Adhesive composition, and method for increasing ratio of shear bond strength and peel strength

Abstract

The objective is to provide an adhesive composition having a sufficiently large ratio of shear force to peel strength, and a method to increase the value of the ratio of shear adhesive force to peel strength.

Description

Technology Field

[0001] The present invention claims the benefit of the filing date of Japanese patent application No. 2019-053061 filed with the Japan Patent Office on March 20, 2019, the entire contents of which are incorporated herein.

[0002] The present invention relates to an adhesive composition for increasing the value of the ratio of shear adhesive strength to peel strength, and a method for increasing the value of the ratio of shear adhesive strength to peel strength. Background Technology

[0003] When returning cargo from factories or warehouses, or transporting it by truck or ship, cargo may collapse due to external vibrations or tilting. In such cases, physically securing the cargo with belts is a viable option; however, this method is unable to withstand vibrations from various directions, leading to instances where the cargo crumbles.

[0004] Furthermore, while methods for securing loads with adhesives exist, various materials such as paper and plastic are envisioned as bondable materials. However, it is difficult to accommodate all bondable materials, and their performance has not been sufficient. Specifically, because the shear adhesive strength is not sufficient to withstand vibrations, there have been cases where the load collapsed, or where the peel strength is too high, making it difficult to detach from the bondable material. Additionally, since manual operation is required, there was the issue of increased time and effort.

[0005] Therefore, there was a problem in that currently commercialized cargo collapse prevention agents did not have sufficient performance, and were not suitable for other applications requiring anisotropic adhesive strength in addition to cargo collapse prevention.

[0006] Easy-to-peel adhesives that facilitate peeling from a bonded material are known. For example, Japanese Patent Publication No. 2017-25130 proposes an easy-to-peel adhesive composition characterized by containing cellulose nanofibers. However, the problem in the said patent document is to have high adhesive strength and easy peeling, and peeling is performed by applying force from one side, that is, by shear force. Therefore, it was not possible to sufficiently obtain the performance required for load collapse prevention agents, such as high shear force and low peel strength (adhesive strength in Japanese Patent Publication No. 2017-25130). Prior art literature

[0007] Japanese Patent Publication No. 2017-25130 The problem to be solved

[0008] Therefore, there was a need for an adhesive composition having greater shear adhesion and lower peel strength than conventional adhesive compositions, and a method to increase the value of the ratio of shear adhesion to peel strength.

[0009] The present invention is made to solve the problems of the prior art and aims to provide an adhesive composition having a sufficiently large ratio of shear force to peel strength, and a method for increasing the value of the ratio of shear adhesive force to peel strength. means of solving the problem

[0010] The inventors arrived at the present invention by carefully examining the above problem and unexpectedly discovering that by using cellulose nanofibers, the value of the ratio of shear adhesion strength to peel strength of the adhesive composition can be increased.

[0011] The objective of the present invention is achieved by an adhesive composition comprising cellulose nanofibers, wherein the value of the ratio of shear adhesive strength to peel strength (shear adhesive strength / peeling strength) is 50 or higher.

[0012] It is preferable that the fiber diameter of the above cellulose nanofiber be 4 nm to 500 nm. In addition, it is preferable that the aspect ratio of the above cellulose nanofiber be 10 or higher.

[0013] It is preferable that the above cellulose nanofibers be included in an amount of 0.01 mass% to 20 mass% with respect to the total mass of the adhesive composition.

[0014] It is preferable that the above adhesive composition further includes one or more selected from the group consisting of acrylic resin, urethane resin, epoxy resin, vinyl acid resin, rosin resin, hydrocarbon resin, and polyvinyl alcohol.

[0015] The present invention also relates to a method for increasing the value of the ratio of shear adhesive strength to peel strength (shear adhesive strength / peele strength) of an adhesive composition, characterized by adding cellulose nanofibers to said adhesive composition.

[0016] In the above method, it is preferable that the fiber diameter of the cellulose nanofiber is 4 nm to 500 nm. In addition, it is preferable that the aspect ratio of the cellulose nanofiber is 10 or more.

[0017] In the above method, it is preferable that the cellulose nanofibers be included in an amount of 0.01 mass% to 20 mass% with respect to the total mass of the adhesive composition.

