JP2008007654A - Elastic film, elastic material and sanitary goods - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stretchable film having anisotropy even without compounding a non-stretchable material and having flexibility. <P>SOLUTION: The stretchable film having specific characteristics is obtained as follows. An aromatic vinyl-conjugated diene block copolymer composition comprising (a) 35-95 wt.% of an aromatic vinyl-conjugated diene block copolymer having ≥2 specific aromatic vinyl polymer blocks, (b) 0-60 wt.% of an aromatic vinyl conjugated diene diblock copolymer and (c) 2-50 wt.% of a polyisoprene having a weight-average molecular weight thereof within a specified range is extruded. In the aromatic vinyl-conjugated diene block copolymer composition, the content of aromatic vinyl monomer units based on the total amount of the components (a) and (b) is 22-45 wt.%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a stretchable film that can be suitably used as a stretchable member for sanitary products such as paper diapers and sanitary products. Specifically, it is made of an aromatic vinyl-conjugated diene block copolymer, has an anisotropy without blending a non-stretchable material, and has a good flexibility. The present invention relates to a hygienic article comprising a sex member and the same member.

Since various sanitary products such as paper diapers and sanitary products are required to follow and fit with the movement of the wearer, stretchable members are used in each part. For example, in a pants-type diaper, which is a type of paper diaper, the member is used in the opening around both legs, the opening around the waist, and the waist on both sides.
As such a stretchable member, a stretchable material made of a thermoplastic elastomer has been used in the form of a film in addition to various synthetic rubbers and natural rubbers. Thermoplastic elastomers are advantageous in sanitary article molding because they do not require a vulcanization operation compared to rubber, and are reusable sanitary polymers. Stretch materials made of thermoplastic elastomers generally exhibit equivalent tensile stress (modulus) in all directions. However, for specific uses such as the opening around the waist of a pant-type diaper, for the convenience and fit of the wearer, the properties (anisotropy) and flexibility differ in tensile modulus (modulus) depending on the direction. A stretchable material having both of the above is preferred.

As a general method of manufacturing an elastic member having anisotropy, it has been known that a laminate is formed by laminating an elastic material made of a thermoplastic elastomer or the like and a non-elastic material made of a polyolefin or the like. (See, for example, Patent Document 1). However, the laminated body is inferior in terms of flexibility, and the manufacturing process is complicated to obtain a laminated body.
As a stretchable material having anisotropy in a single layer, a block copolymer comprising a polymer block mainly composed of vinyl aromatic monomer units and a polymer block mainly composed of conjugated diene monomer units, and An anisotropic film (Patent Document 2) comprising 50 to 99% by weight of a hydrogenated product of the block copolymer and 50 to 1% by weight of an aromatic vinyl polymer, or a block copolymer elastomer component (A) And an anisotropic elastic web (Patent Document 3) in which the polyolefin polymer component (B) is blended in a ratio of A: B = 10: 1 to 0.4: 1 has been proposed. However, in any of the anisotropic materials of Patent Documents 2 and 3, a non-stretchable aromatic vinyl polymer or polyolefin is blended with an aromatic vinyl-conjugated diene block copolymer having stretchability in all directions. As a result, anisotropy is expressed. Therefore, it is lacking in flexibility as a whole.

WO96 / 10481 Japanese Patent Laid-Open No. 5-186611 Special table 2001-520244 gazette

  Accordingly, an object of the present invention is to provide an elastic film having anisotropy and flexibility.

As a result of intensive studies to solve the above problems, the present inventors have identified an aromatic vinyl-conjugated diene block copolymer having at least two aromatic vinyl polymer blocks having a specific weight average molecular weight, and a specific A predetermined amount of polyisoprene having a weight average molecular weight of the above, and if the content of the aromatic vinyl monomer unit is a specific ratio, it has anisotropy without adding a non-stretchable material, and is remarkable In addition, the present inventors have found that a flexible elastic film can be obtained, and have completed the present invention based on this finding.
Thus, according to the first invention, (a) an aromatic vinyl-conjugated diene block copolymer having two or more aromatic vinyl polymer blocks having a weight average molecular weight of 6,000 to 100,000 is 35 to 95% by weight. (B) 0 to 60% by weight of an aromatic vinyl-conjugated diene diblock copolymer, and (c) 2 to 50% by weight of polyisoprene having a weight average molecular weight of 5,000 to 300,000, (a) Stretchable film obtained by extruding an aromatic vinyl-conjugated diene block copolymer composition having an aromatic vinyl monomer unit content of 22 to 45% by weight based on the total amount of the component and component (b) Because
The ratio (MD / TD) of the 100% modulus in the melt flow direction (MD) and the 100% modulus in the direction perpendicular to the melt flow (TD) in the extrusion molding is 1.5 to 10, and A stretchable film having a 100% modulus in a direction perpendicular to the right (TD) of 0.1 to 0.5 MPa. Is provided.
Moreover, according to this 2nd invention, the elastic member which consists of said elastic film is provided.
Furthermore, according to the third aspect of the present invention, a sanitary product comprising the stretchable member is provided.

