Polyurethane resin dispersion, adhesive composition, and adhesive

Abstract

Provided is a polyurethane resin dispersion with which an adhesive having high adhesive force can be formed, and an adhesive that can be easily peeled off after adhesion can be formed.　The present invention relates to a polyurethane resin dispersion obtained by dispersing a polyurethane resin in an aqueous dispersion medium, wherein the polyurethane resin is a reaction product of a polyol compound, a monoalcohol compound, an acrylic compound having a hydroxyl group, and a polyisocyanate compound, the polyol compound is a compound having at least one (meth)acryloyl group, and the monoalcohol compound is a compound having an alkoxy group at the end.

Description

Polyurethane resin dispersion, adhesive composition and pressure-sensitive adhesive

[0001] The present invention relates to a polyurethane resin dispersion, an adhesive composition and a pressure-sensitive adhesive.

[0002] A polyurethane resin dispersion obtained by dispersing a polyurethane resin in an aqueous dispersion medium is widely used in, for example, paints, inks, adhesives, coating agents and the like. In particular, by using an aqueous dispersion of a polyurethane resin, a coating film can be easily formed on a substrate such as a film, so that the substrate can be functionalized with the polyurethane resin, which has extremely high utility value.

[0003] For example, when a polyurethane resin dispersion is applied to adhesive applications, it is required to be capable of exhibiting excellent adhesive force to an adherend. For example, Patent Document 1 discloses an adhesive composition containing a urethane (meth)acrylate having a molecular weight of 4000 or less, a radically polymerizable compound, and a photopolymerization initiator, which is described to be capable of exhibiting excellent adhesiveness.

[0004] Japanese Unexamined Patent Application Publication No. 2007-169580

[0005] In the above-mentioned adhesive applications, depending on the purpose, in addition to being capable of exhibiting excellent adhesive force to an adherend, a property of being easily peelable (that is, easy peelability) may be required. For this reason, it is required for polyurethane resin dispersions applied to adhesive applications to be capable of forming a pressure-sensitive adhesive that can impart high adhesive force and can form a pressure-sensitive adhesive that can be easily peeled off after adhesion.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyurethane resin dispersion that can form a pressure-sensitive adhesive having high adhesive force and can form a pressure-sensitive adhesive that can be easily peeled off after adhesion. Another object of the present invention is to provide an adhesive composition containing the polyurethane resin dispersion and a pressure-sensitive adhesive obtained from the adhesive composition.

[0007] The inventors of this invention conducted extensive research to achieve the above objectives and, as a result, discovered that these objectives can be achieved by using a polyurethane resin formed from specific components, thus completing the present invention.

[0008] In other words, the present invention encompasses, for example, the subject matter described in the following sections: Section 1 A polyurethane resin dispersion comprising a polyurethane resin dispersed in an aqueous dispersion medium, wherein the polyurethane resin is a reaction product of a polyol compound, a monoalcohol compound, an acrylic compound having a hydroxyl group, and a polyisocyanate compound, wherein the polyol compound is a compound having at least one (meth)acryloyl group, and the monoalcohol compound is a compound having an alkoxy group at its terminus. Section 2 The polyurethane resin dispersion according to Section 1, wherein the polyisocyanate compound is a compound having a nurate skeleton. Section 3 The polyurethane resin dispersion according to Section 1 or 2, wherein the polyurethane resin has a structure elongated by a chain extender. Section 4 An adhesive composition comprising the polyurethane resin dispersion according to any one of Sections 1 to 3, and used for bonding. Section 5 The adhesive composition according to Section 4, which is easily peelable. Section 6 An adhesive comprising a cured product of the adhesive composition according to Section 4 or 5.

[0009] The polyurethane resin dispersion obtained by dispersing the polyurethane resin of the present invention in an aqueous dispersion medium can form an adhesive that has high tackiness and can be easily peeled off after adhesion.

[0010] Embodiments of the present invention will be described in detail below. In this specification, the expressions "containing" and "including" include the concepts of "containing," "including," "substantially consisting of," and "consisting only of."

[0011] In the numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in one step can be arbitrarily combined with the upper or lower limit of a numerical range in another step. In the numerical ranges described in this specification, the upper or lower limit of a numerical range may be replaced with values ​​shown in the examples or values ​​that can be uniquely derived from the examples. Furthermore, in this specification, numbers connected by "~" mean a numerical range that includes the numbers before and after "~" as the lower and upper limits.

[0012] 1. Polyurethane Resin Dispersion The polyurethane resin dispersion of the present invention is obtained by dispersing a polyurethane resin in an aqueous dispersion medium. The polyurethane resin is a reaction product of a polyol compound, a monoalcohol compound, an acrylic compound having a hydroxyl group, and a polyisocyanate compound. The polyol compound is a compound having at least one (meth)acryloyl group, and the monoalcohol compound is a compound having an alkoxy group at its terminus.

[0013] The polyurethane resin dispersion of the present invention, by containing the polyurethane resin, can form an adhesive that has high tackiness and can be easily peeled off after bonding. For this reason, the polyurethane resin dispersion of the present invention can be suitably used as an adhesive composition, and is particularly suitable as an easily peelable adhesive composition.