[0018] In the above method, it is preferable that the adhesive composition further comprises one or more selected from the group consisting of acrylic resin, urethane resin, epoxy resin, vinyl acid resin, rosin resin, hydrocarbon resin, and polyvinyl alcohol. Effects of the invention

[0019] According to the present invention, by using cellulose nanofibers, it is possible to provide an adhesive composition having a sufficiently large value of the ratio of shear adhesive strength to peel strength (shear adhesive strength / peeling strength). Furthermore, since the ratio of shear adhesive strength to peel strength is much larger than that of conventional adhesive compositions, it can be applied to new applications where only high shear adhesive strength is required.

[0020] Furthermore, the present invention can sufficiently increase the ratio of shear adhesive strength to peel strength compared to conventional adhesive compositions. That is, the present invention can have the characteristic feature of increasing the ratio of both, rather than increasing only shear strength or only peel strength. Specific details for implementing the invention

[0021] The adhesive composition of the present invention comprises cellulose nanofibers as an essential component.

[0022] In this specification, cellulose nanofibers refer to cellulose microfibrils (nanocellulose), which are hierarchical structural units formed by crystallizing cellulose through hydrogen bonding among trees, for example, having a fiber diameter of 4 nm to 500 nm and a length of 5 μm or more.

[0023] The method for manufacturing cellulose nanofibers is not particularly limited, but methods for manufacturing them from natural cellulose, such as wood, using physical or chemical methods may be cited. Physical methods include the high-pressure homogenizer method, the microfluidizer method, the high-shear kneading method, and the ball mill grinding method, which are referred to as defibrillation methods. Chemical methods include the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation method using a catalyst. Cellulose nanofibers may also be manufactured by combining multiple methods.

[0024] In the present invention, the fiber diameter of the cellulose nanofiber is preferably 4 nm to 500 nm, more preferably 5 nm to 400 nm, and most preferably 10 nm to 300 nm. If the fiber diameter is too large compared to the above values, there is a risk that the dispersibility in the adhesive composition will deteriorate. In addition, the fiber diameter of the cellulose nanofiber can be measured as the average value obtained by randomly measuring 50 or more cellulose nanofibers within the field of view when observed, for example, with an electron microscope.

[0025] In the present invention, the specific surface area of ​​the cellulose nanofiber is 50 m² 2 / g~300m 2 It is preferable that it is / g, and 60m 2 / g~250m 2 It is more desirable that it is / g, and 70m 2 / g~200m 2 It is most desirable to have / g.

[0026] In the present invention, the aspect ratio of the cellulose nanofiber is preferably 10 or higher, more preferably 50 or higher, and most preferably 100 or higher. By making the aspect ratio of the cellulose nanofiber 10 or higher, sufficient shear adhesion can be imparted to the adhesive composition.

[0027] The cellulose nanofibers of the present invention may or may not be surface modified. After manufacturing cellulose nanofibers, surface-modified cellulose nanofibers can be obtained by adding a compound for surface modification and reacting it. Surface modification may be chemical modification or physical modification, and modification may be achieved by reacting with hydroxyl groups on the surface to form chemical covalent bonds, or by physically adsorbing the surface using anionic, cationic, or nonionic surfactants.

[0028] The amount of cellulose nanofibers included in the adhesive composition of the present invention is not particularly limited, but it is preferable that they be included in an amount of 0.01 mass% to 20 mass% with respect to the total mass of the adhesive composition, more preferable that they be included in an amount of 0.05 mass% to 10 mass%, and most preferable that they be included in an amount of 0.1 mass% to 5 mass%.

[0029] The adhesive composition of the present invention preferably further comprises one or more selected from the group consisting of acrylic resin, urethane resin, epoxy resin, vinyl acid resin, rosin resin, hydrocarbon resin, and polyvinyl alcohol. These are used as matrix resins of the adhesive and may be used as a single type or in combination of multiple types. In addition, the acrylic resin, urethane resin, epoxy resin, vinyl acid resin, rosin resin, hydrocarbon resin, or polyvinyl alcohol used may be an oligomer or a polymer, and may be used in the form of a solution or an emulsion using water or the like as a solvent.

