JP2024157721A - Reactive hot melt adhesive composition, adhesive body, and method for producing same - Google Patents

Abstract

The present invention provides a reactive hot melt adhesive composition that can form an adhesive layer having high impact resistance and can be produced with a high biomass raw material content.
[Solution] This is a bio-polyurethane adhesive containing a urethane prepolymer obtained by reacting a polyol component (A) with an isocyanate component (B), in which the polyol component (A) contains a bio-polyester polyol (A1) which is a copolymer of a polyfunctional alcohol component and a polyfunctional carboxylic acid component, and which contains a biomass-derived diol component (a) and a biomass-derived dicarboxylic acid component (b) as raw materials, and a castor oil diol (A2) having an average number of hydroxyl groups of 1.8 to 2.1 and a hydroxyl value of 20 to 300 mgKOH/g, and the urethane prepolymer has a biomass-derived component content of 35 mass% or more.
[Selection diagram] None

Description

This disclosure relates to reactive hot melt adhesive compositions, adhesive bodies, and methods for producing the same.

Hot melt adhesives, which are solvent-free adhesives, are characterized by several advantages, including low environmental and human impact, and the ability to bond in a short time, which can increase the production efficiency of adhesives. Hot melt adhesives can be broadly divided into two types: those that use thermoplastic resins as the main component, and those that use reactive resins as the main component. The reactive resins that are mainly used are urethane prepolymers with isocyanate groups at the ends.

A reactive hot melt adhesive mainly composed of a urethane prepolymer can provide a certain degree of adhesive strength in a short time after application to an adherend by cooling and solidifying the adhesive itself, i.e., the adhesive layer. After that, or at the same time, the terminal isocyanate groups react with moisture (moisture in the air or on the surface of the adherend), causing the urethane prepolymer to polymerize and form crosslinks, which also provide heat resistance. Such adhesives are also called "moisture-curing reactive hot melt adhesives." In contrast to thermoplastic resin-based hot melt adhesives, reactive hot melt adhesives mainly composed of a urethane prepolymer exhibit good adhesive strength even when the bonded body is heated after bonding. Urethane prepolymer adhesive compositions containing polybutadiene polyol as a polyol component to improve impact resistance and urethane prepolymer adhesive compositions having the properties of a tensile modulus of 40 MPa or less and a breaking elongation of 1,000% or more are also known (see, for example, Patent Documents 1 and 2).

International Publication No. 2017/187968 JP 2017-222776 A

The primary objective of various embodiments of the present disclosure is to provide a reactive hot melt adhesive composition that can form an adhesive layer with high impact resistance and can be produced with a high biomass raw material content.

The present disclosure includes the following embodiments.
[1]
A bio-based polyurethane adhesive comprising a urethane prepolymer obtained by reacting a polyol component (A) with an isocyanate component (B),
The polyol component (A) is
A biopolyester polyol (A1) which is a copolymer of a polyfunctional alcohol component and a polyfunctional carboxylic acid component, the copolymer comprising a biomass-derived diol component (a) and a biomass-derived dicarboxylic acid component (b) as raw materials;
and a castor oil diol (A2) having an average number of hydroxyl groups of 1.8 to 2.1 and a hydroxyl value of 20 to 300 mgKOH/g,
The diol component (a) contains at least one selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, and dimer diol, which are derived from biomass; the dicarboxylic acid component (b) contains at least one selected from the group consisting of succinic acid, sebacic acid, dimer acid, adipic acid, azelaic acid, and 2,5-furandicarboxylic acid, which are derived from biomass;
The urethane prepolymer is characterized in that the content of biomass-derived components is 35% by mass or more.
Bio-polyurethane adhesive.
[2]
The biopolyurethane adhesive according to [1], wherein the number average molecular weight (Mn) of the biopolyester polyol (A1) is within the range of 500 to 10,000.
[3]
The bio-polyurethane adhesive according to [1] or [2], wherein the isocyanate component (B) is an aromatic isocyanate, an alicyclic isocyanate, an aliphatic isocyanate, or a combination thereof.
[4]
The method for producing the biopolyurethane adhesive according to any one of [1] to [3], comprising a step of reacting the polyol component (A) and the isocyanate component (B) under conditions that generate a urethane bond to obtain the urethane prepolymer having an isocyanate group.
[5]
A method for producing an adhesive body, comprising: preparing an adhesive body comprising a first adherend, a second adherend, and the adhesive composition according to any one of [1] to [3] that is in contact with both of them; and curing the adhesive composition in the adhesive body in a moisture-present environment.
[6]
An adhesive structure in which a first adherend and a second adherend are adhered via a cured product of the biopolyurethane adhesive according to any one of [1] to [3].

