WO2022210405A1

WO2022210405A1 - Adhesive and adhesive sheet

Info

Publication number: WO2022210405A1
Application number: PCT/JP2022/014593
Authority: WO
Inventors: 恵子味野; 紗英橋本; 孝至森岡
Original assignee: リンテック株式会社
Priority date: 2021-03-30
Filing date: 2022-03-25
Publication date: 2022-10-06
Also published as: TW202300620A; TW202302800A; WO2022210406A1

Abstract

Provided is an adhesive containing an aliphatic polycarbonate resin that has an ether structure in the main chain thereof. The adhesive is biodegradable and can be used as a raw material for producing carbon dioxide. The aliphatic polycarbonate resin preferably contains 0.1-99 mass% of units of the ether structure. The aliphatic polycarbonate resin preferably has a structure represented by general formula (I). (In the formula, R is a hydrogen atom or a hydrocarbon group, n and m are each an integer of 1 or more, and r is an integer of 2 or more.)

Description

Adhesives and adhesive sheets

The present invention relates to a degradable pressure-sensitive adhesive and a pressure-sensitive adhesive sheet having a degradable pressure-sensitive adhesive layer.

Adhesives have traditionally been used for a variety of purposes, but they can have a negative impact on the environment when the parts that use them are discarded. In addition, the spread of plastic products poses a problem of adverse effects on the marine environment. For example, there are persistent organic pollutants (POP) caused by surface treatment components for improving the durability of plastics, and impacts on marine organisms caused by microplastics. Therefore, in recent years, from the viewpoint of environmental protection, adhesives are sometimes required to be degradable (degradable by microorganisms and sunlight in natural environments such as in the soil or in the sea, not by combustion). .

For example, Patent Document 1 discloses a pressure-sensitive adhesive containing polylactic acid, a glass transition temperature lowering agent having a biodegradable material and/or a biological material, and a tackifier.

Japanese Patent Application Laid-Open No. 2006-70091

On the other hand, in recent years, along with the growing demand for building a recycling-based society, gases such as carbon dioxide, methane, and carbon monoxide are attracting attention as sustainable carbon raw materials. For example, it has been reported that an aliphatic polycarbonate having only aliphatic (non-aromatic) groups in the main chain can be produced by copolymerizing carbon dioxide and epoxide, and chemical products using gases such as carbon dioxide as raw materials and its manufacturing technology.

　Since carbon dioxide is said to cause global warming, the effective use of carbon dioxide emitted from factories in the process of manufacturing various materials is useful for environmental protection. It is even more desirable if carbon dioxide can be effectively used in the production of pressure-sensitive adhesives.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that are degradable and can use carbon dioxide as a manufacturing raw material.

In order to achieve the above object, first, the present invention provides a pressure-sensitive adhesive containing an aliphatic polycarbonate resin having an ether structure in its main chain (Invention 1).

The aliphatic polycarbonate resin in the above invention (invention 1) has an ether structure in its main chain, and thus has the property of being easily decomposed by light (particularly sunlight), heat, oxygen, moisture, and the like. Therefore, if a member using the pressure-sensitive adhesive according to the invention (Invention 1) is placed in a natural environment, the pressure-sensitive adhesive decomposes due to the factors described above. In addition, the aliphatic polycarbonate resin having an ether structure in its main chain can be produced using carbon dioxide as a raw material. Therefore, the pressure-sensitive adhesive according to the invention (invention 1) can make effective use of carbon dioxide in its production.

In the above invention (Invention 1), the aliphatic polycarbonate resin preferably contains 0.1% by mass or more and 99% by mass or less of the unit of the ether structure (Invention 2).

In the above inventions (inventions 1 and 2), the aliphatic polycarbonate resin preferably has a structure represented by the following general formula (I) (invention 3).

(Wherein, R is a hydrogen atom or a hydrocarbon group, n and m are each an integer of 1 or more, and r is an integer of 2 or more.)

In the above inventions (Inventions 1 to 3), the aliphatic polycarbonate resin preferably has a number average molecular weight of 10,000 or more and 2,000,000 or less (Invention 4).

In the above inventions (Inventions 1 to 4), the glass transition temperature (Tg) of the aliphatic polycarbonate resin is preferably -60°C or higher and 30°C or lower (Invention 5).

