JPWO2018168647A1 - Block copolymer composition for flexographic printing plate - Google Patents

Abstract

Flexographic plate with high definition printing characteristics, excellent ink swelling resistance and abrasion resistance can be provided, and transparency and flexibility are good, and the block weight for flexographic plate with low anisotropy An integrated composition is provided. It comprises an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer having a specific structure, block copolymer A and block copolymer B, respectively. The ratio of the aromatic vinyl monomer unit to all the monomer units constituting the coalescing component is 18 to 70% by weight, the type A hardness is 25 to 65, and the wavelength of the 25% by weight toluene solution is 360 nm. A block copolymer composition for flexographic plates having a light transmittance of 50% or more and an anisotropy index of 2.0 or less.

Description

  The present invention relates to a block copolymer composition for flexographic plates comprising a block copolymer composition comprising a block copolymer having a conjugated diene polymer block and an aromatic vinyl polymer block. A block copolymer for a flexographic plate that has fine printing characteristics, can provide a flexographic plate excellent in ink swelling resistance and abrasion resistance, has good transparency and flexibility, and has low anisotropy. Composition.

  Flexographic printing is widely used as a printing method for labels, plastic containers, cartons, plastic bags, boxes, envelopes, and the like. As the flexographic printing plate used for the flexographic printing, a photosensitive flexographic printing plate composition comprising an elastomer, a polymerizable ethylenically unsaturated monomer and a photopolymerization initiator is often used.

  The composition for a photosensitive flexographic plate is usually formed into a sheet, a flexible sheet serving as a support is provided on one surface thereof, and a protective film is provided on the other surface, a sheet having a multilayer structure. Supplied as Light is irradiated from the support side of the multilayer sheet to cure the composition to a specific thickness of the photosensitive flexographic printing plate layer. Next, the protective film is peeled off, and a negative film is adhered to the surface, and then light is irradiated from above the negative film. The light-transmitting portion of the photosensitive flexographic printing plate composition is cured, and the uncured portion is removed with an organic solvent or an aqueous solvent to form a flexographic printing plate having an uneven structure.

  As an elastomer used for forming the composition for a photosensitive flexographic plate, a thermoplastic elastomer excellent in processability is widely used. Above all, aromatic vinyl-conjugated diene-aromatic vinyl block copolymers such as styrene-isoprene-styrene block copolymer (SIS) and styrene-butadiene-styrene block copolymer (SBS) are rich in rubber elasticity. Since it has suitable flexibility and rebound resilience for constituting a flexographic plate, it has been awarded as an elastomer for constituting a composition for a photosensitive flexographic plate. In addition, the composition for a photosensitive flexographic plate is required to have abrasion resistance, transparency, ink swelling resistance, and the like in order to enable high-definition printing. Therefore, various studies have been made on the improvement of an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer used for forming a composition for a photosensitive flexographic plate.

  For example, Patent Literature 1 discloses an aromatic vinyl-conjugated diene block copolymer having an aromatic vinyl compound content of 10 to 40% by weight, a toluene insoluble content of 30 ppm or less, a type A hardness of 85 or less, and a conjugated diene. A block copolymer for a photosensitive printing plate material having a vinyl bond content of 50% or less in a polymer block, and a block copolymer for a photosensitive printing plate material containing the block copolymer for a photosensitive printing plate material. A coalescing composition and a photosensitive elastomer composition are disclosed. This block copolymer for photosensitive printing plate material is said to have a small amount of gel and to be excellent in processing stability, image developability and printability.

  Patent Document 2 discloses a photopolymerizable composition for a flexographic plate containing a mixture of SIS and SBS. This photopolymerizable composition is said to have high abrasion resistance and excellent flexibility without excessive hardness. In addition, this photopolymerizable composition does not exhibit anisotropy due to molecular orientation generated during melt molding, and adversely affects printing that occurs when a flexographic plate composed of a material having anisotropy is used. It is said that it can be avoided.

  Further, Patent Document 3 discloses a photopolymerizable composition for a flexographic plate containing an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer in which the conjugated diene polymer block is a random copolymer block of isoprene and butadiene. Is disclosed. This photopolymerizable composition is said to be excellent in transparency.

  Further, Patent Document 4 discloses a block copolymer composition for flexographic printing plates containing a three-branched aromatic vinyl-conjugated diene block copolymer obtained by using a specific coupling agent. The block copolymer composition for a flexographic plate has excellent smoothness and flow resistance (the property of being hardly deformed before curing by exposure to light) and reproducibility of fine lines when a flexographic plate is formed.

  However, even when the compositions described in Patent Documents 1 to 4 are used, it has been difficult to obtain a composition having a good balance in abrasion resistance, flexibility, transparency, and the like.

  That is, the aromatic vinyl-conjugated diene-aromatic vinyl block copolymer has an increased ratio of aromatic vinyl monomer units contained therein, thereby increasing mechanical strength and improving properties such as abrasion resistance. Is known to be. However, if the proportion of the aromatic vinyl monomer unit is increased to such an extent that sufficient abrasion resistance can be imparted for use as a flexographic plate, there is a problem that the polymer loses rubber elasticity.

  Further, when SIS and SBS are mixed as described in Patent Literature 2, there is a problem that SIS and SBS are generally incompatible with each other, and thus have poor transparency. Further, in the composition described in Patent Document 3, although the transparency is improved due to the inclusion of a random copolymer block of isoprene and butadiene, flexibility and abrasion resistance are compatible as described above. It was difficult.

JP 2006-104359 A JP-A-2002-72457 JP 2006-514338 A WO 2005/031449 pamphlet

  The present invention can provide a flexographic printing plate having high-definition printing characteristics, excellent ink swelling resistance and abrasion resistance, and has excellent transparency and flexibility, and further has a small anisotropy. It is an object to provide a block copolymer composition for use.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, each having a specific configuration, including two types of block copolymers having a conjugated diene polymer block and an aromatic vinyl polymer block, and , A type A hardness, a light transmittance and a block copolymer having an anisotropy index within a predetermined range have a good balance between abrasion resistance and rubber elasticity even when the proportion of aromatic vinyl monomer units is increased. Flexo with excellent definition, good transparency, low anisotropy, and high definition printing characteristics, excellent ink swelling resistance and abrasion resistance by using this block copolymer composition. I found that a plate could be obtained. The present invention has been completed based on this finding.

  Thus, according to the present invention, a block for flexographic plate comprising a block copolymer A represented by the following general formula (A) and a block copolymer B represented by the following general formula (B) The aromatic vinyl monomer unit accounts for 18 to 70% by weight of the total monomer units constituting the polymer component in the copolymer composition, and the type A hardness is 25 to 65; A block copolymer composition for flexographic plates having a light transmittance at a wavelength of 360 nm of not less than 50% and an anisotropy index of not more than 2.0 when a weight% toluene solution is prepared is provided.

^{Ar1 a -D a -Ar2 a (A} )
(Ar ^b -D ^b ) _n -X (B)
(In the general formula (A) and (B), Ar @ 1 ^a and Ar ^b are each an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000, Ar @ 2 ^a has a weight average molecular weight of from 40000 to 400000 an aromatic vinyl polymer block, the ratio of the weight average molecular weight of the aromatic vinyl polymer block Ar @ 2 ^a and an aromatic vinyl polymer block Ar1 weight average molecular weight of ^{a (Mw (Ar2 a) /} Mw (Ar1 a)) There is a 2 to 12, D ^a and D ^b are each a vinyl bond content of 20 mol% of the conjugated diene polymer block, X is the residue of a single bond or a coupling agent, n Is an integer of 2 or more.)

  The above block copolymer composition for flexographic printing plate, the ratio of the aromatic vinyl monomer unit to all the monomer units constituting the polymer component in the block copolymer composition for flexographic printing plate is 20 ~. Preferably, it is 70% by weight.

  In the above block copolymer composition for flexographic printing plates, the weight ratio (A / B) of the block copolymer A to the block copolymer B is preferably from 36/64 to 85/15.

  It is preferable that the above-mentioned block copolymer composition for flexographic printing plates further comprises a block copolymer C represented by the following general formula (C).

Ar ^c -D ^{c (C)}
(In the general formula (C), Ar ^c is an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000, and D ^c is a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%. is there.)

  In the above block copolymer composition for flexographic plates, the block copolymer B couples a compound having at least one functional group selected from an alkoxyl group, an ester group and an epoxy group in one molecule. It is preferably obtained using the agent.

  Further, according to the present invention, there is provided a photosensitive flexographic printing plate composition comprising the above block copolymer composition for flexographic printing plate, an ethylenically unsaturated compound having a molecular weight of 5,000 or less, and a photopolymerization initiator. Is done.

  Further, according to the present invention, there is provided a flexographic printing plate comprising the above-mentioned composition for a photosensitive flexographic printing plate.

  According to the present invention, it is possible to provide a flexographic printing plate having high-definition printing characteristics, excellent ink swelling resistance and abrasion resistance, good transparency and flexibility, and low anisotropy. A block copolymer composition for flexographic printing plates can be obtained.

  The block copolymer composition for flexographic printing plates of the present invention comprises at least two types of block copolymers. The block copolymer A, which is one of the two types of block copolymers constituting the block copolymer for flexographic plates of the present invention, has different weight average molecular weights represented by the following general formula (A). It is an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer having two aromatic vinyl polymer blocks.

