Adhesive composition

Abstract

This adhesive composition comprises a cellulose derivative and a solvent component. The cellulose derivative has a degree of substitution with an acetyl group of 1.9-2.6. The solvent component comprises an organic solvent A having a boiling point of 100°C or higher and an SP value of 18-30 (J1 / 2 / cm3 / 2). The amount of the cellulose derivative is 15 mass% to 30 mass% inclusive with respect to the total amount of the cellulose derivative and the organic solvent A.

Description

adhesive composition

[0001] The present disclosure relates to an adhesive composition. Specifically, the present disclosure relates to an adhesive composition and an adhesive, a primer, and a molded article using the adhesive composition.

[0002] Cellulose resins are polymeric materials derived from cellulose, and typical polymeric materials are cellulose derivatives. Because the main raw material for cellulose derivatives is the natural material cellulose, they can be used to produce sustainable molding materials and molded products with low environmental impact.

[0003] Among cellulose derivatives, for example, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate, which have acetyl groups introduced, are known to exhibit thermoplasticity depending on their degree of substitution. Traditionally, cellulose acetate and other materials have been molded using the "extrusion method," in which a specific cross-sectional shape is extruded, or the "block method," in which the material is molded into a mold. Therefore, additional machining processes, such as cutting, have sometimes been required to obtain molded products with complex shapes. In recent years, attempts have been made to manufacture molded products using sustainable materials such as cellulose acetate through melt molding and injection molding. However, cellulose derivatives, especially cellulose acetate, have a problem with their poor melt-flowability compared to conventional synthetic polymers, making injection molding of complex shapes difficult.

[0004] On the other hand, cellulose derivatives, especially cellulose acetate, are known to be highly biodegradable and decompose in activated sludge. Furthermore, cellulose acetate with improved biodegradability, showing marine degradability, has also been proposed. In recent years, growing concern about the global environment has led to a demand for the production of molded articles with complex shapes using biodegradable cellulose derivatives, especially cellulose acetate.

[0005] For example, with metal materials, a technique is known for joining multiple components to produce molded products of a desired size and shape. In contrast, resin components generally have high wetting tension on their surfaces. This makes them difficult to bond with liquid adhesives, and ingenuity is required to bond resin components together. A typical and simple method is to apply a surface treatment agent called a "primer" to the surface of the resin components, then apply an adhesive and bond them together.

[0006] Among cellulose derivatives, there is an exceptional method for bonding components made of cellulose acetate using a solvent that dissolves cellulose acetate. This method involves applying a solvent that dissolves cellulose acetate to the bonding surfaces of the components to be bonded, swelling the surfaces. For example, ketones such as acetone are examples of solvents that dissolve cellulose acetate. An adhesive containing such a solvent is commercially available under the trade name "NO. 250-B Celaceti Adhesive Z" manufactured by Sannishimura Co., Ltd. This adhesive is 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) by weight. This adhesive can be used to bond lightweight, small components such as eyeglass nose pads.

[0007] On the other hand, as the fields of application expand, there is also an increasing demand for molded products with larger sizes and more complex shapes. Depending on the field of application, even greater optical transparency may be required. Because solvents such as acetone have low viscosity, adhesives based on these solvents tend to drip from the applied bonding surface, making them difficult to handle when bonding large areas. Furthermore, because volatile solvents such as acetone evaporate quickly, bonding must be completed within 30 seconds of application, making their application to components with large bonding areas difficult.

[0008] The aforementioned "NO. 250-B Celacetate Adhesive Z" adjusts viscosity and evaporation rate by adding ethyl lactate and ethyl acetate to acetone, but this does not completely solve the problems that arise when joining components with large surfaces. Furthermore, "NO. 250-B Celacetate Adhesive Z" dissolves the joining surfaces of the adherends to join them, so it takes time for it to solidify and stabilize its strength. Furthermore, because it contains high-boiling point solvents such as ethyl lactate, it has poor solubility for cellulose acetate and a slow evaporation rate, making it impractical for joining large components. Until now, there have been no practical adhesives capable of joining large components made of cellulose resin.

[0009] For example, Patent Document 1 (JP 11-172290 A) proposes a solvent composition for plastics containing multiple organic solvents. This solvent composition contains at least one of isopropyl bromide and normal propyl bromide as a primary solvent component, and further contains acetone, ethyl lactate, or the like as a secondary solvent component. Patent Document 2 (JP Patent No. 2505909 A) discloses an adhesive containing a compound having a mercapto group and a masking agent selected from the group consisting of vanillin, lemon oil, and ester-based solvents.

[0010] Japanese Patent Application Publication No. 11-172290 Patent No. 2505909

[0011] The solvent composition disclosed in Patent Document 1 and the adhesive disclosed in Patent Document 2 have poor adhesive properties for members made of cellulose resin. Furthermore, as mentioned above, adhesives made of organic solvents such as acetone and ethyl lactate are difficult to apply to bonding large members. Furthermore, adhesives with low viscosity are difficult to apply uniformly to the bonding surfaces. In particular, when bonding transparent members, unevenness on the bonding surface is visible as light reflection, resulting in poor appearance.

