JP7616486B2 - Urethane-based two-component curing adhesive - Google Patents

Description

The present invention relates to a urethane-based two-component curing adhesive using a glycerol ester-based polyol having a methylol group.

Urethane adhesives are widely used in a variety of fields because they exhibit high strength and can be used to bond dissimilar materials such as metal and plastic due to the flexibility unique to urethane. For example, in recent years, the automotive industry has begun to use resin materials such as fiber-reinforced plastics (FRP) instead of steel plates in order to reduce weight, and this has led to a demand for urethane adhesives with higher performance.

In addition, due to global warming caused by an increase in carbon dioxide concentration and the occurrence of abnormal weather worldwide, there is an increasing demand for bio-based (non-petroleum) resins derived from plants, etc., for adhesive resins. However, for example, the plant-derived polyol disclosed in Japanese Patent No. 5398715 is a polyol having a secondary hydroxyl group derived from castor oil, and there is a problem that polyols having secondary hydroxyl groups have lower reactivity with polyisocyanates than polyols having primary hydroxyl groups. JP-T-2008-504287 discloses a polyol obtained from hydroformylated soybean oil, but soybean oil has a low oleic acid content of 25%, and a urethane cured product having an ideal crosslinking structure cannot be obtained by reaction with polyisocyanates, resulting in poor hardness and physical properties.

JP 2021-536501 A discloses a polyol having a primary hydroxyl group obtained by hydroformylating and hydrogenating algae-derived triacylglycerol. However, this document does not disclose any polyurethane adhesive that meets the requirements at a practical level.

Patent No. 5398715 Special Publication No. 2008-504287 Special table 2021-536501 publication

The object of the present invention is to provide a urethane-based two-component curing adhesive consisting of a glycerol ester polyol and a polyisocyanate, which reduces the use of highly reactive and toxic amine-based reaction accelerators and also takes into consideration the health of workers.

As a result of extensive research to solve the above problems, the inventors discovered that by using a specific glycerol ester polyol as a curing agent, adhesive performance such as curing ability and adhesive strength can be significantly improved without the use of reaction accelerators such as amines, and thus completed the present invention.

That is, the present invention includes the following aspects.
[1] A two-component curing adhesive comprising a base material containing an isocyanate group-containing urethane prepolymer obtained by reacting a polyisocyanate with a polyol A, and/or a tolylene diisocyanate-based polyisocyanate, and a curing agent containing a glycerol ester-based polyol,
The tolylene diisocyanate-based polyisocyanate includes at least one selected from the group consisting of tolylene diisocyanate, an adduct type polyisocyanate composed of tolylene diisocyanate and a polyhydric alcohol, a nurate type polyisocyanate polymerized with tolylene diisocyanate, and an allophanate type polyisocyanate obtained from tolylene diisocyanate and an alcohol,
The glycerol ester polyol contains a compound represented by the following formula (1):
A two-component curing adhesive, wherein the content of fatty acid residues derived from oleic acid in the glycerol ester polyol is 70 mol % or more based on the total amount of fatty acid residues in the glycerol ester polyol.
(One of _X1 and _X2 is hydrogen and the other is a methylol group;
One of _X3 and _X4 is hydrogen and the other is a methylol group;
One of _X5 and _X6 is hydrogen and the other is a methylol group.

（Ｘ_１及びＸ_２は、一方が水素で、かつ他方がメチロール基であり、
Ｘ_３及びＸ_４は、一方が水素で、かつ他方がメチロール基であり、
Ｘ_５及びＸ_６は、一方が水素で、かつ他方がメチロール基であり、
Ｒ及びＲ’は、それぞれ独立して下記式（３）で表される基以外の不飽和脂肪酸もしくは飽和脂肪酸の残基、又は水素である。）
（Ｙ_１及びＹ_２の対は、一方が水素で、かつ他方がメチロール基であり、*は結合手である。）
[３]前記ポリオールＡが、ポリエーテルポリオール、ポリエステルポリオール、ポリアクリルポリオール、ポリオレフィンポリオール、ポリカーボネートポリオール、エポキシ樹脂ポリオール、低分子多価アルコール、及びこれらの部分変性物からなる群から選択される少なくとも１種を含む、[１]に記載の二液硬化型接着剤。
[４]前記ポリイソシアネートが、ジフェニルメタンジイソシアネート、ポリメリックジフェニルメタンジイソシアネート、変性ジフェニルメタンジイソシアネート、トリレンジイソシアネート、トリレンジイソシアネートと多価アルコールからなるアダクト型ポリイソシアネート、トリレンジイソシアネートのヌレート型ポリイソシアネート、及びトリレンジイソシアネートとアルコールから得られるアロハネート型ポリイソシアネートからなる群から選択される少なくとも１種を含む、[１]に記載の二液硬化型接着剤。
[５]前記ウレタンプレポリマーが、ジフェニルメタンジイソシアネート及びトリレンジイソシアネートから選択される少なくとも１種と、ポリエーテルポリオールとの反応から得られる、[１]に記載の二液硬化型接着剤。
[６]前記主剤中のイソシアネート基の前記硬化剤中のグリセロールエステル系ポリオールの水酸基に対する当量比（イソシアネート基／水酸基）が０．３～３．０である、[１]に記載の二液硬化型接着剤。
[７]前記グリセロールエステル系ポリオールが、トリオレイン、オリーブ油、高オレイン酸ベニバナ油、高オレイン酸椿油、及び藻類由来高オレイン酸油脂からなる群から選択される少なくとも１種から得られる、[１]に記載の二液硬化型接着剤。
[８]完全に硬化させた接着剤の剪断強度が、ＪＩＳ Ｋ６８５９に準拠した方法で測定したときに１５ＭＰａ以上であり、かつ硬化反応後７日後の剪断強度を１００％としたときの硬化反応後１日後の剪断強度の割合が７５％以上である、[１]～[７]のいずれかに記載の二液硬化型接着剤。 [2] The two-component curing adhesive according to [1], wherein the glycerol ester polyol further contains a compound represented by the following formula (2-1) and/or formula (2-2):