^{Ar1 a -D a -Ar2 a (A} )

The above general formula ^(A), Ar1 ^a is an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000, Ar @ 2 ^a has a weight average molecular weight of an aromatic vinyl polymer block of 40000 to 400000 , the ratio of the weight average molecular weight of the aromatic vinyl polymer block Ar @ 2 ^a and an aromatic vinyl polymer block Ar1 weight average molecular weight of ^{a (Mw (Ar2 a) /} Mw (Ar1 a)) is 2 to 12, D ^a is a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%.

  Further, the block copolymer B, which is the other of the two block copolymers constituting the block copolymer composition for flexographic printing plates of the present invention, is an aromatic vinyl copolymer represented by the following general formula (B). It is a conjugated diene-aromatic vinyl block copolymer.

(Ar ^b -D ^b ) _n -X (B)

In the above general formula (B), Ar ^b is an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000, and D ^b is a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%. Wherein X is a single bond or a residue of a coupling agent, and n is an integer of 2 or more.

  The block copolymer composition for a flexographic plate of the present invention further comprises an aromatic vinyl-conjugated diene block copolymer represented by the following general formula (C) in addition to the block copolymer A and the block copolymer B. It may be one containing a block copolymer C which is a united one.

Ar ^c -D ^{c (C)}

In the above general formula (C), Ar ^c is an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000, and D ^c is a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%. It is.

Block copolymers A~C aromatic vinyl polymer block ^{(Ar1 a, Ar2 a, Ar} b, Ar c) is a polymer block composed of the aromatic vinyl monomer unit. The aromatic vinyl monomer used to constitute the aromatic vinyl monomer unit of the aromatic vinyl polymer block is not particularly limited as long as it is an aromatic vinyl compound, but styrene, α-methylstyrene, -Methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 4-bromostyrene, 2-methyl-4,6-dichlorostyrene, 2,4-dibromostyrene, vinyl And naphthalene. Among these, it is preferable to use styrene. These aromatic vinyl monomers can be used alone or in combination of two or more in each aromatic vinyl polymer block. Further, in each aromatic vinyl polymer block, the same aromatic vinyl monomer may be used, or different aromatic vinyl monomers may be used.

Block copolymers A~C aromatic vinyl polymer block ^{(Ar1 a, Ar2 a, Ar} b, Ar c) , respectively, it may contain a monomer unit other than the aromatic vinyl monomer unit . Monomers constituting monomer units other than the aromatic vinyl monomer units that can be contained in the aromatic vinyl polymer block include 1,3-butadiene and isoprene (2-methyl-1,3-butadiene) Conjugated diene monomers, α, β-unsaturated nitrile monomers, unsaturated carboxylic acid or acid anhydride monomers, unsaturated carboxylic acid ester monomers, and non-conjugated diene monomers. . The content of monomer units other than the aromatic vinyl monomer unit in each aromatic vinyl polymer block is preferably 20% by weight or less, more preferably 10% by weight or less, and substantially Particularly preferred is 0% by weight.

The conjugated diene polymer blocks (D ^a , D ^b , D ^c ) of the block copolymers A to C are polymer blocks composed of conjugated diene monomer units. The conjugated diene used to constitute the conjugated diene monomer unit of the conjugated diene polymer block is not particularly limited as long as it is a conjugated diene compound. For example, 1,3-butadiene, isoprene, 2,3-dimethyl Examples thereof include -1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Among these, it is preferable to use 1,3-butadiene and / or isoprene, and it is particularly preferable to use isoprene. When the conjugated diene polymer block is composed of isoprene units, the obtained block copolymer composition for flexographic printing plate becomes rich in flexibility, and a flexographic printing plate having excellent flexibility can be obtained. These conjugated diene monomers can be used alone or in combination of two or more in each conjugated diene polymer block. In each conjugated diene polymer block, the same conjugated diene monomer may be used, or different conjugated diene monomers may be used. Further, a part of the unsaturated bond of each conjugated diene polymer block may be subjected to a hydrogenation reaction.

Conjugated diene polymer block of the block copolymer ^{A~C (D a, D b,} D c) , respectively, may contain a monomer unit other than the conjugated diene monomer units. Examples of the monomer constituting a monomer unit other than the conjugated diene monomer unit that can be contained in the conjugated diene polymer block include aromatic vinyl monomers such as styrene and α-methylstyrene, and α, β-unsaturated monomers. Examples thereof include a saturated nitrile monomer, an unsaturated carboxylic acid or acid anhydride monomer, an unsaturated carboxylic acid ester monomer, and a non-conjugated diene monomer. The content of monomer units other than the conjugated diene monomer unit in each conjugated diene polymer block is preferably 20% by weight or less, more preferably 10% by weight or less, and substantially 0% by weight. % Is particularly preferred.

The block copolymer A constituting the block copolymer composition for flexographic printing plates of the present invention is, as represented by the above general formula (A), an aromatic vinyl polymer block having a relatively small weight average molecular weight ( Ar1 ^a ), a conjugated diene polymer block having a specific vinyl bond content (D ^a ), and an aromatic vinyl polymer block having a relatively large weight average molecular weight (Ar2 ^a ) are constituted in this order. It is an asymmetric aromatic vinyl-conjugated diene-aromatic vinyl block copolymer.

The weight average molecular weight (Mw (Ar1 ^a )) of the aromatic vinyl polymer block (Ar1 ^a ) having a relatively small weight average molecular weight is 6,000 to 20,000, preferably 7000 to 18,000, and more preferably 8,000 to 16,000. More preferably, there is. When Mw (Ar1 ^a ) is out of this range, the rubber elasticity of the obtained block copolymer composition for flexographic printing plate may be insufficient. The weight average molecular weight of the aromatic vinyl polymer block (Ar @ 2 ^a) having a relatively large weight average molecular weight (Mw ^(Ar2 a)) is 40000 to 400000, preferably from 42000 to 370000, 45000～ More preferably, it is 350,000. When Mw (Ar2 ^a ) is too small, the obtained block copolymer composition for flexographic printing plate may be inferior in abrasion resistance and easily develop anisotropy, and Mw (Ar2 ^a ) is large. Too much block copolymer A may be difficult to produce.

  In the present invention, the weight average molecular weight of a polymer or a polymer block is determined based on a value in terms of polystyrene measured by high performance liquid chromatography.

In the block copolymer A, the weight average molecular weight (Mw (Ar2 ^a )) of the aromatic vinyl polymer block (Ar2 ^a ) having a relatively large weight average molecular weight and the aromatic vinyl polymer block having a relatively small weight average molecular weight the weight average molecular weight of polymer block ^{(Ar1 a) (Mw (Ar1} a)) and the ratio of ^{(Mw (Ar2 a) / Mw} (Ar1 a)) is 2 to 12, preferably 4 to 12, It is more preferably 4.5 to 12. By configuring the block copolymer A in this manner, the obtained block copolymer composition for flexographic printing plate has a high ratio of the aromatic vinyl monomer unit and excellent wear resistance. Even if there is, rubber elasticity can be maintained.

The conjugated diene polymer block (D ^a ) of the block copolymer A has a vinyl bond content (a ratio of 1,2-vinyl bonds and 3,4-vinyl bonds in all conjugated diene monomer units) of 1 -20 mol%, preferably 2-15 mol%, more preferably 3-10 mol%. If the vinyl bond content is too high, the resulting block copolymer composition for flexographic printing plates may be too hard, resulting in poor flexibility.

The weight average molecular weight (Mw (D ^a )) of the conjugated diene polymer block (D ^a ) of the block copolymer A is not particularly limited, but is usually 40,000 to 200,000, preferably 42,000 to 180,000, and is preferably 45,000. It is more preferable that it is 150,000. By setting Mw (D ^a ) within this range, the resulting block copolymer composition for flexographic printing plates has a high ratio of aromatic vinyl monomer units and excellent abrasion resistance. However, rubber elasticity can be easily maintained.

  The content of the aromatic vinyl monomer unit based on all monomer units of the block copolymer A is not particularly limited, but is preferably 41% by weight or more, and more preferably 43 to 87% by weight. And particularly preferably 45 to 85% by weight. By setting the content of the aromatic vinyl monomer unit to all the monomer units of the block copolymer A in this range, the obtained block copolymer composition for flexographic printing plate has abrasion resistance and ink swelling resistance. It is because it becomes excellent.

  The weight average molecular weight of the entire block copolymer A is not particularly limited, but is usually 90,000 to 500,000, preferably 100,000 to 450,000, and more preferably 110,000 to 400,000.

The block copolymer B constituting the block copolymer composition for flexographic printing plates of the present invention is an aromatic vinyl polymer block (Ar) having a specific weight average molecular weight as represented by the general formula (B). ^b ) and two or more diblocks (Ar ^b -D ^b ) formed by bonding a conjugated diene polymer block (D ^b ) having a specific vinyl bond content, by a direct single bond or a coupling agent Is a block copolymer constituted by bonding via a residue of

The weight average molecular weight (Mw (Ar ^b )) of the aromatic vinyl polymer block (Ar ^b ) constituting the block copolymer B is 6,000 to 20,000, preferably 7000 to 18,000, and more preferably 8,000 to 16,000. More preferably, there is. If Mw (Ar ^b ) is too small, the obtained block copolymer composition for flexographic printing plate may have poor abrasion resistance, and if it is too large, it may be inferior in flexibility and rubber elasticity. is there. The weight average molecular weights (Mw (Ar ^b )) of the aromatic vinyl polymer blocks of the block copolymer B may be the same or different from each other as long as they are within the above range. Good, but preferably substantially equal. The weight average molecular weight (Mw (Ar ^b )) of these aromatic vinyl polymer blocks is determined by the weight average molecular weight of the aromatic vinyl polymer block (Ar1 ^a ) having a relatively small weight average molecular weight of the block copolymer A. More preferably, it is substantially equal to the molecular weight (Mw (Ar1 ^a )).