  According to the present invention, an elastic film having anisotropy and flexibility can be obtained without blending a non-elastic material. The stretchable film is useful as a stretchable member for various sanitary products such as disposable diapers and sanitary products.

The stretchable film of the present invention comprises (a) 35 to 95% by weight of an aromatic vinyl-conjugated diene block copolymer having two or more aromatic vinyl polymer blocks having a weight average molecular weight of 6,000 to 100,000, ( b) 0 to 60% by weight of an aromatic vinyl-conjugated diene diblock copolymer, and (c) 2 to 50% by weight of polyisoprene having a weight average molecular weight of 5,000 to 300,000, (B) A stretchable film obtained by extruding an aromatic vinyl-conjugated diene block copolymer composition having an aromatic vinyl monomer unit content of 22 to 45% by weight based on the total amount of components. And
The ratio (MD / TD) of the 100% modulus in the melt flow direction (MD) and the 100% modulus in the direction perpendicular to the melt flow (TD) in the extrusion molding is 1.5 to 10, and The 100% modulus in the perpendicular direction (TD) is 0.1 to 0.5 MPa.

  Aromatic vinyl-conjugated diene block copolymer (a) used in the present invention [sometimes referred to simply as “component (a)”. ] Has at least one conjugated diene polymer block and two or more aromatic vinyl polymer blocks. The upper limit of the number of aromatic vinyl polymer blocks is usually about 4. Of these, an aromatic vinyl-conjugated diene-aromatic vinyl triblock copolymer can be preferably used.

  The aromatic vinyl polymer block in the component (a) refers to a portion containing the aromatic vinyl monomer unit of the polymer as a main constituent unit, and may be obtained by polymerizing only the aromatic vinyl monomer. Alternatively, an aromatic vinyl monomer and a monomer copolymerizable therewith may be copolymerized.

  Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-ethylstyrene, p-tert-butyl. Examples include styrene. Of these, styrene is preferred. These may be used alone or in combination of two or more.

  The monomer copolymerizable with the aromatic vinyl monomer is preferably a conjugated diene monomer, more preferably 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene may be mentioned. The proportion of monomer units of the monomer copolymerizable with the aromatic vinyl monomer in the aromatic vinyl polymer block in the component (a) is preferably 20% by weight or less, and more preferably 10% by weight or less.

  The weight average molecular weight (Mw) of the aromatic vinyl polymer block in the component (a) is 6,000 to 100,000, preferably 7,000 to 70,000, more preferably 8,000 to 50,000. is there. When Mw is small, the strength of the stretchable film is insufficient, and conversely, when Mw is large, the molding processability of the aromatic vinyl-conjugated diene block copolymer composition is lowered, and extrusion molding becomes difficult.

  Further, the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the aromatic vinyl polymer block is preferably 1.5 or less, and more preferably 1.2 or less.

  The conjugated diene polymer block in the component (a) refers to a portion containing the conjugated diene monomer unit of the polymer as a main constituent unit, and even if only a conjugated diene monomer is polymerized, What copolymerized the monomer and the monomer copolymerizable with this may be used.

  Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, and the like. Among these, 1,3-butadiene and isoprene are preferable, and isoprene is more preferable. These may be used alone or in combination of two or more.

  As the monomer copolymerizable with the conjugated diene monomer, the above aromatic vinyl monomer is preferable. In order for the strength and flexibility of the stretchable film to be good, the ratio of the monomer unit of the monomer copolymerizable with the conjugated diene monomer in the conjugated diene polymer block in the component (a) is 20 % By weight or less is preferable, and 10% by weight or less is more preferable.

  The aromatic vinyl monomer unit content of the component (a) is preferably 22 to 45% by weight, more preferably 22 to 40% by weight, and particularly preferably 22 to 35% by weight. If the content is in the above range, a stretchable film excellent in flexibility showing anisotropy can be obtained.

  From the viewpoint of improving the flexibility of the stretchable film, the ratio (vinyl content) of vinyl bond units to all conjugated diene monomer units in component (a) is preferably 50% by weight or less, more preferably 20% by weight or less. Particularly preferably, it is 5 to 10% by weight.

