Method for manufacturing adhesive-forming compositions

Abstract

To provide an adhesive-forming composition and a method for producing the same, which can impart excellent enzymatic degradability, biodegradability, and tackiness to adhesive compositions and can be easily and inexpensively produced, as well as an adhesive composition having excellent enzymatic degradability, biodegradability, and tackiness, and which can be easily and inexpensively produced. [Solution] A method for producing an adhesive-forming composition, comprising a reaction step of reacting a diol having a polylactic acid structure with (meth)acrylic acid chloride and saturated fatty acid chloride to obtain an adhesive-forming composition, wherein in the reaction step, the molar ratio of the (meth)acrylic acid chloride and the saturated fatty acid chloride is 0.5:0.5.

Description

[Technical Field]

[0001] This invention relates to a method for producing an adhesive-forming composition. [Background technology]

[0002] Due to its high level of convenience, plastic is widely used and produced in large quantities. However, less than 10% of plastic is recycled and reused, and approximately 80% of plastic waste ends up in landfills or dumped into the natural environment. Plastic waste has become a major social problem, and biodegradable plastics, which are broken down into water and carbon dioxide by enzymes secreted by microorganisms in nature, are being researched, developed, and put into practical use.

[0003] Adhesives are film- or sheet-like materials with tackiness (stickiness) that are used to bond materials together. In contrast, adhesives are liquid before use but solidify due to heat, light, or moisture, and then bond materials together. Therefore, adhesives are distinguished from adhesives. Adhesives are used in a wide range of industries, including automobiles, packaging materials, building materials, IT, agriculture, medical care, and DIY-related products. It is expected that making adhesives biodegradable will lead to a reduction in environmental impact. Furthermore, in practical use, it would be beneficial if the adhesive could be detached and decomposed into water and carbon dioxide by the action of enzymes when placed in a buffer solution containing enzymes. Decomposition in nature or artificial compost has the problem of requiring equipment and work because it is soil, and the decomposition process takes a long time.

[0004] The polymers used in adhesive sheets generally have a large molecular weight and low crosslinking density, with a glass transition temperature of -20°C or lower. In contrast, conventional biodegradable plastics have a relatively hard melting point of 50°C or higher, and therefore possess mechanical properties that are the exact opposite of those of adhesive sheets. Thus, considerable ingenuity is required to impart biodegradability or enzymatic degradability to adhesive sheets.

[0005] As an adhesive composition having biodegradability, a design has been proposed in which a bulky group is introduced into the side chain to obtain a polymer physical property state (a soft elastomer gel having adhesiveness) (see, for example, Patent Documents 1 to 6). However, these adhesive compositions have a problem that their production methods are very complicated. Therefore, there is a demand for an adhesive composition having biodegradability and enzymatic degradability that can be produced more simply and at a lower cost. Further, from the viewpoint of reducing the environmental load, it is desired that no solvent is used during the production process and that the raw materials are biomass.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to solve the above-described conventional problems and achieve the following objects. That is, the present invention provides a composition for forming an adhesive and a method for producing the same, which can impart excellent enzymatic degradability, biodegradability, and adhesiveness to an adhesive composition and can form the adhesive composition simply and at a low cost, and an adhesive composition having excellent enzymatic degradability, biodegradability, and adhesiveness and which can be produced simply and at a low cost.

Means for Solving the Problems

[0008] The means to solve the aforementioned problem are as follows: <1> It contains a monofunctional (meth)acrylic monomer having a polylactic acid structure, a polyfunctional (meth)acrylic monomer having a polylactic acid structure, and an unfunctional compound having a polylactic acid structure. The adhesive-forming composition is characterized in that it contains 10 mol% or more of the non-functional compound having the polylactic acid structure. <2> This method is for producing an adhesive-forming composition, characterized by reacting a diol having a polylactic acid structure with (meth)acrylic acid chloride and saturated fatty acid chloride. <3> The molecular weight of a diol having a polylactic acid structure is 1,000 or more based on the hydroxyl value, <2> This is a method for producing the adhesive-forming composition described above. <4> The aforementioned <1> This adhesive composition is characterized by being formed by curing the adhesive-forming composition described in [the relevant document]. <5> The acetone-soluble sol fraction is 30% or more. <4> This is the adhesive composition described in [reference]. <6> The above is degraded by exolipase <4> from <5> The adhesive composition is one of the following. [Effects of the Invention]

[0009] According to the present invention, it is possible to solve the aforementioned problems in the conventional method, achieve the aforementioned objectives, impart excellent enzymatic degradability, biodegradability, and tackiness to adhesive compositions, and provide an adhesive-forming composition and a method for producing the same that can be easily and inexpensively used to form adhesive compositions, as well as an adhesive composition that has excellent enzymatic degradability, biodegradability, and tackiness and can be easily and inexpensively manufactured. [Brief explanation of the drawing]

[0010] [Figure 1]FIG. 1 is a diagram showing a simulation of the molar ratio of at least any one of a monofunctional (meth)acrylic monomer having a polylactic acid structure, a polyfunctional (meth)acrylic monomer having a polylactic acid structure, and a non-functional compound having a polylactic acid structure, when reacting a diol having a polylactic acid structure with at least any one of acrylic acid chloride and propionic acid chloride. The horizontal axis represents the molar ratio of acrylic acid chloride or propionic acid chloride, and the vertical axis represents the molar ratio of at least any one of a monofunctional (meth)acrylic monomer having a polylactic acid structure, a polyfunctional (meth)acrylic monomer having a polylactic acid structure, and a non-functional compound having a polylactic acid structure as the reaction product. In the figure, the gray square (■) represents a monofunctional (meth)acrylic monomer having a polylactic acid structure, the white triangle (△) represents a polyfunctional (meth)acrylic monomer having a polylactic acid structure, and the black circle (●) represents a non-functional compound having a polylactic acid structure.

Mode for Carrying Out the Invention

[0011] (Composition for forming an adhesive) The composition for forming an adhesive of the present invention contains a monofunctional (meth)acrylic monomer having a polylactic acid structure (hereinafter sometimes simply referred to as "monofunctional (meth)acrylic monomer"), a polyfunctional (meth)acrylic monomer having a polylactic acid structure (hereinafter sometimes simply referred to as "polyfunctional (meth)acrylic monomer"), and a non-functional compound having a polylactic acid structure (hereinafter sometimes simply referred to as "non-functional compound"), and further contains other components as necessary. The content of the non-functional compound having a polylactic acid structure in the composition for forming an adhesive is 10 mol% or more.

[0012] In this specification, the term "(meth)acrylic" in "(meth)acrylic acid chloride", "(meth)acrylic monomer", and "(meth)acrylic group" means both acrylic and methacrylic.

[0013] Furthermore, in this specification, the constituent units of polylactic acid in the monofunctional (meth)acrylic monomer having a polylactic acid structure, the polyfunctional (meth)acrylic monomer having a polylactic acid structure, and the nonfunctional compound having a polylactic acid structure may be poly-L-lactic acid consisting only of L-lactic acid, poly-D-lactic acid consisting only of D-lactic acid, or poly-L,D-lactic acid containing both L-lactic acid and D-lactic acid in various molar ratios. Among these, poly-L-lactic acid is preferred.