[0012] In addition, with the increasing popularity of large-scale 3D printers for additive manufacturing, there has been a growing demand for primers (also known as sealers) that enhance interlayer adhesion. For example, in the case of FDM (Fused Deposition Modeling) 3D printers, a semi-liquid or liquid molten thermoplastic material is ejected from a nozzle while the nozzle is moved along a path controlled by a computer to build parts layer by layer. Large components can be manufactured by increasing the nozzle movement range. However, if the nozzle movement path is long, new material is ejected on top of the solidified layer after the ejected thermoplastic material cools and solidifies, resulting in a lack of integration between the layers and the desired molded product. To manufacture large components using a 3D printer, a primer is required that can be applied to the cooled and solidified layer to provide adhesion to the newly ejected layer. In particular, no primers that enhance interlayer adhesion have previously existed in the additive manufacturing of large components using cellulose resins.

[0013] An object of the present disclosure is to provide an adhesive composition that has excellent adhesion to members made of cellulose resin, particularly members made of cellulose acetate, that is capable of producing complex and large molded products, and that has excellent transparency after bonding.

[0014] Another object of the present disclosure is to provide an adhesive suitable for joining large components made of cellulose resin. Still another object of the present disclosure is to provide a primer suitable for interlayer bonding in additive manufacturing using a 3D printer. Furthermore, the present disclosure aims to provide a large molded product made of cellulose resin.

[0015] The adhesive composition according to the present disclosure contains a cellulose derivative and a solvent component. The cellulose derivative has a degree of substitution with an acetyl group of 1.9 or more and 2.6 or less. The solvent component has a boiling point of 100°C or more and an SP value of 18 to 30 (J １／２ / cm ３／２ The adhesive composition contains an organic solvent A in which the cellulose derivative is 15% by mass or more and 30% by mass or less based on the total amount of the cellulose derivative and the organic solvent A.

[0016] This adhesive composition swells the cellulose resin on the surface of the adherend. An adhesive containing this adhesive composition can be used to bond cellulose resin components. Furthermore, because the solvent component, organic solvent A, has low volatility, its adhesiveness is maintained for a certain period of time after application to the bonding surface. Furthermore, because this adhesive composition contains a cellulose derivative, it exhibits higher viscosity than conventional adhesives composed solely of a solvent. This adhesive composition can be applied uniformly to the bonding surface without dripping. After applying this adhesive composition, workers can have sufficient working time. Furthermore, during 3D printing, applying a primer containing this adhesive composition to the dispensed layer allows sufficient working time before a new adherend layer is dispensed. This primer enables the single-step manufacturing of large components using a 3D printer. Furthermore, this adhesive composition can avoid poor appearance due to uneven application. This adhesive composition can also be used to bond transparent components.

[0017] An example of a preferred embodiment will be described in detail below. Each configuration and combination thereof in each embodiment is merely an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but only by the scope of the claims. Furthermore, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification.

[0018] The numerical range of each requirement disclosed herein can be arbitrarily combined with the numerical range of other requirements. For example, the numerical range limit for the degree of acetyl substitution of a cellulose resin can be combined with the numerical range limit for the molecular weight. Furthermore, the numerical range of each requirement disclosed herein can be any range obtained by arbitrarily combining the upper and lower limits.

[0019] (Definition of Terms) "Cellulose derivative" is defined as a general term for compounds in which various substituents have been introduced into at least some of the hydroxyl groups of cellulose molecules. In the present disclosure, cellulose derivatives used as molding materials are particularly referred to as "cellulose resins." "Molding material" refers to the material of a member or molded article as an adherend to be adhered with the adhesive composition of the present disclosure. The cellulose resin may be in a solid or molten state. Hereinafter, cellulose derivatives and cellulose resins as components of the adhesive composition will be referred to separately, but their types and compositions may be the same or different.

[0020] In addition, in this disclosure, the range "X to Y" means "X or more and Y or less." Unless otherwise noted, all test temperatures are room temperature (20°C ± 5°C). In this specification, "wt%" means mass %. Mass% means weight percent, not mass concentration.

[0021] (Cellulose Resin) The material of the adherend to which the adhesive composition of the present disclosure is to be adhered is a cellulose resin. The adhesive properties of the adhesive composition of the present disclosure are exhibited by at least swelling the adhesive surface of the adherend. The type of cellulose resin is not particularly limited as long as this function is not inhibited, but a cellulose resin similar to the cellulose derivative contained in the adhesive composition described below is preferred.

[0022] The adherend to which the adhesive composition of the present disclosure is applied may be a solid cellulose resin or a molten cellulose resin. For example, when a primer containing the adhesive composition of the present disclosure is used for additive manufacturing using a 3D printer, the primer may be applied to a solidified cellulose resin, and then a molten cellulose resin may be laminated thereon. Alternatively, the primer may be applied to a molten cellulose resin, and then a molten cellulose derivative may be laminated thereon.

[0023] The cellulose resin can be obtained by derivatizing at least a portion of the hydroxyl groups of the cellulose molecule. A cellulose resin in which a portion of the hydroxyl groups is esterified is preferred, and a cellulose resin in which a portion of the hydroxyl groups is esterified with an acetyl group is more preferred.

[0024] In other words, a preferred cellulose resin is a cellulose ester. As the cellulose ester, a cellulose fatty acid ester is preferred. Specific examples of the cellulose fatty acid ester 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.

[0025] When the cellulose resin is a cellulose ester, the preferred degree of esterification is about 1 to 3. When the cellulose resin is a cellulose acetate, the degree of acetyl substitution is preferably 1.1 to 2.8, more preferably 1.8 to 2.8, even more preferably 2.2 to 2.7, and particularly preferably 2.4 to 2.6. The lower the upper limit of the acetyl substitution degree, the better the moldability, and the lower the lower limit, the better the biodegradability. The acetyl substitution degree can be adjusted so as to obtain desired biodegradability and moldability.