  The weight average molecular weight (Mw) of the component (a) is preferably 40,000 to 1,000,000, more preferably 60,000 to 700,000, particularly preferably 80,000 to 400,000. If Mw is too small, the strength of the stretchable film may be insufficient. Conversely, if Mw is too large, the processability of the aromatic vinyl-conjugated diene block copolymer composition may be reduced.

  Further, the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the component (a) is preferably 1.5 or less, and more preferably 1.2 or less.

  The content of the component (a) in the aromatic vinyl-conjugated diene block copolymer composition is 35 to 95% by weight, preferably 40 to 90% by weight, more preferably 45 to 85% by weight. (A) If there is little component content, the intensity | strength of a stretchable film will run short, and conversely, if it is large, the flexibility of a stretchable film will fall.

  As the component (a) in the present invention, a styrene-isoprene block copolymer and a styrene-butadiene block copolymer are preferable because the flexibility and stretchability of the stretchable film are good, and the styrene-isoprene block copolymer is preferable. Coalescence is more preferred.

  (A) The manufacturing method of a component is not specifically limited, A well-known manufacturing method can be employ | adopted, for example, an aromatic vinyl polymer block, a conjugated diene block, and an aromatic vinyl polymer block are sequentially each by anion living polymerization method. And a method of producing a block copolymer having a living active terminal consisting of an aromatic vinyl polymer block and a conjugated diene block, and then reacting it with a coupling agent for coupling. Can be adopted.

  When a coupling agent is used, the amount used may be appropriately selected according to the desired weight average molecular weight, the reactivity of the coupling agent, and the like. The number of functional groups of the coupling agent is preferably 2-4. The coupling reaction may be performed according to a conventional method by adding a coupling agent to a predetermined polymer solution and usually at a temperature of 30 to 80 ° C. for about 1 minute to 24 hours.

  Examples of coupling agents include bifunctional halogenated silanes such as dichlorosilane, monomethyldichlorosilane, and dimethyldichlorosilane; bifunctional halogenated alkanes such as dichloroethane, dibromoethane, methylene chloride, and dibromomethane; dichlorotin, monomethyldichloro Bifunctional tin halides such as tin, dimethyldichlorotin, monoethyldichlorotin, diethyldichlorodichloro, monobutyldichlorotin, dibutyldichlorotin; Trifunctional halogenated alkanes such as trichloroethane and trichloropropane; tetrachlorosilane, tetrabromo Tetrafunctional halogenated silanes such as silane; tetrafunctional tin compounds such as tetrachlorotin and tetrabromotin; and organic compounds such as tetramethoxytin, tetraethoxytin and tetrabutoxytin Compound: Dimethyldimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, alkyltriphenoxysilane, methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, bis (trimethoxysilyl) ethane, etc. Organic silicon compounds; unsaturated nitriles such as ethyl acrylonitrile; methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, amyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, trimethyl Ethyl acetate, methyl caproate, ethyl caproate, methyl benzoate, ethyl benzoate, phenyl benzoate, dimethyl adipate, diethyl adipate, dimethyl terephthalate, terephthalate Diethyl Tal, dimethyl phthalate, carboxylic acid esters such as dimethyl isophthalate; tris nonylphenyl phosphite, trimethyl phosphite, organic phosphorus compounds such as triethyl phosphite; divinyl benzene. Among these, organic silicon compounds are preferable, and tetramethoxysilane, tetraethoxysilane, and tetrabutoxysilane are more preferable. These may be used alone or in combination of two or more.

The aromatic vinyl-conjugated diene block copolymer (a) obtained by the above production method is not particularly limited, and examples thereof include ABA, ABA ′ and (AB). _N ) It is composed of a block copolymer having the structure of X. When the aromatic vinyl-conjugated diene block copolymer composition contains such a component (a), the moldability is good and the stretchability of the stretchable film is improved. In the formula, A and A ′ are aromatic vinyl polymer blocks, B is a conjugated diene polymer block, X is a residue of a coupling agent, and n is an integer of 2 to 4.

  Further, the component (a) may be obtained by hydrogenating a part of the double bond in the conjugated diene monomer unit. The hydrogenation method is not particularly limited, and examples thereof include known methods such as bringing a hydrogen-free aromatic vinyl-conjugated diene block copolymer into contact with a palladium catalyst under a hydrogen atmosphere. .

  Aromatic vinyl-conjugated diene diblock copolymer (b) [sometimes referred to simply as “component (b)”. ] Is a block copolymer consisting of only one aromatic vinyl polymer block and only one conjugated diene polymer block.

  The aromatic vinyl polymer block in the component (b) refers to a portion containing an aromatic vinyl monomer unit as a main constituent unit.

  Examples of the aromatic vinyl monomer are the same as those described for the component (a). Of these, styrene is preferred. These may be used alone or in combination of two or more.

