Adhesive composition

Abstract

The adhesive composition contains a cellulose derivative and a solvent component. The cellulose derivative has an acetyl group-based degree of substitution of 1.9 or more and 2.6 or less. The solvent component contains an organic solvent A having a boiling point of 100°C or more and an SP value of 18 to 30 (J / cm 1 / 2 3 / 2 ). The amount of the cellulose derivative is 15 mass% or more and 30 mass% or less relative to the total amount of the cellulose derivative and the organic solvent A.​

Description

Technical Field

[0001] This disclosure relates to adhesive compositions. More specifically, this disclosure relates to adhesive compositions and adhesives, primers, and molded articles using the adhesive compositions. Background Technology

[0002] Cellulose resins are polymeric materials derived from cellulose, with cellulose derivatives being representative examples. The main raw material for cellulose derivatives is cellulose, a natural raw material. Therefore, using cellulose resins can yield environmentally friendly and sustainable molding materials and products.

[0003] It is known that cellulose derivatives, such as cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate with acetyl groups, exhibit thermoplasticity depending on their degree of substitution. Previously, molding of cellulose acetate and the like involved either extrusion ("extrusion method") to form a predetermined cross-sectional shape or block molding ("block method") where the material is placed in a mold. Therefore, machining is sometimes required to obtain molded articles with complex shapes. In recent years, attempts have been made to manufacture molded articles using cellulose acetate and other sustainable materials through melt molding and injection molding. However, cellulose derivatives, especially cellulose acetate, have lower melt flowability compared to conventional synthetic polymers, posing a challenge for injection molding complex shapes.

[0004] On the other hand, cellulose derivatives, especially cellulose acetate, are known to have high biodegradability and can be decomposed by activated sludge. Furthermore, cellulose acetate with improved biodegradability, exhibiting marine biodegradability, has been proposed. In recent years, due to increased concern for the Earth's environment, there has been a demand for manufacturing complex-shaped molded products using biodegradable cellulose derivatives, especially cellulose acetate.

[0005] For example, techniques are known for joining multiple components in metallic materials to manufacture molded articles of desired size and shape. In contrast, resin components typically exhibit high wetting tension on their surfaces. Therefore, liquid adhesives do not fuse, necessitating research into the adhesion between resin components. As a representative and simple method, it is known to apply an adhesive after coating the surface of the resin components with a surface treatment agent known as a "primer."

[0006] For components formed from cellulose acetate, a cellulose derivative, there are exceptional methods of bonding using a solvent that dissolves cellulose acetate. This method involves applying the solvent to the bonding surfaces of the components to be bonded, causing the surfaces to swell. Examples of solvents for dissolving cellulose acetate include ketones such as acetone. A commercially available adhesive containing such a solvent is SAN NISHIMURA's product, "NO.250-B Cellulose Acetate Adhesive Z". This adhesive is composed of a mixture of 20 wt% ethyl acetate (boiling point 77°C), 30 wt% ethyl lactate (boiling point 155°C), and 50 wt% acetone (boiling point 55°C). This adhesive allows for the bonding of lightweight, small components such as nose pads for eyeglasses.

[0007] On the other hand, with the expansion of application areas, the demand for molded products with larger dimensions and more complex shapes is also increasing. Depending on the application, optical transparency is sometimes also required. Because solvents such as acetone have low viscosity, adhesives based on these solvents can cause dripping from the coated bonding surface, which is difficult to handle in large-area bonding. Furthermore, the rapid evaporation rate of volatile solvents such as acetone necessitates bonding within 30 seconds of application, making it difficult to apply to components with large bonding areas.

[0008] The aforementioned "NO.250-B Cellulose Acetate Adhesive Liquid Z" adjusts viscosity and evaporation rate by adding ethyl lactate and ethyl acetate to acetone, but it does not completely solve the problems arising in the bonding of components with large bonding surfaces. Furthermore, for "NO.250-B Cellulose Acetate Adhesive Liquid Z," since it dissolves the bonding surfaces of the materials to be bonded, it takes time for the solidification process to achieve stable strength. Because it contains high-boiling-point solvents such as ethyl lactate, cellulose acetate has poor solubility, and the evaporation rate is slow, making it impractical for bonding large components. Previously, there were no practical adhesives capable of bonding large components formed from cellulose resin materials.

[0009] For example, Patent Document 1 (Japanese Patent Application Publication No. 11-172290) discloses a solvent composition for plastics containing a variety of organic solvents. In this solvent composition, at least one solvent selected from isopropyl bromide or n-propyl bromide is included as a first solvent component, and acetone, ethyl lactate, etc., are included as a second solvent component. Patent Document 2 (Japanese Patent No. 2505909) discloses an adhesive containing a compound having a thiol group and a masking agent selected from the group consisting of vanillin, lemon oil, and ester solvents.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 11-172290

[0013] Patent Document 2: Japanese Patent No. 2505909 Summary of the Invention

[0014] The problem the invention aims to solve

[0015] The solvent composition disclosed in Patent Document 1 and the adhesive disclosed in Patent Document 2 result in poor adhesion of components formed from cellulose resin. Furthermore, as mentioned above, adhesives containing organic solvents such as acetone and ethyl lactate are difficult to apply to the bonding of large components. Moreover, with adhesives of low viscosity, it is difficult to apply them evenly to the bonding surface. In particular, when bonding transparent components, if there are unevenness or irregularities on the bonding surface, it is perceived as light reflection, resulting in a poor appearance.

[0016] Furthermore, in recent years, the demand for primers (also known as sealants) that improve interlayer adhesion has increased in the layer-by-layer modeling of large-scale 3D printers, which are becoming increasingly common. For example, in the case of FDM (Fused Deposition Modeling) 3D printers, molten or liquid thermoplastic material is ejected from a nozzle, which moves along a computer-controlled path to build parts layer by layer. By increasing the nozzle's range of motion, large components can be manufactured. However, when the nozzle's path becomes longer, new material is ejected onto the solidified layers after the ejected thermoplastic material cools and solidifies, resulting in a lack of integration between layers and preventing the desired molded product from being obtained. To manufacture large components using 3D printers, a primer is needed that provides adhesion to newly ejected layers after they have cooled and solidified. In particular, primers that improve interlayer adhesion in the layer-by-layer modeling of large components using cellulose resin have not been available previously.