According to various embodiments of the present disclosure, a reactive hot melt adhesive composition capable of forming an adhesive layer having high impact resistance is provided. The reactive hot melt adhesive composition can be produced with a high biomass raw material content, and thus the advantage of hot melt adhesives, such as low environmental impact, can be further enhanced by reducing the usage rate of petroleum-based materials.

The following describes in detail the modes for carrying out the present invention. However, the present invention is not limited to the individual embodiments described below. For example, it should be understood that embodiments in which a feature described in relation to one embodiment can be incorporated into another described embodiment, or in which that feature is omitted, are also included in the present disclosure unless the context clearly dictates otherwise. In this specification, when an embodiment expressed with the term "including X" is presented, an embodiment expressed with the term "consisting of X" is also possible unless the context clearly dictates otherwise.

In this specification, a numerical range indicated using "~" indicates a range including the numerical values before and after "~" as the minimum and maximum values, respectively. In a numerical range described in stages in this specification, the upper or lower limit of a numerical range of a certain stage can be replaced with the upper or lower limit of a numerical range of another stage. In a numerical range described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example. "A or B" may include either A or B, and may include both as long as it is not contrary to the context. Unless otherwise specified, the materials exemplified in this specification may be used alone or in combination of two or more types. In this specification, the content of each component in a composition means the total amount of the multiple substances present in the composition when multiple substances corresponding to that component are present in the composition, unless otherwise specified.

In this specification, "polyol" means a compound having 1.8 or more hydroxyl groups in the molecule.

In this specification, "polyisocyanate" means a compound having two or more isocyanate groups in the molecule.

[Reactive hot melt adhesive composition]
The reactive hot melt adhesive composition of the present embodiment contains a urethane prepolymer. In this disclosure, the reactive hot melt adhesive composition may be simply referred to as an "adhesive composition", or may be referred to as a bio-polyurethane adhesive or a bio-polyurethane adhesive composition. In general, a "reactive hot melt" adhesive means an adhesive that is moisture-curing, that is, an adhesive that can be polymerized by reacting with moisture in the air or moisture on the surface of an adherend to achieve high molecular weight and adhesive strength, and the adhesive composition of the present embodiment may be partially characterized by this property.

As will be understood by those skilled in the art, a urethane prepolymer means a urethane resin having an isocyanate group at the molecular end obtained by reacting a polyol with an excess equivalent of a polyisocyanate. The urethane prepolymer can be further polymerized and crosslinked as an adhesive due to the presence of these isocyanate groups at the molecular end. The urethane prepolymer typically contains a polymer chain containing a structural unit derived from a polyol, including a polyester polyol or a polyether polyol, and a structural unit derived from a polyisocyanate, and has an isocyanate group as the terminal group of the polymer chain. The urethane prepolymer of this embodiment is a reaction product of a polyol component containing a specific polyol described later and a polyisocyanate component, and has an isocyanate group as the terminal group of the reaction product. The adhesive composition of this embodiment contains such a urethane prepolymer, so that it can provide excellent adhesive strength after moisture curing and form an adhesive layer having high impact resistance.

<Polyol Component (A)>
The polyol component (A) which gives the structural unit derived from the polyol in the urethane prepolymer contains a biopolyester polyol (A1) which is a copolymer of a polyfunctional alcohol component and a polyfunctional carboxylic acid component, the copolymer comprising a biomass-derived diol component (a) and a biomass-derived dicarboxylic acid component (b) as raw materials. In this context, the term "raw material" refers to reactants in the copolymerization reaction of the polyfunctional alcohol component and the polyfunctional carboxylic acid component. The polyol component (A) further contains a castor oil diol (A2) having an average number of hydroxyl groups of 1.8 to 2.1 and a hydroxyl value of 20 to 300 mgKOH/g.

As will be appreciated by those skilled in the art, biomass-derived compounds are compounds that contain carbon atoms that have undergone biosynthesis by modern organisms (particularly plants) and can be distinguished from pure petroleum-derived compounds based on the content of the ¹⁴ C isotope. The biomass-derived diol component (a) in this embodiment is selected from the group consisting of biomass-derived ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, and dimer diol, any of which may be used alone or in combination of two or more. It is also known in the art to determine the "biomass content" of a given material, i.e., what percentage of the carbon is derived from biomass, based on the content of the ¹⁴ C isotope in that material. Biomass-derived diols (and dicarboxylic acids, as described below) can be 100% biomass content.