[0014] One reason why polyurethane resin exhibits the property of easily peeling after bonding (easy peelability) is that the polyurethane resin contained in the polyurethane resin dispersion of the present invention is photocurable, and in particular, because the polyurethane resin has (meth)acryloyl groups. Because the polyurethane resin has (meth)acryloyl groups, curing of the polyurethane resin occurs upon light irradiation, and shrinkage (so-called curing shrinkage) occurs with this curing. It is presumed that this curing shrinkage is what causes the polyurethane resin to exhibit excellent easy peelability. Therefore, the easy peelability of polyurethane resin is a function that is exhibited by light irradiation such as ultraviolet light.

[0015] As described above, the polyurethane resin contained in the polyurethane resin dispersion of the present invention is a reaction product (more specifically, an addition product) of a polyol compound, a monoalcohol compound having an alkoxy group at its terminus (sometimes simply referred to as "monoalcohol compound"), an acrylic compound having a hydroxyl group, and a polyisocyanate compound. In other words, the polyurethane resin is obtained by reacting a polyol compound, a monoalcohol compound, an acrylic compound having a hydroxyl group, and a polyisocyanate compound. To put it another way, the polyurethane resin of the present invention is a compound having a structure derived from a polyol compound, a monoalcohol compound having an alkoxy group at its terminus, an acrylic compound having a hydroxyl group, and a polyisocyanate compound. The following describes each compound that constitutes the polyurethane resin.

[0016] (Polyol Compounds) Polyol compounds are compounds that have at least two hydroxyl groups in their molecule. In particular, polyol compounds are compounds that have at least one (meth)acryloyl group in addition to two or more hydroxyl groups. A (meth)acryloyl group means an acryloyl group or a methacryloyl group.

[0017] In this specification, "(meth)acrylic" means "acrylic" or "methacrylic." For example, "(meth)acrylate" means "acrylate" or "methacrylate," and "(meth)acrylamide" means "acrylamide" or "methacrylamide."

[0018] By including a component derived from a polyol compound in the polyurethane resin, the polyurethane resin dispersion of the present invention can form an adhesive that has excellent tackiness and also excellent peelability.

[0019] In the polyol compound, the number of hydroxyl groups is preferably five or less, more preferably four or less, even more preferably three or less, and particularly preferably two. In this case, the polyurethane resin dispersion of the present invention is more likely to form an adhesive that has superior tackiness and peelability.

[0020] In the polyol compound, the number of (meth)acryloyl groups is preferably five or less, more preferably four or less, even more preferably three or less, and particularly preferably two. In this case, the polyurethane resin dispersion of the present invention is more likely to form an adhesive that has superior tackiness and peelability.

[0021] The type of polyol compound is not particularly limited, as long as it has at least two hydroxyl groups and at least one (meth)acryloyl group. For example, the polyol compound is preferably a reaction product of a compound having at least two (preferably two) epoxy groups and a compound having a (meth)acryloyl group (e.g., (meth)acrylic acid). In this case, the epoxy group and the compound having a (meth)acryloyl group (e.g., (meth)acrylic acid) react to form a (meth)acryloyl group, as well as a hydroxyl group derived from the epoxy group, resulting in the polyol compound described above.

[0022] Examples of polyol compounds include compounds having a bisphenol structure in their molecule. Various bisphenol structures can be used, such as bisphenol A, bisphenol B, bisphenol C, and bisphenol F, with bisphenol A being preferred. In this case, the adhesive obtained from the polyurethane resin dispersion of the present invention has reduced residual resin in the adhesive, making it easier to suppress so-called resin residue.

[0023] Specifically, polyol compounds can preferably include compounds having a bisphenol skeleton, in which the (meth)acryloyl group is directly or indirectly bonded to an oxygen atom in the bisphenol skeleton. In this case, the bisphenol skeleton is preferably a bisphenol A skeleton. When the (meth)acryloyl group is indirectly bonded to an oxygen atom in the bisphenol skeleton, for example, a divalent group derived from epoxy, specifically "-O-CH," is present between the bisphenol skeleton and the (meth)acryloyl group. ２ -CH(OH)-CH ２ A dash (-) may also be included.

[0024] Other examples of polyol compounds include polyol compounds that do not have a bisphenol skeleton, such as adducts of alkylene glycol diglycidyl ether (e.g., ethylene glycol diglycidyl ether or propylene glycol diglycidyl ether) and compounds having a (meth)acryloyl group (e.g., (meth)acrylic acid).

[0025] As mentioned above, the polyol compound is preferably a compound having a bisphenol skeleton, and more preferably a compound having a bisphenol A skeleton. In this case, the adhesive formed from the polyurethane resin dispersion tends to have better adhesive strength, better peelability (better peelability), and in addition, the aforementioned resin residue is easily suppressed.

[0026] The method for producing polyol compounds is not particularly limited; for example, they can be produced by known methods or obtained from commercially available products. Examples of commercially available polyol compounds include Kyoeisha Chemical's "Epoxy Ester 70PA(N) (registered trademark)."

[0027] When a polyol compound is produced, it can be manufactured, for example, by reacting a compound having at least two (preferably two) epoxy groups with a compound having a (meth)acryloyl group (e.g., (meth)acrylic acid). If the compound having epoxy groups is a bisphenol A type epoxy resin, the resulting polyol compound will be a compound having a bisphenol A skeleton. A bisphenol A type epoxy resin can be manufactured, for example, by a condensation reaction between bisphenol A and epichlorohydrin. An example of a bisphenol A type epoxy resin is "jER828®" manufactured by Mitsubishi Chemical Corporation.