[0017] The purpose of this disclosure is to provide an adhesive composition that exhibits excellent adhesion to components formed from cellulose resins, particularly those made of cellulose acetate, enabling the manufacture of complex and large molded articles, and providing excellent transparency after bonding.

[0018] Another object of this disclosure is to provide an adhesive suitable for joining large components formed from cellulose resin. A further object of this disclosure is to provide a primer suitable for interlayer bonding in stacked models using a 3D printer. Furthermore, an object of this disclosure is to provide large molded articles formed from cellulose resin.

[0019] Solution for solving the problem

[0020] The adhesive composition disclosed herein comprises a cellulose derivative and a solvent component. The cellulose derivative has an acetyl-based degree of substitution of 1.9 or more and 2.6 or less. The solvent component comprises components with a boiling point of 100°C or more and an SP value of 18 to 30 (J). 1 / 2 / cm 3 / 2 Organic solvent A. The amount of cellulose derivative in the adhesive composition is 15% by mass or more and 30% by mass or less relative to the total amount of cellulose derivative and organic solvent A.

[0021] The effects of the invention

[0022] This adhesive composition causes the cellulose resin on the surface of the component, which serves as the bonded object, to swell. The adhesive containing this composition can be applied to the bonding of components formed from cellulose resin. Furthermore, since the organic solvent A, as a solvent component, is low in volatility, it maintains its adhesiveness for a certain period after being applied to the bonding surface. Moreover, this adhesive composition contains a cellulose derivative, thus exhibiting a higher viscosity than conventional adhesives composed solely of solvents. According to this adhesive composition, it can be uniformly applied to the bonding surface without dripping. After applying this adhesive composition, the operator can ensure sufficient working time. Furthermore, when manufacturing using a 3D printer, sufficient working time can be obtained by applying a primer containing this adhesive composition to the ejected layer until a new layer, serving as the bonded object, is ejected. According to this primer, large components can be manufactured using the 3D printer process. Furthermore, according to this adhesive composition, appearance defects caused by uneven coating can be avoided. This adhesive composition can also be applied to the bonding of transparent components. Detailed Implementation

[0023] The following describes a preferred embodiment. The structures and combinations thereof in each embodiment are merely examples; additions, omissions, substitutions, and other modifications to the structure can be made appropriately without departing from the spirit of this disclosure. This disclosure is not limited to the embodiments, but only to the claims. Furthermore, the various methods disclosed in this specification can also be combined with any other features disclosed in this specification.

[0024] The numerical ranges of each element disclosed in this specification can be arbitrarily combined with the numerical ranges of other elements. For example, the limitation on the numerical range of the acetyl substitution degree of the cellulose resin can be combined with the limitation on the numerical range of the molecular weight. Furthermore, the numerical ranges of each element disclosed in this specification can be any combination of its upper and lower limits.

[0025] (Definition of the term)

[0026] "Cellulose derivatives" are defined as a general term for compounds in which at least a portion of the hydroxyl groups of cellulose molecules are introduced with various substituents. In this disclosure, cellulose derivatives used as molding materials are specifically referred to as "cellulose resins." "Molding material" refers to the material used as the bonding object, i.e., the component or molded article of the bonded object in the adhesive composition of this disclosure. Cellulose resins can be in a solid or molten state. Hereinafter, cellulose derivatives and cellulose resins, as components of the adhesive composition, are referred to differently, and their types and compositions may be the same or different.

[0027] Additionally, in this disclosure, the range "X~Y" means "above X and below Y". Unless otherwise specified, all test temperatures are room temperature (20℃±5℃). In this specification, "wt%" refers to mass percent. Mass percent refers to weight percent, not mass concentration.

[0028] (cellulose resin)

[0029] The material of the adherends in the adhesive composition of this disclosure is a cellulose resin. The adhesiveness provided by the adhesive composition of this disclosure is manifested by at least causing swelling of the adhesive surfaces of the adherends. The type of cellulose resin is not particularly limited as long as it does not impede this function, but a cellulose resin similar to the cellulose derivatives contained in the adhesive composition described later is preferred.

[0030] The adherend to which the adhesive composition of this disclosure is intended can be a solid cellulose resin or a molten cellulose resin. For example, when using a primer containing the adhesive composition of this disclosure in a 3D printer's layering process, the primer can be applied to a solidified cellulose resin, and then the molten cellulose resin can be layered on top of it. Alternatively, the primer can be applied to a molten cellulose resin, and then a molten cellulose derivative can be layered on top of it.

[0031] Cellulose resins are obtained by derivativeling at least a portion of the hydroxyl groups of cellulose molecules. Preferably, a portion of the hydroxyl groups is esterified; more preferably, a portion of the hydroxyl groups is acetyl-esterified.

[0032] In other words, the preferred cellulose resin is a cellulose ester. As a cellulose ester, a cellulose fatty acid ester is preferred. Specific examples of cellulose fatty acid esters include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate, and cellulose acetate-butyrate. From the viewpoint of excellent biodegradability, cellulose acetate is more preferred. From the viewpoint of excellent moldability in injection molding, cellulose acetate-butyrate and cellulose acetate-propionate are more preferred.

[0033] When the cellulose resin is a cellulose ester, the preferred degree of esterification is approximately 1 to 3. When the cellulose resin is cellulose acetate, the degree of acetyl substitution is preferably 1.1 or higher and 2.8 or lower, more preferably 1.8 or higher and 2.8 or lower, even more preferably 2.2 or higher and 2.7 or lower, and particularly preferably 2.4 or higher and 2.6 or lower. The lower the upper limit of the degree of acetyl substitution, the better the moldability; the lower the lower limit, the better the biodegradability. The degree of acetyl substitution can be adjusted in a way that achieves the desired biodegradability and moldability.

