JP7210969B2 - Adhesive composition and adhesive composition for labels - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive composition for labels, and more particularly to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive composition for labels that are excellent in die-cutting performance when used for labels.

In recent years, from the viewpoint of environmental problems, energy saving, resource saving, etc., adhesive compositions that do not use solvents and can be hot-melt processed have been recommended. Styrene-isoprene- Styrene block copolymers are widely used.

Adhesive properties such as initial adhesive strength, peel adhesive strength and holding power are required for adhesive compositions. Various studies have been conducted for the purpose of improving these adhesive performances.

For example, Patent Document 1 discloses a block copolymer containing an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer (A) and an aromatic vinyl-isoprene diblock copolymer (B). A coalescing composition,
(i) the ratio of the weight average molecular weight Mw _Da of the polyisoprene block of the triblock copolymer (A) to the weight average molecular weight Mw _Db of the polyisoprene block of the diblock copolymer (B) (Mw _Da /Mw _Db ) is 0.5 or more and less than 1,
(ii) the ratio of the aromatic vinyl monomer unit to the total polymer component contained is 10 to 30% by mass;
(iii) A pressure-sensitive adhesive composition containing a block copolymer composition and a tackifying resin, characterized by a breaking strength of less than 8 MPa and a breaking elongation of less than 1100%.

WO2016/052310

However, conventional pressure-sensitive adhesive compositions still have room for improvement in terms of die-cutting performance.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive composition for labels that have excellent die-cutting performance when used for labels.

The present inventors conducted studies to achieve the above object, and found that a block copolymer composition containing a triblock copolymer and a diblock copolymer and a composition containing a hydrocarbon resin, Content of aromatic vinyl monomer units in the block copolymer composition, content of aliphatic monomer units and aromatic monomer units in the hydrocarbon resin, and Z-average molecular weight of the hydrocarbon resin and the breaking strength and breaking elongation are appropriately adjusted, the label obtained using such a composition has excellent die-cutting performance, and has completed the present invention.

That is, according to the present invention, there is provided a pressure-sensitive adhesive composition containing a block copolymer composition and a hydrocarbon resin, wherein the block copolymer composition comprises an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer. It contains a polymer and an aromatic vinyl-isoprene diblock copolymer, and the content of the aromatic vinyl monomer units in the total polymer components in the block copolymer composition is 10 to 30% by mass. wherein the hydrocarbon resin contains an aliphatic monomer unit, or an aliphatic monomer unit and an aromatic monomer unit, and the content of the aromatic monomer unit in the hydrocarbon resin The amount is 40% by mass or less based on the total monomer units, the Z-average molecular weight of the hydrocarbon resin is 5,000 or more, the breaking strength is less than 6.0 MPa, and the breaking elongation is less than 1,300% A pressure-sensitive adhesive composition is provided.

In the pressure-sensitive adhesive composition of the present invention, the hydrocarbon resin preferably has a weight average molecular weight of 2,500 or more and a softening point of 90°C or more.
In the pressure-sensitive adhesive composition of the present invention, the triblock copolymer is
General formula (A): Ar1 ^a -D ^a -Ar2 ^a
(In the formula, Ar1 ^a is a polyaromatic vinyl block with a weight average molecular weight of 5,000 to 20,000, Ar2 ^a is a polyaromatic vinyl block with a weight average molecular weight of 25,000 to 400,000, D ^a represents a polyisoprene block).
In the adhesive composition of the present invention, the content of the hydrocarbon resin is preferably 10 to 500 parts by mass with respect to 100 parts by mass of the block copolymer composition.

Further, according to the present invention, there is provided a pressure-sensitive adhesive composition for labels comprising the pressure-sensitive adhesive composition described above.

ADVANTAGE OF THE INVENTION According to this invention, when using for a label, the adhesive composition and adhesive composition for labels which are excellent in die-cutting performance can be provided.

The pressure-sensitive adhesive composition of the present invention contains a specific block copolymer composition and a specific hydrocarbon resin, and has a breaking strength of less than 6.0 MPa and a breaking elongation of less than 1300%. Since the pressure-sensitive adhesive composition of the present invention has such a structure, it can form the pressure-sensitive adhesive layer of a label, and the resulting label has adhesive properties such as initial adhesive strength, peel adhesive strength and holding power. It has excellent die-cutting performance. That is, even if the label obtained using the adhesive composition of the present invention is cut by a die cutter, the adhesive layer does not pull strings, and the adhesive composition does not adhere to the blade of the die cutter. , can be cut easily.

The breaking strength of the pressure-sensitive adhesive composition of the present invention is less than 6.0 MPa, which provides even better die-cutting performance. is not particularly limited.

In the present invention, the breaking strength is measured by a method according to JIS K 6251 using a 1 mm thick sheet obtained from the pressure-sensitive adhesive composition.

The elongation at break of the pressure-sensitive adhesive composition of the present invention is less than 1,300%, and is preferably less than 1,200%, more preferably less than 1,100%, because more excellent die-cutting performance can be obtained. Although the lower limit is not particularly limited, it may be 100% or more.

In the present invention, the elongation at break is measured by a method according to JIS K 6251 using a 1 mm thick sheet obtained from the pressure-sensitive adhesive composition.

<Block copolymer composition>
The block copolymer composition contained in the adhesive composition of the present invention is an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer (hereinafter sometimes simply referred to as "triblock copolymer"), and an aromatic vinyl-isoprene diblock copolymer (hereinafter sometimes simply referred to as "diblock copolymer").

In the block copolymer composition, the mass ratio of the triblock copolymer and the diblock copolymer (triblock copolymer/diblock copolymer) is preferable because better die cutting performance can be obtained. is 10/90 to 70/30, more preferably 15/85 to 60/40.

The content of the aromatic vinyl monomer unit in the total polymer components in the block copolymer composition is 10 to 30% by mass, and is preferably 12 to 30% because it provides better die-cutting performance. % by mass, more preferably 15 to 28% by mass.

The weight-average molecular weight of the block copolymer composition is not particularly limited, but is preferably 70,000 to 300,000, more preferably 85,000, because better die-cutting performance can be obtained. ~270,000, more preferably 100,000 to 250,000.

The molecular weight distribution represented by the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the block copolymer composition is not particularly limited, but is preferably 1. 01 to 10, more preferably 1.01 to 5, still more preferably 1.01 to 3.

The aromatic vinyl-isoprene-aromatic vinyl triblock copolymer is a triblock copolymer consisting of [polyaromatic vinyl block]-[polyisoprene block]-[polyaromatic vinyl block].

The polyaromatic vinyl block (hereinafter sometimes referred to as "polyaromatic vinyl block (Ar)") possessed by the triblock copolymer is an aromatic vinyl monomer unit in the polymer chain of the triblock copolymer. as a main structural unit.

In the polyaromatic vinyl block (Ar), the content of aromatic vinyl monomer units is preferably 80% by mass or more, more preferably 100% by mass. If the aromatic vinyl monomer unit content in the polyaromatic vinyl block (Ar) is too low, the pressure-sensitive adhesive composition obtained may have poor pressure-sensitive adhesive performance.

Examples of aromatic vinyl monomers for obtaining the polyaromatic vinyl block (Ar) include styrene; α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, alkyl-substituted styrenes such as ethylstyrene and p-tert-butylstyrene; halogen-substituted styrenes such as 4-chlorostyrene, 2-bromostyrene and 3,5-difluorostyrene; 4-methoxystyrene and 3,5-dimethoxystyrene alkoxy-substituted styrenes such as; Among these, styrene and alkyl-substituted styrene are preferred, and styrene is particularly preferred, from the viewpoint of excellent adhesion performance, die-cutting performance, and availability.

The polyaromatic vinyl block (Ar) contains an aromatic vinyl monomer and another monomer copolymerizable with the aromatic vinyl monomer as long as the effects of the present invention are not substantially impaired. may be obtained by copolymerizing.
Specific examples of other monomers copolymerizable with aromatic vinyl monomers include conjugated monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene. A diene monomer can be mentioned.

The weight average molecular weight of the polyaromatic vinyl block (Ar) is preferably 5,000 to 390,000, more preferably 6,000 to 380,000, particularly preferably 7,000 to 370,000. If the weight average molecular weight of the polyaromatic vinyl block (Ar) is too small, the adhesive performance of the obtained adhesive composition may be poor. may become difficult.

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyaromatic vinyl block (Ar) is preferably 2 or less, more preferably 1.5 or less. When this ratio is small, a pressure-sensitive adhesive composition with better pressure-sensitive adhesive performance is obtained.

The content of aromatic vinyl monomer units in the entire triblock copolymer is usually 15-75% by mass, preferably 17-60% by mass, more preferably 20-50% by mass. When the content of the aromatic vinyl monomer unit is in this range, it is possible to efficiently obtain a pressure-sensitive adhesive composition having excellent pressure-sensitive adhesive performance and die-cut performance.

The triblock copolymer has two polyaromatic vinyl blocks as the polyaromatic vinyl block (Ar), which may be the same or different. .

The polyisoprene block (hereinafter sometimes referred to as "polyisoprene block (D)") possessed by the triblock copolymer is a portion containing isoprene units as main structural units in the polymer chain of the triblock copolymer. Say. In the polyisoprene block, the content of isoprene units is preferably 80% by mass or more, more preferably 100% by mass. If the content of isoprene units is too low, the pressure-sensitive adhesive composition obtained may have poor pressure-sensitive adhesive performance.

