JP2009096996A - Main agent for adhesives and production method thereof, composition for preparing urethane resin-based adhesive, and method for production of urethane resin-based adhesives - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive having advantageous compatibility with acrylic adhesives and having removability which is hardly lowered even when the adhesive is aged in a high temperature atmosphere. <P>SOLUTION: This urethane resin-based adhesive is produced by a method including: ring-opening polymerizing an initiator (a) with a dicarboxylic anhydride (b) and an alkylene oxide (c) to obtain a polyester ether polyol (Z); reacting a polyol (A) containing the polyester ether polyol (Z) with a polyisocyanate (B1) to obtain an isocyanate group-terminal prepolymer (UI); reacting the isocyanate group-terminated prepolymer (UI) with a chain extender (C) having three or more active hydrogen groups having reactivities different from each other to obtain an acive hydrogen group-containing chain-extended polyurethane (UIH); and reacting a main agent for adhesives containing the acive hydrogen group-containing chain-extended polyurethane (UIH) with a curing agent containing a second polycyanate (B2). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pressure sensitive adhesive main agent containing a specific active hydrogen group-containing polyurethane, a method for producing the same, a urethane resin pressure sensitive adhesive production composition using the pressure sensitive adhesive main agent, and a method for producing a urethane resin pressure sensitive adhesive. About.

An adhesive having removability (hereinafter also referred to as a removable adhesive) is used for industrial products, daily necessities and the like. Acrylic pressure-sensitive adhesives are widely used as re-peelable pressure-sensitive adhesives. In recent years, urethane resin-based products obtained by reacting these with a urethane resin as the main component and a polyisocyanate compound as a crosslinking agent (curing agent). Adhesives have also been used. Examples of the urethane resin as the main agent include a urethane resin having an ether group and an ester group obtained by reacting a polyether polyol and a polyester polyol with isocyanate using two types of catalysts (see Patent Document 1), a polyol, and the like. An isocyanate group-terminated urethane prepolymer obtained by reacting with a polyisocyanate has been proposed by reacting a chain extender having three or more functional groups that react with an isocyanate group (see Patent Document 2). . These urethane resins have a terminal hydroxyl group or a chain extender-derived functional group that did not react with the isocyanate group-terminated urethane prepolymer in a chain extension reaction. By cross-linking with this cross-linking agent, the cohesive force is increased and the removability is expressed.
Patent Document 3 discloses a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive and a urethane elastomer.
JP 2000-256630 A JP 2003-12751 A JP 2005-194366 A

However, the urethane resin-based adhesives described in Patent Document 1 and Patent Document 2 increase in adhesive strength over time, and as a result, re-peelability may decrease or peel strength may increase. . In particular, the increase in adhesive strength becomes remarkable under high temperature conditions, and improvement in heat resistance is required.
Moreover, as proposed in Patent Document 3, blending acrylic adhesive and urethane resin can be expected to improve the heat resistance of urethane adhesive and impart flexibility to acrylic adhesive. There is a problem that the amount of the urethane resin added cannot be increased due to the poor compatibility.

  The present invention has a good compatibility with acrylic pressure-sensitive adhesive, has removability, and has good heat resistance, and can realize a pressure-sensitive adhesive that does not easily decrease removability over time at high temperatures. It aims at providing the main ingredient for adhesives, its manufacturing method, and the manufacturing method of urethane resin system adhesive.

The present invention includes the following configurations.
[1] A structural unit derived from an initiator (a) having two or more functional groups per molecule, a structural unit derived from a dicarboxylic anhydride (b), and a structural unit derived from an alkylene oxide (c) An active hydrogen group-containing polyurethane having a residue of a polyester ether polyol (Z) and a residue of a polyisocyanate (B1).
[2] In the above [1], the active hydrogen group-containing polyurethane further has a residue of a chain extender (C), and at least a part of the active hydrogen groups present in the active hydrogen group-containing polyurethane. Is a main agent for pressure-sensitive adhesives, which is an active hydrogen group bonded to the residue of the chain extender (C).
[3] The adhesive main agent according to [1], wherein in the active hydrogen group-containing polyurethane, the active hydrogen group is a hydroxyl group bonded to a residue of the polyester ether polyol (Z).

[4] A step of obtaining a polyester ether polyol (Z) by ring-opening polymerization of a mixture of a dicarboxylic acid anhydride (b) and an alkylene oxide (c) to an initiator (a) having two or more hydroxyl groups per molecule. When,
A step of reacting a polyol (A) containing a polyester ether polyol (Z) with a polyisocyanate (B1) to obtain an isocyanate group-terminated prepolymer (UI);
A method for producing a main agent for pressure-sensitive adhesives, comprising a step of obtaining a chain-extended polyurethane (UIH) having an active hydrogen group by reacting the isocyanate group-terminated prepolymer (UI) with a chain extender (C).
[5] In the above [4], the chain extender is preferably one or more compounds selected from the group consisting of the following compound (C1) and the following compound (C2).
(C1) One or two active hydrogen groups having three or more active hydrogen groups, two of which are selected from the group consisting of a primary amino group, a secondary amino group, and a primary hydroxyl group A compound which is a hydrogen group and the remaining active hydrogen groups are one or more active hydrogen groups selected from the group consisting of secondary hydroxyl groups, tertiary hydroxyl groups and carboxy groups.
(C2) having 3 or more active hydrogen groups, and two of these active hydrogen groups are one or two active hydrogen groups selected from the group consisting of a primary amino group and a secondary amino group; A compound in which the remaining active hydrogen groups are primary hydroxyl groups.
[6] In the above [4] or [5], the isocyanate group-terminated prepolymer (UI) preferably has a weight average molecular weight of 4,000 to 40,000.

[7] A step of obtaining a polyester ether polyol (Z) by ring-opening polymerization of a mixture of a dicarboxylic acid anhydride (b) and an alkylene oxide (c) to an initiator (a) having two or more hydroxyl groups per molecule. And a polyol (A) containing a polyester ether polyol (Z) and a polyisocyanate (B1) to react to obtain a hydroxyl group-terminated urethane polymer (UH).
[8] In the above [7], the hydroxyl group-terminated urethane polymer (UH) preferably has a weight average molecular weight of 40,000 to 100,000.

[9] In the above [4] to [8], it is preferable that 10 to 50% by mass of a structural unit derived from the dicarboxylic acid anhydride (b) is contained in the polyester ether polyol (Z).
[10] In [4] to [9], the polyisocyanate (B1) is selected from the group consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. It is preferable that it is a seed or more.

[11] A composition for producing a urethane resin-based pressure-sensitive adhesive, comprising the main agent for pressure-sensitive adhesives of [1] to [3] and a curing agent containing a second polyisocyanate (B2).
[12] The composition for producing a urethane resin-based pressure-sensitive adhesive according to [11], wherein the second polyisocyanate (B2) has an average number of functional groups larger than 2.
[13] A step of producing an adhesive main agent by the method of [4] to [10], and a step of reacting the adhesive main agent and a curing agent containing the second polyisocyanate (B2). A method for producing a urethane resin-based pressure sensitive adhesive.
[14] In the above [13], it is preferable that the average number of functional groups of the second polyisocyanate (B2) is larger than 2.

According to the main agent for pressure-sensitive adhesives and the method for producing the same according to the present invention, by using the main agent for pressure-sensitive adhesives, the compatibility with the acrylic pressure-sensitive adhesive is good, the removability is good, and the heat resistance is good and the heating is performed. It is possible to realize a pressure-sensitive adhesive whose removability does not easily deteriorate even when time passes under the conditions.
The urethane resin-based pressure-sensitive adhesive of the present invention can be obtained by reacting the main component for pressure-sensitive adhesives in this composition with the curing agent.
The urethane resin-based pressure-sensitive adhesive of the present invention has good compatibility with acrylic pressure-sensitive adhesives, has removability, and re-peelability hardly changes over time under heating conditions, and has heat resistance. It is good.