[0014] <Monofunctional (meth)acrylic monomers having a polylactic acid structure> The monofunctional (meth)acrylic monomer having a polylactic acid structure is a monomer having a polylactic acid structure as its main backbone and having one (meth)acrylic group in its molecule, and is a compound represented by the following general formula (1). [ka] However, in the general formula (1) above, R represents a linear or branched alkylene glycol having 2 to 4 carbon atoms, X represents -(CH2)5CO-, and m, n1, n2, l1, and l2 each represent an independent integer. R is preferably butanediol or ethylene glycol, and more preferably butanediol.

[0015] The monofunctional (meth)acrylic monomer, having a polylactic acid structure as its main backbone, can impart enzymatic and biodegradable properties to the adhesive composition obtained using the adhesive-forming composition (hereinafter sometimes referred to as the "cured product"). Furthermore, conventional adhesive compositions have the problem of becoming brittle if the crosslinking density is too high. In contrast, the adhesive-forming composition containing the monofunctional (meth)acrylic monomer has the advantage of preventing the crosslinking density of the cured product from becoming too high, thus providing appropriate tackiness.

[0016] In this specification, "enzyme-degradability" refers to degradation by exo-type lipase, which degrades the polymer from its ends. More specifically, "enzyme-degradability" means that when a substance is immersed in a buffer solution containing a predetermined amount of exo-type lipase for 100 hours at 37°C and atmospheric pressure, the mass of the substance changes relative to its mass before the reaction, and the rate of mass change is greater compared to a substance without added exo-type lipase. Furthermore, in this specification, "biodegradability" refers to degradation by enzymes, including exo-lipases, produced by microorganisms widely present in nature. Therefore, "enzyme degradation" and "biodegradability" are synonymous in terms of their function, differing only in the site of the enzymatic reaction.

[0017] Furthermore, in this specification, "adhesion" refers to the force generated by the contact between the adhesive surface of the adhesive composition and the adherend, and means the force required to peel off the adhered object.

[0018] In the general formula (1) above, the sum of n1 and n2 is not particularly limited as long as it is an integer, and can be appropriately selected depending on the purpose, but 14 to 35 is preferred, and 14 to 30 is more preferred. n1 and n2 may be the same or different.

[0019] In the general formula (1) above, the sum of l1 and l2 is not particularly limited as long as it is an integer, and can be appropriately selected depending on the purpose, but is preferably between 0 and 11, and more preferably between 8 and 11. l1 and l2 may be the same or different.

[0020] In the general formula (1) described above, there are no particular restrictions on the value of m as long as it is an integer, and it can be appropriately selected depending on the purpose. However, from the viewpoint of viscosity and crystallinity, values ​​of 1 to 10 are preferred, and values ​​of 1 to 3 are more preferred.

[0021] There are no particular restrictions on the molecular weight of the monofunctional (meth)acrylic monomer based on its hydroxyl value, and it can be appropriately selected depending on the purpose. However, when the monofunctional (meth)acrylic monomer is obtained by synthesis, a molecular weight of 2,000 or more is preferred, and 2,000 to 3,000 is more preferred. If the molecular weight of the monofunctional (meth)acrylic monomer based on its hydroxyl value is less than 2,000, the molecular weight between crosslinking points of the cured product becomes small, which may cause the cured product to become hard. If it is 3,000 or more, it may become waxy and cease to be liquid. In this specification, there are no particular restrictions on the method for measuring molecular weight by hydroxyl value; conventionally used known methods can be used and can be appropriately selected depending on the purpose. For example, the method for calculating the molecular weight is the hydroxyl value OH A The number of hydroxyl groups in a molecule (OH) B One method involves calculating the hydroxyl value using the following formula 1, based on the molecular weight of potassium hydroxide (56.1). The hydroxyl value can be measured in accordance with JIS K 0070:1992. The number of hydroxyl groups in a molecule can be measured by titrating a potassium hydroxide-ethanol solution.

number

[0022] There are no particular restrictions on the content of the monofunctional (meth)acrylic monomer in the adhesive-forming composition, and it can be appropriately selected depending on the content of the polyfunctional (meth)acrylic monomer and the unfunctional compound. However, it is preferably 40 mol% to 90 mol%, and more preferably 50 mol% to 90 mol%, relative to the total content of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the unfunctional compound. When the content of the monofunctional (meth)acrylic monomer is 40 mol% or more or 90 mol% or less, appropriate tackiness can be obtained. If the content of the monofunctional (meth)acrylic monomer is less than 40 mol% or more than 90 mol% relative to the total content of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the unfunctional compound, the ratio of the polyfunctional (meth)acrylic monomer and the unfunctional compound will be high, which may cause the cured product to become too hard or too soft, resulting in an inability to obtain appropriate tackiness.

[0023] The aforementioned monofunctional (meth)acrylic monomer may be synthesized as appropriate, or a commercially available product may be used. There are no particular restrictions on the method for synthesizing the monofunctional (meth)acrylic monomer, and it can be appropriately selected depending on the purpose, but it can be suitably synthesized by the method described later in the method for producing adhesive-forming compositions. Examples of commercially available monofunctional (meth)acrylic monomers include Poly(L-lactide), acrylate terminated (product number: 775991, number average molecular weight (Mn): 2,500, manufactured by Sigma-Aldrich).

[0024] <Polyfunctional (meth)acrylic monomers having a polylactic acid structure> The polyfunctional (meth)acrylic monomer having the polylactic acid structure is a monomer having a polylactic acid structure as its main backbone and having two or more (meth)acrylic groups in its molecule. The polyfunctional (meth)acrylic monomer, having a polylactic acid structure as its main backbone, can impart enzymatic and biodegradable properties to the cured product. Furthermore, the inclusion of the polyfunctional (meth)acrylic monomer can increase the molecular weight of the cured product, impart appropriate viscosity, and impart flexibility to the cured product.

[0025] The number of (meth)acrylic groups in the polyfunctional (meth)acrylic monomer is not particularly limited as long as there are two or more, and can be appropriately selected depending on the purpose, but it is preferable that there be two, and more preferably that the compound is represented by the following general formula (2). [ka] However, in the general formula (2) above, R represents a linear or branched alkylene glycol having 2 to 4 carbon atoms, X represents -(CH2)5CO-, and n1, n2, l1, and l2 each represent an independent integer. R is preferably butanediol or ethylene glycol, and more preferably butanediol.

[0026] Furthermore, the polyfunctional (meth)acrylic monomer may have functional groups different from the (meth)acrylic group in its structure, to the extent that it does not impair the effects of the present invention. The functional group is not particularly limited and can be appropriately selected depending on the purpose. Examples include vinyl groups, epoxy groups, and oxetane groups.

[0027] In the general formula (2) above, the sum of n1 and n2 is not particularly limited as long as it is an integer, and can be appropriately selected depending on the purpose, but 14 to 35 is preferred, and 14 to 30 is more preferred. n1 and n2 may be the same or different.

[0028] In the general formula (2) above, the sum of l1 and l2 is not particularly limited as long as it is an integer, and can be appropriately selected depending on the purpose, but is preferably between 0 and 11, and more preferably between 8 and 11. l1 and l2 may be the same or different.