[0034] From the viewpoint of easy melt molding, the weight-average molecular weight (Mw) of the cellulose resin is preferably 310,000 or less, more preferably 300,000 or less, and even more preferably 280,000 or less. In 3D printing, such high melt flowability is not required; therefore, the weight-average molecular weight (Mw) of the cellulose resin used as a raw material (printed polymer) for 3D printers can be 150,000 or more. Particularly from the viewpoint of improving the strength of the molded article, the weight-average molecular weight (Mw) of cellulose acetate is preferably 180,000 or more, more preferably 200,000 or more, and even more preferably 220,000 or more. It should be noted that in the chromatogram of cellulose resin (e.g., cellulose acetate) obtained by size exclusion chromatography (GPC analysis), peaks referred to as Pre-hump I, Pre-hump II, Main hump / Main peak, and Post-hump are observed sequentially from the substance with the shortest elution time (smallest molecular weight). In this disclosure, the main peak is used for the calculation of the weight-average molecular weight Mw, and other peaks are not considered.

[0035] The adherend to which the adhesive composition of this disclosure is intended can be a cellulose resin containing a plasticizer. Examples of plasticizers include glycerides, citrates, and adipates. The amount of plasticizer contained in the adherend can be 10 wt% or more and 30 wt% or less, or 15 wt% or more and 25 wt% or less.

[0036] (Adhesive composition)

[0037] The adhesive composition disclosed herein comprises a cellulose derivative having an acetyl substitution degree of 2.1 or higher and 2.6 or lower, and a solvent component. The solvent component comprises components with a boiling point of 100°C or higher and an SP value of 18 to 30 (J). 1 / 2 / cm 3 / 2Organic solvent A. The amount of cellulose derivative in the adhesive composition is 15% by mass or more and 30% by mass or less relative to the total amount of cellulose derivative and organic solvent A. The adhesive composition causes the cellulose resin that becomes the adherend to swell. The adhesive containing this adhesive composition can be applied to the bonding of components made of cellulose resin. The primer containing this adhesive composition is suitable for 3D printing of cellulose resin-based materials. In a preferred embodiment, the solvent component may further include organic solvent B with a boiling point below 100°C.

[0038] (cellulose derivatives)

[0039] The adhesive composition disclosed herein comprises a cellulose derivative with an acetyl substitution degree of 2.1 or more and 2.6 or less. Cellulose derivatives with an acetyl substitution degree of 1.9 or more and 2.6 or less exhibit good solvent solubility. The acetyl substitution degree of the cellulose derivative is preferably 2.0 or more, more preferably 2.1 or more. From the viewpoint of excellent biodegradability, the acetyl substitution degree of the cellulose derivative is preferably 2.56 or less, more preferably 2.50 or less, further preferably 2.40 or less, even more preferably 2.30 or less, and particularly preferably 2.26 or less. The total degree of acetyl substitution of cellulose acetate can be 1.9~2.56, 1.9~2.50, 1.9~2.40, 1.9~2.30, 1.9~2.26, 2.0~2.6, 2.0~2.56, 2.0~2.50, 2.0~2.40, 2.0~2.30, 2.0~2.26, 2.1~2.6, 2.1~2.56, 2.1~2.50, 2.1~2.40, 2.1~2.30, or 2.1~2.26.

[0040] It should be noted that when the cellulose derivative is cellulose acetate, if the degree of acetyl substitution is 2.7 or higher, there is a tendency for it to lack solubility in solvents. Additionally, a degree of acetyl substitution less than 2.0 also tends to result in a lack of solubility in solvents.

[0041] From the viewpoint of the adhesive strength provided by the adhesive composition, the weight-average molecular weight (Mw) of the cellulose derivative is preferably 70,000 or more, more preferably 80,000 or more, even more preferably 90,000 or more, and particularly preferably 100,000 or more. The upper limit of the weight-average molecular weight (Mw) of the cellulose derivative is not particularly limited, but from the viewpoint of the viscosity of the adhesive composition, it is preferably 300,000 or less, more preferably 290,000 or less, and can be 280,000 or less.

[0042] When comparing adhesive compositions with the same concentration of cellulose derivatives, a higher weight-average molecular weight of the cellulose derivative results in a higher viscosity of the adhesive composition. Furthermore, when comparing adhesive compositions with the same weight-average molecular weight of cellulose derivatives, a higher concentration of the cellulose derivative results in a higher viscosity of the adhesive composition. A higher concentration of cellulose derivative leads to a shorter open time (the time at which the adhesive can bond). On the other hand, adhesive compositions with a low concentration of cellulose derivatives containing a high weight-average molecular weight have high viscosity but a longer open time. The weight-average molecular weight of the cellulose derivative can be selected based on the application conditions and purpose of the adhesive composition.

[0043] The molecular weight distribution of cellulose derivatives is evaluated by the ratio of number-average molecular weight (Mn) to weight-average molecular weight (Mw) (Mw / Mn). In this disclosure, in order to maintain a uniform dissolved state of the adhesive composition, the molecular weight distribution Mw / Mn is preferably 3.5 or less, more preferably 3.2 or less, and even more preferably 3.0 or less. From the viewpoint of production efficiency of cellulose derivatives, the molecular weight distribution Mw / Mn of cellulose derivatives is preferably greater than 1.7, more preferably 1.8 or more, even more preferably 2.0 or more, and particularly preferably 2.1 or more.

[0044] Cellulose derivatives are typically semi-synthetic polymers obtained from cellulose as a raw material. Therefore, the molecular weight and molecular weight distribution of cellulose derivatives usually depend on the cellulose used as the raw material. The molecular weight and molecular weight distribution of cellulose derivatives can also be adjusted by using different types of cellulose raw materials.

[0045] The molecular weight and molecular weight distribution of the cellulose derivatives in the adhesive composition can be determined by known methods. Specifically, the molecular weight and molecular weight distribution of the cellulose derivatives are determined by diluting the solids content of the cellulose derivatives in the adhesive composition with acetone and performing size exclusion chromatography (GPC-light scattering) under the following apparatus and conditions.

[0046] Device: Shodex GPC "SYSTEM-21H"

[0047] Solvent: Acetone

[0048] Columns: 2 GMHxl (Tosoh) columns, and guard columns (Tosoh TSKgel guardcolumn HXL-H).

