be combined to form a suitable numerical range. Furthermore, the lower or upper limit of a numerical range described in the present disclosure is a numerical value within that numerical range and may be replaced with a numerical value shown in the examples.

[0016] In this disclosure, "and / or" includes both an "and" relationship and an "or" relationship.

[0017] In this disclosure, "comprising" includes "principally consisting of," "essentially consisting of," and "consisting of," and "principally consisting of" includes "substantially consisting of" and "consisting of," and "substantially consisting of" includes "consisting of."

[0018] In this disclosure, objects referred to in the singular, such as "a," "an," "the," etc., include both the singular and the plural of that object unless expressly indicated otherwise.

[0019] [Embodiments] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments and can be implemented by making appropriate modifications within the scope that does not impair the effects of the present invention. These embodiments may be used alone or in combination. If a specific description given for one embodiment also applies to other embodiments, that description may be omitted in other embodiments. The known techniques and procedures described herein are well understood by those skilled in the art and can be implemented according to standard methods.

[0020] (Hot Melt Adhesive) In one embodiment, a hot melt adhesive having the following formula (I): [In formula (I), R １ are each independently hydrogen or —COR １ is an acyl group represented by R １ is a hydrocarbon group, and n is a natural number. １ The β-1,3-glucan derivative has a structure represented by the formula: ２ A hot melt adhesive as described above is provided. In another embodiment, a method for producing this hot melt adhesive is provided. <Condition 1> A piece of wood measuring 30 mm in length, 25 mm in width, and 10 mm in thickness is used as the adherend. Two pieces of the adherend are sandwiched between them with the hot melt adhesive measuring 25 mm in length, 25 mm in width, and 0.1 mm in thickness, overlapped with the fibers aligned, and hot pressed at a temperature of 190°C, a pressure of 1 MPa, and for 20 minutes, and then bonded by cooling to room temperature while maintaining the pressing pressure of 1 MPa to obtain a test piece. The test piece is measured for compressive shear bond strength (N / mm) using a test method for compressive shear bond strength of adhesives in accordance with JIS K6852. ２ ) is required.

[0021] The hot melt adhesive of this embodiment is highly sustainable because it can use naturally derived biomass raw materials obtained from the genus Euglena, etc. Furthermore, this hot melt adhesive has excellent adhesive properties and is suitable for bonding various materials such as plastics, metals, wood-based materials, paper, and painted surfaces, and is particularly suitable for bonding wood-based materials.

[0022] The hot melt adhesive in this embodiment may be a hot melt adhesive for bonding wood-based materials.

[0023] The hot melt adhesive in this embodiment may consist solely of a β-1,3-glucan derivative, or may further contain other components as necessary (plasticizers, antioxidants, UV absorbers, fillers, release agents, colorants, flame retardant aids, flame retardants, and other additives, polymers other than the β-1,3-glucan derivatives, etc.). In some embodiments, the content of the β-1,3-glucan derivative in the hot melt adhesive may be 50% by mass or more, 60% by mass or more, 80% by mass or more, 90% by mass or more, 98% by mass or more, or even 100% by mass.

[0024] The hot melt adhesive in this embodiment is solid at room temperature and can be processed into an appropriate shape by heat pressing. For example, when the hot melt adhesive is subjected to the above-mentioned compressive shear adhesive strength, the hot melt adhesive is processed into a film having a length of 25 mm, a width of 25 mm, and a thickness of 0.1 mm.

[0025] In some embodiments, the hot melt adhesive may be tack-free at room temperature, which is preferable to a tacky hot melt adhesive at room temperature because it is easier to handle.

[0026] (Compression shear adhesive strength) In this embodiment, the compression shear adhesive strength is 1.0 N / mm ２ Above, 2.0N / mm ２ Above, 3.0N / mm ２ Above, 4.0N / mm ２ Above, 5.0N / mm ２or more, or 5.4 N / mm ２ The compressive shear adhesive strength may be 1.0 N / mm or more. ２ to 9.0 N / mm ２ , 2.0 N / mm ２ to 9.0 N / mm ２ , 3.0 N / mm ２ to 9.0 N / mm ２ , 4.0 N / mm ２ to 9.0 N / mm ２ , 5.0 N / mm ２ to 9.0 N / mm ２ , 5.4 N / mm ２ to 9.0 N / mm ２ , 1.0 N / mm ２ to 5.4 N / mm ２ , 1.0 N / mm ２ to 5.0 N / mm ２ , 1.0 N / mm ２ to 4.0 N / mm ２ , or 2.0 N / mm ２ to 4.0 N / mm ２ The compressive shear adhesive strength may be 1.3 N / mm ２ , 2.3 N / mm ２ , 2.5 N / mm ２ , 2.9 N / mm ２ , 3.6 N / mm ２ , 5.0 N / mm ２ , 5.5 N / mm ２ , 6.0 N / mm ２ , 6.2 N / mm ２ , or 8.6 N / mm ２ The compressive shear bond strength may be within a range having these values ​​as upper or lower limits, or may be a range combining these values ​​as upper and lower limits. Hot melt adhesives having compressive shear bond strengths within these ranges can achieve excellent adhesiveness. Furthermore, by setting the compressive shear bond strength low for applications requiring low adhesion and high for applications requiring high adhesion, the hot melt adhesive can be imparted with adhesiveness appropriate for the application.