[0028] The polyurethane resin of the present invention may contain one or more polyol compounds.

[0029] (Monoalcohol compounds) Monoalcohol compounds are compounds that have an alkoxy group at one end and also have one hydroxyl group.

[0030] By including a component derived from a monoalcohol compound in the polyurethane resin, the polyurethane resin dispersion of the present invention can form an adhesive with excellent peelability. Furthermore, because the polyurethane resin includes a component derived from a monoalcohol compound, gelation and other reactions are less likely to occur during the manufacturing process of the polyurethane resin dispersion of the present invention, allowing for the production of a stable dispersion.

[0031] In monoalcohol compounds, the alkoxy group can be, for example, an alkoxy group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms. Examples of alkoxy groups include methoxy groups and ethoxy groups.

[0032] The type of monoalcohol compound is not particularly limited, as long as it is a compound having an alkoxy group at one end and one hydroxyl group. For example, a chain-like compound having an alkoxy group at one end and a hydroxyl group at the other end can be mentioned.

[0033] A specific example of a monoalcohol compound is polyoxyalkylene monoalkyl ether. Such a compound has a hydroxyl group at one end and an alkoxy group (alkyl ether moiety) at the other end.

[0034] In polyoxyalkylene monoalkyl ethers, the number of carbon atoms in the alkylene moiety is not particularly limited, for example, 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms. Oxyethylene is an example of the oxyalkylene moiety in polyoxyalkylene monoalkyl ethers.

[0035] Examples of monoalcohol compounds include polyoxyethylene monomethyl ether.

[0036] The number-average molecular weight of a monoalcohol compound can be, for example, in the range of 600 to 2500.

[0037] In this specification, the number-average molecular weight (Mn) is measured by GPC (gel permeation chromatography) and calculated using a calibration curve with standard polystyrene. Specifically, the GPC conditions are as follows: Column: TSKgel G4000HXL + TSKgel G3000HXL + TSKgel G2000HXL + TSKgel G1000HXL + TSKgel G1000HXL manufactured by Tosoh Corporation; Mobile phase: THF (tetrahydrofuran); Mobile phase flow rate: 1.0 mL / min; Column temperature: 40°C; Sample injection volume: 50 μL; Sample concentration: 0.2% by mass.

[0038] It is preferable that the monoalcohol compound does not have a (meth)acryloyl group.

[0039] Monoalcohol compounds can be manufactured, for example, by known methods, or can be obtained from commercially available products. Examples of commercially available monoalcohol compounds include NOF Corporation's "Uniox M-100" (registered trademark), which is a type of polyoxyalkylene monoalkyl ether, and Nippon Emulsifier Co., Ltd.'s "MPG-056".

[0040] The polyurethane resin of the present invention may contain one or more monoalcohol compounds.

[0041] (Acrylic compound having a hydroxyl group) By including a component derived from an acrylic compound having a hydroxyl group in the polyurethane resin, the polyurethane resin dispersion of the present invention can form an adhesive with excellent tackiness and excellent peelability. Furthermore, by including a component derived from an acrylic compound having a hydroxyl group in the polyurethane resin, gelation and other reactions are less likely to occur during the manufacturing process of the polyurethane resin dispersion of the present invention, making it possible to produce a stable dispersion.

[0042] Examples of the acrylic compound having a hydroxyl group include compounds having a hydroxyl group and a (meth)acryl group in the molecule, and for example, a (meth)acrylate having a hydroxyl group can be mentioned. The number of hydroxyl groups in the acrylic compound having a hydroxyl group is 1 or more and 4 or less, preferably 3 or less, more preferably 2 or less, and still more preferably 1.

[0043] Note that the acrylic compound having a hydroxyl group excludes the aforementioned monoalcohol compound.

[0044] Examples of the (meth)acrylate having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2,2-dimethyl-2-hydroxyethyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, polyalkylene glycol mono(meth)acrylate, and the like.

[0045] The polyurethane resin of the present invention can contain one or more acrylic compounds having a hydroxyl group.

[0046] (Polyisocyanate Compound) A polyisocyanate compound is a compound having at least two or more isocyanate groups in the molecule.

[0047] When the polyurethane resin contains a component derived from a polyisocyanate compound, the polyurethane resin dispersion of the present invention can form a pressure-sensitive adhesive excellent in adhesive strength and can also form a pressure-sensitive adhesive excellent in easy peelability.

[0048] Examples of polyisocyanate compounds include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. In particular, in the present invention, the polyisocyanate compound is preferably a compound having a nurate skeleton, and more specifically, the polyisocyanate compound is preferably a compound having a nurate skeleton and two or more isocyanate groups. Hereinafter, such a compound will be referred to as a "nurate-type polyisocyanate compound." The nurate skeleton is an isocyanurate ring formed by the trimerization reaction of isocyanates, and has a six-membered ring structure.

[0049] When the polyisocyanate compound is a nurate-type polyisocyanate compound, the polyurethane resin dispersion of the present invention tends to form an adhesive that is superior in both tackiness and peelability, and also tends to improve tackiness. In addition, when the polyisocyanate compound is a compound having a nurate skeleton, gelation and the like are less likely to occur during the reaction process when manufacturing the polyurethane resin dispersion of the present invention, and a stable dispersion with excellent uniformity (monomodality) of polyurethane resin particles can be manufactured.