[0049] Flow rate: 0.8 ml / min

[0050] Temperature: 29℃

[0051] Sample concentration (as a cellulose derivative): 0.25% (wt / vol)

[0052] Injection volume: 100 μl

[0053] Detection: MALLS (Multi-Angle Light Scattering Detector) (Made by Wyatt, "DAWN-EOS")

[0054] MALLS calibration standard material: PMMA (molecular weight 27600)

[0055] It should be noted that the cellulose derivatives are manufactured using well-known methods for manufacturing cellulose derivatives. For example, in the manufacture of cellulose derivatives containing acetyl groups, the so-called acetic acid method, which uses acetic anhydride as an acetylation agent, acetic acid as a diluent, and sulfuric acid as a catalyst, can be cited. As a result of using a sulfuric acid catalyst during manufacturing, trace amounts of sulfate groups (sulfate esters) are sometimes introduced into the cellulose derivatives. In the adhesive compositions disclosed herein, the presence of sulfate groups, which are unavoidably introduced during the manufacture of the cellulose derivatives, is permitted.

[0056] In addition, cellulose derivatives may contain alkaline earth metals such as magnesium (Mg), calcium (Ca), and barium (Ba), and alkali metals such as sodium (Na) and potassium (K). The total content of these metals can be selected in the range of 20 ppm to 300 ppm.

[0057] Cellulose derivatives may further include acyl groups other than acetyl groups. Examples of acyl groups other than acetyl groups include aliphatic acyl groups such as propionyl, butyryl, isobutyryl, valeryl, neovaleryl, hexanoyl, octanoyl, decanoyl, lauroyl, and stearoyl; and aromatic acyl groups such as benzoyl and naphthoyl. From the viewpoint of solvent solubility and safety, aliphatic acyl groups are preferred, aliphatic acyl groups with 15 or fewer carbon atoms are more preferred, and aliphatic acyl groups with 12 or fewer carbon atoms are even more preferred. When the cellulose derivative includes acetyl groups and acyl groups other than acetyl groups, its total degree of substitution can be 2.15 or more, 2.25 or more, or 2.35 or more, with an upper limit of 3.0.

[0058] The degree of acetyl substitution and total substitution of cellulose derivatives are the sum of the degrees of substitution of each acetyl group at positions 2, 3, and 6 of the glucose ring of the cellulose derivative, and can be determined by the following methods. For example, they can be determined by NMR according to the method of Tezuka (Tezuka, Carbonydr. Res. 273, 83 (1995)).

[0059] Within the scope of the effects of this disclosure, the adhesive composition may contain cellulose derivatives having acyl groups other than acetyl groups, in addition to cellulose derivatives with an acetyl substitution degree of 1.9 or more and 2.6 or less. Examples of such cellulose acylates include cellulose acetate propionate and cellulose acetate butyrate.

[0060] From the viewpoint of improved transparency after bonding, the amount of cellulose derivative when the total adhesive composition is set to 100% by mass is preferably more than 8.0% by mass, more preferably 8.2% by mass or more, and even more preferably 8.5% by mass or more. From the viewpoint of solvent solubility, the concentration of cellulose derivative in the adhesive composition is preferably 25% by mass or less, more preferably 24% by mass or less.

[0061] When the amount of cellulose derivative in the adhesive composition is low, the area wetting the cellulose resin expands, and the unevenness of the adhesive interface increases, which sometimes reduces the transparency after bonding. When the concentration of cellulose derivative in the adhesive composition is 25% by mass or more, there is a tendency for the viscosity of the adhesive composition to become too high and the workability to deteriorate.

[0062] (solvent composition)

[0063] The solvent components contained in the adhesive composition disclosed herein will be described below. Here, "boiling point" in this specification refers to the standard boiling point (boiling point at 1 atmosphere), which is determined according to JIS K2254.

[0064] Additionally, "SP value" refers to the value of the solubility parameter. In this application specification, the SP value is defined as the solubility parameter δ (unit: J). 1 / 2 / cm 3 / 2 The solubility parameter δ is based on the molecular structure of the solvent and is calculated using the molar attraction constant ΔF and molar volume Δv of various atomic groups disclosed in "Toshihiko Okitsu, ed., Vol. 40, No. 8, pp. 342-350 (1996), Polymer Journal". It is calculated using the following (Equation 1).

[0065] δ=ΣΔF / ΣΔv (Equation 1)

[0066] In addition, the SP value of the mixed solvent is calculated using the following formula (2).

[0067] δmix=ψ1δ1+ψ2δ2+…+ψ n δ n (Equation 2)

[0068] In Equation 2, ψ represents the volume fraction or mole fraction, ψ1+ψ2+…+ψ n =1.

[0069] (Organic solvent A)

[0070] The solvent component in the adhesive composition disclosed herein comprises components with a boiling point of 100°C or higher and an SP value of 18-30 (J). 1 / 2 / cm 3 / 2The adhesive composition contains organic solvent A. Organic solvent A is low in volatility and has an affinity for cellulose derivatives. By including organic solvent A as a solvent component, the adhesive properties of the adhesive composition can be maintained for a certain period of time after being applied to the bonding surface formed by cellulose resin.

[0071] As a boiling point above 100℃ and SP value of 18~30 (J) 1 / 2 / cm 3 / 2 Organic solvent A can be methyl lactate (boiling point 145℃, SP value 24.8J). 1 / 2 / cm 3 / 2 ), ethyl lactate (boiling point 155℃, SP value 26.3J) 1 / 2 / cm 3 / 2 Lactates such as butyl acetate (boiling point 127℃, SP value 19.73J) 1 / 2 / cm 3 / 2 Acetates such as methyl butyrate (boiling point 120℃, SP value 18.68J) 1 / 2 / cm 3 / 2 ), Ethyl butyrate (boiling point 102℃, SP value 19.04J) 1 / 2 / cm 3 / 2 Butyrates, methyl ethylene glycol (boiling point 124℃, SP value 25.13J), etc. 1 / 2 / cm 3 / 2 ), methyl ethylene glycol acetate (boiling point 145℃, SP value 19.30J) 1 / 2 / cm 3 / 2 Diols, etc. Preferred organic solvent A is one or more selected from the group consisting of methyl lactate, ethyl lactate, and propyl lactate.