The manufacturing method of the adhesive of this invention has the process of making the main ingredient for adhesives containing an active hydrogen group containing polyurethane react with the hardening | curing agent containing 2nd polyisocyanate (B2). By this reaction, a polyurethane (urethane resin-based adhesive) having adhesiveness that can be removed again is obtained. The composition for producing a urethane resin-based pressure-sensitive adhesive of the present invention is a composition for producing a urethane resin-based pressure-sensitive adhesive containing the main agent for pressure-sensitive adhesive and a curing agent.
The active hydrogen group in the present invention means a group containing an active hydrogen atom that can react with an isocyanate group. Examples of the active hydrogen group include a primary amino group, a secondary amino group, a hydroxyl group, a carboxyl group, and a mercapto group. Of these, a functional group selected from the group consisting of a primary amino group, a secondary amino group, and a hydroxyl group is more preferable. The reactivity of the active hydrogen group with the isocyanate group is, in descending order of reactivity, primary amino group> secondary amino group> primary hydroxyl group> secondary hydroxyl group> tertiary hydroxyl group. The carboxyl group is less reactive than the primary hydroxyl group. Therefore, by utilizing this difference in reactivity, in a reaction between a compound having a plurality of active hydrogen groups having different reactivities and a polyisocyanate, an active hydrogen group having a low reactivity among active hydrogen groups is reacted with an isocyanate group. In addition, a reactive product having a free active hydrogen group can be obtained by reacting a highly reactive active hydrogen group with an isocyanate group.
As the active hydrogen group-containing polyurethane contained in the main agent for the pressure-sensitive adhesive, chain-extended polyurethane (UIH) or hydroxyl group-terminated urethane polymer (UH) is used.
The chain-extended polyurethane (UIH) is obtained by reacting the polyol (A) and the polyisocyanate (B1) in an excess ratio of isocyanate groups to form an isocyanate group-terminated prepolymer (UI), and then the isocyanate group-terminated prepolymer (UI). ) With a chain extender (C) and, if necessary, a terminal terminator (D). In this case, as the chain extender (C), it is preferable to use a compound having three or more active hydrogen groups having at least two different reactivities. The active hydrogen group of the chain extender (C) usually has two active hydrogen groups in order from the highly reactive active hydrogen group, reacting with the isocyanate group of the prepolymer (UI), and the activity having relatively low reactivity. Hydrogen groups remain as active hydrogen groups in the active hydrogen group-containing polyurethane.
The hydroxyl group-terminated urethane polymer (UH) is obtained by reacting the polyol (A) with the polyisocyanate (B1) at a ratio of excess hydroxyl group.
An embodiment using the former chain-extended polyurethane (UIH) will be described as a first embodiment, and an embodiment using the latter hydroxyl-terminated urethane polymer (UH) will be described as a second embodiment.

[First embodiment]
[Polyol (A) / Polyester ether polyol (Z)]
The polyol (A) contains a specific polyester ether polyol (Z) as part or all of it. “Polyester ether polyol” refers to a polyol having both an ester bond and an ether bond. The polyester ether polyol (Z) in the present invention is obtained by ring-opening polymerization of a mixture of a dicarboxylic acid anhydride (b) and an alkylene oxide (c) to an initiator (a). The initiator (a) A structural unit derived from the dicarboxylic acid anhydride (b), and a structural unit derived from the alkylene oxide (c). When such polyester ether polyol (Z) is used, the flexibility of the urethane resin-based pressure-sensitive adhesive can be further increased, and the removability is less likely to be lowered. The structural unit derived from the initiator (a) refers to a residue obtained by removing the functional group (usually a hydroxyl group) from the initiator (a), and the structural unit derived from the dicarboxylic acid anhydride (b). A divalent group in which the dicarboxylic acid anhydride (b) is opened is referred to, and the structural unit derived from the alkylene oxide (c) is a divalent group in which the alkylene oxide (c) is opened. The residue of the polyol (A) or the polyester ether polyol (Z) refers to a polyvalent group obtained by removing the terminal hydroxyl group from the polyol (A) or the polyester ether polyol (Z).

[Initiator (a)]
The initiator (a) is a compound having two or more functional groups per molecule, and the functional group is a functional group capable of ring-opening addition of the dicarboxylic acid anhydride (b) and the alkylene oxide (c). This functional group is a group equivalent to the active hydrogen group, and a hydroxyl group is particularly preferable. Examples of the initiator (a) include polyether polyols and polyhydric alcohols. The number of the functional groups per molecule of the initiator (a) is preferably 2 to 4, and more preferably 2 or 3. As the initiator (a), polyhydric alcohols may be used as they are, and further polyether polyols obtained by adding alkylene oxide to polyhydric alcohols may be used.
The polyether polyol is a compound having a molecular weight of 300 to 4000 per hydroxyl group, which is obtained by adding an alkylene oxide to polyhydric alcohols. In the case of using a double metal cyanide complex catalyst as a catalyst in the production of the polyester ether polyol (Z) described later, it is preferable to use a polyether polyol as the initiator (a), and more preferable to use a polyether diol. preferable.
Examples of the polyhydric alcohols include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,4-butanediol, and glycerin.
The alkylene oxide is preferably an alkylene oxide having 2 to 4 carbon atoms, and examples thereof include propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, and ethylene oxide. Alkylene oxide may use only 1 type, or may use 2 or more types together. The alkylene oxide is preferably ethylene oxide or propylene oxide, and more preferably only propylene oxide.

  The molecular weight of the initiator (a) is preferably 62 to 4000, and more preferably 400 to 2000. If the molecular weight is 62 or more, good flexibility can be obtained in the resulting polyurethane (urethane resin-based adhesive). Moreover, if the said molecular weight is 4000 or less, it is preferable when improving the cohesion force of the polyurethane (urethane resin adhesive) obtained.

  In the polyester ether polyol (Z), the constituent unit derived from the initiator (a) is preferably contained in an amount of 1 to 60% by mass, more preferably 10 to 60% by mass. If content of the structural unit derived from an initiator (a) is 1 mass% or more, the target polyester ether polyol (Z) will be easy to be obtained. Moreover, since content of the dicarboxylic acid anhydride (b) in polyester ether polyol (Z) can be increased if content of the structural unit derived from an initiator (a) is 60 mass% or less, the obtained polyurethane ( The cohesive force of the urethane resin-based adhesive) is improved.

[Dicarboxylic anhydride (b)]
Examples of the dicarboxylic acid anhydride (b) include phthalic anhydride, maleic anhydride, and succinic anhydride. In particular, dicarboxylic acid anhydrides having an aromatic nucleus such as phthalic anhydride are preferred.
In the polyester ether polyol (Z), the structural unit derived from the dicarboxylic acid anhydride (b) is preferably contained in an amount of 10 to 50% by mass, and more preferably 15 to 40% by mass. When the content of the structural unit derived from the dicarboxylic acid anhydride (b) is 10% by mass or more, a polyurethane having excellent adhesiveness can be obtained. Moreover, if content of the structural unit derived from dicarboxylic acid anhydride (b) is 50 mass% or less, the polyurethane excellent in the softness | flexibility will be obtained.

[Alkylene oxide (c)]
Examples of the alkylene oxide (c) include alkylene oxides used in the synthesis of the polyether polyol as the initiator (a), and it is more preferable to use propylene oxide or ethylene oxide.

  The polyester ether polyol (Z) is obtained by reacting a mixture of an alkylene oxide (c) and a dicarboxylic acid anhydride (b) with the initiator (a). The molar ratio of the alkylene oxide (c) and the dicarboxylic acid anhydride (b) used for the synthesis of the polyester ether polyol (Z) is [the amount of the alkylene oxide (c) (mol)] / [dicarboxylic acid anhydride (b). ) Of the substance (mol)] = 50/50 to 95/5, more preferably 50/50 to 80/20. If the molar ratio of the alkylene oxide (c) to the dicarboxylic acid anhydride (b) is not less than the lower limit, the amount of unreacted dicarboxylic acid anhydride (b) in the polyester ether polyol (Z) can be suppressed. The acid value of the polyester ether polyol (Z) can be lowered. Moreover, if the molar ratio of alkylene oxide (c) and dicarboxylic acid anhydride (b) is not more than the upper limit, the cohesive force of the resulting polyurethane (urethane resin-based pressure-sensitive adhesive) is improved.

Further, the polyester ether polyol (Z) obtained by using an alkylene oxide (c) in excess of an equimolar amount with respect to the dicarboxylic acid anhydride (b) and subjecting the alkylene oxide (c) to an addition reaction with a block at a terminal. The acid value of can be reduced.
In the copolymer chain of polyester ether polyol (Z) (part where dicarboxylic acid anhydride (b) and alkylene oxide (c) are copolymerized), dicarboxylic acid anhydride (b), alkylene oxide (c) and Are alternately subjected to addition reaction, or alkylene oxide (c) is subjected to block addition reaction. However, in the dicarboxylic acid anhydride (b) and the alkylene oxide (c), the dicarboxylic acid anhydride (b) is more reactive and the dicarboxylic acid anhydrides (c) do not continuously undergo addition reaction. The number of alkylene oxides (c) constituting the block chain in the copolymer chain is as short as several. Therefore, the entire structure of the polyester ether polyol (Z) can be designed by adjusting the molecular weight of the initiator (a) and the addition amount of the alkylene oxide (c) at the terminal portion.
In particular, when polyhydric alcohols are used as the initiator (a), when the polyester ether polyol (Z) is produced, an excess amount of alkylene oxide (c) is used as compared with the dicarboxylic acid anhydride (b). It is preferable that the residual amount of unreacted dicarboxylic acid anhydride can be reduced.

In the production of the polyester ether polyol (Z), it is preferable to use a catalyst from the viewpoint of a high polymerization reaction rate.
As the catalyst, a ring-opening addition polymerization catalyst is suitably used, and examples thereof include alkali catalysts such as potassium hydroxide and cesium hydroxide; double metal cyanide complex catalysts; phosphazene catalysts. Especially, since the polyester ether polyol (Z) with a smaller value of Mw / Mn is obtained, a double metal cyanide complex catalyst is more preferable.
As the double metal cyanide complex catalyst, a zinc hexacyanocobaltate complex coordinated with an organic ligand is preferable. As the organic ligand, ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, and alcohols such as tert-butyl alcohol are preferable.