Secondly, the present invention provides a pressure-sensitive adhesive sheet (Invention 6) having a pressure-sensitive adhesive layer composed of the above-mentioned pressure-sensitive adhesives (Inventions 1 to 5).

According to the present invention, it is possible to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that are degradable by light or the like and that can use carbon dioxide as a manufacturing raw material.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the adhesive sheet which concerns on the 1st Embodiment of this invention. FIG. 4 is a cross-sectional view of a pressure-sensitive adhesive sheet according to a second embodiment of the present invention; 1 is a chart showing the results of ¹ H-NMR measurement of the polymer produced in Example 1. FIG. 4 is a chart showing the results of ¹ H-NMR measurement of the polymer produced in Example 2. FIG. 4 is a chart showing the results of ¹ H-NMR measurement of the polymer produced in Comparative Example 1. FIG.

Embodiments of the present invention will be described below.
[Adhesive]
A pressure-sensitive adhesive according to one embodiment of the present invention is a pressure-sensitive adhesive containing an aliphatic polycarbonate resin having an ether structure in its main chain (hereinafter sometimes referred to as "aliphatic polycarbonate resin A"). The pressure-sensitive adhesive according to the present embodiment may consist of only the aliphatic polycarbonate resin A, or may contain the aliphatic polycarbonate resin A and components other than the aliphatic polycarbonate resin A.

The aliphatic polycarbonate resin A has an ether structure in its main chain. Ether bonds are easily cleaved by light (particularly sunlight), heat, oxygen, moisture, and the like. Therefore, the aliphatic polycarbonate resin A, which has an ether structure in its main chain, has the property of being easily decomposed by light (especially sunlight), heat, oxygen, moisture, etc. in the portion of the ether structure. Therefore, if a member using the adhesive according to the present embodiment is placed in a natural environment, the adhesive decomposes due to the factors described above.

In addition, as will be described later, the aliphatic polycarbonate resin A can be produced using carbon dioxide as a production raw material. Therefore, the pressure-sensitive adhesive according to this embodiment can effectively utilize carbon dioxide in its production.

The aliphatic polycarbonate resin A preferably contains 0.1% by mass or more of an ether structure unit, more preferably 1% by mass or more, particularly preferably 10% by mass or more, and further contains 20% by mass or more. is preferred. Thereby, the aliphatic polycarbonate resin A exhibits good decomposability. In addition, the aliphatic polycarbonate resin A preferably contains 99% by mass or less of an ether structure unit, more preferably 80% by mass or less, particularly preferably 70% by mass or less, and further 60% by mass or less. is preferred. Thereby, the aliphatic polycarbonate resin A exhibits a predetermined adhesiveness. Incidentally, when the content ratio of the ether structural unit in the aliphatic polycarbonate resin A increases, the glass transition temperature (Tg) of the aliphatic polycarbonate resin A tends to decrease and the tackiness of the adhesive tends to increase.

Aliphatic polycarbonate resin A preferably has a structure represented by the following general formula (I).

Since the aliphatic polycarbonate resin A has the structure represented by the above general formula (I), the ether structure portion has the property of being more easily decomposed by light (especially sunlight), heat, oxygen, moisture, etc. Demonstrate.

As described above, R in general formula (I) is a hydrogen atom or a hydrocarbon group, more preferably a hydrocarbon group. Examples of hydrocarbon groups include alkyl groups, allyl groups, vinyl groups, alkynyl groups, and phenyl groups, among which alkyl groups are preferred. As the alkyl group, those having 1 to 12 carbon atoms are preferable, those having 1 to 10 carbon atoms are more preferable, and those having 1 to 8 carbon atoms are particularly preferable. The aliphatic polycarbonate resin A may contain two or more types of R (for example, R ¹ to R ⁴ in general formula (II) described later). When the number of carbon atoms in R increases, the glass transition temperature (Tg) of the aliphatic polycarbonate resin A tends to decrease and the tackiness of the adhesive tends to increase.