[0027] The compressive shear adhesive strength can be adjusted, for example, by adjusting the number of carbon atoms in the acyl group of the β-1,3-glucan derivative described below or the degree of acyl group substitution. １ R of an acyl group represented by １ When the hydrocarbon group contained as a C5 to C7 alkyl group, the degree of acyl group substitution is adjusted to 1.50 to 2.90, thereby making it possible to obtain a compressive shear adhesive strength of 1.0 N / mm ２ It can be more than that.

[0028] In addition, β-1,3-glucan derivatives with a high degree of acyl group substitution generally have high thermoplasticity. On the other hand, β-1,3-glucan derivatives with a low degree of acyl group substitution have high hardness at room temperature. By adjusting the balance between thermoplasticity and hardness at room temperature, it is possible to increase (or decrease) the compressive shear adhesive strength. For example, when paramylon octanoate is contained (i.e., -COR １ R of an acyl group represented by １ In the case where the hydrocarbon group contained as -COR is a C7 alkyl group, the compressive shear adhesive strength is higher when the degree of acyl group substitution is in the range of 1.70 to 2.80. １ R of an acyl group represented by １ When the acyl group substitution degree is in the range of 1.90 to 2.90, the compressive shear adhesive strength becomes higher.

[0029] In the test specimens for compressive shear bond strength tests of adhesives, wood pieces used as adherends are typically, but not limited to, cedar boards. The adherends can be prepared by cutting a rod-shaped board 25 mm wide and approximately 12 mm thick, with the width and thickness perpendicular to the grain, cutting it in the grain direction, planing it to a thickness of 10 mm, and then continuously cutting it to a length of 30 mm in the grain direction. In the test specimens, the adherends are stacked with the grain direction aligned. Heat pressing can be performed using a commercially available hydraulic press (e.g., a multiaxial material testing machine V-1815, Saginomiya Seisakusho) according to the instructions included with the machine. After heat pressing, the test specimens are typically left to stand for one week or longer in an atmosphere at 20°C and 60% relative humidity before being subjected to the compressive shear bond strength test method for adhesives.

[0030] The compression shear bond strength test method for adhesives according to JIS K6852 is outlined below. One of the two adherends contained in the test piece is fixed to a compression tester using a jig. A compressive load is applied to the other adherend in a direction parallel to the adhesive surface at 20°C and a test speed of 2 mm / min. The maximum load (N) and adhesive area (mm) at which the adhesive surface breaks are calculated. ２ ) and the compressive shear adhesive strength (N / mm ２ )=Maximum load (N) / Adhesive area (mm ２ ) ... (1) Based on this, the compressive shear adhesive strength (N / mm ２ ) is calculated. ２ ) is the adhesive surface area of ​​the hot melt adhesive (25 mm length x 25 mm width = 625 mm ２ )

[0031] (β-1,3-glucan derivative) In the β-1,3-glucan derivative represented by the above formula (I), -COR １ R of an acyl group represented by １The hydrocarbon group contained as R is an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be linear, branched, or have a ring structure. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group (an alkyl group) or an unsaturated aliphatic hydrocarbon group (an alkenyl group or an alkynyl group). The aliphatic hydrocarbon group is selected from the group consisting of an aliphatic hydrocarbon group having ease of synthesis, an R １ In terms of the high degree of freedom in the selection of alkyl groups, alkyl groups are preferred. The alkyl group may be a C5-C15 alkyl group, a C5-C13 alkyl group, a C5-C11 alkyl group, a C5-C9 alkyl group, a C5-C7 alkyl group, a C5 alkyl group, a C6 alkyl group, a C7 alkyl group, a C8 alkyl group, a C9 alkyl group, a C10 alkyl group, a C11 alkyl group, a C12 alkyl group, a C13 alkyl group, a C14 alkyl group, or a C15 alkyl group. These alkyl groups may be linear, branched, or may have a cyclic structure, but linear groups are preferred. When the hydrocarbon group is an alkyl group with a higher carbon number, the distance between the acyl groups increases compared to when the hydrocarbon group is an alkyl group with a lower carbon number, and the thermoplasticity of the β-1,3-glucan derivative tends to increase. However, when the hydrocarbon group is an alkyl group with an excessively high carbon number, the interaction between the acyl groups may increase, which may reduce the thermoplasticity of the β-1,3-glucan derivative. It is believed that when the acyl group contains the above-mentioned alkyl group, the intermolecular interactions of the β-1,3-glucan derivative are appropriately adjusted, making it easier to obtain a hot melt adhesive having a compressive shear adhesive strength in the above-mentioned range.