Biomass-derived diols (and dicarboxylic acids (described below)) themselves are publicly known and are described, for example, in Japanese Patent No. 6962505. An example of biomass-derived ethylene glycol is one obtained from known bioethanol via ethylene. An example of biomass-derived 1,2-propanediol is one obtained from fermentation of sugars, and one obtained by hydrogenating glycerin obtained as a by-product of biodiesel using a known method. An example of biomass-derived 1,3-propanediol is one obtained by converting 3-hydroxypropionaldehyde obtained from glycerol, glucose, and other sugars by a known fermentation method into 1,3-propanediol, and one obtained directly from glucose and other sugars by fermentation. An example of biomass-derived 1,4-butanediol is one obtained from glucose by a known fermentation method, one obtained from 1,3-butadiene obtained by fermentation, and one obtained by hydrogenating succinic acid with a reduction catalyst. An example of biomass-derived 1,6-hexanediol is one obtained from adipic acid via a known reaction. An example of biomass-derived 1,10-decanediol is one obtained by hydrogenating sebacic acid directly or its esterification reaction product. An example of biomass-derived dimer diol is one obtained by reducing dimer acid by a known method.

As the biomass-derived diol component (a), ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol are preferred because they can impart particularly excellent impact resistance to the adhesive composition, and 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol are more preferred.

The biomass-derived dicarboxylic acid component (b) is selected from the group consisting of biomass-derived sebacic acid, succinic acid, dimer acid, adipic acid, azelaic acid, and 2,5-furandicarboxylic acid, and any of these dicarboxylic acids may be used alone or two or more of them may be used in combination.

An example of biomass-derived sebacic acid is obtained from vegetable oils such as castor oil through a known cleavage reaction using caustic alkali. An example of biomass-derived succinic acid is obtained from fermentation of corn, sugarcane, cassava, sago palm, etc. by a known method. An example of biomass-derived dimer acid is obtained by dimerizing biomass-derived unsaturated fatty acids by a known method. An example of biomass-derived adipic acid is obtained by microbial fermentation of sugar derived from non-edible biomass. An example of biomass-derived azelaic acid is obtained from biomass-derived oleic acid through a known cleavage reaction. An example of biomass-derived 2,5-furandicarboxylic acid is obtained from fructose and from a known synthesis method using furancarboxylic acid, a furfural derivative, and carbon dioxide.

As the biomass-derived dicarboxylic acid component (b), sebacic acid, dimer acid, adipic acid, and azelaic acid are preferred because they can impart particularly excellent impact resistance to the adhesive composition, and sebacic acid and adipic acid are more preferred.

In addition to the diol component (a) and the dicarboxylic acid component (b) as the polyfunctional alcohol component and the polyfunctional carboxylic acid component, the biopolyester polyol (A1) may contain other polyfunctional alcohol components (e.g., diol components) and/or other polyfunctional carboxylic acid components (e.g., dicarboxylic acid components) as raw materials. However, 50% by mass or more, more preferably 70% by mass or more, more preferably 90% by mass or more, or 100% by mass of the raw materials to be polymerized to form the biopolyester polyol (A1) may be the above-mentioned diol component (a) and dicarboxylic acid component (b). The mass ratio of the polyfunctional alcohol component and the polyfunctional carboxylic acid component to form the polyester polyol can be appropriately determined by a person skilled in the art. The number of hydroxyl groups in the biopolyester polyol (A1) may be, for example, 1.8 to 2.1, and is preferably 2.

Castor oil diol is a diol derived from castor oil and is known in the art (see, for example, Japanese Patent Nos. 5,855,722, 5,090,319, and 5,496,496). Castor oil diol can be characterized in that the hydroxyl groups of the ricinoleic acid hydrocarbon chain, which is a natural component of castor oil, provide the diol group. The castor oil diol (A2) in this embodiment has an average number of hydroxyl groups of 1.8 to 2.1 and a hydroxyl value of 20 to 300 mgKOH/g. In particular, one having an average number of hydroxyl groups of 1.95 to 2.05, for example 2, can be preferably used. If the number of hydroxyl groups exceeds 2.1, the adhesive may thicken due to the formation of a branched or crosslinked structure of the trivalent polyol. The hydroxyl value of the castor oil diol (A2) may be 30 to 270 mgKOH/g, or 40 to 60 mgKOH/g.