The alkyl group may be linear, branched, or have a cyclic structure, but is preferably linear. That is, preferred alkyl groups include methyl, ethyl, propyl, n-butyl, pentyl, hexyl, and octyl groups.

n in general formula (I) is preferably 1 to 99, more preferably 30 to 99, particularly preferably 40 to 99, further preferably 50 to 99. Further, m in the general formula (I) is preferably 1 to 99, more preferably 1 to 70, particularly preferably 1 to 60, and further preferably 1 to 50. preferable. Thereby, the aliphatic polycarbonate resin A exhibits good degradability and adhesiveness. It should be noted that the ratio of n and m is preferably within the range in which the content of units of the ether structure is within the range described above.

r in general formula (I) is preferably from 2 to 100, more preferably from 2 to 50, and particularly preferably from 2 to 10. Thereby, the adhesiveness of the aliphatic polycarbonate resin A becomes better, and the cohesive force becomes better.

The number average molecular weight of the aliphatic polycarbonate resin A is preferably 10,000 or more, more preferably 40,000 or more, and particularly preferably 60,000 or more. Further, the number average molecular weight of the aliphatic polycarbonate resin A is preferably 2,000,000 or less, more preferably 1,000,000 or less, particularly preferably 500,000 or less, further preferably 100,000 or less. is preferred. When the number-average molecular weight of the aliphatic polycarbonate resin A is within the above range, the adhesion becomes better, and the cohesive force also becomes better. In addition, the number average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

The glass transition temperature (Tg) of the aliphatic polycarbonate resin A is preferably −60° C. or higher, more preferably −55° C. or higher, particularly preferably −45° C. or higher, and further −40 °C or higher. Further, the glass transition temperature (Tg) of the aliphatic polycarbonate resin A is preferably 30°C or less, more preferably 20°C or less, particularly preferably 0°C or less, and further -20°C. The following are preferred. When the glass transition temperature (Tg) of the aliphatic polycarbonate resin A is within the above range, the adhesion becomes better, and the cohesive force also becomes better.

Aliphatic polycarbonate resin A is prepared, for example, by adding carbon dioxide (CO ₂ ) and a monomer that polymerizes so that the main chain is composed of aliphatic groups, in the presence of a polymerization catalyst, and optionally adjusting the water content. It can be produced by a production method comprising a step of controlling the amount to be controlled to a fixed amount or less and performing a polymerization reaction. For example, the aliphatic polycarbonate resin A contains carbon dioxide and a compound represented by the following general formula (II) (ethylene oxide (epoxide)) or a derivative thereof (hereinafter sometimes abbreviated as "compound (II)"). , In the presence of a polymerization catalyst, if necessary, the water content is controlled to a predetermined amount or less, and can be produced by a production method having a polymerization reaction step (for example, "International Publication No. 2011/142259" reference). Here, an ether structure can be introduced into the main chain of the aliphatic polycarbonate resin A by selecting an appropriate polymerization catalyst. Since the aliphatic polycarbonate resin A can use carbon dioxide as a production raw material, effective utilization of carbon dioxide can be achieved. As used herein, the term "derivative" means a compound in which one or more hydrogen atoms of the original compound are substituted with a group (substituent) other than a hydrogen atom, and as the "substituent" includes the same substituents as the substituents that R ¹ to R ⁴ described above may have.

(wherein R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom or an optionally substituted alkyl group, alkoxy group, alkenyl group, alkylcarbonyloxyalkyl group, alkenylcarbonyloxy an alkyl group or an aryl group, and when any two or more of R ¹ , R ² , R ³ and R ⁴ are optionally substituted alkyl groups, these two or more alkyl groups are bonded to each other may form a ring.)

Preferred compounds (II) include, for example, ethylene oxide, propylene oxide, 1-butene oxide, 2-butene oxide, isobutylene oxide, 1-pentene oxide, 2-pentene oxide, 1-hexene oxide, 1-octene oxide, 1-decene oxide, cyclopentene oxide, cyclohexene oxide, styrene oxide, vinylcyclohexene oxide, 3-phenylpropylene oxide, 3,3,3-trifluoropropylene oxide, 3-naphthylpropylene oxide, 3-phenoxypropylene oxide, 3-naphtho oxypropylene oxide, butadiene monoxide, 3-vinyloxypropylene oxide, 3-trimethylsilyloxypropylene oxide, 3-methoxypropylene oxide (methyl glycidyl ether), 3-ethoxypropylene oxide (ethyl glycidyl ether), 3-n-propoxypropylene oxide (n-propyl glycidyl ether), 3-n-butoxypropylene oxide (n-butyl glycidyl ether), glycidyl acrylate, glycidyl methacrylate and the like.