The vinyl bond content of the conjugated diene polymer block (D ^b ) of the block copolymer B is 1 to 20 mol%, preferably 2 to 15 mol%, and more preferably 3 to 10 mol%. More preferred. If the vinyl bond content is too high, the resulting block copolymer composition for flexographic printing plates may be too hard, resulting in poor flexibility. The vinyl bond content of the conjugated diene polymer block (D ^b ) of the block copolymer B is substantially equal to the vinyl bond content of the conjugated diene polymer block (D ^a ) of the block copolymer A. Is preferred.

The block copolymer B, aromatic vinyl polymer block (Ar ^b) a conjugated diene polymer block ^{(D b)} and formed by bonding diblock body ^{(Ar b} -D b) is a direct single bond, Alternatively, they are bonded via a residue of a coupling agent. The coupling agent constituting the residue of the coupling agent is not particularly limited, and is an arbitrary bifunctional or higher coupling agent. Examples of the bifunctional coupling agent include bifunctional halogenated silanes such as dichlorosilane, monomethyldichlorosilane and dimethyldichlorosilane; bifunctional alkoxysilanes such as diphenyldimethoxysilane and diphenyldiethoxysilane; dichloroethane and dibromoethane Difunctional tin halides such as dichlorotin, monomethyldichlorotin, dimethyldichlorotin, monoethyldichlorotin, diethyldichlorotin, monobutyldichlorotin, dibutyldichlorotin and the like. Dibromobenzene, benzoic acid, carbon monoxide, 2-chloropropene and the like. Examples of the trifunctional coupling agent include trifunctional halogenated alkanes such as trichloroethane and trichloropropane; trifunctional halogenated silanes such as methyltrichlorosilane and ethyltrichlorosilane; methyltrimethoxysilane, phenyltrimethoxysilane, Trifunctional alkoxysilanes such as phenyltriethoxysilane; and the like. Examples of the tetrafunctional coupling agent include tetrafunctional halogenated alkanes such as carbon tetrachloride, carbon tetrabromide, and tetrachloroethane; tetrafunctional silanes such as tetrachlorosilane and tetrabromosilane; tetramethoxysilane; Tetrafunctional alkoxysilanes such as tetraethoxysilane; tetrafunctional tin halides such as tetrachlorotin and tetrabromotin; and the like. Examples of the coupling agent having five or more functional groups include 1,1,1,2,2-pentachloroethane, perchloroethane, pentachlorobenzene, perchlorobenzene, octabromodiphenyl ether, and decabromodiphenyl ether. One of these coupling agents may be used alone, or two or more thereof may be used in combination.

  In obtaining the block copolymer B, among these coupling agents, at least one functional group selected from an alkoxyl group, an ester group and an epoxy group is used as a functional group that reacts with the active terminal of the polymer. It is preferable to use a compound having two or more in one molecule, and it is particularly preferable to use an alkoxysilane compound having two or more alkoxy groups per molecule directly bonded to a silicon atom. That is, the block copolymer B constituting the block copolymer composition for flexographic plate of the present invention has at least one functional group selected from an alkoxyl group, an ester group and an epoxy group in two or more molecules per molecule. It is preferably obtained using a compound as a coupling agent, and obtained using an alkoxysilane compound having two or more alkoxy groups directly bonded to a silicon atom per molecule as a coupling agent. Is particularly preferred. By using such a coupling agent, the block copolymer composition for flexographic printing plate can be made to have excellent transparency, and a flexographic printing plate having a fine print pattern formed from the obtained photosensitive flexographic printing plate composition. It becomes easy to obtain a plate.

In the block copolymer B, the number to which the diblock (Ar ^b -D ^b ) is bonded (that is, n in the general formula (B)) is not particularly limited as long as it is 2 or more. May be mixed together. N in the general formula (B) is not particularly limited as long as it is an integer of 2 or more, but is usually an integer of 2 to 8, preferably 2 to 4. In addition, as at least a part of the block copolymer B, a diblock (Ar ^b -D ^b ) in which three or more are bonded via a coupling agent (that is, n is 3 or more in the general formula (B)) Is particularly preferred. The block copolymer composition for flexographic printing plates of the present invention has a uniform mechanical property in all directions even when a molding method in which molecular orientation is liable to occur, such as extrusion molding, is used in producing a flexographic printing plate. Can provide a highly isotropic flexographic plate having a diblock body (Ar ^b -D ^b ) as at least a part of the block copolymer B via a coupling agent. This is because the inclusion of a bonded product allows a flexographic plate having particularly high isotropy and hardly causing printing defects to be obtained.

The weight average molecular weight of the conjugated diene polymer block ^{(D b)} of the block copolymer B ^{(Mw (D} b)) is not particularly limited but is usually from 40,000 to 200,000, it is preferably from 42000 to 180000, 45000 It is more preferable that it is 150,000. When Mw (D ^b ) is in this range, the obtained block copolymer composition for flexographic printing plate has a high ratio of aromatic vinyl monomer units and is excellent in abrasion resistance. Also easily maintain rubber elasticity. The weight average molecular weight (Mw (D ^b )) of the conjugated diene polymer block (D ^b ) of the block copolymer B is determined by the weight average molecular weight (M a (D ^a )) of the conjugated diene polymer block (D ^a ) of the block copolymer A. Mw (D ^a )). When an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer produced without using a coupling agent is used as the block copolymer B, the conjugated diene polymer blocks contained therein are all monomeric. The body units are directly bonded, and it cannot be said that the body units are actually composed of two conjugated diene polymer blocks (D ^b ). However, in the present invention, even such a conjugated diene polymer block conceptually has two conjugated diene polymer blocks (D ^b ) having substantially the same weight average molecular weight bonded by a single bond. , And shall be handled. Therefore, for example, in the block copolymer B which is an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer produced without using a coupling agent, the conjugated diene polymer block has a weight average molecular weight of 100,000 as a whole. , The Mw (D ^b ) is treated as being 50,000.

  The content of the aromatic vinyl monomer unit based on all monomer units of the block copolymer B is not particularly limited, but is usually 10 to 35% by weight, preferably 12 to 32% by weight, and more preferably 15 to 32% by weight. More preferably, it is about 30% by weight. The weight average molecular weight of the entire block copolymer B is not particularly limited, but is usually 52,000 to 800,000, preferably 70,000 to 600,000, and more preferably 100,000 to 400,000.

The block copolymer C that can be included in the block copolymer composition for flexographic printing plates of the present invention is an aromatic vinyl polymer block having a specific weight-average molecular weight (as represented by the general formula (C)). It is a block copolymer composed of Ar ^c ) and a conjugated diene polymer block (D ^c ) having a specific vinyl bond content. By including the block copolymer C, the balance between abrasion resistance and rubber elasticity of the block copolymer composition for flexographic printing plates becomes particularly excellent.

The weight average molecular weight of the aromatic vinyl polymer block constituting the block copolymer ^{C (Ar c) (Mw (} Ar c)) is 6,000 to 20,000, preferably from 7,000 to 18,000, with from 8,000 to 16,000 More preferably, there is. The weight average molecular weight (Mw (Ar ^c )) of the aromatic vinyl polymer block (Ar ^c ) of the block copolymer C is the same as the aromatic vinyl polymer having a relatively small weight average molecular weight of the block copolymer A. the weight average molecular weight of the block ^{(Ar1 a) (Mw (Ar1} a)) and at least one substantially in weight average molecular weight of the aromatic vinyl polymer block (Ar ^b) of the block copolymer B (Mw ^(Ar b)) And more preferably substantially equal to both.

The vinyl bond content of the conjugated diene polymer block (D ^c ) of the block copolymer C is 1 to 20 mol%, preferably 2 to 15 mol%, and more preferably 3 to 10 mol%. More preferred. The vinyl bond content of the conjugated diene polymer block (D ^c ) of the block copolymer C is determined by the conjugated diene polymer block (D ^a ) of the block copolymer A and the conjugated diene polymer of the block copolymer B. Preferably, the vinyl bond content of at least one of the blocks (D ^b ) is substantially equal, and more preferably, the vinyl bond content of both is substantially equal.

The weight average molecular weight (Mw (D ^c )) of the conjugated diene polymer block (D ^c ) of the block copolymer C is not particularly limited, but is usually 40,000 to 200,000, preferably 42,000 to 180,000, and is preferably 45,000. It is more preferable that it is 150,000. By setting Mw (D ^c ) within this range, the obtained block copolymer composition for flexographic printing plates will have excellent rubber elasticity. The weight average molecular weight (Mw (D ^c )) of the conjugated diene polymer block (D ^c ) of the block copolymer C is represented by the weight average molecular weight of the conjugated diene polymer block (D ^a ) of the block copolymer A (D ^a ). Mw (D ^a )) and at least one of the weight average molecular weights (M w (D ^b )) of the conjugated diene polymer block (D ^b ) of the block copolymer B are preferably substantially equal to both. It is more preferable that they are equal.