Examples of commercially available castor oil diols (A2) include "URIC HF-2009" (number of hydroxyl groups: 2, hydroxyl value: 44) manufactured by Ito Oil Mills, Ltd., and "URIC H-62" (number of hydroxyl groups: 2, hydroxyl value: 260) manufactured by Ito Oil Mills, Ltd. One type of castor oil diol may be used alone, or two or more types may be used in combination. The castor oil diol is preferably a castor oil-based polyether polyester diol.

The mass ratio of the biopolyester polyol component (A1) to the castor oil diol (A2) may be, for example, in the range of 1:1 to 10:1, preferably 2:1 to 8:1, and more preferably 3:1 to 5:1. The polyol component (A) contains the above-mentioned biopolyester polyol (A1) and castor oil diol (A2) as essential components, but may further contain glycols and/or polyols other than A1 and A2. It is preferable that A1 and A2 (i.e., the sum of A1 and A2) account for 40 to 100 mass% of the polyol component (A). In one embodiment, A1 accounts for 30 to 90 mass% of the polyol component (A). In one embodiment, A2 accounts for 5 to 30 mass% or 10 to 20 mass% of the polyol component (A). Specific examples of glycols and polyols other than A1 and A2 include, but are not limited to, non-biomass-derived polypropylene glycols and non-biomass-derived polyester polyols (e.g., those containing an isophthalic acid component and a neopentyl glycol component). The molecular weight, number of hydroxyl groups, crystallinity, and other conditions of glycols and polyols other than A1 and A2 may be similar to those described for A1 or A2. For example, in one embodiment, glycols and polyols other than A1 and A2 each have a number average molecular weight in the range of 1000 to 5000 and a number of hydroxyl groups of 2. In one embodiment, glycols and polyols other than A1 and A2 are amorphous.

The biopolyester polyol (A1) and the castor oil diol (A2) may be crystalline, amorphous, or a mixture thereof. The determination of crystallinity and amorphousness is performed at 25°C. Thus, a polyol that can exist as a crystal at 25°C is called a crystalline polyol, and a polyol that does not crystallize at 25°C is called an amorphous polyol. From the viewpoint of improving the coatability and initial adhesion of the adhesive composition, it is preferable that both a crystalline polyol and an amorphous polyol are contained in the adhesive composition.

The number average molecular weight (Mn) of the polyester polyol, particularly the biopolyester polyol (A1), may be, for example, in the range of 500 to 10,000, preferably 800 to 9,000, more preferably 1,000 to 8,000, and even more preferably 1,500 to 6,000 or 2,000 to 5,000.

In one embodiment, in order to enhance the waterproofing and adhesive properties of the adhesive composition, a crystalline polyester polyol (particularly biopolyester polyol (A1)) having a number average molecular weight in the range of 500 to 10,000, preferably a crystalline polyester polyol having a number average molecular weight in the range of 800 to 9,000, more preferably 1,000 to 8,000, can be included. For example, 30 to 60 mass % of the polyol component (A) can be such a crystalline polyester polyol.

In one embodiment, the polyol component (A) contains an amorphous polyester polyol having a number average molecular weight of 3000 or less and/or a number average molecular weight of 5000 or more (particularly, biopolyester polyol (A1)). For the amorphous polyester polyol having a number average molecular weight of 3000 or less, the molecular weight is preferably in the range of 500 to 3000, more preferably in the range of 1000 to 3000, from the viewpoint of further improving the adhesiveness of the adhesive composition. For the amorphous polyester polyol having a number average molecular weight of 5000 or more, the molecular weight is preferably in the range of 5000 to 9000, more preferably in the range of 5000 to 8000, from the viewpoint of further improving the impact resistance of the adhesive composition. For example, 5 to 60% by mass of the polyol component (A) may be the amorphous polyester polyol having a number average molecular weight of 3000 or less. 20 to 40% by mass of the polyol component (A) may be the amorphous polyester polyol having a number average molecular weight of 5000 or more.