[0032] -COR １ may be an acetyl group, a propionyl group, an isopropionyl group, a butyryl group, an isobutyryl group, a pentanoyl group, a hexanoyl group, a heptanoyl group, an octanoyl group, a nonanoyl group, a decanoyl group, a lauroyl group, a myristoyl group, a palmitoyl group, a stearoyl group, an oleoyl group, a linoleoyl group, a linolenoyl group, or the like.

[0033] In formula (I), n is not particularly limited as long as it does not impair the scope of the present invention, but is preferably 60 to 3000, more preferably 1000 to 2500, and even more preferably 1500 to 2000. When n is within the above range, a hot melt adhesive having appropriate adhesive properties is easily obtained.

[0034] The weight-average molecular weight Mw of the β-1,3-glucan derivative is more preferably from 300,000 to 600,000, and even more preferably from 400,000 to 500,000. The number-average molecular weight Mn of the β-1,3-glucan derivative is more preferably from 200,000 to 500,000, and even more preferably from 300,000 to 400,000. When the molecular weight of the β-1,3-glucan derivative is within the above range, a hot melt adhesive having appropriate adhesive properties is easily obtained.

[0035] The polydispersity Mw / Mn of the β-1,3-glucan derivative is preferably 1.0 or more and 1.6 or less, more preferably 1.0 to 1.2. When the polydispersity Mw / Mn is within the above range, the monodispersity of the β-1,3-glucan used as the raw material is better maintained, and a β-1,3-glucan derivative that is less likely to develop defects due to differences in melting point can be obtained. Mw is the weight-average molecular weight, and Mn is the number-average molecular weight. Mw and Mn can be calculated using GPC (gel permeation chromatography) in polystyrene equivalent terms.

[0036] The degree of acyl substitution of the β-1,3-glucan derivative is not particularly limited as long as the effects of the present invention are not impaired, but is preferably 1.00 to 2.90, more preferably 1.50 to 2.90, and even more preferably 1.70 to 2.90. When the hydrocarbon group is a C5 or C6 alkyl group (i.e., when the acyl group has 6 or 7 carbon atoms), the degree of acyl substitution of the β-1,3-glucan derivative is preferably 1.50 to 2.90, more preferably 1.70 to 2.90, and even more preferably 1.80 to 2.80. In applications requiring higher adhesiveness, the degree of acyl substitution is preferably 1.90 to 2.90, more preferably 2.0 to 2.90, and even more preferably 2.10 to 2.80. When the hydrocarbon group is a C7 or C8 alkyl group (i.e., when the acyl group has 8 or 9 carbon atoms), the degree of acyl substitution is preferably 1.50 to 2.90, more preferably 1.60 to 2.90, even more preferably 1.80 to 2.90, and in applications requiring higher adhesion, it is preferably 1.70 to 2.80, more preferably 1.70 to 2.40, even more preferably 1.70 to 2.00. When the hydrocarbon group is a C9-C15 alkyl group (i.e., when the acyl group has 10 to 16 carbon atoms), the degree of acyl substitution is preferably 1.50 to 2.60, more preferably 1.70 to 2.60, even more preferably 1.90 to 2.50.

[0037] As described above, β-1,3-glucan derivatives with a high degree of acyl group substitution generally have high thermoplasticity. On the other hand, β-1,3-glucan derivatives with a low degree of acyl group substitution have high hardness at room temperature. It is important for a hot melt adhesive to have both appropriate thermoplasticity and appropriate hardness at room temperature, and such a hot melt adhesive tends to be easily obtained by having an acyl group substitution degree within the above range.

[0038] The degree of acyl group substitution of a β-1,3-glucan derivative is the ratio of acyl groups bonded to one glucose unit of the raw material β-1,3-glucan. For example, an acyl group substitution degree of 1.0 means that one substituent has been introduced per glucose unit. Theoretically, the upper limit of the degree of acyl group substitution is 3.0. The degree of acyl group substitution can be evaluated by a standard method. Such methods include, for example, nuclear magnetic resonance spectroscopy (NMR method) and elemental analysis. When nuclear magnetic resonance spectroscopy (NMR method) is used, typically, １ The degree of acyl group substitution is evaluated by H-NMR based on the integral value of hydrogen atoms directly bonded to the carbon atoms of the glucose unit (hydrogen atoms of methylene and methine groups) and hydrogen atoms of the acyl groups.