  The content of the aromatic vinyl monomer unit with respect to all the monomer units of the block copolymer C is not particularly limited, but is usually 10 to 35% by weight, preferably 12 to 32% by weight, and more preferably 15 to 32% by weight. More preferably, it is about 30% by weight. The content of the aromatic vinyl monomer unit with respect to all the monomer units of the block copolymer C is substantially equal to the content of the aromatic vinyl monomer unit with respect to all the monomer units of the block copolymer B. Are preferably equal. The weight average molecular weight of the block copolymer C as a whole is also not particularly limited, but is usually 46,000 to 200,000, preferably 50,000 to 180,000, and more preferably 55,000 to 160,000.

  The molecular weight distribution represented by the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of each of the polymer blocks constituting the block copolymers A to C is not particularly limited. Usually, it is 1.1 or less, preferably 1.05 or less.

  The weight ratio (A / B) of the block copolymer A and the block copolymer B contained in the block copolymer composition for flexographic plate of the present invention is not particularly limited, but is 36/64 to 85/15. It is more preferably 38/62 to 80/20, and particularly preferably 40/60 to 75/25. By containing the block copolymer A and the block copolymer B at such a ratio, the obtained block copolymer composition for flexographic printing plate has excellent abrasion resistance while maintaining sufficient rubber elasticity. It will be.

  The amount of the block copolymer C that can be contained in the block copolymer composition for a flexographic plate of the present invention is not particularly limited, but the weight ratio (C / C / C) to the total weight of the block copolymer A and the block copolymer B is not limited. (A + B)) is preferably 0/100 to 50/50, more preferably 5/95 to 40/60, and particularly preferably 10/90 to 30/70. By containing the block copolymer C in such a ratio, the balance between the wear resistance and the rubber elasticity of the block copolymer composition for flexographic printing plates becomes particularly excellent.

  The block copolymer composition for a flexographic plate of the present invention may contain only the block copolymers A to C as a polymer component, but may contain a polymer component other than the block copolymers A to C. It may be. Examples of the polymer component other than the block copolymers A to C that can be included in the block copolymer composition for flexographic plate of the present invention include aromatic vinyl-conjugated diene other than the block copolymer A and the block copolymer B. -Aromatic vinyl block copolymer, aromatic vinyl-conjugated diene block copolymer other than block copolymer C, aromatic vinyl homopolymer, conjugated diene homopolymer, aromatic vinyl-conjugated diene random copolymer And these branched polymers, or polyurethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, thermoplastic elastomers such as polyester-based thermoplastic elastomers, polyethylene, polypropylene, polyvinyl chloride, acrylonitrile-styrene copolymer, Acrylonitrile-butadiene-styrene copolymer, poly And thermoplastic resins such as Eniren'eteru the like. In the block copolymer composition for flexographic printing plates of the present invention, the content of the polymer component other than the block copolymers A to C is preferably 20% by weight or less based on the entire polymer component, and is preferably 10% by weight or less. It is more preferable that the content be not more than weight%.

  In the block copolymer composition for flexographic printing plates of the present invention, the ratio of the aromatic vinyl monomer unit to all the monomer units constituting the polymer component (the entire aromatic vinyl unit Monomer unit content) is 18 to 70% by weight, preferably 20 to 70% by weight, more preferably 22 to 60% by weight, and more preferably 25 to 50% by weight. Is particularly preferred. If the total aromatic vinyl monomer unit content is too small, the block copolymer composition for flexographic printing plates may be inferior in abrasion resistance and ink swelling resistance. If the body unit content is too large, the block copolymer composition for flexographic printing plate may lose the rubber elasticity required for the flexographic printing plate. The total content of the aromatic vinyl monomer units is determined by the amount of the block copolymers A to C constituting the flexographic block copolymer composition and the other polymer components and the respective aromatic vinyl monomer units. Can be easily adjusted by adjusting the amount of these components in consideration of the content of In addition, if all the polymer components which comprise the block copolymer composition for flexographic plates are comprised only of an aromatic vinyl monomer unit and a conjugated diene monomer unit, Rubber Chem. Technol. , 45, 1295 (1972), the polymer component of the block copolymer composition for flexographic plate is ozonolyzed and then reduced with lithium aluminum hydride to obtain a conjugated diene monomer unit. Since it is decomposed and only the aromatic vinyl monomer unit portion can be taken out, the entire aromatic vinyl monomer unit content can be easily measured.

  The weight average molecular weight of the entire polymer component constituting the block copolymer composition for flexographic plate of the present invention is not particularly limited, but is usually 50,000 to 500,000, preferably 60,000 to 450,000, and preferably 70,000 to 400,000. More preferably, there is. The molecular weight distribution represented by the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the entire polymer component constituting the block copolymer composition for flexographic plate of the present invention is as follows: Although not particularly limited, it is usually 1.01 to 10, preferably 1.03 to 5, and more preferably 1.05 to 3.

  The block copolymer composition for flexographic plates of the present invention has a type A hardness of 25 to 65, preferably 26 to 64, and more preferably 27 to 63. Even when the type A hardness is within the above range, the block copolymer composition for flexographic printing plates has a high abrasion resistance by increasing the proportion of aromatic vinyl monomer units. The elasticity can be maintained.

  Here, the type A hardness is a value measured using a durometer hardness tester (type A) according to JIS K6253.

  Further, the block copolymer composition for flexographic plate of the present invention has a light transmittance at a wavelength of 360 nm of 50% or more, preferably 55% or more, and more preferably 60% or more when a 25% by weight toluene solution is used. Is more preferable.

  Here, the light transmittance is a value measured by using a 25% by weight toluene solution of the block copolymer composition for flexographic printing plates at an optical path length of 10 mm and a wavelength of 360 nm.

  Moreover, the block copolymer composition for flexographic printing plates of the present invention has an anisotropy index of 2.0 or less, preferably 1.8 or less, more preferably 1.5 or less. When the anisotropy index is in the above range, in producing a flexographic plate, even when a molding method such as extrusion molding that is likely to cause molecular orientation is applied, anisotropy is hardly developed, and isotropic. And a flexographic plate which is less likely to cause printing defects can be obtained.

  Here, the anisotropy index is determined by melt-extrusion of the block copolymer composition for flexographic printing plates to produce a sheet, and using two of the obtained sheets, one of them is along a melt flow direction at the time of molding. The tensile modulus was measured, and the other was measured along the vertical direction of the melt flow during molding, and the tensile modulus was determined by the ratio of (tensile modulus in the melt flow direction / tensile modulus in the vertical direction of the melt flow). Value. The closer the ratio of (tensile elastic modulus in the melt flow direction / tensile elastic modulus in the perpendicular direction of the melt flow) to 1, the smaller the anisotropy and the better the isotropicity.

  The method for obtaining the block copolymer composition for flexographic printing plates of the present invention is not particularly limited. For example, according to a conventional method for producing a block copolymer, block copolymer A and block copolymer B are separately manufactured, and if necessary, block copolymer C and other polymer components are blended. Then, they can be manufactured by mixing them according to a conventional method such as kneading or solution mixing. However, from the viewpoint of obtaining a block copolymer composition having a particularly desirable configuration with higher productivity, the following production method is suitable.

  That is, it is preferable that the block copolymer composition for flexographic printing plate of the present invention is produced by using a production method comprising the following steps (1) to (5).

(1): a step of polymerizing an aromatic vinyl monomer using a polymerization initiator in a solvent (2): a solution containing an aromatic vinyl polymer having an active terminal obtained in the above step (1) (3): adding a conjugated diene monomer to the solution containing the aromatic vinyl-conjugated diene block copolymer having an active terminal obtained in the above step (2); Step (4) of adding a coupling agent in an amount such that the functional group becomes less than 1 molar equivalent to form a block copolymer B: The aromatic vinyl monomer is added to the solution obtained in the above step (3). (5): a step of recovering the block copolymer composition for flexographic plate from the solution obtained in the above step (4)

  In the above method for producing a block copolymer composition for flexographic printing plates, first, an aromatic vinyl monomer is polymerized in a solvent using a polymerization initiator. As the polymerization initiator used, generally, for an aromatic vinyl monomer and a conjugated diene monomer, an organic alkali metal compound known to have anionic polymerization activity, an organic alkaline earth metal compound, Organic lanthanoid-based rare earth metal compounds and the like can be used.

  As the organic alkali metal compound, an organic lithium compound having one or more lithium atoms in a molecule is particularly preferably used, and specific examples thereof include ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, organic monolithium compounds such as sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, stilbenelithium, dialkylaminolithium, diphenylaminolithium, ditrimethylsilylaminolithium, methylenedilithium, tetramethylenedilithium, hexamethylene Organic dilithium compounds such as dilithium, isoprenyldilithium, and 1,4-dilithio-ethylcyclohexane; and organic trilithium compounds such as 1,3,5-trilithiobenzene and the like. It is. Among these, an organic monolithium compound is particularly preferably used.

  Examples of the organic alkaline earth metal compound used as the polymerization initiator include, for example, n-butyl magnesium bromide, n-hexyl magnesium bromide, ethoxy calcium, calcium stearate, t-butoxystrontium, ethoxy barium, isopropoxy barium, ethyl mercapto barium, Examples include t-butoxybarium, phenoxybarium, diethylaminobarium, barium stearate, and ethylbarium.

  Specific examples of other polymerization initiators include a composite catalyst comprising a lanthanoid-based rare earth metal compound containing neodymium, samarium, gadolinium, etc./alkylaluminum/alkylaluminum halide / alkylaluminum hydride, titanium, vanadium, samarium, gadolinium. And those having a living polymerization property in an organic solvent such as a metallocene-type catalyst containing the same.