Among these, the compound (II) is more preferably ethylene oxide, an ethylene oxide derivative, propylene oxide or a propylene oxide derivative, more preferably propylene oxide or a propylene oxide derivative, in that it has a high polymerization reactivity with carbon dioxide. .

The compound (II) used in the polymerization reaction step may be of one type or two or more types, and when two or more types are used, the combination and ratio thereof may be appropriately adjusted according to the purpose.

As the compound (II), it is particularly preferable to have a structure represented by the following general formula (III).

(Wherein, R is a hydrogen atom or a hydrocarbon group.)

As described above, R in general formula (III) is a hydrogen atom or a hydrocarbon group, more preferably a hydrocarbon group. R in general formula (III) corresponds to R in general formula (I) described above, and therefore preferred hydrocarbon groups are as described above.

The polymerization catalyst used for producing the aliphatic polycarbonate resin A is not particularly limited as long as it can introduce an ether structure into the main chain of the aliphatic polycarbonate resin A. Specifically, a composite metal cyanide is used. Complex catalysts (Double Metal Cyanide Complex catalysts; referred to as "DMC catalysts") are preferred. As the metal in the DMC catalyst, a combination of cobalt and zinc, a combination of cobalt and nickel, a combination of zinc and nickel, etc. are preferred, and a combination of cobalt and zinc is particularly preferred. As the DMC catalyst, Zn ₃ (Co[CN] ₆ ) ₂ , Co(Ni[CN] ₄ ), Zn(Ni(CN) ₄ ) and the like are preferable, and Zn ₃ (Co[CN] ₆ ) ₂ is particularly preferable.

As described above, the polymerization reaction of the aliphatic polycarbonate resin A is preferably carried out in a pressure vessel. By changing the amount of the polymerization catalyst used in this polymerization reaction, the pressure of carbon dioxide, the polymerization temperature, the polymerization time, etc., the content ratio of the ether structural unit in the aliphatic polycarbonate resin A and the molecular weight of the aliphatic polycarbonate resin A are adjusted. be able to.

The amount of the polymerization catalyst used, for example, in the case of a DMC catalyst, is preferably 1×10 ⁻⁶ to 1×10 ⁻⁴ mol, particularly 1×10 ⁻⁵ to 1×10 mol, per 1 mol of the epoxy monomer. ⁻⁴ mol, more preferably 5×10 ⁻⁵ to 1×10 ⁻⁴ mol. When the amount of the polymerization catalyst used is reduced, the molecular weight of the aliphatic polycarbonate resin A tends to increase.

The pressure of carbon dioxide is preferably 0.1-10 MPa, particularly preferably 0.5-5 MPa, further preferably 1-4 MPa. When the pressure of carbon dioxide is increased, the content ratio of carbonate structural units in the aliphatic polycarbonate resin A tends to increase.

The polymerization temperature is preferably -15 to 95°C, particularly preferably 0 to 75°C, and further preferably 25 to 70°C. When the polymerization temperature is raised, the content ratio of ether structural units can be increased and the polymerization time can be shortened.

The polymerization time is preferably 1 to 48 hours, particularly preferably 2 to 30 hours, further preferably 5 to 24 hours. If the polymerization time is lengthened within this range, the molecular weight of the aliphatic polycarbonate resin A tends to increase.

The adhesive according to the present embodiment preferably contains 30% by mass or more of the aliphatic polycarbonate resin A, more preferably 50% by mass or more, particularly preferably 70% by mass or more, and further 100% by mass. % by mass is preferably contained. The amount of carbon dioxide introduced into the aliphatic polycarbonate resin A is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more.

Components that the pressure-sensitive adhesive according to the present embodiment may contain in addition to the aliphatic polycarbonate resin A include, for example, a cross-linking agent, a tackifier, an antioxidant, an ultraviolet absorber, a dye, a pigment, an anti-deterioration agent, Various additives known in the adhesive field, such as antistatic agents, flame retardants, light stabilizers, softeners, silane coupling agents, and fillers, can be used. Examples of tackifying resins include rosin and its derivatives (hydrogenated rosin, disproportionated rosin, rosin ester, etc.), terpene and its derivatives (α-pinene resin, β-pinene resin, dipentene resin and their water Additives) are preferable from the viewpoint of degradability.