[0039] The degree of acyl group substitution in a β-1,3-glucan derivative is adjusted by changing the feed ratio of the acylating agent to the glucose units contained in the β-1,3-glucan in the method for producing a β-1,3-glucan derivative described below. The feed ratio of the acylating agent to the glucose units contained in the β-1,3-glucan (acylating agent / glucose units contained in the β-1,3-glucan (mol / mol)) is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 6.0 to 1.0, more preferably 5.0 to 1.5, and even more preferably 4.0 to 2.0. The feed ratio of the acylating agent to the glucose units contained in the β-1,3-glucan may be 2.5, 3.0, or 3.5, or may be within a range with these as the upper or lower limit, or may be a range combining these as the upper and lower limits. By using an acylating agent and glucose units contained in β-1,3-glucan at a charge ratio within these ranges, it tends to be easier to appropriately adjust the degree of acyl group substitution with the acyl groups of the β-1,3-glucan derivative.

[0040] (Method for Producing β-1,3-Glucan Derivatives) Examples of methods for producing β-1,3-glucan derivatives include a synthetic method in which some or all of the hydroxyl groups in the glucose constituting the β-1,3-glucan are acylated with fatty acids. Specifically, as shown in the following formula (2), one example is a method in which a solution in which β-1,3-glucan is dissolved in a solvent is reacted sequentially with a fatty acid chloride, a fatty acid anhydride, or a fatty acid vinyl compound as an acylating agent in the presence of a base.

[0041]

[0042] Here, R is each independently hydrogen or an acyl group, at least a part of R is an acyl group, and n is a natural number.

[0043] Examples of fatty acid chlorides include acetic acid chloride, butylic acid chloride, lauric acid chloride, myristate chloride, palmitic acid chloride, stearic acid chloride, hexadecenoic acid chloride, oleic acid chloride, linoleic acid chloride, and linolenic acid chloride. Examples of fatty acid anhydrides include acetic anhydride, propionic acid anhydride, and butylic acid anhydride. Examples of vinyl fatty acid compounds include vinyl acetate, vinyl propionate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl hexadecenoate, vinyl oleate, vinyl linoleate, and vinyl linolenate. Examples of solvents include N,N-dimethylacetamide-lithium chloride mixed solvents, dimethyl sulfoxide, and 1,3-dimethyl-2-imidazoquidinone-lithium chloride solvents. Examples of bases that can be used include known bases such as pyridine, 4-dimethylaminopyridine, and triethylamine.

[0044] The reaction conditions in this synthesis method, such as reaction temperature and reaction time, can be appropriately determined by those skilled in the art, taking into consideration the type of acylating agent, the degree of acyl group substitution, and the like.

[0045] The resulting β-1,3-glucan derivative can be processed into an appropriate shape, for example, by heat pressing. For example, when the β-1,3-glucan derivative is used as a hot melt adhesive and is subjected to the above-mentioned compressive shear adhesive strength, it can be processed into a film having a length of 25 mm, a width of 25 mm, and a thickness of 0.1 mm. In one embodiment, the β-1,3-glucan derivative can be formed into a film having a thickness of 0.01 mm to 1 mm.

[0046] (Softening Temperature) In this embodiment, the softening temperature of the hot melt adhesive is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 90°C or higher, more preferably 100°C to 200°C, and even more preferably 110°C to 190°C. Furthermore, when the softening temperature is 90°C or higher, it may be 91.8°C, 115.5°C, 149.8°C, 161.4°C, 165.0°C, or 191.7°C, or may be within a range with these as upper or lower limits, or may be a range combining these as upper and lower limits. Having a softening temperature within these ranges tends to make it easier for the hot melt adhesive to undergo the heating-melting-cooling-solidification cycle during adhesion. The softening temperature is the temperature at which the fluidity increases rapidly and deformation begins as the temperature is increased, and can be measured using a thermomechanical analysis dynamic viscoelasticity measuring device (e.g., TMA / SS6000, Hitachi High-Tech Science).