[0026] From the viewpoint of ease of 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. Since high melt fluidity is not required for molding using a 3D printer, the weight average molecular weight Mw of the cellulose resin used as a 3D printer material (printed polymer) may be 150,000 or more. In particular, from the viewpoint of improving the strength of the molded product, 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. In addition, in the chromatogram obtained by size exclusion chromatography (GPC analysis) of cellulose resin (e.g., cellulose acetate), peaks called prehump I, prehump II, main hump (main peak), and posthump are observed in order of shortest elution time (lowest molecular weight). In the present disclosure, the main hump (main peak) is used to calculate the weight average molecular weight Mw, and other peaks are not taken into consideration.

[0027] The adherend to which the adhesive composition of the present disclosure is applied may be a cellulose resin containing a plasticizer. Examples of the plasticizer include glycerin esters, citric acid esters, and adipic acid esters. The amount of plasticizer contained in the adherend may be 10 wt % or more and 30 wt % or less, or 15 wt % or more and 25 wt % or less.

[0028] (Adhesive Composition) The adhesive composition of the present disclosure contains a cellulose derivative having an acetyl substitution degree of 2.1 to 2.6 and a solvent component. This solvent component has a boiling point of 100°C or higher and an SP value of 18 to 30 (J １／２ / cm ３／２The adhesive composition contains an organic solvent A having a boiling point of less than 100°C. The amount of the cellulose derivative in the adhesive composition is 15% by mass or more and 30% by mass or less, based on the total amount of the cellulose derivative and organic solvent A. The adhesive composition swells the cellulose resin that constitutes the adherend. An adhesive containing this adhesive composition can be used to join members made of cellulose resin. A primer containing this adhesive composition is suitable for use in 3D printer modeling using cellulose resin as a material. In a preferred embodiment, the solvent component may further contain an organic solvent B having a boiling point of less than 100°C.

[0029] (Cellulose Derivative) The cellulose derivative contained in the adhesive composition of the present disclosure has a degree of substitution with an acetyl group of 2.1 or more and 2.6 or less. A cellulose derivative having a degree of acetyl substitution of 1.9 or more and 2.6 or less exhibits good solvent solubility. The degree of acetyl substitution of the cellulose derivative is preferably 2.0 or more, more preferably 2.1 or more. From the viewpoint of excellent biodegradability, the degree of acetyl substitution of the cellulose derivative is preferably 2.56 or less, more preferably 2.50 or less, even more 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 the cellulose acetate may be 1.9 to 2.56, or may be 1.9 to 2.50, or may be 1.9 to 2.40, or may be 1.9 to 2.30, or may be 1.9 to 2.26, or may be 2.0 to 2.6, or may be 2.0 to 2.56, or may be 2.0 to 2.50, or may be 2.0 to 2.40, or may be 2.0 to 2.30, or may be 2.0 to 2.26, or may be 2.1 to 2.6, or may be 2.1 to 2.56, or may be 2.1 to 2.50, or may be 2.1 to 2.40, or may be 2.1 to 2.30, or may be 2.1 to 2.26.

[0030] When the cellulose derivative is cellulose acetate, the solubility in the solvent component tends to be poor when the degree of acetyl substitution is 2.7 or more, and also when the degree of acetyl substitution is less than 2.0.

[0031] From the viewpoint of adhesive strength of 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 viscosity of the adhesive composition, it is preferably 300,000 or less, more preferably 290,000 or less, and may be 280,000 or less.

[0032] When comparing adhesive compositions with the same cellulose derivative concentration, the higher the weight-average molecular weight of the cellulose derivative, the higher the viscosity of the adhesive composition. Furthermore, when comparing adhesive compositions with the same weight-average molecular weight of the cellulose derivative, the higher the cellulose derivative concentration, the higher the viscosity of the adhesive composition. An adhesive composition with a high cellulose derivative concentration and high viscosity has a short open time (open time: the time during which adhesion is possible). On the other hand, an adhesive composition containing a low concentration of a cellulose derivative with a high weight-average molecular weight has a high viscosity but a long open time. The weight-average molecular weight of the cellulose derivative can be selected depending on the use conditions and purpose of the adhesive composition.

[0033] The molecular weight distribution of the cellulose derivative is evaluated by the ratio of the number average molecular weight Mn to the weight average molecular weight Mw (Mw / Mn). In the present disclosure, in order to maintain a uniform dissolution 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 the cellulose derivative, the molecular weight distribution Mw / Mn of the cellulose derivative is preferably more than 1.7, more preferably 1.8 or more, even more preferably 2.0 or more, and particularly preferably 2.1 or more.

[0034] Cellulose derivatives are generally semi-synthetic polymers obtained from cellulose as a raw material. Therefore, the molecular weight and molecular weight distribution of cellulose derivatives largely depend on the raw material cellulose. The molecular weight and molecular weight distribution of cellulose derivatives may be adjusted by using different types of cellulose raw materials in combination.