[0072] From the viewpoint of obtaining good coatability and adhesion, and also from the viewpoint of operational safety, the boiling point of organic solvent A is preferably 105°C or higher, more preferably 110°C or higher, and even more preferably 115°C or higher. From the viewpoint of selecting organic solvent A, the boiling point of organic solvent A is preferably 300°C or lower, more preferably 290°C or lower, and even more preferably 280°C or lower.

[0073] Including SP values ​​less than 18J 1 / 2 / cm 3 / 2 In the case of organic solvent A, there is a tendency for the boiling point of the solvent component to decrease, with an SP value greater than 30 J. 1 / 2 / cm 3 / 2 Organic solvent A sometimes exhibits low affinity for cellulose derivatives. The preferred SP value for organic solvent A is 19 J. 1 / 2 / cm 3 / 2 The above is preferred, with 22J being the most desirable. 1 / 2 / cm 3 / 2The above is further optimized to 24J. 1 / 2 / cm 3 / 2 In addition, 29J is preferred. 1 / 2 / cm 3 / 2 Hereinafter, 28J is preferred. 1 / 2 / cm 3 / 2 The following is a further preferred option: 27J 1 / 2 / cm 3 / 2 the following.

[0074] From the viewpoint of improving transparency after bonding, the concentration of organic solvent A when the entire adhesive composition is set to 100% by mass is preferably 35.0% by mass or more, more preferably 40.0% by mass or more, and even more preferably 45.0% by mass or more. From the viewpoint of improving adhesion, the concentration of organic solvent A in the adhesive composition is preferably 85.0% by mass or less, more preferably 80.0% by mass or less.

[0075] The reason why the transparency after bonding increases with the concentration of organic solvent A is not yet clear. However, it is believed that although organic solvent A has the effect of swelling cellulose resin, it does not completely dissolve the crystals of cellulose resin. That is, it is speculated that organic solvent A mainly acts on the amorphous parts of cellulose resin, maintaining the crystalline morphology, thereby improving the transparency after bonding.

[0076] Furthermore, the adhesive composition of this disclosure contains 15% by weight or more of a cellulose derivative relative to the total amount of the cellulose derivative and organic solvent A. Adhesive compositions containing both a cellulose derivative and organic solvent A within this range exhibit higher viscosity than conventional adhesives composed solely of solvents. The higher the content of the cellulose derivative in the adhesive composition, the higher its viscosity. Additionally, the lower the weight-average molecular weight of the cellulose derivative, the lower the viscosity of the adhesive composition. When using the adhesive composition of this disclosure as a primer for a 3D printer, a low weight-average molecular weight cellulose derivative and a high content of the cellulose derivative are preferred.

[0077] According to the adhesive composition disclosed herein, an adhesive can be obtained that enables uniform application without dripping and allows the operator to ensure sufficient working time after application. According to this adhesive, poor appearance caused by uneven application can be avoided. This adhesive can be applied to the bonding of transparent components.

[0078] From the viewpoint of achieving good adhesion and transparency, the amount of cellulose derivative in the adhesive composition is at least 15% by weight, preferably 16% by weight or more, more preferably 17% by weight or more, and even more preferably 18% by weight or more, relative to the total amount of cellulose derivative and organic solvent A. From the viewpoint of solvent solubility, the amount of cellulose derivative in the adhesive composition is preferably 30% by weight or less, more preferably 29% by weight or less, and even more preferably 28% by weight or less, relative to the total amount of cellulose derivative and organic solvent A.

[0079] The viscosity of the adhesive composition can be appropriately adjusted according to the implementation method and the desired open time. By increasing the viscosity of the adhesive composition, less dropleting occurs when applied to the bonding surface, making it suitable for bonding large components. The viscosity of the adhesive composition can be adjusted by the concentration and weight-average molecular weight of the cellulose derivative.

[0080] (Organic solvent B)

[0081] The adhesive composition disclosed herein may contain an organic solvent B with a boiling point below 100°C as a solvent component. Organic solvent B with a boiling point below 100°C evaporates rapidly. This organic solvent B acts as a drying aid in the adhesive composition. Manufacturing efficiency is improved based on the adhesive composition containing organic solvent B as a solvent component and the adhesive containing it. In other words, organic solvent B is used to adjust the open time of the adhesive composition. The higher the content of organic solvent B, the shorter the open time. When used as a primer for 3D printers, a lower content of organic solvent B is preferred. The primer may also not contain organic solvent B.

[0082] The preferred organic solvent B can be any solvent that has an affinity for cellulose derivatives. Examples of organic solvents B with a boiling point less than 100°C and an affinity for cellulose derivatives include acetone (boiling point 56°C), tetrahydrofuran (boiling point 66°C), methyl ethyl ketone (boiling point 79.6°C), methyl acetate (boiling point 57°C), ethyl acetate (boiling point 77°C), acetonitrile (boiling point 81.6°C), dioxolane (boiling point 74°C), methyl formate (boiling point 31.8°C), and chloroform (boiling point 61.2°C).

[0083] From the viewpoint of operational safety, the preferred organic solvent B is one or more selected from the group consisting of acetone, tetrahydrofuran, methyl ethyl ketone, methyl acetate, ethyl acetate, acetonitrile, and dioxolane. More preferably, the organic solvent B contains one or more selected from acetone and tetrahydrofuran.

[0084] From the viewpoint of improving manufacturing efficiency, when the adhesive composition is set to 100% by mass, the concentration of organic solvent B is preferably 5.0% by mass or more, more preferably 5.5% by mass or more, and even more preferably 6.0% by mass or more. From the viewpoint of improving adhesion, the concentration of organic solvent B in the adhesive composition is preferably 60.0% by mass or less, more preferably 55.0% by mass or less. Depending on the application of the adhesive composition, the concentration of organic solvent B can be further reduced, and can be 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less.

[0085] (Any ingredients)

[0086] Within the scope of the effects of this disclosure, the adhesive composition may contain organic solvents other than organic solvent A and organic solvent B. Additionally, the adhesive composition may contain known additives such as plasticizers, stabilizers, viscosity modifiers, and colorants.