  Even if the aromatic vinyl polymer block in component (b) is obtained by polymerizing only the aromatic vinyl monomer, the aromatic vinyl monomer and the monomer copolymerizable therewith are co-polymerized. It may be polymerized. The monomer copolymerizable with the aromatic vinyl monomer is preferably a conjugated diene monomer, more preferably 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene may be mentioned. The proportion of the aromatic vinyl monomer unit in the aromatic vinyl polymer block in the component (b) is preferably 80% by weight or more, and more preferably 90% by weight or more.

  (B) The weight average molecular weight (Mw) of the aromatic vinyl polymer block in the component and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) are as follows. The same range as that of the aromatic vinyl polymer block is preferred.

  The conjugated diene polymer block in the component (b) refers to a part containing a conjugated diene monomer unit as a main constituent unit.

  Examples of the conjugated diene monomer include those described for the component (a). Among these, 1,3-butadiene and isoprene are preferable, and isoprene is more preferable. These may be used alone or in combination of two or more.

  The conjugated diene polymer block in the component (b) is obtained by copolymerizing a conjugated diene monomer and a monomer copolymerizable therewith, even if only a conjugated diene monomer is polymerized. It may be. As the monomer copolymerizable with the conjugated diene monomer, the above aromatic vinyl monomer is preferable. In order for the strength and flexibility of the stretchable film to be good, the proportion of the conjugated diene monomer unit in the conjugated diene polymer block in the component (b) is preferably 80% by weight or more, more preferably 90% by weight or more. preferable.

  The aromatic vinyl monomer unit content of component (b) and the vinyl bond content relative to all conjugated diene monomer units are preferably the same as in component (a).

  The weight average molecular weight (Mw) of (b) component becomes like this. Preferably it is 20,000-500,000, More preferably, it is 30,000-350,000, Most preferably, it is 40,000-200,000. If Mw is too small, the strength of the stretchable film may be insufficient. Conversely, if Mw is too large, the processability of the aromatic vinyl-conjugated diene block copolymer composition may be reduced.

  The ratio (Mw / Mn) between Mw and Mn of the component (b) is preferably the same as that of the component (a).

  The component (b) content of the aromatic vinyl-conjugated diene block copolymer composition used in the present invention is 0 to 60% by weight, preferably 3 to 50% by weight, more preferably 5 to 45% by weight. . In view of making the stretchable film more flexible, it is preferable to contain the component (b). Moreover, when there is much content of (b) component, the intensity | strength of a stretchable film will run short.

  The component (b) is preferably a styrene-isoprene diblock copolymer and / or a styrene-butadiene diblock copolymer because the flexibility of the stretchable film is good, and the styrene-isoprene diblock copolymer. Is more preferable.

  (B) The manufacturing method of a component is not specifically limited, A well-known manufacturing method can be employ | adopted, for example, the method of superposing | polymerizing an aromatic vinyl polymer block and a conjugated diene block sequentially by an anion living polymerization method is employable. .

  The component (b) may be one obtained by hydrogenating a part of the double bond in the conjugated diene monomer unit. The hydrogenation method is not particularly limited.

  The component (a) and the component (b) may be separately produced and used. For example, according to the method described in WO 2004/011551, the component (a) and the component (b) are performed by a series of polymerization operations. It can also be produced and used as a mixture of components.

  The content of the wholly aromatic vinyl monomer unit in the component (a) and the component (b) with respect to the total amount of the component (a) and the component (b) is 22 to 45% by weight, preferably 22 to 40% by weight. More preferably, it is 22 to 35% by weight. When the aromatic vinyl monomer unit content is small, the anisotropy of the stretchable film is not exhibited. On the contrary, when the content is large, the flexibility of the stretchable film is lowered.

  Although there is no limitation in particular as a weight average molecular weight of the mixture of (a) component and (b) component, Preferably it is 50,000-950,000, More preferably, it is 50,000-600,000, Most preferably, 60, 000 to 400,000.

  In the aromatic vinyl-conjugated diene block copolymer composition used in the present invention, the ratio of the component (a) in the total amount of the component (a) and the component (b) {[(a) component / [ (A) component + (b) component]} is preferably 40 to 100% by weight, more preferably 50 to 90% by weight, from the viewpoint of ensuring good film processability.

  Polyisoprene (c) [sometimes referred to simply as “component (c)”. ] Is a weight average molecular weight of 5,000 to 300,000, preferably 10,000 to 200,000, more preferably 30,000 to 100,000. When the said weight average molecular weight is low, the malfunction which bleeds from an elastic film will arise, conversely, when high, the softness | flexibility of an elastic film will fall.