[0047] (5% Weight Loss Temperature) In this embodiment, the 5% weight loss temperature of the hot melt adhesive is not particularly limited as long as it does not detract from the scope of the present invention, but is preferably 250°C or higher, and more preferably 270°C or higher. Furthermore, when the 5% weight loss temperature is 250°C or higher, it may be 274.8°C, 319.8°C, 322.8°C, 333.9°C, 342.6°C, or 347.3°C, or may be within a range with these as upper or lower limit values, or may be a range combining these as upper and lower limit values. By having a 5% weight loss temperature within these ranges, the hot melt adhesive tends to have little weight loss and be able to maintain adhesive strength even when exposed to high temperatures. The "5% weight loss temperature" is the temperature at which a sample is heated to induce thermal decomposition and loses 5% of its weight, based on the weight of the sample at around room temperature, and can be measured using a differential thermal / thermogravimetric simultaneous analyzer (e.g., Thermo plus EVO2 TG 8120, Rigaku).

[0048] (Compressive shear adhesive strength after re-adhesion) In this embodiment, the hot melt adhesive has a compressive shear adhesive strength after re-adhesion determined under the following condition 2 of 1.0 N / mm ２ or more. <Condition 2> A test piece (a) obtained by the method described in <Condition 1> above is prepared. That is, a piece of wood measuring 30 mm in length, 25 mm in width, and 10 mm in thickness is used as the adherend. Two pieces of the adherend are overlapped with a hot melt adhesive measuring 25 mm in length, 25 mm in width, and 0.1 mm in thickness sandwiched between them, and bonded by hot pressing at a temperature of 190°C, a pressure of 1 MPa, and a time of 20 minutes to prepare test piece (a). This test piece (a) is heated to peel the two pieces of the adherend, and the adhesive surfaces of the two peeled pieces of the adherend are re-overlapped and re-adhered by hot pressing at a temperature of 190°C, a pressure of 1 MPa, and a time of 20 minutes to prepare re-adhesion test piece (b). For the re-adhesion test piece (b), the compressive shear adhesive strength (N / mm ) after re-adhesion is measured using the compressive shear adhesive strength test method for adhesives according to JIS K6852 described above. ２The operation of heating the test piece and peeling the two pieces of adherend can be carried out by a standard method. For example, this can be done by using a small heat press (for example, product name AH-2003, AS ONE) and heating at 160°C, 180°C, or 190°C for 30 minutes, followed by applying force by hand.

[0049] The compressive shear adhesive strength after re-adhesion was 1.0 N / mm ２ Above, 2.0N / mm ２ Above, 3.0N / mm ２ Above, 4.0N / mm ２ Above, 5.0N / mm ２ or more, or 5.4 N / mm ２ The compressive shear adhesive strength after re-adhesion may be 1.0 N / mm or more. ２ to 9.0 N / mm ２ , 2.0 N / mm ２ to 9.0 N / mm ２ , 3.0 N / mm ２ to 9.0 N / mm ２ , 4.0 N / mm ２ to 9.0 N / mm ２ , 5.0 N / mm ２ to 9.0 N / mm ２ , 5.4 N / mm ２ to 9.0 N / mm ２ , 1.0 N / mm ２ to 5.4 N / mm ２ , 1.0 N / mm ２ to 5.0 N / mm ２ , 1.0 N / mm ２ to 4.0 N / mm ２ , or 2.0 N / mm ２ to 4.0 N / mm ２ The compressive shear adhesive strength after re-adhesion may be 3.1 N / mm ２ , 5.2 N / mm ２ , or 5.4 N / mm ２ It may be a range having these as upper or lower limit values, or may be a range combining these as upper and lower limit values.

[0050] The compressive shear adhesive strength after re-adhesion is 1.0 N / mm ２The hot melt adhesive described above maintains excellent adhesive properties even when re-bonded. Therefore, even when materials bonded with this hot melt adhesive are peeled off, the hot melt adhesive used the first time can be effectively used for the second bonding without the need to apply a new hot melt adhesive or remove the hot melt adhesive used the first time. Alternatively, the amount of hot melt adhesive required to be newly added can be reduced. This feature of the hot melt adhesive is particularly useful when processing wood into houses or furniture using the hot melt adhesive, and it also makes it easy to reuse wood used in houses or furniture after its useful life has expired. Furthermore, since wood is used for long periods of time after being processed into houses or furniture, it is an excellent material from the perspective of carbon dioxide capture, utilization, and storage (CCUS). However, since most of these materials are incinerated after their useful life has ended, the stored carbon dioxide is released back into the atmosphere. One effective way to avoid this is to reuse wood. Reuse here refers to reusing plywood, particle board, fiberboard, etc. used in products such as furniture in other products. In order to reuse wood, it is often necessary to remove the plywood, etc. that has been glued together. As described above, the hot melt adhesive in this embodiment has excellent adhesive properties and can peel wood by heating, making it easy to reuse wood and highly sustainable.