[0029] There are no particular restrictions on the molecular weight of the polyfunctional (meth)acrylic monomer based on its hydroxyl value, and it can be appropriately selected depending on the purpose. However, when the polyfunctional (meth)acrylic monomer is obtained by synthesis, a molecular weight of 2,000 or more is preferred, and 2,000 to 3,000 is more preferred. If the molecular weight of the polyfunctional (meth)acrylic monomer based on its hydroxyl value is less than 2,000, the cured product may become hard, and sufficient tackiness and adhesive retention may not be obtained. There are no particular restrictions on the content of the polyfunctional (meth)acrylic monomer in the adhesive-forming composition, and it can be appropriately selected depending on the purpose. However, it is preferably 0.1 mol% to 50 mol%, more preferably 1 mol% to 30 mol%, and particularly preferably 0.5 mol% to 30 mol%, relative to the total content of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the unfunctional compound. If the content of the polyfunctional (meth)acrylic monomer is less than 0.1 mol%, the crosslinking density will be low during curing, and sufficient tackiness may not be obtained in the cured product. If it exceeds 50 mol%, the crosslinking density of the cured product will be high, and sufficient tackiness and adhesiveness may not be obtained.

[0030] The aforementioned polyfunctional (meth)acrylic monomer may be synthesized as appropriate, or a commercially available product may be used. There are no particular limitations on the method for synthesizing the polyfunctional (meth)acrylic monomer, and it can be appropriately selected depending on the purpose, but it can be suitably synthesized by the method described later in the method for producing adhesive-forming compositions.

[0031] <Non-functional compounds having a polylactic acid structure> The non-functional compound having the polylactic acid structure is a monomer having a polylactic acid structure as its main backbone and having two saturated hydrocarbon groups in its molecule, and is a compound represented by the following general formula (3). [ka] However, in the general formula (3) above, R represents a linear or branched alkylene glycol having 2 to 4 carbon atoms, X represents -(CH2)5CO-, and m, n1, n2, l1, and l2 each represent an independent integer. R is preferably butanediol or ethylene glycol, and more preferably butanediol.

[0032] Generally, general-purpose acrylic adhesive compositions consist of monofunctional acrylates, polyfunctional acrylates, and tackifiers (plasticizers). In general-purpose acrylic adhesive compositions, the addition of tackifiers improves tackiness because it makes the composition closer to a liquid state, but it has the problem of reducing cohesive force and thus reducing adhesive retention. On the other hand, in the adhesive-forming composition described above, the non-functional compound acts as a tackifier. Therefore, the adhesive composition (cured product) obtained using the adhesive-forming composition has the advantage of having appropriate adhesive retention, good tackiness and adhesiveness without the addition of known tackifiers, and furthermore, good enzymatic and biodegradability.

[0033] In the general formula (3) above, the sum of n1 and n2 is not particularly limited as long as it is an integer, and can be appropriately selected depending on the purpose, but 14 to 35 is preferred, and 14 to 30 is more preferred. n1 and n2 may be the same or different.

[0034] In the general formula (3) above, the sum of l1 and l2 is not particularly limited as long as it is an integer, and can be appropriately selected depending on the purpose, but 0 to 11 is preferred, and 8 to 11 is more preferred. l1 and l2 may be the same or different.

[0035] In the general formula (3) above, there are no particular restrictions on the value of m as long as it is an integer, and it can be appropriately selected depending on the purpose. However, from the viewpoint of viscosity and crystallinity, values ​​from 1 to 6 are preferred, and values ​​from 1 to 4 are more preferred.

[0036] There are no particular restrictions on the molecular weight of the unfunctional compound based on its hydroxyl value, and it can be appropriately selected depending on the purpose. However, when the unfunctional compound is obtained by synthesis, a molecular weight of 1,000 or more is preferred, and 1,000 to 3,000 is more preferred. If the molecular weight of the unfunctional compound based on its hydroxyl value is less than 1,000, the viscosity will be low, and it may not be retained in the cured product and may flow out.

[0037] The content of the non-functional compound in the adhesive-forming composition is 10 mol% or more, relative to the total content of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the non-functional compound, but preferably 10 mol% to 30 mol%, and more preferably 20 mol% to 30 mol%. If the content of the non-functional compound is less than 10 mol%, the cured product will not be able to obtain sufficient tackiness and adhesiveness, as well as enzymatic degradability and biodegradability. Furthermore, if the content of the non-functional compound exceeds 30 mol%, the cured product may not be able to obtain sufficient adhesive retention, or the non-functional compound may leak out of the cured product.

[0038] The aforementioned non-functional compound may be one that has been synthesized as appropriate, or a commercially available product may be used. There are no particular restrictions on the method for synthesizing the aforementioned non-functional compound, and it can be appropriately selected depending on the purpose. However, it can be suitably synthesized by the method described later in the method for producing adhesive-forming compositions.

[0039] The total content of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the non-functional compound in the adhesive-forming composition is not particularly limited and can be appropriately selected depending on the purpose. The adhesive-forming composition may consist only of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the non-functional compound.

[0040] <Other ingredients> The other components in the adhesive-forming composition are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected depending on the purpose. Examples include polymerization initiators, solvents, porous materials, foaming agents, dyes, pigments, inorganic fillers, biodegradable resin fine particles, and various additives such as softeners, anti-aging agents, antioxidants, stabilizers, antifungal agents, thickeners, colorants, defoamers, and adhesion improvers. The composition may also contain monomer components other than the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the nonfunctional compound (hereinafter sometimes referred to as "other monomer components"). These may be used individually or in combination of two or more.

[0041] There are no particular restrictions on the polymerization initiator, and it can be appropriately selected from known ones, such as photopolymerization initiators and thermal polymerization initiators. These may be used individually or in combination of two or more.

[0042] Examples of the photopolymerization initiators include acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, benzophenone, 2-chlorobenzophenone, p,p'-dichlorobenzophenone, p,p-bisdiethylaminobenzophenone, Michler ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-propyl ether, benzoin isobutyl ether, benzoin-n-butyl ether, benzyl methyl ketal, thioxanthone, 2-chlorothioxanthone, 2-hydroxy-2-methyl-1-phenyl-1-one, 1-(4-isopropylphenyl)2-hydroxy-2-methylpropan-1-one, methylbenzoyl formate, 1-hydroxycyclohexylphenyl ketone, azobisisobutyronitrile, benzoyl peroxide, and di-tert-butyl peroxide. These may be used individually or in combination of two or more.

[0043] Examples of the thermal polymerization initiators include azo initiators, peroxide initiators, persulfate initiators, and redox initiators. These may be used individually or in combination of two or more.

[0044] Commercially available azo initiators can be used, such as VA-044, VA-46B, V-50, VA-057, VA-061, VA-067, VA-086, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (VAZO 33), 2,2'-azobis(2-amidinopropane) dihydrochloride (VAZO 50), 2,2'-azobis(2,4-dimethylvaleronitrile) (VAZO 52), 2,2'-azobis(isobutyronitrile) (VAZO 64), 2,2'-azobis-2-methylbutyronitrile (VAZO 67), and 1,1-azobis(1-cyclohexanecarbonitride) (VAZO 88) (all from DuPont). Examples include 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(methylisobutyrate) (V-601) (available from Wako Pure Chemical Industries, Ltd., and others), which are available from Chemical Co., Ltd., and note that "VAZO" is a trademark.

[0045] Examples of the aforementioned peroxide initiators include benzoyl peroxide, acetyl peroxide, lauroyl peroxide, decanoyl peroxide, dicetyl peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate (Perkadox 16S) (available from Akzo Nobel, where "Perkadox" is a trademark), di(2-ethylhexyl)peroxydicarbonate, t-butyl peroxypivalate (Lupersol 11) (available from Elf Atochem, where "Lupersol" is a trademark), t-butyl peroxy-2-ethylhexanoate (Trigonox 21-C50) (available from Akzo Nobel, where "Trigonox" is a trademark), and dicumyl peroxide.