The polyester ether polyol (Z) preferably has a hydroxyl value converted molecular weight per hydroxyl group of 250 to 10,000, more preferably 1,000 to 10,000, and still more preferably 1,000 to 5,000. If the molecular weight in terms of hydroxyl value is 250 or more, the flexibility of the resulting polyurethane (urethane resin-based adhesive) is improved. If the hydroxyl value-converted molecular weight is 10,000 or less, the cohesive strength of the resulting polyurethane is improved, and the viscosity of the solution tends to be low when the polyurethane is dissolved in a solvent.
The molecular weight in terms of hydroxyl value of the polyester ether polyol (Z) can be easily adjusted by appropriately adjusting the number of moles of the dicarboxylic acid anhydride (b) and the alkylene oxide (c) copolymerized with the initiator (a).

The polyester ether polyol (Z) preferably has an average molecular weight (M ′) per copolymer chain of 100 to 3000, more preferably 200 to 2000. The average molecular weight (M ′) per copolymer chain means the average molecular weight per copolymer chain formed by copolymerization of dicarboxylic anhydride (b) and alkylene oxide (c). It is a value obtained by dividing a value obtained by removing the molecular weight of the initiator (a) from the hydroxyl value-converted molecular weight by the number of functional groups of the initiator (a).
When the average molecular weight (M ′) per copolymer chain is 100 or more, the flexibility of the resulting polyurethane (urethane resin-based adhesive) is improved. Further, when the average molecular weight (M ′) per copolymer chain is 3000 or less, the viscosity of the resulting polyester ether polyol (Z) does not become too high. The average molecular weight (M ′) per copolymer chain is appropriately determined by the number of moles of the dicarboxylic acid anhydride (b) and alkylene oxide (c) copolymerized with the initiator (a) as in the case of the hydroxyl value converted molecular weight. It can be easily adjusted by adjusting.

  The acid value of the polyester ether polyol (Z) is preferably 2.0 mgKOH / g or less, more preferably 1.0 mgKOH / g or less, and may be zero. When the acid value of the polyester ether polyol (Z) is 2.0 mgKOH / g or less, the reactivity with the polyisocyanate compound is improved, and the hydrolysis resistance of the resulting polyurethane (urethane resin-based adhesive) is improved. .

The ratio of the polyester ether polyol (Z) in the polyol (A) is preferably 10% by mass or more in order to increase the flexibility of the polyurethane (urethane resin-based pressure-sensitive adhesive) and prevent a decrease in removability. 50 mass% or more is more preferable, and it is most preferable that all the polyols (A) are polyester ether polyols (Z).
The polyester ether polyol (Z) may be one type or a combination of two or more types.

  When a part of the polyol (A) is a polyester ether polyol (Z), any one of a polyoxytetramethylene polyol, a polyoxyalkylene polyol, a polyester polyol, and a polycarbonate polyol is used as another component of the polyol (A). It is preferable to use seeds or two or more kinds.

[Polyisocyanate (B1)]
Examples of the polyisocyanate (B1) include naphthalene-1,5-diisocyanate, polyphenylene polymethylene polyisocyanate, 4,4′-diphenylmethane diisocyanate, and 2,4-tolylene diisocyanate (hereinafter referred to as 2,4-TDI). ), And aromatic polyisocyanates such as 2,6-tolylene diisocyanate (hereinafter referred to as 2,6-TDI); aralkyl polyisocyanates such as xylylene diisocyanate and tetramethylxylylene diisocyanate; hexamethylene diisocyanate ( Hereinafter referred to as HDI.), Aliphatic polyisocyanates such as 2,2,4-trimethyl-hexamethylene diisocyanate, 2,4,4-trimethyl-hexamethylene diisocyanate; isophorone diisocyanate (Hereinafter referred to as IPDI) and 4,4′-methylenebis (cyclohexyl isocyanate) and the like; and urethane-modified products, burette-modified products, allophanate-modified products, and carbodiimides obtained from the polyisocyanates. Examples include modified products and isocyanurate modified products.
Of these, polyisocyanate (B1) having two isocyanate groups is preferred, and 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate are particularly preferred.

  Moreover, when using the urethane-resin-type adhesive of this invention for an optical use, it is preferable to use non-yellowing polyisocyanate as polyisocyanate (B1). For example, aliphatic polyisocyanates such as hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, 2,4,4-trimethyl-hexamethylene diisocyanate; alicyclic rings such as isophorone diisocyanate and methylenebis (4-cyclohexylisocyanate) Group polyisocyanates; aralkyl polyisocyanates such as xylylene diisocyanate.

[Isocyanate group-terminated prepolymer (UI)]
In this embodiment, the polyol (A) and the polyisocyanate (B1) are reacted at an excess ratio of isocyanate groups to form an isocyanate group-terminated prepolymer (UI) (hereinafter, this reaction is referred to as a prepolymer formation reaction). .
Specific examples of the prepolymer forming reaction include a reaction in which the polyol (A) and the polyisocyanate (B1) are heated at 60 to 100 ° C. for 1 to 20 hours in a dry nitrogen stream.
In the prepolymer forming reaction, a urethanization reaction catalyst can be used.
Examples of the urethanization reaction catalyst include organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, and tin 2-ethylhexanoate; iron compounds such as iron acetylacetonate and ferric chloride; And tertiary amine catalysts such as triethylamine and triethylenediamine. Of the urethanization reaction catalysts, organotin compounds are preferred.

  Further, in the prepolymer forming reaction, it may be diluted with a solvent. Examples of the solvent include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone (hereinafter referred to as MEK), and dimethylformamide. And cyclohexanone. These may be used alone or in combination of two or more.

  The ratio of the polyol (A) and the polyisocyanate (B1) in the prepolymer formation reaction is preferably a ratio in which the isocyanate group / hydroxyl group (molar ratio) is 1.1 to 10, and more preferably in a ratio of 1.2 to 6. preferable. If the isocyanate group / hydroxyl group (molar ratio) is 1.1 or more, it is difficult to gel and it is easy to obtain a molecular weight suitable as a prepolymer used in the production of an adhesive. On the other hand, when the molar ratio is 10 or less, the viscosity of the resulting isocyanate group-terminated prepolymer (UI) does not become too low, and the handling property and coating workability of the adhesive coating solution can be enhanced.

The isocyanate group-terminated prepolymer (UI) obtained by the prepolymer formation reaction preferably has an isocyanate group content of 1.5 to 10.0% by mass.
Moreover, 4000-40,000 are preferable, as for the weight average molecular weight (Mw) of isocyanate group terminal prepolymer (UI), 5000-30000 are more preferable, and 7000-25000 are more preferable. When the weight average molecular weight (Mw) is 4000 or more, the produced adhesive has excellent flexibility and adhesive strength, and when it is 40,000 or less, the produced adhesive has excellent cohesive strength.
The weight average molecular weight (Mw) in the present invention is a value measured in terms of polystyrene by gel permeation chromatography (hereinafter the same).

[Chain extended polyurethane (UIH)]
In the present embodiment, the chain extender (C) is reacted with the isocyanate group-terminated prepolymer (UI) (hereinafter, this reaction is referred to as a chain extension reaction), and further, the end stopper (D) is reacted as necessary. (Hereinafter, this reaction is referred to as a termination reaction) to obtain a chain extended polyurethane (UIH).

[Chain extender (C)]
As the chain extender (C), it is preferable to use a compound having three or more active hydrogen groups (that is, a functional group capable of reacting with an isocyanate group). Further, a compound having only two active hydrogen groups may be used in combination. The active hydrogen group is preferably at least one selected from the group consisting of a primary amino group, a secondary amino group, a primary hydroxyl group, a secondary hydroxyl group, a tertiary hydroxyl group, and a carboxy group. In the case of the chain extender (C) having 3 or more active hydrogen groups, the chain extender (C) preferably has two or more active hydrogen groups having different reactivity as described above. By reacting two reactive hydrogen groups with high reactivity of the chain extender (C), the prepolymer chain is extended, and the active hydrogen groups with low active reactivity are not reacted to form active hydrogen groups of the active hydrogen group-containing polyurethane. .
Specific examples of the compound having only two active hydrogen groups include aliphatic diol, aliphatic diamine, alkanolamine, aromatic diamine, phenolamine and the like.