[0035] The molecular weight and molecular weight distribution of the cellulose derivative in the adhesive composition can be determined by a known method. Specifically, the molecular weight and molecular weight distribution of the cellulose derivative are determined by measuring the solids concentration of the cellulose derivative in the adhesive composition, diluting it with acetone, and performing size exclusion chromatography (GPC) measurement using the following apparatus and conditions (GPC-light scattering method). Apparatus: GPC "SYSTEM-21H" manufactured by Shodex Solvent: Acetone Column: Two GMHxl columns (Tosoh), guard column (TSKgel guard column HXL-H manufactured by Tosoh) Flow rate: 0.8 ml / min Temperature: 29°C Sample concentration (as cellulose derivative): 0.25% (wt / vol) Injection volume: 100 μl Detection: MALLS (multi-angle light scattering detector) ("DAWN-EOS" manufactured by Wyatt) MALLS calibration standard: PMMA (molecular weight 27,600)

[0036] The cellulose derivative is produced by a known method for producing a cellulose derivative. For example, a cellulose derivative containing an acetyl group can be produced by the so-called acetic acid method, which uses acetic anhydride as an acetylating agent, acetic acid as a diluent, and sulfuric acid as a catalyst. As a result of using a sulfuric acid catalyst during production, a small amount of sulfate groups (sulfate esters) may be introduced into the cellulose derivative. The adhesive composition of the present disclosure is permitted to contain sulfate groups that are inevitably introduced during the production of the cellulose derivative.

[0037] The cellulose derivative may also contain alkaline earth metals such as magnesium (Mg), calcium (Ca), and barium (Ba), and alkali metals such as sodium (Na), potassium (K), etc. The total content of these metals can be selected within the range of 20 ppm to 300 ppm.

[0038] The cellulose derivative may further contain an acyl group other than an acetyl group. Examples of the acyl group other than an acetyl group include aliphatic acyl groups such as a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, a decanoyl group, a lauroyl group, and a stearoyl group; and aromatic acyl groups such as a benzoyl group and a naphthoyl group. From the viewpoint of solvent solubility and safety, an aliphatic acyl group is preferred, an aliphatic acyl group having 15 or less carbon atoms is more preferred, and an aliphatic acyl group having 12 or less carbon atoms is even more preferred. When the cellulose derivative contains an acetyl group and an acyl group other than an acetyl group, the total degree of substitution may be 2.15 or more, 2.25 or more, or 2.35 or more, with the upper limit being 3.0.

[0039] The degree of acetyl substitution and the total degree of substitution of a cellulose derivative are the sum of the degrees of acetyl substitution at the 2-, 3-, and 6-positions of the glucose ring of the cellulose derivative, and can be measured by the following method, for example, by NMR according to the method of Tezuka (Tezuka, Carbonydr. Res. 273, 83 (1995)).

[0040] The adhesive composition may contain, in addition to the cellulose derivative having an acetyl substitution degree of 1.9 to 2.6, other cellulose derivatives having an acyl group other than an acetyl group, as long as the effects of the present disclosure can be obtained. Examples of such cellulose acylates include cellulose acetate propionate and cellulose acetate butyrate.

[0041] From the viewpoint of improving transparency after adhesion, the amount of the cellulose derivative 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, when the total adhesive composition is taken as 100% by mass. From the viewpoint of solvent solubility, the concentration of the cellulose derivative in the adhesive composition is preferably 25% by mass or less, more preferably 24% by mass or less.

[0042] If the amount of the cellulose derivative in the adhesive composition is small, the area infiltrated with the cellulose resin will be broadened, and the unevenness of the adhesive interface will increase, which may result in a decrease in transparency after adhesion.If the concentration of the cellulose derivative in the adhesive composition is 25% by mass or more, the viscosity of the adhesive composition will become too high, which tends to reduce workability.

[0043] (Solvent Component) The solvent component contained in the adhesive composition of the present disclosure will be described below. Hereinafter, the "boiling point" refers to the standard boiling point (boiling point under 1 atmosphere) measured in accordance with the description of JIS K2254.

[0044] The term "SP value" refers to the value of the solubility parameter. In the present specification, the SP value is a solubility parameter δ (unit: J) calculated based on the molecular structure of a solvent using the molar gravitational constant ΔF and molar volume Δv of various atomic groups disclosed in "Okitsu Toshinao, Adhesion, Vol. 40, No. 8, pp. 342-350 (1996), Polymer Publishing Association" according to the following formula (1): １／２ / cm ３／２ ) δ=ΣΔF / ΣΔv (Equation 1) The SP value of the mixed solvent is calculated by the following (Equation 2): δmix=ψ １ δ １ +ψ ２ δ ２ +...+ψ ｎ δ ｎ (Equation 2) In Equation 2, ψ represents a volume fraction or a mole fraction, and ψ １ +ψ ２ +...+ψ ｎ =1.

[0045] (Organic Solvent A) The solvent component in the adhesive composition of the present disclosure is a solvent having a boiling point of 100° C. or higher and an SP value of 18 to 30 (J １／２ / cm ３／２ ) The organic solvent A has low volatility and affinity for cellulose derivatives. By including the organic solvent A as a solvent component, the adhesive composition can maintain its adhesiveness for a certain period of time after application to a joining surface made of a cellulose resin.

[0046] The boiling point is 100°C or higher and the SP value is 18 to 30 (J１／２ / cm ３／２ As organic solvent A, methyl lactate (boiling point 145°C, SP value 24.8J １／２ / cm ３／２ ), ethyl lactate (boiling point 155°C, SP value 26.3J １／２ / cm ３／２ lactic acid esters such as butyl acetate (boiling point 127°C, SP value 19.73J １／２ / cm ３／２ methyl butyrate (boiling point 120°C, SP value 18.68J) １／２ / cm ３／２ ), ethyl butyrate (boiling point 102°C, SP value 19.04J １／２ / cm ３／２ ), butyric acid esters such as methyl glycol (boiling point 124°C, SP value 25.13J １／２ / cm ３／２ ), methyl glycol acetate (boiling point 145°C, SP value 19.30J １／２ / cm ３／２ The organic solvent A is preferably one or more selected from the group consisting of methyl lactate, ethyl lactate, and propyl lactate.