The degradability of the pressure-sensitive adhesive according to the present embodiment can be evaluated, for example, by the reduction rate (%) of the number average molecular weight after irradiation with ultraviolet rays (UV) for a predetermined period of time (e.g., 50 hours, 100 hours, etc.). can. The reduction rate (%) can be calculated as follows.
Reduction rate [%] = {1-(A/B)} x 100
A: Number average molecular weight (Mn) after UV irradiation
B: Number average molecular weight (Mn) before UV irradiation

The reduction rate is preferably 30% or more, more preferably 40% or more, particularly preferably 50% or more, and further preferably 80% or more.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of this embodiment includes at least a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is composed of the pressure-sensitive adhesive according to the embodiment described above. A specific configuration as an example of the pressure-sensitive adhesive sheet according to this embodiment is shown in FIGS. 1 and 2. FIG.

As shown in FIG. 1, the pressure-sensitive adhesive sheet 1A according to the first embodiment includes, in order from the bottom, a release sheet 12, a pressure-sensitive adhesive layer 11 laminated on the release surface of the release sheet 12, and a pressure-sensitive adhesive layer 11. It is composed of a base material 13 that has been applied.

Moreover, as shown in FIG. 2, the pressure-sensitive adhesive sheet 1B according to the second embodiment includes two

release sheets

12a and 12b, and two

release sheets

12a and 12b so that the release surfaces of the two

release sheets

12a and 12b are in contact with each other. and an adhesive layer 11 sandwiched between

release sheets

12a and 12b. In this specification, the release surface of the release sheet refers to the surface of the release sheet that has releasability, and includes both the surface that has been subjected to a release treatment and the surface that exhibits releasability without being subjected to a release treatment. .

1. Each element 1-1. Adhesive Layer The adhesive layer 11 in this embodiment is composed of the adhesive according to the embodiment described above.

From the viewpoint of adhesiveness, the lower limit of the thickness of the adhesive layer 11 (value measured according to JIS K7130) is preferably 1 μm or more, more preferably 5 μm or more, and particularly 10 μm or more. is preferable, and more preferably 20 μm or more.

The upper limit of the thickness of the pressure-sensitive adhesive layer 11 is preferably 80 μm or less, more preferably 50 μm or less, particularly 40 μm or less, from the viewpoints of degradability, coating properties, handling properties, and the like. is preferable, and more preferably 30 μm or less.

1-2. Release Sheets The

release sheets

12, 12a, 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled off when the

adhesive sheets

1A, 1B (adhesive layer 11) are used. One or both of the

release sheets

12, 12a, 12b are not necessarily required in the

adhesive sheets

1A, 1B according to the present embodiment.

Examples of the

release sheets

12, 12a, 12b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, Polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film , plastic films such as fluororesin films, crosslinked films thereof, and the like; woodfree paper, glassine paper, kraft paper, clay-coated paper, and the like paper. Furthermore, a laminate of these may be used.

The release surfaces of the

release sheets

12, 12a, and 12b (especially the surfaces in contact with the adhesive layer 11) are preferably subjected to a release treatment. Examples of release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Of the

release sheets

12a and 12b, one of the release sheets may be a heavy release type release sheet with a large release force, and the other release sheet may be a light release type release sheet with a small release force.

The thickness of the

release sheets

12, 12a, 12b is not particularly limited, but is usually about 20 to 150 μm.

1-3. Base material The base material 13 is not particularly limited, and any material that is used as a base material sheet for ordinary pressure-sensitive adhesive sheets can be used. For example, in addition to desired optical members, woven fabrics or non-woven fabrics using fibers such as polyester, acrylic, rayon, etc.; synthetic paper; papers such as woodfree paper, glassine paper, impregnated paper, coated paper; metals such as aluminum and copper Foil; Foam such as urethane foam and polyethylene foam; Polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene succinate, polybutylene adipate terephthalate (compound), polyurethane film, polyethylene film, polypropylene film, cellulose film such as triacetyl cellulose, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, acrylic resin film, norbornene resin film, cycloolefin plastic films such as resin films; laminates of two or more of these; The plastic film may be uniaxially or biaxially oriented.

The thickness of the base material 13 varies depending on its type, but is usually 10-150 μm, preferably 20-100 μm, and particularly preferably 25-75 μm.