[0050] When the polyisocyanate compound is a nurate-type polyisocyanate compound, its structure is not particularly limited, but it is more preferable that it be an aliphatic polyisocyanate compound (i.e., a polyisocyanate compound that does not have a cyclic structure such as an aromatic ring). Examples of such polyisocyanate compounds include compounds having an alkylene group between the nurate skeleton and the isocyanate group. The alkylene group has, for example, 1 to 20 carbon atoms, preferably 2 to 10.

[0051] Specific examples of nurate-type polyisocyanate compounds include, for example, polyisocyanates obtained by trimerizing known aliphatic polyisocyanate compounds. Examples of aliphatic polyisocyanate compounds in this case include tetramethylene diisocyanate 1,5-pentamethylene diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate (TMDI), trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, and the like.

[0052] The polyisocyanate compound preferably contains 50% by mass or more of a nurate-type polyisocyanate compound, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0053] The polyisocyanate compounds used in this invention can be manufactured by known methods or obtained from commercially available products. Examples of commercially available nurate-type polyisocyanate compounds include Tosoh Corporation's "Coronate HX," Asahi Kasei Corporation's "Duranate TMA-100" and "TPA-100," and others.

[0054] The polyurethane resin of the present invention may contain one or more isocyanate compounds.

[0055] (Chain elongators) The polyurethane resin may also have a structure elongated by a chain elongator. That is, when manufacturing a polyurethane resin dispersion, a chain elongator can be used to elongate the chain length of the polyurethane.

[0056] The type of chain extender is not particularly limited, and a wide range of known chain extenders used in the production of polyurethane resins can be cited. Examples of chain extenders include polyamine compounds having at least two amino groups. Examples of polyamine compounds include diamine compounds having two amino groups, and other compounds having three or more amino groups. In terms of the tendency for the adhesive obtained from the polyurethane resin dispersion to have high tackiness, it is preferable that the chain extender is a compound having three or more amino groups.

[0057] Specific examples of polyamine compounds include ethylenediamine, trimethylenediamine, piperazine, isophoronediamine, diethylenetriamine, 3,3'-iminobis(propylamine) (also known as dipropylenetriamine), triethylenetetramine, bis(6-aminohexyl)amine, 2-aminomethylpiperazine, and amino group-containing silane coupling agents.

[0058] Polyamine compounds can also have hydroxyl groups, and examples of such compounds include N-(hydroxyalkyl)alkylenediamines such as N-(2-hydroxyethyl)ethylenediamine (also known as N-(2-aminoethyl)ethanolamine), N-(2-hydroxypropyl)ethylenediamine (also known as N-(2-aminoethyl)propanolamine), N-(3-hydroxypropyl)ethylenediamine, and N-(2-hydroxyethyl)-1,3-propanediamine (also known as 3-(2-hydroxyethylamino)propylamine). Furthermore, examples of polyamine compounds having one hydroxyl group and two primary amino groups in one molecule include diamino alcohols such as 1,3-diamino-2-propanol.

[0059] Other polyamine compounds may include polycarbodiimide compounds, for example, Nisshinbo Chemical's crosslinking agent for carbodilite aqueous resins.

[0060] The polyurethane resin of the present invention may contain one or more chain extenders.

[0061] (Polyurethane Resin) The polyurethane resin of the present invention is a reaction product (more specifically, an addition product) of at least a polyol compound, a monoalcohol compound having an alkoxy group at its terminus, an acrylic compound having a hydroxyl group, and a polyisocyanate compound. The polyurethane resin may also be elongated with a chain extender as needed. In this case, the polyurethane resin before being elongated with the chain extender is sometimes referred to as a "urethane prepolymer." The urethane prepolymer has isocyanate groups, and the polyurethane resin can be elongated by the reaction of these isocyanate groups with the chain extender. In this case, the polyurethane resin can be dispersed in the aqueous dispersion medium described later while emulsifying. That is, it is preferable that the polyurethane resin is self-emulsifying.

[0062] The respective content ratios (more precisely, the content ratios of each compound-derived component) of polyol compounds, monoalcohol compounds, hydroxyl-containing acrylic compounds, and polyisocyanate compounds contained in the polyurethane resin can be adjusted within an appropriate range depending on the required adhesive strength and ease of peeling.

[0063] When the total mass of polyol compounds, monoalcohol compounds, hydroxyl group-containing acrylic compounds, and polyisocyanate compounds contained in the polyurethane resin (hereinafter referred to as "total mass S") is 100 parts by mass, the content of the polyol compound is preferably 10 parts by mass or more, more preferably 13 parts by mass or more, even more preferably 15 parts by mass or more, particularly preferably 17 parts by mass or more, and also preferably 30 parts by mass or less, more preferably 27 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 23 parts by mass or less.

[0064] When the total mass S is 100 parts by mass, the content of the monoalcohol compound is preferably 13 parts by mass or more, more preferably 15 parts by mass or more in terms of suppressing resin residue, even more preferably 17 parts by mass or more, particularly preferably 19 parts by mass or more, preferably 35 parts by mass or less, more preferably 33 parts by mass or less, even more preferably 31 parts by mass or less, and particularly preferably 29 parts by mass or less.

[0065] When the total mass S is 100 parts by mass, the content of the acrylic compound having a hydroxyl group is preferably 7 parts by mass or more, more preferably 8 parts by mass or more, even more preferably 9 parts by mass or more, particularly preferably 10 parts by mass or more, and also preferably 20 parts by mass or less, more preferably 17 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 14 parts by mass or less.