[0047] From the viewpoint of obtaining good coatability and adhesion and from the viewpoint of operational safety, the boiling point of the 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 options for the organic solvent A, the boiling point of the organic solvent A is preferably 300° C. or lower, more preferably 290° C. or lower, and even more preferably 280° C. or lower.

[0048] SP value 18J １／２ / cm ３／２ When the organic solvent A is contained in an amount of less than 30 J, the boiling point of the solvent component tends to be low, and the SP value is 30 J. １／２ / cm ３／２ The organic solvent A having an SP value of more than 19J may have low affinity with the cellulose derivative. １／２ / cm ３／２ More than 22J is preferable. １／２ / cm ３／２ More preferably, 24J １／２ / cm ３／２ The above is more preferable, and 29J１／２ / cm ３／２ The following is preferred: 28J １／２ / cm ３／２ The following is more preferred: 27J １／２ / cm ３／２ The following is even more preferred:

[0049] From the viewpoint of improving transparency after bonding, the concentration of the organic solvent A in the adhesive composition is preferably 35.0 mass % or more, more preferably 40.0 mass % or more, and even more preferably 45.0 mass % or more, when the entire adhesive composition is taken as 100 mass %. From the viewpoint of improving adhesiveness, the concentration of the organic solvent A in the adhesive composition is preferably 85.0 mass % or less, more preferably 80.0 mass % or less.

[0050] Although the reason why the transparency after adhesion improves depending on the concentration of organic solvent A is not clear, it is thought that organic solvent A has the effect of swelling the cellulose resin but does not completely melt the crystalline cellulose resin. In other words, it is speculated that organic solvent A acts mainly on the amorphous portion of the cellulose resin, maintaining the crystalline form, thereby improving the transparency after adhesion.

[0051] Furthermore, the adhesive composition of the present disclosure contains 15 wt % or more of the cellulose derivative, based on the total amount of the cellulose derivative and organic solvent A. Adhesive compositions containing the cellulose derivative and organic solvent A in this range exhibit higher viscosity than conventional adhesives consisting of solvent alone. The higher the content of the cellulose derivative in the adhesive composition, the higher the viscosity of the adhesive composition. Furthermore, the smaller the weight-average molecular weight of the cellulose derivative, the lower the viscosity of the adhesive composition. When the adhesive composition of the present disclosure is used as a primer for a 3D printer, an embodiment in which the weight-average molecular weight of the cellulose derivative is low and the content of the cellulose derivative is high is preferred.

[0052] The adhesive composition of the present disclosure can be applied uniformly without dripping, and can provide an adhesive that allows workers to have sufficient working time after application. This adhesive can avoid poor appearance due to uneven application. This adhesive can be used to bond transparent members.

[0053] From the viewpoint of obtaining good adhesion and transparency, the amount of the cellulose derivative in the adhesive composition is at least 15 wt %, preferably 16 wt % or more, more preferably 17 wt % or more, and even more preferably 18 wt % or more, based on the total amount of the cellulose derivative and organic solvent A. From the viewpoint of solvent solubility, the amount of the cellulose derivative in the adhesive composition is preferably 30 wt % or less, more preferably 29 wt % or less, and even more preferably 28 wt % or less, based on the total amount of the cellulose derivative and organic solvent A.

[0054] The viscosity of the adhesive composition can be adjusted appropriately depending on the embodiment and the desired open time. By increasing the viscosity of the adhesive composition, dripping when applied to the joining surface is reduced, making it suitable for joining large components. The viscosity of the adhesive composition can be adjusted by the concentration and weight-average molecular weight of the cellulose derivative.

[0055] (Organic solvent B) The adhesive composition of the present disclosure may contain an organic solvent B having a boiling point of less than 100°C as a solvent component. The evaporation rate of organic solvent B having a boiling point of less than 100°C is high. This organic solvent B acts as a drying aid for the adhesive composition. An adhesive composition containing organic solvent B as a solvent component and an adhesive containing the same improve production efficiency. 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 a 3D printer, the lower the content of organic solvent B, the more preferable. The primer does not have to contain organic solvent B.

[0056] Any solvent having affinity for cellulose derivatives may be used as the organic solvent B. Examples of organic solvents B having a boiling point of less than 100°C and 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).

[0057] From the viewpoint of operational safety, the organic solvent B is preferably one or more selected from the group consisting of acetone, tetrahydrofuran, methyl ethyl ketone, methyl acetate, ethyl acetate, acetonitrile, and dioxolane, and more preferably includes one or more selected from acetone and tetrahydrofuran.

[0058] From the viewpoint of improving production efficiency, the concentration of organic solvent B in the adhesive composition 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, when the entire adhesive composition is taken as 100% by mass. From the viewpoint of improving adhesiveness, 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 may be even lower, such as 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less.

[0059] (Optional Components) As long as the effects of the present disclosure can be obtained, the adhesive composition may contain an organic solvent other than the organic solvent A and the organic solvent B. In addition, the adhesive composition may contain known additives such as a plasticizer, a stabilizer, a viscosity modifier, a colorant, etc.

[0060] (Adhesive) The adhesive of the present disclosure includes the adhesive composition described above. This adhesive contains a solvent component that has high affinity with cellulose resin. This adhesive can be used to bond members made of cellulose resin. By using the adhesive of the present disclosure to bond multiple members with different shapes and sizes, it is possible to produce large molded products with complex shapes.