The polyisoprene block (D) may be obtained by copolymerizing isoprene with other monomers copolymerizable with isoprene as long as it does not substantially impair the effects of the present invention. good. Specific examples of other monomers copolymerizable with isoprene include the above aromatic vinyl monomers; 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, etc. conjugated diene monomers other than isoprene;

The weight average molecular weight of the polyisoprene block (D) is preferably 20,000 to 400,000, more preferably 30,000 to 270,000, particularly preferably 35,000 to 250,000. If the weight-average molecular weight of the polyisoprene block (D) is too small, the pressure-sensitive adhesive composition obtained may have poor adhesion performance. There is a possibility that it will be.

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyisoprene block (D) is preferably 2 or less, more preferably 1.5 or less. When this ratio is small, a pressure-sensitive adhesive composition with better pressure-sensitive adhesive performance is obtained.

The ratio (vinyl bond content) of isoprene units having a vinyl bond (-CH=CH ₂ ) in the polyisoprene block (D) is not particularly limited. Usually, it is 50% by mass or less, preferably 20% by mass or less, more preferably 5 to 10% by mass. Within this range, a pressure-sensitive adhesive composition with superior pressure-sensitive adhesive performance can be obtained.

The weight average molecular weight of the triblock copolymer is usually 80,000 to 450,000, preferably 100,000 to 250,000, more preferably 110,000 to 230,000, particularly preferably 120,000 to 220, 000. If the weight-average molecular weight is too small, the pressure-sensitive adhesive composition to be obtained may be inferior in adhesive performance.

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the triblock copolymer is preferably 2 or less, more preferably 1.5 or less. When this ratio is small, a pressure-sensitive adhesive composition with better pressure-sensitive adhesive performance is obtained.

As the triblock copolymer, a triblock copolymer A represented by the following general formula (A) and a triblock represented by the following general formula (B) are used, since they provide better die-cutting performance. Copolymer B is preferred, and triblock copolymer A is more preferred.

General formula (A): Ar1 ^a -D ^a -Ar2 ^a
(In the formula, Ar1 ^a is a polyaromatic vinyl block with a weight average molecular weight of 5,000 to 20,000, Ar2 ^a is a polyaromatic vinyl block with a weight average molecular weight of 25,000 to 400,000, D ^a represents a polyisoprene block)

General formula (B): (Ar ^b -D ^b ) ₂ -X
(Ar ^b is a polyaromatic vinyl block with a weight average molecular weight of 5,000 to 100,000, D ^b is a polyisoprene block, X is a single bond or a residue of a coupling agent)

In the triblock copolymer A, the polyaromatic vinyl block (Ar1 ^a ) and the polyaromatic vinyl block (Ar2 ^a ) are mainly aromatic vinyl monomer units obtained by polymerizing aromatic vinyl monomers. It is a polymer block constructed as a repeating unit.

The aromatic vinyl monomer used to form the aromatic vinyl monomer units of the polyaromatic vinyl block (Ar1 ^a ) and the polyaromatic vinyl block (Ar2 ^a ) is an aromatic vinyl compound, especially Examples include, but are not limited to, those similar to the polyaromatic vinyl block (Ar) described above.

The polyaromatic vinyl block (Ar1 ^a ) and the polyaromatic vinyl block (Ar2 ^a ) may contain other monomer units as long as the aromatic vinyl monomer unit is the main repeating unit. Examples of the monomer constituting the monomer unit other than the aromatic vinyl monomer unit include the same as the polyaromatic vinyl block (Ar) described above, and the content thereof is also the same. do it. Moreover, the polyaromatic vinyl block (Ar1 ^a ) and the polyaromatic vinyl block (Ar2 ^a ) preferably consist essentially of one or more aromatic vinyl monomer units. , is particularly preferably composed of styrene units only.

In the block copolymer A, the polyaromatic vinyl block (Ar1 ^a ) and the polyaromatic vinyl block (Ar2 ^a ) have different weight average molecular weights. When the pressure-sensitive adhesive composition of the present invention contains such an asymmetric block copolymer A, the pressure-sensitive adhesive composition of the present invention is even more excellent in die cutting performance.

The weight average molecular weight of the polyaromatic vinyl block (Ar1 ^a ) is 5,000 to 20,000, more preferably 10,000 to 20,000, still more preferably 11,000 to 18,000. .

The weight average molecular weight of the polyaromatic vinyl block (Ar2 ^a ) is 25,000 to 400,000, more preferably 25,000 to 300,000, and still more preferably 27,000 to 200,000. .

The weight average molecular weight ratio ((Ar1 ^a ):(Ar2 ^a )) of the polyaromatic vinyl block (Ar1 ^a ) and the polyaromatic vinyl block (Ar2 ^a ) is preferably 1:1 to 1:15. , more preferably 1:2 to 1:10.

The polyisoprene block (D ^a ) is a polymer block composed of isoprene units obtained by polymerizing isoprene as main repeating units.

In addition, the polyisoprene block (D ^a ) may contain monomer units other than isoprene units as long as the isoprene units are main repeating units. Examples thereof include those similar to the polyisoprene block (D), and the content and the vinyl bond content may also be the same. Moreover, it is particularly preferable that the polyisoprene block (D ^a ) consists only of isoprene units.

The weight average molecular weight of the polyisoprene block (D ^a ) is preferably 20,000 to 400,000, more preferably 30,000 to 170,000, still more preferably 35,000 to 150,000. .

The weight average molecular weight of the block copolymer A (that is, the weight average molecular weight of the entire block copolymer A) is preferably 80,000 to 300,000, more preferably 100,000 to 270,000, More preferably 120,000 to 250,000.

The content of the aromatic vinyl monomer units in the block copolymer A is preferably 20 to 60% by mass, more preferably 25 to 60% by mass, based on the total monomer units constituting the block copolymer A. 60% by mass, more preferably 30 to 50% by mass.

The block copolymer A is preferably obtained by a production method in which an aromatic vinyl monomer, isoprene, and then an aromatic vinyl monomer are sequentially polymerized to form a polymer block. Therefore, block copolymer A preferably does not contain a residue of a coupling agent. Details of such a manufacturing method will be described later.

Triblock copolymer B is a copolymer represented by the following general formula (B).
General formula (B): (Ar ^b -D ^b ) ₂ -X
(Ar ^b is a polyaromatic vinyl block with a weight average molecular weight of 5,000 to 100,000, D ^b is a polyisoprene block, X is a single bond or a residue of a coupling agent)

Block copolymer B has a structure in which two diblocks (Ar ^b -D ^b ) are bonded to each other either directly through a single bond or via a residue (X) of a coupling agent. The residue (X) of the coupling agent is not particularly limited as long as it is a divalent residue of the coupling agent, but is preferably a residue of a silicon atom-containing coupling agent, such as a halogenated silane or an alkoxysilane. A residue is more preferred. Examples of the coupling agent that constitutes the residue of the coupling agent include those described below.

Polyaromatic vinyl block (Ar ^b ) is a polymer block composed mainly of repeating units of aromatic vinyl monomer units obtained by polymerizing aromatic vinyl monomers.

The aromatic vinyl monomer used to constitute the aromatic vinyl monomer unit of the polyaromatic vinyl block (Ar ^b ) is not particularly limited as long as it is an aromatic vinyl compound. Examples include those similar to the group vinyl block (Ar).

The polyaromatic vinyl block (Ar ^b ) may contain other monomer units as long as the aromatic vinyl monomer unit is the main repeating unit, and may contain other monomer units than the aromatic vinyl monomer unit. Examples of the monomer constituting the monomer unit include those similar to the polyaromatic vinyl block (Ar) described above, and the content thereof may also be similar. Each polyaromatic vinyl block in the block copolymer B may be composed of the same aromatic vinyl monomer units, or may be composed of different aromatic vinyl monomer units. In addition, the polyaromatic vinyl block (Ar ^b ) is also preferably substantially composed of only one or more aromatic vinyl monomer units, and is composed only of styrene units. is particularly preferred.

The weight average molecular weight of the polyaromatic vinyl block (Ar ^b ) is preferably 5,000 to 100,000, more preferably 6,000 to 80,000, still more preferably 7,000 to 70,000, and particularly preferably It ranges from 7,000 to 20,000.

The weight-average molecular weights of the two polyaromatic vinyl blocks (Ar ^b ) of the block copolymer B may be the same or different, as long as they are within the above range. , are preferably substantially equal.

The polyisoprene block (D ^b ) is a polymer block composed of isoprene units obtained by polymerizing polyisoprene as main repeating units.

In addition, the polyisoprene block (D ^b ) may contain monomer units other than isoprene units as long as the isoprene units are main repeating units. Examples thereof include those similar to the polyisoprene block (D), and the content and the vinyl bond content may also be the same. Moreover, it is particularly preferable that the polyisoprene block (D ^b ) consists only of isoprene units.

The weight average molecular weight of the polyisoprene block (D ^b ) is preferably 20,000 to 400,000, more preferably 30,000 to 170,000, still more preferably 35,000 to 150,000. .