In the chain extender (C) having three or more active hydrogen groups, two of the three or more active hydrogen groups are more reactive with isocyanate groups than the remaining one or more active hydrogen groups Is preferred. In this case, in the chain extension reaction, two highly reactive active hydrogen groups are used for the chain extension reaction, and after the chain extension reaction, the reactive hydrogen is low and not used for the chain extension reaction. The group remains. This remaining active hydrogen group is an active hydrogen group capable of reacting with an isocyanate group of a curing agent described later. Therefore, an active hydrogen group derived from the chain extender (C) is introduced into the isocyanate group-terminated prepolymer (UI) by a chain extension reaction, and a chain extended polyurethane (UIH) having an active hydrogen group is obtained.
The order of reactivity of the active hydrogen group with the isocyanate group in the chain extender (C) is relatively determined, and as described above, the primary amino group, secondary amino group, and primary hydroxyl group generally react. A functional group having high reactivity, and a secondary hydroxyl group, a tertiary hydroxyl group, and a carboxy group are functional groups having low reactivity. In addition, since the primary hydroxyl group is less reactive than the primary amino group and the secondary amino group, a combination of two amino groups and at least one primary hydroxyl group as described later (C2). There may be.

As the chain extender (C), since the removability of the resulting polyurethane (urethane resin-based pressure-sensitive adhesive) can be increased, one or two selected from the group consisting of the following compounds (C1) and (C2) It is preferable to use more than one kind of compound.
(C1) One or two active hydrogen groups having three or more active hydrogen groups, two of which are selected from the group consisting of a primary amino group, a secondary amino group, and a primary hydroxyl group A compound in which the remaining active hydrogen groups are one or more active hydrogen groups selected from the group consisting of secondary hydroxyl groups, tertiary hydroxyl groups and carboxy groups.
(C2) having three or more active hydrogen groups, two of these functional groups being one or two active hydrogen groups selected from the group consisting of primary amino groups and secondary amino groups, and the rest Wherein the active hydrogen group is a primary hydroxyl group.
The priority in specifying “two of these active hydrogen groups” is as follows. First, primary or secondary amino groups are specified preferentially, and if these are 1 or 0, then primary The hydroxyl group is included in “two of these functional groups”.

Examples of the chain extender (C) having 3 or more active hydrogen groups include:
(1) a compound having two amino groups and having at least one hydroxyl group,
(2) a compound having no amino group, having two primary hydroxyl groups, and having at least one carboxy group;
(3) a compound having two amino groups and having at least one carboxy group,
(4) a compound having no secondary amino group, one primary amino group, one primary hydroxyl group, and at least one secondary hydroxyl group,
(5) a compound having no primary amino group, one secondary amino group, one primary hydroxyl group and at least one secondary hydroxyl group,
(6) A compound having no amino group, having two primary hydroxyl groups, having at least one secondary hydroxyl group or at least one tertiary hydroxyl group.

The amino group of the compound (1) may be either a primary amino group or a secondary amino group, and the hydroxyl group may be either a primary, secondary or tertiary hydroxyl group. A compound having a primary hydroxyl group as a hydroxyl group corresponds to the compound (C2).
Specific examples of the compound (1) include a propylene oxide 1 mol adduct of metaxylylenediamine (for example, trade name MXDA-PO1 manufactured by Aoki Yushi Co., Ltd.), a propylene oxide 2 mol adduct of metaxylylenediamine (for example, , Aoki Yushi Co., Ltd., trade name MXDA-PO2), metaxylylene diamine ethylene oxide 1 mol adduct (Aoki Yushi Co., trade name MXDA-EO1), metaxylylene diamine ethylene oxide 2 mol adduct (Aoki Yushi Co., Ltd.) Product name, MXDA-EO2), 2-hydroxyethylaminopropylamine (manufactured by Guangei Chemical Industry Co., Ltd.), aminoethylethanolamine and the like.

  Examples of the compound (2) include dimethylolcarboxylic acids, such as dimethylolpropionic acid (2,2-bis (hydroxymethyl) propionic acid), dimethylolbutanoic acid (2,2-bis (hydroxymethyl)). Butanoic acid), dimethylolpentanoic acid (2,2-bis (hydroxymethyl) pentanoic acid), dimethylolheptanoic acid (2,2-bis (hydroxymethyl) heptanoic acid), dimethyloloctanoic acid (2,2- Bis (hydroxymethyl) octanoic acid), dimethylol nonanoic acid (2,2-bis (hydroxymethyl) nonanoic acid) and the like. These correspond to the above compound (C1).

  Examples of the compound (3) include lysine and arginine. These correspond to the above compound (C1).

  Examples of the compound (4) include 1-amino-2,3-propanediol. This corresponds to the compound (C1).

  Examples of the compound (5) include 1-methylamino-2,3-propanediol, N- (2-hydroxypropyl) ethanolamine and the like. These correspond to the above compound (C1).

(6) The compound having two primary hydroxyl groups and having at least a secondary hydroxyl group or at least a tertiary hydroxyl group is, for example, one selected from the group consisting of diethanolamine, triethanolamine, trimethylolpropane, and pentaerythritol A compound obtained by adding one molecule of an alkylene oxide having 3 to 4 carbon atoms to the above compound (the alkylene oxide having 3 to 4 carbon atoms includes propylene oxide, 1,2-butylene oxide, 3,4-butylene oxide) And glycerin compounds such as glycerin, diglycerin, 1,2,4-butanetriol, 1,2,5-pentanetriol, mannitol, maltose, sorbitol and the like. These correspond to the above compound (C1).
Among these compounds, N- (2-hydroxypropyl) -N and N-di (2-hydroxyethyl) amine obtained by adding one molecule of propylene oxide to diethanolamine are preferable.

  In addition to the compounds (1) to (6), the chain extender (C) having 3 or more active hydrogen groups has one secondary amino group and one primary hydroxyl group, and at least A compound having one tertiary hydroxyl group (having no primary amino group) can also be used. These correspond to the above compound (C1).

[Chain extension reaction]
The method of chain extension reaction is not particularly limited. For example, 1) A method in which an isocyanate group-terminated prepolymer (UI) solution is charged into a reaction vessel, and a chain extension agent (C) is dropped into the reaction vessel and reacted. 2) A method in which a chain extender (C) is charged into a reaction vessel and an isocyanate group-terminated prepolymer (UI) solution is dropped and reacted. 3) The isocyanate group-terminated prepolymer (UI) solution is diluted with a solvent, and then the reaction vessel And a method in which a predetermined amount of the chain extender (C) is added at a time to react. Since the isocyanate group gradually decreases, the method 1) or 3) is preferred in that a uniform chain-extended polyurethane (UIH) can be easily obtained.
As the solvent, the same solvents as those exemplified in the prepolymer formation reaction can be used.

  The addition amount of the chain extender (C) varies depending on the isocyanate group content of the isocyanate group-terminated prepolymer (UI), but the molar ratio between the active hydrogen group present in the chain extender (C) and the isocyanate group is “ The ratio that the value of “isocyanate group / active hydrogen group (molar ratio)” is preferably 0.5 to 0.9, and more preferably 0.6 to 0.75. When the isocyanate group / active hydrogen group (molar ratio) is at least the lower limit of the above range, it is easy to prevent gelation due to rapid thickening during the chain extension reaction. On the other hand, when the molar ratio is less than or equal to the upper limit of the above range, the chain extension reaction proceeds sufficiently and the desired molecular weight is easily obtained.

  The reaction temperature in the chain extension reaction is preferably 80 ° C. or lower. When the reaction temperature exceeds 80 ° C., the reaction rate becomes too fast and it becomes difficult to control the reaction. Therefore, it tends to be difficult to obtain a chain extended polyurethane (UIH) having a desired molecular weight and a desired structure. When the chain extension reaction is performed in the presence of a solvent, the reaction temperature is preferably set to be equal to or lower than the boiling point of the solvent. In particular, 40-60 ° C. is preferred in the presence of MEK and / or ethyl acetate.

[Stop reaction]
After the chain extension reaction, a termination reaction may be performed by adding a terminal terminator (D) as necessary.
The terminal terminator (D) is a compound having an active hydrogen group and having only one active hydrogen group, or a compound having an active hydrogen group and having one highly reactive activity. A compound having one or two hydrogen groups and one or more active hydrogen groups that are less reactive than the active hydrogen group can be used.
As the compound having only one active hydrogen group, a compound having only one primary amino group, secondary amino group, tertiary amino group, primary hydroxyl group or secondary hydroxyl group can be used. Examples thereof include monoamine compounds such as diethylamine and morpholine and monool compounds such as methanol.
Examples of the compound having an active hydrogen group and having one active hydrogen group having a high reactivity and one or two active hydrogen groups having a reactivity lower than that of the active hydrogen group include, for example, an amino group (1 And a compound having 1 to 2 hydroxyl groups as well as one secondary amino group or secondary amino group. Such a compound has two or more active hydrogen groups, but the reactivity of the active hydrogen groups is different. Therefore, after one highly active reactive hydrogen group has reacted, the remaining active hydrogen groups The group remains unreacted. The hydroxyl group is more preferably a secondary hydroxyl group. Specifically, monoamine compounds having one hydroxyl group such as 2-amino-2-methyl-1-propanol, monoisopropanolamine, aminopropanol, and the like can be used.