[0030] Examples of acrylic resins include polyacrylates, polymethacrylates, and copolymers thereof. Examples of vinyl-acetate resins include acrylic-styrene copolymer, acrylic-vinyl acetate copolymer, acrylic-vinyl chloride copolymer, acrylic-ethylene copolymer, polyvinyl acetate, vinyl acetate-vinyl chloride copolymer, vinyl acetate-ethylene copolymer, and vinyl acetate-styrene copolymer. Examples of hydrocarbon-based resins include polyethylene, polypropylene, polybutadiene, polystyrene, polyisobutylene, and styrene-butadiene copolymer.

[0031] The amount of acrylic resin, urethane resin, epoxy resin, vinyl acid resin, rosin resin, hydrocarbon resin, or polyvinyl alcohol included in the adhesive composition of the present invention is not particularly limited, but it is preferable that it be included in an amount of 1% to 99% by mass with respect to the total mass of the adhesive composition, more preferable that it be included in an amount of 5% to 95% by mass, and most preferable that it be included in an amount of 10% to 90% by mass. In addition, the amount of cellulose nanofibers included in the adhesive composition of the present invention is preferably 0.01 mass% to 20 mass% with respect to the total mass of the cellulose nanofibers and the acrylic resin, urethane resin, epoxy resin, vinyl acid resin, rosin resin, hydrocarbon resin, or polyvinyl alcohol, more preferably 0.05 mass% to 10 mass%, and most preferably 0.1 mass% to 5 mass%.

[0032] The adhesive composition of the present invention may further include additives such as plasticizers, light stabilizers, ultraviolet absorbers, lubricants, antioxidants, anti-blocking agents, fluidity improvers, release agents, flame retardants, colorants, fillers, conductive agents, defoaming agents, polymerization inhibitors, antistatic agents, leveling agents, emulsifiers, and viscosity modifiers, provided that the effects of the present invention are not impaired.

[0033] The method for preparing the adhesive composition of the present invention is not particularly limited. For example, it can be prepared by making a dispersion by stirring cellulose nanofibers in a solvent such as water to completely disperse them, adding a resin to the dispersion as needed to dissolve or disperse it, and further adding and mixing other additive components. Alternatively, the solid components may be sufficiently mixed using a mixer before adding a solvent such as water, and then the solvent such as water may be added to disperse and dissolve them.

[0034] The present invention also relates to a method for increasing the value of the ratio of shear adhesive strength to peel strength (shear adhesive strength / peele strength) of an adhesive composition, characterized by adding cellulose nanofibers to the adhesive composition.

[0035] In the method of the present invention, by adding the cellulose nanofiber to the adhesive composition, the value of the ratio of shear adhesive strength to peel strength (shear adhesive strength / peele strength) can be increased. As the adhesive composition, a composition comprising the above acrylic resin, urethane resin, epoxy resin, vinyl acid resin, rosin resin, hydrocarbon resin, or polyvinyl alcohol may be used.

[0036] The adhesive composition of the present invention can be coated by methods such as spraying, wire bar, blade coater, air knife coater, or roll coater. Examples of materials to be adhered to include corrugated cardboard, cartons, cardboard, paper bags, and polyethylene bags, but are not limited thereto.

[0037] [Example]

[0038] The present invention will be explained in more detail below using examples and comparative examples, but the scope of the present invention is not limited to the examples.

[0039] (1) Preparation of a composition

[0040] (Example 1)

[0041] Cellulose nanofiber (Manufactured by Mori Machinery Co., Ltd., CellfFiM C-100, fiber diameter: 30nm–200nm, specific surface area 150m²) 2 600g of acrylic resin (manufactured by Kanae Chemical Industry Co., Ltd., PLT-31, aqueous dispersion) is added to 100g of aqueous dispersion (2 mass% aqueous dispersion) and stirred at room temperature to be thoroughly mixed. After confirming that it is uniformly mixed, the content of cellulose nanofibers is adjusted to 0.25 mass% relative to the total mass of the adhesive composition to prepare Composition 1.

[0042] (Example 2)

[0043] Composition 2 is prepared as in Example 1, except that the amount of acrylic resin added is 215g.