[0046] Examples of the persulfate initiators include potassium persulfate, sodium persulfate, and ammonium persulfate.

[0047] Examples of the redox initiators include combinations of the persulfate initiator with reducing agents such as sodium metabisulfite and sodium bisulfite, systems based on organic peroxides and tertiary amines, such as systems based on benzoyl peroxide and dimethylaniline, systems based on organic hydroperoxides and transition metals, and systems based on cumene hydroperoxide and cobalt naphthate.

[0048] There are no particular restrictions on the content of the polymerization initiator in the adhesive-forming composition, and it can be appropriately selected depending on the purpose.

[0049] The solvent is not particularly limited and can be appropriately selected from known solvents, such as water, acetone, methanol, ethanol, isopropyl alcohol, tetrahydrofuran, methyl ethyl ketone, ethyl acetate, butyl acetate, and methylene chloride. These may be used individually or in combination of two or more.

[0050] There are no particular restrictions on the content of the solvent in the adhesive-forming composition, and it can be appropriately selected depending on the purpose.

[0051] The porous material is not particularly limited as long as it is a porous material that can be used as a filler, and can be appropriately selected according to the purpose. By including the porous material, the hardness of the cured product can be improved, and during decomposition, enzymes can act more easily from the porous regions, thereby improving enzymatic decomposition and biodegradability. Examples of the porous material include diatomaceous earth, zeolite, and activated carbon. There are no particular restrictions on the content of the porous material in the adhesive-forming composition, and it can be appropriately selected depending on the purpose.

[0052] The foaming agent is a material that can be included in the adhesive-forming composition and foamed during curing, thereby making the cured product porous. By making the cured product porous with the foaming agent, the enzymatic degradability and biodegradability of the cured product can be improved. Examples of the foaming agents include azodicarbonamide, N,N'-dinitropentamethylenetetramine, 4,4'-oxybisbenzenesulfonyl hydrazide, bicarbonates, and carbonates. There are no particular restrictions on the content of the foaming agent in the adhesive-forming composition, and it can be appropriately selected depending on the purpose.

[0053] The biodegradable resin microparticles are not particularly limited as long as they are microparticles made of a resin that exhibits enzymatic degradability or biodegradability, and can be appropriately selected according to the purpose. By including the enzymatic degradability or biodegradable resin microparticles in the adhesive-forming composition, the cured product can be easily subdivided during decomposition. That is, by including the enzymatic degradability or biodegradable microparticles in the adhesive-forming composition, it becomes a starting point for decomposition, the cured product can be made finer and its surface area increased, and the enzymatic degradability and biodegradability can be improved. Furthermore, by subdividing the mass of the cured product, enzymatic degradability or biodegradability particles (for example, beads used in model guns) can be produced. Examples of materials for the enzymatically degradable or biodegradable resin fine particles include polylactic acid and polycaprolactone. There are no particular restrictions on the volume-average particle size of the enzymatically degradable or biodegradable resin fine particles, and they can be appropriately selected depending on the purpose, but 5 μm to 1 mm is preferred. There are no particular restrictions on the content of the enzymatically degradable or biodegradable resin fine particles in the adhesive-forming composition, and they can be appropriately selected depending on the purpose.

[0054] The aforementioned other polymer components are not particularly limited as long as they do not impair the effects of the present invention and can be copolymerized with the monofunctional (meth)acrylic monomer or the polyfunctional (meth)acrylic monomer, and can be appropriately selected depending on the purpose. Examples include rosin, dammar, modified rosin, rosin or derivatives of modified rosin, polyterpene resins, terpene modified products, aliphatic hydrocarbon resins, cyclopentadiene resins, aromatic petroleum resins, phenolic resins, alkylphenol-acetylene resins, styrene resins, coumarone indene resins, xylene resins, vinyltoluene-α-methylstyrene copolymers, and hydrogenated styrene resins. In addition, non-functional compounds other than non-functional compounds having a polylactic acid structure may also be included. These may be used individually or in combination of two or more. There are no particular restrictions on the content of the other monomer components in the adhesive-forming composition, and they can be appropriately selected depending on the purpose.

[0055] The viscosity (cP) of the adhesive-forming composition is not particularly limited and can be appropriately selected depending on the purpose, but at 25°C, it is preferably 3,000 mPa·s to 30,000 mPa·s, and more preferably 10,000 mPa·s to 20,000 mPa·s.

[0056] The glass transition temperature (Tg, °C) of the adhesive-forming composition is preferably room temperature (20 ± 15 °C) or lower, more preferably -5 °C or lower, and particularly preferably -10 °C or lower. When the glass transition temperature (Tg, °C) is -10 °C or lower, the cured product can have sufficient adhesiveness. The glass transition temperature (Tg, °C) of the adhesive-forming composition can be measured using a dynamic mechanical analysis (DMA, product name: RSA-3, manufactured by TA Instruments). Specifically, the temperature at the point of maximum tanδ (loss modulus / storage modulus) obtained under measurement conditions of sample size: width 5 mm × length 20 mm, frequency: 1 MHz is defined as the glass transition temperature (Tg, °C).

[0057] The aforementioned adhesive-forming composition is liquid at room temperature and pressure, is used in the manufacture of adhesive compositions, and can be cured by heat, light, etc. The aforementioned adhesive-forming composition can impart excellent enzymatic degradability, biodegradability, and tackiness to the adhesive composition obtained using it, and can form adhesive compositions simply and inexpensively, making it suitable for use in the manufacture of adhesive compositions.

[0058] (Method for producing adhesive-forming compositions) The present invention provides a method for producing an adhesive-forming composition, comprising a step of reacting a diol having a polylactic acid structure with (meth)acrylic acid chloride and saturated fatty acid chloride (hereinafter sometimes referred to as the "reaction step"), and further, if necessary, other steps. The method for producing adhesive-forming compositions has the advantage of being simple and inexpensive to produce.

[0059] <Reaction Process> The aforementioned reaction step involves reacting a diol having a polylactic acid structure with (meth)acrylic acid chloride and saturated fatty acid chloride.

[0060] <<Diol with a polylactic acid structure>> The diol having the polylactic acid structure may be synthesized as appropriate, or a commercially available product may be used. Examples of commercially available diols having the polylactic acid structure include PLA2205 and PLA2105 (both manufactured by Shenzhen ESUN Industrial Co., Ltd.). These may be used individually or in combination of two or more types.

[0061] The molecular weight of the diol having the polylactic acid structure, based on its hydroxyl value, is not particularly limited and can be appropriately selected depending on the purpose. A molecular weight of 2,000 or more is preferred, and 2,000 to 2,500 is more preferred.

[0062] <<(meth)acrylate chloride>> The (meth)acrylate chloride may be synthesized as appropriate, or a commercially available product may be used.