  The addition amount of the terminal terminator (D) is preferably such that the amount of the terminal terminator is 1 to 2 mol relative to 1 mol of the terminal isocyanate group remaining after the chain extension reaction. When the addition amount of the terminal terminator (D) is less than 1 mol relative to 1 mol of the terminal isocyanate group remaining after the chain extension reaction, the isocyanate group remains after the termination reaction, so that the obtained chain extended polyurethane (UHI) It tends to be unstable. On the other hand, when the addition amount of the terminal terminator (D) exceeds 2 moles relative to 1 mole of the terminal isocyanate group remaining after the chain extension reaction, the low molecular weight compounds tend to increase.

  The weight average molecular weight (Mw) of the chain extended polyurethane (UIH) is preferably 50,000 or more, more preferably 65,000 or more from the viewpoint of flexibility and durability. The upper limit is preferably 300,000 or less, more preferably 250,000 or less from the viewpoint of coatability. The number of active hydrogen groups in the chain extended polyurethane (UIH) is preferably 1 to 80 on average per molecule, more preferably 2 to 40. A particularly preferable number of active hydrogen groups is 5 to 15 on average per molecule.

[Main agent for adhesives]
The isocyanate group-terminated prepolymer (UI) is a polyester ether polyol containing a structural unit derived from the initiator (a), a structural unit derived from the dicarboxylic anhydride (b), and a structural unit derived from the alkylene oxide (c). It has a residue of (Z) and a residue of polyisocyanate (B1).
The chain extension polyurethane (UIH) is a polyester ether polyol (Z) containing a structural unit derived from the initiator (a), a structural unit derived from the dicarboxylic anhydride (b), and a structural unit derived from the alkylene oxide (c). ), A polyisocyanate (B1) residue, and a chain extender (C) residue.
The residue of the chain extender (C) is a polyvalent group obtained by removing the active hydrogen group from the chain extender (C). The residue of polyisocyanate (B1) is a polyvalent group obtained by removing isocyanate groups from polyisocyanate (B1).
At least some of the active hydrogen groups present in the active hydrogen group-containing polyurethane are active hydrogen groups bonded to the residue of the chain extender (C). The chain extended polyurethane (UIH) is used as a main agent for pressure-sensitive adhesives.
The chain extension polyurethane (UIH) has an active hydrogen group (active hydrogen group bonded to the residue of the chain extender (C)) derived from the chain extender (C). Furthermore, the chain-extended polyurethane (UIH) produced by using the terminal terminator (D) having two or more active hydrogen groups having different reactivities, in addition to the active hydrogen groups derived from the chain extender (C), It has an active hydrogen group derived from the terminal terminator (D) (an active hydrogen group contained in a structural unit derived from the terminal terminator (D)). The ratio of these active hydrogen groups is that 50 to 100 mol% of the active hydrogen groups (100 mol%) present in the chain extended polyurethane (UIH) are bonded to the residue of the chain extender (C). Preferably it is.
The main agent for the pressure-sensitive adhesive may contain other active hydrogen group-containing components in addition to the chain extended polyurethane (UIH). Furthermore, an additive may be included. It is preferable to use it in the form of a main agent solution for an adhesive containing a main agent for an adhesive and a solvent.
The other active hydrogen group-containing component is preferably a polyol such as polyoxytetramethylene polyol, polyoxyalkylene polyol, polyester polyol, or polycarbonate polyol.
Of the total of the chain-extended polyurethane (UIH) and the other active hydrogen group-containing component, the content of the chain-extended polyurethane (UIH) is preferably 5 to 100% by mass, more preferably 30 to 100% by mass, ˜100 mass% is particularly preferred, and 100 mass% is most preferred.
When the content of the chain extended polyurethane (UIH) is 5% by mass or more, the heat resistance of the obtained polyurethane (urethane resin adhesive) is further improved and the compatibility with the acrylic adhesive is improved. , Flexibility can be further improved.

Specific examples of the additive include the following fillers, reinforcing agents, stabilizers, flame retardants, mold release agents, and antifungal agents.
Examples of the filler or reinforcing agent include carbon black, aluminum hydroxide, calcium carbonate, titanium oxide, silica, glass, bone powder, wood powder, and fiber flakes.
Examples of the stabilizer include an antioxidant, an ultraviolet absorber, and a light stabilizer.
Examples of the flame retardant include chloroalkyl phosphate, dimethylmethylphosphonate, ammonium polyphosphate, and organic bromine compounds.
Examples of the mold release agent include wax, soaps, and silicone oil. Examples of the antifungal agent include pentachlorophenol, pentachlorophenol laurate, and bis (tri-n-butyltin) oxide.
As the solvent, the same solvents as those exemplified in the prepolymer formation reaction can be used. The usage-amount of a solvent can be suitably set so that the viscosity of the main ingredient solution for adhesives may become a desired value.

  The total content of the chain-extended polyurethane (UIH) and the other active hydrogen group-containing component in the main component for the pressure-sensitive adhesive is preferably 1 to 100% by mass, more preferably 30 to 100% by mass. 40 to 100% by mass is particularly preferable. When the total of the chain-extended polyurethane (UIH) and the other active hydrogen group-containing components is 1% by mass or more, the cohesive force increases when the main component for the adhesive and the curing agent are reacted, and the removability is increased. A certain urethane resin adhesive is obtained.

[Curing agent]
The second polyisocyanate (B2) is used as a curing agent. The curing agent may contain an additive. It is preferably used in the form of a curing agent solution containing a curing agent and a solvent.
As the second polyisocyanate (B2), the same polyisocyanate (B1) described above can be used.
The second polyisocyanate (B2) is preferably one having an average functional group number larger than 2 in that it easily forms a crosslinked structure. For example, Duranate P301-75E (manufactured by Asahi Kasei Chemicals Corporation, trimethylolpropane adduct type HDI, isocyanate group content: 12.9% by mass, solid content concentration: 75% by mass), coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd., trimethylolpropane) Adduct type TDI, isocyanate group content: 13.5% by mass, solid content concentration: 75% by mass), Coronate 2031 (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanurate type TDI, isocyanate group content: 7.5% by mass, solid For example, a concentration of 50% by mass).
As an additive, the thing similar to what was illustrated as an additive contained in the main ingredient for adhesives can be used.
As the solvent, the same solvents as those exemplified in the prepolymer formation reaction can be used. The usage-amount of a solvent can be suitably set so that the viscosity of a hardening | curing agent solution may become a desired value.

  The content of the second polyisocyanate (B2) in the curing agent is preferably 10 to 100% by mass, more preferably 30 to 100% by mass, and particularly preferably 40 to 100% by mass. preferable. When the content of the second polyisocyanate (B2) is 10% by mass or more, it becomes easy to apply polyurethane (urethane resin-based pressure-sensitive adhesive) obtained by reacting the main agent for pressure-sensitive adhesive with the curing agent. .

[Method for producing urethane resin adhesive]
The composition for producing a urethane resin-based pressure-sensitive adhesive includes the main agent for pressure-sensitive adhesive and a curing agent. The main component for pressure-sensitive adhesive in this composition and the curing agent are reacted to obtain a urethane resin-based pressure-sensitive adhesive. This composition is preferably used as a coating liquid for coating on a substrate. When this composition is a liquid composition having a relatively low viscosity, it can be used as it is as a coating liquid. When the composition is a highly viscous liquid or solid that is difficult to apply, it is preferably diluted with a solvent. Hereinafter, the composition for producing a urethane resin adhesive will be described as a coating liquid.
In the production of the urethane resin-based pressure-sensitive adhesive, preferably, a coating liquid containing a main agent for pressure-sensitive adhesive and a curing agent is coated on a substrate and cured by heating to form a cured product layer (pressure-sensitive adhesive layer). . The surface of the cured product layer has removable adhesiveness.
The coating solution may contain a solvent. As the solvent, the same solvents as those exemplified in the prepolymer formation reaction can be used. The usage-amount of a solvent can be suitably set so that the viscosity of a coating liquid may become a desired value. The coating liquid may contain an additive. The additive may be added in advance to the main agent for adhesive or the curing agent, or may be added after mixing the main agent for adhesive and the curing agent.
The coating liquid may contain a urethanization catalyst in order to promote the reaction between the adhesive main agent and the curing agent. Examples of the urethanization catalyst include the same urethanization catalysts as exemplified in the prepolymer formation reaction.
The substrate is not particularly limited. For example, a plastic film, a plastic sheet, paper, a urethane resin foam, etc. can be used.

  In the coating liquid, the blending of the adhesive main agent and the curing agent is preferably 0.1 to 50 parts by mass, more preferably 1 to 50 parts by mass with respect to 100 parts by mass of the adhesive main agent. The adhesive strength can be adjusted by the blending amount of the curing agent. If the compounding amount of the curing agent is 0.1 parts by mass or more, the removability can be sufficiently secured, and if it is 50 parts by mass or less, the adhesiveness can be sufficiently secured.