The weight average molecular weights of the two polyisoprene blocks (D ^b ) of the block copolymer B may be the same or different from each other as long as they are within the above range. are preferably identical.

The weight average molecular weight of the block copolymer B (that is, the weight average molecular weight of the entire block copolymer B) is preferably 80,000 to 450,000, more preferably 100,000 to 270,000, More preferably 120,000 to 250,000.

The content of the aromatic vinyl monomer units in the block copolymer B is preferably 20 to 60% by mass, more preferably 25 to 60% by mass, based on the total monomer units constituting the block copolymer B. 60% by mass, more preferably 30 to 50% by mass.

The content of the triblock copolymer in the block copolymer composition is generally 10-90% by mass, preferably 15-85% by mass, more preferably 20-80% by mass. If this ratio is too small, the pressure-sensitive adhesive composition to be obtained tends to have poor adhesion performance, and conversely, if it is too large, the initial adhesive strength and die-cutting performance of the pressure-sensitive adhesive composition tend to be poor.

The aromatic vinyl-isoprene diblock copolymer contained in the adhesive composition of the present invention is a diblock copolymer consisting of [polyaromatic vinyl block]-[polyisoprene block].

The polyaromatic vinyl block (hereinafter sometimes referred to as " ^polyaromatic vinyl block (Arc)") possessed by the diblock copolymer is an aromatic vinyl monomer in the polymer chain of the diblock copolymer. A portion containing a unit as a main structural unit.

In the ^polyaromatic vinyl block (Arc), the aromatic vinyl monomer unit content is preferably 80% by mass or more, more preferably 100% by mass. If the aromatic vinyl monomer unit content in the polyaromatic vinyl block is too low, the pressure-sensitive adhesive composition obtained may have poor pressure-sensitive adhesive performance.

The aromatic vinyl monomer for obtaining the polyaromatic vinyl block (Ar ^c ) is the same as those listed as the aromatic vinyl monomer for obtaining the polyaromatic vinyl block (Ar). is mentioned. Among them, styrene and alkyl-substituted styrene are preferred, and styrene is particularly preferred.

The ^polyaromatic vinyl block (Arc) contains an aromatic vinyl monomer and other monomers copolymerizable with the aromatic vinyl monomer as long as they do not substantially impair the effects of the present invention. It may be obtained by copolymerizing with.
Other monomers copolymerizable with aromatic vinyl monomers include conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene. body.

The weight average molecular weight of the polyaromatic vinyl block (Ar ^c ) is 5,000 to 20,000, more preferably 10,000 to 20,000, still more preferably 11,000 to 18,000. . If the weight average molecular weight of the polyaromatic vinyl block (Ar ^c ) is too small, the pressure-sensitive adhesive composition obtained may have poor adhesive performance. may become difficult.

The ratio (Mw/Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the ^polyaromatic vinyl block (Arc) is preferably 2 or less, more preferably 1.5 or less. preferable. When this ratio is small, a pressure-sensitive adhesive composition with better pressure-sensitive adhesive performance is obtained.

The polyisoprene block of the diblock copolymer (hereinafter sometimes referred to as "polyisoprene block (D ^c )") is a portion containing an isoprene unit as a main structural unit in the polymer chain of the diblock copolymer. Say.
In the polyisoprene block (D ^c ), the content of isoprene units is preferably 80% by mass or more, more preferably 100% by mass. If the isoprene unit content is too low, the resulting pressure-sensitive adhesive composition may have poor initial adhesive strength at low temperatures.

The polyisoprene block (D ^c ) may be a copolymer of isoprene and other monomers copolymerizable with isoprene as long as the effects of the present invention are not substantially impaired. Other monomers copolymerizable with isoprene include the above aromatic vinyl monomers; conjugated diene monomer;

The weight average molecular weight of the polyisoprene block (D ^c ) is preferably 20,000 to 400,000, more preferably 30,000 to 170,000, still more preferably 35,000 to 150,000. . If the weight-average molecular weight of the polyisoprene block (D ^c ) is too small, the pressure-sensitive adhesive composition obtained may have poor adhesive performance. It can be difficult.

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyisoprene block (D ^c ) is preferably 2 or less, more preferably 1.5 or less. When this ratio is small, a pressure-sensitive adhesive composition with better pressure-sensitive adhesive performance is obtained.

The content of the aromatic vinyl monomer units in the entire diblock copolymer is usually 8-50% by mass, preferably 10-40% by mass, more preferably 12-30% by mass. If the content of the aromatic vinyl monomer unit is too low, the pressure-sensitive adhesive composition obtained may have poor adhesion performance. Sometimes.

Among the isoprene units in the diblock copolymer, the ratio of those having a vinyl bond (-CH=CH ₂ ) (vinyl bond content) is not particularly limited, and is usually 50% by mass or less, preferably 20% by mass. % or less, more preferably 5 to 10% by mass. Within this range, a pressure-sensitive adhesive composition having excellent initial adhesive strength at low temperatures can be obtained.

The weight average molecular weight of the diblock copolymer is usually 80,000 to 200,000, preferably 90,000 to 180,000, more preferably 100,000 to 160,000, particularly preferably 110,000 to 140. , 000. If the weight-average molecular weight is too small, the pressure-sensitive adhesive composition to be obtained tends to be inferior in adhesive performance.

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the diblock copolymer is preferably 2 or less, more preferably 1.5 or less. When this ratio is small, a pressure-sensitive adhesive composition with excellent pressure-sensitive adhesive performance can be efficiently obtained.

The content of the diblock copolymer in the block copolymer composition is generally 10-90% by mass, preferably 15-85% by mass, more preferably 20-80% by mass.
When the content of the diblock copolymer is in such a range, a pressure-sensitive adhesive composition with superior pressure-sensitive adhesive performance and die-cut performance can be obtained.

In addition, in the block copolymer composition, the effects of the present invention are exhibited well in a well-balanced manner. Preferably, the combined weight average molecular weight is between 80,000 and 140,000.

In the block copolymer composition, the ratio of the content of the aromatic vinyl monomer unit in the triblock copolymer to the content of the aromatic vinyl monomer unit in the diblock copolymer is 1. It is preferably 5 or more, more preferably 1.6 or more, further preferably 1.7 to 4.0.

The method for producing the triblock copolymer is not particularly limited, and conventionally known production methods can be employed. For example, by an anionic living polymerization method, a method of sequentially polymerizing a polyaromatic vinyl block and a polyisoprene block, respectively, or a block copolymer having a living active terminal is produced, respectively, and these are described later. A method of producing by coupling by reacting with a coupling agent can be employed.

The method for producing the diblock copolymer is not particularly limited, and conventionally known production methods can be employed. For example, a method of sequentially polymerizing a polyaromatic vinyl block and a polyisoprene block by an anionic living polymerization method can be employed.

In addition, the triblock copolymer and the diblock copolymer may be produced separately as described above. , can also be prepared as a mixture of triblock and diblock copolymers. As such a manufacturing method, a first manufacturing method and a second manufacturing method are exemplified.

The first manufacturing method consists of the following first to fifth steps.
(First step) In a polymerization solvent, an aromatic vinyl monomer is polymerized using an anionic polymerization initiator to form a polyaromatic vinyl block chain having a living active terminal.
(Second step) Polymerizing isoprene from a living active end of a polyaromatic vinyl block chain to obtain an aromatic vinyl-isoprene diblock chain having a living active end.
(Third step) A part of the living active terminals of the aromatic vinyl-isoprene diblock chain are deactivated with a polymerization terminator to obtain an aromatic vinyl-isoprene diblock copolymer. At this time, the amount of the polymerization terminator is adjusted to be less than 1 molar equivalent with respect to the active terminal of the aromatic vinyl-isoprene diblock chain.
(Fourth step) adding an aromatic vinyl monomer to the solution obtained in the above (third step), and The ends are reacted with aromatic vinyl monomers to give aromatic vinyl-isoprene-aromatic vinyl triblock chains with living active ends.
(Fifth step) Deactivating the living active terminal of the aromatic vinyl-isoprene-aromatic vinyl triblock chain with a polymerization terminator to obtain an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer. .

The second manufacturing method consists of a total of four steps, the first and second steps and the sixth and seventh steps below.
(First step) In a polymerization solvent, an aromatic vinyl monomer is polymerized using an anionic polymerization initiator to form a polyaromatic vinyl block chain having a living active terminal.
(Second step) Polymerizing isoprene from a living active end of a polyaromatic vinyl block chain to obtain an aromatic vinyl-isoprene diblock chain having a living active end.
(Sixth step) Part of the aromatic vinyl-isoprene diblock chain having a living active terminal is reacted with a coupling agent to form a coupled aromatic vinyl-isoprene-aromatic vinyl triblock copolymer. get coalescence. At this time, the amount of the coupling agent reactive group is adjusted to be less than 1 molar equivalent with respect to the active terminal of the aromatic vinyl-isoprene diblock chain.
(Seventh step) The living active terminal of the aromatic vinyl-isoprene diblock chain is deactivated with a polymerization terminator to obtain an aromatic vinyl-isoprene diblock copolymer.