(One of _X1 and _X2 is hydrogen and the other is a methylol group;
One of _X3 and _X4 is hydrogen and the other is a methylol group;
One of _X5 and _X6 is hydrogen and the other is a methylol group;
R and R' are each independently a residue of an unsaturated or saturated fatty acid other than the group represented by the following formula (3), or hydrogen.
(One of the pair of _Y1 and _Y2 is hydrogen and the other is a methylol group, and * is a bond.)
[3] The two-component curing adhesive according to [1], wherein the polyol A comprises at least one selected from the group consisting of polyether polyols, polyester polyols, polyacrylic polyols, polyolefin polyols, polycarbonate polyols, epoxy resin polyols, low molecular weight polyhydric alcohols, and partially modified products thereof.
[4] The two-component curing adhesive according to [1], wherein the polyisocyanate comprises at least one selected from the group consisting of diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, modified diphenylmethane diisocyanate, tolylene diisocyanate, an adduct type polyisocyanate formed from tolylene diisocyanate and a polyhydric alcohol, a nurate type polyisocyanate of tolylene diisocyanate, and an allophanate type polyisocyanate obtained from tolylene diisocyanate and an alcohol.
[5] The two-component curing adhesive according to [1], wherein the urethane prepolymer is obtained by reacting at least one selected from diphenylmethane diisocyanate and tolylene diisocyanate with a polyether polyol.
[6] The two-component curing adhesive according to [1], wherein the equivalent ratio (isocyanate group/hydroxyl group) of the isocyanate group in the base agent to the hydroxyl group of the glycerol ester-based polyol in the curing agent is 0.3 to 3.0.
[7] The two-component curing adhesive described in [1], wherein the glycerol ester-based polyol is obtained from at least one selected from the group consisting of triolein, olive oil, high oleic acid safflower oil, high oleic acid camellia oil, and algae-derived high oleic acid oils and fats.
[8] A two-component curing adhesive according to any one of [1] to [7], wherein the shear strength of the completely cured adhesive is 15 MPa or more when measured according to a method in accordance with JIS K6859, and the ratio of the shear strength one day after the curing reaction to the shear strength seven days after the curing reaction is 75% or more.

The glycerol ester polyol used in the present invention contains a primary hydroxyl group, and therefore has high reactivity with isocyanate groups. In addition, the proportion of fatty acid residues derived from oleic acid is high, and the structure is highly regular, so the adhesive has high fast curing properties and adhesive properties, and good chemical resistance. In the present invention, a two-part curing adhesive is used, which is a base agent containing a urethane prepolymer and/or a tolylene diisocyanate-based polyisocyanate produced by the reaction of polyisocyanate with polyol A, and a curing agent containing a glycerol ester polyol, and therefore adhesive performance such as fast curing properties and adhesive strength can be further improved. Furthermore, since the adhesive of the present invention has high curing properties, it is possible to reduce the amount of highly toxic reaction accelerators such as amines, and by using bio-derived triacylglycerol, it is possible to reduce petroleum raw materials.

FIG. 1 shows the results of measurement of Polyol 5 by LC/CAD (liquid chromatography/charged aerosol detector).

The adhesive of the present invention is a two-part curing adhesive that contains a base agent and a curing agent. By using an appropriate combination of the base agent and the curing agent, it is possible to further promote curing and further improve the adhesive performance.

(Main ingredient)
The base material used in the two-component curing adhesive of the present invention contains an isocyanate group-containing urethane prepolymer obtained by the reaction of a polyisocyanate with polyol A, and/or a tolylene diisocyanate (TDI)-based polyisocyanate (hereinafter referred to as a TDI-based polyisocyanate). That is, the base material contains either a urethane prepolymer and a TDI-based polyisocyanate, a urethane prepolymer, or a TDI-based polyisocyanate. The TDI-based polyisocyanate contains at least one selected from the group consisting of tolylene diisocyanate, an adduct-type polyisocyanate composed of tolylene diisocyanate and a polyhydric alcohol, a nurate-type polyisocyanate polymerized with tolylene diisocyanate, and an allophanate-type polyisocyanate obtained from tolylene diisocyanate and an alcohol.
When the base agent contains a urethane prepolymer obtained by the reaction of a polyisocyanate with polyol A, a urethane prepolymer containing a plurality of isocyanate groups at the molecular terminals is obtained by the reaction of the polyisocyanate with polyol A. The number average molecular weight of the urethane prepolymer is preferably 500 to 10,000, more preferably 1,000 to 5,000.