According to the pressure-sensitive adhesive production method of the present embodiment, the chain-extended polyurethane (UIH) contained in the main agent for the pressure-sensitive adhesive is reacted with the second polyisocyanate (B2) contained in the curing agent. ) Can be crosslinked to form a crosslinked polyurethane. Although this crosslinked polyurethane has adhesiveness, it has removability because of its high cohesive force, and functions as a removable adhesive.
As a result of investigations by the present inventors, the crosslinked polyurethane obtained by using the main component for pressure-sensitive adhesive containing the above chain-extended polyurethane (UIH) is excellent in flexibility and re-peeled even if time passes at high temperature. It is difficult to decrease the nature.
It was also found that the resulting crosslinked polyurethane was excellent in compatibility with the acrylic resin.
By the way, as described in Patent Document 1, when a polyether polyol and a polyester polyol are used together as a raw material for the pressure-sensitive adhesive, two types of catalysts are used, for example, to form a crosslinked polyurethane. It is easy to control the reaction. On the other hand, it was found that the reaction between the main agent for adhesive and the curing agent can be easily controlled in the production method of the present embodiment using the chain-extended polyurethane (UIH) as the main agent for adhesive.

“Second Embodiment”
In the present embodiment, a hydroxyl group-terminated urethane polymer (UH) obtained by reacting polyol (A) and polyisocyanate (B1) in an excess ratio of hydroxyl groups is used as the active hydrogen group-containing polyurethane contained in the adhesive main agent. It is done.

[Polyol (A) / Polyester ether polyol (Z)]
Part or all of the polyol (A) used in the production of the hydroxyl group-terminated urethane polymer (UH) is a polyester ether polyol (Z). As the polyester ether polyol (Z), the same one as in the first embodiment is used.
The polyol (A) is preferably all polyester ether polyol (Z) for the same reason as in the first embodiment.
When a part of the polyol (A) is the polyester ether polyol (Z), the remainder of the polyol is the same as in the first embodiment.

[Polyisocyanate (B1)]
The polyisocyanate (B1) is the same as that in the first embodiment, including the preferred mode.

[Hydroxyl-terminated urethane polymer (UH)]
The step of producing the hydroxyl group-terminated urethane polymer (UH) is performed at a temperature of 60 to 100 ° C. under a dry nitrogen stream, as in the prepolymer formation reaction of the first embodiment. It can carry out by the method of heating for -20 hours.
In this step, the proportion of the polyol (A) and the polyisocyanate (B1) is preferably such that the isocyanate group / hydroxyl group (molar ratio) is less than 1, and more preferably 0.5 to 0.98. If the isocyanate group / hydroxyl group (molar ratio) is less than 1, a hydroxyl group-terminated urethane polymer can be obtained reliably, and if it is 0.98 or less, it is difficult to gel and has a molecular weight suitable for the main agent for pressure-sensitive adhesives. A terminal urethane polymer is obtained.

In the step of producing the hydroxyl group-terminated urethane polymer (UH), the same urethanization reaction catalyst as in the first embodiment may be used. Moreover, you may dilute with the same solvent as 1st Embodiment.
The hydroxyl group content in the hydroxyl group-terminated urethane polymer (UH) thus obtained is preferably 0.03 to 1.00% by mass.
The weight average molecular weight (Mw) of the hydroxyl group-terminated urethane polymer (UH) is preferably 40,000 to 100,000, more preferably 50,000 to 100,000, and further preferably 60,000 to 80,000. When the weight average molecular weight (Mw) is 40,000 or more, the flexibility is excellent, and when it is 100,000 or less, the coating property is excellent. The number of active hydrogen groups in the hydroxyl group-terminated urethane polymer (UH) is preferably 1 to 10 on average per molecule, and more preferably 2 to 10 in number. A particularly preferred number of active hydrogen groups is 2 to 6 on average per molecule.

[Main agent for adhesives]
The hydroxyl group-terminated urethane polymer (UH) is a polyester ether polyol containing a structural unit derived from the initiator (a), a structural unit derived from the dicarboxylic anhydride (b), and a structural unit derived from the alkylene oxide (c) ( An active hydrogen group-containing polyurethane having a residue of Z) and a residue of polyisocyanate (B1) and having a hydroxyl group at the terminal. The hydroxyl group-terminated urethane polymer (UH) is used as a main agent for an adhesive.
The main agent for pressure-sensitive adhesives may contain other active hydrogen group-containing components in addition to the hydroxyl group-terminated urethane polymer (UH). Furthermore, an additive may be included. It is preferable to use it in the form of a main agent solution for an adhesive containing a main agent for an adhesive and a solvent.
Here, the hydroxyl group at the end of the polymer chain of the hydroxyl group-terminated urethane prepolymer (UH) is preferably a hydroxyl group bonded to the residue of the polyol (A), particularly a hydroxyl group bonded to the residue of the polyester ether polyol (Z). It is preferable that
Of the active hydrogen groups (100 mol%) of the hydroxyl group-terminated urethane prepolymer (UH), the proportion of hydroxyl groups bonded to the structural unit derived from the alkylene oxide (c) located at the polymer chain end is 99-100. It is preferable that it is mol%. That is, almost all active hydrogen groups of the hydroxyl group-terminated urethane prepolymer (UH) are hydroxyl groups bonded to the residue of the polyol (A).
Other active hydrogen group-containing components, additives, and solvents are the same as those in the first embodiment.

Of the total of the hydroxyl group-terminated urethane polymer (UH) and the other active hydrogen group-containing component, the content of the hydroxyl group-terminated urethane polymer (UH) is preferably 5 to 100% by mass, more preferably 30 to 100% by mass. 40 to 100% by mass is particularly preferable, and 100% by mass is most preferable.
When the content of the hydroxyl group-terminated urethane polymer (UH) is 5% by mass or more, the heat resistance of the obtained polyurethane (urethane resin-based adhesive) is further improved, and the compatibility with the acrylic adhesive is improved. Thus, more flexibility can be imparted.

  The total content of the hydroxyl group-terminated urethane polymer (UH) and the other active hydrogen group-containing component in the main component for pressure-sensitive adhesive is preferably 1 to 100% by mass, for the same reason as in the first embodiment. -100 mass% is more preferable, and 40-100 mass% is especially preferable.

[Curing agent]
The curing agent is the same as in the first embodiment, including the preferred mode.
[Method for producing urethane resin adhesive]
Also in the present embodiment, for example, a composition for producing a urethane resin-based pressure-sensitive adhesive containing a main agent for a pressure-sensitive adhesive, a curing agent, and a solvent as necessary is used as a coating liquid, and the coating liquid is used as a base material. It is preferable to coat on and cure by heating to form a cured product layer (adhesive layer).
The solvent, urethanization catalyst, and base material are the same as those in the first embodiment.
0.1-50 mass parts of hardening | curing agents are preferable with respect to 100 mass parts of main agents for adhesives, and the compounding of the main ingredient for adhesives and hardening | curing agent in a coating liquid is more preferable. If the compounding amount of the curing agent is 0.1 parts by mass or more, sufficient removability can be secured, and if it is 50 parts by mass or less, sufficient curability can be obtained.

According to the pressure-sensitive adhesive production method of the present embodiment, the hydroxyl group-terminated urethane polymer (UH) contained in the main agent for pressure-sensitive adhesives is reacted with the second polyisocyanate (B2) contained in the curing agent, thereby producing a hydroxyl group-terminated urethane polymer. A crosslinked polyurethane can be formed by crosslinking (UH). Although this crosslinked polyurethane has adhesiveness, it has removability because of its high cohesive force, and functions as a removable adhesive.
The crosslinked polyurethane is excellent in flexibility, and re-peelability is unlikely to deteriorate even when time passes at high temperatures. It is also excellent in compatibility with acrylic resins.
Moreover, in the manufacturing method of this embodiment, reaction control with the main ingredient for adhesives and a hardening | curing agent is also easy.

  Examples of the present invention will be specifically described below, but the following examples are not intended to limit the present invention.