  These polymerization initiators may be used alone or in a combination of two or more.

  The amount of the polymerization initiator used may be determined according to the molecular weight of each target block copolymer, and is not particularly limited, but is usually 0.01 to 20 mmol, preferably, per 100 g of all monomers used. Is from 0.05 to 15 mmol, more preferably from 0.1 to 10 mmol.

  The solvent used for the polymerization 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 is used. Examples of the chain hydrocarbon solvent include n-butane, isobutane, 1-butene, isobutylene, trans-2-butene, cis-2-butene, 1-pentene, trans-2-pentene, cis-2-pentene, and n-butene. Examples include linear alkanes and alkenes having 4 to 6 carbon atoms, such as pentane, isopentane, neo-pentane, and n-hexane. Specific examples of the cyclic hydrocarbon solvent include aromatic compounds such as benzene, toluene, and xylene; and alicyclic hydrocarbon compounds such as cyclopentane and cyclohexane. These solvents may be used alone or as a mixture of two or more.

  The amount of the solvent used for the polymerization is not particularly limited, but the concentration of the total block copolymer in the solution after the polymerization reaction is usually 5 to 60% by weight, preferably 10 to 55% by weight, more preferably 20 to 50% by weight. Set to%.

  When obtaining a block copolymer composition for flexographic printing plates, a Lewis base compound may be added to a reactor used for polymerization in order to control the structure of each polymer block of each block copolymer. Examples of the Lewis base compound include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether; and ethers such as tetramethylethylenediamine, trimethylamine, triethylamine, pyridine and quinuclidine. Tertiary amines; alkali metal alkoxides such as potassium-t-amyl oxide and potassium-t-butyl oxide; phosphines such as triphenylphosphine; These Lewis base compounds are used alone or in combination of two or more, and are appropriately selected within a range not to impair the object of the present invention.

  The timing of adding the Lewis base compound at the time of the polymerization reaction is not particularly limited, and may be appropriately determined according to the target structure of each block copolymer. For example, it may be added in advance before starting polymerization, or may be added after polymerizing some polymer blocks, and further, may be added in advance before starting polymerization, and then partially added. After the polymer block is polymerized, it may be further added.

  The polymerization reaction temperature is usually 10 to 150 ° C, preferably 30 to 130 ° C, more preferably 40 to 90 ° C. The time required for the polymerization varies depending on the conditions, but is usually within 48 hours, preferably 0.5 to 10 hours. The polymerization pressure is not particularly limited, as long as the polymerization is carried out at a pressure sufficient to maintain the monomer and the solvent in the liquid phase in the above-mentioned polymerization temperature range.

By polymerizing an aromatic vinyl monomer using a polymerization initiator in a solvent under the conditions described above, a solution containing an aromatic vinyl polymer having an active terminal can be obtained. The aromatic vinyl polymer having an active terminal is combined with an aromatic vinyl polymer block (Ar1 ^a ) having a relatively small weight-average molecular weight of the block copolymer A, which constitutes the block copolymer composition. And a vinyl polymer block (Ar ^b ) of united B. Therefore, the amount of the aromatic vinyl monomer used at this time is determined according to the desired weight average molecular weight of these polymer blocks.

The next step is a step of adding a conjugated diene monomer to a solution containing an aromatic vinyl polymer having an active terminal obtained as described above. By the addition of the conjugated diene monomer, a conjugated diene polymer chain is formed from the active end, and a solution containing an aromatic vinyl-conjugated diene block copolymer (diblock) having an active end is obtained. The amount of the conjugated diene monomer used at this time is determined so that the obtained conjugated diene polymer chain has the weight average molecular weight of the conjugated diene polymer block (D ^b ) of the target block copolymer B. .

  In the next step, a solution containing the aromatic vinyl-conjugated diene block copolymer (diblock) having an active terminal obtained as described above has a functional group of less than 1 molar equivalent with respect to the active terminal. The coupling agent is added in such an amount that Examples of the coupling agent added at this time are as described above. The amount of the coupling agent to be added is determined according to the ratio of the block copolymer A and the block copolymer B constituting the block copolymer composition, and the amount of the coupling agent relative to the active terminal of the polymer is determined. There is no particular limitation as long as the amount of the functional group of the ring agent is less than 1 molar equivalent, but usually, the range in which the functional group of the coupling agent is 0.10 to 0.90 molar equivalent with respect to the active terminal of the polymer. And preferably in the range of 0.15 to 0.70 molar equivalents. The conditions for the coupling reaction are not particularly limited, and are usually selected from the range of the above-described polymerization reaction conditions.

  As described above, coupling to a solution containing an aromatic vinyl-conjugated diene block copolymer (diblock) having an active terminal in an amount such that the functional group is less than 1 molar equivalent with respect to the active terminal. When the agent is added, in some of the aromatic vinyl-conjugated diene block copolymers having active terminals (diblocks), the conjugated diene polymer blocks may be linked via the residue of the coupling agent. To form a block copolymer B of the block copolymer composition. Then, the remaining part of the aromatic vinyl-conjugated diene block copolymer (diblock) having an active terminal remains in the solution without being reacted.

In the next step, an aromatic vinyl monomer is added to the solution obtained as described above. When the aromatic vinyl monomer is added to the solution, the aromatic vinyl polymer is reacted from the terminal of the aromatic vinyl-conjugated diene block copolymer (diblock) having an active terminal remaining without reacting with the coupling agent. Chains are formed. This aromatic vinyl polymer chain constitutes an aromatic vinyl polymer block (Ar2 ^a ) having a relatively large weight average molecular weight of the block copolymer A, which constitutes a block copolymer composition for flexographic printing plates. It is what becomes. Therefore, the amount of the aromatic vinyl monomer used at this time is determined according to the target weight average molecular weight of the aromatic vinyl polymer block (Ar2 ^a ). By the step of adding the aromatic vinyl monomer, an asymmetric aromatic vinyl-conjugated diene-aromatic vinyl block copolymer, which constitutes the block copolymer A, is formed. A solution containing the polymer A and the block copolymer B is obtained. Prior to the step of adding the aromatic vinyl monomer, a conjugated solution containing an aromatic vinyl-conjugated diene block copolymer (diblock) having an active terminal that has not reacted with the coupling agent is added. A diene monomer may be added. When the conjugated diene monomer is added in this manner, the weight average molecular weight of the conjugated diene polymer block (D ^a ) of the block copolymer A can be increased as compared with the case where no conjugated diene monomer is added.

  In addition, before the step of adding the aromatic vinyl monomer, for the purpose of making the obtained block copolymer composition for flexographic printing plates contain the block copolymer C, the active terminal that did not react with the coupling agent was added. A polymerization terminator (water, methanol, ethanol, propanol, hydrochloric acid, citric acid, etc.) is added to the solution containing the aromatic vinyl-conjugated diene block copolymer (diblock) in an amount smaller than the equivalent of the active terminal. A step may be provided. When the polymerization terminator is added in this manner, the active terminal of the aromatic vinyl-conjugated diene block copolymer (diblock) is deactivated, and the aromatic vinyl-conjugated diene block copolymer (diblock) obtained thereby is inactivated. ) Can be contained as a block copolymer C in a block copolymer composition for flexographic printing plates. In the case where this step is provided, it is necessary to add the functional group of the coupling agent and the polymerization terminator in a total amount of less than 1 molar equivalent to the active terminal of the aromatic vinyl-conjugated diene block copolymer. There is.

  In the next step, the block copolymer composition for flexographic printing plates is recovered from the solution containing the block copolymer A and the block copolymer B obtained as described above. The method of recovery may be in accordance with a conventional method, and is not particularly limited. For example, after completion of the reaction, if necessary, a polymerization terminator such as water, methanol, ethanol, propanol, hydrochloric acid, or citric acid is added, and if necessary, an additive such as an antioxidant is added. The solution can be recovered by applying a known method such as a direct drying method or steam stripping to the solution. When the block copolymer composition is recovered as a slurry by applying steam stripping or the like, the block copolymer composition is dewatered using an arbitrary dehydrator such as an extruder-type squeezer, and the crumb having a water content of a predetermined value or less is used. Then, the crumb may be dried using an optional dryer such as a band dryer or an expansion extrusion dryer. The block copolymer composition for flexographic plate obtained as described above may be used after being processed into pellets or the like according to a conventional method.

  According to the above production method, since the block copolymer A and the block copolymer B can be continuously obtained in the same reaction vessel, when each block copolymer is produced individually and mixed, In comparison, the desired block copolymer composition for flexographic printing plates can be obtained with extremely excellent productivity. Moreover, the resulting composition has a weight-average molecular weight of each polymer block of each block copolymer, which has a particularly desirable balance as a block copolymer composition for flexographic printing plates. A block copolymer composition for flexographic printing plates having an excellent balance of rubber elasticity can be obtained.