Each of these steps will be described below in order.
The first step in the first production method is to polymerize an aromatic vinyl monomer using an anionic polymerization initiator in a polymerization solvent to produce a polyaromatic vinyl block chain having a living active terminal. It is a process to let

The polymerization solvent to be used is not particularly limited as long as it is inert to the polymerization initiator. For example, a chain hydrocarbon solvent, a cyclic hydrocarbon solvent, or a mixed solvent thereof can be used.
Chain hydrocarbon solvents include n-butane, isobutane, n-hexane, 1-butene, isobutylene, trans-2-butene, cis-2-butene, 1-pentene, trans-2-pentene, cis-2- Examples include pentene, n-pentane, trans-2-pentane, neopentane and mixtures thereof.
Examples of cyclic hydrocarbon solvents include benzene, toluene, xylene, cyclohexane and the like.
Among these, it is preferable to use a mixture of a chain hydrocarbon solvent and a cyclic hydrocarbon solvent, since the polymerization temperature and the molecular weight of the polymer can be easily controlled.
When a chain hydrocarbon solvent and a cyclic hydrocarbon solvent are mixed and used, the mixing ratio is (chain hydrocarbon solvent):(cyclic hydrocarbon solvent) in mass ratio, preferably 5:95 to 50:50, more preferably 10:90 to 40:60.

The total amount of the polymerization solvent used in the first to fourth steps is usually 100 to 1000 parts by weight, preferably 150 to 400 parts by weight, per 100 parts by weight of all the monomers used.

The anionic polymerization initiator is not particularly limited, and any known one can be used as long as it is used for anionic polymerization of aromatic vinyl monomers and isoprene. Specific examples thereof include organic monolithium initiators such as methyllithium, n-propyllithium, n-butyllithium and sec-butyllithium. Among these, n-butyllithium is preferred. The amount of the polymerization initiator to be used may be appropriately determined based on conventional methods so as to obtain a polymer having a desired weight average molecular weight.

Moreover, it is preferable to carry out the polymerization in the presence of a polar compound, since it is easy to adjust the polymerization rate and produce a polymer having a narrow molecular weight distribution.
A polar compound is a compound whose molecule has electrical polarity, specifically, a compound having a dielectric constant measured at 25° C. of preferably 2.5 to 5.0.
Polar compounds include aromatic ethers such as diphenyl ether and anisole; aliphatic ethers such as diethyl ether and dibutyl ether; tertiary monoamines such as trimethylamine, triethylamine and tripropylamine; tertiary polyamines such as tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine; and the like. Among these, N,N,N',N'-tetramethylethylenediamine is preferred.

The amount of the polar compound used is preferably 0.05 to 0.5 mol, more preferably 0.01 to 0.1 mol, per 1 mol of the anionic polymerization initiator.

The second step is to polymerize isoprene from the living active ends of polyaromatic vinyl block chains to obtain aromatic vinyl-isoprene diblock chains with living active ends.
In the second step, isoprene is preferably reacted while being continuously added in order to suppress rapid generation of reaction heat.

The third step is a step of deactivating some of the living active terminals of the aromatic vinyl-isoprene diblock chain with a polymerization terminator to obtain an aromatic vinyl-isoprene diblock copolymer.

The polymerization terminator is not particularly limited as long as it can react with the active terminal to deactivate the active terminal and does not react with another active terminal after reacting with one active terminal, but the resulting composition From the viewpoint of suppressing moisture absorption, it is preferable to use a polymerization terminator that is a compound that does not contain a halogen atom. Polymerization terminating agents that allow Compounds particularly preferably used as the polymerization terminator include water, monohydric alcohols such as methanol and ethanol, and monohydric phenols such as phenol and cresol.

The amount of the polymerization terminator used is determined according to the mass ratio of the triblock copolymer and the diblock copolymer, and is particularly an amount that is less than 1 molar equivalent with respect to the active terminal of the triblock chain. Although not limited, the polymerization terminator is usually in the range of 0.18 to 0.91 molar equivalents, preferably in the range of 0.35 to 0.80 molar equivalents, relative to the active terminal.

In the fourth step, an aromatic vinyl monomer is added to the solution obtained in the above (third step), and the remaining aromatic vinyl-isoprene diblock chain having a living active end is activated for living activity. This is the step of reacting the terminal with the aromatic vinyl monomer.
When the aromatic vinyl monomer is added, the aromatic vinyl chain is extended from the terminal of the aromatic vinyl-isoprene diblock chain having the active terminal remaining without reacting with the polymerization terminator. At this time, if an aromatic vinyl chain having a weight average molecular weight larger than that of the aromatic vinyl chain in the aromatic vinyl-isoprene diblock chain is formed, in the fifth step, finally, the above-mentioned triblock copolymerization Coalescence A is obtained. Further, when an aromatic vinyl chain having a weight average molecular weight equivalent to that of the aromatic vinyl chain in the aromatic vinyl-isoprene diblock chain is formed, in the fifth step, finally, the above-mentioned triblock copolymer B is obtained.

Next, the second manufacturing method will be explained. The first and second steps in the second manufacturing method are as explained in the first manufacturing method.

In the second manufacturing method, the sixth step is performed after the second step. In the sixth step, a portion of the aromatic vinyl-isoprene diblock chain having a living active end is reacted with a coupling agent to form a coupled aromatic vinyl-isoprene-aromatic vinyl triblock copolymer. This is the process of obtaining coalescence.

A coupling agent is a compound having two sites that react with the living active terminal of a polymer molecule to bond with the polymer molecule.

Bifunctional coupling agents having two reaction sites include bifunctional halogenated silanes such as dichlorosilane, monomethyldichlorosilane and dimethyldichlorosilane; bifunctional alkoxysilanes such as diphenyldimethoxysilane and diphenyldiethoxysilane; Bifunctional halogenated alkanes such as dichloroethane, dibromoethane, methylene chloride, dibromomethane; bifunctional dichlorotin, monomethyldichlorotin, dimethyldichlorotin, monoethyldichlorotin, diethyldichlorotin, monobutyldichlorotin, dibutyldichlorotin, etc. benzoic acid, CO, 2-chloropropene and the like. Among them, dimethyldichlorosilane is preferred. The amount of the coupling agent used is such that the amount of the aromatic vinyl-isoprene-aromatic vinyl block copolymer (corresponding to the triblock copolymer (A)) obtained by coupling is within the desired range. , may be determined as appropriate.

The seventh step is to deactivate the living active terminal of the aromatic vinyl-isoprene diblock chain with a polymerization terminator to obtain an aromatic vinyl-isoprene diblock copolymer.

As the polymerization terminator, those commonly used in anionic living polymerization can be used. Specific examples include water; alcohols such as methyl alcohol and ethyl alcohol; inorganic acids such as hydrochloric acid; organic acids such as acetic acid; monofunctional silane compounds such as chlorotrimethylsilane;

A solution containing a mixture of a triblock copolymer and a diblock copolymer is obtained by the above method. An antioxidant may be added to this solution as needed.
The polymer is then separated from the solution by known polymer separation techniques such as steam stripping and the resulting polymer is dried to provide a mixture of triblock and diblock copolymers. .

When a mixture of a triblock copolymer and a diblock copolymer is produced by the above method, the ratio of the triblock copolymer to the total amount of the triblock copolymer and the diblock copolymer is usually 10. ~70% by mass, preferably 15 to 60% by mass. By keeping this ratio within this range, a block copolymer composition having a preferred composition can be obtained without adding a separately produced triblock copolymer when producing the block copolymer composition. can be done.
The ratio of the triblock copolymer to the total amount of the triblock copolymer and the diblock copolymer can be adjusted by adjusting the amount of the polymerization terminator used in the third step or the coupling agent used in the sixth step. .

The method for producing the block copolymer composition is not particularly limited. For example, a method of kneading a triblock copolymer and a diblock copolymer separately produced or obtained in a predetermined ratio, a method of producing a triblock copolymer and a diblock copolymer in a predetermined ratio, respectively A method of mixing in a solution state, separating the polymer by a known method, and drying to produce, and a mixture of the triblock copolymer and the diblock copolymer obtained by the above method as a polymer component as it is. Any method or the like can be adopted.

<Hydrocarbon resin>
The pressure-sensitive adhesive composition of the present invention contains a hydrocarbon resin in addition to the block copolymer composition. The hydrocarbon resin used in the present invention contains aliphatic monomeric units, or contains both aliphatic and aromatic monomeric units. The hydrocarbon resin used in the present invention includes a hydrocarbon resin containing only aliphatic monomer units, and a hydrocarbon resin containing both aliphatic monomer units and aromatic monomer units. At least one selected from the group consisting of hydrocarbon resins having a content of 40% by mass or less relative to the total monomer units is preferred.

In the adhesive composition of the present invention, the hydrocarbon resin contains an aliphatic monomer unit, or contains an aliphatic monomer unit and a predetermined proportion of an aromatic monomer unit, and , with a very defined Z-average molecular weight (Mz). Owing to these characteristics, the pressure-sensitive adhesive composition of the present invention is excellent in adhesive properties such as initial adhesive strength, peel adhesive strength and holding power, and is also excellent in die cutting performance.

The aliphatic monomer units may be those containing no aromatic ring, for example, 1,3-pentadiene monomer units, alicyclic monoolefin monomer units having 4 to 6 carbon atoms, carbon Acyclic monoolefin monomer units of numbers 4 to 8, alicyclic diolefin monomer units and the like are included.