The number average molecular weight described in this specification is measured by gel permeation chromatography (GPC) as a value converted into standard polystyrene. The measurement by GPC can be performed under the following conditions.
Column: "Gelpack GLA130-S", "Gelpack GLA150-S" or "Gelpack GLA160-S" (Resonac Corporation, HPLC packed column)
Eluent: tetrahydrofuran Flow rate: 1.0 mL/min
Column temperature: 40°C
Detector: RI (differential refractive index) detector

<Isocyanate Component (B)>
The isocyanate component (B) may be a polyisocyanate, and in particular may be a diisocyanate. Examples of the isocyanate component (B) include aromatic isocyanates such as diphenylmethane diisocyanate, dimethyldiphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and p-phenylene diisocyanate; alicyclic isocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate. From the viewpoints of reactivity and adhesiveness, the isocyanate component (B) preferably contains an aromatic diisocyanate, and more preferably contains diphenylmethane diisocyanate. The isocyanate component may be used alone or in combination of two or more kinds. For example, the isocyanate component (B) can be an aromatic, cycloaliphatic, or aliphatic isocyanate, such as those described above, or a combination thereof. The molecular weight of the isocyanate component (B) is typically in the range of 150 to 400.

The urethane prepolymer contains a polymer chain containing a structural unit derived from a polyol and a structural unit derived from a polyisocyanate, and has an isocyanate group as the terminal group of the polymer chain. When synthesizing such a urethane prepolymer, the ratio of the isocyanate group (NCO) equivalent of the isocyanate component (B) to the hydroxyl group (OH) of the polyol component (A) (isocyanate group (NCO) equivalent of the isocyanate component (B) / hydroxyl group (OH) equivalent of the polyol component (A) (NCO/OH)) is greater than 1 and may be 1.3 to 3.0 or 1.5 to 2.0. When the NCO/OH ratio is 1.3 or more, the viscosity of the obtained urethane prepolymer is prevented from becoming too high, and the workability tends to be easily improved. When the NCO/OH ratio is 3.0 or less, foaming is less likely to occur during the moisture curing reaction of the adhesive composition, and a decrease in adhesive strength tends to be easily suppressed.

For the urethane prepolymer obtained by reacting the polyol component (A) with the isocyanate component (B), the content of the biomass-derived component (including the biopolyester polyol (A1) and the castor oil diol (A2)) can be 35% by mass or more, and this content can be preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. For the urethane prepolymer, the content of the biomass-derived component is a value calculated as the ratio of the total mass of the biomass-derived reactants to the total mass of the reactants used in the reaction to form the urethane prepolymer. In one embodiment, the biomass degree of the urethane prepolymer obtained by reacting the polyol component (A) with the isocyanate component (B) is 30% or more, preferably 50% or more, and more preferably 70% or more. In one embodiment, the biomass degree of the adhesive composition including other components described later can be within these ranges.

<Other Ingredients>
The adhesive composition according to this embodiment may contain, in addition to the urethane prepolymer obtained by reacting the above-mentioned polyol component (A) with the isocyanate component (B), an appropriate amount of other components, for example, one or more additive components selected from thermoplastic polymers, tackifier resins, catalysts, pigments, UV absorbers, surfactants, flame retardants, fillers, etc. The adhesive composition may preferably contain 50% by mass or more, 70% by mass or more, or 90% by mass or more of the above urethane prepolymer, or may contain 100% by mass of the above urethane prepolymer.

Examples of thermoplastic polymers include polyurethane, ethylene copolymers, propylene copolymers, vinyl chloride copolymers, acrylic copolymers, and styrene-conjugated diene block copolymers. Examples of tackifier resins include rosin resins, rosin ester resins, hydrogenated rosin ester resins, terpene resins, terpene phenol resins, hydrogenated terpene resins, petroleum resins, hydrogenated petroleum resins, coumarone resins, ketone resins, styrene resins, modified styrene resins, xylene resins, and epoxy resins. Examples of catalysts include dibutyltin dilaurate, dibutylthione octate, dimethylcyclohexylamine, dimethylbenzylamine, and trioctylamine.

The coatability of the adhesive composition can be evaluated by measuring the viscosity of the adhesive composition. In order to provide excellent coatability to an adherend, the viscosity of the adhesive composition according to this embodiment, measured using a rotational viscometer, is preferably 15 Pa·s or less at 120°C, more preferably 12 Pa·s or less, and even more preferably 10 Pa·s or less. The lower limit of the viscosity is not particularly limited, but may be, for example, 1 Pa·s or more at 120°C.