[0061] The members to be adhered with the adhesive of the present disclosure can be manufactured by mixing a cellulose resin with known additives such as a plasticizer as needed, followed by known molding techniques such as extrusion molding, blow molding, and injection molding. These members may have mating portions for joining the members together. The mating portions may be bonded to these members.

[0062] (Joining method) From another viewpoint, the present disclosure relates to a method for joining large members together using the above-described adhesive composition. In other words, the joining method of the present disclosure includes a step of joining large members made of cellulose resin together using an adhesive composition containing a cellulose derivative and a solvent component.

[0063] (Primer) The primer of the present disclosure includes the adhesive composition described above. This primer contains a solvent component that has high affinity with cellulose resin. This primer can be applied to an additive manufacturing method using cellulose resin as a material.

[0064] In particular, additive manufacturing using a 3D printer is known as a molding technique for components made of cellulose resin. Additive manufacturing can be applied to the production of three-dimensional molded products made of cellulose resin. For example, in the fused deposition modeling method, a resin layer is formed by supplying heated cellulose resin to a 3D printer and extruding it from a nozzle. This resin layer may be in a molten state, a semi-molten state, or a layer of strand-shaped cellulose resin laminated in a semi-molten state. In the 3D printer, these resin layers are sequentially laminated to form a multilayer structure, thereby producing a molded product of a desired shape.

[0065] The primer of the present disclosure can be used to bond these laminated resin layers together. Specifically, the primer of the present disclosure is applied to the surface of a resin layer extruded from a 3D printer to form an adhesive layer, and then a cellulose resin is extruded onto the adhesive layer to laminate the resin layer, thereby bonding the resin layers together via the adhesive layer. After bonding, the adhesive layer and the resin layer are integrated.

[0066] In conventional 3D printers, a molten resin is extruded to form a resin layer before the resin layer extruded from the nozzle cools and solidifies. In this case, molten or semi-molten resin layers are stacked together and solidified, resulting in a laminated, integrated component. However, when forming large components using a 3D printer, the perimeter of the laminated resin must be increased. With a long perimeter, the next resin is extruded after the resin extruded from the nozzle has completely cooled and solidified, resulting in insufficient interlayer adhesion. This issue has limited the practical application of additive manufacturing technology for large components using 3D printers, especially large components made of cellulose resin.

[0067] The present inventors have discovered that an integrated laminated molded product can be obtained by interposing an adhesive layer made of the aforementioned adhesive composition between laminated resin layers. For example, a device for dispensing the primer of the present disclosure can be installed near the nozzle extruding molten resin in a 3D printer. The primer can then be applied to a cooled and solidified resin layer, and the molten resin can be 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 favorable integrated laminated molding. Furthermore, by applying the primer of the present disclosure to a component molded by injection molding or the like, a cellulose resin can be extruded onto the component using a 3D printer to create a desired shape.

[0068] (Method for manufacturing additively manufactured product) From another viewpoint, the present disclosure relates to a method for manufacturing a large-sized member made of a cellulose resin using a 3D printer. In detail, the present disclosure relates to a method for additively manufacturing a cellulose resin using a 3D printer, the method including a step of applying a primer containing the adhesive composition described above between resin layers made of the cellulose resin to form an adhesive layer.

[0069] (Molded Article) In one embodiment, the molded article of the present disclosure comprises a plurality of members made of a cellulose resin bonded together via an adhesive layer formed from the adhesive composition described above. The adhesive composition of the present disclosure allows for uniform application to the bonding surface, and maintains adhesion for a certain period of time after application. The molded article bonded together via the adhesive layer formed from this adhesive composition has high transparency.

[0070] In another embodiment, the molded article of the present disclosure comprises alternately laminated adhesive layers formed from the adhesive composition and resin layers formed from a cellulose resin. This molded article is obtained by the additive manufacturing technology using the 3D printer described above. The adhesive composition of the present disclosure allows for uniform application to the bonding surface, and maintains adhesion for a certain period of time after application. This adhesive composition and an adhesive containing the same maintain good adhesion after being applied to a resin layer until the next resin layer is laminated. The transparency of molded articles bonded via adhesive layers formed from this adhesive composition is high.

[0071] The effects of the present disclosure will be clarified below by examples, but the present disclosure should not be interpreted as being limited based on the description of these examples.

[0072] (Production of adhesive compositions) The cellulose derivative, organic solvent A, and organic solvent B were placed in a container (volume: 500 ml) according to the formulations shown in Tables 1 to 4 below, and the mixture was stirred at a temperature of 25° C. to obtain adhesive compositions of the examples and comparative examples. Each of the obtained adhesive compositions was liquid, and it was confirmed by visual observation that the cellulose derivative had dissolved.

[0073] (Fixation after bonding) A plurality of plate-shaped test pieces (thickness 2 mm) made of cellulose acetate were prepared. The adhesive surface (adhesion area 2 cm) of one test piece was ２ ) was coated with an adhesive composition over the entire surface, and then another test piece was immediately bonded to it. The state of the test piece was observed 10 seconds and 30 seconds after bonding. The observation results are shown in Table 1-4 below. In the table, "fixed" means that the bonded test pieces were fixed to each other and could not be moved by hand, and "movable" means that the two test pieces were not completely fixed to each other.