The content of 1,3-pentadiene (piperylene) monomer units in the hydrocarbon resin is preferably 1 to 80% by mass, more preferably 20 to 75% by mass, and still more preferably 30 to 70% by mass. . By setting the content ratio of the 1,3-pentadiene monomer unit within the above range, the pressure-sensitive adhesive composition obtained can be made more excellent in pressure-sensitive adhesive performance. The cis/trans isomer ratio in 1,3-pentadiene may be any ratio and is not particularly limited.

The alicyclic monoolefin having 4 to 6 carbon atoms for forming the alicyclic monoolefin monomer unit having 4 to 6 carbon atoms has one ethylenically unsaturated bond and a non-aromatic It is not particularly limited as long as it is a hydrocarbon compound having 4 to 6 carbon atoms and a ring structure, and specific examples thereof include cyclobutene, cyclopentene, cyclohexene, methylcyclobutene, and methylcyclopentene. The hydrocarbon compound having 4 to 6 carbon atoms may be used alone or in combination of two or more, but preferably contains at least cyclopentene, and The proportion of cyclopentene in the alicyclic monoolefin is preferably 50% by mass or more.

The content of alicyclic monoolefin monomer units having 4 to 6 carbon atoms in the hydrocarbon resin is preferably 1 to 30% by mass, more preferably 5 to 30% by mass, and still more preferably 10 to 30% by mass. %. By setting the content of the alicyclic monoolefin monomer unit having 4 to 6 carbon atoms within the above range, the pressure-sensitive adhesive composition obtained can be made more excellent in pressure-sensitive adhesive performance.

The acyclic monoolefin having 4 to 8 carbon atoms for forming the acyclic monoolefin monomer unit having 4 to 8 carbon atoms has one ethylenically unsaturated bond in its molecular structure, It is not particularly limited as long as it is a chain hydrocarbon compound having 4 to 8 carbon atoms and does not have a ring structure. Specific examples thereof include 1-butene, 2-butene, isobutylene (2-methylpropene), and the like. butenes; 1-pentene, 2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene and other pentenes; 1-hexene, 2-hexene, 2- Hexenes such as methyl-1-pentene; Heptenes such as 1-heptene, 2-heptene, and 2-methyl-1-hexene; 1-octene, 2-octene, 2-methyl-1-heptene, diisobutylene (2 , 4,4-trimethylpentene-1 and 2,4,4-trimethylpentene-1); Acyclic monoolefins having 4 to 8 carbon atoms may be used alone or in combination of two or more types, but at least 2-methyl-2-butene, isobutylene and diisobutylene Preferably, at least one selected from the group consisting of 2-methyl-2-butene, isobutylene and diisobutylene accounts for 50% by mass in the alicyclic monoolefin having 4 to 6 carbon atoms. It is more preferable to be above.

The content of the acyclic monoolefin monomer unit having 4 to 8 carbon atoms in the hydrocarbon resin is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and still more preferably 5 to 30% by mass. %. By containing the acyclic monoolefin monomer unit having 4 to 8 carbon atoms in the above ratio, the pressure-sensitive adhesive composition obtained can be made more excellent in pressure-sensitive adhesive performance.

An alicyclic diolefin for forming an alicyclic diolefin monomer unit is a hydrocarbon compound having two or more ethylenically unsaturated bonds and a non-aromatic ring structure in its molecular structure. Specific examples thereof include cyclopentadiene polymers such as cyclopentadiene and dicyclopentadiene, methylcyclopentadiene, and methylcyclopentadiene polymers. The alicyclic diolefin may be used alone or in combination of two or more, but preferably contains at least dicyclopentadiene, and dicyclopentadiene in the alicyclic diolefin More preferably, the proportion of pentadiene is 50% by mass or more.

The content of the aliphatic monomer unit in the hydrocarbon resin is preferably 60% by mass or more, more preferably 65% by mass or more, because more excellent die-cutting performance can be obtained. It is more preferably 70% by mass or more, and although the upper limit is not particularly limited, it may be 100% by mass or less, or 99% by mass or less.

The aromatic monomer unit preferably includes an aromatic monoolefin monomer unit, an aromatic monomer unit having a structure in which two or more cyclic structures are bonded, and the like.

The content of the aromatic monomer unit in the hydrocarbon resin is 40% by mass or less, preferably 35% by mass or less, and 30% by mass or less, since more excellent die-cutting performance can be obtained. and may be 0% by mass or more, or may be 1% by mass or more.

The aromatic monoolefin for forming the aromatic monoolefin monomer unit is a hydrocarbon compound having one ethylenically unsaturated bond in its molecular structure and an aromatic ring structure. Although not particularly limited, specific examples thereof include styrene, α-methylstyrene, vinyltoluene, and the like. The aromatic monoolefin may be used alone or in combination of two or more, but preferably contains at least styrene, and the proportion of styrene in the aromatic monoolefin is 50. % or more is more preferable.

The content of aromatic monoolefin monomer units in the hydrocarbon resin is preferably 0 to 40% by mass, more preferably 0 to 35% by mass, still more preferably 0 to 30% by mass. By containing the aromatic monoolefin monomer unit in the above ratio, the pressure-sensitive adhesive composition obtained can be made more excellent in pressure-sensitive adhesive performance.

An aromatic monomer having a structure in which two or more cyclic structures are bonded for forming an aromatic monomer unit having a structure in which two or more cyclic structures are bonded includes an aromatic ring structure, It is not particularly limited as long as it is a hydrocarbon compound having two or more ring structures. Specific examples thereof include compounds having a naphthalene skeleton such as naphthalene, compounds having a fluorene skeleton such as fluorene, and biphenyl skeletons such as biphenyl. compounds having an anthracene skeleton such as anthracene, compounds having a phenanthrene skeleton such as phenanthrene, compounds having an indene skeleton such as indene, and compounds having a benzothiophene skeleton such as benzothiophene. Only one aromatic monomer having a structure in which two or more cyclic structures are bonded may be used, or two or more thereof may be used in combination.

The content of aromatic monomer units having a structure in which two or more cyclic structures are bonded in the hydrocarbon resin is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and still more preferably 0 to 30% by mass. By containing the aromatic monomer unit having a structure in which two or more cyclic structures are bonded in the above ratio, the pressure-sensitive adhesive composition obtained can be made more excellent in pressure-sensitive adhesive performance.

The hydrocarbon resin may also contain monomer units other than the monomer units described above. Other monomers include, but are not limited to, non-1,3-pentadiene such as 1,3-butadiene, 1,2-butadiene, isoprene, 1,3-hexadiene, and 1,4-pentadiene Cyclic polyenes; alicyclic monoolefins having 7 or more carbon atoms such as cycloheptene; acyclic monoolefins having carbon atoms other than 4 to 8 such as ethylene, propylene and nonene; These may be used alone, or may be used in combination of two or more. The content of other monomer units in the hydrocarbon resin is preferably 0 to 30% by mass, more preferably 0 to 25% by mass, still more preferably 0 to 20% by mass.

The weight average molecular weight (Mw) of the hydrocarbon resin is preferably 2,500 or more, more preferably in the range of 2,500 to 10,000, and still more preferably It is in the range of 2,500 to 8,500, more preferably in the range of 2,700 to 8,000.

The Z-average molecular weight (Mz) of the hydrocarbon resin is in the range of 5,000 or more, and more excellent die cutting performance is obtained, so it is more preferably in the range of 6,000 to 100,000, particularly preferably It ranges from 7,000 to 50,000.

In addition, the hydrocarbon resin has a Z-average molecular weight to weight-average molecular weight ratio (Mz/Mw), which is preferably in the range of 1.0 to 6.0, and more preferably, because it provides even better die-cutting performance. is in the range of 1.2 to 5.5, more preferably in the range of 1.4 to 5.0.

The number average molecular weight (Mn) of the hydrocarbon resin is preferably in the range of 500 to 4,000, more preferably in the range of 750 to 3,500, and still more preferably in the range of 750 to 3,500, since more excellent die cutting performance can be obtained. is in the range of 1,000 to 3,000.

In addition, the hydrocarbon resin has a number-average molecular weight to weight-average molecular weight ratio (Mw/Mn), which is preferably in the range of 1.0 to 5.0, and more preferably, because it provides even better die-cutting performance. is in the range of 1.2 to 4.5, more preferably in the range of 1.4 to 4.0.

In the present invention, the weight-average molecular weight (Mw), Z-average molecular weight (Mz), and number-average molecular weight (Mn) of the hydrocarbon resin are determined as polystyrene-equivalent values measured by high-performance liquid chromatography. In addition, the weight average molecular weight (Mw), Z average molecular weight (Mz), and number average molecular weight (Mn) of the hydrocarbon resin can be adjusted by adjusting the amount of the acyclic monoolefin having 4 to 8 carbon atoms. It can be controlled by adjusting the body composition or by adjusting the production conditions such as adjusting the amount of the Lewis acid catalyst in the production method of the hydrocarbon resin described below.

The softening point of the hydrocarbon resin is preferably 90° C. or higher, more preferably 90 to 170° C., still more preferably 90 to 160° C., and particularly preferably 95 to 150° C., since more excellent die cutting performance can be obtained. is. The softening point of the hydrocarbon resin can be controlled by adjusting the composition of each monomer or by adjusting the production conditions in the method for producing the hydrocarbon resin described below.