  Further, the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the component (c) is preferably 1.5 or less, and more preferably 1.2 or less.

  Component (c) is a polymer containing an isoprene unit as a main constituent unit, and is a copolymer of isoprene and another monomer copolymerizable therewith, even if it is a polymer of isoprene alone. However, it is particularly preferable to polymerize isoprene alone. The proportion of isoprene units in component (c) is preferably 80% by weight or more, more preferably 90% by weight or more. The monomer copolymerizable with isoprene is preferably a conjugated diene monomer other than the aromatic vinyl monomer and isoprene, and more preferably 1,3-butadiene and styrene. These may be used alone or in combination of two or more.

  The vinyl bond content in the total isoprene unit of the component (c) is preferably 50% by weight or less, more preferably 20% by weight or less, particularly preferably 5 to 10% by weight from the viewpoint of improving the flexibility of the stretchable film. %.

(C) The manufacturing method of a component is not specifically limited, A well-known manufacturing method can be employ | adopted, for example, the method of superposing | polymerizing isoprene using a well-known anionic polymerization initiator in a polymerization solvent is employable.
Further, the component (c) may be obtained by hydrogenating a part of the double bond in the isoprene unit.

  The content of the component (c) in the aromatic vinyl-conjugated diene block copolymer composition used in the present invention is 2 to 50% by weight, preferably 5 to 40% by weight, more preferably 10 to 35% by weight. is there. When the content of the component (c) is small, the flexibility of the stretchable film is lowered. Conversely, when the content is large, the strength of the stretchable film is insufficient.

  The method for preparing the aromatic vinyl-conjugated diene block copolymer composition used in the present invention is not particularly limited. The components (a), (b), and (c) produced separately may be mixed and prepared, for example, by a series of polymerization operations according to the method described in WO2004 / 011551. A mixture of the component (a) and the component (b) may be produced, and the component (c) produced separately may be mixed therewith. Furthermore, a mixture of the component (a), the component (b), and the component (c) can be produced and used by a series of polymerization operations, for example, according to the method described in JP-A No. 2003-261740.

  In preparing the aromatic vinyl-conjugated diene block copolymer composition used in the present invention, the means for mixing is not limited. Examples thereof include a method of kneading predetermined components using a kneader, a roll mill, a Banbury mixer, a single-screw or multi-screw extruder, and the like. The mixing temperature is not particularly limited, but is preferably about 180 to 230 ° C.

  As examples of other mixing methods, the predetermined components may be selected from alicyclic hydrocarbon solvents such as cyclohexane, halogenated hydrocarbon solvents such as chloroform, carbon tetrachloride, and trichloroethane; ketone solvents such as diethyl ketone and methyl ethyl ketone; benzene And a method of evaporating the solvent from the resulting solution by dissolving in a solvent such as toluene, an aromatic hydrocarbon solvent such as toluene;

If necessary, a known elastomer other than the component (a), the component (b) and the component (c) may be added to the aromatic vinyl-conjugated diene block copolymer composition used in the present invention. Specific examples of such elastomers include polyurethane-based thermoplastic elastomer block copolymers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, and the like.
In addition, a known thermoplastic resin may be added to the aromatic vinyl-conjugated diene block copolymer composition used in the present invention. Specific examples of such thermoplastic resins include polyethylene and modified products thereof, polypropylene, polyvinyl chloride, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyphenylene ether, and the like.
Various compounding agents may be added to the aromatic vinyl-conjugated diene block copolymer composition used in the present invention. Specific examples of such compounding agents include softeners, antioxidants, antibacterial agents, light stabilizers, ultraviolet absorbers, dyes, lubricants, crosslinking agents, crosslinking accelerators, and the like.

  The stretchable film of the present invention is obtained by extrusion molding, preferably multiaxial extrusion molding, of the above aromatic vinyl-conjugated diene block copolymer composition. In particular, when a twin-screw extruder is used, the preparation of the aromatic vinyl-conjugated diene block copolymer composition and the film molding can be simultaneously performed.

  When the stretchable film of the present invention is produced by extrusion, it is preferable to produce a flat film by extrusion using a T-die. That is, using an ordinary single-screw extruder or twin-screw extruder, an aromatic vinyl-conjugated diene block copolymer composition melted at a temperature of 150 to 250 ° C. is extruded from a T-die attached to the extruder, and a take-off roll is used. A method of winding while cooling (may be simultaneously stretched) is preferred. When winding the film, it is formed into a film while coating a melt of an aromatic vinyl-conjugated diene block copolymer composition on a base material made of polyethylene terephthalate (PET), polypropylene (PP), nonwoven fabric or release paper. Also good. The film thus obtained may be used as it is coated on the substrate or may be used after being peeled off from the substrate.