<Polyisocyanate>
The preferred polyisocyanates used in the urethane prepolymer of the present invention are aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, etc., and two or more of these can be used in combination. Examples of aromatic polyisocyanates include tolylene diisocyanate (TDI) [e.g., 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), etc.], diphenylmethane diisocyanate (MDI) [e.g., 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), etc.], 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, xylylene diisocyanate, etc. Examples of the diisocyanate include tetramethylxylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), triphenylmethane triisocyanate, polymeric diphenylmethane diisocyanate (polymeric MDI) (a compound obtained by increasing the molecular weight of diphenylmethane diisocyanate), and modified diphenylmethane diisocyanate (modified MDI) [for example, isocyanurate-modified MDI, carbodiimide-modified MDI, urethane-modified MDI, and the like]. Examples of the aliphatic or alicyclic polyisocyanate include hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate (NBDI), transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), bis(isocyanatomethyl)cyclohexane (H6XDI), dicyclohexylmethane diisocyanate (H12MDI), carbodiimide modified products thereof, isocyanurate modified products thereof, etc. The polyisocyanate used in the present invention is more preferably MDI, polymeric MDI, modified MDI, TDI, an adduct type polyisocyanate obtained from TDI and a polyhydric alcohol, a nurate type polyisocyanate of TDI, an allophanate type polyisocyanate obtained from TDI and an alcohol, or a combination thereof.

<Polyol A>
The polyol A used in the present invention is, for example, a polyether polyol, a polyester polyol, a polycarbonate polyol, a polyacrylic polyol, an alkylene polyol, an epoxy resin polyol, a polyolefin polyol, a low molecular weight polyhydric alcohol, or a partially modified product thereof, or a combination thereof. The polyol A used in the present invention preferably includes a polyether polyol.

<<Polyether polyol>>
Examples of polyether polyols include polymers or copolymers obtained by combining alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran, styrene oxide, etc. Specific examples include polyoxyethylene diol (polyethylene glycol: PEG), polyoxypropylene diol (polypropylene glycol: PPG), polytetramethylene ether polyol (PTMEG), polyoxypropylene triol, ethylene oxide/propylene oxide copolymer (diol), ethylene oxide/propylene oxide copolymer (triol), etc.

<<Low molecular weight polyhydric alcohol>>
Examples of low molecular weight polyhydric alcohols include low molecular weight polyols such as ethylene glycol (EG), diethylene glycol, propylene glycol (PG), dipropylene glycol, (1,3- or 1,4-)butanediol, pentanediol, neopentyl glycol, hexanediol, cyclohexanedimethanol, glycerin, 1,1,1-trimethylolpropane (TMP), 1,2,5-hexanetriol, and pentaerythritol; and sugars such as sorbitol.

<<Polyester polyol>>
Examples of polyester polyols include condensation polyester polyols and lactone polyester polyols. Condensation polyester polyols are, for example, reaction products of the low molecular weight polyhydric alcohols and polybasic carboxylic acids (glutaric acid, adipic acid, azelaic acid, fumaric acid, maleic acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, dimer acid, pyromellitic acid, oligomer acid, etc.). Lactone polyester polyols are, for example, polycaprolactone polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone, α-methyl-ε-caprolactone, and ε-methyl-ε-caprolactone.

<<Polycarbonate polyol>>
Polycarbonate polyols are polyols obtained by reacting, for example, polyols (various saturated or unsaturated glycols such as 1,6-hexanediol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, octanediol, 1,4-butynediol, dipropylene glycol, tripropylene glycol, polytetramethylene ether glycol, and the like; alicyclic glycols such as 1,4-cyclohexanediglycol and 1,4-cyclohexanedimethanol, and the like) with dialkyl carbonates (dimethyl carbonate, diethyl carbonate, and the like), ethylene carbonate, diphenyl carbonate, and the like.

<<Polyacrylic polyol>>
Polyacrylic polyols can be obtained, for example, by copolymerizing a polymerizable acrylic monomer having one or more hydroxyl groups in one molecule with another monomer copolymerizable therewith (for example, another (meth)acrylic acid monomer and/or another unsaturated monomer). Specific examples of polyacrylic polyols include copolymers of a polymerizable acrylic monomer having one or more hydroxyl groups in one molecule with a vinyl monomer, and ring-opening polymerization adducts of a polymerizable acrylic monomer with lactones such as ε-caprolactone and γ-valerolactone. Examples of polymerizable acrylic monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypentyl (meth)acrylate, monoester of (meth)acrylic acid of glycerin, monoester of (meth)acrylic acid of trimethylolpropane, and 2-hydroxy-3-chloropropyl (meth)acrylate. Examples of vinyl monomers include monoesters of (meth)acrylic acid and glycols having 2 to 10 carbon atoms (hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, etc.), carboxyl group-containing vinyl monomers, amide vinyl monomers, glycidyl group-containing vinyl monomers, styrene and derivatives thereof, acrylonitrile, vinyl toluene, vinyl chloride, vinyl acetate, etc.

<<Alkylene polyol>>
Examples of alkylene polyols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 3,3-dimethylol heptane, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,18-octadecanediol, 2-hydroxystearyl alcohol, 12-hydroxystearyl alcohol, and 1,4-cyclohexanedimethano. glycerin, trimethylolpropane, pentaerythritol, 1,2,2-trimethyl-1,3-propanediol, 2,2-dimethyl-3-isopropyl-1,3-propanediol, 2,2-dimethyl-3-benzyl-1,3-propanediol, 2,2-dimethyl-3-isobutyl-1,3-propanediol, 2,2,3,3-tetramethyl-1,4-butanediol, 2,2,4-trimethyl-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, 2-hydroxypalmityl alcohol, 2,2-bis(4-hydroxycyclohexyl)propane (hydrogenated bisphenol A), and the like.