[0051] (Method for Producing Hot Melt Adhesive) In one embodiment, the hydrogen of at least one hydroxy group in at least one glucose unit of the β-1,3-glucan is replaced with -COR １ (R １represents a hydrocarbon group) to prepare a β-1,3-glucan derivative. This production method is highly sustainable because it can use naturally derived biomass raw materials obtained from the genus Euglena and the like. Furthermore, the hot melt adhesive produced by this production method has excellent adhesive properties and is particularly suitable for use in bonding wood. The method for preparing the β-1,3-glucan derivative is as described above.

[0052] (Bonding Method) In one embodiment, a method for bonding a first adherend and a second adherend is provided, comprising sandwiching the above-described hot melt adhesive between the first adherend and the second adherend. The first adherend and the second adherend are not limited as long as the effects of the present invention are not impaired. However, when the first adherend and the second adherend are wood, the first adherend and the second adherend can be bonded well. Most conventional wood adhesives are synthetic adhesives that rely heavily on fossil resources, such as formaldehyde. However, the use of such synthetic adhesives is undesirable due to restrictions on volatile organic compound (VOC) emissions, considerations for human health and the environment, and sustainability. In contrast, the method of this embodiment uses a hot melt adhesive that can be made from naturally derived biomass materials, such as those obtained from the genus Euglena, thereby reducing the burden on the human body and the environment and providing high sustainability. The bonding method of this embodiment is not particularly limited as long as it does not impair the effects of the present invention. However, when the first adherend and the second adherend are wood, for example, the first adherend and the second adherend can be bonded by sandwiching a hot melt adhesive between them, then hot pressing them at a temperature of 90 to 200°C and a pressure of 0.5 to 10 MPa for 5 to 60 minutes, and then cooling to room temperature.

[0053] (Re-adhesion method) In one embodiment, a method for bonding a first adherend and a second adherend, which includes heat-peeling the first adherend and the second adherend bonded by the above-described method for bonding the first adherend and the second adherend, and re-adhering the first adherend and the second adherend using the hot melt adhesive remaining on the bonding surface of the first adherend and / or the bonding surface of the second adherend. This method allows for the reuse of previously applied hot melt adhesive when reusing the adherend, thereby efficiently utilizing resources. It also reduces the time and effort required for reusing the adherend. The heat-peeling method is not particularly limited as long as it does not impair the effects of the present invention. However, when the first adherend and the second adherend are wood, for example, the bonded first adherend and the second adherend can be peeled by heating the bonded first adherend and the second adherend at 90 to 200°C for 5 to 60 minutes.

[0054] In one embodiment, there is provided a use of the above-described hot melt adhesive for bonding materials. The materials may be any material within the scope of the present invention, but are preferably wood-based materials. The bonding of the materials can be carried out in the same manner as the above-described bonding method.

[0055] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, commercially available reagents, instruments, etc. mentioned in the examples were used in accordance with the manufacturer's instructions or standard procedures.

[0056] [Synthesis of Hot Melt Adhesives] The β-1,3-glucan derivatives paramylon hexanoate (6 acyl carbon atoms), paramylon heptanoate (7 acyl carbon atoms), paramylon octanoate (8 acyl carbon atoms), paramylon decanoate (10 acyl carbon atoms), paramylon laurate (12 acyl carbon atoms), paramylon myristate (14 acyl carbon atoms), and paramylon palmitate (16 acyl carbon atoms) were prepared according to a standard method to produce hot melt adhesives. Examples of standard methods include the method shown in the synthesis scheme below.

[0057]

[0058] Here, R is each independently hydrogen or an acyl group, at least a part of R is an acyl group, and n is a natural number.

[0059] The synthesis method will be described in more detail below, using paramylon hexanoate with an acyl group substitution degree of 2.12 as an example. 2.502 g of paramylon (15.431 mmol) was dispersed in 200 mL of pyridine, followed by the dropwise addition of 6.226 g (46.256 mmol) of hexanoyl chloride. The mixture was then stirred at 65°C under a nitrogen atmosphere. The ratio of the acylating agent to the glucose units contained in the paramylon (acylating agent / glucose units contained in β-1,3-glucan (mol / mol)) was 3.0. After 3 hours, the homogenized solution was poured into 400 mL of water to obtain a pale yellow sticky solid. This solid was removed by decantation, dispersed in 200 mL of methanol, and washed with stirring (10 minutes, twice). It was then dispersed in 50 mL of chloroform and stirred at room temperature until homogenized. After homogenization, the solid was poured into 300 mL of methanol to obtain a white gel. This procedure was repeated twice. Air drying (overnight) followed by vacuum drying at 100°C for 3 hours yielded the target product (4.047 g, 10.972 mmol, acyl group substitution degree 2.12, yield 71.1%). Using a similar synthesis method, various β-1,3-glucan derivatives were obtained by adjusting the acyl group carbon number of the acylating agent and the charge ratio of the acylating agent to the glucose units contained in paramylon as shown in Table 1. For example, paramylon hexanoate with an acyl group substitution degree of 2.76 was obtained by using hexanoyl chloride as the acylating agent and setting the charge ratio of the acylating agent to the glucose units contained in paramylon at 3.5:1.0. Furthermore, by using octanoyl chloride as the acylating agent and adjusting the ratio of the acylating agent to the glucose units contained in paramylon to be 3.5:1.0, paramylon octanoate with an acyl group substitution degree of 2.87 was obtained. The obtained β-1,3-glucan derivative was processed by heat pressing into a sheet measuring 25 mm in length, 25 mm in width, and 0.1 mm in thickness.