  In the above production method, when an alkoxysilane compound having two or more alkoxy groups per molecule directly bonded to a silicon atom is used as a coupling agent, it differs from any of the block copolymers A to C. In some cases, a polymer component having an aromatic vinyl polymer block and a conjugated diene polymer block is contained in the block copolymer composition for flexographic printing plates. In this polymer component, the content of the aromatic vinyl monomer unit with respect to all the monomer units is about intermediate between that of the block copolymer A and that of the block copolymer B, and the weight average The molecular weight is equivalent to about three times the weight average molecular weight of the block copolymer A. Although the structure of this polymer component is not always clear, when the coupling block copolymer is formed, all the alkoxysilyl groups of the coupling agent have an aromatic terminal having an active terminal, and an aromatic vinyl-conjugated diene block copolymer. Does not react, some alkoxysilyl groups remain unreacted, and when an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer having an active terminal is subsequently formed, the active terminal of the aromatic vinyl-conjugated diene-aromatic vinyl block copolymer is changed to a cup. It is presumed to be a block copolymer D represented by the following general formula (D), which can be generated by a mechanism of reacting with an unreacted alkoxysilyl group of the ring agent.

_{^{(Ar b -D b) n-}} 1 -X-Ar2 a -D a -Ar1 a (D)

In the general formula (D), Ar 2 ^a , Ar ^b and D ^b are the same as those in the general formulas (A) and (B), X is a residue of a coupling agent, and n is It is an integer of 2 or more.

  By including the polymer component presumed to be the block copolymer D as described above, the block copolymer composition for flexographic printing plates is particularly excellent in balance between abrasion resistance and rubber elasticity, and is extruded. Even when a molding method in which molecular orientation tends to occur is used, anisotropy is hardly exhibited and excellent isotropy is obtained. Therefore, when the block copolymer composition for flexographic printing plates of the present invention is produced by the above-mentioned production method, an alkoxysilane compound having, as a coupling agent, two or more alkoxy groups directly bonded to silicon atoms per molecule is used. It is particularly preferred to use

  The flexographic block copolymer composition of the present invention as described above, while maintaining sufficient rubber elasticity, has a highly excellent abrasion resistance as compared to the conventional flexographic plate polymer composition. It has good transparency and low anisotropy. Therefore, by using the block copolymer composition for a flexographic plate of the present invention, the abrasion resistance and flexibility are highly balanced, and the flexographic plate having high definition printing characteristics and excellent ink swelling resistance is obtained. Obtainable. The method of obtaining a flexographic printing plate using the block copolymer composition for a flexographic printing plate of the present invention is not particularly limited, but from a photosensitive composition, molded into a sheet, and exposing the sheet to form a flexographic printing plate. The method of obtaining is common.

  That is, the photosensitive flexographic printing plate composition of the present invention comprises the flexographic printing plate copolymer composition of the present invention, an ethylenically unsaturated compound having a molecular weight of 5,000 or less, and a photopolymerization initiator. is there. The amount of the block copolymer composition for flexographic printing plates used is preferably 40 to 95% by weight, more preferably 50 to 95% by weight, based on the total amount of the block copolymer composition for flexographic printing plates and the ethylenically unsaturated compound. % By weight.

  Examples of the ethylenically unsaturated compound having a molecular weight of 5,000 or less include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, 1,4-butanediol, and 1,6-hexanediol. Diacrylate or dimethacrylate; trimethylolpropane triacrylate or trimethacrylate; pentaerythritol tetraacrylate or tetramethacrylate; N, N′-hexamethylenebisacrylamide, N, N′-hexamethylenebismethacrylamide, diacetone Acrylamide, diacetone methacrylamide, styrene, vinyltoluene, divinylbenzene, diallyl phthalate, triallyl cyanu Such as over doors and the like. These may be used alone or in combination of two or more.

  The amount of the ethylenically unsaturated compound to be used is preferably 5 to 60% by weight, more preferably 5 to 50% by weight, based on the total amount of the block copolymer composition for flexographic printing plates and the ethylenically unsaturated compound. .

  The total amount of the block copolymer composition for flexographic printing plates and the ethylenically unsaturated compound is preferably at least 50% by weight, more preferably at least 60% by weight, particularly preferably based on the total amount of the composition for photosensitive flexographic plates. 70% by weight or more.

  As the photopolymerization initiator, for example, methylhydroquinone, benzophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, α-methylbenzoin, α-methylbenzoin methyl ether, α-methoxybenzoin methyl ether Benzoin phenyl ether, α-t-butyl benzoin, anthraquinone, benzanthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, 2-2′-dimethoxydiphenylacetophenone, 2,2-diethoxyphenylacetophenone Examples include phenone, 2,2-diethoxyacetophenone, and piperoin. These may be used alone or in combination of two or more. The amount of the photopolymerization initiator used is preferably 0.1 to 5% by weight based on the total amount of the block copolymer composition for flexographic printing plates and the ethylenically unsaturated compound.

  In the present invention, components other than those described above can be added to the composition for a photosensitive flexographic plate, if necessary. Such components include, for example, plasticizers, thermal polymerization inhibitors, antioxidants, antiozonants, dyes, pigments, fillers, photochromic additives, reducing agents, agents that improve the relief structure, crosslinking. Agents, flow improvers, release agents, and the like.

  The plasticizer is usually used for the purpose of facilitating the production and molding of the composition for a photosensitive flexographic plate, promoting the removal of unexposed portions, and adjusting the hardness of exposed and cured portions. Examples of the plasticizer include hydrocarbon oils such as naphthenic oil and paraffin oil; liquid 1,2-polybutadiene, liquid 1,4-polybutadiene and hydroxides or carboxylates thereof; liquid acrylonitrile-butadiene copolymer; This carboxylated product; liquid styrene-butadiene copolymer and this carboxylated product; low molecular weight polystyrene having a molecular weight of 3,000 or less, α-methylstyrene-vinyltoluene copolymer, petroleum resin, polyacrylate resin, polyester resin, polyterpene resin, etc. Is raised. These may be used alone or in combination of two or more. The plasticizer is generally added to the composition for a photosensitive flexographic plate in an amount of 2 to 50% by weight, depending on the target properties.

  The thermal polymerization inhibitor is used for the purpose of preventing unintended thermal polymerization of an ethylenically unsaturated compound when preparing a composition for a photosensitive flexographic plate. Examples of the thermal polymerization inhibitor include phenols such as hydroquinone, p-methoxyphenol, pt-butylcatechol, 2,6-di-t-butyl-p-cresol, and pyrogallol; benzoquinone, p-toluquinone, -Quinones such as xyloquinone; amines such as phenyl-α-naphthylamine. These may be used alone or in combination of two or more. The amount of the thermal polymerization inhibitor used is usually 0.001 to 2% by weight in the composition for a photosensitive flexographic plate.

  The method for producing the composition for a photosensitive flexographic printing plate of the present invention is not particularly limited. For example, the components constituting the composition are kneaded using a kneader, a roll mill, a Banbury, a single-screw or multi-screw extruder, or the like. Can be manufactured. The obtained composition is usually formed into a sheet-like molded product having a desired thickness by using a molding machine such as a single-screw or multi-screw extruder, a compression molding machine, and a calendar molding machine. When a single-screw or multi-screw extruder is used, the preparation of the photosensitive flexographic printing plate composition and the formation of a sheet-like molded product can be performed simultaneously. Further, the components constituting the composition for photosensitive flexographic printing plate are dissolved in a suitable solvent such as chloroform, carbon tetrachloride, trichloroethane, diethyl ketone, methyl ethyl ketone, benzene, toluene, and tetrahydrofuran, and the solution is placed in a frame. By injecting and evaporating the solvent, a sheet-shaped composition for a photosensitive flexographic plate can be produced.

  The thickness of the sheet is usually 0.1 to 20 mm, preferably 1 to 10 mm.

  The sheet-shaped photosensitive flexographic plate composition is a transparent flexographic plate made of a resin such as polypropylene, polyethylene, or polyethylene terephthalate on its surface in order to prevent contamination or damage of the photosensitive flexographic plate composition during storage or operation. A suitable sheet or film can be provided as a base sheet layer or a protective film layer.

  On the surface of the sheet-shaped composition for a photosensitive flexographic plate, a thin coating material rich in flexibility in order to suppress the adhesiveness of the composition surface and enable reuse of the negative film after light irradiation A layer may be provided. In this case, after the exposure of the composition for a photosensitive flexographic plate is completed, when the unexposed portion is removed with a solvent, the coating material layer must be removed at the same time. As the coating material layer, usually, a soluble polyamide, a cellulose derivative or the like is frequently used.

  The flexographic plate of the present invention can be obtained by exposing the composition for a photosensitive flexographic plate of the present invention to light.

The production of the flexographic plate is generally performed according to the following steps.
(I): a specific thickness of the photosensitive flexographic printing plate composition layer by irradiating light from the base sheet side of a multilayer sheet comprising a protective film, a sheet-shaped photosensitive flexographic printing plate composition layer, and a base sheet. Allow to cure until reaching.
(Ii): The protective film is peeled off, the negative film is adhered, and light having a wavelength of 230 to 450 nm, preferably 350 to 450 nm is irradiated from above the negative film to expose the photosensitive flexographic printing plate composition layer. This exposure cures the light-transmitting portions of the photosensitive flexographic printing plate composition layer.
(Iii): Since the unexposed portion of the composition layer for a photosensitive flexographic plate is in an uncured state, the portion is removed (development).
(Iv): In (iii), since the uncured portion is usually removed using a solvent, the solvent remaining in the flexographic plate is dried.
(V): Post-exposure, if desired.