<<Polyolefin polyol>>
Examples of the polyolefin polyol include polyethylene polyols, polypropylene polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, polyisoprene polyols, and hydrogenated polyisoprene polyols.

<<Epoxy resin polyol>>
Examples of epoxy resin polyols include reaction products of diglycidyl compounds (bisphenol A type epoxy resins, bisphenol F type epoxy resins, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, etc.) with bisphenol compounds (bisphenol A, bisphenol F, biphenol, etc.), and/or polybasic carboxylic acids (glutaric acid, adipic acid, azelaic acid, fumaric acid, maleic acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, dimer acid, pyromellitic acid, oligomer acid, etc.), and/or polyamines (monomethylamine, monoethylamine, monopropylamine, monobutylamine, monomethanolamine, monoethanolamine, monopropanolamine, monobutanolamine, diaminomethane, diaminoethane, diaminopropane, diaminobutane, diaminopolyethylene oxide, diaminopolypropylene oxide, etc.).

<Other ingredients>
The base material may contain, in addition to polyol A as a constituent element of the urethane prepolymer, a polyamine compound as a compound having an active hydrogen group, and may also contain additives within the scope of not impairing the object of the present invention.

<<Polyamine Compounds>>
Examples of the polyamine compound include aliphatic polyamines (ethylenediamine, propylenediamine, butylenediamine, diethylenetriamine, diethylaminopropylamine, triethylenetetramine, etc.), aromatic polyamines (diaminodiphenylmethane, diaminodiphenylsulfone, benzidine, etc.), polyether polyamines (polyoxypropylenediamine, etc.), etc. Since amines are highly toxic, in the present invention, the content of the polyamine compound is preferably 0.1 mol % or less, more preferably 0.01 mol % or less, based on the polyol A, and further preferably no polyamine compound is contained.

<<Additives>>
Examples of the additives include additives commonly used in urethane adhesives, such as fillers (silica such as fumed silica and calcined silica, diatomaceous earth, talc, magnesium oxide, calcium carbonate, heavy calcium carbonate, calcined clay, carbon black, etc.), plasticizers (diisononyl phthalate, dioctyl adipate, isodecyl succinate, diethylene glycol dibenzoate, pentaerythritol esters, etc.), antioxidants (hindered phenol compounds, etc.), antioxidants (butylhydroxytoluene, butylhydroxyanisole, etc.), ultraviolet absorbers, flame retardants, surfactants, dispersants, dehydrating agents, adhesion promoters (phenolic resins, rosin resins, etc.), and antistatic agents (quaternary ammonium salts; polyglycols, ethylene oxide derivatives, etc.).

<Preparation of Base Urethane Prepolymer>
The amounts of polyisocyanate and polyol A in the base urethane prepolymer are preferably such that the isocyanate groups in the polyisocyanate are in excess relative to the hydroxyl groups in the polyol A. The polyol A and polyisocyanate are mixed so that the equivalent ratio of the isocyanate groups in the polyisocyanate to the hydroxyl groups in the polyol A (isocyanate groups/hydroxyl groups) is preferably 1.5 to 5.0, more preferably 2.5 to 4.0, and reacted at 50 to 110°C for 4 to 20 hours, more preferably 70 to 100°C for 6 to 12 hours. By the reaction between the polyisocyanate and polyol A, preferably all of the polyol A reacts to form a urethane prepolymer. In the obtained base, unreacted polyisocyanate is preferably present as residual polyisocyanate. The base may contain residual polyisocyanate in addition to the urethane prepolymer. The content of isocyanate groups (NCO %: weight %) in the base resin obtained by reacting polyisocyanate with polyol A is preferably 2.0 to 15.0%, more preferably 4.0 to 12.0%, when measured by a method in accordance with JIS K-1603-1: 2007. By controlling the content of isocyanate groups within the above range, the obtained adhesive cured product can achieve high adhesive strength and high elastic modulus.

(Hardening agent)
The curing agent contains a glycerol ester polyol having a methylol group. The glycerol ester polyol having a methylol group reacts quickly with the urethane prepolymer and the remaining unreacted polyisocyanate in the base resin to form a cured product.

<Glycerol ester polyol>
The glycerol ester polyol used in the present invention contains a methylol group in the molecule. That is, the glycerol ester polyol used in the present invention contains a compound represented by the following formula (1), and the content of fatty acid residues derived from oleic acid in the glycerol ester polyol is 70 mol % or more based on the total amount of fatty acid residues in the glycerol ester polyol.

(One of _X1 and _X2 is hydrogen and the other is a methylol group;
One of _X3 and _X4 is hydrogen and the other is a methylol group;
One of _X5 and _X6 is hydrogen and the other is a methylol group.

The glycerol ester-based polyol used in the present invention may further contain a compound represented by the following formula (2-1) and/or formula (2-2).

(One of _X1 and _X2 is hydrogen and the other is a methylol group;
One of _X3 and _X4 is hydrogen and the other is a methylol group;
One of _X5 and _X6 is hydrogen and the other is a methylol group;
R and R' are each independently a residue of an unsaturated or saturated fatty acid other than the group represented by the following formula (3), or hydrogen.

(One of the pair of _Y1 and _Y2 is hydrogen and the other is a methylol group, and * is a bond.)