2. Manufacturing Method In order to manufacture the pressure-sensitive adhesive sheet 1A, the release surface of the release sheet 12 is coated with a solution containing the pressure-sensitive adhesive (coating solution), heat-treated to form the pressure-sensitive adhesive layer 11, and then the pressure-sensitive adhesive layer 11 is formed. It is preferable to laminate the substrate 13 on the agent layer 11 .

In order to manufacture the adhesive sheet 1B, a coating solution containing the adhesive is applied to the release surface of one release sheet 12a (or 12b), and heat treatment is performed to form the adhesive layer 11. , the release surface of the other release sheet 12b (or 12a) is preferably superposed on the pressure-sensitive adhesive layer 11 .

Examples of the diluent solvent for diluting the adhesive to form a coating solution include aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; and halogens such as methylene chloride and ethylene chloride. Hydrocarbons, alcohols such as methanol, ethanol, propanol, butanol, 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, cyclohexanone, esters such as ethyl acetate and butyl acetate, ethyl cellosolve, etc. A cellosolve-based solvent, etc., are used.

The concentration/viscosity of the coating solution prepared in this way is not particularly limited as long as it is within a range that allows coating, and can be appropriately selected according to the situation. For example, the adhesive is diluted to a concentration of 10 to 40% by mass. When obtaining the coating solution, the addition of a diluent solvent or the like is not a necessary condition, and the diluent solvent may not be added as long as the adhesive has a viscosity that allows coating. In this case, the adhesive as it is becomes the coating solution.

As a method for applying the coating solution, for example, a bar coating method, a knife coating method, a comma coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

By heat-treating the coating film of the coating solution, the diluted solvent is volatilized and an adhesive layer is formed. The drying conditions are, for example, preferably 30 to 120° C. for 1 to 10 minutes, more preferably 100 to 120° C. for 1 to 5 minutes.

3. Uses of Adhesive Sheets The uses of the

adhesive sheets

1A and 1B according to the present embodiment (including the uses of the adhesive according to the above-described embodiments) are those in fields where degradability is required after use or after disposal. It is not particularly limited. For example, it can be used for labeling on various containers, daily necessities, electric/electronic equipment, various machines, medical instruments, etc., and bonding between members.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is meant to include all design changes and equivalents that fall within the technical scope of the present invention.

For example, the release sheet 12 of the adhesive sheet 1A may be omitted, or either one of the

release sheets

12a and 12b of the adhesive sheet 1B may be omitted.

Although the present invention will be described in more detail with reference to examples and the like, the scope of the present invention is not limited to these examples and the like.

[Example 1]
(1) Synthesis of Polymerization Catalyst 1.33 g of potassium hexacyanocobaltate (III) (K ₃ [Co(CN) ₆ ]; manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 20 mL of deionized water and vigorously stirred at 50°C. of zinc chloride solution (11.42 g of ZnCl ₂ dissolved in a mixed solution of 60 mL of deionized water and 30 mL of t-butyl alcohol) over 45 minutes. The mixture was then vigorously stirred for 60 minutes. The resulting white suspension was centrifuged at 5000 rpm to isolate a white solid. The isolated white solid was resuspended in a solution of t-butyl alcohol and deionized water (t-butyl alcohol:deionized water=5:5 by volume) with vigorous stirring for 30 minutes. Then, while gradually increasing the amount of t-butyl alcohol with respect to water (t-butyl alcohol:deionized water, the volume ratio is changed from 6:4 to 7:3, 8:2, 9:1). , isolation by centrifugation and resuspension were repeated several times. Finally, the white solid was isolated by centrifugation after resuspension in t-butyl alcohol. After that, it was dried under vacuum at 50° C. until it reached a predetermined mass to obtain Zn ₃ (Co[CN] ₆ ) ₂ as a DMC catalyst.

(2) Synthesis of Polymer In a ratio of 1.3×10 ⁴ mol of propylene oxide, which is an epoxy monomer, to 1 mol of the DMC catalyst obtained in (1) above, both components were added into a pressure vessel and an argon atmosphere was added. Stirred down. Subsequently, after purging the inside of the pressure vessel with CO ₂ , CO ₂ was introduced into the pressure vessel by a liquid-sending pump, and the pressure inside the pressure vessel was adjusted to 4 MPa. Then, the mixture was stirred at 60° C. for 18 hours to carry out a polymerization reaction.