[0066] When the total mass S is 100 parts by mass, the content of the polyisocyanate compound is preferably 35 parts by mass or more, more preferably 38 parts by mass or more, even more preferably 40 parts by mass or more, particularly preferably 42 parts by mass or more, and also preferably 55 parts by mass or less, more preferably 52 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 49 parts by mass or less.

[0067] The polyurethane resin preferably contains a total of 80% by mass or more of polyol compounds, monoalcohol compounds, acrylic compounds having hydroxyl groups, and polyisocyanate compounds, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0068] When a polyurethane resin is stretched with a chain extender, the content of the chain extender in the polyurethane resin is preferably 2 parts by mass or less, more preferably 1.8 parts by mass or less, even more preferably 1.6 parts by mass or less, even more preferably 1.5 parts by mass or less, and particularly preferably 1.4 parts by mass or less, with no particular lower limit. For example, it is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 0.7 parts by mass or more, and particularly preferably 0.8 parts by mass or more.

[0069] The polyurethane resin may consist of a polyol compound, a monoalcohol compound, an acrylic compound having a hydroxyl group, a polyisocyanate compound, and a chain extender.

[0070] The number-average molecular weight (Mn) of the polyurethane resin is not particularly limited and may be, for example, 10,000 or more, or 50,000 or more. The average particle size of the aqueous dispersion of the polyurethane resin is not particularly limited and may be, for example, 0.005 to 0.5 μm. Here, the average particle size is the 50% cumulative particle size (D50) measured using "Microtrac UPA-UZ152" manufactured by Nikkiso Co., Ltd.

[0071] (Polyurethane Resin Dispersion) A polyurethane resin dispersion is obtained by dispersing the above-mentioned polyurethane resin in an aqueous dispersion medium. Examples of aqueous dispersion mediums include water, lower alcohols having 1 to 3 carbon atoms, and mixed solvents of water and lower alcohols, with water being preferred. When the dispersion medium is water, the polyurethane resin dispersion can be called an aqueous polyurethane resin dispersion.

[0072] The polyurethane resin dispersion may contain resins other than polyurethane resin, or it may consist solely of polyurethane resin.

[0073] The method for producing the polyurethane resin dispersion is not particularly limited, and for example, known methods for producing polyurethane resin dispersions can be widely employed. For example, a polyurethane resin dispersion can be obtained by reacting a urethane prepolymer, obtained by reacting a polyol compound, a monoalcohol compound, an acrylic compound having a hydroxyl group, and a polyisocyanate compound, with a chain extender (C).

[0074] More specifically, a urethane prepolymer is obtained by reacting a polyol compound, a monoalcohol compound, and an acrylic compound having a hydroxyl group (these three compounds are collectively referred to as "alcohol components") with a polyisocyanate compound in the presence or absence of a polymerization inhibitor. One method involves neutralizing the urethane prepolymer with a neutralizing agent, emulsifying and dispersing it in water, and then reacting the urethane prepolymer with a chain extender.

[0075] In this method, the alcohol component and the polyisocyanate compound are reacted without a solvent or in an organic solvent that does not contain active hydrogen groups to synthesize an isocyanate-terminated urethane prepolymer. In this process, the polyisocyanate compound can be used such that the amount of isocyanate groups is stoichiometrically in excess of the amount of active hydrogen groups contained in the alcohol component, for example, with an equivalent ratio of isocyanate groups to active hydrogen groups of 1:0.8 to 1:0.99.

[0076] After the synthesis of the above urethane prepolymer, anionic hydrophilic groups such as carboxyl groups are neutralized with a neutralizing agent, and then the mixture is emulsified and dispersed in water, so-called self-emulsification. Subsequently, a chain extender is added in an equivalent amount less than the remaining isocyanate groups (for example, an equivalent ratio of isocyanate groups to active hydrogen groups of the chain extender (C) of 1:0.50 to 0.95) to cause an interfacial polymerization reaction between the isocyanate groups in the emulsified micelles and the chain extender to generate urea bonds. This improves the crosslinking density within the emulsified micelles and forms a three-dimensional crosslinked structure. After that, by removing the solvent used as necessary, an aqueous dispersion of polyurethane resin can be obtained. The free NCO content when adding the chain extender is preferably 2.1% by mass or less relative to the urethane prepolymer.

[0077] Examples of the neutralizing agent include non-volatile bases such as sodium hydroxide and potassium hydroxide, tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine, and triethanolamine, and volatile bases such as ammonia. Neutralization can be carried out before, during, or after the urethane reaction.

[0078] Organic solvents that can be optionally used in the synthesis of urethane prepolymers include organic solvents that are inert to isocyanate groups and can dissolve the resulting urethane prepolymer. Examples of such organic solvents include dioxane, methyl ethyl ketone, acetone, dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone, toluene, and propylene glycol monomethyl ether acetate.

[0079] In the synthesis of urethane prepolymers or elongated polyurethane resins, the amount of each compound used can be such that, for example, the content of each compound in the polyurethane resin falls within the range described above. For example, the equivalent ratio NCO / OH of isocyanate groups in the polyisocyanate compound to the total amount of hydroxyl groups in the monoalcohol compound and the acrylic compound having hydroxyl groups is preferably 1 or more, more preferably 1.2 or more, even more preferably 1.4 or more, and preferably 2.5 or less, more preferably 2.2 or less, and even more preferably 2.1 or less.