R and R' in formula (3) are unsaturated fatty acids (e.g., myristoleic acid, palmitoleic acid, sapienic acid, elaidic acid, vaccenic acid, petroselinic acid, eicosene (gondoin) acid, paulic acid, gadoleic acid, erucic acid, brassidic acid, nervonic acid, hexadecatrienoic acid, linoleic acid, linoleelaidic acid, α-linolenic acid, pinolenic acid, stearidonic acid, eicosadienoic acid, mead acid, eicosatrienoic acid, α-linolenic acid, γ-linolenic acid, dihomo-γ-linolenic acid, podocarpic acid, arachidonic acid, eicosatetraenoic acid, Examples of fatty acid residues represented by R and R' include fatty acid residues derived from saturated fatty acids (e.g., palmitic acid, stearic acid, lauric acid, myristic acid, caproic acid, caprylic acid, capric acid, arachidic acid, behenic acid, or lignocerin), or hydrogen, but the fatty acid residues represented by R and R' are not limited to those exemplified above.

The content of fatty acid residues derived from oleic acid in the glycerol ester polyol is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, based on the total amount of fatty acid residues in the glycerol ester polyol (i.e., when the total amount of fatty acid residues in the glycerol ester polyol is 100 mol%). In addition, the amount of triacylglycerol represented by the above formula (1) and triacylglycerol and/or diacylglycerol represented by the above formulas (2-1) and (2-2) in the glycerol ester polyol is preferably 80 mol% or more, more preferably 90 mol% or more, based on the total amount of the glycerol ester polyol.

The glycerol ester polyol used in the present invention has a high content of oleic acid residues and is highly regular. In addition, since it has a primary hydroxyl group (methylol group) in the molecule, it has high reactivity (curability) with isocyanate groups. Therefore, it can bond (cure) quickly without using a reaction accelerator (tertiary amine, etc.) or a curing catalyst (metal catalyst, amine catalyst, etc.).

<Other ingredients>
The curing agent may contain other polyols, polyamine compounds, additives, etc. other than the glycerol ester polyols represented by formula (1), formula (2-1) and formula (2-2) within the scope of the present invention. Examples of the other polyols include polyols that can be used in the polyol A. Examples of polyamine compounds include compounds similar to the polyamine compounds that can be used in the base agent, but since amines are highly toxic, the polyamine compound in the curing agent is preferably 0.1 mol% or less, more preferably 0.01 mol% or less, relative to the glycerol ester polyol, and more preferably the curing agent does not contain any polyamine compound at all. In addition, the additives can be the same as the additives that can be used in the base agent.

<Preparation of Curing Agent>
The glycerol ester polyol in the curing agent is blended so that the equivalent ratio of the isocyanate groups in the base resin to the hydroxyl groups of the glycerol ester polyol in the curing agent (isocyanate groups/hydroxyl groups) is preferably 0.3 to 3.0, more preferably 0.5 to 2.0. If the amount of isocyanate groups relative to the amount of hydroxyl groups of the glycerol ester polyol exceeds the above range, the elastic modulus of the adhesive tends to decrease, and if the amount of isocyanate groups relative to the amount of hydroxyl groups in the curing agent decreases beyond the above range, the adhesive strength tends to decrease.

<<When using other polyols in combination with the curing agent>>
When a polyol other than the above glycerol ester polyol is used in the curing agent, the equivalent ratio (isocyanate group/hydroxyl group) of the isocyanate group in the base material to the hydroxyl group in the curing agent (the combined hydroxyl groups of the glycerol ester polyol and the other polyol) is preferably 0.3 to 3.0, more preferably 0.5 to 2.0. If the amount of isocyanate groups relative to the amount of hydroxyl groups in the curing agent exceeds the above range, the elastic modulus of the adhesive tends to decrease, and if the amount of isocyanate groups relative to the amount of hydroxyl groups in the curing agent decreases beyond the above range, the adhesive strength tends to decrease.

<Synthesis of glycerol ester polyol>
The raw material glycerol ester having an unsaturated fatty acid residue is hydroformylated and then hydrogenated to introduce a primary hydroxyl group (methylol group) into the carbon-carbon double bond of the unsaturated fatty acid residue, thereby producing a glycerol ester polyol.

The glycerol ester used as a raw material for the hardener contains at least one carbon-carbon double bond in the fatty acid residue. In the glycerol ester, preferably, two fatty acid residues are oleic acid residues, and more preferably, three fatty acid residues are oleic acid residues. The glycerol ester used in the present invention may contain triacylglycerol and/or diacylglycerol derived from a diolein compound other than triolein. The content of fatty acid residues derived from oleic acid in the glycerol ester used in the present invention is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more based on the total amount of fatty acid residues in the glycerol ester. The glycerol ester used in the present invention is obtained, for example, from triolein, olive oil, high oleic acid safflower oil, high oleic acid camellia oil, algae-derived high oleic acid oils and fats, or a combination of one or more of these, but is not limited thereto. In the present invention, the glycerol ester used as a raw material is preferably non-petroleum-derived. Non-petroleum-derived raw materials include bio-derived raw materials.
Here, bio refers to biological resources such as animals, plants, and microorganisms. Microorganisms are a general term for microscopic organisms. In this specification, microorganisms include eukaryotes such as unicellular algae (including microalgae) and eukaryotic fungi (molds and yeasts), and prokaryotes such as blue-green algae and bacteria.
Among microalgae, one or more of the following genera and species are preferably used for producing glycerol esters. Examples of microalgae include Chlorella species, Pseudochlorella species, Heterochlorella species, Prototheca species, Arthrospira species, Euglena species, Nannochloropsis species, Phaeodactylum species, Chlamydomonas species, Scenedesmus species, Ostreococcus species, Selenastru species, and the like. Examples of species that may be included include those of the genera Amphibian, Bacteroides, and Clostridium species, such as Amphibians, Amphibians, and Clostridium species, and include those of the genera Amphibian, Amphibians ...
Among yeasts, one or more of the following genera and species are preferably used for producing glycerol esters: Yeasts include, for example, Candida species, Cryptococcus species, Debaromyces species, Endomycopsis species, Geotrichum species, Hyphopichia species, Lipomyces species, Pichia species, Rodosporidium species, Rhodotorula species, Sporobolomyces species, Starmerella species, Torulaspora species, Trichosporon species, Wickerhamomyces species, Yarrowia species, and Zygoascus species.
Among bacteria, one or more of the following genera and species are preferably used to produce glycerol esters: Examples of bacteria include Flavimonas oryzihabitans, Pseudomonas aeruginosa, Morococcus species, Rhodobacter sphaeroides, Rhodococcus opacus, Rhodococcus erythropolis, Streptomyces jeddahensis, Ochrobactrum species, Arthrobacter species, Nocardia species, Mycobacteria species, Gordonia species, Catenisphaera species, and Dietzia species.