  Although the thickness of the stretchable film of the present invention varies depending on the use, it is preferably 0.01 to 50 mm, more preferably 0.03 to 1 mm, and particularly preferably 0 because it is easy to stretch and has good fit. 0.05 to 0.5 mm.

Since the stretchable film of the present invention has anisotropy, the ratio (MD / TD) of 100% modulus in the melt flow direction (MD) and 100% modulus in the direction perpendicular to the melt flow (TD) in extrusion molding. Is from 1.5 to 10, preferably from 2 to 9, more preferably from 3 to 7.
Further, since the stretchable film of the present invention is excellent in flexibility, the 100% modulus in the direction (TD) perpendicular to the melt flow in extrusion molding is 0.1 to 0.5 MPa, preferably 0.15 to 0. .45 MPa, more preferably 0.15 to 0.4 MPa.

  The stretchable film of the present invention has anisotropy because the aromatic vinyl-conjugated diene block copolymer composition has a cylindrical phase separation structure, and the cylinder structure is simultaneously in a certain direction, that is, This is considered to be oriented in the direction of the melt flow (MD) during extrusion molding. The ratio of the major axis to the minor axis average diameter (major axis / minor axis) of the cylinder structure obtained by osmium vapor staining of an ultrathin section of the film and observing with a transmission electron microscope is preferably 2 or more, more preferably 2.5 or more, more preferably 3 or more.

  In the stretchable film of the present invention, the elongation of the film in at least one direction is preferably 1000% or more, more preferably 1100% or more, and particularly preferably 1200% or more. The permanent elongation of the film in at least one direction is preferably 8% or less, more preferably 6% or less, and particularly preferably 4% or less.

  The stretchable member of the present invention is made of the stretchable film. The stretchable film has anisotropy and is excellent in flexibility and stretchability, and therefore is used for a stretchable member that requires anisotropy and flexibility.

  When using a stretchable film as a stretchable member, it can be used alone or laminated with other members. For example, after slitting an elastic film, a hot melt adhesive or the like is applied to form a tape, and the tape is contracted to adhere to a nonwoven fabric, a woven fabric, a plastic film or sheet, and a laminate thereof. By relaxing the tape shrinkage, for example, an anisotropic stretchable gather member can be formed. Furthermore, according to other uses, it is processed appropriately according to a known method, for example, stretchable base materials for stretch ships, gloves, surgical gloves, finger sack, hemostatic bands, contraceptives, headbands, goggles bands, rubber bands, etc. It can be used as a member.

  The sanitary article of the present invention contains the stretchable member. For example, sanitary goods such as paper diapers and sanitary goods provided with anisotropic stretchable gather members having anisotropy and elasticity.

EXAMPLES Hereinafter, although an Example, a comparative example, and a reference example demonstrate this invention in detail, this invention is not limited only to this Example. “Content” is based on weight unless otherwise specified. Measurement and evaluation were performed as follows.
(Measurement of weight average molecular weight)
The molecular weight was determined in terms of polystyrene by high performance liquid chromatography using tetrahydrofuran as a carrier. As the column, HLC8220 manufactured by Tosoh Corporation was used, and the molecular weight was calibrated at 12 points of standard polystyrene (500 to 3,000,000) manufactured by Polymer Laboratory.

(Composition of each block copolymer)
It calculated | required from the peak area ratio of each obtained block copolymer by the high performance liquid chromatography.
(Aromatic vinyl monomer unit content in the copolymer)
Measured by proton NMR.

(Film preparation method)
A T-die is attached to the tip of a twin screw extruder, and the aromatic vinyl-conjugated diene block copolymer composition heated and melted at 200 ° C. is extruded from the T-die and continuously has a thickness of 0.2 mm. A film was formed. The film forming conditions were as follows.
Composition processing speed: 15 kg / hr
Film take-off speed: 10 m / min
Extruder temperature: Adjusted to 140 ° C. for inlet and 160 ° C. for T-die Screw: Full flight Extruder L / D: 42
T-die: 300mm width, 1mm lip

(Tensile modulus of film)
With respect to the melt flow direction (MD) and the direction perpendicular to the melt flow (TD), the tensile modulus of the film was measured using a Tensilon universal testing machine RTC-1210 manufactured by ORIENTEC at a tensile speed of 500 mm / min. The unit of tensile modulus (modulus) at 100% elongation is “MPa”.
(Elongation of film)
With respect to the melt flow direction (MD) and the direction perpendicular to the melt flow (TD), the film elongation was measured using the Tensilon universal testing machine in accordance with JIS K6301 (unit of elongation:%).
(Permanent elongation of film)
With respect to the melt flow direction (MD) and the direction perpendicular to the melt flow (TD), the permanent elongation of the film was measured using the Tensilon universal testing machine according to JIS K6301. In the measurement of permanent elongation, the film was stretched at an elongation rate of 100%, held in that state for 10 minutes, then contracted rapidly without rebounding, and after 10 minutes, the distance between marked lines was measured.
Permanent elongation (%) = (L1-L0) / L0 × 100
L0: Distance between marked lines before extension (mm)
L1: Distance between marked lines after contraction and standing for a specified time (mm)