[0063] <<Saturated fatty acid chloride>> The saturated fatty acid chlorides mentioned above are not particularly limited and can be appropriately selected depending on the purpose. Examples include formic acid chloride, acetate chloride, propionic acid chloride, butanoic acid chloride, butyric acid chloride, valeric acid chloride, isovaleric acid chloride, hexanoic acid chloride, pivalic acid chloride, caproic acid chloride, enanthic acid chloride, caprylic acid chloride, pelargonic acid chloride, capric acid chloride, undecylate acid chloride, lauric acid chloride, tridecyl acid chloride, myristic acid chloride, pentadecyl acid chloride, palmitic acid chloride, margaric acid chloride, stearate chloride, nonadecyl acid chloride, and arachidic acid chloride. These saturated fatty acid chlorides may be used individually or in combination of two or more. Among these, propionic acid chloride is preferred.

[0064] The saturated fatty acid chloride may be synthesized as appropriate, or a commercially available product may be used.

[0065] There are no particular restrictions on the reaction conditions (reaction temperature, reaction time, reaction solvent, etc.) in the reaction step, and they can be appropriately selected from known methods depending on the purpose. Examples of the reaction temperature include -10°C to 15°C. Examples of the reaction time include 3 to 10 hours. Examples of the reaction solvent include tetrahydrofuran, acetone, methylene chloride, and dimethylformamide.

[0066] The above reaction step yields a mixture of a monofunctional (meth)acrylic monomer having a polylactic acid structure, a polyfunctional (meth)acrylic monomer having a polylactic acid structure, and an unfunctional compound having a polylactic acid structure. The monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the nonfunctional compound are as described in the section above (Composition for forming adhesive).

[0067] In the reaction step described above, when propionic acid chloride is used as the saturated fatty acid chloride, since acrylic acid chloride and propionic acid chloride have the same reactivity, the molar ratio of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the unfunctional compound as reaction products can be simulated by calculation. As shown in Figure 1, for example, when 0 mol% (molar ratio = 0) of propionic acid chloride is used for 100 mol% (molar ratio = 1) of acrylic acid chloride, the reaction product will be 100 mol% (molar ratio = 1) of the polyfunctional (meth)acrylic monomer. Also, when 0 mol% (molar ratio = 0) of acrylic acid chloride is used for 100 mol% (molar ratio = 1) of propionic acid chloride, the reaction product will be 100 mol% (molar ratio = 1) of the unfunctional compound. Furthermore, when 50 mol% acrylate chloride and 50 mol% propionate chloride are used, the molar ratio of monofunctional (meth)acrylic monomer: polyfunctional (meth)acrylic monomer: unfunctional compound is 1:2:1.

[0068] The fact that the reaction step yielded a mixture of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the unfunctional compound can be confirmed by analysis using a liquid chromatography-mass spectrometer (LC-MS) (see, for example, Japanese Patent Application Publication No. 2008-120980) or a Fourier transform infrared spectrophotometer (FT-IR). Regarding FT-IR analysis, specifically, when the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the unfunctional compound are synthesized from the polylactic acid structure diol, which is the reaction material, FT-IR analysis at 3,200 cm³ is performed. -1 ~3,700cm -1The peak of the hydroxyl group (OH) (the peak of the hydroxyl group derived from the diol having the polylactic acid structure) disappears, and a peak of a double bond in the vicinity of 1,625 cm -1 can be confirmed. (The peak of the double bond derived from the acrylic group in the monofunctional (meth)acrylic monomer and the polyfunctional (meth)acrylic monomer).) Since the mixture of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the non-functional compound does not have the hydroxyl group, it has excellent stability against humidity.

[0069] <Other steps> The other steps are not particularly limited and can be appropriately selected according to the purpose. For example, a solvent removal step, a purification step, etc. can be mentioned.

[0070] <<Solvent removal step>> The solvent removal step is a step of removing the reaction solvent after the reaction step. The method for removing the reaction solvent is not particularly limited and can be appropriately selected according to the purpose. For example, a method of removing using an evaporator can be mentioned.

[0071] <<Purification step>> The purification step is a step of removing impurities from the mixture obtained in the reaction step. The method for removing the impurities is not particularly limited and can be appropriately selected according to the purpose. For example, a method of suction filtration, a method of obtaining a precipitate by decanting the supernatant after standing for a long time, etc. can be mentioned.

[0072] By the above method, the composition for forming an adhesive can be obtained. The method for producing the composition for forming an adhesive has the advantage that the composition for forming an adhesive can be produced simply and at low cost.

[0073] (Adhesive composition) The adhesive composition of the present invention is obtained by curing the composition for forming an adhesive of the present invention. Therefore, the monomer components constituting the copolymer in the adhesive composition consist of a monofunctional (meth)acrylic monomer having a polylactic acid structure, a polyfunctional (meth)acrylic monomer having a polylactic acid structure, and an unfunctional compound having a polylactic acid structure. As a result, the adhesive composition has excellent enzymatic degradability, biodegradability, and tackiness.

[0074] As mentioned above, the enzymatic degradation of the adhesive composition is by exo-type lipase, which decomposes from the polymer ends. That is, the crosslinked bodies in the adhesive composition are not decomposed by the exo-type lipase, and only the so-called sol components are decomposed. Numerous studies have investigated the differing degradation rates between crystalline and amorphous regions within plastics (see, for example, C. DelRe et al., "Near-complete depolymerization of polyesters with nano-dispersed enzymes", Nature, 2021, 592, pp. 558-563). However, polymers with cross-linked structures lack polymer ends and are therefore only degraded by endo-type enzymes. Endo-type enzymes have the disadvantage of being slower than exo-type enzymes. On the other hand, the non-functional compound constituting the adhesive composition not only functions as a tackifier, but can also be degraded by exo-type lipases, which degrade relatively quickly. Thus, the adhesive composition has improved enzymatic and biodegradability compared to conventional adhesive compositions.

[0075] The enzymatic degradation rate of the adhesive composition by exo-lipase is not particularly limited, as long as the mass of the substance changes relative to its mass before the reaction when immersed in a buffer containing a predetermined amount of exo-lipase for 100 hours at 37°C and atmospheric pressure, and the rate of mass change is greater than that of a substance without exo-lipase, however, 15% or more is preferred, 20% or more is more preferred, and 30% or more is particularly preferred.

[0076] There are no particular restrictions on the molar ratio of the monomer components in the adhesive composition, and they can be appropriately selected depending on the purpose. However, a ratio of monofunctional (meth)acrylic monomer:polyfunctional (meth)acrylic monomer:unfunctional compound of 0.4:0.3:0.3 to 0.9:0.05:0.05 is preferred, and a ratio of 0.7:0.1:0.2 to 0.5:0.25:0.25 is more preferred. When the molar ratio is within the preferred range, the adhesive composition exhibits good enzymatic degradability, biodegradability, and tackiness. The range in which the adhesive composition can be synthesized by simultaneously reacting acrylic acid chloride and aliphatic chloride, which are the raw materials for its synthesis, is shown in Figure 1. However, the adhesive composition may also be manufactured by blending a separately synthesized monofunctional (meth)acrylic monomer having a polylactic acid structure or a commercially available monofunctional (meth)acrylic monomer having a polylactic acid structure (for example, Poly(L-lactide), acrylate terminated, product number: 775991, number average molecular weight (Mn): 2,500, manufactured by Sigma-Aldrich), thereby improving properties such as enzymatic degradability, biodegradability, and tackiness.

[0077] The storage viscoelasticity (E') of the adhesive composition is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 100,000 Pa or more and 600,000 Pa or less at 25°C, and more preferably 120,000 Pa or more and 290,000 Pa or less. The storage viscoelasticity (E') of the aforementioned adhesive composition can be measured using a dynamic mechanical analysis (DMA, product name: RSA-3, manufactured by TA Instruments).