[0080] Furthermore, the amount of polyol compound, monoalcohol compound, acrylic compound having a hydroxyl group, and polyisocyanate compound used can be adjusted so that the number of acryloyl groups in one molecule of the urethane prepolymer is between three and five.

[0081] In the polyurethane resin dispersion, the concentration of the polyurethane resin is not particularly limited and may be, for example, 10 to 50% by mass, 20 to 45% by mass, or 30 to 40% by mass.

[0082] Polyurethane resin dispersions can be blended with various additives. Examples of such additives include pigments, UV absorbers, light stabilizers, surface modifiers, inorganic fillers, organic fillers, dispersion aids, preservatives, rust inhibitors, antioxidants, silane coupling agents, defoamers, viscosity modifiers, antistatic agents, crosslinking agents, and organic solvents.

[0083] When polyurethane resin dispersions are manufactured as described above, gelation during manufacturing is less likely to occur, and they exhibit excellent dispersibility. In particular, polyurethane resins also exhibit excellent monomodulus properties.

[0084] An adhesive can be formed using a polyurethane resin dispersion. Specifically, by forming a film of the polyurethane resin dispersion, the resulting film can be used as an adhesive. Such an adhesive has excellent adhesion to the adherend while also possessing excellent peelability. Furthermore, the adhesive obtained from the polyurethane resin dispersion has excellent tackiness and is less likely to leave resin residue.

[0085] In particular, the polyurethane resin contained in the polyurethane resin dispersion of the present invention contains (meth)acryloyl groups derived from polyol compounds and acrylic compounds having hydroxyl groups, and is therefore photocurable. Consequently, when the polyurethane resin is irradiated with light such as ultraviolet light, the polyurethane resin hardens, and shrinkage occurs as a result of this hardening. It is presumed that this shrinkage leads to easy peeling. Therefore, for example, it is presumed that irradiating an adherend to which a polyurethane resin dispersion film is bonded with ultraviolet light causes hardening shrinkage of the film, thereby making it easier to peel off from the adherend. That is, when adhered to an adherend, (meth)acryloyl groups remain in the polyurethane resin, and upon irradiation with light (ultraviolet light), a hardening reaction based on the (meth)acryloyl groups proceeds, resulting in peeling. From this viewpoint, it is preferable not to irradiate with light such as ultraviolet light when using an adhesive containing polyurethane resin to bond adherends.

[0086] Therefore, when peeling off an adhesive formed from a polyurethane resin dispersion, it is preferable that the method includes a step of irradiating the adherend or the adhesive with light, preferably ultraviolet light.

[0087] The polyurethane resin dispersion of the present invention has excellent adhesive strength and excellent peelability, and is therefore preferably used for adhesives, and is particularly suitable for use as an adhesive composition. Since such an adhesive composition contains a polyurethane resin dispersion, it can form an adhesive with excellent adhesive strength and excellent peelability, and is also suitable for use as an easily peelable adhesive.

[0088] The method for forming an adhesive using an adhesive composition is not particularly limited. For example, an adhesive can be formed by applying the adhesive composition to an adherend or a substrate as described below, thereby forming a film. The film formation is preferably carried out by a method other than light irradiation. For example, it is preferable to form the adhesive by drying a solvent such as water using an appropriate method.

[0089] The adhesive composition may optionally contain other components, as long as it contains the polyurethane resin dispersion of the present invention. These other components are not particularly limited and include, for example, various components that may be included in known adhesive compositions.

[0090] The method for obtaining an adhesive from an adhesive composition is not particularly limited. For example, an adhesive can be obtained by forming a cured product of the adhesive composition on various substrates. The type of substrate is not particularly limited, and a wide range of known substrates used as substrates for adhesive tapes, such as polyethylene terephthalate (PET), can be listed. The method for forming the cured product on the substrate is also not particularly limited. For example, an adhesive can be obtained by applying the adhesive composition to the substrate and forming a cured product using an appropriate method. Various known methods can also be used for forming the cured product.

[0091] By using an adhesive from an adhesive composition, various forms of adhesive materials can be formed, such as tape, thin film, film, and paste. For example, if the adhesive is in tape form, it can be widely applied in semiconductor fields such as backgrinding and dicing applications.

[0092] Since the adhesive contains a cured product formed from the polyurethane resin dispersion of the present invention, it exhibits excellent adhesive strength and also excellent peelability.

[0093] In specifying the inventions contained herein, the components (properties, structures, functions, etc.) described in each embodiment of this disclosure may be combined in any way. That is, this disclosure encompasses all subject matter consisting of any combination of the combinatable components described herein.

[0094] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to the embodiments of these examples.

[0095] (Production Example 1: Production of Polyol Compound Having an Acryloyl Group) In a flask equipped with a thermometer, stirrer, and water-cooled condenser, 189 parts by mass of "jER828 (registered trademark)" manufactured by Mitsubishi Chemical Corporation as a bisphenol A type epoxy resin were added to 72 parts by mass of acrylic acid, 0.26 parts by mass of 4-methoxyphenol as a polymerization inhibitor, and 1.3 parts by mass of tetrabutylammonium bromide as a catalyst to obtain a reaction mixture. This reaction mixture was reacted at a reaction temperature of 95 to 110°C until the epoxy equivalent was 10,000 or more, and then diluted with 65 parts by mass of methyl ethyl ketone to obtain a solution containing polyol compound A-1 having an acryloyl group with a solid content concentration of 80% by mass.