  In the step (iii) of development (removal of unexposed portions), a solvent is usually used. Examples of the solvent include aliphatic or aromatic hydrocarbons such as n-hexane, n-heptane, octane, petroleum ether, naphtha, limonene, terpene, toluene, xylene, ethylbenzene, and isopropylbenzene; acetone, methyl ethyl ketone, and the like. Ketones; ethers such as di-n-butyl ether and di-t-butyl ether; esters such as methyl acetate and ethyl acetate; halogens such as methylene chloride, chloroform, trichloroethane, tetrachloroethylene, dichlorotetrafluoroethane and trichlorotrifluoroethane. And the like. These may be used alone or in combination of two or more. Further, a desired amount of an alcohol such as methanol, ethanol, isopropanol, n-butanol or the like may be added to the above solvent and used. The development can be accelerated by applying a mechanical force using a brush or the like in the presence of the solvent.

  The flexographic printing plate of the present invention has sufficient flexibility, high abrasion resistance, and excellent ink swelling resistance. Therefore, by using the flexographic printing plate of the present invention, printing can be repeated many times even under severe conditions, and the ink transfer during printing is excellent, and flexographic printing can be performed with excellent image quality. In addition, as an object to be printed by flexographic printing, for example, various materials such as paper, cardboard, wood, metal, polyethylene film, polyethylene sheet, polypropylene film, and polypropylene sheet can be applied.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The parts and percentages in each example are based on weight unless otherwise specified.

  Various measurements were performed according to the following methods.

(Weight average molecular weight of block copolymer and block copolymer composition)
The molecular weight was determined as high molecular weight in terms of polystyrene by high performance liquid chromatography using tetrahydrofuran as a carrier at a flow rate of 0.35 ml / min. The apparatus was HLC8220 manufactured by Tosoh Corporation, the column was connected to three Showex KF-404HQ (column temperature: 40 ° C), the detector was a differential refractometer and an ultraviolet detector, and the molecular weight was calibrated by a polymer laboratory. The test was performed on 12 points of the standard polystyrene (5 to 3 million) manufactured by the company.

(Weight ratio of each block copolymer)
It was determined from the area ratio of peaks corresponding to each block copolymer in the chart obtained by the high performance liquid chromatography.

(Weight average molecular weight of styrene polymer block)
Rubber Chem. Technol. The block copolymer was reacted with ozone and reduced with lithium aluminum hydride to decompose the isoprene polymer block of the block copolymer according to the method described in J. Am. Specifically, the following procedure was performed. That is, 300 mg of a sample was dissolved in a reaction vessel containing 100 ml of dichloromethane treated with a molecular sieve. After the reaction vessel was put into a cooling bath at -25 ° C., ozone generated by an ozone generator was introduced while flowing oxygen at a flow rate of 170 ml / min into the reaction vessel. After a lapse of 30 minutes from the start of the reaction, the gas flowing out of the reaction vessel was introduced into an aqueous potassium iodide solution to confirm that the reaction was completed. Next, 50 ml of diethyl ether and 470 mg of lithium aluminum hydride were charged into another reaction vessel purged with nitrogen, and a solution reacted with ozone was slowly dropped into this reaction vessel while cooling the reaction vessel with ice water. Then, the reaction vessel was placed in a water bath, the temperature was gradually raised, and the mixture was refluxed at 40 ° C. for 30 minutes. Thereafter, while stirring the solution, dilute hydrochloric acid was added dropwise to the reaction vessel little by little, and the dropwise addition was continued until almost no generation of hydrogen was observed. After this reaction, a solid product formed in the solution was filtered off, and the solid product was extracted with 100 ml of diethyl ether for 10 minutes. This extract was combined with the filtrate obtained by filtration, and the solvent was distilled off to obtain a solid sample. The weight average molecular weight of the sample thus obtained was measured in accordance with the above-mentioned method of measuring the weight average molecular weight, and the value was defined as the weight average molecular weight of the styrene polymer block.

(Weight average molecular weight of conjugated diene polymer block)
The weight average molecular weight of the corresponding styrene polymer block is subtracted from the weight average molecular weight of the block copolymer obtained as described above, and based on the calculated value, the conjugated diene polymer block (isoprene polymer block) is obtained. Or butadiene polymer block).

(Styrene 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-described high performance liquid chromatography measurement. Incidentally, copolymers having different styrene unit contents were prepared in advance, and a calibration curve was prepared using them.

(Styrene unit content of the block copolymer composition)
It was determined based on the proton NMR measurement.

(Vinyl bond content of conjugated diene polymer block)
It was determined based on the proton NMR measurement.

[Type A hardness of block copolymer composition]
Type A hardness was measured using a durometer hardness tester (type A) according to JIS K6253.

(Light transmittance of the block copolymer composition)
The block copolymer composition was dissolved in dehydrated toluene to obtain a 25% by weight solution. For this toluene solution, light transmittance at a wavelength of 360 nm was measured using a Hitachi spectrophotometer U-3010 manufactured by Hitachi High-Technologies Corporation as a measuring device and a quartz 10 mm cell as a cell.

(Anisotropy index of the block copolymer composition)
The block copolymer composition for flexographic printing plates was heated and melted at 150 ° C. using a twin screw extruder equipped with a T-die, and was continuously extruded to form a sheet having a thickness of 2 mm. The details of the sheet forming conditions are as follows.
Composition processing speed: 25 kg / hr
Pickup speed: 1.0m / min
Extruder temperature: Adjusted to 140 ° C inlet and 160 ° C for T-die Screw: Full flight Extruder L / D: 20
T-die: width 200mm, lip 2.5mm

  Using two sheets obtained, the tensile modulus of one was measured along the melt flow direction during molding, and the tensile modulus was measured along the vertical direction of the melt flow during molding of the other. The measurement procedure is as follows. Using a Tensilon universal tester RTC-1210 manufactured by ORIENTEC, the film is stretched to 100% at a tensile speed of 300 mm / min, and the tensile stress at the time of 100% elongation in the process is measured, and the tensile elasticity of the sheet at the time of 100% elongation The rate was determined. The closer the ratio of (tensile elastic modulus in the melt flow direction / tensile elastic modulus in the perpendicular direction of the melt flow) to 1, the smaller the anisotropy and the better the isotropicity.

(Tensile modulus of photosensitive flexographic plate composition)
The composition for a photosensitive flexographic plate was heated and melted at 150 ° C. using a twin-screw extruder equipped with a T-die, and was continuously extruded to form a sheet having a thickness of 2 mm. The details of the sheet forming conditions are as follows.
Composition processing speed: 25 kg / hr
Pickup speed: 1.0m / min
Extruder temperature: Adjusted to 140 ° C inlet and 160 ° C for T-die Screw: Full flight Extruder L / D: 20
T-die: width 200mm, lip 2.5mm

  The obtained sheet was exposed to actinic rays for 10 minutes using an exposure machine equipped with a 20 W ultraviolet fluorescent lamp (Model JE-A3-SS manufactured by JEOL Ltd.), and exposed to light. Dry for 30 minutes. Using two exposed sheets, the tensile modulus of one was measured along the melt flow direction during molding, and the tensile modulus was measured along the vertical direction of the melt flow during molding. The measurement procedure is as follows. Using a Tensilon universal tester RTC-1210 manufactured by ORIENTEC, the film is stretched to 100% at a tensile speed of 300 mm / min, and the tensile stress at the time of 100% elongation in the process is measured, and the tensile elasticity of the sheet at the time of 100% elongation The rate was determined. The closer the ratio of (tensile elastic modulus in the melt flow direction / tensile elastic modulus in the perpendicular direction of the melt flow) to 1, the smaller the anisotropy and the better the isotropicity.

(Permanent elongation of composition for photosensitive flexographic plate)
A sheet exposed to the photosensitive flexographic printing plate composition was obtained in the same manner as in the measurement of the tensile modulus. This sheet was measured for permanent elongation using the Tensilon universal tester described above in accordance with ASTM 412. Specifically, using DieA as the sample shape, the sheet is stretched at an elongation of 200% with the distance between the marked lines before stretching being 40 mm, and the sheet is kept as it is for 10 minutes and then suddenly shrunk without being rebounded. After standing for 10 minutes, the distance between the marked lines was measured, and the permanent elongation was determined based on the following equation. The lower the value of the permanent elongation, the better the rubber elasticity.
Permanent elongation (%) = (L1-L0) / L0 × 100
L0: Distance between marked lines before extension (mm)
L1: Distance between marked lines after contraction and standing for 10 minutes (mm)
In this measurement, using two sheets, one was measured along the melt flow direction during molding, and the other was measured along the melt flow vertical direction during molding, and the respective values were recorded.

(Abrasion resistance of composition for photosensitive flexographic plate)
A sheet exposed to the photosensitive flexographic printing plate composition was obtained in the same manner as in the measurement of the tensile modulus. Next, using a Haydon abrasion tester (manufactured by Shinto Chemical Co., Ltd.), the obtained sheet and No. 1000 waterproof paper were reciprocally rubbed under the conditions of a load of 100 g and a speed of 6000 mm / sec, and the wear amount of the sheet surface after 1000 cycles. Was measured. This index is indicated by an index with Comparative Example 1 being 100. The larger the index, the better the wear resistance.

(Ink swelling resistance of photosensitive flexographic plate composition)
A sheet exposed to the photosensitive flexographic printing plate composition was obtained in the same manner as in the measurement of the tensile modulus. Next, the sheet whose weight was measured in advance was placed in isopropyl alcohol. It was taken out after 60 minutes, excess isopropyl alcohol was wiped off, and the weight was measured. The ink swelling resistance was measured at the weight ratio (sheet weight after test / sheet weight before test). As this index is closer to 100%, the ink swelling resistance is more excellent.