Hydroformylation is, for example, the reaction of a glycerol ester having an unsaturated fatty acid residue with carbon monoxide and hydrogen, resulting in the addition of a formyl (CHO) group and hydrogen to the carbon-carbon double bond of the unsaturated fatty acid residue. Hydroformylation can be carried out, for example, by pressurizing a reaction vessel containing the glycerol ester and a catalyst to about 500 psi to about 1500 psi with a synthesis gas of carbon monoxide and hydrogen, and reacting at a temperature of about 40°C to about 200°C for about 1 hour to about 10 hours.

Catalysts for hydroformylation include cobalt-based catalysts (hydridotetracarbonylcobalt catalysts, cobalt phosphine catalysts, cobalt catalysts supplemented with precious metals (e.g., palladium, ruthenium, or platinum), etc.), rhodium-based catalysts (e.g., rhodium phosphine catalysts, acetylacetonato-dicarbonylrhodium(I) (Rh(CO) ₂ acac) catalysts, rhodium/cyclohexyldiphenylphosphine (Rh/CHDPP) catalysts, etc.), and any other transition metal-based catalysts suitable for hydroformylation.

Next, the formyl (CHO) group of the hydroformylated triacylglycerol is reduced to a primary alcohol (methylol group) with hydrogen in the presence of a hydrogenation catalyst. Hydrogenation can be carried out, for example, by reacting at a pressure of about 500 psi to about 1500 psi and at a temperature of about 40°C to about 250°C for about 1 hour to about 10 hours.

The hydrogenation catalyst may be a general hydrogenation catalyst, such as Raney nickel (sponge nickel), Urushibara nickel, nickel, palladium, platinum, rhodium, ruthenium, etc.

(Curing reaction)
Since the adhesive of the present invention is a two-component curing adhesive, the base agent and the curing agent are mixed when used, and a curing reaction occurs to bond the adhesive. The glycerol ester polyol used as the curing agent has a primary hydroxyl group (methylol group) and reacts quickly with the isocyanate group, so no reaction accelerator or curing catalyst is required for the curing reaction. The curing performance of the two-component curing adhesive of the present invention is based on an appropriate combination of the base agent and the curing agent. For example, it is based on an appropriate selection of the polyol A and polyisocyanate of the base agent, an appropriate selection of the glycerol ester polyol of the curing agent, and an appropriate mixing ratio of the polyisocyanate and polyol A, and the polyisocyanate and the glycerol ester polyol.

The present invention will be described in more detail below with reference to examples. However, the examples are merely illustrative of the present invention and the present invention is not limited to these examples.

<Synthesis of glycerol ester polyol>
(Synthesis Example 1) Synthesis of Polyol 1 100 g of olive oil (oleic acid content: 75 mol%, iodine value: 80), 0.1 g of (acetylacetonato)dicarbonium rhodium (I) (Sigma-Aldrich) as a catalyst, and 0.5 g of triphenylphosphine (Tokyo Chemical Industry Co., Ltd.) as a ligand were put into a stainless steel high-pressure reaction vessel equipped with a temperature regulator, a gas filling terminal, and a stirrer, and then the system was replaced with synthetic gas (carbon monoxide and hydrogen). Stirring was started and the temperature was raised to 90°C, and then the system was pressurized to 1000 psi with synthetic gas and reacted for 6 hours. After cooling to room temperature, the synthetic gas was discharged. Next, 50 ml of isopropanol and 10 g of Raney nickel were put in, and then the system was replaced with hydrogen gas. Stirring was started and the temperature was raised to 110°C, and then the system was pressurized to 1000 psi with hydrogen gas and reacted for 5 hours. After cooling to room temperature and discharging the gas in the system, 22 ml of isopropanol was added, stirred and mixed, and then filtered and purified. The filtrate was concentrated under reduced pressure, and 20 ml of 5% dilute hydrochloric acid was added and stirred and washed, and then the aqueous phase was removed. The mixture was further stirred and washed twice with 10 ml of ion-exchanged water, and the oil phase was dried under reduced pressure. The obtained polyol 1 had a hydroxyl value of 154 mgKOH/g and a viscosity of 1700 mPa·s.

(Synthesis Examples 2 to 6) Synthesis of Polyols 2 to 6 Polyols 2 to 6 were synthesized in the same manner as in Synthesis Example 1, except that the oils and fats shown in Table 1 were used instead of the olive oil in Synthesis Example 1 (Sigma-Aldrich reagent was used for triolein). The results are shown in Table 1.