[0078] The loss viscoelasticity (E'') of the adhesive composition is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 500 Pa or more and 50,000 Pa or less at 25°C, and more preferably 1,000 Pa or more and 10,000 Pa or less. The loss viscoelasticity (E'') of the adhesive composition can be measured using a dynamic mechanical analysis (DMA, product name: RSA-3, manufactured by TA Instruments).

[0079] One method for quantifying the crosslinking density of the adhesive composition is the molecular weight between crosslinking points (Mc). There are no particular restrictions on the molecular weight between crosslinking points (Mc) of the adhesive composition, and it can be selected as appropriate for the purpose, but 5,000 to 30,000 is preferred, and 10,000 to 25,000 is more preferred. If the molecular weight between crosslinking points (Mc) is less than 5,000, the crosslinking density is high, which may result in poor tackiness, and if it exceeds 30,000, it may be too soft, resulting in insufficient adhesive retention.

[0080] The molecular weight (Mc) between crosslinking points is calculated from the rubber equilibrium modulus E' of the adhesive-forming composition (Tg or higher) and its physical density (d) using the following formula 2. When the molecular weight between crosslinking points (Mc) is large, the crosslinking density decreases, and conversely, when the molecular weight between crosslinking points (Mc) is small, the crosslinking density increases.

number

[0081] The acetone-soluble sol fraction of the adhesive composition is not particularly limited and can be molded into any desired shape as appropriate for the purpose, but it is preferably 30% or more, more preferably 40% or more, and particularly preferably 50% or more. The upper limit of the acetone-soluble sol fraction of the adhesive composition is preferably 90% or less, more preferably 80% or less, and particularly preferably 70% or less from the viewpoint of adhesive retention. The lower and upper limits of the acetone-soluble sol fraction of the adhesive composition can be appropriately combined, for example, 30% to 70% is preferred, 40% to 70% is more preferred, and 50% to 70% is particularly preferred. In this specification, "sol fraction" refers to the value obtained by calculating the acetone-soluble component after the adhesive composition is placed in acetone, sealed, and left at room temperature for one week, using the following formula 4. Sol fraction (%) = (Initial mass - Mass after acetone treatment) / Initial mass × 100 ... Equation 4

[0082] The shape of the adhesive composition is not particularly limited and can be molded into any desired shape as appropriate for the purpose, such as a film, sheet, or tape. Hereinafter, an adhesive composition having such a shape may be referred to as a "molded article." The molded article is also within the scope of the present invention.

[0083] The method for producing the adhesive composition is not particularly limited as long as it can cure the adhesive-forming composition, and can be appropriately selected from known methods. For example, one method involves coating the composition with no solvent or containing a solvent, and if a solvent is included, drying it and then polymerizing each monomer component contained in the adhesive-forming composition by curing means such as visible or ultraviolet irradiation, heating, or electron beam irradiation in the presence of a polymerization initiator.

[0084] There are no particular restrictions on the concentration of each monomer component relative to the solvent when coating with the aforementioned solvent, and it can be appropriately selected depending on the coating apparatus.

[0085] There are no particular restrictions on the concentration of the polymerization initiator during polymerization, and it can be appropriately selected according to the purpose. However, when the total amount of the monomer component is 100 parts by mass, the solid content is preferably 0.5 to 10 parts by mass, and more preferably 0.5 to 3 parts by mass.

[0086] There are no particular limitations on the method for curing the adhesive-forming composition, and it can be appropriately selected depending on the type of polymerization initiator, for example, photopolymerization, thermal polymerization, etc. The polymerization initiator is as described in the section "Other Components" of the above-mentioned (composition for forming adhesive).

[0087] The adhesive composition can be used as is, but if the adhesive composition is formed into a molded body such as a film or sheet, it may have a base material on its surface. In this case, the adhesive composition constitutes an adhesive layer. The molded body may have an adhesive layer on one side by applying the adhesive composition to only one side of the base material, or it may have an adhesive layer on both sides by applying the adhesive composition to both sides of the base material.

[0088] There are no particular restrictions on the aforementioned substrate, and it can be appropriately selected from known materials. Examples include: high-density base paper such as glassine paper, clay-coated paper, kraft paper, Japanese paper, fine paper, and other types of paper; fabrics such as cotton, rayon, chemically synthesized fibers, and nonwoven fabrics; and films such as cellophane, polyethylene, polyester, polyvinyl chloride, acetate, polypropylene, polystyrene, polyvinylidene chloride, polybutadiene, polyacrylonitrile, and polylactic acid.

[0089] Furthermore, from the viewpoint of reducing environmental impact, it is preferable to use biodegradable materials not only for the adhesive composition but also for the substrate. Examples of biodegradable substrates include polysaccharides such as 3-hydroxybutyrate-3-hydroxyvaleric acid copolymer, microfibril cellulose, and pullulan; glycol-aliphatic dicarboxylic acid copolymers such as polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, and polyethylene succinate adipate; polylactic acid; polycaprolactone; poly-γ-methylglutamate; thermoplastic polyvinyl alcohol; starch and modified polyvinyl alcohol; starch and natural resins; chitosan and cellulose. Alternatively, these materials may be combined to form the substrate.

[0090] Furthermore, if necessary, the molded body may have a release layer on the surface of the adhesive layer. There are no particular restrictions on the material of the release layer, and it can be appropriately selected from known materials, such as casein, dextrin, starch, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, and polyvinyl alcohol. These may be used individually or in combination of two or more. Furthermore, the molded body may be laminated with a film-like or sheet-like adhesive composition.

[0091] There are no particular limitations on the method for manufacturing the molded article of the adhesive composition, and it can be manufactured according to conventional methods. For example, one method involves applying the adhesive composition to the release layer surface, drying it to form an adhesive layer, and then bonding the substrate to it. Alternatively, a release layer may be formed by applying water, a solvent, or a solvent-free fluororesin or silicone resin to the substrate of the molded body of the adhesive composition, and curing by heat curing, ionizing radiation irradiation, or the like.

[0092] When applying the adhesive composition to the substrate, a known application apparatus can be used. There are no particular restrictions on the coating apparatus, and it can be appropriately selected from known coating apparatuses. Examples include multi-stage roll coaters, air knife coaters, bar coaters, offset gravure coaters, direct gravure coaters, reverse roll coaters, knife coaters, air knife coaters, bar coaters, slot die coaters, lip coaters, and reverse gravure coaters.

[0093] During the application process, the adhesive composition may be diluted with water, a solvent, or the like to adjust it to a desired viscosity.

[0094] The aforementioned adhesive composition possesses excellent enzymatic degradability, biodegradability, and adhesive properties, and can be manufactured simply and inexpensively. Therefore, it can be suitably used in various industrial fields such as automobiles, packaging materials, building materials, IT, agriculture, medical care, and DIY-related industries, and can also contribute to reducing environmental impact. [Examples]

[0095] The present invention will be specifically described below with reference to synthesis examples, embodiments, and comparative examples, but the present invention is not limited in any way to these synthesis examples and embodiments.