After completion of the reaction, chloroform was added to the content in the pressure vessel to obtain a solution, and the solution was added dropwise to methanol containing 1M hydrochloric acid to perform reprecipitation purification. The resulting precipitate was collected with filter paper, dissolved in chloroform again, and impurities were removed with a membrane filter (manufactured by Advantech, pore size: 3.00 μm). Thereafter, the solution was poured into a Teflon (registered trademark) petri dish and dried in a drying oven at 50°C for 20 hours to obtain a polymer. The structure of this polymer (aliphatic polycarbonate resin) was confirmed by ¹ H-NMR (apparatus: manufactured by Bruker, product name “Biospin Avance 500”). The resulting chart is shown in FIG.

Based on the above results, the ratio of carbonate units to ether structural units was estimated from the integral ratio of the corresponding methylene hydrogens. As a result, the ratio (content) of ether structural units in the obtained aliphatic polycarbonate resin was 23.6%. The ratio of ether structural units is calculated from the following formula based on a, b, and c in the chart.
Ether structural unit ratio [%]={c/(a+b+c)}×100

The aliphatic polycarbonate resin obtained above was dissolved in ethyl acetate, and one side of a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., product name “Lumirror PET50T-60”, thickness: 50 μm) as a base material was applied with an applicator. and dried at 100° C. for 1 minute to obtain a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with a thickness of 25 μm.

[Example 2]
A polymer was produced in the same manner as in Example 1, except that the raw material monomer epoxy monomer was changed to 1,2-epoxydecane (1,2-decylene oxide). The structure of this polymer (aliphatic polycarbonate resin) was confirmed by ¹ H-NMR (apparatus: manufactured by Bruker, product name “Biospin Avance 500”). The resulting chart is shown in FIG.

Based on the above results, the ratio of carbonate units to ether structural units was estimated from the integral ratio of methylene hydrogen corresponding to each. As a result, the ratio (content) of ether structural units in the resulting aliphatic polycarbonate resin was 17.5%.

Also, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using the aliphatic polycarbonate resin.

[Comparative Example 1]
(1) Synthesis of polymerization catalyst (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexane cobalt (II) (manufactured by Sigma-Aldrich Co., Ltd., Product name “(R,R)-salcyCoII”) and pentafluorobenzoic acid (manufactured by Tokyo Kasei Kogyo Co., Ltd.) were weighed at a molar ratio of 1:1.1 and placed in a flask, where dehydrated toluene was added. was added. The flask was shielded from light with aluminum foil and reacted at room temperature for 20 hours. After completion of the reaction, the solvent was removed under reduced pressure and washed several times with excess hexane. After that, vacuum drying was performed at room temperature to obtain a cobalt-salen complex.

(2) Synthesis of Polymer Propylene oxide as an epoxy monomer, the cobalt-salen complex obtained in (1) above as a polymerization catalyst, and bis(triphenylphosphoranylidene)ammonium chloride (PPNCl) as a co-catalyst were The ratio of epoxy monomer:polymerization catalyst:cocatalyst=2000:1:1 was weighed and stirred in a pressure vessel. All of these operations were carried out after replacing the inside of the pressure vessel with an argon atmosphere.

Subsequently, after purging the inside of the pressure vessel with CO ₂ , CO ₂ was introduced into the pressure vessel by a liquid-sending pump, and the pressure inside the pressure vessel was adjusted to 1.5 MPa. Then, the mixture was stirred at 23° C. for 5 hours to carry out a polymerization reaction.

After completion of the reaction, chloroform was added to the contents of the pressure vessel to prepare a chloroform solution, which was concentrated using a rotary evaporator. The concentrated solution was added dropwise to stirring methanol containing 1M hydrochloric acid to precipitate the product. The product was then recovered by vacuum filtration using a diaphragm pump. The collected product was dissolved again in chloroform, and impurities were removed with a membrane filter (manufactured by Advantec, pore size: 3.00 μm). Thereafter, the solution was poured into a Teflon (registered trademark) petri dish and dried in a drying oven at 50°C for 20 hours to obtain a polymer. The structure of this polymer (aliphatic polycarbonate resin) was confirmed by ¹ H-NMR (apparatus: manufactured by Bruker, product name “Biospin Avance 500”). The obtained chart is shown in FIG.