As a method for producing a hydrocarbon resin, a monomer mixture containing each of the monomers described above is subjected to addition polymerization to determine the content of aliphatic monomer units and aromatic monomer units and the Z-average molecular weight (Mz ) is not particularly limited as long as it is possible to obtain a hydrocarbon resin in the above range, for example, it can be produced by addition polymerization using a Friedel-Crafts type cationic polymerization catalyst, especially A method by addition polymerization using a Lewis acid catalyst (A) is preferred.

The Lewis acid catalyst (A) is not limited, but is preferably composed of a metal halide, and is preferably a halide of an element belonging to Group III of the periodic table or a complex thereof from the viewpoint of having good reaction activity. preferable. Specific examples of such Lewis acid catalysts include aluminum trichloride (AlCl ₃ ), aluminum tribromide (AlBr ₃ ), gallium trichloride (GaCl ₃ ), boron trifluoride diethyl ether complex (BF ₃ Et ₂ O) and the like. Among them, AlCl ₃ or BF ₃ ·Et ₂ O is preferably used from the viewpoint of versatility. The Lewis acid catalyst (A) may be used alone or in combination of two or more.

The amount of the Lewis acid catalyst (A) used is not particularly limited, but is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the monomer mixture used for polymerization. is.

In addition, since the Lewis acid catalyst (A) can further increase its polymerization activity, the halogenated hydrocarbon (B1) having a halogen atom bonded to a tertiary carbon atom and the carbon-carbon unsaturated bond are adjacent to It may be used in combination with at least one halogenated hydrocarbon (B) selected from halogenated hydrocarbons (B2) having a halogen atom bonded to the carbon atom.

Specific examples of the halogenated hydrocarbon (B1) having a halogen atom bonded to the tertiary carbon atom include t-butyl chloride, t-butyl bromide, 2-chloro-2-methylbutane and triphenylmethyl chloride. Among these, t-butyl chloride is particularly preferably used because of its excellent balance between activity and ease of handling. Specific examples of the halogenated hydrocarbon (B2) in which a halogen atom is bonded to the carbon atom adjacent to the carbon-carbon unsaturated bond include benzyl chloride, benzyl bromide, (1-chloroethyl)benzene, allyl chloride, 3-chloro- 1-propyne, 3-chloro-1-butene, 3-chloro-1-butyne, cinnamic acid chloride. Among these, benzyl chloride is preferably used because of its excellent balance between activity and ease of handling. The halogenated hydrocarbon (B) may be used alone or in combination of two or more.

The amount of the halogenated hydrocarbon (B) used is not particularly limited, but is preferably in the range of 0.05 to 50, more preferably in the range of 0.1 to 10, in terms of molar ratio to the Lewis acid catalyst (A). .

In carrying out the polymerization reaction, the order of adding the respective components of the monomer mixture and the polymerization catalyst to the polymerization reactor is not particularly limited, and may be added in any order, from the viewpoint of good control of the polymerization reaction. Then, a part of the monomer components constituting the monomer mixture and the Lewis acid catalyst (A) are added in advance to the polymerization reactor, and a part of the monomer components constituting the monomer mixture, It is preferable to start the polymerization reaction by adding the remainder of the monomer components constituting the monomer mixture to the polymerization reactor after contacting the Lewis acid catalyst (A) in advance. In this case, at least an alicyclic monoolefin having 4 to 6 carbon atoms is used as a part of the monomer components constituting the monomer mixture, and the Lewis acid catalyst (A) is added in advance to the polymerization reactor. Then, after contacting an alicyclic monoolefin having 4 to 6 carbon atoms with the Lewis acid catalyst (A) in advance, the remainder of the monomer components constituting the monomer mixture is added to the polymerization reactor. , to initiate the polymerization reaction.

When the halogenated hydrocarbon (B) is used in addition to the Lewis acid catalyst (A), the monomer mixture and the Lewis acid catalyst (A) are added to the polymerization reactor to initiate the polymerization reaction. It is preferred to add the halogenated hydrocarbon (B) to the polymerization reactor after initiation. Alternatively, the monomer mixture, the Lewis acid catalyst (A), and a portion of the halogenated hydrocarbon (B) are added to the polymerization reactor to initiate the polymerization reaction, and then the remainder of the halogenated hydrocarbon (B) is also preferably added to the polymerization reactor.

From the viewpoint of better control of the polymerization reaction, it is preferable to add a solvent to the polymerization reaction system and carry out the polymerization reaction. The type of solvent is not particularly limited as long as it does not inhibit the polymerization reaction, but saturated aliphatic hydrocarbons or aromatic hydrocarbons are suitable. Examples of saturated aliphatic hydrocarbons used as solvents include n-pentane, n-hexane, 2-methylpentane, 3-methylpentane, n-heptane, 2-methylhexane, 3-methylhexane, and 3-ethylpentane. , 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 2,2,3-trimethylbutane, 2,2,4-trimethylpentane, etc. chain saturated aliphatic hydrocarbons of 5 to 10; and cyclic saturated aliphatic hydrocarbons of 5 to 10 carbon atoms such as cyclopentane, cyclohexane, cycloheptane and cyclooctane. Examples of aromatic hydrocarbons used as solvents include aromatic hydrocarbons having 6 to 10 carbon atoms such as benzene, toluene and xylene. One solvent may be used alone, or two or more solvents may be used as a mixed solvent. The amount of the solvent used is not particularly limited, but is preferably 10 to 1000 parts by mass, more preferably 50 to 500 parts by mass, with respect to 100 parts by mass of the monomer mixture used in the polymerization reaction. In addition, for example, a mixture of an addition polymerizable component and a non-addition polymerizable component, such as a mixture of cyclopentane and cyclopentene derived from a C5 fraction, is added to the polymerization reaction system, and the addition polymerizable component is a monomer. It can also be used as a component of the solid mixture, and the non-addition polymerizable component can be used as a solvent.

The polymerization temperature for the polymerization reaction is not particularly limited, but is preferably 85°C or less, more preferably -20 to 85°C, and still more preferably 0 to 75°C. If the polymerization temperature is too low, the polymerization activity may decrease, resulting in poor productivity. If the polymerization temperature is too high, the hue of the resulting hydrocarbon resin may be poor. The pressure during the polymerization reaction may be atmospheric pressure or increased pressure. The polymerization reaction time can be selected as appropriate, and is usually selected within the range of 10 minutes to 12 hours, preferably 30 minutes to 6 hours.

The polymerization reaction can be terminated by adding a polymerization terminator such as methanol, an aqueous sodium hydroxide solution, an aqueous ammonia solution, or the like to the polymerization reaction system when a desired polymerization conversion rate is obtained. The solvent-insoluble catalyst residue that is generated when the polymerization catalyst is deactivated by adding a polymerization terminator may be removed by filtration or the like. After termination of the polymerization reaction, unreacted monomers and solvent are removed, and low-molecular-weight oligomer components are removed by steam distillation or the like, followed by cooling to obtain a solid hydrocarbon resin.

In the hydrocarbon resin thus obtained, if necessary, some or all of the unsaturated bonds remaining in the polymer molecular structure of the hydrocarbon resin are saturated by a hydrogenation reaction (hydrogenation). , may be a hydride.

The hydrogenation reaction method for the hydrogenation reaction of the hydrocarbon resin is not particularly limited, and known methods can be used without limitation. For example, a method of contacting with hydrogen in the presence of a nickel catalyst, etc. are mentioned. The nickel catalyst is not particularly limited, but from the viewpoint of high reactivity, a catalyst containing, as a main component, a compound formed by supporting nickel as a metal on an inorganic compound supported as a carrier is preferred. Specific examples of supported inorganic compounds as carriers include silica, alumina, boria, silica-alumina, diatomaceous earth, clay, clay, magnesia, magnesia-silica (silica-magnesium oxide), titania, and zirconia.

In the pressure-sensitive adhesive composition of the present invention, the content of the hydrocarbon resin is preferably 10 to 500 parts by mass with respect to 100 parts by mass of the block copolymer composition, since more excellent die-cutting performance can be obtained. , more preferably 30 to 400 parts by mass, still more preferably 50 to 300 parts by mass.

The pressure-sensitive adhesive composition of the present invention may further contain other components. Other components that can be contained in the pressure-sensitive adhesive composition of the present invention include waxes, antioxidants, softeners, tackifying resins other than the hydrocarbon resins and hydrides described above, and polymers other than the block copolymers described above. , heat stabilizers, UV absorbers, fillers, etc., can be added. The pressure-sensitive adhesive composition of the present invention is preferably a solvent-free composition containing no solvent.

Waxes that can be blended in the pressure-sensitive adhesive composition of the present invention are not particularly limited. - Tropsh wax, hydrogenated castor oil wax, polypropylene wax, by-product polyethylene wax, hydroxylated stearamide wax, etc. can be used. One type of wax may be used alone, or two or more types may be used in combination. The wax content in the adhesive composition is not particularly limited, but is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, based on 100 parts by mass of the thermoplastic elastomer. When the content of the wax is within this range, the pressure-sensitive adhesive composition obtained is particularly excellent in ease of coating.