[0096] (Synthesis Example 1: Synthesis of PLA mixture) Into a 200 mL three-neck flask, 20 g (0.01 mol) of a diol of poly-L-lactic acid (PLA) (molecular weight based on hydroxyl value: 2,000, product name: PLA2205, manufactured by Shenzhen ESUN Industrial Co., Ltd) was added. Under the condition of 5 °C, 100 mL of tetrahydrofuran was added and stirred until completely dissolved. Next, 2.4 g of triethylamine was slowly added. A reflux tube and a dropping funnel were attached, and it was stirred in an ice bath. 1.1 g (0.012 mol) of acryloyl chloride and 1.1 g (0.012 mol) of propionyl chloride were diluted with 30 mL of tetrahydrofuran and slowly added through the dropping funnel. After stirring for 2 hours as it was, the temperature was raised to 40 °C and stirred for another 2 hours. After the reaction was completed, tetrahydrofuran was removed with an evaporator, redissolved in acetone and stirred for 2 hours. The precipitated hydrochloride of triethylamine was removed by suction filtration, and then acetone was removed with an evaporator to obtain a pale yellow liquid as a PLA mixture (yield: 82 mass%).

[0097] Regarding the obtained pale yellow liquid, when a Fourier transform infrared spectrophotometer (FT-IR, apparatus name: Nicolet iS2, manufactured by Thermo, the same in the following synthesis examples) was used, the peak of the hydroxyl group (OH) at 3,200 cm -1 ~3,700 cm -1 disappeared, and a peak of a double bond around 1,625 cm -1 was confirmed.

[0098] (Synthesis Example 2: Synthesis of PLA mixture) 20 g (0.01 mol) of poly-L-lactic acid diol (molecular weight based on hydroxyl value: 2,000, product name: PLA2205, manufactured by Shenzhen ESUN Industrial Co., Ltd.) was placed in a 200 mL three-necked flask, and 100 mL of tetrahydrofuran was added and stirred until completely dissolved. Next, 2.4 g of triethylamine was slowly added. A reflux condenser and dropping funnel were attached, and the mixture was stirred in an ice bath. 1.54 g (0.017 mol) of acrylate chloride and 0.66 g (0.007 mol) of propionic acid chloride were diluted in 30 mL of tetrahydrofuran and slowly added using a dropping funnel. The mixture was stirred for 2 hours, then the temperature was raised to 40°C and stirred for another 2 hours. After the reaction was complete, the tetrahydrofuran was removed using an evaporator, redissolved in acetone, and stirred for 2 hours. After removing the precipitated triethylamine hydrochloride by suction filtration, acetone was removed using an evaporator to obtain a pale yellow liquid as a PLA mixture (yield: 82% by mass).

[0099] The resulting pale yellow liquid was subjected to FT-IR analysis using the same method as in Synthesis Example 1, and a reading of 3,200 cm³ was obtained. -1 ~3,700cm -1 The hydroxyl group peak disappears at 1,625 cm⁻¹. -1 A peak of a double bond was observed in the vicinity.

[0100] (Synthesis Example 3: Synthesis of PLA2-functionalized acrylate) 20 g (0.01 mol) of poly-L-lactic acid diol (molecular weight based on hydroxyl value: 2,000, product name: PLA2205, manufactured by Shenzhen ESUN Industrial Co., Ltd.) was placed in a 200 mL three-necked flask, and 100 mL of tetrahydrofuran was added and stirred until completely dissolved. Next, 2.4 g of triethylamine was slowly added. A reflux condenser and dropping funnel were attached, and the mixture was stirred in an ice bath. 2.2 g (0.024 mol) of acrylate chloride was diluted in 30 mL of tetrahydrofuran and slowly added using the dropping funnel. The mixture was stirred for 2 hours, then the temperature was raised to 40°C and stirred for another 2 hours. After the reaction was complete, the tetrahydrofuran was removed using an evaporator, redissolved in acetone, and stirred for 2 hours. After removing the precipitated triethylamine hydrochloride by suction filtration, acetone was removed using an evaporator to obtain a pale yellow liquid as PLA2-functionalized acrylate (yield: 80% by mass).

[0101] The resulting pale yellow liquid was subjected to FT-IR analysis using the same method as in Synthesis Example 1, and a reading of 3,200 cm³ was obtained. -1 ~3,700cm -1 The hydroxyl group peak disappears at 1,625 cm⁻¹. -1 A peak of a double bond was observed in the vicinity.

[0102] (Synthesis Example 4: Synthesis of PCL2-functionalized acrylates) 20 g (0.01 mol) of polycaprolactone diol (molecular weight based on hydroxyl value: 2,000, product name: Praxel 230, Daicel Corporation) was placed in a 200 mL three-necked flask, and 100 mL of tetrahydrofuran was added and stirred until completely dissolved. Next, 4.8 g of triethylamine was slowly added. A reflux condenser and dropping funnel were attached, and the mixture was stirred in an ice bath. 2.2 g (0.024 mol) of acrylate chloride was diluted in 30 mL of tetrahydrofuran and slowly added using the dropping funnel. The mixture was stirred for 2 hours, then the temperature was raised to 40°C and stirred for another 2 hours. After the reaction was complete, the tetrahydrofuran was removed using an evaporator, redissolved in acetone, and stirred for 2 hours. The precipitated triethylamine hydrochloride was removed by suction filtration, and then the acetone was removed using an evaporator to obtain a pale yellow liquid as PCL2 functional acrylate (yield: 92% by mass).

[0103] The resulting pale yellow liquid was subjected to FT-IR analysis using the same method as in Synthesis Example 1, and a reading of 3,200 cm³ was obtained. -1 ~3,700cm -1 The hydroxyl group peak disappears at 1,625 cm⁻¹. -1 A peak of a double bond was observed in the vicinity.

[0104] (Example 1) To 100 parts by mass of the PLA mixture obtained in Synthesis Example 1, 1 part by mass of a photopolymerization initiator (product name: Omnirad 1173, manufactured by IGM Resins BV) was added. The mixture was sandwiched between two transparent polyethylene (PET) films and coated, and then irradiated with a UV conveyor (1 J / cm²). 2 ) and a cured film was obtained.

[0105] (Comparative Example 1) In Example 1, a cured film was obtained in the same manner as in Example 1, except that the PLA mixture obtained in Synthesis Example 1 was replaced with the PLA mixture obtained in Synthesis Example 2.

[0106] (Comparative Example 2) In Example 1, a cured film was obtained in the same manner as in Example 1, except that the PLA mixture obtained in Synthesis Example 1 was replaced with the PLA2-functionalized acrylate obtained in Synthesis Example 3.

[0107] (Comparative Example 3) In Example 1, a cured film was obtained in the same manner as in Example 1, except that the PLA mixture obtained in Synthesis Example 1 was replaced with the PCL2 functional acrylate obtained in Synthesis Example 4.

[0108] (Test Example 1: Evaluation of Adhesion) Test films (width 10±0.5 mm, length approximately 150 mm) were prepared from the cured films obtained in Example 1 and Comparative Examples 1-3. The PET film on one side was peeled off, and the exposed side of each test film was attached to a stainless steel plate (SUS304, thickness 1 mm) as the adherend under conditions of a temperature of 23±1°C and a humidity of 50±5%. The surface of the stainless steel plate was pre-roughened with sandpaper (#400) to prevent the stainless steel plate from peeling off the cured film (test film). The transparent PET film was peeled off from the other side of the test film (the side opposite to the side adhered to the stainless steel plate), and a polylactic acid film (width 10 mm, length 150 mm) was attached in its place by pressing a 2 kg load pressure roller back and forth twice. After pressing, the samples were left for 20 minutes. Using a tensile testing machine (Autograph; AGX-50N, manufactured by Shimadzu Corporation), the peel force (mN / 10mm) between the polylactic acid film and the test film was measured when the polylactic acid film was pulled at a 180-degree angle to the test film at a tensile speed of 300 mm / min. The measurement results were taken as the average of three measurements. A higher peel strength value is preferable. The results are shown in Table 1 below. Note that Comparative Examples 1-3 lacked adhesion and could not be bonded.