[0060] The degree of acyl group substitution is １The evaluation was carried out by H-NMR based on the integral values ​​of the hydrogens directly bonded to the carbon atoms of the glucose units (hydrogens of the methylene and methine groups) and the hydrogens of the acyl groups.

[0061] [Evaluation of Softening Temperature] The softening temperature was evaluated using a thermomechanical analyzer (TMA / SS6000, Hitachi High-Tech Science).

[0062] [Evaluation of 5% Weight Loss Temperature] The 5% weight loss temperature was evaluated using a differential thermal / thermogravimetric simultaneous analyzer (Thermo plus EVO2 TG 8120, Rigaku).

[0063] [Evaluation of Compressive Shear Adhesion Strength and Compressive Shear Adhesion Strength after Rebonding] (Preparation of Test Pieces) A ​​rod-shaped board measuring 25 mm wide and approximately 12 mm thick, with the width and thickness perpendicular to the grain, was cut from a cedar board and planed in the thickness direction to a thickness of 10 mm. This rod-shaped board was continuously cut to a length of 30 mm in the grain direction to prepare wood pieces. Two pieces of adherend were aligned in the grain direction, overlapped with the hot melt adhesive measuring 25 mm long, 25 mm wide, and 0.1 mm thick, and then heat-pressed at 190 °C, 1 MPa pressure, and 20 minutes. The test pieces were then bonded by cooling to room temperature while maintaining a pressure of 1 MPa. Heat pressing was performed using a multiaxial material testing machine V-1815 (Saginomiya Seisakusho) according to the instructions included with the machine. The test specimens were allowed to stand for one week or longer in an atmosphere at 20°C and 60% relative humidity before being subjected to the compressive shear bond strength test method for the adhesive.

[0064] (Preparation of re-adhesion test specimens) The test specimens prepared by the above-mentioned method were heated to separate the two adherends, and the adhesive surfaces of the two separated adherends were re-overlapped with the fiber direction aligned, and then heat-pressed again under the above-mentioned conditions and cooled to re-adhere the two adherends to prepare re-adhesion test specimens. The operation of heating the test specimens to separate the two adherends was carried out using a small heat press (e.g., product name AH-2003, AS ONE) by heating at 160 ° C, 180 ° C, or 190 ° C for 30 minutes, followed by applying force by hand. The re-adhesion test specimens were left to stand for one week or longer in an atmosphere at a temperature of 20 ° C and a relative humidity of 60%, and then subjected to the adhesive compressive shear bond strength test method.

[0065] (Evaluation of Compressive Shear Adhesion Strength) The compressive shear adhesive strength of the test piece and the re-adhesion test piece was determined by the compressive shear adhesive strength test method for adhesives in accordance with JIS K6852. That is, one of the two adherends included in the test piece or re-adhesion test piece was fixed to a compression tester (precision universal testing machine AUTOGRAPH AG-X plus, Shimadzu Corporation) using a jig (wood shear test jig, Shimadzu Corporation). A compressive load was applied to the other adherend in a direction parallel to the adhesive surface at 20°C and a test speed of 2 mm / min. The maximum load (N) at which the adhesive surface broke and the adhesive area (mm ２ ) and the compressive shear adhesive strength (N / mm ２ )=Maximum load (N) / Adhesive area (mm ２ ) ... (1) Based on this, the compressive shear adhesive strength (N / mm ２ The compressive shear bond strength was determined independently for two test pieces or two re-adhesion test pieces to two significant figures, and the average value was used for evaluation.

[0066] The results are shown in Table 1.

[0067]

[0068] In Table 1, the charge ratio (mol / mol) is the charge ratio of the acylating agent to the glucose units contained in the β-1,3-glucan (acylating agent / glucose units contained in the β-1,3-glucan (mol / mol)). "-" means that no data is available. "X" means that the test specimen could not be peeled in the above-mentioned procedure, and a re-adhesive test specimen could not be prepared.