[0096] (Production Example 2: Production of Polyol Compound Without Acryloyl Groups) In a flask equipped with a thermometer and a stirrer, 51.6 parts by mass of Kuraray Polyol P-1010 manufactured by Kuraray Co., Ltd., 68.8 parts by mass of sodium dimethyl sulfonate isophthalate, and 2.3 parts by mass of tetrabutoxititanium as a catalyst were added to obtain a reaction mixture. This reaction mixture was reacted at a reaction temperature of 190-200°C while blowing nitrogen to remove methanol by distillation until the hydroxyl value reached 52-54 mg-KOH / g. After cooling, it was diluted with 24.5 parts by mass of methyl ethyl ketone to obtain a solution containing polyol compound a-1 without acryloyl groups, with a solid content concentration of 70% by mass.

[0097] The resin dispersions for each example and comparative example were prepared by selecting a predetermined component from the components listed below.

[0098] [Polyol Compounds] ・Polyol A-1: ​​Bisphenol A type polyol compound having an acryloyl group obtained in Production Example 1 ・Polyol A-2: Kyoeisha Chemical "Epoxy Ester 70 PA (N)" (Acrylic acid adduct of propylene glycol diglycidyl ether)

[0099] [Polyol Compounds (for Comparison)] ・Polyol a-1: Polyol compound without a (meth)acryloyl group obtained in Production Example 2

[0100] [Mono-alcohol compounds] ・Mono-alcohol A-3: Polyoxyethylene monomethyl ether (NOF Corporation "UNIOX M-1000 (registered trademark)")

[0101] [Polyoxyethylene Compounds (for Comparison)] The following polyoxyethylene compounds, which are not monool compounds, were prepared: • Polyoxyethylene a-3: α-[2,2-bis(hydroxymethyl)butyl]-ω-methoxypoly(oxyethylene) (Perstop "Ymer N120")

[0102] [Acrylic compounds containing hydroxyl groups] ・Hydroxyl group-containing acrylate A-4: Hydroxyethyl acrylate (HEA) ・Hydroxyl group-containing acrylate A-5: Hydroxypropyl acrylate (HPA)

[0103] [Polyisocyanate Compounds] ・Polyisocyanate B-1: Nulate-type polyisocyanate compound (Tosoh Corporation "Coronate HXR (registered trademark)") ・Polyisocyanate B-2: 1,6-Hexamethylene diisocyanate (HMDI)

[0104] [Chain elongators] ・Chain elongator C-1: Triethylenetetraamine (TETA) ・Chain elongator C-2: Diethylenetriamine (DETA) ・Chain elongator C-3: Ethylenediamine (EDA)

[0105] (Example 1) In a flask equipped with a thermometer, stirrer, and water-cooled condenser, 21.17 parts by mass of polyol A-1 (solid content), 20.27 parts by mass of monoalcohol A-3, 11.77 parts by mass of hydroxyl group-containing acrylate A-4 (HEA), 46.79 parts by mass of polyisocyanate B-1, 0.05 parts by mass of 4-methoxyphenol as a polymerization inhibitor, and 0.05 parts by mass of catalyst (Neostan U-600) were added, and a mixture was obtained by adjusting the system concentration to 60% by mass with methyl ethyl ketone. This mixture was reacted at a reaction temperature of 65 to 75°C until the amount of free isocyanate was less than 2.1%, then 233 parts by mass of ion-exchanged water was added and the mixture was rapidly stirred to convert it into an aqueous dispersion, and then 1.32 parts by mass of chain extension agent C-2 (DETA) was added to carry out the chain extension reaction. Finally, an antifoaming agent was added, and then the methyl ethyl ketone was removed by vacuum distillation to obtain a polyurethane resin dispersion with a solid content of 30%.

[0106] (Examples 2-6) Polyurethane resin dispersions were obtained in the same manner as in Example 1, except that the compounding conditions shown in Table 1 were changed.

[0107] (Examples 7-12) Polyurethane resin dispersions were obtained in the same manner as in Example 1, except that the compounding conditions shown in Table 2 were changed.

[0108] (Comparative Examples 1-3) Polyurethane resin dispersions were obtained in the same manner as in Example 1, except that the compounding conditions shown in Table 3 were changed.

[0109] (Evaluation Method) [Average Particle Size of Polyurethane Resin Dispersion] The average particle size of the polyurethane resin dispersion was defined as the 50% cumulative particle size (D50) measured using "Microtrac UPA-UZ152" manufactured by Nikkiso Co., Ltd.

[0110] [Particle Size Distribution Shape of Polyurethane Resin] The particle size distribution shape of polyurethane resin is determined by the particle size distribution obtained from the measurement of the particle size (D50) described above. If there is one peak in the distribution curve, it is called "unimodal," and if there are two or more peaks in the distribution curve, it is called "multimodal" (for example, if there are three peaks, it is called "trimodal").