The impact resistance of the adhesive composition can be evaluated by dropping a weight onto a laminate obtained by bonding adherends together using the adhesive composition and visually checking for the presence or absence of peeling. A specific example of a method for evaluating impact resistance is detailed in the Examples section of this application. The adhesive composition of this embodiment can have such high impact resistance that when a weight of 200 g is dropped onto the laminate from a height of 200 mm according to the evaluation method described in the Examples below, the number of drops before peeling occurs is 100 or more, 200 or more, or 500 or more.

[Method of producing reactive hot melt adhesive composition]
The adhesive composition according to the present embodiment can be produced by a method including a step of reacting the polyol component (A) and the isocyanate component (B) under conditions that generate urethane bonds to obtain a urethane prepolymer having an isocyanate group. The polyol component (A), the isocyanate component (B), and the appropriate amount ratio thereof are as described above. For example, the polyol component (A) and the isocyanate component (B) can be mixed under conditions that the polyisocyanate group is in excess relative to the polyol group, and the mixture can be reacted by maintaining the mixture at a temperature of 100 to 150°C for 0.5 hours or more to obtain a urethane prepolymer. The reaction time can be 1 hour or more, or 2 hours or more. The upper limit of the reaction time is not particularly limited, but typically the reaction time is 24 hours or less, 12 hours or less, or 6 hours or less. Those skilled in the art can appropriately find conditions that result in an excess of polyisocyanate groups relative to the polyol group based on the molecular weight and the number of functional groups of the polyol component (A) and the isocyanate component (B). The ratio of the number of isocyanate groups to the number of hydroxyl groups therebetween may be, for example, within the range of 1.1 to 5 or 1.1 to 3. The method may include, as necessary based on the common knowledge of a person skilled in the art, dehydrating the polyol component (A) under vacuum or reduced pressure before or after mixing, and/or degassing the mixture after the reaction under vacuum or reduced pressure.

[Adhesive]
In one aspect, the present disclosure provides a method for using the adhesive composition described above, i.e., a method for producing an adhesive body using the adhesive composition described above. This method includes preparing an adhesive body including a first adherend and a second adherend and the adhesive composition present in contact with both of them, and curing the adhesive composition in the adhesive body in an environment in the presence of moisture. This method may include applying the molten adhesive composition to the first adherend, the second adherend, or both of them before preparing the adhesive body. The first adherend and the second adherend may be any substrate. That is, their materials are not particularly limited and can be appropriately selected by those skilled in the art according to individual applications. The material of the adherend may be, for example, polycarbonate, polyamide, polybutylene terephthalate, glass, aluminum, or SUS (stainless steel), but is not limited thereto. The material of the first adherend and the material of the second adherend may be the same or different. The moisture may be moisture present in the air, or in addition to or instead of moisture, moisture may be present on the adherend surface. A person skilled in the art can easily find a suitable temperature for melting and curing each adhesive composition based on his/her general knowledge. Melting can be performed at a temperature at which the adhesive composition is in a molten state, for example, 80°C to 120°C. Solidification can be performed, for example, by cooling the adhesive composition to a temperature range of room temperature to 40°C. Curing can be performed, for example, for 10 minutes to 48 hours. After curing, an adhesive body is obtained in which a first adherend and a second adherend are bonded via a cured product of the adhesive composition. Thus, in one aspect, the present disclosure provides an adhesive body in which a first adherend and a second adherend are bonded via a cured product of the adhesive composition. The adhesive body may be called a laminate, but the first adherend and the second adherend are not necessarily planar, and the bonding surfaces of the two are not necessarily parallel to each other.

The above has discussed hot melt adhesive compositions and adhesive bodies containing components derived from biomass, and methods for producing the same. Corresponding hot melt adhesive compositions and adhesive bodies having the same composition but containing components not necessarily derived from biomass, and methods for producing the same, are also included in the present disclosure.

The present invention will be explained in more detail below based on examples. However, the examples are merely illustrative of representative materials and results, and the present invention is not limited to these specific examples.