[0087] (Adhesive)

[0088] The adhesive disclosed herein comprises the aforementioned adhesive composition. This adhesive contains a solvent component with high affinity for cellulose resin. This adhesive can be applied to the bonding of components formed from cellulose resin. By using the adhesive of this disclosure to bond multiple components of different shapes and sizes, it is possible to manufacture large molded articles with complex shapes.

[0089] The components used as the adhesives of this disclosure can be manufactured by mixing known additives such as plasticizers into a cellulose resin as needed, and then using known molding techniques such as extrusion molding, blow molding, and injection molding. These components may also have interlocking parts for assembling them separately. These interlocking parts can also be bonded to these components.

[0090] (Jointing method)

[0091] From another perspective, this disclosure relates to a method for joining large components together using the aforementioned adhesive composition. In other words, the joining method of this disclosure includes the process of joining large components formed of cellulose resin together using an adhesive composition comprising a cellulose derivative and a solvent component.

[0092] (primer)

[0093] The primer disclosed herein comprises the aforementioned adhesive composition. This primer contains a solvent component with high affinity for cellulose resin. This primer can be applied to lamination molding methods using cellulose resin as a raw material.

[0094] Specifically, as a molding technology for components formed from cellulose resin, the layer-by-layer molding method using a 3D printer is known. The layer-by-layer molding method can be applied to the manufacture of three-dimensional molded articles formed from cellulose resin. For example, according to the fused deposition modeling method, heated cellulose resin supplied to a 3D printer is extruded from a nozzle, thereby forming resin layers. These resin layers can be in a molten state, a semi-molten state, or layers of filamentous cellulose resin stacked in a semi-molten state. In the 3D printer, by sequentially stacking these resin layers, a multi-layer structure is formed, thereby manufacturing a molded article of the desired shape.

[0095] The primer disclosed herein can be used to bond the resin layers to be laminated together. Specifically, after applying the primer disclosed herein to the surface of the resin layer formed by extrusion from a 3D printer to form an adhesive layer, cellulose resin is extruded onto the adhesive layer to laminate the resin layers, thereby bonding the resin layers by means of the adhesive layer. After bonding, the adhesive layer and the resin layer become integrated.

[0096] In conventional 3D printers, molten resin is extruded to form resin layers before they cool and solidify. In this case, the molten or semi-molten resin layers are stacked on top of each other and solidify, resulting in a laminated, integrated component. However, when forming large components using 3D printers, it is necessary to extend the perimeter of the laminated resin. With a long perimeter, the resin extruded from the nozzle completely cools and solidifies before the next layer is extruded, leading to insufficient interlayer adhesion. This problem has become a limitation in the practical application of lamination modeling techniques for large components using 3D printers, particularly those made from cellulose resin.

[0097] The inventors have discovered that by placing an adhesive layer formed from the aforementioned adhesive composition between resin layers to be laminated, a laminated and integrally formed article can be obtained. For example, an apparatus for spraying the primer of this disclosure can be provided near the nozzle of a 3D printer that extrudes molten resin. After applying the primer to a cooled and solidified resin layer, molten resin is extruded onto the primer to form the next resin layer. This strengthens the interlayer adhesion between the cooled and solidified resin layer and the next resin layer, achieving proper lamination integration. Furthermore, the primer of this disclosure can be applied to a component formed by injection molding or the like, and cellulose resin can be extruded onto the component using a 3D printer to laminate and shape it into a desired form.

[0098] (Methods for manufacturing layered decorative items)

[0099] From another perspective, this disclosure relates to a method for manufacturing large components made of cellulose resin using a 3D printer. More specifically, this disclosure is a manufacturing method for layering cellulose resin using a 3D printer, the method comprising the step of applying a primer containing the aforementioned adhesive composition between resin layers formed of cellulose resin to form adhesive layers.

[0100] (Molded product)

[0101] In one embodiment, the molded article of this disclosure bonds multiple components made of cellulose resin together by means of an adhesive layer formed by the aforementioned adhesive composition. According to the adhesive composition of this disclosure, it is possible to uniformly coat the bonding surfaces and maintain adhesion for a certain period of time after coating. The molded article bonded by the adhesive layer formed by this adhesive composition has high transparency.

[0102] In other embodiments, the molded article of this disclosure alternately comprises an adhesive layer formed of the aforementioned adhesive composition and a resin layer formed of cellulose resin. The molded article is obtained using the aforementioned lamination technique employing a 3D printer. According to the adhesive composition of this disclosure, it can be uniformly applied to the bonding surface and maintain adhesion for a certain period after application. The adhesive composition and the adhesive containing it exhibit good adhesion from the application of the resin layer until the next resin layer is laminated. The molded article bonded by the adhesive layer formed by this adhesive composition has high transparency.

[0103] Example

[0104] The effects of this disclosure are illustrated below through examples, but this disclosure should not be interpreted in a limiting way based on the description of these examples.

[0105] (Preparation of the adhesive composition)

[0106] Following the formulations shown in Tables 1-4 below, cellulose derivatives, organic solvent A, and organic solvent B were added to a container (capacity 500 ml) and stirred at 25°C to obtain the adhesive compositions of the examples and comparative examples. Each adhesive composition was liquid, and the dissolution of the cellulose derivative was visually confirmed.

[0107] (Fixed after joining)

[0108] Prepare multiple cellulose acetate plate-shaped test pieces (2 mm thick). On the bonding surface of one test piece (bonding area 2 cm²),... 2After applying the adhesive composition to the entire surface of the substrate, other test pieces were immediately attached. The state of the test pieces was observed 10 seconds and 30 seconds after attachment. The observation results are shown in Tables 1-4 below. In the tables, "fixed" means that the attached test pieces are fixed to each other and cannot be moved by hand, and "movable" means that the two test pieces are not completely fixed.