*Oleic acid content was quantified using LC/CAD.

The structures of Polyols 1 to 6 obtained in Synthesis Examples 1 to 6 are shown below.

Comparative Synthesis Examples 1 and 2: Synthesis of Comparative Polyols 1 and 2 Comparative polyols 1 and 2 were synthesized in the same manner as in Synthesis Example 1, except that the oils and fats shown in Table 3 were used instead of the olive oil in Synthesis Example 1. The results are shown in Table 3.

<Preparation of Curing Agent>
Preparation Example 1 Preparation of Polyol Curing Agent (1) Polyol 1 (667 parts by mass), fumed silica (AEROSIL (registered trademark) 200 manufactured by EVONIC Corporation) (10 parts by mass), and calcium carbonate ( _CaCO3 ) (light calcium carbonate manufactured by Omi Chemical Industry Co., Ltd.) (323 parts by mass) were charged into a container and thoroughly stirred and mixed with a disper until no solid content remained, and then the mixture was degassed in vacuum to obtain a white polyol curing agent (1).

Preparation Examples 2 to 6: Preparation of polyol curing agents (2) to (6) Polyol curing agents (2) to (6) were obtained in the same manner as in Preparation Example 1, except that polyols 2 to 6 were used instead of polyol 1. The blending compositions are shown in Table 4.

(Comparative Preparation Examples 1 to 5) Preparation of Comparative Curing Agents (1) to (5) Comparative curing agents (1) to (5) were prepared in the same manner as in Preparation Example 1, except that Comparative Polyol 1 to Comparative Polyol 2, Actocol (registered trademark) T-1000 (polypropylene glycol manufactured by Mitsui Chemicals, Inc., hydroxyl value: 164 mg KOH / g), PTMG-650 (polytetramethylene glycol manufactured by Mitsubishi Chemical Corporation, hydroxyl value: 172 mg KOH / g), and castor oil (castor oil HS2G-160R manufactured by Toyokuni Oil Mills, Ltd., hydroxyl value: 158 mg KOH / g) were used instead of Polyol 1. The comparative curing agents (1) to (5) were prepared in the same manner as in Preparation Example 1. The blending compositions are shown in Table 5.

<Preparation of base agent>
(Synthesis Example 7) Synthesis of urethane prepolymer (1) In a flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet tube, Millionate MT (MDI: diphenylmethane diisocyanate, NCO%: 33.2%) (363 parts by mass) manufactured by Tosoh Corporation was charged under a nitrogen atmosphere and heated to 70°C, the MDI was melted, stirring was started, and at the same temperature, polyoxypropylene polymer (Actocol (registered trademark) T-2000, Mw: 2000, number of functional groups: 3) (637 parts by mass) manufactured by Mitsui Chemicals, Inc. was charged in portions over 2 hours. The temperature in the system was raised to 80°C, and the reaction was carried out for 6 hours to obtain urethane prepolymer (1). The NCO% of the obtained urethane prepolymer (1) was 8.0%.

(Synthesis Examples 8 to 9) Synthesis of Urethane Prepolymers (2) to (3) Urethane prepolymers (2) to (3) were obtained in the same manner as in Synthesis Example 7, except that the polyols and polyisocyanates shown in Table 6 below were used instead of Actocol (registered trademark) T-2000 and Millionate MT. The blend compositions are shown in Table 6.

Actocol T-1000: Actocol (registered trademark) T-1000 (Mw: 1000, number of functional groups: 3) (PP polyol manufactured by Mitsui Chemicals, Inc.)
Actocol T-2000: Actocol (registered trademark) T-2000 (Mw: 2000, number of functional groups: 3) (PP polyol manufactured by Mitsui Chemicals, Inc.)
Actocol ED-56: Actocol (registered trademark) ED-56 (Mw: 2000, number of functional groups: 2) (PE-PP polyol manufactured by Mitsui Chemicals, Inc.)
Millionate MT (MDI: diphenylmethane diisocyanate, NCO%: 33.2) (manufactured by Tosoh Corporation)
Coronate 1391 (MDI-based polyisocyanate, NCO%: 33.2) (manufactured by Tosoh Corporation)

<Evaluation method>
<<Tensile shear test>>
The tensile shear strength was measured at 25° C. using an AUTOGRAPH AG-XPlus 100 kN (manufactured by Shimadzu Corporation) according to a method in accordance with JIS K6859 (creep rupture test for adhesives).

<<Confirmation of molecular structure by LC/CAD>>
The polyol 5 prepared in Synthesis Example 5 was measured by LC/CAD (UltiMate3000RS/CoronaVeo (Thermo) (manufactured by Thermo Fisher Scientific)) to identify the molecular structure.

<Two-component curing adhesive>
(Example 1) Preparation and evaluation of adhesive 1 Preparation and application of adhesive 1 were performed using a two-liquid micro-metering mixer with a heating device and a static mixer nozzle. The adhesive 1 was obtained from a vacuum-defoamed urethane prepolymer (1) and a polyol curing agent (1), with a mixing mass ratio of 1/1 (isocyanate group/hydroxyl group equivalent ratio: 1/1) and a mixing temperature of 50°C. The adhesive thus prepared was evaluated for adhesive strength by tensile shear strength, and the drying time (curing speed) was evaluated by the ratio of the tensile shear strength after 1 day to the tensile shear strength after 7 days of curing, which was taken as 100%. The results are shown in Table 7.