[Production Example 1]
23.3 kg of cyclohexane, 2.5 mmol of N, N, N ', N'-tetramethylethylenediamine (hereinafter referred to as TMEDA) and 1.33 kg of styrene were added to the pressure-resistant reactor, and the mixture was stirred at 40 ° C. Meanwhile, 166.7 mmol of n-butyllithium was added, and polymerization was carried out for 1 hour while heating to 50 ° C. The polymerization conversion of styrene was 100%. Subsequently, 7.00 kg of isoprene was continuously added to the reactor over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After the addition of isoprene was completed, the polymerization was continued for 1 hour. The polymerization conversion of isoprene was 100%. Next, 30.5 mmol of tetramethoxysilane was added as a coupling agent, and a coupling reaction was carried out for 2 hours to form a styrene-isoprene-styrene block copolymer to be a block copolymer B. Next, the active terminal of some styrene-isoprene block copolymers was deactivated by adding 31.7 mmol of methanol to the reactor. Thereafter, 1.67 kg of styrene was continuously added over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After the addition of styrene was completed, the mixture was further polymerized for 1 hour to form a styrene-isoprene-styrene block copolymer which was a block copolymer A. The polymerization conversion of styrene was 100%. Thereafter, 333.4 mmol of methanol was added as a polymerization terminator and mixed well to terminate the reaction. The amounts of each reagent used in the reaction are summarized in Table 1. A part of the obtained reaction solution is taken out, the weight average molecular weight of each block copolymer and the block copolymer composition, the weight average molecular weight of each styrene polymer block, the weight average molecular weight of each isoprene polymer block, each block The styrene unit content of the copolymer, the styrene unit content of the block copolymer composition, the vinyl bond content of the isoprene polymer block, and the weight ratio of each block copolymer were determined. These values are shown in Table 2. To 100 parts of the reaction solution obtained as described above (containing 30 parts of the polymer component), 0.3 part of 2,6-di-tert-butyl-p-cresol as an antioxidant was added and mixed. The mixed solution was dropped little by little into warm water heated to 85 to 95 ° C. to volatilize the solvent to obtain a precipitate. The precipitate was pulverized and dried at 85 ° C. with hot air to produce Production Example 1. Was recovered.

[Production Example 2]
The block copolymer composition of Production Example 2 was prepared in the same manner as in Production Example 1 except that the amounts of styrene, n-butyllithium, isoprene, tetramethoxysilane, and methanol were respectively changed as shown in Table 1. Collected. For the block copolymer composition of Production Example 2, the same measurements as in Production Example 1 were performed. Table 2 shows the results.

[Production Example 3]
To a pressure-resistant reactor, 23.3 kg of cyclohexane, 1.9 mmol of TMEDA and 1.50 kg of styrene were added. While stirring at 40 ° C., 128.8 mmol of n-butyllithium was added, and the temperature was raised to 50 ° C. The polymerization was carried out for 1 hour. The polymerization conversion of styrene was 100%. Subsequently, 7.00 kg of isoprene was continuously added to the reactor over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After the addition of isoprene was completed, the polymerization was continued for 1 hour. The polymerization conversion of isoprene was 100%. Thereafter, 1.50 kg of styrene was continuously added over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After the addition of styrene was completed, the mixture was further polymerized for 1 hour to form a styrene-isoprene-styrene block copolymer. The polymerization conversion of styrene was 100%. Thereafter, 257.6 mmol of methanol was added as a polymerization terminator and mixed well to terminate the reaction. A part of the obtained reaction solution was taken out and subjected to the same measurement as in Production Example 1. These values are shown in Table 2. The following operation was the same as in Production Example 1, and the block copolymer composition of Production Example 3 was recovered.

[Production Examples 4 and 5]
Except that the amounts of styrene, n-butyllithium, TMEDA, isoprene, and methanol were respectively changed as shown in Table 1, the block copolymer compositions of Production Examples 4 to 5 were prepared in the same manner as in Production Example 3. Collected. About the block copolymer composition of the manufacture examples 4-5, the same measurement as the manufacture example 1 was performed. Table 2 shows the results.

[Production Example 6]
Instead of 7.00 kg of isoprene, 7.50 kg of butadiene was used, and in the same manner as in Production Example 3 except that the amounts of styrene, n-butyllithium, TMEDA, and methanol were changed as shown in Table 1, respectively. The block copolymer composition of Production Example 6 was recovered. For the block copolymer composition of Production Example 6, the same measurements as in Production Example 1 were performed. Table 2 shows the results.

[Example 1]
100 parts of the block copolymer composition of Production Example 1, 10 parts of liquid polybutadiene (NISSO-PB-B-1000: manufactured by Nippon Soda Co., Ltd.), and 2 parts of 2,6-di-t-butyl-p-cresol Was kneaded at 170 ° C. using a kneader-kneader. Subsequently, the kneading temperature was lowered to 130 ° C., and 5 parts of 1,4-butanediol diacrylate, 5 parts of 1,6-hexanediol dimethacrylate, 0.01 part of methylhydroquinone and 0.8 part of benzoin isopropyl ether were added. Then, the composition for a photosensitive flexographic plate of Example 1 was obtained. The composition for a photosensitive flexographic plate was measured for tensile modulus, permanent elongation, abrasion resistance and ink swelling resistance. Table 3 shows the results.

[Example 2]
A composition for a photosensitive flexographic plate of Example 2 was obtained in the same manner as in Example 1 except that the block copolymer composition used was changed to the block copolymer composition of Production Example 2. With respect to the composition for a photosensitive flexographic plate of Example 2, the tensile modulus, permanent elongation, abrasion resistance and ink swelling resistance were measured. Table 3 shows the results.

[Comparative Examples 1 to 4]
Except for changing the block copolymer composition to be used to the block copolymer compositions of Production Examples 3 to 6, in the same manner as in Example 1, the compositions for photosensitive flexographic plates of Comparative Examples 1 to 4 were obtained. Was. With respect to the compositions for photosensitive flexographic plates of Comparative Examples 1 to 4, the tensile modulus, permanent elongation, abrasion resistance and ink swelling resistance were measured. Table 3 shows the results.

  Tables 2 and 3 show the following. That is, the block copolymer composition for flexographic plates of the present invention (Production Examples 1 and 2) has good flexibility and transparency, has low anisotropy, and has a block copolymer composition for flexographic plates of the present invention. The composition for a photosensitive flexographic plate of the present invention obtained from a product has both low permanent elongation and high abrasion resistance, is said to be excellent in rubber elasticity and abrasion resistance, and also has excellent ink swelling resistance and isotropy. Excellent (Examples 1-2). On the other hand, the block copolymer compositions (Production Examples 3 to 6) which do not correspond to the block copolymer composition for flexographic printing plates of the present invention have at least one of flexibility, transparency and anisotropy sufficiently. Instead, when these block copolymer compositions were used, the balance between rubber elasticity and abrasion resistance was poor, and anisotropy was exhibited (Comparative Examples 1 to 4).

Claims (7)

It comprises a block copolymer A represented by the following general formula (A) and a block copolymer B represented by the following general formula (B). The ratio of the aromatic vinyl monomer unit to all the monomer units constituting the coalescing component is 18 to 70% by weight, the type A hardness is 25 to 65, and a 25% by weight toluene solution. A block copolymer composition for flexographic plates having a light transmittance at a wavelength of 360 nm of 50% or more and an anisotropy index of 2.0 or less.
^{Ar1 a -D a -Ar2 a (A} )
(Ar ^b -D ^b ) _n -X (B)
(In the general formula (A) and (B), Ar @ 1 ^a and Ar ^b are each an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000, Ar @ 2 ^a has a weight average molecular weight of from 40000 to 400000 an aromatic vinyl polymer block, the ratio of the weight average molecular weight of the aromatic vinyl polymer block Ar @ 2 ^a and an aromatic vinyl polymer block Ar1 weight average molecular weight of ^{a (Mw (Ar2 a) /} Mw (Ar1 a)) There is a 2 to 12, D ^a and D ^b are each a vinyl bond content of 20 mol% of the conjugated diene polymer block, X is the residue of a single bond or a coupling agent, n Is an integer of 2 or more.)   The flexo according to claim 1, wherein the ratio of the aromatic vinyl monomer unit to all the monomer units constituting the polymer component in the flexographic block copolymer composition is 20 to 70% by weight. Block copolymer composition for plate.   The block copolymer composition for a flexographic plate according to claim 1 or 2, wherein a weight ratio (A / B) of the block copolymer A and the block copolymer B is 36/64 to 85/15. object. The block copolymer composition for flexographic plates according to any one of claims 1 to 3, further comprising a block copolymer C represented by the following general formula (C).
Ar ^c -D ^{c (C)}
(In the general formula (C), Ar ^c is an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000, and D ^c is a conjugated diene polymer block having a vinyl bond content of 1 to 20 mol%. is there.)   The block copolymer B is obtained by using, as a coupling agent, a compound having at least one functional group selected from an alkoxyl group, an ester group and an epoxy group in one molecule. The block copolymer composition for flexographic printing plates according to any one of claims 1 to 4.   A photosensitive flexographic printing plate comprising the block copolymer composition for a flexographic printing plate according to any one of claims 1 to 5, an ethylenically unsaturated compound having a molecular weight of 5,000 or less, and a photopolymerization initiator. Composition.   A flexographic plate comprising the composition for a photosensitive flexographic plate according to claim 6.