(Polyol)
In the following examples, the following polyols were used. Of the following, the polyols (P4) and (P5) correspond to the polyester ether polyol (Z) in the present invention.
Polyol (P1): Polyoxypropylene diol having a hydroxyl value of 112.0 mgKOH / g and a molecular weight of 1,000, produced by reacting propylene oxide with propylene glycol as an initiator and using a KOH catalyst.
Polyol (P2): Polyoxypropylene diol having a hydroxyl value of 160.3 mg KOH / g and a molecular weight of 700, produced by reacting propylene oxide with propylene glycol as an initiator and using a KOH catalyst.
Polyol (P3): Polyoxypropylene diol having a hydroxyl value of 56.0 mgKOH / g and a molecular weight of 2,000, produced by reacting propylene oxide with propylene glycol as an initiator and using a KOH catalyst.
Polyol (P4): Ring-opening polymerization of a mixture of propylene oxide and phthalic anhydride in a molar ratio of 79/21 using the polyol (P1) as an initiator in the presence of a zinc hexacyanocobaltate-tert-butyl alcohol complex catalyst The hydroxyl value 57.9 mgKOH / g (hydroxyl value conversion molecular weight 1940), the average molecular weight per copolymer chain (M ′) 470, the acid value 0.05 mgKOH / g, and the structural unit derived from phthalic anhydride, produced by the reaction. Diol having a content of 20% by mass.
Polyol (P5): Ring-opening polymerization of a mixture of propylene oxide and phthalic anhydride in a molar ratio of 76/24 using the above polyol (P2) as an initiator in the presence of a zinc hexacyanocobaltate-tert-butyl alcohol complex catalyst Produced by reaction, hydroxyl value 58.1 mgKOH / g, (hydroxyl value converted molecular weight 1930), average molecular weight per copolymer chain (M ′) 615, acid value 0.09 mgKOH / g, structural unit derived from phthalic anhydride A diol having a content of 30% by mass.
Polyol (P6): The following polyoxyalkylene polyol (P0) was used as an initiator, and a mixture of ethylene oxide and ε-caprolactone in a molar ratio of 50/50 was opened in the presence of a zinc hexacyanocobaltate-tert-butyl alcohol complex catalyst. Polyester ether polyol having a hydroxyl value of 56.4 mgKOH / g, produced by ring polymerization.
Polyol (P0): Polyoxypropylene diol having a hydroxyl value of 160.3 mgKOH / g, produced by reacting propylene oxide with propylene glycol as an initiator and using a potassium hydroxide catalyst.
Polyester polyol (PE): Kuraray P-1010 (poly ((3-methyl-1,5-pentanediol) -alt- (adipic acid)), hydroxyl value 112 mgKOH / g).

(Chain extender)
In the following examples, the following compounds (C-1) and (C-2) were used as the chain extender (C), and the following compound (D-1) was used as the terminal terminator (D).
Compound (C-1): N- (2-hydroxypropyl) -N, N-di (2-hydroxyethyl) amine.
Compound (C-2): N- (2-hydroxypropyl) ethanolamine.
Compound (D-1): monoisopropanolamine.

(Production Example 1: Production of main agent solution U1 for pressure-sensitive adhesive containing chain-extended polyurethane)
A urethane resin solution U1 was manufactured according to the formulation shown in Table 1 below.
First, 665.6 g of polyol (P4) and 2,4-tolylene diisocyanate (hereinafter referred to as TDI) as a polyisocyanate (B1) in a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel. Along with 86.8 g of Nippon Polyurethane Industry Co., Ltd. (trade name: Coronate T-100), dibutyltin dilaurate (DBTDL) as a urethanization catalyst is based on the total amount of polyol (P4) and TDI-100. An amount corresponding to 25 ppm was charged. In the charged amount, the isocyanate group / hydroxyl group (molar ratio) was 1.50.
Subsequently, the temperature was gradually raised to 85 ° C., and a prepolymer formation reaction was performed for 3 hours to obtain an isocyanate group-terminated prepolymer (a). In the obtained isocyanate group-terminated prepolymer (a), the isocyanate group content (hereinafter referred to as NCO%) was 1.66% by mass, and the weight average molecular weight (Mw) was 12,200.
Thereafter, the mixture was cooled to room temperature, 341.7 g of ethyl acetate and 341.7 g of MEK were added, and then 17.2 g of compound (C-2) was added as a chain extender and reacted. After continuing the reaction at 50 ° C., 0.94 g of a terminal terminator (D-1) was added to carry out a termination reaction, and it was confirmed by IR that the NCO peak had disappeared.
A mixed solvent of ethyl acetate and MEK was added to the solution containing the chain extended polyurethane thus obtained, and the viscosity at 25 ° C. (hereinafter the same) was adjusted to 3240 mPa · s using an E-type viscometer. An agent base solution U1 was obtained. The obtained main agent solution U1 for pressure-sensitive adhesive was colorless and transparent, and the solid content concentration was 53% by mass.
Moreover, it was 89,000 when the weight average molecular weight (Mw) of resin in the main ingredient solution U1 for adhesives was measured in terms of polystyrene by gel permeation chromatography.

(Production Examples 2 to 5: Production of main agent solutions U2 to U5 for pressure-sensitive adhesives containing chain-extended polyurethane)
Except having changed into the mixing | blending shown in Table 1, it carried out similarly to the manufacture example 1, and obtained the main ingredient solutions U2-U5 for adhesives. IPDI in the table is isophorone diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., trade name: Desmodur I).
Isocyanate group / hydroxyl group (molar ratio) in the charged amount, isocyanate group content (mass%) in the isocyanate group-terminated prepolymer, solid content concentration (mass%) in the resulting adhesive main agent solution, viscosity at 25 ° C ( mPa · s) and weight average molecular weight (Mw) are shown in Table 1 (the same applies to Production Example 6).

(Production Example 6: Production of main agent solution U6 for pressure-sensitive adhesive containing chain-extended polyurethane)
Isocyanate group-terminated prepolymers f and g were obtained in the same manner as in Production Example 1 except that the polyol, polyisocyanate (B1) and chain extender (C) were changed to the formulations shown in Table 1. The isocyanate group-terminated prepolymers f and g were each cooled to room temperature and then mixed. Then, instead of the isocyanate group-terminated prepolymer a, a mixture of the isocyanate group-terminated prepolymers f and g is used, the chain extender (C) is changed to the formulation shown in Table 1, and the terminal terminator (D) is not used. Otherwise in the same manner as in Production Example 1, an adhesive main agent solution U6 was obtained.

(Production Example 7: Production of acrylic adhesive solution A)
37.5 parts by mass of ethyl acetate was placed in a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, and 94 parts by mass of butyl acrylate and carboxyl group-containing vinyl alone As a monomer, 6 parts by mass of acrylic acid was added and mixed to form a monomer mixture, and 25 parts by mass of the monomer mixture was added to the flask. Next, after the air in the flask was replaced with nitrogen gas, 0.08 parts by mass of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the mixture in the flask was stirred in a nitrogen atmosphere. The temperature was raised to 80 ° C. and an initial reaction was performed for about 20 minutes. Continue heating and reflux with a mixture of 75 parts by weight of the remaining monomer mixture, 32.5 parts by weight of ethyl acetate and 0.24 parts by weight of AIBN added sequentially over about 1.5 hours. It was made to react with. Subsequently, the reaction was continued while maintaining the temperature at reflux for an additional 1.5 hours. Thereafter, a solution in which 0.25 part by mass of AIBN was dissolved in 25 parts by mass of ethyl acetate was added dropwise in a reflux state over 30 minutes, and the reaction was further performed for 2 hours. After completion of the reaction, 35 parts by mass of ethyl acetate and 20 parts by mass of t-butyl alcohol were added to the reaction mixture for dilution to obtain an acrylic pressure-sensitive adhesive solution A having a solid content concentration of 40.1% by mass.
It was 550000 when the weight average molecular weight (Mw) of resin in the obtained acrylic adhesive solution A was measured by the gel permeation chromatography method in polystyrene conversion.

Example 1
Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd., trimethylolpropane adduct type) as a solution containing a curing agent (second polyisocyanate compound (B2)) with respect to 40 g of the adhesive main agent solution U1 obtained in Production Example 1 1.10 g of TDI (solid content concentration: 75% by mass) diluted with ethyl acetate to a solid content concentration of 25% by mass was added and stirred and mixed at 40 rpm for 1 minute to urethane resin adhesive A composition for production (hereinafter referred to as urethane resin-based pressure-sensitive adhesive solution) was obtained.
In addition, the addition amount of the hardening | curing agent was adjusted so that adhesive force might be 14 N / 25mm or more. In this example, the blending ratio (in terms of solid content) of the main component for pressure-sensitive adhesive (chain-extended polyurethane) and the curing agent (second polyisocyanate) used in the preparation of the urethane resin-based pressure-sensitive adhesive solution is the main agent for pressure-sensitive adhesive 100. It was 1.3 mass parts of hardening | curing agents with respect to the mass part.

(Examples 2-3, Comparative Examples 1-3)
In the formulation shown in Table 2, the same curing agent as in Example 1 was added to the adhesive main agent solution, and the mixture was stirred and mixed under the same conditions as in Example 1 to obtain a urethane resin adhesive solution. The addition amount of the curing agent was adjusted so that the adhesive strength was 14 N / 25 mm or more.

(Example 4: Production of pressure-sensitive adhesive using hydroxyl-terminated urethane polymer (UH))
A 4-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, a dropping funnel, 200 g of polyol (P4) and 20 of 2,4-tolylene diisocyanate (TDI-100) as polyisocyanate (B1) Along with .6 g, dibutyltin dilaurate (DBTDL) as a urethanization catalyst is charged in an amount corresponding to 25 ppm with respect to the total amount of polyol (P4) and TDI-100. In the charged amount, the isocyanate group / hydroxyl group (molar ratio) is 0.80.
Next, the temperature is gradually raised to 85 ° C. to perform a polymer formation reaction. The reaction time is adjusted so that the weight average molecular weight (Mw) of the hydroxyl group-terminated urethane polymer (UH) is about 60,000.
A mixed solvent of ethyl acetate and MEK is added to the obtained reaction product, and the viscosity is adjusted to about 4,000 mPa · s to obtain an adhesive main agent solution.
A solution obtained by diluting coronate L with ethyl acetate as a solution containing a curing agent (second polyisocyanate compound (B2)) is added to the main agent solution for the pressure-sensitive adhesive thus obtained. The addition amount of the curing agent is adjusted so that the adhesive strength is 14 N / 25 mm or more. This is stirred and mixed to obtain a urethane resin adhesive solution.