[0069] As shown in Table 1, the hot melt adhesives of Examples 1 to 10 had better compressive shear bond strength and were shown to have excellent adhesive properties compared to the hot melt adhesive of Comparative Example 1. In particular, the hot melt adhesives of Examples 1 to 6 exhibited high compressive shear bond strength and were therefore useful in applications requiring high adhesion, while the hot melt adhesives of Examples 7 to 10 exhibited relatively low compressive shear bond strength and were therefore considered to be useful in applications requiring low adhesion. Furthermore, the hot melt adhesives of Examples 5 to 7 were also shown to have good compressive shear bond strength after re-adhesion. Furthermore, the hot melt adhesives of Examples 1 to 3 and 5 to 7 were shown to have good softening temperatures and 5% weight loss temperatures.

[0070] The hot melt adhesives of Examples 1 to 10 were all non-sticky at room temperature and easier to handle, whereas the hot melt adhesive of Comparative Example 1 was sticky at room temperature.

[0071] The disclosures of all patents, patent applications and publications cited in this disclosure are hereby incorporated by reference in their entireties.

[0072] The hot melt adhesive of the present invention can be suitably used for bonding various materials used in final or intermediate industrial products. Therefore, the present invention has industrial applicability.

Claims

1. The following formula (I): 【Chemistry 1】 [In formula (I), R １ are each independently hydrogen or an acyl group represented by —COR2, where R2 is a hydrocarbon group and n is a natural number, provided that one or more —COR2 is included. The β-1,3-glucan derivative has a structure represented by the following formula: ２ That's it, hot melt adhesive. <Condition 1> A piece of wood measuring 30 mm in length, 25 mm in width and 10 mm in thickness is used as the adherend. Two pieces of the adherend were placed one on top of the other with the fiber direction aligned and a piece of the hot melt adhesive measuring 25 mm in length, 25 mm in width, and 0.1 mm in thickness sandwiched between them, and then hot pressed at a temperature of 190°C, a pressure of 1 MPa, and a time of 20 minutes.Then, the pieces were bonded together by cooling to room temperature while maintaining the pressing pressure of 1 MPa, to form a test piece. The test piece was subjected to a compressive shear bond strength test according to JIS K6852. ２ ) is required.

2. 2. The hot melt adhesive according to claim 1, having a softening temperature of 90°C or higher.

3. 3. The hot melt adhesive according to claim 1 or 2, which has a 5% weight loss temperature of 250°C or higher.

4. 3. The hot melt adhesive according to claim 1 or 2, wherein R2 is a C5-C15 alkyl group.

5. 3. The hot melt adhesive according to claim 1 or 2, wherein R2 is a C5-C11 alkyl group.

6. 3. The hot melt adhesive according to claim 1 or 2, wherein R2 is a C5-C7 alkyl group.

7. The hot melt adhesive according to claim 1 or 2, wherein the β-1,3-glucan derivative has an acyl group substitution degree of 1.00 to 2.

90.

8. The compressive shear adhesive strength after re-adhesion determined under the following condition 2 is 1.0 N / mm ２ The hot melt adhesive according to claim 1 or 2. <Condition 2> The test piece is heated to peel the two pieces of adherend, and the adhesive surfaces of the two peeled pieces of adherend are re-placed and hot-pressed at a temperature of 190°C, a pressure of 1 MPa, and a time of 20 minutes.Then, the pieces are cooled to room temperature while maintaining the pressing pressure of 1 MPa, thereby re-adhering them to form a re-adhesion test piece. The re-adhesion test piece was subjected to a compressive shear bond strength test method for adhesives in accordance with JIS K6852 to measure the compressive shear bond strength (N / mm ２ ) is required.

9. A method for producing a hot melt adhesive according to claim 1 or 2, A production method comprising substituting the hydrogen of at least one hydroxy group in at least one glucose unit of a β-1,3-glucan with -COR2 (R2 represents a hydrocarbon group) to prepare a β-1,3-glucan derivative.

10. 3. A method for bonding a first adherend and a second adherend, comprising applying the hot melt adhesive according to claim 1 or 2 between the first adherend and the second adherend.

11. The method of claim 10 , wherein the first and second adherends are wood-based materials.

12. Heating and peeling the first adherend and the second adherend bonded by the method according to claim 10; and Re-adhering the first adherend and the second adherend by the hot melt adhesive remaining on the adhesive surface of the first adherend and / or the adhesive surface of the second adherend. A method for bonding the first adherend and the second adherend, comprising:

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