(Observation of micro phase separation structure)
A sample piece having a width of 5 mm and a length of 10 mm was cut out from the produced film, and an ultrathin section was prepared at −80 ° C. using a cryoultramicrotome, followed by osmium vapor staining for 30 minutes. A bright-field image was observed with a transmission electron microscope (trade name “H-7500”, manufactured by Hitachi, Ltd.) at an acceleration voltage of 80 kV, and the phase separation structure was determined by image analysis. The orientation direction of the cylinder structure, the average diameter of the major axis and the minor axis, and the ratio of the major axis / minor axis are examined. If the orientation direction is the melt flow direction, “MD” is indicated.

(Reference Example 1)
31.3 kg of cyclohexane, 187.6 mmol of N, N, N ′, N′-tetramethylethylenediamine (hereinafter referred to as TMEDA) and 2.6 kg of styrene were added to the pressure-resistant reactor and stirred at 40 ° C. N-Butyllithium 187.6Kg was added there, and it superposed | polymerized for 1 hour, raising polymerization temperature to 50 degreeC. At this time, the polymerization conversion rate of styrene was 100% by weight, and the weight average molecular weight of the polystyrene block was 16,700.

  Subsequently, 7.4 kg of isoprene was continuously added over 1 hour while maintaining the polymerization temperature at 50 to 60 ° C. After completing the addition of isoprene, polymerization was continued for an additional hour. The polymerization conversion rate was 100%. Styrene-isoprene diblock copolymer [equivalent to component (b)]. The weight average molecular weight was 80,000.

Subsequently, 84.4 mmol of dimethyldichlorosilane was added as a coupling agent and a coupling reaction was performed for 2 hours to form a styrene-isoprene-styrene triblock copolymer [corresponding to the component (a)]. Thereafter, 281.4 mmol of methanol was added as a polymerization terminator and mixed well to stop the reaction.
By the above, a styrene-isoprene block copolymer mixture {hereinafter, referred to as “[(a) + (b)] component”. } Was obtained. The weight average molecular weight of the [(a) + (b)] component was 150,000.

To 100 parts of a solution prepared by adding cyclohexane to the resulting reaction solution to a solid content concentration of 30% by weight, 0.3 part of an antioxidant 2,6-di-tert-butyl-p-cresol was added. The mixed solution was added dropwise little by little to warm water heated to 85 to 95 ° C. to volatilize the solvent. The resulting precipitate was pulverized and dried with hot air at 85 ° C.
The pulverized product was supplied to a single-screw extruder equipped with an underwater hot cut device at the tip of the extruder to obtain cylindrical pellets having an average diameter of 5 mm and an average length of about 5 mm.

(Reference Examples 2-6)
In Reference Example 1, pellets were obtained in the same manner as in Reference Example 1 except that the amounts of styrene, n-butyllithium, TMEDA, isoprene, dimethyldichlorosilane and methanol were changed as shown in Table 1. Table 1 shows the characteristics of the component (a) and the component (b).

(Reference Example 7)
A pressure-resistant reactor was charged with 16.7 kg of cyclohexane, 6.41 mmol of TMEDA, and 213.7 mmol of n-butyllithium, and while stirring at 40 ° C., 5.0 kg of isoprene was increased to 60 ° C. over 1 hour while raising the polymerization temperature. After addition of isoprene, polymerization was further performed at 60 ° C. for 1 hour. The polymerization conversion rate of isoprene was 100%. Thereafter, 0.2 part of methanol was added to the reactor as a polymerization terminator and mixed well to stop the reaction, whereby polyisoprene [corresponding to the component (c)] was obtained. When the weight average molecular weight of polyisoprene was measured, it was 40,000.