Antioxidants that can be blended in the pressure-sensitive adhesive composition of the present invention are not particularly limited. Hindered phenols such as 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-di-t-butyl-p-cresol, and di-t-butyl-4-methylphenol compounds; thiodicarboxylate esters such as dilaurylthiopropionate; phosphites such as tris(nonylphenyl)phosphite; The amount of the antioxidant to be used is not particularly limited, but it is usually 10 parts by mass or less, preferably 0.5 to 5 parts by mass, per 100 parts by mass of the thermoplastic elastomer. In addition, antioxidant may be used individually by 1 type, and may be used in combination of 2 or more type.

The softener that can be blended in the pressure-sensitive adhesive composition of the present invention is not particularly limited. For example, aromatic, paraffinic or naphthenic process oils; liquid polymers such as polybutene and polyisobutylene can be used. can. A softening agent may be used individually by 1 type, and may be used in combination of 2 or more type.

Conventionally known tackifying resins can be used as tackifying resins other than hydrocarbon resins that can be blended in the pressure-sensitive adhesive composition of the present invention. Specifically, rosin; modified rosins such as disproportionated rosin and dimerized rosin; glycol, glycerin, esters of polyhydric alcohols such as pentaerythritol and rosin or modified rosins; terpene resins; , aromatic, alicyclic or aliphatic-aromatic copolymer hydrocarbon resins or hydrides thereof; phenolic resins; coumarone-indene resins; These tackifying resins may be used singly or in combination of two or more.

Other polymers that can be blended in the pressure-sensitive adhesive composition of the present invention include conjugated diene homopolymers such as polybutadiene and polyisoprene, (styrene-butadiene) random copolymers, and (styrene-isoprene) random copolymers. aromatic vinyl-conjugated diene random copolymers such as (styrene-butadiene) block copolymers such as aromatic vinyl-conjugated diene block copolymers, aromatic vinyl homopolymers such as polystyrene, isobutylene-based polymers, Polymers having elasticity at room temperature (23° C.) such as acrylic polymers, ester polymers, ether polymers, urethane polymers, polyvinyl chloride, etc., but are not limited to these. . In the pressure-sensitive adhesive composition of the present invention, the content of these polymers is preferably 20% by mass or less, more preferably 10% by mass or less, relative to the total amount of the pressure-sensitive adhesive composition.

In preparing the pressure-sensitive adhesive composition of the present invention, the method of mixing the hydrocarbon resin and/or hydride, thermoplastic elastomer, and other optional components is not particularly limited. Examples include a method of dissolving each component in a solvent and uniformly mixing them, and then removing the solvent by heating or the like, and a method of melting and mixing each component with a kneader or the like. Among these methods, melt mixing is preferable from the viewpoint of more efficient mixing. The temperature for melt-mixing is not particularly limited, but is usually in the range of 100 to 200°C.

The pressure-sensitive adhesive composition of the present invention can be applied to adhesion of various members. Moreover, the pressure-sensitive adhesive composition of the present invention can be applied to various uses, and the uses are not limited. For example, it can be used to form a pressure-sensitive adhesive layer of a label. . That is, the pressure-sensitive adhesive composition of the present invention can be suitably used as a pressure-sensitive adhesive composition for labels, and a label obtained from the pressure-sensitive adhesive composition for labels has excellent adhesive performance and excellent die-cutting performance.

The pressure-sensitive adhesive composition of the present invention can be applied to the production of labels according to conventional methods. The label preferably comprises a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition of the present invention and a support. The pressure-sensitive adhesive layer can usually be formed by applying the pressure-sensitive adhesive composition of the present invention onto a support and drying it.

The support to be used is not particularly limited, and examples include papers such as kraft paper, Japanese paper, fine paper and synthetic paper; cloths such as cotton cloth, staple cloth and polyester cloth; cellophane film, polyvinyl chloride film and polypropylene film. and resin films such as polyethylene films; metal foils such as aluminum foil and copper foil; nonwoven fabrics such as polyester nonwoven fabrics and rayon nonwoven fabrics.

These supports may be previously subjected to a corona discharge treatment on the surface or coated with a primary coating agent.

The coating method is not particularly limited, and conventionally known methods can be employed. For example, a method of dissolving the pressure-sensitive adhesive composition of the present invention in a suitable organic solvent to adjust the viscosity and applying the obtained coating liquid, a method of heating and melting the pressure-sensitive adhesive composition and directly applying it, or using an emulsifier. Alternatively, a method of dispersing the pressure-sensitive adhesive composition in water to prepare an emulsion and applying the emulsion can be employed.

Examples of the organic solvent for dissolving the adhesive composition include aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; and halides thereof.

A label can be produced by applying a coating liquid containing an adhesive composition onto a support and drying it to form an adhesive layer. In addition, the label is produced by melting the adhesive composition by heating, applying the obtained melt onto the release agent layer of the release sheet, and drying it as necessary to form an adhesive layer, After that, it may be produced by a method (transfer coating method) of bonding to a support. Alternatively, the label can be produced by melting the pressure-sensitive adhesive composition by heating, applying the obtained melt directly to the support, drying it as necessary to form a pressure-sensitive adhesive layer, and then applying the pressure-sensitive adhesive It may be produced by a method (direct coating method) in which a layer and a release agent layer of a release sheet are attached together.

Since the pressure-sensitive adhesive layer obtained is formed using the pressure-sensitive adhesive composition of the present invention, it has excellent adhesive performance and excellent die-cutting performance.
The thickness of the adhesive layer is usually 10 μm to 100 μm, preferably 20 μm to 70 μm.

The label obtained using the pressure-sensitive adhesive composition of the present invention may be cut or punched into an appropriate shape according to its intended use. Furthermore, the pressure-sensitive adhesive layer of the label using the pressure-sensitive adhesive composition of the present invention is not limited to one formed continuously. For example, it may be a pressure-sensitive adhesive layer formed in a regular or random pattern such as dots or stripes.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. In the following, "parts" are based on mass unless otherwise specified. In addition, the test and evaluation were as follows.

[Number Average Molecular Weight, Weight Average Molecular Weight, Z Average Molecular Weight and Molecular Weight Distribution]
A sample hydrocarbon resin is analyzed by gel permeation chromatography, and the number average molecular weight (Mn), weight average molecular weight (Mw) and Z average molecular weight (Mz) of standard polystyrene conversion values are obtained. It is indicated by the ratio of Mw/Mn or the ratio of Mz/Mw. In addition, gel permeation chromatography analysis uses "HLC-8320GPC" manufactured by Tosoh Corporation as a measuring device, and the column is made by connecting three "TSKgel SuperMultiporeHZ" manufactured by Tosoh Corporation, and tetrahydrofuran is used as a solvent. , 40° C. and a flow rate of 1.0 ml/min.

[Softening point (°C)]
The hydrocarbon resin used as a sample was measured by the ring and ball method in accordance with JIS K2207.

[Block copolymer composition and weight average molecular weight of each block copolymer in the block copolymer composition]
It was obtained as polystyrene-equivalent molecular weight by high-performance liquid chromatography using tetrahydrofuran as a carrier at a flow rate of 0.35 mL/min. The apparatus is HLC8220 (manufactured by Tosoh Corporation), the column is Shodex (registered trademark) [KF-404HQ, manufactured by Showa Denko Co., Ltd.] three connected (column temperature 40 ° C.), and the detector is a differential refractometer and an ultraviolet detector. The molecular weight calibration was performed with 12 points of standard polystyrene (5-3 million) from Polymer Laboratories.

[Content of each block copolymer in block copolymer composition]
It was determined from the peak area ratio corresponding to each block copolymer in the chart obtained by the above high performance liquid chromatography.

[Weight Average Molecular Weight of Polyaromatic Vinyl Block of Block Copolymer]
Rubber Chem. Technol. , 45, 1295 (1972), the polyisoprene blocks of the block copolymer were decomposed by reacting the block copolymer with ozone and reducing with lithium aluminum hydride. Specifically, the procedure was as follows. Specifically, 300 mg of a sample was dissolved in a reaction vessel containing 100 mL of dichloromethane treated with molecular sieves. After the reaction vessel was placed in a cooling bath and cooled to −25° C., ozone generated by an ozone generator was introduced while oxygen was supplied to the reaction vessel at a flow rate of 170 mL/min. After 30 minutes had elapsed from the start of the reaction, the completion of the reaction was confirmed by introducing the gas flowing out of the reaction vessel into the potassium iodide aqueous solution. The resulting reaction solution is referred to as reaction solution 1.
Next, 50 mL of diethyl ether and 470 mg of lithium aluminum hydride were charged into another reaction vessel whose interior was purged with nitrogen, and reaction liquid 1 was slowly added dropwise to this reaction vessel while cooling the reaction vessel with ice water. Then, the reaction vessel was placed in a water bath, and the temperature was gradually raised to reflux at 40° C. for 30 minutes. After completion of the reaction, dilute hydrochloric acid was added dropwise to the reaction vessel while stirring the solution, and the dropwise addition was continued until almost no hydrogen was generated. The resulting reaction solution is referred to as reaction solution 2. The solid product generated in the reaction liquid 2 was separated by filtration, 100 mL of diethyl ether was added to the solid product separated by filtration, the whole volume was stirred for 10 minutes, and then filtered to obtain an extract. This extract was combined with the filtrate from the filtration, and the solvent was distilled off from the combined solution to obtain a solid sample.
The weight-average molecular weight of the sample thus obtained was measured according to the weight-average molecular weight measurement method described above, and the value was taken as the weight-average molecular weight of the polyaromatic vinyl block.