[material]
(Polyol Component)
As the biopolyester polyol (A1), polyester polyol A1-a (crystalline polyester polyol obtained mainly from sebacic acid and 1,2-propanediol, number of hydroxyl groups: 2, number average molecular weight: 2000), polyester polyol A1-b (amorphous polyester polyol obtained mainly from sebacic acid and 1,4-butanediol, number of hydroxyl groups: 2, number average molecular weight: 5000), and polyester polyol A1-c (crystalline polyester polyol obtained mainly from sebacic acid and 1,6-hexanediol, number of hydroxyl groups: 2, number average molecular weight: 2000) were prepared. As the castor oil diol (A2), castor oil-based polyether polyester diol (number of hydroxyl groups: 2, hydroxyl value: 44, manufactured by Ito Oil Mills, trade name "URIC HF-2009", biomass degree 80% or more) was prepared. In the following Table 1, the biomass degree of this product is assumed to be 80%, and the biomass degree of the composition is calculated. As other polyols, polyester polyol Ca (amorphous polyester polyol obtained from isophthalic acid and neopentyl glycol as main components, number of hydroxyl groups: 2, number average molecular weight: 3000) and polypropylene glycol Cb (number of hydroxyl groups: 2, number average molecular weight: 2000) were prepared.

(Isocyanate component)
As the isocyanate component (B), diphenylmethane diisocyanate (number of isocyanate groups: 2) was prepared.

[Example 1]
31 parts (parts by mass) of polyester polyol A1-b, which had been previously dehydrated using a vacuum dryer, 10 parts of castor oil diol A2, and, as other polyols, 50 parts of polyester polyol Ca and 9 parts of polypropylene glycol C-b were added and mixed, and then 16 parts of diphenylmethane diisocyanate was further added and mixed. Next, the resulting mixture was reacted at 110°C for 1 hour, and further stirred at 110°C for 1 hour while degassing under reduced pressure, to obtain an adhesive composition containing a urethane prepolymer having an isocyanate group.

[Example 2]
As polyol components, 40 parts of polyester polyol A1-a, 31 parts of polyester polyol A1-b, 10 parts of castor oil diol A2, 10 parts of polyester polyol Ca, and 10 parts of polypropylene glycol Cb were added and mixed, and then 22 parts of diphenylmethane diisocyanate was further added and mixed. The rest of the procedure was the same as in Example 1 to obtain an adhesive composition.

[Example 3]
As polyol components, 40 parts of polyester polyol A1-a, 31 parts of polyester polyol A1-b, 10 parts of polyester polyol A1-c, and 19 parts of castor oil diol A2 were added and mixed, and then 25 parts of diphenylmethane diisocyanate was further added and mixed. The rest of the procedure was the same as in Example 1 to obtain an adhesive composition.

[Comparative Example 1]
As polyol components, 10 parts of castor oil diol A2, 81 parts of polypropylene glycol Ca, and 9 parts of polyester polyol Cb were added and mixed, and then 32 parts of diphenylmethane diisocyanate was further added and mixed. The rest of the procedure was the same as in Example 1 to obtain an adhesive composition.

[Comparative Example 2]
As polyol components, 40 parts of polyester polyol A1-a, 31 parts of polyester polyol A1-b, 10 parts of polyester polyol A1-c, and 19 parts of polypropylene glycol Ca were added and mixed, and then 23 parts of diphenylmethane diisocyanate was further added and mixed. The rest of the procedure was the same as in Example 1 to obtain an adhesive composition.

[Evaluation of Adhesive Composition]
<Viscosity>
The melt viscosity of the adhesive composition was measured under the following conditions using a BH-HH type small volume rotational viscometer (manufactured by Toki Sangyo Co., Ltd.).
Rotor: No. 4 rotor Sample weight: 15g
Rotor rotation speed: 50 min ^-1
Temperature: 120°C

<Adhesiveness>
The adhesive composition was melted at 100°C and placed in a syringe container (manufactured by Musashi Engineering Co., Ltd., product name "PSY-30E") equipped with a precision nozzle with an inner diameter of 0.40 mm (manufactured by Musashi Engineering Co., Ltd., product name "SHN-0.40N"), and the molten adhesive composition was dispensed onto adherend A using a dispenser (manufactured by Musashi Engineering Co., Ltd., product name "SHOTMASTER 200DS") that had been preheated to 100°C. Specifically, a circle of 25 mm diameter was drawn on the adherend A (polycarbonate plate: width 80 mm x length 60 mm x thickness 5 mm, with a hole of 15 mm inner diameter in the center) with the discharged molten adhesive composition so as to surround the hole, and then adherend B (polycarbonate plate: width 50 mm x length 50 mm x thickness 5 mm) was attached thereto, and the width of the adhesive layer (i.e., the thickness of the line forming the circle) was adjusted to 1.0 mm and the thickness to 0.15 mm, thereby producing a laminate in which adherend A, adhesive layer, and adherend B were laminated in this order. This laminate was left for 2 days in an environment of temperature 23 ° C. and humidity 50%. Thereafter, in an environment of temperature 23 ° C. and humidity 50%, the laminate was fixed so that the adherend B side was facing downwards, and the pressing adhesive force was measured using a precision universal testing machine (manufactured by Shimadzu Corporation, product name "Autograph AGS-X").
Pressing tool diameter: 10 mm
Push-in speed: 10 mm/min