(Example 1)
To 100 parts of a 30% by weight cyclohexane solution of the pellets obtained in Reference Example 1 (styrene-isoprene block copolymer mixture), 43 parts of a 30% by weight cyclohexane solution of polyisoprene obtained in Reference Example 7 was added, and an antioxidant was further added. 0.3 part of 2,6-di-tert-butyl-p-cresol was added and mixed, and the mixed solution was added dropwise to warm water heated to 85 to 95 ° C. to volatilize the solvent. The obtained precipitate was pulverized and dried with hot air at 85 ° C. to obtain an aromatic vinyl-conjugated diene block copolymer composition. The results of measuring the styrene monomer unit content of the [(a) + (b)] component of the composition and the content (% by weight) of each component (a), (b), and (c) It shows in Table 2.
Using the aromatic vinyl-conjugated diene block copolymer composition, a film was formed by the above-mentioned film production method. The film was measured for 100% modulus, modulus ratio, elongation and permanent elongation, and a cylindrical phase separation structure was observed with an electron microscope. The results are shown in Table 2.

(Example 2)
A film was produced in the same manner as in Example 1 except that the pellets obtained in Reference Example 1 were changed to those obtained in Reference Example 2 in Example 1.
Table 2 shows the contents of the components (a), (b) and (c) of the aromatic vinyl-conjugated diene block copolymer composition. The characteristics of the produced film were measured in the same manner as in Example 1. The results are shown in Table 2.

(Example 3)
In Example 1, the pellets were changed from those obtained in Reference Example 1 to those obtained in Reference Example 3, and the amount of polyisoprene obtained in Reference Example 7 was changed to the amount described in Table 2 Produced a film in the same manner as in Example 1.
Table 2 shows the contents of the components (a), (b) and (c) of the aromatic vinyl-conjugated diene block copolymer composition. The characteristics of the produced film were measured in the same manner as in Example 1. The results are shown in Table 2.

Example 4
In Example 1, except that pellets were changed from those obtained in Reference Example 1 to those obtained in Reference Example 4, and the amount of polyisoprene obtained in Reference Example 7 was changed to the amount described in Table 2 Produced a film in the same manner as in Example 1.
Table 2 shows the contents of the components (a), (b) and (c) of the aromatic vinyl-conjugated diene block copolymer composition. The characteristics of the produced film were measured in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 1)
In Example 1, the pellet was changed from that obtained in Reference Example 1 to that obtained in Reference Example 5, and a film was produced in the same manner as in Example 1 except that the polyisoprene obtained in Reference Example 7 was not added. did.
Table 2 shows the contents of the components (a) and (b) of the aromatic vinyl-conjugated diene block copolymer composition. The characteristics of the produced film were measured in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 2)
In Example 1, except that the pellets were changed from those obtained in Reference Example 1 to those obtained in Reference Example 6, and the amount of polyisoprene obtained in Reference Example 7 was changed to the amount described in Table 2. A film was prepared in the same manner as in Example 1.
Table 2 shows the contents of the components (a), (b) and (c) of the aromatic vinyl-conjugated diene block copolymer composition. The characteristics of the produced film were measured in the same manner as in Example 1. The results are shown in Table 2.

As Table 2 shows, all of the films obtained in Examples 1 to 4 have a 100% modulus TD / MD ratio of 3.5 to 6.7, sufficiently large and anisotropic, in the TD direction. Since the 100% modulus is remarkably low, the flexibility is excellent, and the elongation of MD and TD is both as large as 1200% or more, and the elasticity is excellent. Further, it was observed with a transmission electron microscope that cylindrical microphase separation structures were formed and they were all aligned in the melt flow direction (MD).
On the other hand, the film containing no polyisoprene in Comparative Example 1 has anisotropy, but lacks flexibility because of its high 100% modulus in the TD direction.
Moreover, the film in which the styrene unit content with respect to the total amount of the component (a) and the component (b) in Comparative Example 2 is less than the value specified in the present invention has a low 100% modulus for both MD and TD and is excellent in flexibility. However, it shows little anisotropy.

Claims (3)

(A) 35 to 95% by weight of an aromatic vinyl-conjugated diene block copolymer having two or more aromatic vinyl polymer blocks having a weight average molecular weight of 6,000 to 100,000, and (b) aromatic vinyl-conjugated diene. It contains 0 to 60% by weight of an diblock copolymer, and (c) 2 to 50% by weight of polyisoprene having a weight average molecular weight of 5,000 to 300,000, and is based on the total amount of component (a) and component (b) A stretchable film obtained by extrusion molding an aromatic vinyl-conjugated diene block copolymer composition having an aromatic vinyl monomer unit content of 22 to 45% by weight,
The ratio (MD / TD) of the 100% modulus in the melt flow direction (MD) and the 100% modulus in the direction perpendicular to the melt flow (TD) in the extrusion molding is 1.5 to 10, and A stretchable film having a 100% modulus in a direction perpendicular to the right (TD) of 0.1 to 0.5 MPa.   A stretchable member comprising the stretchable film according to claim 1. A sanitary article comprising the stretchable member according to claim 2.