[0109] (Test Example 2: Method for Measuring Sol Fraction) Test films (1 cm × 1 cm) were prepared from the cured films obtained in Example 1 and Comparative Examples 1-3, and the mass of each test film (hereinafter sometimes referred to as "initial mass") was measured. Each test film and 20 mL of acetone were placed in a glass container, sealed, and left at room temperature for one week. After that, the container was opened, the film portion inside the glass container was removed by filtration, dried, and its mass (hereinafter sometimes referred to as "mass after acetone treatment") was measured. The sol fraction (percentage of acetone-soluble components) (%) was calculated using formula 4 below. The results are shown in Table 1 below. Sol fraction (%) = (Initial mass - Mass after acetone treatment) / Initial mass × 100 ... Equation 4

[0110] (Test Example 3: Evaluation of Enzyme Degradability) Test films (1 cm × 1 cm) were prepared from the cured films obtained in Example 1 and Comparative Examples 1 to 3, and the mass of each test film (hereinafter sometimes referred to as "initial mass") was measured. First, 3.8944 g of sodium dihydrogen phosphate dodecahydrate (NaH2PO4·12H2O = 358.14) was weighed and dissolved in 500 mL of pure water. The solution was then subjected to sonication for more than 10 minutes to further dissolve the chemical, and solution 1 was prepared. Next, 8.9535 g of disodium monohydrogen phosphate dihydrate (Na2HPO4·2H2O = 156.01) was weighed and dissolved in 500 mL of pure water. The solution was then subjected to sonication for more than 10 minutes to further dissolve the chemical, and solution 2 was prepared. Solution 1 and solution 2 were mixed to prepare a phosphate buffer solution. Next, exo-type lipase (product name: Lipase PS, manufactured by Amano Enzyme Co., Ltd.) or endo-type lipase (product name: Lipase B, manufactured by Sigma-Aldrich) was prepared using a phosphate buffer solution at a concentration of 10 U per 1 mg of polymer in each test film. Each test film was placed in a glass container, along with 20 mL each of phosphate buffer containing the exo-type lipase, phosphate buffer containing the endo-type lipase, or phosphate buffer alone (without lipase) as a control. The containers were sealed and left at 37°C for 100 hours. After opening, the containers were opened, the film was removed from the glass containers by filtration, dried, and its mass (hereinafter sometimes referred to as "mass after enzyme treatment") was measured. The mass reduction rate (%) was calculated using formula 5 below. The results are shown in Table 1 below. Mass reduction rate (%) = (initial mass - mass after enzyme treatment) / initial mass x 100...Equation 5

[0111] (Test Example 4: Evaluation of Glass Transition Temperature) The glass transition temperature (Tg) of the PLA mixture obtained in Synthesis Example 1, the PLA mixture obtained in Synthesis Example 2, the PLA2-functionalized acrylate obtained in Synthesis Example 3, or the PCL2-functionalized acrylate obtained in Synthesis Example 4 was determined using a Dynamic Mechanical Analysis (DMA, product name: RSA-3, manufactured by TA Instruments Inc.) under the following measurement conditions: sample size: width 5 mm x length 20 mm, frequency: 1 MHz. The temperature at the point of maximum tanδ (loss modulus / storage modulus) was defined as the glass transition temperature (Tg, °C).

[0112] (Test Example 5: Evaluation of molecular weight between crosslinking points) The cured films obtained in Example 1 and Comparative Examples 1-3 were measured using a dynamic mechanical analysis (DMA, product name: RSA-3, manufactured by TA Instruments Inc.), and the inter-crosslinking molecular weight (Mc) was calculated using the following formula 2.

number

[0113] [Table 1]

[0114] A comparison of Example 1 with Comparative Examples 1 and 2 suggested that a lower crosslink density, i.e., a larger molecular weight between crosslinking points, resulted in better adhesion. Furthermore, a comparison of Example 1 with Comparative Example 3 showed that the polycaprolactone skeleton did not exhibit adhesion. Additionally, in Example 1 and Comparative Examples 1-3, the mass reduction rates by exo-type lipase (Lipase PS) and endo-type lipase (Lipase B) were greater than those without enzymes, suggesting that the polyester structure is degraded by lipase. Lipase B is exo-type and degrades the crosslink structure itself, thus degrading even high-crosslink density structures like Comparative Example 2. Degradation did not change even with a lower crosslink density and higher sol component content. Conversely, the degradation of exo-type lipase (Lipase PS) increased as the sol component content increased. Therefore, Example 1 suggests that both adhesion and enzymatic degradability are achieved. [Industrial applicability]

[0115] The adhesive-forming composition of the present invention is used in the manufacture of adhesive compositions, can be cured by heat, light, etc., and can impart excellent enzymatic degradability, biodegradability, and tackiness to adhesive compositions manufactured using this adhesive-forming composition. Because it allows for the simple and inexpensive formation of adhesive compositions, it is suitably used in the manufacture of adhesive compositions. Furthermore, the adhesive composition possesses excellent enzymatic degradability, biodegradability, and adhesive properties, and can be manufactured simply and inexpensively. Therefore, it can be suitably used in various industrial fields such as automobiles, packaging materials, building materials, IT, agriculture, medical, and DIY-related industries, and can also contribute to reducing environmental impact.

Claims

1. The reaction step includes reacting a diol having a polylactic acid structure with (meth)acrylic acid chloride and saturated fatty acid chloride to obtain a composition for forming adhesives. A method for producing an adhesive-forming composition, characterized in that, in the reaction step, the molar ratio of the (meth)acrylic acid chloride and the saturated fatty acid chloride is 0.5:0.5 for the (meth)acrylic acid chloride and the saturated fatty acid chloride.

2. The method for producing the adhesive-forming composition according to claim 1, wherein the adhesive-forming composition contains a monofunctional (meth)acrylic monomer having a polylactic acid structure, a polyfunctional (meth)acrylic monomer having a polylactic acid structure, and an unfunctional compound having a polylactic acid structure.

3. A method for producing an adhesive-forming composition according to claim 2, wherein the molar ratio of the monofunctional (meth)acrylic monomer, the polyfunctional (meth)acrylic monomer, and the unfunctional compound is 1:2:

1.

4. A method for producing an adhesive-forming composition according to any one of claims 1 to 3, wherein the molecular weight of the diol having the polylactic acid structure, based on its hydroxyl value, is 1,000 or more.

5. A method for producing an adhesive composition, comprising curing an adhesive-forming composition produced by the method for producing an adhesive-forming composition described in any one of claims 1 to 4.

6. A method for producing the adhesive composition according to claim 5, wherein the inter-crosslinking molecular weight of the adhesive composition is 5,000 to 30,000.

7. A method for producing the adhesive composition according to claim 5 or 6, wherein the acetone-soluble sol fraction of the adhesive composition is 30% or more.

8. A method for producing the adhesive composition according to any one of claims 5 to 7, wherein the adhesive composition is decomposed by an exo-type lipase.

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