[0111] [Adhesion (before UV curing)] 0.9 parts by mass of Omnirad 2959 (IGM Resins B.V.), a photopolymerization initiator, was added to 100 parts by mass of polyurethane resin dispersion and mixed in a gyro mixer until uniformly dissolved to prepare the coating solution. A rectangular test specimen measuring 25 mm x 300 mm was prepared using PET film (Toray Industries, Inc. "Lumirror® #50-T60"). The coating solution was applied to the test specimen using a coater to a film thickness of 50 μm, dried at 80°C for 10 minutes, and then left to stand for 10 minutes in a constant temperature and humidity chamber at 20°C and 40% humidity. After standing, the coated surface of the test specimen was pressed onto a 50 mm x 125 mm SUS plate using a 2 kg pressure roller, passing it back and forth twice. After pressing, the specimen was again left to stand in the constant temperature and humidity chamber for 30 minutes to prepare the sample. The adhesive strength of the polyurethane resin dispersion was evaluated by measuring the adhesive strength when the sample was placed on a benchtop autograph (Shimadzu Corporation "Benchtop Autograph AGS-X20N") and a 180° peel test was performed at a test speed of 300 mm / min.

[0112] [Residual resin on SUS plates after adhesion test] The SUS plates were visually inspected after the adhesion test described above to evaluate whether any resin remained on the plates.

[0113] [Removability (after UV irradiation)] 0.9 parts by mass of Omnirad 2959 (IGM Resins B.V.), a photopolymerization initiator, was added to 100 parts by mass of polyurethane resin dispersion and mixed in a gyro mixer until uniformly dissolved to prepare the coating solution. A rectangular test specimen measuring 25 mm x 300 mm was prepared using PET film (Toray Industries, Inc. "Lumirror® #50-T60"). The coating solution was applied to the test specimen with a coater to a film thickness of 50 μm, dried at 80°C for 10 minutes, and then left to stand for 10 minutes in a constant temperature and humidity chamber at 20°C and 40% humidity. After standing, the coated surface of the test specimen was pressed onto a 50 mm x 125 mm SUS plate using a 2 kg pressure roller, passing it back and forth twice. Immediately after pressing, an 80 W / cm high-pressure mercury lamp was used to apply an integrated illuminance of 5000 mJ / cm². ２ The samples were prepared by photocuring under the specified conditions and then standing in a constant temperature and humidity chamber for 30 minutes. The samples were placed on a benchtop autograph (Shimadzu Corporation's "Benchtop Autograph AGS-X20N"), and the peeling force was measured by performing a 180° peel test at a test speed of 300 mm / min to evaluate the peelability.

[0114] [Tackiness Evaluation] To 100 parts by mass of polyurethane resin dispersion, 0.9 parts by mass of Omnirad 2959 (IGM Resins B.V.), a photopolymerization initiator, was added and mixed in a gyro mixer until uniformly dissolved to prepare the coating solution. The coating solution was applied to a 6 cm square PET film (Toray Industries, Inc. "Lumirror® #50-T60") using a coater to a film thickness of 50 μm, dried at 80°C for 10 minutes, and then left to stand for 10 minutes in a constant temperature and humidity chamber at 20°C and 40% humidity. After standing, the tackiness of the surface was checked by touching it with a finger and evaluated according to the following criteria. <<Criteria>> A: Tackiness was present and the tackiness was extremely good. B: There was some tackiness and the tackiness was good. C: There was no tackiness and the tackiness was poor.

[0115] (Evaluation Results) Tables 1 to 3 show the synthesis conditions and evaluation results for the polyurethane resin dispersions prepared in each example and comparative example. In the formulation conditions in Tables 1 to 3, blank spaces indicate that the raw material was not used.

[0116] In Table 1, "Total (A + B)" refers to the total mass of polyol compounds, monoalcohol compounds, and acrylic compounds having hydroxyl groups (including those used for comparison), and "Total (A + B + C)" refers to the amount obtained by adding the amount of chain extender used to "Total (A + B)".

[0117] From the comparison of the examples and comparative examples shown in Tables 1 to 3, it was demonstrated that a polyurethane resin composed of a reaction product of a predetermined polyol compound, a monoalcohol compound having an alkoxy group at its terminus, an acrylic compound having a hydroxyl group, and a polyisocyanate compound (i.e., a polyurethane resin having components derived from the predetermined compounds) can form an adhesive with high tackiness. Furthermore, it was found that the adhesive formed from the polyurethane resin dispersion obtained in the examples could be easily peeled off by ultraviolet irradiation after bonding, demonstrating excellent peelability.

[0118] On the other hand, as shown in Comparative Examples 1 to 3, polyurethane resins that do not contain components derived from the specified compounds cannot achieve both adhesiveness and easy peelability (Comparative Example 1), or gelation or the like occurs during the synthesis of the polyurethane resin dispersion, making it impossible to obtain the desired dispersion.

[0119]

[0120]

[0121]

Claims

1. A polyurethane resin dispersion comprising a polyurethane resin dispersed in an aqueous dispersion medium, wherein the polyurethane resin is a reaction product of a polyol compound, a monoalcohol compound, an acrylic compound having a hydroxyl group, and a polyisocyanate compound, the polyol compound is a compound having at least one (meth)acryloyl group, and the monoalcohol compound is a compound having an alkoxy group at its terminus.

2. The polyurethane resin dispersion according to claim 1, wherein the polyisocyanate compound is a compound having a nurate skeleton.

3. The polyurethane resin dispersion according to claim 1, wherein the polyurethane resin has a structure that has been elongated by a chain extender.

4. An adhesive composition comprising a polyurethane resin dispersion according to any one of claims 1 to 3, and used for bonding.

5. The adhesive composition according to claim 4, which is easily peelable.

6. An adhesive comprising a cured product of the adhesive composition described in claim 4.

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