(Evaluation of the physical properties)
About the urethane resin adhesive obtained in the said Examples 1-3 and Comparative Examples 1-3, each physical property was evaluated by the following method. The evaluation results are shown in Table 2.
In the evaluation, each urethane resin adhesive solution obtained in Examples and Comparative Examples was used as a coating solution, and an adhesive sheet prepared by coating this on a PET film was used. The method for producing the pressure-sensitive adhesive sheet is as follows. First, a urethane resin-based pressure-sensitive adhesive solution is applied onto a PET film having a thickness of 25 μm so that the film thickness after drying becomes 25 μm, and dried at 100 ° C. for 1 minute in a circulation oven. did. Next, after curing at 23 ° C. for 1 week, the plate was left for 2 hours in an environment of 23 ° C. and a relative humidity of 65% to obtain an adhesive sheet for evaluation.

[Initial adhesive strength]: Adhesive sheet was attached to a 1.5 mm thick stainless steel plate (SUS304 (JIS)) at room temperature, pressure-bonded with a 2 kg rubber roll, and a tensile tester specified in JIS B 7721 after 24 hours. Was used to measure peel strength (180 degree peel, tensile speed 300 mm / min, unit: N / 25 mm).

[Adhesive strength increase]: The adhesive sheet was attached to a stainless steel plate in the same manner as in the evaluation of initial adhesive strength, and then left in a constant temperature bath at 60 ° C. for 1 week. Thereafter, the film was cooled to 23 ° C. and a relative humidity of 65%, and the peel strength was measured in the same manner as the initial adhesive strength. The value of the ratio of the adhesive strength after standing at 60 ° C. for 1 week to the initial adhesive strength (adhesive strength after standing for 1 week / initial adhesive strength) was defined as the adhesive strength increasing property.

[Re-peelability after heating]: In the above test for increasing the adhesive strength, the state of the stainless steel plate after measuring the peel strength was visually observed. A sample in which the pressure-sensitive adhesive was transferred was marked with x.

[Compatibility with acrylic resin-based pressure-sensitive adhesive]: Mass ratio of solid content of each urethane resin-based pressure-sensitive adhesive solution obtained in Examples and Comparative Examples and acrylic pressure-sensitive adhesive solution A obtained in Production Example 7 (Urethane resin adhesive solution: acrylic resin solution A) was weighed and mixed so as to be 20:80, and allowed to stand at room temperature to evaluate the state after 24 hours. The case where they were compatible with each other was evaluated as ○, the case where they were separated as x, and the case where they were cloudy as “white turbidity”.

From the results shown in Table 2, the urethane resin-based adhesives obtained in Examples 1 to 3 according to the present invention have a small increase in adhesive force and excellent heat resistance even when time passes under heating conditions. Also, re-peelability was maintained well. Furthermore, the compatibility with the acrylic pressure-sensitive adhesive was also good.
On the other hand, in the comparative example 1 using the polyoxypropylene diol (P3) which does not have the structural unit derived from dicarboxylic anhydride as a polyol (A) used for manufacture of the main ingredient for adhesives, heating conditions When time passed below, the adhesive strength increased and the removability decreased. The compatibility with the acrylic adhesive was not good.
In Comparative Example 2 using a polyol (P6) having no structural unit derived from dicarboxylic anhydride and having a structural unit derived from ε-caprolactone as the polyol (A) used for the production of the main agent for the pressure-sensitive adhesive, When time passed under heating conditions, the adhesive strength increased and the removability decreased.
Moreover, the prepolymer manufactured using the polyoxypropylene diol (P3) and polyester polyol (PE) which do not have the structural unit derived from dicarboxylic anhydride as a polyol (A) used for manufacture of the main ingredient for adhesives In Comparative Example 3 in which was mixed, re-peelability decreased when time passed under heating conditions, and compatibility with the acrylic pressure-sensitive adhesive was not good.

The urethane resin pressure-sensitive adhesive of the present invention is applied to protective films, pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive seals, non-slip sheets, double-sided pressure-sensitive adhesive tapes, etc. used in various fields such as the electronic field, medical field, sports field, and building field. it can.
Further, by using non-yellowing isocyanate as the polyisocyanate (B1) and the second polyisocyanate (B2), it is possible to produce a colorless and transparent urethane resin-based pressure-sensitive adhesive. Such a urethane resin-based pressure-sensitive adhesive can be applied to a use for attaching a polarizing film or a protective film for a display.

Claims (14)

A structural unit derived from an initiator (a) having two or more functional groups per molecule;
A structural unit derived from dicarboxylic anhydride (b);
A residue of a polyester ether polyol (Z) comprising a structural unit derived from an alkylene oxide (c), and
An active hydrogen group-containing polyurethane having a polyisocyanate (B1) residue is contained.   The active hydrogen group-containing polyurethane further has a residue of the chain extender (C), and at least a part of the active hydrogen groups present in the active hydrogen group-containing polyurethane is a residue of the chain extender (C). The base agent for adhesives of Claim 1 which is an active hydrogen group couple | bonded with group.   The main agent for pressure-sensitive adhesives according to claim 1, wherein in the active hydrogen group-containing polyurethane, the active hydrogen-containing group is a hydroxyl group bonded to a residue of the polyester ether polyol (Z). A step of ring-opening polymerization of a mixture of a dicarboxylic acid anhydride (b) and an alkylene oxide (c) to an initiator (a) having two or more hydroxyl groups per molecule to obtain a polyester ether polyol (Z);
A step of reacting a polyol (A) containing a polyester ether polyol (Z) with a polyisocyanate (B1) to obtain an isocyanate group-terminated prepolymer (UI);
A method for producing a main agent for pressure-sensitive adhesives, comprising a step of obtaining a chain-extended polyurethane (UIH) having an active hydrogen group by reacting the isocyanate group-terminated prepolymer (UI) with a chain extender (C). The manufacturing method of the main ingredient for adhesives of Claim 4 whose said chain extender is 1 type, or 2 or more types of compounds chosen from the group which consists of the compound of the following (C1) and the following (C2).
(C1) One or two active hydrogen groups having three or more active hydrogen groups, two of which are selected from the group consisting of a primary amino group, a secondary amino group, and a primary hydroxyl group A compound which is a hydrogen group and the remaining active hydrogen groups are one or more active hydrogen groups selected from the group consisting of secondary hydroxyl groups, tertiary hydroxyl groups and carboxy groups.
(C2) having 3 or more active hydrogen groups, and two of these active hydrogen groups are one or two active hydrogen groups selected from the group consisting of a primary amino group and a secondary amino group; A compound in which the remaining active hydrogen groups are primary hydroxyl groups.   The manufacturing method of the main ingredient for adhesives of Claim 4 or 5 whose weight average molecular weights of the said isocyanate group terminal prepolymer (UI) are 4000-40,000. A step of ring-opening polymerization of a mixture of a dicarboxylic acid anhydride (b) and an alkylene oxide (c) to an initiator (a) having two or more hydroxyl groups per molecule to obtain a polyester ether polyol (Z);
The manufacturing method of the main ingredient for adhesives characterized by having the process of making the polyol (A) containing polyester ether polyol (Z) and polyisocyanate (B1) react, and obtaining a hydroxyl-terminated urethane polymer (UH).   The manufacturing method of the main ingredient for adhesives of Claim 7 whose weight average molecular weights of the said hydroxyl-terminated urethane polymer (UH) are 40,000-100,000.   The main component for pressure-sensitive adhesives according to any one of claims 4 to 8, wherein the polyester ether polyol (Z) contains 10 to 50% by mass of a structural unit derived from the dicarboxylic acid anhydride (b). Production method.   The polyisocyanate (B1) is one or more selected from the group consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. The manufacturing method of the main ingredient for adhesives of one term | claim. The main agent for pressure-sensitive adhesives according to any one of claims 1 to 3,
A composition for producing a urethane resin-based pressure-sensitive adhesive, comprising a curing agent containing a second polyisocyanate (B2).   The composition for producing a urethane resin-based pressure-sensitive adhesive according to claim 11, wherein the second polyisocyanate (B2) has an average functional group number greater than 2. The process of manufacturing the main ingredient for adhesives by the method as described in any one of Claims 4-10,
A method for producing a urethane resin-based pressure-sensitive adhesive, comprising a step of reacting the main agent for pressure-sensitive adhesive with a curing agent containing a second polyisocyanate (B2).   The method for producing a urethane resin-based pressure-sensitive adhesive according to claim 13, wherein the average number of functional groups of the second polyisocyanate (B2) is larger than 2.