[0109] (Adhesion after standing)

[0110] Prepare multiple cellulose acetate plate-shaped test pieces (2 mm thick). On the bonding surface of one test piece (bonding area 2 cm²),... 2 After applying the adhesive composition to the entire surface of the sample, it was allowed to stand at room temperature. Other test pieces were then bonded together 1 minute, 5 minutes, and 10 minutes after application to evaluate adhesion. The evaluation results are shown in Tables 1-4 below. In the tables, "good adhesion" means that the two test pieces are joined together and cannot be peeled off, and "not bonded" means that they cannot be bonded at all.

[0111] (Transparency after standing)

[0112] Prepare multiple cellulose acetate plate-shaped test pieces (2 mm thick). On the bonding surface of one test piece (bonding area 2 cm²),... 2 After applying the adhesive composition to the entire surface of the sample, it was allowed to stand at room temperature. Other test pieces were then bonded together 1 minute, 5 minutes, and 10 minutes after application, and the transparency of the bonded test pieces was visually evaluated. The evaluation results are shown in Tables 1-4 below. In the tables, "A" indicates that the bonded test piece is entirely transparent, "B" indicates that wrinkles or unevenness are observed at the bonding interface, and "C" indicates that the wrinkles or unevenness are large and the transparency is reduced. It should be noted that in Comparative Example 1, since it was impossible to bond the two test pieces, the transparency was not evaluated.

[0113] [Table 1]

[0114]

[0115] [Table 2]

[0116]

[0117] [Table 3]

[0118]

[0119] [Table 4]

[0120]

[0121] Ethyl lactate: manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 155℃, SP value 26.3 (J) 1 / 2 / cm 3 / 2)

[0122] Methyl lactate: manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 145℃, SP value 24.8 (J) 1 / 2 / cm 3 / 2 )

[0123] CA: Cellulose acetate manufactured by Daicel, trade name "L50", degree of acetyl substitution 2.5, weight average molecular weight Mw 200,000, molecular weight distribution Mw / Mn 5.0, viscosity-average degree of polymerization 180.

[0124] Acetone: Manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 57℃, SP value 19.3 (J) 1 / 2 / cm 3 / 2 )

[0125] THF: Tetrahydrofuran manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 66℃, SP value 17.5 (J) 1 / 2 / cm 3 / 2 )

[0126] As shown in Table 1, in Comparative Example 1, which does not contain organic solvent A and cellulose derivative, the bonding was completed within 10 seconds immediately after coating, but no adhesion was observed after 1 minute. On the other hand, in Comparative Example 2, which contains only organic solvent A, the component could not be fixed (bonded) even after 30 seconds after bonding.

[0127] As shown in Tables 1-4, in Comparative Examples 3-6, where the amount of cellulose derivative was less than 15% by mass relative to the total amount of cellulose derivative and organic solvent A, the unevenness at the bonding interface was large, resulting in reduced transparency. In contrast, in Examples 1-10, which contained cellulose derivative of 15% by mass or more relative to the total amount of cellulose derivative and organic solvent A, adhesion was achieved even after 5 minutes of coating, and the appearance was also good (transparent). Furthermore, in Examples 1-3 and 7-10, where the concentration of cellulose derivative in the bonding composition exceeded 8.0% by mass, no wrinkled unevenness was formed even after 10 minutes of coating, resulting in a good (transparent) appearance.

[0128] [Comparative Example 7]

[0129] First, 100 parts by weight of cellulose acetate (trade name "L50" manufactured by Daicel, with a degree of substitution of 2.5, a weight-average molecular weight of 200,000, a molecular weight distribution of 5.0, and a viscosity-average degree of polymerization of 180) as a cellulose resin and 20 parts by weight of triacetin (trade name "DRA-150" manufactured by Daicel, as a plasticizer) as a plasticizer were added to a Henschel mixer and stirred and mixed to achieve a frictional heat of 70°C or higher within the mixer to obtain a mixture. This mixture was then fed to a twin-screw extruder (barrel temperature: 200°C, die temperature: 220°C) and extruded to obtain granules (cellulose resin 1).

[0130] The obtained granules (cellulose resin 1) are fed into an injection molding machine and injection molded under the conditions of barrel temperature 200℃, mold temperature 50℃, and molding cycle of 30 seconds (15 seconds of injection and 15 seconds of cooling time) to obtain an L-shaped cellulose resin component with a thickness of 10mm, a length of 200mm (50mm for clamping part and 150mm for bonding part) and a width of 25mm.

[0131] Next, the aforementioned granules (cellulose resin 1) were supplied to a 3D printer (product name "Teahouse GEM" manufactured by S.lab, maximum model size: width 3m × depth 3m × height 3m, nozzle diameter: 12mm, tabletop heater temperature: room temperature setting) and extruded onto the back of an L-shaped cellulose resin component, thereby forming a cellulose resin layer (clamping part 50mm, adhesive part 150mm), resulting in a test piece of Comparative Example 7 with the shape described in JIS K6854-3 ("Adhesive-Peel Bond Strength Test Method Part 3: T-shaped Peel")

[0132] Using the obtained test pieces, a peel test (180° peel method) was performed according to JIS K6854-3 (“Adhesives – Test Method for Peel Bond Strength Part 3: T-shaped Peel”) to determine the peel strength between the cellulose resin component and the cellulose resin layer. The test was conducted using a universal tensile testing machine. Specifically, the cellulose resin component was fixed in the lower clamp of the universal tensile testing machine, and the cellulose resin layer was fixed in the upper clamp. The peel strength over a width of 25 mm was measured at a test speed of 100 mm / min. The obtained peel strength was 70 g / 25 mm, which is the strength of a simple peel. The peel surface is the interface between the cellulose resin component and the cellulose resin layer.

[0133] [Example 12]

[0134] Before forming the cellulose resin layer using a 3D printer, the adhesive composition of Example 11 was coated onto the back of the cellulose resin component. Otherwise, the procedure was the same as in Comparative Example 7, resulting in the test piece of Example 12. In other words, in this test piece of Example 12, an adhesive layer formed by the adhesive composition of Example 11 was formed between the cellulose resin component and the cellulose resin layer. Using the test piece of Example 11, peel strength was measured under the same test conditions as in Comparative Example 7, but even with a load of 20 kg from the load sensor of the universal tensile testing machine, peeling did not occur.