[0074] (Adhesion after standing) A plurality of plate-shaped test pieces (thickness 2 mm) made of cellulose acetate were prepared. The adhesive surface of one test piece (adhesion area 2 cm ２ The adhesive composition was applied to the entire surface of the test piece, and then the test piece was left to stand at room temperature. One minute, five minutes, and ten minutes after application of the adhesive composition, another test piece was attached to the test piece and the adhesion was evaluated. The evaluation results are shown in Table 1-4 below. In the table, "good adhesion" means that the two test pieces were joined together and could not be separated, and "not bonded" means that no adhesion was possible at all.

[0075] (Transparency after standing) A plurality of plate-shaped test pieces (thickness: 2 mm) made of cellulose acetate were prepared. The adhesive surface (adhesion area: 2 cm) of one test piece was measured. ２ ) and then allowed to stand at room temperature. 1 minute, 5 minutes, and 10 minutes after application of the adhesive composition, another test piece was attached to the bonded test piece, and the transparency of the bonded test piece was evaluated visually. The evaluation results are shown in Table 1-4 below. In the table, "A" means that the entire test piece was transparent after bonding, "B" means that wrinkle-like irregularities were visible at the bonded interface, and "C" means that the wrinkle-like irregularities were large and the transparency was reduced. Note that in Comparative Example 1, the two test pieces could not be bonded, so transparency was not evaluated.

[0076]

[0077]

[0078]

[0079]

[0080] Ethyl lactate: manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 155°C, SP value 26.3 (J １／２ / cm ３／２ Methyl lactate: manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 145°C, SP value 24.8 (J １／２ / cm ３／２CA: Cellulose acetate manufactured by Daicel Corporation, trade name "L50", acetyl substitution degree 2.5, weight average molecular weight Mw 200,000, molecular weight distribution Mw / Mn 5.0, viscosity average degree of polymerization 180. Acetone: manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 57°C, SP value 19.3 (J １／２ / cm ３／２ THF: Tetrahydrofuran manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 66°C, SP value 17.5 (J １／２ / cm ３／２ )

[0081] As shown in Table 1, in Comparative Example 1, which did not contain organic solvent A and a cellulose derivative, solidification (adhesion) occurred in 10 seconds when the materials were bonded immediately after application, but no adhesion was observed 1 minute after application. On the other hand, in Comparative Example 2, which contained only organic solvent A, the materials could not be fixed (adhere) even 30 seconds after bonding.

[0082] As shown in Table 1-4, in Comparative Example 3-6, in which the amount of cellulose derivative was less than 15% by mass relative to the total amount of cellulose derivative and organic solvent A, significant unevenness occurred at the bonding interface and transparency was reduced. In contrast, in Example 1-10, which contained 15% or more by mass of cellulose derivative relative to the total amount of cellulose derivative and organic solvent A, adhesion was possible even 5 minutes after application and the appearance was good (transparent). Furthermore, in Examples 1-3 and 7-10, in which the cellulose derivative concentration in the adhesive composition exceeded 8.0% by mass, no wrinkle-like unevenness was formed even 10 minutes after application, and a good (transparent) appearance was obtained.

[0083] [Comparative Example 7] First, 100 parts by mass of cellulose acetate (trade name "L50" manufactured by Daicel Corporation, degree of substitution 2.5, weight average molecular weight Mw 200,000, molecular weight distribution Mw / Mn 5.0, viscosity average degree of polymerization 180) and 20 parts by mass of triacetin (trade name "DRA-150" manufactured by Daicel Corporation) as a plasticizer were added to a Henschel mixer, and the mixture was stirred and mixed to a temperature of 70 ° C. or higher due to frictional heat within the mixer to obtain a mixture. This mixture was then fed to a twin-screw extruder (cylinder temperature: 200 ° C., die temperature: 220 ° C.) and extruded to obtain pellets (cellulose resin 1).

[0084] The obtained pellets (cellulose resin 1) were supplied to an injection molding machine and injection molded under the conditions of a cylinder temperature of 200°C, a mold temperature of 50°C, and a molding cycle of 30 seconds (injection time 15 seconds, cooling time 15 seconds), to obtain an L-shaped cellulose resin member having a thickness of 10 mm, a length of 200 mm (chuck gripping portion 50 mm, adhesive portion 150 mm), and a width of 25 mm.

[0085] Next, the pellets (cellulose resin 1) were supplied to a 3D printer (manufactured by S. Lab., trade name "Tea Room GEM", maximum modeling size: width 3 m x depth 3 m x height 3 m, nozzle diameter: 12 mm, table heater temperature: room temperature setting) and extruded onto the back of an L-shaped cellulose resin member to form a cellulose resin layer (chuck grip portion 50 mm, adhesive portion 150 mm), and a test piece of Comparative Example 7 having the shape described in JIS K6854-3 ("Adhesive - Peel Adhesion Strength Test Method Part 3: T-Shaped Peel") was obtained.

[0086] Using the obtained test piece, a peel test (180° peel method) was performed in accordance with the description of JIS K6854-3 ("Adhesive - Peel Adhesion Strength Test Method Part 3: T-Shaped Peel") to measure the peel strength between the cellulose resin member and the cellulose resin layer. A universal tensile tester was used for the measurement. Specifically, the chuck gripping portion of the cellulose resin member was fixed with the lower chuck of the universal tensile tester, and the chuck gripping portion of the cellulose resin layer was fixed with the upper chuck, and the peel strength was measured over a width of 25 mm at a test speed of 100 mm / min. The obtained peel strength was 70 g / 25 mm, which was a strength that allowed easy peeling. The peel surface was the interface between the cellulose resin member and the cellulose resin layer.