[0044] (Example 3)

[0045] Instead of cellulose nanofibers (Mori Machinery Co., Ltd., CellfFiM C-100), cellulose nanofibers (Mori Machinery Co., Ltd., CellfFiM L-45, fiber diameter: 50nm–300nm, specific surface area: 90m² 2 Composition 3 is prepared as in Example 1, except that a water dispersion of 2 mass% ( / g) is used.

[0046] (Example 4)

[0047] Composition 4 is prepared as in Example 2, except that cellulose nanofiber (CellfFiM L-45, manufactured by Mori Machinery Co., Ltd.) is used instead of cellulose nanofiber (CellfFiM C-100, manufactured by Mori Machinery Co., Ltd.).

[0048] (Example 5)

[0049] Composition 5 is prepared as in Example 1, except that cellulose nanofibers (Daiichi Industrial Pharmaceutical Co., Ltd., Leocrista I-2SX, fiber diameter: 2nm to 10nm) are used instead of cellulose nanofibers (Mori Machinery Co., Ltd., CellfFiM C-100).

[0050] (Example 6)

[0051] Composition 6 is prepared as in Example 2, except that cellulose nanofiber (Daiichi Industrial Pharmaceutical Co., Ltd., Leocrista I-2SX) is used instead of cellulose nanofiber (Mori Machinery Co., Ltd., CellfFiM C-100).

[0052] (Comparative Example 1)

[0053] A comparative composition is prepared by adding an appropriate amount of water to an acrylic resin (manufactured by Kanae Chemical Industry Co., Ltd., PLT-31, aqueous dispersion).

[0054] (2) Preparation of test specimens

[0055] An unbleached packaging paper in the shape of a long rectangle with a thickness of 150㎛, a width of 10mm, and a length of 50mm is used as the bonding material. A test specimen with an adhesive area of ​​10mm × 10mm is prepared and used to measure the following shear adhesion strength and peel strength.

[0056] (3) Measurement of shear adhesion

[0057] Shear adhesion is measured by using a tensile testing device to tensile a test specimen at a speed of 25 mm / min under an atmosphere of room temperature (25℃).

[0058] (4) Measurement of peel strength

[0059] The peel strength is measured by fixing one side of the test specimen horizontally under an atmosphere of room temperature (25℃) and measuring the force when peeling by stretching the other side at an upward angle of 90°.

[0060] Shear adhesion, peel strength, and the ratio of shear adhesion to peel strength of each composition Shear adhesion (N / cm) 2 ) Peel strength (N / cm) 2 ) Ratio of shear adhesion to peel strength Composition 1 4 0.035 114 Composition 2 6 0.03 200 Composition 3 4.5 0.04 113 Composition 4 6.5 0.04 163 Composition 5 3.5 0.04 88 Composition 6 3.9 0.04 98 Comparative composition 3 0.1 30

[0061] As can be seen in Table 1, the adhesive composition of the present invention containing cellulose nanofibers has a higher value of shear adhesive strength and a lower value of peel strength compared to a comparative composition not containing cellulose nanofibers. In addition, it is confirmed that the ratio of peel strength (shear adhesive strength / peeling strength) is increased accordingly, and the anisotropy of adhesive strength is strengthened.

[0062] The adhesive composition of the present invention is useful because it is possible to obtain an adhesive composition in which the value of the ratio of shear adhesive strength to peel strength (shear adhesive strength / peele strength) is sufficiently large.

Claims

Claim 1 An adhesive composition for preventing cargo collapse, comprising cellulose nanofibers, wherein the ratio of shear adhesion to peel strength (shear adhesion / peele strength) is 50 or more and 200 or less. Claim 2 An adhesive composition for preventing droplet collapse according to claim 1, wherein the fiber diameter of the cellulose nanofiber is 4 nm to 500 nm. Claim 3 delete Claim 4 An adhesive composition for preventing cargo collapse according to claim 1, wherein the cellulose nanofibers are included in an amount of 0.01 mass% to 20 mass% with respect to the total mass of the adhesive composition. Claim 5 An adhesive composition for preventing cargo collapse, comprising, in any one of claims 1, 2 and 4, further comprising one or more selected from the group consisting of acrylic resin, urethane resin, epoxy resin, vinyl acid resin, rosin resin, hydrocarbon resin and polyvinyl alcohol. Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 delete