[0135] [Example 13]

[0136] The same procedure as in Comparative Example 7 was followed to obtain granules (cellulose resin 1). These granules (cellulose resin 1) were fed into a 3D printer (trade name "Teahouse GEM" manufactured by S.lab, maximum dimensions: width 3m × depth 3m × height 3m, nozzle diameter: 12mm, desktop heater temperature: room temperature setting) to create a small house. The house was 2m long, 2m wide, and 2.6m high, with a corner radius of 100mm (the same for the floor and walls), a floor thickness of approximately 12mm, wall thickness of approximately 24mm, and a barrel shape without a roof. It should be noted that during 3D printing, the adhesive composition of Example 11 was applied using a brush (brush width approximately 20mm) at a distance of 200-500mm from the nozzle tip in the direction of travel, and then cellulose resin 1 was extruded from the nozzle towards the coating surface, thereby forming a cellulose resin layer. It should be noted that the adhesive composition was not applied to the central 500mm portion of the floor. In addition, the coating speed of the adhesive composition is synchronized with the nozzle movement speed of 200 mm / s. The coating width of the adhesive composition is set to 20 mm, and the approximate equivalent calculated from the coating length and the amount of adhesive composition used is 150 mg / m². 2 .

[0137] It has been confirmed that although the resulting cabin is a large structure, it can be manufactured normally, with good interlayer strength and no peeling. The resulting cabin is translucent. In Example 13, good interlayer adhesion can be maintained even without the use of a benchtop heater, and light transmission can also be ensured. Furthermore, even without using the insulated chamber included with a small 3D printer, good interlayer adhesion strength can be obtained as described above.

[0138] As the test results above show, the adhesive compositions of the embodiments exhibit excellent properties. Based on these evaluation results, the superiority of this disclosure is evident.

[0139] [Public Projects]

[0140] The following items disclose preferred implementation methods.

[0141] [Project 1]

[0142] An adhesive composition comprising a cellulose derivative and a solvent component,

[0143] The degree of substitution based on the acetyl group of the above-mentioned cellulose derivatives is 1.9 or more and 2.6 or less.

[0144] The solvent components mentioned above contain components with a boiling point above 100℃ and an SP value of 18~30 (J). 1 / 2 / cm 3 / 2 Organic solvent A,

[0145] The amount of the aforementioned cellulose derivative relative to the total amount of the aforementioned cellulose derivative and the aforementioned organic solvent A is 15% by mass or more and 30% by mass or less.

[0146] [Project 2]

[0147] According to the adhesive composition of Project 1, the cellulose derivative further comprises acyl groups other than acetyl groups.

[0148] [Project 3]

[0149] According to the adhesive composition of Project 1 or 2, wherein the organic solvent A is one or more selected from the group consisting of methyl lactate, ethyl lactate, and propyl lactate.

[0150] [Project 4]

[0151] The adhesive composition according to any one of items 1 to 3, wherein the solvent component further comprises an organic solvent B with a boiling point below 100°C.

[0152] [Project 5]

[0153] According to the adhesive composition of Project 4, the organic solvent B is one or more selected from the group consisting of acetone, tetrahydrofuran, methyl ethyl ketone, methyl acetate, ethyl acetate, acetonitrile and dioxolane.

[0154] [Project 6]

[0155] According to the adhesive composition of item 4 or 5, the concentration of the organic solvent B is 5.0% by mass or more and less than 60.0% by mass.

[0156] [Project 7]

[0157] The adhesive composition according to any one of items 1 to 6, wherein the weight-average molecular weight of the cellulose derivative is 70,000 or more and 300,000 or less.

[0158] [Project 8]

[0159] An adhesive for cellulose resins comprising the adhesive composition described in any one of items 1 to 7.

[0160] [Project 9]

[0161] A primer comprising the adhesive composition described in any one of items 1 to 7.

[0162] [Project 10]

[0163] A molded article that bonds together a plurality of components formed of cellulose resin by means of an adhesive layer, said adhesive layer being formed of any one of items 1 to 7.

[0164] [Project 11]

[0165] A molded article having an adhesive layer and a resin layer alternately stacked, the adhesive layer being formed of an adhesive composition as described in any one of items 1 to 7, and the resin layer being formed of a cellulose resin.

[0166] Industrial availability

[0167] The adhesive compositions disclosed herein can be applied to the joining and manufacturing of various molded articles made of cellulose derivatives.

Claims

1. An adhesive composition comprising a cellulose derivative and a solvent component, The degree of substitution based on the acetyl group of the cellulose derivative is 1.9 or more and 2.6 or less. The solvent component contains components with a boiling point above 100℃ and an SP value of 18~30J. 1 / 2 / cm 3 / 2 Organic solvent A, The amount of the cellulose derivative is 15% by mass or more and 30% by mass or less relative to the total amount of the cellulose derivative and the organic solvent A.

2. The adhesive composition according to claim 1, wherein, The cellulose derivative also contains acyl groups other than acetyl groups.

3. The adhesive composition according to claim 1, wherein, The organic solvent A is one or more selected from the group consisting of methyl lactate, ethyl lactate, and propyl lactate.

4. The adhesive composition according to claim 1, wherein, The solvent component also includes organic solvent B with a boiling point below 100°C.

5. The adhesive composition according to claim 4, wherein, The organic solvent B is selected from one or more of the group consisting of acetone, tetrahydrofuran, methyl ethyl ketone, methyl acetate, ethyl acetate, acetonitrile, and dioxolane.

6. The adhesive composition according to claim 4, wherein, The concentration of organic solvent B is 5.0% by mass or more and less than 60.0% by mass.

7. The adhesive composition according to claim 1, wherein, The cellulose derivative has a weight-average molecular weight of 70,000 or more and 300,000 or less.

8. An adhesive for cellulose resins comprising the adhesive composition of claim 1.

9. A primer comprising the adhesive composition of claim 1.

10. A molded article which bonds a plurality of components formed of cellulose resin by means of an adhesive layer, said adhesive layer being formed of the adhesive composition of claim 1.

11. A molded article having an adhesive layer and a resin layer alternately laminated thereon, the adhesive layer being formed of the adhesive composition of claim 1, and the resin layer being formed of a cellulose resin.

Images