<Impact resistance>
In the same manner as described above with respect to the adhesiveness measurement, a laminate in which the adherend A, the adhesive layer, and the adherend B were laminated in this order was prepared, and left for 2 days in an environment at a temperature of 23°C and a humidity of 50%. Thereafter, in an environment at a temperature of 23°C and a humidity of 50%, the adherend A side of the laminate was fixed to a DuPont impact machine (manufactured by Tester Sangyo Co., Ltd., product name "DuPont impact tester") so that the adherend B side of the laminate was facing downward. Next, a shot mold (radius 4.76 mm) was placed so as to contact the surface of the adherend B (the surface exposed in the hole on the side having the adhesive) from above through the hole of the adherend A. Then, a weight with a load of 200 g was dropped from a height of 200 mm above and collided with the shot mold, thereby applying a force vertically downward to the adherend B of the laminate, and then the presence or absence of peeling of the adherend B from the laminate was visually confirmed. The number of weight drops required until the adherend B peeled off was recorded.

[result]
The experimental compositions and results are summarized in Table 1 below. The unit of component amounts in Table 1 is parts by mass. For each urethane prepolymer, the content of the biomass-derived component was 35% in Example 1, 66% in Example 2, 80% in Example 3, 8% in Comparative Example 1, and 66% in Comparative Example 2. Table 1 also shows an estimate of the biomass degree at the carbon atom level.

The moisture-curable polyurethane hot melt adhesive composition of the examples has a high biomass content, and has excellent application properties and adhesive strength comparable to or greater than those of the comparative examples, and furthermore, is shown to have significantly higher impact resistance.

On the other hand, Comparative Example 1 is a composition lacking the A1 component and having a low biomass content, but has poor impact resistance. Comparative Example 2 is a composition that does not contain biomass-derived castor oil diol in the polyol, but this also had poor impact resistance. It can be seen that the remarkably high impact resistance, which had not shown any signs of being achieved with only the A1 component or only the A2 component, was achieved synergistically by combining the two.

Claims (6)

A bio-based polyurethane adhesive comprising a urethane prepolymer obtained by reacting a polyol component (A) with an isocyanate component (B),
The polyol component (A) is
A biopolyester polyol (A1) which is a copolymer of a polyfunctional alcohol component and a polyfunctional carboxylic acid component, the copolymer comprising a biomass-derived diol component (a) and a biomass-derived dicarboxylic acid component (b) as raw materials;
and a castor oil diol (A2) having an average number of hydroxyl groups of 1.8 to 2.1 and a hydroxyl value of 20 to 300 mgKOH/g,
The diol component (a) contains at least one selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, and dimer diol, which are derived from biomass; the dicarboxylic acid component (b) contains at least one selected from the group consisting of succinic acid, sebacic acid, dimer acid, adipic acid, azelaic acid, and 2,5-furandicarboxylic acid, which are derived from biomass;
The urethane prepolymer is characterized in that the content of biomass-derived components is 35% by mass or more.
Bio-polyurethane adhesive. The biopolyurethane adhesive according to claim 1, wherein the number average molecular weight (Mn) of the biopolyester polyol (A1) is in the range of 500 to 10,000. The biopolyurethane adhesive of claim 1, wherein the isocyanate component (B) is an aromatic isocyanate, an alicyclic isocyanate, an aliphatic isocyanate, or a combination thereof. The method for producing the biopolyurethane adhesive according to any one of claims 1 to 3, comprising the step of reacting the polyol component (A) and the isocyanate component (B) under conditions that produce urethane bonds to obtain the urethane prepolymer having an isocyanate group. A method for producing an adhesive body, comprising: preparing an adhesive body comprising a first adherend, a second adherend, and the adhesive composition according to any one of claims 1 to 3 that is in contact with both of them; and curing the adhesive composition in the adhesive body in a moisture-present environment. An adhesive body in which a first adherend and a second adherend are bonded via a cured product of the biopolyurethane adhesive according to any one of claims 1 to 3.