Based on the above results, the ratio of carbonate units to ether structural units was estimated from the integral ratio of methylene hydrogen corresponding to each. As a result, the ratio (content) of ether structural units in the obtained aliphatic polycarbonate resin was 0.0%.

[Comparative Example 2]
As an adhesive, an acrylic adhesive (manufactured by Nippon Carbide Industry Co., Ltd., product name "Nisetsu PE121") was subjected to the test described later. Also, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using the acrylic pressure-sensitive adhesive.

[Test Example 1] <Measurement of number average molecular weight (Mn)>
The number average molecular weights (Mn) of the polymers (adhesives) of Examples and Comparative Examples were measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement) and converted to standard polystyrene. Table 1 shows the results.
[Measurement condition]
・ GPC measurement device: HLC-8020 manufactured by Tosoh Corporation
・ GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (x2)
TSK gel G2000HXL
・Measurement solvent: tetrahydrofuran ・Measurement temperature: 40°C

[Test Example 2] <Measurement of glass transition temperature (Tg)>
The glass transition temperature (Tg) of the polymers (adhesives) of Examples and Comparative Examples was measured by a differential scanning calorimeter (manufactured by TA Instruments Japan, product name "DSC Q2000"). The temperature was measured at a cooling rate of 20°C/min. Table 1 shows the results.

[Test Example 3] <Evaluation of degradability>
0.01 g of the polymers (adhesives) of Examples and Comparative Examples were each weighed into vials. This sample was irradiated with ultraviolet rays (UV) for 50 hours and 100 hours using an ultraviolet auto fade meter (manufactured by Suga Test Instruments Co., Ltd., product name "U48 type", light source: ultraviolet carbon arc lamp). Then, the number average molecular weight (Mn) of the polymer (adhesive) after irradiation for each time was measured in the same manner as in Test Example 1. Based on the results, the reduction rate (%) was calculated as follows. Table 1 shows the results.
Reduction rate [%] = {1-(A/B)} x 100
A: Number average molecular weight (Mn) after UV irradiation
B: Number average molecular weight (Mn) before UV irradiation

[Test Example 4] <Calculation of CO ₂ introduction rate>
The CO ₂ introduction rate (% by mass) in the polymers (adhesives) of Examples and Comparative Examples was calculated based on the following formula. It can be said that the larger the value of the CO ₂ introduction rate, the more effectively the carbon dioxide is used. Table 2 shows the results.
CO ₂ introduction rate [mass%] = (CO ₂ amount in polymer [g]/polymer amount [g]) x 100
_CO2 amount in polymer [g] = 44 x (carbonate ratio [%])
Polymer weight [g] = {(unit molecular weight of carbonate portion in polymer) x (carbonate ratio [%])} + {(unit molecular weight of ether portion in polymer) x (ether structural unit ratio [%])}
Carbonate ratio [%] = 100 - ether structural unit ratio [%]

As can be seen from Tables 1 and 2, the adhesives of Examples effectively used carbon dioxide while exhibiting excellent degradability against ultraviolet irradiation.

The pressure-sensitive adhesive and pressure-sensitive adhesive sheet according to the present invention can be suitably used, for example, for labeling or bonding members of articles that require degradability after use or disposal.

DESCRIPTION OF

SYMBOLS

1A, 1B... Adhesive sheet 11...

Adhesive layer

12, 12a, 12b... Release sheet 13... Base material

Claims

A pressure-sensitive adhesive containing an aliphatic polycarbonate resin with an ether structure in its main chain.
The pressure-sensitive adhesive according to claim 1, wherein the aliphatic polycarbonate resin contains 0.1% by mass or more and 99% by mass or less of the unit of the ether structure.
3. The pressure-sensitive adhesive according to claim 1, wherein the aliphatic polycarbonate resin has a structure represented by the following general formula (I).

(Wherein, R is a hydrogen atom or a hydrocarbon group, n and m are each an integer of 1 or more, and r is an integer of 2 or more.)
The adhesive according to any one of claims 1 to 3, wherein the aliphatic polycarbonate resin has a number average molecular weight of 10,000 or more and 2,000,000 or less.
The adhesive according to any one of claims 1 to 4, wherein the aliphatic polycarbonate resin has a glass transition temperature (Tg) of -60°C or higher and 30°C or lower.
A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive according to any one of claims 1 to 5.