[Weight Average Molecular Weight of Polyisoprene Block of Block Copolymer]
Subtract the weight average molecular weight of the corresponding polyaromatic vinyl block from the weight average molecular weight of the block copolymer obtained as described above, and obtain the weight average molecular weight of the polyisoprene block based on the calculated value. rice field.

[Aromatic Vinyl Monomer Unit Content of Block Copolymer]
It was determined based on the detection intensity ratio between the differential refractometer and the ultraviolet detector in the above high performance liquid chromatography measurement. Copolymers having different aromatic vinyl monomer unit contents were prepared in advance, and a calibration curve was created using them.

[Aromatic vinyl monomer unit content of block copolymer composition (whole)]
It was obtained based on the measurement of ¹ H-NMR.

[Breaking strength and breaking elongation]
Using a 1 mm thick sheet of the pressure-sensitive adhesive composition press-molded at 170° C., the breaking strength and breaking elongation were measured according to JIS K 6251. As for the dumbbell shape, JIS-7113-2 (1/2 size) was used.

[Die-cutting performance]
The adhesive composition was applied to a polyester film having a thickness of 55 μm to prepare an A4 size adhesive film. The pressure-sensitive adhesive film was adhered to a release paper to prepare a label, and 10 sheets of the obtained label were stacked to obtain a sample. A sample was cut using a guillotine cutter, and the presence or absence of contamination on the blade of the guillotine cutter and the presence or absence of stringiness of the pressure-sensitive adhesive composition were visually observed and evaluated according to the following criteria.
Appearance of the blade after cutting 〇: No staining was observed ×: Staining was observed Presence or absence of stringiness after cutting 〇: No stringing was observed ×: Stringing was observed

[Production Example 1]
A mixture of 36.9 parts of cyclopentane, 15.2 parts of cyclopentene and 2.1 parts of toluene was charged into a polymerization reactor, heated to 55° C., and then 0.75 parts of aluminum trichloride was added. Subsequently, a mixture of 68.7 parts of 1,3-pentadiene, 12.2 parts of cyclopentene and 2.4 parts of isobutylene was continuously added to the polymerization reactor over 60 minutes while maintaining the temperature at 70°C. Polymerization was carried out. After that, an aqueous sodium hydroxide solution was added to the polymerization reactor to stop the polymerization reaction. The polymerization conversion rate at this time was 85%. The types and amounts of the components in the polymerization reactor during the polymerization reaction depend on the components constituting the monomer mixture (addition-polymerizable components), the components corresponding to the solvent (non-addition-polymerizable components), and the polymerization catalyst. They are classified and shown in Table 1. After removing the precipitate formed by the termination of the polymerization by filtration, the obtained polymer solution was put into a still and heated under a nitrogen atmosphere to remove the polymerization solvent and unreacted monomers. Then, while blowing saturated steam at 240° C. or higher, low-molecular-weight oligomer components were distilled off. Pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name “Irganox (registered trademark) 1010”) is added as an antioxidant to 100 parts of the molten resin. , manufactured by BASF) was added and mixed, and then the molten resin was taken out from the still and allowed to cool to room temperature to obtain a hydrocarbon resin. Physical properties of the obtained hydrocarbon resin were measured. Table 1 shows the results.

[Production Examples 2 to 7]
A hydrocarbon resin was obtained in the same manner as in Production Example 1, except that the types and amounts of the components added to the polymerization reactor were changed as shown in Table 1, and the physical properties were measured in the same manner as in Production Example 1. Table 1 shows the results.

[Production example of block copolymer composition]
23.3 kg of cyclohexane, 2.8 mmol of N,N,N',N'-tetramethylethylenediamine (hereinafter referred to as TMEDA) and 1.31 kg of styrene were added to a pressure-resistant reactor and stirred at 40°C. 92.10 millimoles of n-butyllithium was added thereto, and the mixture was polymerized for 1 hour while the temperature was raised to 50°C. The polymerization conversion of styrene was 100%.
Subsequently, 6.61 kg of isoprene was continuously added to the reactor over 1 hour while controlling the temperature to maintain 50-60°C.
After the addition of isoprene was completed, the polymerization was continued for another hour, and then 64.3 millimoles of methanol as a polymerization terminator was added to the reactor to conduct the polymerization termination reaction for one hour to obtain one diblock chain having an active terminal. A styrene-isoprene diblock copolymer was formed by deactivating the active ends of the moieties.
Thereafter, 0.80 kg of styrene was continuously added over 1 hour while controlling the temperature so as to maintain 50-60°C. After the styrene addition was complete, polymerize for an additional hour to allow triblock chain formation. The polymerization conversion of styrene was 100%. Thereafter, 300 millimoles of methanol as a polymerization terminator was added and mixed to deactivate all the active terminals of the triblock chains to form a styrene-isoprene-styrene triblock copolymer.
A portion of the reaction liquid containing the block copolymer composition obtained as described above was taken out, and the block copolymer composition was evaluated according to the above-described measuring method. Table 2 shows the results.

0.3 parts of 2,6-di-tert-butyl-p-cresol was added as an antioxidant to 100 parts of the reaction solution (containing 30 parts of the polymer component) obtained as described above and mixed. , The mixed solution is dropped little by little into hot water heated to 85 to 95 ° C. to volatilize the solvent to obtain a precipitate, which is pulverized and dried with hot air at 85 ° C. to block copolymerization. A coalesced composition was recovered.

[Example 1]
100 parts of the block copolymer composition obtained in the above Production Example was charged into a stirring blade type kneader, and 150 parts of the hydrocarbon resin obtained in Production Example 1 and a softening agent (trade name “Sunpure N90”) were added thereto. , Naphthenic process oil, manufactured by Nippon Sun Oil Co., Ltd.) 50 parts and antioxidant (trade name "Irganox 1010" manufactured by BASF) 1.5 parts were added, and the system was replaced with nitrogen gas. An adhesive composition was prepared by kneading at ~180°C for 1 hour.

Using the resulting pressure-sensitive adhesive composition, the strength at break and elongation at break were measured by the methods described above to evaluate the die cutting performance. Table 3 shows the results.

[Examples 2 to 6, Comparative Examples 1 to 3]
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the composition was changed to that shown in Table 3, and evaluated in the same manner as in Example 1. Table 3 shows the results. The softening agent used in Example 5 and the like is "Knifelex 222B" (trade name), a naphthenic process oil manufactured by Nanas.

From Table 3, the following points can be confirmed.
That is, a block copolymer composition containing a triblock copolymer and a diblock copolymer and having a content ratio of aromatic vinyl monomer units in the total polymer component of 10 to 30% by mass, and an aromatic A hydrocarbon resin having a group monomer unit content of 40% by mass or less relative to all monomer units, a Z-average molecular weight of 5,000 or more, a breaking strength of less than 6.0 MPa, and a breaking elongation A label obtained using an adhesive composition having a viscosity of less than 1,300% could be cut with a guillotine cutter without staining the knife and without the adhesive composition stringing. Therefore, it was found that the pressure-sensitive adhesive composition was excellent in die-cutting performance (Examples 1 to 6).
On the other hand, a label obtained by using a pressure-sensitive adhesive composition containing a block copolymer composition and a hydrocarbon resin having a too small Z-average molecular weight and having too high breaking strength and breaking elongation can be cut with a guillotine cutter. was stained, and the adhesive composition was stringy (Comparative Examples 1 to 3).

Claims (5)

A pressure-sensitive adhesive composition containing a block copolymer composition and a non- hydrogenated hydrocarbon resin,
The block copolymer composition contains an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer and an aromatic vinyl-isoprene diblock copolymer, and The content of the aromatic vinyl monomer units in the total combined component is 10 to 30% by mass,
The hydrocarbon resin contains an aliphatic monomer unit, or an aliphatic monomer unit and an aromatic monomer unit,
the hydrocarbon resin contains a 1,3-pentadiene unit as the aliphatic monomer unit,
The content of the aromatic monomer units in the hydrocarbon resin is 40% by mass or less with respect to the total monomer units, and the Z-average molecular weight of the hydrocarbon resin is 5,000 or more,
A pressure-sensitive adhesive composition having a breaking strength of less than 6.0 MPa and a breaking elongation of less than 1,300%. The pressure-sensitive adhesive composition according to claim 1, wherein the hydrocarbon resin has a weight average molecular weight of 2,500 or more and a softening point of 90°C or more. The triblock copolymer is
General formula (A): Ar1 ^a -D ^a -Ar2 ^a
(In the formula, Ar1 ^a is a polyaromatic vinyl block with a weight average molecular weight of 5,000 to 20,000, Ar2 ^a is a polyaromatic vinyl block with a weight average molecular weight of 25,000 to 400,000, D ^a represents a polyisoprene block). The adhesive composition according to any one of claims 1 to 3, wherein the content of the hydrocarbon resin is 10 to 500 parts by mass with respect to 100 parts by mass of the block copolymer composition. A pressure-sensitive adhesive composition for labels comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 4.