(Examples 2 to 7) Preparation and evaluation of adhesives 2 to 7 Instead of the combination of polyol curing agent (1)/urethane prepolymer (1) in Example 1, the combination of polyol curing agent (2)/urethane prepolymer (2), polyol curing agent (3)/urethane prepolymer (3), polyol curing agent (4)/urethane prepolymer (1), polyol curing agent (5)/urethane prepolymer (1), polyol curing agent (6)/urethane prepolymer (1), or polyol curing agent (6)/D-750-45* was used. The drying time (curing speed) and adhesive strength were evaluated using adhesives 2 to 7 prepared in the same manner as in Example 1. The results are shown in Table 7.
*D-750-45: Burnock D-750-45 (tolylene diisocyanate adduct type polyisocyanate manufactured by DIC Corporation, NCO%: 7.9%)

Comparative Examples 1 to 5: Preparation and Evaluation of Comparative Adhesives 1 to 5 The drying time (curing speed) and adhesive strength were evaluated using comparative adhesives 1 to 5 prepared in the same manner as in Example 1, except that the combination of comparative curing agent (1)/urethane prepolymer (1), comparative curing agent (2)/urethane prepolymer (1), comparative curing agent (3)/urethane prepolymer (1), comparative curing agent (4)/urethane prepolymer (1), or comparative curing agent (5)/urethane prepolymer (1) was used instead of the combination of polyol curing agent (1)/urethane prepolymer (1) in Example 1. The results are shown in Table 8.

The adhesives of the present invention using polyols 1 to 6 had a tensile shear strength of 19 to 25 MPa after 7 days when completely cured, and a ratio of the tensile shear strength after 1 day to the tensile shear strength after 7 days taken as 100% was 79 to 92%, which was significantly improved in adhesive strength and curing speed compared to comparative adhesives using comparative polyol 1 (comparative curing agent 1) derived from soybeans with a low oleic acid content, comparative polyol 2 (comparative curing agent 2) derived from rapeseed oil, and polypropylene glycol (comparative curing agent 3), polytetramethylene glycol (comparative curing agent 4), or castor oil (comparative curing agent 5) (tensile shear strength after 7 days: 5 to 11 MPa, ratio of tensile shear strength after 1 day to the tensile shear strength after 7 days taken as 100%: 57 to 73%).

Claims (9)

A two-component curing adhesive comprising a base material containing an isocyanate group- containing urethane prepolymer obtained by reacting a polyisocyanate with a polyol A, and a curing agent containing a glycerol ester polyol ,
The glycerol ester polyol contains a compound represented by the following formula (1):
A two-component curing adhesive, wherein the content of fatty acid residues derived from oleic acid in the glycerol ester polyol is 70 mol % or more based on the total amount of fatty acid residues in the glycerol ester polyol.
(One of _X1 and _X2 is hydrogen and the other is a methylol group;
One of _X3 and _X4 is hydrogen and the other is a methylol group;
One of _X5 and _X6 is hydrogen and the other is a methylol group. The two-component curing adhesive according to claim 1, wherein the content (NCO%) of isocyanate groups in the base resin is in the range of 2.0 to 15.0%. The two-component curing adhesive according to claim 1, wherein the glycerol ester polyol further contains a compound represented by the following formula (2-1) and/or formula (2-2):

(One of _X1 and _X2 is hydrogen and the other is a methylol group;
One of _X3 and _X4 is hydrogen and the other is a methylol group;
One of _X5 and _X6 is hydrogen and the other is a methylol group;
R and R' are each independently a residue of an unsaturated or saturated fatty acid other than the group represented by the following formula (3), or hydrogen.
(One of the pair of _Y1 and _Y2 is hydrogen and the other is a methylol group, and * is a bond.) The two-component curing adhesive according to claim 1, wherein the polyol A comprises at least one selected from the group consisting of polyether polyols, polyester polyols, polyacrylic polyols, polyolefin polyols, polycarbonate polyols, epoxy resin polyols, low molecular weight polyhydric alcohols, and partially modified products thereof. The two-component curing adhesive according to claim 1, wherein the polyisocyanate comprises at least one selected from the group consisting of diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, modified diphenylmethane diisocyanate, tolylene diisocyanate, an adduct type polyisocyanate made of tolylene diisocyanate and a polyhydric alcohol, a nurate type polyisocyanate of tolylene diisocyanate, and an allophanate type polyisocyanate obtained from tolylene diisocyanate and an alcohol. The two-component curing adhesive according to claim 1, wherein the urethane prepolymer is obtained by reacting at least one selected from diphenylmethane diisocyanate and tolylene diisocyanate with a polyether polyol. The two-component curing adhesive according to claim 1, wherein the equivalent ratio (isocyanate group/hydroxyl group) of the isocyanate group in the base agent to the hydroxyl group of the glycerol ester polyol in the curing agent is 0.3 to 3.0. The two-component curing adhesive according to claim 1, wherein the glycerol ester polyol is obtained from at least one selected from the group consisting of triolein, olive oil, high oleic acid safflower oil, high oleic acid camellia oil, and algae-derived high oleic acid oils and fats. A two-component curing adhesive according to any one of claims 1 to 8, in which the shear strength when completely cured is 15 MPa or more when measured according to a method conforming to JIS K6859, and the ratio of the shear strength 1 day after the curing reaction to the shear strength 7 days after the curing reaction is 100% is 75% or more.

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