[0087] [Example 12] A test piece of Example 12 was obtained in the same manner as in Comparative Example 7, except that the adhesive composition of Example 11 was applied to the back surface of the cellulose resin member before forming the cellulose resin layer with a 3D printer. In other words, in the test piece of Example 12, an adhesive layer made of the adhesive composition of Example 11 was formed between the cellulose resin member and the cellulose resin layer. Using this test piece of Example 11, the peel strength was measured under the same test conditions as in Comparative Example 7, but no peeling occurred even with a load capacity of 20 kg on the load cell of the universal tensile tester.

[0088] Example 13 Pellets (cellulose resin 1) were obtained in the same manner as in Comparative Example 7. These pellets (cellulose resin 1) were fed into a 3D printer (manufactured by S.Labo, product name "Tea Room GEM," maximum build size: 3 m wide x 3 m deep x 3 m high, nozzle diameter: 12 mm, table heater temperature: set to room temperature) to create a hut. The created hut was 2 m long, 2 m wide, and 2.6 m high, with wall corners of 100 mm radius (same for each floor and wall), a floor thickness of approximately 12 mm, wall thickness of approximately 24 mm, and a tub-like shape without a roof. When the 3D printer was operated, the adhesive composition of Example 11 was applied with a brush (brush width approximately 20 mm) to a position 200 to 500 mm away from the tip of the nozzle in the direction of nozzle travel, and then cellulose resin 1 was extruded from the nozzle toward the coated surface to form a cellulose resin layer. The adhesive composition was not applied to the central 500 mm portion of the floor. The application speed of the adhesive composition was synchronized with the nozzle movement speed of 200 mm / sec. The application width of the adhesive composition was 20 mm, and the approximate equivalent weight calculated from the application length and the amount of adhesive composition used was 150 mg / m ２ It was.

[0089] Although the resulting hut was a large structure, it was successfully created, had good interlayer strength, and no peeling or other issues were confirmed. The resulting hut was translucent. In Example 13, good interlayer adhesion was maintained without heating using a table heater, and light transmittance was also ensured. Furthermore, as described above, good interlayer adhesion strength was achieved without using the heat-retaining chamber attached to the small 3D printer.

[0090] As shown by the above test results, the adhesive compositions of the examples are excellent in various performances. These evaluation results clearly demonstrate the superiority of the present disclosure.

[0091] Disclosed Items Each of the following items discloses a preferred embodiment.

[0092] [Item 1] A method for producing a cellulose ester copolymer comprising the steps of: (1) containing a cellulose derivative and a solvent component; (2) the cellulose derivative has a degree of substitution with an acetyl group of 1.9 or more and 2.6 or less; and (3) the solvent component has a boiling point of 100°C or more and an SP value of 18 to 30 (J １／２ / cm ３／２ an organic solvent A containing the cellulose derivative in an amount of 15% by mass or more and 30% by mass or less based on the total amount of the cellulose derivative and the organic solvent A.

[0093] [Item 2] The adhesive composition according to Item 1, wherein the cellulose derivative further contains an acyl group other than an acetyl group.

[0094] [Item 3] The adhesive composition according to item 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.

[0095] [Item 4] The adhesive composition according to any one of Items 1 to 3, wherein the solvent component further comprises an organic solvent B having a boiling point of less than 100°C.

[0096] [Item 5] The adhesive composition according to Item 4, wherein 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.

[0097] [Item 6] The adhesive composition according to Item 4 or 5, wherein the concentration of the organic solvent B is 5.0% by mass or more and less than 60.0% by mass.

[0098] [Item 7] The adhesive composition according to any one of Items 1 to 6, wherein the cellulose derivative has a weight average molecular weight of 70,000 or more and 300,000 or less.

[0099] [Item 8] An adhesive for cellulose resins, comprising the adhesive composition according to any one of items 1 to 7.

[0100] [Item 9] A primer comprising the adhesive composition according to any one of items 1 to 7.

[0101] [Item 10] A molded article in which a plurality of members made of a cellulose resin are bonded together via an adhesive layer formed from the adhesive composition according to any one of items 1 to 7.

[0102] [Item 11] A molded article in which adhesive layers formed from the adhesive composition according to any one of items 1 to 7 and resin layers formed from a cellulose resin are alternately laminated.

[0103] The adhesive composition according to the present disclosure can be applied to the joining and manufacturing of various molded articles made of cellulose derivatives.

Claims

1. A cellulose derivative and a solvent component are included, the cellulose derivative has a degree of substitution with an acetyl group of 1.9 or more and 2.6 or less, the solvent component has a boiling point of 100°C or more and an SP value of 18 to 30J. １／２ / cm ３／２ an organic solvent A represented by the formula (1), wherein the amount of the cellulose derivative is 15 mass % or more and 30 mass % or less based on the total amount of the cellulose derivative and the organic solvent A.

2. The adhesive composition of claim 1, wherein said cellulose derivative further comprises an acyl group other than an acetyl group.

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 further comprises an organic solvent B having a boiling point of less than 100°C.

5. The adhesive composition according to claim 4, wherein 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.

6. The adhesive composition according to claim 4, wherein the concentration of the 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 weight average molecular weight of said cellulose derivative is 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 in which a plurality of members made of cellulose resin are bonded together via an adhesive layer formed from the adhesive composition according to claim 1.

11. A molded article in which adhesive layers formed from the adhesive composition according to claim 1 and resin layers formed from a cellulose resin are alternately laminated.

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